Bounding Analysis of Effects of Fractionation of Radionuclides inFallout on Estimation of Doses to Atomic Veterans

DTIC Science & Technology

2007-05-04

140 Sm-156 Y-91m Rh - 103m Cd-115 Te-129 La-141 Eu-156 Y-91 Ru-105 In-115m I-130 Ce-141 Eu-157 Sr-92 Rh -105m Sn-121 Te-131m Ce-143 Gd-159 Y-92 Rh ...Tc-99m 6.02 h R 1.09E+00n (0.886) Ru-103 39.35 d V 2.04E-07 9.65E-01 6.81E-12 Rh - 103m 56.119 m V 1.00E+00n (0.997) 1.00E+00 Ru-105 4.44 h...08 1.24E-08 9.09E-09 Rh - 103m 6.36E-09 1.34E-08 1.23E-08 9.07E-09 Ru-105 1.20E-02 5.36E-02 4.05E-02 3.22E-02 2.90E-10 1.30E-09 9.79E-10 7.78E-10

Hypo-electronic triple-decker sandwich complexes: synthesis and structural characterization of [(Cp*Mo)2{μ-η(6):η(6)-B4H4E-Ru(CO)3}] (E = S, Se, Te or Ru(CO)3 and Cp* = η(5)-C5Me5).

PubMed

Mondal, Bijan; Bhattacharyya, Moulika; Varghese, Babu; Ghosh, Sundargopal

2016-07-05

The syntheses and structural characterization of hypo-electronic di-molybdenum triple-decker sandwich clusters are reported. Thermolysis of [Ru3(CO)12] with an in situ generated intermediate obtained from the reaction of [Cp*MoCl4] with [LiBH4·THF] yielded an electron deficient triple-decker sandwich complex, [(Cp*Mo)2{μ-η(6):η(6)-B4H4Ru2(CO)6}], . In an effort to generate analogous triple-deckers containing group-16 elements, we isolated [(Cp*Mo)2{μ-η(6):η(6)-B4H4ERu(CO)3}] (: E = Te; : E = S; : E = Se). These clusters show a high metal coordination number and cross cluster Mo-Mo bond. The formal cluster electron count of these compounds is four or three skeletal electron pairs less than required for a canonical closo-structure of the same nuclearity. Therefore, these compounds represent a novel class of triple-decker sandwich complex with 22 or 24 valence-electrons (VE), wherein the "chair" like hexagonal middle ring is composed of B, Ru and chalcogen. One of the key differences among the synthesized triple-decker molecules is the puckering nature of the middle ring [B4RuE], which increases in the order S < Se < Ru(CO)3 < Te. In addition, Fenske-Hall and quantum-chemical calculations with DFT methods at the BP86 level of theory have been used to analyze the bonding of these novel complexes. The studies not only explain the electron unsaturation of the molecules, but also reveal the reason for the significant puckering of the middle deck. All the compounds have been characterized by IR, (1)H, (11)B, and (13)C NMR spectroscopy in solution and the solid state structures were established by crystallographic analysis.

A MAGNETAR-LIKE EVENT FROM LS I +61 Degree-Sign 303 AND ITS NATURE AS A GAMMA-RAY BINARY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Torres, Diego F.; Rea, Nanda; Esposito, Paolo

2012-01-10

We report on the Swift Burst Alert Telescope detection of a short burst from the direction of the TeV binary LS I +61 Degree-Sign 303, resembling those generally labeled as magnetar-like. We show that it is likely that the short burst was indeed originating from LS I +61 Degree-Sign 303 (although we cannot totally exclude the improbable presence of a far-away, line-of-sight magnetar) and that it is a different phenomenon with respect to the previously observed ks-long flares from this system. Accepting the hypothesis that LS I +61 Degree-Sign 303 is the first magnetar detected in a binary system, wemore » study those implications. We find that a magnetar-composed LS I +61 Degree-Sign 303 system would most likely be (i.e., for the usual magnetar parameters and mass-loss rate) subject to a flip-flop behavior, from a rotationally powered regime (in the apastron) to a propeller regime (in the periastron) along each of the LS I +61 Degree-Sign 303 eccentric orbital motion. We prove that, unlike near an apastron, where an interwind shock can lead to the normally observed LS I +61 Degree-Sign 303 behavior, during TeV emission the periastron propeller is expected to efficiently accelerate particles only to sub-TeV energies. This flip-flop scenario would explain the system's behavior when a recurrent TeV emission only appears near the apastron, the anti-correlation of the GeV and TeV emission, and the long-term TeV variability (which seems correlated to LS I +61 Degree-Sign 303's super-orbital period), including the appearance of a low TeV state. Finally, we qualitatively put the multi-wavelength phenomenology into the context of our proposed model and make some predictions for further testing.« less

EXCEPTIONALLY BRIGHT TEV FLARES FROM THE BINARY LS I +61° 303

DOE Office of Scientific and Technical Information (OSTI.GOV)

Archambault, S.; Archer, A.; Buckley, J. H.

2016-01-20

The TeV binary system LS I +61° 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5% and 15% of the steady flux from the Crab Nebula (>300 GeV). In this article, VERITAS observations of LS I +61° 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30% of the Crab Nebula flux were detected. This is the brightest such activity frommore » this source ever seen in the TeV regime. The strong outbursts have rise and fall times of less than a day. The short timescale of the flares, in conjunction with the observation of 10 TeV photons from LS I +61° 303 during the flares, provides constraints on the properties of the accelerator in the source.« less

Application of regular associated solution model to the liquidus curves of the Sn-Te and Sn-SnS systems

NASA Astrophysics Data System (ADS)

Eric, H.

1982-12-01

The liquidus curves of the Sn-Te and Sn-SnS systems were evaluated by the regular associated solution model (RAS). The main assumption of this theory is the existence of species A, B and associated complexes AB in the liquid phase. Thermodynamic properties of the binary A-B system are derived by ternary regular solution equations. Calculations based on this model for the Sn-Te and Sn-SnS systems are in agreement with published data.

Fabrication of thermoelectric modules with Mg2Si and SrRuO3 by the spark plasma sintering method

NASA Astrophysics Data System (ADS)

Nishio, Keishi; Sawada, Yukie; Arai, Koya; Sakamoto, Tatsuya; Kogo, Yasuo; Iida, Tsutomu

2012-06-01

Thermoelectric (TE) modules with a π structure were fabricated by the spark plasma sintering method. The modules were composed of SrRuO3 for the p-type semiconductor, Mg2Si for the n-type semiconductor, and Ni for the electrodes. The SrRuO3 powder was synthesized using the metal-citric-acid complex decomposition method. Mg2Si bulk prepared by meltquenching was ground into powder and sieved to a particle size of 75 μm or less. To obtain the sintered body of SrRuO3, the powder was sintered using spark plasma sintering (SPS). For SPS, the precursor powder was placed in a graphite die and kept at that temperature under a uni-axial pressure of 50 MPa and in vacuum conditions (less than 7 Pa). After sintering by SPS, the ceramic sample was annealed at 1573K in air because the SrRuO3 was slightly reduced during the SPS process in the graphite die. These TE sintered bodies were cut and polished. The dimensions of the samples used for fabrication of the p-type parts of the TE modules were 4.50×9.50×7.45 mm3 and those for the n-type parts were 5.50×11.45×7.45 mm3. Pressed Ni powder was put between these TE materials and the Ni electrodes in order to connect them together, and electrical power was passed through the electrodes from the SPS equipment. The output power under temperature differences ΔT ranging from 100 to 500 K was measured. The open-circuit voltage, maximum output current and maximum output power increased with increasing temperature difference ΔT. The open-circuit voltage of the single module was 91.0 mV, and the maximum output current and maximum output power were 5000 mA and 110 mW at ΔT=500 K, respectively.

Vaporization thermodynamic studies by high-temperature mass spectrometry on some three-phase regions over the MnO-TeO2 binary line in the Mn-Te-O ternary system.

PubMed

Narasimhan, T S Lakshmi; Sai Baba, M; Viswanathan, R

2006-12-28

Knudsen effusion mass spectrometric measurements have been performed in the temperature range of 850-950 K over four three-phase mixtures, each phase mixture having at least one phase lying on the MnO-TeO2 binary line of the Mn-Te-O phase diagram, and the rest of the phases lying above this binary line. The three-phase mixtures investigated are Mn3O4 + MnO + Mn6Te5O16; Mn3O4 + Mn6Te5O16 + MnTeO3; Mn3O4 + Mn3TeO6 + MnTeO3; and Mn3TeO6 + MnTeO3 + Mn2Te3O8. The vapor pressures of the gaseous species TeO2, TeO, and Te2 over these three-phase mixtures were measured, and various heterogeneous solid-gas reactions were evaluated along with the homogeneous gas-phase reaction TeO2(g) + 0.5Te2(g) = 2 TeO(g). The enthalpy and Gibbs free energy of formation of the four ternary Mn-Te-O phases were deduced at T = 900 K. These values (in kJ.mol-1), along with the estimated uncertainties in them are Delta(f)H(o)m = 4150 +/- 19, 752 +/- 11, 1710 +/- 11, 1924 +/- 40, and Delta(f)G(o)m= 2835 +/- 28, 511 +/- 11, 1254 +/- 19, 1238 +/- 38, for Mn6Te5O16, MnTeO3, Mn3TeO6, and Mn2Te3O8, respectively. A thermochemical assessment was made to examine the conditions under which the ternary Mn-Te-O phases could be formed on a stainless steel clad of mixed-oxide-fueled (MO2; M = U + Pu) fast breeder nuclear reactors. The phase Mn3TeO6 could be formed when the fuel is even slightly hyperstoichiometric (O/M = 2.0002) and the phase Mn6Te5O16 could also be formed when O/M = 2.0004. The threshold tellurium potential for the formation of Mn3TeO6 is higher than that for MnTe0.80 and CrTe1.10, but is comparable to that for MoTe1.10, and even lower than that for FeTe0.81 or NiTe0.63.

Alloy Design Data Generated for B2-Ordered Compounds

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Bozzolo, Guillermo; Abel, Phillip B.

2003-01-01

Developing alloys based on ordered compounds is significantly more complicated than developing designs based on disordered materials. In ordered compounds, the major constituent elements reside on particular sublattices. Therefore, the addition of a ternary element to a binary-ordered compound is complicated by the manner in which the ternary addition is made (at the expense of which binary component). When ternary additions are substituted for the wrong constituent, the physical and mechanical properties usually degrade. In some cases the resulting degradation in properties can be quite severe. For example, adding alloying additions to NiAl in the wrong combination (i.e., alloying additions that prefer the Al sublattice but are added at the expense of Ni) will severely embrittle the alloy to the point that it can literally fall apart during processing on cooling from the molten state. Consequently, alloying additions that strongly prefer one sublattice over another should always be added at the expense of that component during alloy development. Elements that have a very weak preference for a sublattice can usually be safely added at the expense of either element and will accommodate any deviation from stoichiometry by filling in for the deficient component. Unfortunately, this type of information is not known beforehand for most ordered systems. Therefore, a computational survey study, using a recently developed quantum approximate method, was undertaken at the NASA Glenn Research Center to determine the preferred site occupancy of ternary alloying additions to 12 different B2-ordered compounds including NiAl, FeAl, CoAl, CoFe, CoHf, CoTi, FeTi, RuAl, RuSi, RuHf, RuTi, and RuZr. Some of these compounds are potential high temperature structural alloys; others are used in thin-film magnetic and other electronic applications. The results are summarized. The italicized elements represent the previous sum total alloying information known and verify the computational method used to establish the table. Details of the computational procedures used to determine the preferred site occupancy can be found in reference 2. As further substantiation of the validity of the technique, and its extension to even more complicated systems, it was applied to two simultaneous alloying additions in an ordered alloy.

Properties of binary transition-metal arsenides (TAs)

NASA Astrophysics Data System (ADS)

Saparov, Bayrammurad; Mitchell, Jonathan E.; Sefat, Athena S.

2012-08-01

We present thermodynamic and transport properties of transition-metal (T) arsenides, TAs, with T = Sc to Ni (3d), Zr, Nb, Ru (4d), Hf and Ta (5d). Characterization of these binaries is carried out with powder x-ray diffraction, temperature- and field-dependent magnetization and resistivity, temperature-dependent heat capacity, Seebeck coefficient, and thermal conductivity. All binaries show metallic behavior except TaAs and RuAs. TaAs, NbAs, ScAs and ZrAs are diamagnetic, while CoAs, VAs, TiAs, NiAs and RuAs show approximately Pauli paramagnetic behavior. FeAs and CrAs undergo antiferromagnetic ordering below TN ≈ 71 K and TN ≈ 260 K, respectively. MnAs is a ferromagnet below TC ≈ 317 K and undergoes hexagonal-orthorhombic-hexagonal transitions at TS ≈ 317 K and 384 K, respectively. For TAs, Seebeck coefficients vary between + 40 and - 40 μV K-1 in the 2-300 K range, whereas thermal conductivity values stay below 18 W m-1 K-1. The Sommerfeld coefficients γ are less than 10 mJ K-2 mol-1. At room temperature with application of 8 T magnetic field, large positive magnetoresistance is found for TaAs (˜25%), MnAs (˜90%) and NbAs (˜75%).

Liquidus Projections of Bi-Se-Ga and Bi-Se-Te Ternary Systems

NASA Astrophysics Data System (ADS)

Lin, Po-han; Chen, Sinn-wen; Hwang, Jenn-dong; Chu, Hsu-shen

2016-12-01

This study determines the liquidus projections of both Bi-Se-Ga and Bi-Se-Te ternary systems which are constituent ternary systems of promising Bi-Se-Te-Ga thermoelectric materials. Ternary Bi-Se-Ga and Bi-Se-Te alloys are prepared. Their primary solidification phases are experimentally determined, and thermal analysis experiments are carried out. The liquidus projections are determined based on the ternary experimental results and phase diagrams of constituent binary systems. The Bi-Se-Ga system includes seven primary solidification phases, Bi, Ga, GaSe, Ga2Se3, Se, Bi2Se3, and (Bi2)n(Bi2Se3)m. In the Bi-Se-Te system, there are five primary solidification phases, Bi, (Bi2)n(Bi2Te3)m, Bi2(Se,Te)3, (Se,Te), and (Bi2)n(Bi2Se3)m. Both the (Bi2)n(Bi2Te3)m and (Bi2)n(Bi2Se3)m phases are not a single phase, but a collection of series undetermined phases. Large miscibility gaps are observed in the Bi-Se-Ga system. The temperatures of the invariant reactions, Liquid + Bi + GaSe = Ga and Liquid + Ga2Se3 = Bi + GaSe, are at 495 K (222 °C) and 533 K (260 °C), respectively.

Electrical properties and transport mechanisms in phase change memory thin films of quasi-binary-line GeTe–Sb{sub 2}Te{sub 3} chalcogenide semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sherchenkov, A. A.; Kozyukhin, S. A., E-mail: sergkoz@igic.ras.ru; Lazarenko, P. I.

The temperature dependences of the resistivity and current–voltage (I–V) characteristics of phase change memory thin films based on quasi-binary-line GeTe–Sb{sub 2}Te{sub 3} chalcogenide semiconductors Ge{sub 2}Sb{sub 2}Te{sub 5}, GeSb{sub 2}Te{sub 5}, and GeSb{sub 4}Te{sub 7} are investigated. The effect of composition variation along the quasibinary line on the electrical properties and transport mechanisms of the thin films is studied. The existence of three ranges with different I–V characteristics is established. The position and concentration of energy levels controlling carrier transport are estimated. The results obtained show that the electrical properties of the thin films can significantly change during a shiftmore » along the quasi-binary line GeTe–Sb{sub 2}Te{sub 3}, which is important for targeted optimization of the phase change memory technology.« less

Discovery of variable VHE γ-ray emission from the binary system 1FGL J1018.6-5856

NASA Astrophysics Data System (ADS)

H. E. S. S. Collaboration; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E. O.; Backes, M.; Balzer, A.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Birsin, E.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Carr, J.; Casanova, S.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; O'C. Drury, L.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Grudzińska, M.; Hadasch, D.; Häffner, S.; Hahn, J.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kerszberg, D.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Lui, R.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Morå, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niemiec, J.; Oakes, L.; Odaka, H.; Öttl, S.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Arribas, M. Paz; Pekeur, N. W.; Pelletier, G.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reichardt, I.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seyffert, A. S.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van der Walt, J.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Żywucka, N.

2015-05-01

Re-observations with the HESS telescope array of the very high-energy (VHE) source HESS J1018-589 A that is coincident with the Fermi-LAT γ-ray binary 1FGL J1018.6-5856 have resulted in a source detection significance of more than 9σ and the detection of variability (χ2/ν of 238.3/155) in the emitted γ-ray flux. This variability confirms the association of HESS J1018-589 A with the high-energy γ-ray binary detected by Fermi-LAT and also confirms the point-like source as a new VHE binary system. The spectrum of HESS J1018-589 A is best fit with a power-law function with photon index Γ = 2.20 ± 0.14stat ± 0.2sys. Emission is detected up to ~20 TeV. The mean differential flux level is (2.9 ± 0.4) × 10-13 TeV-1 cm-2 s-1 at 1 TeV, equivalent to ~1% of the flux from the Crab Nebula at the same energy. Variability is clearly detected in the night-by-night light curve. When folded on the orbital period of 16.58 days, the rebinned light curve peaks in phase with the observed X-ray and high-energy phaseograms. The fit of the HESS phaseogram to a constant flux provides evidence of periodicity at the level of Nσ> 3σ. The shape of the VHE phaseogram and measured spectrum suggest a low-inclination, low-eccentricity system with amodest impact from VHE γ-ray absorption due to pair production (τ ≲ 1 at 300 GeV).

Phase-field crystal modeling of compositional domain formation in ultrathin films.

PubMed

Muralidharan, Srevatsan; Haataja, Mikko

2010-09-17

Bulk-immiscible binary systems often form stress-induced miscible alloy phases when deposited on a substrate. Both alloying and surface dislocation formation lead to the decrease of the elastic strain energy, and the competition between these two strain-relaxation mechanisms gives rise to the emergence of pseudomorphic compositional nanoscale domains, often coexisting with a partially coherent single phase. In this work, we develop a phase-field crystal model for compositional patterning in monolayer aggregates of binary metallic systems. We first demonstrate that the model naturally incorporates the competition between alloying and misfit dislocations, and quantify the effects of misfit and line tension on equilibrium domain size. Then, we quantitatively relate the parameters of the phase-field crystal model to a specific system, CoAg/Ru(0001), and demonstrate that the simulations capture experimentally observed morphologies.

Advanced methods for preparation and characterization of infrared detector materials. [crystallization and phase diagrams of Hg sub 1-x Cd sub x Te

NASA Technical Reports Server (NTRS)

Lehoczy, S. L.

1979-01-01

Crystal growth of Hg sub 1-x Cd sub x Te and density measurements of ingot slices are discussed. Radial compositional variations are evaluated from the results of infrared transmission edge mapping. The pseudo-binary HgTe-CdTe phase diagram is examined with reference to differential thermal analysis measurements. The phase equilibria calculations, based on the 'regular association solution' theory (R.A.S.) are explained and, using the obtained R.A.S. parameters, the activities of Hg, Cd, and Te vapors and their partial pressures over the pseudo-binary melt are calculated.

Raman characterization of a new Te-rich binary compound: CdTe2.

PubMed

Rousset, Jean; Rzepka, Edouard; Lincot, Daniel

2009-04-02

Structural characterization by Raman spectroscopy of CdTe thin films electrodeposited in acidic conditions is considered in this work. This study focuses on the evolution of material properties as a function of the applied potential and the film thickness, demonstrating the possibility to obtain a new Te-rich compound with a II/VI ratio of 1/2 under specific bath conditions. Raman measurements carried out on etched samples first allow the elimination of the assumption of a mixture of phases CdTe + Te and tend to confirm the formation of the CdTe(2) binary compound. The signature of this phase on the Raman spectrum is the increase of the LO band intensity compared to that obtained for the CdTe. The influence of the laser power is also considered. While no effect is observed on CdTe films, the increase of the incident irradiation power leads to the decomposition of the CdTe(2) compound into two more stable phases namely CdTe and Te.

Structural and dynamical studies of molecular and network forming chalcogenide glasses and supercooled liquids with NMR and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Gjersing, Erica Lee

The techniques of Nuclear Magnetic Resonance (NMR) and Raman spectroscopy have been employed to study structure and dynamics in Ge-Se, Ge/As-Te, and As-S binary and complex Ge-As-Te and P-As-S ternary chalcogenide glasses. Structural studies were conducted on Ge-Se glasses and on binary Ge/As-Te and ternary Ge-As-Te systems. The structure of the GexSe100-x glass series, with 5≤x≤33, is investigated with 77Se Magic Angle Spinning (MAS) NMR and then compared with three different proposed structural models. For the binary Ge-Te and As-Te and ternary Ge-As-Te glass systems the structure is studied using Raman spectroscopy and correlated with physical properties such as molar volume, viscosity, optical band gap and thermophysical properties. Studies on glass transition dynamics were conducted on systems with a range of structural features including an As4S3 inorganic molecular glass former, an As-P-S system where molecules are bonded to the As-S network, and network glasses in the Ge-Se system. Timescales of the rotational dynamics of As4S3 cage molecules in the molecular As-sulfide glass and supercooled liquid show remarkably large decoupling from the timescales of viscous flow and shear relaxation at temperatures below and near Tg (312K). Next, the dynamic behavior of a (As 2S3)90(P2S5)10 glass, which is proposed to consist of As2P2S8 molecular structures which are connected to an As-S network, is investigated with 31P NMR. The rotational dynamics of selenium chains in network forming GexSe100-x glasses and supercooled liquids with 5≤x≤23 are investigated with variable temperature 77Se NMR spectroscopy to determine the relationship between rigidity percolation and dynamic behavior. The timescale of the motion of the Se atoms is observed to be nearly identical for x≤17 and ≤2.36. However, for the x=20 and 23 compositions where ≤2.4, above the rigidity percolation threshold, the timescale slows down abruptly. Finally, the Ge20Se 80 glass and supercooled liquid have been the focus of a variable temperature Raman spectroscopy study to investigate the vibrational mode softening behavior and the importance of vibrational entropy in glass transition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, Rupam; Huang, Zhi-Feng; Nadgorny, Boris

Multiple percolation transitions are observed in a binary system of RuO{sub 2}-CaCu{sub 3}Ti{sub 4}O{sub 12} metal-semiconductor nanoparticle composites near percolation thresholds. Apart from a classical percolation transition, associated with the appearance of a continuous conductance path through RuO{sub 2} metal oxide nanoparticles, at least two additional tunneling percolation transitions are detected in this composite system. Such behavior is consistent with the recently emerged picture of a quantum conductivity staircase, which predicts several percolation tunneling thresholds in a system with a hierarchy of local tunneling conductance, due to various degrees of proximity of adjacent conducting particles distributed in an insulating matrix.more » Here, we investigate a different type of percolation tunneling staircase, associated with a more complex conductive and insulating particle microstructure of two types of non-spherical constituents. As tunneling is strongly temperature dependent, we use variable temperature measurements to emphasize the hierarchical nature of consecutive tunneling transitions. The critical exponents corresponding to specific tunneling percolation thresholds are found to be nonuniversal and temperature dependent.« less

Multiwavelength observations of the TeV binary LS I +61° 303 with Veritas, Fermi-LAT, and Swift/xrt during a TeV outburst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aliu, E.; Archambault, S.; Behera, B.

2013-12-10

We present the results of a multiwavelength observational campaign on the TeV binary system LS I +61° 303 with the VERITAS telescope array (>200 GeV), Fermi-LAT (0.3-300 GeV), and Swift/XRT (2-10 keV). The data were taken from 2011 December through 2012 January and show a strong detection in all three wavebands. During this period VERITAS obtained 24.9 hr of quality selected livetime data in which LS I +61° 303 was detected at a statistical significance of 11.9σ. These TeV observations show evidence for nightly variability in the TeV regime at a post-trial significance of 3.6σ. The combination of the simultaneouslymore » obtained TeV and X-ray fluxes do not demonstrate any evidence for a correlation between emission in the two bands. For the first time since the launch of the Fermi satellite in 2008, this TeV detection allows the construction of a detailed MeV-TeV spectral energy distribution from LS I +61° 303. This spectrum shows a distinct cutoff in emission near 4 GeV, with emission seen by the VERITAS observations following a simple power-law above 200 GeV. This feature in the spectrum of LS I +61° 303, obtained from overlapping observations with Fermi-LAT and VERITAS, may indicate that there are two distinct populations of accelerated particles producing the GeV and TeV emission.« less

Effect of Cr contents on the diffusion behavior of Te in Ni-based alloy

NASA Astrophysics Data System (ADS)

Jia, Yanyan; Li, Zhefu; Ye, Xiangxi; Liu, Renduo; Leng, Bin; Qiu, Jie; Liu, Min; Li, Zhijun

2017-12-01

The embrittlement of Ni-based structural alloys caused by fission production Te is one of the major challenges for molten salt reactors. It has been reported that solution element Cr can prevent the situation of intergranular cracks caused by Te. However, there is no detailed mechanism explanation on this phenomenon. In this study, the effect of Cr on Te diffusion in Ni-Cr binary system was investigated by diffusion experiments at 800 °C for 100 h. Results show that Te reacts with the alloy mainly forming Ni3Te2, and strip shaped Cr3Te4 is only found on the surface of Ni-15%Cr alloy. According to the discussion of thermodynamic chemical reaction process, Cr3Te4 exhibits the best stability and preferential formation compound in Te/Ni-Cr system as its Gibbs free energy of formation is the lowest. With the increase of Cr content in the alloy, the diffusion depth of Te along grain boundaries significantly decreases. Moreover, the formation process of reaction product and diffusion process are described. The diffusion of Te can be suppressed by high content of Cr in Ni-Cr alloy due to the formation of Cr3Te4 and thus the grain boundary is protected from Te corroding.

Comparative acid-base properties of the surface of components of the CdTe-ZnS system in series of substitutional solid solutions and their analogs

NASA Astrophysics Data System (ADS)

Kirovskaya, I. A.; Kasatova, I. Yu.

2011-07-01

The acid-base properties of the surface of solid solutions and binary components of the CdTe-ZnS system are studied by hydrolytic adsorption, nonaqueous conductometric titration, mechanochemistry, IR spectroscopy, and Raman scattering spectroscopy. The strength, nature, and concentration of acid centers on the original surface and that exposed to CO are determined. The changes in acid-base properties in dependence on the composition of the system under investigation in the series of CdB6, ZnB6 analogs are studied.

Crystal phase-based epitaxial growth of hybrid noble metal nanostructures on 4H/fcc Au nanowires

NASA Astrophysics Data System (ADS)

Lu, Qipeng; Wang, An-Liang; Gong, Yue; Hao, Wei; Cheng, Hongfei; Chen, Junze; Li, Bing; Yang, Nailiang; Niu, Wenxin; Wang, Jie; Yu, Yifu; Zhang, Xiao; Chen, Ye; Fan, Zhanxi; Wu, Xue-Jun; Chen, Jinping; Luo, Jun; Li, Shuzhou; Gu, Lin; Zhang, Hua

2018-03-01

Crystal-phase engineering offers opportunities for the rational design and synthesis of noble metal nanomaterials with unusual crystal phases that normally do not exist in bulk materials. However, it remains a challenge to use these materials as seeds to construct heterometallic nanostructures with desired crystal phases and morphologies for promising applications such as catalysis. Here, we report a strategy for the synthesis of binary and ternary hybrid noble metal nanostructures. Our synthesized crystal-phase heterostructured 4H/fcc Au nanowires enable the epitaxial growth of Ru nanorods on the 4H phase and fcc-twin boundary in Au nanowires, resulting in hybrid Au-Ru nanowires. Moreover, the method can be extended to the epitaxial growth of Rh, Ru-Rh and Ru-Pt nanorods on the 4H/fcc Au nanowires to form unique hybrid nanowires. Importantly, the Au-Ru hybrid nanowires with tunable compositions exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction in alkaline media.

First-principles study of amorphous Ga4Sb6Te3 phase-change alloys

NASA Astrophysics Data System (ADS)

Bouzid, Assil; Gabardi, Silvia; Massobrio, Carlo; Boero, Mauro; Bernasconi, Marco

2015-05-01

First-principles molecular dynamics simulations within the density functional theory framework were performed to generate amorphous models of the Ga4Sb6Te3 phase change alloy by quenching from the melt. We find that Ga-Sb and Ga-Te are the most abundant bonds with only a minor amount of Sb-Te bonds participating to the alloy network. Ga and four-coordinated Sb atoms present a tetrahedral-like geometry, whereas three-coordinated Sb atoms are in a pyramidal configuration. The tetrahedral-like geometries are similar to those of the crystalline phase of the two binary compounds GaTe and GaSb. A sizable fraction of Sb-Sb bonds is also present, indicating a partial nanoscale segregation of Sb. Despite the fact that the composition Ga4Sb6Te3 lies on the pseudobinary Ga Sb -Sb2Te3 tie line, the amorphous network can be seen as a mixture of the two binary compounds GaTe and GaSb with intertwined elemental Sb.

Comparative Study of Novel Ratio Spectra and Isoabsorptive Point Based Spectrophotometric Methods: Application on a Binary Mixture of Ascorbic Acid and Rutin.

PubMed

Darwish, Hany W; Bakheit, Ahmed H; Naguib, Ibrahim A

2016-01-01

This paper presents novel methods for spectrophotometric determination of ascorbic acid (AA) in presence of rutin (RU) (coformulated drug) in their combined pharmaceutical formulation. The seven methods are ratio difference (RD), isoabsorptive_RD (Iso_RD), amplitude summation (A_Sum), isoabsorptive point, first derivative of the ratio spectra ((1)DD), mean centering (MCN), and ratio subtraction (RS). On the other hand, RU was determined directly by measuring the absorbance at 358 nm in addition to the two novel Iso_RD and A_Sum methods. The work introduced in this paper aims to compare these different methods, showing the advantages for each and making a comparison of analysis results. The calibration curve is linear over the concentration range of 4-50 μg/mL for AA and RU. The results show the high performance of proposed methods for the analysis of the binary mixture. The optimum assay conditions were established and the proposed methods were successfully applied for the assay of the two drugs in laboratory prepared mixtures and combined pharmaceutical tablets with excellent recoveries. No interference was observed from common pharmaceutical additives.

Comparative Study of Novel Ratio Spectra and Isoabsorptive Point Based Spectrophotometric Methods: Application on a Binary Mixture of Ascorbic Acid and Rutin

PubMed Central

Darwish, Hany W.; Bakheit, Ahmed H.; Naguib, Ibrahim A.

2016-01-01

This paper presents novel methods for spectrophotometric determination of ascorbic acid (AA) in presence of rutin (RU) (coformulated drug) in their combined pharmaceutical formulation. The seven methods are ratio difference (RD), isoabsorptive_RD (Iso_RD), amplitude summation (A_Sum), isoabsorptive point, first derivative of the ratio spectra (1DD), mean centering (MCN), and ratio subtraction (RS). On the other hand, RU was determined directly by measuring the absorbance at 358 nm in addition to the two novel Iso_RD and A_Sum methods. The work introduced in this paper aims to compare these different methods, showing the advantages for each and making a comparison of analysis results. The calibration curve is linear over the concentration range of 4–50 μg/mL for AA and RU. The results show the high performance of proposed methods for the analysis of the binary mixture. The optimum assay conditions were established and the proposed methods were successfully applied for the assay of the two drugs in laboratory prepared mixtures and combined pharmaceutical tablets with excellent recoveries. No interference was observed from common pharmaceutical additives. PMID:26885440

Neutron Scattering Studies on Correlated Transition-Metal Oxides

NASA Astrophysics Data System (ADS)

Zhu, Mengze

We have explored the collective phenomena of correlated electrons in two different transition-metal oxides, Ruddlesden-Popper type ruthenates (Sr,Ca) n+1RunO3n+1 and inverse-trirutile chromates Cr2MO6 (M = Te, Mo and W), using neutron scattering in combination with various material characterization methods. (Sr,Ca)n+1RunO 3n+1 are 4d transition-metal oxides exhibiting competing magnetic and electronic tendencies. The delicate balance among the competing states can be readily tuned by perturbations, such as chemical doping and magnetic field, which gives rise to emergent phenomena. We have investigated the effects of 3d transition-metal doping on the magnetic and electronic properties of layered ruthenates. For instance, the single-layer (n = 1) Sr2RuO4 is an unconventional superconductor possessing an incommensurate spin density wave instability with a wave vector qic= (0.3 0.3 L) driven by Fermi surface nesting. Upon Fe substitution, we have unveiled an unexpected commensurate spin density wave order with a propagation vector qc= (0.25 0.25 0) in Sr2Ru1-xFexO 4 (x = 0.03 and 0.05), despite the magnetic fluctuations persisting at qic. The latter feature is corroborated by the first principles calculations, which show that Fe doping barely changes the nesting vector of the Fermi surface. These results suggest that in addition to the known incommensurate magnetic instability, Sr2RuO4 is also in proximity to a commensurate magnetic tendency that can be stabilized via Fe doping. We have also studied the effects of a magnetic field. For example, the bilayer (n = 2) Ca3(Ru1-xTi x)2O7 (x = 0.03) is a G-type antiferromagnetic Mott insulator. We have revealed that a modest magnetic field can lead to colossal magnetoresistance arising from an anomalous collapse of the Mott insulating state. Such an insulator-to-metal transition is accompanied by magnetic and structural transitions. These findings call for deeper theoretical studies to reexamine the magnetic field tuning of Mott systems with magnetic and electronic instabilities, as a magnetic field usually stabilizes the insulating ground state in Mott-Hubbard systems. Cr2MO6 (M = Te, W and Mo) are spin dimer systems with the magnetic ions Cr3+ structurally dimerized favoring a singlet ground state. However, all three compounds investigated exhibit long-range antiferromagnetic orders at low temperature owing to the inter-dimer interactions. We have shown that the inter-dimer exchange coupling can be tuned from antiferromagnetic in Cr2TeO6 to ferromagnetic in Cr2WO6 and Cr2MoO6, by altering the degree of d-p orbital hybridization between W(Mo) and O atoms. The tunability of the inter-dimer interactions without introducing additional complexities such as structural distortions and carrier doping offers a rare opportunity to drive the system toward the quantum critical point (QCP) separating the dimer-based quantum disordered state and the classical long-range antiferromagnetic order. Moreover, we have unraveled Higgs amplitude modes in the magnetic excitation spectra of Cr2TeO6 and Cr2WO6, which are generally believed to survive only in systems close to the QCP where the ordered moment is suppressed significantly from its fully saturated value by quantum fluctuations. However, these two compounds are away from the QCP with the ordered moment reduced only by 24%. This study suggests that Higgs amplitude modes are not the privilege of ordered systems in the vicinity of the QCP, but may be common excitation modes in ordered spin dimer systems.

Rapid synthesis of platinum-ruthenium bimetallic nanoparticles dispersed on carbon support as improved electrocatalysts for ethanol oxidation.

PubMed

Gu, Zhulan; Li, Shumin; Xiong, Zhiping; Xu, Hui; Gao, Fei; Du, Yukou

2018-07-01

Bimetallic nanocatalysts with small particle size benefit from markedly enhanced electrocatalytic activity and stability during small molecule oxidation. Herein, we report a facile method to synthesize binary Pt-Ru nanoparticles dispersed on a carbon support at an optimum temperature. Because of its monodispersed nanostructure, synergistic effects were observed between Pt and Ru and the PtRu/C electrocatalysts showed remarkably enhanced electrocatalytic activity towards ethanol oxidation. The peak current density of the Pt 1 Ru 1 /C electrocatalyst is 3731 mA mg -1 , which is 9.3 times higher than that of commercial Pt/C (401 mA mg -1 ). Furthermore, the synthesized Pt 1 Ru 1 /C catalyst exhibited higher stability during ethanol oxidation in an alkaline medium and maintained a significantly higher current density after successive cyclic voltammograms (CVs) of 500 cycles than commercial Pt/C. Our work highlights the significance of the reaction temperature during electrocatalyst synthesis, leading to enhanced catalytic performance towards ethanol oxidation. The Pt 1 Ru 1 /C electrocatalyst has great potential for application in direct ethanol fuel cells. Copyright © 2018 Elsevier Inc. All rights reserved.

MULTI-WAVELENGTH STUDY OF HESS J1741–302

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hare, Jeremy; Rangelov, Blagoy; Sonbas, Eda

2016-01-10

We present the results of two Chandra X-ray Observatory (CXO) observations of TeV γ-ray source HESS J1741–302. We investigate whether there is any connection between HESS J1741−302 and the sources seen at lower energies. One of the brightest X-ray sources in the HESS J1741–302 field, CXOU J174112.1−302908, appears to be associated with a low-mass star (possibly representing a quiescent low-mass X-ray binary or cataclysmic variable (CV)), hence, it is unlikely to be a source of TeV γ-rays. In the same field we have potentially detected X-rays from WR 98a, which is likely to be a colliding wind binary with massive stars. Nomore » TeV emission has been reported so far from such systems although predictions have been made. Finally, we found that the previously reported Suzaku source, Suzaku J1740.5–3014 (which is not covered by the CXO observations), appears to be a hard X-ray source detected by INTERGAL ISGRI, which supports the magnetized CV classification but makes its association with the TeV emission unlikely. The young pulsar PSR B1737–30, so far undetected in X-rays and projected on the sky near the CV, may be the contributor of relativistic particles responsible for the TeV emission.« less

Tailoring the composition of ultrathin, ternary alloy PtRuFe nanowires for the methanol oxidation reaction and formic acid oxidation reaction

DOE PAGES

Scofield, Megan E.; Koenigsmann, Christopher; Wang, Lei; ...

2014-11-25

In the search for alternatives to conventional Pt electrocatalysts, we have synthesized ultrathin, ternary PtRuFe nanowires (NW), possessing different chemical compositions in order to probe their CO tolerance as well as electrochemical activity as a function of composition for both (i) the methanol oxidation reaction (MOR) and (ii) the formic acid oxidation reaction (FAOR). As-prepared ‘multifunctional’ ternary NW catalysts exhibited both higher MOR and FAOR activity as compared with binary Pt₇Ru₃ NW, monometallic Pt NW, and commercial catalyst control samples. In terms of synthetic novelty, we utilized a sustainably mild, ambient wet-synthesis method never previously applied to the fabrication ofmore » crystalline, pure ternary systems in order to fabricate ultrathin, homogeneous alloy PtRuFe NWs with a range of controlled compositions. Thus, these NWs were subsequently characterized using a suite of techniques including XRD, TEM, SAED, and EDAX in order to verify not only the incorporation of Ru and Fe into the Pt lattice but also their chemical homogeneity, morphology, as well as physical structure and integrity. Lastly, these NWs were electrochemically tested in order to deduce the appropriateness of conventional explanations such as (i) the bi-functional mechanism as well as (ii) the ligand effect to account for our MOR and FAOR reaction data. Specifically, methanol oxidation appears to be predominantly influenced by the Ru content, whereas formic acid oxidation is primarily impacted by the corresponding Fe content within the ternary metal alloy catalyst itself.« less

Some properties of low-vapor-pressure braze alloys for thermionic converters

NASA Technical Reports Server (NTRS)

Bair, V. L.

1978-01-01

Property measurements were made for arc-melted, rod-shaped specimens. Density and dc electrical resistivity at 296 K were measured for various binary eutectic alloys. Thermal conductivity was inferred from the electrical conductivity using the Wiedemann, Franz, Lorenz relation. Linear thermal expansion from 293 K to two-thirds melting point, under a helium atmosphere, was measured for Zr, 21.7-wt percent Ru; Zr, 13-wt percent W; Zr, 22.3-wt percent Nb; Nb, 66.9-wt percent Ru; and Zr, 25.7-wt percent Ta.

TeV Gamma-Ray Observations of the Binary Neutron Star Merger GW170817 with H.E.S.S.

NASA Astrophysics Data System (ADS)

Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Caroff, S.; Carosi, A.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Colafrancesco, S.; Condon, B.; Conrad, J.; Davids, I. D.; Decock, J.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Donath, A.; O'C. Drury, L.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Emery, G.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Funk, S.; Füssling, M.; Gabici, S.; Gallant, Y. A.; Garrigoux, T.; Gaté, F.; Giavitto, G.; Giebels, B.; Glawion, D.; Glicenstein, J. F.; Gottschall, D.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Malyshev, D.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Ndiyavala, H.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poireau, V.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Rauth, R.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rinchiuso, L.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Shiningayamwe, K.; Simoni, R.; Sol, H.; Spanier, F.; Spir-Jacob, M.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steppa, C.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsirou, M.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Zorn, J.; Zywucka, N.; H. E. S. S. Collaboration

2017-12-01

We search for high-energy gamma-ray emission from the binary neutron star merger GW170817 with the H.E.S.S. Imaging Air Cherenkov Telescopes. The observations presented here have been obtained starting only 5.3 hr after GW170817. The H.E.S.S. target selection identified regions of high probability to find a counterpart of the gravitational-wave event. The first of these regions contained the counterpart SSS17a that has been identified in the optical range several hours after our observations. We can therefore present the first data obtained by a ground-based pointing instrument on this object. A subsequent monitoring campaign with the H.E.S.S. telescopes extended over several days, covering timescales from 0.22 to 5.2 days and energy ranges between 270 {GeV} to 8.55 {TeV}. No significant gamma-ray emission has been found. The derived upper limits on the very-high-energy gamma-ray flux for the first time constrain non-thermal, high-energy emission following the merger of a confirmed binary neutron star system.

On the influence of tetrahedral covalent-hybridization on electronic band structure of topological insulators from first principles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, X. M.; Xu, G. Z.; Liu, E. K.

Based on first-principles calculations, we investigate the influence of tetrahedral covalent-hybridization between main-group and transition-metal atoms on the topological band structures of binary HgTe and ternary half-Heusler compounds, respectively. Results show that, for the binary HgTe, when its zinc-blend structure is artificially changed to rock-salt one, the tetrahedral covalent-hybridization will be removed and correspondingly the topologically insulating band character lost. While for the ternary half-Heusler system, the strength of covalent-hybridization can be tuned by varying both chemical compositions and atomic arrangements, and the competition between tetrahedral and octahedral covalent-hybridization has been discussed in details. As a result, we found thatmore » a proper strength of tetrahedral covalent-hybridization is probably in favor to realizing the topologically insulating state with band inversion occurring at the Γ point of the Brillouin zone.« less

Low Pt content direct methanol fuel cell anode catalyst: nanophase PtRuNiZr

NASA Technical Reports Server (NTRS)

Whitacre, Jay F. (Inventor); Narayanan, Sekharipuram R. (Inventor)

2010-01-01

A method for the preparation of a metallic material having catalytic activity that includes synthesizing a material composition comprising a metal content with a lower Pt content than a binary alloy containing Pt but that displays at least a comparable catalytic activity on a per mole Pt basis as the binary alloy containing Pt; and evaluating a representative sample of the material composition to ensure that the material composition displays a property of at least a comparable catalytic activity on a per mole Pt basis as a representative binary alloy containing Pt. Furthermore, metallic compositions are disclosed that possess substantial resistance to corrosive acids.

New catalysts and adsorbents on the basis of the InSb-CdTe semiconducting system

NASA Astrophysics Data System (ADS)

Kirovskaya, I. A.

2007-04-01

The acid-base properties of solid solutions and binary components of the InSb-CdTe system were studied by IR spectroscopy, pH isoelectric point measurements, and conductometric titration; adsorption properties with respect to CO, O2, NO2, NH3, CO + O2, and NO2 + NH3, by piezoquartz microweighing; and catalytic properties in the oxidation of carbon(II) oxide and reduction of nitrogen(IV) oxide with ammonia, by the pulsed and circulation flow methods. The nature, strength, and concentration of acid centers were determined. Changes in the concentration of acid centers under the action of gases (NO2 and NH3), gamma irradiation, and composition variations were estimated. The experimental dependences, thermodynamic and kinetic adsorption characteristics, the electrophysical, acid-base, and other physicochemical characteristics of the adsorbents, and adsorption characteristic-composition phase diagrams were analyzed taking into account the electronic nature of adsorbate molecules to determine the mechanism and characteristics of adsorption processes depending on the conditions of adsorption and the composition of the system. The results of adsorption studies were used to preliminarily determine the temperature regions of the occurrence and the mechanism of the reactions studied. A shock mechanism was suggested. Separate components (predominantly, solid solutions) of the InSb-CdTe system showed high catalytic activity at comparatively low temperatures. Along with behavior common to the system and its binary compounds (InSb and CdTe), solid solutions exhibited features characteristic of multi-component systems. These were the presence of extrema in the pHiso-composition, adsorption characteristic-composition, and catalytic activity-composition diagrams. The use of these diagrams allowed us to discover system components most active with respect to the gases and reactions studied and create high-sensitivity and selective sensors and high-activity and selective catalysts on the basis of these components.

Hercules X-1: Pulsed gamma-rays detected above 150 GeV

NASA Technical Reports Server (NTRS)

Cawley, M. F.; Fegan, D. J.; Gibbs, K. G.; Gorham, P. W.; Kenny, S.; Lamb, R. C.; Liebing, D. F.; Porter, N. A.; Stenger, V. J.; Weekes, T. C.

1985-01-01

The 1.24 second binary pulsar Her X-1, first observed in X-rays in 1971 by UHURU has now been seen as a sporadic gamma ray source from 1 TeV up to at least 500 TeV. In addition, reprocessed optical and infrared pulses are seen from the companion star HZ Herculis. Thus measurements of the Her X-1/HZ Herculis system span 15 decades in energy, rivaling both the Crab pulsar and Cygnus X-3 in this respect for a discrete galactic source.

First-principles study of the amorphous In3SbTe2 phase change compound

NASA Astrophysics Data System (ADS)

Los, Jan H.; Kühne, Thomas D.; Gabardi, Silvia; Bernasconi, Marco

2013-11-01

Ab initio molecular dynamics simulations based on density functional theory were performed to generate amorphous models of the phase change compound In3SbTe2 by quenching from the melt. In-Sb and In-Te are the most abundant bonds with only a minor fraction of Sb-Te bonds. The bonding geometry in the amorphous phase is, however, strongly dependent on the density in the range 6.448-5.75 g/cm3 that we investigated. While at high density the bonding geometry of In atoms is mostly octahedral-like as in the cubic crystalline phase of the ternary compound In3SbTe2, at low density we observed a sizable fraction of tetrahedral-like geometries similar to those present in the crystalline phase of the two binary compounds InTe and InSb that the ternary system can be thought to be made of. We show that the different ratio between octahedral-like and tetrahedral-like bonding geometries has fingerprints in the optical and vibrational spectra.

Controls on ferromanganese crust composition and reconnaissance resource potential, Ninetyeast Ridge, Indian Ocean

USGS Publications Warehouse

Hein, James; Conrad, Tracey A.; Mizell, Kira; Banakar, Virupaxa K.; Frey, Frederick A.; Sager, William W.

2016-01-01

The southern third of NER has Fe-Mn crusts with the highest Co (0.91%), Ni (0.43%), ΣREY (0.33%), Cu (0.22%), Te (146 ppm), Pt (1.5 ppm), Ru (52 ppb), and Rh (99 ppb) contents. These are among the highest Pt, Ru, and Rh concentrations measured in marine Fe-Mn deposits. Because of these high metal concentrations, exploration is warranted for the southern sector of the NER, especially at shallower-water sites where the platinum group elements (PGE) and Co are likely to be even more enriched.

Advanced thermoelectric materials with enhanced crystal lattice structure and methods of preparation

NASA Technical Reports Server (NTRS)

Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

1998-01-01

New skutterudite phases including Ru.sub.0.5 Pd.sub.0.5 Sb.sub.3, RuSb.sub.2 Te, and FeSb.sub.2 Te, have been prepared having desirable thermoelectric properties. In addition, a novel thermoelectric device has been prepared using skutterudite phase Fe.sub.0.5 Ni.sub.0.5 Sb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor compounds and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor materials having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using powder metallurgy techniques. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities and good Seebeck coefficients. These materials have low thermal conductivity and relatively low electrical resistivity, and are good candidates for low temperature thermoelectric applications.

Raman spectrum, quantum mechanical calculations and vibrational assignments of (95% alpha-TeO2/5% Sm2O3) glass.

PubMed

Shaltout, I; Mohamed, Tarek A

2007-06-01

Chozen system of tellurite glasses doped with rare earth oxides (95% alpha-TeO(2)+5% Sm2O3) was prepared by melt quenching. Consequently, the Raman spectrum (150-1250 cm(-1)) of the modified tellurite have been recorded. As a continuation to our normal coordinate analysis, force constants and quantum mechanical (QM) calculations for tbp TeO4(4-) (triagonal bipyramid, C(2v)) and TeO(3+1); Te2O7(6-) (bridged tetrahedral), we have carried out ab initio frequency calculations for tpy TeO3(2-) (triagonal pyramidal, C(3v) and C(s)) and tp TeO3(2-) (triagonal planar, D(3h)) ions. The quantum mechanical calculations at the levels of RHF, B3LYP and MP2 allow confident vibrational assignments and structural identification in the binary oxide glass (95% alpha-TeO2 +5% Sm2O3). The dominant three-dimensional network structures in the modified glass are triagonal pyramidal TeO3 with minor features of short range distorted tbp TeO4 and bridged tetrahedral unit of TeO(3+1), leading to a structure of infinite chain. Therefore, alpha-TeO2/Sm2O3 (95/5%) glass experience structural changes from TeO4 (tbp); Te2O7 (TeO(3+1))-->TeO3 (tpy).

Synthesis and Characterization of CO-and H2S-Tolerant Electrocatalysts for PEM Fuel Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shamsuddin Ilias

2005-12-22

The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary,more » ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period we synthesized four Pt-based electrocatalysts catalysts (Pt/Ru/Mo/Se, Pt/Ru/Mo/Ir, Pt/Ru/Mo/W, Ptr/Ru/Mo/Co) on Vulcan XG72 Carbon support by both conventional and ultra-sonication method. From current-voltage performance study, the catalytic activity was found in the increasing order of Pt/Ru/Mo/Ir > Pt/Ru/Mo/W > Pt/Ru/Mo/Co > Pt/Ru/MO/Se. Sonication method appears to provide better dispersion of catalysts on carbon support.« less

TeV Gamma-Ray Observations of the Binary Neutron Star Merger GW170817 with H.E.S.S.

DOE PAGES

Abdalla, H.; Abramowski, A.; Aharonian, F.; ...

2017-11-22

Here, we search for high-energy gamma-ray emission from the binary neutron star merger GW170817 with the H.E.S.S. Imaging Air Cherenkov Telescopes. The observations presented here have been obtained starting only 5.3 hr after GW170817. The H.E.S.S. target selection identified regions of high probability to find a counterpart of the gravitational-wave event. The first of these regions contained the counterpart SSS17a that has been identified in the optical range several hours after our observations. We can therefore present the first data obtained by a ground-based pointing instrument on this object. A subsequent monitoring campaign with the H.E.S.S. telescopes extended over several days, covering timescales from 0.22 to 5.2 days and energy ranges betweenmore » $$270\\,\\mathrm{GeV}$$ to $$8.55\\,\\mathrm{TeV}$$. No significant gamma-ray emission has been found. The derived upper limits on the very-high-energy gamma-ray flux for the first time constrain non-thermal, high-energy emission following the merger of a confirmed binary neutron star system.« less

TeV Gamma-Ray Observations of the Binary Neutron Star Merger GW170817 with H.E.S.S.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdalla, H.; Abramowski, A.; Aharonian, F.

Here, we search for high-energy gamma-ray emission from the binary neutron star merger GW170817 with the H.E.S.S. Imaging Air Cherenkov Telescopes. The observations presented here have been obtained starting only 5.3 hr after GW170817. The H.E.S.S. target selection identified regions of high probability to find a counterpart of the gravitational-wave event. The first of these regions contained the counterpart SSS17a that has been identified in the optical range several hours after our observations. We can therefore present the first data obtained by a ground-based pointing instrument on this object. A subsequent monitoring campaign with the H.E.S.S. telescopes extended over several days, covering timescales from 0.22 to 5.2 days and energy ranges betweenmore » $$270\\,\\mathrm{GeV}$$ to $$8.55\\,\\mathrm{TeV}$$. No significant gamma-ray emission has been found. The derived upper limits on the very-high-energy gamma-ray flux for the first time constrain non-thermal, high-energy emission following the merger of a confirmed binary neutron star system.« less

THE MULTI-WAVELENGTH CHARACTERISTICS OF THE TeV BINARY LS I+61°303

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saha, L.; Chitnis, V. R.; Shukla, A.

2016-06-01

We study the characteristics of the TeV binary LS I+61°303 in radio, soft X-ray, hard X-ray, and gamma-ray (GeV and TeV) energies. The long-term variability characteristics are examined as a function of the phase of the binary period of 26.496 days as well as the phase of the superorbital period of 1626 days, dividing the observations into a matrix of 10 × 10 phases of these two periods. We find that the long-term variability can be described by a sine function of the superorbital period, with the phase and amplitude systematically varying with the binary period phase. We also findmore » a definite wavelength-dependent change in this variability description. To understand the radiation mechanism, we define three states in the orbital/superorbital phase matrix and examine the wideband spectral energy distribution. The derived source parameters indicate that the emission geometry is dominated by a jet structure showing a systematic variation with the orbital/superorbital period. We suggest that LS I+61°303 is likely a microquasar with a steady jet.« less

Modeling Fluid-Structure Interaction in ANSYS Workbench

DTIC Science & Technology

2016-08-31

IB U TI O N S TA TE M EN T A .A pp ro ve d fo rp ub lic re le as e; di st rib...Q R M Si er ra L ob o, In c. M od el in g Fl ui d- St ru ct ur e In te ra ct io n in A N SY S W or kb en ch 31 A ug us t 2 01 6 2 D IS TR IB ...S) G ro up 3 D IS TR IB U TI O N S TA TE M EN T A .A pp ro ve d fo rp ub lic re le as e; di st rib

Thermodynamic modelling of the C-U and B-U binary systems

NASA Astrophysics Data System (ADS)

Chevalier, P. Y.; Fischer, E.

2001-02-01

The thermodynamic modelling of the carbon-uranium (C-U) and boron-uranium (B-U) binary systems is being performed in the framework of the development of a thermodynamic database for nuclear materials, for increasing the basic knowledge of key phenomena which may occur in the event of a severe accident in a nuclear power plant. Applications are foreseen in the nuclear safety field to the physico-chemical interaction modelling, on the one hand the in-vessel core degradation producing the corium (fuel, zircaloy, steel, control rods) and on the other hand the ex-vessel molten corium-concrete interaction (MCCI). The key O-U-Zr ternary system, previously modelled, allows us to describe the first interaction of the fuel with zircaloy cladding. Then, the three binary systems Fe-U, Cr-U and Ni-U were modelled as a preliminary work for modelling the O-U-Zr-Fe-Cr-Ni multicomponent system, allowing us to introduce the steel components in the corium. In the existing database (TDBCR, thermodynamic data base for corium), Ag and In were introduced for modelling AIC (silver-indium-cadmium) control rods which are used in French pressurized water reactors (PWR). Elsewhere, B 4C is also used for control rods. That is why it was agreed to extend in the next years the database with two new components, B and C. Such a work needs the thermodynamic modelling of all the binary and pseudo-binary sub-systems resulting from the combination of B, B 2O 3 and C with the major components of TDBCR, O-U-Zr-Fe-Cr-Ni-Ag-In-Ba-La-Ru-Sr-Al-Ca-Mg-Si + Ar-H. The critical assessment of the very numerous experimental information available for the C-U and B-U binary systems was performed by using a classical optimization procedure and the Scientific Group Thermodata Europe (SGTE). New optimized Gibbs energy parameters are given, and comparisons between calculated and experimental equilibrium phase diagrams or thermodynamic properties are presented. The self-consistency obtained is quite satisfactory.

Binary photonic crystal for refractometric applications (TE case)

NASA Astrophysics Data System (ADS)

Taya, Sofyan A.; Shaheen, Somaia A.

2018-04-01

In this work, a binary photonic crystal is proposed as a refractometric sensor. The dispersion relation and the sensitivity are derived for transverse electric (TE) mode. In our analysis, the first layer is considered to be the analyte layer and the second layer is assumed to be left-handed material (LHM), dielectric or metal. It is found that the sensitivity of the LHM structure is the highest among other structures. It is possible for LHM photonic crystal to achieve a sensitivity improvement of 412% compared to conventional slab waveguide sensor.

Preparation and Thermoelectric Properties of the Skutterudite-Related Phase Ru(0.5)Pd(0.5)Sb3

NASA Technical Reports Server (NTRS)

Caillat, T.; Kulleck, J.; Borshchevsky, A.; Fleurial, J.-P.

1996-01-01

A new skutterudite phase Ru(0.5)Pd(0.5)Sb3 was prepared. This new phase adds to a large number of already known materials with the skutterudite structure which have shown good potential for thermoelectric applications. Single phase, polycrystalline samples were prepared and characterized by x-ray analysis, electron probe microanalysis, density, sound velocity, thermal-expansion coefficient, and differential thermal analysis measurements. Ru(0.5)Pd(0.5)Sb3 has a cubic lattice, space group Im3 (T(sup 5, sub h)), with a = 9.298 A and decomposes at about 920 K. The Seebeck coefficient, the electrical resistivity, the Hall effect, and the thermal conductivity were measured on hot-pressed samples over a wide range of temperatures. Preliminary results show that Ru(0.5)Pd(0.5)Sb3 behaves as a heavily doped semiconductor with an estimated band gap of about 0.6 eV. The lattice thermal conductivity of Ru(0.5)Pd(0.5)Sb3 is substantially lower than that of the binary isostructural compounds CoSb3 and IrSb3. The unusually low thermal conductivity might be explained by additional hole and charge transfer phonon scattering in this material. The potential of this material for thermoelectric applications is discussed.

Influence of Element Substitution on Corrosion Behavior of Bi2Te3-Based Compounds

NASA Astrophysics Data System (ADS)

Kohri, Hitoshi; Yagasaki, Takayoshi

2018-02-01

Atmospheric water may condense on the surface of Bi2Te3-based compounds constituting the Peltier module, depending on the operating environment used. In the stage of disposal, Bi2Te3-based compounds may come into contact with water in waste disposal sites. There are very few publications about the influence of condensed water on Peltier modules. Bi2Te3-Sb2Te3 or Bi2Te3-Bi2Se3 pseudo binary system compounds are used as p-type material or n-type material, respectively. The lattice distortion will be induced in the crystal of Bi2Te3-based compounds by element substitution due to the reduction in their thermal conductivity. However, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds remains unclear. In this study, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds with practical compositions has been investigated. Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 was prepared by the vertical Bridgman method. The electrochemical properties at room temperature were evaluated by cyclic voltammetry in a standard three-electrode cell. The working electrolyte was a naturally aerated 0.6 or 3.0 mass% NaCl solution. From the tendency for corrosion potential for all the samples, the corrosion sensitivity of ternary compounds was slightly higher than that of binary compounds. From the trend of current density, it was found that Bi0.5Sb1.5Te3 had a corrosion resistance intermediate between Bi2Te3 and Sb2Te3. On the other hand, corrosion resistance was affected despite a small amount of Se substitution, and the corrosion resistance of Bi2Te2.85Se0.15 was close to or lower than that of Bi2Se3. From the observation results of the corrosion products, the trends of morphology and composition of corrosion products for Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 were consistent with those of Sb2Te3 or Bi2Se3, respectively. From the results of x-ray photoelectron spectroscopy for the electrolyte after testing, the possibility that a corrosion product diffuses to the environment including the salt was suggested in Bi0.5Sb1.5Te3. However, the amount of dissolved corrosion product was very low, and the chemical stability of the corrosion product was not changed or improved by element substitution.

Influence of Element Substitution on Corrosion Behavior of Bi2Te3-Based Compounds

NASA Astrophysics Data System (ADS)

Kohri, Hitoshi; Yagasaki, Takayoshi

2018-06-01

Atmospheric water may condense on the surface of Bi2Te3-based compounds constituting the Peltier module, depending on the operating environment used. In the stage of disposal, Bi2Te3-based compounds may come into contact with water in waste disposal sites. There are very few publications about the influence of condensed water on Peltier modules. Bi2Te3-Sb2Te3 or Bi2Te3-Bi2Se3 pseudo binary system compounds are used as p-type material or n-type material, respectively. The lattice distortion will be induced in the crystal of Bi2Te3-based compounds by element substitution due to the reduction in their thermal conductivity. However, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds remains unclear. In this study, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds with practical compositions has been investigated. Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 was prepared by the vertical Bridgman method. The electrochemical properties at room temperature were evaluated by cyclic voltammetry in a standard three-electrode cell. The working electrolyte was a naturally aerated 0.6 or 3.0 mass% NaCl solution. From the tendency for corrosion potential for all the samples, the corrosion sensitivity of ternary compounds was slightly higher than that of binary compounds. From the trend of current density, it was found that Bi0.5Sb1.5Te3 had a corrosion resistance intermediate between Bi2Te3 and Sb2Te3. On the other hand, corrosion resistance was affected despite a small amount of Se substitution, and the corrosion resistance of Bi2Te2.85Se0.15 was close to or lower than that of Bi2Se3. From the observation results of the corrosion products, the trends of morphology and composition of corrosion products for Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 were consistent with those of Sb2Te3 or Bi2Se3, respectively. From the results of x-ray photoelectron spectroscopy for the electrolyte after testing, the possibility that a corrosion product diffuses to the environment including the salt was suggested in Bi0.5Sb1.5Te3. However, the amount of dissolved corrosion product was very low, and the chemical stability of the corrosion product was not changed or improved by element substitution.

Anode materials for lithium ion batteries

DOEpatents

Abouimrane, Ali; Amine, Khalil

2017-04-11

An electrochemical device includes a composite material of general Formula (1-x)J-(x)Q wherein: J is a metal carbon alloy of formula Sn.sub.zSi.sub.z'Met.sub.wMet'.sub.w'C.sub.t; Q is a metal oxide of formula A.sub..gamma.M.sub..alpha.M'.sub..alpha.'O.sub..beta.; and wherein: A is Li, Na, or K; M and M' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; Met and Met' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; 0

RF pulse compression for future linear colliders

NASA Astrophysics Data System (ADS)

Wilson, Perry B.

1995-07-01

Future (nonsuperconducting) linear colliders will require very high values of peak rf power per meter of accelerating structure. The role of rf pulse compression in producing this power is examined within the context of overall rf system design for three future colliders at energies of 1.0-1.5 TeV, 5 TeV, and 25 TeV. In order to keep the average AC input power and the length of the accelerator within reasonable limits, a collider in the 1.0-1.5 TeV energy range will probably be built at an x-band rf frequency, and will require a peak power on the order of 150-200 MW per meter of accelerating structure. A 5 TeV collider at 34 GHz with a reasonable length (35 km) and AC input power (225 MW) would require about 550 MW per meter of structure. Two-beam accelerators can achieve peak powers of this order by applying dc pulse compression techniques (induction linac modules) to produce the drive beam. Klystron-driven colliders achieve high peak power by a combination of dc pulse compression (modulators) and rf pulse compression, with about the same overall rf system efficiency (30-40%) as a two-beam collider. A high gain (6.8) three-stage binary pulse compression system with high efficiency (80%) is described, which (compared to a SLED-II system) can be used to reduce the klystron peak power by about a factor of two, or alternatively, to cut the number of klystrons in half for a 1.0-1.5 TeV x-band collider. For a 5 TeV klystron-driven collider, a high gain, high efficiency rf pulse compression system is essential.

Electrodeposition of MWNT/Bi2Te3 Composite Thermoelectric Films

NASA Astrophysics Data System (ADS)

Xu, Han; Wang, Wei

2013-07-01

The effect of multiwalled carbon nanotubes (MWNTs) on the electrochemical behavior of the Bi-Te binary system in nitric acid baths was investigated by means of cyclic voltammetry and electrochemical impedance spectroscopy. Based on the results, MWNT/Bi2Te3 composite thermoelectric films were prepared by potentiostatic electrodeposition at room temperature. The morphology, composition, and structure of the MWNT/Bi2Te3 composite films were analyzed by environmental scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction. The results show that addition of MWNTs to the electrolyte did not change the electrochemical reduction mechanisms of Bi3+, HTeO{2/+} or their mixture, but the reduction processes of Bi3+, HTeO{2/+}, and their mixture become easier. MWNT/Bi2Te3 composite thermoelectric films can be obtained by potentiostatic electrodeposition at a wide range of potentials with subsequent annealing. The MWNTs in the films act as nucleation sites for Bi2Te3 compound and thereby elevate the film deposition rate. The content of Bi element and MWNTs in the films increased as the potential was shifted negatively. In addition, the MWNTs can enhance the crystallization of Bi2Te3 film.

The composition effect on the thermal and optical properties across CdZnTe crystals

NASA Astrophysics Data System (ADS)

Strzałkowski, K.

2016-11-01

Cd1-x Zn x Te mixed crystals investigated in this work were grown from the melt using the vertical Bridgman-Stockbarger method in the whole range of composition 0  <  x  <  1 that is from one binary crystal (CdTe) to another (ZnTe). The real composition of grown crystals was measured with the SEM/EDS method along the growth axis. The segregation coefficient of Zn in a CdTe matrix has been evaluated as being close to unity. The energy gap as a function of the composition was determined from transmission spectroscopy. Thanks to that, the bowing parameter of this ternary alloy was found to be 0.458. In this work the systematical study of thermal properties of Cd1-x Zn x Te alloys from one binary crystal (CdTe) to another (ZnTe) grown by the vertical Bridgman technique were undertaken for the first time. The thermal diffusivity and effusivity of the investigated crystals were derived from the experimental data and allowed the thermal conductivity to be calculated. Diagrams of the thermal conductivity versus composition were analyzed applying the model for mixed semiconducting crystals given by Sadao Adachi. Thanks to that, the contribution of the thermal resistivity arising from the lattice disorder to the total resistivity of the crystal has been determined.

The Acid-Base Properties and Chemical Composition of the Surface of the InSb-ZnTe System

NASA Astrophysics Data System (ADS)

Kirovskaya, I. A.; Shubenkova, E. G.; Timoshenko, O. T.; Filatova, T. N.

2008-04-01

The acid-base properties and chemical composition of the surface of solid solutions and binary components of the InSb-ZnTe system were studied by the hydrolytic adsorption, nonaqueous conductometric titration, mechanochemistry, IR spectroscopy, and mass spectrometry methods. The strength, nature, and concentration of acid centers were determined. Changes in the concentration of acid centers caused by surface exposure to CO and changes in the composition of the system were also studied. The mechanism of acid-base interactions was established. The chemical composition of the surface of system components exposed to air included adsorbed H2O molecules, OH- groups, hydrocarbon and oxocarbon compounds, and the products of surface atom oxidation. After thermal treatment in a vacuum, the composition of the surface approached the stoichiometric composition.

Numerical Modeling of HgCdTe Solidification: Effects of Phase Diagram, Double-Diffusion Convection and Microgravity Level

NASA Technical Reports Server (NTRS)

Bune, Andris V.; Gillies, Donald C.; Lehoczky, Sandor L.

1997-01-01

Melt convection, along with species diffusion and segregation on the solidification interface are the primary factors responsible for species redistribution during HgCdTe crystal growth from the melt. As no direct information about convection velocity is available, numerical modeling is a logical approach to estimate convection. Furthermore influence of microgravity level, double-diffusion and material properties should be taken into account. In the present study, HgCdTe is considered as a binary alloy with melting temperature available from a phase diagram. The numerical model of convection and solidification of binary alloy is based on the general equations of heat and mass transfer in two-dimensional region. Mathematical modeling of binary alloy solidification is still a challenging numericial problem. A Rigorous mathematical approach to this problem is available only when convection is not considered at all. The proposed numerical model was developed using the finite element code FIDAP. In the present study, the numerical model is used to consider thermal, solutal convection and a double diffusion source of mass transport.

Recoilless fractions calculated with the nearest-neighbour interaction model by Kagan and Maslow

NASA Astrophysics Data System (ADS)

Kemerink, G. J.; Pleiter, F.

