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Sample records for advanced electronic structure

  1. Advanced accelerating structures and their interaction with electron beams.

    SciTech Connect

    Gai, W.; High Energy Physics

    2008-01-01

    In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a {approx}80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

  2. Advanced Accelerating Structures and Their Interaction with Electron Beams

    SciTech Connect

    Gai Wei

    2009-01-22

    In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a {approx}80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

  3. Preface: Special Topic Section on Advanced Electronic Structure Methods for Solids and Surfaces

    SciTech Connect

    Michaelides, Angelos; Martinez, Todd J.; Alavi, Ali; Kresse, Georg

    2015-09-14

    This Special Topic section on Advanced Electronic Structure Methods for Solids and Surfaces contains a collection of research papers that showcase recent advances in the high accuracy prediction of materials and surface properties. It provides a timely snapshot of a growing field that is of broad importance to chemistry, physics, and materials science.

  4. Advancing Efficient All-Electron Electronic Structure Methods Based on Numeric Atom-Centered Orbitals for Energy Related Materials

    NASA Astrophysics Data System (ADS)

    Blum, Volker

    This talk describes recent advances of a general, efficient, accurate all-electron electronic theory approach based on numeric atom-centered orbitals; emphasis is placed on developments related to materials for energy conversion and their discovery. For total energies and electron band structures, we show that the overall accuracy is on par with the best benchmark quality codes for materials, but scalable to large system sizes (1,000s of atoms) and amenable to both periodic and non-periodic simulations. A recent localized resolution-of-identity approach for the Coulomb operator enables O (N) hybrid functional based descriptions of the electronic structure of non-periodic and periodic systems, shown for supercell sizes up to 1,000 atoms; the same approach yields accurate results for many-body perturbation theory as well. For molecular systems, we also show how many-body perturbation theory for charged and neutral quasiparticle excitation energies can be efficiently yet accurately applied using basis sets of computationally manageable size. Finally, the talk highlights applications to the electronic structure of hybrid organic-inorganic perovskite materials, as well as to graphene-based substrates for possible future transition metal compound based electrocatalyst materials. All methods described here are part of the FHI-aims code. VB gratefully acknowledges contributions by numerous collaborators at Duke University, Fritz Haber Institute Berlin, TU Munich, USTC Hefei, Aalto University, and many others around the globe.

  5. Advances in Single-Particle Electron Cryomicroscopy Structure Determination applied to Sub-tomogram Averaging

    PubMed Central

    Bharat, Tanmay A.M.; Russo, Christopher J.; Löwe, Jan; Passmore, Lori A.; Scheres, Sjors H.W.

    2015-01-01

    Summary Recent innovations in specimen preparation, data collection, and image processing have led to improved structure determination using single-particle electron cryomicroscopy (cryo-EM). Here we explore some of these advances to improve structures determined using electron cryotomography (cryo-ET) and sub-tomogram averaging. We implement a new three-dimensional model for the contrast transfer function, and use this in a regularized likelihood optimization algorithm as implemented in the RELION program. Using direct electron detector data, we apply both single-particle analysis and sub-tomogram averaging to analyze radiation-induced movements of the specimen. As in single-particle cryo-EM, we find that significant sample movements occur during tomographic data acquisition, and that these movements are substantially reduced through the use of ultrastable gold substrates. We obtain a sub-nanometer resolution structure of the hepatitis B capsid, and show that reducing radiation-induced specimen movement may be central to attempts at further improving tomogram quality and resolution. PMID:26256537

  6. Advanced Electronic Technology.

    DTIC Science & Technology

    1978-11-15

    It AD AObS 062 MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB F/S 9/S ADVANCED ELECTRONIC TECHNOLOGY .(U) NOV 78 A J MCLAUGHLIN. A L MCWHORTER...T I T U T E OF T E C H N O L O G Y L I N C O L N L A B O R A T O R Y ADVANCED ELECTRONIC TECHNOLOGY QUARTERLY TECKNICAL SUMMAR Y REPORT TO THE AIR...Division 8 (Solid State) on the Advanced Electronic Technology Program. Hi

  7. Recent advances in electronic structure theory and their influence on the accuracy of ab initio potential energy surfaces

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

    1988-01-01

    Recent advances in electronic structure theory and the availability of high speed vector processors have substantially increased the accuracy of ab initio potential energy surfaces. The recently developed atomic natural orbital approach for basis set contraction has reduced both the basis set incompleteness and superposition errors in molecular calculations. Furthermore, full CI calculations can often be used to calibrate a CASSCF/MRCI approach that quantitatively accounts for the valence correlation energy. These computational advances also provide a vehicle for systematically improving the calculations and for estimating the residual error in the calculations. Calculations on selected diatomic and triatomic systems will be used to illustrate the accuracy that currently can be achieved for molecular systems. In particular, the F+H2 yields HF+H potential energy hypersurface is used to illustrate the impact of these computational advances on the calculation of potential energy surfaces.

  8. Recent advances in electronic structure theory and their influence on the accuracy of ab initio potential energy surfaces

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

    1989-01-01

    Recent advances in electronic structure theory and the availability of high speed vector processors have substantially increased the accuracy of ab initio potential energy surfaces. The recently developed atomic natural orbital approach for basis set contraction has reduced both the basis set incompleteness and superposition errors in molecular calculations. Furthermore, full CI calculations can often be used to calibrate a CASSCF/MRCI approach that quantitatively accounts for the valence correlation energy. These computational advances also provide a vehicle for systematically improving the calculations and for estimating the residual error in the calculations. Calculations on selected diatomic and triatomic systems will be used to illustrate the accuracy that currently can be achieved for molecular systems. In particular, the F + H2 yields HF + H potential energy hypersurface is used to illustrate the impact of these computational advances on the calculation of potential energy surfaces.

  9. Advanced three-dimensional electron microscopy techniques in the quest for better structural and functional materials

    PubMed Central

    Schryvers, D; Cao, S; Tirry, W; Idrissi, H; Van Aert, S

    2013-01-01

    After a short review of electron tomography techniques for materials science, this overview will cover some recent results on different shape memory and nanostructured metallic systems obtained by various three-dimensional (3D) electron imaging techniques. In binary Ni–Ti, the 3D morphology and distribution of Ni4Ti3 precipitates are investigated by using FIB/SEM slice-and-view yielding 3D data stacks. Different quantification techniques will be presented including the principal ellipsoid for a given precipitate, shape classification following a Zingg scheme, particle distribution function, distance transform and water penetration. The latter is a novel approach to quantifying the expected matrix transformation in between the precipitates. The different samples investigated include a single crystal annealed with and without compression yielding layered and autocatalytic precipitation, respectively, and a polycrystal revealing different densities and sizes of the precipitates resulting in a multistage transformation process. Electron tomography was used to understand the interaction between focused ion beam-induced Frank loops and long dislocation structures in nanobeams of Al exhibiting special mechanical behaviour measured by on-chip deposition. Atomic resolution electron tomography is demonstrated on Ag nanoparticles in an Al matrix. PMID:27877554

  10. Advanced Power Electronics Components

    NASA Technical Reports Server (NTRS)

    Schwarze, Gene E.

    2004-01-01

    This paper will give a description and status of the Advanced Power Electronics Materials and Components Technology program being conducted by the NASA Glenn Research Center for future aerospace power applications. The focus of this research program is on the following: 1) New and/or significantly improved dielectric materials for the development of power capacitors with increased volumetric efficiency, energy density, and operating temperature. Materials being investigated include nanocrystalline and composite ceramic dielectrics and diamond-like carbon films; 2) New and/or significantly improved high frequency, high temperature, low loss soft magnetic materials for the development of transformers/inductors with increased power/energy density, electrical efficiency, and operating temperature. Materials being investigated include nanocrystalline and nanocomposite soft magnetic materials; 3) Packaged high temperature, high power density, high voltage, and low loss SiC diodes and switches. Development of high quality 4H- and 6H- SiC atomically smooth substrates to significantly improve device performance is a major emphasis of the SiC materials program; 4) Demonstration of high temperature (> 200 C) circuits using the components developed above.

  11. Ultrastructure Processing and Environmental Stability of Advanced Structural and Electronic Materials.

    DTIC Science & Technology

    1983-03-01

    network dissolution, electron beam simulated desorption, electron signal decay, oxidation, oxide layer , growth kinetics, silicon carbide, assivation...surface layers on silicate glasses are reviewed. A type IIIB glass surface is proposed. The mechanisms of hydrothermal attack of two phase lithia...method to make reliable lifetime predictions. Use of electron beam techniques is essential for understanding surface layers formed on glasses (Section III

  12. ADVANCED ELECTRONIC PACKAGING TECHNIQUES

    DTIC Science & Technology

    MICROMINIATURIZATION (ELECTRONICS), *PACKAGED CIRCUITS, CIRCUITS, EXPERIMENTAL DATA, MANUFACTURING, NONDESTRUCTIVE TESTING, RESISTANCE (ELECTRICAL), SEMICONDUCTORS, TESTS, THIN FILMS (STORAGE DEVICES), WELDING.

  13. Magnetic and Structural characterization of Co nanowires using advanced electron microscopy techniques

    NASA Astrophysics Data System (ADS)

    Cantu-Valle, Jesus; Ruiz-Zepeda, Francisco; Sanchez, John Eder; Mendoza-Santoyo, Fernando; Ponnce, Arturo; UTSA Team

    2015-03-01

    We report the magnetic imaging and crystalline structure of high aspect ratio cobalt nanowires. Experimental results of magnetization reversal in cobalt nanowires are presented to illustrate the functionality of the in situ magnetization process through the manipulation of the objective lens. By making use of this applicability, we measure the magnetization and show experimental evidence of the magnetic flux distribution in polycrystalline cobalt nanowires using off-axis electron holography. The retrieved phase map can distinguishes the magnetic contribution from the crystalline contribution with high accuracy. To determine the size and orientation of the grains within the Co nanowires, PED-assisted orientation mapping was performed. Finally, the magnetic analysis performed at individual nanowires was correlated with the crystalline orientation map, obtained by PED-assisted crystal phase orientation mapping. The large shape anisotropy determines the mayor magnetization direction rather than the magneto-crystalline anisotropy in the studied nanowires. The combination of the two techniques allowed us to directly visualize the effects of the crystallographic texture on the magnetization of the nanowire. The authors would like to acknowledge Dr. B.J.H. Stadler for providing the samples and financial support from NSF PREM #DMR 0934218, CONACYT, #215762 and Department of Defense #64756-RT-REP.

  14. Advanced electron microscopy for advanced materials.

    PubMed

    Van Tendeloo, Gustaaf; Bals, Sara; Van Aert, Sandra; Verbeeck, Jo; Van Dyck, Dirk

    2012-11-08

    The idea of this Review is to introduce newly developed possibilities of advanced electron microscopy to the materials science community. Over the last decade, electron microscopy has evolved into a full analytical tool, able to provide atomic scale information on the position, nature, and even the valency atoms. This information is classically obtained in two dimensions (2D), but can now also be obtained in 3D. We show examples of applications in the field of nanoparticles and interfaces.

  15. Experimentally characterizing the electronic structures of f-electron systems using advanced high resolution Fourier transform microwave spectroscopies

    SciTech Connect

    Cooke, Stephen, A

    2013-02-03

    We aim to (i) provide data that directly addresses the fundamental roles of actinide valence electrons in chemical bonding, and (ii) serve to provide prototypical data for the heavy element computational chemistry community. These goals will be achieved through the first pure rotational spectroscopic measurements on prototypical systems at ultra-high resolution. These systems encompass low oxidation state uranium and thorium compounds including, but not limited to, UX and ThX, X = F, Cl, Br, I, and UY and ThY, Y = O, S, and other simple U and Th-containing compounds. Our primary experimental tools involve time-domain rotational spectroscopy achieving line widths and resolutions of a few kHz.

  16. Ultrastructure Processing and Environmental Stability of Advanced Structural and Electronic Materials

    DTIC Science & Technology

    1988-09-01

    the Proceedings of the MRS Spring Meeting, Reno, Nevada, April 5-9, 1988. "Physical and Structural Evolution of Sol - Gel Derived TiO2 -SiO 2 Glasses...science oE chemically derived, ultrastructure processing of ceramics, glasses and composites. Five research areas were pursued. (A) Sol - Gel Processing...Procedures for reliable and reproducible drying of sol - gel silica monoliths were developed using drying control chemical additives (DCCA’s

  17. Advanced Electron Microscopy in Materials Physics

    SciTech Connect

    Zhu, Y.; Jarausch, K.

    2009-06-01

    Aberration correction has opened a new frontier in electron microscopy by overcoming the limitations of conventional round lenses, providing sub-angstrom-sized probes and extending information limits. The imaging and analytical performance of these corrector-equipped microscopes affords an unprecedented opportunity to study structure-property relationships of matter at the atomic scale. This new generation of microscopes is able to retrieve high-quality structural information comparable to neutron and synchrotron x-ray experiments, but with local atomic resolution. These advances in instrumentation are accelerating the research and development of various functional materials ranging from those for energy generation, conversion, transportation and storage to those for catalysis and nano-device applications. The dramatic improvements in electron-beam illumination and detection also present a host of new challenges for the interpretation and optimization of experiments. During 7-9 November 2007, a workshop, entitled 'Aberration Corrected Electron Microscopy in Material Physics', was convened at the Center for Functional Nanomaterials, Brookhaven National Laboratories (BNL) to address these opportunities and challenges. The workshop was co-sponsored by Hitachi High Technologies, a leader in electron microscopy instrumentation, and BNL's Institute of Advanced Electron Microscopy, a leader in materials physics research using electron microscopy. The workshop featured presentations by internationally prominent scientists working at the frontiers of electron microscopy, both on developing instrumentation and applying it in materials physics. The meeting, structured to stimulate scientific exchanges and explore new capabilities, brought together {approx}100 people from over 10 countries. This special issue complies many of the advances in instrument performance and materials physics reported by the invited speakers and attendees at the workshop.

  18. Advanced uncooled infrared system electronics

    NASA Astrophysics Data System (ADS)

    Neal, Henry W.

    1998-07-01

    Over the past two decades, Raytheon Systems Company (RSC), formerly Texas Instruments Defense Systems & Electronics Group, developed a robust family of products based on a low- cost, hybrid ferroelectric (FE) uncooled focal-plane array (FPA) aimed at meeting the needs for thermal imaging products across both military and commercial markets. Over the years, RSC supplied uncooled infrared (IR) sensors for applications such as in combat vehicles, man-portable weaponry, personnel helmets, and installation security. Also, various commercial IR systems for use in automobiles, boats, law enforcement, hand-held applications, building/site security, and fire fighting have been developed. These products resulted in a high degree of success where cooled IR platforms are too bulky and costly, and other uncooled implementations are less reliable or lack significant cost advantage. Proof of this great success is found in the large price reductions, the unprecedented monthly production rates, and the wide diversity of products and customers realized in recent years. The ever- changing needs of these existing and potential customers continue to fuel the advancement of both the primary technologies and the production capabilities of uncooled IR systems at RSC. This paper will describe a development project intended to further advance the system electronics capabilities of future uncooled IR products.

  19. Advances in nonlethal electronic weaponry

    NASA Astrophysics Data System (ADS)

    McNulty, James F.

    1998-12-01

    Non-lethal electronic weapons in the form of tasers (a stand-off incapacitation device with a range of about 15 feet) and stun guns (which are not a gun, but a close contact stun device) have been used by law enforcement for over 18 years. The taser has dominated this market, since it does not require the close physical contact (with the resultant injuries) that the stun gun requires. Tasers are effective against even determined assailants where OC or pepper sprays consistently fail. The taser also does not have the close range lethality of low impact munitions. These electronic non-lethal weapons have saved the lives of thousands of suspects and have prevented the injury of thousands of law enforcement officers. Recent advances in laser sight technology have permitted the development of a patented dual laser sight that not only increased accuracy, but have made these weapons even more intimidating, increasing surrender rates. Now increased ranges are feasible and r & d on non-lethal military weapons to replace the anti-personnel landmine has resulted in new, unmanned, non-lethal taser weapons for law enforcement corrections and border patrol perimeter control use.

  20. Advances in X-ray free electron laser (XFEL) diffraction data processing applied to the crystal structure of the synaptotagmin-1 / SNARE complex.

    PubMed

    Lyubimov, Artem Y; Uervirojnangkoorn, Monarin; Zeldin, Oliver B; Zhou, Qiangjun; Zhao, Minglei; Brewster, Aaron S; Michels-Clark, Tara; Holton, James M; Sauter, Nicholas K; Weis, William I; Brunger, Axel T

    2016-10-12

    X-ray free electron lasers (XFELs) reduce the effects of radiation damage on macromolecular diffraction data and thereby extend the limiting resolution. Previously, we adapted classical post-refinement techniques to XFEL diffraction data to produce accurate diffraction data sets from a limited number of diffraction images (Uervirojnangkoorn et al., 2015), and went on to use these techniques to obtain a complete data set from crystals of the synaptotagmin-1 / SNARE complex and to determine the structure at 3.5 Å resolution (Zhou et al., 2015). Here, we describe new advances in our methods and present a reprocessed XFEL data set of the synaptotagmin-1 / SNARE complex. The reprocessing produced small improvements in electron density maps and the refined atomic model. The maps also contained more information than those of a lower resolution (4.1 Å) synchrotron data set. Processing a set of simulated XFEL diffraction images revealed that our methods yield accurate data and atomic models.

  1. Recent advances in PC-Linux systems for electronic structure computations by optimized compilers and numerical libraries.

    PubMed

    Yu, Jen-Shiang K; Yu, Chin-Hui

    2002-01-01

    One of the most frequently used packages for electronic structure research, GAUSSIAN 98, is compiled on Linux systems with various hardware configurations, including AMD Athlon (with the "Thunderbird" core), AthlonMP, and AthlonXP (with the "Palomino" core) systems as well as the Intel Pentium 4 (with the "Willamette" core) machines. The default PGI FORTRAN compiler (pgf77) and the Intel FORTRAN compiler (ifc) are respectively employed with different architectural optimization options to compile GAUSSIAN 98 and test the performance improvement. In addition to the BLAS library included in revision A.11 of this package, the Automatically Tuned Linear Algebra Software (ATLAS) library is linked against the binary executables to improve the performance. Various Hartree-Fock, density-functional theories, and the MP2 calculations are done for benchmarking purposes. It is found that the combination of ifc with ATLAS library gives the best performance for GAUSSIAN 98 on all of these PC-Linux computers, including AMD and Intel CPUs. Even on AMD systems, the Intel FORTRAN compiler invariably produces binaries with better performance than pgf77. The enhancement provided by the ATLAS library is more significant for post-Hartree-Fock calculations. The performance on one single CPU is potentially as good as that on an Alpha 21264A workstation or an SGI supercomputer. The floating-point marks by SpecFP2000 have similar trends to the results of GAUSSIAN 98 package.

  2. Electron Structure of Francium

    NASA Astrophysics Data System (ADS)

    Koufos, Alexander

    2012-02-01

    This talk presents the first calculations of the electronic structure of francium for the bcc, fcc and hcp structures, using the Augmented Plane Wave (APW) method in its muffin-tin and linearized general potential forms. Both the Local Density Approximation (LDA) and Generalized Gradient Approximation (GGA), were used to calculate the electronic structure and total energy of francium (Fr). The GGA and LDA both found the total energy of the hcp structure slightly below that of the fcc and bcc structure, respectively. This is in agreement with similar results for the other alkali metals using the same methodology. The equilibrium lattice constant, bulk modulus and superconductivity parameters were calculated. We found that under pressures, in the range of 1-5 GPa, Fr could be a superconductor at a critical temperature of about 4K.

  3. Advanced Electronics. Curriculum Development. Bulletin 1778.

    ERIC Educational Resources Information Center

    Eppler, Thomas

    This document is a curriculum guide for a 180-hour course in advanced electronics for 11th and 12th grades that has four instructional units. The instructional units are orientation, discrete components, integrated circuits, and electronic systems. The document includes a course flow chart; a two-page section that describes the course, lists…

  4. Advanced electron microscopy characterization of multimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna Raj

    Research in noble metal nanoparticles has led to exciting progress in a versatile array of applications. For the purpose of better tailoring of nanoparticles activities and understanding the correlation between their structures and properties, control over the composition, shape, size and architecture of bimetallic and multimetallic nanomaterials plays an important role on revealing their new or enhanced functions for potentials application. Advance electron microscopy techniques were used to provide atomic scale insights into the structure-properties of different materials: PtPd, Au-Au3Cu, Cu-Pt, AgPd/Pt and AuCu/Pt nanoparticles. The objective of this work is to understand the physical and chemical properties of nanomaterials and describe synthesis, characterization, surface properties and growth mechanism of various bimetallic and multimetallic nanoparticles. The findings have provided us with novel and significant insights into the physical and chemical properties of noble metal nanoparticles. Different synthesis routes allowed us to synthesize bimetallic: Pt-Pd, Au-Au3Cu, Cu-Pt and trimetallic: AgPd/Pt, AuCu/Pt, core-shell and alloyed nanoparticles with monodispersed sizes, controlled shapes and tunable surface properties. For example, we have synthesized the polyhedral PtPd core-shell nanoparticles with octahedral, decahedral, and triangular plates. Decahedral PtPd core-shell structures are novel morphologies for this system. For the first time we fabricated that the Au core and Au3Cu alloyed shell nanoparticles passivated with CuS2 surface layers and characterized by Cs-corrected scanning transmission electron microscopy. The analysis of the high-resolution micrographs reveals that these nanoparticles have decahedral structure with shell periodicity, and that each of the particles is composed by Au core and Au3Cu ordered superlattice alloyed shell surrounded by CuS 2 surface layer. Additionally, we have described both experimental and theoretical methods of

  5. Advanced Developments of Electron Spin Labeling as High-Resolution Sensors of Protein Structure and Conformational Switching

    DTIC Science & Technology

    2007-11-02

    Myoglobin (Myb) and Cellular Retinol Binding Protein (CRBP) were prepared, and the corresponding EPR spectra analyzed by simulation techniques. In...unprecedented level of sophistication in interpretation of the EPR spectra of labeled proteins, and establish the feasibility of separating structural and...protein as well as local structure, but to date the level of interpretation has been largely qualitative and it has not been possible to separate the

  6. Advanced Polymer Network Structures

    DTIC Science & Technology

    2016-02-01

    13. SUPPLEMENTARY NOTES 14. ABSTRACT Polymer networks and gels are important classes of materials for defense applications . In an effort to......it is no longer needed. Do not return it to the originator. ARL-TR-7612 ● FEB 2016 US Army Research Laboratory Advanced Polymer

  7. 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.

  8. Advances in X-ray free electron laser (XFEL) diffraction data processing applied to the crystal structure of the synaptotagmin-1 / SNARE complex

    PubMed Central

    Lyubimov, Artem Y; Uervirojnangkoorn, Monarin; Zeldin, Oliver B; Zhou, Qiangjun; Zhao, Minglei; Brewster, Aaron S; Michels-Clark, Tara; Holton, James M; Sauter, Nicholas K; Weis, William I; Brunger, Axel T

    2016-01-01

    X-ray free electron lasers (XFELs) reduce the effects of radiation damage on macromolecular diffraction data and thereby extend the limiting resolution. Previously, we adapted classical post-refinement techniques to XFEL diffraction data to produce accurate diffraction data sets from a limited number of diffraction images (Uervirojnangkoorn et al., 2015), and went on to use these techniques to obtain a complete data set from crystals of the synaptotagmin-1 / SNARE complex and to determine the structure at 3.5 Å resolution (Zhou et al., 2015). Here, we describe new advances in our methods and present a reprocessed XFEL data set of the synaptotagmin-1 / SNARE complex. The reprocessing produced small improvements in electron density maps and the refined atomic model. The maps also contained more information than those of a lower resolution (4.1 Å) synchrotron data set. Processing a set of simulated XFEL diffraction images revealed that our methods yield accurate data and atomic models. DOI: http://dx.doi.org/10.7554/eLife.18740.001 PMID:27731796

  9. Advanced technology composite aircraft structures

    NASA Technical Reports Server (NTRS)

    Ilcewicz, Larry B.; Walker, Thomas H.

    1991-01-01

    Work performed during the 25th month on NAS1-18889, Advanced Technology Composite Aircraft Structures, is summarized. The main objective of this program is to develop an integrated technology and demonstrate a confidence level that permits the cost- and weight-effective use of advanced composite materials in primary structures of future aircraft with the emphasis on pressurized fuselages. The period from 1-31 May 1991 is covered.

  10. Ion beam processing of advanced electronic materials

    SciTech Connect

    Cheung, N.W.; Marwick, A.D.; Roberto, J.B.; International Business Machines Corp., Yorktown Heights, NY . Thomas J. Watson Research Center; Oak Ridge National Lab., TN )

    1989-01-01

    This report contains research programs discussed at the materials research society symposia on ion beam processing of advanced electronic materials. Major topics include: shallow implantation and solid-phase epitaxy; damage effects; focused ion beams; MeV implantation; high-dose implantation; implantation in III-V materials and multilayers; and implantation in electronic materials. Individual projects are processed separately for the data bases. (CBS)

  11. Advanced Electronics Systems 1, Industrial Electronics 3: 9327.03.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    The 135 clock-hour course for the 12th year consists of outlines for blocks of instruction on transistor applications to basic circuits, principles of single sideband communications, maintenance practices, preparation for FCC licenses, application of circuits to advanced electronic systems, nonsinusoidal wave shapes, multivibrators, and blocking…

  12. Overview of advanced law enforcement electronic technology

    NASA Astrophysics Data System (ADS)

    Harden, W. R.

    1995-05-01

    Law enforcement and security management are using advanced electronic equipment to increase the effectiveness and efficiency of the budget restricted police officer force. Currently there is also significant national attention concerning the possible utilization of 'military' electronic hardware to implement the much sought after 'force multiplier' which can help to alleviate each jurisdictions economic restrictions. However, as we are now finding, the transfer of 'military' hardware for utilization by law enforcement personnel is not as economically viable as hoped. This paper will address some of the recent advances in electronic technology that are being derived from the military technology base. Additionally, comments are given concerning the economic impact as the technology is transferred to the law enforcement community.

  13. Electronic structure quantum Monte Carlo

    NASA Astrophysics Data System (ADS)

    Bajdich, Michal; Mitas, Lubos

    2009-04-01

    Quantum Monte Carlo (QMC) is an advanced simulation methodology for studies of manybody quantum systems. The QMC approaches combine analytical insights with stochastic computational techniques for efficient solution of several classes of important many-body problems such as the stationary Schrödinger equation. QMC methods of various flavors have been applied to a great variety of systems spanning continuous and lattice quantum models, molecular and condensed systems, BEC-BCS ultracold condensates, nuclei, etc. In this review, we focus on the electronic structure QMC, i.e., methods relevant for systems described by the electron-ion Hamiltonians. Some of the key QMC achievements include direct treatment of electron correlation, accuracy in predicting energy differences and favorable scaling in the system size. Calculations of atoms, molecules, clusters and solids have demonstrated QMC applicability to real systems with hundreds of electrons while providing 90-95% of the correlation energy and energy differences typically within a few percent of experiments. Advances in accuracy beyond these limits are hampered by the so-called fixed-node approximation which is used to circumvent the notorious fermion sign problem. Many-body nodes of fermion states and their properties have therefore become one of the important topics for further progress in predictive power and efficiency of QMC calculations. Some of our recent results on the wave function nodes and related nodal domain topologies will be briefly reviewed. This includes analysis of few-electron systems and descriptions of exact and approximate nodes using transformations and projections of the highly-dimensional nodal hypersurfaces into the 3D space. Studies of fermion nodes offer new insights into topological properties of eigenstates such as explicit demonstrations that generic fermionic ground states exhibit the minimal number of two nodal domains. Recently proposed trial wave functions based on Pfaffians with

  14. Advanced thermal management technologies for defense electronics

    NASA Astrophysics Data System (ADS)

    Bloschock, Kristen P.; Bar-Cohen, Avram

    2012-05-01

    Thermal management technology plays a key role in the continuing miniaturization, performance improvements, and higher reliability of electronic systems. For the past decade, and particularly, the past 4 years, the Defense Advanced Research Projects Agency (DARPA) has aggressively pursued the application of micro- and nano-technology to reduce or remove thermal constraints on the performance of defense electronic systems. The DARPA Thermal Management Technologies (TMT) portfolio is comprised of five technical thrust areas: Thermal Ground Plane (TGP), Microtechnologies for Air-Cooled Exchangers (MACE), NanoThermal Interfaces (NTI), Active Cooling Modules (ACM), and Near Junction Thermal Transport (NJTT). An overview of the TMT program will be presented with emphasis on the goals and status of these efforts relative to the current State-of-the-Art. The presentation will close with future challenges and opportunities in the thermal management of defense electronics.

  15. Advances in positron and electron scattering*

    NASA Astrophysics Data System (ADS)

    Limão-Vieira, Paulo; García, Gustavo; Krishnakumar, E.; Petrović, Zoran; Sullivan, James; Tanuma, Hajime

    2016-10-01

    The topical issue on Advances in Positron and Electron Scattering" combines contributions from POSMOL 2015 together with others devoted to celebrate the unprecedented scientific careers of our loyal colleagues and trusted friends Steve Buckman (Australian National University, Australia) and Michael Allan (University of Fribourg, Switzerland) on the occasion of their retirements. POSMOL 2015, the XVIII International Workshop on Low-Energy Positron and Positronium Physics and the XIX International Symposium on Electron-Molecule Collisions and Swarms, was held at Universidade NOVA de Lisboa, Lisboa, Portugal, from 17-20 July 2015. The international workshop and symposium allowed to achieve a very privileged forum of sharing and developing our scientific expertise on current aspects of positron, positronium and antiproton interactions with electrons, atoms, molecules and solid surfaces, and related topics, as well as electron interactions with molecules in both gaseous and condensed phases. Particular topics include studies of electron interactions with biomolecules, electron induced surface chemistry and the study of plasma processes. Recent developments in the study of swarms are also fully addressed.

  16. Advanced textile applications for primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Jackson, Anthony C.; Barrie, Ronald E.; Shah, Bharat M.; Shukla, Jay G.

    1992-01-01

    Advanced composite primary structural concepts were evaluated for low cost, damage tolerant structures. Development of advanced textile preforms for fuselage structural applications with resin transfer molding and powder epoxy materials are now under development.

  17. Advanced textile applications for primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Jackson, Anthony C.; Barrie, Ronald E.; Shah, Bharat M.; Shukla, Jay G.

    1992-01-01

    Advanced composite primary structural concepts have been evaluated for low cost, damage tolerant structures. Development of advanced textile preforms for fuselage structural applications with resin transfer molding and powder epoxy material is now under development.

  18. Advanced electronics for the CTF MEG system.

    PubMed

    McCubbin, J; Vrba, J; Spear, P; McKenzie, D; Willis, R; Loewen, R; Robinson, S E; Fife, A A

    2004-11-30

    Development of the CTF MEG system has been advanced with the introduction of a computer processing cluster between the data acquisition electronics and the host computer. The advent of fast processors, memory, and network interfaces has made this innovation feasible for large data streams at high sampling rates. We have implemented tasks including anti-alias filter, sample rate decimation, higher gradient balancing, crosstalk correction, and optional filters with a cluster consisting of 4 dual Intel Xeon processors operating on up to 275 channel MEG systems at 12 kHz sample rate. The architecture is expandable with additional processors to implement advanced processing tasks which may include e.g., continuous head localization/motion correction, optional display filters, coherence calculations, or real time synthetic channels (via beamformer). We also describe an electronics configuration upgrade to provide operator console access to the peripheral interface features such as analog signal and trigger I/O. This allows remote location of the acoustically noisy electronics cabinet and fitting of the cabinet with doors for improved EMI shielding. Finally, we present the latest performance results available for the CTF 275 channel MEG system including an unshielded SEF (median nerve electrical stimulation) measurement enhanced by application of an adaptive beamformer technique (SAM) which allows recognition of the nominal 20-ms response in the unaveraged signal.

  19. Advanced Structures: 2000-2004

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This custom bibliography from the NASA Scientific and Technical Information Program lists a sampling of records found in the NASA Aeronautics and Space Database. The scope of this topic includes technologies for extremely lightweight, multi-function structures with modular interfaces - the building-block technology for advanced spacecraft. This area of focus is one of the enabling technologies as defined by NASA s Report of the President s Commission on Implementation of United States Space Exploration Policy, published in June 2004.

  20. Structural physiology based on electron crystallography

    PubMed Central

    Fujiyoshi, Yoshinori

    2011-01-01

    There are many questions in brain science, which are extremely interesting but very difficult to answer. For example, how do education and other experiences during human development influence the ability and personality of the adult? The molecular mechanisms underlying such phenomena are still totally unclear. However, technological and instrumental advancements of electron microscopy have facilitated comprehension of the structures of biological components, cells, and organelles. Electron crystallography is especially good for studying the structure and function of membrane proteins, which are key molecules of signal transduction in neural and other cells. Electron crystallography is now an established technique to analyze the structures of membrane proteins in lipid bilayers, which are close to their natural biological environment. By utilizing cryo-electron microscopes with helium cooled specimen stages, which were developed through a personal motivation to understand functions of neural systems from a structural point of view, structures of membrane proteins were analyzed at a resolution higher than 3 Å. This review has four objectives. First, it is intended to introduce the new research field of structural physiology. Second, it introduces some of the personal struggles, which were involved in developing the cryo-electron microscope. Third, it discusses some of the technology for the structural analysis of membrane proteins based on cryo-electron microscopy. Finally, it reviews structural and functional analyses of membrane proteins. PMID:21416541

  1. Surface chemical deposition of advanced electronic materials

    NASA Astrophysics Data System (ADS)

    Bjelkevig, Cameron

    The focus of this work was to examine the direct plating of Cu on Ru diffusion barriers for use in interconnect technology and the substrate mediated growth of graphene on boron nitride for use in advanced electronic applications. The electrodeposition of Cu on Ru(0001) and polycrystalline substrates (with and without pretreatment in an iodine containing solution) has been studied by cyclic voltammetry (CV), current--time transient measurements (CTT), in situ electrochemical atomic force microscopy (EC-AFM), and X-ray photoelectron spectroscopy (XPS). The EC-AFM data show that at potentials near the OPD/UPD threshold, Cu crystallites exhibit pronounced growth anisotropy, with lateral dimensions greatly exceeding vertical dimensions. XPS measurements confirmed the presence and stability of adsorbed I on the Ru surface following pre-treatment in a KI/H2SO4 solution and following polarization to at least -200 mV vs. Ag/AgCl. CV data of samples pre-reduced in I-containing electrolyte exhibited a narrow Cu deposition peak in the overpotential region and a UPD peak. The kinetics of the electrodeposited Cu films was investigated by CTT measurements and applied to theoretical models of nucleation. The data indicated that a protective I adlayer may be deposited on an airexposed Ru electrode as the oxide surface is electrochemically reduced, and that this layer will inhibit reformation of an oxide during the Cu electroplating process. A novel method for epitaxial graphene growth directly on a dielectric substrate of systematically variable thickness was studied. Mono/multilayers of BN(111) were grown on Ru(0001) by atomic layer deposition (ALD), exhibiting a flat (non-nanomesh) R30(✓3x✓3) structure. BN(111) was used as a template for growth of graphene by chemical vapor deposition (CVD) of C2H4 at 1000 K. Characterization by LEED, Auger, STM/STS and Raman indicate the graphene is in registry with the BN substrate, and exhibits a HOPG-like 0 eV bandgap density

  2. Advanced technology commercial fuselage structure

    NASA Technical Reports Server (NTRS)

    Ilcewicz, L. B.; Smith, P. J.; Walker, T. H.; Johnson, R. W.

    1991-01-01

    Boeing's program for Advanced Technology Composite Aircraft Structure (ATCAS) has focused on the manufacturing and performance issues associated with a wide body commercial transport fuselage. The primary goal of ATCAS is to demonstrate cost and weight savings over a 1995 aluminum benchmark. A 31 foot section of fuselage directly behind the wing to body intersection was selected for study purposes. This paper summarizes ATCAS contract plans and review progress to date. The six year ATCAS program will study technical issues for crown, side, and keel areas of the fuselage. All structural details in these areas will be included in design studies that incorporate a design build team (DBT) approach. Manufacturing technologies will be developed for concepts deemed by the DBT to have the greatest potential for cost and weight savings. Assembly issues for large, stiff, quadrant panels will receive special attention. Supporting technologies and mechanical tests will concentrate on the major issues identified for fuselage. These include damage tolerance, pressure containment, splices, load redistribution, post-buckled structure, and durability/life. Progress to date includes DBT selection of baseline fuselage concepts; cost and weight comparisons for crown panel designs; initial panel fabrication for manufacturing and structural mechanics research; and toughened material studies related to keel panels. Initial ATCAS studies have shown that NASA's Advanced Composite Technology program goals for cost and weight savings are attainable for composite fuselage.

  3. Advanced Power Electronics and Electric Motors Annual Report -- 2013

    SciTech Connect

    Narumanchi, S.; Bennion, K.; DeVoto, D.; Moreno, G.; Rugh, J.; Waye, S.

    2015-01-01

    This report describes the research into advanced liquid cooling, integrated power module cooling, high temperature air cooled power electronics, two-phase cooling for power electronics, and electric motor thermal management by NREL's Power Electronics group in FY13.

  4. Advances in superconducting quantum electronic microcircuit fabrication

    NASA Technical Reports Server (NTRS)

    Kirschman, R. K.; Notarys, H. A.; Mercereau, J. E.

    1975-01-01

    Standard microelectronic fabrication techniques have been utilized to produce batch quantities of superconducting quantum electronic devices and circuits. The overall goal is a fabrication technology yielding circuits that are rugged and stable and capable of being fabricated controllably and reproducibly in sizeable quantities. Our progress toward this goal is presented, with primary emphasis on the most recent work, which includes the use of electron-beam lithography and techniques of hybrid microelectronics. Several prototype microcircuits have been successfully fabricated. These microcircuits are formed in a thin-film parent material consisting of layers of superconducting and normal metals, and use proximity-effect structures as the active circuit elements.

  5. The Electronic Structure of Heavy Element Complexes

    SciTech Connect

    Bursten, Bruce E.

    2000-07-25

    The area of study is the bonding in heavy element complexes, and the application of more sophisticated electronic structure theories. Progress is recounted in several areas: (a) technological advances and current methodologies - Relativistic effects are extremely important in gaining an understanding of the electronic structure of compounds of the actinides, transactinides, and other heavy elements. Therefore, a major part of the continual benchmarking was the proper inclusion of the appropriate relativistic effects for the properties under study. (b) specific applications - These include organoactinide sandwich complexes, CO activation by actinide atoms, and theoretical studies of molecules of the transactinide elements. Finally, specific directions in proposed research are described.

  6. Advanced strategic interceptor composite structures

    SciTech Connect

    Ennis, D.H.; Patty, C.E. Jr.

    1993-12-31

    Launch mass reduction, stiffness increase, and primary bending mode frequency increase remain the prime focus of the US Army Strategic Defense Command (USASDC) advanced composite material development and testing program. The initial activity was directed toward fabrication of a demonstration structure consistent with the Ground-Based Interceptor (GBI) ERIS flight design. The objectives of this phase of the work were three-fold: selection of the optimum composite materials; concurrent bonding and joining technology development; evaluation of the performance of each test structure relative to its metal counterpart and relative to alternative composites. The effort exceeded model predictions. The resin matrix composite structure mass was 52% lower than the metal design. Modal testing demonstrated a 200% increase in stiffness and a 41% gain in first mode bending frequency. Given the demonstrated level of success, an additional element was added to the task focus: cost-effective, mass quantity fabrication techniques. Single step technology has been successfully applied to a relatively simple thermoset based bridge structure. Two step molding and assembly have been demonstrated for a GBI-X class thermoplastic structure. Preliminary testing has been completed to isolate and resolve problems associated with single step fabrication of the more complex GBI-X class structure. Fabrication of an appropriate test article as preparation for modal survey evaluation of the latter is in progress. Results are presented. Future program directions are summarized.

  7. Structural tailoring of advanced turboprops

    NASA Technical Reports Server (NTRS)

    Brown, K. W.; Hopkins, Dale A.

    1988-01-01

    The Structural Tailoring of Advanced Turboprops (STAT) computer program was developed to perform numerical optimization on highly swept propfan blades. The optimization procedure seeks to minimize an objective function defined as either: (1) direct operating cost of full scale blade or, (2) aeroelastic differences between a blade and its scaled model, by tuning internal and external geometry variables that must satisfy realistic blade design constraints. The STAT analysis system includes an aerodynamic efficiency evaluation, a finite element stress and vibration analysis, an acoustic analysis, a flutter analysis, and a once-per-revolution forced response life prediction capability. STAT includes all relevant propfan design constraints.

  8. Quantum functional devices for advanced electronics

    NASA Astrophysics Data System (ADS)

    Yokoyama, N.; Muto, S.; Imamura, K.; Takatsu, M.; Mori, T.; Sugiyama, Y.; Sakuma, Y.; Nakao, H.; Adachihara, T.

    Recent research in semiconductor device technology seems to be focused on reducing the cost and power dissipation of traditional Si CMOS integrated circuits, rather than developing new and advanced semiconductor devices. We believe however, that devices enter the nanometer-scale regime in the next century, where quantum mechanical effects play an important role in the device's function; therefore, it is important to continue basic research into the physics and technology of nanometer scale structures and device applications in order to cultivate "nanoelectronics". This paper reviews our research activities on quantum functional devices and discusses our future research direction.

  9. Advanced Electronic Systems. Curriculum Guide for Technology Education.

    ERIC Educational Resources Information Center

    Patrick, Dale R.

    This curriculum for a 1-semester or 1-year course in electronics is designed to take students from basic through advanced electronic systems. It covers several electronic areas, such as digital electronics, communication electronics, industrial process control, instrumentation, programmable controllers, and robotics. The guide contains…

  10. High resolution X-ray CT for advanced electronics packaging

    NASA Astrophysics Data System (ADS)

    Oppermann, M.; Zerna, T.

    2017-02-01

    Advanced electronics packaging is a challenge for non-destructive Testing (NDT). More, smaller and mostly hidden interconnects dominate modern electronics components and systems. To solve the demands of customers to get products with a high functionality by low volume, weight and price (e.g. mobile phones, personal medical monitoring systems) often the designers use System-in-Package solutions (SiP). The non-destructive testing of such devices is a big challenge. So our paper will impart fundamentals and applications for non-destructive evaluation of inner structures of electronics packaging for quality assurance and reliability investigations with a focus on X-ray methods, especially on high resolution X-ray computed tomography (CT).

  11. Commercial applications of electron beam advanced oxidation technology

    NASA Astrophysics Data System (ADS)

    Curry, Randy D.; Bosma, John T.

    1995-03-01

    Emerging commercial applications of electron-beam advanced oxidation technology offer a significant advancement in the treatment of waste steams. Both electron beam and X-ray (Brehmsstrahlung) advanced oxidation processes have been shown to be effective in the destruction of volatile and semivolatile organic compounds. Emerging commercial applications, however, far exceed in scope current applications of oxidation technologies for the destruction of simple semivolatile and volatile organic compounds in water. Emerging applications include direct treatment of contaminated soil, removal of metal ions from water and sterilization of water, sludges, and food. Application of electron beam advanced oxidation technologies are reviewed, along with electron- beam-generated X-ray (Brehmsstrahlung) advanced oxidation processes. Advantages of each technology are discussed along with advanced accelerator technologies which are applicable for commercial processing of waste streams. An overview of the U.S. companies and laboratories participating in this research area are included in this discussion.

  12. Theoretical electronic structure of structurally modified graphene

    NASA Astrophysics Data System (ADS)

    Dvorak, Marc David

    Graphene has emerged as a promising replacement for silicon in next-generation electronics and optoelectronic devices. If graphene is to be used in semiconductor devices, however, it must acquire an electronic band gap. Numerous approaches have been proposed to control the band gap of graphene, including the periodic patterning of defects. However, the mechanism for band gap opening and the associated physics in graphene patterned with defects remain unclear. Using both analytic theory and first-principles calculations, we show that periodic patterning of defects on graphene can open a large and tunable band gap, induce strong absorption peaks at optical wavelengths, and host a giant band gap quantum spin Hall phase. First, a geometric rule is analytically derived for the arrangements of defects that open a band gap in graphene, with one ninth of all possible patterns opening a band gap. Next, we perform ab-initio density functional calculations to compare the effects of structural vacancies, hexagonal BN dopants, and passivants on the electronic structure of graphene. Qualitatively, these three types of structural defects behave the same, with only slight differences in their resulting band structures. By adjusting the shape of structural defects, we show how to move the Dirac cones in reciprocal space in accordance with the tight-binding model for the anisotropic honeycomb lattice, while the fundamental mechanism for band gap opening remains the same. To quantitatively predict the band gap and optical properties of these materials, we employ many-body perturbation theory with Green's functions (GW/Bethe-Salpeter equation) to directly include electron-electron and electron-hole interactions. Structurally modified graphene shows a strong renormalization of the fundamental band gap over single particle descriptions, and a strong electron-hole interaction as indicated by strong exciton binding energies (> 0.5 eV). Finally, we show that structurally modified graphene

  13. Electronic Structure Principles and Aromaticity

    ERIC Educational Resources Information Center

    Chattaraj, P. K.; Sarkar, U.; Roy, D. R.

    2007-01-01

    The relationship between aromaticity and stability in molecules on the basis of quantities such as hardness and electrophilicity is explored. The findings reveal that aromatic molecules are less energetic, harder, less polarizable, and less electrophilic as compared to antiaromatic molecules, as expected from the electronic structure principles.

  14. Electron Scattering and Nuclear Structure

    ERIC Educational Resources Information Center

    Trower, W. P.; Ficenec, J. R.

    1971-01-01

    Presents information about the nucleus gained by studies of electron scattering. Discusses what can be implied about the shape of the charge distribution, the nucleus positions, the vibrational modes of the nucleus, the momentum of the nucleus, and the granularity and core structures of the nucleus. (DS)

  15. Advanced Concepts for Electron-Ion Collider

    SciTech Connect

    Yaroslav Derbenev

    2002-08-01

    A superconducting energy recovery linac (ERL) of 5 to 10 GeV was proposed earlier as an alternative to electron storage rings to deliver polarized electron beam for electron-ion collider (EIC). To enhance the utilization efficiency of electron beam from a polarized source, it is proposed to complement the ERL by circulator ring (CR) wherein the injected electrons undergo up to 100 revolutions colliding with the ion beam. In this way, electron injector and linac operate in pulsed current (beam energy recovery) regime of a relatively low average current, while the polarization is still easily delivered and preserved. To make it also easier delivering and manipulating the proton and light ion polarization, twisted (figure 8) synchrotrons are proposed for heavy particle booster and collider ring. Same type of beam orbit can be used then for electron circulator. Electron cooling (EC) of the ion beam is considered an inevitable component of high luminosity EIC (1033/s. cm2 or above). It is recognized that EC also gives a possibility to obtain very short ion bunches, that allows much stronger final focusing. At the same time, short bunches make feasible the crab crossing (and traveling focus for ion beam) at collision points, hence, allow maximizing the collision rate. As a result, one can anticipate the luminosity increase by one or two orders of magnitude.

  16. Advanced nanoimprint patterning for functional electronics and biochemical sensing

    NASA Astrophysics Data System (ADS)

    Wang, Chao

    Nano-fabrication has been widely used for a variety of disciplines, including electronics, material science, nano-optics, and nano-biotechnology. This dissertation focuses on nanoimprint lithography (NIL) based novel nano-patterning techniques for fabricating functional structures, and discusses their applications in advanced electronics and high-sensitivity molecular sensing. In this dissertation, examples of using nano-fabricated structures for promising electronic applications are presented. For instance, 10 nm and 18 nm features are NIL-fabricated for Si/SiGe heterojunction tunneling transistors and graphene nano-ribbon transistors, using shadow evaporation and line-width shrinking techniques, respectively. An ultrafast laser melting based method is applied on flexible plastic substrates to correct defects of nano-features. Nano-texturing of sapphire substrate is developed to improve the light extraction of GaN light emitting diodes (LEDs) by 70 %. A novel multi-layer nano-patterned Si-mediated catalyst is discovered to grow straight and uniform Si nanowires with optimized properties in size, location, and crystallization on amorphous SiO2 substrate. Nano-structures are also functionalized into highly sensitive bio-chemical sensors. Plasmonic nano-bar antenna arrays are demonstrated to effectively sense infrared molecules >10 times better than conventional plasmonic sensors. As small as 20 nm wide nano-channel fluidic devices are developed to linearize and detect DNA molecules for potential DNA sequencing. An integrated fluidic system is built to incorporate plasmonic nano-structures for 30X-enhanced fluorescence detection of large DNA molecules.

  17. Structural Dynamics of Electronic Systems

    NASA Astrophysics Data System (ADS)

    Suhir, E.

    2013-03-01

    The published work on analytical ("mathematical") and computer-aided, primarily finite-element-analysis (FEA) based, predictive modeling of the dynamic response of electronic systems to shocks and vibrations is reviewed. While understanding the physics of and the ability to predict the response of an electronic structure to dynamic loading has been always of significant importance in military, avionic, aeronautic, automotive and maritime electronics, during the last decade this problem has become especially important also in commercial, and, particularly, in portable electronics in connection with accelerated testing of various surface mount technology (SMT) systems on the board level. The emphasis of the review is on the nonlinear shock-excited vibrations of flexible printed circuit boards (PCBs) experiencing shock loading applied to their support contours during drop tests. At the end of the review we provide, as a suitable and useful illustration, the exact solution to a highly nonlinear problem of the dynamic response of a "flexible-and-heavy" PCB to an impact load applied to its support contour during drop testing.

  18. Advances in High-Temperature Electronics

    NASA Astrophysics Data System (ADS)

    Normann, R. A.; Henfling, J. A.

    2001-05-01

    It has long been known that SOI (Silicon-On-Insulator) electronics are more resistant to elevated temperatures and radiation than common bulk silicon devices. Bulk silicon devices are used in consumer grade electronics. A new line of SOI devices have a proven life of 5 years at 225\\deg C where commercial electronics have an 80% failure rate at 180\\deg C and above. This improvement is the result of building each transistor on a non-conductive 'glass' substrate. The transistor isolation reduces the effects of heat, radiation and in general provides for better performing devices with greatly increased life expectancies. This paper shows how SOI electronics can greatly increase the instrumentation life of permanently installed electronics within the wellbore at any temperature. Information is provided from an SOI designed logging tool operating without any heat-shielding up to 300\\deg C. Additional information is provided on the future of micro-machines built out of silicon, silicon-carbide, and diamond. Silicon micro-machines are already being used to measure pressure, inclination, rotation and vibration. In the future, these micro-machines will offer a significant jump in technology for wellbore instrumentation.

  19. Hot electron injector Gunn diode for advanced driver assistance systems

    NASA Astrophysics Data System (ADS)

    Förster, A.; Lepsa, M. I.; Freundt, D.; Stock, J.; Montanari, S.

    2007-06-01

    This paper reviews the main aspects of the design, fabrication and characterization of GaAs Gunn diodes intended to be used in advanced driver assistance systems. The corresponding Gunn diode based oscillators operate at the microwave frequency of 77 GHz and deliver an output power up to 19.2 dBm (83.2 mW). To fulfill the high demands of the automotive industry, temperature stability and a high grade of frequency purity, the Gunn diode structure includes a hot electron injector. This is based on the heteroepitaxy of a graded gap AlxGa1-xAs layer and an adjacent thin highly doped GaAs layer. The hot electron injector properties are investigated using dc and rf electrical measurements, including the temperature influence as well. Specific production related data of the cavity oscillators using our Gunn diodes are presented. New alternatives, such as the resonant tunneling emitter as a hot electron injector and the Gunn diode based MMIC as oscillator, are introduced.

  20. Electronic structure investigations of quasicrystals

    NASA Astrophysics Data System (ADS)

    Rotenberg, E.; Theis, W.; Horn, K.

    2004-08-01

    We present a review of the determination of density of states (DOS) of quasicrystals using valence band photoemission spectroscopy. The absence of fine or spiky structure in the angle-integrated DOS of quasicrystals suggests the possibility of delocalized electronic states. These were confirmed with angle-resolved photoemission studies, which clearly establish the presence of dispersing features attributed to momentum-dependent bandstructure. Such dispersing states are observed not only for deeper-lying sp states, but also for d-derived bands near the Fermi level. Data from three different high symmetry surfaces of decagonal Al-Ni-Co, an ideal model system, are presented. We find that only a few dominant reciprocal lattice vectors are sufficient to describe the quasiperiodic potential, and the implications for electronic properties are discussed.

  1. Advanced analytical electron microscopy for alkali-ion batteries

    DOE PAGES

    Qian, Danna; Ma, Cheng; Meng, Ying Shirley; ...

    2015-01-01

    Lithium-ion batteries are a leading candidate for electric vehicle and smart grid applications. However, further optimizations of the energy/power density, coulombic efficiency and cycle life are still needed, and this requires a thorough understanding of the dynamic evolution of each component and their synergistic behaviors during battery operation. With the capability of resolving the structure and chemistry at an atomic resolution, advanced analytical transmission electron microscopy (AEM) is an ideal technique for this task. The present review paper focuses on recent contributions of this important technique to the fundamental understanding of the electrochemical processes of battery materials. A detailed reviewmore » of both static (ex situ) and real-time (in situ) studies will be given, and issues that still need to be addressed will be discussed.« less

  2. Advanced analytical electron microscopy for alkali-ion batteries

    SciTech Connect

    Qian, Danna; Ma, Cheng; Meng, Ying Shirley; More, Karren; Chi, Miaofang

    2015-01-01

    Lithium-ion batteries are a leading candidate for electric vehicle and smart grid applications. However, further optimizations of the energy/power density, coulombic efficiency and cycle life are still needed, and this requires a thorough understanding of the dynamic evolution of each component and their synergistic behaviors during battery operation. With the capability of resolving the structure and chemistry at an atomic resolution, advanced analytical transmission electron microscopy (AEM) is an ideal technique for this task. The present review paper focuses on recent contributions of this important technique to the fundamental understanding of the electrochemical processes of battery materials. A detailed review of both static (ex situ) and real-time (in situ) studies will be given, and issues that still need to be addressed will be discussed.

  3. Los Alamos Advanced Free-Electron Laser

    SciTech Connect

    Chan, K.C.D.; Kraus, R.H.; Ledford, J.; Meier, K.L.; Meyer, R.E.; Nguyen, D.; Sheffield, R.L.; Sigler, F.L.; Young, L.M.; Wang, T.S.; Wilson, W.L.; Wood, R.L.

    1991-01-01

    At Los Alamos, we are building a free-electron laser (FEL) for industrial, medical, and research applications. This FEL, which will incorporate many of the new technologies developed over the last decade, will be compact in size, robust, and user-friendly. Electrons produced by a photocathode will be accelerated to 20 MeV by a high-brightness accelerator and transported using permanent-magnet quadrupoles and dipoles. They will form an electron beam with an excellent instantaneous beam quality of 10 {pi} mm mrad in transverse emittance and 0.3% in energy spread at a peak current up to 300 A. Including operation at higher harmonics, the laser wavelength extends form 3.7 {mu}m to 0.4 {mu}m. In this paper, we will describe the project and the programs to date. 10 refs., 10 figs., 1 tab.

  4. Electronic instrumentation for smart structures

    NASA Astrophysics Data System (ADS)

    Blanar, George J.

    1995-04-01

    The requirements of electronic instrumentation for smart structures are similar to those of data acquisition systems at our national particle physics laboratories. Modern high energy and heavy ion physics experiments may have tens of thousands of channels of data sources producing data that must be converted to digital form, compacted, stored and interpreted. In parallel, multiple sensors distributed in and around smart structures generate either binary or analog signals that are voltage, charge, or time like in their information content. In all cases, they must be transmitted, converted and preserved into a unified digital format for real-time processing. This paper will review the current status of practical large scale electronic measurement systems with special attention to architectures and physical organization. Brief surveys of the current state of the art will include preamplifiers and amplifiers, comparators and discriminators, voltage or charge analog-to-digital converters, time internal meters or time-to-digital converters, and finally, counting or scalar systems. The paper will conclude by integrating all of these ideas in a concept for an all-digital readout of a smart structure using the latest techniques used in physics research today.

  5. 75 FR 21367 - Advanced Electronics, Inc.; Boston, MA; Notice of Negative Determination on Remand

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-23

    ... Employment and Training Administration Advanced Electronics, Inc.; Boston, MA; Notice of Negative... Department of Labor (Department) for further investigation Former Employees of Advanced Electronics, Inc. v... Adjustment Assistance (ATAA) applicable to workers and former workers of Advanced Electronics, Inc.,...

  6. Deployable truss structure advanced technology

    NASA Technical Reports Server (NTRS)

    Dyer, J. E.; Dudeck, M. P.

    1986-01-01

    The 5-meter technology antenna program demonstrated the overall feasibility of integrating a mesh reflector surface with a deployable truss structure to achieve a precision surface contour compatible with future, high-performance antenna requirements. Specifically, the program demonstrated: the feasibility of fabricating a precision, edge-mounted, deployable, tetrahedral truss structure; the feasibility of adjusting a truss-supported mesh reflector contour to a surface error less than 10 mils rms; and good RF test performance, which correlated well with analytical predictions. Further analysis and testing (including flight testing) programs are needed to fully verify all the technology issues, including structural dynamics, thermodynamics, control, and on-orbit RF performance, which are associated with large, deployable, truss antenna structures.

  7. The electronic structure of Lu

    NASA Astrophysics Data System (ADS)

    Tibbetts, T. A.; Harmon, B. N.

    1982-12-01

    The electronic structure of hcp Lu has been calculated using a linearized augmented plane wave (LAPW) method and the Hedin-Lundqvist local density approximation for exchange and correlation. Although complete self-consistency was hindered by the proximity of the 4f levels to the Fermi energy, the valence bands were converged and the calculation yielded a Fermi surface remarkably similar to that calculated by Keeton and Loucks. Comparison is made with recent de Haas-van Alphen and neutron magnetic form factor experiments.

  8. Center for Space Power and Advanced Electronics, Auburn University

    NASA Technical Reports Server (NTRS)

    Deis, Dan W.; Hopkins, Richard H.

    1991-01-01

    The union of Auburn University's Center for Space Power and Advanced Electronics and the Westinghouse Science and Technology Center to form a Center for the Commercial Development of Space (CCDS) is discussed. An area of focus for the CCDS will be the development of silicon carbide electronics technology, in terms of semiconductors and crystal growth. The discussion is presented in viewgraph form.

  9. Recent Advancements in Functionalized Paper-Based Electronics.

    PubMed

    Lin, Yang; Gritsenko, Dmitry; Liu, Qian; Lu, Xiaonan; Xu, Jie

    2016-08-17

    Building electronic devices on ubiquitous paper substrates has recently drawn extensive attention due to its light weight, low cost, environmental friendliness, and ease of fabrication. Recently, a myriad of advancements have been made to improve the performance of paper electronics for various applications, such as basic electronic components, energy storage devices, generators, antennas, and electronic circuits. This review aims to summarize this progress and discuss different perspectives of paper electronics as well as the remaining challenges yet to be overcome in this field. Other aspects included in this review are the fundamental characteristics of paper, modification of paper with functional materials, and various methods for device fabrication.

  10. Advanced High Temperature Structural Seals

    NASA Technical Reports Server (NTRS)

    Newquist, Charles W.; Verzemnieks, Juris; Keller, Peter C.; Rorabaugh, Michael; Shorey, Mark

    2002-01-01

    This program addresses the development of high temperature structural seals for control surfaces for a new generation of small reusable launch vehicles. Successful development will contribute significantly to the mission goal of reducing launch cost for small, 200 to 300 pound payloads. Development of high temperature seals is mission enabling. For instance, ineffective control surface seals can result in high temperature (3100 F) flows in the elevon area exceeding structural material limits. Longer sealing life will allow use for many missions before replacement, contributing to the reduction of hardware, operation and launch costs.

  11. Advanced power electronics and electric machinery program

    SciTech Connect

    None, None

    2007-12-01

    The U.S. Department of Energy (DOE) and the U.S. Council for Automotive Research (composed of automakers Ford, General Motors, and Chrysler) announced in January 2002 a new cooperative research effort. Known as "FreedomCAR" (derived from "Freedom" and "Cooperative Automotive Research"), it represents DOE's commitment to developing public/private partnerships to fund high-risk, high-payoff research into advanced automotive technologies. Efficient fuel cell technology, which uses hydrogen to power automobiles without air pollution, is a very promising pathway to achieving the ultimate vision. The new partnership replaces and builds upon the Partnership for a New Generation of Vehicles initiative that ran from 1993 through 2001.

