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Sample records for advanced electronic structure

  1. Recent advances in electronic structure theory

    NASA Astrophysics Data System (ADS)

    Piecuch, Piotr; Kowalski, Karol; Pimienta, Ian S. O.; McGuire, Michael J.

    The recently developed new approach to the many-electron correlation problem in atoms and molecules, termed the method of moments of coupled-cluster (CC) equations (MMCC), is reviewed. The ground-state MMCC formalism and its extension to excited electronic states via the equation-of-motion coupled-cluster (EOMCC) approach are discussed. The main principle of all MMCC methods is that of the non-iterative energy corrections which, when added to the ground- and excited-state energies obtained in the standard CC calculations, such as CCSD or EOMCCSD, recover the exact, full configuration interaction (CI) energies. Three types of the MMCC approximations are reviewed in detail: (i) the CI-corrected MMCC methods, which can be applied to ground and excited states; (ii) the renormalized and completely renormalized CC methods for ground states; and (iii) the quasi-variational MMCC approaches for the ground-state problem, including the quadratic MMCC models. It is demonstrated that the MMCC formalism provides a new theoretical framework for designing 'black-box' CC approaches that lead to an excellent description of entire potential energy surfaces of ground- and excited-state molecular systems with an ease of use of the standard single-reference methods. The completely renormalized (CR) CCSD(T) and CCSD(TQ) methods and their quadratic and excited-state MMCC analogues remove the failing of the standard CCSD, CCSD(T), EOMCCSD and similar methods at larger internuclear separations and for states that normally require a genuine multireference description. All theoretical ideas are illustrated by numerical examples involving bond breaking, excited vibrational states, reactive potential energy surfaces and difficult cases of excited electronic states. The description of the existing and well-established variants of the MMCC theory, such as CR-CCSD(T), is augmented by the discussion of future prospects and potentially useful recent developments, including the extension of the black

  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. 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.

  4. Development and Applications of Advanced Electronic Structure Methods

    NASA Astrophysics Data System (ADS)

    Bell, Franziska

    This dissertation contributes to three different areas in electronic structure theory. The first part of this thesis advances the fundamentals of orbital active spaces. Orbital active spaces are not only essential in multi-reference approaches, but have also become of interest in single-reference methods as they allow otherwise intractably large systems to be studied. However, despite their great importance, the optimal choice and, more importantly, their physical significance are still not fully understood. In order to address this problem, we studied the higher-order singular value decomposition (HOSVD) in the context of electronic structure methods. We were able to gain a physical understanding of the resulting orbitals and proved a connection to unrelaxed natural orbitals in the case of Moller-Plesset perturbation theory to second order (MP2). In the quest to find the optimal choice of the active space, we proposed a HOSVD for energy-weighted integrals, which yielded the fastest convergence in MP2 correlation energy for small- to medium-sized active spaces to date, and is also potentially transferable to coupled-cluster theory. In the second part, we studied monomeric and dimeric glycerol radical cations and their photo-induced dissociation in collaboration with Prof. Leone and his group. Understanding the mechanistic details involved in these processes are essential for further studies on the combustion of glycerol and carbohydrates. To our surprise, we found that in most cases, the experimentally observed appearance energies arise from the separation of product fragments from one another rather than rearrangement to products. The final chapters of this work focus on the development, assessment, and application of the spin-flip method, which is a single-reference approach, but capable of describing multi-reference problems. Systems exhibiting multi-reference character, which arises from the (near-) degeneracy of orbital energies, are amongst the most

  5. 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.

  6. 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.

  7. Unravelling electronic and structural requisites of triplet-triplet energy transfer by advanced electron paramagnetic resonance and density functional theory

    NASA Astrophysics Data System (ADS)

    Di Valentin, M.; Salvadori, E.; Barone, V.; Carbonera, D.

    2013-10-01

    Advanced electron paramagnetic resonance (EPR) techniques, in combination with Density Functional theory (DFT), have been applied to the comparative study of carotenoid triplet states in two major photosynthetic antenna complexes, the Peridinin-chlorophyll a-protein of dinoflagellates and the light-harvesting complex II of higher plants. Carotenoid triplet states are populated by triplet-triplet energy transfer (TTET) from chlorophyll molecules to photoprotect the system from singlet oxygen formation under light-stress conditions. The TTET process is strongly dependent on the relative arrangement and on the electronic properties of the triplet states involved. The proposed spectroscopic approach exploits the concept of spin conservation during TTET, which leads to recognisable spin polarisation effects in the time-resolved and field-swept echo-detected EPR spectra. The electron spin polarisation produced at the carotenoid acceptor site depends on the initial polarisation of the chlorophyll donor and on the relative geometrical arrangement of the donor-acceptor zero-field splitting axes. We have demonstrated that a proper analysis of the spectra in the framework of spin angular momentum conservation allows to derive the pathways of TTET and to gain insight into the structural requirements of this mechanism for those antenna complexes, whose X-ray structure is available. We have further proved that this method, developed for natural antenna complexes of known X-ray structure, can be extended to systems lacking structural information in order to derive the relative arrangement of the partners in the energy transfer process. The structural requirements for efficient TTET, obtained from time-resolved and pulse EPR, have been complemented by a detailed description of the electronic structure of the carotenoid triplet state, provided by pulse Electron-Nuclear DOuble Resonance (ENDOR) experiments. Triplet-state hyperfine couplings of the α- and β-protons of the

  8. Advances in structural and functional analysis of membrane proteins by electron crystallography

    PubMed Central

    Wisedchaisri, Goragot; Reichow, Steve L.; Gonen, Tamir

    2011-01-01

    Summary Electron crystallography is a powerful technique for the study of membrane protein structure and function in the lipid environment. When well-ordered two-dimensional crystals are obtained the structure of both protein and lipid can be determined and lipid-protein interactions analyzed. Protons and ionic charges can be visualized by electron crystallography and the protein of interest can be captured for structural analysis in a variety of physiologically distinct states. This review highlights the strengths of electron crystallography and the momentum that is building up in automation and the development of high throughput tools and methods for structural and functional analysis of membrane proteins by electron crystallography. PMID:22000511

  9. Prospects of application of superconducting electrodynamic structures in electronic devices for their advancement to the terahertz range

    NASA Astrophysics Data System (ADS)

    Kuraev, A. A.; Kurkin, S. A.; Koronovskii, A. A.; Rak, A. O.; Sinitsyn, A. K.; Hramov, A. E.

    2015-04-01

    It is shown that the application of superconducting electrodynamic structures in microwave electronic devices not only improves their characteristics, but also creates premises for implementation of devices like the autophase traveling-wave tube (TWT) and peniotron operating in the millimeter range with their further advancement to the terahertz range, which is impossible for conventional electrodynamic structures with Ohmic losses. Superconducting corrugated waveguides make it possible to suspend limitations imposed on the output power of pulsed relativistic Cherenkov oscillators, which are associated with thermal degradation of the working surface of conventional waveguides with Ohmic losses.

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  14. 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.

  15. 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.

  16. 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.

  17. Skylab electronic technological advancements

    NASA Technical Reports Server (NTRS)

    Hornback, G. L.

    1974-01-01

    The present work describes three electronic devices designed for use in the Skylab airlock module: the teleprinter system, the quartz crystal microbalance contamination monitor (QCM), and the speaker. Design considerations, operation, characteristics, and system development are described for these systems, with accompanying diagrams, graphs, and photographs. The teleprinter is a thermal dot printer used to produce hard copy messages by electrically heating print elements in contact with heat-sensitive paper. The QCM was designed to estimate contamination buildup on optical surfaces of the earth resources experiment package. A vibrating quartz crystal is used as a microbalance relating deposited mass to shifts in the crystal's resonant frequency. Audio devices provide communication between crew members and between crew and STDN, and also provide audible alarms, via the caution and warning system, of out-of-limit-conditions.

  18. Self-consistent Green's function embedding for advanced electronic structure methods based on a dynamical mean-field concept

    NASA Astrophysics Data System (ADS)

    Chibani, Wael; Ren, Xinguo; Scheffler, Matthias; Rinke, Patrick

    2016-04-01

    We present an embedding scheme for periodic systems that facilitates the treatment of the physically important part (here a unit cell or a supercell) with advanced electronic structure methods, that are computationally too expensive for periodic systems. The rest of the periodic system is treated with computationally less demanding approaches, e.g., Kohn-Sham density-functional theory, in a self-consistent manner. Our scheme is based on the concept of dynamical mean-field theory formulated in terms of Green's functions. Our real-space dynamical mean-field embedding scheme features two nested Dyson equations, one for the embedded cluster and another for the periodic surrounding. The total energy is computed from the resulting Green's functions. The performance of our scheme is demonstrated by treating the embedded region with hybrid functionals and many-body perturbation theory in the GW approach for simple bulk systems. The total energy and the density of states converge rapidly with respect to the computational parameters and approach their bulk limit with increasing cluster (i.e., computational supercell) size.

  19. Characterization of advanced electronic materials

    SciTech Connect

    Arko, A.J.; Heffner, R.H.; Hundley, M.F.

    1997-08-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Our goal has been to extend the Laboratory`s competency in nuclear and advanced materials by characterizing (measuring and interpreting) physical properties of advanced electronic materials and in this process to bridge the gap between materials synthesis and theoretical understanding. Attention has focused on discovering new physics by understanding the ground states of materials in which electronic correlations dominate their properties. Among several accomplishments, we have discovered and interpreted pressure-induced superconductivity in CeRh{sub 2}Si{sub 2}, boron content in UBe{sub 13-x}B{sub x} and the origin of small gaps in the spin and charge excitation spectra of Ce{sub 3}Bi{sub 4}Pt{sub 3}, and we provided seminal understanding of large magnetoresistive effects in La{sub 1-x}Ca{sub x}MnO{sub 3}. This work has established new research directions at LANL and elsewhere, involved numerous collaborators from throughout the world and attracted several postdoctoral fellows.

  20. 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.

  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. PMID:12086529

  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 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.

  4. Advanced cryocooler electronics for space

    NASA Astrophysics Data System (ADS)

    Harvey, D.; Danial, A.; Davis, T.; Godden, J.; Jackson, M.; McCuskey, J.; Valenzuela, P.

    2004-06-01

    Space pulse-tube cryocoolers require electronics to control the cooling temperature and self-induced vibration. Other functions include engineering diagnostics, telemetry and safety protection of the unit against extreme environments and operational anomalies. The electronics must survive the harsh conditions of launch and orbit, and in some cases severe radiation environments for periods exceeding 10 years. A number of our current generation high reliability radiation hardened electronics units have been launched and others are in various stages of assembly or integration on a number of space flight programs. This paper describes the design features and performance of our next generation flight electronics designed for the STSS payloads. The electronics provides temperature control with better than +/-50 mK short-term stability. Self-induced vibration is controlled to low levels on all harmonics up to the 16th. A unique active power filter limits peak-to-peak reflected ripple current on the primary power bus to less than 3% of the average DC current. The 3 kg unit is capable of delivering 180 W continuous to NGST's high-efficiency cryocooler (HEC).

  5. 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.

  6. 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

  7. 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…

  8. Programmed electronic advance for engines

    SciTech Connect

    Dogadko, P.

    1987-03-03

    An ignition advance control is described for an internal combustion engine including a crankshaft, a throttle control, and at least one cylinder, the ignition advance control comprising a spark ignition circuit associated with the cylinder and including trigger means operative to cause an ignition spark, means for generating a control pulse associated with the cylinder, latch means for enabling the trigger means in response to generation of the control pulse, means for generating a constant plurality of sequentially occurring electrical reference pulses during each revolution of the crankshaft, means for counting the reference pulses developed during each revolution of the crankshaft, means for firing the enabled trigger means in response to the counting means counting a predetermined number of the reference pulses to cause the ignition spark at a predetermined ignition point in each revolution of the crankshaft, means for sensing the position of the throttle control, and means responsive to the throttle sensing means for varying the predetermined number of reference pulses solely in accordance with the position of the throttle control to vary the predetermined ignition point as appropriate for the position of the throttle control.

  9. 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)

  10. 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…

  11. 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.

  12. 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.

  13. 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.

  14. Advanced superconducting materials for electronic applications

    NASA Astrophysics Data System (ADS)

    Beasley, M. R.

    1980-10-01

    Developments in the fabrication of tunnel junctions using Nb- and V-base transition-metal compounds and alloys are summarized. Particular attention is given to the advances in codeposition of these refractory high-transition-temperature superconductors and the properties of thin films deposited by the dual-electron-beam coevaporation technique. Problems associated with these materials are identified, and prospects for the future are discussed. Of the materials reviewed, Nb3Sn is singled out as one deserving further development.

  15. 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.

  16. Electronic spark advance-type ignition system

    SciTech Connect

    Koike, H.

    1986-12-09

    An electronic spark advance-type ignition system is described for an internal combustion engine comprising: an ignition coil; a magnetic pickup for generating a pair of pulse signals with a time interval therebetween substantially corresponding to a maximum advance angle in terms of crankshaft rotation degrees for each rotation of a crankshaft of the engine; signal generating means responsive to the pair of pulse signals for the pickup for generating a pair of comparison signals of different levels within each of the crankshaft rotation degrees of the maximum advance angle and the other crankshaft rotation degrees; and control means for comparing the signal levels of each of the pairs of comparison signals to generate an energization starting position signal and an ignition timing determining ignition position signal for the ignition coil, the signal generating means including means for controlling the waveform of one of the pair of comparison signals so that the ignition position signal is advanced in angle with respect to the energization starting position signal. The energization starting position signal is generated under all conditions prior to the timing of generation of the earlier one of the next pair of pulse signals generated from the pickup. The ignition position signal is generated within the maximum advance angle at a point in time following generation of the earlier one of the next pair of pulse signals by at least a predetermined amount.

  17. MCSNA: Experimental Benchmarking of Pu Electronic Structure

    SciTech Connect

    Tobin, J G

    2007-01-29

    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.

  18. 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.

  19. 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

    2004-01-01

    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. PMID:16012695

  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. Electron energy loss spectroscopy in advanced materials

    SciTech Connect

    Zaluzec, N.J.

    1991-01-01

    The combination of a Transmission Electron Microscope (TEM) with an electron energy loss spectrometer (EELS) yields a powerful tool for the microcharacterization of materials. However, the application of this technique to advanced materials problems can only be fully appreciated when the information obtained using EELS is related to that obtained from other analytical spectroscopies. In this chapter, we briefly discuss the relative performance of X-ray, Auger and Photoelectron Spectroscopies with EELS pointing out the limitations and merits of each. This comparison is followed by examples of the application of EELS to investigations involving high {Tc} superconductors, artificial metallic superlattices, amorphous magnetic materials and the characterization of metallic hydride phases. 14 refs., 22 figs.

  2. Advanced diesel electronic fuel injection and turbocharging

    NASA Astrophysics Data System (ADS)

    Beck, N. J.; Barkhimer, R. L.; Steinmeyer, D. C.; Kelly, J. E.

    1993-12-01

    The program investigated advanced diesel air charging and fuel injection systems to improve specific power, fuel economy, noise, exhaust emissions, and cold startability. The techniques explored included variable fuel injection rate shaping, variable injection timing, full-authority electronic engine control, turbo-compound cooling, regenerative air circulation as a cold start aid, and variable geometry turbocharging. A Servojet electronic fuel injection system was designed and manufactured for the Cummins VTA-903 engine. A special Servojet twin turbocharger exhaust system was also installed. A series of high speed combustion flame photos was taken using the single cylinder optical engine at Michigan Technological University. Various fuel injection rate shapes and nozzle configurations were evaluated. Single-cylinder bench tests were performed to evaluate regenerative inlet air heating techniques as an aid to cold starting. An exhaust-driven axial cooling air fan was manufactured and tested on the VTA-903 engine.

  3. 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

  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. Membrane protein structure determination by electron crystallography

    PubMed Central

    Ubarretxena-Belandia, Iban; Stokes, David L.

    2012-01-01

    During the past year, electron crystallography of membrane proteins has provided structural insights into the mechanism of several different transporters and into their interactions with lipid molecules within the bilayer. From a technical perspective there have been important advances in high-throughput screening of crystallization trials and in automated imaging of membrane crystals with the electron microscope. There have also been key developments in software, and in molecular replacement and phase extension methods designed to facilitate the process of structure determination. PMID:22572457

  6. 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.

  7. 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.

  8. Electron speckle photography: some recent advances

    NASA Astrophysics Data System (ADS)

    Chiang, Fu-pen

    2006-09-01

    When the speckle pattern is displaced, the displacement vector can be obtained by performing a correlation comparison between the two patterns, either optically or numerically. The so-called speckle photography technique has become an important metrological, strain analysis and fluid mechanics tool. The resolution of speckle technique depends on the size of the speckles employed. For an optical recording system, it is essentially limited to the wavelength of the light used and is about 0.5μm within the visible spectrum. In 1982 Chiang introduced the electron speckle photography concept whereby sub-micron and nanometer speckles were created via a process of physical vapor deposition and recording was made by an electron microscope, either a SEM or a TEM. As a result the resolution of speckle photography was increased by several orders of magnitude. With the advancement of digital speckle techniques the method is now fully automated. This paper discusses the current state art of this technique, and its application to the determination of differential thermal strains in electronic packaging, shear band formation in the lamellar interfaces of TiAl and prediction of the crack growth, the size effect of MEMS material SU-8, the micro-mechanical properties of artificial tissues, and the mechanical properties of metal oxide nanofibers. Also discussed in the paper are potential applications of this technique to nanotechnology and bio mechanics.

  9. Advanced fabrication technologies for nano-electronics

    SciTech Connect

    Simmons, J.A.; Weckwerth, M.V.; Baca, W.E.

    1996-03-01

    Three novel fabrication technologies are presented which greatly increase the tools available for the realization of nano-electronic devices. First, a sub-micron area post structure descending from a metallic airbridge allows gating of regions as small as 0.1 {mu}m in diameter. This has enabled the study of such quantum phenomena as coupling of parallel quantum point contacts, and electron focusing around a tunable quantum antidot. We also describe two new techniques for backgating multiquantum well structures with submicron lateral resolution. These techniques enable separate ohmic contacts to individual quantum wells spaced as closely as 100 {Angstrom}, and thus allow the fabrication of novel quantum tunneling devices. The first technique uses regrowth over a patterned ion-implanted substrate. The second involves a novel epoxy-bond-and-stop-etch (EBASE) processing scheme, whereby the original substrate is etched away and the backside then patterned using conventional methods.

  10. Electronics for Piezoelectric Smart Structures

    NASA Technical Reports Server (NTRS)

    Warkentin, D. J.; Tani, J.

    1997-01-01

    This paper briefly presents work addressing some of the basic considerations for the electronic components used in smart structures incorporating piezoelectric elements. After general remarks on the application of piezoelectric elements to the problem of structural vibration control, three main topics are described. Work to date on the development of techniques for embedding electronic components within structural parts is presented, followed by a description of the power flow and dissipation requirements of those components. Finally current work on the development of electronic circuits for use in an 'active wall' for acoustic noise is introduced.

  11. 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…

  12. Resolving Presynaptic Structure by Electron Tomography

    PubMed Central

    Perkins, Guy A.; Jackson, Dakota R.; Spirou, George A.

    2016-01-01

    A key goal in neurobiology is to generate a theoretical framework that merges structural, physiological and molecular explanations of brain function. These categories of explanation do not advance in synchrony; advances in one category define new experiments in other categories. For example, the synapse was defined physiologically and biochemically before it was visualized using electron microscopy. Indeed, the original descriptions of synapses in the 1950s were lent credence by the presence of spherical vesicles in presynaptic terminals that were considered to be the substrate for quantal neurotransmission. In the last few decades, our understanding of synaptic function has again been driven by physiological and molecular techniques. The key molecular players for synaptic vesicle structure, mobility and fusion were identified and applications of the patch clamp technique permitted physiological estimation of neurotransmitter release and receptor properties. These advances demand higher resolution structural images of synapses. During the 1990s a second renaissance in cell biology driven by EM was fueled by improved techniques for electron tomography (ET) with the ability to compute virtual images with nm resolution between image planes. Over the last fifteen years, ET has been applied to the presynaptic terminal with special attention to the active zone and organelles of the nerve terminal. In this review, we first summarize the technical improvements that have led to a resurgence in utilization of ET and then we summarize new insights gained by the application of ET to reveal the high-resolution structure of the nerve terminal. PMID:25683026

  13. Resolving presynaptic structure by electron tomography.

    PubMed

    Perkins, Guy A; Jackson, Dakota R; Spirou, George A

    2015-05-01

    A key goal in neurobiology is to generate a theoretical framework that merges structural, physiological, and molecular explanations of brain function. These categories of explanation do not advance in synchrony; advances in one category define new experiments in other categories. For example, the synapse was defined physiologically and biochemically before it was visualized using electron microscopy. Indeed, the original descriptions of synapses in the 1950s were lent credence by the presence of spherical vesicles in presynaptic terminals that were considered to be the substrate for quantal neurotransmission. In the last few decades, our understanding of synaptic function has again been driven by physiological and molecular techniques. The key molecular players for synaptic vesicle structure, mobility and fusion were identified and applications of the patch clamp technique permitted physiological estimation of neurotransmitter release and receptor properties. These advances demand higher resolution structural images of synapses. During the 1990s a second renaissance in cell biology driven by EM was fueled by improved techniques for electron tomography (ET) with the ability to compute virtual images with nm resolution between image planes. Over the last 15 years, ET has been applied to the presynaptic terminal with special attention to the active zone and organelles of the nerve terminal. In this review, we first summarize the technical improvements that have led to a resurgence in utilization of ET and then we summarize new insights gained by the application of ET to reveal the high-resolution structure of the nerve terminal. PMID:25683026

  14. Advances in digital video for electronic media.

    PubMed

    McAfooes, J A

    1997-01-01

    From media's early days of film strips and records, to today's multimedia CD-ROMs, nurses have embraced educational tools. Today, the capabilities of these tools have placed a tremendous demand for providing information any time, any where. This has led to increasing digitization of sights and sounds. Once digitized, this information can travel over information highways made up of telephone lines, fiberoptic cables, microwaves and satellites, or it can be stored on magnetic and optical media. Technological advances have made it possible for computer users to create, store and retrieve high quality digital still and moving video and audio for inclusion in electronic media. Methods for digitizing include capturing and converting the information with cameras, scanners and capture boards. Digital video compression/decompression (codec) standards vary in quality. Potential uses of digital video abound including video on demand, videoconferencing, distance learning, telemedicine, on-line education and computer-based training. Examples illustrating the differences in digital video formats will be shown during the presentation. PMID:10175444

  15. 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

  16. Electronic structure and correlation effects in actinides

    SciTech Connect

    Albers, R.C.

    1998-12-01

    This report consists of the vugraphs given at a conference on electronic structure. Topics discussed are electronic structure, f-bonding, crystal structure, and crystal structure stability of the actinides and how they are inter-related.

  17. 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)

  18. 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.

  19. Structural and electronic properties of sodium nanoclusters

    NASA Astrophysics Data System (ADS)

    Perez, Luis A.; Reyes-Nava, Juan A.; Garzon, Ignacio L.

    2006-03-01

    Recent advances on mass selection of sodium nanoclusters and their characterization by photoemission electron spectroscopy [1] have given useful data for a variety of clusters sizes. These data may lead to assignments of the relevant structures by comparing the measured photoelectron spectra (PES) with the electronic density of states (DOS) obtained from DFT calculations. In this work, the lowest energy structures modeled by the many-body Gupta potential, are obtained by using molecular dynamics simulations for Nan (n= 178, 204, 271, 298-300, 309). DFT calculations were then performed for neutral, positively- and negatively-charged Nan clusters. A comparison between the DOS of clusters of the same size but different charge will be presented, as well as between the available experimental PES and the theoretical obtained DOS.[1] H. Haberland, T. Hippler, J. Donges, O. Kostko, M. Schmidt, B. von Issendorff, Phys. Rev. Lett. 94, 035701 (2005).

  20. Advanced Power Electronics for LED Drivers: Advanced Technologies for integrated Power Electronics

    SciTech Connect

    2010-09-01

    ADEPT Project: MIT is teaming with Georgia Institute of Technology, Dartmouth College, and the University of Pennsylvania (UPenn) to create more efficient power circuits for energy-efficient light-emitting diodes (LEDs) through advances in 3 related areas. First, the team is using semiconductors made of high-performing gallium nitride grown on a low-cost silicon base (GaN-on-Si). These GaN-on-Si semiconductors conduct electricity more efficiently than traditional silicon semiconductors. Second, the team is developing new magnetic materials and structures to reduce the size and increase the efficiency of an important LED power component, the inductor. This advancement is important because magnetics are the largest and most expensive part of a circuit. Finally, the team is creating an entirely new circuit design to optimize the performance of the new semiconductors and magnetic devices it is using.

  1. 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.

  2. Electronic structure of black sodalite

    NASA Astrophysics Data System (ADS)

    Sankey, Otto F.; Demkov, Alexander A.; Lenosky, Thomas

    1998-06-01

    The electronic structure of black sodalite, Na8(AlSiO4)6, is determined in the local-spin-density approximation (LSDA). This structure has six Na atoms to compensate the six Al atoms, leaving two excess Na atoms. A band-gap electronic state is induced in the wide oxide gap by the excess sodium, and has ``particle in a box'' behavior. Magnetic orderings of these gap states are studied. Analytic models show that an antiferromagnetic ordering is lowest in energy in the LSDA. A self-consistent LSDA calculation shows the system to change from a metal to an antiferromagnetic insulator when spin orderings are allowed. Hopping and Hubbard-U parameters are estimated, and the many-body correlated Hubbard model is solved using a constrained path Monte Carlo technique, which again predicts the system to be antiferromagnetic with a Tc of order 50 K.