1986-08-01

The recoilless fraction is calculated for a number of Mössbauer atoms that are natural constituents of HfC, TaC, NdSb, FeO, NiO, EuO, EuS, EuSe, EuTe, SnTe, PbTe and CsF. The calculations are based on a model developed by Kagan and Maslow for binary compounds with rocksalt structure. With the exception of SnTe and, to a lesser extent, PbTe, the results are in reasonable agreement with the available experimental data and values derived from other models.

Intermediate phases in some rare earth-ruthenium systems

NASA Technical Reports Server (NTRS)

Sharifrazi, P.; Raman, A.; Mohanty, R. C.

1984-01-01

The phase equilibria and crystal structures of intermediate phases were investigated in eight representative RE-Ru systems using powder X-ray diffraction and metallographic techniques. The Fe3C, Mn5C2 and Er5Ru3 structures occur in all but the Ce-Ru systems. Phases analogous to Er5Ru3 possess an unknown crystal structure similar to Er5Rh3(I). MgCu2 and MgZn2 type Laves phases are encountered in the light rare earth and heavy rare earth systems, respectively, and RERu2 phases, where RE = Nd and Sm, possess both the Laves phase structures. An intermediate phase, NdRu, with an unknown structure, occurs only in the Nd-Ru system. A bcc structure with 40 atoms per unit cell is encountered in the phases Er3Ru2 and Y3Ru2. The behavior of cerium in Ce-Ru alloys is unique in that four unidentified structures, not encountered in other RE-Ru systems, have been encountered. Also a phase designated as Ce3Ru is found with the Th7Fe3 type structure.

Synthesis and Characterization of CO- and H2S-Tolerant Electrocatalysts for PEM Fuel Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shamsuddin Ilias

2006-05-18

The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary,more » ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period we used four Pt-based electrocatalysts (Pt/Ru/Mo/Se, Pt/Ru/Mo/Ir, Pt/Ru/Mo/W, Ptr/Ru/Mo/Co) in MEAs and these were evaluated for CO-tolerance with 20 and 100 ppm CO concentration in H{sub 2}-fuel. From current-voltage performance study, the catalytic activity was found in the increasing order of Pt/Ru/Mo/Ir > Pt/Ru/Mo/W > Pt/Ru/Mo/Co > Pt/Ru/MO/Se. From preliminary cost analysis it appears that could of the catalyst metal loading can reduced by 40% to 60% depending on the selection of metal combinations without compromising the fuel cell performance.« less

Mass correlation between light and heavy reaction products in multinucleon transfer 197Au+130Te collisions

NASA Astrophysics Data System (ADS)

Galtarossa, F.; Corradi, L.; Szilner, S.; Fioretto, E.; Pollarolo, G.; Mijatović, T.; Montanari, D.; Ackermann, D.; Bourgin, D.; Courtin, S.; Fruet, G.; Goasduff, A.; Grebosz, J.; Haas, F.; Jelavić Malenica, D.; Jeong, S. C.; Jia, H. M.; John, P. R.; Mengoni, D.; Milin, M.; Montagnoli, G.; Scarlassara, F.; Skukan, N.; Soić, N.; Stefanini, A. M.; Strano, E.; Tokić, V.; Ur, C. A.; Valiente-Dobón, J. J.; Watanabe, Y. X.

2018-05-01

We studied multinucleon transfer reactions in the 197Au+130Te system at Elab=1.07 GeV by employing the PRISMA magnetic spectrometer coupled to a coincident detector. For each light fragment we constructed, in coincidence, the distribution in mass of the heavy partner of the reaction. With a Monte Carlo method, starting from the binary character of the reaction, we simulated the de-excitation process of the produced heavy fragments to be able to understand their final mass distribution. The total cross sections for pure neutron transfer channels have also been extracted and compared with calculations performed with the grazing code.

Size versus electronic factors in transition metal carbide and TCP phase stability

NASA Astrophysics Data System (ADS)

Pettifor, D. G.; Seiser, B.; Margine, E. R.; Kolmogorov, A. N.; Drautz, R.

2013-09-01

The contributions of atomic size and electronic factors to the structural stability of transition metal carbides and topologically close-packed (TCP) phases are investigated. The hard-sphere model that has been used by Cottrell to rationalize the occurrence of the octahedral and trigonal local coordination polyhedra within the transition metal carbides is shown to have limitations in TiC since density functional theory (DFT) predicts that the second most metastable phase closest to the B1 (NaCl) ground state takes the B? (BN) structure type with 5-atom local coordination polyhedra with very short Ti-C bond lengths. The importance of electronic factors in the TCP phases is demonstrated by DFT predictions that the A15, ? and ? phases are stabilized between groups VI and VII of the elemental transition metals, whereas the ? and Laves phases are destabilized. The origin of this difference is related to the bimodal shape parameter of the electronic density of states by using the bond-order potential expansion of the structural energy within a canonical tight-binding model. The importance of the size factor in the TCP phases is illustrated by the DFT heats of formation for the binary systems Mo-Re, Mo-Ru, Nb-Re and Nb-Ru which show that the ? and Laves phases become more and more stable compared to A15, ? and ? as the size factor increases from Mo-Re through to Nb-Ru.

Computational identification of promising thermoelectric materials among known quasi-2D binary compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gorai, Prashun; Toberer, Eric S.; Stevanović, Vladan

Quasi low-dimensional structures are abundant among known thermoelectric materials, primarily because of their low lattice thermal conductivities. In this work, we have computationally assessed the potential of 427 known binary quasi-2D structures in 272 different chemistries for thermoelectric performance. To assess the thermoelectric performance, we employ an improved version of our previously developed descriptor for thermoelectric performance [Yan et al., Energy Environ. Sci., 2015, 8, 983]. The improvement is in the explicit treatment of van der Waals interactions in quasi-2D materials, which leads to significantly better predictions of their crystal structures and lattice thermal conductivities. The improved methodology correctly identifiesmore » known binary quasi-2D thermoelectric materials such as Sb2Te3, Bi2Te3, SnSe, SnS, InSe, and In2Se3. As a result, we propose candidate quasi-2D binary materials, a number of which have not been previously considered for thermoelectric applications.« less

Investigations of Nuclear Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarantites, Demetrios; Reviol, W.

The proposal addresses studies of nuclear structure at low-energies and development of instrumentation for that purpose. The structure studies deal with features of neutron-rich nuclei with unexplored shapes (football- or pear-shaped nuclei). The regions of interest are: neutron rich nuclei like 132-138Sn, or 48-54Ca, and the Zr, Mo, and Ru isotopes. The tools used can be grouped as follows: either Gammasphere or Gretina multi-gamma detector arrays and auxiliary detectors (Microball, Neutron Shell, and the newly completed Phoswich Wall).The neutron-rich nuclei are accessed by radioactive-beam binary reactions or by 252Cf spontaneous fission. The experiments with heavy radioactive beams aim at excitingmore » the beam nuclei by pick-up or transfer a neutron or a proton from a light target like 13C, 9Be, 11B or 14N .For these binary-reaction studies the Phoswich Wall detector system is essential. It is based on four multi-anode photomultiplier tubes on which CsI and thin fast-timing plastic scintillators are attached. Their signals are digitized with a high density microchip system.« less

Mass-independent isotope fractionation of Mo, Ru, Cd, and Te

NASA Astrophysics Data System (ADS)

Fujii, T.; Moynier, F.; Albarède, F.

2006-12-01

The variation of the mean charge distribution in the nucleus with the neutron number of different isotopes induces a tenuous shift of the nuclear field. The mass fractionation induced during phase changes is irregular, notably with 'staggering' between odd and even masses, and becomes increasingly non-linear for neutron-rich isotopes. A strong correlation is observed between the deviation of the isotopic effects from the linear dependence with mass and the corresponding nuclear charge radii. We first demonstrated on a number of elements the existence of such mass-independent isotope fractionation in laboratory experiments of solvent extraction with a macrocyclic compound. The isotope ratios were analyzed by multiple-collector inductively coupled plasma mass spectrometry with a typical precision of <100 ppm. The isotopes of odd and even atomic masses are enriched in the solvent to an extent that closely follows the variation of their nuclear charge radii. The present results fit Bigeleisen's (1996) model, which is the standard mass-dependent theory modified to include a correction term named the nuclear field shift effect. For heavy elements like uranium, the mass-independent effect is important enough to dominate the mass-dependent effect. We subsequently set out to compare the predictions of Bigeleisen's theory with the isotopic anomalies found in meteorites. Some of these anomalies are clearly inconsistent with nucleosynthetic effects (either s- or r-processes). Isotopic variations of Mo and Ru in meteorites, especially in Allende (CV3), show a clear indication of nucleosynthetic components. However, the mass-independent anomaly of Ru observed in Murchison (CM2) is a remarkable exception which cannot be explained by the nucleosynthetic model, but fits the nuclear field shift theory extremely well. The abundances of the even atomic mass Te isotopes in the leachates of carbonaceous chondrites, Allende, Murchison, and Orgueil, fit a mass-dependent law well, but the odd atomic mass isotope ^{125}Te clearly deviates from this correlation. The nuclear field shift theory shows that there is no effect on ^{130}Te but that the ^{125}Te anomaly is real. Carbonaceous chondrites do not reveal significant isotope fractionation of Cd isotopes, but a nuclear field shift effect is clearly present in type-3 (unequilibrated) ordinary chondrites. The nuclear field shift effect is temperature dependent and is probably more frequent in nature than commonly thought. It remains, together with nucleosynthetric anomalies, perfectly visible through the normalization of isotopic ratios to a reference value. In meteorites, this effect may originate both during condensation/evaporation processes in the nebular gas and during the metamorphism of the meteorite parent bodies.

Local structure of amorphous Ag5In5Sb60Te30 and In3SbTe2 phase change materials revealed by X-ray photoelectron and Raman spectroscopic studies

NASA Astrophysics Data System (ADS)

Sahu, Smriti; Manivannan, Anbarasu; Shaik, Habibuddin; Mohan Rao, G.

2017-07-01

Reversible switching between highly resistive (binary "0") amorphous phase and low resistive (binary "1") crystalline phase of chalcogenide-based Phase Change Materials is accredited for the development of next generation high-speed, non-volatile, data storage applications. The doped Sb-Te based materials have shown enhanced electrical/optical properties, compared to Ge-Sb-Te family for high-speed memory devices. We report here the local atomic structure of as-deposited amorphous Ag5In5Sb60Te30 (AIST) and In3SbTe2 (IST) phase change materials using X-ray photoelectron and Raman spectroscopic studies. Although AIST and IST materials show identical crystallization behavior, they differ distinctly in their crystallization temperatures. Our experimental results demonstrate that the local environment of In remains identical in the amorphous phase of both AIST and IST material, irrespective of its atomic fraction. In bonds with Sb (˜44%) and Te (˜56%), thereby forming the primary matrix in IST with a very few Sb-Te bonds. Sb2Te constructs the base matrix for AIST (˜63%) along with few Sb-Sb bonds. Furthermore, an interesting assimilation of the role of small-scale dopants such as Ag and In in AIST, reveals rare bonds between themselves, while showing selective substitution in the vicinity of Sb and Te. This results in increased electronegativity difference, and consequently, the bond strength is recognized as the factor rendering stability in amorphous AIST.

Incorporating Information Value into Navy Tactical Data System: System Configuration Management Through the Delphi Method

DTIC Science & Technology

1989-03-01

e"-s tcc,: -e .- r reverse of necessary an., ice-tfy by bi.-:’ ru-’ce," 5uz"ou configuration management. Delphi method. Command and Control 19 Ac-s:’a...Aos!,ac: 21 Aostraczt Security Classitcator : R uncassf~’! i~e sa-e as renc- E 0orC users Unclassified 22a Na-e of Respon’s :e iro, v c a 22o Te’eo’one...i!r’ciule A’ea coce’ 22: C’" ce . Thomnas 1’. Mitchell (4081 646-2620 155k.11i DD FORI, 1473.6.: VAR 63 A-- R e-.!c- rnay be usec~ unti exhausted se

Simultaneous observation of the gamma-ray binary LS I+61 303 with GLAST and Suzaku

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Takuya; Fukazawa, Yasushi; Mizuno, Tsunefumi

2007-07-12

The gamma-ray binary LS I+61 303 is a bright gamma-ray source, and thus an attracting object for GLAST. We proposed to observe this object with the X-ray satellite Suzaku (AO-2), simultaneously with GLAST, radio wave, and optical spectro-polarimetry, in order to probe the geometrical state of the binary system emitting the gamma-ray radiation, as a function of the binary orbital phase for the first time. This is essential to understand the mechanism of jet production and gamma-ray emission. The idea is not only to measure the multi-band overall continuum shape, but also to make use of continuous monitoring capability ofmore » GLAST, wide X-ray band of Suzaku, and good accessibility of the Kanata optical/NIR telescope (Hiroshima University) with the sensitive optical spectro-polarimetry. Further collaboration with TeV gamma-ray telescopes is also hoped to constrain the jet constitution.« less

Discussion Meeting on Thermodynamics of Alloys Held in Sant Feliu de Guixols, Spain on 23-26 May 1990. Abstracts

DTIC Science & Technology

1990-05-26

OFFICE OF THE U.S. ARMY EUROPEAN RESEARCH OFFICE OF THE U.S. AIR FORCE MINISTERIO DE EDUCACION Y CIENCIA I I Wednesday, May 23 8.30 Registration 9.00... especially regarding the structural but less the thermodynamic proper- ties). The third binary system Ag-Te has been investigated in detail by our group. No

Loaded delay lines for future RF pulse compression systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, R.M.; Wilson, P.B.; Kroll, N.M.

1995-05-01

The peak power delivered by the klystrons in the NLCRA (Next Linear Collider Test Accelerator) now under construction at SLAC is enhanced by a factor of four in a SLED-II type of R.F. pulse compression system (pulse width compression ratio of six). To achieve the desired output pulse duration of 250 ns, a delay line constructed from a 36 m length of circular waveguide is used. Future colliders, however, will require even higher peak power and larger compression factors, which favors a more efficient binary pulse compression approach. Binary pulse compression, however, requires a line whose delay time is approximatelymore » proportional to the compression factor. To reduce the length of these lines to manageable proportions, periodically loaded delay lines are being analyzed using a generalized scattering matrix approach. One issue under study is the possibility of propagating two TE{sub o} modes, one with a high group velocity and one with a group velocity of the order 0.05c, for use in a single-line binary pulse compression system. Particular attention is paid to time domain pulse degradation and to Ohmic losses.« less

Observation of the black widow B1957+20 millisecond pulsar binary system with the MAGIC telescopes

NASA Astrophysics Data System (ADS)

Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Arcaro, C.; Babić, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carosi, R.; Carosi, A.; Chatterjee, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Cumani, P.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; De Oña Wilhelmi, E.; Di Pierro, F.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Gozzini, S. R.; Griffiths, S.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Sillanpää, A.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D. F.; Torres-Albà, N.; Treves, A.; Vanzo, G.; Vazquez Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zarić, D.; MAGIC Collaboration; Cognard, I.; Guillemot, L.

2017-10-01

B1957+20 is a millisecond pulsar located in a black-widow-type compact binary system with a low-mass stellar companion. The interaction of the pulsar wind with the companion star wind and/or the interstellar plasma is expected to create plausible conditions for acceleration of electrons to TeV energies and subsequent production of very high-energy γ-rays in the inverse Compton process. We performed extensive observations with the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) telescopes of B1957+20. We interpret results in the framework of a few different models, namely emission from the vicinity of the millisecond pulsar, the interaction of the pulsar and stellar companion wind region or bow shock nebula. No significant steady very high-energy γ-ray emission was found. We derived a 95 per cent confidence level upper limit of 3.0 × 10-12 cm-2 s-1 on the average γ-ray emission from the binary system above 200 GeV. The upper limits obtained with the MAGIC constrain, for the first time, different models of the high-energy emission in B1957+20. In particular, in the inner mixed wind nebula model with mono-energetic injection of electrons, the acceleration efficiency of electrons is constrained to be below ˜2-10 per cent of the pulsar spin-down power. For the pulsar emission, the obtained upper limits for each emission peak are well above the exponential cut-off fits to the Fermi-LAT data, extrapolated to energies above 50 GeV. The MAGIC upper limits can rule out a simple power-law tail extension through the sub-TeV energy range for the main peak seen at radio frequencies.

The ultrasound-assisted oxidative scission of monoenic fatty acids by ruthenium tetroxide catalysis: influence of the mixture of solvents.

PubMed

Rup, Sandrine; Zimmermann, François; Meux, Eric; Schneider, Michel; Sindt, Michele; Oget, Nicolas

2009-02-01

Carboxylic acids and diacids were synthesized from monoenic fatty acids by using RuO4 catalysis, under ultrasonic irradiation, in various mixtures of solvents. Ultrasound associated with Aliquat 336 have promoted in water, the quantitative oxidative cleavage of the CH=CH bond of oleic acid. A design of experiment (DOE) shows that the optimal mixture of solvents (H2O/MeCN, ratio 1/1, 2.2% RuCl3/4.1 eq. NaIO4) gives 81% azelaic acid and 97% pelargonic acid. With the binary heterogeneous mixture H2O/AcOEt, the oxidation of the oleic acid leads to a third product, the alpha-dione 9,10-dioxostearic acid.

Structural studies of Bi 2 O 3 -Nb 2 O 5 -TeO 2 glasses

DOE PAGES

Wilding, Martin C.; Delaizir, Gaelle; Benmore, Chris J.; ...

2016-07-25

Bi 2O 3-Nb 2O 5-TeO 2 glasses show unusual annealing behavior with appearance of spherulites within the matrix glass structure for the Bi 0.5Nb 0.5Te 3O 8 composition. The textures resemble those found previously among polyamorphic Al 2O 3-Y 2O 3 glasses containing metastably co-existing high- and low-density phases produced during quenching. However the spherulites produced within the Bi 2O 3-Nb 2O 5-TeO 2 glass are crystalline and can be identified as an “anti-glass” phase related to β-Bi 2Te 4O 11. Here, we used high energy synchrotron X-ray diffraction data to study structures of binary and ternary glasses quenched frommore » liquids within the Bi 2O 3-Nb 2O 5-TeO 2 system. These reveal a glassy network based on interconnected TeO 4 and TeO 3 units that is related to TeO 2 crystalline materials but with larger Te…Te separations due to the presence of TeO 3 groups and non-bridging oxygens linked to modifier (Bi 3 +, Nb 5 +) cations. Analysis of the viscosity-temperature relations indicates that the glass-forming liquids are “fragile” and there is no evidence for a LLPT occurring in the supercooled liquid. The glasses obtained by quenching likely correspond to a high-density amorphous (HDA) state. Subsequent annealing above T g shows mainly evidence for direct crystallization of the “anti-glass” tellurite phase. But, some evidence may exist for simultaneous formation of nanoscale amorphous spherulites that could correspond to the LDA polyamorph. The quenching and annealing behavior of Bi 2O 3-Nb 2O 5-TeO 2 supercooled liquids and glasses is compared with similar materials in the Al 2O 3-Y 2O 3 system.« less

Reactivity of O2 on Pd/Ru(0001) and PdRu/Ru(0001) surface alloys

NASA Astrophysics Data System (ADS)

Farías, D.; Minniti, M.; Miranda, R.

2017-05-01

The reactivity of a Pd monolayer epitaxially grown on Ru(0001) toward O2 has been investigated by molecular beam techniques. O2 initial sticking coefficients were determined using the King and Wells method in the incident energy range of 40-450 meV and for sample temperatures of 100 K and 300 K, and compared to the corresponding values measured on the clean Ru(0001) and Pd(111) surfaces. In contrast to the high reactivity shown by Ru(0001) at 100 K, the Pd/Ru(0001) system exhibits a monotonic decrease in the sticking probability of O2 as a function of normal incident energy. At room temperature, the system was found to be inert. Thermal desorption measurements show that O2 is adsorbed molecularly at 100 K. A completely different behaviour has been measured for the Pd0.95Ru0.05/Ru(0001) surface alloy. On this surface, the O2 sticking probability increases with incident energy and resembles the one observed on the clean Ru(0001) surface, even at 300 K. Thermal desorption measurements point to dissociative adsorption of O2 in this system. Both the charge transfer from the Pd to the Ru substrate and the compressive strain on the Pd monolayer contribute to decrease in the reactivity of the Pd/Ru(0001) system well below those of both Ru(0001) and Pd(111).

H.E.S.S. observations of the binary system PSR B1259-63/LS 2883 around the 2010/2011 periastron passage

NASA Astrophysics Data System (ADS)

H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chaves, R. C. G.; Cheesebrough, A.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Göring, D.; Grondin, M.-H.; Grudzińska, M.; Häer, S.; Hague, J. D.; Hahn, J.; Hampf, D.; Harris, J.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Krayzel, F.; Krüger, P. P.; Lan, H.; Lamanna, G.; Lefaucheur, J.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Menzler, U.; Moderski, R.; Mohamed, M.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nguyen, N.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sheidaei, F.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Willmann, P.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

2013-03-01

Aims: We present very high energy (VHE; E > 100 GeV) data from the γ-ray binary system PSR B1259-63/LS 2883 taken around its periastron passage on 15th of December 2010 with the High Energy Stereoscopic System (H.E.S.S.) of Cherenkov Telescopes. We aim to search for a possible TeV counterpart of the GeV flare detected by the Fermi LAT. In addition, we aim to study the current periastron passage in the context of previous observations taken at similar orbital phases, testing the repetitive behaviour of the source. Methods: Observations at VHEs were conducted with H.E.S.S. from 9th to 16th of January 2011. The total dataset amounts to ~6 h of observing time. The data taken around the 2004 periastron passage were also re-analysed with the current analysis techniques in order to extend the energy spectrum above 3 TeV to fully compare observation results from 2004 and 2011. Results: The source is detected in the 2011 data at a significance level of 11.5σ revealing an averaged integral flux above 1 TeV of (1.01 ± 0.18stat ± 0.20sys) × 10-12 cm-2 s-1. The differential energy spectrum follows a power-law shape with a spectral index Γ = 2.92 ± 0.30stat ± 0.20sys and a flux normalisation at 1 TeV of N0 = (1.95 ± 0.32stat ± 0.39sys) × 10-12 TeV-1 cm-2 s-1. The measured light curve does not show any evidence for variability of the source on the daily scale. The re-analysis of the 2004 data yields results compatible with the published ones. The differential energy spectrum measured up to ~10 TeV is consistent with a power law with a spectral index Γ = 2.81 ± 0.10stat ± 0.20sys and a flux normalisation at 1 TeV of N0 = (1.29 ± 0.08stat ± 0.26sys) × 10-12 TeV-1 cm-2 s-1. Conclusions: The measured integral flux and the spectral shape of the 2011 data are compatible with the results obtained around previous periastron passages. The absence of variability in the H.E.S.S. data indicates that the GeV flare observed by Fermi LAT in the time period covered also by H.E.S.S. observations originates in a different physical scenario than the TeV emission. Moreover, the comparison of the new results to the results from the 2004 observations made at a similar orbital phase provides a stronger evidence of the repetitive behaviour of the source.

PIPSI/Navy - Rapid Evaluation of Propulsion System Effects for the Navy Gas Turbine Engine Code, NEPCOMP

DTIC Science & Technology

1979-10-11

E.TqIE’JI*c*H* rt IaT F : rti5’ :TFL’-1H E’rl-aFiw liSsTFI’JIt1 riSET.Ir’ 11cisar1 tnt .L Qsa 41W HLUTEEST rU I- AUE DF 1 N(..’t’FE. HUIETO T A ’E...TE’STOLIT UScEF.: LJFABF1’ WPi:Sri281TTY F. ILEES(S) READ’,~ 3FILE NAME FILE CONTENTS BOEING1 Dry Turbofan Engine Uninstalled Data BOEING2 Afterburning ...Turbofan Engine Uninstalled Data BONGTJD Dry Turbojet Engine Uninstalled Data £BONGTJW Afterburning Turbojet Engine Uninstalled Data NADC7 Source Deck

FERMI STUDY OF 5–300 GeV EMISSION FROM THE HIGH-MASS PULSAR BINARY PSR B1259-63/LS 2883

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xing, Yi; Wang, Zhongxiang; Takata, Jumpei

2016-09-01

We report the results from our detailed analysis of the Fermi Large Area Telescope data for the pulsar binary PSR B1259−63/LS 2883. During the GeV flares that occurred when the pulsar was in the periastron passages, we have detected a 5–300 GeV component at ≃5 σ in emission from the binary. The detection verifies the presence of the component that has been marginally found in previous studies of the binary. Furthermore, we have discovered that this component was marginally present even in the quiescent state of the binary, specifically the mean anomaly phase 0.7–0.9. The component can be described bymore » a power law with a photon index Γ ∼ 1.4, and the flux in the flares is approximately one order of magnitude higher than that in quiescence. We discuss the origin of this component. It likely arises from the inverse-Compton process: due to the interaction between the winds from the pulsar and its massive companion, high-energy particles from the shock scatter the seed photons from the companion to GeV/TeV energies. Based on this scenario, model fits to the broad-band X-ray to TeV spectra of the binary in the flaring and quiescent states are provided.« less

Effects of Norfolk Harbor Deepening on Management of Craney Island Disposal Area.

DTIC Science & Technology

1983-04-01

VICKSBURG MS ENVIRONMENTAL LAB UNCLASSIFIED D F HAVES 01 APR 03 F/G 13/2 N smmmhhhhhhhhh smhmhhhhhomhl Ehhhhhhmhrnmm .4’ -Te SIBM 11-25 -A MIROOP RU4TT-oif...CLASSIFICATION OUNCLASSIFIEUNUMTED 1l SAMEAS ItP . C0 W USERS Unclasslfteg 22a. NAME OF RESPONSIBLE INDIVIDUAL 22b. TtLE VOtElA. Ale Code) U&, OfFICE

Improved electron density through hetero-junction binary sensitized TiO2/ CdTe / D719 system as photoanode for dye sensitized solar cell

NASA Astrophysics Data System (ADS)

Pandey, A. K.; Ahmad, Muhammad Shakeel; Alizadeh, Mahdi; Rahim, Nasrudin Abd

2018-07-01

The combined effect of dual sensitization and hetero-junction symmetry has been investigated on the performance of TiO2 based dye sensitized solar cell. CdTe nanoparticles have been introduced in TiO2 matrix to function as sensitizer as well as act as hetero-junction between D719 dye and TiO2 nanoarchitecture. Four concentrations of CdTe i.e. 0.5 wt%, 2 wt%, 5 wt% and 8 wt% have been investigated. Morphological and compositional studies have been conducted using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. Light absorption characteristics have been investigated by employing Uv-vis spectroscopy and the overall performance has been studied using solar simulator and electrochemical impedance spectroscopy (EIS). Performance has been found to be increased with the addition of CdTe due to high electron density and reduction in recombination reactions. An increase of 41.73% in incident photo conversion efficiency (IPCE) and 75.57% in short circuit current density (Jsc) have been recorded for the specimens containing 5 wt% CdTe compared to bare TiO2 based DSSCs. Further addition of CdTe leads to reduction in overall performance of DSSCs.

Systematic approach for simultaneously correcting the band-gap and p - d separation errors of common cation III-V or II-VI binaries in density functional theory calculations within a local density approximation

DOE PAGES

Wang, Jianwei; Zhang, Yong; Wang, Lin-Wang

2015-07-31

We propose a systematic approach that can empirically correct three major errors typically found in a density functional theory (DFT) calculation within the local density approximation (LDA) simultaneously for a set of common cation binary semiconductors, such as III-V compounds, (Ga or In)X with X = N,P,As,Sb, and II-VI compounds, (Zn or Cd)X, with X = O,S,Se,Te. By correcting (1) the binary band gaps at high-symmetry points , L, X, (2) the separation of p-and d-orbital-derived valence bands, and (3) conduction band effective masses to experimental values and doing so simultaneously for common cation binaries, the resulting DFT-LDA-based quasi-first-principles methodmore » can be used to predict the electronic structure of complex materials involving multiple binaries with comparable accuracy but much less computational cost than a GW level theory. This approach provides an efficient way to evaluate the electronic structures and other material properties of complex systems, much needed for material discovery and design.« less

Systematic approach for simultaneously correcting the band-gap and p -d separation errors of common cation III-V or II-VI binaries in density functional theory calculations within a local density approximation

NASA Astrophysics Data System (ADS)

Wang, Jianwei; Zhang, Yong; Wang, Lin-Wang

2015-07-01

We propose a systematic approach that can empirically correct three major errors typically found in a density functional theory (DFT) calculation within the local density approximation (LDA) simultaneously for a set of common cation binary semiconductors, such as III-V compounds, (Ga or In)X with X =N ,P ,As ,Sb , and II-VI compounds, (Zn or Cd)X , with X =O ,S ,Se ,Te . By correcting (1) the binary band gaps at high-symmetry points Γ , L , X , (2) the separation of p -and d -orbital-derived valence bands, and (3) conduction band effective masses to experimental values and doing so simultaneously for common cation binaries, the resulting DFT-LDA-based quasi-first-principles method can be used to predict the electronic structure of complex materials involving multiple binaries with comparable accuracy but much less computational cost than a GW level theory. This approach provides an efficient way to evaluate the electronic structures and other material properties of complex systems, much needed for material discovery and design.

Testing Modified Gravity Theories via Wide Binaries and GAIA

NASA Astrophysics Data System (ADS)

Pittordis, Charalambos; Sutherland, Will

2018-06-01

The standard ΛCDM model based on General Relativity (GR) including cold dark matter (CDM) is very successful at fitting cosmological observations, but recent non-detections of candidate dark matter (DM) particles mean that various modified-gravity theories remain of significant interest. The latter generally involve modifications to GR below a critical acceleration scale ˜10-10 m s-2. Wide-binary (WB) star systems with separations ≳ 5 kAU provide an interesting test for modified gravity, due to being in or near the low-acceleration regime and presumably containing negligible DM. Here, we explore the prospects for new observations pending from the GAIA spacecraft to provide tests of GR against MOND or TeVes-like theories in a regime only partially explored to date. In particular, we find that a histogram of (3D) binary relative velocities, relative to equilibrium circular velocity predicted from the (2D) projected separation predicts a rather sharp feature in this distribution for standard gravity, with an 80th (90th) percentile value close to 1.025 (1.14) with rather weak dependence on the eccentricity distribution. However, MOND/TeVeS theories produce a shifted distribution, with a significant increase in these upper percentiles. In MOND-like theories without an external field effect, there are large shifts of order unity. With the external field effect included, the shifts are considerably reduced to ˜0.04 - 0.08, but are still potentially detectable statistically given reasonably large samples and good control of contaminants. In principle, followup of GAIA-selected wide binaries with ground-based radial velocities accurate to ≲ 0.03 { km s^{-1}} should be able to produce an interesting new constraint on modified-gravity theories.

Some properties of low-vapor-pressure braze alloys for thermionic converters

NASA Technical Reports Server (NTRS)

Bair, V. L.

1978-01-01

Density, dc electrical resistivity, thermal conductivity, and linear thermal expansion are measured for arc-melted rod-shaped samples of binary eutectics of Zr, Hf, Ru, Nb, Ir, Mo, Ta, Os, Re, and W selected as very-low-pressure braze fillers for thermionic converters. The first two properties are measured at 296 K for Zr-21.7 at% Ru, Zr-13 wt% W, Zr-19 wt% W, Zr-22.3 at% Nb, Nb-66.9 at% Ru, Hf-25.3 wt% Re, Zr-25.7 at% Ta, Hf-22.5 at% W, and Nb-35 wt% Mo. The last property is measured from 293 K to 2/3 melting point for specified alloys of different compositions. Resistivities of 0.000055 to 0.000181 ohm-cm are observed with the alloys having resistivities about ten times that of the less resistive constituent metal and about three times that of the more resistive constituent metal, except for Zr-19 wt% W and Nb-35 wt% Mo (greater resistivities). Thermal expansion coefficients vary from 0.000006 to 0.0000105/K. All brazes exhibit linear thermal expansion near that of their constituent metals.

Associating Long-term Gamma-ray Variability with the Superorbital Period of LS I + 61 Deg. 303

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bonamente, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.;

Searches for Periodic Neutrino Emission from Binary Systems with 22 and 40 Strings of IceCube

NASA Technical Reports Server (NTRS)

Abassi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Allen, M. M.; Altmann, D.; Andeen, K.;

Superconductivity in YTE2Ge2 compounds (TE = d-electron transition metal)

NASA Astrophysics Data System (ADS)

Chajewski, G.; Samsel-Czekała, M.; Hackemer, A.; Wiśniewski, P.; Pikul, A. P.; Kaczorowski, D.

2018-05-01

Polycrystalline samples of YTE2Ge2 with TE = Co, Ni, Ru, Rh, Pd and Pt were synthesized and characterized by means of X-ray powder diffraction and low-temperature electrical resistivity and specific heat measurements, supplemented by fully relativistic full-potential local-orbital band structure calculations. We confirm that most of the compounds studied crystallize in a body-centered tetragonal ThCr2S2 -type structure (space group I 4 / mmm) and have three-dimensional Fermi surfaces, while only one of them (YPt2Ge2) forms with a primitive tetragonal CaBe2Ge2 -type unit cell (space group P 4 / nmm) and possesses quasi-two-dimensional Fermi surface sheets with some nesting. Physical properties data show conventional superconductivity in the phases with TE = Co, Pd and Pt, i.e. independently of the structure type (and hence the dimensionality of the Fermi surface).

A C-Te-based binary OTS device exhibiting excellent performance and high thermal stability for selector application.

PubMed

Chekol, Solomon Amsalu; Yoo, Jongmyung; Park, Jaehyuk; Song, Jeonghwan; Sung, Changhyuck; Hwang, Hyunsang

2018-08-24

In this letter, we demonstrate a new binary ovonic threshold switching (OTS) selector device scalable down to ø30 nm based on C-Te. Our proposed selector device exhibits outstanding performance such as a high switching ratio (I on /I off  > 10 5 ), an extremely low off-current (∼1 nA), an extremely fast operating speed of <10 ns (transition time of <2 ns and delay time of <8 ns), high endurance (10 9 ), and high thermal stability (>450 °C). The observed high thermal stability is caused by the relatively small atomic size of C, compared to Te, which can effectively suppress the segregation and crystallization of Te in the OTS film. Furthermore, to confirm the functionality of the selector in a crossbar array, we evaluated a 1S-1R device by integrating our OTS device with a ReRAM (resistive random access memory) device. The 1S-1R integrated device exhibits a successful suppression of leakage current at the half-selected cell and shows an excellent read-out margin (>2 12 word lines) in a fast read operation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Min Ho; Rhyee, Jong-Soo, E-mail: jsrhyee@khu.ac.kr

We investigated the thermoelectric properties of PbTe/Ag{sub 2}Te bulk composites, synthesized by hand milling, mixing, and hot press sintering. From x-ray diffraction and energy dispersive x-ray spectroscopy measurements, we observed Ag{sub 2}Te phase separation in the PbTe matrix without Ag atom diffusion. In comparison with previously reported pseudo-binary (PbTe){sub 1−x}(Ag{sub 2}Te){sub x} composites, synthesized by high temperature phase separation, the PbTe/Ag{sub 2}Te bulk composites fabricated with a low temperature phase mixing process give rise to p-type conduction of carriers with significantly decreased electrical conductivity. This indicates that Ag atom diffusion in the PbTe matrix changes the sign of the Seebeckmore » coefficient to n-type and also increases the carrier concentration. Effective p-type doping with low temperature phase separation by mixing and hot press sintering can enhance the thermoelectric performance of PbTe/Ag{sub 2}Te bulk composites, which can be used as a p-type counterpart of n-type (PbTe){sub 1−x}(Ag{sub 2}Te){sub x} bulk composites.« less

Ultra high energy gamma rays, cosmic rays and neutrinos from accreting degenerate stars

NASA Technical Reports Server (NTRS)

Brecher, K.; Chanmugam, G.

1985-01-01

Super-Eddington accretion for a recently proposed unipolar induction model of cosmic ray acceleration in accreting binary star systems containing magnetic white dwarfs or neutron stars is considered. For sufficiently high accretion rates and low magnetic fields, the model can account for: (1) acceleration of cosmic ray nuclei up to energies of 10 to the 19th power eV; (2) production of more or less normal solar cosmic ray composition; (3) the bulk of cosmic rays observed with energies above 1 TeV, and probably even down to somewhat lower energies as well; and (4) possibly the observed antiproton cosmic ray flux. It can also account for the high ultra high energy (UHE) gamma ray flux observed from several accreting binary systems (including Cygnus X-3), while allowing the possibility of an even higher neutrino flux from these sources, with L sub nu/L sub gamma is approximately 100.

Detection of variable VHE γ-ray emission from the extra-galactic γ-ray binary LMC P3

NASA Astrophysics Data System (ADS)

HESS Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Angüner, E. O.; Arakawa, M.; Armand, C.; Arrieta, M.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Caroff, S.; Carosi, A.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Colafrancesco, S.; Condon, B.; Conrad, J.; Davids, I. D.; Decock, J.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Donath, A.; Drury, L. O.'C.; Dyks, J.; Edwards, T.; Egberts, K.; Emery, G.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Funk, S.; Füßling, M.; Gabici, S.; Gallant, Y. A.; Garrigoux, T.; Gaté, F.; Giavitto, G.; Glawion, D.; Glicenstein, J. F.; Gottschall, D.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lefaucheur, J.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Malyshev, D.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Ndiyavala, H.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poireau, V.; Prokhorov, D. A.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Rauth, R.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rinchiuso, L.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Shiningayamwe, K.; Simoni, R.; Sol, H.; Spanier, F.; Spir-Jacob, M.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steppa, C.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsirou, M.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Zorn, J.; Żywucka, N.

2018-03-01

Context. Recently, the high-energy (HE, 0.1-100 GeV) γ-ray emission from the object LMC P3 in the Large Magellanic Cloud (LMC) has been discovered to be modulated with a 10.3-day period, making it the first extra-galactic γ-ray binary. Aim. This work aims at the detection of very-high-energy (VHE, >100 GeV) γ-ray emission and the search for modulation of the VHE signal with the orbital period of the binary system. Methods: LMC P3 has been observed with the High Energy Stereoscopic System (H.E.S.S.); the acceptance-corrected exposure time is 100 h. The data set has been folded with the known orbital period of the system in order to test for variability of the emission. Results: VHE γ-ray emission is detected with a statistical significance of 6.4 σ. The data clearly show variability which is phase-locked to the orbital period of the system. Periodicity cannot be deduced from the H.E.S.S. data set alone. The orbit-averaged luminosity in the 1-10 TeV energy range is (1.4 ± 0.2) × 1035 erg s-1. A luminosity of (5 ± 1) × 1035 erg s-1 is reached during 20% of the orbit. HE and VHE γ-ray emissions are anti-correlated. LMC P3 is the most luminous γ-ray binary known so far.

Detection of variable VHE γ -ray emission from the extra-galactic γ -ray binary LMC P3

DOE PAGES

Abdalla, H.; Abramowski, A.; Aharonian, F.; ...

2018-02-01

Context. Recently, the high-energy (HE, 0.1–100 GeV) γ-ray emission from the object LMC P3 in the Large Magellanic Cloud (LMC) has been discovered to be modulated with a 10.3-day period, making it the first extra-galactic γ-ray binary. Aim. This work aims at the detection of very-high-energy (VHE, >100 GeV) γ-ray emission and the search for modulation of the VHE signal with the orbital period of the binary system. Methods. LMC P3 has been observed with the High Energy Stereoscopic System (H.E.S.S.); the acceptance-corrected exposure time is 100 h. The data set has been folded with the known orbital period ofmore » the system in order to test for variability of the emission. Results. VHE γ-ray emission is detected with a statistical significance of 6.4 σ. The data clearly show variability which is phase-locked to the orbital period of the system. Periodicity cannot be deduced from the H.E.S.S. data set alone. The orbit-averaged luminosity in the 1–10 TeV energy range is (1.4 ± 0.2) × 1035 erg s -1. A luminosity of (5 ± 1) × 1035 erg s -1 is reached during 20% of the orbit. HE and VHE γ-ray emissions are anti-correlated. In conclucion, LMC P3 is the most luminous γ-ray binary known so far.« less

Detection of variable VHE γ -ray emission from the extra-galactic γ -ray binary LMC P3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdalla, H.; Abramowski, A.; Aharonian, F.

Context. Recently, the high-energy (HE, 0.1–100 GeV) γ-ray emission from the object LMC P3 in the Large Magellanic Cloud (LMC) has been discovered to be modulated with a 10.3-day period, making it the first extra-galactic γ-ray binary. Aim. This work aims at the detection of very-high-energy (VHE, >100 GeV) γ-ray emission and the search for modulation of the VHE signal with the orbital period of the binary system. Methods. LMC P3 has been observed with the High Energy Stereoscopic System (H.E.S.S.); the acceptance-corrected exposure time is 100 h. The data set has been folded with the known orbital period ofmore » the system in order to test for variability of the emission. Results. VHE γ-ray emission is detected with a statistical significance of 6.4 σ. The data clearly show variability which is phase-locked to the orbital period of the system. Periodicity cannot be deduced from the H.E.S.S. data set alone. The orbit-averaged luminosity in the 1–10 TeV energy range is (1.4 ± 0.2) × 1035 erg s -1. A luminosity of (5 ± 1) × 1035 erg s -1 is reached during 20% of the orbit. HE and VHE γ-ray emissions are anti-correlated. In conclucion, LMC P3 is the most luminous γ-ray binary known so far.« less

Hydrodynamic Interaction between the Be Star and the Pulsar in the TeV Binary PSR B1259-63/LS 2883

NASA Astrophysics Data System (ADS)

Okazaki, Atsuo T.; Nagataki, Shigehiro; Naito, Tsuguya; Kawachi, Akiko; Hayasaki, Kimitake; Owocki, Stanley P.; Takata, Jumpei

2011-08-01

We have been studying the interaction between the Be star and the pulsar in the TeV binary PSR B1259-63/LS 2883, using 3-D SPH simulations of the tidal and wind interactions in this Be-pulsar system. We first ran a simulation without pulsar wind nor Be wind, while taking into account only the gravitational effect of the pulsar on the Be disk. In this simulation, the gas particles are ejected at a constant rate from the equatorial surface of the Be star, which is tilted in a direction consistent with multi-waveband observations. We ran the simulation until the Be disk was fully developed and started to repeat a regular tidal interaction with the pulsar. Then, we turned on the pulsar wind and the Be wind. We ran two simulations with different wind mass-loss rates for the Be star, one for a B2 V type and the other for a significantly earlier spectral type. Although the global shape of the interaction surface between the pulsar wind and the Be wind agrees with the analytical solution, the effect of the pulsar wind on the Be disk is profound. The pulsar wind strips off an outer part of the Be disk, truncating the disk at a radius significantly smaller than the pulsar orbit. Our results, therefore, rule out the idea that the pulsar passes through the Be disk around periastron, which has been assumed in previous studies. It also turns out that the location of the contact discontinuity can be significantly different between phases when the pulsar wind directly hits the Be disk and those when the pulsar wind collides with the Be wind. It is thus important to adequately take into account the circumstellar environment of the Be star, in order to construct a satisfactory model for this prototypical TeV binary.

Constraints on particle acceleration in SS433/W50 from MAGIC and H.E.S.S. observations

NASA Astrophysics Data System (ADS)

MAGIC Collaboration; Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Arcaro, C.; Babić, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Carosi, R.; Carosi, A.; Chatterjee, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Cumani, P.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; de Oña Wilhelmi, E.; di Pierro, F.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Griffiths, S.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Oramas, A.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Minev, M.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Munar-Adrover, P.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D. F.; Torres-Albà, N.; Treves, A.; Vanzo, G.; Vazquez Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zarić, D.; H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; Dewilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'c.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de Los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Safi-Harb, S.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Zywucka, N.

2018-04-01

Context. The large jet kinetic power and non-thermal processes occurring in the microquasar SS 433 make this source a good candidate for a very high-energy (VHE) gamma-ray emitter. Gamma-ray fluxes above the sensitivity limits of current Cherenkov telescopes have been predicted for both the central X-ray binary system and the interaction regions of SS 433 jets with the surrounding W50 nebula. Non-thermal emission at lower energies has been previously reported, indicating that efficient particle acceleration is taking place in the system. Aim. We explore the capability of SS 433 to emit VHE gamma rays during periods in which the expected flux attenuation due to periodic eclipses (Porb 13.1 days) and precession of the circumstellar disk (Ppre 162 days) periodically covering the central binary system is expected to be at its minimum. The eastern and western SS 433/W50 interaction regions are also examined using the whole data set available. We aim to constrain some theoretical models previously developed for this system with our observations. Methods: We made use of dedicated observations from the Major Atmospheric Gamma Imaging Cherenkov telescopes (MAGIC) and High Energy Spectroscopic System (H.E.S.S.) of SS 433 taken from 2006 to 2011. These observation were combined for the first time and accounted for a total effective observation time of 16.5 h, which were scheduled considering the expected phases of minimum absorption of the putative VHE emission. Gamma-ray attenuation does not affect the jet/medium interaction regions. In this case, the analysis of a larger data set amounting to 40-80 h, depending on the region, was employed. Results: No evidence of VHE gamma-ray emission either from the central binary system or from the eastern/western interaction regions was found. Upper limits were computed for the combined data set. Differential fluxes from the central system are found to be ≲ 10-12-10-13 TeV-1 cm-2 s-1 in an energy interval ranging from few × 100 GeV to few TeV. Integral flux limits down to 10-12-10-13 ph cm-2 s-1 and 10-13-10-14 ph cm-2 s-1 are obtainedat 300 and 800 GeV, respectively. Our results are used to place constraints on the particle acceleration fraction at the inner jetregions and on the physics of the jet/medium interactions. Conclusions: Our findings suggest that the fraction of the jet kinetic power that is transferred to relativistic protons must be relatively small in SS 433, qp ≤ 2.5 × 10-5, to explain the lack of TeV and neutrino emission from the central system. At the SS 433/W50 interface, the presence of magnetic fields ≳10 μG is derived assuming a synchrotron origin for the observed X-ray emission. This also implies the presence of high-energy electrons with Ee- up to 50 TeV, preventing an efficient production of gamma-ray fluxes in these interaction regions.

The isothermal section of Gd-Ni-Si system at 1070 K

NASA Astrophysics Data System (ADS)

Morozkin, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Manfrinetti, P.; Pani, M.; Provino, A.; Nirmala, R.; Quezado, S.; Malik, S. K.

2016-03-01

The Gd-Ni-Si system has been investigated at 1070 K by X-ray and microprobe analyses. The existence of the known compounds, i.e.: GdNi10Si2, GdNi8Si3, GdNi5Si3, GdNi7Si6, GdNi6Si6, GdNi4Si, GdNi2Si2, GdNiSi3, Gd3Ni6Si2, GdNiSi, GdNiSi2, GdNi0.4Si1.6, Gd2Ni2.35Si0.65, Gd3NiSi2, Gd3NiSi3 and Gd6Ni1.67Si3, has been confirmed. Moreover, five new phases have been identified in this system. The crystal structure for four of them has been determined: Gd2Ni16-12.8Si1-4.2 (Th2Zn17-type), GdNi6.6Si6 (GdNi7Si6-type), Gd3Ni8Si (Y3Co8Si-type) and Gd3Ni11.5Si4.2(Gd3Ru4Ga12-type). The compound with composition ~Gd2Ni4Si3 still remains with unknown structure. Quasi-binary phases, solid solutions, were detected at 1070 K to be formed by the binaries GdNi5, GdNi3, GdNi2, GdNi, GdSi2 and GdSi1.67; while no appreciable solubility was observed for the other binary compounds of the Gd-Ni-Si system. Magnetic properties of the GdNi6Si6, GdNi6.6Si6 and Gd3Ni11.5Si4.2 compounds have also been investigated and are here reported.

HESS J1844-030: A New Gamma-Ray Binary?

NASA Astrophysics Data System (ADS)

McCall, Hannah; Errando, Manel

2018-01-01

Gamma-ray binaries are comprised of a massive, main-sequence star orbiting a neutron star or black hole that generates bright gamma-ray emission. Only six of these systems have been discovered. Here we report on a candidate stellar-binary system associated with the unidentified gamma-ray source HESS J1844-030, whose detection was revealed in the H.E.S.S. galactic plane survey. Analysis of 60 ks of archival Chandra data and over 100 ks of XMM-Newton data reveal a spatially associated X-ray counterpart to this TeV-emitting source (E>1012 eV), CXO J1845-031. The X-ray spectra derived from these exposures yields column density absorption in the range nH = (0.4 - 0.7) x 1022 cm-2, which is below the total galactic value for that part of the sky, indicating that the source is galactic. The flux from CXO J1845-031 increases with a factor of up to 2.5 in a 60 day timescale, providing solid evidence for flux variability at a confidence level exceeding 7 standard deviations. The point-like nature of the source, the flux variability of the nearby X-ray counterpart, and the low column density absorption are all indicative of a binary system. Once confirmed, HESS J1844-030 would represent only the seventh known gamma-ray binary, providing valuable data to advance our understanding of the physics of pulsars and stellar winds and testing high-energy astrophysical processes at timescales not present in other classes of objects.

Average and recommended half-life values for two neutrino double beta decay: Upgrade-2013

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barabash, A. S.

2013-12-30

All existing positive results on two neutrino double beta decay in different nuclei were analyzed. Using the procedure recommended by the Particle Data Group, weighted average values for half-lives of {sup 48}Ca, {sup 76}Ge, {sup 82}Se, {sup 96}Zr, {sup 100}Mo, {sup 100}Mo−{sup 100}Ru (0{sub 1}{sup +}), {sup 116}Cd, {sup 130}Te, {sup 136}Xe, {sup 150}Nd, {sup 150}Nd−{sup 150}Sm (0{sub 1}{sup +}) and {sup 238}U were obtained. Existing geochemical data were analyzed and recommended values for half-lives of {sup 128}Te and {sup 130}Ba are proposed. I recommend the use of these results as the most currently reliable values for half-lives.

Spin-powered Pulsars in the CTA Era

NASA Astrophysics Data System (ADS)

Romani, Roger W.

2016-04-01

What can CTA do for the study of isolated and binary neutron stars? Are the recent Crab observations the vanguard of numerous strong pulsed detections in the CTA era? Will the typical pulsar show only the tail of the Fermi spectrum? Or will we be tantalized by a handful of new unusual sources? I review our current HE picture and suggest that pulsar binaries represent a new TeV frontier.

NIR-Emitting Alloyed CdTeSe QDs and Organic Dye Assemblies: A Nontoxic, Stable, and Efficient FRET System.

PubMed

Ramírez-Herrera, Doris E; Rodríguez-Velázquez, Eustolia; Alatorre-Meda, Manuel; Paraguay-Delgado, Francisco; Tirado-Guízar, Antonio; Taboada, Pablo; Pina-Luis, Georgina

2018-04-11

In the present work, we synthesize Near Infrared (NIR)-emitting alloyed mercaptopropionic acid (MPA)-capped CdTeSe quantum dots (QDs) in a single-step one-hour process, without the use of an inert atmosphere or any pyrophoric ligands. The quantum dots are water soluble, non-toxic, and highly photostable and have high quantum yields (QYs) up to 84%. The alloyed MPA-capped CdTeSe QDs exhibit a red-shifted emission, whose color can be tuned between visible and NIR regions (608-750 nm) by controlling the Te:Se molar ratio in the precursor mixtures and/or changing the time reaction. The MPA-capped QDs were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and zeta potential measurements. Photostability studies were performed by irradiating the QDs with a high-power xenon lamp. The ternary MPA-CdTeSe QDs showed greater photostability than the corresponding binary MPA-CdTe QDs. We report the Förster resonance energy transfer (FRET) from the MPA-capped CdTeSe QDs as energy donors and Cyanine5 NHS-ester (Cy5) dye as an energy acceptor with efficiency ( E ) up to 95%. The distance between the QDs and dye ( r ), the Förster distance ( R ₀), and the binding constant ( K ) are reported. Additionally, cytocompatibility and cell internalization experiments conducted on human cancer cells (HeLa) cells revealed that alloyed MPA-capped CdTeSe QDs are more cytocompatible than MPA-capped CdTe QDs and are capable of ordering homogeneously all over the cytoplasm, which allows their use as potential safe, green donors for biological FRET applications.

NIR-Emitting Alloyed CdTeSe QDs and Organic Dye Assemblies: A Nontoxic, Stable, and Efficient FRET System

PubMed Central

Ramírez-Herrera, Doris E.; Rodríguez-Velázquez, Eustolia; Alatorre-Meda, Manuel; Paraguay-Delgado, Francisco; Tirado-Guízar, Antonio; Taboada, Pablo; Pina-Luis, Georgina

2018-01-01

In the present work, we synthesize Near Infrared (NIR)-emitting alloyed mercaptopropionic acid (MPA)-capped CdTeSe quantum dots (QDs) in a single-step one-hour process, without the use of an inert atmosphere or any pyrophoric ligands. The quantum dots are water soluble, non-toxic, and highly photostable and have high quantum yields (QYs) up to 84%. The alloyed MPA-capped CdTeSe QDs exhibit a red-shifted emission, whose color can be tuned between visible and NIR regions (608–750 nm) by controlling the Te:Se molar ratio in the precursor mixtures and/or changing the time reaction. The MPA-capped QDs were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and zeta potential measurements. Photostability studies were performed by irradiating the QDs with a high-power xenon lamp. The ternary MPA-CdTeSe QDs showed greater photostability than the corresponding binary MPA-CdTe QDs. We report the Förster resonance energy transfer (FRET) from the MPA-capped CdTeSe QDs as energy donors and Cyanine5 NHS-ester (Cy5) dye as an energy acceptor with efficiency (E) up to 95%. The distance between the QDs and dye (r), the Förster distance (R0), and the binding constant (K) are reported. Additionally, cytocompatibility and cell internalization experiments conducted on human cancer cells (HeLa) cells revealed that alloyed MPA-capped CdTeSe QDs are more cytocompatible than MPA-capped CdTe QDs and are capable of ordering homogeneously all over the cytoplasm, which allows their use as potential safe, green donors for biological FRET applications. PMID:29641435

Associating long-term γ-ray variability with the superorbital period of LS I +61°303

DOE PAGES

Ackermann, M.; Ajello, M.; Ballet, J.; ...

2013-08-07

Gamma-ray binaries are stellar systems for which the spectral energy distribution (discounting the thermal stellar emission) peaks at high energies. Detected from radio to TeV gamma rays, the γ-ray binary LS I +61°303 is highly variable across all frequencies. One aspect of this system's variability is the modulation of its emission with the timescale set by the ~26.4960 day orbital period. Here we show that, during the time of our observations, the γ-ray emission of LS I +61°303 also presents a sinusoidal variability consistent with the previously known superorbital period of 1667 days. This modulation is more prominently seen atmore » orbital phases around apastron, whereas it does not introduce a visible change close to periastron. It is also found in the appearance and disappearance of variability at the orbital period in the power spectrum of the data. This behavior could be explained by a quasi-cyclical evolution of the equatorial outflow of the Be companion star, whose features influence the conditions for generating gamma rays. Furthermore, these findings open the possibility to use γ-ray observations to study the outflows of massive stars in eccentric binary systems.« less

ASSOCIATING LONG-TERM {gamma}-RAY VARIABILITY WITH THE SUPERORBITAL PERIOD OF LS I +61 Degree-Sign 303

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ackermann, M.; Buehler, R.; Ajello, M.

2013-08-20

Gamma-ray binaries are stellar systems for which the spectral energy distribution (discounting the thermal stellar emission) peaks at high energies. Detected from radio to TeV gamma rays, the {gamma}-ray binary LS I +61 Degree-Sign 303 is highly variable across all frequencies. One aspect of this system's variability is the modulation of its emission with the timescale set by the {approx}26.4960 day orbital period. Here we show that, during the time of our observations, the {gamma}-ray emission of LS I +61 Degree-Sign 303 also presents a sinusoidal variability consistent with the previously known superorbital period of 1667 days. This modulation ismore » more prominently seen at orbital phases around apastron, whereas it does not introduce a visible change close to periastron. It is also found in the appearance and disappearance of variability at the orbital period in the power spectrum of the data. This behavior could be explained by a quasi-cyclical evolution of the equatorial outflow of the Be companion star, whose features influence the conditions for generating gamma rays. These findings open the possibility to use {gamma}-ray observations to study the outflows of massive stars in eccentric binary systems.« less

DISCOVERY OF EXTENDED AND VARIABLE RADIO STRUCTURE FROM THE GAMMA-RAY BINARY SYSTEM PSR B1259-63/LS 2883

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moldon, Javier; Ribo, Marc; Paredes, Josep M.

2011-05-01

PSR B1259-63 is a 48 ms pulsar in a highly eccentric 3.4 year orbit around the young massive star LS 2883. During the periastron passage the system displays transient non-thermal unpulsed emission from radio to very high energy gamma rays. It is one of the three galactic binary systems clearly detected at TeV energies, together with LS 5039 and LS I +61 303. We observed PSR B1259-63 after the 2007 periastron passage with the Australian Long Baseline Array at 2.3 GHz to trace the milliarcsecond (mas) structure of the source at three different epochs. We have discovered extended and variablemore » radio structure. The peak of the radio emission is detected outside the binary system near periastron, at projected distances of 10-20 mas (25-45 AU assuming a distance of 2.3 kpc). The total extent of the emission is {approx}50 mas ({approx}120 AU). This is the first observational evidence that non-accreting pulsars orbiting massive stars can produce variable extended radio emission at AU scales. Similar structures are also seen in LS 5039 and LS I +61 303, in which the nature of the compact object is unknown. The discovery presented here for the young non-accreting pulsar PSR B1259-63 reinforces the link with these two sources and supports the presence of pulsars in these systems as well. A simple kinematical model considering only a spherical stellar wind can approximately trace the extended structures if the binary system orbit has a longitude of the ascending node of {Omega} {approx} -40{sup 0} and a magnetization parameter of {sigma} {approx} 0.005.« less

Astrometric observations of visual binaries using 26-inch refractor during 2007-2014 at Pulkovo

NASA Astrophysics Data System (ADS)

Izmailov, I. S.; Roshchina, E. A.

2016-04-01

We present the results of 15184 astrometric observations of 322 visual binaries carried out in 2007-2014 at Pulkovo observatory. In 2007, the 26-inch refractor ( F = 10413 mm, D = 65 cm) was equipped with the CCD camera FLI ProLine 09000 (FOV 12' × 12', 3056 × 3056 pixels, 0.238 arcsec pixel-1). Telescope automation and weather monitoring system installation allowed us to increase the number of observations significantly. Visual binary and multiple systems with an angular distance in the interval 1."1-78."6 with 7."3 on average were included in the observing program. The results were studied in detail for systematic errors using calibration star pairs. There was no detected dependence of errors on temperature, pressure, and hour angle. The dependence of the 26-inch refractor's scale on temperature was taken into account in calculations. The accuracy of measurement of a single CCD image is in the range of 0."0005 to 0."289, 0."021 on average along both coordinates. Mean errors in annual average values of angular distance and position angle are equal to 0."005 and 0.°04 respectively. The results are available here http://izmccd.puldb.ru/vds.htmand in the Strasbourg Astronomical Data Center (CDS). In the catalog, the separations and position angles per night of observation and annual average as well as errors for all the values and standard deviations of a single observation are presented. We present the results of comparison of 50 pairs of stars with known orbital solutions with ephemerides.

Superior thermoelectric performance in PbTe-PbS pseudo-binary. Extremely low thermal conductivity and modulated carrier concentration

DOE PAGES

Wu, D.; Zhao, L. -D.; Tong, X.; ...

2015-05-19

Lead chalcogenides have exhibited their irreplaceable role as thermoelectric materials at the medium temperature range, owing to highly degenerate electronic bands and intrinsically low thermal conductivities. PbTe-PbS pseudo-binary has been paid extensive attentions due to the even lower thermal conductivity which originates largely from the coexistence of both alloying and phase-separated precipitations. To investigate the competition between alloying and phase separation and its pronounced effect on the thermoelectric performance in PbTe-PbS, we systematically studied Spark Plasma Sintered (SPSed), 3 at% Na- doped (PbTe) 1-x(PbS)x samples with x=10%, 15%, 20%, 25%, 30% and 35% by means of transmission electron microscopy (TEM)more » observations and theoretical calculations. Corresponding to the lowest lattice thermal conductivity as a result of the balance between point defect- and precipitates- scattering, the highest figure of merit ZT~2.3 was obtained at 923 K when PbS phase fraction x is at 20%. The consistently lower lattice thermal conductivities in SPSed samples compared with corresponding ingots, resulting from the powdering and follow-up consolidation processes, also contribute to the observed superior ZT. Notably, the onset of carrier concentration modulation ~600 K due to excessive Na’s diffusion and re-dissolution leads to the observed saturations of electrical transport properties, which is believed equally crucial to the outstanding thermoelectric performance of SPSed PbTe-PbS samples.« less

Compositional effects in Ru, Pd, Pt, and Rh-doped mesoporous tantalum oxide catalysts for ammonia synthesis.

PubMed

Yue, Chaoyang; Qiu, Longhui; Trudeau, Michel; Antonelli, David

2007-06-11

A series of early metal-promoted Ru-, Pd-, Pt-, and Rh-doped mesoporous tantalum oxide catalysts were synthesized using a variety of dopant ratios and dopant precursors, and the effects of these parameters on the catalytic activity of NH3 synthesis from H2 and N2 were explored. Previous studies on this system supported an unprecedented mechanism in which N-N cleavage occurred at the Ta sites rather than on Ru. The results of the present study showed, for all systems, that Ba is a better promoter than Cs or La and that the nitrate is a superior precursor for Ba than the isopropoxide or the hydroxide. 15N-labeling studies showed that residual nitrate functions as the major ammonia source in the first hour but that it does not account for the ammonia produced after the nitrate is completely consumed. Ru3(CO)12 proved to be a better Ru precursor than RuCl(3).3H2O, and an almost linear increase in activity with increasing Ru loading level was observed at 350 degrees C (623 K). However, at 175 degrees C (448 K), the increase in Ru had no effect on the reaction rate. Pd functioned with comparable rates to Ru, while Pt and Rh functioned far less efficiently. The surprising activities for the Pd-doped catalysts, coupled with XPS evidence for low-valent Ta in this catalyst system, support a mechanism in which cleavage of the N-N triple bond occurs on Ta rather than the precious metal because the Ea value for N-N cleavage on Pd is 2.5 times greater than that for Ru, and the 9.3 kJ mol-1 Ea value measured previously for the Ru system suggests that N-N cleavage cannot occur at the Ru surface.

Ruthenium nano-oxide layer in CoFe-Ru-CoFe trilayer system: An x-ray reflectivity study

NASA Astrophysics Data System (ADS)

Asgharizadeh, S.; Sutton, M.; Altounian, Z.; Mao, M.; Lee, C. L.

2008-05-01

A grazing incidence x-ray reflectivity technique is used to determine the electron density profile as a function of depth in CoFe-Ru-CoFe and CoFe-Ru nano-oxide layer (NOL)-CoFe trilayers. Four trilayers with ruthenium thicknesses of 8, 8.5, and 9Å and one with Ru 8.5Å NOL, prepared by a dc planetary sputtering system, were investigated. For all samples, the electron density profile (EDP) shows a central peak that is related to the Ru layer. Natural oxidation in all of the samples introduces a graded EDP of the top CoFe layers, which decreases gradually to zero. The large surface resistivity of Ru 8.5Å NOL as compared to Ru 8.5Å is related to the remarkable difference between their EDPs. EDP changes have also been investigated in Ru NOL trilayers after annealing at 280°C. The Ru phase in the EDP was observed to confirm the thermal stability of the spacer layer after annealing.

Enhanced thermal stability of RuO2/polyimide interface for flexible device applications

NASA Astrophysics Data System (ADS)

Music, Denis; Schmidt, Paul; Chang, Keke

2017-09-01

We have studied the thermal stability of RuO2/polyimide (Kapton) interface using experimental and theoretical methods. Based on calorimetric and spectroscopic analyses, this inorganic-organic system does not exhibit any enthalpic peaks as well as all bonds in RuO2 and Kapton are preserved up to 500 °C. In addition, large-scale density functional theory based molecular dynamics, carried out in the same temperature range, validates the electronic structure and points out that numerous Ru-C and a few Ru-O covalent/ionic bonds form across the RuO2/Kapton interface. This indicates strong adhesion, but there is no evidence of Kapton degradation upon thermal excitation. Furthermore, RuO2 does not exhibit any interfacial bonds with N and H in Kapton, providing additional evidence for the thermal stability notion. It is suggested that the RuO2/Kapton interface is stable due to aromatic architecture of Kapton. This enhanced thermal stability renders Kapton an appropriate polymeric substrate for RuO2 containing systems in various applications, especially for flexible microelectronic and energy devices.

Ru sub 3 (CO) sub 12 and Mo(CO) sub 6 adsorbed on Ru(001) and Au/Ru: An infrared reflection-absorption study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malik, I.J.; Hrbek, J.

1990-01-01

The authors obtained infrared reflection absorption (IRAS) and thermal desorption spectroscopy (TDS) data for Ru{sub 3}(CO){sub 12}/Ru(001) and Mo(CO){sub 6}/Au/Ru systems for metal carbonyl coverages between submonolayer and approximately 20 monolayers. They characterized the C-O stretching mode of both systems (4cm{sup {minus}1}FWHM) and a deformation mode of Mo(CO){sub 6} at 608cm{sup {minus}1} (1 cm{sup {minus}1}FWHM). Both IRAS and TDS data suggest adsorption and desorption of metal carbonyls as molecular species with a preferential orientation in the overlayers. The IR intensity of the C-O stretch per a C-O bond projected onto the surface normal is approximately twice (five times) larger formore » Ru{sub 3}(CO){sub 12} (Mo(CO){sub 6}) at submonolayer coverages than for CO/Ru(001) at {theta}{sub CO}=0.68.« less

Ru sub 3 (CO) sub 12 and Mo(CO) sub 6 adsorbed on Ru(001) and Au/Ru: An infrared reflection-absorption study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malik, I.J.; Hrbek, J.

1990-01-01

We obtained IRAS and TDS data for Ru{sub 3}(CO){sub 12}/Ru(001) and Mo(CO){sub 6}/Au/Ru systems for metal carbonyl coverages between submonolayer and approximately 20 monolayers. We characterized the C-O stretching mode of both systems (4 cm{sup {minus}1} FWHM) and a deformation mode of Mo(CO){sub 6} at 608 cm{sup {minus}1} (1 cm{sup {minus}1} FWHM). Both IRAS and TDS data suggest adsorption and desorption of metal carbonyls as molecular species with a preferential orientation in the overlayers. The IR intensity of the C-O stretch per a C-O bond projected onto the surface normal is approximately twice (five times) larger for Ru{sub 3}(CO){sub 12}more » (Mo(CO){sub 6}) at submonolayer coverages than for CO/Ru(001) at {theta}{sub CO}=0.68. 31 refs., 4 figs.« less

Nature-Inspired, Highly Durable CO2 Reduction System Consisting of a Binuclear Ruthenium(II) Complex and an Organic Semiconductor Using Visible Light.

PubMed

Kuriki, Ryo; Matsunaga, Hironori; Nakashima, Takuya; Wada, Keisuke; Yamakata, Akira; Ishitani, Osamu; Maeda, Kazuhiko

2016-04-20

A metal-free organic semiconductor of mesoporous graphitic carbon nitride (C3N4) coupled with a Ru(II) binuclear complex (RuRu') containing photosensitizer and catalytic units selectively reduced CO2 into HCOOH under visible light (λ > 400 nm) in the presence of a suitable electron donor with high durability, even in aqueous solution. Modification of C3N4 with Ag nanoparticles resulted in a RuRu'/Ag/C3N4 photocatalyst that exhibited a very high turnover number (>33000 with respect to the amount of RuRu'), while maintaining high selectivity for HCOOH production (87-99%). This turnover number was 30 times greater than that reported previously using C3N4 modified with a mononuclear Ru(II) complex, and by far the highest among the metal-complex/semiconductor hybrid systems reported to date. The results of photocatalytic reactions, emission decay measurements, and time-resolved infrared spectroscopy indicated that Ag nanoparticles on C3N4 collected electrons having lifetimes of several milliseconds from the conduction band of C3N4, which were transferred to the excited state of RuRu', thereby promoting photocatalytic CO2 reduction driven by two-step photoexcitation of C3N4 and RuRu'. This study also revealed that the RuRu'/Ag/C3N4 hybrid photocatalyst worked efficiently in water containing a proper electron donor, despite the intrinsic hydrophobic nature of C3N4 and low solubility of CO2 in an aqueous environment.