  12. Probing Structural and Electronic Dynamics with Ultrafast Electron Microscopy

    SciTech Connect

    Plemmons, DA; Suri, PK; Flannigan, DJ

    2015-05-12

    In this Perspective, we provide an overview,of the field of ultrafast electron microscopy (UEM). We begin by briefly discussing the emergence of methods for probing ultrafast structural dynamics and the information that can be obtained. Distinctions are drawn between the two main types a probes for femtosecond (fs) dynamics fast electrons and X-ray photons and emphasis is placed on hour the nature of charged particles is exploited in ultrafast electron-based' experiments:. Following this, we describe the versatility enabled by the ease with which electron trajectories and velocities can be manipulated with transmission electron microscopy (TEM): hardware configurations, and we emphasize how this is translated to the ability to measure scattering intensities in real, reciprocal, and energy space from presurveyed and selected rianoscale volumes. Owing to decades of ongoing research and development into TEM instrumentation combined with advances in specimen holder technology, comprehensive experiments can be conducted on a wide range of materials in various phases via in situ methods. Next, we describe the basic operating concepts, of UEM, and we emphasize that its development has led to extension of several of the formidable capabilities of TEM into the fs domain, dins increasing the accessible temporal parameter spade by several orders of magnitude. We then divide UEM studies into those conducted in real (imaging), reciprocal (diffraction), and energy (spectroscopy) spate. We begin each of these sections by providing a brief description of the basic operating principles and the types of information that can be gathered followed by descriptions of how these approaches are applied in UM, the type of specimen parameter space that can be probed, and an example of the types of dynamics that can be resolved. We conclude with an Outlook section, wherein we share our perspective on some future directions of the field pertaining to continued instrument development and

  13. Advanced thermal management techniques for space power electronics

    NASA Astrophysics Data System (ADS)

    Reyes, Angel Samuel

    1992-01-01

    Modern electronic systems used in space must be reliable and efficient with thermal management unaffected by outer space constraints. Current thermal management techniques are not sufficient for the increasing waste heat dissipation of novel electronic technologies. Many advanced thermal management techniques have been developed in recent years that have application in high power electronic systems. The benefits and limitations of emerging cooling technologies are discussed. These technologies include: liquid pumped devices, mechanically pumped two-phase cooling, capillary pumped evaporative cooling, and thermoelectric devices. Currently, liquid pumped devices offer the most promising alternative for electronics thermal control.

  14. Electronic transport in nanoscale structures

    NASA Astrophysics Data System (ADS)

    Lagerqvist, Johan

    In this dissertation electronic transport in nanoscale structures is discussed. An expression for the shot noise, a fluctuation in current due to the discreteness of charge, is derived directly from the wave functions of a nanoscale system. Investigation of shot noise is of particular interest due to the rich fundamental physics involved. For example, the study of shot noise can provide fundamental insight on the nature of electron transport in a nanoscale junction. We report calculations of the shot noise properties of parallel wires in the regime in which the interwire distance is much smaller than the inelastic mean free path. The validity of quantized transverse momenta in a nanoscale structure and its effect on shot noise is also discussed. We theoretically propose and show the feasibility of a novel protocol for DNA sequencing based on the electronic signature of single-stranded DNA while it translocates through a nanopore. We find that the currents for the bases are sufficiently different to allow for efficient sequencing. Our estimates reveal that sequencing of an entire human genome could be done with very high accuracy in a matter of hours, e.g., orders of magnitude faster than present techniques. We also find that although the overall magnitude of the current may change dramatically with different detection conditions, the intrinsic distinguishability of the bases is not significantly affected by pore size and transverse field strength. Finally, we study the ability of water to screen charges in nanopores by using all-atom molecular dynamics simulations coupled to electrostatic calculations. Due to the short length scales of the nanopore geometry and the large local field gradient of a single ion, the energetics of transporting an ion through the pore is strongly dependent on the microscopic details of the electric field. We show that as long as the pore allows the first hydration shell to stay intact, e.g., ˜6 nearby water molecules, the electric field

  15. Initial performance of Los Alamos Advanced Free Electron Laser

    SciTech Connect

    Nguyen, D.C.; Baca, D.M.; Chan, K.C.D.; Cheairs, R.B.; Fortgang, C.M.; Gierman, S.M.; Johnson, W.J.D.; Holcomb, D.E.; Kinross-Wright, J.; McCann, S.W.; Meier, K.L.; Plato, J.G.; Sheffield, R.L.; Sherwood, B.A.; Sigler, F.E.; Timmer, C.A.; Warren, R.W.; Weber, M.E.; Wilson, W.L.

    1992-09-01

    We report recent results on the high-brightness electron linac and initial performance of the Advanced FEL at Los Alamos. The design and construction of the Advanced FEL beamline are based upon integration of advanced technologies such as high-brightness photoinjector, high-gradient compact linac, and permanent-magnet beamline components. With the use of microwiggler, both permanent magnet and pulsed electromagnet, and compact optical resonator, the Advanced FEL will be the first of its kind small enough to be mounted on an optical table and yet capable of providing highpower optical output spanning the near-ir and visible regions. A schematic of the Advanced FEL is shown in. The source of high-current electron pulses is a laser-gated photoelectron injector which forms-an integral part of a high-gradient 1.2-m long rf linear accelerator. The latter is capable of accelerating electrons up to 20 MeV with room temperature operation and 25 MeV at 77K. The electrons are produced in 10-ps pulses with peak currents as high as 300 A. These electron pulses are transported in a brightness-preserving beamline consisting of permanent magnet dipoles and quadrupoles. The beamline has three 30{degrees} bends. The first bend allows for the photocathode drive laser input; the second allows for the FEL output and the third turns the electron beam into the floor for safety reasons. Additional information on the design physics of the Advanced FEL can be found elsewhere.

  16. Initial performance of Los Alamos Advanced Free Electron Laser

    SciTech Connect

    Nguyen, D.C.; Baca, D.M.; Chan, K.C.D.; Cheairs, R.B.; Fortgang, C.M.; Gierman, S.M.; Johnson, W.J.D.; Holcomb, D.E.; Kinross-Wright, J.; McCann, S.W.; Meier, K.L.; Plato, J.G.; Sheffield, R.L.; Sherwood, B.A.; Sigler, F.E.; Timmer, C.A.; Warren, R.W.; Weber, M.E.; Wilson, W.L.

    1992-01-01

    We report recent results on the high-brightness electron linac and initial performance of the Advanced FEL at Los Alamos. The design and construction of the Advanced FEL beamline are based upon integration of advanced technologies such as high-brightness photoinjector, high-gradient compact linac, and permanent-magnet beamline components. With the use of microwiggler, both permanent magnet and pulsed electromagnet, and compact optical resonator, the Advanced FEL will be the first of its kind small enough to be mounted on an optical table and yet capable of providing highpower optical output spanning the near-ir and visible regions. A schematic of the Advanced FEL is shown in. The source of high-current electron pulses is a laser-gated photoelectron injector which forms-an integral part of a high-gradient 1.2-m long rf linear accelerator. The latter is capable of accelerating electrons up to 20 MeV with room temperature operation and 25 MeV at 77K. The electrons are produced in 10-ps pulses with peak currents as high as 300 A. These electron pulses are transported in a brightness-preserving beamline consisting of permanent magnet dipoles and quadrupoles. The beamline has three 30{degrees} bends. The first bend allows for the photocathode drive laser input; the second allows for the FEL output and the third turns the electron beam into the floor for safety reasons. Additional information on the design physics of the Advanced FEL can be found elsewhere.

  17. A Hybrid Solid-State NMR and Electron Microscopy Structure-Determination Protocol for Engineering Advanced para-Crystalline Optical Materials.

    PubMed

    Thomas, Brijith; Rombouts, Jeroen; Oostergetel, Gert T; Gupta, Karthick B S S; Buda, Francesco; Lammertsma, Koop; Orru, Romano; de Groot, Huub J M

    2017-01-24

    Hybrid magic-angle spinning (MAS) NMR spectroscopy and TEM were demonstrated for de novo structure determination of para-crystalline materials with a bioinspired fused naphthalene diimide (NDI)-salphen-phenazine prototype light-harvesting compound. Starting from chiral building blocks with C2 molecular symmetry, the asymmetric unit was determined by MAS NMR spectroscopy, index low-resolution TEM diffraction data, and resolve reflection conditions, and for the first time the ability to determine the space group from reciprocal space data using this hybrid approach was shown. Transfer of molecular C2 symmetry into P2/c packing symmetry provided a connection across length scales to overcome both lack of long-range order and missing diffraction-phase information. Refinement with heteronuclear distance constraints confirmed the racemic P2/c packing that was scaffolded by molecular recognition of salphen zinc in a pseudo-octahedral environment with bromide and with alkyl chains folding along the phenazine. The NDI light-harvesting stacks ran orthogonal to the intermolecular electric dipole moment present in the solid. Finally, the orientation of flexible lamellae on an electrode surface was determined.

  18. Using advanced electron microscopy for the characterization of catalytic materials

    NASA Astrophysics Data System (ADS)

    Pyrz, William D.

    Catalysis will continue to be vitally important to the advancement and sustainability of industrialized societies. Unfortunately, the petroleum-based resources that currently fuel the energy and consumer product needs of an advancing society are becoming increasingly difficult and expensive to extract as supplies diminish and the quality of sources degrade. Therefore, the development of sustainable energy sources and the improvement of the carbon efficiency of existing chemical processes are critical. Further challenges require that these initiatives are accomplished in an environmentally friendly fashion since the effects of carbon-based emissions are proving to be a serious threat to global climate stability. In this dissertation, materials being developed for sustainable energy and process improvement initiatives are studied. Our approach is to use materials characterization, namely advanced electron microscopy, to analyze the targeted systems at the nano- or Angstrom-scale with the goal of developing useful relationships between structure, composition, crystalline order, morphology, and catalytic performance. One area of interest is the complex Mo-V-M-O (M=Te, Sb, Ta, Nb) oxide system currently being developed for the selective oxidation/ammoxidation of propane to acrylic acid or acrylonitrile, respectively. Currently, the production of acrylic acid and acrylonitrile rely on propylene-based processes, yet significant cost savings could be realized if the olefin-based feeds could be replaced by paraffin-based ones. The major challenge preventing this feedstock replacement is the development of a suitable paraffin-activating catalyst. Currently, the best candidate is the Mo-V-Nb-Te-O complex oxide catalyst that is composed of two majority phases that are commonly referred to as M1 and M2. However, there is a limited understanding of the roles of each component with respect to how they contribute to catalyst stability and the reaction mechanism. Aberration

  19. Advances and trends in computational structural mechanics

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Atluri, Satya N.

    1987-01-01

    The development status and applicational range of techniques in computational structural mechanics (CSM) are evaluated with a view to advances in computational models for material behavior, discrete-element technology, quality assessment, the control of numerical simulations of structural response, hybrid analysis techniques, techniques for large-scale optimization, and the impact of new computing systems on CSM. Primary pacers of CSM development encompass prediction and analysis of novel materials for structural components, computational strategies for large-scale structural calculations, and the assessment of response prediction reliability together with its adaptive improvement.

  20. Synchrotron-Radiation-based Investigationsof the Electronic Structure of Pu

    SciTech Connect

    Tobin, J; Chung, B; Terry, J; Schulze, R; Farr, J; Heinzelman, K; Rotenberg, E; Shuh, D

    2004-09-27

    Synchrotron radiation from the Advanced Light Source has been used to investigate the electronic structure of {alpha}-Pu and {delta}-Pu. Measurements include core level and valence band photoelectron spectroscopy, Resonant Photoelectron Spectroscopy (REPES), and X-ray Absorption Spectroscopy (XAS).

  1. BORON NITRIDE CAPACITORS FOR ADVANCED POWER ELECTRONIC DEVICES

    SciTech Connect

    N. Badi; D. Starikov; C. Boney; A. Bensaoula; D. Johnstone

    2010-11-01

    This project fabricates long-life boron nitride/boron oxynitride thin film -based capacitors for advanced SiC power electronics with a broad operating temperature range using a physical vapor deposition (PVD) technique. The use of vapor deposition provides for precise control and quality material formation.

  2. FY2009 Annual Progress Report for Advanced Power Electronics

    SciTech Connect

    Rogers, Susan A.

    2010-01-01

    The Advanced Power Electronics and Electric Machines (APEEM) subprogram within the Vehicle Technologies Program provides support and guidance for many cutting-edge automotive technologies now under development. Research is focused on understanding and improving the way the various new components of tomorrow's automobiles will function as a unified system to improve fuel efficiency.

  3. Epidermal electronics with advanced capabilities in near-field communication.

    PubMed

    Kim, Jeonghyun; Banks, Anthony; Cheng, Huanyu; Xie, Zhaoqian; Xu, Sheng; Jang, Kyung-In; Lee, Jung Woo; Liu, Zhuangjian; Gutruf, Philipp; Huang, Xian; Wei, Pinghung; Liu, Fei; Li, Kan; Dalal, Mitul; Ghaffari, Roozbeh; Feng, Xue; Huang, Yonggang; Gupta, Sanjay; Paik, Ungyu; Rogers, John A

    2015-02-25

    Epidermal electronics with advanced capabilities in near field communications (NFC) are presented. The systems include stretchable coils and thinned NFC chips on thin, low modulus stretchable adhesives, to allow seamless, conformal contact with the skin and simultaneous capabilities for wireless interfaces to any standard, NFC-enabled smartphone, even under extreme deformation and after/during normal daily activities.

  4. Advanced electron microscopy characterization of nanomaterials for catalysis

    DOE PAGES

    Su, Dong

    2017-02-11

    Transmission electron microscopy (TEM) has become one of the most powerful techniques in the fields of material science, inorganic chemistry and nanotechnology. In terms of resolutions, advanced TEM may reach a high spatial resolution of 0.05 nm, a high energy-resolution of 7 meV. In addition, in situ TEM can help researcher to image the process happened within 1 ms. This paper reviews the recent technical approaches of applying advanced TEM characterization on nanomaterials for catalysis. The text is organized according to the demanded information of nanocrystals from the perspective of application: for example, size, composition, phase, strain, and morphology. Themore » electron beam induced effect and in situ TEM are also introduced. As a result, I hope this review can help the scientists in related fields to take advantage of advanced TEM to their own researches.« less

  5. Electronic processes in multilayer memory structures

    NASA Astrophysics Data System (ADS)

    Plotnikov, A. F.

    The papers presented in this volume contain results of recent theoretical and experimental research related to electron processes in optoelectronic memory media based on structures consisting of a metal, an amorphous insulating layer, and a semiconductor. Topics discussed include photostimulated electron processes in metal-insulator-semiconductor structures, electron transfer phenomena in amorphous dielectric layers, degradation phenomena in MNOS memory elements under prolonged charge injection into the dielectric layer, and characteristics of charge relaxation in MNOS structures following multiple reprogramming.

  6. Future opportunities for advancing glucose test device electronics.

    PubMed

    Young, Brian R; Young, Teresa L; Joyce, Margaret K; Kennedy, Spencer I; Atashbar, Massood Z

    2011-09-01

    Advancements in the field of printed electronics can be applied to the field of diabetes testing. A brief history and some new developments in printed electronics components applicable to personal test devices, including circuitry, batteries, transmission devices, displays, and sensors, are presented. Low-cost, thin, and lightweight materials containing printed circuits with energy storage or harvest capability and reactive/display centers, made using new printing/imaging technologies, are ideal for incorporation into personal-use medical devices such as glucose test meters. Semicontinuous rotogravure printing, which utilizes flexible substrates and polymeric, metallic, and/or nano "ink" composite materials to effect rapidly produced, lower-cost printed electronics, is showing promise. Continuing research advancing substrate, "ink," and continuous processing development presents the opportunity for research collaboration with medical device designers.

  7. Future Opportunities for Advancing Glucose Test Device Electronics

    PubMed Central

    Young, Brian R; Young, Teresa L; Joyce, Margaret K; Kennedy, Spencer I; Atashbar, Massood Z

    2011-01-01

    Advancements in the field of printed electronics can be applied to the field of diabetes testing. A brief history and some new developments in printed electronics components applicable to personal test devices, including circuitry, batteries, transmission devices, displays, and sensors, are presented. Low-cost, thin, and lightweight materials containing printed circuits with energy storage or harvest capability and reactive/display centers, made using new printing/imaging technologies, are ideal for incorporation into personal-use medical devices such as glucose test meters. Semicontinuous rotogravure printing, which utilizes flexible substrates and polymeric, metallic, and/or nano “ink” composite materials to effect rapidly produced, lower-cost printed electronics, is showing promise. Continuing research advancing substrate, “ink,” and continuous processing development presents the opportunity for research collaboration with medical device designers. PMID:22027300

  8. Magneto-Structural Correlations in Pseudotetrahedral Forms of the [Co(SPh)4](2-) Complex Probed by Magnetometry, MCD Spectroscopy, Advanced EPR Techniques, and ab Initio Electronic Structure Calculations.

    PubMed

    Suturina, Elizaveta A; Nehrkorn, Joscha; Zadrozny, Joseph M; Liu, Junjie; Atanasov, Mihail; Weyhermüller, Thomas; Maganas, Dimitrios; Hill, Stephen; Schnegg, Alexander; Bill, Eckhard; Long, Jeffrey R; Neese, Frank

    2017-03-06

    The magnetic properties of pseudotetrahedral Co(II) complexes spawned intense interest after (PPh4)2[Co(SPh)4] was shown to be the first mononuclear transition-metal complex displaying slow relaxation of the magnetization in the absence of a direct current magnetic field. However, there are differing reports on its fundamental magnetic spin Hamiltonian (SH) parameters, which arise from inherent experimental challenges in detecting large zero-field splittings. There are also remarkable changes in the SH parameters of [Co(SPh)4](2-) upon structural variations, depending on the counterion and crystallization conditions. In this work, four complementary experimental techniques are utilized to unambiguously determine the SH parameters for two different salts of [Co(SPh)4](2-): (PPh4)2[Co(SPh)4] (1) and (NEt4)2[Co(SPh)4] (2). The characterization methods employed include multifield SQUID magnetometry, high-field/high-frequency electron paramagnetic resonance (HF-EPR), variable-field variable-temperature magnetic circular dichroism (VTVH-MCD), and frequency domain Fourier transform THz-EPR (FD-FT THz-EPR). Notably, the paramagnetic Co(II) complex [Co(SPh)4](2-) shows strong axial magnetic anisotropy in 1, with D = -55(1) cm(-1) and E/D = 0.00(3), but rhombic anisotropy is seen for 2, with D = +11(1) cm(-1) and E/D = 0.18(3). Multireference ab initio CASSCF/NEVPT2 calculations enable interpretation of the remarkable variation of D and its dependence on the electronic structure and geometry.

  9. Recent progress of the Los Alamos advanced free electron laser

    SciTech Connect

    Nguyen, D.C.; Austin, R.H.; Chan, K.C.D.; Feldman, D.W.; Goldstein, J.C.; Gierman, S.M.; Kinross-Wright, J.M.; Kong, S.H.; Plato, J.G.; Russell, S.J.

    1994-05-01

    Many industrial and research applications can benefit from the availability of a compact, user-friendly, broadly tunable and high average power free electron laser (FEL). Over the past four years, the Los Alamos Advanced FEL has been built with these design goals. The key to a compact FEL is the integration of advanced beam technologies such as a high-brightness photoinjector, a high-gradient compact linac, and permanent magnet beamline components. These technologies enable the authors to shrink the FEL size yet maintain its high average power capability. The Advanced FEL has been in operation in the near ir (4-6 {mu}m) since early 1993. Recent results of the Advanced FEL lasing at saturation and upgrades to improve its average power are presented.

  10. Electronic correlation contributions to structural energies

    NASA Astrophysics Data System (ADS)

    Haydock, Roger

    2015-03-01

    The recursion method is used to calculate electronic excitation spectra including electron-electron interactions within the Hubbard model. The effects of correlation on structural energies are then obtained from these spectra and applied to stacking faults. http://arxiv.org/abs/1405.2288 Supported by the Richmond F. Snyder Fund and Gifts.

  11. The design of repairable advanced composite structures

    NASA Technical Reports Server (NTRS)

    Hart-Smith, L. J.

    1985-01-01

    This paper addresses the repair of advanced composite structures by mechanical fasteners or by adhesive bonding. It is shown that many of today's composite designs are unreasonably difficult to repair. Conversely, the knowledge to design repairable structures is already available, if only it is applied during the initial design stage. Bolted or riveted repairs require only the avoidance of extremely orthotropic composite fiber patterns; those near the quasi-isotropic layup are the most suitable. Mildly orthotropic fiber patterns are appropriate for structures in which there is a dominant load direction. Thick composite structures are shown to require bolted or riveted repairs while thin structures favor adhesively bonded permanent repairs, although provisions can be easily made for temporary mechanical repairs. The reasons why integrally stiffened cocured composite designs are usually impractical to repair are explained and alternative repairable design concepts are presented.

  12. Structure and electronic properties of lead-selenide nanocrystal solids

    NASA Astrophysics Data System (ADS)

    Whitham, Kevin

    Recent advances in the controlled formation of nanocrystal superlattices have potential for creating materials with properties by design. The ability to tune nanocrystal size, shape and composition as well as symmetry of the superlattice opens routes to new materials. Calculations of such materials predict interesting electronic phenomena including topological states and Dirac cones, however experimental support is lacking. We have investigated electron localization in nanocrystal superlattices using a combination of advanced structural characterization techniques and charge transport measurements. Recent experimental efforts to improve the electronic properties of nanocrystal solids have focused on increasing inter-dot coupling. However, this approach only leads to electronic bands if the coupling energy can overcome energetic and translational disorder. We have investigated oriented-attachment as a method to create nanocrystal superlattices with increased coupling and translational order. We show that epitaxially connected superlattices form by a coherent phase transformation that is sensitive to structural defects and ligand length. In order to measure intrinsic electronic properties we demonstrate control over electronic defects by tailoring surface chemistry and device architecture. To probe charge transport in these structures we performed variable temperature field-effect measurements. By integrating structure analysis, surface chemistry, and transport measurements we find that carriers are localized to a few superlattice constants due to disorder. Importantly, our analysis shows that greater delocalization is possible by optimizing dot-to-dot bonding, thus providing a path forward to create quantum dot solids in which theoretically predicted properties can be realized.

  13. Electronic structure of lithium tetraborate

    NASA Astrophysics Data System (ADS)

    Wooten, David J.

    Due to many of its attributes, Li2B4O7 provides a possible material for incorporation as either a primary or companion material in future solid state neutron detectors. There is however a lack of fundamental characterization information regarding this useful material, particularly its electronic configuration. To address this, an investigation of Li2B4O7(110) and Li2B 4O7(100) was undertaken, utilizing photoemission and inverse photoemission spectroscopic techniques. The measured band gap depended on crystallographic direction with the band gaps ranging from 8.9+/-0.5 eV to 10.1+/-0.5 eV. The measurement yielded a density of states that qualitatively agreed with the theoretical results from model bulk band structure calculations for Li2B4O7; albeit with a larger band gap than predicted, but consistent with the known deficiencies of Local Density Approximation and Density Functional Theory calculations. The occupied states of both surfaces were extremely flat; to the degree that resolving periodic dispersion of the occupied states was inconclusive, within the resolution of the system. However, both surfaces demonstrated clear periodic dispersion within the empty states very close to theoretical Brillouin zone values. These attributes also translated to a lighter charge carrier effective mass in the unoccupied states. Of the two surfaces, Li2B4O 7(110) yielded the more consistent values in orthogonal directions for energy states. The presence of a bulk band gap surface state and image potential state in Li2B4O7(110) was indicative of a defect-free surface. The absence of both in the more polar, more dielectric Li2B4O7(100) was attributed to the presence of defects determined to be O vacancies. The results from Li2B 4O7(110) were indicative of a more stable surface than Li 2B4O7(100). In addition, Li 1s bulk and surface core level components were determined at the binding energies of -56.5+0.4 and -53.7+0.5 eV. Resonance features were observed along the [001

  14. Materials Advances for Next-Generation Ingestible Electronic Medical Devices.

    PubMed

    Bettinger, Christopher J

    2015-10-01

    Electronic medical implants have collectively transformed the diagnosis and treatment of many diseases, but have many inherent limitations. Electronic implants require invasive surgeries, operate in challenging microenvironments, and are susceptible to bacterial infection and persistent inflammation. Novel materials and nonconventional device fabrication strategies may revolutionize the way electronic devices are integrated with the body. Ingestible electronic devices offer many advantages compared with implantable counterparts that may improve the diagnosis and treatment of pathologies ranging from gastrointestinal infections to diabetes. This review summarizes current technologies and highlights recent materials advances. Specific focus is dedicated to next-generation materials for packaging, circuit design, and on-board power supplies that are benign, nontoxic, and even biodegradable. Future challenges and opportunities are also highlighted.

  15. Advanced design concepts for shuttle airframe structure

    NASA Technical Reports Server (NTRS)

    Card, M. F.; Davis, J. G., Jr.; Shideler, J. L.

    1972-01-01

    The development of weight-saving advanced design concepts for shuttle airframe structure is presented. Design concepts under investigation employ selective composite reinforcement and/or efficient geometric arrangements. An effort to develop metallic panel designs which exploit the relaxation of smooth external-surface requirements for skin structure is reviewed. Available highlights from research and development studies which investigate the application of composite reinforcement to the design of two types of fuselage panels, a shear web, a large fuselage frame, and a landing-gear-door assembly are presented. Preliminary results from these studies suggest weight savings of 25 percent can be obtained.

  16. Applications and Advances in Electronic-Nose Technologies

    PubMed Central

    Wilson, Alphus D.; Baietto, Manuela

    2009-01-01

    Electronic-nose devices have received considerable attention in the field of sensor technology during the past twenty years, largely due to the discovery of numerous applications derived from research in diverse fields of applied sciences. Recent applications of electronic nose technologies have come through advances in sensor design, material improvements, software innovations and progress in microcircuitry design and systems integration. The invention of many new e-nose sensor types and arrays, based on different detection principles and mechanisms, is closely correlated with the expansion of new applications. Electronic noses have provided a plethora of benefits to a variety of commercial industries, including the agricultural, biomedical, cosmetics, environmental, food, manufacturing, military, pharmaceutical, regulatory, and various scientific research fields. Advances have improved product attributes, uniformity, and consistency as a result of increases in quality control capabilities afforded by electronic-nose monitoring of all phases of industrial manufacturing processes. This paper is a review of the major electronic-nose technologies, developed since this specialized field was born and became prominent in the mid 1980s, and a summarization of some of the more important and useful applications that have been of greatest benefit to man. PMID:22346690

  17. Testing aspects of advanced coherent electron cooling technique

    SciTech Connect

    Litvinenko, V.; Jing, Y.; Pinayev, I.; Wang, G.; Samulyak, R.; Ratner, D.

    2015-05-03

    An advanced version of the Coherent-electron Cooling (CeC) based on the micro-bunching instability was proposed. This approach promises significant increase in the bandwidth of the CeC system and, therefore, significant shortening of cooling time in high-energy hadron colliders. In this paper we present our plans of simulating and testing the key aspects of this proposed technique using the set-up of the coherent-electron-cooling proof-of-principle experiment at BNL.

  18. Architectural development of an advanced EVA Electronic System

    NASA Technical Reports Server (NTRS)

    Lavelle, Joseph

    1992-01-01

    An advanced electronic system for future EVA missions (including zero gravity, the lunar surface, and the surface of Mars) is under research and development within the Advanced Life Support Division at NASA Ames Research Center. As a first step in the development, an optimum system architecture has been derived from an analysis of the projected requirements for these missions. The open, modular architecture centers around a distributed multiprocessing concept where the major subsystems independently process their own I/O functions and communicate over a common bus. Supervision and coordination of the subsystems is handled by an embedded real-time operating system kernel employing multitasking software techniques. A discussion of how the architecture most efficiently meets the electronic system functional requirements, maximizes flexibility for future development and mission applications, and enhances the reliability and serviceability of the system in these remote, hostile environments is included.

  19. Advances in Structures for Large Space Systems

    NASA Technical Reports Server (NTRS)

    Belvin, W. Keith

    2004-01-01

    The development of structural systems for scientific remote sensing and space exploration has been underway for four decades. The seminal work from 1960 to 1980 provided the basis for many of the design principles of modern space systems. From 1980- 2000 advances in active materials and structures and the maturing of composites technology led to high precision active systems such those used in the Space Interferometry Mission. Recently, thin-film membrane or gossamer structures are being investigated for use in large area space systems because of their low mass and high packaging efficiency. Various classes of Large Space Systems (LSS) are defined in order to describe the goals and system challenges in structures and materials technologies. With an appreciation of both past and current technology developments, future technology challenges are used to develop a list of technology investments that can have significant impacts on LSS development.

  20. Electronic Structure of Lithium Tetraborate

    DTIC Science & Technology

    2010-06-01

    binding energies of -56.5+0.4 and -53.7+0.5 eV. Resonance features were observed along the [001] direction and were attributed to a Coster- Kronig ...could be theoretically explained as an Auger electron [12] or Coster- Kronig process [13] of a Li 1s electron photoexcitation to an unoccupied 2p...Coster Kronig , which requires only one Li atom. Such a Coster Kronig mechanism is pictorially displayed below in Figure 7.9. 128 Figure 7.9

  1. Electron tomography of dislocation structures

    SciTech Connect

    Liu, G.S.; House, S.D.; Kacher, J.; Tanaka, M.; Higashida, K.; Robertson, I.M.

    2014-01-15

    Recent developments in the application of electron tomography for characterizing microstructures in crystalline solids are described. The underlying principles for electron tomography are presented in the context of typical challenges in adapting the technique to crystalline systems and in using diffraction contrast imaging conditions. Methods for overcoming the limitations associated with the angular range, the number of acquired images, and uniformity of image contrast are introduced. In addition, a method for incorporating the real space coordinate system into the tomogram is presented. As the approach emphasizes development of experimental solutions to the challenges, the solutions developed and implemented are presented in the form of examples.

  2. Goeppert-Mayer Award Recipient: Electron Scattering and Nucleon Structure

    NASA Astrophysics Data System (ADS)

    Beise, Elizabeth

    1998-04-01

    Electron scattering from hydrogen and light nuclear targets has long been recognized as one of the best tools for understanding the electromagnetic structure of protons, neutrons and few-nucleon systems. In the last decade, considerable progress has been made in the field through advances in polarized beams and polarized targets. Improvements in polarized electron sources has made it feasible to also study the structure of the nucleon through parity-violating electron scattering, where the nucleon's neutral weak structure is probed. In this talk, a summary of the present experimental status of the nucleon's electroweak structure will be presented, with an emphasis on recent results from the MIT-Bates and Jefferson Laboratories.

  3. Electron gun controlled smart structure

    DOEpatents

    Martin, Jeffrey W.; Main, John Alan; Redmond, James M.; Henson, Tammy D.; Watson, Robert D.

    2001-01-01

    Disclosed is a method and system for actively controlling the shape of a sheet of electroactive material; the system comprising: one or more electrodes attached to the frontside of the electroactive sheet; a charged particle generator, disposed so as to direct a beam of charged particles (e.g. electrons) onto the electrode; a conductive substrate attached to the backside of the sheet; and a power supply electrically connected to the conductive substrate; whereby the sheet changes its shape in response to an electric field created across the sheet by an accumulation of electric charge within the electrode(s), relative to a potential applied to the conductive substrate. Use of multiple electrodes distributed across on the frontside ensures a uniform distribution of the charge with a single point of e-beam incidence, thereby greatly simplifying the beam scanning algorithm and raster control electronics, and reducing the problems associated with "blooming". By placing a distribution of electrodes over the front surface of a piezoelectric film (or other electroactive material), this arrangement enables improved control over the distribution of surface electric charges (e.g. electrons) by creating uniform (and possibly different) charge distributions within each individual electrode. Removal or deposition of net electric charge can be affected by controlling the secondary electron yield through manipulation of the backside electric potential with the power supply. The system can be used for actively controlling the shape of space-based deployable optics, such as adaptive mirrors and inflatable antennae.

  4. Complex structures of dense lithium: Electronic origin

    NASA Astrophysics Data System (ADS)

    Degtyareva, V. F.

    2016-11-01

    Lithium—the lightest alkali metal exhibits unexpected structures and electronic behavior at high pressures. Like the heavier alkali metals, Li is bcc at ambient pressure and transforms first to fcc (at 7.5 GPa). The post-fcc high-pressure form Li-cI 16 (at 40-60 GPa) is similar to Na-cI 16 and related to more complex structures of heavy alkalis Rb-oC52 and Cs- oC84. The other high pressure phases for Li (oC88, oC40, oC24) observed at pressures up to 130 GPa are found only in Li. The different route of Li high-pressure structures correlates with its special electronic configuration containing the only 3 electrons (at 1s and 2s levels). Crystal structures for Li are analyzed within the model of Fermi sphere-Brillouin zone interactions. Stability of post-fcc structures for Li are supported by the Hume-Rothery arguments when new diffraction plains appear close to the Fermi level producing pseudogaps near the Fermi level and decreasing the crystal energy. The filling of Brillouin-Jones zones by electron states for a given structure defines the physical properties as optical reflectivity, electrical resistivity and superconductivity. To understand the complexity of structural and physical properties of Li above 60 GPa it is necessary to assume the valence electron band overlap with the core electrons and increase the valence electron count under compression.

  5. Electronic Structure of Small Lanthanide Containing Molecules

    NASA Astrophysics Data System (ADS)

    Kafader, Jared O.; Ray, Manisha; Topolski, Josey E.; Chick Jarrold, Caroline

    2016-06-01

    Lanthanide-based materials have unusual electronic properties because of the high number of electronic degrees of freedom arising from partial occupation of 4f orbitals, which make these materials optimal for their utilization in many applications including electronics and catalysis. Electronic spectroscopy of small lanthanide molecules helps us understand the role of these 4f electrons, which are generally considered core-like because of orbital contraction, but are energetically similar to valence electrons. The spectroscopy of small lanthanide-containing molecules is relatively unexplored and to broaden this understanding we have completed the characterization of small cerium, praseodymium, and europium molecules using photoelectron spectroscopy coupled with DFT calculations. The characterization of PrO, EuH, EuO/EuOH, and CexOy molecules have allowed for the determination of their electron affinity, the assignment of numerous anion to neutral state transitions, modeling of anion/neutral structures and electron orbital occupation.

  6. Study of nanoscale structural biology using advanced particle beam microscopy

    NASA Astrophysics Data System (ADS)

    Boseman, Adam J.

    This work investigates developmental and structural biology at the nanoscale using current advancements in particle beam microscopy. Typically the examination of micro- and nanoscale features is performed using scanning electron microscopy (SEM), but in order to decrease surface charging, and increase resolution, an obscuring conductive layer is applied to the sample surface. As magnification increases, this layer begins to limit the ability to identify nanoscale surface structures. A new technology, Helium Ion Microscopy (HIM), is used to examine uncoated surface structures on the cuticle of wild type and mutant fruit flies. Corneal nanostructures observed with HIM are further investigated by FIB/SEM to provide detailed three dimensional information about internal events occurring during early structural development. These techniques are also used to reconstruct a mosquito germarium in order to characterize unknown events in early oogenesis. Findings from these studies, and many more like them, will soon unravel many of the mysteries surrounding the world of developmental biology.

  7. Nonlinearity in structural and electronic materials

    SciTech Connect

    Bishop, A.R.; Beardmore, K.M.; Ben-Naim, E.

    1997-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project strengthens a nonlinear technology base relevant to a variety of problems arising in condensed matter and materials science, and applies this technology to those problems. In this way the controlled synthesis of, and experiments on, novel electronic and structural materials provide an important focus for nonlinear science, while nonlinear techniques help advance the understanding of the scientific principles underlying the control of microstructure and dynamics in complex materials. This research is primarily focused on four topics: (1) materials microstructure: growth and evolution, and porous media; (2) textures in elastic/martensitic materials; (3) electro- and photo-active polymers; and (4) ultrafast photophysics in complex electronic materials. Accomplishments included the following: organization of a ``Nonlinear Materials`` seminar series and international conferences including ``Fracture, Friction and Deformation,`` ``Nonequilibrium Phase Transitions,`` and ``Landscape Paradigms in Physics and Biology``; invited talks at international conference on ``Synthetic Metals,`` ``Quantum Phase Transitions,`` ``1996 CECAM Euroconference,`` and the 1995 Fall Meeting of the Materials Research Society; large-scale simulations and microscopic modeling of nonlinear coherent energy storage at crack tips and sliding interfaces; large-scale simulation and microscopic elasticity theory for precursor microstructure and dynamics at solid-solid diffusionless phase transformations; large-scale simulation of self-assembling organic thin films on inorganic substrates; analysis and simulation of smoothing of rough atomic surfaces; and modeling and analysis of flux pattern formation in equilibrium and nonequilibrium Josephson junction arrays and layered superconductors.

  8. Advanced Technology Composite Fuselage-Structural Performance

    NASA Technical Reports Server (NTRS)

    Walker, T. H.; Minguet, P. J.; Flynn, B. W.; Carbery, D. J.; Swanson, G. D.; Ilcewicz, L. B.

    1997-01-01

    Boeing is studying the technologies associated with the application of composite materials to commercial transport fuselage structure under the NASA-sponsored contracts for Advanced Technology Composite Aircraft Structures (ATCAS) and Materials Development Omnibus Contract (MDOC). This report addresses the program activities related to structural performance of the selected concepts, including both the design development and subsequent detailed evaluation. Design criteria were developed to ensure compliance with regulatory requirements and typical company objectives. Accurate analysis methods were selected and/or developed where practical, and conservative approaches were used where significant approximations were necessary. Design sizing activities supported subsequent development by providing representative design configurations for structural evaluation and by identifying the critical performance issues. Significant program efforts were directed towards assessing structural performance predictive capability. The structural database collected to perform this assessment was intimately linked to the manufacturing scale-up activities to ensure inclusion of manufacturing-induced performance traits. Mechanical tests were conducted to support the development and critical evaluation of analysis methods addressing internal loads, stability, ultimate strength, attachment and splice strength, and damage tolerance. Unresolved aspects of these performance issues were identified as part of the assessments, providing direction for future development.

  9. 78 FR 46621 - Status of the Office of New Reactors' Implementation of Electronic Distribution of Advanced...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-01

    ... COMMISSION Status of the Office of New Reactors' Implementation of Electronic Distribution of Advanced Reactor Correspondence AGENCY: Nuclear Regulatory Commission. ACTION: Implementation of electronic distribution of advanced reactor correspondence; issuance. SUMMARY: The U.S. Nuclear Regulatory Commission...

  10. Application of scanning acoustic microscopy to advanced structural ceramics

    NASA Technical Reports Server (NTRS)

    Vary, Alex; Klima, Stanley J.

    1987-01-01

    A review is presentod of research investigations of several acoustic microscopy techniques for application to structural ceramics for advanced heat engines. Results obtained with scanning acoustic microscopy (SAM), scanning laser acoustic microscopy (SLAM), scanning electron acoustic microscopy (SEAM), and photoacoustic microscopy (PAM) are compared. The techniques were evaluated on research samples of green and sintered monolithic silicon nitrides and silicon carbides in the form of modulus-of-rupture bars containing deliberately introduced flaws. Strengths and limitations of the techniques are described with emphasis on statistics of detectability of flaws that constitute potential fracture origins.

  11. Instructional Approach to Molecular Electronic Structure Theory

    ERIC Educational Resources Information Center

    Dykstra, Clifford E.; Schaefer, Henry F.

    1977-01-01

    Describes a graduate quantum mechanics projects in which students write a computer program that performs ab initio calculations on the electronic structure of a simple molecule. Theoretical potential energy curves are produced. (MLH)

  12. Computational Chemistry Using Modern Electronic Structure Methods

    ERIC Educational Resources Information Center

    Bell, Stephen; Dines, Trevor J.; Chowdhry, Babur Z.; Withnall, Robert

    2007-01-01

    Various modern electronic structure methods are now days used to teach computational chemistry to undergraduate students. Such quantum calculations can now be easily used even for large size molecules.

  13. Advances in Electronic-Nose Technologies Developed for Biomedical Applications

    PubMed Central

    Wilson, Alphus D.; Baietto, Manuela

    2011-01-01

    The research and development of new electronic-nose applications in the biomedical field has accelerated at a phenomenal rate over the past 25 years. Many innovative e-nose technologies have provided solutions and applications to a wide variety of complex biomedical and healthcare problems. The purposes of this review are to present a comprehensive analysis of past and recent biomedical research findings and developments of electronic-nose sensor technologies, and to identify current and future potential e-nose applications that will continue to advance the effectiveness and efficiency of biomedical treatments and healthcare services for many years. An abundance of electronic-nose applications has been developed for a variety of healthcare sectors including diagnostics, immunology, pathology, patient recovery, pharmacology, physical therapy, physiology, preventative medicine, remote healthcare, and wound and graft healing. Specific biomedical e-nose applications range from uses in biochemical testing, blood-compatibility evaluations, disease diagnoses, and drug delivery to monitoring of metabolic levels, organ dysfunctions, and patient conditions through telemedicine. This paper summarizes the major electronic-nose technologies developed for healthcare and biomedical applications since the late 1980s when electronic aroma detection technologies were first recognized to be potentially useful in providing effective solutions to problems in the healthcare industry. PMID:22346620

  14. Advances in Hot-Structure Development

    NASA Technical Reports Server (NTRS)

    Rivers, H. Kevin; Glass, David E.

    2006-01-01

    The National Aeronautics and Space Administration has actively participated in the development of hot structures technology for application to hypersonic flight systems. Hot structures have been developed for vehicles including the X-43A, X-37, and the Space Shuttle. These trans-atmospheric and atmospheric entry flight systems that incorporate hot-structures technology are lighter weight and require less maintenance than those that incorporate parasitic, thermal-protection materials that attach to warm or cool substructure. The development of hot structures requires a thorough understanding of material performance in an extreme environment, boundary conditions and load interactions, structural joint performance, and thermal and mechanical performance of integrated structural systems that operate at temperatures ranging from 1500 C to 3000 C, depending on the application. This paper will present recent advances in the development of hot structures, including development of environmentally durable, high temperature leading edges and control surfaces, integrated thermal protection systems, and repair technologies. The X-43A Mach-10 vehicle utilized carbon/carbon (C/C) leading edges on the nose, horizontal control surface, and vertical tail. The nose and vertical and horizontal tail leading edges were fabricated out of a 3:1 biased, high thermal conductivity C/C. The leading edges were coated with a three-layer coating comprised of a SiC conversion of the C/C, followed by a CVD layer of SiC, followed by a thin CVD layer of HfC. Work has also been performed on the development of an integrated structure and was focused on both hot and warm (insulated) structures and integrated fuselage/tank/TPS systems. The objective was to develop integrated multifunctional airframe structures that eliminate fragile external thermal-protection systems and incorporate the insulating function within the structure. The approach taken to achieve this goal was to develop candidate hypersonic

  15. Controlling the Electronic Structure of Bilayer Graphene

    NASA Astrophysics Data System (ADS)

    Ohta, Taisuke; Bostwick, Aaron; Seyller, Thomas; Horn, Karsten; Rotenberg, Eli

    2006-08-01

    We describe the synthesis of bilayer graphene thin films deposited on insulating silicon carbide and report the characterization of their electronic band structure using angle-resolved photoemission. By selectively adjusting the carrier concentration in each layer, changes in the Coulomb potential led to control of the gap between valence and conduction bands. This control over the band structure suggests the potential application of bilayer graphene to switching functions in atomic-scale electronic devices.

  16. 76 FR 12144 - Advanced Optics Electronics, Inc.; Order of Suspension of Trading

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-04

    ... COMMISSION Advanced Optics Electronics, Inc.; Order of Suspension of Trading March 2, 2011. It appears to the... securities of Advanced Optics Electronics, Inc. because it has not filed any periodic reports since the... of investors require a suspension of trading in Advanced Optics Electronics, Inc. Therefore, it...

  17. Advanced Paramagnetic Resonance Spectroscopies of Iron-Sulfur Proteins: Electron Nuclear Double Resonance (ENDOR) and Electron Spin Echo Envelope Modulation (ESEEM)

    PubMed Central

    Cutsail, George E.; Telser, Joshua; Hoffman, Brian M.

    2015-01-01

    The advanced electron paramagnetic resonance (EPR) techniques, electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM) spectroscopies, provide unique insights into the structure, coordination chemistry, and biochemical mechanism of Nature’s widely distributed iron-sulfur cluster (FeS) proteins. This review describes the ENDOR and ESEEM techniques and then provides a series of case studies on their application to a wide variety of FeS proteins including ferredoxins, nitrogenase, and radical SAM enzymes. PMID:25686535

  18. High-resolution electron microscopy of advanced materials

    SciTech Connect

    Mitchell, T.E.; Kung, H.H.; Sickafus, K.E.; Gray, G.T. III; Field, R.D.; Smith, J.F.

    1997-11-01

    This final report chronicles a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The High-Resolution Electron Microscopy Facility has doubled in size and tripled in quality since the beginning of the three-year period. The facility now includes a field-emission scanning electron microscope, a 100 kV field-emission scanning transmission electron microscope (FE-STEM), a 300 kV field-emission high-resolution transmission electron microscope (FE-HRTEM), and a 300 kV analytical transmission electron microscope. A new orientation imaging microscope is being installed. X-ray energy dispersive spectrometers for chemical analysis are available on all four microscopes; parallel electron energy loss spectrometers are operational on the FE-STEM and FE-HRTEM. These systems enable evaluation of local atomic bonding, as well as chemical composition in nanometer-scale regions. The FE-HRTEM has a point-to-point resolution of 1.6 {angstrom}, but the resolution can be pushed to its information limit of 1 {angstrom} by computer reconstruction of a focal series of images. HRTEM has been used to image the atomic structure of defects such as dislocations, grain boundaries, and interfaces in a variety of materials from superconductors and ferroelectrics to structural ceramics and intermetallics.

  19. Fine precipitation scenarios of AlZnMg(Cu) alloys revealed by advanced atomic-resolution electron microscopy study Part I: Structure determination of the precipitates in AlZnMg(Cu) alloys

    SciTech Connect

    Liu, J.Z.; Chen, J.H.; Yuan, D.W.; Wu, C.L.; Zhu, J.; Cheng, Z.Y.

    2015-01-15

    Although they are among the most important precipitation-hardened materials for industry applications, the high-strength AlZnMg(Cu) alloys have thus far not yet been understood adequately about their underlying precipitation scenarios in relation with the properties. This is partly due to the fact that the structures of a number of different precipitates involved in electron microscopy in association with quantitative image simulations have to be employed; a systematic study of these hardening precipitates in different alloys is also necessary. In Part I of the present study, it is shown that there are five types of structurally different precipitates including the equilibrium η-phase precipitate. Using two state-of-the-art atomic-resolution imaging techniques in electron microscopy in association with quantitative image simulations, we have determined and clarified all the unknown precipitate structures. It is demonstrated that atomic-resolution imaging can directly suggest approximate structure models, whereas quantitative image analysis can refine the structure details that are much smaller than the resolution of the microscope. This combination is crucially important for solving the difficult structure problems of the strengthening precipitates in AlZnMg(Cu) alloys. - Highlights: Part I: • We determine and verify all the key precipitate structures in AlMgZn(Cu) alloys. • We employ aberration-corrected scanning transmission electron microscopy (STEM). • We use aberration-corrected high-resolution TEM (HRTEM) for the investigations. • We obtain atomic-resolution images of the precipitates and model their structures. • We refine all precipitate structures with quantitative image simulation analysis. Part II: • The hardening precipitates in AlZnMg alloys shall be classified into two groups. • Two precipitation scenarios coexist in the alloys. • The precipitation behavior of such an alloy depends on the alloy's composition. • Very detailed phase/structure

  20. Advancements in vibroacoustic evaluation of satellite structures

    NASA Astrophysics Data System (ADS)

    Stavrinidis, C.; Witting, M.; Ikoss, S. I.; Klein, M.

    2001-02-01

    The importance of the launcher vibroacoustic environment is increasing with respect to satellite loads due to the increase in size and decrease in surface mass of lightweight appendages like antennas and solar arrays. The loads generated by the vibroacoustic environment need to be covered adequately to ensure satellite structural integrity. This is of particular importance in the low-frequency range where the low frequencies of light appendages and equipment couple with the acoustic environment. In order to cope with the increasing demand for prediction of structural loads due to the acoustic environment, various methods have been developed in the frame of ESA research and development activities. These range from simplified approaches with partial fluid-structure coupling, e.g. the POSTAR package provided by INTESPACE (France) to more sophisticated approaches with full fluid-structure coupling. In the frequency domain this includes pure finite element modelling techniques, where specific tools have been developed by FFA (Sweden) using the ASKA package, as well as coupled finite element—boundary element approaches that have been developed in cooperation with DASA-Dornier (Germany), STRACO (France) and FFA using the commercial packages ASKA and RAYON. For fully coupled fluid structure analysis in the time domain the ASTRYD code from METRAVIB (France) is employed where advancements have been supported by CNES. Applications of these tools range from simple benchmarks such as simply supported plates, cavity enclosures or generic satellite-fairing models to complex satellite structure configurations. Evaluations of antenna reflector structures (Artemis communication antenna) and satellite equipment panels (polar platform) are presented. The paper covers also the investigation of payload/fairing effects (influence of fairing helium purging on the coupled-system response) together with DASA-Dornier, FFA and STRACO, as well as the vibroacoustic analysis of solar array

  1. Advanced electron crystallography through model-based imaging

    PubMed Central

    Van Aert, Sandra; De Backer, Annick; Martinez, Gerardo T.; den Dekker, Arnold J.; Van Dyck, Dirk; Bals, Sara; Van Tendeloo, Gustaaf

    2016-01-01

    The increasing need for precise determination of the atomic arrangement of non-periodic structures in materials design and the control of nanostructures explains the growing interest in quantitative transmission electron microscopy. The aim is to extract precise and accurate numbers for unknown structure parameters including atomic positions, chemical concentrations and atomic numbers. For this purpose, statistical parameter estimation theory has been shown to provide reliable results. In this theory, observations are considered purely as data planes, from which structure parameters have to be determined using a parametric model describing the images. As such, the positions of atom columns can be measured with a precision of the order of a few picometres, even though the resolution of the electron microscope is still one or two orders of magnitude larger. Moreover, small differences in average atomic number, which cannot be distinguished visually, can be quantified using high-angle annular dark-field scanning transmission electron microscopy images. In addition, this theory allows one to measure compositional changes at interfaces, to count atoms with single-atom sensitivity, and to reconstruct atomic structures in three dimensions. This feature article brings the reader up to date, summarizing the underlying theory and highlighting some of the recent applications of quantitative model-based transmisson electron microscopy. PMID:26870383

  2. Initial performance of Los Alamos Advanced Free Electron Laser

    SciTech Connect

    Nguyen, D.C.; Austin, R.H.; Chan, K.C.D.

    1993-09-01

    The Los Alamos compact Advanced FEL has lased at 4.7 and 5.2 {mu}m with a 1-cm period wiggler and a high-brightness electron beam at 16.8 and 15.8 MeV, respectively. The measured electron beam normalized emittance is 1.7 {pi}{center_dot}mm{center_dot}mrad at a peak current of 100 A, corresponding to a beam brightness greater than 2 {times} 10{sup 12} A/m{sup 2}rad{sup 2}. Initial results indicate that the AFEL small signal gain is {approximately}8% at 0.3 nC (30 A peak). The maximum output energy is 7 mJ over a 2-{mu}s macropulse. The AFEL performance can be significantly enhanced by improvements in the rf and drive laser stability.

  3. Radiation-Hardened Electronics for Advanced Communications Systems

    NASA Technical Reports Server (NTRS)

    Whitaker, Sterling

    2015-01-01

    Novel approach enables high-speed special-purpose processors Advanced reconfigurable and reprogrammable communication systems will require sub-130-nanometer electronics. Legacy single event upset (SEU) radiation-tolerant circuits are ineffective at speeds greater than 125 megahertz. In Phase I of this project, ICs, LLC, demonstrated new base-level logic circuits that provide SEU immunity for sub-130-nanometer high-speed circuits. In Phase II, the company developed an innovative self-restoring logic (SRL) circuit and a system approach that provides high-speed, SEU-tolerant solutions that are effective for sub-130-nanometer electronics scalable to at least 22-nanometer processes. The SRL system can be used in the design of NASA's next-generation special-purpose processors, especially reconfigurable communication processors.

  4. Foil support structure for large electron guns

    SciTech Connect

    Brucker, J.P.; Rose, E.A.

    1993-08-01

    This paper describes a novel support structure for a vacuum diode used to pump a gaseous laser with an electron beam. Conventional support structures are designed to hold a foil flat and rigid. This new structure takes advantage of the significantly greater strength of metals in pure tension, utilizing curved shapes for both foil and support structure. The shape of the foil is comparable to the skin of a balloon, and the shape of the support structures is comparable to the cables of a suspension bridge. This design allows a significant reduction in foil thickness and support structure mass, resulting in a lower electron-beam loss between diode and laser gas. In addition, the foil is pre-formed in the support structure at pressures higher than operating pressure. Therefore, the foil is operated far from the yield point. Increased reliability is anticipated.

  5. Atomic Structure. Independent Learning Project for Advanced Chemistry (ILPAC). Unit S2.

    ERIC Educational Resources Information Center

    Inner London Education Authority (England).

    This unit on atomic structure is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit consists of two levels. Level one focuses on the atomic nucleus. Level two focuses on the arrangement of extranuclear electrons, approaching atomic orbitals through both electron bombardment and spectra.…

  6. Correlative Light Electron Microscopy: Connecting Synaptic Structure and Function

    PubMed Central

    Begemann, Isabell; Galic, Milos

    2016-01-01

    Many core paradigms of contemporary neuroscience are based on information obtained by electron or light microscopy. Intriguingly, these two imaging techniques are often viewed as complementary, yet separate entities. Recent technological advancements in microscopy techniques, labeling tools, and fixation or preparation procedures have fueled the development of a series of hybrid approaches that allow correlating functional fluorescence microscopy data and ultrastructural information from electron micrographs from a singular biological event. As correlative light electron microscopy (CLEM) approaches become increasingly accessible, long-standing neurobiological questions regarding structure-function relation are being revisited. In this review, we will survey what developments in electron and light microscopy have spurred the advent of correlative approaches, highlight the most relevant CLEM techniques that are currently available, and discuss its potential and limitations with respect to neuronal and synapse-specific applications. PMID:27601992

  7. Nanofabrication by advanced electron microscopy using intense and focused beam∗

    PubMed Central

    Furuya, Kazuo

    2008-01-01

    The nanogrowth and nanofabrication of solid substances using an intense and focused electron beam are reviewed in terms of the application of scanning and transmission electron microscopy (SEM, TEM and STEM) to control the size, position and structure of nanomaterials. The first example discussed is the growth of freestanding nanotrees on insulator substrates by TEM. The growth process of the nanotrees was observed in situ and analyzed by high-resolution TEM (HRTEM) and was mainly controlled by the intensity of the electron beam. The second example is position- and size-controlled nanofabrication by STEM using a focused electron beam. The diameters of the nanostructures grown ranged from 4 to 20 nm depending on the size of the electron beam. Magnetic nanostructures were also obtained using an iron-containing precursor gas, Fe(CO)5. The freestanding iron nanoantennas were examined by electron holography. The magnetic field was observed to leak from the nanostructure body which appeared to act as a ‘nanomagnet’. The third example described is the effect of a vacuum on the size and growth process of fabricated nanodots containing W in an ultrahigh-vacuum field-emission TEM (UHV-FE-TEM). The size of the dots can be controlled by changing the dose of electrons and the partial pressure of the precursor. The smallest particle size obtained was about 1.5 nm in diameter, which is the smallest size reported using this method. Finally, the importance of a smaller probe and a higher electron-beam current with atomic resolution is emphasized and an attempt to develop an ultrahigh-vacuum spherical aberration corrected STEM (Cs-corrected STEM) at NIMS is reported. PMID:27877936

  8. Electronic structure and polarizability of metallic nanoshells

    NASA Astrophysics Data System (ADS)

    Prodan, E.; Nordlander, P.

    2002-01-01

    An efficient method for the calculation of the electronic structure of metallic nanoshells is developed. The method is applied to a large nanoshell (of 10 nm in diameter) containing more than 2.5×10 4 conduction electrons. The calculations show that the density of states of the nanoshell is relatively bulk-like. The frequency dependent polarizability is calculated and shown to display strong confinement effects and features similar to what is predicted by semi-classical electrodynamic theory.

  9. Arc Welders' pneumoconiosis: application of advanced scanning electron microscopy.

    PubMed

    Guidotti, T L; Abraham, J L; DeNee, P B; Smith, J R

    1978-01-01

    Study of lung tissue from necropsy of a 58-year-old arc welder with arc welders' pneumoconiosis, confirmed by history, chest radiography, and pathology, demonstrates the versatility and usefulness of new techniques in scanning electron microscopy (SEM). Secondary electron imaging, the most familiar SEM mode, showed heavy cellular infiltrates in alveoli, the interstitium, and within the interstices of loose whorled fibrotic nodules. Backscattered electron imaging, in which contrast is proportional to elemental atomic number, revealed intracellular metal particles not otherwise visible. Microprobe analysis, energy-dispersive x-ray spectrometry, mapped elemeental iron over the particle image and identified traces of silicon in the whorled nodules. Arc welders' pneumoconiosis appears to be more than a benign siderosis resulting from particulate iron deposition. Simultaneous exposure to other components of welding fumes may alter the pathologic picture, inducing a more complicated fibrotic reaction. The more recently developed advanced techniques of SEM are well suited to the study of pneumoconioses and other problems of heterogenous tissue and mixed chemical systems.

  10. Structural and electronic properties for atomic clusters

    NASA Astrophysics Data System (ADS)

    Sun, Yan

    We have studied the structural and electronic properties for different groups of atomic clusters by doing a global search on the potential energy surface using the Taboo Search in Descriptors Space (TSDS) method and calculating the energies with Kohn-Sham Density Functional Theory (KS-DFT). Our goal was to find the structural and electronic principles for predicting the structure and stability of clusters. For Ben (n = 3--20), we have found that the evolution of geometric and electronic properties with size reflects a change in the nature of the bonding from van der Waals to metallic and then bulk-like. The cluster sizes with extra stability agree well with the predictions of the jellium model. In the 4d series of transition metal (TM) clusters, as the d-type bonding becomes more important, the preferred geometric structure changes from icosahedral (Y, Zr), to distorted compact structures (Nb, Mo), and FCC or simple cubic crystal fragments (Tc, Ru, Rh) due to the localized nature of the d-type orbital. Analysis of relative isomer energies and their electronic density of states suggest that these clusters tend to follow a maximum hardness principle (MHP). For A4B12 clusters (A is divalent, B is monovalent), we found unusually large (on average 1.95 eV) HOMO-LUMO gap values. This shows the extra stability at an electronic closed shell (20 electrons) predicted by the jellium model. The importance of symmetry, closed electronic and ionic shells in stability is shown by the relative stability of homotops of Mg4Ag12 which also provides support for the hypothesis that clusters that satisfy more than one stability criterion ("double magic") should be particularly stable.

  11. Advanced electron microscopy characterization of tri-layer rare-earth oxide superlattices

    NASA Astrophysics Data System (ADS)

    Phillips, Patrick; Disa, Ankit; Ismail-Beigi, Sohrab; Klie, Robert; University of Illinois-Chicago Team; Yale University Team

    2015-03-01

    Rare-earth nickelates are known to display complex electronic and magnetic behaviors owed to a very localized and sensitive Ni-site atomic and electronic structure. Toward realizing the goal of manipulating of the energetic ordering of Ni d orbitals and 2D conduction, the present work focuses on the experimental characterization of thin film superlattice structures consisting of alternating layers of LaTiO3 and LaNiO3 sandwiched between a dull insulator, LaAlO3. Using advanced scanning transmission electron microscopy (STEM)-based methods, properties such as interfacial sharpness, electron transfer, O presence, and local electronic structure can be probed at the atomic scale, and will be discussed at length. By combining both energy dispersive X-ray (EDX) and electronic energy loss (EEL) spectroscopies in an aberration-corrected STEM, it is possible to attain energy and spatial resolutions of 0.35 eV and 100 pm, respectively. Focus of the talk will remain not only on the aforementioned properties, but will also include details and parameters of the acquisitions to facilitate future characterization at this level.

