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Sample records for atom wire formation

  1. Quantum stability and magic lengths of metal atom wires

    NASA Astrophysics Data System (ADS)

    Cui, Ping; Choi, Jin-Ho; Lan, Haiping; Cho, Jun-Hyung; Niu, Qian; Yang, Jinlong; Zhang, Zhenyu

    2016-06-01

    Metal atom wires represent an important class of nanomaterials in the development of future electronic devices and other functional applications. Using first-principles calculations within density functional theory, we carry out a systematic study of the quantum stability of freestanding atom wires consisting of prototypical metal elements with s -, s p -, and s d -valence electrons. We explore how the quantum mechanically confined motion and local bonding of the valence electrons in these different wire systems can dictate their overall structural stability and find that the formation energy of essentially all the wires oscillates with respect to their length measured by the number n of atoms contained in the wires, establishing the existence of highly preferred (or magic) lengths. Furthermore, different wire classes exhibit distinctively different oscillatory characteristics and quantum stabilities. Alkali metal wires possessing an unpaired s valence electron per atom exhibit simple damped even-odd oscillations. In contrast, Al and Ga wires containing three s2p1 valence electrons per atom generally display much larger and undamped even-odd energy oscillations due to stronger local bonding of the p orbitals. Among the noble metals, the s -dominant Ag wires behave similarly to the linear alkali metal wires, while Au and Pt wires distinctly prefer to be structurally zigzagged due to strong relativistic effects. These findings are discussed in connection with existing experiments and should also be instrumental in future experimental realization of different metal atom wires in freestanding or supported environments with desirable functionalities.

  2. Realization of a Strained Atomic Wire Superlattice.

    PubMed

    Song, Inkyung; Goh, Jung Suk; Lee, Sung-Hoon; Jung, Sung Won; Shin, Jin Sung; Yamane, Hiroyuki; Kosugi, Nobuhiro; Yeom, Han Woong

    2015-11-24

    A superlattice of strained Au-Si atomic wires is successfully fabricated on a Si surface. Au atoms are known to incorporate into the stepped Si(111) surface to form a Au-Si atomic wire array with both one-dimensional (1D) metallic and antiferromagnetic atomic chains. At a reduced density of Au, we find a regular array of Au-Si wires in alternation with pristine Si nanoterraces. Pristine Si nanoterraces impose a strain on the neighboring Au-Si wires, which modifies both the band structure of metallic chains and the magnetic property of spin chains. This is an ultimate 1D version of a strained-layer superlattice of semiconductors, defining a direction toward the fine engineering of self-assembled atomic-scale wires. PMID:26446292

  3. Magnetism and spin-polarized transport in carbon atomic wires

    NASA Astrophysics Data System (ADS)

    Li, Z. Y.; Sheng, W.; Ning, Z. Y.; Zhang, Z. H.; Yang, Z. Q.; Guo, H.

    2009-09-01

    We report ab initio calculations of magnetic and spin-polarized quantum transport properties of pure and nitrogen-doped carbon atomic wires. For finite-sized wires with even number of carbon atoms, total magnetic moment of 2μB is found. On the other hand, wires with odd number atoms have no net magnetic moment. Doped with one or two nitrogen atom(s), the carbon atomic wires exhibit a spin-density-wave-like state. The magnetic properties can be rationalized through bonding patterns and unpaired states. When the wire is sandwiched between Au electrodes to form a transport junction, perfect spin filtering effect can be induced by slightly straining the wire.

  4. Wired up: interconnecting two-dimensional materials with one-dimensional atomic chains.

    PubMed

    Rong, Youmin; Warner, Jamie H

    2014-12-23

    Atomic wires are chains of atoms sequentially bonded together and epitomize the structural form of a one-dimensional (1D) material. In graphene, they form as interconnects between regions when the nanoconstriction eventually becomes so narrow that it is reduced to one atom thick. In this issue of ACS Nano, Cretu et al. extend the discovery of 1D atomic wire interconnects in two-dimensional (2D) materials to hexagonal boron nitride. We highlight recent progress in the area of 1D atomic wires within 2D materials, with a focus on their atomic-level structural analysis using aberration-corrected transmission electron microscopy. We extend this discussion to the formation of nanowires in transition metal dichalcogenides under similar electron-beam irradiation conditions. The future outlook for atomic wires is considered in the context of new 2D materials and hybrids of C, B, and N. PMID:25474120

  5. Current-assisted cooling in atomic wires.

    PubMed

    McEniry, Eunan J; Todorov, Tchavdar N; Dundas, Daniel

    2009-05-13

    The effects of inelastic interactions between current-carrying electrons and vibrational modes of a nanoscale junction are a major limiting factor on the stability of such devices. A method for dynamical simulation of inelastic electron-ion interactions in nanoscale conductors is applied to a model system consisting of an adatom bonded to an atomic wire. It is found that the vibrational energy of such a system may decrease under bias, and furthermore that, as the bias is increased, the rate of cooling, within certain limits, will increase. This phenomenon can be understood qualitatively through low-order perturbation theory, and is due to the presence of an anti-resonance in the transmission function of the system at the Fermi level. Such current-assisted cooling may act as a stabilization mechanism, and may form the basis for a nanoscale cooling 'fan'. PMID:21825478

  6. Reaction and Protection of Electrical Wire Insulators in Atomic-oxygen Environments

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Cantrell, Gidget

    1994-01-01

    Atomic-oxygen erosion on spacecraft in low Earth orbit is an issue which is becoming increasingly important because of the growing number of spacecraft that will fly in the orbits which have high concentrations of atomic oxygen. In this investigation, the atomic-oxygen durability of three types of electrical wire insulation (carbon-based, fluoropolymer, and polysiloxane elastomer) were evaluated. These insulation materials were exposed to thermal-energy atomic oxygen, which was obtained by RF excitation of air at a pressure of 11-20 Pa. The effects of atomic-oxygen exposure on insulation materials indicate that all carbon-based materials erode at about the same rate as polyamide Kapton and, therefore, are not atomic-oxygen durable. However, the durability of fluoropolymers needs to be evaluated on a case by case basis because the erosion rates of fluoropolymers vary widely. For example, experimental data suggest the formation of atomic fluorine during atomic-oxygen amorphous-fluorocarbon reactions. Dimethyl polysiloxanes (silicone) do not lose mass during atomic-oxygen exposure, but develop silica surfaces which are under tension and frequently crack as a result of loss of methyl groups. However, if the silicone sample surfaces were properly pretreated to provide a certain roughness, atomic oxygen exposure resulted in a sturdy, non-cracked atomic-oxygen durable SiO2 layer. Since the surface does not crack during such silicone-atomic oxygen reaction, the crack-induced contamination by silicone can be reduced or completely stopped. Therefore, with proper pretreatment, silicone can be either a wire insulation material or a coating on wire insulation materials to provide atomic-oxygen durability.

  7. Rectification in substituted atomic wires: a theoretical insight.

    PubMed

    Asai, Yoshihiro

    2012-04-25

    Recently, there have been discussions that the giant diode property found experimentally in diblock molecular junctions could be enhanced by the many-body electron correlation effect beyond the mean field theory. In addition, the effect of electron-phonon scattering on an electric current through the diode molecule, measured by inelastic tunneling spectroscopy (IETS), was found to be symmetric with respect to the voltage sign change even though the current is asymmetric. The reason for this behavior is a matter of speculation. In order to clarify whether or not this feature is limited to organic molecules in the off-resonant tunneling region, we discuss the current asymmetry effect on IETS in the resonant region. We introduced heterogeneous atoms into an atomic wire and found that IETS becomes asymmetric in this substituted atomic wire case. Our conclusion gives the other example of intrinsic differences between organic molecules and metallic wires. While the contribution of electron-phonon scattering to IETS is not affected by the current asymmetry in the former case, it is affected in the latter case. The importance of the contribution of the electron-hole excitation to phonon damping in bringing about the current asymmetry effect in IETS in the latter case is discussed. PMID:22466527

  8. Carbon-atom wires: 1-D systems with tunable properties

    NASA Astrophysics Data System (ADS)

    Casari, C. S.; Tommasini, M.; Tykwinski, R. R.; Milani, A.

    2016-02-01

    This review provides a discussion of the current state of research on linear carbon structures and related materials based on sp-hybridization of carbon atoms (polyynes and cumulenes). We show that such systems have widely tunable properties and thus represent an intriguing and mostly unexplored field for both fundamental and applied sciences. We discuss the rich interplay between the structural, vibrational, and electronic properties focusing on recent advances and the future perspectives of carbon-atom wires and novel hybrid sp-sp2-carbon architectures.

  9. Carbon-atom wires: 1-D systems with tunable properties.

    PubMed

    Casari, C S; Tommasini, M; Tykwinski, R R; Milani, A

    2016-02-28

    This review provides a discussion of the current state of research on linear carbon structures and related materials based on sp-hybridization of carbon atoms (polyynes and cumulenes). We show that such systems have widely tunable properties and thus represent an intriguing and mostly unexplored field for both fundamental and applied sciences. We discuss the rich interplay between the structural, vibrational, and electronic properties focusing on recent advances and the future perspectives of carbon-atom wires and novel hybrid sp-sp(2)-carbon architectures. PMID:26847474

  10. Substrate effect on the band gap of semiconducting atomic wires

    NASA Astrophysics Data System (ADS)

    Simbeck, Adam J.; Nayak, Saroj K.

    2014-03-01

    The electronic structure of free-standing and supported semiconducting atomic wires is investigated using a combination of first-principles density functional theory (DFT) and many-body perturbation theory (MBPT). The band gaps predicted from DFT for SiH2 and GeH2 atomic wires are unaffected by the presence of the substrate, whereas the gaps calculated using MBPT under the GW approximation are reduced by about 1eV when the wires are supported. The reduction in the band gap is attributed to a change in the electronic correlation energy, which can be understood as a screened Coulomb interaction. These results highlight the importance of the role played by the substrate in manipulating the electronic and optical properties of quantum confined Si and Ge systems. Work supported by the Interconnect Focus Center (MARCO program), State of New York, NSF IGERT Program, Grant no. 0333314, NSF Petascale Simulations and Analysis (PetaApps) program, Grant No. 0749140, and computing resources of the CCNI at RPI.

  11. Electronic Conduction through Atomic Chains, Quantum Well and Quantum Wire

    NASA Astrophysics Data System (ADS)

    Sharma, A. C.

    2011-07-01

    Charge transport is dynamically and strongly linked with atomic structure, in nanostructures. We report our ab-initio calculations on electronic transport through atomic chains and the model calculations on electron-electron and electron-phonon scattering rates in presence of random impurity potential in a quantum well and in a quantum wire. We computed synthesis and ballistic transport through; (a) C and Si based atomic chains attached to metallic electrodes, (b) armchair (AC), zigzag (ZZ), mixed, rotated-AC and rotated-ZZ geometries of small molecules made of 2S, 6C & 4H atoms attaching to metallic electrodes, and (c) carbon atomic chain attached to graphene electrodes. Computed results show that synthesis of various atomic chains are practically possible and their transmission coefficients are nonzero for a wide energy range. The ab-initio calculations on electronic transport have been performed with the use of Landauer-type scattering formalism formulated in terms of Grben's functions in combination with ground-state DFT. The electron-electron and electron-phonon scattering rates have been calculated as function of excitation energy both at zero and finite temperatures for disordered 2D and 1D systems. Our model calculations suggest that electron scattering rates in a disordered system are mainly governed by effective dimensionality of a system, carrier concentration and dynamical screening effects.

  12. Droplet Formation in Wire Array Plasmas

    NASA Astrophysics Data System (ADS)

    de Groot, J. S.; Rosenthal, S.; Cochrane, K.; Haill, T.; Mehlhorn, T.

    2003-10-01

    Wires in high power z-pinch wire array implosions are heated so rapidly that the liquid metal is heated beyond the normal boiling temperature and becomes metastable. The metastable liquid is heated to a point close to the spinodal, where explosive, homogeneous boiling rapidly ( ns) transforms the liquid to a mixed phase consisting of liquid fragments, droplets, and vapor. It is important to understand this process since the metastable liquid and the mixed state have an EOS and resistivity that can be quite different than equilibrium models. In addition, the liquid droplets can pass through the confining magnetic field so that mass is left behind the imploding plasma. We have modified the 3-D MHD code Alegra to incorporate of the nonequilibrium state. Initial 1-D Alegra calculations of the heating of a tungsten wire indicates that the explosive boiling occurs first near the outside of the plasma and then occurs successively into the center of the plasma. We are also using models to calculate the dynamics of the mixed state and to predict the fraction of the mass that is left behind. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the United States Department of Energy Under Contract DE-AC04-94AL85000.

  13. Electronic instabilities in self-assembled atom wires

    SciTech Connect

    Snijders, Paul C; Weitering, Harm H

    2010-01-01

    Low dimensional systems have fascinated physicists for a long time due to their unusual properties such as charge fractionalization, semionic statistics, and Luttinger liquid behavior among others. In nature, however, low dimensional systems often suffer from thermal fluctuations that can make these systems structurally unstable. Human beings, however, can trick nature by producing artificial structures which are not naturally produced. This Colloquium reviews the problem of self-assembled atomic wires on solid surfaces from an experimental and theoretical point of view. These materials represent a class of one-dimensional systems with very unusual properties that can open doors to the study of exotic physics that cannot be studied otherwise.

  14. Single-molecule conductance in atomically precise germanium wires.

    PubMed

    Su, Timothy A; Li, Haixing; Zhang, Vivian; Neupane, Madhav; Batra, Arunabh; Klausen, Rebekka S; Kumar, Bharat; Steigerwald, Michael L; Venkataraman, Latha; Nuckolls, Colin

    2015-09-30

    While the electrical conductivity of bulk-scale group 14 materials such as diamond carbon, silicon, and germanium is well understood, there is a gap in knowledge regarding the conductivity of these materials at the nano and molecular scales. Filling this gap is important because integrated circuits have shrunk so far that their active regions, which rely so heavily on silicon and germanium, begin to resemble ornate molecules rather than extended solids. Here we unveil a new approach for synthesizing atomically discrete wires of germanium and present the first conductance measurements of molecular germanium using a scanning tunneling microscope-based break-junction (STM-BJ) technique. Our findings show that germanium and silicon wires are nearly identical in conductivity at the molecular scale, and that both are much more conductive than aliphatic carbon. We demonstrate that the strong donor ability of C-Ge σ-bonds can be used to raise the energy of the anchor lone pair and increase conductance. Furthermore, the oligogermane wires behave as conductance switches that function through stereoelectronic logic. These devices can be trained to operate with a higher switching factor by repeatedly compressing and elongating the molecular junction. PMID:26373928

  15. Band-Structure Engineering of Gold Atomic Wires on Silicon by Controlled Doping

    NASA Astrophysics Data System (ADS)

    Choi, Won Hoon; Kang, Pil Gyu; Ryang, Kyung Deuk; Yeom, Han Woong

    2008-03-01

    We report on the systematic tuning of the electronic band structure of atomic wires by controlling the density of impurity atoms. The atomic wires are self-assembled on Si(111) by substitutional gold adsorbates and extra silicon atoms are deposited as the impurity dopants. The one-dimensional electronic band of gold atomic wires, measured by angle-resolved photoemission, changes from a fully metallic to semiconducting one with its band gap increasing above 0.3 eV along with an energy shift as a linear function of the Si dopant density. The gap opening mechanism is suggested to be related to the ordering of the impurities.

  16. Cooperative interplay between impurities and charge density wave in the phase transition of atomic wires

    NASA Astrophysics Data System (ADS)

    Shim, Hyungjoon; Lee, Geunseop; Hyun, Jung-Min; Kim, Hanchul

    2015-09-01

    Impurities interact with a charge density wave (CDW) and affect the phase transitions in low-dimensional systems. By using scanning tunneling microscopy, we visualize the interaction between oxygen impurities and the CDW in indium atomic wires on Si(111), a prototypical one-dimensional electronic system, and unveil the microscopic mechanism of the intriguing O-induced increase of the transition temperature (Tc). Driven by the fluctuating CDW, the O atoms adopt an asymmetric structure. By adjusting the asymmetry, a pair of O impurities in close distance can pin the one-dimensional CDW, which develops into the two-dimensional domains. First-principles calculations showed that the asymmetric interstitially-incorporated O defects induce shear strains, which assists the formation of hexagon structure of the CDW phase. The cooperative interplay between the O impurities and the CDW is responsible for the enhancement of the CDW condensation and the consequent increase in Tc.

  17. The effect of semi-infinite crystalline electrodes on transmission of gold atomic wires using DFT

    NASA Astrophysics Data System (ADS)

    Sattar, Abdul; Amjad, Raja Junaid; Yasmeen, Sumaira; Javed, Hafsa; Latif, Hamid; Mahmood, Hasan; Iqbal, Azmat; Usman, Arslan; Akhtar, Majid Niaz; Khan, Salman Naeem; Dousti, M. R.

    2016-05-01

    First principle calculations of the conductance of gold atomic wires containing chain of 3-8 atoms each with 2.39 Å bond lengths are presented using density functional theory. Three different configurations of wire/electrodes were used. For zigzag wire with semi-infinite crystalline electrodes, even-odd oscillation is observed which is consistent with the previously reported results. A lower conductance is observed for the chain in semi-infinite crystalline electrodes compared to the chains suspended in wire-like electrode. The calculated transmission spectrum for the straight and zig-zag wires suspended between semi-infinite crystalline electrodes showed suppression of transmission channels due to electron scattering occurring at the electrode-wire interface.

  18. Microscopic mechanism of templated self-assembly: Indium metallic atomic wires on Si(553)-Au

    NASA Astrophysics Data System (ADS)

    Kang, Pil-Gyu; Jeong, Hojin; Yeom, Han Woong

    2009-03-01

    We report on the self-assembly of metallic atomic wires utilizing a templated semiconductor surface. A well-ordered template is provided by a vicinal Si surface reacted with Au, Si(553)-Au, which has a regular and robust step array. The scanning tunneling microscopy study shows that In atoms preferentially adsorb and diffuse actively along step edges to form well-ordered atomic wires. The local spectroscopy indicates the metallic property of In atomic wires formed. Ab initio calculations reveal the microscopic mechanism of the templated self-assembly as based on well-aligned preferential adsorption sites and the strongly anisotropic surface diffusion. This template can, thus, be widely applied to fabricate various atomic or molecular wires.

  19. Platinum atomic wire encapsulated in gold nanotubes: A first principle study

    SciTech Connect

    Nigam, Sandeep Majumder, Chiranjib; Sahoo, Suman K.; Sarkar, Pranab

    2014-04-24

    The nanotubes of gold incorporated with platinum atomic wire have been investigated by means of firstprinciples density functional theory with plane wave pseudopotential approximation. The structure with zig-zag chain of Pt atoms in side gold is found to be 0.73 eV lower in energy in comparison to straight chain of platinum atoms. The Fermi level of the composite tube was consisting of d-orbitals of Pt atoms. Further interaction of oxygen with these tubes reveals that while tube with zig-zag Pt prefers dissociative adsorption of oxygen molecule, the gold tube with linear Pt wire favors molecular adsorption.

  20. Platinum atomic wire encapsulated in gold nanotubes: A first principle study

    NASA Astrophysics Data System (ADS)

    Nigam, Sandeep; Sahoo, Suman K.; Sarkar, Pranab; Majumder, Chiranjib

    2014-04-01

    The nanotubes of gold incorporated with platinum atomic wire have been investigated by means of firstprinciples density functional theory with plane wave pseudopotential approximation. The structure with zig-zag chain of Pt atoms in side gold is found to be 0.73 eV lower in energy in comparison to straight chain of platinum atoms. The Fermi level of the composite tube was consisting of d-orbitals of Pt atoms. Further interaction of oxygen with these tubes reveals that while tube with zig-zag Pt prefers dissociative adsorption of oxygen molecule, the gold tube with linear Pt wire favors molecular adsorption.

  1. Characterization of Launched Atoms Leading to Observations of Cold Rydberg Atoms in the Field of a Charged Wire

    NASA Astrophysics Data System (ADS)

    Goodsell, Anne; Erwin, Emma

    2016-05-01

    We are preparing to accelerate and decelerate cold Rydberg atoms in the field of a charged wire. We cool and launch rubidium atoms and observe the distribution of atoms up to 16 mm above the trap location. We report a transverse speed less than 1/10 of the longitudinal launch speed. For Rydberg-atom observations, the cold cloud will be illuminated in mid-flight to promote atoms into the desired Rydberg state (e.g. n = 33-40). With a three-photon sequence we will access nf states and the nearby manifolds with linear Stark shifts. We observed the first two steps of this process using counter-propagating beams of 780 nm and 776 nm in a Rb cell. For cold Rydberg atoms, we will compare states that are strongly accelerated to states that are strongly decelerated by the field around the charged-wire target. We calculate that the displacement during the Rydberg lifetime (e.g. n = 35, τ = 30 μs) will be 200-300 μm farther for extreme attracted states. Detection will occur by spatially-dependent field ionization. Observations of atoms with zero angular momentum around the wire can be extended to atoms with nonzero angular momentum and also to study dynamics of Rydberg atoms with a quadratic Stark shift, building on previous work with ground-state atoms.

  2. Intermetallic compound formation at Cu-Al wire bond interface

    SciTech Connect

    Bae, In-Tae; Young Jung, Dae; Chen, William T.; Du Yong

    2012-12-15

    Intermetallic compound (IMC) formation and evolution at Cu-Al wire bond interface were studied using focused ion beam /scanning electron microscopy, transmission electron microscopy (TEM)/energy dispersive x-ray spectroscopy (EDS), nano beam electron diffraction (NBED) and structure factor (SF) calculation. It was found that discrete IMC patches were formed at the Cu/Al interface in as-packaged state and they grew toward Al pad after high temperature storage (HTS) environment at 150 Degree-Sign C. TEM/EDS and NBED results combined with SF calculation revealed the evidence of metastable {theta} Prime -CuAl{sub 2} IMC phase (tetragonal, space group: I4m2, a = 0.404 nm, c= 0.580 nm) formed at Cu/Al interfaces in both of the as-packaged and the post-HTS samples. Two feasible mechanisms for the formation of the metastable {theta} Prime -CuAl{sub 2} phase are discussed based on (1) non-equilibrium cooling of wire bond that is attributed to highly short bonding process time and (2) the epitaxial relationships between Cu and {theta} Prime -CuAl{sub 2}, which can minimize lattice mismatch for {theta} Prime -CuAl{sub 2} to grow on Cu.

  3. Correlating Electronic Transport to Atomic Structures in Self-Assembled Quantum Wires

    SciTech Connect

    Li, An-Ping; Qin, Shengyong; Kim, Tae Hwan; Ouyang, Wenjie; Zhang, Yanning; Weitering, Harm H; Shih, Chih-Kang; Baddorf, Arthur P; Wu, Ruiqian

    2012-01-01

    Quantum wires, as a smallest electronic conductor, are expected to be a fundamental component in all quantum architectures. The electronic conductance in quantum wires, however, is often dictated by structural instabilities and electron localization at the atomic scale. Here we report on the evolutions of electronic transport as a function of temperature and interwire coupling as the quantum wires of GdSi{sub 2} are self-assembled on Si(100) wire-by-wire. The correlation between structure, electronic properties, and electronic transport are examined by combining nanotransport measurements, scanning tunneling microscopy, and density functional theory calculations. A metal-insulator transition is revealed in isolated nanowires, while a robust metallic state is obtained in wire bundles at low temperature. The atomic defects lead to electron localizations in isolated nanowire, and interwire coupling stabilizes the structure and promotes the metallic states in wire bundles. This illustrates how the conductance nature of a one-dimensional system can be dramatically modified by the environmental change on the atomic scale.

  4. Preparation for Acceleration and Deceleration of Cold Rydberg Atoms in the Field of a Charged Wire

    NASA Astrophysics Data System (ADS)

    Goodsell, Anne; Nawarat, Poomirat; Harper, W. Colleen

    2015-05-01

    We are preparing for experiments using cold Rydberg atoms in linear Stark states. We cool and launch Rb atoms at 2-12 m/s toward a charged wire with a cylindrically-symmetric electric field. The cold cloud will be illuminated in mid-flight to promote atoms into the desired Rydberg state (e.g. n = 33-40). With a three-photon sequence we will access nf states and the nearby manifolds (parabolic quantum number 0 <=n1 <= (n -4)) with linear Stark shifts. This requires specific detuning of the the excitation laser, which allows us to selectively compare states that are strongly accelerated to states that are strongly decelerated. With the wire at +10 V, atoms launched at 10 m/s, and excitation near 750 μm from the wire, the displacement during the Rydberg lifetime (e.g. n = 35, τ = 30 μs) will be 200-300 μm farther for extreme attracted states (n1 = 0) than for extreme repelled states (n1 = 31). Detection will occur by spatially-dependent field ionization. Observations of atoms with zero angular momentum around the wire can be extended to atoms with nonzero angular momentum and also to study the dynamics of Rydberg atoms with a quadratic Stark shift, building on previous work with ground-state atoms. (Current address: Rensselaer Polytechnic Institute, Troy, NY).

  5. Impurity-Mediated Early Condensation of a Charge Density Wave in an Atomic Wire Array.

    PubMed

    Yeom, Han Woong; Oh, Deok Mahn; Wippermann, Stefan; Schmidt, Wolf Gero

    2016-01-26

    We directly show how impurity atoms induce the condensation of a representative electronic phase, the charge density wave (CDW) phase, in atomic scale with scanning tunneling microscopy. Oxygen impurity atoms on the self-assembled metallic atomic wire array on a silicon crystal condense the CDW locally above the pristine transition temperature. More interestingly, the CDW along the wires is induced not by a single atomic impurity but by the cooperation of multiple impurities. First-principles calculations disclose the mechanism of the cooperation as the coherent superposition of the local lattice strain induced by impurities, stressing the coupled electronic and lattice degrees of freedom for the CDW. This opens the possibility of the strain engineering over electronic phases of atomic-scale systems. PMID:26634634

  6. A model of optical trapping cold atoms using a metallic nano wire with surface plasmon effect

    NASA Astrophysics Data System (ADS)

    Thi Phuong Lan, Nguyen; Thi Nga, Do; Viet, Nguyen Ai

    2016-06-01

    In this work, we construct a new model of optical trapping cold atoms with a metallic nano wire by using surface plasmon effect generated by strong field of laser beams. Using the skin effect, we send a strong oscillated electromagnetic filed through the surface of a metallic nano wire. The local field generated by evanescent effect creates an effective attractive potential near the surface of metallic nano wires. The consideration of some possible boundary and frequency conditions might lead to non-trivial bound state solution for a cold atom. We discus also the case of the laser reflection optical trap with shell-core design, and compare our model with another recent schemes of cold atom optical traps using optical fibers and carbon nanotubes.

  7. Wire melting and droplet atomization in a high velocity oxy-fuel jet

    SciTech Connect

    Neiser, R.A.; Brockmann, J.E.; O`Hern, T.J.

    1995-07-01

    Coatings produced by feeding a steel wire into a high-velocity oxy-fuel (HVOF) torch are being intensively studied by the automotive industry as a cost-effective alternative to the more expensive cast iron sleeves currently used in aluminum engine blocks. The microstructure and properties of the sprayed coatings and the overall economics of the process depend critically on the melting and atomization occurring at the wire tip. This paper presents results characterizing several aspects of wire melting and droplet breakup in an HVOF device. Fluctuations in the incandescent emission of the plume one centimeter downstream from the wire tip were recorded using a fast photodiode. A Fourier transform of the light traces provided a measure of the stripping rate of molten material from the wire tip. Simultaneous in-flight measurement of atomized particle size and velocity distributions were made using a Phase Doppler Particle Analyzer (PDPA). The recorded size distributions approximate a log-normal distribution. Small particles traveled faster than large particles, but the difference was considerably smaller than simple aerodynamic drag arguments would suggest. A set of experiments was carried out to determine the effect that variations in torch gas flow rates have on wire melt rate, average particle size, and average particle velocity. The observed variation of particle size with spray condition is qualitatively consistent with a Weber breakup of the droplets coming off the wire. The measurements also showed that it was possible to significantly alter atomized particle size and velocity without appreciably changing the wire melt rate.

  8. Formation of nanometer-size wires using infiltration into latent nuclear tracks

    DOEpatents

    Musket, Ronald G.; Felter, Thomas E.

    2002-01-01

    Nanometer-size wires having a cross-sectional dimension of less than 8 nm with controllable lengths and diameters are produced by infiltrating latent nuclear or ion tracks formed in trackable materials with atomic species. The trackable materials and atomic species are essentially insoluble in each other, thus the wires are formed by thermally driven, self-assembly of the atomic species during annealing, or re-crystallization, of the damage in the latent tracks. Unlike conventional ion track lithography, the inventive method does not require etching of the latent tracks.

  9. Searching for efficient X-ray radiators for wire array Z-pinch plasmas using mid-atomic-number single planar wire arrays on Zebra at UNR

    NASA Astrophysics Data System (ADS)

    Safronova, A. S.; Esaulov, A. A.; Kantsyrev, V. L.; Ouart, N. D.; Shlyaptseva, V.; Weller, M. E.; Keim, S. F.; Williamson, K. M.; Shrestha, I.; Osborne, G. C.

    2011-12-01

    We continue to search for more efficient X-ray radiators from wire array Z-pinch plasmas. The results of recent experiments with single planar wire array (SPWA) loads made from mid-atomic-number material wires such as Alumel, Cu, Mo, and Ag are presented and compared. In particular, two new efficient X-ray radiators, Alumel (95% Ni, 2% Al, and 2% Si) and Ag, are introduced, and their radiative properties are discussed in detail. The experiments were performed on the 1 MA Zebra generator at UNR. The X-ray yields from such mid-atomic-number SPWAs exceed twice those from low-atomic-number SPWAs, such as Al, and increase with the atomic number to reach more than 27-29 kJ for Ag. To consider the main contributions to the total radiation, we divided the time interval of the Z-pinch dynamic where wire ablation and implosion, stagnation, and plasma expansion occur in corresponding phases and studied the radiative and implosion characteristics within them. Theoretical tools such as non-LTE kinetics and wire ablation dynamic models were applied in the data analysis. These results and the models developed have much broader applications, not only for SPWAs on Zebra, but for other HED plasmas with mid-atomic-number ions.

  10. Electronic conductance via atomic wires: a phase field matching theory approach

    NASA Astrophysics Data System (ADS)

    Szczęśniak, D.; Khater, A.

    2012-06-01

    A model is presented for the quantum transport of electrons, across finite atomic wire nanojunctions between electric leads, at zero bias limit. In order to derive the appropriate transmission and reflection spectra, familiar in the Landauer-Büttiker formalism, we develop the algebraic phase field matching theory (PFMT). In particular, we apply our model calculations to determine the electronic conductance for freely suspended monatomic linear sodium wires (MLNaW) between leads of the same element, and for the diatomic copper-cobalt wires (DLCuCoW) between copper leads on a Cu(111) substrate. Calculations for the MLNaW system confirm the correctness and functionality of our PFMT approach. We present novel transmission spectra for this system, and show that its transport properties exhibit the conductance oscillations for the odd- and even-number wires in agreement with previously reported first-principle results. The numerical calculations for the DLCuCoW wire nanojunctions are motivated by the stability of these systems at low temperatures. Our results for the transmission spectra yield for this system, at its Fermi energy, a monotonic exponential decay of the conductance with increasing wire length of the Cu-Co pairs. This is a cumulative effect which is discussed in detail in the present work, and may prove useful for applications in nanocircuits. Furthermore, our PFMT formalism can be considered as a compact and efficient tool for the study of the electronic quantum transport for a wide range of nanomaterial wire systems. It provides a trade-off in computational efficiency and predictive capability as compared to slower first-principle based methods, and has the potential to treat the conductance properties of more complex molecular nanojunctions.

  11. Transport through single-channel atomic wires: Effects of connected sites on scattering phase and odd-even parity oscillations

    NASA Astrophysics Data System (ADS)

    Zhai, Feng; Xu, H. Q.

    2005-11-01

    Theoretical studies of scattering phase and odd-even parity oscillations of the conductance are presented for a finite atomic wire system, which is either connected with two single-channel leads or side-coupled to a single-channel perfect wire. The effects of connected sites on the scattering properties are examined. For a uniform atomic wire connected with two single-channel leads, it is found that when the number of atoms in the wire, n , and the two sequence numbers of the connected atomic sites, n1 and n2 (1⩽n1⩽n2⩽n) , satisfy the condition that (n+1)/gcd(n1,n+1-n2) is not an integer, the transmission coefficient, as a function of the incident electron energy, has zeros of second order. At these zeros the transmission phase is continuous. The zeros of the reflection coefficient, however, are always of first order, and the reflection phase has a lapse precisely by π at each of these zeros. For an atomic wire system side coupled to a perfect lead, the conclusions are reversed: the transmission zeros are always of first order, while the reflection zeros can be of high order. It is also shown that in this side-coupled configuration, both the transmission zeros and the reflection zeros are related to the generic properties of the isolated atomic wire system. The odd-even oscillations of the conductance have also been investigated for finite atomic wire systems in both configurations. It is found that the transmission of a finite atomic wire system depends not only on the parity of the number of atomic sites in the system, but also on the parity of the sequence numbers of the atomic sites through which the atomic wire system is connected with the leads. Finally, by taking a simple one-dimensional quantum wire system with several attached side branches as an example, we show that the transmission zeros of higher order can be found in a quantum system built from one-dimensional wires.

  12. Adsorbate-induced reconstruction of an array of atomic wires: Indium on the Si(553)-Au surface

    NASA Astrophysics Data System (ADS)

    Ahn, J. R.; Kang, P. G.; Byun, J. H.; Yeom, H. W.

    2008-01-01

    The In-induced surface reconstruction of the Si(553)-Au surface has been studied using the combined experiment of low-energy-electron diffraction, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy. Low-energy-electron diffraction revealed that In adsorbates interact actively with the surface above 150°C , widening the terraces uniformly and forming a new atomic wire array. This wire structure has a ×2 period along the wires, where the phase coherence across the wires was much better than that of the pristine Si(553)-Au surface. The In-induced uniform terrace widening was confirmed by scanning tunneling microscopy. More interestingly, the In adsorbates alter the metallic atomic wires of the Si(553)-Au surface with highly dispersive one-dimensional bands into insulating ones with still large dispersion.

  13. Formation quality optimization of laser hot wire cladding for repairing martensite precipitation hardening stainless steel

    NASA Astrophysics Data System (ADS)

    Wen, Peng; Feng, Zhenhua; Zheng, Shiqing

    2015-01-01

    Laser cladding is an advantaged repairing technology due to its low heat input and high flexibility. With preheating wire by resistance heat, laser hot wire cladding shows better process stability and higher deposition efficiency compared to laser cold wire/powder cladding. Multi-pass layer were cladded on the surface of martensite precipitation hardening stainless steel FV520B by fiber laser with ER410NiMo wire. Wire feed rate and preheat current were optimized to obtain stable wire transfer, which guaranteed good formation quality of single pass cladding. Response surface methodology (RSM) was used to optimize processing parameters and predict formation quality of multi-pass cladding. Laser power P, scanning speed Vs, wire feed rate Vf and overlap ratio η were selected as the input variables, while flatness ratio, dilution and incomplete fusion value as the responses. Optimal clad layer with flat surface, low dilution and no incomplete fusion was obtained by appropriately reducing Vf, and increasing P, Vs and η. No defect like pore or crack was found. The tensile strength and impact toughness of the clad layer is respectively 96% and 86% of those of the substrate. The clad layer showed nonuniform microstructure and was divided into quenched areas with coarse lath martensite and tempered areas with tempered martensite due to different thermal cycles in adjacent areas. The tempered areas showed similar hardness to the substrate.

  14. Zinc oxide formation in galvanized metallic wire by simple selective growth method

    NASA Astrophysics Data System (ADS)

    Sivanantham, A.; Abinaya, C.; Vishnukanthan, V.; Jayabal, P.; Boobalan, K.; Mohanraj, S.; Mayandi, J.

    2015-06-01

    ZnO nanostructures were synthesized by a simple method of oxidizing metallic wire by direct electrical heating. A galvanized iron wire was used as the source of zinc. Several optical techniques were employed on the synthesized ZnO nanostructure such as photoluminescence, Raman and FTIR spectroscopy. The formation of ZnO nanostructures was confirmed from the spectra of different optical studies and also determined by XRD. SEM analysis shows the signature of nanorod formation on the surface of the wire. The oxidation state and ferromagnetic property of these oxidized metallic wires were discussed with the help of EPR spectrum. In summation to the properties studied, a growth mechanism was suggested based on the observations and method of the oxidation procedure.

  15. On the formation of silicon wires produced by high-energy ion irradiation

    NASA Astrophysics Data System (ADS)

    Dang, Z. Y.; Song, J.; Azimi, S.; Breese, M. B. H.; Forneris, J.; Vittone, E.

    2013-02-01

    We present a detailed study of simulated and experimentally observed factors which influence the formation of wires in p-type silicon which is irradiated with a high energy, small diameter proton beam, and subsequently electrochemically etched in dilute hydrofluoric acid. A better understanding of the variety of factors influencing wire formation enables a better control of their size, gap between adjacent wires and shape. This addresses a previous limitation in fabricating such structures, such as uncontrollable wire shape and undefined minimum gaps. Furthermore it removes limitations in their application in photonics, such as the difficulty in coupling light between adjacent waveguides, a smearing of the band gap of photonic crystals due to imperfect periodicity, and difficulty in moving the photonic band gap towards near infra-red range. Therefore, the present work allows better control in fabricating components for three dimensional silicon machining and silicon photonics using ion irradiation in conjunction with electrochemical etching.

  16. Fabrication and Characterization of Oriented Carbon Atom Wires Assembled on Gold

    SciTech Connect

    Xue,K.H.; Wu,L.; Chen, S.-P.; Wanga, L.X.; Wei, R.-B.; Xu, S.-M.; Cui, L.; Mao, B.-W.; Tian, Z.-Q.; Zen, C.-H.; Sun, S.-G.; Zhu, Y.-M.

    2009-02-17

    Carbon atom wires (CAWs) are of the sp-hybridized allotrope of carbon. To augment the extraordinary features based on sp-hybridization, we developed an approach to make CAWs be self-assembled and orderly organized on Au substrate. The self-assembling process was investigated in situ by using scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM). The properties of the assembled film were characterized by voltammetry, Raman spectroscopy, electron energy loss spectroscopy (EELS), and the contact angle measurements. Experimental results indicated that the assembled CAW film was of the good structural integrity and well organized, with the sp-hybridized features enhanced.

  17. Study of the strata formation during the explosion of a wire in vacuum

    NASA Astrophysics Data System (ADS)

    Rousskikh, A. G.; Oreshkin, V. I.; Chaikovsky, S. A.; Labetskaya, N. A.; Shishlov, A. V.; Beilis, I. I.; Baksht, R. B.

    2008-10-01

    The formation of strata during fast electrical explosions of aluminum wires at current densities of (1-1.4)×108 A/cm2 has been studied experimentally. To observe the strata, the soft x radiation generated at the hot point of an x-pinch was used. It has been revealed that strata are formed before the voltage collapse, that is, at the stage of heating of the wire metal. Two wire explosion modes were realized: with and without cutoff of the current carried by the exploding wire. Analysis of the experimental results shows that the stratification is most probably due to the thermal instability that develops as a consequence of the increase in metal resistivity with temperature.

  18. Study of the strata formation during the explosion of a wire in vacuum

    SciTech Connect

    Rousskikh, A. G.; Oreshkin, V. I.; Chaikovsky, S. A.; Labetskaya, N. A.; Shishlov, A. V.; Beilis, I. I.; Baksht, R. B.

    2008-10-15

    The formation of strata during fast electrical explosions of aluminum wires at current densities of (1-1.4)x10{sup 8} A/cm{sup 2} has been studied experimentally. To observe the strata, the soft x radiation generated at the hot point of an x-pinch was used. It has been revealed that strata are formed before the voltage collapse, that is, at the stage of heating of the wire metal. Two wire explosion modes were realized: with and without cutoff of the current carried by the exploding wire. Analysis of the experimental results shows that the stratification is most probably due to the thermal instability that develops as a consequence of the increase in metal resistivity with temperature.

  19. Formation of extended directional breakdown channels produced by a copper wire exploding in the atmosphere

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.; Pletnev, N. V.

    2013-12-01

    Experimental data for switching initiated by the electrical breakdown of air gaps up to 1.9 m long with an arbitrary geometry that are produced by an exploding copper wire 90 μm in diameter are presented. At an initial voltage of 11 kV, the stored energy equals 100-2100 J. Two channel formation conditions are possible: explosion of a wire without electrical breakdown and electrical breakdown in a channel produced by an exploding wire with a delay (current pause) no longer than 250 μs. Current and voltage waveforms across the discharge gap, as well as the resistivity values, under the electrical breakdown conditions are shown. Mechanisms and conditions for streamer initiation at a mean electric field strength in the discharge gap of 5.3-17.0 kV/m are discussed. The geometrical dimensions of plasma objects in the forming channel, the run of the electrical current under breakdown, and the formation mechanism of wire explosion products are found from color microphotographs. The formation mechanism of large aerosols in the form of tiny spherical copper and copper oxide (CuO, Cu2O) particles under wire explosion conditions is discussed.

  20. Non-equilibrium 8π Josephson effect in atomic Kitaev wires.

    PubMed

    Laflamme, C; Budich, J C; Zoller, P; Dalmonte, M

    2016-01-01

    The identification of fractionalized excitations, such as Majorana quasi-particles, would be a striking signal of the realization of exotic quantum states of matter. While the paramount demonstration of such excitations would be a probe of their non-Abelian statistics via controlled braiding operations, alternative proposals exist that may be easier to access experimentally. Here we identify a signature of Majorana quasi-particles, qualitatively different from the behaviour of a conventional superconductor, which can be detected in cold atom systems using alkaline-earth-like atoms. The system studied is a Kitaev wire interrupted by an extra site, which gives rise to super-exchange coupling between two Majorana-bound states. We show that this system hosts a tunable, non-equilibrium Josephson effect with a characteristic 8π periodicity of the Josephson current. The visibility of the 8π periodicity of the Josephson current is then studied including the effects of dephasing and particle losses. PMID:27481540

  1. Atomic absorption determination of traces of cadmium in urine after electrodeposition onto a tungsten wire.

    PubMed

    Zhang, G; Li, J; Fu, D; Hao, D; Xiang, P

    1993-03-01

    A three-coil tungsten wire is used as electrode for the preconcentration of cadmium, which is then placed in a graphite tube for atomization and atomic absorption measurement. The heating parameters of the graphite furnace are optimized using the Modified and Weighted Centroid Simplex Method (MWCS), and computer program for automatic calculation. Sulphuric acid is selected as the supporting electrolyte for electrodeposition. The linear range of the calibration graph is 0.00-0.55 ng/ml. The detection limit is 0.01 ng/ml. For 0.1 ng/ml cadmium the coefficient of variation is 3.35% for ten parallel determinations. No interference occurs in the presence of more than 20 coexisting ions. Traces of cadmium in urine of normal people and in river water and the recoveries for cadmium are determined. The results are satisfactory. PMID:18965645

  2. Non-equilibrium 8π Josephson effect in atomic Kitaev wires

    PubMed Central

    Laflamme, C.; Budich, J. C.; Zoller, P.; Dalmonte, M.

    2016-01-01

    The identification of fractionalized excitations, such as Majorana quasi-particles, would be a striking signal of the realization of exotic quantum states of matter. While the paramount demonstration of such excitations would be a probe of their non-Abelian statistics via controlled braiding operations, alternative proposals exist that may be easier to access experimentally. Here we identify a signature of Majorana quasi-particles, qualitatively different from the behaviour of a conventional superconductor, which can be detected in cold atom systems using alkaline-earth-like atoms. The system studied is a Kitaev wire interrupted by an extra site, which gives rise to super-exchange coupling between two Majorana-bound states. We show that this system hosts a tunable, non-equilibrium Josephson effect with a characteristic 8π periodicity of the Josephson current. The visibility of the 8π periodicity of the Josephson current is then studied including the effects of dephasing and particle losses. PMID:27481540

  3. Non-equilibrium 8π Josephson effect in atomic Kitaev wires

    NASA Astrophysics Data System (ADS)

    Laflamme, C.; Budich, J. C.; Zoller, P.; Dalmonte, M.

    2016-08-01

    The identification of fractionalized excitations, such as Majorana quasi-particles, would be a striking signal of the realization of exotic quantum states of matter. While the paramount demonstration of such excitations would be a probe of their non-Abelian statistics via controlled braiding operations, alternative proposals exist that may be easier to access experimentally. Here we identify a signature of Majorana quasi-particles, qualitatively different from the behaviour of a conventional superconductor, which can be detected in cold atom systems using alkaline-earth-like atoms. The system studied is a Kitaev wire interrupted by an extra site, which gives rise to super-exchange coupling between two Majorana-bound states. We show that this system hosts a tunable, non-equilibrium Josephson effect with a characteristic 8π periodicity of the Josephson current. The visibility of the 8π periodicity of the Josephson current is then studied including the effects of dephasing and particle losses.

  4. Indium segregation during III–V quantum wire and quantum dot formation on patterned substrates

    SciTech Connect

    Moroni, Stefano T.; Dimastrodonato, Valeria; Chung, Tung-Hsun; Juska, Gediminas; Gocalinska, Agnieszka; Pelucchi, Emanuele; Vvedensky, Dimitri D.

    2015-04-28

    We report a model for metalorganic vapor-phase epitaxy on non-planar substrates, specifically V-grooves and pyramidal recesses, which we apply to the growth of InGaAs nanostructures. This model—based on a set of coupled reaction-diffusion equations, one for each facet in the system—accounts for the facet-dependence of all kinetic processes (e.g., precursor decomposition, adatom diffusion, and adatom lifetimes) and has been previously applied to account for the temperature-, concentration-, and temporal-dependence of AlGaAs nanostructures on GaAs (111)B surfaces with V-grooves and pyramidal recesses. In the present study, the growth of In{sub 0.12}Ga{sub 0.88}As quantum wires at the bottom of V-grooves is used to determine a set of optimized kinetic parameters. Based on these parameters, we have modeled the growth of In{sub 0.25}Ga{sub 0.75}As nanostructures formed in pyramidal site-controlled quantum-dot systems, successfully producing a qualitative explanation for the temperature-dependence of their optical properties, which have been reported in previous studies. Finally, we present scanning electron and cross-sectional atomic force microscopy images which show previously unreported facetting at the bottom of the pyramidal recesses that allow quantum dot formation.

  5. Evolution of atomic structure during nanoparticle formation

    PubMed Central

    Tyrsted, Christoffer; Lock, Nina; Jensen, Kirsten M. Ø.; Christensen, Mogens; Bøjesen, Espen D.; Emerich, Hermann; Vaughan, Gavin; Billinge, Simon J. L.; Iversen, Bo B.

    2014-01-01

    Understanding the mechanism of nanoparticle formation during synthesis is a key prerequisite for the rational design and engineering of desirable materials properties, yet remains elusive due to the difficulty of studying structures at the nanoscale under real conditions. Here, the first comprehensive structural description of the formation of a nanoparticle, yttria-stabilized zirconia (YSZ), all the way from its ionic constituents in solution to the final crystal, is presented. The transformation is a complicated multi-step sequence of atomic reorganizations as the material follows the reaction pathway towards the equilibrium product. Prior to nanoparticle nucleation, reagents reorganize into polymeric species whose structure is incompatible with the final product. Instead of direct nucleation of clusters into the final product lattice, a highly disordered intermediate precipitate forms with a local bonding environment similar to the product yet lacking the correct topology. During maturation, bond reforming occurs by nucleation and growth of distinct domains within the amorphous intermediary. The present study moves beyond kinetic modeling by providing detailed real-time structural insight, and it is demonstrated that YSZ nanoparticle formation and growth is a more complex chemical process than accounted for in conventional models. This level of mechanistic understanding of the nanoparticle formation is the first step towards more rational control over nanoparticle synthesis through control of both solution precursors and reaction intermediaries. PMID:25075335

  6. Evolution of atomic structure during nanoparticle formation.

    PubMed

    Tyrsted, Christoffer; Lock, Nina; Jensen, Kirsten M Ø; Christensen, Mogens; Bøjesen, Espen D; Emerich, Hermann; Vaughan, Gavin; Billinge, Simon J L; Iversen, Bo B

    2014-05-01

    Understanding the mechanism of nanoparticle formation during synthesis is a key prerequisite for the rational design and engineering of desirable materials properties, yet remains elusive due to the difficulty of studying structures at the nanoscale under real conditions. Here, the first comprehensive structural description of the formation of a nanoparticle, yttria-stabilized zirconia (YSZ), all the way from its ionic constituents in solution to the final crystal, is presented. The transformation is a complicated multi-step sequence of atomic reorganizations as the material follows the reaction pathway towards the equilibrium product. Prior to nanoparticle nucleation, reagents reorganize into polymeric species whose structure is incompatible with the final product. Instead of direct nucleation of clusters into the final product lattice, a highly disordered intermediate precipitate forms with a local bonding environment similar to the product yet lacking the correct topology. During maturation, bond reforming occurs by nucleation and growth of distinct domains within the amorphous intermediary. The present study moves beyond kinetic modeling by providing detailed real-time structural insight, and it is demonstrated that YSZ nanoparticle formation and growth is a more complex chemical process than accounted for in conventional models. This level of mechanistic understanding of the nanoparticle formation is the first step towards more rational control over nanoparticle synthesis through control of both solution precursors and reaction intermediaries. PMID:25075335

  7. Experimental observation of plasma formation and current transfer in fine wire expansion experiments.

    SciTech Connect

    Deeney, Christopher E.; Duselis, Peter U. (Cornell University, Ithaca, NY); Kusse, Bruce; Sinars, Daniel Brian

    2003-05-01

    When several kA pulses are passed through single, fine 25 {micro}m diameter wires, the wire material heats, melts, vaporizes and expands. Initially the voltage across--and current through--a wire increases until an abrupt voltage collapse occurs. After this collapse the voltage remains at a relative small value while the current continues to increase. In order to understand how this early time behavior may affect the subsequent implosion, small-scale experiments at Cornell University's Laboratory of Plasma Studies concentrated on diagnosing expanding single wire dynamics. X-ray backlighting, interferometry and Schlieren imaging as well as current and voltage measurements have been employed. The voltage collapse has been attributed to the formation of plasma around the wire and a transfer of current to this highly conducting coronal plasma. Interferometry has confirmed the plasma formation, but the current transfer has only been postulated. Subsequent experiments on the Z-Facility at Sandia National Laboratories have produced impressive x-ray yields etc.

  8. Hopping Domain Wall Induced by Paired Adatoms on an Atomic Wire: Si(111)-(5×2)-Au

    NASA Astrophysics Data System (ADS)

    Kang, Pil-Gyu; Jeong, Hojin; Yeom, Han Woong

    2008-04-01

    We observed an inhomogeneous fluctuation along one-dimensional atomic wires self-assembled on a Si(111) surface using scanning tunneling microscopy. The fluctuation exhibits dynamic behavior at room temperature and is observed only in a specific geometric condition; the spacing between two neighboring adatom defects is discommensurate with the wire lattice. Upon cooling, the dynamic fluctuation freezes to show the existence of an atomic-scale dislocation or domain wall induced by such “unfavorably” paired adatoms. The microscopic characteristics of the dynamic fluctuation are explained in terms of a hopping solitonic domain wall, and a local potential for this motion imposed by the adatoms is quantified.

  9. Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires

    PubMed Central

    Milani, Alberto; Tommasini, Matteo; Russo, Valeria; Li Bassi, Andrea; Lucotti, Andrea; Cataldo, Franco

    2015-01-01

    Summary Graphene, nanotubes and other carbon nanostructures have shown potential as candidates for advanced technological applications due to the different coordination of carbon atoms and to the possibility of π-conjugation. In this context, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level. Carbon-atom wires (CAWs) can be arranged in two possible structures: a sequence of double bonds (cumulenes), resulting in a 1D metal, or an alternating sequence of single–triple bonds (polyynes), expected to show semiconducting properties. The electronic and optical properties of CAWs can be finely tuned by controlling the wire length (i.e., the number of carbon atoms) and the type of termination (e.g., atom, molecular group or nanostructure). Although linear, sp-hybridized carbon systems are still considered elusive and unstable materials, a number of nanostructures consisting of sp-carbon wires have been produced and characterized to date. In this short review, we present the main CAW synthesis techniques and stabilization strategies and we discuss the current status of the understanding of their structural, electronic and vibrational properties with particular attention to how these properties are related to one another. We focus on the use of vibrational spectroscopy to provide information on the structural and electronic properties of the system (e.g., determination of wire length). Moreover, by employing Raman spectroscopy and surface enhanced Raman scattering in combination with the support of first principles calculations, we show that a detailed understanding of the charge transfer between CAWs and metal nanoparticles may open the possibility to tune the electronic structure from alternating to equalized bonds. PMID:25821689

  10. Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires.

    PubMed

    Milani, Alberto; Tommasini, Matteo; Russo, Valeria; Li Bassi, Andrea; Lucotti, Andrea; Cataldo, Franco; Casari, Carlo S

    2015-01-01

    Graphene, nanotubes and other carbon nanostructures have shown potential as candidates for advanced technological applications due to the different coordination of carbon atoms and to the possibility of π-conjugation. In this context, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level. Carbon-atom wires (CAWs) can be arranged in two possible structures: a sequence of double bonds (cumulenes), resulting in a 1D metal, or an alternating sequence of single-triple bonds (polyynes), expected to show semiconducting properties. The electronic and optical properties of CAWs can be finely tuned by controlling the wire length (i.e., the number of carbon atoms) and the type of termination (e.g., atom, molecular group or nanostructure). Although linear, sp-hybridized carbon systems are still considered elusive and unstable materials, a number of nanostructures consisting of sp-carbon wires have been produced and characterized to date. In this short review, we present the main CAW synthesis techniques and stabilization strategies and we discuss the current status of the understanding of their structural, electronic and vibrational properties with particular attention to how these properties are related to one another. We focus on the use of vibrational spectroscopy to provide information on the structural and electronic properties of the system (e.g., determination of wire length). Moreover, by employing Raman spectroscopy and surface enhanced Raman scattering in combination with the support of first principles calculations, we show that a detailed understanding of the charge transfer between CAWs and metal nanoparticles may open the possibility to tune the electronic structure from alternating to equalized bonds. PMID:25821689

  11. Lattice-Directed Formation of Covalent and Organometallic Molecular Wires by Terminal Alkynes on Ag Surfaces.

    PubMed

    Liu, Jing; Chen, Qiwei; Xiao, Lianghong; Shang, Jian; Zhou, Xiong; Zhang, Yajie; Wang, Yongfeng; Shao, Xiang; Li, Jianlong; Chen, Wei; Xu, Guo Qin; Tang, Hao; Zhao, Dahui; Wu, Kai

    2015-06-23

    Surface reactions of 2,5-diethynyl-1,4-bis(phenylethynyl)benzene on Ag(111), Ag(110), and Ag(100) were systematically explored and scrutinized by scanning tunneling microscopy, molecular mechanics simulations, and density functional theory calculations. On Ag(111), Glaser coupling reaction became dominant, yielding one-dimensional molecular wires formed by covalent bonds. On Ag(110) and Ag(100), however, the terminal alkynes reacted with surface metal atoms, leading to one-dimensional organometallic nanostructures. Detailed experimental and theoretical analyses revealed that such a lattice dependence of the terminal alkyne reaction at surfaces originated from the matching degree between the periodicities of the produced molecular wires and the substrate lattice structures. PMID:25990647

  12. Effects of gapless bosonic fluctuations on Majorana fermions in an atomic wire coupled to a molecular reservoir

    NASA Astrophysics Data System (ADS)

    Hu, Ying; Baranov, Mikhail A.

    2015-11-01

    We discuss the effects of quantum and thermal fluctuations on the Majorana edge states in a topological atomic wire coupled to a superfluid molecular gas with gapless excitations. We find that the coupling between the Majorana edge states remains exponentially decaying with the length of the wire, even at finite temperatures smaller than the energy gap for bulk excitations in the wire. This exponential dependence is controlled solely by the localization length of the Majorana states. The fluctuations, on the other hand, provide the dominant contribution to the preexponential factor, which increases with temperature and the length of the wire. More important is that thermal fluctuations give rise to a decay of an initial correlation between Majorana edge states to its stationary value after some thermalization time. This stationary value is sensitive to the temperature and to the length of the wire and, although vanishing in the thermodynamic limit, can still be feasible in a mesoscopic system at sufficiently low temperatures. The thermalization time, on the other hand, is found to be much larger than the typical time scales in the wire and is sufficient for quantum operations with Majorana fermions before the temperature-induced decoherence sets in.

  13. Plasma formation and dynamics in conical wire arrays in the Llampudken pulsed power generator

    SciTech Connect

    Muñoz, C. Gonzalo E-mail: fveloso@fis.puc.cl; Valenzuela, Vicente E-mail: fveloso@fis.puc.cl; Veloso, Felipe E-mail: fveloso@fis.puc.cl; Favre, Mario E-mail: fveloso@fis.puc.cl; Wyndham, Edmund E-mail: fveloso@fis.puc.cl

    2014-12-15

    Plasma formation and dynamics from conical wire array is experimentally studied. Ablation from the wires is observed, forming plasma accumulation at the array axis and subsequently a jet outflow been expelled toward the top of the array. The arrays are composed by 16 equally spaced 25μ diameter tungsten wires. Their dimensions are 20mm height, with base diameters of 8mm and 16mm top diameter. The array loads are design to be overmassed, hence no complete ablation of the wires is observed during the current rise. The experiments have been carried out in the Llampudken. pulsed power generator (∼350kA in ∼350ns). Plasma dynamics is studied in both side-on and end-on directions. Laser probing (shadowgraphy) is achieved using a frequency doubled Nd:YAG laser (532nm, 12ps FWHM) captured by CCD cameras. Pinhole XUV imaging is captured using gated microchannel plate cameras with time resolution ∼5ns. Results on the jet velocity and the degree of collimation indicating the plausibility on the use of these jets as comparable to the study astrophysically produced jets are presented and discussed.