Dynamic probe of ZnTe(110) surface by scanning tunneling microscopy

PubMed Central

Kanazawa, Ken; Yoshida, Shoji; Shigekawa, Hidemi; Kuroda, Shinji

2015-01-01

The reconstructed surface structure of the II–VI semiconductor ZnTe (110), which is a promising material in the research field of semiconductor spintronics, was studied by scanning tunneling microscopy/spectroscopy (STM/STS). First, the surface states formed by reconstruction by the charge transfer of dangling bond electrons from cationic Zn to anionic Te atoms, which are similar to those of IV and III–V semiconductors, were confirmed in real space. Secondly, oscillation in tunneling current between binary states, which is considered to reflect a conformational change in the topmost Zn–Te structure between the reconstructed and bulk-like ideal structures, was directly observed by STM. Third, using the technique of charge injection, a surface atomic structure was successfully fabricated, suggesting the possibility of atomic-scale manipulation of this widely applicable surface of ZnTe. PMID:27877752

Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system

NASA Technical Reports Server (NTRS)

Blum, Joel D.; Wasserburg, G. J.; Hutcheon, I. D.; Beckett, J. R.; Stolper, E. M.

1989-01-01

Results are presented on thin-film diffusion experiments designed to investigate phase equilibria in systems containing high concentrations of Pt-group elements, such as Ni-Fe-Ru-rich systems containing Pt, at temperatures of 1273, 1073, and 873 K. The rate of Ru diffusion in Ni was determined as a function of temperature, and, in addition, the degree of Pt and Ir partitioning between phases in a Ni-Fe-Ru-rich system and of V between phases in a Ni-Fe-O-rich system at 873 were determined. It was found that Pt preferentially partitions into the (gamma)Ni-Fe phase, whereas Ir prefers the (epsilon)Ru-Fe phase. V partitions strongly into Fe oxides relative to (gamma)Ni-Fe. These results have direct application to the origin and thermal history of the alloys rich in Pt-group elements in meteorites.

X-ray reflectivity of ruthenium nano-oxide layer in a CoFe-Ru-CoFe trilayer system

NASA Astrophysics Data System (ADS)

Asghari Zadeh, Saeid; Sutton, Mark; Altonian, Zaven; Mao, Ming; Lee, Chih-Ling

2006-03-01

A grazing incidence X-ray reflectivity technique is used to determine electron density profile(EDP) as a function of depth in CoFe-Ru-CoFe and CoFe-Ru nano oxide layer(NOL)-CoFe trilayers. Four trilayers with ruthenium thicknesses of 8,8.5 and 9 å.08cm and one with Ru8.5.05cmå.05cmNOL, prepared by a dc planetary sputtering system, were investigated. For all samples, EDP shows a central peak which is related to the Ru layer. Natural oxidation in all samples introduces a graded EDP of the top CoFe layer that decreases gradually to zero. The large surface resistivity of Ru8.5 å.05cm NOL compared to Ru 8.5å.08cm can be related to the remarkable difference between their EDP.

High-Performance Ru1 /CeO2 Single-Atom Catalyst for CO Oxidation: A Computational Exploration.

PubMed

Li, Fengyu; Li, Lei; Liu, Xinying; Zeng, Xiao Cheng; Chen, Zhongfang

2016-10-18

By means of density functional theory computations, we examine the stability and CO oxidation activity of single Ru on CeO 2 (111), TiO 2 (110) and Al 2 O 3 (001) surfaces. The heterogeneous system Ru 1 /CeO 2 has very high stability, as indicated by the strong binding energies and high diffusion barriers of a single Ru atom on the ceria support, while the Ru atom is rather mobile on TiO 2 (110) and Al 2 O 3 (001) surfaces and tends to form clusters, excluding these systems from having a high efficiency per Ru atom. The Ru 1 /CeO 2 exhibits good catalytic activity for CO oxidation via the Langmuir-Hinshelwood mechanism, thus is a promising single-atom catalyst. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Off-stoichiometric silver antimony telluride: An experimental study of transport properties with intrinsic and extrinsic doping

DOE PAGES

Nielsen, Michele D.; Jaworski, Christopher M.; Heremans, Joseph P.

2015-03-20

AgSbTe 2 is a thermoelectric semiconductor with an intrinsically low thermal conductivity and a valence band structure that is favorable to obtaining a high thermoelectric figure of merit zT. It also has a very small energy gap Eg ~ 7.6 ± 3 meV. As this gap is less than the thermal excitation energy at room temperature, near-intrinsic AgSbTe 2 is a two carrier system having both holes (concentration p) and electrons ( n). Good thermoelectric performance requires heavy p-type doping ( p > > n). This can be achieved with native defects or with extrinsic doping, e.g. with transition metalmore » element. The use of defect doping is complicated by the fact that many of the ternary Ag-Sb-Te and pseudo-binary Sb 2Te 3-Ag 2Te phase diagrams are contradictory. This paper determines the compositional region most favorable to creating a single phase material. Through a combination of intrinsic and extrinsic doping, values of zT > 1 are achieved, though not on single-phased material. In addition, we show that thermal conductivity is not affected by defects, further demonstrating that the low lattice thermal conductivity of I-V-VI 2 materials is due to an intrinsic mechanism, insensitive to changes in defect structure.« less

Thermodynamic assessment of the rhodium-ruthenium-oxygen (Rh-Ru-O) system

NASA Astrophysics Data System (ADS)

Gossé, S.; Bordier, S.; Guéneau, C.; Brackx, E.; Domenger, R.; Rogez, J.

2018-03-01

Ruthenium (Ru) and rhodium (Rh) are abundant platinum-group metals formed during burn-up of nuclear fuels. Under normal operating conditions, Rh and Ru accumulate and predominantly form metallic precipitates with other fission products like Mo, Pd and Tc. In the framework of vitrification of high-level nuclear waste, these fission products are poorly soluble in molten glasses. They precipitate as metallic particles and oxide phases. Moreover, these Ru and Rh rich phases strongly depend on temperature and the oxygen fugacity of the glass melt. In case of severe accidental conditions with air ingress, oxidation of the Ru and Rh is possible. At low temperatures (T < 1422 K for rhodium sesquioxide and T < 1815 K for ruthenium dioxide), the formed oxides are relatively stable. On the other hand, at high temperatures (T > 1422 K for rhodium sesquioxide and T > 1815 K for ruthenium dioxide), they may decompose into (Rh)-FCC or (Ru)-HCP metallic phases and radiotoxic volatile gaseous species. A thermodynamic assessment of the Rh-Ru-O system will enable the prediction of: (1) the metallic and oxide phases that form during the vitrification of high-level nuclear wastes and (2) the release of volatile gaseous species during a severe accident. The Calphad method developed herein employs a thermodynamic approach in the investigation of the thermochemistry of rhodium and ruthenium at high temperatures. Current literature on the thermodynamic properties and phase diagram data enables preliminary thermodynamic assessments of the Rh-O and Ru-O systems. Additionally, select compositions in the ternary Rh-Ru-O system underwent experimental tests to complement data found in literature and to establish the phase equilibria in the ternary system.

Neutron Stars and NuSTAR

NASA Astrophysics Data System (ADS)

Bhalerao, Varun

2012-05-01

My thesis centers around the study of neutron stars, especially those in massive binary systems. To this end, it has two distinct components: the observational study of neutron stars in massive binaries with a goal of measuring neutron star masses and participation in NuSTAR, the first imaging hard X-ray mission, one that is extremely well suited to the study of massive binaries and compact objects in our Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing high energy X-ray telescope to orbit. NuSTAR has an order-of-magnitude better angular resolution and has two orders of magnitude higher sensitivity than any currently orbiting hard X-ray telescope. I worked to develop, calibrate, and test CdZnTe detectors for NuSTAR. I describe the CdZnTe detectors in comprehensive detail here - from readout procedures to data analysis. Detailed calibration of detectors is necessary for analyzing astrophysical source data obtained by the NuSTAR. I discuss the design and implementation of an automated setup for calibrating flight detectors, followed by calibration procedures and results. Neutron stars are an excellent probe of fundamental physics. The maximum mass of a neutron star can put stringent constraints on the equation of state of matter at extreme pressures and densities. From an astrophysical perspective, there are several open questions in our understanding of neutron stars. What are the birth masses of neutron stars? How do they change in binary evolution? Are there multiple mechanisms for the formation of neutron stars? Measuring masses of neutron stars helps answer these questions. Neutron stars in high-mass X-ray binaries have masses close to their birth mass, providing an opportunity to disentangle the role of "nature" and "nurture" in the observed mass distributions. In 2006, masses had been measured for only six such objects, but this small sample showed the greatest diversity in masses among all classes of neutron star binaries. Intrigued by this diversity - which points to diverse birth masses - we undertook a systematic survey to measure the masses of neutron stars in nine high-mass X-ray binaries. In this thesis, I present results from this ongoing project. While neutron stars formed the primary focus of my work, I also explored other topics in compact objects. Appendix A describes the discovery and complete characterization of a 1RXS J173006.4+033813, a polar cataclysmic variable. Appendix B describes the discovery of a diamond planet orbiting a millisecond pulsar, and our search for its optical counterpart.

Chevrel-phase solid solution Mo 6Se 8- xTe x. Study of its superconducting, magnetic and NMR properties

NASA Astrophysics Data System (ADS)

Hamard1a, C.; Auffret, V.; Peña, O.; Le Floch, M.; Nowak, B.; Wojakowski, A.

2000-09-01

The Chevrel-phase solid solution Mo 6Se 8-Mo 6Te 8 was studied by X-ray diffraction, AC and DC magnetic susceptibility and 77Se and 125Te NMR spectroscopy. From the smooth evolution of the lattice parameters and superconducting critical temperatures, a progressive substitution of selenium atoms by tellurium is shown, on the whole range of composition 0⩽ x⩽8, in the formulation Mo 6Se 8- xTe x: the unit-cell volume increases linearly because of the larger ionic size of tellurium, while Tc decreases rapidly (from 6.45 down to 0 K) because of the different formal oxidation states of the anions and a probable evolution of the Fermi level in the density of states. Results of magnetic susceptibility support this model and suggest the inhibition of the intrinsic metallic behavior with increasing x. The NMR spectra of the binaries Mo 6Se 8 and Mo 6Te 8 reveal two significant features, attributed to two different chalcogen positions in the R 3¯ symmetry. At low Se contents in Mo 6Se 8- xTe x ( x=7.5, 7 and 6), selenium first fills the two X(2) sites along the three-fold axis (2c positions), and then it becomes statistically distributed over the general 6f positions, leading to broad 77Se NMR lines. On the other hand, substitution of Te atoms in Mo 6Se 8 seems to occur in a random way, creating large perturbations on the 125Te NMR spectra, over the whole range of x. Theoretical analysis based on the presence of two anisotropic lines (of axial and non-axial symmetries, respectively) allowed us to estimate their anisotropy factors and to perfectly simulate the frequency response of both Mo 6Se 8 and Mo 6Te 8 binaries. Analysis of the Knight shift anisotropy leads us to conclude about the importance of the molybdenum z 2 molecular orbital contribution which controls the Mo-X dipolar interactions.

Reinforcement of double-exchange ferromagnetic coupling by Ru in La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7} manganite system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumaresavanji, M., E-mail: vanji.hplt@gmail.com; Fontes, M.B.; Lopes, A.M.L.

2014-03-01

Highlights: • Effect of Mn-site doping by Ru has been studied in La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7}. • Electrical resistance, magnetoresistance and magnetic properties were measured. • Ru substitution enhances the ferromagnetism and metallicity. • Results were interpreted by the ferromagnetically coupled Ru with Mn ions in Mn–O–Ru network. - Abstract: The effect of Mn-site doping on magnetic and transport properties in the bilayer manganites La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7} (y = 0.0, 0.04, 0.08 and 0.15) has been studied. The undoped compound La{sub 1.24}Sr{sub 1.76}Mn{sub 2}O{sub 7} exhibits a ferromagnetic metal to paramagnetic insulator transition at T{submore » C} = 130 K and the substitution of Ru shifts the transition temperatures to higher temperature values. The increased metal–insulator transition by Ru substitution, obtained from temperature dependence of resistivity measurements, indicates that the Ru substitution enhances the metallic state at low temperature regime and favours the Mn–Ru pairs in the Ru doped samples. Moreover, the activation energy values calculated from the temperature dependence of resistivity curves suggest that the Ru substitution weakens the formation of polarons. The increased magnetoresistance ratio from 108% to 136% by Ru substitution, measured at 5 K, points out that the Ru substitution also enhances the inter-grain tunneling magnetoresistance. Thus, the ferromagnetic order and metallic state in La{sub 1.24}Sr{sub 1.76}Mn{sub 2}O{sub 7} system have been enhanced by the presence of Ru in the Mn-site. These reinforcements of ferromagnetic metallic state and magnetoresistance have been interpreted by the ferromagnetically coupled high spin states of Ru with Mn ions in the Mn–O–Ru network.« less

Automatic Target Cueing (ATC) Task 1 Report - Literature Survey on ATC

DTIC Science & Technology

2013-10-30

xa s In st ru m en t D aV in ci c hi p C ++ O ut da te d in fo rm at io n as w eb pa ge w as la st u pd at ed in...techniques such as contrast/ edge enhancement to increase the detectability of targets in the urban terrain. [P-4] restores long-distance thermal...Range? Sensor Experimental Setup Results [P-3] Contrast enhancement Edge enhancement Multi-scale edge domain Still images Yes IR

Binary Thinking in a Complex World: The Failure of NATO Deterrence since 1994 and Implications for the NATO Readiness Action Plan

DTIC Science & Technology

2017-05-25

Russian Federation, April 3, 2008, accessed November 9, 2016, http://www.mid.ru/en/ web /guest/foreign_policy/international_safety/conflicts...Gerasimov in March 2015, when he stated “Hybrid is the dark reflection of our comprehensive approach. We use a combination of military and non...Source: Micheal Kofman, “Russian Hybrid Warfare and Other Dark Arts,” War on the Rocks, March, 11, 2016, accessed November 29, 2016. https

Influence of Nanoinclusions on Thermoelectric Properties of n-Type Bi2Te3 Nanocomposites

NASA Astrophysics Data System (ADS)

Fan, Shufen; Zhao, Junnan; Yan, Qingyu; Ma, Jan; Hng, Huey Hoon

2011-05-01

n-Type Bi2Te3 nanocomposites with enhanced figure of merit, ZT, were fabricated by a simple, high-throughput method of mixing nanostructured Bi2Te3 particles obtained through melt spinning with micron-sized particles. Moderately high power factors were retained, while the thermal conductivity of the nanocomposites was found to decrease with increasing weight percent of nanoinclusions. The peak ZT values for all the nanocomposites were above 1.1, and the maximum shifted to higher temperature with increasing amount of nanoinclusions. A maximum ZT of 1.18 at 42°C was obtained for the 10 wt.% nanocomposite, which is a 43% increase over the bulk sample at the same temperature. This is the highest ZT reported for n-type Bi2Te3 binary material, and higher ZT values are expected if state-of-the-art Bi2Te3- x Se x materials are used.

The Advanced Gamma-ray Imaging System (AGIS)

NASA Astrophysics Data System (ADS)

Buckley, James

2008-04-01

We describe a concept for a ˜km^2 ground-based gamma-ray experiment (AGIS) comprised of an array of ˜100 imaging atmospheric Cherenkov telescopes achieving a sensitivity an order of magnitude better than the current generation of space or ground-based instruments in the energy range of 40 GeV to ˜100 TeV. We present the scientific drivers for AGIS including the prospects for contributions to understanding extragalactic sources such as nearby galaxies, active galaxies, galaxy clusters and GRB; galactic sources such as X-ray binaries, supernova remnants, and pulsar wind nebulae; as well as probes of fundamental physics including indirectly detecting dark matter and probing TeV-scale physics. With the current generation of atmospheric Cherenkov telescope arrays, TeV astronomy has become well established, with the number TeV gamma-ray sources now nearing 100, including many unidentified and serendipitous sources. Improvements in the instantaneous field of view, angular resolution, effective area and energy resolution of AGIS are certain to provide great scientific returns in high energy astrophysics as well as opening up new discovery space. Here we present an overview of the ongoing design studies for AGIS including the optimization of array parameters as well as an overview of the technical drivers for the observatory.

Skeletal Ru/Cu catalysts prepared from crystalline and quasicrystalline ternary alloy precursors: characterization by X-ray absorption spectroscopy and CO oxidation.

PubMed

Highfield, James; Liu, Tao; Loo, Yook Si; Grushko, Benjamin; Borgna, Armando

2009-02-28

The Ru/Cu system is of historical significance in catalysis. The early development and application of X-ray absorption spectroscopy (XAS) led to the original 'bimetallic cluster" concept for highly-immiscible systems. This work explores alkali leaching of Al-based ternary crystalline and quasicrystalline precursors as a potential route to bulk Ru/Cu alloys. Single-phase ternary alloys at 3 trial compositions; Al(71)Ru(22)Cu(7), Al(70.5)Ru(17)Cu(12.5), and Al(70)Ru(10)Cu(20), were prepared by arc melting of the pure metal components. After leaching, the bimetallic residues were characterized principally by transmission XAS, "as-leached" and after annealing in H(2) (and passivation) in a thermobalance. XRD and BET revealed a nanocrystalline product with a native structure of hexagonal Ru. XPS surface analysis of Ru(22)Cu(7) and Ru(17)Cu(12.5) found only slight enrichment by Cu in the as-leached forms, with little change upon annealing. Ru(10)Cu(20) was highly segregated as-leached. XANES data showed preferential oxidation of Cu in Ru(22)Cu(7), implying that it exists as an encapsulating layer. TG data supports this view since it does not show the distinct two-stage O(2) uptake characteristic of skeletal Ru. Cu K-edge EXAFS data for Ru(22)Cu(7) were unique in showing a high proportion of Ru neighbours. The spacing, d(CuRu) = 2.65 A, was that expected from a hypothetical (ideal) solid solution at this composition, but this is unlikely in such a bulk-immiscible system and Ru K-edge EXAFS failed to confirm bulk alloying. Furthermore its invariance under annealing was more indicative of an interfacial bond between bulk components, although partial alloying with retention of local order cannot entirely be ruled out. The XAS and XPS data were reconciled in a model involving surface and bulk segregation, Cu being present at both the grain exterior and in ultra-fine internal pores. This structure can be considered as the 3-dimensional analogue of the classical type. Preliminary studies in CO and H(2) oxidation were made in a DRIFTS flow reactor with on-line MS, and their activities and selectivities were compared against skeletal Ru and Cu controls, Ru/Al(2)O(3), and Au/Fe(2)O(3). All samples were active in CO oxidation above approximately 50 degrees C, showing light-off temperatures in the range 60-70 degrees C. Ru(22)Cu(7) and Ru(17)Cu(12.5) also showed good selectivities (vs. H(2) oxidation), attributed tentatively to Ru-modified Cu surfaces of varying thickness. These compositions are promising candidates to test in a (PROX) fuel processor to supply purified (CO-free) H(2) to a PEM fuel cell.

Bifunctional supramolecular systems on the platform of p-sulfonatothiacalix[4]arene containing photochromic mononitrosyl Ru (II) and paramagnetic aqua Gd or Dy complexes

NASA Astrophysics Data System (ADS)

Kushch, L. A.; Yagubskii, E. B.; Dmitriev, A. I.; Morgunov, R. B.; Emel'Yanov, V. A.; Mustafina, A. R.; Gubaidullin, A. T.; Burilov, V. A.; Solovieva, S. E.; Schaniel, D.; Woike, Th.

2010-06-01

Two bifunctional supramolecular systems [RuNO(NH3)4OH]2+·[RuNO(NH3)4H2O]3+·Gd3+(H2O)6·2[TCAS]4-·4H2O (1) and [RuNO(NH3)4OH]2+·[RuNO(NH3)4H2O]3+·Dy3+(H2O)6·2[TCAS]4-·4H2O (2) on the platform of p-sulfonatothiacalix[4]arene containing photochromic mononitrosyl Ru and paramagnetic rare-earth (Gd3+, Dy3+) cations have been synthesized. The crystal structures of 1 and 2 are discussed. Their photochromic, magnetic and photomagnetic properties studied by IR and SQUID experimental techniques are presented

Transverse momentum dependence of inclusive primary charged-particle production in p–Pb collisions at $$\\sqrt{s_\\mathrm{{NN}}}=5.02~\\text {TeV}$$ = 5.02 TeV

DOE PAGES

Abelev, B.; Adam, J.; Adamová, D.; ...

2014-09-16

The transverse momentum (p T) distribution of primary charged particles is measured at midrapidity in minimum-bias p–Pb collisions at √s NN = 5.02 TeV with the ALICE detector at the LHC in the range. The spectra are compared to the expectation based on binary collision scaling of particle production in pp collisions, leading to a nuclear modification factor consistent with unity for p T larger than 2 GeV/c, with a weak indication of a Cronin-like enhancement for p T around 4 GeV/c. The measurement is compared to theoretical calculations and to data in Pb–Pb collisions at √s NN = 2.76 TeV.

Ternary PtRuPd/C catalyst for high-performance, low-temperature direct dimethyl ether fuel cells

DOE PAGES

Dumont, Joseph Henry; Martinez, Ulises; Chung, Hoon T.; ...

2016-08-19

Here, dimethyl ether (DME) is a promising alternative fuel option for direct-feed low-temperature fuel cells. Until recently, DME had not received the same attention as alcohol fuels, such as methanol or ethanol, despite its notable advantages. These advantages include a high theoretical open-cell voltage (1.18 V at 25 °C) that is similar to that of methanol (1.21 V), much lower toxicity than methanol, and no need for the carbon–carbon bond scission that is needed in ethanol oxidation. DME is biodegradable, has a higher energy content than methanol (8.2 vs. 6.1 kWh kg –1), and, like methanol, can be synthesized frommore » recycled carbon dioxide. Although the performance of direct DME fuel cells (DDMEFCs) has progressed over the past few years, DDMEFCs have not been viewed as fully viable. In this work, we report much improved performance from the ternary Pt 55Ru 35Pd 10/C anode catalyst, allowing DDMEFCs to compete directly with direct methanol fuel cells (DMFCs). We also report results involving binary Pt alloys as reference catalysts and an in situ infrared electrochemical study to better understand the mechanism of DME electro-oxidation on ternary PtRuPd/C catalysts.« less

A RADIO PULSAR SEARCH OF THE {gamma}-RAY BINARIES LS I +61 303 AND LS 5039

DOE Office of Scientific and Technical Information (OSTI.GOV)

Virginia McSwain, M.; Ray, Paul S.; Ransom, Scott M.

2011-09-01

LS I +61 303 and LS 5039 are exceptionally rare examples of high-mass X-ray binaries with MeV-TeV emission, making them two of only five known '{gamma}-ray binaries'. There has been disagreement within the literature over whether these systems are microquasars, with stellar winds accreting onto a compact object to produce high energy emission and relativistic jets, or whether their emission properties might be better explained by a relativistic pulsar wind colliding with the stellar wind. Here we present an attempt to detect radio pulsars in both systems with the Green Bank Telescope. The upper limits of flux density are betweenmore » 4.1 and 14.5 {mu}Jy, and we discuss the null results of the search. Our spherically symmetric model of the wind of LS 5039 demonstrates that any pulsar emission will be strongly absorbed by the dense wind unless there is an evacuated region formed by a relativistic colliding wind shock. LS I +61 303 contains a rapidly rotating Be star whose wind is concentrated near the stellar equator. As long as the pulsar is not eclipsed by the circumstellar disk or viewed through the densest wind regions, detecting pulsed emission may be possible during part of the orbit.« less

Large enhancement of oscillating chemiluminescence with [Ru(bpy)3 ](2+) -catalyzed Belousov-Zhabotinsky reaction in the presence of tri-n-propylamine.

PubMed

Lan, Xiaolan; Zheng, Baozhan; Zhao, Yan; Yuan, Hongyan; Du, Juan; Xiao, Dan

2013-01-01

Oscillating chemiluminescence enhanced by the addition of tri-n-propylamine (TPrA) to the typical Belousov-Zhabotinsky (BZ) reaction system catalyzed by ruthenium(II)tris(2.2'-bipyridine)(Ru(bpy)3 (2+) ) was investigated using a luminometry method. The [Ru(bpy)3 ](2+) /TPrA system was first used as the catalyst for a BZ oscillator in a closed system, which exhibited a shorter induction period, higher amplitude and much more stable chemiluminescence (CL) oscillation. The effects of various concentrations of TPrA, oxygen and nitrogen flow rate on the oscillating behavior of this system were examined. In addition, the CL intensity of the [Ru(bpy)3 ](2+) /TPrA-BZ system was found to be inhibited by phenol, thus providing a way for use of the BZ system in the determination of phenolic compounds. Moreover, the possible mechanism of the oscillating CL reaction catalyzed by [Ru(bpy)3 ](2+) /TPrA and the inhibition effects of oxygen and phenol on this oscillating CL system were considered. Copyright © 2012 John Wiley & Sons, Ltd.

Use of rotation to suppress thermosolutal convection in directionally solidified binary alloys

NASA Technical Reports Server (NTRS)

Pearlstein, Arne J.

1994-01-01

Effects of rotation on onset of convection during plane-front directional solidification of Pb-Sn and the pseudobinary system mercury cadmium telluride (Hg(1-x)Cd(x)Te), and on dendritic solidification of Pb-Sn have been studied by means of linear stability analysis. Incorporating Coriolis and centrifugal accelerations into the momentum equation of Coriell et al., we find that under realistic processing conditions, a large degree of stabilization can be achieved using modest rotation rates for both Pb-Sn and mercury cadmium telluride. At a growth velocity of 5 micron/sec and nominal liquid-side temperature gradient of 200 K/cm in Pb-Sn, rotation at 500 rpm results in a hundredfold increase in the critical Sn concentration. Large increases in the maximum allowable growth velocity at fixed melt composition are also attainable with modest rotation rates. The effect is amplified under conditions of reduced gravitational acceleration. For Hg(1-x)Cd(x)Te, we have also studied the nonrotating case. The key differences are due to the existence of a composition range for Hg(1-x)Cd(x)Te in which the melt density has a local maximum as a function of temperature. When the melt solidifies by cooling from below, the liquid density may initially increase with distance above the interface, before ultimately decreasing as the melt temperature increases above the value at which the local density maximum occurs. In contrast to the Pb-Sn case where density depends monotonically on temperature and composition, for Hg(1-x)Cd(x)Te there exists a critical value of the growth velocity above which plane-front solidification is unstable for all bulk CdTe mole fractions. Again, rotation leads to significant inhibition of onset. We identify the predicted stabilization with the Taylor-Proudman mechanism by which rotation inhibits thermal convection in a single-component fluid heated from below. In a binary liquid undergoing solidification, rotation inhibits the onset of buoyancy-driven convection, and has no effect on the short-wavelength morphological instability. At large growth velocities, the plane-front interface between liquid and solid becomes unstable with respect to a morphological instability and solidification occurs dendritically, with a mushy zone of dendrites and interdendritic fluid separating the solid from the melt. For the Pb-Sn system, rotation substantially suppresses the onset of convection in the mushy zone and in the overlying liquid, holding open the promise that rotation can suppress freckling and other macrosegregation defects.

ASTROPHYSICAL PARAMETERS OF LS 2883 AND IMPLICATIONS FOR THE PSR B1259-63 GAMMA-RAY BINARY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Negueruela, Ignacio; Lorenzo, Javier; Ribo, Marc

2011-05-01

Only a few binary systems with compact objects display TeV emission. The physical properties of the companion stars represent basic input for understanding the physical mechanisms behind the particle acceleration, emission, and absorption processes in these so-called gamma-ray binaries. Here we present high-resolution and high signal-to-noise optical spectra of LS 2883, the Be star forming a gamma-ray binary with the young non-accreting pulsar PSR B1259-63, showing it to rotate faster and be significantly earlier and more luminous than previously thought. Analysis of the interstellar lines suggests that the system is located at the same distance as (and thus is likelymore » a member of) Cen OB1. Taking the distance to the association, d = 2.3 kpc, and a color excess of E(B - V) = 0.85 for LS 2883 results in M{sub V} {approx} -4.4. Because of fast rotation, LS 2883 is oblate (R{sub eq} {approx_equal} 9.7 R{sub sun} and R{sub pole} {approx_equal} 8.1 R{sub sun}) and presents a temperature gradient (T{sub eq}{approx} 27,500 K, log g{sub eq} = 3.7; T{sub pole}{approx} 34,000 K, log g{sub pole} = 4.1). If the star did not rotate, it would have parameters corresponding to a late O-type star. We estimate its luminosity at log(L{sub *}/L{sub sun}) {approx_equal} 4.79 and its mass at M{sub *} {approx} 30 M{sub sun}. The mass function then implies an inclination of the binary system i{sub orb} {approx} 23{sup 0}, slightly smaller than previous estimates. We discuss the implications of these new astrophysical parameters of LS 2883 for the production of high-energy and very high-energy gamma rays in the PSR B1259-63/LS 2883 gamma-ray binary system. In particular, the stellar properties are very important for prediction of the line-like bulk Comptonization component from the unshocked ultrarelativistic pulsar wind.« less

Catalytic activity of platinum on ruthenium electrodes with modified (electro)chemical states.

PubMed

Park, Kyung-Won; Sung, Yung-Eun

2005-07-21

Using Pt on Ru thin-film electrodes with various (electro)chemical states designed by the sputtering method, the effect of Ru states on the catalytic activity of Pt was investigated. The chemical and electrochemical properties of Pt/Ru thin-film samples were confirmed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. In addition, Pt nanoparticles on Ru metal or oxide for an actual fuel cell system showed an effect of Ru states on the catalytic activity of Pt in methanol electrooxidation. Finally, it was concluded that such an enhancement of methanol electrooxidation on the Pt is responsible for Ru metallic and/or oxidation sites compared to pure Pt without any Ru state.

Thermoluminescent properties of nanocrystalline ZnTe thin films: Structural and morphological studies

NASA Astrophysics Data System (ADS)

Rajpal, Shashikant; Kumar, S. R.

2018-04-01

Zinc Telluride (ZnTe) is a binary II-VI direct band gap semiconducting material with cubic structure and having potential applications in different opto-electronic devices. Here we investigated the effects of annealing on the thermoluminescence (TL) of ZnTe thin films. A nanocrystalline ZnTe thin film was successfully electrodeposited on nickel substrate and the effect of annealing on structural, morphological, and optical properties were studied. The TL emission spectrum of as deposited sample is weakly emissive in UV region at ∼328 nm. The variation in the annealing temperature results into sharp increase in emission intensity at ∼328 nm along with appearance of a new peak at ∼437 nm in visible region. Thus, the deposited nanocrystalline ZnTe thin films exhibited excellent thermoluminescent properties upon annealing. Furthermore, the influence of annealing (annealed at 400 °C) on the solid state of ZnTe were also studied by XRD, SEM, EDS, AFM. It is observed that ZnTe thin film annealed at 400 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.

Interactive system for geomagnetic data analysis

NASA Astrophysics Data System (ADS)

Solovev, Igor

2017-10-01

The paper suggests the methods for analyzing geomagnetic field variations, which are implemented in "Aurora" software system for complex analysis of geophysical parameters. The software system allows one to perform a detailed magnetic data analysis. The methods allow one to estimate the intensity of geomagnetic perturbations and to allocate increased geomagnetic activity periods. The software system is publicly available (http://aurorasa.ikir.ru:8580, http://www.ikir.ru:8280/lsaserver/MagneticPage.jsp). This research was supported by the Russian Science Foundation (Project No. 14-11-00194).

Air radioactivity levels following the Fukushima reactor accident measured at the Laboratoire Souterrain de Modane, France.

PubMed

Loaiza, P; Brudanin, V; Piquemal, F; Reyss, J-L; Stekl, I; Warot, G; Zampaolo, M

2012-12-01

The radioactivity levels in the air of the radionuclides released by the Fukushima accident were measured at the Laboratoire Souterrain de Modane, in the South-East of France, during the period 25 March-18 April 2011. Air-filters from the ventilation system exposed for one or two days were measured using low-background gamma-ray spectrometry. In this paper we present the activity concentrations obtained for the radionuclides (131)I, (132)Te, (134)Cs, (137)Cs, (95)Nb, (95)Zr, (106)Ru, (140)Ba/La and (103)Ru. The activity concentration of (131)I was of the order of 100 μBq/m(3), more than 100 times higher than the activities of other fission products. The highest activities of (131)I were measured as a first peak on 30 March and a second peak on 3-4 April. The activity concentrations of (134)Cs and (137)Cs varied from 5 to 30 μBq/m(3). The highest activity concentration recorded for Cs corresponded to the same period as for (131)I, with a peak on 2-3 April. The results of the radioactivity concentration levels in grass and mushrooms exposed to the air in the Modane region were also measured. Activity concentrations of (131)I of about 100 mBq/m(2) were found in grass. Copyright © 2012 Elsevier Ltd. All rights reserved.

Electrogenerated chemiluminescence of tris(2,2'-bipyridine)ruthenium(II) using N-(3-aminopropyl)diethanolamine as coreactant.

PubMed

Kitte, Shimeles Addisu; Wang, Chao; Li, Suping; Zholudov, Yuriy; Qi, Liming; Li, Jianping; Xu, Guobao

2016-10-01

Coreactant plays a critical role for the application of electrochemiluminescence (ECL). Herein, N-(3-aminopropyl)diethanolamine (APDEA) has been explored as a potential coreactant for enhancing tris(2,2'-bipyridyl)ruthenium(II) ECL. It is much more effective than tripropylamine at gold and platinum electrodes although it has one primary amine group besides a tertiary amine group. The presence of primary amine group and hydroxyl groups in APDEA promotes the oxidation rates of amine and thus remarkably increases ECL intensity. The ECL intensities of the Ru(bpy)3 (2+)/APDEA system are approximately 10 and 36 times stronger than that of Ru(bpy)3 (2+)/tripropylamine system and about 1.6 and 1.14 times stronger than that of Ru(bpy)3 (2+)/N-butyldiethanolamine system at Au and Pt electrodes, respectively. The ECL intensity of the Ru(bpy)3 (2+)/APDEA system is 2.42 times stronger than that of Ru(bpy)3 (2+)/N-butyldiethanolamine at glassy carbon electrodes.

Ruthenium nanoparticles supported on CeO2 for catalytic permanganate oxidation of butylparaben.

PubMed

Zhang, Jing; Sun, Bo; Guan, Xiaohong; Wang, Hui; Bao, Hongliang; Huang, Yuying; Qiao, Junlian; Zhou, Gongming

2013-11-19

This study developed a heterogeneous catalytic permanganate oxidation system with ceria supported ruthenium, Ru/CeO2 (0.8‰ as Ru), as catalyst for the first time. The catalytic performance of Ru/CeO2 toward butylparaben (BP) oxidation by permanganate was strongly dependent on its dosage, pH, permanganate concentration and temperature. The presence of 1.0 g L(-1) Ru/CeO2 increased the oxidation rate of BP by permanganate at pH 4.0-8.0 by 3-96 times. The increase in Ru/CeO2 dosage led to a progressive enhancement in the oxidation rate of BP by permanganate at neutral pH. The XANES analysis revealed that (1) Ru was deposited on the surface of CeO2 as Ru(III); (2) Ru(III) was oxidized by permanganate to its higher oxidation state Ru(VI) and Ru(VII), which acted as the co-oxidants in BP oxidation; (3) Ru(VI) and Ru(VII) were reduced by BP to its initial state of Ru(III). Therefore, Ru/CeO2 acted as an electron shuttle in catalytic permanganate oxidation process. LC-MS/MS analysis implied that BP was initially attacked by permanganate or Ru(VI) and Ru(VII) at the aromatic ring, leading to the formation of various hydroxyl-substituted and ring-opening products. Ru/CeO2 could maintain its catalytic activity during the six successive runs. In conclusion, catalyzing permanganate oxidation with Ru/CeO2 is a promising technology for degrading phenolic pollutants in water treatment.

Theoretical calculations of structural, electronic, and elastic properties of CdSe1-x Te x : A first principles study

NASA Astrophysics Data System (ADS)

M, Shakil; Muhammad, Zafar; Shabbir, Ahmed; Muhammad Raza-ur-rehman, Hashmi; M, A. Choudhary; T, Iqbal

2016-07-01

The plane wave pseudo-potential method was used to investigate the structural, electronic, and elastic properties of CdSe1-x Te x in the zinc blende phase. It is observed that the electronic properties are improved considerably by using LDA+U as compared to the LDA approach. The calculated lattice constants and bulk moduli are also comparable to the experimental results. The cohesive energies for pure CdSe and CdTe binary and their mixed alloys are calculated. The second-order elastic constants are also calculated by the Lagrangian theory of elasticity. The elastic properties show that the studied material has a ductile nature.

Magnetic and magnetocaloric properties of Ba and Ti co-doped SrRuO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal

2014-12-28

Temperature evolution of magnetic properties in Ba and Ti doped SrRuO{sub 3} has been investigated to observe the effects of larger ionic radius Ba at Sr site and isovalent nonmagnetic impurity Ti at Ru site. Ionic radius mismatch and different electronic configuration in comparison with Ru modify Sr(Ba)-O and Ru(Ti)-O bond lengths and Ru-O-Ru bond angle. The apical and basal Ru-O-Ru bond angles vary significantly with Ti doping. Ferromagnetic Curie temperature decreases from 161 K to 149 K monotonically with Ba (10%) and Ti (10%) substitutions at Sr and Ru sites. The zero field cooled (ZFC) magnetization reveals a prominent peak whichmore » shifts towards lower temperature with application of magnetic field. The substitution of tetravalent Ti with localized 3d{sup 0} orbitals for Ru with more delocalized 4d{sup 4} orbitals leads to a broad peak in ZFC magnetization. A spontaneous ZFC magnetization becomes negative below 160 K for all the compositions. The occurrence of both normal and inverse magnetocaloric effects in Ba and Ti co-doped SrRuO{sub 3} makes the system more interesting.« less

Volatile trace elements and the characterization of the Cayley Formation and the primitive lunar crust

NASA Technical Reports Server (NTRS)

Jovanovic, S.; Reed, G. W., Jr.

1973-01-01

Two types of highland terrain appear to be present at the Apollo 16 landing site. The Plains Formation called Cayley is ubiquitous and blankets even those regions that were presumably a part of the mountainous Descartes Formation. The second type of terrain is that associated with the ejectae from North and South Ray craters. The stratigraphy sampled by the ejectae underlays the Cayley layer as characterized above and may permit a redefinition of Descartes Formation as that which underlays the smooth Plains deposits. These conclusions are based on the concentrations and chemical coherence between elements such as Cl-F-P2O5 and Ru-Os. The primitive lunar crust may be characterized by the type of feldspathic rocks which are enriched in trace elements, such as Cl, Br, U, Te, Ru, and Os, as found in 'rusty' rock 66095 and in 61016; other feldspathic rocks are depleted and may be of secondary origin.

Determinations of the {sup 12}C/{sup 13}C Ratio for the Secondary Stars of AE Aquarii, SS Cygni, and RU Pegasi

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, Thomas E.; Marra, Rachel E., E-mail: tharriso@nmsu.edu, E-mail: rmarra@nmsu.edu

We present new moderate-resolution near-infrared spectroscopy of three CVs obtained using GNIRS on Gemini-North. These spectra covered three {sup 13}CO bandheads found in the K -band, allowing us to derive the isotopic abundance ratios for carbon. We find small {sup 12}C/{sup 13}C ratios for all three donor stars. In addition, these three objects show carbon deficits, with AE Aqr being the most extreme ([C/Fe] = −1.4). This result confirms the conjecture that the donor stars in some long-period CVs have undergone considerable nuclear evolution prior to becoming semi-contact binaries. In addition to the results for carbon, we find that themore » abundance of sodium is enhanced in these three objects, and the secondary stars in both RU Peg and SS Cyg suffer magnesium deficits. Explaining such anomalies appears to require higher mass progenitors than commonly assumed for the donor stars of CVs.« less

Simulating Ru L 3 -Edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Kuiken, Benjamin E.; Valiev, Marat; Daifuku, Stephanie L.

2013-05-30

Ruthenium L3-edge X-ray absorption (XA) spectroscopy probes unoccupied 4d orbitals of the metal atom and is increasingly being used to investigate the local electronic structure in ground and excited electronic states of Ru complexes. The simultaneous development of computational tools for simulating Ru L3-edge spectra is crucial for interpreting the spectral features at a molecular level. This study demonstrates that time-dependent density functional theory (TDDFT) is a viable and predictive tool for simulating ruthenium L3-edge XA spectroscopy. We systematically investigate the effects of exchange correlation functional and implicit and explicit solvent interactions on a series of RuII and RuIII complexesmore » in their ground and electronic excited states. The TDDFT simulations reproduce all of the experimentally observed features in Ru L3-edge XA spectra within the experimental resolution (0.4 eV). Our simulations identify ligand-specific charge transfer features in complicated Ru L3-edge spectra of [Ru(CN)6]4- and RuII polypyridyl complexes illustrating the advantage of using TDDFT in complex systems. We conclude that the B3LYP functional most accurately predicts the transition energies of charge transfer features in these systems. We use our TDDFT approach to simulate experimental Ru L3-edge XA spectra of transition metal mixed-valence dimers of the form [(NC)5MII-CN-RuIII(NH3)5] (where M = Fe or Ru) dissolved in water. Our study determines the spectral signatures of electron delocalization in Ru L3-edge XA spectra. We find that the inclusion of explicit solvent molecules is necessary for reproducing the spectral features and the experimentally determined valencies in these mixed-valence complexes. This study validates the use of TDDFT for simulating Ru 2p excitations using popular quantum chemistry codes and providing a powerful interpretive tool for equilibrium and ultrafast Ru L3-edge XA spectroscopy.« less

Nanocrystal growth and morphology of PbTeSe-ZnSe composite thin films prepared by one-step synthesis method

NASA Astrophysics Data System (ADS)

Sato, Kazuhisa; Abe, Seishi

2016-10-01

The microstructure of polycrystalline PbTe1-xSex-ZnSe composite thin films has been studied by scanning transmission electron microscopy and electron diffraction. The films were prepared by the one-step synthesis method using simultaneous evaporation of PbTe and ZnSe. The nanocrystals of PbTe1-xSex are formed in a ZnSe matrix. Tellurium concentration can be tuned by controlling the PbTe evaporation source temperatures between 753 K and 793 K. Binary PbSe nanocrystals were formed at 753 K, while ternary PbTe1-xSex nanocrystals were formed at 793 K. The nanocrystals grow in a granular shape at the initial stage of film growth, and the morphology changes to nanowire-shape as the film grows, irrespective of the Te concentration. The ternary PbTe1-xSex nanocrystals were composed of two phases with different Te concentration; Te-rich (Se-poor) granular crystals were formed near the bottom half parts of the film and Te-poor (Se-rich) nanowires were formed at the upper half parts of the film. Columnar ZnSe crystals contain high-density {111} stacking faults due to the low stacking fault energy of ZnSe. A balance of deposition and re-evaporation on the substrate during the film growth will be responsible for the resultant nanocrystal morphology.

Coverage evolution of the unoccupied Density of States in sulfur superstructures on Ru(0001)

NASA Astrophysics Data System (ADS)

Pisarra, M.; Bernardo-Gavito, R.; Navarro, J. J.; Black, A.; Díaz, C.; Calleja, F.; Granados, D.; Miranda, R.; Martín, F.; Vázquez de Parga, A. L.

2018-03-01

Sulfur adsorbed on Ru(0001) presents a large number of ordered structures. This characteristic makes S/Ru(0001) the ideal system to investigate the effect of different periodicities on the electronic properties of interfaces. We have performed scanning tunneling microscopy/spectroscopy experiments and density functional theory calculations showing that a sulfur adlayer generates interface states inside the Γ directional gap of Ru(0001) and that the position of such states varies monotonically with sulfur coverage. This is the result of the interplay between band folding effects arising from the new periodicity of the system and electron localization on the sulfur monolayer. As a consequence, by varying the amount of sulfur in S/Ru(0001) one can control the electronic properties of these interfacial materials.

Mixed-valent metals bridged by a radical ligand: fact or fiction based on structure-oxidation state correlations.

PubMed

Sarkar, Biprajit; Patra, Srikanta; Fiedler, Jan; Sunoj, Raghavan B; Janardanan, Deepa; Lahiri, Goutam Kumar; Kaim, Wolfgang

2008-03-19

Electron-rich Ru(acac)2 (acac- = 2,4-pentanedionato) binds to the pi electron-deficient bis-chelate ligands L, L = 2,2'-azobispyridine (abpy) or azobis(5-chloropyrimidine) (abcp), with considerable transfer of negative charge. The compounds studied, (abpy)Ru(acac)2 (1), meso-(mu-abpy)[Ru(acac)2]2 (2), rac-(mu-abpy)[Ru(acac)2]2 (3), and (mu-abcp)[Ru(acac)2]2 (4), were calculated by DFT to assess the degree of this metal-to-ligand electron shift. The calculated and experimental structures of 2 and 3 both yield about 1.35 A for the length of the central N-N bond which suggests a monoanion character of the bridging ligand. The NBO analysis confirms this interpretation, and TD-DFT calculations reproduce the observed intense long-wavelength absorptions. While mononuclear 1 is calculated with a lower net ruthenium-to-abpy charge shift as illustrated by the computed 1.30 A for d(N-N), compound 4 with the stronger pi accepting abcp bridge is calculated with a slightly lengthened N-N distance relative to that of 2. The formulation of the dinuclear systems with monoanionic bridging ligands implies an obviously valence-averaged Ru(III)Ru(II) mixed-valent state for the neutral molecules. Mixed valency in conjunction with an anion radical bridging ligand had been discussed before in the discussion of MLCT excited states of symmetrically dinuclear coordination compounds. Whereas 1 still exhibits a conventional electrochemical and spectroelectrochemical behavior with metal centered oxidation and two ligand-based one-electron reduction waves, the two one-electron oxidation and two one-electron reduction processes for each of the dinuclear compounds Ru2.5(L*-)Ru2.5 reveal more unusual features via EPR and UV-vis-NIR spectroelectrochemistry. In spite of intense near-infrared absorptions, the EPR results show that the first reduction leads to Ru(II)(L*-)Ru(II) species, with an increased metal contribution for system 4*-. The second reduction to Ru(II)(L2-)Ru(II) causes the disappearance of the NIR band. One-electron oxidation of the Ru2.5(L*-)Ru2.5 species produces a metal-centered spin for which the alternatives RuIII(L0)Ru(II) or Ru(III)(L*-)Ru(III) can be formulated. The absence of NIR bands as common for mixed-valent species with intervalence charge transfer (IVCT) absorption favors the second alternative. The second one-electron oxidation is likely to produce a dication with Ru(III)(L0)Ru(III) formulation. The usefulness and limitations of the increasingly popular structure/oxidation state correlations for complexes with noninnocent ligands is being discussed.

Counterinsurgency in Somalia: Lessons Learned from the African Union Mission in Somalia, 2007-2013

DTIC Science & Technology

2014-09-01

J S O U R e p o rt 1 4 -5 C o u n te rin s u rg e n c y in S o m a lia B ru to n / W illia m s Counterinsurgency...REPORT unclassified b. ABSTRACT unclassified c . THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Joint...Force Ret., Resident Senior Fellows Anna-Marie Wyant, M.A., English, JSOU Press Editor Editorial Advisory Board Roby C . Barrett Ph.D., Middle

Examination of Chemical Adsorption and Marine Biofouling on Metal Surfaces Using Raman Scattering Techniques and Electrochemical Impedance Spectroscopy

DTIC Science & Technology

1989-01-13

aromatic amino acids adsorbed on conditioned Ag electrodes in 0.1 N KCl. A. tryptophan. B. phenylalanine. Ribulose biphosphate carboxylase ( RuBisCo ) has...Preliminary runs with a silver electrode, UV-oxidized seawater, and a putative fouling protein, Ribulose 1,5 biphosphate carboxylase ( RuBisCo ) have been...completed. Prior to adding RuBisCo to the system, a series of runs were made to establish functionality of the cell and system parameters. The system

Ruthenium isotopic evidence for an inner Solar System origin of the late veneer

NASA Astrophysics Data System (ADS)

Fischer-Gödde, Mario; Kleine, Thorsten

2017-01-01

The excess of highly siderophile elements in the Earth’s mantle is thought to reflect the addition of primitive meteoritic material after core formation ceased. This ‘late veneer’ either comprises material remaining in the terrestrial planet region after the main stages of the Earth’s accretion, or derives from more distant asteroidal or cometary sources. Distinguishing between these disparate origins is important because a late veneer consisting of carbonaceous chondrite-like asteroids or comets could be the principal source of the Earth’s volatiles and water. Until now, however, a ‘genetic’ link between the late veneer and such volatile-rich materials has not been established or ruled out. Such genetic links can be determined using ruthenium (Ru) isotopes, because the Ru in the Earth’s mantle predominantly derives from the late veneer, and because meteorites exhibit Ru isotope variations arising from the heterogeneous distribution of stellar-derived dust. Although Ru isotopic data and the correlation of Ru and molybdenum (Mo) isotope anomalies in meteorites were previously used to argue that the late veneer derives from the same type of inner Solar System material as do Earth’s main building blocks, the Ru isotopic composition of carbonaceous chondrites has not been determined sufficiently well to rule them out as a source of the late veneer. Here we show that all chondrites, including carbonaceous chondrites, have Ru isotopic compositions distinct from that of the Earth’s mantle. The Ru isotope anomalies increase from enstatite to ordinary to carbonaceous chondrites, demonstrating that material formed at greater heliocentric distance contains larger Ru isotope anomalies. Therefore, these data refute an outer Solar System origin for the late veneer and imply that the late veneer was not the primary source of volatiles and water on the Earth.

Raman and electronic transport characterization of few- and single-layer-thick α-RuCl3

NASA Astrophysics Data System (ADS)

Zhou, Boyi; Henriksen, Erik

The layered magnetic semiconductor α-RuCl3, having a honeycomb lattice of spin-1/2 moments, has been identified as a potential candidate material to realize the Kitaev quantum spin liquid. In particular, bulk RuCl3 crystals have been studied and found to be on the cusp of manifesting QSL behavior. As the QSL is primarily a two-dimensional phenomenon, and since the layers of RuCl3 are weakly coupled, we propose to create and study a 2D spin-1/2 honeycomb system by isolating single sheets. Here we report the exfoliation of RuCl3 down to few- and single-layer-thick samples, which we characterize by Raman spectroscopy and atomic force microscopy at room temperature. We will also report our progress on measurements of basic electronic transport properties in the 2D RuCl3 system by controlling the chemical potential via gating in a field-effect configuration.

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production.

PubMed

Reynal, Anna; Pastor, Ernest; Gross, Manuela A; Selim, Shababa; Reisner, Erwin; Durrant, James R

2015-08-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye ( RuP ) and a nickel bis(diphosphine) electrocatalyst ( NiP ) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H 2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP - NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH <4.5, the efficiency of the system is limited by the yield of RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP , which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP - NiP photocatalytic system, which can be widely applied to other photocatalytic systems.

Single and double beta decays in the A=100, A=116 and A=128 triplets of isobars

NASA Astrophysics Data System (ADS)

Suhonen, J.; Civitarese, O.

2014-04-01

In this paper we analyze the ground-state-to-ground-state two-neutrino double beta (2νββ) decays and single EC and β- decays for the A=100 (100Mo-100Tc-100Ru), A=116 (116Cd-116In-116Sn) and A=128 (128Te-128I-128Xe) triplets of isobars. We use the proton-neutron quasiparticle random-phase approximation (pnQRPA) with realistic G-matrix-derived effective interactions in very large single-particle bases. The purpose is to access the effective value of the axial-vector coupling constant gA in the pnQRPA calculations. We show that the three triplets of isobars represent systems with different characteristics of orbital occupancies and cumulative 2νββ nuclear matrix elements. Our analysis points to a considerably quenched averaged effective value of ≈0.6±0.2 in the pnQRPA calculations.

III-V semiconductor solid solution single crystal growth

NASA Technical Reports Server (NTRS)

Gertner, E. R.

1982-01-01

The feasibility and desirability of space growth of bulk IR semiconductor crystals for use as substrates for epitaxial IR detector material were researched. A III-V ternary compound (GaInSb) and a II-VI binary compound were considered. Vapor epitaxy and quaternary epitaxy techniques were found to be sufficient to permit the use of ground based binary III-V crystals for all major device applications. Float zoning of CdTe was found to be a potentially successful approach to obtaining high quality substrate material, but further experiments were required.

Direct catalytic conversion of methane and light hydrocarbon gases. Quarterly report No. 9, October 1--December 31, 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, R.B. Jr.; Posin, B.M.; Chan, Yee Wai

The goal of this research is to develop catalysts that directly convert methane and light hydrocarbons to intermediates that later can be converted to either liquid fuels or value-added chemicals, as economics dictate. During this reporting period, we completed our IR spectroscopic examination of the Ru{sub 4}/MgO and FeRu{sub 3}/MgO systems under nitrogen and methane by examining FeRu{sub 3}/MgO under methane. This system behaved quite differently than the same system under nitrogen. Under methane, only one very broad peak is observed at room temperature. Upon heating, the catalyst transformed so that by 300{degrees}C, the spectrum of FeRu{sub 3}/MgO under methanemore » was the same as that of Ru{sub 4}/MgO. This suggests that methane promotes the segregation of the metals in the mixed metal system. The differences in catalytic activity between the FeRu{sub 3}/MgO and Ru{sub 4}/MgO systems may then be due to the presence of IR transparent species such as iron ions which cause different nucleation in the ruthenium clusters. We examined several systems for activity in the methane dehydrogenation reaction. Focusing on systems which produce C{sub 6} hydrocarbons since this is the most useful product. These systems all displayed low activity so that the amount of hydrocarbon product is very low. Some C{sub 6} hydrocarbon is observed over zeolite supports, but its production ceases after the first few hours of reaction. We prepared a new system, Ru{sub 4} supported on carbon, and examined its reactivity. Its activity was very low and in fact the carbon support had the same level of activity. We synthesized four new systems for examination as catalysts in the partial oxidation of methane. Three of these (PtTSPC/MgO, PtTSPC and PdTSPC on carbon) are analogs of PdTSPC/MgO. This system is of interest because we have observed the production of ethane from methane oxidation over PdTSPC/MgO at relatively low temperatures and we wished to explore its generality among close analogs.« less

H.E.S.S. and CTA, present and perspectives in ground-based gamma-ray astronomy

NASA Astrophysics Data System (ADS)

Sol, H.

2016-12-01

Very high energy (VHE) gamma-ray astronomy emerged as a new branch of astronomy about ten years ago with the major discoveries achieved by the High Energy Stereocopic System (H.E.S.S.) operating in Namibia, quickly followed by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) in the Canary Islands and the Very Energetic Radiation Imaging Telescope Array System (VERITAS) in the USA. These experiments succeeded to start exploring the cosmos at TeV energies, with the present detection of 178 sources in this range, mostly pulsar wind nebulae, supernova remnants, binary systems, blazars, and a variety of other types of sources. Based on these promizing results, the scientific community soon defined a next generation global project with significantly improved performance, the Cherenkov Telescope Array (CTA), in order to implement an open observatory at extreme energies, allowing a deep analysis of the sky in the highest part of the electromagnetic spectrum, from 20 GeV to 300 TeV. The CTA preparation phase is now completed. Production of the first telescopes should start in 2017 for deployment in 2018, in the perspective of an array fully operational at the horizon 2022.

Magnetic impurities in conducting oxides. II. (Sr1-xLax)(Ru1-xCox)O3 system

NASA Astrophysics Data System (ADS)

Mamchik, A.; Dmowski, W.; Egami, T.; Chen, I.-Wei

2004-09-01

The perovskite solid solution between ferromagnetic SrRuO3 and antiferromagnetic LaCoO3 is studied and its structural, electronic,and magnetic properties are compared with (Sr1-xLax)(Ru1-xFex)O3 . The lower 3d energy levels of Co3+ cause a local charge transfer from 4dRu4+ , a reaction that has the novel feature of being sensitive to the local atomic structure such as cation order. Despite such a complication, Co , like Fe , spin-polarizes the itinerant electrons in SrRuO3 to form a large local magnetic moment that is switchable at high fields. In the spin glass regime when Anderson localization dominates, a large negative magnetoresistance emerges as a result of spin polarization of mobile electronic carriers that occupy states beyond the mobility edge. A phenomenological model predicting an inverse relation between magnetoresistance and saturation magnetization is proposed to explain the composition dependence of magnetoresistance for both (Sr1-xLax)(Ru1-xCOx)O3 and (Sr1-xLax)(Ru1-xFex)O3 systems.

Pressure evolution of electrical transport in the 3D topological insulator (Bi,Sb)2(Te,Se)3

NASA Astrophysics Data System (ADS)

Jeffries, Jason; Butch, N. P.; Vohra, Y. K.; Weir, S. T.

2014-03-01

The group V-VI compounds--like Bi2Se3, Sb2Te3, or Bi2Te3--have been widely studied in recent years for their bulk topological properties. The high-Z members of this series form with the same crystal structure, and are therefore amenable to isostructural substitution studies. It is possible to tune the Bi-Sb and Te-Se ratios such that the material exhibits insulating behavior, thus providing an excellent platform for understanding how a topological insulator evolves with applied pressure. We report our observations of the pressure-dependent electrical transport and compare that behavior with other binary V-VI compounds under pressure. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

Exploring Photoinduced Excited State Evolution in Heterobimetallic Ru(II)-Co(III) Complexes.

PubMed

Kuhar, Korina; Fredin, Lisa A; Persson, Petter

2015-06-18

Quantum chemical calculations provide detailed theoretical information concerning key aspects of photoinduced electron and excitation transfer processes in supramolecular donor-acceptor systems, which are particularly relevant to fundamental charge separation in emerging molecular approaches for solar energy conversion. Here we use density functional theory (DFT) calculations to explore the excited state landscape of heterobimetallic Ru-Co systems with varying degrees of interaction between the two metal centers, unbound, weakly bound, and tightly bound systems. The interplay between structural and electronic factors involved in various excited state relaxation processes is examined through full optimizations of multiple charge/spin states of each of the investigated systems. Low-energy relaxed heterobimetallic states of energy transfer and excitation transfer character are characterized in terms of energy, structure, and electronic properties. These findings support the notion of efficient photoinduced charge separation from a Ru(II)-Co(III) ground state, via initial optical excitation of the Ru-center, to low-energy Ru(III)-Co(II) states. The strongly coupled system has significant involvement of the conjugated bridge, qualitatively distinguishing it from the other two weakly coupled systems. Finally, by constructing potential energy surfaces for the three systems where all charge/spin state combinations are projected onto relevant reaction coordinates, excited state decay pathways are explored.

Design, crystal growth, and physical properties of low-temperature thermoelectric materials

NASA Astrophysics Data System (ADS)

Fuccillo, Michael K.

Thermoelectric materials serve as the foundation for two important modern technologies, namely 1) solid-state cooling, which enables small-area refrigeration without vibrations or moving parts, and 2) thermoelectric power generation, which has important implications for waste heat recovery and improved sources of alternative energy. Although the overall field of thermoelectrics research has been active for decades, and several consumer and industrial products have already been commercialized, the design and synthesis of new thermoelectrics that outperform long-standing state of the art materials has proven extremely challenging. This is particularly true for low-temperature refrigeration applications, which is the focus of this work; however, scientific advances in this area generally support power generation as well. In order to achieve more efficient materials for virtually all thermoelectric applications, improved materials design principles must be developed and synthetic procedures must be better understood. We aim to contribute to these goals by studying two classes of materials, namely 1) the tetradymites Bi2TeSe 2 and Bi2Te2Se, which are close relatives of state of the art thermoelectric cooling materials, and 2) Kondo insulating (-like) FeSb2 and FeSi, which possess anomalously enhanced low-temperature thermoelectric properties that arise from exotic electronic and magnetic properties. The organization of this dissertation is as follows: Chapter 1 is a brief perspective on solid-state chemistry. Chapter 2 presents experimental methods for synthesizing and characterizing thermoelectric materials. In Chapter 3, two original research projects are discussed: first, work on the tetradymite Bi2TeSe2 doped with Sb to achieve an n- to p-type transition, and second, the tetradymite Bi2Te2Se with chemical defects through two different methods. Chapter 4 gives the magnetic and transport properties of FeSb 2--RuSb2 alloys, a family of compounds exemplifying what we consider to be the next generation of thermoelectric materials for low-temperature cooling due to their anomalously enhanced low-temperature thermoelectric properties, along with an outlook for seeking additional materials with similarly enhanced properties. Lastly, in Chapter 5, a brief outlook on the future of thermoelectrics is discussed, along with our current and future work on FeSi-RuSi alloys.

Properties of Kilonovae from Dynamical and Post-merger Ejecta of Neutron Star Mergers

NASA Astrophysics Data System (ADS)

Tanaka, Masaomi; Kato, Daiji; Gaigalas, Gediminas; Rynkun, Pavel; Radžiūtė, Laima; Wanajo, Shinya; Sekiguchi, Yuichiro; Nakamura, Nobuyuki; Tanuma, Hajime; Murakami, Izumi; Sakaue, Hiroyuki A.

2018-01-01

Ejected material from neutron star mergers gives rise to electromagnetic emission powered by radioactive decays of r-process nuclei, the so-called kilonova or macronova. While properties of the emission are largely affected by opacities in the ejected material, available atomic data for r-process elements are still limited. We perform atomic structure calculations for r-process elements: Se (Z = 34), Ru (Z = 44), Te (Z = 52), Ba (Z = 56), Nd (Z = 60), and Er (Z = 68). We confirm that the opacities from bound–bound transitions of open f-shell, lanthanide elements (Nd and Er) are higher than those of the other elements over a wide wavelength range. The opacities of open s-shell (Ba), p-shell (Se and Te), and d-shell (Ru) elements are lower than those of open f-shell elements, and their transitions are concentrated in the ultraviolet and optical wavelengths. We show that the optical brightness can be different by > 2 mag depending on the element abundances in the ejecta such that post-merger, lanthanide-free ejecta produce brighter and bluer optical emission. Such blue emission from post-merger ejecta can be observed from the polar directions if the mass of the preceding dynamical ejecta in these regions is small. For the ejecta mass of 0.01 {M}ȯ , observed magnitudes of the blue emission will reach 21.0 mag (100 Mpc) and 22.5 mag (200 Mpc) in the g and r bands within a few days after the merger, which are detectable with 1 m or 2 m class telescopes.

Oxygen-Dependent Photocatalytic Water Reduction with a Ruthenium(imidazolium) Chromophore and a Cobaloxime Catalyst.

PubMed

Petermann, Lydia; Staehle, Robert; Pfeifer, Maxim; Reichardt, Christian; Sorsche, Dieter; Wächtler, Maria; Popp, Jürgen; Dietzek, Benjamin; Rau, Sven

2016-06-06

Detailed investigations of a photocatalytic system capable of producing hydrogen under pre-catalytic aerobic conditions are reported. This system consists of the NHC precursor chromophore [Ru(tbbpy)2 (RR'ip)][PF6 ]3 (abbreviated as Ru(RR'ip)[PF6 ]3 ; tbbpy=4,4'-di-tert-butyl-2,2'-bipyridine, RR'ip=1,3-disubstituted-1H-imidazo[4,5-f][1,10]phenanthrolinium), the reduction catalyst Co(dmgH)2 (dmgH=dimethylglyoximato), and the electron donor ascorbic acid (AA). Screening studies with respect to solvent, cobaloxime catalyst, electron donor, pH, and concentrations of the individual components yielded optimized photocatalytic conditions. The system shows high activity based on Ru, with turnover numbers up to 2000 under oxygen-free and pre-catalytic aerobic conditions. The turnover frequency in the latter case was even higher than that for the oxygen-free catalyst system. The Ru complexes show high photostability and their first excited state is primarily located on the RR'ip ligand. X-ray crystallographic analysis of the rigid cyclophane-type ligand dd(ip)2 (Br)2 (dd(ip)2 =1,1',3,3'-bis(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(1H-imidazo[4,5-f][1,10]phenanthrolinium)) and the catalytic activity of its Ru complex [{(tbbpy)2 Ru}2 (μ-dd(ip)2 )][PF6 ]6 (abbreviated as Ru2 (dd(ip)2 )[PF6 ]6 ) suggest an intermolecular catalytic cycle. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase stabilities of pyrite-related MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te): A systematic DFT study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bachhuber, Frederik; School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland; Krach, Alexander

2015-03-15

Pyrite-type and related systems appear for a wide range of binary and ternary combinations of transition metals and main group elements that form Zintl type dumbbell anion units. Those representatives with 20 valence electrons exhibit an extraordinary structural flexibility and interesting properties as low-gap semiconductors or thermoelectric and electrode materials. This work is devoted to the systematic exploration of novel compounds within the class of MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te) by means of density functional calculations. Their preferred structures are predicted from an extended scheme of colored pyrites and marcasites. To determine theirmore » stabilities, competing binary MT{sub 2} and MCh{sub 2} boundary phases are taken into account as well as ternary M{sub 3}T{sub 2}Ch{sub 2} and M{sub 2}T{sub 3}Ch{sub 3} systems. Recently established stability diagrams are presented to account for MTCh ordering phenomena with a focus on a not-yet-reported ordering variant of the NiAs{sub 2} type. Due to the good agreement with experimental data available for several PtTCh systems, the predictions for the residual systems are considered sufficiently accurate. - Graphical abstract: Compositional and structural stability of MTCh compounds is investigated from first principle calculations. A conceptional approach is presented to study and predict novel stable and metastable compounds and structures of low gap semiconductors with TCh dumbbell units that are isoelectronic and structurally related to pyrite (FeS{sub 2}). - Highlights: • Study of compositional stability of MTCh vs. M{sub 3}T{sub 2}Ch{sub 2} and M{sub 2}T{sub 3}Ch{sub 3} compounds. • Study of structural stability of known and novel MTCh compounds. • Prediction of novel stable and metastable structures and compounds isoelectronic to pyrite, FeS{sub 2}.« less

Direct evidence for double-exchange coupling in Ru- substituted La0.7Pb0.3Mn 1 - x Ru x O3, 0.0 <= x <= 0.4

NASA Astrophysics Data System (ADS)

Sundar Manoharan, S.; Sahu, R. K.; Rao, M. L.; Elefant, D.; Schneider, C. M.

2002-08-01

The La0.7Pb0.3Mn 1 - x Ru x O3 (0.0 <= x <= 0.4) system shows an innate relationship between Mn and Ru ions by a unique double-exchange mediated transport behavior. This is exonerated by the coexistence of Tp and Tc (range 330 K 245 K for 0.0 <= x <= 0.4). For Ru > 30%, the hole carrier mass influences the transport property. X-ray absorption spectra suggest that the Tc-Tp match is due to the transport mediated by the Mn3+/Mn4+ leftrightarrow Ru4+/Ru5+ redox pair and also due to the broad low-spin Ru:4d conduction band. For x > 0.2, T < 0.5Tc obeys a modified variable-range hopping model, where kT0 propto (M/Ms)2, suggesting a random magnetic potential which localizes the charge carriers.