  12. Advanced post-acceleration methodology for pseudospark-sourced electron beam

    NASA Astrophysics Data System (ADS)

    Zhao, J.; Yin, H.; Zhang, L.; Shu, G.; He, W.; Zhang, Q.; Phelps, A. D. R.; Cross, A. W.

    2017-02-01

    During its conductive phase, a pseudospark discharge is able to generate a low energy electron beam with a higher combined current density and brightness compared with electron beams formed from any other known type of electron source. In this paper, a configuration is proposed to post-accelerate an electron beam extracted from a single-gap pseudospark discharge cavity in order to achieve high quality high energy intense electron beams. The major advancement is that the triggering of the pseudospark discharge, the pseudospark discharge itself, and the post-accelerating of the electron beam are all driven by a single high voltage pulse. An electron beam with a beam current of ˜20 A, beam voltage of 40 kV, and duration of ˜180 ns has been generated using this structure. The beam energy can be adjusted through adjusting the amplitude of the voltage pulse and the operating voltage of the whole structure, which can be varied from 24 to 50 kV with an efficient triggering method under fixed gas pressure below ˜10 Pa.

  13. A pseudo-tetragonal tungsten bronze superstructure: a combined solution of the crystal structure of K6.4(Nb,Ta)(36.3)O94 with advanced transmission electron microscopy and neutron diffraction.

    PubMed

    Paria Sena, Robert; Babaryk, Artem A; Khainakov, Sergiy; Garcia-Granda, Santiago; Slobodyanik, Nikolay S; Van Tendeloo, Gustaaf; Abakumov, Artem M; Hadermann, Joke

    2016-01-21

    The crystal structure of the K6.4Nb28.2Ta8.1O94 pseudo-tetragonal tungsten bronze-type oxide was determined using a combination of X-ray powder diffraction, neutron diffraction and transmission electron microscopy techniques, including electron diffraction, high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), annular bright field STEM (ABF-STEM) and energy-dispersive X-ray compositional mapping (STEM-EDX). The compound crystallizes in the space group Pbam with unit cell parameters a = 37.468(9) Å, b = 12.493(3) Å, c = 3.95333(15) Å. The structure consists of corner sharing (Nb,Ta)O6 octahedra forming trigonal, tetragonal and pentagonal tunnels. All tetragonal tunnels are occupied by K(+) ions, while 1/3 of the pentagonal tunnels are preferentially occupied by Nb(5+)/Ta(5+) and 2/3 are occupied by K(+) in a regular pattern. A fractional substitution of K(+) in the pentagonal tunnels by Nb(5+)/Ta(5+) is suggested by the analysis of the HAADF-STEM images. In contrast to similar structures, such as K2Nb8O21, also parts of the trigonal tunnels are fractionally occupied by K(+) cations.

  14. Defect Induced Electronic Structure of Uranofullerene

    PubMed Central

    Dai, Xing; Cheng, Cheng; Zhang, Wei; Xin, Minsi; Huai, Ping; Zhang, Ruiqin; Wang, Zhigang

    2013-01-01

    The interaction between the inner atoms/cluster and the outer fullerene cage is the source of various novel properties of endohedral metallofullerenes. Herein, we introduce an adatom-type spin polarization defect on the surface of a typical endohedral stable U2@C60 to predict the associated structure and electronic properties of U2@C61 based on the density functional theory method. We found that defect induces obvious changes in the electronic structure of this metallofullerene. More interestingly, the ground state of U2@C61 is nonet spin in contrast to the septet of U2@C60. Electronic structure analysis shows that the inner U atoms and the C ad-atom on the surface of the cage contribute together to this spin state, which is brought about by a ferromagnetic coupling between the spin of the unpaired electrons of the U atoms and the C ad-atom. This discovery may provide a possible approach to adapt the electronic structure properties of endohedral metallofullerenes. PMID:23439318

  15. Advanced composite combustor structural concepts program

    NASA Technical Reports Server (NTRS)

    Sattar, M. A.; Lohmann, R. P.

    1984-01-01

    An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.

  16. Boron Fullerenes: An Electronic Structure Study

    NASA Astrophysics Data System (ADS)

    Sadrzadeh, Arta; Pupysheva, Olga; Boustani, Ihsan; Yakobson, Boris

    2008-03-01

    Using ab initio calculations, we study electronic structure and frequency modes of B80, a member of boron fullerene family made from boron isomorphs of carbon fullerenes with additional atoms in the centers of hexagons. We also investigate geometrical and electronic structural properties of double-rings with various diameters, which are important as building blocks of boron nanotubes, and as the most stable clusters among the studied isomers with no more than 36 atoms. Double-rings also appear as building blocks of B80. Furthermore, we investigate the possibility of further stabilizing some of fullerenes by depleting them.

  17. Structural materials challenges for advanced reactor systems

    NASA Astrophysics Data System (ADS)

    Yvon, P.; Carré, F.

    2009-03-01

    Key technologies for advanced nuclear systems encompass high temperature structural materials, fast neutron resistant core materials, and specific reactor and power conversion technologies (intermediate heat exchanger, turbo-machinery, high temperature electrolytic or thermo-chemical water splitting processes, etc.). The main requirements for the materials to be used in these reactor systems are dimensional stability under irradiation, whether under stress (irradiation creep or relaxation) or without stress (swelling, growth), an acceptable evolution under ageing of the mechanical properties (tensile strength, ductility, creep resistance, fracture toughness, resilience) and a good behavior in corrosive environments (reactor coolant or process fluid). Other criteria for the materials are their cost to fabricate and to assemble, and their composition could be optimized in order for instance to present low-activation (or rapid desactivation) features which facilitate maintenance and disposal. These requirements have to be met under normal operating conditions, as well as in incidental and accidental conditions. These challenging requirements imply that in most cases, the use of conventional nuclear materials is excluded, even after optimization and a new range of materials has to be developed and qualified for nuclear use. This paper gives a brief overview of various materials that are essential to establish advanced systems feasibility and performance for in pile and out of pile applications, such as ferritic/martensitic steels (9-12% Cr), nickel based alloys (Haynes 230, Inconel 617, etc.), oxide dispersion strengthened ferritic/martensitic steels, and ceramics (SiC, TiC, etc.). This article gives also an insight into the various natures of R&D needed on advanced materials, including fundamental research to investigate basic physical and chemical phenomena occurring in normal and accidental operating conditions, lab-scale tests to characterize candidate materials

  18. New Millennium DS2 electronic packaging an advanced electronic packaging "sandbox".

    NASA Astrophysics Data System (ADS)

    Arakaki, G.; D'Agostino, S.

    New Millennium Deep Space 2 (DS2), managed by the Jet Propulsion Laboratory (JPL), consists of a pair of probes that will be carried to Mars by the Mars Polar Lander. After release from the Lander, both probes enter the atmosphere, impact and penetrate the Martian surface. After impact, a soil sample is taken and analyzed for the presence of water. Other scientific data is collected during descent and after impact. The proposed size and mass of the probes imposed enormous constraints on the packaging of the electronics. To fit the electronics within the probe envelope, the DS2 became a virtual advanced packaging experiment: Chip-on-Board (COB) technology, High Density Interconnect (HDI) technology, and novel flexible interconnects were used in a highly integrated package to meet the requirements. This paper describes the development and testing of the DS2 electronics package and possible follow-on developments at JPL.

  19. Development of Damped Metal Matrix Composites for Advanced Structural Applications

    DTIC Science & Technology

    1990-04-01

    DTIP FiLE COPY Applied Research Laboratory (Dto 00 CD Technical Report NO DEVELOPMENT OF DAMPED METAL MATRIX COMPOSITES FOR ADVANCED STRUCTURAL...DEVELOPMENT OF DAMPED METAL MATRIX COMPOSITES FOR ADVANCED STRUCTURAL APPLICATIONS by Clark A. Updike Ram B. Bhagat Technical Report No. TR 90-004 April 1990... Metal Matrix Composites for Advanced Structural Applications 12 PERSONAL AUTHOR(S) C.A. Updike, R. Bhagat 1 3a TYPE OF REPORT 13b TIME COVERED 14. DATE

  20. Advances in hadronic structure from Lattice QCD

    NASA Astrophysics Data System (ADS)

    Constantinou, Martha

    2017-01-01

    Understanding nucleon structure is considered a milestone of hadronic physics and new facilities are planned devoted to its study. A future Electron-Ion-Collider proposed by the scientific community will greatly deepen our knowledge on the fundamental constituents of the visible world. To achieve this goal, a synergy between the experimental and theoretical sectors is imperative, and Lattice QCD is in a unique position to provide input from first principle calculations. In this talk we will discuss recent progress in nucleon structure from Lattice QCD, focusing on the evaluation of matrix elements using state-of-the-art simulations with pion masses at their physical value. The axial form factors, electromagnetic radii, the quark momentum fraction and the spin content of the nucleon will be discussed. We will also highlight quantities that may guide New Physics searches, such as the scalar and tensor charges. Finally, we will give updates on a new direct approach to compute quark parton distributions functions on the lattice.

  1. Electronic and structural properties of functional nanostructures

    NASA Astrophysics Data System (ADS)

    Yang, Teng

    In this Thesis, I present a study of electronic and structural properties of functional nanostructures such as MoSxIy nanowires, self-assembled monolayer on top of metallic surfaces and structural changes induced in graphite by photo excitations. MoSxI y nanowires, which can be easily synthesized in one step, show many advantages over conventional carbon nanotubes in molecular electronics and many other applications. But how to self-assemble them into desired pattern for practical electronic network? Self-assembled monolayers of polymers on metallic surfaces may help to guide pattern formation of some nanomaterials such as MoSxIy nanowires. I have investigated the physical properties of these nanoscale wires and microscopic self-assembly mechanisms of patterns by total energy calculations combined with molecular dynamics simulations and structure optimization. First, I studied the stability of novel Molybdenum chaicohalide nanowires, a candidate for molecular electronics applications. Next, I investigated the self-assembly of nanoparticles into ordered arrays with the aid of a template. Such templates, I showed, can be formed by polymer adsorption on surfaces such as highly ordered pyrolytic graphite and Ag(111). Finally, I studied the physical origin of of structural changes induced in graphite by light in form of a femtosecond laser pulse.

  2. 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.

  3. Investigation of relativistic runaway electrons in electron cyclotron resonance heating discharges on Korea Superconducting Tokamak Advanced Research

    SciTech Connect

    Kang, C. S.; Lee, S. G.

    2014-07-15

    The behavior of relativistic runaway electrons during Electron Cyclotron Resonance Heating (ECRH) discharges is investigated in the Korea Superconducting Tokamak Advanced Research device. The effect of the ECRH on the runaway electron population is discussed. Observations on the generation of superthermal electrons during ECRH will be reported, which will be shown to be consistent with existing theory for the development of a superthermal electron avalanche during ECRH [A. Lazaros, Phys. Plasmas 8, 1263 (2001)].

  4. Electronic structure of Mn and Fe oxides

    NASA Astrophysics Data System (ADS)

    Harrison, Walter

    2008-03-01

    We present a clear, simple tight-binding representation of the electronic structure and cohesive energy (energy of atomization) of MnO, Mn2O3, and MnO2, in which the formal charge states Mn^2+, Mn^3+, and Mn^4+, respectively, occur. It is based upon localized cluster orbitals for each Mn and its six oxygen neighbors. This approach is fundamentally different from local-density theory (or LDA+U), and perhaps diametrically opposite to Dynamical Mean Field Theory. Electronic states were calculated self-consistently using existing parameters [1], but it is found that the charge density is quite insensitive to charge state, so that the starting parameters are adequate. The cohesive energy per Mn is dominated by the transfer of two s electrons to oxygen p states, the same for all three compounds. The differing transfer of majority d electrons to oxygen p states, and the coupling between them, accounts for the observed variation in cohesion in the series. The same description applies to the perovskites, such as LaxSr1-xMnO3, and can be used for FeO, Fe2O3 (and FeO2), Because the formulation is local, it is equally applicable to impurities, defects and surfaces. [1] Walter A. Harrison, Elementary Electronic Structure, World Scientific (Singapore, 1999), revised edition (2004).

  5. Advanced Strained-Superlattice Photocathodes for Polarized Electron Sources

    SciTech Connect

    Dr. Aaron Moy

    2005-01-31

    Polarized electrons have been essential for high-energy parity-violating experiments and measurements of the nucleon spin structure. The availability of a polarized electron beam was crucial to the success of the Stanford Linear Collider (SLC) in achieving a precise measurement of the electroweak mixing angle, and polarized electron beams will be required for all future linear colliders. Polarized electrons are readily produced by GaAs photocathode sources. When a circularly polarized laser beam tuned to the bandgap minimum is directed to the negative-electron-affinity (NEA) surface of a GaAs crystal, longitudinally polarized electrons are emitted into vacuum. The electron polarization is easily reversed by reversing the laser polarization. The important properties of these photocathodes for accelerator applications are: degree of polarization of the extracted beam; ability to extract sufficient charge to meet accelerator pulse-structure requirements; efficiency and stability of operation; and absence of any asymmetries in the beam properties (charge, position, energy, etc.) upon polarization reversal. The performance of GaAs photocathodes has improved significantly since they were first introduced in 1978 [1]. The theoretical maximum polarization of 50% for natural GaAs was first exceeded in 1991 using the lattice mismatch of a thin InGaAs layer epitaxially grown over a GaAs substrate to generate a strain in the former that broke the natural degeneracy between the heavy- and light-hole valence bands [2]. Polarizations as high as 78% were produced for the SLC from photocathodes based on a thin GaAs epilayer grown on GaAsP [3,4]. After 10 years of experience with many cathode samples at several laboratories [5], the maximum polarization using the GaAs/GaAsP single strained-layer cathode remained limited to 80%, while the quantum efficiency (QE) for a 100-nm epilayer is only 0.3% or less. Two factors were known to limit the polarization of these cathodes: (1) the

  6. Electronic structure engineering of various structural phases of phosphorene.

    PubMed

    Kaur, Sumandeep; Kumar, Ashok; Srivastava, Sunita; Tankeshwar, K

    2016-07-21

    We report the tailoring of the electronic structures of various structural phases of phosphorene (α-P, β-P, γ-P and δ-P) based homo- and hetero-bilayers through in-plane mechanical strains, vertical pressure and transverse electric field by employing density functional theory. In-plane biaxial strains have considerably modified the electronic bandgap of both homo- and hetero-bilayers while vertical pressure induces metallization in the considered structures. The γ-P homo-bilayer structure showed the highest ultimate tensile strength (UTS ∼ 6.21 GPa) upon in-plane stretching. Upon application of a transverse electric field, the variation in the bandgap of hetero-bilayers was found to be strongly dependent on the polarity of the applied field which is attributed to the counterbalance between the external electric field and the internal field induced by different structural phases and heterogeneity in the arrangements of atoms of each surface of the hetero-bilayer system. Our results demonstrate that the electronic structures of the considered hetero- and homo-bilayers of phosphorene could be modified by biaxial strain, pressure and electric field to achieve the desired properties for future nano-electronic devices.

  7. [Structured electronic consultation letter for shoulder disorders].

    PubMed

    Paloneva, Juha; Oikari, Marjo; Ylinen, Jari; Ingalsuo, Minna; Ilkka, Kunnamo; Ilkka, Kiviranta

    2012-01-01

    Referral to a specialist has a significant influence on management of the patient and costs associated with the treatments. However, development and research of the process by which patients are referred has been almost neglected. Expectations considering the purpose, contents, and timing of the referral of the consulting physician and the consultant do not always meet. A structured, electronic consultation letter was developed to respond this need. Functionality and interactivity are the key elements of the referral, including (1) an electronic referral letter to a specialist, (2) interactive education in clinical examination and management of shoulder disorders, and (3) an instrument of clinical examination and documentation of shoulder disorders.

  8. The electronic structure of nonpolyhex carbon nanotubes.

    PubMed

    László, István

    2004-01-01

    Generalizing the folding method to any periodic two-dimensional planar carbon structures we have calculated the corresponding electronic structures in the framework of the one orbital one site tight-binding (Bloch-Hückel) method by solving the eigenvalue problems in a numerical way. We discussed the metallic or the nonmetallic behavior of the nanotubes by applying the folding vectors of parameters (m, n). We extended the topological coordinate method to two-dimensional periodic planar structures as well. Nearly regular hexagonal, pentagonal, and heptagonal polygons were obtained. The curvatures of the final relaxed structures can be read from the sizes of the polygons. Thus relying only on the topological information we could describe the shape of the tubular structures and their conductivity behaviors.

  9. Electronic and structural reconstruction in titanate heterostructures from first principles

    NASA Astrophysics Data System (ADS)

    Mulder, Andrew T.; Fennie, Craig J.

    2014-03-01

    Recent advances in transition metal oxide heterostructures have opened new routes to create materials with novel functionalities and properties. One direction has been to combine a Mott insulating perovskite with an electronic d1 configuration, such as LaTiO3, with a band insulating d0 perovskite, such as SrTiO3. An exciting recent development is the demonstration of interfacial conductivity in GdTiO3/SrTiO3 heterostructures that display a complex structural motif of octahedral rotations and ferromagnetic properties similar to bulk GdTiO3. In this talk we present our first principles investigation of the interplay of structural, electronic, magnetic, and orbital degrees of freedom for a wide range of d1/d0 titanate heterostructures. We find evidence for both rotation driven ferroelectricity and a symmetry breaking electronic reconstruction with a concomitant structural distortion at the interface. We argue that these materials represent an ideal platform to realize novel functionalities such as the electric field control of electronic and magnetic properties.

  10. Status and Perspectives of Ion Track Electronics for Advanced Biosensing

    NASA Astrophysics Data System (ADS)

    Fink, D.; Muñoz, H. Gerardo; Alfonta, L.; Mandabi, Y.; Dias, J. F.; de Souza, C. T.; Bacakova, L. E.; Vacík, J.; Hnatowicz, V.; Kiv, A. E.; Fuks, D.; Papaleo, R. M.

    New multifunctional ion irradiation-based three-dimensional electronic structures are developed for biotechnological applications, specifically for sensing of biomaterials, bacteria and mammalian cells. This is accomplished by combined micrometric surface and nanometric bulk microstructuring of insulators (specifically of polymer foils and SiO2/Si hybride structures) by adequate ion beams. Our main goal is the production of a cheap small universal generic working platform with multifunctional properties for biomedical analysis. Surface engineering of this platform enables cell bonding and its bulk engineering enables the extraction of cell secrets, for the sake of intercepting and analyzing the biomolecules used in cell communication. The exact knowledge of the spectrum of these cell-secreted signalling molecules should enable one to identify unambiguously the cell type. This knowledge will help developing strategies for preventive quorum sensing of bacteria, with the aim of fighting bacterial infections in an ecologically secure way.

  11. Advanced fertility diagnosis in stallion semen using transmission electron microscopy.

    PubMed

    Pesch, Sandra; Bostedt, Hartwig; Failing, Klaus; Bergmann, Martin

    2006-02-01

    Routine semen analysis of stallions is based on light microscopy (LM). However, there are still a number of animals that are subfertile or even infertile not being identified with conventional semen analysis. The objective of this study was to investigate the suitability of transmission electron microscopy (TEM) for advanced fertility diagnosis in stallion. We examined ejaculates of 46 stallions with known fertility. Animals were divided into three different groups: group 1, fertile stallions (pregnant mares> or =70%, n=29); group 2, subfertile stallions (pregnant mares 10-69%, n=14); group 3, infertile stallions (pregnant mares<10%, n=3). Ejaculates were collected in spring 2002. Conventional semen analysis (volume, sperm concentration, motility, live:dead ratio and percentage of morphologically normal sperm) was immediately performed after semen collection. Ultrastructural analysis included the evaluation of 200 acrosomes, heads, midpieces and cross-sections of tails as well as 100 longitudinal sections of tails from every ejaculate. Using LM, we found a significant increase of morphological deviations from 24.5% (x ) in group 1 to 34.5% in group 2 and 73.5% in group 3. Using TEM, we found a significant increase of detached acrosomes from 6.1% in group 1 to 7.6% in group 2 and 21.4% in group 3. Deviations in tubule pattern were also increased (but not significant) from 2.7% in fertile and 2.8% in subfertile to 11.4% in infertile stallions as well as multiple tails from 1.9% in fertile to 2.0% in subfertile and 8.9% in infertile. Our data indicate that TEM is suitable for advanced fertility diagnostic in stallions, giving a connection between fertility and morphology. It suggests that the most likely reason for sub- and infertility in stallion in case of increased LM pathomorphology of semen are acrosomal alterations, especially detached acrosomes.

  12. Advanced methods of structural and trajectory analysis for transport aircraft

    NASA Technical Reports Server (NTRS)

    Ardema, Mark D.

    1995-01-01

    This report summarizes the efforts in two areas: (1) development of advanced methods of structural weight estimation, and (2) development of advanced methods of trajectory optimization. The majority of the effort was spent in the structural weight area. A draft of 'Analytical Fuselage and Wing Weight Estimation of Transport Aircraft', resulting from this research, is included as an appendix.

  13. 8th international conference on electronic spectroscopy and structure

    SciTech Connect

    Robinson, Art

    2000-10-16

    Gathering from 33 countries around the world, 408 registrants and a number of local drop-in participants descended on the Clark Kerr Campus of the University of California, Berkeley, from Monday, August 7 through Saturday, August 12, 2000 for the Eighth International Conference on Electronic Structure and Spectroscopy (ICESS8). At the conference, participants benefited from an extensive scientific program comprising more than 100 oral presentations (plenary lectures and invited and contributed talks) and 330 poster presentations, as well as ample time for socializing and a tour of the Advanced Light Source (ALS) at the nearby Lawrence Berkeley National Laboratory.

  14. Advanced Power Electronic Interfaces for Distributed Energy Systems Part 1: Systems and Topologies

    SciTech Connect

    Kramer, W.; Chakraborty, S.; Kroposki, B.; Thomas, H.

    2008-03-01

    This report summarizes power electronic interfaces for DE applications and the topologies needed for advanced power electronic interfaces. It focuses on photovoltaic, wind, microturbine, fuel cell, internal combustion engine, battery storage, and flywheel storage systems.

  15. Electronic structure of worm-eaten graphene

    NASA Astrophysics Data System (ADS)

    Negishi, Hayato; Takeda, Kyozaburo

    2017-02-01

    We theoretically study the electronic structure of graphenes having several kinds of imperfections such as atomic vacancies and heteroatom replacements. We consider 12 different configurations of vacancies and 39 different geometries of heteroatom replacements in order to approximately take into account the random conformations of imperfections. To systematically provide a perspective understanding of the defect π and σ states caused by atomistic voids and/or vacancies and heteroatom replacements, we have carried out a tight-binding (TB) calculation. We study the orbital hybridization to clarify the origin and formation of π and σ defect states arising from such imperfections. We also discuss the electronic structure around the Fermi level through the TB band calculation.

  16. Advances in experimental mechanics for advanced aircraft structures

    NASA Astrophysics Data System (ADS)

    O'Brien, Eddie W.

    1997-03-01

    The industrial requirement for higher efficiency, lean performance, airframe structures to form the basis of more cost effective Commercial Aircraft has encouraged developments in all aspects of aeronautical design and manufacture. Until recently the main emphasis has been in the area of computer and numerical analysis, however new developments in experimental mechanics are emerging as very powerful tools for use in the validation of numerical analyses and for primary stress analysis data. The developments described have been forced by economic drivers that address more efficient analysis techniques with respect to cost, specific weight and expended time for analysis.

  17. Electronic structure investigation of biphenylene films

    NASA Astrophysics Data System (ADS)

    Totani, R.; Grazioli, C.; Zhang, T.; Bidermane, I.; Lüder, J.; de Simone, M.; Coreno, M.; Brena, B.; Lozzi, L.; Puglia, C.

    2017-02-01

    Photoelectron Spectroscopy (PS) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The obtained results have been compared to previous gas phase spectra and single molecule Density Functional Theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, NEXAFS measurements allowed characterizing the variation of the molecular arrangement with the film thickness and helped to clarify the substrate-molecule interaction.

  18. Atomic and Electronic Structure of Solids

    NASA Astrophysics Data System (ADS)

    Kaxiras, Efthimios

    2003-01-01

    Preface; Acknowledgements; Part I. Crystalline Solids: 1. Atomic structure of crystals; 2. The single-particle approximation; 3. Electrons in crystal potential; 4. Band structure of crystals; 5. Applications of band theory; 6. Lattice vibrations; 7. Magnetic behaviour of solids; 8. Superconductivity; Part II. Defects, Non-Crystalline Solids and Finite Structures: 9. Defects I: point defects; 10. Defects II: line defects; 11. Defects III: surfaces and interfaces; 12. Non-crystalline solids; 13. Finite structures; Part III. Appendices: A. Elements of classical electrodynamics; B. Elements of quantum mechanics; C. Elements of thermodynamics; D. Elements of statistical mechanics; E. Elements of elasticity theory; F. The Madelung energy; G. Mathematical tools; H. Nobel Prize citations; I. Units and symbols; References; Index.

  19. Controlling the Electronic Structure of Bilayer Graphene

    NASA Astrophysics Data System (ADS)

    Ohta, Taisuke; Bostwick, Aaron; McChesney, Jessica; Seyller, Thomas; Horn, Karsten; Rotenberg, Eli

    2007-03-01

    Carbon-based materials such as carbon nanotubes, graphite intercalation compounds, fullerenes, and ultrathin graphite films exhibit many exotic phenomena such as superconductivity and an anomalous quantum Hall effect. These findings have caused renewed interest in the electronic structure of ultrathin layers of graphene: a single honeycomb carbon layer that is the building block for these materials. There is a strong motivation to incorporate graphene multilayers into atomic-scale devices, spurred on by rapid progress in their fabrication and manipulation. We have synthesized bilayer graphene thin films deposited on insulating silicon carbide and characterized their electronic band structure using angle-resolved photoemission. By selectively adjusting the carrier concentration in each layer, changes in the Coulomb potential led to control of the gap between valence and conduction bands [1]. This control over the band structure suggests the potential application of bilayer graphene to switching functions in atomic scale electronic devices. [1] T. Ohta, A. Bostwick, T. Seyller, K. Horn, E. Rotenberg, Science, 313, 951 (2006).

  20. Advances in the modeling of single electron transistors for the design of integrated circuit.

    PubMed

    Chi, Yaqing; Sui, Bingcai; Yi, Xun; Fang, Liang; Zhou, Hailiang

    2010-09-01

    Single electron transistor (SET) has become a promising candidate for the key device of logic circuit in the near future. The advances of recent 5 years in the modeling of SETs are reviewed for the simulation of SET/hybrid CMOS-SET integrated circuit. Three dominating SET models, Monte Carlo model, master equation model and macro model, are analyzed, tested and compared on their principles, characteristics, applicability and development trend. The Monte Carlo model is suitable for SET structure research and simulation of small scale SET circuit, while the analytical model based on combination with master equation and macro model is suitable to simulate the SET circuit at balanceable efficiency and accuracy.

  1. Quantum mirages formed by coherent projection of electronic structure

    PubMed

    Manoharan; Lutz; Eigler

    2000-02-03

    Image projection relies on classical wave mechanics and the use of natural or engineered structures such as lenses or resonant cavities. Well-known examples include the bending of light to create mirages in the atmosphere, and the focusing of sound by whispering galleries. However, the observation of analogous phenomena in condensed matter systems is a more recent development, facilitated by advances in nanofabrication. Here we report the projection of the electronic structure surrounding a magnetic Co atom to a remote location on the surface of a Cu crystal; electron partial waves scattered from the real Co atom are coherently refocused to form a spectral image or 'quantum mirage'. The focusing device is an elliptical quantum corral, assembled on the Cu surface. The corral acts as a quantum mechanical resonator, while the two-dimensional Cu surface-state electrons form the projection medium. When placed on the surface, Co atoms display a distinctive spectroscopic signature, known as the many-particle Kondo resonance, which arises from their magnetic moment. By positioning a Co atom at one focus of the ellipse, we detect a strong Kondo signature not only at the atom, but also at the empty focus. This behaviour contrasts with the usual spatially-decreasing response of an electron gas to a localized perturbation.

  2. Electronic structure theory of the superheavy elements

    NASA Astrophysics Data System (ADS)

    Eliav, Ephraim; Fritzsche, Stephan; Kaldor, Uzi

    2015-12-01

    High-accuracy calculations of atomic properties of the superheavy elements (SHE) up to element 122 are reviewed. The properties discussed include ionization potentials, electron affinities and excitation energies, which are associated with the spectroscopic and chemical behavior of these elements, and are therefore of considerable interest. Accurate predictions of these quantities require high-order inclusion of relativity and electron correlation, as well as large, converged basis sets. The Dirac-Coulomb-Breit Hamiltonian, which includes all terms up to second order in the fine-structure constant α, serves as the framework for the treatment; higher-order Lamb shift terms are considered in some selected cases. Electron correlation is treated by either the multiconfiguration self-consistent-field approach or by Fock-space coupled cluster theory. The latter is enhanced by the intermediate Hamiltonian scheme, allowing the use of larger model (P) spaces. The quality of the calculations is assessed by applying the same methods to lighter homologs of the SHEs and comparing with available experimental information. Very good agreement is obtained, within a few hundredths of an eV, and similar accuracy is expected for the SHEs. Many of the properties predicted for the SHEs differ significantly from what may be expected by straightforward extrapolation of lighter homologs, demonstrating that the structure and chemistry of SHEs are strongly affected by relativity. The major scientific challenge of the calculations is to find the electronic structure and basic atomic properties of the SHE and assign its proper place in the periodic table. Significant recent developments include joint experimental-computational studies of the excitation spectrum of Fm and the ionization energy of Lr, with excellent agreement of experiment and theory, auguring well for the future of research in the field.

  3. Nanomaterial datasets to advance tomography in scanning transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Levin, Barnaby D. A.; Padgett, Elliot; Chen, Chien-Chun; Scott, M. C.; Xu, Rui; Theis, Wolfgang; Jiang, Yi; Yang, Yongsoo; Ophus, Colin; Zhang, Haitao; Ha, Don-Hyung; Wang, Deli; Yu, Yingchao; Abruña, Hector D.; Robinson, Richard D.; Ercius, Peter; Kourkoutis, Lena F.; Miao, Jianwei; Muller, David A.; Hovden, Robert

    2016-06-01

    Electron tomography in materials science has flourished with the demand to characterize nanoscale materials in three dimensions (3D). Access to experimental data is vital for developing and validating reconstruction methods that improve resolution and reduce radiation dose requirements. This work presents five high-quality scanning transmission electron microscope (STEM) tomography datasets in order to address the critical need for open access data in this field. The datasets represent the current limits of experimental technique, are of high quality, and contain materials with structural complexity. Included are tomographic series of a hyperbranched Co2P nanocrystal, platinum nanoparticles on a carbon nanofibre imaged over the complete 180° tilt range, a platinum nanoparticle and a tungsten needle both imaged at atomic resolution by equal slope tomography, and a through-focal tilt series of PtCu nanoparticles. A volumetric reconstruction from every dataset is provided for comparison and development of post-processing and visualization techniques. Researchers interested in creating novel data processing and reconstruction algorithms will now have access to state of the art experimental test data.

  4. 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.

  5. Thin dielectric film thickness determination by advanced transmission electron microscopy

    SciTech Connect

    Diebold, A.C.; Foran, B.; Kisielowski, C.; Muller, D.; Pennycook, S.; Principe, E.; Stemmer, S.

    2003-09-01

    High Resolution Transmission Electron Microscopy (HR-TEM) has been used as the ultimate method of thickness measurement for thin films. The appearance of phase contrast interference patterns in HR-TEM images has long been confused as the appearance of a crystal lattice by non-specialists. Relatively easy to interpret crystal lattice images are now directly observed with the introduction of annular dark field detectors for scanning TEM (STEM). With the recent development of reliable lattice image processing software that creates crystal structure images from phase contrast data, HR-TEM can also provide crystal lattice images. The resolution of both methods was steadily improved reaching now into the sub Angstrom region. Improvements in electron lens and image analysis software are increasing the spatial resolution of both methods. Optimum resolution for STEM requires that the probe beam be highly localized. In STEM, beam localization is enhanced by selection of the correct aperture. When STEM measurement is done using a highly localized probe beam, HR-TEM and STEM measurement of the thickness of silicon oxynitride films agree within experimental error. In this paper, the optimum conditions for HR-TEM and STEM measurement are discussed along with a method for repeatable film thickness determination. The impact of sample thickness is also discussed. The key result in this paper is the proposal of a reproducible method for film thickness determination.

  6. ELECTRON HOLOGRAPHY OF ELECTROMAGNETIC FIELDS - RECENT THEORETICAL ADVANCES.

    SciTech Connect

    BELEGGIA,M.; POZZI, G.; TONOMURA, A.

    2007-01-01

    It has been shown in this work that the Fourier space approach can be fruitfully applied to the calculation of the fields and the associated electron optical phase shift of several magnetic and electrostatic structures, like superconducting vortices in conventional and high-T{sub c} superconductors, reverse biased p-n junctions, magnetic domains and nanoparticles. In all these cases, this novel approach has led to unexpected but extremely interesting results, very often expressed in analytical form, which allow the quantitative and reliable interpretation of the experimental data collected by means of electron holography or of more conventional Lorentz microscopy techniques. Moreover, it is worth recalling that whenever long-range electromagnetic fields are involved, a physical model of the object under investigation is necessary in order to take into account correctly the perturbation of the reference wave induced by the tail of the field protruding into the vacuum. For these reasons, we believe that the Fourier space approach for phase computations we have introduced and discussed in this chapter will represent an invaluable tool for the investigation of electromagnetic fields at the meso- and nano-scale.

  7. Nanomaterial datasets to advance tomography in scanning transmission electron microscopy

    PubMed Central

    Levin, Barnaby D.A.; Padgett, Elliot; Chen, Chien-Chun; Scott, M.C.; Xu, Rui; Theis, Wolfgang; Jiang, Yi; Yang, Yongsoo; Ophus, Colin; Zhang, Haitao; Ha, Don-Hyung; Wang, Deli; Yu, Yingchao; Abruña, Hector D.; Robinson, Richard D.; Ercius, Peter; Kourkoutis, Lena F.; Miao, Jianwei; Muller, David A.; Hovden, Robert

    2016-01-01

    Electron tomography in materials science has flourished with the demand to characterize nanoscale materials in three dimensions (3D). Access to experimental data is vital for developing and validating reconstruction methods that improve resolution and reduce radiation dose requirements. This work presents five high-quality scanning transmission electron microscope (STEM) tomography datasets in order to address the critical need for open access data in this field. The datasets represent the current limits of experimental technique, are of high quality, and contain materials with structural complexity. Included are tomographic series of a hyperbranched Co2P nanocrystal, platinum nanoparticles on a carbon nanofibre imaged over the complete 180° tilt range, a platinum nanoparticle and a tungsten needle both imaged at atomic resolution by equal slope tomography, and a through-focal tilt series of PtCu nanoparticles. A volumetric reconstruction from every dataset is provided for comparison and development of post-processing and visualization techniques. Researchers interested in creating novel data processing and reconstruction algorithms will now have access to state of the art experimental test data. PMID:27272459

  8. Nanomaterial datasets to advance tomography in scanning transmission electron microscopy.

    PubMed

    Levin, Barnaby D A; Padgett, Elliot; Chen, Chien-Chun; Scott, M C; Xu, Rui; Theis, Wolfgang; Jiang, Yi; Yang, Yongsoo; Ophus, Colin; Zhang, Haitao; Ha, Don-Hyung; Wang, Deli; Yu, Yingchao; Abruña, Hector D; Robinson, Richard D; Ercius, Peter; Kourkoutis, Lena F; Miao, Jianwei; Muller, David A; Hovden, Robert

    2016-06-07

    Electron tomography in materials science has flourished with the demand to characterize nanoscale materials in three dimensions (3D). Access to experimental data is vital for developing and validating reconstruction methods that improve resolution and reduce radiation dose requirements. This work presents five high-quality scanning transmission electron microscope (STEM) tomography datasets in order to address the critical need for open access data in this field. The datasets represent the current limits of experimental technique, are of high quality, and contain materials with structural complexity. Included are tomographic series of a hyperbranched Co2P nanocrystal, platinum nanoparticles on a carbon nanofibre imaged over the complete 180° tilt range, a platinum nanoparticle and a tungsten needle both imaged at atomic resolution by equal slope tomography, and a through-focal tilt series of PtCu nanoparticles. A volumetric reconstruction from every dataset is provided for comparison and development of post-processing and visualization techniques. Researchers interested in creating novel data processing and reconstruction algorithms will now have access to state of the art experimental test data.

  9. Actinide electronic structure and atomic forces

    NASA Astrophysics Data System (ADS)

    Albers, R. C.; Rudin, Sven P.; Trinkle, Dallas R.; Jones, M. D.

    2000-07-01

    We have developed a new method[1] of fitting tight-binding parameterizations based on functional forms developed at the Naval Research Laboratory.[2] We have applied these methods to actinide metals and report our success using them (see below). The fitting procedure uses first-principles local-density-approximation (LDA) linear augmented plane-wave (LAPW) band structure techniques[3] to first calculate an electronic-structure band structure and total energy for fcc, bcc, and simple cubic crystal structures for the actinide of interest. The tight-binding parameterization is then chosen to fit the detailed energy eigenvalues of the bands along symmetry directions, and the symmetry of the parameterization is constrained to agree with the correct symmetry of the LDA band structure at each eigenvalue and k-vector that is fit to. By fitting to a range of different volumes and the three different crystal structures, we find that the resulting parameterization is robust and appears to accurately calculate other crystal structures and properties of interest.

  10. Topological Signatures in the Electronic Structure of Graphene Spirals

    PubMed Central

    Avdoshenko, Stas M.; Koskinen, Pekka; Sevinçli, Haldun; Popov, Alexey A.; Rocha, Claudia G.

    2013-01-01

    Topology is familiar mostly from mathematics, but also natural sciences have found its concepts useful. Those concepts have been used to explain several natural phenomena in biology and physics, and they are particularly relevant for the electronic structure description of topological insulators and graphene systems. Here, we introduce topologically distinct graphene forms - graphene spirals - and employ density-functional theory to investigate their geometric and electronic properties. We found that the spiral topology gives rise to an intrinsic Rashba spin-orbit splitting. Through a Hamiltonian constrained by space curvature, graphene spirals have topologically protected states due to time-reversal symmetry. In addition, we argue that the synthesis of such graphene spirals is feasible and can be achieved through advanced bottom-up experimental routes that we indicate in this work. PMID:23568379

  11. Advances in structure elucidation of small molecules using mass spectrometry

    PubMed Central

    Fiehn, Oliver

    2010-01-01

    The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules. Electronic supplementary material The online version of this article (doi:10.1007/s12566-010-0015-9) contains supplementary material, which is available to authorized users. PMID:21289855

  12. Electronic bandstructure of semiconductor dilute bismide structures

    NASA Astrophysics Data System (ADS)

    Erucar, T.; Nutku, F.; Donmez, O.; Erol, A.

    2017-02-01

    In this work electronic band structure of dilute bismide GaAs/GaAs1-xBix quantum well structures with 1.8% and 3.75% bismuth compositions have been investigated both experimentally and theoretically. Photoluminescence (PL) measurements reveal that effective bandgap of the samples decreases approximately 65 meV per bismuth concentration. Temperature dependence of the effective bandgap is obtained to be higher for the sample with higher bismuth concentration. Moreover, both asymmetric characteristic at the low energy tail of the PL and full width at half maximum (FWHM) of PL peak increase with increasing bismuth composition as a result of increased Bi related defects located above valence band (VB). In order to explain composition dependence of the effective bandgap quantitatively, valence band anti-crossing (VBAC) model is used. Bismuth composition and temperature dependence of effective bandgap in a quantum well structure is modeled by solving Schrödinger equation and compared with experimental PL data.

  13. Electronic structure interpolation via atomic orbitals.

    PubMed

    Chen, Mohan; Guo, G-C; He, Lixin

    2011-08-17

    We present an efficient scheme for accurate electronic structure interpolation based on systematically improvable optimized atomic orbitals. The atomic orbitals are generated by minimizing the spillage value between the atomic basis calculations and the converged plane wave basis calculations on some coarse k-point grid. They are then used to calculate the band structure of the full Brillouin zone using the linear combination of atomic orbitals algorithms. We find that usually 16-25 orbitals per atom can give an accuracy of about 10 meV compared to the full ab initio calculations, and the accuracy can be systematically improved by using more atomic orbitals. The scheme is easy to implement and robust, and works equally well for metallic systems and systems with complicated band structures. Furthermore, the atomic orbitals have much better transferability than Shirley's basis and Wannier functions, which is very useful for perturbation calculations.

  14. Predicting Career Advancement with Structural Equation Modelling

    ERIC Educational Resources Information Center

    Heimler, Ronald; Rosenberg, Stuart; Morote, Elsa-Sofia

    2012-01-01

    Purpose: The purpose of this paper is to use the authors' prior findings concerning basic employability skills in order to determine which skills best predict career advancement potential. Design/methodology/approach: Utilizing survey responses of human resource managers, the employability skills showing the largest relationships to career…

  15. Thermal transfer structures coupling electronics card(s) to coolant-cooled structure(s)

    DOEpatents

    David, Milnes P; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Parida, Pritish R; Schmidt, Roger R

    2014-12-16

    Cooling apparatuses and coolant-cooled electronic systems are provided which include thermal transfer structures configured to engage with a spring force one or more electronics cards with docking of the electronics card(s) within a respective socket(s) of the electronic system. A thermal transfer structure of the cooling apparatus includes a thermal spreader having a first thermal conduction surface, and a thermally conductive spring assembly coupled to the conduction surface of the thermal spreader and positioned and configured to reside between and physically couple a first surface of an electronics card to the first surface of the thermal spreader with docking of the electronics card within a socket of the electronic system. The thermal transfer structure is, in one embodiment, metallurgically bonded to a coolant-cooled structure and facilitates transfer of heat from the electronics card to coolant flowing through the coolant-cooled structure.

  16. Advances in cryogenic transmission electron microscopy for the characterization of dynamic self-assembling nanostructures

    PubMed Central

    Newcomb, Christina J.; Moyer, Tyson J.; Lee, Sungsoo S.; Stupp, Samuel I.

    2012-01-01

    Elucidating the structural information of nanoscale materials in their solvent-exposed state is crucial, as a result, cryogenic transmission electron microscopy (cryo-TEM) has become an increasingly popular technique in the materials science, chemistry, and biology communities. Cryo-TEM provides a method to directly visualize the specimen structure in a solution-state through a thin film of vitrified solvent. This technique complements X-ray, neutron, and light scattering methods that probe the statistical average of all species present; furthermore, cryo-TEM can be used to observe changes in structure over time. In the area of self-assembly, this tool has been particularly powerful for the characterization of natural and synthetic small molecule assemblies, as well as hybrid organic–inorganic composites. In this review, we discuss recent advances in cryogenic TEM in the context of self-assembling systems with emphasis on characterization of transitions observed in response to external stimuli. PMID:23204913

  17. Advances in cryogenic transmission electron microscopy for the characterization of dynamic self-assembling nanostructures.

    PubMed

    Newcomb, Christina J; Moyer, Tyson J; Lee, Sungsoo S; Stupp, Samuel I

    2012-12-01

    Elucidating the structural information of nanoscale materials in their solvent-exposed state is crucial, as a result, cryogenic transmission electron microscopy (cryo-TEM) has become an increasingly popular technique in the materials science, chemistry, and biology communities. Cryo-TEM provides a method to directly visualize the specimen structure in a solution-state through a thin film of vitrified solvent. This technique complements X-ray, neutron, and light scattering methods that probe the statistical average of all species present; furthermore, cryo-TEM can be used to observe changes in structure over time. In the area of self-assembly, this tool has been particularly powerful for the characterization of natural and synthetic small molecule assemblies, as well as hybrid organic-inorganic composites. In this review, we discuss recent advances in cryogenic TEM in the context of self-assembling systems with emphasis on characterization of transitions observed in response to external stimuli.

  18. Extraordinary electronic properties in uncommon structure types

    NASA Astrophysics Data System (ADS)

    Ali, Mazhar Nawaz

    In this thesis I present the results of explorations into several uncommon structure types. In Chapter 1 I go through the underlying idea of how we search for new compounds with exotic properties in solid state chemistry. The ideas of exploring uncommon structure types, building up from the simple to the complex, using chemical intuition and thinking by analogy are discussed. Also, the history and basic concepts of superconductivity, Dirac semimetals, and magnetoresistance are briefly reviewed. In chapter 2, the 1s-InTaS2 structural family is introduced along with the discovery of a new member of the family, Ag0:79VS2; the synthesis, structure, and physical properties of two different polymorphs of the material are detailed. Also in this chapter, we report the observation of superconductivity in another 1s structure, PbTaSe2. This material is especially interesting due to it being very heavy (resulting in very strong spin orbit coulping (SOC)), layered, and noncentrosymmetric. Electronic structure calculations reveal the presence of a bulk 3D Dirac cone (very similar to graphene) that is gapped by SOC originating from the hexagonal Pb layer. In Chapter 3 we show the re-investigation of the crystal structure of the 3D Dirac semimetal, Cd3As2. It is found to be centrosymmetric, rather than noncentrosymmetric, and as such all bands are spin degenerate and there is a 4-fold degenerate bulk Dirac point at the Fermi level, making Cd3As2 a 3D electronic analog to graphene. Also, for the first time, scanning tunneling microscopy experiments identify a 2x2 surface reconstruction in what we identify as the (112) cleavage plane of single crystals; needle crystals grow with a [110] long axis direction. Lastly, in chapter 4 we report the discovery of "titanic" (sadly dubbed ⪉rge, nonsaturating" by Nature editors and given the acronym XMR) magnetoresistance (MR) in the non-magnetic, noncentrosymmetric, layered transition metal dichalcogenide WTe2; over 13 million% at 0.53 K in

  19. Pu electronic structure and photoelectron spectroscopy

    SciTech Connect

    Joyce, John J; Durakiewicz, Tomasz; Graham, Kevin S; Bauer, Eric D; Moore, David P; Mitchell, Jeremy N; Kennison, John A; Martin, Richard L; Roy, Lindsay E; Scuseria, G. E.

    2010-01-01

    The electronic structure of PuCoGa{sub 5}, Pu metal, and PuO{sub 2} is explored using photoelectron spectroscopy. Ground state electronic properties are inferred from temperature dependent photoemission near the Fermi energy for Pu metal. Angle-resolved photoemission details the energy vs. crystaJ momentum landscape near the Fermi energy for PuCoGa{sub 5} which shows significant dispersion in the quasiparticle peak near the Fermi energy. For the Mott insulators AnO{sub 2}(An = U, Pu) the photoemission results are compared against hybrid functional calculations and the model prediction of a cross over from ionic to covalent bonding is found to be reasonable.

  20. Structural and electronic properties of fluorographene.

    PubMed

    Samarakoon, Duminda K; Chen, Zhifan; Nicolas, Chantel; Wang, Xiao-Qian

    2011-04-04

    The structural and electronic characteristics of fluorinated graphene are investigated based on first-principles density-functional calculations. A detailed analysis of the energy order for stoichiometric fluorographene membranes indicates that there exists prominent chair and stirrup conformations, which correlate with the experimentally observed in-plane lattice expansion contrary to a contraction in graphane. The optical response of fluorographene is investigated using the GW-Bethe-Salpeter equation approach. The results are in good conformity with the experimentally observed optical gap and reveal predominant charge-transfer excitations arising from strong electron-hole interactions. The appearance of bounded excitons in the ultraviolet region can result in an excitonic Bose-Einstein condensate in fluorographene.

  1. Advanced Materials and Multifunctional Structures for Aerospace Vehicles

    DTIC Science & Technology

    2006-10-01

    through covalent integration of functional nanotubes ”, Advanced Functional Materials, 14(7) (2004) 643-648. 185 R.Z. Ma, J. Wu, B.Q. Wei, J. Liang, and...on Advanced Materials for Multi Functional Structures in Aerospace Vehicles. The advanced synthesis, processing and the characterization techniques...when more than one primary function is performed either simultaneously or sequentially in time. These systems are based on metallic, ceramic and

  2. Electronic Structure of Buried Interfaces - Oral Presentation

    SciTech Connect

    Porter, Zachary

    2015-08-25

    In the electronics behind computer memory storage, the speed and size are dictated by the performance of permanent magnets inside devices called read heads. Complicated magnets made of stacked layers of thin films can be engineered to have properties that yield more energy storage and faster switching times compared to conventional iron or cobalt magnets. The reason is that magnetism is a result of subtle interactions amongst electrons; just how neurons come together on large scales to make cat brains and dog brains, ensembles of electrons interact and become ferromagnets and paramagnets. These interactions make magnets too difficult to study in their entirety, so I focus on the interfaces between layers, which are responsible for the coupling materials physicists hope to exploit to produce next-generation magnets. This project, I study a transition metal oxide material called LSCO, Lanthanum Cobaltite, which can be a paramagnet or a ferromagnet depending on how you tweak the electronic structure. It exhibits an exciting behavior: its sum is greater than the sum of its parts. When another similar material called a LSMO, Lanthanum Manganite, is grown on top of it, their interface has a different type of magnetism from the LSCO or the LSMO! I hope to explain this by demonstrating differently charged ions in the interface. The typical method for quantifying this is x-ray absorption, but all conventional techniques look at every layer simultaneously, averaging the interfaces and the LSCO layers that we want to characterize separately. Instead, I must use a new reflectivity technique, which tracks the intensity of reflected x-rays at different angles, at energies near the absorption peaks of certain elements, to track changes in the electronic structure of the material. The samples were grown by collaborators at the Takamura group at U.C. Davis and probed with this “resonant reflectivity” technique on Beamline 2-1 at the Stanford Synchrotron Radiation Lightsource

  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. Application of advanced electronics to a future spacecraft computer design

    NASA Technical Reports Server (NTRS)

    Carney, P. C.

    1980-01-01

    Advancements in hardware and software technology are summarized with specific emphasis on spacecraft computer capabilities. Available state of the art technology is reviewed and candidate architectures are defined.

  5. Surface structure and electronic properties of materials

    NASA Technical Reports Server (NTRS)

    Siekhaus, W. J.; Somorjai, G. A.

    1975-01-01

    A surface potential model is developed to explain dopant effects on chemical vapor deposition. Auger analysis of the interaction between allotropic forms of carbon and silicon films has shown Si-C formation for all forms by glassy carbon. LEED intensity measurements have been used to determine the mean square displacement of surface atoms of silicon single crystals, and electron loss spectroscopy has shown the effect of structure and impurities on surface states located within the band gap. A thin film of Al has been used to enhance film crystallinity at low temperature.

  6. Structural, electronic and optical properties of carbonnitride

    SciTech Connect

    Cohen, Marvin L.

    1996-01-31

    Carbon nitride was proposed as a superhard material and a structural prototype, Beta-C3N4, was examined using several theoretical models. Some reports claiming experimental verifications have been made recently. The current status of the theory and experiment is reviewed, and a detailed discussion is presented of calculations of the electronic and optical properties of this material. These calculations predict that Beta-C3N4 will have a minimum gap which is indirect at 6.4 plus or minus 0.5 eV. A discussion of the possibility of carbon nitride nanotubes is also presented.

  7. Advanced Standing and Bridge Courses: Structures and Issues

    ERIC Educational Resources Information Center

    GlenMaye, Linnea F.; Lause, Timothy W.; Bolin, Brien L.

    2010-01-01

    This study explores the issue of advanced standing in MSW programs in light of the new Educational Policy and Accreditation Standards (EPAS). Advanced standing structures of MSW programs were studied using a purposive sample consisting of 203 MSW program directors with a response rate of 28% (N=58). The results indicate that slightly more than 15%…

  8. Electron Precipitation at Mars: Advancing Our Understanding with MAVEN

    NASA Astrophysics Data System (ADS)

    Al Noori, H.; Lillis, R. J.; Fillingim, M. O.

    2015-12-01

    Electrons from the solar wind enter the Martian upper atmosphere from space in a process known as electron precipitation. These electrons are confined to move along magnetic field lines and, when those field lines intersect the atmosphere, the electrons collide with atmospheric neutral particles, resulting in heating, dissociation, ionization and excitation of those neutrals. Electron precipitation is an important source of energy input to the Mars upper atmosphere, and is typically the dominant source on the nightside. Past observations from Mars Global Surveyor have characterized patterns of electron precipitation, but only at ~400 km and ~2 AM local time. The MAVEN mission and in particular the SWEA instrument, provides an opportunity to study the distribution of suprathermal electrons in near-Mars space, over a range of altitudes from 120-6000 km and at a range of local times. We will present preliminary observations of flux patterns of these electrons.

  9. Advanced Data Structure and Geographic Information Systems

    NASA Technical Reports Server (NTRS)

    Peuquet, D. (Principal Investigator)

    1984-01-01

    The current state of the art in specified areas of Geographic Information Systems GIS technology is examined. Study of the question of very large, efficient, heterogeneous spatial databases is required in order to explore the potential application of remotely sensed data for studying the long term habitability of the Earth. Research includes a review of spatial data structures and storage, development of operations required by GIS, and preparation of a testbed system to compare Vaster data structure with NASA's Topological Raster Structure.

  10. Predicting RNA structure: advances and limitations.

    PubMed

    Hofacker, Ivo L; Lorenz, Ronny

    2014-01-01

    RNA secondary structures can be predicted using efficient algorithms. A widely used software package implementing a large number of computational methods is the ViennaRNA Package. This chapter describes how to use programs from the ViennaRNA Package to perform common tasks such as prediction of minimum free-energy structures, suboptimal structures, or base pairing probabilities, and generating secondary structure plots with reliability annotation. Moreover, we present recent methods to assess the folding kinetics of an RNA via 2D projections of the energy landscape, identification of local minima and energy barriers, or simulation of RNA folding as a Markov process.

  11. The CECAM Electronic Structure Library: community-driven development of software libraries for electronic structure simulations

    NASA Astrophysics Data System (ADS)

    Oliveira, Micael

    The CECAM Electronic Structure Library (ESL) is a community-driven effort to segregate shared pieces of software as libraries that could be contributed and used by the community. Besides allowing to share the burden of developing and maintaining complex pieces of software, these can also become a target for re-coding by software engineers as hardware evolves, ensuring that electronic structure codes remain at the forefront of HPC trends. In a series of workshops hosted at the CECAM HQ in Lausanne, the tools and infrastructure for the project were prepared, and the first contributions were included and made available online (http://esl.cecam.org). In this talk I will present the different aspects and aims of the ESL and how these can be useful for the electronic structure community.

  12. Electronic-structural dynamics in graphene.

    PubMed

    Gierz, Isabella; Cavalleri, Andrea

    2016-09-01

    We review our recent time- and angle-resolved photoemission spectroscopy experiments, which measure the transient electronic structure of optically driven graphene. For pump photon energies in the near infrared ([Formula: see text]), we have discovered the formation of a population-inverted state near the Dirac point, which may be of interest for the design of THz lasing devices and optical amplifiers. At lower pump photon energies ([Formula: see text]), for which interband absorption is not possible in doped samples, we find evidence for free carrier absorption. In addition, when mid-infrared pulses are made resonant with an infrared-active in-plane phonon of bilayer graphene ([Formula: see text]), a transient enhancement of the electron-phonon coupling constant is observed, providing interesting perspective for experiments that report light-enhanced superconductivity in doped fullerites in which a similar lattice mode was excited. All the studies reviewed here have important implications for applications of graphene in optoelectronic devices and for the dynamical engineering of electronic properties with light.

  13. Electronic-structural dynamics in graphene

    PubMed Central

    Gierz, Isabella; Cavalleri, Andrea

    2016-01-01

    We review our recent time- and angle-resolved photoemission spectroscopy experiments, which measure the transient electronic structure of optically driven graphene. For pump photon energies in the near infrared (ℏωpump=950 meV), we have discovered the formation of a population-inverted state near the Dirac point, which may be of interest for the design of THz lasing devices and optical amplifiers. At lower pump photon energies (ℏωpump<400 meV), for which interband absorption is not possible in doped samples, we find evidence for free carrier absorption. In addition, when mid-infrared pulses are made resonant with an infrared-active in-plane phonon of bilayer graphene (ℏωpump=200 meV), a transient enhancement of the electron-phonon coupling constant is observed, providing interesting perspective for experiments that report light-enhanced superconductivity in doped fullerites in which a similar lattice mode was excited. All the studies reviewed here have important implications for applications of graphene in optoelectronic devices and for the dynamical engineering of electronic properties with light. PMID:27822486

  14. Electron beam coupling to a metamaterial structure

    SciTech Connect

    French, David M.; Shiffler, Don; Cartwright, Keith

    2013-08-15

    Microwave metamaterials have shown promise in numerous applications, ranging from strip lines and antennas to metamaterial-based electron beam driven devices. In general, metamaterials allow microwave designers to obtain electromagnetic characteristics not typically available in nature. High Power Microwave (HPM) sources have in the past drawn inspiration from work done in the conventional microwave source community. In this article, the use of metamaterials in an HPM application is considered by using an effective medium model to determine the coupling of an electron beam to a metamaterial structure in a geometry similar to that of a dielectric Cerenkov maser. Use of the effective medium model allows for the analysis of a wide range of parameter space, including the “mu-negative,”“epsilon-negative,” and “double negative” regimes of the metamaterial. The physics of such a system are modeled analytically and by utilizing the particle-in-cell code ICEPIC. For this geometry and effective medium representation, optimum coupling of the electron beam to the metamaterial, and thus the optimum microwave or RF production, occurs in the epsilon negative regime of the metamaterial. Given that HPM tubes have been proposed that utilize a metamaterial, this model provides a rapid method of characterizing a source geometry that can be used to quickly understand the basic physics of such an HPM device.

  15. Analysis of boron carbides' electronic structure

    NASA Technical Reports Server (NTRS)

    Howard, Iris A.; Beckel, Charles L.

    1986-01-01

    The electronic properties of boron-rich icosahedral clusters were studied as a means of understanding the electronic structure of the icosahedral borides such as boron carbide. A lower bound was estimated on bipolaron formation energies in B12 and B11C icosahedra, and the associated distortions. While the magnitude of the distortion associated with bipolaron formation is similar in both cases, the calculated formation energies differ greatly, formation being much more favorable on B11C icosahedra. The stable positions of a divalent atom relative to an icosahedral borane was also investigated, with the result that a stable energy minimum was found when the atom is at the center of the borane, internal to the B12 cage. If incorporation of dopant atoms into B12 cages in icosahedral boride solids is feasible, novel materials might result. In addition, the normal modes of a B12H12 cluster, of the C2B10 cage in para-carborane, and of a B12 icosahedron of reduced (D sub 3d) symmetry, such as is found in the icosahedral borides, were calculated. The nature of these vibrational modes will be important in determining, for instance, the character of the electron-lattice coupling in the borides, and in analyzing the lattice contribution to the thermal conductivity.

  16. Experimental Benchmarking of Pu Electronic Structure

    SciTech Connect

    Tobin, J.G.; Moore, K.T.; Chung, B.W.; Wall, M.A.; Schwartz, A.J.; Ebbinghaus, B.B.; Butterfield, M.T.; Teslich, Jr., N.E.; Bliss, R.A.; Morton, S.A.; Yu, S.W.; Komesu, T.; Waddill, G.D.; van der Laan, G.; Kutepov, A.L.

    2008-10-30

    The standard method to determine the band structure of a condensed phase material is to (1) obtain a single crystal with a well defined surface and (2) map the bands with angle resolved photoelectron spectroscopy (occupied or valence bands) and inverse photoelectron spectroscopy (unoccupied or conduction bands). Unfortunately, in the case of Pu, the single crystals of Pu are either nonexistent, very small and/or having poorly defined surfaces. Furthermore, effects such as electron correlation and a large spin-orbit splitting in the 5f states have further complicated the situation. Thus, we have embarked upon the utilization of unorthodox electron spectroscopies, to circumvent the problems caused by the absence of large single crystals of Pu with well-defined surfaces. Our approach includes the techniques of resonant photoelectron spectroscopy, x-ray absorption spectroscopy, electron energy loss spectroscopy, Fano Effect measurements, and Bremstrahlung Isochromat Spectroscopy, including the utilization of micro-focused beams to probe single-crystallite regions of polycrystalline Pu samples.