  14. A highly sensitive method for the determination of mercury using vapor generation gold wire microextraction and electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Hashemi, Payman; Rahimi, Akram

    2007-04-01

    The study introduces a new simple and highly sensitive method for headspace solid phase microextraction (HS-SPME) coupled with electrothermal atomic absorption spectrometric determination of mercury. In the proposed method, a gold wire, mounted in the headspace of a sample solution in a sealed bottle, is used for collection of mercury vapor generated by addition of sodium tetrahydroborate. The gold wire is then simply inserted in the sample introduction hole of a graphite furnace of an electrothermal atomic absorption spectrometry instrument. By applying an atomization temperature of 600 °C, mercury is rapidly desorbed from the wire and determined with high sensitivity. Factorial design and response surface analysis methods were used for optimization of the effect of five different variables in order to maximize the mercury signal. By using a 0.75 mm diameter gold wire, a sample volume of about 8 ml and an extraction time of 11 min, the sensitivity of mercury determination was enhanced up to 10 4 times in comparison to its ordinary ETAAS determination with direct injection of 10 μl sample solutions. A detection limit of 0.006 ng ml - 1 and a precision better than 4.6% (relative standard deviation) were obtained. The method was successfully applied to the determination of mercury in industrial wastewaters and tuna fish samples.

  15. Thermoelectric voltage measurements of atomic and molecular wires using microheater-embedded mechanically-controllable break junctions

    NASA Astrophysics Data System (ADS)

    Morikawa, Takanori; Arima, Akihide; Tsutsui, Makusu; Taniguchi, Masateru

    2014-06-01

    We developed a method for simultaneous measurements of conductance and thermopower of atomic and molecular junctions by using a microheater-embedded mechanically-controllable break junction. We find linear increase in the thermoelectric voltage of Au atomic junctions with the voltage added to the heater. We also detect thermopower oscillations at several conductance quanta reflecting the quantum confinement effects in the atomic wire. Under high heater voltage conditions, on the other hand, we observed a peculiar behaviour in the conductance dependent thermopower, which was ascribed to a disordered contact structure under elevated temperatures.

  16. Radially arrayed nanopillar formation on metallic stent wire surface via radio-frequency plasma.

    PubMed

    Loya, Mariana C; Park, Eunsung; Chen, Li Han; Brammer, Karla S; Jin, Sungho

    2010-04-01

    MP35N (Co-Ni-Cr-Mo alloy) is an important stent implant material for which many aspects, that include nanostructured surfaces, are yet to be understood. The present study provides the first creation of radially emanating metallic nanopillar structures on the surface of MP35N stent alloy wires; a novel textured surface structuring derived via controlled RF processing technique. The goal of this study was to characterize the newly found structures, identify evolution stages of nanopillar formations, as well as optimize RF process parameters for controlled surface texturing technique for stent wire materials. The exposure of a stent alloy wire, 250 microm diameter Co-Ni-Cr-Mo alloy (MP35N), to parameter-controlled RF environment resulted in dense surface nanostructures consisting of high-aspect-ratio dendritic nanopillars/nanowires. Extensive surface characterization and local compositional analyses by Transmission Electron Microscopy (TEM), Energy Dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) show increased values of Mo contents on the outer edges of protruding nanopillars, indicating a possibility of the higher Mo content phase contributing to the differential plasma sputter etching on the MP35N surface and resultant nanowire formation. A comparative investigation on single phase alloy versus multi-phase alloy seems to point to the importance of phase segregation for successful nanowire formation by RF plasma treatment. In addition to MP35N, some specific single phased materials, such as Fe-Ni and Fe-Cr alloys or Pt metal wire, were exposed in same RF plasma conditions and results did not form the complex structures found on MP35N samples. For the purpose of this study, metallic stent wires that have nanostructured surfaces can be considered a "polymer-less" approach to surface modification, The creation and characterization of radially arrayed nanostructured surfaces has been demonstrated on MP35N stent alloy wires using this RF plasma

  17. Effect of Base Sequence on G-Wire Formation in Solution

    PubMed Central

    Spindler, Lea; Rigler, Martin; Drevenšek-Olenik, Irena; Ma'ani Hessari, Nason; Webba da Silva, Mateus

    2010-01-01

    The formation and dimensions of G-wires by different short G-rich DNA sequences in solution were investigated by dynamic light scattering (DLS) and polyacrilamide gel electrophoresis (PAGE). To explore the basic principles of wire formation, we studied the effects of base sequence, method of preparation, temperature, and oligonucleotide concentration. Both DLS and PAGE show that thermal annealing induces much less macromolecular self-assembly than dialysis. The degree of assembly and consequently length of G-wires (5-6 nm) are well resolved by both methods for DNA sequences with intermediate length, while some discrepancies appear for the shortest and longest sequences. As expected, the longest DNA sequence gives the longest macromolecular aggregates with a length of about 11 nm as estimated by DLS. The quadruplex topologies show no concentration dependence in the investigated DNA concentration range (0.1 mM–0.4 mM) and no structural change upon heating. PMID:20725621

  18. InAs/InP single quantum wire formation and emission at 1.5 {mu}m

    SciTech Connect

    Alen, B.; Fuster, D.; Gonzalez, Y.; Gonzalez, L.; Martinez-Pastor, J.

    2006-12-04

    Isolated InAs/InP self-assembled quantum wires have been grown using in situ accumulated stress measurements to adjust the optimal InAs thickness. Atomic force microscopy imaging shows highly asymmetric nanostructures with average length exceeding more than ten times their width. High resolution optical investigation of as-grown samples reveals strong photoluminescence from individual quantum wires at 1.5 {mu}m. Additional sharp features are related to monolayer fluctuations of the two-dimensional InAs layer present during the early stages of the quantum wire self-assembling process.

  19. Exploring the Formation and Evolution of Plasma from Exploding Single Wires

    NASA Astrophysics Data System (ADS)

    Duselis, P. U.; McCrorey, D. L.; Hu, Min; Kusse, B. R.

    2001-10-01

    At Cornell’s Laboratory of Plasma Studies, single wires of Ag, Cu, Au, Al, and W 1 to 3 cm in length and 10 to 25 microns in diameter were driven by a 100ns current pulse with a current rise time of 20 A/ns. Previously it has been found that the wires generally experienced a 50-85 ns resistive heating phase that was terminated by a rapid collapse of voltage [1]. We attributed this voltage collapse to the formation of a coronal plasma around the wire and used a framing camera, streak camera, laser interferometry, and a vacuum diode to examine the temporal and spatial dynamics of the plasma expansion. Results from the different diagnostics will be compared. Calculations are made to see if sufficient plasma is present to account for voltage collapse. [1] D. B. Sinars, Min Hu, K. M. Chandler, T. A. Shelkovenko, S. A. Pikuz, J. B. Greenly, D. A. Hammer, and B. R. Kusse, Physics of Plasmas 8, pp216-230.

  20. Regularities in positronium formation for atoms and molecules

    NASA Astrophysics Data System (ADS)

    Machacek, J. R.; Blanco, F.; Garcia, G.; Buckman, S. J.; Sullivan, J. P.

    2016-03-01

    In an effort to aid the modelling of positron and positronium (Ps) transport in biological media we have compiled recent experimental results for the total Ps formation in positron scattering from atoms and molecules. A simple function was found to adequately describe the total Ps formation cross section for both atoms and molecules. The parameters of this function describe the magnitude and shape of the Ps formation cross section and are compared to physical characteristics of the target atoms and molecules. A general trend in the magnitude of the total Ps formation cross section is observed as a function of the target atom/molecule dipole polarisability. The functional form may enable quick estimation of the Ps cross section for molecules for which experimental measurements or theoretical estimates do not exist.

  1. Mid-Atomic-Number Cylindrical Wire Array Precursor Plasma Studies on Zebra

    SciTech Connect

    Stafford, A; Safronova, A. S.; Kantsyrev, V. L.; Coverdale, Christine Anne; Weller, M. E.; Shrestha, I.; Shlyaptseva, V. V.; Chuvatin, A. S.

    2014-12-30

    The precursor plasmas from low wire number cylindrical wire arrays (CWAs) were previously shown to radiate at temperatures >300 eV for Ni-60 (94% Cu and 6% Ni) wires in experiments on the 1-MA Zebra generator. Continued research into precursor plasmas has studied additional midatomic-number materials including Cu and Alumel (95% Ni, 2% Al, 2% Mn, and 1% Si) to determine if the >300 eV temperatures are common for midatomic-number materials. Additionally, current scaling effects were observed by performing CWA precursor experiments at an increased current of 1.5 MA using a load current multiplier. Our results show an increase in a linear radiation yield of ~50% (16 versus 10 kJ/cm) for the experiments at increased current. However, plasma conditions inferred through the modeling of X-ray time-gated spectra are very similar for the precursor plasma in both current conditions.

  2. Mid-Atomic-Number Cylindrical Wire Array Precursor Plasma Studies on Zebra

    DOE PAGESBeta

    Stafford, A; Safronova, A. S.; Kantsyrev, V. L.; Coverdale, Christine Anne; Weller, M. E.; Shrestha, I.; Shlyaptseva, V. V.; Chuvatin, A. S.

    2014-12-30

    The precursor plasmas from low wire number cylindrical wire arrays (CWAs) were previously shown to radiate at temperatures >300 eV for Ni-60 (94% Cu and 6% Ni) wires in experiments on the 1-MA Zebra generator. Continued research into precursor plasmas has studied additional midatomic-number materials including Cu and Alumel (95% Ni, 2% Al, 2% Mn, and 1% Si) to determine if the >300 eV temperatures are common for midatomic-number materials. Additionally, current scaling effects were observed by performing CWA precursor experiments at an increased current of 1.5 MA using a load current multiplier. Our results show an increase in amore » linear radiation yield of ~50% (16 versus 10 kJ/cm) for the experiments at increased current. However, plasma conditions inferred through the modeling of X-ray time-gated spectra are very similar for the precursor plasma in both current conditions.« less

  3. Glass formation and local topological instability of atomic structure

    SciTech Connect

    Egami, T.

    1997-12-31

    A direct connection between the local topology of the atomic structure of liquids and glasses and thermodynamic quantities through the atomic level stresses is suggested for metallic alloys. In particular the role of local topological instability in the phase transformation involving liquid and glass will be discussed. It is pointed out that a single local geometrical criterion can explain various phase transformations, such as melting, glass transition, and glass formation by solid state reaction and liquid quenching.

  4. Determination of heavy metals in bee honey with connected and not connected metal wires using inductively coupled plasma atomic emission spectrometry (ICP-AES).

    PubMed

    Özcan, Mehmet Musa; Al Juhaimi, Fahad Y

    2012-04-01

    Two honey samples are taken from two parts of the same honeycomb: one that contacts to the surface of the wire and the other taken from the surface that does not contact the wires. Heavy metal contents of these two samples were determined by inductively coupled plasma atomic emission spectrometry). The Mo, Cd, Cr, Fe, Mn, Ni and Zn contents of the honey in contact with wire is higher when compared to the other. Especially, Fe and Zn contents of honey in contact with wire is much higher than the non-contact one. These values are, respectively, 190.21 and 112.76 ppm. Besides, Ni content of honey in contact with wire is approximately 50% higher. PMID:21573852

  5. Atomic scale investigation of redistribution of alloying elements in pearlitic steel wires upon cold-drawing and annealing.

    PubMed

    Li, Y J; Choi, P; Goto, S; Borchers, C; Raabe, D; Kirchheim, R

    2013-09-01

    A local electrode atom probe has been employed to analyze the redistribution of alloying elements including Si, Mn, and Cr in pearlitic steel wires upon cold-drawing and subsequent annealing. It has been found that the three elements undergo mechanical mixing upon cold-drawing at large strains, where Mn and Cr exhibit a nearly homogeneous distribution throughout both ferrite and cementite, whereas Si only dissolves slightly in cementite. Annealing at elevated temperatures leads to a reversion of the mechanical alloying. Si atoms mainly segregate at well-defined ferrite (sub)grain boundaries formed during annealing. Cr and Mn are strongly concentrated in cementite adjacent to the ferrite/cementite interface due to their lower diffusivities in cementite than in ferrite. PMID:23237772

  6. Studies on Beam Formation in an Atomic Beam Source

    SciTech Connect

    Nass, A.; Steffens, E.; Stancari, M.

    2009-08-04

    Atomic beam sources (ABS) are widely used workhorses producing polarized atomic beams for polarized gas targets and polarized ion sources. Although they have been used for decades the understanding of the beam formation processes is crude. Models were used more or less successfully to describe the measured intensity and beam parameters. ABS's are also foreseen for future experiments, such as PAX [1]. An increase of intensity at a high polarization would be beneficial. A direct simulation Monte-Carlo method (DSMC)[2] was used to describe the beam formation of a hydrogen or deuterium beam in an ABS. For the first time a simulation of a supersonic gas expansion on a molecular level for this application was performed. Beam profile and Time-of-Flight measurements confirmed the simulation results. Furthermore a new method of beam formation was tested, the Carrier Jet method [3], based on an expanded beam surrounded by an over-expanded carrier jet.

  7. X-ray emission from a high-atomic-number z-pinch plasma created from compact wire arrays

    SciTech Connect

    Sanford, T.W.L.; Nash, T.J.; Marder, B.M.

    1996-03-01

    Thermal and nonthermal x-ray emission from the implosion of compact tungsten wire arrays, driven by 5 MA from the Saturn accelerator, are measured and compared with LLNL Radiation-Hydro-Code (RHC) and SNL Hydro-Code (HC) numerical models. Multiple implosions, due to sequential compressions and expansions of the plasma, are inferred from the measured multiple x-radiation bursts. Timing of the multiple implosions and the thermal x-ray spectra measured between 1 and 10 keV are consistent with the RHC simulations. The magnitude of the nonthermal x-ray emission measured from 10 to 100 keV ranges from 0.02 to 0.08% of the total energy radiated and is correlated with bright-spot emission along the z-axis, as observed in earlier Gamble-11 single exploding-wire experiments. The similarities of the measured nonthermal spectrum and bright-spot emission with those measured at 0.8 MA on Gamble-II suggest a common production mechanism for this process. A model of electron acceleration across magnetic fields in highly-collisional, high-atomic-number plasmas is developed, which shows the existence of a critical electric field, E{sub c}, below which strong nonthermal electron creation (and the associated nonthermal x rays) do not occur. HC simulations show that significant nonthermal electrons are not expected in this experiment (as observed) because the calculated electric fields are at least one to two orders-of-magnitude below E{sub c}. These negative nonthermal results are confirmed by RHC simulations using a nonthermal model based on a Fokker-Plank analysis. Lastly, the lower production efficiency and the larger, more irregular pinch spots formed in this experiment relative to those measured on Gamble II suggest that implosion geometries are not as efficient as single exploding-wire geometries for warm x-ray production.

  8. Molecular hydrogen formation by excited atom radiative association

    NASA Technical Reports Server (NTRS)

    Latter, William B.; Black, John H.

    1991-01-01

    The results from a semiclassical calculation of the thermal rate coefficient for the radiative association process H(n = 2) + H(n = 1) - H2 + hv are presented (n is the principal quantum number of the separated hydrogen atoms). The relative importance of this reaction in various environments is briefly discussed. Models of the early universe around the epoch of recombination and protostellar winds have been calculated which include the excited atom process. Not surprisingly, it is shown that the excited atom process will not be important in the general interstellar medium, except possibly in environments where the amount of Ly-alpha photon trapping is large. Examples may be the material surrounding quasars, active galactic nuclei, and bright H II regions. The most likely application of this process might be within rapidly evolving systems where a large transient n = 2 population of neutral hydrogen could result in a burst of molecular hydrogen formation.

  9. Fabrication of Microstripline Wiring for Large Format Transition Edge Sensor Arrays

    NASA Technical Reports Server (NTRS)

    Chervenak, James A.; Adams, J. M.; Bailey, C. N.; Bandler, S.; Brekosky, R. P.; Eckart, M. E.; Erwin, A. E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Sadlier, J. E.; Smith, S. J.

    2012-01-01

    We have developed a process to integrate microstripline wiring with transition edge sensors (TES). The process includes additional layers for metal-etch stop and dielectric adhesion to enable recovery of parameters achieved in non-microstrip pixel designs. We report on device parameters in close-packed TES arrays achieved with the microstrip process including R(sub n), G, and T(sub c) uniformity. Further, we investigate limits of this method of producing high-density, microstrip wiring including critical current to determine the ultimate scalability of TES arrays with two layers of wiring.

  10. Formation spectra of pionic atoms in the Green's function method

    NASA Astrophysics Data System (ADS)

    Ikeno, Natsumi; Yamagata-Sekihara, Junko; Nagahiro, Hideko; Hirenzaki, Satoru

    2015-03-01

    We study the formation spectra of deeply bound pionic atoms in the (d, ^3He) reactions using the Green's function method, stimulated by recent developments in experimental techniques. The Green's function method is considered to be a better theoretical formalism than the effective number approach to evaluate the formation rate of unstable systems. We compare the calculated results by the Green's function method with those by the effective number approach in various cases. We find that the differences between the results obtained by both methods are reasonably small and we can reaffirm that the effective number approach is a good theoretical method for the analyses of the previous experimental data with typical binding-energy errors of Δ B.E. ≳ 20keV for the deeply bound pionic atoms. On the other hand, we think that theoretical results using the Green's function method will be necessary in the near future to deduce precise information on the pion properties in nuclei from analyses of the pionic atom data with better accuracy than before.

  11. Autoionization following nanoplasma formation in atomic and molecular clusters

    NASA Astrophysics Data System (ADS)

    Schütte, Bernd; Lahl, Jan; Oelze, Tim; Krikunova, Maria; Vrakking, Marc J. J.; Rouzée, Arnaud

    2016-05-01

    Nanoplasmas resulting from the ionization of nano-scale particles by intense laser pulses are typically described by quasiclassical models, where electron emission is understood to take place via thermal processes. Recently, we discovered that, following the interaction of intense near-infrared (NIR) laser pulses with molecular oxygen clusters, electron emission from nanoplasmas can also occur from atomic bound states via autoionization [Schütte et al., Phys. Rev. Lett. 114, 123002 (2015)]. Here we extend these studies and demonstrate that the formation and decay of doubly-excited atoms and ions is a very common phenomenon in nanoplasmas. We report on the observation of autoionization involving spin-orbit excited states in molecular oxygen and carbon dioxide clusters as well as in atomic krypton and xenon clusters ionized by intense NIR pulses, for which we find clear bound-state signatures in the electron kinetic energy spectra. By applying terahertz (THz) streaking, we show that the observed autoionization processes take place on a picosecond to nanosecond timescale after the interaction of the NIR laser pulse with the clusters. Contribution to the Topical Issue "Atomic Cluster Collisions (7th International Symposium)", edited by Gerardo Delgado Barrio, Andrey Solov'Yov, Pablo Villarreal, Rita Prosmiti.

  12. Atom formation processes in the presence of ammonium thiocyanate in a thin-wall tungsten tube atomizer for atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Ohta, Kiyohisa; Mizuno, Takayuki

    Processes of atom formation of Ag, Al, As, Bi, Cd, Cr, Fe, Mn, Ni, Pb, Sb, Se, Sn, Sr and Te in the presence of ammonium thiocyanate in a thin-wall tungsten tube atomizer are described. It was found from a thermodynamic approach that AI, Bi, Cd, Cr, Fe, Ni and Te formed complexes with ammonium thiocyanate and are atomized through the sulfides in argon-hydrogen atmosphere. Atom formation processess for the other elements are different.

  13. Effect of Punica granatum L. Flower Water Extract on Five Common Oral Bacteria and Bacterial Biofilm Formation on Orthodontic Wire

    PubMed Central

    VAHID DASTJERDI, Elahe; ABDOLAZIMI, Zahra; GHAZANFARIAN, Marzieh; AMDJADI, Parisa; KAMALINEJAD, Mohammad; MAHBOUBI, Arash

    2014-01-01

    Background: Use of herbal extracts and essences as natural antibacterial compounds has become increasingly popular for the control of oral infectious diseases. Therefore, finding natural antimicrobial products with the lowest side effects seems necessary. The present study sought to assess the effect of Punica granatum L. water extract on five oral bacteria and bacterial biofilm formation on orthodontic wire. Methods: Antibacterial property of P. granatum L. water extract was primarily evaluated in brain heart infusion agar medium using well-plate method. The minimum inhibitory concentration and minimum bactericidal concentration were determined by macro-dilution method. The inhibitory effect on orthodontic wire bacterial biofilm formation was evaluated using viable cell count in biofilm medium. At the final phase, samples were fixed and analyzed by Scanning Electron Microscopy. Results: The growth inhibition zone diameter was proportional to the extract concentration. The water extract demonstrated the maximum antibacterial effect on Streptococcus sanguinis ATCC 10556 with a minimum inhibitory concentration of 6.25 mg/ml and maximum bactericidal effect on S. sanguinis ATCC 10556 and S. sobrinus ATCC 27607 with minimum bactericidal concentration of 25 mg/ml. The water extract decreased bacterial biofilm formation by S. sanguinis, S. sobrinus, S. salivarius, S. mutans ATCC 35608 and E. faecalis CIP 55142 by 93.7–100%, 40.6–99.9%, 85.2–86.5%, 66.4–84.4% and 35.5–56.3% respectively. Conclusion: Punica granatum L. water extract had significant antibacterial properties against 5 oral bacteria and prevented orthodontic wire bacterial biofilm formation. However, further investigations are required to generalize these results to the clinical setting. PMID:26171362

  14. Origin of the metal-insulator transition of indium atom wires on Si(111)

    NASA Astrophysics Data System (ADS)

    Kim, Sun-Woo; Cho, Jun-Hyung

    2016-06-01

    As a prototypical one-dimensional electron system, self-assembled indium (In) nanowires on the Si(111) surface have been believed to drive a metal-insulator transition by a charge-density-wave (CDW) formation due to Fermi surface nesting. Here, our first-principles calculations demonstrate that the structural phase transition from the high-temperature 4 ×1 phase to the low-temperature 8 ×2 phase occurs through an exothermic reaction with the consecutive bond-breaking and bond-making processes, giving rise to an energy barrier between the two phases as well as a gap opening. This atomistic picture for the phase transition not only identifies its first-order nature but also solves a long-standing puzzle of the origin of the metal-insulator transition in terms of the ×2 periodic lattice reconstruction of In hexagons via bond breakage and new bond formation, not by the Peierls-instability-driven CDW formation.

  15. Rydberg-atom formation in strongly correlated ultracold plasmas

    SciTech Connect

    Bannasch, G.; Pohl, T.

    2011-11-15

    In plasmas at very low temperatures, the formation of neutral atoms is dominated by collisional three-body recombination, owing to the strong {approx}T{sup -9/2} scaling of the corresponding recombination rate with the electron temperature T. While this law is well established at high temperatures, the unphysical divergence as T{yields}0 clearly suggests a breakdown in the low-temperature regime. Here, we present a combined molecular dynamics Monte Carlo study of electron-ion recombination over a wide range of temperatures and densities. Our results reproduce the known behavior of the recombination rate at high temperatures, but reveal significant deviations with decreasing temperature. We discuss the fate of the kinetic bottleneck and resolve the divergence problem as the plasma enters the ultracold, strongly coupled domain.

  16. Improvements in the Formation of Boron-Doped Diamond Coatings on Platinum Wires Using the Novel Nucleation Process (NNP)

    PubMed Central

    Fhaner, Mathew; Zhao, Hong; Bian, Xiaochun; Galligan, James J.; Swain, Greg M.

    2010-01-01

    In order to increase the initial nucleation density for the growth of boron-doped diamond on platinum wires, we employed the novel nucleation process (NNP) originally developed by Rotter et al. and discussed by others [1–3]. This pretreatment method involves (i) the initial formation of a thin carbon layer over the substrate followed by (ii) ultrasonic seeding of this “soft” carbon layer with nanoscale particles of diamond. This two-step pretreatment is followed by the deposition of boron-doped diamond by microwave plasma-assisted CVD. Both the diamond seed particles and sites on the carbon layer itself function as the initial nucleation zones for diamond growth from an H2-rich source gas mixture. We report herein on the characterization of the pre-growth carbon layer formed on Pt as well as boron-doped films grown for 2, 4 and 6 h post NNP pretreatment. Results from scanning electron microscopy, Raman spectroscopy and electrochemical studies are reported. The NNP method increases the initial nucleation density on Pt and leads to the formation of a continuous diamond film in a shorter deposition time than is typical for wires pretreated by conventional ultrasonic seeding. The results indicate that the pregrowth layer itself consists of nanoscopic domains of diamond and functions well to enhance the initial nucleation of diamond without any diamond powder seeding. PMID:21617759

  17. Positron impact excitations of hydrogen atom embedded in weakly coupled plasmas: Formation of Rydberg atoms

    SciTech Connect

    Rej, Pramit; Ghoshal, Arijit

    2014-09-15

    Formation of Rydberg atoms due to 1s→nlm excitations of hydrogen, for arbitrary n, l, m, by positron impact in weakly coupled plasma has been investigated using a distorted-wave theory in the momentum space. The interactions among the charged particles in the plasma have been represented by Debye-Huckel potentials. Making use of a simple variationally determined wave function for the hydrogen atom, it has been possible to obtain the distorted-wave scattering amplitude in a closed analytical form. A detailed study has been made on the effects of plasma screening on the differential and total cross sections in the energy range 20–300 eV of incident positron. For the unscreened case, our results agree nicely with some of the most accurate results available in the literature. To the best of our knowledge, such a study on the differential and total cross sections for 1s→nlm inelastic positron-hydrogen collisions for arbitrary n, l, m in weakly coupled plasmas is the first reported in the literature.

  18. Sintered wire annode

    DOEpatents

    Falce, Louis R.; Ives, R. Lawrence

    2007-12-25

    A plurality of high atomic number wires are sintered together to form a porous rod that is parted into porous disks which will be used as x-ray targets. A thermally conductive material is introduced into the pores of the rod, and when a stream of electrons impinges on the sintered wire target and generates x-rays, the heat generated by the impinging x-rays is removed by the thermally conductive material interspersed in the pores of the wires.

  19. Optical Pattern Formation in Cold Atoms: Explaining the Red-Blue Asymmetry

    NASA Astrophysics Data System (ADS)

    Schmittberger, Bonnie; Gauthier, Daniel

    2013-05-01

    The study of pattern formation in atomic systems has provided new insight into fundamental many-body physics and low-light-level nonlinear optics. Pattern formation in cold atoms in particular is of great interest in condensed matter physics and quantum information science because atoms undergo self-organization at ultralow input powers. We recently reported the first observation of pattern formation in cold atoms but found that our results were not accurately described by any existing theoretical model of pattern formation. Previous models describing pattern formation in cold atoms predict that pattern formation should occur using both red and blue-detuned pump beams, favoring a lower threshold for blue detunings. This disagrees with our recent work, in which we only observed pattern formation with red-detuned pump beams. Previous models also assume a two-level atom, which cannot account for the cooling processes that arise when beams counterpropagate through a cold atomic vapor. We describe a new model for pattern formation that accounts for Sisyphus cooling in multi-level atoms, which gives rise to a new nonlinearity via spatial organization of the atoms. This spatial organization causes a sharp red-blue detuning asymmetry, which agrees well with our experimental observations. We gratefully acknowledge the financial support of the NSF through Grant #PHY-1206040.

  20. Positron impact excitations of hydrogen atom embedded in dense quantum plasmas: Formation of Rydberg atoms

    SciTech Connect

    Rej, Pramit; Ghoshal, Arijit

    2014-11-15

    Formation of Rydberg atoms due to 1 s → nlm excitations of hydrogen by positron impact, for arbitrary n, l, m, in dense quantum plasma has been investigated using a distorted wave theory which includes screened dipole polarization potential. The interactions among the charged particles in the plasma have been represented by exponential cosine-screened Coulomb potentials. Making use of a simple variationally determined hydrogen wave function, it has been possible to obtain the distorted wave scattering amplitude in a closed analytical form. A detailed study has been made to explore the structure of differential and total cross sections in the energy range 20–300 eV of incident positron. For the unscreened case, our results agree nicely with some of the most accurate results available in the literature. To the best of our knowledge, such a study on the differential and total cross sections for 1 s → nlm inelastic positron-hydrogen collisions in dense quantum plasma is the first reported in the literature.

  1. Space Charge Formation and Electrical Breakdown at High Temperature Region in PVC for Electrical Wiring Assembly

    NASA Astrophysics Data System (ADS)

    Miura, Masakazu; Fukuma, Masumi; Kishida, Satoru

    The Polyvinyl chloride (PVC), the most popular insulating material, is used as an insulating material of various electric products. When using an electrical wiring assembly code over the power capacity, PVC could melt by the joule heating and cause an electrical breakdown. Therefore, it is necessary to clarify the electrical breakdown phenomena near the melting point (170°C) in PVC. In this paper, space charge distribution and conduction current have been measured in PVC sheets up to the electrical breakdown in the range from room temperature to 200°C under DC electric field. The breakdown strength decreases with temperature in PVC. Small hetero-space charges are accumulated near both of the electrodes at room temperature region. At high temperature region above 100°C, it is observed that positive charges are injected from anode and move toward the cathode; the electric field is emphasized near the cathode due to the packet-like positive charge in PVC. It shows a thermal breakdown process of the electric fields due to positive charge behavior and conduction current increase with temperature near the melting point in PVC.

  2. Wurtzite GaAs Quantum Wires: One-Dimensional Subband Formation.

    PubMed

    Vainorius, Neimantas; Lehmann, Sebastian; Gustafsson, Anders; Samuelson, Lars; Dick, Kimberly A; Pistol, Mats-Erik

    2016-04-13

    It is of contemporary interest to fabricate nanowires having quantum confinement and one-dimensional subband formation. This is due to a host of applications, for example, in optical devices, and in quantum optics. We have here fabricated and optically investigated narrow, down to 10 nm diameter, wurtzite GaAs nanowires which show strong quantum confinement and the formation of one-dimensional subbands. The fabrication was bottom up and in one step using the vapor-liquid-solid growth mechanism. Combining photoluminescence excitation spectroscopy with transmission electron microscopy on the same individual nanowires, we were able to extract the effective masses of the electrons in the two lowest conduction bands as well as the effective masses of the holes in the two highest valence bands. Our results, combined with earlier demonstrations of thin crystal phase nanodots in GaAs, set the stage for the fabrication of crystal phase quantum dots having full three-dimensional confinement. PMID:27004550

  3. Formation of positron-atom bound states in collisions between Rydberg Ps and neutral atoms

    NASA Astrophysics Data System (ADS)

    Swann, A. R.; Cassidy, D. B.; Deller, A.; Gribakin, G. F.

    2016-05-01

    Predicted 20 years ago, positron binding to neutral atoms has not yet been observed experimentally. A scheme is proposed to detect positron-atom bound states by colliding Rydberg positronium (Ps) with neutral atoms. Estimates of the charge-transfer reaction cross section are obtained using the first Born approximation for a selection of neutral atom targets and a wide range of incident Ps energies and principal quantum numbers. We also estimate the corresponding Ps ionization cross section. The accuracy of the calculations is tested by comparison with earlier predictions for charge transfer in Ps collisions with hydrogen and antihydrogen. We describe an existing Rydberg Ps beam suitable for producing positron-atom bound states and estimate signal rates based on the calculated cross sections and realistic experimental parameters. We conclude that the proposed methodology is capable of producing such states and of testing theoretical predictions of their binding energies.

  4. Formation Mechanism of SiO2-Type Inclusions in Si-Mn-Killed Steel Wires Containing Limited Aluminum Content

    NASA Astrophysics Data System (ADS)

    Wang, Kunpeng; Jiang, Min; Wang, Xinhua; Wang, Ying; Zhao, Haoqian; Cao, Zhanmin

    2015-10-01

    The origin, formation mechanism, and evolution of SiO2-type inclusions in Si-Mn-killed steel wires were studied by pilot trials with systematical samplings at the refining ladle, casting tundish, as-cast bloom, reheated bloom, and hot-rolled rods. It was found that the inclusions in tundish were well controlled in the low melting point region. By contrast, MnO-SiO2-Al2O3 inclusions in the as-cast bloom were with compositions located in the primary region of SiO2, and most CaO-SiO2-Al2O3-MnO inclusions lied in primary phase region of anorthite. Therefore, precipitation of SiO2 particles in MnO-SiO2-Al2O3 inclusions can be easier than in CaO-SiO2-Al2O3-MnO inclusions to form dual-phase inclusions in the as-cast bloom. Thermodynamic calculation by the software FactSage 6.4 (CRCT-ThermFact Inc., Montréal, Canada) showed that mass transfer between liquid steel and inclusions resulted in the rise of SiO2 content in inclusions from tundish to as-cast bloom and accelerated the precipitation of pure SiO2 phase in the formed MnO-SiO2-Al2O3 inclusions. As a result, the inclusions characterized by dual-phase structure of pure SiO2 in MnO-SiO2-Al2O3 matrix were observed in both as-cast and reheated blooms. Moreover, the ratio of such dual-phase SiO2-type inclusions witnessed an obvious increase from 0 to 25.4 pct before and after casting, whereas it changed little during the reheating and rolling. Therefore, it can be reasonably concluded that they were mainly formed during casting. Comparing the evolution of the inclusions composition and morphology in as-cast bloom and rolled products, a formation mechanism of the SiO2-type inclusions in wire rods was proposed, which included (1) precipitation of SiO2 in the formed MnO-SiO2-Al2O3 inclusion during casting and (2) solid-phase separation of the undeformed SiO2 precipitation from its softer MnO-SiO2-Al2O3 matrix during multipass rolling.

  5. Crossed-Wire Laser Microwelding of Pt-10 Pct Ir to 316 Low-Carbon Vacuum Melted Stainless Steel: Part I. Mechanism of Joint Formation

    NASA Astrophysics Data System (ADS)

    Zou, G. S.; Huang, Y. D.; Pequegnat, A.; Li, X. G.; Khan, M. I.; Zhou, Y.

    2012-04-01

    The excellent biocompatibility and corrosion properties of Pt alloys and 316 low-carbon vacuum melted (LVM) stainless steel (SS) make them attractive for biomedical applications. With the increasing complexity of medical devices and in order to lower costs, the challenge of joining dissimilar materials arises. In this study, laser microwelding (LMW) of crossed Pt-10 pct Ir to 316 LVM SS wires was performed and the weldability of these materials was determined. The joint geometry, joining mechanism, joint breaking force (JBF), and fracture modes were investigated using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and microtensile testing. It was shown that the mechanisms of joint formation transitioned from (1) brazing, (2) a combination of brazing and fusion welding, and (3) fusion welding with increasing pulsed laser energy. The joints demonstrated various tensile failure modes including (1) interfacial failure below a peak power of 0.24 kW, (2) partial interfacial failure that propagated into the Pt-Ir wire, (3) failure in the Pt-Ir wire, and (4) failure in the SS wire due to porosity and severe undercutting caused by overwelding. During this study, the optimal laser peak power range was identified to produce joints with good joint geometry and 90 pct of the tensile strength of the Pt-10 pct Ir wire.

  6. Basic Wiring.

    ERIC Educational Resources Information Center

    Kaltwasser, Stan; And Others

    This module is the first in a series of three wiring publications; it serves as the foundation for students enrolled in a wiring program. It is a prerequisite to either "Residential Wiring" or "Commercial and Industrial Wiring." The module contains 16 instructional units that cover the following topics: occupational introduction; general safety;…

  7. Wiring a plant: genetic networks for phloem formation in Arabidopsis thaliana roots.

    PubMed

    Rodriguez-Villalon, Antia

    2016-04-01

    45 I. 45 II. 46 III. 46 IV. 47 V. 48 VI. 48 49 References 49 SUMMARY: In plants, phloem conduits form a specialized vascular network mediating the exchange of nutrients and signaling molecules between distantly separated organs. To become effective transport elements, protophloem cells undergo a rather unique, differentiation program that involves nucleus degradation, organelle rearrangement and cell wall thickening. Yet, protophloem sieve elements remain alive because their essential metabolic functions are supported by their neighboring companion cells. In spite of the importance of the phloem, the molecular mechanisms orchestrating protophloem specification and differentiation remain still poorly understood. In this review, I provide a summary of recent discoveries regarding morphogenetic events that determine phloem formation, and also a discussion of the systemic effects on root architecture derived from impaired protophloem differentiation programs. PMID:26171671

  8. Kinetic analysis of MgB2 layer formation in advanced internal magnesium infiltration (AIMI) processed MgB2 wires

    PubMed Central

    Li, G. Z.; Sumption, M. D.; Collings, E. W.

    2015-01-01

    Significantly enhanced critical current density (Jc) for MgB2 superconducting wires can be obtained following the advanced internal Mg infiltration (AIMI) route. But unless suitable precautions are taken, the AIMI-processed MgB2 wires will exhibit incomplete MgB2 layer formation, i.e. reduced superconductor core size and hence suppressed current-carrying capability. Microstructural characterization of AIMI MgB2 wires before and after the heat treatment reveals that the reaction mechanism changes from a “Mg infiltration-reaction” at the beginning of the heat treatment to a “Mg diffusion-reaction” once a dense MgB2 layer is formed. A drastic drop in the Mg transport rate from infiltration to diffusion causes the termination of the MgB2 core growth. To quantify this process, a two-stage kinetic model is built to describe the MgB2 layer formation and growth. The derived kinetic model and the associated experimental observations indicate that fully reacted AIMI-processed MgB2 wires can be achieved following the optimization of B particle size, B powder packing density, MgB2 reaction activation energy and its response to the additions of dopants. PMID:26973431

  9. Infrared atomic hydrogen line formation in luminous stars

    NASA Technical Reports Server (NTRS)

    Krolik, J. H.; Smith, H. A.

    1981-01-01

    Infrared atomic hydrogen lines observed in luminous stars, generally attributed to compact circumstellar H II regions, can also be formed in the winds likely to emanate from these stars. Implications are discussed for the class of obscured infrared point sources showing these lines, and an illustrative model is derived for the BN object in Orion. Such stellar winds should also produce weak, but detectable, radio emission.

  10. Passage time statistics in the formation of ultracold dimers from fermionic atoms

    NASA Astrophysics Data System (ADS)

    Uys, Hermann

    2005-05-01

    We investigate the temporal fluctuations characteristic of the formation of molecular dimers from ultracold fermionic atoms via either photoassociation or a Feshbach resonance. The quantum fluctuations inherent to the initial atomic state result in large fluctuations in the passage time from atoms to molecules. A heuristic classical stochastic model yields an excellent agreement with the full quantum treatment in the initial stages of the dynamics. We also show that in contrast to the association of atoms into dimers, the reverse process of dissociation from a condensate of bosonic dimers exhibits little passage time fluctuations.

  11. Electronic structure of Ag-induced atomic wires on Si(5 5 7) investigated by STS and angle-resolved photoemission

    NASA Astrophysics Data System (ADS)

    Morikawa, Harumo; Kang, Pil Gyu; Yeom, Han Woong

    2008-12-01

    One-dimensional (1D) superstructures on the Si(5 5 7) surface induced by Ag adsorption have been investigated by scanning tunneling microscopy/spectroscopy (STM/STS) and angle-resolved photoemission. The deposition of ˜0.3 ML of Ag at 450-620 °C yields three different kinds of 1D structures along step edges. These structures form domains of different morphology, whose areal ratio depends on the growth temperature. They commonly share a characteristic atomic-scale wire structure with a ×2 periodicity. These structures are insulating with a band gap of about 0.5 eV as revealed by STS and confirmed consistently by angle-resolved photoemission, in clear contrast to the very recent inverse photoemission result (Phys. Rev. B 77 (2008) 125419).

  12. Structure and Formation of Kaonic Atoms and Kaonic Nuclei

    NASA Astrophysics Data System (ADS)

    Yamagata, Junko; Hirenzaki, Satoru; Nagahiro, Hideko; Jido, Daisuke

    We study theoretically the in-flight (K-, N) reactions for the formation of bar {K}NN systems using the microscopic chiral unitary s-wave bar {K}N amplitude to get deeper physical insights on the expected spectra, and to investigate the experimental feasibility of the reaction at J-PARC facility. We show the missing mass spectra of the (K-, N) reactions accompanied by the particle emissions due to bar {K} absorption in nucleus.

  13. Fluctuations in the formation time of ultracold dimers from fermionic atoms

    NASA Astrophysics Data System (ADS)

    Uys, H.; Miyakawa, T.; Meiser, D.; Meystre, P.

    2005-11-01

    We investigate the temporal fluctuations characteristic of the formation of molecular dimers from ultracold fermionic atoms via Raman photoassociation. The quantum fluctuations inherent to the initial atomic state result in large fluctuations in the passage time from atoms to molecules. Assuming degeneracy of kinetic energies of atoms in the strong coupling limit, we find that a heuristic classical stochastic model yields qualitative agreement with the full quantum treatment in the initial stages of the dynamics. We also show that in contrast to the association of atoms into dimers, the reverse process of dissociation from a condensate of bosonic dimers exhibits little passage time fluctuations. Finally, we explore effects due to the nondegeneracy of atomic kinetic energies.

  14. Local Control of Lung Derived Tumors by Diffusing Alpha-Emitting Atoms Released From Intratumoral Wires Loaded With Radium-224

    SciTech Connect

    Cooks, Tomer; Schmidt, Michael; Bittan, Hadas; Lazarov, Elinor; Arazi, Lior; Kelson, Itzhak; Keisari, Yona

    2009-07-01

    Purpose: Diffusing alpha-emitters radiation therapy (DART) is a new form of brachytherapy enabling the treatment of solid tumors with alpha radiation. The present study examines the antitumoral effects resulting from the release of alpha emitting radioisotopes into solid lung carcinoma (LL2, A427, and NCI-H520). Methods and Materials: An in vitro setup tested the dose-dependent killing of tumor cells exposed to alpha particles. In in vivo studies, radioactive wires (0.3 mm diameter, 5 mm long) with {sup 224}Ra activities in the range of 21-38 kBq were inserted into LL/2 tumors in C57BL/6 mice and into human-derived A427 or NCI-H520 tumors in athymic mice. The efficacy of the short-lived daughters of {sup 224}Ra to produce tumor growth retardation and prolong life was assessed, and the spread of radioisotopes inside tumors was measured using autoradiography. Results: The insertion of a single DART wire into the center of 6- to 7-mm tumors had a pronounced retardation effect on tumor growth, leading to a significant inhibition of 49% (LL2) and 93% (A427) in tumor development and prolongations of 48% (LL2) in life expectancy. In the human model, more than 80% of the treated tumors disappeared or shrunk. Autoradiographic analysis of the treated sectioned tissue revealed the intratumoral distribution of the radioisotopes, and histological analysis showed corresponding areas of necrosis. In vitro experiments demonstrated a dose-dependent killing of tumors cells exposed to alpha particles. Conclusions: Short-lived diffusing alpha-emitters produced tumor growth retardation and increased survival in mice bearing lung tumor implants. These results justify further investigations with improved dose distributions.

  15. WIP and WICH/WIRE co-ordinately control invadopodium formation and maturation in human breast cancer cell invasion

    PubMed Central

    García, Esther; Ragazzini, Chiara; Yu, Xinzi; Cuesta-García, Elena; Bernardino de la Serna, Jorge; Zech, Tobias; Sarrió, David; Machesky, Laura M.; Antón, Inés M.

    2016-01-01

    Cancer cells form actin-rich degradative protrusions (invasive pseudopods and invadopodia), which allows their efficient dispersal during metastasis. Using biochemical and advanced imaging approaches, we demonstrate that the N-WASP-interactors WIP and WICH/WIRE play non-redundant roles in cancer cell invasion. WIP interacts with N-WASP and cortactin and is essential for invadopodium assembly, whereas WICH/WIRE regulates N-WASP activation to control invadopodium maturation and degradative activity. Our data also show that Nck interaction with WIP and WICH/WIRE modulates invadopodium maturation; changes in WIP and WICH/WIRE levels induce differential distribution of Nck. We show that WIP can replace WICH/WIRE functions and that elevated WIP levels correlate with high invasiveness. These findings identify a role for WICH/WIRE in invasiveness and highlight WIP as a hub for signaling molecule recruitment during invadopodium generation and cancer progression, as well as a potential diagnostic biomarker and an optimal target for therapeutic approaches. PMID:27009365

  16. Search for laser-induced formation of antihydrogen atoms.

    PubMed

    Amoretti, M; Amsler, C; Bonomi, G; Bowe, P D; Canali, C; Carraro, C; Cesar, C L; Charlton, M; Ejsing, A M; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Kellerbauer, A; Lagomarsino, V; Lodi Rizzini, E; Macrì, M; Madsen, N; Manuzio, G; Mitchard, D; Montagna, P; Posada, L G C; Pruys, H; Regenfus, C; Rotondi, A; Telle, H H; Testera, G; Van der Werf, D P; Variola, A; Venturelli, L; Yamazaki, Y; Zurlo, N

    2006-11-24

    Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n = 11 quantum state by the introduction of light from a CO2 continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration. PMID:17155742

  17. Formation of massive protostars in atomic cooling haloes

    NASA Astrophysics Data System (ADS)

    Becerra, Fernando; Greif, Thomas H.; Springel, Volker; Hernquist, Lars E.

    2015-01-01

    We present the highest-resolution three-dimensional simulation to date of the collapse of an atomic cooling halo in the early Universe. We use the moving-mesh code AREPO with the primordial chemistry module introduced in Greif, which evolves the chemical and thermal rate equations for over more than 20 orders of magnitude in density. Molecular hydrogen cooling is suppressed by a strong Lyman-Werner background, which facilitates the near-isothermal collapse of the gas at a temperature of about 104 K. Once the central gas cloud becomes optically thick to continuum emission, it settles into a Keplerian disc around the primary protostar. The initial mass of the protostar is about 0.1 M⊙, which is an order of magnitude higher than in minihaloes that cool via molecular hydrogen. The high accretion rate and efficient cooling of the gas catalyse the fragmentation of the disc into a small protostellar system with 5-10 members. After about 12 yr, strong gravitational interactions disrupt the disc and temporarily eject the primary protostar from the centre of the cloud. By the end of the simulation, a secondary clump has collapsed at a distance of ≃ 150 au from the primary clump. If this clump undergoes a similar evolution as the first, the central gas cloud may evolve into a wide binary system. High accretion rates of both the primary and secondary clumps suggest that fragmentation is not a significant barrier for forming at least one massive black hole seed.

  18. Developing new theoretical models of the formation of atomic collision cascades and subcascades in irradiated solids

    SciTech Connect

    Metelkin, E. V.; Ryazanov, A. I. Semenov, E. V.

    2008-09-15

    A new theoretical model is developed for the investigation of atomic collision cascades and subcascades in irradiated solids consisting of atoms of a single type. The model is based on an analytical description of the elastic collisions between moving atoms knocked out of the crystal lattice sites and the immobile atoms of the lattice. The description is based on the linear kinetic Boltzmann equation describing the retardation of primary recoil atoms (PRAs) in irradiated solids. The laws of conservation for the total number and the kinetic energy of moving atoms, which follow from the kinetic Boltzmann equation, are analyzed using the proposed model. An analytical solution is obtained for the stationary kinetic Boltzmann equation, which describes the retardation of PRAs for a given source responsible for their production. A kinetic equation for the moving atoms and the corresponding laws of conservation are also analyzed with allowance for the binding energy of atoms at the crystal lattice sites. A criterion for determining the threshold energy of subcascade formation in irradiated solids is formulated. Based on this criterion, the threshold energy of subcascade formation is calculated using the Thomas-Fermi potential. Formulas are presented for determining the mean size and number of subcascades formed in a solid as functions of the PRA energy.

  19. Point defects along metallic atomic wires on vicinal Si surfaces: Si(5 5 7)-Au and Si(5 5 3)-Au

    NASA Astrophysics Data System (ADS)

    Kang, Pil-Gyu; Shin, Jin Sung; Yeom, Han Woong

    2009-08-01

    Point defects on the metallic atomic wires induced by Au adsorbates on vicinal Si surfaces were investigated using scanning tunneling microscopy and spectroscopy (STM and STS). High-resolution STM images revealed that there exist several different types of defects on the Si(5 5 7)-Au surface, which are categorized by their apparent bias-dependent images and compared to the previous report on Si(5 5 3)-Au [Phys. Rev. B (2007) 205325]. The chemical characteristics of these defects were investigated by monitoring them upon the variation of the Au coverage and the adsorption of water molecules. The chemical origins and the tentative atomic structures of the defects are suggested as Si adatoms (and dimers) in different registries, the Au deficiency on terraces, and water molecules adsorbed dissociatively on step edges, respectively. STS measurements disclosed the electronic property of the majority kinds of defects on both Si(5 5 7)-Au and Si(5 5 3)-Au surfaces. In particular, the dominating water-induced defects on both surfaces induce a substantial band gap of about 0.5 eV in clear contrast to Si adatom-type defects. The conduction channels along the metallic step-edge chains thus must be very susceptible to the contamination through the electronic termination by the water adsorption.

  20. Atomic and electronic structure peculiarities of silicon wires formed on substrates with varied resistivity according to ultrasoft X-ray emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Turishchev, S. Yu.; Terekhov, V. A.; Nesterov, D. N.; Koltygina, K. G.; Sivakov, V. A.; Domashevskaya, E. P.

    2015-04-01

    Silicon wires arrays have been produced by metal-assisted wet chemical etching with the use of crystalline silicon substrates. The arrays and individual nanowires have been studied by scanning and transmission electron microscopy. The electronic structure and phase composition of the surface and near-surface layers of the arrays have been studied by ultrasoft X-ray emission spectroscopy. It is shown that the morphologically more developed sample formed on a substrate with low resistivity is considerably more strongly subject to oxidation with noticeable formation of phases of intermediate silicon oxides. The array of nanowires formed on a substrate with high resistivity also undergoes natural oxidation, but does so to a substantially lesser extent and, with increasing depth of analysis, mostly contains the phase of crystalline silicon constituting the bulk of the nanowires being formed.

  1. Measurement of Rydberg atom formation in low-density ultracold neutral plasmas

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Ting; Witte, Craig; Roberts, Jacob

    2016-05-01

    Rydberg atoms are formed in ultracold neutral plasmas primarily through three-body recombination for typical experimental conditions. At low densities the relative importance of electron-Rydberg state-changing collisions in the dynamical evolution of the Rydberg atom state populations is increased, leading to temperature scalings significantly different from the usual T - 9 / 2 scaling associated with the three-body recombination rate. We report our measurement of Rydberg atoms in low-density ultracold neutral plasmas and discuss their utility in calibrating the electron temperature and determining the amount of heating due to continuum lowering that occurs during the formation of the ultracold plasma. This work supported by the AFOSR.

  2. Formation of nanostructures on HOPG surface in presence of surfactant atom during low energy ion irradiation

    NASA Astrophysics Data System (ADS)

    Ranjan, M.; Joshi, P.; Mukherjee, S.

    2016-07-01

    Low energy ions beam often develop periodic patterns on surfaces under normal or off-normal incidence. Formation of such periodic patterns depends on the substrate material, the ion beam parameters, and the processing conditions. Processing conditions introduce unwanted contaminant atoms, which also play strong role in pattern formation by changing the effective sputtering yield of the material. In this work we have analysed the effect of Cu, Fe and Al impurities introduced during low energy Ar+ ion irradiation on HOPG substrate. It is observed that by changing the species of foreign atoms the surface topography changes drastically. The observed surface topography is co-related with the modified sputtering yield of HOPG. Presence of Cu and Fe amplify the effective sputtering yield of HOPG, so that the required threshold for the pattern formation is achieved with the given fluence, whereas Al does not lead to any significant change in the effective yield and hence no pattern formation occurs.

  3. Kinetics of spin relaxation in quantum wires and channels: Boundary spin echo and formation of a persistent spin helix

    SciTech Connect

    Slipko, Valeriy A.; Pershin, Yuriy V.

    2011-10-15

    In this paper we use a spin kinetic equation to study spin-polarization dynamics in one-dimensional (1D) wires and 2D channels. The spin kinetic equation is valid in both diffusive and ballistic spin transport regimes and therefore is more general than the usual spin drift-diffusion equations. In particular, we demonstrate that in infinite 1D wires with Rashba spin-orbit interaction the exponential spin-relaxation decay can be modulated by an oscillating function. In the case of spin relaxation in finite length 1D wires, it is shown that an initially homogeneous spin polarization spontaneously transforms into a persistent spin helix. We find that a propagating spin-polarization profile reflects from a system boundary and returns back to its initial position similarly to the reflectance of sound waves from an obstacle. The Green's function of the spin kinetic equation is derived for both finite and infinite 1D systems. Moreover, we demonstrate explicitly that the spin relaxation in specifically oriented 2D channels with Rashba and Dresselhaus spin-orbit interactions of equal strength occurs similarly to that in 1D wires of finite length. Finally, a simple transformation mapping 1D spin kinetic equation into the Klein-Gordon equation with an imaginary mass is found thus establishing an interesting connection between semiconductor spintronics and relativistic quantum mechanics.

  4. Optical Pattern Formation in Spatially Bunched Atoms: A Self-Consistent Model and Experiment

    NASA Astrophysics Data System (ADS)

    Schmittberger, Bonnie L.; Gauthier, Daniel J.

    2014-05-01

    The nonlinear optics and optomechanical physics communities use different theoretical models to describe how optical fields interact with a sample of atoms. There does not yet exist a model that is valid for finite atomic temperatures but that also produces the zero temperature results that are generally assumed in optomechanical systems. We present a self-consistent model that is valid for all atomic temperatures and accounts for the back-action of the atoms on the optical fields. Our model provides new insights into the competing effects of the bunching-induced nonlinearity and the saturable nonlinearity. We show that it is crucial to keep the fifth and seventh-order nonlinearities that arise when there exists atomic bunching, even at very low optical field intensities. We go on to apply this model to the results of our experimental system where we observe spontaneous, multimode, transverse optical pattern formation at ultra-low light levels. We show that our model accurately predicts our experimentally observed threshold for optical pattern formation, which is the lowest threshold ever reported for pattern formation. We gratefully acknowledge the financial support of the NSF through Grant #PHY-1206040.

  5. Theoretical survey on positronium formation and ionisation in positron atom scattering

    NASA Technical Reports Server (NTRS)

    Basu, Madhumita; Ghosh, A. S.

    1990-01-01

    The recent theoretical studies are surveyed and reported on the formation of exotic atoms in positron-hydrogen, positron-helium and positron-lithium scattering specially at intermediate energy region. The ionizations of these targets by positron impact was also considered. Theoretical predictions for both the processes are compared with existing measured values.

  6. Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping

    NASA Astrophysics Data System (ADS)

    Frasinski, L. J.; Zhaunerchyk, V.; Mucke, M.; Squibb, R. J.; Siano, M.; Eland, J. H. D.; Linusson, P.; v. d. Meulen, P.; Salén, P.; Thomas, R. D.; Larsson, M.; Foucar, L.; Ullrich, J.; Motomura, K.; Mondal, S.; Ueda, K.; Osipov, T.; Fang, L.; Murphy, B. F.; Berrah, N.; Bostedt, C.; Bozek, J. D.; Schorb, S.; Messerschmidt, M.; Glownia, J. M.; Cryan, J. P.; Coffee, R. N.; Takahashi, O.; Wada, S.; Piancastelli, M. N.; Richter, R.; Prince, K. C.; Feifel, R.

    2013-08-01

    When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called “partial covariance mapping” to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

  7. Formation of surface oxides and Ag2O thin films with atomic oxygen on Ag(111)

    NASA Astrophysics Data System (ADS)

    Derouin, Jonathan; Farber, Rachael G.; Heslop, Stacy L.; Killelea, Daniel R.

    2015-11-01

    The nature of the oxygen species adsorbed to silver surfaces is a key component of the heterogeneously catalyzed epoxidation of ethylene and partial oxidation of methanol over silver catalysts. We report the formation of two different silver-oxygen species depending on the flux and energy of incident gas-phase oxygen atoms on an Ag(111) surface. A combination of surface science techniques was used to characterize the oxidized surfaces. Atomic oxygen was generated with an Ir filament; lower temperatures created surface oxides previously reported. When O was deposited with a higher filament temperature, the surface became highly corrugated, little subsurface oxygen was observed, and thin layers of Ag2O were likely formed. These results show that the energy and flux of oxygen are important parameters in the chemical identity and abundance of oxygen on silver surfaces and suggest that formation of the Ag2O thin film hinders formation of subsurface oxygen.

  8. Designing potentials by sculpturing wires

    SciTech Connect

    Della Pietra, Leonardo; Aigner, Simon; Groth, Soenke; Hagen, Christoph von; Schmiedmayer, Joerg; Bar-Joseph, Israel; Lezec, Henri J.

    2007-06-15

    Magnetic trapping potentials for atoms on atom chips are determined by the current flow in the chip wires. By modifying the shape of the conductor we can realize specialized current flow patterns and therefore microdesign the trapping potentials. We have demonstrated this by nano-machining an atom chip using the focused ion beam technique. We built a trap, a barrier, and using a Bose-Einstein Condensate as a probe we showed that by polishing the conductor edge the potential roughness on the selected wire can be reduced. Furthermore, we give different other designs and discuss the creation of a one-dimensional magnetic lattice on an atom chip.

  9. Study of the effect of current rise time on the formation of the precursor column in cylindrical wire array Z pinches at 1 MA

    SciTech Connect

    Bott, S. C.; Haas, D. M.; Eshaq, Y.; Ueda, U.; Beg, F. N.; Hammer, D. A.; Kusse, B.; Greenly, J.; Shelkovenko, T. A.; Pikuz, S. A.; Blesener, I. C.; McBride, R. D.; Douglass, J. D.; Bell, K.; Knapp, P.; Chittenden, J. P.; Lebedev, S. V.; Bland, S. N.; Hall, G. N.; Suzuki Vidal, F. A.