Gamma–Gamma Absorption in the γ-ray Binary System PSR B1259-63/LS 2883

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sushch, Iurii; Van Soelen, Brian, E-mail: iurii.sushch@desy.de, E-mail: vansoelenb@ufs.ac.za

2017-03-10

The observed TeV light curve from the γ -ray binary PSR B1259-63/LS 2883 shows a decrease in the flux at periastron that has not been fully explained by emission mechanisms alone. This observed decrease can, however, be explained by γγ absorption due to the stellar and disk photons. We calculate the γγ absorption in PSR B1259-63/LS 2883 taking into account photons from both the circumstellar disk and star, assuming that the γ -rays originate at the position of the pulsar. The γγ absorption due to the circumstellar disk photons produces a ≈14% decrease in the flux, and there is amore » total decrease of ≈52% (>1 TeV) within a few days before periastron, accompanied by a hardening of the γ -ray photon index. While the γγ absorption alone is not sufficient to explain the full complexity of the H.E.S.S. γ -ray light curve, it results in a significant decrease in the predicted flux, which is coincident with the observed decrease. In addition, we have calculated an upper limit on the γγ absorption, assuming that the emission is produced at the apex of the bow shock. Future observations with CTA during the 2021 periastron passage may be able to confine the location of the emission based on the degree of γγ absorption, as well as measure the hardening of the spectrum around periastron.« less

NuSTAR Hard X-Ray Observation of the Gamma-Ray Binary Candidate HESS J1832-093

NASA Astrophysics Data System (ADS)

Mori, Kaya; Gotthelf, E. V.; Hailey, Charles J.; Hord, Ben J.; de Oña Wilhelmi, Emma; Rahoui, Farid; Tomsick, John A.; Zhang, Shuo; Hong, Jaesub; Garvin, Amani M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.

2017-10-01

We present a hard X-ray observation of the TeV gamma-ray binary candidate HESS J1832-093, which is coincident with the supernova remnant G22.7-0.2, using the Nuclear Spectroscopic Telescope Array. Non-thermal X-ray emission from XMMU J183245-0921539, the X-ray source associated with HESS J1832-093, is detected up to ˜30 keV and is well-described by an absorbed power-law model with a best-fit photon index {{Γ }}=1.5+/- 0.1. A re-analysis of archival Chandra and XMM-Newton data finds that the long-term X-ray flux increase of XMMU J183245-0921539 is {50}-20+40 % (90% C.L.), much less than previously reported. A search for a pulsar spin period or binary orbit modulation yields no significant signal to a pulse fraction limit of {f}p< 19 % in the range 4 ms < P< 40 ks. No red noise is detected in the FFT power spectrum to suggest active accretion from a binary system. While further evidence is required, we argue that the X-ray and gamma-ray properties of XMMU J183245-0921539 are most consistent with a non-accreting binary generating synchrotron X-rays from particle acceleration in the shock formed as a result of the pulsar and stellar wind collision. We also report on three nearby hard X-ray sources, one of which may be associated with diffuse emission from a fast-moving supernova fragment interacting with a dense molecular cloud.

The barium iron ruthenium oxide system

NASA Technical Reports Server (NTRS)

Kemmler-Sack, S.; Ehmann, A.

1986-01-01

In the system BaFe(1-x)Ru(x)O(3-y), three phases, separated by immiscibility gaps, are present: an Fe-rich phase (x = 0 to 0.75) with hexagonal BaTiO3 structure (6H; sequence (hcc)2), a Ru-rich phase (x = 0.9) of hexagonal 4H-type (sequence (hc)2), and the pure Ru compounds BaRuO3 with rhombohedral 9R structure (sequence (hhc)3). By vibrational spectroscopic investigations in the 6H phase a transition from n-type semiconduction (Fe-rich compounds with complete O lattice) can be detected. The 4H and 9R stacking polytypes are good, metal-like conductors. The lattice parameters are given.

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc01349f Click here for additional data file.

PubMed Central

Pastor, Ernest; Gross, Manuela A.; Selim, Shababa

2015-01-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye (RuP) and a nickel bis(diphosphine) electrocatalyst (NiP) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP–NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH <4.5, the efficiency of the system is limited by the yield of RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP, which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP–NiP photocatalytic system, which can be widely applied to other photocatalytic systems. PMID:28717491

Photochemical Properties and Reactivity of a Ru Compound Containing an NAD/NADH-Functionalized 1,10-Phenanthroline Ligand.

PubMed

Kobayashi, Katsuaki; Ohtsu, Hideki; Nozaki, Koichi; Kitagawa, Susumu; Tanaka, Koji

2016-03-07

An NAD/NADH-functionalized ligand, benzo[b]pyrido[3,2-f][1,7]-phenanthroline (bpp), was newly synthesized. A Ru compound containing the bpp ligand, [Ru(bpp)(bpy)2](2+), underwent 2e(-) and 2H(+) reduction, generating the NADH form of the compound, [Ru(bppHH)(bpy)2](2+), in response to visible light irradiation in CH3CN/TEA/H2O (8/1/1). The UV-vis and fluorescent spectra of both [Ru(bpp)(bpy)2](2+) and [Ru(bppHH)(bpy)2](2+) resembled the spectra of [Ru(bpy)3](2+). Both complexes exhibited strong emission, with quantum yields of 0.086 and 0.031, respectively; values that are much higher than those obtained from the NAD/NADH-functionalized complexes [Ru(pbn)(bpy)2](2+) and [Ru(pbnHH)(bpy)2](2+) (pbn = (2-(2-pyridyl)benzo[b]-1.5-naphthyridine, pbnHH = hydrogenated form of pbn). The reduction potential of the bpp ligand in [Ru(bpp)(bpy)2](2+) (-1.28 V vs SCE) is much more negative than that of the pbn ligand in [Ru(pbn)(bpy)2](2+) (-0.74 V), although the oxidation potentials of bppHH and pbnHH are essentially equal (0.95 V). These results indicate that the electrochemical oxidation of the dihydropyridine moiety in the NADH-type ligand was independent of the π system, including the Ru polypyridyl framework. [Ru(bppHH)(bpy)2](2+) allowed the photoreduction of oxygen, generating H2O2 in 92% yield based on [Ru(bppHH)(bpy)2](2+). H2O2 production took place via singlet oxygen generated by the energy transfer from excited [Ru(bppHH)(bpy)2](2+) to triplet oxygen.

Synthesis, crystal structures and luminescence properties of the Eu 3+-doped yttrium oxotellurates(IV) Y 2Te 4O 11 and Y 2Te 5O 13

NASA Astrophysics Data System (ADS)

Höss, Patrick; Osvet, Andres; Meister, Frank; Batentschuk, Miroslaw; Winnacker, Albrecht; Schleid, Thomas

2008-10-01

Y 2Te 4O 11:Eu 3+ and Y 2Te 5O 13:Eu 3+ single crystals in sub-millimeter scale were synthesized from the binary oxides (Y 2O 3, Eu 2O 3 and TeO 2) using CsCl as fluxing agent. Crystallographic structures of the undoped yttrium oxotellurates(IV) Y 2Te 4O 11 and Y 2Te 5O 13 have been determined and refined from single-crystal X-ray diffraction data. In Y 2Te 4O 11, a layered structure is present where the reticulated sheets consisting of edge-sharing [YO 8] 13- polyhedra are interconnected by the oxotellurate(IV) units, whereas in Y 2Te 5O 13 only double chains of condensed yttrium-oxygen polyhedra with coordination numbers of 7 and 8 are left, now linked in two crystallographic directions by the oxotellurate(IV) entities. The Eu 3+ luminescence spectra and the decay time from different energy levels of the doped compounds were investigated and all detected emission levels were identified. Luminescence properties of the Eu 3+ cations have been interpreted in consideration of the now accessible detailed crystallographic data of the yttrium compounds, providing the possibility to examine the influence of the local symmetry of the oxygen coordination spheres.

Electrochemical, spectroscopic, and photophysical properties of structurally diverse polyazine-bridged Ru(II),Pt(II) and Os(II),Ru(II),Pt(II) supramolecular motifs.

PubMed

Knoll, Jessica D; Arachchige, Shamindri M; Wang, Guangbin; Rangan, Krishnan; Miao, Ran; Higgins, Samantha L H; Okyere, Benjamin; Zhao, Meihua; Croasdale, Paul; Magruder, Katherine; Sinclair, Brian; Wall, Candace; Brewer, Karen J

2011-09-19

Five new tetrametallic supramolecules of the motif [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) and three new trimetallic light absorbers [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) (TL = bpy = 2,2'-bipyridine or phen = 1,10-phenanthroline; M = Ru(II) or Os(II); BL = dpp = 2,3-bis(2-pyridyl)pyrazine, dpq = 2,3-bis(2-pyridyl)quinoxaline, or bpm = 2,2'-bipyrimidine) were synthesized and their redox, spectroscopic, and photophysical properties investigated. The tetrametallic complexes couple a Pt(II)-based reactive metal center to Ru and/or Os light absorbers through two different polyazine BL to provide structural diversity and interesting resultant properties. The redox potential of the M(II/III) couple is modulated by M variation, with the terminal Ru(II/III) occurring at 1.58-1.61 V and terminal Os(II/III) couples at 1.07-1.18 V versus Ag/AgCl. [{(TL)(2)M(dpp)}(2)Ru(BL)](PF(6))(6) display terminal M(dπ)-based highest occupied molecular orbitals (HOMOs) with the dpp(π*)-based lowest unoccupied molecular orbital (LUMO) energy relatively unaffected by the nature of BL. The coupling of Pt to the BL results in orbital inversion with localization of the LUMO on the remote BL in the tetrametallic complexes, providing a lowest energy charge separated (CS) state with an oxidized terminal Ru or Os and spatially separated reduced BL. The complexes [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) and [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) efficiently absorb light throughout the UV and visible regions with intense metal-to-ligand charge transfer (MLCT) transitions in the visible at about 540 nm (M = Ru) and 560 nm (M = Os) (ε ≈ 33,000-42,000 M(-1) cm(-1)) and direct excitation to the spin-forbidden (3)MLCT excited state in the Os complexes about 720 nm. All the trimetallic and tetrametallic Ru-based supramolecular systems emit from the terminal Ru(dπ)→dpp(π*) (3)MLCT state, λ(max)(em) ≈ 750 nm. The tetrametallic systems display complex excited state dynamics with quenching of the (3)MLCT emission at room temperature to populate the lowest-lying (3)CS state population of the emissive (3)MLCT state.

Durable pd-based alloy and hydrogen generation membrane thereof

DOEpatents

Benn, Raymond C.; Opalka, Susanne M.; Vanderspurt, Thomas Henry

2010-02-02

A durable Pd-based alloy is used for a H.sub.2-selective membrane in a hydrogen generator, as in the fuel processor of a fuel cell plant. The Pd-based alloy includes Cu as a binary element, and further includes "X", where "X" comprises at least one metal from group "M" that is BCC and acts to stabilize the .beta. BCC phase for stability during operating temperatures. The metal from group "M" is selected from the group consisting of Fe, Cr, Nb, Ta, V, Mo, and W, with Nb and Ta being most preferred. "X" may further comprise at least one metal from a group "N" that is non-BCC, preferably FCC, that enhances other properties of the membrane, such as ductility. The metal from group "N" is selected from the group consisting of Ag, Au, Re, Ru, Rh, Y, Ce, Ni, Ir, Pt, Co, La and In. The at. % of Pd in the binary Pd--Cu alloy ranges from about 35 at. % to about 55 at. %, and the at. % of "X" in the higher order alloy, based on said binary alloy, is in the range of about 1 at. % to about 15 at. %. The metals are selected according to a novel process.

Roles of aromatic side chains and template effects of the hydrophobic cavity of a self-assembled peptide nanoarchitecture for anisotropic growth of gold nanocrystals.

PubMed

Tomizaki, Kin-ya; Kishioka, Kohei; Kobayashi, Hiroki; Kobayashi, Akitsugu; Yamada, Naoki; Kataoka, Shunsuke; Imai, Takahito; Kasuno, Megumi

2015-11-15

Gold nanocrystals are promising as catalysts and for use in sensing/imaging systems, photonic/plasmonic devices, electronics, drug delivery systems, and for photothermal therapy due to their unique physical, chemical, and biocompatible properties. The use of various organic templates allows control of the size, shape, structure, surface modification and topology of gold nanocrystals; in particular, currently the synthesis of gold nanorods requires a cytotoxic surfactant to control morphology. To control the shape of gold nanocrystals, we previously demonstrated the de novo design and synthesis of a β-sheet-forming nonapeptide (RU006: Ac-AIAKAXKIA-NH2, X=L-2-naphthylalanine, Nal) and the fabrication of gold nanocrystals by mixing RU006 and HAuCl4 in water. The reaction afforded ultrathin gold nanoribbons 50-100 nm wide, several nanometers high, and microns long. To understand the mechanism underlying gold nanoribbon formation by the RU006 system, we here report (i) the effects of replacement of the Nal aromatic side chain in the RU006 sequence with other aromatic moieties, (ii) the electrochemical properties of aromatic side chains in the de novo designed template peptides to estimate the redox potential and number of electrons participating in the gold crystallization process, and (iii) the stoichiometry of the RU006 system for gold nanoribbon synthesis. Interestingly, RU006 bearing a naphthalene moiety (oxidation peak potential of 1.50 V vs Ag/Ag(+)) and an analog [Ant(6)]-RU006 bearing a bulky anthracene moiety (oxidation peak potential of 1.05 V vs Ag/Ag(+)) allowed the growth of anisotropic (ribbon-like) and isotropic (round) gold nanocrystals, respectively. This trend in morphology of gold nanocrystals was attributed to spatially-arranged hydrophobic cavities sufficiently large to accommodate the gold precursor and to allow directed crystal growth driven by cross-linking reactions among the naphthalene rings. Support for this mechanism was obtained by decreasing the mole fraction of [Ant(6)]-RU006 against the total concentration of [Ant(6)]-RU006 and [Phe(6)]-RU006: absorption spectra similar to that for RU006 were obtained. Differences in the redox properties of the anthracene and naphthalene moieties scarcely affected morphology. We propose that construction of an appropriate hydrophobic cavity is important for templating gold nanocrystal architectures by peptide self-assembly. This mechanism would be applicable for developing simple, low toxicity, mild synthetic methods for constructing metallic nanomaterials for therapeutic use. Copyright © 2015 Elsevier Ltd. All rights reserved.

The isothermal section of Gd–Ni–Si system at 1070 K

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru; Knotko, A.V.; Yapaskurt, V.O.

2016-03-15

The Gd–Ni–Si system has been investigated at 1070 K by X-ray and microprobe analyses. The existence of the known compounds, i.e.: GdNi{sub 10}Si{sub 2}, GdNi{sub 8}Si{sub 3}, GdNi{sub 5}Si{sub 3}, GdNi{sub 7}Si{sub 6}, GdNi{sub 6}Si{sub 6}, GdNi{sub 4}Si, GdNi{sub 2}Si{sub 2}, GdNiSi{sub 3}, Gd{sub 3}Ni{sub 6}Si{sub 2}, GdNiSi, GdNiSi{sub 2}, GdNi{sub 0.4}Si{sub 1.6}, Gd{sub 2}Ni{sub 2.35}Si{sub 0.65}, Gd{sub 3}NiSi{sub 2}, Gd{sub 3}NiSi{sub 3} and Gd{sub 6}Ni{sub 1.67}Si{sub 3}, has been confirmed. Moreover, five new phases have been identified in this system. The crystal structure for four of them has been determined: Gd{sub 2}Ni{sub 16−12.8}Si{sub 1−4.2} (Th{sub 2}Zn{sub 17}-type), GdNi{sub 6.6}Si{submore » 6} (GdNi{sub 7}Si{sub 6}-type), Gd{sub 3}Ni{sub 8}Si (Y{sub 3}Co{sub 8}Si-type) and Gd{sub 3}Ni{sub 11.5}Si{sub 4.2}(Gd{sub 3}Ru{sub 4}Ga{sub 12}-type). The compound with composition ~Gd{sub 2}Ni{sub 4}Si{sub 3} still remains with unknown structure. Quasi-binary phases, solid solutions, were detected at 1070 K to be formed by the binaries GdNi{sub 5}, GdNi{sub 3}, GdNi{sub 2}, GdNi, GdSi{sub 2} and GdSi{sub 1.67}; while no appreciable solubility was observed for the other binary compounds of the Gd–Ni–Si system. Magnetic properties of the GdNi{sub 6}Si{sub 6}, GdNi{sub 6.6}Si{sub 6} and Gd{sub 3}Ni{sub 11.5}Si{sub 4.2} compounds have also been investigated and are here reported. - Graphical abstract: The Gd–Ni–Si system has been investigated at 1070 K by X-ray and microprobe analyses. The known GdNi{sub 10}Si{sub 2}, GdNi{sub 8}Si{sub 3}, GdNi{sub 5}Si{sub 3}, GdNi{sub 7}Si{sub 6}, GdNi{sub 6}Si{sub 6}, GdNi{sub 4}Si, GdNi{sub 2}Si{sub 2}, GdNiSi{sub 3}, Gd{sub 3}Ni{sub 6}Si{sub 2}, GdNiSi, GdNiSi{sub 2}, GdNi{sub 0.4}Si{sub 1.6}, Gd{sub 2}Ni{sub 2.35}Si{sub 0.65}, Gd{sub 3}NiSi{sub 2}, Gd{sub 3}NiSi{sub 3} and Gd{sub 6}Ni{sub 1.67}Si{sub 3} compounds have been confirmed and five new ~Gd{sub 2}Ni{sub 4}Si{sub 3} (unknown type), Gd{sub 2}Ni{sub 16−12.8}Si{sub 1−4.2} (Th{sub 2}Zn{sub 17}-type), GdNi{sub 6.6}Si{sub 6} (GdNi{sub 7}Si{sub 6}-type), Gd{sub 3}Ni{sub 8}Si (Y{sub 3}Co{sub 8}Si-type) and Gd{sub 3}Ni{sub 11.5}Si{sub 4.2} (Gd{sub 3}Ru{sub 4}Ga{sub 12}-type) compounds have been detected in Gd–Ni–Si system at 1070 K. Quasi-binary phases, solid solutions, were detected at 1070 K to be formed by the binaries GdNi{sub 5}, GdNi{sub 3}, GdNi{sub 2}, GdNi, GdSi{sub 2} and GdSi{sub 1.67}; while no detectable solubility was observed for the other binary compounds of the Gd–Ni–Si system. Magnetic properties of the GdNi{sub 6}Si{sub 6}, GdNi{sub 6.6}Si{sub 6} and Gd{sub 3}Ni{sub 11.5}Si{sub 4.2} compounds have also been investigated and are here reported. - Highlights: • Gd–Ni–Si isothermal section was obtained at 1070 K. • Sixteen known ternary gadolinium nickel silicides were confirmed in Gd–Ni–Si. • Five new gadolinium nickel silicides were detected in Gd–Ni–Si. • GdNi{sub 6}Si{sub 6}, GdNi{sub 6.6}Si{sub 6} and Gd{sub 3}Ni{sub 11.5}Si{sub 4.2} show ferromagnetic-type ordering.« less

Regulation of Ribulose-1,5-Bisphosphate Carboxylase Activity by the Activase System in Lysed Spinach Chloroplasts

PubMed Central

Parry, Martin A. J.; Keys, Alfred J.; Foyer, Christine H.; Furbank, Robert T.; Walker, David A.

1988-01-01

Ribulose-1,5-bisphosphate (RuBP) carboxylase in lysed spinach (Spinacia oleracea L. cv virtuosa) chloroplasts that had been partly inactivated at low CO2 and Mg2+ by incubating in darkness with 4 millimolar partially purified RuBP was reactivated by light. If purified RuBP was used to inhibit dark activation of the enzyme, reactivation by light was not observed unless fructose-1,6-bisphosphate, ATP, or ADP plus inorganic phosphate were also added. Presumably, ADP plus inorganic phosphate acted as an ATP-generating system with a requirement for the generation of ΔpH across the thylakoid membrane. When the RuBP obtained from Sigma Chemical Co. was used, light did not reactivate the enzyme. There was no direct correlation between ΔpH and activation. Therefore, thylakoids are required in the ribulose-1,5-bisphosphate carboxylase activase system largely to synthesize ATP. Inactivation of RuBP carboxylase in isolated chloroplasts or in the lysed chloroplast system was not promoted simply by a transition from light to dark conditions but was caused by low CO2 and Mg2+. PMID:16666184

Synthesis, crystal structure, and properties of KSbO{sub 3}-type Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Manrong; Retuerto, Maria; Bok Go, Yong

2013-01-15

Single crystals of Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} were prepared from NaCl+KCl flux. This compound adopts KSbO{sub 3}-type crystal structure as evidenced by electron and single crystal X-ray diffraction analysis. The three-dimensional channel structure is formed by corner-sharing octahedral (Mn{sub 0.63}Te{sub 0.37}){sub 2}O{sub 10} dimers and two identical (Bi1){sub 4}(Bi2){sub 2} interpenetrating lattices. The intra-dimer Mn/Te-Mn/Te distances in Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} are short and are consistent with weak metal-metal interactions. The mixed oxidation state of manganese and the edge-sharing octahedral features are confirmed by X-ray near edge absorption spectroscopy measurements, which indicate Bi{sub 3}(Mn{sup III}{sub 1.1}Mn{sup IV}{sub 0.8})Te{supmore » VI}{sub 1.1}O{sub 11} with 57.7% Mn{sup 3+} and 42.3% Mn{sup 4+}. The partial substitution of Te for Mn perturbs long-range magnetic interactions, thereby destroying the ferromagnetic ordering found in Bi{sub 3}Mn{sub 3}O{sub 11} (T{sub C}=150 K). - Graphical abstract: Single crystal of Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} was grown from NaCl+KCl binary flux, suggesting that the high pressure Bi{sub 3}Mn{sub 3}O{sub 11} phase can be stabilized by partial substitution of Mn by Te at ambient pressure. Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} adopts a typical three dimensional KSbO{sub 3}-type crystal structure with three interpenetrating lattices and weak intra-dimmer metal-metal interaction caused by the d electrons of Mn. The edge-shared (Mn{sub 0.63}Te{sub 0.37}){sub 2}O{sub 10} octahedral dimer and mixed oxidation state of manganese (Bi{sub 3}(Mn{sup III}{sub 1.1}Mn{sup IV}{sub 0.8})Te{sup VI}{sub 1.1}O{sub 11} with 57.7% Mn{sup 3+} and 42.3% Mn{sup 4+}) features were evidenced by X-ray absorption near edge spectroscopy. Compared with Bi{sub 3}Mn{sub 3}O{sub 11}, the Te substituted Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} relaxes the crystal structure, but destroys the long-range magnetic ordering and gives short-range magnetic ordering below 5 K. Highlights: Black-Right-Pointing-Pointer High pressure Bi{sub 3}Mn{sub 3}O{sub 11} is stabilized by partial Te substitution at ambient pressure. Black-Right-Pointing-Pointer New KSbO{sub 3}-type Bi{sub 3}Mn{sub 1.9}Te{sub 1.1}O{sub 11} single crystal was grown from binary flux. Black-Right-Pointing-Pointer The presence of mixed oxidation state of manganese is evidenced by XANES study. Black-Right-Pointing-Pointer The Te-substitution destroys the long-range magnetic ordering and relaxes the structure.« less

Spin-orbit excitations and electronic structure of the putative Kitaev magnet α -RuCl3

NASA Astrophysics Data System (ADS)

Sandilands, Luke J.; Tian, Yao; Reijnders, Anjan A.; Kim, Heung-Sik; Plumb, K. W.; Kim, Young-June; Kee, Hae-Young; Burch, Kenneth S.

2016-02-01

Mott insulators with strong spin-orbit coupling have been proposed to host unconventional magnetic states, including the Kitaev quantum spin liquid. The 4 d system α -RuCl3 has recently come into view as a candidate Kitaev system, with evidence for unusual spin excitations in magnetic scattering experiments. We apply a combination of optical spectroscopy and Raman scattering to study the electronic structure of this material. Our measurements reveal a series of orbital excitations involving localized total angular momentum states of the Ru ion, implying that strong spin-orbit coupling and electron-electron interactions coexist in this material. Analysis of these features allows us to estimate the spin-orbit coupling strength, as well as other parameters describing the local electronic structure, revealing a well-defined hierarchy of energy scales within the Ru d states. By comparing our experimental results with density functional theory calculations, we also clarify the overall features of the optical response. Our results demonstrate that α -RuCl3 is an ideal material system to study spin-orbit coupled magnetism on the honeycomb lattice.

Synthesis, structure, and electronic properties of a dimer of Ru(bpy)2 doubly bridged by methoxide and pyrazolate.

PubMed

Jude, Hershel; Rein, Francisca N; White, Peter S; Dattelbaum, Dana M; Rocha, Reginaldo C

2008-09-01

The heterobridged dinuclear complex cis,cis-[(bpy) 2Ru(mu-OCH 3)(mu-pyz)Ru(bpy) 2] (2+) ( 1; bpy = 2,2'-bipyridine; pyz = pyrazolate) was synthesized and isolated as a hexafluorophosphate salt. Its molecular structure was fully characterized by X-ray crystallography, (1)H NMR spectroscopy, and ESI mass spectrometry. The compound 1.(PF 6) 2 (C 44H 38F 12N 10OP 2Ru 2) crystallizes in the monoclinic space group P2 1/ c with a = 13.3312(4) A, b = 22.5379(6) A, c = 17.2818(4) A, beta = 99.497(2) degrees , V = 5121.3(2) A (3), and Z = 4. The meso diastereoisomeric form was exclusively found in the crystal structure, although the NMR spectra clearly demonstrated the presence of two stereoisomers in solution (rac and meso forms at approximately 1:1 ratio). The electronic properties of the complex in acetonitrile were investigated by cyclic voltammetry and UV-vis and NIR-IR spectroelectrochemistries. The stepwise oxidation of the Ru (II)-Ru (II) complex into the mixed-valent Ru (II)-Ru (III) and fully oxidized Ru (III)-Ru (III) states is fully reversible on the time scale of the in situ (spectro)electrochemical measurements. The mixed-valent species displays strong electronic coupling, as evidenced by the large splitting between the redox potentials for the Ru(III)/Ru(II) couples (Delta E 1/2 = 0.62 V; K c = 3 x 10 (10)) and the appearance of an intervalence transfer (IT) band at 1490 nm that is intense, narrow, and independent of solvent. Whereas this salient band in the NIR region originates primarily from highest-energy of the three IT transitions predicted for Ru(II)-Ru(III) systems, a weaker absorption band corresponding to the lowest-energy IT transition was clearly evidenced in the IR region ( approximately 3200 cm (-1)). The observation of totally coalesced vibrational peaks in the 1400-1650 cm (-1) range for a set of five bpy spectator vibrations in Ru (II)-Ru (III) relative to Ru (II)-Ru (II) and Ru (III)-Ru (III) provided evidence for rapid electron transfer and valence averaging on the picosecond time scale. Other than a relatively short Ru...Ru distance (3.72 A for the crystalline Ru (II)-Ru (II) complex), the extensive communication between metal centers is attributed mostly to the pi-donor ability of the bridging ligands (pyz, OMe) combined with the pi-acceptor ability of the peripheral (bpy) ligands.

Variable noninnocence of substituted azobis(phenylcyanamido)diruthenium complexes.

PubMed

Choudhuri, Mohommad M R; Behzad, Mahdi; Al-Noaimi, Mousa; Yap, Glenn P A; Kaim, Wolfgang; Sarkar, Biprajit; Crutchley, Robert J

2015-02-16

The synthetic chemistry of substituted 4,4'-azobis(phenylcyanamide) ligands was investigated, and the complexes [{Ru(tpy)(bpy)}2(μ-L)][PF6]2, where L = 2,2':5,5'-tetramethyl-4,4'-azobis(phenylcyanamido) (Me4adpc(2-)), 2,2'-dimethyl-4,4'-azobis(phenylcyanamido) (Me2adpc(2-)), unsubstituted (adpc(2-)), 3,3'-dichloro-4,4'-azobis(phenylcyanamido) (Cl2adpc(2-)), and 2,2':5,5'-tetrachloro-4,4'-azobis(phenylcyanamido) (Cl4adpc(2-)), were prepared and characterized by cyclic voltammetry and vis-near-IR (NIR) and IR spectroelectrochemistry. The room temperature electron paramagnetic resonance spectrum of [{Ru(tpy)(bpy)}2(μ-Me4adpc)](3+) showed an organic radical signal and is consistent with an oxidation-state description [Ru(II), Me4adpc(•-), Ru(II)](3+), while that of [{Ru(tpy)(bpy)}2(μ-Cl2adpc)](3+) at 10 K showed a low-symmetry Ru(III) signal, which is consistent with the description [Ru(III), Cl2adpc(2-), Ru(II)](3+). IR spectroelectrochemistry data suggest that [{Ru(tpy)(bpy)}2(μ-adpc)](3+) is delocalized and [{Ru(tpy)(bpy)}2(μ-Cl2adpc)](3+) and [{Ru(tpy)(bpy)}2(μ-Cl4adpc)](3+) are valence-trapped mixed-valence systems. A NIR absorption band that is unique to all [{Ru(tpy)(bpy)}2(μ-L)](3+) complexes is observed; however, its energy and intensity vary depending on the nature of the bridging ligand and, hence, the complexes' oxidation-state description.

Multicomponent order parameter superconductivity of Sr2RuO4 revealed by topological junctions

NASA Astrophysics Data System (ADS)

Anwar, M. S.; Ishiguro, R.; Nakamura, T.; Yakabe, M.; Yonezawa, S.; Takayanagi, H.; Maeno, Y.

2017-06-01

Single crystals of the Sr2RuO4 -Ru eutectic system are known to exhibit enhanced superconductivity at 3 K in addition to the bulk superconductivity of Sr2RuO4 at 1.5 K. The 1.5 K phase is believed to be a spin-triplet, chiral p -wave state with a multicomponent order parameter, giving rise to chiral domain structure. In contrast, the 3 K phase is attributable to enhanced superconductivity of Sr2RuO4 in the strained interface region between Ru inclusion of a few to tens of micrometers in size and the surrounding Sr2RuO4 . We investigate the dynamic behavior of a topological junction, where a superconductor is surrounded by another superconductor. Specifically, we fabricated Nb/Ru/Sr2RuO4 topological superconducting junctions, in which the difference in phase winding between the s -wave superconductivity in Ru microislands induced from Nb and the superconductivity of Sr2RuO4 mainly governs the junction behavior. Comparative results of the asymmetry, hysteresis, and noise in junctions with different sizes, shapes, and configurations of Ru inclusions are explained by the chiral domain-wall motion in these topological junctions. Furthermore, a striking difference between the 1.5 and 3 K phases is clearly revealed: the large noise in the 1.5 K phase sharply disappears in the 3 K phase. These results confirm the multicomponent order-parameter superconductivity of the bulk Sr2RuO4 , consistent with the chiral p -wave state, and the proposed nonchiral single-component superconductivity of the 3 K phase.

The Japanese Space Program (Le Programme Spatial Japonais),

DTIC Science & Technology

1982-04-22

three-axis stabilization, study of vertical * structure of the earth); --series of probes for exploration of the moon and the planets. Future Missions...in foreground and 7 rr IArk j I, I *151 Fig. 9. Structural detail of the MU 3S (rear skirt) Fi. 1. St u tu a de ai of MU 3S..’’ ’ -, t r-’ ,’ s:,ru...ture) The total l t of te M I is 2-8. 2 m, - . The Fig. i. Structural detail of tU S (ri er sit)ctre 1.65 mthiamr. ach bfotitaniu wll have a

IUE spectrophotometry of the DA4 primary in the short-period white dwarf-red dwarf spectroscopic binary Case 1

NASA Technical Reports Server (NTRS)

Sion, E. M.; Guinan, E. F.; Wesemael, F.

1984-01-01

Low-resolution ultraviolet International Ultraviolet Explorer spectra of the DA white dwarf Case 1 are presented. The spectra show the presence of the 1400 A feature, already discovered in several other DA stars, and of a shallower trough in the 1550-1700 A range. A model atmosphere analysis of the ultraviolet energy distribution of the Ly-alpha red wing yields T(e) = 13,000 + or - 500 K. Possible interpretations of the 1400 A feature are reviewed. Case 1 is the coolest white dwarf found in a short-period, detached white dwarf-red dwarf binary, and its cooling time is consistent with estimates of the efficiency of angular momentum removal mechanisms in the phases subsequent to common envelope binary evolution.

Bio-hybrid integrated system for wide-spectrum solar energy harvesting

DOE PAGES

Martin, Kathleen; Erdman, Matthew; Quintana, Hope; ...

2014-03-07

An integrated hybrid photovoltaic-thermoelectric system has been developed using multiple layers of organic photosensitizers on inorganic semiconductors in order to efficiently convert UV-visible and IR energy into electricity. The hot anode of n-type ZnO nanowires was fabricated using a thermal process on pre-seeded layer and results to be crystalline with a transmittance up to 92 % and a bandgap of 3.32 eV. The visible-UV light-active organic layer was deposited between the anode and cathode at room temperature using a layer-by-layer deposition onto ITO and ZnO and Bi2Te3 nanowires from aqueous solution. The organic layer, a cooperative binary ionic (CBI) solidmore » is composed of oppositely charged porphyrin metal (Zn(II) and Sn(IV)(OH–)2) derivatives that are separately water soluble, but when combined form a virtually insoluble solid. The electron donor/acceptor properties (energy levels, band gaps) of the solid can be controlled by the choice of metals and the nature of the peripheral substituent groups of the porphyrin ring. The highly thermoelectric structure, which acts as a cold cathode, is composed of p-type Bi2Te3 nanowires with a thermoelectric efficiency (ZT) between ~0.7 to 1, values that are twice that expected for bulk Bi2Te3. Lastly, efficiency of the integrated device, was found to be 35 at 0.2 suns illumination and thermoelectric properties are enhanced by the charge transfer between the CBI and the Bi2Te3 is presented in terms of photo- and thermogenerated current and advantages of the low cost fabrication process is discussed.« less

Application of strong vertical magnetic fields to growth of II-VI pseudo-binary alloys - HgMnTe

NASA Astrophysics Data System (ADS)

Becla, Piotr; Han, Jian-Chiu; Motakef, Shahryar

1992-07-01

HgMnTe crystals are grown by the vertical Bridgman method in the presence of an applied vertical magnetic field of 30 kG. Reduction of convective intensity in the melt through application of the magnetic field is found to decrease radial macro-segregation and eliminate small-scale compositional undulations in the grown material; the axial compositional profile is found not to be influenced by the magnetic field. These observations are shown to be consistent with a previously proposed model for the residual convection present during growth of this and other similar materials.

BOREAS TE-17 Production Efficiency Model Images

NASA Technical Reports Server (NTRS)

Hall, Forrest G.; Papagno, Andrea (Editor); Goetz, Scott J.; Goward, Samual N.; Prince, Stephen D.; Czajkowski, Kevin; Dubayah, Ralph O.

2000-01-01

A Boreal Ecosystem-Atmospheric Study (BOREAS) version of the Global Production Efficiency Model (http://www.inform.umd.edu/glopem/) was developed by TE-17 (Terrestrial Ecology) to generate maps of gross and net primary production, autotrophic respiration, and light use efficiency for the BOREAS region. This document provides basic information on the model and how the maps were generated. The data generated by the model are stored in binary image-format files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Catalyzing the oxidation of sulfamethoxazole by permanganate using molecular sieves supported ruthenium nanoparticles.

PubMed

Zhang, Jing; Sun, Bo; Huang, Yuying; Guan, Xiaohong

2015-12-01

This study developed a heterogeneous catalytic permanganate oxidation system with three molecular sieves, i.e., nanosized ZSM-5 (ZSM-5A), microsized ZSM-5 (ZSM-5B) and MCM-41, supported ruthenium nanoparticles as catalyst, denoted as Ru/ZSM-5A, Ru/ZSM-5B and Ru/MCM-41, respectively. The presence of 0.5gL(-1) Ru/ZSM-5A, Ru/ZSM-5B and Ru/MCM-41 increased the oxidation rate of sulfamethoxazole (SMX) by permanganate at pH 7.0 by 27-1144 times. The catalytic performance of Ru catalysts toward SMX oxidation by permanganate was strongly dependent on Ru loading on the catalysts. The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses confirmed that Ru catalyst acted as an electron shuttle in catalytic permanganate oxidation process. Ru(III) deposited on the surface of catalysts was oxidized by permanganate to its higher oxidation state Ru(VII), which could work as a co-oxidant with permanganate to decompose SMX and was then reduced to its initial tri-valence. During the successive runs, Ru/ZSM-5A could not maintain its catalytic activity due to the deposition of MnO2, which was the reductive product of permanganate, onto the surface of Ru/ZSM-5A. Thus, the regeneration of partially deactivated Ru catalysts by reductant NH2OH⋅HCl or ascorbic acid was proposed. Ru/ZSM-5A regenerated by NH2OH⋅HCl displayed comparable catalytic ability to its virgin counterpart, while ascorbic acid could not completely remove the deposited MnO2. A trace amount of leaching of Ru into the reaction solution was also observed, which would be ameliorated by improving the preparation conditions in the future study. Copyright © 2015 Elsevier Ltd. All rights reserved.

The valence of Ru, Ce and Eu ions in the magneto-superconductor Eu 1.5Ce 0.5RuSr 2Cu 2O 10

NASA Astrophysics Data System (ADS)

Felner, I.; Asaf, U.; Godart, C.; Alleno, E.

1999-01-01

The superconducting (T c∼32 K) Eu 1.5Ce 0.5RuSr 2Cu 2O 10 (Ru-2122) material is also magnetically ordered (T M∼122 K) with TM≫ Tc. Superconductivity (SC) is confined to the CuO 2 planes, whereas magnetism is due to the Ru sublattice. Mossbauer spectroscopy performed at 90 and 300 K on 151Eu shows a single narrow line with an isomer shift=0.69(2) and a quadrupole splitting of 1.84 mm/s, indicating that the Eu ions are trivalent with a nonmagnetic J=0 ground state. This is in agreement with X-ray-absorption spectroscopy (XAS) taken at L III edges of Eu, Ce which shows that Eu is trivalent and Ce is tetravalent. XAS experiments at the K edge of Ru indicate that Ru is pentavalent. This indicates, that in the M-2122 system, SC exists only for pentavalent M ions such as Ta, Nb and Ru.

Thermodynamic properties of model CdTe/CdSe mixtures

DOE PAGES

van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; ...

2015-02-20

We report on the thermodynamic properties of binary compound mixtures of model groups II–VI semiconductors. We use the recently introduced Stillinger–Weber Hamiltonian to model binary mixtures of CdTe and CdSe. We use molecular dynamics simulations to calculate the volume and enthalpy of mixing as a function of mole fraction. The lattice parameter of the mixture closely follows Vegard's law: a linear relation. This implies that the excess volume is a cubic function of mole fraction. A connection is made with hard sphere models of mixed fcc and zincblende structures. We found that the potential energy exhibits a positive deviation frommore » ideal soluton behaviour; the excess enthalpy is nearly independent of temperatures studied (300 and 533 K) and is well described by a simple cubic function of the mole fraction. Using a regular solution approach (combining non-ideal behaviour for the enthalpy with ideal solution behaviour for the entropy of mixing), we arrive at the Gibbs free energy of the mixture. The Gibbs free energy results indicate that the CdTe and CdSe mixtures exhibit phase separation. The upper consolute temperature is found to be 335 K. Finally, we provide the surface energy as a function of composition. Moreover, it roughly follows ideal solution theory, but with a negative deviation (negative excess surface energy). This indicates that alloying increases the stability, even for nano-particles.« less

Use of a Soluble Anode in Electrodeposition of Thick Bismuth Telluride Layers

NASA Astrophysics Data System (ADS)

Maas, M.; Diliberto, S.; de Vaulx, C.; Azzouz, K.; Boulanger, C.

2014-10-01

Integration of thermoelectric devices within an automotive heat exchanger could enable conversion of lost heat into electrical energy, contributing to improved total output from the engine. For this purpose, synthesis of thick bismuth telluride (Bi2Te3) films is required. Bismuth telluride has been produced by an electrochemical method in nitric acid with a sacrificial bismuth telluride anode as the source of cations. The binary layer grows on the working electrode while the counter-electrode, a Bi2Te3 disk obtained by high frequency melting, is oxidized to BiIII and TeIV. This process leads to auto-regeneration of the solution without modification of its composition. The thickness of films deposited by use of the Bi2Te3 anode was approximately 10 times that without. To demonstrate the utility of a soluble anode in electrochemical deposition, we report characterization of the composition and morphology of the films obtained under different experimental conditions. Perfectly dense and regular Bi2Te3 films (˜400 μm) with low internal stress and uniform composition across the cross-section were prepared. Their thermoelectric properties were assessed.

Photophysical properties of [Ru(2,2‧-bipyridine)3]2+ encapsulated within the Uio-66 zirconium based metal organic framework

NASA Astrophysics Data System (ADS)

Larsen, Randy W.; Wojtas, Lukasz

2017-03-01

The ability to encapsulate photo-active guest molecules within the pores of metal organic frameworks (MOFs) affords the opportunity to develop robust photocatalysts as well as solar energy conversion systems. An important criteria for such systems is stability of the new materials towards moisture, high temperatures, etc which preclude the use of many MOF frameworks. Here, the ability to encapsulate [Ru(II)(2,2‧-bipyridine)3]2+([Ru(bpy)3]2+) into the cavities of the zirconium based MOF Uio-66 as well as the photophysical properties of the complex are reported. The X-ray powder diffraction data of the orange Uio-66 powder are consistent with the formation of Uio-66 in the presence of [Ru(bpy)3]2+. The steady state emission exhibits a significant bathochromic shift from 603 nm in ethanol to 610 nm in Uio-66. The corresponding emission decay of the encapsulated [Ru(bpy)3]2+ complex is biexponential with a fast component of 128 ns and a slower component of 1176 ns (20 deg C). The slow component is consistent with encapsulation of [Ru(bpy)3]2+ into cavities with restricted volume that prevents the population of a triplet ligand field transition that is anti-bonding with respect to the Ru-N bonds. The origin of the fast component is unclear but may involve interactions of the [Ru(bpy)3]2+ encapsulated within large cavities formed through missing ligand defect sites within the Uio-66 materials. Co-encapsulated quenchers contained within these larger cavities gives rise to the reduced lifetimes of the [Ru(bpy)3]2+ complexes.

A hydrodynamics-informed, radiation model for HESS J0632+057 from radio to gamma rays

NASA Astrophysics Data System (ADS)

Barkov, Maxim V.; Bosch-Ramon, Valenti

2018-06-01

Relativistic hydrodynamical simulations of the eccentric gamma-ray binary HESS J0632+057 show that the energy of a putative pulsar wind should accumulate in the binary surroundings between periastron and apastron, being released by fast advection close to apastron. To assess whether this could lead to a maximum of the non-thermal emission before apastron, we derive simple prescriptions for the non-thermal energy content, the radiation efficiency, and the impact of energy losses on non-thermal particles, in the simulated hydrodynamical flow. These prescriptions are used to estimate the non-thermal emission in radio, X-rays, GeV, and TeV, from the shocked pulsar wind in a binary system simulated using a simplified 3-dimensional scheme for several orbital cycles. Lightcurves at different wavelengths are derived, together with synthetic radio images for different orbital phases. The dominant peak in the computed lightcurves is broad and appears close to, but before, apastron. This peak is followed by a quasi-plateau shape, and a minor peak only in gamma rays right after periastron. The radio maps show ejection of radio blobs before apastron in the periastron-apastron direction. The results show that a scenario with a highly eccentric high-mass binary hosting a young pulsar can explain the general phenomenology of HESS J0632+057: despite its simplicity, the adopted approach yields predictions that are robust at a semi-quantitative level and consistent with multiwavelength observations.

Bulk Dissolution Rates of Cadmium and Bismuth Tellurides As a Function of pH, Temperature and Dissolved Oxygen.

PubMed

Biver, Marc; Filella, Montserrat

2016-05-03

The toxicity of Cd being well established and that of Te suspected, the bulk, surface-normalized steady-state dissolution rates of two industrially important binary tellurides-polycrystalline cadmium and bismuth tellurides- were studied over the pH range 3-11, at various temperatures (25-70 °C) and dissolved oxygen concentrations (0-100% O2 in the gas phase). The behavior of both tellurides is strikingly different. The dissolution rates of CdTe monotonically decreased with increasing pH, the trend becoming more pronounced with increasing temperature. Activation energies were of the order of magnitude associated with surface controlled processes; they decreased with decreasing acidity. At pH 7, the CdTe dissolution rate increased linearly with dissolved oxygen. In anoxic solution, CdTe dissolved at a finite rate. In contrast, the dissolution rate of Bi2Te3 passed through a minimum at pH 5.3. The activation energy had a maximum in the rate minimum at pH 5.3 and fell below the threshold for diffusion control at pH 11. No oxygen dependence was detected. Bi2Te3 dissolves much more slowly than CdTe; from one to more than 3.5 orders of magnitude in the Bi2Te3 rate minimum. Both will readily dissolve under long-term landfill deposition conditions but comparatively slowly.

Investigating the Electron-Phonon Coupling of Molecular Beam Epitaxy-Grown Hg1-x Cd x Se Semiconductor Alloys

NASA Astrophysics Data System (ADS)

Peiris, F. C.; Lewis, M. V.; Brill, G.; Doyle, Kevin; Myers, T. H.

2018-03-01

Using spectroscopic ellipsometry, the temperature-dependence of the dielectric functions of a series of Hg1-x Cd x Se thin films deposited on both ZnTe/Si(112) and GaSb(112) substrates were investigated. Initially, for each sample, room-temperature ellipsometric spectra were obtained from 35 meV to 6 eV using two different ellipsometers. Subsequently, ellipsometry spectra were obtained from 10 K to 300 K by incorporating a cryostat to the ellipsometer. Using a standard inversion technique, the spectroscopic ellipsometric data were modeled in order to obtain the temperature-dependent dielectric functions of each of the Hg1-x Cd x Se thin films. The results indicate that the E 1 critical point blue-shifts as a function of Cd-alloy concentration. The temperature-dependence of E 1 was fitted to a Bose-Einstein occupation distribution function, which consequently allowed us to determine the electron-phonon coupling of Hg1-x Cd x Se alloys. From the fitting results, we obtain a value of 17 ± 2 meV for the strength of the electron-phonon coupling for Hg1-x Cd x Se alloy system, which compares nominally with the binary systems, such as CdSe and CdTe, which have values around 38 meV and 16 meV, respectively. This implies that the addition of Hg into the CdSe binary system does not significantly alter its electron-phonon coupling strength. Raman spectroscopy measurements performed on all the samples show the HgSe-like transverse optic (TO) and longitudinal optic (LO) phonons (˜ 130 cm-1 and ˜ 160 cm-1, respectively) for all the samples. While there is a slight red-shift of the HgSe-like TO peak as a function of the Cd-concentration, HgSe-like LO peak does not significantly change with the alloy concentration.

A ruthenium(II) complex inhibits tumor growth in vivo with fewer side-effects compared with cisplatin.

PubMed

Wang, Jin-Quan; Zhang, Ping-Yu; Ji, Liang-Nian; Chao, Hui

2015-05-01

The antitumor activity of a ruthenium(II) polypyridyl complex, Δ-[Ru(bpy)2(HPIP)](ClO4)2 (Δ-Ru1, where bpy=2,2'-bipyridine, HPIP=2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline), was evaluated. The in vivo experiments showed that Δ-Ru1 inhibited the growth of a human cervical carcinoma cell line (HeLa) xenotransplanted into nude mice with efficiency similar to that of cisplatin. Histopathology examination of the tumors from treated xenograft models was consistent with apoptosis in tumor cells. Importantly, in striking contrast with cisplatin, Δ-Ru1 did not cause any detectable side effects on the kidney, liver, peripheral neuronal system, or the hematological system at the pharmacologically effective dose. The preclinical studies reported here provide support for the clinical use of Δ-Ru1 as an exciting new drug candidate with lower toxicity than cisplatin, endowed with proapoptotic properties. Copyright © 2015 Elsevier Inc. All rights reserved.

Re-Search for Extinct 99Tc and 98Tc in the Early Solar System

NASA Astrophysics Data System (ADS)

Yin, Q.; Jagoutz, E.; Wanke, H.

1992-07-01

The recent advances in negative thermal ionization mass spectrometry (N-TIMS) of Re and Os (Creaser et al., 1991) offer a new chance to search for isotopic anomalies of ruthenium (Ru) (and possibly Mo) in meteorites. The Ru isotopes are particularly important since they contain two daughter decay products of technicium, ^98Tc (tau(sub)1/2=4.2x10^6 yr) and ^99Tc (tau(sub)1/2=2.1x10^5 yr). Natural Tc is now extinct on Earth due to their short half-life, but may have been present in the early solar system; Ru isotopes might also bear witness of the various processes of nucleosynthesis and of the imperfect mixing of their products in the pre-solar nebula; Ru isotopic composition in fission is drastically different from natural; ^99Tc is crucial because of its very short half-life and is observed directly for several half-lives in s-process-enriched stars during the thermally pulsing, AGB (asymptotic giant branch) phase of evolution. The probability of detecting ^99Tc in this type of stars is typically 70% (Smith and Lambert, 1988). The chemical similarities between Ru and Os yield correspondingly high ionization efficiency for Ru with N-TIMS. Ru is obtained as a byproduct of Os chemistry, as Ru co-distills with Os. This unique combination conveniently enables a survey for extinct Tc by determining isotopic composition of Ru on a wide range of samples together with extensive studies of Re-Os system in geochemical community in the years to come. These arguments prompted us to carry out a systematic re-search for Ru isotopic anomalies initiated by Herr and coworkers more than 30 years ago (Herr et al., 1958). We have measured Ru isotopic composition in one bulk sample and a magnetic fraction of Maralinga carbonaceous chondrite and one bulk sample of the iron meteorite Gibeon. The bulk sample of Maralinga is found to be isotopically indistinguishable from the terrestrial values within analytical uncertainties. In the magnetic fraction, however, a positive deviation (0.89+- 0.24epsilon) of the ^99Ru/^101Ru ratio from the terrestrial mean is observed, a first indication that ^99Tc was alive in the early solar system. With the production ratio of ^99Tc/^99Ru=0.75 (Kappeler et al., 1989), a 2.9+-0.2 m.y. time interval (delta) between the nucleosynthetic process and formation of Maralinga is calculated, assuming there is no significant Tc/Ru fractionation since their production. This time interval is consistent with delta>=1.8 m.y. set by ^41Ca (tau(sub)1/2=1.03x10^5 yr) result (Hutcheon et al., 1984) and delta<=~3 m.y. inferred from ^26Al (tau(sub)1/2=7.16x10^5 yr) result (Lee et al., 1977), and gives the most stringent control on delta for the related nucleosynthetic process. The ^99Ru/^101Ru ratio in Gibeon is within error of the laboratory standard value. Since the nucleosynthetic origins of ^107Pd and ^99Tc are similar, the absence of ^99Ru anomaly (^99Ru*) and the presence of ^107Ag* in Gibeon (Chen and Wasserburg, 1990) indicate that core-mantle differentiation in the parent body of Gibeon happened between 2 and 10 m.y. after the nucleosynthetic sources produced these two parent nuclides. In this time span ^26Al was still alive and thus supports the model of ^26Al being a heat source for early planetary differentiation. Chen, J. H. and Wasserburg, G. J. , Geochim. Cosmochim. Acta. (1990) 54, 1729-1743. Creaser, R. A., Papanastassiou, D. A. and Wasserburg, G. J. (1991) Geochim. Cosmochim. Acta. 55, 397-401. Herr, W., Merz, E., Eberhardt, P., Geiss, J., Lang, C. and Signer, P. (1958) Geochim. Cosmochim. Acta. 14, 158. Hutcheon, I. D., Armstrong, J. T., and Wasserburg, G. J. (1984) LPSC XV, 387-388 (abstract). Kappeler, F., Beer, H., and Wisshak, K. (1989) Rep. Prog. Phys. 52. 945-1013. Lee, T., Papanastassiou, D. A. and Wasserburg, G. J. (1977) Astrophys. J. (Letters) 211, L107-L110. Smith, V. V. and Lambert, D. L. (1988)t. Astrophys. J., 333, 219- 226.

Triple Quenching of a Novel Self-Enhanced Ru(II) Complex by Hemin/G-Quadruplex DNAzymes and Its Potential Application to Quantitative Protein Detection.

PubMed

Zhao, Min; Liao, Ni; Zhuo, Ying; Chai, Ya-Qin; Wang, Ji-Peng; Yuan, Ruo

2015-08-04

Herein, a novel "on-off" electrochemiluminescence (ECL) aptasensor for highly sensitive determination of thrombin has been constructed based on the triple quenching of the effect of hemin/G-quadruplex DNAzymes upon the Ru(II) complex-based ECL system. First, a strong initial ECL signal was achieved by the dual amplification strategies of (i) intramolecular coreaction of a self-enhanced Ru(II)-based molecule (PTCA-PEI-Ru(II)) and (ii) intermolecular coreaction between PTCA-PEI-Ru(II) and nicotinamide adenine dinucleotide (NADH), which was named the signal-on state. Then, a novel triple quenching of the effect of multifunctional hemin/G-quadruplex DNAzymes upon the Ru(II) complex-based ECL system was designed to realize the desirable signal-off state, which was outlined as follows: (i) the hemin/G-quadruplex DNAzymes mimicked NADH oxidase to oxidize NADH and in situ generate the H2O2, consuming the coreactant of NADH; (ii) its active center of hemin could oxidize the excited state PTCA-PEI-Ru(II)* to PTCA-PEI-Ru(III), making the energy and electron transfer quench; (iii) it also acted as horseradish peroxidase (HRP) to catalyze the H2O2 for in situ producing the quencher of O2. Based on triple quenching of the effect of hemin/G-quadruplex DNAzymes, the highly sensitive "on-off" thrombin aptasensor was developed with a wide linear detection range of 1.0 × 10(-14) M to 1.0 × 10(-10) M and a detection limit down to the femtomolar level.

Structure of zinc and niobium tellurite glasses by neutron and x-ray diffraction

NASA Astrophysics Data System (ADS)

Hoppe, U.; Yousef, E.; Rüssel, C.; Neuefeind, J.; Hannon, A. C.

2004-03-01

Neutron and x-ray diffraction experiments of high resolving power with neutrons from a spallation source and high-energy photons from a synchrotron have been performed on compositional series of binary Zn, Nb and on mixed Zn/Nb tellurite glasses. The Te-O, Zn-O and Nb-O coordination numbers are determined by Gaussian fitting of the first-neighbour peaks in the neutron and x-ray data simultaneously. The transition of TeO4 to TeO3 units with increasing fraction of a second component is indicated by decreasing total Te-O coordination numbers. This transition appears different for glasses with ZnO or Nb2O5 additions. Details of the Te-O peaks suggest there are two species of Te-O bonds with lengths of {\\sim }0.19 and {\\sim }0.21 nm. The change of their fractions shows excellent agreement with the existence of TeO4 trigonal bipyramids and TeO3 trigonal pyramids. All oxygen atoms from ZnO and Nb2O5 are used for rupture of Te-O-Te bridges, which is accompanied with a change of nearly all participating TeO4 to TeO3 groups. The tendency for a {\\mathrm {TeO}}_{4} \\to {\\mathrm {TeO}}_{3} change decreases for glasses of higher second component content which is accompanied by the occurrence of TeO4 groups with non-bridging oxygens. The Nb tellurite glasses show transition to network-forming behaviour with the formation of Nb-O-Nb bridges. The fractions of TeO3 units of ternary Zn/Nb tellurite glasses agree with an additivity behaviour of the modifying effects of ZnO and Nb2O5 additions. Some of these results have already been presented in thesis work: Yousef E 2003 A study of some physical properties of tellurite glass (Al-Azhar University, Assiut Egypt).

Photophysical properties of [Ru(2,2′-bipyridine){sub 3}]{sup 2+} encapsulated within the Uio-66 zirconium based metal organic framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larsen, Randy W., E-mail: rwlarsen@usf.edu; Wojtas, Lukasz

2017-03-15

The ability to encapsulate photo-active guest molecules within the pores of metal organic frameworks (MOFs) affords the opportunity to develop robust photocatalysts as well as solar energy conversion systems. An important criteria for such systems is stability of the new materials towards moisture, high temperatures, etc which preclude the use of many MOF frameworks. Here, the ability to encapsulate [Ru(II)(2,2′-bipyridine){sub 3}]{sup 2+}([Ru(bpy){sub 3}]{sup 2+}) into the cavities of the zirconium based MOF Uio-66 as well as the photophysical properties of the complex are reported. The X-ray powder diffraction data of the orange Uio-66 powder are consistent with the formation ofmore » Uio-66 in the presence of [Ru(bpy){sub 3}]{sup 2+}. The steady state emission exhibits a significant bathochromic shift from 603 nm in ethanol to 610 nm in Uio-66. The corresponding emission decay of the encapsulated [Ru(bpy){sub 3}]{sup 2+} complex is biexponential with a fast component of 128 ns and a slower component of 1176 ns (20 deg C). The slow component is consistent with encapsulation of [Ru(bpy){sub 3}]{sup 2+} into cavities with restricted volume that prevents the population of a triplet ligand field transition that is anti-bonding with respect to the Ru-N bonds. The origin of the fast component is unclear but may involve interactions of the [Ru(bpy){sub 3}]{sup 2+} encapsulated within large cavities formed through missing ligand defect sites within the Uio-66 materials. Co-encapsulated quenchers contained within these larger cavities gives rise to the reduced lifetimes of the [Ru(bpy){sub 3}]{sup 2+} complexes. - Graphical abstract: One-pot synthesis of Ru(II)tris(2,2-bipyridine)@Uio-66 (left) and the effects of encapsulation on the excited state energy levels and decay pathways of the Ru(II)tris(2,2-bipyridine) complex (right).« less

Fermi Surface Properties, Metamagnetic Transition and Quantum Phase Transition of CeRu2Si2 and Its Alloys Probed by the dHvA Effect

NASA Astrophysics Data System (ADS)

Aoki, Haruyoshi; Kimura, Noriaki; Terashima, Taichi

2014-07-01

This article describes the Fermi surface properties of CeRu2Si2 and its alloy systems CeRu2(SixGe1-x)2 and CexLa1-xRu2Si2 studied by the de Haas-van Alphen (dHvA) effect. We pay particular attention to how the Fermi surface properties and the f electron state change with magnetic properties, in particular how they change associated with metamagnetic transition and quantum phase transition. After summarizing the important physical properties of CeRu2Si2, we present the magnetic phase diagrams of CeRu2(SixGe1-x)2 and CexLa1-xRu2Si2 as a function of temperature, magnetic field and concentration x. From the characteristic features of the magnetic phase diagram, we argue that the ferromagnetic interaction in addition to the antiferromagnetic interaction and the Kondo effect is responsible for the magnetic properties and that the metamagnetic transitions in these systems are relevant to the ferromagnetic interaction. We summarize the Fermi surface properties of CeRu2Si2 in fields below the metamagnetic transition where the f electron state is now well understood theoretically as well as experimentally. We present experimental results in fields above the metamagnetic transitions in CeRu2(SixGe1-x)2 and CexLa1-xRu2Si2 as well as CeRu2Si2 to show that the Fermi surface properties above the metamagnetic transitions are significantly different from those below in many important aspects. We argue that the Fermi surface properties above the metamagnetic transitions are not appropriately described in terms of either itinerant or localized f electron. The experimental results in fields below the metamagnetic transitions in CeRu2(SixGe1-x)2 and CexLa1-xRu2Si2 are presented to discuss the f electron state in the ground state. The Fermi surface properties of dilute Kondo alloys of CexLa1-xRu2Si2 have been revealed as a function of Ce concentration and temperature. We show that the f electron state can be regarded as itinerant in the ground state together with the definition of the term "itinerant" in this case. The Fermi surface properties are measured also in high concentration alloys of CeRu2(SixGe1-x)2 and CexLa1-xRu2Si2 as a function of x. With the help of the angle resolved photoemission spectroscopy studies, we show that the f electron nature does not change at the quantum phase transition between the paramagnetic and antiferromagnetic phases. However, the picture for the f electron state may be ambiguous and depend on which property one considers in the magnetic states of these systems. The ambiguity and confusion of the f electron state may come from the inherent dual nature of the f electron and we would like to point out that it is sometimes misleading and may not be fruitful to discriminate the f electron state either as itinerant or localized without any clear definition for the terms "itinerant" and "localized".

Multiplexed analysis combining distinctly-sized CdTe-MPA quantum dots and chemometrics for multiple mutually interfering analyte determination.

PubMed

Bittar, Dayana B; Ribeiro, David S M; Páscoa, Ricardo N M J; Soares, José X; Rodrigues, S Sofia M; Castro, Rafael C; Pezza, Leonardo; Pezza, Helena R; Santos, João L M

2017-11-01

Semiconductor quantum dots (QDs) have demonstrated a great potential as fluorescent probes for heavy metals monitoring. However, their great reactivity, whose tunability could be difficult to attain, could impair selectivity yielding analytical results with poor accuracy. In this work, the combination in the same analysis of multiple QDs, each with a particular ability to interact with the analyte, assured a multi-point detection that was not only exploited for a more precise analyte discrimination but also for the simultaneous discrimination of multiple mutually interfering species, in the same sample. Three different MPA-CdTe QDs (2.5, 3.0 and 3.8nm) with a good size distribution, confirmed by the FWHM values of 48.6, 55.4 and 80.8nm, respectively, were used. Principal component analysis (PCA) and partial least squares regression (PLS) were used for fluorescence data analysis. Mixtures of two MPA-CdTe QDs, emitting at different wavelength namely 549/566, 549/634 and 566/634nm were assayed. The 549/634nm emitting QDs mixture provided the best results for the discrimination of distinct ions on binary and ternary mixtures. The obtained RMSECV and R 2 CV values for the binary mixture were good, namely, from 0.01 to 0.08mgL -1 and from 0.74 to 0.89, respectively. Regarding the ternary mixture the RMSECV and R 2 CV values were good for Hg(II) (0.06 and 0.73mgL -1 , respectively) and Pb(II) (0.08 and 0.87mg L -1 , respectively) and acceptable for Cu(II) (0.02 and 0.51mgL -1 , respectively). In conclusion, the obtained results showed that the developed approach is capable of resolve binary and ternary mixtures of Pb (II), Hg (II) and Cu (II), providing accurate information about lead (II) and mercury (II) concentration and signaling the occurrence of Cu (II). Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of Binders and Solvents on Stability of Ru/RuOx Nanoparticles on ITO Nanocrystals as Li-O2 Battery Cathodes.

PubMed

Vankova, Svetoslava; Francia, Carlotta; Amici, Julia; Zeng, Juqin; Bodoardo, Silvia; Penazzi, Nerino; Collins, Gillian; Geaney, Hugh; O'Dwyer, Colm

2017-02-08

Fundamental research on Li-O 2 batteries remains critical, and the nature of the reactions and stability are paramount for realising the promise of the Li-O 2 system. We report that indium tin oxide (ITO) nanocrystals with supported 1-2 nm oxygen evolution reaction (OER) catalyst Ru/RuO x nanoparticles (NPs) demonstrate efficient OER processes, reduce the recharge overpotential of the cell significantly and maintain catalytic activity to promote a consistent cycling discharge potential in Li-O 2 cells even when the ITO support nanocrystals deteriorate from the very first cycle. The Ru/RuO x nanoparticles lower the charge overpotential compared with those for ITO and carbon-only cathodes and have the greatest effect in DMSO electrolytes with a solution-processable F-free carboxymethyl cellulose (CMC) binder (<3.5 V) instead of polyvinylidene fluoride (PVDF). The Ru/RuO x /ITO nanocrystalline materials in DMSO provide efficient Li 2 O 2 decomposition from within the cathode during cycling. We demonstrate that the ITO is actually unstable from the first cycle and is modified by chemical etching, but the Ru/RuO x NPs remain effective OER catalysts for Li 2 O 2 during cycling. The CMC binders avoid PVDF-based side-reactions and improve the cyclability. The deterioration of the ITO nanocrystals is mitigated significantly in cathodes with a CMC binder, and the cells show good cycle life. In mixed DMSO-EMITFSI [EMITFSI=1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide] ionic liquid electrolytes, the Ru/RuO x /ITO materials in Li-O 2 cells cycle very well and maintain a consistently very low charge overpotential of 0.5-0.8 V. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metal-insulator transition in Ba3Fe1 -xRu2 +xO9 : Interplay between site disorder, chemical percolation, and electronic structure

NASA Astrophysics Data System (ADS)

Middey, S.; Aich, Payel; Meneghini, C.; Mukherjee, K.; Sampathkumaran, E. V.; Siruguri, V.; Mahadevan, P.; Ray, Sugata

2016-11-01

Perovskites containing barium metal at the A site often take up unusual hexagonal structures having more than one type of possible sites for the B cation to occupy. This opens up various different B -B - or B -O-B -type connectivities and consequent physical properties which are naturally missing in cubic perovskites. BaRuO3 is one such system where doping of Ru (4 d4 ) by other transition metals (Mn +) creates similar conditions, giving rise to various M -Ru interactions. Interestingly, the 6 H hexagonal structure of doped barium ruthenate triple perovskite (Ba3M Ru2O9 ) seems to possess some internal checks because within the structure M ion always occupies the 2 a site and Ru goes to the 4 f site, allowing only M -O-Ru 180∘ and Ru-O-Ru 90∘ interactions to occur. The only exception is observed in the case of the Fe dopant, which allows us to study almost the full Ba3Fe1 -xRu2 +xO9 series of compounds with wide ranges of x because here Fe ions have the ability to freely go to the 4 f sites and Ru readily takes up the 2 a positions. Therefore, here one has the opportunity to probe the evolution of electronic and magnetic properties as a function of doping by going from BaRuO3 (paramagnetic metal) to BaFeO3 (ferromagnetic insulator). Our detailed experimental and theoretical results show that the series does exhibit a percolative metal-insulator transition with an accompanying but not coincidental magnetic transition as a function of x .

Synthesis and anisotropic properties of single crystalline Ln{sub 2}Ru{sub 3}Al{sub 15+x} (Ln=Gd, Tb)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrison, Gregory; Prestigiacomo, Joseph; Haldolaarachchige, Neel

2016-04-15

Single crystals of Ln{sub 2}Ru{sub 3}Al{sub 15+x} (Ln=Gd, Tb) have been grown using the self-flux method under Ru-poor conditions. The structure of the Gd analog is found to be highly dependent on the synthesis method. Gd{sub 2}Ru{sub 3}Al{sub 15.08} orders antiferromagnetically at 17.5 K. Tb{sub 2}Ru{sub 3}Al{sub 15.05} enters an antiferromagnetic state at 16.6 K followed by a likely incommensurate-to-commensurate transition at 14.9 K for crystals oriented with H//ab. For crystals oriented with H//c, a broad maximum is observed in the temperature dependent M/H, indicative of a highly anisotropic magnetic system with the hard axis in the c-direction. The magnetizationmore » as a function of field and magnetoresistance along the ab-direction of Tb{sub 2}Ru{sub 3}Al{sub 15.05} display a stepwise behavior and indicate strong crystalline electric field effects. - Graphical abstract: Single crystal, structure, and highly anisotropic magnetoresistance due to strong crystalline electric field effects of Tb{sub 2}Ru{sub 3}Al{sub 15.05}. - Highlights: • Single crystals of Ln{sub 2}Ru{sub 3}Al{sub 15+x} were grown for the first time via flux growth. • The structure of Gd{sub 2}Ru{sub 3}Al{sub 15.09} differs from that of arc melted Gd{sub 2}Ru{sub 3.08}Al{sub 15}. • Tb{sub 2}Ru{sub 3}Al{sub 15.05} exhibits highly anisotropic magnetic and transport properties. • The properties of Tb{sub 2}Ru{sub 3}Al{sub 15.05} arise due to crystalline electric field effects.« less

Discovering the balance of steric and electronic factors needed to provide a new structural motif for photocatalytic hydrogen production from water.

PubMed

White, Travis A; Whitaker, Brittany N; Brewer, Karen J

2011-10-05

Ru,Rh,Ru supramolecules are known to undergo multielectron photoreduction and reduce H(2)O to H(2). Ru,Rh bimetallics were recently shown to photoreduce but not catalyze H(2)O reduction. Careful tuning of sterics and electronics for [(TL)(2)Ru(dpp)RhCl(2)(TL')](3+) produce active bimetallic photocatalysts (TL = terminal ligand). The system with TL,TL' = Ph(2)phen photocatalytically reduces H(2)O to H(2) while TL,TL' = phen,bpy or bpy,(t)Bu(2)bpy do not.