  3. Electronic structure of Calcium hexaborides

    SciTech Connect

    Lee, Byounghak; Wang, Lin-Wang

    2005-06-15

    We present a theoretical study of crystal and electronic structures of CaB6 within a screened-exchange local density approximation (sX-LDA). Our ab initio total energy calculations show that CaB6 is a semiconductor with a gap of >1.2 eV, in agreement with recent experimental observations. We show a very sensitive band gap dependence on the crystal internal parameter, which might partially explain the scatter of previous theoretical results. Our calculation demonstrates that it is essential to study this system simultaneously for both crystal structures and electronic properties, and that the sX-LDA provides an ideal method for this problem.

  4. Drafting. Advanced Print Reading--Electronics.

    ERIC Educational Resources Information Center

    Oregon State Dept. of Education, Salem.

    This document is a workbook for drafting students learning the basics of reading and interpreting electronic drawings and diagrams. The workbook contains eight units covering the following material: basic symbols; circuit symbols; electron tube symbols; winding symbols; semiconductor symbols; miscellaneous symbols; schematic diagrams; and…

  5. Advanced High Temperature Structural Seals

    NASA Technical Reports Server (NTRS)

    Newquist, Charles W.; Verzemnieks, Juris; Keller, Peter C.; Shorey, Mark W.; Steinetz, Bruce (Technical Monitor)

    2000-01-01

    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 lb 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. During the first phase of this program the existing launch vehicle control surface sealing concepts were reviewed, the aerothermal environment for a high temperature seal design was analyzed and a mock up of an arc-jet test fixture for evaluating seal concepts was fabricated.

  6. 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.

  7. Advances and trends in computational structural mechanics

    NASA Technical Reports Server (NTRS)

    Noor, A. K.

    1986-01-01

    Recent developments in computational structural mechanics are reviewed with reference to computational needs for future structures technology, advances in computational models for material behavior, discrete element technology, assessment and control of numerical simulations of structural response, hybrid analysis, and techniques for large-scale optimization. Research areas in computational structural mechanics which have high potential for meeting future technological needs are identified. These include prediction and analysis of the failure of structural components made of new materials, development of computational strategies and solution methodologies for large-scale structural calculations, and assessment of reliability and adaptive improvement of response predictions.

  8. Advances in Defocused-Beam Electron-Probe Microanalysis

    NASA Astrophysics Data System (ADS)

    Carpenter, P. K.; Zeigler, R. A.; Jolliff, B. L.

    2010-03-01

    Advances in defocused-beam electron-probe microanalysis are presented, with an Excel VBA algorithm which uses a polynomial alpha factor correction algorithm coupled with a catanorm procedure to correct DBA data.

  9. 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.

  10. 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.

  11. Advanced analytical electron microscopy for alkali-ion batteries

    DOE PAGESBeta

    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 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

  12. Electronic structure of graphite oxide

    NASA Astrophysics Data System (ADS)

    Jeong, Hae Kyung; Yang, Cheolsoo; Kim, Bong Soo; Kim, Ki-Jeong

    2011-03-01

    We have investigated the electronic structure of graphite oxide by photoelectron spectroscopy at the Pohang Accelerator Laboratory, Korea. The typical sp 2 hybridization states found in graphite were also seen in graphite oxide. However, the π state disappeared near the Fermi level because of bonding between the π and oxygen-related states originating from graphite oxide, indicating electron transfer from graphite to oxygen and resulting in a downward shift of the highest occupied molecular orbital (HOMO) state to higher binding energies. The band gap opening increased to about 1.8 eV, and additional oxygen-related peaks were observed at 8.5 and 27 eV. This research was supported by the Basic Science Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology (2010-0004592), and partly by the MEST (2009-0087138). Experiments at the PLS were supported in part by POSTECH and MEST.

  13. 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

  14. 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.

  15. Advances in DC photocathode electron guns

    SciTech Connect

    Bruce M. Dunham; P. Heartmann; Reza Kazimi; Hongxiu Liu; B. M. Poelker; J. S. Price; P. M. Rutt; W. J. Schneider; Charles K. Sinclair

    1998-07-01

    At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughout. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion backbombardment, and precise control of all of the electrons emitted from the cathode. In this paper, the authors will review recent results and discuss implications for future photocathode guns.

  16. 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.

  17. Electronic structure of lithium amide

    NASA Astrophysics Data System (ADS)

    Kamakura, N.; Takeda, Y.; Saitoh, Y.; Yamagami, H.; Tsubota, M.; Paik, B.; Ichikawa, T.; Kojima, Y.; Muro, T.; Kato, Y.; Kinoshita, T.

    2011-01-01

    The electronic structure of the insulator lithium amide (LiNH2), which is a lightweight complex hydride being considered as a high-capacity hydrogen storage material, is investigated by N 1s soft x-ray emission spectroscopy (XES) and absorption spectroscopy (XAS). The XES and XAS spectra show a band gap between the valence and conduction bands. The valence band in the XES spectrum consists of three peaks, which extend up to ~-8 eV from the valence band top. The band calculation within the local-density approximation (LDA) for LiNH2shows energetically separated three peaks in the occupied N 2p partial density of states (pDOS) and the band gap. The energy distribution of three peaks in the XES spectrum agrees with that in the calculated pDOS except for the peak at the highest binding energy, which is attributed to the strongly hybridized state between N 2p and H 1s. The XES experiment has clarified that the strongly hybridized state with H 1s in LiNH2is located at binding energy higher than that of the LDA calculation, while the overall feature of the electronic structure of LiNH2experimentally obtained by XES and XAS is consistent with the calculated result.

  18. 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. PMID:27463253

  19. 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.

  20. Advanced flexible electronics: challenges and opportunities

    NASA Astrophysics Data System (ADS)

    Bedell, Stephen W.; Shahrjerdi, Davood; Fogel, Keith; Lauro, Paul; Bayram, Can; Hekmatshoar, Bahman; Li, Ning; Ott, John; Sadana, Devendra

    2014-06-01

    Thin, lightweight and flexible electronics are being regarded as an important evolutionary step in the development of novel technological products. Interestingly, this trend has emerged in a wide range of industries; from microelectronics to photovoltaics and even solid state lighting. Historically, most attempts to enable flexibility have focused on the introduction of new material systems that, so far, severely compromise the performance compared to state-of-the-art products. The few approaches that do attempt to render contemporary high-performance materials flexible rely on layer transfer techniques that are complicated, expensive and material-specific. In this paper, we review a method of removing surface layers from brittle substrates called Controlled Spalling Technology that allows one to simple peel material or device layers from their host substrate after they have been fabricated. This allows one to fabricate high-performance electronic products in a manner of their choosing, and make them flexible afterwards. This technique is simple, inexpensive and largely independent of substrate material or size. We demonstrate the power and generality of Controlled Spalling by application to a number of disparate applications including high-performance integrated circuits, high-efficiency photovoltaics and GaN-based solid state lighting.

  1. 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

  2. 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.

  3. 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.

  4. Advanced fiber placement of composite fuselage structures

    NASA Technical Reports Server (NTRS)

    Anderson, Robert L.; Grant, Carroll G.

    1991-01-01

    The Hercules/NASA Advanced Composite Technology (ACT) program will demonstrate the low cost potential of the automated fiber placement process. The Hercules fiber placement machine was developed for cost effective production of composite aircraft structures. The process uses a low cost prepreg tow material form and achieves equivalent laminate properties to structures fabricated with prepreg tape layup. Fiber placement demonstrations planned for the Hercules/NASA program include fabrication of stiffened test panels which represent crown, keel, and window belt segments of a typical transport aircraft fuselage.

  5. 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.

  6. 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.

  7. Advanced Undergraduate Laboratory Experiment in Inelastic Electron Tunneling Spectroscopy.

    ERIC Educational Resources Information Center

    White, H. W.; Graves, R. J.

    1982-01-01

    An advanced undergraduate laboratory experiment in inelastic electron tunneling spectroscopy is described. Tunnel junctions were fabricated, the tunneling spectra of several molecules absorbed on the surface of aluminum oxide measured, and mode assignments made for several of the prominent peaks in spectra using results obtained from optical…

  8. 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.

  9. Electronic structure of herbicides: Atrazine and bromoxynil

    NASA Astrophysics Data System (ADS)

    Novak, Igor; Kovač, Branka

    2011-06-01

    The electronic structures of herbicides atrazine and bromoxynil have been investigated by UV photoelectron spectroscopy (UPS), quantum chemical calculations and comparison with X-ray diffraction, molecular docking and molecular dynamics studies. Their electronic and molecular structures are discussed in the context of their biological activity. This is the first report which correlates the molecular mechanism of biological activity of these herbicides with their experimentally determined electronic and molecular structures.

  10. On the feasibility to investigate point defects by advanced electron microscopy

    SciTech Connect

    Kisielowski, C.; Jinschek, J.R.

    2002-10-02

    Transmission Electron Microscopy evolves rapidly as a primary tool to investigate nano structures on a truly atomic level. Its resolution reaches into the sub Angstrom region by now. Together with a better correction of lens aberrations, sensitivities are drastically enhanced. Utilizing advanced electron microscopes, it is feasible to promote experiments that aim to detect single atoms. This enables local investigations of non-stoichiometry. This paper reviews the current state-of-the-art.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Structural Tailoring of Advanced Turboprops (STAT)

    NASA Technical Reports Server (NTRS)

    Brown, Kenneth W.

    1988-01-01

    This interim report describes the progress achieved in the structural Tailoring of Advanced Turboprops (STAT) 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. This report provides a detailed description of the input, optimization procedures, approximate analyses and refined analyses, as well as validation test cases for the STAT program. In addition, conclusions and recommendations are summarized.

  16. 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.

  17. 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

  18. 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

  19. Advanced tow placement of composite fuselage structure

    NASA Technical Reports Server (NTRS)

    Anderson, Robert L.; Grant, Carroll G.

    1992-01-01

    The Hercules NASA ACT program was established to demonstrate and validate the low cost potential of the automated tow placement process for fabrication of aircraft primary structures. The program is currently being conducted as a cooperative program in collaboration with the Boeing ATCAS Program. The Hercules advanced tow placement process has been in development since 1982 and was developed specifically for composite aircraft structures. The second generation machine, now in operation at Hercules, is a production-ready machine that uses a low cost prepreg tow material form to produce structures with laminate properties equivalent to prepreg tape layup. Current program activities are focused on demonstration of the automated tow placement process for fabrication of subsonic transport aircraft fuselage crown quadrants. We are working with Boeing Commercial Aircraft and Douglas Aircraft during this phase of the program. The Douglas demonstration panels has co-cured skin/stringers, and the Boeing demonstration panel is an intricately bonded part with co-cured skin/stringers and co-bonded frames. Other aircraft structures that were evaluated for the automated tow placement process include engine nacelle components, fuselage pressure bulkheads, and fuselage tail cones. Because of the cylindrical shape of these structures, multiple parts can be fabricated on one two placement tool, thus reducing the cost per pound of the finished part.

  20. 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. PMID:26403162

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Membrane protein structures without crystals, by single particle electron cryomicroscopy

    PubMed Central

    Vinothkumar, Kutti R

    2015-01-01

    It is an exciting period in membrane protein structural biology with a number of medically important protein structures determined at a rapid pace. However, two major hurdles still remain in the structural biology of membrane proteins. One is the inability to obtain large amounts of protein for crystallization and the other is the failure to get well-diffracting crystals. With single particle electron cryomicroscopy, both these problems can be overcome and high-resolution structures of membrane proteins and other labile protein complexes can be obtained with very little protein and without the need for crystals. In this review, I highlight recent advances in electron microscopy, detectors and software, which have allowed determination of medium to high-resolution structures of membrane proteins and complexes that have been difficult to study by other structural biological techniques. PMID:26435463

  7. 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.

  8. Structural change of graphite during electron irradiation

    SciTech Connect

    Koike, J. . Dept. of Mechanical Engineering); Pedraza, D.F. )

    1992-01-01

    Highly oriented pyrolytic graphite was irradiated at room temperature with 300-keV electrons. High resolution transmission electron microscopy and electron energy loss spectroscopy were employed to study the structure of electron-irradiated graphite. Results consistently indicated absence of long-range order periodicity in the basal plane, and loose retention of the c-axis periodicity. Structure was modeled based on a mixture of sixfold and non-sixfold atom rings. Formation of non-sixfold atom rings was related to the observed buckling and discontinuity of the original graphite basal plane.

  9. Structural change of graphite during electron irradiation

    SciTech Connect

    Koike, J.; Pedraza, D.F.

    1992-12-31

    Highly oriented pyrolytic graphite was irradiated at room temperature with 300-keV electrons. High resolution transmission electron microscopy and electron energy loss spectroscopy were employed to study the structure of electron-irradiated graphite. Results consistently indicated absence of long-range order periodicity in the basal plane, and loose retention of the c-axis periodicity. Structure was modeled based on a mixture of sixfold and non-sixfold atom rings. Formation of non-sixfold atom rings was related to the observed buckling and discontinuity of the original graphite basal plane.

  10. About zitterbewegung and electron structure

    NASA Astrophysics Data System (ADS)

    Rodrigues, Waldyr A.; Vaz, Jayme; Recami, Erasmo; Salesi, Giovanni

    1993-12-01

    We start from the spinning electron model by Barut and Zanghi, which has been recently translated into the Clifford algebra language. We ``complete'' such a translation, first of all, by expressing in the Clifford formalism a particular Barut-Zanghi (BZ) solution, which refers (at the classical limit) to an ``internal'' helical motion with a time-like speed (and is here shown to originate from the superposition of positive and negative frequency solutions of the Dirac equation). Then, we show how to construct solutions of the Dirac equation describing helical motions with light-like speed, which meet very well the standard interpretation of the velocity operator in the Dirac equation theory (and agree with the solution proposed by Hestenes, on the basis - however - of ad-hoc assumptions that are unnecessary in the present approach). The above results appear to support the conjecture that the zitterbewegung motion (a helical motion, at the classical limit) is responsible for the electron spin.

  11. Advanced electronic displays and their potential in future transport aircraft

    NASA Technical Reports Server (NTRS)

    Hatfield, J. J.

    1981-01-01

    It is pointed out that electronic displays represent one of the keys to continued integration and improvement of the effectiveness of avionic systems in future transport aircraft. An employment of modern electronic display media and generation has become vital in connection with the increases in modes and functions of modern aircraft. Requirements for electronic systems of future transports are examined, and a description is provided of the tools which are available for cockpit integration, taking into account trends in information processing and presentation, trends in integrated display devices, and trends concerning input/output devices. Developments related to display media, display generation, and I/O devices are considered, giving attention to a comparison of CRT and flat-panel display technology, advanced HUD technology and multifunction controls. Integrated display formats are discussed along with integrated systems and cockpit configurations.

  12. Electronic structure of metallic glasses

    SciTech Connect

    Oelhafen, P.; Lapka, R.; Gubler, U.; Krieg, J.; DasGupta, A.; Guentherodt, H.J.; Mizoguchi, T.; Hague, C.; Kuebler, J.; Nagel, S.R.

    1981-01-01

    This paper is organized in six sections and deals with (1) the glassy transition metal alloys, their d-band structure, the d-band shifts on alloying and their relation to the alloy heat of formation (..delta..H) and the glass forming ability, (2) the glass to crystal phase transition viewed by valence band spectroscopy, (3) band structure calculations, (4) metallic glasses prepared by laser glazing, (5) glassy normal metal alloys, and (6) glassy hydrides.

  13. Electron-phonon renormalization of the electronic structure of diamond

    NASA Astrophysics Data System (ADS)

    Giustino, Feliciano; Louie, Steven G.; Cohen, Marvin L.

    2011-03-01

    The calculation of band structures from first-principles has reached a high level of accuracy. Calculations combining density-functional theory with many-body perturbation theory often are in good agreement with measurements by photoemission, tunneling, and other spectroscopic probes. While significant efforts have been devoted to improving the description of electron-electron interactions in these calculations, the effect of lattice vibrations has largely been overlooked so far. In this work we study from first principles the electron-phonon renormalization of the band gap of diamond. The calculated temperature dependence of the gap and the broadening of the absorption edge are in excellent agreement with spectroscopic ellipsometry data. Interestingly we find a gap renormalization due to zero-point vibrations as large as 0.6 eV. We discuss the implications of our findings for the electronic structure of other carbon-based bulk materials and nanostructures.

  14. 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.…

  15. 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

  16. 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)

  17. 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.

  18. Advanced Metal Foam Structures for Outer Space

    NASA Technical Reports Server (NTRS)

    Hanan, Jay; Johnson, William; Peker, Atakan

    2005-01-01

    A document discusses a proposal to use advanced materials especially bulk metallic glass (BMG) foams in structural components of spacecraft, lunar habitats, and the like. BMG foams, which are already used on Earth in some consumer products, are superior to conventional metal foams: BMG foams have exceptionally low mass densities and high strength-to-weight ratios and are more readily processable into strong, lightweight objects of various sizes and shapes. These and other attractive properties of BMG foams would be exploited, according to the proposal, to enable in situ processing of BMG foams for erecting and repairing panels, shells, containers, and other objects. The in situ processing could include (1) generation of BMG foams inside prefabricated deployable skins that would define the sizes and shapes of the objects thus formed and (2) thermoplastic deformation of BMG foams. Typically, the generation of BMG foams would involve mixtures of precursor chemicals that would be subjected to suitable pressure and temperature schedules. In addition to serving as structural components, objects containing or consisting of BMG foams could perform such functions as thermal management, shielding against radiation, and shielding against hypervelocity impacts of micrometeors and small debris particles.

  19. Electronic structure and photophysical properties of polyimides

    SciTech Connect

    LaFemina, J.P.; Kafafi, S.A.

    1992-04-01

    The quantum mechanical AM1 and CNDO/S3 models were used to examine the effect of isoelectronic substitutions on the conformation, electronic structure, and optical absorption spectra for a series of aromatic polyimides. An analysis of the geometric changes at the substitution site and its effect on the electronic structure allowed for the prediction of changes in the ICT band of the optical absorption spectra.

  20. 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

  1. 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.

  2. 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...

  3. 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

  4. Optical Fiber Sensors for Advanced Civil Structures

    NASA Astrophysics Data System (ADS)

    de Vries, Marten Johannes Cornelius

    1995-01-01

    The objective of this dissertation is to develop, analyze, and implement optical fiber-based sensors for the nondestructive quantitative evaluation of advanced civil structures. Based on a comparative evaluation of optical fiber sensors that may be used to obtain quantitative information related to physical perturbations in the civil structure, the extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensor is selected as the most attractive sensor. The operation of the EFPI sensor is explained using the Kirchhoff diffraction approach. As is shown in this dissertation, this approach better predicts the signal-to-noise ratio as a function of gap length than methods employed previously. The performance of the optical fiber sensor is demonstrated in three different implementations. In the first implementation, performed with researchers in the Civil Engineering Department at the University of Southern California in Los Angeles, optical fiber sensors were used to obtain quantitative strain information from reinforced concrete interior and exterior column-to-beam connections. The second implementation, performed in cooperation with researchers at the United States Bureau of Mines in Spokane, Washington, used optical fiber sensors to monitor the performance of roof bolts used in mines. The last implementation, performed in cooperation with researchers at the Turner-Fairbanks Federal Highway Administration Research Center in McLean, Virginia, used optical fiber sensors, attached to composite prestressing strands used for reinforcing concrete, to obtain absolute strain information. Multiplexing techniques including time, frequency and wavelength division multiplexing are briefly discussed, whereas the principles of operation of spread spectrum and optical time domain reflectometery (OTDR) are discussed in greater detail. Results demonstrating that spread spectrum and OTDR techniques can be used to multiplex optical fiber sensors are presented. Finally, practical

  5. 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.

  6. 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

  7. Advances in modeling and simulation of vacuum electronic devices

    SciTech Connect

    Antonsen, T.M. Jr.; Mondelli, A.A.; Levush, B.; Verboncoeur, J.P.; Birdsall, C.K.

    1999-05-01

    Recent advances in the modeling and simulation of vacuum electronic devices are reviewed. Design of these devices makes use of a variety of physical models and numerical code types. Progress in the development of these models and codes is outlined and illustrated with specific examples. The state of the art in device simulation is evolving to the point such that devices can be designed on the computer, thereby eliminating many trial and error fabrication and test steps. The role of numerical simulation in the design process can be expected to grow further in the future.

  8. 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.

  9. Advanced electron crystallography through model-based imaging.

    PubMed

    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

  10. 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

  11. 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.

  12. 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.

  13. Electronic structure calculations in arbitrary electrostatic environments

    NASA Astrophysics Data System (ADS)

    Watson, Mark A.; Rappoport, Dmitrij; Lee, Elizabeth M. Y.; Olivares-Amaya, Roberto; Aspuru-Guzik, Alán

    2012-01-01

    Modeling of electronic structure of molecules in electrostatic environments is of considerable relevance for surface-enhanced spectroscopy and molecular electronics. We have developed and implemented a novel approach to the molecular electronic structure in arbitrary electrostatic environments that is compatible with standard quantum chemical methods and can be applied to medium-sized and large molecules. The scheme denoted CheESE (chemistry in electrostatic environments) is based on the description of molecular electronic structure subject to a boundary condition on the system/environment interface. Thus, it is particularly suited to study molecules on metallic surfaces. The proposed model is capable of describing both electrostatic effects near nanostructured metallic surfaces and image-charge effects. We present an implementation of the CheESE model as a library module and show example applications to neutral and negatively charged molecules.

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

    PubMed

    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

  15. 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

  16. 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. PMID:26646168

  17. The Electronic Structure of Amorphous Carbon Nanodots.

    PubMed

    Margraf, Johannes T; Strauss, Volker; Guldi, Dirk M; Clark, Timothy

    2015-06-18

    We have studied hydrogen-passivated amorphous carbon nanostructures with semiempirical molecular orbital theory in order to provide an understanding of the factors that affect their electronic properties. Amorphous structures were first constructed using periodic calculations in a melt/quench protocol. Pure periodic amorphous carbon structures and their counterparts doped with nitrogen and/or oxygen feature large electronic band gaps. Surprisingly, descriptors such as the elemental composition and the number of sp(3)-atoms only influence the electronic structure weakly. Instead, the exact topology of the sp(2)-network in terms of effective conjugation defines the band gap. Amorphous carbon nanodots of different structures and sizes were cut out of the periodic structures. Our calculations predict the occurrence of localized electronic surface states, which give rise to interesting effects such as amphoteric reactivity and predicted optical band gaps in the near-UV/visible range. Optical and electronic gaps display a dependence on particle size similar to that of inorganic colloidal quantum dots. PMID:25731776

  18. Advanced Diagnostics for Developing High-Brightness Electron Beams

    SciTech Connect

    Ben-Zvi, I.; Babzien, M.; Malone, R.; Wang, X.-J.; Yakimenko, V.

    1998-11-24

    The production of high-brightness particle beams calls for the development of advanced beam diagnostics. High brightness beams, meaning beams with a high density in phase space, are important for many applications, such as short-wavelength Free-Electron Lasers and advanced accelerator systems. A diagnostic that provides detailed information on the density distribution of the electron bunch in multi-dimensional phase-space is an essential tool for obtaining small emittance at a high charge. This diagnostic system has been developed at Brookhaven National Laboratory. One component of the system is the measurement of a slice emittance which provides a measurement of transverse beam properties (such as emittance) as a function of the longitudinal position. Changing the laser pulse profile of a photocathode RF gun has been suggested as one way to achieve non-linear emittance compensation and improve the brightness and that can be diagnosed by the slice emittance system. The other element of the diagnostic is the tomographic reconstruction of the transverse phase. In our work we give special attention to the accuracy of the phase space reconstruction and present an analysis using a transport line with nine focusing magnets and techniques to control the optical functions and phases. This high precision phase space tomography together with the ability to modify the radial charge distribution of the electron beam presents an opportunity to improve the emittance and apply non-linear radial emittance corrections. Combining the slice emittance and tomography diagnostics leads to an unprecedented visualization of phase space distributions in 5 dimensional phase-space and an opportunity to perform high-order emittance corrections. This should lead to great improvements in the beam brightness.

  19. ADVANCED DIAGNOSTICS FOR DEVELOPING HIGH-BRIGHTNESS ELECTRON BEAMS.

    SciTech Connect

    BEN-ZVI,I.

    1998-11-24

    The production of high-brightness particle beams calls for the development of advanced beam diagnostics. High brightness beams, meaning beams with a high density in phase space, are important for many applications, such as short-wavelength Free-Electron Lasers and advanced accelerator systems. A diagnostic that provides detailed information on the density distribution of the electron bunch in multi-dimensional phase-space is an essential tool for obtaining small emittance at a high charge. This diagnostic system has been developed at Brookhaven National Laboratory. One component of the system is the measurement of a slice emittance which provides a measurement of transverse beam properties (such as emittance) as a function of the longitudinal position. Changing the laser pulse profile of a photocathode RF gun has been suggested as one way to achieve non-linear emittance compensation and improve the brightness and that can be diagnosed by the slice emittance system. The other element of the diagnostic is the tomographic reconstruction of the transverse phase. In our work we give special attention to the accuracy of the phase space reconstruction and present an analysis using a transport line with nine focusing magnets and techniques to control the optical functions and phases. This high precision phase space tomography together with the ability to modify the radial charge distribution of the electron beam presents an opportunity to improve the emittance and apply non-linear radial emittance corrections. Combining the slice emittance and tomography diagnostics leads to an unprecedented visualization of phase space distributions in 5 dimensional phase-space and an opportunity to perform high-order emittance corrections. This should lead to great improvements in the beam brightness.

  20. Cryo electron microscopy to determine the structure of macromolecular complexes.

    PubMed

    Carroni, Marta; Saibil, Helen R

    2016-02-15

    Cryo-electron microscopy (cryo-EM) is a structural molecular and cellular biology technique that has experienced major advances in recent years. Technological developments in image recording as well as in processing software make it possible to obtain three-dimensional reconstructions of macromolecular assemblies at near-atomic resolution that were formerly obtained only by X-ray crystallography or NMR spectroscopy. In parallel, cryo-electron tomography has also benefitted from these technological advances, so that visualization of irregular complexes, organelles or whole cells with their molecular machines in situ has reached subnanometre resolution. Cryo-EM can therefore address a broad range of biological questions. The aim of this review is to provide a brief overview of the principles and current state of the cryo-EM field. PMID:26638773

  1. 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.

