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Sample records for 3d electron diffraction

  1. Atomic resolution 3D electron diffraction microscopy

    SciTech Connect

    Miao, Jianwei; Ohsuna, Tetsu; Terasaki, Osamu; O'Keefe, Michael A.

    2002-03-01

    Electron lens aberration is the major barrier limiting the resolution of electron microscopy. Here we describe a novel form of electron microscopy to overcome electron lens aberration. By combining coherent electron diffraction with the oversampling phasing method, we show that the 3D structure of a 2 x 2 x 2 unit cell nano-crystal (framework of LTA [Al12Si12O48]8) can be ab initio determined at the resolution of 1 Angstrom from a series of simulated noisy diffraction pattern projections with rotation angles ranging from -70 degrees to +70 degrees in 5 degrees increments along a single rotation axis. This form of microscopy (which we call 3D electron diffraction microscopy) does not require any reference waves, and can image the 3D structure of nanocrystals, as well as non-crystalline biological and materials science samples, with the resolution limited only by the quality of sample diffraction.

  2. Layered nano-gratings by electron beam writing to form 3-level diffractive optical elements for 3D phase-offset holographic lithography

    NASA Astrophysics Data System (ADS)

    Yuan, Liang (Leon); Herman, Peter R.

    2015-11-01

    A multi-level nanophotonic structure is a major goal in providing advanced optical functionalities as found in photonic crystals and metamaterials. A three-level nano-grating phase mask has been fabricated in an electron-beam resist (ma-N) to meet the requirement of holographic generation of a diamond-like 3D nanostructure in photoresist by a single exposure step. A 2D mask with 600 nm periodicity is presented for generating first order diffracted beams with a preferred π/2 phase shift on the X- and Y-axes and with sufficient 1st order diffraction efficiency of 3.5% at 800 nm wavelength for creating a 3D periodic nanostructure in SU-8 photoresist. The resulting 3D structure is anticipated to provide an 8% complete photonic band gap (PBG) upon silicon inversion. A thin SiO2 layer was used to isolate the grating layers and multiple spin-coating steps served to planarize the final resist layer. A reversible soft coating (aquaSAVE) was introduced to enable SEM inspection and verification of each insulating grating layer. This e-beam lithographic method is extensible to assembling multiple layers of a nanophotonic structure.

  3. A pseudo-3D approach based on electron backscatter diffraction and backscatter electron imaging to study the character of phase boundaries between Mg and long period stacking ordered phase in a Mg–2Y–Zn alloy

    SciTech Connect

    Afshar, Mehran Zaefferer, Stefan

    2015-03-15

    In Mg–2 at.% Y–1 at.% Zn alloys, the LPSO (Long Period Stacking Ordered) phase is important to improve mechanical properties of the material. The aim of this paper is to present a study on the phase boundary character in these two-phase alloys. Using EBSD pattern analysis it was found that the 24R structure is the dominant LPSO phase structure in the current alloy. The phase boundary character between the Mg matrix and the LPSO phase was investigated using an improved pseudo-3D EBSD (electron backscatter diffraction) technique in combination with BSE or SE (backscatter or secondary electron) imaging. A large amount of very low-angle phase boundaries was detected. The (0 0 0 2) plane in the Mg matrix which is parallel to the (0 0 0 24) plane in the LPSO phase was found to be the most frequent plane for these phase boundaries. This plane is supposed to be the habit plane of the eutectic co-solidification of the Mg matrix and the LPSO phase. - Highlights: • It is shown that for the investigated alloy the LPSO phase has mainly 24R crystal structure. • A new method is presented which allows accurate determination of the 5-parameter grain or phase boundary character. • It is found that the low-angle phase boundaries appearing in the alloy all have basal phase boundary planes.

  4. Ultrafast electron diffraction from aligned molecules

    SciTech Connect

    Centurion, Martin

    2015-08-17

    The aim of this project was to record time-resolved electron diffraction patterns of aligned molecules and to reconstruct the 3D molecular structure. The molecules are aligned non-adiabatically using a femtosecond laser pulse. A femtosecond electron pulse then records a diffraction pattern while the molecules are aligned. The diffraction patterns are then be processed to obtain the molecular structure.

  5. Fixing the focus shift caused by 3D mask diffraction

    NASA Astrophysics Data System (ADS)

    Yenikaya, Bayram; Chuyeshov, Constantin; Bakir, Onur; Han, Youngae

    2014-03-01

    As the feature sizes printed with optical lithography get smaller, Kirchhoff's thin mask approximation used in full chip optical proximity corrections (OPC) fails to yield acceptable accuracy due to thick mask diffraction effects. One of the most observed effects of the thick mask diffraction is that it creates different focus shift for different patterns. When Bossung curves (CD plots with respect to defocus) of various patterns are observed from rigorous simulations and from actual wafer data one can notice that each pattern has a different best focus. Depending on the pattern, Bossung curves can be offset in either positive or negative direction. This significantly reduces the common depth of focus (DOF) for which all patterns print with acceptable fidelity. Even though each pattern by itself may have an acceptable DOF, the common DOF may not be acceptable. Several extensions to the thin mask approximation have been developed that model this behavior accurately, such as boundary layer approximations and domain decomposition methods. These methods provide a more accurate approximation than the thin mask model while still being computationally efficient to be useful for full chip OPC. Even though these approximations model and predict the focus shift accurately, to the best knowledge of the authors no method has been published to use these modeling capabilities to automatically fix this focus shift during OPC. In this paper we provide an optimization method to significantly reduce focus shift due to 3D mask effects during OPC. We show that our 3D mask model can predict this focus shift fairly accurately and we also demonstrate how we use this model in OPC to reduce focus shift, which significantly improves the common DOF for the entire layout.

  6. Quantitative 3D imaging of whole, unstained cells by using X-ray diffraction microscopy.

    PubMed

    Jiang, Huaidong; Song, Changyong; Chen, Chien-Chun; Xu, Rui; Raines, Kevin S; Fahimian, Benjamin P; Lu, Chien-Hung; Lee, Ting-Kuo; Nakashima, Akio; Urano, Jun; Ishikawa, Tetsuya; Tamanoi, Fuyuhiko; Miao, Jianwei

    2010-06-22

    Microscopy has greatly advanced our understanding of biology. Although significant progress has recently been made in optical microscopy to break the diffraction-limit barrier, reliance of such techniques on fluorescent labeling technologies prohibits quantitative 3D imaging of the entire contents of cells. Cryoelectron microscopy can image pleomorphic structures at a resolution of 3-5 nm, but is only applicable to thin or sectioned specimens. Here, we report quantitative 3D imaging of a whole, unstained cell at a resolution of 50-60 nm by X-ray diffraction microscopy. We identified the 3D morphology and structure of cellular organelles including cell wall, vacuole, endoplasmic reticulum, mitochondria, granules, nucleus, and nucleolus inside a yeast spore cell. Furthermore, we observed a 3D structure protruding from the reconstructed yeast spore, suggesting the spore germination process. Using cryogenic technologies, a 3D resolution of 5-10 nm should be achievable by X-ray diffraction microscopy. This work hence paves a way for quantitative 3D imaging of a wide range of biological specimens at nanometer-scale resolutions that are too thick for electron microscopy.

  7. Lensfree diffractive tomography for the imaging of 3D cell cultures

    PubMed Central

    Momey, F.; Berdeu, A.; Bordy, T.; Dinten, J.-M.; Marcel, F. Kermarrec; Picollet-D’hahan, N.; Gidrol, X.; Allier, C.

    2016-01-01

    New microscopes are needed to help realize the full potential of 3D organoid culture studies. In order to image large volumes of 3D organoid cultures while preserving the ability to catch every single cell, we propose a new imaging platform based on lensfree microscopy. We have built a lensfree diffractive tomography setup performing multi-angle acquisitions of 3D organoid culture embedded in Matrigel and developed a dedicated 3D holographic reconstruction algorithm based on the Fourier diffraction theorem. With this new imaging platform, we have been able to reconstruct a 3D volume as large as 21.5 mm3 of a 3D organoid culture of prostatic RWPE1 cells showing the ability of these cells to assemble in 3D intricate cellular network at the mesoscopic scale. Importantly, comparisons with 2D images show that it is possible to resolve single cells isolated from the main cellular structure with our lensfree diffractive tomography setup. PMID:27231600

  8. Evolution in boron-based GEM detectors for diffraction measurements: from planar to 3D converters

    NASA Astrophysics Data System (ADS)

    Albani, Giorgia; Perelli Cippo, Enrico; Croci, Gabriele; Muraro, Andrea; Schooneveld, Erik; Scherillo, Antonella; Hall-Wilton, Richard; Kanaki, Kalliopi; Höglund, Carina; Hultman, Lars; Birch, Jens; Claps, Gerardo; Murtas, Fabrizio; Rebai, Marica; Tardocchi, Marco; Gorini, Giuseppe

    2016-11-01

    The so-called ‘3He-crisis’ has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising ‘3He-free’ technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.

  9. A 3-D numerical study of pinhole diffraction to predict the accuracy of EUV point diffraction interferometry

    SciTech Connect

    Goldberg, K.A. |; Tejnil, E.; Bokor, J. |

    1995-12-01

    A 3-D electromagnetic field simulation is used to model the propagation of extreme ultraviolet (EUV), 13-nm, light through sub-1500 {Angstrom} dia pinholes in a highly absorptive medium. Deviations of the diffracted wavefront phase from an ideal sphere are studied within 0.1 numerical aperture, to predict the accuracy of EUV point diffraction interferometersused in at-wavelength testing of nearly diffraction-limited EUV optical systems. Aberration magnitudes are studied for various 3-D pinhole models, including cylindrical and conical pinhole bores.

  10. Electron diffraction from cylindrical nanotubes

    SciTech Connect

    Qin, L.C. )

    1994-09-01

    Electron diffraction intensities from cylindrical objects can be conveniently analyzed using Bessel functions. Analytic formulas and geometry of the diffraction patterns from cylindrical carbon nanotubes are presented in general forms in terms of structural parameters, such as the pitch angle and the radius of a tubule. As an example the Fraunhofer diffraction pattern from a graphitic tubule of structure [18,2] has been simulated to illustrate the characteristics of such diffraction patterns. The validity of the projection approximation is also discussed.

  11. Design and verification of diffractive optical elements for speckle generation of 3-D range sensors

    NASA Astrophysics Data System (ADS)

    Du, Pei-Qin; Shih, Hsi-Fu; Chen, Jenq-Shyong; Wang, Yi-Shiang

    2016-12-01

    The optical projection using speckles is one of the structured light methods that have been applied to three-dimensional (3-D) range sensors. This paper investigates the design and fabrication of diffractive optical elements (DOEs) for generating the light field with uniformly distributed speckles. Based on the principles of computer generated holograms, the iterative Fourier transform algorithm was adopted for the DOE design. It was used to calculate the phase map for diffracting the incident laser beam into a goal pattern with distributed speckles. Four patterns were designed in the study. Their phase maps were first examined by a spatial light modulator and then fabricated on glass substrates by microfabrication processes. Finally, the diffraction characteristics of the fabricated devices were verified. The experimental results show that the proposed methods are applicable to the DOE design of 3-D range sensors. Furthermore, any expected diffraction area and speckle density could be possibly achieved according to the relations presented in the paper.

  12. Field lens multiplexing in holographic 3D displays by using Bragg diffraction based volume gratings

    NASA Astrophysics Data System (ADS)

    Fütterer, G.

    2016-11-01

    Applications, which can profit from holographic 3D displays, are the visualization of 3D data, computer-integrated manufacturing, 3D teleconferencing and mobile infotainment. However, one problem of holographic 3D displays, which are e.g. based on space bandwidth limited reconstruction of wave segments, is to realize a small form factor. Another problem is to provide a reasonable large volume for the user placement, which means to provide an acceptable freedom of movement. Both problems should be solved without decreasing the image quality of virtual and real object points, which are generated within the 3D display volume. A diffractive optical design using thick hologram gratings, which can be referred to as Bragg diffraction based volume gratings, can provide a small form factor and high definition natural viewing experience of 3D objects. A large collimated wave can be provided by an anamorphic backlight unit. The complex valued spatial light modulator add local curvatures to the wave field he is illuminated with. The modulated wave field is focused onto to the user plane by using a volume grating based field lens. Active type liquid crystal gratings provide 1D fine tracking of approximately +/- 8° deg. Diffractive multiplex has to be implemented for each color and for a set of focus functions providing coarse tracking. Boundary conditions of the diffractive multiplexing are explained. This is done in regards to the display layout and by using the coupled wave theory (CWT). Aspects of diffractive cross talk and its suppression will be discussed including longitudinal apodized volume gratings.

  13. Femtosecond single-electron diffraction

    PubMed Central

    Lahme, S.; Kealhofer, C.; Krausz, F.; Baum, P.

    2014-01-01

    Ultrafast electron diffraction allows the tracking of atomic motion in real time, but space charge effects within dense electron packets are a problem for temporal resolution. Here, we report on time-resolved pump-probe diffraction using femtosecond single-electron pulses that are free from intra-pulse Coulomb interactions over the entire trajectory from the source to the detector. Sufficient average electron current is achieved at repetition rates of hundreds of kHz. Thermal load on the sample is avoided by minimizing the pump-probe area and by maximizing heat diffusion. Time-resolved diffraction from fibrous graphite polycrystals reveals coherent acoustic phonons in a nanometer-thick grain ensemble with a signal-to-noise level comparable to conventional multi-electron experiments. These results demonstrate the feasibility of pump-probe diffraction in the single-electron regime, where simulations indicate compressibility of the pulses down to few-femtosecond and attosecond duration. PMID:26798778

  14. High performance 3D printed electronics using electroless plated copper

    NASA Astrophysics Data System (ADS)

    Jian, Jin Rong; Kim, Taeil; Park, Jae Sung; Wang, Jiacheng; Kim, Woo Soo

    2017-03-01

    This paper presents design and performance validation of 3D printed electronic components, 3D toroidal air-core inductors, fabricated by multi-material based Fused Deposition Modelling (FDM) 3D printing technology and electroless copper plating. Designs of toroidal inductor is investigated with different core shapes and winding numbers; circular and half-circular cores with 10 and 13 turns of windings. Electroless plated copper thin film ensures 3D printed toroidal plastic structures to possess inductive behaviors. The inductance is demonstrated reliably with an applied source frequency from 100 kHz to 2 MHz as designs vary. An RL circuit is utilized to test the fabricated inductors' phase-leading characteristics with corresponding phase angle changes.

  15. Beat the diffraction limit in 3D direct laser writing in photosensitive glass.

    PubMed

    Bellec, Matthieu; Royon, Arnaud; Bousquet, Bruno; Bourhis, Kevin; Treguer, Mona; Cardinal, Thierry; Richardson, Martin; Canioni, Lionel

    2009-06-08

    Three-dimensional (3D) femtosecond laser direct structuring in transparent materials is widely used for photonic applications. However, the structure size is limited by the optical diffraction. Here we report on a direct laser writing technique that produces subwavelength nanostructures independently of the experimental limiting factors. We demonstrate 3D nanostructures of arbitrary patterns with feature sizes down to 80 nm, less than one tenth of the laser processing wavelength. Its ease of implementation for novel nanostructuring, with its accompanying high precision will open new opportunities for the fabrication of nanostructures for plasmonic and photonic devices and for applications in metamaterials.

  16. Electron diffraction by plasmon waves

    NASA Astrophysics Data System (ADS)

    García de Abajo, F. J.; Barwick, B.; Carbone, F.

    2016-07-01

    An electron beam traversing a structured plasmonic field is shown to undergo diffraction with characteristic angular patterns of both elastic and inelastic outgoing electron components. In particular, a plasmonic grating (e.g., a standing wave formed by two counterpropagating plasmons in a thin film) produces diffraction orders of the same parity as the net number of exchanged plasmons. Large diffracted beam fractions are predicted to occur for realistic plasmon intensities in attainable geometries due to a combination of phase and amplitude changes locally imprinted on the passing electron wave. Our study opens vistas in the study of multiphoton exchanges between electron beams and evanescent optical fields with unexplored effects related to the transversal component of the electron wave function.

  17. Laser embedding electronics on 3D printed objects

    NASA Astrophysics Data System (ADS)

    Kirleis, Matthew A.; Simonson, Duane; Charipar, Nicholas A.; Kim, Heungsoo; Charipar, Kristin M.; Auyeung, Ray C. Y.; Mathews, Scott A.; Piqué, Alberto

    2014-03-01

    Additive manufacturing techniques such as 3D printing are able to generate reproductions of a part in free space without the use of molds; however, the objects produced lack electrical functionality from an applications perspective. At the same time, techniques such as inkjet and laser direct-write (LDW) can be used to print electronic components and connections onto already existing objects, but are not capable of generating a full object on their own. The approach missing to date is the combination of 3D printing processes with direct-write of electronic circuits. Among the numerous direct write techniques available, LDW offers unique advantages and capabilities given its compatibility with a wide range of materials, surface chemistries and surface morphologies. The Naval Research Laboratory (NRL) has developed various LDW processes ranging from the non-phase transformative direct printing of complex suspensions or inks to lase-and-place for embedding entire semiconductor devices. These processes have been demonstrated in digital manufacturing of a wide variety of microelectronic elements ranging from circuit components such as electrical interconnects and passives to antennas, sensors, actuators and power sources. At NRL we are investigating the combination of LDW with 3D printing to demonstrate the digital fabrication of functional parts, such as 3D circuits. Merging these techniques will make possible the development of a new generation of structures capable of detecting, processing, communicating and interacting with their surroundings in ways never imagined before. This paper shows the latest results achieved at NRL in this area, describing the various approaches developed for generating 3D printed electronics with LDW.

  18. X-ray Laue Diffraction Microscopy in 3D at the Advanced Photon Source

    SciTech Connect

    Liu, W.; Zschack, P.; Tischler, Jonathan Zachary; Ice, Gene E; Larson, Ben C

    2011-01-01

    Studies of materials on mesoscopic length-scales require a penetrating structural probe with submicron point-to-point spatial resolution. The principle research activities at beamline 34-ID-E of the Advanced Photon Source (APS) involve development of exciting new micro-/nano-diffraction techniques for characterization and microscopy in support of both applied engineering and fundamental materials research. Taking advantage of the high brightness of the source, advanced focusing mirrors, a novel depth profiling technique, and high-speed area detectors, three-dimensional scanning Laue diffraction microscopy provides detailed local structural information of crystalline materials, such as crystallographic orientation, orientation gradients, and strain tensors. It is general and applicable to single-crystal, polycrystalline, composite, deformed, and functionally graded materials. Applications include 3D diffraction investigations for a diverse and growing user community with interests in materials deformation, electro-migration, recrystallization, fatigue, solid-solution precipitation, high-pressure environments, and condensed matter physics.

  19. Recent progress in printed 2/3D electronic devices

    NASA Astrophysics Data System (ADS)

    Klug, Andreas; Patter, Paul; Popovic, Karl; Blümel, Alexander; Sax, Stefan; Lenz, Martin; Glushko, Oleksandr; Cordill, Megan J.; List-Kratochvil, Emil J. W.

    2015-09-01

    New, energy-saving, efficient and cost-effective processing technologies such as 2D and 3D inkjet printing (IJP) for the production and integration of intelligent components will be opening up very interesting possibilities for industrial applications of molecular materials in the near future. Beyond the use of home and office based printers, "inkjet printing technology" allows for the additive structured deposition of photonic and electronic materials on a wide variety of substrates such as textiles, plastics, wood, stone, tiles or cardboard. Great interest also exists in applying IJP in industrial manufacturing such as the manufacturing of PCBs, of solar cells, printed organic electronics and medical products. In all these cases inkjet printing is a flexible (digital), additive, selective and cost-efficient material deposition method. Due to these advantages, there is the prospect that currently used standard patterning processes can be replaced through this innovative material deposition technique. A main issue in this research area is the formulation of novel functional inks or the adaptation of commercially available inks for specific industrial applications and/or processes. In this contribution we report on the design, realization and characterization of novel active and passive inkjet printed electronic devices including circuitry and sensors based on metal nanoparticle ink formulations and the heterogeneous integration into 2/3D printed demonstrators. The main emphasis of this paper will be on how to convert scientific inkjet knowledge into industrially relevant processes and applications.

  20. Perturbation theory in electron diffraction

    NASA Astrophysics Data System (ADS)

    Bakken, L. N.; Marthinsen, K.; Hoeier, R.

    1992-12-01

    The Bloch-wave approach is used for discussing multiple inelastic electron scattering and higher-order perturbation theory in inelastic high-energy electron diffraction. In contrast to previous work, the present work describes three-dimensional diffraction so that higher-order Laue zone (HOLZ) effects are incorporated. Absorption is included and eigenvalues and eigenvectors are calculated from a structure matrix with the inclusion of an absorptive potential. Centrosymmetric as well as non-centrosymmetric crystal structures are allowed. An iteration method with a defined generalized propagation function for solving the inelastic coupling equations is described. It is shown that a similar iteration method with the same propagation function can be used for obtaining higher-order perturbation terms for the wave-function when a perturbation is added to the crystal potential. Finally, perturbation theory by matrix calculations when a general perturbation is added to the structure matrix is considered.

  1. Computational-optical microscopy for 3D biological imaging beyond the diffraction limit

    NASA Astrophysics Data System (ADS)

    Grover, Ginni

    In recent years, super-resolution imaging has become an important fluorescent microscopy tool. It has enabled imaging of structures smaller than the optical diffraction limit with resolution less than 50 nm. Extension to high-resolution volume imaging has been achieved by integration with various optical techniques. In this thesis, development of a fluorescent microscope to enable high resolution, extended depth, three dimensional (3D) imaging is discussed; which is achieved by integration of computational methods with optical systems. In the first part of the thesis, point spread function (PSF) engineering for volume imaging is discussed. A class of PSFs, referred to as double-helix (DH) PSFs, is generated. The PSFs exhibit two focused spots in the image plane which rotate about the optical axis, encoding depth in rotation of the image. These PSFs extend the depth-of-field up to a factor of ˜5. Precision performance of the DH-PSFs, based on an information theoretical analysis, is compared with other 3D methods with conclusion that the DH-PSFs provide the best precision and the longest depth-of-field. Out of various possible DH-PSFs, a suitable PSF is obtained for super-resolution microscopy. The DH-PSFs are implemented in imaging systems, such as a microscope, with a special phase modulation at the pupil plane. Surface-relief elements which are polarization-insensitive and ˜90% light efficient are developed for phase modulation. The photon-efficient DH-PSF microscopes thus developed are used, along with optimal position estimation algorithms, for tracking and super-resolution imaging in 3D. Imaging at depths-of-field of up to 2.5 microm is achieved without focus scanning. Microtubules were imaged with 3D resolution of (6, 9, 39) nm, which is in close agreement with the theoretical limit. A quantitative study of co-localization of two proteins in volume was conducted in live bacteria. In the last part of the thesis practical aspects of the DH-PSF microscope are

  2. Hybrid additive manufacturing of 3D electronic systems

    NASA Astrophysics Data System (ADS)

    Li, J.; Wasley, T.; Nguyen, T. T.; Ta, V. D.; Shephard, J. D.; Stringer, J.; Smith, P.; Esenturk, E.; Connaughton, C.; Kay, R.

    2016-10-01

    A novel hybrid additive manufacturing (AM) technology combining digital light projection (DLP) stereolithography (SL) with 3D micro-dispensing alongside conventional surface mount packaging is presented in this work. This technology overcomes the inherent limitations of individual AM processes and integrates seamlessly with conventional packaging processes to enable the deposition of multiple materials. This facilitates the creation of bespoke end-use products with complex 3D geometry and multi-layer embedded electronic systems. Through a combination of four-point probe measurement and non-contact focus variation microscopy, it was identified that there was no obvious adverse effect of DLP SL embedding process on the electrical conductivity of printed conductors. The resistivity maintained to be less than 4  ×  10-4 Ω · cm before and after DLP SL embedding when cured at 100 °C for 1 h. The mechanical strength of SL specimens with thick polymerized layers was also identified through tensile testing. It was found that the polymerization thickness should be minimised (less than 2 mm) to maximise the bonding strength. As a demonstrator a polymer pyramid with embedded triple-layer 555 LED blinking circuitry was successfully fabricated to prove the technical viability.

  3. Advanced prior modeling for 3D bright field electron tomography

    NASA Astrophysics Data System (ADS)

    Sreehari, Suhas; Venkatakrishnan, S. V.; Drummy, Lawrence F.; Simmons, Jeffrey P.; Bouman, Charles A.

    2015-03-01

    Many important imaging problems in material science involve reconstruction of images containing repetitive non-local structures. Model-based iterative reconstruction (MBIR) could in principle exploit such redundancies through the selection of a log prior probability term. However, in practice, determining such a log prior term that accounts for the similarity between distant structures in the image is quite challenging. Much progress has been made in the development of denoising algorithms like non-local means and BM3D, and these are known to successfully capture non-local redundancies in images. But the fact that these denoising operations are not explicitly formulated as cost functions makes it unclear as to how to incorporate them in the MBIR framework. In this paper, we formulate a solution to bright field electron tomography by augmenting the existing bright field MBIR method to incorporate any non-local denoising operator as a prior model. We accomplish this using a framework we call plug-and-play priors that decouples the log likelihood and the log prior probability terms in the MBIR cost function. We specifically use 3D non-local means (NLM) as the prior model in the plug-and-play framework, and showcase high quality tomographic reconstructions of a simulated aluminum spheres dataset, and two real datasets of aluminum spheres and ferritin structures. We observe that streak and smear artifacts are visibly suppressed, and that edges are preserved. Also, we report lower RMSE values compared to the conventional MBIR reconstruction using qGGMRF as the prior model.

  4. Terahertz 3D printed diffractive lens matrices for field-effect transistor detector focal plane arrays.

    PubMed

    Szkudlarek, Krzesimir; Sypek, Maciej; Cywiński, Grzegorz; Suszek, Jarosław; Zagrajek, Przemysław; Feduniewicz-Żmuda, Anna; Yahniuk, Ivan; Yatsunenko, Sergey; Nowakowska-Siwińska, Anna; Coquillat, Dominique; But, Dmytro B; Rachoń, Martyna; Węgrzyńska, Karolina; Skierbiszewski, Czesław; Knap, Wojciech

    2016-09-05

    We present the concept, the fabrication processes and the experimental results for materials and optics that can be used for terahertz field-effect transistor detector focal plane arrays. More specifically, we propose 3D printed arrays of a new type - diffractive multi-zone lenses of which the performance is superior to that of previously used mono-zone diffractive or refractive elements and evaluate them with GaN/AlGaN field-effect transistor terahertz detectors. Experiments performed in the 300-GHz atmospheric window show that the lens arrays offer both a good efficiency and good uniformity, and may improve the signal-to-noise ratio of the terahertz field-effect transistor detectors by more than one order of magnitude. In practice, we tested 3 × 12 lens linear arrays with printed circuit board THz detector arrays used in postal security scanners and observed significant signal-to-noise improvements. Our results clearly show that the proposed technology provides a way to produce cost-effective, reproducible, flat optics for large-size field-effect transistor THz-detector focal plane arrays.

  5. Cryptotomography: reconstructing 3D Fourier intensities from randomly oriented single-shot diffraction patterns (CXIDB ID 9)

    DOE Data Explorer

    Loh, Ne-Te Duane

    2011-08-01

    These 2000 single-shot diffraction patterns include were either background-scattering only or hits (background-scattering plus diffraction signal from sub-micron ellipsoidal particles at random, undetermined orientations). Candidate hits were identified by eye, and the remainder were presumed as background. 54 usable, background-subtracted hits in this set (procedure in referenced article) were used to reconstruct the 3D diffraction intensities of the average ellipsoidal particle.

  6. 3D Observation of GEMS by Electron Tomography

    NASA Technical Reports Server (NTRS)

    Matsuno, Junya; Miyake, Akira; Tsuchiyama, Akira; Nakamura-Messenger, Keiko; Messenger, Scott

    2014-01-01

    Amorphous silicates in chondritic porous interplanetary dust particles (CP-IDPs) coming from comets are dominated by glass with embedded metal and sulfides (GEMS). GEMS grains are submicron-sized rounded objects (typically 100-500) nm in diameter) with anaometer-sized (10-50 nm) Fe-Ni metal and sulfide grains embedded in an amorphous silicate matrix. Several formation processes for GEMS grains have been proposed so far, but these models are still being debated [2-5]. Bradley et al. proposed that GEMS grains are interstellar silicate dust that survived various metamorphism or alteration processes in the protoplanetary disk and that they are amorphiation products of crystalline silicates in the interstellar medium by sputter-deposition of cosmic ray irradiation, similar to space weathering [2,4]. This consideration is based on the observation of nano-sized crystals (approximately 10 nm) called relict grains in GEMS grains and their shapes are pseudomorphs to the host GEMS grains. On the other hand, Keller and Messenger proposed that most GEMS formed in the protoplanetary disk as condensates from high temperature gas [3,5]. This model is based on the fact that most GEMS grains have solar isotopic compositions and have extremely heterogeneous and non-solar elemental compositions. Keller and Messenger (2011) also reported that amorphous silicates in GEMS grains are surrounded by sulfide grains, which formed as sulfidization of metallic iron grains located on the GEMS surface. The previous studies were performed with 2D observation by using transmission electron microscopy (TEM) or scanning TEM (STEM). In order to understand the structure of GEMS grains described above more clearly, we observed 3D structure of GEMS grains by electron tomography using a TEM/STEM (JEM-2100F, JEOL) at Kyoto University. Electron tomography gives not only 3D structures but also gives higher spatial resolution (approximately a few nm) than that in conventional 2D image, which is restricted by

  7. 3D Printing: 3D Printing of Shape Memory Polymers for Flexible Electronic Devices (Adv. Mater. 22/2016).

    PubMed

    Zarek, Matt; Layani, Michael; Cooperstein, Ido; Sachyani, Ela; Cohn, Daniel; Magdassi, Shlomo

    2016-06-01

    On page 4449, D. Cohn, S. Magdassi, and co-workers describe a general and facile method based on 3D printing of methacrylated macromonomers to fabricate shape-memory objects that can be used in flexible and responsive electrical circuits. Such responsive objects can be used in the fabrication of soft robotics, minimal invasive medical devices, sensors, and wearable electronics. The use of 3D printing overcomes the poor processing characteristics of thermosets and enables complex geometries that are not easily accessible by other techniques.

  8. Note: An improved 3D imaging system for electron-electron coincidence measurements

    SciTech Connect

    Lin, Yun Fei; Lee, Suk Kyoung; Adhikari, Pradip; Herath, Thushani; Lingenfelter, Steven; Winney, Alexander H.; Li, Wen

    2015-09-15

    We demonstrate an improved imaging system that can achieve highly efficient 3D detection of two electrons in coincidence. The imaging system is based on a fast frame complementary metal-oxide semiconductor camera and a high-speed waveform digitizer. We have shown previously that this detection system is capable of 3D detection of ions and electrons with good temporal and spatial resolution. Here, we show that with a new timing analysis algorithm, this system can achieve an unprecedented dead-time (<0.7 ns) and dead-space (<1 mm) when detecting two electrons. A true zero dead-time detection is also demonstrated.

  9. Methods For Electronic 3-D Moving Pictures Without Glasses

    NASA Astrophysics Data System (ADS)

    Collender, Robert B.

    1987-06-01

    This paper describes implementation approaches in image acquisition and playback for 3-D computer graphics, 3-D television and 3-D theatre movies without special glasses. Projection lamps, spatial light modulators, CRT's and dynamic scanning are all eliminated by the application of an active image array, all static components and a semi-specular screen. The resulting picture shows horizontal parallax with a wide horizontal view field (up to 360 de-grees) giving a holographic appearance in full color with smooth continuous viewing without speckle. Static component systems are compared with dynamic component systems using both linear and circular arrays. Implementation of computer graphic systems are shown that allow complex shaded color images to extend from the viewer's eyes to infinity. Large screen systems visible by hundreds of people are feasible by the use of low f-stops and high gain screens in projection. Screen geometries and special screen properties are shown. Viewing characteristics offer no restrictions in view-position over the entire view-field and have a "look-around" feature for all the categories of computer graphics, television and movies. Standard video cassettes and optical discs can also interface the system to generate a 3-D window viewable without glasses. A prognosis is given for technology application to 3-D pictures without glasses that replicate the daily viewing experience. Super-position of computer graphics on real-world pictures is shown feasible.

  10. An Electronic Analog of the Diffraction Grating.

    ERIC Educational Resources Information Center

    MacLeod, A. M.

    1978-01-01

    Gives an outline description of electronic circuitry which is analogous to the optical diffraction grating or to crystals used in the Bragg reflection of X-rays or electron waves, and explains how to use it. (Author/GA)

  11. Coherent 3D nanostructure of γ-Al2O3: Simulation of whole X-ray powder diffraction pattern

    NASA Astrophysics Data System (ADS)

    Pakharukova, V. P.; Yatsenko, D. A.; Gerasimov, E. Yu.; Shalygin, A. S.; Martyanov, O. N.; Tsybulya, S. V.

    2017-02-01

    The structure and nanostructure features of nanocrystalline γ-Al2O3 obtained by dehydration of boehmite with anisotropic platelet-shaped particles were investigated. The original models of 3D coherent nanostructure of γ-Al2O3 were constructed. The models of nanostructured γ-Al2O3 particles were first confirmed by a direct simulation of powder X-Ray diffraction (XRD) patterns using the Debye Scattering Equation (DSE) with assistance of high-resolution transmission electron microscopy (HRTEM) study. The average crystal structure of γ-Al2O3 was shown to be tetragonally distorted. The experimental results revealed that thin γ-Al2O3 platelets were heterogeneous on a nanometer scale and nanometer-sized building blocks were separated by partially coherent interfaces. The XRD simulation results showed that a specific packing of the primary crystalline blocks in the nanostructured γ-Al2O3 particles with formation of planar defects on {001}, {100}, and {101} planes nicely accounted for pronounced diffuse scattering, anisotropic peak broadening and peak shifts in the experimental XRD pattern. The identified planar defects in cation sublattice seem to be described as filling cation non-spinel sites in existing crystallographic models of γ-Al2O3 structure. The overall findings provided an insight into the complex nanostructure, which is intrinsic to the metastable γ-Al2O3 oxide.

  12. A 3D profile function suitable for integration of neutron time-of-flight single crystal diffraction peaks

    NASA Astrophysics Data System (ADS)

    Gutmann, Matthias J.

    2017-03-01

    A 3D profile function is presented suitable to integrate reflections arising in time-of-flight (TOF) single crystal neutron diffraction experiments. In order to account for the large asymmetry of the peak shape in the TOF direction, a 3D Gaussian ellipsoid in the pixel (x, z) and time-of-flight coordinates is convoluted with a rising and falling exponential along the time-of-flight direction. An analytic expression is derived, making it suitable for least-squares fitting. The application of this function in detector space or reciprocal space is straightforward.

  13. Electron crystallography of ultrathin 3D protein crystals: atomic model with charges.

    PubMed

    Yonekura, Koji; Kato, Kazuyuki; Ogasawara, Mitsuo; Tomita, Masahiro; Toyoshima, Chikashi

    2015-03-17

    Membrane proteins and macromolecular complexes often yield crystals too small or too thin for even the modern synchrotron X-ray beam. Electron crystallography could provide a powerful means for structure determination with such undersized crystals, as protein atoms diffract electrons four to five orders of magnitude more strongly than they do X-rays. Furthermore, as electron crystallography yields Coulomb potential maps rather than electron density maps, it could provide a unique method to visualize the charged states of amino acid residues and metals. Here we describe an attempt to develop a methodology for electron crystallography of ultrathin (only a few layers thick) 3D protein crystals and present the Coulomb potential maps at 3.4-Å and 3.2-Å resolution, respectively, obtained from Ca(2+)-ATPase and catalase crystals. These maps demonstrate that it is indeed possible to build atomic models from such crystals and even to determine the charged states of amino acid residues in the Ca(2+)-binding sites of Ca(2+)-ATPase and that of the iron atom in the heme in catalase.

  14. Ultrafast Time-Resolved Electron Diffraction with Megavolt Electron Beams

    SciTech Connect

    Hastings, J.B.; Rudakov, F.M.; Dowell, D.H.; Schmerge, J.F.; Cardoza, J.D.; Castro, J.M.; Gierman, S.M.; Loos, H.; Weber, P.M.; /Brown U.

    2006-10-24

    An rf photocathode electron gun is used as an electron source for ultrafast time-resolved pump-probe electron diffraction. We observed single-shot diffraction patterns from a 160 nm Al foil using the 5.4 MeV electron beam from the Gun Test Facility at the Stanford Linear Accelerator. Excellent agreement with simulations suggests that single-shot diffraction experiments with a time resolution approaching 100 fs are possible.

  15. FIJI Macro 3D ART VeSElecT: 3D Automated Reconstruction Tool for Vesicle Structures of Electron Tomograms

    PubMed Central

    Kaltdorf, Kristin Verena; Schulze, Katja; Helmprobst, Frederik; Kollmannsberger, Philip; Stigloher, Christian

    2017-01-01

    Automatic image reconstruction is critical to cope with steadily increasing data from advanced microscopy. We describe here the Fiji macro 3D ART VeSElecT which we developed to study synaptic vesicles in electron tomograms. We apply this tool to quantify vesicle properties (i) in embryonic Danio rerio 4 and 8 days past fertilization (dpf) and (ii) to compare Caenorhabditis elegans N2 neuromuscular junctions (NMJ) wild-type and its septin mutant (unc-59(e261)). We demonstrate development-specific and mutant-specific changes in synaptic vesicle pools in both models. We confirm the functionality of our macro by applying our 3D ART VeSElecT on zebrafish NMJ showing smaller vesicles in 8 dpf embryos then 4 dpf, which was validated by manual reconstruction of the vesicle pool. Furthermore, we analyze the impact of C. elegans septin mutant unc-59(e261) on vesicle pool formation and vesicle size. Automated vesicle registration and characterization was implemented in Fiji as two macros (registration and measurement). This flexible arrangement allows in particular reducing false positives by an optional manual revision step. Preprocessing and contrast enhancement work on image-stacks of 1nm/pixel in x and y direction. Semi-automated cell selection was integrated. 3D ART VeSElecT removes interfering components, detects vesicles by 3D segmentation and calculates vesicle volume and diameter (spherical approximation, inner/outer diameter). Results are collected in color using the RoiManager plugin including the possibility of manual removal of non-matching confounder vesicles. Detailed evaluation considered performance (detected vesicles) and specificity (true vesicles) as well as precision and recall. We furthermore show gain in segmentation and morphological filtering compared to learning based methods and a large time gain compared to manual segmentation. 3D ART VeSElecT shows small error rates and its speed gain can be up to 68 times faster in comparison to manual annotation

  16. Electron Diffraction of Wet Phospholipid Bilayers

    PubMed Central

    Hui, S. W.; Parsons, D. F.; Cowden, M.

    1974-01-01

    The structure of fully hydrated dipalmitoyl lecithin single bilayers, and monolayers deposited on Formvar substrates are studied by electron diffraction, using a hydration stage fitted to an electron microscope. Selective area diffraction patterns of these films indicate that there are domains consisting of mosaics of crystallites of hexagonally packed lipid chains. The size of these domains are typically several μm in diameter. The diffraction intensity agrees with that calculated from the electron scattering factor of the hydrocarbon chains of the lipid molecule. Images PMID:4531037

  17. Structure refinement from precession electron diffraction data.

    PubMed

    Palatinus, Lukáš; Jacob, Damien; Cuvillier, Priscille; Klementová, Mariana; Sinkler, Wharton; Marks, Laurence D

    2013-03-01

    Electron diffraction is a unique tool for analysing the crystal structures of very small crystals. In particular, precession electron diffraction has been shown to be a useful method for ab initio structure solution. In this work it is demonstrated that precession electron diffraction data can also be successfully used for structure refinement, if the dynamical theory of diffraction is used for the calculation of diffracted intensities. The method is demonstrated on data from three materials - silicon, orthopyroxene (Mg,Fe)(2)Si(2)O(6) and gallium-indium tin oxide (Ga,In)(4)Sn(2)O(10). In particular, it is shown that atomic occupancies of mixed crystallographic sites can be refined to an accuracy approaching X-ray or neutron diffraction methods. In comparison with conventional electron diffraction data, the refinement against precession diffraction data yields significantly lower figures of merit, higher accuracy of refined parameters, much broader radii of convergence, especially for the thickness and orientation of the sample, and significantly reduced correlations between the structure parameters. The full dynamical refinement is compared with refinement using kinematical and two-beam approximations, and is shown to be superior to the latter two.

  18. Dynamic diffraction-limited light-coupling of 3D-maneuvered wave-guided optical waveguides.

    PubMed

    Villangca, Mark; Bañas, Andrew; Palima, Darwin; Glückstad, Jesper

    2014-07-28

    We have previously proposed and demonstrated the targeted-light delivery capability of wave-guided optical waveguides (WOWs). As the WOWs are maneuvered in 3D space, it is important to maintain efficient light coupling through the waveguides within their operating volume. We propose the use of dynamic diffractive techniques to create diffraction-limited spots that will track and couple to the WOWs during operation. This is done by using a spatial light modulator to encode the necessary diffractive phase patterns to generate the multiple and dynamic coupling spots. The method is initially tested for a single WOW and we have experimentally demonstrated dynamic tracking and coupling for both lateral and axial displacements.

  19. Dynamics of electronically inelastic collisions from 3D Doppler measurements

    SciTech Connect

    Suits, A.G.; de Pujo, P.; Sublemontier, O.; Visticot, J.; Berlande, J.; Cuvellier, J.; Gustavsson, T.; Mestdagh, J.; Meynadier, P. ); Lee, Y.T. )

    1991-11-25

    Flux-velocity contour maps were obtained for the inelastic collision process Ba({sup 1}{ital P}{sub 1})+O{sub 2}N{sub 2}{r arrow}Ba({sup 3}{ital P}{sub 2})+O{sub 2}N{sub 2} from Doppler scans of scattered Ba({sup 3}{ital P}{sub 2}) taken over a range of probe laser directions in a crossed-beam experiment. Collision with O{sub 2} resulted in sharply forward scattered Ba({sup 3}{ital P}{sub 2}), with efficient conversion of inital electronic energy into O{sub 2} internal energy and little momentum transfer. Collision with N{sub 2} was dominated by wide-angle scattering with most of the available electronic energy appearing in product translation. The results suggest the importance of large-impact-parameter collisions and a near-resonant energy transfer in the case of O{sub 2}, while for N{sub 2} close collisions dominate despite the presence of an analogous near-resonant channel. The results represent the first direct experimental demonstration of a near-resonant quenching process.

  20. Quantitative moment study and coupling of 4 f rare earth and 3 d metal by transmitted electrons

    NASA Astrophysics Data System (ADS)

    Fu, X.; Warot-Fonrose, B.; Arras, R.; Dumesnil, K.; Serin, V.

    2016-10-01

    We report a simultaneous investigation of 3 d and 4 f magnetic moments by exploring the Fe -L2 ,3 and Dy -M4 ,5 electron energy-loss edges of a DyF e2/YF e2 superlattice using the energy-loss magnetic chiral dichroism (EMCD) technique. Specific EMCD sum rules for M4 ,5 edges were established and carefully applied to the dichroic signal at Dy -M4 ,5 edges, giving an orbital to the effective spin moment ratio of 5.1 ±1.8 . With dynamic diffraction effects considered, the opposite signs of Fe -L3 and Dy -M5 dichroic peaks unambiguously indicate the antiparallel alignment of net Fe 3 d and Dy 4 f moments. The EMCD technique is shown to be an effective tool to locally characterize the 4 f moment of rare earth elements and study 3 d -4 f moment coupling.

  1. 3D Printing of Shape Memory Polymers for Flexible Electronic Devices.

    PubMed

    Zarek, Matt; Layani, Michael; Cooperstein, Ido; Sachyani, Ela; Cohn, Daniel; Magdassi, Shlomo

    2016-06-01

    The formation of 3D objects composed of shape memory polymers for flexible electronics is described. Layer-by-layer photopolymerization of methacrylated semicrystalline molten macromonomers by a 3D digital light processing printer enables rapid fabrication of complex objects and imparts shape memory functionality for electrical circuits.

  2. Diffraction effects incorporated design of a parallax barrier for a high-density multi-view autostereoscopic 3D display.

    PubMed

    Yoon, Ki-Hyuk; Ju, Heongkyu; Kwon, Hyunkyung; Park, Inkyu; Kim, Sung-Kyu

    2016-02-22

    We present optical characteristics of view image provided by a high-density multi-view autostereoscopic 3D display (HD-MVA3D) with a parallax barrier (PB). Diffraction effects that become of great importance in such a display system that uses a PB, are considered in an one-dimensional model of the 3D display, in which the numerical simulation of light from display panel pixels through PB slits to viewing zone is performed. The simulation results are then compared to the corresponding experimental measurements with discussion. We demonstrate that, as a main parameter for view image quality evaluation, the Fresnel number can be used to determine the PB slit aperture for the best performance of the display system. It is revealed that a set of the display parameters, which gives the Fresnel number of ∼ 0.7 offers maximized brightness of the view images while that corresponding to the Fresnel number of 0.4 ∼ 0.5 offers minimized image crosstalk. The compromise between the brightness and crosstalk enables optimization of the relative magnitude of the brightness to the crosstalk and lead to the choice of display parameter set for the HD-MVA3D with a PB, which satisfies the condition where the Fresnel number lies between 0.4 and 0.7.

  3. Application of Electron Diffraction to Biological Electron Microscopy

    PubMed Central

    Glaeser, Robert M.; Thomas, Gareth

    1969-01-01

    Three methods by which electron diffraction may be applied to problems in electron microscopy are discussed from a fundamental point of view, and experimental applications with biological specimens are demonstrated for each case. It is shown that wide-angle electron diffraction provides valuable information for evaluating specimen damage that can occur either during specimen preparation or while in the electron beam. Dark-field electron microscopy can be used both to enhance the image contrast and to provide highly restricted and therefore highly specific information about the object. Low-angle electron diffraction provides quantitative information about the object structure in the range from 20 A to ∼ 1000 A. Lowangle electron diffraction also demonstrates the important role of Fourier contrast with biological specimens, which are usually characterized by structural features with dimensions of 20 A or larger. ImagesFigure 1Figure 2Figure 5Figure 6Figure 7Figure 8Figure 9Figure 10Figure 11Figure 13 PMID:4896898

  4. High Energy Electron Diffraction from Transverse Stacking Faults.

    NASA Astrophysics Data System (ADS)

    Jesson, David Edward

    1987-12-01

    Available from UMI in association with The British Library. The principal aim of this work is to study electron diffraction phenomena associated with high symmetry zone axes of crystals which contain transverse stacking faults. A theory is developed to describe diffraction effects visible in convergent beam electron diffraction (CBED) patterns obtained from faulted crystals. In particular, it is shown that the idea of Bloch wave excitation transfers is of importance in understanding the origin of the diffraction phenomena. Three-dimensional (3D) diffraction is treated under pseudo-kinematic assumptions and an expression is derived for the higher order Laue zone (HOLZ) intensity profile associated with a single fault. As a basis for studying the faulted crystal, CBED patterns are obtained from perfect samples of the layered structure 2Hb MoS_2. Wide angle CBED (WACBED) results are simulated computationally and understood in terms of the dispersion surface construction. In particular, the relationship between HOLZ intensities and kinematic structure factors is investigated for the 2Hb polytype. In the case of faulted crystals, it is shown how the projected displacement vector can be determined from the symmetry of zone axis patterns (ZAP's). The sensitivity of pattern features to fault depth is examined by computer simulation and in some cases it is found useful to describe the excitation transfers in terms of tight binding functions. The phenomenon of HOLZ line splitting is clarified and it is shown how 3D diffraction can be used to provide information on the full displacement vector, including the non-zero layer component. Finally, absorption effects are shown to be important in simulating HOLZ intensity profiles from faulted crystals.

  5. Controlled double-slit electron diffraction

    NASA Astrophysics Data System (ADS)

    Bach, Roger; Pope, Damian; Liou, Sy-Hwang; Batelaan, Herman

    2013-03-01

    Double-slit diffraction is a corner stone of quantum mechanics. It illustrates key features of quantum mechanics: interference and the particle-wave duality of matter. In 1965, Richard Feynman presented a thought experiment to show these features. Here we demonstrate the full realization of his famous thought experiment. By placing a movable mask in front of a double-slit to control the transmission through the individual slits, probability distributions for single- and double-slit arrangements were observed. Also, by recording single electron detection events diffracting through a double-slit, a diffraction pattern was built up from individual events.

  6. Strain Determination Using Electron Backscatter Diffraction

    SciTech Connect

    Krause, M.; Graff, A.; Altmann, F.

    2010-11-24

    In the present paper we demonstrate the use of electron backscatter diffraction (EBSD) for high resolution elastic strain determination. Here, we focus on analysis methods based on determination of small shifts in EBSD pattern with respect to a reference pattern using cross-correlation algorithms. Additionally we highlight the excellent spatial and depth resolution of EBSD and introduce the use of simulated diffraction patterns based on dynamical diffraction theory for sensitivity estimation. Moreover the potential of EBSD for strain analysis of strained thin films with particular emphasis on appropriate target preparation which respect to occurring lattice defects is demonstrated.

  7. 3D laser inspection of fuel assembly grid spacers for nuclear reactors based on diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Finogenov, L. V.; Lemeshko, Yu A.; Zav'yalov, P. S.; Chugui, Yu V.

    2007-06-01

    Ensuring the safety and high operation reliability of nuclear reactors takes 100% inspection of geometrical parameters of fuel assemblies, which include the grid spacers performed as a cellular structure with fuel elements. The required grid spacer geometry of assembly in the transverse and longitudinal cross sections is extremely important for maintaining the necessary heat regime. A universal method for 3D grid spacer inspection using a diffractive optical element (DOE), which generates as the structural illumination a multiple-ring pattern on the inner surface of a grid spacer cell, is investigated. Using some DOEs one can inspect the nomenclature of all produced grids. A special objective has been developed for forming the inner surface cell image. The problems of diffractive elements synthesis, projecting optics calculation, adjusting methods as well as calibration of the experimental measuring system are considered. The algorithms for image processing for different constructive elements of grids (cell, channel hole, outer grid spacer rim) and the experimental results are presented.

  8. Contiguous 3 d and 4 f Magnetism: Strongly Correlated 3 d Electrons in YbFe2Al10

    NASA Astrophysics Data System (ADS)

    Khuntia, P.; Peratheepan, P.; Strydom, A. M.; Utsumi, Y.; Ko, K.-T.; Tsuei, K.-D.; Tjeng, L. H.; Steglich, F.; Baenitz, M.

    2014-11-01

    We present magnetization, specific heat, and Al 27 NMR investigations on YbFe2Al10 over a wide range in temperature and magnetic field. The magnetic susceptibility at low temperatures is strongly enhanced at weak magnetic fields, accompanied by a ln (T0/T ) divergence of the low-T specific heat coefficient in zero field, which indicates a ground state of correlated electrons. From our hard-x-ray photoemission spectroscopy study, the Yb valence at 50 K is evaluated to be 2.38. The system displays valence fluctuating behavior in the low to intermediate temperature range, whereas above 400 K, Yb3 + carries a full and stable moment, and Fe carries a moment of about 3.1 μB. The enhanced value of the Sommerfeld-Wilson ratio and the dynamic scaling of the spin-lattice relaxation rate divided by T [(1 /T1T ) 27 ] with static susceptibility suggests admixed ferromagnetic correlations. (1 /T1T ) 27 simultaneously tracks the valence fluctuations from the 4 f Yb ions in the high temperature range and field dependent antiferromagnetic correlations among partially Kondo screened Fe 3 d moments at low temperature; the latter evolve out of an Yb 4 f admixed conduction band.

  9. Angular distribution of Auger electrons due to 3d-shell impact ionization of krypton

    NASA Technical Reports Server (NTRS)

    Omidvar, K.

    1977-01-01

    Cross sections for electron impact ionization of krypton due to ejection of a 3d-shell electron have been calculated using screened hydrogenic and Hartree-Slater wavefunctions for the target atom. While the total ionization cross sections in the two approximations are within 10% of each other, the Auger electron angular distribution, related to cross sections for specific magnetic quantum numbers of the 3d electrons, are widely different in the two approximations. The angular distribution due to the Hartree-Slater approximation is in excellent agreement with measurement. The physical reason for the discrepancies in the two approximations is explained.

  10. Effect of 3d doping on the electronic structure of BaFe2As2

    SciTech Connect

    McLeod, John A.; Buling, A.; Green, R.J.; Boyko, T.D.; Skorikov, N.A.; Kurmaev, E.Z.; Neumann, M.; Finkelstein, L.D.; Ni, Ni; Thaler, Alexander; Budko, Serguei L.; Canfield, Paul; Moewes, A.

    2012-04-25

    The electronic structure of BaFe2As2 doped with Co, Ni and Cu has been studied by a variety of experimental and theoretical methods, but a clear picture of the dopant 3d states has not yet emerged. Herein we provide experimental evidence of the distribution of Co, Ni and Cu 3d states in the valence band. We conclude that the Co and Ni 3d states provide additional free carriers to the Fermi level, while the Cu 3d states are found at the bottom of the valence band in a localized 3d10 shell. These findings help shed light on why superconductivity can occur in BaFe2As2 doped with Co and Ni but not Cu.

  11. 3D objects enlargement technique using an optical system and multiple SLMs for electronic holography.

    PubMed

    Yamamoto, Kenji; Ichihashi, Yasuyuki; Senoh, Takanori; Oi, Ryutaro; Kurita, Taiichiro

    2012-09-10

    One problem in electronic holography, which is caused by the display performance of spatial light modulators (SLM), is that the size of reconstructed 3D objects is small. Although methods for increasing the size using multiple SLMs have been considered, they typically had the problem that some parts of 3D objects were missing as a result of the gap between adjacent SLMs or 3D objects lost the vertical parallax. This paper proposes a method of resolving this problem by locating an optical system containing a lens array and other components in front of multiple SLMs. We used an optical system and 9 SLMs to construct a device equivalent to an SLM with approximately 74,600,000 pixels and used this to reconstruct 3D objects in both the horizontal and vertical parallax with an image size of 63 mm without losing any part of 3D objects.

  12. 3D Modeling Activity for Novel High Power Electron Guns at SLAC

    SciTech Connect

    Krasnykh, Anatoly

    2003-07-29

    The next generation of powerful electronic devices requires new approaches to overcome the known limitations of existing tube technology. Multi-beam and sheet beam approaches are novel concepts for the high power microwave devices. Direct and indirect modeling methods are being developed at SLAC to meet the new requirements in the 3D modeling. The direct method of solving of Poisson's equations for the multi-beam and sheet beam guns is employed in the TOPAZ 3D tool. The combination of TOPAZ 2D and EGUN (in the beginning) with MAFIA 3D and MAGIC 3D (at the end) is used in an indirect method to model the high power electron guns. Both methods complement each other to get reliable representation of the beam trajectories. Several gun ideas are under consideration at the present time. The collected results of these simulations are discussed.

  13. Analysis of the 3D distribution of stacked self-assembled quantum dots by electron tomography

    PubMed Central

    2012-01-01

    The 3D distribution of self-assembled stacked quantum dots (QDs) is a key parameter to obtain the highest performance in a variety of optoelectronic devices. In this work, we have measured this distribution in 3D using a combined procedure of needle-shaped specimen preparation and electron tomography. We show that conventional 2D measurements of the distribution of QDs are not reliable, and only 3D analysis allows an accurate correlation between the growth design and the structural characteristics. PMID:23249477

  14. Characterization of 3D Trench PZT Capacitors for High Density FRAM Devices by Synchrotron X-ray Micro-diffraction

    SciTech Connect

    Shin, Sangmin; Park, Youngsoo; Han, Hee; Park, Yong Jun; Baik, Sunggi; Choi, Jae-Young

    2007-01-19

    3D trench PbZrxTi1-xO3 (PZT) capacitors for 256 Mbit 1T-1C FRAM devices were characterized by synchrotron X-ray micro-diffraction at Pohang Light Source. Three layers, Ir/PZT/Ir were deposited on SiO2 trench holes with different widths ranging from 180 nm to 810 nm and 400 nm in depth by ALD and MOCVD. Each hole is separated from neighboring holes by 200 nm. The cross sectional TEM analysis for the trenches revealed that the PZT layers were consisted of columnar grains at the trench entrance and changes to polycrystalline granular grains at the lower part of the trench. The transition from columnar to granular grains was dependent on the trench size. The smaller trenches were favorable to granular grain formation. High resolution synchrotron X-ray diffraction analysis was performed to determine the crystal structure of each region. The beam was focused to about 500 {mu}m and the diffraction patterns were obtained from a single trench. Only the peaks corresponding to ferroelectric tetragonal phases are observed for the trenches larger than 670 nm, which consist of fully columnar grains. However, the trenches smaller than 670 nm showed the peaks corresponding the pyrochlore phases, which suggested that the granular grains are of pyrochlore phases and non-ferroelectric.

  15. A Simple, Low-Cost Conductive Composite Material for 3D Printing of Electronic Sensors

    PubMed Central

    Leigh, Simon J.; Bradley, Robert J.; Purssell, Christopher P.; Billson, Duncan R.; Hutchins, David A.

    2012-01-01

    3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes (‘rapid prototyping’) before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term ‘carbomorph’ and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes. PMID:23185319

  16. A simple, low-cost conductive composite material for 3D printing of electronic sensors.

    PubMed

    Leigh, Simon J; Bradley, Robert J; Purssell, Christopher P; Billson, Duncan R; Hutchins, David A

    2012-01-01

    3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes ('rapid prototyping') before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term 'carbomorph' and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes.

  17. Femtosecond gas phase electron diffraction with MeV electrons.

    PubMed

    Yang, Jie; Guehr, Markus; Vecchione, Theodore; Robinson, Matthew S; Li, Renkai; Hartmann, Nick; Shen, Xiaozhe; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Gaffney, Kelly; Gorkhover, Tais; Hast, Carsten; Jobe, Keith; Makasyuk, Igor; Reid, Alexander; Robinson, Joseph; Vetter, Sharon; Wang, Fenglin; Weathersby, Stephen; Yoneda, Charles; Wang, Xijie; Centurion, Martin

    2016-12-16

    We present results on ultrafast gas electron diffraction (UGED) experiments with femtosecond resolution using the MeV electron gun at SLAC National Accelerator Laboratory. UGED is a promising method to investigate molecular dynamics in the gas phase because electron pulses can probe the structure with a high spatial resolution. Until recently, however, it was not possible for UGED to reach the relevant timescale for the motion of the nuclei during a molecular reaction. Using MeV electron pulses has allowed us to overcome the main challenges in reaching femtosecond resolution, namely delivering short electron pulses on a gas target, overcoming the effect of velocity mismatch between pump laser pulses and the probe electron pulses, and maintaining a low timing jitter. At electron kinetic energies above 3 MeV, the velocity mismatch between laser and electron pulses becomes negligible. The relativistic electrons are also less susceptible to temporal broadening due to the Coulomb force. One of the challenges of diffraction with relativistic electrons is that the small de Broglie wavelength results in very small diffraction angles. In this paper we describe the new setup and its characterization, including capturing static diffraction patterns of molecules in the gas phase, finding time-zero with sub-picosecond accuracy and first time-resolved diffraction experiments. The new device can achieve a temporal resolution of 100 fs root-mean-square, and sub-angstrom spatial resolution. The collimation of the beam is sufficient to measure the diffraction pattern, and the transverse coherence is on the order of 2 nm. Currently, the temporal resolution is limited both by the pulse duration of the electron pulse on target and by the timing jitter, while the spatial resolution is limited by the average electron beam current and the signal-to-noise ratio of the detection system. We also discuss plans for improving both the temporal resolution and the spatial resolution.

  18. A compact electron gun for time-resolved electron diffraction

    SciTech Connect

    Robinson, Matthew S.; Lane, Paul D.; Wann, Derek A.

    2015-01-15

    A novel compact time-resolved electron diffractometer has been built with the primary goal of studying the ultrafast molecular dynamics of photoexcited gas-phase molecules. Here, we discuss the design of the electron gun, which is triggered by a Ti:Sapphire laser, before detailing a series of calibration experiments relating to the electron-beam properties. As a further test of the apparatus, initial diffraction patterns have been collected for thin, polycrystalline platinum samples, which have been shown to match theoretical patterns. The data collected demonstrate the focusing effects of the magnetic lens on the electron beam, and how this relates to the spatial resolution of the diffraction pattern.

  19. High-purity 3D nano-objects grown by focused-electron-beam induced deposition

    NASA Astrophysics Data System (ADS)

    Córdoba, Rosa; Sharma, Nidhi; Kölling, Sebastian; Koenraad, Paul M.; Koopmans, Bert

    2016-09-01

    To increase the efficiency of current electronics, a specific challenge for the next generation of memory, sensing and logic devices is to find suitable strategies to move from two- to three-dimensional (3D) architectures. However, the creation of real 3D nano-objects is not trivial. Emerging non-conventional nanofabrication tools are required for this purpose. One attractive method is focused-electron-beam induced deposition (FEBID), a direct-write process of 3D nano-objects. Here, we grow 3D iron and cobalt nanopillars by FEBID using diiron nonacarbonyl Fe2(CO)9, and dicobalt octacarbonyl Co2(CO)8, respectively, as starting materials. In addition, we systematically study the composition of these nanopillars at the sub-nanometer scale by atom probe tomography, explicitly mapping the homogeneity of the radial and longitudinal composition distributions. We show a way of fabricating high-purity 3D vertical nanostructures of ˜50 nm in diameter and a few micrometers in length. Our results suggest that the purity of such 3D nanoelements (above 90 at% Fe and above 95 at% Co) is directly linked to their growth regime, in which the selected deposition conditions are crucial for the final quality of the nanostructure. Moreover, we demonstrate that FEBID and the proposed characterization technique not only allow for growth and chemical analysis of single-element structures, but also offers a new way to directly study 3D core-shell architectures. This straightforward concept could establish a promising route to the design of 3D elements for future nano-electronic devices.

  20. A novel diamond anvil cell for x-ray diffraction at cryogenic temperatures manufactured by 3D printing

    NASA Astrophysics Data System (ADS)

    Jin, H.; Woodall, C. H.; Wang, X.; Parsons, S.; Kamenev, K. V.

    2017-03-01

    A new miniature high-pressure diamond anvil cell was designed and constructed using 3D micro laser sintering technology. This is the first application of the use of rapid prototyping technology to construct high-pressure apparatus. The cell is specifically designed for use as an X-ray diffraction cell that can be used with commercially available diffractometers and open-flow cryogenic equipment to collect data at low temperature and high pressure. The cell is constructed from stainless steel 316L and is about 9 mm in diameter and 7 mm in height, giving it both small dimensions and low thermal mass, and it will fit into the cooling envelope of a standard CryostreamTM cooling system. The cell is clamped using a customized miniature buttress thread of diameter 7 mm and pitch of 0.5 mm enabled by 3D micro laser sintering technology; such dimensions are not attainable using conventional machining. The buttress thread was used as it has favourable uniaxial load properties allowing for higher pressure and better anvil alignment. The clamp can support the load of at least 1.5 kN according to finite element analysis (FEA) simulations. FEA simulations were also used to compare the performance of the standard thread and the buttress thread, and demonstrate that stress is distributed more uniformly in the latter. Rapid prototyping of the pressure cell by the laser sintering resulted in a substantially higher tensile yield strength of the 316L stainless steel (675 MPa compared to 220 MPa for the wrought type of the same material), which increased the upper pressure limit of the cell. The cell is capable of reaching pressures of up to 15 GPa with 600 μm diameter culets of diamond anvils. Sample temperature and pressure changes on cooling were assessed using X-ray diffraction on samples of NaCl and HMT-d12.

  1. On the alignment for precession electron diffraction

    PubMed Central

    Liao, Yifeng; Marks, Laurence D.

    2013-01-01

    Precession electron diffraction has seen a fast increase in its adoption as a technique for solving crystallographic structures as well as an alternative to conventional selected-area and converged-beam diffraction methods. One of the key issues of precession is the pivot point alignment, as a stationary apparent beam does not guarantee a fixed pivot point. A large precession tilt angle, along with pre-field and post-field misalignment, induces shift in the image plane. We point out here that the beam should be aligned to the pre-field optic axis to keep the electron illumination stationary during the rocking process. A practical alignment procedure is suggested with the focus placed on minimizing the beam wandering on the specimen, and is demonstrated for a (110)-oriented silicon single crystal and for a carbide phase (~20 nm in size) within a cast cobalt–chromium–molybdenum alloy. PMID:22634134

  2. Band like Electronic Structures in Square Hollow Quantum Dots by 3D-MHFKS Calculation

    NASA Astrophysics Data System (ADS)

    Takizawa, Tokihiro; Okada, Hoshihito; Matsuse, Takehiro

    To find novel aspects of the electronic structures in quantum dots (QD) from a view point of spatial broken symmetry, 3-dimensional-mesh Hartree-Fock-Kohn-Sham (3D-MHFKS) calculations1 are applied to the interacting electron system of electron number N in a symmetry broken hollow QD. For the case of a square hollow quantum dot confined in square hard wall (HW) potential (SSHQD), the magnetic (B) field dependence of the obtained single particle energy levels and chemical potentials in B-N diagram are shown to have a band like electronic structures over the wide B-field range up to 20T. To clarify the origin of the band like electronic structures in SSHQD, 3D-MHFKS calculations are also applied for the mixed symmetry QD's with a circular hollow in square HW potential (SCHQD) and with a square hollow in circular HW potential (CSHQD).

  3. Classification and 3D averaging with missing wedge correction in biological electron tomography ☆

    PubMed Central

    Bartesaghi, A.; Sprechmann, P.; Liu, J.; Randall, G.; Sapiro, G.; Subramaniam, S.

    2008-01-01

    Strategies for the determination of 3D structures of biological macromolecules using electron crystallography and single-particle electron microscopy utilize powerful tools for the averaging of information obtained from 2D projection images of structurally homogeneous specimens. In contrast, electron tomographic approaches have often been used to study the 3D structures of heterogeneous, one-of-a-kind objects such as whole cells where image-averaging strategies are not applicable. Complex entities such as cells and viruses, nevertheless, contain multiple copies of numerous macromolecules that can individually be subjected to 3D averaging. Here we present a complete framework for alignment, classification, and averaging of volumes derived by electron tomography that is computationally efficient and effectively accounts for the missing wedge that is inherent to limited-angle electron tomography. Modeling the missing data as a multiplying mask in reciprocal space we show that the effect of the missing wedge can be accounted for seamlessly in all alignment and classification operations. We solve the alignment problem using the convolution theorem in harmonic analysis, thus eliminating the need for approaches that require exhaustive angular search, and adopt an iterative approach to alignment and classification that does not require the use of external references. We demonstrate that our method can be successfully applied for 3D classification and averaging of phantom volumes as well as experimentally obtained tomograms of GroEL where the outcomes of the analysis can be quantitatively compared against the expected results. PMID:18440828

  4. Diffraction of electrons at intermediate energies

    NASA Astrophysics Data System (ADS)

    Ascolani, H.; Barrachina, R. O.; Guraya, M. M.; Zampieri, G.

    1992-08-01

    We present a theory of the elastic scattering of electrons from crystalline surfaces that contains both low-energy-electron-diffraction (LEED) effects at low energies and x-ray-photoelectron- and Auger-electron-diffraction (XPD/AED) effects at intermediate energies. The theory is based on a cluster-type approach to the scattering problem and includes temperature effects. The transition from one regime to the other may be explained as follows: At low energies all the scattered waves add coherently, and the intensity is dominated by LEED effects. At intermediate energies the thermal vibration of the atoms destroys the long-range coherency responsible for the LEED peaks, but affects little the interference of those waves that share parts of their paths inside the solid. Thus, the interference of these waves comes to dominate the intensity, giving rise to structures similar to those observed in XPD/AED experiments. We perform a calculation of the elastic reflection of electrons from Cu(001) that is in good agreement with the experiment in the range 200-1500 eV. At low energies the intensity is dominated by LEED peaks; at 400 eV LEED peaks and XPD/AED structures coexist; and above this energy the intensity is dominated by the latter. We analyze the contributions to the intensity at intermediate energies of the interferences in the incoming and outgoing parts of the electron path.