  17. Experimental Benchmarking of Pu Electronic Structure

    SciTech Connect

    Tobin, J G; Moore, K T; Chung, B W; Wall, M A; Schwartz, A J; Ebbinghaus, B B; Butterfield, M T; Teslich, Jr., N E; Bliss, R A; Morton, S A; Yu, S W; Komesu, T; Waddill, G D; der Laan, G v; Kutepov, A L

    2005-10-13

    The standard method to determine the band structure of a condensed phase material is to (1) obtain a single crystal with a well defined surface and (2) map the bands with angle resolved photoelectron spectroscopy (occupied or valence bands) and inverse photoelectron spectroscopy (unoccupied or conduction bands). Unfortunately, in the case of Pu, the single crystals of Pu are either nonexistent, very small and/or having poorly defined surfaces. Furthermore, effects such as electron correlation and a large spin-orbit splitting in the 5f states have further complicated the situation. Thus, we have embarked upon the utilization of unorthodox electron spectroscopies, to circumvent the problems caused by the absence of large single crystals of Pu with well-defined surfaces. Our approach includes the techniques of resonant photoelectron spectroscopy [1], x-ray absorption spectroscopy [1,2,3,4], electron energy loss spectroscopy [2,3,4], Fano Effect measurements [5], and Bremstrahlung Isochromat Spectroscopy [6], including the utilization of micro-focused beams to probe single-crystallite regions of polycrystalline Pu samples. [2,3,6

  18. Electronic structure, aromaticity and spectra of hetero[8]circulenes

    NASA Astrophysics Data System (ADS)

    Baryshnikov, G. V.; Minaev, B. F.; Minaeva, V. A.

    2015-05-01

    The present review highlights recent advances in experimental and theoretical chemistry dealing with investigation of the electronic structures and physicochemical properties of hetero[8]circulenes. These compounds are the only representatives of planar heteroannulated cyclooctatetraenes. It is shown that high molecular symmetry of hetero[8]circulenes and the extended specific π-conjugated chain are the main factors responsible for high stability of the crystal packing modes and the optical and magnetic properties of these compounds. These effects also determine numerous selection rules for electronic and vibrational transitions in UV-Vis, IR and Raman spectra. Emphasis is given to the aromaticity of hetero[8]circulenes containing the inner antiaromatic cyclooctatetraene core. The planar structure of the latter is stabilized by a polyaromatic system composed of benzene rings and five-membered heterocycles. Due to high thermal and chemical stability of most hetero[8]circulenes combined with semiconducting properties, these compounds can be considered as promising materials for molecular electronics and nanophotonics, in particular for the production of organic light-emitting diodes and field-effect transistors. The bibliography includes 154 references.

  19. Advanced Structural and Inflatable Hybrid Spacecraft Module

    NASA Technical Reports Server (NTRS)

    Schneider, William C. (Inventor); delaFuente, Horacio M. (Inventor); Edeen, Gregg A. (Inventor); Kennedy, Kriss J. (Inventor); Lester, James D. (Inventor); Gupta, Shalini (Inventor); Hess, Linda F. (Inventor); Lin, Chin H. (Inventor); Malecki, Richard H. (Inventor); Raboin, Jasen L. (Inventor)

    2001-01-01

    An inflatable module comprising a structural core and an inflatable shell, wherein the inflatable shell is sealingly attached to the structural core. In its launch configuration, the wall thickness of the inflatable shell is collapsed by vacuum. Also in this configuration, the inflatable shell is collapsed and efficiently folded around the structural core. Upon deployment, the wall thickness of the inflatable shell is inflated; whereby the inflatable shell itself, is thereby inflated around the structural core, defining therein a large enclosed volume. A plurality of removable shelves are arranged interior to the structural core in the launch configuration. The structural core also includes at least one longeron that, in conjunction with the shelves, primarily constitute the rigid, strong, and lightweight load-bearing structure of the module during launch. The removable shelves are detachable from their arrangement in the launch configuration so that, when the module is in its deployed configuration and launch loads no longer exist, the shelves can be rearranged to provide a module interior arrangement suitable for human habitation and work. In the preferred embodiment, to provide efficiency in structural load paths and attachments, the shape of the inflatable shell is a cylinder with semi-toroidal ends.

  20. Advances in structure-based vaccine design

    PubMed Central

    Kulp, Daniel W; Schief, William R

    2014-01-01

    Despite the tremendous successes of current vaccines, infectious diseases still take a heavy toll on the global population, and that provides strong rationale for broadening our vaccine development repertoire. Structural vaccinology, in which protein structure information is utilized to design immunogens, has promise to provide new vaccines against traditionally difficult targets. Crystal structures of antigens containing one or more protection epitopes, especially when in complex with a protective antibody, are the launching point for immunogen design. Integrating structure and sequence information for families of broadly neutralizing antibodies (bNAbs) has recently enabled the creation of germline-targeting immunogens that bind and activate germline B-cells in order to initiate the elicitation of such antibodies. The contacts between antigen and neutralizing antibody define a structural epitope, and methods have been developed to transplant epitopes to scaffold proteins for structural stabilization, and to design minimized antigens that retain one or more key epitopes while eliminating other potentially distracting or unnecessary features. To develop vaccines that protect against antigenically variable pathogens, pioneering structure-based work demonstrated that multiple strain-specific epitopes could be engineered onto a single immunogen. We review these recent structural vaccinology efforts to engineer germline-targeting, epitope-specific, and/or broad coverage immunogens. PMID:23806515

  1. Structure and navigation for electronic publishing

    NASA Astrophysics Data System (ADS)

    Tillinghast, John; Beretta, Giordano B.

    1998-01-01

    The sudden explosion of the World Wide Web as a new publication medium has given a dramatic boost to the electronic publishing industry, which previously was a limited market centered around CD-ROMs and on-line databases. While the phenomenon has parallels to the advent of the tabloid press in the middle of last century, the electronic nature of the medium brings with it the typical characteristic of 4th wave media, namely the acceleration in its propagation speed and the volume of information. Consequently, e-publications are even flatter than print media; Shakespeare's Romeo and Juliet share the same computer screen with a home-made plagiarized copy of Deep Throat. The most touted tool for locating useful information on the World Wide Web is the search engine. However, due to the medium's flatness, sought information is drowned in a sea of useless information. A better solution is to build tools that allow authors to structure information so that it can easily be navigated. We experimented with the use of ontologies as a tool to formulate structures for information about a specific topic, so that related concepts are placed in adjacent locations and can easily be navigated using simple and ergonomic user models. We describe our effort in building a World Wide Web based photo album that is shared among a small network of people.

  2. Multigrid Methods in Electronic Structure Calculations

    NASA Astrophysics Data System (ADS)

    Briggs, Emil

    1996-03-01

    Multigrid techniques have become the method of choice for a broad range of computational problems. Their use in electronic structure calculations introduces a new set of issues when compared to traditional plane wave approaches. We have developed a set of techniques that address these issues and permit multigrid algorithms to be applied to the electronic structure problem in an efficient manner. In our approach the Kohn-Sham equations are discretized on a real-space mesh using a compact representation of the Hamiltonian. The resulting equations are solved directly on the mesh using multigrid iterations. This produces rapid convergence rates even for ill-conditioned systems with large length and/or energy scales. The method has been applied to both periodic and non-periodic systems containing over 400 atoms and the results are in very good agreement with both theory and experiment. Example applications include a vacancy in diamond, an isolated C60 molecule, and a 64-atom cell of GaN with the Ga d-electrons in valence which required a 250 Ry cutoff. A particular strength of a real-space multigrid approach is its ready adaptability to massively parallel computer architectures. The compact representation of the Hamiltonian is especially well suited to such machines. Tests on the Cray-T3D have shown nearly linear scaling of the execution time up to the maximum number of processors (512). The MPP implementation has been used for studies of a large Amyloid Beta Peptide (C_146O_45N_42H_210) found in the brains of Alzheimers disease patients. Further applications of the multigrid method will also be described. (in collaboration D. J. Sullivan and J. Bernholc)

  3. Advanced Power Electronics Interfaces for Distributed Energy Workshop Summary: August 24, 2006, Sacramento, California

    SciTech Connect

    Treanton, B.; Palomo, J.; Kroposki, B.; Thomas, H.

    2006-10-01

    The Advanced Power Electronics Interfaces for Distributed Energy Workshop, sponsored by the California Energy Commission Public Interest Energy Research program and organized by the National Renewable Energy Laboratory, was held Aug. 24, 2006, in Sacramento, Calif. The workshop provided a forum for industry stakeholders to share their knowledge and experience about technologies, manufacturing approaches, markets, and issues in power electronics for a range of distributed energy resources. It focused on the development of advanced power electronic interfaces for distributed energy applications and included discussions of modular power electronics, component manufacturing, and power electronic applications.

  4. Electronic Structure and Bonding in Complex Biomolecule

    NASA Astrophysics Data System (ADS)

    Ouyang, Lizhi

    2005-03-01

    For over a century vitamin B12 and its enzyme cofactor derivates have persistently attracted research efforts for their vital biological role, unique Co-C bonding, rich red-ox chemistry, and recently their candidacies as drug delivery vehicles etc. However, our understanding of this complex metalorganic molecule's efficient enzyme activated catalytic power is still controversial. We have for the first time calculated the electronic structure, Mulliken effective charge and bonding of a whole Vitamin B12 molecule without any structural simplification by first- principles approaches based on density functional theory using structures determined by high resolution X-ray diffraction. A partial density of states analysis shows excellent agreement with X-ray absorption data and has been used successfully to interpret measured optical absorption spectra. Mulliken bonding analysis of B12 and its derivatives reveal noticeable correlations between the two axial ligands which could be exploited by the enzyme to control the catalytic process. Our calculated X-ray near edge structure of B12 and its derivates using Slater's transition state theory are also in good agreement with experiments. The same approach has been applied to other B12 derivatives, ferrocene peptides, and recently DNA molecules.

  5. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...-approved electronic data interchange system. (1) Through cargo in transit to a foreign country. Cargo... contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable of...

  6. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...-approved electronic data interchange system. (1) Through cargo in transit to a foreign country. Cargo... contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable of...

  7. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...-approved electronic data interchange system. (1) Through cargo in transit to a foreign country. Cargo... contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable of...

  8. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...-approved electronic data interchange system. (1) Through cargo in transit to a foreign country. Cargo... contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable of...

  9. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... rail carrier must use a CBP-approved electronic data interchange system. (1) Through cargo in transit... and contact information (address) in the “Notify Party” field of the advance electronic data transmission to CBP, to the extent that the CBP-approved electronic data interchange system is capable...

  10. Electronic structure of Ca, Sr, and Ba under pressure.

    NASA Technical Reports Server (NTRS)

    Animalu, A. O. E.; Heine, V.; Vasvari, B.

    1967-01-01

    Electronic band structure calculations phase of Ca, Sr and Ba over wide range of atomic volumes under pressure electronic band structure calculations for fcc phase of Ca, Sr and Ba over wide range of atomic volumes under pressure electronic band structure calculations for fcc phase of Ca, Sr and Ba over wide range of atomic volumes under pressure

  11. Electron acceleration with advanced injection methods at the ASTRA laser

    NASA Astrophysics Data System (ADS)

    Poder, Kristjan; Carreira-Lopes, Nelson; Wood, Jonathan; Cole, Jason; Dangor, Bucker; Foster, Peta; Gopal, Ram; Kamperidis, Christos; Kononenko, Olena; Mangles, Stuart; Olgun, Halil; Palmer, Charlotte; Symes, Daniel; Pattathil, Rajeev; Najmudin, Zulfikar; Imperial College London Team; Central Laser Facility Collaboration; Tata InsituteFundamental Research Collaboration; DESY Collaboration

    2015-11-01

    Recent electron acceleration results from the ASTRA laser facility are presented. Experiments were performed using both the 40 TW ASTRA and the 350 TW ASTRA-Gemini laser. Fundamental electron beam properties relating to its quality were investigated both experimentally and with PIC simulations. For increased control over such parameters, various injection mechanisms such as self-injection and ionization injection were employed. Particular interest is given to the dynamics of ionization injected electrons in strongly driven wakes.

  12. USMC Electronic Warfare 2025: Trading Expertise for Advanced Technology

    DTIC Science & Technology

    2011-04-15

    airborne electronic warlare during the transition period away from legacy equipment. EA-6B pilots and Electroilic Countermeasures Officers ( ECMOs ...Electronic Warfare (EW) capability. As an EA-6B Electronic Countenneasures Officer ( ECMO ), I anticipate that both the United States Marine Corps and all... ECMOs . An increased workload for Radio Battalion will have the same effect that the assumption of an additional function of Marine aviation will have on

  13. Reversible Hydrogen Storage Materials – Structure, Chemistry, and Electronic Structure

    SciTech Connect

    Robertson, Ian M.; Johnson, Duane D.

    2014-06-21

    To understand the processes involved in the uptake and release of hydrogen from candidate light-weight metal hydride storage systems, a combination of materials characterization techniques and first principle calculation methods have been employed. In addition to conventional microstructural characterization in the transmission electron microscope, which provides projected information about the through thickness microstructure, electron tomography methods were employed to determine the three-dimensional spatial distribution of catalyst species for select systems both before and after dehydrogenation. Catalyst species identification as well as compositional analysis of the storage material before and after hydrogen charging and discharging was performed using a combination of energy dispersive spectroscopy, EDS, and electron energy loss spectroscopy, EELS. The characterization effort was coupled with first-principles, electronic-structure and thermodynamic techniques to predict and assess meta-stable and stable phases, reaction pathways, and thermodynamic and kinetic barriers. Systems studied included:NaAlH4, CaH2/CaB6 and Ca(BH4)2, MgH2/MgB2, Ni-Catalyzed Magnesium Hydride, TiH2-Catalyzed Magnesium Hydride, LiBH4, Aluminum-based systems and Aluminum

  14. Advanced textile structural composites -- status and outlook

    SciTech Connect

    Arendts, F.J.; Drechsler, K.; Brandt, J.

    1993-12-31

    Composites with 3D woven, braided or knitted fiber reinforcement offer a high potential for the cost-effective manufacturing of structures featuring an interesting mechanical performance, for example with regard to damage tolerance or energy absorption capability. In this paper, the properties of various textile structural composites with regard to stiffness, strength, damage tolerance, energy absorption capability as well as the respective manufacturing processes (RTM or thermoplastic hybrid-yarn technique) are presented in comparison to conventional ud tape based composites. The influence of the fiber architecture on the mechanical performance (tensile stiffness and strength, compression strength, interlaminar shear strength, compression strength after impact, fracture mechanical properties, through-penetration resistance) of monolithic and composite sandwich structures has been evaluated in an experimental study. It has been shown that composites involving new 3D weavings with minimum fiber crimp can compete with tape-based laminates as far as stiffness and strength are concerned. Using knittings makes it possible to manufacture composites having superior through-penetration resistance. The specific feature of the 3D braiding process is the ability to produce complex shaped structures having a high degree of freedom with regard to fiber geometry. Finally, the application of various textile structural composites will be presented on the basis of three demonstrator components (automotive engine mount, aircraft leading edge and motor cycle helmet), and the potential for further developments will be discussed.

  15. Electronic band structure of defect chalcopyrites

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaoshu; Lambrecht, Walter R. L.

    2001-03-01

    The defect chalcopyrites of chemical composition II-III-VI4 in which II, III and VI mean group-II elements such as Cd or Hg, group-III elements such as Al and Ga and group-VI elements such as S, Se, Te, form an interesting family of semiconductor compounds with potential nonlinear optical applications. They can be thought of as derived from the regular I-III-VI2 chalcopyrites by doubling the formula unit and replacing the group I element, for example, Ag by the group-II element and a vacancy in an ordered manner. The chalcopyrites themselves are derived from II-VI compounds by replacing the group-II by a group I and a group-III element. In this contribution we present electronic band structure calculations of some of these compounds, calculated using the linear muffin-tin orbital method combined with the local density functional approximation. We discuss the relation of the band structures of the corresponding zincblende, chalcopyrite and defect chalcopyrite compounds. In particular, the role of the group I or group II d-band energy will be shown to be important. The trends with chemical substutions and the effects of structural distortions c/a and internal parameters accompanying the chemical distortion will be discussed.

  16. Advanced control evaluation for structures (ACES) programs

    NASA Technical Reports Server (NTRS)

    Pearson, Jerome; Waites, Henry

    1988-01-01

    The ACES programs are a series of past, present, and future activities at the Marshall Space Flight Center (MSFC) Ground facility for Large Space Structure Control Verification (GF/LSSCV). The main objectives of the ACES programs are to implement control techniques on a series of complex dynamical systems, to determine the control/structure interaction for the control techniques, and to provide a national facility in which dynamics and control verification can be effected. The focus is on these objectives and how they are implemented under various engineering and economic constraints. Future plans that will be effected in upcoming ACES programs are considered.

  17. Recent advances in the application of electron tomography to materials chemistry.

    PubMed

    Leary, Rowan; Midgley, Paul A; Thomas, John Meurig

    2012-10-16

    Nowadays, tomography plays a central role in pureand applied science, in medicine, and in many branches of engineering and technology. It entails reconstructing the three-dimensional (3D) structure of an object from a tilt series of two-dimensional (2D) images. Its origin goes back to 1917, when Radon showed mathematically how a series of 2D projection images could be converted to the 3D structural one. Tomographic X-ray and positron scanning for 3D medical imaging, with a resolution of ∼1 mm, is now ubiquitous in major hospitals. Electron tomography, a relatively new chemical tool, with a resolution of ∼1 nm, has been recently adopted by materials chemists as an invaluable aid for the 3D study of the morphologies, spatially-discriminating chemical compositions, and defect properties of nanostructured materials. In this Account, we review the advances that have been made in facilitating the recording of the required series of 2D electron microscopic images and the subsequent process of 3D reconstruction of specimens that are vulnerable, to a greater or lesser degree, to electron beam damage. We describe how high-fidelity 3D tomograms may be obtained from relatively few 2D images by incorporating prior structural knowledge into the reconstruction process. In particular, we highlight the vital role of compressed sensing, a recently developed procedure well-known to information theorists that exploits ideas of image compression and "sparsity" (that the important image information can be captured in a reduced data set). We also touch upon another promising approach, "discrete" tomography, which builds into the reconstruction process a prior assumption that the object can be described in discrete terms, such as the number of constituent materials and their expected densities. Other advances made recently that we outline, such as the availability of aberration-corrected electron microscopes, electron wavelength monochromators, and sophisticated specimen goniometers

  18. Electronic structures of ytterbocene-imine complexes

    SciTech Connect

    Da Re, R. E.; Kuehl, C. J.; John, K. D.; Morris, D. E.

    2004-01-01

    The electronic structures of complexes of the form [(C{sub 5}Me{sub 5}){sub 2}Yb(L)]{sup +/0} (L = bipyridine, phenanthroline, terpyridine) have been probed using cyclic voltammetry and electronic spectroscopy. Remarkably, the voltammetric data reveal that the imine-based LUMO is stabilized and the redox-active metal f orbital is destabilized by ca. 1 V each upon formation of the ytterbocene-imine adduct, which is presumably responsible for the [(f){sup 13}({pi}*(L)){sup 1}] charge-transfer ground state characteristic of these complexes. The ca. 0.8 V separation between ligand-based oxidation and metal-based reduction waves for each ytterbocene adduct correlates with the energy of its optically promoted {pi}*(L)-f(Yb) charge transfer (LMCT) transition (ca. 5000 cm{sup -1}). The coupling between this LMCT excited state and the {sup 2}F{sub 7/2} ground and {sup 2}F{sub 5/2} excited states of Yb(III) leads to unusually large intensities ({var_epsilon} {approx} 1000) for the metal-localized f-f bands, which will be discussed in the context of an intensity borrowing mechanism that invokes exchange between the ligand-based {sup 2}S and metal-based {sup 2}F spin states.

  19. Electron Liquids in Semiconductor Quantum Structures

    SciTech Connect

    Aron Pinczuk

    2009-05-25

    The groups led by Stormer and Pinczuk have focused this project on goals that seek the elucidation of novel many-particle effects that emerge in two-dimensional electron systems (2DES) as the result from fundamental quantum interactions. This experimental research is conducted under extreme conditions of temperature and magnetic field. From the materials point of view, the ultra-high mobility systems in GaAs/AlGaAs quantum structures continue to be at the forefront of this research. The newcomer materials are based on graphene, a single atomic layer of graphite. The graphene research is attracting enormous attention from many communities involved in condensed matter research. The investigated many-particle phenomena include the integer and fractional quantum Hall effect, composite fermions, and Dirac fermions, and a diverse group of electron solid and liquid crystal phases. The Stormer group performed magneto-transport experiments and far-infrared spectroscopy, while the Pinczuk group explores manifestations of such phases in optical spectra.

  20. Electronic structures of reconstructed zigzag silicene nanoribbons

    SciTech Connect

    Ding, Yi E-mail: wangyanli-04@tsinghua.org.cn; Wang, Yanli E-mail: wangyanli-04@tsinghua.org.cn

    2014-02-24

    Edge states and magnetism are crucial for spintronic applications of nanoribbons. Here, using first-principles calculations, we explore structural stabilities and electronic properties of zigzag silicene nanoribbons (ZSiNRs) with Klein and pentagon-heptagon reconstructions. Comparing to unreconstructed zigzag edges, deformed bare pentagon-heptagon ones are favored under H-poor conditions, while H-rich surroundings stabilize di-hydrogenated Klein edges. These Klein edges have analogous magnetism to zigzag ones, which also possess the electric-field-induced half-metallicity of nanoribbons. Moreover, diverse magnetic states can be achieved by asymmetric Klein and zigzag edges into ZSiNRs, which could be transformed from antiferromagnetic-semiconductors to bipolar spin-gapless-semiconductors and ferromagnetic-metals depending on edge hydrogenations.

  1. Multilevel domain decomposition for electronic structure calculations

    SciTech Connect

    Barrault, M. . E-mail: maxime.barrault@edf.fr; Cances, E. . E-mail: cances@cermics.enpc.fr; Hager, W.W. . E-mail: hager@math.ufl.edu; Le Bris, C. . E-mail: lebris@cermics.enpc.fr

    2007-03-01

    We introduce a new multilevel domain decomposition method (MDD) for electronic structure calculations within semi-empirical and density functional theory (DFT) frameworks. This method iterates between local fine solvers and global coarse solvers, in the spirit of domain decomposition methods. Using this approach, calculations have been successfully performed on several linear polymer chains containing up to 40,000 atoms and 200,000 atomic orbitals. Both the computational cost and the memory requirement scale linearly with the number of atoms. Additional speed-up can easily be obtained by parallelization. We show that this domain decomposition method outperforms the density matrix minimization (DMM) method for poor initial guesses. Our method provides an efficient preconditioner for DMM and other linear scaling methods, variational in nature, such as the orbital minimization (OM) procedure.

  2. Structure, Stability and Electronic Properties of Nanodiamonds

    NASA Astrophysics Data System (ADS)

    Galli, Giulia

    Diamond nanoparticles, or nanodiamonds, have the most disparate origins. They are found in crude oil at concentrations up to thousands of parts per million, in meteorites, interstellar dust, and protoplanetary nebulae, as well as in certain sediment layers on Earth. They can also be produced in the laboratory by chemical vapor deposition or by detonating high explosive materials. Here we summarize what is known about nanodiamond sources; we then describe the atomic and electronic structure, and stability of diamond nanoparticles, highlighting the role of theory and computations in understanding and predicting their properties. Possible technological applications of thin films composed of nanodiamonds, ranging from micro-resonators to substrates for drug delivery, are briefly discussed.

  3. Advances in tunable powerful lasers: The advanced free-electron laser

    SciTech Connect

    Singer, S.; Sheffield, R.

    1993-12-31

    In the past several decades, remarkable progress in laser science and technology has made it possible to obtain laser light from the ultra-violet to the far infra-red from a variety of laser types, and at power levels from milliwatts to kilowatts (and, some day, megawatts). However, the availability of tunable lasers at ``high`` power (above a few tens of watts) is more limited. Figure 1, an assessment of the availability of tunable lasers, shows the covered range to be about 400 to 2000 nanometers. A variety of dye lasers cover the visible and near infra red, each one of which is tunable over approximately a 10% range. In the same region, the TI:saphire laser is adjustable over a 20 to 25% range. And finally, optical parametric oscillators can cover the range from about 400 nanometers out to about 2000 nm (even farther at reduced energy output). The typical output energy per pulse may vary from a few to one hundred millijoules, and since repetition rates of 10 to 100 Hertz are generally attainable, average output powers of tens of watts are possible. In recent years, a new approach to powerful tunable lasers -- the Free-Electron Laser (FEL) -- has emerged. In this paper we will discuss advances in FEL technology which not only enable tunability at high average power over a very broad range of wavelengths, but also make this device more usable. At present, that range is about one micron to the far infra red; with extensions of existing technology, it should be extendable to the vacuum ultra violet region.

  4. Advances in direct and diffraction methods for surface structural determination

    NASA Astrophysics Data System (ADS)

    Tong, S. Y.

    1999-08-01

    I describe recent advances in low-energy electron diffraction holography and photoelectron diffraction holography. These are direct methods for determining the surface structure. I show that for LEED and PD spectra taken in an energy and angular mesh, the relative phase between the reference wave and the scattered wave has a known geometric form if the spectra are always taken from within a small angular cone in the near backscattering direction. By using data in the backscattering small cone at each direction of interest, a simple algorithm is developed to invert the spectra and extract object atomic positions with no input of calculated dynamic factors. I also describe the use of a convergent iterative method of PD and LEED. 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. Both the Rehr-Albers separable-propagator cluster approach and the slab-type non-separable approach can be cast in the new iterative form. With substantial savings in computational time and no loss in numerical accuracy, this method is very useful in applications of multiple scattering theory, particularly for systems involving either very large unit cells (>300 atoms) or where no long-range order is present.

  5. Advances in Nanocarbon Metals: Fine Structure

    DTIC Science & Technology

    2015-03-01

    SUPPLEMENTARY NOTES 14. ABSTRACT This study is an investigation of the structure and some properties of silver, copper, and aluminum alloy covetics...Covetics can incorporate large amounts of carbon (C) in a nanoscale form to alter physical and mechanical properties of the base metal or alloy ...and properties can be obtained. 15. SUBJECT TERMS covetic, nanocarbon silver, aluminum , copper 16. SECURITY CLASSIFICATION OF: 17. LIMITATION

  6. Advances in Computational Stability Analysis of Composite Aerospace Structures

    SciTech Connect

    Degenhardt, R.; Araujo, F. C. de

    2010-09-30

    European aircraft industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents different advances from the area of computational stability analysis of composite aerospace structures which contribute to that field. For stringer stiffened panels main results of the finished EU project COCOMAT are given. It investigated the exploitation of reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. For unstiffened cylindrical composite shells a proposal for a new design method is presented.

  7. Advanced organic composite materials for aircraft structures: Future program

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

  8. Advanced reliability methods for structural evaluation

    NASA Technical Reports Server (NTRS)

    Wirsching, P. H.; Wu, Y.-T.

    1985-01-01

    Fast probability integration (FPI) methods, which can yield approximate solutions to such general structural reliability problems as the computation of the probabilities of complicated functions of random variables, are known to require one-tenth the computer time of Monte Carlo methods for a probability level of 0.001; lower probabilities yield even more dramatic differences. A strategy is presented in which a computer routine is run k times with selected perturbed values of the variables to obtain k solutions for a response variable Y. An approximating polynomial is fit to the k 'data' sets, and FPI methods are employed for this explicit form.

  9. Electron Beam Transport in Advanced Plasma Wave Accelerators

    SciTech Connect

    Williams, Ronald L

    2013-01-31

    The primary goal of this grant was to develop a diagnostic for relativistic plasma wave accelerators based on injecting a low energy electron beam (5-50keV) perpendicular to the plasma wave and observing the distortion of the electron beam's cross section due to the plasma wave's electrostatic fields. The amount of distortion would be proportional to the plasma wave amplitude, and is the basis for the diagnostic. The beat-wave scheme for producing plasma waves, using two CO2 laser beam, was modeled using a leap-frog integration scheme to solve the equations of motion. Single electron trajectories and corresponding phase space diagrams were generated in order to study and understand the details of the interaction dynamics. The electron beam was simulated by combining thousands of single electrons, whose initial positions and momenta were selected by random number generators. The model was extended by including the interactions of the electrons with the CO2 laser fields of the beat wave, superimposed with the plasma wave fields. The results of the model were used to guide the design and construction of a small laboratory experiment that may be used to test the diagnostic idea.

  10. Development of advanced electron holographic techniques and application to industrial materials and devices.

    PubMed

    Yamamoto, Kazuo; Hirayama, Tsukasa; Tanji, Takayoshi

    2013-06-01

    The development of a transmission electron microscope equipped with a field emission gun paved the way for electron holography to be put to practical use in various fields. In this paper, we review three advanced electron holography techniques: on-line real-time electron holography, three-dimensional (3D) tomographic holography and phase-shifting electron holography, which are becoming important techniques for materials science and device engineering. We also describe some applications of electron holography to the analysis of industrial materials and devices: GaAs compound semiconductors, solid oxide fuel cells and all-solid-state lithium ion batteries.

  11. Transmission Electron Microscopy Advances Reveal Subtle Comet Dust Differences

    NASA Astrophysics Data System (ADS)

    Ishii, H. A.; Bradley, J. P.

    2015-07-01

    TEM advances in multi-SDD-detector EDX mapping applied to Wild 2 dust and likely-cometary CP IDPs demonstrates chondritic fine-grained material at terminal particles is unlike GEMS and consistent with debris generated during the deceleration process.

  12. Recent advancement in optical fiber sensing for aerospace composite structures

    NASA Astrophysics Data System (ADS)

    Minakuchi, Shu; Takeda, Nobuo

    2013-12-01

    Optical fiber sensors have attracted considerable attention in health monitoring of aerospace composite structures. This paper briefly reviews our recent advancement mainly in Brillouin-based distributed sensing. Damage detection, life cycle monitoring and shape reconstruction systems applicable to large-scale composite structures are presented, and new technical concepts, "smart crack arrester" and "hierarchical sensing system", are described as well, highlighting the great potential of optical fiber sensors for the structural health monitoring (SHM) field.

  13. Experimental and theoretical electronic structure of quinacridone

    NASA Astrophysics Data System (ADS)

    Lüftner, Daniel; Refaely-Abramson, Sivan; Pachler, Michael; Resel, Roland; Ramsey, Michael G.; Kronik, Leeor; Puschnig, Peter

    2014-08-01

    The energy positions of frontier orbitals in organic electronic materials are often studied experimentally by (inverse) photoemission spectroscopy and theoretically within density functional theory. However, standard exchange-correlation functionals often result in too small fundamental gaps, may lead to wrong orbital energy ordering, and do not capture polarization-induced gap renormalization. Here we examine these issues and a strategy for overcoming them by studying the gas phase and bulk electronic structure of the organic molecule quinacridone (5Q), a promising material with many interesting properties for organic devices. Experimentally we perform angle-resolved photoemission spectroscopy (ARUPS) on thin films of the crystalline β phase of 5Q. Theoretically we employ an optimally tuned range-separated hybrid functional (OT-RSH) within density functional theory. For the gas phase molecule, our OT-RSH result for the ionization potential (IP) represents a substantial improvement over the semilocal PBE and the PBE0 hybrid functional results, producing an IP in quantitative agreement with experiment. For the bulk crystal we take into account the correct screening in the bulk, using the recently developed optimally tuned screened range-separated hybrid (OT-SRSH) approach, while retaining the optimally tuned parameters for the range separation and the short-range Fock exchange. This leads to a band gap narrowing due to polarization effects and results in a valence band spectrum in excellent agreement with experimental ARUPS data, with respect to both peak positions and heights. Finally, full-frequency G0W0 results based on a hybrid functional starting point are shown to agree with the OT-SRSH approach, improving substantially on the PBE-starting point.

  14. RESCU: A real space electronic structure method

    NASA Astrophysics Data System (ADS)

    Michaud-Rioux, Vincent; Zhang, Lei; Guo, Hong

    2016-02-01

    In this work we present RESCU, a powerful MATLAB-based Kohn-Sham density functional theory (KS-DFT) solver. We demonstrate that RESCU can compute the electronic structure properties of systems comprising many thousands of atoms using modest computer resources, e.g. 16 to 256 cores. Its computational efficiency is achieved from exploiting four routes. First, we use numerical atomic orbital (NAO) techniques to efficiently generate a good quality initial subspace which is crucially required by Chebyshev filtering methods. Second, we exploit the fact that only a subspace spanning the occupied Kohn-Sham states is required, and solving accurately the KS equation using eigensolvers can generally be avoided. Third, by judiciously analyzing and optimizing various parts of the procedure in RESCU, we delay the O (N3) scaling to large N, and our tests show that RESCU scales consistently as O (N2.3) from a few hundred atoms to more than 5000 atoms when using a real space grid discretization. The scaling is better or comparable in a NAO basis up to the 14,000 atoms level. Fourth, we exploit various numerical algorithms and, in particular, we introduce a partial Rayleigh-Ritz algorithm to achieve efficiency gains for systems comprising more than 10,000 electrons. We demonstrate the power of RESCU in solving KS-DFT problems using many examples running on 16, 64 and/or 256 cores: a 5832 Si atoms supercell; a 8788 Al atoms supercell; a 5324 Cu atoms supercell and a small DNA molecule submerged in 1713 water molecules for a total 5399 atoms. The KS-DFT is entirely converged in a few hours in all cases. Our results suggest that the RESCU method has reached a milestone of solving thousands of atoms by KS-DFT on a modest computer cluster.

  15. Electron Trajectory Reconstruction for Advanced Compton Imaging of Gamma Rays

    NASA Astrophysics Data System (ADS)

    Plimley, Brian Christopher

    Gamma-ray imaging is useful for detecting, characterizing, and localizing sources in a variety of fields, including nuclear physics, security, nuclear accident response, nuclear medicine, and astronomy. Compton imaging in particular provides sensitivity to weak sources and good angular resolution in a large field of view. However, the photon origin in a single event sequence is normally only limited to the surface of a cone. If the initial direction of the Compton-scattered electron can be measured, the cone can be reduced to a cone segment with width depending on the uncertainty in the direction measurement, providing a corresponding increase in imaging sensitivity. Measurement of the electron's initial direction in an efficient detection material requires very fine position resolution due to the electron's short range and tortuous path. A thick (650 mum), fully-depleted charge-coupled device (CCD) developed for infrared astronomy has 10.5-mum position resolution in two dimensions, enabling the initial trajectory measurement of electrons of energy as low as 100 keV. This is the first time the initial trajectories of electrons of such low energies have been measured in a solid material. In this work, the CCD's efficacy as a gamma-ray detector is demonstrated experimentally, using a reconstruction algorithm to measure the initial electron direction from the CCD track image. In addition, models of fast electron interaction physics, charge transport and readout were used to generate modeled tracks with known initial direction. These modeled tracks allowed the development and refinement of the reconstruction algorithm. The angular sensitivity of the reconstruction algorithm is evaluated extensively with models for tracks below 480 keV, showing a FWHM as low as 20° in the pixel plane, and 30° RMS sensitivity to the magnitude of the out-of-plane angle. The measurement of the trajectories of electrons with energies as low as 100 keV have the potential to make electron

  16. Recent advances in molecular electronics based on carbon nanotubes.

    PubMed

    Bourgoin, Jean-Philippe; Campidelli, Stéphane; Chenevier, Pascale; Derycke, Vincent; Filoramo, Arianna; Goffman, Marcelo F

    2010-01-01

    Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: (i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties, (ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes, and (iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we outline the main issues concerning the development of carbon nanotubes based electronics applications and review our recent results in the field.

  17. Deformation and Damage Studies for Advanced Structural Materials

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Advancements made in understanding deformation and damage of advanced structural materials have enabled the development of new technologies including the attainment of a nationally significant NASA Level 1 Milestone and the provision of expertise to the Shuttle Return to Flight effort. During this collaborative agreement multiple theoretical and experimental research programs, facilitating safe durable high temperature structures using advanced materials, have been conceived, planned, executed. Over 26 publications, independent assessments of structures and materials in hostile environments, were published within this agreement. This attainment has been recognized by 2002 Space Flight Awareness Team Award, 2004 NASA Group Achievement Award and 2003 and 2004 OAI Service Awards. Accomplishments in the individual research efforts are described as follows.

  18. Individual Particle Analysis of Ambient PM 2.5 Using Advanced Electron Microscopy Techniques

    SciTech Connect

    Gerald J. Keeler; Masako Morishita

    2006-12-31

    The overall goal of this project was to demonstrate a combination of advanced electron microscopy techniques that can be effectively used to identify and characterize individual particles and their sources. Specific techniques to be used include high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), STEM energy dispersive X-ray spectrometry (EDX), and energy-filtered TEM (EFTEM). A series of ambient PM{sub 2.5} samples were collected in communities in southwestern Detroit, MI (close to multiple combustion sources) and Steubenville, OH (close to several coal fired utility boilers). High-resolution TEM (HRTEM) -imaging showed a series of nano-metal particles including transition metals and elemental composition of individual particles in detail. Submicron and nano-particles with Al, Fe, Ti, Ca, U, V, Cr, Si, Ba, Mn, Ni, K and S were observed and characterized from the samples. Among the identified nano-particles, combinations of Al, Fe, Si, Ca and Ti nano-particles embedded in carbonaceous particles were observed most frequently. These particles showed very similar characteristics of ultrafine coal fly ash particles that were previously reported. By utilizing HAADF-STEM, STEM-EDX, and EF-TEM, this investigation was able to gain information on the size, morphology, structure, and elemental composition of individual nano-particles collected in Detroit and Steubenville. The results showed that the contributions of local combustion sources - including coal fired utilities - to ultrafine particle levels were significant. Although this combination of advanced electron microscopy techniques by itself can not identify source categories, these techniques can be utilized as complementary analytical tools that are capable of providing detailed information on individual particles.

  19. Advanced fabrication techniques for cooled engine structures

    NASA Technical Reports Server (NTRS)

    Buchmann, O. A.

    1978-01-01

    An improved design for regeneratively cooled engine structures was identified. This design uses photochemically machined (PCM) coolant passages. It permits the braze joint to be placed in a relatively cool area, remote from the critical hot face sheet. The geometry of the passages at the face sheet also minimizes stress concentration and, therefore, enhances the low cycle fatigue performance. The two most promising alloys identified for this application are Inconel 617 and Nickel 201. Inconel 617 was selected because it has excellent creep rupture properties, while Nickel 201 was selected because of its predicted good performance under low cycle fatigue loading. The fabrication of the PCM coolant passages in both Inconel 617 and Nickel 201 was successfully developed. During fabrication of Inconel 617, undesirable characteristics were observed in the braze joints. A development program to resolve this condition was undertaken and led to definition of an isothermal solidification process for joining Inconel 617 panels. This process produced joints which approach parent metal strength and homogeneity.

  20. Advanced Opto-Electronics (LIDAR and Microsensor Development)

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern C. (Technical Monitor); Spangler, Lee H.

    2005-01-01

    Our overall intent in this aspect of the project were to establish a collaborative effort between several departments at Montana State University for developing advanced optoelectronic technology for advancing the state-of-the-art in optical remote sensing of the environment. Our particular focus was on development of small systems that can eventually be used in a wide variety of applications that might include ground-, air-, and space deployments, possibly in sensor networks. Specific objectives were to: 1) Build a field-deployable direct-detection lidar system for use in measurements of clouds, aerosols, fish, and vegetation; 2) Develop a breadboard prototype water vapor differential absorption lidar (DIAL) system based on highly stable, tunable diode laser technology developed previously at MSU. We accomplished both primary objectives of this project, in developing a field-deployable direct-detection lidar and a breadboard prototype of a water vapor DIAL system. Paper summarizes each of these accomplishments.

  1. L1 Report for the Enhanced Surveillance Campaign Experimental Benchmarking of Pu Electronic Structure

    SciTech Connect

    Tobin, J G; Chung, B W; Moore, K T; Yu, S; Schwartz, A J; Wall, M A; Morton, S A; Ebbinghaus, B B; Fluss, M J; Haslam, J J; Blobaum, K M; Terry, J; Schulze, R K; Lashley, J; Farr, J D; Zocco, T; Blau, M; Heizelmann, K; Rotenberg, E; Shuh, D K; der Laan, G v; Kutepov, A L; Komesu, T; Waddill, G D

    2006-01-30

    The objective of this work is to develop and/or apply advanced diagnostics to the understanding of aging of Pu. Advanced characterization techniques such as photoelectron and x-ray absorption spectroscopy will provide fundamental data on the electronic structure of Pu phases. These data are crucial for the validation of the electronic structure methods. The fundamental goal of this project is to narrow the parameter space for the theoretical modeling of Pu aging. The short-term goal is to perform experiments to validate electronic structure calculations of Pu. The long-term goal is to determine the effects of aging upon the electronic structure of Pu. Many of the input parameters for aging models are not directly measurable. These parameters will need to be calculated or estimated. Thus a First Principles-Approach Theory is needed, but it is unclear what terms are important in the Hamiltonian (H{Psi} = E{Psi}). Therefore, experimental data concerning the 5f electronic structure are needed, to determine which terms in the Hamiltonian are important. The data obtained in this task are crucial for reducing the uncertainty of Task LL-01-developed models and predictions. The data impact the validation of electronic structure methods, the calculation of defect properties, the evaluation of helium diffusion, and the validation of void nucleation models. The importance of these activities increases if difficulties develop with the accelerating aging alloy approach.

  2. Advanced in-situ electron-beam lithography for deterministic nanophotonic device processing

    SciTech Connect

    Kaganskiy, Arsenty; Gschrey, Manuel; Schlehahn, Alexander; Schmidt, Ronny; Schulze, Jan-Hindrik; Heindel, Tobias; Rodt, Sven Reitzenstein, Stephan; Strittmatter, André

    2015-07-15

    We report on an advanced in-situ electron-beam lithography technique based on high-resolution cathodoluminescence (CL) spectroscopy at low temperatures. The technique has been developed for the deterministic fabrication and quantitative evaluation of nanophotonic structures. It is of particular interest for the realization and optimization of non-classical light sources which require the pre-selection of single quantum dots (QDs) with very specific emission features. The two-step electron-beam lithography process comprises (a) the detailed optical study and selection of target QDs by means of CL-spectroscopy and (b) the precise retrieval of the locations and integration of target QDs into lithographically defined nanostructures. Our technology platform allows for a detailed pre-process determination of important optical and quantum optical properties of the QDs, such as the emission energies of excitonic complexes, the excitonic fine-structure splitting, the carrier dynamics, and the quantum nature of emission. In addition, it enables a direct and precise comparison of the optical properties of a single QD before and after integration which is very beneficial for the quantitative evaluation of cavity-enhanced quantum devices.

  3. Advanced in-situ electron-beam lithography for deterministic nanophotonic device processing

    NASA Astrophysics Data System (ADS)

    Kaganskiy, Arsenty; Gschrey, Manuel; Schlehahn, Alexander; Schmidt, Ronny; Schulze, Jan-Hindrik; Heindel, Tobias; Strittmatter, André; Rodt, Sven; Reitzenstein, Stephan

    2015-07-01

    We report on an advanced in-situ electron-beam lithography technique based on high-resolution cathodoluminescence (CL) spectroscopy at low temperatures. The technique has been developed for the deterministic fabrication and quantitative evaluation of nanophotonic structures. It is of particular interest for the realization and optimization of non-classical light sources which require the pre-selection of single quantum dots (QDs) with very specific emission features. The two-step electron-beam lithography process comprises (a) the detailed optical study and selection of target QDs by means of CL-spectroscopy and (b) the precise retrieval of the locations and integration of target QDs into lithographically defined nanostructures. Our technology platform allows for a detailed pre-process determination of important optical and quantum optical properties of the QDs, such as the emission energies of excitonic complexes, the excitonic fine-structure splitting, the carrier dynamics, and the quantum nature of emission. In addition, it enables a direct and precise comparison of the optical properties of a single QD before and after integration which is very beneficial for the quantitative evaluation of cavity-enhanced quantum devices.

  4. Automated S/TEM metrology on advanced semiconductor gate structures

    NASA Astrophysics Data System (ADS)

    Strauss, M.; Arjavac, J.; Horspool, D. N.; Nakahara, K.; Deeb, C.; Hobbs, C.

    2012-03-01

    Alternate techniques for obatining metrology data from advanced semiconductor device structures may be required. Automated STEM-based dimensional metrology (CD-STEM) was developed for complex 3D geometries in read/write head metrology in teh hard disk drive industry. It has been widely adopted, and is the process of record for metrology. Fully automated S/TEM metrology on advanced semiconductor gate structures is viable, with good repeatability and robustness. Consistent automated throughput of 10 samples per hour was achieved. Automated sample preparation was developed with sufficient throughput and quality to support the automated CD-STEM.

  5. Advancing Small Satellite Electronics Heritage for Microfluidic Biological Experiments

    NASA Technical Reports Server (NTRS)

    White, Bruce; Mazmanian, Edward; Tapio, Eric

    2016-01-01

    DLR's Eu:CROPIS (Euglena and Combined Regenerative Organic-Food Production in Space) mission, launching in 2017, will carry multiple biological payloads into a sun-synchronous orbit, including NASA Ames' PowerCell experiment. PowerCell will attempt to characterize the viability of synthetic biology at micro-g, Lunar, and Martian gravity levels. PowerCell experiment requirements demand an electronic system similar to previous microfluidic biology payloads, but with an expanded feature set. As such, the system was based on PharmaSat (Diaz-Aguado et al. 2009), a previous successful biology payload from NASA Ames, and improved upon. Newer, more miniaturized electronics allow for greater capability with a lower part count and smaller size. Two identical PowerCell enclosures will fly. Each enclosure contains two separate and identical experiments with a 48-segment optical density measurement system, grow light system, microfluidic system for nutrient delivery and waste flushing, plus thermal control and environmental sensing/housekeeping including temperature, pressure, humidity, and acceleration. Electronics consist of a single Master PCB that interfaces to the spacecraft bus and regulates power and communication, plus LED, Detector, and Valve Manifold PCBs for each experiment. To facilitate ease of reuse on future missions, experiment electronics were designed to be compatible with a standard 3U small sat form factor and power bus, or to interface with a Master power/comm PCB for use in a larger satellite as in the case of PowerCell's flight on Eu:CROPIS.

  6. Electronic structure of cyclohexane on Ni(111)

    NASA Astrophysics Data System (ADS)

    Huber, W.; Zebisch, P.; Bornemann, T.; Steinrück, H.-P.

    1990-12-01

    Mono- and multilayers of cyclohexane adsorbed on a Ni(111) surface have been studied by angle resolved UV photoelectron spectroscopy (ARUPS) using linearly polarized synchrotron radiation, temperature programmed desorption (TPD) and low energy electron diffraction (LEED). Cyclohexane is molecularly adsorbed on Ni(111) at temperatures below 200 K and desorbs without dehydrogenation. Desorption from the first layer exhibits zeroth-order desorption behavior indicative of desorption from two-dimensional islands. The first layer exhibits a well ordered ( 7 × 7)R19.1° LEED structure starting at coverages of 0.04 ML up to the saturation coverage of 0.143 ML, also indicative of island formation. For cyclohexane in the first layer the binding energies of the various molecular levels are, apart from an overall shift to smaller values by 0.7 eV, within ± 0.1 eV identical to those of condensed cyclohexane. This absence of chemical shifts indicates that there is only very weak (if any) chemical interaction between cyclohexane and the Ni(111) surface. From the normal emission ARUPS spectra and symmetry selection rules we conclude that the symmetry of cyclohexane adsorbed on Ni(111) is lower than C 3v. This is attributed to a slightly inclined adsorption geometry with intramolecular C 3v symmetry of the adsorbed molecules.

  7. Angle-Resolved Photoemission Spectroscopy on Electronic Structure and Electron-Phonon Coupling in Cuprate Superconductors

    SciTech Connect

    Zhou, X.J.

    2010-04-30

    thought possible only a decade ago. This revolution of the ARPES technique and its scientific impact result from dramatic advances in four essential components: instrumental resolution and efficiency, sample manipulation, high quality samples and well-matched scientific issues. The purpose of this treatise is to go through the prominent results obtained from ARPES on cuprate superconductors. Because there have been a number of recent reviews on the electronic structures of high-T{sub c} materials, we will mainly present the latest results not covered previously, with a special attention given on the electron-phonon interaction in cuprate superconductors. What has emerged is rich information about the anomalous electron-phonon interaction well beyond the traditional views of the subject. It exhibits strong doping, momentum and phonon symmetry dependence, and shows complex interplay with the strong electron-electron interaction in these materials. ARPES experiments have been instrumental in identifying the electronic structure, observing and detailing the electron-phonon mode coupling behavior, and mapping the doping evolution of the high-T{sub c} cuprates. The spectra evolve from the strongly coupled, polaronic spectra seen in underdoped cuprates to the Migdal-Eliashberg like spectra seen in the optimally and overdoped cuprates. In addition to the marked doping dependence, the cuprates exhibit pronounced anisotropy with direction in the Brillouin zone: sharp quasiparticles along the nodal direction that broaden significantly in the anti-nodal region of the underdoped cuprates, an anisotropic electron-phonon coupling vertex for particular modes identified in the optimal and overdoped compounds, and preferential scattering across the two parallel pieces of Fermi surface in the antinodal region for all doping levels. This also contributes to the pseudogap effect. To the extent that the Migdal-Eliashberg picture applies, the spectra of the cuprates bear resemblance to that

  8. Structural Configuration Systems Analysis for Advanced Aircraft Fuselage Concepts

    NASA Technical Reports Server (NTRS)

    Mukhopadhyay, Vivek; Welstead, Jason R.; Quinlan, Jesse R.; Guynn, Mark D.

    2016-01-01

    Structural configuration analysis of an advanced aircraft fuselage concept is investigated. This concept is characterized by a double-bubble section fuselage with rear mounted engines. Based on lessons learned from structural systems analysis of unconventional aircraft, high-fidelity finite-element models (FEM) are developed for evaluating structural performance of three double-bubble section configurations. Structural sizing and stress analysis are applied for design improvement and weight reduction. Among the three double-bubble configurations, the double-D cross-section fuselage design was found to have a relatively lower structural weight. The structural FEM weights of these three double-bubble fuselage section concepts are also compared with several cylindrical fuselage models. Since these fuselage concepts are different in size, shape and material, the fuselage structural FEM weights are normalized by the corresponding passenger floor area for a relative comparison. This structural systems analysis indicates that an advanced composite double-D section fuselage may have a relative structural weight ratio advantage over a conventional aluminum fuselage. Ten commercial and conceptual aircraft fuselage structural weight estimates, which are empirically derived from the corresponding maximum takeoff gross weight, are also presented and compared with the FEM- based estimates for possible correlation. A conceptual full vehicle FEM model with a double-D fuselage is also developed for preliminary structural analysis and weight estimation.

  9. Probabilistic Evaluation of Advanced Ceramic Matrix Composite Structures

    NASA Technical Reports Server (NTRS)

    Abumeri, Galib H.; Chamis, Christos C.

    2003-01-01

    The objective of this report is to summarize the deterministic and probabilistic structural evaluation results of two structures made with advanced ceramic composites (CMC): internally pressurized tube and uniformly loaded flange. The deterministic structural evaluation includes stress, displacement, and buckling analyses. It is carried out using the finite element code MHOST, developed for the 3-D inelastic analysis of structures that are made with advanced materials. The probabilistic evaluation is performed using the integrated probabilistic assessment of composite structures computer code IPACS. The affects of uncertainties in primitive variables related to the material, fabrication process, and loadings on the material property and structural response behavior are quantified. The primitive variables considered are: thermo-mechanical properties of fiber and matrix, fiber and void volume ratios, use temperature, and pressure. The probabilistic structural analysis and probabilistic strength results are used by IPACS to perform reliability and risk evaluation of the two structures. The results will show that the sensitivity information obtained for the two composite structures from the computational simulation can be used to alter the design process to meet desired service requirements. In addition to detailed probabilistic analysis of the two structures, the following were performed specifically on the CMC tube: (1) predicted the failure load and the buckling load, (2) performed coupled non-deterministic multi-disciplinary structural analysis, and (3) demonstrated that probabilistic sensitivities can be used to select a reduced set of design variables for optimization.

  10. Recent Advances in Electron Tomography: TEM and HAADF-STEM Tomography for Materials Science and IC Applications

    SciTech Connect

    Kubel, C; Voigt, A; Schoenmakers, R; Otten, M; Su, D; Lee, T; Carlsson, A; Engelmann, H; Bradley, J

    2005-11-09

    Electron tomograph tomography is a well y well-established technique for three-dimensional structure determination of (almost) amorphous specimens in life science applications. With the recent advances in nanotechnology and the semiconductor industry, there is also an increasing need for high-resolution 3D structural information in physical sciences. In this paper, we evaluate the capabilities and limitations of TEM and HAADF-STEM tomography for the 3D structural characterization of partially crystalline to highly crystalline materials. Our analysis of catalysts, a hydrogen storage material, and different semiconductor devices shows that features with a diameter as small as 1-2 nm can be resolved in 3D by electron tomography. For partially crystalline materials with small single crystalline domains, TEM tomography provides reliable 3D structural information. HAADF-STEM tomography is more versatile and can also be used for high-resolution 3D imaging of highly crystalline materials such as semiconductor devices.

  11. Electronic Structure and Dynamics of Nitrosyl Porphyrins

    PubMed Central

    Scheidt, W. Robert; Barabanschikov, Alexander; Pavlik, Jeffrey W.; Silvernail, Nathan J.; Sage, J. Timothy

    2010-01-01

    fully successful at capturing the interaction between the axial NO and imidazole ligands. This supports previous conclusions that hemeNO complexes exhibit an unusual degree of variability with respect to computational method, and we speculate that this variability hints at a genuine electronic instability that a protein can exploit to tune reactivity. We anticipate that ongoing characterization of heme-NO complexes will deepen our understanding of their structure, dynamics, and reactivity. PMID:20666384

  12. RNA Structure: Advances and Assessment of 3D Structure Prediction.

    PubMed

    Miao, Zhichao; Westhof, Eric

    2017-03-30

    Biological functions of RNA molecules are dependent upon sustained specific three-dimensional (3D) structures of RNA, with or without the help of proteins. Understanding of RNA structure is frequently based on 2D structures, which describe only the Watson-Crick (WC) base pairs. Here, we hierarchically review the structural elements of RNA and how they contribute to RNA 3D structure. We focus our analysis on the non-WC base pairs and on RNA modules. Several computer programs have now been designed to predict RNA modules. We describe the RNA-Puzzles initiative, which is a community-wide, blind assessment of RNA 3D structure prediction programs to determine the capabilities and bottlenecks of current predictions. The assessment metrics used in RNA-Puzzles are briefly described. The detection of RNA 3D modules from sequence data and their automatic implementation belong to the current challenges in RNA 3D structure prediction. Expected final online publication date for the Annual Review of Biophysics Volume 46 is May 20, 2017. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

  13. Probing Actinide Electronic Structure through Pu Cluster Calculations

    DOE PAGES

    Ryzhkov, Mickhail V.; Mirmelstein, Alexei; Yu, Sung-Woo; ...

    2013-02-26

    The calculations for the electronic structure of clusters of plutonium have been performed, within the framework of the relativistic discrete-variational method. Moreover, these theoretical results and those calculated earlier for related systems have been compared to spectroscopic data produced in the experimental investigations of bulk systems, including photoelectron spectroscopy. Observation of the changes in the Pu electronic structure as a function of size provides powerful insight for aspects of bulk Pu electronic structure.

  14. Graph-based linear scaling electronic structure theory

    NASA Astrophysics Data System (ADS)

    Niklasson, Anders M. N.; Mniszewski, Susan M.; Negre, Christian F. A.; Cawkwell, Marc J.; Swart, Pieter J.; Mohd-Yusof, Jamal; Germann, Timothy C.; Wall, Michael E.; Bock, Nicolas; Rubensson, Emanuel H.; Djidjev, Hristo

    2016-06-01

    We show how graph theory can be combined with quantum theory to calculate the electronic structure of large complex systems. The graph formalism is general and applicable to a broad range of electronic structure methods and materials, including challenging systems such as biomolecules. The methodology combines well-controlled accuracy, low computational cost, and natural low-communication parallelism. This combination addresses substantial shortcomings of linear scaling electronic structure theory, in particular with respect to quantum-based molecular dynamics simulations.

  15. Graph-based linear scaling electronic structure theory.

    PubMed

    Niklasson, Anders M N; Mniszewski, Susan M; Negre, Christian F A; Cawkwell, Marc J; Swart, Pieter J; Mohd-Yusof, Jamal; Germann, Timothy C; Wall, Michael E; Bock, Nicolas; Rubensson, Emanuel H; Djidjev, Hristo

    2016-06-21

    We show how graph theory can be combined with quantum theory to calculate the electronic structure of large complex systems. The graph formalism is general and applicable to a broad range of electronic structure methods and materials, including challenging systems such as biomolecules. The methodology combines well-controlled accuracy, low computational cost, and natural low-communication parallelism. This combination addresses substantial shortcomings of linear scaling electronic structure theory, in particular with respect to quantum-based molecular dynamics simulations.

  16. Advanced manufacturing of SIMOX for low power electronics

    NASA Astrophysics Data System (ADS)

    Alles, Michael; Krull, Wade

    1996-04-01

    Silicon-on-insulator (SOI) has emerged as a key technology for low power electronics. The merits of SOI technology have been demonstrated, and are gaining acceptance in the semiconductor industry. In order for the SOI approach to be viable, several factors must converge, including the availability of SOI substrates in sufficient quantity, of acceptable quality, and at a competitive price. This work describes developments in SIMOX manufacturing technology and summarizes progress in each of these areas.

  17. Advanced accelerator and mm-wave structure research at LANL

    SciTech Connect

    Simakov, Evgenya Ivanovna

    2016-06-22

    This document outlines acceleration projects and mm-wave structure research performed at LANL. The motivation for PBG research is described first, with reference to couplers for superconducting accelerators and structures for room-temperature accelerators and W-band TWTs. These topics are then taken up in greater detail: PBG structures and the MIT PBG accelerator; SRF PBG cavities at LANL; X-band PBG cavities at LANL; and W-band PBG TWT at LANL. The presentation concludes by describing other advanced accelerator projects: beam shaping with an Emittance Exchanger, diamond field emitter array cathodes, and additive manufacturing of novel accelerator structures.

  18. Advanced Composite Structures At NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Eldred, Lloyd B.

    2015-01-01

    Dr. Eldred's presentation will discuss several NASA efforts to improve and expand the use of composite structures within aerospace vehicles. Topics will include an overview of NASA's Advanced Composites Project (ACP), Space Launch System (SLS) applications, and Langley's ISAAC robotic composites research tool.

  19. The Commercial Opportunities for New Advanced Electronic Materials

    DTIC Science & Technology

    1989-08-07

    perovskite structure. Superconducting materials and dopings. The band-gap structure of the layers consist of complex linked arrays of perovskite cells ...its con parts only. The annual turnover for the solar cells OFF value. The importance of this device is that small alone is estimated to exceed $50...outer surface of a cyl- energy into electrical energy. Present day solar cells con- indrical drum. The properties required for an ideal vert 12-13

  20. Dramatic changes in electronic structure revealed by fractionally charged nuclei

    NASA Astrophysics Data System (ADS)

    Cohen, Aron J.; Mori-Sánchez, Paula

    2014-01-01

    Discontinuous changes in the electronic structure upon infinitesimal changes to the Hamiltonian are demonstrated. These are revealed in one and two electron molecular systems by full configuration interaction (FCI) calculations when the realm of the nuclear charge is extended to be fractional. FCI electron densities in these systems show dramatic changes in real space and illustrate the transfer, hopping, and removal of electrons. This is due to the particle nature of electrons seen in stretched systems and is a manifestation of an energy derivative discontinuity at constant number of electrons. Dramatic errors of density functional theory densities are seen in real space as this physics is missing from currently used approximations. The movements of electrons in these simple systems encapsulate those in real physical processes, from chemical reactions to electron transport and pose a great challenge for the development of new electronic structure methods.