BOREAS TE-20 Soils Data Over the NSA-MSA and Tower Sites in Raster Format

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Veldhuis, Hugo; Knapp, David; Veldhuis, Hugo

2000-01-01

The BOREAS TE-20 team collected several data sets for use in developing and testing models of forest ecosystem dynamics. This data set was gridded from vector layers of soil maps that were received from Dr. Hugo Veldhuis, who did the original mapping in the field during 1994. The vector layers were gridded into raster files that cover the NSA-MSA and tower sites. The data are stored in binary, image format files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Center (DAAC).

Electronic structures and superconductivity in LuTE2Si2 phases (TE = d-electron transition metal)

NASA Astrophysics Data System (ADS)

Samsel-Czekała, M.; Chajewski, G.; Wiśniewski, P.; Romanova, T.; Hackemer, A.; Gorzelniak, R.; Pikul, A. P.; Kaczorowski, D.

2018-05-01

In the course of our search for unconventional superconductors amidst the 1:2:2 phases, we have re-investigated the LuTE2Si2 compounds with TE = Fe, Co, Ni, Ru, Pd and Pt. In this paper, we present the results of our fully relativistic ab initio calculations of the band structures, performed using the full-potential local-orbital code. The theoretical data are supplemented by the results of low-temperature electrical transport and specific heat measurements performed down to 0.35 K. All the materials studied but LuPt2Si2 crystallize with the body-centered tetragonal ThCr2Si2-type structure (space group I4/mmm). Their Fermi surfaces exhibit a three-dimensional multi-band character. In turn, the Pt-bearing compound adopts the primitive tetragonal CaBe2Ge2-type structure (space group P4/nmm), and its Fermi surface consists of predominantly quasi-two-dimensional sheets. Bulk superconductivity was found only in LuPd2Si2 and LuPt2Si2 (independent of the structure type and dimensionality of the Fermi surface). The key superconducting characteristics indicate a fully-gapped BCS type character. Though the electronic structure of LuFe2Si2 closely resembles that of the unconventional superconductor YFe2Ge2, this Lu-based silicide exhibits neither superconductivity nor spin fluctuations at least down to 0.35 K.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skibo, A.

SRNL has considerable experience in designing, engineering, and operating systems for removing iodine-129 (I-129) and ruthenium-106 (Ru-106) from waste streams that are directly analogous to the Advanced Liquid Processing System (ALPS) waste streams. SRNL proposes to provide the technical background and design and engineering support for an improved I-129 and Ru-106 removal system for application to ALPS on the Fukushima Daiichi Nuclear Power Station (NPS).

Observing the Non-Thermal Universe with the Highest Energy Photons

NASA Astrophysics Data System (ADS)

Dingus, Brenda L.; HAWC, VERITAS, CTA

2016-01-01

Astrophysical sources of relativistic particles radiate gamma rays to such high energies that they can be detected from the ground. The existence of high energy gamma rays implies that even higher energy particles are being accelerated placing strong constraints on these non-thermal accelerators. Within our galaxy, TeV gamma rays have been detected from supernova remnants, pulsar wind nebula, x-ray binaries and some yet to be identified sources in the Galactic plane. In addition, these gamma rays have sufficient energy to be attenuated by the interaction with infrared photons producing an electron-positron pair. Thus the spectrum of gamma rays can also constrain the infrared photon density, which for distant extragalactic sources is a direct probe of cosmology. The known extragalactic TeV sources are primarily the blazer class of active galactic nuclei. And TeV gamma rays might even be produced by annihilating dark matter.The US currently supports two ground-based gamma-ray observatories—HAWC and VERITAS—and NSF is developing a prototype for the international Cherenkov Telescope Array (CTA) observatory. The HAWC (High Altitude Water Cherenkov) observatory just began operation of the full detector in March 2015 and with its wide field of view scans ~2/3 of the sky each day for TeV sources. VERITAS (Very EneRgetic Imaging Telescope Array System) is an array of four imaging atmospheric Cherenkov telescopes that follows individual sources to produce lightcurves and spectra from 85 GeV to > 30 TeV. The combination of both a survey and pointed observatory is very complementary with a broad scientific reach that includes the study of extragalactic and Galactic objects as well as the search for astrophysical signatures of dark matter and the measurement of cosmic rays. I will present the current view of the TeV sky and the latest results from HAWC and VERITAS as well as plans for CTA.

Enhanced thermoelectric performance driven by high-temperature phase transition in the phase change material Ge 4SbTe 5

DOE PAGES

Williams, Jared B.; Lara-Curzio, Edgar; Cakmak, Ercan; ...

2015-05-15

Phase change materials are identified for their ability to rapidly alternate between amorphous and crystalline phases and have large contrast in the optical/electrical properties of the respective phases. The materials are primarily used in memory storage applications, but recently they have also been identified as potential thermoelectric materials. Many of the phase change materials researched today can be found on the pseudo-binary (GeTe) 1-x(Sb 2Te 3) x tie-line. While many compounds on this tie-line have been recognized as thermoelectric materials, here we focus on Ge 4SbTe 5, a single phase compound just off of the (GeTe) 1-x(Sb 2Te 3) xmore » tie-line, that forms in a stable rocksalt crystal structure at room temperature. We find that stoichiometric and undoped Ge 4SbTe 5 exhibits a thermal conductivity of ~1.2 W/m-K at high temperature and a large Seebeck coefficient of ~250 μV/K. The resistivity decreases dramatically at 623 K due to a structural phase transition which lends to a large enhancement in both thermoelectric power factor and thermoelectric figure of merit at 823 K. In a more general sense the research presents evidence that phase change materials can potentially provide a new route to highly efficient thermoelectric materials for power generation at high temperature.« less

VizieR Online Data Catalog: New minima timings and RVs for 3 eclipsing binaries (Zasche+, 2017)

NASA Astrophysics Data System (ADS)

Zasche, P.; Jurysek, J.; Nemravova, J.; Uhlar, R.; Svoboda, P.; Wolf, M.; Honkova, K.; Masek, M.; Prouza, M.; Cechura, J.; Korcakova, D.; Slechta, M.

2018-04-01

Spectroscopy was obtained in two observatories. Most of the data points for these systems came from the Ondrejov observatory and its 2 m telescope (resolution R~12500). Additionally, data on BR Ind and some data on QS Aql were obtained with the FEROS instrument mounted on the 2.2 m MPG telescope located in La Silla Observatory in Chile (R~48000). Photometry for these three systems was collected over the time span of 2008 to 2016. Owing to the relatively high brightness of the targets, only rather small telescopes were used for these photometric observations. The system V773 Cas was observed (by one of the authors, PS) with a 34 mm refractor at a private observatory in Brno, Czech Republic, using an SBIG ST-7XME CCD camera. The star QS Aql was monitored (by one of the authors, RU) with a similar instrument at a private observatory in Jilove u Prahy, Czech Republic, using a G2-0402 CCD camera. The only southern star, BR Ind, was observed with the FRAM telescope (Prouza et al. 2010AdAst2010E..31P), installed and operated at the Pierre Auger Observatory at Malargue, Argentina. (2 data files).

Antiferromagnetic instability in Sr3Ru2O7: stabilized and revealed by dilute Mn impurities

NASA Astrophysics Data System (ADS)

Hossain, Muhammed; Bohnenbuck, B.; Chuang, Y.-D.; Cruz, E.; Wu, H.-H.; Tjeng, L. H.; Elfimov, I. S.; Hussain, Z.; Keimer, B.; Sawatzky, G. A.; Damascelli, A.

2009-03-01

X-ray Absorption Spectroscopy (XAS) and Resonant Elastic Soft X-ray Scattering (RESXS) studies have been performed on Mn-doped Sr3Ru2O7, both on the Ru and Mn L-edges, to investigate the origin of the metal insulator transition. Extensive simulations based on our experimental findings point toward an intrinsic antiferromagnetic instability in the parent Sr3Ru2O7 compound that is stabilized by the dilute Mn impurities. We show that the metal-insulator transition is a direct consequence of the antiferromagnetic order and we propose a phenomenological model that may be applicable also to metal-insulator transitions seen in other oxides. Moreover, a comparison of Ru and Mn L-edge data on 5% Mn doped system reveals that dilute Mn impurities are generating much more intense signal than Ru which is occupying 95% of the lattice sites. This suggests the embedding of dilute impurities as a powerful mean to probe weak and, possibly, spatially inhomogeneous order in solid-state systems. In collaboration with: Y. Yoshida (AIST), J. Geck, D.G. Hawthorn (UBC), M.W. Haverkort, Z. Hu, C. Sch"ußler-Langeheine (Cologne), R. Mathieu, Y. Tokura, S. Satow, H. Takagi (Tokyo), J.D. Denlinger (ALS).

New Bond Coat Materials for Thermal Barrier Coating Systems Processed Via Different Routes

NASA Astrophysics Data System (ADS)

Soare, A.; Csaki, I.; Sohaciu, M.; Oprea, C.; Soare, S.; Costina, I.; Petrescu, M. I.

2017-06-01

This paper aims at describing the development of new Ru-based Bond Coats (BC) as part of Thermal Barrier Coatings. The challenge of this research was to obtain an adherent and uniform layer of alumina protective layer after high temperature exposure. We have prepared a RuAl 50/50 at% alloy in an induction furnace which was subsequently subjected to oxidation in an electric furnace, in air, at 1100C, for 10h and 100h. Mechanical alloying of Ru and Al powders was another processing route used in an attempt to obtain a stoichiometric RuAl. The alloy was sintered by Spark Plasma Sintering (SPS) and then oxidized at 1100C for 1 and10h. The alloys obtained as such were analysed before and after oxidation using advanced microscopy techniques (SEM and TEM). The encouraging results in case of RuAl alloys prepared by induction melting reveal that we obtained an adherent and uniform layer of alumina, free of delta-Ru. The results for the samples processed by powder metallurgy were positive but need to be further investigated. We should note here the novelty of this method for this particular type of application - as a BC part of a TBC system.

LS 5039 - the counterpart of the unidentified MeV source GRO J1823-12

NASA Astrophysics Data System (ADS)

Collmar, W.; Zhang, S.

2014-05-01

Context. The COMPTEL experiment on CGRO observed the γ-ray sky at energies from 0.75 MeV to 30 MeV between April 1991 and June 2000. COMPTEL detected many γ-ray sources, among them an unidentified one labeled GRO J1823-12. It is located near l/b = 17.5°/-0.5° and positionally consistent with the prominent γ-ray binary LS 5039. Aims: LS 5039 was established as a γ-ray source at TeV energies by HESS and at GeV energies by Fermi/LAT during recent years, whose γ-ray radiation is modulated along its binary orbit. Given this new information we reanalyzed the COMPTEL data of GRO J1823-12 including an orbital-resolved analysis. Methods: We applied the standard methods, proper event selections and data binning with subsequent maximum-likelihood deconvolution, to analyze the COMPTEL data. In addition we developed a tool for selecting and binning the COMPTEL data in a phase-resolved manner. We present the orbit-averaged, as well as orbit-resolved MeV analyses, light curves, and spectra, and put them into a multifrequency context. Results: The COMPTEL data show a significant MeV source, which is positionally consistent with LS 5039, but also with other closeby Fermi/LAT sources. The orbit-resolved analysis provides strong evidence, at about the 3σ level, that the MeV flux of GRO J1823-12 is modulated along the binary orbit of about 3.9 days of LS 5039. We show that at MeV energies, the source is brighter at the orbital part around the inferior conjunction than at the part of the superior conjunction, so it is in phase with X-rays and TeV γ-rays, but in anti-phase with GeV γ-rays. The high-energy spectral energy distribution (X-rays to TeV γ-rays) shows the high-energy emission maximum of LS 5039 at MeV energies. Conclusions: We conclude that the COMPTEL source GRO J1823-12 is the counterpart of the microquasar LS 5039, at least for the majority of its MeV emission. The COMPTEL fluxes, put into multifrequency perspective, provide new constraints on the modeling of the high-energy emission pattern of the γ-ray binary LS 5039. Table 1 is available in electronic form at http://www.aanda.org

Experimental partitioning of Tc, Mo, Ru, and Re between solid and liquid during crystallization in Fe-Ni-S 1

NASA Astrophysics Data System (ADS)

Lazar, C.; Walker, D.; Walker, R. J.

2004-02-01

Technetium isotopes 97Tc, 98Tc and 99Tc decay to 97Mo, 98Ru and 99Ru, with half-lives of 2.6 My, 4.1 My, and 0.21 My respectively. If there were early solar system processes that resulted in significant fractionation of Tc from the daughter elements, decay of extant Tc could have led to the creation of Mo and Ru isotopic heterogeneities. To assess the potential of metallic core crystallization to fractionate these elements, we examine the partitioning behavior of Tc relative to Re, Mo and Ru in the Fe-Ni-S system between solid metal and liquid metal alloy. The experimental evidence shows that Tc behaves more like the modestly compatible siderophile element Ru than the more highly compatible siderophile element Re, and that Tc is substantially more compatible than Mo. We also demonstrate a pressure effect in the partitioning of Mo during the crystallization of Fe-Ni-S melts. For a sulfur concentration in the liquid fraction of the core of 10 wt% (16.3 at%), the Jones and Malvin (1990) parameter is -ln(1-2 × 1.09 × 0.163) ≅ 0.44, which yields: D(Re) ≅ 4.1; D(Ru) ≅ 2.3; D(Tc) ≅ 1.7; D(Mo) Lo-P ≅ 1.0;.and D(Mo) Hi-P ≅ 0.5. Our results suggest that detectable Tc-induced isotopic anomalies (≥0.1 ɛ unit) in Ru and Mo could only be produced by unrealistically extreme degrees of crystallization of metal during asteroidal core fractionation, regardless of the time scales and initial Tc abundances involved.

Between metamagnetic transition and spin-flip behavior in Ce 122 system of (Ce-Gd)Ru2Si2

NASA Astrophysics Data System (ADS)

Yano, K.; Amakai, Y.; Hara, Y.; Sato, K.; Kita, E.; Takano, H.; Ohta, T.; Murayama, S.

2018-03-01

Aiming at getting some clues to the mechanism of meta-magnetic transition and surprisingly small magnetic moment of Ce along hard axis in CeRu2Si2, the (Ce-Gd)Ru2Si2 system where Ce was substituted by Gd were studied through magnetic properties mainly in Gd-rich regions. At Gd=0, i.e. in CeRu2Si2, the magnetic moment of Ce showed a symptom of saturation in M-H curve under H=90,000 Oe at 2 K and the Ce magnetic moment at 4.2 K can be nearly identical to that at 2 K employing 1/H plot. At Gd-rich content of 0.8, Ce magnetic moment coupled parallel to that of Gd, Ce ↑ Gd ↑ both in easy and hard axis and the extremely smallness of Ce magnetic moment in hard axis disappeared perfectly at x=0.8. Furthermore at Gd=1, GdRu2Si2, Gd magnetic moment caused 2-step like spin-flip in both easy and hard axis.

First-principle study of single TM atoms X (X=Fe, Ru or Os) doped monolayer WS2 systems

NASA Astrophysics Data System (ADS)

Zhu, Yuan-Yan; Zhang, Jian-Min

2018-05-01

We report the structural, magnetic and electronic properties of the pristine and single TM atoms X (X = Fe, Ru or Os) doped monolayer WS2 systems based on first-principle calculations. The results show that the W-S bond shows a stronger covalent bond, but the covalency is obviously weakened after the substitution of W atom with single X atoms, especially for Ru (4d75s1) with the easily lost electronic configuration. The smaller total energies of the doped systems reveal that the spin-polarized states are energetically favorable than the non-spin-polarized states, and the smallest total energy of -373.918 eV shows the spin-polarized state of the Os doped monolayer WS2 system is most stable among three doped systems. In addition, although the pristine monolayer WS2 system is a nonmagnetic-semiconductor with a direct band gap of 1.813 eV, single TM atoms Fe and Ru doped monolayer WS2 systems transfer to magnetic-HM with the total moments Mtot of 1.993 and 1.962 μB , while single TM atom Os doped monolayer WS2 systems changes to magnetic-metal with the total moments Mtot of 1.569 μB . Moreover, the impurity states with a positive spin splitting energies of 0.543, 0.276 and 0.1999 eV near the Fermi level EF are mainly contributed by X-dxy and X-dx2-y2 states hybridized with its nearest-neighbor atom W-dz2 states for Fe, Ru and Os doped monolayer WS2 system, respectively. Finally, we hope that the present study on monolayer WS2 will provide a useful theoretical guideline for exploring low-dimensional spintronic materials in future experiments.

Transport properties of nonelectrolyte liquid mixtures—V. Viscosity coefficients for binary mixtures of benzene plus alkanes at saturation pressure from 283 to 393 K

NASA Astrophysics Data System (ADS)

Dymond, J. H.; Young, K. J.

1981-09-01

Viscosity coefficient measurements at saturation pressure are reported for benzene + n-hexane, benzene + n-octane, benzene + n-decane, benzene + n-dodecane, benzene + n-hexadecane, and benzene + cyclohexane at temperatures from 283 to 393 K. The characteristic parameter G in the Grunberg and Nissan equation 10765_2004_Article_BF00504187_TeX2GIFE1.gif ell nη = x_1 ell nη _1 + x_2 ell nη _2 + x_1 x_2 G is found to be both composition and temperature dependent for benzene + n-alkane mixtures, but it is independent of composition for the system benzene + cyclohexane.

Discovery of the VHE gamma-ray source HESS J1832-093 in the vicinity of SNR G22.7-0.2

NASA Astrophysics Data System (ADS)

HESS Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Clapson, A.-C.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zabalza, V.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

2015-01-01

The region around the supernova remnant (SNR) W41 contains several TeV sources and has prompted the HESS Collaboration to perform deep observations of this field of view. This resulted in the discovery of the new very high energy (VHE) source HESS J1832-093, at the position {RA=18^h 32^m 50^s ± 3^s_{stat} ± 2^s_{syst}}, {Dec=-9*deg;22'36" ± 32"}_{stat} ± 20^' '}_{syst} (J2000)}, spatially coincident with a part of the radio shell of the neighbouring remnant G22.7-0.2. The photon spectrum is well described by a power law of index Γ = 2.6 ± 0.3stat ± 0.1syst and a normalization at 1 TeV of Φ _0=(4.8 ± 0.8_stat± 1.0_syst) × 10^{-13} cm ^{-2} s^{-1} TeV^{-1}. The location of the gamma-ray emission on the edge of the SNR rim first suggested a signature of escaping cosmic rays illuminating a nearby molecular cloud. Then a dedicated XMM-Newton observation led to the discovery of a new X-ray point source spatially coincident with the TeV excess. Two other scenarios were hence proposed to identify the nature of HESS J1832-093. Gamma-rays from inverse Compton radiation in the framework of a pulsar wind nebula scenario or the possibility of gamma-ray production within a binary system are therefore also considered. Deeper multiwavelength observations will help to shed new light on this intriguing VHE source.

MoRu/Be multilayers for extreme ultraviolet applications

DOEpatents

Bajt, Sasa C.; Wall, Mark A.

2001-01-01

High reflectance, low intrinsic roughness and low stress multilayer systems for extreme ultraviolet (EUV) lithography comprise amorphous layers MoRu and crystalline Be layers. Reflectance greater than 70% has been demonstrated for MoRu/Be multilayers with 50 bilayer pairs. Optical throughput of MoRu/Be multilayers can be 30-40% higher than that of Mo/Be multilayer coatings. The throughput can be improved using a diffusion barrier to make sharper interfaces. A capping layer on the top surface of the multilayer improves the long-term reflectance and EUV radiation stability of the multilayer by forming a very thin native oxide that is water resistant.

Convective Influence on Radial Segregation During Unidirectional Solidification of the Binary Alloy HgCdTe

NASA Technical Reports Server (NTRS)

Watring, D. A.; Gillies, D. C.; Lehoczky, S. L.; Szofran, F. R.; Alexander, H.

1996-01-01

In order to simulate the space environment for basic research into the crystal growth mechanism, Hg(0.8)Cd(0.2)Te crystals were grown by the vertical Bridgman-Stockbarger method in the presence of an applied axial magnetic field. The influence of convection, by magneto hydrodynamic damping, on mass transfer in the melt and segregation at the solid-liquid interface was investigated by measuring the axial and radial compositional variations in the grown samples. The reduction of convective mixing in the melt through the application of the magnetic field is found to have a large effect on radial segregation and interface morphology in the grown crystals. Direct comparisons are made with a Hg(0.8)Cd(0.2)Te crystal grown without field and also in the microgravity environment of space during the second United States Microgravity Payload Mission (USMP-2).

High temperature behavior of B2-based ruthenium aluminide systems

NASA Astrophysics Data System (ADS)

Cao, Fang

Ru-modified NiAl-based bond coats have the potential to improve the durability of Superalloy-Thermal Barrier Coating systems (TBCs) for advanced gas turbine engines. A fundamental understanding of the high temperature mechanical behavior across the Ni-Al-Ru B2 phase field can provide direction for the development of these new bond coats for TBCs. The purpose of this study has been to describe the fundamental processes of creep deformation in single phase B2 Ru-Al-Ni ternary alloys which would form the basis for the bond coats. To accomplish this, five ternary alloys with compositions located within the B2 field across the NiAl-RuAl phase region were fabricated and investigated. Special emphasis was placed on characterizing creep deformation and describing the operative creep mechanisms in these alloys. At room temperature, brittle failure was observed in the Ni-rich alloys in compression, while improved strength and ductility were displayed in two Ru-rich ternary alloys at temperatures up to 700°C. Exceptional creep strength was observed in these alloys, as compared to other high melting temperature B2 intermetallics. A continuous increase of the melting temperature and creep resistance with the increasing of the Ru/Ni ratio in these alloys was observed. Post-creep dislocation analyses identified the presence of <100> and <110> edge dislocations in the Ni-rich alloys, while uniformly distributed jogged <100> screw dislocations predominated in the Ru-rich ternary alloys. A transition of the creep mechanism from viscous glide controlled to jogged screw motion in these Ru-Al-Ni ternary B2 alloys with increasing Ru/Ni ratio is demonstrated by the characteristics of the creep deformation process, stress change creep tests, post-creep dislocation analyses, and numerical modeling. Additionally, the knowledge of the cyclic oxidation behavior of ruthenium aluminide-based alloy is essential, as many high-temperature applications for which this intermetallic might be utilized undergo repeated severe thermal cycling. Thus the second portion of this thesis focuses on the characterization of the cyclic oxidation properties of RuAl-based alloys. The cyclic oxidation behavior of six RuAl-based alloys was studied in air over the temperature range of 1000°C to 1300°C. Oxidation kinetics have been shown to be influenced by microstructure as well as the addition of platinum.

Ruthenium porphyrin-induced photodamage in bladder cancer cells.

PubMed

Bogoeva, Vanya; Siksjø, Monica; Sæterbø, Kristin G; Melø, Thor Bernt; Bjørkøy, Astrid; Lindgren, Mikael; Gederaas, Odrun A

2016-06-01

Photodynamic therapy (PDT) is a noninvasive treatment for solid malignant and flat tumors. Light activated sensitizers catalyze photochemical reactions that produce reactive oxygen species which can cause cancer cell death. In this work we investigated the photophysical properties of the photosensitizer ruthenium(II) porphyrin (RuP), along with its PDT efficiency onto rat bladder cancer cells (AY27). Optical spectroscopy verified that RuP is capable to activate singlet oxygen via blue and red absorption bands and inter system crossing (ISC) to the triplet state. In vitro experiments on AY27 indicated increased photo-toxicity of RuP (20μM, 18h incubation) after cell illumination (at 435nm), as a function of blue light exposure. Cell survival fraction was significantly reduced to 14% after illumination of 20μM RuP with 15.6J/cm(2), whereas the "dark toxicity" of 20μM RuP was 17%. Structural and morphological changes of cells were observed, due to RuP accumulation, as well as light-dependent cell death was recorded by confocal microscopy. Flow cytometry verified that PDT-RuP (50μM) triggered significant photo-induced cellular destruction with a photoxicity of (93%±0.9%). Interestingly, the present investigation of RuP-PDT showed that the dominating mode of cell death is necrosis. RuP "dark toxicity" compared to the conventional chemotherapeutic drug cisplatin was higher, both evaluated by the MTT assay (24h). In conclusion, the present investigation shows that RuP with or without photoactivation induces cell death of bladder cancer cells. Copyright © 2016 Elsevier B.V. All rights reserved.

Highly efficient bioinspired molecular Ru water oxidation catalysts with negatively charged backbone ligands.

PubMed

Duan, Lele; Wang, Lei; Li, Fusheng; Li, Fei; Sun, Licheng

2015-07-21

The oxygen evolving complex (OEC) of the natural photosynthesis system II (PSII) oxidizes water to produce oxygen and reducing equivalents (protons and electrons). The oxygen released from PSII provides the oxygen source of our atmosphere; the reducing equivalents are used to reduce carbon dioxide to organic products, which support almost all organisms on the Earth planet. The first photosynthetic organisms able to split water were proposed to be cyanobacteria-like ones appearing ca. 2.5 billion years ago. Since then, nature has chosen a sustainable way by using solar energy to develop itself. Inspired by nature, human beings started to mimic the functions of the natural photosynthesis system and proposed the concept of artificial photosynthesis (AP) with the view to creating energy-sustainable societies and reducing the impact on the Earth environments. Water oxidation is a highly energy demanding reaction and essential to produce reducing equivalents for fuel production, and thereby effective water oxidation catalysts (WOCs) are required to catalyze water oxidation and reduce the energy loss. X-ray crystallographic studies on PSII have revealed that the OEC consists of a Mn4CaO5 cluster surrounded by oxygen rich ligands, such as oxyl, oxo, and carboxylate ligands. These negatively charged, oxygen rich ligands strongly stabilize the high valent states of the Mn cluster and play vital roles in effective water oxidation catalysis with low overpotential. This Account describes our endeavors to design effective Ru WOCs with low overpotential, large turnover number, and high turnover frequency by introducing negatively charged ligands, such as carboxylate. Negatively charged ligands stabilized the high valent states of Ru catalysts, as evidenced by the low oxidation potentials. Meanwhile, the oxygen production rates of our Ru catalysts were improved dramatically as well. Thanks to the strong electron donation ability of carboxylate containing ligands, a seven-coordinate Ru(IV) species was isolated as a reaction intermediate, shedding light on the reaction mechanisms of Ru-catalyzed water oxidation chemistry. Auxiliary ligands have dramatic effects on the water oxidation catalysis in terms of the reactivity and the reaction mechanism. For instance, Ru-bda (H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid) water oxidation catalysts catalyze Ce(IV)-driven water oxidation extremely fast via the radical coupling of two Ru(V)═O species, while Ru-pda (H2pda = 1,10-phenanthroline-2,9-dicarboxylic acid) water oxidation catalysts catalyze the same reaction slowly via water nucleophilic attack on a Ru(V)═O species. With a number of active Ru catalysts in hands, light driven water oxidation was accomplished using catalysts with low catalytic onset potentials. The structures of molecular catalysts could be readily tailored to introduce additional functional groups, which favors the fabrication of state-of-the-art Ru-based water oxidation devices, such as electrochemical water oxidation anodes and photo-electrochemical anodes. The development of efficient water oxidation catalysts has led to a step forward in the sustainable energy system.

The HEXITEC Hard X-Ray Pixelated CdTe Imager for Fast Solar Observations

NASA Technical Reports Server (NTRS)

Baumgartner, Wayne H.; Christe, Steven D.; Ryan, Daniel; Inglis, Andrew R.; Shih, Albert Y.; Gregory, Kyle; Wilson, Matt; Seller, Paul; Gaskin, Jessica; Wilson-Hodge, Colleen

2016-01-01

There is an increasing demand in solar and astrophysics for high resolution X-ray spectroscopic imaging. Such observations would present ground breaking opportunities to study the poorly understood high energy processes in our solar system and beyond, such as solar flares, X-ray binaries, and active galactic nuclei. However, such observations require a new breed of solid state detectors sensitive to high energy X-rays with fine independent pixels to sub-sample the point spread function (PSF) of the X-ray optics. For solar observations in particular, they must also be capable of handling very high count rates as photon fluxes from solar flares often cause pile up and saturation in present generation detectors. The Rutherford Appleton Laboratory (RAL) has recently developed a new cadmium telluride (CdTe) detector system, called HEXITEC (High Energy X-ray Imaging Technology). It is an 80 x 80 array of 250 micron independent pixels sensitive in the 2-200 keV band and capable of a high full frame read out rate of 10 kHz. HEXITEC provides the smallest independently read out CdTe pixels currently available, and are well matched to the few arcsecond PSF produced by current and next generation hard X-ray focusing optics. NASA's Goddard and Marshall Space Flight Centers are collaborating with RAL to develop these detectors for use on future space borne hard X-ray focusing telescopes. We show the latest results on HEXITEC's imaging capability, energy resolution, high read out rate, and reveal it to be ideal for such future instruments.

Structure and magnetic properties of Fe12X clusters

NASA Astrophysics Data System (ADS)

Gutsev, G. L.; Johnson, L. E.; Belay, K. G.; Weatherford, C. A.; Gutsev, L. G.; Ramachandran, B. R.

2014-02-01

The electronic and geometrical structures of a Fe12X family of binary clusters Fe12Al, Fe12Sc, Fe12Ti, Fe12V, Fe12Cr, Fe12Mn, Fe12Co, Fe12Ni, Fe12Cu, Fe12Zn, Fe12Y, Fe12Zr, Fe12Nb, Fe12Mo, Fe12Tc, Fe12Ru, Fe12Rh, Fe12Pd, Fe12Ag, Fe12Cd, and Fe12Gd are studied using density functional theory within generalized gradient approximation. It is found that the geometrical structures corresponding to the lowest total energy states found for the Fe12X clusters possess icosahedral shape with the substituent atom occupying the central or a surface site. The only exception presents Fe12Nb where a squeezed cage structure is the energetically most favorable. The substitution of an atom in the Fe13 cluster results in the decrease of its total spin magnetic moment of 44 μB, except for Fe12Mn and Fe12Gd. The Fe12X clusters are more stable than the parent Fe13 cluster when X = Al, Sc, Ti, V, Co, Y, Zr, Nb, Mo, Tc, Ru, and Rh.

Indium local geometry in In-Sb-Te thin films using XANES and DFT calculations

NASA Astrophysics Data System (ADS)

Bilovol, V.; Gil Rebaza, A. V.; Mudarra Navarro, A. M.; Errico, L.; Fontana, M.; Arcondo, B.

2017-12-01

In-Sb-Te when is a thin film presents a huge difference in its electrical resistivity when transform from the amorphous (insulating) to the crystalline (conducting) phase. This property made this system one of the main phase-change materials used in the data storage industry. The change in the electrical conductivity is probably associated to a change in the bonding geometry of some of its constituents. To explore this point, we present in this work an study of the bonding geometry of In atoms in In-Sb-Te films by means of In K-edge X-ray absorption near edge structure (XANES) spectroscopy using synchrotron radiation in both as deposited (amorphous) and crystalline thin films obtained as a result of resistance (R) vs temperature (T) measurements. Comparison of the XANES spectra obtained for ternary amorphous films and binary crystalline reference films suggests that in amorphous films the bonding geometry of In atoms is tetrahedral-like. After the thermal annealing has been carried out the differences in the XANES spectra of the as deposited and the annealed films indicate that the bonding geometry of In atoms changes. Based on X-ray diffraction results and ab initio calculations in the framework of the Density Functional Theory (DFT) we show that the new coordination geometry is associated with a tendency of In atoms towards octahedral-like.

CO oxidation on Ru-Pt bimetallic nanoclusters supported on TiO2(101): The effect of charge polarization

NASA Astrophysics Data System (ADS)

Jia, Chuanyi; Zhong, Wenhui; Deng, Mingsen; Jiang, Jun

2018-03-01

Pt-based catalyst is widely used in CO oxidation, while its catalytic activity is often undermined because of the CO poisoning effect. Here, using density functional theory, we propose the use of a Ru-Pt bimetallic cluster supported on TiO2 for CO oxidation, to achieve both high activity and low CO poisoning effect. Excellent catalytic activity is obtained in a Ru1Pt7/TiO2(101) system, which is ascribed to strong electric fields induced by charge polarization between one Ru atom and its neighboring Pt atoms. Because of its lower electronegativity, the Ru atom donates electrons to neighboring Pt. This induces strong electric fields around the top-layered Ru, substantially promoting the adsorption of O2/CO + O2 and eliminating the CO poisoning effect. In addition, the charge polarization also drives the d-band center of the Ru1Pt7 cluster to up-shift to the Fermi level. For surface O2 activation/CO oxidation, the strong electric field and d-band center close to the Fermi level can promote the adsorption of O2 and CO as well as reduce the reaction barrier of the rate-determining step. Meanwhile, since O2 easily dissociates on Ru1Pt7/TiO2(101) resulting in unwanted oxidation of Ru and Pt, a CO-rich condition is necessary to protect the catalyst at high temperature.

Ruthenium in komatiitic chromite

NASA Astrophysics Data System (ADS)

Locmelis, Marek; Pearson, Norman J.; Barnes, Stephen J.; Fiorentini, Marco L.

2011-07-01

The distinction between Ru in solid solution and Ru-bearing inclusions is essential for the predictive modeling of platinum-group element (PGE) geochemistry in applications such as the lithogeochemical exploration for magmatic sulfide deposits in komatiites. This study investigates the role of chromite in the fractionation of Ru in ultramafic melts by analyzing chromite grains from sulfide-undersaturated komatiites and a komatiitic basalt from the Yilgarn Craton in Western Australia. In situ analysis using laser ablation ICP-MS yields uniform Ru concentrations in chromites both within-grain and on a sample scale, with concentrations between 220 and 540 ppb. All other platinum-group elements are below the detection limit of the laser ablation ICP-MS analysis. Carius tube digestion isotope dilution ICP-MS analysis of chromite concentrates confirms the accuracy of the in-situ method. Time resolved laser ablation ICP-MS analyses have identified the presence of sub-micron Ir-bearing inclusions in some chromite grains from the komatiitic basalt. However, Ru-bearing inclusions have not been recognized in the analyzed chromites and this combined with the in situ data suggests that Ru exists in solid solution in the crystal lattice of chromite. These results show that chromite can control the fractionation and concentration of Ru in ultramafic systems.

Cellular accumulation of the new ketolide RU 64004 by human neutrophils: comparison with that of azithromycin and roxithromycin.

PubMed Central

Vazifeh, D; Abdelghaffar, H; Labro, M T

1997-01-01

We analyzed the uptake of RU 64004 by human neutrophils (polymorphonuclear leukocytes [PMNs]) relative to those of azithromycin and roxithromycin. RU 64004 was strongly and rapidly accumulated by PMNs, with a cellular concentration/extracellular concentration ratio (C/E) of greater than 200 in the first 5 min, and this was followed by a plateau at 120 to 180 min, with a C/E of 461 +/- 14.8 (10 experiments) at 180 min. RU 64004 uptake was moderately sensitive to external pH, and activation energy was also moderate (63 +/- 3.8 kJ/mol). RU 64004 was mainly located in PMN granules (about 70%) and egressed slowly from loaded cells, owing to avid reuptake. The possibility that PMN uptake of RU 64004 and other macrolides occurs through a carrier-mediated system was suggested by three key results. First, there existed a strong interindividual variability in uptake kinetics, suggesting variability in the numbers or activity of a transport protein. Second, macrolide uptake displayed saturation kinetics characteristic of that of a carrier-mediated transport system: RU 64004 had the highest Vmax value (3,846 ng/2.5 x 10(6) PMNs/5 min) and the lowest Km value (about 28 microM), indicating a high affinity for the transporter. Third, as observed previously with other erythromycin A derivatives, Ni2+ (a blocker of the Na+/Ca2+ exchanger which mediates Ca2+ influx in resting neutrophils) impaired RU 64004 uptake by PMNs, with a 50% inhibitory concentration of about 3.5 mM. In addition, we found that an active process is also involved in macrolide efflux, because verapamil significantly potentiated the release of all three macrolides tested. This effect of verapamil does not seem to be related to an inhibition of Ca2+ influx, because neither EGTA [ethylene glycol-bis (beta-aminoethyl ether)-N,N',N'-tetraacetic acid] nor Ni2+ modified macrolide efflux. The nature and characteristics of the entry- and efflux-mediating carrier systems are under investigation. PMID:9333032

Ru-Catalyzed Estragole Isomerization under Homogeneous and Ionic Liquid Biphasic Conditions

PubMed Central

2017-01-01

The isomerization of estragole to trans-anethole is an important reaction and is industrially performed using an excess of NaOH or KOH in ethanol at high temperatures with very low selectivity. Simple Ru-based transition-metal complexes, under homogeneous, ionic liquid (IL)-supported (biphasic) and “solventless” conditions, can be used for this reaction. The selectivity of this reaction is more sensitive to the solvent/support used than the ligands associated with the metal catalyst. Thus, under the optimized reaction conditions, 100% conversion can be achieved in the estragole isomerization, using as little as 4 × 10–3 mol % (40 ppm) of [RuHCl(CO)(PPh3)3] in toluene, reflecting a total turnover number (TON) of 25 000 and turnover frequencies (TOFs) of up to 500 min–1 at 80 °C. Using a dimeric Ru precursor, [RuCl(μ-Cl)(η3:η3-C10H16)]2, in ethanol associated with P(OEt)3, a TON of 10 000 and a TOF of 125 min–1 are obtained with 100% conversion and 99% selectivity. These two Ru catalytic systems can be transposed to biphasic IL systems by using ionic-tagged P-ligands such as 1-(3-(diphenylphosphanyl)propyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide immobilized in 1-(3-hydroxypropyl)-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl) imide with up to 99% selectivity and almost complete estragole conversion. However, the reaction is much slower than that performed under solventless or homogeneous conditions. The use of ionic-tagged ligands significantly reduces the Ru leaching to the organic phase, compared to that in reactions performed under homogeneous conditions, where the catalytic system loses catalytic performance after the second recycling. Detailed kinetic investigations of the reaction catalyzed by [RuHCl(CO)(PPh3)3] indicate that a simplified kinetic model (a monomolecular reversible first-order reaction) is adequate for fitting the homogeneous reaction at 80 °C and under biphasic conditions. However, the kinetics of the reaction are better described if all of the elementary steps are taken into consideration, especially at 40 °C. PMID:28393133

Thermodynamic description of multicomponent nickel-base superalloys containing aluminum, chromium, ruthenium and platinum: A computational thermodynamic approach coupled with experiments

NASA Astrophysics Data System (ADS)

Zhu, Jun

Ru and Pt are candidate additional component for improving the high temperature properties of Ni-base superalloys. A thermodynamic description of the Ni-Al-Cr-Ru-Pt system, serving as an essential knowledge base for better alloy design and processing control, was developed in the present study by means of thermodynamic modeling coupled with experimental investigations of phase equilibria. To deal with the order/disorder transition occurring in the Ni-base superalloys, a physical sound model, Cluster/Site Approximation (CSA) was used to describe the fcc phases. The CSA offers computational advantages, without loss of accuracy, over the Cluster Variation Method (CVM) in the calculation of multicomponent phase diagrams. It has been successfully applied to fcc phases in calculating technologically important Ni-Al-Cr phase diagrams. Our effort in this study focused on the two key ternary systems: Ni-Al-Ru and Ni-Al-Pt. The CSA calculated Ni-Al-Ru ternary phase diagrams are in good agreement with the experimental results in the literature and from the current study. A thermodynamic description of quaternary Ni-Al-Cr-Ru was obtained based on the descriptions of the lower order systems and the calculated results agree with experimental data available in literature and in the current study. The Ni-Al-Pt system was thermodynamically modeled based on the limited experimental data available in the literature and obtained from the current study. With the help of the preliminary description, a number of alloy compositions were selected for further investigation. The information obtained was used to improve the current modeling. A thermodynamic description of the Ni-Al-Cr-Pt quaternary was then obtained via extrapolation from its constituent lower order systems. The thermodynamic description for Ni-base superalloy containing Al, Cr, Ru and Pt was obtained via extrapolation. It is believed to be reliable and useful to guide the alloy design and further experimental investigation.

Centrality dependence of charged jet production in p-Pb collisions at √{s_NN} = 5.02 TeV

NASA Astrophysics Data System (ADS)

Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; Ahn, S. U.; Aiola, S.; Akindinov, A.; Alam, S. N.; Albuquerque, D. S. D.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Almaraz, J. R. M.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; Andrei, C.; Andronic, A.; Anguelov, V.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Arnaldi, R.; Arnold, O. W.; Arsene, I. C.; Arslandok, M.; Audurier, B.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Balasubramanian, S.; Baldisseri, A.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Barth, K.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Belmont, R.; Belmont-Moreno, E.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biro, G.; Biswas, R.; Biswas, S.; Bjelogrlic, S.; Blair, J. T.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Bossú, F.; Botta, E.; Bourjau, C.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Butt, J. B.; Buxton, J. T.; Cabala, J.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Carnesecchi, F.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Cerkala, J.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chauvin, A.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Cho, S.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danisch, M. C.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; De, S.; De Caro, A.; de Cataldo, G.; de Conti, C.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; Deisting, A.; Deloff, A.; Dénes, E.; Deplano, C.; Dhankher, P.; Di Bari, D.; Di Mauro, A.; Di Nezza, P.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Drozhzhova, T.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Endress, E.; Engel, H.; Epple, E.; Erazmus, B.; Erdemir, I.; Erhardt, F.; Espagnon, B.; Estienne, M.; Esumi, S.; Eum, J.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabbietti, L.; Fabris, D.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Feuillard, V. J. G.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Fleck, M. G.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fronze, G. G.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Gasik, P.; Gauger, E. F.; Germain, M.; Gheata, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-Dziadus, E.; Glässel, P.; Goméz Coral, D. M.; Gomez Ramirez, A.; Gonzalez, A. S.; Gonzalez, V.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Grachov, O. A.; Graczykowski, L. K.; Graham, K. L.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Gronefeld, J. M.; Grosse-Oetringhaus, J. F.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gunji, T.; Gupta, A.; Gupta, R.; Haake, R.; Haaland, Ø.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hamon, J. C.; Harris, J. W.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Hellbär, E.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Hess, B. A.; Hetland, K. F.; Hillemanns, H.; Hippolyte, B.; Horak, D.; Hosokawa, R.; Hristov, P.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Inaba, M.; Incani, E.; Ippolitov, M.; Irfan, M.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jacazio, N.; Jacobs, P. M.; Jadhav, M. B.; Jadlovska, S.; Jadlovsky, J.; Jahnke, C.; Jakubowska, M. J.; Jang, H. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kamin, J.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karayan, L.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Mohisin Khan, M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, D. W.; Kim, D. J.; Kim, D.; Kim, H.; Kim, J. S.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-Bösing, C.; Klewin, S.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobdaj, C.; Kofarago, M.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kopcik, M.; Kostarakis, P.; Kour, M.; Kouzinopoulos, C.; Kovalenko, O.; Kovalenko, V.; Kowalski, M.; Koyithatta Meethaleveedu, G.; Králik, I.; Kravčáková, A.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kuhn, C.; Kuijer, P. G.; Kumar, A.; Kumar, J.; Kumar, L.; Kumar, S.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; Ladron de Guevara, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lapidus, K.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lea, R.; Leardini, L.; Lee, G. R.; Lee, S.; Lehas, F.; Lehner, S.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; León Monzón, I.; León Vargas, H.; Leoncino, M.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loginov, V.; Loizides, C.; Lopez, X.; López Torres, E.; Lowe, A.; Luettig, P.; Lunardon, M.; Luparello, G.; Lutz, T. H.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manko, V.; Manso, F.; Manzari, V.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martin, N. A.; Martin Blanco, J.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martinez Pedreira, M.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzoni, M. A.; Mcdonald, D.; Meddi, F.; Melikyan, Y.; Menchaca-Rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Miake, Y.; Mieskolainen, M. M.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Moreira De Godoy, D. A.; Moreno, L. A. P.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Mulligan, J. D.; Munhoz, M. G.; Munzer, R. H.; Murakami, H.; Murray, S.; Musa, L.; Musinsky, J.; Naik, B.; Nair, R.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; Natal da Luz, H.; Nattrass, C.; Navarro, S. R.; Nayak, K.; Nayak, R.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Nellen, L.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Noris, J. C. C.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Ohlson, A.; Okatan, A.; Okubo, T.; Olah, L.; Oleniacz, J.; Oliveira Da Silva, A. C.; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Orava, R.; Oravec, M.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Pachmayer, Y.; Pagano, D.; Pagano, P.; Paić, G.; Pal, S. K.; Pan, J.; Pandey, A. K.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Paticchio, V.; Patra, R. N.; Paul, B.; Pei, H.; Peitzmann, T.; Pereira Da Costa, H.; Peresunko, D.; Perez Lezama, E.; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pimentel, L. O. D. L.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, J.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Rami, F.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Read, K. F.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Rocco, E.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ruzza, B. D.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Saarinen, S.; Sadhu, S.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Šándor, L.; Sandoval, A.; Sano, M.; Sarkar, D.; Sarkar, N.; Sarma, P.; Scapparone, E.; Scarlassara, F.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schmidt, M.; Schuchmann, S.; Schukraft, J.; Schulc, M.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Šefčík, M.; Seger, J. E.; Sekiguchi, Y.; Sekihata, D.; Selyuzhenkov, I.; Senosi, K.; Senyukov, S.; Serradilla, E.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shahzad, M. I.; Shangaraev, A.; Sharma, A.; Sharma, M.; Sharma, M.; Sharma, N.; Sheikh, A. I.; Shigaki, K.; Shou, Q.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singha, S.; Singhal, V.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Song, J.; Song, M.; Song, Z.; Soramel, F.; Sorensen, S.; Souza, R. D. de; Sozzi, F.; Spacek, M.; Spiriti, E.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Stachel, J.; Stan, I.; Stankus, P.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Suljic, M.; Sultanov, R.; Šumbera, M.; Sumowidagdo, S.; Szabo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Tabassam, U.; Takahashi, J.; Tambave, G. J.; Tanaka, N.; Tarhini, M.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thäder, J.; Thakur, D.; Thomas, D.; Tieulent, R.; Tikhonov, A.; Timmins, A. R.; Toia, A.; Trogolo, S.; Trombetta, G.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vala, M.; Valencia Palomo, L.; Vallero, S.; Van Der Maarel, J.; Van Hoorne, J. W.; van Leeuwen, M.; Vanat, T.; Vande Vyvre, P.; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Vázquez Doce, O.; Vechernin, V.; Veen, A. M.; Veldhoen, M.; Velure, A.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Verweij, M.; Vickovic, L.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Villatoro Tello, A.; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Vislavicius, V.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; Haller, B. von; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Watanabe, D.; Watanabe, Y.; Weber, M.; Weber, S. G.; Weiser, D. F.; Wessels, J. P.; Westerhoff, U.; Whitehead, A. M.; Wiechula, J.; Wikne, J.; Wilk, G.; Wilkinson, J.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yang, P.; Yano, S.; Yasin, Z.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yoon, J. H.; Yurchenko, V.; Zaborowska, A.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zaporozhets, S.; Zardoshti, N.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhang, C.; Zhang, Z.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zyzak, M.

2016-05-01

Measurements of charged jet production as a function of centrality are presented for p-Pb collisions recorded at √{s_{NN}}= 5.02 TeV with the ALICE detector. Centrality classes are determined via the energy deposit in neutron calorimeters at zero degree, close to the beam direction, to minimise dynamical biases of the selection. The corresponding number of participants or binary nucleon-nucleon collisions is determined based on the particle production in the Pb-going rapidity region. Jets have been reconstructed in the central rapidity region from charged particles with the anti-k_{T} algorithm for resolution parameters R = 0.2 and R = 0.4 in the transverse momentum range 20 to 120 GeV/ c. The reconstructed jet momentum and yields have been corrected for detector effects and underlying-event background. In the five centrality bins considered, the charged jet production in p-Pb collisions is consistent with the production expected from binary scaling from pp collisions. The ratio of jet yields reconstructed with the two different resolution parameters is also independent of the centrality selection, demonstrating the absence of major modifications of the radial jet structure in the reported centrality classes.

Discovery of VHE emission towards the Carina arm region with the H.E.S.S. telescope array: HESS J1018-589

NASA Astrophysics Data System (ADS)

H. E. S. S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker, J.; Bernlöh, K.; Birsin, E.; Biteau, J.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Büsching, I.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Cologna, G.; Conrad, J.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gallant, Y. A.; Gast, H.; Gérard, L.; Gerbig, D.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Göring, D.; Häffner, S.; Hague, J. D.; Hahn, J.; Hampf, D.; Harris, J.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Keogh, D.; Khélifi, B.; Klochkov, D.; Klużniak, D.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Krayzel, F.; Laffon, H.; Lamanna, G.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Moderski, R.; Mohamed, M.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Rayner, S. M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sheidaei, F.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

2012-05-01

The Carina arm region, containing the supernova remnant SNR G284.3-1.8, the high-energy (HE; E > 100 MeV) binary 1FGL J1018.6-5856 and the energetic pulsar PSR J1016-5857 and its nebula, has been observed with the H.E.S.S. telescope array. The observational coverage of the region in very-high-energy (VHE; E > 0.1 TeV) γ-rays benefits from deep exposure (40 h) of the neighboring open cluster Westerlund 2. The observations have revealed a new extended region of VHE γ-ray emission. The new VHE source HESS J1018-589 shows a bright, point-like emission region positionally coincident with SNR G284.3-1.8 and 1FGL J1018.6-5856 and a diffuse extension towards the direction of PSR J1016-5857. A soft (Γ = 2.7 ± 0.5stat)photon index, with a differential flux at 1 TeV of N0 = (4.2 ± 1.1) × 10-13 TeV-1 cm-2 s-1 is found for the point-like source, whereas the total emission region including the diffuse emission region is well fit by a power-law function with spectral index Γ = 2.9 ± 0.4stat and differential flux at 1 TeV of N0 = (6.8 ± 1.6) × 10-13 TeV-1 cm-2 s-1. This H.E.S.S. detection motivated follow-up X-ray observations with the XMM-Newton satellite to investigate the origin of the VHE emission. The analysis of the XMM-Newton data resulted in the discovery of a bright, non-thermal point-like source (XMMU J101855.4-58564) with a photon index of Γ = 1.65 ± 0.08 in the center of SNR G284.3-1.8, and a thermal, extended emission region coincident with its bright northern filament. The characteristics of this thermal emission are used to estimate the plasma density in the region as n ≈ 0.5 cm-3 (2.9 kpc/d)2. The position of XMMU J101855.4-58564 is compatible with the position reported by the Fermi-LAT collaboration for the binary system 1FGL J1018.6-5856 and the variable Swift XRT source identified with it. The new X-ray data are used alongside archival multi-wavelength data to investigate the relationship between the VHE γ-ray emission from HESS J1018-589 and the various potential counterparts in the Carina arm region.

Chandra follow up analysis on HESS J1841-055

NASA Astrophysics Data System (ADS)

Wilbert, Sven

2012-07-01

State of the art Imaging Atmospheric Cherenkow Telescopes (IACTs) like the Very Energetic Radiation Imaging Telescope Array System (VERITAS) and the High Energy Stereoscopic System (H.E.S.S) made surveys of the sky in order to discover new sources. The first and most famous is the H.E.S.S survey of the inner Galactic plane. So far more than 50 Galactic TeV Gamma-ray sources have been detected, a large number of which remain unidentified. HESS J1841-055 is one of the largest and most complex among these unidentified sources with an extension of approximately 1°. Follow up observations of the HESS J1841-055 region with Chandra, which is due to its high resolution good suited for searching for X-Ray counterparts and add-on analysis have revealed several X-ray sources spatially coincident with the multiple TeV emission peaks. The search for counterparts brought out the fact that not a single source itself but a bunch of sources of different nature, could be indeed the creators of this complex diffuse emission region; among them the SNR Kes 73, the pulsar within Kes 73, 1E 1841-45 and also the High Mass X-Ray Binary AX 184100.4-0536 and others.

Very High Energy Emission from the Binary System Cyg X-3

NASA Astrophysics Data System (ADS)

Sinitsyna, V. G.; Sinitsyna, V. Yu.

2018-03-01

Cyg X-3 is actively studied in the entire range of the electromagnetic spectrum from the radio band to ultrahigh energies. Based on the detection of ultrahigh-energy gamma-ray emission, it has been suggested that Cyg X-3 could be one of the most powerful sources of charged cosmic-ray particles in the Galaxy. We present the results of long-term observations of the Cygnus X-3 region at energies 800 GeV-100 TeV by the SHALON mirror Cherenkov telescope. In 1995 the SHALON observations revealed a new Galactic source of very high energy gamma-ray emission coincident in its coordinates with the microquasar Cyg X-3. To reliably identify the detected source with Cyg X-3, an analysis has been performed and an orbital period of 4.8 h has been found, which is a signature of Cyg X-3. A series of flares in Cyg X-3 at energies >800 GeV and their correlation with the activity in the X-ray and radio bands have been observed. The results obtained in a wide energy range for Cyg X-3, including those during the periods of relativistic jet events, are needed to find the connection and to understand the different components of an accreting binary system.

Oxidation of Bromide to Bromine by Ruthenium(II) Bipyridine-Type Complexes Using the Flash-Quench Technique.

PubMed

Tsai, Kelvin Yun-Da; Chang, I-Jy

2017-07-17

Six ruthenium complexes, [Ru(bpy) 3 ] 2+ (1), [Ru(bpy) 2 (deeb)] 2+ (2), [Ru(deeb) 2 (dmbpy)] 2+ (3), [Ru(deeb) 2 (bpy)] 2+ (4), [Ru(deeb) 3 ] 2+ (5), and [Ru(deeb) 2 (bpz)] 2+ (6) (bpy: 2,2'-bipyridine; deeb: 4,4'-diethylester-2,2'-bipyridine; dmbpy: 4,4'-dimethyl-2,2'-bipyridine, bpz: 2,2'-bipyrazine), have been employed to sensitize photochemical oxidation of bromide to bromine. The oxidation potential for complexes 1-6 are 1.26, 1.36, 1.42, 1.46, 1.56, and 1.66 V vs SCE, respectively. The bimolecular rate constants for the quenching of complexes 1-6 by ArN 2 + (bromobenzenediazonium) are determined as 1.1 × 10 9 , 1.6 × 10 8 , 1.4 × 10 8 , 1.2 × 10 8 , 6.4 × 10 7 , and 8.9 × 10 6 M -1 s -1 , respectively. Transient kinetics indicated that Br - reacted with photogenerated Ru(III) species at different rates. Bimolecular rate constants for the oxidation of Br - by the Ru(III) species derived from complexes 1-5 are observed as 1.2 × 10 8 , 1.3 × 10 9 , 4.0 × 10 9 , 4.8 × 10 9 , and 1.1 × 10 10 , M -1 s -1 , respectively. The last reaction kinetics observed in the three-component system consisting of a Ru sensitizer, quencher, and bromide is shown to be independent of the Ru sensitizer. The final product was identified as bromine by its reaction with hexene. The last reaction kinetics is assigned to the disproportionation reaction of Br 2 -• ions, for which the rate constant is determined as 5 × 10 9 M -1 s -1 . Though complex 6 has the highest oxidation potential in the Ru(II)/Ru(III) couple, its excited state fails to react with ArN 2 + sufficiently for subsequent reactions. The Ru(III) species derived from complex 1 reacts with Br - at the slowest rate. Complexes 2-5 are excellent photosensitizers to drive photooxidation of bromide to bromine.

Nanoporous Ru as a carbon- and binder-free cathode for Li-O2 batteries.

PubMed

Liao, Kaiming; Zhang, Tao; Wang, Yongqing; Li, Fujun; Jian, Zelang; Yu, Haijun; Zhou, Haoshen

2015-04-24

Porous carbon-free cathodes are critical to achieve a high discharge capacity and efficient cycling for rechargeable Li-O2 battery. Herein, we present a very simple method to directly grow nanoporous Ru (composed of polycrystalline particles of ∼5 nm) on one side of a current collector of Ni foam via a galvanic replacement reaction. The resulting Ru@Ni can be employed as a carbon- and binder-free cathode for Li-O2 batteries and delivers a specific capacity of 3720 mAh gRu (-1) at a current density of 200 mA gRu (-1) . 100 cycles of continuous discharge and charge are obtained at a very narrow terminal voltage window of 2.75∼3.75 V with a limited capacity of 1000 mAh gRu (-1) . The good performance of the nanoporous Ru@Ni cathode can be mainly attributed to the effective suppression of the by-products related to carbon or binder, the good adhesion of the catalyst to the current collector, and the good permeation of O2 and electrolyte into the active sites of the nanoporous Ru with the open pore system. This new type electrode provides a snapshot toward developing high-performance carbon- and binder-free Li-O2 batteries. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stable monolayer honeycomb-like structures of RuX2 (X =S,Se)

NASA Astrophysics Data System (ADS)

Ersan, Fatih; Cahangirov, Seymur; Gökoǧlu, Gökhan; Rubio, Angel; Aktürk, Ethem

2016-10-01

Recent studies show that several metal oxides and dichalcogenides (M X2) , which exist in nature, can be stable in two-dimensional (2D) form and each year several new M X2 structures are explored. The unstable structures in H (hexagonal) or T (octahedral) forms can be stabilized through Peierls distortion. In this paper, we propose new 2D forms of RuS2 and RuSe2 materials. We investigate in detail the stability, electronic, magnetic, optical, and thermodynamic properties of 2D Ru X2 (X =S,Se) structures from first principles. While their H and T structures are unstable, the distorted T structures (T'-Ru X2) are stable and have a nonmagnetic semiconducting ground state. The molecular dynamic simulations also confirm that T'-Ru X2 systems are stable even at 500 K without any structural deformation. T'-RuS2 and T'-RuSe2 have indirect band gaps with 0.745 eV (1.694 eV with HSE) and 0.798 eV (1.675 eV with HSE) gap values, respectively. We also examine their bilayer and trilayer forms and find direct and smaller band gaps. We find that AA stacking is more favorable than the AB configuration. The new 2D materials obtained can be good candidates with striking properties for applications in semiconductor electronic, optoelectronic devices, and sensor technology.

Nucleosynthesis of Mo and Ru isotopes in neutrino-driven winds

NASA Astrophysics Data System (ADS)

Bliss, Julia; Arcones, Almudena

2018-01-01

The solar system origin of the p-isotopes 92,94Mo and 96,98Ru is a long-lasting mystery. Several astrophysical scenarios failed to explain their formation. Moreover, SiC X grains show a different abundance ratio of 95,97Mo than in the solar system. We have investigated if neutrino-driven winds can offer a solution to those problems.

Hadronic gamma-ray and neutrino emission from Cygnus X-3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahakyan, N.; Piano, G.; Tavani, M., E-mail: narek@icra.it

2014-01-01

Cygnus X-3 (Cyg X-3) is a remarkable Galactic microquasar (X-ray binary) emitting from radio to γ-ray energies. In this paper, we consider the hadronic model of emission of γ-rays above 100 MeV and their implications. We focus on the joint γ-ray and neutrino production resulting from proton-proton interactions within the binary system. We find that the required proton injection kinetic power, necessary to explain the γ-ray flux observed by AGILE and Fermi-LAT, is L{sub p} ∼ 10{sup 38} erg s{sup –1}, a value in agreement with the average bolometric luminosity of the hypersoft state (when Cyg X-3 was repeatedly observedmore » to produce transient γ-ray activity). If we assume an increase of the wind density at the superior conjunction, the asymmetric production of γ-rays along the orbit can reproduce the observed modulation. According to observational constraints and our modeling, a maximal flux of high-energy neutrinos would be produced for an initial proton distribution with a power-law index α = 2.4. The predicted neutrino flux is almost two orders of magnitude less than the two-month IceCube sensitivity at ∼1 TeV. If the protons are accelerated up to PeV energies, the predicted neutrino flux for a prolonged 'soft X-ray state' would be a factor of about three lower than the one-year IceCube sensitivity at ∼10 TeV. This study shows that, for a prolonged soft state (as observed in 2006) possibly related to γ-ray activity and a hard distribution of injected protons, Cyg X-3 might be close to being detectable by cubic-kilometer neutrino telescopes such as IceCube.« less

Ultrafast relaxation dynamics of amine-substituted bipyridyl ruthenium(II) complexes

NASA Astrophysics Data System (ADS)

Song, Hongwei; Wang, Xian; Yang, WenWen; He, Guiying; Kuang, Zhuoran; Li, Yang; Xia, Andong; Zhong, Yu-Wu; Kong, Fan'ao

2017-09-01

The excited state properties of a series of ruthenium(II) amine-substituted bipyridyl complexes, [Ru(bpy)n(NNbpy)3-n]2+, were investigated by steady-state and transient absorption spectroscopy, as well as quantum chemical calculations. The steady-state absorption spectra of these complexes in CH3CN show a distinct red-shift of the 1MLCT absorption with increasing numbers of amine substituent, whereas the emission spectra indicate an energy gap order of [Ru(bpy)3]2+ > [Ru(bpy)2(NNbpy)]2+ > [Ru(NNbpy)3]2+ > [Ru(bpy)(NNbpy)2]2+. Nanosecond, femtosecond transient absorption and electrochemical measurements suggest that NNbpy ligand has a strong influence on the electronic and emission properties of these complexes, due to electron-rich amine substituent. We illustrate how the numbers of amine substituent modulate the spectroscopic properties of transition metal complexes, which is related to the design of new electro-active systems with novel photoelectrochemical properties.

Production of Primary Amines by Reductive Amination of Biomass-Derived Aldehydes/Ketones.

PubMed

Liang, Guanfeng; Wang, Aiqin; Li, Lin; Xu, Gang; Yan, Ning; Zhang, Tao

2017-03-06

Transformation of biomass into valuable nitrogen-containing compounds is highly desired, yet limited success has been achieved. Here we report an efficient catalyst system, partially reduced Ru/ZrO 2 , which could catalyze the reductive amination of a variety of biomass-derived aldehydes/ketones in aqueous ammonia. With this approach, a spectrum of renewable primary amines was produced in good to excellent yields. Moreover, we have demonstrated a two-step approach for production of ethanolamine, a large-market nitrogen-containing chemical, from lignocellulose in an overall yield of 10 %. Extensive characterizations showed that Ru/ZrO 2 -containing multivalence Ru association species worked as a bifunctional catalyst, with RuO 2 as acidic promoter to facilitate the activation of carbonyl groups and Ru as active sites for the subsequent imine hydrogenation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coupled Electronic and Magnetic Phase Transition in the Infinite-Layer Phase LaSrNiRuO4.

PubMed

Patino, Midori Amano; Zeng, Dihao; Bower, Ryan; McGrady, John E; Hayward, Michael A

2016-09-06

Topochemical reduction of the ordered double perovskite LaSrNiRuO6 with CaH2 yields LaSrNiRuO4, an extended oxide phase containing infinite sheets of apex-linked, square-planar Ni(1+)O4 and Ru(2+)O4 units ordered in a checkerboard arrangement. At room temperature the localized Ni(1+) (d(9), S = (1)/2) and Ru(2+) (d(6), S = 1) centers behave paramagnetically. However, on cooling below 250 K the system undergoes a cooperative phase transition in which the nickel spins align ferromagnetically, while the ruthenium cations appear to undergo a change in spin configuration to a diamagnetic spin state. Features of the low-temperature crystal structure suggest a symmetry lowering Jahn-Teller distortion could be responsible for the observed diamagnetism of the ruthenium centers.

Heterojunctions of model CdTe/CdSe mixtures

DOE PAGES

van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; ...

2015-03-18

We report on the strain behavior of compound mixtures of model group II-VI semiconductors. We use the Stillinger-Weber Hamiltonian that we recently introduced, specifically developed to model binary mixtures of group II-VI compounds such as CdTe and CdSe. We also employ molecular dynamics simulations to examine the behavior of thin sheets of material, bilayers of CdTe and CdSe. The lattice mismatch between the two compounds leads to a strong bending of the entire sheet, with about a 0.5 to 1° deflection between neighboring planes. To further analyze bilayer bending, we introduce a simple one-dimensional model and use energy minimization tomore » find the angle of deflection. The analysis is equivalent to a least-squares straight line fit. We consider the effects of bilayers which are asymmetric with respect to the thickness of the CdTe and CdSe parts. We thus learn that the bending can be subdivided into four kinds depending on the compressive/tensile nature of each outer plane of the sheet. We use this approach to directly compare our findings with experimental results on the bending of CdTe/CdSe rods. To reduce the effects of the lattice mismatch we explore diffuse interfaces, where we mix (i.e. alloy) Te and Se, and estimate the strain response.« less

Electronic and optical properties of mixed Be-chalcogenides

NASA Astrophysics Data System (ADS)

Khan, Imad; Ahmad, Iftikhar; Zhang, D.; Rahnamaye Aliabad, H. A.; Jalali Asadabadi, S.

2013-02-01

The electronic and optical properties of BeSxSe1-x, BeSxTe1-x and BeSexTe1-x, (0≤x≤1) are studied using the highly accurate modified Beck and Johnson (mBJ) potential. The binary Be-chalcogenides are wide and indirect band gap semiconductors and hence they are not efficient materials for optoelectronics. In order to modify them into optically active materials, the anion chalcogen atoms are partially replaced by other chalcogen atoms like BeSxSe1-x, BeSxTe1-x and BeSexTe1-x (0≤x≤1). The modified ternary compounds are of direct band gap nature and hence they are optically active. Some of these direct band gap materials are lattice matched with silicon and can possibly replace Si in semiconductor devices. Keeping in view the importance of these materials in optoelectronics, the optical properties of BeSxSe1-x, BeSxTe1-x and BeSexTe1-x in the full composition range are investigated. It is found that these materials are transparent in the IR, visible and near UV spectral regions. The alloys for the most of the concentrations have band gaps larger than 3 eV, so it is expected that they may be efficient materials for blue, green and UV light emitting diodes.

Energy level shifts at the silica/Ru(0001) heterojunction driven by surface and interface dipoles

DOE PAGES

Wang, Mengen; Zhong, Jian -Qiang; Kestell, John; ...

2016-09-12

Charge redistribution at heterogeneous interfaces is a fundamental aspect of surface chemistry. Manipulating the amount of charges and the magnitude of dipole moments at the interface in a controlled way has attracted tremendous attention for its potential to modify the activity of heterogeneous catalysts in catalyst design. Two-dimensional ultrathin silica films with well-defined atomic structures have been recently synthesized and proposed as model systems for heterogeneous catalysts studies. R. Wlodarczyk et al. (Phys. Rev. B, 85, 085403 (2012)) have demonstrated that the electronic structure of silica/Ru(0001) can be reversibly tuned by changing the amount of interfacial chemisorbed oxygen. Here wemore » carried out systematic investigations to understand the underlying mechanism through which the electronic structure at the silica/Ru(0001) interface can be tuned. As corroborated by both in situ X-ray photoelectron spectroscopy and density functional theory calculations, the observed interface energy level alignments strongly depend on the surface and interfacial charge transfer induced dipoles at the silica/Ru(0001) heterojunction. These observations may help to understand variations in catalytic performance of the model system from the viewpoint of the electronic properties at the confined space between the silica bilayer and the Ru(0001) surface. As a result, the same behavior is observed for the aluminosilicate bilayer, which has been previously proposed as a model system for zeolites.« less

Visible-Light-Driven Oxidation of Organic Substrates with Dioxygen Mediated by a [Ru(bpy)3 ](2+) /Laccase System.

PubMed

Schneider, Ludovic; Mekmouche, Yasmina; Rousselot-Pailley, Pierre; Simaan, A Jalila; Robert, Viviane; Réglier, Marius; Aukauloo, Ally; Tron, Thierry

2015-09-21

Oxidation reactions are highly important chemical transformations that still require harsh reaction conditions and stoichiometric amounts of chemical oxidants that are often toxic. To circumvent these issues, olefins oxidation is achieved in mild conditions upon irradiation of an aqueous solution of the complex [Ru(bpy)3 ](2+) and the enzyme laccase. Epoxide formation is coupled to the light-driven reduction of O2 by [Ru(bpy)3 ](2+) /laccase system. The reactivity can be explained by dioxygen acting both as an oxidative agent and as renewable electron acceptor, avoiding the use of a sacrificial electron acceptor. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical and surface analysis of the Fe-Cr-Ru system in non-oxidizing acid solutions

NASA Astrophysics Data System (ADS)

Tjong, S. C.