  2. Structure and Dynamics with Ultrafast Electron Microscopes

    NASA Astrophysics Data System (ADS)

    Siwick, Bradley

    In this talk I will describe how combining ultrafast lasers and electron microscopes in novel ways makes it possible to directly `watch' the time-evolving structure of condensed matter, both at the level of atomic-scale structural rearrangements in the unit cell and at the level of a material's nano- microstructure. First, I will briefly describe my group's efforts to develop ultrafast electron diffraction using radio- frequency compressed electron pulses in the 100keV range, a system that rivals the capabilities of xray free electron lasers for diffraction experiments. I will give several examples of the new kinds of information that can be gleaned from such experiments. In vanadium dioxide we have mapped the detailed reorganization of the unit cell during the much debated insulator-metal transition. In particular, we have been able to identify and separate lattice structural changes from valence charge density redistribution in the material on the ultrafast timescale. In doing so we uncovered a previously unreported optically accessible phase/state of vanadium dioxide that has monoclinic crystallography like the insulator, but electronic structure and properties that are more like the rutile metal. We have also combined these dynamic structural measurements with broadband ultrafast spectroscopy to make detailed connections between structure and properties for the photoinduced insulator to metal transition. Second, I will show how dynamic transmission electron microscopy (DTEM) can be used to make direct, real space images of nano-microstructural evolution during laser-induced crystallization of amorphous semiconductors at unprecedented spatio-temporal resolution. This is a remarkably complex process that involves several distinct modes of crystal growth and the development of intricate microstructural patterns on the nanosecond to ten microsecond timescales all of which can be imaged directly with DTEM.

  3. Electronic structure of disordered conjugated polymers: Polythiophenes

    SciTech Connect

    Vukmirovic, Nenad; Wang, Lin-Wang

    2008-11-26

    Electronic structure of disordered semiconducting conjugated polymers was studied. Atomic structure was found from a classical molecular dynamics simulation and the charge patching method was used to calculate the electronic structure with the accuracy similar to the one of density functional theory in local density approximation. The total density of states, the local density of states at different points in the system and the wavefunctions of several states around the gap were calculated in the case of poly(3-hexylthiophene) (P3HT) and polythiophene (PT) systems to gain insight into the origin of disorder in the system, the degree of carrier localization and the role of chain interactions. The results indicated that disorder in the electronic structure of alkyl substituted polythiophenes comes from disorder in the conformation of individualchains, while in the case of polythiophene there is an additional contribution due to disorder in the electronic coupling between the chains. Each of the first several wavefunctions in the conduction and valence band of P3HT is localized over several rings of a single chain. It was shown that the localization can be caused in principle both by ring torsions and chain bending, however the effect of ring torsions is much stronger. PT wavefunctions are more complicated due to larger interchain electronic coupling and are not necessarily localized on a single chain.

  4. 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

  5. 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.

  6. 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.

  7. Electronic structure in the crossover regimes in lower dimensional structures

    NASA Astrophysics Data System (ADS)

    Batabyal, R.; Dev, B. N.

    2014-11-01

    Modern growth and fabrication techniques can produce lower dimensional structures in the crossover regimes. Such structures in the crossover regimes can provide tunability of various properties of materials. For example, a zero-dimensional (0-D) structure (quantum dot) evolving towards a 3-D structure (bulk) shows electronic structure, which is neither 0-D-like, nor 3-D-like in the dimensional crossover regime. Within the crossover regime the electronic density of states (DOS) at Fermi level (Ef) keeps on changing as the size of the system changes. DOS at Ef determines many properties of materials, such as electronic specific heat, spin susceptibility, etc. Such properties can be tuned by controlling the size of the system in the crossover regimes. Keeping the importance of DOS at Ef in mind, we determine their values and other details of electronic structure of lower dimensional structures, in the 0-D to 1-D, 1-D to 2-D, 2-D to 3-D, 0-D to 2-D, 0-D to 3-D and 1-D to 3-D crossover regimes, in a simple free electron model. We compare our results with analytical theory and experimental results, wherever available. We also present some results obtained by scanning tunneling spectroscopy measurements on Ag islands on Si(1 1 1) substrates evolving from a 0-D to a 2-D structure. This simple model is quite useful in understanding lower dimensional structures in the crossover regimes and, in general, in nanoscale science. Fabrication of such structures would provide control on materials properties.

  8. Abrasive wear of advanced structural materials

    NASA Astrophysics Data System (ADS)

    Lee, Gun-Young

    Wear of advanced structural materials, namely composites and ceramics, in abrasion has been examined in the present study. A simple physically-based model for the abrasive wear of composite materials is presented based on the mechanics and mechanisms associated with sliding wear in soft (ductile) matrix composites containing hard (brittle) reinforcement particles. The model is based on the assumption that any portion of the reinforcement that is removed as wear debris cannot contribute to the wear resistance of the matrix material. The size of this non-contributing portion of reinforcement is estimated by modeling three primary wear mechanisms, specifically plowing, cracking at the matrix/reinforcement interface or in the reinforcement, and particle removal. Critical variables describing the role of the reinforcement, such as the relative size, fracture toughness, and the nature of the matrix/reinforcement interface, are characterized by a single contribution coefficient, C. Predictions are compared with the results of experimental two-body (pin-on-drum) abrasive wear tests performed on a model aluminum particulate-reinforced epoxy-matrix composite material. In addition, the effects of post heat-treatment on the wear behavior of toughened silicon carbide (ABC-SiC) are investigated by characterizing the role of the microstructures introduced during the post annealing processes. When the annealing temperature is above 1300°C, an aluminum rich secondary phase (nano-precipitate) forms and grows inside the SiC grains. This toughened silicon carbide (ABC-SiC), annealed at temperatures ranging from 0 to 1600°C, is subjected to two- and three-body abrasions with different sizes of abrasives (3˜70 mum). The test results exhibit that the effect of nano-precipitates on wear resistance of post-annealed ABC-SiC is restricted to the abrasion with fine abrasives (3 mum), since nano-precipitates, in the range from 4 nm at 1300°C to 25 nm at 1600°C, are comparable in dimension

  9. 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. PMID:23403968

  10. Advanced paramagnetic resonance spectroscopies of iron-sulfur proteins: Electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM).

    PubMed

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

    2015-06-01

    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. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases. PMID:25686535

  11. 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. PMID:27334095

  12. 19 CFR 123.91 - Electronic information for rail cargo required in advance of arrival.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... HOMELAND SECURITY; DEPARTMENT OF THE TREASURY CUSTOMS RELATIONS WITH CANADA AND MEXICO Advance Information... United States by way of Canada or Mexico is not subject to the advance electronic information...

  13. 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…

  14. Electronic structure and electron momentum density in TiSi

    NASA Astrophysics Data System (ADS)

    Ghaleb, A. M.; Mohammad, F. M.; Sahariya, Jagrati; Sharma, Mukesh; Ahuja, B. L.

    2013-03-01

    We report the electron momentum density in titanium monosilicide using 241Am Compton spectrometer. Experimental Compton profile has been compared with the theoretical profiles computed using linear combination of atomic orbitals (LCAO). The energy bands, density of states and Fermi surface structures of TiSi are reported using the LCAO and the full potential linearized augmented plane wave methods. Theoretical anisotropies in directional Compton profiles are interpreted in terms of energy bands. To confirm the conducting behavior, we also report the real space analysis of experimental Compton profile of TiSi.

  15. 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

  16. Electronic structure of bacterial surface protein layers

    SciTech Connect

    Maslyuk, Volodymyr V.; Mertig, Ingrid; Bredow, Thomas; Mertig, Michael; Vyalikh, Denis V.; Molodtsov, Serguei L.

    2008-01-15

    We report an approach for the calculation of the electronic density of states of the dried two-dimensional crystalline surface protein layer (S layer) of the bacterium Bacillus sphaericus NCTC 9602. The proposed model is based on the consideration of individual amino acids in the corresponding conformation of the peptide chain which additively contribute to the electronic structure of the entire protein complex. The derived results agree well with the experimental data obtained by means of photoemission (PE), resonant PE, and near-edge x-ray absorption spectroscopy.

  17. 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)].

  18. 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

  19. 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.

  20. Electronic structures of carbon nanotube peopods

    NASA Astrophysics Data System (ADS)

    Kuk, Young

    2003-03-01

    Carbon nanotubes have been successfully used for nanometer-sized devices such as diodes and transistors. These discrete devices utilize the spatially varying electronic structures of processed nanotubes by creating defect junctions or introducing substitutional or interstitial dopants. It was recently found that adsorption or insertion of molecules inside or outside of a nanotube modifies the electronic structure as observed with a low-temperature scanning tunneling microscope (LTSTM). We report a method to form spatial variation of the electronic structure by inserting various molecules such as fullerenes, metallo-fullerenes, metals or insulators. The results suggest that one can synthesize this band gap-engineered 1-dimensional wire by self-assembly instead of epitaxial growth. We propose a new type of device structure made by this processing technology. 1. J. Lee, H.J. Kim, G. Kim, Y.-W. Son, J. Ihm, S.J. Kahng, H. Kato, Z.W. Wang, T. Okazaki, H. Shinohara, and Y. Kuk, Nature, 415, 1005 (2002)

  1. Electronic structure theory: Applications and geometrical aspects

    NASA Astrophysics Data System (ADS)

    Coh, Sinisa

    This thesis contains several applications of the first-principles electronic-structure theory with special emphasis in parts of the thesis on the geometrical aspects of the theory. We start by reviewing the basics of the first-principles electronic-structure methods which are then used throughout the thesis. The first application of these methods is on the analysis of the stability and lattice dynamics of alpha- and beta-cristobalite phases of SiO2. We also map the complete low-energy landscape connecting these two structures and give implications on the phase transition in this compound. Next we study a family of Pbnm perovskites that are promising candidates for silicon-compatible high-K dielectrics. We calculate their structure and dielectric response, and compare with experimental results where available. The third application of these methods is to the large isosymmetric reorientation of oxygen octahedra rotation axes in epitaxially strained perovskites. We explain the origin of the peculiar energy landscape topology as a function of epitaxial strain. In the part of the thesis devoted to the geometrical aspects of electronic structure theory, we begin by extending the concept of electronic polarization to a Chern insulators. These insulators are characterized by a non-zero off-diagonal sigma_xy conductivity tensor component, quantized in units of e 2/h. Finally we discuss another geometrical quantity, the Chern-Simons orbital magnetoelectric coupling. We present a first-principles based calculation of this quantity in several compounds, and motivated by recent developments in the theory of topological insulators, we speculate about the existence of "large-theta materials," in which this kind of coupling could be unusually large.

  2. 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.

  3. Electronic structure of oxygen functionalized graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Simbeck, Adam; Gu, Deyang; Kharche, Neerav; Nayak, Saroj

    2013-03-01

    We investigate the electronic and magnetic properties of armchair graphene nanoribbons whose edges are passivated by oxygen. Using a first-principles density functional approach and the many-body GW method we find that oxygen-passivation results in a rich geometrical environment which in turn determines the electronic and magnetic properties of the ribbon. For planar systems we report magnetic ground states whose electronic structure depends upon the magnetic coupling between edges. For non-planar ribbons we report a nonmagnetic ground state with a band gap that decreases as a function of increasing ribbon width. Our results will be discussed in light of previous experimental and computational studies. Interconnect Focus Center (MARCO program), State of New York, NSF IGERT program, Grant no. 0333314, and computing resources of the Computationial Center for Nanotechnology Innovation (CCNI), RPI

  4. 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%…

  5. 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.

  6. Electronic Structure of Iridium Clusters on Graphene

    NASA Astrophysics Data System (ADS)

    Barker, Bradford A.; Bradley, Aaron J.; Ugeda, Miguel M.; Coh, Sinisa; Zettl, Alex; Crommie, Michael F.; Cohen, Marvin L.; Louie, Steven G.

    2015-03-01

    Graphene was predicted to exhibit non-trivial Z2 topology, but its exceedingly weak spin-orbit coupling prevented this from being observed. Previous theoretical work has proposed enhancing the spin-orbit coupling strength by depositing individual adatoms adsorbed onto the surface of graphene. We show experimental evidence that the iridium adatoms cluster, with a cluster size of at least two atoms. We investigate through theoretical calculations the orientation of the iridium dimers on graphene, contrast the electronic structure of iridium dimers with iridium monomers, and compare the theoretical iridium dimer electronic structure calculations with the experimental results determined via scanning tunneling spectroscopy. This work was supported by NSF Grant No. DMR10-1006184 and U.S. DOE under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at LBNL's NERSC facility.

  7. Electronic structure of the multivacancies in Si

    NASA Astrophysics Data System (ADS)

    Ren, Shang Yuan; Mao, Deqiang; Li, Mingfu

    A complete set of equations for determining the energy levels and the wavefunctions with different symmetries of electronic states of several well-known multivacancies in Si is given using the Koster-Slater Green's function method. By using an empirical tight binding Hamiltonian for the band structure of the host and the central-cell perturbation approximation for the defect, only the on-site and the off-site Green's functions of the host and their derivatives with respect to energy E appear in these equations. The electronic structure of the ideal multivacancies, especially the divacancy, are investigated and compared with known experimental results and previous qualitative analyses. Some misunderstandings of the experimental results are analyzed. The wavefunctions of some multivacancy states are accurately evaluated and compared with the EPR and ENDOR data for the first time.

  8. Electronic structure tuning of diamondoids through functionalization

    NASA Astrophysics Data System (ADS)

    Rander, Torbjörn; Staiger, Matthias; Richter, Robert; Zimmermann, Tobias; Landt, Lasse; Wolter, David; Dahl, Jeremy E.; Carlson, Robert M. K.; Tkachenko, Boryslav A.; Fokina, Natalie A.; Schreiner, Peter R.; Möller, Thomas; Bostedt, Christoph

    2013-01-01

    We investigated the changes in electronic structures induced by chemical functionalization of the five smallest diamondoids using valence photoelectron spectroscopy. Through the variation of three parameters, namely functional group (thiol, hydroxy, and amino), host cluster size (adamantane, diamantane, triamantane, [121]tetramantane, and [1(2,3)4]pentamantane), and functionalization site (apical and medial) we are able to determine to what degree these affect the electronic structures of the overall systems. We show that unlike, for example, in the case of halobenzenes, the ionization potential does not show a linear dependence on the electronegativity of the functional group. Instead, a linear correlation exists between the HOMO-1 ionization potential and the functional group electronegativity. This is due to localization of the HOMO on the functional group and the HOMO-1 on the diamondoid cage. Density functional theory supports our interpretations.

  9. 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.

  10. Structural and electronic properties of thallium compounds

    NASA Astrophysics Data System (ADS)

    Paliwal, Neetu; Srivastava, Vipul

    2016-05-01

    The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of thallium pnictides TlX (X=Sb, Bi) at high pressure. As a function of volume, the total energy is evaluated. Apart from this, the lattice parameter (a0), bulk modulus (B0), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in TlSb and TlBi compounds. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.

  11. Structure and Electronic Properties of Polycrystalline Dielectrics

    SciTech Connect

    Mckenna, Keith P.; Shluger, AL

    2013-07-07

    We present an overview of the theoretical approaches that can be employed to model polycrystalline oxides along with a discussion of their limitations and associated challenges. We then present results for two metal oxide materials, MgO and HfO2, where theory and experiment have come together to provide insight into the structure and electronic properties of grain boundaries. Finally, we conclude with a discussion and outlook.

  12. Polycrystalline graphene with single crystalline electronic structure.

    PubMed

    Brown, Lola; Lochocki, Edward B; Avila, José; Kim, Cheol-Joo; Ogawa, Yui; Havener, Robin W; Kim, Dong-Ki; Monkman, Eric J; Shai, Daniel E; Wei, Haofei I; Levendorf, Mark P; Asensio, María; Shen, Kyle M; Park, Jiwoong

    2014-10-01

    We report the scalable growth of aligned graphene and hexagonal boron nitride on commercial copper foils, where each film originates from multiple nucleations yet exhibits a single orientation. Thorough characterization of our graphene reveals uniform crystallographic and electronic structures on length scales ranging from nanometers to tens of centimeters. As we demonstrate with artificial twisted graphene bilayers, these inexpensive and versatile films are ideal building blocks for large-scale layered heterostructures with angle-tunable optoelectronic properties. PMID:25207847

  13. Smart electronics and MEMS for aerospace structures

    NASA Astrophysics Data System (ADS)

    Varadan, Vijay K.; Varadan, Vasundara V.

    1995-09-01

    In this paper, smart electronics and MEMS are employed to sense and control the drag in aircraft structures. The sensors are fabricated with interdigital transducers printed on a piezoelectric polymer. They in turn are mounted onto an ultra thin Penn State's novel RF antenna (Patent field). The sensor are designed to measure both pressure and shear of the fluid flow on aerospace structures. The wave form measurements may be monitored at a remote location either at the cockpit or elsewhere via the antennas in the sensors and an outside antenna. The integrated MEMS actuators which comprise of cantilever-, diaphram- and microbridge-based MEMS with suitable smart electronics etched onto the structure are controlled by the built-in antennas through feedback and feedforward control architecture. The integration of such materials and smart electronics into the skin of airfoil is ideal for sensing and controlling drag. The basic idea of this concept involves detection of the point of transition from laminar to turbulent flow and transmitting acoustical energy into the boundary layer so that the low energy fluid particles accelerate in the transverse direction and mix with the high energy flow outside of the boundary layer. 3D microriblets can be fabricated using stereo lithography and UV curable conducting polymers. The control of drag using these active microriblets are outlined.

  14. 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.

  15. Quantum mirages formed by coherent projection of electronic structure

    PubMed

    Manoharan; Lutz; Eigler

    2000-02-01

    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. PMID:10676952

  16. 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.

  17. 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.

  18. Recent Advances in Flexible and Stretchable Bio-Electronic Devices Integrated with Nanomaterials.

    PubMed

    Choi, Suji; Lee, Hyunjae; Ghaffari, Roozbeh; Hyeon, Taeghwan; Kim, Dae-Hyeong

    2016-06-01

    Flexible and stretchable electronics and optoelectronics configured in soft, water resistant formats uniquely address seminal challenges in biomedicine. Over the past decade, there has been enormous progress in the materials, designs, and manufacturing processes for flexible/stretchable system subcomponents, including transistors, amplifiers, bio-sensors, actuators, light emitting diodes, photodetector arrays, photovoltaics, energy storage elements, and bare die integrated circuits. Nanomaterials prepared using top-down processing approaches and synthesis-based bottom-up methods have helped resolve the intrinsic mechanical mismatch between rigid/planar devices and soft/curvilinear biological structures, thereby enabling a broad range of non-invasive, minimally invasive, and implantable systems to address challenges in biomedicine. Integration of therapeutic functional nanomaterials with soft bioelectronics demonstrates therapeutics in combination with unconventional diagnostics capabilities. Recent advances in soft materials, devices, and integrated systems are reviewes, with representative examples that highlight the utility of soft bioelectronics for advanced medical diagnostics and therapies. PMID:26779680

  19. 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.

  20. 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

  1. 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

    2016-01-01

    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

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. Electronic structure theory of weakly interacting bilayers

    NASA Astrophysics Data System (ADS)

    Fang, Shiang; Kaxiras, Efthimios

    2016-06-01

    We derive electronic structure models for weakly interacting bilayers such as graphene-graphene and graphene-hexagonal boron nitride, based on density functional theory calculations followed by Wannier transformation of electronic states. These transferable interlayer coupling models can be applied to investigate the physics of bilayers with arbitrary translations and twists. The functional form, in addition to the dependence on the distance, includes the angular dependence that results from higher angular momentum components in the Wannier pz orbitals. We demonstrate the capabilities of the method by applying it to a rotated graphene bilayer, which produces the analytically predicted renormalization of the Fermi velocity, Van Hove singularities in the density of states, and moiré pattern of the electronic localization at small twist angles. We further extend the theory to obtain the effective couplings by integrating out neighboring layers. This approach is instrumental for the design of van der Walls heterostructures with desirable electronic features and transport properties and for the derivation of low-energy theories for graphene stacks, including proximity effects from other layers.

  7. Advanced beaded and tubular structural panels

    NASA Technical Reports Server (NTRS)

    Musgrove, M. D.; Greene, B. E.

    1975-01-01

    A program to develop lightweight beaded and tubular structural panels is described. Applications include external surfaces, where aerodynamically acceptable, and primary structure protected by heat shields. The design configurations were optimized and selected with a computer code which iterates geometric parameters to satisfy strength, stability, and weight constraints. Methods of fabricating these configurations are discussed. Nondestructive testing produced extensive combined compression, shear, and bending test data on local buckling specimens and large panels. The optimized design concepts offer 25 to 30% weight savings compared to conventional stiffened sheet construction.

  8. 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.

  9. Spin Structure Functions from Electron Scattering

    SciTech Connect

    Seonho Choi

    2012-09-01

    The spin structure of the nucleon can play a key testing ground for Quantum Chromo-Dynamics (QCD) at wide kinematic ranges from smaller to large four momentum transfer Q{sup 2}. The pioneering experiments have confirmed several QCD sum rules at high Q{sup 2} where a perturbative picture holds. For a full understanding of QCD at various scales, various measurements were made at intermediate and small Q{sup 2} region and their interpretation would be a challenging task due to the non-perturbative nature. Jefferson Lab has been one of the major experimental facilities for the spin structure with its polarized electron beams and various polarized targets. A few QCD sum rules have been compared with the measured spin structure functions g{sub 1}(x, Q{sup 2}) and g{sub 2}(x, Q{sup 2}) at low Q{sup 2} and surprising results have been obtained for the spin polarizabilities, {gamma}{sub 0} and {delta}{sub LT} . As for the proton spin structure functions, the lack of data for g{sub 2}(x,Q{sup 2}) structure functions has been complemented with a new experiment at Jefferson Lab, SANE. The results from SANE will provide a better picture of the proton spin structure at a wide kinematic range in x and Q{sup 2}.

  10. Fabrication and evaluation of advanced titanium and composite structural panels

    NASA Technical Reports Server (NTRS)

    Bales, T. T.; Hoffman, E. L.; Payne, L.; Carter, A. L.

    1976-01-01

    Advanced manufacturing methods for titanium and composite material structures are being developed and evaluated. The focus for the manufacturing effort is the fabrication of full-scale structural panels which replace an existing shear panel on the upper wing surface of the NASA YF-12 aircraft. The program involves design, fabrication, ground testing, and Mach 3 flight service of full-scale structural panels and laboratory testing of representative structural element specimens.

  11. 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

  12. 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.

  13. Electronic Structure of B12 coenzymes

    NASA Astrophysics Data System (ADS)

    Ouyang, Lizhi; Ching, W. Y.; Randaccio, Lucio

    2001-06-01

    We have carried out an ab-initio local density functional calculations of the two most important B12 coenzymes, adoensyl-cobalamin (Ado-Cbl) and methyl-cobalamin (Me-Cbl). The crystal structures were determined by accurate X-ray synchrotron radiation measurements. Both crystals have space group P2121 with four molecules, or about 800 atoms, per unit cell. Our electronic structure calculation is based on one full molecule including the side chains. Results are analyzed in terms of atom and orbital resolved partial density of states (PDOS), Mulliken effective charges and bond orders. The PDOS analysis shows that the Co complexes of both B12 coenzymes had a HOMO/LUMO gap of about 1.5 eV. The Co-C bond order in Me-Cbl is smaller than that in Ado-Cbl. This appears to be in contradiction with the measured bond dissociated energies. However, this could also indicate the importance of the effects of solvents, which were not included in the calculation. We are investigating whether the effect of the solvents could dramatically modify the electronic structures of Ado-Cbl and Me-Cbl.

  14. 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.

  15. 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

  16. Advancing contact angles on large structured surfaces

    NASA Astrophysics Data System (ADS)

    Yoshitake, Yumiko; Itakura, Yoshinori; Gobo, Junichi; Takahashi, Tsutomu

    2014-11-01

    To understand wetting phenomena on complex surfaces, simple modeling experiments in two-dimension system would be one of the most efficient approaches. We develop a new experimental method for wetting dynamics using a large pseudo two- dimensional droplet. This method is useful to examine theoretical studies developed in two dimensional systems. In this study, we examine a pinning and depinning phenomena on millimeter-size structured surface to explain the origin of contact angle hysteresis. Contact lines of the droplet are pinned and deppined at the edge of surface texture. The contact lines can move when the contact angle is equal to the Young's contact angle which are determined by the balance of the surface and interfacial tension immediate vicinity of the contact lines, which is different from the Wenzel's low. Our approach enables to realize a macroscopic modelling experiment of wetting on complex surfaces, which opens a path to design functional surfaces with chemical and physical structure.

  17. 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.

  18. Electronic and magnetic structures of chain structured iron selenide compounds

    NASA Astrophysics Data System (ADS)

    Li, Wei; Setty, Chandan; Chen, X. H.; Hu, Jiangping

    2014-08-01

    Electronic and magnetic structures of iron selenide compounds Ce2O2FeSe2 (2212*) and BaFe2Se3 (123*) are studied by the first-principles calculations. We find that while all these compounds are composed of one-dimensional (1D) Fe chain (or ladder) structures, their electronic structures are not close to be quasi-1D. The magnetic exchange couplings between two nearest-neighbor (NN) chains in 2212* and between two NN two-leg-ladders in 123* are both antiferromagnetic (AFM), which is consistent with the presence of significant third NN AFM coupling, a common feature shared in other iron-chalcogenides, FeTe (11*) and K y Fe2- x Se2 (122*). In magnetic ground states, each Fe chain of 2212* is ferromagnetic and each two-leg ladder of 123* form a block-AFM structure. We suggest that all magnetic structures in iron-selenide compounds can be unified into an extended J 1- J 2- J 3 model. Spin-wave excitations of the model are calculated and can be tested by future experiments on these two systems.