  5. Bragg's Law diffraction simulations for electron backscatter diffraction analysis.

    PubMed

    Kacher, Josh; Landon, Colin; Adams, Brent L; Fullwood, David

    2009-08-01

    In 2006, Angus Wilkinson introduced a cross-correlation-based electron backscatter diffraction (EBSD) texture analysis system capable of measuring lattice rotations and elastic strains to high resolution. A variation of the cross-correlation method is introduced using Bragg's Law-based simulated EBSD patterns as strain free reference patterns that facilitates the use of the cross-correlation method with polycrystalline materials. The lattice state is found by comparing simulated patterns to collected patterns at a number of regions on the pattern using the cross-correlation function and calculating the deformation from the measured shifts of each region. A new pattern can be simulated at the deformed state, and the process can be iterated a number of times to converge on the absolute lattice state. By analyzing an iteratively rotated single crystal silicon sample and recovering the rotation, this method is shown to have an angular resolution of approximately 0.04 degrees and an elastic strain resolution of approximately 7e-4. As an example of applications, elastic strain and curvature measurements are used to estimate the dislocation density in a single grain of a compressed polycrystalline Mg-based AZ91 alloy.

  6. 3D structure of eukaryotic flagella/cilia by cryo-electron tomography.

    PubMed

    Ishikawa, Takashi

    2013-01-01

    Flagella/cilia are motile organelles with more than 400 proteins. To understand the mechanism of such complex systems, we need methods to describe molecular arrange-ments and conformations three-dimensionally in vivo. Cryo-electron tomography enabled us such a 3D structural analysis. Our group has been working on 3D structure of flagella/cilia using this method and revealed highly ordered and beautifully organized molecular arrangement. 3D structure gave us insights into the mechanism to gener-ate bending motion with well defined waveforms. In this review, I summarize our recent structural studies on fla-gella/cilia by cryo-electron tomography, mainly focusing on dynein microtubule-based ATPase motor proteins and the radial spoke, a regulatory protein complex.

  7. Building Proteins in a Day: Efficient 3D Molecular Structure Estimation with Electron Cryomicroscopy.

    PubMed

    Punjani, Ali; Brubaker, Marcus A; Fleet, David J

    2017-04-01

    Discovering the 3D atomic-resolution structure of molecules such as proteins and viruses is one of the foremost research problems in biology and medicine. Electron Cryomicroscopy (cryo-EM) is a promising vision-based technique for structure estimation which attempts to reconstruct 3D atomic structures from a large set of 2D transmission electron microscope images. This paper presents a new Bayesian framework for cryo-EM structure estimation that builds on modern stochastic optimization techniques to allow one to scale to very large datasets. We also introduce a novel Monte-Carlo technique that reduces the cost of evaluating the objective function during optimization by over five orders of magnitude. The net result is an approach capable of estimating 3D molecular structure from large-scale datasets in about a day on a single CPU workstation.

  8. Precession electron diffraction – a topical review

    PubMed Central

    Midgley, Paul A.; Eggeman, Alexander S.

    2015-01-01

    In the 20 years since precession electron diffraction (PED) was introduced, it has grown from a little-known niche technique to one that is seen as a cornerstone of electron crystallography. It is now used primarily in two ways. The first is to determine crystal structures, to identify lattice parameters and symmetry, and ultimately to solve the atomic structure ab initio. The second is, through connection with the microscope scanning system, to map the local orientation of the specimen to investigate crystal texture, rotation and strain at the nanometre scale. This topical review brings the reader up to date, highlighting recent successes using PED and providing some pointers to the future in terms of method development and how the technique can meet some of the needs of the X-ray crystallography community. Complementary electron techniques are also discussed, together with how a synergy of methods may provide the best approach to electron-based structure analysis. PMID:25610633

  9. Electron Diffraction from Surfaces with Atomic Steps

    NASA Astrophysics Data System (ADS)

    Lent, Craig Stanley

    The presence of atomic steps on solid surfaces is important in catalysis, crystal growth and dissolution processes. Because of the decreased coordination of atoms at step edges, these sites are frequently more reactive than others. Knowledge of the step distribution on the surface is required in order to adequately incorporate the effects of steps in models of physical processes. We examine the sensitivity of electron diffraction, particularly Reflection High Energy Electron Diffraction (RHEED), to the atomic step distribution on the surface. The RHEED instrument response length is considerably larger than other diffraction instruments, making it particularly suited for studying surface steps. Several calculations are presented to assess the effect of various step distributions on the intensity profiles of diffracted beams at various angles of incidence. The geometric distribution of steps corresponds to the limit of no interactions between step edges. A Markov matrix method of calculating the diffracted intensity from a geometric distribution of surface steps is presented. This reduces the calculation to a simple eigenvalue problem. The diffracted intensity profile is the sum of a sharp central spike, corresponding to the instrument response function, and several Lorenztians, whose widths are related to the eigenvalues of the matrix describing the distribution. The Markov approach also leads to the important distinction between reversible and irreversible step distributions. More general calculations, valid for any step distribution reveal that the separation into a central spike and step-broadened terms is retained. The shapes of the broad terms depend on the details of the distribution. The relative contributions of the step-broadened parts and the central spike vary as incident angle is changed and depend on the surface coverage. RHEED beam profiles have been measured from surfaces prepared by Molecular Beam Epitaxy. Submonolayer amounts of GaAs and AlAs were

  10. Electrochemical fields within 3D reconstructed microstructures of mixed ionic and electronic conducting devices

    NASA Astrophysics Data System (ADS)

    Zhang, Yanxiang; Chen, Yu; Lin, Ye; Yan, Mufu; Harris, William M.; Chiu, Wilson K. S.; Ni, Meng; Chen, Fanglin

    2016-11-01

    The performance and stability of the mixed ionic and electronic conducting (MIEC) membrane devices, such as solid oxide cells (SOCs) and oxygen separation membranes (OSMs) interplay tightly with the transport properties and the three-dimensional (3D) microstructure of the membrane. However, development of the MIEC devices is hindered by the limited knowledge about the distribution of electrochemical fields within the 3D local microstructures, especially at surface and interface. In this work, a generic model conforming to local thermodynamic equilibrium is developed to calculate the electrochemical fields, such as electric potential and oxygen chemical potential, within the 3D microstructure of the MIEC membrane. Stability of the MIEC membrane is evaluated by the distribution of oxygen partial pressure. The cell-level performance such as polarization resistance and voltage vs. current curve can be further calculated. Case studies are performed to demonstrate the capability of the framework by using X-ray computed tomography reconstructed 3D microstructures of a SOC and an OSM. The calculation method demonstrates high computational efficiency for large size 3D tomographic microstructures, and permits parallel calculation. The framework can serve as a powerful tool for correlating the transport properties and the 3D microstructure to the performance and the stability of MIEC devices.

  11. Shape-Controlled, Self-Wrapped Carbon Nanotube 3D Electronics.

    PubMed

    Wang, Huiliang; Wang, Yanming; Tee, Benjamin C-K; Kim, Kwanpyo; Lopez, Jeffrey; Cai, Wei; Bao, Zhenan

    2015-09-01

    The mechanical flexibility and structural softness of ultrathin devices based on organic thin films and low-dimensional nanomaterials have enabled a wide range of applications including flexible display, artificial skin, and health monitoring devices. However, both living systems and inanimate systems that are encountered in daily lives are all 3D. It is therefore desirable to either create freestanding electronics in a 3D form or to incorporate electronics onto 3D objects. Here, a technique is reported to utilize shape-memory polymers together with carbon nanotube flexible electronics to achieve this goal. Temperature-assisted shape control of these freestanding electronics in a programmable manner is demonstrated, with theoretical analysis for understanding the shape evolution. The shape control process can be executed with prepatterned heaters, desirable for 3D shape formation in an enclosed environment. The incorporation of carbon nanotube transistors, gas sensors, temperature sensors, and memory devices that are capable of self-wrapping onto any irregular shaped-objects without degradations in device performance is demonstrated.

  12. 3D image reconstruction algorithms for cryo-electron-microscopy images of virus particles

    NASA Astrophysics Data System (ADS)

    Doerschuk, Peter C.; Johnson, John E.

    2000-11-01

    A statistical model for the object and the complete image formation process in cryo electron microscopy of viruses is presented. Using this model, maximum likelihood reconstructions of the 3D structure of viruses are computed using the expectation maximization algorithm and an example based on Cowpea mosaic virus is provided.

  13. Crystal, magnetic and electronic structures of 3d-5d ordered double perovskite Ba2CoReO6

    NASA Astrophysics Data System (ADS)

    Musa Saad H.-E., M.; Rammeh, N.

    2016-12-01

    A comprehensive study on crystal, magnetic and electronic structures of ordered double perovskite Ba2CoReO6 was carried out using X-ray powder diffraction (XRD) and superconducting quantum interference device (SQUID). Also, the density functional theory (DFT) calculations were performed by full potential linear muffin-tin orbital (FP-LMTO) method within the localized spin density approximation (LSDA+U) and generalized gradient approximation (GGA+U). At room temperature, the crystal structure of Ba2CoReO6 is face-centered cubic, space group Fm 3 bar m , containing an almost completely ordered arrangement of CoO6-ReO6 octahedra. Magnetic structure showed an antiferromagnetic (AF) behavior below TN=41 K. The magnetic and electronic structures are consistent with the electronic configurations Co2+(3d7)-Re6+(5d1) having a total spin magnetic moment of about 2.0 μB/f.u. DFT electronic structures predicted half-metallic yields from 3d-t2g↓ and 5d-t2g↓ through O2-.

  14. A Review on Energy Harvesting Using 3D Printed Fabrics for Wearable Electronics

    NASA Astrophysics Data System (ADS)

    Gowthaman, Swaminathan; Chidambaram, Gowri Shankar; Rao, Dilli Babu Govardhana; Subramya, Hemakumar Vyudhayagiri; Chandrasekhar, Udhayagiri

    2016-06-01

    Embedding of energy harvesting systems into wearable health and environment monitoring systems, like integration of smart piezoelectric fibers into soldier fabric structures opens up avenues in generating electricity from natural mechanical movements for self-powering of wearable electronics. Emergence of multitudinous of materials and manufacturing technologies has enabled realization of various energy harvesting systems from mechanical movements. The materials and manufacturing related to 3D printing of energy harvesting fabrics are reviewed in this paper. State-of-the-art energy harvesting sources are briefly described following which an in-depth analysis on the materials and 3D printing techniques for energy harvesting fabrics are presented. While tremendous motivation and opportunity exists for wider-scale adoption of 3D printing for this niche area, the success depends on efficient design of three critical factors namely materials, process and structure. The present review discusses on the complex issues of materials selection, modelling and processing of 3D printed fabrics. The paper culminates by presenting a discussion on how future advancements in 3D printing technology might be useful for development of wearable electronics.

  15. Novel scanning electron microscopy methods for analyzing the 3D structure of the Golgi apparatus.

    PubMed

    Koga, Daisuke; Ushiki, Tatsuo; Watanabe, Tsuyoshi

    2017-01-01

    The structure of the Golgi apparatus has been extensively examined by light and electron microscopy, but details of its three-dimensional (3D) structure have remained unclear because of the technical limitations of conventional microscopy techniques. To overcome this problem, we have developed several novel scanning electron microscopy (SEM) methods for observing the 3D structure of subcellular organelles including the Golgi apparatus: (1) an osmium maceration method that facilitates SEM observation of membranous organelles, including the Golgi apparatus, by selectively removing soluble cytoplasmic proteins, (2) an osmium impregnation/maceration method that combines an osmium impregnation method with the osmium maceration method to determine the polarity of the Golgi apparatus by SEM, (3) a correlative light and SEM method that combines a cryosectioning technique with the osmium maceration method to enable correlation of the immunocytochemical distribution of molecules with the 3D ultrastructure of the Golgi apparatus, and (4) array tomography based on the systematic collection and integration of SEM images of serial ultrathin sections on glass slides for revealing the 3D ultrastructure of the entire Golgi apparatus. Together, the novel SEM techniques listed above can reveal the complete 3D structure of the Golgi apparatus in different cell types.

  16. Prediction of spin-dependent electronic structure in 3d-transition-metal doped antimonene

    NASA Astrophysics Data System (ADS)

    Yang, L. F.; Song, Y.; Mi, W. B.; Wang, X. C.

    2016-07-01

    We investigate the geometric structure and electronic and magnetic properties of 3d-transition-metal atom doped antimonene using spin-polarized first-principles calculations. Strong orbital hybridization exhibits between 3d-transition-metal and Sb atoms, where covalent bonds form in antimonene. A spin-polarized semiconducting state appears in Cr-doped antimonene, while half-metallic states appear by doping Ti, V, and Mn. These findings indicate that once combined with doping states, the bands of antimonene systems offer a variety of features. Specific dopants lead to half-metallic characters with high spin polarization that has potential application in spintronics.

  17. Dynamics of electron emission in double photoionization processes near the krypton 3d threshold

    NASA Astrophysics Data System (ADS)

    Penent, F.; Sheinerman, S.; Andric, L.; Lablanquie, P.; Palaudoux, J.; Becker, U.; Braune, M.; Viefhaus, J.; Eland, J. H. D.

    2008-02-01

    Two-electron emission following photoabsorption near the Kr 3d threshold is investigated both experimentally and theoretically. On the experimental side, electron/electron coincidences using a magnetic bottle time-of-flight spectrometer allow us to observe the complete double photo ionization (DPI) continua of selected Kr2+ final states, and to see how these continua are affected by resonant processes in the vicinity of the Kr 3d threshold. The analysis is based on a quantum mechanical approach that takes into account the contribution of three different processes: (A) Auger decay of the inner 3d vacancy with the associated post-collision interaction (PCI) effects, (B) capture of slow photoelectrons into discrete states followed by valence multiplet decay (VMD) of the excited ionic states and (C) valence shell DPI. The dominant process for each Kr2+(4p-2) final state is the photoionization of the inner shell followed by Auger decay of the 3d vacancies. Moreover, for the 4p-2(3P) and 4p-2(1D) final ionic states an important contribution comes from the processes of slow photoelectron capture followed by VMD as well as from double ionization of the outer shell involving also VMD.

  18. Resonant structure of the 3d electron`s angular distribution in a free Mn{sup +}Ion

    SciTech Connect

    Amusia, M.Y.; Dolmatov, V.K.

    1995-08-01

    The 3d-electron angular anisotropy parameter of the free Mn{sup +} ion is calculated using the {open_quotes}spin-polarized{close_quotes} random-phase approximation with exchange. Strong resonance structure is discovered, which is due to interference with the powerful 3p {yields} 3d discrete excitation. The effect of the 3p {yields} 4s transition is also noticeable. The ordering of these respective resonances with phonon energy increase proved to be opposite in angular anisotropy parameter to that in 3d-photoionization cross section. A paper describing these results was published.

  19. Tuning the electronic and magnetic properties of borophene by 3d transition-metal atom adsorption

    NASA Astrophysics Data System (ADS)

    Li, J. Y.; Lv, H. Y.; Lu, W. J.; Shao, D. F.; Xiao, R. C.; Sun, Y. P.

    2016-12-01

    The electronic and magnetic properties of borophene functionalized by 3d transition metal (TM) atom adsorption are investigated by using first-principles calculations. The results show that the 3d TM atoms can be adsorbed on borophene with high binding energies ranging between 5.9 and 8.3 eV. Interestingly, the originally nonmagnetic borophene tends to be ferromagnetic when Ti, V, Cr, Mn, and Fe atoms are adsorbed, and the magnetic moments are dominated by the TM atoms. The origin of the ferromagnetism is discussed based on the Stoner criterion. Our results indicate that the magnetic properties of borophene can be effectively tuned through the adsorption of 3d TM atoms, which could have promising applications in spintronics and nanoelectronics.

  20. Injectable 3-D Fabrication of Medical Electronics at the Target Biological Tissues

    NASA Astrophysics Data System (ADS)

    Jin, Chao; Zhang, Jie; Li, Xiaokang; Yang, Xueyao; Li, Jingjing; Liu, Jing

    2013-12-01

    Conventional transplantable biomedical devices generally request sophisticated surgery which however often causes big trauma and serious pain to the patients. Here, we show an alternative way of directly making three-dimensional (3-D) medical electronics inside the biological body through sequential injections of biocompatible packaging material and liquid metal ink. As the most typical electronics, a variety of medical electrodes with different embedded structures were demonstrated to be easily formed at the target tissues. Conceptual in vitro experiments provide strong evidences for the excellent performances of the injectable electrodes. Further in vivo animal experiments disclosed that the formed electrode could serve as both highly efficient ECG (Electrocardiograph) electrode and stimulator electrode. These findings clarified the unique features and practicability of the liquid metal based injectable 3-D fabrication of medical electronics. The present strategy opens the way for directly manufacturing electrophysiological sensors or therapeutic devices in situ via a truly minimally invasive approach.

  1. Injectable 3-D Fabrication of Medical Electronics at the Target Biological Tissues

    PubMed Central

    Jin, Chao; Zhang, Jie; Li, Xiaokang; Yang, Xueyao; Li, Jingjing; Liu, Jing

    2013-01-01

    Conventional transplantable biomedical devices generally request sophisticated surgery which however often causes big trauma and serious pain to the patients. Here, we show an alternative way of directly making three-dimensional (3-D) medical electronics inside the biological body through sequential injections of biocompatible packaging material and liquid metal ink. As the most typical electronics, a variety of medical electrodes with different embedded structures were demonstrated to be easily formed at the target tissues. Conceptual in vitro experiments provide strong evidences for the excellent performances of the injectable electrodes. Further in vivo animal experiments disclosed that the formed electrode could serve as both highly efficient ECG (Electrocardiograph) electrode and stimulator electrode. These findings clarified the unique features and practicability of the liquid metal based injectable 3-D fabrication of medical electronics. The present strategy opens the way for directly manufacturing electrophysiological sensors or therapeutic devices in situ via a truly minimally invasive approach. PMID:24309385

  2. Hollow Cone Electron Imaging for Single Particle 3D Reconstruction of Proteins

    PubMed Central

    Tsai, Chun-Ying; Chang, Yuan-Chih; Lobato, Ivan; Van Dyck, Dirk; Chen, Fu-Rong

    2016-01-01

    The main bottlenecks for high-resolution biological imaging in electron microscopy are radiation sensitivity and low contrast. The phase contrast at low spatial frequencies can be enhanced by using a large defocus but this strongly reduces the resolution. Recently, phase plates have been developed to enhance the contrast at small defocus but electrical charging remains a problem. Single particle cryo-electron microscopy is mostly used to minimize the radiation damage and to enhance the resolution of the 3D reconstructions but it requires averaging images of a massive number of individual particles. Here we present a new route to achieve the same goals by hollow cone dark field imaging using thermal diffuse scattered electrons giving about a 4 times contrast increase as compared to bright field imaging. We demonstrate the 3D reconstruction of a stained GroEL particle can yield about 13.5 Å resolution but using a strongly reduced number of images. PMID:27292544

  3. Hollow Cone Electron Imaging for Single Particle 3D Reconstruction of Proteins.

    PubMed

    Tsai, Chun-Ying; Chang, Yuan-Chih; Lobato, Ivan; Van Dyck, Dirk; Chen, Fu-Rong

    2016-06-13

    The main bottlenecks for high-resolution biological imaging in electron microscopy are radiation sensitivity and low contrast. The phase contrast at low spatial frequencies can be enhanced by using a large defocus but this strongly reduces the resolution. Recently, phase plates have been developed to enhance the contrast at small defocus but electrical charging remains a problem. Single particle cryo-electron microscopy is mostly used to minimize the radiation damage and to enhance the resolution of the 3D reconstructions but it requires averaging images of a massive number of individual particles. Here we present a new route to achieve the same goals by hollow cone dark field imaging using thermal diffuse scattered electrons giving about a 4 times contrast increase as compared to bright field imaging. We demonstrate the 3D reconstruction of a stained GroEL particle can yield about 13.5 Å resolution but using a strongly reduced number of images.

  4. Hollow Cone Electron Imaging for Single Particle 3D Reconstruction of Proteins

    NASA Astrophysics Data System (ADS)

    Tsai, Chun-Ying; Chang, Yuan-Chih; Lobato, Ivan; van Dyck, Dirk; Chen, Fu-Rong

    2016-06-01

    The main bottlenecks for high-resolution biological imaging in electron microscopy are radiation sensitivity and low contrast. The phase contrast at low spatial frequencies can be enhanced by using a large defocus but this strongly reduces the resolution. Recently, phase plates have been developed to enhance the contrast at small defocus but electrical charging remains a problem. Single particle cryo-electron microscopy is mostly used to minimize the radiation damage and to enhance the resolution of the 3D reconstructions but it requires averaging images of a massive number of individual particles. Here we present a new route to achieve the same goals by hollow cone dark field imaging using thermal diffuse scattered electrons giving about a 4 times contrast increase as compared to bright field imaging. We demonstrate the 3D reconstruction of a stained GroEL particle can yield about 13.5 Å resolution but using a strongly reduced number of images.

  5. Simulation-Guided 3D Nanomanufacturing via Focused Electron Beam Induced Deposition

    SciTech Connect

    Fowlkes, Jason D.; Winkler, Robert; Lewis, Brett B.; Stanford, Michael G.; Plank, Harald; Rack, Philip D.

    2016-06-10

    Focused electron beam induced deposition (FEBID) is one of the few techniques that enables direct-write synthesis of free-standing 3D nanostructures. While the fabrication of simple architectures such as vertical or curving nanowires has been achieved by simple trial and error, processing complex 3D structures is not tractable with this approach. This is due, inpart, to the dynamic interplay between electron–solid interactions and the transient spatial distribution of absorbed precursor molecules on the solid surface. Here, we demonstrate the ability to controllably deposit 3D lattice structures at the micro/nanoscale, which have received recent interest owing to superior mechanical and optical properties. Moreover, a hybrid Monte Carlo–continuum simulation is briefly overviewed, and subsequently FEBID experiments and simulations are directly compared. Finally, a 3D computer-aided design (CAD) program is introduced, which generates the beam parameters necessary for FEBID by both simulation and experiment. In using this approach, we demonstrate the fabrication of various 3D lattice structures using Pt-, Au-, and W-based precursors.

  6. Simulation-Guided 3D Nanomanufacturing via Focused Electron Beam Induced Deposition

    DOE PAGES

    Fowlkes, Jason D.; Winkler, Robert; Lewis, Brett B.; ...

    2016-06-10

    Focused electron beam induced deposition (FEBID) is one of the few techniques that enables direct-write synthesis of free-standing 3D nanostructures. While the fabrication of simple architectures such as vertical or curving nanowires has been achieved by simple trial and error, processing complex 3D structures is not tractable with this approach. This is due, inpart, to the dynamic interplay between electron–solid interactions and the transient spatial distribution of absorbed precursor molecules on the solid surface. Here, we demonstrate the ability to controllably deposit 3D lattice structures at the micro/nanoscale, which have received recent interest owing to superior mechanical and optical properties.more » Moreover, a hybrid Monte Carlo–continuum simulation is briefly overviewed, and subsequently FEBID experiments and simulations are directly compared. Finally, a 3D computer-aided design (CAD) program is introduced, which generates the beam parameters necessary for FEBID by both simulation and experiment. In using this approach, we demonstrate the fabrication of various 3D lattice structures using Pt-, Au-, and W-based precursors.« less

  7. 3D Magnetic Induction Maps of Nanoscale Materials Revealed by Electron Holographic Tomography

    PubMed Central

    2015-01-01

    The investigation of three-dimensional (3D) ferromagnetic nanoscale materials constitutes one of the key research areas of the current magnetism roadmap and carries great potential to impact areas such as data storage, sensing, and biomagnetism. The properties of such nanostructures are closely connected with their 3D magnetic nanostructure, making their determination highly valuable. Up to now, quantitative 3D maps providing both the internal magnetic and electric configuration of the same specimen with high spatial resolution are missing. Here, we demonstrate the quantitative 3D reconstruction of the dominant axial component of the magnetic induction and electrostatic potential within a cobalt nanowire (NW) of 100 nm in diameter with spatial resolution below 10 nm by applying electron holographic tomography. The tomogram was obtained using a dedicated TEM sample holder for acquisition, in combination with advanced alignment and tomographic reconstruction routines. The powerful approach presented here is widely applicable to a broad range of 3D magnetic nanostructures and may trigger the progress of novel spintronic nonplanar nanodevices. PMID:27182110

  8. Future of Electron Scattering and Diffraction

    SciTech Connect

    Hall, Ernest; Stemmer, Susanne; Zheng, Haimei; Zhu, Yimei; Maracas, George

    2014-02-25

    The ability to correlate the atomic- and nanoscale-structure of condensed matter with physical properties (e.g., mechanical, electrical, catalytic, and optical) and functionality forms the core of many disciplines. Directing and controlling materials at the quantum-, atomic-, and molecular-levels creates enormous challenges and opportunities across a wide spectrum of critical technologies, including those involving the generation and use of energy. The workshop identified next generation electron scattering and diffraction instruments that are uniquely positioned to address these grand challenges. The workshop participants identified four key areas where the next generation of such instrumentation would have major impact: A – Multidimensional Visualization of Real Materials B – Atomic-scale Molecular Processes C – Photonic Control of Emergence in Quantum Materials D – Evolving Interfaces, Nucleation, and Mass Transport Real materials are comprised of complex three-dimensional arrangements of atoms and defects that directly determine their potential for energy applications. Understanding real materials requires new capabilities for three-dimensional atomic scale tomography and spectroscopy of atomic and electronic structures with unprecedented sensitivity, and with simultaneous spatial and energy resolution. Many molecules are able to selectively and efficiently convert sunlight into other forms of energy, like heat and electric current, or store it in altered chemical bonds. Understanding and controlling such process at the atomic scale require unprecedented time resolution. One of the grand challenges in condensed matter physics is to understand, and ultimately control, emergent phenomena in novel quantum materials that necessitate developing a new generation of instruments that probe the interplay among spin, charge, orbital, and lattice degrees of freedom with intrinsic time- and length-scale resolutions. Molecules and soft matter require imaging and

  9. Fabrication of 3D polymer microstructures using electron beam lithography and nanoimprinting technologies

    NASA Astrophysics Data System (ADS)

    Chen, Kuo-Shen; Lin, I.-Kuan; Ko, Fu-Hsang

    2005-10-01

    Recently, with the advancement in bio-MEMS and micro optoelectromechanical systems (MOEMS), 3D microstructures have become increasingly important and efficient fabrication processes are currently being sought. In this paper, a novel 3D fabrication process has been proposed by utilizing the proximity effect of electron beam lithography (EBL) to create 3D microstructures on negative photoresists as the primary molds, which are subsequently transferred to their corresponding negative molds using nanoimprinting lithography (NIL), and to form the final replicas by either electroforming or polymer spin casting to reduce cost. The effect of electron backscattering on the 3D topography is firstly investigated and the relationship among the spatial distribution of electron beam irradiation, the spot size and the dosage level of irradiation is experimentally characterized in SU-8 to establish a dosage kernel distribution function. A mathematical procedure based on linear operation of this kernel function is then proposed to mimic the EBL fabrication process. The subsequent experiments indicate that the predicted surface profiles agree with the experimental results to large extent and the proposed mathematical operations are valid for the purpose of designing the fabrication process. Finally, the SU-8 primary molds are transferred to NEB to form secondary molds via the nanoimprinting process. It shows that the nanoimprinting process can essentially reproduce the shape and geometry of the primary molds. However, due to the nature of polymer-to-polymer contact printing, the elastic restitution of materials induces a slight deviation of the final device size and a further study should be made in the future to minimize such types of error. Although the above problems are reported, nevertheless, the primary experimental results indicate that this proposed fabrication process is capable of creating 3D shape microstructure in the order of 1 µm and should be useful for related

  10. 3D structural fluctuation of IgG1 antibody revealed by individual particle electron tomography

    DOE PAGES

    Zhang, Xing; Zhang, Lei; Tong, Huimin; ...

    2015-05-05

    Commonly used methods for determining protein structure, including X-ray crystallography and single-particle reconstruction, often provide a single and unique three-dimensional (3D) structure. However, in these methods, the protein dynamics and flexibility/fluctuation remain mostly unknown. Here, we utilized advances in electron tomography (ET) to study the antibody flexibility and fluctuation through structural determination of individual antibody particles rather than averaging multiple antibody particles together. Through individual-particle electron tomography (IPET) 3D reconstruction from negatively-stained ET images, we obtained 120 ab-initio 3D density maps at an intermediate resolution (~1–3 nm) from 120 individual IgG1 antibody particles. Using these maps as a constraint, wemore » derived 120 conformations of the antibody via structural flexible docking of the crystal structure to these maps by targeted molecular dynamics simulations. Statistical analysis of the various conformations disclosed the antibody 3D conformational flexibility through the distribution of its domain distances and orientations. This blueprint approach, if extended to other flexible proteins, may serve as a useful methodology towards understanding protein dynamics and functions.« less

  11. 3D structural fluctuation of IgG1 antibody revealed by individual particle electron tomography

    SciTech Connect

    Zhang, Xing; Zhang, Lei; Tong, Huimin; Peng, Bo; Rames, Matthew J.; Zhang, Shengli; Ren, Gang

    2015-05-05

    Commonly used methods for determining protein structure, including X-ray crystallography and single-particle reconstruction, often provide a single and unique three-dimensional (3D) structure. However, in these methods, the protein dynamics and flexibility/fluctuation remain mostly unknown. Here, we utilized advances in electron tomography (ET) to study the antibody flexibility and fluctuation through structural determination of individual antibody particles rather than averaging multiple antibody particles together. Through individual-particle electron tomography (IPET) 3D reconstruction from negatively-stained ET images, we obtained 120 ab-initio 3D density maps at an intermediate resolution (~1–3 nm) from 120 individual IgG1 antibody particles. Using these maps as a constraint, we derived 120 conformations of the antibody via structural flexible docking of the crystal structure to these maps by targeted molecular dynamics simulations. Statistical analysis of the various conformations disclosed the antibody 3D conformational flexibility through the distribution of its domain distances and orientations. This blueprint approach, if extended to other flexible proteins, may serve as a useful methodology towards understanding protein dynamics and functions.

  12. Extensions of 1d Bgk Electron Solitary Wave Solutions To 3d Magnetized and Unmagnetized Plasmas

    NASA Astrophysics Data System (ADS)

    Chen, Li-Jen; Parks, George K.

    This paper will compare the key results for BGK electron solitary waves in 3D mag- netized and unmagnetized plasmas. For 3D magnetized plasmas with highly magnetic field-aligned electrons, our results predict that the parallel widths of the solitary waves can be smaller than one Debye length, the solitary waves can be large scale features of the magnetosphere, and the parallel width-amplitude relation has a dependence on the perpendicular size. We can thus obtain an estimate on the typical perpendicular size of the observed solitary waves assuming a series of consecutive solitary waves are in the same flux tude with a particular perpendicular span. In 3D unmagnetized plasma systems such as the neutral sheet and magnetic reconnection sites, our theory indi- cates that although mathematical solutions can be constructed as the time-stationary solutions for the nonlinear Vlasov-Poisson equations, there does not exist a param- eter range for the solutions to be physical. We conclude that single-humped solitary potential pulses cannot be self-consistently supported by charged particles in 3D un- magnetized plasmas.

  13. Real time 3-D electron density reconstruction over Europe by using TaD profiler

    NASA Astrophysics Data System (ADS)

    Kutiev, I.; Marinov, P.; Belehaki, A.

    2016-07-01

    The TaD (Topside Sounder Model (TSM)-assisted Digisonde) profiler, developed on the basis of the Topside Sounder Model (TSM), provides vertical electron density profiles (EDP) over Digisondes from the bottomside ionosphere up to Global Navigation Satellite Systems (GNSS) orbit heights. TaD EDP uses the Digisonde bottomside profile and extends it above the F2 layer peak, representing O+ distribution by α-Chapman formula and H+ distribution by a single exponent. Topside scale height HT and transition height hT are taken from TSM, while the plasmasphere scale height Hp is defined as a function of HT. All profile parameters are adjusted to the current conditions comparing the profile integral with the GNSS vertical total electron content (TEC) retrieved from the European Reference Frame (EUREF) maps. To expand to three dimensions (3-D), European maps of foF2 and hmF2 are produced, based on Digisonde data, with spatial resolution 1°×1° in latitude and longitude, and TaD profiles are calculated at each grid node. Electron density (ED) at any point of the 3-D space is obtained by linear interpolation of TaD parameters between neighbor nodes. Samples of two dimensional (2-D) electron density distribution (EDD) at different cross sections of the 3-D space between 200 km and 1150 km over the mapping area are presented, along with distributions of the electron density along various raypaths of GNSS signals. The modeled 3-D EDD is compared with vertical (vTEC) and slant (sTEC) TEC parameters calculated from individual GNSS receivers. The model error (relative deviation of model from the data), based on 6780 data values, is 10% for sTEC and 6% for vTEC.

  14. Potential of 3D printing technologies for fabrication of electron bolus and proton compensators.

    PubMed

    Zou, Wei; Fisher, Ted; Zhang, Miao; Kim, Leonard; Chen, Ting; Narra, Venkat; Swann, Beth; Singh, Rachana; Siderit, Richard; Yin, Lingshu; Teo, Boon-Keng Kevin; McKenna, Michael; McDonough, James; Ning, Yue J

    2015-05-08

    In electron and proton radiotherapy, applications of patient-specific electron bolus or proton compensators during radiation treatments are often necessary to accommodate patient body surface irregularities, tissue inhomogeneity, and variations in PTV depths to achieve desired dose distributions. Emerging 3D printing technologies provide alternative fabrication methods for these bolus and compensators. This study investigated the potential of utilizing 3D printing technologies for the fabrication of the electron bolus and proton compensators. Two printing technologies, fused deposition modeling (FDM) and selective laser sintering (SLS), and two printing materials, PLA and polyamide, were investigated. Samples were printed and characterized with CT scan and under electron and proton beams. In addition, a software package was developed to convert electron bolus and proton compensator designs to printable Standard Tessellation Language file format. A phantom scalp electron bolus was printed with FDM technology with PLA material. The HU of the printed electron bolus was 106.5 ± 15.2. A prostate patient proton compensator was printed with SLS technology and polyamide material with -70.1 ± 8.1 HU. The profiles of the electron bolus and proton compensator were compared with the original designs. The average over all the CT slices of the largest Euclidean distance between the design and the fabricated bolus on each CT slice was found to be 0.84 ± 0.45 mm and for the compensator to be 0.40 ± 0.42 mm. It is recommended that the properties of specific 3D printed objects are understood before being applied to radiotherapy treatments.

  15. 3D scanning electron microscopy applied to surface characterization of fluorosed dental enamel.

    PubMed

    Limandri, Silvina; Galván Josa, Víctor; Valentinuzzi, María Cecilia; Chena, María Emilia; Castellano, Gustavo

    2016-05-01

    The enamel surfaces of fluorotic teeth were studied by scanning electron stereomicroscopy. Different whitening treatments were applied to 25 pieces to remove stains caused by fluorosis and their surfaces were characterized by stereomicroscopy in order to obtain functional and amplitude parameters. The topographic features resulting for each treatment were determined through these parameters. The results obtained show that the 3D reconstruction achieved from the SEM stereo pairs is a valuable potential alternative for the surface characterization of this kind of samples.

  16. SU-C-213-06: Dosimetric Verification of 3D Printed Electron Bolus

    SciTech Connect

    Rasmussen, K; Corbett, M; Pelletier, C; Huang, Z; Feng, Y; Jung, J

    2015-06-15

    Purpose: To determine the dosimetric effect of 3D printed bolus in an anthropomorphic phantom. Methods: Conformable bolus material was generated for an anthropomorphic phantom from a DICOM volume. The bolus generated was a uniform expansion of 5mm applied to the nose region of the phantom, as this is a difficult area to uniformly apply bolus clinically. A Printrbot metal 3D Printer using PLA plastic generated the bolus. A 9MeV anterior beam with a 5cm cone was used to deliver dose to the nose of the phantom. TLD measurements were compared to predicted values at the phantom surface. Film planes were analyzed for the printed bolus, a standard 5mm bolus sheet placed on the phantom, and the phantom with no bolus applied to determine depth and dose distributions. Results: TLDs measured within 2.5% of predicted value for the 3D bolus. Film demonstrated a more uniform dose distribution in the nostril region for the 3d printed bolus than the standard bolus. This difference is caused by the air gap created around the nostrils by the standard bolus, creating a secondary build-up region. Both demonstrated a 50% central axis dose shift of 5mm relative to the no bolus film. HU for the bolus calculated the PLA electron density to be ∼1.1g/cc. Physical density was measured to be 1.3g/cc overall. Conclusion: 3D printed PLA bolus demonstrates improved dosimetric performance to standard bolus for electron beams with complex phantom geometry.

  17. Magnetic and Electronic Phase Diagram of Sr2VFeAsO3-d

    NASA Astrophysics Data System (ADS)

    Tojo, Yujiro; Shibuya, Taizo; Nakamura, Tetsuro; Shoji, Koichiro; Matoba, Masanori; Yasui, Shintaro; Itoh, Mitsuru; Kitao, Shinji; Seto, Makoto; Kamihara, Yoichi; Research Grants From Keio Univ. Collaboration; Msl Collaborative Research Project Collaboration; Joint Usage in Krri Collaboration

    2014-03-01

    Ae2MFePnO3 (so-called 21113 systems) with perovskite-type layers such as Ae2MO3, where Ae denotes alkaline earth metals, M does Sc, Ti, Cr, V and other transition metal atoms and Pn does As and P shows superconductivity at T <46 K. Sr2VFeAsO3-d is a representative compound in 21113 systems. [Zhu et al, Phys. Rev. B (2009); Ogino et al, Supercond. Sci. Technol. (2009); Ogino et al, Supercond. Sci. Technol. (2009)] Although the oxygen deficiency (d) as a function of Tc is still controversial in Sr2VFeAsO3-d, many samples have been reported as superconductors with Tc = 24-37 K. In this study, a polycrystalline Sr2VFeAsO3-d (d = ~ 0.1- 0.6) were prepared by a solid state reaction using an alumina tube in a sealed silica tube. DC electrical resistivity was measured by a four-probe technique. Magnetization measurements were performed on a superconducting quantum interference device. 57Fe Mossbauer spectra were obtained using conventional equipment. The electronic and magnetic phase diagram of Sr2VFeAsO3-d is elucidated.

  18. Suppression of electron-hole correlations in 3D polymer materials.

    PubMed

    Puschnig, Peter; Ambrosch-Draxl, Claudia

    2002-07-29

    We present an ab initio study of the optical absorption spectra of isolated as well as crystalline trans-polyacetylene. We include excitonic effects by solving the Bethe-Salpeter equation for the electron-hole two-particle correlation function. We observe that the strength of the electron-hole interactions drastically reduces when going from an isolated polymer chain to a crystalline arrangement. This is not only a result of enhanced screening in the 3D material, but also of the increased spatial extent of the exciton perpendicular to the polymer chains. We point out that these findings apply to crystalline phases of conjugated polymers and molecular crystals in general.

  19. Front-end receiver electronics for a matrix transducer for 3-D transesophageal echocardiography.

    PubMed

    Yu, Zili; Blaak, Sandra; Chang, Zu-yao; Yao, Jiajian; Bosch, Johan G; Prins, Christian; Lancée, Charles T; de Jong, Nico; Pertijs, Michiel A P; Meijer, Gerard C M

    2012-07-01

    There is a clear clinical need for creating 3-D images of the heart. One promising technique is the use of transesophageal echocardiography (TEE). To enable 3-D TEE, we are developing a miniature ultrasound probe containing a matrix piezoelectric transducer with more than 2000 elements. Because a gastroscopic tube cannot accommodate the cables needed to connect all transducer elements directly to an imaging system, a major challenge is to locally reduce the number of channels, while maintaining a sufficient signal-to-noise ratio. This can be achieved by using front-end receiver electronics bonded to the transducers to provide appropriate signal conditioning in the tip of the probe. This paper presents the design of such electronics, realizing time-gain compensation (TGC) and micro-beamforming using simple, low-power circuits. Prototypes of TGC amplifiers and micro-beamforming cells have been fabricated in 0.35-μm CMOS technology. These prototype chips have been combined on a printed circuit board (PCB) to form an ultrasound-receiver system capable of reading and combining the signals of three transducer elements. Experimental results show that this design is a suitable candidate for 3-D TEE.

  20. Computer Simulation of Reflection High Energy Electron Diffraction and Low Energy Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Flexner, Soren; Davidson, Bruce; Odonnell, James; Eckstein, J. N.

    2000-03-01

    Simulation software for Reflection High Energy Electron Diffraction (RHEED) and Low Energy Electron Diffraction (LEED) imaging has been developed using the C programming language. This software models experimental electron diffraction patterns obtained in-situ during deposition of oxide films by molecular beam epitaxy in our lab. Using the kinematical approximation the software considers the phase contributions from scatterers via a modifiable, finite, two or three-dimensional real lattice to construct the RHEED and LEED images. We have found quantitative agreement in the positions of diffraction maxima, and proceed to use the software to explore the qualitative aspects of La and Mn termination in LaMnO2, surface Jahn-Teller distortion in perovskites, terracing in various materials, and domain formation in a-axis DBCO resulting from in-plane rotation of the c-axis. In addition the software is used to examine proposed surface reconstructions capable of producing, e.g. the elevated half-order streaks seen along the [100] azimuth during growth of LaMnO2.

  1. Computational methods for constructing protein structure models from 3D electron microscopy maps.

    PubMed

    Esquivel-Rodríguez, Juan; Kihara, Daisuke

    2013-10-01

    Protein structure determination by cryo-electron microscopy (EM) has made significant progress in the past decades. Resolutions of EM maps have been improving as evidenced by recently reported structures that are solved at high resolutions close to 3Å. Computational methods play a key role in interpreting EM data. Among many computational procedures applied to an EM map to obtain protein structure information, in this article we focus on reviewing computational methods that model protein three-dimensional (3D) structures from a 3D EM density map that is constructed from two-dimensional (2D) maps. The computational methods we discuss range from de novo methods, which identify structural elements in an EM map, to structure fitting methods, where known high resolution structures are fit into a low-resolution EM map. A list of available computational tools is also provided.

  2. Synthesizing a 3D auditory scene for use in an electronic travel aid for the blind

    NASA Astrophysics Data System (ADS)

    Bujacz, Michał; Strumiłło, Paweł

    2008-01-01

    A system for auditory presentation of 3D scenes to the blind is presented, with the focus of the paper on the synthesis of sound codes suitable to carry important scene information. First, a short review of existing electronic travel aids for the blind (ETAs) is provided. Second, the project of the wearable ETA device, currently under development at the Technical University of Lodz, is outlined, along with the system modules: 3D scene reconstruction, object (obstacle) selection, synthesis of the sound code and the application of head related transfer functions (HRTFs) for generating spatialized sound. The importance of psychoacoustics, especially Bregman's theory of sound streams, is analyzed and proposed methods of sound code synthesis are presented, along with the software used for their verification.

  3. Staining and embedding of human chromosomes for 3-d serial block-face scanning electron microscopy.

    PubMed

    Yusuf, Mohammed; Chen, Bo; Hashimoto, Teruo; Estandarte, Ana Katrina; Thompson, George; Robinson, Ian

    2014-12-01

    The high-order structure of human chromosomes is an important biological question that is still under investigation. Studies have been done on imaging human mitotic chromosomes using mostly 2-D microscopy methods. To image micron-sized human chromosomes in 3-D, we developed a procedure for preparing samples for serial block-face scanning electron microscopy (SBFSEM). Polyamine chromosomes are first separated using a simple filtration method and then stained with heavy metal. We show that the DNA-specific platinum blue provides higher contrast than osmium tetroxide. A two-step procedure for embedding chromosomes in resin is then used to concentrate the chromosome samples. After stacking the SBFSEM images, a familiar X-shaped chromosome was observed in 3-D.

  4. Strain measurement of a mouse bone by 3D-electronic speckle pattern interferometry (3D-ESPI)

    NASA Astrophysics Data System (ADS)

    Samala, Praveen R.; Su, Min; Liu, Sheng; Jiang, Hui H.; Yokota, Hiroki; Yang, Lianxiang

    2005-08-01

    Bone is a mechanosensitive tissue that adapts its mass, architecture and mechanical properties to mechanical loading. Appropriate mechanical loads provide an effective means to stimulate bone remodeling and prevent from bone loss. It is controversial whether in situ strain in bone is a critical determinant in enhancement of bone formation, and it is therefore important to evaluate load-driven strain in bone. Using electronic speckle pattern interferometry, we determined high-resolution three-dimensional strains on the mouse femur in response to two loading modalities: an axial loading modality (ALM) and a knee loading modality (KLM). We demonstrated that these two loading modalities induced a different pattern of strain distributions. ALM generated strain in the midshaft of cortical bone, while strains with KLM were concentrated on the distal epiphysis of the mouse femur. Since KLM is capable of enhancing bone formation in cortical bone distant from the knee, the current results indicate that in situ strain is not always necessary for load-driven bone formation.

  5. Electron Microscopy: From 2D to 3D Images with Special Reference to Muscle

    PubMed Central

    2015-01-01

    This is a brief and necessarily very sketchy presentation of the evolution in electron microscopy (EM) imaging that was driven by the necessity of extracting 3-D views from the essentially 2-D images produced by the electron beam. The lens design of standard transmission electron microscope has not been greatly altered since its inception. However, technical advances in specimen preparation, image collection and analysis gradually induced an astounding progression over a period of about 50 years. From the early images that redefined tissues, cell and cell organelles at the sub-micron level, to the current nano-resolution reconstructions of organelles and proteins the step is very large. The review is written by an investigator who has followed the field for many years, but often from the sidelines, and with great wonder. Her interest in muscle ultrastructure colors the writing. More specific detailed reviews are presented in this issue. PMID:26913146

  6. Self-Consistent 3D Modeling of Electron Cloud Dynamics and Beam Response

    SciTech Connect

    Furman, Miguel; Furman, M.A.; Celata, C.M.; Kireeff-Covo, M.; Sonnad, K.G.; Vay, J.-L.; Venturini, M.; Cohen, R.; Friedman, A.; Grote, D.; Molvik, A.; Stoltz, P.

    2007-04-02

    We present recent advances in the modeling of beam electron-cloud dynamics, including surface effects such as secondary electron emission, gas desorption, etc, and volumetric effects such as ionization of residual gas and charge-exchange reactions. Simulations for the HCX facility with the code WARP/POSINST will be described and their validity demonstrated by benchmarks against measurements. The code models a wide range of physical processes and uses a number of novel techniques, including a large-timestep electron mover that smoothly interpolates between direct orbit calculation and guiding-center drift equations, and a new computational technique, based on a Lorentz transformation to a moving frame, that allows the cost of a fully 3D simulation to be reduced to that of a quasi-static approximation.

  7. 3-D readout-electronics packaging for high-bandwidth massively paralleled imager

    DOEpatents

    Kwiatkowski, Kris; Lyke, James

    2007-12-18

    Dense, massively parallel signal processing electronics are co-packaged behind associated sensor pixels. Microchips containing a linear or bilinear arrangement of photo-sensors, together with associated complex electronics, are integrated into a simple 3-D structure (a "mirror cube"). An array of photo-sensitive cells are disposed on a stacked CMOS chip's surface at a 45.degree. angle from light reflecting mirror surfaces formed on a neighboring CMOS chip surface. Image processing electronics are held within the stacked CMOS chip layers. Electrical connections couple each of said stacked CMOS chip layers and a distribution grid, the connections for distributing power and signals to components associated with each stacked CSMO chip layer.

  8. 3D Imaging of Diatoms with Ion-abrasion Scanning Electron Microscopy

    PubMed Central

    Hildebrand, Mark; Kim, Sang; Shi, Dan; Scott, Keana; Subramaniam, Sriram

    2009-01-01

    Ion-abrasion scanning electron microscopy (IASEM) takes advantage of focused ion beams to abrade thin sections from the surface of bulk specimens, coupled with SEM to image the surface of each section, enabling 3D reconstructions of subcellular architecture at ~ 30 nm resolution. Here, we report the first application of IASEM for imaging a biomineralizing organism, the marine diatom Thalassiosira pseudonana. Diatoms have highly patterned silica-based cell wall structures that are unique models for the study and application of directed nanomaterials synthesis by biological systems. Our study provides new insights into the architecture and assembly principles of both the “hard” (siliceous) and “soft” (organic) components of the cell. From 3D reconstructions of developmentally synchronized diatoms captured at different stages, we show that both micro- and nanoscale siliceous structures can be visualized at specific stages in their formation. We show that not only are structures visualized in a whole-cell context, but demonstrate that fragile, early-stage structures are visible, and that this can be combined with elemental mapping in the exposed slice. We demonstrate that the 3D architectures of silica structures, and the cellular components that mediate their creation and positioning can be visualized simultaneously, providing new opportunities to study and manipulate mineral nanostructures in a genetically tractable system. PMID:19269330

  9. A nanofiber based artificial electronic skin with high pressure sensitivity and 3D conformability

    NASA Astrophysics Data System (ADS)

    Zhong, Weibin; Liu, Qiongzhen; Wu, Yongzhi; Wang, Yuedan; Qing, Xing; Li, Mufang; Liu, Ke; Wang, Wenwen; Wang, Dong

    2016-06-01

    Pressure sensors with 3D conformability are highly desirable components for artificial electronic skin or e-textiles that can mimic natural skin, especially for application in real-time monitoring of human physiological signals. Here, a nanofiber based electronic skin with ultra-high pressure sensitivity and 3D conformability is designed and built by interlocking two elastic patterned nanofibrous membranes. The patterned membrane is facilely prepared by casting conductive nanofiber ink into a silicon mould to form an array of semi-spheroid-like protuberances. The protuberances composed of intertwined elastic POE nanofibers and PPy@PVA-co-PE nanofibers afford a tunable effective elastic modulus that is capable of capturing varied strains and stresses, thereby contributing to a high sensitivity for pressure sensing. This electronic skin-like sensor demonstrates an ultra-high sensitivity (1.24 kPa-1) below 150 Pa with a detection limit as low as about 1.3 Pa. The pixelated sensor array and a RGB-LED light are then assembled into a circuit and show a feasibility for visual detection of spatial pressure. Furthermore, a nanofiber based proof-of-concept wireless pressure sensor with a bluetooth module as a signal transmitter is proposed and has demonstrated great promise for wireless monitoring of human physiological signals, indicating a potential for large scale wearable electronic devices or e-skin.Pressure sensors with 3D conformability are highly desirable components for artificial electronic skin or e-textiles that can mimic natural skin, especially for application in real-time monitoring of human physiological signals. Here, a nanofiber based electronic skin with ultra-high pressure sensitivity and 3D conformability is designed and built by interlocking two elastic patterned nanofibrous membranes. The patterned membrane is facilely prepared by casting conductive nanofiber ink into a silicon mould to form an array of semi-spheroid-like protuberances. The

  10. 3D structure of eukaryotic flagella in a quiescent state revealed by cryo-electron tomography

    PubMed Central

    Nicastro, Daniela; McIntosh, J. Richard; Baumeister, Wolfgang

    2005-01-01

    We have used cryo-electron tomography to investigate the 3D structure and macromolecular organization of intact, frozen-hydrated sea urchin sperm flagella in a quiescent state. The tomographic reconstructions provide information at a resolution better than 6 nm about the in situ arrangements of macromolecules that are key for flagellar motility. We have visualized the heptameric rings of the motor domains in the outer dynein arm complex and determined that they lie parallel to the plane that contains the axes of neighboring flagellar microtubules. Both the material associated with the central pair of microtubules and the radial spokes display a plane of symmetry that helps to explain the planar beat pattern of these flagella. Cryo-electron tomography has proven to be a powerful technique for helping us understand the relationships between flagellar structure and function and the design of macromolecular machines in situ. PMID:16246999

  11. Electronic Properties of COPPER-3d Transition-Metal Pairs in Silicon

    NASA Astrophysics Data System (ADS)

    Justo, João F.; Assali, Lucy V. C.

    We report a theoretical investigation of the chemical trends in the electronic properties of the substitutional Cu-interstitial 3d-transition-metal (Cr, Mn, Fe) trigonal pairs in silicon. The calculations were carried out in the framework of the multiple-scattering Xα molecular cluster model. The electronic structures show that the stability of these pairs is mostly the result of a covalent interaction between the molecular orbitals coming not only from the Cu and TM atoms but also from the neighboring Si atoms. These results are in contrast to an ionic model which has been generally invoked to explain the stability of those pairs, but in agreement with some recent experimental findings. The Fermi contact terms for all the stable pairs in different charge states were computed and compared to available experimental data. We speculate on the existence of a different microscopic structure to explain these Cu-related complex pairs.

  12. 3D mapping of nanoscale electric potentials in semiconductor structures using electron-holographic tomography

    NASA Astrophysics Data System (ADS)

    Wolf, Daniel; Lubk, Axel; Prete, Paola; Lovergine, Nico; Lichte, Hannes

    2016-09-01

    Off-axis electron holography (EH) is a powerful method for mapping projected electric potentials, such as built-in potentials in semiconductor devices, in two dimensions (2D) at nanometer resolution. However, not well-defined thickness profiles, surface effects, and composition changes of the sample under investigation complicate the interpretation of the projected potentials. Here, we demonstrate how these problems can be overcome by combining EH with tomographic techniques, that is, electron holographic tomography (EHT), reconstructing electric potentials in 3D. We present EHT reconstructions of an n-type MOSFET including its dopant-related built-in potentials inside the device, as well as of a GaAs/AlGaAs core-multishell nanowire containing a 5 nm thick quantum well tube.

  13. Cellulose Nanocrystals as Chiral Inducers: Enantioselective Catalysis and Transmission Electron Microscopy 3D Characterization.

    PubMed

    Kaushik, Madhu; Basu, Kaustuv; Benoit, Charles; Cirtiu, Ciprian M; Vali, Hojatollah; Moores, Audrey

    2015-05-20

    Cellulose nanocrystals (CNCs), derived from cellulose, provide us with an opportunity to devise more sustainable solutions to current technological challenges. Enantioselective catalysis, especially heterogeneous, is the preferred method for the synthesis of pure chiral molecules in the fine chemical industries. Cellulose has been long sought as a chiral inducer in enantioselective catalysis. We report herein an unprecedentedly high enantiomeric excess (ee) for Pd patches deposited onto CNCs used as catalysts for the hydrogenation of prochiral ketones in water at room temperature and 4 bar H2. Our system, where CNCs acted as support and sole chiral source, achieved an ee of 65% with 100% conversions. Cryo-electron microscopy, high-resolution transmission electron microscopy, and tomography were used for the first time to study the 3D structure of a metal functionalized CNC hybrid. It established the presence of sub-nanometer-thick Pd patches at the surface of CNCs and provided insight into the chiral induction mechanism.

  14. Design and production of 3D printed bolus for electron radiation therapy.

    PubMed

    Su, Shiqin; Moran, Kathryn; Robar, James L

    2014-07-08

    This is a proof-of-concept study demonstrating the capacity for modulated electron radiation therapy (MERT) dose distributions using 3D printed bolus. Previous reports have involved bolus design using an electron pencil beam model and fabrication using a milling machine. In this study, an in-house algorithm is presented that optimizes the dose distribution with regard to dose coverage, conformity, and homogeneity within the planning target volume (PTV). The algorithm takes advantage of a commercial electron Monte Carlo dose calculation and uses the calculated result as input. Distances along ray lines from the distal side of 90% isodose line to distal surface of the PTV are used to estimate the bolus thickness. Inhomogeneities within the calculation volume are accounted for using the coefficient of equivalent thickness method. Several regional modulation operators are applied to improve the dose coverage and uniformity. The process is iterated (usually twice) until an acceptable MERT plan is realized, and the final bolus is printed using solid polylactic acid. The method is evaluated with regular geometric phantoms, anthropomorphic phantoms, and a clinical rhabdomyosarcoma pediatric case. In all cases the dose conformity are improved compared to that with uniform bolus. For geometric phantoms with air or bone inhomogeneities, the dose homogeneity is markedly improved. The actual printed boluses conform well to the surface of complex anthropomorphic phantoms. The correspondence of the dose distribution between the calculated synthetic bolus and the actual manufactured bolus is shown. For the rhabdomyosarcoma patient, the MERT plan yields a reduction of mean dose by 38.2% in left kidney relative to uniform bolus. MERT using 3D printed bolus appears to be a practical, low-cost approach to generating optimized bolus for electron therapy. The method is effective in improving conformity of the prescription isodose surface and in sparing immediately adjacent normal

  15. Predicting the Electronic Properties of 3D, Million-atom Semiconductor nanostructure Architectures

    SciTech Connect

    Jack Dongarra; Stanimire Tomov

    2012-03-15

    This final report describes the work done by Jack Dongarra (University Distinguished Professor) and Stanimire Tomov (Research Scientist) related to the DOE project entitled Predicting the Electronic Properties of 3D, Million-Atom Semiconductor Nanostructure Architectures. In this project we addressed the mathematical methodology required to calculate the electronic and transport properties of large nanostructures with comparable accuracy and reliability to that of current ab initio methods. This capability is critical for further developing the field, yet it is missing in all the existing computational methods. Additionally, quantitative comparisons with experiments are often needed for a qualitative understanding of the physics, and for guiding the design of new nanostructures. We focused on the mathematical challenges of the project, in particular on solvers and preconditioners for large scale eigenvalue problems that occur in the computation of electronic states of large nanosystems. Usually, the states of interest lie in the interior of the spectrum and their computation poses great difficulties for existing algorithms. The electronic properties of a semiconductor nanostructure architecture can be predicted/determined by computing its band structure. Of particular importance are the 'band edge states' (electronic states near the energy gap) which can be computed from a properly defined interior eigenvalue problem. Our primary mathematics and computational challenge here has been to develop an efficient solution methodology for finding these interior states for very large systems. Our work has produced excellent results in terms of developing both new and extending current state-of-the-art techniques.

  16. NIST/Sandia/ICDD Electron Diffraction Database: A Database for Phase Identification by Electron Diffraction.

    PubMed

    Carr, M J; Chambers, W F; Melgaard, D; Himes, V L; Stalick, J K; Mighell, A D

    1989-01-01

    A new database containing crystallographic and chemical information designed especially for application to electron diffraction search/match and related problems has been developed. The new database was derived from two well-established x-ray diffraction databases, the JCPDS Powder Diffraction File and NBS CRYSTAL DATA, and incorporates 2 years of experience with an earlier version. It contains 71,142 entries, with space group and unit cell data for 59,612 of those. Unit cell and space group information were used, where available, to calculate patterns consisting of all allowed reflections with d-spacings greater than 0.8 A for ~ 59,000 of the entries. Calculated patterns are used in the database in preference to experimental x-ray data when both are available, since experimental x-ray data sometimes omits high d-spacing data which falls at low diffraction angles. Intensity data are not given when calculated spacings are used. A search scheme using chemistry and r-spacing (reciprocal d-spacing) has been developed. Other potentially searchable data in this new database include space group, Pearson symbol, unit cell edge lengths, reduced cell edge length, and reduced cell volume. Compound and/or mineral names, formulas, and journal references are included in the output, as well as pointers to corresponding entries in NBS CRYSTAL DATA and the Powder Diffraction File where more complete information may be obtained. Atom positions are not given. Rudimentary search software has been written to implement a chemistry and r-spacing bit map search. With typical data, a full search through ~ 71,000 compounds takes 10~20 seconds on a PDP 11/23-RL02 system.

  17. The 3d Rydberg (3A2) electronic state observed by Herzberg and Shoosmith for methylene

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yukio; Schaefer, Henry F., III

    1997-06-01

    In 1959 and 1961 Herzberg and Shoosmith reported the vacuum ultraviolet spectrum of the triplet state of CH2. The present study focuses on a characterization of the upper state, the 3d Rydberg (3A2) state, observed at 1415 Å. The theoretical interpretation of these experiments is greatly complicated by the presence of a lower-lying 3A2 valence state with a very small equilibrium bond angle. Ab initio electronic structure methods involving self-consistent-field (SCF), configuration interaction with single and double excitations (CISD), complete active space (CAS) SCF, state-averaged (SA) CASSCF, coupled cluster with single and double excitations (CCSD), CCSD with perturbative triple excitations [CCSD(T)], CASSCF second-order (SO) CI, and SACASSCF-SOCI have been employed with six distinct basis sets. With the largest basis set, triple zeta plus triple polarization with two sets of higher angular momentum functions and three sets of diffuse functions TZ3P(2 f,2d)+3diff, the CISD level of theory predicts the equilibrium geometry of the 3d Rydberg (3A2) state to be re=1.093 Å and θe=141.3 deg. With the same basis set the energy (Te value) of the 3d Rydberg state relative to the ground (X˜ 3B1) state has been determined to be 201.6 kcal mol-1 (70 500 cm-1) at the CCSD (T) level, 200.92kcal mol-1 (70 270 cm-1) at the CASSCF-SOCI level, and 200.89kcal mol-1 (70 260 cm-1) at the SACASSCF-SOCI level of theory. These predictions are in excellent agreement with the experimental T0 value of 201.95 kcalmol-1 (70 634 cm-1) reported by Herzberg.

  18. BioMEA: a versatile high-density 3D microelectrode array system using integrated electronics.

    PubMed

    Charvet, Guillaume; Rousseau, Lionel; Billoint, Olivier; Gharbi, Sadok; Rostaing, Jean-Pierre; Joucla, Sébastien; Trevisiol, Michel; Bourgerette, Alain; Chauvet, Philippe; Moulin, Céline; Goy, François; Mercier, Bruno; Colin, Mikael; Spirkovitch, Serge; Fanet, Hervé; Meyrand, Pierre; Guillemaud, Régis; Yvert, Blaise

    2010-04-15

    Microelectrode arrays (MEAs) offer a powerful tool to both record activity and deliver electrical microstimulations to neural networks either in vitro or in vivo. Microelectronics microfabrication technologies now allow building high-density MEAs containing several hundreds of microelectrodes. However, dense arrays of 3D micro-needle electrodes, providing closer contact with the neural tissue than planar electrodes, are not achievable using conventional isotropic etching processes. Moreover, increasing the number of electrodes using conventional electronics is difficult to achieve into compact devices addressing all channels independently for simultaneous recording and stimulation. Here, we present a full modular and versatile 256-channel MEA system based on integrated electronics. First, transparent high-density arrays of 3D-shaped microelectrodes were realized by deep reactive ion etching techniques of a silicon substrate reported on glass. This approach allowed achieving high electrode aspect ratios, and different shapes of tip electrodes. Next, we developed a dedicated analog 64-channel Application Specific Integrated Circuit (ASIC) including one amplification stage and one current generator per channel, and analog output multiplexing. A full modular system, called BIOMEA, has been designed, allowing connecting different types of MEAs (64, 128, or 256 electrodes) to different numbers of ASICs for simultaneous recording and/or stimulation on all channels. Finally, this system has been validated experimentally by recording and electrically eliciting low-amplitude spontaneous rhythmic activity (both LFPs and spikes) in the developing mouse CNS. The availability of high-density MEA systems with integrated electronics will offer new possibilities for both in vitro and in vivo studies of large neural networks.

  19. A toolbox for ab initio 3-D reconstructions in single-particle electron microscopy.

    PubMed

    Voss, Neil R; Lyumkis, Dmitry; Cheng, Anchi; Lau, Pick-Wei; Mulder, Anke; Lander, Gabriel C; Brignole, Edward J; Fellmann, Denis; Irving, Christopher; Jacovetty, Erica L; Leung, Albert; Pulokas, James; Quispe, Joel D; Winkler, Hanspeter; Yoshioka, Craig; Carragher, Bridget; Potter, Clinton S

    2010-03-01

    Structure determination of a novel macromolecular complex via single-particle electron microscopy depends upon overcoming the challenge of establishing a reliable 3-D reconstruction using only 2-D images. There are a variety of strategies that deal with this issue, but not all of them are readily accessible and straightforward to use. We have developed a "toolbox" of ab initio reconstruction techniques that provide several options for calculating 3-D volumes in an easily managed and tightly controlled work-flow that adheres to standard conventions and formats. This toolbox is designed to streamline the reconstruction process by removing the necessity for bookkeeping, while facilitating transparent data transfer between different software packages. It currently includes procedures for calculating ab initio reconstructions via random or orthogonal tilt geometry, tomograms, and common lines, all of which have been tested using the 50S ribosomal subunit. Our goal is that the accessibility of multiple independent reconstruction algorithms via this toolbox will improve the ease with which models can be generated, and provide a means of evaluating the confidence and reliability of the final reconstructed map.

  20. The Heisenberg Uncertainty Principle Demonstrated with An Electron Diffraction Experiment

    ERIC Educational Resources Information Center

    Matteucci, Giorgio; Ferrari, Loris; Migliori, Andrea

    2010-01-01

    An experiment analogous to the classical diffraction of light from a circular aperture has been realized with electrons. The results are used to introduce undergraduate students to the wave behaviour of electrons. The diffraction fringes produced by the circular aperture are compared to those predicted by quantum mechanics and are exploited to…

  1. Three-dimensional analysis by electron diffraction methods of nanocrystalline materials.

    PubMed

    Gammer, Christoph; Mangler, Clemens; Karnthaler, Hans-Peter; Rentenberger, Christian

    2011-12-01

    To analyze nanocrystalline structures quantitatively in 3D, a novel method is presented based on electron diffraction. It allows determination of the average size and morphology of the coherently scattering domains (CSD) in a straightforward way without the need to prepare multiple sections. The method is applicable to all kinds of bulk nanocrystalline materials. As an example, the average size of the CSD in nanocrystalline FeAl made by severe plastic deformation is determined in 3D. Assuming ellipsoidal CSD, it is deduced that the CSD have a width of 19 ± 2 nm, a length of 18 ± 1 nm, and a height of 10 ± 1 nm.

  2. 3D hybrid simulations with gyrokinetic particle ions and fluid electrons

    SciTech Connect

    Belova, E.V.; Park, W.; Fu, G.Y.; Strauss, H.R.; Sugiyama, L.E.

    1998-12-31

    The previous hybrid MHD/particle model (MH3D-K code) represented energetic ions as gyrokinetic (or drift-kinetic) particles coupled to MHD equations using the pressure or current coupling scheme. A small energetic to bulk ion density ratio was assumed, n{sub h}/n{sub b} {much_lt} 1, allowing the neglect of the energetic ion perpendicular inertia in the momentum equation and the use of MHD Ohm`s law E = {minus}v{sub b} {times} B. A generalization of this model in which all ions are treated as gyrokinetic/drift-kinetic particles and fluid description is used for the electron dynamics is considered in this paper.

  3. Digital electron diffraction – seeing the whole picture

    SciTech Connect

    Beanland, Richard; Thomas, Paul J.; Woodward, David I.; Thomas, Pamela A.; Roemer, Rudolf A.

    2013-07-01

    Computer control of beam tilt and image capture allows the collection of electron diffraction patterns over a large angular range, without any overlap in diffraction data and from a region limited only by the size of the electron beam. This results in a significant improvement in data volumes and ease of interpretation. The advantages of convergent-beam electron diffraction for symmetry determination at the scale of a few nm are well known. In practice, the approach is often limited due to the restriction on the angular range of the electron beam imposed by the small Bragg angle for high-energy electron diffraction, i.e. a large convergence angle of the incident beam results in overlapping information in the diffraction pattern. Techniques have been generally available since the 1980s which overcome this restriction for individual diffracted beams, by making a compromise between illuminated area and beam convergence. Here a simple technique is described which overcomes all of these problems using computer control, giving electron diffraction data over a large angular range for many diffracted beams from the volume given by a focused electron beam (typically a few nm or less). The increase in the amount of information significantly improves the ease of interpretation and widens the applicability of the technique, particularly for thin materials or those with larger lattice parameters.