1990-03-01

The effect of ruthenium addition on the spontaneous passivation behaviour of Fe-40Cr alloy in 0.5M H 2SO 4 and 0.5M HCl acid solutions has been studied. Auger and XPS techniques were also used to investigate the surface chemistries of the spontaneously passivated film. Electrochemical measurements indicate that the Fe-40Cr-0.1Ru and Fe-40Cr-0.2Ru alloys exhibit spontaneous passivation upon exposing them in both hydrochloric and sulphuric acid solutions from 25 to 85 ° C. However, the transition time for spontaneous passivation reduces dramatically with an increase in the ruthenium content and solution temperature. Furthermore, this transition time also decreases for the investigated alloys exposed in a less aggressive sulphuric acid solution. AES results show that ruthenium and chromium are enriched in the spontaneous passive films formed on the Fe-40Cr-0.1Ru alloy in both hydrochloric and sulphuric acid solutions at 25 °C, and also in the spontaneous passive film formed on the Fe-40Cr-0.2Ru alloy in hydrochloric acid solution at 25 ° C. AES does not detect the presence of ruthenium in the spontaneous passive film formed on the Fe-40Cr-0.2Ru alloy in sulphuric acid solution. However, XPS analysis shows that ruthenium and chromium are incorporated into the spontaneous passive films formed on the Fe-40Cr-0.1Ru and Fe-40Cr-0.2Ru alloys in both hydrochloric and sulphuric acid solutions as Ru 4+ and Cr 3+ species.

Inner-shell photodetachment of transition metal negative ions

NASA Astrophysics Data System (ADS)

Dumitriu, Ileana

This thesis focuses on the study of inner-shell photodetachment of transition metal negative ions, specifically Fe- and Ru- . Experimental investigations have been performed with the aim of gaining new insights into the physics of negative atomic ions and providing valuable absolute cross section data for astrophysics. The experiments were performed using the X-ray radiation from the Advanced Light Source, Lawrence Berkeley National Laboratory, and the merged-beam technique for photoion spectroscopy. Negative ions are a special class of atomic systems very different from neutral atoms and positive ions. The fundamental physics of the interaction of transition metal negative ions with photons is interesting but difficult to analyze in detail because the angular momentum coupling generates a large number of possible terms resulting from the open d shell. Our work reports on the first inner-shell photodetachment studies and absolute cross section measurements for Fe- and Ru -. In the case of Fe-, an important astrophysical abundant element, the inner-shell photodetachment cross section was obtained by measuring the Fe+ and Fe2+ ion production over the photon energy range of 48--72 eV. The absolute cross sections for the production of Fe+ and Fe2+ were measured at four photon energies. Strong shape resonances due to the 3p→3d photoexcitation were measured above the 3p detachment threshold. The production of Ru+, Ru2+, and Ru3+ from Ru- was measured over 30--90 eV photon energy range The absolute photodetachment cross sections of Ru - ([Kr] 4d75s 2) leading to Ru+, Ru2+, and Ru 3+ ion production were measured at three photon energies. Resonance effects were observed due to interference between transitions of the 4 p-electrons to the quasi-bound 4p54d85s 2 states and the 4d→epsilonf continuum. The role of many-particle effects, intershell interaction, and polarization seems much more significant in Ru- than in Fe- photodetachment.

Electrochemiluminescence detection of TNT by resonance energy transfer through the formation of a TNT-amine complex.

PubMed

Qi, Wenjing; Xu, Min; Pang, Lei; Liu, Zhongyuan; Zhang, Wei; Majeed, Saadat; Xu, Guobao

2014-04-14

2,4,6-Trinitrotoluene (TNT) is a widely used nitroaromatic explosive with significant detrimental effects on the environment and human health. Its detection is of great importance. In this study, both electrochemiluminescence (ECL)-based detection of TNT through the formation of a TNT-amine complex and the detection of TNT through electrochemiluminescence resonance energy transfer (ECRET) are developed for the first time. 3-Aminopropyltriethoxysilane (APTES)-modified [Ru(phen)3](2+) (phen=1,10-phenanthroline)-doped silica nanoparticles (RuSiNPs) with uniform sizes of (73±3) nm were synthesized. TNT can interact with APTES-modified RuSiNPs through charge transfer from electron-rich amines in the RuSiNPs to the electron-deficient aromatic ring of TNT to form a red TNT-amine complex. The absorption spectrum of this complex overlaps with the ECL spectrum of the APTES-modified RuSiNPs/triethylamine system. As a result, ECL signals of the APTES-modified RuSiNPs/triethylamine system are turned off in the presence of TNT owing to resonance energy transfer from electrochemically excited RuSiNPs to the TNT-amine complex. This ECRET method has been successfully applied for the sensitive determination of TNT with a linear range from 1×10(-9) to 1×10(-6) M with a fast response time within 1 min. The limit of detection is 0.3 nM. The method exhibits good selectivity towards 2,4-dinitrotoluene, p-nitrotoluene, nitrobenzene, phenol, p-quinone, 8-hydroxyquinoline, p-phenylenediamine, K3[Fe(CN)6], Fe(3+), NO3(-), NO2(-), Cr(3+), Fe(2+), Pb(2+), SO3(2-), formaldehyde, oxalate, proline, and glycine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of PbO on optical properties of tellurite glass

NASA Astrophysics Data System (ADS)

Elazoumi, S. H.; Sidek, H. A. A.; Rammah, Y. S.; El-Mallawany, R.; Halimah, M. K.; Matori, K. A.; Zaid, M. H. M.

2018-03-01

Binary (1 - x)(TeO2) - x(PbO), x = 0, 0.10, 0.15, 0.20, 0.25, 0.30 mol% glass system was fabricated using melt quenching method. X-ray diffraction (XRD) technique was employed to confirm the amorphous nature. The microanalysis of the major components was performed using energy dispersive EDX and X-ray spectrometry. Both the molar volume and the density were measured. FTIR and UV spectra were recorded at 400-4000 cm-1 and 220-800 nm, respectively. The optical band gap (Eopt), Urbach's energy (Eu), index of refraction (n) were calculated using absorption spectrum fitting (ASF) and derivation of absorption spectrum fitting (DASF) methods. Molar refraction Rm and molecular polarizability αm have been calculated according to (ASF) method.

Rhodium-105 Bombesin Analogs for Prostate Cancer Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silvia S. Jurisson, PhD

2005-12-31

Over the period of this grant (11/01/2001 to 12/31/2005), the consistent and reproducible production of Rh-105, synthesis and evaluation of three new chelate systems based on hydroxymethyl phosphines, development of a new non-hydroxymethyl phosphine N{sub 2}P{sub 2} chelate system, conjugation of two of the chelates to the bombesin peptide analog BBN[7-14]NH{sub 2}, evaluation of the bombesin conjugates and their Rh-105 complexes for stability, cell binding affinity, and in vivo biodistribution in normal mice has been developed. The BBN analogs bind to GRP receptors that are overexpressed on PC-3 prostate tumor cells. A dedicated glove box is used for the separationmore » and isolation of {sup 105}Rh from the target ({sup 104}Ru). All tubing/connections/valves from the point of the Cl{sub 2} tank are made of Teflon to minimize/eliminate the introduction of any metal into the process (e.g., iron from stainless steel corrosion). The separation of {sup 105}Rh produced from the enriched {sup 104}Ru target involves oxidation of the enriched {sup 104}Ru metal target to ruthenium tetroxide with chlorine gas and sodium hydroxide solution to generate hypochlorite in situ. The RuO4 is removed by distillation and the {sup 105}Rh remaining in the reaction vial is converted into {sup 105}Rh-chloride by acidification with hydrochloric acid and heating. The {sup 105}Rh production process has become reproducible over the past year to consistently make 10-30 mCi of {sup 105}Rh from 1-3 mg of an enriched (99.21%) {sup 104}Ru target. The process itself involves irradiation of the enriched {sup 104}Ru target in the core of the reactor (University of Missouri Research Reactor (MURR)) for one week to yield 16-40 mCi of {sup 105}Rh. The irradiated target is processed to separate the Rh-105 in high specific activity from the {sup 104}Ru target. The irradiated target is dissolved in NaOH (2M, 3 mL) by bubbling Cl{sub 2} gas through the solution (generating NaOCl in situ) to generate RuO{sub 4} and Rh(III). The RuO{sub 4} is distilled from the solution into an HCl trap to allow for recovery of the enriched Ru as RuO{sub 2}. The {sup 105}Rh remains in the reaction vessel, and on acidification with 0.1 M HCl, {sup 105}Rh-chloride is available for use. A schematic of the purification and Ru-104 recovery process is shown.« less

Gold Nanoclusters@Ru(bpy)₃²⁺-Layered Double Hydroxide Ultrathin Film as a Cathodic Electrochemiluminescence Resonance Energy Transfer Probe.

PubMed

Yu, Yingchang; Lu, Chao; Zhang, Meining

2015-08-04

Herein, it is the first report that a cathodic electrochemiluminescence (ECL) resonance energy transfer (ERET) system is fabricated by layer-by-layer (LBL) electrostatic assembly of CoAl layered double hydroxide (LDH) nanosheets with a mixture of blue BSA-gold nanoclusters (AuNCs) and Ru(bpy)3(2+) (denoted as AuNCs@Ru) on an Au electrode. The possible ECL mechanism indicates that the appearance of CoAl-LDH nanosheets generates a long-range stacking order of the AuNCs@Ru on an Au electrode, facilitating the occurrence of the ERET between BSA-AuNC donors and Ru(bpy)3(2+) acceptors on the as-prepared AuNCs@Ru-LDH ultrathin films (UTFs). Furthermore, it is observed that the cathodic ECL intensity can be quenched efficiently in the presence of 6-mercaptopurine (6-MP) in a linear range of 2.5-100 nM with a detection limit of 1.0 nM. On the basis of these interesting phenomena, a facile cathodic ECL sensor has successfully distinguished 6-MP from other thiol-containing compounds (e.g., cysteine and glutathione) in human serum and urine samples. The proposed sensing scheme opens a way for employing the layered UTFs as a platform for the cathodic ECL of Ru(bpy)3(2+).

Structural peculiarities and Raman spectra of TeO{sub 2}/WO{sub 3}-based glasses: A fresh look at the problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mirgorodsky, Andreie; Colas, Maggy; Smirnov, Mikhael

2012-06-15

Ideas currently dominating the field of structural studies of TeO{sub 2}-based glasses are critically considered. A new physically and chemically consistent approach to the constitution of binary TeO{sub 2}-WO{sub 3} glasses is proposed, in which the reasoning coming from the Raman spectra reexamination are correlated with the basic principles of thermodynamics. Separation into two phases is suggested in such glasses. One phase is TeO{sub 2}, and another is Te(WO{sub 4}){sub 2} consisting of tetrahedral [WO{sub 4}]{sup 2-} anions and of Te{sup 4+} cations. Supplementary M{sub n}O{sub k} oxides added to the glasses are found incorporated in the former phase, thusmore » producing solid solutions (for M=Ti, Nb) or tellurite compounds (for M=Nd). - Graphical abstract: Raman scattering spectra of TeO{sub 2}-based glasses with the following compositions (mol%): (a) pure TeO{sub 2}, (b) 85TeO{sub 2}-15WO{sub 3}, (c) 80TeO{sub 2}-15WO{sub 3}-5TiO{sub 2} ,(d) 80TeO{sub 2}-10WO{sub 3}-5TiO{sub 2}-5Nb{sub 2}O{sub 5}, (e) 80TeO{sub 2}-12WO{sub 3}-5TiO{sub 2}-3 Nd{sub 2}O{sub 3}, (f) 80TeO{sub 2}-10WO{sub 3}-5TiO{sub 2}-5Nd{sub 2}O{sub 3}. Highlights: Black-Right-Pointing-Pointer Structural studies of TeO{sub 2}-WO{sub 3} glasses are critically considered. Black-Right-Pointing-Pointer The oxide glass formation is analyzed from Raman spectra and thermodynamic principles. Black-Right-Pointing-Pointer Separation into two phases, TeO{sub 2} and Te(WO{sub 4}){sub 2}, is intrinsic in such glasses. Black-Right-Pointing-Pointer TiO{sub 2} or Nb{sub 2}O{sub 5} addition to TeO{sub 2}-WO{sub 3} glasses leads to produce solid solutions. Black-Right-Pointing-Pointer Nd{sub 2}O{sub 3} addition to TeO{sub 2}-WO{sub 3} glasses leads to produce a tellurite compound.« less

Photoinduced water oxidation sensitized by a tetranuclear Ru(II) dendrimer.

PubMed

La Ganga, Giuseppina; Nastasi, Francesco; Campagna, Sebastiano; Puntoriero, Fausto

2009-12-07

A multimetallic ruthenium(II) dendrimer is used for the first time to photosensitize dioxygen production from water by IrO2 nanoparticles; the system is more efficient than an analogous system based on the more commonly used [Ru(bpy)3]2+-type photosensitizers, in particular for the ability of the dendrimer to take advantage of the red portion of the solar spectrum.

Determining the isotopic compositions of uranium and fission products in radioactive environmental microsamples using laser ablation ICP-MS with multiple ion counters.

PubMed

Boulyga, Sergei F; Prohaska, Thomas

2008-01-01

This paper presents the application of a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS)--a Nu Plasma HR--equipped with three ion-counting multipliers and coupled to a laser ablation system (LA) for the rapid and sensitive determination of the 235U/238U, 236U/238U, 145Nd/143Nd, 146Nd/143Nd, 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios in microsamples collected in the vicinity of Chernobyl. Microsamples with dimensions ranging from a hundred mum to about 1 mm and with surface alpha activities of 3-38 mBq were first identified using nuclear track radiography. U, Nd and Ru isotope systems were then measured sequentially for the same microsample by LA-MC-ICP-MS. The application of a zoom ion optic for aligning the ion beams into the ion counters allows fast switching between different isotope systems, which enables all of the abovementioned isotope ratios to be measured for the same microsample within a total analysis time of 15-20 min (excluding MC-ICP-MS optimization and calibration). The 101Ru/(99Ru+99Tc) and 102Ru/(99Ru+99Tc) isotope ratios were measured for four microsamples and were found to be significantly lower than the natural ratios, indicating that the microsamples were contaminated with the corresponding fission products (Ru and Tc). A slight depletion in 146Nd of about 3-5% was observed in the contaminated samples, but the Nd isotopic ratios measured in the contaminated samples coincided with natural isotopic composition within the measurement uncertainty, as most of the Nd in the analyzed samples originates from the natural soil load of this element. The 235U/238U and 236U/238U isotope ratios were the most sensitive indicators of irradiated uranium. The present work yielded a significant variation in uranium isotope ratios in microsamples, in contrast with previously published results from the bulk analysis of contaminated samples originating from the vicinity of Chernobyl. Thus, the 235U/238U ratios measured in ten microsamples varied in the range from 0.0073 (corresponding to the natural uranium isotopic composition) to 0.023 (corresponding to initial 235U enrichment in reactor fuel). An inverse correlation was observed between the 236U/238U and 235U/238U isotope ratios, except in the case of one sample with natural uranium. The heterogeneity of the uranium isotope composition is attributed to the different burn-up grades of uranium in the fuel rods from which the microsamples originated.

The series of carbon-chain complexes {Ru(dppe)Cp*}₂{μ-(C≡C )x} (x = 4–8, 11): Synthesis, structures, properties and some reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruce, Michael I.; Cole, Marcus L.; Ellis, Benjamin G.

The construction of a series of compounds {Ru(dppe)Cp*} 2(μ-C 2x) (Ru*-C2x-Ru*, x = 4–8, 11)) is described. A direct reaction between RuCl(dppe)Cp* and Me 3Si(Ctriple bond; length of mdashC) 4SiMe 3 afforded Ru*-C8-Ru* in 89% yield. The Pd(0)/Cu(I)-catalysed coupling of Ru{Ctriple bond; length of mdashCCtriple bond; length of mdashCAu(PPh 3)}(dppe)Cp*Ru*-C4-Au (2 equiv.) with diiodoethyne gave Ru*-C10-Ru* (64%), or of 1 equiv. with I(Ctriple bond; length of mdashC) 3I gave Ru*-C14-Ru* (36%); similarly, Ru{(Ctriple bond; length of mdashC) 4Au(PPh 3)}(dppe)Cp*Ru*-C8-Au and I(Ctriple bond; length of mdashC) 3I gave Ru*-C22-Ru* (12%). Desilylation (TBAF) of Ru{(Ctriple bond; length of mdashC)xSiMe 3}(dppe)Cp*Ru*-C2x-Si (x =more » 3, 4) followed by oxidative coupling [Cu(OAc) 2/py] gave Ru*-C12-Ru* (82%) and Ru*-C16-Ru* (58%), respectively. Similar oxidative coupling of Ru(Ctriple bond; length of mdashCCtriple bond; length of mdashCH)(dppe)Cp* was a second route to Ru*-C8-Ru* (82%). Appropriate precursors are already known, or obtained by coupling of Ru*-C2x-Si (x = 2, 4) with AuCl(PPh 3)/NaOMe [Ru*-C4-Au, 95%; Ru*-C8-Au, 74%] or from Pd(0)/Cu(I) catalysed coupling of Ru*-C2x-Au (x = 2, 3) with I(Ctriple bond; length of mdashC) 2SiMe 3 (Ru*-C8-Si, 64%; Ru*-C10-Si, 2%). Reactions between Ru*-C2x-Ru* (x = 3, 4) and Fe 2(CO) 9 gave {Fe 3(CO) 9}{μ 3-CCtriple bond; length of mdashC[Ru(dppe)Cp*]} 2Fe(C 3-Ru*) 2 and {Fe 3(CO) 9}{μ 3-CCtriple bond; length of mdashC[Ru(dppe)Cp*]}{μ 3-C(Ctriple bond; length of mdashC) 2[Ru(dppe)Cp*]} Fe(C 3-Ru*)(C 5-Ru*), respectively. The redox properties of the series of complexes with 2x = 2–16 were measured and showed a diminution of the separation of the first two oxidation potentials, ΔE = E 2 - E 1, with increasing carbon chain length. The X-ray-determined molecular structures of Ru*-C8-Si, Ru*-C8-Ru*, Ru*-C14-Ru* (two C 6H 6 solvates), {Ru(PPh 3) 2Cp} 2{μ-(Ctriple bond; length of mdashC) 4}·4CHCl 3Ru-C 8-Ru·4CHCl 3 and of Fe(C 3-Ru*) 2 and Fe(C 3-Ru*)(C 5-Ru*) are reported.« less

Proto Supermassive Binary Black Hole Detected in X-rays

NASA Astrophysics Data System (ADS)

2006-04-01

An international team of astrophysicists, led by D. Hudson from the University of Bonn and including the U.S. Naval Research Laboratory and the University of Virginia, presents their X-ray detection of a proto supermassive binary black hole. Their results will be published in an upcoming issue of Astronomy & Astrophysics. The image of this proto binary black hole was obtained with NASA's Chandra X-ray Observatory. The two black holes have already been seen in radio images. The new X-ray images provide unique evidence that these two black holes are in the process of forming a binary system; that is, they are gravitationally bound and orbit each other. Chandra X-ray Image of 3C 75 Chandra X-ray Image of 3C 75 The two black holes are located in the nearby galaxy cluster Abell 400. With high-resolution Chandra data, the team was able to spatially resolve the two supermassive black holes (separated by 15") at the centre of the cluster. Each black hole is located at the centre of its respective host galaxy and the host galaxies appear to be merging. It is not, however, just the two host galaxies that are colliding - the whole cluster in which they live is merging into another neighbouring galaxy cluster. Using these new data, the team show that the two black holes are moving through the intracluster medium at the supersonic speed of about 1200 km/s. The wind from such a motion would cause the radio plasma emitted from these two black holes to bend backwards. Although this bending had been observed previously, the cause of it was still being debated. Since the bending of the jets due to this motion is in the same direction, it suggests that the two black holes are travelling along the same path within the cluster and are therefore gravitationally bound. Black Hole Merger Animation Black Hole Merger Animation These two black holes became gravitationally bound when their host galaxies collided. In several million years, the two black holes will probably coalesce causing a burst of gravitational waves, as predicted by Einstein's theory of relativity. This event will produce one of the brightest sources of gravitational radiation in the Universe. Although we will not be around to see this particular one, the observations provide additional evidence that such bound systems exist and are currently merging. The gravitational waves produced by these mergers are believed to be the biggest source of gravitational waves to be detected by the future Laser Interferometer Space Antenna (LISA). Notes to the Editors The team includes D.S. Hudson (AIfA,Germany), T.H. Reiprich (AIfA,Germany), T.E. Clarke (NRL & Interferometrics Inc.,USA), and C.L. Sarazin (UVa,USA). X-ray detection of the proto supermassive binary black hole at the centre of Abell 400 by D.S Hudson, T.H. Reiprich, T.E. Clarke, and C.L. Sarazin. To be published in Astronomy & Astrophysics (DOI number: 10.1051/0004-6361:20064955) Full article available in PDF format. Electronic edition of the press release available at http://www.edpsciences.org/aa.

High turnover in a photocatalytic system for water reduction to produce hydrogen using a Ru,  Rh,  Ru photoinitiated electron collector.

PubMed

Arachchige, Shamindri M; Shaw, Ryan; White, Travis A; Shenoy, Vimal; Tsui, Hei-Man; Brewer, Karen J

2011-04-18

Covalent coupling of Ru(II) light absorbers to a Rh(III) electron collecting site through polyazine bridging ligands affords photocatalytic production of H(2) in the presence of visible light and a sacrificial electron donor. A robust photocatalytic system displaying a high turnover of the photocatalyst has been developed using the photoinitiated electron collector [{(bpy)(2)Ru(dpp)}(2)RhBr(2)](5+) (bpy=2,2'-bipyridine; dpp=2,3-bis(2-pyridyl)pyrazine) and N,N-dimethylaniline in DMF/H(2)O. Studies have shown that increased [DMA], the headspace volume, and the use of DMF solvent improves the systems performance and stability providing mechanistic insight into the deactivation routes of the photocatalytic system. Photolysis of the system at 460 nm generates 20 mL of H(2) in 19.5 h with a maximum Φ=0.023 based on H(2) produced and an overall Φ=0.014 and 280 turnovers of the photocatalyst. The photocatalytic system also displays long-term photostability with 30 mL of H(2) generated and 420 turnovers in 50 h under the same conditions. Prolonged photolysis provides 820 mol H(2) per mole of catalyst. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neutrinos from colliding wind binaries: future prospects for PINGU and ORCA

NASA Astrophysics Data System (ADS)

Becker Tjus, J.

2014-05-01

Massive stars play an important role in explaining the cosmic ray spectrum below the knee, possibly even up to the ankle, i.e. up to energies of 1015 or 1018.5 eV, respectively. In particular, Supernova Remnants are discussed as one of the main candidates to explain the cosmic ray spectrum. Even before their violent deaths, during the stars' regular life times, cosmic rays can be accelerated in wind environments. High-energy gamma-ray measurements indicate hadronic acceleration binary systems, leading to both periodic gamma-ray emission from binaries like LSI + 60 303 and continuous emission from colliding wind environments like η-Carinae. The detection of neutrinos and photons from hadronic interactions are one of the most promising methods to identify particle acceleration sites. In this paper, future prospects to detect neutrinos from colliding wind environments in massive stars are investigated. In particular, the seven most promising candidates for emission from colliding wind binaries are investigated to provide an estimate of the signal strength. The expected signal of a single source is about a factor of 5-10 below the current IceCube sensitivity and it is therefore not accessible at the moment. What is discussed in addition is future the possibility to measure low-energy neutrino sources with detectors like PINGU and ORCA: the minimum of the atmospheric neutrino flux at around 25 GeV from neutrino oscillations provides an opportunity to reduce the background and increase the significance to searches for GeV-TeV neutrino sources. This paper presents the first idea, detailed studies including the detector's effective areas will be necessary in the future to test the feasibility of such an approach.

Synthesis of ruthenium(II) complexes containing hydroxymethylphosphines and their catalytic activities for hydrogenation of supercritical carbon dioxide.

PubMed

Kayaki, Yoshihito; Shimokawatoko, Yoshiki; Ikariya, Takao

2007-07-09

Ligand substitution of RuCl2[P(C6H5)3]3 and Cp*RuCl(isoprene) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) complexes with hydroxymethylphosphines was investigated to develop new catalyst systems for CO2 hydrogenation. A reaction of P(C6H5)2CH2OH with RuCl2[P(C6H5)3]3 in CH2Cl2 gave Ru(H)Cl(CO)[P(C6H5)2CH2OH]3 (1), which was characterized by NMR spectroscopy and X-ray crystallographic analysis. An isotope labeling experiment using P(C6H5)213CH2OH indicated that the carbonyl moiety in complex 1 originated from formaldehyde formed by degradation of the hydroxymethylphosphine. Elimination of formaldehyde from PCy2CH2OH (Cy=cyclohexyl) was also promoted by treatment of RuCl2[P(C6H5)3]3 in ethanol to give RuCl2(PHCy2)4 under mild conditions. On the other hand, the substitution reaction using Cp*RuCl(isoprene) with the hydroxymethylphosphine ligands proceeded smoothly with formation of Cp*RuCl(L)2 [2a-2c; L=P(C6H5)2CH2OH, PCy(CH2OH)2, and P(CH2OH)3] in good yields. The isolable hydroxymethylphosphine complexes 1 and 2 efficiently catalyzed the hydrogenative amidation of supercritical carbon dioxide (scCO2) to N,N-dimethylformamide (DMF).

Screening of Possible Re-Substitutional Elements in Single-Crystal Ni-Based Superalloys: A Viewpoint From Interdiffusion Coefficients in Ni-Al-X Ternaries

NASA Astrophysics Data System (ADS)

Chen, Juan; Zhang, Lijun; Lu, Xiao-Gang

2018-07-01

A popular area of research in the field of high-temperature alloys concerns the search of substitutional elements for Re in order to manufacture single-crystal Ni-based superalloys with less or even no Re addition. To find the elements with similar or even lower diffusion coefficients than Re is an effective strategy. Based on 29 fcc diffusion couples in ternary Ni-Al-X (X = Re, Os, and Ir) systems, high-throughput measurement of composition- and temperature-dependent interdiffusivity matrices was performed using our recently developed numerical inverse method implemented in HitDIC software. The reliability of the determined interdiffusivities was validated by comprehensively comparing the model-predicted composition/interdiffusion flux profiles for each diffusion couple with the corresponding experimental data. Moreover, we also conducted a comparison with the interdiffusivities evaluated using the traditional Matano-Kirkaldy method as well as those from the literature and in boundary binary systems. After that, a comprehensive comparison of the interdiffusion coefficients in fcc Ni-2 wt pct Al-6 wt pct X (X = Ti, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, and Pt) alloys at 1423 K to 1573 K was conducted. Results indicate that the diffusion rate of Re is lower than that of Os at 1473 K and 1523 K; but higher at 1573 K, while the diffusion rate of Ir is always slightly higher than those of Os and Re at 1473 K to 1573 K. Further analysis of the magnitude of the interdiffusion coefficient correlates with the alloying concentration, activation energy, atomic number, and atomic radius of different diffusing transition metal species ( i.e., Ti, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, and Pt) was conducted, which is expected to provide useful information regarding element choice in the development of new-generation Ni-based single-crystal superalloys.

Screening of Possible Re-Substitutional Elements in Single-Crystal Ni-Based Superalloys: A Viewpoint From Interdiffusion Coefficients in Ni-Al-X Ternaries

NASA Astrophysics Data System (ADS)

Chen, Juan; Zhang, Lijun; Lu, Xiao-Gang

2018-05-01

A popular area of research in the field of high-temperature alloys concerns the search of substitutional elements for Re in order to manufacture single-crystal Ni-based superalloys with less or even no Re addition. To find the elements with similar or even lower diffusion coefficients than Re is an effective strategy. Based on 29 fcc diffusion couples in ternary Ni-Al-X (X = Re, Os, and Ir) systems, high-throughput measurement of composition- and temperature-dependent interdiffusivity matrices was performed using our recently developed numerical inverse method implemented in HitDIC software. The reliability of the determined interdiffusivities was validated by comprehensively comparing the model-predicted composition/interdiffusion flux profiles for each diffusion couple with the corresponding experimental data. Moreover, we also conducted a comparison with the interdiffusivities evaluated using the traditional Matano-Kirkaldy method as well as those from the literature and in boundary binary systems. After that, a comprehensive comparison of the interdiffusion coefficients in fcc Ni-2 wt pct Al-6 wt pct X (X = Ti, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, and Pt) alloys at 1423 K to 1573 K was conducted. Results indicate that the diffusion rate of Re is lower than that of Os at 1473 K and 1523 K; but higher at 1573 K, while the diffusion rate of Ir is always slightly higher than those of Os and Re at 1473 K to 1573 K. Further analysis of the magnitude of the interdiffusion coefficient correlates with the alloying concentration, activation energy, atomic number, and atomic radius of different diffusing transition metal species (i.e., Ti, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir, and Pt) was conducted, which is expected to provide useful information regarding element choice in the development of new-generation Ni-based single-crystal superalloys.

Comparative absorption, electroabsorption and electrochemical studies of intervalence electron transfer and electronic coupling in cyanide-bridged bimetallic systems: ancillary ligand effects

NASA Astrophysics Data System (ADS)

Vance, Fredrick W.; Slone, Robert V.; Stern, Charlotte L.; Hupp, Joseph T.

2000-03-01

Electroabsorption or Stark spectroscopy has been used to evaluate the systems (NC) 5M II-CN-Ru III(NH 3) 51- and (NC) 5M II-CN-Ru III(NH 3) 4py 1-, where M II=Fe II or Ru II. When a pyridine ligand is present in the axial position on the Ru III acceptor, the effective optical electron transfer distance - as measured by the change in dipole moment, |Δ μ| - is increased by more than 35% relative to the ammine substituted counterpart. Comparison of the charge transfer distances to the crystal structure of Na[(CN) 5Fe-CN-Ru(NH 3) 4py] · 6H 2O reveals that the Stark derived distances are ˜50% to ˜90% of the geometric separation of the metal centers. The differences result in an upward revision in the Hush delocalization parameter, c b2, and of the electronic coupling matrix element, H ab, relative to those parameters obtained exclusively from electronic absorption measurements. The revised parameters are compared to those, which are obtained via electrochemical techniques and found to be in only fair agreement. We conclude that the absorption/electroabsorption analysis likely yields a more reliable set of mixing and coupling parameters.

Future science issues for Galactic very-high-energy gamma-ray astronomy

NASA Astrophysics Data System (ADS)

Torres, Diego F.

2008-12-01

This work intends to provide a brief summary of some of the Galactic science issues for the next generation of very high energy (VHE) instruments. The latter is here generically understood, as an instrument or set of instruments providing about one order of magnitude more sensitivity at its central energy (at about 1 TeV), but extending the observational window to have a real broadband capability (from a few tens of GeV up to tens of TeV) exceeding at low energies the current VHE threshold for observations set by MAGIC as well as the few-tens-of-GeV sensitivity set by Fermi. Science topics regarding populations of emitters, pulsars and their nebula, binaries, supernova remnants, stars, and their associations, are discussed.

BOREAS TE-18 Landsat TM Maximum Likelihood Classification Image of the NSA

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Knapp, David

2000-01-01

The BOREAS TE-18 team focused its efforts on using remotely sensed data to characterize the successional and disturbance dynamics of the boreal forest for use in carbon modeling. The objective of this classification is to provide the BOREAS investigators with a data product that characterizes the land cover of the NSA. A Landsat-5 TM image from 20-Aug-1988 was used to derive this classification. A standard supervised maximum likelihood classification approach was used to produce this classification. The data are provided in a binary image format file. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

Secondary ion mass spectrometric investigation on ruthenium oxide systems: a comparison between poly- and nanocrystalline deposits

PubMed

Barison; Barreca; Daolio; Fabrizio; Piccirillo

2000-01-01

The influence of different RuO(2) crystallite sizes was investigated by secondary ion mass spectrometry (SIMS) on the oxide deposited on various support materials (Ni, Ti, Al(2)O(3), oxidized Si(100)). In order to examine the effect of an oxidic environment on the film structure, RuO(2) 20%-TiO(2) 80% at. mixed oxide was deposited on Ti. The polycrystalline coatings were prepared by heating the Ru (and Ti)-containing solution dropped on the supports.1 RuO(2) nanocrystalline coatings were grown by chemical vapor deposition (CVD) from Ru(COD)(eta(3)-allyl)(2).2 The identification of mixed oxide clusters showed the higher reactivity of Ni and Al(2)O(3) over the other substrates. Diffusion and migration characteristics were observed to be influenced by the nature of the support. The results are complementary to those of a previous SIMS investigation.3 Copyright 2000 John Wiley & Sons, Ltd.

SULFUR REDUCTION IN GASOLINE AND DIESEL FUELS BY EXTRACTION/ADSORPTION OF REFRACTORY DIBENZOTHIOPHENES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scott G. McKinley; Celedonio M. Alvarez

2003-03-01

The purpose of this study was to remove thiophene, benzothiophene and dibenzothiophene from a simulated gasoline feedstock. We found that Ru(NH{sub 3}){sub 5}(H{sub 2}O){sup 2+} reacts with a variety of thiophenes (Th*), affording Ru(NH{sub 3}){sub 5}(Th*){sup 2+}. We used this reactivity to design a biphasic extraction process that removes more than 50% of the dibenzothiophene in the simulated feedstock. This extraction system consists of a hydrocarbon phase (simulated petroleum feedstock) and extractant Ru(NH{sub 3}){sub 5}(H{sub 2}O){sup 2+} in an aqueous phase (70% dimethylformamide, 30% H{sub 2}O). The DBT is removed in situ from the newly formed Ru(NH{sub 3}){sub 5}(DBT){sup 2+}more » by either an oxidation process or addition of H{sub 2}O, to regenerate Ru(NH{sub 3}){sub 5}(H{sub 2}O){sup 2+}.« less

New isomer and decay half-life of {sup 115}Ru

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurpeta, J.; Plochocki, A.; Rissanen, J.

2010-12-15

Exotic, neutron-rich nuclei of mass A=115 produced in proton-induced fission of {sup 238}U were extracted using the IGISOL mass separator. The beam of isobars was transferred to the JYFLTRAP Penning trap system for further separation to the isotopic level. Monoisotopic samples of {sup 115}Ru nuclei were used for {gamma}and {beta} coincidence spectroscopy. In {sup 115}Ru we have observed excited levels, including an isomer with a half-life of 76(6) ms and (7/2{sup -}) spin and parity. The first excited 61.7-keV level in {sup 115}Ru with spins and parity (3/2{sup +}) may correspond to an oblate 3/2{sup +}[431] Nilsson orbital. A half-lifemore » of 318(19) ms for the {beta}{sup -} decay of the (1/2{sup +}) ground state in {sup 115}Ru has been firmly established in two independent measurements, a value which is significantly shorter than that previously reported.« less

Infrared vibrational spectroscopy of [Ru(bpy)2(bpm)]2+ and [Ru(bpy)3]2+ in the excited triplet state.

PubMed

Mukuta, Tatsuhiko; Fukazawa, Naoto; Murata, Kei; Inagaki, Akiko; Akita, Munetaka; Tanaka, Sei'ichi; Koshihara, Shin-ya; Onda, Ken

2014-03-03

This work involved a detailed investigation into the infrared vibrational spectra of ruthenium polypyridyl complexes, specifically heteroleptic [Ru(bpy)2(bpm)](2+) (bpy = 2,2'-bipyridine and bpm = 2,2'-bipyrimidine) and homoleptic [Ru(bpy)3](2+), in the excited triplet state. Transient spectra were acquired 500 ps after photoexcitation, corresponding to the vibrational ground state of the excited triplet state, using time-resolved infrared spectroscopy. We assigned the observed bands to specific ligands in [Ru(bpy)2(bpm)](2+) based on the results of deuterium substitution and identified the corresponding normal vibrational modes using quantum-chemical calculations. Through this process, the more complex vibrational bands of [Ru(bpy)3](2+) were assigned to normal vibrational modes. The results are in good agreement with the model in which excited electrons are localized on a single ligand. We also found that the vibrational bands of both complexes associated with the ligands on which electrons are little localized appear at approximately 1317 and 1608 cm(-1). These assignments should allow the study of the reaction dynamics of various photofunctional systems including ruthenium polypyridyl complexes.

Precipitation of anion inclusions and plasticity under hydrostatic pressure in II-VI crystals

NASA Astrophysics Data System (ADS)

Lindberg, G. P.; Weinstein, B. A.

2016-10-01

Precipitation of anion nanocrystals (NCs) in initially stoichiometric II-VI crystals under hydrostatic pressure and light exposure is explored by Raman spectroscopy, and the mechanism for this effect is analyzed by model calculations. ZnSe, ZnTe, and CdSe crystals are studied in bulk and/or epitaxial-film forms. Se and Te NCs in the trigonal (t) phase precipitate in ZnSe and ZnTe, but the effect is absent or minimal in CdSe. The precipitation is induced by pressure and assisted by sub-band-gap light. In ZnSe, t-Se NCs appear for pressure exceeding 4.8 GPa and light flux above 50 -70 W /m m2 . In ZnTe, the precipitation of t-Te NCs requires less pressure to initiate, and there is a clear upper-pressure limit for t-Te nuclei to form. We find also that ZnTe samples with cleavage damage or elevated zinc-vacancy content are more prone to form t-Te NCs at lower pressures (even 1 atm in some cases) and lower flux. The precipitation seen in ZnSe and ZnTe occurs at pressures far below their phase transitions, and cannot be due to those transitions. Rather, we propose that the NCs nucleate on dislocations that arise from hydrostatic-pressure induced plastic flow triggered by noncubic defect sites. Calculations of the kinetic barrier for growth of an optimally shaped nucleus are performed, including hydrostatic pressure in the energy minimization scheme. Using sensible values for the model parameters related to the cohesive energies of Se and Te, the calculations account for our main observations, including the existence of an upper pressure limit for precipitation, and the absence of precipitation in CdSe. We consider the effects of pressure-induced precipitate formation on the I-II phase transitions in a variety of binary semiconductors and make predictions of when this effect should be important.

Synthesis of PtRu/Ru heterostructure for efficient methanol electrooxidation: The role of extra Ru

NASA Astrophysics Data System (ADS)

Bai, Lei

2018-03-01

Platinum-ruthenium (PtRu) nanocubes and PtRu/Ru heterostructure via epitaxial growth were synthesized by varying the amount of Ru precursor. As model catalysts, the PtRu/Ru heterostructure demonstrated the highest catalytic performance in electrooxidation of methanol, which was possibly due to the more hydroxyl species produced from the extra Ru nanoparticles as well as enhanced adsorption of methanol of PtRu alloys in the PtRu/Ru heterostructure. The catalytic performance of the catalysts was closely related with the structure, which was well characterized by a series of methods. It was expected that the present work could provide a new insight for the synthesis of PtRu based nanocatalysts.

Internal stresses in wear and corrosion resistant amorphous metallic coatings of (W/0.6/Re/0.4/)76B24 and (Mo/0.6/Ru/0.4/)82B18

NASA Technical Reports Server (NTRS)

Thakoor, A. P.; Lamb, J. L.; Williams, R. M.; Khanna, S. K.

1985-01-01

Hard protective coatings in the W-Re-B and Mo-Ru-B alloy systems have been deposited by magnetron sputtering onto soda-lime glass and heat-treated AISI 52100 steel substrates. X-ray diffraction has confirmed the amorphous nature of the as-deposited coatings, and their crystallization temperatures were determined by differential thermal analysis to be 1000 and 790 C for W-Re-B and Mo-Ru-B coatings, respectively. Both coatings exhibit high microhardness; Mo-Ru-B, in addition, has excellent corrosion resistance by comparison with pure Mo at high anodic potentials. Attention is given to the influence of internal stresses on the protective properties of the coatings deposited under different conditions.

Enhanced interfacial Dzyaloshinskii-Moriya interaction and isolated skyrmions in the inversion-symmetry-broken Ru/Co/W/Ru films

NASA Astrophysics Data System (ADS)

Samardak, Alexander; Kolesnikov, Alexander; Stebliy, Maksim; Chebotkevich, Ludmila; Sadovnikov, Alexandr; Nikitov, Sergei; Talapatra, Abhishek; Mohanty, Jyoti; Ognev, Alexey

2018-05-01

An enhancement of the spin-orbit effects arising on an interface between a ferromagnet (FM) and a heavy metal (HM) is possible through the strong breaking of the structural inversion symmetry in the layered films. Here, we show that an introduction of an ultrathin W interlayer between Co and Ru in Ru/Co/Ru films enables to preserve perpendicular magnetic anisotropy (PMA) and simultaneously induce a large interfacial Dzyaloshinskii-Moriya interaction (iDMI). The study of the spin-wave propagation in the Damon-Eshbach geometry by Brillouin light scattering spectroscopy reveals the drastic increase in the iDMI value with the increase in W thickness (tW). The maximum iDMI of -3.1 erg/cm2 is observed for tW = 0.24 nm, which is 10 times larger than for the quasi-symmetrical Ru/Co/Ru films. We demonstrate the evidence of the spontaneous field-driven nucleation of isolated skyrmions supported by micromagnetic simulations. Magnetic force microscopy measurements reveal the existence of sub-100-nm skyrmions in the zero magnetic field. The ability to simultaneously control the strength of PMA and iDMI in quasi-symmetrical HM/FM/HM trilayer systems through the interface engineered inversion asymmetry at the nanoscale excites new fundamental and practical interest in ultrathin ferromagnets, which are a potential host for stable magnetic skyrmions.

Transparent metal selenide alloy counter electrodes for high-efficiency bifacial dye-sensitized solar cells.

PubMed

Duan, Yanyan; Tang, Qunwei; Liu, Juan; He, Benlin; Yu, Liangmin

2014-12-22

The exploration of cost-effective and transparent counter electrodes (CEs) is a persistent objective in the development of bifacial dye-sensitized solar cells (DSSCs). Transparent counter electrodes based on binary-alloy metal selenides (M-Se; M=Co, Ni, Cu, Fe, Ru) are now obtained by a mild, solution-based method and employed in efficient bifacial DSSCs. Owing to superior charge-transfer ability for the I(-) /I3 (-) redox couple, electrocatalytic activity toward I3 (-) reduction, and optical transparency, the bifacial DSSCs with CEs consisting of a metal selenide alloy yield front and rear efficiencies of 8.30 % and 4.63 % for Co0.85 Se, 7.85 % and 4.37 % for Ni0.85 Se, 6.43 % and 4.24 % for Cu0.50 Se, 7.64 % and 5.05 % for FeSe, and 9.22 % and 5.90 % for Ru0.33 Se in comparison with 6.18 % and 3.56 % for a cell with an electrode based on pristine platinum, respectively. Moreover, fast activity onset, high multiple start/stop capability, and relatively good stability demonstrate that these new electrodes should find applications in solar panels. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A VNTR element associated with steroid sulfatase gene deletions stimulates recombination in cultured cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Y.; Li, X.M.; Shapiro, L.J.

1994-09-01

Steroid sulfatase deficiency is a common genetic disorder, with a prevalence of approximately one in every 3500 males world wide. About 90% of these patients have complete gene deletions, which appear to result from recombination between members of a low-copy repeat family (CRI-232 is the prototype) that flank the gene. RU1 and RU2 are two VNTR elements found within each of these family members. RU1 consists of 30 bp repeating units and its length shows minimal variation among individuals. The RU2 element consists of repeating sequences which are highly asymmetric, with about 90% purines and no C`s on one strand,more » and range from 0.6 kb to over 23 kb among different individuals. We conducted a study to determine if the RU1 or RU2 elements can promote recombination in an in vivo test system. We inserted these elements adjacent to the neo gene in each of two pSV2neo derivatives, one of which has a deletion in the 5{prime} portion of the neo gene and the other having a deletion in the 3{prime} portion. These plasmids were combined and used to transfect EJ cells. Survival of cells in G418 indicates restoration of a functional neo gene by recombination between two deletion constructs. Thus counting G418 resistant colonies gives a quantitative measure of the enhancement of recombination by the inserted VNTR elements. The results showed no effect on recombination by the inserted RU1 element (compared to the insertion of a nonspecific sequence), while the RU2 element stimulated recombination by 3.5-fold (P<0.01). A separate set of constructs placed RU1 or RU2 within the intron of an exon trapping vector. Following tranfection of cells, recombination events were monitored by a PCR assay that detected the approximation of primer binding sites (as a result of recombination). These studies showed that, as in the first set of experiments, the highly variable RU2 element is capable of stimulating somatic recombination in mammalian cells.« less

Homogeneous and label-free electrochemiluminescence aptasensor based on the difference of electrostatic interaction and exonuclease-assisted target recycling amplification.

PubMed

Ni, Jiancong; Yang, Weiqiang; Wang, Qingxiang; Luo, Fang; Guo, Longhua; Qiu, Bin; Lin, Zhenyu; Yang, Huanghao

2018-05-15

The difference of electrostatic interaction between free Ru(phen) 3 2+ and Ru(phen) 3 2+ embedded in double strand DNA (dsDNA) to the negatively charged indium tin oxide (ITO) electrode has been applied to develop a homogeneous and label-free electrochemiluminescence (ECL) aptasensor for the first time. Ochratoxin A (OTA) has been chosen as the model target. The OTA aptamer is first hybridized with its complementary single strand DNA (ssDNA) to form dsDNA and then interacted with Ru(phen) 3 2+ via the grooves binding mode to form dsDNA-Ru(phen) 3 2+ complex, which remains negatively charged feature as well as low diffusion capacity to the negatively charged ITO electrode surface owing to the electrostatic repulsion. Meanwhile, the intercalated Ru(phen) 3 2+ in the grooves of dsDNA works as an ECL signal reporter instead of the labor-intensive labeling steps and can generate much more ECL signal than that from the labeling probe. In the presence of target, the aptamer prefers to form an aptamer-target complex in lieu of dsDNA, which induces the releasing of Ru(phen) 3 2+ from the dsDNA-Ru(phen) 3 2+ complex into the solution. With the assistance of RecJ f exonuclease (a ssDNA specific exonuclease), the released ssDNA and the aptamer in the target-complex were digested into mononucleotides. In the meantime, the target can be also liberated from OTA-aptamer complex and induce target cycling and large amount of free Ru(phen) 3 2+ present in the solution. Since Ru(phen) 3 2+ contains positive charges, which can diffuses easily to the ITO electrode surface because of electrostatic attraction, causing an obviously enhanced ECL signal detected. Under the optimal conditions, the enhanced ECL of the system has a linear relationship with the OTA concentration in the range of 0.01-1.0 ng/mL with a detection limit of 2 pg/mL. This innovative system not only expands the immobilization-free sensors in the electrochemiluminescent fields, but also can be developed for the detection of different targets easily with the same strategy by changing the aptamer used. Copyright © 2018 Elsevier B.V. All rights reserved.

Centrality dependence of charged jet production in p-Pb collisions at [Formula: see text] = 5.02 TeV.

PubMed

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Gonzalez, V; González-Zamora, P; Gorbunov, S; Görlich, L; Gotovac, S; Grabski, V; Grachov, O A; Graczykowski, L K; Graham, K L; Grelli, A; Grigoras, A; Grigoras, C; Grigoriev, V; Grigoryan, A; Grigoryan, S; Grinyov, B; Grion, N; Gronefeld, J M; Grosse-Oetringhaus, J F; Grosso, R; Guber, F; Guernane, R; Guerzoni, B; Gulbrandsen, K; Gunji, T; Gupta, A; Gupta, R; Haake, R; Haaland, Ø; Hadjidakis, C; Haiduc, M; Hamagaki, H; Hamar, G; Hamon, J C; Harris, J W; Harton, A; Hatzifotiadou, D; Hayashi, S; Heckel, S T; Hellbär, E; Helstrup, H; Herghelegiu, A; Herrera Corral, G; Hess, B A; Hetland, K F; Hillemanns, H; Hippolyte, B; Horak, D; Hosokawa, R; Hristov, P; Humanic, T J; Hussain, N; Hussain, T; Hutter, D; Hwang, D S; Ilkaev, R; Inaba, M; Incani, E; Ippolitov, M; Irfan, M; Ivanov, M; Ivanov, V; Izucheev, V; Jacazio, N; Jacobs, P M; Jadhav, M B; Jadlovska, S; Jadlovsky, J; Jahnke, C; Jakubowska, M J; Jang, H J; Janik, M A; Jayarathna, P H S Y; Jena, C; Jena, S; Jimenez Bustamante, R T; Jones, P G; 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Orava, R; Oravec, M; Ortiz Velasquez, A; Oskarsson, A; Otwinowski, J; Oyama, K; Ozdemir, M; Pachmayer, Y; Pagano, D; Pagano, P; Paić, G; Pal, S K; Pan, J; Pandey, A K; Papikyan, V; Pappalardo, G S; Pareek, P; Park, W J; Parmar, S; Passfeld, A; Paticchio, V; Patra, R N; Paul, B; Pei, H; Peitzmann, T; Pereira Da Costa, H; Peresunko, D; Perez Lezama, E; Peskov, V; Pestov, Y; Petráček, V; Petrov, V; Petrovici, M; Petta, C; Piano, S; Pikna, M; Pillot, P; Pimentel, L O D L; Pinazza, O; Pinsky, L; Piyarathna, D B; Płoskoń, M; Planinic, M; Pluta, J; Pochybova, S; Podesta-Lerma, P L M; Poghosyan, M G; Polichtchouk, B; Poljak, N; Poonsawat, W; Pop, A; Porteboeuf-Houssais, S; Porter, J; Pospisil, J; Prasad, S K; Preghenella, R; Prino, F; Pruneau, C A; Pshenichnov, I; Puccio, M; Puddu, G; Pujahari, P; Punin, V; Putschke, J; Qvigstad, H; Rachevski, A; Raha, S; Rajput, S; Rak, J; Rakotozafindrabe, A; Ramello, L; Rami, F; Raniwala, R; Raniwala, S; Räsänen, S S; Rascanu, B T; Rathee, D; Read, K F; Redlich, K; Reed, R J; Rehman, A; Reichelt, P; Reidt, F; Ren, X; Renfordt, R; Reolon, A R; Reshetin, A; Reygers, K; Riabov, V; Ricci, R A; Richert, T; Richter, M; Riedler, P; Riegler, W; Riggi, F; Ristea, C; Rocco, E; Rodríguez Cahuantzi, M; Rodriguez Manso, A; Røed, K; Rogochaya, E; Rohr, D; Röhrich, D; Ronchetti, F; Ronflette, L; Rosnet, P; Rossi, A; Roukoutakis, F; Roy, A; Roy, C; Roy, P; Rubio Montero, A J; Rui, R; Russo, R; Ruzza, B D; Ryabinkin, E; Ryabov, Y; Rybicki, A; Saarinen, S; Sadhu, S; Sadovsky, S; Šafařík, K; Sahlmuller, B; Sahoo, P; Sahoo, R; Sahoo, S; Sahu, P K; Saini, J; Sakai, S; Saleh, M A; Salzwedel, J; Sambyal, S; Samsonov, V; Šándor, L; Sandoval, A; Sano, M; Sarkar, D; Sarkar, N; Sarma, P; Scapparone, E; Scarlassara, F; Schiaua, C; Schicker, R; Schmidt, C; Schmidt, H R; Schmidt, M; Schuchmann, S; Schukraft, J; Schulc, M; Schutz, Y; Schwarz, K; Schweda, K; Scioli, G; Scomparin, E; Scott, R; Šefčík, M; Seger, J E; Sekiguchi, Y; Sekihata, D; Selyuzhenkov, I; Senosi, K; Senyukov, S; Serradilla, E; Sevcenco, A; Shabanov, A; Shabetai, A; Shadura, O; Shahoyan, R; Shahzad, M I; Shangaraev, A; Sharma, A; Sharma, M; Sharma, M; Sharma, N; Sheikh, A I; Shigaki, K; Shou, Q; Shtejer, K; Sibiriak, Y; Siddhanta, S; Sielewicz, K M; Siemiarczuk, T; Silvermyr, D; Silvestre, C; Simatovic, G; Simonetti, G; Singaraju, R; Singh, R; Singha, S; Singhal, V; Sinha, B C; Sinha, T; Sitar, B; Sitta, M; Skaali, T B; Slupecki, M; Smirnov, N; Snellings, R J M; Snellman, T W; Song, J; Song, M; Song, Z; Soramel, F; Sorensen, S; Souza, R D de; Sozzi, F; Spacek, M; Spiriti, E; Sputowska, I; Spyropoulou-Stassinaki, M; Stachel, J; Stan, I; Stankus, P; Stenlund, E; Steyn, G; Stiller, J H; Stocco, D; Strmen, P; Suaide, A A P; Sugitate, T; Suire, C; Suleymanov, M; Suljic, M; Sultanov, R; Šumbera, M; Sumowidagdo, S; Szabo, A; Szarka, I; Szczepankiewicz, A; Szymanski, M; Tabassam, U; Takahashi, J; Tambave, G J; Tanaka, N; Tarhini, M; Tariq, M; Tarzila, M G; Tauro, A; Tejeda Muñoz, G; Telesca, A; Terasaki, K; Terrevoli, C; Teyssier, B; Thäder, J; Thakur, D; Thomas, D; Tieulent, R; Tikhonov, A; Timmins, A R; Toia, A; Trogolo, S; Trombetta, G; Trubnikov, V; Trzaska, W H; Tsuji, T; Tumkin, A; Turrisi, R; Tveter, T S; Ullaland, K; Uras, A; Usai, G L; Utrobicic, A; Vala, M; Valencia Palomo, L; Vallero, S; Van Der Maarel, J; Van Hoorne, J W; van Leeuwen, M; Vanat, T; Vande Vyvre, P; Varga, D; Vargas, A; Vargyas, M; Varma, R; Vasileiou, M; Vasiliev, A; Vauthier, A; Vázquez Doce, O; Vechernin, V; Veen, A M; Veldhoen, M; Velure, A; Vercellin, E; Vergara Limón, S; Vernet, R; Verweij, M; Vickovic, L; Viinikainen, J; Vilakazi, Z; Villalobos Baillie, O; Villatoro Tello, A; Vinogradov, A; Vinogradov, L; Vinogradov, Y; Virgili, T; Vislavicius, V; Viyogi, Y P; Vodopyanov, A; Völkl, M A; Voloshin, K; Voloshin, S A; Volpe, G; Haller, B von; Vorobyev, I; Vranic, D; Vrláková, J; Vulpescu, B; Wagner, B; Wagner, J; Wang, H; Wang, M; Watanabe, D; Watanabe, Y; Weber, M; Weber, S G; Weiser, D F; Wessels, J P; Westerhoff, U; Whitehead, A M; Wiechula, J; Wikne, J; Wilk, G; Wilkinson, J; Williams, M C S; Windelband, B; Winn, M; Yang, P; Yano, S; Yasin, Z; Yin, Z; Yokoyama, H; Yoo, I-K; Yoon, J H; Yurchenko, V; Zaborowska, A; Zaccolo, V; Zaman, A; Zampolli, C; Zanoli, H J C; Zaporozhets, S; Zardoshti, N; Zarochentsev, A; Závada, P; Zaviyalov, N; Zbroszczyk, H; Zgura, I S; Zhalov, M; Zhang, H; Zhang, X; Zhang, Y; Zhang, C; Zhang, Z; Zhao, C; Zhigareva, N; Zhou, D; Zhou, Y; Zhou, Z; Zhu, H; Zhu, J; Zichichi, A; Zimmermann, A; Zimmermann, M B; Zinovjev, G; Zyzak, M

2016-01-01

Measurements of charged jet production as a function of centrality are presented for  p-Pb  collisions recorded at [Formula: see text] TeV with the ALICE detector. Centrality classes are determined via the energy deposit in neutron calorimeters at zero degree, close to the beam direction, to minimise dynamical biases of the selection. The corresponding number of participants or binary nucleon-nucleon collisions is determined based on the particle production in the Pb-going rapidity region. Jets have been reconstructed in the central rapidity region from charged particles with the anti-[Formula: see text] algorithm for resolution parameters [Formula: see text] and [Formula: see text] in the transverse momentum range 20 to 120 GeV/ c . The reconstructed jet momentum and yields have been corrected for detector effects and underlying-event background. In the five centrality bins considered, the charged jet production in  p-Pb   collisions is consistent with the production expected from binary scaling from pp collisions. The ratio of jet yields reconstructed with the two different resolution parameters is also independent of the centrality selection, demonstrating the absence of major modifications of the radial jet structure in the reported centrality classes.

Centrality dependence of charged jet production in p–Pb collisions at $$\\sqrt{s_\\mathrm{NN}}$$ = 5.02 TeV

DOE PAGES

Adam, J.; Adamová, D.; Aggarwal, M. M.; ...

2016-05-17

Measurements of charged jet production as a function of centrality are presented for p–Pb collisions recorded atmore » $$\\sqrt{s_\\mathrm{NN}}$$= 5.02 TeV with the ALICE detector. Centrality classes are determined via the energy deposit in neutron calorimeters at zero degree, close to the beam direction, to minimise dynamical biases of the selection. The corresponding number of participants or binary nucleon–nucleon collisions is determined based on the particle production in the Pb-going rapidity region. Jets have been reconstructed in the central rapidity region from charged particles with the anti-k T algorithm for resolution parameters R = 0.2 and R = 0.4 in the transverse momentum range 20 to 120 GeV/c. The reconstructed jet momentum and yields have been corrected for detector effects and underlying-event background. In the five centrality bins considered, the charged jet production in p–Pb collisions is consistent with the production expected from binary scaling from pp collisions. The ratio of jet yields reconstructed with the two different resolution parameters is also independent of the centrality selection, demonstrating the absence of major modifications of the radial jet structure in the reported centrality classes.« less

Simultaneous speciation of inorganic arsenic, selenium and tellurium in environmental water samples by dispersive liquid liquid microextraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry.

PubMed

Liu, Ying; He, Man; Chen, Beibei; Hu, Bin

2015-09-01

A new method based on dispersive liquid liquid microextraction (DLLME) combined with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) was developed for the simultaneous speciation of inorganic arsenic (As), selenium (Se) and tellurium (Te) with sodium diethyldithiocarbamate (DDTC) as both chelating reagent and chemical modifier. As(III), Se(IV) and Te(IV) were transformed into DDTC-chelates at pH 7 and extracted into the fine droplets formed by injecting the binary solution of bromobenzene (extraction solvent) and methanol (dispersive solvent) into the sample solution. After phase separation by centrifugation, As(III), Se(IV) and Te(IV) preconcentrated in the organic phase were determined by ETV-ICP-MS. Total inorganic As, Se and Te were obtained by reducing As(V), Se(VI) and Te(VI) to As(III), Se(IV) and Te(IV) with L-cysteine, which were then subjected to the same DLLME-ETV-ICP-MS process. The concentration of As(V), Se(VI), Te(VI) were calculated by subtracting the concentration of As(III), Se(IV) and Te(IV) from the total inorganic As, Se and Te, respectively. The main factors affecting the microextraction efficiency and the vaporization behavior of target species were investigated in detail. Under the optimal conditions, the limits of detection were 2.5, 8.6 and 0.56 ng L(-1) for As(III), Se(IV) and Te(IV), respectively, with the relative standard deviations (n=7) of 8.5-9.7%. The developed method was applied to the speciation of inorganic As, Se and Te in Certified Reference Materials of GSBZ50004-88, GBW(E)080395 and GBW(E)080548 environmental waters, and the determined values are in good agreement with the certified values. The method was also successfully applied to the simultaneous speciation of inorganic As, Se and Te in different environmental water samples with the recoveries in the range of 86.3-107% for the spiked samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Double Diffusive Convection in Materials Processing

NASA Technical Reports Server (NTRS)

Ramachandra, Narayanan; Leslie, Fred W.

1999-01-01

A great number of crystals grown in space are plagued by convective motions which contribute to structural flaws. The character of these instabilities is not well understood but is associated with density variations in the presence of residual gravity (g-jitter). As a specific example, past HgCdTe crystal growth space experiments by Lehoczky and co-workers indicate radial compositional asymmetry in the grown crystals. In the case of HgCdTe the rejected component into the melt upon solidification is HgTe which is denser than the melt. The space grown crystals indicate the presence of three dimensional flow with the heavier HgTe-rich material clearly aligned with the residual gravity (0.55-1.55 micro g) vector. This flow stems from double-diffusive convection, namely, thermal and solutal buoyancy driven flow in the melt. The study of double-diffusive convection is multi-faceted and rather vast. In our investigation, we seek to focus on one specific aspect of this discipline that is of direct relevance to materials processing especially crystal growth, namely, the side ways heating regime. This problem has been widely studied, both experimentally and numerically, in the context of solar ponds wherein the system is characterized by a linear salt (solutal) gradient with an imposed lateral temperature gradient. The induced flow instabilities arise from the wide disparity between the fluid thermal diffusivity and the solute diffusivity. The extension of the analysis to practical crystal growth applications has however not been rigorously made and understood. One subtle but important difference in crystal growth systems is the fact that die system solute gradient is non-linear (typically exponential). Besides, the crystal growth problem has the added complexities of solidification, both lateral and longitudinal thermal gradients and segregation phenomena in systems where binary and ternary compounds are being grown. This paper treats the side ways heating problem alone in a model fluid system. Results from detailed numerical calculations, mainly two dimensional are provided. The interactions between a non-linear solute gradient and an imposed transverse thermal gradient are investigated. The buoyancy effects are treated in the traditional Boussinesq approximation and also in a more complete density formulation to address recent concerns of the first approach especially in simulations of the system response in a reduced gravity environment. Detailed flow, temperature and solute field plots along with heat and mass transfer results are presented in the paper. Implications to practical crystal growth systems as discerned from the modeling results are also explored and reported.

Multiwavelength observations of the binary system PSR B1259-63/LS 2883 around the 2010-2011 periastron passage

DOE PAGES

Chernyakova, M.; Abdo, A. A.; Neronov, A.; ...

2014-01-30

Here, we report on broad multiwavelength observations of the 2010–2011 periastron passage of the γ-ray loud binary system PSR B1259-63. High-resolution interferometric radio observations establish extended radio emission trailing the position of the pulsar. Observations with the FermiGamma-ray Space Telescope reveal GeV γ-ray flaring activity of the system, reaching the spin-down luminosity of the pulsar, around 30 d after periastron. Furthermore, there are no clear signatures of variability at radio, X-ray and TeV energies at the time of the GeV flare. Variability around periastron in the Hα emission line, can be interpreted as the gravitational interaction between the pulsar andmore » the circumstellar disc. The equivalent width of the Hα grows from a few days before periastron until a few days later, and decreases again between 18 and 46 d after periastron. In near-infrared we observe the similar decrease of the equivalent width of Brγ line between the 40th and 117th day after the periastron. For the idealized disc, the variability of the Hα line represents the variability of the mass and size of the disc. Finally, we discuss possible physical relations between the state of the disc and GeV emission under assumption that GeV flare is directly related to the decrease of the disc size.« less

High-energy emissions from the gamma-ray binary LS 5039

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takata, J.; Leung, Gene C. K.; Cheng, K. S.

2014-07-20

We study mechanisms of multi-wavelength emissions (X-ray, GeV, and TeV gamma-rays) from the gamma-ray binary LS 5039. This paper is composed of two parts. In the first part, we report on results of observational analysis using 4 yr data of the Fermi Large Area Telescope. Due to the improvement of instrumental response function and increase of the statistics, the observational uncertainties of the spectrum in the ∼100-300 MeV bands and >10 GeV bands are significantly improved. The present data analysis suggests that the 0.1-100 GeV emissions from LS 5039 contain three different components: (1) the first component contributes to <1more » GeV emissions around superior conjunction, (2) the second component dominates in the 1-10 GeV energy bands, and (3) the third component is compatible with the lower-energy tail of the TeV emissions. In the second part, we develop an emission model to explain the properties of the phase-resolved emissions in multi-wavelength observations. Assuming that LS 5039 includes a pulsar, we argue that emissions from both the magnetospheric outer gap and the inverse-Compton scattering process of cold-relativistic pulsar wind contribute to the observed GeV emissions. We assume that the pulsar is wrapped by two kinds of termination shock: Shock-I due to the interaction between the pulsar wind and the stellar wind and Shock-II due to the effect of the orbital motion. We propose that the X-rays are produced by the synchrotron radiation at the Shock-I region and the TeV gamma-rays are produced by the inverse-Compton scattering process at the Shock-II region.« less

Magnetic phase transitions and magnetization reversal in MnRuP

NASA Astrophysics Data System (ADS)

Lampen-Kelley, P.; Mandrus, D.

The ternary phosphide MnRuP is an incommensurate antiferromagnetic metal crystallizing in the non-centrosymmetric Fe2P-type crystal structure. Below the Neel transition at 250 K, MnRuP exhibits hysteretic anomalies in resistivity and magnetic susceptibility curves as the propagation vectors of the spiral spin structure change discontinuously across T1 = 180 K and T2 = 100 K. Temperature-dependent X-ray diffraction data indicate that the first-order spin reorientation occurs in the absence of a structural transition. A strong magnetization reversal (MR) effect is observed upon cooling the system through TN in moderate dc magnetic fields. Positive magnetization is recovered on further cooling through T1 and maintained in subsequent warming curves. The field dependence and training of the MR effect in MnRuP will be discussed in terms of the underlying magnetic structures and compared to anomalous MR observed in vanadate systems. This work is supported by the Gordon and Betty Moore Foundation GBMF4416 and U.S. DOE, Office of Science, BES, Materials Science and Engineering Division.

Simulation studies of GST phase change alloys

NASA Astrophysics Data System (ADS)

Martyna, Glenn

2008-03-01

In order to help drive post-Moore's Law technology development, switching processes involving novel materials, in particular, GeSbTe (GST) alloys are being investigated for use in memory and eFuse applications. An anneal/quench thermal process crystallizes/amorphosizes a GST alloy which then has a low/high resistance and thereby forms a readable/writeable bit; for example, a ``one'' might be the low resistance, conducting crystalline state and a ``zero'' might be the high resistance, glassy state. There are many open questions about the precise nature of the structural transitions and the coupling to electronic structure changes. Computational and experimental studies of the effect of pressure on the GST materials were initiated in order to probe the physics behind the thermal switching process. A new pathway to reversible phase change involving pressure-induced structural metal insulator transitions was discovered. In a binary GS system, a room-temperature, direct, pressure-induced transformation from the high resistance amorphous phase to the low resistance crystalline phase was observed experimentally while the reverse process under tensile load was demonstrated via ab initio MD simulations performed on IBM's Blue Gene/L enabled by massively parallel software. Pressure induced transformations of the ternary material GST-225 (Ge2Sb2Te5) were, also, examined In the talk, the behavior of the two systems will be compared and insight into the nature of the phase change given.

Testing Room-Temperature Ionic Liquid Solutions for Depot Repair of Aluminum Coatings

DTIC Science & Technology

2011-05-01

Ne 3 Na Mg IIIB IVB VB VIB VIIB ------ VIIIB ------ IB IIB Al Si P S Cl Ar 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc...Ru Rh Pd Ag Cd In Sn Sb Te I Xe 6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 7 Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np...Electroplating Bath Lid Arrangement ;:::::::::::=== Thermometer Purge gas vent Anode lead Cathode lead (Extractable from the lid) Purge feed gas

Interagency Contact and Training for a Comprehensive Approach to Operations: Assessment of the Formation Operations Center of Excellence ’Civil-Military Seminar’

DTIC Science & Technology

2012-03-01

T ru st . T he o th er e xp lo re s t he d yn am ic s o f i nt er ac tin g w ith d iff er en t a sp ec ts o f t he p...ho d o th e jo bs , a nd to im pr ov e tra in in g fo r t he se c on te xt s. W ith th is in m in d w e w on de re d w he th er y ou...st io ns th at d es cr ib e yo ur se

DETECTION OF THE {gamma}-RAY BINARY LS I +61 Degree-Sign 303 IN A LOW-FLUX STATE AT VERY HIGH ENERGY {gamma}-RAYS WITH THE MAGIC TELESCOPES IN 2009

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksic, J.; Blanch, O.; Alvarez, E. A.