  19. Electronic structure and optical properties of resin

    NASA Astrophysics Data System (ADS)

    Rao, Zhi-Fan; Zhou, Rong-Feng

    2013-03-01

    We used the density of functional theory (DFT) to study the electronic structure and density of states of resin by ab initio calculation. The results show the band gap of resin is 1.7 eV. The covalent bond is combined C/O atoms with H atoms. The O 2p orbital is the biggest effect near the Fermi level. The results of optical properties show the reflectivity is low, and the refractive index is 1.7 in visible light range. The highest absorption coefficient peak is in 490 nm and the value is 75,000.

  20. Lattice Boltzmann Model for Electronic Structure Simulations

    NASA Astrophysics Data System (ADS)

    Mendoza, M.; Herrmann, H. J.; Succi, S.

    2015-09-01

    Recently, a new connection between density functional theory and kinetic theory has been proposed. In particular, it was shown that the Kohn-Sham (KS) equations can be reformulated as a macroscopic limit of the steady-state solution of a suitable single-particle kinetic equation. By using a discrete version of this new formalism, the exchange and correlation energies of simple atoms and the geometrical configuration of the methane molecule were calculated accurately. Here, we discuss the main ideas behind the lattice kinetic approach to electronic structure computations, offer some considerations for prospective extensions, and also show additional numerical results, namely the geometrical configuration of the water molecule.

  1. 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.

  2. Electronic structure of cobalt nanocrystals suspended inliquid

    SciTech Connect

    Liu, Hongjian; Guo, Jinghua; Yin, Yadong; Augustsson, Andreas; Dong, Chungli; Nordgren, Joseph; Chang, Chinglin; Alivisatos, Paul; Thornton, Geoff; Ogletree, D. Frank; Requejo, Felix G.; de Groot, Frank; Salmeron, Miquel

    2007-07-16

    The electronic structure of cobalt nanocrystals suspended in liquid as a function of size has been investigated using in-situ x-ray absorption and emission spectroscopy. A sharp absorption peak associated with the ligand molecules is found that increases in intensity upon reducing the nanocrystal size. X-ray Raman features due to d-d and to charge-transfer excitations of ligand molecules are identified. The study reveals the local symmetry of the surface of {var_epsilon}-Co phase nanocrystals, which originates from a dynamic interaction between Co nanocrystals and surfactant + solvent molecules.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Towards scalable electronic structure calculations for alloys

    SciTech Connect

    Stocks, G.M.; Nicholson, D.M.C.; Wang, Y.; Shelton, W.A.; Szotek, Z.; Temmermann, W.M.

    1994-06-01

    A new approach to calculating the properties of large systems within the local density approximation (LDA) that offers the promise of scalability on massively parallel supercomputers is outlined. The electronic structure problem is formulated in real space using multiple scattering theory. The standard LDA algorithm is divided into two parts. Firstly, finding the self-consistent field (SCF) electron density, Secondly, calculating the energy corresponding to the SCF density. We show, at least for metals and alloys, that the former problem is easily solved using real space methods. For the second we take advantage of the variational properties of a generalized Harris-Foulkes free energy functional, a new conduction band Fermi function, and a fictitious finite electron temperature that again allow us to use real-space methods. Using a compute-node {R_arrow} atom equivalence the new method is naturally highly parallel and leads to O(N) scaling where N is the number of atoms making up the system. We show scaling data gathered on the Intel XP/S 35 Paragon for systems up to 512-atoms/simulation cell. To demonstrate that we can achieve metallurgical-precision, we apply the new method to the calculation the energies of disordered CuO{sub 0.5}Zn{sub 0.5} alloys using a large random sample.

  10. Electronic structure of rare-earth hexaborides

    NASA Astrophysics Data System (ADS)

    Kimura, S.; Nanba, T.; Tomikawa, M.; Kunii, S.; Kasuya, T.

    1992-11-01

    Reflectivity spectra of all rare-earth hexaboride RB6 (R=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, and Y) single crystals have been measured systematically in the energy region from 1 meV to 40 eV at 300 K in order to investigate the electronic state and the contribution of the 4f electron to the band structure. The analysis of the optical conductivity and the loss-function spectra, which were derived from the Kramers-Kronig transformation of the reflectivity spectra, allowed us to make clear the origin of the peak structure in the spectrum due to the various interband transitions. The origins of the main peaks in the spectrum were assigned to the interband transitions from the bonding to the antibonding bands of the boron 2s and 2p states and to the rare-earth 5d state. The intra-atomic transition from the 4f and the 5p to the 5d(t2g) states in the rare-earth ion was also observed.

  11. 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.

  12. Electronic tagging and population structure of Atlantic bluefin tuna.

    PubMed

    Block, Barbara A; Teo, Steven L H; Walli, Andreas; Boustany, Andre; Stokesbury, Michael J W; Farwell, Charles J; Weng, Kevin C; Dewar, Heidi; Williams, Thomas D

    2005-04-28

    Electronic tags that archive or transmit stored data to satellites have advanced the mapping of habitats used by highly migratory fish in pelagic ecosystems. Here we report on the electronic tagging of 772 Atlantic bluefin tuna in the western Atlantic Ocean in an effort to identify population structure. Reporting electronic tags provided accurate location data that show the extensive migrations of individual fish (n = 330). Geoposition data delineate two populations, one using spawning grounds in the Gulf of Mexico and another from the Mediterranean Sea. Transatlantic movements of western-tagged bluefin tuna reveal site fidelity to known spawning areas in the Mediterranean Sea. Bluefin tuna that occupy western spawning grounds move to central and eastern Atlantic foraging grounds. Our results are consistent with two populations of bluefin tuna with distinct spawning areas that overlap on North Atlantic foraging grounds. Electronic tagging locations, when combined with US pelagic longline observer and logbook catch data, identify hot spots for spawning bluefin tuna in the northern slope waters of the Gulf of Mexico. Restrictions on the time and area where longlining occurs would reduce incidental catch mortalities on western spawning grounds. PMID:15858572

  13. 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.

  14. 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)

  15. Electronic and structural properties of metallic microclusters

    SciTech Connect

    Maiti, A.

    1992-04-01

    The first part of this thesis presents a first-order pseudopotential calculation at T=O of the total energy of small sodium clusters of size N<800. The calculation is based on a local-pseudopotential scheme and local-density correlation and exchange. A temperature-size (T-N) phase-diagram is then derived using the T=O results and Lindemann`s criterion for melting. The phase-diagram contains three regions of stability: (1) a liquid (jellium) phase at temperatures above the melting line T{sub M}(N) where cluster-stability occurs at electronic magic numbers: (2) a phase related to complete geometrical shells of body-centered-cubic structure at temperatures below the melting line; and (3) a close-packed structure at very low temperatures and sufficiently large N. The melting line drops to T{sub M}(N)=O for N<65, where electronic magic numbers are stable even at T=O. The phase diagram reduces asymptotically to the known phases of sodium as N{yields}{infinity}, including the known martensitic transformation at T{approximately}5 K. The second and the last part of this thesis consists of a study of small-cluster many-body systems by means of an on-site ``local`` chemical potential which allows the continuous variation of local electron-density. This method yields a criterion to distinguish particular features of a small cluster that are likely to survive in the large-N thermodynamic limit from those discontinuities that arise only from finite-size effects.

  16. Electronic and structural properties of metallic microclusters

    SciTech Connect

    Maiti, A.

    1992-04-01

    The first part of this thesis presents a first-order pseudopotential calculation at T=O of the total energy of small sodium clusters of size N<800. The calculation is based on a local-pseudopotential scheme and local-density correlation and exchange. A temperature-size (T-N) phase-diagram is then derived using the T=O results and Lindemann's criterion for melting. The phase-diagram contains three regions of stability: (1) a liquid (jellium) phase at temperatures above the melting line T{sub M}(N) where cluster-stability occurs at electronic magic numbers: (2) a phase related to complete geometrical shells of body-centered-cubic structure at temperatures below the melting line; and (3) a close-packed structure at very low temperatures and sufficiently large N. The melting line drops to T{sub M}(N)=O for N<65, where electronic magic numbers are stable even at T=O. The phase diagram reduces asymptotically to the known phases of sodium as N{yields}{infinity}, including the known martensitic transformation at T{approximately}5 K. The second and the last part of this thesis consists of a study of small-cluster many-body systems by means of an on-site local'' chemical potential which allows the continuous variation of local electron-density. This method yields a criterion to distinguish particular features of a small cluster that are likely to survive in the large-N thermodynamic limit from those discontinuities that arise only from finite-size effects.

  17. 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.

  18. An advanced structural analysis/synthesis capability - ACCESS 2

    NASA Technical Reports Server (NTRS)

    Schmit, L. A.; Miura, H.

    1976-01-01

    An advanced automated design procedure for minimum-weight design of structures (ACCESS 2) is reported. Design variable linking, constraint deletion, and explicit constraint approximation are used to combine effectively finite-element and nonlinear mathematical programming techniques. The approximation-concepts approach to structural synthesis is extended to problems involving fiber composite structure, thermal effects, and natural frequency constraints in addition to the usual static stress and displacement limitations. Sample results illustrating these features are given.

  19. An advanced structural analysis/synthesis capability - ACCESS 2

    NASA Technical Reports Server (NTRS)

    Schmit, L. A.; Miura, H.

    1978-01-01

    An advanced automated design procedure for minimum weight design of structures (ACCESS 2) is reported. Design variable linking, constraint deletion, and explicit constraint approximation are used to effectively combine finite element and nonlinear mathematical programming techniques. The approximation concepts approach to structural synthesis is extended to problems involving fiber composite structure, thermal effects and natural frequency constraints in addition to the usual static stress and displacement limitations. Sample results illustrating these new features are given.

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 19 CFR 123.92 - Electronic information for truck cargo required in advance of arrival.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 1 2014-04-01 2014-04-01 false Electronic information for truck cargo required in... Cargo Arriving by Rail or Truck § 123.92 Electronic information for truck cargo required in advance of... electronic data interchange system no later than either 30 minutes or 1 hour prior to the carrier's...

  5. 19 CFR 123.92 - Electronic information for truck cargo required in advance of arrival.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 1 2012-04-01 2012-04-01 false Electronic information for truck cargo required in... Cargo Arriving by Rail or Truck § 123.92 Electronic information for truck cargo required in advance of... electronic data interchange system no later than either 30 minutes or 1 hour prior to the carrier's...

  6. 19 CFR 123.92 - Electronic information for truck cargo required in advance of arrival.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 1 2013-04-01 2013-04-01 false Electronic information for truck cargo required in... Cargo Arriving by Rail or Truck § 123.92 Electronic information for truck cargo required in advance of... electronic data interchange system no later than either 30 minutes or 1 hour prior to the carrier's...

  7. Recent advances in structural dynamics of large space structures

    NASA Technical Reports Server (NTRS)

    Pinson, Larry D.

    1987-01-01

    Recent progress in the area of structural dynamics of large space structures is reviewed. Topics include system identification, large angle slewing of flexible structures, definition of scaling limitations in structural models, and recent results on a tension-stabilized antenna concept known as the hoop-column. Increasingly complex laboratory experiments guide most of the activities leading to realistic technological developments. Theoretical progress in system identification based on system realization theory resulting in unification of several methods is reviewed. Experimental results from implementation of a theoretical large-angle slewing control approach are shown. Status and results of the development of a research computer program for analysis of the transient dynamics of large angle motion of flexible structures are presented. Correlation of results from analysis and vibration tests of the hoop-column antenna concepts are summarized.

  8. Recent advances in structural dynamics of large space structures

    NASA Technical Reports Server (NTRS)

    Pinson, Larry D.

    1987-01-01

    Recent progress in the area of structural dynamics of large space structures is reviewed. Topics include system identification, large angle slewing of flexible structures, definition of scaling limitations in structural models, and recent results on a tension-stabilized antenna concept known as the hoop-column. Increasingly complex laboratory experiments guide most of the activities leading to realistic technological developments. Theoretical progress in system identification based on system realization theory resulting in unification of several methods is reviewed. Experimental results from implementation of a theoretical large-angle slewing control approach are shown. Status and results of the development of a research computer program for analysis of the transient dynamics of large angle motion of flexible structures are presented. Correlation of results from analysis and vibration tests of the hoop-column antenna concept are summarized.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Electronic Structure Calculations of Highly Charged Ions

    NASA Astrophysics Data System (ADS)

    Bromley, Steve; Ziolkowski, Marcin; Marler, Joan

    2016-05-01

    Exotic systems like Highly Charged Ions (HCIs) are attracting more attention based on their properties and possible interactions. Abundance of HCIs in the solar wind and their interaction with the upper atmosphere puts them in the attention of astro- and atmospheric physicists. Also, their unique properties originating in the high charge make them an excellent candidate for precision measurements and the next generation of atomic clocks. For a better understanding of the dynamics of processes involving HCIs a combined theoretical and experimental effort is needed to study their basic properties and interactions. Both theory and experiment need to be combined due to the extreme nature of these systems. We present preliminary insight into electronic structure of light HCIs, their interactions with neutral atoms and dynamics of charge transfer processes.

  16. 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.

  17. 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

  18. Advanced simulation of electron heat transport in fusion plasmas

    SciTech Connect

    Lin, Zhihong; Xiao, Y.; Klasky, Scott A; Lofstead, J.

    2009-01-01

    Electron transport in burning plasmas is more important since fusion products first heat electrons. First-principles simulations of electron turbulence are much more challenging due to the multi-scale dynamics of the electron turbulence, and have been made possible by close collaborations between plasma physicists and computational scientists. The GTC simulations of collisionless trapped electron mode (CTEM) turbulence show that the electron heat transport exhibits a gradual transition from Bohm to gyroBohm scaling when the device size is increased. The deviation from the gyroBohm scaling can be induced by large turbulence eddies, turbulence spreading, and non-diffusive transport processes. Analysis of radial correlation function shows that CTEM turbulence eddies are predominantly microscopic but with a significant tail in the mesoscale. A comprehensive analysis of kinetic and fluid time scales shows that zonal flow shearing is the dominant decorrelation mechanism. The mesoscale eddies result from a dynamical process of linear streamers breaking by zonal flows and merging of microscopic eddies. The radial profile of the electron heat conductivity only follows the profile of fluctuation intensity on a global scale, whereas the ion transport tracks more sensitively the local fluctuation intensity. This suggests the existence of a nondiffusive component in the electron heat flux, which arises from the ballistic radial E x B drift of trapped electrons due to a combination of the presence of mesoscale eddies and the weak de-tuning of the toroidal precessional resonance that drives the CTEM instability. On the other hand, the ion radial excursion is not affected by the mesoscale eddies due to a parallel decorrelation, which is not operational for the trapped electrons because of a bounce averaging process associated with the electron fast motion along magnetic field lines. The presence of the nondiffusive component raises question on the applicability of the usual

  19. Advanced Simulation of Electron Heat Transport in Fusion Plasmas

    SciTech Connect

    Lin, Z.; Xiao, Y.; Holod, I.; Zhang, W. L.; Deng, Wenjun; Klasky, Scott A; Lofstead, J.; Kamath, Chandrika; Wichmann, Nathan

    2009-01-01

    Electron transport in burning plasmas is more important since fusion products first heat electrons. First-principles simulations of electron turbulence are much more challenging due to the multi-scale dynamics of the electron turbulence, and have been made possible by close collaborations between plasma physicists and computational scientists. The GTC simulations of collisionless trapped electron mode (CTEM) turbulence show that the electron heat transport exhibits a gradual transition from Bohm to gyroBohm scaling when the device size is increased. The deviation from the gyroBohm scaling can be induced by large turbulence eddies, turbulence spreading, and non-diffusive transport processes. Analysis of radial correlation function shows that CTEM turbulence eddies are predominantly microscopic but with a significant tail in the mesoscale. A comprehensive analysis of kinetic and fluid time scales shows that zonal flow shearing is the dominant decorrelation mechanism. The mesoscale eddies result from a dynamical process of linear streamers breaking by zonal flows and merging of microscopic eddies. The radial profile of the electron heat conductivity only follows the profile of fluctuation intensity on a global scale, whereas the ion transport tracks more sensitively the local fluctuation intensity. This suggests the existence of a nondiffusive component in the electron heat flux, which arises from the ballistic radial E x B drift of trapped electrons due to a combination of the presence of mesoscale eddies and the weak de-tuning of the toroidal precessional resonance that drives the CTEM instability. On the other hand, the ion radial excursion is not affected by the mesoscale eddies due to a parallel decorrelation, which is not operational for the trapped electrons because of a bounce averaging process associated with the electron fast motion along magnetic field lines. The presence of the nondiffusive component raises question on the applicability of the usual

  20. Advanced actuators for the control of large space structures

    NASA Technical Reports Server (NTRS)

    Downer, James; Hockney, Richard; Johnson, Bruce; Misovec, Kathleen

    1993-01-01

    The objective of this research was to develop advanced six-degree-of-freedom actuators employing magnetic suspensions suitable for the control of structural vibrations in large space structures. The advanced actuators consist of a magnetically suspended mass that has three-degrees-of-freedom in both translation and rotation. The most promising of these actuators featured a rotating suspended mass providing structural control torques in a manner similar to a control moment gyro (CMG). These actuators employ large-angle-magnetic suspensions that allow gimballing of the suspended mass without mechanical gimbals. Design definitions and sizing algorithms for these CMG type as well as angular reaction mass actuators based on multi-degree-of-freedom magnetic suspensions were developed. The performance of these actuators was analytically compared with conventional reaction mass actuators for a simple space structure model.

  1. 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.

  2. Structural tailoring of advanced turboprops (STAT): User's manual

    NASA Technical Reports Server (NTRS)

    Brown, K. W.

    1991-01-01

    This user's manual describes the Structural Tailoring of Advanced Turboprops program. It contains instructions to prepare the input for optimization, blade geometry and analysis, geometry generation, and finite element program control. In addition, a sample input file is provided as well as a section describing special applications (i.e., non-standard input).

  3. 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

  4. 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.

  5. 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

    ... Reactor Correspondence AGENCY: Nuclear Regulatory Commission. ACTION: Implementation of electronic distribution of advanced reactor correspondence; issuance. SUMMARY: The U.S. Nuclear Regulatory Commission (NRC... the Division of Operating Reactor Licensing (DORL) in October 2008. All four regions are...

  6. 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.

  7. 19 CFR 103.31a - Advance electronic information for air, truck, and rail cargo; Importer Security Filing...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 1 2010-04-01 2010-04-01 false Advance electronic information for air, truck, and... AVAILABILITY OF INFORMATION Other Information Subject to Restricted Access § 103.31a Advance electronic... following types of advance electronic information are per se exempt from disclosure under §...

  8. 41 CFR 301-71.105 - Must we issue a written or electronic travel authorization in advance of travel?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... or electronic travel authorization in advance of travel? 301-71.105 Section 301-71.105 Public... Must we issue a written or electronic travel authorization in advance of travel? Yes, except when advance written or electronic authorization is not possible or practical and approval is in...

  9. 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

  10. 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.

  11. 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.

  12. The electronic structure of hard materials

    NASA Astrophysics Data System (ADS)

    Winarski, Robert Paul

    This research dissertation involves an experimental as well as a theoretical examination of the electronic structure of hard materials. The materials that are presented in this dissertation cover a wide class of materials, consisting of transition metal borides, irradiated polymer films, theoretically predicted superhard semiconductors, doped intermetallic alloys, and transition metal carbides. The borides are traditionally used in high temperature, hard coating applications, such as rocket nozzle linings, extreme wear surfaces, and corrosion coatings. Measurements of the borides appear to show that the bonding in these hard materials is primarily between the boron atoms in these systems. Also of note are the remarkably short interatomic distances between the boron atoms and between the boron and metal atoms in these materials. Irradiated polymer films are being developed for electronic applications, in the hopes that circuits can be developed that can benefit from the high thermal stability, dielectric properties, and mechanical properties provided by these materials. C3N4 is a theoretically predicted superhard material, and some of the first soft x-ray emission measurements of well-characterized samples of this compound are discussed in this work. Intermetallic alloys, in particular Ni3Al, are rather hard, but brittle metallic alloys. It has been found that the addition of boron atoms, in rather low concentrations, can increase the ductility of these alloys, allowing them to be utilized in a wider variety of applications. Measurements of this system have examined a question regarding the positioning of the boron atoms in the structures of this alloy. Finally, the transition metal carbides are used extensively as coatings in industrial applications such as cutting and grinding tools, and polishing compounds. Measurements of these materials suggest that the high degree of covalency between the metal and carbon atoms is primarily responsible for the hardness of

  13. 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

  14. 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.

  15. Nonlinear displacement analysis of advanced propeller structures using NASTRAN

    NASA Technical Reports Server (NTRS)

    Lawrence, C.; Kielb, R. E.

    1984-01-01

    The steady state displacements of a rotating advanced turboprop are computed using the geometrically nonlinear capabilities of COSMIC NASTRAN Rigid Format 4 and MSC NASTRAN Solution 64. A description of the modified Newton-Raphson algorithm used by Solution 64 and the iterative scheme used by Rigid Format 4 is provided. A representative advanced turboprop, SR3, was used for the study. Displacements for SR3 are computed for rotational speeds up to 10,000 rpm. The results show Solution 64 to be superior for computating displacements of flexible rotating structures. This is attributed to its ability to update the displacement dependent centrifugal force during the solution process.

  16. 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.

  17. 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.

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

    PubMed

    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. PMID:26233395

  19. 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.

  20. 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.

  1. Electron beam welding of aircraft structures. [joining of titanium alloy wing structures on F-14 aircraft

    NASA Technical Reports Server (NTRS)

    Witt, R. H.

    1972-01-01

    Requirements for advanced aircraft have led to more extensive use of titanium alloys and the resultant search for joining processes which can produce lightweight, high strength airframe structures efficiently. As a result, electron beam welding has been investigated. The following F-14A components are now being EB welded in production and are mainly annealed Ti-6Al-4V except for the upper wing cover which is annealed Ti-6Al-6V-2Sn: F-14A wing center section box, and F-14A lower and upper wing covers joined to wing pivot fitting assemblies. Criteria for selection of welding processes, the EB welding facility, development work on EB welding titanium alloys, and F-14A production and sliding seal electron beam welding are reported.

  2. Advanced Structural Analyses by Third Generation Synchrotron Radiation Powder Diffraction

    SciTech Connect

    Sakata, M.; Aoyagi, S.; Ogura, T.; Nishibori, E.

    2007-01-19

    Since the advent of the 3rd generation Synchrotron Radiation (SR) sources, such as SPring-8, the capabilities of SR powder diffraction increased greatly not only in an accurate structure refinement but also ab initio structure determination. In this study, advanced structural analyses by 3rd generation SR powder diffraction based on the Large Debye-Scherrer camera installed at BL02B2, SPring-8 is described. Because of high angular resolution and high counting statistics powder data collected at BL02B2, SPring-8, ab initio structure determination can cope with a molecular crystals with 65 atoms including H atoms. For the structure refinements, it is found that a kind of Maximum Entropy Method in which several atoms are omitted in phase calculation become very important to refine structural details of fairy large molecule in a crystal. It should be emphasized that until the unknown structure is refined very precisely, the obtained structure by Genetic Algorithm (GA) or some other ab initio structure determination method using real space structural knowledge, it is not possible to tell whether the structure obtained by the method is correct or not. In order to determine and/or refine crystal structure of rather complicated molecules, we cannot overemphasize the importance of the 3rd generation SR sources.

  3. 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.

  4. Advances in electron kinetics and theory of gas discharges

    SciTech Connect

    Kolobov, Vladimir I.

    2013-10-15

    Electrons, like people, are fertile and infertile: high-energy electrons are fertile and able to reproduce.”—Lev TsendinModern physics of gas discharges increasingly uses physical kinetics for analysis of non-equilibrium plasmas. The description of underlying physics at the kinetic level appears to be important for plasma applications in modern technologies. In this paper, we attempt to grasp the legacy of Professor Lev Tsendin, who advocated the use of the kinetic approach for understanding fundamental problems of gas discharges. We outline the fundamentals of electron kinetics in low-temperature plasmas, describe elements of the modern kinetic theory of gas discharges, and show examples of the theoretical approach to gas discharge problems used by Lev Tsendin. Important connections between electron kinetics in gas discharges and semiconductors are also discussed. Using several examples, we illustrate how Tsendin's ideas and methods are currently being developed for the implementation of next generation computational tools for adaptive kinetic-fluid simulations of gas discharges used in modern technologies.

  5. 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.

  6. 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.

  7. 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.

  8. 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…

  9. 19 CFR 122.48a - Electronic information for air cargo required in advance of arrival.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 1 2011-04-01 2011-04-01 false Electronic information for air cargo required in advance of arrival. 122.48a Section 122.48a Customs Duties U.S. CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY AIR COMMERCE REGULATIONS Aircraft Entry and Entry Documents; Electronic Manifest...

  10. [The role of electronic techniques for advanced neuroelectrophysiology].

    PubMed

    Wang, Min; Zhang, Lijun; Cao, Maoyong

    2008-12-01

    The rapid development in the fields of electroscience, computer science, and biomedical engineering are propelling the electrophysiologyical techniques. Recent technological advances have made it possible to simultaneously record the activity of large numbers of neurons in awake and behaving animals using implanted extracellular electrodes. Several laboratories use chronically implanted electrode arrays in freely moving animals because they allow stable recordings of discriminated single neurons and/or field potentials from up to hundreds of electrodes over long time periods. In this review, we focus on the new technologies for neuroelectrophysiology. PMID:19166233

  11. The Reactivity and Structural Dynamics of Supported Metal Nanoclusters Using Electron Microscopy, in situ X-Ray Spectroscopy, Electronic Structure Theories, and Molecular Dynamics Simulations.

    SciTech Connect

    Judith C. Yang; Ralph G. Nuzzo, Duane Johnson, Anatoly Frenkel

    2008-07-01

    The distinguishing feature of our collaborative program of study is the focus it brings to emergent phenomena originating from the unique structural/electronic environments found in nanoscale materials. We exploit and develop frontier methods of atomic-scale materials characterization based on electron microscopy (Yang) and synchrotron X-ray absorption spectroscopy (Frenkel) that are in turn coupled innately with advanced first principles theory and methods of computational modeling (Johnson). In the past year we have made significant experimental advances that have led to important new understandings of the structural dynamics of what are unquestionably the most important classes of heterogeneous catalysts—the materials used to both produce and mitigate the consequences of the use of liquid hydrocarbon fuels.