  4. Tunable electronic behavior in 3d transition metal doped 2H-WSe2

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Huang, Songlei; Li, Hongping; Zhang, Quan; Li, Changsheng; Liu, Xiaojuan; Meng, Jian; Tian, Yi

    2017-03-01

    Structural and electronic properties of 3d transition metal Sc, Ti, Cr and Mn incorporated 2H-WSe2 have been systematically investigated by first-principles calculations based on density functional theory. The calculated formation energies reveal that all the doped systems are thermodynamically more favorable under Se-rich condition than W-rich condition. The geometry structures almost hold that of the pristine 2H-WSe2 albeit with slight lattice distortion. More importantly, the electronic properties have been significantly tuned by the dopants, i.e., metal and semimetal behavior has been found in Sc, Ti and Mn-doped 2H-WSe2, respectively, semiconducting nature with narrowed band gap is expected in Cr-doped case, just as that of the pristine 2H-WSe2. In particular, magnetic character is realized by incorporation of Mn impurity with a total magnetic moment of 0.96 μB. Our results suggest chemical doping is an effective way to precisely tailor the electronic structure of layered transition metal dichalcogenide 2H-WSe2 for target technological applications.

  5. Immuno- and correlative light microscopy-electron tomography methods for 3D protein localization in yeast.

    PubMed

    Mari, Muriel; Geerts, Willie J C; Reggiori, Fulvio

    2014-10-01

    Compartmentalization of eukaryotic cells is created and maintained through membrane rearrangements that include membrane transport and organelle biogenesis. Three-dimensional reconstructions with nanoscale resolution in combination with protein localization are essential for an accurate molecular dissection of these processes. The yeast Saccharomyces cerevisiae is a key model system for identifying genes and characterizing pathways essential for the organization of cellular ultrastructures. Electron microscopy studies of yeast, however, have been hampered by the presence of a cell wall that obstructs penetration of resins and cryoprotectants, and by the protein dense cytoplasm, which obscures the membrane details. Here we present an immuno-electron tomography (IET) method, which allows the determination of protein distribution patterns on reconstructed organelles from yeast. In addition, we extend this IET approach into a correlative light microscopy-electron tomography procedure where structures positive for a specific protein localized through a fluorescent signal are resolved in 3D. These new investigative tools for yeast will help to advance our understanding of the endomembrane system organization in eukaryotic cells.

  6. Single-Particle Cryo-EM and 3D Reconstruction of Hybrid Nanoparticles with Electron-Dense Components.

    PubMed

    Yu, Guimei; Yan, Rui; Zhang, Chuan; Mao, Chengde; Jiang, Wen

    2015-10-01

    Single-particle cryo-electron microscopy (cryo-EM), accompanied with 3D reconstruction, is a broadly applicable tool for the structural characterization of macromolecules and nanoparticles. Recently, the cryo-EM field has pushed the limits of this technique to higher resolutions and samples of smaller molecular mass, however, some samples still present hurdles to this technique. Hybrid particles with electron-dense components, which have been studied using single-particle cryo-EM yet with limited success in 3D reconstruction due to the interference caused by electron-dense elements, constitute one group of such challenging samples. To process such hybrid particles, a masking method is developed in this work to adaptively remove pixels arising from electron-dense portions in individual projection images while maintaining maximal biomass signals for subsequent 2D alignment, 3D reconstruction, and iterative refinements. As demonstrated by the success in 3D reconstruction of an octahedron DNA/gold hybrid particle, which has been previously published without a 3D reconstruction, the devised strategy that combines adaptive masking and standard single-particle 3D reconstruction approach has overcome the hurdle of electron-dense elements interference, and is generally applicable to cryo-EM structural characterization of most, if not all, hybrid nanomaterials with electron-dense components.

  7. Pulse requirements for electron diffraction imaging of single biological molecules

    SciTech Connect

    Hau-Riege, S; London, R; Chapman, H

    2004-10-20

    The pulse requirements for electron diffraction imaging of single biological molecules are calculated. We find that the electron fluence and pulse length requirements imposed by the damage limit and by the need to classify the diffraction patterns according to their angular orientation cannot be achieved with today's electron beam technology. A simple analytical model shows that the pulse requirements cannot be achieved due to beam broadening due to spacecharge effects.

  8. Cellular uptake mechanisms of functionalised multi-walled carbon nanotubes by 3D electron tomography imaging

    NASA Astrophysics Data System (ADS)

    Al-Jamal, Khuloud T.; Nerl, Hannah; Müller, Karin H.; Ali-Boucetta, Hanene; Li, Shouping; Haynes, Peter D.; Jinschek, Joerg R.; Prato, Maurizio; Bianco, Alberto; Kostarelos, Kostas; Porter, Alexandra E.

    2011-06-01

    Carbon nanotubes (CNTs) are being investigated for a variety of biomedical applications. Despite numerous studies, the pathways by which carbon nanotubes enter cells and their subsequent intracellular trafficking and distribution remain poorly determined. Here, we use 3-D electron tomography techniques that offer optimum enhancement of contrast between carbon nanotubes and the plasma membrane to investigate the mechanisms involved in the cellular uptake of shortened, functionalised multi-walled carbon nanotubes (MWNT-NH3+). Both human lung epithelial (A549) cells, that are almost incapable of phagocytosis and primary macrophages, capable of extremely efficient phagocytosis, were used. We observed that MWNT-NH3+ were internalised in both phagocytic and non-phagocytic cells by any one of three mechanisms: (a) individually via membrane wrapping; (b) individually by direct membrane translocation; and (c) in clusters within vesicular compartments. At early time points following intracellular translocation, we noticed accumulation of nanotube material within various intracellular compartments, while a long-term (14-day) study using primary human macrophages revealed that MWNT-NH3+ were able to escape vesicular (phagosome) entrapment by translocating directly into the cytoplasm.Carbon nanotubes (CNTs) are being investigated for a variety of biomedical applications. Despite numerous studies, the pathways by which carbon nanotubes enter cells and their subsequent intracellular trafficking and distribution remain poorly determined. Here, we use 3-D electron tomography techniques that offer optimum enhancement of contrast between carbon nanotubes and the plasma membrane to investigate the mechanisms involved in the cellular uptake of shortened, functionalised multi-walled carbon nanotubes (MWNT-NH3+). Both human lung epithelial (A549) cells, that are almost incapable of phagocytosis and primary macrophages, capable of extremely efficient phagocytosis, were used. We observed

  9. Electronic structure and local magnetism of 3d-5d impurity substituted CeFe2

    NASA Astrophysics Data System (ADS)

    Das, Rakesh; Das, G. P.; Srivastava, S. K.

    2016-04-01

    We present here a systematic first-principles study of electronic structure and local magnetic properties of Ce[Fe0.75M0.25]2 compounds, where M is a 3d, 4d or 5d transition or post-transition element, using the generalized gradient approximation of the density functional theory. The d-f band hybridizations existing in CeFe2 get modified by the impurity M in an orderly manner across a period for each impurity series: the hybridization is strongest for the Mn group impurity in the period and gets diminished on either side of it. The weakening of the d-f hybridization strength is also associated with a relative localization of the Ce 4f states with respect to the delocalized 4f states in CeFe2. The above effects are most prominent for 3d impurity series, while for 4d and 5d impurities, the hybridizations and relocalizations are relatively weak due primarily to the relatively extended nature of 4d and 5d wavefunctions. The Ce local moment is found to decrease from the CeFe2 value in proportion to the strength of relocalization, thus following almost the same orderly trend as obeyed by the d-f hybridization. Further, depending on the way the spin-up and spin-down densities of states of an impurity shift relative to the Fermi energy, the impurity local moments are highest for Mn or Fe group, reduce on either side, become zero for Ni to Ga, and are small but negative for V and Ti. The Ce hyperfine field is found to follow the M local moment in a linear fashion, and vice-versa.

  10. MO-H-19A-03: Patient Specific Bolus with 3D Printing Technology for Electron Radiotherapy

    SciTech Connect

    Zou, W; Swann, B; Siderits, R; McKenna, M; Khan, A; Yue, N; Zhang, M; Fisher, T

    2014-06-15

    Purpose: Bolus is widely used in electron radiotherapy to achieve desired dose distribution. 3D printing technologies provide clinicians with easy access to fabricate patient specific bolus accommodating patient body surface irregularities and tissue inhomogeneity. This study presents the design and the clinical workflow of 3D printed bolus for patient electron therapy in our clinic. Methods: Patient simulation CT images free of bolus were exported from treatment planning system (TPS) to an in-house developed software package. Bolus with known material properties was designed in the software package and then exported back to the TPS as a structure. Dose calculation was carried out to examine the coverage of the target. After satisfying dose distribution was achieved, the bolus structure was transferred in Standard Tessellation Language (STL) file format for the 3D printer to generate the machine codes for printing. Upon receiving printed bolus, a quick quality assurance was performed with patient resimulated with bolus in place to verify the bolus dosimetric property before treatment started. Results: A patient specific bolus for electron radiotherapy was designed and fabricated in Form 1 3D printer with methacrylate photopolymer resin. Satisfying dose distribution was achieved in patient with bolus setup. Treatment was successfully finished for one patient with the 3D printed bolus. Conclusion: The electron bolus fabrication with 3D printing technology was successfully implemented in clinic practice.

  11. Potential energy curves and electronic structure of 3d transition metal hydrides and their cations.

    PubMed

    Goel, Satyender; Masunov, Artëm E

    2008-12-07

    We investigate gas-phase neutral and cationic hydrides formed by 3d transition metals from Sc to Cu with density functional theory (DFT) methods. The performance of two exchange-correlation functionals, Boese-Martin for kinetics (BMK) and Tao-Perdew-Staroverov-Scuseria (TPSS), in predicting bond lengths and energetics, electronic structures, dipole moments, and ionization potentials is evaluated in comparison with available experimental data. To ensure a unique self-consistent field (SCF) solution, we use stability analysis, Fermi smearing, and continuity analysis of the potential energy curves. Broken-symmetry approach was adapted in order to get the qualitatively correct description of the bond dissociation. We found that on average BMK predicted values of dissociation energies and ionization potentials are closer to experiment than those obtained with high level wave function theory methods. This agreement deteriorates quickly when the fraction of the Hartree-Fock exchange in DFT functional is decreased. Natural bond orbital (NBO) population analysis was used to describe the details of chemical bonding in the systems studied. The multireference character in the wave function description of the hydrides is reproduced in broken-symmetry DFT description, as evidenced by NBO analysis. We also propose a new scheme to correct for spin contamination arising in broken-symmetry DFT approach. Unlike conventional schemes, our spin correction is introduced for each spin-polarized electron pair individually and therefore is expected to yield more accurate energy values. We derive an expression to extract the energy of the pure singlet state from the energy of the broken-symmetry DFT description of the low spin state and the energies of the high spin states (pentuplet and two spin-contaminated triplets in the case of two spin-polarized electron pairs). The high spin states are build with canonical natural orbitals and do not require SCF convergence.

  12. Crystal growth and electronic properties of a 3D Rashba material, BiTeI, with adjusted carrier concentrations.

    PubMed

    Kanou, Manabu; Sasagawa, Takao

    2013-04-03

    3D Rashba materials can be a leading player in spin-related novel phenomena, ranging from the metallic extreme (unconventional superconductivity) to the transport intermediate (spin Hall effects) to the novel insulating variant (3D topological insulating states). As the essential backbone for both fundamental and applied research of such a 3D Rashba material, this study established the growth of sizeable single crystals of a candidate compound BiTeI with adjusted carrier concentrations. Three techniques (standard vertical Bridgman, modified horizontal Bridgman, and vapour transport) were employed, and BiTeI crystals (>1 × 1 × 0.2 mm(3)) with fundamentally different electronic states from metallic to insulating were successfully grown by the chosen technique. The 3D Rashba electronic states, including the Fermi surface topology, for the corresponding carrier concentrations of the obtained BiTeI crystals were revealed by relativistic first-principles calculations.

  13. Using low-contrast negative-tone PMMA at cryogenic temperatures for 3D electron beam lithography.

    PubMed

    Schnauber, Peter; Schmidt, Ronny; Kaganskiy, Arsenty; Heuser, Tobias; Gschrey, Manuel; Rodt, Sven; Reitzenstein, Stephan

    2016-05-13

    We report on a 3D electron beam lithography (EBL) technique using polymethyl methacrylate (PMMA) in the negative-tone regime as a resist. First, we briefly demonstrate 3D EBL at room temperature. Then we concentrate on cryogenic temperatures where PMMA exhibits a low contrast, which allows for straightforward patterning of 3D nano- and microstructures. However, conventional EBL patterning at cryogenic temperatures is found to cause severe damage to the microstructures. Through an extensive study of lithography parameters, exposure techniques, and processing steps we deduce a hypothesis for the cryogenic PMMA's structural evolution under electron beam irradiation that explains the damage. In accordance with this hypothesis, a two step lithography technique involving a wide-area pre-exposure dose slightly smaller than the onset dose is applied. It enables us to demonstrate a >95% process yield for the low-temperature fabrication of 3D microstructures.

  14. X-Ray-Diffraction Tests Of Irradiated Electronic Devices: II

    NASA Technical Reports Server (NTRS)

    Shaw, David C.; Lowry, Lynn E.; Barnes, Charles E.

    1993-01-01

    Report describes research on use of x-ray diffraction to measure stresses in metal conductors of complementary metal oxide/semiconductor (CMOS) integrated circuits exposed to ionizing radiation. Expanding upon report summarized in "X-Ray-Diffraction Tests Of Irradiated Electronic Devices: I" (NPO-18803), presenting data further suggesting relationship between electrical performances of circuits and stresses and strains in metal conductors.

  15. Relativistic electron diffraction at the UCLA Pegasus photoinjector laboratory.

    PubMed

    Musumeci, P; Moody, J T; Scoby, C M

    2008-10-01

    Electron diffraction holds the promise to yield real-time resolution of atomic motion in an easily accessible environment like a university laboratory at a fraction of the cost of fourth-generation X-ray sources. Currently the limit in time-resolution for conventional electron diffraction is set by how short an electron pulse can be made. A very promising solution to maintain the highest possible beam intensity without excessive pulse broadening from space charge effects is to increase the electron energy to the MeV level where relativistic effects significantly reduce the space charge forces. Rf photoinjectors can in principle deliver up to 10(7)-10(8) electrons packed in bunches of approximately 100-fs length, allowing an unprecedented time resolution and enabling the study of irreversible phenomena by single-shot diffraction patterns. The use of rf photoinjectors as sources for ultrafast electron diffraction has been recently at the center of various theoretical and experimental studies. The UCLA Pegasus laboratory, commissioned in early 2007 as an advanced photoinjector facility, is the only operating system in the country, which has recently demonstrated electron diffraction using a relativistic beam from an rf photoinjector. Due to the use of a state-of-the-art ultrashort photoinjector driver laser system, the beam has been measured to be sub-100-fs long, at least a factor of 5 better than what measured in previous relativistic electron diffraction setups. Moreover, diffraction patterns from various metal targets (titanium and aluminum) have been obtained using the Pegasus beam. One of the main laboratory goals in the near future is to fully develop the rf photoinjector-based ultrafast electron diffraction technique with particular attention to the optimization of the working point of the photoinjector in a low-charge ultrashort pulse regime, and to the development of suitable beam diagnostics.

  16. Electron impact excitation of Fe-peak elements: forbidden transitions in the 3d5 manifold of Fe IV

    NASA Astrophysics Data System (ADS)

    McLaughlin, B. M.; Hibbert, A.; Scott, M. P.; Noble, C. J.; Burke, V. M.; Burke, P. G.

    2005-06-01

    Electron-impact excitation collision strengths of the Fe-peak element Fe IV are calculated in the close-coupling approximation using the R-matrix suite of codes PRMAT designed for parallel processors. One hundred and eight LS-coupled states arising from the 3d5, 3d44s and 3d44p configurations of Fe IV, are retained in the present calculations. Detailed multi-configuration interaction target wavefunctions are used with the aid of 3p2 → 3d2 electron promotions and a \\rm 4\\overline{d} correlation orbital in the present calculations. Effective collision strengths for optically forbidden transitions, which are extremely important in the analysis of lines in the Fe IV spectra, are obtained by averaging the electron collision strengths for a wide range of incident electron energies, over a Maxwellian distribution of velocities. Results are presented for electron temperatures (Te in Kelvin) in the range 3.3 <= Log Te<= 6.0 applicable to many laboratory and astrophysical plasmas for transitions within the 3d5 manifold. The present results compared to previous investigations provide improved results for important lines in the Fe IV spectrum.

  17. Single particle cryo-electron microscopy and 3-D reconstruction of viruses.

    PubMed

    Guo, Fei; Jiang, Wen

    2014-01-01

    With fast progresses in instrumentation, image processing algorithms, and computational resources, single particle electron cryo-microscopy (cryo-EM) 3-D reconstruction of icosahedral viruses has now reached near-atomic resolutions (3-4 Å). With comparable resolutions and more predictable outcomes, cryo-EM is now considered a preferred method over X-ray crystallography for determination of atomic structure of icosahedral viruses. At near-atomic resolutions, all-atom models or backbone models can be reliably built that allow residue level understanding of viral assembly and conformational changes among different stages of viral life cycle. With the developments of asymmetric reconstruction, it is now possible to visualize the complete structure of a complex virus with not only its icosahedral shell but also its multiple non-icosahedral structural features. In this chapter, we will describe single particle cryo-EM experimental and computational procedures for both near-atomic resolution reconstruction of icosahedral viruses and asymmetric reconstruction of viruses with both icosahedral and non-icosahedral structure components. Procedures for rigorous validation of the reconstructions and resolution evaluations using truly independent de novo initial models and refinements are also introduced.

  18. A resource from 3D electron microscopy of hippocampal neuropil for user training and tool development

    PubMed Central

    Harris, Kristen M.; Spacek, Josef; Bell, Maria Elizabeth; Parker, Patrick H.; Lindsey, Laurence F.; Baden, Alexander D.; Vogelstein, Joshua T.; Burns, Randal

    2015-01-01

    Resurgent interest in synaptic circuitry and plasticity has emphasized the importance of 3D reconstruction from serial section electron microscopy (3DEM). Three volumes of hippocampal CA1 neuropil from adult rat were imaged at X-Y resolution of ~2 nm on serial sections of ~50–60 nm thickness. These are the first densely reconstructed hippocampal volumes. All axons, dendrites, glia, and synapses were reconstructed in a cube (~10 μm3) surrounding a large dendritic spine, a cylinder (~43 μm3) surrounding an oblique dendritic segment (3.4 μm long), and a parallelepiped (~178 μm3) surrounding an apical dendritic segment (4.9 μm long). The data provide standards for identifying ultrastructural objects in 3DEM, realistic reconstructions for modeling biophysical properties of synaptic transmission, and a test bed for enhancing reconstruction tools. Representative synapses are quantified from varying section planes, and microtubules, polyribosomes, smooth endoplasmic reticulum, and endosomes are identified and reconstructed in a subset of dendrites. The original images, traces, and Reconstruct software and files are freely available and visualized at the Open Connectome Project (Data Citation 1). PMID:26347348

  19. Single Particle Cryo-electron Microscopy and 3-D Reconstruction of Viruses

    PubMed Central

    Guo, Fei; Jiang, Wen

    2014-01-01

    With fast progresses in instrumentation, image processing algorithms, and computational resources, single particle electron cryo-microscopy (cryo-EM) 3-D reconstruction of icosahedral viruses has now reached near-atomic resolutions (3–4 Å). With comparable resolutions and more predictable outcomes, cryo-EM is now considered a preferred method over X-ray crystallography for determination of atomic structure of icosahedral viruses. At near-atomic resolutions, all-atom models or backbone models can be reliably built that allow residue level understanding of viral assembly and conformational changes among different stages of viral life cycle. With the developments of asymmetric reconstruction, it is now possible to visualize the complete structure of a complex virus with not only its icosahedral shell but also its multiple non-icosahedral structural features. In this chapter, we will describe single particle cryo-EM experimental and computational procedures for both near-atomic resolution reconstruction of icosahedral viruses and asymmetric reconstruction of viruses with both icosahedral and non-icosahedral structure components. Procedures for rigorous validation of the reconstructions and resolution evaluations using truly independent de novo initial models and refinements are also introduced. PMID:24357374

  20. Acoustic backing in 3-D integration of CMUT with front-end electronics.

    PubMed

    Berg, Sigrid; Rønnekleiv, Arne

    2012-07-01

    Capacitive micromachined ultrasonic transducers (CMUTs) have shown promising qualities for medical imaging. However, there are still some problems to be investigated, and some challenges to overcome. Acoustic backing is necessary to prevent SAWs excited in the surface of the silicon substrate from affecting the transmit pattern from the array. In addition, echoes resulting from bulk waves in the substrate must be removed. There is growing interest in integrating electronic circuits to do some of the beamforming directly below the transducer array. This may be easier to achieve for CMUTs than for traditional piezoelectric transducers. We will present simulations showing that the thickness of the silicon substrate and thicknesses and acoustic properties of the bonding material must be considered, especially when designing highfrequency transducers. Through simulations, we compare the acoustic properties of 3-D stacks bonded with three different bonding techniques; solid-liquid interdiffusion (SLID) bonding, direct fusion bonding, and anisotropic conductive adhesives (ACA). We look at a CMUT array with a center frequency of 30 MHz and three silicon wafers underneath, having a total silicon thickness of 100 μm. We find that fusion bonding is most beneficial if we want to prevent surface waves from damaging the array response, but SLID and ACA are also promising if bonding layer thicknesses can be reduced.

  1. Signal-to-noise in femtosecond electron diffraction.

    PubMed

    Kealhofer, Catherine; Lahme, Stefan; Urban, Theresa; Baum, Peter

    2015-12-01

    Pump-probe electron diffraction can directly record atomic-scale motion within molecules or materials. However, the available current in femtosecond experiments is limited, making it challenging to reach the sensitivity required for detecting the fastest structural dynamics, which are encoded in time-dependent diffraction intensities. Here we present a unified analysis of signal-to-noise for an ultrafast electron diffraction apparatus. We characterize the noise of realistic ultrafast electron sources and detectors, test the performance on crystalline and polycrystalline samples and discuss practical approaches for improving measurement sensitivity. The analysis is found sufficient to predict the achievable signal-to-noise ratio in pump-probe electron diffraction before actually starting an investigation.

  2. Ultrafast Electron Diffraction: How It Works

    SciTech Connect

    2015-08-05

    A new technology at SLAC uses high-energy electrons to unravel motions in materials that are faster than a tenth of a trillionth of a second, opening up new research opportunities in ultrafast science.

  3. Ultrafast Electron Diffraction: How It Works

    ScienceCinema

    None

    2016-07-12

    A new technology at SLAC uses high-energy electrons to unravel motions in materials that are faster than a tenth of a trillionth of a second, opening up new research opportunities in ultrafast science.

  4. 3D printed electromagnetic transmission and electronic structures fabricated on a single platform using advanced process integration techniques

    NASA Astrophysics Data System (ADS)

    Deffenbaugh, Paul Issac

    3D printing has garnered immense attention from many fields including in-office rapid prototyping of mechanical parts, outer-space satellite replication, garage functional firearm manufacture, and NASA rocket engine component fabrication. 3D printing allows increased design flexibility in the fabrication of electronics, microwave circuits and wireless antennas and has reached a level of maturity which allows functional parts to be printed. Much more work is necessary in order to perfect the processes of 3D printed electronics especially in the area of automation. Chapter 1 shows several finished prototypes of 3D printed electronics as well as newly developed techniques in fabrication. Little is known about the RF and microwave properties and applications of the standard materials which have been developed for 3D printing. Measurement of a wide variety of materials over a broad spectrum of frequencies up to 10 GHz using a variety of well-established measurement methods is performed throughout chapter 2. Several types of high frequency RF transmission lines are fabricated and valuable model-matched data is gathered and provided in chapter 3 for future designers' use. Of particular note is a fully 3D printed stripline which was automatically fabricated in one process on one machine. Some core advantages of 3D printing RF/microwave components include rapid manufacturing of complex, dimensionally sensitive circuits (such as antennas and filters which are often iteratively tuned) and the ability to create new devices that cannot be made using standard fabrication techniques. Chapter 4 describes an exemplary fully 3D printed curved inverted-F antenna.

  5. Utilization of a 3D printer to fabricate boluses used for electron therapy of skin lesions of the eye canthi.

    PubMed

    Łukowiak, Magdalena; Jezierska, Karolina; Boehlke, Marek; Więcko, Marzena; Łukowiak, Adam; Podraza, Wojciech; Lewocki, Mirosław; Masojć, Bartłomiej; Falco, Michał

    2017-01-01

    This work describes the use of 3D printing technology to create individualized boluses for patients treated with electron beam therapy for skin lesions of the eye canthi. It aimed to demonstrate the effectiveness of 3D-printed over manually fabricated paraffin boluses. The study involved 11 patients for whom the construction of individual boluses were required. CT scans of the fabricated 3D-printed boluses and paraffin boluses were acquired and superimposed onto patient CT scans to compare their fitting, bolus homogeneity, and underlying dose distribution. To quantify the level of matching, multiple metrics were utilized. Matching Level Index (ML) values ranged from 0 to 100%, where 100% indicated a perfect fit between the reference bolus (planned in treatment planning system) and 3D-printed and paraffin bolus. The average ML (± 1 SD) of the 3D-printed boluses was 95.1 ± 2.1%, compared to 46.0 ± 10.1% for the manually fabricated paraffin bolus. Correspondingly, mean doses were closer to the prescribed doses, and dose spreads were less for the dose distributions from the 3D-printed boluses, as compared to those for the manually fabricated paraffin boluses. It was concluded that 3D-printing technology is a viable method for fabricating boluses for small eye lesions and provides boluses superior to our boluses manually fabricated from paraffin sheets.

  6. Femtosecond time-resolved MeV electron diffraction

    DOE PAGES

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; ...

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 × 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing themore » evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.« less

  7. Femtosecond time-resolved MeV electron diffraction

    SciTech Connect

    Zhu, Pengfei; Zhu, Y.; Hidaka, Y.; Wu, L.; Cao, J.; Berger, H.; Geck, J.; Kraus, R.; Pjerov, S.; Shen, Y.; Tobey, R. I.; Hill, J. P.; Wang, X. J.

    2015-06-02

    We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 × 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Lastly, our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction.

  8. Calibrating MMS Electron Drift Instrument (EDI) Ambient Electron Flux Measurements and Characterizing 3D Electric Field Signatures of Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Shuster, J. R.; Torbert, R. B.; Vaith, H.; Argall, M. R.; Li, G.; Chen, L. J.; Ergun, R. E.; Lindqvist, P. A.; Marklund, G. T.; Khotyaintsev, Y. V.; Russell, C. T.; Magnes, W.; Le Contel, O.; Pollock, C. J.; Giles, B. L.

    2015-12-01

    The electron drift instruments (EDIs) onboard each MMS spacecraft are designed with large geometric factors (~0.01cm2 str) to facilitate detection of weak (~100 nA) electron beams fired and received by the two gun-detector units (GDUs) when EDI is in its "electric field mode" to determine the local electric and magnetic fields. A consequence of the large geometric factor is that "ambient mode" electron flux measurements (500 eV electrons having 0°, 90°, or 180° pitch angle) can vary depending on the orientation of the EDI instrument with respect to the magnetic field, a nonphysical effect that requires a correction. Here, we present determinations of the θ- and ø-dependent correction factors for the eight EDI GDUs, where θ (ø) is the polar (azimuthal) angle between the GDU symmetry axis and the local magnetic field direction, and compare the corrected fluxes with those measured by the fast plasma instrument (FPI). Using these corrected, high time resolution (~1,000 samples per second) ambient electron fluxes, combined with the unprecedentedly high resolution 3D electric field measurements taken by the spin-plane and axial double probes (SDP and ADP), we are equipped to accurately detect electron-scale current layers and electric field waves associated with the non-Maxwellian (anisotropic and agyrotropic) particle distribution functions predicted to exist in the reconnection diffusion region. We compare initial observations of the diffusion region with distributions and wave analysis from PIC simulations of asymmetric reconnection applicable for modeling reconnection at the Earth's magnetopause, where MMS will begin Science Phase 1 as of September 1, 2015.

  9. Digital electron diffraction – seeing the whole picture

    PubMed Central

    Beanland, Richard; Thomas, Paul J.; Woodward, David I.; Thomas, Pamela A.; Roemer, Rudolf A.

    2013-01-01

    The advantages of convergent-beam electron diffraction for symmetry determination at the scale of a few nm are well known. In practice, the approach is often limited due to the restriction on the angular range of the electron beam imposed by the small Bragg angle for high-energy electron diffraction, i.e. a large convergence angle of the incident beam results in overlapping information in the diffraction pattern. Techniques have been generally available since the 1980s which overcome this restriction for individual diffracted beams, by making a compromise between illuminated area and beam convergence. Here a simple technique is described which overcomes all of these problems using computer control, giving electron diffraction data over a large angular range for many diffracted beams from the volume given by a focused electron beam (typically a few nm or less). The increase in the amount of information significantly improves the ease of interpretation and widens the applicability of the technique, particularly for thin materials or those with larger lattice parameters. PMID:23778099

  10. Teaching electron diffraction and imaging of macromolecules.

    PubMed Central

    Chiu, W; Schmid, M F; Prasad, B V

    1993-01-01

    Electron microscopic analysis can be used to determine the three-dimensional structures of macromolecules at resolutions ranging between 3 and 30 A. It differs from nuclear magnetic resonance spectroscopy or x-ray crystallography in that it allows an object's Coulomb potential functions to be determined directly from images and can be used to study relatively complex macromolecular assemblies in a crystalline or noncrystalline state. Electron imaging already has provided valuable structural information about various biological systems, including membrane proteins, protein-nucleic acid complexes, contractile and motile protein assemblies, viruses, and transport complexes for ions or macromolecules. This article, organized as a series of lectures, presents the biophysical principles of three-dimensional analysis of objects possessing different symmetries. Images FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 FIGURE 13 FIGURE 17 FIGURE 18 PMID:8324196

  11. Multiple scattering theory of electron diffraction

    NASA Astrophysics Data System (ADS)

    Pendry, J. B.

    1994-01-01

    In the early 1960's surface science set itself some fundamental goals: to make a quantitative science out of surface crystallography; to understand the nature of electronic structure and bonding at surfaces; and to enhance the tools available for study of surfaces. The effort has very much been a collective one, reflected in the wide authorship of the present volume. Here I contribute to the picture my personal perspective on developments in the past 30 years of surface science, and describe some of the highlights in my own research and that of my close colleagues.

  12. Structure refinement using precession electron diffraction tomography and dynamical diffraction: theory and implementation.

    PubMed

    Palatinus, Lukáš; Petříček, Václav; Corrêa, Cinthia Antunes

    2015-03-01

    Accurate structure refinement from electron-diffraction data is not possible without taking the dynamical-diffraction effects into account. A complete three-dimensional model of the structure can be obtained only from a sufficiently complete three-dimensional data set. In this work a method is presented for crystal structure refinement from the data obtained by electron diffraction tomography, possibly combined with precession electron diffraction. The principle of the method is identical to that used in X-ray crystallography: data are collected in a series of small tilt steps around a rotation axis, then intensities are integrated and the structure is optimized by least-squares refinement against the integrated intensities. In the dynamical theory of diffraction, the reflection intensities exhibit a complicated relationship to the orientation and thickness of the crystal as well as to structure factors of other reflections. This complication requires the introduction of several special parameters in the procedure. The method was implemented in the freely available crystallographic computing system Jana2006.

  13. Excitation of phonons in medium-energy electron diffraction

    NASA Astrophysics Data System (ADS)

    Alvarez, M. A. Vicente; Ascolani, H.; Zampieri, G.

    1996-03-01

    The ``elastic'' backscattering of electrons from crystalline surfaces presents two regimes: a low-energy regime, in which the characteristic low-energy electron diffraction (LEED) pattern is observed, and a medium-energy regime, in which the diffraction pattern is similar to those observed in x-ray photoemission diffraction (XPD) and Auger electron diffraction (AED) experiments. We present a model for the electron scattering which, including the vibrational degrees of freedom of the crystal, contains both regimes and explains the passage from one regime to the other. Our model is based on a separation of the electron and atomic motions (adiabatic approximation) and on a cluster-type formulation of the multiple scattering of the electron. The inelastic scattering events (excitation and/or absorption of phonons) are treated as coherent processes and no break of the phase relation between the incident and the exit paths of the electron is assumed. The LEED and the medium-energy electron diffraction regimes appear naturally in this model as the limit cases of completely elastic scattering and of inelastic scattering with excitation and/or absorption of multiple phonons. Intensity patterns calculated with this model are in very good agreement with recent experiments of electron scattering on Cu(001) at low and medium energies. We show that there is a correspondence between the type of intensity pattern and the mean number of phonons excited and/or absorbed during the scattering: a LEED-like pattern is observed when this mean number is less than 2, LEED-like and XPD/AED-like features coexist when this number is 3-4, and a XPD/AED-like pattern is observed when this number is greater than 5-6.

  14. 3D electron density imaging using single scattered x rays with application to breast CT and mammographic screening

    NASA Astrophysics Data System (ADS)

    van Uytven, Eric Peter

    Screening mammography is the current standard in detecting breast cancer. However, its fundamental disadvantage is that it projects a 3D object into a 2D image. Small lesions are difficult to detect when superimposed over layers of normal tissue. Commercial Computed Tomography (CT) produces a true 3D image yet has a limited role in mammography due to relatively low resolution and contrast. With the intent of enhancing mammography and breast CT, we have developed an algorithm which can produce 3D electron density images using a single projection. Imaging an object with x rays produces a characteristic scattered photon spectrum at the detector plane. A known incident beam spectrum, beam shape, and arbitrary 3D matrix of electron density values enable a theoretical scattered photon distribution to be calculated. An iterative minimization algorithm is used to make changes to the electron density voxel matrix to reduce regular differences between the theoretical and the experimentally measured distributions. The object is characterized by the converged electron density image. This technique has been validated in simulation using data produced by the EGSnrc Monte Carlo code system. At both mammographic and CT energies, a scanning polychromatic pencil beam was used to image breast tissue phantoms containing lesion-like inhomogeneities. The resulting Monte Carlo data is processed using a Nelder-Mead iterative algorithm (MATLAB) to produce the 3D matrix of electron density values. Resulting images have confirmed the ability of the algorithm to detect various 1x1x2.5 mm3 lesions with calcification content as low as 0.5% (p<0.005) at a dose comparable to mammography.

  15. Influence of 3 d metal atoms on the geometry, electronic structure, and stability of a Mg13H26 cluster

    NASA Astrophysics Data System (ADS)

    Shelyapina, M. G.; Siretskiy, M. Yu.

    2010-09-01

    This paper reports on the results of the theoretical investigation of magnesium hydride nanoclusters doped with 3 d metals (from Sc to Zn). The influence of transition metal atoms on the geometry, electronic structure, and energy characteristics of the clusters has been analyzed. The results of the performed calculations have been compared with the available experimental data. This comparison has made it possible to predict which 3 d transition elements can serve as the most effective catalysts for the improvement of the thermodynamic characteristics of MgH2.

  16. Auger electron diffraction study of the growth of Fe(001) films on ZnSe(001)

    NASA Astrophysics Data System (ADS)

    Jonker, B. T.; Prinz, G. A.

    1991-03-01

    The growth of Fe films on ZnSe(001) epilayers and bulk GaAs(001) substrates has been studied to determine the mode of film growth, the formation of the interface, and the structure of the overlayer at the 1-10 monolayer level. Auger electron diffraction (AED), x-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction data are obtained for incremental deposition of the Fe(001) overlayer. The coverage dependence of the AED forward scattering peaks reveals a predominantly layer-by-layer mode of film growth at 175 °C on ZnSe, while a more three-dimensional growth mode occurs on the oxide-desorbed GaAs(001) substrate. XPS studies of the semiconductor 3d levels indicate that the Fe/ZnSe interface is less reactive than the Fe/GaAs interface.

  17. A method for 3D electron density imaging using single scattered x-rays with application to mammographic screening.

    PubMed

    Van Uytven, Eric; Pistorius, Stephen; Gordon, Richard

    2008-10-07

    Screening mammography is the current standard in detecting breast cancer. However, its fundamental disadvantage is that it projects a 3D object into a 2D image. Small lesions are difficult to detect when superimposed over layers of normal, heterogeneous tissue. In this work, we examine the potential of single scattered photon electron density imaging in a mammographic environment. Simulating a low-energy (<20 keV) scanning pencil beam, we have developed an algorithm capable of producing 3D electron density images from a single projection. We have tested the algorithm by imaging parts of a simulated mammographic accreditation phantom containing lesions of various sizes. The results indicate that the group of imaged lesions differ significantly from background breast tissue (p<0.005), confirming that electron density imaging may be a useful diagnostic test for the presence of breast cancer.

  18. 3 d -electron Heisenberg pyrochlore Mn2Sb2O7

    NASA Astrophysics Data System (ADS)

    Peets, Darren C.; Sim, Hasung; Avdeev, Maxim; Park, Je-Geun

    2016-11-01

    In frustrated magnetic systems, geometric constraints or the competition among interactions introduce extre-mely high degeneracy and prevent the system from readily selecting a low-temperature ground state. The most frustrated known spin arrangement is on the pyrochlore lattice, but nearly all magnetic pyrochlores have unquenched orbital angular momenta, constraining the spin directions through spin-orbit coupling. Pyrochlore Mn2Sb2O7 is an extremely rare Heisenberg pyrochlore system with directionally unconstrained spins and low chemical disorder. We show that it undergoes a spin-glass transition at 5.5 K, which is suppressed by disorder arising from Mn vacancies, indicating this ground state to be a direct consequence of the spins' interactions. The striking similarities to 3 d transition-metal pyrochlores with unquenched angular momenta suggests that the low spin-orbit coupling in the 3 d block makes Heisenberg pyrochlores far more accessible than previously imagined.

  19. Application of Electron Backscatter Diffraction to Phase Identification

    SciTech Connect

    El-Dasher, B S; Deal, A

    2008-07-16

    The identification of crystalline phases in solids requires knowledge of two microstructural properties: crystallographic structure and chemical composition. Traditionally, this has been accomplished using X-ray diffraction techniques where the measured crystallographic information, in combination with separate chemical composition measurements for specimens of unknown pedigrees, is used to deduce the unknown phases. With the latest microstructural analysis tools for scanning electron microscopes, both the crystallography and composition can be determined in a single analysis utilizing electron backscatter diffraction and energy dispersive spectroscopy, respectively. In this chapter, we discuss the approach required to perform these experiments, elucidate the benefits and limitations of this technique, and detail via case studies how composition, crystallography, and diffraction contrast can be used as phase discriminators.

  20. Highlighting material structure with transmission electron diffraction correlation coefficient maps.

    PubMed

    Kiss, Ákos K; Rauch, Edgar F; Lábár, János L

    2016-04-01

    Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast.

  1. Development of splitting convergent beam electron diffraction (SCBED).

    PubMed

    Houdellier, Florent; Röder, Falk; Snoeck, Etienne

    2015-12-01

    Using a combination of condenser electrostatic biprism with dedicated electron optic conditions for sample illumination, we were able to split a convergent beam electron probe focused on the sample in two half focused probes without introducing any tilt between them. As a consequence, a combined convergent beam electron diffraction pattern is obtained in the back focal plane of the objective lens arising from two different sample areas, which could be analyzed in a single pattern. This splitting convergent beam electron diffraction (SCBED) pattern has been tested first on a well-characterized test sample of Si/SiGe multilayers epitaxially grown on a Si substrate. The SCBED pattern contains information from the strained area, which exhibits HOLZ lines broadening induced by surface relaxation, with fine HOLZ lines observed in the unstrained reference part of the sample. These patterns have been analyzed quantitatively using both parts of the SCBED transmitted disk. The fine HOLZ line positions are used to determine the precise acceleration voltage of the microscope while the perturbed HOLZ rocking curves in the stained area are compared to dynamical simulated ones. The combination of these two information leads to a precise evaluation of the sample strain state. Finally, several SCBED setups are proposed to tackle fundamental physics questions as well as applied materials science ones and demonstrate how SCBED has the potential to greatly expand the range of applications of electron diffraction and electron holography.

  2. All-3 d Electron-Hole Bilayers in CrN /MgO (111 ) Multilayers for Thermoelectric Applications

    NASA Astrophysics Data System (ADS)

    Botana, Antia S.; Pardo, Victor; Pickett, Warren E.

    2017-02-01

    CrN /MgO (111 ) multilayers modeled via ab initio calculations give rise to nanoscale, scalable, spatially separated two-dimensional electron and hole gases, each confined to its own CrN interface. Because of the Cr 3 d3 configuration, both electron and hole gases are based on correlated transition-metal layers involving bands of 3 d character. Transport calculations predict each subsystem will have a large thermopower, on the order of 250 μ V /K at room temperature. These heterostructures combine a large thermoelectric efficiency with scalable nanoscale conducting sheets; for example, operating at a temperature difference of 50 K, 40 bilayers could produce a 1-V voltage with a film thickness of 100 nm.

  3. Web-based visualisation and analysis of 3D electron-microscopy data from EMDB and PDB☆

    PubMed Central

    Lagerstedt, Ingvar; Moore, William J.; Patwardhan, Ardan; Sanz-García, Eduardo; Best, Christoph; Swedlow, Jason R.; Kleywegt, Gerard J.

    2013-01-01

    The Protein Data Bank in Europe (PDBe) has developed web-based tools for the visualisation and analysis of 3D electron microscopy (3DEM) structures in the Electron Microscopy Data Bank (EMDB) and Protein Data Bank (PDB). The tools include: (1) a volume viewer for 3D visualisation of maps, tomograms and models, (2) a slice viewer for inspecting 2D slices of tomographic reconstructions, and (3) visual analysis pages to facilitate analysis and validation of maps, tomograms and models. These tools were designed to help non-experts and experts alike to get some insight into the content and assess the quality of 3DEM structures in EMDB and PDB without the need to install specialised software or to download large amounts of data from these archives. The technical challenges encountered in developing these tools, as well as the more general considerations when making archived data available to the user community through a web interface, are discussed. PMID:24113529

  4. Web-based visualisation and analysis of 3D electron-microscopy data from EMDB and PDB.

    PubMed

    Lagerstedt, Ingvar; Moore, William J; Patwardhan, Ardan; Sanz-García, Eduardo; Best, Christoph; Swedlow, Jason R; Kleywegt, Gerard J

    2013-11-01

    The Protein Data Bank in Europe (PDBe) has developed web-based tools for the visualisation and analysis of 3D electron microscopy (3DEM) structures in the Electron Microscopy Data Bank (EMDB) and Protein Data Bank (PDB). The tools include: (1) a volume viewer for 3D visualisation of maps, tomograms and models, (2) a slice viewer for inspecting 2D slices of tomographic reconstructions, and (3) visual analysis pages to facilitate analysis and validation of maps, tomograms and models. These tools were designed to help non-experts and experts alike to get some insight into the content and assess the quality of 3DEM structures in EMDB and PDB without the need to install specialised software or to download large amounts of data from these archives. The technical challenges encountered in developing these tools, as well as the more general considerations when making archived data available to the user community through a web interface, are discussed.

  5. Electron diffraction of CBr4 in superfluid helium droplets: A step towards single molecule diffraction.

    PubMed

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-07-21

    We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr4 as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr4 similar to those of gas phase molecules can be observed. The experimental data from CBr4 doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules.

  6. Electron diffraction of CBr4 in superfluid helium droplets: A step towards single molecule diffraction

    NASA Astrophysics Data System (ADS)

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-07-01

    We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr4 as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr4 similar to those of gas phase molecules can be observed. The experimental data from CBr4 doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules.

  7. Visualization of Mesenchymal Stromal Cells in 2Dand 3D-Cultures by Scanning Electron Microscopy with Lanthanide Contrasting.

    PubMed

    Novikov, I A; Vakhrushev, I V; Antonov, E N; Yarygin, K N; Subbot, A M

    2017-02-01

    Mesenchymal stromal cells from deciduous teeth in 2D- and 3D-cultures on culture plastic, silicate glass, porous polystyrene, and experimental polylactoglycolide matrices were visualized by scanning electron microscopy with lanthanide contrasting. Supravital staining of cell cultures with a lanthanide-based dye (neodymium chloride) preserved normal cell morphology and allowed assessment of the matrix properties of the carriers. The developed approach can be used for the development of biomaterials for tissue engineering.

  8. Study of materials and machines for 3D printed large-scale, flexible electronic structures using fused deposition modeling

    NASA Astrophysics Data System (ADS)

    Hwang, Seyeon

    The 3 dimensional printing (3DP), called to additive manufacturing (AM) or rapid prototyping (RP), is emerged to revolutionize manufacturing and completely transform how products are designed and fabricated. A great deal of research activities have been carried out to apply this new technology to a variety of fields. In spite of many endeavors, much more research is still required to perfect the processes of the 3D printing techniques especially in the area of the large-scale additive manufacturing and flexible printed electronics. The principles of various 3D printing processes are briefly outlined in the Introduction Section. New types of thermoplastic polymer composites aiming to specified functional applications are also introduced in this section. Chapter 2 shows studies about the metal/polymer composite filaments for fused deposition modeling (FDM) process. Various metal particles, copper and iron particles, are added into thermoplastics polymer matrices as the reinforcement filler. The thermo-mechanical properties, such as thermal conductivity, hardness, tensile strength, and fracture mechanism, of composites are tested to figure out the effects of metal fillers on 3D printed composite structures for the large-scale printing process. In Chapter 3, carbon/polymer composite filaments are developed by a simple mechanical blending process with an aim of fabricating the flexible 3D printed electronics as a single structure. Various types of carbon particles consisting of multi-wall carbon nanotube (MWCNT), conductive carbon black (CCB), and graphite are used as the conductive fillers to provide the thermoplastic polyurethane (TPU) with improved electrical conductivity. The mechanical behavior and conduction mechanisms of the developed composite materials are observed in terms of the loading amount of carbon fillers in this section. Finally, the prototype flexible electronics are modeled and manufactured by the FDM process using Carbon/TPU composite filaments and

  9. Enhanced Electron Heating and Mixing in a 3D Kinetic Simulation for MMS Magnetopause Crossings with Weak Guide Fields

    NASA Astrophysics Data System (ADS)

    Le, Ari; Daughton, William; Chen, Li-Jen; Egedal, Jan

    2016-10-01

    We present a 3D kinetic simulation of asymmetric reconnection with plasma parameters matching the MMS magetopause diffusion region crossing reported by Burch et al. (Science 2016). The simulation was performed with the code VPIC on LANL's Trinity machine, which enabled relatively high grid resolution and numerical particle numbers to resolve the electron diffusion region dynamics. The simulation not only reproduces the reported crescent distributions but also appears to account for new features observed by MMS in other diffusion region events with weak guide fields. Compared to a 2D simulation with the same plasma parameters, drift turbulence in the 3D simulation substantially enhances the mixing and parallel heating of electrons on the magnetosphere side. This modifies the reconnection rate inferred from a recently introduced electron mixing diagnostic. To the magnetosphere side of the in-plane magnetic null, the parallel electric field exhibits a bipolar structure with polarities opposite to the large-scale parallel electric field. The 3D structure of the X line and the particle signature of the inverted bipolar parallel electric field have been observed by MMS.

  10. Simulation of the 3-D Evolution of Electron Scale Magnetic Reconnection - Motivated by Laboratory Experiments Predictions for MMS

    NASA Astrophysics Data System (ADS)

    Buechner, J.; Jain, N.; Sharma, A.

    2013-12-01

    The four s/c of the Magnetospheric Multiscale (MMS) mission, to be launched in 2014, will use the Earth's magnetosphere as a laboratory to study the microphysics of three fundamental plasma processes. One of them is magnetic reconnection, an essentially multi-scale process. While laboratory experiments and past theoretical investigations have shown that important processes necessary to understand magnetic reconnection take place at electron scales the MMS mission for the first time will be able to resolve these scales by in space observations. For the measurement strategy of MMS it is important to make specific predictions of the behavior of current sheets with a thickness of the order of the electron skin depth which play an important role in the evolution of collisionless magnetic reconnection. Since these processes are highly nonlinear and non-local numerical simulation is needed to specify the current sheet evolution. Here we present new results about the nonlinear evolution of electron-scale current sheets starting from the linear stage and using 3-D electron-magnetohydrodynamic (EMHD) simulations. The growth rates of the simulated instabilities compared well with the growth rates obtained from linear theory. Mechanisms and conditions of the formation of flux ropes and of current filamentation will be discussed in comparison with the results of fully kinetic simulations. In 3D the X- and O-point configurations of the magnetic field formed in reconnection planes alternate along the out-of-reconnection-plane direction with the wavelength of the unstable mode. In the presence of multiple reconnection sites, the out-of-plane magnetic field can develop nested structure of quadrupoles in reconnection planes, similar to the 2-D case, but now with variations in the out-of-plane direction. The structures of the electron flow and magnetic field in 3-D simulations will be compared with those in 2-D simulations to discriminate the essentially 3D features. We also discuss

  11. Biocompatible 3D Matrix with Antimicrobial Properties.

    PubMed

    Ion, Alberto; Andronescu, Ecaterina; Rădulescu, Dragoș; Rădulescu, Marius; Iordache, Florin; Vasile, Bogdan Ștefan; Surdu, Adrian Vasile; Albu, Madalina Georgiana; Maniu, Horia; Chifiriuc, Mariana Carmen; Grumezescu, Alexandru Mihai; Holban, Alina Maria

    2016-01-20

    The aim of this study was to develop, characterize and assess the biological activity of a new regenerative 3D matrix with antimicrobial properties, based on collagen (COLL), hydroxyapatite (HAp), β-cyclodextrin (β-CD) and usnic acid (UA). The prepared 3D matrix was characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Microscopy (FT-IRM), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). In vitro qualitative and quantitative analyses performed on cultured diploid cells demonstrated that the 3D matrix is biocompatible, allowing the normal development and growth of MG-63 osteoblast-like cells and exhibited an antimicrobial effect, especially on the Staphylococcus aureus strain, explained by the particular higher inhibitory activity of usnic acid (UA) against Gram positive bacterial strains. Our data strongly recommend the obtained 3D matrix to be used as a successful alternative for the fabrication of three dimensional (3D) anti-infective regeneration matrix for bone tissue engineering.

  12. Ultrafast molecular imaging by laser-induced electron diffraction

    SciTech Connect

    Peters, M.; Nguyen-Dang, T. T.; Cornaggia, C.; Saugout, S.; Charron, E.; Keller, A.; Atabek, O.

    2011-05-15

    We address the feasibility of imaging geometric and orbital structures of a polyatomic molecule on an attosecond time scale using the laser-induced electron diffraction (LIED) technique. We present numerical results for the highest molecular orbitals of the CO{sub 2} molecule excited by a near-infrared few-cycle laser pulse. The molecular geometry (bond lengths) is determined within 3% of accuracy from a diffraction pattern which also reflects the nodal properties of the initial molecular orbital. Robustness of the structure determination is discussed with respect to vibrational and rotational motions with a complete interpretation of the laser-induced mechanisms.

  13. Status report on the 'Merging' of the Electron-Cloud Code POSINST with the 3-D Accelerator PIC CODE WARP

    SciTech Connect

    Vay, J.-L.; Furman, M.A.; Azevedo, A.W.; Cohen, R.H.; Friedman, A.; Grote, D.P.; Stoltz, P.H.

    2004-04-19

    We have integrated the electron-cloud code POSINST [1] with WARP [2]--a 3-D parallel Particle-In-Cell accelerator code developed for Heavy Ion Inertial Fusion--so that the two can interoperate. Both codes are run in the same process, communicate through a Python interpreter (already used in WARP), and share certain key arrays (so far, particle positions and velocities). Currently, POSINST provides primary and secondary sources of electrons, beam bunch kicks, a particle mover, and diagnostics. WARP provides the field solvers and diagnostics. Secondary emission routines are provided by the Tech-X package CMEE.

  14. Angular distribution of Auger electrons due to 3d-shell ionization of krypton

    NASA Technical Reports Server (NTRS)

    Omidvar, K.

    1977-01-01

    Cross sections for electron impact ionization of krypton due to ejection of a 3rd shell electron have been calculated using screened hydrogenic and Hartree-Slater wave functions for target atom. While the total ionization cross sections in the two approximations are within 10% of each other, the Auger electron angular distribution, related to cross sections for specific magnetic quantum numbers of the 3rd electrons, is widely different in the two approximations. The angular distribution due to Hartree-Slater approximation is in excellent agreement with measurement. The physical reason for the discrepancies in the two approximations is explained.

  15. From Voxels to Knowledge: A Practical Guide to the Segmentation of Complex Electron Microscopy 3D-Data

    PubMed Central

    Tsai, Wen-Ting; Hassan, Ahmed; Sarkar, Purbasha; Correa, Joaquin; Metlagel, Zoltan; Jorgens, Danielle M.; Auer, Manfred

    2014-01-01

    Modern 3D electron microscopy approaches have recently allowed unprecedented insight into the 3D ultrastructural organization of cells and tissues, enabling the visualization of large macromolecular machines, such as adhesion complexes, as well as higher-order structures, such as the cytoskeleton and cellular organelles in their respective cell and tissue context. Given the inherent complexity of cellular volumes, it is essential to first extract the features of interest in order to allow visualization, quantification, and therefore comprehension of their 3D organization. Each data set is defined by distinct characteristics, e.g., signal-to-noise ratio, crispness (sharpness) of the data, heterogeneity of its features, crowdedness of features, presence or absence of characteristic shapes that allow for easy identification, and the percentage of the entire volume that a specific region of interest occupies. All these characteristics need to be considered when deciding on which approach to take for segmentation. The six different 3D ultrastructural data sets presented were obtained by three different imaging approaches: resin embedded stained electron tomography, focused ion beam- and serial block face- scanning electron microscopy (FIB-SEM, SBF-SEM) of mildly stained and heavily stained samples, respectively. For these data sets, four different segmentation approaches have been applied: (1) fully manual model building followed solely by visualization of the model, (2) manual tracing segmentation of the data followed by surface rendering, (3) semi-automated approaches followed by surface rendering, or (4) automated custom-designed segmentation algorithms followed by surface rendering and quantitative analysis. Depending on the combination of data set characteristics, it was found that typically one of these four categorical approaches outperforms the others, but depending on the exact sequence of criteria, more than one approach may be successful. Based on these data

  16. Parallel 3D Finite Element Numerical Modelling of DC Electron Guns

    SciTech Connect

    Prudencio, E.; Candel, A.; Ge, L.; Kabel, A.; Ko, K.; Lee, L.; Li, Z.; Ng, C.; Schussman, G.; /SLAC

    2008-02-04

    In this paper we present Gun3P, a parallel 3D finite element application that the Advanced Computations Department at the Stanford Linear Accelerator Center is developing for the analysis of beam formation in DC guns and beam transport in klystrons. Gun3P is targeted specially to complex geometries that cannot be described by 2D models and cannot be easily handled by finite difference discretizations. Its parallel capability allows simulations with more accuracy and less processing time than packages currently available. We present simulation results for the L-band Sheet Beam Klystron DC gun, in which case Gun3P is able to reduce simulation time from days to some hours.

  17. Web-based volume slicer for 3D electron-microscopy data from EMDB.

    PubMed

    Salavert-Torres, José; Iudin, Andrii; Lagerstedt, Ingvar; Sanz-García, Eduardo; Kleywegt, Gerard J; Patwardhan, Ardan

    2016-05-01

    We describe the functionality and design of the Volume slicer - a web-based slice viewer for EMDB entries. This tool uniquely provides the facility to view slices from 3D EM reconstructions along the three orthogonal axes and to rapidly switch between them and navigate through the volume. We have employed multiple rounds of user-experience testing with members of the EM community to ensure that the interface is easy and intuitive to use and the information provided is relevant. The impetus to develop the Volume slicer has been calls from the EM community to provide web-based interactive visualisation of 2D slice data. This would be useful for quick initial checks of the quality of a reconstruction. Again in response to calls from the community, we plan to further develop the Volume slicer into a fully-fledged Volume browser that provides integrated visualisation of EMDB and PDB entries from the molecular to the cellular scale.

  18. Uncertainty studies of topographical measurements on steel surface corrosion by 3D scanning electron microscopy.

    PubMed

    Kang, K W; Pereda, M D; Canafoglia, M E; Bilmes, P; Llorente, C; Bonetto, R

    2012-02-01

    Pitting corrosion is a damage mechanism quite serious and dangerous in both carbon steel boiler tubes for power plants which are vital to most industries and stainless steels for orthopedic human implants whose demand, due to the increase of life expectation and rate of traffic accidents, has sharply increased. Reliable methods to characterize this kind of damage are becoming increasingly necessary, when trying to evaluate the advance of damage and to establish the best procedures for component inspection in order to determine remaining lives and failure mitigation. A study about the uncertainties on the topographies of corrosion pits from 3D SEM images, obtained at low magnifications (where errors are greater) and different stage tilt angles were carried out using an in-house software previously developed. Additionally, measurements of pit depths on biomaterial surfaces, subjected to two different surface treatments on stainless steels, were carried out. The different depth distributions observed were in agreement with electrochemical measurements.

  19. Observations of the 3-D distribution of interplanetary electrons and ions from solar wind plasma to low energy cosmic rays

    NASA Technical Reports Server (NTRS)

    Lin, R. P.; Anderson, K. A.; Ashford, S.; Carlson, C.; Curtis, D.; Ergun, R.; Larson, D.; McFadden, J.; McCarthy, M.; Parks, G. K.

    1995-01-01

    The 3-D Plasma and Energetic Particle instrument on the GGS Wind spacecraft (launched November 1, 1994) is designed to make measurements of the full three-dimensional distribution of suprathermal electrons and ions from solar wind plasma to low energy cosmic rays, with high sensitivity, wide dynamic range, good energy and angular resolution, and high time resolution. Three pairs of double-ended telescopes, each with two or three closely sandwiched passivated ion implanted silicon detectors measure electrons and ions from approximately 20 keV to greater than or equal to 300 keV. Four top-hat symmetrical spherical section electrostatic analyzers with microchannel plate detectors, a large and a small geometric factor analyzer for electrons and a similar pair for ions, cover from approximately 3 eV to 30 keV. We present preliminary observations of the electron and ion distributions in the absence of obvious solar impulsive events and upstream particles. The quiet time electron energy spectrum shows a smooth approximately power law fall-off extending from the halo population at a few hundred eV to well above approximately 100 keV The quiet time ion energy spectrum also shows significant fluxes over this energy range. Detailed 3-D distributions and their temporal variations will be presented.

  20. Three-Dimensional (3-D) Plastic Part Extrusion And Conductive Ink Printing For Flexible Electronics

    DTIC Science & Technology

    2012-04-01

    ORGANIZATION NAME(S) AND ADDRESS(ES) Commander, U.S. Army Research, Development, and Engineering Command ATTN: RDMR- WSI Redstone Arsenal, AL...Schmalbach Electronic Ron.Schmalbach@us.army.mil RDMR- WSI Wayne Davenport Electronic Wayne.Davenport@us.army.mil Dr. Tracy D. Hudson

  1. Role of Emission Character in Auger Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Idzerda, Y. U.

    A review of the interpretation of the angle-dependent Auger intensity pattern by both Auger electron diffraction (AED), which is concerned with identifying the nearby atomic structure, and angle-resolved Auger electron spectroscopy (ARAES), which is concerned with identifying the character of the emitted electron source function, is presented. The importance of the emission character of the Auger electron (in terms of its angular momentum, l, and its magnetic quantum number, m) in understanding the generation of the AED and ARAES patterns is described. Understanding of how the various direct and secondary mechanisms for the Auger electron generation can affect the populations of these states can also be used to help identify the multiplet structure within the Auger lineshape as well as elucidate the core hole generation process.

  2. Viral Infection at High Magnification: 3D Electron Microscopy Methods to Analyze the Architecture of Infected Cells.

    PubMed

    Romero-Brey, Inés; Bartenschlager, Ralf

    2015-12-03

    As obligate intracellular parasites, viruses need to hijack their cellular hosts and reprogram their machineries in order to replicate their genomes and produce new virions. For the direct visualization of the different steps of a viral life cycle (attachment, entry, replication, assembly and egress) electron microscopy (EM) methods are extremely helpful. While conventional EM has given important information about virus-host cell interactions, the development of three-dimensional EM (3D-EM) approaches provides unprecedented insights into how viruses remodel the intracellular architecture of the host cell. During the last years several 3D-EM methods have been developed. Here we will provide a description of the main approaches and examples of innovative applications.

  3. Viral Infection at High Magnification: 3D Electron Microscopy Methods to Analyze the Architecture of Infected Cells

    PubMed Central

    Romero-Brey, Inés; Bartenschlager, Ralf

    2015-01-01

    As obligate intracellular parasites, viruses need to hijack their cellular hosts and reprogram their machineries in order to replicate their genomes and produce new virions. For the direct visualization of the different steps of a viral life cycle (attachment, entry, replication, assembly and egress) electron microscopy (EM) methods are extremely helpful. While conventional EM has given important information about virus-host cell interactions, the development of three-dimensional EM (3D-EM) approaches provides unprecedented insights into how viruses remodel the intracellular architecture of the host cell. During the last years several 3D-EM methods have been developed. Here we will provide a description of the main approaches and examples of innovative applications. PMID:26633469

  4. The diffracted distribution of classical trajectories and interference between electrons

    NASA Astrophysics Data System (ADS)

    Zhao, Guo-Peng; Zhang, Yan-Hui; Cai, Xiang-Ji; Xu, Xiu-Lan; Kang, Li-Sha

    2016-10-01

    We use a semiclassical approximation to study the escape of electrons through a circular mesostructure with the diffractive effect at the entrance lead taken into consideration. We find that the fluctuating shapes of the escape probability manifests a good agreement with the diffracted distributions of the incident angles for different transverse modes, and show that several classical trajectories with certain lengths have prominent contributions on the escape probability. In addition, we define the coherence factor to investigate the interference between electrons for different transverse modes and we find that it is the coherent backscattering that is responsible for the prominent interference. Moreover, we find there is a good correspondence between the distribution of classical trajectories and the time-reversed path.

  5. Space charge effects in ultrafast electron diffraction and imaging

    NASA Astrophysics Data System (ADS)

    Tao, Zhensheng; Zhang, He; Duxbury, P. M.; Berz, Martin; Ruan, Chong-Yu

    2012-02-01

    Understanding space charge effects is central for the development of high-brightness ultrafast electron diffraction and microscopy techniques for imaging material transformation with atomic scale detail at the fs to ps timescales. We present methods and results for direct ultrafast photoelectron beam characterization employing a shadow projection imaging technique to investigate the generation of ultrafast, non-uniform, intense photoelectron pulses in a dc photo-gun geometry. Combined with N-particle simulations and an analytical Gaussian model, we elucidate three essential space-charge-led features: the pulse lengthening following a power-law scaling, the broadening of the initial energy distribution, and the virtual cathode threshold. The impacts of these space charge effects on the performance of the next generation high-brightness ultrafast electron diffraction and imaging systems are evaluated.

  6. 3D tracking of single nanoparticles and quantum dots in living cells by out-of-focus imaging with diffraction pattern recognition.

    PubMed

    Gardini, Lucia; Capitanio, Marco; Pavone, Francesco S

    2015-11-03

    Live cells are three-dimensional environments where biological molecules move to find their targets and accomplish their functions. However, up to now, most single molecule investigations have been limited to bi-dimensional studies owing to the complexity of 3d-tracking techniques. Here, we present a novel method for three-dimensional localization of single nano-emitters based on automatic recognition of out-of-focus diffraction patterns. Our technique can be applied to track the movements of single molecules in living cells using a conventional epifluorescence microscope. We first demonstrate three-dimensional localization of fluorescent nanobeads over 4 microns depth with accuracy below 2 nm in vitro. Remarkably, we also establish three-dimensional tracking of Quantum Dots, overcoming their anisotropic emission, by adopting a ligation strategy that allows rotational freedom of the emitter combined with proper pattern recognition. We localize commercially available Quantum Dots in living cells with accuracy better than 7 nm over 2 microns depth. We validate our technique by tracking the three-dimensional movements of single protein-conjugated Quantum Dots in living cell. Moreover, we find that important localization errors can occur in off-focus imaging when improperly calibrated and we give indications to avoid them. Finally, we share a Matlab script that allows readily application of our technique by other laboratories.

  7. Web-based volume slicer for 3D electron-microscopy data from EMDB

    PubMed Central

    Salavert-Torres, José; Iudin, Andrii; Lagerstedt, Ingvar; Sanz-García, Eduardo; Kleywegt, Gerard J.; Patwardhan, Ardan

    2016-01-01

    We describe the functionality and design of the Volume slicer – a web-based slice viewer for EMDB entries. This tool uniquely provides the facility to view slices from 3D EM reconstructions along the three orthogonal axes and to rapidly switch between them and navigate through the volume. We have employed multiple rounds of user-experience testing with members of the EM community to ensure that the interface is easy and intuitive to use and the information provided is relevant. The impetus to develop the Volume slicer has been calls from the EM community to provide web-based interactive visualisation of 2D slice data. This would be useful for quick initial checks of the quality of a reconstruction. Again in response to calls from the community, we plan to further develop the Volume slicer into a fully-fledged Volume browser that provides integrated visualisation of EMDB and PDB entries from the molecular to the cellular scale. PMID:26876163

  8. Structure refinement using precession electron diffraction tomography and dynamical diffraction: tests on experimental data.

    PubMed

    Palatinus, Lukáš; Corrêa, Cinthia Antunes; Steciuk, Gwladys; Jacob, Damien; Roussel, Pascal; Boullay, Philippe; Klementová, Mariana; Gemmi, Mauro; Kopeček, Jaromír; Domeneghetti, M Chiara; Cámara, Fernando; Petříček, Václav

    2015-12-01

    The recently published method for the structure refinement from three-dimensional precession electron diffraction data using dynamical diffraction theory [Palatinus et al. (2015). Acta Cryst. A71, 235-244] has been applied to a set of experimental data sets from five different samples - Ni2Si, PrVO3, kaolinite, orthopyroxene and mayenite. The data were measured on different instruments and with variable precession angles. For each sample a reliable reference structure was available. A large series of tests revealed that the method provides structure models with an average error in atomic positions typically between 0.01 and 0.02 Å. The obtained structure models are significantly more accurate than models obtained by refinement using kinematical approximation for the calculation of model intensities. The method also allows a reliable determination of site occupancies and determination of absolute structure. Based on the extensive tests, an optimal set of the parameters for the method is proposed.

  9. Application of a Novel Multiple-Scattering Approach to Photoelectron Diffraction and Auger Electron Diffraction.

    NASA Astrophysics Data System (ADS)

    Kaduwela, Ajith P.

    We apply a new separable-Green's-function matrix method due to Rehr and Albers (Phys. Rev. B4l (1990) 8139) to a multiple scattering treatment of photoelectron diffraction and Auger electron diffraction. This cluster -based method permits building up successive orders of scattering and judging the approach to convergence in a convenient and time-saving way. We include multiple scattering up to tenth order and can treat photoelectron emission form any initial state (s, p, d, or f) with full final-state interference. This new approach is used to simulate emission from linear and bent chains of atoms, from epitaxial overlayers and multilayer substrates and from atomic and molecular adsorbates, and various conclusions are drawn concerning the range of utility of the method and the geometric structures for which multiple scattering effects must be considered.