    2009-07-15

    The limited understanding of the mechanisms driving the mass ablation rate of cylindrical wires arrays is presently one of the major limitations in predicting array performance at the higher current levels required for inertial confinement fusion (ICF) ignition. Continued investigation of this phenomenon is crucial to realize the considerable potential for wire arrays to drive both ICF and inertial fusion energy, by enabling a predictive capability in computational modeling. We present the first study to directly compare the mass ablation rates of wire arrays as a function of the current rise rate. Formation of the precursor column is investigated on both the MAPGIE (1 MA, 250ns [Mitchell et al., Rev. Sci. Instrum. 67, 1533 (1996)]) and COBRA (1 MA, 100ns [Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)]) generators, and results are used to infer the change in the effective ablation velocity induced by the rise rate of the drive current. Laser shadowography, gated extreme ultraviolet (XUV) imaging, and x-ray diodes are used to compare the dynamical behavior on the two generators, and X-pinch radiography and XUV spectroscopy provide density evolution and temperature measurements respectively. Results are compared to predictions from an analytical scaling model developed previously from MAGPIE data, based on a fixed ablation velocity. For COBRA the column formation time occurs at 116{+-}5 ns and for Al arrays and 146{+-}5 ns for W arrays, with Al column temperature in the range of 70-165 eV. These values lie close to model predictions, inferring only a small change in the ablation velocity is induced by the factor of 2.5 change in current rise time. Estimations suggest the effective ablation velocities for MAGPIE and COBRA experiments vary by a maximum of 30%.

  10. Residential Wiring.

    ERIC Educational Resources Information Center

    Taylor, Mark

    The second in a series of three curriculum packages on wiring, these materials for a five-unit course were developed to prepare postsecondary students for entry-level employment in the residential wiring trade. The five units are: (1) blueprint reading and load calculations; (2) rough-in; (3) service; (4) trim out and troubleshooting; and (5) load…

  11. Wire chamber

    DOEpatents

    Atac, Muzaffer

    1989-01-01

    A wire chamber or proportional counter device, such as Geiger-Mueller tube or drift chamber, improved with a gas mixture providing a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor.

  12. Investigation of the effect of process parameters on the formation and characteristics of recast layer in wire-EDM of Inconel 718

    SciTech Connect

    Newton, Thomas R; Melkote, Shreyes N; Watkins, Thomas R; Trejo, Rosa M; Riester, Laura

    2009-01-01

    Inconel 718 is a high nickel content superalloy possessing high strength at elevated temperatures and resistance to oxidation and corrosion. The non-traditional manufacturing process of wire-electrical discharge machining (EDM) possesses many advantages over traditional machining during the manufacture of Inconel 718 parts. However, certain detrimental effects are also present and are due in large part to the formation of the recast layer. An experimental investigation was conducted to determine the main EDM parameters which contribute to recast layer formation in Inconel 718. It was found that average recast layer thickness increased primarily with energy per spark, peak discharge current, and current pulse duration. Over the range of parameters tested, the recast layer was observed to be between 5 and 9 {micro}m in average thickness, although highly variable in nature. The recast material was found to possess in-plane tensile residual stresses, as well as lower hardness and elastic modulus than the bulk material.

  13. Modeling the Formation of Tropical Rings of Atomic Bromine and Iodine

    NASA Astrophysics Data System (ADS)

    Saiz-Lopez, A.; Fernandez, R.; Salawitch, R. J.; Kinnison, D. E.; Lamarque, J. F.; Ordoñez, C.; Gomez Martin, J. C.; Tilmes, S.

    2014-12-01

    Very short-lived (VSL) bromo- and iodocarbons are produced at a prodigious rate by ocean biology and these source compounds (SGVSL), together with their degradation inorganic products (PGVSL), are lofted by vigorous convection to the tropical tropopause layer (TTL). Using a state-of-the-art photochemical mechanism within a global model, we investigate the partitioning and loading of reactive inorganic halogens within the TTL. The specific low ozone and low temperature conditions of this region of the atmosphere changes the steady-state between halogen atoms and oxides, making the atoms the dominant species. We suggest that this leads to the formation of two daytime "tropical rings" of both atomic bromine and iodine that circle the tropics with the sun. In addition to a description of this photochemical phenomenon, this communication the partitioning of inorganic halogen reservoirs within the TTL and assess its relevance for the injection of bromine to stratosphere.

  14. Modeling the formation of tropical rings of atomic bromine and iodine

    NASA Astrophysics Data System (ADS)

    Saiz-Lopez, Alfonso; Fernandez, Rafael; Gomez Martin, Juan Carlos; Salawitch, Ross; Kinnison, Douglas; Lamarque, Jean-Francois; Tilmes, Simone

    2015-04-01

    Very short-lived (VSL) bromo- and iodocarbons are produced at a prodigious rate by ocean biology and these source compounds (SGVSL), together with their degradation inorganic products (PGVSL), are lofted by vigorous convection to the tropical tropopause layer (TTL). Using a state-of-the-art photochemical mechanism within a global model, we investigate the partitioning and loading of reactive inorganic halogens within the TTL. The specific low ozone and low temperature conditions of this region of the atmosphere changes the steady-state between halogen atoms and oxides, making the atoms the dominant species. We suggest that this leads to the formation of two daytime "tropical rings" of both atomic bromine and iodine that circle the tropics with the sun. In addition to a description of this photochemical phenomenon, this communication the partitioning of inorganic halogen reservoirs within the TTL and assess its relevance for the injection of bromine to stratosphere.

  15. Solid Hydrogen Experiments for Atomic Propellants: Particle Formation, Imaging, Observations, and Analyses

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    2005-01-01

    This report presents particle formation observations and detailed analyses of the images from experiments that were conducted on the formation of solid hydrogen particles in liquid helium. Hydrogen was frozen into particles in liquid helium, and observed with a video camera. The solid hydrogen particle sizes and the total mass of hydrogen particles were estimated. These newly analyzed data are from the test series held on February 28, 2001. Particle sizes from previous testing in 1999 and the testing in 2001 were similar. Though the 2001 testing created similar particles sizes, many new particle formation phenomena were observed: microparticles and delayed particle formation. These experiment image analyses are some of the first steps toward visually characterizing these particles, and they allow designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

  16. Solid Hydrogen Experiments for Atomic Propellants: Particle Formation Energy and Imaging Analyses

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    2002-01-01

    This paper presents particle formation energy balances and detailed analyses of the images from experiments that were conducted on the formation of solid hydrogen particles in liquid helium during the Phase II testing in 2001. Solid particles of hydrogen were frozen in liquid helium and observed with a video camera. The solid hydrogen particle sizes and the total mass of hydrogen particles were estimated. The particle formation efficiency is also estimated. Particle sizes from the Phase I testing in 1999 and the Phase II testing in 2001 were similar. Though the 2001 testing created similar particles sizes, many new particle formation phenomena were observed. These experiment image analyses are one of the first steps toward visually characterizing these particles and it allows designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

  17. Spatial Distributions of Metal Atoms During Carbon SWNTs Formation: Measurements and Modelling

    NASA Technical Reports Server (NTRS)

    Cau, M.; Dorval, N.; Attal-Tretout, B.; Cochon, J. L.; Loiseau, A.; Farhat, S.; Hinkov, I.; Scott, C. D.

    2004-01-01

    Experiments and modelling have been undertaken to clarify the role of metal catalysts during single-wall carbon nanotube formation. For instance, we wonder whether the metal catalyst is active as an atom, a cluster, a liquid or solid nanoparticle [1]. A reactor has been developed for synthesis by continuous CO2-laser vaporisation of a carbon-nickel-cobalt target in laminar helium flow. The laser induced fluorescence technique [2] is applied for local probing of gaseous Ni, Co and CZ species throughout the hot carbon flow of the target heated up to 3500 K. A rapid depletion of C2 in contrast to the spatial extent of metal atoms is observed in the plume (Fig. 1). This asserts that C2 condenses earlier than Ni and Co atoms.[3, 4]. The depletion is even faster when catalysts are present. It may indicate that an interaction between metal atoms and carbon dimers takes place in the gas as soon as they are expelled from the target surface. Two methods of modelling are used: a spatially I-D calculation developed originally for the arc process [5], and a zero-D time dependent calculation, solving the chemical kinetics along the streamlines [6]. The latter includes Ni cluster formation. The peak of C2 density is calculated close to the target surface where the temperature is the highest. In the hot region, C; is dominant. As the carbon products move away from the target and mix with the ambient helium, they recombine into larger clusters, as demonstrated by the peak of C5 density around 1 mm. The profile of Ni-atom density compares fairly well with the measured one (Fig. 2). The early increase is due to the drop of temperature, and the final decrease beyond 6 mm results from Ni cluster formation at the eutectic temperature (approx.1600 K).

  18. Measurements of Polyatomic Molecule Formation on an Icy Grain Analog Using Fast Atoms

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Madsunkov, S.; Shortt, B. J.; MacAskill, J. A.; Darrach, M. R.

    2006-01-01

    Carbon dioxide has been produced from the impact of a monoenergetic O(P-3) beam upon a surface cooled to 4.8 K and covered with a CO ice. Using temperature-programmed desorption and mass spectrometer detection, we have detected increasing amounts of CO2 formation with O(P-3) energies of 2, 5, 10, and 14 eV. This is the first measurement of polyatomic molecule formation on a surface with superthermal atoms. The goal of this work is to detect other polyatomic species, such as CH3OH, which can be formed under conditions that simulate the grain temperature, surface coverage, and superthermal atoms present in shock-heated circumstellar and interstellar regions.

  19. Atomic Step Formation on Sapphire Surface in Ultra-precision Manufacturing.

    PubMed

    Wang, Rongrong; Guo, Dan; Xie, Guoxin; Pan, Guoshun

    2016-01-01

    Surfaces with controlled atomic step structures as substrates are highly relevant to desirable performances of materials grown on them, such as light emitting diode (LED) epitaxial layers, nanotubes and nanoribbons. However, very limited attention has been paid to the step formation in manufacturing process. In the present work, investigations have been conducted into this step formation mechanism on the sapphire c (0001) surface by using both experiments and simulations. The step evolutions at different stages in the polishing process were investigated with atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). The simulation of idealized steps was constructed theoretically on the basis of experimental results. It was found that (1) the subtle atomic structures (e.g., steps with different sawteeth, as well as steps with straight and zigzag edges), (2) the periodicity and (3) the degree of order of the steps were all dependent on surface composition and miscut direction (step edge direction). A comparison between experimental results and idealized step models of different surface compositions has been made. It has been found that the structure on the polished surface was in accordance with some surface compositions (the model of single-atom steps: Al steps or O steps). PMID:27444267

  20. Atomic Step Formation on Sapphire Surface in Ultra-precision Manufacturing

    NASA Astrophysics Data System (ADS)

    Wang, Rongrong; Guo, Dan; Xie, Guoxin; Pan, Guoshun

    2016-07-01

    Surfaces with controlled atomic step structures as substrates are highly relevant to desirable performances of materials grown on them, such as light emitting diode (LED) epitaxial layers, nanotubes and nanoribbons. However, very limited attention has been paid to the step formation in manufacturing process. In the present work, investigations have been conducted into this step formation mechanism on the sapphire c (0001) surface by using both experiments and simulations. The step evolutions at different stages in the polishing process were investigated with atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). The simulation of idealized steps was constructed theoretically on the basis of experimental results. It was found that (1) the subtle atomic structures (e.g., steps with different sawteeth, as well as steps with straight and zigzag edges), (2) the periodicity and (3) the degree of order of the steps were all dependent on surface composition and miscut direction (step edge direction). A comparison between experimental results and idealized step models of different surface compositions has been made. It has been found that the structure on the polished surface was in accordance with some surface compositions (the model of single-atom steps: Al steps or O steps).

  1. Muonic Atom Deexcitation via Formation of Metastable Molecular States, in Light of Experimental Verification

    NASA Astrophysics Data System (ADS)

    Wallenius, J.; Jonsell, S.; Kino, Y.; Froelich, P.

    2001-12-01

    In a recent experiment performed at PSI, a peak in the time-of-flight distribution of pμ(1s) atoms could be identified with decay of ppμ* molecular ions situated below the 2s threshold, providing 900 eV of kinetic energy to the pμ atom. This finding may be interpreted in terms of the side path model which suggests that metastable muonic molecules may form with high probability in resonant collisions between muonic hydrogen in the 2s state and hydrogen molecules, e.g. pμ (2s) + {text{H}}_{text{2}} to [(ppμ ^* )_{vJ}^{pq} - pee]_{vK} to [(ppμ ^* )_{v'J'}^{p'q'} - pe]^ + + e^ - . The Coulombic decay of the Auger stabilised ppμ* molecular ion then leads to the formation of highly energetic pμ(1s) atoms. In the present paper calculations of resonant formation rates in pure hydrogen are presented and compared to the quenching rate of pμ(2s) atoms measured at low hydrogen density.

  2. Atomic Step Formation on Sapphire Surface in Ultra-precision Manufacturing

    PubMed Central

    Wang, Rongrong; Guo, Dan; Xie, Guoxin; Pan, Guoshun

    2016-01-01

    Surfaces with controlled atomic step structures as substrates are highly relevant to desirable performances of materials grown on them, such as light emitting diode (LED) epitaxial layers, nanotubes and nanoribbons. However, very limited attention has been paid to the step formation in manufacturing process. In the present work, investigations have been conducted into this step formation mechanism on the sapphire c (0001) surface by using both experiments and simulations. The step evolutions at different stages in the polishing process were investigated with atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). The simulation of idealized steps was constructed theoretically on the basis of experimental results. It was found that (1) the subtle atomic structures (e.g., steps with different sawteeth, as well as steps with straight and zigzag edges), (2) the periodicity and (3) the degree of order of the steps were all dependent on surface composition and miscut direction (step edge direction). A comparison between experimental results and idealized step models of different surface compositions has been made. It has been found that the structure on the polished surface was in accordance with some surface compositions (the model of single-atom steps: Al steps or O steps). PMID:27444267

  3. The effects of cooking on wire and stone barbecue at different cooking levels on the formation of heterocyclic aromatic amines and polycyclic aromatic hydrocarbons in beef steak.

    PubMed

    Oz, Fatih; Yuzer, M Onur

    2016-07-15

    The effects of type of barbecue (wire and stone) and cooking levels (rare, medium, well-done and very well-done) on the formation of heterocyclic aromatic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) in beef steak were investigated. Varying levels of IQx (up to 0.29 ng/g), IQ (up to 0.93 ng/g), MeIQx (up to 0.08 ng/g), MeIQ (up to 0.75 ng/g), 7,8-DiMeIQx (up to 0.08 ng/g), 4,8-DiMeIQx (up to 4.95 ng/g), PhIP (up to 6.24 ng/g) and AαC (up to 0.20 ng/g) were determined, while MeAαC was not detected. The total HCA amounts in wire barbecued samples were higher than stone barbecued samples. Total HCA contents of the samples ranged between nd and 13.52 ng/g. In terms of PAHs, varying levels of BaA (up to 0.34 ng/g), Chry (up to 0.28 ng/g), BbF (up to 0.39 ng/g), BkF (up to 0.90 ng/g), BaP (up to 0.29 ng/g) and Bghip (up to 0.43 ng/g) were determined, while DahA and IncdP were not detected. The total PAH amounts in stone barbecued samples were higher than those of wire barbecued samples. Total PAH amounts of the samples ranged between nd and 2.63 ng/g. PMID:26948589

  4. Wire Wise.

    ERIC Educational Resources Information Center

    Swanquist, Barry

    1998-01-01

    Discusses how today's technology is encouraging schools to invest in furnishings that are adaptable to computer use and telecommunications access. Explores issues concerning modularity, wiring management, ergonomics, durability, price, and aesthetics. (GR)

  5. A density functional study of silver clusters on a stepped graphite surface: formation of self-assembled nano-wires.

    PubMed

    Singh, Akansha; Sen, Prasenjit

    2015-05-21

    Adsorption and diffusion of silver adatoms and clusters containing up to eight atoms on an HOPG substrate with an armchair step are studied using density functional methods. Step edges act as attractive sinks for adatoms and clusters. The diffusion barrier of an Ag adatom along the step edge is much larger than that on a clean terrace. At zero temperature, Ag clusters either distort or dissociate by forming covalent bonds with the edge C atoms. At 600 K, Ag5 and Ag8 clusters diffuse to the step edges, and then break up so as to maximize Ag-C bonds. The Ag atoms try to form a nanowire structure along the step edge. At such high temperatures, diffusion of clusters along the step edge involves diffusion of individual Ag atoms not bonded to the edge C atoms. Assumption of complete immobility of clusters trapped at step edges in the Gates-Robins model is not valid at high temperatures in this particular system. PMID:25903308

  6. Kinetics of Mo atom formation and consumption in UV multiphoton dissociation of Mo(CO)6 at room temperature

    NASA Astrophysics Data System (ADS)

    Eremin, A. V.; Gurentsov, E. V.; Musikhin, S. A.

    2015-12-01

    This study is devoted to the investigation of molybdenum atom formation and consumption after UV laser pulse photolysis of molybdenum hexacarbonyl vapor diluted by various bath gases. The processes of formation and consumption of Mo atoms were observed using atomic resonance absorption spectroscopy (ARAS) technique at the Mo-I resonance line (λ = 386.41 nm) providing the time profiles of molybdenum atoms concentration in the ground state. The increase of Mo atoms concentration was detected immediately after laser pulse and was determined mainly by spontaneous radiative quenching of excited Mo atoms produced in photolysis of molybdenum hexacarbonyl. It was found that collision quenching with bath gas molecules played a minor role. The following decrease of Mo atoms concentration after a maximum was attributed to the reactions of recombination, cluster formation and other secondary reactions. Based on the experimental data obtained, the kinetic mechanism of Mo atoms formation and consumption in photo-dissociation of Mo(CO)6 was developed. The rate constants of basic reactions responsible for this mechanism were estimated using the frequencies of gas-kinetics collisions or were extracted directly from experimental data by the fitting of measured and calculated time profiles of Mo atoms concentration.

  7. Effect of Current Rise-time on the Formation of Precursor Structures and Mass Ablation Rate in Cylindrical Wire Array Z-Pinches

    SciTech Connect

    Bott, S. C.; Eshaq, Y.; Ueda, U.; Haas, D. M.; Beg, F. N.; Hammer, D. A.; Kusse, B.; Greenly, J.; Shelkovenko, T. A.; Pikuz, S. A.; Blesener, I. C.; McBride, R. D.; Douglass, J. D.; Bell, K.; Knapp, P.; Chittenden, J. P.; Lebedev, S. V.; Bland, S. N.; Hall, G. N.; Suzuki, F. A.

    2009-01-21

    We present the first study to directly compare the mass ablation rates of cylindrical wire arrays as a function of the current rise-rate. Formation of the precursor column is investigated on both the MAPGIE (1 MA, 250 ns) and COBRA (1 MA, 100 ns) generators, and results are used to infer the change in the mass ablation rate induced by the rise-rate of the drive current. Laser shadowography, gated XUV imaging and x-ray diodes are used to compare the dynamical behavior both generators, and x-pinch radiography and XUV spectroscopy and provide density evolution and temperature measurements respectively. Results are compared to predictions from an analytical scaling model based on a fixed ablation rate, and the close correlation achieved suggests that the effective ablation velocity is not a strong function of the current rise rate.

  8. Galaxy Zoo and ALFALFA: atomic gas and the regulation of star formation in barred disc galaxies

    NASA Astrophysics Data System (ADS)

    Masters, Karen L.; Nichol, Robert C.; Haynes, Martha P.; Keel, William C.; Lintott, Chris; Simmons, Brooke; Skibba, Ramin; Bamford, Steven; Giovanelli, Riccardo; Schawinski, Kevin

    2012-08-01

    We study the observed correlation between atomic gas content and the likelihood of hosting a large-scale bar in a sample of 2090 disc galaxies. Such a test has never been done before on this scale. We use data on morphologies from the Galaxy Zoo project and information on the galaxies' H I content from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) blind H I survey. Our main result is that the bar fraction is significantly lower among gas-rich disc galaxies than gas-poor ones. This is not explained by known trends for more massive (stellar) and redder disc galaxies to host more bars and have lower gas fractions: we still see at fixed stellar mass a residual correlation between gas content and bar fraction. We discuss three possible causal explanations: (1) bars in disc galaxies cause atomic gas to be used up more quickly, (2) increasing the atomic gas content in a disc galaxy inhibits bar formation and (3) bar fraction and gas content are both driven by correlation with environmental effects (e.g. tidal triggering of bars, combined with strangulation removing gas). All three explanations are consistent with the observed correlations. In addition our observations suggest bars may reduce or halt star formation in the outer parts of discs by holding back the infall of external gas beyond bar co-rotation, reddening the global colours of barred disc galaxies. This suggests that secular evolution driven by the exchange of angular momentum between stars in the bar, and gas in the disc, acts as a feedback mechanism to regulate star formation in intermediate-mass disc galaxies. This publication has been made possible by the participation of more than 200 000 volunteers in the Galaxy Zoo project. Their contributions are individually acknowledged at South East Physics Network, E-mail: karen.masters@port.ac.ukEinstein fellow.

  9. Gas-phase formation of silicon carbides, oxides, and sulphides from atomic silicon ions

    NASA Technical Reports Server (NTRS)

    Bohme, Diethard K.; Wlodek, Stanislaw; Fox, Arnold

    1989-01-01

    A systematic experimental study of the kinetics and mechanisms of the chemical reactions in the gas phase between ground-state Si(+)2p and a variety of astrophysical molecules. The aim of this study is to identify the reactions which trigger the formation of chemical bonds between silicon and carbon, oxygen and sulphur, and the chemical pathways which lead to further molecular growth. Such knowledge is valuable in the identification of new extraterrestrial silicon-bearing molecules and for an assessment of the gas-phase transition from atomic silicon to silicon carbide and silicate grain particles in carbon-rich and oxygen-rich astrophysical environments.

  10. H{sup −} formation by neutral resonant ionization of H(n=2) atoms

    SciTech Connect

    Vogel, John S.

    2015-04-08

    A mechanism for producing hydrogen anions in a low density, low energy hydrogen plasma is proposed. The observation in a plasma ion source that the anion output is quadratically related to the Lyman-α radiation suggests that anions could be formed in collisions between atoms in the first excited state. A potential energy plot for the hydrogen molecule is developed that includes a high energy ionic state, comprising a proton and the weakly bound H{sup −}(2p{sup 2} {sup 3}P{sup e}) ion, revealing a path to stable anion formation.

  11. Formation of heavy-Rydberg ion-pair states in Rydberg atom collisions with attaching targets

    NASA Astrophysics Data System (ADS)

    Wang, Changhao; Kelley, Michael; Buathong, Sitti; Dunning, F. Barry

    2014-05-01

    Electron transfer in collisions between K(np)Rydberg atoms and electron attaching molecules can lead to formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair orbiting at large internuclear separations. In the present work ion-pair states are created in a small collision cell and allowed to exit into an analysis region where their binding energy and velocity distributions are determined with the aid of electric-field-induced dissociation and a position sensitive detector. Ion pair production is analyzed using a Monte Carlo collision code that models both the initial Rydberg electron capture and the subsequent behavior of the product ion pair. The data demonstrate that collisions with SF6 and CCl4 lead to formation of long-lived ion pair states with a broad distribution of binding energies whose velocity distribution is strongly peaked in the forward direction. Research supported by the Robert A. Welch Foundation.

  12. Positronium formation in the n = 2 level in positron scattering from hydrogen and helium atoms

    SciTech Connect

    Khan, P.; Mazumdar, P.S.; Ghosh, A.S.

    1985-03-01

    A distorted-wave model (Phys. Rev. A 27, 1904 (1983); 28, 2180 (1983)) is applied to calculate the formation of positronium in the n = 2 states in e/sup +/ scattering from hydrogen and helium atoms. The incident wave is represented by a polarized-orbital method. The first-Born-approximation results of the 2p-excited-state capture cross section in the case of helium is reported for the first time. The first Born approximation is found to be unsuitable for prediction of the rearrangement processes. The present total (ground- and excited-state) positronium-formation cross sections have been compared with the corresponding observed values of Fornari et al. (Phys. Rev. Lett. 51, 2276 (1983)) and of Charlton et al. (J. Phys. B 16, L465 (1983)).

  13. Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

    DOE PAGESBeta

    Wang, Yanggang; Mei, Donghai; Glezakou, Vassiliki Alexandra; Li, Jun; Rousseau, Roger J.

    2015-03-04

    Ab initio Molecular Dynamics simulations and static Density Functional Theory calculations have been performed to investigate the reaction mechanism of CO oxidation on Au/CeO2 catalyst. It is found that under reaction condition CO adsorption significantly labializes the surface atoms of the Au cluster and leads to the formation of isolated Au+-CO species that resides on the support in the vicinity of the Au particle. In this context, we identified a dynamic single-atom catalytic mechanism at the interfacial area for CO oxidation on Au/CeO2 catalyst, which is a lower energy pathway than that of CO oxidation at the interface with themore » metal particle. This results from the ability of the single atom site to strongly couple with the redox properties of the support in a synergistic manner thereby lowering the barrier for redox reactions. We find that the single Au+ ion, which only exists under reaction conditions, breaks away from the Au cluster to catalyze CO oxidation and returns to the Au cluster after the catalytic cycle is completed. Generally, our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in a catalytic process.« less

  14. Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

    SciTech Connect

    Wang, Yanggang; Mei, Donghai; Glezakou, Vassiliki Alexandra; Li, Jun; Rousseau, Roger J.

    2015-03-04

    Ab initio Molecular Dynamics simulations and static Density Functional Theory calculations have been performed to investigate the reaction mechanism of CO oxidation on Au/CeO2 catalyst. It is found that under reaction condition CO adsorption significantly labializes the surface atoms of the Au cluster and leads to the formation of isolated Au+-CO species that resides on the support in the vicinity of the Au particle. In this context, we identified a dynamic single-atom catalytic mechanism at the interfacial area for CO oxidation on Au/CeO2 catalyst, which is a lower energy pathway than that of CO oxidation at the interface with the metal particle. This results from the ability of the single atom site to strongly couple with the redox properties of the support in a synergistic manner thereby lowering the barrier for redox reactions. We find that the single Au+ ion, which only exists under reaction conditions, breaks away from the Au cluster to catalyze CO oxidation and returns to the Au cluster after the catalytic cycle is completed. Generally, our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in a catalytic process.

  15. Direct collapse black hole formation from synchronized pairs of atomic cooling haloes

    NASA Astrophysics Data System (ADS)

    Visbal, Eli; Haiman, Zoltán; Bryan, Greg L.

    2014-11-01

    High-redshift quasar observations imply that supermassive black holes (SMBHs) larger than ˜109 M⊙ formed before z ˜ 6. That such large SMBHs formed so early in the history of the Universe remains an open theoretical problem. One possibility is that gas in atomic cooling haloes exposed to strong Lyman-Werner (LW) radiation forms 104-106 M⊙ supermassive stars which quickly collapse into black holes. We propose a scenario for direct collapse black hole (DCBH) formation based on synchronized pairs of pristine atomic cooling haloes. We consider haloes at very small separation with one halo being a subhalo of the other. The first halo to surpass the atomic cooling threshold forms stars. Soon after these stars are formed, the other halo reaches the cooling threshold and due to its small distance from the newly formed galaxy, it is exposed to the critical LW intensity required to form a DCBH. The main advantage of this scenario is that synchronization can potentially prevent photoevaporation and metal pollution in DCBH-forming haloes. We use N-body simulations and an analytic approximation to estimate the abundance of DCBHs formed in this way. The density of DCBHs formed in this scenario could explain the SMBHs implied by z ˜ 6 quasar observations. Metal pollution and photoevaporation could potentially reduce the abundance of DCBHs below that required to explain the observations in other models that rely on a high LW flux.

  16. Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

    SciTech Connect

    Wang, Yanggang; Mei, Donghai; Glezakou, Vassiliki Alexandra; Li, Jun; Rousseau, Roger J.

    2015-03-04

    Ab initio Molecular Dynamics simulations and static Density Functional Theory calculations have been performed to investigate the reaction mechanism of CO oxidation on Au/CeO2 catalyst. It is found that under reaction condition CO adsorption significantly labializes the surface atoms of the Au cluster and leads to the formation of isolated Au+-CO species that resides on the support in the vicinity of the Au particle. In this context, we identified a dynamic single-atom catalytic mechanism at the interfacial area for CO oxidation on Au/CeO2 catalyst, which is a lower energy pathway than that of CO oxidation at the interface with the metal particle. This results from the ability of the single atom site to strongly couple with the redox properties of the support in a synergistic manner thereby lowering the barrier for redox reactions. We find that the single Au+ ion, which only exists under reaction conditions, breaks away from the Au cluster to catalyze CO oxidation and returns to the Au cluster after the catalytic cycle is completed. Generally, our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in a catalytic process.

  17. Unified treatment of hadronic annihilation and protonium formation in slow collisions of antiprotons with hydrogen atoms

    NASA Astrophysics Data System (ADS)

    Sakimoto, Kazuhiro

    2013-07-01

    Antiproton (p¯) collisions with hydrogen atoms, resulting in the hadronic process of particle-antiparticle annihilation and the atomic process of protonium (p¯p) formation (or p¯ capture), are investigated theoretically. As the collision energy decreases, the collision time required for the p¯ capture becomes necessarily longer. Then, there is the possibility that the p¯-p annihilation occurs significantly before the p¯ capture process completes. In such a case, one can no longer consider the annihilation decay separately from the p¯ capture process. The present study develops a rigorous unified quantum-mechanical treatment of the annihilation and p¯ capture processes. For this purpose, an R-matrix approach for atomic collisions is extended to have complex-valued R-matrix elements allowing for the hadronic annihilation. Detailed calculations are carried out at low collision energies ranging from 10-8 to 10-1 eV, and the annihilation and the p¯ capture (total and product-state selected) cross sections are reported. Consideration is given to the difference between the direct annihilation occurring during the collision and the annihilation of p¯p occurring after the p¯ capture. The present annihilation process is also compared with the annihilation in two-body p¯+p collisions.

  18. Surface effects on the mechanical elongation of AuCu nanowires: De-alloying and the formation of mixed suspended atomic chains

    SciTech Connect

    Lagos, M. J.; Autreto, P. A. S.; Galvao, D. S. Ugarte, D.; Bettini, J.; Sato, F.; Dantas, S. O.

    2015-03-07

    We report here an atomistic study of the mechanical deformation of Au{sub x}Cu{sub (1−x)} atomic-size wires (nanowires (NWs)) by means of high resolution transmission electron microscopy experiments. Molecular dynamics simulations were also carried out in order to obtain deeper insights on the dynamical properties of stretched NWs. The mechanical properties are significantly dependent on the chemical composition that evolves in time at the junction; some structures exhibit a remarkable de-alloying behavior. Also, our results represent the first experimental realization of mixed linear atomic chains (LACs) among transition and noble metals; in particular, surface energies induce chemical gradients on NW surfaces that can be exploited to control the relative LAC compositions (different number of gold and copper atoms). The implications of these results for nanocatalysis and spin transport of one-atom-thick metal wires are addressed.

  19. No Wires.

    ERIC Educational Resources Information Center

    DeLoughry, Thomas J.

    1995-01-01

    The University of California at Santa Cruz has completed a successful test of a wireless computer network that would enable students and professors to get on line from anywhere on campus. The network, linked by radio waves, could save millions of dollars in campus wiring costs and would better meet student and faculty information needs. (MSE)

  20. Creation and recovery of a W(111) single atom gas field ion source

    SciTech Connect

    Pitters, Jason L.; Urban, Radovan; Wolkow, Robert A.

    2012-04-21

    Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development.

  1. Log-normal diameter distribution of Pd-based metallic glass droplet and wire

    PubMed Central

    Yaginuma, S.; Nakajima, C.; Kaneko, N.; Yokoyama, Y.; Nakayama, K. S.

    2015-01-01

    We have studied the formation of Pd42.5Cu30Ni7.5P20 metallic glass droplets and wires in the gas atomization process. We demonstrate that the sizes of droplets and wires can be distinguished by the Ohnesorge number (Oh), which is the proportion of the spinnability to the capillary instability, and the diameter distributions follow a log-normal distribution function, implying cascade fragmentation. For droplets, the number significantly increases at Oh < 1 but the diameter gradually decreases. For wires, the number greatly increases at Oh > 1 while the diameter steadies below 400 nm. Further, the wire diameter is quadrupled at Oh = 16 due to the high viscosity which suppresses both capillary breakup and ligament elongation. PMID:26030090

  2. Coke Formation in a Zeolite Crystal During the Methanol-to-Hydrocarbons Reaction as Studied with Atom Probe Tomography.

    PubMed

    Schmidt, Joel E; Poplawsky, Jonathan D; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D A Matthijs; Meirer, Florian; Bare, Simon R; Weckhuysen, Bert M

    2016-09-01

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using (13) C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30-60 (13) C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. This nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation. PMID:27485276

  3. Coke formation in a zeolite crystal during the methanol-to-hydrocarbons reaction as studied with atom probe tomography

    DOE PAGESBeta

    Schmidt, Joel E.; Poplawsky, Jonathan D.; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D. A. Matthijs; Meirer, Florian; Bare, Simon R.; Weckhuysen, Bert M.

    2016-08-03

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using 13C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30–60 13C atoms. These clusters correlate with local increases in Brønsted acid sitemore » density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. Here, this nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.« less

  4. Preformed template fluctuations promote fibril formation: Insights from lattice and all-atom models

    SciTech Connect

    Kouza, Maksim Kolinski, Andrzej; Co, Nguyen Truong; Nguyen, Phuong H.; Li, Mai Suan

    2015-04-14

    Fibril formation resulting from protein misfolding and aggregation is a hallmark of several neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases. Despite the fact that the fibril formation process is very slow and thus poses a significant challenge for theoretical and experimental studies, a number of alternative pictures of molecular mechanisms of amyloid fibril formation have been recently proposed. What seems to be common for the majority of the proposed models is that fibril elongation involves the formation of pre-nucleus seeds prior to the creation of a critical nucleus. Once the size of the pre-nucleus seed reaches the critical nucleus size, its thermal fluctuations are expected to be small and the resulting nucleus provides a template for sequential (one-by-one) accommodation of added monomers. The effect of template fluctuations on fibril formation rates has not been explored either experimentally or theoretically so far. In this paper, we make the first attempt at solving this problem by two sets of simulations. To mimic small template fluctuations, in one set, monomers of the preformed template are kept fixed, while in the other set they are allowed to fluctuate. The kinetics of addition of a new peptide onto the template is explored using all-atom simulations with explicit water and the GROMOS96 43a1 force field and simple lattice models. Our result demonstrates that preformed template fluctuations can modulate protein aggregation rates and pathways. The association of a nascent monomer with the template obeys the kinetics partitioning mechanism where the intermediate state occurs in a fraction of routes to the protofibril. It was shown that template immobility greatly increases the time of incorporating a new peptide into the preformed template compared to the fluctuating template case. This observation has also been confirmed by simulation using lattice models and may be invoked to understand the role of template fluctuations in

  5. Preformed template fluctuations promote fibril formation: Insights from lattice and all-atom models

    NASA Astrophysics Data System (ADS)

    Kouza, Maksim; Co, Nguyen Truong; Nguyen, Phuong H.; Kolinski, Andrzej; Li, Mai Suan

    2015-04-01

    Fibril formation resulting from protein misfolding and aggregation is a hallmark of several neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Despite the fact that the fibril formation process is very slow and thus poses a significant challenge for theoretical and experimental studies, a number of alternative pictures of molecular mechanisms of amyloid fibril formation have been recently proposed. What seems to be common for the majority of the proposed models is that fibril elongation involves the formation of pre-nucleus seeds prior to the creation of a critical nucleus. Once the size of the pre-nucleus seed reaches the critical nucleus size, its thermal fluctuations are expected to be small and the resulting nucleus provides a template for sequential (one-by-one) accommodation of added monomers. The effect of template fluctuations on fibril formation rates has not been explored either experimentally or theoretically so far. In this paper, we make the first attempt at solving this problem by two sets of simulations. To mimic small template fluctuations, in one set, monomers of the preformed template are kept fixed, while in the other set they are allowed to fluctuate. The kinetics of addition of a new peptide onto the template is explored using all-atom simulations with explicit water and the GROMOS96 43a1 force field and simple lattice models. Our result demonstrates that preformed template fluctuations can modulate protein aggregation rates and pathways. The association of a nascent monomer with the template obeys the kinetics partitioning mechanism where the intermediate state occurs in a fraction of routes to the protofibril. It was shown that template immobility greatly increases the time of incorporating a new peptide into the preformed template compared to the fluctuating template case. This observation has also been confirmed by simulation using lattice models and may be invoked to understand the role of template fluctuations in

  6. Preformed template fluctuations promote fibril formation: insights from lattice and all-atom models.

    PubMed

    Kouza, Maksim; Co, Nguyen Truong; Nguyen, Phuong H; Kolinski, Andrzej; Li, Mai Suan

    2015-04-14

    Fibril formation resulting from protein misfolding and aggregation is a hallmark of several neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Despite the fact that the fibril formation process is very slow and thus poses a significant challenge for theoretical and experimental studies, a number of alternative pictures of molecular mechanisms of amyloid fibril formation have been recently proposed. What seems to be common for the majority of the proposed models is that fibril elongation involves the formation of pre-nucleus seeds prior to the creation of a critical nucleus. Once the size of the pre-nucleus seed reaches the critical nucleus size, its thermal fluctuations are expected to be small and the resulting nucleus provides a template for sequential (one-by-one) accommodation of added monomers. The effect of template fluctuations on fibril formation rates has not been explored either experimentally or theoretically so far. In this paper, we make the first attempt at solving this problem by two sets of simulations. To mimic small template fluctuations, in one set, monomers of the preformed template are kept fixed, while in the other set they are allowed to fluctuate. The kinetics of addition of a new peptide onto the template is explored using all-atom simulations with explicit water and the GROMOS96 43a1 force field and simple lattice models. Our result demonstrates that preformed template fluctuations can modulate protein aggregation rates and pathways. The association of a nascent monomer with the template obeys the kinetics partitioning mechanism where the intermediate state occurs in a fraction of routes to the protofibril. It was shown that template immobility greatly increases the time of incorporating a new peptide into the preformed template compared to the fluctuating template case. This observation has also been confirmed by simulation using lattice models and may be invoked to understand the role of template fluctuations in

  7. Effect of an Axial Wire on Conical Wire Array Z-Pinch Radiation

    SciTech Connect

    Presura, R.; Martinez, D.; Wright, S.; Plechaty, C.; Neff, S.; Wanex, L.; Ampleford, D. J.

    2009-01-21

    Adding a wire on the axis of wire arrays significantly affects the x-ray emission of the conical arrays, and much less that of the cylindrical ones. The radiation of the conical wire arrays increases with the thickness of the central wire, surpassing that of the equivalent cylindrical arrays. Significant energy is emitted early on, around the time of the conical shock formation, before the pinch stagnation.

  8. Secondary aerosol formation from the oxidation of biogenic hydrocarbons by chlorine atoms

    NASA Astrophysics Data System (ADS)

    Cai, Xuyi; Griffin, Robert J.

    2006-07-01

    The chlorine atom (Cl) is a potential oxidant of volatile organic compounds (VOCs) in the atmosphere and is hypothesized to lead to secondary organic aerosol (SOA) formation in coastal and industrialized areas. The purpose of this paper is to test this hypothesis and to quantify the SOA formation potentials of the common monoterpenes α-pinene, β-pinene, and d-limonene when oxidized by Cl in laboratory chamber experiments. Results indicate that the oxidation of these monoterpenes generates significant amounts of aerosol. The SOA yields of α-pinene, β-pinene, and d-limonene in this study are comparable to those when they are oxidized by ozone, by nitrate radical, and in photooxidation scenarios. For aerosol mass up to 30.0 μg m-3, their yields reach approximately 0.20, 0.20, and 0.30, respectively. For d-limonene, data indicate two yield curves that depend on the initial concentration ratio of Cl precursor to d-limonene. It is argued theoretically that multiple SOA yield curves may be common for VOCs, depending on the initial concentration ratio of oxidant to VOC. SOA formation from the three typical monoterpenes when oxidized by Cl in the marine boundary layer, coastal areas, and inland industrialized areas could be a source of organic aerosol in the early morning.

  9. An assessment of the formation of electrodeposited scales using scanning electron and atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Morizot, A. P.; Neville, A.; Taylor, J. D.

    2002-04-01

    The deposition of insoluble salts onto surfaces in process systems represents an important operational problem. Mineral scale formation (e.g. CaCO 3 and BaSO 4) can result from fluid streams becoming supersaturated when incompatible waters combine (e.g. in oil recovery) or can be formed when cathodic protection is applied and electrodeposition occurs. In this study, electrodeposition is studied on metal rotating disk electrodes (RDE) in artificial seawater under static conditions and under rotation at 400 rpm. Also, a Ca-free brine and a Mg-free brine of the same dissolved solids level were used in static tests. The focus of the study is the assessment of the electrochemical response of the system under potentiostatic control and correlation of the current versus time measurements to the characteristics of the scale determined via scanning electron microscopy and atomic force microscopy analysis.

  10. First analysis of radiative properties of moderate-atomic-number planar wire arrays on Zebra at UNR at higher current of 1.7 MA.

    SciTech Connect

    Keim, S. F.; Chuvatin, Alexander S.; Osborne, Glenn C.; Esaulov, Andrey A.; Presura, R.; Shrestha, I.; Kantsyrev, Victor Leonidovich; Shlyaptseva, V.; Coverdale, Christine Anne; Williamson, K. M.; Ouart, Nicholas D.; Astanovitsky, A. L.; Weller, M. E.; Safronova, Alla S.; LeGalloudec, B.

    2010-11-01

    The analysis of implosions of Cu and Ag planar wire array (PWA) loads recently performed at the enhanced 1.7 MA Zebra generator at UNR is presented. Experiments were performed with a Load Current Multiplier with a 1cm anode-cathode gap (twice shorter than in a standard 1 MA mode). A full diagnostic set included more than ten different beam-lines with the major focus on time-gated and time-integrated x-ray imaging and spectra, total radiation yields, and fast, filtered x-ray detector data. In particular, the experimental results for a double PWA load consisting of twelve 10 {micro}m Cu wires in each row (total mass M {approx} 175 {micro}g) and a much heavier single PWA load consisting of ten 30 {micro}m Ag wires (M {approx} 750 {micro}g) were analyzed using a set of theoretical codes. The effects of both a decreased a-c gap and an increased current on radiative properties of these loads are discussed.

  11. Formation of a Single Attosecond Pulse via Interaction of Resonant Radiation with a Strongly Perturbed Atomic Transition

    NASA Astrophysics Data System (ADS)

    Antonov, V. A.; Radeonychev, Y. V.; Kocharovskaya, Olga

    2013-05-01

    We propose a technique to form a single few-cycle attosecond pulse from vacuum ultraviolet or extreme ultraviolet radiation via resonant interaction with hydrogenlike atoms, irradiated by a high-intensity far-off-resonant laser field. The laser field strongly perturbs excited atomic energy levels via the Stark effect and ionizes atoms from the excited states. We show that an isolated attosecond pulse can be formed using either a short incident femtosecond pulse of the resonant radiation or a steep front edge of the laser field. We propose an experimental realization of a single subfemtosecond pulse formation at 121.6 nm in atomic hydrogen and a single sub-100 as pulse formation at 13.5 nm in Li2+ plasma.

  12. Threshold for formation of atom-photon bound states in a coherent photonic band-gap reservoir

    NASA Astrophysics Data System (ADS)

    Wu, Yunan; Wang, Jing; Zhang, Hanzhuang

    2016-05-01

    We study the threshold for the formation of atom-photon bound (APB) states from a two-level atom embedded in a coherent photonic band-gap (PBG) reservoir. It is shown that the embedded position of the atom plays an important role in the threshold. By varying the atomic embedded position, a part of formation range of APB states can be moved from inside to outside the band gap. The direct link between the steady-state entanglement and APB states is also investigated. We show that the values of entanglement between reservoir modes reflect the amount of bounded energy caused by APB states. The feasible experimental systems for verifying the above phenomena are discussed. Our results provide a clear clue on how to form and control APB states in PBG materials.

  13. Precision wire feeder for small diameter wire

    DOEpatents

    Brandon, E.D.; Hooper, F.M.; Reichenbach, M.L.

    1992-08-11

    A device for feeding small diameter wire having a diameter less than 0.04 mm (16 mil) to a welding station includes a driving wheel for controllably applying a non-deforming driving force to the wire to move the free end of the wire towards the welding station; and a tension device such as a torque motor for constantly applying a reverse force to the wire in opposition to the driving force to keep the wire taut. 1 figure.

  14. Precision wire feeder for small diameter wire

    DOEpatents

    Brandon, Eldon D.; Hooper, Frederick M.; Reichenbach, Marvin L.

    1992-01-01

    A device for feeding small diameter wire having a diameter less than 0.04 mm (16 mil) to a welding station includes a driving wheel for controllably applying a non-deforming driving force to the wire to move the free end of the wire towards the welding station; and a tension device such as a torque motor for constantly applying a reverse force to the wire in opposition to the driving force to keep the wire taut.

  15. Formation of hydrogen atom in 2s state in proton-sodium inelastic scattering

    NASA Astrophysics Data System (ADS)

    Sabbah, A. Elkilany

    2015-03-01

    The inelastic collision of protons with sodium atoms are treated for the first time within the framework of the coupled-static and frozen core approximations. The method is used for calculating partial and total cross-sections with the assumption that only two channels (elastic and hydrogen formation in 2s state) are open. In each case, the calculations are carried out for seven values of the total angular momentum ℓ(0 ≤ ℓ ≤ 6). The target is described using the Clementi Roetti wave functions within the framework of the one valence electron model. We use Lipmann-Swinger equation to solve the derived equations of the problem, then apply an iterative numerical method to obtain the code of computer to calculate iterative partial cross-sections. This can be done through calculating the reactance matrix at different values of considered energies to obtain the transition matrix that gives partial and total cross sections. The present results for total hydrogen (2s state) formation cross sections are in agreement with results of other available ones in wide range of incident energy.

  16. Atomic arrangement and the formation of partially coherent interfaces in the Ti-V-N system

    SciTech Connect

    Chen, J.K.; Purdy, G.R.; Weatherly, G.C.; Kroupa, A.

    1998-08-01

    The precipitation of (V,Ti) (bcc structure) in a (Ti,V)N (NaCl structure) matrix is considered in the current study. The lattice parameter ratio of this system, a{sub f}/a{sub b} = 1.34, is quite different from most previous studies (a{sub f}/a{sub b} {approximately} 1.26) and provides an opportunity to test recent models proposed for the formation of precipitate morphology and the interface structure. Like many other fcc:bcc precipitation systems, the Ti-V-N system involves an invariant line transformation strain. In this system, the invariant line is associated with a high-index orientation relationship (OR). The observed OR is in good agreement with a predicted relationship based upon a geometric matching criterion proposed by Ryan et al. The Burgers vectors for the interfacial defects were determined directly by making high-resolution transmission electron microscope (HRTEM) observations along three different directions. The observations confirm that the formation of the precipitate facets, the spacings of misfit dislocations, and the direction of interfacial defects all agree with atom-matching considerations.

  17. Atomic arrangement and the formation of partially coherent interfaces in the Ti-V-N system

    NASA Astrophysics Data System (ADS)

    Chen, J. K.; Purdy, G. R.; Weatherly, G. C.; Kroupa, A.

    1998-08-01

    The precipitation of (V,Ti) (bcc structure) in a (Ti,V)N (NaCl structure) matrix is considered in the current study. The lattice parameter ratio of this system, a f /a b =1.34, is quite different from most previous studies ( a f /a b ˜ 1.26) and provides an opportunity to test recent models proposed for the formation of precipitate morphology and the interface structure. Like many other fcc:bcc precipitation systems, the Ti-V-N system involves an invariant line transformation strain. In this system, the invariant line is associated with a high-index orientation relationship (OR). The observed OR is in good agreement with a predicted relationship based upon a geometric matching criterion proposed by Ryan et al. The Burgers vectors for the interfacial defects were determined directly by making high-resolution transmission electron microscope (HRTEM) observations along three different directions. The observations confirm that the formation of the precipitate facets, the spacings of misfit dislocations, and the direction of interfacial defects all agree with atom-matching considerations.

  18. NASA wiring for space applications program

    NASA Technical Reports Server (NTRS)

    Schulze, Norman

    1995-01-01

    An overview of the NASA Wiring for Space Applications Program and its relationship to NASA's space technology enterprise is given in viewgraph format. The mission of the space technology enterprise is to pioneer, with industry, the development and use of space technology to secure national economic competitiveness, promote industrial growth, and to support space missions. The objectives of the NASA Wiring for Space Applications Program is to improve the safety, performance, and reliability of wiring systems for space applications and to develop improved wiring technologies for NASA flight programs and commercial applications. Wiring system failures in space and commercial applications have shown the need for arc track resistant wiring constructions. A matrix of tests performed versus wiring constructions is presented. Preliminary data indicate the performance of the Tensolite and Filotex hybrid constructions are the best of the various candidates.

  19. Structure of the alkali-metal-atom + strontium molecular ions: Towards photoassociation and formation of cold molecular ions

    SciTech Connect

    Aymar, M.; Dulieu, O.; Guerout, R.

    2011-08-14

    The potential energy curves, permanent and transition dipole moments, and the static dipolar polarizability, of molecular ions composed of one alkali-metal atom and a strontium ion are determined with a quantum chemistry approach. The molecular ions are treated as effective two-electron systems and are treated using effective core potentials including core polarization, large gaussian basis sets, and full configuration interaction. In the perspective of upcoming experiments aiming at merging cold atom and cold ion traps, possible paths for radiative charge exchange, photoassociation of a cold lithium or rubidium atom and a strontium ion are discussed, as well as the formation of stable molecular ions.

  20. Morphological evolution of InAs/InP quantum wires through aberration-corrected scanning transmission electron microscopy.

    PubMed

    Sales, D L; Varela, M; Pennycook, S J; Galindo, P L; González, L; González, Y; Fuster, D; Molina, S I

    2010-08-13

    Evolution of the size, shape and composition of self-assembled InAs/InP quantum wires through the Stranski-Krastanov transition has been determined by aberration-corrected Z-contrast imaging. High resolution compositional maps of the wires in the initial, intermediate and final formation stages are presented. (001) is the main facet at their very initial stage of formation, which is gradually reduced in favour of [114] or [118], ending with the formation of mature quantum wires with {114} facets. Significant changes in wire dimensions are measured when varying slightly the amount of InAs deposited. These results are used as input parameters to build three-dimensional models that allow calculation of the strain energy during the quantum wire formation process. The observed morphological evolution is explained in terms of the calculated elastic energy changes at the growth front. Regions of the wetting layer close to the nanostructure perimeters have higher strain energy, causing migration of As atoms towards the quantum wire terraces, where the structure is partially relaxed; the thickness of the wetting layer is reduced in these zones and the island height increases until the (001) facet is removed. PMID:20647625

  1. Wire diameter dependence in the catalytic decomposition of H2

    NASA Astrophysics Data System (ADS)

    Umemoto, Hironobu

    2014-01-01

    Jansen et al. have demonstrated that the dissociaiton rate of H2 molecules on hot wire surfaces, normalized per unit surface area, depends on the wire diameter based on the electrical power consumption measurements [J. Appl. Phys. 66, 5749 (1989)]. Mathematical modeling calculations have also been presented to support their experimental results. In the present paper, it is shown that such a wire diameter dependence cannot be observed and that the H-atom density normalized by the wire surface area depends little on the wire diameter. Modeling calculations also show that the wire diameter dependence of the dissociation rate cannot be expected under typical decomposition conditions.

  2. On the interplay between relaxation, defect formation, and atomic Sn distribution in Ge{sub (1−x)}Sn{sub (x)} unraveled with atom probe tomography

    SciTech Connect

    Kumar, A. Bran, J. Melkonyan, D. Shimura, Y. Vandervorst, W.; Demeulemeester, J. Bogdanowicz, J. Fleischmann, C. Loo, R.; Gencarelli, F. Wang, W.

    2015-07-14

    Ge{sub (1−x)}Sn{sub (x)} has received a lot of interest for opto-electronic applications and for strain engineering in advanced complementary-metal-oxide-semiconductor technology, because it enables engineering of the band gap and inducing strain in the alloy. To target a reliable technology for mass application in microelectronic devices, the physical problem to be addressed is to unravel the complex relationship between strain relaxation (as induced by the growth of large layer thicknesses or a thermal anneal) and defect formation, and/or stable Sn-cluster formation. In this paper, we study the onset of Sn-cluster formation and its link to strain relaxation using Atom Probe Tomography (APT). To this end, we also propose a modification of the core-linkage [Stephenson et al., Microsc. Microanal. 13, 448 (2007)] cluster analysis method, to overcome the challenges of limited detection efficiency and lateral resolution of APT, and the quantitative assessment for very small clusters (<40 atoms) embedded in a random distribution of Sn-atoms. We concluded that the main relaxation mechanism for these layers is defect generation (misfit dislocations, threading dislocations, etc.), irrespective of the cause (thickness of layer or thermal anneal) of relaxation and is independent of the cluster formation. The low thermodynamic solubility limit of Sn in Ge seems to be the driving force for Sn-cluster formation. Finally, we also discuss the spatial distribution of Sn in clusters and relate them to the theoretically predicted stable Sn clusters [Ventura et al., Phys. Rev. B 79, 155202 (2009)].

  3. Secondary Aerosol Formation from Oxidation of Aromatics Hydrocarbons by Cl atoms

    NASA Astrophysics Data System (ADS)

    Cai, X.; Griffin, R.

    2006-12-01

    Aerosol Formation From the Oxidation of Aromatic Hydrocarbons by Chlorine Atmospheric secondary organic aerosol (SOA) affects regional and global air quality. The formation mechanisms of SOA via the oxidation of volatile organic compounds by hydroxyl radicals, ozone, and nitrate radicals have been studied intensively during the last decade. Chlorine atoms (Cl) also have been hypothesized to be effective oxidants in marine and industrially influenced areas. Recent work by the authors has indicated that significant amounts of SOA are formed from the oxidation of monoterpenes by Cl. Aromatic hydrocarbons are important for generation of both SOA and ozone in urban areas because of their large emission rates and high reactivity. The goal of this work was to quantify the SOA formation potentials of two representative aromatic hydrocarbons through laboratory chamber experiments in which oxidation was initiated by Cl. The system constructed for this study includes an experimental chamber, a gas chromatograph for quantification of aromatic mixing ratios, a Scanning Mobility Particle Spectrometer to measure SOA size distributions, a zero air generator, and an illuminating system. The model aromatic hydrocarbons chosen for this study are toluene and m-xylene. Aerosol yields are estimated based on measured aerosol volume concentration, the concentration of consumed hydrocarbon, and estimation of wall loss of the newly formed aerosol. Toluene and m-xylene exhibit similar SOA yields from the oxidation initiated by Cl. The toluene SOA yield from Cl-initiated oxidation, however, depends on the ratio between the mixing ratios of the initial chlorine source and toluene in the chamber. For toluene experiments with higher such ratios, SOA yields vary from 0.05 to 0.079 for generated aerosol ranging from 4.2 to12.0 micrograms per cubic meter. In the lower ratio experiments, SOA yields are from 0.033 to 0.064, corresponding to generated aerosol from 3.0 to 11.0 micrograms per cubic

  4. Thioether bond formation by SPASM domain radical SAM enzymes: Cα H-atom abstraction in subtilosin A biosynthesis.

    PubMed

    Benjdia, Alhosna; Guillot, Alain; Lefranc, Benjamin; Vaudry, Hubert; Leprince, Jérôme; Berteau, Olivier

    2016-05-01

    AlbA is a radical SAM enzyme catalyzing the formation of three unusual thioether bonds in the antibiotic subtilosin A. We demonstrate here that AlbA catalyzes direct Cα H-atom abstraction and likely contains three essential [4Fe-4S] centers. This leads us to propose novel mechanistic perspectives for thioether bond catalysis by radical SAM enzymes. PMID:27087315

  5. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles

    PubMed Central

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B.; Chen, Wenli

    2015-01-01

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of −3.0 ± 0.4 nN and −330 ± 43 aJ (10−18 J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions. PMID:26585552

  6. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles.

    PubMed

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B; Chen, Wenli

    2015-01-01

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of -3.0 ± 0.4 nN and -330 ± 43 aJ (10(-18) J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions. PMID:26585552

  7. Pregalactic Black Hole Formation with an Atomic Hydrogen Equation of State

    NASA Astrophysics Data System (ADS)

    Spaans, Marco; Silk, Joseph

    2006-12-01

    The polytropic equation of state of an atomic hydrogen gas is examined for primordial halos with baryonic masses of Mh~107-109 Msolar. For roughly isothermal collapse around 104 K, we find that line trapping of Lyα (H I and He II) photons causes the polytropic exponent to stiffen to values significantly above unity. Under the assumptions of zero H2 abundance and very modest pollution by metals (<10-4 solar), fragmentation is likely to be inhibited for such an equation of state. We argue on purely thermodynamic grounds that a single black hole of ~(0.02-0.003)Mh can form at the center of a halo for z=10-20 when the free-fall time is less than the time needed for a resonantly scattered Lyα photon to escape from the halo. The absence of H2 follows naturally from the high temperatures, >104 K, that are attained when Lyα photons are trapped in the dense and massive halos that we consider. An H2-dissociating UV background is needed if positive feedback effects on H2 formation from X-rays occur. The black hole-to-baryon mass fraction is suggestively close to what is required for these intermediate-mass black holes, of mass MBH~104-106 Msolar, to act as seeds for forming the supermassive black holes of mass ~0.001Mspheroid found in galaxies today.

  8. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles

    NASA Astrophysics Data System (ADS)

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B.; Chen, Wenli

    2015-11-01

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of -3.0 ± 0.4 nN and -330 ± 43 aJ (10-18 J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions.