2012-02-10

We present very high energy (E > 100 GeV) {gamma}-ray observations of the {gamma}-ray binary system LS I +61 Degree-Sign 303 obtained with the MAGIC stereo system between 2009 October and 2010 January. We detect a 6.3{sigma} {gamma}-ray signal above 400 GeV in the combined data set. The integral flux above an energy of 300 GeV is F(E > 300 GeV) = (1.4 {+-} 0.3{sub stat} {+-} 0.4{sub syst}) Multiplication-Sign 10{sup -12} cm{sup -2} s{sup -1}, which corresponds to about 1.3% of the Crab Nebula flux in the same energy range. The orbit-averaged flux of LS I +61 Degree-Sign 303more » in the orbital phase interval 0.6-0.7, where a maximum of the TeV flux is expected, is lower by almost an order of magnitude compared to our previous measurements between 2005 September and 2008 January. This provides evidence for a new low-flux state in LS I +61 Degree-Sign 303. We find that the change to the low-flux state cannot be solely explained by an increase of photon-photon absorption around the compact star.« less

Syntheses, structures, and physicochemical properties of diruthenium compounds of tetrachlorocatecholate with metal-metal bonded Ru(3+)(mu-OR)(2)Ru(3+) and Ru(3.5+)(mu-OR)(2)Ru(3.5+) cores (R = CH(3) and C(2)H(5)).

PubMed

Miyasaka, H; Chang, H C; Mochizuki, K; Kitagawa, S

2001-07-02

Metal-metal bonded Ru(3+)(mu-OR)(2)Ru(3+) and Ru(3.5+)(mu-OR)(2)Ru(3.5+) (R = CH(3) and CH(3)CH(2)) compounds with tetrachlorocatecholate (Cl(4)Cat) have been synthesized in the corresponding alcohol, MeOH and EtOH, from a nonbridged Ru(2+)-Ru(3+) compound, Na(3)[Ru(2)(Cl(4)Cat)(4)(THF)].3H(2)O.7THF (1). In alcohol solvents, compound 1 is continuously oxidized by oxygen to form Ru(3+)(mu-OR)(2)Ru(3+) and Ru(3.5+)(mu-OR)(2)Ru(3.5+) species. The presence of a characteristic countercation leads to selective isolation of either Ru(3+)(mu-OR)(2)Ru(3+) or Ru(3.5+)(mu-OR)(2)Ru(3.5+) as a stable adduct species. In methanol, Ph(4)PCl and dibenzo-18-crown-6-ether afford Ru(3+)(mu-OMe)(2)Ru(3+) species, [A](2)[Ru(2)(Cl(4)Cat)(4)(mu-OMe)(2)Na(2)(MeOH)(6)] ([A](+) = Ph(4)P(+) (2), [Na(dibenzo-18-crown-6)(H(2)O)(MeOH)](+) (3)), while benzo-15-crown-5-ether provides a Ru(3.5+)(mu-OMe)(2)Ru(3.5+) species, [Na(benzo-15-crown-5)(2)][Ru(2)(Cl(4)Cat)(4)(mu-OMe)(2)Na(2)(MeOH)(6)] (4). The air oxidation of 1 in a MeOH/EtOH mixed solvent (1:1 v/v) containing benzo-15-crown-5-ether provides a Ru(3.5+)(mu-OMe)(2)Ru(3.5+) species, [Na(benzo-15-crown-5)(H(2)O)][Ru(2)(Cl(4)Cat)(2)(mu-OMe)(2)Na(2)(EtOH)(2)(H(2)O)(2)(MeOH)(2)].(benzo-15-crown-5) (5). Similarly, the oxidation of 1 in ethanol with Ph(4)PCl provides a Ru(3.5+)(mu-OEt)(2)Ru(3.5+) species, (Ph(4)P)[Ru(2)(Cl(4)Cat)(4)(mu-OEt)(2)Na(2)(EtOH)(6)] (7). A selective formation of a Ru(3+)(mu-OEt)(2)Ru(3+) species, (Ph(4)P)(2)[Ru(2)(Cl(4)Cat)(4)(mu-OEt)(2)Na(2)(EtOH)(2)(H(2)O)(2)] (6), is found in the presence of pyrazine or 2,5-dimethylpyrazine. The crystal structures of these compounds, except 2 and 7, have been determined by X-ray crystallography, and all compounds have been characterized by several spectroscopic and magnetic investigations. The longer Ru-Ru bonds are found in the Ru(3+)(mu-OR)(2)Ru(3+) species (2.606(1) and 2.628(2) A for 3 and 6, respectively) compared with those of Ru(3.5+)(mu-OMe)(2)Ru(3.5+) species (2.5260(6) A and 2.514(2) A for 4 and 5, respectively). These structural features and magnetic and ESR data revealed the electronic configurations of sigma(2)pi(2)delta(2)delta(2)pi(2) and sigma(2)pi(2)delta(2)delta(2)pi(1) for Ru(3+)(mu-OR)(2)Ru(3+) and Ru(3.5+)(mu-OR)(2)Ru(3.5+), respectively, in which the former is diamagnetic and the latter is paramagnetic with S = (1)/(2) ground state. Compound 5 forms a one-dimensional chain with alternating arrangement of a Ru(3.5+)(mu-OMe)(2)Ru(3.5+) unit and a free benzo-15-crown-5-ether molecule by intermolecular hydrogen bonds (O(H(2)O).O(crown-ether) = 2.91-3.04 A). The cyclic voltammetry in DMF affords characteristic metal-origin voltammograms; two reversible and two quasi-reversible redox waves were observed. The feature of cyclic voltammograms for the Ru(3+)(mu-OR)(2)Ru(3+) species (2, 3, and 6) and the Ru(3.5+)(mu-OR)(2)Ru(3.5+) species (4 and 7) are similar to each other, indicating that both species are electrochemically stable. The isolation of the pyrazine-trans-coordinated species, [Ph(4)P][Ru(Cl(4)Cat)(2)(L)(2)] (L = pyrazine (8), 2,5-dimethylpyrazine (9)), revealed the selective isolation of 6 from pyrazine-containing solution. UV-vis spectral variation by ethanolysis for 9 demonstrated the selective conversion from the pyrazine-trans-coordinated species to the Ru(3+)(mu-OEt)(2)Ru(3+) species without an oxidation to the Ru(3.5+)(mu-OEt)(2)Ru(3.5+) species. This result suggests the presence of equilibrium between [Ru(Cl(4)Cat)(2)(L)(2)](-) and Ru(3+)(mu-OEt)(2)Ru(3+) species in the synthetic condition for 6.

1,5-Diamido-9,10-anthraquinone, a Centrosymmetric Redox-Active Bridge with Two Coupled β-Ketiminato Chelate Functions: Symmetric and Asymmetric Diruthenium Complexes.

PubMed

Ansari, Mohd Asif; Mandal, Abhishek; Paretzki, Alexa; Beyer, Katharina; Fiedler, Jan; Kaim, Wolfgang; Lahiri, Goutam Kumar

2016-06-06

The dinuclear complexes {(μ-H2L)[Ru(bpy)2]2}(ClO4)2 ([3](ClO4)2), {(μ-H2L)[Ru(pap)2]2}(ClO4)2 ([4](ClO4)2), and the asymmetric [(bpy)2Ru(μ-H2L)Ru(pap)2](ClO4)2 ([5](ClO4)2) were synthesized via the mononuclear species [Ru(H3L)(bpy)2]ClO4 ([1]ClO4) and [Ru(H3L)(pap)2]ClO4 ([2]ClO4), where H4L is the centrosymmetric 1,5-diamino-9,10-anthraquinone, bpy is 2,2'-bipyridine, and pap is 2-phenylazopyridine. Electrochemistry of the structurally characterized [1]ClO4, [2]ClO4, [3](ClO4)2, [4](ClO4)2, and [5](ClO4)2 reveals multistep oxidation and reduction processes, which were analyzed by electron paramagnetic resonance (EPR) of paramagnetic intermediates and by UV-vis-NIR spectro-electrochemistry. With support by time-dependent density functional theory (DFT) calculations the redox processes could be assigned. Significant results include the dimetal/bridging ligand mixed spin distribution in 3(3+) versus largely bridge-centered spin in 4(3+)-a result of the presence of Ru(II)-stabilizig pap coligands. In addition to the metal/ligand alternative for electron transfer and spin location, the dinuclear systems allow for the observation of ligand/ligand and metal/metal site differentiation within the multistep redox series. DFT-supported EPR and NIR absorption spectroscopy of the latter case revealed class II mixed-valence behavior of the oxidized asymmetric system 5(3+) with about equal contributions from a radical bridge formulation. In comparison to the analogues with the deprotonated 1,4-diaminoanthraquinone isomer the centrosymmetric H2L(2-) bridge shows anodically shifted redox potentials and weaker electronic coupling between the chelate sites.

In situ formed catalytically active ruthenium nanocatalyst in room temperature dehydrogenation/dehydrocoupling of ammonia-borane from Ru(cod)(cot) precatalyst.

PubMed

Zahmakiran, Mehmet; Ayvalı, Tuğçe; Philippot, Karine

2012-03-20

The development of simply prepared and effective catalytic materials for dehydrocoupling/dehydrogenation of ammonia-borane (AB; NH(3)BH(3)) under mild conditions remains a challenge in the field of hydrogen economy and material science. Reported herein is the discovery of in situ generated ruthenium nanocatalyst as a new catalytic system for this important reaction. They are formed in situ during the dehydrogenation of AB in THF at 25 °C in the absence of any stabilizing agent starting with homogeneous Ru(cod)(cot) precatalyst (cod = 1,5-η(2)-cyclooctadiene; cot = 1,3,5-η(3)-cyclooctatriene). The preliminary characterization of the reaction solutions and the products was done by using ICP-OES, ATR-IR, TEM, XPS, ZC-TEM, GC, EA, and (11)B, (15)N, and (1)H NMR, which reveal that ruthenium nanocatalyst is generated in situ during the dehydrogenation of AB from homogeneous Ru(cod)(cot) precatalyst and B-N polymers formed at the initial stage of the catalytic reaction take part in the stabilization of this ruthenium nanocatalyst. Moreover, following the recently updated approach (Bayram, E.; et al. J. Am. Chem. Soc.2011, 133, 18889) by performing Hg(0), CS(2) poisoning experiments, nanofiltration, time-dependent TEM analyses, and kinetic investigation of active catalyst formation to distinguish single metal or in the present case subnanometer Ru(n) cluster-based catalysis from polymetallic Ru(0)(n) nanoparticle catalysis reveals that in situ formed Ru(n) clusters (not Ru(0)(n) nanoparticles) are kinetically dominant catalytically active species in our catalytic system. The resulting ruthenium catalyst provides 120 total turnovers over 5 h with an initial turnover frequency (TOF) value of 35 h(-1) at room temperature with the generation of more than 1.0 equiv H(2) at the complete conversion of AB to polyaminoborane (PAB; [NH(2)BH(2)](n)) and polyborazylene (PB; [NHBH](n)) units.

Trans-packaging of human immunodeficiency virus type 1 genome into Gag virus-like particles in Saccharomyces cerevisiae.

PubMed

Tomo, Naoki; Goto, Toshiyuki; Morikawa, Yuko

2013-03-26

Yeast is recognized as a generally safe microorganism and is utilized for the production of pharmaceutical products, including vaccines. We previously showed that expression of human immunodeficiency virus type 1 (HIV-1) Gag protein in Saccharomyces cerevisiae spheroplasts released Gag virus-like particles (VLPs) extracellularly, suggesting that the production system could be used in vaccine development. In this study, we further establish HIV-1 genome packaging into Gag VLPs in a yeast cell system. The nearly full-length HIV-1 genome containing the entire 5' long terminal repeat, U3-R-U5, did not transcribe gag mRNA in yeast. Co-expression of HIV-1 Tat, a transcription activator, did not support the transcription. When the HIV-1 promoter U3 was replaced with the promoter for the yeast glyceraldehyde-3-phosphate dehydrogenase gene, gag mRNA transcription was restored, but no Gag protein expression was observed. Co-expression of HIV-1 Rev, a factor that facilitates nuclear export of gag mRNA, did not support the protein synthesis. Progressive deletions of R-U5 and its downstream stem-loop-rich region (SL) to the gag start ATG codon restored Gag protein expression, suggesting that a highly structured noncoding RNA generated from the R-U5-SL region had an inhibitory effect on gag mRNA translation. When a plasmid containing the HIV-1 genome with the R-U5-SL region was coexpressed with an expression plasmid for Gag protein, the HIV-1 genomic RNA was transcribed and incorporated into Gag VLPs formed by Gag protein assembly, indicative of the trans-packaging of HIV-1 genomic RNA into Gag VLPs in a yeast cell system. The concentration of HIV-1 genomic RNA in Gag VLPs released from yeast was approximately 500-fold higher than that in yeast cytoplasm. The deletion of R-U5 to the gag gene resulted in the failure of HIV-1 RNA packaging into Gag VLPs, indicating that the packaging signal of HIV-1 genomic RNA present in the R-U5 to gag region functions similarly in yeast cells. Our data indicate that selective trans-packaging of HIV-1 genomic RNA into Gag VLPs occurs in a yeast cell system, analogous to a mammalian cell system, suggesting that yeast may provide an alternative packaging system for lentiviral RNA.

AuRu/AC as an effective catalyst for hydrogenation reactions

DOE PAGES

Villa, Alberto; Chan-Thaw, Carine E.; Campisi, Sebastiano; ...

2015-03-23

AuRu bimetallic catalysts have been prepared by sequential deposition of Au on Ru or vice versa obtaining different nanostructures: when Ru has been deposited on Au, a Au core–Ru shell has been observed, whereas the deposition of Au on Ru leads to a bimetallic phase with Ru enrichment on the surface. In the latter case, the unexpected Ru enrichment could be attributed to the weak adhesion of Ru on the carbon support, thus allowing Ru particles to diffuse on Au particles. Both structures result very active in catalysing the liquid phase hydrogenolysis of glycerol and levulinic acid but the activity,more » the selectivity and the stability depend on the structure of the bimetallic nanoparticles. Ru@Au/AC core–shell structure mostly behaved as the monometallic Ru, whereas the presence of bimetallic AuRu phase in Au@Ru/AC provides a great beneficial effect on both activity and stability.« less

Magnetization measurements of Sr2RuO4-Ru eutectic microplates using dc-SQUIDs

NASA Astrophysics Data System (ADS)

Nago, Y.; Sakuma, D.; Ishiguro, R.; Kashiwaya, S.; Nomura, S.; Kono, K.; Maeno, Y.; Takayanagi, H.

2018-03-01

We report magnetization measurements of Sr2RuO4-Ru eutectic microplates using micro-dc-SQUIDs. Sr2RuO4 is considered as a chiral p-wave superconductor and hence Sr2RuO4-Ru eutectic becomes in an unstable state with a superconducting phase frustration between a chiral p-wave state of Sr2RuO4 and a s-wave state of Ru. To compensate the frustration, a single quantum vortex is spontaneously formed at the center of the Ru inclusion at sufficiently low temperatures. However, such a spontaneous vortex state has not been experimentally observed yet. In this study, we prepared a micro-dc-SQUID and a Sr2RuO4-Ru eutectic microplate containing a single Ru-inclusion at the center of the microplate. We performed magnetization measurements down below the superconducting transition temperature of the Ru inclusion to investigate the spontaneous Ru-center vortex state.

Tetra- and Heptametallic Ru(II),Rh(III) Supramolecular Hydrogen Production Photocatalysts

DOE PAGES

Manbeck, Gerald F.; Fujita, Etsuko; Brewer, Karen J.

2017-06-01

Supramolecular mixed metal complexes combining the trimetallic chromophore [{(bpy) 2Ru(dpp)} 2Ru(dpp)] 6+ (Ru 3) with [Rh(bpy)Cl 2] + or [RhCl 2] + catalytic fragments to form [{(bpy) 2Ru(dpp)} 2Ru(dpp)RhCl 2(bpy)](PF 6) 7 (Ru 3Rh) or [{(bpy) 2Ru(dpp)} 2Ru(dpp)] 2RhCl 2(PF 6) 13 (Ru 3RhRu 3) (bpy = 2,2'-bipyridine and dpp = 2,3-bis(2-pyridyl)pyrazine) catalyze the photochemical reduction of protons to H 2. This first example of a heptametallic Ru,Rh photocatalyst produces over 300 turnovers of H 2 upon photolysis of a solution of acetonitrile, water, triflic acid, and N,N-dimethylaniline as an electron donor. Conversely, the tetrametallic Ru 3Rh produces only 40more » turnovers of H 2 due to differences in the excited state properties and nature of the catalysts upon reduction as ascertained from electrochemical data, transient absorption spectroscopy, and flash-quench experiments. And while the lowest unoccupied molecular orbital of Ru 3Rh is localized on a bridging ligand, it is Rh-centered in Ru 3RhRu 3 facilitating electron collection at Rh in the excited state and reductively quenched state. The Ru → Rh charge separated state of Ru 3RhRu 3 is endergonic with respect to the emissive Ru → dpp 3MLCT excited and cannot be formed by static electron transfer quenching of the 3MLCT state. Instead, a mechanism of subnanosecond charge separation from high lying states is proposed. Multiple reductions of Ru 3 and Ru 3Rh using sodium amalgam were carried out to compare UV–vis absorption spectra of reduced species and to evaluate the stability of highly reduced complexes. Furthermore, the Ru 3 and Ru 3Rh can be reduced by 10 and 13 electrons, respectively, to final states with all bridging ligands doubly reduced and all bpy ligands singly reduced.« less

X-ray observations of Galactic H.E.S.S. sources: an update

NASA Astrophysics Data System (ADS)

Puehlhofer, G.; Eger, P.; Sasaki, M.; Gottschall, D.; Capasso, M.; H. E. S. S. Collaboration

2016-06-01

X-ray diagnostics of TeV sources continues to be an important tool to identify the nature of newly detected sources as well as to pinpoint the physics processes that are at work in these highly energetic objects. The contribution aims at giving a review of recent studies that we have performed on TeV sources with H.E.S.S. and XMM-Newton and also other X-ray facilities. Here, we will mainly focus on Galactic objects such as gamma-ray binaries, pulsar wind nebulae, and supernova remnants (SNRs). Particular emphasis will be given to SNR studies, including recently identified SNRs such as HESS J1731-347 and HESS J1534-571 as well as a revisit of RX J1713.7-3946.

Measurement of Z boson production in Pb-Pb collisions at sqrt[s(NN)]=2.76  TeV with the ATLAS detector.

PubMed

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Duflot, L; Dufour, M-A; Duguid, L; Dunford, M; Duran Yildiz, H; Duxfield, R; Dwuznik, M; Dydak, F; Düren, M; Ebenstein, W L; Ebke, J; Eckweiler, S; Edmonds, K; Edson, W; Edwards, C A; Edwards, N C; Ehrenfeld, W; Eifert, T; Eigen, G; Einsweiler, K; Eisenhandler, E; Ekelof, T; El Kacimi, M; Ellert, M; Elles, S; Ellinghaus, F; Ellis, K; Ellis, N; Elmsheuser, J; Elsing, M; Emeliyanov, D; Engelmann, R; Engl, A; Epp, B; Erdmann, J; Ereditato, A; Eriksson, D; Ernst, J; Ernst, M; Ernwein, J; Errede, D; Errede, S; Ertel, E; Escalier, M; Esch, H; Escobar, C; Espinal Curull, X; Esposito, B; Etienne, F; Etienvre, A I; Etzion, E; Evangelakou, D; Evans, H; Fabbri, L; Fabre, C; Fakhrutdinov, R M; Falciano, S; Fang, Y; Fanti, M; Farbin, A; Farilla, A; Farley, J; Farooque, T; Farrell, S; Farrington, S M; Farthouat, P; Fassi, F; Fassnacht, P; Fassouliotis, D; Fatholahzadeh, B; Favareto, A; Fayard, L; Fazio, S; Febbraro, R; Federic, P; Fedin, O L; Fedorko, W; Fehling-Kaschek, M; Feligioni, L; Fellmann, D; 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Roda Dos Santos, D; Roe, A; Roe, S; Røhne, O; Rolli, S; Romaniouk, A; Romano, M; Romeo, G; Romero Adam, E; Rompotis, N; Roos, L; Ros, E; Rosati, S; Rosbach, K; Rose, A; Rose, M; Rosenbaum, G A; Rosenberg, E I; Rosendahl, P L; Rosenthal, O; Rosselet, L; Rossetti, V; Rossi, E; Rossi, L P; Rotaru, M; Roth, I; Rothberg, J; Rousseau, D; Royon, C R; Rozanov, A; Rozen, Y; Ruan, X; Rubbo, F; Rubinskiy, I; Ruckstuhl, N; Rud, V I; Rudolph, C; Rudolph, G; Rühr, F; Ruiz-Martinez, A; Rumyantsev, L; Rurikova, Z; Rusakovich, N A; Rutherfoord, J P; Ruzicka, P; Ryabov, Y F; Rybar, M; Rybkin, G; Ryder, N C; Saavedra, A F; Sadeh, I; Sadrozinski, H F-W; Sadykov, R; Safai Tehrani, F; Sakamoto, H; Salamanna, G; Salamon, A; Saleem, M; Salek, D; Salihagic, D; Salnikov, A; Salt, J; Salvachua Ferrando, B M; Salvatore, D; Salvatore, F; Salvucci, A; Salzburger, A; Sampsonidis, D; Samset, B H; Sanchez, A; Sanchez Martinez, V; Sandaker, H; Sander, H G; Sanders, M P; Sandhoff, M; Sandoval, T; Sandoval, C; Sandstroem, R; Sankey, D P C; Sansoni, A; Santamarina Rios, C; Santoni, C; Santonico, R; Santos, H; Saraiva, J G; Sarangi, T; Sarkisyan-Grinbaum, E; Sarri, F; Sartisohn, G; Sasaki, O; Sasaki, Y; Sasao, N; Satsounkevitch, I; Sauvage, G; Sauvan, E; Sauvan, J B; Savard, P; Savinov, V; Savu, D O; Sawyer, L; Saxon, D H; Saxon, J; Sbarra, C; Sbrizzi, A; Scannicchio, D A; Scarcella, M; Schaarschmidt, J; Schacht, P; Schaefer, D; Schäfer, U; Schaelicke, A; Schaepe, S; Schaetzel, S; Schaffer, A C; Schaile, D; Schamberger, R D; Schamov, A G; Scharf, V; Schegelsky, V A; Scheirich, D; Schernau, M; Scherzer, M I; Schiavi, C; Schieck, J; Schioppa, M; Schlenker, S; Schmidt, E; Schmieden, K; Schmitt, C; Schmitt, S; Schmitz, M; Schneider, B; Schnoor, U; Schoeffel, L; Schoening, A; Schorlemmer, A L S; Schott, M; Schouten, D; Schovancova, J; Schram, M; Schroeder, C; Schroer, N; Schultens, M J; Schultes, J; Schultz-Coulon, H-C; Schulz, H; Schumacher, M; Schumm, B A; Schune, Ph; Schwanenberger, C; Schwartzman, A; Schwegler, Ph; Schwemling, Ph; Schwienhorst, R; Schwierz, R; Schwindling, J; Schwindt, T; Schwoerer, M; Sciolla, G; Scott, W G; Searcy, J; Sedov, G; Sedykh, E; Seidel, S C; Seiden, A; Seifert, F; Seixas, J M; Sekhniaidze, G; Sekula, S J; Selbach, K E; Seliverstov, D M; Sellden, B; Sellers, G; Seman, M; Semprini-Cesari, N; Serfon, C; Serin, L; Serkin, L; Seuster, R; Severini, H; Sfyrla, A; Shabalina, E; Shamim, M; Shan, L Y; Shank, J T; Shao, Q T; Shapiro, M; Shatalov, P B; Shaw, K; Sherman, D; Sherwood, P; Shimizu, S; Shimojima, M; Shin, T; Shiyakova, M; Shmeleva, A; Shochet, M J; Short, D; Shrestha, S; Shulga, E; Shupe, M A; Sicho, P; Sidoti, A; Siegert, F; Sijacki, Dj; Silbert, O; Silva, J; Silver, Y; Silverstein, D; Silverstein, S B; Simak, V; Simard, O; Simic, Lj; Simion, S; Simioni, E; Simmons, B; Simoniello, R; Simonyan, M; Sinervo, P; Sinev, N B; Sipica, V; Siragusa, G; Sircar, A; Sisakyan, A N; Sivoklokov, S Yu; Sjölin, J; Sjursen, T B; Skinnari, L A; Skottowe, H P; Skovpen, K; Skubic, P; Slater, M; Slavicek, T; Sliwa, K; Smakhtin, V; Smart, B H; Smestad, L; Smirnov, S Yu; Smirnov, Y; Smirnova, L N; Smirnova, O; Smith, B C; Smith, D; Smith, K M; Smizanska, M; Smolek, K; Snesarev, A A; Snow, S W; Snow, J; Snyder, S; Sobie, R; Sodomka, J; Soffer, A; Solans, C A; Solar, M; Solc, J; Soldatov, E Yu; Soldevila, U; Solfaroli Camillocci, E; Solodkov, A A; Solovyanov, O V; Solovyev, V; Soni, N; Sopko, V; Sopko, B; Sosebee, M; Soualah, R; Soukharev, A; Spagnolo, S; Spanò, F; Spighi, R; Spigo, G; Spiwoks, R; Spousta, M; Spreitzer, T; Spurlock, B; St Denis, R D; Stahlman, J; Stamen, R; Stanecka, E; Stanek, R W; Stanescu, C; Stanescu-Bellu, M; Stanitzki, M M; Stapnes, S; Starchenko, E A; Stark, J; Staroba, P; Starovoitov, P; Staszewski, R; Staude, A; Stavina, P; Steele, G; Steinbach, P; Steinberg, P; Stekl, I; Stelzer, B; Stelzer, H J; Stelzer-Chilton, O; Stenzel, H; Stern, S; Stewart, G A; Stillings, J A; Stockton, M C; Stoerig, K; Stoicea, G; Stonjek, S; Strachota, P; Stradling, A R; Straessner, A; Strandberg, J; Strandberg, S; Strandlie, A; Strang, M; Strauss, E; Strauss, M; Strizenec, P; Ströhmer, R; Strom, D M; Strong, J A; Stroynowski, R; Stugu, B; Stumer, I; Stupak, J; Sturm, P; Styles, N A; Soh, D A; Su, D; Subramania, Hs; Subramaniam, R; Succurro, A; Sugaya, Y; Suhr, C; Suk, M; Sulin, V V; Sultansoy, S; Sumida, T; Sun, X; Sundermann, J E; Suruliz, K; Susinno, G; Sutton, M R; Suzuki, Y; Suzuki, Y; Svatos, M; Swedish, S; Sykora, I; Sykora, T; Sánchez, J; Ta, D; Tackmann, K; Taffard, A; Tafirout, R; Taiblum, N; Takahashi, Y; Takai, H; Takashima, R; Takeda, H; Takeshita, T; Takubo, Y; Talby, M; Talyshev, A; Tamsett, M C; Tanaka, J; Tanaka, R; Tanaka, S; Tanaka, S; Tanasijczuk, A J; Tani, K; Tannoury, N; Tapprogge, S; Tardif, D; Tarem, S; Tarrade, F; Tartarelli, G F; Tas, P; Tasevsky, M; Tassi, E; Tatarkhanov, M; Tayalati, Y; Taylor, C; Taylor, F E; Taylor, G N; Taylor, W; Teinturier, M; Teischinger, F A; Teixeira Dias Castanheira, M; Teixeira-Dias, P; Temming, K K; Ten Kate, H; Teng, P K; Terada, S; Terashi, K; Terron, J; Testa, M; Teuscher, R J; Therhaag, J; Theveneaux-Pelzer, T; Thoma, S; Thomas, J P; Thompson, E N; Thompson, P D; Thompson, P D; Thompson, A S; Thomsen, L A; Thomson, E; Thomson, M; Thong, W M; Thun, R P; Tian, F; Tibbetts, M J; Tic, T; Tikhomirov, V O; Tikhonov, Y A; Timoshenko, S; Tiouchichine, E; Tipton, P; Tisserant, S; Todorov, T; Todorova-Nova, S; Toggerson, B; Tojo, J; Tokár, S; Tokushuku, K; Tollefson, K; Tomoto, M; Tompkins, L; Toms, K; Tonoyan, A; Topfel, C; Topilin, N D; Torchiani, I; Torrence, E; Torres, H; Torró Pastor, E; Toth, J; Touchard, F; Tovey, D R; Trefzger, T; Tremblet, L; Tricoli, A; Trigger, I M; Trincaz-Duvoid, S; Tripiana, M F; Triplett, N; Trischuk, W; Trocmé, B; Troncon, C; Trottier-McDonald, M; Trzebinski, M; Trzupek, A; Tsarouchas, C; Tseng, J C-L; Tsiakiris, M; Tsiareshka, P V; Tsionou, D; Tsipolitis, G; Tsiskaridze, S; Tsiskaridze, V; Tskhadadze, E G; Tsukerman, I I; Tsulaia, V; Tsung, J-W; Tsuno, S; Tsybychev, D; Tua, A; Tudorache, A; Tudorache, V; Tuggle, J M; Turala, M; Turecek, D; Turk Cakir, I; Turlay, E; Turra, R; Tuts, P M; Tykhonov, A; Tylmad, M; Tyndel, M; Tzanakos, G; Uchida, K; Ueda, I; Ueno, R; Ugland, M; Uhlenbrock, M; Uhrmacher, M; Ukegawa, F; Unal, G; Undrus, A; Unel, G; Unno, Y; Urbaniec, D; Urquijo, P; Usai, G; Uslenghi, M; Vacavant, L; Vacek, V; Vachon, B; Vahsen, S; Valenta, J; Valentinetti, S; Valero, A; Valkar, S; Valladolid Gallego, E; Vallecorsa, S; Valls Ferrer, J A; Van Berg, R; Van Der Deijl, P C; van der Geer, R; van der Graaf, H; Van Der Leeuw, R; van der Poel, E; van der Ster, D; van Eldik, N; van Gemmeren, P; van Vulpen, I; Vanadia, M; Vandelli, W; Vaniachine, A; Vankov, P; Vannucci, F; Vari, R; Varol, T; Varouchas, D; Vartapetian, A; Varvell, K E; Vassilakopoulos, V I; Vazeille, F; Vazquez Schroeder, T; Vegni, G; Veillet, J J; Veloso, F; Veness, R; Veneziano, S; Ventura, A; Ventura, D; Venturi, M; Venturi, N; Vercesi, V; Verducci, M; Verkerke, W; Vermeulen, J C; Vest, A; Vetterli, M C; Vichou, I; Vickey, T; Vickey Boeriu, O E; Viehhauser, G H A; Viel, S; Villa, M; Villaplana Perez, M; Vilucchi, E; Vincter, M G; Vinek, E; Vinogradov, V B; Virchaux, M; Virzi, J; Vitells, O; Viti, M; Vivarelli, I; Vives Vaque, F; Vlachos, S; Vladoiu, D; Vlasak, M; Vogel, A; Vokac, P; Volpi, G; Volpi, M; Volpini, G; von der Schmitt, H; von Radziewski, H; von Toerne, E; Vorobel, V; Vorwerk, V; Vos, M; Voss, R; Voss, T T; Vossebeld, J H; Vranjes, N; Vranjes Milosavljevic, M; Vrba, V; Vreeswijk, M; Vu Anh, T; Vuillermet, R; Vukotic, I; Wagner, W; Wagner, P; Wahlen, H; Wahrmund, S; Wakabayashi, J; Walch, S; Walder, J; Walker, R; Walkowiak, W; Wall, R; Waller, P; Walsh, B; Wang, C; Wang, H; Wang, H; Wang, J; Wang, J; Wang, R; Wang, S M; Wang, T; Warburton, A; Ward, C P; Warsinsky, M; Washbrook, A; Wasicki, C; Watanabe, I; Watkins, P M; Watson, A T; Watson, I J; Watson, M F; Watts, G; Watts, S; Waugh, A T; Waugh, B M; Weber, M S; Weber, P; Webster, J S; Weidberg, A R; Weigell, P; Weingarten, J; Weiser, C; Wells, P S; Wenaus, T; Wendland, D; Weng, Z; Wengler, T; Wenig, S; Wermes, N; Werner, M; Werner, P; Werth, M; Wessels, M; Wetter, J; Weydert, C; Whalen, K; Wheeler-Ellis, S J; White, A; White, M J; White, S; Whitehead, S R; Whiteson, D; Whittington, D; Wicek, F; Wicke, D; Wickens, F J; Wiedenmann, W; Wielers, M; Wienemann, P; Wiglesworth, C; Wiik-Fuchs, L A M; Wijeratne, P A; Wildauer, A; Wildt, M A; Wilhelm, I; Wilkens, H G; Will, J Z; Williams, E; Williams, H H; Willis, W; Willocq, S; Wilson, J A; Wilson, M G; Wilson, A; Wingerter-Seez, I; Winkelmann, S; Winklmeier, F; Wittgen, M; Wollstadt, S J; Wolter, M W; Wolters, H; Wong, W C; Wooden, G; Wosiek, B K; Wotschack, J; Woudstra, M J; Wozniak, K W; Wraight, K; Wright, M; Wrona, B; Wu, S L; Wu, X; Wu, Y; Wulf, E; Wynne, B M; Xella, S; Xiao, M; Xie, S; Xu, C; Xu, D; Yabsley, B; Yacoob, S; Yamada, M; Yamaguchi, H; Yamamoto, A; Yamamoto, K; Yamamoto, S; Yamamura, T; Yamanaka, T; Yamazaki, T; Yamazaki, Y; Yan, Z; Yang, H; Yang, U K; Yang, Y; Yang, Z; Yanush, S; Yao, L; Yao, Y; Yasu, Y; Ybeles Smit, G V; Ye, J; Ye, S; Yilmaz, M; Yoosoofmiya, R; Yorita, K; Yoshida, R; Yoshihara, K; Young, C; Young, C J; Youssef, S; Yu, D; Yu, J; Yu, J; Yuan, L; Yurkewicz, A; Zabinski, B; Zaidan, R; Zaitsev, A M; Zajacova, Z; Zanello, L; Zanzi, D; Zaytsev, A; Zeitnitz, C; Zeman, M; Zemla, A; Zendler, C; Zenin, O; Ženiš, T; Zinonos, Z; Zenz, S; Zerwas, D; Zevi della Porta, G; Zhang, D; Zhang, H; Zhang, J; Zhang, X; Zhang, Z; Zhao, L; Zhao, Z; Zhemchugov, A; Zhong, J; Zhou, B; Zhou, N; Zhou, Y; Zhu, C G; Zhu, H; Zhu, J; Zhu, Y; Zhuang, X; Zhuravlov, V; Zieminska, D; Zimin, N I; Zimmermann, R; Zimmermann, S; Zimmermann, S; Ziolkowski, M; Zitoun, R; Živković, L; Zmouchko, V V; Zobernig, G; Zoccoli, A; zur Nedden, M; Zutshi, V; Zwalinski, L

2013-01-11

The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15  nb(-1) of integrated luminosity obtained in the 2011 LHC Pb+Pb run at sqrt[s(NN)]=2.76  TeV. The Z bosons are reconstructed via dielectron and dimuon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.

On-line measurements of RuO{sub 4} during a PWR severe accident

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reymond-Laruinaz, S.; Doizi, D.; Manceron, L.

After the Fukushima accident, it became essential to have a way to monitor in real time the evolution of a nuclear reactor during a severe accident, in order to react efficiently and minimize the industrial, ecological and health consequences of the accident. Among gaseous fission products, the tetroxide of ruthenium RuO{sub 4} is of prime importance since it has a significant radiological impact. Ruthenium is a low volatile fission product but in case of the rupture of the vessel lower head by the molten corium, the air entering into the vessel oxidizes Ru into gaseous RuO{sub 4}, which is notmore » trapped by the Filtered Containment Venting Systems. To monitor the presence of RuO{sub 4} allows making a diagnosis of the core degradation and quantifying the release into the atmosphere. To determine the presence of RuO{sub 4}, FTIR spectrometry was selected. To study the feasibility of the monitoring, high-resolution IR measurements were realized at the French synchrotron facility SOLEIL on the infrared beam line AILES. Thereafter, theoretical calculations were done to simulate the FTIR spectrum to describe the specific IR fingerprint of the molecule for each isotope and based on its partial pressure in the air. (authors)« less

Atomic layer deposition of TiO2 on nitrogen-doped carbon nanofibers supported Ru nanoparticles for flexible Li-O2 battery: A combined DFT and experimental study

NASA Astrophysics Data System (ADS)

Yang, Jingbo; Mi, Hongwei; Luo, Shan; Li, Yongliang; Zhang, Peixin; Deng, Libo; Sun, Lingna; Ren, Xiangzhong

2017-11-01

Flexible Li-O2 batteries have attracted worldwide research interests and been considered to be potential alternatives for the next-generation flexible devices. Nitrogen-doped carbon nanofibers (N-CNFs) prepared by electrospinning are used as flexible substrate and an amorphous TiO2 layer is coated by atomic layer deposition (ALD) and then decorated with Ru nanoparticles. The Ru/N-CNFs@TiO2 composite is directly used as a free-standing electrode for Li-O2 batteries and the electrode delivers a high specific capacity, improved round-trip efficiency and good cycling ability. The superior electrochemical performance can be attributed to the amorphous TiO2 protecting layer and superior catalytic activity of Ru nanoparticles. Based on density functional theory (DFT) calculations from first principles, the carbon electrode after coating with TiO2 is more stable during discharge/charge process. The analysis of Li2O2 on three different interfaces (Li2O2/N-CNFs, Li2O2/TiO2, and Li2O2/Ru) indicates that the electron transport capacity was higher on Ru and TiO2 compared with N-CNFs, therefore, Li2O2 could be formed and decomposed more easily on the Ru/N-CNFs@TiO2 cathode. This work paves a way to develop the free-standing cathode materials for the future development of high-performance flexible energy storage systems.

Effect of a Nonplanar Melt-Solid Interface on Lateral Compositional Distribution during Unidirectional Solidification of a Binary Alloy with a Constant Growth Velocity V. Part 1; Theory

NASA Technical Reports Server (NTRS)

Wang, Jai-Ching; Watring, Dale A.; Lehoczky, Sandor L.; Su, Ching-Hua; Gillies, Don; Szofran, Frank

1999-01-01

Infrared detector materials, such as Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te have energy gaps almost linearly proportional to its composition. Due to the wide separation of liquidus and solidus curves of their phase diagram, there are compositional segregations in both of axial and radial directions of these crystals grown in the Bridgman system unidirectionally with constant growth rate. It is important to understand the mechanisms which affect lateral segregation such that large uniform radial composition crystal is possible. Following Coriell, etc's treatment, we have developed a theory to study the effect of a curved melt-solid interface shape on the lateral composition distribution. The system is considered to be cylindrical system with azimuthal symmetric with a curved melt-solid interface shape which can be expressed as a linear combination of a series of Bessell's functions. The results show that melt-solid interface shape has a dominate effect on lateral composition distribution of these systems. For small values of b, the solute concentration at the melt-solid interface scales linearly with interface shape with a proportional constant of the product of b and (1 - k), where b = VR/D, with V as growth velocity, R as sample radius, D as diffusion constant and k as distribution constant. A detailed theory will be presented. A computer code has been developed and simulations have been performed and compared with experimental results. These will be published in another paper.

Electrochemical oxidation of methanol using dppm-bridged Ru/Pd, Ru/Pt and Ru/Au catalysts.

PubMed

Yang, Ying; McElwee-White, Lisa

2004-08-07

The electrochemical oxidation of methanol was carried out using a series of dppm-bridged Ru/Pd, Ru/Pt and Ru/Au heterobimetallic complexes as catalysts. The major oxidation products were formaldehyde dimethyl acetal (dimethoxymethane, DMM) and methyl formate (MF). The Ru/Pd and Ru/Pt bimetallic catalysts generally afforded lower product ratios of DMM/MF and higher current efficiencies than the Ru/Au catalysts. The Ru/Au bimetallics exhibited product ratios and current efficiencies similar to those obtained from the Ru mononuclear compound CpRu(PPh(3))(2)Cl. Increasing the methanol concentration afforded higher current efficiencies, while the addition of water to the samples shifted the product distribution toward the more highly oxidized product, MF.

Raman scattering studies of the orbital, magnetic, and conducting phases in double layer ruthenates

NASA Astrophysics Data System (ADS)

Karpus, John Francis

In this dissertation, light scattering techniques are used to probe the exotic orbital, magnetic, and conducting phases of the double layer ruthenate, Ca3Ru2O7, as functions of temperature, applied pressure, and applied magnetic field. These phases result from a rich interplay between the orbital, spin, and electronic degrees of freedom in such a strongly coupled system as Ca3Ru2O7. The Raman-active phonon and magnon excitations in Ca3Ru2O7 convey sufficient information to map out the orbital, magnetic, and conducting (H, T) and (P, T) phase diagrams of this material. This study finds that quasihydrostatic pressure causes a linear suppression of the orbital-ordering temperature (TOO = 48 K at P = 0), up to a T = 0 critical point near P* ˜ 55 kbar, above which the material is in a metallic, orbital-degenerate phase. This pressure-induced collapse of the antiferromagnetic orbital-ordered phase is associated with a suppression of the RuO6 octahedral distortions that are responsible for orbital-ordering. It is also shown that an applied magnetic field at low temperatures induces a change from an orbital-ordered to an orbital-degenerate phase for fields aligned along the in-plane hard-axis, but induces a reentrant orbital-ordered to orbital-disordered to orbital-ordered phase change for fields aligned along the in-plane easy-axis. This complex magnetic field dependence betrays the importance of the spin-orbit coupling in this system, which makes the field-induced phase behavior highly sensitive to both the applied magnetic field magnitude and direction. It is further shown that rapid field-induced changes in the structure and orbital populations are responsible for the highly field-tunable conducting properties of Ca3Ru2O7, and that the most dramatic magneto-conductivities are associated with an "orbital disordered" phase regime in which there is a random mixture of a- and b-axis oriented Ru moments and d-orbital populations on the Ru ions. Dilute La doping in Ca3Ru2O7 changes the lattice parameter along the c-axis and also adds an extra electron, providing bandwidth and band filling control, respectively. This addition of La also lowers the orbital ordering temperature to T ˜ 43 K, and provides a greater sensitivity of the orbital phases to applied magnetic fields, as evidenced by changes in the phases occurring at lower fields and over a greater field range than seen in the undoped system.

Electronic structure investigation of atomic layer deposition ruthenium(oxide) thin films using photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Schaefer, Michael; Schlaf, Rudy

2015-08-01

Analyzing and manipulating the electronic band line-up of interfaces in novel micro- and nanoelectronic devices is important to achieve further advancement in this field. Such band alignment modifications can be achieved by introducing thin conformal interfacial dipole layers. Atomic layer deposition (ALD), enabling angstrom-precise control over thin film thickness, is an ideal technique for this challenge. Ruthenium (Ru0) and its oxide (RuO2) have gained interest in the past decade as interfacial dipole layers because of their favorable properties like metal-equivalent work functions, conductivity, etc. In this study, initial results of the electronic structure investigation of ALD Ru0 and RuO2 films via photoemission spectroscopy are presented. These experiments give insight into the band alignment, growth behavior, surface structure termination, and dipole formation. The experiments were performed in an integrated vacuum system attached to a home-built, stop-flow type ALD reactor without exposing the samples to the ambient in between deposition and analysis. Bis(ethylcyclopentadienyl)ruthenium(II) was used as precursor and oxygen as reactant. The analysis chamber was outfitted with X-ray photoemission spectroscopy (LIXPS, XPS). The determined growth modes are consistent with a strong growth inhibition situation with a maximum average growth rate of 0.21 Å/cycle for RuO2 and 0.04 Å/cycle for Ru.0 An interface dipole of up to -0.93 eV was observed, supporting the assumption of a strongly physisorbed interface. A separate experiment where the surface of a RuO film was sputtered suggests that the surface is terminated by an intermediate, stable, non-stoichiometric RuO2/OH compound whose surface is saturated with hydroxyl groups.

Localized-itinerant dichotomy and unconventional magnetism in SrRu2O6

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okamoto, Satoshi; Ochi, Masayuki; Arita, Ryotaro

Electron correlations tend to generate local magnetic moments that usually order if the lattices are not too frustrated. The hexagonal compound SrRumore » $$_2$$O$$_6$$ has a relatively high N{\\'e}el temperature but small local moments, which seem to be at odds with the nominal valence of Ru$$^{5+}$$ in the $$t_{2g}^3$$ configuration. Here, we investigate the electronic and magnetic properties of SrRu$$_2$$O$$_6$$ using density functional theory (DFT) combined with dynamical mean field theory (DMFT). We find that the strong hybridization between Ru $d$ and O $p$ states results in a Ru valence that is closer to $+4$, leading to the small ordered moment, consistent with a DFT prediction. While the agreement with DFT might indicate that SrRu$$_2$$O$$_6$$ is in the weak coupling regime, our DMFT studies provide evidence from the mass enhancement and local moment formation that indicate correlation effects play a significant role. The local moment per Ru site is about a factor 2 larger than the ordered moment at low temperatures and remains finite in the whole temperature range investigated. Our theoretical N{\\'e}el temperature $$\\sim 700$$~K is in reasonable agreement with experimental observations. Due to a small lattice distortion, the degenerate $$t_{2g}$$ manifold is split and the quasiparticle weight is renormalized significantly in the $$a_{1g}$$ state, while correlation effects in $$e_g'$$ states are about a factor of 2--3 weaker. SrRu$$_2$$O$$_6$$ is a unique system in which localized and itinerant electrons coexist with the proximity to an orbitally-selective Mott transition within the $$t_{2g}$$ sector.« less

Solar photocatalytic disinfection of E. coli and bacteriophages MS2, ΦX174 and PR772 using TiO2, ZnO and ruthenium based complexes in a continuous flow system.

PubMed

Mac Mahon, Joanne; Pillai, Suresh C; Kelly, John M; Gill, Laurence W

2017-05-01

The performance of photocatalytic treatment processes were assessed using different photocatalysts against E. coli and bacteriophages MS2, ΦX174 and PR772, in a recirculating continuous flow compound parabolic collector system under real sunlight conditions. Suspended TiO 2 and ZnO nanoparticle powders and Tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate in solution were tested separately, as well as in combination, using E. coli. For a 3-log reduction of E. coli in distilled water, inactivation rates in terms of cumulative dose were in the order Ru(bpy) 3 Cl 2 >(TiO 2 & Ru(bpy) 3 Cl 2 )>(ZnO & Ru(bpy) 3 Cl 2 )>ZnO>TiO 2 >photolysis. Reactivation of E. coli was observed following all trials despite the detection limit being reached, although the reactivated colonies were observed to be under stress and much slower growing when compared to original colonies. Treatment with Ru(bpy) 3 Cl 2 was also compared against standard photolysis of bacteriophages MS2, ΦX174 and PR772 with the order of photolytic inactivation for a 3-log reduction in terms of cumulative UV-A dose being ΦX174>PR772>MS2. However, MS2 was found to be the most susceptible bacteriophage to treatment with Ru(bpy) 3 Cl 2 , with complete removal of the phage observed within the first 15min of exposure. Ru(bpy) 3 Cl 2 also significantly improved inactivation rates for PR772 and ΦX174. Copyright © 2017 Elsevier B.V. All rights reserved.

Real-time observation of the dehydrogenation processes of methanol on clean Ru(001) and Ru(001)-p(2×2) O surfaces by a temperature-programmed electron-stimulated desorption ion angular distribution/time-of-flight system

NASA Astrophysics Data System (ADS)

Sasaki, Takehiko; Itai, Yuichiro; Iwasawa, Yasuhiro

1999-12-01

Decomposition processes of methanol on clean and oxygen-precovered Ru(001) surfaces have been visualized in real time with a temperature-programmed (TP) electron-stimulated desorption ion angular distribution (ESDIAD)/time-of-flight (TOF) system. The mass of desorbed ions during temperature-programmed surface processes was identified by TOF measurements. In the case of methanol (CH 3OD) adsorption on Ru(001)-p(2×2)-O, a halo pattern of H + from the methyl group of methoxy species was observed at 100-200 K, followed by a broad pattern from the methyl group at 230-250 K and by a near-center pattern from O + ions originating from adsorbed CO above 300 K. The halo pattern is attributed to a perpendicular conformation of the CO bond axis of the methoxy species, leading to off-normal CH bond scission. On the other hand, methanol adsorbed on clean Ru(001) did not give any halo pattern but a broad pattern was observed along the surface normal, indicating that the conformation of the methoxy species is not ordered on the clean surface. Comparison between the ESDIAD images of the oxygen-precovered surface and the clean surface suggests that the precovered oxygen adatoms induce ordering of the methoxy species. Real-time ESDIAD measurements revealed that the oxygen atoms at the Ru(001)-p(2×2)-O surface have a positive effect on selective dehydrogenation of the methoxy species to CO+H 2 and a blocking effect on CO bond breaking of the methoxy species.

Enhanced photocatalytic CO2 reduction to CH4 over separated dual co-catalysts Au and RuO2

NASA Astrophysics Data System (ADS)

Dong, Chunyang; Hu, Songchang; Xing, Mingyang; Zhang, Jinlong

2018-04-01

A spatially separated, dual co-catalyst photocatalytic system was constructed by the stepwise introduction of RuO2 and Au nanoparticles (NPs) at the internal and external surfaces of a three dimensional, hierarchically ordered TiO2-SiO2 (HTSO) framework (the final photocatalyst was denoted as Au/HRTSO). Characterization by HR-TEM, EDS-mapping, XRD and XPS confirmed the existence and spatially separated locations of Au and RuO2. In CO2 photocatalytic reduction (CO2PR), Au/HRTSO (0.8%) shows the optimal performance in both the activity and selectivity towards CH4; the CH4 yield is almost twice that of the singular Au/HTSO or HRTSO (0.8%, weight percentage of RuO2) counterparts. Generally, Au NPs at the external surface act as electron trapping agents and RuO2 NPs at the inner surface act as hole collectors. This advanced spatial configuration could promote charge separation and transfer efficiency, leading to enhanced CO2PR performance in both the yield and selectivity toward CH4 under simulated solar light irradiation.

The Mystery of the Electronic Spectrum of Ruthenium Monophosphide

NASA Astrophysics Data System (ADS)

Adam, Allan G.; Christensen, Ryan M.; Dore, Jacob M.; Konder, Ricarda M.; Tokaryk, Dennis W.

2016-06-01

Using PH3 as a reactant gas and ruthenium as the target metal in the UNB laser ablation spectrometer, the ruthenium monophosphide molecule (RuP) has been detected. Dispersed fluorescence experiments have been performed to determine ground state vibrational frequencies and the presence of any low-lying electronic states. Rotationally resolved spectra of two vibrational bands at 577nm and 592nm have been taken; the bands have been identified as 1-0 and 0-0 bands based on isotopic shifts. Ruthenium has seven stable isotopes and rotational transitions have been observed for six of the RuP isotopologues. RuP is isoelectronic to RuN so it is expected that RuP will have a 2Σ+ ground state and low resolution spectra indicated a likely 2Σ+ - 2Σ+ electronic transition. Further investigation has led us to believe we are observing a 2Π - 2Σ+ transition but mysteriously some important rotational branches are missing. It is hoped that new data to be recorded on a second electronic system we have observed at 535nm will help shed light on this mystery.

Bandgap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures.

PubMed

Zhang, Qiang; Chen, Yuxuan; Zhang, Chendong; Pan, Chi-Ruei; Chou, Mei-Yin; Zeng, Changgan; Shih, Chih-Kang

2016-12-14

The van der Waals interaction in vertical heterostructures made of two-dimensional (2D) materials relaxes the requirement of lattice matching, therefore enabling great design flexibility to tailor novel 2D electronic systems. Here we report the successful growth of MoSe 2 on single-layer hexagonal boron nitride (hBN) on the Ru(0001) substrate using molecular beam epitaxy. Using scanning tunnelling microscopy and spectroscopy, we found that the quasi-particle bandgap of MoSe 2 on hBN/Ru is about 0.25 eV smaller than those on graphene or graphite substrates. We attribute this result to the strong interaction between hBN/Ru, which causes residual metallic screening from the substrate. In addition, the electronic structure and the work function of MoSe 2 are modulated electrostatically with an amplitude of ∼0.13 eV. Most interestingly, this electrostatic modulation is spatially in phase with the Moiré pattern of hBN on Ru(0001) whose surface also exhibits a work function modulation of the same amplitude.

Photochemical Synthesis and Ligand Exchange Reactions of Ru(CO)[subscript 4] (Eta[superscript 2]-Alkene) Compounds

ERIC Educational Resources Information Center

Cooke, Jason; Berry, David E.; Fawkes, Kelli L.

2007-01-01

The photochemical synthesis and subsequent ligand exchange reactions of Ru(CO)[subscript 4] (eta[superscript2]-alkene) compounds has provided a novel experiment for upper-level inorganic chemistry laboratory courses. The experiment is designed to provide a system in which the changing electronic properties of the alkene ligands could be easily…

Synthesis and Characterization of Platinum-Ruthenium-Tin Catalysts

NASA Astrophysics Data System (ADS)

Uffalussy, Karen

Magnesia-supported trimetallic Pt-Ru-Sn catalysts prepared through a cluster and a conventional synthetic route have been investigated in terms of their structural properties and their catalytic activity for the hydrogenation of citral and crotonaldehyde. FTIR results indicate that the majority of the stabilizing ligands remain attached to the PtRu5(μ-SnPh 2)(C)(CO)15 cluster used following impregnation onto the MgO support. Under H2 reduction conditions, partial and full ligand removal are both observed at 473 and 573 K, respectively. HRSTEM analysis shows that cluster-derived samples exhibit significantly smaller average metal particle sizes, as well as narrower particle size distributions than the corresponding conventionally prepared ones. EDX measurements show that in the cluster-derived catalysts, the majority of the metal particles present are trimetallic in nature, with metal compositions similar to those of the original cluster. In contrast, the conventionally prepared materials contain mostly bimetallic and monometallic particles with variable compositions. XPS was used to determine how the variation in method of Sn addition to bimetallic Pt-Ru affects the electronic state for the trimetallic Pt-Ru-Sn/MgO system prepared by impregnation using multimetallic clusters, metal-salts, and the combination of both precursor types. Results show that the PtRu5Sn/MgO material has a significantly higher percentage of Sn0 in comparison to Pt-Ru-Sn/MgO and PtRu5-Sn/MgO, and a corresponding shift in both Pt and Ru peaks can be correlated to this relative change in Sn oxidation state. The formation of smaller metal particles and electronic modification of Pt and Ru by Sn in the cluster-derived catalysts and the presence of the three metals in these particles in close proximity result in higher activity and selectivity to the unsaturated alcohols for the hydrogenation of both citral and crotonaldehyde.

Versatile Photocatalytic Systems for H2 Generation in Water Based on an Efficient DuBois-Type Nickel Catalyst

PubMed Central

2013-01-01

The generation of renewable H2 through an efficient photochemical route requires photoinduced electron transfer (ET) from a light harvester to an efficient electrocatalyst in water. Here, we report on a molecular H2 evolution catalyst (NiP) with a DuBois-type [Ni(P2R′N2R″)2]2+ core (P2R′N2R″ = bis(1,5-R′-diphospha-3,7-R″-diazacyclooctane), which contains an outer coordination sphere with phosphonic acid groups. The latter functionality allows for good solubility in water and immobilization on metal oxide semiconductors. Electrochemical studies confirm that NiP is a highly active electrocatalyst in aqueous electrolyte solution (overpotential of approximately 200 mV at pH 4.5 with a Faradaic yield of 85 ± 4%). Photocatalytic experiments and investigations on the ET kinetics were carried out in combination with a phosphonated Ru(II) tris(bipyridine) dye (RuP) in homogeneous and heterogeneous environments. Time-resolved luminescence and transient absorption spectroscopy studies confirmed that directed ET from RuP to NiP occurs efficiently in all systems on the nano- to microsecond time scale, through three distinct routes: reductive quenching of RuP in solution or on the surface of ZrO2 (“on particle” system) or oxidative quenching of RuP when the compounds were immobilized on TiO2 (“through particle” system). Our studies show that NiP can be used in a purely aqueous solution and on a semiconductor surface with a high degree of versatility. A high TOF of 460 ± 60 h–1 with a TON of 723 ± 171 for photocatalytic H2 generation with a molecular Ni catalyst in water and a photon-to-H2 quantum yield of approximately 10% were achieved for the homogeneous system. PMID:24320740

Stabilization of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} through Si–Ti substitution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Weiwei, E-mail: weiweix@princeton.edu; Fuccillo, M.K.; Phelan, B.F.

2015-07-15

We report a route for designing and synthesizing Ti{sub 3}Co{sub 5}B{sub 2}-type compounds in the Ti–Ru–B system by using chemical substitution of Si for Ti to decrease the d-electron-based antibonding interactions that it is argued would otherwise drive an instability in this structure for unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2}. Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} with x=0.75, 1.00 and 1.25 nominal compositions crystalizes in the Ti{sub 3}Co{sub 5}B{sub 2} structure type using arc melting methods, whereas at lower doping levels (x=0.0, 0.25 and 0.50) the more complex Zn{sub 11}Rh{sub 18}B{sub 8}-type structure is stable. Electronic structure calculations show that in hypothetical,more » unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2} with the Ti{sub 3}Co{sub 5}B{sub 2}-type structure, the antibonding interactions are strong around the Fermi level between the Ti and Ru in the structure that form tetragonal prisms. We propose that weakening these strong interactions through the partial substitution of isovalent Si for Ti leads to the observed stability of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} for x≈1. - Graphical abstract: We present the designing and synthesizing of Ti{sub 3}Co{sub 5}B{sub 2}-type compounds in the Ti–Ru–B system by using chemical substitution of Si for Ti to decrease the d-electron-based antibonding interactions that would otherwise drive an instability in this structure for unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2}. Electronic structure calculations show that in hypothetical, unsubstituted Ti{sub 3}Ru{sub 5}B{sub 2} with the Ti{sub 3}Co{sub 5}B{sub 2}-type structure, the antibonding interactions are strong around the Fermi level between the Ti and Ru in the structure that form tetragonal prisms. We propose that weakening these strong interactions through the partial substitution of isovalent Si for Ti leads to the observed stability of the Ti{sub 3}Co{sub 5}B{sub 2}-type structure for Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} for x≈1. - Highlights: • New quaternary phase Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} in Ti{sub 3}Co{sub 5}B{sub 2}-type structure is reported. • Chemical substitution of isovalent Si for Ti is used to stabilize the phase. • Decreasing the d-electron-based antibonding interactions is proved by calculation. • Physical properties of Ti{sub 3−x}Si{sub x}Ru{sub 5}B{sub 2} are presented down to 0.4 K.« less

Effect of Ru thickness on spin pumping in Ru/Py bilayer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Behera, Nilamani; Singh, M. Sanjoy; Chaudhary, Sujeet

2015-05-07

We report the effect of Ru thickness (t{sub Ru}) on ferromagnetic resonance (FMR) line-width of Ru(t{sub Ru})/Py(23 nm) bilayer samples grown on Si(100)/SiO{sub 2} substrates at room temperature by magnetron sputtering. The FMR line-width is found to vary linearly with frequency for all thicknesses of Ru, indicating intrinsic origin of damping. For Ru thicknesses below 15 nm, Gilbert-damping parameter, α is almost constant. We ascribe this behavior to spin back flow that is operative for Ru thicknesses lower than the spin diffusion length in Ru, λ{sub sd}. For thicknesses >15 nm (>λ{sub sd}), the damping constant increases with Ru thickness, indicating spin pumpingmore » from Py into Ru.« less

Effects of nanoscale coatings on reliability of MEMS ohmic contact switches

NASA Astrophysics Data System (ADS)

Tremper, Amber Leigh

This thesis examines how the electrical and mechanical behavior of Au thin films is altered by the presence of ultra-thin metallic coatings. To examine the mechanical behavior, nanoindentation, nano-scratch, and atomic force microscopy (AFM) testing was performed. The electrical behavior was evaluated through Kelvin probe contact resistance measurements. This thesis shows that ultra-thin, hard, ductile coatings on a softer, ductile underlying layer (such as Ru or Pt on Au) had a significant effect on mechanical behavior of the system, and can be tailored to control the deformation resistance of the thin film system. Despite Ru and Pt having a higher hardness and plane strain modulus than Au, the Ru and Pt coatings decreased both the hardness and plane strain modulus of the layered system when the indentation depth was on the order of the coating thickness. Alternately, when the indentation depth was several times the coating thickness, the ductile, plastically hard, elastically stiff layer significantly hardened the contact response. These results correlate well with membrane stress theoretical predictions, and demonstrate that membrane theory can be applied even when the ratio of indentation depth, h, to coating thickness, t, is very large ( h/t<10). The transition from film-substrate models to membrane models occurs when the indent penetration depth to coating thickness ratio is less than ˜0.5. When the electrical behavior of the Ru-coated Au films was examined, it was found that all the measured resistances of the Au-only film and Ru-coated systems were several orders of magnitude larger than those predicted by Holm's law, but were still in good agreement with previously reported values in the literature. Previous studies attributed the high contact resistances to a variety of causes, including the buildup of an insulating contamination layer. This thesis determined the cause of the deviations to be large sheet resistance contributions to the total measured resistance. Further, studies on aged samples (with thicker contamination layers) conclusively showed that, while contamination increases the contact resistance, it also increases the dependence on force. This thesis also details that the relative contribution of contact resistance to the total measured resistance can be maximized by decreasing the probe spacing and tip radius. AFM testing of the layered systems showed that the coated samples had larger predicted plane strain moduli than the Au sample, in contrast to the nanoindentation testing. Thus, when the contact depth was kept sufficiently small, the contact stiffness increased as predicted by substrate models. When the contact depth was on the order of the coating thickness, the contact stiffness actually decreased. Additionally, the forceseparation plots showed that the Ru and Pt surfaces either accumulated large amounts of contamination or were less susceptible to being wiped clean than the Au film. Further, scratch testing of the Au film and Ru and Pt coatings show that the hard surface coatings reduce material removal and contact wear. Ultra-thin Ru and Pt surface coatings on Au films are shown to be improved material systems for ohmic contact switches. The wear is reduced for coated materials, while the resistance and power consumption through the coating are not significantly affected.

Viscosity Relaxation in Molten HgZnTe

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Lehoczky, S. L.; Kim, Yeong Woo; Baird, James K.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Rotating cup measurements of the viscosity of the pseudo-binary melt, HgZnTe have shown that the isothermal liquid with zinc mole fraction 0.16 requires tens of hours of equilibration time before a steady viscous state can be achieved. Over this relaxation period, the viscosity at 790 C increases by a factor of two, while the viscosity at 810 C increases by 40%. Noting that the Group VI elements tend to polymerize when molten, we suggest that the viscosity of the melt is enhanced by the slow formation of Te atom chains. To explain the build-up of linear Te n-mers, we propose a scheme, which contains formation reactions with second order kinetics that increase the molecular weight, and decomposition reactions with first order kinetics that inactivate the chains. The resulting rate equations can be solved for the time dependence of each molecular weight fraction. Using these molecular weight fractions, we calculate the time dependence of the average molecular weight. Using the standard semi-empirical relation between polymer average molecular weight and viscosity, we then calculate the viscosity relaxation curve. By curve fitting, we find that the data imply that the rate constant for n-mer formation is much smaller than the rate constant for n-mer deactivation, suggesting that Te atoms only weakly polymerize in molten HgZnTe. The steady state toward which the melt relaxes occurs as the rate of formation of an n-mer becomes exactly balanced by the sum of the rate for its deactivation and the rate for its polymerization to form an (n+1)-mer.

Variable electron correlation in high-quality MBE- and PLD-grown SrRuO3 thin films.

NASA Astrophysics Data System (ADS)

Siemons, Wolter; Koster, Gertjan; Yamamoto, Hideki; Vailionis, Arturas; Geballe, Theodore; Blank, Dave; Beasley, Malcolm

2007-03-01

We show that systematic variations in the degree of correlation can occur within SrRuO3 as a function of disorder/off-stoichiometry. In particular, we find that one source of disorder can be controlled in SrRuO3 thin films by varying the deposition conditions or the deposition technique. Specifically, we clearly demonstrate that variation of vacancies on the ruthenium site gives rise to a variation in correlated behavior as seen in the photoemission spectra (XPS and UPS),. Moreover, the transport properties of our samples are clearly linked to their photoemission spectra, and independently the crystal unit cell parameters. SrRuO3 appears to be a system where these effects can be studied in a more systematic fashion, usually not easily accessible, but we suspect that the underlying physics is generic in complex oxidesWork supported by the DoE BES and EPRI.

Half-metallic ferromagnetism in Sr3Ru2O7

NASA Astrophysics Data System (ADS)

Rivero, Pablo; Meunier, Vincent; Shelton, William

2017-05-01

The bilayered member of the Ruddesden-Popper family of ruthenates, Sr3Ru2O7 , has received increasing attention due to its interesting properties and phases. By using first principle calculations we find that the ground state is characterized by a ferromagnetic (FM) half-metallic state. This state strongly competes with an antiferromagnetic metallic phase, which indicates the possible presence of a particular state characterized by the existence of different magnetic domains. To drive the system towards a phase transition we studied the electronic and magnetic properties as a function of RuO6 octahedra rotations and found that the magnetic phase does not couple with the rotation angle. Our results provide accurate electronic, structure, and magnetic ground-state properties of Sr3Ru2O7 and stimulate the investigation of other types of octahedra rotations and distortions in the search of phase transitions.

Infrared spectra of RuTPP, RuCOTPP, and Ru(CO)2TPP isolated in solid argon.

PubMed

Krim, Lahouari; Sorgues, Sébastien; Soep, Benoit; Shafizadeh, Niloufar

2005-09-22

Infrared spectra of unstable species such as CO-free ruthenium tetraphenylporphyrin RuTPP and RuCOTPP (species with vacant coordination sites) isolated in solid argon at 8 K have been recorded. Selective deposition conditions allow the isolation of either RuTPP and RuCOTPP or RuCOTPP and Ru(CO)2TPP. This depends on the preparation conditions of the sample. A specific Ru-CO bending mode has been characterized at 590.1 cm(-1) for Ru(CO)2TPP. The behavior of each vibrational mode of RuTPP, RuCOTPP, and Ru(CO)2TPP has been analyzed. Modes such as gamma8 at 721.3 cm(-1) (out-of-plane stretching mode gamma(Cbeta-H)sym) and nu41 at 1342.8 cm(-1) (nuCalpha-N coupled with deltaCalpha-Cm) reflect the charge transfer in the porphyrin. Indeed, the addition of one or two CO ligands to RuTPP reduces the charge transfer between the metal center and the porphyrin, which appears as an increase in the frequency of the nu41 mode and in a decrease in that of the gamma8 mode.

Exceeding the filling fraction limit: An approach to enhancement of thermoelectric properties of filled - Co4Sb12 skutterudite

NASA Astrophysics Data System (ADS)

Graff, Jennifer Whitney

Currently the world energy usage has nearly tripled since 1950 and is projected to grow at a rate of 1.5% per year and predicted to at least double from the beginning of the millennium to 2050. The United States alone is currently consuming more energy than it can produce (≈ 97 Quadrillion BTU's consumed in 2011).(1) Presently, fossil fuels make up over 85% of our energy landscape, including both the stationary grid (like coal and nuclear power plants) and the mobile grid (automobiles using gas and oil). This presents a major demand for developing methods of saving, storing, and renewing energy. Answers to these existing energy demands must come from a variety of renewable sources including: solar, wind, biomass, geothermal and others. But currently, most renewable sources are only a small part of the big energy picture. One approach to this exponentially growing problem, lies within high efficiency (15%-20%) thermoelectric (TE) materials which address small, yet very important and specific, parts of a bigger problem. Specifically, Co4Sb12-based skutterudites, an increasingly favorable thermoelectric material for mid to high temperature applications (currently used in General Motors TE Generator devices). These materials have the ability to be 'tuned' or controlled thermally and electrically through doping and filling mechanisms, as you will see in this dissertation. However, one of the major drawbacks of TE materials is the difficulty in optimizing both electrical and thermal properties simultaneously. Typically, different control parameters are used in order to enhance the electrical and thermal properties individually. It is very rare to observe optimization of both in a TE material via one control parameter. However, the work presented herein successfully augments all TE properties, with one control variable, by using an approach that can be applied to all doped skutterudites and clathrate materials. Skutterudites are novel materials in that they are a binary system with a crystalline framework and a narrow band gap, so they naturally possess relatively good electrical properties. This dissertation seeks to answer the question: Can we continue to improve the efficiency of one of the leading TE materials in power generation applications -- skutterudites? In trying to answer this question we discovered a material that had never been tested for its TE properties and found that it exhibits behavior not typically observed in these materials as well as showing improvements in all TE properties (electrical and thermal) via one control parameter. We also successfully improved the TE efficiencies of several different filled skutterudites by a single approach which can be applied to other skutterudite and cage-like materials.