  10. Photons, Electrons and Positrons Transport in 3D by Monte Carlo Techniques

    SciTech Connect

    2014-12-01

    Version 04 FOTELP-2014 is a new compact general purpose version of the previous FOTELP-2K6 code designed to simulate the transport of photons, electrons and positrons through three-dimensional material and sources geometry by Monte Carlo techniques, using subroutine package PENGEOM from the PENELOPE code under Linux-based and Windows OS. This new version includes routine ELMAG for electron and positron transport simulation in electric and magnetic fields, RESUME option and routine TIMER for obtaining starting random number and for measuring the time of simulation.

  11. MicroDiffraction in the Scanning Electron Microscope (SEM)

    SciTech Connect

    Goehner, R.P.; Michael, J.R.; Schlienger, M.E.

    1997-12-31

    The identification of crystallographic phases in the scanning electron microscope (SEM) has been limited by the lack of a simple way to obtain electron diffraction data of an unknown while observing the micro structure of the specimen. With the development of Charge Coupled Device (CCD) based detectors, backscattered electron Kikuchi patterns (BEKP), alternately referred to as electron backscattered diffraction patterns (EBSP), can be easily collected. Previously, BEKP has been limited to crystallographic orientation studies due to the poor pattern quality collected with video rate detector systems. With CCD detectors, a typical BEKP can now be acquired from a micron or sub-micron-sized crystal using an exposure time of 1-10 seconds with an accelerating voltage of 10-40 kV and a beam current as low as 0.1 nA. Crystallographic phase analysis using BEKP is unique in that the properly equipped SEM permits high magnification images, BEKP`s, and elemental information to be collected from bulk specimens. BEKP in the SEM has numerous advantages over other electron microscopy crystallographic techniques. The large angular view ( 70 degrees) provided by BEKP and the lack of difficult specimen preparation are distinct advantages of the technique. No sample preparation beyond what is commonly used for SEM specimens is required for BEKP.

  12. Fabrication and characterisation of a fully auxetic 3D lattice structure via selective electron beam melting

    NASA Astrophysics Data System (ADS)

    Warmuth, Franziska; Osmanlic, Fuad; Adler, Lucas; Lodes, Matthias A.; Körner, Carolin

    2017-02-01

    A three-dimensional fully auxetic cellular structure with negative Poisson’s ratio is presented. Samples are fabricated from Ti6Al4V powder via selective electron beam melting. The influence of the strut thickness and the amplitude of the strut on the mechanical properties and the deformation behaviour of cellular structures is studied.

  13. Inelastic low energy electron diffraction at metal surfaces

    NASA Astrophysics Data System (ADS)

    Nazarov, V. U.; Nishigaki, S.

    2001-06-01

    The role of incident electrons penetration under a metal surface in electron energy loss spectroscopy is considered within the fully quantum-mechanical approach. The stabilized jellium model of the surface in the semi-infinite geometry and the time-dependent local density approximation for the dynamical response are used. The travel of the projectile electron inside the target metal is treated within the kinematic low energy electron diffraction theory. Confirming our simplified hard-wall reflection model results [Phys. Rev. B 59 (1999) 9866], the dramatic enhancement of the multipole plasmon peak as compared with the dipole-mode calculations is obtained for Na and Cs, which is in a qualitative agreement with the experiment. However, for K the calculation fails to explain the experiment, which discrepancy is discussed and the future improvements of the method are outlined.

  14. Electronic and structural properties of 3D, 2D and 1D materials

    NASA Astrophysics Data System (ADS)

    Ribeiro, Filipe Joao

    In this work several applications of the ab initio pseudopotential density functional theory method are presented. With this method it is possible to calculate the electronic ground state properties of many systems like bulk solids, surfaces, nanotubes, and nanowires, and draw conclusions about the systems structural and electronic properties. With modifications of this approach excited states can also be treated. The first chapter of this thesis gives a brief description of the computational techniques employed. The second chapter describes results of calculations on the structural and electronic properties of carbon and germanium. We try to shed some light on a still poorly understood structural phase transition of graphite under pressure at low temperatures, which is different from the high temperature regime. Next, we study the phase transition path of germanium under pressure and predict the existence of a new phase. The following chapter explores the possibility of superconductivity in the graphite-like compound BC3 since there are many similarities between the electronic structure of this material and the 39 K superconductor MgB2. Subsequently, results of calculations on the adsorption of indium atoms on carbon nanotubes and graphite-like surfaces are presented. These studies explain some very interesting experimental results of In migration on nanotubes in an electrical potential. In the following chapters the electronic properties of very thin metallic MoSe nanowires are studied, and the different regimes of stability of metallic monatomic chains of Au, Al, Ag, Pd, Rh, and Ru are investigated and compared. Chapter 7 addresses the possible polymerization of C60 molecules inside carbon and boron nitride nanotubes. Finally, the propagation of a light signal in a medium with gains and losses is investigated, and the possibility of a discontinuity in the index of refraction is discussed.

  15. Electron Diffraction and High-Resolution Electron Microscopy of Mineral Structures

    NASA Astrophysics Data System (ADS)

    Nord, Gordon L., Jr.

    This book is a well-written English translation of the original 1981 Russian edition, Strukturnoye issledovaniye mineralov metodami mikrodifraktsii i elechtronnoi mikroskopii vysokogo razresheniya. The 1987 English version has been extensively updated and includes references up to 1986. The book is essentially a text on the theoretical and experimental aspects of transmission electron microscopy and has chapters on the reciprocal lattice, electron diffraction (both kinematic and dynamic), and high-resolution electron microscopy.Electron diffraction is emphasized, especially its use for structure analysis of poorly crystalline and fine-grained phases not readily determined by the more exact X ray diffraction method. Two methods of electron diffraction are discussed: selected area electron diffraction (SAED) and oblique-texture electron diffraction (OTED); the latter technique is rarely used in the west and is never discussed in western electron microscopy texts. A SAED pattern is formed by isolating a small micrometer-size area with an aperture and obtaining single-crystal patterns from the diffracted beams. By tilting the sample and obtaining many patterns, a complete picture of the reciprocal lattice can be taken. An OTED pattern is formed when the incident electron beam passes through an inclined preparation consisting of a great number of thin platy crystals lying normal to the texture axis (axis normal to the support grid). To form an OTED pattern, the plates must all lie on a common face, such as a basal plane in phyllosilicates. Upon tilting the plates, an elliptical powder diffraction pattern is formed. Intensities measured from these patterns are used for a structural analysis of the platy minerals.

  16. Measuring surface topography with scanning electron microscopy. I. EZEImage: a program to obtain 3D surface data.

    PubMed

    Ponz, Ezequiel; Ladaga, Juan Luis; Bonetto, Rita Dominga

    2006-04-01

    Scanning electron microscopy (SEM) is widely used in the science of materials and different parameters were developed to characterize the surface roughness. In a previous work, we studied the surface topography with fractal dimension at low scale and two parameters at high scale by using the variogram, that is, variance vs. step log-log graph, of a SEM image. Those studies were carried out with the FERImage program, previously developed by us. To verify the previously accepted hypothesis by working with only an image, it is indispensable to have reliable three-dimensional (3D) surface data. In this work, a new program (EZEImage) to characterize 3D surface topography in SEM has been developed. It uses fast cross correlation and dynamic programming to obtain reliable dense height maps in a few seconds which can be displayed as an image where each gray level represents a height value. This image can be used for the FERImage program or any other software to obtain surface topography characteristics. EZEImage also generates anaglyph images as well as characterizes 3D surface topography by means of a parameter set to describe amplitude properties and three functional indices for characterizing bearing and fluid properties.

  17. Electronic properties of hexagonal tungsten monocarbide ( h-WC) with 3 d impurities from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Suetin, D. V.; Shein, I. R.; Ivanovskii, A. L.

    2009-07-01

    First-principles FLAPW-GGA calculations have been performed to predict the structural, electronic, cohesive and magnetic properties for hexagonal tungsten monocarbide ( h-WC) doped with all 3 d metals. The optimized lattice parameters, density of states, cohesive and formation energies have been obtained and analyzed for ternary solid solutions with nominal compositions W 0.875M 0.125C (where M=Sc, Ti…Ni, Cu). In addition, the magnetic properties of these solid solutions have been examined, and magnetization has been established for W 0.875Co 0.125C.

  18. Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengyang; Lambrev, Petar H.; Wells, Kym L.; Garab, Győző; Tan, Howe-Siang

    2015-07-01

    During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems.

  19. Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy

    PubMed Central

    Zhang, Zhengyang; Lambrev, Petar H.; Wells, Kym L.; Garab, Győző; Tan, Howe-Siang

    2015-01-01

    During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems. PMID:26228055

  20. 3-D structures of crack-tip dislocations and their shielding effect revealed by electron tomography.

    PubMed

    Tanaka, Masaki; Honda, Masaki; Sadamatsu, Sunao; Higashida, Kenji

    2010-08-01

    Three-dimensional structures of crack-tip dislocations in silicon crystals have been examined by combining scanning transmission electron microscopy and computed tomography. Cracks were introduced by a Vickers hardness tester at room temperature, and the sample was heated at 823 K for 1 h in order to introduce dislocations around the crack tips. Dislocation segments cut out from loops were observed around the crack tip, the three-dimensional structure of which was characterized by using by electron tomography. Their Burgers vectors including the sings were also determined by oscillating contrasts along dislocations. In order to investigate the effect of the dislocations on fracture behaviours, local stress intensity factor due to one dislocation was calculated, which indicates the dislocations observed were shielding type to increase fracture toughness.

  1. Reconstruction of the ionospheric 3D electron density distribution by assimilation of ionosonde measurements and operational TEC estimations

    NASA Astrophysics Data System (ADS)

    Gerzen, Tatjana; Wilken, Volker; Jakowski, Norbert; Hoque, Mainul M.

    2013-04-01

    New methods to generate maps of the F2 layer peak electron density of the ionosphere (NmF2) and to reconstruct the ionospheric 3D electron density distribution will be presented. For validation, reconstructed NmF2 maps will be compared with peak electron density measurements from independent ionosonde stations. The ionosphere is the ionized part of the upper Earth's atmosphere lying between about 50 km and 1000 km above the Earth's surface. From the applications perspective the electron density, Ne, is certainly one of the most important parameters of the ionosphere because of its strong impact on radio signal propagation. Especially the critical frequency, foF2, which is related to the F2 layer peak electron density, NmF2, according to the equation NmF2-m3 = 1.24 ? 1010(foF2-MHz)2 and builds the lower limit for the maximum usable frequency MUF, is of particular interest with regard to the HF radio communication applications. In a first order approximation the ionospheric delay of transionospheric radio waves of frequency f is proportional to 1-f2 and to the integral of the electron density (total electron content - TEC) along the ray path. Thus, the information about the total electron content along the receiver-to-satellite ray path can be obtained from the dual frequency measurements permanently transmitted by GNSS satellites. As data base for our reconstruction approaches we use the vertical sounding measurements of the ionosonde stations providing foF2 and routinely generated TEC maps in SWACI (http://swaciweb.dlr.de) at DLR Neustrelitz. The basic concept of our approach is the following one: To reconstruct NmF2 maps we assimilate the ionosonde data into the global Neustrelitz F2 layer Peak electron Density Model (NPDM) by means of a successive corrections method. The TEC maps are produced by assimilating actual ground based GPS measurements providing TEC into an operational version of Neustrelitz TEC Model (NTCM). Finally, the derived NmF2 and TEC maps in

  2. Measuring 3D Hand and Finger Kinematics—A Comparison between Inertial Sensing and an Opto-Electronic Marker System

    PubMed Central

    van den Noort, Josien C.; Kortier, Henk G.; van Beek, Nathalie; Veeger, DirkJan H. E. J.; Veltink, Peter H.

    2016-01-01

    Objective analysis of hand and finger kinematics is important to increase understanding of hand function and to quantify motor symptoms for clinical diagnosis. The aim of this paper is to compare a new 3D measurement system containing multiple miniature inertial sensors (PowerGlove) with an opto-electronic marker system during specific finger tasks in three healthy subjects. Various finger movements tasks were performed: flexion, fast flexion, tapping, hand open/closing, ab/adduction and circular pointing. 3D joint angles of the index finger joints and position of the thumb and index were compared between systems. Median root mean square differences of the main joint angles of interest ranged between 3.3 and 8.4deg. Largest differences were found in fast and circular pointing tasks, mainly in range of motion. Smallest differences for all 3D joint angles were observed in the flexion tasks. For fast finger tapping, the thumb/index amplitude showed a median difference of 15.8mm. Differences could be explained by skin movement artifacts caused by relative marker movements of the marker system, particularly during fast tasks; large movement accelerations and angular velocities which exceeded the range of the inertial sensors; and by differences in segment calibrations between systems. The PowerGlove is a system that can be of value to measure 3D hand and finger kinematics and positions in an ambulatory setting. The reported differences need to be taken into account when applying the system in studies understanding the hand function and quantifying hand motor symptoms in clinical practice. PMID:27812139

  3. A complete comparison of simulated electron diffraction patterns using different parameterizations of the electron scattering factors.

    PubMed

    Lobato, I; Van Dyck, D

    2015-08-01

    The steadily improving experimental possibilities in instrumental resolution as in sensitivity and quantization of the data recording put increasingly higher demands on the precision of the scattering factors, which are the key ingredients for electron diffraction or high-resolution imaging simulation. In the present study, we will systematically investigate the accuracy of fitting of the main parameterizations of the electron scattering factor for the calculation of electron diffraction intensities. It is shown that the main parameterizations of the electron scattering factor are consistent to calculate electron diffraction intensities for thin specimens and low angle scattering. Parameterizations of the electron scattering factor with the correct asymptotic behavior (Lobato and Dyck [5], Kirkland [4], and Weickenmeier and Kohl [2]) produce similar results for both the undisplaced lattice model and the frozen phonon model, except for certain thicknesses and reflections.

  4. 3D Electron Spin Relaxation Control by Electric Field in Quantum Wells

    NASA Astrophysics Data System (ADS)

    Marie, Xavier

    2012-02-01

    We have measured the electron spin relaxation time in (111)-oriented GaAs quantum wells by time-resolved photoluminescence. By embedding the QWs in a PIN or NIP structure we demonstrate the tuning of the conduction band spin splitting and hence the spin relaxation time with an applied external electric field applied along the growth z direction . The application of an external electric field of 50 kV/cm yields a two-order of magnitude increase of the spin relaxation time which can reach values larger than 30 ns; this is a consequence of the electric field tuning of the spin-orbit conduction band splitting which can almost vanish when the Rashba term compensates exactly the Dresselhaus one [1]. The spin quantum beats measurements under transverse magnetic field prove that the D'Yakonov-Perel (DP) spin relaxation time is not only increased for the Sz electron spin component but also for both Sx and Sy. These results contrast drastically with the (001) and (110) quantum wells.The role of the cubic Dresselhaus terms on the spin relaxation anisotropy will finally be discussed. The tuning or suppression of the DP electron spin relaxation demonstrated here for GaAs/AlGaAs quantum wells grown on (111) substrates is also possible in many other III-V and II-VI zinc-blende nanostructures since the principle relies only on symmetry considerations. [4pt] [1] A. Balocchi, Q. H. Duong, P. Renucci, B. L. Liu, C. Fontaine, T. Amand, D. Lagarde, and X. Marie, Phys. Rev. Lett 107, 136604(2011)

  5. Auger electron diffraction study of the initial stage of Ge heteroepitaxy on Si(001)

    NASA Astrophysics Data System (ADS)

    Sasaki, M.; Abukawa, T.; Yeom, H. W.; Yamada, M.; Suzuki, S.; Sato, S.; Kono, S.

    1994-12-01

    The initial stage of pure and surfactant (Sb)-assisted Ge growth on a Si(001) surface has been studied by Auger electron diffraction (AED) and X-ray photoelectron diffraction (XPD). A single-domain Si(001)2 × 1 substrate was used to avoid the ambiguity arising from the usual double-domain substrate. For the pure Ge growth, 1 monolayer of Ge was deposited onto the room temperature substrate followed by annealing at 350°C-600°C, which appeared to have (1 × 2) periodicity by LEED. Ge LMM AED patterns were measured to find that a substantial amount of Ge atoms diffuse to the bulk Si positions up to the fourth layer at least. For the Sb-assisted Ge growth, a Sb(1 × 2)/Si(001) surface was first prepared and Sb 3d XPD patterns were measured to find that Sb forms dimers on the substrate. 1 ML of Ge was deposited onto the Sb(1 × 2)/Si(001) surface and then the surface was annealed at 600°C. Ge LMM AED and Sb 3d XPD patterns measured for this surface showed that surfactant Sb atoms are indeed present on the first layer forming dimers and that Ge atoms are present mainly on the second layer with a substantial amount of Ge diffused into the third and fourth layers.

  6. EMRinger: side chain–directed model and map validation for 3D cryo-electron microscopy

    DOE PAGES

    Barad, Benjamin A.; Echols, Nathaniel; Wang, Ray Yu-Ruei; ...

    2015-08-17

    Advances in high-resolution cryo-electron microscopy (cryo-EM) require the development of validation metrics to independently assess map quality and model geometry. We report that EMRinger is a tool that assesses the precise fitting of an atomic model into the map during refinement and shows how radiation damage alters scattering from negatively charged amino acids. EMRinger (https://github.com/fraser-lab/EMRinger) will be useful for monitoring progress in resolving and modeling high-resolution features in cryo-EM.

  7. The linearly scaling 3D fragment method for large scale electronic structure calculations

    SciTech Connect

    Zhao, Zhengji; Meza, Juan; Lee, Byounghak; Shan, Hongzhang; Strohmaier, Erich; Bailey, David; Wang, Lin-Wang

    2009-07-28

    The Linearly Scaling three-dimensional fragment (LS3DF) method is an O(N) ab initio electronic structure method for large-scale nano material simulations. It is a divide-and-conquer approach with a novel patching scheme that effectively cancels out the artificial boundary effects, which exist in all divide-and-conquer schemes. This method has made ab initio simulations of thousand-atom nanosystems feasible in a couple of hours, while retaining essentially the same accuracy as the direct calculation methods. The LS3DF method won the 2008 ACM Gordon Bell Prize for algorithm innovation. Our code has reached 442 Tflop/s running on 147,456 processors on the Cray XT5 (Jaguar) at OLCF, and has been run on 163,840 processors on the Blue Gene/P (Intrepid) at ALCF, and has been applied to a system containing 36,000 atoms. In this paper, we will present the recent parallel performance results of this code, and will apply the method to asymmetric CdSe/CdS core/shell nanorods, which have potential applications in electronic devices and solar cells.

  8. The Linearly Scaling 3D Fragment Method for Large Scale Electronic Structure Calculations

    SciTech Connect

    Zhao, Zhengji; Meza, Juan; Lee, Byounghak; Shan, Hongzhang; Strohmaier, Erich; Bailey, David; Wang, Lin-Wang

    2009-06-26

    The Linearly Scaling three-dimensional fragment (LS3DF) method is an O(N) ab initio electronic structure method for large-scale nano material simulations. It is a divide-and-conquer approach with a novel patching scheme that effectively cancels out the artificial boundary effects, which exist in all divide-and-conquer schemes. This method has made ab initio simulations of thousand-atom nanosystems feasible in a couple of hours, while retaining essentially the same accuracy as the direct calculation methods. The LS3DF method won the 2008 ACM Gordon Bell Prize for algorithm innovation. Our code has reached 442 Tflop/s running on 147,456 processors on the Cray XT5 (Jaguar) at OLCF, and has been run on 163,840 processors on the Blue Gene/P (Intrepid) at ALCF, and has been applied to a system containing 36,000 atoms. In this paper, we will present the recent parallel performance results of this code, and will apply the method to asymmetric CdSe/CdS core/shell nanorods, which have potential applications in electronic devices and solar cells.

  9. The linearly scaling 3D fragment method for large scale electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Zhao, Zhengji; Meza, Juan; Lee, Byounghak; Shan, Hongzhang; Strohmaier, Erich; Bailey, David; Wang, Lin-Wang

    2009-07-01

    The linearly scaling three-dimensional fragment (LS3DF) method is an O(N) ab initio electronic structure method for large-scale nano material simulations. It is a divide-and-conquer approach with a novel patching scheme that effectively cancels out the artificial boundary effects, which exist in all divide-and-conquer schemes. This method has made ab initio simulations of thousand-atom nanosystems feasible in a couple of hours, while retaining essentially the same accuracy as the direct calculation methods. The LS3DF method won the 2008 ACM Gordon Bell Prize for algorithm innovation. Our code has reached 442 Tflop/s running on 147,456 processors on the Cray XT5 (Jaguar) at OLCF, and has been run on 163,840 processors on the Blue Gene/P (Intrepid) at ALCF, and has been applied to a system containing 36,000 atoms. In this paper, we will present the recent parallel performance results of this code, and will apply the method to asymmetric CdSe/CdS core/shell nanorods, which have potential applications in electronic devices and solar cells.

  10. Tunable electronic and magnetic properties in stanene by 3d transition metal atoms absorption

    NASA Astrophysics Data System (ADS)

    Xing, Dan-Xu; Ren, Ceng-Ceng; Zhang, Shu-Feng; Feng, Yong; Chen, Xin-Lian; Zhang, Chang-Wen; Wang, Pei-Ji

    2017-03-01

    The electronic and magnetic properties of transition metal (TM) atoms (V, Cr, Mn, Fe, Co, Ni) adsorption on stanene are investigated by first-principles calculations. The results indicate that the TM atoms prefer to be relaxed on a H site on stanene except V atom which lies on the valley site. Fe-absorbed stanene is a spin gapless semiconductor with up-spin electron and down-spin hole carriers allowing the coexistence of charge current and the pure spin current. Co-absorbed stanene lies in the half metal phase. The V-, Cr-, Mn-, and Cu-absorbed stanene turn the stanene into metal, while Ni- and Zn-absorbed stanene open a narrow band gap. For V-, Cr-, Mn-, Fe-, and Co-absorbed stanene, the magnetic moment of the TM will survive while the Ni-, Cu-, and Zn-absorbed stanene will be non-magnetic material. These findings may have great potential in the design of new electrically controllable spintronic devices.

  11. Implementing Transmission Electron Backscatter Diffraction for Atom Probe Tomography.

    PubMed

    Rice, Katherine P; Chen, Yimeng; Prosa, Ty J; Larson, David J

    2016-06-01

    There are advantages to performing transmission electron backscattering diffraction (tEBSD) in conjunction with focused ion beam-based specimen preparation for atom probe tomography (APT). Although tEBSD allows users to identify the position and character of grain boundaries, which can then be combined with APT to provide full chemical and orientation characterization of grain boundaries, tEBSD can also provide imaging information that improves the APT specimen preparation process by insuring proper placement of the targeted grain boundary within an APT specimen. In this report we discuss sample tilt angles, ion beam milling energies, and other considerations to optimize Kikuchi diffraction pattern quality for the APT specimen geometry. Coordinated specimen preparation and analysis of a grain boundary in a Ni-based Inconel 600 alloy is used to illustrate the approach revealing a 50° misorientation and trace element segregation to the grain boundary.

  12. Incident-beam effects in electron-stimulated Auger-electron diffraction

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Cao, Jianming

    1991-04-01

    We have examined incident-beam effects in electron-stimulated Auger-electron diffraction (AED) on a cleaved GaAs(110) surface. The results indicate that incident-beam diffraction is significant in an AED experiment, and that the dissipative nature of the incident beam in contributing to the Auger process must be accounted for. We have developed a qualitative model that describes the trend of the polar-angle dependence of the Auger intensity for both the incident and exit beams. In calculating the diffraction features, we used a zeroth-order approximation to simulate the dissipation of the incident beam, which is found to adequately describe the experimental data.

  13. Present State of Electron Backscatter Diffraction and Prospective Developments

    SciTech Connect

    Schwarzer, R A; Field, D P; Adams, B L; Kumar, M; Schwartz, A J

    2008-10-24

    Electron backscatter diffraction (EBSD), when employed as an additional characterization technique to a scanning electron microscope (SEM), enables individual grain orientations, local texture, point-to-point orientation correlations, and phase identification and distributions to be determined routinely on the surfaces of bulk polycrystals. The application has experienced rapid acceptance in metallurgical, materials, and geophysical laboratories within the past decade (Schwartz et al. 2000) due to the wide availability of SEMs, the ease of sample preparation from the bulk, the high speed of data acquisition, and the access to complementary information about the microstructure on a submicron scale. From the same specimen area, surface structure and morphology of the microstructure are characterized in great detail by the relief and orientation contrast in secondary and backscatter electron images, element distributions are accessed by energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), or cathodoluminescence analysis, and the orientations of single grains and phases can now be determined, as a complement, by EBSD.

  14. Runaway electron production in DIII-D killer pellet experiments, calculated with the CQL3D/KPRAD model

    SciTech Connect

    Harvey, R. W.; Chan, V. S.; Chiu, S. C.; Evans, T. E.; Rosenbluth, M. N.; Whyte, D. G.

    2000-11-01

    Runaway electrons are calculated to be produced during the rapid plasma cooling resulting from ''killer pellet'' injection experiments, in general agreement with observations in the DIII-D [J. L. Luxon , Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] tokamak. The time-dependent dynamics of the kinetic runaway distributions are obtained with the CQL3D [R. W. Harvey and M. G. McCoy, ''The CQL3D Code,'' in Proceedings of the IAEA Technical Committee Meeting on Numerical Modeling, Montreal, 1992 (International Atomic Energy Agency, Vienna, 1992), p. 489] collisional Fokker--Planck code, including the effect of small and large angle collisions and stochastic magnetic field transport losses. The background density, temperature, and Z{sub eff} are evolved according to the KPRAD [D. G. Whyte and T. E. Evans , in Proceedings of the 24th European Conference on Controlled Fusion and Plasma Physics, Berchtesgaden, Germany (European Physical Society, Petit-Lancy, 1997), Vol. 21A, p. 1137] deposition and radiation model of pellet--plasma interactions. Three distinct runway mechanisms are apparent: (1) prompt ''hot-tail runaways'' due to the residual hot electron tail remaining from the pre-cooling phase, (2) ''knock-on'' runaways produced by large-angle Coulomb collisions on existing high energy electrons, and (3) Dreicer ''drizzle'' runaway electrons due to diffusion of electrons up to the critical velocity for electron runaway. For electron densities below {approx}1x10{sup 15}cm{sup -3}, the hot-tail runaways dominate the early time evolution, and provide the seed population for late time knock-on runaway avalanche. For small enough stochastic magnetic field transport losses, the knock-on production of electrons balances the losses at late times. For losses due to radial magnetic field perturbations in excess of {approx}0.1% of the background field, i.e., {delta}B{sub r}/B{>=}0.001, the losses

  15. A Detailed Study of FDIRC Prototype with Waveform Digitizing Electronics in Cosmic Ray Telescope Using 3D Tracks.

    SciTech Connect

    Nishimura, K

    2012-07-01

    We present a detailed study of a novel Cherenkov imaging detector called the Focusing DIRC (FDIRC) with waveform digitizing electronics. In this test study, the FDIRC prototype has been instrumented with seven Hamamatsu H-8500 MaPMTs. Waveforms from ~450 pixels are digitized with waveform sampling electronics based on the BLAB2 ASIC, operating at a sampling speed of ~2.5 GSa/s. The FDIRC prototype was tested in a large cosmic ray telescope (CRT) providing 3D muon tracks with ~1.5 mrad angular resolution and muon energy of Emuon greater than 1.6 GeV. In this study we provide a detailed analysis of the tails in the Cherenkov angle distribution as a function of various variables, compare experimental results with simulation, and identify the major contributions to the tails. We demonstrate that to see the full impact of these tails on the Cherenkov angle resolution, it is crucial to use 3D tracks, and have a full understanding of the role of ambiguities. These issues could not be fully explored in previous FDIRC studies where the beam was perpendicular to the quartz radiator bars. This work is relevant for the final FDIRC prototype of the PID detector at SuperB, which will be tested this year in the CRT setup.

  16. A Detailed Study of FDIRC Prototype with Waveform Digitizing Electronics in Cosmic Ray Telescope Using 3D Tracks

    SciTech Connect

    Nishimura, K.; Dey, B.; Aston, D.; Leith, D.W.G.S.; Ratcliff, B.; Roberts, D.; Ruckman, L.; Shtol, D.; Varner, G.S.; Va'vra, J.; Vavra, Jerry; /SLAC

    2012-07-30

    We present a detailed study of a novel Cherenkov imaging detector called the Focusing DIRC (FDIRC) with waveform digitizing electronics. In this test study, the FDIRC prototype has been instrumented with seven Hamamatsu H-8500 MaPMTs. Waveforms from {approx}450 pixels are digitized with waveform sampling electronics based on the BLAB2 ASIC, operating at a sampling speed of {approx}2.5 GSa/s. The FDIRC prototype was tested in a large cosmic ray telescope (CRT) providing 3D muon tracks with {approx}1.5 mrad angular resolution and muon energy of E{sub muon} > 1.6 GeV. In this study we provide a detailed analysis of the tails in the Cherenkov angle distribution as a function of various variables, compare experimental results with simulation, and identify the major contributions to the tails. We demonstrate that to see the full impact of these tails on the Cherenkov angle resolution, it is crucial to use 3D tracks, and have a full understanding of the role of ambiguities. These issues could not be fully explored in previous FDIRC studies where the beam was perpendicular to the quartz radiator bars. This work is relevant for the final FDIRC prototype of the PID detector at SuperB, which will be tested this year in the CRT setup.

  17. Computing the 3-D structure of viruses from unoriented cryo electron microscope images: a fast algorithm for a statistical approach.

    PubMed

    Lee, Junghoon; Zheng, Yili; Doerschuk, Peter C

    2006-01-01

    In a cryo electron microscopy experiment, the data is noisy 2-D projection images of the 3-D electron scattering intensity where the orientation of the projections is not known. In previous work we have developed a solution for this problem based on a maximum likelihood estimator that is computed by an expectation maximization algorithm. In the expectation maximization algorithm the expensive step is the expectation which requires numerical evaluation of 3- or 5-dimensional integrations of a square matrix of dimension equal to the number of Fourier series coefficients used to describe the 3-D reconstruction. By taking advantage of the rotational properties of spherical harmonics, we can reduce the integrations of a matrix to integrations of a scalar. The key property is that a rotated spherical harmonic can be expressed as a linear combination of the other harmonics of the same order and the weights in the linear combination factor so that each of the three factors is a function of only one of the Euler angles describing the orientation of the projection. Numerical example of the reconstructions is provided based on Nudaurelia Omega Capensis virus.

  18. Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector

    PubMed Central

    van Genderen, E.; Clabbers, M. T. B.; Das, P. P.; Stewart, A.; Nederlof, I.; Barentsen, K. C.; Portillo, Q.; Pannu, N. S.; Nicolopoulos, S.; Gruene, T.; Abrahams, J. P.

    2016-01-01

    Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enabling ab initio phasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e− Å−2 s−1) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS, SHELX) and for electron crystallography (ADT3D/PETS, SIR2014). PMID:26919375

  19. Assessing the performance of density functional theory for the electronic structure of metal-salens: the 3d(0)-metals.

    PubMed

    Sears, John S; Sherrill, C David

    2008-04-17

    A series of metal-salen complexes of the 3d(0) metals Sc(III), Ti(IV), V(V), Cr(VI), and Mn(VII) have been explored using high-level electronic structure methods including coupled-cluster theory with singles, doubles, and perturbative triples as well as complete active-space third-order perturbation theory. The performance of three common density functional theory approaches has been assessed for both the geometries and the relative energies of the low-lying electronic states. The nondynamical correlation effects are demonstrated to be extremely large in all of the systems examined. Although density functional theory provides reasonable results for some of the systems, the overall agreement is quite poor. This said, the density functional theory approaches are shown to outperform the single-reference perturbation theory and coupled-cluster theory approaches for cases of strong nondynamical correlation.

  20. Sci—Thur AM: YIS - 07: Design and production of 3D printed bolus for electron radiation therapy

    SciTech Connect

    Su, Shiqin; Moran, Kathryn; Robar, James L.

    2014-08-15

    This is a proof-of-concept study demonstrating the capacity for modulated electron radiation therapy (MERT) using 3D printed bolus. Previous reports have involved bolus design using an electron pencil beam model and fabrication using a milling machine. In this study, an in-house algorithm is presented that optimizes the dose distribution with regard to dose coverage, conformity and homogeneity within planning target volume (PTV). The algorithm uses calculated result of a commercial electron Monte Carlo dose calculation as input. Distances along ray lines from distal side of 90% isodose to distal surface of PTV are used to estimate the bolus thickness. Inhomogeneities within the calculation volume are accounted for using coefficient of equivalent thickness method. Several regional modulation operators are applied to improve dose coverage and uniformity. The process is iterated (usually twice) until an acceptable MERT plan is realized, and the final bolus is printed using solid polylactic acid. The method is evaluated with regular geometric phantoms, anthropomorphic phantoms and a clinical rhabdomyosarcoma pediatric case. In all cases the dose conformity is improved compared to that with uniform bolus. The printed boluses conform well to the surface of complex anthropomorphic phantoms. For the rhabdomyosarcoma patient, the MERT plan yields a reduction of mean dose by 38.2% in left kidney relative to uniform bolus. MERT using 3D printed bolus appears to be a practical, low cost approach to generating optimized bolus for electron therapy. The method is effective in improving conformity of prescription isodose surface and in sparing immediately adjacent normal tissues.

  1. Diffractive electron imaging of nanoparticles on a substrate.

    PubMed

    Wu, Jinsong; Weierstall, U; Spence, John C H

    2005-12-01

    The observation of the detailed atomic arrangement within nanostructures has previously required the use of an electron microscope for imaging. The development of diffractive (lensless) imaging in X-ray science and electron microscopy using ab initio phase retrieval provides a promising tool for nanostructural characterization. We show that it is possible experimentally to reconstruct the atomic-resolution complex image (exit-face wavefunction) of a small particle lying on a thin carbon substrate from its electron microdiffraction pattern alone. We use a modified iterative charge-flipping algorithm and an estimate of the complex substrate image is subtracted at each iteration. The diffraction pattern is recorded using a parallel beam with a diameter of approximately 50 nm, illuminating a gold nanoparticle of approximately 13.6 nm diameter. Prior knowledge of the boundary of the object is not required. The method has the advantage that the reconstructed exit-face wavefunction is free of the aberrations of the objective lens normally used in the microscope, whereas resolution is limited only by thermal vibration and noise.

  2. Linearly Scaling 3D Fragment Method for Large-Scale Electronic Structure Calculations

    SciTech Connect

    Wang, Lin-Wang; Lee, Byounghak; Shan, Hongzhang; Zhao, Zhengji; Meza, Juan; Strohmaier, Erich; Bailey, David H.

    2008-07-01

    We present a new linearly scaling three-dimensional fragment (LS3DF) method for large scale ab initio electronic structure calculations. LS3DF is based on a divide-and-conquer approach, which incorporates a novel patching scheme that effectively cancels out the artificial boundary effects due to the subdivision of the system. As a consequence, the LS3DF program yields essentially the same results as direct density functional theory (DFT) calculations. The fragments of the LS3DF algorithm can be calculated separately with different groups of processors. This leads to almost perfect parallelization on tens of thousands of processors. After code optimization, we were able to achieve 35.1 Tflop/s, which is 39percent of the theoretical speed on 17,280 Cray XT4 processor cores. Our 13,824-atom ZnTeO alloy calculation runs 400 times faster than a direct DFTcalculation, even presuming that the direct DFT calculation can scale well up to 17,280 processor cores. These results demonstrate the applicability of the LS3DF method to material simulations, the advantage of using linearly scaling algorithms over conventional O(N3) methods, and the potential for petascale computation using the LS3DF method.

  3. Nonlinear, nonlaminar-3D computation of electron motion through the output cavity of a klystron

    NASA Technical Reports Server (NTRS)

    Albers, L. U.; Kosmahl, H. G.

    1971-01-01

    The equations of motion used in the computation are discussed along with the space charge fields and the integration process. The following assumptions were used as a basis for the computation: (1) The beam is divided into N axisymmetric discs of equal charge and each disc into R rings of equal charge. (2) The velocity of each disc, its phase with respect to the gap voltage, and its radius at a specified position in the drift tunnel prior to the interaction gap is known from available large signal one dimensional programs. (3) The fringing rf fields are computed from exact analytical expressions derived from the wave equation assuming a known field shape between the tunnel tips at a radius a. (4) The beam is focused by an axisymmetric magnetic field. Both components of B, that is B sub z and B sub r, are taken into account. (5) Since this integration does not start at the cathode but rather further down the stream prior to entering the output cavity it is assumed that each electron moved along a laminar path from the cathode to the start of integration.

  4. Femtosecond electron diffraction: heralding the era of atomically resolved dynamics

    NASA Astrophysics Data System (ADS)

    Sciaini, Germán; Miller, R. J. Dwayne

    2011-09-01

    One of the great dream experiments in Science is to directly observe atomic motions as they occur. Femtosecond electron diffraction provided the first 'light' of sufficient intensity to achieve this goal by attaining atomic resolution to structural changes on the relevant timescales. This review covers the technical progress that made this new level of acuity possible and gives a survey of the new insights gained from an atomic level perspective of structural dynamics. Atomic level views of the simplest possible structural transition, melting, are discussed for a number of systems in which both thermal and purely electronically driven atomic displacements can be correlated with the degree of directional bonding. Optical manipulation of charge distributions and effects on interatomic forces/bonding can be directly observed through the ensuing atomic motions. New phenomena involving strongly correlated electron-lattice systems are also discussed in which optically induced changes in the potential energy landscape lead to ballistic structural changes. Concepts such as the structural order parameters are now directly observable at the atomic level of inspection to give a remarkable view of the extraordinary degree of cooperativity involved in strongly correlated electron-lattice systems. These recent examples, in combination with time-resolved real space imaging now possible with electron probes, are truly defining an emerging field that holds great promise to make a significant impact in how we understand structural dynamics. This article is dedicated to the memory of Professor David John Hugh Cockayne, a world leader in electron microscopy, who sadly passed away in December.

  5. An electron diffraction study of alkali chloride vapors

    NASA Technical Reports Server (NTRS)

    Mawhorter, R. J.; Fink, M.; Hartley, J. G.

    1985-01-01

    A study of monomers and dimers of the four alkali chlorides NaCl, KCl, RbCl, and CsCl in the vapor phase using the counting method of high energy electron diffraction is reported. Nozzle temperatures from 850-960 K were required to achieve the necessary vapor pressures of approximately 0.01 torr. Using harmonic calculations for the monomer and dimer 1 values, a consistent set of structures for all four molecules was obained. The corrected monomer distances reproduce the microwave values very well. The experiment yields information on the amount of dimer present in the vapor, and these results are compared with thermodynamic values.

  6. Dual nature of 3 d electrons in YbT 2 Zn 20 (T = Co; Fe) evidenced by electron spin resonance

    DOE PAGES

    Ivanshin, V. A.; Litvinova, T. O.; Gimranova, K.; ...

    2015-03-18

    The electron spin resonance experiments were carried out in the single crystals YbFe2Zn20. The observed spin dynamics is compared with that in YbCo2Zn20 and Yb2Co12P7 as well as with the data of inelastic neutron scattering and electronic band structure calculations. Our results provide direct evidence that 3d electrons are itinerant in YbFe2Zn20 and localized in YbCo2Zn20. Possible connection between spin paramagnetism of dense heavy fermion systems, quantum criticality effects, and ESR spectra is discussed.

  7. Carbon Nanofibers Synthesized on Selective Substrates for Nonvolatile Memory and 3D Electronics

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Khan, Abdur R.

    2011-01-01

    A plasma-enhanced chemical vapor deposition (PECVD) growth technique has been developed where the choice of starting substrate was found to influence the electrical characteristics of the resulting carbon nanofiber (CNF) tubes. It has been determined that, if the tubes are grown on refractory metallic nitride substrates, then the resulting tubes formed with dc PECVD are also electrically conducting. Individual CNFs were formed by first patterning Ni catalyst islands using ebeam evaporation and liftoff. The CNFs were then synthesized using dc PECVD with C2H2:NH3 = [1:4] at 5 Torr and 700 C, and approximately equal to 200-W plasma power. Tubes were grown directly on degenerately doped silicon <100> substrates with resistivity rho approximately equal to 1-5 meterohm-centimeter, as well as NbTiN. The approximately equal to 200-nanometer thick refractory NbTiN deposited using magnetron sputtering had rho approximately equal to 113 microohm-centimeter and was also chemically compatible with CNF synthesis. The sample was then mounted on a 45 beveled Al holder, and placed inside a SEM (scanning electron microscope). A nanomanipulator probe stage was placed inside the SEM equipped with an electrical feed-through, where tungsten probes were used to make two-terminal electrical measurements with an HP 4156C parameter analyzer. The positive terminal nanoprobe was mechanically manipulated to physically contact an individual CNF grown directly on NbTiN as shown by the SEM image in the inset of figure (a), while the negative terminal was grounded to the substrate. This revealed the tube was electrically conductive, although measureable currents could not be detected until approximately equal to 6 V, after which point current increased sharply until compliance (approximately equal to 50 nA) was reached at approximately equal to 9.5 V. A native oxide on the tungsten probe tips may contribute to a tunnel barrier, which could be the reason for the suppressed transport at low biases

  8. Electron diffraction from polycrystalline materials showing stress induced preferred orientation

    NASA Astrophysics Data System (ADS)

    McKenzie, D. R.; Bilek, M. M. M.

    1999-07-01

    The Gibbs free energy as generalized by J. F. Nye [Physical Properties of Crystals (Clarendon Press, Oxford, 1957), p. 179] is minimized in thermodynamic systems held at constant temperature and constant stress. This function is orientation dependent in all crystal systems in stress fields which are not purely hydrostatic. There are situations in which preferred orientation arises as a result of the synthesis of materials under impressed stress conditions such as thin film growth under ion bombardment and the pressing of powders into solids. Here, we derive the orientational constraints for cubic crystals which result from growth under a general biaxial stress field. The sign of the expression δ=s11-s12-1/2s44 determines the behavior of a cubic crystal. Electron diffraction patterns of face-centered-cubic specimens with both positive and negative values of δ are calculated using a program in MATLAB and displayed in a form suitable for direct comparison with experiment. The use of a biaxial stress with unequal principal components for producing highly oriented polycrystalline material is discussed. In the case of δ positive, as occurs in silicon, the preferred orientation is simply an alignment of the <100> directions along the principal stresses. For δ negative, as occurs in titanium nitride, the preferred orientation depends on the ratio of the principal stresses and low index directions are aligned with the principal stresses only when the principal stresses are either equal or one of them is zero. In the general case, arc-like diffraction patterns are produced. The results of a calculation of a diffraction pattern from a cross-sectional TiN film are compared with diffraction patterns reported by L. Hultman et al. [J. Appl. Phys. 78, 5395 (1995)] and show good agreement.

  9. Diffraction effects and special advantages in electronic heterodyne moire deflectometry

    NASA Technical Reports Server (NTRS)

    Stricker, J.

    1986-01-01

    Effects of diffraction on the performance of electronic heterodyne readout of moire fringes are investigated. The sensitivity, accuracy, and resolution of the system are calculated, and it is shown that these features are significantly improved compared with the conventional intensity moire readout technique. The sensitivity of the system can be tripled without changing the distance between gratings. The system was evaluated experimentally by measuring the refractive-index derivatives of a weak phase object consisting of a large KD(asterisk)P crystal. Effects of nonlinear fringe modulation were studied both theoretically and experimentally. It is shown that in this case the electronic phase is not linearly related to the fringe shift, and calibration of the system is necessary.

  10. Recent developments in two fundamental aspects of electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Mingard, K. P.; Day, A. P.; Quested, P. N.

    2014-03-01

    Two very different aspects of electron backscatter diffraction (EBSD) are considered in this paper. Firstly, the use of the technique for the measurement of grain size is discussed with particular reference to the development of international standards to help ensure reproducible and repeatable measurements. In particular the lessons learnt for both calibration of the complete SEM-EBSD system and in choice of the correct data acquisition and processing parameters from an international round robin are summarized. Secondly, extending the capability of EBSD through development of new detectors is discussed. New shadow casting methods provide a means to achieve better accuracy in definition of sample-pattern geometry, while increased detail can be obtained by larger cameras and ultimately direct electron detection.

  11. All oxide semiconductor-based bidirectional vertical p-n-p selectors for 3D stackable crossbar-array electronics

    NASA Astrophysics Data System (ADS)

    Bae, Yoon Cheol; Lee, Ah Rahm; Baek, Gwang Ho; Chung, Je Bock; Kim, Tae Yoon; Park, Jea Gun; Hong, Jin Pyo

    2015-08-01

    Three-dimensional (3D) stackable memory devices including nano-scaled crossbar array are central for the realization of high-density non-volatile memory electronics. However, an essential sneak path issue affecting device performance in crossbar array remains a bottleneck and a grand challenge. Therefore, a suitable bidirectional selector as a two-way switch is required to facilitate a major breakthrough in the 3D crossbar array memory devices. Here, we show the excellent selectivity of all oxide p-/n-type semiconductor-based p-n-p open-based bipolar junction transistors as selectors in crossbar memory array. We report that bidirectional nonlinear characteristics of oxide p-n-p junctions can be highly enhanced by manipulating p-/n-type oxide semiconductor characteristics. We also propose an associated Zener tunneling mechanism that explains the unique features of our p-n-p selector. Our experimental findings are further extended to confirm the profound functionality of oxide p-n-p selectors integrated with several bipolar resistive switching memory elements working as storage nodes.

  12. All oxide semiconductor-based bidirectional vertical p-n-p selectors for 3D stackable crossbar-array electronics

    PubMed Central

    Bae, Yoon Cheol; Lee, Ah Rahm; Baek, Gwang Ho; Chung, Je Bock; Kim, Tae Yoon; Park, Jea Gun; Hong, Jin Pyo

    2015-01-01

    Three-dimensional (3D) stackable memory devices including nano-scaled crossbar array are central for the realization of high-density non-volatile memory electronics. However, an essential sneak path issue affecting device performance in crossbar array remains a bottleneck and a grand challenge. Therefore, a suitable bidirectional selector as a two-way switch is required to facilitate a major breakthrough in the 3D crossbar array memory devices. Here, we show the excellent selectivity of all oxide p-/n-type semiconductor-based p-n-p open-based bipolar junction transistors as selectors in crossbar memory array. We report that bidirectional nonlinear characteristics of oxide p-n-p junctions can be highly enhanced by manipulating p-/n-type oxide semiconductor characteristics. We also propose an associated Zener tunneling mechanism that explains the unique features of our p-n-p selector. Our experimental findings are further extended to confirm the profound functionality of oxide p-n-p selectors integrated with several bipolar resistive switching memory elements working as storage nodes. PMID:26289565

  13. All oxide semiconductor-based bidirectional vertical p-n-p selectors for 3D stackable crossbar-array electronics.

    PubMed

    Bae, Yoon Cheol; Lee, Ah Rahm; Baek, Gwang Ho; Chung, Je Bock; Kim, Tae Yoon; Park, Jea Gun; Hong, Jin Pyo

    2015-08-20

    Three-dimensional (3D) stackable memory devices including nano-scaled crossbar array are central for the realization of high-density non-volatile memory electronics. However, an essential sneak path issue affecting device performance in crossbar array remains a bottleneck and a grand challenge. Therefore, a suitable bidirectional selector as a two-way switch is required to facilitate a major breakthrough in the 3D crossbar array memory devices. Here, we show the excellent selectivity of all oxide p-/n-type semiconductor-based p-n-p open-based bipolar junction transistors as selectors in crossbar memory array. We report that bidirectional nonlinear characteristics of oxide p-n-p junctions can be highly enhanced by manipulating p-/n-type oxide semiconductor characteristics. We also propose an associated Zener tunneling mechanism that explains the unique features of our p-n-p selector. Our experimental findings are further extended to confirm the profound functionality of oxide p-n-p selectors integrated with several bipolar resistive switching memory elements working as storage nodes.

  14. Hybrid approach for structural modeling of biological systems from X-ray free electron laser diffraction patterns.

    PubMed

    Tokuhisa, Atsushi; Jonic, Slavica; Tama, Florence; Miyashita, Osamu

    2016-06-01

    We present a new hybrid approach for structural modeling using X-ray free electron laser (XFEL) diffraction patterns from non-crystalline biological samples. Reconstruction of a 3D structure requires a large number of diffraction patterns; however, in the current XFEL experiments with biological systems, the analysis often relies on a small number of 2D diffraction patterns. In this study, we explore the strategies to identify plausible 3D structural models by combining the 2D analysis of such diffraction patterns with computational modeling (normal mode analysis or molecular dynamics simulations). As the first step toward such hybrid modeling, we established a protocol to assess the agreement between the model structure and the target XFEL diffraction pattern and showed that XFEL data can be used to study the conformational transitions of biological molecules. We tested the proposed algorithms using data of three biomolecular complexes of different sizes (elongation factor 2, CCM virus, and ribosome) and examined the experimental conditions that are required to perform such studies, in particular the XFEL beam intensity requirements. The results indicate that the current beam intensity is close to a strength that enables us to study conformational transitions of macromolecules, such as ribosomes. The proposed algorithm can be combined with molecular mechanics approaches, such as molecular dynamics simulations and normal mode analysis, to generate a large number of candidate structures to perform hybrid structural modeling.

  15. Structure-Function Studies of Blood and Air Capillaries in Chicken Lung Using 3D Electron Microscopy

    PubMed Central

    West, John B.; Fu, Zhenxing; Deerinck, Thomas J.; Mackey, Mason R.; Obayashi, James T.; Ellisman, Mark H.

    2010-01-01

    Avian pulmonary capillaries differ from those of mammals in three important ways. The blood-gas barrier is much thinner, it is more uniform in thickness, and the capillaries are far more rigid when their transmural pressure is altered. The thinness of the barrier is surprising because it predisposes the capillaries to stress failure. A possible mechanism for these differences is that avian pulmonary capillaries, unlike mammalian, are supported from the outside by air capillaries, but the details of the support are poorly understood. To clarify this we studied the blood and air capillaries in chicken lung using transmission electron microscopy (EM) and two relatively new techniques that allow 3D visualization: electron tomography and serial block-face scanning EM. These studies show that the pulmonary capillaries are flanked by epithelial bridges composed of two extremely thin epithelial cells with large surface areas. The junctions of the bridges with the capillary walls show thickening of the epithelial cells and an accumulation of extracellular matrix. Collapse of the pulmonary capillaries when the pressure outside them is increased is apparently prevented by the guy wire-like action of the epithelial bridges. The enlarged junctions between the bridges and the walls could provide a mechanism that limits the hoop stress in the capillary walls when the pressure inside them is increased. The support of the pulmonary capillaries may also be explained by an interdependence mechanism whereby the capillaries are linked to a rigid assemblage of air capillaries. These EM studies show the supporting structures in greater detail than has previously been possible, particularly in 3D, and they allow a more complete analysis of the mechanical forces affecting avian pulmonary capillaries. PMID:20038456

  16. 3D reconstruction of VZV infected cell nuclei and PML nuclear cages by serial section array scanning electron microscopy and electron tomography.

    PubMed

    Reichelt, Mike; Joubert, Lydia; Perrino, John; Koh, Ai Leen; Phanwar, Ibanri; Arvin, Ann M

    2012-01-01

    Varicella-zoster virus (VZV) is a human alphaherpesvirus that causes varicella (chickenpox) and herpes zoster (shingles). Like all herpesviruses, the VZV DNA genome is replicated in the nucleus and packaged into nucleocapsids that must egress across the nuclear membrane for incorporation into virus particles in the cytoplasm. Our recent work showed that VZV nucleocapsids are sequestered in nuclear cages formed from promyelocytic leukemia protein (PML) in vitro and in human dorsal root ganglia and skin xenografts in vivo. We sought a method to determine the three-dimensional (3D) distribution of nucleocapsids in the nuclei of herpesvirus-infected cells as well as the 3D shape, volume and ultrastructure of these unique PML subnuclear domains. Here we report the development of a novel 3D imaging and reconstruction strategy that we term Serial Section Array-Scanning Electron Microscopy (SSA-SEM) and its application to the analysis of VZV-infected cells and these nuclear PML cages. We show that SSA-SEM permits large volume imaging and 3D reconstruction at a resolution sufficient to localize, count and distinguish different types of VZV nucleocapsids and to visualize complete PML cages. This method allowed a quantitative determination of how many nucleocapsids can be sequestered within individual PML cages (sequestration capacity), what proportion of nucleocapsids are entrapped in single nuclei (sequestration efficiency) and revealed the ultrastructural detail of the PML cages. More than 98% of all nucleocapsids in reconstructed nuclear volumes were contained in PML cages and single PML cages sequestered up to 2,780 nucleocapsids, which were shown by electron tomography to be embedded and cross-linked by an filamentous electron-dense meshwork within these unique subnuclear domains. This SSA-SEM analysis extends our recent characterization of PML cages and provides a proof of concept for this new strategy to investigate events during virion assembly at the single cell

  17. 3D Reconstruction of VZV Infected Cell Nuclei and PML Nuclear Cages by Serial Section Array Scanning Electron Microscopy and Electron Tomography

    PubMed Central

    Reichelt, Mike; Joubert, Lydia; Perrino, John; Koh, Ai Leen; Phanwar, Ibanri; Arvin, Ann M.

    2012-01-01

    Varicella-zoster virus (VZV) is a human alphaherpesvirus that causes varicella (chickenpox) and herpes zoster (shingles). Like all herpesviruses, the VZV DNA genome is replicated in the nucleus and packaged into nucleocapsids that must egress across the nuclear membrane for incorporation into virus particles in the cytoplasm. Our recent work showed that VZV nucleocapsids are sequestered in nuclear cages formed from promyelocytic leukemia protein (PML) in vitro and in human dorsal root ganglia and skin xenografts in vivo. We sought a method to determine the three-dimensional (3D) distribution of nucleocapsids in the nuclei of herpesvirus-infected cells as well as the 3D shape, volume and ultrastructure of these unique PML subnuclear domains. Here we report the development of a novel 3D imaging and reconstruction strategy that we term Serial Section Array-Scanning Electron Microscopy (SSA-SEM) and its application to the analysis of VZV-infected cells and these nuclear PML cages. We show that SSA-SEM permits large volume imaging and 3D reconstruction at a resolution sufficient to localize, count and distinguish different types of VZV nucleocapsids and to visualize complete PML cages. This method allowed a quantitative determination of how many nucleocapsids can be sequestered within individual PML cages (sequestration capacity), what proportion of nucleocapsids are entrapped in single nuclei (sequestration efficiency) and revealed the ultrastructural detail of the PML cages. More than 98% of all nucleocapsids in reconstructed nuclear volumes were contained in PML cages and single PML cages sequestered up to 2,780 nucleocapsids, which were shown by electron tomography to be embedded and cross-linked by an filamentous electron-dense meshwork within these unique subnuclear domains. This SSA-SEM analysis extends our recent characterization of PML cages and provides a proof of concept for this new strategy to investigate events during virion assembly at the single cell

  18. Runaway electron distributions obtained with the CQL3D Fokker-Planck code under tokamak disruption conditions

    SciTech Connect

    Harvey, R.W.; Chan, V.S.

    1996-12-31

    Runaway of electrons to high energy during plasma disruptions occurs due to large induced toroidal electric fields which tend to maintain the toroidal plasma current, in accord with Lenz law. This has been observed in many tokamaks. Within the closed flux surfaces, the bounce-averaged CQL3D Fokker-Planck code is well suited to obtain the resulting electron distributions, nonthermal contributions to electrical conductivity, and runaway rates. The time-dependent 2D in momentum-space (p{sub {parallel}} and p{sub {perpendicular}}) distributions axe calculated on a radial array of noncircular flux surfaces, including bounce-averaging of the Fokker-Planck equation to account for toroidal trapping effects. In the steady state, the resulting distributions represent a balance between applied toroidal electric field, relativistic Coulomb collisions, and synchrotron radiation. The code can be run in a mode where the electrons are sourced at low velocity and run off the high velocity edge of the computational mesh, giving runaway rates at steady state. At small minor radius, the results closely match previous results reported by Kulsrud et al. It is found that the runaway rate has a strong dependence on inverse aspect ratio e, decreasing by a factor {approx} 5 as e increases from 0.0 to 0.3. The code can also be run with a radial diffusion and pinching term, simulating radial transport with plasma pinching to maintain a given density profile. Results show a transport reduction of runaways in the plasma center, and an enhancement towards the edge due to the electrons from the plasma center. Avalanching of runaways due to a knock-on electron source is being included.

  19. Transmission Electron Diffraction Studies of Xenon Adsorbed on Graphite.

    NASA Astrophysics Data System (ADS)

    Faisal, A. Q. D.

    1987-09-01

    Available from UMI in association with The British Library. Adsorption studies of xenon on graphite were performed using the Hitachi HU-11B Transmission Electron Microscope (TEM). It has been used as a Transmission High Energy Electron Diffraction (THEED) camera. This has been modified to include an Ultra High Vacuum (UHV) environmental chamber. This chamber was isolated from the microscope vacuum by two 400 μm diameter differentially pumped apertures. Pressures of {~}10 ^{-6} torr and {~ }10^{-9} torr were achieved inside the microscope column and the environmental chamber respectively. The chamber was fitted with a new sample holder designed with double "O" rings. The sample was cooled with liquid helium. Previous THEED experiments by Venables et al and Schabes-Retchkiman and Venables revealed the presence of a 2D-solid incommensurate (I)-commensurate (C) phase transition as the temperature is lowered. These results were confirmed and extended in the present work. Hong et al have recently interpreted their X-ray diffraction experiments as showing an incommensurate-striped domain phase transition at {~}65rm K. No evidence was found for the existence of a striped domain structure on any part of the xenon phase diagram studied. Experiments of xenon adsorbed on the basal plane (0001) of graphite were carried out at pressures from {~}1.5 times 10^{-5} torr to {~}1.8 times 10^{-8} torr over a temperature range from 55K^.90K. A set of lattice parameter (misfit) measurements were made as a function of temperature at constant pressure with an accuracy of +/-0.1% rather than +/-0.3% previously obtained. The misfit data was fitted to a power law formula, i.e. misfit m = B_{rm o} (rm T - rm T_{rm o})^{rm A} , where A is a constant and equal to 0.8. It was found that B_{rm o} and T_{rm o} are functions of log(P). The data fell into two groups corresponding to two phase transitions. The same power law was used for both sets of data. Two transitions were found, one is I-C and

  20. Enantiomorph identification in organic crystals by electron diffraction

    NASA Astrophysics Data System (ADS)

    Tanaka, K.; Fujio, S.; Inui, H.; Ueji, R.; Sumida, N.

    2009-05-01

    The convergent-beam electron diffraction (CBED) method we proposed recently for enantiomorph identification has successfully been applied to some amino acid crystals such as glutamic acid and threonin. Enantiomorph identification (either left-handed or right-handed form) can readily be made within the framework of the proposed method by noting the asymmetric intensity distribution of Bijvoet pairs of reflections in the CBED pattern taken along an appropriate zone-axis orientation. Although the proposed method usually requires only a single CBED pattern, some effort to eliminate the ambiguity of 180°-rotation of the CBED pattern about the incident beam is needed for enantiomorph identification for these organic crystals because of the lack of HOLZ (higher-order Laue zone) reflection disks.

  1. Measuring Strain in Semiconductor Nanostructures by Convergent Beam Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Clément, L.; Rouviere, J.-L.; Cacho, F.; Pantel, R.

    Convergent beam electron diffraction (CBED) experiments and simulations, and finite element calculations are used to measure the strain and stress in a complex device such as a series of periodic MOS transistors. When approaching the transistor active regions, the HOLZ lines in the CBED patterns acquired in the silicon substrate, become increasingly broad. This HOLZ line broadening, which is due to the relaxation of stress in the lamella, is used to determine quantitatively the strain and stress in the thin lamella and then in the bulk device. Two parameters, the intrinsic material stresses in the NiSi and Si3N4 layers of the transistors, are successfully fitted by trial and error. These fitted values are, respectively, equal to 1.2 and 0.95GPa.

  2. The molecular structure of naphthalene by electron diffraction

    NASA Astrophysics Data System (ADS)

    Ketkar, S. N.; Fink, M.

    1981-11-01

    The molecular structure of gaseous naphthalene has been studied by electron diffraction at a nozzle tip temperature of about 25°C. The molecule has D 2h symmetry to within experimental error. The results for the distances ( ra), bond angle and r.m.s. amplitude ( l) are r(CH) = 1.092(6) Å, r(C 9C 1) = 1.422(2) Å, r(C 1C 2) = 1.381(2) Å, r(C 2C 3) = 1.417(4) Å, r(C 10C 9) = 1.412(8) Å, ∠C 10C 9C 1 = 119.5(3)°, ∠CCH = 119.9(7)°, l(CH) = 0.076(6) Å, l(CC) = 0.047(2) Å.

  3. Structural, electronic and magnetic properties of 3d metal trioxide clusters-doped monolayer graphene: A first-principles study

    NASA Astrophysics Data System (ADS)

    Rafique, Muhammad; Shuai, Yong; Tan, He-Ping; Hassan, Muhammad

    2017-03-01

    We present first-principles density-functional calculations for the structural, electronic and magnetic properties of monolayer graphene doped with 3d (Ti, V, Cr, Fe, Co, Mn and Ni) metal trioxide TMO3 halogen clusters. In this paper we used two approaches for 3d metal trioxide clusters (i) TMO3 halogen cluster was embedded in monolayer graphene substituting four carbon (C) atoms (ii) three C atoms were substituted by three oxygen (O) atoms in one graphene ring and TM atom was adsorbed at the hollow site of O atoms substituted graphene ring. All the impurities were tightly bonded in the graphene ring. In first case of TMO3 doped graphene layer, the bond length between Csbnd O atom was reduced and bond length between TM-O atom was increased. In case of Cr, Fe, Co and Ni atoms substitution in between the O atoms, leads to Fermi level shifting to conduction band thereby causing the Dirac cone to move into valence band, however a band gap appears at high symmetric K-point. In case of TiO3 and VO3 substitution, system exhibits semiconductor properties. Interestingly, TiO3-substituted system shows dilute magnetic semiconductor behavior with 2.00 μB magnetic moment. On the other hand, the substitution of CoO3, CrO3, FeO3 and MnO3 induced 1.015 μB, 2.347 μB, 2.084 μB and 3.584 μB magnetic moment, respectively. In second case of O atoms doped in graphene and TM atoms adsorbed at the hollow site, the O atom bulges out of graphene plane and bond length between TM-O atom is increased. After TM atoms adsorption at the O substituted graphene ring the Fermi level (EF) shifts into conduction band. In case of Cr and Ni adsorption, system displays indirect band gap semiconductor properties with 0.0 μB magnetic moment. Co adsorption exhibits dilute magnetic semiconductor behavior producing 0.916 μB magnetic moment. Fe, Mn, Ti and V adsorption introduces band gap at high symmetric K-point also inducing 1.54 μB, 0.9909 μB, 1.912 μB, and 0.98 μB magnetic moments, respectively

  4. 3D Ion and Electron Distribution Function Measurements from the Fast Plasma Investigation on the Magnetospheric Multiscale Mission

    NASA Astrophysics Data System (ADS)

    Giles, B. L.; Pollock, C. J.; Avanov, L. A.; Barrie, A. C.; Burch, J. L.; Chandler, M. O.; Clark, G. B.; Coffey, V. N.; Dickson, C.; Dorelli, J.; Ergun, R. E.; Fuselier, S. A.; Gershman, D. J.; Gliese, U.; Holland, M. P.; Jacques, A. D.; Kreisler, S.; Lavraud, B.; MacDonald, E.; Mauk, B.; Moore, T. E.; Mukai, T.; Nakamura, R.; Paterson, W. R.; Rager, A. C.; Saito, Y.; Salo, C.; Sauvaud, J. A.; Torbert, R. B.; Vinas, A. F.; Yokota, S.

    2015-12-01

    The primary focus of the Magnetospheric Multiscale (MMS) mission, launched in March 2015, is magnetic reconnection and associated processes. Understanding hinges critically on the kinetic physics that allows reconnection to take place. The Fast Plasma Investigation (FPI) provides electron and ion distribution functions at 4.5s cadence and, for select periods of time, at cadences of 30ms for electrons and 150ms for ions. These select time periods are chosen after in situ acquisition based on inspection of the low resolution data. Thus the FPI provides, independent of spacecraft spin rate, the time resolution needed to resolve the small, fast-moving reconnection diffusion regions. The first mission phase focuses on the dayside magnetopause and this presentation is intended to demonstrate the capabilities of FPI to resolve the important spatial scales relevant to the reconnection process. Magnetopause and other boundary crossings will be examined and the phase-space trajectories identified at the tetrahedral satellite locations through analysis of the 3D distribution functions.

  5. 3D nanostructured inkjet printed graphene via UV-pulsed laser irradiation enables paper-based electronics and electrochemical devices.

    PubMed

    Das, Suprem R; Nian, Qiong; Cargill, Allison A; Hondred, John A; Ding, Shaowei; Saei, Mojib; Cheng, Gary J; Claussen, Jonathan C

    2016-09-21

    Emerging research on printed and flexible graphene-based electronics is beginning to show tremendous promise for a wide variety of fields including wearable sensors and thin film transistors. However, post-print annealing/reduction processes that are necessary to increase the electrical conductivity of the printed graphene degrade sensitive substrates (e.g., paper) and are whole substrate processes that are unable to selectively anneal/reduce only the printed graphene-leaving sensitive device components exposed to damaging heat or chemicals. Herein a pulsed laser process is introduced that can selectively irradiate inkjet printed reduced graphene oxide (RGO) and subsequently improve the electrical conductivity (Rsheet∼0.7 kΩ□(-1)) of printed graphene above previously published reports. Furthermore, the laser process is capable of developing 3D petal-like graphene nanostructures from 2D planar printed graphene. These visible morphological changes display favorable electrochemical sensing characteristics-ferricyanide cyclic voltammetry with a redox peak separation (ΔEp) ≈ 0.7 V as well as hydrogen peroxide (H2O2) amperometry with a sensitivity of 3.32 μA mM(-1) and a response time of <5 s. Thus this work paves the way for not only paper-based electronics with graphene circuits, it enables the creation of low-cost and disposable graphene-based electrochemical electrodes for myriad applications including sensors, biosensors, fuel cells, and theranostic devices.

  6. 2D/3D electron temperature fluctuations near explosive MHD instabilities accompanied by minor and major disruptions

    NASA Astrophysics Data System (ADS)

    Choi, M. J.; Park, H. K.; Yun, G. S.; Lee, W.; Luhmann, N. C., Jr.; Lee, K. D.; Ko, W.-H.; Park, Y.-S.; Park, B. H.; In, Y.

    2016-06-01

    Minor and major disruptions by explosive MHD instabilities were observed with the novel quasi 3D electron cyclotron emission imaging (ECEI) system in the KSTAR plasma. The fine electron temperature (T e) fluctuation images revealed two types of minor disruptions: a small minor disruption is a q∼ 2 localized fast transport event due to a single m/n  =  2/1 magnetic island growth, while a large minor disruption is partial collapse of the q≤slant 2 region with two successive fast heat transport events by the correlated m/n  =  2/1 and m/n  =  1/1 instabilities. The m/n  =  2/1 magnetic island growth during the minor disruption is normally limited below the saturation width. However, as the additional interchange-like perturbation grows near the inner separatrix of the 2/1 island, the 2/1 island can expand beyond the limit through coupling with the cold bubble formed by the interchange-like perturbation.

  7. Ultrafast electron diffraction with megahertz MeV electron pulses from a superconducting radio-frequency photoinjector

    SciTech Connect

    Feng, L. W.; Lin, L.; Huang, S. L.; Quan, S. W.; Hao, J. K.; Zhu, F.; Wang, F.; Liu, K. X.; Jiang, T.; Zhu, P. F.; Fu, F.; Wang, R.; Zhao, L.; Xiang, D.