  9. Inhibitive formation of nanocavities by introduction of Si atoms in Ge nanocrystals produced by ion implantation

    SciTech Connect

    Cai, R. S.; Shang, L.; Liu, X. H.; Zhang, Y. J.; Wang, Y. Q. E-mail: barba@emt.inrs.ca; Ross, G. G.; Barba, D. E-mail: barba@emt.inrs.ca

    2014-05-28

    Germanium nanocrystals (Ge-nc) were successfully synthesized by co-implantation of Si and Ge ions into a SiO{sub 2} film thermally grown on (100) Si substrate and fused silica (pure SiO{sub 2}), respectively, followed by subsequent annealing at 1150 °C for 1 h. Transmission electron microscopy (TEM) examinations show that nanocavities only exist in the fused silica sample but not in the SiO{sub 2} film on a Si substrate. From the analysis of the high-resolution TEM images and electron energy-loss spectroscopy spectra, it is revealed that the absence of nanocavities in the SiO{sub 2} film/Si substrate is attributed to the presence of Si atoms inside the formed Ge-nc. Because the energy of Si-Ge bonds (301 kJ·mol{sup −1}) are greater than that of Ge-Ge bonds (264 kJ·mol{sup −1}), the introduction of the Si-Ge bonds inside the Ge-nc can inhibit the diffusion of Ge from the Ge-nc during the annealing process. However, for the fused silica sample, no crystalline Si-Ge bonds are detected within the Ge-nc, where strong Ge outdiffusion effects produce a great number of nanocavities. Our results can shed light on the formation mechanism of nanocavities and provide a good way to avoid nanocavities during the process of ion implantation.

  10. Three-wire magnetic trap for direct forced evaporative cooling

    NASA Astrophysics Data System (ADS)

    Du, Shengwang; Oh, Eun

    2009-01-01

    We propose a simple three-wire-based magnetic trap potential for direct forced evaporative cooling of neutral atoms without using induced spin-flip technologies. We have devised a method for controlling the trap depth without sacrificing its frequencies by only varying wire currents and external magnetic fields. By having multiples of these wires on different levels integrated into an atom chip, it is possible to attain Bose-Einstein condensation without the conventional forced evaporation technique.

  11. EXPERIMENTAL EVIDENCE FOR THE FORMATION OF HIGHLY SUPERHYDROGENATED POLYCYCLIC AROMATIC HYDROCARBONS THROUGH H ATOM ADDITION AND THEIR CATALYTIC ROLE IN H{sub 2} FORMATION

    SciTech Connect

    Thrower, J. D.; Jorgensen, B.; Friis, E. E.; Baouche, S.; Luntz, A. C.; Andersen, M.; Hammer, B.; Hornekaer, L.; Mennella, V.

    2012-06-10

    Mass spectrometry measurements show the formation of highly superhydrogenated derivatives of the polycyclic aromatic hydrocarbon molecule coronene through H atom addition reactions. The observed product mass distribution provides evidence also for abstraction reactions resulting in H{sub 2} formation, in agreement with recent IR measurements. Complementary density functional theory calculations confirm the stability of the observed superhydrogenated species toward spontaneous H and H{sub 2} loss indicating that abstraction reactions may be the dominant route to H{sub 2} formation involving neutral polycyclic aromatic hydrocarbons (PAHs). The results indicate that highly superhydrogenated PAHs could well be formed and could act as efficient catalysts for H{sub 2} formation in the interstellar medium in low UV flux regions.

  12. In situ studies on controlling an atomically-accurate formation process of gold nanoclusters

    NASA Astrophysics Data System (ADS)

    Yang, Lina; Cheng, Hao; Jiang, Yong; Huang, Ting; Bao, Jie; Sun, Zhihu; Jiang, Zheng; Ma, Jingyuan; Sun, Fanfei; Liu, Qinghua; Yao, Tao; Deng, Huijuan; Wang, Shuxin; Zhu, Manzhou; Wei, Shiqiang

    2015-08-01

    Knowledge of the molecular formation mechanism of metal nanoclusters is essential for developing chemistry for accurate control over their synthesis. Herein, the ``top-down'' synthetic process of monodisperse Au13 nanoclusters via HCl etching of polydisperse Aun clusters (15 <= n <= 65) is traced by a combination of in situ X-ray/UV-vis absorption spectroscopy and time-dependent mass spectrometry. It is revealed experimentally that the HCl-induced synthesis of Au13 is achieved by accurately controlling the etching process with two distinctive steps, in sharp contrast to the traditional thiol-etching mechanism through release of the Au(i) complex. The first step involves the direct fragmentation of the initial larger Aun clusters into metastable intermediate Au8-Au13 smaller clusters. This is a critical step, which allows for the secondary size-growth step of the intermediates toward the atomically monodisperse Au13 clusters via incorporating the reactive Au(i)-Cl species in the solution. Such a secondary-growth pathway is further confirmed by the successful growth of Au13 through reaction of isolated Au11 clusters with AuClPPh3 in the HCl environment. This work addresses the importance of reaction intermediates in guiding the way towards controllable synthesis of metal nanoclusters.Knowledge of the molecular formation mechanism of metal nanoclusters is essential for developing chemistry for accurate control over their synthesis. Herein, the ``top-down'' synthetic process of monodisperse Au13 nanoclusters via HCl etching of polydisperse Aun clusters (15 <= n <= 65) is traced by a combination of in situ X-ray/UV-vis absorption spectroscopy and time-dependent mass spectrometry. It is revealed experimentally that the HCl-induced synthesis of Au13 is achieved by accurately controlling the etching process with two distinctive steps, in sharp contrast to the traditional thiol-etching mechanism through release of the Au(i) complex. The first step involves the direct

  13. Influence of supersaturation and spontaneous catalyst formation on the growth of PbS wires: toward a unified understanding of growth modes.

    PubMed

    Nichols, Patricia L; Sun, Minghua; Ning, Cun-Zheng

    2011-11-22

    High quality stoichiometric lead sulfide (PbS) wires were synthesized by a simple chemical vapor deposition (CVD) process using pure PbS powder as the material source. Growth mechanisms were systematically investigated under various growth conditions, with three modes of growth identified: direct vapor-liquid-solid (VLS) wire growth nucleating from the substrate surface, bulk PbS crystallites by vapor-solid (VS) deposition, and subsequent VLS growth nucleating on top of the bulk deposition through spontaneously formed catalyst particles. Furthermore, we found that these growth modes can be organized in terms of different levels of supersaturation, with VS bulk deposition dominating at high supersaturation and VLS wire growth on the substrate dominating at low supersaturation. At intermediate supersaturation, the bulk VS deposition can form larger crystallites with domains of similarly oriented wires extending from the flat facets. Both predeposited catalysts and spontaneously formed Pb particles were observed as nucleation catalysts, and their interplay leads to various interesting growth scenarios such as reversely tapered growth with increasing diameter. The VLS growth mechanism was confirmed by the presence of Pb-rich caps revealed in an elaborate cross-sectional transmission electron microscopy (TEM) experiment after focused ion beam milling in a modified lift-out procedure. Temperature-dependent photoluminescence (PL) of PbS wires was performed in the mid-infrared wavelength range for the first time, demonstrating strong light emission from band edge, blue-shifted with increasing temperature. The high optical quality of PbS wires may lead to important applications in mid-infrared photonics. The substrate growth temperature as low as 400 °C allows for silicon-compatible processing for integrated optoelectronics applications. PMID:21981350

  14. Hypernuclei formation probability as a function of the atomic mass number A

    NASA Astrophysics Data System (ADS)

    Bonomi, G.; Finuda Collaboration

    2012-09-01

    The creation of a hypernucleus [2], that is a nucleus in which a nucleon is replaced by an hyperon, requires the injection of strangeness into the nucleus. This is possible in different ways [3], mainly using π+ or K- beams on nuclear targets; recently, also electron beams have been used. The FINUDA experiment at the DAΦNE Φ factory of the INFN "Laboratori Nazionali di Frascati" produced Λ-hypernuclei by stopping, in thin nuclear targets (0.1-0.2 g/cm2), the negative kaons originating from the Φ decay through the strangeness-exchange reaction Kstop-+AZ→A/ΛZ+π-, where AZ indicates the target nucleus and A/ΛZ the Λ hypernucleus in which a Λ particle replaced a neutron. FINUDA, an unconventional and innovative apparatus, allowed the positioning of 8 different target modules around the interaction region. In this way different targets could be studied contemporaneously, with the same apparatus and with the same analysis technique, allowing for a direct comparison between different nuclei. In particular FINUDA could study the production of Λ-hypernuclei on 7Li, 9Be, 12C, 13C and 16O targets. Both the Λ binding energy and the hypernuclei production probabilities have been measured [1]. The new measurements on 7/ΛLi, 9/ΛBe, 13/ΛC and 16/ΛO, along with previous measurements on 12/ΛC, allowed for a meaningful study of the formation of p-shell hypernuclei from the two-body capture of K- at rest, giving for the first time the possibility of disentangling the effects due to atomic wave-function of the captured K- from those due to the pion optical nuclear potential and from those due to the specific hypernuclear states [4].

  15. Thermodynamic properties of arsenic compounds and the heat of formation of the As atom from high level electronic structure calculations.

    PubMed

    Feller, David; Vasiliu, Monica; Grant, Daniel J; Dixon, David A

    2011-12-29

    Structures, vibrational frequencies, atomization energies at 0 K, and heats of formation at 0 and 298 K are predicted for the compounds As(2), AsH, AsH(2), AsH(3), AsF, AsF(2), and AsF(3) from frozen core coupled cluster theory calculations performed with large correlation consistent basis sets, up through augmented sextuple zeta quality. The coupled cluster calculations involved up through quadruple excitations. For As(2) and the hydrides, it was also possible to examine the impact of full configuration interaction on some of the properties. In addition, adjustments were incorporated to account for extrapolation to the frozen core complete basis set limit, core/valence correlation, scalar relativistic effects, the diagonal Born-Oppenheimer correction, and atomic spin orbit corrections. Based on our best theoretical D(0)(As(2)) and the experimental heat of formation of As(2), we propose a revised 0 K arsenic atomic heat of formation of 68.86 ± 0.8 kcal/mol. While generally good agreement was found between theory and experiment, the heat of formation of AsF(3) was an exception. Our best estimate is more than 7 kcal/mol more negative than the single available experimental value, which argues for a re-examination of that measurement. PMID:22091635

  16. Windows: Life after Wire.

    ERIC Educational Resources Information Center

    Razwick, Jerry

    2003-01-01

    Although wired glass is extremely common in school buildings, the International Building Code adopted new standards that eliminate the use of traditional wired glass in K-12 schools, daycare centers, and athletic facilities. Wired glass breaks easily, and the wires can cause significant injuries by forming dangerous snags when the glass breaks.…

  17. Torsional Deformations in Subnanometer MoS Interconnecting Wires.

    PubMed

    Koh, Ai Leen; Wang, Shanshan; Ataca, Can; Grossman, Jeffrey C; Sinclair, Robert; Warner, Jamie H

    2016-02-10

    We use aberration-corrected transmission electron microscopy to track the real time atomic level torsional dynamics of subnanometer wires of MoS interconnecting monolayer regions of MoS2. An in situ heating holder is used inside the transmission electron microscope to raise the temperature of the sample to 400 °C to increase crystallization rates of the wires and reduce contamination effects. Frequent rotational twisting of the MoS wire is captured, demonstrating elastic torsional deformation of the MoS wires. We show that torsional rotations of the crystal structure of the MoS wires depend upon the specific atomic structure of the anchored sections of the suspended wire and the number of unit cells that make up the wire length. Elastic torsional flexibility of the MoS wires is revealed to help their self-adapting connectivity during the structural changes. Plastic torsional deformation is also seen for MoS wires that contain defects in their crystal structure, which produce small scale rotational disorder within the wires. Upon removal of the defects, the wire returns back to pristine form. These results provide detailed insights into how the atomic structure of the anchoring site significantly influences the nanowire configurations relative to the monolayered MoS2. PMID:26785319

  18. Preparation and characterization of Sc doped MgB2 wires

    NASA Astrophysics Data System (ADS)

    Grivel, J.-C.; Burdusel, M.

    2016-09-01

    The in-situ technique was used to manufacture scandium (Sc) doped MgB2 wires in a composite Cu-Nb sheath. After reaction at 700 °C, at most 1 at.% Mg was replaced by Sc in the MgB2 phase, without significant influence on its superconducting transition temperature. For higher Sc concentrations in the nominal composition, the formation of Sc-rich impurity phases was evidenced by SEM/EDS observations. The critical current density and accommodation field of the wires are weakly dependant on the Sc content. It is believed that these effects are related more to modifications of the thermal behaviour of the precursor powders revealed by DTA measurements than to actual doping. The best performance was obtained in a wire with Mg:Sc = 0.995_0.005 atomic ratio.

  19. Crystal structure control in Au-free self-seeded InSb wire growth.

    PubMed

    Mandl, Bernhard; Dick, Kimberly A; Kriegner, Dominik; Keplinger, Mario; Bauer, Günther; Stangl, Julian; Deppert, Knut

    2011-04-01

    In this work we demonstrate experimentally the dependence of InSb crystal structure on the ratio of Sb to In atoms at the growth front. Epitaxial InSb wires are grown by a self-seeded particle assisted growth technique on several different III-V substrates. Detailed investigations of growth parameters and post-growth energy dispersive x-ray spectroscopy indicate that the seed particles initially consist of In and incorporate up to 20 at.% Sb during growth. By applying this technique we demonstrate the formation of zinc-blende, 4H and wurtzite structure in the InSb wires (identified by transmission electron microscopy and synchrotron x-ray diffraction), and correlate this sequential change in crystal structure to the increasing Sb/In ratio at the particle-wire interface. The low ionicity of InSb and the large diameter of the wire structures studied in this work are entirely outside the parameters for which polytype formation is predicted by current models of particle seeded wire growth, suggesting that the V/III ratio at the interface determines crystal structure in a manner well beyond current understanding. These results therefore provide important insight into the relationship between the particle composition and the crystal structure, and demonstrate the potential to selectively tune the crystal structure in other III-V compound materials as well. PMID:21346304

  20. Unusual Conductance in Cumulene Molecular Wires

    NASA Astrophysics Data System (ADS)

    Prasongkit, Jariyanee; Grigoriev, Anton; Wendin, Göran; Ahuja, Rajeev

    2009-03-01

    We report current-voltage curves and conductance of cumulene molecular wire suspended between Au(111) surfaces via thiolate bonds with full self-consistent ab initio calculation under external bias. The conductance of cumulene wires shows oscillatory behavior depending on the number of carbon atoms. Among all conjugated oligomers, we find that odd-number cumulene wires yield the highest conductance and present ballistic-like transport behavior. The reason has been traced to two factors: high density of state at the Fermi level, and the alignment of molecular orbital closed to Fermi level. Since the conductance depends weakly on applied bias, and the current voltage characteristic is linear under bias region -0.9 to 0.9 V, odd-number cumulene wire is a possible candidate as a near- perfect, ballistic one-dimensional molecular wire.

  1. Stretched Wire Mechanics

    SciTech Connect

    Bowden, Gordon; /SLAC

    2005-09-06

    Stretched wires are beginning to play an important role in the alignment of accelerators and synchrotron light sources. Stretched wires are proposed for the alignment of the 130 meter long LCLS undulator. Wire position technology has reached sub-micron resolution yet analyses of perturbations to wire straightness are hard to find. This paper considers possible deviations of stretched wire from the simple 2-dimensional catenary form.

  2. On the formation of tropical rings of atomic halogens: Causes and implications

    NASA Astrophysics Data System (ADS)

    Saiz-Lopez, Alfonso; Fernandez, Rafael P.

    2016-03-01

    Halogens produced by ocean biological and photochemical processes reach the tropical tropopause layer (TTL), where cold temperatures and the prevailing low ozone abundances favor the diurnal photochemical enhancement of halogen atoms. Under these conditions atomic bromine and iodine are modeled to be the dominant inorganic halogen species in the sunlit TTL, surpassing the abundance of the commonly targeted IO and BrO radicals. We suggest that due to the rapid photochemical equilibrium between halogen oxides and halogen atoms a natural atmospheric phenomenon evolves, which we have collectively termed "tropical rings of atomic halogens." We describe the main causes controlling the modeled appearance and variability of these superposed rings of bare bromine and iodine atoms that circle the tropics following the Sun. Some potential implications for atmospheric oxidizing capacity are also explored. Our model results suggest that if experimentally confirmed, the extent and intensity of the halogen rings would directly respond to changes in oceanic halocarbon emissions, their atmospheric transport, and photochemistry.

  3. Formation of Triplet Positron-helium Bound State by Stripping of Positronium Atoms in Collision with Ground State Helium

    NASA Technical Reports Server (NTRS)

    Drachman, Richard J.

    2006-01-01

    Formation of triplet positron-helium bound state by stripping of positronium atoms in collision with ground state helium JOSEPH DI RlENZI, College of Notre Dame of Maryland, RICHARD J. DRACHMAN, NASA/Goddard Space Flight Center - The system consisting of a positron and a helium atom in the triplet state e(+)He(S-3)(sup e) was conjectured long ago to be stable [1]. Its stability has recently been established rigorously [2], and the values of the energies of dissociation into the ground states of Ps and He(+) have also been reported [3] and [4]. We have evaluated the cross-section for this system formed by radiative attachment of a positron in triplet He state and found it to be small [5]. The mechanism of production suggested here should result in a larger cross-section (of atomic size) which we are determining using the Born approximation with simplified initial and final wave functions.

  4. Formation of two-dimensional nonspreading atomic wave packets in the field of two standing light waves

    SciTech Connect

    Efremov, M A; Fedorov, Mikhail V; Petropavlovsky, S V; Yakovlev, V P; Schleich, Wolfgang P

    2005-08-31

    The formation of two-dimensional nonspreading atomic wave packets produced in the interaction of a beam of two-level atoms with two standing light waves polarised in the same plane is considered. The mechanism providing a dispersionless particle dynamics is the balance of two processes: a rapid decay of the atomic wave function away from the field nodes due to spontaneous transitions to nonresonance states and the quantum broadening of the wave packets formed in the close vicinity of field nodes. Coordinate-dependent amplitudes and phases of the two-dimensional wave packets were found for the j{sub g}=0 {r_reversible} j{sub e}=1 transition. (fourth seminar to the memory of d.n. klyshko)

  5. Comparison of DC and AC Transport in 1.5-7.5 nm Oligophenylene Imine Molecular Wires across Two Junction Platforms: Eutectic Ga-In versus Conducting Probe Atomic Force Microscope Junctions.

    PubMed

    Sangeeth, C S Suchand; Demissie, Abel T; Yuan, Li; Wang, Tao; Frisbie, C Daniel; Nijhuis, Christian A

    2016-06-15

    We have utilized DC and AC transport measurements to measure the resistance and capacitance of thin films of conjugated oligophenyleneimine (OPI) molecules ranging from 1.5 to 7.5 nm in length. These films were synthesized on Au surfaces utilizing the imine condensation chemistry between terephthalaldehyde and 1,4-benzenediamine. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy yielded molecular tilt angles of 33-43°. To probe DC and AC transport, we employed Au-S-OPI//GaOx/EGaIn junctions having contact areas of 9.6 × 10(2) μm(2) (10(9) nm(2)) and compared to previously reported DC results on the same OPI system obtained using Au-S-OPI//Au conducting probe atomic force microscopy (CP-AFM) junctions with 50 nm(2) areas. We found that intensive observables agreed very well across the two junction platforms. Specifically, the EGaIn-based junctions showed: (i) a crossover from tunneling to hopping transport at molecular lengths near 4 nm; (ii) activated transport for wires >4 nm in length with an activation energy of 0.245 ± 0.008 eV for OPI-7; (iii) exponential dependence of conductance with molecular length with a decay constant β = 2.84 ± 0.18 nm(-1) (DC) and 2.92 ± 0.13 nm(-1) (AC) in the tunneling regime, and an apparent β = 1.01 ± 0.08 nm(-1) (DC) and 0.99 ± 0.11 nm(-1) (AC) in the hopping regime; (iv) previously unreported dielectric constant of 4.3 ± 0.2 along the OPI wires. However, the absolute resistances of Au-S-OPI//GaOx/EGaIn junctions were approximately 100 times higher than the corresponding CP-AFM junctions due to differences in metal-molecule contact resistances between the two platforms. PMID:27172452

  6. The Star Formation Rate Efficiency of Atomic-dominated Hydrogen Gas from z~1 to z~3

    NASA Astrophysics Data System (ADS)

    Rafelski, Marc; Gardner, Jonathan P.; Teplitz, Harry I.; Neeleman, Marcel; Fumagalli, Michele; UVUDF

    2016-01-01

    Current observational evidence suggests that the star formation rate (SFR) efficiency of neutral atomic hydrogen gas measured in Damped Lyman-alpha System (DLAs) at z~3 is a factor of 10 lower than predicted by the Kennicutt-Schmidt relation. To understand the origin of this deficit, we measure the SFR efficiency of atomic gas at z~1, z~2, and z~3 to investigate possible coevolution with galactic properties. We use new robust photometric redshifts to create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies' outskirts. Contrary to simulations and models that predict a reduced SFR efficiency with decreasing metallicity and thus with increasing redshift, we find no significant evolution in the SFR efficiency. We conclude that the reduced SFR efficiency is driven by the low molecular content of this atomic-dominated phase, with metallicity playing a second order effect in regulating the conversion between atomic and molecular gas. This interpretation is supported by the similarity between the observed SFR efficiency and that observed in local atomic-dominated gas, such as in the outskirts of local spiral galaxies or local dwarf galaxies.

  7. THE FORMATION OF IRIS DIAGNOSTICS. I. A QUINTESSENTIAL MODEL ATOM OF Mg II AND GENERAL FORMATION PROPERTIES OF THE Mg II h and k LINES

    SciTech Connect

    Leenaarts, J.; Pereira, T. M. D.; Carlsson, M.; De Pontieu, B.; Uitenbroek, H. E-mail: tiago.pereira@astro.uio.no E-mail: bdp@lmsal.com

    2013-08-01

    NASA's Interface Region Imaging Spectrograph (IRIS) space mission will study how the solar atmosphere is energized. IRIS contains an imaging spectrograph that covers the Mg II h and k lines as well as a slit-jaw imager centered at Mg II k. Understanding the observations will require forward modeling of Mg II h and k line formation from three-dimensional (3D) radiation-MHD models. This paper is the first in a series where we undertake this forward modeling. We discuss the atomic physics pertinent to h and k line formation, present a quintessential model atom that can be used in radiative transfer computations, and discuss the effect of partial redistribution (PRD) and 3D radiative transfer on the emergent line profiles. We conclude that Mg II h and k can be modeled accurately with a four-level plus continuum Mg II model atom. Ideally radiative transfer computations should be done in 3D including PRD effects. In practice this is currently not possible. A reasonable compromise is to use one-dimensional PRD computations to model the line profile up to and including the central emission peaks, and use 3D transfer assuming complete redistribution to model the central depression.

  8. Formation of bimetallic clusters in superfluid helium nanodroplets analysed by atomic resolution electron tomography

    PubMed Central

    Haberfehlner, Georg; Thaler, Philipp; Knez, Daniel; Volk, Alexander; Hofer, Ferdinand; Ernst, Wolfgang E.; Kothleitner, Gerald

    2015-01-01

    Structure, shape and composition are the basic parameters responsible for properties of nanoscale materials, distinguishing them from their bulk counterparts. To reveal these in three dimensions at the nanoscale, electron tomography is a powerful tool. Advancing electron tomography to atomic resolution in an aberration-corrected transmission electron microscope remains challenging and has been demonstrated only a few times using strong constraints or extensive filtering. Here we demonstrate atomic resolution electron tomography on silver/gold core/shell nanoclusters grown in superfluid helium nanodroplets. We reveal morphology and composition of a cluster identifying gold- and silver-rich regions in three dimensions and we estimate atomic positions without using any prior information and with minimal filtering. The ability to get full three-dimensional information down to the atomic scale allows understanding the growth and deposition process of the nanoclusters and demonstrates an approach that may be generally applicable to all types of nanoscale materials. PMID:26508471

  9. Concealed wire tracing apparatus

    DOEpatents

    Kronberg, James W.

    1994-01-01

    An apparatus and method that combines a signal generator and a passive signal receiver to detect and record the path of partially or completely concealed electrical wiring without disturbing the concealing surface. The signal generator applies a series of electrical pulses to the selected wiring of interest. The applied pulses create a magnetic field about the wiring that can be detected by a coil contained within the signal receiver. An audible output connected to the receiver and driven by the coil reflects the receivers position with respect to the wiring. The receivers audible signal is strongest when the receiver is directly above the wiring and the long axis of the receivers coil is parallel to the wiring. A marking means is mounted on the receiver to mark the location of the wiring as the receiver is directed over the wiring's concealing surface. Numerous marks made on various locations of the concealing surface will trace the path of the wiring of interest.

  10. Wire Test Grip Fixture

    NASA Technical Reports Server (NTRS)

    Burke, Christopher S.

    2011-01-01

    Wire-testing issues, such as the gripping strains imposed on the wire, play a critical role in obtaining clean data. In a standard test frame fitted with flat wedge grips, the gripping action alone creates stresses on the wire specimen that cause the wire to fail at the grip location. A new test frame, which is outfitted with a vacuum chamber, negated the use of any conventional commercially available wire test fixtures, as only 7 in. (17.8 cm) existed between the grip faces. An innovative grip fixture was designed to test thin gauge wire for a variety of applications in an existing Instron test frame outfitted with a vacuum chamber.

  11. Routes to formation of highly excited neutral atoms in the break-up of strongly driven hydrogen molecule

    NASA Astrophysics Data System (ADS)

    Emmanouilidou, Agapi

    2012-06-01

    We present a theoretical quasiclassical treatment of the formation, during Coulomb explosion, of highly excited neutral H atoms for strongly-driven hydrogen molecule. This process, where after the laser field is turned off, one electron escapes to the continuum while the other occupies a Rydberg state, was recently reported in an experimental study in Phys. Rev. Lett 102, 113002 (2009). We find that two-electron effects are important in order to correctly account for all pathways leading to highly excited neutral hydrogen formation [1]. We identify two pathways where the electron that escapes to the continuum does so either very quickly or after remaining bound for a few periods of the laser field. These two pathways of highly excited neutral H formation have distinct traces in the probability distribution of the escaping electron momentum components. [4pt] [1] A. Emmanouilidou, C. Lazarou, A. Staudte and U. Eichmann, Phys. Rev. A (Rapid) 85 011402 (2012).

  12. Chemically etched modulation in wire radius for wire array Z-pinch perturbation studies

    SciTech Connect

    Jones, B.; Deeney, C.; McKenney, J.L.; Garrity, J.E.; Lobley, D.K.; Martin, K.L.; Griego, A.E.; Ramacciotti, J.P.; Bland, S.N.; Lebedev, S.V.; Bott, S.C.; Ampleford, D.J.; Palmer, J.B.A.; Rapley, J.; Hall, G.

    2004-11-01

    A technique for manufacturing wires with imposed modulation in radius with axial wavelengths as short as 1 mm is presented. Extruded aluminum 5056 with 15 {mu}m diameter was masked and chemically etched to reduce the radius by {approx}20% in selected regions. Characterized by scanning electron microscopy, the modulation in radius is a step function with a {approx}10 {mu}m wide conical transition between thick and thin segments, with some pitting in etched regions. Techniques for mounting and aligning these wires in arrays for fast z-pinch experiments will be discussed. Axially mass-modulated wire arrays of this type will allow the study of seeded Rayleigh-Taylor instabilities in z pinches, corona formation, wire initiation with varying current density in the wire core, and correlation of perturbations between adjacent wires. This tool will support magnetohydrodynamics code validation in complex three-dimensional geometries, and perhaps x-ray pulse shaping.

  13. Numerical simulation of atomic nitrogen formation in plasma of glow discharge in nitrogen-argon mixture

    NASA Astrophysics Data System (ADS)

    Khomich, V. A.; Ryabtsev, A. V.; Didyk, E. G.; Zhovtyansky, V. A.; Nazarenko, V. G.

    2010-10-01

    We consider the problem of determining the content of atomic nitrogen as an active component responsible for the efficiency of metal surface modification in plasma of stationary low-pressure glow discharge in nitrogen-argon mixture (widely used in this technology). The influence of the gas mixture composition on the rate constant of molecular nitrogen dissociation, which determines the atomic nitrogen production, has been calculated, The parameters of plasma have been experimentally determined using the method of double probes. The electron energy distribution function is found by numerically integrating the Boltzmann equation in a two-term approximation for the molecular nitrogen-argon mixture.

  14. Atomic structure of Ag(111) saturated with chlorine: Formation of Ag3Cl7 clusters

    NASA Astrophysics Data System (ADS)

    Andryushechkin, B. V.; Cherkez, V. V.; Gladchenko, E. V.; Zhidomirov, G. M.; Kierren, B.; Fagot-Revurat, Y.; Malterre, D.; Eltsov, K. N.

    2011-08-01

    The structure of saturated chlorine layer on Ag(111) has been studied with low temperature scanning tunneling microscopy and density functional theory. For the first time atomic-resolution STM images of saturated chlorine coverage have been obtained. STM images demonstrate coexistence of the domain with (3 × 3)-like reconstruction and numerous bright objects identified as Ag3Cl7 clusters. According to our model supported by DFT calculations, clusters are formed on the boundaries between the adjacent (3×3) antiphase domains. These boundaries have a characteristic triangular shape and are formed by six chlorine atoms chemisorbed on the triangular silver island with local periodicity (1 × 1).

  15. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1998-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: 3.7 amps per wire, bundle of 15 or more wires, 70 C environment, and vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  16. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1998-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire; (2) bundle of 15 or more wires; (3) 70 C environment: and (4) vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  17. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1999-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 degree C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire (2) bundle of 15 or more wires (3) 70 C environment (4) vacuum of 10(exp -5) torr or less To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  18. Mechanism of Electromigration in Ag-Alloy Bonding Wires with Different Pd and Au Content

    NASA Astrophysics Data System (ADS)

    Chuang, Tung-Han; Lin, Hsin-Jung; Wang, Hsi-Ching; Chuang, Chien-Hsun; Tsai, Chih-Hsin

    2015-02-01

    The mechanism of electromigration in Ag-alloy wires containing different amounts of Pd and Au has been studied. Thinning and thickening accompanying grain growth were observed in worn bonding wire after current stress. The mean time-to-failure of bonding wires stressed with different current densities is highly dependent on their electrical resistivity, and wire temperature increases during current stress, owing to the Joule effect. An indirect method is proposed for in situ assessment of the temperatures of these fine wires under current stress. A mode of failure of these bonding wires was deduced by kinetic analysis. This mode can be correlated with atomic diffusion in the wire.

  19. Photoinduced ethane formation from reaction of ethene with matrix-isolated Ti, V, or Nb atoms.

    PubMed

    Thompson, Matthew G K; Parnis, J Mark

    2005-10-27

    The reactions of matrix-isolated Ti, V, or Nb atoms with ethene (C(2)H(4)) have been studied by FTIR absorption spectroscopy. Under conditions where the ethene dimer forms, metal atoms react with the ethene dimer to yield matrix-isolated ethane (C(2)H(6)) and methane. Under lower ethene concentration conditions ( approximately 1:70 ethene/Ar), hydridic intermediates of the types HMC(2)H(3) and H(2)MC(2)H(2) are also observed, and the relative yield of hydrocarbons is diminished. Reactions of these metals with perdeuterioethene, and equimolar mixtures of C(2)H(4) and C(2)D(4), yield products that are consistent with the production of ethane via a metal atom reaction involving at least two C(2)H(4) molecules. The absence of any other observed products suggests the mechanism also involves production of small, highly symmetric species such as molecular hydrogen and metal carbides. Evidence is presented suggesting that ethane production from the ethene dimer is a general photochemical process for the reaction of excited-state transition-metal atoms with ethene at high concentrations of ethene. PMID:16866395

  20. Laser Wire Stripper

    NASA Technical Reports Server (NTRS)

    1983-01-01

    NASA-developed space shuttle technology is used in a laser wire stripper designed by Raytheon Company. Laser beams cut through insulation on a wire without damaging conductive metal, because laser radiation that melts plastic insulation is reflected by the metal. The laser process is fast, clean, precise and repeatable. It eliminates quality control problems and the expense of rejected wiring.

  1. The Mopra-STO-Nanten2 Atomic and Molecular Gas Survey: The Formation of Giant Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Burton, Michael; Rathborne, Jill; Pineda Galvez, Jorge Luis; Simon, Robert; Urquhart, James; Stark, Antony A.; Rowell, Gavin; Tothill, Nick; Storey, John; Langer, William D.; Martin, Christopher; Walker, Chris; Kulesa, Craig; Stutzki, Juergen; Hollenbach, David; Au, Cheryl; Glueck, Christian

    2012-04-01

    We propose to continue our Mopra CO survey across a spiral arm in the fourth quadrant of our Galaxy, covering a region containing ~25% of the Galaxy's molecular gas. Mopra will provide the distribution and dynamics of the CO molecule here, measuring the emission from its three brightest isotopologues. As one application of this survey, we will determine how the formation of giant molecular clouds occurs. This fundamental process, which is the rate-determining step for star formation, has not yet been observed. To do so, we will make use of the high spectral and spatial resolution of the Mopra, Nanten2 and STO telescopes, combined with archival 21 cm atomic hydrogen data, to measure the best cloud tracers via the spectral lines emitted from the molecular and atomic gas in the interstellar medium along the galactic plane. These lines (from CO, [CI], [CII] and HI) provide diagnostics that can trace the state and dynamics of the gas, including how and where molecular cloud formation is taking place.

  2. Ripples and the formation of anisotropic lipid domains: imaging two-component supported double bilayers by atomic force microscopy.

    PubMed Central

    Leidy, Chad; Kaasgaard, Thomas; Crowe, John H; Mouritsen, Ole G; Jørgensen, Kent

    2002-01-01

    Direct visualization of the fluid-phase/ordered-phase domain structure in mica-supported bilayers composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-distearoyl-sn-glycero-3-phosphocholine mixtures is performed with atomic force microscopy. The system studied is a double bilayer supported on a mica surface in which the top bilayer (which is not in direct contact with the mica) is visualized as a function of temperature. Because the top bilayer is not as restricted by the interactions with the surface as single supported bilayers, its behavior is more similar to a free-standing bilayer. Intriguing straight-edged anisotropic fluid-phase domains were observed in the fluid-phase/ordered-phase coexistence temperature range, which resemble the fluid-phase/ordered-phase domain patterns observed in giant unilamellar vesicles composed of such phospholipid mixtures. With the high resolution provided by atomic force microscopy, we investigated the origin of these anisotropic lipid domain patterns, and found that ripple phase formation is directly responsible for the anisotropic nature of these domains. The nucleation and growth of fluid-phase domains are found to be directed by the presence of ripples. In particular, the fluid-phase domains elongate parallel to the ripples. The results show that ripple phase formation may have implications for domain formation in biological systems. PMID:12414696

  3. [Prognostic assessment for formation of a group of cardiovascular high risk among personnel participating in atomic submarines utilization].

    PubMed

    Sosiukin, A E; Vasiliuk, V B; Ivanchenko, A V; Saenko, S A; Semenchuk, O A; Dokhov, M A; Verveda, A B

    2014-01-01

    Ultrasound scanning of main vessels (common carotid, internal carotid, common and superficial femoral, posterior tibial arteries) in staffers of shipyard "Nerpa"--branch of JSC "Shipbuilding center Zvezdochka" (Snezhnogorsk city Murmansk region)--engaged into atomic submarines utilization. Findings are atherosclerotic changes in common carotid and common femoral arteries--increased thickness of intima-media complex over the reference values or atherosclerotic plaque formation. The changes were maximal in a group of males aged over 50 with length of service over 25 years. Discriminant analysis helped to suggest a mathematic model to forecast cardiovascular diseases in personnel of "Nerpa" shipyard. PMID:25845142

  4. Dynamical resonant electron capture in atom surface collisions: H- formation in H-Al(111) collisions

    NASA Astrophysics Data System (ADS)

    Borisov, A. G.; Teillet-Billy, D.; Gauyacq, J. P.

    1992-05-01

    The formation of H- ion by grazing-angle collisions of hydrogen on an Al(111) surface is investigated with the newly developed coupled angular mode method. The capture process involves a dynamical resonant process induced by the collision velocity. All the resonance properties of the H- level in front of an Al(111) surface are determined: position, width, and angular distribution of ejected electrons. The results are shown to account for the recent observations on H- formation by Wyputta, Zimny, and Winter.

  5. Formation rate for Rb 2 + molecular ions created in collisions of Rb Rydberg and ground-state atoms

    NASA Astrophysics Data System (ADS)

    Stanojevic, Jovica; Côté, Robin

    2016-05-01

    We calculate the formation rate of the molecular Rb2+ion in its various bound states produced in the associative ionization of a Rydberg and a ground-state atom. Before the formation takes place, the colliding atoms are accelerated by an attractive force between the collision partners. In this way the ground-state atom is first captured by the Rydberg electron and then guided towards the positive ion-core where a molecular ion is subsequently formed. As recently demonstrated, this process results in giant collisional cross sections for the molecular ion formation, with the cross sections essentially determined by the size of the Rydberg atom. For sufficient high principal quantum numbers and atomic densities, many ground-state atoms are already located inside the Rydberg atom and ready to participate in the associative ionization. The same process can occur between a Rydberg and a ground-state atom that form a long-range Rydberg molecule, possibly contributing to the shortening of the lifetimes of Rydberg atoms and molecules. Partial support from the US Army Research Office (ARO-MURI W911NF-14-1-0378), and from NSF (Grant No. PHY-1415560).

  6. The formation of molecules in interstellar clouds from singly and multiply ionized atoms

    NASA Technical Reports Server (NTRS)

    Langer, W. D.

    1978-01-01

    The suggestion is considered that multiply ionized atoms produced by K- and L-shell X-ray ionization and cosmic-ray ionization can undergo ion-molecule reactions and also initiate molecule production. The role of X-rays in molecule production in general is discussed, and the contribution to molecule production of the C(+) radiative association with hydrogen is examined. Such gas-phase reactions of singly and multiply ionized atoms are used to calculate molecular abundances of carbon-, nitrogen-, and oxygen-bearing species. The column densities of the molecules are evaluated on the basis of a modified version of previously developed isobaric cloud models. It is found that reactions of multiply ionized carbon with H2 can contribute a significant fraction of the observed CH in diffuse interstellar clouds in the presence of diffuse X-ray structures or discrete X-ray sources and that substantial amounts of CH(+) can be produced under certain conditions.

  7. Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

    PubMed Central

    Wang, Yang-Gang; Mei, Donghai; Glezakou, Vassiliki-Alexandra; Li, Jun; Rousseau, Roger

    2015-01-01

    Catalysis by gold supported on reducible oxides has been extensively studied, yet issues such as the nature of the catalytic site and the role of the reducible support remain fiercely debated topics. Here we present ab initio molecular dynamics simulations of an unprecedented dynamic single-atom catalytic mechanism for the oxidation of carbon monoxide by ceria-supported gold clusters. The reported dynamic single-atom catalytic mechanism results from the ability of the gold cation to strongly couple with the redox properties of the ceria in a synergistic manner, thereby lowering the energy of redox reactions. The gold cation can break away from the gold nanoparticle to catalyse carbon monoxide oxidation, adjacent to the metal/oxide interface and subsequently reintegrate back into the nanoparticle after the reaction is completed. Our study highlights the importance of the dynamic creation of active sites under reaction conditions and their essential role in catalysis. PMID:25735407

  8. Heavy-Rydberg ion-pair formation in collisions of Rydberg atoms with attaching targets

    NASA Astrophysics Data System (ADS)

    Wang, Changhao; Kelley, Michael; Dunning, F. Barry

    2012-06-01

    Collisions between K(np) Rydberg atoms and electron attaching targets can lead to the creation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair orbiting at large internuclear separations. The lifetimes of such states and their correlation with binding energy and the channels available for decay, which can be controlled by varying n, the Rydberg atom velocity, and the target species, are being investigated. The ion-pair states are produced in a small collision cell and allowed to exit to form a beam that passes between a pair of electrodes where their number and binding energy distribution is determined by electric field induced dissociation. Ion-pair production is analyzed with the aid of a Monte Carlo collision code that models both initial Rydberg electron capture and the subsequent evolution of the product ion pair. Research supported by the Robert A Welch Foundation.

  9. Formation of hydrogen atoms in pyrolysis of 2,2-dimethylpropane behind shock waves

    SciTech Connect

    Bernfeld, D.; Skinner, G.B.

    1983-09-15

    Dilute mixtures (5 to 20 ppM) of 2,2-dimethylpropane (neopentane) were pyrolyzed behind reflected shock waves at temperatures of 1140 to 1300 K and total pressures of 2 to 3 atm. Progress of the reaction was followed by analysis for H atoms using resonance absorption spectroscopy. Appearance of H atoms was a first-order process with respect to time, an Arrhenius equation for the appearance of H atoms, based on 61 experiments, being k/sub H/ = 2.65 x 10/sup 17/ exp(-86300/RT) s/sup -1/, where the activation energy is in calories. Taking into account two minor side reactions, the first-order rate constant for the first step in neopentane pyrolysis, (CH/sub 3/)/sub 4/C ..-->.. (CH/sub 3/)/sub 3/C. + CH/sub 3/ (1) was found to be k/sub 1/ = 1.7 x 10/sup 17/ exp(-84000/RT) s/sup -1/ with an estimated uncertainty of a factor of 2 in k/sub H/ and k/sub 1/. 2 figures.

  10. Force-controlled lifting of molecular wires

    NASA Astrophysics Data System (ADS)

    Fournier, N.; Wagner, C.; Weiss, C.; Temirov, R.; Tautz, F. S.

    2011-07-01

    Lifting a single molecular wire off the surface with a combined frequency-modulated atomic force and tunneling microscope it is possible to monitor the evolution of both the wire configuration and the contacts simultaneously with the transport conductance experiment. In particular, critical points where individual bonds to the surface are broken and instabilities where the wire is prone to change its contact configuration can be identified in the force gradient and dissipation responses of the junction. This additional mechanical information can be used to unambiguously determine the conductance of a true molecular wire, that is, of a molecule that is contacted via a pointlike “crocodile clip” to each of the electrodes but is otherwise free.

  11. FORMATION OF CARBON DIOXIDE, METHANOL, ETHANOL, AND FORMIC ACID ON AN ICY GRAIN ANALOG USING FAST OXYGEN ATOMS

    SciTech Connect

    Madzunkov, S. M.; MacAskill, J. A.; Chutjian, A.

    2010-03-20

    Carbon dioxide (CO{sub 2}), methanol (CH{sub 3}OH), ethanol (CH{sub 3}CH{sub 2}OH), and formic acid (HCOOH) have been formed in collisions of a superthermal, 9 eV beam of O({sup 3} P) atoms with CH{sub 4} molecules, with an over coat of CO molecules, adsorbed on a gold surface at 4.8 K. The products are detected using temperature programmed-desorption and quadrupole mass spectrometry. Identification of the species is carried out through use of the Metropolis random walk algorithm as constrained by the fractionation patterns of the detected species. Relative formation yields are reported and reaction sequences are given to account for possible formation routes.

  12. 'Chrysanthemum petal' arrangements of silver nano wires.

    PubMed

    Cui, Hui-Wang; Jiu, Jin-Ting; Sugahara, Tohru; Nagao, Shijo; Suganuma, Katsuaki; Uchida, Hiroshi

    2014-12-01

    Highly ordered 'Chrysanthemum petal' arrangements of silver nano wires were fabricated in a biodegradable polymer of polyvinyl alcohol using a simple one-step blending method without any template. The degree of the arrangement increased with the decreasing content of polyvinyl alcohol. The mechanism for the formation of these 'Chrysanthemum petal' arrangements was discussed specifically. These 'Chrysanthemum petal' arrangements will be helpful to increase the electrical conductivity of silver nano wires films. PMID:25397618

  13. Transfer of a weakly bound electron in collisions of Rydberg atoms with neutral particles. II. Ion-pair formation and resonant quenching of the Rb(nl) and Ne(nl) States by Ca, Sr, and Ba atoms

    SciTech Connect

    Narits, A. A.; Mironchuk, E. S.; Lebedev, V. S.

    2013-10-15

    Electron-transfer processes are studied in thermal collisions of Rydberg atoms with alkaline-earth Ca(4s{sup 2}), Sr(5s{sup 2}), and Ba(6s{sup 2}) atoms capable of forming negative ions with a weakly bound outermost p-electron. We consider the ion-pair formation and resonant quenching of highly excited atomic states caused by transitions between Rydberg covalent and ionic terms of a quasi-molecule produced in collisions of particles. The contributions of these reaction channels to the total depopulation cross section of Rydberg states of Rb(nl) and Ne(nl) atoms as functions of the principal quantum number n are compared for selectively excited nl-levels with l Much-Less-Than n and for states with large orbital quantum numbers l = n - 1, n - 2. It is shown that the contribution from resonant quenching dominates at small values of n, and the ion-pair formation process begins to dominate with increasing n. The values and positions of the maxima of cross sections for both processes strongly depend on the electron affinity of an alkaline-earth atom and on the orbital angular momentum l of a highly excited atom. It is shown that in the case of Rydberg atoms in states with large l {approx} n - 1, the rate constants of ion-pair formation and collisional quenching are considerably lower than those for nl-levels with l Much-Less-Than n.

  14. Modeling three-dimensional network formation with an atomic lattice model: Application to silicic acid polymerization

    NASA Astrophysics Data System (ADS)

    Jin, Lin; Auerbach, Scott M.; Monson, Peter A.

    2011-04-01

    We present an atomic lattice model for studying the polymerization of silicic acid in sol-gel and related processes for synthesizing silica materials. Our model is based on Si and O atoms occupying the sites of a body-centered-cubic lattice, with all atoms arranged in SiO4 tetrahedra. This is the simplest model that allows for variation in the Si-O-Si angle, which is largely responsible for the versatility in silica polymorphs. The model describes the assembly of polymerized silica structures starting from a solution of silicic acid in water at a given concentration and pH. This model can simulate related materials—chalcogenides and clays—by assigning energy penalties to particular ring geometries in the polymerized structures. The simplicity of this approach makes it possible to study the polymerization process to higher degrees of polymerization and larger system sizes than has been possible with previous atomistic models. We have performed Monte Carlo simulations of the model at two concentrations: a low density state similar to that used in the clear solution synthesis of silicalite-1, and a high density state relevant to experiments on silica gel synthesis. For the high concentration system where there are NMR data on the temporal evolution of the Qn distribution, we find that the model gives good agreement with the experimental data. The model captures the basic mechanism of silica polymerization and provides quantitative structural predictions on ring-size distributions in good agreement with x-ray and neutron diffraction data.

  15. Atomic pattern formation at the onset of stress-induced elastic instability: Fracture versus phase change

    NASA Astrophysics Data System (ADS)

    Milstein, Frederick; Zhao, Jianhua; Maroudas, Dimitrios

    2004-11-01

    A systematic theoretical study is presented of the stress-induced structural response of initially cubic single crystals to uniaxial [100] loading based on elastic stability analysis and isostress molecular-dynamics simulations through a classical description of interatomic interactions in model metallic crystals. Special emphasis is placed on the study of the atomic pattern formation characteristics in the crystal’s structural response to loading at and beyond the onset of elastic instability. The instability is reached at a rigorously defined critical stress level that occurs in association with the vanishing of a shear modulus, i.e., when C22/C23-1=0 , where Crs are stress-dependent elastic moduli. Although the atomic mechanism for the onset of instability is invariant, two divergent atomic processes are found to occur beyond the onset of instability, depending on subtle differences in the elastic properties of the crystals. Our analyses and simulations of a crystal model with the relatively small initial value of C22/C23-1=0.41 (based on the elastic moduli of copper) reveal an inhomogeneous structural transformation mechanism, through the creation of individual rotating domains that lead to formation of a new hexagonal single crystal without loss of strength. This theoretical result is consistent with what is known experimentally for metals with relatively small values of (C22/C23-1) , e.g., certain copper alloys and the alkali metals, which can undergo various cubic-to-hexagonal structural transformations. However, a crystal model based on the elastic moduli of nickel, with the larger initial value of C22/C23-1=0.73 , fails to exhibit domain rotation beyond the onset of elastic instability and, as a result, the initial destabilization of the crystal structure then leads to fracture.

  16. Induced water condensation and bridge formation by electric fieldsin Atomic Force Microscopy

    SciTech Connect

    Sacha, G.M.; Verdaguer, A.; Salmeron, M.

    2006-02-22

    We present an analytical model that explains how in humidenvironments the electric field near a sharp tip enhances the formationof water meniscii and bridges between tip and sample. The predictions ofthe model are compared with experimental measurements of the criticaldistance where the field strength causes bridge formation.

  17. Characterization of plasma formation and outflow emission from different wire-based z-pinch experiments driven at the 350kA, 1kA/ns Llampudken pulsed power driver

    NASA Astrophysics Data System (ADS)

    Veloso, Felipe; Muñoz-Cordovez, Gonzalo; Valenzuela-Villaseca, Vicente; Vescovi, Milenko; Favre, Mario; Wyndham, Edmund

    2015-11-01

    We present results on tungsten and aluminium wire-based z-pinch plasma experiments driven by the 350kA, 1kA/ns Llampudken generator at P Universidad Catolica de Chile. Our experiments are concentrated in the formation and subsequent emission of plasma from two different configurations: conical arrays and modified cylindrical arrays using different wire diameters within the load. The former produce collimated jet-like outflows by the zippering effect at the axis of the conical array, whereas the latter produce emission of an unstructured dense plasma object by the temporal variations on the global magnetic field topology of the cylindrical array. We present measurements of the ablation process in both configurations and the main features of the outflows obtained, such as plasma densities and propagation velocities. It is found that an appropriate mass per unit length in the load is particularly important for producing outflows from modified cylindrical arrays, and that high pressure background gas embedding the load hampers the emission of plasma outflows in conical arrays. In addition, the analysis of the dimensionless parameters that characterize each outflow will be presented. This work has been funded by FONDECYT 11121621. G Munoz is funded by a doctorate scholarship awarded by CONICYT.

  18. Fabrication of mesoscopic floating Si wires by introducing dislocations

    NASA Astrophysics Data System (ADS)

    Motohashi, Mitsuya; Shimizu, Kazuya; Suzuki, Toshiaki; Niwa, Masaaki

    2014-12-01

    We fabricated a mesoscopic Si wire by introducing dislocations in a silicon wafer before HF anodization. The dislocations formed along the (111) crystal plane. The outline of the dislocation line was an inverted triangle. The resulting wire floated on a bridge girder and had a hybrid structure consisting of a porous layer and crystalline Si. The cross section of the wire had an inverted triangle shape. The wire formation mechanism is discussed in terms of carrier transport, crystal structure, and dislocation formation during anodization.

  19. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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  20. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 75.1003 Section 75.1003... Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires...

  1. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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  2. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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  3. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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  4. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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  5. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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  6. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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  7. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 77.1802 Section 77.1802... Wires and Trolley Feeder Wires § 77.1802 Insulation of trolley wires, trolley feeder wires and...

  8. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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  9. Formation of molecular ions by radiative association of cold trapped atoms and ions

    NASA Astrophysics Data System (ADS)

    Dulieu, Olivier; da Silva, Humberto, Jr.; Aymar, Mireille; Raoult, Maurice

    2015-05-01

    Radiative emission during cold collisions between trapped laser-cooled Rb atoms and alkaline-earth ions (Ca+ , Sr+ , Ba+) and Yb+ are studied theoretically, using accurate effective-core-potential based quantum chemistry calculations of potential energy curves and transition dipole moments of the related molecular ions. Radiative association of molecular ions is predicted to occur for all systems with a cross section two to ten times larger than the radiative charge transfer one. Partial and total rate constants are also calculated and compared to available experiments. Narrow shape resonances are expected, which could be detectable at low temperature with an experimental resolution at the limit of the present standards. Vibrational distributions show that the final molecular ions are not created in their ground state level. Supported by the Marie-Curie ITN ``COMIQ: Cold Molecular Ions at the Quantum limit'' of the EU (#607491).

  10. Formation of dimers of light noble atoms under encapsulation within fullerene's voids.

    PubMed

    Nikolaienko, Tymofii Yu; Kryachko, Eugene S

    2015-01-01

    Van der Waals (vdW) He2 diatomic trapped inside buckminsterfullerene's void and preserving its diatomic bonding is itself a controversial phenomenon due to the smallness of the void diameter comparing to the He-He equilibrium distance. We propound a computational approach, including smaller fullerenes, C20 and C28, to demonstrate that encapsulation of He2 inside the studied fullerenes exhibits an interesting quantum behavior resulting in a binding at shorter, non-vdW internuclear distances, and we develop a computational model to interpret these He-He bonding patterns in terms of Bader's atom-in-molecule theory. We also conjecture a computational existence of He2@C60 on a solid basis of its theoretical UV absorption spectrum and a comparison with that of C60. PMID:25983673

  11. Formation and disruption of current paths of anodic porous alumina films by conducting atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Oyoshi, K.; Nigo, S.; Inoue, J.; Sakai, O.; Kitazawa, H.; Kido, G.

    2010-11-01

    Anodic porous alumina (APA) films have a honeycomb cell structure of pores and a voltage-induced bi-stable switching effect. We have applied conducting atomic force microscopy (CAFM) as a method to form and to disrupt current paths in the APA films. A bi-polar switching operation was confirmed. We have firstly observed terminals of current paths as spots or areas typically on the center of the triangle formed by three pores. In addition, though a part of the current path showed repetitive switching, most of them were not observed again at the same position after one cycle of switching operations in the present experiments. This suggests that a part of alumina structure and/or composition along the current paths is modified during the switching operations.

  12. Thin wire pointing method

    NASA Technical Reports Server (NTRS)

    Green, G.; Mattauch, R. J. (Inventor)

    1983-01-01

    A method is described for forming sharp tips on thin wires, in particular phosphor bronze wires of diameters such as one-thousandth inch used to contact micron size Schottky barrier diodes, which enables close control of tip shape and which avoids the use of highly toxic solutions. The method includes dipping an end of a phosphor bronze wire into a dilute solution of sulfamic acid and applying a current through the wire to electrochemically etch it. The humidity in the room is controlled to a level of less than 50%, and the voltage applied between the wire and another electrode in the solutions is a half wave rectified voltage. The current through the wire is monitored, and the process is stopped when the current falls to a predetermined low level.

  13. Spectroscopy of a plasma formed in the vicinity of implosion of the shock wave generated by underwater electrical explosion of spherical wire array

    SciTech Connect

    Antonov, O.; Efimov, S.; Gurovich, V. Tz.; Krasik, Ya. E.; Bernshtam, V.

    2015-05-15

    The results of visible spectroscopy of the plasma formed inside a copper capillary placed at the equatorial plane of an underwater electrically exploded spherical wire array (30 mm in diameter; 40 wires, each of 100 μm in diameter) are reported. In the experiments, a pulsed power generator with current amplitude of ∼300 kA and rise time of ∼1.1 μs was used to produce wire array explosion accompanied by the formation of a converging strong shock wave. The data obtained support the assumption of uniformity of the shock wave along the main path of its convergence. The spectroscopic measurements show that this rather simple method of formation of a converging strong shock wave can be used successfully for studying the shock wave's interaction with matter and the evaporation processes of atoms from a target.

  14. Zinc wired rebar

    SciTech Connect

    Zhang, X.G.; Hwang, J.

    1997-02-01

    A novel method for corrosion protection of rebar in concrete is reported wherein it is galvanically protected by attaching a zinc wire along its length. The self-corrosion and galvanic-corrosion loss of the zinc wire is dependent on the water/cement ratio, the size of the cathode, and the concrete cover thickness. The wire acts as a sacrificial anode when the rebar embedded in concrete is exposed to corrosive environments.

  15. Using Nested Contractions and a Hierarchical Tensor Format To Compute Vibrational Spectra of Molecules with Seven Atoms.

    PubMed

    Thomas, Phillip S; Carrington, Tucker

    2015-12-31

    We propose a method for solving the vibrational Schrödinger equation with which one can compute hundreds of energy levels of seven-atom molecules using at most a few gigabytes of memory. It uses nested contractions in conjunction with the reduced-rank block power method (RRBPM) described in J. Chem. Phys. 2014, 140, 174111. Successive basis contractions are organized into a tree, the nodes of which are associated with eigenfunctions of reduced-dimension Hamiltonians. The RRBPM is used recursively to compute eigenfunctions of nodes in bases of products of reduced-dimension eigenfunctions of nodes with fewer coordinates. The corresponding vectors are tensors in what is called CP-format. The final wave functions are therefore represented in a hierarchical CP-format. Computational efficiency and accuracy are significantly improved by representing the Hamiltonian in the same hierarchical format as the wave function. We demonstrate that with this hierarchical RRBPM it is possible to compute energy levels of a 64-D coupled-oscillator model Hamiltonian and also of acetonitrile (CH3CN) and ethylene oxide (C2H4O), for which we use quartic potentials. The most accurate acetonitrile calculation uses 139 MB of memory and takes 3.2 h on a single processor. The most accurate ethylene oxide calculation uses 6.1 GB of memory and takes 14 d on 63 processors. The hierarchical RRBPM shatters the memory barrier that impedes the calculation of vibrational spectra. PMID:26555177

  16. Concealed wire tracing apparatus

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    An apparatus and method that combines a signal generator and a passive signal receiver to detect and record the path of partially or completely concealed electrical wiring without disturbing the concealing surface is disclosed. The signal generator applies a series of electrical pulses to the selected wiring of interest. The applied pulses create a magnetic field about the wiring that can be detected by a coil contained within the signal receiver. An audible output connected to the receiver and driven by the coil reflects the receivers position with respect to the wiring. The receivers audible signal is strongest when the receiver is directly above the wiring and the long axis of the receivers coil is parallel to the wiring. A marking means is mounted on the receiver to mark the location of the wiring as the receiver is directed over the wiring's concealing surface. Numerous marks made on various locations of the concealing surface will trace the path of the wiring of interest. 4 figs.

  17. Weld Wire Investigation Summary

    SciTech Connect

    Cunningham, M.A.