  12. 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

  13. 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.

  14. Probing Actinide Electronic Structure through Pu Cluster Calculations

    DOE PAGESBeta

    Ryzhkov, Mickhail V.; Mirmelstein, Alexei; Yu, Sung-Woo; Chung, Brandon W.; Tobin, James G.

    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.

  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. PMID:27334148

  16. Materials issues for advanced electronic and optoelectronic connectors

    NASA Astrophysics Data System (ADS)

    Crane, J.; Wen, S.

    1990-09-01

    Trends of increased speed, density and power of electronic devices and circuitry translate to a need for connector substrate materials with improved form-ability and mechanical stability. Many contact surface requirements will continue to be met by precious metals for low contact force and tin in moderate contact force connectors. However, the demands for lower insertion forces, increased wear resistance, higher operating temperatures and improved corrosion resistance will challenge materials experts and connector designers to develop and utilize cost-effective replacements for tin and gold in electronic connectors. The stability and compatibility requirements of optoelectronic connectors provide challenges over a wide range of materials with the added dimension of accommodating essential optical characteristics.

  17. 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.

  18. Advances in Structural Studies of Materials using Scattering Probes

    SciTech Connect

    Huq, Ashfia; Bozin, Emil; Welberry, Dr. Richard

    2010-01-01

    Study of contemporary materials and their remarkable properties is a challenging problem. To understand these complex properties and develop better materials it is essential to understand their structures, as the two are intimately linked. Great advances in materials scattering have been achieved due to the advent of synchrotron and neutron sources along with the availability of high-speed computational algorithms. Materials scientists can now collect data with high resolution, high throughput from very small amount of sample (both single crystal and powder), and analyze vast amount of data to unravel detailed structural description that was not possible before. This article presents some of these great advances in using scattering probes for materials characterization.

  19. A formal structure for advanced automatic flight-control systems

    NASA Technical Reports Server (NTRS)

    Meyer, G.; Cicolani, L. S.

    1975-01-01

    Techniques were developed for the unified design of multimode, variable authority automatic flight-control systems for powered-lift STOL and VTOL aircraft. A structure for such systems is developed to deal with the strong nonlinearities inherent in this class of aircraft, to admit automatic coupling with advanced air traffic control, and to admit a variety of active control tasks. The aircraft being considered is the augmentor wing jet STOL research aircraft.

  20. 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.

  1. 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.

  2. 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.

  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. An Advanced Time Averaging Modelling Technique for Power Electronic Circuits

    NASA Astrophysics Data System (ADS)

    Jankuloski, Goce

    For stable and efficient performance of power converters, a good mathematical model is needed. This thesis presents a new modelling technique for DC/DC and DC/AC Pulse Width Modulated (PWM) converters. The new model is more accurate than the existing modelling techniques such as State Space Averaging (SSA) and Discrete Time Modelling. Unlike the SSA model, the new modelling technique, the Advanced Time Averaging Model (ATAM) includes the averaging dynamics of the converter's output. In addition to offering enhanced model accuracy, application of linearization techniques to the ATAM enables the use of conventional linear control design tools. A controller design application demonstrates that a controller designed based on the ATAM outperforms one designed using the ubiquitous SSA model. Unlike the SSA model, ATAM for DC/AC augments the system's dynamics with the dynamics needed for subcycle fundamental contribution (SFC) calculation. This allows for controller design that is based on an exact model.

  5. 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.

  6. ADVANCED SOLIDS NMR STUDIES OF COAL STRUCTURE AND CHEMISTRY

    SciTech Connect

    1998-03-01

    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. The main activity during this granting period was a detailed comparative analysis of the suite of spectral editing results obtained on the Argonne coals. We have extended our fitting procedure to include carbons of all types in the analysis.

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

    SciTech Connect

    Cohen, Aron J.; Mori-Sánchez, Paula

    2014-01-28

    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.

  8. 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.

  9. Three dimensional electron microscopy and in silico tools for macromolecular structure determination

    PubMed Central

    Borkotoky, Subhomoi; Meena, Chetan Kumar; Khan, Mohammad Wahab; Murali, Ayaluru

    2013-01-01

    Recently, structural biology witnessed a major tool - electron microscopy - in solving the structures of macromolecules in addition to the conventional techniques, X-ray crystallography and nuclear magnetic resonance (NMR). Three dimensional transmission electron microscopy (3DTEM) is one of the most sophisticated techniques for structure determination of molecular machines. Known to give the 3-dimensional structures in its native form with literally no upper limit on size of the macromolecule, this tool does not need the crystallization of the protein. Combining the 3DTEM data with in silico tools, one can have better refined structure of a desired complex. In this review we are discussing about the recent advancements in three dimensional electron microscopy and tools associated with it. PMID:27092033

  10. Chemical and Structural Stability of Lithium-Ion Battery Electrode Materials under Electron Beam

    PubMed Central

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

    2014-01-01

    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 LiNi0.4Mn0.4Co0.18Ti0.02O2 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. PMID:25027190

  11. Chemical and Structural Stability of Lithium-Ion Battery Electrode Materials under Electron Beam

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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 LiNi0.4Mn0.4Co0.18Ti0.02O2 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.

  12. 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

    2014-01-01

    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. PMID:25027190

  13. 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.

  14. 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.

  15. Electronic band structure and photoemission: A review and projection

    SciTech Connect

    Falicov, L.M.

    1987-09-01

    A brief review of electronic-structure calculations in solids, as a means of interpreting photoemission spectra, is presented. The calculations are, in general, of three types: ordinary one-electron-like band structures, which apply to bulk solids and are the basis of all other calculations; surface modified calculations, which take into account, self-consistently if at all possible, the presence of a vacuum-solid interface and of the electronic modifications caused thereby; and many-body calculations, which go beyond average-field approximations and consider dynamic rearrangement effects caused by electron-electron correlations during the photoemission process. 44 refs.

  16. Spatial and electron structure of substituted gold clusters

    NASA Astrophysics Data System (ADS)

    Yarzhemsky, V. G.; Kazaryan, M. A.; Bulychev, N. A.; Dyakov, Y. A.; Kosheleva, O. K.; Chen, C. H.

    2015-12-01

    The structure of intermetallic clusters Au12M (M=Hf, Ta, W, Re, Os) and features of their interaction with electron donors and acceptor atoms, i.e. H and F, were investigated making use computer calculation based of density functional theory. In was found that metal clusters with effective electron number equal to 18 have more symmetrical shape then that with a number of electrons differing from 18. The interaction of gold nanoparticles with silica was modeled by attachment of SiO4H groups and the connection of the electronic structure with electronic transitions in spaser is discussed.

  17. Development of multi-functional composite structures with embedded electronics for space application

    NASA Astrophysics Data System (ADS)

    Seong Jang, Tae; Soo Oh, Dae; Kyu Kim, Jin; In Kang, Kyung; Ho Cha, Won; Woo Rhee, Seung

    2011-01-01

    Conventional spacecraft structural function has been limited to supporting loads and mounting avionics only. In contrast, the technology of 'multi-functional structures' can integrate thermal and electronic functions into the spacecraft's inherent load-bearing capability. In addition, sufficient radiation shielding effectiveness can be provided for the anticipated mission environment. Utilizing this concept, the ratio of electrical functionality to spacecraft volume can be dramatically increased and significant mass savings can be obtained. In this paper, spacecraft electronics are miniaturized using advanced IT applications such as flexible circuitry, miniaturized components, featherweight connectors, and so on, that they can be easily embedded within a structural panel. A sandwich structural panel consists of an aluminum honeycomb core and lightweight CFRP facesheets. Integration of electronics is implemented within the panel by mounting electronics on a multi-layered composite enclosure with multi-materials. This composite enclosure provides a load-bearing, effective thermal conduction, radiation shielding capabilities and an available space for embedding electronics. A series of environmental tests and analyses is carried out to demonstrate that the flight hardware is qualified for the expected mission environments. This approach will be utilized for the advanced small satellite 'STSAT-3' to validate the multi-functional structures concept.

  18. 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,

  19. Imaging doped silicon test structures using low energy electron microscopy.

    SciTech Connect

    Nakakura, Craig Yoshimi; Anderson, Meredith Lynn; Kellogg, Gary Lee

    2010-01-01

    This document is the final SAND Report for the LDRD Project 105877 - 'Novel Diagnostic for Advanced Measurements of Semiconductor Devices Exposed to Adverse Environments' - funded through the Nanoscience to Microsystems investment area. Along with the continuous decrease in the feature size of semiconductor device structures comes a growing need for inspection tools with high spatial resolution and high sample throughput. Ideally, such tools should be able to characterize both the surface morphology and local conductivity associated with the structures. The imaging capabilities and wide availability of scanning electron microscopes (SEMs) make them an obvious choice for imaging device structures. Dopant contrast from pn junctions using secondary electrons in the SEM was first reported in 1967 and more recently starting in the mid-1990s. However, the serial acquisition process associated with scanning techniques places limits on the sample throughput. Significantly improved throughput is possible with the use of a parallel imaging scheme such as that found in photoelectron emission microscopy (PEEM) and low energy electron microscopy (LEEM). The application of PEEM and LEEM to device structures relies on contrast mechanisms that distinguish differences in dopant type and concentration. Interestingly, one of the first applications of PEEM was a study of the doping of semiconductors, which showed that the PEEM contrast was very sensitive to the doping level and that dopant concentrations as low as 10{sup 16} cm{sup -3} could be detected. More recent PEEM investigations of Schottky contacts were reported in the late 1990s by Giesen et al., followed by a series of papers in the early 2000s addressing doping contrast in PEEM by Ballarotto and co-workers and Frank and co-workers. In contrast to PEEM, comparatively little has been done to identify contrast mechanisms and assess the capabilities of LEEM for imaging semiconductor device strictures. The one exception is the

  20. 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. PMID:19308085

  1. Advanced Main Combustion Chamber structural jacket strength analysis

    NASA Technical Reports Server (NTRS)

    Johnston, L. M.; Perkins, L. A.; Denniston, C. L.; Price, J. M.

    1993-01-01

    The structural analysis of the Advanced Main Combustion Chamber (AMCC) is presented. The AMCC is an advanced fabrication concept of the Space Shuttle Main Engine main combustion chamber (MCC). Reduced cost and fabrication time of up to 75 percent were the goals of the AMCC with cast jacket with vacuum plasma sprayed or platelet liner. Since the cast material for the AMCC is much weaker than the wrought material for the MCC, the AMCC is heavier and strength margins much lower in some areas. Proven hand solutions were used to size the manifolds cutout tee areas for combined pressure and applied loads. Detailed finite element strength analyses were used to size the manifolds, longitudinal ribs, and jacket for combined pressure and applied local loads. The design of the gimbal actuator strut attachment lugs were determined by finite element analyses and hand solutions.

  2. New Insights into the Structure of Multimetallic Nanoparticles and their Advanced Characterization

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna; Bhattarai, Nabraj; Velázquez-Salazar, Jesus; Guisbiers, Gregory; Jose-Yacaman, Miguel

    2015-03-01

    Noble multimetallic nanoparticles have 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: Pt-Pd, Au-Au3Cu, Cu-Pt, AgPd-Pt and AuCu/Pt nanoparticles. These multimetallic nanoparticles have raised interest for their various applications in fuel cells, ethanol and methanol oxidation reactions, hydrogen storage, and so on. The nanostructures were analyzed by transmission electron microscopy (TEM) and by aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM), in combination with high angle annular dark field (HAADF), bright field (BF), energy dispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) detectors. These techniques allowed us to probe the structure at the atomic level of the nanoparticles revealing new structural information and elemental composition of the nanoparticles.

  3. 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.

  4. 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.

  5. Cryo-electron tomography: The challenge of doing structural biology in situ

    PubMed Central

    Lučić, Vladan; Rigort, Alexander

    2013-01-01

    Electron microscopy played a key role in establishing cell biology as a discipline, by producing fundamental insights into cellular organization and ultrastructure. Many seminal discoveries were made possible by the development of new sample preparation methods and imaging modalities. Recent technical advances include sample vitrification that faithfully preserves molecular structures, three-dimensional imaging by electron tomography, and improved image-processing methods. These new techniques have enabled the extraction of high fidelity structural information and are beginning to reveal the macromolecular organization of unperturbed cellular environments. PMID:23918936

  6. 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. PMID:11198324

  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. Advanced educational program in optoelectronics for undergraduates and graduates in electronics

    NASA Astrophysics Data System (ADS)

    Vladescu, Marian; Schiopu, Paul

    2015-02-01

    The optoelectronics education included in electronics curricula at Faculty of Electronics, Telecommunications and Information Technology of "Politehnica" University of Bucharest started in early '90s, and evolved constantly since then, trying to address the growing demand of engineers with a complex optoelectronics profile and to meet the increased requirements of microelectronics, optoelectronics, and lately nanotechnologies. Our goal is to provide a high level of theoretical background combined with advanced experimental tools in laboratories, and also with simulation platforms. That's why we propose an advanced educational program in optoelectronics for both grades of our study program, bachelor and master.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Recent Advances in Radical SAM Enzymology: New Structures and Mechanisms

    PubMed Central

    2015-01-01

    The radical S-adenosylmethionine (SAM) superfamily of enzymes catalyzes an amazingly diverse variety of reactions ranging from simple hydrogen abstraction to complicated multistep rearrangements and insertions. The reactions they catalyze are important for a broad range of biological functions, including cofactor and natural product biosynthesis, DNA repair, and tRNA modification. Generally conserved features of the radical SAM superfamily include a CX3CX2C motif that binds an [Fe4S4] cluster essential for the reductive cleavage of SAM. Here, we review recent advances in our understanding of the structure and mechanisms of these enzymes that, in some cases, have overturned widely accepted mechanisms. PMID:25009947

  14. Structural thermal tests on Advanced Neutron Source reactor fuel plates

    SciTech Connect

    Swinson, W.F.; Battiste, R.L.; Yahr, G.T.

    1995-08-01

    The thin aluminum-clad fuel plates proposed for the Advanced Neutron Source reactor are stressed by the high-velocity coolant flowing on each side of the plates and by the thermal gradients in the plates. The total stress, composed of the sum of the flow stress and the thermal stress at a point, could be reduced if the thermal loads tend to relax when the stress magnitude approaches the yield stress of the material. The potential of this occurring would be very significant in assessing the structural reliability of the fuel plates and has been investigated through experiment. The results of this investigation are given in this report.

  15. Vibroacoustic behavior and noise control studies of advanced composite structures

    NASA Astrophysics Data System (ADS)

    Li, Deyu

    The research presented in this thesis is devoted to the problems of sound transmission and noise transmission control for advanced composite payload fairings. There are two advanced composite fairings under study. The first is a tapered, cylindrical advanced grid-stiffened composite fairing, and the second is a cylindrical ChamberCore composite fairing. A fully coupled mathematical model for characterizing noise transmission into a finite elastic cylindrical structure with application to the ChamberCore fairing is developed. It combines advantages of wave radiation principles and structural-acoustic modal interaction, and provides an ideal noise transmission model that can be extended to other finite cylindrical structures. Structural-acoustic dynamic parameters of the two fairings are obtained using a combination of numerical, analytical, and experimental approaches. An in-situ method for experimentally characterizing sound transmission into the fairings called noise reduction spectrum (NRS) is developed based on noise reduction. The regions of interest in the NRS curves are identified and verified during a passive control investigation, where various fill materials are added into wall-chambers of the ChamberCore fairing. Both Helmholtz resonators (HRs) and long T-shaped acoustic resonators (ARs) are also used to successfully control noise transmission into the ChamberCore fairing. In the process, an accurate model for the resonant frequency calculation and design of cylindrical HRs is derived. Further, a novel and more general model for the design of multi-modal, long, T-shaped ARs is developed, including three new end-correction equations that are validated experimentally. The control results show that noise attenuation is significant in the controlled modes, and the control is also observed in some modes that are not targeted, due to acoustic modal coupling via the structure. Helmholtz resonators are found to produce between 2.0 and 7.7 dB increase in NRS in

  16. Ceramic matrix composites -- Advanced high-temperature structural materials

    SciTech Connect

    Lowden, R.A.; Ferber, M.K.; Hellmann, J.R.; Chawla, K.K.; DiPietro, S.G.

    1995-10-01

    This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy`s Office of Industrial Technology`s Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for advanced, high-temperature applications, ceramic matrix composites are leading candidates. The symposium was organized such that papers concerning constituents--fibers and matrices--were presented first, followed by composite processing, modeling of mechanical behavior, and thermomechanical testing. More stable reinforcements are necessary to enhance the performance and life of fiber-reinforced ceramic composites, and to ensure final acceptance of these materials for high-temperature applications. Encouraging results in the areas of polymer-derived SiC fibers and single crystal oxide filaments were given, suggesting composites with improved thermomechanical properties and stability will be realized in the near future. The significance of the fiber-matrix interface in the design and performance of these materials is evident. Numerous mechanical models to relate interface properties to composite behavior, and interpret test methods and data, were enthusiastically discussed. One issue of great concern for any advanced material for use in extreme environments is stability. This theme arose frequently throughout the symposium and was the topic of focus on the final day. Fifty nine papers have been processed separately for inclusion on the data base.

  17. 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.

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

    PubMed

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

    2016-02-01

    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

  19. 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.

  20. Advanced Smart Structures Flight Experiments for Precision Spacecraft

    NASA Astrophysics Data System (ADS)

    Denoyer, Keith K.; Erwin, R. Scott; Ninneman, R. Rory

    2000-07-01

    This paper presents an overview as well as data from four smart structures flight experiments directed by the U.S. Air Force Research Laboratory's Space Vehicles Directorate in Albuquerque, New Mexico. The Middeck Active Control Experiment $¯Flight II (MACE II) is a space shuttle flight experiment designed to investigate modeling and control issues for achieving high precision pointing and vibration control of future spacecraft. The Advanced Controls Technology Experiment (ACTEX-I) is an experiment that has demonstrated active vibration suppression using smart composite structures with embedded piezoelectric sensors and actuators. The Satellite Ultraquiet Isolation Technology Experiment (SUITE) is an isolation platform that uses active piezoelectric actuators as well as damped mechanical flexures to achieve hybrid passive/active isolation. The Vibration Isolation, Suppression, and Steering Experiment (VISS) is another isolation platform that uses viscous dampers in conjunction with electromagnetic voice coil actuators to achieve isolation as well as a steering capability for an infra-red telescope.

  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. 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.

  3. Electronic structure and stability of some silicon compounds

    NASA Astrophysics Data System (ADS)

    Novak, Igor; Abu-Izneid, Tareq; Kovač, Branka

    2010-05-01

    The electronic structures of N,1,3-tris(1,1-dimethylethyl)-cyclodisilazan-2-amine ( I) and 2,3,5,5-tetrakis(trimethylsilyl)cyclopentadiene ( II) have been investigated by HeI and HeII UV photoelectron spectroscopy (UPS) and quantum chemical calculations. We discuss the influence of substituent effects on their electronic structure and thermodynamic stability. Our study shows that trimethylsilyl substituents have strong influence on the electronic structure of cyclopentadiene via inductive effect. Their influence on thermodynamic stability is also pronounced. In substituted cyclodisilazanes hyperconjugative influence of alkylsilyl groups was shown to cause relative thermodynamic stabilization of the cyclodisilazane system.

  4. Electronic Structure Contributions to Reactivity in Xanthine Oxidase Family Enzymes

    PubMed Central

    Stein, Benjamin W.; Kirk, Martin L.

    2016-01-01

    We review the xanthine oxidase (XO) family of pyranopterin molybdenum enzymes with a specific emphasis on electronic structure contributions to reactivity. In addition to xanthine and aldehyde oxidoreductases, which catalyze the 2-electron oxidation of aromatic heterocycles and aldehyde substrates, this mini-review highlights recent work on the closely related carbon monoxide dehydrogenase (CODH) that catalyzes the oxidation of CO using a unique Mo-Cu heterobimetallic active site. A primary focus of this mini-review relates to how spectroscopy and computational methods have been used to develop an understanding of critical relationships between geometric structure, electronic structure, and catalytic function. PMID:25425163

  5. Spectral differences in real-space electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Jordan, D. K.; Mazziotti, D. A.

    2004-01-01

    Real-space grids for electronic structure calculations are efficient because the potential is diagonal while the second derivative in the kinetic energy may be sparsely evaluated with finite differences or finite elements. In applications to vibrational problems in chemical physics a family of methods known as spectral differences has improved finite differences by several orders of magnitude. In this paper the use of spectral differences for electronic structure is studied. Spectral differences are implemented in two electronic structure programs PARSEC and HARES which currently employ finite differences. Applications to silicon clusters and lattices indicate that spectral differences achieve the same accuracy as finite differences with less computational work.

  6. 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)

  7. Kinetic effects on robustness of electron magnetohydrodynamic structures

    SciTech Connect

    Hata, M.; Sakagami, H.; Das, A.

    2013-04-15

    Following recent remarkable progress in the development of high-power short-pulse lasers, exploration is ongoing into hitherto unknown phenomena at fast time scales of electrons, the understanding of which is becoming crucial. For a simplified description of such phenomena, the Electron Magnetohydrodynamics (EMHDs) fluid description is often adopted. For the possibility of electron transport in high-density plasma, exact solutions of the EMHD model in the form of electron vortex currents, together with their associated magnetic fields, have been considered. However, the fluid EMHD model does not incorporate kinetic effects. Here, the finite Larmor radius effects owing to a finite electron temperature on the robustness of the exact EMHD structures are investigated using two-dimensional particle-in-cell simulations. It is found that larger EMHD vortex structures can sustain themselves for long periods, even in high temperature plasma; however, sustaining structures at higher temperatures tends to be difficult. With increasing temperature, electrons with finite Larmor radii become disengaged from the localized region. It is also shown that structures localized in smaller regions are more difficult to sustain. A quantitative criterion in terms of the structure size and Larmor radius has been established by simulations over a wide range of parameters. Finally, we conclude that a structure, larger than about eight times the typical Larmor radius at r=R, could form and exist even under the effects of finite electron temperature.

  8. Recent advances in copper-catalyzed dehydrogenative functionalization via a single electron transfer (SET) process.

    PubMed

    Zhang, Chun; Tang, Conghui; Jiao, Ning

    2012-05-01

    Copper salts have been developed as versatile catalysts for oxidative coupling reactions in organic synthesis. During these processes, Cu-catalysts are often proposed to serve as a one-electron oxidant to promote the single-electron transfer process. Recently, the transition-metal catalyzed direct dehydrogenative transformation has attracted considerable attention. This tutorial review summarizes the recent advances in the copper-catalyzed dehydrogenative functionalization via a single electron transfer (SET) process achieving C-C, C-N, C-O, C-halogen atoms, C-P, and N-N bond formation. PMID:22349590

  9. Electronic-structure calculation for metals by local optimization

    SciTech Connect

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

    1989-03-15

    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 Schlueter. 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.

  10. Modeling Polymorphic Molecular Crystals with Electronic Structure Theory.

    PubMed

    Beran, Gregory J O

    2016-05-11

    Interest in molecular crystals has grown thanks to their relevance to pharmaceuticals, organic semiconductor materials, foods, and many other applications. Electronic structure methods have become an increasingly important tool for modeling molecular crystals and polymorphism. This article reviews electronic structure techniques used to model molecular crystals, including periodic density functional theory, periodic second-order Møller-Plesset perturbation theory, fragment-based electronic structure methods, and diffusion Monte Carlo. It also discusses the use of these models for predicting a variety of crystal properties that are relevant to the study of polymorphism, including lattice energies, structures, crystal structure prediction, polymorphism, phase diagrams, vibrational spectroscopies, and nuclear magnetic resonance spectroscopy. Finally, tools for analyzing crystal structures and intermolecular interactions are briefly discussed. PMID:27008426

  11. Unveiling nanometric plasmons optical properties with advanced electron spectroscopy in the Scanning Transmission Electron Microscope

    NASA Astrophysics Data System (ADS)

    Kociak, Mathieu

    Since the pioneering work of Yamamoto, the use of electron spectroscopy such as Cathodoluminescence (CL) and Electron Energy Loss Spectroscopy (EELS) in a Scanning (Transmission) Electron Microscope (STEM) has considerably helped improving our understanding of the optical properties of metallic nanoparticles. The resemblance of spectroscopic signals from electron and pure optical techniques leads to the intuition that both types of techniques are very close, an idea theoretically discussed by F.J. Garcia de Abajo and coworkers. However, it is also quite intuitive that CL and EELS should be different. For example, EELS helps detecting any sort of modes while CL can only detect radiative ones. On the other hand, even between optical spectroscopy techniques, clear differences such as energy shifts or spectral shapes changes are expected in the case of plasmons. The lack of adapted instrumentation capable of performing combined EELS and CL, as well as theoretical developments allowing to account for the generic difference between EELS and CL and their optical counterparts impeached a comprehensive understanding of plasmons physics with the otherwise amazing electron spectroscopies. In this talk, I will present recent experimental results showing combined EELS and CL spectral mapping of plasmonic properties for nanoparticles with several shapes (triangles, cubes, stars...) and composition (gold, silver, aluminum...). Helped with different theoretical tools, I will try to show how these results can be related to their optical counterparts (extinction, scattering), and what type of physical insights can be gained from these combined measurements. Finally, if time allows, pointing the weaknesses of state-of-the-art CL and EELS (in terms of spectral range and/or spectral resolution), I will present EELS results obtained on highly monochromated electron beams that could cope with these limitations

  12. Electron structure: Shape, size, and generalized parton distributions in QED

    NASA Astrophysics Data System (ADS)

    Miller, Gerald A.