  1. Advanced Electron Holography Applied to Electromagnetic Field Study in Materials Science.

    PubMed

    Shindo, Daisuke; Tanigaki, Toshiaki; Park, Hyun Soon

    2016-11-17

    Advances and applications of electron holography to the study of electromagnetic fields in various functional materials are presented. In particular, the development of split-illumination electron holography, which introduces a biprism in the illumination system of a holography electron microscope, enables highly accurate observations of electromagnetic fields and the expansion of the observable area. First, the charge distributions on insulating materials were studied by using split-illumination electron holography and including a mask in the illumination system. Second, the three-dimensional spin configurations of skyrmion lattices in a helimagnet were visualized by using a high-voltage holography electron microscope. Third, the pinning of the magnetic flux lines in a high-temperature superconductor YBa2 Cu3 O7-y was analyzed by combining electron holography and scanning ion microscopy. Finally, the dynamic accumulation and collective motions of electrons around insulating biomaterial surfaces were observed by utilizing the amplitude reconstruction processes of electron holography.

  2. Systems integration and demonstration of advanced reusable structure for ALS

    NASA Technical Reports Server (NTRS)

    Gibbins, Martin N.

    1991-01-01

    The objective was to investigate the potential of advanced material to achieve life cycle cost (LCC) benefits for reusable structure on the advanced launch system. Three structural elements were investigated - all components of an Advanced Launch System reusable propulsion/avionics module. Leading aeroshell configurations included sandwich structure using titanium, graphite/polyimide (Gr/PI), or high-temperature aluminum (HTA) face sheets. Thrust structure truss concepts used titanium, graphite/epoxy, or silicon carbide/aluminum struts. Leading aft bulkhead concepts employed graphite epoxy and aluminum. The technical effort focused on the aeroshell because the greatest benefits were expected there. Thermal analyses show the structural temperature profiles during operation. Finite element analyses show stresses during splash-down. Weight statements and manufacturing cost estimates were prepared for calculation of LCC for each design. The Gr/PI aeroshell showed the lowest potential LCC, but the HTA aeroshell was judged to be lower risk. A technology development plan was prepared to validate the applicable structural technology.

  3. Applications of advanced electric/electronic technology to conventional aircraft

    NASA Technical Reports Server (NTRS)

    Heimbold, R. L.

    1980-01-01

    The desirability of seven advanced technologies as applied to three commercial aircraft of 1985 to 1995 was investigated. Digital fly by wire, multiplexing, ring laser gyro, integrated avionics, all electric airplane, electric load management, and fiber optics were considered for 500 passenger, 50 passenger, and 30 passenger aircraft. The major figure of merit used was Net Value of Technology based on procurement and operating cost over the life of the aircraft. An existing computer program, ASSET, was used to resize the aircraft and evalute fuel usage and maintenance costs for each candidate configuration. Conclusions were that, for the 500 passenger aircraft, all candidates had a worthwhile payoff with the all electric airplane having a large payoff.

  4. Report on sodium compatibility of advanced structural materials.

    SciTech Connect

    Li, M.; Natesan, K.; Momozaki, Y.; Rink, D.L.; Soppet, W.K.; Listwan, J.T.

    2012-07-09

    This report provides an update on the evaluation of sodium compatibility of advanced structural materials. The report is a deliverable (level 3) in FY11 (M3A11AN04030403), under the Work Package A-11AN040304, 'Sodium Compatibility of Advanced Structural Materials' performed by Argonne National Laboratory (ANL), as part of Advanced Structural Materials Program for the Advanced Reactor Concepts. This work package supports the advanced structural materials development by providing corrosion and tensile data from the standpoint of sodium compatibility of advanced structural alloys. The scope of work involves exposure of advanced structural alloys such as G92, mod.9Cr-1Mo (G91) ferritic-martensitic steels and HT-UPS austenitic stainless steels to a flowing sodium environment with controlled impurity concentrations. The exposed specimens are analyzed for their corrosion performance, microstructural changes, and tensile behavior. Previous reports examined the thermodynamic and kinetic factors involved in the purity of liquid sodium coolant for sodium reactor applications as well as the design, fabrication, and construction of a forced convection sodium loop for sodium compatibility studies of advanced materials. This report presents the results on corrosion performance, microstructure, and tensile properties of advanced ferritic-martensitic and austenitic alloys exposed to liquid sodium at 550 C for up to 2700 h and at 650 C for up to 5064 h in the forced convection sodium loop. The oxygen content of sodium was controlled by the cold-trapping method to achieve {approx}1 wppm oxygen level. Four alloys were examined, G92 in the normalized and tempered condition (H1 G92), G92 in the cold-rolled condition (H2 G92), G91 in the normalized and tempered condition, and hot-rolled HT-UPS. G91 was included as a reference to compare with advanced alloy, G92. It was found that all four alloys showed weight loss after sodium exposures at 550 and 650 C. The weight loss of the four

  5. Advances in molecular electronics: Synthesis and testing of potential molecular electronic devices

    NASA Astrophysics Data System (ADS)

    Price, David Wilson, Jr.

    New potential molecular electronics devices have been synthesized based on our knowledge of previous systems that have come out of our group. Previous studies and current studies have shown that simple molecular systems demonstrate negative differential resistance (NDR) and memory characteristics. The new systems rely primarily on the redox properties of the compounds to improve upon the solid state properties already observed. Most of these new organic compounds use thiol-based "alligator clips" for attachment to metal surfaces. Some of the compounds, however, contain different "alligator clips," primarily isonitriles, for attachment to metal substrates. It is our hope that these new "alligator clips" will offer lower conductivity barriers (higher current density). Electrochemical tests have been performed in order to evaluate those redox properties and in the hope of using those electrochemical results as a predictive tool to evaluate the usefulness of those compounds. Also, organic structures with polymerizable functionalities have been synthesized in order to cross-link the molecules once they are a part of a self-assembled monolayer (SAM). This has been shown to enable the electrochemical growth of polypyrrole from a SAM in a controllable manner.

  6. Chemical and structural stability of lithium-ion battery electrode materials under electron beam.

    PubMed

    Lin, Feng; Markus, Isaac M; Doeff, Marca M; Xin, Huolin L

    2014-07-16

    The investigation of chemical and structural dynamics in battery materials is essential to elucidation of structure-property relationships for rational design of advanced battery materials. Spatially resolved techniques, such as scanning/transmission electron microscopy (S/TEM), are widely applied to address this challenge. However, battery materials are susceptible to electron beam damage, complicating the data interpretation. In this study, we demonstrate that, under electron beam irradiation, the surface and bulk of battery materials undergo chemical and structural evolution equivalent to that observed during charge-discharge cycling. In a lithiated NiO nanosheet, a Li2CO3-containing surface reaction layer (SRL) was gradually decomposed during electron energy loss spectroscopy (EELS) acquisition. For cycled LiNi(0.4)Mn(0.4)Co(0.18)Ti(0.02)O2 particles, repeated electron beam irradiation induced a phase transition from an layered structure to an rock-salt structure, which is attributed to the stoichiometric lithium and oxygen removal from 3a and 6c sites, respectively. Nevertheless, it is still feasible to preserve pristine chemical environments by minimizing electron beam damage, for example, using fast electron imaging and spectroscopy. Finally, the present study provides examples of electron beam damage on lithium-ion battery materials and suggests that special attention is necessary to prevent misinterpretation of experimental results.

  7. Observation of interface band structure by ballistic-electron-emission microscopy

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Kaiser, W. J.

    1988-01-01

    The paper reports an advanced ballistic electron spectroscopy technique that was used to directly measure semiconductor band structure properties at a subsurface interface. Two interface systems having contrasting band structures were investigated by this method: Au-Si and Au-GaAs. It is concluded that the proposed method, based on scanning tunneling microscopy, enables the spatially resolved carrier-transport spectroscopy of interfaces.

  8. Affordable, Lightweight, Highly Conductive Polymer Composite Electronic Packaging Structures

    DTIC Science & Technology

    1996-06-01

    matrix composite materials and how various material designs can be utilized in various structural/thermal configurations to produce electronic housings and...conductive polymer composite electronic packaging (i.e., electronic housings and heat sinks). The research will center on predominately polymer

  9. Recent Advances In Optimization Of Aerospace Structures And Engines

    NASA Astrophysics Data System (ADS)

    Rao*, J. S.

    Optimization theories have been well advanced during the last few decades; however when it came to handle real life engineering structures it has been always time consuming and approximate when the structure geometry is highly complex. Design of Experiments has helped in understanding the influence of size and shape parameters on achieving a specified objective function with required constraints and a suitable analysis platform, but has its limitations in arriving at the final optimal solution. There are several commercial codes that addressed this need to handle large size structures subjected to dynamic loads. Most advanced tools in this category are Altair OptiStruct and Altair HyperStudy available in Altair HyperWorks suite. Application of these tools in achieving optimum solutions for linear advanced aircraft structures for minimization of weight are first explained. The application of these tools for globally elastic and locally plastic nonlinear structures to reduce local plastic strains and achieve higher life under dynamic loads will then be discussed.

  10. Adding structure to the transition process to advanced mathematical activity

    NASA Astrophysics Data System (ADS)

    Engelbrecht, Johann

    2010-03-01

    The transition process to advanced mathematical thinking is experienced as traumatic by many students. Experiences that students had of school mathematics differ greatly to what is expected from them at university. Success in school mathematics meant application of different methods to get an answer. Students are not familiar with logical deductive reasoning, required in advanced mathematics. It is necessary to assist students in this transition process, in moving from general to mathematical thinking. In this article some structure is suggested for this transition period. This essay is an argumentative exposition supported by personal experience and international literature. This makes this study theoretical rather than empirical.

  11. Topology Zero: Advancing Theory and Experimentation for Power Electronics Education

    NASA Astrophysics Data System (ADS)

    Luchino, Federico

    For decades, power electronics education has been based on the fundamentals of three basic topologies: buck, boost, and buck-boost. This thesis presents the analytical framework for the Topology Zero, a general circuit topology that integrates the basic topologies and provides significant insight into the behaviour of converters. As demonstrated, many topologies are just particular cases of the Topology Zero, an important contribution towards the understanding, integration, and conceptualization of topologies. The investigation includes steady-state, small-signal, and frequency response analysis. The Topology Zero is physically implemented as an educational system. Experimental results are presented to show control applications and power losses analysis using the educational system. The steady-state and dynamic analyses of the Topology Zero provide profuse proof of its suitability as an integrative topology, and of its ability to be indirectly controlled. As well, the implementation of the Topology Zero within an experimentation system is explained and application examples are provided.

  12. Advances and applications of electronic speckle pattern interferometry /ESPI/

    NASA Astrophysics Data System (ADS)

    Lokberg, O. J.

    1980-05-01

    The principle of electronic speckle pattern interferometry (ESPI) is explained by means of comparison with conventional holography. Because ESPI image recording and reconstruction are performed by videotechniques, laboratory experiments may be studied through real-time presentations of readily interpretable vibration patterns on a large TV screen, with a new image being formed every 1/25 sec. These properties, combined with the high sensitivity, noncontact, and nondestructive properties of the method, make ESPI a measuring tool uniquely suited for studies of extremely unstable objects. Among examples of applications covered are: the testing of sonar transducers in both air and water, the analysis of loudspeakers, studies of the behavior of piezoelectric transducers, the classification of turbine blade resonances, and the observation of the human eardrum.

  13. Polymeric and Molecular Materials for Advanced Organic Electronics

    DTIC Science & Technology

    2014-10-20

    id tags, and solar modules which can then be integrated with textiles, printed batteries, solar cells , and aircraft/satellite structures. iv The...polymer-based CMOS circuits, and all-polymer solar cells . We designed a completely new building block, 4,4’-dialkoxy-5,5’- bithiazole, BTzOR (Fig. 2...ordered active layers exhibiting very large Vocs (0.8-0.9V), unprecedented fill factors (FFs) reminiscent of inorganic solar cells (~80%), in accord with

  14. Advanced Relay Design and Technology for Energy-Efficient Electronics

    DTIC Science & Technology

    2011-07-07

    4.3.2.2. Monotonicity Analysis vs. Finite - Element -Method Analysis .......................... 53 4.3.3. Summary of Design Optimization Study... film thickness. The movable structure is gradually buckled upward from its anchors toward its geometric center (it appears like an open umbrella...pull-in mode (with a TCONTACT-to-TACT ratio of 0.7 to 0.8) [25]. To validate the new relay design, Finite - Element -Method (FEM) analysis was performed

  15. The Assurance Challenges of Advanced Packaging Technologies for Electronics

    NASA Technical Reports Server (NTRS)

    Sampson, Michael J.

    2010-01-01

    Advances in microelectronic parts performance are driving towards finer feature sizes, three-dimensional geometries and ever-increasing number of transistor equivalents that are resulting in increased die sizes and interconnection (I/O) counts. The resultant packaging necessary to provide assemble-ability, environmental protection, testability and interconnection to the circuit board for the active die creates major challenges, particularly for space applications, Traditionally, NASA has used hermetically packaged microcircuits whenever available but the new demands make hermetic packaging less and less practical at the same time as more and more expensive, Some part types of great interest to NASA designers are currently only available in non-hermetic packaging. It is a far more complex quality and reliability assurance challenge to gain confidence in the long-term survivability and effectiveness of nonhermetic packages than for hermetic ones. Although they may provide more rugged environmental protection than the familiar Plastic Encapsulated Microcircuits (PEMs), the non-hermetic Ceramic Column Grid Array (CCGA) packages that are the focus of this presentation present a unique combination of challenges to assessing their suitability for spaceflight use. The presentation will discuss the bases for these challenges, some examples of the techniques proposed to mitigate them and a proposed approach to a US MIL specification Class for non-hermetic microcircuits suitable for space application, Class Y, to be incorporated into M. IL-PRF-38535. It has recently emerged that some major packaging suppliers are offering hermetic area array packages that may offer alternatives to the nonhermetic CCGA styles but have also got their own inspectability and testability issues which will be briefly discussed in the presentation,

  16. Structure and bonding at the atomic scale by scanning transmission electron microscopy.

    PubMed

    Muller, David A

    2009-04-01

    A new generation of electron microscopes is able to explore the microscopic properties of materials and devices as diverse as transistors, turbine blades and interfacial superconductors. All of these systems are made up of dissimilar materials that, where they join at the atomic scale, display very different behaviour from what might be expected of the bulk materials. Advances in electron optics have enabled the imaging and spectroscopy of these buried interface states and other nanostructures with atomic resolution. Here I review the capabilities, prospects and ultimate limits for the measurement of physical and electronic properties of nanoscale structures with these new microscopes.

  17. Recent advances in computational structural reliability analysis methods

    NASA Technical Reports Server (NTRS)

    Thacker, Ben H.; Wu, Y.-T.; Millwater, Harry R.; Torng, Tony Y.; Riha, David S.

    1993-01-01

    The goal of structural reliability analysis is to determine the probability that the structure will adequately perform its intended function when operating under the given environmental conditions. Thus, the notion of reliability admits the possibility of failure. Given the fact that many different modes of failure are usually possible, achievement of this goal is a formidable task, especially for large, complex structural systems. The traditional (deterministic) design methodology attempts to assure reliability by the application of safety factors and conservative assumptions. However, the safety factor approach lacks a quantitative basis in that the level of reliability is never known and usually results in overly conservative designs because of compounding conservatisms. Furthermore, problem parameters that control the reliability are not identified, nor their importance evaluated. A summary of recent advances in computational structural reliability assessment is presented. A significant level of activity in the research and development community was seen recently, much of which was directed towards the prediction of failure probabilities for single mode failures. The focus is to present some early results and demonstrations of advanced reliability methods applied to structural system problems. This includes structures that can fail as a result of multiple component failures (e.g., a redundant truss), or structural components that may fail due to multiple interacting failure modes (e.g., excessive deflection, resonate vibration, or creep rupture). From these results, some observations and recommendations are made with regard to future research needs.

  18. Differently Structured Advance Organizers Lead to Different Initial Schemata and Learning Outcomes

    ERIC Educational Resources Information Center

    Gurlitt, Johannes; Dummel, Sebastian; Schuster, Silvia; Nuckles, Matthias

    2012-01-01

    Does the specific structure of advance organizers influence learning outcomes? In the first experiment, 48 psychology students were randomly assigned to three differently structured advance organizers: a well-structured, a well-structured and key-concept emphasizing, and a less structured advance organizer. These were followed by a sorting task, a…

  19. Unbunched beam electron-proton instability in the PSR and advanced hadron facilities

    SciTech Connect

    Wang, Tai-Sen; Pisent, A.; Neuffer, D.V.

    1989-01-01

    We studied the possibility of the occurrence of transverse instability induced by trapped electrons in unbunched beams in the Proton Storage Ring and the proposed Advance Hadron Facility (AHF) at Los Alamos, as well as in the proposed Kaon Factory at TRIUMF. We found that the e-p instability may be possible for unbunched beams in the PSR but is unlikely to occur in the advanced hadron facilities. 8 refs., 4 figs.

  20. Advances in Fatigue and Fracture Mechanics Analyses for Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.

    1999-01-01

    This paper reviews some of the advances that have been made in stress analyses of cracked aircraft components, in the understanding of the fatigue and fatigue-crack growth process, and in the prediction of residual strength of complex aircraft structures with widespread fatigue damage. Finite-element analyses of cracked structures are now used to determine accurate stress-intensity factors for cracks at structural details. Observations of small-crack behavior at open and rivet-loaded holes and the development of small-crack theory has lead to the prediction of stress-life behavior for components with stress concentrations under aircraft spectrum loading. Fatigue-crack growth under simulated aircraft spectra can now be predicted with the crack-closure concept. Residual strength of cracked panels with severe out-of-plane deformations (buckling) in the presence of stiffeners and multiple-site damage can be predicted with advanced elastic-plastic finite-element analyses and the critical crack-tip-opening angle (CTOA) fracture criterion. These advances are helping to assure continued safety of aircraft structures.

  1. Computerized structural mechanics for 1990's: Advanced aircraft needs

    NASA Technical Reports Server (NTRS)

    Viswanathan, A. V.; Backman, B. F.

    1989-01-01

    The needs for computerized structural mechanics (CSM) as seen from the standpoint of the aircraft industry are discussed. These needs are projected into the 1990's with special focus on the new advanced materials. Preliminary design/analysis, research, and detail design/analysis are identified as major areas. The role of local/global analyses in these different areas is discussed. The lessons learned in the past are used as a basis for the design of a CSM framework that could modify and consolidate existing technology and include future developments in a rational and useful way. A philosophy is stated, and a set of analyses needs driven by the emerging advanced composites is enumerated. The roles of NASA, the universities, and the industry are identified. Finally, a set of rational research targets is recommended based on both the new types of computers and the increased complexity the industry faces. Computerized structural mechanics should be more than new methods in structural mechanics and numerical analyses. It should be a set of engineering applications software products that combines innovations in structural mechanics, numerical analysis, data processing, search and display features, and recent hardware advances and is organized in a framework that directly supports the design process.

  2. Structural Change Can Be Detected in Advanced-Glaucoma Eyes

    PubMed Central

    Belghith, Akram; Medeiros, Felipe A.; Bowd, Christopher; Liebmann, Jeffrey M.; Girkin, Christopher A.; Weinreb, Robert N.; Zangwill, Linda M.

    2016-01-01

    Purpose To compare spectral-domain optical coherence tomography (SD-OCT) standard structural measures and a new three-dimensional (3D) volume optic nerve head (ONH) change detection method for detecting change over time in severely advanced-glaucoma (open-angle glaucoma [OAG]) patients. Methods Thirty-five eyes of 35 patients with very advanced glaucoma (defined as a visual field mean deviation < −21 dB) and 46 eyes of 30 healthy subjects to estimate aging changes were included. Circumpapillary retinal fiber layer thickness (cpRNFL), minimum rim width (MRW), and macular retinal ganglion cell–inner plexiform layer (GCIPL) thicknesses were measured using the San Diego Automated Layer Segmentation Algorithm (SALSA). Progression was defined as structural loss faster than 95th percentile of healthy eyes. Three-dimensional volume ONH change was estimated using the Bayesian-kernel detection scheme (BKDS), which does not require extensive retinal layer segmentation. Results The number of progressing glaucoma eyes identified was highest for 3D volume BKDS (13, 37%), followed by GCPIL (11, 31%), cpRNFL (4, 11%), and MRW (2, 6%). In advanced-OAG eyes, only the mean rate of GCIPL change reached statistical significance, −0.18 μm/y (P = 0.02); the mean rates of cpRNFL and MRW change were not statistically different from zero. In healthy eyes, the mean rates of cpRNFL, MRW, and GCIPL change were significantly different from zero. (all P < 0.001). Conclusions Ganglion cell–inner plexiform layer and 3D volume BKDS show promise for identifying change in severely advanced glaucoma. These results suggest that structural change can be detected in very advanced disease. Longer follow-up is needed to determine whether changes identified are false positives or true progression. PMID:27454660

  3. Velocity-space structure of runaway electrons

    SciTech Connect

    Fuchs, V.; Cairns, R.A.; Lashmore-Davies, C.N.; Shoucri, M.M.

    1986-09-01

    The region of velocity space is determined in which electron runaway occurs because of a dc electric field. Phase-space analysis of the relaxation equations describing test electrons, corroborated by two-dimensional (2-D) numerical integration of the Fokker--Planck equation, reveals that the Dreicer condition for runaway v-italic/sup 2//sub parallel/> or =(2+Z-italic/sub i-italic/)E-italic/sub c-italic//E-italic is only sufficient. A weaker condition v-italic/sup 2//sub parallel/> or =(2+Z-italic/sub i-italic/)/sup 1//sup ///sup 2/E-italic/sub c-italic//E-italic is established, and it is shown, in general, that runaway in velocity space only occurs for those electrons that are outside one of the separatrices of the relaxation equations. The scaling with v-italic/sub parallel/ of the parallel distribution function and of the perpendicular temperature is also derived.

  4. The Scanning Electron Microscope As An Accelerator For The Undergraduate Advanced Physics Laboratory

    SciTech Connect

    Peterson, Randolph S.; Berggren, Karl K.; Mondol, Mark

    2011-06-01

    Few universities or colleges have an accelerator for use with advanced physics laboratories, but many of these institutions have a scanning electron microscope (SEM) on site, often in the biology department. As an accelerator for the undergraduate, advanced physics laboratory, the SEM is an excellent substitute for an ion accelerator. Although there are no nuclear physics experiments that can be performed with a typical 30 kV SEM, there is an opportunity for experimental work on accelerator physics, atomic physics, electron-solid interactions, and the basics of modern e-beam lithography.

  5. Understanding the Influence of the Electronic Structure on the Crystal Structure of a TTF-PTM Radical Dyad.

    PubMed

    Vela, Sergi; Souto, Manuel; Ratera, Imma; Rovira, Concepció; Veciana, Jaume

    2016-12-29

    The understanding of the crystal structure of organic compounds, and its relationship to their physical properties, have become essential to design new advanced molecular materials. In this context, we present a computational study devoted to rationalize the different crystal packing displayed by two closely related organic systems based on the TTF-PTM dyad (TTF = tetrathiafulvalene, PTM = polychlorotriphenylmethane) with almost the same molecular structure but a different electronic one. The radical species (1), with an enhanced electronic donor-acceptor character, exhibits a herringbone packing, whereas the nonradical protonated analogue (2) is organized forming dimers. The stability of the possible polymorphs is analyzed in terms of the cohesion energy of the unit cell, intermolecular interactions between pairs, and molecular flexibility of the dyad molecules. It is observed that the higher electron delocalization in radical compound 1 has a direct influence on the geometry of the molecule, which seems to dictate its preferential crystal structure.

  6. Applications of Isotopes in Advancing Structural & Functional Heparanomics

    PubMed Central

    Tran, Vy M.; Nu Nguyen, Thao Kim; Raman, Karthik; Kuberan, Balagurunathan

    2011-01-01

    Heparanomics is the study of all the biologically active oligosaccharide domain structures in the entire heparanome and the nature of interactions among these domains and their protein ligands. Structural elucidation of heparan sulfate and heparin oligosaccharides is a major obstacle in advancing structure-function relationships and the study of heparanomics. There are several factors that exacerbate challenges involved in the structural elucidation of heparin and heparan sulfate. Therefore, there is a great interest in developing novel strategies and analytical tools to overcome the barriers in decoding the enigmatic heparanome. This review article focuses on the applications of isotopes, both radioisotopes and stable isotopes, in the structural elucidation of the complex heparanome at the disaccharide or oligosaccharide level using liquid chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry. This review article also outlines the utility of isotopes in determining the substrate specificity of biosynthetic enzymes that eventually dictate the emergence of biologically active oligosaccharides. PMID:20838780

  7. Novel engineered compound semiconductor heterostructures for advanced electronics applications

    NASA Astrophysics Data System (ADS)

    Stillman, Gregory E.; Holonyak, Nick, Jr.; Coleman, James J.

    1992-06-01

    To provide the technology base that will enable SDIO capitalization on the performance advantages offered through novel engineered multiple-lavered compound semiconductor structures, this project has focussed on three specific areas: (1) carbon doping of AlGaAs/GaAs and InP/InGaAs materials for reliable high frequency heterojunction bipolar transistors; (2) impurity induced layer disordering and the environmental degradation of AlxGal-xAs-GaAs quantum-well heterostructures and the native oxide stabilization of AlxGal-xAs-GaAs quantum well heterostructure lasers; and (3) non-planar and strained-layer quantum well heterostructure lasers and laser arrays. The accomplishments in this three year research are reported in fifty-six publications and the abstracts included in this report.

  8. Canada's national initiative to advance access to electronic journals.

    PubMed

    Groen, F

    2000-12-01

    This paper describes a national experiment in the licensing of full text information in journals, primarily in the fields of science, technology and medicine. It discusses the initiative of the federal government of Canada through the creation of the Canada Foundation for Innovation as a new funding agency, with an objective of improving research and creativity in Canadian science. The successful efforts initiated by the Canadian Association of Research Libraries/Association des bibliothèques de recherche du Canada to create a funding opportunity to develop the 'information infrastructure' for Canadian researchers and the resulting Canadian National Site Licensing Project (CNSLP) progress is discussed. The evolution of a project governance structure to maintain the support of the 64 participating institutions is reviewed and the need to develop an appropriate exit strategy at the conclusion of the federal funding is also considered.

  9. Overview of an Advanced Hypersonic Structural Concept Test Program

    NASA Technical Reports Server (NTRS)

    Stephens, Craig A.; Hudson, Larry D.; Piazza, Anthony

    2007-01-01

    This viewgraph presentation provides an overview of hypersonics M&S advanced structural concepts development and experimental methods. The discussion on concepts development includes the background, task objectives, test plan, and current status of the C/SiC Ruddervator Subcomponent Test Article (RSTA). The discussion of experimental methods examines instrumentation needs, sensors of interest, and examples of ongoing efforts in the development of extreme environment sensors.

  10. Structural Tailoring of Advanced Turboprops (STAT) programmer's manual

    NASA Technical Reports Server (NTRS)

    Brown, K. W.; Harvey, P. R.

    1989-01-01

    The Structural Tailoring of Advanced Turboprops (STAT) computer program was developed to perform numerical optimizations on highly swept propfan blades. This manual describes the functionality of the STAT system from a programmer's viewpoint. It provides a top-down description of module intent and interaction. The purpose of this manual is to familiarize the programmer with the STAT system should he/she wish to enhance or verify the program's function.

  11. Advanced stress analysis methods applicable to turbine engine structures

    NASA Technical Reports Server (NTRS)

    Pian, T. H. H.

    1985-01-01

    Advanced stress analysis methods applicable to turbine engine structures are investigated. Constructions of special elements which containing traction-free circular boundaries are investigated. New versions of mixed variational principle and version of hybrid stress elements are formulated. A method is established for suppression of kinematic deformation modes. semiLoof plate and shell elements are constructed by assumed stress hybrid method. An elastic-plastic analysis is conducted by viscoplasticity theory using the mechanical subelement model.

  12. ADVANCED SOLIDS NMR STUDIES OF COAL STRUCTURE AND CHEMISTRY

    SciTech Connect

    1997-09-01

    This report covers the progress made on the title project for the project period. The study of coal chemical structure is a vital component of research efforts to develop better chemical utilization of coals, and for furthering our basic understanding of coal geochemistry. In this grant we are addressing several structural questions pertaining to coals with advances in state of the art solids NMR methods. The main activity during this granting period was a completion of a detailed comparative analysis of the suite of spectral editing techniques developed in our laboratory for this purpose. The appended report is a manuscript being submitted to the Journal of Magnetic Resonance on this subject.

  13. Syntheses and electronic structures of decamethylmetallocenes

    SciTech Connect

    Robbins, J.L.

    1981-04-01

    The synthesis of decamethylmanganocene ((eta-C/sub 5/(CH/sub 3/)/sub 5/)/sub 2/Mn or (Me/sub 5/Cp)/sub 2/Mn)) is described. Magnetic susceptibility and electron paramagnetic resonance (EPR) studies show that (Me/sub 5/Cp)/sub 2/Mn is a low-spin, 17-electron compound with an orbitally degenerate, /sup 2/E/sub 2g/ (e/sub 2g//sup 3/ a/sub 1g//sup 2/) ground state. An x-ray crystallographic study of (Me/sub 5/Cp)/sub 2/Mn shows that it is a monomeric, D/sub 5d/ decamethylmetallocene with metal to ring carbon distances that are about 0.3 A shorter than those determined for high-spin manganocenes. The syntheses of new (Me/sub 5/Cp)/sub 2/M (M = Mg,V,Cr,Co, and Ni) and ((Me/sub 5/Cp)/sub 2/M)PF/sub 6/ (M = Cr,Co, and Ni) compounds are described. In addition, a preparative route to a novel, dicationic decamethylmetallocene, ((Me/sub 5/Cp)/sub 2/Ni)(PF/sub 6/)/sub 2/ is reported. Infrared, nuclear magnetic resonance, magnetic susceptibility, and/or x-ray crystallographic studies indicate that all the above compounds are D/sub 5d/ or D/sub 5h/ decamethylmetallocenes with low-spin electronic configurations. Cyclic voltammetry studies verify the reversibility and the one-electron nature of the (Me/sub 5/Cp)/sub 2/M ..-->.. ((Me/sub 5/Cp)/sub 2/M)/sup +/ (M = Cr,Mn,Fe,Co,Ni), ((Me/sub 5/Cp)/sub 2/Mn)/sup -/ ..-->.. (Me/sub 5/Cp)/sub 2/Mn and ((Me/sub 5/Cp)/sub 2/Ni)/sup +/ ..-->.. (Me/sub 5/Cp)/sub 2/Ni)/sup 2 +/ redox reactions. These studies reveal that the neutral decamethylmetallocenes are much more easily oxidized than their metallocene counterparts. This result attests to the electron-donating properties of the ten substituent methyl groups. Proton and carbon-13 NMR data are reported for the diamagnetic Mg(II), Mn(I), Fe(II), Co(III), and Ni(IV) decamethylmetallocenes and for ((Me/sub 5/Cp)/sub 2/V(CO)/sub 2/)/sup +/. The uv-visible absorption spectra of the 15-, 18- and 20- electron decamethylmetallocenes are also reported.

  14. Electronic structure and optical properties of solid C 60

    NASA Astrophysics Data System (ADS)

    Mattesini, M.; Ahuja, R.; Sa, L.; Hugosson, H. W.; Johansson, B.; Eriksson, O.

    2009-06-01

    The electronic structure and the optical properties of face-centered-cubic C 60 have been investigated by using an all-electron full-potential method. Our ab initio results show that the imaginary dielectric function for high-energy values looks very similar to that of graphite, revealing close electronic structure similarities between the two systems. We have also identified the origin of different peaks in the dielectric function of fullerene by means of the calculated electronic density of states. The computed optical spectrum compares fairly well with the available experimental data for the Vis-UV absorption spectrum of solid C 60.

  15. Energy-filtered Electron Transport Structures for Low-power Low-noise 2-D Electronics

    PubMed Central

    Pan, Xuan; Qiu, Wanzhi; Skafidas, Efstratios

    2016-01-01

    In addition to cryogenic techniques, energy filtering has the potential to achieve high-performance low-noise 2-D electronic systems. Assemblies based on graphene quantum dots (GQDs) have been demonstrated to exhibit interesting transport properties, including resonant tunnelling. In this paper, we investigate GQDs based structures with the goal of producing energy filters for next generation lower-power lower-noise 2-D electronic systems. We evaluate the electron transport properties of the proposed GQD device structures to demonstrate electron energy filtering and the ability to control the position and magnitude of the energy passband by appropriate device dimensioning. We also show that the signal-to-thermal noise ratio performance of the proposed nanoscale device can be modified according to device geometry. The tunability of two-dimensional GQD structures indicates a promising route for the design of electron energy filters to produce low-power and low-noise electronics. PMID:27796343

  16. Energy-filtered Electron Transport Structures for Low-power Low-noise 2-D Electronics.

    PubMed

    Pan, Xuan; Qiu, Wanzhi; Skafidas, Efstratios

    2016-10-31

    In addition to cryogenic techniques, energy filtering has the potential to achieve high-performance low-noise 2-D electronic systems. Assemblies based on graphene quantum dots (GQDs) have been demonstrated to exhibit interesting transport properties, including resonant tunnelling. In this paper, we investigate GQDs based structures with the goal of producing energy filters for next generation lower-power lower-noise 2-D electronic systems. We evaluate the electron transport properties of the proposed GQD device structures to demonstrate electron energy filtering and the ability to control the position and magnitude of the energy passband by appropriate device dimensioning. We also show that the signal-to-thermal noise ratio performance of the proposed nanoscale device can be modified according to device geometry. The tunability of two-dimensional GQD structures indicates a promising route for the design of electron energy filters to produce low-power and low-noise electronics.

  17. Energy-filtered Electron Transport Structures for Low-power Low-noise 2-D Electronics

    NASA Astrophysics Data System (ADS)

    Pan, Xuan; Qiu, Wanzhi; Skafidas, Efstratios

    2016-10-01

    In addition to cryogenic techniques, energy filtering has the potential to achieve high-performance low-noise 2-D electronic systems. Assemblies based on graphene quantum dots (GQDs) have been demonstrated to exhibit interesting transport properties, including resonant tunnelling. In this paper, we investigate GQDs based structures with the goal of producing energy filters for next generation lower-power lower-noise 2-D electronic systems. We evaluate the electron transport properties of the proposed GQD device structures to demonstrate electron energy filtering and the ability to control the position and magnitude of the energy passband by appropriate device dimensioning. We also show that the signal-to-thermal noise ratio performance of the proposed nanoscale device can be modified according to device geometry. The tunability of two-dimensional GQD structures indicates a promising route for the design of electron energy filters to produce low-power and low-noise electronics.

  18. Composite Structure Modeling and Analysis of Advanced Aircraft Fuselage Concepts

    NASA Technical Reports Server (NTRS)

    Mukhopadhyay, Vivek; Sorokach, Michael R.

    2015-01-01

    NASA Environmentally Responsible Aviation (ERA) project and the Boeing Company are collabrating to advance the unitized damage arresting composite airframe technology with application to the Hybrid-Wing-Body (HWB) aircraft. The testing of a HWB fuselage section with Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) construction is presently being conducted at NASA Langley. Based on lessons learned from previous HWB structural design studies, improved finite-element models (FEM) of the HWB multi-bay and bulkhead assembly are developed to evaluate the performance of the PRSEUS construction. In order to assess the comparative weight reduction benefits of the PRSEUS technology, conventional cylindrical skin-stringer-frame models of a cylindrical and a double-bubble section fuselage concepts are developed. Stress analysis with design cabin-pressure load and scenario based case studies are conducted for design improvement in each case. Alternate analysis with stitched composite hat-stringers and C-frames are also presented, in addition to the foam-core sandwich frame and pultruded rod-stringer construction. The FEM structural stress, strain and weights are computed and compared for relative weight/strength benefit assessment. The structural analysis and specific weight comparison of these stitched composite advanced aircraft fuselage concepts demonstrated that the pressurized HWB fuselage section assembly can be structurally as efficient as the conventional cylindrical fuselage section with composite stringer-frame and PRSEUS construction, and significantly better than the conventional aluminum construction and the double-bubble section concept.

  19. Electron Precipitation Associated with Small-Scale Auroral Structures

    NASA Astrophysics Data System (ADS)

    Michell, R.; Samara, M.; Grubbs, G. A., II; Hampton, D. L.; Bonnell, J. W.; Ogasawara, K.

    2014-12-01

    We present results from the Ground-to-Rocket Electrons Electrodynamics Correlative Experiment (GREECE) sounding rocket mission, where we combined high-resolution ground-based auroral imaging with high time-resolution precipitating electron measurements. The GREECE payload successfully launched from Poker Flat, Alaska on 03 March 2014 and reached an apogee of approximately 335 km. The narrow field-of-view auroral imaging was taken from Venetie, AK, which is directly under apogee. This enabled the small-scale auroral features at the magnetic footpoint of the rocket payload to be imaged in detail. The electron precipitation was measured with the Acute Precipitating Electron Spectrometer (APES) onboard the payload. Features in the electron data are matched up with their corresponding auroral structures and boundaries, enabling measurement of the exact electron distributions responsible for the specific small-scale auroral features. These electron distributions will then be used to infer what the potential electron acceleration processes were.

  20. Structural phase transition and electronic properties of NdBi

    SciTech Connect

    Sahu, Ashvini K.; Patiya, Jagdish; Sanyal, Sankar P.

    2015-06-24

    The structural and electronic properties of NdBi from an electronic structure calculation have been presented. The calculation is performed using self-consistent tight binding linear muffin tin orbital (TB-LMTO) method within the local density approximation (LDA). The calculated equilibrium structural parameters are in good agreement with the available experimental results. It is found that this compound shows metallic behavior under ambient condition and undergoes a structural phase transition from the NaCl structure to the CsCl structure at the pressure 20.1 GPa. The electronic structures of NdBi under pressure are investigated. It is found that NdBi have metallization and the hybridizations of atoms in NdBi under pressure become stronger.

  1. Advanced Undergraduate-Laboratory Experiment on Electron Spin Resonance in Single-Crystal Ruby

    ERIC Educational Resources Information Center

    Collins, Lee A.; And Others

    1974-01-01

    An electron-spin-resonance experiment which has been successfully performed in an advanced undergraduate physics laboratory is described. A discussion of that part of the theory of magnetic resonance necessary for the understanding of the experiment is also provided in this article. (DT)

  2. Code qualification of structural materials for AFCI advanced recycling reactors.

    SciTech Connect

    Natesan, K.; Li, M.; Majumdar, S.; Nanstad, R.K.; Sham, T.-L.

    2012-05-31

    This report summarizes the further findings from the assessments of current status and future needs in code qualification and licensing of reference structural materials and new advanced alloys for advanced recycling reactors (ARRs) in support of Advanced Fuel Cycle Initiative (AFCI). The work is a combined effort between Argonne National Laboratory (ANL) and Oak Ridge National Laboratory (ORNL) with ANL as the technical lead, as part of Advanced Structural Materials Program for AFCI Reactor Campaign. The report is the second deliverable in FY08 (M505011401) under the work package 'Advanced Materials Code Qualification'. The overall objective of the Advanced Materials Code Qualification project is to evaluate key requirements for the ASME Code qualification and the Nuclear Regulatory Commission (NRC) approval of structural materials in support of the design and licensing of the ARR. Advanced materials are a critical element in the development of sodium reactor technologies. Enhanced materials performance not only improves safety margins and provides design flexibility, but also is essential for the economics of future advanced sodium reactors. Code qualification and licensing of advanced materials are prominent needs for developing and implementing advanced sodium reactor technologies. Nuclear structural component design in the U.S. must comply with the ASME Boiler and Pressure Vessel Code Section III (Rules for Construction of Nuclear Facility Components) and the NRC grants the operational license. As the ARR will operate at higher temperatures than the current light water reactors (LWRs), the design of elevated-temperature components must comply with ASME Subsection NH (Class 1 Components in Elevated Temperature Service). However, the NRC has not approved the use of Subsection NH for reactor components, and this puts additional burdens on materials qualification of the ARR. In the past licensing review for the Clinch River Breeder Reactor Project (CRBRP) and the

  3. Writing silica structures in liquid with scanning transmission electron microscopy.

    PubMed

    van de Put, Marcel W P; Carcouët, Camille C M C; Bomans, Paul H H; Friedrich, Heiner; de Jonge, Niels; Sommerdijk, Nico A J M

    2015-02-04

    Silica nanoparticles are imaged in solution with scanning transmission electron microscopy (STEM) using a liquid cell with silicon nitride (SiN) membrane windows. The STEM images reveal that silica structures are deposited in well-defined patches on the upper SiN membranes upon electron beam irradiation. The thickness of the deposits is linear with the applied electron dose. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrate that the deposited patches are a result of the merging of the original 20 nm-diameter nanoparticles, and that the related surface roughness depends on the electron dose rate used. Using this approach, sub-micrometer scale structures are written on the SiN in liquid by controlling the electron exposure as function of the lateral position.

  4. Electronic Structure of PbSe Nanowires

    NASA Astrophysics Data System (ADS)

    Avdeev, I. D.; Nestoklon, M. O.

    2016-11-01

    We present the tight binding calculations of the lead selenide nanowires: energy spectra of quantum confined states as a function of nanowire radius, dispersion in the full Brillouin zone, and the radial part of local electronic state density, which helps us to recognise valley splitting in the spectra. Also, we compare our results to KP perturbation theory predictions. We show that the value of the valley splitting is comparable with the distance between two levels of size quantization and that it strongly depends on the arrangement of the atoms in the wire.

  5. Electronic-structure calculation for metals by local optimization

    NASA Astrophysics Data System (ADS)

    Woodward, C.; Min, B. I.; Benedek, R.; Garner, J.

    1989-03-01

    Recent work by Car and Parrinello has generated considerable interest in the calculation of electronic structure by nonlinear optimization. The technique introduced by these authors, dynamical simulated annealing, is designed for problems that involve energy barriers. When local optimization suffices to determine the energy minimum, more direct methods are available. In this paper we apply the algorithm suggested by Williams and Soler to calculate the electronic structure of metals, using a plane-wave expansion for the electronic orbitals and an electron-ion pseudopotential of the Kleinman-Bylander form. Radial pseudopotentials were taken from the compilation of Bachelet, Hamann, and Schlüter. Calculations are performed to optimize the electronic structure (i) with fixed atomic configuration, or (ii) with the atomic volume being optimized simultaneously. It is found that the dual optimization (ii) converges in essentially the same number of steps as the static lattice optimization (i). Numerical results are presented for Li, K, Al, and simple-cubic P.

  6. Microstructure, chemistry, and electronic structure of natural hybrid composites in abalone shell.

    PubMed

    Srot, Vesna; Wegst, Ulrike G K; Salzberger, Ute; Koch, Christoph T; Hahn, Kersten; Kopold, Peter; van Aken, Peter A

    2013-05-01

    The crystal structure and chemical composition at the inorganic/inorganic and inorganic/organic interfaces in abalone shell (genus Haliotis) were investigated using advanced analytical transmission electron microscopy (TEM) methods. Electron energy-loss near-edge structures (ELNES) of Ca-M2,3, C-K, Ca-L2,3, O-K and low-loss EEL spectra acquired from aragonite and calcite are distinctly different. When comparing biogenic with inorganic material for aragonite, only minor differences in C-K fine structures could be detected. The crystal structure of the mineral bridges was confirmed by ELNES experiments. ELNES and energy-filtered TEM (EFTEM) experiments of regular and self-healed interfaces between nacreous aragonite and prismatic calcite reveal relatively rough transitions. In this work, the importance of TEM specimen preparation and specimen damage on structural features is discussed.

  7. Electronic Structure, Statistical Mechanical Simulations, and EXAFS Spectroscopy of Aqueous Potassium

    SciTech Connect

    Glezakou, Vanda A.; Chen, Yongsheng; Fulton, John L.; Schenter, Gregory K.; Dang, Liem X.

    2006-03-01

    We investigate the solvation structure of aqueous potassium ions, using a combination of electronic structure calculations, statistical mechanical simulations with a derived polarizable empirical potential and experimental measurement of the Extended X-ray Absorption Fine Structure (EXAFS) spectra. The potassium K-edge (at 3608 eV) EXAFS spectra were acquired on the bending magnet of sector 20 at the Advanced Photon source, at ambient conditions and for the concentrations of 1m and 4m KCl. We focus on the coordination distances and the degree of disorder of the first hydration shell as determined by electronic structure calculations, molecular dynamics simulations and experimental measurement. Finally, we characterize the changes of the structure in the first hydration shell with increasing temperature as predicted by molecular simulation.

  8. Basis functions for electronic structure calculations on spheres

    SciTech Connect

    Gill, Peter M. W. Loos, Pierre-François Agboola, Davids

    2014-12-28

    We introduce a new basis function (the spherical Gaussian) for electronic structure calculations on spheres of any dimension D. We find general expressions for the one- and two-electron integrals and propose an efficient computational algorithm incorporating the Cauchy-Schwarz bound. Using numerical calculations for the D = 2 case, we show that spherical Gaussians are more efficient than spherical harmonics when the electrons are strongly localized.

  9. Advancement in thermal interface materials for future high-performance electronic applications. Part 1.

    SciTech Connect

    Jakaboski, Blake Elaine; Wong, Chung-Nin Channy; Huber, Dale L.; Rightley, Michael J.; Emerson, John Allen

    2006-02-01

    As electronic assemblies become more compact and increase in processing bandwidth, escalating thermal energy has become more difficult to manage. The major limitation has been nonmetallic joining using poor thermal interface materials (TIM). The interfacial, versus bulk, thermal conductivity of an adhesive is the major loss mechanism and normally accounts for an order magnitude loss in conductivity per equivalent thickness. The next generation TIM requires a sophisticated understanding of material and surface sciences, heat transport at submicron scales, and the manufacturing processes used in packaging of microelectronics and other target applications. Only when this relationship between bond line manufacturing processes, structure, and contact resistance is well-understood on a fundamental level will it be possible to advance the development of miniaturized microsystems. This report examines using thermal and squeeze-flow modeling as approaches to formulate TIMs incorporating nanoscience concepts. Understanding the thermal behavior of bond lines allows focus on the interfacial contact region. In addition, careful study of the thermal transport across these interfaces provides greatly augmented heat transfer paths and allows the formulation of very high resistance interfaces for total thermal isolation of circuits. For example, this will allow the integration of systems that exhibit multiple operational temperatures, such as cryogenically cooled detectors.

  10. Secondary electron emission from surfaces with small structure

    NASA Astrophysics Data System (ADS)

    Dzhanoev, A. R.; Spahn, F.; Yaroshenko, V.; Lühr, H.; Schmidt, J.

    2015-09-01

    It is found that for objects possessing small surface structures with differing radii of curvature the secondary electron emission (SEE) yield may be significantly higher than for objects with smooth surfaces of the same material. The effect is highly pronounced for surface structures of nanometer scale, often providing a more than 100 % increase of the SEE yield. The results also show that the SEE yield from surfaces with structure does not show a universal dependence on the energy of the primary, incident electrons as it is found for flat surfaces in experiments. We derive conditions for the applicability of the conventional formulation of SEE using the simplifying assumption of universal dependence. Our analysis provides a basis for studying low-energy electron emission from nanometer structured surfaces under a penetrating electron beam important in many technological applications.

  11. Linear Scaling Electronic Structure Methods with Periodic Boundary Conditions

    SciTech Connect

    Gustavo E. Scuseria

    2008-02-08

    The methodological development and computational implementation of linear scaling quantum chemistry methods for the accurate calculation of electronic structure and properties of periodic systems (solids, surfaces, and polymers) and their application to chemical problems of DOE relevance.

  12. Stacking dependent electronic structures of transition metal dichalcogenides heterobilayer

    NASA Astrophysics Data System (ADS)

    Lee, Yea-Lee; Park, Cheol-Hwan; Ihm, Jisoon

    The systematic study of the electronic structures and optical properties of the transition metal dichalcogenides (TMD) heterobilayers can significantly improve the designing of new electronic and optoelectronic devices. Here, we theoretically study the electronic structures and optical properties of TMD heterobilayers using the first-principles methods. The band structures of TMD heterobilayer are shown to be determined by the band alignments of the each layer, the weak interlayer interactions, and angle dependent stacking patterns. The photoluminescence spectra are investigated using the calculated band structures, and the optical absorption spectra are examined by the GW approximations including the electron-hole interaction through the solution of the Bethe-Salpeter equation. It is expected that the weak interlayer interaction gives rise to the substantial interlayer optical transition which will be corresponding to the interlayer exciton.

  13. Fundamental studies of structure borne noise for advanced turboprop applications

    NASA Technical Reports Server (NTRS)

    Eversman, W.; Koval, L. R.

    1985-01-01

    The transmission of sound generated by wing-mounted, advanced turboprop engines into the cabin interior via structural paths is considered. The structural model employed is a beam representation of the wing box carried into the fuselage via a representative frame type of carry through structure. The structure for the cabin cavity is a stiffened shell of rectangular or cylindrical geometry. The structure is modelled using a finite element formulation and the acoustic cavity is modelled using an analytical representation appropriate for the geometry. The structural and acoustic models are coupled by the use of hard wall cavity modes for the interior and vacuum structural modes for the shell. The coupling is accomplished using a combination of analytical and finite element models. The advantage is the substantial reduction in dimensionality achieved by modelling the interior analytically. The mathematical model for the interior noise problem is demonstrated with a simple plate/cavity system which has all of the features of the fuselage interior noise problem.

  14. Electron Diffraction Determination of Nanoscale Structures

    SciTech Connect

    Parks, Joel H

    2013-03-01

    Dominant research results on adsorption on gold clusters are reviewed, including adsorption of H{sub 2}O and O{sub 2} on gold cluster cations and anions, kinetics of CO adsorption to middle sized gold cluster cations, adsorption of CO on Au{sub n}{sup +} with induced changes in structure, and H{sub 2}O enhancement of CO adsorption.

  15. Structural analysis of advanced polymeric foams by means of high resolution X-ray computed tomography

    NASA Astrophysics Data System (ADS)

    Nacucchi, M.; De Pascalis, F.; Scatto, M.; Capodieci, L.; Albertoni, R.

    2016-06-01

    Advanced polymeric foams with enhanced thermal insulation and mechanical properties are used in a wide range of industrial applications. The properties of a foam strongly depend upon its cell structure. Traditionally, their microstructure has been studied using 2D imaging systems based on optical or electron microscopy, with the obvious disadvantage that only the surface of the sample can be analysed. To overcome this shortcoming, the adoption of X-ray micro-tomography imaging is here suggested to allow for a complete 3D, non-destructive analysis of advanced polymeric foams. Unlike metallic foams, the resolution of the reconstructed structural features is hampered by the low contrast in the images due to weak X-ray absorption in the polymer. In this work an advanced methodology based on high-resolution and low-contrast techniques is used to perform quantitative analyses on both closed and open cells foams. Local structural features of individual cells such as equivalent diameter, sphericity, anisotropy and orientation are statistically evaluated. In addition, thickness and length of the struts are determined, underlining the key role played by the achieved resolution. In perspective, the quantitative description of these structural features will be used to evaluate the results of in situ mechanical and thermal test on foam samples.

  16. Prospects for advanced electron cyclotron resonance and electron beam ion source charge breeding methods for EURISOL

    SciTech Connect

    Delahaye, P.; Jardin, P.; Maunoury, L.; Traykov, E.; Varenne, F.; Angot, J.; Lamy, T.; Sortais, P.; Thuillier, T.; Ban, G.; Celona, L.; Lunney, D.; Choinski, J.; Gmaj, P.; Jakubowski, A.; Steckiewicz, O.; Kalvas, T.; and others

    2012-02-15

    As the most ambitious concept of isotope separation on line (ISOL) facility, EURISOL aims at producing unprecedented intensities of post-accelerated radioactive isotopes. Charge breeding, which transforms the charge state of radioactive beams from 1+ to an n+ charge state prior to post-acceleration, is a key technology which has to overcome the following challenges: high charge states for high energies, efficiency, rapidity and purity. On the roadmap to EURISOL, a dedicated R and D is being undertaken to push forward the frontiers of the present state-of-the-art techniques which use either electron cyclotron resonance or electron beam ion sources. We describe here the guidelines of this R and D.

  17. Advanced composite structural concepts and material technologies for primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Jackson, Anthony

    1991-01-01

    Structural weight savings using advanced composites have been demonstrated for many years. Most military aircraft today use these materials extensively and Europe has taken the lead in their use in commercial aircraft primary structures. A major inhibiter to the use of advanced composites in the United States is cost. Material costs are high and will remain high relative to aluminum. The key therefore lies in the significant reduction in fabrication and assembly costs. The largest cost in most structures today is assembly. As part of the NASA Advanced Composite Technology Program, Lockheed Aeronautical Systems Company has a contract to explore and develop advanced structural and manufacturing concepts using advanced composites for transport aircraft. Wing and fuselage concepts and related trade studies are discussed. These concepts are intended to lower cost and weight through the use of innovative material forms, processes, structural configurations and minimization of parts. The approach to the trade studies and the downselect to the primary wing and fuselage concepts is detailed. The expectations for the development of these concepts is reviewed.

  18. Direct investigation of subsurface interface electronic structure by ballistic-electron-emission microscopy

    NASA Technical Reports Server (NTRS)

    Kaiser, W. J.; Bell, L. D.

    1988-01-01

    A new technique for spectroscopic investigation of subsurface interface electronic structure has been developed. The method, ballistic-electron-emission microscopy (BEEM), is based on scanning tunneling microscopy. BEEM makes possible, for the first time, direct imaging of subsurface interface properties with nanometer spatial resolution. The first application of BEEM to subsurface Schottky-barrier interfaces is reported.

  19. Advanced composites in sailplane structures: Application and mechanical properties

    NASA Technical Reports Server (NTRS)

    Muser, D.

    1979-01-01

    Advanced Composites in sailplanes mean the use of carbon and aramid fibers in an epoxy matrix. Weight savings were in the range of 8 to 18% in comparison with glass fiber structures. The laminates will be produced by hand-layup techniques and all material tests were done with these materials. These values may be used for calculation of strength and stiffness, as well as for comparison of the materials to get a weight-optimum construction. Proposals for material-optimum construction are mentioned.

  20. Advanced stress analysis methods applicable to turbine engine structures

    NASA Technical Reports Server (NTRS)

    Pian, Theodore H. H.

    1991-01-01

    The following tasks on the study of advanced stress analysis methods applicable to turbine engine structures are described: (1) constructions of special elements which contain traction-free circular boundaries; (2) formulation of new version of mixed variational principles and new version of hybrid stress elements; (3) establishment of methods for suppression of kinematic deformation modes; (4) construction of semiLoof plate and shell elements by assumed stress hybrid method; and (5) elastic-plastic analysis by viscoplasticity theory using the mechanical subelement model.

  1. Electronic structure calculations of ESR parameters of melanin units.

    PubMed

    Batagin-Neto, Augusto; Bronze-Uhle, Erika Soares; Graeff, Carlos Frederico de Oliveira

    2015-03-21

    Melanins represent an important class of natural pigments present in plants and animals that are currently considered to be promising materials for applications in optic and electronic devices. Despite their interesting properties, some of the basic features of melanins are not satisfactorily understood, including the origin of their intrinsic paramagnetism. A number of experiments have been performed to investigate the electron spin resonance (ESR) response of melanin derivatives, but until now, there has been no consensus regarding the real structure of the paramagnetic centers involved. In this work, we have employed electronic structure calculations to evaluate the ESR parameters of distinct melanin monomers and dimers in order to identify the possible structures associated with unpaired spins in this biopolymer. The g-factors and hyperfine constants of the cationic, anionic and radicalar structures were investigated. The results confirm the existence of at least two distinct paramagnetic centers in melanin structure, identifying the chemical species associated with them and their roles in electrical conductivity.

  2. Structural properties of amorphous silicon produced by electron irradiation

    SciTech Connect

    Yamasaki, J.; Takeda, S.

    1999-07-01

    The structural properties of the amorphous Si (a-Si), which was created from crystalline silicon by 2 MeV electron irradiation at low temperatures about 25 K, are examined in detail by means of transmission electron microscopy and transmission electron diffraction. The peak positions in the radial distribution function (RDF) of the a-Si correspond well to those of a-Si fabricated by other techniques. The electron-irradiation-induced a-Si returns to crystalline Si after annealing at 550 C.

  3. Distinct electronic structure for the extreme magnetoresistance in YSb

    SciTech Connect

    He, Junfeng; Zhang, Chaofan; Ghimire, Nirmal J.; Liang, Tian; Jia, Chunjing; Jiang, Juan; Tang, Shujie; Chen, Sudi; He, Yu; Mo, S. -K.; Hwang, C. C.; Hashimoto, M.; Lu, D. H.; Moritz, B.; Devereaux, T. P.; Chen, Y. L.; Mitchell, J. F.; Shen, Z. -X.

    2016-12-23

    An extreme magnetoresistance (XMR) has recently been observed in several nonmagnetic semimetals. Increasing experimental and theoretical evidence indicates that the XMR can be driven by either topological protection or electron-hole compensation. Moreover, by investigating the electronic structure of a XMR material, YSb, we present spectroscopic evidence for a special case which lacks topological protection and perfect electron-hole compensation. Further investigations reveal that a cooperative action of a substantial difference between electron and hole mobility and a moderate carrier compensation might contribute to the XMR in YSb.

  4. Electronic structure modulation of graphene edges by chemical functionalization

    NASA Astrophysics Data System (ADS)

    Taira, Remi; Yamanaka, Ayaka; Okada, Susumu

    2016-11-01

    Using the density functional theory with the effective screening medium method, we study the electronic properties of graphene nanoribbons with zigzag edges that are terminated by hydrogen and ketone, hydroxyl, carbonyl, and carboxyl functional groups. Our calculations showed that the work function and electronic structures of the edges of the nanoribbons are sensitive to the functional groups attached to the edges. The nearly free electron state emerges in the vacuum region outside the hydroxylated edges and crosses the Fermi level, indicating the possibility of negative electron affinity at the edges.

  5. Electron beam enhanced surface modification for making highly resolved structures

    DOEpatents

    Pitts, John R.

    1986-01-01

    A method for forming high resolution submicron structures on a substrate is provided by direct writing with a submicron electron beam in a partial pressure of a selected gas phase characterized by the ability to dissociate under the beam into a stable gaseous leaving group and a reactant fragment that combines with the substrate material under beam energy to form at least a surface compound. Variations of the method provide semiconductor device regions on doped silicon substrates, interconnect lines between active sites, three dimensional electronic chip structures, electron beam and optical read mass storage devices that may include color differentiated data areas, and resist areas for use with selective etching techniques.

  6. Electron beam enhanced surface modification for making highly resolved structures

    DOEpatents

    Pitts, J.R.

    1984-10-10

    A method for forming high resolution submicron structures on a substrate is provided by direct writing with a submicron electron beam in a partial pressure of a selected gas phase characterized by the ability to dissociate under the beam into a stable gaseous leaving group and a reactant fragment that combines with the substrate material under beam energy to form at least a surface compound. Variations of the method provide semiconductor device regions on doped silicon substrates, interconnect lines between active sites, three dimensional electronic chip structures, electron beam and optical read mass storage devices that may include color differentiated data areas, and resist areas for use with selective etching techniques.

  7. Solitary structures with ion and electron thermal anisotropy

    NASA Astrophysics Data System (ADS)

    Khusroo, Murchana; Bora, Madhurjya P.

    2015-11-01

    The formation of electrostatic solitary structures is analysed for a magnetised plasma with ion and electron thermal anisotropies. The ion thermal anisotropy is modelled with the help of the Chew-Goldberger-Low (CGL) double adiabatic equations of state while the electrons are treated as inertia-less species with an anisotropic bi-Maxwellian velocity distribution function. A negative electron thermal anisotropy ≤ft({{T}e\\bot}/{{T}e\\parallel}>1\\right) is found to help form large amplitude solitary structures which are in agreement with observational data.

  8. Advancing multiscale structural mapping of the brain through fluorescence imaging and analysis across length scales

    PubMed Central

    Hogstrom, L. J.; Guo, S. M.; Murugadoss, K.; Bathe, M.