    1999-03-22

    After GTA welding reservoir A production/process prove-in assemblies, X-ray examination detected a lack of sidewall fusion. After examining several possible causes, it was determined that the weld wire filler metal was responsible, particularly the wire cleaning process. The final conclusion was that the filler wire must be abrasively cleaned in a particular manner to perform as required. The abrasive process was incorporated into the wire material specification, ensuring consistency for all reservoir GTA welding at AlliedSignal Federal Manufacturing and Technologies (FM and T).

  18. Wire-inhomogeneity detector

    DOEpatents

    Gibson, G.H.; Smits, R.G.; Eberhard, P.H.

    1982-08-31

    A device for uncovering imperfections in electrical conducting wire, particularly superconducting wire, by detecting variations in eddy currents. Eddy currents effect the magnetic field in a gap of an inductor, contained in a modified commercial ferrite core, through which the wire being tested is passed. A small increase or decrease in the amount of conductive material, such as copper, in a fixed cross section of wire will unbalance a bridge used to measure the impedance of the inductor, tripping a detector and sounding an alarm.

  19. Ferromagnetism of the repulsive atomic Fermi gas: three-body recombination and domain formation

    NASA Astrophysics Data System (ADS)

    Zintchenko, Ilia; Wang, Lei; Troyer, Matthias

    2016-08-01

    The simplest model for itinerant ferromagnetism, the Stoner model, has so far eluded experimental observation in repulsive ultracold fermions due to rapid three-body recombination at large scattering lengths. Here we show that a ferromagnetic phase can be stabilised by imposing a moderate optical lattice. The reduced kinetic energy drop upon formation of a polarized phase in an optical lattice extends the ferromagnetic phase to smaller scattering lengths where three-body recombination is small enough to permit experimental detection of the phase. We also show, using time dependent density functional theory, that in such a setup ferromagnetic domains emerge rapidly from a paramagnetic initial state.

  20. 1998 wire development workshop proceedings

    SciTech Connect

    1998-04-01

    This report consists of vugraphs of the presentations at the conference. The conference was divided into the following sessions: (1) First Generation Wire Development: Status and Issues; (2) First Generation Wire in Pre-Commercial Prototypes; (3) Second Generation Wire Development: Private Sector Progress and Issues; (4) Second Generation Wire Development: Federal Laboratories; and (5) Fundamental Research Issues for HTS Wire Development.

  1. Discharge formation systems for generating atomic iodine in a pulse-periodic oxygen–iodine laser

    SciTech Connect

    Aksinin, V I; Kazantsev, S Yu; Kononov, I G; Podlesnykh, S V; Firsov, K N; Antsiferov, S A; Velikanov, S D; Gerasimov, A Yu; Gostev, I V; Kalinovskii, V V; Konovalov, V V; Mikhalkin, V N; Sevryugin, I V

    2014-01-31

    Generation characteristics of a pulse-periodic oxygen–iodine laser with the electro-discharge production of atomic iodine were compared with inductively stabilised edged or anisotropic- resistive cathodes used for ignition of the volume discharge. The discharge was initiated by the radiation of a barrier discharge from the side of a grid anode. It was found that at equal specific electrical energy depositions to the gas-discharge plasma, the system with the anisotropic-resistive cathode provides a more stable and uniform volume discharge with the possibility of varying the composition and pressure of working mixtures over a wide range and a greater specific extraction of laser energy is observed (up to 2.4 J L{sup -1}). At a high pulse repetition rate of laser pulses (50 – 100 Hz) and long duration of the pulse trains (longer than a minute) the surface of anisotropic-resistive cathode became eroded. (laser applications and other topics in quantum electronics)

  2. Ultrafast formation of interlayer hot excitons in atomically thin MoS2/WS2 heterostructures.

    PubMed

    Chen, Hailong; Wen, Xiewen; Zhang, Jing; Wu, Tianmin; Gong, Yongji; Zhang, Xiang; Yuan, Jiangtan; Yi, Chongyue; Lou, Jun; Ajayan, Pulickel M; Zhuang, Wei; Zhang, Guangyu; Zheng, Junrong

    2016-01-01

    Van der Waals heterostructures composed of two-dimensional transition-metal dichalcogenides layers have recently emerged as a new family of materials, with great potential for atomically thin opto-electronic and photovoltaic applications. It is puzzling, however, that the photocurrent is yielded so efficiently in these structures, despite the apparent momentum mismatch between the intralayer/interlayer excitons during the charge transfer, as well as the tightly bound nature of the excitons in 2D geometry. Using the energy-state-resolved ultrafast visible/infrared microspectroscopy, we herein obtain unambiguous experimental evidence of the charge transfer intermediate state with excess energy, during the transition from an intralayer exciton to an interlayer exciton at the interface of a WS2/MoS2 heterostructure, and free carriers moving across the interface much faster than recombining into the intralayer excitons. The observations therefore explain how the remarkable charge transfer rate and photocurrent generation are achieved even with the aforementioned momentum mismatch and excitonic localization in 2D heterostructures and devices. PMID:27539942

  3. Ultrafast formation of interlayer hot excitons in atomically thin MoS2/WS2 heterostructures

    PubMed Central

    Chen, Hailong; Wen, Xiewen; Zhang, Jing; Wu, Tianmin; Gong, Yongji; Zhang, Xiang; Yuan, Jiangtan; Yi, Chongyue; Lou, Jun; Ajayan, Pulickel M.; Zhuang, Wei; Zhang, Guangyu; Zheng, Junrong

    2016-01-01

    Van der Waals heterostructures composed of two-dimensional transition-metal dichalcogenides layers have recently emerged as a new family of materials, with great potential for atomically thin opto-electronic and photovoltaic applications. It is puzzling, however, that the photocurrent is yielded so efficiently in these structures, despite the apparent momentum mismatch between the intralayer/interlayer excitons during the charge transfer, as well as the tightly bound nature of the excitons in 2D geometry. Using the energy-state-resolved ultrafast visible/infrared microspectroscopy, we herein obtain unambiguous experimental evidence of the charge transfer intermediate state with excess energy, during the transition from an intralayer exciton to an interlayer exciton at the interface of a WS2/MoS2 heterostructure, and free carriers moving across the interface much faster than recombining into the intralayer excitons. The observations therefore explain how the remarkable charge transfer rate and photocurrent generation are achieved even with the aforementioned momentum mismatch and excitonic localization in 2D heterostructures and devices. PMID:27539942

  4. Defect formation on the GaSb (001) surface induced by hydrogen atom adsorption

    NASA Astrophysics Data System (ADS)

    Bermudez, V. M.

    2015-06-01

    Density functional theory has been used to characterize the effects of adsorbed H on the electronic structure of the GaSb (001)-α(4×3) surface, which consists of a combination of Ga-Sb and Sb-Sb dimers. Adsorption of two H atoms at a Ga-Sb adatom dimer either has little effect on surface states above the bulk valence band maximum (VBM) or else eliminates them, depending on the mode of adsorption. However, adsorption at the Sb-Sb dimer in the terminating layer produces a state farther into the gap at ~0.10 eV above the clean-surface VBM. Relaxation accompanying the breaking of the Sb-Sb dimer bond leads to increased interactions involving three-fold-coordinated Sb sites in the terminating layer, which in turn raises the energies of the non-bonding lone-pair orbitals. This defect state, which appears to be unique to the reconstructed GaSb (001) surface, could potentially function as a hole trap on the surface of p-type GaSb.

  5. Partial Redistribution in Multilevel Atoms. I. Method and Application to the Solar Hydrogen Line Formation

    NASA Astrophysics Data System (ADS)

    Hubeny, I.; Lites, B. W.

    1995-12-01

    We present a robust method for solution of multilevel non-LTE line transfer problems including the effects of partial frequency redistribution (PRD). This method allows the self-consistent solution for redistribution of scattered line photons simultaneously in multiple transitions of a model atom, including the effects of resonant Raman scattering ("cross-redistribution") among lines sharing common upper levels. The method is incorporated into the framework of the widely used non-LTE complete redistribution code MULTI. We have applied this method to the problem of transfer in hydrogen lines in a plane-parallel solar model atmosphere, including cross-redistribution between the Hα and Lβ, using general redistribution functions for the Lα and Lβ lines which are not restricted by the impact approximation. The convergence properties of this method are demonstrated to be comparable to that of the equivalent complete redistribution problem. In this solar model, PRD in the Lα line produces the dominant influence on the level populations. It changes considerably the populations of the excited states of hydrogen, as well as the proton number density, in the middle and upper chromosphere, owing to modification of the Lα wing radiation. The population of the hydrogen ground state undergoes only modest changes, however. The influence of cross-redistribution and PRD in Lβ has a much smaller influence on the level populations but a considerable influence on the wing intensity of the Lβ line.

  6. VIEW SOUTHEASTBUILDING 4 NO. 1 WIRE MILL (1871) WIRE DRAWING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW SOUTHEAST-BUILDING 4 NO. 1 WIRE MILL (1871) WIRE DRAWING MACHINE - John A. Roebling's Sons Company & American Steel & Wire Company, South Broad, Clark, Elmer, Mott & Hudson Streets, Trenton, Mercer County, NJ

  7. Design for a compact CW atom laser

    NASA Astrophysics Data System (ADS)

    Power, Erik; Raithel, Georg

    2011-05-01

    We present a design for a compact continuous-wave atom laser on a chip. A 2D spiral-shaped quadrupole guide is formed by two 0.5 mm × 0.5 mm wires carrying 5 A each embedded in a Si wafer; a 1.5 mm × 0.5 mm wire on the bottom layer carries -10 A, producing a horizontal B-field that pushes the guiding channel center above the chip surface. The center-to-center separation between the top wires is varied from 1.6 mm at the start of the guide to 1 mm at the end, decreasing the guide height from ~ 500 μm to ~ 25 μm above the surface as the atoms travel the 70 cm-long guide. The magnetic gradient of the guiding channel gradually increases from ~ 100 G /cm to ~ 930 G /cm . These features result in continuous surface adsorption evaporative cooling and progressive magnetic compression. Spin flip losses are mitigated by a solenoid sewn around the guide to produce a longitudinal B-field. 87Rb atoms are gravitationally loaded into the guide. A far off-resonant light shift barrier at the end of the guide traps the atoms and allows formation of a BEC. Tuning the barrier height to create a non-zero tunneling rate equal to the loading rate completes the implementation of a CW atom laser. Two options for atom interferometry are implemented on the first-generation chip (matter-wave Fabry-Perot interferometer and guide-based Mach-Zehnder interferometer). Current construction status and challenges will be discussed, along with preliminary results.

  8. Generation of Projector Augmented-Wave atomic data: A 71 element validated table in the XML format

    NASA Astrophysics Data System (ADS)

    Jollet, François; Torrent, Marc; Holzwarth, Natalie

    2014-04-01

    In the Projector Augmented Wave (PAW) method developed by Blöchl (1994), a PAW data file is needed for each element, taking the role of the pseudopotential file used with the norm-conserving or ultrasoft formalisms. In this paper, we review methods for generating PAW data files and for evaluating their accuracy, transferability, and numerical efficiency in simulations of bulk solids. We have developed a new set of PAW atomic data files for most of the stable elements in the periodic table. These files are provided in a standard XML format for use in any PAW electronic structure code. The new dataset performs well as measured by the "Δ" evaluation criterion introduced by Lejaeghere et al. (2014), and also performs well in a modified evaluation scheme proposed in the present paper.

  9. Atomic scale observation of phase separation and formation of silicon clusters in Hf higk-κ silicates

    NASA Astrophysics Data System (ADS)

    Talbot, E.; Roussel, M.; Genevois, C.; Pareige, P.; Khomenkova, L.; Portier, X.; Gourbilleau, F.

    2012-05-01

    Hafnium silicate films were fabricated by RF reactive magnetron sputtering technique. Fine microstructural analyses of the films were performed by means of high-resolution transmission electron microscopy and atom probe tomography. A thermal treatment of as-grown homogeneous films leads to a phase separation process. The formation of SiO2 and HfO2 phases as well as pure Si one was revealed. This latter was found to be amorphous Si nanoclusters, distributed uniformly in the film volume. Their mean diameter and density were estimated to be about 2.8 nm and (2.9 ± 0.4) × 1017 Si-ncs/cm3, respectively. The mechanism of the decomposition process was proposed. The obtained results pave the way for future microelectronic and photonic applications of Hf-based high-κ dielectrics with embedded Si nanoclusters.

  10. Atomic scale observation of phase separation and formation of silicon clusters in Hf higk-{kappa} silicates

    SciTech Connect

    Talbot, E.; Roussel, M.; Genevois, C.; Pareige, P.; Khomenkova, L.; Portier, X.; Gourbilleau, F.

    2012-05-15

    Hafnium silicate films were fabricated by RF reactive magnetron sputtering technique. Fine microstructural analyses of the films were performed by means of high-resolution transmission electron microscopy and atom probe tomography. A thermal treatment of as-grown homogeneous films leads to a phase separation process. The formation of SiO{sub 2} and HfO{sub 2} phases as well as pure Si one was revealed. This latter was found to be amorphous Si nanoclusters, distributed uniformly in the film volume. Their mean diameter and density were estimated to be about 2.8 nm and (2.9 {+-} 0.4) x 10{sup 17} Si-ncs/cm{sup 3}, respectively. The mechanism of the decomposition process was proposed. The obtained results pave the way for future microelectronic and photonic applications of Hf-based high-{kappa} dielectrics with embedded Si nanoclusters.

  11. Wire Array Photovoltaics

    NASA Astrophysics Data System (ADS)

    Turner-Evans, Dan

    Over the past five years, the cost of solar panels has dropped drastically and, in concert, the number of installed modules has risen exponentially. However, solar electricity is still more than twice as expensive as electricity from a natural gas plant. Fortunately, wire array solar cells have emerged as a promising technology for further lowering the cost of solar. Si wire array solar cells are formed with a unique, low cost growth method and use 100 times less material than conventional Si cells. The wires can be embedded in a transparent, flexible polymer to create a free-standing array that can be rolled up for easy installation in a variety of form factors. Furthermore, by incorporating multijunctions into the wire morphology, higher efficiencies can be achieved while taking advantage of the unique defect relaxation pathways afforded by the 3D wire geometry. The work in this thesis shepherded Si wires from undoped arrays to flexible, functional large area devices and laid the groundwork for multijunction wire array cells. Fabrication techniques were developed to turn intrinsic Si wires into full p-n junctions and the wires were passivated with a-Si:H and a-SiNx:H. Single wire devices yielded open circuit voltages of 600 mV and efficiencies of 9%. The arrays were then embedded in a polymer and contacted with a transparent, flexible, Ni nanoparticle and Ag nanowire top contact. The contact connected >99% of the wires in parallel and yielded flexible, substrate free solar cells featuring hundreds of thousands of wires. Building on the success of the Si wire arrays, GaP was epitaxially grown on the material to create heterostructures for photoelectrochemistry. These cells were limited by low absorption in the GaP due to its indirect bandgap, and poor current collection due to a diffusion length of only 80 nm. However, GaAsP on SiGe offers a superior combination of materials, and wire architectures based on these semiconductors were investigated for multijunction

  12. Formation of ultrashort pulses via quantum interference between Stark-split atomic transitions in a hydrogenlike medium

    NASA Astrophysics Data System (ADS)

    Antonov, V. A.; Radeonychev, Y. V.; Kocharovskaya, Olga

    2013-11-01

    We derive the analytical solution uncovering the origin of the ultrashort pulse formation from the resonant radiation in a hydrogenlike medium [Y. V. Radeonychev, V. A. Polovinkin, and O. Kocharovskaya, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.183902 105, 183902 (2010)], which is a quantum interference of the atomic transitions from the ground to the first excited energy level split by an intense far-off-resonant laser field due to the instantaneous Stark effect into the periodically oscillating sublevels and interference of the resonantly scattered radiation with the incident one. The analytical solution shows that the pulses are almost bandwidth limited and can be produced in a wide range of parameters in excellent agreement with the more general numerical simulation. The experimental schemes to form few-femtosecond pulses from 122-nm radiation in atomic hydrogen as well as few-hundred-attosecond pulses from 13.74-nm radiation in a Li2+ medium are discussed.

  13. Estimation of Enthalpy of Formation of Liquid Transition Metal Alloys: A Modified Prescription Based on Macroscopic Atom Model of Cohesion

    NASA Astrophysics Data System (ADS)

    Raju, Subramanian; Saibaba, Saroja

    2016-09-01

    The enthalpy of formation Δo H f is an important thermodynamic quantity, which sheds significant light on fundamental cohesive and structural characteristics of an alloy. However, being a difficult one to determine accurately through experiments, simple estimation procedures are often desirable. In the present study, a modified prescription for estimating Δo H f L of liquid transition metal alloys is outlined, based on the Macroscopic Atom Model of cohesion. This prescription relies on self-consistent estimation of liquid-specific model parameters, namely electronegativity ( ϕ L) and bonding electron density ( n b L ). Such unique identification is made through the use of well-established relationships connecting surface tension, compressibility, and molar volume of a metallic liquid with bonding charge density. The electronegativity is obtained through a consistent linear scaling procedure. The preliminary set of values for ϕ L and n b L , together with other auxiliary model parameters, is subsequently optimized to obtain a good numerical agreement between calculated and experimental values of Δo H f L for sixty liquid transition metal alloys. It is found that, with few exceptions, the use of liquid-specific model parameters in Macroscopic Atom Model yields a physically consistent methodology for reliable estimation of mixing enthalpies of liquid alloys.

  14. Estimation of Enthalpy of Formation of Liquid Transition Metal Alloys: A Modified Prescription Based on Macroscopic Atom Model of Cohesion

    NASA Astrophysics Data System (ADS)

    Raju, Subramanian; Saibaba, Saroja

    2016-07-01

    The enthalpy of formation Δo H f is an important thermodynamic quantity, which sheds significant light on fundamental cohesive and structural characteristics of an alloy. However, being a difficult one to determine accurately through experiments, simple estimation procedures are often desirable. In the present study, a modified prescription for estimating Δo H {f/L} of liquid transition metal alloys is outlined, based on the Macroscopic Atom Model of cohesion. This prescription relies on self-consistent estimation of liquid-specific model parameters, namely electronegativity (ϕ L) and bonding electron density (n {b/L}). Such unique identification is made through the use of well-established relationships connecting surface tension, compressibility, and molar volume of a metallic liquid with bonding charge density. The electronegativity is obtained through a consistent linear scaling procedure. The preliminary set of values for ϕ L and n {b/L}, together with other auxiliary model parameters, is subsequently optimized to obtain a good numerical agreement between calculated and experimental values of Δo H {f/L} for sixty liquid transition metal alloys. It is found that, with few exceptions, the use of liquid-specific model parameters in Macroscopic Atom Model yields a physically consistent methodology for reliable estimation of mixing enthalpies of liquid alloys.

  15. Formation of Globular Clusters in Atomic-cooling Halos Via Rapid Gas Condensation and Fragmentation during the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Kimm, Taysun; Cen, Renyue; Rosdahl, Joakim; Yi, Sukyoung K.

    2016-05-01

    We investigate the formation of metal-poor globular clusters (GCs) at the center of two dark matter halos with {M}{{halo}}˜ 4× {10}7 {M}ȯ at z\\gt 10 using cosmological radiation-hydrodynamics simulations. We find that very compact (≲1 pc) and massive (˜ 6× {10}5 {M}ȯ ) clusters form rapidly when pristine gas collapses isothermally with the aid of efficient Lyα emission during the transition from molecular-cooling halos to atomic-cooling halos. Because the local free-fall time of dense star-forming gas is very short (\\ll 1 {{Myr}}), a large fraction of the collapsed gas is turned into stars before stellar feedback processes blow out the gas and shut down star formation. Although the early stage of star formation is limited to a small region of the central star-forming disk, we find that the disk quickly fragments due to metal enrichment from supernovae. Sub-clusters formed in the fragmented clouds eventually merge with the main cluster at the center. The simulated clusters closely resemble the local GCs in mass and size but show a metallicity spread that is much wider than found in the local GCs. We discuss a role of pre-enrichment by Pop III and II stars as a potential solution to the latter issue. Although not without shortcomings, it is encouraging that a naive blind (not tuned) cosmological simulation presents a possible channel for the formation of at least some massive GCs.

  16. First-principles study of one-dimensional sandwich wires [(P)5TM]∞ (TM = Ti, V, Cr, Mn, Fe, Co)

    NASA Astrophysics Data System (ADS)

    Ma, Yandong; Dai, Ying; Li, Xinru; Li, Zhujie; Huang, Baibiao

    2013-10-01

    Since the discovery of ferrocene, many one-dimensional metallic sandwich molecular wires have been identified. However, most of the known systems are assembled from organic molecules. Suffering from many drawbacks has, however, hampered their widespread applications. With the goal of breaking this logjam, we provide a blueprint for the designing of a variety of novel sandwich molecular wires ([(P)5TM]∞, TM = Ti, V, Cr, Mn, Fe, and Co) assembled from ferrocene-like inorganic molecules (P)5TM, offering evidence of the existence of inorganic molecular wires in this class. We present first-principles calculations to investigate systematically the electronic and magnetic properties of such novel inorganic sandwich molecular wires. Compared with the organic molecular wires, all the inorganic [(P)5TM]∞ wires are of large magnetic moment. Among them, we find that [(P)5V]∞, [(P)5Cr]∞ and [(P)5Mn]∞ display ferromagnetic character, while for [(P)5Ti]∞, [(P)5Fe]∞ and [(P)5Co]∞, the magnetic coupling is antiferromagnetic. More remarkably, the TM atoms distributed in these wires show regular docking and lead to structures with ordered spin signals, which is a long-term dream of spintronics. We propose that the difference in magnetic coupling for the studied systems is related to the competition between two exchange interactions of TM atoms. Specifically, we propound that the general mechanism for the formation of stable 1D [(P)5TM]∞ involves the transfer of one electron from the TM atom to the P5 ligand forming ({P})_{5}^{-} and TM+ alternating structure.

  17. Ionization dynamics of a single wire z-pinch

    NASA Astrophysics Data System (ADS)

    Johnston, Mark Darren

    This thesis explored the ionization dynamics of a single wire z-pinch. Experiments were conducted on fine wires of aluminum, copper, silver, and tungsten ranging in diameter from 7.5--50mum with lengths of 2.5cm. These wires were subjected to a pulsed current of ˜2kA, 500ns half-cycle from a spark-gap triggered, negatively-charged capacitor bank discharge. The results of this thesis are divided into three parts which cover the entire dynamic evolution of the wires during the first ˜500ns of the current pulse. The first part examined surface impurity evolution and its contribution to the voltage collapse and initial plasma formation. It was discovered that hydrocarbon impurities contribute significantly to the initial plasma formation, for all wires studied, and that high ionization states of carbon (CIII and CIV) are present at the point of the voltage collapse. The second portion of the thesis dealt with laser imaging and the observation of instability growth at the core/corona boundary of expanding z-pinch wire plasmas. From the increased sensitivity of the resonant XeCl excimer laser diagnostics, it was determined that, for aluminum wires, these instabilities were consistent with a hydrodynamic Rayleigh-Taylor instability of a decelerating plasma plume front. The third portion of the thesis focused on potential seeding mechanisms for instability growth in single wire z-pinches and their relevance to wire array experiments. It was observed in copper wires that do pre-heating of wires caused surface alterations due to recrystallization. It was also discovered, during the course of these studies, that electrical current pulses on the timescale of the experimental pulse (500ns half-cycle) could also alter the surface structure of copper wires and lead to coronal instabilities. Finally, preliminary investigations into the possibility of crystal/grain growth behavior in tungsten wires is given, along with the idea of using potassium doped tungsten wires as a means

  18. Self-assembly of tin wires via phase transformation of heteroepitaxial germanium-tin on germanium substrate

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Li, Lingzi; Tok, Eng Soon; Yeo, Yee-Chia

    2015-06-01

    This work demonstrates and describes for the first time an unusual strain-relaxation mechanism by the formation and self-assembly of well-ordered tin wires during the thermal annealing of epitaxial Ge0.83Sn0.17-on-Ge(001) substrate. Fully strained germanium-tin alloys (Ge0.83Sn0.17) were epitaxially grown on Ge(001) substrate by molecular beam epitaxy. The morphological and compositional evolution of Ge0.83Sn0.17 during thermal annealing is studied by atomic force microscopy, X-ray diffraction, transmission electron microscopy. Under certain annealing conditions, the Ge0.83Sn0.17 layer decomposes into two stable phases, and well-defined Sn wires that are preferentially oriented along two orthogonal ⟨100⟩ azimuths are formed. The formation of the Sn wires is related to the annealing temperature and the Ge0.83Sn0.17 thickness, and can be explained by the nucleation of a grain with Sn islands on the outer front, followed by grain boundary migration. The Sn wire formation process is found to be thermally activated, and an activation enthalpy (Ec) of 0.41 eV is extracted. This thermally activated phase transformation, i.e., 2D epitaxial layer to 3D wires, occurs via a mechanism akin to "cellular precipitation." This synthesis route of Sn wires opens new possibilities for creation of nanoscale patterns at high-throughput without the need for lithography.

  19. Self-assembly of tin wires via phase transformation of heteroepitaxial germanium-tin on germanium substrate

    SciTech Connect

    Wang, Wei; Li, Lingzi; Yeo, Yee-Chia; Tok, Eng Soon

    2015-06-14

    This work demonstrates and describes for the first time an unusual strain-relaxation mechanism by the formation and self-assembly of well-ordered tin wires during the thermal annealing of epitaxial Ge{sub 0.83}Sn{sub 0.17}-on-Ge(001) substrate. Fully strained germanium-tin alloys (Ge{sub 0.83}Sn{sub 0.17}) were epitaxially grown on Ge(001) substrate by molecular beam epitaxy. The morphological and compositional evolution of Ge{sub 0.83}Sn{sub 0.17} during thermal annealing is studied by atomic force microscopy, X-ray diffraction, transmission electron microscopy. Under certain annealing conditions, the Ge{sub 0.83}Sn{sub 0.17} layer decomposes into two stable phases, and well-defined Sn wires that are preferentially oriented along two orthogonal 〈100〉 azimuths are formed. The formation of the Sn wires is related to the annealing temperature and the Ge{sub 0.83}Sn{sub 0.17} thickness, and can be explained by the nucleation of a grain with Sn islands on the outer front, followed by grain boundary migration. The Sn wire formation process is found to be thermally activated, and an activation enthalpy (E{sub c}) of 0.41 eV is extracted. This thermally activated phase transformation, i.e., 2D epitaxial layer to 3D wires, occurs via a mechanism akin to “cellular precipitation.” This synthesis route of Sn wires opens new possibilities for creation of nanoscale patterns at high-throughput without the need for lithography.

  20. Commercial and Industrial Wiring.

    ERIC Educational Resources Information Center

    Kaltwasser, Stan; Flowers, Gary

    This module is the third in a series of three wiring publications, includes additional technical knowledge and applications required for job entry in the commercial and industrial wiring trade. The module contains 15 instructional units that cover the following topics: blueprint reading and load calculations; tools and equipment; service;…

  1. 2016 MOST WIRED.

    PubMed

    Barr, Paul; Butcher, Lola; Hoppszallern, Suzanna

    2016-07-01

    This year's IT survey shows that hospitals are aggressively fighting cyber crime and looking for ways to use data to help in the transition to value-based care. Find out who made the 2016 lists of Most Wired, Most Advanced, Most Improved and Most Wired-Small and Rural. PMID:27526506

  2. The exploding wire phenomenon

    NASA Astrophysics Data System (ADS)

    Aspden, H.

    1985-02-01

    Graneau's recent interpretation of the exploding wire phenomenon as an electrodynamic effect verifying Ampère's classical formulation is questioned. Instead, it is shown that the rupturing force arising from the imbalance of the self-induced electromotive force and the ohmic potential during an explosive current surge will account for the wire breaking into several segments, as is observed.

  3. Water Desalination with Wires.

    PubMed

    Porada, S; Sales, B B; Hamelers, H V M; Biesheuvel, P M

    2012-06-21

    We show the significant potential of water desalination using a novel capacitive wire-based technology in which anode/cathode wire pairs are constructed from coating a thin porous carbon electrode layer on top of electrically conducting rods (or wires). By alternately dipping an array of electrode pairs in freshwater with and in brine without an applied cell voltage, we create an ion adsorption/desorption cycle. We show experimentally how in six subsequent cycles we can reduce the salinity of 20 mM feed (brackish) water by a factor of 3, while application of a cation exchange membrane on the cathode wires makes the desalination factor increase to 4. Theoretical modeling rationalizes the experimental findings, and predicts that system performance can be significantly enhanced by material modifications. To treat large volumes of water, multiple stacks of wire pairs can be used simultaneously in a "merry-go-round" operational mode. PMID:26285717

  4. Visualization of the evolution of charged droplet formation and jet transition in electrostatic atomization

    SciTech Connect

    Huo, Yuanping Wang, Junfeng Zuo, Ziwen; Fan, Yajun

    2015-11-15

    A detailed experimental study on the evolution of charged droplet formation and jet transition from a capillary is reported. By means of high-speed microscopy, special attention has been paid to the dynamics of the liquid thread and satellite droplets in the dripping mode, and a method for calculating the surface charge on the satellite droplet is proposed. Jet transition behavior based on the electric Bond number has been visualized, droplet sizes and velocities are measured to obtain the ejection characteristic of the spray plume, and the charge and hydrodynamic relaxation are linked to give explanations for ejection dynamics with different properties. The results show that the relative length is very sensitive to the hydrodynamic relaxation time. The magnitude of the electric field strength dominates the behavior of coalescence and noncoalescence, with the charge relationship between the satellite droplet and the main droplet being clear for every noncoalescence movement. Ejection mode transitions mainly depend on the magnitude of the electric Bond number, and the meniscus dynamics is determined by the ratio of the charge relaxation time to the hydrodynamic relaxation time.

  5. Visualization of the evolution of charged droplet formation and jet transition in electrostatic atomization

    NASA Astrophysics Data System (ADS)

    Huo, Yuanping; Wang, Junfeng; Zuo, Ziwen; Fan, Yajun

    2015-11-01

    A detailed experimental study on the evolution of charged droplet formation and jet transition from a capillary is reported. By means of high-speed microscopy, special attention has been paid to the dynamics of the liquid thread and satellite droplets in the dripping mode, and a method for calculating the surface charge on the satellite droplet is proposed. Jet transition behavior based on the electric Bond number has been visualized, droplet sizes and velocities are measured to obtain the ejection characteristic of the spray plume, and the charge and hydrodynamic relaxation are linked to give explanations for ejection dynamics with different properties. The results show that the relative length is very sensitive to the hydrodynamic relaxation time. The magnitude of the electric field strength dominates the behavior of coalescence and noncoalescence, with the charge relationship between the satellite droplet and the main droplet being clear for every noncoalescence movement. Ejection mode transitions mainly depend on the magnitude of the electric Bond number, and the meniscus dynamics is determined by the ratio of the charge relaxation time to the hydrodynamic relaxation time.

  6. Formation of manganese {delta}-doped atomic layer in wurtzite GaN

    SciTech Connect

    Shi Meng; Chinchore, Abhijit; Wang Kangkang; Mandru, Andrada-Oana; Liu Yinghao; Smith, Arthur R.

    2012-09-01

    We describe the formation of a {delta}-doped manganese layer embedded within c-plane wurtzite gallium nitride using a special molecular beam epitaxy growth process. Manganese is first deposited on the gallium-poor GaN (0001) surface, forming a {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign reconstructed phase. This well-defined surface reconstruction is then nitrided using plasma nitridation, and gallium nitride is overgrown. The manganese content of the {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign phase, namely one Mn per each {radical}(3) Multiplication-Sign {radical}(3)-R30 Degree-Sign unit cell, implies that the MnGaN alloy layer has a Mn concentration of up to 33%. The structure and chemical content of the surface are monitored beginning from the initial growth stage up through the overgrowth of 20 additional monolayers (MLs) of GaN. An exponential-like drop-off of the Mn signal with increasing GaN monolayers, as measured by Auger electron spectroscopy, indicates that the highly concentrated Mn layer remains at the {delta}-doped interface. A model of the resultant {delta}-doped structure is formulated based on the experimental data, and implications for possible spintronic applications are discussed.

  7. International space station wire program

    NASA Technical Reports Server (NTRS)

    May, Todd

    1995-01-01

    Hardware provider wire systems and current wire insulation issues for the International Space Station (ISS) program are discussed in this viewgraph presentation. Wire insulation issues include silicone wire contamination, Tefzel cold temperature flexibility, and Russian polyimide wire insulation. ISS is a complex program with hardware developed and managed by many countries and hundreds of contractors. Most of the obvious wire insulation issues are known by contractors and have been precluded by proper selection.

  8. Atomic force microscopy imaging reveals the formation of ASIC/ENaC cross-clade ion channels

    SciTech Connect

    Jeggle, Pia; Smith, Ewan St. J.; Stewart, Andrew P.; Haerteis, Silke; Korbmacher, Christoph; Edwardson, J. Michael

    2015-08-14

    ASIC and ENaC are co-expressed in various cell types, and there is evidence for a close association between them. Here, we used atomic force microscopy (AFM) to determine whether ASIC1a and ENaC subunits are able to form cross-clade hybrid ion channels. ASIC1a and ENaC could be co-isolated from detergent extracts of tsA 201 cells co-expressing the two subunits. Isolated proteins were incubated with antibodies against ENaC and Fab fragments against ASIC1a. AFM imaging revealed proteins that were decorated by both an antibody and a Fab fragment with an angle of ∼120° between them, indicating the formation of ASIC1a/ENaC heterotrimers. - Highlights: • There is evidence for a close association between ASIC and ENaC. • We used AFM to test whether ASIC1a and ENaC subunits form cross-clade ion channels. • Isolated proteins were incubated with subunit-specific antibodies and Fab fragments. • Some proteins were doubly decorated at ∼120° by an antibody and a Fab fragment. • Our results indicate the formation of ASIC1a/ENaC heterotrimers.

  9. Investigation of Kp- and Kd-atom formation and their collisional processes with hydrogen and deuterium targets by the classical-trajectory Monte Carlo method

    SciTech Connect

    Raeisi, G. M.; Kalantari, S. Z.

    2010-10-15

    The classical-trajectory Monte Carlo method has been used to study the capture of negative kaons by hydrogen and deuterium atoms; subsequently, the elastic scattering, Stark mixing, and Coulomb deexcitation cross sections of Kp and Kd atoms have been determined. The results for kaonic atom formation confirm the initial conditions that have been parametrically applied by most atomic cascade models. Our results show that Coulomb deexcitation in Kp and Kd atoms with {Delta}n>1 is important in addition to n=1. We have shown that the contribution of molecular structure effects to the cross sections of the collisional processes is larger than the isotopic effects of the targets. We have also compared our results with the semiclassical approaches.

  10. Body of Knowledge (BOK) for Copper Wire Bonds

    NASA Technical Reports Server (NTRS)

    Rutkowski, E.; Sampson, M. J.

    2015-01-01

    Copper wire bonds have replaced gold wire bonds in the majority of commercial semiconductor devices for the latest technology nodes. Although economics has been the driving mechanism to lower semiconductor packaging costs for a savings of about 20% by replacing gold wire bonds with copper, copper also has materials property advantages over gold. When compared to gold, copper has approximately: 25% lower electrical resistivity, 30% higher thermal conductivity, 75% higher tensile strength and 45% higher modulus of elasticity. Copper wire bonds on aluminum bond pads are also more mechanically robust over time and elevated temperature due to the slower intermetallic formation rate - approximately 1/100th that of the gold to aluminum intermetallic formation rate. However, there are significant tradeoffs with copper wire bonding - copper has twice the hardness of gold which results in a narrower bonding manufacturing process window and requires that the semiconductor companies design more mechanically rigid bonding pads to prevent cratering to both the bond pad and underlying chip structure. Furthermore, copper is significantly more prone to corrosion issues. The semiconductor packaging industry has responded to this corrosion concern by creating a palladium coated copper bonding wire, which is more corrosion resistant than pure copper bonding wire. Also, the selection of the device molding compound is critical because use of environmentally friendly green compounds can result in internal CTE (Coefficient of Thermal Expansion) mismatches with the copper wire bonds that can eventually lead to device failures during thermal cycling. Despite the difficult problems associated with the changeover to copper bonding wire, there are billions of copper wire bonded devices delivered annually to customers. It is noteworthy that Texas Instruments announced in October of 2014 that they are shipping microcircuits containing copper wire bonds for safety critical automotive applications

  11. Formation and decay of (3P(J))O atoms in the laser flash photolysis of chlorine dioxide (OClO) at 308 nm

    NASA Technical Reports Server (NTRS)

    Colussi, A. J.

    1990-01-01

    The quantum yields of O(3P(J)) and Cl(2P(3/2)) atoms released in the laser flash photolysis of OClO at 308 and 298 K were determined and the kinetics of the subsequent oxygen atom decay was investigated using time-resolved atomic resonance fluorescence measurements. The results are consistent with the formation of sym-ClO3 having a Delta Hf(ClO3) (formed in the reaction O + OClO + Ar) of 55.6 +/-4 kcal/mol.

  12. Dispersion interaction between crossed conducting wires

    SciTech Connect

    Dobson, John F.; Gould, Timothy; Klich, Israel

    2009-07-15

    We compute the T=0 K Van der Waals (nonretarded Casimir) interaction energy E between two infinitely long, crossed conducting wires separated by a minimum distance D much greater than their radius. We find that, up to a logarithmic correction factor, E{proportional_to}-D{sup -1}|sin {theta}|{sup -1}f({theta}), where f({theta}) is a smooth bounded function of the angle {theta} between the wires. We recover a conventional result of the form E{proportional_to}-D{sup -4}|sin {theta}|{sup -1}g({theta}) when we include an electronic energy gap in our calculation. Our prediction of gap-dependent energetics may be observable experimentally for carbon nanotubes either via atomic force microscopy detection of the Van der Waals force or torque or indirectly via observation of mechanical oscillations. This shows that strictly parallel wires, as assumed in previous predictions, are not needed to see a unique effect of this type.

  13. Seeded perturbations in wire array Z-Pinches.

    SciTech Connect

    Robinson, Allen Conrad; Fedin, Dmitry; Kantsyrev, Victor Leonidovich; Wunsch, Scott Edward; Oliver, Bryan Velten; Lebedev, Sergey V.; Coverdale, Christine Anne; Ouart, Nicholas D.; LePell, Paul David; Safronova, Alla S.; Shrestha, I.; McKenney, John Lee; Ampleford, David J.; Rapley, J.; Bott, S. C.; Palmer, J. B. A.; Sotnikov, Vladimir Isaakovich; Bland, Simon Nicholas; Ivanov, Vladimir V.; Chittenden, Jeremy Paul; Jones, B.; Garasi, Christopher Joseph; Hall, Gareth Neville; Yilmaz, M. Faith; Mehlhorn, Thomas Alan; Deeney, Christopher; Pokala, S.; Nalajala, V.

    2005-07-01

    Controlled seeding of perturbations is employed to study the evolution of wire array z-pinch implosion instabilities which strongly impact x-ray production when the 3D plasma stagnates on axis. Wires modulated in radius exhibit locally enhanced magnetic field and imploding bubble formation at discontinuities in wire radius due to the perturbed current path. Wires coated with localized spectroscopic dopants are used to track turbulent material flow. Experiments and MHD modeling offer insight into the behavior of z-pinch instabilities.

  14. Next Generation Wiring

    NASA Technical Reports Server (NTRS)

    Medelius, Petro; Jolley, Scott; Fitzpatrick, Lilliana; Vinje, Rubiela; Williams, Martha; Clayton, LaNetra; Roberson, Luke; Smith, Trent; Santiago-Maldonado, Edgardo

    2007-01-01

    Wiring is a major operational component on aerospace hardware that accounts for substantial weight and volumetric space. Over time wire insulation can age and fail, often leading to catastrophic events such as system failure or fire. The next generation of wiring must be reliable and sustainable over long periods of time. These features will be achieved by the development of a wire insulation capable of autonomous self-healing that mitigates failure before it reaches a catastrophic level. In order to develop a self-healing insulation material, three steps must occur. First, methods of bonding similar materials must be developed that are capable of being initiated autonomously. This process will lead to the development of a manual repair system for polyimide wire insulation. Second, ways to initiate these bonding methods that lead to materials that are similar to the primary insulation must be developed. Finally, steps one and two must be integrated to produce a material that has no residues from the process that degrades the insulating properties of the final repaired insulation. The self-healing technology, teamed with the ability to identify and locate damage, will greatly improve reliability and safety of electrical wiring of critical systems. This paper will address these topics, discuss the results of preliminary testing, and remaining development issues related to self-healing wire insulation.

  15. Formation of gallaoxetanes: C-O activation of 1,2-epoxybutane by ground-state Ga atoms.

    PubMed

    Joly, Helen A; Beaudet, Luc; Levesque, Michelle; Myre, Maxine

    2011-10-27

    (69/71)Ga atoms were reacted with 1,2-epoxybutane and its isotopomers, 1,2-epoxybutane-1,1-d(2) (CH(3)CH(2)CHOCD(2)) and 1,2-epoxybutane-2-d(1) (CH(3)CH(2)CDOCH(2)), under matrix-isolation conditions. The novel gallaoxetanes CH(3)CH(2)CHCH(2)GaO and CH(3)CH(2)CHCH(2)OGa, resulting from the insertion of the metal atom in the C(1)-O and C(2)-O bonds, respectively, of the 1,2-epoxybutane, were detected by EPR spectroscopy. The Ga and H hyperfine interaction (hfi) values of the gallaoxetanes, calculated using a DFT method, were used to help assign the EPR spectra. A third Ga-centered species, detected at 190 K, underwent spectral changes similar to those of the C(2)-O insertion product upon isotopic substitution of the 1,2-epoxybutane. Although the Ga hfi for this species was 36% smaller than that of the C(2)-O insertion product, the values for the H hfi were similar, suggesting that the carrier of the spectrum was the C(2)-O insertion product where Ga was perturbed by the matrix constraints. The alkyl radical CH(3)CH(2)(•CH)CH(2)OGa, resulting from ring-opening at the C(2)-O bond of 1,2-epoxybutane, was observed at temperatures below 150 K. This radical has been implicated in the formation of the C(2)-O insertion product. The unusually small value found for two of the β-hydrogens of the alkyl radical is discussed. PMID:21899276

  16. Orbiter Kapton wire operational requirements and experience

    NASA Technical Reports Server (NTRS)

    Peterson, R. V.

    1994-01-01

    The agenda of this presentation includes the Orbiter wire selection requirements, the Orbiter wire usage, fabrication and test requirements, typical wiring installations, Kapton wire experience, NASA Kapton wire testing, summary, and backup data.

  17. Dynamics of vapor emissions at wire explosion thresholda)

    NASA Astrophysics Data System (ADS)

    Belony, Paul A.; Kim, Yong W.

    2010-10-01

    X-pinch plasmas have been actively studied in the recent years. Numerical simulation of the ramp-up of metallic vapor emissions from wire specimens shows that under impulsive Ohmic heating the wire core invariably reaches a supercritical state before explosion. The heating rate depends sensitively on the local wire resistance, leading to highly variable vapor emission flux along the wire. To examine the vapor emission process, we have visualized nickel wire explosions by means of shock formation in air. In a single explosion as captured by shadowgraphy, there usually appear several shocks with spherical or cylindrical wave front originating from different parts of the wire. Growth of various shock fronts in time is well characterized by a power-law scaling in one form or another. Continuum emission spectra are obtained and calibrated to measure temperature near the explosion threshold. Shock front structures and vapor plume temperature are examined.

  18. Gas infall into atomic cooling haloes: on the formation of protogalactic discs and supermassive black holes at z > 10

    NASA Astrophysics Data System (ADS)

    Prieto, Joaquin; Jimenez, Raul; Haiman, Zoltán

    2013-12-01

    We have performed hydrodynamical simulations from cosmological initial conditions using the Adaptive Mesh Refinement (AMR) code RAMSES to study atomic cooling haloes (ACHs) at z = 10 with masses in the range 5 × 107 M⊙ ≲ M ≲ 2 × 109 M⊙. We assume the gas has primordial composition and H2-cooling and prior star formation in the haloes have been suppressed. We present a comprehensive analysis of the gas and dark matter (DM) properties of 19 haloes at a spatial resolution of ˜10 (proper) pc, selected from simulations with a total volume of ˜2000 (comoving) Mpc3. This is the largest statistical hydro-simulation study of ACHs at z > 10 to date. We examine the morphology, angular momentum, thermodynamical state and turbulent properties of these haloes, in order to assess the prevalence of discs and massive overdensities that may lead to the formation of supermassive black holes (SMBHs). We find no correlation between either the magnitude or the direction of the angular momentum of the gas and its parent DM halo. Only three of the haloes form rotationally supported cores. Two of the most massive haloes, however, form massive, compact overdense blobs, which migrate to the outer region of the halo. These blobs have an accretion rate between ˜10-1 and 10-3 M⊙ yr-1 (at a distance of 100 pc from their centre), and are possible sites of SMBH formation. Our results suggest that the degree of rotational support and the fate of the gas in a halo is determined by its large-scale environment and merger history. In particular, the two haloes that form overdense blobs are located at knots of the cosmic web, cooled their gas early on (z > 17) and experienced many mergers. The gas in these haloes is thus lumpy and highly turbulent, with Mach numbers M≳ 5. In contrast, the haloes forming rotationally supported cores are relatively more isolated, located mid-way along filaments of the cosmic web, cooled their gas more recently and underwent fewer mergers. As a result, the

  19. Radiation from mixed multi-planar wire arrays

    NASA Astrophysics Data System (ADS)

    Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Chuvatin, A. S.; Weller, M. E.; Shlyaptseva, V. V.; Shrestha, I.; Keim, S. F.; Stafford, A.; Coverdale, C. A.; Apruzese, J. P.; Ouart, N. D.; Giuliani, J. L.

    2014-03-01

    The study of radiation from different wire materials in wire array Z-pinch plasma is a very challenging topic because it is almost impossible to separate different plasmas at the stagnation. A new approach is suggested based on planar wire array (PWA) loads to assess this problem. Multi-planar wire arrays are implemented that consist of few planes, each with the same number of wires and masses but from different wire materials, arranged in parallel rows. In particular, the experimental results obtained with triple PWAs (TPWAs) on the UNR Zebra generator are analyzed with Wire Ablation Dynamics Model, non-local thermodynamic equilibrium kinetic model, and 2D radiation magneto-hydrodynamic to illustrate this new approach. In TPWAs, two wire planes were from mid-atomic-number wire material and another plane was from alloyed Al, placed either in the middle or at the edge of the TPWA. Spatial and temporal properties of K-shell Al and L-shell Cu radiations were analyzed and compared from these two configurations of TPWAs. Advantages of the new approach are demonstrated and future work is discussed.

  20. Radiation from mixed multi-planar wire arrays

    SciTech Connect

    Safronova, A. S.; Kantsyrev, V. L.; Esaulov, A. A.; Weller, M. E.; Shlyaptseva, V. V.; Shrestha, I.; Keim, S. F.; Stafford, A.; Chuvatin, A. S.; Coverdale, C. A.; Apruzese, J. P.; Ouart, N. D.; Giuliani, J. L.

    2014-03-15

    The study of radiation from different wire materials in wire array Z-pinch plasma is a very challenging topic because it is almost impossible to separate different plasmas at the stagnation. A new approach is suggested based on planar wire array (PWA) loads to assess this problem. Multi-planar wire arrays are implemented that consist of few planes, each with the same number of wires and masses but from different wire materials, arranged in parallel rows. In particular, the experimental results obtained with triple PWAs (TPWAs) on the UNR Zebra generator are analyzed with Wire Ablation Dynamics Model, non-local thermodynamic equilibrium kinetic model, and 2D radiation magneto-hydrodynamic to illustrate this new approach. In TPWAs, two wire planes were from mid-atomic-number wire material and another plane was from alloyed Al, placed either in the middle or at the edge of the TPWA. Spatial and temporal properties of K-shell Al and L-shell Cu radiations were analyzed and compared from these two configurations of TPWAs. Advantages of the new approach are demonstrated and future work is discussed.

  1. Liquid atomization

    SciTech Connect

    Walzel, P. )

    1993-01-01

    A systematic review of different liquid atomizers is presented, accompanied by a discussion of various mechanisms of droplet formation in a gas atmosphere as a function of the liquid flow-regime and the geometry of the atomizer. Equations are presented for the calculation of the mean droplet-diameter. In many applications, details of the droplet size distribution are, also, important, e.g., approximate values of the breadth of the droplet formation are given. The efficiency of utilization of mechanical energy in droplet formation is indicated for the different types of atomizers. Atomization is used, in particular, for the following purposes: (1) atomization of fuels; (2) making granular products; (3) carrying out mass-transfer operations; and (4) coating of surfaces.

  2. Dual wire weld feed proportioner

    NASA Technical Reports Server (NTRS)

    Nugent, R. E.

    1968-01-01

    Dual feed mechanism enables proportioning of two different weld feed wires during automated TIG welding to produce a weld alloy deposit of the desired composition. The wires are fed into the weld simultaneously. The relative feed rates of the wires and the wire diameters determine the weld deposit composition.

  3. Reactions of OOH radical with beta-carotene, lycopene, and torulene: hydrogen atom transfer and adduct formation mechanisms.

    PubMed

    Galano, Annia; Francisco-Marquez, Misaela

    2009-08-13

    The relative free radical scavenging activity of beta-carotene, lycopene, and torulene toward OOH radicals has been studied using density functional theory. Hydrogen atom transfer (HAT) and radical adduct formation (RAF) mechanisms have been considered. All the possible reaction sites have been included in the modeling, and detailed branching ratios are reported for the first time. The reactions of hydrocarbon carotenoids (Car) with peroxyl radicals, in both polar and nonpolar environments, are predicted to proceed via RAF mechanism, with contributions higher than 98% to the overall OOH + Car reactions. Lycopene and torulene were found to be more reactive than beta-carotene. In nonpolar environments the reactivity of the studied carotenoids toward peroxyl radical follows the trend LYC > TOR > BC, whereas in aqueous solutions it is TOR > LYC > BC. OOH adducts are predicted to be formed mainly at the terminal sites of the conjugated polyene chains. The main addition sites were found to be C5 for beta-carotene and lycopene and C30 for torulene. The general agreement between the calculated magnitudes and the available experimental data supports the predictions from this work. PMID:19627101

  4. High Star Formation Rates in Turbulent Atomic-dominated Gas in the Interacting Galaxies IC 2163 and NGC 2207

    NASA Astrophysics Data System (ADS)

    Elmegreen, Bruce G.; Kaufman, Michele; Bournaud, Frédéric; Elmegreen, Debra Meloy; Struck, Curtis; Brinks, Elias; Juneau, Stéphanie

    2016-05-01

    CO observations of the interacting galaxies IC 2163 and NGC 2207 are combined with HI, Hα, and 24 μm observations to study the star formation rate (SFR) surface density as a function of the gas surface density. More than half of the high-SFR regions are HI dominated. When compared to other galaxies, these HI-dominated regions have excess SFRs relative to their molecular gas surface densities but normal SFRs relative to their total gas surface densities. The HI-dominated regions are mostly located in the outer part of NGC 2207 where the HI velocity dispersion is high, 40–50 km s‑1. We suggest that the star-forming clouds in these regions have envelopes at lower densities than normal, making them predominantly atomic, and cores at higher densities than normal because of the high turbulent Mach numbers. This is consistent with theoretical predictions of a flattening in the density probability distribution function for compressive, high Mach number turbulence.

  5. Thioozonide decomposition: sulfur and oxygen atom transfer. Evidence for the formation of a carbonyl O-sulfide intermediate

    SciTech Connect

    Matturro, M.G.; Reynolds, R.P.; Kastrup, R.V.; Pictroski, C.F.

    1986-05-14

    The chemistry of ozonides is of considerable interest from a practical and theoretical viewpoint. Thioozonide 1, formally the monosulfur-substituted ozonide of dimethylcyclobutadiene, has been proposed as an intermediate in the room temperature photooxidation of 2,5-dimethylthiophene. Subsequent low-temperature studies confirmed this structural assignment. When 1 is allowed to warm to room temperature, it rearranges to a mixture of sulfine 2 and cis- and trans-3-hexene-2,5-diones (3c and 3t). Recent examination of the thermal decomposition of 1 has led to a proposed mechanism involving a carbonyl sulfide 4 as an intermediate along the sulfur expulsion pathway to 3c; however, no experimental support for this hypothesis was given. Carbonyl O-sulfides have also been implicated as intermediates from the photolysis of oxathiiranes. The authors report evidence for the formation of 4 during the decomposition of 1 and that elemental sulfur (S/sub 8/) is formed during the reaction by concatenation of sulfur atoms or fragments (S/sub 2/, S/sub 3/, etc.).

  6. High velocity pulsed wire-arc spray

    NASA Technical Reports Server (NTRS)

    Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor); Kincaid, Russell W. (Inventor)

    1999-01-01

    Wire arc spraying using repetitively pulsed, high temperature gas jets, usually referred to as plasma jets, and generated by capillary discharges, substantially increases the velocity of atomized and entrained molten droplets. The quality of coatings produced is improved by increasing the velocity with which coating particles impact the coated surface. The effectiveness of wire-arc spraying is improved by replacing the usual atomizing air stream with a rapidly pulsed high velocity plasma jet. Pulsed power provides higher coating particle velocities leading to improved coatings. 50 micron aluminum droplets with velocities of 1500 m/s are produced. Pulsed plasma jet spraying provides the means to coat the insides of pipes, tubes, and engine block cylinders with very high velocity droplet impact.

  7. H-atom addition and abstraction reactions in mixed CO, H2CO and CH3OH ices - an extended view on complex organic molecule formation

    NASA Astrophysics Data System (ADS)

    Chuang, K.-J.; Fedoseev, G.; Ioppolo, S.; van Dishoeck, E. F.; Linnartz, H.

    2016-01-01

    Complex organic molecules (COMs) have been observed not only in the hot cores surrounding low- and high-mass protostars, but also in cold dark clouds. Therefore, it is interesting to understand how such species can be formed without the presence of embedded energy sources. We present new laboratory experiments on the low-temperature solid state formation of three complex molecules - methyl formate (HC(O)OCH3), glycolaldehyde (HC(O)CH2OH) and ethylene glycol (H2C(OH)CH2OH) - through recombination of free radicals formed via H-atom addition and abstraction reactions at different stages in the CO→H2CO→CH3OH hydrogenation network at 15 K. The experiments extend previous CO hydrogenation studies and aim at resembling the physical-chemical conditions typical of the CO freeze-out stage in dark molecular clouds, when H2CO and CH3OH form by recombination of accreting CO molecules and H-atoms on ice grains. We confirm that H2CO, once formed through CO hydrogenation, not only yields CH3OH through ongoing H-atom addition reactions, but is also subject to H-atom-induced abstraction reactions, yielding CO again. In a similar way, H2CO is also formed in abstraction reactions involving CH3OH. The dominant methanol H-atom abstraction product is expected to be CH2OH, while H-atom additions to H2CO should at least partially proceed through CH3O intermediate radicals. The occurrence of H-atom abstraction reactions in ice mantles leads to more reactive intermediates (HCO, CH3O and CH2OH) than previously thought, when assuming sequential H-atom addition reactions only. This enhances the probability to form COMs through radical-radical recombination without the need of UV photolysis or cosmic rays as external triggers.

  8. Splicing Wires Permanently With Explosives

    NASA Technical Reports Server (NTRS)

    Bement, Laurence J.; Kushnick, Anne C.

    1990-01-01

    Explosive joining process developed to splice wires by enclosing and metallurgically bonding wires within copper sheets. Joints exhibit many desirable characteristics, 100-percent conductivity and strength, no heat-induced annealing, no susceptibility to corrosion in contacts between dissimilar metals, and stability at high temperature. Used to join wires to terminals, as well as to splice wires. Applicable to telecommunications industry, in which millions of small wires spliced annually.

  9. Wire chambers revisited.

    PubMed

    Ott, R J

    1993-04-01

    Detectors used for radioisotope imaging have, historically, been based on scintillating crystal/photomultiplier combinations in various forms. From the rectilinear scanner through to modern gamma cameras and positron cameras, the basic technology has remained much the same. Efforts to overcome the limitations of this form of technology have foundered on the inability to reproduce the required sensitivity, spatial resolution and sensitive area at acceptable cost. Multiwire proportional chambers (MWPCs) have long been used as position-sensitive charged particle detectors in nuclear and high-energy physics. MWPCs are large-area gas-filled ionisation chambers in which large arrays of fine wires are used to measure the position of ionisation produced in the gas by the passage of charged particles. The important properties of MWPCs are high-spatial-resolution, large-area, high-count-rate performance at low cost. For research applications, detectors several metres square have been built and small-area detectors have a charged particle resolution of 0.4 mm at a count rate of several million per second. Modification is required to MWPCs for nuclear medicine imaging. As gamma rays or X-rays cannot be detected directly, they must be converted into photo- or Compton scatter electrons. Photon-electron conversion requires the use of high atomic number materials in the body of the chamber. Pressurised xenon is the most useful form of "gas only" photon-electron convertor and has been used successfully in a gamma camera for the detection of gamma rays at energies below 100 keV. This camera has been developed specifically for high-count-rate first-pass cardiac imaging. This high-pressure xenon gas MWPC is the key to a highly competitive system which can outperform scintillator-based systems. The count rate performance is close to a million counts per second and the intrinsic spatial resolution is better than the best scintillator-based camera. The MWPC camera produces quantitative

  10. Demonstration of a cold atom beam splitter on atom chip

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaojun; Li, Xiaolin; Zhang, Haichao; Wang, Yuzhu

    2016-08-01

    We report an experimental demonstration of a new scheme to split cold atoms on an atom chip. The atom chip consists of a U-wire and a Z-wire. The cold atom cloud is initially loaded and prepared in the Z-trap, which is split into two separate parts by switching on the current of the U-wire. The two separate atom clouds have a distance more than one millimeter apart from each other and show almost symmetrical profiles, corresponding to about a 50/50 splitting ratio. Project supported by the State Key Basic Research Program of China (Grant No. 2011CB921504) and the National Natural Science Foundation of China (Grant No. 91536107).