    2014-12-01

    The shape of the electron is studied using lowest-order perturbation theory. Quantities used to probe the structure of the proton—form factors, generalized parton distributions, transverse densities, Wigner distributions and the angular momentum content—are computed for the electron-photon component of the electron wave function. The influence of longitudinally polarized photons, demanded by the need for infrared regularization via a nonzero photon mass, is included. The appropriate value of the photon mass depends on experimental conditions, and consequently the size of the electron (as defined by the slope of its Dirac form factor) bound in a hydrogen atom is found to be about four times larger than when the electron is in a continuum scattering state. The shape of the electron, as determined from the transverse density and generalized parton distributions, is shown not to be round, and the continuum electron is shown to be far less round than the bound electron. An electron distribution function (analogous to the quark distribution function) is defined, and that of the bound electron is shown to be suppressed compared to that of the continuum electron. If the relative transverse momentum of the virtual electron and photon is large compared with the electron mass, the virtual electron and photon each carry nearly the total angular momentum of the physical electron (1 /2 ), with the orbital angular momentum being nearly (-1 /2 ). Including the nonzero photon mass leads to the suppression of end-point contributions to form factors. Implications for proton structure and color transparency are discussed.

  13. 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.

  14. Basis functions for electronic structure calculations on spheres.

    PubMed

    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. PMID:25554128

  15. 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.

  16. 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

  17. 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.

  18. Revealing the hidden correlated electronic structure of strained graphene

    NASA Astrophysics Data System (ADS)

    Craco, L.; Selli, D.; Seifert, G.; Leoni, S.

    2015-05-01

    We explore the effect of isotropic strain on the electronic structure of graphene. It is shown that the interplay between one-particle band narrowing and sizable multiorbital Coulomb interactions induces a transition from a Dirac-liquid semimetal to an orbital selective metal characterized by narrow π -orbital Kondo clouds and abrupt downshift of σ* states. The correlated electronic structure we derive is promising in the sense that it leads to results that might explain the reshaped electronic structure of graphene nanobubbles probed in scanning tunneling microscopy. Our proposal is a key step in understanding the intricate and interdependent changes in orbital and electronic degrees of freedom of strained materials with hexagonal lattice structure.

  19. 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.

  20. 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.

  1. 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.

  2. Electronic structure of carbon-boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Sanginés-Mendoza, Raúl; Martinez, Edgar

    2013-03-01

    Structures of carbon and boron nitride nanotubes (CNTs, BNNTs) are quite similar, conversely, electronic properties are radically different from each other. Carbon nanotubes, whose electronic properties can be either metallic or semiconducting depending on their chiral structure, boron nitride nanotubes are always semiconductors with bandgaps over 4 eV. We have looked to hybrid systems, to predict a new kind of nanostructures with novel electronic properties. In this way, we explore the electronic properties of C-BN nanotubes. In particular, we studied the electronic structure of armchair C-BN nanotubes. The calculations were performed using the pseudopotential LCAO method with a Generalized Gradient Approximation for the exchange-correlation energy functional. The band structure of most of these systems have semiconductor character with an indirect gap smaller than its analogous BNNTs. In addition, the most prominent feature of these systems is the existence of flat bands both at the valence band top and at the conduction band minimum. Such flat bands results in sharp and narrow peaks on the total density of states. The behavior of these flat bands mainly indicates that electrons are largely localized. Thus, a detailed analysis on the electronic band structure shows that hybridization between those orbitals on the interfaces is responsible to exhibit localization effects on the hybrid systems.This research was supported by Conacyt under Grant No. 133022.

  3. 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

  4. 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

  5. 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.

  6. An advanced probabilistic structural analysis method for implicit performance functions

    NASA Technical Reports Server (NTRS)

    Wu, Y.-T.; Millwater, H. R.; Cruse, T. A.

    1989-01-01

    In probabilistic structural analysis, the performance or response functions usually are implicitly defined and must be solved by numerical analysis methods such as finite element methods. In such cases, the most commonly used probabilistic analysis tool is the mean-based, second-moment method which provides only the first two statistical moments. This paper presents a generalized advanced mean value (AMV) method which is capable of establishing the distributions to provide additional information for reliability design. The method requires slightly more computations than the second-moment method but is highly efficient relative to the other alternative methods. In particular, the examples show that the AMV method can be used to solve problems involving non-monotonic functions that result in truncated distributions.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. New Insight into Carbon Nanotube Electronic Structure Selectivity

    SciTech Connect

    Sumpter, Bobby G; Meunier, Vincent; Jiang, Deen

    2009-01-01

    The fundamental role of aryl diazonium salts for post synthesis selectivity of carbon nanotubes is investigated using extensive electronic structure calculations. The resulting understanding for diazonium salt based selective separation of conducting and semiconducting carbon nanotubes shows how the primary contributions come from the interplay between the intrinsic electronic structure of the carbon nanotubes and that of the anion of the salt. We demonstrate how the electronic transport properties change upon the formation of charge transfer complexes and upon their conversion into covalently attached functional groups. Our results are found to correlate well with experiments and provide for the first time an atomistic description for diazonium salt based chemical separation of carbon nanotubes

  12. Improving Boundary Conditions for Electronic Structure Calculations

    NASA Astrophysics Data System (ADS)

    Benesh, G. A.; Haydock, Roger

    Boundary conditions imposed on a local system joined to a much larger substrate system routinely introduce unphysical reflections that affect the calculation of electronic properties such as energies, charge densities, and densities of states. These problems persist in atomic cluster, slab, and supercell calculations alike. However, wave functions in real, physical systems do not reflect at artificial boundaries. Instead, they carry current smoothly across the surface separating the local system from the underlying medium. Haydock and Nex have derived a non-reflecting boundary condition that works well for discrete systems [Phys. Rev. B 75, 205121 (2006)]. Solutions satisfying their maximal breaking of time-reversal symmetry (MBTS) boundary condition carry current away from the boundary at a maximal rate--in much the same way as exact wave functions in physical systems. The MBTS approach has now been extended to studies employing continuous basis functions. In model systems, MBTS boundary conditions work well for calculating wave functions, eigenenergies, and densities of states. Results are reported for an Al(001) surface. Comparisons are made with slab calculations, embedding calculations, and experiment.

  13. MATERIALS WITH COMPLEX ELECTRONIC/ATOMIC STRUCTURES

    SciTech Connect

    D. M. PARKIN; L. CHEN; ET AL

    2000-09-01

    We explored both experimentally and theoretically the behavior of materials at stresses close to their theoretical strength. This involves the preparation of ultra fine scale structures by a variety of fabrication methods. In the past year work has concentrated on wire drawing of in situ composites such as Cu-Ag and Cu-Nb. Materials were also fabricated by melting alloys in glass and drawing them into filaments at high temperatures by a method known as Taylor wire technique. Cu-Ag microwires have been drawn by this technique to produce wires 10 {micro}m in diameter that consist of nanoscale grains of supersaturated solid solution. Organogels formed from novel organic gelators containing cholesterol tethered to squaraine dyes or trans-stilbene derivatives have been studied from several different perspectives. The two types of molecules are active toward several organic liquids, gelling in some cases at w/w percentages as low as 0.1. While relatively robust, acroscopically dry gels are formed in several cases, studies with a variety of probes indicate that much of the solvent may exist in domains that are essentially liquid-like in terms of their microenvironment. The gels have been imaged by atomic force microscopy and conventional and fluorescence microscopy, monitoring both the gelator fluorescence in the case of the stilbene-cholesterol gels and, the fluorescence of solutes dissolved in the solvent. Remarkably, our findings show that several of the gels are composed of similarly appearing fibrous structures visible at the nano-, micro-, and macroscale.

  14. In Situ Cryo-Electron Tomography: A Post-Reductionist Approach to Structural Biology.

    PubMed

    Asano, Shoh; Engel, Benjamin D; Baumeister, Wolfgang

    2016-01-29

    Cryo-electron tomography is a powerful technique that can faithfully image the native cellular environment at nanometer resolution. Unlike many other imaging approaches, cryo-electron tomography provides a label-free method of detecting biological structures, relying on the intrinsic contrast of frozen cellular material for direct identification of macromolecules. Recent advances in sample preparation, detector technology, and phase plate imaging have enabled the structural characterization of protein complexes within intact cells. Here, we review these technical developments and outline a detailed computational workflow for in situ structural analysis. Two recent studies are described to illustrate how this workflow can be adapted to examine both known and unknown cellular complexes. The stage is now set to realize the promise of visual proteomics-a complete structural description of the cell's native molecular landscape. PMID:26456135

  15. New fine structure cooling rate. [electron impact transitions in the ionosphere

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.

    1976-01-01

    One of the dominant electron cooling processes in the ionosphere is caused by electron impact induced fine structure transitions among the ground state levels of atomic oxygen. This fine structure cooling rate is based on theoretical cross sections. Recent advances in the numerical cross section determinations to include polarization effects and more accurate representations of the atomic target result in new lower values. These cross sections are employed in this paper to derive a new fine structure cooling rate which is between 40% and 60% of the currently used rate. A new generalized formula is presented for the cooling rate (from which the fine structure cooling rate is derived), valid for arbitrary mass and temperature difference of the colliding particles and arbitrary inelastic energy difference.

  16. 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.

  17. Graphene Oxide: Synthesis, Characterization, Electronic Structure, and Applications

    NASA Astrophysics Data System (ADS)

    Stewart, Derek A.; Mkhoyan, K. Andre

    While graphite oxide was first identified in 1855 [1, 2], the recent discovery of stable graphene sheets has led to renewed interest in the chemical structure and potential applications of graphene oxide sheets. These structures have several physical properties that could aid in the large scale development of a graphene electronics industry. Depending on the degree of oxidization, graphene oxide layers can be either semiconducting or insulating and provide an important complement to metallic graphene layers. In addition, the electronic and optical properties of these films can be controlled by the selective removal or addition of oxygen. For example, selective oxidationof graphene sheets could lead to electronic circuit fabrication on the scale of a single atomic layer. Graphene oxide is also dispersible in water and other solvents and this provides a facile route for graphene deposition on a wide range of substrates for macroelectronics applications. Although graphite oxide has been known for roughly 150 years, key questions remain in regards to its chemical structure, electronic properties, and fabrication. Answering these issues has taken on special urgency with the development of graphene electronics. In this chapter, we will provide an overview of the field with special focus on synthesis, characterization, and first principles analysis of bonding and electronic structures. Finally, we will also address some of the most promising applications for graphene oxide in electronics and other industries.

  18. 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.

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

    PubMed

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

    2016-03-17

    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. PMID:26457406

  20. Advanced Electron Beam Ion Sources (EBIS) for 2-nd generation carbon radiotherapy facilities

    NASA Astrophysics Data System (ADS)

    Shornikov, A.; Wenander, F.

    2016-04-01

    In this work we analyze how advanced Electron Beam Ion Sources (EBIS) can facilitate the progress of carbon therapy facilities. We will demonstrate that advanced ion sources enable operation of 2-nd generation ion beam therapy (IBT) accelerators. These new accelerator concepts with designs dedicated to IBT provide beams better suited for therapy and, are more cost efficient than contemporary IBT facilities. We will give a sort overview of the existing new IBT concepts and focus on those where ion source technology is the limiting factor. We will analyse whether this limitation can be overcome in the near future thanks to ongoing EBIS development.

  1. Electronic spectra of structurally deformed lutein.

    PubMed

    Macernis, Mindaugas; Sulskus, Juozas; Duffy, Christopher D P; Ruban, Alexander V; Valkunas, Leonas

    2012-10-11

    Quantum chemical calculations have been employed for the investigation of the lowest excited electronic states of lutein, with particular reference to its function within light harvesting antenna complexes of higher plants. Through comparative analysis obtained by using different methods based on gas-phase calculations of the spectra, it was determined that variations in the lengths of the long C-C valence bonds and the dihedral angles of the polyene chain are the dominant factors in determining the spectral properties of Lut 1 and Lut 2 corresponding to the deformed lutein molecules taken from crystallographic data of the major pigment-protein complex of photosystem II. By MNDO-CAS-CI method, it was determined that the two singlet B(u) states of lutein (nominally 1B(u)(-)* and 1B(u)(+)) arise as a result of mixing of the canonical 1B(u)(-) and 1B(u)(+) states of the all-trans polyene due to the presence of the ending rings in lutein. The 1B(u)(-)* state of lutein is optically allowed, while the 1B(u)(-) of a pure all-trans polyene chain is optically forbidden. As demonstrated, the B(u) states are much more sensitive to minor distortions of the conjugated chain due to mixing of the canonical states, resulting in states of poorly defined particle-hole symmetry. Conversely, the A(g) states are relatively robust with respect to geometric distortion, and their respective inversion and particle-hole symmetries remain relatively well-defined. PMID:22974387

  2. 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.

  3. Electronic, Thermal and Structural Properties of Graphene Oxide Frameworks

    SciTech Connect

    Zhu, Pan; Sumpter, Bobby G; Meunier, V.

    2013-01-01

    We report a theoretical study of the electronic, thermal, and structural properties of a series of graphene oxide frameworks (GOFs) using first-principles calculations based on density functional theory. The molecular structure of GOFs is systematically studied by varying the nature and concentration of linear boronic acid pillars and the thermal stability is assessed using ab initio molecular dynamics. The results demonstrate that GOFs are thermally stable up to 550 K and that electronic properties, such as their band gap, can be modified controllably by an appropriate choice of pillaring unit and pillar concentration. The tunability of the electronic structure using non-chemical means, e.g., mechanical strain, is also quantified. Overall, this class of materials is predicted to offer highly tunable materials electronic properties ranging from metallic to semiconducting.

  4. Electronic, Thermal, and Structural Properties of Graphene Oxide Frameworks

    SciTech Connect

    Zhu, Pan; Sumpter, Bobby G; Meunier, V.

    2013-01-01

    We report a theoretical study of the electronic, thermal, and structural properties of a series of graphene oxide frameworks (GOFs) using first-principles calculations based on density functional theory. The molecular structure of GOFs is systematically studied by varying the nature and concentration of linear boronic acid pillars, and the thermal stability is assessed using ab initio molecular dynamics. The results demonstrate that GOFs are thermally stable up to 550 K and that electronic properties, such as their band gap, can be modified controllably by an appropriate choice of pillaring unit and pillar concentration. The tunability of the electronic structure using nonchemical means, e.g., mechanical strain, is also quantified. Overall, this class of materials is predicted to offer highly tunable materials electronic properties ranging from metallic to semiconducting.

  5. 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.

  6. ESTIMATION OF ELECTRON AFFINITY BASED ON STRUCTURE ACTIVITY RELATIONSHIPS

    EPA Science Inventory

    Electron affinity for a wide range of organic molecules was calculated from molecular structure using the chemical reactivity models developed in SPARC. hese models are based on fundamental chemical structure theory applied to the prediction of chemical reactivities for organic m...

  7. 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.

  8. Electronic properties in a quantum well structure of Weyl semimetal

    NASA Astrophysics Data System (ADS)

    You, Wen-Long; Wang, Xue-Feng; Oleś, Andrzej M.; Zhou, Jiao-Jiao

    2016-04-01

    We investigate the confined states and transport of three-dimensional Weyl electrons around a one-dimensional external rectangular electrostatic potential. The confined states with finite transverse wave vector exist at energies higher than the half well depth or lower than the half barrier height. The rectangular potential appears completely transparent to the normal incident electrons but not otherwise. The tunneling transmission coefficient is sensitive to their incident angle and shows resonant peaks when their energy coincides with the confined spectra. In addition, for the electrons in the conduction (valence) band through a potential barrier (well), the transmission spectrum has a gap of width increasing with the incident angle. Interestingly, the electron linear zero-temperature conductance over the potential can approach zero when the Fermi energy is aligned to the top and bottom energies of the potential, when only electron beams normal to the potential interfaces can pass through. The considered structure can be used to collimate the Weyl electron beams.

  9. 76 FR 43983 - Request for Information on How To Structure Proposed New Program: Advanced Manufacturing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-22

    ... Program: Advanced Manufacturing Technology Consortia (AMTech) AGENCY: National Institute of Standards and... structure a new public-private partnership program, the Advanced Manufacturing Technology Consortia (AMTech... or newly created industry-led consortia to develop precompetitive enabling manufacturing...

  10. 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.

  11. 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.

  12. 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.

  13. Role of interface band structure on hot electron transport

    NASA Astrophysics Data System (ADS)

    Garramone, John J.

    Knowledge of electron transport through materials and interfaces is fundamentally and technologically important. For example, metal interconnects within integrated circuits suffer increasingly from electromigration and signal delay due to an increase in resistance from grain boundary and sidewall scattering since their dimensions are becoming shorter than the electron mean free path. Additionally, all semiconductor based devices require the transport of electrons through materials and interfaces where scattering and parallel momentum conservation are important. In this thesis, the inelastic and elastic scattering of hot electrons are studied in nanometer thick copper, silver and gold films deposited on silicon substrates. Hot electrons are electron with energy greater than kBT above the Fermi level (EF). This work was performed utilizing ballistic electron emission microscopy (BEEM) which is a three terminal scanning tunneling microscopy (STM) technique that measures the percentage of hot electrons transmitted across a Schottky barrier interface. Hot electron attenuation lengths of the metals were extracted by measuring the BEEM current as a function of metal overlayer thickness for both hot electron and hot hole injection at 80 K and under ultra high vacuum. The inelastic and elastic scattering lengths were extracted by fitting the energetic dependence of the measured attenuation lengths to a Fermi liquid based model. A sharp increase in the attenuation length is observed at low injection energies, just above the Schottky barrier height, only for metals on Si(001) substrates. In contrast, the attenuation length measured on Si(111) substrates shows a sharp decrease. These results indicate that interface band structure and parallel momentum conservation have significant impact upon the transport of hot electrons across non epitaxial metal-semiconductor interfaces. In addition, they help to separate effects upon hot electron transport that are inherent to the metal

  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. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Electronic Structure and Phase Stability of PdPt Nanoparticles.

    PubMed

    Ishimoto, Takayoshi; Koyama, Michihisa

    2016-03-01

    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. PMID:26862885

  3. Sub-band structure engineering for advanced CMOS channels

    NASA Astrophysics Data System (ADS)

    Takagi, Shin-ichi; Mizuno, T.; Tezuka, T.; Sugiyama, N.; Nakaharai, S.; Numata, T.; Koga, J.; Uchida, K.

    2005-05-01

    This paper reviews our recent studies of novel CMOS channels based on the concept of sub-band structure engineering. This device design concept can be realized as strained-Si channel MOSFETs, ultra-thin SOI MOSFETs and Ge-on-Insulator (GOI) MOSFETs. An important factor for the electron mobility enhancement is the introduction of larger sub-band energy splitting between the 2- and 4-fold valleys on a (1 0 0) surface, which can be obtained in strained-Si and ultra-thin body channels. The electrical properties of strained-Si MOSFETs are summarized with an emphasis on strained-SOI structures. Also, the importance of the precise control of ultra-thin SOI thickness is pointed out from the experimental results of the SOI thickness dependence of mobility. Furthermore, it is shown that the increase in the sub-band energy splitting can also be effective in obtaining higher current drive of n-channel MOSFETs under ballistic transport regime. This suggests that the current drive enhancement based on MOS channel engineering utilizing strain and ultra-thin body structures can be extended to ultra-short channel MOSFETs dominated by ballistic transport.

  4. 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.

  5. Advanced composite combustor structural concepts program. Final Report

    SciTech Connect

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

    1984-12-01

    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.

  6. Electronic systems for transverse coupled-bunch feedback in the Advanced Light Source (ALS)

    SciTech Connect

    Barry, W.; Lambertson, G.R.; Lo, C.C.

    1993-10-01

    In order to effectively control a large number of transverse coupled-bunch modes in the LBL Advanced Light Source (ALS) storage ring, a broad-band, bunch-by-bunch feedback system has been designed, and is beginning to undergo testing and commissioning. This paper addresses, in some detail, the major electronic components of the feedback system. In particular, the components described include: broad-band microwave position detection receivers, closed orbit offset signal rejection circuitry, and baseband quadrature processing circuitry.

  7. Structure and electronic properties of (+)-catechin: aqueous solvent effects.

    PubMed

    Bentz, Erika N; Pomilio, Alicia B; Lobayan, Rosana M

    2014-02-01

    We report a study of the structure of (+)-catechin, which belongs to the family of the flavan-3-ols-one of the five most widely distributed phenolic groups. The biological activities and pharmaceutical utility of these compounds are related to antioxidant activity due to their ability to scavenge free radicals. A breakthrough in the study of the conformational space of this compound, so far absent in the literature, is presented herein. A detailed analysis of the electronic distribution, charge delocalization effects, and stereoelectronic effects is presented following application of the theory of atoms in molecules (AIM) and natural bond orbital analysis. The stability order, and the effects of electron delocalization in the structures were analyzed in depth. The molecular electrostatic potential (MEP) was also obtained, assessing changes in the electronic distribution in aqueous solution, the effects of the solvent on the intrinsic electronic properties, and molecular geometry. The effect of the aqueous solvent on MEP was also quantified, and rationalized by charge delocalization mechanisms, relating them to structural changes and topological properties of the electronic charge density. To further analyze the effects of the aqueous solvent, as well as investigating the molecular and structural properties of these compounds in a biological environment, the polarizabilities for all conformers characterized were also calculated. All results were interpreted on the basis of our accumulated knowledge on (4α→6", 2α→O→1")-phenylflavans in previous reports, thus enriching and deepening the analysis of both types of structure. PMID:24526380

  8. Electronic structure of Fe-based amorphous alloys studied using electron-energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, H. J.; Gu, X. J.; Poon, S. J.; Shiflet, G. J.

    2008-01-01

    The local atomic electronic structures of Fe-Mo-C-B metallic glasses are investigated using electron energy-loss spectroscopy (EELS). The fracture behavior of this Fe-based amorphous alloy system undergoes the transition from being ductile to exhibiting brittleness when alloyed with Cr or Er atoms. In addition, the glass-forming ability is also enhanced. This plastic-to-brittle transition is suggested to correlate with the change of local atomic short-range order or bonding configurations. Therefore, the bonding configuration of Fe-Mo-C-B-Er(Cr) amorphous alloys is investigated by studying the electronic structure of Fe and C atoms using electron energy-loss spectroscopy. It is shown that the normalized EELS white line intensities of Fe-L2,3 edges decrease slightly with an increasing amount of Er additions, while no noticeable difference is obtained with Cr additions. As for the C K edge, a prominent change of edge shape is observed for both alloy systems, where the first peak corresponding to a 1s→1π* transition increases with increasing Er and Cr additions. Accordingly, it is concluded that changes in the local atomic and electronic structure occur around Fe and C atoms when Er and Cr are introduced into the alloys. Furthermore, it is pointed out that the formation of Er-C and Cr-C carbide like local order inferred from the observed C K edge spectra can provide a plausible explanation for the plastic-to-brittle transition observed in these Fe-based amorphous alloys. In spite of the complexity of electronic and atomic structure in this multicomponent Fe-based metallic glass system, this study could serve as a starting point for providing a qualitative interpretation between electronic structure and plasticity in the Fe-Mo-C-B amorphous alloy system. Complimentary techniques, such as x-ray diffraction and high-resolution transmission electron microscope are also employed, providing a more complete structural characterization.

  9. The Electronic Structure of Single-Layer Graphene

    NASA Astrophysics Data System (ADS)

    Siegel, David Alan

    Single-layer graphene has been widely researched in recent years due to its perceived technological applicability and its scientific importance as a unique model system with relativistic Dirac Fermions. Because of its unique geometric and electronic structure, the properties of graphene can be tuned or manipulated in several ways. This tunability is important for technological applications in its own right, and it also allows us to study the fundamental properties of Dirac Fermions, including unique many-body interactions and the nature of the quasiparticles at half-filling. This thesis is a detailed examination of the electronic and structural properties of graphene, studied with angle-resolved photoemission spectroscopy (ARPES) and other surface science techniques like low-energy electron microscopy and diffraction. This thesis is organized as follows. Chapter 1 gives an introduction to the electronic and structural properties of single-layer graphene. It provides a brief historical overview of major theoretical and experimental milestones and sets the stage for the important theoretical and experimental questions that this thesis addresses. Chapters 2 and 3 describe the experimental setup. Chapter 2 discusses the experimental techniques used in this thesis with particular focus on the mechanics of ARPES. Chapter 3 discusses the different graphene growth techniques that were used to create our sample with particular focus on our characterization of epitaxial graphene on SiC(0001). Chapters 4 and 5 form the meat of this thesis: they provide a thorough discussion of the electronic properties of graphene as studied by ARPES. Chapter 4 describes how various perturbations can result in the manipulation of the bare electronic band structure, including the deposition of atomic or molecular species on top of an epitaxial graphene sheet as well as the interactions between graphene and its substrate. Chapter 5 describes the many-body physics in single-layer graphene. It

  10. 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.

  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. Electronic structure of the silicon vacancy color center in diamond.

    PubMed

    Hepp, Christian; Müller, Tina; Waselowski, Victor; Becker, Jonas N; Pingault, Benjamin; Sternschulte, Hadwig; Steinmüller-Nethl, Doris; Gali, Adam; Maze, Jeronimo R; Atatüre, Mete; Becher, Christoph

    2014-01-24

    The negatively charged silicon vacancy (SiV) color center in diamond has recently proven its suitability for bright and stable single photon emission. However, its electronic structure so far has remained elusive. We here explore the electronic structure by exposing single SiV defects to a magnetic field where the Zeeman effect lifts the degeneracy of magnetic sublevels. The similar responses of single centers and a SiV ensemble in a low strain reference sample prove our ability to fabricate almost perfect single SiVs, revealing the true nature of the defect's electronic properties. We model the electronic states using a group-theoretical approach yielding a good agreement with the experimental observations. Furthermore, the model correctly predicts polarization measurements on single SiV centers and explains recently discovered spin selective excitation of SiV defects. PMID:24484153

  13. 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.

  14. Instrumentation and beam dynamics study of advanced electron-photon facility in Indiana University

    NASA Astrophysics Data System (ADS)

    Luo, Tianhuan

    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 speci ed. 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.

  15. 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.

  16. Electron Energy Loss Spectroscopy of a Chiral Plasmonic Structure

    NASA Astrophysics Data System (ADS)

    Paterson, G. W.; Karimullah, A.; Williamson, SDR; Kadodwala, M.; MacLaren, D. A.