    2016-01-01

    Brain function emerges from hierarchical neuronal structure that spans orders of magnitude in length scale, from the nanometre-scale organization of synaptic proteins to the macroscopic wiring of neuronal circuits. Because the synaptic electrochemical signal transmission that drives brain function ultimately relies on the organization of neuronal circuits, understanding brain function requires an understanding of the principles that determine hierarchical neuronal structure in living or intact organisms. Recent advances in fluorescence imaging now enable quantitative characterization of neuronal structure across length scales, ranging from single-molecule localization using super-resolution imaging to whole-brain imaging using light-sheet microscopy on cleared samples. These tools, together with correlative electron microscopy and magnetic resonance imaging at the nanoscopic and macroscopic scales, respectively, now facilitate our ability to probe brain structure across its full range of length scales with cellular and molecular specificity. As these imaging datasets become increasingly accessible to researchers, novel statistical and computational frameworks will play an increasing role in efforts to relate hierarchical brain structure to its function. In this perspective, we discuss several prominent experimental advances that are ushering in a new era of quantitative fluorescence-based imaging in neuroscience along with novel computational and statistical strategies that are helping to distil our understanding of complex brain structure. PMID:26855758

  9. Electron-interface phonon interaction in multiple quantum well structures

    NASA Astrophysics Data System (ADS)

    Sun, J. P.; Teng, H. B.; Haddad, G. I.; Stroscio, M. A.

    1998-08-01

    Intersubband relaxation rates due to electron interactions with the interface phonons are evaluated for multiple quantum well structures designed for step quantum well lasers operating at mid-infrared to submillimetre wavelengths. The interface phonon modes and electron-phonon interaction Hamiltonians for the structures are derived using the transfer matrix method, based on the macroscopic dielectric continuum model, whereas the electron wavefunctions are obtained by solving the Schrödinger equation. Fermi's golden rule is employed to calculate the electron relaxation rates between the subbands in these structures. The relaxation rates for two different structures are examined and compared with those calculated using the bulk phonon modes and the Fröhlich interaction Hamiltonian. The sum rule for the relationship between the form factors of the various localized phonon modes and the bulk phonon modes is verified. The results obtained in this work illustrate that the transfer matrix method provides a convenient way for deriving the properties of the interface phonon modes in different structures of current interest and that, for preferential electron relaxation in intersubband laser structures, the effects of the interface phonon modes are significant and should be considered for optimal design of these laser structures.

  10. Nano-structured electron transporting materials for perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Hefei; Huang, Ziru; Wei, Shiyuan; Zheng, Lingling; Xiao, Lixin; Gong, Qihuang

    2016-03-01

    Organic-inorganic hybrid perovskite solar cells have been developing rapidly in the past several years, and their power conversion efficiency has reached over 20%, nearing that of polycrystalline silicon solar cells. Because the diffusion length of the hole in perovskites is longer than that of the electron, the performance of the device can be improved by using an electron transporting layer, e.g., TiO2, ZnO and TiO2/Al2O3. Nano-structured electron transporting materials facilitate not only electron collection but also morphology control of the perovskites. The properties, morphology and preparation methods of perovskites are reviewed in the present article. A comprehensive understanding of the relationship between the structure and property will benefit the precise control of the electron transporting process and thus further improve the performance of perovskite solar cells.

  11. Nano-structured electron transporting materials for perovskite solar cells.

    PubMed

    Liu, Hefei; Huang, Ziru; Wei, Shiyuan; Zheng, Lingling; Xiao, Lixin; Gong, Qihuang

    2016-03-28

    Organic-inorganic hybrid perovskite solar cells have been developing rapidly in the past several years, and their power conversion efficiency has reached over 20%, nearing that of polycrystalline silicon solar cells. Because the diffusion length of the hole in perovskites is longer than that of the electron, the performance of the device can be improved by using an electron transporting layer, e.g., TiO2, ZnO and TiO2/Al2O3. Nano-structured electron transporting materials facilitate not only electron collection but also morphology control of the perovskites. The properties, morphology and preparation methods of perovskites are reviewed in the present article. A comprehensive understanding of the relationship between the structure and property will benefit the precise control of the electron transporting process and thus further improve the performance of perovskite solar cells.

  12. Structural complexities in the active layers of organic electronics.

    PubMed

    Lee, Stephanie S; Loo, Yueh-Lin

    2010-01-01

    The field of organic electronics has progressed rapidly in recent years. However, understanding the direct structure-function relationships between the morphology in electrically active layers and the performance of devices composed of these materials has proven difficult. The morphology of active layers in organic electronics is inherently complex, with heterogeneities existing across multiple length scales, from subnanometer to micron and millimeter range. A major challenge still facing the organic electronics community is understanding how the morphology across all of the length scales in active layers collectively determines the device performance of organic electronics. In this review we highlight experiments that have contributed to the elucidation of structure-function relationships in organic electronics and also point to areas in which knowledge of such relationships is still lacking. Such knowledge will lead to the ability to select active materials on the basis of their inherent properties for the fabrication of devices with prespecified characteristics.

  13. Electronic band structure of surface-doped black phosphorus

    NASA Astrophysics Data System (ADS)

    Kim, Jimin; Ryu, Sae Hee; Sohn, Yeongsup; Kim, Keun Su

    2015-03-01

    There are rapidly growing interests in the study of few-layer black phosphorus owing to its promising device characteristics that may impact our future electronics technology. The low-energy band structure of black phosphorus has been widely predicted to be controllable by external perturbations, such as strain and doping. In this work, we attempt to control the electronic band structure of black phosphorous by in-situ surface deposition of alkali-metal atoms. We found that surface doping induces steep band bending towards the bulk, leading to the emergence of new 2D electronic states that are confined within only few phosphorene layers of black phosphorus. Using angle-resolved photoemission spectroscopy, we directly measured the electronic band structure and its evolution as a function of dopant density. Supported by IBS.

  14. Electronic structure of a graphene superlattice with massive Dirac fermions

    SciTech Connect

    Lima, Jonas R. F.

    2015-02-28

    We study the electronic and transport properties of a graphene-based superlattice theoretically by using an effective Dirac equation. The superlattice consists of a periodic potential applied on a single-layer graphene deposited on a substrate that opens an energy gap of 2Δ in its electronic structure. We find that extra Dirac points appear in the electronic band structure under certain conditions, so it is possible to close the gap between the conduction and valence minibands. We show that the energy gap E{sub g} can be tuned in the range 0 ≤ E{sub g} ≤ 2Δ by changing the periodic potential. We analyze the low energy electronic structure around the contact points and find that the effective Fermi velocity in very anisotropic and depends on the energy gap. We show that the extra Dirac points obtained here behave differently compared to previously studied systems.

  15. Corrosion performance of advanced structural materials in sodium.

    SciTech Connect

    Natesan, K.; Momozaki, Y.; Li, M.; Rink, D.L.

    2012-05-16

    This report gives a description of the activities in design, fabrication, construction, and assembling of a pumped sodium loop for the sodium compatibility studies on advanced structural materials. The work is the Argonne National Laboratory (ANL) portion of the effort on the work project entitled, 'Sodium Compatibility of Advanced Fast Reactor Materials,' and is a part of Advanced Materials Development within the Reactor Campaign. The objective of this project is to develop information on sodium corrosion compatibility of advanced materials being considered for sodium reactor applications. This report gives the status of the sodium pumped loop at Argonne National Laboratory, the specimen details, and the technical approach to evaluate the sodium compatibility of advanced structural alloys. This report is a deliverable from ANL in FY2010 (M2GAN10SF050302) under the work package G-AN10SF0503 'Sodium Compatibility of Advanced Fast Reactor Materials.' Two reports were issued in 2009 (Natesan and Meimei Li 2009, Natesan et al. 2009) which examined the thermodynamic and kinetic factors involved in the purity of liquid sodium coolant for sodium reactor applications as well as the design specifications for the ANL pumped loop for testing advanced structural materials. Available information was presented on solubility of several metallic and nonmetallic elements along with a discussion of the possible mechanisms for the accumulation of impurities in sodium. That report concluded that the solubility of many metals in sodium is low (<1 part per million) in the temperature range of interest in sodium reactors and such trace amounts would not impact the mechanical integrity of structural materials and components. The earlier report also analyzed the solubility and transport mechanisms of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen in laboratory sodium loops and in reactor systems such as Experimental Breeder Reactor-II, Fast Flux Test Facility, and

  16. Topological Insulators: Electronic Band Structure and Spectroscopy

    NASA Astrophysics Data System (ADS)

    Palaz, S.; Koc, H.; Mamedov, A. M.; Ozbay, E.

    2017-02-01

    In this study, we present the results of our ab initio calculation of the elastic constants, density of states, charge density, and Born effective charge tensors for ferroelectric (rhombohedral) and paraelectric phases (cubic) of the narrow band ferroelectrics (GeTe, SnTe) pseudopotentials. The related quantities such as bulk modulus and shear modulus using obtained elastic constants have also been estimated in the present work. The total and partial densities of states corresponding to the band structure of Sn(Ge)Te(S,Se) were calculated. We also calculated the Born effective charge tensor of an atom (for instance, Ge, Sn, Te, etc.), which is defined as the induced polarization of the solid along the main direction by a unit displacement in the perpendicular direction of the sublattice of an atom at the vanishing electric field.

  17. Electronic Structure and Transport in Magnetic Multilayers

    SciTech Connect

    2008-02-18

    ORNL assisted Seagate Recording Heads Operations in the development of CIPS pin Valves for application as read sensors in hard disk drives. Personnel at ORNL were W. H. Butler and Xiaoguang Zhang. Dr. Olle Heinonen from Seagate RHO also participated. ORNL provided codes and materials parameters that were used by Seagate to model CIP GMR in their heads. The objectives were to: (1) develop a linearized Boltzmann transport code for describing CIP GMR based on realistic models of the band structure and interfaces in materials in CIP spin valves in disk drive heads; (2) calculate the materials parameters needed as inputs to the Boltzmann code; and (3) transfer the technology to Seagate Recording Heads.

  18. Observation of runaway electron beams by visible color camera in the Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Shi, Yuejiang; Fu, Jia; Li, Jiahong; Yang, Yu; Wang, Fudi; Li, Yingying; Zhang, Wei; Wan, Baonian; Chen, Zhongyong

    2010-03-01

    The synchrotron radiation originated from the energetic runaway electrons has been measured by a visible complementary metal oxide semiconductor camera working in the wavelength ranges of 380-750 nm in the Experimental Advanced Superconducting Tokamak [H. Q. Liu et al., Plasma Phys. Contr. Fusion 49, 995 (2007)]. With a tangential viewing into the plasma in the direction of electron approach on the equatorial plane, the synchrotron radiation from the energetic runaway electrons was measured in full poloidal cross section. The synchrotron radiation diagnostics provides a direct pattern of the runaway beam inside the plasma. The energy and pitch angle of runaway electrons have been obtained according to the synchrotron radiation pattern. A stable shell shape of synchrotron radiation has been observed in a few runaway discharges.

  19. Observation of runaway electron beams by visible color camera in the Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Shi Yuejiang; Fu Jia; Li Jiahong; Yang Yu; Wang Fudi; Li Yingying; Zhang Wei; Wan Baonian; Chen Zhongyong

    2010-03-15

    The synchrotron radiation originated from the energetic runaway electrons has been measured by a visible complementary metal oxide semiconductor camera working in the wavelength ranges of 380-750 nm in the Experimental Advanced Superconducting Tokamak [H. Q. Liu et al., Plasma Phys. Contr. Fusion 49, 995 (2007)]. With a tangential viewing into the plasma in the direction of electron approach on the equatorial plane, the synchrotron radiation from the energetic runaway electrons was measured in full poloidal cross section. The synchrotron radiation diagnostics provides a direct pattern of the runaway beam inside the plasma. The energy and pitch angle of runaway electrons have been obtained according to the synchrotron radiation pattern. A stable shell shape of synchrotron radiation has been observed in a few runaway discharges.

  20. Observation of runaway electron beams by visible color camera in the Experimental Advanced Superconducting Tokamak.

    PubMed

    Shi, Yuejiang; Fu, Jia; Li, Jiahong; Yang, Yu; Wang, Fudi; Li, Yingying; Zhang, Wei; Wan, Baonian; Chen, Zhongyong

    2010-03-01

    The synchrotron radiation originated from the energetic runaway electrons has been measured by a visible complementary metal oxide semiconductor camera working in the wavelength ranges of 380-750 nm in the Experimental Advanced Superconducting Tokamak [H. Q. Liu et al., Plasma Phys. Contr. Fusion 49, 995 (2007)]. With a tangential viewing into the plasma in the direction of electron approach on the equatorial plane, the synchrotron radiation from the energetic runaway electrons was measured in full poloidal cross section. The synchrotron radiation diagnostics provides a direct pattern of the runaway beam inside the plasma. The energy and pitch angle of runaway electrons have been obtained according to the synchrotron radiation pattern. A stable shell shape of synchrotron radiation has been observed in a few runaway discharges.

  1. Status of Advanced Stitched Unitized Composite Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn C.; Velicki, Alex

    2013-01-01

    NASA has created the Environmentally Responsible Aviation (ERA) Project to explore and document the feasibility, benefits and technical risk of advanced vehicle configurations and enabling technologies that will reduce the impact of aviation on the environment. A critical aspect of this pursuit is the development of a lighter, more robust airframe that will enable the introduction of unconventional aircraft configurations that have higher lift-to-drag ratios, reduced drag, and lower community noise levels. The primary structural concept being developed under the ERA project in the Airframe Technology element is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. This paper describes how researchers at NASA and The Boeing Company are working together to develop fundamental PRSEUS technologies that could someday be implemented on a transport size aircraft with high aspect ratio wings or unconventional shapes such as a hybrid wing body airplane design.

  2. Thin-film infrared absorber structures for advanced thermal detectors

    NASA Astrophysics Data System (ADS)

    Parsons, A. D.; Pedder, D. J.

    1988-06-01

    Imaging thermal detector technology is a rapidly advancing field in which the current emphasis is towards the development of very large arrays of very small pyroelectric detector elements. For maximum responsivity, each of the thin pyroelectric elements in an array must be provided with a thermal absorber to convert incoming infrared radiation into heat. This paper describes one such absorber structure, comprising a thin metal film, impedance matched to free space, and a quarter-wave polymer film which offers an acceptably low thermal mass. The structure and properties of this thin-film absorber are compared with those of an electroplated platinum black absorber commonly used in thermal detectors. The theory of the absorber is presented and good agreement is shown between calculated and experimentally derived absorption spectra.

  3. On the Mechanical Behavior of Advanced Composite Material Structures

    NASA Astrophysics Data System (ADS)

    Vinson, Jack

    During the period between 1993 and 2004, the author, as well as some colleagues and graduate students, had the honor to be supported by the Office of Naval Research to conduct research in several aspects of the behavior of structures composed of composite materials. The topics involved in this research program were numerous, but all contributed to increasing the understanding of how various structures that are useful for marine applications behaved. More specifically, the research topics focused on the reaction of structures that were made of fiber reinforced polymer matrix composites when subjected to various loads and environmental conditions. This included the behavior of beam, plate/panel and shell structures. It involved studies that are applicable to fiberglass, graphite/carbon and Kevlar fibers imbedded in epoxy, polyester and other polymeric matrices. Unidirectional, cross-ply, angle ply, and woven composites were involved, both in laminated, monocoque as well as in sandwich constructions. Mid-plane symmetric as well as asymmetric laminates were studied, the latter involving bending-stretching coupling and other couplings that only can be achieved with advanced composite materials. The composite structures studied involved static loads, dynamic loading, shock loading as well as thermal and hygrothermal environments. One major consideration was determining the mechanical properties of composite materials subjected to high strain rates because the mechanical properties vary so significantly as the strain rate increases. A considerable number of references are cited for further reading and study for those interested.

  4. Electronic correlation in magnetic contributions to structural energies

    NASA Astrophysics Data System (ADS)

    Haydock, Roger

    For interacting electrons the density of transitions [see http://arxiv.org/abs/1405.2288] replaces the density of states in calculations of structural energies. Extending previous work on paramagnetic metals, this approach is applied to correlation effects on the structural stability of magnetic transition metals. Supported by the H. V. Snyder Gift to the University of Oregon.

  5. Hot-Electron Gallium Nitride Two Dimensional Electron Gas Nano-bolometers For Advanced THz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Rahul

    Two-dimensional electron gas (2DEG) in semiconductor heterostructures was identified as a promising medium for hot-electron bolometers (HEB) in the early 90s. Up until now all research based on 2DEG HEBs is done using high mobility AlGaAs/GaAs heterostructures. These systems have demonstrated very good performance, but only in the sub terahertz (THz) range. However, above ˜0.5 THz the performance of AlGaAs/GaAs detectors drastically deteriorates. It is currently understood, that detectors fabricated from standard AlGaAs/GaAs heterostructures do not allow for reasonable coupling to THz radiation while maintaining high conversion efficiency. In this work we have developed 2DEG HEBs based on disordered Gallium Nitride (GaN) semiconductor, that operate at frequencies beyond 1THz at room temperature. We observe strong free carrier absorption at THz frequencies in our disordered 2DEG film due to Drude absorption. We show the design and fabrication procedures of novel micro-bolometers having ultra-low heat capacities. In this work the mechanism of 2DEG response to THz radiation is clearly identified as bolometric effect through our direct detection measurements. With optimal doping and detector geometry, impedances of 10--100 O have been achieved, which allow integration of these devices with standard THz antennas. We also demonstrate performance of the antennas used in this work in effectively coupling THz radiation to the micro-bolometers through polarization dependence and far field measurements. Finally heterodyne mixing due to hot electrons in the 2DEG micro-bolometer has been performed at sub terahertz frequencies and a mixing bandwidth greater than 3GHz has been achieved. This indicates that the characteristic cooling time in our detectors is fast, less than 50ps. Due to the ultra-low heat capacity; these detectors can be used in a heterodyne system with a quantum cascade laser (QCL) as a local oscillator (LO) which typically provides output powers in the micro

  6. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    SciTech Connect

    Haynes, Christopher T. Burgess, David; Sundberg, Torbjorn; Camporeale, Enrico

    2015-01-15

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  7. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    NASA Astrophysics Data System (ADS)

    Haynes, Christopher T.; Burgess, David; Camporeale, Enrico; Sundberg, Torbjorn

    2015-01-01

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  8. Probing the band structure and local electronic properties of low-dimensional semiconductor structures

    NASA Astrophysics Data System (ADS)

    Walrath, Jenna Cherie

    Low-dimensional semiconductor structures are important for a wide variety of applications, and recent advances in nanoscale fabrication are paving the way for increasingly precise nano-engineering of a wide range of materials. It is therefore essential that the physics of materials at the nanoscale are thoroughly understood to unleash the full potential of nanotechnology, requiring the development of increasingly sophisticated instrumentation and modeling. Of particular interest is the relationship between the local density of states (LDOS) of low-dimensional structures and the band structure and local electronic properties. This dissertation presents the investigation of the band structure, LDOS, and local electronic properties of nanostructures ranging from zero-dimensional (0D) quantum dots (QDs) to two-dimensional (2D) thin films, synthesizing computational and experimental approaches including Poisson-Schrodinger band structure calculations, scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and scanning thermoelectric microscopy (SThEM). A method is presented for quantifying the local Seebeck coefficient (S) with SThEM, using a quasi-3D conversion matrix approach to directly convert temperature gradient-induced voltages S. For a GaAs p-n junction, the resulting S-profile is consistent with that computed using the free carrier concentration profile. This combined computational-experimental approach is expected to enable nanoscale measurements of S across a wide variety of heterostructure interfaces. The local carrier concentration, n, is profiled across epitaxial InAs/GaAs QDs, where SThEM is used to profile the temperature gradient-induced voltage, which is converted to a profile of the local S and finally to an n profile. The S profile is converted to a conduction band-edge profile and compared with Poisson-Schrodinger band-edge simulations. The combined computational-experimental approach suggests a reduced n in the QD center in

  9. Decoupling of structural and electronic phase transitions in VO2.

    PubMed

    Tao, Zhensheng; Han, Tzong-Ru T; Mahanti, Subhendra D; Duxbury, Phillip M; Yuan, Fei; Ruan, Chong-Yu; Wang, Kevin; Wu, Junqiao

    2012-10-19

    Using optical, TEM, and ultrafast electron diffraction experiments we find that single crystal VO(2) microbeams gently placed on insulating substrates or metal grids exhibit different behaviors, with structural and metal-insulator transitions occurring at the same temperature for insulating substrates, while for metal substrates a new monoclinic metal phase lies between the insulating monoclinic phase and the metallic rutile phase. The structural and electronic phase transitions in these experiments are strongly first order and we discuss their origins in the context of current understanding of multiorbital splitting, strong correlation effects, and structural distortions that act cooperatively in this system.

  10. Electronic states in hybrid boron nitride and graphene structures

    NASA Astrophysics Data System (ADS)

    Zhao, M.; Huang, Y. H.; Ma, F.; Hu, T. W.; Xu, K. W.; Chu, Paul K.

    2013-08-01

    The energy bands and electronic states of hybrid boron nitride (BN) and graphene structures are studied by first principle calculations. The electronic states change from semi-metallic to insulating depending on the number of B and N atoms as well as domain symmetry. When there are unequal numbers of B and N atoms, mid-gap states usually appear around the Fermi level and the corresponding hybrid structure possesses magnetic and semi-metallic properties. However, when the numbers of B and N atoms are equal, a band gap exists indicative of a semiconducting or insulating nature which depends on the structural symmetry.

  11. Engineering the Electronic Band Structure for Multiband Solar Cells

    SciTech Connect

    Lopez, N.; Reichertz, L.A.; Yu, K.M.; Campman, K.; Walukiewicz, W.

    2010-07-12

    Using the unique features of the electronic band structure of GaNxAs1-x alloys, we have designed, fabricated and tested a multiband photovoltaic device. The device demonstrates an optical activity of three energy bands that absorb, and convert into electrical current, the crucial part of the solar spectrum. The performance of the device and measurements of electroluminescence, quantum efficiency and photomodulated reflectivity are analyzed in terms of the Band Anticrossing model of the electronic structure of highly mismatched alloys. The results demonstrate the feasibility of using highly mismatched alloys to engineer the semiconductor energy band structure for specific device applications.

  12. Engineering the electronic band structure for multiband solar cells.

    PubMed

    López, N; Reichertz, L A; Yu, K M; Campman, K; Walukiewicz, W

    2011-01-14

    Using the unique features of the electronic band structure of GaN(x)As(1-x) alloys, we have designed, fabricated and tested a multiband photovoltaic device. The device demonstrates an optical activity of three energy bands that absorb, and convert into electrical current, the crucial part of the solar spectrum. The performance of the device and measurements of electroluminescence, quantum efficiency and photomodulated reflectivity are analyzed in terms of the band anticrossing model of the electronic structure of highly mismatched alloys. The results demonstrate the feasibility of using highly mismatched alloys to engineer the semiconductor energy band structure for specific device applications.

  13. Electronic structure and bonding in skutterudite-type phosphides

    NASA Astrophysics Data System (ADS)

    Llunell, Miquel; Alemany, Pere; Alvarez, Santiago; Zhukov, Vladlen P.; Vernes, Andreas

    1996-04-01

    The electronic structures of the skutterudite-type phosphides CoP3 and NiP3 have been investigated by means of first-principles linear muffin-tin orbital-atomic sphere approximation band-structure calculations. The presence of P4 rings in the skutterudite structure is of great importance in determining the nature of the electronic bands around the Fermi level, composed mainly of π-type molecular orbitals of these units. The metallic character found for NiP3 should be ascribed to the phosphorus framework rather than to the metal atoms.

  14. High energy density capacitors for power electronic applications using nano-structure multilayer technology

    SciTech Connect

    Barbee, T.W. Jr.; Johnson, G.W.

    1995-09-01

    Power electronics applications are currently limited by capacitor size and performance. Only incremental improvements are anticipated in existing capacitor technologies, while significant performance advances are required in energy density and overall performance to meet the technical needs of the applications which are important for U.S. economic competitiveness. One application, the Power Electronic Building Block (PEBB), promises a second electronics revolution in power electronic design. High energy density capacitors with excellent electrical thermal and mechanical performance represent an enabling technology in the PEBB concept. We propose a continuing program to research and develop LLNL`s nano-structure multilayer technologies for making high voltage, high energy density capacitors. Our controlled deposition techniques are capable of synthesizing extraordinarily smooth sub-micron thick layers of dielectric and conductor materials. We have demonstrated that, with this technology, high voltage capacitors with an order of magnitude improvement in energy density are achievable.

  15. Temporal Electron-bunch Shaping from a Photoinjector for Advanced Accelerator Applications

    SciTech Connect

    Lemery, Francois; Piot, Philippe

    2014-07-01

    Advanced-accelerator applications often require the production of bunches with shaped temporal distributions. An example of sought-after shape is a linearly-ramped current profile that can be improve the transformer ratio in beam-driven acceleration, or produce energy-modulated pulse for, e.g., the subsequent generation of THz radiation. Typically,  such a shaping is achieved by manipulating ultra-relativistic electron bunches. In this contribution we discuss the possibility of shaping the bunch via photoemission and demonstrate using particle-in-cell simulations the production of MeV electron bunches with quasi-ramped current profile.

  16. FY2010 Annual Progress Report for Advanced Power Electronics and Electric Motors

    SciTech Connect

    Rogers, Susan A.

    2011-01-01

    The Advanced Power Electronics and Electric Machines (APEEM) subprogram within the Vehicle Technologies Program provides support and guidance for many cutting-edge automotive technologies now under development. Research is focused on developing revolutionary new power electronics (PE) and electric motor technologies that will leapfrog current on-the-road technologies. The research and development (R&D) is also aimed at achieving a greater understanding of and improvements in the way the various new components of tomorrow’s automobiles will function as a unified system to improve fuel efficiency.

  17. FY2011 Advanced Power Electronics and Electric Motors Annual Progress Report

    SciTech Connect

    Rogers, Susan A.

    2012-01-31

    The Advanced Power Electronics and Electric Motors (APEEM) program within the DOE Vehicle Technologies Program (VTP) provides support and guidance for many cutting-edge automotive technologies now under development. Research is focused on developing revolutionary new power electronics (PE), electric motor (EM), thermal management, and traction drive system technologies that will leapfrog current on-the-road technologies. The research and development (R&D) is also aimed at achieving a greater understanding of and improvements in the way the various new components of tomorrow’s automobiles will function as a unified system to improve fuel efficiency.

  18. FY2012 Advanced Power Electronics and Electric Motors Annual Progress Report

    SciTech Connect

    Rogers, Susan A.

    2013-03-01

    The Advanced Power Electronics and Electric Motors (APEEM) program within the DOE Vehicle Technologies Office (VTO) provides support and guidance for many cutting-edge automotive technologies now under development. Research is focused on developing revolutionary new power electronics (PE), electric motor (EM), thermal management, and traction drive system technologies that will leapfrog current on-the-road technologies. The research and development is also aimed at achieving a greater understanding of and improvements in the way the various new components of tomorrow's automobiles will function as a unified system to improve fuel efficiency.

  19. Structure of a Bacterial Cell Surface Decaheme Electron Conduit

    SciTech Connect

    Clarke, Thomas A.; Edwards, Marcus; Gates, Andrew J.; Hall, Andrea; White, Gaye; Bradley, Justin; Reardon, Catherine L.; Shi, Liang; Beliaev, Alex S.; Marshall, Matthew J.; Wang, Zheming; Watmough, Nicholas; Fredrickson, Jim K.; Zachara, John M.; Butt, Julea N.; Richardson, David J.

    2011-05-23

    Some bacterial species are able to utilize extracellular mineral forms of iron and manganese as respiratory electron acceptors. In Shewanella oneidensis this involves deca-heme cytochromes that are located on the bacterial cell surface at the termini of trans-outermembrane (OM) electron transfer conduits. The cell surface cytochromes can potentially play multiple roles in mediating electron transfer directly to insoluble electron sinks, catalyzing electron exchange with flavin electron shuttles or participating in extracellular inter-cytochrome electron exchange along ‘nanowire’ appendages. We present a 3.2 Å crystal structure of one of these deca-heme cytochromes, MtrF, that allows the spatial organization of the ten hemes to be visualized for the first time. The hemes are organized across four domains in a unique crossed conformation, in which a staggered 65 Å octa-heme chain transects the length of the protein and is bisected by a planar 45 Å tetra-heme chain that connects two extended Greek key split β-barrel domains. The structure provides molecular insight into how reduction of insoluble substrate (e.g. minerals), soluble substrates (e.g. flavins) and cytochrome redox partners might be possible in tandem at different termini of a trifurcated electron transport chain on the cell surface.

  20. Structure of a bacterial cell surface decaheme electron conduit.

    PubMed

    Clarke, Thomas A; Edwards, Marcus J; Gates, Andrew J; Hall, Andrea; White, Gaye F; Bradley, Justin; Reardon, Catherine L; Shi, Liang; Beliaev, Alexander S; Marshall, Matthew J; Wang, Zheming; Watmough, Nicholas J; Fredrickson, James K; Zachara, John M; Butt, Julea N; Richardson, David J

    2011-06-07

    Some bacterial species are able to utilize extracellular mineral forms of iron and manganese as respiratory electron acceptors. In Shewanella oneidensis this involves decaheme cytochromes that are located on the bacterial cell surface at the termini of trans-outer-membrane electron transfer conduits. The cell surface cytochromes can potentially play multiple roles in mediating electron transfer directly to insoluble electron sinks, catalyzing electron exchange with flavin electron shuttles or participating in extracellular intercytochrome electron exchange along "nanowire" appendages. We present a 3.2-Å crystal structure of one of these decaheme cytochromes, MtrF, that allows the spatial organization of the 10 hemes to be visualized for the first time. The hemes are organized across four domains in a unique crossed conformation, in which a staggered 65-Å octaheme chain transects the length of the protein and is bisected by a planar 45-Å tetraheme chain that connects two extended Greek key split β-barrel domains. The structure provides molecular insight into how reduction of insoluble substrate (e.g., minerals), soluble substrates (e.g., flavins), and cytochrome redox partners might be possible in tandem at different termini of a trifurcated electron transport chain on the cell surface.

  1. Electronic Structure and Phase Stability of PdPt Nanoparticles.

    PubMed

    Ishimoto, Takayoshi; Koyama, Michihisa

    2016-03-03

    To understand the origin of the physicochemical nature of bimetallic PdPt nanoparticles, we theoretically investigated the phase stability and electronic structure employing the PdPt nanoparticles models consisting of 711 atoms (ca. 3 nm). For the Pd-Pt core-shell nanoparticle, the PdPt solid-solution phase was found to be a thermodynamically stable phase in the nanoparticle as the result of difference in surface energy of Pd and Pt nanoparticles and configurational entropy effect, while it is well known that the Pd and Pt are the immiscible combination in the bulk phase. The electronic structure of nanoparticles is conducted to find that the electron transfer occurs locally within surface and subsurface layers. In addition, the electron transfer from Pd to Pt at the interfacial layers in core-shell nanoparticles is observed, which leads to unique geometrical and electronic structure changes. Our results show a clue for the tunability of the electronic structure of nanoparticles by controlling the arrangement in the nanoparticles.

  2. Aircrew Training Devices: Utility and Utilization of Advanced Instructional Features. Phase III. Electronic Warfare Trainers.

    DTIC Science & Technology

    1986-04-01

    Devices: Utility and Utilization of Advanced Instructional Features (Phase III- Electronic Warfare Trainers) 12 PERSONAL AUTHOR(S) Polzella . Donald J...Features, addressed a portion of this subthrust. Dr. Wayne Waag (AFHRL/OTU) was the Contract Monitor and Dr. Donald J. Polzella and Dr. David C. Hubbard...training is practicable (see Polzella , 1983, p.8). However, instructional features are expensive to implement, especially those features that require the

  3. Advanced search of the electronic medical record: augmenting safety and efficiency in radiology.

    PubMed

    Zalis, Michael; Harris, Mitchell

    2010-08-01

    The integration of electronic medical record (EMR) systems into clinical practice has been spurred by general consensus and recent federal incentives and is set to become a standard feature of clinical practice in the US. We discuss how the addition of advanced search capabilities to the EMR can improve the radiologist's ability to integrate contextual data into workflows associated with both for diagnostic and interventional procedures.

  4. Parallel adaptive mesh refinement for electronic structure calculations

    SciTech Connect

    Kohn, S.; Weare, J.; Ong, E.; Baden, S.

    1996-12-01

    We have applied structured adaptive mesh refinement techniques to the solution of the LDA equations for electronic structure calculations. Local spatial refinement concentrates memory resources and numerical effort where it is most needed, near the atomic centers and in regions of rapidly varying charge density. The structured grid representation enables us to employ efficient iterative solver techniques such as conjugate gradients with multigrid preconditioning. We have parallelized our solver using an object-oriented adaptive mesh refinement framework.

  5. The use of advanced materials in space structure applications

    NASA Astrophysics Data System (ADS)

    Eaton, D. C. G.; Slachmuylders, E. J.

    The last decade has seen the Space applications of composite materials become almost commonplace in the construction of configurations requiring high stiffness and/or dimensional stability, particularly in the field of antennas. As experience has been accumulated, applications for load carrying structures utilizing the inherent high specific strength/stiffness of carbon fibres have become more frequent. Some typical examples of these and their design development criteria are reviewed. As these structures and the use of new plastic matrices emerge, considerable attention has to be given to establishing essential integrity control requirements from both safety and cost aspects. The advent of manned European space flight places greater emphasis on such requirements. Attention is given to developments in the fields of metallic structures with discussion of the advantages and disadvantages of their application. The design and development of hot structures, thermal protection systems and air-breathing engines for future launch vehicles necessitates the use of the emerging metal/matrix and other advanced materials. Some of their important features are outlined. Means of achieving such objectives by greater harmonization within Europe are emphasized. Typical examples of on-going activities to promote such collaboration are described.

  6. Variability of Protein Structure Models from Electron Microscopy.

    PubMed

    Monroe, Lyman; Terashi, Genki; Kihara, Daisuke

    2017-03-02

    An increasing number of biomolecular structures are solved by electron microscopy (EM). However, the quality of structure models determined from EM maps vary substantially. To understand to what extent structure models are supported by information embedded in EM maps, we used two computational structure refinement methods to examine how much structures can be refined using a dataset of 49 maps with accompanying structure models. The extent of structure modification as well as the disagreement between refinement models produced by the two computational methods scaled inversely with the global and the local map resolutions. A general quantitative estimation of deviations of structures for particular map resolutions are provided. Our results indicate that the observed discrepancy between the deposited map and the refined models is due to the lack of structural information present in EM maps and thus these annotations must be used with caution for further applications.

  7. Development of Stitched Composite Structure for Advanced Aircraft

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn; Przekop, Adam; Rouse, Marshall; Lovejoy, Andrew; Velicki, Alex; Linton, Kim; Wu, Hsi-Yung; Baraja, Jaime; Thrash, Patrick; Hoffman, Krishna

    2015-01-01

    NASA has created the Environmentally Responsible Aviation Project to develop technologies which will reduce the impact of aviation on the environment. A critical aspect of this pursuit is the development of a lighter, more robust airframe that will enable the introduction of unconventional aircraft configurations. NASA and The Boeing Company are working together to develop a structural concept that is lightweight and an advancement beyond state-of-the-art composites. The Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) is an integrally stiffened panel design where elements are stitched together and designed to maintain residual load-carrying capabilities under a variety of damage scenarios. With the PRSEUS concept, through-the-thickness stitches are applied through dry fabric prior to resin infusion, and replace fasteners throughout each integral panel. Through-the-thickness reinforcement at discontinuities, such as along flange edges, has been shown to suppress delamination and turn cracks, which expands the design space and leads to lighter designs. The pultruded rod provides stiffening away from the more vulnerable skin surface and improves bending stiffness. A series of building blocks were evaluated to explore the fundamental assumptions related to the capability and advantages of PRSEUS panels. These building blocks addressed tension, compression, and pressure loading conditions. The emphasis of the development work has been to assess the loading capability, damage arrestment features, repairability, post-buckling behavior, and response of PRSEUS flat panels to out-of plane pressure loading. The results of this building-block program from coupons through an 80%-scale pressure box have demonstrated the viability of a PRSEUS center body for the Hybrid Wing Body (HWB) transport aircraft. This development program shows that the PRSEUS benefits are also applicable to traditional tube-andwing aircraft, those of advanced configurations, and other

  8. Development of a Power Electronics Controller for the Advanced Stirling Radioisotope Generator

    NASA Technical Reports Server (NTRS)

    Leland, Douglas K.; Priest, Joel F.; Keiter, Douglas E.; Schreiber, Jeffrey G.

    2008-01-01

    Under a U.S. Department of Energy program for radioisotope power systems, Lockheed Martin is developing an Engineering Unit of the Advanced Stirling Radioisotope Generator (ASRG). This is an advanced version of the previously reported SRG110 generator. The ASRG uses Advanced Stirling Convertors (ASCs) developed by Sunpower Incorporated under a NASA Research Announcement contract. The ASRG makes use of a Stirling controller based on power electronics that eliminates the tuning capacitors. The power electronics controller synchronizes dual-opposed convertors and maintains a fixed frequency operating point. The controller is single-fault tolerant and uses high-frequency pulse width modulation to create the sinusoidal currents that are nearly in phase with the piston velocity, eliminating the need for large series tuning capacitors. Sunpower supports this effort through an extension of their controller development intended for other applications. Glenn Research Center (GRC) supports this effort through system dynamic modeling, analysis and test support. The ASRG design arrived at a new baseline based on a system-level trade study and extensive feedback from mission planners on the necessity of single-fault tolerance. This paper presents the baseline design with an emphasis on the power electronics controller detailed design concept that will meet space mission requirements including single fault tolerance.

  9. Recent Advances and New Techniques in Visualization of Ultra-short Relativistic Electron Bunches

    SciTech Connect

    Xiang, Dao; /SLAC

    2012-06-05

    Ultrashort electron bunches with rms length of {approx} 1 femtosecond (fs) can be used to generate ultrashort x-ray pulses in FELs that may open up many new regimes in ultrafast sciences. It is also envisioned that ultrashort electron bunches may excite {approx}TeV/m wake fields for plasma wake field acceleration and high field physics studies. Recent success of using 20 pC electron beam to drive an x-ray FEL at LCLS has stimulated world-wide interests in using low charge beam (1 {approx} 20 pC) to generate ultrashort x-ray pulses (0.1 fs {approx} 10 fs) in FELs. Accurate measurement of the length (preferably the temporal profile) of the ultrashort electron bunch is essential for understanding the physics associated with the bunch compression and transportation. However, the shorter and shorter electron bunch greatly challenges the present beam diagnostic methods. In this paper we review the recent advances in the measurement of ultra-short electron bunches. We will focus on several techniques and their variants that provide the state-of-the-art temporal resolution. Methods to further improve the resolution of these techniques and the promise to break the 1 fs time barrier is discussed. We review recent advances in the measurement of ultrashort relativistic electron bunches. We will focus on several techniques and their variants that are capable of breaking the femtosecond time barrier in measurements of ultrashort bunches. Techniques for measuring beam longitudinal phase space as well as the x-ray pulse shape in an x-ray FEL are also discussed.

  10. Electronic structure of tetraphenylporphyrin layers on Ag(100)

    NASA Astrophysics Data System (ADS)

    Classen, Andrej; Pöschel, Rebecca; Di Filippo, Gianluca; Fauster, Thomas; Malcıoǧlu, Osman Barış; Bockstedte, Michel

    2017-03-01

    The electronic structure of Mg and free-base tetraphenylporphyrin films on Ag(100) is investigated by one- and two-photon photoemission in combination with electronic structure calculations using density functional theory and the self-consistent G W0 method. We determine the two highest occupied and the nearly degenerate lowest unoccupied molecular orbitals. Higher unoccupied states are seen in an enhanced emission as a final-state effect. For photon energies close to the prominent absorption of the Soret band we observe a strong electron emission attributed to the break up of the bound electron-hole pairs in the S2 excited state. The experimental results on the occupied and unoccupied energy levels for the molecular films on Ag(100) nicely agree with calculated quasiparticle energies and experiments of the molecules in the gas phase.

  11. Enhancement of electron mobility in asymmetric coupled quantum well structures

    SciTech Connect

    Das, S.; Nayak, R. K.; Sahu, T. Panda, A. K.

    2014-02-21

    We study the low temperature multisubband electron mobility in a structurally asymmetric GaAs/Al{sub x}Ga{sub 1-x}As delta doped double quantum well. We calculate the subband energy levels and wave functions through selfconsistent solution of the coupled Schrodinger equation and Poisson's equation. We consider ionized impurity scattering, interface roughness scattering, and alloy disorder scattering to calculate the electron mobility. The screening of the scattering potentials is obtained by using static dielectric response function formalism within the random phase approximation. We analyze, for the first time, the effect of asymmetric structure parameters on the enhancement of multisubband electron mobility through intersubband interactions. We show that the asymmetric variation of well width, doping concentration, and spacer width considerably influences the interplay of scattering mechanisms on mobility. Our results of asymmetry induced enhancement of electron mobility can be utilized for low temperature device applications.

  12. Development of advanced structural analysis methodologies for predicting widespread fatigue damage in aircraft structures

    NASA Technical Reports Server (NTRS)

    Harris, Charles E.; Starnes, James H., Jr.; Newman, James C., Jr.

    1995-01-01

    NASA is developing a 'tool box' that includes a number of advanced structural analysis computer codes which, taken together, represent the comprehensive fracture mechanics capability required to predict the onset of widespread fatigue damage. These structural analysis tools have complementary and specialized capabilities ranging from a finite-element-based stress-analysis code for two- and three-dimensional built-up structures with cracks to a fatigue and fracture analysis code that uses stress-intensity factors and material-property data found in 'look-up' tables or from equations. NASA is conducting critical experiments necessary to verify the predictive capabilities of the codes, and these tests represent a first step in the technology-validation and industry-acceptance processes. NASA has established cooperative programs with aircraft manufacturers to facilitate the comprehensive transfer of this technology by making these advanced structural analysis codes available to industry.

  13. Instrumentation and Beam Dynamics Study of Advanced Electron-Photon Facility in Indiana University

    SciTech Connect

    Luo, Tianhuan

    2011-08-01

    The Advanced eLectron-PHoton fAcility (ALPHA) is a compact electron accelerator under construction and being commissioned at the Indiana University Center for Exploration of Energy and Matter (CEEM). In this thesis, we have studied the refurbished Cooler Injector Synchrotron (CIS) RF cavity using both the transmission line model and SUPERFISH simulation. Both low power and high power RF measurements have been carried out to characterize the cavity. Considering the performance limit of ferrite, we have designed a new ferrite loaded, co-axial quarter wave like cavity with similar structure but a more suitable ferrite material. We have also designed a traveling wave stripline kicker for fast extraction by POISSON and Microwave Studio. The strips geometry is trimmed to maximize the uniformity of the kicking field and match the impedance of the power cables. The time response simulation shows the kicker is fast enough for machine operation. The pulsed power supply requirement has also been specified. For the beam diagnosis in the longitudinal direction, we use a wideband Wall Gap Monitor (WGM) served in CIS. With proper shielding and amplification to get good WGM signal, we have characterized the injected and extracted beam signal in single pass commissioning, and also verified the debunching effect of the ALPHA storage ring. A modulation-demodulation signal processing method is developed to measure the current and longitudinal profile of injected beam. By scanning the dipole strength in the injection line, we have reconstructed the tomography of the longitudinal phase space of the LINAC beam. In the accumulation mode, ALPHA will be operated under a low energy and high current condition, where intra beam scattering (IBS) becomes a dominant effect on the beam emittance. A self consistent simulation, including IBS effect, gas scattering and linear coupling, has been carried out to calculate the emittance of the stored beam.

  14. Quality Assurance Protocol for AFCI Advanced Structural Materials Testing

    SciTech Connect

    Busby, Jeremy T

    2009-05-01

    The objective of this letter is to inform you of recent progress on the development of advanced structural materials in support of advanced fast reactors and AFCI. As you know, the alloy development effort has been initiated in recent months with the procurement of adequate quantities of the NF616 and HT-UPS alloys. As the test alloys become available in the coming days, mechanical testing, evaluation of optimizing treatments, and screening of environmental effects will be possible at a larger scale. It is therefore important to establish proper quality assurance protocols for this testing effort in a timely manner to ensure high technical quality throughout testing. A properly implemented quality assurance effort will also enable preliminary data taken in this effort to be qualified as NQA-1 during any subsequent licensing discussions for an advanced design or actual prototype. The objective of this report is to describe the quality assurance protocols that will be used for this effort. An essential first step in evaluating quality protocols is assessing the end use of the data. Currently, the advanced structural materials effort is part of a long-range, basic research and development effort and not, as yet, involved in licensing discussions for a specific reactor design. After consultation with Mark Vance (an ORNL QA expert) and based on the recently-issued AFCI QA requirements, the application of NQA-1 quality requirements will follow the guidance provided in Part IV, Subpart 4.2 of the NQA-1 standard (Guidance on Graded Application of QA for Nuclear-Related Research and Development). This guidance mandates the application of sound scientific methodology and a robust peer review process in all phases, allowing for the data to be qualified for use even if the programmatic mission changes to include licensing discussions of a specific design or prototype. ORNL has previously implemented a QA program dedicated to GNEP activities and based on an appropriately graded

  15. Vibrational stability and electronic structure of a B80 fullerene

    NASA Astrophysics Data System (ADS)

    Baruah, Tunna; Pederson, Mark R.; Zope, Rajendra R.

    2008-07-01

    We investigate the vibrational stability and the electronic structure of the proposed icosahedral fullerenelike cage structure of B80 [N. G. Szwacki, A. Sadrzadeh, and B. I. Yakobson, Phys. Rev. Lett. 98, 166804 (2007)], by an all electron density-functional theory using polarized Gaussian basis functions containing 41 basis functions per atom. The vibrational analysis of B80 indicates that the icosahedral structure is vibrationally unstable with seven imaginary frequencies. The equilibrium structure has Th symmetry and a smaller gap of 0.96 eV between the highest occupied and the lowest unoccupied molecular orbital energy levels compared to the icosahedral structure. The static dipole polarizability of a B80 cage is 149Å3 , and the first ionization energy is 6.4 eV. The B80 cage has rather large electron affinity of 3 eV making it a useful candidate as electron acceptor if it is synthesized. The infrared and Raman spectra of the highly symmetric structure are characterized by a few absorption peaks.

  16. Human enamel structure studied by high resolution electron microscopy

    SciTech Connect

    Wen, S.L. )

    1989-01-01

    Human enamel structural features are characterized by high resolution electron microscopy. The human enamel consists of polycrystals with a structure similar to Ca10(PO4)6(OH)2. This article describes the structural features of human enamel crystal at atomic and nanometer level. Besides the structural description, a great number of high resolution images are included. Research into the carious process in human enamel is very important for human beings. This article firstly describes the initiation of caries in enamel crystal at atomic and unit-cell level and secondly describes the further steps of caries with structural and chemical demineralization. The demineralization in fact, is the origin of caries in human enamel. The remineralization of carious areas in human enamel has drawn more and more attention as its potential application is realized. This process has been revealed by high resolution electron microscopy in detail in this article. On the other hand, the radiation effects on the structure of human enamel are also characterized by high resolution electron microscopy. In order to reveal this phenomenon clearly, a great number of electron micrographs have been shown, and a physical mechanism is proposed. 26 references.

  17. Electronic band structure and Fermi surface of ferromagnetic Tb: Experiment and theory

    NASA Astrophysics Data System (ADS)

    Döbrich, K. M.; Bihlmayer, G.; Starke, K.; Prieto, J. E.; Rossnagel, K.; Koh, H.; Rotenberg, E.; Blügel, S.; Kaindl, G.

    2007-07-01

    We have investigated the bulk valence-band structure of Tb metal in the ferromagnetic phase by angle-resolved photoelectron spectroscopy and full-potential-linearized-augmented-plane-wave calculations. The experiments were performed at undulator beamline 7.0.1 of the Advanced Light Source using a three-axis rotatable low-temperature goniometer and a display-type photoelectron spectrometer that give access to a large region of momentum space. The results of our calculations, which make use of recent progress in the theoretical description of the magnetic properties of 4f metals, are in remarkably good agreement with experiment. This can be best seen from a comparison of the electronic structure in high-symmetry directions, at critical points, on Fermi contours, and at band crossings with the Fermi level. To our knowledge, the present work represents the most detailed combined experimental and theoretical study of the electronic structure of a magnetic lanthanide metal to date.

  18. Electronic and optical properties of novel carbon structures

    NASA Astrophysics Data System (ADS)

    Matthews, Manyalibo Joseph

    Novel carbon structures in the form of fullerenes and disordered carbon clusters offer a wide variety of physical systems, possessing both long or short range order, which can generally be tuned through non- combustive heat-treatment at various elevated temperatures, THT. Due to the sheer complexity and diversity of the possible nanoscale arrangements, the optical and electronic properties of carbon structures with finite dimensions and crystallinity are still not fully understood. In this study, we focus mainly on the structures produced from carbonization of the hydrocarbon polymer polyparaphenylene (PPP), but we also present experimental results from carbons based on other precursors (e.g. mesophase pitch) which yield quite different structures with both comparable and contrasting physical properties. In terms of electronic properties, we show that in the low-THT PPP-based structures, which exemplify extreme disorder, the electronic states are strongly localized, giving rise to a Mott T1/4 hopping conductivity and self-trapped spin defects AS evidenced by low-temperature transport and electron spin resonance experiments. Electronic transitions which give rise to ~2-3 eV photoluminescent emissions in PPP-based structures are found to be influenced most strongly by residual semi-localized polymeric states which weakly couple to low-frequency PPP phonon modes. However, at intermediate heat-treatment temperatures (THT~ 1500[-]2500oC), all sp2-bonded carbon compounds in this study exhibit a characteristic phonon spectrum (as evidenced by Raman spectroscopy) in which disorder may be characterized by non-zone-center phonon scattering arising from finite crystallite sizes. Because of its intimate connection to carrier confinement and structural disorder, the anomalous 'disorder-induced' graphite D-band is thoroughly investigated by use of Raman spectroscopy, showing that strong dispersion effects are due to a photon-phonon coupling mediated by electronic transitions

  19. Electron microscopic study of hemolysis: a proposal of formation of a weak structural region in the erythrocyte membrane.

    PubMed

    Lin, P S

    1981-02-01

    Numerous theories have been advanced to explain the erythrocyte shape in terms of membrane structure. One of the most controversial points has been whether the erythrocyte membrane is a uniform shell. Electron microscopy studies of erythrocytes undergoing osmotic lysis show that the release of hemoglobin is confined to one large area, suggesting that this area is more fragile structurally than that of the rest of the surface membrane. Hypotheses are presented to explain the formation of structurally weak areas on the erythrocyte membrane.

  20. Atomic and electronic structure of exfoliated black phosphorus

    SciTech Connect

    Wu, Ryan J.; Topsakal, Mehmet; Jeong, Jong Seok; Wentzcovitch, Renata M.; Mkhoyan, K. Andre; Low, Tony; Robbins, Matthew C.; Haratipour, Nazila; Koester, Steven J.

    2015-11-15

    Black phosphorus, a layered two-dimensional crystal with tunable electronic properties and high hole mobility, is quickly emerging as a promising candidate for future electronic and photonic devices. Although theoretical studies using ab initio calculations have tried to predict its atomic and electronic structure, uncertainty in its fundamental properties due to a lack of clear experimental evidence continues to stymie our full understanding and application of this novel material. In this work, aberration-corrected scanning transmission electron microscopy and ab initio calculations are used to study the crystal structure of few-layer black phosphorus. Directly interpretable annular dark-field images provide a three-dimensional atomic-resolution view of this layered material in which its stacking order and all three lattice parameters can be unambiguously identified. In addition, electron energy-loss spectroscopy (EELS) is used to measure the conduction band density of states of black phosphorus, which agrees well with the results of density functional theory calculations performed for the experimentally determined crystal. Furthermore, experimental EELS measurements of interband transitions and surface plasmon excitations are also consistent with simulated results. Finally, the effects of oxidation on both the atomic and electronic structure of black phosphorus are analyzed to explain observed device degradation. The transformation of black phosphorus into amorphous PO{sub 3} or H{sub 3}PO{sub 3} during oxidation may ultimately be responsible for the degradation of devices exposed to atmosphere over time.

  1. Momentum space analysis of the electronic structure of biphenyl

    NASA Astrophysics Data System (ADS)

    Morini, F.; Shojaei, S. H. Reza; Deleuze, M. S.

    2014-11-01

    The results of a yet to come experimental study of the electronic structure of biphenyl employing electron momentum spectroscopy (EMS) have been theoretically predicted, taking into account complications such as structural mobility in the electronic ground state, electronic correlation and relaxation, and a dispersion of the inner-valence ionization intensity to electronically excited (shake-up) configurations in the cation. The main purpose of this work is to explore the current limits of EMS in unraveling details of the molecular structure, namely the torsional characteristics of large and floppy aromatic molecules. At the benchmark ADC(3)/cc-pVDZ level of theory, the influence of the twist angle between the two phenyl rings is found to be extremely limited, except for individual orbital momentum profiles corresponding to ionization lines at electron binding energies ranging from 15 to 18 eV. When taking band overlap effects into account, this influence is deceptively far too limited to allow for any experimental determination of the torsional characteristics of biphenyl by means of EMS.

  2. Theoretical studies of the electronic structure of small metal clusters

    NASA Technical Reports Server (NTRS)

    Jordan, K. D.

    1982-01-01

    Theoretical studies of the electronic structure of metal clusters, in particular clusters of Group IIA and IIB atoms were conducted. Early in the project it became clear that electron correlation involving d orbitals plays a more important role in the binding of these clusters than had been previously anticipated. This necessitated that computer codes for calculating two electron integrals and for constructing the resulting CI Hamiltonions be replaced with newer, more efficient procedures. Program modification, interfacing and testing were performed. Results of both plans are reported.

  3. Electronic Structure Methods Based on Density Functional Theory

    DTIC Science & Technology

    2010-01-01

    L. Nordström, L. Tongming, and B. Johansson, “Relativistic Effects on the Thermal Expansion of the Actinide Elements ”, Phys. Rev. B 42, 1990, p 4544...In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6. AUTHOR(S) Christopher F. Woodward (AFRL/RXLMD) 5d. PROJECT NUMBER 4347 5e...in valence electrons change the structure of the core electrons. For example in the actinides , where the f-electrons are coupled to the core states

  4. Structural and electronic properties of dense liquid and amorphous nitrogen

    SciTech Connect

    Boates, B; Bonev, S A

    2011-02-11

    We present first-principles calculations of the structural and electronic properties of liquid nitrogen in the pressure-temperature range of 0-200 GPa and 2000-6000 K. The molecular-polymerization and molecular-atomic liquid phase boundaries have been mapped over this region. We find the polymeric liquid to be metallic, similar to what has been reported for the higher-temperature atomic fluid. An explanation of the electronic properties is given based on the structure and bonding character of the transformed liquids. We discuss the structural and bonding differences between the polymeric liquid and insulating solid cubic-gauche nitrogen to explain the differences in their electronic properties. Furthermore, we discuss the mechanism responsible for charge transport in polymeric nitrogen systems to explain the conductivity of the polymeric fluid and the semi-conducting nature of low-temperature amorphous nitrogen.

  5. Electronic structure and enthalpy of hydrogen and helium mixtures

    NASA Astrophysics Data System (ADS)

    Ross, M.; Klepeis, J. E.; Schafer, K. J.; Barbee, T. W., III

    1992-11-01

    The first local density approximation (LDA) calculations of the electronic structure, equation of state, and enthalpy of mixing were carried out for a number of different compositions of hydrogen and helium in bcc and fcc lattices. These are fully quantum mechanical, self-consistent calculations utilizing state-of-the-art methods of electron band theory, which make no assumptions regarding pressure ionization. The major approximation in the LDA method is that the exchange and correlation energy is given by a free electron functional in terms of the local electron density. The majority of previous mixture calculations start with the assumption that both hydrogen and helium are pressure-ionized so that the electronic structure is approximately that of free or weakly screened electrons in the presence of positive ions. Stevenson used a hard-sphere mixture model for the ions with an ion-ion pseudopotential to account for electron screening and predicted that a mixture containing 7% helium by number, the composition believed to be present in Jupiter and Saturn, would phase separate at a temperature of about 7000 K at 8 Mbar. Subsequent calculations carried out for the fully ionized mixture and for a mixture of screened ions (linear response theory) have all arrived at predictions similar to those of Stevenson. MacFarlane and Hubbard performed Thomas-Fermi-Dirac calculations for mixing enthalpies of hydrogen and helium in bcc and fcc lattices and predicted that phase separation would not occur at any temperature.

  6. Electronic Structure Analysis for Proteins on the FMO Method

    NASA Astrophysics Data System (ADS)

    Kobori, Tomoki; Tsuneyuki, Shinji; Sodeyama, Keitaro; Akagi, Kazuto; Terakura, Kiyoyuki; Fukuyama, Hidetoshi

    2009-03-01

    The enormity and complexity of proteins have rendered their electronic structure calculation very costly. Although recently established Fragment Molecular Orbital (FMO) method enables us to calculate total energy of a huge protein precisely based on quantum mechanics, the method does not refer to one-electron orbitals and one-electron energy spectrum. In this paper we propose a method of analyzing electronic structure of a protein based on first principles calculation with reasonable accuracy and CPU cost. We construct one- electron Hamiltonian of proteins by assembling the output of the FMO method: fragment orbitals are determined by fragment monomer calculation, while interaction and overlap between fragment orbitals in different fragments are obtained from dimer calculation. After one-electron Hamiltonian matrix of the whole system is fabricated with the fragment orbital basis, one- electron energy spectrum is obtained by its diagonalization. If the matrix dimension is too large, unimportant orbitals are eliminated from the matrix so that the diagonalization of the Hamiltonian becomes feasible. The method is applicable to both the Hartree-Fock method and the density functional theory. In this paper, validity of the method is verified by some test calculations of small peptides.

  7. Electronic Structure and Effectively Unpaired Electron Density Topology in closo-Boranes: Nonclassical Three-Center Two-Electron Bonding.

    PubMed

    Lobayan, Rosana M; Bochicchio, Roberto C; Torre, Alicia; Lain, Luis

    2011-04-12

    This article provides a detailed study of the structure and bonding in closo-borane cluster compounds X2B3H3 (X = BH(-), P, SiH, CH, N), with particular emphasis on the description of the electron distribution using the topology of the quantum many-body effectively unpaired density. The close relationship observed between the critical points of this quantity and the localization of the electron cloud allows us to characterize the nonclassical bonding patterns of these systems. The obtained results confirm the suitability of the local rule to detect three-center two-electron bonds, which was conjectured in our previous study on boron hydrides.

  8. The requisite electronic structure theory to describe photoexcited nonadiabatic dynamics: nonadiabatic derivative couplings and diabatic electronic couplings.

    PubMed

    Subotnik, Joseph E; Alguire, Ethan C; Ou, Qi; Landry, Brian R; Fatehi, Shervin

    2015-05-19

    Electronically photoexcited dynamics are complicated because there are so many different relaxation pathways: fluorescence, phosphorescence, radiationless decay, electon transfer, etc. In practice, to model photoexcited systems is a very difficult enterprise, requiring accurate and very efficient tools in both electronic structure theory and nonadiabatic chemical dynamics. Moreover, these theoretical tools are not traditional tools. On the one hand, the electronic structure tools involve couplings between electonic states (rather than typical single state energies and gradients). On the other hand, the dynamics tools involve propagating nuclei on multiple potential energy surfaces (rather than the usual ground state dynamics). In this Account, we review recent developments in electronic structure theory as directly applicable for modeling photoexcited systems. In particular, we focus on how one may evaluate the couplings between two different electronic states. These couplings come in two flavors. If we order states energetically, the resulting adiabatic states are coupled via derivative couplings. Derivative couplings capture how electronic wave functions change as a function of nuclear geometry and can usually be calculated with straightforward tools from analytic gradient theory. One nuance arises, however, in the context of time-dependent density functional theory (TD-DFT): how do we evaluate derivative couplings between TD-DFT excited states (which are tricky, because no wave function is available)? This conundrum was recently solved, and we review the solution below. We also discuss the solution to a second, pesky problem of origin dependence, whereby the derivative couplings do not (strictly) satisfy translation variance, which can lead to a lack of momentum conservation. Apart from adiabatic states, if we order states according to their electronic character, the resulting diabatic states are coupled via electronic or diabatic couplings. The couplings

  9. Banded Electron Structure Formation in the Inner Magnetosphere

    NASA Technical Reports Server (NTRS)

    Liemohn, M. W.; Khazanov, G. V.