  11. Metallurgical investigation of wire breakage of tyre bead grade

    PubMed Central

    Palit, Piyas; Das, Souvik; Mathur, Jitendra

    2015-01-01

    Tyre bead grade wire is used for tyre making application. The wire is used as reinforcement inside the polymer of tyre. The wire is available in different size/section such as 1.6–0.80 mm thin Cu coated wire. During tyre making operation at tyre manufacturer company, wire failed frequently. In this present study, different broken/defective wire samples were collected from wire mill for detailed investigation of the defect. The natures of the defects were localized and similar in nature. The fracture surface was of finger nail type. Crow feet like defects including button like surface abnormalities were also observed on the broken wire samples. The defect was studied at different directions under microscope. Different advanced metallographic techniques have been used for detail investigation. The analysis revealed that, white layer of surface martensite was formed and it caused the final breakage of wire. In this present study we have also discussed about the possible reason for the formation of such kind of surface martensite (hard-phase). PMID:26973808

  12. Matrix-isolation studies on the radiation-induced chemistry in H₂O/CO₂ systems: reactions of oxygen atoms and formation of HOCO radical.

    PubMed

    Ryazantsev, Sergey V; Feldman, Vladimir I

    2015-03-19

    The radiation-induced transformations occurring upon X-ray irradiation of solid CO2/H2O/Ng systems (Ng = Ar, Kr, Xe) at 8-10 K and subsequent annealing up to 45 K were studied by Fourier transform infrared spectroscopy. The infrared (IR) spectra of deposited matrices revealed the presence of isolated monomers, dimers, and intermolecular H2O···CO2 complexes. Irradiation resulted in effective decomposition of matrix-isolated carbon dioxide and water yielding CO molecules and OH radicals, respectively. Annealing of the irradiated samples led to formation of O3, HO2, and a number of xenon hydrides of HXeY type (in the case of xenon matrices). The formation of these species was used for monitoring of the postirradiation thermally induced chemical reactions involving O and H atoms generated by radiolysis. It was shown that the radiolysis of CO2 in noble-gas matrices produced high yields of stabilized oxygen atoms. In all cases, the temperatures at which O atoms become mobile and react are lower than those of H atoms. Dynamics and reactivity of oxygen atoms was found to be independent of the precursor nature. In addition, the formation of HOCO radicals was observed in all the noble-gas matrices at remarkably low temperatures. The IR spectra of HOCO and DOCO were first characterized in krypton and xenon matrices. It was concluded that the formation of HOCO was mainly due to the radiation-induced evolution of the weakly bound H2O···CO2 complexes. This result indicates the significance of weak intermolecular interactions in the radiation-induced chemical processes in inert low-temperature media. PMID:25469518

  13. Understanding the Formation Mechanism of Two-Dimensional Atomic Islands on Crystal Surfaces by the Condensing Potential Model

    NASA Astrophysics Data System (ADS)

    Yin, Cong; Lin, Zheng-Zhe; Li, Min; Tang, Hao

    2016-04-01

    A condensing potential (CP) model was established for predicting the geometric structure of two-dimensional (2D) atomic islands on crystal surfaces. To further verify the CP model, statistical molecular dynamics simulations are performed to investigate the trapping adatom process of atomic island steps on Pt (111). According to the detailed analysis on the adatom trapping process, the CP model should be a universal theory to understand the shape of the 2D atomic islands on crystal surfaces.

  14. Atomic collisions in suprafluid helium-nanodroplets: timescales for metal-cluster formation derived from He-density functional theory

    PubMed Central

    Volk, Alexander; Thaler, Philipp

    2015-01-01

    Collision times for the coinage metal atoms Cu, Ag and Au in He-droplets are derived from helium density functional theory and molecular dynamics simulations. The strength of the attractive interaction between the metal atoms turns out to be less important than the mass of the propagating metal atoms. Even for small droplets consisting of a few thousand helium atoms, the collision times are shortest for Cu, followed by Ag and Au, despite the higher binding energy of Au2 compared to Cu2. PMID:25812719

  15. Wire brush fastening device

    SciTech Connect

    Meigs, R.A.

    1993-08-31

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus.

  16. Wire brush fastening device

    DOEpatents

    Meigs, Richard A.

    1995-01-01

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus.

  17. Wire brush fastening device

    DOEpatents

    Meigs, R.A.

    1995-09-19

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus. 13 figs.

  18. Dielectric coated wire antennas

    NASA Technical Reports Server (NTRS)

    Richmond, J. H.; Newman, E. H.

    1976-01-01

    An electrically thin dielectric insulating shell on an antenna composed of electrically thin circular cylindrical wires is examined. A moment method solution is obtained, and the insulating shell is modeled by equivalent volume polarization currents. These polarization currents are related in a simple manner to the surface charge density on the wire antenna. In this way the insulating shell causes no new unknowns to be introduced, and the size of the impedance matrix is the same as for the uninsulated wires. The insulation is accounted for entirely through a modification of the symmetric impedance matrix. This modification influences the current distribution, impedance, efficiency, field patterns, and scattering properties. The theory is compared with measurement for dielectric coated antennas in air.

  19. 2. TYPICAL OVERHEAD WIRE CONSTRUCTION CURVE GUY WIRE ARRANGEMENT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. TYPICAL OVERHEAD WIRE CONSTRUCTION - CURVE GUY WIRE ARRANGEMENT (ABANDONED WEST LEG OF WYE AT SIXTH AVENUE AND PINE STREET) - Yakima Valley Transportation Company Interurban Railroad, Trackage, Yakima, Yakima County, WA

  20. Flying wires at Fermilab

    SciTech Connect

    Gannon, J.; Crawford, C.; Finley, D.; Flora, R.; Groves, T.; MacPherson, M.

    1989-03-01

    Transverse beam profile measurement systems called ''Flying Wires'' have been installed and made operational in the Fermilab Main Ring and Tevatron accelerators. These devices are used routinely to measure the emittance of both protons and antiprotons throughout the fill process, and for emittance growth measurements during stores. In the Tevatron, the individual transverse profiles of six proton and six antiproton bunches are obtained simultaneously, with a single pass of the wire through the beam. Essential features of the hardware, software, and system operation are explained in the rest of the paper. 3 refs., 4 figs.

  1. Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: An Investigation of the Metal Catalyst by Laser Ablation Atomic Fluorescence Spectroscopy

    NASA Technical Reports Server (NTRS)

    deBoer, Gary; Scott, Carl

    2003-01-01

    Carbon nanotubes, elongated molecular tubes with diameters of nanometers and lengths in microns, hold great promise for material science. Hopes for super strong light-weight material to be used in spacecraft design is the driving force behind nanotube work at JSC. The molecular nature of these materials requires the appropriate tools for investigation of their structure, properties, and formation. The mechanism of nanotube formation is of particular interest because it may hold keys to controlling the formation of different types of nanotubes and allow them to be produced in much greater quantities at less cost than is currently available. This summer's work involved the interpretation of data taken last summer and analyzed over the academic year. The work involved diagnostic studies of carbon nanotube formation processes occurring in a laser-produced plume. Laser ablation of metal doped graphite to produce a plasma plume in which carbon nanotubes self assemble is one method of making carbon nanotube. The laser ablation method is amenable to applying the techniques of laser spectroscopy, a powerful tool for probing the energies and dynamics of atomic and molecular species. The experimental work performed last summer involved probing one of the metal catalysts, nickel, by laser induced fluorescence. The nickel atom was studied as a function of oven temperature, probe laser wavelength, time after ablation, and position in the laser produced plume. This data along with previously obtained data on carbon was analyzed over the academic year. Interpretations of the data were developed this summer along with discussions of future work. The temperature of the oven in which the target is ablated greatly influences the amount of material ablated and the propagation of the plume. The ablation conditions and the time scale of atomic and molecular lifetimes suggest that initial ablation of the metal doped carbon target results in atomic and small molecular species. The metal

  2. Wiring for space applications program

    NASA Technical Reports Server (NTRS)

    Hammoud, Ahmad

    1994-01-01

    The insulation testing and analysis consists of: identifying and prioritizing NASA wiring requirements; selecting candidate wiring constructions; developing test matrix and formulating test program; managing, coordinating, and conducting tests; and analyzing and documenting data, establishing guidelines and recommendations.

  3. Charge transfer and formation of reduced Ce3+ upon adsorption of metal atoms at the ceria (110) surface

    NASA Astrophysics Data System (ADS)

    Nolan, Michael

    2012-04-01

    The modification of cerium dioxide with nanoscale metal clusters is intensely researched for catalysis applications, with gold, silver, and copper having been particularly well studied. The interaction of the metal cluster with ceria is driven principally by a localised interaction between a small number of metal atoms (as small as one) and the surface and understanding the fundamentals of the interaction of metal atoms with ceria surfaces is therefore of great interest. Much attention has been focused on the interaction of metals with the (111) surface of ceria, since this is the most stable surface and can be grown as films, which are probed experimentally. However, nanostructures exposing other surfaces such as (110) show high activity for reactions including CO oxidation and require further study; these nanostructures could be modified by deposition of metal atoms or small clusters, but there is no information to date on the atomic level details of metal-ceria interactions involving the (110) surface. This paper presents the results of density functional theory (DFT) corrected for on-site Coulomb interactions (DFT+U) calculations of the adsorption of a number of different metal atoms at an extended ceria (110) surface; the metals are Au, Ag, Cu, Al, Ga, In, La, Ce, V, Cr, and Fe. Upon adsorption all metals are oxidised, transferring electron(s) to the surface, resulting in localised surface distortions. The precise details depend on the identity of the metal atom. Au, Ag, Cu each transfer one electron to the surface, reducing one Ce ion to Ce3+, while of the trivalent metals, Al and La are fully oxidised, but Ga and In are only partially oxidised. Ce and the transition metals are also partially oxidised, with the number of reduced Ce ions possible in this surface no more than three per adsorbed metal atom. The predicted oxidation states of the adsorbed metal atoms should be testable in experiments on ceria nanostructures modified with metal atoms.

  4. NewsWire, 2002.

    ERIC Educational Resources Information Center

    Byrom, Elizabeth, Ed.; Bingham, Margaret, Ed.; Bowman, Gloria, Ed.; Shoemaker, Dan, Ed.

    2002-01-01

    This document presents the 3 2002 issues of the newsletter "NewsWire," (volume 5). Issue Number One focuses on collaborative Web projects. This issue begins with descriptions of four individual projects: "iEARN"; "Operation RubyThroat"; "Follow the Polar Huskies!"; and "Log in Your Animal Roadkill!" Features that follow include: "Bringing the…

  5. Basic Wiring. Second Edition.

    ERIC Educational Resources Information Center

    Kaltwasser, Stan; And Others

    This guide is designed to assist teachers conducting a foundation course to prepare students for additional courses of training for entry-level employment in either the residential or commercial and industrial wiring trades. Included in the guide are 17 instructional units and the following sections of information for teachers: guidelines in using…

  6. Improved wire chamber

    DOEpatents

    Atac, M.

    1987-05-12

    An improved gas mixture for use with proportional counter devices, such as Geiger-Mueller tubes and drift chambers. The improved gas mixture provides a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor. 2 figs.

  7. Caroviologens: Towards molecular wires

    NASA Astrophysics Data System (ADS)

    Blanchard-Desce, M.; Arrhenius, T. S.; Dvolaïtzky, M.; Kugimiya, S.-I.; Lazrak, T.; Lehn, J.-M.

    1992-07-01

    Bispyridinium conjugated polyenes of different lengths and charges have been synthesized. Since they combine the features of carotenoids and of viologens, they have been termed caroviologens. Such molecules, possessing an extended conjugated chain fitted with polar electroactive endgroups, and having a length sufficient to span a lipid membrane could function as transmembrane electron channels, i.e., as molecular wires.

  8. A World without Wires

    ERIC Educational Resources Information Center

    Panettieri, Joseph C.

    2006-01-01

    The wireless bandwagon is rolling across Mississippi, picking up a fresh load of converts and turning calamity into opportunity. Traditional wired school networks, many of which unraveled during Hurricane Katrina, are giving way to advanced wireless mesh networks that frequently include voice-over-IP (VoIP) capabilities. Vendor funding is helping…

  9. Residential Wiring. Second Edition.

    ERIC Educational Resources Information Center

    Taylor, Mark; And Others

    This guide is designed to assist teachers conducting a course to prepare students for entry-level employment in the residential wiring trade. Included in the guide are six instructional units and the following sections of information for teachers: guidelines in using the unit components; academic and workplace skills classifications and…

  10. Easily-wired toggle switch

    NASA Technical Reports Server (NTRS)

    Dean, W. T.; Stringer, E. J.

    1979-01-01

    Crimp-type connectors reduce assembly and disassembly time. With design, no switch preparation is necessary and socket contracts are crimped to wires inserted in module attached to back of toggle switch engaging pins inside module to make electrical connections. Wires are easily removed with standard detachment tool. Design can accommodate wires of any gage and as many terminals can be placed on switch as wire gage and switch dimensions will allow.

  11. Wire EDM for Refractory Materials

    NASA Technical Reports Server (NTRS)

    Zellars, G. R.; Harris, F. E.; Lowell, C. E.; Pollman, W. M.; Rys, V. J.; Wills, R. J.

    1982-01-01

    In an attempt to reduce fabrication time and costs, Wire Electrical Discharge Machine (Wire EDM) method was investigated as tool for fabricating matched blade roots and disk slots. Eight high-strength nickel-base superalloys were used. Computer-controlled Wire EDM technique provided high quality surfaces with excellent dimensional tolerances. Wire EDM method offers potential for substantial reductions in fabrication costs for "hard to machine" alloys and electrically conductive materials in specific high-precision applications.

  12. The Star Formation Rate Efficiency of Neutral Atomic-dominated Hydrogen Gas in the Outskirts of Star-forming Galaxies from z ~ 1 to z ~3

    NASA Astrophysics Data System (ADS)

    Rafelski, Marc; Gardner, Jonathan P.; Fumagalli, Michele; Neeleman, Marcel; Teplitz, Harry I.; Grogin, Norman; Koekemoer, Anton M.; Scarlata, Claudia

    2016-07-01

    Current observational evidence suggests that the star formation rate (SFR) efficiency of neutral atomic hydrogen gas measured in damped Lyα systems (DLAs) at z∼ 3 is more than 10 times lower than predicted by the Kennicutt–Schmidt (KS) relation. To understand the origin of this deficit, and to investigate possible evolution with redshift and galaxy properties, we measure the SFR efficiency of atomic gas at z ∼ 1, z ∼ 2, and z∼ 3 around star-forming galaxies. We use new robust photometric redshifts in the Hubble Ultra Deep Field to create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies’ outskirts. We find that the SFR efficiency of H i gas at z\\gt 1 is ∼1%–3% of that predicted by the KS relation. Contrary to simulations and models that predict a reduced SFR efficiency with decreasing metallicity and thus with increasing redshift, we find no significant evolution in the SFR efficiency with redshift. Our analysis instead suggests that the reduced SFR efficiency is driven by the low molecular content of this atomic-dominated phase, with metallicity playing a secondary effect in regulating the conversion between atomic and molecular gas. This interpretation is supported by the similarity between the observed SFR efficiency and that observed in local atomic-dominated gas, such as in the outskirts of local spiral galaxies and local dwarf galaxies.

  13. The mammalian verprolin, WIRE induces filopodia independent of N-WASP through IRSp53.

    PubMed

    Misra, Ashish; Rajmohan, Rajamuthiah; Lim, Rina Pei Zhi; Bhattacharyya, Swagata; Thanabalu, Thirumaran

    2010-10-15

    The mammalian verprolin family of proteins, WIP (WASP Interacting Protein), CR16 (Corticoid Regulated) and WIRE (WIp-RElated) regulate the actin cytoskeleton through WASP/N-WASP (Wiskott Aldrich Syndrome Protein and Neural-WASP). In order to characterize the WASP/N-WASP-independent function of WIRE, we screened and identified IRSp53 (Insulin Receptor Substrate) as a WIRE interacting protein. Expression of IRSp53 with WIRE in N-WASP(-/-) mouse fibroblast cells induced filopodia while co-expression of IRSp53 with WIP did not. The induction of filopodia is dependent on WIRE-IRSp53 interaction as mutation in the SH3 domain of IRSp53 abolished WIRE-IRSp53 interaction as well as the ability to induce filopodia. Similarly, the Verprolin (V)-domain of WIRE is critical for IRSp53-WIRE interaction and for filopodia formation. The interaction between WIRE and IRSp53 is regulated by Cdc42 as mutations which abolish Cdc42-IRSp53 interaction lead to loss of IRSp53-WIRE interaction as shown by pull down assay. The plasma membrane localization of IRSp53 is dependent on Cdc42 and WIRE. Expression of Cdc42(G12V) (active mutant) with WIRE-IRSp53 caused significant increase in the number of filopodia per cell. Thus our results show that Cdc42 regulates the activity of IRSp53 by regulating the IRSp53-WIRE interaction as well as localization of the complex to plasma membrane to generate filopodia. PMID:20678498

  14. 1997 wire development workshop: Proceedings

    SciTech Connect

    1997-04-01

    This conference is divided into the following sections: (1) First Generation Wires I; (2) First Generation Wires II; (3) Coated conductors I; and (4) Coated conductors II. Applications of the superconducting wires include fault current limiters, superconducting motors, transformers, and power transmission lines.

  15. Production of hot-wires

    NASA Astrophysics Data System (ADS)

    Dickinson, S. C.

    1983-04-01

    Several methods for producing hot-wire probes are described. Discussion includes the manufacture of probe bodies, soldering plated wires to the prongs etching Walaston type wires, and finishing the probe. This report is written as an instruction manual for researchers who desire to produce or repair their own sensors.

  16. Resonant formation of few-cycle pulses by hydrogen-like atoms with time-dependent resonance

    NASA Astrophysics Data System (ADS)

    Radeonychev, Y. V.; Antonov, V. A.; Kocharovskaya, O. A.

    2013-08-01

    We show the possibility of producing a short bunch of nearly bandwidth-limited few-cycle attosecond pulses based on time-dependent resonant interaction of an incident radiation pulse with the bound states of hydrogen-like atoms. Time-dependence of an atomic resonance is provided by a laser pulse far from resonance with an intensity well below the atomic ionization threshold via time-dependent tunnel ionization from the excited states and time-dependent adiabatic Stark splitting of the excited energy levels. Without external matching of the spectral components it is possible to produce pulses with durations up to 80 as at the carrier wavelength of 13.5 nm in Li2+-plasma, as well as pulses with durations up to 600 as at the carrier wavelength of 122 nm in atomic hydrogen.

  17. Formation and atomic configuration of binary metallic glasses studied by ion beam mixing and molecular dynamics simulation

    SciTech Connect

    Tai, K. P.; Gao, N.; Dai, X. D.; Li, J. H.; Liu, B. X.

    2007-06-15

    Metallic glasses are obtained in an immiscible Ag-Nb system with overall composition ranging from 25 to 90 at. % of Nb by ion beam mixing. Interestingly, the diffraction analysis shows that the formed Nb-rich metallic glass features are two distinct atomic configurations. In atomistic modeling, an n-body Ag-Nb potential is derived, under the assistance of ab initio calculation, and then applied in molecular dynamics simulations. An atomic configuration is discovered, i.e., an icositetrahedral ordering, and as well as an icosahedral ordering observed in the Ag-Nb metallic glasses and in some previously reported systems. Simulations confirm that the two dominate local atomic packing units are formed through a structural phase transition from the Nb-based bcc and fcc solid solutions, respectively, suggesting a concept of structural heredity that the crystalline structure of the constituent metals play a decisive role in determining the atomic structure of the resultant metallic glasses.

  18. Delocalization in weakly coupled disordered wires: application to conjugated polymers.

    PubMed

    Martens, H C F

    2006-02-24

    It is well known that even for minimal disorder one-dimensional wires are insulators: all 1D electron states are localized. Here, the influence of interwire coupling on delocalization of 1D states is examined. Based on perturbation theoretic arguments for the formation of 3D states in coupled wires and subsequent scaling analysis, practical expressions for the microscopic conditions of electronic delocalization and coherent conductivity of coupled 1D wires are obtained. The model quantitatively explains the temperature dependent dc conductivity in conducting polymers at both sides of the metal-insulator transition and links the experimental data to microscopic material parameters. PMID:16606118

  19. Laser-induced fluorescence measurements and kinetic analysis of Si atom formation in a rotating disk chemical vapor deposition reactor

    SciTech Connect

    Ho, P.; Coltrin, M.E.; Breiland, W.G. )

    1994-10-06

    An extensive set of laser-induced fluorescence (LIF) measurements of Si atoms during the chemical vapor deposition (CVD) of silicon from silane and disilane in a research rotating disk reactor are presented. The experimental results are compared in detail with predictions from a numerical model of CVD from silane and disilane that treats the fluid flow coupled to gas-phase and gas-surface chemistry. The comparisons showed that the unimolecular decomposition of SiH[sub 2] could not account for the observed gas-phase Si atom density profiles. The H[sub 3]SiSiH [leftrightarrow] Si + SiH[sub 4] and H[sub 3]SiSiH + SiH[sub 2] [leftrightarrow] Si + Si[sub 2]H[sub 6] reactions are proposed as the primary Si atom production routes. The model is in good agreement with the measured shapes of the Si atom profiles and the trends in Si atom density with susceptor temperature, pressure, and reactant gas mixture. 33 refs., 12 figs., 3 tabs.

  20. Silver-sheathed multifilament wires

    NASA Astrophysics Data System (ADS)

    Wu, C. T.; Goretta, K. C.; Shi, D.; Lanagan, M. T.; Poeppel, R. B.

    1991-01-01

    The process for manufacturing Ag-sheathed multifilament superconducting wires was investigated. Bi2Sr(1.7)CaCu2O(x), Pb-doped Bi2Sr2Ca2Cu3O(x), or YBa2Cu3O(x) powders were packed into Ag tubes and swaged into long wires. Pieces were cut from each wire, packed into a second Ag tube and swaged or rolled into multifilament wires. Each wire was then sintered to produce a superconductor. Processing considerations included the sheath workability, effects of compacting and residual stresses, and heat treatment schedules. The superconducting properties of the Bi-based wires were superior to those of the YBa2Cu3O(x) wires at 4.2 K, but not at 77 K.

  1. Characterization of Cu-Zn Alloy Nanocrystalline Powders Prepared by Wire Electrical Explosion

    NASA Astrophysics Data System (ADS)

    Qun, Wang; Hai-Bin, Yang; Wei-Li, Guo; Guang-Tian, Zou

    2000-02-01

    Nanocrystalline powders of Cu-Zn alloy in size ranging from 10 to 140 nm was prepared from α-Cu-Zn alloy wire containing 39.8 at.% Zn by an electrical explosion method. The particles are identified from x-ray diffraction as a mixture of the α, β, γ, and ɛ phases of Cu-Zn alloy. Most of the particles are hexagonal in shape, with only a small part being spherical and cubic. The composition of Zn in the explosion products varied from 6.9 to 45.2 at.% in different particles as determined by energy dispersive x-ray spectrometer. A possible mechanism for the formation of the alloy nanocrystalline powders is proposed, in which a redistribution process occurred caused by strong collision and diffusion between the two kinds of atoms during the powder formation.

  2. ‘Chrysanthemum petal’ arrangements of silver nano wires

    NASA Astrophysics Data System (ADS)

    Cui, Hui-Wang; Jiu, Jin-Ting; Sugahara, Tohru; Nagao, Shijo; Suganuma, Katsuaki; Uchida, Hiroshi

    2014-12-01

    Highly ordered ‘Chrysanthemum petal’ arrangements of silver nano wires were fabricated in a biodegradable polymer of polyvinyl alcohol using a simple one-step blending method without any template. The degree of the arrangement increased with the decreasing content of polyvinyl alcohol. The mechanism for the formation of these ‘Chrysanthemum petal’ arrangements was discussed specifically. These ‘Chrysanthemum petal’ arrangements will be helpful to increase the electrical conductivity of silver nano wires films.

  3. Implosion Dynamics in Conical Wire Array Z-pinches

    SciTech Connect

    Ampleford, D.J.; Lebedev, S.V.; Chittenden, J.P.; Bland, S.N.; Bott, S.C.; Hall, G.N.; Palmer, J.B.A.; Rapley, J.; Kantsyrev, V.L.; Safronova, A.S.; Ivanov, V.V.; Fedin, D.A.; Laca, P.J.; Sotnikov, V.I.; Yilmaz, F.; Ouart, N.; Nalajala, V.; Shrestha, I.; Pokala, S.; Jones, B.

    2006-01-05

    We present initial results from imploding conical wire array experiments performed on both the MAGPIE generator (1MA, 240ns) at Imperial College London and the Nevada Terawatt Facility's Zebra generator (1MA, 100ns) at University of Nevada, Reno. This paper will discuss the implosion dynamics of conical wire arrays, including initial implosion of the cathode end of the array and the formation of a magnetic bubble.

  4. From wires to cosmology

    NASA Astrophysics Data System (ADS)

    Amin, Mustafa A.; Baumann, Daniel

    2016-02-01

    We provide a statistical framework for characterizing stochastic particle production in the early universe via a precise correspondence to current conduction in wires with impurities. Our approach is particularly useful when the microphysics is uncertain and the dynamics are complex, but only coarse-grained information is of interest. We study scenarios with multiple interacting fields and derive the evolution of the particle occupation numbers from a Fokker-Planck equation. At late times, the typical occupation numbers grow exponentially which is the analog of Anderson localization for disordered wires. Some statistical features of the occupation numbers show hints of universality in the limit of a large number of interactions and/or a large number of fields. For test cases, excellent agreement is found between our analytic results and numerical simulations.

  5. Dental Arch Wire

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Straightening teeth is an arduous process requiring months, often years, of applying corrective pressure by means of arch wires-better known as brace-which may have to be changed several times in the course of treatment. A new method has been developed by Dr. George Andreasen, orthodontist and dental scientist at the University of Iowa. The key is a new type of arch wire material, called Nitinol, with exceptional elasticity which helps reduce the required number of brace changes. An alloy of nickel and titanium, Nitinol was originally developed for aerospace applications by the Naval Ordnance Laboratory, now the Naval Surface Weapons Laboratory, White Oaks, Maryland. NASA subsequently conducted additional research on the properties of Nitinol and on procedures for processing the metal.

  6. Wire insulation defect detector

    NASA Technical Reports Server (NTRS)

    Greulich, Owen R. (Inventor)

    2004-01-01

    Wiring defects are located by detecting a reflected signal that is developed when an arc occurs through the defect to a nearby ground. The time between the generation of the signal and the return of the reflected signal provides an indication of the distance of the arc (and therefore the defect) from the signal source. To ensure arcing, a signal is repeated at gradually increasing voltages while the wire being tested and a nearby ground are immersed in a conductive medium. In order to ensure that the arcing occurs at an identifiable time, the signal whose reflection is to be detected is always made to reach the highest potential yet seen by the system.

  7. Wiring for aerospace applications

    NASA Technical Reports Server (NTRS)

    Christian, J. L., Jr.; Dickman, J. E.; Bercaw, R. W.; Myers, I. T.; Hammoud, A. N.; Stavnes, M.; Evans, J.

    1992-01-01

    In this paper, the authors summarize the current state of knowledge of arc propagation in aerospace power wiring and efforts by the National Aeronautics and Space Administration (NASA) towards the understanding of the arc tracking phenomena in space environments. Recommendations will be made for additional testing. A database of the performance of commonly used insulating materials will be developed to support the design of advanced high power missions, such as Space Station Freedom and Lunar/Mars Exploration.

  8. Plated wire memory subsystem

    NASA Technical Reports Server (NTRS)

    Reynolds, L.; Tweed, H.

    1972-01-01

    The work performed entailed the design, development, construction and testing of a 4000 word by 18 bit random access, NDRO plated wire memory for use in conjunction with a spacecraft imput/output unit and central processing unit. The primary design parameters, in order of importance, were high reliability, low power, volume and weight. A single memory unit, referred to as a qualification model, was delivered.

  9. Cyclic Oxidation of High-Temperature Alloy Wires in Air

    NASA Technical Reports Server (NTRS)

    Reigel, Marissa M.

    2004-01-01

    High-temperature alloy wires are proposed for use in seal applications for future re-useable space vehicles. These alloys offer the potential for improved wear resistance of the seals. The wires must withstand the high temperature environments the seals are subjected to as well as maintain their oxidation resistance during the heating and cooling cycles of vehicle re-entry. To model this, the wires were subjected to cyclic oxidation in stagnant air. of this layer formation is dependent on temperature. Slow growing oxides such as chromia and alumina are desirable. Once the oxide is formed it can prevent the metal from further reacting with its environment. Cyclic oxidation models the changes in temperature these wires will undergo in application. Cycling the temperature introduces thermal stresses which can cause the oxide layer to break off. Re-growth of the oxide layer consumes more metal and therefore reduces the properties and durability of the material. were used for cyclic oxidation testing. The baseline material, Haynes 188, has a Co base and is a chromia former while the other two alloys, Kanthal A1 and PM2000, both have a Fe base and are alumina formers. Haynes 188 and Kanthal A1 wires are 250 pm in diameter and PM2000 wires are 150 pm in diameter. The coiled wire has a total surface area of 3 to 5 sq cm. The wires were oxidized for 11 cycles at 1204 C, each cycle containing a 1 hour heating time and a minimum 20 minute cooling time. Weights were taken between cycles. After 11 cycles, one wire of each composition was removed for analysis. The other wire continued testing for 70 cycles. Post-test analysis includes X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) for phase identification and morphology.

  10. Seal Wire Integrity Verification Instrument: Evaluation of Laboratory Prototypes

    SciTech Connect

    Good, Morris S.; Skorpik, James R.; Kravtchenko, Victor; Wishard, Bernard; Prince, James M.; Pardini, Allan F.; Heasler, Patrick G.; Santiago-Rojas, Emiliano; Mathews, Royce; Khayyat, Sakher; Tanner, Jennifer E.; Undem, Halvor A.

    2009-10-07

    Tamper indicating devices (TIDs) provide evidence that sensitive items, to which they have been applied, have been tampered with or not. Passive wire-loop seals, a class of TIDs, are generally comprised of a multi-strand seal wire that is threaded through or around key features and a unique seal body that captures and restrains the seal wire. Seal integrity resides with unique identification of the seal and the integrity of the seal body and the seal wire. Upon inspection, the seal wire may be cut and the full length inspected. A new seal may be applied in the field as a replacement, if desired. Seal wire inspection typically requires visual and tactile examinations, which are both subjective. A need therefore exists to develop seal wire inspection technology that is easy to use in the field, is objective, provides an auditable data trail, and has low error rates. Expected benefits, if successfully implemented, are improved on-site inspection reliability and security. The work scope for this effort was restricted to integrity of seal wire used by the International Atomic Energy Agency (IAEA) and resulted in development of a wire integrity verification instrument (WIVI) laboratory prototype. Work included a performance evaluation of a laboratory-bench-top system, and design and delivery of two WIVI laboratory prototypes. The paper describes the basic physics of the eddy current measurement, a description of the WIVI laboratory prototype, and an initial evaluation performed by IAEA personnel. --- Funding was provided by the U.S. Program for Technical Assistance to IAEA Safeguards (POTAS).

  11. Dual wire welding torch and method

    DOEpatents

    Diez, Fernando Martinez; Stump, Kevin S.; Ludewig, Howard W.; Kilty, Alan L.; Robinson, Matthew M.; Egland, Keith M.

    2009-04-28

    A welding torch includes a nozzle with a first welding wire guide configured to orient a first welding wire in a first welding wire orientation, and a second welding wire guide configured to orient a second welding wire in a second welding wire orientation that is non-coplanar and divergent with respect to the first welding wire orientation. A method of welding includes moving a welding torch with respect to a workpiece joint to be welded. During moving the welding torch, a first welding wire is fed through a first welding wire guide defining a first welding wire orientation and a second welding wire is fed through a second welding wire guide defining a second welding wire orientation that is divergent and non-coplanar with respect to the first welding wire orientation.

  12. Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade

    NASA Astrophysics Data System (ADS)

    Kolmogorov, A.; Atoian, G.; Davydenko, V.; Ivanov, A.; Ritter, J.; Stupishin, N.; Zelenski, A.

    2014-02-01

    The RHIC polarized H- ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H2 gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ˜0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce "geometrical" beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench.

  13. Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade

    SciTech Connect

    Kolmogorov, A. Stupishin, N.; Atoian, G.; Ritter, J.; Zelenski, A.; Davydenko, V.; Ivanov, A.

    2014-02-15

    The RHIC polarized H{sup −} ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H{sub 2} gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ∼0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce “geometrical” beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench.

  14. Production, formation, and transport of high-brightness atomic hydrogen beam studies for the relativistic heavy ion collider polarized source upgrade.

    PubMed

    Kolmogorov, A; Atoian, G; Davydenko, V; Ivanov, A; Ritter, J; Stupishin, N; Zelenski, A

    2014-02-01

    The RHIC polarized H(-) ion source had been successfully upgraded to higher intensity and polarization by using a very high brightness fast atomic beam source developed at BINP, Novosibirsk. In this source the proton beam is extracted by a four-grid multi-aperture ion optical system and neutralized in the H2 gas cell downstream from the grids. The proton beam is extracted from plasma emitter with a low transverse ion temperature of ∼0.2 eV which is formed by plasma jet expansion from the arc plasma generator. The multi-hole grids are spherically shaped to produce "geometrical" beam focusing. Proton beam formation and transport of atomic beam were experimentally studied at test bench. PMID:24593468

  15. Wire detecting apparatus and method

    SciTech Connect

    Kronberg, J.W.

    1991-12-31

    This invention is comprised of an apparatus and method that combines a signal generator and a passive signal receiver to detect and record the path of partially or completely concealed electrical wiring without disturbing the concealing surface. The signal generator applies a series of electrical pulses to the selected wiring of interest. The applied pulses create a magnetic field about the wiring that can be detected by a coil contained within the signal receiver. An audible output connected to the receiver and driven by the coil reflects the receiver`s position with respect to the wiring. The receiver`s audible signal is strongest when the receiver is directly above the wiring and the long axis of the receiver`s coil is parallel to the wiring. A marking means is mounted on the receiver to mark the location of the wiring as the receiver is directed over the wiring`s concealing surface. Numerous marks made on various locations of the concealing surface will trace the path of the wiring of interest.

  16. Manually Operated Welding Wire Feeder

    NASA Technical Reports Server (NTRS)

    Rybicki, Daniel J. (Inventor)

    2001-01-01

    A manual welding wire feeder apparatus comprising a bendable elongate metal frame with a feed roller mounted at the center thereof for rotation about an axis transverse to the longitudinal axis of the frame. The frame ends are turned up as tabs and each provided with openings in alignment with each other and the mid-width center of the roller surface. The tab openings are sized to accommodate welding wire and each extends to a side edge of the tab, both opening on the same side of the frame, whereby welding wire can be side-loaded onto the frame. On the side of the frame, opposite the roller a lock ring handle is attached tangentially and is rotatable about the attachment point and an axis perpendicular to the frame. The device is grasped in the hand normally used to hold the wire. A finger is placed through the loop ring and the frame positioned across the palm and lower fingers. The thumb is positioned atop the wire so it can be moved from the back of the frame across the roller, and towards the front. In doing so, the wire is advanced at a steady rate in axial alignment with the tab openings and roller. To accommodate different wire diameters the frame is bendable about its center in the plane of the frame axis and wire so as to keep the wire in sufficient tension against the roller and to keep the wire fixed when the frame is tilted and thumb pressure released.

  17. Metering Wheel-Wire Track Wire Boom Deployment Mechanism

    NASA Technical Reports Server (NTRS)

    Granoff, Mark S.

    2014-01-01

    The NASA MMS Spin Plane Double Probe (SDP) Deployer utilizes a helical path, rotating Metering Wheel and a spring loaded Wire "Holding" Track to pay out a "fixed end" 57 meter x 1.5 mm diameter Wire Boom stored between concentric storage cylinders. Unlike rotating spool type storage devices, the storage cylinders remain stationary, and the boom wire is uncoiled along the length of the cylinder via the rotation of the Metering Wheel. This uncoiling action avoids the need for slip-ring contacts since the ends of the wire can remain stationary. Conventional fixed electrical connectors (Micro-D type) are used to terminate to operational electronics.

  18. The Molybdenum Active Site of Formate Dehydrogenase Is Capable of Catalyzing C-H Bond Cleavage and Oxygen Atom Transfer Reactions.

    PubMed

    Hartmann, Tobias; Schrapers, Peer; Utesch, Tillmann; Nimtz, Manfred; Rippers, Yvonne; Dau, Holger; Mroginski, Maria Andrea; Haumann, Michael; Leimkühler, Silke

    2016-04-26

    Formate dehydrogenases (FDHs) are capable of performing the reversible oxidation of formate and are enzymes of great interest for fuel cell applications and for the production of reduced carbon compounds as energy sources from CO2. Metal-containing FDHs in general contain a highly conserved active site, comprising a molybdenum (or tungsten) center coordinated by two molybdopterin guanine dinucleotide molecules, a sulfido and a (seleno-)cysteine ligand, in addition to a histidine and arginine residue in the second coordination sphere. So far, the role of these amino acids in catalysis has not been studied in detail, because of the lack of suitable expression systems and the lability or oxygen sensitivity of the enzymes. Here, the roles of these active site residues is revealed using the Mo-containing FDH from Rhodobacter capsulatus. Our results show that the cysteine ligand at the Mo ion is displaced by the formate substrate during the reaction, the arginine has a direct role in substrate binding and stabilization, and the histidine elevates the pKa of the active site cysteine. We further found that in addition to reversible formate oxidation, the enzyme is further capable of reducing nitrate to nitrite. We propose a mechanistic scheme that combines both functionalities and provides important insights into the distinct mechanisms of C-H bond cleavage and oxygen atom transfer catalyzed by formate dehydrogenase. PMID:27054466

  19. Low-temperature surface formation of NH3 and HNCO: hydrogenation of nitrogen atoms in CO-rich interstellar ice analogues

    NASA Astrophysics Data System (ADS)

    Fedoseev, G.; Ioppolo, S.; Zhao, D.; Lamberts, T.; Linnartz, H.

    2015-01-01

    Solid-state astrochemical reaction pathways have the potential to link the formation of small nitrogen-bearing species, like NH3 and HNCO, and prebiotic molecules, specifically amino acids. To date, the chemical origin of such small nitrogen-containing species is still not well understood, despite the fact that ammonia is an abundant constituent of interstellar ices towards young stellar objects and quiescent molecular clouds. This is mainly because of the lack of dedicated laboratory studies. The aim of this work is to experimentally investigate the formation routes of NH3 and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant temperatures. This study focuses on the formation of NH3 and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in dark interstellar cloud regions, well before thermal and energetic processing start to become relevant. We demonstrate and discuss the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH3 upon sequential hydrogenation of N atoms. The importance of HNCO for astrobiology is discussed.

  20. Topography and transport properties of oligo(phenylene ethynylene) molecular wires studied by scanning tunneling microscopy

    NASA Technical Reports Server (NTRS)

    Dholakia, Geetha R.; Fan, Wendy; Koehne, Jessica; Han, Jie; Meyyappan, M.

    2003-01-01

    Conjugated phenylene(ethynylene) molecular wires are of interest as potential candidates for molecular electronic devices. Scanning tunneling microscopic study of the topography and current-voltage (I-V) characteristics of self-assembled monolayers of two types of molecular wires are presented here. The study shows that the topography and I-Vs, for small scan voltages, of the two wires are quite similar and that the electronic and structural changes introduced by the substitution of an electronegative N atom in the central phenyl ring of these wires does not significantly alter the self-assembly or the transport properties.

  1. Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires

    SciTech Connect

    Perkins, R.A.

    1994-12-31

    Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on the surfaces of the wires and the cell wall. If the electrical conductivity of the fluid is large enough there is also significant power generation in the fluid. These measurement uncertainties can be eliminated by electrically insulating the hot wires with a thin film. The use of tantalum hot wires with an anodized layer of tantalum pentoxide is demonstrated with measurements on nonpolar argon and polar 1,1,1,2 tetrafluoroethane (R134a). Although coated tantalum hot wires have been used previously in a transient mode to measure the thermal conductivity of liquids, this work is the first demonstration of the use of coated wires to measure thermal conductivity in the liquid, vapor, and supercritical gas phases.

  2. Tailoring of silver wires and their performance as transparent conductive coatings.

    PubMed

    Lu, Y C; Chou, K S

    2010-05-28

    A feasible way to manipulate the scales of Ag wires through the polyol process is presented. By adjusting the amounts of either Pd or Ag precursor used in this process, we demonstrated the ability to control the scale of the wires. The presence of Pd ultrafine particles reduced by EG in advance served as the nuclei for inducing the subsequent formation of Ag wires, and the diameter of the resulting wires was observed to be inversely proportional to the quantity of Pd added. Further, the wire length was demonstrated to be proportional to and highly correlated with the total amount of Ag added, by a linear relationship. A glass plate coated with Ag wire film by the spray method is shown to be both transparent and conductive. The effect of scaling the wires on their performance is also discussed. PMID:20431210

  3. Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires

    SciTech Connect

    Perkins, R.A.

    1994-09-01

    Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on the surfaces of the wires and the cell wall. If the electrical conductivity of the fluid is large enough there is also significant power generation in the fluid. These measurement uncertainties can be eliminated by electrically insulating the hot wires with a thin film. The use of tantalum hot wires with an anodized layer of tantalum pentoxide is demonstrated with measurements on nonpolar argon and polar 1,1,1,2 tetrafluorethane (R134a). Although coated tantalum hot wires have been used previously in a transient mode to measure the thermal conductivity of liquids, this work is the first demonstration of the use of coated wires to measure thermal conductivity in the liquid, vapor, and supercritical gas phases.

  4. Review of wire chamber aging

    SciTech Connect

    Va'Vra, J.

    1986-02-01

    This paper makes an overview of the wire chamber aging problems as a function of various chamber design parameters. It emphasizes the chemistry point of view and many examples are drawn from the plasma chemistry field as a guidance for a possible effort in the wire chamber field. The paper emphasizes the necessity of variable tuning, the importance of purity of the wire chamber environment, as well as it provides a practical list of presently known recommendations. In addition, several models of the wire chamber aging are qualitatively discussed. The paper is based on a summary talk given at the Wire Chamber Aging Workshop held at LBL, Berkeley on January 16-17, 1986. Presented also at Wire Chamber Conference, Vienna, February 25-28, 1986. 74 refs., 18 figs., 11 tabs.

  5. Formation of Attosecond XUV Pulses via Resonance with Hydrogen-Like Atoms Irradiated by Intense Laser Field

    NASA Astrophysics Data System (ADS)

    Polovinkin, V. A.; Radeonychev, Y. V.; Kocharovskaya, Olga; Ryabikin, M. Yu.

    We show the possibility to produce a short bunch of few nearly bandwidth-limited few-cycle attosecond pulses via the time-dependent resonant interaction of an incident radiation pulse with the bound states of hydrogenlike atoms. Time-dependence of the resonant interaction is based on time-dependent tunnel ionization from the excited states and temporal adiabatic Stark splitting of the excited energy levels, provided by far-off-resonant laser pulse whose intensity is much below the atomic ionization threshold. Without external synchronization of the spectral components it is possible to produce pulses of XUV radiation with duration up to 80 as at the carrier wavelength 13.5 nm in Li2 +-plasma.

  6. Magnetic behavior of nanostructured glass covered metallic wires

    NASA Astrophysics Data System (ADS)

    Chiriac, H.; Óvári, T. A.; Pop, Gh.; Barariu, Firuta

    1997-04-01

    We present a study of the evolution of the magnetic properties and behavior of Fe73.5Cu1Nb3Si13.5B9 glass covered wires and wires after glass removal with the annealing temperature up to 600 °C starting from the amorphous state. The changes induced in the magnetic properties of these wires are determined by the stress relief process occurring at temperatures below 550 °C, and by the appearance of the nanosized α-FeSi crystalline grains after annealing for 1 h at 550 °C. The nanocrystalline phase formation leads to an improvement of the soft magnetic properties of these wires—increase of permeability and decrease of the coercive force—but also determines the disappearance of the large Barkhausen effect presented by these wires in the amorphous state. Annealing at temperatures over 550 °C determines a depreciation of the soft magnetic properties of both glass covered wires and wires after glass removal. The magnetic behavior of such wires can be fully explained by taking into account the relaxation of the internal stresses with increasing the annealing temperature as well as the changes in the magnetostriction constant due to the appearance of the nanocrystalline grains.

  7. Spatial evolutions of Co and Ni atoms during single-walled carbon nanotubes formation: measurements and modeling.

    PubMed

    Cau, M; Dorval, N; Cao, B; Attal-Trétout, B; Cochon, J L; Loiseau, A; Farhat, S; Scott, C D

    2006-05-01

    Spatial investigations of nickel and cobalt atoms and of C2 and C3 radicals are performed by laser induced fluorescence (LIF) in a continuous CO2 laser-vaporization reactor during the synthesis of single-walled carbon nanotubes. The chemical composition of the gas vaporized from bimetallic Ni/Co catalysts-carbon targets is determined using a chemical kinetic model. In this model, the evolution of Ni and Co atoms is driven by kinetics of condensation/evaporation process of pure metal clusters. Metal-carbon clusters are assumed to form from soot particles (C80) and 128-atom metal clusters. Spatial profiles of Ni and Co atoms obtained by LIF are compared with the calculations to validate the modeling and to adjust the input data. The value of the initial molar fraction of carbon-metal mixture diluted in helium is determined through a parametric study. Good agreement is found between the measured and the calculated evolution of Ni for a molar fraction of the helium diluent ranging from 10 to 15%. To fit the spatial profile of Co, the activation energy is adjusted in the evaporation rate, changing the cobalt dimer bond energy. The latter is found to be largely uncertain; and three values are tested: 167, 208, and 230 kJ x mol(-1). From comparison, the activation energy is found to be 208 kJ x mol(-1). However, the C2 LIF profiles show that the depletion of C2 is accelerated when cobalt is present. The observed Co evolutions suggest that small Co-C clusters are easier and/or faster to form compared to Ni-C clusters. PMID:16792356

  8. Discrete versus continuous wires on quantum networks.

    PubMed

    Aharony, Amnon; Entin-Wohlman, Ora

    2009-03-26

    Mesoscopic systems and large molecules are often modeled by graphs of one-dimensional wires connected at vertices. In this paper, we discuss the solutions of the Schrödinger equation on such graphs, which have been named "quantum networks". Such solutions are needed for finding the energy spectrum of single electrons on such finite systems or for finding the transmission of electrons between leads which connect such systems to reservoirs. Specifically, we compare two common approaches. In the "continuum" approach, one solves the one-dimensional Schrödinger equation on each continuous wire and then uses the Neumann-Kirchoff-de Gennes matching conditions at the vertices. Alternatively, one replaces each wire by a finite number of "atoms" and then uses the tight binding model for the solution. Here, we show that these approaches cannot generally give the same results, except for special energies, unless the lattice constant of the tight binding model tends to zero. Even in the limit of the vanishing lattice constant, the two approaches coincide only if the tight binding parameters obey very special relations. The different consequences of the two approaches are then demonstrated via the example of a T-shaped scatterer. PMID:19673064

  9. Atom chips on direct bonded copper substrates

    NASA Astrophysics Data System (ADS)

    Squires, Matthew B.; Stickney, James A.; Carlson, Evan J.; Baker, Paul M.; Buchwald, Walter R.; Wentzell, Sandra; Miller, Steven M.

    2011-02-01

    We present the use of direct bonded copper (DBC) for the straightforward fabrication of high power atom chips. Atom chips using DBC have several benefits: excellent copper/substrate adhesion, high purity, thick (>100 μm) copper layers, high substrate thermal conductivity, high aspect ratio wires, the potential for rapid (<8 h) fabrication, and three-dimensional atom chip structures. Two mask options for DBC atom chip fabrication are presented, as well as two methods for etching wire patterns into the copper layer. A test chip, able to support 100 A of current for 2 s without failing, is used to determine the thermal impedance of the DBC. An assembly using two DBC atom chips is used to magnetically trap laser cooled 87Rb atoms. The wire aspect ratio that optimizes the magnetic field gradient as a function of power dissipation is determined to be 0.84:1 (height:width).

  10. Atom chips on direct bonded copper substrates

    SciTech Connect

    Squires, Matthew B.; Stickney, James A.; Carlson, Evan J.; Baker, Paul M.; Buchwald, Walter R.; Wentzell, Sandra; Miller, Steven M.

    2011-02-15

    We present the use of direct bonded copper (DBC) for the straightforward fabrication of high power atom chips. Atom chips using DBC have several benefits: excellent copper/substrate adhesion, high purity, thick (>100 {mu}m) copper layers, high substrate thermal conductivity, high aspect ratio wires, the potential for rapid (<8 h) fabrication, and three-dimensional atom chip structures. Two mask options for DBC atom chip fabrication are presented, as well as two methods for etching wire patterns into the copper layer. A test chip, able to support 100 A of current for 2 s without failing, is used to determine the thermal impedance of the DBC. An assembly using two DBC atom chips is used to magnetically trap laser cooled {sup 87}Rb atoms. The wire aspect ratio that optimizes the magnetic field gradient as a function of power dissipation is determined to be 0.84:1 (height:width).

  11. Electronic and magnetic properties of silicon supported organometallic molecular wires: a density functional theory (DFT) study.

    PubMed

    Liu, Xia; Tan, Yingzi; Li, Xiuling; Wu, Xiaojun; Pei, Yong

    2015-08-28

    The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to the well-studied gas phase TM-benzene molecular wires. Si-[Mn(styrene)]∞ and Si-[Cr(styrene)]∞ single molecular wires (SMWs) are a ferromagnetic semiconductor and half metal, respectively. Creation of H-atom defects on the silicon surface can introduce an impurity metallic band, which leads to novel half-metallic magnetism of a Si-[Mn(styrene)]∞ system. Moreover, double molecular wires (DMWs) containing two identical or hetero SMWs are theoretically designed. The [Mn(styrene)]∞-[Cr(styrene)]∞ DMW exhibits half-metallic magnetism where the spin-up and spin-down channels are contributed by two single molecular wires. Finally, we demonstrate that introducing a TM-defect may significantly affect the electronic structure and magnetic properties of molecular wires. These studies provide new insights into the structure and properties of surface supported 1-D sandwiched molecular wires and may inspire the future experimental synthesis of substrate confined organometallic sandwiched molecular wires. PMID:26219748

  12. Neural wiring optimization.

    PubMed

    Cherniak, Christopher

    2012-01-01

    Combinatorial network optimization theory concerns minimization of connection costs among interconnected components in systems such as electronic circuits. As an organization principle, similar wiring minimization can be observed at various levels of nervous systems, invertebrate and vertebrate, including primate, from placement of the entire brain in the body down to the subcellular level of neuron arbor geometry. In some cases, the minimization appears either perfect, or as good as can be detected with current methods. One question such best-of-all-possible-brains results raise is, what is the map of such optimization, does it have a distinct neural domain? PMID:22230636

  13. Plated wire memory subsystem

    NASA Technical Reports Server (NTRS)

    Carpenter, K. H.

    1974-01-01

    The design, construction, and test history of a 4096 word by 18 bit random access NDRO Plated Wire Memory for use in conjunction with a spacecraft input/output and central processing unit is reported. A technical and functional description is given along with diagrams illustrating layout and systems operation. Test data is shown on the procedures and results of system level and memory stack testing, and hybrid circuit screening. A comparison of the most significant physical and performance characteristics of the memory unit versus the specified requirements is also included.

  14. Texture development in Galfenol wire

    NASA Astrophysics Data System (ADS)

    Boesenberg, A. J.; Restorff, J. B.; Wun-Fogle, M.; Sailsbury, H.; Summers, E.

    2013-05-01

    Galfenol (Fe-Ga alloy) wire fabrication provides a low cost alternative to directional solidification methods. This work evaluates the compositional dependence of the wire drawing suitability of Fe-Ga and characterizes the microstructural and magnetic properties of these wires. Wire has been produced with Ga contents between 10 at. % and 17 at. % to allow determination of the ductile to brittle transition (DTBT) in wire manufacture. Published results on chill cast bend specimens indicated that a DTBT occurs at roughly 15 at. % Ga. This DTBT was observed under tensile loading with a corresponding change in fracture behavior from transverse fracture to intergranular fracture. For improved magnetostrictive performance, higher Ga contents are desired, closer to the 17 at. % Ga evaluated in this work. Electron backscattered diffraction B-H loop and resonance measurements as a function of magnetic field (to determine modulus and coupling factor) are presented for as-drawn, furnace, and direct current (DC) annealed wire. Galfenol wire produced via traditional drawing methods is found to have a strong <110> (α) texture parallel to the drawing direction. As-drawn wire was observed to have a lower magnetic permeability and larger hysteresis than DC annealed wire. This is attributed to the presence of a large volume of crystalline defects; such as vacancies and dislocations.

  15. Evaluation of Pd-Cr Wires for Strain Gage Application

    NASA Technical Reports Server (NTRS)

    Lei, Jih-Fen; Greer, L. C., III; Oberle, L. G.

    1995-01-01

    A newly developed alloy, palladium-13 weight percent chromium (Pd13Cr), was identified by United Technologies Research Center under a NASA contract to be the best material for high temperature strain gage applications. An electrical resistance strain gage that can provide accurate static strain measurement to a temperature higher than that of a commercially available gage is urgently needed in aerospace and aeronautics research. A strain gage made of a 25.4 micron (1 mil) diameter Pd13Cr wire has been recently demonstrated to be usable for static strain measurements to 800 C. This compares to the 400 C temperature limit of the commercially available strain gages. The performance of the Pd-Cr gage, however, strongly depends on the quality of the Pd13Cr wire. Four batches of Pd-Cr wires purchased from three different manufacturers were therefore evaluated to determine the best source of the wire for strain gage applications. The three suppliers were Precious Metal Institute in China, Sigmund Cohn Co., and G & S Titanium, Inc. in the United States. Two batches of wires obtained from Previous Metal Institute in 1987 and 1992, respectively are referred to herein as China87 and China92 wires. The mechanical, chemical and electrical properties of these wires, both as-received and after high temperature exposures at 800 C for 50 hours were analyzed. The elastic modulus and the failure strength of the wires were evaluated using a tensile test machine equipped with a laser speckle strain measurement system. The chemical and microstructural properties of the wires were inspected using a plasma atomic emission spectrometer and a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscope (EDS). The electrical stability and repeatability of the wires were determined by measuring the electrical resistance of the wires during three thermal cycles to 1000 C and a ten-hour soak at 1000 C. As a result of this study, the wire which has the highest

  16. Evaluation of Pd-Cr wires for strain gage application

    NASA Astrophysics Data System (ADS)

    Lei, Jih-Fen; Greer, L. C., III; Oberle, L. G.

    1995-02-01

    A newly developed alloy, palladium-13 weight percent chromium (Pd13Cr), was identified by United Technologies Research Center under a NASA contract to be the best material for high temperature strain gage applications. An electrical resistance strain gage that can provide accurate static strain measurement to a temperature higher than that of a commercially available gage is urgently needed in aerospace and aeronautics research. A strain gage made of a 25.4 micron (1 mil) diameter Pd13Cr wire has been recently demonstrated to be usable for static strain measurements to 800 C. This compares to the 400 C temperature limit of the commercially available strain gages. The performance of the Pd-Cr gage, however, strongly depends on the quality of the Pd13Cr wire. Four batches of Pd-Cr wires purchased from three different manufacturers were therefore evaluated to determine the best source of the wire for strain gage applications. The three suppliers were Precious Metal Institute in China, Sigmund Cohn Co., and G & S Titanium, Inc. in the United States. Two batches of wires obtained from Previous Metal Institute in 1987 and 1992, respectively are referred to herein as China87 and China92 wires. The mechanical, chemical and electrical properties of these wires, both as-received and after high temperature exposures at 800 C for 50 hours were analyzed. The elastic modulus and the failure strength of the wires were evaluated using a tensile test machine equipped with a laser speckle strain measurement system. The chemical and microstructural properties of the wires were inspected using a plasma atomic emission spectrometer and a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscope (EDS). The electrical stability and repeatability of the wires were determined by measuring the electrical resistance of the wires during three thermal cycles to 1000 C and a ten-hour soak at 1000 C. As a result of this study, the wire which has the highest

  17. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  18. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  19. 49 CFR 234.241 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... underground wire. 234.241 Section 234.241 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION GRADE CROSSING SIGNAL SYSTEM SAFETY... of insulated wire; splice in underground wire. Insulated wire shall be protected from...

  20. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  1. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  2. 49 CFR 234.241 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... underground wire. 234.241 Section 234.241 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION GRADE CROSSING SIGNAL SYSTEM SAFETY... of insulated wire; splice in underground wire. Insulated wire shall be protected from...

  3. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  4. Subwavelength-diameter silica wires for microscale optical components

    NASA Astrophysics Data System (ADS)

    Tong, Limin; Mazur, Eric

    2005-04-01

    Subwavelength-diameter silica wires fabricated using a taper-drawing approach exhibit excellent diameter uniformity and atomic-level smoothness, making them suitable for low-loss optical wave guiding from the UV to the near-infrared. Such air-clad silica wires can be used as single-mode waveguides; depending on wavelength and wire diameter, they either tightly confine the optical fields or leave a certain amount of guided energy outside the wire in the form of evanescent waves. Using these wire waveguides as building blocks we assembled microscale optical components such as linear waveguides, waveguide bends and branch couplers on a low-index, non-dissipative silica aerogel substrate. These components are much smaller than comparable existing devices and have low optical loss, indicating that the wire-assembly technique presented here has great potential for developing microphotonics devices for future applications in a variety of fields such as optical communication, optical sensing and high-density optical integration.