    2015-11-30

    We report ultrafast relativistic electron diffraction operating at the megahertz repetition rate where the electron beam is produced in a superconducting radio-frequency (rf) photoinjector. We show that the beam quality is sufficiently high to provide clear diffraction patterns from gold and aluminium samples. With the number of electrons, several orders of magnitude higher than that from a normal conducting photocathode rf gun, such high repetition rate ultrafast MeV electron diffraction may open up many new opportunities in ultrafast science.

  8. Advanced characterization of twins using automated electron backscatter diffraction

    SciTech Connect

    Wright, S. I.; Bingert, J. F.; Mason, T. A.; Larson, R. J.

    2002-01-01

    This paper describes results obtained using an automated, crystallographically-based technique for twin identification. The technique is based on the automated collection of spatially specific orientation measurements by electron backscatter diffraction (EBSD) in the scanning electron microscope (SEM). The key features of the analysis are identification of potential twin boundaries by their misorientation character, identification of the distinct boundary planes among the symmetrically equivalent candidates, and validation of these boundaries through comparison with the boundary and twin plane traces in the sample cross section. Results on the application of this technique to deformation twins in zirconium are analyzed for the effect of twin type and amount and sense of uniaxial deformation. The accumulation of strain tends to increase the misorientation deviation at least to the degree of the trace deviation compared with recrystallization twins in nickel. In addition to the results on characterizing the twin character, results on extending the twin analysis to automated identification of parent and daughter material for structures exhibiting twin deformation are reported as well.

  9. Fast character projection electron beam lithography for diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Harzendorf, Torsten; Fuchs, Frank; Banasch, Michael; Zeitner, Uwe D.

    2014-05-01

    Electron beam lithography becomes attractive also for the fabrication of large scale diffractive optical elements by the use of the character projection (CP) technique. Even in the comparable fast variable shaped beam (VSB) exposure approach for conventional electron beam writers optical nanostructures may require very long writing times exceeding 24 hours per wafer because of the high density of features, as required by e.g. sub-wavelength nanostructures. Using character projection, the writing time can be reduced by more than one order of magnitude, due to the simultaneous exposure of multiple features. The benefit of character projection increases with increasing complexity of the features and decreasing period. In this contribution we demonstrate the CP technique for a grating of hexagonal symmetry at 350nm period. The pattern is designed to provide antireflective (AR) properties, which can be adapted in their spectral and angular domain for applications from VIS to NIR by changing the feature size and the etching depth of the nanostructure. This AR nanostructure can be used on the backside of optical elements e.g. gratings, when an AR coating stack could not be applied for the reason of climatic conditions or wave front accuracy.

  10. Using Quasi-3D OSIRIS simulations of LWFA to study generating high brightness electron beams using ionization and density downramp injection

    NASA Astrophysics Data System (ADS)

    Dalichaouch, Thamine; Davidson, Asher; Xu, Xinlu; Yu, Peicheng; Tsung, Frank; Mori, Warren; Li, Fei; Zhang, Chaojie; Lu, Wei; Vieira, Jorge; Fonseca, Ricardo

    2016-10-01

    In the past few decades, there has been much progress in theory, simulation, and experiment towards using Laser wakefield acceleration (LWFA) as the basis for designing and building compact x-ray free-electron-lasers (XFEL) as well as a next generation linear collider. Recently, ionization injection and density downramp injection have been proposed and demonstrated as a controllable injection scheme for creating higher quality and ultra-bright relativistic electron beams using LWFA. However, full-3D simulations of plasma-based accelerators are computationally intensive, sometimes taking 100 millions of core-hours on today's computers. A more efficient quasi-3D algorithm was developed and implemented into OSIRIS using a particle-in-cell description with a charge conserving current deposition scheme in r - z and a gridless Fourier expansion in ϕ. Due to the azimuthal symmetry in LWFA, quasi-3D simulations are computationally more efficient than 3D cartesian simulations since only the first few harmonics in are needed ϕ to capture the 3D physics of LWFA. Using the quasi-3D approach, we present preliminary results of ionization and down ramp triggered injection and compare the results against 3D LWFA simulations. This work was supported by DOE and NSF.

  11. A study of 3D structure of nighttime electron density enhancement in the mid-latitude ionosphere by GPS tomography

    NASA Astrophysics Data System (ADS)

    Chen, C.; Saito, A.

    2011-12-01

    The mid-latitude summer nighttime anomaly (MSNA) is a feature that the nighttime electron density larger than that in the daytime mid-latitude ionosphere. This anomaly was first detected in the southern hemisphere five decades ago and observed in the northern hemisphere recently by ionosondes and satellites. Previous studies presented the electron density structure of MSNA by using COSMIC occultation data and found that MSNA is clearly seen around 300 km altitude during local summer. However, due to lack of observation, the day-to-day variation of MSNA was not investigated. A GPS tomography method by SPEL of Kyoto University using the total electron content (TEC) data measured by the ground-based GPS receiver network is employed in this study. The wide coverage and continuous observation of GPS receivers are suitable for investigating the spatial and day-to-day variations of ionospheric electron densities. The algorithm of the GPS tomography developed by SPEL of Kyoto University use a constraint condition that the gradient of election density tends to be smooth in the horizontal direction and steep in the vicinity of the F2 peak, instead of inputting the initial conditions. Therefore, the algorithm is independent of any ionospheric and plasmaspheric electron density distribution models. The dense ground-based GPS receiver network around European region is used to study the three dimensional (3D) structure of MSNA with GPS tomography. Results show that the MSNA usually appear around the geomagnetic mid-latitude region during local summer nighttime. The feature of MSNA is most obvious at the ionospheric F2-peak altitudes. The result also shows a day-to-day variation in the formation of MSNA, in terms of the occurrence time, intensity, and spatial extent. The tomographic results are compared with the ionosondes, satellites, and radar measurements. A theoretical model simulation, SAMI2, is also used to further discuss the mechanism of MSNA. The comparison with other

  12. Longitudinal imaging of HIV-1 spread in humanized mice with parallel 3D immunofluorescence and electron tomography

    PubMed Central

    Kieffer, Collin; Ladinsky, Mark S; Ninh, Allen; Galimidi, Rachel P; Bjorkman, Pamela J

    2017-01-01

    Dissemination of HIV-1 throughout lymphoid tissues leads to systemic virus spread following infection. We combined tissue clearing, 3D-immunofluorescence, and electron tomography (ET) to longitudinally assess early HIV-1 spread in lymphoid tissues in humanized mice. Immunofluorescence revealed peak infection density in gut at 10–12 days post-infection when blood viral loads were low. Human CD4+ T-cells and HIV-1–infected cells localized predominantly to crypts and the lower third of intestinal villi. Free virions and infected cells were not readily detectable by ET at 5-days post-infection, whereas HIV-1–infected cells surrounded by pools of free virions were present in ~10% of intestinal crypts by 10–12 days. ET of spleen revealed thousands of virions released by individual cells and discreet cytoplasmic densities near sites of prolific virus production. These studies highlight the importance of multiscale imaging of HIV-1–infected tissues and are adaptable to other animal models and human patient samples. DOI: http://dx.doi.org/10.7554/eLife.23282.001 PMID:28198699

  13. Optical sectioning and 3D reconstructions as an alternative to scanning electron microscopy for analysis of cell shape1

    PubMed Central

    Landis, Jacob B.; Ventura, Kayla L.; Soltis, Douglas E.; Soltis, Pamela S.; Oppenheimer, David G.

    2015-01-01

    Premise of the study: Visualizing flower epidermal cells is often desirable for investigating the interaction between flowers and their pollinators, in addition to the broader range of ecological interactions in which flowers are involved. We developed a protocol for visualizing petal epidermal cells without the limitations of the commonly used method of scanning electron microscopy (SEM). Methods: Flower material was collected and fixed in glutaraldehyde, followed by dehydration in an ethanol series. Flowers were dissected to collect petals, and subjected to a Histo-Clear series to remove the cuticle. Material was then stained with aniline blue, mounted on microscope slides, and imaged using a compound fluorescence microscope to obtain optical sections that were reconstructed into a 3D image. Results: This optical sectioning method yielded high-quality images of the petal epidermal cells with virtually no damage to cells. Flowers were processed in larger batches than are possible using common SEM methods. Also, flower size was not a limiting factor as often observed in SEM studies. Flowers up to 5 cm in length were processed and mounted for visualization. Conclusions: This method requires no special equipment for sample preparation prior to imaging and should be seen as an alternative method to SEM. PMID:25909040

  14. Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

    NASA Astrophysics Data System (ADS)

    Willensdorfer, M.; Denk, S. S.; Strumberger, E.; Suttrop, W.; Vanovac, B.; Brida, D.; Cavedon, M.; Classen, I.; Dunne, M.; Fietz, S.; Fischer, R.; Kirk, A.; Laggner, F. M.; Liu, Y. Q.; Odstrčil, T.; Ryan, D. A.; Viezzer, E.; Zohm, H.; Luhmann, I. C.; The ASDEX Upgrade Team; The EUROfusion MST1 Team

    2016-11-01

    The plasma response from an external n  =  2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. The measured amplitudes of the helical displacement around the outboard midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the predictions from the vacuum field calculations and indicate the presence of a kink response at the edge, which amplifies the perturbation. VMEC and MARS-F have been used to calculate the properties of this kink mode. The poloidal mode structure of the magnetic perturbation of this kink mode at the edge peaks at poloidal mode numbers larger than the resonant components |m|>|nq| , whereas the poloidal mode structure of its displacement is almost resonant |m|≈ |nq| . This is expected from ideal MHD in the proximity of rational surfaces. The displacement measured by ECE-I confirms this resonant response.

  15. Runaway electrons mitigation by 3D fields: new insights from ASDEX Upgrade and RFX-mod experiments

    NASA Astrophysics Data System (ADS)

    Gobbin, M.; Papp, G.; Marrelli, L.; McCarthy, P. J.; Nocente, M.; Pautasso, G.; Suttrop, W.; Piovesan, P.; Terranova, D.; Valisa, M.

    2016-10-01

    Disruption-generated runaway electron (RE) beams represent a severe threat for tokamak plasma-facing components, thus motivating the search of mitigation techniques. The application of optimized 3D fields might aid this purpose, as was recently investigated in ASDEX Upgrade and RFX-mod. In ASDEX Upgrade discharges, the application of n =1 resonant magnetic perturbations (RMPs) by the B-coils before and during the disruption results in a longer current quench time together with a lower RE current in the post-disruption phase. The strength of the observed effects depends on the upper-to-lower B-coil phasing, i.e. on the poloidal spectrum of the RMPs. These results are analyzed by means of numerical tools, like the guiding center code ORBIT, and the role of plasma response is also investigated. Similar experiments have been performed in RFX-mod low density plasmas where magnetic perturbations of various amplitudes, applied by non-axisymmetric coils, have been found to partially suppress REs. ORBIT simulations indicate, in this case, that RE orbit losses are associated to a raised level of stochasticity in the edge plasma region.

  16. Resonant soft x-ray magnetic scattering from the 4f and 3d electrons in DyFe{sub 4}Al{sub 8}: Magnetic interactions in a cycloidal antiferromagnet

    SciTech Connect

    Beale, T. A. W.; Hatton, P. D.; Wilkins, S. B.; Abbamonte, P.; Stanescu, S.; Paixao, J. A.

    2007-05-01

    Soft x-ray resonant scattering has been used to examine the charge and magnetic interactions in the cycloidal antiferromagnetic compound DyFe{sub 4}Al{sub 8}. By tuning to the Dy M{sub 4} and M{sub 5} absorption edges and the Fe L{sub 2} and L{sub 3} absorption edges, we can directly observe the behavior of the Dy 4f and Fe 3d electron shells. Magnetic satellites surrounding the (110) Bragg peak were observed below 65 K. The diffraction peaks display complex spectra at the Dy M{sub 5} edge, indicative of a split 4f electron band. This is in contrast to the simple resonance observed at the Fe L{sub 3} absorption edge, which probes the Fe 3d electron shell. Temperature-dependent measurements detail the ordering of the magnetic moments on both the iron and the dysprosium antiferromagnetic cycloids. The ratio between the superlattice peak intensities of the Dy M{sub 4} and M{sub 5} absorption edges remained constant throughout the temperature range, in contrast to a previous study conducted at the Dy L{sub 2,3} edges. Our results demonstrate the ability of soft x-ray diffraction to separate the individual magnetic components in complicated multielement magnetic structures.

  17. Low-kilovolt coherent electron diffractive imaging instrument based on a single-atom electron source

    SciTech Connect

    Lin, Chun-Yueh; Chang, Wei-Tse; Chen, Yi-Sheng; Hwu, En-Te; Chang, Chia-Seng; Hwang, Ing-Shouh; Hsu, Wei-Hao

    2016-03-15

    In this work, a transmission-type, low-kilovolt coherent electron diffractive imaging instrument was constructed. It comprised a single-atom field emitter, a triple-element electrostatic lens, a sample holder, and a retractable delay line detector to record the diffraction patterns at different positions behind the sample. It was designed to image materials thinner than 3 nm. The authors analyzed the asymmetric triple-element electrostatic lens for focusing the electron beams and achieved a focused beam spot of 87 nm on the sample plane at the electron energy of 2 kV. High-angle coherent diffraction patterns of a suspended graphene sample corresponding to (0.62 Å){sup −1} were recorded. This work demonstrated the potential of coherent diffractive imaging of thin two-dimensional materials, biological molecules, and nano-objects at a voltage between 1 and 10 kV. The ultimate goal of this instrument is to achieve atomic resolution of these materials with high contrast and little radiation damage.

  18. Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory.

    PubMed

    Weathersby, S P; Brown, G; Centurion, M; Chase, T F; Coffee, R; Corbett, J; Eichner, J P; Frisch, J C; Fry, A R; Gühr, M; Hartmann, N; Hast, C; Hettel, R; Jobe, R K; Jongewaard, E N; Lewandowski, J R; Li, R K; Lindenberg, A M; Makasyuk, I; May, J E; McCormick, D; Nguyen, M N; Reid, A H; Shen, X; Sokolowski-Tinten, K; Vecchione, T; Vetter, S L; Wu, J; Yang, J; Dürr, H A; Wang, X J

    2015-07-01

    Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition rate with outstanding performance. In this paper, we report on the SLAC MeV UED system and its performance, including the reciprocal space resolution, temporal resolution, and machine stability.

  19. Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory

    SciTech Connect

    Weathersby, S. P.; Brown, G.; Chase, T. F.; Coffee, R.; Corbett, J.; Eichner, J. P.; Frisch, J. C.; Fry, A. R.; Gühr, M.; Hartmann, N.; Hast, C.; Hettel, R.; Jobe, R. K.; Jongewaard, E. N.; Lewandowski, J. R.; Li, R. K. Lindenberg, A. M.; Makasyuk, I.; May, J. E.; McCormick, D.; and others

    2015-07-15

    Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition rate with outstanding performance. In this paper, we report on the SLAC MeV UED system and its performance, including the reciprocal space resolution, temporal resolution, and machine stability.

  20. Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory

    SciTech Connect

    Weathersby, S. P.; Brown, G.; Centurion, M.; Chase, T. F.; Coffee, R.; Corbett, J.; Eichner, J. P.; Frisch, J. C.; Fry, A. R.; Gühr, M.; Hartmann, N.; Hast, C.; Hettel, R.; Jobe, R. K.; Jongewaard, E. N.; Lewandowski, J. R.; Li, R. K.; Lindenberg, A. M.; Makasyuk, I.; May, J. E.; McCormick, D.; Nguyen, M. N.; Reid, A. H.; Shen, X.; Sokolowski-Tinten, K.; Vecchione, T.; Vetter, S. L.; Wu, J.; Yang, J.; Dürr, H. A.; Wang, X. J.

    2015-07-01

    Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used to study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic electron beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time and length scales. SLAC National Accelerator Laboratory recently launched the Ultrafast Electron Diffraction (UED) and microscopy Initiative aiming at developing the next generation ultrafast electron scattering instruments. As the first stage of the Initiative, a mega-electron-volt (MeV) UED system has been constructed and commissioned to serve ultrafast science experiments and instrumentation development. The system operates at 120-Hz repetition rate with outstanding performance. In this paper, we report on the SLAC MeV UED system and its performance, including the reciprocal space resolution, temporal resolution, and machine stability.

  1. A New Approach to Sap Flow Measurement Using 3D Printed Gauges and Open-source Electronics

    NASA Astrophysics Data System (ADS)

    Ham, J. M.; Miner, G. L.; Kluitenberg, G. J.

    2015-12-01

    A new type of sap flow gauge was developed to measure transpiration from herbaceous plants using a modified heat pulse technique. Gauges were fabricated using 3D-printing technology and low-cost electronics to keep the materials cost under $20 (U.S.) per sensor. Each gauge consisted of small-diameter needle probes fastened to a 3D-printed frame. One needle contained a resistance heater to provide a 6 to 8 second heat pulse while the other probes measured the resultant temperature increase at two distances from the heat source. The data acquisition system for the gauges was built from a low-cost Arduino microcontroller. The system read the gauges every 10 minutes and stored the results on a SD card. Different numerical techniques were evaluated for estimating sap velocity from the heat pulse data - including analytical solutions and parameter estimation approaches . Prototype gauges were tested in the greenhouse on containerized corn and sunflower. Sap velocities measured by the gauges were compared to independent gravimetric measurements of whole plant transpiration. Results showed the system could measure daily transpiration to within 3% of the gravimetric measurements. Excellent agreement was observed when two gauges were attached the same stem. Accuracy was not affected by rapidly changing transpiration rates observed under partly cloudy conditions. The gauge-based estimates of stem thermal properties suggested the system may also detect the onset of water stress. A field study showed the gauges could run for 1 to 2 weeks on a small battery pack. Sap flow measurements on multiple corn stems were scaled up by population to estimate field-scale transpiration. During full canopy cover, excellent agreement was observed between the scaled-up sap flow measurements and reference crop evapotranspiration calculated from weather data. Data also showed promise as a way to estimate real-time canopy resistance required for model verification and development. Given the low

  2. Electron diffraction from free-standing, metal-coated transmission gratings

    NASA Astrophysics Data System (ADS)

    Gronniger, Glen; Barwick, Brett; Batelaan, Herman; Savas, Tim; Pritchard, Dave; Cronin, Alex

    2005-09-01

    Electron diffraction from a free-standing nanofabricated transmission grating was demonstrated, with energies ranging from 125 eV to 25 keV. Observation of 21 diffraction orders highlights the quality of the gratings. The image charge potential due to one electron was measured by rotating the grating. These gratings may pave the way to low-energy electron interferometry.

  3. Ab initio structure determination of nanocrystals of organic pharmaceutical compounds by electron diffraction at room temperature using a Timepix quantum area direct electron detector

    SciTech Connect

    Genderen, E. van; Clabbers, M. T. B.; Das, P. P.; Stewart, A.; Nederlof, I.; Barentsen, K. C.; Portillo, Q.; Pannu, N. S.; Nicolopoulos, S.; Gruene, T.; Abrahams, J. P.

    2016-02-05

    A specialized quantum area detector for electron diffraction studies makes it possible to solve the structure of small organic compound nanocrystals in non-cryo conditions by direct methods. Until recently, structure determination by transmission electron microscopy of beam-sensitive three-dimensional nanocrystals required electron diffraction tomography data collection at liquid-nitrogen temperature, in order to reduce radiation damage. Here it is shown that the novel Timepix detector combines a high dynamic range with a very high signal-to-noise ratio and single-electron sensitivity, enabling ab initio phasing of beam-sensitive organic compounds. Low-dose electron diffraction data (∼0.013 e{sup −} Å{sup −2} s{sup −1}) were collected at room temperature with the rotation method. It was ascertained that the data were of sufficient quality for structure solution using direct methods using software developed for X-ray crystallography (XDS, SHELX) and for electron crystallography (ADT3D/PETS, SIR2014)

  4. A scalable diffraction-based scanning 3D colour video display as demonstrated by using tiled gratings and a vertical diffuser

    PubMed Central

    Jia, Jia; Chen, Jhensi; Yao, Jun; Chu, Daping

    2017-01-01

    A high quality 3D display requires a high amount of optical information throughput, which needs an appropriate mechanism to distribute information in space uniformly and efficiently. This study proposes a front-viewing system which is capable of managing the required amount of information efficiently from a high bandwidth source and projecting 3D images with a decent size and a large viewing angle at video rate in full colour. It employs variable gratings to support a high bandwidth distribution. This concept is scalable and the system can be made compact in size. A horizontal parallax only (HPO) proof-of-concept system is demonstrated by projecting holographic images from a digital micro mirror device (DMD) through rotational tiled gratings before they are realised on a vertical diffuser for front-viewing. PMID:28304371

  5. A scalable diffraction-based scanning 3D colour video display as demonstrated by using tiled gratings and a vertical diffuser

    NASA Astrophysics Data System (ADS)

    Jia, Jia; Chen, Jhensi; Yao, Jun; Chu, Daping

    2017-03-01

    A high quality 3D display requires a high amount of optical information throughput, which needs an appropriate mechanism to distribute information in space uniformly and efficiently. This study proposes a front-viewing system which is capable of managing the required amount of information efficiently from a high bandwidth source and projecting 3D images with a decent size and a large viewing angle at video rate in full colour. It employs variable gratings to support a high bandwidth distribution. This concept is scalable and the system can be made compact in size. A horizontal parallax only (HPO) proof-of-concept system is demonstrated by projecting holographic images from a digital micro mirror device (DMD) through rotational tiled gratings before they are realised on a vertical diffuser for front-viewing.

  6. Crystal structure of nacrite from the electron diffraction data

    SciTech Connect

    Zhukhlistov, A. P.

    2008-01-15

    The crystal structure of the nacrite mineral of the kaolin group (space group Cc; R = 2.76%; 634 unique reflections) is refined from the digital oblique-texture electron diffraction patterns obtained with the use of imaging plates. The maxima characterizing the locations and potentials of the hydrogen atoms of the hydroxyl groups are revealed from the difference Fourier-potential syntheses. The O-H interatomic distances and the angles of inclination of the O-H bond with respect to the ab plane are equal to 0.97 A and -18.3 deg. for the inner hydroxyl group and 0.92, 0.85, 0.93 A and 60.8 deg., 67.8 deg., 58.4 deg. for the outer hydroxyl groups, respectively. The O{sub donor}-O{sub acceptor} interatomic distances are 2.940, 2.949, and 3.121 A. It is established that the electrostatic potential distributions of the hydrogen atoms of the inner hydroxyl group and one of the outer hydroxyl groups located in the vicinity of the symmetry pseudoplane m of the layer are characterized by anisotropy, which can indicate a statistical distribution of these hydrogen atoms.

  7. Crystallographic Orientation of Cuttlebone Shield Determined by Electron Backscatter Diffraction

    NASA Astrophysics Data System (ADS)

    Cusack, Maggie; Chung, Peter

    2014-01-01

    In common with many cephalopod mollusks, cuttlefish produce an internal biomineral buoyancy device. This cuttlebone is analogous to a surf board in shape and structure, providing rigidity and a means of controlling buoyancy. The cuttlebone is composed of calcium carbonate in the form of aragonite and comprises an upper dorsal shield and a lower lamellar matrix. The lamellar matrix comprises layers of chambers with highly corrugated walls. The dorsal shield comprises bundles of aragonite needles stacked on top of each other. Electron backscatter diffraction analyses of the dorsal shield reveal that the c-axis of aragonite is parallel with the long axis of the needles in the bundles such that any spread in crystallographic orientation is consistent with the spread in orientation of the fibers as they radiate to form the overall structure of the dorsal shield. This arrangement of c-axis coincident with the long axis of the biomineral structure is similar to the arrangement in corals and in contrast to the situation in the molluskan aragonite nacre of brachiopod calcite where the c-axis is perpendicular to the aragonite tablet or calcite fiber, respectively.

  8. Molecular structure of tetramethylgermane from gas electron diffraction

    NASA Astrophysics Data System (ADS)

    Csákvári, Éva; Rozsondai, Béla; Hargittai, István

    1991-05-01

    The molecular structure of Ge(CH 3) 4 has been determined from gas-phase electron diffraction augmented by a normal coordinate analysis. Assuming tetrahedral symmetry for the germanium bond configuration, the following structural parameters are found: rg(GeC) = 1.958 ± 0.004 Å, rg(CH) = 1.111 ± 0.003 Å and ∠(GeCH) = 110.7 ± 0.2° ( R=4.0%). The methyl torsional barrier V 0 is estimated to be 1.3 kJ mol -1 on the basis of an effective angle of torsion 23.0 ± 1.5°, from the staggered form, yielded directly by the analysis. The GeC bond length of Ge(CH 3) 4 is the same, within experimental error, as that of Ge(C 6H 5) 4 and is in agreement with the prediction of a modified Schomaker-Stevenson relationship.

  9. Diffraction of 0.5 keV electrons from free-standing transmission gratings

    NASA Astrophysics Data System (ADS)

    McMorran, Ben; Perreault, John; Savas, Tim; Cronin, Alex

    2006-05-01

    A nanostructured grating was used to diffract a low-energy (500 eV) electron beam, and the current transmitted into the zeroth diffraction order was greater than 5% of the incident beam current. This diffraction efficiency indicates that the 55-nm-wide grating bars absorb electrons but the 45-nm-wide slots between bars transmit electron de Broglie waves coherently. The diffraction patterns can be asymmetric, and can be explained by a model that incorporates an electrostatic potential energy for electrons within 20 nm of the grating structure calculated by the method of images.

  10. Clinical application of 3D-printed-step-bolus in post-total-mastectomy electron conformal therapy.

    PubMed

    Park, Kwangwoo; Park, Sungjin; Jeon, Mi-Jin; Choi, Jinhyun; Kim, Jun Won; Cho, Yoon Jin; Jang, Won-Seok; Keum, Yo Sup; Lee, Ik Jae

    2016-10-23

    The 3D-printed boluses were used during the radiation therapy of the chest wall in six patients with breast cancer after modified radical mastectomy (MRM). We measured the in-vivo skin doses while both conventional and 3D-printed boluses were placed on the chest wall and compared the mean doses delivered to the ipsilateral lung and the heart. The homogeneity and conformity of the dose distribution in the chest wall for both types of boluses were also evaluated. The uniformity index on the chest skin was improved when the 3D-printed boluses were used, with the overall average skin dose being closer to the prescribed one in the former case (-0.47% versus -4.43%). On comparing the dose-volume histogram (DVH), it was found that the 3D-printed boluses resulted in a reduction in the mean dose to the ipsilateral lung by up to 20%. The precision of dose delivery was improved by 3% with the 3D-printed boluses; in contrast, the conventional step bolus resulted in a precision level of 5%. In conclusion, the use of the 3D-printed boluses resulted in better dose homogeneity and conformity to the chest wall as well as the sparing of the normal organs, especially the lung. This suggested that their routine use on the chest wall as a therapeutic approach during post-mastectomy radiation therapy offers numerous advantages over conventional step boluses.

  11. A Method for 3D-Reconstruction of a Muscle Thick Filament Using the Tilt Series Images of a Single Filament Electron Tomogram

    PubMed Central

    Márquez, G.; Pinto, A.; Alamo, L.; Baumann, B.; Ye, F.; Winkler, H.; Taylor, K.; Padrón, R.

    2014-01-01

    Summary Myosin interacting-heads (MIH) motifs are visualized in 3D-reconstructions of thick filaments from striated muscle. These reconstructions are calculated by averaging methods using images from electron micrographs of grids prepared using numerous filament preparations. Here we propose an alternative method to calculate the 3D-reconstruction of a single thick filament using only a tilt series images recorded by electron tomography. Relaxed thick filaments, prepared from tarantula leg muscle homogenates, were negatively stained. Single-axis tilt series of single isolated thick filaments were obtained with the electron microscope at a low electron dose, and recorded on a CCD camera by electron tomography. An IHRSR 3D-recontruction was calculated from the tilt series images of a single thick filament. The reconstruction was enhanced by including in the search stage dual tilt image segments while only single tilt along the filament axis is usually used, as well as applying a band pass filter just before the back projection. The reconstruction from a single filament has a 40 Å resolution and clearly shows the presence of MIH motifs. In contrast, the electron tomogram 3D-reconstruction of the same thick filament –calculated without any image averaging and/or imposition of helical symmetry- only reveals MIH motifs infrequently. This is –to our knowledge- the first application of the IHRSR method to calculate a 3D reconstruction from tilt series images. This single filament IHRSR reconstruction method (SF-IHRSR) should provide a new tool to assess structural differences between well-ordered thick (or thin) filaments in a grid by recording separately their electron tomograms. PMID:24727133

  12. A method for 3D-reconstruction of a muscle thick filament using the tilt series images of a single filament electron tomogram.

    PubMed

    Márquez, G; Pinto, A; Alamo, L; Baumann, B; Ye, F; Winkler, H; Taylor, K; Padrón, R

    2014-05-01

    Myosin interacting-heads (MIH) motifs are visualized in 3D-reconstructions of thick filaments from striated muscle. These reconstructions are calculated by averaging methods using images from electron micrographs of grids prepared using numerous filament preparations. Here we propose an alternative method to calculate the 3D-reconstruction of a single thick filament using only a tilt series images recorded by electron tomography. Relaxed thick filaments, prepared from tarantula leg muscle homogenates, were negatively stained. Single-axis tilt series of single isolated thick filaments were obtained with the electron microscope at a low electron dose, and recorded on a CCD camera by electron tomography. An IHRSR 3D-recontruction was calculated from the tilt series images of a single thick filament. The reconstruction was enhanced by including in the search stage dual tilt image segments while only single tilt along the filament axis is usually used, as well as applying a band pass filter just before the back projection. The reconstruction from a single filament has a 40 Å resolution and clearly shows the presence of MIH motifs. In contrast, the electron tomogram 3D-reconstruction of the same thick filament - calculated without any image averaging and/or imposition of helical symmetry - only reveals MIH motifs infrequently. This is - to our knowledge - the first application of the IHRSR method to calculate a 3D reconstruction from tilt series images. This single filament IHRSR reconstruction method (SF-IHRSR) should provide a new tool to assess structural differences between well-ordered thick (or thin) filaments in a grid by recording separately their electron tomograms.

  13. Task reports on developing techniques for scattering by 3D composite structures and to generate new solutions in diffraction theory using higher order boundary conditions

    NASA Technical Reports Server (NTRS)

    Volakis, John L.

    1991-01-01

    There are two tasks described in this report. First, an extension of a two dimensional formulation is presented for a three dimensional body of revolution. A Fourier series expansion of the vector electric and magnetic fields is employed to reduce the dimensionality of the system, and an exact boundary condition is employed to terminate the mesh. The mesh termination boundary is chosen such that it leads to convolutional boundary operators for low O(n) memory demand. Second, rigorous uniform geometrical theory of diffraction (UTD) diffraction coefficients are presented for a coated convex cylinder simulated with generalized impedance boundary conditions. Ray solutions are obtained which remain valid in the transition region and reduce uniformly those in the deep lit and shadow regions. A uniform asymptotic solution is also presented for observations in the close vicinity of the cylinder.

  14. Comparison of radiotherapy dosimetry for 3D-CRT, IMRT, and SBRT based on electron density calibration

    NASA Astrophysics Data System (ADS)

    Kartutik, K.; Wibowo, W. E.; Pawiro, S. A.

    2016-03-01

    Accurate calculation of dose distribution affected by inhomogeneity tissue is required in radiotherapy planning. This study was performed to determine the ratio between radiotherapy planning using 3D-CRT, IMRT, and SBRT based on a calibrated curve of CT-number in the lung for different target's shape in 3D-CRT, IMRT, and spinal cord for SBRT. Calibration curves of CT-number were generated under measurement basis and introduced into TPS, then planning was performed for 3D-CRT, IMRT, and SBRT with 7, and 15 radiation fields. Afterwards, planning evaluation was performed by comparing the DVH curve, HI, and CI. 3D-CRT and IMRT produced the lowest HI at calibration curve of CIRS 002LFC with the value 0.24 and 10. Whereas SBRT produced the lowest HI on a linear calibration curve with a value of 0.361. The highest CI in IMRT and SBRT technique achieved using a linear calibration curve was 0.97 and 1.77 respectively. For 3D-CRT, the highest CI was obtained by using calibration curve of CIRS 062M with the value of 0.45. From the results of CI and HI, it is concluded that the calibration curve of CT-number does not significantly differ with Schneider's calibrated curve, and inverse planning gives a better result than forward planning.

  15. Low Energy Electron Diffraction and Cyclic Voltammetry Studies of Flame-Annealed Platinum Single Crystals.

    DTIC Science & Technology

    Low energy electron diffraction (LEED) and cyclic voltammetry were used to examine the surface structure of flame-annealed platinum (I 00), (II 0...electron diffraction studies of platinum single crystal surfaces, Cyclic voltammetry of flamed-annealed platinum single crystal.

  16. Using a time-domain higher-order boundary element method to simulate wave and current diffraction from a 3-D body

    NASA Astrophysics Data System (ADS)

    Liu, Zhen; Teng, Bin; Ning, De-Zhi; Sun, Liang

    2010-06-01

    To study wave-current actions on 3-D bodies a time-domain numerical model was established using a higher-order boundary element method (HOBEM). By assuming small flow velocities, the velocity potential could be expressed for linear and higher order components by perturbation expansion. A 4th-order Runge-Kutta method was applied for time marching. An artificial damping layer was adopted at the outer zone of the free surface mesh to dissipate scattering waves. Validation of the numerical method was carried out on run-up, wave exciting forces, and mean drift forces for wave-currents acting on a bottom-mounted vertical cylinder. The results were in close agreement with the results of a frequency-domain method and a published time-domain method. The model was then applied to compute wave-current forces and run-up on a Seastar mini tension-leg platform.

  17. Imagerie 2D et 3D de matériaux monocristallins : topographie et tomographie en diffraction rayons X de très haute énergie

    NASA Astrophysics Data System (ADS)

    Hamelin, B.; Bastie, P.; Richard, D.; Eiaazzouzi, A.

    2004-11-01

    La caractérisation en volume de matériaux cristallins de forte épaisseur (plusieurs cm) n'est possible que par l'utilisation de sources de rayonnement X de forte énergie (diffractomètres gamma, lignes haute énergie du rayonnement synchrotron) ou encore par l'utilisation de faisceau de neutrons. L'Institut Laue Langevin a développé et construit, en coopération avec le Laboratoire de Spectrométrie Physique, un nouveau type d'instrument utilisant le spectre continu rayons X à très haute énergie (typiquement 100 à 400 keV) émis par un générateur rayons X à foyer fin utilisé pour des radiographies. Ce diffractomètre permet la caractérisation rapide, précise et en volume d'échantillons de forte épaisseur. Outre des applications variées dans différents domaines (structure cristalline, mesure de paramètre de maille, contraintes, textures,ldots), il est possible de caractériser complètement des échantillons cristallins à partir d'une série de mesures en diffraction. Il est en particulier possible de visualiser (localiser) les désorientations du réseau cristallin au sein d'un échantillon (topographie en transmission). Il est également possible de visualiser les volumes diffractants dans une section de l'échantillon en utilisant une reconstruction de type tomographique à partir d'une série d'acquisitions en diffraction. Ces nouvelles possibilités s'avèrent être particulièrement utiles pour le contrôle non destructif de matériaux cristallins.

  18. Method for dose-reduced 3D catheter tracking on a scanning-beam digital x-ray system using dynamic electronic collimation

    PubMed Central

    Dunkerley, David A. P.; Funk, Tobias; Speidel, Michael A.

    2016-01-01

    Scanning-beam digital x-ray (SBDX) is an inverse geometry x-ray fluoroscopy system capable of tomosynthesis-based 3D catheter tracking. This work proposes a method of dose-reduced 3D tracking using dynamic electronic collimation (DEC) of the SBDX scanning x-ray tube. Positions in the 2D focal spot array are selectively activated to create a region-of-interest (ROI) x-ray field around the tracked catheter. The ROI position is updated for each frame based on a motion vector calculated from the two most recent 3D tracking results. The technique was evaluated with SBDX data acquired as a catheter tip inside a chest phantom was pulled along a 3D trajectory. DEC scans were retrospectively generated from the detector images stored for each focal spot position. DEC imaging of a catheter tip in a volume measuring 11.4 cm across at isocenter required 340 active focal spots per frame, versus 4473 spots in full-FOV mode. The dose-area-product (DAP) and peak skin dose (PSD) for DEC versus full field-of-view (FOV) scanning were calculated using an SBDX Monte Carlo simulation code. DAP was reduced to 7.4% to 8.4% of the full-FOV value, consistent with the relative number of active focal spots (7.6%). For image sequences with a moving catheter, PSD was 33.6% to 34.8% of the full-FOV value. The root-mean-squared-deviation between DEC-based 3D tracking coordinates and full-FOV 3D tracking coordinates was less than 0.1 mm. The 3D distance between the tracked tip and the sheath centerline averaged 0.75 mm. Dynamic electronic collimation can reduce dose with minimal change in tracking performance. PMID:27375314

  19. Nanopatterning on fragile or 3D surfaces with sterol-based vapor-deposited electron beam resist

    NASA Astrophysics Data System (ADS)

    Legario, Ron R.; Kelkar, Prasad S.; Beauvais, Jacques; Lavallee, Eric; Drouin, Dominique; Cloutier, Melanie; Turcotte, David; Yang, Pan; Mun, Lau K.; Awad, Yousef; Lafrance, Pierre J.

    2004-05-01

    A novel and effective approach to nano-fabrication lithography is the vapour deposition of the negative tone electron beam resists QSR-5 and QSR-15 (Quantiscript"s sterol based resist) onto a substrate. Vapour deposition is especially conducive for patterning thin delicate membranes (e.g. advanced masks for X-ray lithography - XRL, and Low Energy Electron Proximity Projection Lithography - LEEPL), that are susceptible to breakage during the spin coating process. With the capability for depositing highly uniform thin layers (<50nm) and a demonstrated resolution better than 60nm, QSR-5 and QSR-15 have potential for the fabrication of next generation lithography masks. Optimized for low energy electron exposure where proximity effects become negligible and thus well suited for 1X lithography mask patterning, QSR-5 and QSR-15 have shown exposure doses as low as 100μC/cm2 at 3KeV. In addition to this type of application, the versatility of QSR-5 and QSR-15 have also been demonstrated by the fabrication of a Fresnel zone plate lens on the tip of an optical fibre with the goal of improving the coupling of diode laser emission into the fiber. This application clearly shows the capabilities of this process for producing nano-scale patterns on very small area surfaces that are completely unsuitable for spin-coating of the resist. A second demonstration of the resist's capabilities is the patterning of optical diffractive elements directly on the facet of a semiconductor laser. This opens the way to direct patterning on laser diode facets in order to control the emission profile from the device. It has also proven capabilities in the manufacture of delicate photo masks. In their natural state, QSR-5 and QSR-15 are solids at room temperature and are sterol based heterocyclic compounds, with unsaturated bonding capable of cross linking. On their own merit, QSR-5 and QSR-15 are capable of cross linking under electron beam exposure and are comparable in certain properties to

  20. Electron Backscatter Diffraction (EBSD) Characterization of Uranium and Uranium Alloys

    SciTech Connect

    McCabe, Rodney J.; Kelly, Ann Marie; Clarke, Amy J.; Field, Robert D.; Wenk, H. R.

    2012-07-25

    Electron backscatter diffraction (EBSD) was used to examine the microstructures of unalloyed uranium, U-6Nb, U-10Mo, and U-0.75Ti. For unalloyed uranium, we used EBSD to examine the effects of various processes on microstructures including casting, rolling and forming, recrystallization, welding, and quasi-static and shock deformation. For U-6Nb we used EBSD to examine the microstructural evolution during shape memory loading. EBSD was used to study chemical homogenization in U-10Mo, and for U-0.75Ti, we used EBSD to study the microstructure and texture evolution during thermal cycling and deformation. The studied uranium alloys have significant microstructural and chemical differences and each of these alloys presents unique preparation challenges. Each of the alloys is prepared by a sequence of mechanical grinding and polishing followed by electropolishing with subtle differences between the alloys. U-6Nb and U-0.75Ti both have martensitic microstructures and both require special care in order to avoid mechanical polishing artifacts. Unalloyed uranium has a tendency to rapidly oxidize when exposed to air and a two-step electropolish is employed, the first step to remove the damaged surface layer resulting from the mechanical preparation and the second step to passivate the surface. All of the alloying additions provide a level of surface passivation and different one and two step electropolishes are employed to create good EBSD surfaces. Because of its low symmetry crystal structure, uranium exhibits complex deformation behavior including operation of multiple deformation twinning modes. EBSD was used to observe and quantify twinning contributions to deformation and to examine the fracture behavior. Figure 1 shows a cross section of two mating fracture surfaces in cast uranium showing the propensity of deformation twinning and intergranular fracture largely between dissimilarly oriented grains. Deformation of U-6Nb in the shape memory regime occurs by the motion

  1. Conformations and Coherences in Structure Determination by Ultrafast Electron Diffraction

    PubMed Central

    Lin, Milo M.; Shorokhov, Dmitry; Zewail, Ahmed H.

    2009-01-01

    In this article we consider consequences of spatial coherences and conformations in diffraction of (macro)molecules with different potential energy landscapes. The emphasis is on using this understanding to extract structural and temporal information from diffraction experiments. The theoretical analysis of structural interconversions spans an increased range of complexity, from small hydrocarbons to proteins. For each molecule considered, we construct the potential energy landscape and assess the characteristic conformational states available. For molecules that are quasi-harmonic in the vicinity of energy minima, we find that the distinct conformer model is sufficient even at high temperatures. If, however, the energy surface is either locally flat around the minima or the molecule includes many degrees of conformational freedom, a Boltzmann ensemble must be used, in what we define as the pseudoconformer approach, to reproduce the diffraction. For macromolecules with numerous energy minima, the ensemble of hundreds of structures is considered, but we also utilize the concept of the persistence length to provide information on orientational coherence and its use to assess the degree of resonance contribution to diffraction. It is shown that the erosion of the resonant features in diffraction which are characteristic of some quasi-periodic structural motifs can be exploited in experimental studies of conformational interconversions triggered by a laser-induced temperature jump. PMID:19320469

  2. Spatial 3D infrastructure: display-independent software framework, high-speed rendering electronics, and several new displays

    NASA Astrophysics Data System (ADS)

    Chun, Won-Suk; Napoli, Joshua; Cossairt, Oliver S.; Dorval, Rick K.; Hall, Deirdre M.; Purtell, Thomas J., II; Schooler, James F.; Banker, Yigal; Favalora, Gregg E.

    2005-03-01

    We present a software and hardware foundation to enable the rapid adoption of 3-D displays. Different 3-D displays - such as multiplanar, multiview, and electroholographic displays - naturally require different rendering methods. The adoption of these displays in the marketplace will be accelerated by a common software framework. The authors designed the SpatialGL API, a new rendering framework that unifies these display methods under one interface. SpatialGL enables complementary visualization assets to coexist through a uniform infrastructure. Also, SpatialGL supports legacy interfaces such as the OpenGL API. The authors" first implementation of SpatialGL uses multiview and multislice rendering algorithms to exploit the performance of modern graphics processing units (GPUs) to enable real-time visualization of 3-D graphics from medical imaging, oil & gas exploration, and homeland security. At the time of writing, SpatialGL runs on COTS workstations (both Windows and Linux) and on Actuality"s high-performance embedded computational engine that couples an NVIDIA GeForce 6800 Ultra GPU, an AMD Athlon 64 processor, and a proprietary, high-speed, programmable volumetric frame buffer that interfaces to a 1024 x 768 x 3 digital projector. Progress is illustrated using an off-the-shelf multiview display, Actuality"s multiplanar Perspecta Spatial 3D System, and an experimental multiview display. The experimental display is a quasi-holographic view-sequential system that generates aerial imagery measuring 30 mm x 25 mm x 25 mm, providing 198 horizontal views.

  3. Combination of 3-D deformation and shape measurement by electronic speckle pattern interferometry for quantitative strain-stress analysis

    NASA Astrophysics Data System (ADS)

    Ettemeyer, Andreas

    2000-01-01

    Laser speckle interferometry as a full-field noncontact measuring technique offers interesting opportunities for strain-stress analysis on components. While its application in material testing and material research has already achieved some acceptance in research and industry, its application to complex industrial components like car bodies, gear boxes, engines, and suspensions has been limited. Basic difficulties have arisen from the relatively large rigid-body movements of components under test, harsh environmental conditions in the real test world, and the often complex shape of the analyzed component, especially in the most interesting areas. The commercial availability of a radically miniaturized 3D speckle interferometer has led to the new laser-optical measuring device, the MicroStarTM, which can be used for quantitative strain-stress measurement on nearly any industrial component. The device uses 3D speckle interferometry to measure the shape and the 3D deformation in the area of interest. The combination of shape and deformation provides all necessary data for quantitative 3D strain analysis. The principle stresses as well as the bending and tensile components of the strains can be easily determined. In this paper, the principle and applications of this new system are presented.

  4. High resolution electron diffraction analysis of structural changes associated with the photocycle of bacteriorhodopsin

    SciTech Connect

    Han, B. -G.

    1994-04-01

    Changes in protein structure that occur during the formation of the M photointermediate of bacteriorhodopsin can be directly visualized by electron diffraction techniques. Samples containing a high percentage of the M intermediate were trapped by rapidly cooling the crystals with liquid nitrogen following illumination with filtered green light at 240K and 260K respectively. Difference Fourier projection maps for M minus bR at two temperatures and for M{sub 260K} minus M{sub 240K} are presented. While it is likely that a unique M-substate is trapped when illuminated at 260K produces a mixture of the M{sub 240K} substate and a second M-substate which may have a protein structure similar to the N-intermediate. The diffraction data clearly show that statistically significant structural changes occur upon formation of the M{sub 240K} specimen and then further upon formation of the second substate which is present in the mixture that is produced at 260K. A preliminary 3-D difference map, based on data collected with samples tilted up to 30{degree}, has been constructed at a resolution of 3.5{angstrom} parallel to the membrane plane and a resolution of 8.5{angstrom} perpendicular to the membrane. The data have been analyzed by a number of different criteria to ensure that the differences seen reflect real conformation changes at a level which is significantly above the noise in the map. Furthermore, a comparison of the positions of specific backbone and side-chain groups relative to significant difference peaks suggests that it will be necessary to further refine the atomic resolution model before it will be possible to interpret the changes in chemical structure that occur in the protein at this stage of the photocycle.

  5. Task reports on developing techniques for scattering by 3D composite structures and to generate new solutions in diffraction theory using higher order boundary conditions

    NASA Technical Reports Server (NTRS)

    Volakis, John L.

    1990-01-01

    There are two tasks described in this report. First, an extension of a two dimensional formulation is presented for a three dimensional body of revolution. With the introduction of a Fourier expansion of the vector electric and magnetic fields, a coupled two dimensional system is generated and solved via the finite element method. An exact boundary condition is employed to terminate the mesh and the fast fourier transformation is used to evaluate the boundary integrals for low O(n) memory demand when an iterative solution algorithm is used. Second, the diffraction by a material discontinuity in a thick dielectric/ferrite layer is considered by modeling the layer as a distributed current sheet obeying generalized sheet transition conditions (GSTC's).

  6. X-ray Diffraction Study of Order-Disorder Phase Transition in CuMPt6 (M=3d Elements) Alloys

    NASA Astrophysics Data System (ADS)

    Ahmed, Ejaz; Takahashi, Miwako; Iwasaki, Hiroshi; Ohshima, Ken-ichi

    2009-01-01

    We investigated the ordering behavior of ternary CuMPt6 alloys with M=Ti, V, Cr, Mn, Fe, Co, and Ni by high-temperature polycrystalline X-ray diffraction. The alloys undergo a phase transition from the fcc disordered state to the Cu3Au-type ordered state, except for the alloy with M=Ni, in which only short-range order forms. The transition temperature Tc is highest (1593 K) for M=Ti and decreases almost monotonically with increasing atomic number to 1153 K for M=Co. The observed dependence of ordering tendency on the atomic number of M is discussed in the light of the theory of ordering in transition-metal alloys and its significance for the study of ordering in ternary alloys.

  7. 3-D Ultrasound Localization Microscopy for Identifying Microvascular Morphology Features of Tumor Angiogenesis at a Resolution Beyond the Diffraction Limit of Conventional Ultrasound

    PubMed Central

    Lin, Fanglue; Shelton, Sarah E.; Espíndola, David; Rojas, Juan D.; Pinton, Gianmarco; Dayton, Paul A.

    2017-01-01

    Angiogenesis has been known as a hallmark of solid tumor cancers for decades, yet ultrasound has been limited in its ability to detect the microvascular changes associated with malignancy. Here, we demonstrate the potential of 'ultrasound localization microscopy' applied volumetrically in combination with quantitative analysis of microvascular morphology, as an approach to overcome this limitation. This pilot study demonstrates our ability to image complex microvascular patterns associated with tumor angiogenesis in-vivo at a resolution of tens of microns - substantially better than the diffraction limit of traditional clinical ultrasound, yet using an 8 MHz clinical ultrasound probe. Furthermore, it is observed that data from healthy and tumor-bearing tissue exhibit significant differences in microvascular pattern and density. Results suggests that with continued development of these novel technologies, ultrasound has the potential to detect biomarkers of cancer based on the microvascular 'fingerprint' of malignant angiogenesis rather than through imaging of blood flow dynamics or the tumor mass itself. PMID:28042327

  8. Homoepitaxial growth of metal halide crystals investigated by reflection high-energy electron diffraction

    DOE PAGES

    Chen, Pei; Kuttipillai, Padmanaban S.; Wang, Lili; ...

    2017-01-10

    Here, we report the homoepitaxial growth of a metal halide on single crystals investigated with in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). Epitaxial growth of NaCl on NaCl (001) is explored as a function of temperature and growth rate which provides the first detailed report of RHEED oscillations for metal halide growth. Layer-by-layer growth is observed at room temperature accompanied by clear RHEED oscillations while the growth mode transitions to an island (3D) mode at low temperature. At higher temperatures (>100 °C), RHEED oscillations and AFM data indicate a transition to a step-flowmore » growth mode. To show the importance of such metal halide growth, green organic light-emitting diodes (OLEDs) are demonstrated using a doped NaCl film with a phosphorescent emitter as the emissive layer. This study demonstrates the ability to perform in situ and non-destructive RHEED monitoring even on insulating substrates and could enable doped single crystals and crystalline substrates for a range of optoelectronic applications.« less

  9. Homoepitaxial Growth of Metal Halide Crystals Investigated by Reflection High-Energy Electron Diffraction

    PubMed Central

    Chen, Pei; Kuttipillai, Padmanaban S.; Wang, Lili; Lunt, Richard R.

    2017-01-01

    We report the homoepitaxial growth of a metal halide on single crystals investigated with in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). Epitaxial growth of NaCl on NaCl (001) is explored as a function of temperature and growth rate which provides the first detailed report of RHEED oscillations for metal halide growth. Layer-by-layer growth is observed at room temperature accompanied by clear RHEED oscillations while the growth mode transitions to an island (3D) mode at low temperature. At higher temperatures (>100 °C), RHEED oscillations and AFM data indicate a transition to a step-flow growth mode. To show the importance of such metal halide growth, green organic light-emitting diodes (OLEDs) are demonstrated using a doped NaCl film with a phosphorescent emitter as the emissive layer. This study demonstrates the ability to perform in situ and non-destructive RHEED monitoring even on insulating substrates and could enable doped single crystals and crystalline substrates for a range of optoelectronic applications. PMID:28071732

  10. Homoepitaxial Growth of Metal Halide Crystals Investigated by Reflection High-Energy Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Chen, Pei; Kuttipillai, Padmanaban S.; Wang, Lili; Lunt, Richard R.

    2017-01-01

    We report the homoepitaxial growth of a metal halide on single crystals investigated with in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). Epitaxial growth of NaCl on NaCl (001) is explored as a function of temperature and growth rate which provides the first detailed report of RHEED oscillations for metal halide growth. Layer-by-layer growth is observed at room temperature accompanied by clear RHEED oscillations while the growth mode transitions to an island (3D) mode at low temperature. At higher temperatures (>100 °C), RHEED oscillations and AFM data indicate a transition to a step-flow growth mode. To show the importance of such metal halide growth, green organic light-emitting diodes (OLEDs) are demonstrated using a doped NaCl film with a phosphorescent emitter as the emissive layer. This study demonstrates the ability to perform in situ and non-destructive RHEED monitoring even on insulating substrates and could enable doped single crystals and crystalline substrates for a range of optoelectronic applications.

  11. X-Ray-Diffraction Tests Of Irradiated Electronic Devices: I

    NASA Technical Reports Server (NTRS)

    Shaw, David C.; Lowry, Lynn E.; Barnes, Charles E.

    1993-01-01

    X-ray-diffraction tests performed on aluminum conductors in commercial HI1-507A complementary metal oxide/semiconductor (CMOS) integrated-circuit analog multiplexers, both before and after circuits exposed to ionizing radiation from Co(60) source, and after postirradiation annealing at ambient and elevated temperatures. Tests in addition to electrical tests performed to determine effects of irradiation and of postirradiation annealing on electrical operating characteristics of circuits. Investigators sought to determine whether relationship between effects of irradiation on devices and physical stresses within devices. X-ray diffraction potentially useful for nondestructive measurement of stresses.

  12. Ultrafast electron diffraction optimized for studying structural dynamics in thin films and monolayers

    PubMed Central

    Badali, D. S.; Gengler, R. Y. N.; Miller, R. J. D.

    2016-01-01

    A compact electron source specifically designed for time-resolved diffraction studies of free-standing thin films and monolayers is presented here. The sensitivity to thin samples is achieved by extending the established technique of ultrafast electron diffraction to the “medium” energy regime (1–10 kV). An extremely compact design, in combination with low bunch charges, allows for high quality diffraction in a lensless geometry. The measured and simulated characteristics of the experimental system reveal sub-picosecond temporal resolution, while demonstrating the ability to produce high quality diffraction patterns from atomically thin samples. PMID:27226978

  13. Bulk crystal growth and electronic characterization of the 3D Dirac semimetal Na{sub 3}Bi

    SciTech Connect

    Kushwaha, Satya K.; Krizan, Jason W.; Cava, R. J.; Feldman, Benjamin E.; Gyenis, András; Randeria, Mallika T.; Xiong, Jun; Xu, Su-Yang; Alidoust, Nasser; Belopolski, Ilya; Liang, Tian; Zahid Hasan, M.; Ong, N. P.; Yazdani, A.

    2015-04-01

    High quality hexagon plate-like Na{sub 3}Bi crystals with large (001) plane surfaces were grown from a molten Na flux. The freshly cleaved crystals were analyzed by low temperature scanning tunneling microscopy and angle-resolved photoemission spectroscopy, allowing for the characterization of the three-dimensional (3D) Dirac semimetal (TDS) behavior and the observation of the topological surface states. Landau levels were observed, and the energy-momentum relations exhibited a linear dispersion relationship, characteristic of the 3D TDS nature of Na{sub 3}Bi. In transport measurements on Na{sub 3}Bi crystals, the linear magnetoresistance and Shubnikov-de Haas quantum oscillations are observed for the first time.

  14. Nuclear contribution into single-event upset in 3D on-board electronics at moderate energy cosmic proton impact

    NASA Astrophysics Data System (ADS)

    Chechenin, N. G.; Chuvilskaya, T. V.; Shirokova, A. A.

    2016-05-01

    In continuation and development of our previous works where nuclear reactions of moderate energy (10 - 400 MeV) protons with Si, Al and W have been investigated, the results of reactions with Cu are reported in this paper. Cu is a most important component in composition of materials in contact pads and pathways of modern and perspective ultra large-scale integration circuitry, especially in 3D topology.

  15. 3D-hybrid material design with electron/lithium-ion dual-conductivity for high-performance Li-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Tan, Rui; Yang, Jie; Wang, Kai; Gao, Rongtan; Liu, Dong; Liu, Yidong; Yang, Jinlong; Pan, Feng

    2017-02-01

    We report a novel 3D-hybrid cathode material with three-dimensional (3D) N-GO/CNT framework to load sulfur (77.6 wt %), and sulfonated polyaniline (SPANI) of coating layer. Used as a cathode material, it possesses a high capacity (1196 mAh g-1@0.3 A g-1@1.6 mg cm-2), excellent charging-discharging rate (680 mAh g-1@7.5 A g-1) and long-life performance (maintaining 71.1% capacity over 450 cycles), which is mainly attributed to the benefits of excellent electronic/Li-ionic dual-conductivity and confinement effect of the 3D-hybrid N-GO/CNT framework coated by self-doping conducting polymer SPANI. Thus, a 3D sulfur cathode modified with electronic/Li-ionic dual-conduction network can significantly enhance the electrochemical performance and stability, and this novel type of material is very promising for commercial applications that require high energy and power density, long life, and excellent abuse tolerance.

  16. Improved strain precision with high spatial resolution using nanobeam precession electron diffraction

    SciTech Connect

    Rouviere, Jean-Luc Martin, Yannick; Denneulin, Thibaud; Cooper, David

    2013-12-09

    NanoBeam Electron Diffraction is a simple and efficient technique to measure strain in nanostructures. Here, we show that improved results can be obtained by precessing the electron beam while maintaining a few nanometer probe size, i.e., by doing Nanobeam Precession Electron Diffraction (N-PED). The precession of the beam makes the diffraction spots more uniform and numerous, making N-PED more robust and precise. In N-PED, smaller probe size and better precision are achieved by having diffraction disks instead of diffraction dots. Precision in the strain measurement better than 2 × 10{sup −4} is obtained with a probe size approaching 1 nm in diameter.

  17. Time-resolved measurements with streaked diffraction patterns from electrons generated in laser plasma wakefield

    NASA Astrophysics Data System (ADS)

    He, Zhaohan; Nees, John; Hou, Bixue; Krushelnick, Karl; Thomas, Alec; Beaurepaire, Benoît; Malka, Victor; Faure, Jérôme

    2013-10-01

    Femtosecond bunches of electrons with relativistic to ultra-relativistic energies can be robustly produced in laser plasma wakefield accelerators (LWFA). Scaling the electron energy down to sub-relativistic and MeV level using a millijoule laser system will make such electron source a promising candidate for ultrafast electron diffraction (UED) applications due to the intrinsic short bunch duration and perfect synchronization with the optical pump. Recent results of electron diffraction from a single crystal gold foil, using LWFA electrons driven by 8-mJ, 35-fs laser pulses at 500 Hz, will be presented. The accelerated electrons were collimated with a solenoid magnetic lens. By applying a small-angle tilt to the magnetic lens, the diffraction pattern can be streaked such that the temporal evolution is separated spatially on the detector screen after propagation. The observable time window and achievable temporal resolution are studied in pump-probe measurements of photo-induced heating on the gold foil.

  18. Teaching Diffraction of Light and Electrons: Classroom Analogies to Classic Experiments

    ERIC Educational Resources Information Center

    Velentzas, Athanasios

    2014-01-01

    Diffraction and interference are phenomena that demonstrate the wave nature of light and of particles. Experiments relating to the diffraction/interference of light can easily be carried out in an educational lab, but it may be impossible to perform experiments involving electrons because of the lack of specialized equipment needed for such…

  19. Gamma-ray and neutron diffraction studies of CoF2: magnetostriction, electron density and magnetic moments.

    PubMed

    Jauch, W; Reehuis, M; Schultz, A J

    2004-01-01

    Accurate structure factors up to sin theta/lambda = 1.6 A(-1) have been measured with 316.5 keV gamma-rays from CoF(2), both at room temperature and in the antiferromagnetic state at 10 K. The same crystal was used to collect extended time-of-flight neutron diffraction data in the two magnetic states, which allowed an accurate determination of the fluorine positional parameter. For room temperature, the standard structural parameters are reported. At 10 K, a complete charge-density study has been carried out. The total number of 3d electrons on Co is found to be 6.95 (3). The experimental populations of the d orbitals agree with expectation from crystal field theory. The fluorine valence region exhibits a strong dipolar deformation. Electronic properties at the bond critical points and integrated atomic properties are derived from the static model electron density, revealing the Co-F interactions as purely ionic. On magnetic ordering, a shift of the fluorine ions of 1.5 (4) x 10(-3) A is found which confirms a prediction from theory of optical birefringence. The effect of magnetostriction on the distortion of the ligand coordination octahedra is compared for the late members of the 3d transition-metal difluorides. From neutron powder diffraction, an ordered magnetic moment of 2.60 (4) mu(B) per cobalt ion is found. Despite the strong deviation from the ideal spin value of 3 mu(B), there is still an appreciable orbital contribution to the local magnetic moment.

  20. Electronic structure of the chiral helimagnet and 3d-intercalated transition metal dichalcogenide Cr1/3NbS2

    DOE PAGES

    Sirca, N.; Mo, S. -K.; Bondino, F.; ...

    2016-08-18

    The electronic structure of the chiral helimagnet Cr1/3NbS2 has been studied with core level and angle-resolved photoemission spectroscopy (ARPES). Intercalated Cr atoms are found to be effective in donating electrons to the NbS2 layers but also cause significant modifications of the electronic structure of the host NbS2 material. Specifically, the data provide evidence that a description of the electronic structure of Cr1/3NbS2 on the basis of a simple rigid band picture is untenable. The data also reveal substantial inconsistencies with the predictions of standard density functional theory. In conclusion, the relevance of these results to the attainment of a correctmore » description of the electronic structure of chiral helimagnets, magnetic thin films/multilayers, and transition metal dichalcogenides intercalated with 3d magnetic elements is discussed.« less

  1. Electronic structure of the chiral helimagnet and 3d-intercalated transition metal dichalcogenide Cr1/3NbS2

    SciTech Connect

    Sirca, N.; Mo, S. -K.; Bondino, F.; Pis, I.; Nappini, S.; Vilmercati, P.; Yi, Jieyu; Gai, Zheng; Snijders, Paul C.; Das, P. K.; Vobornik, I.; Ghimire, N. J.; Koehler, Michael R.; Sopkota, D.; Parker, David S.; Mandrus, D. G.; Mannella, Norman

    2016-08-18

    The electronic structure of the chiral helimagnet Cr1/3NbS2 has been studied with core level and angle-resolved photoemission spectroscopy (ARPES). Intercalated Cr atoms are found to be effective in donating electrons to the NbS2 layers but also cause significant modifications of the electronic structure of the host NbS2 material. Specifically, the data provide evidence that a description of the electronic structure of Cr1/3NbS2 on the basis of a simple rigid band picture is untenable. The data also reveal substantial inconsistencies with the predictions of standard density functional theory. In conclusion, the relevance of these results to the attainment of a correct description of the electronic structure of chiral helimagnets, magnetic thin films/multilayers, and transition metal dichalcogenides intercalated with 3d magnetic elements is discussed.

  2. Convergent N2-scaling iterative method of photoelectron diffraction and low-energy electron diffraction for ordered or disordered systems

    NASA Astrophysics Data System (ADS)

    Wu, Huasheng; Tong, S. Y.

    1999-01-01

    We present results of a convergent iterative method of photoelectron diffraction and low-energy electron diffraction. The computation time of this method scales as N2, where N is the dimension of the propagator matrix, rather than N3 as in conventional Gaussian substitutional methods. We show that the Rehr-Albers separable-representation cluster approach or slab-type nonseparable methods can all be cast in this iterative form. The convergence of this method is demonstrated for different materials. With the substantial savings in computational time and no loss in numerical accuracy, this method will be very useful in future applications of multiple-scattering theory, particularly for systems either involving very large unit cells (200-700 atoms) or where no long-range order is present.

  3. Lattice constant measurement from electron backscatter diffraction patterns.

    PubMed

    Saowadee, N; Agersted, K; Bowen, J R

    2017-02-20

    Kikuchi bands in election backscattered diffraction patterns (EBSP) contain information about lattice constants of crystallographic samples that can be extracted via the Bragg equation. An advantage of lattice constant measurement from EBSPs over diffraction (XRD) is the ability to perform local analysis. In this study, lattice constants of cubic STN and cubic YSZ in the pure materials and in co-sintered composites were measured from their EBSPs acquired at 10 kV using a silicon single crystal as a calibration reference. The EBSP distortion was corrected by spherical back projection and Kikuchi band analysis was made using in-house software. The error of the lattice constant measurement was determined to be in the range of 0.09-1.12% compared to values determined by XRD and from literature. The confidence level of the method is indicated by the standard deviation of the measurement, which is approximately 0.04 Å. Studying Kikuchi band size dependence of the measurement precision shows that the measurement error decays with increasing band size (i.e. decreasing lattice constant). However, in practice, the sharpness of wide bands tends to be low due to their low intensity, thus limiting the measurement precision. Possible methods to improve measurement precision are suggested.

  4. Molecular vibrations kof iron trifluoride and aluminum trifluoride from gas-phase electron diffraction

    NASA Astrophysics Data System (ADS)

    Hargittai, Magdolna; Subbotina, Natalya Yu.; Gershikov, Alexander G.

    1991-04-01

    A vibrational analysis of the electron diffraction intensity data of iron trifluoride provides firm evidence for the planarity of this molecule. The optimized deformation frequencies of iron trifluoride, ν 2 110(17) and ν 4 158(17) cm -1, appear to be much lower than the available estimates. The optimized symmetric streching frequency for aluminium trifluoride is 683(54) cm -1 from the joint analysis of electron diffraction intensities and vibrational frequencies. Force constants are also obtained for both molecules.

  5. Atomic-scale diffractive imaging of sub-cycle electron dynamics in condensed matter

    DOE PAGES

    Yakovlev, Vladislav S.; Stockman, Mark I.; Krausz, Ferenc; ...

    2015-09-28

    For interaction of light with condensed-matter systems, we show with simulations that ultrafast electron and X-ray diffraction can provide a time-dependent record of charge-density maps with sub-cycle and atomic-scale resolutions. Using graphene as an example material, we predict that diffraction can reveal localised atomic-scale origins of optical and electronic phenomena. Here, we point out nontrivial relations between microscopic electric current and density in undoped graphene.

  6. Atomic-scale diffractive imaging of sub-cycle electron dynamics in condensed matter

    PubMed Central

    Yakovlev, Vladislav S.; Stockman, Mark I.; Krausz, Ferenc; Baum, Peter

    2015-01-01

    For interaction of light with condensed-matter systems, we show with simulations that ultrafast electron and X-ray diffraction can provide a time-dependent record of charge-density maps with sub-cycle and atomic-scale resolutions. Using graphene as an example material, we predict that diffraction can reveal localised atomic-scale origins of optical and electronic phenomena. In particular, we point out nontrivial relations between microscopic electric current and density in undoped graphene. PMID:26412407

  7. The hybridizations of cobalt 3 d bands with the electron band structure of the graphene/cobalt interface on a tungsten substrate

    NASA Astrophysics Data System (ADS)

    Hwang, Jinwoong; Hwang, Choongyu; Chung, Nak-Kwan; N'Diaye, A. D.; Schmid, A. K.; Denlinger, Jonathan

    2016-08-01

    The interface between graphene and a ferromagnetic substrate has attracted recent research interests due to its potential for spintronic applications. We report an angle-resolved photoemission spectroscopy study on the interface between graphene and cobalt epitaxially grown on a tungsten substrate. We find that the electron band structure of the interface exhibits clear discontinuities at the crossing points with cobalt 3 d bands. These observations indicate strong hybridizations between the electronic states in the interface and provide an important clue to understand the intriguing electromagnetic properties of the graphene/ferromagnet interface.

  8. Diffraction of electrons at intermediate energies: The role of phonons

    NASA Astrophysics Data System (ADS)

    Ascolani, H.; Zampieri, G.

    1996-07-01

    The intensity of electrons reflected ``elastically'' from crystalline surfaces presents two regimes: the low-energy or LEED regime (<500 eV), in which the electrons are reflected along the Bragg directions, and the intermediate-energy or XPD/AED regime (>500 eV), in which the maxima of intensity are along the main crystallographic axes. We present a model which explains this transition in terms of the excitation/absorption of phonons during the scattering.