    1997-01-01

    Banded electron structures in energy-time spectrograms have been observed in the inner magnetosphere concurrent with a sudden relaxation of geomagnetic activity. In this study, the formation of these banded structures is considered with a global, bounce-averaged model of electron transport, and it is concluded that this structure is a natural occurrence when plasma sheet electrons are captured on closed drift paths near the Earth. These bands do not appear unless there is capture of plasma sheet electrons; convection along open drift paths making open pass around the Earth do not have time to develop this feature. The separation of high-energy bands from the injection population due to the preferential advection of the gradient-curvature drift creates spikes in the energy distribution, which overlap to form a series of bands in the energy spectrograms. The lowest band is the bulk of the injected population in the sub-key energy range. Using the Kp history for an observed banded structure event, a cloud of plasma sheet electrons is captured and the development of their distribution function is examined and discussed.

  10. Advances in biomimetic regeneration of elastic matrix structures

    PubMed Central

    Sivaraman, Balakrishnan; Bashur, Chris A.

    2012-01-01

    Elastin is a vital component of the extracellular matrix, providing soft connective tissues with the property of elastic recoil following deformation and regulating the cellular response via biomechanical transduction to maintain tissue homeostasis. The limited ability of most adult cells to synthesize elastin precursors and assemble them into mature crosslinked structures has hindered the development of functional tissue-engineered constructs that exhibit the structure and biomechanics of normal native elastic tissues in the body. In diseased tissues, the chronic overexpression of proteolytic enzymes can cause significant matrix degradation, to further limit the accumulation and quality (e.g., fiber formation) of newly deposited elastic matrix. This review provides an overview of the role and importance of elastin and elastic matrix in soft tissues, the challenges to elastic matrix generation in vitro and to regenerative elastic matrix repair in vivo, current biomolecular strategies to enhance elastin deposition and matrix assembly, and the need to concurrently inhibit proteolytic matrix disruption for improving the quantity and quality of elastogenesis. The review further presents biomaterial-based options using scaffolds and nanocarriers for spatio-temporal control over the presentation and release of these biomolecules, to enable biomimetic assembly of clinically relevant native elastic matrix-like superstructures. Finally, this review provides an overview of recent advances and prospects for the application of these strategies to regenerating tissue-type specific elastic matrix structures and superstructures. PMID:23355960

  11. Generation of high-quality electron beams from a laser-based advanced accelerator

    NASA Astrophysics Data System (ADS)

    Ahmed, M. M. Elsied; Nasr, A. M. Hafz; Li, Song; Mohammad, Mirzaie; Thomas, Sokollik; Zhang, Jie

    2015-06-01

    At Shanghai Jiao Tong University (SJTU) we have established a research laboratory for advanced acceleration research based on high-power lasers and plasma technologies. In a primary experiment based on the laser wakefield acceleration (LWFA) scheme, multi-hundred MeV electron beams of reasonable quality are generated using 20-40 TW, 30 femtosecond laser pulses interacting independently with helium, neon, nitrogen and argon gas jet targets. The laser-plasma interaction conditions are optimized for stabilizing the electron beam generation from each type of gas. The electron beam pointing angle stability and divergence angle as well as the energy spectra from each gas jet are measured and compared. Supported by 973 National Basic Research Program of China (2013CBA01504) and Natural Science Foundation of China NSFC (11121504, 11334013, 11175119, 11374209)

  12. An aberration corrected photoemission electron microscope at the advanced light source

    SciTech Connect

    Feng, J.; MacDowell, A.A.; Duarte, R.; Doran, A.; Forest, E.; Kelez, N.; Marcus, M.; Munson, D.; Padmore, H.; Petermann, K.; Raoux, S.; Robin, D.; Scholl, A.; Schlueter, R.; Schmid, P.; Stohr, J.; Wan, W.; Wei, D.H.; Wu, Y.

    2003-11-01

    Design of a new aberration corrected Photoemission electron microscope PEEM3 at the Advanced Light Source is outlined. PEEM3 will be installed on an elliptically polarized undulator beamline and will be used for the study of complex materials at high spatial and spectral resolution. The critical components of PEEM3 are the electron mirror aberration corrector and aberration-free magnetic beam separator. The models to calculate the optical properties of the electron mirror are discussed. The goal of the PEEM3 project is to achieve the highest possible transmission of the system at resolutions comparable to our present PEEM2 system (50 nm) and to enable significantly higher resolution, albeit at the sacrifice of intensity. We have left open the possibility to add an energy filter at a later date, if it becomes necessary driven by scientific need to improve the resolution further.

  13. High Energy Laboratory Astrophysics Experiments using electron beam ion traps and advanced light sources

    NASA Astrophysics Data System (ADS)

    Brown, Gregory V.; Beiersdorfer, Peter; Bernitt, Sven; Eberle, Sita; Hell, Natalie; Kilbourne, Caroline; Kelley, Rich; Leutenegger, Maurice; Porter, F. Scott; Rudolph, Jan; Steinbrugge, Rene; Traebert, Elmar; Crespo-Lopez-Urritia, Jose R.

    2015-08-01

    We have used the Lawrence Livermore National Laboratory's EBIT-I electron beam ion trap coupled with a NASA/GSFC microcalorimeter spectrometer instrument to systematically address problems found in the analysis of high resolution X-ray spectra from celestial sources, and to benchmark atomic physics codes employed by high resolution spectral modeling packages. Our results include laboratory measurements of transition energies, absolute and relative electron impact excitation cross sections, charge exchange cross sections, and dielectronic recombination resonance strengths. More recently, we have coupled to the Max-Plank Institute for Nuclear Physics-Heidelberg's FLASH-EBIT electron beam ion trap to third and fourth generation advanced light sources to measure photoexcitation and photoionization cross sections, as well as, natural line widths of X-ray transitions in highly charged iron ions. Selected results will be presented.

  14. Structural Assessment of Advanced Composite Tow-Steered Shells

    NASA Technical Reports Server (NTRS)

    Wu, K. Chauncey; Stanford, Bret K.; Hrinda, Glenn A.; Wang, Zhuosong; Martin, Robert a.; Kim, H. Alicia

    2013-01-01

    The structural performance of two advanced composite tow-steered shells, manufactured using a fiber placement system, is assessed using both experimental and analytical methods. The fiber orientation angles vary continuously around the shell circumference from 10 degrees on the shell crown and keel, to 45 degrees on the shell sides. The two shells differ in that one shell has the full 24-tow course applied during each pass of the fiber placement system, while the second shell uses the fiber placement system s tow drop/add capability to achieve a more uniform shell wall thickness. The shells are tested in axial compression, and estimates of their prebuckling axial stiffnesses and bifurcation buckling loads are predicted using linear finite element analyses. These preliminary predictions compare well with the test results, with an average agreement of approximately 10 percent.

  15. Recent Advances in the Structural Mechanisms of DNA Glycosylases

    PubMed Central

    Brooks, Sonja C.; Adhikary, Suraj; Rubinson, Emily H.; Eichman, Brandt F.

    2012-01-01

    DNA glycosylases safeguard the genome by locating and excising a diverse array of aberrant nucleobases created from oxidation, alkylation, and deamination of DNA. Since the discovery 28 years ago that these enzymes employ a base flipping mechanism to trap their substrates, six different protein architectures have been identified to perform the same basic task. Work over the past several years has unraveled details for how the various DNA glycosylases survey DNA, detect damage within the duplex, select for the correct modification, and catalyze base excision. Here, we provide a broad overview of these latest advances in glycosylase mechanisms gleaned from structural enzymology, highlighting features common to all glycosylases as well as key differences that define their particular substrate specificities. PMID:23076011

  16. The electronic structure and chemical bonding of vitamin B12

    NASA Astrophysics Data System (ADS)

    Kurmaev, E. Z.; Moewes, A.; Ouyang, L.; Randaccio, L.; Rulis, P.; Ching, W. Y.; Bach, M.; Neumann, M.

    2003-05-01

    The electronic structure and chemical bonding of vitamin B12 (cyanocobalamin) and B12-derivative (methylcobalamin) are studied by means of X-ray emission (XES) and photoelectron (XPS) spectroscopy. The obtained results are compared with ab initio electronic structure calculations using the orthogonalized linear combination of the atomic orbital method (OLCAO). We show that the chemical bonding in vitamin B12 is characterized by the strong Co-C bond and relatively weak axial Co-N bond. It is further confirmed that the Co-C bond in cyanocobalamin is stronger than that of methylcobalamin resulting in their different biological activity.

  17. Structural and luminescent properties of electron-irradiated silicon

    SciTech Connect

    Sobolev, N. A.; Loshachenko, A. S.; Aruev, P. N.; Kalyadin, A. E.; Shek, E. I.; Zabrodskiy, V. V.; Shtel'makh, K. F.; Vdovin, V. I.; Xiang, Luelue; Yang, Deren

    2014-02-21

    Structural defects induced by electron irradiation of p-Cz-Si wafers were identified. The influence of the annealing conditions in a chlorine-containing atmosphere on the structural and luminescent properties of the samples was examined. Light-emitting diodes based on electron-irradiated and high-temperature-annealed wafers were fabricated by a vapour-phase epitaxy technique and their luminescence properties were studied. A high-intensity dislocation-related D1 line was observed at 1.6 μm in the room-temperature electroluminescence spectrum.

  18. Electronic structure of Sn/Cu(100)-[Formula: see text].

    PubMed

    Martínez-Blanco, J; Joco, V; Fujii, J; Segovia, P; Michel, E G

    2009-02-04

    We present measurements of the Fermi surface and underlying band structure of Sn/Cu(100)-[Formula: see text]. This phase is observed for a coverage of 0.60-0.65 monolayers. Its electronic structure is characterized by a free-electron-like surface band folded with the reconstruction periodicity. At variance with other surface phases of Sn on Cu(100), no temperature-induced phase transition is observed for this phase from 100 K up to the desorption of Sn.

  19. Electronic Structure of Lanthanum Hydrides with Switchable Optical Properties

    SciTech Connect

    Ng, K.; Zhang, F.; Ng, K.; Zhang, F.; Anisimov, V.; Rice, T.; Anisimov, V.

    1997-02-01

    Recent dramatic changes in the optical properties of LaH{sub 2+x} and YH{sub 2+x} films discovered by Huiberts {ital et al.}[Nature (London) {bold 380}, 231 (1996)] suggest their electronic structure is described best by a local model. Electron correlation is important in H{sup -} centers and in explaining the transparent insulating behavior of LaH{sub 3}. The metal-insulator transition at x{approximately}0.8 takes place in a band of highly localized states centered on the H vacancies in the LaH{sub 3} structure. {copyright} {ital 1997} {ital The American Physical Society}

  20. Comparison of electronic structure between monolayer silicenes on Ag (111)

    NASA Astrophysics Data System (ADS)

    Chun-Liang, Lin; Ryuichi, Arafune; Maki, Kawai; Noriaki, Takagi

    2015-08-01

    The electronic structures of monolayer silicenes (4 × 4 and ) grown on Ag (111) surface are studied by scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations. While both phases have similar electronic structures around the Fermi level, significant differences are observed in the higher energy unoccupied states. The DFT calculations show that the contributions of Si 3pz orbitals to the unoccupied states are different because of their different buckled configurations. Project supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) through Grants-in-Aid for Scientific Research (Grant Nos. 24241040 and 25110008) and the World Premier International Research Center Initiative (WPI), MEXT, Japan.

  1. Free electron laser-driven ultrafast rearrangement of the electronic structure in Ti

    PubMed Central

    Principi, E.; Giangrisostomi, E.; Cucini, R.; Bencivenga, F.; Battistoni, A.; Gessini, A.; Mincigrucci, R.; Saito, M.; Di Fonzo, S.; D'Amico, F.; Di Cicco, A.; Gunnella, R.; Filipponi, A.; Giglia, A.; Nannarone, S.; Masciovecchio, C.

    2015-01-01

    High-energy density extreme ultraviolet radiation delivered by the FERMI seeded free-electron laser has been used to create an exotic nonequilibrium state of matter in a titanium sample characterized by a highly excited electron subsystem at temperatures in excess of 10 eV and a cold solid-density ion lattice. The obtained transient state has been investigated through ultrafast absorption spectroscopy across the Ti M2,3-edge revealing a drastic rearrangement of the sample electronic structure around the Fermi level occurring on a time scale of about 100 fs. PMID:26798835

  2. Structural and electronic properties of monolayer group III monochalcogenides

    NASA Astrophysics Data System (ADS)

    Demirci, S.; Avazlı, N.; Durgun, E.; Cahangirov, S.

    2017-03-01

    We investigate the structural, mechanical, and electronic properties of the two-dimensional hexagonal structure of group III-VI binary monolayers, M X (M =B , Al, Ga, In and X =O , S, Se, Te) using first-principles calculations based on the density functional theory. The structural optimization calculations and phonon spectrum analysis indicate that all of the 16 possible binary compounds are thermally stable. In-plane stiffness values cover a range depending on the element types and can be as high as that of graphene, while the calculated bending rigidity is found to be an order of magnitude higher than that of graphene. The obtained electronic band structures show that M X monolayers are indirect band-gap semiconductors. The calculated band gaps span a wide optical spectrum from deep ultraviolet to near infrared. The electronic structure of oxides (M O ) is different from the rest because of the high electronegativity of oxygen atoms. The dispersions of the electronic band edges and the nature of bonding between atoms can also be correlated with electronegativities of constituent elements. The unique characteristics of group III-VI binary monolayers can be suitable for high-performance device applications in nanoelectronics and optics.

  3. Electron-Phonon Renormalization of Electronic Band Structures of C Allotropes and BN Polymorphs

    NASA Astrophysics Data System (ADS)

    Tutchton, Roxanne M.; Marchbanks, Christopher; Wu, Zhigang

    The effect of lattice vibration on electronic band structures has been mostly neglected in first-principles calculations because the electron-phonon (e-ph) renormalization of quasi-particle energies is often small (< 100 meV). However, in certain materials, such as diamond, the electron-phonon coupling reduces the band gap by nearly 0.5 eV, which is comparable to the many-body corrections of the electronic band structures calculated using the density functional theory (DFT). In this work, we compared two implementations of the Allen-Heine-Cardona theory in the EPW code and the ABINIT package respectively. Our computations of Si and diamond demonstrate that the ABINIT implementation converges much faster. Using this method, the e-ph renormalizations of electronic structures of three C allotropes (diamond, graphite, graphene) and four BN polymorphs (zincblend, wurtzite, mono-layer, and layered-hexagonal) were calculated. Our results suggest that (1) all of the zero-point renormalizations of band gaps in these materials, except for graphene, are larger than 100 meV, and (2) there are large variations in e-ph renormalization of band gaps due to differences in crystal structure. This work was supported by a U.S. DOE Early Career Award (Grant No. DE-SC0006433). Computations were carried out at the Golden Energy Computing Organization at CSM and the National Energy Research Scientific Computing Center (NERSC).

  4. Effects of inverse degree on electronic structure and electron energy-loss spectrum in zinc ferrites

    NASA Astrophysics Data System (ADS)

    Sun, D.; Wang, M. X.; Zhang, Z. H.; Tao, H. L.; He, M.; Song, B.; Li, Q.

    2015-12-01

    First-principles calculations were performed to study the effects of inverse degree in zinc ferrite on electronic structure and properties. The electron energy-loss near-edge fine structure (ELNES) were simulated, and the splitting of peak and intensities of the oxygen K-edges can be used to identify the inversion of zinc ferrite. More Fe3+ transferring from the octahedral sites to the tetrahedral sites lead to the changing of the ligand shells surrounding the absorbing atom, accounting for the observed changing in ELNES. The standard criterion for determining the reversal extent of the cations in zinc ferrite by ELNES was given.

  5. Electronic structure of nitrides PuN and UN

    NASA Astrophysics Data System (ADS)

    Lukoyanov, A. V.; Anisimov, V. I.

    2016-11-01

    The electronic structure of uranium and plutonium nitrides in ambient conditions and under pressure is investigated using the LDA + U + SO band method taking into account the spin-orbit coupling and the strong correlations of 5 f electrons of actinoid ions. The parameters of these interactions for the equilibrium cubic structure are calculated additionally. The application of pressure reduces the magnetic moment in PuN due to predominance of the f 6 configuration and the jj-type coupling. An increase in the occupancy of the 5 f state in UN leads to a decrease in the magnetic moment, which is also detected in the trigonal structure of the UN x β phase (La2O3-type structure). The theoretical results are in good agreement with the available experimental data.

  6. Chiral phosphorus nanotubes: structure, bonding, and electronic properties.

    PubMed

    Fernández-Escamilla, H N; Quijano-Briones, J J; Tlahuice-Flores, A

    2016-05-14

    The study of black phosphorus nanotubes (PNTs) had been devoted to zigzag and armchair structures, with no consideration of chiral structures to date. In this communication, we studied the structural and electronic (band structure) properties of chiral nanotubes using a periodic plane wave-pseudopotential approach. We found that some chiral nanotubes display similar bandgaps and binding energies per atom (BEA) as armchair PNTs and Born-Oppenheimer molecular dynamics (BOMD) calculations attest their thermal stability. Interestingly, we determined that the bandgap is tuned by varying the PNTs chirality and it is not related to their diameters. This feature can be exploited in optical and electronic applications wherein a direct and sizable bandgap is required.

  7. Structural and electronic properties of small silicon clusters

    NASA Astrophysics Data System (ADS)

    Baturin, V. S.; Lepeshkin, S. V.; Magnitskaya, M. V.; Matsko, N. L.; Uspenskii, Yu A.

    2014-05-01

    The atomic structure and electronic spectrum of silicon nanoclusters (Si-ncs) Si7, Si10,Si10H16 and Si10H20 are calculated using the evolutionary algorithm with total energy computed within density functional theory and generalized gradient approximation (DFT-GGA). When analysing the low-energy structures, we pay significant attention to their symmetry and interatomic bond geometry. The candidate structures arising in the process of evolutionary algorithm convergence are also considered and classified by their topology and grouping near local energy minima. Possible ways to improve the convergence of evolutionary computation are discussed. Addressing qualitative criteria for the ground-state atomic structure of Si-ncs, we consider correlations between the density of electronic states and the total energetics of clusters in the ground state and low-energy-isomer configurations.

  8. ADVANCED SOLIDS NMR STUDIES OF COAL STRUCTURE AND CHEMISTRY

    SciTech Connect

    1997-03-01

    This report covers the progress made on the title project for the project period. The study of coal chemical structure is a vital component of research efforts to develop better chemical utilization of coals, and for furthering our basic understanding of coal geochemistry. In this grant we are addressing several structural questions pertaining to coals with advances in state of the art solids NMR methods. Our goals are twofold. First, we are interested in developing new methods that will enable us to measure important structural parameters in whole coals not directly accessible by other techniques. In parallel with these efforts we will apply these NMR methods in a study of the chemical differences between gas-sourcing and oil-sourcing coals. The NMR methods work will specifically focus on determination of the number and types of methylene groups, determination of the number and types of methane groups, identification of carbons adjacent to nitrogen and sites with exchangeable protons, and methods to more finely characterize the distribution of hydrogen in coals. The motivation for investigating these specific structural features of coals arises from their relevance to the chemical reactivity of coals, and their suitability for possible correlations with the oil sourcing potential of some types of coals. The coals to be studied and contrasted include oil-prone coals from Australia and Indonesia, those comprising the Argonne Premium Coal Sample bank, and other relevant samples. In this report period we have focused our work on 1 segment of the program. Our last report outlined progress in using our NMR editing methods with higher field operation where higher magic angle spinning rates are required. Significant difficulties were identified, and these have been the main subject of study during the most recent granting period.

  9. Layer-stacking effect on electronic structures of bilayer arsenene

    NASA Astrophysics Data System (ADS)

    Mi, Kui; Xie, Jiafeng; Si, M. S.; Gao, C. X.

    2017-01-01

    A monolayer of orthorhombic arsenic (arsenene) is a promising candidate for nano-electronic devices due to the uniquely electronic properties. To further extend its practical applications, an additional layer is introduced to tune the electronic structures. Four layer-stacking manners, namely AA-, AB-, AB‧-, and AC-stacking, are constructed and studied through using first-principles calculations. Compared with monolayer, an indirect-direct gap transition is realized in AB-stacking. More importantly, a semimetal feature appears in the AC- and AB‧-stacked bilayers, leaving the electronic structure of AA-stacking trivial. In addition, the energy dispersion around Γ is largely tuned from the layer-stacking effect. To understand the underlying physics, the \\textbf{k}\\cdot\\textbf{p} approximation is taken to address this issue. Our results show that the level repulsion from the additional layer domaintes the anisotropy of energy dispersion around Γ. The works like ours would shed new light on the tunability of the electronic structure in layered arsenene.

  10. Molecular and electronic structure of electroactive self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Méndez De Leo, Lucila P.; de la Llave, Ezequiel; Scherlis, Damián; Williams, Federico J.

    2013-03-01

    Self-assembled monolayers (SAMs) containing electroactive functional groups are excellent model systems for the formation of electronic devices by self-assembly. In particular ferrocene-terminated alkanethiol SAMs have been extensively studied in the past. However, there are still open questions related with their electronic structure including the influence of the ferrocene group in the SAM-induced work function changes of the underlying metal. We have thus carried out a thorough experimental and theoretical investigation in order to determine the molecular and electronic structure of ferrocene-terminated alkanethiol SAMs on Au surfaces. In agreement with previous studies we found that the Fc-containing alkanethiol molecules adsorb forming a thiolate bond with the Au surface with a molecular geometry 30° tilted with respect to the surface normal. Measured surface coverages indicate the formation of a compact monolayer. We found for the first time that the ferrocene group has little influence on the observed work function decrease which is largely determined by the alkanethiol. Furthermore, the ferrocene moiety lies 14 Å above the metal surface covalently bonded to the alkanethiol SAM and its HOMO is located at -1.6 eV below the Fermi level. Our results provide new valuable insight into the molecular and electronic structure of electroactive SAMs which are of fundamental importance in the field of molecular electronics.

  11. Molecular and electronic structure of electroactive self-assembled monolayers.

    PubMed

    Méndez De Leo, Lucila P; de la Llave, Ezequiel; Scherlis, Damián; Williams, Federico J

    2013-03-21

    Self-assembled monolayers (SAMs) containing electroactive functional groups are excellent model systems for the formation of electronic devices by self-assembly. In particular ferrocene-terminated alkanethiol SAMs have been extensively studied in the past. However, there are still open questions related with their electronic structure including the influence of the ferrocene group in the SAM-induced work function changes of the underlying metal. We have thus carried out a thorough experimental and theoretical investigation in order to determine the molecular and electronic structure of ferrocene-terminated alkanethiol SAMs on Au surfaces. In agreement with previous studies we found that the Fc-containing alkanethiol molecules adsorb forming a thiolate bond with the Au surface with a molecular geometry 30° tilted with respect to the surface normal. Measured surface coverages indicate the formation of a compact monolayer. We found for the first time that the ferrocene group has little influence on the observed work function decrease which is largely determined by the alkanethiol. Furthermore, the ferrocene moiety lies 14 Å above the metal surface covalently bonded to the alkanethiol SAM and its HOMO is located at -1.6 eV below the Fermi level. Our results provide new valuable insight into the molecular and electronic structure of electroactive SAMs which are of fundamental importance in the field of molecular electronics.

  12. Advances in the field of single-particle cryo-electron microscopy over the last decade.

    PubMed

    Frank, Joachim

    2017-02-01

    In single-particle cryo-electron microscopy (cryo-EM), molecules suspended in a thin aqueous layer are rapidly frozen and imaged at cryogenic temperature in the transmission electron microscope. From the random projection views, a three-dimensional image is reconstructed, enabling the structure of the molecule to be obtained. In this article I discuss technological progress over the past decade, which has, in my own field of study, culminated in the determination of ribosome structure at 2.5-Å resolution. I also discuss likely future improvements in methodology.

  13. 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.

  14. Electronic Structure of Crystalline 4He at High Pressures

    SciTech Connect

    Mao, Ho Kwang; Shirley, Eric L.; Ding, Yang; Eng, Peter; Cai, Yong Q.; Chow, Paul; Xiao, Yuming; Jinfu Shu, A=Kao, Chi-Chang; Hemley, Russell J.; Kao, Chichang; Mao, Wendy L.; /Stanford U., Geo. Environ. Sci. /SLAC

    2011-01-10

    Using inelastic X-ray scattering techniques, we have succeeded in probing the high-pressure electronic structure of helium crystal at 300 K which has the widest known electronic energy bandgap of all materials, that was previously inaccessible to measurements due to the extreme energy and pressure range. We observed rich electron excitation spectrum, including a cut-off edge above 23 eV, a sharp exciton peak showing linear volume dependence, and a series of excitations and continuum at 26 to 45 eV. We determined electronic dispersion along the {Gamma}-M direction over two Brillouin zones, and provided a quantitative picture of the helium exciton beyond the simplified Wannier-Frenkel description.

  15. Modulated structures in calcian dolomite: A study by electron microscopy

    NASA Astrophysics Data System (ADS)

    van Tendeloo, G.; Wenk, H. R.; Gronsky, R.

    1985-11-01

    Calcian dolomite from the Devonian Lost Burro formation has been investigated with electron microscopy techniques. Electron diffraction shows evidence for “c” and “d” type reflections which may occur independently and are indicative of ordered superstructures. High resolution electron microscopy combined with selected area optical diffraction is the basis for models to explain the superstructures in calcian dolomite. It is proposed that “c” reflections are due to ordered substitution of Mg by Ca in basal cation layers. “d” reflections result when the rhombohedral stacking of basal layers is interrupted by intercalation of additional Ca layers. During electron irradiation at 1 MeV the Mg-Ca distribution becomes disordered and the crystal structure attains calcite symmetry. The arrangement of CO3 groups remains ordered.

  16. Electronic structure and isomer shifts of neptunium compounds

    NASA Astrophysics Data System (ADS)

    Svane, A.; Petit, L.; Temmerman, W. M.; Szotek, Z.

    2002-08-01

    The electronic structures of αNp metal and 28 Np compounds are calculated with the generalized gradient approximation to density-functional theory, implemented with the full-potential linear-muffin-tin-orbital method. The calculations are compared to experimental isomer shifts providing a calibration of the 237Np isomeric transition with a value of Δ=(-40.1+/-1.3)×10- 3 fm2 for the difference in nuclear radius between the excited isomeric level and the ground state. The isomer shift is primarily determined by the chemical environment. Decreasing the volume, either by external or chemical pressure, causes an f-->s+d charge transfer on Np, which leads to a higher electron contact density. The possible f-electron localization in Np compounds is discussed using self-interaction corrections, and it is concluded that f-electron localization has only a minor influence on the isomer shift.

  17. Superconducting properties and electronic structure of NaBi.

    PubMed

    Kushwaha, S K; Krizan, J W; Xiong, J; Klimczuk, T; Gibson, Q D; Liang, T; Ong, N P; Cava, R J

    2014-05-28

    Resistivity, dc magnetization, and heat capacity measurements are reported for superconducting NaBi. T(c), the electronic contribution to the specific heat γ, the ΔC(p)/γT(c) ratio, and the Debye temperature are found to be 2.15 K, 3.4 mJ mol(-1) K(-2), 0.78, and 140 K respectively. The calculated electron-phonon coupling constant (λ(ep) = 0.62) implies that NaBi is a moderately coupled superconductor. The upper critical field and coherence length are found to be 250 Oe and 115 nm, respectively. Electronic structure calculations show NaBi to be a good metal, in agreement with the experiments; the p(x) and p(y) orbitals of Bi dominate the electronic states at the Fermi Energy.

  18. Surface crystallography and electronic structure of potassium yttrium tungstate

    SciTech Connect

    Atuchin, V. V.; Pokrovsky, L. D.; Khyzhun, O. Yu.; Sinelnichenko, A. K.; Ramana, C. V.

    2008-08-01

    Structural and electronic characteristics of KY(WO{sub 4}){sub 2} (KYW) (010) crystal surfaces have been studied using reflection high-energy electron diffraction (RHEED) and x-ray photoelectron spectroscopy (XPS). The results indicate that the crystal structure and chemical composition of the mechanically polished pristine surface is stoichiometrically well maintained as expected for KYW crystals. Combined measurements of RHEED and XPS as a function of 1.5 keV Ar{sup +} ion irradiation of the KYW (010) surfaces indicate amorphization, partial loss of potassium atoms, and partial transformation of chemical valence state of tungsten from W{sup 6+} to a lower valence state, W{sup 0} state predominantly, which induces electronic states at the top of valence band.

  19. Structural and electronic properties of a tetrahedral amorphous carbon surface

    NASA Astrophysics Data System (ADS)

    Dong, Jianjun; Drabold, D. A.

    1997-03-01

    We present ab initio studies of a model of tetrahedral amorphous carbon (ta-C) surface. Our methodology is LDA (with Harris functional and local basis) molecular dynamics simulations. The surface is modeled by a 216 atom slab supercell. Several candidate slabs are constructed by starting with the DTW model (B.R. Djordjevic, M.F. Thorpe and F. Wooten, Phys. Rev. B 52) 5685 (1995) and applying various simulated heating/quenching cycles. We analyze the structural and electronic properties of the surface , with special attention forcused on the electronic signatures of surface structural defects. Preliminary results indicate that the surface layer significantly graphitizes, and many surface gap states are present in the electronic density of states.

  20. Electronic, magnetic, and geometric structure of metallo-carbohedrenes

    SciTech Connect

    Reddy, B.V.; Khanna, S.N.; Jena, P. )

    1992-12-04

    The energetics and the electronic, magnetic, and geometric structure of the metallocarbohedrene Ti[sub 8]C[sub 12] have been calculated self-consistently in the density functional formulation. The structure of Ti[sub 8]C[sub 12] is a distorted dodecahedron with a binding energy of 6.1 electron volts per atom. The unusual stability is derived from covalent-like bonding between carbon atoms and between titanium and carbon atoms with no appreciable interaction between titanium atoms. The density of states at the Fermi energy is high and is derived from a strong hybridization between titanium 3d and carbon sp electrons. Titanium sites carry a small magnetic moment of 0.35 Bohr magneton per atom and the cluster is only weakly magnetic. 13 refs., 3 figs., 1 tab.

  1. Advance in orientation microscopy: quantitative analysis of nanocrystalline structures.

    PubMed

    Seyring, Martin; Song, Xiaoyan; Rettenmayr, Markus

    2011-04-26

    The special properties of nanocrystalline materials are generally accepted to be a consequence of the high density of planar defects (grain and twin boundaries) and their characteristics. However, until now, nanograin structures have not been characterized with similar detail and statistical relevance as coarse-grained materials, due to the lack of an appropriate method. In the present paper, a novel method based on quantitative nanobeam diffraction in transmission electron microscopy (TEM) is presented to determine the misorientation of adjacent nanograins and subgrains. Spatial resolution of <5 nm can be achieved. This method is applicable to characterize orientation relationships in wire, film, and bulk materials with nanocrystalline structures. As a model material, nanocrystalline Cu is used. Several important features of the nanograin structure are discovered utilizing quantitative analysis: the fraction of twin boundaries is substantially higher than that observed in bright-field images in the TEM; small angle grain boundaries are prominent; there is an obvious dependence of the grain boundary characteristics on grain size distribution and mean grain size.

  2. Electronic origin of structural transition in 122 Fe based superconductors

    NASA Astrophysics Data System (ADS)

    Ghosh, Haranath; Sen, Smritijit; Ghosh, Abyay

    2017-03-01

    Direct quantitative correlations between the orbital order and orthorhombicity is achieved in a number of Fe-based superconductors of 122 family. The former (orbital order) is calculated from first principles simulations using experimentally determined doping and temperature dependent structural parameters while the latter (the orthorhombicity) is taken from already established experimental studies; when normalized, both the above quantities quantitatively corresponds to each other in terms of their doping as well as temperature variations. This proves that the structural transition in Fe-based materials is electronic in nature due to orbital ordering. An universal correlations among various structural parameters and electronic structure are also obtained. Most remarkable among them is the mapping of two Fe-Fe distances in the low temperature orthorhombic phase, with the band energies Edxz, Edyz of Fe at the high symmetry points of the Brillouin zone. The fractional co-ordinate zAs of As which essentially determines anion height is inversely (directly) proportional to Fe-As bond distances (with exceptions of K doped BaFe2As2) for hole (electron) doped materials as a function of doping. On the other hand, Fe-As bond-distance is found to be inversely (directly) proportional to the density of states at the Fermi level for hole (electron) doped systems. Implications of these results to current issues of Fe based superconductivity are discussed.

  3. 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.

  4. Electron Heat Flux in Pressure Balance Structures at Ulysses

    NASA Technical Reports Server (NTRS)

    Yamauchi, Yohei; Suess, Steven T.; Sakurai, Takashi; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Pressure balance structures (PBSs) are a common feature in the high-latitude solar wind near solar minimum. Rom previous studies, PBSs are believed to be remnants of coronal plumes and be related to network activity such as magnetic reconnection in the photosphere. We investigated the magnetic structures of the PBSs, applying a minimum variance analysis to Ulysses/Magnetometer data. At 2001 AGU Spring meeting, we reported that PBSs have structures like current sheets or plasmoids, and suggested that they are associated with network activity at the base of polar plumes. In this paper, we have analyzed high-energy electron data at Ulysses/SWOOPS to see whether bi-directional electron flow exists and confirm the conclusions more precisely. As a result, although most events show a typical flux directed away from the Sun, we have obtained evidence that some PBSs show bi-directional electron flux and others show an isotropic distribution of electron pitch angles. The evidence shows that plasmoids are flowing away from the Sun, changing their flow direction dynamically in a way not caused by Alfven waves. From this, we have concluded that PBSs are generated due to network activity at the base of polar plumes and their magnetic structures axe current sheets or plasmoids.

  5. Structural and electronic properties of perylene from first principles calculations.

    PubMed

    Fedorov, I A; Zhuravlev, Y N; Berveno, V P

    2013-03-07

    The electronic structure of crystalline perylene has been investigated within the framework of density functional theory including van der Waals interactions. The computations of the lattice parameters and cohesive energy have good agreement with experimental values. We have also calculated the binding distance and energy of perylene dimers, using different schemes, which include van der Waals interactions.

  6. Geometric and electronic structures of potassium-adsorbed rubrene complexes

    SciTech Connect

    Li, Tsung-Lung; Lu, Wen-Cai

    2015-06-28

    The geometric and electronic structures of potassium-adsorbed rubrene complexes are studied in this article. It is found that the potassium-rubrene (K{sub 1}RUB) complexes inherit the main symmetry characteristics from their pristine counterparts and are thus classified into D{sub 2}- and C{sub 2h}-like complexes according to the relative orientations of the four phenyl side groups. The geometric structures of K{sub 1}RUB are governed by two general effects on the total energy: Deformation of the carbon frame of the pristine rubrene increases the total energy, while proximity of the potassium ion to the phenyl ligands decreases the energy. Under these general rules, the structures of D{sub 2}- and C{sub 2h}-like K{sub 1}RUB, however, exhibit their respective peculiarities. These peculiarities can be illustrated by their energy profiles of equilibrium structures. For the potassium adsorption-sites, the D{sub 2}-like complexes show minimum-energy basins, whereas the C{sub 2h}-like ones have single-point minimum-energies. If the potassium atom ever has the energy to diffuse from the minimum-energy site, the potassium diffusion path on the D{sub 2}-like complexes is most likely along the backbone in contrast to the C{sub 2h}-like ones. Although the electronic structures of the minimum-energy structures of D{sub 2}- and C{sub 2h}-like K{sub 1}RUB are very alike, decompositions of their total spectra reveal insights into the electronic structures. First, the spectral shapes are mainly determined by the facts that, in comparison with the backbone carbons, the phenyl carbons have more uniform chemical environments and far less contributions to the electronic structures around the valence-band edge. Second, the electron dissociated from the potassium atom mainly remains on the backbone and has little effects on the electronic structures of the phenyl groups. Third, the two phenyls on the same side of the backbone as the potassium atom have more similar chemical environments

  7. LiNiFe-based layered structure oxide and composite for advanced single layer fuel cells

    NASA Astrophysics Data System (ADS)

    Zhu, Bin; Fan, Liangdong; Deng, Hui; He, Yunjune; Afzal, Muhammad; Dong, Wenjing; Yaqub, Azra; Janjua, Naveed K.

    2016-06-01

    A layered structure metal oxide, LiNi0.1Fe0.90O2-δ (LNF), is explored for the advanced single layer fuel cells (SLFCs). The temperature dependent impedance profiles and concentration cells (hydrogen concentration, oxygen concentration, and H2/air atmospheres) tests prove LNF to be an intrinsically electronic conductor in air while mixed electronic and proton conductor in H2/air environment. SLFCs constructed by pure LNF materials show significant short circuiting reflected by a low device OCV and power output (175 mW cm-2 at 500 °C) due to high intrinsic electronic conduction. The power output is improved up to 640 and 760 mW cm-2, respectively at 500 and 550 °C by compositing LNF with ion conducting material, e.g., samarium doped ceria (SDC), to balance the electronic and ionic conductivity; both reached at 0.1 S cm-1 level. Such an SLFC gives super-performance and simplicity over the conventional 3-layer (anode, electrolyte and cathode) FCs, suggesting strong scientific and commercial impacts.

  8. The role of quantum effects on structural and electronic fluctuations in neat and charged water.

    PubMed

    Giberti, Federico; Hassanali, Ali A; Ceriotti, Michele; Parrinello, Michele

    2014-11-20

    In this work, we revisit the role of nuclear quantum effects on the structural and electronic properties of the excess proton in bulk liquid water using advanced molecular dynamics techniques. The hydronium ion is known to be a weak acceptor of a hydrogen bond which gives it some hydrophobic character. Quantum effects reduce the degree of this hydrophobicity which facilitates the fluctuations of the protons along the wires compared to the classical proton. Although the Eigen and Zundel species still appear to be dominant motifs, quantum fluctuations result in rather drastic events where both transient autoionization and delocalization over extended proton wires can simultaneously occur. These wild fluctuations also result in a significant change of the electronic properties of the system such as the broadening of the electronic density of states. An analysis of the Wannier functions indicate that quantum fluctuations of neat water molecules result in transient charging with subtle similarities and differences to that of the excess proton.

  9. Light Water Reactor Sustainability Program Advanced Seismic Soil Structure Modeling

    SciTech Connect

    Bolisetti, Chandrakanth; Coleman, Justin Leigh

    2015-06-01

    Risk calculations should focus on providing best estimate results, and associated insights, for evaluation and decision-making. Specifically, seismic probabilistic risk assessments (SPRAs) are intended to provide best estimates of the various combinations of structural and equipment failures that can lead to a seismic induced core damage event. However, in some instances the current SPRA approach has large uncertainties, and potentially masks other important events (for instance, it was not the seismic motions that caused the Fukushima core melt events, but the tsunami ingress into the facility). SPRA’s are performed by convolving the seismic hazard (this is the estimate of all likely damaging earthquakes at the site of interest) with the seismic fragility (the conditional probability of failure of a structure, system, or component given the occurrence of earthquake ground motion). In this calculation, there are three main pieces to seismic risk quantification, 1) seismic hazard and nuclear power plants (NPPs) response to the hazard, 2) fragility or capacity of structures, systems and components (SSC), and 3) systems analysis. Two areas where NLSSI effects may be important in SPRA calculations are, 1) when calculating in-structure response at the area of interest, and 2) calculation of seismic fragilities (current fragility calculations assume a lognormal distribution for probability of failure of components). Some important effects when using NLSSI in the SPRA calculation process include, 1) gapping and sliding, 2) inclined seismic waves coupled with gapping and sliding of foundations atop soil, 3) inclined seismic waves coupled with gapping and sliding of deeply embedded structures, 4) soil dilatancy, 5) soil liquefaction, 6) surface waves, 7) buoyancy, 8) concrete cracking and 9) seismic isolation The focus of the research task presented here-in is on implementation of NLSSI into the SPRA calculation process when calculating in-structure response at the area

  10. Gold-copper nanostars as photo-thermal agents: synthesis and advanced electron microscopy characterization

    NASA Astrophysics Data System (ADS)

    Bazán-Díaz, Lourdes; Mendoza-Cruz, Rubén; Velázquez-Salazar, J. Jesús; Plascencia-Villa, Germán; Romeu, David; Reyes-Gasga, José; Herrera-Becerra, Raúl; José-Yacamán, Miguel; Guisbiers, Grégory

    2015-12-01

    Nanoalloys have emerged as multi-functional nanoparticles with applications in biomedicine and catalysis. This work reports the efficient production and the advanced transmission electron microscopy characterization of gold-copper pentagonal nanostars. The morphology of the branches is controlled by the adequate choice of the capping agent. When oleylamine is used rounded nanostars are produced, while pointed nanostars are obtained by using hexadecylamine. Both types of nanostars were proved to be thermally stable and could therefore be used as therapeutic agents in photo-thermal therapies as confirmed by the near-infrared absorption spectra.Nanoalloys have emerged as multi-functional nanoparticles with applications in biomedicine and catalysis. This work reports the efficient production and the advanced transmission electron microscopy characterization of gold-copper pentagonal nanostars. The morphology of the branches is controlled by the adequate choice of the capping agent. When oleylamine is used rounded nanostars are produced, while pointed nanostars are obtained by using hexadecylamine. Both types of nanostars were proved to be thermally stable and could therefore be used as therapeutic agents in photo-thermal therapies as confirmed by the near-infrared absorption spectra. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06491k

  11. Relationship of decrease in fecundity with advancing age to structural changes in mouse endometrium

    PubMed Central

    SHIMIZU, KIYOSHI; YAMADA, JINZO

    2000-01-01

    The aim of this study was to determine whether a relationship exists between decrease in fecundity and structural changes in the antimesometrial endometrium of the mouse. Fecundity was calculated as the number of animals showing a placental sign/number of copulated animals ×100 (%). Structural changes in the endometrium were examined by electron microscopy. A negative correlation between age and fecundity was found. Fecundity was 50% at 7 mo of age. At this age, amorphous material appeared in the region between the basement membrane deep to the luminal epithelium and the subepithelial cells. This material was sometimes attached to the basement membrane. It increased in amount with advancing age, as fecundity decreased. The structure of the uterine luminal epithelial cells did not alter with age. The results indicated that decrease in fecundity with advancing age is correlated with the appearance of amorphous material beneath the basal lamina of the endometrial epithelium. It is suggested that this could impair communication between the luminal epithelium and the endometrial stroma, which plays an important role in implantation. PMID:10697293

  12. Advanced photonic, electronic, and web engineering systems: WILGA Symposium, January 2013

    NASA Astrophysics Data System (ADS)

    Romaniuk, Ryszard S.

    2013-10-01

    The cycle of WILGA Symposia [wilga.ise.pw.edu.pl] on Photonics and Web Engineering, Advanced Electronic Systems, under the auspices of SPIE, IEEE, KEiT PAN and WEiTI PW was initiated in 1998 by a Research Team PERG/ELHEP ISE PW. The WILGA conferences take place two times a year and the participants are young scientists from this country and abroad. This paper debates chosen topical tracks and some papers presented during the 31 WILGA Multi-Conference, which took place on 8-10 February 2013 at the Faculty of WEiTI PW. The January conference was attended by around 100 persons. Here we discuss closer the subjects of biomedical photonics, electronics and informatics, as well as chosen aspects of applications of advanced photonic, electronic circuits and systems. The 32 nd WILGA Symposium took place on 27 May - 02 June 2013 in WUT WILGA resort near Warsaw. These two editions of WILGA Conferences - January and May have generated more than 250 articles, from which around 100 were chosen by the Symposium and Conference Committees to be published in this volume of Proc.SPIE. WILGA Symposium papers are traditionally submitted via the WILGA web page [wilga.ise.pw.edu.pl] to the SPIE Proceedings publishing system [spie.org]. Email for the correspondence is: photonics@ise.pw.edu.pl. All Wilga papers are published in journals Elektronika, IJET-PAN and in Proc.SPIE. Topical tracks of the symposium usually embrace, among others, new technologies for photonics, sensory and nonlinear optical fibers, object oriented design of hardware, photonic metrology, optoelectronics and photonics applications, photonics-electronics co-design, optoelectronic and electronic systems for astronomy and high energy physics experiments, JET and pi-of-the sky experiments development. The symposium In its two editions a year is a summary of the development of numerable Ph.D. theses carried out in this country and this geographical region in the area of advanced electronic and photonic systems. It is also

  13. DOE FreedomCAR and vehicle technologies program advanced power electronic and electrical machines annual review report

    SciTech Connect

    Olszewski, Mitch

    2006-10-11

    This report is a summary of the Review Panel at the FY06 DOE FreedomCAR and Vehicle Technologies (FCVT) Annual Review of Advanced Power Electronics and Electric Machine (APEEM) research activities held on August 15-17, 2006.

  14. Writing Electron Dot Structures: Abstract of Issue 9905M

    NASA Astrophysics Data System (ADS)

    Magnell, Kenneth R.

    1999-10-01

    Writing Electron Dot Structures is a computer program for Mac OS that provides drill with feedback for students learning to write electron dot structures. While designed for students in the first year of college general chemistry it may also be used by high school chemistry students. A systematic method similar to that found in many general chemistry texts is employed:

    1. determine the number of valence shell electrons,
    2. select the central atom,
    3. construct a skeleton,
    4. add electrons to complete octets,
    5. examine the structure for resonance forms.
    During the construction of a structure, the student has the option of quitting, selecting another formula, or returning to a previous step. If an incorrect number of electrons is entered the student may not proceed until the correct number is entered. The symbol entered for the central atom must follow accepted upper/lower case practice, and entry of the correct symbol must be accomplished before proceeding to the next step. A periodic table is accessible and feedback provides assistance for these steps. Construction of the skeleton begins with the placement of the central atom. Atoms can be added, moved, or removed. Prompts and feedback keep the student informed of progress and problems. A correct skeleton is required before proceeding to the next step. Completion of the structure begins with the addition of electron pairs to form the required bonds. Remaining electrons are added to complete the formation of multiple bonds, assure compliance with the octet rule, and form expanded octets. Resonance forms are made by moving or removing and replacing electron pairs in the existing skeleton. Prompts and feedback guide the student through this process. A running tally of bond pairs, unshared pairs, octets, electrons used, and electrons remaining is provided during this step. Structural and Electronic Investigations of Complex Intermetallic Compounds

    SciTech Connect

    Ko, Hyunjin

    2008-01-01

    In solid state chemistry, numerous investigations have been attempted to address the relationships between chemical structure and physical properties. Such questions include: (1) How can we understand the driving forces of the atomic arrangements in complex solids that exhibit interesting chemical and physical properties? (2) How do different elements distribute themselves in a solid-state structure? (3) Can we develop a chemical understanding to predict the effects of valence electron concentration on the structures and magnetic ordering of systems by both experimental and theoretical means? Although these issues are relevant to various compound classes, intermetallic compounds are especially interesting and well suited for a joint experimental and theoretical effort. For intermetallic compounds, the questions listed above are difficult to answer since many of the constituent atoms simply do not crystallize in the same manner as in their separate, elemental structures. Also, theoretical studies suggest that the energy differences between various structural alternatives are small. For example, Al and Ga both belong in the same group on the Periodic Table of Elements and share many similar chemical properties. Al crystallizes in the fcc lattice with 4 atoms per unit cell and Ga crystallizes in an orthorhombic unit cell lattice with 8 atoms per unit cell, which are both fairly simple structures (Figure 1). However, when combined with Mn, which itself has a very complex cubic crystal structure with 58 atoms per unit cell, the resulting intermetallic compounds crystallize in a completely different fashion. At the 1:1 stoichiometry, MnAl forms a very simple tetragonal lattice with two atoms per primitive unit cell, while MnGa crystallizes in a complicated rhombohedral unit cell with 26 atoms within the primitive unit cell. The mechanisms influencing the arrangements of atoms in numerous crystal structures have been studied theoretically by calculating electronic

  15. Understanding the structure of nanocatalysts with high resolution scanning/transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Francis, L. D.; Rivas, J.; José-Yacamán, M.

    2014-03-01

    Nanomaterials including nanoparticles, nanowires and nanotubes play an important role in heterogeneous catalysis. Thanks to the rapid improvement of the electron microscopic techniques and with the advent of aberration corrected electron microscopy as well as theoretical methodologies, the potential effects induced by nanocatalysts are better understood than before by unravelling their atomic structure. A brief introduction to advanced electron microscopic techniques namely aberration corrected scanning transmission electron microscopy (Cs-STEM) is presented and subsequently two examples of nanocatalysts are considered in the present review. The first example will focus on the study of bimetallic/core-shell nanoalloys. In heterogeneous catalysis, catalysts containing two or more metals might show significantly different catalytic properties compared to the parent metals and thus are widely utilized in several catalytic reactions. Atom-by-atom insights of the nanoalloy based catalysts ex: Au-Pd will be described in the present review using a combination of advanced electron microscopic and spectroscopic techniques. A related example on the understanding of bimetallic clusters by HAADF-STEM will also be presented in addition to nanoparticles. In the second case understanding the structure of transition metal chalcogenide based nanocatalysts by HRTEM and aberration corrected STEM, for the case of MoS2 will be discussed. MoS2-based catalysts serve as model catalysts and are employed in the hydrodesulphurisations (HDS) reactions in the removal of sulphur from gasoline and related petrochemical products. They have been studied in various forms including nanowires, nanotubes and nanoplates. Their structure, atomic insights and as a consequence elucidation of their corresponding catalytic activity are thus important.

  16. Shigella flexneri Spa15 Crystal Structure Verified in Solution by Double Electron Electron Resonance

    PubMed Central

    Lillington, James E.D.; Lovett, Janet E.; Johnson, Steven; Roversi, Pietro; Timmel, Christiane R.; Lea, Susan M.

    2011-01-01

    Shigella flexneri Spa15 is a chaperone of the type 3 secretion system, which binds a number of effectors to ensure their stabilization prior to secretion. One of these effectors is IpgB1, a mimic of the human Ras-like Rho guanosine triphosphatase RhoG. In this study, Spa15 alone and in complex with IpgB1 has been studied by double electron electron resonance, an experiment that gives distance information showing the spacial separation of attached spin labels. This distance is explained by determining the crystal structure of the spin-labeled Spa15 where labels are seen to be buried in hydrophobic pockets. The double electron electron resonance experiment on the Spa15 complex with IpgB1 shows that IpgB1 does not bind Spa15 in the same way as is seen in the homologous Salmonella sp. chaperone:effector complex InvB:SipA. PMID:21075116

  17. Advanced glycation end products induce differential structural modifications and fibrillation of albumin

    NASA Astrophysics Data System (ADS)

    Awasthi, Saurabh; Sankaranarayanan, Kamatchi; Saraswathi, N. T.

    2016-06-01

    Glycation induced amyloid fibrillation is fundamental to the development of many neurodegenerative and cardiovascular complications. Excessive non-enzymatic glycation in conditions such as hyperglycaemia results in the increased accumulation of advanced glycation end products (AGEs). AGEs are highly reactive pro-oxidants, which can lead to the activation of inflammatory pathways and development of oxidative stress. Recently, the effect of non-enzymatic glycation on protein structure has been the major research area, but the role of specific AGEs in such structural alteration and induction of fibrillation remains undefined. In this study, we determined the specific AGEs mediated structural modifications in albumin mainly considering carboxymethyllysine (CML), carboxyethyllysine (CEL), and argpyrimidine (Arg-P) which are the major AGEs formed in the body. We studied the secondary structural changes based on circular dichroism (CD) and spectroscopic analysis. The AGEs induced fibrillation was determined by Congo red binding and examination of scanning and transmission electron micrographs. The amyloidogenic regions in the sequence of BSA were determined using FoldAmyloid. It was observed that CEL modification of BSA leads to the development of fibrillar structures, which was evident from both secondary structure changes and TEM analysis.

  18. Electronic structure tuning via surface modification in semimetallic nanowires

    NASA Astrophysics Data System (ADS)

    Sanchez-Soares, Alfonso; O'Donnell, Conor; Greer, James C.

    2016-12-01

    Electronic structure properties of nanowires (NWs) with diameters of 1.5 and 3 nm based on semimetallic α -Sn are investigated by employing density functional theory and perturbative GW methods. We explore the dependence of electron affinity, band structure, and band-gap values with crystallographic orientation, NW cross-sectional size, and surface passivants of varying electronegativity. We consider four chemical terminations in our study: methyl (CH3), hydrogen (H ), hydroxyl (OH ), and fluorine (F ). Results suggest a high degree of elasticity of Sn-Sn bonds within the Sn NWs' cores with no significant structural variations for nanowires with different surface passivants. Direct band gaps at Brillouin-zone centers are found for most studied structures with quasiparticle corrected band-gap magnitudes ranging from 0.25 to 3.54 eV in 1.5-nm-diameter structures, indicating an exceptional range of properties for semimetal NWs below the semimetal-to-semiconductor transition. Band-gap variations induced by changes in surface passivants indicate the possibility of realizing semimetal-semiconductor interfaces in NWs with constant cross-section and crystallographic orientation, allowing the design of novel dopant-free NW-based electronic devices.

  19. Molecular and electronic structures of cerium and cerium suboxide clusters

    NASA Astrophysics Data System (ADS)

    Kafader, Jared O.; Topolski, Josey E.; Jarrold, Caroline Chick

    2016-10-01

    The anion photoelectron (PE) spectra of Ce2Oy- (y = 1, 2), Ce3Oy- (y = 0-4), Ce4Oy- (y = 0-2), and Ce5Oy- (y = 1, 2) are reported and analyzed with supporting results from density functional theory calculations. The PE spectra all exhibit an intense electronic transition to the neutral ground state, all falling in the range of 0.7 to 1.1 eV electron binding energy, with polarization dependence consistent with detachment from diffuse Ce 6s-based molecular orbitals. There is no monotonic increase in electron affinity with increasing oxidation. A qualitative picture of how electronic structure evolves with an oxidation state emerges from comparison between the spectra and the computational results. The electronic structure of the smallest metallic cluster observed in this study, Ce3, is similar to the bulk structure in terms of atomic orbital occupancy (4f 5d2 6s). Initial cerium cluster oxidation involves largely ionic bond formation via Ce 5d and O 2p orbital overlap (i.e., larger O 2p contribution), with Ce—O—Ce bridge bonding favored over Ce=O terminal bond formation. With subsequent oxidation, the Ce 5d-based molecular orbitals are depleted of electrons, with the highest occupied orbitals described as diffuse Ce 6s based molecular orbitals. In the y ≤ (x + 1) range of oxidation states, each Ce center has a singly occupied non-bonding 4f orbital. The PE spectrum of Ce3O4- is unique in that it exhibits a single nearly vertical transition. The highly symmetric structure predicted computationally is the same structure determined from Ce3O4+ IR predissociation spectra [A. M. Burow et al., Phys. Chem. Chem. Phys. 13, 19393 (2011)], indicating that this structure is stable in -1, 0, and +1 charge states. Spectra of clusters with x ≥ 3 exhibit considerable continuum signal above the ground state transition; the intensity of the continuum signal decreases with increasing oxidation. This feature is likely the result of numerous quasi-bound anion states or two-electron

  1. Defective graphene and nanoribbons: electronic, magnetic and structural properties

    NASA Astrophysics Data System (ADS)

    Guerra, Thiago; Azevedo, Sérgio; Machado, Marcelo

    2016-03-01

    We make use of first-principles calculations, based on the density functional theory (DFT), to investigate the alterations at the structural, energetic, electronic and magnetic properties of graphene and zigzag graphene nanoribbons (ZGNRs) due to the inclusion of different types of line and punctual defects. For the graphene it is found that the inclusion of defects breaks the translational symmetry of the crystal with drastic changes at its electronic structure, going from semimetallic to semiconductor and metallic. Regarding the magnetic properties, no magnetization is observed for the defective graphene. We also show that the inclusion of defects at ZGNRs is a good way to create and control pronounced peaks at the Fermi level. Furthermore, defective ZGNRs structures show magnetic moment by supercell up to 2.0 μ B . For the non defective ZGNRs is observed a switch of the magnetic coupling between opposite ribbon edges from the antiferromagnetic to the ferrimagnetic and ferromagnetic configurations.

  2. Biomechanics of DNA structures visualized by 4D electron microscopy

    PubMed Central

    Lorenz, Ulrich J.; Zewail, Ahmed H.

    2013-01-01

    We present a technique for in situ visualization of the biomechanics of DNA structural networks using 4D electron microscopy. Vibrational oscillations of the DNA structure are excited mechanically through a short burst of substrate vibrations triggered by a laser pulse. Subsequently, the motion is probed with electron pulses to observe the impulse response of the specimen in space and time. From the frequency and amplitude of the observed oscillations, we determine the normal modes and eigenfrequencies of the structures involved. Moreover, by selective “nano-cutting” at a given point in the network, it was possible to obtain Young’s modulus, and hence the stiffness, of the DNA filament at that position. This experimental approach enables nanoscale mechanics studies of macromolecules and should find applications in other domains of biological networks such as origamis. PMID:23382239

  3. Characterization of electronic structure of periodically strained graphene

    SciTech Connect

    Aslani, Marjan; Garner, C. Michael Nishi, Yoshio; Kumar, Suhas; Nordlund, Dennis; Pianetta, Piero

    2015-11-02

    We induced periodic biaxial tensile strain in polycrystalline graphene by wrapping it over a substrate with repeating pillar-like structures with a periodicity of 600 nm. Using Raman spectroscopy, we determined to have introduced biaxial strains in graphene in the range of 0.4% to 0.7%. Its band structure was characterized using photoemission from valance bands, shifts in the secondary electron emission, and x-ray absorption from the carbon 1s levels to the unoccupied graphene conduction bands. It was observed that relative to unstrained graphene, strained graphene had a higher work function and higher density of states in the valence and conduction bands. We measured the conductivity of the strained and unstrained graphene in response to a gate voltage and correlated the changes in their behavior to the changes in the electronic structure. From these sets of data, we propose a simple band diagram representing graphene with periodic biaxial strain.

  4. Characterization of electronic structure of periodically strained graphene

    SciTech Connect

    Aslani, Marjan; Garner, C. Michael; Kumar, Suhas; Nordlund, Dennis; Pianetta, Piero; Nishi, Yoshio

    2015-11-03

    We induced periodic biaxial tensile strain in polycrystalline graphene by wrapping it over a substrate with repeating pillar-like structures with a periodicity of 600 nm. Using Raman spectroscopy, we determined to have introduced biaxial strains in graphene in the range of 0.4% to 0.7%. Its band structure was characterized using photoemission from valance bands, shifts in the secondary electron emission, and x-ray absorption from the carbon 1s levels to the unoccupied graphene conduction bands. It was observed that relative to unstrained graphene, strained graphene had a higher work function and higher density of states in the valence and conduction bands. Furthermore, we measured the conductivity of the strained and unstrained graphene in response to a gate voltage and correlated the changes in their behavior to the changes in the electronic structure. From these sets of data, we propose a simple band diagram representing graphene with periodic biaxial strain.

  5. Local atomic order, electronic structure and electron transport properties of Cu-Zr metallic glasses

    NASA Astrophysics Data System (ADS)

    Antonowicz, J.; Pietnoczka, A.; Pekała, K.; Latuch, J.; Evangelakis, G. A.

    2014-05-01

    We studied atomic and electronic structures of binary Cu-Zr metallic glasses (MGs) using combined experimental and computational methods including X-ray absorption fine structure spectroscopy, electrical resistivity, thermoelectric power (TEP) measurements, molecular dynamics (MD) simulations, and ab-initio calculations. The results of MD simulations and extended X-ray absorption fine structure analysis indicate that atomic order of Cu-Zr MGs and can be described in terms of interpenetrating icosahedral-like clusters involving five-fold symmetry. MD configurations were used as an input for calculations of theoretical electronic density of states (DOS) functions which exhibits good agreement with the experimental X-ray absorption near-edge spectra. We found no indication of minimum of DOS at Fermi energy predicted by Mott's nearly free electron (NFE) model for glass-forming alloys. The theoretical DOS was subsequently used to test Mott's model describing the temperature variation of electrical resistivity and thermoelectric power of transition metal-based MGs. We demonstrate that the measured temperature variations of electrical resistivity and TEP remain in a contradiction with this model. On the other hand, the experimental temperature dependence of electrical resistivity can be explained by incipient localization of conduction electrons. It is shown that weak localization model works up to relatively high temperatures when localization is destroyed by phonons. Our results indicate that electron transport properties of Cu-Zr MGs are dominated by localization effects rather than by electronic structure. We suggest that NFE model fails to explain a relatively high glass-forming ability of binary Cu-Zr alloys.