  5. Formation of nitrate and ammonium ions in titanium dioxide mediated photocatalytic degradation of organic compounds containing nitrogen atoms

    SciTech Connect

    Low, G.K.-C.; McEvoy, S.R.; Matthews, R.W. )

    1991-03-01

    The photocatalytic oxidation of a related series of primary, secondary, and tertiary amines and other nitrogen- and sulfur-containing organic compounds over a UV-illuminated film of TiO{sub 2} has been studied. The compounds were as follows: n-pentylamine, piperidine, pyridine, phenylalanine, desipramine, thioridazine, penicillamine, isosorbide dinitrate, 4-nitrocatechol, 2,4-dinitrophenol, cyclophosphamide, 5-fluorouracil, atrazine, ethylenediaminetetracetic acid, and tetrabutylammonium phosphate. Both ammonium and nitrate ions were formed. The relative concentration of the two ions depended on the nature of the nitrogen in a compound, but was also influenced by the illumination time and concentration of the solute. It was found that for n-pentylamine, piperidine and pyridine, the rate of formation of ammonium ions was n-pentylamine {much gt} pyridine > piperidine. The order of rates of nitrate formation was pyridine = piperidine {much gt} pentylamine. For n-pentylamine the rate of formation of ammonium ions was {approximately}100 times that of nitrate.

  6. Reaction between atomic N(4S) and molecular CO at very low temperature: possible formation of HNCO in the Oort cloud

    NASA Astrophysics Data System (ADS)

    Nourry, Sendres; Zins, Emilie-Laure; Krim, Lahouari

    2015-07-01

    Beyond the Kuiper belt, the Oort cloud is characterized by particularly cold temperatures and the absence of energetic particles. Specific chemical processes involving cold radicals may occur in this reservoir of comets. A microwave-driven atomic source can be used to generate cold atomic nitrogen (N (4S)) for reactivity study of ices relevant to the Oort cloud. Without any additional source of energy, atomic nitrogen does not react with CO molecules to form NCO. This is consistent with a previous theoretical investigation carried out by Yazidi et al., who have shown that the potential energy surface for the CO (X1Σ+) + N (4S) system is purely dissociative. On the other hand, a very small amount of water is sufficient to induce a reaction between these two species. This three-body reaction leads to the formation of the HNCO monomer, the (HNCO)(H2O) complex, and the hydroxyl radical. Such reactions, leading to prebiotic molecules, may take place in the Oort cloud and in the Kuiper belt, from which most of the comets come.

  7. Two-Wire to Four-Wire Audio Converter

    NASA Technical Reports Server (NTRS)

    Talley, G. L., Jr; Seale, B. L.

    1983-01-01

    Simple circuit provides interface between normally incompatible voicecommunication lines. Circuit maintains 40 dB of isolation between input and output halves of four-wire line permitting two-wire line to be connected. Balancing potentiometer, Rg, adjusts gain of IC2 to null feed through from input to output. Adjustment is done on workbench just after assembly.

  8. Soft magnetic wires

    NASA Astrophysics Data System (ADS)

    Vázquez, M.

    2001-06-01

    An overview of the present state of the art on the preparation techniques, outstanding magnetic properties and applications of soft magnetic micro and nanowires is presented. Rapid solidification techniques (in-rotating-water quenching and drawing methods) to fabricate amorphous microwires with diameter in the range from 100 down to 1 μm are first described. Electrodeposition is also employed to prepare composite microtubes (magnetic coatings) and to fill porous membranes (diameter of the order of 0.1 μm). Magnetic behaviours of interest are related to the different hysteresis loops of samples: square-shaped loops typical of bistable behaviour, and nearly non-hysteretic loop with well-defined transverse anisotropy field. The role played by magnetic dipolar interactions in the magnetic behaviour of arrays of micro and nanowires is described. A particular analysis is done on the giant magnetoimpedance (GMI) effect in the radio and microwave frequency ranges exhibited by ultrasoft microwires. Finally, a few examples of applications are introduced for magnetostrictive and non-magnetostrictive wires, they are: “magnetoelastic pens”, micromotors; DC current-sensors based on GMI, and sharpened amorphous wire tips in spin polarised scanning tunneling microscopy.

  9. Improved superconducting magnet wire

    DOEpatents

    Schuller, I.K.; Ketterson, J.B.

    1983-08-16

    This invention is directed to a superconducting tape or wire composed of alternating layers of copper and a niobium-containing superconductor such as niobium of NbTi, Nb/sub 3/Sn or Nb/sub 3/Ge. In general, each layer of the niobium-containing superconductor has a thickness in the range of about 0.05 to 1.5 times its coherence length (which for Nb/sub 3/Si is 41 A) with each copper layer having a thickness in the range of about 170 to 600 A. With the use of very thin layers of the niobium composition having a thickness within the desired range, the critical field (H/sub c/) may be increased by factors of 2 to 4. Also, the thin layers of the superconductor permit the resulting tape or wire to exhibit suitable ductility for winding on a magnet core. These compositions are also characterized by relatively high values of critical temperature and therefore will exhibit a combination of useful properties as superconductors.

  10. Role of hydrogen atoms in the photoinduced formation of stable electron centers in H-doped 12CaO•7 Al2 O3

    NASA Astrophysics Data System (ADS)

    Sushko, Peter V.; Shluger, Alexander L.; Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

    2006-01-01

    In this work we investigate a variety of chemical and photoinduced processes in which different hydrogenous species including H2 molecules, H- ions, and H0 atoms interact with the bulk of a complex nanoporous oxide 12CaO•7Al2O3 . Our results provide a detailed and consistent explanation of the recently observed phenomenon of photoinduced conversion of the insulating H-doped 12CaO•7Al2O3 to a conductor [K. Hayashi , Nature (London) 419, 462 (2002)]. The formation of a large and thermally stable concentration of electron centers in this process is facilitated by a large concentration (up to 1020cm-3 ) of extraframework O2- naturally present in this material and homogeneously distributed in its bulk. We show that these species are able to split H2 molecules into pairs of H+ and H- ions and convert H0 atoms into H+ and e- promoting the photoinduced conversion process. The similarity of the mechanisms described in this work to those known for low-coordinated sites at MgO surfaces indicates that the formation of electronic centers in oxides interacting with hydrogenous species could be a generic feature.

  11. Ripple formation on atomically flat cleaved Si surface with roughness of 0.038 nm rms by low-energy Ar{sup 1+} ion bombardment

    SciTech Connect

    Pahlovy, Shahjada A.; Mahmud, S. F.; Yanagimoto, K.; Miyamoto, I.

    2011-03-15

    The authors have conducted research regarding ripple formation on an atomically flat cleaved Si surface by low-energy Ar{sup +} ion bombardment. The cleaved atomically flat and smooth plane of a Si wafer was obtained by cutting vertically against the orientation of a Si (100) wafer. Next, the cleaved surface was sputtered by a 1 keV Ar{sup +} ion beam at ion-incidence angles of 0 deg., 60 deg., 70 deg., and 80 deg. The results confirm the successful ripple formation at ion-incidence angles of 60 deg. - 80 deg. and that the wavelength of the ripples increases with the increase of the ion-incidence angle, as well as the inverse of ion doses. The direction of the ripple also changes from perpendicular to parallel to the projection of the ion-beam direction along the surface with the increasing ion-incidence angle. The authors have also observed the dose effects on surface roughness of cleaved Si surface at the ion-incidence angle of 60 deg., where the surface roughness increases with the increased ion dose. Finally, to understand the roughening mechanism, the authors studied the scaling behavior, measured the roughness exponent {alpha}, and compared the evolution of scaling regimes with Cuerno's one-dimensional simulation results.

  12. Formation of the muonic helium atom /alpha particle-muon-electron/ and observation of its Larmor precession

    NASA Technical Reports Server (NTRS)

    Souder, P. A.; Casperson, D. E.; Crane, T. W.; Hughes, V. W.; Lu, D. C.; Yam, M. H.; Orth, H.; Reist, H. W.; Zu Putlitz, G.

    1975-01-01

    Experiments are described in which it proved possible to form the muonic helium atom by stopping polarized negative muons in a helium gas with a 2% xenon admixture at a pressure of 14 atm. The observed Larmor precession amplitudes are plotted against the gyromagnetic ratio for both muons and antimuons stopped in He + 2% Xe. In addition, a non-zero residual polarization of 0.06 plus or minus 0.01 was measured for muons stopped in pure helium gas, which corresponds to a depolarization factor of 18 plus or minus 3.

  13. Mechanism of the formation of hydrogen tetroxide and peroxide via low-temperature interaction between hydrogen atoms and molecular oxygen

    NASA Astrophysics Data System (ADS)

    Levanov, A. V.; Isaikina, O. Ya.; Antipenko, E. E.; Lunin, V. V.

    2014-09-01

    A mechanism and kinetic model for the synthesis of peroxide radical condensate via the low-temperature interaction of hydrogen atoms with O2 molecules is proposed. The main components of the reaction, hydrogen tetroxide H2O4 and hydrogen peroxide H2O2, are formed in a low-temperature liquid layer formed near the cold surface during synthesis. Molecules of H2O4 and H2O2 are stabilized by transitioning to the solid phase. The dependences of the ratio on the ratio of concentrations of H and O2 in the gas phase, calculated on the basis of the model, are consistent with the experimental data.

  14. Specific features of the formation of atomic magnetic moments in amorphous films RE-Co ( RE = La, Gd, Tb)

    NASA Astrophysics Data System (ADS)

    Vas'kovskiy, V. O.; Adanakova, O. A.; Balymov, K. G.; Kulesh, N. A.; Svalov, A. V.; Stepanova, E. A.

    2015-06-01

    A systematic investigation of the magnetic properties of amorphous films in ( RE) x Co100 - x binary systems in the ground state with rare-earth elements ( RE) of different types has been performed. The concentration dependences of the average atomic magnetic moments of cobalt ( m Co), gadolinium ( m Gd), and terbium ( m Tb) have been determined from the analysis of the spontaneous magnetization of the films with a nonmagnetic rare-earth element (La), a rare-earth element with a spherical electron shell (Gd), and a rareearth element with a large orbital magnetic moment (Tb). It has been shown that, in the range 0 < x < 50 at %, the magnetic moment m Co decreases from 1.7 μB to zero, the magnetic moment m Gd remains unchanged and almost coincides with the magnetic moment of the free atom (7 μB), and the value of m Tb decreases monotonically, but the rate of decrease depends on the method of the sample preparation. The revealed regularities are associated with the concentration change in the electronic structure of cobalt and with the specificity of the magnetic structure of the films, which has a ferromagnetic, ferrimagnetic, or sperimagnetic character for samples containing La, Gd, or Tb, respectively.

  15. Colorimetric and atomic absorption spectrometric determination of mucolytic drug ambroxol through ion-pair formation with iron and thiocyanate.

    PubMed

    Levent, Abdulkadir; Sentürk, Zühre

    2010-09-01

    Colorimetric and atomic absorption spectrometric methods have been developed for the determination of mucolytic drug Ambroxol. These procedures depend upon the reaction of iron(III) metal ion with the drug in the presence of thiocyanate ion to form stable ion-pair complex which extractable chloroform. The red-coloured complex was determined either colorimetrically at 510 nm or by indirect atomic absorption spectrometry (AAS) via the determination of the iron content in the formed complex. The optimum experimental conditions for pH, concentrations of Fe(3+) and SCN(-), shaking time, phase ratio, and the number of extractions were determined. Under the proposed conditions, linearity was obeyed in the concentration ranges 4.1x10(-6) - 5.7x10(-5) M (1.7-23.6 µg mL(-1)) using both methods, with detection limits of 4.6x10(-7) M (0.19 µg mL(-1)) for colorimetry and 1.1x10(-6) M (0.46 µg mL(-1)) for AAS. The proposed methods were applied for the determination of Ambroxol in tablet dosage forms. The results obtained were statistically analyzed and compared with those obtained by applying the high-performance liquid chromatographic method with diode-array detection. PMID:20426742

  16. Formation and propagation of ultraslow three-wave-vector optical solitons in a cold seven-level triple-Λ atomic system under Raman excitation

    NASA Astrophysics Data System (ADS)

    Si, Liu-Gang; Yang, Wen-Xing; Lü, Xin-You; Hao, Xiangying; Yang, Xiaoxue

    2010-07-01

    In this article, a theoretical scheme is proposed to investigate the formation and propagation of three-wave coupled vector optical solitons with ultraslow group velocities in a lifetime-broadened seven-state triple-Λ atomic system under Raman excitation. We show that in the presence of a weak applied magnetic field that removes the degeneracy of the corresponding sublevels of the atomic medium, three continuous-wave control fields with circularly left or right polarized fields induce a quantum interference effect which can largely suppress the absorption of the three low-intensity pulsed fields, that is, the circularly σ- (right), the linearly π, and the circularly σ+ (left) polarized fields converted from one weak linear-polarized probe field. By means of the standard method of multiple scales, we solve the equations of motion of atomic response and probe-control electromagnetic fields and derive three-coupled nonlinear Schrödinger equations that govern the nonlinear evolution of the envelopes of the probe fields in this scheme. We then demonstrate that because of the nonlinear coupling to one another, the three probe fields can evolve into three-wave temporal, group velocity, and amplitude-matched optical solitons under appropriate conditions, which are produced from the delicate balance of the dispersion effects and the self- and cross-phase modulation effects. This scheme may thus pave the way to generate ultraslow vector optical solitons composed of three field components in a highly resonant atomic medium and result in a substantial impact on this field of nonlinear optics.

  17. Characteristics of high-T c oxide wire

    NASA Astrophysics Data System (ADS)

    Kohno, O.; Ikeno, Y.; Sadakata, N.; Sugimoto, M.; Nakagawa, M.

    1987-12-01

    We have prepared an Y-Ba-Cu-O superconducting wire with silver sheath by a powder metallurgy technique. The crystal structure of the oxide core was orthorhombic and no structural change was found after cold-drawing. The wire showed superconductivity after heat-treatment at 890°C. Diffusion behavior of oxygen atoms through the sheath material is discussed. The highest critical current density of 640 A/cm 2 was obtained for the sample heat-treated in oxygen flow.

  18. The Current in a Wire

    ERIC Educational Resources Information Center

    Thompson, Keith

    2009-01-01

    This little problem arose because I was frustrated with the standard electromagnetism texts, which show the magnetic field due to a current-bearing wire outside the wire [proportional to] 1/r and inside [proportional to] r. However, they never point out that the moving electrons must be influenced by the magnetic field created by the other moving…

  19. Aircraft wiring program status report

    NASA Technical Reports Server (NTRS)

    Beach, Rex

    1995-01-01

    In this Naval Air Warfare Center (NAWC) Aircraft Division status report, the general and wire and cable component activities, the systems engineering activities, the aircraft wiring lead maintenance activities, the NAVAIR/NASA interface activities, and the Base Realignment and Closure (BRAC) Commission recommendations are presented.

  20. First Wire-Free Pacemaker Approved

    MedlinePlus

    ... Wire-Free Pacemaker Approved Treats irregular heartbeat without wired leads To use the sharing features on this ... said in a news release. In traditional pacemakers, wired leads may malfunction and require the device to ...

  1. Welding wire pressure sensor assembly

    NASA Technical Reports Server (NTRS)

    Morris, Timothy B. (Inventor); Milly, Peter F., Sr. (Inventor); White, J. Kevin (Inventor)

    1994-01-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  2. Welding wire pressure sensor assembly

    NASA Astrophysics Data System (ADS)

    Morris, Timothy B.; Milly, Peter F.; White, J. Kevin

    1993-05-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  3. Welding wire pressure sensor assembly

    NASA Astrophysics Data System (ADS)

    Morris, Timothy B.; Milly, Peter F., Sr.; White, J. Kevin

    1994-04-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  4. Apollo experience report: Electrical wiring subsystem

    NASA Technical Reports Server (NTRS)

    White, L. D.

    1975-01-01

    The general requirements of the electrical wiring subsystems and the problem areas and solutions that occurred during the major part of the Apollo Program are detailed in this report. The concepts and definitions of specific requirements for electrical wiring; wire-connecting devices; and wire-harness fabrication, checkout, and installation techniques are discussed. The design and development of electrical wiring and wire-connecting devices are described. Mission performance is discussed, and conclusions and recommendations for future programs are presented.

  5. Electrode carrying wire for GTAW welding

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E. (Inventor); Dyer, Gerald E. (Inventor)

    1990-01-01

    A welding torch for gas tungsten arc welding apparatus has a hollow tungsten electrode including a ceramic liner and forms the filler metal wire guide. The wire is fed through the tungsten electrode thereby reducing the size of the torch to eliminate clearance problems which exist with external wire guides. Since the wire is preheated from the tungsten more wire may be fed into the weld puddle, and the wire will not oxidize because it is always within the shielding gas.

  6. Internal wire guide for GTAW welding

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E. (Inventor); Dyer, Gerald E. (Inventor)

    1989-01-01

    A welding torch for gas tungsten arc welding apparatus has a filler metal wire guide positioned within the torch, and within the shielding gas nozzle. The wire guide is adjacent to the tungsten electrode and has a ceramic liner through which the wire is fed. This reduces the size of the torch and eliminates the outside clearance problems that exit with external wire guides. Additionally, since the wire is always within the shielding gas, oxidizing of the wire is eliminated.

  7. SkfB Abstracts a Hydrogen Atom from Cα on SkfA To Initiate Thioether Cross-Link Formation.

    PubMed

    Bruender, Nathan A; Bandarian, Vahe

    2016-08-01

    Sulfur to α-carbon thioether-containing peptides (sactipeptides) are ribosomally synthesized post-translationally modified peptides with bacteriocidal activities. The thioether cross-link, which is required for biological activity, is installed by a member of the radical S-adenosyl-l-methionine (SAM) superfamily in the peptide substrate. Herein, we show that the radical SAM enzyme, SkfB, utilizes the 5'-deoxyadenosyl radical generated from the reductive cleavage of SAM to abstract a hydrogen atom from the α-carbon of the amino acid at position 12 in the substrate, SkfA, to initiate the installation of a thioether cross-link. The insights from this work can be applied to all radical SAM sactipeptide maturases. PMID:27410522

  8. The Role of Plasma Sheet Conditions in Ring Current Formation and Energetic Neutral Atom Emissions: TWINS Results and CRCM Comparison

    NASA Astrophysics Data System (ADS)

    Fok, M.; Buzulukova, N.; McComas, D.; Brandt, P.; Goldstein, J.; Valek, P.; Alquiza, J.

    2009-05-01

    The dynamics of the ring current is sensitive to plasma sheet density and temperature. The situation is further complicated by ionospheric feedback and the existence of electric shielding at low latitudes. Most of the ring current pressure is carried by ions with energies of ~5-50 keV. In this energy range, H-H+ charge exchange cross section falls sharply with increasing energy. As a result, the intensity of energetic neutral atoms (ENA) emitted from the ring current is very sensitive to the ion energy distribution, which, in turn, is controlled by the plasma sheet temperature. Using the Comprehensive Ring Current Model (CRCM) with different plasma sheet models, we calculate ENA emissions during several moderate storms in years 2008 and 2009. We compare the simulated images with those from the TWINS imagers and study the effects of plasma sheet conditions on the ring current and the associated ENA emissions.

  9. Simultaneous measurements of wire electrode surface contamination and corona discharge characteristics in an air-cleaning electrostatic precipitator

    SciTech Connect

    Kanazawa, Seiji; Ohkubo, Toshikazu; Nomoto, Yukiharu; Adachi, Takayoshi; Chang, J.S.

    1997-01-01

    Contamination of the corona wire in a wire-to-plate type air-cleaning electrostatic precipitator is studied experimentally. In order to enhance the contamination of wire, air containing dusts is directly supplied to a part of the wire electrode. Spores of Lycopodium and cigarette smoke particles are used as test dusts. Simultaneous measurements of wire electrode optical images and corona discharge modes are carried out during contamination processes. Results show that corona discharge modes and optical emission from the wire electrode change with time due to the surface contamination. In the case of cigarette smoke, after a time elapsed, streamer coronas appear due to the buildup of smoke particles on the wire surface. After the first streamer generation, the corona current fluctuates with time because the formation and diminution of the projections occur alternately at the different parts on the wire electrode surface.

  10. Microstructure and mechanical properties of Fe-Ni-Cr-Al steel wires produced by in-rotating-water spinning method

    NASA Astrophysics Data System (ADS)

    Inoue, A.; Tomioka, H.; Masumoto, T.

    1985-02-01

    Nonequilibrium austenite, γ, or duplex austenite + lath martensite,γ + α' L, phase wires with high strengths and large elongation have been produced in Fe-Ni-Cr-Al-C alloy system by the in-rotating-water spinning method in which a melt stream is ejected into a rotating water layer. These wires have a circular cross section and a white luster, and the wire diameter is in the range of 80 to 180 µm. The γ phase has a grain size as small as about 1 to 4 µm. The yield strength, Σy, tensile fracture strength, ay, and elongation, ɛp, are about 340 to 655 MPa, 440 to 975 MPa, and 12 to 22 pct for the γ single phase wires and about 465 to 865 MPa, 640 to 1350 MPa, and 2 to 18 pct for the α'L+ γ duplex phase wires. A cold drawing causes significant increases in Σy and Σf, and the attained values are about 3200 MPa and 4030 MPa for Fe-8Ni-12.5Cr-2.5Al-3C wire drawn to about 95 pct reduction in area owing to the formation of a strain-induced α'L phase and a remarkable work-hardening ability of γ and α'L phases. On the subsequent low-temperature annealing around 673 K, the Σy and Σf increase further to 4000 MPa and 4240 MPa, respectively, probably because of the enhancement of the interaction between dislocations and interstitial carbon atoms. Around the temperature (≃800 K) where the γ phase decomposes into a stable mixed structure of α + ordered bec compound + M7C3 on annealing, the ɛp decreases drastically and the fracture surface morphology changes from a dimple pattern to a cleavage pattern. It has been therefore inferred that the high strengths and good ductility of the melt-quenched y and γ + α'L wires are due to the suppression of the phase transformation of y to a mixed structure of γ + ordered bec compound + M7C3 carbide by the melt-quenching technique.

  11. Sintered wire cathode

    DOEpatents

    Falce, Louis R.; Ives, R. Lawrence

    2009-06-09

    A porous cathode structure is fabricated from a plurality of wires which are placed in proximity to each other in elevated temperature and pressure for a sintering time. The sintering process produces the porous cathode structure which may be divided into a plurality of individual porous cathodes, one of which may be placed into a dispenser cathode support which includes a cavity for containing a work function reduction material such as BaO, CaO, and Al.sub.2O.sub.3. The work function reduction material migrates through the pores of the porous cathode from a work replenishment surface adjacent to the cavity of the dispenser cathode support to an emitting cathode surface, thereby providing a dispenser cathode which has a uniform work function and therefore a uniform electron emission.

  12. Direct determination of arsenic in soil samples by fast pyrolysis-chemical vapor generation using sodium formate as a reductant followed by nondispersive atomic fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Duan, Xuchuan; Zhang, Jingya; Bu, Fanlong

    2015-09-01

    This new study shows for the first time that sodium formate can react with trace arsenic to form volatile species via fast pyrolysis - chemical vapor generation. We found that the presence of thiourea greatly enhanced the generation efficiency and eliminated the interference of copper. We studied the reaction temperature, the volume of sodium formate, the reaction acidity, and the carried argon rate using nondispersive atomic fluorescence spectrometry. Under optimal conditions of T = 500 °C, the volumes of 30% sodium formate and 10% thiourea were 0.2 ml and 0.05 ml, respectively. The carrier argon rate was 300 ml min- 1 and the detection limit and precision of arsenic were 0.39 ng and 3.25%, respectively. The amount of arsenic in soil can be directly determined by adding trace amount of hydrochloric acid as a decomposition reagent without any sample pretreatment. The method was successfully applied to determine trace amount of arsenic in two soil-certified reference materials (GBW07453 and GBW07450), and the results were found to be in agreement with certified reference values.

  13. Dynamics of conical wire array Z-pinch implosions

    SciTech Connect

    Ampleford, D. J.; Lebedev, S. V.; Bland, S. N.; Bott, S. C.; Chittenden, J. P.; Jennings, C. A.; Kantsyrev, V. L.; Safronova, A. S.; Ivanov, V. V.; Fedin, D. A.; Laca, P. J.; Yilmaz, M. F.; Nalajala, V.; Shrestha, I.; Williamson, K.; Osborne, G.; Haboub, A.; Ciardi, A.

    2007-10-15

    A modification of the wire array Z pinch, the conical wire array, has applications to the understanding of wire array implosions and potentially to pulse shaping relevant to inertial confinement fusion. Results are presented from imploding conical wire array experiments performed on university scale 1 MA generators--the MAGPIE generator (1 MA, 240 ns) at Imperial College London [I. H. Mitchell et al., Rev. Sci Instrum. 67, 1533 (1996)] and the Nevada Terawatt Facility's Zebra generator (1 MA, 100 ns) at the University of Nevada, Reno [B. Bauer et al., in Dense Z-Pinches, edited by N. Pereira, J. Davis, and P. Pulsifer (AIP, New York, 1997), Vol. 409, p. 153]. This paper will discuss the implosion dynamics of conical wire arrays. Data indicate that mass ablation from the wires in this complex system can be reproduced with a rocket model with fixed ablation velocity. Modulations in the ablated plasma are present, the wavelength of which is invariant to a threefold variation in magnetic field strength. The axial variation in the array leads to a zippered precursor column formation. An initial implosion of a magnetic bubble near the cathode is followed by the implosion zippering upwards. Spectroscopic data demonstrating a variation of plasma parameters (e.g., electron temperature) along the Z-pinch axis is discussed, and experimental data are compared to magnetohydrodynamic simulations.

  14. Plasma chemistry in wire chambers

    SciTech Connect

    Wise, J.

    1990-05-01

    The phenomenology of wire chamber aging is discussed and fundamentals of proportional counters are presented. Free-radical polymerization and plasma polymerization are discussed. The chemistry of wire aging is reviewed. Similarities between wire chamber plasma (>1 atm dc-discharge) and low-pressure rf-discharge plasmas, which have been more widely studied, are suggested. Construction and use of a system to allow study of the plasma reactions occurring in wire chambers is reported. A proportional tube irradiated by an {sup 55}Fe source is used as a model wire chamber. Condensable species in the proportional tube effluent are concentrated in a cryotrap and analyzed by gas chromatography/mass spectrometry. Several different wire chamber gases (methane, argon/methane, ethane, argon/ethane, propane, argon/isobutane) are tested and their reaction products qualitatively identified. For all gases tested except those containing methane, use of hygroscopic filters to remove trace water and oxygen contaminants from the gas resulted in an increase in the average molecular weight of the products, consistent with results from low-pressure rf-discharge plasmas. It is suggested that because water and oxygen inhibit polymer growth in the gas phase that they may also reduce polymer deposition in proportional tubes and therefore retard wire aging processes. Mechanistic implications of the plasma reactions of hydrocarbons with oxygen are suggested. Unresolved issues in this work and proposals for further study are discussed.

  15. Influence of Different Defects in Vertically Aligned Carbon Nanotubes on TiO2 Nanoparticle Formation through Atomic Layer Deposition.

    PubMed

    Acauan, Luiz; Dias, Anna C; Pereira, Marcelo B; Horowitz, Flavio; Bergmann, Carlos P

    2016-06-29

    The chemical inertness of carbon nanotubes (CNT) requires some degree of "defect engineering" for controlled deposition of metal oxides through atomic layer deposition (ALD). The type, quantity, and distribution of such defects rules the deposition rate and defines the growth behavior. In this work, we employed ALD to grow titanium oxide (TiO2) on vertically aligned carbon nanotubes (VACNT). The effects of nitrogen doping and oxygen plasma pretreatment of the CNT on the morphology and total amount of TiO2 were systematically studied using transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The induced chemical changes for each functionalization route were identified by X-ray photoelectron and Raman spectroscopies. The TiO2 mass fraction deposited with the same number of cycles for the pristine CNT, nitrogen-doped CNT, and plasma-treated CNT were 8, 47, and 80%, respectively. We demonstrate that TiO2 nucleation is dependent mainly on surface incorporation of heteroatoms and their distribution rather than structural defects that govern the growth behavior. Therefore, selecting the best way to functionalize CNT will allow us to tailor TiO2 distribution and hence fabricate complex heterostructures. PMID:27269125

  16. Volumetric intensity dependence on the formation of molecular and atomic ions within a high intensity laser focus.

    PubMed

    Robson, Lynne; Ledingham, Kenneth W D; McKenna, Paul; McCanny, Thomas; Shimizu, Seiji; Yang, Jiamin M; Wahlström, Claes-Göran; Lopez-Martens, Rodrigo; Varju, Katalin; Johnsson, Per; Mauritsson, Johan

    2005-01-01

    The mechanism of atomic and molecular ionization in intense, ultra-short laser fields is a subject which continues to receive considerable attention. An inherent difficulty with techniques involving the tight focus of a laser beam is the continuous distribution of intensities contained within the focus, which can vary over several orders of magnitude. The present study adopts time of flight mass spectrometry coupled with a high intensity (8 x 10(15) Wcm(-2)), ultra-short (20 fs) pulse laser in order to investigate the ionization and dissociation of the aromatic molecule benzene-d1 (C(6)H(5)D) as a function of intensity within a focused laser beam, by scanning the laser focus in the direction of propagation, while detecting ions produced only in a "thin" slice (400 and 800 microm) of the focus. The resultant TOF mass spectra varies significantly, highlighting the dependence on the range of specific intensities accessed and their volumetric weightings on the ionization/dissociation pathways accessed. PMID:15653366

  17. Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation

    NASA Astrophysics Data System (ADS)

    Ragab, Gamal H.; Amin, Alaa S.

    2004-03-01

    Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at λmax 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 μg ml -1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15±1.15, 99.30±1.40, 99.60±1.50, and 99.00±1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.

  18. Direct formation of anatase TiO2 nanoparticles on carbon nanotubes by atomic layer deposition and their photocatalytic properties.

    PubMed

    Huang, Sheng-Hsin; Liao, Shih-Yun; Wang, Chih-Chieh; Kei, Chi-Chung; Gan, Jon-Yiew; Perng, Tsong-Pyng

    2016-10-01

    TiO2 with different morphology was deposited on acid-treated multi-walled carbon nanotubes (CNTs) by atomic layer deposition at 100 °C-300 °C to form a TiO2@CNT structure. The TiO2 fabricated at 100 °C was an amorphous film, but became crystalline anatase nanoparticles when fabricated at 200 °C and 300 °C. The saturation growth rates of TiO2 nanoparticles at 300 °C were about 1.5 and 0.4 Å/cycle for substrate-enhanced growth and linear growth processes, respectively. It was found that the rate constants for methylene blue degradation by the TiO2@CNT structure formed at 300 °C were more suitable to fit with second-order reaction. The size of 9 nm exhibited the best degradation efficiency, because of the high specific area and appropriate diffusion length for the electrons and holes. PMID:27576914

  19. Formation of a ZnO{sub 2} layer on the surface of single crystal ZnO substrates with oxygen atoms by hydrogen peroxide treatment

    SciTech Connect

    Kashiwaba, Y.; Abe, T.; Nakagawa, A.; Niikura, I.; Kashiwaba, Y.; Daibo, M.; Fujiwara, T.; Osada, H.

    2013-03-21

    Formation of a ZnO{sub 2} layer by H{sub 2}O{sub 2} treatment for single crystal ZnO (0001) substrates was studied. X-ray diffraction (XRD) peaks of ZnO{sub 2} with a pyrite structure were observed in XRD 2{theta}-{omega} scan patterns of the O-face of single crystal ZnO (0001) substrates with H{sub 2}O{sub 2} treatment, but these peaks were not observed in patterns of the Zn-face of ZnO (0001) substrates with H{sub 2}O{sub 2} treatment. XRD {omega} scan patterns of the ZnO (0002) plane of the O-face of single crystal ZnO (0001) substrates were broadened at the tail of the pattern by H{sub 2}O{sub 2} treatment, but such broadening was not observed in that plane of the Zn-face. Grain structure of ZnO{sub 2} layers was clearly observed in atomic force microscopy (AFM) images for the O-face of ZnO (0001) substrates with H{sub 2}O{sub 2} treatment. Spectra of X-ray photoelectron spectroscopy (XPS) of the O-face of ZnO (0001) substrates with H{sub 2}O{sub 2} treatment showed a definite peak shift of the O 1s peak. It is thought that a pyrite structure of ZnO{sub 2} is easily formed around an O atom of the O-face of ZnO (0001) substrates. Results of XRD measurements, the AFM image, and XPS measurement of the H{sub 2}O{sub 2}-treated single crystal ZnO (1010) substrate that has oxygen atoms on the surface appeared to be the same as those of the O-face of ZnO (0001) substrates.

  20. Requirements for printed wiring boards

    NASA Technical Reports Server (NTRS)

    1984-01-01

    In order to maintain the high standards of the NASA printed wiring programs, this publication: prescribes NASA's requirements for assuring reliable rigid printed wiring boards; describes and incorporates basic considerations necessary to assure reliable rigid printed wiring boards; establishes the supplier's responsibility to train and certify personnel; provides for supplier documentation of the fabrication and inspection procedures to be used for NASA work, including supplier innovations and changes in technology; and provides visual workmanship standards to aid those responsible for determining quality conformance to the established requirements.

  1. Mechanism for formation of atmospheric Cl atom precursors in the reaction of dinitrogen oxides with HCl/Cl(-) on aqueous films.

    PubMed

    Hammerich, Audrey Dell; Finlayson-Pitts, Barbara J; Gerber, R Benny

    2015-07-15

    Nitryl chloride (ClNO2) and nitrosyl chloride (ClNO) are potential sources of highly reactive atmospheric chlorine atoms, hence of much interest, but their formation pathways are unknown. This work predicts production of these nitrogen oxychlorides from ab initio molecular dynamics (AIMD) simulations of N2O5 or an NO2 dimer on the surface of a thin film of water which is struck by gaseous HCl. Both of these heterogeneous reactions proceed at the liquid/vapor interface by an SN2 mechanism where the nucleophile is chloride ion formed from the ionization of HCl on the aqueous surface. The film of water enhances the otherwise very slow gas phase reaction to occur by (1) stabilizing and localizing the adsorbed N2O5 or NO2 dimer so it is physically accessible for reaction, (2) ionizing the impinging HCl, and (3) activating the adsorbed oxide for nucleophilic attack by chloride. Though both nitrogen oxychloride products are produced by SN2 reactions, the N2O5 mechanism is unusual in that the electrophilic N atom to be attacked oscillates between the two normally equivalent NO2 groups. Chloride ion is found to react with N2O5 less efficiently than with N2O4. The simulations provide an explanation for this. These substitution/elimination mechanisms are new for NOx/y chemistry on thin water films and cannot be derived from small cluster models. PMID:26140681

  2. Influence of resinous compounds in petroleum oils on formation of protective films by additives with labeled atoms

    SciTech Connect

    Faradzhev, K.F.

    1988-09-01

    The role of resinous compounds present in oil media in terms of their effects of protective film formation and corrosive wear of metal is investigated. Radioactive additives consisting of barium salts of an alkylphenol sulfide and an alkylphenol disulfide, containing a functional group of sulfur 35, were synthesized. These additives were added to the test oil in an amount of 3%. In most cases, the additives tend to form more stable films on the metal surface when they are used in oils containing resinous compounds than when they are used in individual groups of hydrocarbons. The quantity and efficiency of the protective film formed by the additive depends not only on the hydrocarbon structure of the oil hydrocarbons, but also on the quality of the additive, the nature of the metal, and the content of resinous compounds in the oil and the structure of these compounds.

  3. Corrosion resistance of stressed NiTi and stainless steel orthodontic wires in acid artificial saliva.

    PubMed

    Huang, Her-Hsiung

    2003-09-15

    The purpose of this study was to investigate the corrosion resistance of stressed NiTi and stainless steel orthodontic wires using cyclic potentiodynamic and potentiostatic tests in acid artificial saliva at 37 degrees C. An atomic force microscope was used to measure the 3-D surface topography of as-received wires. Scanning electron microscope observations were carried out before and after the cyclic potentiodynamic tests. The surface chemical analysis was characterized using X-ray photoelectron spectroscopy and Auger electron spectroscopy after the potentiostatic tests. The cyclic potentiodynamic test results showed that the pH had a significant influence on the corrosion parameters of the stressed NiTi and stainless steel wires (p < 0.05). The pitting potential, protection potential, and passive range of stressed NiTi and stainless steel wires decreased on decreasing pH, whereas the passive current density increased on decreasing pH. The load had no significant influence on the above corrosion parameters (p > 0.05). For all pH and load conditions, stainless steel wire showed higher pitting potential and wider passive range than NiTi wire (p < 0.001), whereas NiTi wire had lower passive current density than stainless steel wire (p < 0.001). The corrosion resistance of the stressed NiTi and stainless steel wires was related to the surface characterizations, including surface defect and passive film. PMID:12926035

  4. Electron transport through dangling-bond silicon wires on H-passivated Si(100).

    PubMed

    Kepenekian, Mikaël; Novaes, Frederico D; Robles, Roberto; Monturet, Serge; Kawai, Hiroyo; Joachim, Christian; Lorente, Nicolás

    2013-01-16

    We compute the electron transmission through different types of dangling-bond wire on Si(100)-H (2 × 1). Recent progress in the construction of atomic-size interconnects (Weber et al 2012 Science 335 64) shows the possibility to achieve atomic-size circuits via atomic-size wires using silicon surfaces. Hence, electron transport through quasi-1D Si-based structures is a compelling reality. Prior to these achievements, wires formed by controlled desorption of passivating H atoms off the monohydride Si(100) surface have been shown to be subject to 1D correlations and instabilities (Hitosugi et al 1999 Phys. Rev. Lett. 82 4034). The present calculations are based on density functional theory and evaluate the electron transmission though the minimum-energy 1D structures that can be formed when creating dangling-bonds on Si(100)-(2 × 1)-H. The purpose of this study is twofold: (i) to assess the transport properties of these atomic-size wires in the presence of 1D instabilities; (ii) to provide a fingerprint for experimental identification of the instability through the transport characteristics of the wires. To these aims, we evaluate the electron transport through the wires in the absence of instabilities, in the presence of distortions (Jahn-Teller instabilities) and in the presence of magnetic instabilities (ferro- and antiferro-ordering). We find that instabilities substantially reduce the transport capabilities of dangling-bond wires leading to transmissions that vary so differently with electron energy that an unambiguous identification of the wire type should be accessible in transport experiments. PMID:23197188

  5. The Nation's First Wire Service: Evidence Supporting a Footnote.

    ERIC Educational Resources Information Center

    Schwarzlose, Richard A.

    The Associated Press's claim that it is the oldest wire service in the United States (tracing its origin to formation of the New York City Associated Press in 1948) has been regularly sustained in journalism's history literature. This claim has been challenged by Alfred McClung Lee in his book "The Daily Newspaper in America," in which he contends…

  6. Ohm's law survives to the atomic scale.

    PubMed

    Weber, B; Mahapatra, S; Ryu, H; Lee, S; Fuhrer, A; Reusch, T C G; Thompson, D L; Lee, W C T; Klimeck, G; Hollenberg, L C L; Simmons, M Y

    2012-01-01

    As silicon electronics approaches the atomic scale, interconnects and circuitry become comparable in size to the active device components. Maintaining low electrical resistivity at this scale is challenging because of the presence of confining surfaces and interfaces. We report on the fabrication of wires in silicon--only one atom tall and four atoms wide--with exceptionally low resistivity (~0.3 milliohm-centimeters) and the current-carrying capabilities of copper. By embedding phosphorus atoms within a silicon crystal with an average spacing of less than 1 nanometer, we achieved a diameter-independent resistivity, which demonstrates ohmic scaling to the atomic limit. Atomistic tight-binding calculations confirm the metallicity of these atomic-scale wires, which pave the way for single-atom device architectures for both classical and quantum information processing. PMID:22223802

  7. Demonstrating Forces between Parallel Wires.

    ERIC Educational Resources Information Center

    Baker, Blane

    2000-01-01

    Describes a physics demonstration that dramatically illustrates the mutual repulsion (attraction) between parallel conductors using insulated copper wire, wooden dowels, a high direct current power supply, electrical tape, and an overhead projector. (WRM)

  8. Method of manufacturing superconductor wire

    SciTech Connect

    Motowidlo, Leszek

    2014-09-16

    A method for forming Nb.sub.3Sn superconducting wire is provided. The method employs a powder-in-tube process using a high-tin intermetallic compound, such as MnSn.sub.2, for producing the Nb.sub.3Sn. The use of a high-tin intermetallic compound enables the process to perform hot extrusion without melting the high-tin intermetallic compound. Alternatively, the method may entail drawing the wire without hot extrusion.

  9. Smart Wire Grid: Resisting Expectations

    SciTech Connect

    Ramsay, Stewart; Lowe, DeJim

    2014-03-03

    Smart Wire Grid's DSR technology (Discrete Series Reactor) can be quickly deployed on electrical transmission lines to create intelligent mesh networks capable of quickly rerouting electricity to get power where and when it's needed the most. With their recent ARPA-E funding, Smart Wire Grid has been able to move from prototype and field testing to building out a US manufacturing operation in just under a year.

  10. Smart Wire Grid: Resisting Expectations

    ScienceCinema

    Ramsay, Stewart; Lowe, DeJim

    2014-04-09

    Smart Wire Grid's DSR technology (Discrete Series Reactor) can be quickly deployed on electrical transmission lines to create intelligent mesh networks capable of quickly rerouting electricity to get power where and when it's needed the most. With their recent ARPA-E funding, Smart Wire Grid has been able to move from prototype and field testing to building out a US manufacturing operation in just under a year.

  11. Enhanced formation of a confined nano-water meniscus using a 780 nm laser with a quartz tuning fork-atomic force microscope.

    PubMed

    An, Sangmin; Lee, Kunyoung; Moon, Geol; Bak, Wan; Kim, Gunn; Jhe, Wonho

    2012-07-01

    Demonstrated herein is the optical-field-induced enhancement of the formation of a confined nanowater meniscus using a distance-regulated quartz tuning fork-atomic force microscope (QTF-AFM) with a 780 nm laser. While a pulled optical fiber tip approaches the surface, the laser is suddenly turned on and focuses on the front spot of the tip by the shape of the pulled optical fiber, which plays the role of an objective lens and induces the gathering effect of the water molecules directed to the electromagnetic-field gradient in air. This phenomenon facilitates a new boundary condition to form a long-range confined nano-scale liquid bridge between the tip and the surface. After the pulling of the optical fiber, 20-nm-thick gold was sputtered on the apex (diameter: approximately 100 nm) of the tip to guide and focus the beam on the spot. The critical power of the laser to overcome the barrier for the formation of a new boundary is 100 microW at the distance of 22 nm from the substrate. PMID:22966648

  12. Eliminating a Major Cause of Wire Drawing Breakage in A-15 High-Field Superconductors

    SciTech Connect

    Austen, Alfred R.

    2003-05-20

    justify the development of an integrated compact production type Advanced Wire Drawing Station. New insights into the formation and growth of a shear type defect that causes breakage lead to improved drawing technology and it will be the basis for further study and improvements included in a Phase 2 proposal. Potential application of the research: This new capability now justifies the development of an integrated compact production type Advanced Wire Drawing Station to replace the bulky, slower and research oriented equipment that currently uses four independent operations for each wire diameter reduction. In a Phase 2 proposal, the designs for each operation were to be optimized for their performance and so they could be used to integrate these individual operations into an Advanced Wire Drawing Station. This station will perform all the mechanical conditioning, cleaning, lubrication, guidance and drawing operations simultaneously and it will be tested to verify wire drawing performance targets. A portable Advanced Wire Drawing Station will be developed and constructed in the final stage of the proposed Phase 2 program and it will be used in an outside manufacturing facility for superconductor composite wire drawing field trials.

  13. Current-driven atomic waterwheels

    NASA Astrophysics Data System (ADS)

    Dundas, Daniel; McEniry, Eunan J.; Todorov, Tchavdar N.

    2009-02-01

    A current induces forces on atoms inside the conductor that carries it. It is now possible to compute these forces from scratch, and to perform dynamical simulations of the atomic motion under current. One reason for this interest is that current can be a destructive force-it can cause atoms to migrate, resulting in damage and in the eventual failure of the conductor. But one can also ask, can current be made to do useful work on atoms? In particular, can an atomic-scale motor be driven by electrical current, as it can be by other mechanisms? For this to be possible, the current-induced forces on a suitable rotor must be non-conservative, so that net work can be done per revolution. Here we show that current-induced forces in atomic wires are not conservative and that they can be used, in principle, to drive an atomic-scale waterwheel.

  14. Current-driven atomic waterwheels.

    PubMed

    Dundas, Daniel; McEniry, Eunan J; Todorov, Tchavdar N

    2009-02-01

    A current induces forces on atoms inside the conductor that carries it. It is now possible to compute these forces from scratch, and to perform dynamical simulations of the atomic motion under current. One reason for this interest is that current can be a destructive force--it can cause atoms to migrate, resulting in damage and in the eventual failure of the conductor. But one can also ask, can current be made to do useful work on atoms? In particular, can an atomic-scale motor be driven by electrical current, as it can be by other mechanisms? For this to be possible, the current-induced forces on a suitable rotor must be non-conservative, so that net work can be done per revolution. Here we show that current-induced forces in atomic wires are not conservative and that they can be used, in principle, to drive an atomic-scale waterwheel. PMID:19197311

  15. 30 CFR 75.701-4 - Grounding wires; capacity of wires.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Grounding wires; capacity of wires. 75.701-4... SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Grounding § 75.701-4 Grounding wires; capacity of wires. Where grounding wires are used to ground metallic sheaths, armors, conduits,...

  16. 30 CFR 75.701-4 - Grounding wires; capacity of wires.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Grounding wires; capacity of wires. 75.701-4... SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Grounding § 75.701-4 Grounding wires; capacity of wires. Where grounding wires are used to ground metallic sheaths, armors, conduits,...

  17. HTS Wire Development Workshop: Proceedings

    SciTech Connect

    Not Available

    1994-07-01

    The 1994 High-Temperature Superconducting Wire Development Workshop was held on February 16--17 at the St. Petersburg Hilton and Towers in St. Petersburg, Florida. The meeting was hosted by Florida Power Corporation and sponsored by the US Department of Energy`s Superconductivity Program for Electric Power Systems. The meeting focused on recent high-temperature superconducting wire development activities in the Department of Energy`s Superconductivity Systems program. The meeting opened with a general discussion on the needs and benefits of superconductivity from a utility perspective, the US global competitiveness position, and an outlook on the overall prospects of wire development. The meeting then focused on four important technology areas: Wire characterization: issues and needs; technology for overcoming barriers: weak links and flux pinning; manufacturing issues for long wire lengths; and physical properties of HTS coils. Following in-depth presentations, working groups were formed in each technology area to discuss the most important current research and development issues. The working groups identified research areas that have the potential for greatly enhancing the wire development effort. These areas are discussed in the summary reports from each of the working groups. This document is a compilation of the workshop proceedings including all general session presentations and summary reports from the working groups.

  18. 1 mil gold bond wire study.

    SciTech Connect

    Huff, Johnathon; McLean, Michael B.; Jenkins, Mark W.; Rutherford, Brian Milne

    2013-05-01

    In microcircuit fabrication, the diameter and length of a bond wire have been shown to both affect the current versus fusing time ratio of a bond wire as well as the gap length of the fused wire. This study investigated the impact of current level on the time-to-open and gap length of 1 mil by 60 mil gold bond wires. During the experiments, constant current was provided for a control set of bond wires for 250ms, 410ms and until the wire fused; non-destructively pull-tested wires for 250ms; and notched wires. The key findings were that as the current increases, the gap length increases and 73% of the bond wires will fuse at 1.8A, and 100% of the wires fuse at 1.9A within 60ms. Due to the limited scope of experiments and limited data analyzed, further investigation is encouraged to confirm these observations.

  19. Influence of inelastic collisions with hydrogen atoms on the formation of AlI and SiI lines in stellar spectra

    NASA Astrophysics Data System (ADS)

    Mashonkina, L. I.; Belyaev, A. K.; Shi, J.-R.

    2016-06-01

    We have performed calculations by abandoning the assumption of local thermodynamic equilibrium (within the so-called non-LTE approach) for Al I and Si I with model atmospheres corresponding to stars of spectral types F-G-Kwith differentmetal abundances. To take into account inelastic collisions with hydrogen atoms, for the first time we have applied the cross sections calculated by Belyaev et al. using model approaches within the formalism of the Born-Oppenheimer quantum theory. We show that for Al I non-LTE leads to higher ionization (overionization) than in LTE in the spectral line formation region and to a weakening of spectral lines, which is consistent with earlier non-LTE studies. However, our results, especially for the subordinate lines, differ quantitatively from the results of predecessors. Owing to their large cross sections, the ion-pair production and mutual neutralization processes Al I( nl) + HI(1 s) ↔ Al II(3 s 2) + H- provide a close coupling of highly excited Al I levels with the Al II ground state, which causes the deviations from the equilibrium level population to decrease compared to the calculations where the collisions only with electrons are taken into account. For three moderately metal-deficient dwarf stars, the aluminum abundance has been determined from seven Al I lines in different models of their formation. Under the assumption of LTE and in non-LTE calculations including the collisions only with electrons, the Al I 3961 ˚A resonance line gives a systematically lower abundance than the mean abundance from the subordinate lines, by 0.25-0.45 dex. The difference for each star is removed by taking into account the collisions with hydrogen atoms, and the rms error of the abundance derived from all seven Al I lines decreases by a factor of 1.5-3 compared to the LTE analysis. We have calculated the non- LTE corrections to the abundance for six subordinate Al I lines as a function of the effective temperature (4500 K ≤ T eff ≤ 6500 K

  20. Energetics and electronic properties of Pt wires of different topologies on monolayer MoSe2

    NASA Astrophysics Data System (ADS)

    Jamdagni, Pooja; Kumar, Ashok; Thakur, Anil; Pandey, Ravindra; Ahluwalia, P. K.

    2016-05-01

    The energetics and electronic properties of different topology of Pt wires including linear, zigzag and ladder structures on MoSe2 monolayer have been investigated in the framework of density functional theory (DFT). The predicted order of stability of Pt wire on MoSe2 monolayer is found to be: linear > ladder > zigzag. Pt wires induce states near the Fermi level of MoSe2 that results into metallic characteristics of Pt-wire/MoSe2 assembled system. Valence band charge density signifies most of the contribution from Pt atoms near the Fermi energy of assembled wire/MoSe2 system. These findings are expected to be important for the fabrication of devices based on MoSe2 layers for flexible nanoelectronics.

  1. Absorption spectroscopy of wire-array plasma at the non-radiative stage

    NASA Astrophysics Data System (ADS)

    Ivanov, V. V.; Hakel, P.; Mancini, R. C.; Wiewior, P.; Durmaz, T.; Anderson, A.; Astanovitskiy, A.; Chalyy, O.; Altemara, S. D.; Papp, D.; McKee, E.; Chittenden, J. P.; Niasse, N.; Shevelko, A. P.

    2010-11-01

    Absorption spectroscopy was applied to 1 MA wire-array Z-pinches. The 50 TW Leopard laser was coupled with the Zebra generator for x-ray backlighting of wire arrays. Wire-array plasmas were investigated at the ablation and implosion stages. Broadband x-ray radiation from a laser produced Sm plasma was used to backlight Al star wire arrays in the range of 7-9 å. Two time-integrated x-ray conical spectrometers recorded reference and main spectra. The backlighting radiation was separated from the powerful Z-pinch x-ray burst by collimators. A comparison of the backlighting radiation spectra that passed through the plasma with reference spectra indicates absorption lines in the range of 8.2-8.4 å. A plasma density profile was simulated with a 3D resistive MHD code. Simulations with atomic kinetics models derived an electron temperature of Al wire-array plasma.

  2. Investigation of the dipole formation and growth behavior at In2O3|TiO2 heterojunctions using photoemission spectroscopy and atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Schaefer, Michael; Halpegamage, Sandamali; Batzill, Matthias; Schlaf, Rudy

    2016-02-01

    This paper discusses the investigation of the dipole formation at In2O3|TiO2 heterojunctions depending on preparation conditions, i.e., cleaning methods. In2O3 films were deposited using atomic layer deposition (ALD) onto solvent and in situ cleaned anatase and rutile film substrates. The interface dipole strength and film thickness were evaluated by photoemission spectroscopy. Our results indicate the formation of a large intrinsic and film thickness dependent interface dipole that reaches its maximum strength at monolayer thick ALD films. In addition, it was observed that UV photoelectron spectroscopy measurements introduced UV induced surface hydroxylation, which resulted in dipole potentials of -0.70 eV and -0.50 eV on solvent cleaned anatase and rutile, respectively. The overlayers also introduced small amounts of band bending (˜0.10 eV) at the interfaces. Taking these effects into account, the total dipole strength at monolayer thick In2O3 films was determined to be -0.96 eV for solvent cleaned anatase and rutile and -0.81 eV for in situ cleaned rutile. The deposition of single ALD cycles on differently cleaned rutile substrates resulted in similar work function values, suggesting little influence of the sample preparation method prior to ALD deposition on the dipole formation. This was assigned to the fact that ALD oxides benefit from ambient water related contamination by integrating the molecules into the growing ALD layer. Highest initial growth was observed on solvent cleaned rutile, followed by in-situ cleaned rutile and solvent cleaned anatase. The In2O3 growth converged at 0.3 Å/c past the nucleation regime.

  3. Relationship between spontaneous γH2AX foci formation and progenitor functions in circulating hematopoietic stem and progenitor cells among atomic-bomb survivors.

    PubMed

    Kajimura, Junko; Kyoizumi, Seishi; Kubo, Yoshiko; Misumi, Munechika; Yoshida, Kengo; Hayashi, Tomonori; Imai, Kazue; Ohishi, Waka; Nakachi, Kei; Weng, Nan-Ping; Young, Lauren F; Shieh, Jae-Hung; Moore, Malcolm A; van den Brink, Marcel R M; Kusunoki, Yoichiro

    2016-05-01

    Accumulated DNA damage in hematopoietic stem cells is a primary mechanism of aging-associated dysfunction in human hematopoiesis. About 70 years ago, atomic-bomb (A-bomb) radiation induced DNA damage and functional decreases in the hematopoietic system of A-bomb survivors in a radiation dose-dependent manner. The peripheral blood cell populations then recovered to a normal range, but accompanying cells derived from hematopoietic stem cells still remain that bear molecular changes possibly caused by past radiation exposure and aging. In the present study, we evaluated radiation-related changes in the frequency of phosphorylated (Ser-139) H2AX (γH2AX) foci formation in circulating CD34-positive/lineage marker-negative (CD34+Lin-) hematopoietic stem and progenitor cells (HSPCs) among 226Hiroshima A-bomb survivors. An association between the frequency of γH2AX foci formation in HSPCs and the radiation dose was observed, but the γH2AX foci frequency was not significantly elevated by past radiation. We found a negative correlation between the frequency of γH2AX foci formation and the length of granulocyte telomeres. A negative interaction effect between the radiation dose and the frequency of γH2AX foci was suggested in a proportion of a subset of HSPCs as assessed by the cobblestone area-forming cell assay (CAFC), indicating that the self-renewability of HSPCs may decrease in survivors who were exposed to a higher radiation dose and who had more DNA damage in their HSPCs. Thus, although many years after radiation exposure and with advancing age, the effect of DNA damage on the self-renewability of HSPCs may be modified by A-bomb radiation exposure. PMID:27169377

  4. Fabrication of Pd-Cr wire

    NASA Technical Reports Server (NTRS)

    Diamond, Sidney; Leach, Dennen M.

    1989-01-01

    Fabrication of Pd-13 percent Cr alloy wires is described. Melting, casting, swaging and annealing processes are discussed. Drawing to reach two diameters (0.003 inch and 0.00176 inch) of wire is described. Representative micrographs of the Pd-Cr alloy at selected stages during wire fabrication are included. The resistance of the wire was somewhat lower, by about 15 to 20 percent, than comparable wire of other alloys used for strain gages.

  5. Experimental Results for Space-Wire-D

    NASA Astrophysics Data System (ADS)

    Parkes, Steve; Gibson, David; Ferrer, Albert

    2015-09-01

    SpaceWire-D is a deterministic extension to SpaceWire that uses time-division multiplexing to schedule traffic within time-slots. It allows a single SpaceWire network to be used for both time-critical avionics control applications and asynchronous payload data-handling simultaneously using existing SpaceWire technology. In this paper we describe the services of SpaceWire-D and present experimental results for each service.

  6. Connecting to Thermocouples with Fewer Lead Wires

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2003-01-01

    A simple technique has been devised to reduce the number of lead wires needed to connect an array of thermocouples to the instruments (e.g., voltmeters) used to read their output voltages. Because thermocouple wires are usually made of expensive metal alloys, reducing the number of lead wires can effect a considerable reduction in the cost of such an array. Reducing the number of wires also reduces the number of terminals and the amount of space needed to accommodate the wires.

  7. Larger sized wire arrays on 1.5 MA Z-pinch generator

    SciTech Connect

    Safronova, A. S. Kantsyrev, V. L. Weller, M. E. Shlyaptseva, V. V. Shrestha, I. K. Esaulov, A. A. Stafford, A.; Chuvatin, A. S.; Coverdale, C. A.; Jones, B.

    2014-12-15

    Experiments on the UNR Zebra generator with Load Current Multiplier (LCM) allow for implosions of larger sized wire array loads than at standard current of 1 MA. Advantages of larger sized planar wire array implosions include enhanced energy coupling to plasmas, better diagnostic access to observable plasma regions, and more complex geometries of the wire loads. The experiments with larger sized wire arrays were performed on 1.5 MA Zebra with LCM (the anode-cathode gap was 1 cm, which is half the gap used in the standard mode). In particular, larger sized multi-planar wire arrays had two outer wire planes from mid-atomic-number wires to create a global magnetic field (gmf) and plasma flow between them. A modified central plane with a few Al wires at the edges was put in the middle between outer planes to influence gmf and to create Al plasma flow in the perpendicular direction (to the outer arrays plasma flow). Such modified plane has different number of empty slots: it was increased from 6 up to 10, hence increasing the gap inside the middle plane from 4.9 to 7.7 mm, respectively. Such load configuration allows for more independent study of the flows of L-shell mid-atomic-number plasma (between the outer planes) and K-shell Al plasma (which first fills the gap between the edge wires along the middle plane) and their radiation in space and time. We demonstrate that such configuration produces higher linear radiation yield and electron temperatures as well as advantages of better diagnostics access to observable plasma regions and how the load geometry (size of the gap in the middle plane) influences K-shell Al radiation. In particular, K-shell Al radiation was delayed compared to L-shell mid-atomic-number radiation when the gap in the middle plane was large enough (when the number of empty slots was increased up to ten)

  8. Larger sized wire arrays on 1.5 MA Z-pinch generator

    NASA Astrophysics Data System (ADS)

    Safronova, A. S.; Kantsyrev, V. L.; Weller, M. E.; Shlyaptseva, V. V.; Shrestha, I. K.; Esaulov, A. A.; Stafford, A.; Chuvatin, A. S.; Coverdale, C. A.; Jones, B.