    2015-10-01

    A detailed analysis of the plasmonic excitations within a nanopatterned gold chiral biosensor element, measured by scanning transmission electron microscopy electron energy loss spectroscopy, is presented. We discuss aspects of data acquisition, processing, analysis and simulation. The localised surface plasmonic resonance modes in the structure are extracted using non-negative matrix factorisation and we use simulations to correlate notable deviations from the idealised spectrum to nanometric fabrication imperfections. The methodology presented has wide applicability to a variety of metamaterials.

  17. 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.

  18. 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.

  19. Advanced glycation end products induce differential structural modifications and fibrillation of albumin.

    PubMed

    Awasthi, Saurabh; Sankaranarayanan, Kamatchi; Saraswathi, N T

    2016-06-15

    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. PMID:27037764

  20. Electron Crystallography – The Waking Beauty of Structural Biology

    PubMed Central

    Pope, Christopher R; Unger, Vinzenz M

    2012-01-01

    Since its debut in the mid 70ties, electron crystallography has been a valuable alternative in the structure determination of biological macromolecules. Its reliance on single- or double-layered two-dimensionally ordered arrays and the ability to obtain structural information from small and disordered crystals make this approach particularly useful for the study of membrane proteins in a lipid bilayer environment. Despite its unique advantages, technological hurdles have kept electron crystallography from reaching its full potential. Addressing the issues, recent initiatives developed high-throughput pipelines for crystallization and screening. Adding progress in automating data collection, image analysis and phase extension methods, electron crystallography is poised to raise its profile and may lead the way in exploring the structural biology of macromolecular complexes. PMID:22525160

  1. 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.

  2. The electronic structure of diodes probed under bias

    NASA Astrophysics Data System (ADS)

    Glans, Per-Anders; Guo, Jinghua; Park, Jeong; Gabor, Somorjai

    2009-03-01

    Chemists have known for decades that when metal nano-particles are affixed to a catalytically inactive oxide surface, the catalytic turnover rate of the array is more than 10 times that of a metal surface alone. However, the mechanism behind the effect is not clear. To understand the catalytic activity of the interface between the metal nano-structures and the oxide substrate, we have investigated the electronic structure of Pt and Pd doped diodes on a TiO2 substrate. The devices were put under bias during the measurements in an attempt to reproduce the potential differences found over the diode when used as a catalyst. This is challenging for electron based measuring techniques, but using photon-in, photon-out techniques we have successfully probed the electronic structure of Pt and Pd doped diodes under bias. The results from soft x-ray absorption and emission will be presented.

  3. 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.

  4. Heterogeneous electron transfer at nanoscopic electrodes: importance of electronic structures and electric double layers.

    PubMed

    Chen, Shengli; Liu, Yuwen; Chen, Junxiang

    2014-08-01

    Heterogeneous electron-transfer (ET) processes at solid electrodes play key roles in molecular electronics and electrochemical energy conversion and sensing. Electrode nanosization and/or nanostructurization are among the major current strategies for performance promotion in these fields. Besides, nano-sized/structured electrodes offer great opportunities to characterize electrochemical structures and processes with high spatial and temporal resolution. This review presents recent insights into the nanoscopic size and structure effects of electrodes and electrode materials on heterogeneous ET kinetics, by emphasizing the importance of the electric double-layer (EDL) at the electrode/electrolyte interface and the electronic structure of electrode materials. It is shown, by general conceptual analysis and recent example demonstrations of representative electrode systems including electrodes of nanometer sizes and gaps and of nanomaterials such as sp(2) hybridized nanocarbons and semiconductor quantum dots, how the heterogeneous ET kinetics, the electronic structures of electrodes, the EDL structures at the electrode/electrolyte interface and the nanoscopic electrode sizes and structures may be related. PMID:24871071

  5. 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.

  6. Electronic structure of spatially aligned graphene nanoribbons on Au(788).

    PubMed

    Linden, S; Zhong, D; Timmer, A; Aghdassi, N; Franke, J H; Zhang, H; Feng, X; Müllen, K; Fuchs, H; Chi, L; Zacharias, H

    2012-05-25

    We report on a bottom-up approach of the selective and precise growth of subnanometer wide straight and chevron-type armchair nanoribbons (GNRs) on a stepped Au(788) surface using different specific molecular precursors. This process creates spatially well-aligned GNRs, as characterized by STM. High-resolution direct and inverse photoemission spectroscopy of occupied and unoccupied states allows the determination of the energetic position and momentum dispersion of electronic states revealing the existence of band gaps of several electron volts for straight 7-armchair, 13-armchair, and chevron-type GNRs in the electronic structure. PMID:23003288

  7. Super instruction architecture of petascale electronic structure software: the story

    NASA Astrophysics Data System (ADS)

    Lotrich, V. F.; Ponton, J. M.; Perera, A. S.; Deumens, E.; Bartlett, R. J.; Sanders, B. A.

    2010-11-01

    Theoretical methods in chemistry lead to algorithms for the computation of electronic energies and other properties of electronic wave functions that require large numbers of floating point operations and involve large data sets. Thus, computational chemists are very interested in using massively parallel computer systems and in particular the new petascale systems. In this paper we discuss a new programming paradigm that was developed at the Quantum Theory Project to construct electronic structure software that can scale to large numbers of cores of the order of 100,000 and beyond to solve problems in materials engineering relevant to the problems facing society today.

  8. 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.

  9. New development of advanced superconducting electron cyclotron resonance ion source SECRAL (invited)

    SciTech Connect

    Zhao, H. W.; Sun, L. T.; Zhang, X. Z.; Guo, X. H.; Zhao, H. Y.; Feng, Y. C.; Li, J. Y.; Ma, H. Y.; Ma, B. H.; Wang, H.; Li, X. X.; Xie, D. Z.; Lu, W.; Cao, Y.; Shang, Y.

    2010-02-15

    Superconducting electron cyclotron resonance ion source with advance design in Lanzhou (SECRAL) is an 18-28 GHz fully superconducting electron cyclotron resonance (ECR) ion source dedicated for highly charged heavy ion beam production. SECRAL, with an innovative superconducting magnet structure of solenoid-inside-sextupole and at lower frequency and lower rf power operation, may open a new way for developing compact and reliable high performance superconducting ECR ion source. One of the recent highlights achieved at SECRAL is that some new record beam currents for very high charge states were produced by 18 GHz or 18+14.5 GHz double frequency heating, such as 1 e {mu}A of {sup 129}Xe{sup 43+}, 22 e {mu}A of {sup 209}Bi{sup 41+}, and 1.5 e {mu}A of {sup 209}Bi{sup 50+}. To further enhance the performance of SECRAL, a 24 GHz/7 kW gyrotron microwave generator was installed and SECRAL was tested at 24 GHz. Some promising and exciting results at 24 GHz with new record highly charged ion beam intensities were produced, such as 455 e {mu}A of {sup 129}Xe{sup 27+} and 152 e {mu}A of {sup 129}Xe{sup 30+}, although the commissioning time was limited within 3-4 weeks and rf power only 3-4 kW. Bremsstrahlung measurements at 24 GHz show that x-ray is much stronger with higher rf frequency, higher rf power. and higher minimum mirror magnetic field (minimum B). Preliminary emittance measurements indicate that SECRAL emittance at 24 GHz is slightly higher that at 18 GHz. SECRAL has been put into routine operation at 18 GHz for heavy ion research facility in Lanzhou (HIRFL) accelerator complex since May 2007. The total operation beam time from SECRAL for HIRFL accelerator has been more than 2000 h, and {sup 129}Xe{sup 27+}, {sup 78}Kr{sup 19+}, {sup 209}Bi{sup 31+}, and {sup 58}Ni{sup 19+} beams were delivered. All of these new developments, the latest results, and long-term operation for the accelerator have again demonstrated that SECRAL is one of the best in the performance of

  10. New development of advanced superconducting electron cyclotron resonance ion source SECRAL (invited).

    PubMed

    Zhao, H W; Sun, L T; Lu, W; Zhang, X Z; Guo, X H; Cao, Y; Zhao, H Y; Feng, Y C; Li, J Y; Ma, H Y; Shang, Y; Ma, B H; Wang, H; Li, X X; Xie, D Z

    2010-02-01

    Superconducting electron cyclotron resonance ion source with advance design in Lanzhou (SECRAL) is an 18-28 GHz fully superconducting electron cyclotron resonance (ECR) ion source dedicated for highly charged heavy ion beam production. SECRAL, with an innovative superconducting magnet structure of solenoid-inside-sextupole and at lower frequency and lower rf power operation, may open a new way for developing compact and reliable high performance superconducting ECR ion source. One of the recent highlights achieved at SECRAL is that some new record beam currents for very high charge states were produced by 18 GHz or 18+14.5 GHz double frequency heating, such as 1 e microA of (129)Xe(43+), 22 e microA of (209)Bi(41+), and 1.5 e microA of (209)Bi(50+). To further enhance the performance of SECRAL, a 24 GHz/7 kW gyrotron microwave generator was installed and SECRAL was tested at 24 GHz. Some promising and exciting results at 24 GHz with new record highly charged ion beam intensities were produced, such as 455 e microA of (129)Xe(27+) and 152 e microA of (129)Xe(30+), although the commissioning time was limited within 3-4 weeks and rf power only 3-4 kW. Bremsstrahlung measurements at 24 GHz show that x-ray is much stronger with higher rf frequency, higher rf power. and higher minimum mirror magnetic field (minimum B). Preliminary emittance measurements indicate that SECRAL emittance at 24 GHz is slightly higher that at 18 GHz. SECRAL has been put into routine operation at 18 GHz for heavy ion research facility in Lanzhou (HIRFL) accelerator complex since May 2007. The total operation beam time from SECRAL for HIRFL accelerator has been more than 2000 h, and (129)Xe(27+), (78)Kr(19+), (209)Bi(31+), and (58)Ni(19+) beams were delivered. All of these new developments, the latest results, and long-term operation for the accelerator have again demonstrated that SECRAL is one of the best in the performance of ECR ion source for highly charged heavy ion beam production

  11. 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.

  12. 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.

  13. Chemistry and Electronic Structure of Iron-Based Superconductors

    SciTech Connect

    Safa-Sefat, Athena; Singh, David J

    2011-01-01

    The solid state provides a richly varied fabric for intertwining chemical bonding, electronic structure, and magnetism. The discovery of superconductivity in iron pnictides and chalcogenides has revealed new aspects of this interplay, especially involving magnetism and superconductivity. Moreover, it has challenged prior thinking about high-temperature superconductivity by providing a set of materials that differ in many crucial aspects from the previously known cuprate superconductors. Here we review some of what is known about the superconductivity and its interplay with magnetism, chemistry, and electronic structure in Fe-based superconductors.

  14. Orientation-dependent C-60 electronic structures revealed byphotoemission spectroscopy

    SciTech Connect

    Brouet, V.; Yang, W.L.; Zhou, X.J.; Choi, H.J.; Louie, S.G.; Cohen, M.L.; Goldoni, A.; Parmigiani, F.; Hussain, Z.; Shen, Z.X.

    2008-01-17

    We observe, with angle-resolved photoemission, a dramaticchange in the electronic structure of two C60 monolayers, deposited,respectively, on Ag (111) and (100) substrates, and similarly doped withpotassium to half filling of the C60 lowest unoccupied molecular orbital.The Fermi surface symmetry, the bandwidth, and the curvature of thedispersion at gamma point are different. Orient ations of the C60molecules on the two substrates are known to be the main structuraldifference between the two monolayers, and we present new band-structurecalculations for some of these orientations. We conclude thatorientations play a key role in the electronic structure offullerides.

  15. 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.

  16. 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.

  17. 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.

  18. New and unconventional approaches for advancing resolution in biological transmission electron microscopy by improving macromolecular specimen preparation and preservation.

    SciTech Connect

    Massover, W.; Materials Science Division

    2011-02-01

    Resolution in transmission electron microscopy (TEM) now is limited by the properties of specimens, rather than by those of instrumentation. The long-standing difficulties in obtaining truly high-resolution structure from biological macromolecules with TEM demand the development, testing, and application of new ideas and unconventional approaches. This review concisely describes some new concepts and innovative methodologies for TEM that deal with unsolved problems in the preparation and preservation of macromolecular specimens. The selected topics include use of better support films, a more protective multi-component matrix surrounding specimens for cryo-TEM and negative staining, and, several quite different changes in microscopy and micrography that should decrease the effects of electron radiation damage; all these practical approaches are non-traditional, but have promise to advance resolution for specimens of biological macromolecules beyond its present level of 3-10 {angstrom} (0.3-1.0 nm). The result of achieving truly high resolution will be a fulfillment of the still unrealized potential of transmission electron microscopy for directly revealing the structure of biological macromolecules down to the atomic level.

  19. 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.

  20. 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.

  1. Contributions of Electron Cyclotron Waves to Performance in Advanced Regimes on DIII-D

    SciTech Connect

    Petty, C. C.; Burrell, K. H.; DeBoo, J. C.; Ferron, J. R.; Garofalo, A. M.; Hyatt, A. W.; Jackson, G. L.; Lohr, J.; Luce, T. C.; Politzer, P. A.; Prater, R.; Smith, S. P.; Staebler, G. M.; Turnbull, A. D.; Van Zeeland, M. A.; Austin, M. E.; Brennan, D. P.; Takahashi, R.; Doyle, E. J.; Hillesheim, J. C.

    2011-12-23

    High-power electron cyclotron (EC) waves are used to increase performance in several Advanced Tokamak (AT) regimes on DIII-D where there is a simultaneous need for high noninductive current and high beta. In the Quiescent High-confinement mode (QH-mode), a direct measurement of the electron cyclotron current drive (ECCD) profile is made using modulation techniques, and a trapped electron mode (TEM) dominated regime with core T{sub e}>T{sub i} is created. In the 'highq{sub min}' AT scenario, ECCD provides part of the off-axis noninductive current and helps to produce a tearing stable equilibrium. In the hybrid regime, strong central current drive from EC waves and other sources increases the noninductive current fraction to {approx_equal}100%. Surprisingly, the core safety factor remains above unity, meaning good alignment between the current drive profile and the desired plasma current profile is not necessary in this scenario.

  2. Advanced diesel electronic fuel injection and turbocharging. Final report, July 1990-December 1993

    SciTech Connect

    Beck, N.J.; Barkhimer, R.L.; Steinmeyer, D.C.; Kelly, J.E.

    1993-12-01

    The program investigated advanced diesel air charging and fuel injection systems to improve specific power, fuel economy, noise, exhaust emissions, and cold startability. The techniques explored included variable fuel injection rate shaping, variable injection timing, full-authority electronic engine control, turbo-compound cooling, regenerative air circulation as a cold start aid, and variable geometry turbocharging. A Servojet electronic fuel injection system was designed and manufactured for the Cummins VTA-903 engine. A special Servojet twin turbocharger exhaust system was also installed. A series of high speed combustion flame photos was taken using the single cylinder optical engine at Michigan Technological University. Various fuel injection rate shapes and nozzle configurations were evaluated. Single-cylinder bench tests were performed to evaluate regenerative inlet air heating techniques as an aid to cold starting. An exhaust-driven axial cooling air fan was manufactured and tested on the VTA-903 engine. Electronic fuel injection, Turbocharging, Diesel combustion, Cold starting, Flame photography.

  3. 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

  4. High charge short electron bunches for wakefield accelerator structures development.

    SciTech Connect

    Conde, M. E.

    1998-09-25

    The Argonne Wakefield Accelerator group develops accelerating structures based on dielectric loaded waveguides. We use high charge short electron bunches to excite wakefields in dielectric loaded structures, and a second (low charge) beam to probe the wakefields left behind by the drive beam. We report measurements of beam parameters and also initial results of the dielectric loaded accelerating structures. We have studied acceleration of the probe beam in these structures and we have also made measurements on the RF pulses that are generated by the drive beam. Single drive bunches, as well as multiple bunches separated by an integer number of RF periods have been used to generate the accelerating wakefields.

  5. 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.

  6. New quinternary selenides: Syntheses, characterizations, and electronic structure calculations

    SciTech Connect

    Chung, Ming-Yan; Lee, Chi-Shen

    2013-06-01

    Five quinternary selenides, Sr₂.₆₃Y₀.₃₇Ge₀.₆₃Sb₂.₃₇Se₈ (I), Sr₂.₆₃La₀.₃₇Ge₀.₆₃Sb₂.₃₇Se₈ (II), Sr₂.₇₁La₀.₂₉Sn₀.₇₇Bi₂.₂₃Se₈ (III), Ba₂.₆₇ La₀.₃₃ Sn₀.₆₇Sb₂.₃₃Se₈ (IV), and Ba₂.₆₇ La₀.₃₃Sn₀.₆₇Bi₂.₃₃Se₈ (V), were synthesized by solid-state reaction in fused silica tubes. These compounds are isostructural and crystallize in the Sr₃GeSb₂Se₈ structural-type, which belongs to the orthorhombic space group Pnma (no. 62). Three structural units, 1[MSe₃], 1[M₄Se₁₀] (M=Tt, Pn) and M´ (M´=groups II and III element), comprise the entire one-dimensional structure, separated by M´. Measurements of electronic resistivity and diffused reflectance suggest that IV and V have semiconducting properties. Electronic structure calculations confirm the site preferences of Sr/La element discovered by crystal structure refinement. - Graphical abstract: Quinternary selenides Ae₂.₆₇M₀.₃₃Tt₀.₆₇Pn₂.₃₃Se₈ (Ae, M, Tt, Pn=Sr/Ba, Y/La, Ge/Sn, Sb/Bi) were synthesized and their site preferences were characterized by single-crystal X-ray diffraction and electronic structure calculation. Highlights: • Five new quinternary selenides were synthesized and characterized. • Structural units, 1[MSe₃] and 1[M₄Se₁₀] (M=Tt, Pn), construct the one-dimensional structure. • Calculations of electronic structure confirm site preference of Sr/La sites.

  7. 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.

  8. Electronic structure and electron correlation in weakly confining spherical quantum dot potentials

    NASA Astrophysics Data System (ADS)

    Kimani, Peter Borgia Ndungu

    The electronic structure and electron correlations in weakly confining spherical quantum dots potentials are investigated. Following a common practice, the investigation starts with the restricted Hartree-Fock (HF) approximation. Then electron correlation is added in steps in a series of approximations based on the single particle Green's function approach: (i) Second-order Green function (GF) (ii) 2ph-Tamm-Dancoff approximation (TDA) and (iii) an extended version thereof (XTDA) which introduces ground-state correlation into the TDA. The study includes as well Hartree-Fock V (N-1) potential approximation in which framework the Hartree-Fock virtual orbitals are calculated in the field of the N-1 electrons as opposed to the regular but unphysical N-electron field Hartree-Fock calculation of virtual orbitals. For contrast and comparison, the same approximation techniques are applied to few-electron closed-shell atoms and few-electron negative ions for which pertinent data is readily available. The results for the weakly confining spherical quantum dot potentials and the standard atomic systems exhibit fundamental similarities as well as significant differences. For the most part the results of these calculations are in favor of application of HF, GF, and TDA techniques in the modeling of three-dimensional weakly confining quantum dot potentials. The observed differences emphasize the significance of confinement and electronic features unique to quantum dots such as the increased binding of electrons with higher angular momentum and the modified shell filling sequences.

  9. 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. PMID:27094567

  10. 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

  11. 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

  12. Hartree-Fock electronic structure calculations for free atoms and immersed atoms in an electron gas

    NASA Astrophysics Data System (ADS)

    Walsh, Kenneth Charles

    Electronic structure calculations for free and immersed atoms are performed in the context of unrestricted Hartree-Fock Theory. Spherical symmetry is broken, lifting degeneracies in electronic configurations involving the magnetic quantum number mℓ. Basis sets, produced from density functional theory, are then explored for completeness. Comparison to spectroscopic data is done by a configurational interaction of the appropriate L and S symmetry. Finally, a perturbation technique by Lowdin is used to couple the bound atomic states to a neutral, uniform background electronic gas (jellium).

  13. 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).

  14. Electronic structure of hydrogenated diamond: Microscopical insight into surface conductivity

    NASA Astrophysics Data System (ADS)

    Iacobucci, S.; Alippi, Paola; Calvani, P.; Girolami, M.; Offi, F.; Petaccia, L.; Trucchi, D. M.

    2016-07-01

    We have correlated the surface conductivity of hydrogen-terminated diamond to the electronic structure in the Fermi region. Significant density of electronic states (DOS) in proximity of the Fermi edge has been measured by photoelectron spectroscopy (PES) on surfaces exposed to air, corresponding to a p -type electric conductive regime, while upon annealing a depletion of the DOS has been achieved, resembling the diamond insulating state. The surface and subsurface electronic structure has been determined, exploiting the different probing depths of PES applied in a photon energy range between 7 and 31 eV. Ab initio density functional calculations including surface charge depletion and band-bending effects favorably compare with electronic states measured by angular-resolved photoelectron spectroscopy. Such states are organized in the energy-momentum space in a twofold structure: one, bulk-derived, band disperses in the Γ -X direction with an average hole effective mass of (0.43 ±0.02 ) m0 , where m0 is the bare electron mass; a second flatter band, with an effective mass of (2.2 ±0.9 ) m0 , proves that a hole gas confined in the topmost layers is responsible for the conductivity of the (2 ×1 ) hydrogen-terminated diamond (100 ) surface.

  15. 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

  16. Geometric and electronic structures of potassium-adsorbed rubrene complexes

    NASA Astrophysics Data System (ADS)

    Li, Tsung-Lung; Lu, Wen-Cai

    2015-06-01

    The geometric and electronic structures of potassium-adsorbed rubrene complexes are studied in this article. It is found that the potassium-rubrene (K1RUB) complexes inherit the main symmetry characteristics from their pristine counterparts and are thus classified into D2- and C2h-like complexes according to the relative orientations of the four phenyl side groups. The geometric structures of K1RUB 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 D2- and C2h-like K1RUB, however, exhibit their respective peculiarities. These peculiarities can be illustrated by their energy profiles of equilibrium structures. For the potassium adsorption-sites, the D2-like complexes show minimum-energy basins, whereas the C2h-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 D2-like complexes is most likely along the backbone in contrast to the C2h-like ones. Although the electronic structures of the minimum-energy structures of D2- and C2h-like K1RUB 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 than the other two on the opposite side, which leads to the largely enhanced

  17. Electronic Structure and Properties of Organic Bulk-Heterojunction Interfaces.

    PubMed

    Street, Robert A

    2016-05-01

    The electronic structure and physical mechanisms of carrier generation and transport in the organic bulk heterojunction are reviewed. The electronic structure describes the bands and band-tail states, the band alignment at the bulk-heterojunction interface, and the overall density-of-states model. The different electronic character of excitons and mobile charge is discussed, the former being highly molecular and the latter more delocalized. Dissociation of the exciton via the charge-transfer (CT) states is attributed to weak binding of the CT state arising from charge delocalization. Carrier transport and charge collection is strongly influenced by the presence of localized band-tail states. Recombination is attributed primarily to transitions from mobile carriers to band-tail or deep trap states. PMID:26603977

  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. 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. PMID:26866276

  20. Flat pack interconnection structure simplifies modular electronic assemblies

    NASA Technical Reports Server (NTRS)

    Katzin, L.

    1967-01-01

    Flat pack interconnection structure composed of stick modules simplifies modular electronic assemblies by allowing a single axis mother board. Two of the wiring planes are located in the stick module, which is the lower level of assembly, with the third wiring plane in the mother board.

  1. The electronic structure of grain boundaries in Nb

    SciTech Connect

    Sowa, E.C.; Gonis, A. ); Zhang, X.G. )

    1990-11-01

    We present first-principles calculations of the electronic structure of Nb grain boundaries. These are the first such calculations for a bcc metal using the real-space multiple-scattering theory (RSMST). Local densities of states near a {Sigma}5 twist grain boundary are compared to those for bulk Nb. 5 refs., 1 fig.

  2. The electronic structure of heavy fermions: Narrow temperature independent bands

    SciTech Connect

    Arko, A.J.; Joyce, J.J.; Smith, J.L.; Andrews, A.B.

    1996-08-01

    The electronic structure of both Ce and U heavy fermions appears to consist of extremely narrow temperature independent bands. There is no evidence from photoemission for a collective phenomenon normally referred to as the Kondo resonance. In uranium compounds a small dispersion of the bands is easily measurable.

  3. 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.

  4. Controlling electron-phonon scattering with metamaterial plasmonic structures

    NASA Astrophysics Data System (ADS)

    Kempa, Krzysztof; Wu, Xueyuan; Kong, Jiantao; Broido, David

    Electron-plasmon scattering can be faster than electron-phonon scattering. While in metals plasmons occur in the UV range, phonons dominate behavior at much lower frequencies (far IR range), and this typically decouples these phenomena. In metamaterial plasmonic structures, however, plasma effects can be tuned down to the far IR range, allowing for their interference with phonons. It was recently shown, that such interference can protect hot electron energy induced in a solar cell, from dissipation into heat. In this work we explore the possibility of using such an effect to control the electron-phonon interaction and transport in semiconductors. We demonstrate, that this could lead to a novel path to enhancing the electrical and thermal conductivities and the thermoelectric figure of merit.

  5. 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.

  6. Effect of Structural Relaxation on the Electronic Structure of Graphene on Hexagonal Boron Nitride.

    PubMed

    Slotman, G J; van Wijk, M M; Zhao, Pei-Liang; Fasolino, A; Katsnelson, M I; Yuan, Shengjun

    2015-10-30

    We performed calculations of electronic, optical, and transport properties of graphene on hexagonal boron nitride with realistic moiré patterns. The latter are produced by structural relaxation using a fully atomistic model. This relaxation turns out to be crucially important for electronic properties. We describe experimentally observed features such as additional Dirac points and the "Hofstadter butterfly" structure of energy levels in a magnetic field. We find that the electronic structure is sensitive to many-body renormalization of the local energy gap. PMID:26565485

  7. Effect of Structural Relaxation on the Electronic Structure of Graphene on Hexagonal Boron Nitride

    NASA Astrophysics Data System (ADS)

    Slotman, G. J.; van Wijk, M. M.; Zhao, Pei-Liang; Fasolino, A.; Katsnelson, M. I.; Yuan, Shengjun

    2015-10-01

    We performed calculations of electronic, optical, and transport properties of graphene on hexagonal boron nitride with realistic moiré patterns. The latter are produced by structural relaxation using a fully atomistic model. This relaxation turns out to be crucially important for electronic properties. We describe experimentally observed features such as additional Dirac points and the "Hofstadter butterfly" structure of energy levels in a magnetic field. We find that the electronic structure is sensitive to many-body renormalization of the local energy gap.