  6. Local atomic order, electronic structure and electron transport properties of Cu-Zr metallic glasses

    SciTech Connect

    Antonowicz, J. Pietnoczka, A.; Pękała, K.; Latuch, J.; Evangelakis, G. A.

    2014-05-28

    We studied atomic and electronic structures of binary Cu-Zr metallic glasses (MGs) using combined experimental and computational methods including X-ray absorption fine structure spectroscopy, electrical resistivity, thermoelectric power (TEP) measurements, molecular dynamics (MD) simulations, and ab-initio calculations. The results of MD simulations and extended X-ray absorption fine structure analysis indicate that atomic order of Cu-Zr MGs and can be described in terms of interpenetrating icosahedral-like clusters involving five-fold symmetry. MD configurations were used as an input for calculations of theoretical electronic density of states (DOS) functions which exhibits good agreement with the experimental X-ray absorption near-edge spectra. We found no indication of minimum of DOS at Fermi energy predicted by Mott's nearly free electron (NFE) model for glass-forming alloys. The theoretical DOS was subsequently used to test Mott's model describing the temperature variation of electrical resistivity and thermoelectric power of transition metal-based MGs. We demonstrate that the measured temperature variations of electrical resistivity and TEP remain in a contradiction with this model. On the other hand, the experimental temperature dependence of electrical resistivity can be explained by incipient localization of conduction electrons. It is shown that weak localization model works up to relatively high temperatures when localization is destroyed by phonons. Our results indicate that electron transport properties of Cu-Zr MGs are dominated by localization effects rather than by electronic structure. We suggest that NFE model fails to explain a relatively high glass-forming ability of binary Cu-Zr alloys.

  7. Theoretical Studies of the Electronic Structure of the Compounds of the Actinide Elements

    SciTech Connect

    Kaltsoyannis, Nikolas; Hay, P. Jeffrey; Li, Jun; Blaudeau, Jean-Philippe; Bursten, Bruce E.

    2006-02-02

    structure of actinide systems have developed in concert with the experimental studies, and have been greatly facilitated by the extraordinary recent advances in high-performance computational technology. We will focus on computational studies of the electronic structure of discrete (molecular or ionic) actinide-containing systems. We begin by discussing some of the general tenets of bonding that are relevant to the actinide elements and some of the challenges that are unique to this field. We then present the results of computational electronic structure studies on a variety of molecular actinide systems. The literature of molecular electronic structure of actinide systems has been compiled by Pyykko¨ (1986, 1993, 2001), as well as being available as a database on the web (http://www.csc.fi/rtam). Pepper and Bursten (1991) reviewed the methodology and applications in the field in 1991. The reader is referred to those reviews for some of the details on earlier studies in this field. We restrict our discussion in this chapter to molecular actinide systems and do not discuss the extensive body of research in the use of theoretical electronic structure methods to model solid-state actinide chemistry. The reader is referred to Chapter 21 and some recent review articles (Lander et al., 1994; Soderlind, 1998; Wills and Eriksson, 2000) for discussions of theoretical electronic structure methods applied to the metallic actinide elements and solid-state actinide compounds. We will also have minimal discussion of compounds of the transactinide elements in this chapter. The electronic structure of compounds of the transactinides is discussed in Chapter 14 and in the excellent review by Pershina (1996).

  8. Possibilities and limitations of advanced transmission electron microscopy for carbon-based nanomaterials.

    PubMed

    Ke, Xiaoxing; Bittencourt, Carla; Van Tendeloo, Gustaaf

    2015-01-01

    A major revolution for electron microscopy in the past decade is the introduction of aberration correction, which enables one to increase both the spatial resolution and the energy resolution to the optical limit. Aberration correction has contributed significantly to the imaging at low operating voltages. This is crucial for carbon-based nanomaterials which are sensitive to electron irradiation. The research of carbon nanomaterials and nanohybrids, in particular the fundamental understanding of defects and interfaces, can now be carried out in unprecedented detail by aberration-corrected transmission electron microscopy (AC-TEM). This review discusses new possibilities and limits of AC-TEM at low voltage, including the structural imaging at atomic resolution, in three dimensions and spectroscopic investigation of chemistry and bonding. In situ TEM of carbon-based nanomaterials is discussed and illustrated through recent reports with particular emphasis on the underlying physics of interactions between electrons and carbon atoms.

  9. Possibilities and limitations of advanced transmission electron microscopy for carbon-based nanomaterials

    PubMed Central

    Bittencourt, Carla; Van Tendeloo, Gustaaf

    2015-01-01

    Summary A major revolution for electron microscopy in the past decade is the introduction of aberration correction, which enables one to increase both the spatial resolution and the energy resolution to the optical limit. Aberration correction has contributed significantly to the imaging at low operating voltages. This is crucial for carbon-based nanomaterials which are sensitive to electron irradiation. The research of carbon nanomaterials and nanohybrids, in particular the fundamental understanding of defects and interfaces, can now be carried out in unprecedented detail by aberration-corrected transmission electron microscopy (AC-TEM). This review discusses new possibilities and limits of AC-TEM at low voltage, including the structural imaging at atomic resolution, in three dimensions and spectroscopic investigation of chemistry and bonding. In situ TEM of carbon-based nanomaterials is discussed and illustrated through recent reports with particular emphasis on the underlying physics of interactions between electrons and carbon atoms. PMID:26425406

  10. Electronic structure of multi-walled carbon fullerenes

    NASA Astrophysics Data System (ADS)

    Doore, Keith; Cook, Matthew; Clausen, Eric; Lukashev, Pavel V.; Kidd, Tim E.; Stollenwerk, Andrew J.

    2017-02-01

    Despite an enormous amount of research on carbon based nanostructures, relatively little is known about the electronic structure of multi-walled carbon fullerenes, also known as carbon onions. In part, this is due to the very high computational expense involved in estimating electronic structure of large molecules. At the same time, experimentally, the exact crystal structure of the carbon onion is usually unknown, and therefore one relies on qualitative arguments only. In this work we present the results of a computational study on a series of multi-walled fullerenes and compare their electronic structures to experimental data. Experimentally, the carbon onions were fabricated using ultrasonic agitation of isopropanol alcohol and deposited onto the surface of highly ordered pyrolytic graphite using a drop cast method. Scanning tunneling microscopy images indicate that the carbon onions produced using this technique are ellipsoidal with dimensions on the order of 10 nm. The majority of differential tunneling spectra acquired on individual carbon onions are similar to that of graphite with the addition of molecular-like peaks, indicating that these particles span the transition between molecules and bulk crystals. A smaller, yet sizable number exhibited a semiconducting gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels. These results are compared with the electronic structure of different carbon onion configurations calculated using first-principles. Similar to the experimental results, the majority of these configurations are metallic with a minority behaving as semiconductors. Analysis of the configurations investigated here reveals that each carbon onion exhibiting an energy band gap consisted only of non-metallic fullerene layers, indicating that the interlayer interaction is not significant enough to affect the total density of states in these structures.

  11. Unraveling electronic and magnetic structure at cuprate-manganite interfaces

    NASA Astrophysics Data System (ADS)

    Freeland, John

    2014-03-01

    Oxide interfaces offer a rich variety of physics and a pathway to create new classes of functional oxide materials. The interface between the cuprate high-temperature superconductors and ferromagnetic manganites is of particular interest due to the strongly antagonistic nature of the superconducting and ferromagnetic phases. Advancements in the synthesis of oxide heterostructure offers the opportunity to merge these two dissimilar oxides with atomic precision to understand the fundamental limits of bringing such states into close proximity. However, the main challenge is to understand the physical framework that describes the behavior of strongly correlated electrons near oxide interfaces. One aspect that will be addressed here is the use of advanced tools to gain detailed electronic and magnetic information from the boundary region. In this talk, recent work will be addressed both in connection to visualizing the interface with spatially resolved tools as well as harnessing layer-by-layer growth to explore the limits in ultrathin superlattices. These insights allow us to better understand the physics behind the interfacial spin and orbital reconstruction observed in this system. Work at Argonne is supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

  12. Electronic structure and crystal phase stability of palladium hydrides

    SciTech Connect

    Houari, Abdesalem; Matar, Samir F.; Eyert, Volker

    2014-11-07

    The results of electronic structure calculations for a variety of palladium hydrides are presented. The calculations are based on density functional theory and used different local and semilocal approximations. The thermodynamic stability of all structures as well as the electronic and chemical bonding properties are addressed. For the monohydride, taking into account the zero-point energy is important to identify the octahedral Pd-H arrangement with its larger voids and, hence, softer hydrogen vibrational modes as favorable over the tetrahedral arrangement as found in the zincblende and wurtzite structures. Stabilization of the rocksalt structure is due to strong bonding of the 4d and 1s orbitals, which form a characteristic split-off band separated from the main d-band group. Increased filling of the formerly pure d states of the metal causes strong reduction of the density of states at the Fermi energy, which undermines possible long-range ferromagnetic order otherwise favored by strong magnetovolume effects. For the dihydride, octahedral Pd-H arrangement as realized, e.g., in the pyrite structure turns out to be unstable against tetrahedral arrangement as found in the fluorite structure. Yet, from both heat of formation and chemical bonding considerations, the dihydride turns out to be less favorable than the monohydride. Finally, the vacancy ordered defect phase Pd{sub 3}H{sub 4} follows the general trend of favoring the octahedral arrangement of the rocksalt structure for Pd:H ratios less or equal to one.

  13. Electronic structures of Ascaris trypsin inhibitor in solution

    NASA Astrophysics Data System (ADS)

    Zheng, Haoping

    2003-11-01

    The electronic structures of Ascaris trypsin inhibitor in solution are obtained by the first-principles, all-electron, ab initio calculation using the self-consistent cluster-embedding (SCCE) method. The inhibitor, made up of 62 amino acid residues with 912 atoms, has two three-dimensional solution structures: 1ata and 1atb. The calculated ground-state energy of structure 1atb is lower than that of structure 1ata by 6.12 eV. The active sites are determined and explained: only structure 1atb has a N terminal at residue ARG+31. This shows that the structure 1atb is the stable and active form of the inhibitor, which is in agreement with the experimental results. The calculation reveals that some parts of the inhibitor can be easily changed while the inhibitor’s biological activity may be kept. This kind of information may be helpful in fighting viruses such as AIDS, SARS, and flu, since these viruses have higher variability. The calculation offers an independent theoretical estimate of the precision of structure determination.

  14. Electronic structure and crystal phase stability of palladium hydrides

    NASA Astrophysics Data System (ADS)

    Houari, Abdesalem; Matar, Samir F.; Eyert, Volker

    2014-11-01

    The results of electronic structure calculations for a variety of palladium hydrides are presented. The calculations are based on density functional theory and used different local and semilocal approximations. The thermodynamic stability of all structures as well as the electronic and chemical bonding properties are addressed. For the monohydride, taking into account the zero-point energy is important to identify the octahedral Pd-H arrangement with its larger voids and, hence, softer hydrogen vibrational modes as favorable over the tetrahedral arrangement as found in the zincblende and wurtzite structures. Stabilization of the rocksalt structure is due to strong bonding of the 4d and 1s orbitals, which form a characteristic split-off band separated from the main d-band group. Increased filling of the formerly pure d states of the metal causes strong reduction of the density of states at the Fermi energy, which undermines possible long-range ferromagnetic order otherwise favored by strong magnetovolume effects. For the dihydride, octahedral Pd-H arrangement as realized, e.g., in the pyrite structure turns out to be unstable against tetrahedral arrangement as found in the fluorite structure. Yet, from both heat of formation and chemical bonding considerations, the dihydride turns out to be less favorable than the monohydride. Finally, the vacancy ordered defect phase Pd3H4 follows the general trend of favoring the octahedral arrangement of the rocksalt structure for Pd:H ratios less or equal to one.

  15. Uses of electronic health records for public health surveillance to advance public health.

    PubMed

    Birkhead, Guthrie S; Klompas, Michael; Shah, Nirav R

    2015-03-18

    Public health surveillance conducted by health departments in the United States has improved in completeness and timeliness owing to electronic laboratory reporting. However, the collection of detailed clinical information about reported cases, which is necessary to confirm the diagnosis, to understand transmission, or to determine disease-related risk factors, is still heavily dependent on manual processes. The increasing prevalence and functionality of electronic health record (EHR) systems in the United States present important opportunities to advance public health surveillance. EHR data have the potential to further increase the breadth, detail, timeliness, and completeness of public health surveillance and thereby provide better data to guide public health interventions. EHRs also provide a unique opportunity to expand the role and vision of current surveillance efforts and to help bridge the gap between public health practice and clinical medicine.

  16. FY2013 Advanced Power Electronics and Electric Motors R&D Annual Progress Report

    SciTech Connect

    Rogers, Susan A.

    2014-02-01

    The Advanced Power Electronics and Electric Motors (APEEM) technology area within the DOE Vehicle Technologies Office (VTO) provides support and guidance for many cutting-edge automotive technologies now under development. Research is focused on developing revolutionary new power electronics (PE), electric motor, and traction drive system (TDS) technologies that will leapfrog current on-the-road technologies, leading to lower cost and better efficiency in transforming battery energy to useful work. The research and development (R&D) is also aimed at achieving a greater understanding of and improvements in the way the various new components of tomorrow’s automobiles will function as a unified system to improve fuel efficiency through research in more efficient TDSs.

  17. Financing electronic waste recycling Californian households' willingness to pay advanced recycling fees.

    PubMed

    Nixon, Hilary; Saphores, Jean-Daniel M

    2007-09-01

    The growth of electronic waste (e-waste) is of increasing concern because of its toxic content and low recycling rates. The e-waste recycling infrastructure needs to be developed, yet little is known about people's willingness to fund its expansion. This paper examines this issue based on a 2004 mail survey of California households. Using an ordered logit model, we find that age, income, beliefs about government and business roles, proximity to existing recycling facilities, community density, education, and environmental attitudes are significant factors for explaining people's willingness to pay an advanced recycling fee (ARF) for electronics. Most respondents are willing to support a 1% ARF. Our results suggest that policymakers should target middle-aged and older adults, improve programs in communities with existing recycling centers or in rural communities, and consider public-private partnerships for e-waste recycling programs.

  18. Toward the origin of exciton electronic structure in phycobiliproteins

    NASA Astrophysics Data System (ADS)

    Womick, Jordan M.; Miller, Stephen A.; Moran, Andrew M.

    2010-07-01

    Femtosecond laser spectroscopies are used to examine the electronic structures of two proteins found in the phycobilisome antenna of cyanobacteria, allophycocyanin (APC) and C-phycocyanin (CPC). The wave function composition involving the pairs of phycocyanobilin pigments (i.e., dimers) found in both proteins is the primary focus of this investigation. Despite their similar geometries, earlier experimental studies conducted in our laboratory and elsewhere observe clear signatures of exciton electronic structure in APC but not CPC. This issue is further investigated here using new experiments. Transient grating (TG) experiments employing broadband quasicontinuum probe pulses find a redshift in the signal spectrum of APC, which is almost twice that of CPC. Dynamics in the TG signal spectra suggest that the sub-100 fs dynamics in APC and CPC are respectively dominated by internal conversion and nuclear relaxation. A specialized technique, intraband electronic coherence spectroscopy (IECS), photoexcites electronic and nuclear coherences with nearly full suppression of signals corresponding to electronic populations. The main conclusion drawn by IECS is that dephasing of intraband electronic coherences in APC occurs in less than 25 fs. This result rules out correlated pigment fluctuations as the mechanism enabling exciton formation in APC and leads us to propose that the large Franck-Condon factors of APC promote wave function delocalization in the vibronic basis. For illustration, we compute the Hamiltonian matrix elements involving the electronic origin of the α84 pigment and the first excited vibronic level of the β84 pigment associated with a hydrogen out-of-plane wagging mode at 800 cm-1. For this pair of vibronic states, the -51 cm-1 coupling is larger than the 40 cm-1 energy gap, thereby making wave function delocalization a feasible prospect. By contrast, CPC possesses no pair of vibronic levels for which the intermolecular coupling is larger than the energy

  19. Electronic Structure of Fullerene Acceptors in Organic Bulk-Heterojunctions. A Combined EPR and DFT Study

    SciTech Connect

    Mardis, Kristy L.; Webb, J.; Holloway, Tarita; Niklas, Jens; Poluektov, Oleg G.

    2015-12-03

    Organic photovoltaic (OPV) devices are a promising alternative energy source. Attempts to improve their performance have focused on the optimization of electron-donating polymers, while electron-accepting fullerenes have received less attention. Here, we report an electronic structure study of the widely used soluble fullerene derivatives PC61BM and PC71BM in their singly reduced state, that are generated in the polymer:fullerene blends upon light-induced charge separation. Density functional theory (DFT) calculations characterize the electronic structures of the fullerene radical anions through spin density distributions and magnetic resonance parameters. The good agreement of the calculated magnetic resonance parameters with those determined experimentally by advanced electron paramagnetic resonance (EPR) allows the validation of the DFT calculations. Thus, for the first time, the complete set of magnetic resonance parameters including directions of the principal g-tensor axes were determined. For both molecules, no spin density is present on the PCBM side chain, and the axis of the largest g-value lies along the PCBM molecular axis. While the spin density distribution is largely uniform for PC61BM, it is not evenly distributed for PC71BM.

  20. Grid-based electronic structure calculations: The tensor decomposition approach

    SciTech Connect

    Rakhuba, M.V.; Oseledets, I.V.

    2016-05-01

    We present a fully grid-based approach for solving Hartree–Fock and all-electron Kohn–Sham equations based on low-rank approximation of three-dimensional electron orbitals. Due to the low-rank structure the total complexity of the algorithm depends linearly with respect to the one-dimensional grid size. Linear complexity allows for the usage of fine grids, e.g. 8192{sup 3} and, thus, cheap extrapolation procedure. We test the proposed approach on closed-shell atoms up to the argon, several molecules and clusters of hydrogen atoms. All tests show systematical convergence with the required accuracy.

  1. Multi-million atom electronic structure calculations for quantum dots

    NASA Astrophysics Data System (ADS)

    Usman, Muhammad

    Quantum dots grown by self-assembly process are typically constructed by 50,000 to 5,000,000 structural atoms which confine a small, countable number of extra electrons or holes in a space that is comparable in size to the electron wavelength. Under such conditions quantum dots can be interpreted as artificial atoms with the potential to be custom tailored to new functionality. In the past decade or so, these nanostructures have attracted significant experimental and theoretical attention in the field of nanoscience. The new and tunable optical and electrical properties of these artificial atoms have been proposed in a variety of different fields, for example in communication and computing systems, medical and quantum computing applications. Predictive and quantitative modeling and simulation of these structures can help to narrow down the vast design space to a range that is experimentally affordable and move this part of nanoscience to nano-Technology. Modeling of such quantum dots pose a formidable challenge to theoretical physicists because: (1) Strain originating from the lattice mismatch of the materials penetrates deep inside the buffer surrounding the quantum dots and require large scale (multi-million atom) simulations to correctly capture its effect on the electronic structure, (2) The interface roughness, the alloy randomness, and the atomistic granularity require the calculation of electronic structure at the atomistic scale. Most of the current or past theoretical calculations are based on continuum approach such as effective mass approximation or k.p modeling capturing either no or one of the above mentioned effects, thus missing some of the essential physics. The Objectives of this thesis are: (1) to model and simulate the experimental quantum dot topologies at the atomistic scale; (2) to theoretically explore the essential physics i.e. long range strain, linear and quadratic piezoelectricity, interband optical transition strengths, quantum confined

  2. Electronic structures of solids made of C20 clusters

    NASA Astrophysics Data System (ADS)

    Hussain, M. B.; Xu, L. H.; Wu, S. Q.; Zhu, Z. Z.

    2017-02-01

    By performing first-principles calculations based on the density functional theory, we have investigated the optimized structures, cohesive energies and electronic properties of crystalline solids made of C20 clusters. A very interesting result is found from the optimized diamond structure made of C20's, where the dimered C20 clusters, i.e., (C20)2 dimmers, are formed. Such (C20)2 dimers are then condensed by weak van der Waals interaction between them, leading to the formation of a molecular solid. We also found that one-dimensional molecular solid could be formed when C20 clusters are head to head. Results on C20 clusters arranged in the two-dimensional graphene structure and in fcc structure both show that there are significant coalescences of neighboring C20 fullerenes, leading to metallic characters for both the graphene and fcc structures.

  3. Antistiction technique using elastomer contact structure in woven electronic textiles

    NASA Astrophysics Data System (ADS)

    Yamashita, Takahiro; Takamatsu, Seiichi; Miyake, Koji; Itoh, Toshihiro

    2014-01-01

    In this paper, we present an antistiction technique using an elastomer contact structure in woven electronic textiles (e-textiles). A coating of poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate) (PEDOT:PSS) in the form of a solid conductive film on a hemispherical silicone elastomer structure is employed in creating an electrical circuit embedded into the fabric of a woven e-textile, where the contact structure reduces the contact area and capillary force generated by the moisture in air between weft and warp ribbons. Stiction occurs between a weft and a warp without the contact structure under an RH of 80%, and the detachment of the stuck ribbon requires a delamination load of about 0.2 N. On the other hand, in the case of contact between the contact structure and the ribbon coated with plain PEDOT:PSS, stiction does not occur as the relative humidity increases from 20 to 80%.

  4. Fluctuation electron microscopy studies of complex structured materials

    NASA Astrophysics Data System (ADS)

    Zhao, Gongpu; Rougée, Annick; Buseck, Peter; Treacy, Michael

    2008-03-01

    Fluctuation electron microscopy (FEM) is a hybrid imaging-diffraction technique. This technique is particularly sensitive to paracrystalline structures of dimension 0.5-2 nm, which are difficult to detect by either imaging or diffraction techniques alone. It has been successfully deployed to study paracrystalline structures in amorphous silicon, germanium thin film. This technique has also been used to study metallic glasses and oxide glasses. Until now, FEM has not been used to study disordered geological materials. In this talk we present our FEM studies of shungite, a naturally occurring disordered carbonaceous material, reveal that trace quantities of tightly curved graphene structures such as C60, or fragments of C60, is present in shungite. We also present results from our study of metamict zircon, whose crystal structure is destroyed by self-radiation during naturally occurring α decay events. Work is in progress to study the structural evolution during the metamictization process.

  5. Electronic and Thermal Properties of Graphene and Carbon Structures

    NASA Astrophysics Data System (ADS)

    Anthony, Gilmore; Khatun, Mahfuza

    2011-10-01

    We will present the general properties of carbon structures. The research involves the study of carbon structures: Graphene, Graphene nanoribbons (GNRs), and Carbon Nanotubes (CNTs). A review of electrical and thermal conduction phenomena of the structures will be discussed. Particularly carbon nanoribbons and CNTs have many interesting physical properties, and have the potential for device applications. Our research interests include the study of electronic structures, electrical and thermal transport properties of the carbon structures. Results are produced analytically as well as by simulation. The numerical simulations are conducted using various tools such as Visual Molecular Dynamics (VMD), Large Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), NanoHub at Purdue University and the Beowulf Cluster at Ball State University.

  6. Electronic Structure and Morphology of Graphene Layers on SiC

    NASA Astrophysics Data System (ADS)

    Ohta, Taisuke

    2008-03-01

    Recent years have witnessed the discovery and the unique electronic properties of graphene, a sheet of carbon atoms arranged in a honeycomb lattice. The unique linear dispersion relation of charge carriers near the Fermi level (``Dirac Fermions'') lead to exciting transport properties, such as an unusual quantum Hall effect, and have aroused scientific and technological interests. On the way towards graphene-based electronics, a knowledge of the electronic band structure and the morphology of epitaxial graphene films on silicon carbide substrates is imperative. We have studied the evolution of the occupied band structure and the morphology of graphene layers on silicon carbide by systematically increasing the layer thickness. Using angle-resolved photoemission spectroscopy (ARPES), we examine this unique 2D system in its development from single layer to multilayers, by characteristic changes in the π band, the highest occupied state, and the dispersion relation in the out-of-plane electron wave vector in particular. The evolution of the film morphology is evaluated by the combination of low-energy electron microscopy and ARPES. By exploiting the sensitivity of graphene's electronic states to the charge carrier concentration, changes in the on-site Coulomb potential leading to a change of π and π* bands can be examined using ARPES. We demonstrate that, in a graphene bilayer, the gap between π and π* bands can be controlled by selectively adjusting relative carrier concentrations, which suggests a possible application of the graphene bilayer for switching functions in electronic devices. This work was done in collaboration with A. Bostwick, J. L. McChesney, and E. Rotenberg at Advanced Light Source, Lawrence Berkeley National Laboratory, K. Horn at Fritz-Haber-Institut, K. V. Emtsev and Th. Seyller at Lehrstuhl für Technische Physik, Universität Erlangen-Nürnberg, and F. El Gabaly and A. K. Schmid at National Center for Electron Microscopy, Lawrence Berkeley

  7. Structural Tailoring of Advanced Turboprops (STAT). Theoretical manual

    NASA Technical Reports Server (NTRS)

    Brown, K. W.

    1992-01-01

    This manual describes the theories in the Structural Tailoring of Advanced Turboprops (STAT) computer program, which was developed to perform numerical optimizations on highly swept propfan blades. The optimization procedure seeks to minimize an objective function, defined as either direct operating cost or aeroelastic differences between a blade and its scaled model, by tuning internal and external geometry variables that must satisfy realistic blade design constraints. The STAT analyses include an aerodynamic efficiency evaluation, a finite element stress and vibration analysis, an acoustic analysis, a flutter analysis, and a once-per-revolution (1-p) forced response life prediction capability. The STAT constraints include blade stresses, blade resonances, flutter, tip displacements, and a 1-P forced response life fraction. The STAT variables include all blade internal and external geometry parameters needed to define a composite material blade. The STAT objective function is dependent upon a blade baseline definition which the user supplies to describe a current blade design for cost optimization or for the tailoring of an aeroelastic scale model.

  8. Remote Structural Health Monitoring and Advanced Prognostics of Wind Turbines

    SciTech Connect

    Douglas Brown; Bernard Laskowski

    2012-05-29

    The prospect of substantial investment in wind energy generation represents a significant capital investment strategy. In order to maximize the life-cycle of wind turbines, associated rotors, gears, and structural towers, a capability to detect and predict (prognostics) the onset of mechanical faults at a sufficiently early stage for maintenance actions to be planned would significantly reduce both maintenance and operational costs. Advancement towards this effort has been made through the development of anomaly detection, fault detection and fault diagnosis routines to identify selected fault modes of a wind turbine based on available sensor data preceding an unscheduled emergency shutdown. The anomaly detection approach employs spectral techniques to find an approximation of the data using a combination of attributes that capture the bulk of variability in the data. Fault detection and diagnosis (FDD) is performed using a neural network-based classifier trained from baseline and fault data recorded during known failure conditions. The approach has been evaluated for known baseline conditions and three selected failure modes: pitch rate failure, low oil pressure failure and a gearbox gear-tooth failure. Experimental results demonstrate the approach can distinguish between these failure modes and normal baseline behavior within a specified statistical accuracy.

  9. Compressed Sensing Electron Tomography for Determining Biological Structure

    NASA Astrophysics Data System (ADS)

    Guay, Matthew D.; Czaja, Wojciech; Aronova, Maria A.; Leapman, Richard D.

    2016-06-01

    There has been growing interest in applying compressed sensing (CS) theory and practice to reconstruct 3D volumes at the nanoscale from electron tomography datasets of inorganic materials, based on known sparsity in the structure of interest. Here we explore the application of CS for visualizing the 3D structure of biological specimens from tomographic tilt series acquired in the scanning transmission electron microscope (STEM). CS-ET reconstructions match or outperform commonly used alternative methods in full and undersampled tomogram recovery, but with less significant performance gains than observed for the imaging of inorganic materials. We propose that this disparity stems from the increased structural complexity of biological systems, as supported by theoretical CS sampling considerations and numerical results in simulated phantom datasets. A detailed analysis of the efficacy of CS-ET for undersampled recovery is therefore complicated by the structure of the object being imaged. The numerical nonlinear decoding process of CS shares strong connections with popular regularized least-squares methods, and the use of such numerical recovery techniques for mitigating artifacts and denoising in reconstructions of fully sampled datasets remains advantageous. This article provides a link to the software that has been developed for CS-ET reconstruction of electron tomographic data sets.

  10. Oligothiophene wires: impact of torsional conformation on the electronic structure.

    PubMed

    Kislitsyn, D A; Taber, B N; Gervasi, C F; Zhang, L; Mannsfeld, S C B; Prell, J S; Briseno, A L; Nazin, G V

    2016-02-14

    Charge transport in polymer- and oligomer-based semiconductor materials depends strongly on the structural ordering of the constituent molecules. Variations in molecular conformations influence the electronic structures of polymers and oligomers, and thus impact their charge-transport properties. In this study, we used Scanning Tunneling Microscopy and Spectroscopy (STM/STS) to investigate the electronic structures of different alkyl-substituted oligothiophenes displaying varied torsional conformations on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes self-assemble into chain-like structures, binding to each other via interdigitated alkyl ligands. The molecules adopted distinct planar conformations with alkyl ligands forming cis- or trans- mutual orientations. For each molecule, by using STS mapping, we identify a progression of particle-in-a-box-like states corresponding to the LUMO, LUMO+1 and LUMO+2 orbitals. Analysis of STS data revealed very similar unoccupied molecular orbital energies for different possible molecular conformations. By using density functional theory calculations, we show that the lack of variation in molecular orbital energies among the different oligothiophene conformers implies that the effect of the Au-oligothiophene interaction on molecular orbital energies is nearly identical for all studied torsional conformations. Our results suggest that cis-trans torsional disorder may not be a significant source of electronic disorder and charge carrier trapping in organic semiconductor devices based on oligothiophenes.

  11. Electronic structural investigations of ruthenium compounds and anticancer prodrugs.

    PubMed

    Harris, Travis V; Szilagyi, Robert K; McFarlane Holman, Karen L

    2009-08-01

    Several Ru(III) compounds are propitious anticancer agents although the precise mechanisms of action remain unknown. With this paper we start to establish an experimental library of X-ray absorption spectroscopy (XAS) data for ten Ru compounds wherein the ligands [Cl(-), dimethyl sulfoxide, imidazole, and indazole] were varied systematically to provide electronic structural information for future use in correlating spectroscopic signatures with chemical properties. Despite the considerable difference in the coordination environments of the complexes studied, the overall differences in spectral features and electronic structures calculated using density functional theory are unexpectedly small. However, the differences in the electronic structure of the Ru(III) prodrugs KP1019 ([IndH][trans-RuCl(4)(Ind)(2)], Ind is indazole) and ICR ([ImH][trans-RuCl(4)(Im)(2)], Im is imidazole) observed in the XAS data show correlation with known chemical and biological activities in addition to the donor abilities of imidazole compared with indazole and reduction potentials of the complexes. These semiquantitative results lay the groundwork for future biochemical studies into the structure-function relationships of Ru-based anticancer drugs.

  12. Compressed Sensing Electron Tomography for Determining Biological Structure

    PubMed Central

    Guay, Matthew D.; Czaja, Wojciech; Aronova, Maria A.; Leapman, Richard D.

    2016-01-01

    There has been growing interest in applying compressed sensing (CS) theory and practice to reconstruct 3D volumes at the nanoscale from electron tomography datasets of inorganic materials, based on known sparsity in the structure of interest. Here we explore the application of CS for visualizing the 3D structure of biological specimens from tomographic tilt series acquired in the scanning transmission electron microscope (STEM). CS-ET reconstructions match or outperform commonly used alternative methods in full and undersampled tomogram recovery, but with less significant performance gains than observed for the imaging of inorganic materials. We propose that this disparity stems from the increased structural complexity of biological systems, as supported by theoretical CS sampling considerations and numerical results in simulated phantom datasets. A detailed analysis of the efficacy of CS-ET for undersampled recovery is therefore complicated by the structure of the object being imaged. The numerical nonlinear decoding process of CS shares strong connections with popular regularized least-squares methods, and the use of such numerical recovery techniques for mitigating artifacts and denoising in reconstructions of fully sampled datasets remains advantageous. This article provides a link to the software that has been developed for CS-ET reconstruction of electron tomographic data sets. PMID:27291259

  13. Real-time feedback from iterative electronic structure calculations.

    PubMed

    Vaucher, Alain C; Haag, Moritz P; Reiher, Markus

    2016-04-05

    Real-time feedback from iterative electronic structure calculations requires to mediate between the inherently unpredictable execution times of the iterative algorithm used and the necessity to provide data in fixed and short time intervals for real-time rendering. We introduce the concept of a mediator as a component able to deal with infrequent and unpredictable reference data to generate reliable feedback. In the context of real-time quantum chemistry, the mediator takes the form of a surrogate potential that has the same local shape as the first-principles potential and can be evaluated efficiently to deliver atomic forces as real-time feedback. The surrogate potential is updated continuously by electronic structure calculations and guarantees to provide a reliable response to the operator for any molecular structure. To demonstrate the application of iterative electronic structure methods in real-time reactivity exploration, we implement self-consistent semiempirical methods as the data source and apply the surrogate-potential mediator to deliver reliable real-time feedback.

  14. Studies of noise transmission in advanced composite material structures

    NASA Technical Reports Server (NTRS)

    Roussos, L. A.; Mcgary, M. C.; Powell, C. A.

    1983-01-01

    Noise characteristics of advanced composite material fuselages were discussed from the standpoints of applicable research programs and noise transmission theory. Experimental verification of the theory was also included.

  15. Advanced composite structures. [metal matrix composites - structural design criteria for spacecraft construction materials

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A monograph is presented which establishes structural design criteria and recommends practices to ensure the design of sound composite structures, including composite-reinforced metal structures. (It does not discuss design criteria for fiber-glass composites and such advanced composite materials as beryllium wire or sapphire whiskers in a matrix material.) Although the criteria were developed for aircraft applications, they are general enough to be applicable to space vehicles and missiles as well. The monograph covers four broad areas: (1) materials, (2) design, (3) fracture control, and (4) design verification. The materials portion deals with such subjects as material system design, material design levels, and material characterization. The design portion includes panel, shell, and joint design, applied loads, internal loads, design factors, reliability, and maintainability. Fracture control includes such items as stress concentrations, service-life philosophy, and the management plan for control of fracture-related aspects of structural design using composite materials. Design verification discusses ways to prove flightworthiness.

  16. Structural, optical and electronic structure studies of Al doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Devi, Vanita; Kumar, Manish; Shukla, D. K.; Choudhary, R. J.; Phase, D. M.; Kumar, Ravindra; Joshi, B. C.

    2015-07-01

    Structural, optical and electronic structure of Al doped ZnO thin films grown using pulsed laser deposition on glass substrate are investigated. X-ray diffraction measurements reveal that all the films are textured along the c-axis and have wurtzite structure. Al doping in ZnO films leads to increase in grain size due to relaxation in compressive stress. Enhancement in band gap of ZnO films with the Al doping is also noticed which can be ascribed to the Brustein-Moss shift. The changes in the electronic structure caused by Al in the doped thin film samples are understood through X-ray absorption measurements.

  17. Electronic Structure of Crystalline 4He at High Pressure

    SciTech Connect

    Mao, H.K.; Cai, Y.; Shirley, E.L.; Ding, Y.; Eng, P.; Chow, P.; Xiao, Y.; Shu, J.; Hemley, R.J.; Kao, C.C.; Mao, W.L.

    2010-10-29

    Using inelastic x-ray scattering techniques, we have succeeded in probing the high-pressure electronic structure of helium at 300 K. Helium has the widest known valence-conduction band gap of all materials a property whose high-pressure response has been inaccessible to direct measurements. We observed a rich electron excitation spectrum, including a cutoff edge above 23 eV, a sharp exciton peak showing linear volume dependence, and a series of excitations and continuum at 26 to 45 eV. We determined the electronic dispersion along the {Gamma}-M direction over two Brillouin zones, and provided a quantitative picture of the helium exciton beyond the simplified Wannier-Frenkel description.

  18. Approximate ab initio calculations of electronic structure of amorphous silicon

    NASA Astrophysics Data System (ADS)

    Durandurdu, M.; Drabold, D. A.; Mousseau, N.

    2000-12-01

    We report on ab initio calculations of electronic states of two large and realistic models of amorphous silicon generated using a modified version of the Wooten-Winer-Weaire algorithm and relaxed, in both cases, with a Keating and a modified Stillinger-Weber potentials. The models have no coordination defects and a very narrow bond-angle distribution. We compute the electronic density-of-states and pay particular attention to the nature of the band-tail states around the electronic gap. All models show a large and perfectly clean optical gap and realistic Urbach tails. Based on these results and the extended quasi-one-dimensional stringlike structures observed for certain eigenvalues in the band tails, we postulate that the generation of model a-Si without localized states might be achievable under certain circumstances.

  19. DFT investigation on the electronic structure of Faujasite

    NASA Astrophysics Data System (ADS)

    Popeneciu, Horea; Calborean, Adrian; Tudoran, Cristian; Buimaga-Iarinca, Luiza

    2013-11-01

    We report here first-principle pseudopotential DFT calculations to investigate relevant aspects of the electronic structure of zeolites based FAU. Fundamental molecular issues of the band-gap and electronic population analysis were reviewed under GGA/RPBE level of theory, corroborated with a DZP basis set and Troullier-Martins norm conserving pseudo-potentials. The atom-projected density of states and the analysis of HOMO-LUMO frontier orbitals at Gamma point were performed. Their electronic transfers are discussed through the alignment and relative positions of orbitals in order to determine the way that the molecule interacts with adsorbed molecules and other practical applications. Mulliken population analysis was employed for describing atomic charge distribution in the chosen systems.

  20. Sorting carbon nanotubes by electronic structure using density differentiation.

    PubMed

    Arnold, Michael S; Green, Alexander A; Hulvat, James F; Stupp, Samuel I; Hersam, Mark C

    2006-10-01

    The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) precludes their widespread application in electronics, optics and sensing. We report on the sorting of carbon nanotubes by diameter, bandgap and electronic type using structure-discriminating surfactants to engineer subtle differences in their buoyant densities. Using the scalable technique of density-gradient ultracentrifugation, we have isolated narrow distributions of SWNTs in which >97% are within a 0.02-nm-diameter range. Furthermore, using competing mixtures of surfactants, we have produced bulk quantities of SWNTs of predominantly a single electronic type. These materials were used to fabricate thin-film electrical devices of networked SWNTs characterized by either metallic or semiconducting behaviour.

  1. Electronic structure and energetics of graphene antidot lattice

    NASA Astrophysics Data System (ADS)

    Sakurai, Masahiro; Saito, Susumu; Takada, Yasutami

    2012-02-01

    We have made a systematic study of the electronic structure and the energetics of graphene with periodic array of vacancy clusters (graphene antidot lattice) in the framework of the density-functional theory (DFT). We find that the electronic property of the system is well controlled by its lattice periodicity. More specifically, this system can be either metallic or semiconducting, depending on its lattice geometry. Interestingly, some of them are predicted to be direct-gap semiconductors. For example, graphene sheet with high-symmetry arrangements of periodic circle-shape vacancies always has a direct fundamental gap [1]. The DFT total-energy calculations indicate that the geometry of hole edges plays an important role in determining its stability. [1] ``Electronic properties of graphene and boron-nitride based nanostructured materials'' M. Sakurai, Y. Sakai, and S. Saito, J. Phys.: Conf. Ser. 302 (2011) 012018.

  2. Spatially Resolved Electronic Structures of Atomically Precise Armchair Graphene Nanoribbons

    PubMed Central

    Huang, Han; Wei, Dacheng; Sun, Jiatao; Wong, Swee Liang; Feng, Yuan Ping; Neto, A. H. Castro; Wee, Andrew Thye Shen

    2012-01-01

    Graphene has attracted much interest in both academia and industry. The challenge of making it semiconducting is crucial for applications in electronic devices. A promising approach is to reduce its physical size down to the nanometer scale. Here, we present the surface-assisted bottom-up fabrication of atomically precise armchair graphene nanoribbons (AGNRs) with predefined widths, namely 7-, 14- and 21-AGNRs, on Ag(111) as well as their spatially resolved width-dependent electronic structures. STM/STS measurements reveal their associated electron scattering patterns and the energy gaps over 1 eV. The mechanism to form such AGNRs is addressed based on the observed intermediate products. Our results provide new insights into the local properties of AGNRs, and have implications for the understanding of their electrical properties and potential applications. PMID:23248746

  3. Anomalous electronic structure and magnetoresistance in TaAs2

    PubMed Central

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; Scott, B.; Wakeham, N.; Ghimire, N. J.; Bauer, E. D.; Thompson, J. D.; Ronning, F.

    2016-01-01

    The change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. Density functional calculations find that TaAs2 is a new topological semimetal [ℤ2 invariant (0;111)] without Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions. PMID:27271852

  4. Anomalous electronic structure and magnetoresistance in TaAs2

    DOE PAGES

    Luo, Yongkang; McDonald, R. D.; Rosa, P. F. S.; ...

    2016-01-01

    We report that the change in resistance of a material in a magnetic field reflects its electronic state. In metals with weakly- or non-interacting electrons, the resistance typically increases upon the application of a magnetic field. In contrast, negative magnetoresistance may appear under some circumstances, e.g., in metals with anisotropic Fermi surfaces or with spin-disorder scattering and semimetals with Dirac or Weyl electronic structures. Here we show that the non-magnetic semimetal TaAs2 possesses a very large negative magnetoresistance, with an unknown scattering mechanism. In conclusion, density functional calculations find that TaAs2 is a new topological semimetal [Z2 invariant (0;111)] withoutmore » Dirac dispersion, demonstrating that a negative magnetoresistance in non-magnetic semimetals cannot be attributed uniquely to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.« less

  5. Response to waste electrical and electronic equipments in China: legislation, recycling system, and advanced integrated process.

    PubMed

    Zhou, Lei; Xu, Zhenming

    2012-05-01

    Over the past 30 years, China has been suffering from negative environmental impacts from distempered waste electrical and electronic equipments (WEEE) recycling activities. For the purpose of environmental protection and resource reusing, China made a great effort to improve WEEE recycling. This article reviews progresses of three major fields in the development of China's WEEE recycling industry: legal system, formal recycling system, and advanced integrated process. Related laws concerning electronic waste (e-waste) management and renewable resource recycling are analyzed from aspects of improvements and loopholes. The outcomes and challenges for existing formal recycling systems are also discussed. The advantage and deficiency related to advanced integrated recycling processes for typical e-wastes are evaluated respectively. Finally, in order to achieve high disposal rates of WEEE, high-quantify separation of different materials in WEEE and high added value final products produced by separated materials from WEEE, an idea of integrated WEEE recycling system is proposed to point future development of WEEE recycling industry.

  6. A manufacturing database of advanced materials used in spacecraft structures

    NASA Technical Reports Server (NTRS)

    Bao, Han P.

    1994-01-01

    Cost savings opportunities over the life cycle of a product are highest in the early exploratory phase when different design alternatives are evaluated not only for their performance characteristics but also their methods of fabrication which really control the ultimate manufacturing costs of the product. In the past, Design-To-Cost methodologies for spacecraft design concentrated on the sizing and weight issues more than anything else at the early so-called 'Vehicle Level' (Ref: DOD/NASA Advanced Composites Design Guide). Given the impact of manufacturing cost, the objective of this study is to identify the principal cost drivers for each materials technology and propose a quantitative approach to incorporating these cost drivers into the family of optimization tools used by the Vehicle Analysis Branch of NASA LaRC to assess various conceptual vehicle designs. The advanced materials being considered include aluminum-lithium alloys, thermoplastic graphite-polyether etherketone composites, graphite-bismaleimide composites, graphite- polyimide composites, and carbon-carbon composites. Two conventional materials are added to the study to serve as baseline materials against which the other materials are compared. These two conventional materials are aircraft aluminum alloys series 2000 and series 7000, and graphite-epoxy composites T-300/934. The following information is available in the database. For each material type, the mechanical, physical, thermal, and environmental properties are first listed. Next the principal manufacturing processes are described. Whenever possible, guidelines for optimum processing conditions for specific applications are provided. Finally, six categories of cost drivers are discussed. They include, design features affecting processing, tooling, materials, fabrication, joining/assembly, and quality assurance issues. It should be emphasized that this database is not an exhaustive database. Its primary use is to make the vehicle designer

  7. {ELECTRONIC Structure and Spectroscopy of O_2 and O_2^+}

    NASA Astrophysics Data System (ADS)

    Vazquez, Gabriel J.; Lefebvre-Brion, H.; Liebermann, Hans P.

    2014-06-01

    We carried out a comprehensive SCF MRD--CI ab initio study of the electronic structure of O_2 and O_2^+. Potential energy curves (PECs) of about 150 electronic states of O_2 and about 100 of O_2^+, as well as a number of states of O_2++ were computed. The cc--pVQZ basis set augmented with diffuse functions was employed. Spectroscopic parameters (T_e, T_v, ω_e, ω_ex_e, B_e, D_e, D_0, μ, IP, etc.) are reported. A preliminary sample of the results will be presented. The electronic absorption spectrum of O_2 has proved difficult to analyze/interpret due to the unusually large number of electronic states which arise from the peculiar open--shell structure of both the oxygen atomic fragments and the O_2 molecule. For instance, there are 62 valence molecular electronic states which correlate to the six lowest dissociation limits resulting from the three valence O atom fragment states (^3P, ^1D, ^1S). In addition, there are several nlλ Rydberg series converging to the X^2Π_g ground ionic state and to the lowest two excited states of the cation, a^4Π_u_i and A^2Π_u. Furthermore, a number of interactions of various types among several electronic states result in rovibronic perturbations which manifest themselves, e.g., as irregular vibronic structure, hence severely complicating the assignment of the absorption features and the analysis and interpretation of the spectrum. An overview of the electronic states and spectroscopy of O_2 will be presented. A chief motivation of this study of O_2 was to try to provide a theoretical insight on the nature, energetic position, shape, and dissociation asymptotes, of electronic states located in the 4 eV energy region encompassed between the O_2^+ ground state X^2Π_g (IP=12.07 eV) and the first excited state of the cation a^4Π_u_i (IP=16.10 eV). This in order to aid in the interpretation of experimental data related to the mechanism(s) of the neutral dissociation of the O_2** (Rydberg) superexcited states, which competes with

  8. Advances in target imaging of deep Earth structure

    NASA Astrophysics Data System (ADS)

    Masson, Y.; Romanowicz, B. A.; Clouzet, P.

    2015-12-01

    A new generation of global tomographic models (Lekić and Romanowicz, 2011; French et al, 2013, 2014) has emerged with the development of accurate numerical wavefield computations in a 3D earth combined with access to enhanced HPC capabilities. These models have sharpened up mantle images and unveiled relatively small scale structures that were blurred out in previous generation models. Fingerlike structures have been found at the base of the oceanic asthenosphere, and vertically oriented broad low velocity plume conduits extend throughout the lower mantle beneath those major hotspots that are located within the perimeter of the deep mantle large low shear velocity provinces (LLSVPs). While providing new insights into our understanding of mantle dynamics, the detailed morphology of these features, requires further efforts to obtain higher resolution images. The focus of our ongoing effort is to develop advanced tomographic methods to image remote regions of the Earth at fine scales. We have developed an approach in which distant sources (located outside of the target region) are replaced by an equivalent set of local sources located at the border of the computational domain (Masson et al., 2014). A limited number of global simulations in a reference 3D earth model is then required. These simulations are computed prior to the regional inversion, while iterations of the model need to be performed only within the region of interest, potentially allowing us to include shorter periods at limited additional computational cost. Until now, the application was limited to a distribution of receivers inside the target region. This is particularly suitable for studies of upper mantle structure in regions with dense arrays (e.g. see our companion presentation Clouzet et al., this Fall AGU). Here we present our latest development that now can include teleseismic data recorded outside the imaged region. This allows us to perform regional waveform tomography in the situation where

  9. Near net shape forming of advanced structural ceramic devices

    NASA Astrophysics Data System (ADS)

    Liu, Hao-Chih

    This research applied a combination of rapid prototyping techniques and ceramic gelcasting processes in the design and manufacturing of advanced structural ceramic components that cannot be fabricated by other shape-forming processes. An Assembly Mold SDM process, a derivative process of Shape Deposition Manufacturing, was adopted along with modified gelcasting with great success. The fabricated gas turbine rotors, inlet nozzles, and mesoscale burner arrays have demonstrated superior shape accuracy, mechanical strength, and surface smoothness with a feature size of 200 mum. The design concepts and functionalities of the ceramic devices were verified with performance tests. The shape complexity and surface quality of ceramic parts have been further improved by the use of a mold assembly made of a low melting temperature metal alloy. The introduction of metal alloy required modifications in the mold design, machining procedure, and ceramic processing. A complete shape forming process (from slurry to final parts) was developed for the low melting temperature metal alloy. In addition, the choice of ceramic material now includes SiC, which is critical to the development of micro heat exchangers. Forty-channel, high-aspect-ratio structured SiC heat exchangers were fabricated, and the thermal conductivity value of SiC was found to be comparable to that of steel. The catalyst deposition and ceramic precursor impregnation processes were proposed to enable use of the SiC heat exchangers as micro reactors. Micro-electro-mechanical-systems (MEMS)-related techniques such as SU-8 deep photolithography and polydimethylsiloxane (PDMS) soft lithography were combined with gelcasting to make micro patterns on structural ceramics. A feature size of 125 mum and aspect ratio of 8 have been achieved in the preliminary experiments. Based on the fabricated ceramic devices, a graphical method to characterize the shape attributes of complex-shaped components was proposed and used to compare

  10. Perspective: Explicitly correlated electronic structure theory for complex systems

    NASA Astrophysics Data System (ADS)

    Grüneis, Andreas; Hirata, So; Ohnishi, Yu-ya; Ten-no, Seiichiro

    2017-02-01

    The explicitly correlated approach is one of the most important breakthroughs in ab initio electronic structure theory, providing arguably the most compact, accurate, and efficient ansatz for describing the correlated motion of electrons. Since Hylleraas first used an explicitly correlated wave function for the He atom in 1929, numerous attempts have been made to tackle the significant challenges involved in constructing practical explicitly correlated methods that are applicable to larger systems. These include identifying suitable mathematical forms of a correlated wave function and an efficient evaluation of many-electron integrals. R12 theory, which employs the resolution of the identity approximation, emerged in 1985, followed by the introduction of novel correlation factors and wave function ansätze, leading to the establishment of F12 theory in the 2000s. Rapid progress in recent years has significantly extended the application range of explicitly correlated theory, offering the potential of an accurate wave-function treatment of complex systems such as photosystems and semiconductors. This perspective surveys explicitly correlated electronic structure theory, with an emphasis on recent stochastic and deterministic approaches that hold significant promise for applications to large and complex systems including solids.

  11. Electronic absorption and ground state structure of carotenoid molecules.

    PubMed

    Mendes-Pinto, Maria M; Sansiaume, Elodie; Hashimoto, Hideki; Pascal, Andrew A; Gall, Andrew; Robert, Bruno

    2013-09-26

    Predicting the complete electronic structure of carotenoid molecules remains an extremely complex problem, particularly in anisotropic media such as proteins. In this paper, we address the electronic properties of nine relatively simple carotenoids by the combined use of electronic absorption and resonance Raman spectroscopies. Linear carotenoids exhibit an excellent correlation between (i) the inverse of their conjugation chain length N, (ii) the energy of their S0 → S2 electronic transition, and (iii) the position of their ν1 Raman band (corresponding to the stretching mode of their conjugated C═C bonds). For cyclic carotenoids such as β-carotene, this correlation is also observed between the latter two parameters (S0 → S2 energy and ν1 frequency), whereas their "nominal" conjugation length N does not follow the same relationship. We conclude that β-carotene and cyclic carotenoids in general exhibit a shorter effective conjugation length than that expected from their chemical structure. In addition, the effect of solvent polarizability on these molecular parameters was investigated for four of the carotenoids used in this study. We demonstrate that resonance Raman spectroscopy can discriminate between the different effects underlying shifts in the S0 → S2 transition of carotenoid molecules.

  12. Electronic Structure of Silicon Nanowires Matrix from Ab Initio Calculations

    NASA Astrophysics Data System (ADS)

    Monastyrskii, Liubomyr S.; Boyko, Yaroslav V.; Sokolovskii, Bogdan S.; Potashnyk, Vasylyna Ya.

    2016-01-01

    An investigation of the model of porous silicon in the form of periodic set of silicon nanowires has been carried out. The electronic energy structure was studied using a first-principle band method—the method of pseudopotentials (ultrasoft potentials in the basis of plane waves) and linearized mode of the method of combined pseudopotentials. Due to the use of hybrid exchange-correlation potentials (B3LYP), the quantitative agreement of the calculated value of band gap in the bulk material with experimental data is achieved. The obtained results show that passivation of dangling bonds with hydrogen atoms leads to substantial transformation of electronic energy structure. At complete passivation of the dangling silicon bonds by hydrogen atoms, the band gap value takes the magnitude which substantially exceeds that for bulk silicon. The incomplete passivation gives rise to opposite effect when the band gap value decreases down the semimetallic range.

  13. Strongly correlated electron materials. I. Theory of the quasiparticle structure

    SciTech Connect

    Lopez-Aguilar, F.; Costa-Quintana, J.; Puig-Puig, L. )

    1993-07-01

    In this paper we give a method for analyzing the renormalized electronic structure of the Hubbard systems. The first step is the determination of effective interactions from the random-phase approximation (RPA) and from an extended RPA (ERPA) that introduces vertex effects within the bubble polarization. The second step is the determination of the density of states deduced from the spectral functions. Its analysis leads us to conclude that these systems can exhibit three types of resonances in their electronic structures: the lower-, middle-, and upper-energy resonances. Furthermore, we analyze the conditions for which there is only one type of resonance and the causes that lead to the disappearance of the heavy-fermion state. We finally introduce the RPA and ERPA effective interactions within the strong-coupling theory and we give the conditions for obtaining coupling and superconductivity.

  14. Electronic structure of Gd-doped MgO

    NASA Astrophysics Data System (ADS)

    Lukoyanov, A. V.; Anisimov, V. I.

    2016-02-01

    The electronic structure of Gd-doped MgO is investigated using the LSDA+U (local spin density approximation with U-correction) method and compared with the MgO structure. The total density of states obtained accounting for the correlation effects in the 4 f shell of gadolinium is found to be formed by the oxygen 2 p states at the valence band and the 4 f gadolinium occupied states, while the conduction band is represented by a mixture of empty electronic states. Magnetic properties of the calculated Gd-doped MgO are found to be formed solely by the Gd-4 f-magnetic moment of about 7μB, in good agreement with recent experimental results suggesting a ferromagnetic coupling of the local magnetic moments induced by Gd.

  15. Atomic and electronic structure of Ni-Nb metallic glasses

    SciTech Connect

    Yuan, C. C.; Yang, Y.-F. Xi, X. K.

    2013-12-07

    Solid state {sup 93}Nb nuclear magnetic resonance spectroscopy has been employed to investigate the atomic and electronic structures in Ni-Nb based metallic glass (MG) model system. {sup 93}Nb nuclear magnetic resonance (NMR) isotropic metallic shift of Ni{sub 60}Nb{sub 35}Sn{sub 5} has been found to be ∼100 ppm lower than that of Ni{sub 60}Nb{sub 35}Zr{sub 5} MG, which is correlated with their intrinsic fracture toughness. The evolution of {sup 93}Nb NMR isotropic metallic shifts upon alloying is clearly an electronic origin, as revealed by both local hyperfine fields analysis and first-principle computations. This preliminary result indicates that, in addition to geometrical considerations, atomic form factors should be taken into a description of atomic structures for better understanding the mechanical behaviors of MGs.

  16. Structural and electronic properties of arsenic nitrogen monolayer

    NASA Astrophysics Data System (ADS)

    Liu, Pei; Nie, Yao-zhuang; Xia, Qing-lin; Guo, Guang-hua

    2017-03-01

    We present our first-principles calculations of a new two-dimensional material, arsenic nitrogen monolayer. The structural, electronic, and mechanical properties are investigated in detail by means of density functional theory computations. The calculated binding energy and the phonon spectra demonstrate that the AsN can form stable monolayer in puckered honeycomb structure. It is a semiconductor with indirect band gap of 0.73 eV, and displays highly anisotropic mechanical properties. Strain has obvious influence on the electronic properties of AsN monolayer. It is found that in the armchair direction, a moderate compression strain (-12%) can trigger an indirect to direct band gap transition and a tensile strain of 18% can make the AsN becoming a stable metal. In the zigzag direction, a rather smaller strain than armchair direction (12% for compression and 8% for stretch) can induce the indirect band gap to metal transition.

  17. Electronic structure of polyimide and related monomers: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Kowalczyk, Steven P.; Stafström, Sven; Brédas, J. L.; Salaneck, William R.; Jordan-Sweet, Jean L.

    1990-01-01

    The electronic structure of polymide and several related compounds was investigated theoretically and experimentally. The compounds include pyromellitic dianhydride, oxydianiline, and polyamic acid. Experimental electronic-structure determinations for poly(methyl phenylene oxide) and poly(vinyl methyl ketone) are also reported. The theoretical approach employed valence-effective-Hamiltonian calculations. Photoelectron spectroscopy (x-ray photoelectron spectroscopy, soft-x-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy) was used to experimentally measure the total valence-band density of states (VBDOS) from thin films of the above compounds. The theoretical VBDOS's were cross-section modulated to facilitate comparison with experiment. Very good agreement is found between the theoretical results and the experimental VBDOS's.

  18. Electronic structure of spontaneously strained graphene on hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    San-Jose, Pablo; Gutiérrez-Rubio, A.; Sturla, Mauricio; Guinea, Francisco

    2014-09-01

    Hexagonal boron nitride substrates have been shown to dramatically improve the electric properties of graphene. Recently, it has been observed that when the two honeycomb crystals are close to perfect alignment, strong lattice distortions develop in graphene due to the moiré adhesion landscape. Simultaneously, a gap opens at the Dirac point. Here, we derive a simple low-energy electronic model for graphene aligned with the substrate, taking into account spontaneous strains at equilibrium and pseudogauge fields. We carry out a detailed characterization of the modified band structure, gap, local and global density of states, and band topology in terms of physical parameters. We show that the overall electronic structure is strongly modified by the spontaneous strains.

  19. Electronic Structure Rearrangements in Hybrid Ribozyme/Protein Catalysis

    NASA Astrophysics Data System (ADS)

    Kang, Jiyoung; Kino, Hiori; Field, Martin J.; Tateno, Masaru

    2017-04-01

    We analyzed the electronic structural changes that occur in the reaction cycle of a biological catalyst composed of RNA and protein, and elucidated the dynamical rearrangements of the electronic structure that was obtained from our previous study in which ab initio quantum mechanics/molecular mechanics molecular dynamics simulations were performed. Notable results that we obtained include the generation of a reactive HOMO that is responsible for bond formation in the initial stages of the reaction, and the appearance of a reactive LUMO that is involved in the bond rupture that leads to products. We denote these changes as dynamical induction of the reactive HOMO (DIRH) and LUMO (DIRL), respectively. Interestingly, we also find that the induction of the reactive HOMO is enhanced by the formation of a low-barrier hydrogen bond (LBHB), which, to the best of our knowledge, represents a novel role for LBHBs in enzymatic systems.

  20. Electronic Structure of Silicon Nanowires Matrix from Ab Initio Calculations.

    PubMed

    Monastyrskii, Liubomyr S; Boyko, Yaroslav V; Sokolovskii, Bogdan S; Potashnyk, Vasylyna Ya

    2016-12-01

    An investigation of the model of porous silicon in the form of periodic set of silicon nanowires has been carried out. The electronic energy structure was studied using a first-principle band method-the method of pseudopotentials (ultrasoft potentials in the basis of plane waves) and linearized mode of the method of combined pseudopotentials. Due to the use of hybrid exchange-correlation potentials (B3LYP), the quantitative agreement of the calculated value of band gap in the bulk material with experimental data is achieved. The obtained results show that passivation of dangling bonds with hydrogen atoms leads to substantial transformation of electronic energy structure. At complete passivation of the dangling silicon bonds by hydrogen atoms, the band gap value takes the magnitude which substantially exceeds that for bulk silicon. The incomplete passivation gives rise to opposite effect when the band gap value decreases down the semimetallic range.