  9. Electron diffraction using ultrafast electron bunches from a laser-wakefield accelerator at kHz repetition rate

    NASA Astrophysics Data System (ADS)

    He, Z.-H.; Thomas, A. G. R.; Beaurepaire, B.; Nees, J. A.; Hou, B.; Malka, V.; Krushelnick, K.; Faure, J.

    2013-02-01

    We show that electron bunches in the 50-100 keV range can be produced from a laser wakefield accelerator using 10 mJ, 35 fs laser pulses operating at 0.5 kHz. It is shown that using a solenoid magnetic lens, the electron bunch distribution can be shaped. The resulting transverse and longitudinal coherence is suitable for producing diffraction images from a polycrystalline 10 nm aluminum foil. The high repetition rate, the stability of the electron source, and the fact that its uncorrelated bunch duration is below 100 fs make this approach promising for the development of sub-100 fs ultrafast electron diffraction experiments.

  10. Accurate measurement of relative tilt and azimuth angles in electron tomography: A comparison of fiducial marker method with electron diffraction

    SciTech Connect

    Hayashida, Misa; Malac, Marek; Egerton, Ray F.; Bergen, Michael; Li, Peng

    2014-08-15

    Electron tomography is a method whereby a three-dimensional reconstruction of a nanoscale object is obtained from a series of projected images measured in a transmission electron microscope. We developed an electron-diffraction method to measure the tilt and azimuth angles, with Kikuchi lines used to align a series of diffraction patterns obtained with each image of the tilt series. Since it is based on electron diffraction, the method is not affected by sample drift and is not sensitive to sample thickness, whereas tilt angle measurement and alignment using fiducial-marker methods are affected by both sample drift and thickness. The accuracy of the diffraction method benefits reconstructions with a large number of voxels, where both high spatial resolution and a large field of view are desired. The diffraction method allows both the tilt and azimuth angle to be measured, while fiducial marker methods typically treat the tilt and azimuth angle as an unknown parameter. The diffraction method can be also used to estimate the accuracy of the fiducial marker method, and the sample-stage accuracy. A nano-dot fiducial marker measurement differs from a diffraction measurement by no more than ±1°.

  11. Accurate measurement of relative tilt and azimuth angles in electron tomography: a comparison of fiducial marker method with electron diffraction.

    PubMed

    Hayashida, Misa; Malac, Marek; Bergen, Michael; Egerton, Ray F; Li, Peng

    2014-08-01

    Electron tomography is a method whereby a three-dimensional reconstruction of a nanoscale object is obtained from a series of projected images measured in a transmission electron microscope. We developed an electron-diffraction method to measure the tilt and azimuth angles, with Kikuchi lines used to align a series of diffraction patterns obtained with each image of the tilt series. Since it is based on electron diffraction, the method is not affected by sample drift and is not sensitive to sample thickness, whereas tilt angle measurement and alignment using fiducial-marker methods are affected by both sample drift and thickness. The accuracy of the diffraction method benefits reconstructions with a large number of voxels, where both high spatial resolution and a large field of view are desired. The diffraction method allows both the tilt and azimuth angle to be measured, while fiducial marker methods typically treat the tilt and azimuth angle as an unknown parameter. The diffraction method can be also used to estimate the accuracy of the fiducial marker method, and the sample-stage accuracy. A nano-dot fiducial marker measurement differs from a diffraction measurement by no more than ±1°.

  12. Numerical simulation of THz-wave-assisted electron diffraction for ultrafast molecular imaging

    NASA Astrophysics Data System (ADS)

    Kanya, Reika; Yamanouchi, Kaoru

    2017-03-01

    A scheme for achieving high temporal resolution in gas electron diffraction is proposed, in which time-dependent electron diffraction patterns can be obtained from energy-resolved angular distributions of electrons scattered by molecules in dynamical processes under the presence of a single-cycle THz-wave pulse. Derived formulae of the differential cross section and numerical simulations of electron signals scattered by Ar atoms and C l2 molecules show that the temporal resolution of the proposed method can be <10 fs in the pump-probe measurement without scanning the time delay.

  13. Extracellular vesicles of calcifying turkey leg tendon characterized by immunocytochemistry and high voltage electron microscopic tomography and 3-D graphic image reconstruction

    NASA Technical Reports Server (NTRS)

    Landis, W. J.; Hodgens, K. J.; McKee, M. D.; Nanci, A.; Song, M. J.; Kiyonaga, S.; Arena, J.; McEwen, B.

    1992-01-01

    To gain insight into the structure and possible function of extracellular vesicles in certain calcifying vertebrate tissues, normally mineralizing leg tendons from the domestic turkey, Meleagris gallopavo, have been studied in two separate investigations, one concerning the electron microscopic immunolocalization of the 66 kDa phosphoprotein, osteopontin, and the other detailing the organization and distribution of mineral crystals associated with the vesicles as determined by high voltage microscopic tomography and 3-D graphic image reconstruction. Immunolabeling shows that osteopontin is related to extracellular vesicles of the tendon in the sense that its initial presence appears coincident with the development of mineral associated with the vesicle loci. By high voltage electron microscopy and 3-D imaging techniques, mineral crystals are found to consist of small irregularly shaped particles somewhat randomly oriented throughout individual vesicles sites. Their appearance is different from that found for the mineral observed within calcifying tendon collagen, and their 3-D disposition is not regularly ordered. Possible spatial and temporal relationships of vesicles, osteopontin, mineral, and collagen are being examined further by these approaches.

  14. NON-EQUILIBRIUM MODELING OF THE FE XVII 3C/3D LINE RATIO IN AN INTENSE X-RAY FREE-ELECTRON LASER EXCITED PLASMA

    SciTech Connect

    Loch, S. D.; Ballance, C. P.; Li, Y.; Fogle, M.; Fontes, C. J.

    2015-03-01

    Recent measurements using an X-ray Free Electron Laser (XFEL) and an Electron Beam Ion Trap at the Linac Coherent Light Source facility highlighted large discrepancies between the observed and theoretical values for the Fe xvii 3C/3D line intensity ratio. This result raised the question of whether the theoretical oscillator strengths may be significantly in error, due to insufficiencies in the atomic structure calculations. We present time-dependent spectral modeling of this experiment and show that non-equilibrium effects can dramatically reduce the predicted 3C/3D line intensity ratio, compared with that obtained by simply taking the ratio of oscillator strengths. Once these non-equilibrium effects are accounted for, the measured line intensity ratio can be used to determine a revised value for the 3C/3D oscillator strength ratio, giving a range from 3.0 to 3.5. We also provide a framework to narrow this range further, if more precise information about the pulse parameters can be determined. We discuss the implications of the new results for the use of Fe xvii spectral features as astrophysical diagnostics and investigate the importance of time-dependent effects in interpreting XFEL-excited plasmas.

  15. Diffraction of electrons at intermediate energies: The role of phonons

    SciTech Connect

    Ascolani, H.; Zampieri, G.

    1996-07-01

    The intensity of electrons reflected {open_quote}{open_quote}elastically{close_quote}{close_quote} from crystalline surfaces presents two regimes: the low-energy or LEED regime ({lt}500 eV), in which the electrons are reflected along the Bragg directions, and the intermediate-energy or XPD/AED regime ({gt}500 eV), in which the maxima of intensity are along the main crystallographic axes. We present a model which explains this transition in terms of the excitation/absorption of phonons during the scattering. {copyright} {ital 1996 American Institute of Physics.}

  16. Precession electron diffraction in scanning transmission electron microscopy: phase, orientation and strain mapping at the nanometer scale

    NASA Astrophysics Data System (ADS)

    Sharp, T. G.

    2015-12-01

    Precession electron diffraction is a technique used in scanning transmission electron microscopy (STEM) to collect electron diffraction patterns while precessing the beam in a cone around the optic axis of the microscope. Electrons are strongly scattered by matter, resulting in dynamical diffraction effects and complex intensity distributions. Precession diffraction produces patterns that are nearly kinematical and lack the complicated intensity distributions of dynamical scattering. These patterns are readily indexed by computer, which allows for the structural characterization of the sample at each pixel. This technique is analogous to electron backscatter diffraction (EBSD), but with higher spatial resolution. Like EBSD, precession diffraction is used to make phase and orientation maps in polycrystalline aggregates and deformed crystals. The technique also provides quantitative strain mapping at the nanometer scale for characterization of defects and coherent interfaces. This technique is especially useful for characterizing nano-scale intergrowths that are produced in high-pressure experiments and in naturally shocked samples. We are using this technique on our aberration corrects JEOL ARM200F STEM. Examples of experimentally and naturally transformed olivine will be presented.

  17. Total-scattering pair-distribution function of organic material from powder electron diffraction data

    DOE PAGES

    Gorelik, Tatiana E.; Billinge, Simon J. L.; Schmidt, Martin U.; ...

    2015-04-01

    This paper shows for the first time that pair-distribution function analyses can be carried out on organic and organo-metallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction (SAED) and nanodiffraction in transmission electron microscopy (TEM) or nanodiffraction in scanning transmission electron microscopy (STEM) modes. The methods were demonstrated on organo-metallic complexes (chlorinated and unchlorinated copper-phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering datamore » and avoiding beam-damage of the sample are possible to resolve.« less

  18. Total-scattering pair-distribution function of organic material from powder electron diffraction data

    SciTech Connect

    Gorelik, Tatiana E.; Billinge, Simon J. L.; Schmidt, Martin U.; Kolb, Ute

    2015-04-01

    This paper shows for the first time that pair-distribution function analyses can be carried out on organic and organo-metallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction (SAED) and nanodiffraction in transmission electron microscopy (TEM) or nanodiffraction in scanning transmission electron microscopy (STEM) modes. The methods were demonstrated on organo-metallic complexes (chlorinated and unchlorinated copper-phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam-damage of the sample are possible to resolve.

  19. The significance of Bragg's law in electron diffraction and microscopy, and Bragg's second law.

    PubMed

    Humphreys, C J

    2013-01-01

    Bragg's second law, which deserves to be more widely known, is recounted. The significance of Bragg's law in electron diffraction and microscopy is then discussed, with particular emphasis on differences between X-ray and electron diffraction. As an example of such differences, the critical voltage effect in electron diffraction is described. It is then shown that the lattice imaging of crystals in high-resolution electron microscopy directly reveals the Bragg planes used for the imaging process, exactly as visualized by Bragg in his real-space law. Finally, it is shown how in 2012, for the first time, on the centennial anniversary of Bragg's law, single atoms have been identified in an electron microscope using X-rays emitted from the specimen. Hence atomic resolution X-ray maps of a crystal in real space can be formed which give the positions and identities of the different atoms in the crystal, or of a single impurity atom in the crystal.

  20. Electron diffraction and microscopy of single-wall carbon nanotube bundles produced by different methods

    NASA Astrophysics Data System (ADS)

    Colomer, J.-F.; Henrard, L.; Lambin, Ph.; van Tendeloo, G.

    2002-05-01

    The atomic structure of single-wall carbon nanotube bundles produced by three different techniques (laser ablation, electric arc discharge and catalytic chemical vapor deposition (CCVD)) has been characterized by electron diffraction and microscopy. Information on the helicity and the lattice packing has been obtained. Concerning the helicity, small bundles produced by CCVD exhibit only one or two tube helicities within a single bundle. The diffraction patterns of laser-ablation produced bundles also present well-defined but more diversified chiralities within a single bundle. By contrast the data acquired on bundles formed by arc discharge show a more diffuse pattern, characteristic of a random chirality dispersion within a single bundle. Concerning the lattice packing, informations are obtained via a detailed study of the equatorial line of the diffraction pattern for bundles produced by the three techniques. This electron diffraction study is completed by high-resolution electron microscopy.

  1. Effect of time-dependent 3-D electron density gradients on high angle of incidence HF radiowave propagation

    NASA Astrophysics Data System (ADS)

    Zawdie, K. A.; Drob, D. P.; Huba, J. D.; Coker, C.

    2016-07-01

    One of the challenges for the utilization of HF radiowaves in practical applications is to understand how the signals propagate in time- and range-dependent multipath environments. For typical quiescent ionospheric conditions it is often reasonably straightforward to interpret received HF signals. For disturbed ionospheric conditions, however, such as in the presence of large tilts, irregularities, and medium-scale traveling ionospheric disturbances (MSTIDs), data interpretation and utilization often becomes challenging. This paper presents a theoretical HF propagation modeling study that exploits the capabilities of a first principles, mesoscale resolution ionosphere code, SAMI3 (Sami3 is Another Model of the Ionosphere) and a new implementation of the 3-D ray trace equations, MoJo-15 (Modernized Jones Code) in order to examine the relationship between various HF propagation observables and MSTID characteristics. This paper demonstrates the implications of MSTIDS on high angle of incidence HF propagation during typical low-latitude, postsunset ionospheric conditions and examines the spatiotemporal evolution of multiple propagation paths that may connect a given source and receiver.

  2. Strain mapping in TEM using precession electron diffraction

    DOEpatents

    Taheri, Mitra Lenore; Leff, Asher Calvin

    2017-02-14

    A sample material is scanned with a transmission electron microscope (TEM) over multiple steps having a predetermined size at a predetermined angle. Each scan at a predetermined step and angle is compared to a template, wherein the template is generated from parameters of the material and the scanning. The data is then analyzed using local mis-orientation mapping and/or Nye's tensor analysis to provide information about local strain states.

  3. Electron and lattice dynamics of transition metal thin films observed by ultrafast electron diffraction and transient optical measurements

    PubMed Central

    Nakamura, A.; Shimojima, T.; Nakano, M.; Iwasa, Y.; Ishizaka, K.

    2016-01-01

    We report the ultrafast dynamics of electrons and lattice in transition metal thin films (Au, Cu, and Mo) investigated by a combination of ultrafast electron diffraction (UED) and pump-probe optical methods. For a single-crystalline Au thin film, we observe the suppression of the diffraction intensity occuring in 10 ps, which direcly reflects the lattice thermalization via the electron-phonon interaction. By using the two-temperature model, the electron-phonon coupling constant (g) and the electron and lattice temperatures (Te, Tl) are evaluated from UED, with which we simulate the transient optical transmittance. The simulation well agrees with the experimentally obtained transmittance data, except for the slight deviations at the initial photoexcitation and the relaxed quasi-equilibrium state. We also present the results similarly obtained for polycrystalline Au, Cu, and Mo thin films and demonstrate the electron and lattice dynamics occurring in metals with different electron-phonon coupling strengths. PMID:28004010

  4. Hydrogen in polar intermetallics: Syntheses and structures of the ternary Ca5Bi3D0.93, Yb5Bi3Hx, and Sm5Bi3H~1 by powder neutron or single crystal X-ray diffraction

    SciTech Connect

    Leon-Escamilla, E. Alejandro; Dervenagas, Panagiotis; Stasis, Constantine; Corbett, John D.

    2010-01-01

    The syntheses of the title compounds are described in detail. Structural characterizations from refinements of single crystal X-ray diffraction data for Yb{sub 5}Bi{sub 3}H{sub x} and Sm{sub 5}Bi{sub 3}H{sub 1} and of powder neutron diffraction data for Ca{sub 5}Bi{sub 3}D{sub 0.93(3)} are reported. These confirm that all three crystallize with the heavy atom structure type of {beta}-Yb{sub 5}Sb{sub 3}, and the third gives the first proof that the deuterium lies in the center of nominal calcium tetrahedra, isostructural with the Ca{sub 5}Sb{sub 3}F-type structure. These Ca and Yb phases are particularly stable with respect to dissociation to Mn{sub 5}Si{sub 3}-type product plus H{sub 2}. Some contradictions in the literature regarding Yb{sub 5}Sb{sub 3} and Yb{sub 5}Sb{sub 3}H{sub x} phases are considered in terms of adventitious hydrogen impurities that are generated during reactions in fused silica containers at elevated temperatures.

  5. Electron-correlation effects on the 3C to 3D line-intensity ratio in the Ne-like ions Ar8+ to Kr26+

    DOE PAGES

    Santana, Juan A.; Lepson, Jaan K.; Trabert, Elmar; ...

    2015-01-07

    We present a theoretical and experimental investigation of the 3d→2p resonance to the intercombination line ratio in low- to mid-Z neonlike ions of astrophysical interest, i.e., of the 2p1/22p43/23d3/21Po1 → 2p61S0 and 2p21/22p33/23d5/23Do1 → 2p61S0 transitions commonly labeled 3C and 3D, respectively. In particular, we have employed the configuration-interaction method with three different numbers of basis states and the many-body perturbation theory method to calculate oscillator strengths and energies for neonlike ions from Z = 18 to 36. Combining our calculations with a systematic study of previous works in the literature, we show that these methods can predict accurate andmore » converged energies for these transitions. We also find convergence for the oscillator strengths, but the ratio of oscillator strengths, which can be compared to experimental values of the relative intensity ratios of these lines, appears to converge to values higher than measured. We speculate that this is due to the role of electron-electron correlations. While the amount of electron correlations associated with the intercombination line 3D appears to be well described, it seems that the contributions from highly excited states are not sufficiently accounted for in the case of the resonance line 3C. In order to augment the body of available experimental data for neonlike ions, we present a measurement of the 3C and 3D lines in neonlike Ar8+. We report a wavelength of 41.480±0.001 Å for line 3C and 42.005±0.001 Å for line 3D. Lastly, the intensity ratio of the two lines was determined to be I(3C)/I(3D)=11.32±1.40.« less

  6. Ultrafast electron diffraction and electron microscopy: present status and future prospects

    NASA Astrophysics Data System (ADS)

    Ishchenko, A. A.; Aseyev, S. A.; Bagratashvili, V. N.; Panchenko, V. Ya; Ryabov, E. A.

    2014-07-01

    Acting as complementary research tools, high time-resolved spectroscopy and diffractometry techniques proceeding from various physical principles open up new possibilities for studying matter with necessary integration of the 'structure-dynamics-function' triad in physics, chemistry, biology and materials science. Since the 1980s, a new field of research has started at the leading research laboratories, aimed at developing means of filming the coherent dynamics of nuclei in molecules and fast processes in biological objects ('atomic and molecular movies'). The utilization of ultrashort laser pulse sources has significantly modified traditional electron beam approaches to and provided high space-time resolution for the study of materials. Diffraction methods using frame-by-frame filming and the development of the main principles of the study of coherent dynamics of atoms have paved the way to observing wave packet dynamics, the intermediate states of reaction centers, and the dynamics of electrons in molecules, thus allowing a transition from the kinetics to the dynamics of the phase trajectories of molecules in the investigation of chemical reactions.

  7. Coupling Automated Electron Backscatter Diffraction with Transmission Electron and Atomic Force Microscopies

    SciTech Connect

    Schwartz, A.J.; Kumar, M.; Bedrossian, P.J.; King, W.E.

    2000-01-26

    Grain boundary network engineering is an emerging field that encompasses the concept that modifications to conventional thermomechanical processing can result in improved properties through the disruption of the random grain boundary network. Various researchers have reported a correlation between the grain boundary character distribution (defined as the fractions of special and random grain boundaries) and dramatic improvements in properties such as corrosion and stress corrosion cracking, creep, etc. While much early work in the field emphasized property improvements, the opportunity now exists to elucidate the underlying materials science of grain boundary network engineering. Recent investigations at LLNL have coupled automated electron backscatter diffraction (EBSD) with transmission electron microscopy (TEM) and atomic force microscopy (AFM) to elucidate these fundamental mechanisms. This investigation provides evidence that grain boundary network engineering and the formation of annealing twins disrupt the connectivity of the random grain boundary network and is likely responsible for the experimentally observed improvement in properties. This work illustrates that coupling of automated EBSD with other microstructural probes such as TEM and AFM provides data of greater value than any single technique in isolation. The coupled techniques have been applied to aid in understanding the underlying mechanisms of grain boundary network engineering and the corrosion properties of individual boundaries.

  8. Synergy between transmission electron microscopy and powder diffraction: application to modulated structures.

    PubMed

    Batuk, Dmitry; Batuk, Maria; Abakumov, Artem M; Hadermann, Joke

    2015-04-01

    The crystal structure solution of modulated compounds is often very challenging, even using the well established methodology of single-crystal X-ray crystallography. This task becomes even more difficult for materials that cannot be prepared in a single-crystal form, so that only polycrystalline powders are available. This paper illustrates that the combined application of transmission electron microscopy (TEM) and powder diffraction is a possible solution to the problem. Using examples of anion-deficient perovskites modulated by periodic crystallographic shear planes, it is demonstrated what kind of local structural information can be obtained using various TEM techniques and how this information can be implemented in the crystal structure refinement against the powder diffraction data. The following TEM methods are discussed: electron diffraction (selected area electron diffraction, precession electron diffraction), imaging (conventional high-resolution TEM imaging, high-angle annular dark-field and annular bright-field scanning transmission electron microscopy) and state-of-the-art spectroscopic techniques (atomic resolution mapping using energy-dispersive X-ray analysis and electron energy loss spectroscopy).

  9. Initial Self-Consistent 3D Electron-Cloud Simulations of the LHC Beam with the Code WARP+POSINST

    SciTech Connect

    Vay, J; Furman, M A; Cohen, R H; Friedman, A; Grote, D P

    2005-10-11

    We present initial results for the self-consistent beam-cloud dynamics simulations for a sample LHC beam, using a newly developed set of modeling capability based on a merge [1] of the three-dimensional parallel Particle-In-Cell (PIC) accelerator code WARP [2] and the electron-cloud code POSINST [3]. Although the storage ring model we use as a test bed to contain the beam is much simpler and shorter than the LHC, its lattice elements are realistically modeled, as is the beam and the electron cloud dynamics. The simulated mechanisms for generation and absorption of the electrons at the walls are based on previously validated models available in POSINST [3, 4].

  10. Structural damage reduction in protected gold clusters by electron diffraction methods.

    PubMed

    Ortega, Eduardo; Ponce, Arturo; Santiago, Ulises; Alducin, Diego; Benitez-Lara, Alfredo; Plascencia-Villa, Germán; José-Yacamán, Miguel

    2017-01-01

    The present work explores electron diffraction methods for studying the structure of metallic clusters stabilized with thiol groups, which are susceptible to structural damage caused by electron beam irradiation. There is a compromise between the electron dose used and the size of the clusters since they have small interaction volume with electrons and as a consequence weak reflections in the diffraction patterns. The common approach of recording individual clusters using nanobeam diffraction has the problem of an increased current density. Dosage can be reduced with the use of a smaller condenser aperture and a higher condenser lens excitation, but even with those set ups collection times tend to be high. For that reason, the methods reported herein collects in a faster way diffraction patterns through the scanning across the clusters under nanobeam diffraction mode. In this way, we are able to collect a map of diffraction patterns, in areas with dispersed clusters, with short exposure times (milliseconds) using a high sensitive CMOS camera. When these maps are compared with their theoretical counterparts, oscillations of the clusters can be observed. The stability of the patterns acquired demonstrates that our methods provide a systematic and precise way to unveil the structure of atomic clusters without extensive detrimental damage of their crystallinity.

  11. Feynman Path Integral Approach to Electron Diffraction for One and Two Slits: Analytical Results

    ERIC Educational Resources Information Center

    Beau, Mathieu

    2012-01-01

    In this paper we present an analytic solution of the famous problem of diffraction and interference of electrons through one and two slits (for simplicity, only the one-dimensional case is considered). In addition to exact formulae, various approximations of the electron distribution are shown which facilitate the interpretation of the results.…

  12. Disentangling atomic-layer-specific x-ray absorption spectra by Auger electron diffraction spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsui, Fumihiko; Matsushita, Tomohiro; Kato, Yukako; Hashimoto, Mie; Daimon, Hiroshi

    2009-11-01

    In order to investigate the electronic and magnetic structures of each atomic layer at subsurface, we have proposed a new method, Auger electron diffraction spectroscopy, which is the combination of x-ray absorption spectroscopy (XAS) and Auger electron diffraction (AED) techniques. We have measured a series of Ni LMM AED patterns of the Ni film grown on Cu(001) surface for various thicknesses. Then we deduced a set of atomic-layer-specific AED patterns in a numerical way. Furthermore, we developed an algorithm to disentangle XANES spectra from different atomic layers using these atomic-layer-specific AED patterns. Surface and subsurface core level shift were determined for each atomic layer.

  13. Application of convergent beam electron diffraction to two-dimensional strain mapping in silicon devices

    NASA Astrophysics Data System (ADS)

    Armigliato, A.; Balboni, R.; Carnevale, G. P.; Pavia, G.; Piccolo, D.; Frabboni, S.; Benedetti, A.; Cullis, A. G.

    2003-03-01

    A method of obtaining quantitative two-dimensional (2D) maps of strain by the convergent beam electron diffraction technique in a transmission electron microscope is described. It is based on the automatic acquisition of a series of diffraction patterns generated from digital rastering the electron spot in a matrix of points within a selected area of the sample. These patterns are stored in a database and the corresponding strain tensor at each point is calculated, thus yielding a 2D strain map. An example of application of this method to cross-sectioned cells fabricated for the 0.15 μm technology of flash memories is reported.

  14. Probing phase transitions at surfaces with ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Horn von Hoegen, Michael

    2013-03-01

    The multitude of possible processes that can occur at surfaces cover many orders of magnitude in the time domain. While large scale growth and structure formation happens on a timescale of minutes and seconds, diffusion is already much faster, but can still be observed by electron microscopy. Many other processes as chemical reactions, phonon dynamics, or phase transitions, however, take place on the femto- and picosecond timescale and are yet way to fast for imaging techniques. In order to study such ultrafast processes at surfaces we have combined modern surface science techniques with fs laser pulses in a pump probe scheme. We use a RHEED setup with grazing incident electrons of 7 - 30 keV to ensure surface sensitivity. In order to overcome the velocity mismatch between light and electrons a tilted pulse front scheme is used to achieve a time resolution of less than 2 ps. The sample is excited with 800 nm photons with a pulse energy of 0.5 mJ at 5 kHz repetition rate. The huge potential of this technique for the study of transient surface phenomena is demonstrated with the non-equilibrium dynamics of the In induced c(8x2) reconstruction on Si(111). This surface exhibits a Peierls-like phase transition at 100 K from a c(8x2) groundstate, which is accompanied by the formation of a charge density wave (CDW), to (4x1) excited state. Upon excitation by the fs-laser pulse this structural phase transition is driven into the excited (4x1) state at a sample temperature of 20 K. The surface is only excited electronically, the CDW is lifted by photo doping and the surface remains up to 500 ps in a super cooled excited (4x1) state. Relaxation into the c(8x2) groundstate happens delayed through the nucleation of the c(8x2) at defects which triggers a 1-dim. recrystallisation front which propagates with the velocity of sound. Utilizing the Debye Waller effect, the excitation, conversion and relaxation of vibrational excitations in monolayer adsorbate systems like the Pb

  15. Optimization of 3D conformal electron beam therapy in inhomogeneous media by concomitant fluence and energy modulation

    NASA Astrophysics Data System (ADS)

    Åsell, Mats; Hyödynmaa, Simo; Gustafsson, Anders; Brahme, Anders

    1997-11-01

    The possibilities of using simultaneous fluence and energy modulation techniques in electron beam therapy to shape the dose distribution and almost eliminate the influences of tissue inhomogeneities have been investigated. By using a radiobiologically based optimization algorithm the radiobiological properties of the tissues can be taken into account when trying to find the best possible dose delivery. First water phantoms with differently shaped surfaces were used to study the effect of surface irregularities. We also studied water phantoms with internal inhomogeneities consisting of air or cortical bone. It was possible to improve substantially the dose distribution by fluence modulation in these cases. In addition to the fluence modulation the most suitable single electron energy in each case was also determined. Finally, the simultaneous use of several preselected electron beam energies was also tested, each with an individually optimized fluence profile. One to six electron energies were used, resulting in a slow improvement in complication-free cure with increasing number of beam energies. To apply these techniques to a more clinically relevant situation a post-operative breast cancer patient was studied. For simplicity this patient was treated with only one anterior beam portal to clearly illustrate the effect of inhomogeneities like bone and lung on the dose distribution. It is shown that by using fluence modulation the influence of dose inhomogeneities can be significantly reduced. When two or more electron beam energies with individually optimized fluence profiles are used the dose conformality to the internal target volume is further increased, particularly for targets with complex shapes.

  16. Evolution of chemical bonding and electron density rearrangements during D(3h) → D(3d) reaction in monolayered TiS2: a QTAIM and ELF study.

    PubMed

    Ryzhikov, Maxim R; Slepkov, Vladimir A; Kozlova, Svetlana G; Gabuda, Svyatoslav P

    2014-08-15

    Monolayered titanium disulfide TiS2, a prospective nanoelectronic material, was previously shown to be subject to an exothermic solid-state D3h -D3d reaction that proceeds via a newly discovered transition state. Here, we study the reaction in detail using topological methods of quantum chemistry (quantum theory of atoms in molecules and electron localization function analysis) and show how electron density and chemical bonding between the atoms change in the course of the reaction. The reaction is shown to undergo a series of topological catastrophes, associated with elementary chemical events such as break and formation of bonds (including the unexpected formation of S-S bonding between sulfur layers), and rearrangement of electron density of outer valence and core shells.

  17. High-Throughput Top-Down and Bottom-Up Processes for Forming Single-Nanotube Based Architectures for 3D Electronics

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Megerian, Krikor G.; von Allmen, Paul; Kowalczyk, Robert; Baron, Richard

    2009-01-01

    We have developed manufacturable approaches to form single, vertically aligned carbon nanotubes, where the tubes are centered precisely, and placed within a few hundred nm of 1-1.5 micron deep trenches. These wafer-scale approaches were enabled by chemically amplified resists and inductively coupled Cryo-etchers for forming the 3D nanoscale architectures. The tube growth was performed using dc plasma-enhanced chemical vapor deposition (PECVD), and the materials used for the pre-fabricated 3D architectures were chemically and structurally compatible with the high temperature (700 C) PECVD synthesis of our tubes, in an ammonia and acetylene ambient. Tube characteristics were also engineered to some extent, by adjusting growth parameters, such as Ni catalyst thickness, pressure and plasma power during growth. Such scalable, high throughput top-down fabrication techniques, combined with bottom-up tube synthesis, should accelerate the development of PECVD tubes for applications such as interconnects, nano-electromechanical (NEMS), sensors or 3D electronics in general.

  18. Front-end electronics and data acquisition system for a multi-wire 3D gas tracker

    NASA Astrophysics Data System (ADS)

    Łojek, K.; Rozpȩdzik, D.; Bodek, K.; Perkowski, M.; Severijns, N.

    2015-12-01

    This paper presents the design and implementation of the front-end electronics and the data acquisition (DAQ) system for readout of multi-wire drift chambers (MWDC). Apart of the conventional drift time measurement the system delivers the hit position along the wire utilizing the charge division technique. The system consists of preamplifiers, and analog and digital boards sending data to a back-end computer via an Ethernet interface. The data logging software formats the received data and enables an easy access to the data analysis software. The use of specially designed preamplifiers and peak detectors allows the charge-division readout of the low resistance signal wire. The implication of the charge-division circuitry onto the drift time measurement was studied and the overall performance of the electronic system was evaluated in dedicated off-line tests.

  19. Preconditioning techniques for constrained vector potential integral equations, with application to 3-D magnetoquasistatic analysis of electronic packages

    SciTech Connect

    Kamon, M.; Phillips, J.R.

    1994-12-31

    In this paper techniques are presented for preconditioning equations generated by discretizing constrained vector integral equations associated with magnetoquasistatic analysis. Standard preconditioning approaches often fail on these problems. The authors present a specialized preconditioning technique and prove convergence bounds independent of the constraint equations and electromagnetic excitation frequency. Computational results from analyzing several electronic packaging examples are given to demonstrate that the new preconditioning approach can sometimes reduce the number of GMRES iterations by more than an order of magnitude.

  20. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    DOE PAGES

    Wang, Zhenyu; Lin, Yu; Wang, Xueyi; ...

    2016-07-07

    The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio mi/me. In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me. The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location wheremore » $$\\vec{k}$$• $$\\vec{B}$$ =0, consistent with previous analytical and simulation studies. Here, $$\\vec{B}$$ is the equilibrium magnetic field and $$\\vec{k}$$ is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at $$\\vec{k}$$ •$$\\vec{B}$$ ≠0. Additionally, the simulation results indicate that varying mi/me, the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.« less

  1. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    NASA Astrophysics Data System (ADS)

    Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu

    2016-07-01

    The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio mi/me . In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me . The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location where k →.B → =0 , consistent with previous analytical and simulation studies. Here, B → is the equilibrium magnetic field and k → is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at k →.B → ≠0 . In addition, the simulation results indicate that varying mi/me , the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.

  2. 3D analysis of synaptic vesicle density and distribution after acute foot-shock stress by using serial section transmission electron microscopy.

    PubMed

    Khanmohammadi, M; Darkner, S; Nava, N; Nyengaard, J R; Wegener, G; Popoli, M; Sporring, J

    2017-01-01

    Behavioural stress has shown to strongly affect neurotransmission within the neocortex. In this study, we analysed the effect of an acute stress model on density and distribution of neurotransmitter-containing vesicles within medial prefrontal cortex. Serial section transmission electron microscopy was employed to compare two groups of male rats: (1) rats subjected to foot-shock stress and (2) rats with sham stress as control group. Two-dimensional (2D) density measures are common in microscopic images and are estimated by following a 2D path in-section. However, this method ignores the slant of the active zone and thickness of the section. In fact, the active zone is a surface in three-dimension (3D) and the 2D measures do not accurately reflect the geometric configuration unless the active zone is perpendicular to the sectioning angle. We investigated synaptic vesicle density as a function of distance from the active zone in 3D. We reconstructed a 3D dataset by estimating the thickness of all sections and by registering all the image sections into a common coordinate system. Finally, we estimated the density as the average number of vesicles per area and volume and modelled the synaptic vesicle distribution by fitting a one-dimensional parametrized distribution that took into account the location uncertainty due to section thickness. Our results showed a clear structural difference in synaptic vesicle density and distribution between stressed and control group with improved separation by 3D measures in comparison to the 2D measures. Our results showed that acute foot-shock stress exposure significantly affected both the spatial distribution and density of the synaptic vesicles within the presynaptic terminal.

  3. Evidence for the suppression of incident beam effects in Auger electron diffraction

    NASA Astrophysics Data System (ADS)

    Davoli, I.; Gunnella, R.; Bernardini, R.; De Crescenzi, M.

    1998-01-01

    Auger electron diffraction (AED) of the Cu(100) surface has been studied through the anisotropy of the elastic backdiffused beam electrons, the L 2,3M 4,5M 4,5 (LVV) and the M 2,3M 4,5M 4,5 (MVV) transitions in polar scan along the two main directions [001], [011] and in azimuth scan at normal emission. The intensity anisotropies of the low and high kinetic energy Auger lines are in antiphase to each other as in experiments in which these transitions are excited by X-ray photons. This behaviour has been exploited to single out the origin of the physical mechanisms accompanying the diffraction of the emitted electrons. Incident beam effects appear to be sizeable only when the collection of the AED spectra are made with an angle integrating electron analyser (cylindrical mirror analyser or low electron energy diffraction apparatus), but they appear negligible when electron collection is performed through a small solid-angle detector. The conclusions reached by our measurements are supported by good agreement with experimental and theoretical X-ray photoelectron diffraction data and demonstrate that, when the incident beam energy is sufficiently higher than the kinetic energy of the Auger electron detected, the influence of the incident beam on AED is negligible.

  4. SUePDF: a program to obtain quantitative pair distribution functions from electron diffraction data

    PubMed Central

    Tran, Dung Trung; Svensson, Gunnar; Tai, Cheuk-Wai

    2017-01-01

    SUePDF is a graphical user interface program written in MATLAB to achieve quantitative pair distribution functions (PDFs) from electron diffraction data. The program facilitates structural studies of amorphous materials and small nanoparticles using electron diffraction data from transmission electron microscopes. It is based on the physics of electron scattering as well as the total scattering methodology. A method of background modeling is introduced to treat the intensity tail of the direct beam, inelastic scattering and incoherent multiple scattering. Kinematical electron scattering intensity is scaled using the electron scattering factors. The PDFs obtained after Fourier transforms are normalized with respect to number density, nanoparticle form factor and the non-negativity of probability density. SUePDF is distributed as free software for academic users. PMID:28190994

  5. Detection of electron magnetic circular dichroism signals under zone axial diffraction geometry.

    PubMed

    Song, Dongsheng; Rusz, Jan; Cai, Jianwang; Zhu, Jing

    2016-10-01

    EMCD (electron magnetic circular dichroism) technique provides us a new opportunity to explore magnetic properties in the transmission electron microscope. However, specific diffraction geometry is the major limitation. Only the two-beam and three-beam case are demonstrated in the experiments until now. Here, we present the more general case of zone axial (ZA) diffraction geometry through which the EMCD signals can be detected even with the very strong sensitivity to dynamical diffraction conditions. Our detailed calculations and well-controlled diffraction conditions lead to experiments in agreement with theory. The effect of dynamical diffraction conditions on EMCD signals are discussed both in theory and experiments. Moreover, with the detailed analysis of dynamical diffraction effects, we experimentally obtain the separate EMCD signals for each crystallographic site in Y3Fe5O12, which is also applicable for other materials and cannot be achieved by site-specific EMCD and XMCD technique directly. Our work extends application of more general diffraction geometries and will further promote the development of EMCD technique.

  6. EBSD characterization and modeling of columnar dendritic grains growing in the presence of fluid flow[Electron Backscattered Diffraction

    SciTech Connect

    Takatani, H.; Gandin, C.A.; Rappaz, M.

    2000-02-09

    Columnar dendritic grains of steel growth in the presence of fluid flow (e.g., solidified on turning rolls) have been characterized by Electron Backscattered Diffraction (EBSD) technique. It is shown that grains have a random crystallographic orientation at the surfaces of the sheet in contact with the mould. In the middle of the sheet, the grains which have survived the growth selection mechanisms exhibit a (100) texture in which the average dendrite trunk direction is not exactly aligned with the thermal gradient (i.e., the normal to the surfaces of the sheet). It is tilted by about 15{degree} toward the upstream direction. This deviation is examined by simulations of grain structure formation based on a three-dimensional Cellular Automation (CA)-Finite Element (FE) (3D CAFE) model, which has been modified in order to account for fluid flow effects. The modified Ca algorithm includes a growth kinetics of the dendrites which is a function of both the undercooling and fluid flow direction. It is validated by comparing the predicted shape of an individual grain growing under given thermal and fluid flow conditions with an analytical solution. The 3D CAFE predictions of the columnar grains grown in the presence of fluid flow are in good agreement with the experimental EBSB results.

  7. 3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

    SciTech Connect

    Wang, Zhenyu; Lin, Yu; Wang, Xueyi; Tummel, Kurt; Chen, Liu

    2016-07-07

    The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio mi/me. In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic mi/me. The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location where $\\vec{k}$• $\\vec{B}$ =0, consistent with previous analytical and simulation studies. Here, $\\vec{B}$ is the equilibrium magnetic field and $\\vec{k}$ is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at $\\vec{k}$ •$\\vec{B}$ ≠0. Additionally, the simulation results indicate that varying mi/me, the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.

  8. Toroidal mode number estimation of the edge-localized modes using the KSTAR 3-D electron cyclotron emission imaging system

    SciTech Connect

    Lee, J.; Yun, G. S. Lee, J. E.; Kim, M.; Choi, M. J.; Lee, W.; Park, H. K.; Domier, C. W.; Luhmann, N. C.; Sabbagh, S. A.; Park, Y. S.; Lee, S. G.; Bak, J. G.

    2014-06-15

    A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle α{sub *} of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α{sub *} is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.

  9. Toroidal mode number estimation of the edge-localized modes using the KSTAR 3-D electron cyclotron emission imaging system

    NASA Astrophysics Data System (ADS)

    Lee, J.; Yun, G. S.; Lee, J. E.; Kim, M.; Choi, M. J.; Lee, W.; Park, H. K.; Domier, C. W.; Luhmann, N. C.; Sabbagh, S. A.; Park, Y. S.; Lee, S. G.; Bak, J. G.

    2014-06-01

    A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle α* of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α* is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.

  10. Toroidal mode number estimation of the edge-localized modes using the KSTAR 3-D electron cyclotron emission imaging system.

    PubMed

    Lee, J; Yun, G S; Lee, J E; Kim, M; Choi, M J; Lee, W; Park, H K; Domier, C W; Luhmann, N C; Sabbagh, S A; Park, Y S; Lee, S G; Bak, J G

    2014-06-01

    A new and more accurate technique is presented for determining the toroidal mode number n of edge-localized modes (ELMs) using two independent electron cyclotron emission imaging (ECEI) systems in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The technique involves the measurement of the poloidal spacing between adjacent ELM filaments, and of the pitch angle α* of filaments at the plasma outboard midplane. Equilibrium reconstruction verifies that α* is nearly constant and thus well-defined at the midplane edge. Estimates of n obtained using two ECEI systems agree well with n measured by the conventional technique employing an array of Mirnov coils.

  11. Regional 3-D ionospheric electron density specification on the basis of data assimilation of ground-based GNSS and radio occultation data

    NASA Astrophysics Data System (ADS)

    Aa, Ercha; Liu, Siqing; Huang, Wengeng; Shi, Liqin; Gong, Jiancun; Chen, Yanhong; Shen, Hua; Li, Jianyong

    2016-06-01

    In this paper, a regional 3-D ionospheric electron density specification over China and adjacent areas (70°E-140°E in longitude, 15°N-55°N in latitude, and 100-900 km in altitude) is developed on the basis of data assimilation technique. The International Reference Ionosphere (IRI) is used as a background model, and a three-dimensional variational technique is used to assimilate both the ground-based Global Navigation Satellite System (GNSS) observations from the Crustal Movement Observation Network of China (CMONOC) and International GNSS Service (IGS) and the ionospheric radio occultation (RO) data from FORMOSAT-3/COSMIC (F3/C) satellites. The regional 3-D gridded ionospheric electron densities can be generated with temporal resolution of 5 min in universal time, horizontal resolution of 2° × 2° in latitude and longitude, and vertical resolution of 20 km between 100 and 500 km and 50 km between 500 and 900 km. The data assimilation results are validated through extensive comparison with several sources of electron density information, including (1) ionospheric total electron content (TEC); (2) Abel-retrieved F3/C electron density profiles (EDPs); (3) ionosonde foF2 and bottomside EDPs; and (4) the Utah State University Global Assimilation of Ionospheric Measurements (USU-GAIM) under both geomagnetic quiet and disturbed conditions. The validation results show that the data assimilation procedure pushes the climatological IRI model toward the observation, and a general accuracy improvement of 15-30% can be expected. Thecomparisons also indicate that the data assimilation results are more close to the Center for Orbit Determination of Europe (CODE) TEC and Madrigal TEC products than USU-GAIM. These initial results might demonstrate the effectiveness of the data assimilation technique in improving specification of local ionospheric morphology.

  12. Angle Resolved Photoelectron and Auger Electron Diffraction as a Structural Probe for Surfaces, Interfaces, and Epitaxial Films.

    NASA Astrophysics Data System (ADS)

    Li, Hong

    The recently developed techniques of angle-resolved photoelectron and Auger electron diffraction (ARXPD/AED) have shown promise in identifying the structures of epitaxial films. This is due to the realization that electrons scattered by other atoms are enhanced along the forward direction. In this dissertation research, we have further investigated the capabilities of the ARXPD/AED technique. First, the complete polar angle distribution of the Auger electron intensity from Cu(001) was measured from the (100) to the (110) azimuth. The presentation of the ARAED in the form of a contour map clearly shows the relationship of the constructive and destructive interference of electron scattering to the crystallographic index of the crystal. Secondly, the angular distributions of electron emissions with initial states of 3p, 3d, 4d, and the Auger emission with electron kinetic energies ranging from 348 eV to 1477 eV were measured for single crystal Ag(001). The results show that all of these electron emissions have similar electron forward scattering enhancements along the directions of nearest and next nearest neighbour atoms in the crystal. The forward scattering enhancements do not shift as the electron kinectic energy changes. The ARXPD/AED combined with low energy electron diffraction (LEED) has been demonstrated to be a very powerful technique in probing both the long range order and the short range order of the epitaxial films. The epitaxial films studied include Co on Cu(001), Fe on Ag(001), Co on Ag(001), and Co on an ultra-thin film of Fe(001), which was epitaxially grown on Ag(001). We find that up to 20 ML thickness of high quality metastable fcc Co can be stabilized on Cu(001) at room temperature. We have directly verified that the Fe on Ag(001) is bcc. The Co on Ag(001) is neither bcc nor fcc for coverages of less than 3 ML. Thick films of Co on Ag(001) are disordered, of which a very small portion has a local structure of bcc. The bcc Co phases has been

  13. Genetically targeted 3D visualisation of Drosophila neurons under Electron Microscopy and X-Ray Microscopy using miniSOG

    PubMed Central

    Ng, Julian; Browning, Alyssa; Lechner, Lorenz; Terada, Masako; Howard, Gillian; Jefferis, Gregory S. X. E.

    2016-01-01

    Large dimension, high-resolution imaging is important for neural circuit visualisation as neurons have both long- and short-range patterns: from axons and dendrites to the numerous synapses at terminal endings. Electron Microscopy (EM) is the favoured approach for synaptic resolution imaging but how such structures can be segmented from high-density images within large volume datasets remains challenging. Fluorescent probes are widely used to localise synapses, identify cell-types and in tracing studies. The equivalent EM approach would benefit visualising such labelled structures from within sub-cellular, cellular, tissue and neuroanatomical contexts. Here we developed genetically-encoded, electron-dense markers using miniSOG. We demonstrate their ability in 1) labelling cellular sub-compartments of genetically-targeted neurons, 2) generating contrast under different EM modalities, and 3) segmenting labelled structures from EM volumes using computer-assisted strategies. We also tested non-destructive X-ray imaging on whole Drosophila brains to evaluate contrast staining. This enabled us to target specific regions for EM volume acquisition. PMID:27958322

  14. Electronic and magnetic properties of 2 H -NbS2 intercalated by 3 d transition metals

    NASA Astrophysics Data System (ADS)

    Mankovsky, S.; Polesya, S.; Ebert, H.; Bensch, W.

    2016-11-01

    The electronic structure and magnetic properties of the 2 H -NbS2 compound intercalated by Cr, Mn, and Fe, respectively, have been investigated by means of the Korringa-Kohn-Rostoker method. Magnetic torque calculations result in an easy plane magnetocrystalline anisotropy (MCA) of Cr1 /3NbS2 for the ground state (T =0 K). Relativistic disorder local moment calculations show that the corresponding anisotropy constant decreases monotonously with rising temperature in line with experiment. Going from the Cr and Mn to the Fe intercalated system, the modification of the electronic structure results in a change of the easy axis from in-plane to out-of-plane. It is shown that for Cr1 /3NbS2 and Mn1 /3NbS2 , the in-plane MCA and Dzyaloshinskii-Moriya interactions give rise to a helimagnetic structure along the hexagonal c axis, following the experimental observations. The negative exchange interactions in the Fe1 /3NbS2 compound result in a noncollinear frustrated magnetic structure if the MCA is not taken into account. It is shown, however, that a strong MCA along the hexagonal c axis leads to a magnetic ordering referred to as an ordering of the third kind, which was observed experimentally.

  15. Out-of-field doses from pediatric craniospinal irradiations using 3D-CRT, IMRT, helical tomotherapy and electron-based therapy.

    PubMed

    De Saint-Hubert, Marijke; Verellen, Dirk; Poels, Kenneth; Crijns, Wouter; Magliona, Federica; Depuydt, Tom; Vanhavere, Filip; Struelens, Lara

    2017-04-11

    Medulloblastoma treatment involves irradiation of the entire central nervous system, i.e craniospinal irradiation (CSI). This is associated with significant exposure of large volumes of healthy tissue with a growing concern regarding treatment associated side effects. The current study compares out-of-field organ doses in children receiving CSI with three-dimensional-conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT), helical tomotherapy (HT) and an electron-based technique, including as well radiation doses resulting from imaging performed during treatment. An extensive phantom study is performed, using an anthropomorphic phantom corresponding to a 5-year old child, in which organ absorbed doses are measured using thermoluminescent detectors (TLDs). Additionally the study evaluates and explores tools for calculating out-of-field patient doses using the treatment planning system (TPS) and analytical models. In our study, 3D-CRT resulted in very high doses to a limited number of organs while it was able to spare organs such as the lungs and breast when compared to IMRT and HT. Both IMRT and HT spread the dose over more organs and were able to spare heart, thyroid, bladder, uterus and testes when compared to 3D-CRT. The electron-based technique considerably decreased the out-of-field doses in deep seated organs but cannot avoid nearby out-of-field organs such as lungs, ribs, adrenals, kidneys and uterus. Daily imaging dose is small compared to the treatment dose burden. TPS error for out-of-field doses was most pronounced for organs further away from the target nevertheless no systematic underestimation was observed for any of the studied TPS systems. Finally analytical modeling was most optimal for 3D-CRT although the number of organs that can be modeled was limited. To conclude none of the techniques studied was able to spare doses in all organs. Nevertheless the electron-based technique showed most promising for out-of-field organ dose

  16. X-ray diffraction and scanning electron microscopy of galvannealed coatings on steel.

    PubMed

    Schmid, P; Uran, K; Macherey, F; Ebert, M; Ullrich, H-J; Sommer, D; Friedel, F

    2009-04-01

    The formation of Fe-Zn intermetallic compounds, as relevant in the commercial product galvannealed steel sheet, was investigated by scanning electron microscopy and different methods of X-ray diffraction. A scanning electron microscope with high resolution was applied to investigate the layers of the galvannealed coating and its topography. Grazing incidence X-ray diffraction (GID) was preferred over conventional Bragg-Brentano geometry for analysing thin crystalline layers because of its lower incidence angle alpha and its lower depth of information. Furthermore, in situ experiments at an environmental scanning electron microscope (ESEM) with an internal heating plate and at an X-ray diffractometer equipped with a high-temperature chamber were carried out. Thus, it was possible to investigate the phase evolution during heat treatment by X-ray diffraction and to display the growth of the zeta crystals in the ESEM.

  17. Numerical simulations - Some results for the 2- and 3-D Hubbard models and a 2-D electron phonon model

    NASA Technical Reports Server (NTRS)

    Scalapino, D. J.; Sugar, R. L.; White, S. R.; Bickers, N. E.; Scalettar, R. T.

    1989-01-01

    Numerical simulations on the half-filled three-dimensional Hubbard model clearly show the onset of Neel order. Simulations of the two-dimensional electron-phonon Holstein model show the competition between the formation of a Peierls-CDW state and a superconducting state. However, the behavior of the partly filled two-dimensional Hubbard model is more difficult to determine. At half-filling, the antiferromagnetic correlations grow as T is reduced. Doping away from half-filling suppresses these correlations, and it is found that there is a weak attractive pairing interaction in the d-wave channel. However, the strength of the pair field susceptibility is weak at the temperatures and lattice sizes that have been simulated, and the nature of the low-temperature state of the nearly half-filled Hubbard model remains open.

  18. 3D ELECTRON DENSITY DISTRIBUTIONS IN THE SOLAR CORONA DURING SOLAR MINIMA: ASSESSMENT FOR MORE REALISTIC SOLAR WIND MODELING

    SciTech Connect

    Patoul, Judith de; Foullon, Claire; Riley, Pete E-mail: c.foullon@exeter.ac.uk

    2015-11-20

    Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996–1997 and 2008–2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models are more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar regions, and we find that the density in tomographic and thermodynamic solutions varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the predicted large-scale heliospheric current sheet or its helmet streamer but can follow the locations of pseudo-streamers. We deduce that tomography offers reliable density distributions in the corona, reproducing the slow time evolution of coronal structures, without prior knowledge of the coronal magnetic field over a full rotation. Finally, we suggest that the highest-density structures show a differential rotation well above the surface depending on how they are magnetically connected to the surface. Such valuable information on the rotation of large-scale structures could help to connect the sources of the solar wind to their in situ counterparts in future missions such as Solar Orbiter and Solar Probe Plus.

  19. From Dynamic Live Cell Imaging to 3D Ultrastructure: Novel Integrated Methods for High Pressure Freezing and Correlative Light-Electron Microscopy

    PubMed Central

    Spiegelhalter, Coralie; Tosch, Valérie; Hentsch, Didier; Koch, Marc; Kessler, Pascal; Schwab, Yannick; Laporte, Jocelyn

    2010-01-01

    Background In cell biology, the study of proteins and organelles requires the combination of different imaging approaches, from live recordings with light microscopy (LM) to electron microscopy (EM). Methodology To correlate dynamic events in adherent cells with both ultrastructural and 3D information, we developed a method for cultured cells that combines confocal time-lapse images of GFP-tagged proteins with electron microscopy. With laser micro-patterned culture substrate, we created coordinates that were conserved at every step of the sample preparation and visualization processes. Specifically designed for cryo-fixation, this method allowed a fast freezing of dynamic events within seconds and their ultrastructural characterization. We provide examples of the dynamic oligomerization of GFP-tagged myotubularin (MTM1) phosphoinositides phosphatase induced by osmotic stress, and of the ultrastructure of membrane tubules dependent on amphiphysin 2 (BIN1) expression. Conclusion Accessible and versatile, we show that this approach is efficient to routinely correlate functional and dynamic LM with high resolution morphology by EM, with immuno-EM labeling, with 3D reconstruction using serial immuno-EM or tomography, and with scanning-EM. PMID:20140253

  20. Golgi apparatus dis- and reorganizations studied with the aid of 2-deoxy-D-glucose and visualized by 3D-electron tomography.

    PubMed

    Ranftler, Carmen; Meisslitzer-Ruppitsch, Claudia; Neumüller, Josef; Ellinger, Adolf; Pavelka, Margit

    2017-04-01

    We studied Golgi apparatus disorganizations and reorganizations in human HepG2 hepatoblastoma cells by using the nonmetabolizable glucose analogue 2-deoxy-D-glucose (2DG) and analyzing the changes in Golgi stack architectures by 3D-electron tomography. Golgi stacks remodel in response to 2DG-treatment and are replaced by tubulo-glomerular Golgi bodies, from which mini-Golgi stacks emerge again after removal of 2DG. The Golgi stack changes correlate with the measured ATP-values. Our findings indicate that the classic Golgi stack architecture is impeded, while cells are under the influence of 2DG at constantly low ATP-levels, but the Golgi apparatus is maintained in forms of the Golgi bodies and Golgi stacks can be rebuilt as soon as 2DG is removed. The 3D-electron microscopic results highlight connecting regions that interlink membrane compartments in all phases of Golgi stack reorganizations and show that the compact Golgi bodies mainly consist of continuous intertwined tubules. Connections and continuities point to possible new transport pathways that could substitute for other modes of traffic. The changing architectures visualized in this work reflect Golgi stack dynamics that may be essential for basic cell physiologic and pathologic processes and help to learn, how cells respond to conditions of stress.

  1. Transmission Kikuchi diffraction and transmission electron forescatter imaging of electropolished and FIB manufactured TEM specimens

    SciTech Connect

    Zieliński, W. Płociński, T.; Kurzydłowski, K.J.

    2015-06-15

    We present a study of the efficiency of the utility of scanning electron microscope (SEM)-based transmission methods for characterizing grain structure in thinned bulk metals. Foils of type 316 stainless steel were prepared by two methods commonly used for transmission electron microscopy — double-jet electropolishing and focused ion beam milling. A customized holder allowed positioning of the foils in a configuration appropriate for both transmission electron forward scatter diffraction, and for transmission imaging by the use of a forescatter detector with two diodes. We found that both crystallographic orientation maps and dark-field transmitted images could be obtained for specimens prepared by either method. However, for both methods, preparation-induced artifacts may affect the quality or accuracy of transmission SEM data, especially those acquired by the use of transmission Kikuchi diffraction. Generally, the quality of orientation data was better for specimens prepared by electropolishing, due to the absence of ion-induced damage. - Highlights: • The transmission imaging and diffraction techniques are emerging in scanning electron microscopy (SEM) as promising new field of materials characterization. • The manuscript titled: “Transmission Kikuchi Diffraction and Transmission Electron Forescatter Imaging of Electropolished and FIB Manufactured TEM Specimens” documents how different specimen thinning procedures can effect efficiency of transmission Kikuchi diffraction and transmission electron forescatter imaging. • The abilities to make precision crystallographic orientation maps and dark-field images in transmission was studied on electropolished versus focus ion beam manufactured TEM specimens. • Depending on the need, electropolished and focused ion beam technique may produce suitable specimens for transmission imaging and diffraction in SEM.

  2. Imaging single electrons to enable the generation of ultrashort beams for single-shot femtosecond relativistic electron diffraction

    SciTech Connect

    Li, R. K.; Musumeci, P.; Bender, H. A.; Wilcox, N. S.; Wu, M.

    2011-10-01

    The generation and control of relativistic electron beams well suited for ultrafast electron diffraction application has rapidly advanced, greatly benefiting from the overlap in techniques and expertise with the accelerator community. However, imaging the diffracted MeV electrons with high detection efficiency has remained an under-explored area. In this paper, we report on a quantitative study of the imaging of MeV electrons using a detection system consisting of a phosphor screen, a lens-coupling optics, and a charge-coupled device camera. It is shown that every MeV electron in the beam yields a signal well above the camera noise. With this detection efficiency, only {approx}10{sup 5} electrons per pulse are needed to obtain a high quality single-shot diffraction pattern from a crystalline sample. We measured that such a low charge beam can be as short as 30 fs rms. Further, we discuss the possibility of compressing these electron beams to sub-5 fs rms bunch length by velocity bunching using a short high gradient rf accelerating structure scheduled to be installed next year at the UCLA Pegasus Laboratory. This opens the possibility of single-shot determinations of structural changes in many ultrafast physical processes like nonequilibrium phonon dynamics or relaxation pathways in systems with strong electron-phonon coupling.

  3. Imaging single electrons to enable the generation of ultrashort beams for single-shot femtosecond relativistic electron diffraction

    NASA Astrophysics Data System (ADS)

    Li, R. K.; Musumeci, P.; Bender, H. A.; Wilcox, N. S.; Wu, M.

    2011-10-01

    The generation and control of relativistic electron beams well suited for ultrafast electron diffraction application has rapidly advanced, greatly benefiting from the overlap in techniques and expertise with the accelerator community. However, imaging the diffracted MeV electrons with high detection efficiency has remained an under-explored area. In this paper, we report on a quantitative study of the imaging of MeV electrons using a detection system consisting of a phosphor screen, a lens-coupling optics, and a charge-coupled device camera. It is shown that every MeV electron in the beam yields a signal well above the camera noise. With this detection efficiency, only ˜105 electrons per pulse are needed to obtain a high quality single-shot diffraction pattern from a crystalline sample. We measured that such a low charge beam can be as short as 30 fs rms. Further, we discuss the possibility of compressing these electron beams to sub-5 fs rms bunch length by velocity bunching using a short high gradient rf accelerating structure scheduled to be installed next year at the UCLA Pegasus Laboratory. This opens the possibility of single-shot determinations of structural changes in many ultrafast physical processes like nonequilibrium phonon dynamics or relaxation pathways in systems with strong electron-phonon coupling.

  4. Low-energy Auger electron diffraction: influence of multiple scattering and angular momentum

    NASA Astrophysics Data System (ADS)

    Chassé, A.; Niebergall, L.; Kucherenko, Yu.

    2002-04-01

    The angular dependence of Auger electrons excited from single-crystal surfaces is treated theoretically within a multiple-scattering cluster model taking into account the full Auger transition matrix elements. In particular the model has been used to discuss the influence of multiple scattering and angular momentum of the Auger electron wave on Auger electron diffraction (AED) patterns in the region of low kinetic energies. Theoretical results of AED patterns are shown and discussed in detail for Cu(0 0 1) and Ni(0 0 1) surfaces, respectively. Even though Cu and Ni are very similar in their electronic and scattering properties recently strong differences have been found in AED patterns measured in the low-energy region. It is shown that the differences may be caused to superposition of different electron diffraction effects in an energy-integrated experiment. A good agreement between available experimental and theoretical results has been achieved.

  5. Determination of the chiral indices (n,m) of carbon nanotubes by electron diffraction.

    PubMed

    Qin, Lu-Chang

    2007-01-07

    The atomic structure of a carbon nanotube can be defined by the chiral indices, (n,m), that specify its perimeter vector (chiral vector), with which the diameter and helicity are also determined. The fine electron beam available in a modern Transmission Electron Microscope (TEM) offers a unique and powerful probe to reveal the atomic structure of individual nanotubes. This article covers two aspects related to the use of the electron probe in the TEM for the study of carbon nanotubes: (i) to express the electron diffraction intensity distribution in the electron diffraction patterns of carbon nanotubes and (ii) to obtain the chiral indices (n,m) of carbon nanotubes from their electron diffraction patterns. For a nanotube of given chiral indices (n,m), the electron scattering amplitude from the carbon nanotube can be expressed analytically in closed form using the helical diffraction theory, from which its electron diffraction pattern can be calculated and understood. The reverse problem, i.e., assignment of the chiral indices (n,m) of a carbon nanotube from its electron diffraction pattern, is approached from the relationship between the electron diffraction intensity distribution and the chiral indices (n,m). The first method is to obtain indiscriminately the chiral indices (n,m) by reading directly the intensity distribution on the three principal layer lines, l(1), l(2), and l(3), which have intensities proportional to the square of the Bessel functions of orders m, n, and n + m: I(l1) proportional, variant |J(m) (pidR)|(2), I(l2) proportional, variant |J(n) (pidR)|(2), and I(l3) proportional, variant |J(n+m) (pidR)|(2). The second method is to obtain and use the ratio of the indices n/m = (2D(1)-D(2))/(2D(2)-D(1)) in which D(1) and D(2) are the spacings of principal layer lines l(1) and l(2), respectively. Examples of using these methods are also illustrated in the determination of chiral indices of isolated individual single-walled carbon nanotubes, a bundle

  6. Patterns of organelle ontogeny through a cell cycle revealed by whole-cell reconstructions using 3D electron microscopy.

    PubMed

    Hughes, Louise; Borrett, Samantha; Towers, Katie; Starborg, Tobias; Vaughan, Sue

    2017-02-01

    The major mammalian bloodstream form of the African sleeping sickness parasite Trypanosoma brucei multiplies rapidly, and it is important to understand how these cells divide. Organelle inheritance involves complex spatiotemporal re-arrangements to ensure correct distribution to daughter cells. Here, serial block face scanning electron microscopy (SBF-SEM) was used to reconstruct whole individual cells at different stages of the cell cycle to give an unprecedented temporal, spatial and quantitative view of organelle division, inheritance and abscission in a eukaryotic cell. Extensive mitochondrial branching occurred only along the ventral surface of the parasite, but the mitochondria returned to a tubular form during cytokinesis. Fission of the mitochondrion occurred within the cytoplasmic bridge during the final stage of cell division, correlating with cell abscission. The nuclei were located underneath each flagellum at mitosis and the mitotic spindle was located along the ventral surface, further demonstrating the asymmetric arrangement of cell cleavage in trypanosomes. Finally, measurements demonstrated that multiple Golgi bodies were accurately positioned along the flagellum attachment zone, suggesting a mechanism for determining the location of Golgi bodies along each flagellum during the cell cycle.

  7. Space Electron Density Gradient Studies using a 3D Embedded Reconfigurable Sounder and ESA/NASA CLUSTER Mission

    NASA Astrophysics Data System (ADS)

    Dekoulis, George

    2016-07-01

    This paper provides a direct comparison between data captured by a new embedded reconfigurable digital sounder, different ground-based ionospheric sounders spread around Europe and the ESA/NASA CLUSTER mission. The CLUSTER mission consists of four identical space probes flying in a formation that allows measurements of the electron density gradient in the local magnetic field. Both the ground-based and the spacecraft instrumentations assist in studying the motion, geometry and boundaries of the plasmasphere. The comparison results are in accordance to each other. Some slight deviations among the captured data were expected from the beginning of this investigation. These small discrepancies are reasonable and seriatim analyzed. The results of this research are significant, since the level of the plasma's ionization, which is related to the solar activity, dominates the propagation of electromagnetic waves through it. Similarly, unusually high solar activity presents serious hazards to orbiting satellites, spaceborne instrumentation, satellite communications and infrastructure located on the Earth's surface. Long-term collaborative study of the data is required to continue, in order to identify and determine the enhanced risk in advance. This would allow scientists to propose an immediate cure.

  8. Electronic structures and nonlinear optical properties of highly deformed halofullerenes C(3v) C60F18 and D(3d) C60Cl30.

    PubMed

    Tang, Shu-Wei; Feng, Jing-Dong; Qiu, Yong-Qing; Sun, Hao; Wang, Feng-Di; Chang, Ying-Fei; Wang, Rong-Shun

    2010-11-15

    Electronic structures and nonlinear optical properties of two highly deformed halofullerenes C(3v) C(60)F(18) and D(3d) C(60)Cl(30) have been systematically studied by means of density functional theory. The large energy gaps (3.62 and 2.61 eV) between the highest occupied and lowest unoccupied molecular orbitals (HOMOs and LUMOs) and the strong aromatic character (with nucleus-independent chemical shifts varying from -15.08 to -23.71 ppm) of C(60)F(18) and C(60)Cl(30) indicate their high stabilities. Further investigations of electronic property show that C(60)F(18) and C(60)Cl(30) could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states and frontier molecular orbitals are also calculated, which present that HOMOs and LUMOs are mainly distributed in the tortoise shell subunit of C(60)F(18) and the aromatic [18] trannulene ring of C(60)Cl(30), and the influence from halogen atoms is secondary. In addition, the static linear polarizability and second-order hyperpolarizability of C(60)F(18) and C(60)Cl(30) are calculated using finite-field approach. The values of and for C(60)F(18) and C(60)Cl(30) molecules are significantly larger than those of C(60) because of their lower symmetric structures and high delocalization of pi electrons.

  9. RADICAL SITES IN M. TUBERCULOSIS KATG IDENTIFIED USING EPR SPECTROSCOPY, THE 3-D CRYSTAL STRUCTURE AND ELECTRON-TRANSFER COUPLINGS†

    PubMed Central

    Ranguelova, Kalina; Girotto, Stefania; Gerfen, Gary J.; Yu, Shengwei; Suarez, Javier; Metlitsky, Leonid; Magliozzo, Richard S.

    2007-01-01

    Catalase-peroxidase (KatG) from Mycobacterium tuberculosis, a Class I peroxidase, exhibits high catalase activity and peroxidase activity with various substrates, and is responsible for activation of the commonly used antitubercular drug, isoniazid (INH). KatG readily forms amino acid based radicals during turnover with alkyl peroxides and this work focuses on extending the identification and characterization of radicals forming on the millisecond to seconds time scale. Rapid freeze- quench electron paramagnetic resonance spectroscopy (RFQ-EPR) reveals a change in the structure of the initially formed radical in the presence of INH. Heme-pocket binding of the drug, and knowledge that KatG[Y229F] lacks this signal provides evidence for radical formation on residue Y229. High-field RFQ-EPR spectroscopy confirmed a tryptophanyl radical signal and new analyses of X-band RFQ-EPR spectra also established its presence. High-field EPR spectroscopy also confirmed that the majority radical species is a tyrosyl radical. Site-directed mutagenesis, along with simulations of EPR spectra based on X-ray structural data for particular tyrosine and tryptophan residues enabled assignments based on predicted hyperfine coupling parameters. KatG mutants W107F, Y229F and the double mutant W107F/Y229F showed alteration in type and yield of radical species. Results are consistent with formation of a tyrosyl radical reasonably assigned to residue Y229 within the first few milliseconds of turnover. This is followed by a mixture of tyrosyl and tryptophanyl radical species, and finally to only a tyrosyl radical on residue Y353, which lies more distant from the heme. Radical processing of enzyme lacking the Trp107-Tyr229-Met255 adduct, found as a unique structural feature of catalase-peroxidases, is suggested to be a reasonable assignment of the phenomena. PMID:17204474

  10. Theoretical study of precision and accuracy of strain analysis by nano-beam electron diffraction.

    PubMed

    Mahr, Christoph; Müller-Caspary, Knut; Grieb, Tim; Schowalter, Marco; Mehrtens, Thorsten; Krause, Florian F; Zillmann, Dennis; Rosenauer, Andreas

    2015-11-01

    Measurement of lattice strain is important to characterize semiconductor nanostructures. As strain has large influence on the electronic band structure, methods for the measurement of strain with high precision, accuracy and spatial resolution in a large field of view are mandatory. In this paper we present a theoretical study of precision and accuracy of measurement of strain by convergent nano-beam electron diffraction. It is found that the accuracy of the evaluation suffers from halos in the diffraction pattern caused by a variation of strain within the area covered by the focussed electron beam. This effect, which is expected to be strong at sharp interfaces between materials with different lattice plane distances, will be discussed for convergent-beam electron diffraction patterns using a conventional probe and for patterns formed by a precessing electron beam. Furthermore, we discuss approaches to optimize the accuracy of strain measured at interfaces. The study is based on the evaluation of diffraction patterns simulated for different realistic structures that have been investigated experimentally in former publications. These simulations account for thermal diffuse scattering using the frozen-lattice approach and the modulation-transfer function of the image-recording system. The influence of Poisson noise is also investigated.