    2014-12-01

    Experiments on the UNR Zebra generator with Load Current Multiplier (LCM) allow for implosions of larger sized wire array loads than at standard current of 1 MA. Advantages of larger sized planar wire array implosions include enhanced energy coupling to plasmas, better diagnostic access to observable plasma regions, and more complex geometries of the wire loads. The experiments with larger sized wire arrays were performed on 1.5 MA Zebra with LCM (the anode-cathode gap was 1 cm, which is half the gap used in the standard mode). In particular, larger sized multi-planar wire arrays had two outer wire planes from mid-atomic-number wires to create a global magnetic field (gmf) and plasma flow between them. A modified central plane with a few Al wires at the edges was put in the middle between outer planes to influence gmf and to create Al plasma flow in the perpendicular direction (to the outer arrays plasma flow). Such modified plane has different number of empty slots: it was increased from 6 up to 10, hence increasing the gap inside the middle plane from 4.9 to 7.7 mm, respectively. Such load configuration allows for more independent study of the flows of L-shell mid-atomic-number plasma (between the outer planes) and K-shell Al plasma (which first fills the gap between the edge wires along the middle plane) and their radiation in space and time. We demonstrate that such configuration produces higher linear radiation yield and electron temperatures as well as advantages of better diagnostics access to observable plasma regions and how the load geometry (size of the gap in the middle plane) influences K-shell Al radiation. In particular, K-shell Al radiation was delayed compared to L-shell mid-atomic-number radiation when the gap in the middle plane was large enough (when the number of empty slots was increased up to ten).

  9. Experiments in cold atom optics towards precision atom interferometry

    NASA Astrophysics Data System (ADS)

    Aveline, David C.

    Atom optics has been a highly active field of research with many scientific breakthroughs over the past two decades, largely due to successful advances in laser technology, microfabrication techniques, and the development of laser cooling and trapping of neutral atoms. This dissertation details several atom optics experiments with the motivation to develop tools and techniques for precision atom wave interferometry. It provides background information about atom optics and the fundamentals behind laser cooling and trapping, including basic techniques for cold gas thermometry and absorptive detection of atoms. A brief overview of magnetic trapping and guiding in tight wire-based traps is also provided before the experimental details are presented. We developed a novel laser source of 780 nm light using frequency-doubled 1560 nm fiber amplifier. This laser system provided up to a Watt of tunable frequency stabilized light for two Rb laser cooling and trapping experiments. One system generates Bose-Einstein condensates in an optical trap while the second is based on atom chip magnetic traps. The atom chip system, detailed in this thesis, was designed and built to develop the tools necessary for transport and loading large numbers of cold atoms and explore the potential for guided atom interferometry. Techniques and results from this experiment are presented, including an efficient magnetic transport and loading method to deliver cold atom to atom chip traps. We also developed a modeling tool for the magnetic fields formed by coiled wire geometries, as well as planar wire patterns. These models helped us design traps and determine adiabatic transportation of cold atoms between macro-scale traps and micro-traps formed on atom chips. Having achieved near unity transfer efficiency, we demonstrated that this approach promises to be a consistent method for loading large numbers of atoms into micro-traps. Furthermore, we discuss an in situ imaging technique to investigate

  10. Free-Space Nanometer Wiring via Nanotip Manipulation

    PubMed Central

    Kizuka, Tokushi; Ashida, Shin

    2015-01-01

    Relentless efforts in semiconductor technology have driven nanometer-scale miniaturization of transistors, diodes, and interconnections in electronic chips. Free-space writing enables interconnections of stacked modules separated by an arbitrary distance, leading to ultimate integration of electronics. We have developed a free-space method for nanometer-scale wiring on the basis of manipulating a metallic nanotip while applying a bias voltage without radiative heating, lithography, etching, or electrodeposition. The method is capable of fabricating wires with widths as low as 1–6 nm and lengths exceeding 200 nm with a breakdown current density of 8 TA/m2. Structural evolution and conduction during wire formation were analyzed by direct atomistic visualization using in situ high-resolution transmission electron microscopy. PMID:26306613

  11. Free-Space Nanometer Wiring via Nanotip Manipulation

    NASA Astrophysics Data System (ADS)

    Kizuka, Tokushi; Ashida, Shin

    2015-08-01

    Relentless efforts in semiconductor technology have driven nanometer-scale miniaturization of transistors, diodes, and interconnections in electronic chips. Free-space writing enables interconnections of stacked modules separated by an arbitrary distance, leading to ultimate integration of electronics. We have developed a free-space method for nanometer-scale wiring on the basis of manipulating a metallic nanotip while applying a bias voltage without radiative heating, lithography, etching, or electrodeposition. The method is capable of fabricating wires with widths as low as 1-6 nm and lengths exceeding 200 nm with a breakdown current density of 8 TA/m2. Structural evolution and conduction during wire formation were analyzed by direct atomistic visualization using in situ high-resolution transmission electron microscopy.

  12. Free-Space Nanometer Wiring via Nanotip Manipulation.

    PubMed

    Kizuka, Tokushi; Ashida, Shin

    2015-01-01

    Relentless efforts in semiconductor technology have driven nanometer-scale miniaturization of transistors, diodes, and interconnections in electronic chips. Free-space writing enables interconnections of stacked modules separated by an arbitrary distance, leading to ultimate integration of electronics. We have developed a free-space method for nanometer-scale wiring on the basis of manipulating a metallic nanotip while applying a bias voltage without radiative heating, lithography, etching, or electrodeposition. The method is capable of fabricating wires with widths as low as 1-6 nm and lengths exceeding 200 nm with a breakdown current density of 8 TA/m(2). Structural evolution and conduction during wire formation were analyzed by direct atomistic visualization using in situ high-resolution transmission electron microscopy. PMID:26306613

  13. In situ formation and characterisation of singly ionised atomic europium in rare gas matrices—Luminescence spectroscopy and MP2 calculations

    SciTech Connect

    Byrne, Owen; Davis, Barry; McCaffrey, John G.

    2015-02-07

    Irradiation of atomic europium isolated in the solid rare gases, with low intensity laser excitation of the y{sup 8}P←a{sup 8}S resonance transition at ca. 465 nm, is found to produce singly charged europium cations (Eu{sup +}) in large amounts in xenon and in smaller amounts in argon. Confirmation of the formation of matrix-isolated Eu{sup +} is obtained from characteristic absorption bands in the UV and in the visible spectral regions. The luminescence produced with excitation of the cation bands is presented in greatest detail for Eu/Xe and assigned. Excitation of the 4f{sup 7}({sup 8}S{sub 7/2})6p{sub 3/2} absorption bands of Eu{sup +} between 390 and 410 nm produces emission which is quite distinct from that resulting from excitation of the 4f{sup 7}({sup 8}S{sub 7/2})6p{sub 1/2} absorption (430 to 450 nm) features. The latter consists of narrow, resolved emission bands with Stokes shifts ten times smaller than the former. The observed spectral differences are discussed in relation to the different spatial symmetries of the p{sub 3/2} and p{sub 1/2} orbitals in these j-j coupled (7/2, 3/2){sub J} and the (7/2, 1/2){sub J} levels. Møller-Plesset calculations are conducted to obtain the molecular parameters of the neutral Eu-RG and cationic Eu{sup +}-RG diatomics (RG = Ar, Kr, Xe). From the short bond lengths and the strong binding energies obtained for the Eu{sup +}-RG species, these values suggest the isolation of the ion in small, possibly interstitial sites especially in xenon. In contrast, but consistent with previous work [O. Byrne and J. G. McCaffrey, J. Chem. Phys. 134, 124501 (2011)], the interaction potentials calculated herein for the Eu-RG diatomics suggest that the neutral Eu atom occupies tetra-vacancy (tv) and hexa-vacancy (hv) sites in the solid rare gas hosts. Possible reasons for the facile production of Eu{sup +} in the solid rare gases are discussed. The mechanism proposed is that atomic europium is also acting as an electron acceptor

  14. Identification of the mechanisms responsible for static strain ageing in heavily drawn pearlitic steel wires

    NASA Astrophysics Data System (ADS)

    Lamontagne, A.; Kleber, X.; Massardier-Jourdan, V.; Mari, D.

    2014-08-01

    The microstructural changes occurring during drawing and ageing in pearlitic steel wires have been studied using the thermoelectric power (TEP) measurements combined with atom probe tomography (APT) and differential scanning calorimetry (DSC). APT analysis confirmed that cementite dissolution occurs during the cold-drawing process. The high sensitivity of TEP to solute atoms allowed two ageing mechanisms to be identified, both related to a redistribution of carbon atoms. The complementary use of tensile tests and DSC confirmed these results.

  15. Plasma arc torch with coaxial wire feed

    DOEpatents

    Hooper, Frederick M

    2002-01-01

    A plasma arc welding apparatus having a coaxial wire feed. The apparatus includes a plasma arc welding torch, a wire guide disposed coaxially inside of the plasma arc welding torch, and a hollow non-consumable electrode. The coaxial wire guide feeds non-electrified filler wire through the tip of the hollow non-consumable electrode during plasma arc welding. Non-electrified filler wires as small as 0.010 inches can be used. This invention allows precision control of the positioning and feeding of the filler wire during plasma arc welding. Since the non-electrified filler wire is fed coaxially through the center of the plasma arc torch's electrode and nozzle, the wire is automatically aimed at the optimum point in the weld zone. Therefore, there is no need for additional equipment to position and feed the filler wire from the side before or during welding.

  16. Californium Recovery from Palladium Wire

    SciTech Connect

    Burns, Jon D.

    2014-08-01

    The recovery of 252Cf from palladium-252Cf cermet wires was investigated to determine the feasibility of implementing it into the cermet wire production operation at Oak Ridge National Laboratory’s Radiochemical Engineering Development Center. The dissolution of Pd wire in 8 M HNO3 and trace amounts of HCl was studied at both ambient and elevated temperatures. These studies showed that it took days to dissolve the wire at ambient temperature and only 2 hours at 60°C. Adjusting the ratio of the volume of solvent to the mass of the wire segment showed little change in the kinetics of dissolution, which ranged from 0.176 mL/mg down to 0.019 mL/mg. A successful chromatographic separation of 153Gd, a surrogate for 252Cf, from Pd was demonstrated using AG 50x8 cation exchange resin with a bed volume of 0.5 mL and an internal diameter of 0.8 cm.

  17. Antenna coupled photonic wire lasers.

    PubMed

    Kao, Tsung-Yu; Cai, Xiaowei; Lee, Alan W M; Reno, John L; Hu, Qing

    2015-06-29

    Slope efficiency (SE) is an important performance metric for lasers. In conventional semiconductor lasers, SE can be optimized by careful designs of the facet (or the modulation for DFB lasers) dimension and surface. However, photonic wire lasers intrinsically suffer low SE due to their deep sub-wavelength emitting facets. Inspired by microwave engineering techniques, we show a novel method to extract power from wire lasers using monolithically integrated antennas. These integrated antennas significantly increase the effective radiation area, and consequently enhance the power extraction efficiency. When applied to wire lasers at THz frequency, we achieved the highest single-side slope efficiency (~450 mW/A) in pulsed mode for DFB lasers at 4 THz and a ~4x increase in output power at 3 THz compared with a similar structure without antennas. This work demonstrates the versatility of incorporating microwave engineering techniques into laser designs, enabling significant performance enhancements. PMID:26191717

  18. Electron Diffraction Evidence for the Ordering of Excess Nickel Atoms by Relation to Stoichiometry in Nickel-Rich Beta'-Nial Formation of a Nickel-Aluminum (Ni2al) Superlattices

    NASA Technical Reports Server (NTRS)

    Reynaud, F.

    1988-01-01

    In electron diffraction patterns of nickel-rich beta-NiAl alloys, many anomalies are observed. One of these is the appearance of diffuse intensity maxima between the reflexions of the B2 structure. This is explained by the short-range ordering of the excess nickel atoms on the simple cubic sublattice occupied only by aluminum atoms in the stoichiometric, perfectly ordered NiAl alloy. After annealing Ni 37.5 atomic percent Al and Ni 37.75 atomic percent Al for 1 week at 300 and 400 C, the diffuse intensity maxima transformed into sharp superstructure reflexions. These reflexions are explained by the formation of the four possible variants of an ordered hexagonal superstructure corresponding to the Ni2Al composition. This structure is closely related to the Ni2Al3 structure (same space group) formed by the ordering of vacancies on the nickel sublattice in aluminum-rich beta-NiAl alloys.

  19. Improved performance of dye-sensitized solar cells with TiO 2/alumina core-shell formation using atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Ganapathy, V.; Karunagaran, B.; Rhee, Shi-Woo

    Alumina (Al 2O 3) shell formation on TiO 2 core nanoparticles by atomic layer deposition (ALD) is studied to suppress the recombination of charge carriers generated in a dye-sensitized solar cell (DSSC). It is relatively easy to control the shell thickness using the ALD method by controlling the number of cycles. An optimum thickness can be identified, which allows tunneling of the forward current while suppressing recombination. High-resolution TEM measurements show that a uniform Al 2O 3 shell is formed around the TiO 2 core particles and elemental mapping of the porous TiO 2 layer reveals that the Al 2O 3 distribution is uniform throughout the layer. The amount of dye absorption is increased with increase in the shell thickness but electrochemical impedance spectroscopic (EIS) measurement shows a drastic increase in the resistance. With an optimum Al 2O 3 thickness of 2 nm deposited by ALD, a 35% improvement in the cell efficiency (from 6.2 to 8.4%) is achieved.

  20. Formation and collision-induced dissociation of adduct ions [matrix + C]+ (C = Li, Na, Cs and NH4) produced under fast atom bombardment conditions

    NASA Astrophysics Data System (ADS)

    Takayama, Mitsuo

    1994-09-01

    The formation of adduct ions of matrices B with organic/metallic cations C+, [B + C]+ (C = Li, Na, Cs and NH4), under fast atom bombardment (FAB) conditions has been examined. The cation affinity (CA) for various matrix materials, glycerol, thioglycerol, dithiothreitol, m-nitrobenzylalcohol and diethanolamine, was evaluated from the positive-ion FAB mass spectra obtained for the salts LiCl, NaCl, CsCl or NH4Cl added to matrix B. The order of the CA of matrices for relatively small cations Li+ and Na+ was in accordance with that of the proton affinity (PA) of the matrices used. The collision-induced dissociation (CID) spectra of [B + H]+ and [B + C]+ ions have been obtained. The PA differences between matrix B and ammonia (NH3) molecules were roughly estimated from the CID spectra of [B + NH4]+ ions. The CID spectra of [B + C]+ ions, which have different dissociation windows from [B + H]+ ions, were analyzed by proposing multidentate-binding structures of the adduct ions. Some dissociations of [B + C]+ ions could be explained by charge-remote fragmentations. The results obtained suggest that the binding energy for the coordination complex (B...C+) can be evaluated from the CID patterns.

  1. Ketyl Radical Formation via Proton-Coupled Electron Transfer in an Aqueous Solution versus Hydrogen Atom Transfer in Isopropanol after Photoexcitation of Aromatic Carbonyl Compounds.

    PubMed

    Zhang, Xiting; Ma, Jiani; Li, Songbo; Li, Ming-De; Guan, Xiangguo; Lan, Xin; Zhu, Ruixue; Phillips, David Lee

    2016-07-01

    The excited nπ* and ππ* triplets of two benzophenone (BP) and two anthraquinone (AQ) derivatives have been observed in acetonitrile, isopropanol, and mixed aqueous solutions using time-resolved resonance Raman spectroscopic and nanosecond transient absorption experiments. These experimental results, combined with results from density functional theory calculations, reveal the effects of solvent and substituents on the properties, relative energies, and chemical reactivities of the nπ* and ππ* triplets. The triplet nπ* configuration was found to act as the reactive species for a subsequent hydrogen atom transfer reaction to produce a ketyl radical intermediate in the isopropanol solvent, while the triplet ππ* undergoes a proton-coupled electron transfer (PCET) in aqueous solutions to produce a ketyl radical intermediate. This PCET reaction, which occurs via a concerted proton transfer (to the excited carbonyl group) and electron transfer (to the excited phenyl ring), can account for the experimental observation by several different research groups over the past 40 years of the formation of ketyl radicals after photolysis of a number of BP and AQ derivatives in aqueous solutions, although water is considered to be a relatively "inert" hydrogen-donor solvent. PMID:27266916

  2. Solvation and kinetic isotope effects in H and D abstraction reactions from formate ions by D, H, and Mu atoms in aqueous solutions.

    SciTech Connect

    Lossack, A. M.; Roduner, E.; Bartels, D. M.; Chemistry; Univ. of Stuttgart

    2001-01-01

    Electron paramagnetic resonance free induction decay attenuation and muon spin rotation measurements were performed in the temperature range of liquid water for the reactions of the hydrogen isotopes D, H, and Mu with undeuterated and deuterated formate ions. Accurate rate constants were determined, and excellent Arrhenius behavior represented bywas found in all cases. Ab initio calculations at the MP2 and the QCISD level with the aug-cc-pvDZ basis set reveal that the reaction has no electronic barrier in the gas phase. This contrasts with quite sizeable activation energies observed in aqueous solution, and it suggests that the barrier is entirely solvent induced. Calculations at the above mentioned ab initio level using a polarized dielectric continuum for the solvated reaction system restore a realistic barrier and confirm this interpretation. It is shown that the solvent effect is a consequence of a pronounced change of polarization of the system along the reaction path. It may be more appropriate to describe the reaction as a consecutive electron-proton transfer rather than an H atom abstraction.

  3. Experimental investigation on the energy deposition and expansion rate under the electrical explosion of aluminum wire in vacuum

    SciTech Connect

    Shi, Zongqian; Wang, Kun; Shi, Yuanjie; Wu, Jian; Han, Ruoyu

    2015-12-28

    Experimental investigations on the electrical explosion of aluminum wire using negative polarity current in vacuum are presented. Current pulses with rise rates of 40 A/ns, 80 A/ns, and 120 A/ns are generated for investigating the influence of current rise rate on energy deposition. Experimental results show a significant increase of energy deposition into the wire before the voltage breakdown with the increase of current rise rate. The influence of wire dimension on energy deposition is investigated as well. Decreasing the wire length allows more energy to be deposited into the wire. The energy deposition of a 0.5 cm-long wire explosion is ∼2.5 times higher than the energy deposition of a 2 cm-long wire explosion. The dependence of the energy deposition on wire diameter demonstrates a maximum energy deposition of 2.7 eV/atom with a diameter of ∼18 μm. Substantial increase in energy deposition is observed in the electrical explosion of aluminum wire with polyimide coating. A laser probe is applied to construct the shadowgraphy, schlieren, and interferometry diagnostics. The morphology and expansion trajectory of exploding products are analyzed based on the shadowgram. The interference phase shift is reconstructed from the interferogram. Parallel dual wires are exploded to estimate the expansion velocity of the plasma shell.

  4. Experimental investigation on the energy deposition and expansion rate under the electrical explosion of aluminum wire in vacuum

    NASA Astrophysics Data System (ADS)

    Shi, Zongqian; Wang, Kun; Shi, Yuanjie; Wu, Jian; Han, Ruoyu

    2015-12-01

    Experimental investigations on the electrical explosion of aluminum wire using negative polarity current in vacuum are presented. Current pulses with rise rates of 40 A/ns, 80 A/ns, and 120 A/ns are generated for investigating the influence of current rise rate on energy deposition. Experimental results show a significant increase of energy deposition into the wire before the voltage breakdown with the increase of current rise rate. The influence of wire dimension on energy deposition is investigated as well. Decreasing the wire length allows more energy to be deposited into the wire. The energy deposition of a 0.5 cm-long wire explosion is ˜2.5 times higher than the energy deposition of a 2 cm-long wire explosion. The dependence of the energy deposition on wire diameter demonstrates a maximum energy deposition of 2.7 eV/atom with a diameter of ˜18 μm. Substantial increase in energy deposition is observed in the electrical explosion of aluminum wire with polyimide coating. A laser probe is applied to construct the shadowgraphy, schlieren, and interferometry diagnostics. The morphology and expansion trajectory of exploding products are analyzed based on the shadowgram. The interference phase shift is reconstructed from the interferogram. Parallel dual wires are exploded to estimate the expansion velocity of the plasma shell.

  5. Electronic and magnetic properties of silicon supported organometallic molecular wires: a density functional theory (DFT) study

    NASA Astrophysics Data System (ADS)

    Liu, Xia; Tan, Yingzi; Li, Xiuling; Wu, Xiaojun; Pei, Yong

    2015-08-01

    The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to the well-studied gas phase TM-benzene molecular wires. Si-[Mn(styrene)]∞ and Si-[Cr(styrene)]∞ single molecular wires (SMWs) are a ferromagnetic semiconductor and half metal, respectively. Creation of H-atom defects on the silicon surface can introduce an impurity metallic band, which leads to novel half-metallic magnetism of a Si-[Mn(styrene)]∞ system. Moreover, double molecular wires (DMWs) containing two identical or hetero SMWs are theoretically designed. The [Mn(styrene)]∞-[Cr(styrene)]∞ DMW exhibits half-metallic magnetism where the spin-up and spin-down channels are contributed by two single molecular wires. Finally, we demonstrate that introducing a TM-defect may significantly affect the electronic structure and magnetic properties of molecular wires. These studies provide new insights into the structure and properties of surface supported 1-D sandwiched molecular wires and may inspire the future experimental synthesis of substrate confined organometallic sandwiched molecular wires.The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to

  6. Atomic phenomena in dense plasmas

    SciTech Connect

    Weisheit, J.C.

    1981-03-01

    The following chapters are included: (1) the plasma environment, (2) perturbations of atomic structure, (3) perturbations of atomic collisions, (4) formation of spectral lines, and (5) dielectronic recombination. (MOW)

  7. Wire Detection Algorithms for Navigation

    NASA Technical Reports Server (NTRS)

    Kasturi, Rangachar; Camps, Octavia I.

    2002-01-01

    In this research we addressed the problem of obstacle detection for low altitude rotorcraft flight. In particular, the problem of detecting thin wires in the presence of image clutter and noise was studied. Wires present a serious hazard to rotorcrafts. Since they are very thin, their detection early enough so that the pilot has enough time to take evasive action is difficult, as their images can be less than one or two pixels wide. Two approaches were explored for this purpose. The first approach involved a technique for sub-pixel edge detection and subsequent post processing, in order to reduce the false alarms. After reviewing the line detection literature, an algorithm for sub-pixel edge detection proposed by Steger was identified as having good potential to solve the considered task. The algorithm was tested using a set of images synthetically generated by combining real outdoor images with computer generated wire images. The performance of the algorithm was evaluated both, at the pixel and the wire levels. It was observed that the algorithm performs well, provided that the wires are not too thin (or distant) and that some post processing is performed to remove false alarms due to clutter. The second approach involved the use of an example-based learning scheme namely, Support Vector Machines. The purpose of this approach was to explore the feasibility of an example-based learning based approach for the task of detecting wires from their images. Support Vector Machines (SVMs) have emerged as a promising pattern classification tool and have been used in various applications. It was found that this approach is not suitable for very thin wires and of course, not suitable at all for sub-pixel thick wires. High dimensionality of the data as such does not present a major problem for SVMs. However it is desirable to have a large number of training examples especially for high dimensional data. The main difficulty in using SVMs (or any other example-based learning

  8. Adjustable microchip ring trap for cold atoms and molecules

    SciTech Connect

    Baker, Paul M.; Stickney, James A.; Squires, Matthew B.; Scoville, James A.; Carlson, Evan J.; Buchwald, Walter R.; Miller, Steven M.

    2009-12-15

    We describe the design and function of a circular magnetic waveguide produced from wires on a microchip for atom interferometry using de Broglie waves. The guide is a two-dimensional magnetic minimum for trapping weak-field seeking states of atoms or molecules with a magnetic dipole moment. The design consists of seven circular wires sharing a common radius. We describe the design, the time-dependent currents of the wires and show that it is possible to form a circular waveguide with adjustable height and gradient while minimizing perturbation resulting from leads or wire crossings. This maximal area geometry is suited for rotation sensing with atom interferometry via the Sagnac effect using either cold atoms, molecules and Bose-condensed systems.

  9. Magnetism of ultrathin wires suspended in free space and adsorbed on vicinal surfaces

    NASA Astrophysics Data System (ADS)

    Spišák, D.; Hafner, J.

    2003-06-01

    On the basis of total-energy calculations within density functional theory the possibility of magnetic ordering in ultrathin, one or two atom wide nanowires is studied. Specifically, we investigate nanowires composed of fifth and sixth row elements, which are nonmagnetic in the solid phase. At first, the unsupported straight wires are discussed and then, similar to experimental conditions, the wires are placed along step ledges of vicinal surfaces of copper and silver. Free-standing wires show only a weak tendency towards magnetic ordering at the equilibrium bond length. In analogy with their 3d homologues Mo, Tc, W, Re are found to order antiferromagnetically, Ru, Rh, and Ir ferromagnetically. Surprisingly, ferromagnetism is also predicted for the early transition metals Zr and Ta and for the simple metals In and Tl. This picture is profoundly modified for supported wires, where the expansion of the bond length enforced through the epitaxial relationship with the substrate favors magnetic ordering but hybridization with the substrate electrons tends to quench magnetism. It turns out that wires on a Cu substrate prefer a ferromagnetic order, whereas on a Ag substrate most elements tend to antiferromagnetism. A second row of atoms added to the wires destroys the magnetism in wires on a Cu substrate, and reduces it in wires on a Ag substrate, except for the late transition metals (Rh, Ir) where an enhancement of magnetic moments is observed. Two possible growth modes of nanowires — a row-by-row growth and island growth — are explored. The results allow us to suggest that Ru, Rh, and Os wires on Ag stepped surfaces are the most promising systems in which magnetism could be verified experimentally.

  10. Wire-shaped perovskite solar cell based on TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyan; Kulkarni, Sneha A.; Li, Zhen; Xu, Wenjing; Batabyal, Sudip K.; Zhang, Sam; Cao, Anyuan; Wong, Lydia Helena

    2016-05-01

    In this work, a wire-shaped perovskite solar cell based on TiO2 nanotube (TNT) arrays is demonstrated for the first time by integrating a perovskite absorber on TNT-coated Ti wire. Anodization was adopted for the conformal growth of TNTs on Ti wire, together with the simultaneous formation of a compact TiO2 layer. A sequential step dipping process is employed to produce a uniform and compact perovskite layer on top of TNTs with conformal coverage as the efficient light absorber. Transparent carbon nanotube film is wrapped around Ti wire as the hole collector and counter electrode. The integrated perovskite solar cell wire by facile fabrication approaches shows a promising future in portable and wearable textile electronics.

  11. Wire-shaped perovskite solar cell based on TiO2 nanotubes.

    PubMed

    Wang, Xiaoyan; Kulkarni, Sneha A; Li, Zhen; Xu, Wenjing; Batabyal, Sudip K; Zhang, Sam; Cao, Anyuan; Wong, Lydia Helena

    2016-05-20

    In this work, a wire-shaped perovskite solar cell based on TiO2 nanotube (TNT) arrays is demonstrated for the first time by integrating a perovskite absorber on TNT-coated Ti wire. Anodization was adopted for the conformal growth of TNTs on Ti wire, together with the simultaneous formation of a compact TiO2 layer. A sequential step dipping process is employed to produce a uniform and compact perovskite layer on top of TNTs with conformal coverage as the efficient light absorber. Transparent carbon nanotube film is wrapped around Ti wire as the hole collector and counter electrode. The integrated perovskite solar cell wire by facile fabrication approaches shows a promising future in portable and wearable textile electronics. PMID:27070991

  12. Anode wire aging tests with selected gases

    SciTech Connect

    Kadyk, J.; Wise, J.; Hess, D.; Williams, M. )

    1990-04-01

    As a continuation of earlier wire aging investigations, additional candidates for wire chamber gas and wire have been tested. These include the gases: argon/ethane, HRS gas, dimethyl ether, carbon dioxide/ethane, and carbon tetrafluoride/isobutane. Wires used were: gold- plated tungsten, Stablohm, Nicotin, and Stainless Steel. Measurements were made of the effects upon wire aging of impurities from plumbing materials or contamination from various types of oil. Attempts were made to induce wire aging by adding measured amounts of oxygen and halogen (methyl chloride) with negative results. In this paper, the possible role of electronegativity in the wire aging process is discussed, and measurements of electronegativity are made with several single carbon Freons, using both an electron capture detector and a wire chamber operating with dimethyl ether.

  13. Electrical wire insulation and electromagnetic coil

    DOEpatents

    Bich, George J.; Gupta, Tapan K.

    1984-01-01

    An electromagnetic coil for high temperature and high radiation application in which glass is used to insulate the electrical wire. A process for applying the insulation to the wire is disclosed which results in improved insulation properties.

  14. Quality control of microelectronic wire bonds

    NASA Technical Reports Server (NTRS)

    Thiel, R. A.; Schmidt, G. D.

    1975-01-01

    Report evaluates ultrasonic bonding of small-diameter aluminum wire joined to ceramic substrates metalized with thin-film and thick-film gold. Quick testing technique for nondestructive location of poor wire bonds is also presented.

  15. Put Your Cable Wiring to the Test.

    ERIC Educational Resources Information Center

    Day, C. William

    2001-01-01

    Discusses why schools and universities should use testing procedures in any wire bid specification for cable wiring and also know how experienced the installers are in testing and installing structured cabling systems. Key cabling terms are included. (GR)

  16. New insulation constructions for aerospace wiring applications

    NASA Technical Reports Server (NTRS)

    Slenski, George

    1994-01-01

    Outlined in this presentation is the background to insulation constructions for aerospace wiring applications, the Air Force wiring policy, the purpose and contract requirements of new insulation constructions, the test plan, and the test results.

  17. A manually set magnetic wire counter

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Magnetic storage wire counter design principles are given. Magnetic storage wire was coupled with two phase propagational driver in manual set counter shift register. Time delay between magnetic counter domain insertion and corresponding output pulse provides counting functions.

  18. Technique for stripping Teflon insulated wire

    NASA Technical Reports Server (NTRS)

    Babb, B. D.

    1967-01-01

    Cryogenic stripping of Teflon insulated wire leaves no residue and produces no physical damage. After the wire is immersed in liquid nitrogen, bent slightly, and returned to room temperature, the Teflon is removed by fingernails or flat-nosed pliers.

  19. Wire Capture Programs for Macintosh and IBM.

    ERIC Educational Resources Information Center

    Wiley, Gale

    1989-01-01

    Discusses wire capture programs (computer programs which gather and process wire services such as the Associated Press or United Press) for computer labs in journalism departments. Describes details of such programs for Macintosh, IBM, and IBM clones. (SR)

  20. Electrical Wire Insulation and Electromagnetic Coil

    SciTech Connect

    Bich, G. J.; Gupta, T. K.

    1984-01-31

    An electromagnetic coil for high temperature and high radiation application in which glass is used to insulate the electrical wire. A process for applying the insulation to the wire is disclosed which results in improved insulation properties.

  1. The Atomic Dating Game.

    ERIC Educational Resources Information Center

    Cummo, Evelyn; Matthews, Catherine E.

    2002-01-01

    Presents an activity designed to provide students with opportunities to practice drawing atomic models and discover the logical pairings of whole families on the periodic table. Follows the format of a television game show. (DDR)

  2. REACH. Residential Electrical Wiring Units.

    ERIC Educational Resources Information Center

    Ansley, Jimmy; Ennis, Mike

    As a part of the REACH (Refrigeration, Electro-Mechanical, Air-Conditioning, Heating) electromechanical cluster, this student manual contains individualized instructional units in the area of residential electrical wiring. The instructional units focus on grounded outlets, service entrance, and blueprint reading. Each unit follows a typical format…

  3. Flexible substrate for printed wiring

    NASA Technical Reports Server (NTRS)

    Asakura, M.; Yabe, K.; Tanaka, H.; Soda, A.

    1982-01-01

    A very flexible substrate for printed wiring is disclosed which is composed of a blend of phenoxy resin-polyisocyanate-brominated epoxy resin in which the equivalent ration of the functional groups is hydroxyl grouped: isocyanate group: epoxy group = 1:0.2 to 2:0.5 to 3. The product has outstanding solder resistance and is applied to metal without using adhesives.

  4. Health care's 100 most wired.

    PubMed

    Solovy, A; Serb, C

    1999-02-01

    They're wired all right, and America's 100 most techno-savvy hospitals and health systems share one more thing: a commitment to using technology to link with employees, patients, suppliers, and insurers. "We want to be a health care travel agency for our community," says one chief information officer. "And we see Internet technology as a key." PMID:10081454

  5. Regeneration: New Neurons Wire Up.

    PubMed

    Raymond, Pamela A

    2016-09-12

    Functional repair of damage in the nervous system requires re-establishment of precise patterns of synaptic connectivity. A new study shows that after selective ablation, zebrafish retinal neurons regenerate and reconstruct some, although not all, of their stereotypic wiring. PMID:27623258

  6. Fabrication of tungsten wire needles

    SciTech Connect

    Roder, A.

    1983-02-01

    Fine point needles for field emissoin are conventionally produced by electrolytically or chemically etching tungsten wire. Points formed in this manner have a typical tip radius of about 0.5 microns and a cone angle of some 30 degrees. The construction of needle matrix detector chambers has created a need for tungsten needles whose specifications are: 20 mil tungsten wire, 1.5 inch total length, 3 mm-long taper (resulting in a cone angle of about 5 degrees), and 25 micron-radius point (similar to that found on sewing needles). In the process described here for producing such needles, tungsten wire, immersed in a NaOH solution and in the presence of an electrode, is connected first to an ac voltage and then to a dc supply, to form a taper and a point on the end of the wire immersed in the solution. The process parameters described here are for needles that will meet the above specifications. Possible variations will be discussed under each approprite heading.

  7. Plated wire random access memories

    NASA Technical Reports Server (NTRS)

    Gouldin, L. D.

    1975-01-01

    A program was conducted to construct 4096-work by 18-bit random access, NDRO-plated wire memory units. The memory units were subjected to comprehensive functional and environmental tests at the end-item level to verify comformance with the specified requirements. A technical description of the unit is given, along with acceptance test data sheets.

  8. Wire-Wrap Chatter Detector

    NASA Technical Reports Server (NTRS)

    Fisch, G. Z.; Borden, T. J.

    1982-01-01

    Monitoring circuit responds to changes in resistance as little as 0.1 ohm. Has been used to detect defective wire-wrap connections during thermal and vibration tests. Defect is indicated to operator by light-emitting diode and by increase in count on a two-digit display.

  9. Ultrasonic Calibration Wire Test Phantom

    SciTech Connect

    Lehman, S K; Fisher, K A; Werve, M; Chambers, D H

    2004-09-24

    We designed and built a phantom consisting of vertical wires maintained under tension to be used as an ultrasonic test, calibration, and reconstruction object for the Lawrence Livermore National Laboratory annular array scanner. We provide a description of the phantom, present example data sets, preliminary reconstructions, example metadata, and MATLAB codes to read the data.

  10. Transport Through Carbon Nanotube Wires

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Kwak, Dochan (Technical Monitor)

    2001-01-01

    This viewgraph presentation deals with the use of carbon nanotubes as a transport system. Contact, defects, tubular bend, phonons, and mechanical deformations all contribute to reflection within the nanotube wire. Bragg reflection, however, is native to an ideal energy transport system. Transmission resistance depends primarily on the level of energy present. Finally, the details regarding coupling between carbon nanotubes and simple metals are presented.

  11. Metal atom oxidation laser

    DOEpatents

    Jensen, R.J.; Rice, W.W.; Beattie, W.H.

    1975-10-28

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides.

  12. Metal atom oxidation laser

    DOEpatents

    Jensen, R.J.; Rice, W.W.; Beattie, W.H.

    1975-10-28

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides. (auth)

  13. Novel Wiring Technologies for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Gibson, Tracy L.; Parrish, Lewis M.

    2014-01-01

    Because wire failure in aerospace vehicles could be catastrophic, smart wiring capabilities have been critical for NASA. Through the years, researchers at Kennedy Space Center (KSC) have developed technologies, expertise, and research facilities to meet this need. In addition to aerospace applications, NASA has applied its knowledge of smart wiring, including self-healing materials, to serve the aviation industry. This webinar will discuss the development efforts of several wiring technologies at KSC and provide insight into both current and future research objectives.

  14. Further Studies Of Hot-Wire Anemometry

    NASA Technical Reports Server (NTRS)

    Mckenzie, Robert; Logan, Pamela; Bershader, Daniel

    1990-01-01

    Report discusses factors affecting readings of hot-wire anemometer in turbulent supersonic boundary layer. Represents extension of work described in "Hot-Wire Anemometry Versus Laser-Induced Fluorescence" (ARC-11802). Presents theoretical analysis of responses of hot-wire probe to changes in flow; also compares measurements by hot-wire probe with measurements of same flows by laser-induced fluorescence (LIF).

  15. Different mechanical properties in Seldinger guide wires

    PubMed Central

    Schummer, Wolfram

    2015-01-01

    Background and Aims: Most central venous catheters are placed using Seldinger guide wires. EN ISO 11070 is the guideline for testing guide wire flexing performance and tensile strength, and we can safely assume that guide wires in use meet these requirements. Unfortunately, EN ISO 11070 guidelines do not reflect the clinical requirements and we continue to see mechanical failures and their associated complications. Material and Methods: This in vitro study was performed in an accredited laboratory. With regard to flexing, we: (1) Established the minimum flexing performance needed to meet clinical requirements, (2) developed flexing performance tests which mimic clinical requirement, and (3) evaluated the mechanical properties of various guide wires relative to these requirements. With regard to tensile strength, we used the testing method prescribed in ISO 11070, but did not end the test at 5 Newton (N). We continued until the guide wire was damaged, or we reached maximum tractive force. We then did a wire-to-wire comparison. We examined two basic wire constructions, monofil and core and coil. Results: Tensile strength: All wires tested, except one, met EN ISO 11070 requirements for 5 N tensile strength. The mean of the wire types tested ranged from 15.06 N to 257.76 N. Flexing performance: None of the wires kinked. The monofil had no evidence of bending. Two core/coil wires displayed minor bending (angle 1.5°). All other wires displayed bending angles between 22.5° and 43.0°. Conclusion: We recommend that: (1) Clinicians use guide wires with high-end mechanical properties, (2) EN ISO 11070 incorporate our flexing test into their testing method, raise the flexing requirement to kink-proof, (3) and raise the tensile strength requirement to a minimum of 30 N, and (3) all manufacturers and suppliers be required to display mechanical properties of all guide wire, and guide wire kits sold. PMID:26702209

  16. NEMA wire and cable standards development programs

    NASA Technical Reports Server (NTRS)

    Baird, Robert W.

    1994-01-01

    The National Electrical Manufacturers Association (NEMA) is the nation's largest trade association for manufacturers of electrical equipment. Its member companies produce components, end-use equipment and systems for the generation, transmission, distribution, control and use of electricity. The wire and cable division is presented in 6 sections: building wire and cable, fabricated conductors, flexible cords, high performance wire and cable, magnet wire, and power and control cable. Participating companies are listed.

  17. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  18. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  19. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  20. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  1. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  2. 49 CFR 236.838 - Wire, shunt.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Wire, shunt. 236.838 Section 236.838 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Wire, shunt. A wire forming part of a shunt circuit....

  3. 30 CFR 57.12047 - Guy wires.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Guy wires. 57.12047 Section 57.12047 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Electricity Surface and Underground § 57.12047 Guy wires. Guy wires of...

  4. Getting "Wired" for McLuhan's Cyberculture.

    ERIC Educational Resources Information Center

    McMurdo, George

    1995-01-01

    Examines the introduction of the computing magazine, "Wired", into the United Kingdom's (UK) market. Presents conversations with the founder and editorial staff of the UK edition, and discusses the accessibility of "Wired" via the World Wide Web. Describes 10 articles from United States "Wired" back-issues and presents critiques of a utopian…

  5. 49 CFR 393.28 - Wiring systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 5 2010-10-01 2010-10-01 false Wiring systems. 393.28 Section 393.28 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY... NECESSARY FOR SAFE OPERATION Lamps, Reflective Devices, and Electrical Wiring § 393.28 Wiring...

  6. Home and School Technology: Wired versus Wireless.

    ERIC Educational Resources Information Center

    Van Horn, Royal

    2001-01-01

    Presents results of informal research on smart homes and appliances, structured home wiring, whole-house audio/video distribution, hybrid cable, and wireless networks. Computer network wiring is tricky to install unless all-in-one jacketed cable is used. Wireless phones help installers avoid pre-wiring problems in homes and schools. (MLH)

  7. Coupled cluster investigation on the thermochemistry of dimethyl sulphide, dimethyl disulphide and their dissociation products: the problem of the enthalpy of formation of atomic sulphur

    NASA Astrophysics Data System (ADS)

    Denis, Pablo A.

    2014-04-01

    By means of coupled cluster theory and correlation consistent basis sets we investigated the thermochemistry of dimethyl sulphide (DMS), dimethyl disulphide (DMDS) and four closely related sulphur-containing molecules: CH3SS, CH3S, CH3SH and CH3CH2SH. For the four closed-shell molecules studied, their enthalpies of formation (EOFs) were derived using bomb calorimetry. We found that the deviation of the EOF with respect to experiment was 0.96, 0.65, 1.24 and 1.29 kcal/mol, for CH3SH, CH3CH2SH, DMS and DMDS, respectively, when ΔHf,0 = 65.6 kcal/mol was utilised (JANAF value). However, if the recently proposed ΔHf,0 = 66.2 kcal/mol was used to estimate EOF, the errors dropped to 0.36, 0.05, 0.64 and 0.09 kcal/mol, respectively. In contrast, for the CH3SS radical, a better agreement with experiment was obtained if the 65.6 kcal/mol value was used. To compare with experiment avoiding the problem of the ΔHf,0 (S), we determined the CH3-S and CH3-SS bond dissociation energies (BDEs) in CH3S and CH3SS. At the coupled cluster with singles doubles and perturbative triples correction level of theory, these values are 48.0 and 71.4 kcal/mol, respectively. The latter BDEs are 1.5 and 1.2 kcal/mol larger than the experimental values. The agreement can be considered to be acceptable if we take into consideration that these two radicals present important challenges when determining their EOFs. It is our hope that this work stimulates new studies which help elucidate the problem of the EOF of atomic sulphur.

  8. X-ray Diffraction Investigations of Shape Memory NiTi Wire

    NASA Astrophysics Data System (ADS)

    Honarvar, Mohammad; Konh, Bardia; Podder, Tarun K.; Dicker, Adam P.; Yu, Yan; Hutapea, Parsaoran

    2015-08-01

    Outstanding properties of nitinol, known as shape memory and superelasticity, make them suitable alternatives in several biomedical, aerospace, and civil applications. For instance, nitinol wires have been used as the actuator components in many innovative medical devices aiming to make surgical tasks less invasive and more efficient. In most of these applications, it is desired to have a consistent strain response of nitinol wires; therefore, it is necessary to investigate the internal phase transformations from microstructural point of view. In this study, the effect of influencing factors such as biased stress during thermal cycle, the maximum temperature wires experienced during heating part of thermal cycle, and also wire diameters on the amount of unrecovered strain occurred between the first and the second thermal cycles has been investigated. The generation of different phase compositions in the same thermomechanical condition for different wire diameters has been discussed using x-ray diffraction (XRD) method. The location and intensity of characteristic peaks were studied prior and after the loading cycles. It was observed that nitinol wires of diameters less than 0.19 mm exhibit unrecovered strain while heated to the range of 70-80 °C in a thermal cycle, whereas no unrecovered strain was found in wires with larger diameter. The observation was supported by the XRD patterns where the formation of R-phase instead of martensite was shown in wire diameters of less than 0.19 mm after cooling back to room temperature.

  9. Understanding Irreversible Degradation of Nb3Sn Wires with Fundamental Fracture Mechanics

    SciTech Connect

    Zhai, Yuhu; Calzolaio, Ciro; Senatore, Carmine

    2014-08-01

    Irreversible performance degradation of advanced Nb3Sn superconducting wires subjected to transverse or axial mechanical loading is a critical issue for the design of large-scale fusion and accelerator magnets such as ITER and LHC. Recent SULTAN tests indicate that most cable-in-conduit conductors for ITER coils made of Nb3Sn wires processed by various fabrication techniques show similar performance degradation under cyclic loading. The irreversible degradation due to filament fracture and local strain accumulation in Nb3Sn wires cannot be described by the existing strand scaling law. Fracture mechanic modeling combined with X-ray diffraction imaging of filament micro-crack formation inside the wires under mechanical loading may reveal exciting insights to the wire degradation mechanisms. We apply fundamental fracture mechanics with a singularity approach to study influence of wire filament microstructure of initial void size and distribution to local stress concentration and potential crack propagation. We report impact of the scale and density of the void structure on stress concentration in the composite wire materials for crack initiation. These initial defects result in an irreversible degradation of the critical current beyond certain applied stress. We also discuss options to minimize stress concentration in the design of the material microstructure for enhanced wire performance for future applications.

  10. Potential energy surfaces for atomic oxygen reactions: Formation of singlet and triplet biradicals as primary reaction products with unsaturated organic molecules

    NASA Technical Reports Server (NTRS)

    Jaffe, Richard L.

    1987-01-01

    The experimental study of the interaction of atomic oxygen with organic polymer films under LEO conditions has been hampered by the inability to conduct detailed experiments in situ. As a result, studies of the mechanism of oxygen atom reactions have relied on laboratory O-atom sources that do not fully reproduce the orbital environment. For example, it is well established that only ground electronic state O atoms are present at LEO, yet most ground-based sources are known to produce singlet O atoms and molecules and ions in addition to O(3P). Engineers should not rely on such facilities unless it can be demonstrated either that these different O species are inert or that they react in the same fashion as ground state atoms. Ab initio quantum chemical calculations have been aimed at elucidating the biradical intermediates formed during the electrophilic addition of ground and excited-state O atoms to carbon-carbon double bonds in small olefins and aromatic molecules. These biradicals are critical intermediates in any possible insertion, addition and elimination reaction mechanisms. Through these calculations, we will be able to comment on the relative importance of these pathways for O(3P) and O(1D) reactions. The reactions of O atoms with ethylene and benzene are used to illustrate the important features of the mechanisms of atomic oxygen reaction with unsaturated organic compounds and polymeric materials.

  11. Frequency response in short thermocouple wires

    NASA Technical Reports Server (NTRS)

    Forney, L. J.; Meeks, E. L.; Ma, J.; Fralick, G. C.

    1992-01-01

    Theoretical expressions are derived for the steady state frequency response of a thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for a nonuniform wire with unequal material properties and wire diameters across the junction. The amplitude ratio at low frequency omega approaches 0 agrees with the results of Scadron and Warshawsky (1952) for a steady state temperature distribution. Moreover, the frequency response for a nonuniform wire in the limit of infinite length l approaches infinity is shown to reduce to a simple expression that is analogous to the classic first order solution for a thermocouple wire with uniform properties. Theoretical expressions are also derived for the steady state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire and a two material wire with unequal material properties across the junction. For the case of a one material supported wire, an exact solution is derived which compares favorably with an approximate expression that only matches temperatures at the support junction. Moreover, for the case of a two material supported wire, an analytical expression is derived that closely correlates numerical results. Experimental measurements are made for the steady state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire (type K) and a two material wire (type T) with unequal material properties across the junction. The data for the amplitude ratio and phase angle are correlated to within 10 pct. with the theoretical predictions of Forney and Fralick (1991). This is accomplished by choosing a natural frequency omega sub n for the wire data to correlate the first order response at large gas temperature frequencies. It is found that a large bead size, however, will increase the amplitude ratio at

  12. WIRED 4 - A Generic Event Display Plugin for JAS 3

    SciTech Connect

    Donszelmann, M.

    2004-10-21

    WIRED 4 is an experiment independent event display plugin module for the JAS 3 (Java Analysis Studio) generic analysis framework. Both WIRED and JAS are written in Java. WIRED, which uses HepRep (HEP Representables for Event Display) as its input format, supports viewing of events using either conventional 3D projections as well as specialized projections, such as a fish-eye or a {rho}-Z projection. Projections allow the user to scale, rotate, position or change parameters on the plot as he wishes. All interactions are handled as separate edits which can be undone and/or redone, so the user can try out things and get back to a previous situation. All edits are scriptable by any of the scripting languages supported by JAS, such as pnuts, jython or java itself. Hits and tracks can be picked to display physics information and cuts can be made on physics parameters to allow the user to filter the number of objects drawn into the plot. Multiple event display plots can be laid out on pages combined with histograms and other plots, available from JAS itself or from other plugin modules. Configuration information on the state of all plots can be saved and restored allowing the user to save his session, share it with others or later continue where he left off. This version of WIRED is written to be easily extensible by the user/developer. Projections, representations, interaction handlers and edits are all services and new ones can be added by writing additional plugins. Both JAS 3 and WIRED 4 are built on top of the FreeHEP Java Libraries, which support a multitude of vector graphics output formats, such as PostScript, PDF, SVG, SWF and EMF, allowing document quality output of event display plots and histograms.

  13. The nucleation mechanism of wire explosion

    NASA Astrophysics Data System (ADS)

    Tkachenko, S. I.; Vorob'ev, V. S.; Malyshenko, S. P.

    2004-02-01

    This study deals with the nucleation mechanism of electric explosion of wires allowing estimation of wire parameters at the start of the explosion for a wide range of experimental conditions. We analyse the dependence of the limit value of the energy deposited during the initial resistive phase of heating of the wire on the parameters of the wire and circuit as well as the size distribution of metal particles formed on electrical explosion of the wire. We discuss the correspondence of these results with previously published experimental data.

  14. Electron Beam-Induced Writing of Nanoscale Iron Wires on a Functional Metal Oxide

    PubMed Central

    2013-01-01

    Electron beam-induced surface activation (EBISA) has been used to grow wires of iron on rutile TiO2(110)-(1 × 1) in ultrahigh vacuum. The wires have a width down to ∼20 nm and hence have potential utility as interconnects on this dielectric substrate. Wire formation was achieved using an electron beam from a scanning electron microscope to activate the surface, which was subsequently exposed to Fe(CO)5. On the basis of scanning tunneling microscopy and Auger electron spectroscopy measurements, the activation mechanism involves electron beam-induced surface reduction and restructuring. PMID:24159366

  15. Arc-Plasma Wire Spraying: An Optical Study of Process Phenomenology

    NASA Astrophysics Data System (ADS)

    Gulyaev, I. P.; Dolmatov, A. V.; Kharlamov, M. Yu.; Gulyaev, P. Yu.; Jordan, V. I.; Krivtsun, I. V.; Korzhyk, V. M.; Demyanov, O. I.

    2015-12-01

    In the present paper, we report on the results of an experimental study of heat- and mass-transfer processes in a Plazer 30-PL-W plasma-jet facility used for arc-plasma wire spraying. Using an original optical diagnostic system, we have studied melting behavior of the metal wire, break up and atomization of liquid metal. For the first time, experimental data on the in-flight velocity and temperature of spray particles in arc-plasma wire spraying were obtained. In spite of moderate particle velocities (about 50 m/s), the obtained steel coatings proved to have a low porosity of 1.5%. While studying the spraying process of tungsten wire, we observed the occurrence of anomalous high-velocity (over 4000 m/s) outbursts ejected from the surface of liquid metal droplets. The nature of such outbursts calls for further study.

  16. Secondary ion mass spectrometry of vapor-liquid-solid grown, Au-catalyzed, Si wires.

    PubMed

    Putnam, Morgan C; Filler, Michael A; Kayes, Brendan M; Kelzenberg, Michael D; Guan, Yunbin; Lewis, Nathan S; Eiler, John M; Atwater, Harry A

    2008-10-01

    Knowledge of the catalyst concentration within vapor-liquid-solid (VLS) grown semiconductor wires is needed in order to assess potential limits to electrical and optical device performance imposed by the VLS growth mechanism. We report herein the use of secondary ion mass spectrometry to characterize the Au catalyst concentration within individual, VLS-grown, Si wires. For Si wires grown by chemical vapor deposition from SiCl 4 at 1000 degrees C, an upper limit on the bulk Au concentration was observed to be 1.7 x 10(16) atoms/cm(3), similar to the thermodynamic equilibrium concentration at the growth temperature. However, a higher concentration of Au was observed on the sidewalls of the wires. PMID:18767881

  17. Electromagnetic scattering by a straight thin wire

    NASA Technical Reports Server (NTRS)

    Shamansky, Harry T.; Dominek, Allen K.; Peters, Leon, Jr.

    1989-01-01

    The traveling-wave energy, which multiply diffracts on a straight thin wire, is represented as a sum of terms, each with a distinct physical meaning, that can be individually examined in the time domain. Expressions for each scattering mechanism on a straight thin wire are cast in the form of four basic electromagnetic wave concepts: diffraction, attachment, launch, and reflection. Using the basic mechanisms from P. Ya. Ufimtsev (1962), each of the scattering mechanisms is included into the total scattered field for the straight thin wire. Scattering as a function of angle and frequency is then compared to the moment-method solution. These analytic expressions are then extended to a lossy wire with a simple approximate modification using the propagation velocity on the wire as derived from the Sommerfeld wave on a straight lossy wire. Both the perfectly conducting and lossy wire solutions are compared to moment-method results, and excellent agreement is found. As is common with asymptotic solutions, when the electrical length of wire is smaller than 0.2 lambda the results lose accuracy. The expressions modified to approximate the scattering for the lossy thin wire yield excellent agreement even for lossy wires where the wire radius is on the order of skin depth.

  18. SpaceWire Data Handling Demonstration System

    NASA Astrophysics Data System (ADS)

    Mills, S.; Parkes, S. M.; O'Gribin, N.

    2007-08-01

    The SpaceWire standard was published in 2003 with the aim of providing a standard for onboard communications, defining the physical and data link layers of an interconnection, in order to improve reusability, reliability and to reduce the cost of mission development. The many benefits which it provides mean that it has already been used in a number of missions, both in Europe and throughout the world. Recent work by the SpaceWire community has included the development of higher level protocols for SpaceWire, such as the Remote Memory Access Protocol (RMAP) which can be used for many purposes, including the configuration of SpaceWire devices. Although SpaceWire has become very popular, the various ways in which it can be used are still being discovered, as are the most efficient ways to use it. At the same time, some in the space industry are not even aware of SpaceWire's existence. This paper describes the SpaceWire Data Handling Demonstration System that has been developed by the University of Dundee. This system simulates an onboard data handling network based on SpaceWire. It uses RMAP for all communication, and so demonstrates how SpaceWire and standardised higher level protocols can be used onboard a spacecraft. The system is not only a good advert for those who are unfamiliar with the benefits of SpaceWire, it is also a useful tool for those using SpaceWire to test ideas.

  19. Comparative Study on Magnetic Properties and Microstructure of As-prepared and Alternating Current Joule Annealed Wires

    NASA Astrophysics Data System (ADS)

    Liu, J. S.; Wang, X. D.; Chen, D. M.; Qin, F. X.; Wang, H.; Xing, D. W.; Xue, X.; Sun, J. F.

    X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), magnetic measurement including impedance measurement were used for investigating the microstructure and magnetic properties of as-prepared and alternating current Joule annealed (ACJA) Co-rich amorphous microwires for potential sensor applications. Experimental results indicated that as-cast and ACJA wires both were amorphous characteristic, while ACJA wire has an enhanced local ordering degree of atom arrangement. There was a transform of magnetic properties after ACJA treatment, namely increasing coercivity, maximum magnetic permeability and saturation magnetization, resulting from the coactions of magnetic anisotropy and magnetic moment exchange coupling. Moreover, ACJA treatment can drastically improve the GMI property of melt-extracted wires. At 5 MHz, the maximum GMI ratio [ΔZ/Z0]max of ACJA wire increases to 205.93%, which is nearly 4.1 times of 50.62% for as-cast wire, and the field response sensitivity ξmax of ACJA wire increases to 463.70%/Oe by more than 2 times of 212.15%/Oe for as-cast wire. From sensor application perspective, the sensor applied frequency range (SAFR) of ACJA wire is 3MHz-7 MHz (the better working frequency is at 5 MHz). It can therefore be concluded that the ACJA wire (60 mA, 480s, 50 Hz) has better GMI and magnetic properties, is more suitable for potential magnetic sensor applications working at low-frequency and relatively high-working-magnetic field.

  20. Wire Crimp Connectors Verification using Ultrasonic Inspection

    NASA Technical Reports Server (NTRS)

    Cramer, K. Elliott; Perey, Daniel F.; Yost, William T.

    2007-01-01

    The development of a new ultrasonic measurement technique to quantitatively assess wire crimp connections is discussed. The amplitude change of a compressional ultrasonic wave propagating through the junction of a crimp connector and wire is shown to correlate with the results of a destructive pull test, which previously has been used to assess crimp wire junction quality. Various crimp junction pathologies (missing wire strands, incorrect wire gauge, incomplete wire insertion in connector) are ultrasonically tested, and their results are correlated with pull tests. Results show that the ultrasonic measurement technique consistently (as evidenced with pull-testing data) predicts good crimps when ultrasonic transmission is above a certain threshold amplitude level. A physics-based model, solved by finite element analysis, describes the compressional ultrasonic wave propagation through the junction during the crimping process. This model is in agreement within 6% of the ultrasonic measurements. A prototype instrument for applying the technique while wire crimps are installed is also presented.