  8. 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

  9. 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

  10. 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

  11. 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.

  12. Electronics speckle interferometry applications for NDE of spacecraft structural components

    NASA Astrophysics Data System (ADS)

    Rao, M. V.; Samuel, R.; Ananthan, A.; Dasgupta, S.; Nair, P. S.

    2008-09-01

    The spacecraft components viz., central cylinder, deck plates, solar panel substrates, antenna reflectors are made of aluminium/composite honeycomb sandwich construction. Detection of these defects spacecraft structural components is important to assess the integrity of the spacecraft structure. Electronic Speckle Interferometry (ESI) techniques identify the defects as anomalous regions in the interferometric fringe patterns of the specklegram while the component is suitably stressed to give rise to differential displacement/strain around the defective region. Calibration studies, different phase shifting methods associated with ESI and the development of a prototype Twin Head ESSI System (THESSIS) and its use for the NDE of a typical satellite structural component are presented.

  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. Electronically induced structure transformations in graphite & silver, studied using ultrafast electron crystallography

    NASA Astrophysics Data System (ADS)

    Raman, Ramani K.

    Electronically induced structure transformations are a unique class of phenomena in which material transformation can be effected by impulsive excitation of the electronic system, often resulting in exotic structural phases and transformation pathways inaccessible to thermodynamic channels. Using ultrafast electron crystallography (UEC), we have directly observed such photodinduced atomic dynamics in two systems - graphite and silver nanocrystals (Ag NC) that appear to be driven by the strong coupling between the laser excitation and lattice perturbations in the form of strongly coupled optical phonons and laser induced electron redistribution. In graphite, structural changes resulting from photoexcitation with p-polarized, near-IR, femtosecond laser pulses are observed to lead to the nonthermal creation of a transient state with sp3 like bonding characteristics. At laser fluences approaching, but below the damage threshold, the average inter-layer spacing contracts along with creation of new inter-layer distances at ≈ 2 A while the lattice is only moderately heated. The advantage of using electrons (which carry a charge) as a probe is demonstrated, as it reveals the transformation to be driven by a hitherto unobserved surface dipole field, observed here via a Coulomb refraction shift of the scattered electrons within the sub-surface region. Ab initio density functional theory calculations are employed to relate these structural changes to a nonthermal heating of the electrons, followed by a photoinduced charge separation causing a compressive Coulomb stress. To quantify the role and dynamics of electrons emitted from photoexcited surfaces, a novel 'point-projection method' is introduced, capable of directly imaging the spatiotemporal evolution of such photoemitted electron bunches. The method is shown to provide sufficient sensitivity to image electron bunches (as small as 1010 e/cm3) and permit quantitative investigation of the electron emission from

  15. Electronic Structure Studies of Silicon Carbide Cationic Nanoclusters

    NASA Astrophysics Data System (ADS)

    Pradhan, Prachi

    2005-03-01

    As a continuation of our studies on the high stabilities and associated electronic structure properties of Si8C2 to Si14C2 and Si20Cn (n=3-6) clusters,^1 we report here detailed ab initio electronic and geometric structure studies of small SimCn^+ (1< m, n < 4) cationic clusters. The theoretical formalism used is the local density approximation (LDA) to density functional theory (DFT) and the Gaussian03 suite of programs^2 with an all electron 6-311++G** basis set has been used. Complete geometry optimizations of different possible structures have been carried out. The stability of the clusters varies with the ratio of the number of silicon to carbon atoms in the cluster. In contrast to the neutral clusters,^3 cationic clusters appear to prefer more open structures. Results will be presented for binding energies, relative energies, fragmentation energies, vibrational frequencies, and adiabatic ionization potentials^3 for the optimized clusters. Detailed comparisons with published data in the literature will also be presented. * Work supported, in part, by the Welch Foundation, Houston, Texas (Grant No. Y-1525) ^1M. N. Huda and A. K. Ray, Phys. Rev. A (R) 69, 011201 (2004); Eur. Phys. J. D 31, 63 (2004). ^2 Gaussian03, Revision A.1, M. J. Frisch et al., Gaussian Inc., Pittsburgh, PA , 2003. ^3 P. Pradhan and A. K. Ray, J. Mol. Structure (Theochem), in press.

  16. Ultrafast Structural Dynamics of Tertiary Amines upon Electronic Excitation

    NASA Astrophysics Data System (ADS)

    Cheng, Xinxin; Minitti, Michael P.; Deb, Sanghamitra; Zhang, Yao; Budarz, James; Weber, Peter M.

    2011-06-01

    The structural response of several tertiary amines to electronic excitation has been investigated using Rydberg Fingerprint Spectroscopy. The 3p Rydberg states are reached by excitation with a 5.93 eV photon while 3s states are populated by electronic relaxation from 3p state. We observe binding energy shifts on ultrafast time scales in all peaks that reflect the structural change of the molecular ion cores. The shifts are in the range of 15 meV to 30 meV, within time scales of less than 500 fs, depending on the specific molecular systems and the nature of the electronic state. In cases where the p states are spectrally separate, the trends of the energy shifts are different for the p_z and p_x_y Rydberg states whereas the p_z and s states are similar. This suggests that the response of the Rydberg states to structural displacements depends on the symmetry. Very fast binding energy shifts, observed on sub-picosecond time scales, are attributed to the structural adjustment from a pyramidal to a planar structure upon Rydberg excitation. The quantitative values of the binding energy shifts can also be affected by laser chirp, which we model using simulations.

  17. Detection of Secondary and Supersecondary Structures of Proteins from Cryo-Electron Microscopy

    PubMed Central

    Bajaj, Chandrajit; Goswami, Samrat; Zhang, Qin

    2012-01-01

    Recent advances in three-dimensional electron microscopy (3D EM) have enabled the quantitative visualization of the structural building blocks of proteins at improved resolutions. We provide algorithms to detect the secondary structures (α-helices and β-sheets) from proteins for which the volumetric maps are reconstructed at 6–10Å resolution. Additionally, we show that when the resolution is coarser than 10Å, some of the super-secondary structures can be detected from 3D EM maps. For both these algorithms, we employ tools from computational geometry and differential topology, specifically the computation of stable/unstable manifolds of certain critical points of the distance function induced by the molecular surface. Our results connect mathematically well-defined constructions with bio-chemically induced structures observed in proteins. PMID:22186625

  18. 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.

  19. 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.

  1. Correlation of Local Structure and Electronic Properties of Glass Materials

    NASA Astrophysics Data System (ADS)

    Lordi, Vincenzo; Adelstein, Nicole

    2015-03-01

    Wide band gap glasses such as silica and its derivatives are typically considered insulators. However, electronic transport in glasses can be important for certain applications, such as when used as the host material for a scintillator radiation detector. Here we explore the relationship between local structure in glass materials and the corresponding electronic properties of carrier transport and charge trapping. We present a novel analysis that decomposes the distribution of localized band tail states in terms of specific local structural features in the glass. Comparison of the structure-related transport properties of different glass compositions is given, using silica and sodium silicate as prototypes. Prepared by LLNL under Contract DE-AC52-07NA27344.

  2. 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.

  3. 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).

  4. 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.

  5. 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.

  6. ATF (Advanced Toroidal Facility) ECH (Electron Cyclotron Heating) waveguide component development and testing

    SciTech Connect

    Bigelow, T.S.; White, T.L.; Kimrey, H.D.

    1987-01-01

    The Advanced Toroidal Facility (ATF) Electron Cyclotron Heating (ECH) system presently under construction will consist of two 53.2-GHz, 200-kW continuous-wave (cw) gyrotrons with a mode-controlled waveguide system and polarized launcher optimized for maximum power in the ATF plasma. Several components, such as a waveguide mode-analyzing directional coupler, a TiO/sub 2/ mode absorber, miter bends, and a polarization-selectable beamed launcher, have been developed and tested. Laboratory results and initial high-power operation of the system are presented. 2 refs., 2 figs.

  7. Gold-copper nanostars as photo-thermal agents: synthesis and advanced electron microscopy characterization.

    PubMed

    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

    2015-12-28

    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. PMID:26602429

  8. 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.

  9. Mapping the Electronic States of One Dimensional Peapod Structures

    NASA Astrophysics Data System (ADS)

    Hornbaker, D. J.

    2003-03-01

    A key issue of potential technological importance is how the electronic properties of single wall carbon nanotubes are altered by their interactions with other molecules. We address this question by examining the properties of carbon heterostructures formed by the encapsulation of C_60 molecules within the hollow interiors of single wall nanotubes.^1 We study the properties of these novel macromolecules (dubbed 'peapods') using a low temperature, ultra-high vacuum scanning tunneling microscope (STM). Our experiments reveal that while no discernable change in the atomic structure of the encapsulating nanotubes is evident, the presence of interior C_60 molecules can dramatically affect the electronic structure of the nanotube cage. Constant current STM images of peapods display pronounced spatial modulation of the electronic density at sample biases greater than 1V, with a periodicity consistent with the intermolecular spacing of close-packed C_60 molecules inside the nanotube. This effect has been observed on peapods displaying both semiconducting and metallic densities of states. Coincident with this modulation is the appearance of characteristic features in the electronic band structure measured via tunneling spectroscopy. Theoretical modeling^2,3 indicates these features arise from coupling between the valence states of the encapsulated fullerenes, leading to the formation of a hybrid electronic band. Our experiments demonstrate that encapsulation of molecules is a viable route for selectively altering the electronic properties of carbon nanotubes. ^1B.W. Smith and D.E. Luzzi, Chem. Phys. Lett. 321, 169 (2000). ^2D.J. Hornbaker et al. Science 295, 828 (2002). ^3C. Kane et al. Phys. Rev. B (submitted).

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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%.

  15. 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.

  16. 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.

  17. 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

  18. PREFACE: Symposium 1: Advanced Structure Analysis and Characterization of Ceramic Materials

    NASA Astrophysics Data System (ADS)

    Yashima, Masatomo

    2011-05-01

    Preface to Symposium 1 (Advanced Structure Analysis and Characterization of Ceramic Materials) of the International Congress of Ceramics III, held 14-18 November 2010 in Osaka, Japan Remarkable developments have been made recently in the structural analysis and characterization of inorganic crystalline and amorphous materials, such as x-ray, neutron, synchrotron and electron diffraction, x-ray/neutron scattering, IR/Raman scattering, NMR, XAFS, first-principle calculations, computer simulations, Rietveld analysis, the maximum-entropy method, in situ measurements at high temperatures/pressures and electron/nuclear density analysis. These techniques enable scientists to study not only static and long-range periodic structures but also dynamic and short-/intermediate-range structures. Multi-scale characterization from the electron to micrometer levels is becoming increasingly important as a means of understanding phenomena at the interfaces, grain boundaries and surfaces of ceramic materials. This symposium has discussed the structures and structure/property relationships of various ceramic materials (electro, magnetic and optical ceramics; energy and environment related ceramics; bio-ceramics; ceramics for reliability secure society; traditional ceramics) through 38 oral presentations including 8 invited lectures and 49 posters. Best poster awards were given to six excellent poster presentations (Y-C Chen, Tokyo Institute of Technology; C-Y Chung, Tohoku University; T Stawski, University of Twente; Y Hirano, Nagoya Institute of Technology; B Bittova, Charles University Prague; Y Onodera, Kyoto University). I have enjoyed working with my friends in the ICC3 conference. I would like to express special thanks to other organizers: Professor Scott T Misture, Alfred University, USA, Professor Xiaolong Chen, Institute of Physics, CAS, China, Professor Takashi Ida, Nagoya Institute of Technology, Japan, Professor Isao Tanaka, Kyoto University, Japan. I also acknowledge the

  19. Recent Advances in Structures for Hypersonic Flight, part 2

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The papers at this symposium were presented by 24 speakers representing airframe, missile, and engine manufacturers, the U.S. Air Force, and two NASA Research Centers. The papers cover a variety of topics including engine structures, cooled airframe structures, hot structures, thermal protection systems, cryogenic tankage structures, cryogenic insulations, and analysis methods for thermal/structures.

  20. 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.

    2015-11-16

    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.

  1. Electronic Structure of Fullerene Acceptors in Organic Bulk-Heterojunctions: A Combined EPR and DFT Study.

    PubMed

    Mardis, Kristy L; Webb, Jeremy N; Holloway, Tarita; Niklas, Jens; Poluektov, Oleg G

    2015-12-01

    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. PMID:26569578

  2. Electronic and magnetic structures of CeTe2

    NASA Astrophysics Data System (ADS)

    Shim, J. H.; Youn, S. J.; Park, Min Sik; Min, B. I.

    2005-05-01

    We have investigated electronic structures of CeTe2 to explore the correlation between the magnetic, charge density wave, and superconducting phases by using the local spin density approximation (LSDA) and LSDA +U (U =on-site Coulomb interaction) methods. We have found that the contribution near EF from Ce 4f states is negligible, suggesting that Ce 4f electrons are not the superconducting carriers. The total energy calculation indicates that the ABBA-type antiferromagnetic configuration is the most stable, while the stability is weakened by pressure. We have discussed the possible superconducting mechanism in the magnetic phase of CeTe1.82.

  3. The surface electronic structure of silicon terminated (100) diamond

    NASA Astrophysics Data System (ADS)

    Schenk, A. K.; Tadich, A.; Sear, M. J.; Qi, D.; Wee, A. T. S.; Stacey, A.; Pakes, C. I.

    2016-07-01

    A combination of synchrotron-based x-ray spectroscopy and contact potential difference measurements have been used to examine the electronic structure of the (3 × 1) silicon terminated (100) diamond surface under ultra high vacuum conditions. An occupied surface state which sits 1.75 eV below the valence band maximum has been identified, and indications of mid-gap unoccupied surface states have been found. Additionally, the pristine silicon terminated surface is shown to possess a negative electron affinity of ‑0.86 ± 0.1 eV.

  4. Electronic structure basis for the extraordinary magnetoresistance in WTe2.

    PubMed

    Pletikosić, I; Ali, Mazhar N; Fedorov, A V; Cava, R J; Valla, T

    2014-11-21

    The electronic structure basis of the extremely large magnetoresistance in layered nonmagnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at low temperatures, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic Fermi surface from which the pronounced anisotropy of the magnetoresistance follows. A change in the Fermi surface with temperature was found and a high-density-of-states band that may take over conduction at higher temperatures and cause the observed turn-on behavior of the magnetoresistance in WTe2 was identified. PMID:25479512

  5. Electronic Structure Basis for the Extraordinary Magnetoresistance in WTe2

    NASA Astrophysics Data System (ADS)

    Pletikosić, I.; Ali, Mazhar N.; Fedorov, A. V.; Cava, R. J.; Valla, T.

    2014-11-01

    The electronic structure basis of the extremely large magnetoresistance in layered nonmagnetic tungsten ditelluride has been investigated by angle-resolved photoelectron spectroscopy. Hole and electron pockets of approximately the same size were found at low temperatures, suggesting that carrier compensation should be considered the primary source of the effect. The material exhibits a highly anisotropic Fermi surface from which the pronounced anisotropy of the magnetoresistance follows. A change in the Fermi surface with temperature was found and a high-density-of-states band that may take over conduction at higher temperatures and cause the observed turn-on behavior of the magnetoresistance in WTe2 was identified.

  6. Grid-based electronic structure calculations: The tensor decomposition approach

    NASA Astrophysics Data System (ADS)

    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. 81923 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.

  7. The surface electronic structure of silicon terminated (100) diamond.

    PubMed

    Schenk, A K; Tadich, A; Sear, M J; Qi, D; Wee, A T S; Stacey, A; Pakes, C I

    2016-07-01

    A combination of synchrotron-based x-ray spectroscopy and contact potential difference measurements have been used to examine the electronic structure of the (3 × 1) silicon terminated (100) diamond surface under ultra high vacuum conditions. An occupied surface state which sits 1.75 eV below the valence band maximum has been identified, and indications of mid-gap unoccupied surface states have been found. Additionally, the pristine silicon terminated surface is shown to possess a negative electron affinity of -0.86 ± 0.1 eV. PMID:27211214

  8. Structure and dynamics in two-electron atoms

    NASA Astrophysics Data System (ADS)

    Shuman, Edward Somerville

    In this dissertation, I present experimental studies of two-electron atoms. I have been primarily concerned with the effects of external perturbations on dielectronic recombination (DR). Specifically I have examined dielectronic recombination in the presence of electric, microwave, and combined electric and magnetic fields. These measurements illustrate that any external perturbation must have a coupling in excess of the autoionization rate to affect the DR rate. I have also studied the structure of two-electron atoms using microwave resonance techniques. In particular I present experiments which provide new insight into the core polarization model and which provide techniques for measuring both bound and autoionizing energy levels with microwaves.

  9. Dual-phase steel structure visualized by extremely slow electrons.

    PubMed

    Mikmeková, Šárka; Yamada, Katsumi; Noro, Hisato

    2015-12-01

    Mechanical properties of complex steels are affected by their multi-phase structure. Scanning electron microscopy (SEM) is routinely used for characterizing dual-phase (DP) steels, although the identification of steel constituents is not straightforward. In fact, there are several ways of enabling the ferrite-martensite segmentation by SEM, and a wide range of electron energies can be utilized. This study demonstrates the phase identification of DP steels at high, low and extremely low landing energies of the primary electrons from tens of keV to tens of eV. Visualization of the specimen surface at very low landing energies has been achieved by inserting an earthed detector between the pole piece and the negatively biased specimen. This 'cathode lens mode' enables the use of the full energy range up to the primary electron energies. It has been found that extremely slow electrons (<100 eV) are exceptionally suitable for separation of the martensite from the ferrite matrix due to high surface sensitivity, enabling visualization of very fine features. Moreover, the channelling contrast is significantly suppressed at the landing energy of tens of eV of the primary electrons, which enables separation of the phases clearly even in the images acquired at low magnification. The contrast between the phases at tens of eV can be explained by the different thickness of native oxide covering the martensite and the ferrite phase. PMID:26497974

  10. Real-time feedback from iterative electronic structure calculations.

    PubMed

    Vaucher, Alain C; Haag, Moritz P; Reiher, Markus

    2016-04-01

    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. © 2015 Wiley Periodicals, Inc. PMID:26678030

  11. Compressed Sensing Electron Tomography for Determining Biological Structure.

    PubMed

    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

  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. Electronic structure and insulating gap in epitaxial VO2 polymorphs

    DOE PAGESBeta

    Lee, Shinbuhm; Meyer, Tricia L.; Sohn, Changhee; Lee, Donghwa; Nichols, John A.; Lee, Dongkyu; Seo, Sung Seok Ambrose; Freeland, John W.; Noh, Tae Won; Lee, Ho Nyung

    2015-12-24

    Here, determining the origin of the insulating gap in the monoclinic VO2(M1) is a long-standing issue. The difficulty of this study arises from the simultaneous occurrence of structural and electronic transitions upon thermal cycling. Here, we compare the electronic structure of the M1 phase with that of single crystalline insulating VO2(A) and VO2(B) thin films to better understand the insulating phase of VO2. As these A and B phases do not undergo a structural transition upon thermal cycling, we comparatively study the origin of the gap opening in the insulating VO2 phases. By x-ray absorption and optical spectroscopy, we findmore » that the shift of unoccupied t2g orbitals away from the Fermi level is a common feature, which plays an important role for the insulating behavior in VO2 polymorphs. The distinct splitting of the half-filled t2g orbital is observed only in the M1 phase, widening the bandgap up to ~0.6 eV. Our approach of comparing all three insulating VO2 phases provides insight into a better understanding of the electronic structure and the origin of the insulating gap in VO2.« less

  14. 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. PMID:26804474

  15. 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.

  16. Electrochemically Deposited Ceria Structures for Advanced Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Brown, Evan C.

    As the pursuit towards emissions reduction intensifies with growing interest and nascent technologies, solid oxide fuel cells (SOFCs) remain an illustrious candidate for achieving our goals. Despite myriad advantages, SOFCs are still too costly for widespread deployment, even as unprecedented materials developments have recently emerged. This suggests that, in addition to informed materials selection, the necessary power output--and, thereby, cost-savings--gains must come from the fuel cell architecture. The work presented in this manuscript primarily investigates cathodic electrochemical deposition (CELD) as a scalable micro-/nanoscale fabrication tool for engineering ceria-based components in a SOFC assembly. Also, polymer sphere lithography was utilized to deposit fully connected, yet fully porous anti-dot metal films on yttira-stabilized zirconia (YSZ) with specific and knowable geometries, useful for mechanistic studies. Particular attention was given to anode structures, for which anti-dot metal films on YSZ served as composite substrates for subsequent CELD of doped ceria. By tuning the applied potential, a wide range of microstructures from high surface area coatings to planar, thin films was possible. In addition, definitive deposition was shown to occur on the electronically insulating YSZ surfaces, producing quality YSZ|ceria interfaces. These CELD ceria deposits exhibited promising electrochemical activity, as probed by A.C. Impedance Spectroscopy. In an effort to extend its usefulness as a SOFC fabrication tool, the CELD of ceria directly onto common SOFC cathode materials without a metallic phase was developed, as well as templated deposition schemes producing ceria nanowires and inverse opals.

  17. Geometric, electronic, and magnetic structure of FexOy+ clusters

    NASA Astrophysics Data System (ADS)

    Logemann, R.; de Wijs, G. A.; Katsnelson, M. I.; Kirilyuk, A.

    2015-10-01

    Correlation between geometry, electronic structure, and magnetism of solids is both intriguing and elusive. This is particularly strongly manifested in small clusters, where a vast number of unusual structures appear. Here, we employ density functional theory in combination with a genetic search algorithm GGA +U and a hybrid functional to determine the structure of gas phase FexOy+/0 clusters. For FexOy+ cation clusters we also calculate the corresponding vibration spectra and compare them with experiments. We successfully identify Fe3O4+ , Fe4O5+ , Fe4O6+ , Fe5O7+ and propose structures for Fe6O8+ . Within the triangular geometric structure of Fe3O4+ , a noncollinear, ferrimagnetic, and ferromagnetic state are comparable in energy. Fe4O5+ and Fe4O6+ are ferrimagnetic with a residual magnetic moment of 1 μB due to ionization. Fe5O7+ is ferrimagnetic due to the odd number of Fe atoms. We compare the electronic structure with bulk magnetite and find Fe4O5+ , Fe4O6+ , Fe6O8+ to be mixed valence clusters. In contrast, in Fe3O4+ and Fe5O7+ , all Fe are found to be trivalent.

  18. Electronic structure of germanium selenide investigated using ultra-violet photo-electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Mishra, P.; Lohani, H.; Kundu, A. K.; Patel, R.; Solanki, G. K.; Menon, Krishnakumar S. R.; Sekhar, B. R.

    2015-07-01

    The valence band electronic structure of GeSe single crystals has been investigated using angle resolved photoemission spectroscopy (ARPES) and x-ray photoelectron spectroscopy. The experimentally observed bands from ARPES, match qualitatively with our LDA-based band structure calculations along the Γ-Z, Γ-Y and Γ-T symmetry directions. The valence band maximum occurs nearly midway along the Γ-Z direction, at a binding energy of -0.5 eV, substantiating the indirect band gap of GeSe. Non-dispersive features associated with surface states and indirect transitions have been observed. The difference in hybridization of Se and Ge 4p orbitals leads to the variation of dispersion along the three symmetry directions. The predominance of the Se 4pz orbitals, evidenced from theoretical calculations, may be the cause for highly dispersive bands along the Γ-T direction. Detailed electronic structure analysis reveals the significance of the cation-anion 4p orbitals hybridization in the valence band dispersion of IV-VI semiconductors. This is the first comprehensive report of the electronic structure of a GeSe single crystal using ARPES in conjugation with theoretical band structure analysis.

  19. Environmental Factors Influencing the Hyperfine Structure of Manganous Low-Temperature Electron Paramagnetic Resonance Spectra

    PubMed Central

    Nebert, D. W.; Allen, B. T.

    1966-01-01

    Hyperfine structure is observed in low temperature (T = -180°C) EPR (electron paramagnetic resonance) spectra of a number of solutions containing Mn++ ions 13, 15) which have characteristics in common with low temperature EPR spectra from biological substances such as mitochondria and microsomes (1-4). This investigation is an attempt to understand the features of these signals in terms of the molecular environment of the manganous ion, and a qualitative explanation for the observations reported here is advanced in terms of the amount of axial distortion of a manganese hydrate in different environments. PMID:4289642

  20. Electronic structure of the unoccupied electron energy states in FeSe1-xTex

    NASA Astrophysics Data System (ADS)

    Mishra, Pramita; Lohani, Himanshu; Maniraj, M.; Nayak, Jayita; Zargar, R. A.; Awana, V. P. S.; Barman, Sudipta Roy; Sekhar, Biju Raja

    2015-10-01

    Inverse photoemission spectroscopic (IPES) measurements along with LDA based band structure calculations have been used to investigate the unoccupied electronic structure of FeSe1-xTex system. The observed doping and temperature dependent pseudogap in this system is found to be linked to the change in the chalcogen height in their geometric structure. The depletion in spectral weight from the near EF states at low temperature in IPES has been correlated with the enhancement of the 3z2-r2 orbitals in the photoemission spectroscopy (PES). The Coulomb correlation energy U, estimated from the combined PES and IPES spectra, signifies the enhancement in electron correlations in FeSe1-xTex, with doping. The formation of pseudogap in PES and IPES confirms the importance of correlations in the 11 family of Fe superconductors.