  11. Characterization of domain boundaries in Ni{sub 4}Mo by convergent beam electron diffraction

    SciTech Connect

    Cao, S.; Brooks, C.R.; Allard, L.F.

    1996-02-01

    The alloy Ni-20 at.% Mo (Ni{sub 4}Mo) is disordered ({alpha}) above 868 C and ordered {beta} below this temperature. Upon the formation of {beta} from the {alpha}, a variety of interfaces between the ordered domains is formed. Characterizing the domain interfaces by using conventional selected-area diffraction can be difficult since, in some orientations, superlattice diffraction spots are identical with those of the {alpha}-phase. However, convergent beam electron diffraction can be used to examine the higher-order Laue zone patterns, in which superlattice spots can be revealed. Also this technique produces the diffraction pattern from a very small analysis area. The authors have used this method to identify some of the characteristics of domain boundaries in the ordered Ni{sub 4}Mo alloy.

  12. PCED2.0--a computer program for the simulation of polycrystalline electron diffraction pattern.

    PubMed

    Li, X Z

    2010-03-01

    A computer program for the simulation of polycrystalline electron diffraction patterns is described. PCED2.0, an upgraded version of the previous JECP/PCED, can be used as a teaching aid and research tool for phase identification, microstructure texture analysis, and phase fraction determination. In addition to kinematical theory for diffraction intensity calculation of polycrystalline samples, Blackman two-beam dynamical correction is included. March model is used for out-of-plane and in-plane texture simulation. A pseudo-Voigt function is used for the peak profile fitting of diffraction rings. User-friendly interface is improved in the handling of experimental diffraction data and the flexibility of indexing. Application of the program for the analysis of FePt thin films is given as an example.

  13. Application of δ recycling to electron automated diffraction tomography data from inorganic crystalline nanovolumes.

    PubMed

    Rius, Jordi; Mugnaioli, Enrico; Vallcorba, Oriol; Kolb, Ute

    2013-07-01

    δ Recycling is a simple procedure for directly extracting phase information from Patterson-type functions [Rius (2012). Acta Cryst. A68, 399-400]. This new phasing method has a clear theoretical basis and was developed with ideal single-crystal X-ray diffraction data. On the other hand, introduction of the automated diffraction tomography (ADT) technique has represented a significant advance in electron diffraction data collection [Kolb et al. (2007). Ultramicroscopy, 107, 507-513]. When combined with precession electron diffraction, it delivers quasi-kinematical intensity data even for complex inorganic compounds, so that single-crystal diffraction data of nanometric volumes are now available for structure determination by direct methods. To check the tolerance of δ recycling to missing data-collection corrections and to deviations from kinematical behaviour of ADT intensities, δ recycling has been applied to differently shaped nanocrystals of various inorganic materials. The results confirm that it can phase ADT data very efficiently. In some cases even more complete structure models than those derived from conventional direct methods and least-squares refinement have been found. During this study it has been demonstrated that the Wilson-plot scaling procedure is largely insensitive to sample thickness variations and missing absorption corrections affecting electron ADT intensities.

  14. Europeana and 3D

    NASA Astrophysics Data System (ADS)

    Pletinckx, D.

    2011-09-01

    The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.

  15. Low-energy electron diffraction and induced damage in hydrated DNA

    SciTech Connect

    Orlando, Thomas M.; Oh, Doogie; Chen Yanfeng; Aleksandrov, Alexandr B.

    2008-05-21

    Elastic scattering of 5-30 eV electrons within the B-DNA 5{sup '}-CCGGCGCCGG-3{sup '} and A-DNA 5{sup '}-CGCGAATTCGCG-3{sup '} DNA sequences is calculated using the separable representation of a free-space electron propagator and a curved wave multiple scattering formalism. The disorder brought about by the surrounding water and helical base stacking leads to a featureless amplitude buildup of elastically scattered electrons on the sugar and phosphate groups for all energies between 5 and 30 eV. However, some constructive interference features arising from diffraction are revealed when examining the structural waters within the major groove. These appear at 5-10, 12-18, and 22-28 eV for the B-DNA target and at 7-11, 12-18, and 18-25 eV for the A-DNA target. Although the diffraction depends on the base-pair sequence, the energy dependent elastic scattering features are primarily associated with the structural water molecules localized within 8-10 A spheres surrounding the bases and/or the sugar-phosphate backbone. The electron density buildup occurs in energy regimes associated with dissociative electron attachment resonances, direct electronic excitation, and dissociative ionization. Since diffraction intensity can be localized on structural water, compound H{sub 2}O:DNA states may contribute to energy dependent low-energy electron induced single and double strand breaks.

  16. Structural states of myelin observed by x-ray diffraction and freeze- fracture electron microscopy

    PubMed Central

    1979-01-01

    Coordinated freeze-fracture electron microscopy and x-ray diffraction were used to visualize the morphological relation between compacted and native period membrane arrays in myelinated nerves treated with dimethylsulfoxide (DMSO). Comparison of x-ray diffraction at room temperature and at low temperature was used as a critical measure of the extent of structural preservation. Our x-ray diffraction patterns show that in the presence of cryoprotective agents, it is possible to preserve with only small changes the myelin structure which exists at room temperature. These changes include a slight increase in packing disorder of the membrane, a small, negative thermal expansion of the membrane unit, and some reorganization in the cytoplasmic half of the bilayer. The freeze-fracture electron microscopy clearly demonstrates continuity of compact and native period phases in DMSO-treated myelin. Finally, the use of freezing to trap the transient, intermediate structure during a structural transition in glycerol is demonstrated. PMID:479295

  17. Ultrafast Electron Diffraction Tomography for Structure Determination of the New Zeolite ITQ-58

    PubMed Central

    2016-01-01

    In this work a new ultrafast data collection strategy for electron diffraction tomography is presented that allows reducing data acquisition time by one order of magnitude. This methodology minimizes the radiation damage of beam-sensitive materials, such as microporous materials. This method, combined with the precession of the electron beam, provides high quality data enabling the determination of very complex structures. Most importantly, the implementation of this new electron diffraction methodology is easily affordable in any modern electron microscope. As a proof of concept, we have solved a new highly complex zeolitic structure named ITQ-58, with a very low symmetry (triclinic) and a large unit cell volume (1874.6 Å3), containing 16 silicon and 32 oxygen atoms in its asymmetric unit, which would be very difficult to solve with the state of the art techniques. PMID:27478889

  18. Improvement of the precision of lattice parameter determination by nano-beam electron diffraction.

    PubMed

    Saitoh, Koh; Nakahara, Hirotaka; Tanaka, Nobuo

    2013-01-01

    A highly precise determination of lattice parameters using higher-order Laue zone (HOLZ) reflections observed in nano-beam electron diffraction is presented. The introduction of more than 40 HOLZ reflections, whose positions are corrected by considering the aberration of the electron optics and are determined with an accuracy of 0.04 nm⁻¹, allows us to achieve a remarkable high precision of a 0.02% error, which is four times higher than the precision without HOLZ reflections.

  19. Pontriagin's maximum principle in problems of the optimization of diffraction electronic instruments

    NASA Astrophysics Data System (ADS)

    Tarasov, M. M.; Tretiakov, O. A.; Shestopalov, V. P.; Shmatko, A. A.

    The possibilities afforded by the use of Pontriagin's maximum principle in electronics are demonstrated by applying it to an optimization problem of practical interest. The problem consists of optimizing the parameters of a maximum-efficiency diffraction oscillator for a given power output over a specified frequency range for a selected electron gun. As an example, the optimization problem is solved numerically for an oscillator with a Gaussian distribution of the high-frequency field envelope in an open resonator.

  20. Electron backscatter diffraction characterization of plasma immersion ion implantation effects in stainless steel

    NASA Astrophysics Data System (ADS)

    Davis, Joel; Short, Ken; Wuhrer, Richard; Phillips, Matthew R.; Lumpkin, Gregory R.; Whittle, Karl R.

    2013-01-01

    In these experiments plasma immersion ion implantation is utilised to simulate some of the radiation effects in a nuclear reactor environment. Scanning electron microscopy using the angular selective backscatter detector has revealed observable changes in crystallographic contrast after irradiation with helium ions. Further studies using electron backscatter diffraction in both plan and cross section view allow us to visualize the extent and depth of damage and observe differences in the behavior of different crystalline phases present in several grades of stainless steel.

  1. Characterization of calcium crystals in Abelia using x-ray diffraction and electron microscopes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Localization, chemical composition, and morphology of calcium crystals in leaves and stems of Abelia mosanensis and A. ×grandiflora were analyzed with a variable pressure scanning electron microscope (VP-SEM) equipped with an X-ray diffraction system, low temperature SEM (LT-SEM) and a transmission ...

  2. Photoelectron dynamics in x-ray free-electron-laser diffractive imaging of biological samples.

    PubMed

    Hau-Riege, Stefan P

    2012-06-08

    X-ray free electron lasers hold the promise of enabling atomic-resolution diffractive imaging of single biological molecules. We develop a hybrid continuum-particle model to describe the x-ray induced damage and find that the photoelectron dynamics and electrostatic confinement strongly affect the time scale of the damage processes. These phenomena are not fully captured in hydrodynamic modeling approaches.

  3. Electro-optic sampling for time resolving relativistic ultrafast electron diffraction

    SciTech Connect

    Scoby, C. M.; Musumeci, P.; Moody, J.; Gutierrez, M.; Tran, T.

    2009-01-22

    The Pegasus laboratory at UCLA features a state-of-the-art electron photoinjector capable of producing ultrashort (<100 fs) high-brightness electron bunches at energies of 3.75 MeV. These beams recently have been used to produce static diffraction patterns from scattering off thin metal foils, and it is foreseen to take advantage of the ultrashort nature of these bunches in future pump-probe time-resolved diffraction studies. In this paper, single shot 2-d electro-optic sampling is presented as a potential technique for time of arrival stamping of electron bunches used for diffraction. Effects of relatively low bunch charge (a few 10's of pC) and modestly relativistic beams are discussed and background compensation techniques to obtain high signal-to-noise ratio are explored. From these preliminary tests, electro-optic sampling is suitable to be a reliable nondestructive time stamping method for relativistic ultrafast electron diffraction at the Pegasus lab.

  4. Optical diffraction studies of crystalline structures in electron micrographs. I. Theoretical considerations.

    PubMed

    Berger, J E

    1969-12-01

    Determination of the unit cell of crystalline particles by optical diffraction analysis of electron micrographs may establish the identity and help in approximating the molecular weight of the substances contained in the crystal. This technique may be particularly helpful when isolation and purification of the crystalline material cannot be accomplished.

  5. Structural characterization of titania by X-ray diffraction, photoacoustic, Raman spectroscopy and electron paramagnetic resonance spectroscopy.

    PubMed

    Kadam, R M; Rajeswari, B; Sengupta, Arijit; Achary, S N; Kshirsagar, R J; Natarajan, V

    2015-02-25

    A titania mineral (obtained from East coast, Orissa, India) was investigated by X-ray diffraction (XRD), photoacoustic spectroscopy (PAS), Raman and Electron Paramagnetic Resonance (EPR) studies. XRD studies indicated the presence of rutile (91%) and anatase (9%) phases in the mineral. Raman investigation supported this information. Both rutile and anatase phases have tetragonal structure (rutile: space group P4(2)/mnm, a=4.5946(1) Å, c=2.9597(1) Å, V=62.48(1) (Å)(3), Z=2; anatase: space group I4(1)/amd, 3.7848(2) Å, 9.5098(11) Å, V=136.22(2) (Å)(3), Z=4). The deconvoluted PAS spectrum showed nine peaks around 335, 370, 415,485, 555, 605, 659, 690,730 and 785 nm and according to the ligand field theory, these peaks were attributed to the presence of V(4+), Cr(3+), Mn(4+) and Fe(3+) species. EPR studies revealed the presence of transition metal ions V(4+)(d(1)), Cr(3+)(d(3)), Mn(4+)(d(3)) and Fe(3+)(d(5)) at Ti(4+) sites. The EPR spectra are characterized by very large crystal filed splitting (D term) and orthorhombic distortion term (E term) for multiple electron system (s>1) suggesting that the transition metal ions substitute the Ti(4+) in the lattice which is situated in distorted octahedral coordination of oxygen. The possible reasons for observation of unusually large D and E term in the EPR spectra of transition metal ions (S=3/2 and 5/2) are discussed.

  6. Momentum-resolved view of mixed 2D and nonbulklike 3D electronic structure of the surface state on SrTiO3 (001)

    NASA Astrophysics Data System (ADS)

    Plumb, N. C.; Salluzzo, M.; Razzoli, E.; Mansson, M.; Krempasky, J.; Matt, C. E.; Schmitt, T.; Shi, M.; Mesot, J.; Patthey, L.; Radovic, M.

    2014-03-01

    The recent discovery of a metallic surface state on SrTiO3 may open a route to simplified low-dimensional oxide-based conductors, as well as give new insights into interfacial phenomena in heterostructures such as LaAlO3/SrTiO3. Our recent angle-resolved photoemission spectroscopy (ARPES) study demonstrates that not only quasi-2D but also non-bulklike 3D Fermi surface components make up the surface state. Like their more 2D counterparts, the size and character of the 3D components are fixed with respect to a broad range of sample preparations. As seen in previous studies, the surface state can be ``prepared'' by photon irradiation under UHV conditions. An extremely high fraction of the surface valence states are affected by this process, especially in relation to the stability of oxygen core level intensity during the same exposure, which points to a key role of electronic/structural changes that spread over the surface as the metal emerges.

  7. PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITHOUT TURB3D)

    NASA Technical Reports Server (NTRS)

    Buning, P.

    1994-01-01

    Apollo's 3-dimensional graphics hardware, but does not take advantage of the shading and hidden line/surface removal capabilities of the Apollo DN10000. Although this implementation does not offer a capability for putting text on plots, it does support the use of a mouse to translate, rotate, or zoom in on views. The version 3.6b+ Apollo implementations of PLOT3D (ARC-12789) and PLOT3D/TURB3D (ARC-12785) were developed for use on Apollo computers running UNIX System V with BSD 4.3 extensions and the graphics library GMR3D Version 2.0. The standard distribution media for each of these programs is a 9-track, 6250 bpi magnetic tape in TAR format. Customers purchasing one implementation version of PLOT3D or PLOT3D/TURB3D will be given a $200 discount on each additional implementation version ordered at the same time. Version 3.6b+ of PLOT3D and PLOT3D/TURB3D are also supported for the following computers and graphics libraries: 1) generic UNIX Supercomputer and IRIS, suitable for CRAY 2/UNICOS, CONVEX, and Alliant with remote IRIS 2xxx/3xxx or IRIS 4D (ARC-12779, ARC-12784); 2) VAX computers running VMS Version 5.0 and DISSPLA Version 11.0 (ARC-12777, ARC-12781); 3) generic UNIX and DISSPLA Version 11.0 (ARC-12788, ARC-12778); and (4) Silicon Graphics IRIS 2xxx/3xxx or IRIS 4D workstations (ARC-12783, ARC-12782). Silicon Graphics Iris, IRIS 4D, and IRIS 2xxx/3xxx are trademarks of Silicon Graphics Incorporated. VAX and VMS are trademarks of Digital Electronics Corporation. DISSPLA is a trademark of Computer Associates. CRAY 2 and UNICOS are trademarks of CRAY Research, Incorporated. CONVEX is a trademark of Convex Computer Corporation. Alliant is a trademark of Alliant. Apollo and GMR3D are trademarks of Hewlett-Packard, Incorporated. UNIX is a registered trademark of AT&T.

  8. PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITH TURB3D)

    NASA Technical Reports Server (NTRS)

    Buning, P.

    1994-01-01

    Apollo's 3-dimensional graphics hardware, but does not take advantage of the shading and hidden line/surface removal capabilities of the Apollo DN10000. Although this implementation does not offer a capability for putting text on plots, it does support the use of a mouse to translate, rotate, or zoom in on views. The version 3.6b+ Apollo implementations of PLOT3D (ARC-12789) and PLOT3D/TURB3D (ARC-12785) were developed for use on Apollo computers running UNIX System V with BSD 4.3 extensions and the graphics library GMR3D Version 2.0. The standard distribution media for each of these programs is a 9-track, 6250 bpi magnetic tape in TAR format. Customers purchasing one implementation version of PLOT3D or PLOT3D/TURB3D will be given a $200 discount on each additional implementation version ordered at the same time. Version 3.6b+ of PLOT3D and PLOT3D/TURB3D are also supported for the following computers and graphics libraries: 1) generic UNIX Supercomputer and IRIS, suitable for CRAY 2/UNICOS, CONVEX, and Alliant with remote IRIS 2xxx/3xxx or IRIS 4D (ARC-12779, ARC-12784); 2) VAX computers running VMS Version 5.0 and DISSPLA Version 11.0 (ARC-12777, ARC-12781); 3) generic UNIX and DISSPLA Version 11.0 (ARC-12788, ARC-12778); and (4) Silicon Graphics IRIS 2xxx/3xxx or IRIS 4D workstations (ARC-12783, ARC-12782). Silicon Graphics Iris, IRIS 4D, and IRIS 2xxx/3xxx are trademarks of Silicon Graphics Incorporated. VAX and VMS are trademarks of Digital Electronics Corporation. DISSPLA is a trademark of Computer Associates. CRAY 2 and UNICOS are trademarks of CRAY Research, Incorporated. CONVEX is a trademark of Convex Computer Corporation. Alliant is a trademark of Alliant. Apollo and GMR3D are trademarks of Hewlett-Packard, Incorporated. UNIX is a registered trademark of AT&T.

  9. 3d-3d correspondence revisited

    DOE PAGES

    Chung, Hee -Joong; Dimofte, Tudor; Gukov, Sergei; ...

    2016-04-21

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d N = 2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. As a result, we also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

  10. Quantitative electron diffraction evidence for one-dimensional ordering in magnetite above the Verwey transition.

    PubMed

    Pacaud, J; Zuo, J M; Hoier, R; Matsumura, S

    2003-10-01

    Energy-filtered electron diffraction and three-dimensional reciprocal lattice mapping was used to study the nature of diffuse scattering in magnetite above the Verwey transition temperature. Characteristic Huang scattering associated with a single molecular polaron is observed at room temperature. As the temperature is lowered, the experiment shows narrowing of diffuse scattering in the (001) directions and additional ringlike diffuse scattering at q approximately 0.8, which suggests the presence of one-dimensional structures above the Verwey transition. Experimental measurements of temperature-dependent correlation lengths and diffuse scattering intensity indicate an increase in the number and length of the one-dimensional structure as the temperature is cooled toward the transition. This study demonstrates the electron sensitivity to atomic displacement and the quality of electron diffraction data for studying phase transition in complex materials.

  11. Foucault imaging and small-angle electron diffraction in controlled external magnetic fields.

    PubMed

    Nakajima, Hiroshi; Kotani, Atsuhiro; Harada, Ken; Ishii, Yui; Mori, Shigeo

    2016-12-01

    We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La0.7Sr0.3MnO3 (LSMO) and Nd0.5Sr0.5MnO3, in order to visualize magnetic domains and their magnetic responses to external magnetic fields. In rhombohedral-structured LSMO, pinning of magnetic domain walls at crystallographic twin boundaries was found to have a strong influence on the generation of new magnetic domains in external applied magnetic fields.

  12. Carrier relaxation and lattice heating dynamics in silicon revealed by femtosecond electron diffraction.

    PubMed

    Harb, Maher; Ernstorfer, Ralph; Dartigalongue, Thibault; Hebeisen, Christoph T; Jordan, Robert E; Miller, R J Dwayne

    2006-12-21

    We report on the use of femtosecond electron diffraction to resolve the dynamics of electron-phonon relaxation in silicon. Nanofabricated free-standing membranes of polycrystalline silicon were excited below the damage threshold with 387 nm light at a fluence of 5.6 mJ/cm2 absorbed (corresponding to a carrier density of 2.2 x 10(21) cm(-3)). The diffraction pattern was captured over a range of delay times with a time resolution of 350 fs. All of the detected Bragg peaks exhibited intensity loss with a time constant of less than 2 ps. Beyond the initial decay, there was no further change in the diffracted intensity up to 700 ps. We find that the loss of intensity in the diffracted orders is accounted for by the Debye-Waller effect on a time scale indicative of a thermally driven process as opposed to an electronically driven one. Furthermore, the relaxation time constant is consistent with the excitation regime where the phonon emission rate is reduced due to carrier screening.

  13. A Low-Dose Electron Diffraction Assay for Protection of Protein Structure against Damage from Drying

    NASA Astrophysics Data System (ADS)

    Massover, William H.

    2004-04-01

    A new assay using low-dose electron diffraction to measure the protection of protein structure against damage from drying is described. When thin single crystals of catalase are dried within water alone, low-dose electron diffraction yields no Bragg spots. Drying within an experimental aqueous solution that permits detection of diffraction spots thereby indicates a positive result, and the extent of these Bragg reflections into the high angle range gives a quantitative measure of the degree of protection. Bragg spots out to 3.7 3.9 [Angstrom capital A, ring] are recorded for drying within 100 mM solutions of the known structure-preserving sugars, sucrose, tannin, and trehalose. The ability of trehalose to maintain native protein structure during drying starts between 10 and 25 mM, and changes only slightly at concentrations above this threshold; with drying in 150-mM trehalose, catalase crystals yield diffraction spots out to 3.7 [Angstrom capital A, ring]. Drying within the organic nonsugar polymer polyvinylpyrrolidone gives Bragg spots to 4.0 [Angstrom capital A, ring]. This new assay should be useful to measure the unexamined structure-preserving capabilities of modified sugars, other nonsugars, and mixtures to identify which protective matrix maintains native protein structure to the greatest extent during drying; electron crystallography using that optimal matrix should yield protein structure at improved levels of high resolution.

  14. Mapping 180° polar domains using electron backscatter diffraction and dynamical scattering simulations

    SciTech Connect

    Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth; De Graef, Marc; Dickey, Elizabeth C.

    2016-11-18

    A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO3 single crystals. Furthermore, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system.

  15. Mapping 180° polar domains using electron backscatter diffraction and dynamical scattering simulations

    DOE PAGES

    Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth; ...

    2016-11-18

    A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO3 single crystals. Furthermore, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system.

  16. Application of electron backscatter diffraction techniques to quenched and partitioned steels.

    PubMed

    Thomas, Grant; Speer, John; Matlock, David; Michael, Joseph

    2011-06-01

    Electron backscatter diffraction (EBSD) techniques were used to characterize "hot-rolled" quenched and partitioned microstructures produced via Gleeble thermal simulations representing a hot-strip cooling practice for steel. In particular, EBSD was utilized to positively identify the morphology and location of retained austenite, to qualitatively distinguish martensite from ferrite, and in an attempt to identify transition carbides. Large pools of retained austenite and some thin films were accurately indexed; however, there was some disparity between austenite volume fractions measured by EBSD and those measured by X-ray diffraction. Due to similarities between the crystal structures of martensite and ferrite (body centered tetragonal versus body centered cubic, respectively), martensite could not be distinguished from ferrite by indexing of diffraction patterns; however, martensite could qualitatively be distinguished from ferrite by regions of low image quality based on the very high dislocation density of martensite.

  17. Three-dimensional nanostructure determination from a large diffraction data set recorded using scanning electron nanodiffraction

    DOE PAGES

    Meng, Yifei; Zuo, Jian-Min

    2016-07-04

    A diffraction-based technique is developed for the determination of three-dimensional nanostructures. The technique employs high-resolution and low-dose scanning electron nanodiffraction (SEND) to acquire three-dimensional diffraction patterns, with the help of a special sample holder for large-angle rotation. Grains are identified in three-dimensional space based on crystal orientation and on reconstructed dark-field images from the recorded diffraction patterns. Application to a nanocrystalline TiN thin film shows that the three-dimensional morphology of columnar TiN grains of tens of nanometres in diameter can be reconstructed using an algebraic iterative algorithm under specified prior conditions, together with their crystallographic orientations. The principles can bemore » extended to multiphase nanocrystalline materials as well. Thus, the tomographic SEND technique provides an effective and adaptive way of determining three-dimensional nanostructures.« less

  18. ELECTRON MICROSCOPE AND X-RAY DIFFRACTION STUDIES ON A HOMOLOGOUS SERIES OF SATURATED PHOSPHATIDYLCHOLINES.

    PubMed

    ELBERS, P F; VERVERGAERT, P H

    1965-05-01

    Three homologous saturated phosphatidylcholines were studied by electron microscopy after tricomplex fixation. The results are compared with those obtained by x-ray diffraction analysis of the same and some other homologous compounds, in the dry crystalline state and after tricomplex fixation. By electron microscopy alternating dark and light bands are observed which are likely to correspond to phosphatide double layers. X-Ray diffraction reveals the presence of lamellar structures of regular spacing. The layer spacings obtained by both methods are in good agreement. From the electron micrographs the width of the polar parts of the double layers can be derived directly. The width of the carboxylglycerylphosphorylcholine moiety of the layers is found by extrapolating the x-ray diffraction data to zero chain length of the fatty acids. When from this width the contribution of the carboxylglyceryl part of the molecules is subtracted, again we find good agreement with the electron microscope measurements. An attempt has been made to account for the different layer spacings measured in terms of orientation of the molecules within the double layers.

  19. Three-dimensional rotation electron diffraction: software RED for automated data collection and data processing.

    PubMed

    Wan, Wei; Sun, Junliang; Su, Jie; Hovmöller, Sven; Zou, Xiaodong

    2013-12-01

    Implementation of a computer program package for automated collection and processing of rotation electron diffraction (RED) data is described. The software package contains two computer programs: RED data collection and RED data processing. The RED data collection program controls the transmission electron microscope and the camera. Electron beam tilts at a fine step (0.05-0.20°) are combined with goniometer tilts at a coarse step (2.0-3.0°) around a common tilt axis, which allows a fine relative tilt to be achieved between the electron beam and the crystal in a large tilt range. An electron diffraction (ED) frame is collected at each combination of beam tilt and goniometer tilt. The RED data processing program processes three-dimensional ED data generated by the RED data collection program or by other approaches. It includes shift correction of the ED frames, peak hunting for diffraction spots in individual ED frames and identification of these diffraction spots as reflections in three dimensions. Unit-cell parameters are determined from the positions of reflections in three-dimensional reciprocal space. All reflections are indexed, and finally a list with hkl indices and intensities is output. The data processing program also includes a visualizer to view and analyse three-dimensional reciprocal lattices reconstructed from the ED frames. Details of the implementation are described. Data collection and data processing with the software RED are demonstrated using a calcined zeolite sample, silicalite-1. The structure of the calcined silicalite-1, with 72 unique atoms, could be solved from the RED data by routine direct methods.

  20. Electron tomography of cryo-immobilized plant tissue: a novel approach to studying 3D macromolecular architecture of mature plant cell walls in situ.

    PubMed

    Sarkar, Purbasha; Bosneaga, Elena; Yap, Edgar G; Das, Jyotirmoy; Tsai, Wen-Ting; Cabal, Angelo; Neuhaus, Erica; Maji, Dolonchampa; Kumar, Shailabh; Joo, Michael; Yakovlev, Sergey; Csencsits, Roseann; Yu, Zeyun; Bajaj, Chandrajit; Downing, Kenneth H; Auer, Manfred

    2014-01-01

    Cost-effective production of lignocellulosic biofuel requires efficient breakdown of cell walls present in plant biomass to retrieve the wall polysaccharides for fermentation. In-depth knowledge of plant cell wall composition is therefore essential for improving the fuel production process. The precise spatial three-dimensional (3D) organization of cellulose, hemicellulose, pectin and lignin within plant cell walls remains unclear to date since the microscopy techniques used so far have been limited to two-dimensional, topographic or low-resolution imaging, or required isolation or chemical extraction of the cell walls. In this paper we demonstrate that by cryo-immobilizing fresh tissue, then either cryo-sectioning or freeze-substituting and resin embedding, followed by cryo- or room temperature (RT) electron tomography, respectively, we can visualize previously unseen details of plant cell wall architecture in 3D, at macromolecular resolution (∼ 2 nm), and in near-native state. Qualitative and quantitative analyses showed that wall organization of cryo-immobilized samples were preserved remarkably better than conventionally prepared samples that suffer substantial extraction. Lignin-less primary cell walls were well preserved in both self-pressurized rapidly frozen (SPRF), cryo-sectioned samples as well as high-pressure frozen, freeze-substituted and resin embedded (HPF-FS-resin) samples. Lignin-rich secondary cell walls appeared featureless in HPF-FS-resin sections presumably due to poor stain penetration, but their macromolecular features could be visualized in unprecedented details in our cryo-sections. While cryo-tomography of vitreous tissue sections is currently proving to be instrumental in developing 3D models of lignin-rich secondary cell walls, here we confirm that the technically easier method of RT-tomography of HPF-FS-resin sections could be used immediately for routine study of low-lignin cell walls. As a proof of principle, we characterized the

  1. Electron Tomography of Cryo-Immobilized Plant Tissue: A Novel Approach to Studying 3D Macromolecular Architecture of Mature Plant Cell Walls In Situ

    PubMed Central

    Sarkar, Purbasha; Bosneaga, Elena; Yap, Edgar G.; Das, Jyotirmoy; Tsai, Wen-Ting; Cabal, Angelo; Neuhaus, Erica; Maji, Dolonchampa; Kumar, Shailabh; Joo, Michael; Yakovlev, Sergey; Csencsits, Roseann; Yu, Zeyun; Bajaj, Chandrajit; Downing, Kenneth H.; Auer, Manfred

    2014-01-01

    Cost-effective production of lignocellulosic biofuel requires efficient breakdown of cell walls present in plant biomass to retrieve the wall polysaccharides for fermentation. In-depth knowledge of plant cell wall composition is therefore essential for improving the fuel production process. The precise spatial three-dimensional (3D) organization of cellulose, hemicellulose, pectin and lignin within plant cell walls remains unclear to date since the microscopy techniques used so far have been limited to two-dimensional, topographic or low-resolution imaging, or required isolation or chemical extraction of the cell walls. In this paper we demonstrate that by cryo-immobilizing fresh tissue, then either cryo-sectioning or freeze-substituting and resin embedding, followed by cryo- or room temperature (RT) electron tomography, respectively, we can visualize previously unseen details of plant cell wall architecture in 3D, at macromolecular resolution (∼2 nm), and in near-native state. Qualitative and quantitative analyses showed that wall organization of cryo-immobilized samples were preserved remarkably better than conventionally prepared samples that suffer substantial extraction. Lignin-less primary cell walls were well preserved in both self-pressurized rapidly frozen (SPRF), cryo-sectioned samples as well as high-pressure frozen, freeze-substituted and resin embedded (HPF-FS-resin) samples. Lignin-rich secondary cell walls appeared featureless in HPF-FS-resin sections presumably due to poor stain penetration, but their macromolecular features could be visualized in unprecedented details in our cryo-sections. While cryo-tomography of vitreous tissue sections is currently proving to be instrumental in developing 3D models of lignin-rich secondary cell walls, here we confirm that the technically easier method of RT-tomography of HPF-FS-resin sections could be used immediately for routine study of low-lignin cell walls. As a proof of principle, we characterized the

  2. 3D and Education

    NASA Astrophysics Data System (ADS)

    Meulien Ohlmann, Odile

    2013-02-01

    Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method of initiation to 3D creation that entails the spatial/temporal experience of the holographic visual. She will present some different tools and techniques used for this learning, their advantages and disadvantages, programs and issues of educational policies, constraints and expectations related to the development of new techniques for 3D imaging. Although the creation of display holograms is very much reduced compared to the creation of the 90ies, the holographic concept is spreading in all scientific, social, and artistic activities of our present time. She will also raise many questions: What means 3D? Is it communication? Is it perception? How the seeing and none seeing is interferes? What else has to be taken in consideration to communicate in 3D? How to handle the non visible relations of moving objects with subjects? Does this transform our model of exchange with others? What kind of interaction this has with our everyday life? Then come more practical questions: How to learn creating 3D visualization, to learn 3D grammar, 3D language, 3D thinking? What for? At what level? In which matter? for whom?

  3. Determining Projections of Grain Boundaries from Diffraction Data in Transmission Electron Microscope.

    PubMed

    Kiss, Ákos K; Lábár, János L

    2016-06-01

    Grain boundaries (GB) are characterized by disorientation of the neighboring grains and the direction of the boundary plane between them. A new approach presented here determines the projection of GB that can be used to determine the latter one. The novelty is that an additional parameter of GB is quantified in addition to the ones provided by the orientation maps, namely the width of the projection of the GB is measured from the same set of diffraction patterns that were recorded for the orientation map, without the need to take any additional images. The diffraction patterns are collected in nanobeam diffraction mode in a transmission electron microscope, pixel-by-pixel, from an area containing two neighboring grains and the boundary between them. In our case, the diffraction patterns were recorded using the beam scanning function of a commercially available system (ASTAR). Our method is based on non-negative matrix factorization applied to the mentioned set of diffraction patterns. The method is encoded in a MATLAB environment, making the results easy to interpret and visualize. The measured GB-projection width is used to determine the orientation of the GB-plane, as given in the study by Kiss et al.

  4. Multiobjective optimizations of a novel cryocooled dc gun based ultrafast electron diffraction beam line

    NASA Astrophysics Data System (ADS)

    Gulliford, Colwyn; Bartnik, Adam; Bazarov, Ivan

    2016-09-01

    We present the results of multiobjective genetic algorithm optimizations of a single-shot ultrafast electron diffraction beam line utilizing a 225 kV dc gun with a novel cryocooled photocathode system and buncher cavity. Optimizations of the transverse projected emittance as a function of bunch charge are presented and discussed in terms of the scaling laws derived in the charge saturation limit. Additionally, optimization of the transverse coherence length as a function of final rms bunch length at the sample location have been performed for three different sample radii: 50, 100, and 200 μ m , for two final bunch charges: 1 05 electrons (16 fC) and 1 06 electrons (160 fC). Example optimal solutions are analyzed, and the effects of disordered induced heating estimated. In particular, a relative coherence length of Lc ,x/σx=0.27 nm /μ m was obtained for a final bunch charge of 1 05 electrons and final bunch length of σt≈100 fs . For a final charge of 1 06 electrons the cryogun produces Lc ,x/σx≈0.1 nm /μ m for σt≈100 - 200 fs and σx≥50 μ m . These results demonstrate the viability of using genetic algorithms in the design and operation of ultrafast electron diffraction beam lines.

  5. Strain Distribution Measurement in Stainless Steels by Convergent-Beam Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Saito, Masakazu; Aoyama, Takashi; Nakata, Kiyotomo; Suzuki, Takaya

    1995-01-01

    A convergent-beam electron diffraction technique was utilized to measure local strain distributions in stainless steels. Electron beams were focused into {210} crystal planes and the higher order Laue zone (HOLZ) lines diffracted from {375} and {119} planes were characterized by measuring the distances between the intersections of these HOLZ lines. Four parameters, including strains in three directions and one magnification factor, were calculated based on the least squares method. Strain distributions near a chromium carbide precipitate were measured in sensitized SUS 304 and it was confirmed that parallel tensile strain and vertical compressive strain to the edge of the precipitate existed and that they decreased with the distance from the edge of precipitate.

  6. Chopped sample heating for quantitative profile analysis of low energy electron diffraction spots at high temperatures

    SciTech Connect

    Kury, P.; Zahl, P.; Horn-von Hoegen, M.; Voges, C.; Frischat, H.; Guenter, H.-L.; Pfnuer, H.; Henzler, M.

    2004-11-01

    Spot profile analysis low energy electron diffraction (SPA-LEED) is one of the most versatile and powerful methods for the determination of the structure and morphology of surfaces even at elevated temperatures. In setups where the sample is heated directly by an electric current, the resolution of the diffraction images at higher temperatures can be heavily degraded due to the inhomogeneous electric and magnetic fields around the sample. Here we present an easily applicable modification of the common data acquisition hardware of the SPA-LEED, which enables the system to work in a pulsed heating mode: Instead of heating the sample with a constant current, a square wave is used and electron counting is only performed when the current through the sample vanishes. Thus, undistorted diffration images can be acquired at high temperatures.

  7. Electron backscattering diffraction analysis of an ancient wootz steel blade from central India

    SciTech Connect

    Barnett, M.R. Sullivan, A.; Balasubramaniam, R.

    2009-04-15

    The electron backscattering diffraction technique was used to analyse the nature of carbides present in an ancient wootz steel blade. Bulky carbides, pro-eutectoid carbide along the prior austenite grain boundaries and fine spheroidized carbides were detected. Electron backscattering diffraction was employed to understand the texture of these carbides. The orientations of the cementite frequently occur in clusters, which points to a common origin of the members of the cluster. For the bands of coarse cementite, the origin is probably large coarse particles formed during the original cooling of the wootz cake. Pearlite formed earlier in the forging process has led to groups of similarly oriented fine cementite particles. The crystallographic texture of the cementite is sharp whereas that of the ferrite is weak. The sharp cementite textures point to the longevity of the coarse cementite throughout the repeated forging steps and to the influence of existing textured cementite on the nucleation of new cementite during cooling.

  8. Intramolecular electron diffraction in vibrationally resolved K-shell photoionization of methane

    NASA Astrophysics Data System (ADS)

    Plésiat, Etienne; Argenti, Luca; Kukk, Edwin; Miron, Catalin; Ueda, Kiyoshi; Decleva, Piero; Martín, Fernando

    2012-02-01

    Current techniques based on x-ray or electron diffraction are successfully employed for structure determination in condensed matter but are sometimes limited when applied to low density media such as the gas phase. Here we show that vibrationally resolved photoelectron spectroscopy based on x rays generated by third generation synchrotron light sources can be used to infer the structure of isolated molecules in a simple and efficient way. In particular, we show that vibrational ratios obtained from inner shell C 1s photoelectron spectroscopy of isolated methane molecules exhibit pronounced oscillations that are the fingerprints of electron diffraction by the surrounding atomic centers, thus providing the necessary information for the determination of the molecular geometry.

  9. Diffractive imaging of a rotational wavepacket in nitrogen molecules with femtosecond megaelectronvolt electron pulses

    SciTech Connect

    Yang, Jie; Guehr, Markus; Vecchione, Theodore; Robinson, Matthew S.; Li, Renkai; Hartmann, Nick; Shen, Xiaozhe; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Gaffney, Kelly; Gorkhover, Tais; Hast, Carsten; Jobe, Keith; Makasyuk, Igor; Reid, Alexander; Robinson, Joseph; Vetter, Sharon; Wang, Fenglin; Weathersby, Stephen; Yoneda, Charles; Centurion, Martin; Wang, Xijie

    2016-04-05

    Imaging changes in molecular geometries on their natural femtosecond timescale with sub-Angström spatial precision is one of the critical challenges in the chemical sciences, as the nuclear geometry changes determine the molecular reactivity. For photoexcited molecules, the nuclear dynamics determine the photoenergy conversion path and efficiency. Here we report a gas-phase electron diffraction experiment using megaelectronvolt (MeV) electrons, where we captured the rotational wavepacket dynamics of nonadiabatically laser-aligned nitrogen molecules. We achieved a combination of 100 fs root-mean-squared temporal resolution and sub-Angstrom (0.76 Å) spatial resolution that makes it possible to resolve the position of the nuclei within the molecule. In addition, the diffraction patterns reveal the angular distribution of the molecules, which changes from prolate (aligned) to oblate (anti-aligned) in 300 fs. Lastly, our results demonstrate a significant and promising step towards making atomically resolved movies of molecular reactions.

  10. Microstructure Characterization of Magnetic-Pulse-Welded AA 6061-T6 by Electron Backscattered Diffraction

    SciTech Connect

    Zhang, Yuan; Babu, Suresh; Zhang, P; Kenik, Edward A; Daehn, Glenn

    2008-01-01

    The grain boundary crystallographic misorientations of magnetic-pulse-welded (MPW) aluminum alloy (AA) 6061-T6 in linear and tubular configurations were examined using the electron backscattered diffraction (EBSD) technique. A refined structure of heavily deformed grains with higher grain boundary angles was observed in linear welds. Significant spalling was observed away from the joints, in the interior of tubular welds. The results show the complex interaction of shock waves with the materials during this impact welding process.

  11. Strain mapping at the nanoscale using precession electron diffraction in transmission electron microscope with off axis camera

    SciTech Connect

    Vigouroux, M. P.; Delaye, V.; Bernier, N.; Lafond, D.; Audoit, G.; Bertin, F.; Cipro, R.; Baron, T.; Martin, M.; Rouvière, J. L.; Chenevier, B.

    2014-11-10

    Precession electron diffraction is an efficient technique to measure strain in nanostructures by precessing the electron beam, while maintaining a few nanometre probe size. Here, we show that an advanced diffraction pattern treatment allows reproducible and precise strain measurements to be obtained using a default 512 × 512 DigiSTAR off-axis camera both in advanced or non-corrected transmission electron microscopes. This treatment consists in both projective geometry correction of diffraction pattern distortions and strain Delaunay triangulation based analysis. Precision in the strain measurement is improved and reached 2.7 × 10{sup −4} with a probe size approaching 4.2 nm in diameter. This method is applied to the study of the strain state in InGaAs quantum-well (QW) devices elaborated on Si substrate. Results show that the GaAs/Si mismatch does not induce in-plane strain fluctuations in the InGaAs QW region.

  12. The 3D-tomography of the nano-clusters formed by Fe-coating and annealing of diamond films for enhancing their surface electron field emitters

    NASA Astrophysics Data System (ADS)

    Chen, Huang-Chin; Lo, Shen-Chuan; Lin, Li-Jiaun; Huang, Pin-Chang; Shih, Wen-Ching; Lin, I.-Nan; Lee, Chi-Young

    2012-09-01

    The Fe-coating and H2-annealed processes markedly increased the conductivity and enhanced the surface electron field emission (s-EFE) properties for the diamond films. The enhancement on the s-EFE properties for the diamond films is presumably owing to the formation of nano-graphite clusters on the surface of the films via the Fe-to-diamond interaction. However, the extent of enhancement varied with the granular structure of the diamond films. For the microcrystalline (MCD) films, the s-EFE process can be turned on at (E0)MCD = 1.9 V/μm, achieving a large s-EFE current density of (Je)MCD = 315 μA/cm2 at an applied field of 8.8 V/μm. These s-EFE properties are markedly better than those for Fe-coated/annealed ultrananocrystalline diamond (UNCD) films with (E0)UNCD = 2.0 V/μm and (Je)UNCD = 120 μA/cm2. The transmission electron microscopy showed that the nano-graphite clusters formed an interconnected network for MCD films that facilitated the electron transport more markedly, as compared with the isolated nano-graphitic clusters formed at the surface of the UNCD films. Therefore, the Fe-coating/annealing processes improved the s-EFE properties for the MCD films more markedly than that for the UNCD films. The understanding on the distribution of the nano-clusters is of critical importance in elucidating the authentic factor that influences the s-EFE properties of the diamond films. Such an understanding is possible only through the 3D-tomographic investigations.

  13. Observation of Femtosecond, Sub-Angstrom Molecular Bond Relaxation Using Laser-Induced Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Blaga, Cosmin I.; Dichiara, Anthony D.; Zhang, Kaikai; Sistrunk, Emily; Agostini, Pierre; Dimauro, Louis F.; Xu, Junliang; Lin, Chii-Dong; Miller, Terry A.

    2011-06-01

    Imaging, or the determination of the atomic positions in molecules, has always occupied an essential role in physical, chemical and biological sciences. For structural determination, the well established methods of X-ray and electron diffraction easily achieve sub-Angstrom spatial resolution. However, these conventional approaches are not suitable for investigating structural transformations, such as the reaction of molecules or the function of biological systems that occur on the timescales faster than a picosecond. Over the past decade, major efforts directed at developing femtosecond pulsed sources, e.g. X-ray free-electron lasers and electron beams, have resulted in pioneering investigations on imaging large biological molecules and condensed phase dynamics. We report on a different approach, laser-induced electron diffraction (LIED), for achieving sub-femtosecond, sub-Angstrom spatio-temporal resolution for investigating gas-phase molecular dynamics. In contrast to the above mentioned techniques, the LIED method generates bursts of coherent electron wave packets directly from the molecule under interrogation. The study is performed by measuring the diffracted photoelectron momentum distribution produced by strong-field ionization of oxygen and nitrogen molecules at several mid-infrared wavelengths (1.7-2.3 μm). The bond lengths retrieved from the LIED analysis show sensitivity to a change of 0.05 Å in 1 fs. This initial report provides the first direct evidence of bond relaxation following an electronic excitation and establishes the foundation of the LIED method as a general approach for ultrafast imaging of molecular dynamics.

  14. SU-E-T-678: Response Calibration Using Electron Depth-Dose Data for MRI-Based 3D Polymer Gel Dosimetry

    SciTech Connect

    Watanabe, Y; Warmington, L; Gopishankar, N

    2015-06-15

    Purpose: To evaluate a calibration method using the depth-dose data of an electron beam for MRI-based polymer gel dosimetry. Methods: MAGAT was manufactured in-house to fill two 400mL-cylindrical phantoms and nine 22mL-glass vials. Phantom-A was irradiated along the cylinder axis with a 9MeV electron beam of 6 cm x 6 cm field size (FS). Phantom-B was irradiated with a 6MV photon beam of 3 cm x 3 cm FS by a 360-degree arc technique. Eight vials were irradiated in a water-bath to various doses with a 20 cm x 20 cm FS 6MV photon beam. All irradiated phantoms and one un-irradiated vial were scanned with a 3T MRI scanner to obtain the spin-spin relaxation rate (R2) distributions. By comparing the measured R2-to-depth data with the known depth-dose data for Phantom-A, R2-to-dose calibration data were obtained (e-beam method). Another calibration data were obtained from the 9 vials data (9-vial method). We tested two regression equations, i.e., third-order polynomial and tangent functions, and two dose normalization methods, i.e., one-point and two-point methods. Then, these two calibration methods were used to obtain the 3D dose distribution of Phantom-B and evaluated by comparing the measured data with the dose distribution from a treatment planning system. The comparison was made with gamma passing rate (2%/2mm criteria). Results: We did not observe a clear advantage of the e-beam method over the 9-vial method for the 3D dose comparison with the test case. Nevertheless, we found that the e-beam method required a smaller dose scaling for the dose comparison. Furthermore, the tangent function showed better data fitting than the polynomial function with smaller uncertainty of the estimated coefficients. Conclusions: Considering the overall superior performance, we recommend the e-beam method with the tangent function as the regression equation and one-point dose normalization for the MRI-based polymer gel dosimetry.

  15. Three-dimensional surface topography of graphene by divergent beam electron diffraction

    PubMed Central

    Latychevskaia, Tatiana; Hsu, Wei-Hao; Chang, Wei-Tse; Lin, Chun-Yueh; Hwang, Ing-Shouh

    2017-01-01

    There are only a handful of scanning techniques that can provide surface topography at nanometre resolution. At the same time, there are no methods that are capable of non-invasive imaging of the three-dimensional surface topography of a thin free-standing crystalline material. Here we propose a new technique—the divergent beam electron diffraction (DBED) and show that it can directly image the inhomogeneity in the atomic positions in a crystal. Such inhomogeneities are directly transformed into the intensity contrast in the first-order diffraction spots of DBED patterns and the intensity contrast linearly depends on the wavelength of the employed probing electrons. Three-dimensional displacement of atoms as small as 1 angstrom can be detected when imaged with low-energy electrons (50–250 eV). The main advantage of DBED is that it allows visualization of the three-dimensional surface topography and strain distribution at the nanometre scale in non-scanning mode, from a single shot diffraction experiment. PMID:28195123

  16. X-ray laser–induced electron dynamics observed by femtosecond diffraction from nanocrystals of Buckminsterfullerene

    PubMed Central

    Abbey, Brian; Dilanian, Ruben A.; Darmanin, Connie; Ryan, Rebecca A.; Putkunz, Corey T.; Martin, Andrew V.; Wood, David; Streltsov, Victor; Jones, Michael W. M.; Gaffney, Naylyn; Hofmann, Felix; Williams, Garth J.; Boutet, Sébastien; Messerschmidt, Marc; Seibert, M. Marvin; Williams, Sophie; Curwood, Evan; Balaur, Eugeniu; Peele, Andrew G.; Nugent, Keith A.; Quiney, Harry M.

    2016-01-01

    X-ray free-electron lasers (XFELs) deliver x-ray pulses with a coherent flux that is approximately eight orders of magnitude greater than that available from a modern third-generation synchrotron source. The power density of an XFEL pulse may be so high that it can modify the electronic properties of a sample on a femtosecond time scale. Exploration of the interaction of intense coherent x-ray pulses and matter is both of intrinsic scientific interest and of critical importance to the interpretation of experiments that probe the structures of materials using high-brightness femtosecond XFEL pulses. We report observations of the diffraction of extremely intense 32-fs nanofocused x-ray pulses by a powder sample of crystalline C60. We find that the diffraction pattern at the highest available incident power significantly differs from the one obtained using either third-generation synchrotron sources or XFEL sources operating at low output power and does not correspond to the diffraction pattern expected from any known phase of crystalline C60. We interpret these data as evidence of a long-range, coherent dynamic electronic distortion that is driven by the interaction of the periodic array of C60 molecular targets with intense x-ray pulses of femtosecond duration. PMID:27626076

  17. Sub-phonon-period compression of electron pulses for atomic diffraction

    PubMed Central

    Gliserin, A.; Walbran, M.; Krausz, F.; Baum, P.

    2015-01-01

    Visualizing the rearrangement of atoms in a wide range of molecular and condensed-matter systems requires resolving picometre displacements on a 10-fs timescale, which is achievable using pump–probe diffraction, given short enough pulses. Here we demonstrate the compression of single-electron pulses with a de Broglie wavelength of 0.08 ångström to a full-width at half-maximum duration of 28 fs or equivalently 12-fs root-mean square, substantially shorter than most phonon periods and molecular normal modes. Atomic resolution diffraction from a complex organic molecule is obtained with good signal-to-noise ratio within a data acquisition period of minutes. The electron-laser timing is found to be stable within 5 fs (s.d.) over several hours, allowing pump–probe diffraction at repetitive excitation. These measurements show the feasibility of laser-pump/electron-probe scans that can resolve the fastest atomic motions relevant in reversible condensed-matter transformations and organic chemistry. PMID:26502750

  18. Three-dimensional surface topography of graphene by divergent beam electron diffraction

    NASA Astrophysics Data System (ADS)

    Latychevskaia, Tatiana; Hsu, Wei-Hao; Chang, Wei-Tse; Lin, Chun-Yueh; Hwang, Ing-Shouh

    2017-02-01

    There are only a handful of scanning techniques that can provide surface topography at nanometre resolution. At the same time, there are no methods that are capable of non-invasive imaging of the three-dimensional surface topography of a thin free-standing crystalline material. Here we propose a new technique--the divergent beam electron diffraction (DBED) and show that it can directly image the inhomogeneity in the atomic positions in a crystal. Such inhomogeneities are directly transformed into the intensity contrast in the first-order diffraction spots of DBED patterns and the intensity contrast linearly depends on the wavelength of the employed probing electrons. Three-dimensional displacement of atoms as small as 1 angstrom can be detected when imaged with low-energy electrons (50-250 eV). The main advantage of DBED is that it allows visualization of the three-dimensional surface topography and strain distribution at the nanometre scale in non-scanning mode, from a single shot diffraction experiment.

  19. Guide for 3D WARP simulations of hollow electron beam lenses. Practical explanation on basis of Tevatron electron lens test stand

    SciTech Connect

    Moens, Vince

    2014-06-08

    The purpose of this guide is to help successive students handle WARP. It outlines the installation of WARP on personal computers as well as super-computers and clusters. It furthermore teaches the reader how to handle the WARP environment and run basic scripts. Lastly it outlines how to execute the current Hollow Electron Beam Lens scripts.

  20. Ultrafast electron diffraction from non-equilibrium phonons in femtosecond laser heated Au films

    SciTech Connect

    Chase, T.; Trigo, M.; Reid, A. H.; Li, R.; Vecchione, T.; Shen, X.; Weathersby, S.; Coffee, R.; Hartmann, N.; Reis, D. A.; Wang, X. J.; Dürr, H. A.

    2016-01-25

    We use ultrafast electron diffraction to detect the temporal evolution of non-equilibrium phonons in femtosecond laser-excited ultrathin single-crystalline gold films. From the time-dependence of the Debye-Waller factor, we extract a 4.7 ps time-constant for the increase in mean-square atomic displacements. The observed increase in the diffuse scattering intensity demonstrates that the energy transfer from laser-heated electrons to phonon modes near the X and K points in the Au fcc Brillouin zone proceeds with timescales of 2.3 and 2.9 ps, respectively, faster than the Debye-Waller average mean-square displacement.

  1. Diffractive optical elements on non-flat substrates using electron beam lithography

    NASA Technical Reports Server (NTRS)

    Maker, Paul D. (Inventor); Muller, Richard E. (Inventor); Wilson, Daniel W. (Inventor)

    2002-01-01

    The present disclosure describes a technique for creating diffraction gratings on curved surfaces with electron beam lithography. The curved surface can act as an optical element to produce flat and aberration-free images in imaging spectrometers. In addition, the fabrication technique can modify the power structure of the grating orders so that there is more energy in the first order than for a typical grating. The inventors noticed that by using electron-beam lithography techniques, a variety of convex gratings that are well-suited to the requirements of imaging spectrometers can be manufactured.

  2. Coulomb interaction-induced jitter amplification in RF-compressed high-brightness electron source ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Qi, Yingpeng; Pei, Minjie; Qi, Dalong; Li, Jing; Yang, Yan; Jia, Tianqing; Zhang, Shian; Sun, Zhenrong

    2017-02-01

    We have theoretically and experimentally demonstrated an RF compression-based jitter-amplification effect in high-brightness electron source ultrafast electron diffraction (UED), which degrades the temporal resolution significantly. A detailed analysis and simulations reveal the crucial role of the longitudinal and transverse Coulomb interaction for this jitter-amplification effect, which accord very well with experimental results. An optimized compact UED structure for full compression has been proposed, which can suppress the jitter by half and improve the temporal resolution to sub-100 fs. This Coulomb interaction-induced jitter amplification exists in nearly the whole ultrafast physics field where laser-electron synchronization is required. Moreover, it cannot be suppressed completely. The quantified explanation for the mechanism and optimization provides important guidance for photocathode accelerators and other compression-based ultrashort electron pulse generation and precise control.

  3. High-Resolution Infrared and Electron-Diffraction Studies of Trimethylenecyclopropane ([3]-Radialene)

    SciTech Connect

    Wright, Corey; Holmes, Joshua; Nibler, Joseph W.; Hedberg, Kenneth; White, James D.; Hedberg, Lise; Weber, Alfons; Blake, Thomas A.

    2013-05-16

    Combined high-resolution spectroscopic, electron-diffraction, and quantum theoretical methods are particularly advantageous for small molecules of high symmetry and can yield accurate structures that reveal subtle effects of electron delocalization on molecular bonds. The smallest of the radialene compounds, trimethylenecyclopropane, [3]-radialene, has been synthesized and examined in the gas phase by these methods. The first high-resolution infrared spectra have been obtained for this molecule of D3h symmetry, leading to an accurate B0 rotational constant value of 0.1378629(8) cm-1, within 0.5% of the value obtained from electronic structure calculations (density functional theory (DFT) B3LYP/cc-pVTZ). This result is employed in an analysis of electron-diffraction data to obtain the rz bond lengths (in Å): C-H = 1.072 (17), C-C = 1.437 (4), and C=C = 1.330 (4). The analysis does not lead to an accurate value of the HCH angle; however, from comparisons of theoretical and experimental angles for similar compounds, the theoretical prediction of 117.5° is believed to be reliable to within 2°. The effect of electron delocalization in radialene is to reduce the single C-C bond length by 0.07 Å compared to that in cyclopropane.

  4. Measurements of Auger Electron Diffraction Using a 180° Deflection Toroidal Analyzer

    NASA Astrophysics Data System (ADS)

    Shiraki, Susumu; Ishii, Hideshi; Nihei, Yoshimasa; Owari, Masanori

    A 180° deflection toroidal analyzer is a novel electron spectrometer, which allows the simultaneous registration of the wide range of polar angles in a given azimuth of the sample. Therefore, measurements of photo- and Auger electron intensities over π steradians can be performed rapidly by azimuthal rotation of the sample. Using this analyzer, two-dimensional patterns of electron-beam-excited O KVV and Mg KVV Auger electron diffraction (AED) from a MgO(001) surface were measured in short acquisition times. The AED patterns obtained were compared with theoretical ones calculated by the multiple-scattering scheme. The agreement between experimental and theoretical data was good for both O KVV and Mg KVV transitions.

  5. 3D Imaging.

    ERIC Educational Resources Information Center

    Hastings, S. K.

    2002-01-01

    Discusses 3 D imaging as it relates to digital representations in virtual library collections. Highlights include X-ray computed tomography (X-ray CT); the National Science Foundation (NSF) Digital Library Initiatives; output peripherals; image retrieval systems, including metadata; and applications of 3 D imaging for libraries and museums. (LRW)

  6. Phase recovery and lensless imaging by iterative methods in optical, X-ray and electron diffraction.

    PubMed

    Spence, J C H; Weierstall, U; Howells, M

    2002-05-15

    Thomas Young's quantitative analysis of interference effects provided the confidence needed to revive the wave theory of light, and firmly established the concept of phase in optics. Phase plays a similarly fundamental role in matter-wave interferometry, for which the field-emission electron microscope provides ideal instrumentation. The wave-particle duality is vividly demonstrated by experimental 'Young's fringes' using coherent electron beams under conditions in which the flight time is less than the time between particle emission. A brief historical review is given of electron interferometry and holography, including the Aharonov-Bohm effect and the electron Sagnac interferometer. The simultaneous development of phase-contrast imaging at subnanometre spatial resolution has greatly deepened our understanding of atomic processes in biology, materials science and condensed-matter physics, while electron holography has become a routine tool for the mapping of electrostatic and magnetic fields in materials on a nanometre scale. The encoding of phase information in scattered farfield intensities is discussed, and non-interferometric, non-crystallographic methods for phase retrieval are reviewed in relationship to electron holography. Examples of phase measurement and diffraction-limited imaging using the hybrid input-output iterative algorithm are given, including simulations for soft X-ray imaging, and new experimental results for coherent electron and visible-light scattering. Image reconstruction is demonstrated from experimental electron and visible-light Fraunhofer diffraction patterns. The prospects this provides for lensless imaging using particles for which no lenses exist (such as neutrons, condensates, coherent atom beams and X-rays) are discussed. These new interactions can be expected to provide new information, perhaps, for example, in biology, with the advantage of less damage to samples.

  7. Numerical Solution of 3D Poisson-Nernst-Planck Equations Coupled with Classical Density Functional Theory for Modeling Ion and Electron Transport in a Confined Environment

    SciTech Connect

    Meng, Da; Zheng, Bin; Lin, Guang; Sushko, Maria L.

    2014-08-29

    We have developed efficient numerical algorithms for the solution of 3D steady-state Poisson-Nernst-Planck equations (PNP) with excess chemical potentials described by the classical density functional theory (cDFT). The coupled PNP equations are discretized by finite difference scheme and solved iteratively by Gummel method with relaxation. The Nernst-Planck equations are transformed into Laplace equations through the Slotboom transformation. Algebraic multigrid method is then applied to efficiently solve the Poisson equation and the transformed Nernst-Planck equations. A novel strategy for calculating excess chemical potentials through fast Fourier transforms is proposed which reduces computational complexity from O(N2) to O(NlogN) where N is the number of grid points. Integrals involving Dirac delta function are evaluated directly by coordinate transformation which yields more accurate result compared to applying numerical quadrature to an approximated delta function. Numerical results for ion and electron transport in solid electrolyte for Li ion batteries are shown to be in good agreement with the experimental data and the results from previous studies.

  8. A Modular and Affordable Time-Lapse Imaging and Incubation System Based on 3D-Printed Parts, a Smartphone, and Off-The-Shelf Electronics

    PubMed Central

    Schwan, Emil; Fatsis-Kavalopoulos, Nikos; Kreuger, Johan

    2016-01-01

    Time-lapse imaging is a powerful tool for studying cellular dynamics and cell behavior over long periods of time to acquire detailed functional information. However, commercially available time-lapse imaging systems are expensive and this has limited a broader implementation of this technique in low-resource environments. Further, the availability of time-lapse imaging systems often present workflow bottlenecks in well-funded institutions. To address these limitations we have designed a modular and affordable time-lapse imaging and incubation system (ATLIS). The ATLIS enables the transformation of simple inverted microscopes into live cell imaging systems using custom-designed 3D-printed parts, a smartphone, and off-the-shelf electronic components. We demonstrate that the ATLIS provides stable environmental conditions to support normal cell behavior during live imaging experiments in both traditional and evaporation-sensitive microfluidic cell culture systems. Thus, the system presented here has the potential to increase the accessibility of time-lapse microscopy of living cells for the wider research community. PMID:28002463

  9. A Modular and Affordable Time-Lapse Imaging and Incubation System Based on 3D-Printed Parts, a Smartphone, and Off-The-Shelf Electronics.

    PubMed

    Hernández Vera, Rodrigo; Schwan, Emil; Fatsis-Kavalopoulos, Nikos; Kreuger, Johan

    2016-01-01

    Time-lapse imaging is a powerful tool for studying cellular dynamics and cell behavior over long periods of time to acquire detailed functional information. However, commercially available time-lapse imaging systems are expensive and this has limited a broader implementation of this technique in low-resource environments. Further, the availability of time-lapse imaging systems often present workflow bottlenecks in well-funded institutions. To address these limitations we have designed a modular and affordable time-lapse imaging and incubation system (ATLIS). The ATLIS enables the transformation of simple inverted microscopes into live cell imaging systems using custom-designed 3D-printed parts, a smartphone, and off-the-shelf electronic components. We demonstrate that the ATLIS provides stable environmental conditions to support normal cell behavior during live imaging experiments in both traditional and evaporation-sensitive microfluidic cell culture systems. Thus, the system presented here has the potential to increase the accessibility of time-lapse microscopy of living cells for the wider research community.

  10. Accurate electronic and chemical properties of 3d transition metal oxides using a calculated linear response U and a DFT + U(V) method.

    PubMed

    Xu, Zhongnan; Joshi, Yogesh V; Raman, Sumathy; Kitchin, John R

    2015-04-14

    We validate the usage of the calculated, linear response Hubbard U for evaluating accurate electronic and chemical properties of bulk 3d transition metal oxides. We find calculated values of U lead to improved band gaps. For the evaluation of accurate reaction energies, we first identify and eliminate contributions to the reaction energies of bulk systems due only to changes in U and construct a thermodynamic cycle that references the total energies of unique U systems to a common point using a DFT + U(V) method, which we recast from a recently introduced DFT + U(R) method for molecular systems. We then introduce a semi-empirical method based on weighted DFT/DFT + U cohesive energies to calculate bulk oxidation energies of transition metal oxides using density functional theory and linear response calculated U values. We validate this method by calculating 14 reactions energies involving V, Cr, Mn, Fe, and Co oxides. We find up to an 85% reduction of the mean average error (MAE) compared to energies calculated with the Perdew-Burke-Ernzerhof functional. When our method is compared with DFT + U with empirically derived U values and the HSE06 hybrid functional, we find up to 65% and 39% reductions in the MAE, respectively.

  11. Accurate electronic and chemical properties of 3d transition metal oxides using a calculated linear response U and a DFT + U(V) method

    SciTech Connect

    Xu, Zhongnan; Kitchin, John R.; Joshi, Yogesh V.; Raman, Sumathy

    2015-04-14

    We validate the usage of the calculated, linear response Hubbard U for evaluating accurate electronic and chemical properties of bulk 3d transition metal oxides. We find calculated values of U lead to improved band gaps. For the evaluation of accurate reaction energies, we first identify and eliminate contributions to the reaction energies of bulk systems due only to changes in U and construct a thermodynamic cycle that references the total energies of unique U systems to a common point using a DFT + U(V ) method, which we recast from a recently introduced DFT + U(R) method for molecular systems. We then introduce a semi-empirical method based on weighted DFT/DFT + U cohesive energies to calculate bulk oxidation energies of transition metal oxides using density functional theory and linear response calculated U values. We validate this method by calculating 14 reactions energies involving V, Cr, Mn, Fe, and Co oxides. We find up to an 85% reduction of the mean average error (MAE) compared to energies calculated with the Perdew-Burke-Ernzerhof functional. When our method is compared with DFT + U with empirically derived U values and the HSE06 hybrid functional, we find up to 65% and 39% reductions in the MAE, respectively.

  12. Characterization of a sub-assembly of 3D position sensitive cadmium zinc telluride detectors and electronics from a sub-millimeter resolution PET system

    NASA Astrophysics Data System (ADS)

    Abbaszadeh, Shiva; Gu, Yi; Reynolds, Paul D.; Levin, Craig S.

    2016-09-01

    Cadmium zinc telluride (CZT) offers key advantages for small animal positron emission tomography (PET), including high spatial and energy resolution and simple metal deposition for fabrication of very small pixel arrays. Previous studies have investigated the intrinsic spatial, energy, and timing resolution of an individual sub-millimeter resolution CZT detector. In this work we present the first characterization results of a system of these detectors. The 3D position sensitive dual-CZT detector module and readout electronics developed in our lab was scaled up to complete a significant portion of the final PET system. This sub-system was configured as two opposing detection panels containing a total of twelve 40~\\text{mm}× 40~\\text{mm}× 5 mm monolithic CZT crystals for proof of concept. System-level characterization studies, including optimizing the trigger threshold of each channel’s comparators, were performed. 68Ge and 137Cs radioactive isotopes were used to characterize the energy resolution of all 468 anode channels in the sub-system. The mean measured global 511 keV photopeak energy resolution over all anodes was found to be 7.35+/- 1.75 % FWHM after correction for photon interaction depth-dependent signal variation. The measured global time resolution was 37 ns FWHM, a parameter to be further optimized, and the intrinsic spatial resolution was 0.76 mm FWHM.

  13. Stacking disorder in silicon carbide supported cobalt crystallites: an X-ray diffraction, electron diffraction and high resolution electron microscopy study.

    PubMed

    du Plessis, H E; de Villiers, J P R; Tuling, A; Olivier, E J

    2016-11-21

    Supported cobalt Fischer-Tropsch catalysts are characteristically nanoparticulate and the reduced SiC supported catalyst was found to contain both HCP and FCC polymorphs. This is reflected in the powder XRD patterns and generally there is a poor fit between the experimental and calculated diffractograms. This was ascribed to small crystallite sizes and the occurrence of disorder, manifested as peak broadening and peak shifts. Selected area electron diffraction data of suitably oriented cobalt catalyst grains on silicon carbide supports show non-periodic disorder in the zone axis orientations that contain the common (001) (HCP) and (111) (FCC) reciprocal lattice planes. Both FCC and HCP polymorphs are present in the same grains and these show disorder mainly in the HCP component. The disorder is further examined using high angle annular dark field (HAADF) scanning transmission electron microscopy at atomic resolution and the stacking sequences elucidated. Random sequences of mainly FCC are interrupted by HCP sequences and twin surfaces with reverse stacking sequences are also present. This study highlights the presence of significant disorder in cobalt catalyst grains confirmed by HAADF microscopy.

  14. 3D Micro-topography of Transferred Laboratory and Natural Ice Crystal Surfaces Imaged by Cryo and Environmental Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Magee, N. B.; Boaggio, K.; Bancroft, L.; Bandamede, M.

    2015-12-01

    Recent work has highlighted micro-scale roughness on the surfaces of ice crystals grown and imaged in-situ within the chambers of environmental scanning electron microscopes (ESEM). These observations appear to align with theoretical and satellite observations that suggest a prevalence of rough ice in cirrus clouds. However, the atmospheric application of the lab observations are indeterminate because the observations have been based only on crystals grown on substrates and in pure-water vapor environments. In this work, we present details and results from the development of a transfer technique which allows natural and lab-grown ice and snow crystals to be captured, preserved, and transferred into the ESEM for 3D imaging. Ice crystals were gathered from 1) natural snow, 2) a balloon-borne cirrus particle capture device, and 3) lab-grown ice crystals from a diffusion chamber. Ice crystals were captured in a pre-conditioned small-volume (~1 cm3) cryo-containment cell. The cell was then sealed closed and transferred to a specially-designed cryogenic dewer (filled with liquid nitrogen or crushed dry ice) for transport to a new Hitachi Field Emission, Variable Pressure SEM (SU-5000). The cryo-cell was then removed from the dewer and quickly placed onto the pre-conditioned cryo transfer stage attached to the ESEM (Quorum 3010T). Quantitative 3D topographical digital elevation models of ice surfaces are reported from SEM for the first time, including a variety of objective measures of statistical surface roughness. The surfaces of the transported crystals clearly exhibit signatures of mesoscopic roughening that are similar to examples of roughness seen in ESEM-grown crystals. For most transported crystals, the habits and crystal edges are more intricate that those observed for ice grown directly on substrates within the ESEM chamber. Portions of some crystals do appear smooth even at magnification greater than 1000x, a rare observation in our ESEM-grown crystals. The

  15. Teaching Diffraction of Light and Electrons: Classroom Analogies to Classic Experiments

    NASA Astrophysics Data System (ADS)

    Velentzas, Athanasios

    2014-11-01

    Diffraction and interference are phenomena that demonstrate the wave nature of light and of particles. Experiments relating to the diffraction/interference of light can easily be carried out in an educational lab, but it may be impossible to perform experiments involving electrons because of the lack of specialized equipment needed for such experiments. It would, however, be possible for students to analyze data from scientific experiments by analogy to experiments they themselves had performed. Based on this rationale, this paper describes two pairs of experiments that may be of interest to teachers aiming to teach the wave nature of light and of particles to upper secondary school (or to college) students. Specifically, students are asked to (i) carry out a double-slit experiment by using monochromatic light, thus repeating in a way the historical experiment of Young,1 and then analyze real data from Jönsson's2-3 scientific double-slit experiment with electrons, and (ii) perform an experiment involving diffraction of monochromatic light using a compact disc (CD) as a reflection grating, and then by analogy analyze data from the experiment of Davisson and Germer.4 The proposed real experiments are not original, and different versions of them have been wi dely described in the literature.5,6 The educational value of the present work lies in the use of the analogy between experiments carried out in the school lab and experiments performed in the scientific lab.

  16. Extracting conformational structure information of benzene molecules via laser-induced electron diffraction

    DOE PAGES

    Ito, Yuta; Wang, Chuncheng; Le, Anh-Thu; ...

    2016-05-01

    Here, we have measured the angular distributions of high energy photoelectrons of benzene molecules generated by intense infrared femtosecond laser pulses. These electrons arise from the elastic collisions between the benzene ions with the previously tunnel-ionized electrons that have been driven back by the laser field. Theory shows that laser-free elastic differential cross sections (DCSs) can be extracted from these photoelectrons, and the DCS can be used to retrieve the bond lengths of gas-phase molecules similar to the conventional electron diffraction method. From our experimental results, we have obtained the C-C and C-H bond lengths of benzene with a spatialmore » resolution of about 10 pm. Our results demonstrate that laser induced electron diffraction (LIED) experiments can be carried out with the present-day ultrafast intense lasers already. Looking ahead, with aligned or oriented molecules, more complete spatial information of the molecule can be obtained from LIED, and applying LIED to probe photo-excited molecules, a “molecular movie” of the dynamic system may be created with sub-A°ngstrom spatial and few-ten femtosecond temporal resolutions.« less

  17. Extracting conformational structure information of benzene molecules via laser-induced electron diffraction

    SciTech Connect

    Ito, Yuta; Wang, Chuncheng; Le, Anh-Thu; Okunishi, Misaki; Ding, Dajun; Lin, C. D.; Ueda, Kiyoshi

    2016-05-01

    Here, we have measured the angular distributions of high energy photoelectrons of benzene molecules generated by intense infrared femtosecond laser pulses. These electrons arise from the elastic collisions between the benzene ions with the previously tunnel-ionized electrons that have been driven back by the laser field. Theory shows that laser-free elastic differential cross sections (DCSs) can be extracted from these photoelectrons, and the DCS can be used to retrieve the bond lengths of gas-phase molecules similar to the conventional electron diffraction method. From our experimental results, we have obtained the C-C and C-H bond lengths of benzene with a spatial resolution of about 10 pm. Our results demonstrate that laser induced electron diffraction (LIED) experiments can be carried out with the present-day ultrafast intense lasers already. Looking ahead, with aligned or oriented molecules, more complete spatial information of the molecule can be obtained from LIED, and applying LIED to probe photo-excited molecules, a “molecular movie” of the dynamic system may be created with sub-A°ngstrom spatial and few-ten femtosecond temporal resolutions.

  18. Extracting conformational structure information of benzene molecules via laser-induced electron diffraction

    PubMed Central

    Ito, Yuta; Wang, Chuncheng; Le, Anh-Thu; Okunishi, Misaki; Ding, Dajun; Lin, C. D.; Ueda, Kiyoshi

    2016-01-01

    We have measured the angular distributions of high energy photoelectrons of benzene molecules generated by intense infrared femtosecond laser pulses. These electrons arise from the elastic collisions between the benzene ions with the previously tunnel-ionized electrons that have been driven back by the laser field. Theory shows that laser-free elastic differential cross sections (DCSs) can be extracted from these photoelectrons, and the DCS can be used to retrieve the bond lengths of gas-phase molecules similar to the conventional electron diffraction method. From our experimental results, we have obtained the C-C and C-H bond lengths of benzene with a spatial resolution of about 10 pm. Our results demonstrate that laser induced electron diffraction (LIED) experiments can be carried out with the present-day ultrafast intense lasers already. Looking ahead, with aligned or oriented molecules, more complete spatial information of the molecule can be obtained from LIED, and applying LIED to probe photo-excited molecules, a “molecular movie” of the dynamic system may be created with sub-Ångström spatial and few-ten femtosecond temporal resolutions. PMID:27462650

  19. 2D-3D transition of gold cluster anions resolved

    NASA Astrophysics Data System (ADS)

    Johansson, Mikael P.; Lechtken, Anne; Schooss, Detlef; Kappes, Manfred M.; Furche, Filipp

    2008-05-01

    Small gold cluster anions Aun- are known for their unusual two-dimensional (2D) structures, giving rise to properties very different from those of bulk gold. Previous experiments and calculations disagree about the number of gold atoms nc where the transition to 3D structures occurs. We combine trapped ion electron diffraction and state of the art electronic structure calculations to resolve this puzzle and establish nc=12 . It is shown that theoretical studies using traditional generalized gradient functionals are heavily biased towards 2D structures. For a correct prediction of the 2D-3D crossover point it is crucial to use density functionals yielding accurate jellium surface energies, such as the Tao-Perdew-Staroverov-Scuseria (TPSS) functional or the Perdew-Burke-Ernzerhof functional modified for solids (PBEsol). Further, spin-orbit effects have to be included, and large, flexible basis sets employed. This combined theoretical-experimental approach is promising for larger gold and other metal clusters.

  20. Reconstruction of two-dimensional molecular structure with laser-induced electron diffraction from laser-aligned polyatomic molecules

    DOE PAGES

    Yu, Chao; Wei, Hui; Wang, Xu; ...

    2015-10-27

    Imaging the transient process of molecules has been a basic way to investigate photochemical reactions and dynamics. Based on laser-induced electron diffraction and partial one-dimensional molecular alignment, here we provide two effective methods for reconstructing two-dimensional structure of polyatomic molecules. We demonstrate that electron diffraction images in both scattering angles and broadband energy can be utilized to retrieve complementary structure information, including positions of light atoms. Lastly, with picometre spatial resolution and the inherent femtosecond temporal resolution of lasers, laser-induced electron diffraction method offers significant opportunities for probing atomic motion in a large molecule in a typical pump-probe measurement.

  1. The precession technique in electron diffraction and its application to structure determination of nano-size precipitates in alloys.

    PubMed

    Gjønnes, J; Hansen, V; Kverneland, A

    2004-02-01

    Crystal structure of nano-scale precipitates in age-hardening aluminum alloys is a challenge to crystallography. The utility of selected area electron diffraction intensities from embedded precipitates is limited by double scattering via matrix reflections. This effect can be signally reduced by the precession technique, which we have used to collect extensive intensity data from the semicoherent, metastable eta-precipitate in the Al-Zn-Mg alloy system. A structure model in the space group P-62c is proposed from high-resolution microscopy and electron diffraction intensities. The advantages of using the precession technique for quantitative electron diffraction is discussed.

  2. Bunch evolution study in optimization of MeV ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Lu, Xian-Hai; Du, Ying-Chao; Huang, Wen-Hui; Tang, Chuan-Xiang

    2014-12-01

    Megaelectronvolt ultrafast electron diffraction (UED) is a promising detection tool for ultrafast processes. The quality of diffraction image is determined by the transverse evolution of the probe bunch. In this paper, we study the contributing terms of the emittance and space charge effects to the bunch evolution in the MeV UED scheme, employing a mean-field model with an ellipsoidal distribution as well as particle tracking simulation. The small transverse dimension of the drive laser is found to be critical to improve the reciprocal resolution, exploiting both smaller emittance and larger transverse bunch size before the solenoid. The degradation of the reciprocal spatial resolution caused by the space charge effects should be carefully controlled.

  3. Metallographic preparation of Zn-21Al-2Cu alloy for analysis by electron backscatter diffraction (EBSD).

    PubMed

    Rodríguez-Hernández, M G; Martínez-Flores, E E; Torres-Villaseñor, G; Escalera, M Dolores

    2014-08-01

    Samples of Zn-21Al-2Cu alloy (Zinalco) that will be heavily deformed were prepared using five different manual mechanical metallographic methods. Samples were analyzed before tensile testing using the orientation imaging microscopy-electron backscatter diffraction (OIM-EBSD) technique. The effect of type and particle size during the final polishing stages for this material were studied in order to identify a method that produces a flat, damage free surface with a roughness of about 50 nm and clean from oxide layers, thereby producing diffraction patterns with high image quality (IQ) and adequate confidence indexes (CI). Our results show that final polishing with alumina and silica, as was previously suggested by other research groups for alloys that are difficult to prepare or alloys with low melting point, are not suitable for manual metallographic preparation of this alloy. Indexes of IQ and CI can be used to evaluate methods of metallographic preparation of samples studied using the OIM-EBSD technique.

  4. Epitaxy of Fe/Cu/Si(1 1 1) ultrathin films: an Auger electron diffraction study

    NASA Astrophysics Data System (ADS)

    Castrucci, P.; Gunnella, R.; Bernardini, R.; Montecchiari, A.; Carboni, R.; De Crescenzi, M.

    2001-06-01

    Epitaxial Fe films, with thickness in the range between 1 and 50 ML (monolayer, ML), were grown in ultrahigh vacuum conditions on the 7×7 reconstructed (1 1 1)-Si surface. The films were evaporated on a Cu thick buffer layer to avoid iron silicides formation. Auger electron diffraction (AED) technique has been used to investigate the growth of the pseudomorphic film of fcc γ-Fe(1 1 1) and the successive growth of bcc Fe(1 1 0) domains in the Kurdjumov-Sachs orientation. The early stages of growth have been carefully investigated through AED to assess the pseudomorphism of iron γ-phase. AED patterns clearly show the presence of diffraction features that are fingerprints of the existence of a few bcc arranged atomic structures even for 1 ML iron coverage.

  5. Computer programs for unit-cell determination in electron diffraction experiments.

    PubMed

    Li, X Z

    2005-03-01

    A set of computer programs for unit-cell determination from an electron diffraction tilt series and pattern indexing has been developed on the basis of several well-established algorithms. In this approach, a reduced direct primitive cell is first determined from experimental data, in the means time, the measurement errors of the tilt angles are checked and minimized. The derived primitive cell is then checked for possible higher lattice symmetry and transformed into a proper conventional cell. Finally a least-squares refinement procedure is adopted to generate optimum lattice parameters on the basis of the lengths of basic reflections in each diffraction pattern and the indices of these reflections. Examples are given to show the usage of the programs.

  6. Spectrometer for hard X-ray free-electron laser based on diffraction focusing.

    PubMed

    Kohn, V G; Gorobtsov, O Y; Vartanyants, I A

    2013-03-01

    X-ray free-electron lasers (XFELs) generate sequences of ultra-short spatially coherent pulses of X-ray radiation. A diffraction focusing spectrometer (DFS), which is able to measure the whole energy spectrum of the radiation of a single XFEL pulse with an energy resolution of ΔE/E 2 × 10(-6), is proposed. This is much better than for most modern X-ray spectrometers. Such resolution allows one to resolve the fine spectral structure of the XFEL pulse. The effect of diffraction focusing occurs in a single-crystal plate due to dynamical scattering, and is similar to focusing in a Pendry lens made from a metamaterial with a negative refraction index. Such a spectrometer is easier to operate than those based on bent crystals. It is shown that the DFS can be used in a wide energy range from 5 keV to 20 keV.

  7. High energy gain of trapped electrons in a tapered, diffraction-dominated inverse-free-electron laser.

    PubMed

    Musumeci, P; Tochitsky, S Ya; Boucher, S; Clayton, C E; Doyuran, A; England, R J; Joshi, C; Pellegrini, C; Ralph, J E; Rosenzweig, J B; Sung, C; Tolmachev, S; Travish, G; Varfolomeev, A A; Varfolomeev, A A; Yarovoi, T; Yoder, R B

    2005-04-22

    Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an inverse-free-electron-laser (IFEL) accelerator experiment. A 14.5 MeV electron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and field amplitude. The Rayleigh range of the laser, approximately 1.8 cm, is much shorter than the undulator length yielding a diffraction-dominated interaction. Experimental results on the dependence of the acceleration on injection energy, laser focus position, and laser power are discussed. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV/m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator.

  8. FPGA architectures for electronically scanned wide-band RF beams using 3-D FIR/IIR digital filters for rectangular array aperture receivers

    NASA Astrophysics Data System (ADS)

    Wijayaratna, Sewwandi; Madanayake, Arjuna; Beall, Brandon D.; Bruton, Len T.

    2014-05-01

    Real-time digital implementation of three-dimensional (3-D) infinite impulse response (IIR) beam filters are discussed. The 3-D IIR filter building blocks have filter coefficients, which are defined using algebraic closed-form expressions that are functions of desired beam personalities, such as the look-direction of the aperture, the bandwidth and sampling frequency of interest, inter antenna spacing, and 3dB beam size. Real-time steering of such 3-D beam filters are obtained by proposed calculation of filter coefficients. Application specific computing units for rapidly calculating the 3-D IIR filter coefficients at nanosecond speed potentially allows fast real-time tracking of low radar cross section (RCS) objects at close range. Proposed design consists of 3-D IIR beam filter with 4 4 antenna grid and the filter coefficient generation block in separate FPGAs. The hardware is designed and co-simulated using a Xilinx Virtex-6 XC6VLX240T FPGA. The 3-D filter operates over 90 MHz and filter coefficient computing structure can operate at up to 145 MHz.

  9. The first 3D malonate bridged copper [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O]: Structure, properties and electronic structure

    SciTech Connect

    Seguatni, A.; Fakhfakh, M.; Smiri, L.S.; Gressier, P.; Boucher, F.; Jouini, N.

    2012-03-15

    A new inorganic-organic compound [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O] ([Cumal]) was hydrothermally synthesized and characterized by IR spectroscopy, thermal analysis and single crystal X-ray diffraction. [Cumal] is the first three-dimensional compound existing in the system Cu(II)-malonic acid-H{sub 2}O. Its framework is built up through carboxyl bridged copper where CuO{sub 6} octahedra are elongated with an almost D{sub 4h} symmetry (4+2) due to the Jahn-Teller effect. The magnetic properties were studied by measuring its magnetic susceptibility in the temperature range of 2-300 K indicating the existence of weak ferromagnetic interactions. The electronic structure of [Cumal] was calculated within the density functional theory (DFT) framework. Structural features are well reproduced using DFT structural optimizations and the optical spectra, calculated within the dielectric formalism, explain very well the light blue colour of the compound. It is shown that a GGA+U approach with a U{sub eff} value of about 6 eV is necessary for a better correlation with the experiment. - Graphical abstract: [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O]: the first 3D hybrid organic-inorganic compound built up carboxyl groups. The network presents a diamond-like structure achieved via carboxyl. Highlights: Black-Right-Pointing-Pointer A new organic-inorganic material with an unprecedented topology is synthesized. Black-Right-Pointing-Pointer Crystallographic structure is determined using single crystal X-ray diffraction. Black-Right-Pointing-Pointer Electronic structure is obtained from DFT, GGA+U calculation. Black-Right-Pointing-Pointer Framework can be described as formed from CuC{sub 4} tetrahedron sharing four corners. Black-Right-Pointing-Pointer This structure can be classified as an extended diamond structure.

  10. Auger electron diffraction in thin CoO films on Au(1 1 1)

    NASA Astrophysics Data System (ADS)

    Chassé, A.; Niebergall, L.; Heiler, M.; Neddermeyer, H.; Schindler, K.-M.

    The local structure of thin CoO films grown on a single crystal Au(1 1 1) surface has been studied by Auger electron diffraction (AED). Therefore, the angular dependence of the Auger electron intensity of Co-LMM and O-KLL Auger electrons was recorded in the total half-space above the film. Such 2 π-scans immediately reflect the symmetry of the surface and the local structure of the film. The experimental data are compared to multiple-scattering cluster calculations, where both the influence of multiple-scattering effects and effects of Auger transition matrix elements have been investigated. We have found that the AED patterns of a CoO film in forward-scattering conditions do not always provide straightforward information on the local structure of the film, whereas the multiple-scattering approximation applied gives very good agreement between experimental and theoretical results.

  11. Strain mapping at nanometer resolution using advanced nano-beam electron diffraction

    SciTech Connect

    Ozdol, V. B.; Ercius, P.; Ophus, C.; Ciston, J.; Gammer, C. E-mail: aminor@lbl.gov; Jin, X. G.; Minor, A. M. E-mail: aminor@lbl.gov

    2015-06-22

    We report on the development of a nanometer scale strain mapping technique by means of scanning nano-beam electron diffraction. Only recently possible due to fast acquisition with a direct electron detector, this technique allows for strain mapping with a high precision of 0.1% at a lateral resolution of 1 nm for a large field of view reaching up to 1 μm. We demonstrate its application to a technologically relevant strain-engineered GaAs/GaAsP hetero-structure and show that the method can even be applied to highly defected regions with substantial changes in local crystal orientation. Strain maps derived from atomically resolved scanning transmission electron microscopy images were used to validate the accuracy, precision and resolution of this versatile technique.

  12. Carrier-envelope phase mapping in laser-induced electron diffraction

    NASA Astrophysics Data System (ADS)

    Geiseler, Henning; Ishii, Nobuhisa; Kaneshima, Keisuke; Geier, Florian; Kanai, Teruto; Tolstikhin, Oleg I.; Morishita, Toru; Itatani, Jiro

    2016-09-01

    We present laser-induced electron diffraction measurements of elastic differential scattering cross sections (DCSs) of a photoelectron on the parent ion for argon, krypton, and xenon, using waveform-controlled few-cycle pulses. Considering only cutoff electrons and employing the adiabatic theory for the analysis enables us to eliminate ambiguities in extracting the DCSs from experimental spectra. Contrary to previous works, which mainly focused on the angular dependence of the DCS, our method allows us to extract also its dependence on the scattering momentum. In the case of xenon, we demonstrate how this method can be used to obtain the complete angular and momentum dependence of the DCS in a range of these variables determined by the pulse. The obtained results are compared to theoretical calculations based on the single-active-electron approximation, which shows a high level of agreement. Further investigations may provide opportunities to study multielectron effects when more advanced theoretical models become available.

  13. Three-dimensional cathodoluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions

    NASA Astrophysics Data System (ADS)

    Wiggers de Vries, D. F.; Drury, M. R.; de Winter, D. A. M.; Bulanova, G. P.; Pearson, D. G.; Davies, G. R.

    2011-04-01

    As a step towards resolving the genesis of inclusions in diamonds, a new technique is presented. This technique combines cathodoluminescence (CL) and electron backscatter diffraction (EBSD) using a focused ion beam-scanning electron microscope (FIB-SEM) instrument with the aim of determining, in detail, the three-dimensional diamond zonation adjacent to a diamond inclusion. EBSD reveals that mineral inclusions in a single diamond have similar crystallographic orientations to the host, within ±0.4°. The chromite inclusions record a systematic change in Mg# and Cr# from core to the rim of the diamond that corresponds with a ~80°C decrease of their formation temperature as established by zinc thermometry. A chromite inclusion, positioned adjacent to a boundary between two major diamond growth zones, is multi-faceted with preferred octahedral and cubic faces. The chromite is surrounded by a volume of non-luminescent diamond (CL halo) that partially obscures any diamond growth structures. The CL halo has apparent crystallographic morphology with symmetrically oriented pointed features. The CL halo is enriched in ~200 ppm Cr and ~80 ppm Fe and is interpreted to have a secondary origin as it overprints a major primary diamond growth structure. The diamond zonation adjacent to the chromite is complex and records both syngenetic and protogenetic features based on current inclusion entrapment models. In this specific case, a syngenetic origin is favoured with the complex form of the inclusion and growth layers indicating changes of growth rates at the diamond-chromite interface. Combined EBSD and 3D-CL imaging appears an extremely useful tool in resolving the ongoing discussion about the timing of inclusion growth and the significance of diamond inclusion studies.

  14. Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders.

    PubMed

    Yun, Yifeng; Zou, Xiaodong; Hovmöller, Sven; Wan, Wei

    2015-03-01

    Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED) data collection, namely automated diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed. Compared with X-ray diffraction (XRD) and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD) provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni-Se-O-Cl crystals, zeolites, germanates, metal-organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three-dimensional ED methods

  15. Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders

    PubMed Central

    Yun, Yifeng; Zou, Xiaodong; Hovmöller, Sven; Wan, Wei

    2015-01-01

    Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED) data collection, namely automated diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed. Compared with X-ray diffraction (XRD) and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD) provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni–Se–O–Cl crystals, zeolites, germanates, metal–organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three-dimensional ED

  16. Imaging polyatomic molecules with ultrafast laser-induced electron diffraction (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Le, Anh-Thu; Lin, Chii-Dong

    2016-10-01

    Molecular structure determination of chemical reactions or processes has been one of the grand challenges in physics, chemistry, and biology. To image these processes, it typically requires sub-Angstrom spatial and femtosecond temporal resolutions. One of the standard imaging techniques, X-ray diffraction, however, currently suffers from temporal jitters and is available only at large facilities. Furthermore, it also suffers from very low elastic scattering cross sections, which make it difficult to apply to gas phase molecules. Another technique, ultrafast electron diffraction (UED), overcomes this low cross section problem, but the temporal resolution is still limited to hundreds of femtoseconds, mainly due to Coulomb repulsion in electron beam and velocity mismatch between laser-pump pulse and electron probe pulse in a typical pump-probe scheme. The recently proposed laser-induced electron diffraction (LIED) is based on two basic ideas. First, an electron wave packet can be generated from a target itself by an intense laser pulse and driven back within the subsequent half-cycle of the laser to rescatter from the parent ion, thus realizing a self-imaging process. Laser-free elastic differential cross sections (DCS) can then be extracted from high-energy electron spectra, as demonstrated by the Quantitative Rescattering theory (QRS). Second, the target structure information can be retrieved from the DCS. This retrieval is further simplified by using back-scattered electrons with collision energy of about 100 eV, for which the independent-atom model (IAM) can be employed to quite accurately simulate the DCS. Demonstration of ultrafast imaging with the LIED has been reported so far on simple diatomic molecules. Here we discuss recent progress in LIED with polyatomic molecules in two examples. The first one is aligned acetylene (C2H2) and the second one is benzene (C6H6). In both cases, two bond lengths, C-C and C-H have been successfully retrieved. For even more

  17. AE3D

    SciTech Connect

    Spong, Donald A

    2016-06-20

    AE3D solves for the shear Alfven eigenmodes and eigenfrequencies in a torodal magnetic fusion confinement device. The configuration can be either 2D (e.g. tokamak, reversed field pinch) or 3D (e.g. stellarator, helical reversed field pinch, tokamak with ripple). The equations solved are based on a reduced MHD model and sound wave coupling effects are not currently included.

  18. Orbital angular momentum in electron diffraction and its use to determine chiral crystal symmetries

    NASA Astrophysics Data System (ADS)

    Juchtmans, Roeland; Verbeeck, Jo

    2015-10-01

    In this work we present an alternative way to look at electron diffraction in a transmission electron microscope. Instead of writing the scattering amplitude in Fourier space as a set of plane waves, we use the cylindrical Fourier transform to describe the scattering amplitude in a basis of orbital angular momentum (OAM) eigenstates. We show how working in this framework can be very convenient when investigating, e.g., rotation and screw-axis symmetries. For the latter we find selection rules on the OAM coefficients that unambiguously reveal the handedness of the screw axis. Detecting the OAM coefficients of the scattering amplitude thus offers the possibility to detect the handedness of crystals without the need for dynamical simulations, the thickness of the sample, nor the exact crystal structure. We propose an experimental setup to measure the OAM components where an image of the crystal is taken after inserting a spiral phase plate in the diffraction plane and perform multislice simulations on α quartz to demonstrate how the method indeed reveals the chirality. The experimental feasibility of the technique is discussed together with its main advantages with respect to chirality determination of screw axes. The method shows how the use of a spiral phase plate can be extended from a simple phase imaging technique to a tool to measure the local OAM decomposition of an electron wave, widening the field of interest well beyond chiral space group determination.

  19. Do-It-Yourself: 3D Models of Hydrogenic Orbitals through 3D Printing

    ERIC Educational Resources Information Center

    Griffith, Kaitlyn M.; de Cataldo, Riccardo; Fogarty, Keir H.

    2016-01-01

    Introductory chemistry students often have difficulty visualizing the 3-dimensional shapes of the hydrogenic electron orbitals without the aid of physical 3D models. Unfortunately, commercially available models can be quite expensive. 3D printing offers a solution for producing models of hydrogenic orbitals. 3D printing technology is widely…

  20. Macrophage podosomes go 3D.

    PubMed

    Van Goethem, Emeline; Guiet, Romain; Balor, Stéphanie; Charrière, Guillaume M; Poincloux, Renaud; Labrousse, Arnaud; Maridonneau-Parini, Isabelle; Le Cabec, Véronique

    2011-01-01

    Macrophage tissue infiltration is a critical step in the immune response against microorganisms and is also associated with disease progression in chronic inflammation and cancer. Macrophages are constitutively equipped with specialized structures called podosomes dedicated to extracellular matrix (ECM) degradation. We recently reported that these structures play a critical role in trans-matrix mesenchymal migration mode, a protease-dependent mechanism. Podosome molecular components and their ECM-degrading activity have been extensively studied in two dimensions (2D), but yet very little is known about their fate in three-dimensional (3D) environments. Therefore, localization of podosome markers and proteolytic activity were carefully examined in human macrophages performing mesenchymal migration. Using our gelled collagen I 3D matrix model to obligate human macrophages to perform mesenchymal migration, classical podosome markers including talin, paxillin, vinculin, gelsolin, cortactin were found to accumulate at the tip of F-actin-rich cell protrusions together with β1 integrin and CD44 but not β2 integrin. Macrophage proteolytic activity was observed at podosome-like protrusion sites using confocal fluorescence microscopy and electron microscopy. The formation of migration tunnels by macrophages inside the matrix was accomplished by degradation, engulfment and mechanic compaction of the matrix. In addition, videomicroscopy revealed that 3D F-actin-rich protrusions of migrating macrophages were as dynamic as their 2D counterparts. Overall, the specifications of 3D podosomes resembled those of 2D podosome rosettes rather than those of individual podosomes. This observation was further supported by the aspect of 3D podosomes in fibroblasts expressing Hck, a master regulator of podosome rosettes in macrophages. In conclusion, human macrophage podosomes go 3D and take the shape of spherical podosome rosettes when the cells perform mesenchymal migration. This work

  1. 3D Printed Bionic Nanodevices.

    PubMed

    Kong, Yong Lin; Gupta, Maneesh K; Johnson, Blake N; McAlpine, Michael C

    2016-06-01

    The ability to three-dimensionally interweave biological and functional materials could enable the creation of bionic devices possessing unique and compelling geometries, properties, and functionalities. Indeed, interfacing high performance active devices with biology could impact a variety of fields, including regenerative bioelectronic medicines, smart prosthetics, medical robotics, and human-machine interfaces. Biology, from the molecular scale of DNA and proteins, to the macroscopic scale of tissues and organs, is three-dimensional, often soft and stretchable, and temperature sensitive. This renders most biological platforms incompatible with the fabrication and materials processing methods that have been developed and optimized for functional electronics, which are typically planar, rigid and brittle. A number of strategies have been developed to overcome these dichotomies. One particularly novel approach is the use of extrusion-based multi-material 3D printing, which is an additive manufacturing technology that offers a freeform fabrication strategy. This approach addresses the dichotomies presented above by (1) using 3D printing and imaging for customized, hierarchical, and interwoven device architectures; (2) employing nanotechnology as an enabling route for introducing high performance materials, with the potential for exhibiting properties not found in the bulk; and (3) 3D printing a range of soft and nanoscale materials to enable the integration of a diverse palette of high quality functional nanomaterials with biology. Further, 3D printing is a multi-scale platform, allowing for the incorporation of functional nanoscale inks, the printing of microscale features, and ultimately the creation of macroscale devices. This blending of 3D printing, novel nanomaterial properties, and 'living' platforms may enable next-generation bionic systems. In this review, we highlight this synergistic integration of the unique properties of nanomaterials with the

  2. Analysis of local strain in aluminum interconnects by convergent beam electron diffraction

    NASA Astrophysics Data System (ADS)

    Krämer, Stephan; Mayer, Joachim

    1999-11-01

    Energy filtered convergent beam electron diffraction (CBED) was used to investigate localized strain in aluminum interconnects. An analysis of the higher order Laue zone (HOLZ) line positions in CBED patterns makes it possible to measure the lattice strain with high accuracy (˜104) and high spatial resolution (10 to 100 nm). The strain development in a single grain was measured during thermal cycling between -170 °C and +100 °C. The grain showed reversible, elastic behavior over the whole temperature range building up large strains at low temperatures. By comparing with finite element simulations, a detailed understanding of the tri-axial strain state could be achieved.

  3. Molecular structure of gaseous copper nitrate as studied by electron diffraction

    NASA Astrophysics Data System (ADS)

    Shibata, Shuzo; Iijima, Kinya

    1984-06-01

    The molecular structure of copper nitrate has been reinvestigated by gaseous electron diffraction. The experimental data were found to be consistent with a square-planar arrangement of the oxygen atoms of two bidentate nitrate groups. The bond distances and angles were determined as follows: CuO = 1.946 ± 0.003 A, NO(coordinated) = 1.298 ± 0.003 A, NO(terminal) = 1.205 ± 0.005 A, OCuO = 67.8 ± 0.2°. The sample of copper nitrate was also found to be considerably decomposed by heating at 150°C.

  4. ARPGE: a computer program to automatically reconstruct the parent grains from electron backscatter diffraction data

    PubMed Central

    Cayron, Cyril

    2007-01-01

    A computer program called ARPGE written in Python uses the theoretical results generated by the computer program GenOVa to automatically reconstruct the parent grains from electron backscatter diffraction data obtained on phase transition materials with or without residual parent phase. The misorientations between daughter grains are identified with operators, the daughter grains are identified with indexed variants, the orientations of the parent grains are determined, and some statistics on the variants and operators are established. Some examples with martensitic transformations in iron and titanium alloys were treated. Variant selection phenomena were revealed. PMID:19461849

  5. Transmission electron microscopy and x-ray diffraction studies of the detonation soot of high explosives

    NASA Astrophysics Data System (ADS)

    Kashkarov, A. O.; Pruuel, E. R.; Ten, K. A.; Rubtsov, I. A.; Gerasimov, E. Yu; Zubkov, P. I.

    2016-11-01

    This paper presents the results of electron microscopy and x-ray diffraction studies of the recovered carbonaceous residue (soot) from the detonation of some high explosives: TNT, a mixture of TNT and RDX (50/50), benzotrifuroxane, and triaminotrinitrobenzene. The use of the same experimental setup allowed a qualitative and quantitative comparison of the detonation products formed under similar conditions. The results clearly show differences in the morphology of graphite-like and diamond inclusions and in the quantitative content of nanodiamonds for the explosives used in this study.

  6. Fraunhofer diffraction of atomic matter waves: electron transfer studies with a laser cooled target.

    PubMed

    van der Poel, M; Nielsen, C V; Gearba, M A; Andersen, N

    2001-09-17

    We have constructed an apparatus combining the experimental techniques of cold target recoil ion momentum spectroscopy and a laser cooled target. We measure angle differential cross sections in Li(+)+Na-->Li+Na(+) electron transfer collisions in the keV energy regime with a momentum resolution of 0.12 a.u. yielding an order of magnitude better angular resolution than previous measurements. We resolve Fraunhofer-type diffraction patterns in the differential cross sections. Good agreement with predictions of the semiclassical impact parameter method is obtained.

  7. Phase analysis on dual-phase steel using band slope of electron backscatter diffraction pattern.

    PubMed

    Kang, Jun-Yun; Park, Seong-Jun; Moon, Man-Been

    2013-08-01

    A quantitative and automated phase analysis of dual-phase (DP) steel using electron backscatter diffraction (EBSD) was attempted. A ferrite-martensite DP microstructure was produced by intercritical annealing and quenching. An EBSD map of the microstructure was obtained and post-processed for phase discrimination. Band slope (BS), which was a measure of pattern quality, exhibited much stronger phase contrast than another conventional one, band contrast. Owing to high sensitivity to lattice defect and little orientation dependence, BS provided handiness in finding a threshold for phase discrimination. Its grain average gave a superior result on the discrimination and volume fraction measurement of the constituent phases in the DP steel.

  8. Non-marine radiaxial fibrous calcites—examples of speleothems proved by electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Neuser, R. D.; Richter, D. K.

    2007-02-01

    The occurrence of radiaxial fibrous calcites (RFC) in speleothems is documented for the first time using the new electron backscatter diffraction (EBSD) method. Up to now, in speleothems these precipitates have only been observed as Mg-containing calcites in close association with aragonite, in caves of the temperate to cool Central European regions with mean annual temperatures between 4 and 16 °C. As the four studied occurrences are located in caves in dolomitic and/or ankeritic host rocks, magnesium is considered to be of particular importance for triggering the formation of radiaxial fibrous (Mg-) calcite.

  9. Dynamical scattering and electron diffraction from thin polymer lamellar crystals - poly(tert-butylethylene sulfide).

    PubMed

    Dorset; Dumas; Cartier; Lotz

    1999-09-01

    Strong violations of Friedel symmetry are observed in hk0 electron diffraction patterns from lamellar crystals of poly(tert-butylethylene sulfide) obtained at 120 kV. These deviations are largely explained by a multislice dynamical scattering calculation based on the crystal structure model. Further improvement is found when a secondary scattering component is added, in keeping with a perfect crystallite thickness less than that of the lamellar thickness. Despite the multiple-scattering perturbations, the frustrated chain packing can still be determined by direct methods followed by Fourier refinement. However, the Friedel-related intensities must be averaged before calculation of normalized structure factors.

  10. An investigation into the use of electron back scattered diffraction to measure recrystallized fraction

    SciTech Connect

    Black, M.P.; Higginson, R.L. . Dept. of Engineering Materials)

    1999-06-18

    The Electron Back-Scattered Diffraction (EBSD) technique is in its infancy and is a highly promising area of development. Use of EBSD has been predominantly for the determination of crystallographic textures. Other applications have also been considered, which include: crystal structure determination, phase determination, grain boundary studies and both elastic and plastic deformation measurement. Although it has been acknowledged that an important use of the EBSD could be in the measurement of recrystallization and its kinetics there are a number of inherent problems with such measurements using EBSD. These problems include the ability of the system to index deformed microstructures even those on a fine scale, the difficulties of analyzing patterns in the region of grain boundaries and the problems of sample preparation which is critical in the quality of the diffraction patterns obtained. The aim of the present study is to determine whether it is possible to measure the volume fraction recrystallized using EBSP of partially recrystallized stainless steel. This has been done by investigation of the quality of matching between the observed and calculated diffraction patterns, and the quality of the observed patterns measured in terms of their contrast. The material used was stainless steel 316L.

  11. Femtosecond Diffractive Imaging with a Soft-X-ray Free-Electron Laser

    SciTech Connect

    Chapman, H N; Barty, A; Bogan, M; Boutet, S; Frank, M; Hau-Riege, S P; Marchesini, S; Woods, B; Bajt, S; Benner, W H; London, R; Ploenjes-Palm, E; Kuhlmann, M; Treusch, R; Dusterer, S; Tschentscher, T; Schneider, J; Spiller, E; Moller, T; Bostedt, C; Hoener, M; Shapiro, D; Hodgson, K O; der Spoel, D v; Burmeister, F; Bergh, M; Caleman, C; Huldt, G; Seibert, M; Maia, F; Lee, R; Szoke, A; Timneanu, N; Hajdu, J

    2006-03-13

    Theory predicts that with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus, or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft X-ray free-electron laser. An intense 25 fs, 4 x 10{sup 13} W/cm{sup 2} pulse, containing 10{sup 12} photons at 32 nm wavelength, produced a coherent diffraction pattern from a nano-structured non-periodic object, before destroying it at 60,000 K. A novel X-ray camera assured single photon detection sensitivity by filtering out parasitic scattering and plasma radiation. The reconstructed image, obtained directly from the coherent pattern by phase retrieval through oversampling, shows no measurable damage, and extends to diffraction-limited resolution. A three-dimensional data set may be assembled from such images when copies of a reproducible sample are exposed to the beam one by one.

  12. Femtosecond Diffractive Imaging with a Soft-X-Ray Free-Electron Laser

    SciTech Connect

    Chapman, Henry N.; Barty, Anton: AUTHOR = Bogan, Michael J.; Boutet, Sebastian; Frank, Matthias; Hau-Riege, Stefan P.; Marchesini, Stefano; Woods, Bruce W.; Bajt, Sasa; Benner, W.Henry; London, Richard A.; Plonjes, Elke; Kuhlmann, Marion; Treusch, Rolf; Dusterer, Stefan; Tschentscher, Thomas; Schneider, Jochen R.; Spiller, Eberhard; Moller, Thomas; Bostedt, Christoph; Hoener, Matthias; Shapiro, David A.; /UC, Davis /SLAC /Uppsala U. /LLNL, Livermore /Uppsala U. /Uppsala U. /SLAC /Uppsala U.

    2010-10-07

    Theory predicts that with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus, or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft X-ray free-electron laser. An intense 25 fs, 4 x 10{sup 13} W/cm{sup 2} pulse, containing 10{sup 12} photons at 32 nm wavelength, produced a coherent diffraction pattern from a nano-structured non-periodic object, before destroying it at 60,000 K. A novel X-ray camera assured single photon detection sensitivity by filtering out parasitic scattering and plasma radiation. The reconstructed image, obtained directly from the coherent pattern by phase retrieval through oversampling, shows no measurable damage, and extends to diffraction-limited resolution. A three-dimensional data set may be assembled from such images when copies of a reproducible sample are exposed to the beam one by one.

  13. Multiscale phase mapping of LiFePO4-based electrodes by transmission electron microscopy and electron forward scattering diffraction.

    PubMed

    Robert, Donatien; Douillard, Thierry; Boulineau, Adrien; Brunetti, Guillaume; Nowakowski, Pawel; Venet, Denis; Bayle-Guillemaud, Pascale; Cayron, Cyril

    2013-12-23

    LiFePO4 and FePO4 phase distributions of entire cross-sectioned electrodes with various Li content are investigated from nanoscale to mesoscale, by transmission electron microscopy and by the new electron forward scattering diffraction technique. The distributions of the fully delithiated (FePO4) or lithiated particles (LiFePO4) are mapped on large fields of view (>100 × 100 μm(2)). Heterogeneities in thin and thick electrodes are highlighted at different scales. At the nanoscale, the statistical analysis of 64 000 particles unambiguously shows that the small particles delithiate first. At the mesoscale, the phase maps reveal a core-shell mechanism at the scale of the agglomerates with a preferential pathway along the electrode porosities. At larger scale, lithiation occurs in thick electrodes "stratum by stratum" from the surface in contact with electrolyte toward the current collector.

  14. Neutron diffraction of titanium aluminides formed by continuous electron-beam treatment

    NASA Astrophysics Data System (ADS)

    Valkov, S.; Neov, D.; Luytov, D.; Petrov, P.

    2016-03-01

    Ti-Al-based alloys were produced by hybrid electron-beam technologies. A composite Ti-Al film was deposited on a Ti substrate by electron-beam evaporation (EBE), followed by electron-beam treatment (EBT) by a continuously scanned electron beam. The speed of the specimens motion during the EBT were V 1 = 1 cm/sec and V 2 = 5 cm/sec, in order to realize two different alloying mechanisms -- by surface melting and by electron-beam irradiation without melting the surface. The samples prepared were characterized by XRD and neutron diffraction to study the crystal structure on the surface and in depth. SEM/EDX analysis was conducted to explore the surface structure and analyze the chemical composition. Nanoindentation measurements were also carried out. No intermetallic phases were registered in the sample treated at velocity V 1, while the sample treated at V 2 exhibited a Ti3Al/TiAl structure on the surface, transformed to Ti/TiAl in depth. The nanoindentation test demonstrated a significant negative hardness gradient from the surface to the depth of the sample.

  15. Relativistic ultrafast electron diffraction from molecules in the gas phase (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Yang, Jie; Guehr, Markus; Vecchione, Theodore; Robinson, Matthew S.; Li, Renkai; Hartmann, Nick; Shen, Xiaozhe; Centurion, Martin; Wang, Xijie

    2016-10-01

    Ultrafast electron diffraction (UED) is a powerful technique that can be used to resolve structural changes of gas molecules during a photochemical reaction. However, the temporal resolution in pump-probe experiments has been limited to the few-ps level by the space-charge effect that broadens the electron pulse duration and by velocity mismatch between the pump laser pulses and the probe electron pulses, making only long-lived intermediate states accessible. Taking advantage of relativistic effects, Mega-electron-volt (MeV) electrons can be used to suppress both the space-charge effect and the velocity mismatch, and hence to achieve a temporal resolution that is fast enough to follow coherent nuclear motion in the target molecules. In this presentation, we show the first MeV UED experiments on gas phase targets. These experiments not only demonstrate that femtosecond temporal resolution is achieved, but also show that the spatial resolution is not compromised. This unprecedented combination of spatiotemporal resolution is sufficient to image coherent nuclear motions, and opens the door to a new class of experiments where the structural changes can be followed simultaneously in both space and time.

  16. Photoinduced phase transitions in vanadium dioxide revealed by ultrafast electron diffraction and mid-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Tiwari, Kunal; Morrison, Vance; Chatelain, Robert; Hendaoui, Ali; Bruhacs, Andrew; Chaker, Mohamed; Siwick, Bradley

    2015-03-01

    The complex interplay between strong electron-electron correlations and structural distortions is thought to determine the electronic properties of many oxides, but the respective role of these two contributions is often difficult to determine. We report combined radio-frequency compressed ultrafast electron diffraction (RF-UED) and infrared transmissivity experiments in which we directly monitor and separate the lattice and charge density reorganizations associated with the optically induced semiconductor-to-metal phase transition in vanadium dioxide. These studies have uncovered a previously unreported photoinduced transition to a metastable phase retaining the periodic lattice distortion characteristic of the insulating phase, but differing by a reorganization of charge density along the vanadium dimer chains and a transition to metal-like mid IR optical properties. These results demonstrate that UED is able to follow details of both lattice and electronic structural dynamics on the ultrafast timescale. Supported by Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the Canada Research Chairs program, NSERC PGS-D and CGS-D fellowships, and Fonds de Récherche du Québec-Nature et Technologies.

  17. Characterization of ultrafine grained Cu-Ni-Si alloys by electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Altenberger, I.; Kuhn, H. A.; Gholami, M.; Mhaede, M.; Wagner, L.

    2014-08-01

    A combination of rotary swaging and optimized precipitation hardening was applied to generate ultra fine grained (UFG) microstructures in low alloyed high performance Cu-based alloy CuNi3Si1Mg. As a result, ultrafine grained (UFG) microstructures with nanoscopically small Ni2Si-precipitates exhibiting high strength, ductility and electrical conductivity can be obtained. Grain boundary pinning by nano-precipitates enhances the thermal stability. Electron channeling contrast imaging (ECCI) and especially electron backscattering diffraction (EBSD) are predestined to characterize the evolving microstructures due to excellent resolution and vast crystallographic information. The following study summarizes the microstructure after different processing steps and points out the consequences for the most important mechanical and physical properties such as strength, ductility and conductivity.

  18. Imaging an aligned polyatomic molecule with laser-induced electron diffraction

    NASA Astrophysics Data System (ADS)

    Pullen, Michael G.; Wolter, Benjamin; Le, Anh-Thu; Baudisch, Matthias; Hemmer, Michaël; Senftleben, Arne; Schröter, Claus Dieter; Ullrich, Joachim; Moshammer, Robert; Lin, C. D.; Biegert, Jens

    2015-06-01

    Laser-induced electron diffraction is an evolving tabletop method that aims to image ultrafast structural changes in gas-phase polyatomic molecules with sub-Ångström spatial and femtosecond temporal resolutions. Here we demonstrate the retrieval of multiple bond lengths from a polyatomic molecule by simultaneously measuring the C-C and C-H bond lengths in aligned acetylene. Our approach takes the method beyond the hitherto achieved imaging of simple diatomic molecules and is based on the combination of a 160 kHz mid-infrared few-cycle laser source with full three-dimensional electron-ion coincidence detection. Our technique provides an accessible and robust route towards imaging ultrafast processes in complex gas-phase molecules with atto- to femto-second temporal resolution.

  19. Estimation of dislocation density from precession electron diffraction data using the Nye tensor.

    PubMed

    Leff, A C; Weinberger, C R; Taheri, M L

    2015-06-01

    The Nye tensor offers a means to estimate the geometrically necessary dislocation density of a crystalline sample based on measurements of the orientation changes within individual crystal grains. In this paper, the Nye tensor theory is applied to precession electron diffraction automated crystallographic orientation mapping (PED-ACOM) data acquired using a transmission electron microscope (TEM). The resulting dislocation density values are mapped in order to visualize the dislocation structures present in a quantitative manner. These density maps are compared with other related methods of approximating local strain dependencies in dislocation-based microstructural transitions from orientation data. The effect of acquisition parameters on density measurements is examined. By decreasing the step size and spot size during data acquisition, an increasing fraction of the dislocation content becomes accessible. Finally, the method described herein is applied to the measurement of dislocation emission during in situ annealing of Cu in TEM in order to demonstrate the utility of the technique for characterizing microstructural dynamics.

  20. Quantum diffraction and shielding effects on the low-energy electron-ion bremsstrahlung in two-component semiclassical plasmas

    SciTech Connect

    Lee, Myoung-Jae; Jung, Young-Dae

    2015-10-15

    The quantum diffraction and shielding effects on the low-energy bremsstrahlung process are investigated in two-component semiclassical plasmas. The impact-parameter analysis with the micropotential taking into account the quantum diffraction and shielding effects is employed to obtain the electron-ion bremsstrahlung radiation cross section as a function of the de Broglie wavelength, density parameter, impact parameter, photon energy, and projectile energy. The result shows that the influence of quantum diffraction and shielding strongly suppresses the bremsstrahlung radiation spectrum in semiclassical plasmas. It is found that the quantum diffraction and shielding effects have broaden the photon emission domain. It is also found that the photon emission domain is almost independent of the radiation photon energy. In addition, it is found that the influence of quantum diffraction and shielding on the bremsstrahlung spectrum decreases with an increase of the projectile energy. The density effect on the electron-ion bremsstrahlung cross section is also discussed.

  1. 3D Nanostructuring of Semiconductors

    NASA Astrophysics Data System (ADS)

    Blick, Robert

    2000-03-01

    Modern semiconductor technology allows to machine devices on the nanometer scale. I will discuss the current limits of the fabrication processes, which enable the definition of single electron transistors with dimensions down to 8 nm. In addition to the conventional 2D patterning and structuring of semiconductors, I will demonstrate how to apply 3D nanostructuring techniques to build freely suspended single-crystal beams with lateral dimension down to 20 nm. In transport measurements in the temperature range from 30 mK up to 100 K these nano-crystals are characterized regarding their electronic as well as their mechanical properties. Moreover, I will present possible applications of these devices.

  2. Beta-MnO2 3D nanostructures: mineralizer-assisted synthesis, characterization, and growth mechanism.

    PubMed

    Zhou, Fu; Zhao, Xuemei; Yuan, Cunguang; Xu, Hai

    2007-09-01

    The beta-MnO2 three-dimensional (3D) nanostructures were synthesized in large area by a mineralizer-assisted hydrothermal route. KNO3 was introduced as inorganic mineralizer to direct the growth of beta-MnO2 3D nanostructures from Mn(NO3)2 solutions. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Possible growth mechanism of beta-MnO2 3D nanostructures was proposed based on comparative experiments, indicating that KNO3 mineralizer and the concentration of Mn(NO3)2 solution were the two decisive factors in the fabrication of beta-MnO2 3D nanostructures.

  3. The beta-SiC(100) surface studied by low energy electron diffraction, Auger electron spectroscopy, and electron energy loss spectra

    NASA Technical Reports Server (NTRS)

    Dayan, M.

    1986-01-01

    The beta-SiC(100) surface has been studied by low energy electron diffraction, Auger electron spectroscopy, high resolution electron energy loss spectra (HREELS), and core level excitation EELS. Two new Si-terminated phases have been discovered, one with (3 x 2) symmetry, and the other with (2 x 1) symmetry. Models are presented to describe these phases. New results, for the C-rich surface, are presented and discussed. In addition, core level excitation EELS results are given and compared with theory.

  4. Diffractive ρ production at small x in future electron-ion colliders

    NASA Astrophysics Data System (ADS)

    Gonçalves, V. P.; Navarra, F. S.; Spiering, D.

    2016-09-01

    The future electron-ion (eA) collider is expected to probe the high energy regime of the quantum chromodynamics (QCD), with the exclusive vector meson production cross section being one of the most promising observables. In this paper we complement previous studies of exclusive processes presenting a comprehensive analysis of diffractive ρ production at small x. We compute the coherent and incoherent cross sections taking into account non-linear QCD dynamical effects and considering different models for the dipole-proton scattering amplitude and vector meson wave function. The dependence of these cross sections on the energy, photon virtuality, nuclear mass number and squared momentum transfer is analysed in detail. Moreover, we compare the non-linear predictions with those obtained in the linear regime. Finally, we also estimate the exclusive photon, J/{{\\Psi }} and ϕ production and compare with the results obtained for ρ production. Our results demonstrate that the analysis of diffractive ρ production in future electron-ion colliders will be important in understanding the non-linear QCD dynamics.

  5. Electron diffraction based analysis of phase fractions and texture in nanocrystalline thin films, part II: implementation.

    PubMed

    Lábár, János L

    2009-02-01

    This series of articles describes a method that performs (semi)quantitative phase analysis for nanocrystalline transmission electron microscope samples from selected area electron diffraction (SAED) patterns. Volume fractions of phases and their textures are obtained separately in the method. First, the two-dimensional SAED pattern is converted into an X-ray diffraction-like one-dimensional distribution. Volume fractions of the nanocrystalline components are determined by fitting the spectral components, calculated for the previously identified phases with a priori known structures. Blackman correction is also applied to take into account dynamic effects for medium grain sizes. Peak shapes and experimental parameters (camera length, etc.) are refined during the fitting iterations. Parameter space is explored with the help of the Downhill-SIMPLEX algorithm. Part I presented the principles, while Part II now elaborates current implementation, and Part III will demonstrate its usage by examples. The method is implemented in a computer program that runs under the Windows operating system on IBM PC compatible machines.

  6. Coherent transition and diffraction radiation from a bunched 6.1 MeV electron beam

    NASA Astrophysics Data System (ADS)

    Naumenko, G. A.; Aleinik, A. N.; Aryshev, A. S.; Kalinin, B. N.; Potylitsyn, A. P.; Saruev, G. A.; Sharafutdinov, A. F.

    2005-01-01

    The theory of transition radiation (TR) from an ideally conducting infinite target is well known. During the last several years the theory of diffraction radiation (DR) from simple geometry targets has further been developed. In a few experiments coherent TR and coherent DR were used to measure the electron bunch length. However, experimental investigations of coherent TR (or DR) look rather poor for finite size targets. The experimental results of investigation of coherent backward transition radiation (CBTR) and coherent backward diffraction radiation (CBDR) are presented. The intensity of CBTR and CBDR from a finite conducting target for different impact-parameters depending on the target inclination angle θ ( θ-scan) has been investigated using the 6 MeV electron beam of the Tomsk microtron. The model allowing to calculate both TR and DR characteristics for any impact-parameter h (the shortest distance between particle trajectory and target edge) was developed and tested by comparison with experimental results. The calculations were performed for the real experimental conditions. For γλ ≫ h ( γ - Lorentz-factor, λ - TR (DR) wavelength) and large detector bandwidth {γ(λmax-λmin)}/{h}>1 the measured TR angular distribution shows a single maximum only (like DR one) in contrast to a lobe-shaped OTR distribution.

  7. Auger electron diffraction study of V/Fe(100) interface formation

    NASA Astrophysics Data System (ADS)

    Huttel, Y.; Avila, J.; Asensio, M. C.; Bencok, P.; Richter, C.; Ilakovac, V.; Heckmann, O.; Hricovini, K.

    1998-05-01

    Vanadium atoms present a magnetic moment different to zero when they are part of a thin film deposited on Fe or as a bimetallic Fe-V alloy. The understanding of this phenomenon can only be achieved with a correct structural description of these types of systems. We report an Auger electron diffraction investigation of V films grown on body cubic centred (b.c.c.) Fe(100) substrates. Angular-scanned Auger electron diffraction (AED) patterns of V L 23M 23M 4 (473 eV) and Fe L 3VV (703 eV) show the formation of a well-ordered V/Fe interface even at room temperature. The AED patterns of V films in the range of vanadium submonolayer provide evidence of an isotropic Auger emission, indicating the absence of interdiffusion of V atoms into the Fe substrate and absence of cluster growth of the V film. The annealing of these films up to 400°C does not activate the substitution of the topmost Fe surface layers by V atoms.

  8. Structure and conformations of isoprene by vibrational spectroscopy and gas electron diffraction

    NASA Astrophysics Data System (ADS)

    Traetteberg, M.; Paulen, G.; Cyvin, S. J.; Panchenko, Yu. N.; Mochalov, V. I.

    1984-04-01

    The structure of the isoprene (2-methyl-buta-1,3-diene) molecule has been studied by vibrational spectroscopy and gas electron diffraction techniques. A normal coordinate analysis was used to calculate the vibrational frequencies for the anti ( s-trans), gauche and syn ( s-cis) conformers of the molecule. Assignments of some frequencies of the anti form were revised. The experimental bands at 1255, 635, 555, 419 and 311 cm -1 are assigned as fundamentals of the gauche conformer with a high degree of confidence. Among the structural parameters determined by electron diffraction are the following bond distances (in Å): CC 1.340, CC 1.463, CC methyl 1.512, CH 1.076 and CmethylH 1.110. The abundance of the anti form was determined to be 95.3%, while the rest (4.7%) was interpreted as the gauche form with a dihedral angle of 73.5°.

  9. Magnesium: Comparison of density functional theory calculations with electron and x-ray diffraction experiments

    NASA Astrophysics Data System (ADS)

    Friis, J.; Madsen, G. K. H.; Larsen, F. K.; Jiang, B.; Marthinsen, K.; Holmestad, R.

    2003-12-01

    Accurate experimental structure factors for Mg have been measured and compared with density functional theory (DFT) to test some commonly used functionals and self-interaction correction (SIC) schemes. Low order structure factors, free of extinction and on absolute scale, were measured accurately by quantitative convergent beam electron diffraction. In addition, a complete set of structure factors up to sin θ/λ=1.6 Å-1 was measured by x-ray diffraction at 10 K. The DFT calculations were performed using the full potential linearized augmented plane wave method. It was found that the agreement with experiment increases when going from the local density approximation (LDA) to the generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhofer and further to the GGA of Engel and Vosko. Applying the SIC of Perdew and Zunger to the core states for LDA does not improve the agreement with theory, while applying the SIC of Lundin and Eriksson results in a significantly improved agreement. This implies that the main source of error in the LDA functional comes from the description of the core densities. Using the functional which agrees best with experiment, a non-nuclear maximum is established in the calculated electron density of beryllium but not of magnesium.

  10. Influence of orbital symmetry on diffraction imaging with rescattering electron wave packets

    PubMed Central

    Pullen, M. G.; Wolter, B.; Le, A. -T.; Baudisch, M.; Sclafani, M.; Pires, H.; Schröter, C. D.; Ullrich, J.; Moshammer, R.; Pfeifer, T.; Lin, C. D.; Biegert, J.

    2016-01-01

    The ability to directly follow and time-resolve the rearrangement of the nuclei within molecules is a frontier of science that requires atomic spatial and few-femtosecond temporal resolutions. While laser-induced electron diffraction can meet these requirements, it was recently concluded that molecules with particular orbital symmetries (such as πg) cannot be imaged using purely backscattering electron wave packets without molecular alignment. Here, we demonstrate, in direct contradiction to these findings, that the orientation and shape of molecular orbitals presents no impediment for retrieving molecular structure with adequate sampling of the momentum transfer space. We overcome previous issues by showcasing retrieval of the structure of randomly oriented O2 and C2H2 molecules, with πg and πu symmetries, respectively, and where their ionization probabilities do not maximize along their molecular axes. While this removes a serious bottleneck for laser-induced diffraction imaging, we find unexpectedly strong backscattering contributions from low-Z atoms. PMID:27329236

  11. Diffractive imaging of a rotational wavepacket in nitrogen molecules with femtosecond megaelectronvolt electron pulses

    PubMed Central

    Yang, Jie; Guehr, Markus; Vecchione, Theodore; Robinson, Matthew S.; Li, Renkai; Hartmann, Nick; Shen, Xiaozhe; Coffee, Ryan; Corbett, Jeff; Fry, Alan; Gaffney, Kelly; Gorkhover, Tais; Hast, Carsten; Jobe, Keith; Makasyuk, Igor; Reid, Alexander; Robinson, Joseph; Vetter, Sharon; Wang, Fenglin; Weathersby, Stephen; Yoneda, Charles; Centurion, Martin; Wang, Xijie

    2016-01-01

    Imaging changes in molecular geometries on their natural femtosecond timescale with sub-Angström spatial precision is one of the critical challenges in the chemical sciences, as the nuclear geometry changes determine the molecular reactivity. For photoexcited molecules, the nuclear dynamics determine the photoenergy conversion path and efficiency. Here we report a gas-phase electron diffraction experiment using megaelectronvolt (MeV) electrons, where we captured the rotational wavepacket dynamics of nonadiabatically laser-aligned nitrogen molecules. We achieved a combination of 100 fs root-mean-squared temporal resolution and sub-Angstrom (0.76 Å) spatial resolution that makes it possible to resolve the position of the nuclei within the molecule. In addition, the diffraction patterns reveal the angular distribution of the molecules, which changes from prolate (aligned) to oblate (anti-aligned) in 300 fs. Our results demonstrate a significant and promising step towards making atomically resolved movies of molecular reactions. PMID:27046298

  12. Diffractive imaging of a rotational wavepacket in nitrogen molecules with femtosecond megaelectronvolt electron pulses

    DOE PAGES

    Yang, Jie; Guehr, Markus; Vecchione, Theodore; ...

    2016-04-05

    Imaging changes in molecular geometries on their natural femtosecond timescale with sub-Angström spatial precision is one of the critical challenges in the chemical sciences, as the nuclear geometry changes determine the molecular reactivity. For photoexcited molecules, the nuclear dynamics determine the photoenergy conversion path and efficiency. Here we report a gas-phase electron diffraction experiment using megaelectronvolt (MeV) electrons, where we captured the rotational wavepacket dynamics of nonadiabatically laser-aligned nitrogen molecules. We achieved a combination of 100 fs root-mean-squared temporal resolution and sub-Angstrom (0.76 Å) spatial resolution that makes it possible to resolve the position of the nuclei within the molecule.more » In addition, the diffraction patterns reveal the angular distribution of the molecules, which changes from prolate (aligned) to oblate (anti-aligned) in 300 fs. Lastly, our results demonstrate a significant and promising step towards making atomically resolved movies of molecular reactions.« less

  13. Influence of orbital symmetry on diffraction imaging with rescattering electron wave packets

    DOE PAGES

    Pullen, M. G.; Wolter, B.; Le, A. -T.; ...

    2016-06-22

    The ability to directly follow and time-resolve the rearrangement of the nuclei within molecules is a frontier of science that requires atomic spatial and few-femtosecond temporal resolutions. While laser-induced electron diffraction can meet these requirements, it was recently concluded that molecules with particular orbital symmetries (such as pg) cannot be imaged using purely backscattering electron wave packets without molecular alignment. Here, we demonstrate, in direct contradiction to these findings, that the orientation and shape of molecular orbitals presents no impediment for retrieving molecular structure with adequate sampling of the momentum transfer space. We overcome previous issues by showcasing retrieval ofmore » the structure of randomly oriented O2 and C2H2 molecules, with πg and πu symmetries, respectively, and where their ionization probabilities do not maximize along their molecular axes. As a result, while this removes a serious bottleneck for laser-induced diffraction imaging, we find unexpectedly strong backscattering contributions from low-Z atoms.« less

  14. Influence of orbital symmetry on diffraction imaging with rescattering electron wave packets

    SciTech Connect

    Pullen, M. G.; Wolter, B.; Le, A. -T.; Baudisch, M.; Sclafani, M.; Pires, H.; Schroter, C. D.; Ullrich, J.; Moshammer, R.; Pfeifer, T.; Lin, C. D.; Biegert, J.

    2016-06-22

    The ability to directly follow and time-resolve the rearrangement of the nuclei within molecules is a frontier of science that requires atomic spatial and few-femtosecond temporal resolutions. While laser-induced electron diffraction can meet these requirements, it was recently concluded that molecules with particular orbital symmetries (such as pg) cannot be imaged using purely backscattering electron wave packets without molecular alignment. Here, we demonstrate, in direct contradiction to these findings, that the orientation and shape of molecular orbitals presents no impediment for retrieving molecular structure with adequate sampling of the momentum transfer space. We overcome previous issues by showcasing retrieval of the structure of randomly oriented O2 and C2H2 molecules, with πg and πu symmetries, respectively, and where their ionization probabilities do not maximize along their molecular axes. As a result, while this removes a serious bottleneck for laser-induced diffraction imaging, we find unexpectedly strong backscattering contributions from low-Z atoms.

  15. 3-D Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Moore, Gregory F.

    2009-05-01

    This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three-dimensional (3-D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3-D seismic data acquisition and processing. Standard 3-D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple-azimuth and wide-azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.

  16. Radiochromic 3D Detectors

    NASA Astrophysics Data System (ADS)

    Oldham, Mark

    2015-01-01

    Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.

  17. Doubly-excited {sup 1,3}D{sup e} resonance states of two-electron positive ions Li{sup +} and Be{sup 2+} in Debye plasmas

    SciTech Connect

    Kar, Sabyasachi; Wang, Yang; Jiang, Zishi; Li, Shuxia; Ratnavelu, K.

    2014-01-15

    We investigate the bound {sup 1,3}D states and the doubly-excited {sup 1,3}D{sup e} resonance states of two-electron positive ions Li{sup +} and Be{sup 2+} by employing correlated exponential wave functions. In the framework of the stabilization method, we are able to extract three series (2pnp, 2snd, 2pnf) of {sup 1}D{sup e} resonances and two series (2pnp, 2snd) of {sup 3}D{sup e} resonances below the N = 2 threshold. The {sup 1,3}D{sup e} resonance parameters (resonance energies and widths) for Li{sup +} and Be{sup 2+} along with the bound-excited 1s3d {sup 1,3}D state energies are reported for the first time as functions of the screening parameter. Accurate resonance energies and widths are also reported for Li{sup +} and Be{sup 2+} in vacuum. For free-atomic cases, comparisons are made with the reported results and few resonance states are reported for the first time.

  18. Metallographic Preparation of Space Shuttle Reaction Control System Thruster Electron Beam Welds for Electron Backscatter Diffraction

    NASA Technical Reports Server (NTRS)

    Martinez, James

    2011-01-01

    A Space Shuttle Reaction Control System (RCS) thruster failed during a firing test at the NASA White Sands Test Facility (WSTF), Las Cruces, New Mexico. The firing test was being conducted to investigate a previous electrical malfunction. A number of cracks were found associated with the fuel closure plate/injector assembly (Fig 1). The firing test failure generated a flight constraint to the launch of STS-133. A team comprised of several NASA centers and other research institutes was assembled to investigate and determine the root cause of the failure. The JSC Materials Evaluation Laboratory was asked to compare and characterize the outboard circumferential electron beam (EB) weld between the fuel closure plate (Titanium 6Al-4V) and the injector (Niobium C-103 alloy) of four different RCS thrusters, including the failed RCS thruster. Several metallographic challenges in grinding/polishing, and particularly in etching were encountered because of the differences in hardness, ductility, and chemical resistance between the two alloys and the bimetallic weld. Segments from each thruster were sectioned from the outboard weld. The segments were hot-compression mounted using a conductive, carbon-filled epoxy. A grinding/polishing procedure for titanium alloys was used [1]. This procedure worked well on the titanium; but a thin, disturbed layer was visible on the niobium surface by means of polarized light. Once polished, each sample was micrographed using bright field, differential interference contrast optical microscopy, and scanning electron microscopy (SEM) using a backscatter electron (BSE) detector. No typical weld anomalies were observed in any of the cross sections. However, areas of large atomic contrast were clearly visible in the weld nugget, particularly along fusion line interfaces between the titanium and the niobium. This prompted the need to better understand the chemistry and microstructure of the weld (Fig 2). Energy Dispersive X-Ray Spectroscopy (EDS