Ru-N-C Hybrid Nanocomposite for Ammonia Dehydrogenation: Influence of N-doping on Catalytic Activity

PubMed Central

Hien, Nguyen Thi Bich; Kim, Hyo Young; Jeon, Mina; Lee, Jin Hee; Ridwan, Muhammad; Tamarany, Rizcky; Yoon, Chang Won

2015-01-01

For application to ammonia dehydrogenation, novel Ru-based heterogeneous catalysts, Ru-N-C and Ru-C, were synthesized via simple pyrolysis of a mixture of RuCl3·6H2O and carbon black with or without dicyandiamide as a nitrogen-containing precursor at 550 °C. Characterization of the prepared Ru-N-C and Ru-C catalysts via scanning transmission electron microscopy, in conjunction with energy dispersive X-ray spectroscopy, indicated the formation of hollow nanocomposites in which the average sizes of the Ru nanoparticles were 1.3 nm and 5.1 nm, respectively. Compared to Ru-C, the Ru-N-C nanocomposites not only proved to be highly active for ammonia dehydrogenation, giving rise to a NH3 conversion of >99% at 550 °C, but also exhibited high durability. X-ray photoelectron spectroscopy revealed that the Ru active sites in Ru-N-C were electronically perturbed by the incorporated nitrogen atoms, which increased the Ru electron density and ultimately enhanced the catalyst activity.

Novel Electronic Structures of Ru-pnictides RuPn (Pn = P, As, Sb)

NASA Astrophysics Data System (ADS)

Goto, H.; Toriyama, T.; Konishi, T.; Ohta, Y.

Density-functional-theory-based electronic structure calculations are made to consider the novel electronic states of Ru-pnictides RuP and RuAs where the intriguing phase transitions and superconductivity under doping of Rh have been reported. We find that there appear nearly degenerate flat bands just at the Fermi level in the high-temperature metallic phase of RuP and RuAs; the flat-band states come mainly from the 4dxy orbitals of Ru ions and the Rh doping shifts the Fermi level just above the flat bands. The splitting of the flat bands caused by their electronic instability may then be responsible for the observed phase transition to the nonmagnetic insulating phase at low temperatures. We also find that the band structure calculated for RuSb resembles that of the doped RuP and RuAs, which is consistent with experiment where superconductivity occurs in RuSb without Rh doping.

EG&G Florida, Inc., KSC base operations contractor Launch Readiness Assessment System

NASA Technical Reports Server (NTRS)

Geaslen, W. D.

1988-01-01

A computerized Launch Readiness Assessment System (LRAS) which compares 'current status' of readiness against the 'required status' of readiness for the Space Shuttle. The five subsystems of the LRAS are examined in detail. The LRAS Plan specifies the overall system requirements, procedures, and reports. The LRAS Manager drives the operation of the LRAS system. The Responding Units (RU) maintain support plans and procedures which specify the detail requirements for each mission or milestone. The Master Data Tables contain the milestone, responsible RU relationships, and requirements assessment categories. The LRAS Status System serves as the launch readiness assessment reporting system. The relationships between these subsystems are displayed in diagrams.

Platinum-group elements fractionation by selective complexing, the Os, Ir, Ru, Rh-arsenide-sulfide systems above 1020 °C

NASA Astrophysics Data System (ADS)

Helmy, Hassan M.; Bragagni, Alessandro

2017-11-01

The platinum-group element (PGE) contents in magmatic ores and rocks are normally in the low μg/g (even in the ng/g) level, yet they form discrete platinum-group mineral (PGM) phases. IPGE (Os, Ir, Ru) + Rh form alloys, sulfides, and sulfarsenides while Pt and Pd form arsenides, tellurides, bismuthoids and antimonides. We experimentally investigate the behavior of Os, Ru, Ir and Rh in As-bearing sulfide system between 1300 and 1020 °C and show that the prominent mineralogical difference between IPGE (+Rh) and Pt and Pd reflects different chemical preference in the sulfide melt. At temperatures above 1200 °C, Os shows a tendency to form alloys. Ruthenium forms a sulfide (laurite RuS2) while Ir and Rh form sulfarsenides (irarsite IrAsS and hollingworthite RhAsS, respectively). The chemical preference of PGE is selective: IPGE + Rh form metal-metal, metal-S and metal-AsS complexes while Pt and Pd form semimetal complexes. Selective complexing followed by mechanical separation of IPGE (and Rh)-ligand from Pt- and Pd-ligand associations lead to PGE fractionation.

Examining ruthenium chromophores for the photochemical reduction of CO2 to methanol

NASA Astrophysics Data System (ADS)

Boston, David J.

Our consumption of energy for transportation and electricity has been growing as quickly as our population. As this demand for energy increases we increase our production of carbon dioxide by the burning of fossil fuels to try and meet this increasing demand. A sustainable method to convert carbon dioxide (CO2) to a viable liquid fuel is one potential way in which both the increasing energy demand and increasing CO2 concentration issues can both be helped. Currently such methods being investigated include thermal, electrochemical, and photochemical processes. Because thermal conversion is not an ideal situation because of the requirement of strong reducing agents or extreme conditions such as steam reformation reactions, we need to find better alternatives such as electrochemical and photochemical methods. Both electrochemical and photochemical methods have the ability to be sustainable, however, the vast majority of these systems are limited to producing CO and/or formic acid, with only a few performing deeper reduction to products such formaldehyde, methanol and methane. All of the systems capable of reducing CO2 past two electrons involve either a heterogeneous catalyst (e.g. TiO2) or an electrode. In recent times Bocarsly and coworkers have shown that pyridine was capable of reducing CO2 to methanol through a sequential process of proton and electron transfers. This process seems to start with the formation of a CO2-pyridine adduct in solution that is reduced one more time to form formate/formic acid. The next reduction is a slow process and allows for a buildup of formate in solution leading to a higher formate concentration in solution. The subsequent reductions seem to occur very rapidly and form methanol at good efficiencies. Theoretical work done recently has argued for the necessity of the Pt, Pd, or GaP surface in the electrochemistry. Carter and coworkers have claimed that the surface of the electrode is a necessary part of the catalysis with the pyridinium being only a cocatalyst for the reduction of CO2. However, Musgrave and coworkers predict that the homogeneous reductions can take place with the aid of water molecules in solution. They allow for a PCET process to take place between the CO 2 and the pyridinium radical. This would allow for a second pathway for the catalytic reduction of CO2 to methanol. Work done during this dissertation has shown that the photochemical reduction of carbon dioxide to methanol is possible using pyridine in a similar manner to Bocarsly and coworkers in their electrochemical system. By replacing the electrode with Ru(phen)3Cl2 it is still possible to drive the reaction using excited states of the chromophore to provide the electrons with enough energy to reduce the pyridinium to the radical species. This system has been shown to produce up to 66 BM methanol after 6 hours of irradiation of 470 nm light. Production of formate is also observed, with ~27 mM being observed within the first hour of irradiation. This system was further investigated with the incorporation of the pyridine catalyst into a chromophore system using the complex [Ru(phen)2dppz](PF 6)2, [Ru(phen)2pbtpalpha](PF6) 2, and [Ru(phen)2pbtpbeta](PF6)2. Cyclic voltammetry experiments for these complexes show similar reduction potentials for with ~100 mV difference between them with [Ru(phen)2dppz](PF 6)2 being the most negative and [Ru(phen)2pbtpbeta](PF 6)2 being the most positive. When the electrolyte solution was saturated with CO2 only [Ru(phen)2pbtpalpha](PF 6)2 and [Ru(phen)2pbtpbeta](PF6) 2 showed a response signifying catalysis was taking place. Initial photochemical tests with these complexes showed that [Ru(phen)2pbtpalpha](PF 6)2 seemed to undergo dimer formation in the absence of CO 2 with [Ru(phen)2pbtpbeta](PF6)2 forming a singly reduced species that is oxidized upon introduction of additional CO2. Electrolysis of [Ru(phen)2pbtpbeta](PF6 )2 produces ~900 BM methanol with both CO and formate being produced as well. Photolysis of [Ru(phen)2pbtpbeta](PF6 )2 in DMF with 1 M H2O and 0.1M TEA, no CO formation observed, however, both methanol and formic acid were observed after 1 hours of irradiation with methanol reaching 45 BM, 285 microM formaldehyde and 650 microM formate.

Mechanism study on inorganic oxidants induced inhibition of Ru(bpy)₃²+ electrochemiluminescence and its application for sensitive determination of some inorganic oxidants.

PubMed

Qiu, Bin; Xue, Lingling; Wu, Yanping; Lin, Zhenyu; Guo, Longhua; Chen, Guonan

2011-07-15

Inhibited Ru(bpy)(3)(2+) electrochemiluminescence by inorganic oxidants is investigated. Results showed that a number of inorganic oxidants can quench the ECL of Ru(bpy)(3)(2+)/tri-n-propylamine (TPrA) system, and the logarithm of the decrease in ECL intensity (ΔI) was proportional to the logarithm of analyte concentrations. Based on which, a sensitive approach for detection of these inorganic oxidants was established, e.g. the log-log plots of ΔI versus the concentration of MnO(4)(-), Cr(2)O(7)(2-) and Fe(CN)(6)(3-) are linear in the range of 1×10(-7) to 3×10(-4)M for MnO(4)(-) and Cr(2)O(7)(2-), and 1×10(-7) to 1×10(-4)M for Fe(CN)(6)(3-), with the limit of detection (LOD) of 8.0×10(-8)M, 2×10(-8)M, and 1×10(-8)M, respectively. A series of experiments such as a comparison of the inhibitory effect of different compounds on Ru(bpy)(3)(2+)/TPrA ECL, ECL emission spectra, UV-Vis absorption spectra etc. were investigated in order to discover how these inorganic analytes quench the ECL of Ru(bpy)(3)(2+)/TPrA system. A mechanism based on consumption of TPrA intermediate (TPrA(·)) by inorganic oxidants was proposed. Copyright © 2011 Elsevier B.V. All rights reserved.

Bond strength of primer/cement systems to zirconia subjected to artificial aging.

PubMed

Zhao, Li; Jian, Yu-Tao; Wang, Xiao-Dong; Zhao, Ke

2016-11-01

Creating reliable and durable adhesion to the nonactive zirconia surface is difficult and has limited zirconia use. The introduction of functional monomers such as 10-methacryloyloxydecyl dihydrogen phosphate (MDP) appears to have enhanced bond strength to zirconia. The purpose of this in vitro study was to evaluate the long-term bond strength of several MDP-containing primer/cement systems to zirconia. Zirconia blocks were divided into 6 groups (n=24) according to the 3 primers/cements to be bonded, as follows: Scotchbond Universal/RelyX Ultimate (SU/RU; consisting of MDP-containing primer/MDP-free cement); Clearfil ceramic primer/Panavia F (CCP/PAN; consisting ofMDP-containing/MDP-containing); and Z-Prime Plus/Duo-Link (ZP/DUO; consisting ofMDP-containing/MDP-free), which were compared with 3 nonprimed groups, RU, PAN, and DUO. After bonding, each group was further divided into 3 subgroups (n=8) according to the level of aging: 24-hour storage in water at 37°C (24H); 30-day storage at 37°C (30D); and 30-day storage at 37°C followed by 3000 thermal cycles (30D/TC). After aging, a shear bond strength test and failure mode analysis were performed. The data were analyzed using 2-way ANOVA (α=.05). After aging, nearly all primer/cement groups presented significantly higher bond strength than the related nonprimed groups for each level of aging (P<.05), except for CCP/PAN versus PAN with 24H (P=.741). SU/RU had the highest bond strength among the groups for all treatments (P<.05), except for CCP/PAN versus SU/RU with 30D/TC (P=.171). Among the nonprimed groups, only RU went through 30D/TC without premature debonding. With 24H and 30D, the failure modes in SU/RU and CCP/PAN were purely mixed, whereas those in the other groups were mainly adhesive, except for RU. The superiority of the initial bond strength in SU/RU may result from some functional components other than MDP. The presence of MDP in the cement did not appear to have a positive effect on long-term bond strength to zirconia. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Computational studies of the geometry and electronic structure of an all-inorganic and homogeneous tetra-Ru-polyoxotungstate catalyst for water oxidation and its four subsequent one-electron oxidized forms.

PubMed

Quiñonero, David; Kaledin, Alexey L; Kuznetsov, Aleksey E; Geletii, Yurii V; Besson, Claire; Hill, Craig L; Musaev, Djamaladdin G

2010-01-14

Geometry and electronic structure of five species [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](10-) (1), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](9-) (2), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](8-) (3), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](7-) (4), and [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](6-) (5) with different oxidation states of Ru centers were studied at the density functional and COSMO levels of theory. These species are expected to be among the possible intermediates of the recently reported 1-catalyzed water oxidation (Geletii, Y. V.; Botar, B.; Kogerler, P.; Hillesheim, D. A.; Musaev, D. G.; Hill, C. L. Angew. Chem. Int. Ed. 2008, 47, 3896-3899 and Sartorel, A.; Carraro, M.; Scorrano, G.; Zorzi, R. D.; Geremia, S.; McDaniel, N. D.; Bernhard, S.; Bonchio, M. J. Am. Chem. Soc. 2008, 130, 5006-5007). It was shown that RI-BP86 correctly describes the geometry and energy of the low-lying electronic states of compound 1, whereas the widely used B3LYP approach overestimates the energy of its high-spin states. Including the solvent and/or countercation effects into calculations improves the agreement between the calculated and experimental data. It was found that the several HOMOs and LUMOs of the studied complexes are bonding and antibonding orbitals of the [Ru(4)O(4)(OH)(2)(H(2)O)(4)](6+) core, and four subsequent one-electron oxidations of 1, leading to formation of 2, 3, 4, and 5, respectively, involve only {Ru(4)} core orbitals. In other words, catalyst instability due to ligand oxidation in the widely studied Ru-blue dimer, [(bpy)(2)(O)Ru(V)-(mu-O)-Ru(V)(O)(bpy)(2)](4+), is not operable for 1: the latter all-inorganic catalyst is predicted to be stable under water oxidation turnover conditions. The calculated HOMOs and LUMOs of all the studied species are very close in energy and exhibit a "quasi-continuum" or "nanoparticle-type" electronic structure similar to that of nanosized transition metal clusters. This conclusion closely correlates with the experimentally reported oxidation and reduction features of 1 and explains the unusual linear dependence of oxidation potential versus charges for these compounds. The decrease in total negative charge of the system via 1 > 2 > 3 > 4 > 5, on average, decreases the {Ru(4)}-{SiW(10)} distance. It is predicted that at higher pH compound 1 will, initially, release protons from the mu-O(Ru) oxygen centers.

Combined crystal chemistry and DFT studies of ThNCl and Th2N2X (X: chalcogen) behaving as pseudo-binaries

NASA Astrophysics Data System (ADS)

Matar, Samir F.; Kfoury, Charbel N.

2018-02-01

Common features and peculiar differentiations characterize binary and ternary thorium nitride Th3N4, thorium nitride chloride ThNCl and the family of thorium nitride chalcogenides Th2N2X (X = O, S, Se, Te) investigated in the framework of the quantum density functional theory DFT. Particularly the dominant effect of the Th-N covalent bond stronger than ionic Th-Cl/Th-X ones as identified from analyses of bonding from overlap integral, electron localization function mapping, electronic density of states and charge transfer, is found at the origin of the layered-like structural arrangements in Th-N monolayers within ThNCl (Cl / [ThN]/ Cl) and Th-N double layers in Th2N2X (X / [Th2N2] / X) with the result of pseudo binary compounds: [ThN]+Cl- and [Th2N2] 2+X2-. All compounds are found semi-conducting with ∼2 eV band gap. It is claimed that such insights into Solid State Chemistry can help rationalizing complex compounds more comprehensively (two examples given).

Electron microscope studies of nano-domain structures in Ru-based magneto-superconductors: RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212).

PubMed

Yokosawa, Tadahiro; Awana, V P S Veer Pal Singh; Kimoto, Koji; Takayama-Muromachi, Eiji; Karppinen, Maarit; Yamauchi, Hisao; Matsui, Yoshio

2004-01-01

Microstructures of the RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212) magneto-superconductors have been investigated by using selected-area electron diffraction, convergent-beam electron diffraction, dark-field electron microscopy and high-resolution electron microscopy at room temperature. Both Ru-1212 and Ru-1222 consist of nm-size domains stacked along the [Formula: see text] direction, where the domains are formed by two types of superstructures due to ordering of rotated RuO(6) octahedra about the c-axis. In Ru-1212, both primitive-and body-centered tetragonal superstructures (the possible space groups: P4/mbm and I4/mcm) are derived to form the corresponding nm-domains. It is of great interest that Ru-1212 consists of domains of two crystallographically different superstructures, while the similar domains observed in Ru-1222 have crystallographically identical superstructure with an orthorhombic symmetry (possible space group: Aeam), related by 90 degrees rotation around the c-axis (Yokosawa et al., 2003, submitted for publication).

Enhancement of activity of RuSex electrocatalyst by modification with nanostructured iridium towards more efficient reduction of oxygen

NASA Astrophysics Data System (ADS)

Dembinska, Beata; Kiliszek, Malgorzata; Elzanowska, Hanna; Pisarek, Marcin; Kulesza, Pawel J.

2013-12-01

Electrocatalytic activity of carbon (Vulcan XC-72) supported selenium-modified ruthenium, RuSex/C, nanoparticles for reduction of oxygen was enhanced through intentional decoration with iridium nanostructures (dimensions, 2-3 nm). The catalytic materials were characterized in oxygenated 0.5 mol dm-3 H2SO4 using cyclic and rotating ring disk voltammetric techniques as well as using transmission electron microscopy and scanning electron microscopy equipped with X-ray dispersive analyzer. Experiments utilizing gas diffusion electrode aimed at mimicking conditions existing in the low-temperature fuel cell. Upon application of our composite catalytic system, the reduction of oxygen proceeded at more positive potentials, and higher current densities were observed when compared to the behavior of the simple iridium-free system (RuSex/C) investigated under the analogous conditions. The enhancement effect was more pronounced than that one would expect from simple superposition of voltammetric responses for the oxygen reduction at RuSex/C and iridium nanostructures studied separately. Nanostructured iridium acted here as an example of a powerful catalyst for the reduction of H2O2 (rather than O2) and, when combined with such a moderate catalyst as ruthenium-selenium (for O2 reduction), it produced an integrated system of increased electrocatalytic activity in the oxygen reduction process. The proposed system retained its activity in the presence of methanol that could appear in a cathode compartment of alcohol fuel cell.

Magnetic Properties of Restacked 2D Spin 1/2 honeycomb RuCl3 Nanosheets.

PubMed

Weber, Daniel; Schoop, Leslie M; Duppel, Viola; Lippmann, Judith M; Nuss, Jürgen; Lotsch, Bettina V

2016-06-08

Spin 1/2 honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still in demand. Here, we report the exfoliation of the magnetic semiconductor α-RuCl3 into the first halide monolayers and the magnetic characterization of the spin 1/2 honeycomb arrangement of turbostratically stacked RuCl3 monolayers. The exfoliation is based on a reductive lithiation/hydration approach, which gives rise to a loss of cooperative magnetism due to the disruption of the spin 1/2 state by electron injection into the layers. The restacked, macroscopic pellets of RuCl3 layers lack symmetry along the stacking direction. After an oxidative treatment, cooperative magnetism similar to the bulk is restored. The oxidized pellets of restacked single layers feature a magnetic transition at TN = 7 K if the field is aligned parallel to the ab-plane, while the magnetic properties differ from bulk α-RuCl3 if the field is aligned perpendicular to the ab-plane. The deliberate introduction of turbostratic disorder to manipulate the magnetic properties of RuCl3 is of interest for research in frustrated magnetism and complex magnetic order as predicted by the Kitaev-Heisenberg model.

Catalysts for ultrahigh current density oxygen cathodes for space fuel cell applications

NASA Technical Reports Server (NTRS)

Tryk, D.; Yeager, E.; Shingler, M.; Aldred, W.; Wang, C.

1990-01-01

The objective of this research was to identify promising electrocatalyst/support systems for the oxygen cathode in alkaline fuel cells operating at relatively high temperatures, O2 pressures and current densities. A number of materials were prepared, including Pb-Ru and Pb-Ir pyrochlores, RuO2 and Pt-doped RuO2, and lithiated NiO. Several of these were prepared using techniques that had not been previously used to prepare them. Particularly interesting is the use of the alkaline solution technique to prepare the Pt-doped Pb-Ru pyrochlore in high area form. Well-crystallized Pb(2)Ru(2)O(7-y) was used to fabricate high performance O2 cathodes with relatively good stability in room temperature KOH. This material was also found to be stable over a useful potential range at approximately 140 C in concentrated KOH. Other pyrochlores were found to be either unstable (amorphous samples) or the fabrication of the gas-fed electrodes could not be fully optimized during this project period. Future work may be directed at this problem. High area platinum supported on conductive metal oxide supports produced mixed results: small improvements in O2 reduction performance for Pb(2)Ru(2)O(7-y) but a large improvement for Li-doped NiO at room temperature. Nearly reversible behavior was observed for the O2/OH couple for Li-doped NiO at approximately 200 C.

Inhibition of ammonia poisoning by addition of platinum to Ru/α-Al2 O3 for preferential CO oxidation in fuel cells.

PubMed

Sato, Katsutoshi; Yagi, Sho; Zaitsu, Shuhei; Kitayama, Godai; Kayada, Yuto; Teramura, Kentaro; Takita, Yusaku; Nagaoka, Katsutoshi

2014-12-01

In polymer electrolyte fuel cell (PEFC) systems, small amounts of ammonia (NH3 ) present in the reformate gas deactivate the supported ruthenium catalysts used for preferential oxidation (PROX) of carbon monoxide (CO). In this study, we investigated how the addition of a small amount of platinum to a Ru/α-Al2 O3 catalyst (Pt/Ru=1:9 w/w) affected the catalyst's PROX activity in both the absence and the presence of NH3 (130 ppm) under conditions mimicking the reformate conditions during steam reforming of natural gas. The activity of undoped Ru/α-Al2 O3 decreased sharply upon addition of NH3 , whereas Pt/Ru/α-Al2 O3 exhibited excellent PROX activity even in the presence of NH3 . Ruthenium K-edge X-ray absorption near-edge structure (XANES) spectra indicated that in the presence of NH3 , some of the ruthenium in the undoped catalyst was oxidized in the presence of NH3 , whereas ruthenium oxidation was not observed with Pt/Ru/α-Al2 O3 . These results suggest that ruthenium oxidation is retarded by the platinum, so that the catalyst shows high activity even in the presence of NH3 . © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photosynthesis and Ribulose 1,5-Bisphosphate Concentrations in Intact Leaves of Xanthium strumarium L. 1

PubMed Central

Mott, Keith A.; Jensen, Richard G.; O'Leary, James W.; Berry, Joseph A.

1984-01-01

The interacting effects of the rate of ribulose 1,5-bisphosphate (RuBP) regeneration and the rate of RuBP utilization as influenced by the amount and activation of RuBP carboxylase on photosynthesis and RuBP concentrations were resolved in experiments which examined the kinetics of the response of photosynthesis and RuBP concentrations after step changes from a rate-saturating to a rate-limiting light intensity in Xanthium strumarium. Because RuBP carboxylase requires several minutes to deactivate in vivo, it was possible to observe the effect of reducing the rate of RuBP regeneration on the RuBP concentration at constant enzyme activation state by sampling very soon after reducing the light intensity. Samples taken over longer time periods showed the effect of changes in enzyme activation at constant RuBP regeneration rate on RuBP concentration and photosynthetic rate. Within 15 s of lowering the light intensity from 1500 to 600 microEinsteins per square meter per second the RuBP concentration in the leaves dropped below the enzyme active site concentration, indicating that RuBP regeneration rate was limiting for photosynthesis. After longer intervals of time, the RuBP concentration in the leaf increased as the RuBP carboxylase assumed a new steady state activation level. No change in the rate of photosynthesis was observed during the interval that RuBP concentration increased. It is concluded that the rate of photosynthesis at the lower light intensity was limited by the rate of RuBP regeneration and that parallel changes in the activation of RuBP carboxylase occurred such that concentrations of RuBP at steady state were not altered by changes in light intensity. PMID:16663982

Photosynthesis and Ribulose 1,5-Bisphosphate Concentrations in Intact Leaves of Xanthium strumarium L.

PubMed

Mott, K A; Jensen, R G; O'leary, J W; Berry, J A

1984-12-01

The interacting effects of the rate of ribulose 1,5-bisphosphate (RuBP) regeneration and the rate of RuBP utilization as influenced by the amount and activation of RuBP carboxylase on photosynthesis and RuBP concentrations were resolved in experiments which examined the kinetics of the response of photosynthesis and RuBP concentrations after step changes from a rate-saturating to a rate-limiting light intensity in Xanthium strumarium. Because RuBP carboxylase requires several minutes to deactivate in vivo, it was possible to observe the effect of reducing the rate of RuBP regeneration on the RuBP concentration at constant enzyme activation state by sampling very soon after reducing the light intensity. Samples taken over longer time periods showed the effect of changes in enzyme activation at constant RuBP regeneration rate on RuBP concentration and photosynthetic rate. Within 15 s of lowering the light intensity from 1500 to 600 microEinsteins per square meter per second the RuBP concentration in the leaves dropped below the enzyme active site concentration, indicating that RuBP regeneration rate was limiting for photosynthesis. After longer intervals of time, the RuBP concentration in the leaf increased as the RuBP carboxylase assumed a new steady state activation level. No change in the rate of photosynthesis was observed during the interval that RuBP concentration increased. It is concluded that the rate of photosynthesis at the lower light intensity was limited by the rate of RuBP regeneration and that parallel changes in the activation of RuBP carboxylase occurred such that concentrations of RuBP at steady state were not altered by changes in light intensity.

Stress-controlled thermoelectric module for energy harvesting and its application for the significant enhancement of the power factor of Bi2Te3-based thermoelectrics

NASA Astrophysics Data System (ADS)

Korobeinikov, Igor V.; Morozova, Natalia V.; Lukyanova, Lidia N.; Usov, Oleg A.; Kulbachinskii, Vladimir A.; Shchennikov, Vladimir V.; Ovsyannikov, Sergey V.

2018-01-01

We propose a model of a thermoelectric module in which the performance parameters can be controlled by applied tuneable stress. This model includes a miniature high-pressure anvil-type cell and a specially designed thermoelectric module that is compressed between two opposite anvils. High thermally conductive high-pressure anvils that can be made, for instance, of sintered technical diamonds with enhanced thermal conductivity, would enable efficient heat absorption or rejection from a thermoelectric module. Using a high-pressure cell as a prototype of a stress-controlled thermoelectric converter, we investigated the effect of applied high pressure on the power factors of several single-crystalline thermoelectrics, including binary p-type Bi2Te3, and multi-component (Bi,Sb)2Te3 and Bi2(Te,Se,S)3 solid solutions. We found that a moderate applied pressure of a few GPa significantly enhances the power factors of some of these thermoelectrics. Thus, they might be more efficiently utilized in stress-controlled thermoelectric modules. In the example of one of these thermoelectrics crystallizing in the same rhombohedral structure, we examined the crystal lattice stability under moderate high pressures. We uncovered an abnormal compression of the rhombohedral lattice of (Bi0.25,Sb0.75)2Te3 along the c-axis in a hexagonal unit cell, and detected two phase transitions to the C2/m and C2/c monoclinic structures above 9.5 and 18 GPa, respectively.

Chemical interference with iron transport systems to suppress bacterial growth of Streptococcus pneumoniae.

PubMed

Yang, Xiao-Yan; Sun, Bin; Zhang, Liang; Li, Nan; Han, Junlong; Zhang, Jing; Sun, Xuesong; He, Qing-Yu

2014-01-01

Iron is an essential nutrient for the growth of most bacteria. To obtain iron, bacteria have developed specific iron-transport systems located on the membrane surface to uptake iron and iron complexes such as ferrichrome. Interference with the iron-acquisition systems should be therefore an efficient strategy to suppress bacterial growth and infection. Based on the chemical similarity of iron and ruthenium, we used a Ru(II) complex R-825 to compete with ferrichrome for the ferrichrome-transport pathway in Streptococcus pneumoniae. R-825 inhibited the bacterial growth of S. pneumoniae and stimulated the expression of PiuA, the iron-binding protein in the ferrichrome-uptake system on the cell surface. R-825 treatment decreased the cellular content of iron, accompanying with the increase of Ru(II) level in the bacterium. When the piuA gene (SPD_0915) was deleted in the bacterium, the mutant strain became resistant to R-825 treatment, with decreased content of Ru(II). Addition of ferrichrome can rescue the bacterial growth that was suppressed by R-825. Fluorescence spectral quenching showed that R-825 can bind with PiuA in a similar pattern to the ferrichrome-PiuA interaction in vitro. These observations demonstrated that Ru(II) complex R-825 can compete with ferrichrome for the ferrichrome-transport system to enter S. pneumoniae, reduce the cellular iron supply, and thus suppress the bacterial growth. This finding suggests a novel antimicrobial approach by interfering with iron-uptake pathways, which is different from the mechanisms used by current antibiotics.

Modeling of the Thermoelectric Properties of p-Type IrSb(sub 3)

NASA Technical Reports Server (NTRS)

Fleurial, J.

1994-01-01

IrSb(sub 3) is a compound of the skutterudite family of materials now being investigated at JPL. A combination of experimental and theoretical approaches has been recently applied at JPL to evaluate the potential of several thermoelectric materials such as n-type and p-type Si(sub 80) Ge(sub 20) alloys, n-type and p-type Bi(sub 2) Te(sub 3)-based alloys and p-type Ru(sub 2) Ge(sub 3) compound. The use of a comprehensive model for the thermal and electrical transport properties of a given material over its full temperature range of usefulness is a powerful tool for guiding experimental optimization of the composition, temperature and doping level as well as for predicting the maximum ZT value likely to be achieved.

Uncertainties in nuclear transition matrix elements for neutrinoless {beta}{beta} decay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rath, P. K.

Uncertainties in nuclear transition matrix elements M{sup (0{nu})} and M{sub N}{sup (0{nu})} due to the exchange of light and heavy Majorana neutrinos, respectively have been estimated by calculating sets of twelve nuclear transition matrix elements for the neutrinoless {beta}{beta} decay of {sup 94,96}Zr, {sup 98,100}Mo, {sup 104}Ru, {sup 110}Pd, {sup 128,130}Te and {sup 150}Nd isotopes in the case of 0{sup +}{yields}0{sup +} transition by considering four different parameterizations of a Hamiltonian with pairing plus multipolar effective two-body interaction and three different parameterizations of Jastrow short range correlations. Exclusion of nuclear transition matrix elements calculated with the Miller-Spencer parametrization reduces themore » uncertainties by 10%-15%.« less

Ternary oxide nanostructures and methods of making same

DOEpatents

Wong, Stanislaus S [Stony Brook, NY; Park, Tae-Jin [Port Jefferson, NY

2009-09-08

A single crystalline ternary nanostructure having the formula A.sub.xB.sub.yO.sub.z, wherein x ranges from 0.25 to 24, and y ranges from 1.5 to 40, and wherein A and B are independently selected from the group consisting of Ag, Al, As, Au, B, Ba, Br, Ca, Cd, Ce, Cl, Cm, Co, Cr, Cs, Cu, Dy, Er, Eu, F, Fe, Ga, Gd, Ge, Hf, Ho, I, In, Ir, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Os, P, Pb, Pd, Pr, Pt, Rb, Re, Rh, Ru, S, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Tc, Te, Ti, Tl, Tm, U, V, W, Y, Yb, and Zn, wherein the nanostructure is at least 95% free of defects and/or dislocations.

The Data Base for the May 1979 Marine Surface Layer Micrometeorological Experiment at San Nicolas Island, California.

DTIC Science & Technology

1982-05-07

ATIO VE LOC I TY HUMIDITY TEMP. L ENGTH ClIFF. 72% 7TO 160 4% 53% IS 5% A8t RZ lit 492 29% 23% END Of DATA RIiM 29 MARINE SURFACE LAYER...DRAG NO.AT GMM AlTOIM FL UX FLUX FLUX FL UX FLU X RTATIO VK LOC ITTY HUtMIDITY TEMP. LEN4GTH COE. 160% 161% 116% 167% 128% 9% 124% 295% s8% 109% 71...SCC PSI 90951!4 DRAG; NT, VT "MXT ’tI TIM ELS L X H Sy I 1(09rU F LT PtX ATIO VE LOC ITY ((IIDITIY TE MP. L EM!.TIH ItF 11% (1, .14% Il 195 Tx 5% 2A

Experimental Proof of the Bifunctional Mechanism for the Hydrogen Oxidation in Alkaline Media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jingkun; Ghoshal, Shraboni; Bates, Michael K.

Realization of the hydrogen economy relies on effective hydrogen production, storage, and utilization. The slow kinetics of hydrogen evolution and oxidation reaction (HER/HOR) in alkaline media limits many practical applications involving hydrogen generation and utilization, and how to overcome this fundamental limitation remains debatable. Here we present a kinetic study of the HOR on representative catalytic systems in alkaline media. Electrochemical measurements show that the HOR rate of Pt-Ru/C and Ru/C systems is decoupled to their hydrogen binding energy (HBE), challenging the current prevailing HBE mechanism. The alternative bifunctional mechanism is verified by combined electrochemical and in situ spectroscopic data,more » which provide convincing evidence for the presence of hydroxy groups on surface Ru sites in the HOR potential region and its key role in promoting the rate-determining Volmer step. The conclusion presents important references for design and selection of HOR catalysts.« less

Experimental Proof of the Bifunctional Mechanism for the Hydrogen Oxidation in Alkaline Media

DOE PAGES

Li, Jingkun; Ghoshal, Shraboni; Bates, Michael K.; ...

2017-10-16

Realization of the hydrogen economy relies on effective hydrogen production, storage, and utilization. The slow kinetics of hydrogen evolution and oxidation reaction (HER/HOR) in alkaline media limits many practical applications involving hydrogen generation and utilization, and how to overcome this fundamental limitation remains debatable. Here we present a kinetic study of the HOR on representative catalytic systems in alkaline media. Electrochemical measurements show that the HOR rate of Pt-Ru/C and Ru/C systems is decoupled to their hydrogen binding energy (HBE), challenging the current prevailing HBE mechanism. The alternative bifunctional mechanism is verified by combined electrochemical and in situ spectroscopic data,more » which provide convincing evidence for the presence of hydroxy groups on surface Ru sites in the HOR potential region and its key role in promoting the rate-determining Volmer step. The conclusion presents important references for design and selection of HOR catalysts.« less

Isotopic And Geochemical Investigations Of Meteorites

NASA Technical Reports Server (NTRS)

Walker, Richard J.

2005-01-01

The primary goals of our research over the past four years are to constrain the timing of certain early planetary accretion/differentiation events, and to constrain the proportions and provenance of materials involved in these processes. This work was achieved via the analysis and interpretation of long- and short-lived isotope systems, and the study of certain trace elements. Our research targeted these goals primarily via the application of the Re-187, Os-187, Pt-190 Os-186 Tc-98 Ru-99 and Tc-99 Ru-99 isotopic systems, and the determination/modeling of abundances of the highly siderophile elements (HSE; including Re, Os, Ir, Ru, Pd, Pt, and maybe Tc). The specific events we examined include the segregation and crystallization histories of asteroidal cores, the accretion and metamorphic histories of chondrites and chondrite components, and the accretionary and differentiation histories of Mars and the Moon.

Gamma-ray flare activity from PSR B1259-63 during 2014 Periastron Passage and comparison to its 2010 passage

DOE PAGES

Caliandro, G. A.; Cheung, C. C.; Li, J.; ...

2015-09-22

PSR B1259–63/LS 2883 is a gamma-ray binary system containing a radio pulsar in a highly elliptical ~3.4-year orbit around a Be star. In its 2010 periastron passage, multiwavelength emission from radio to TeV was observed, as well as an unexpected GeV flare measured by the Fermi Large Area Telescope (LAT). We report the results of LAT monitoring of PSR B1259–63 during its most recent 2014 periastron passage. We also compare the gamma-ray behavior in this periastron with the former in 2010 and find that PSR B1259–63 shows a recurrent GeV flare. Furthermore, the similarities and differences in the phenomenology ofmore » both periastron passages are discussed.« less

GAMMA-RAY FLARE ACTIVITY FROM PSR B1259–63 DURING 2014 PERIASTRON PASSAGE AND COMPARISON TO ITS 2010 PASSAGE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caliandro, G. A.; Cheung, C. C.; Wood, K. S.

2015-09-20

PSR B1259–63/LS 2883 is a gamma-ray binary system containing a radio pulsar in a highly elliptical ∼3.4-year orbit around a Be star. In its 2010 periastron passage, multiwavelength emission from radio to TeV was observed, as well as an unexpected GeV flare measured by the Fermi Large Area Telescope (LAT). Here, we report the results of LAT monitoring of PSR B1259–63 during its most recent 2014 periastron passage. We compare the gamma-ray behavior in this periastron with the former in 2010 and find that PSR B1259–63 shows a recurrent GeV flare. The similarities and differences in the phenomenology of bothmore » periastron passages are discussed.« less

Swift, XMM-Newton, and NuSTAR Observations of PSR J2032+4127/MT91 213

NASA Astrophysics Data System (ADS)

Li, K. L.; Kong, A. K. H.; Tam, P. H. T.; Hou, X.; Takata, J.; Hui, C. Y.

2017-07-01

We report our recent Swift, NuSTAR, and XMM-Newton X-ray and Lijiang optical observations on PSR J2032+4127/MT91 213, the γ-ray binary candidate with a period of 45-50 years. The coming periastron of the system was predicted to be in 2017 November, around which high-energy flares from keV to TeV are expected. Recent studies with Chandra and Swift X-ray observations taken in 2015/2016 showed that its X-ray emission has been brighter by a factors of ˜10 than that before 2013, probably revealing some ongoing activities between the pulsar wind and the stellar wind. Our new Swift/XRT lightcurve shows no strong evidence of a single vigorous brightening trend, but rather several strong X-ray flares on weekly to monthly timescales with a slowly brightening baseline, namely the low state. The NuSTAR and XMM-Newton observations taken during the flaring and the low states, respectively, show a denser environment and a softer power-law index during the flaring state, implying that the pulsar wind interacted with the stronger stellar winds of the companion to produce the flares. These precursors would be crucial in studying the predicted giant outburst from this extreme γ-ray binary during the periastron passage in late 2017.

Resposta do detector de ondas gravitacionais Mario Schenberg ao "ringdown" de buraco negros

NASA Astrophysics Data System (ADS)

Costa, C. A.; Aguiar, O. D.; Magalhães, N. S.

2003-08-01

Acredita-se que quando duas estrelas de nêutrons coalescem, elas, eventualmente, formam um buraco negro com massa igual a soma das massas dos objetos originais. Durante a formação do buraco negro, o espaço-tempo em torno do sistema sofre perturbações que se propagam na forma de radiação gravitacional. A forma de onda associada a radiação gravitacional, durante este estágio, aproxima-se a uma senóide exponencialmente amortecida. Este tipo de sinal é conhecido como "ringdown", e seu comportamento e parametrização são muito bem conhecidos. Neste trabalho, simulamos computacionalmente sinais provenientes do "ringdown" de buracos negros, com a finalidade de testar o desempenho do detector de ondas gravitacionais Mario Schenberg em observá-los, quando entrar em funcionamento. Este primeiro teste teórico ajudou-nos a criar estratégias de detecção de sinais imersos no ruído instrumental. Calculamos a relação sinal-ruído como uma função da frequência, bem como sua integral dentro da faixa de sensibilidade do detector. Os resultados obtidos mostraram que o detector Schenberg terá sensibilidade suficiente para detectar este tipo de sinal, proveniente de fontes astrofísicas localizadas dentro de um raio de ~100kpc.

Light-harvesting photocatalysis for water oxidation using mesoporous organosilica.

PubMed

Takeda, Hiroyuki; Ohashi, Masataka; Goto, Yasutomo; Ohsuna, Tetsu; Tani, Takao; Inagaki, Shinji

2014-07-14

An organic-based photocatalysis system for water oxidation, with visible-light harvesting antennae, was constructed using periodic mesoporous organosilica (PMO). PMO containing acridone groups in the framework (Acd-PMO), a visible-light harvesting antenna, was supported with [Ru(II)(bpy)3(2+)] complex (bpy = 2,2'-bipyridyl) coupled with iridium oxide (IrO(x)) particles in the mesochannels as photosensitizer and catalyst, respectively. Acd-PMO absorbed visible light and funneled the light energy into the Ru complex in the mesochannels through excitation energy transfer. The excited state of Ru complex is oxidatively quenched by a sacrificial oxidant (Na2S2O8) to form Ru(3+) species. The Ru(3+) species extracts an electron from IrO(x) to oxidize water for oxygen production. The reaction quantum yield was 0.34 %, which was improved to 0.68 or 1.2 % by the modifications of PMO. A unique sequence of reactions mimicking natural photosystem II, 1) light-harvesting, 2) charge separation, and 3) oxygen generation, were realized for the first time by using the light-harvesting PMO. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determinations of the 12C/13C Ratio for the Secondary Stars of AE Aquarii, SS Cygni, and RU Pegasi

NASA Astrophysics Data System (ADS)

Harrison, Thomas E.; Marra, Rachel E.

2017-07-01

We present new moderate-resolution near-infrared spectroscopy of three CVs obtained using GNIRS on Gemini-North. These spectra covered three 13CO bandheads found in the K-band, allowing us to derive the isotopic abundance ratios for carbon. We find small 12C/13C ratios for all three donor stars. In addition, these three objects show carbon deficits, with AE Aqr being the most extreme ([C/Fe] = -1.4). This result confirms the conjecture that the donor stars in some long-period CVs have undergone considerable nuclear evolution prior to becoming semi-contact binaries. In addition to the results for carbon, we find that the abundance of sodium is enhanced in these three objects, and the secondary stars in both RU Peg and SS Cyg suffer magnesium deficits. Explaining such anomalies appears to require higher mass progenitors than commonly assumed for the donor stars of CVs. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil).

Search for the elusive magnetic state of hexagonal iron: The antiferromagnetic Fe71Ru29 hcp alloy

NASA Astrophysics Data System (ADS)

Petrillo, C.; Postorino, P.; Orecchini, A.; Sacchetti, F.

2018-03-01

The magnetic states of iron and their dependence on crystal structure represent an important case study for the physics of magnetism and its role in fundamental and applied science, including geophysical sciences. hcp iron is the most elusive structure as it exists only at high pressure but, at the same time, it is expected to be stable up to very high temperature. Exploring the magnetic state of pure Fe at high pressure is difficult and no conclusive results have been obtained. Simple binary alloys where the hexagonal phase of Fe is stabilized, offer a more controllable alternative to investigate iron magnetism. We carried out a neutron diffraction experiment on hcp Fe71Ru29 disordered alloy as a function of temperature. Fe in the hexagonal lattice of this specific alloy results to be antiferromagnetically aligned with a rather complex structure and a small magnetic moment. The temperature dependence suggests a Néel temperature TN = 124 ± 10 K, a value consistent with the low magnetic moment of 1.04 ± 0.10 μB obtained from the diffraction data that also suggest a non-commensurate magnetic structure with magnetic moments probably aligned along the c axis. The present data provide evidence for magnetic ordering in hcp Fe and support the theoretical description of magnetism of pure Fe at high pressure.

Albibacter methylovorans gen. nov., sp. nov., a novel aerobic, facultatively autotrophic and methylotrophic bacterium that utilizes dichloromethane.

PubMed

Doronina, N V; Trotsenko, Y A; Tourova, T P; Kuznetsov, B B; Leisinger, T

2001-05-01

A novel genus, Albibacter, with one species, Albibacter methylovorans sp. nov., is proposed for a facultatively chemolithotrophic and methylotrophic bacterium (strain DM10T) with the ribulose bisphosphate (RuBP) pathway of C1 assimilation. The bacterium is a Gram-negative, aerobic, asporogenous, nonmotile, colourless rod that multiplies by binary fission. The organism utilizes dichloromethane, methanol, methylamine, formate and CO2/H2, as well as a variety of polycarbon compounds, as carbon and energy sources. It is neutrophilic and mesophilic. The major cellular fatty acids are straight-chain unsaturated C18:1, saturated C16:0 and cyclopropane C19:0 acids. The main ubiquinone is Q-10. The dominant phospholipids are phosphatidyl ethanolamine, phosphatidyl glycerol, phosphatidyl choline and cardiolipin. The DNA G+C content is 66.7 mol%. Strain DM10T has a very low degree of DNA-DNA hybridization (4-7%) with the type species of the genera Paracoccus, Xanthobacter, Blastobacter, Angulomicrobium, Ancylobacter and Ralstonia of RuBP pathway methylobacteria. Another approach, involving comparative 16S rDNA analysis, has shown that the novel isolate represents a separate branch within the alpha-2 subgroup of the Proteobacteria. The type species of the new genus is Albibacter methylovorans sp. nov.; the type strain is DM10T (= VKM B-2236T = DSM 13819T).

Effect of a Nonplanar Melt-Solid Interface On Lateral Compositional Distribution During Unidirectional Solidification of a Binary Alloy with a Constant Growth Velocity V. Pt. 1; Theory

NASA Technical Reports Server (NTRS)

Wang, Jai-Ching; Watring, D.; Lehoczky. S. L.; Su, C. H.; Gillies, D.; Szofran, F.; Sha, Y. G.; Sha, Y. G.

1999-01-01

Infrared detected materials, such as Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te have energy gaps almost linearly proportional to their composition. Due to the wide separation of liquidus and solidus curves of their phase diagram, there are compositional segregation in both of the axial and radial directions of these crystals grown in the Bridgman system unidirectionally with constant growth rate. It is important to understand the mechanisms, which affect lateral segregation such that large radially uniform composition crystal can be produced. Following Coriel, etc's treatment, we have developed a theory to study the effect of a curved melt-solid interface shape on lateral composition distribution. The model is considered to be a cylindrical system with azimuthal symmetry and a curved melt-solid interface shape which can be expressed as a linear combination of a series of Bessell's functions. The results show that melt-solid interface shape has a dominant effect on the lateral composition distribution of these systems. For small values of beta, the solute concentration at the melt-solid interface scales linearly with interface shape with a proportional constant of the produce of beta and (1 -k), where beta = VR/D, with V as growth velocity, R as the sample radius, D as the diffusion constant and k as the distribution constant. A detailed theory will be presented. A computer code has been developed and simulations have been performed and compared with experimental results. These will be published in another paper.

Evidence that Ribulose 1,5-Bisphosphate (RuBP) Binds to Inactive Sites of RuBP Carboxylase in Vivo and an Estimate of the Rate Constant for Dissociation 1

PubMed Central

Cardon, Zoe G.; Mott, Keith A.

1989-01-01

The binding of ribulose 1,5-bisphosphate (RuBP) to inactive (noncarbamylated) sites of the enzyme RuBP carboxylase in vivo was investigated in Spinacia oleracea and Helianthus annuus. The concentrations of RuBP and inactive sites were determined in leaf tissue as a function of time after a change to darkness. RuBP concentrations fell rapidly after the change to darkness and were approximately equal to the concentration of inactive sites after 60 s. Variations in the concentration of inactive sites, which were induced by differences in the light intensity before the light-dark transition, correlated with the concentration of RuBP between 60 and 120 s after the change to darkness. These data are discussed as evidence that RuBP binds to inactive sites of RuBP carboxylase in vivo. After the concentration of RuBP fell below that of inactive sites (at times longer than 60 s of darkness), the decline in RuBP was logarithmic with time. This would be expected if the dissociation of RuBP from inactive sites controlled the decline in RuBP concentration. These data were used to estimate the rate constant for dissociation of RuBP from inactive sites in vivo. PMID:16666692

RuO2 supported NaY zeolite catalysts: Effect of preparation methods on catalytic performance during aerobic oxidation of benzyl alcohol

NASA Astrophysics Data System (ADS)

Jung, Dasom; Lee, Sunwoo; Na, Kyungsu

2017-10-01

The effects of preparation method for RuO2 supported zeolite catalysts on the catalytic consequences during the aerobic oxidation of benzyl alcohol to benzaldehyde were investigated. Three preparation methods, i.e., (i) simultaneous crystallization of the zeolite framework in the presence of RuCl3 (Ru(SC)/NaY), (ii) post ion-exchange with RuCl3 on the zeolite framework (Ru(IE)/NaY), and (iii) post support of preformed Ru metal nanoparticles on the zeolite surface (Ru(PS)/NaY), were used to construct three different RuO2 supported NaY zeolite catalysts. The catalyst performance was investigated as functions of the reaction time and temperature, in correlation with the structural changes of the catalysts, as analyzed by X-ray diffraction (XRD). The results revealed that the catalytic consequences were dramatically affected by the preparation methods. Although similar conversion was achieved with all three catalysts, the turnover frequency (TOF) differed. The Ru(PS)/NaY catalyst exhibited the highest TOF (33-48 h-1), whereas the other catalysts produced much lower TOFs (9-12 h-1). The Ru(PS)/NaY catalyst also had the highest activation energy (Ea) of 48.39 kJ mol-1, whereas the Ru(SC)/NaY and Ru(IE)/NaY catalysts had Ea values of 18.58 and 24.11 kJ mol-1, respectively. Notably, the Ru(PS)/NaY catalyst yielded a significantly higher pre-exponential factor of 5.22 × 105 h-1, which is about 5 orders of magnitude larger than that of the Ru(SC)/NaY catalyst (7.15 × 100 h-1). This suggests that collision between benzyl alcohol and molecular oxygen was very intensive on the Ru(PS)/NaY catalyst, which explains the higher TOF of the Ru(PS)/NaY catalyst relative to the others in spite of the higher Ea value of the former. In terms of recyclability, the pristine crystallinity of the zeolite framework was maintained in the Ru(SC)/NaY catalyst and the RuO2 phase exhibited an insignificant loss of the initial activity up to three catalytic cycles, whereas Ru(PS)/NaY showed slight loss of activity and Ru(IE)/NaY showed a significant loss of activity due to the disappearance of the RuO2 phase.

Tuning Magnetic Order in Transition Metal Oxide Thin Films

NASA Astrophysics Data System (ADS)

Grutter, Alexander John

In recent decades, one of the most active and promising areas of condensed matter research has been that of complex oxides. With the advent of new growth techniques such as pulsed laser deposition and molecular beam epitaxy, a wealth of new magnetic and electronic ground states have emerged in complex oxide heterostructures. The wide variety of ground states in complex oxides is well known and generally attributed to the unprecedented variety of valence, structure, and bonding available in these systems. The tunability of this already diverse playground of states and interactions is greatly multiplied in thin films and heterostructures by the addition of parameters such as substrate induced strain and interfacial electronic reconstruction. Thus, recent studies have shown emergent properties such as the stabilization of ferromagnetism in a paramagnetic system, conductivity at the interface of two insulators, and even exchange bias at the interface between a paramagnet and a ferromagnet. Despite these steps forward, there remains remarkable disagreement on the mechanisms by which these emergent phenomena are stabilized. The contributions of strain, stoichiometry, defects, intermixing, and electronic reconstruction are often very difficult to isolate in thin films and superlattices. This thesis will present model systems for isolating the effects of strain and interfacial electronic interactions on the magnetic state of complex oxides from alternative contributions. We will focus first on SrRuO3, an ideal system in which to isolate substrate induced strain effects. We explore the effects of structural distortions in the simplest case of growth on (100) oriented substrates. We find that parameters including saturated magnetic moment and Curie temperature are all highly tunable through substrate induced lattice distortions. We also report the stabilization of a nonmagnetic spin-zero configuration of Ru4+ in tetragonally distorted films under tensile strain. Through growth on (110) and (111) oriented substrates we explore the effects of different distortion symmetries on SrRuO3 and demonstrate the first reported strain induced transition to a high-spin state of Ru 4+. Finally, we examine the effects of strain on SrRuO3 thin films and demonstrate a completely reversible universal out-of-plane magnetic easy axis on films grown on different substrate orientations. Having demonstrated the ability to tune nearly every magnetic parameter of SrRuO 3 through strain, we turn to magnetic properties at interfaces. We study the emergent interfacial ferromagnetism in superlattices of the paramagnetic metal CaRuO3 and the antiferromagnetic insulator CaMnO3 and demonstrate that the interfacial ferromagnetic layer in this system is confined to a single unit cell of CaMnO3 at the interface. We discuss the remarkable oscillatory dependence of the saturated magnetic moment on the thickness of the CaMnO3 layers and explore mechanisms by which this oscillation may be stabilized. We find long range coherence of the antiferromagnetism of the CaMnO3 layers across intervening layers of paramagnetic CaRuO3. Finally, we utilize the system of LaNiO3/CaMnO3 to separate the effects of intermixing and interfacial electronic reconstruction and conclusively demonstrate intrinsic interfacial ferromagnetism at the interface between a paramagnetic metal and an antiferromagnetic insulator. We find that the emergent ferromagnetism is stabilized through interfacial double exchange and that the leakage of conduction electrons from the paramagnetic metal to the antiferromagnetic insulator is critical to establishing the ferromagnetic ground state.

Platinum-ruthenium nanotubes and platinum-ruthenium coated copper nanowires as efficient catalysts for electro-oxidation of methanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jie; Cullen, David A.; Forest, Robert V.

2015-01-15

The sluggish kinetics of methanol oxidation reaction (MOR) is a major barrier to the commercialization of direct methanol fuel cells (DMFCs). In this study, we report a facile synthesis of platinum–ruthenium nanotubes (PtRuNTs) and platinum–ruthenium-coated copper nanowires (PtRu/CuNWs) by galvanic displacement reaction using copper nanowires as a template. The PtRu compositional effect on MOR is investigated; the optimum Pt/Ru bulk atomic ratio is about 4 and surface atomic ratio about 1 for both PtRuNTs and PtRu/CuNWs. Enhanced specific MOR activities are observed on both PtRuNTs and PtRu/CuNWs compared with the benchmark commercial carbon-supported PtRu catalyst (PtRu/C, Hispec 12100). Finally, x-raymore » photoelectron spectroscopy (XPS) reveals a larger extent of electron transfer from Ru to Pt on PtRu/CuNWs, which may lead to a modification of the d-band center of Pt and consequently a weaker bonding of CO (the poisoning intermediate) on Pt and a higher MOR activity on PtRu/CuNWs.« less

Adsorption of n-butane on graphene/Ru(0001)—A molecular beam scattering study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sivapragasam, Nilushni; Nayakasinghe, Mindika T.; Burghaus, Uwe, E-mail: uwe.burghaus@ndsu.edu

2016-07-15

Adsorption kinetics/dynamics of n-butane on graphene, physical vapor deposited on Ru(0001) (hereafter G/Ru), and bare Ru(0001) (hereafter Ru) are discussed. The chemical activity of the supported-graphene as well as the support was probed by thermal desorption spectroscopy (adsorption kinetics). In addition and to the best of our knowledge, for the first time, molecular beam scattering data of larger molecules were collected for graphene (probing the adsorption dynamics). Furthermore, samples were inspected by x-ray photoelectron spectroscopy and Auger electron spectroscopy. At the measuring conditions used here, n-butane adsorption kinetics/dynamics are molecular and nonactivated. Binding energies of butane on Ru and G/Rumore » are indistinguishable within experimental uncertainty. Thus, G/Ru is “kinetically transparent.” Initial adsorption probabilities, S{sub 0}, of n-butane decrease with increasing impact energy (0.76–1.72 eV) and are adsorption temperature independent for both Ru and G/Ru, again consistent with molecular adsorption. Also, S{sub 0} of Ru and G/Ru are indistinguishable within experimental uncertainty. Thus, G/Ru is “dynamically transparent.” Coverage dependent adsorption probabilities indicate precursor effects for graphene/Ru.« less

The Ruinous Influence of Close Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Mann, Andrew; Huber, Daniel; Dupuy, Trent J.

2017-01-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. When the binary population is parametrized with a semimajor axis cutoff a cut and a suppression factor inside that cutoff S bin, we find with correlated uncertainties that inside acut = 47 +59/-23 AU, the planet occurrence rate in binary systems is only Sbin = 0.34 +0.14/-0.15 times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion.

The Ruinous Influence of Close Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Mann, Andrew; Huber, Daniel; Dupuy, Trent J.

2017-06-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. When the binary population is parametrized with a semimajor axis cutoff a cut and a suppression factor inside that cutoff S bin, we find with correlated uncertainties that inside acut = 47 +59/-23 AU, the planet occurrence rate in binary systems is only Sbin = 0.34+0.14/-0.15 times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion.

Development and Application of Operando TEM to a Ruthenium Catalyst for CO Oxidation

NASA Astrophysics Data System (ADS)

Miller, Benjamin Kyle

Operando transmission electron microscopy (TEM) is an extension of in-situ TEM in which the performance of the material being observed is measured simultaneously. This is of great value, since structure-performance relationships lie at the heart of materials science. For catalyst materials, like the SiO2-supported Ru nanoparticles studied, the important performance metric, catalyst activity, is measured inside the microscope by determining the gas composition during imaging. This is accomplished by acquisition of electron energy loss spectra (EELS) of the gas in the environmental TEM while catalysis is taking place. In this work, automated methods for rapidly quantifying low-loss and core-loss EELS of gases were developed. A new sample preparation method was also established to increase catalytic conversion inside a differentially-pumped environmental TEM, and the maximum CO conversion observed was about 80%. A system for mixing gases and delivering them to the environmental TEM was designed and built, and a method for locating and imaging nanoparticles in zone axis orientations while minimizing electron dose rate was determined. After atomic resolution images of Ru nanoparticles observed during CO oxidation were obtained, the shape and surface structures of these particles was investigated. A Wulff model structure for Ru particles was compared to experimental images both by manually rotating the model, and by automatically determining a matching orientation using cross-correlation of shape signatures. From this analysis, it was determined that most Ru particles are close to Wulff-shaped during CO oxidation. While thick oxide layers were not observed to form on Ru during CO oxidation, thin RuO2 layers on the surface of Ru nanoparticles were imaged with atomic resolution for the first time. The activity of these layers is discussed in the context of the literature on the subject, which has thus far been inconclusive. We conclude that disordered oxidized ruthenium, rather than crystalline RuO2 is the most active species.

Synthesis of 4‧-substituted-2,2‧;6‧,2″-terpyridine Ru(II) complexes electrochemical, fluorescence quenching and antibacterial studies

NASA Astrophysics Data System (ADS)

Ezhilarasu, Tamilarasu; Sathiyaseelan, Anbazhagan; Kalaichelvan, Pudupalayam Thangavelu; Balasubramanian, Sengottuvelan

2017-04-01

Three new Ru(II) terpyridine complexes viz. [Ru(BBtpy)2](PF6)2 [Ru(L1)] (BBtpy = 4‧-(4-benzyloxybenzaldehyde)-2,2‧:6‧,2″-terpyridine), [Ru(BMBtpy)2](PF6)2 [Ru(L2)] (BMBtpy = 4‧-(4-benzyloxy-3-methoxybenzaldehyde)-2,2‧:6‧,2″-terpyridine) and [Ru(BEBtpy)2](PF6)2 [Ru(L3)] (BEBtpy = 4‧-(4-benzyloxy-3-ethoxybenzaldehyde)-2,2‧:6‧,2″-terpyridine) have been synthesized and characterized. The MALDI-TOF/MS fragmentation pattern of [Ru(BMBtpy)2](PF6)2 complex exhibits a molecular ion peak at m/z = 987.09 [M-2PF6]2+ fragment. These Ru(II) complexes are redox active, show both metal centered oxidation and ligand centered reduction processes. The peak potential and peak current Ipa and Ipc also undergo definite shift and increase with increase in the scan rate (20-120 mV/s). The fluorescence of Ru(II) complexes [Ru(L1)], [Ru(L2)] and [Ru(L3)] are effectively quenched by 1,4-benzoquinone and 1,4-naphthoquinone in acetonitrile. The antibacterial activity of ruthenium(II) complexes were screened against four human pathogens both gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) and gram negative bacteria (Escherichia coli, Klebsiella pneumonia) by the well diffusion method. The antibacterial activity of Ru(II) complexes is comparable to that of standard antibiotics like tetracycline.

Synthesis of Pd 9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yu; Hsieh, Yu -Chi; Chang, Li -Chung

2014-11-22

Nanoparticles of PdRu, Pd₃Ru, and Pd₉Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, Pd xRu/C (x=1/3/9), suggest succesful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of Pd xRu/C. Among these samples, the Pd₉Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in anmore » oxygen-saturated 0.1 M aqueous HClO₄ solution. Subsequently, the Pd₉Ru/C undegoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd₉Ru surface (Pd₉Ru@Pt). The Pd₉Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA μg⁻¹ Pt, as compared to that of commercially available Pt nanoparticles (0.107 mA μg⁻¹ Pt). Thus, the mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd₉Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost.« less

Synthesis of Pd9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes

NASA Astrophysics Data System (ADS)

Sun, Yu; Hsieh, Yu-Chi; Chang, Li-Chung; Wu, Pu-Wei; Lee, Jyh-Fu

2015-03-01

Nanoparticles of PdRu, Pd3Ru, and Pd9Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, PdxRu/C (x = 1/3/9), suggest successful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of PdxRu/C. Among these samples, the Pd9Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in an oxygen-saturated 0.1 M aqueous HClO4 solution. Subsequently, the Pd9Ru/C undergoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd9Ru surface (Pd9Ru@Pt). The Pd9Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA μg-1Pt, as compared to that of commercially available Pt nanoparticles (0.107 mA μg-1Pt). The mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd9Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost.

Valuation Diagramming and Accounting of Transactive Energy Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makhmalbaf, Atefe; Hammerstrom, Donald J.; Huang, Qiuhua

Transactive energy (TE) systems support both economic and technical objectives of a power system including efficiency and reliability. TE systems utilize value-driven mechanisms to coordinate and balance responsive supply and demand in the power system. Economic performance of TE systems cannot be assessed without estimating their value. Estimating the potential value of transactive energy systems requires a systematic valuation methodology that can capture value exchanges among different stakeholders (i.e., actors) and ultimately estimate impact of one TE design and compare it against another one. Such a methodology can help decision makers choose the alternative that results in preferred outcomes. Thismore » paper presents a valuation methodology developed to assess value of TE systems. A TE use-case example is discussed, and metrics identified in the valuation process are quantified using a TE simulation program.« less

Exploring the color of transition metal ions in irregular coordination geometries: new colored inorganic oxides based on the spiroffite structure, Zn(2-x)M(x)Te3O8 (M = Co, Ni, Cu).

PubMed

Tamilarasan, S; Sarma, Debajit; Bhattacharjee, S; Waghmare, U V; Natarajan, S; Gopalakrishnan, J

2013-05-20

We describe the synthesis, crystal structures, and optical absorption spectra of transition metal-substituted spiroffite derivatives, Zn(2-x)M(x)Te3O8 (M(II) = Co, Ni, Cu; 0 < x ≤ 1.0). The oxides are readily synthesized by solid state reaction of stoichiometric mixtures of the constituent binaries at 620 °C. Reitveld refinement of the crystal structures from powder X-ray diffraction (XRD) data shows that the Zn/MO6 octahedra are strongly distorted, as in the parent Zn2Te3O8 structure, consisting of five relatively short Zn/M(II)-O bonds (1.898-2.236 Å) and one longer Zn/M(II)-O bond (2.356-2.519 Å). We have interpreted the unique colors and the optical absorption/diffuse reflectance spectra of Zn(2-x)M(x)Te3O8 in the visible, in terms of the observed/irregular coordination geometry of the Zn/M(II)-O chromophores. We could not however prepare the fully substituted M2Te3O8 (M(II) = Co, Ni, Cu) by the direct solid state reaction method. Density Functional Theory (DFT) modeling of the electronic structure of both the parent and the transition metal substituted derivatives provides new insights into the bonding and the role of transition metals toward the origin of color in these materials. We believe that transition metal substituted spiroffites Zn(2-x)M(x)Te3O8 reported here suggest new directions for the development of colored inorganic materials/pigments featuring irregular/distorted oxygen coordination polyhedra around transition metal ions.

Long-Range Intramolecular Electronic Communication in a Trinuclear Ruthenium Tropolonate Complex.

PubMed

Yoshida, Jun; Kuwahara, Kyohei; Suzuki, Kota; Yuge, Hidetaka

2017-02-20

Dinuclear and trinuclear ruthenium complexes, [Ru(trop) 2 (C 2 trop)Ru(dppe)Cp] [2b; trop = tropolonato, C 2 trop = ethynyltropolonato, dppe = 1,2-bis(diphenylphosphino)ethane] and [Ru(trop){(C 2 trop)Ru(dppe)Cp} 2 ] (3), were synthesized, and their electronic and electrochemical properties were investigated in comparison with our previously reported complex [Ru(acac) 2 (C 2 trop)Ru(dppe)Cp] (2a). The electron-donating Ru II (dppe)Cp unit and electron-accepting Ru III O 6 unit are connected by C 2 trop in these complexes. 2a incorporates acetylacetonate as an ancillary ligand, while 2b and 3 incorporate tropolonate as an ancillary ligand. Every complex, 2a, 2b, and 3, exhibits similar UV-vis-near-IR (NIR) absorption spectra, demonstrating the lack of explicit intramolecular electronic communication between the units at least in the neutral state. The weak NIR absorption in 2a further diminished upon electrochemical oxidation, indicating almost no electronic communication between the units. In contrast, 2b and 3 exhibit broad NIR absorptions upon oxidation. Additionally, 3 exhibits four stepwise redox couples in the electrochemical study, which are formally attributed to [Ru II (trop) 3 ] - /[Ru III (trop) 3 ], two [Ru II (dppe)Cp]/[Ru III (dppe)Cp] + , and [Ru III (trop) 3 ]/[Ru IV (trop) 3 ] + couples. Clear separation of the redox couples attributed to the two terminal [Ru(dppe)Cp] units demonstrates the thermodynamic stability of the intermediate oxidation states with respect to disproportionation. Further electrochemical studies using an electrolyte including perfluorinated weakly coordinating anions and density functional theory/time-dependent density functional theory calculations confirmed the effect of ancillary ligands, acetylacetonate and tropolonate. In the case of 2a, electronic delocalization over the whole complex, especially over the [Ru(acac) 2 (trop)] unit, appears to be small. In contrast, the electronic communication between [Ru(dppe)Cp] and [Ru(trop) 3 ] units in 3 seems to be enhanced upon oxidation, resulting in the long-range intramolecular electronic communication.

Surface-enhanced molecularly imprinted electrochemiluminescence sensor based on Ru@SiO2 for ultrasensitive detection of fumonisin B1.

PubMed

Zhang, Wei; Xiong, Huiwen; Chen, Miaomiao; Zhang, Xiuhua; Wang, Shengfu

2017-10-15

A novel molecularly imprinted electrochemiluminescence (MIP-ECL) sensor based on Ru(bpy) 3 2+ -doped silica nanoparticles (Ru@SiO 2 NPs) is developed for highly sensitive detection of fumonisin B 1 (FB 1 ). Gold-nanoparticles (AuNPs), Ru@SiO 2 NPs with chitosan (CS) composites and a molecularly imprinted polymer (MIP) are assembled on a glassy carbon electrode (GCE) to fabricate an ECL platform step by step. AuNPs could greatly promote the ECL intensity and improve the analytical sensitivity according to the localized surface plasmon resonance (LSPR) and the electrochemical effect. In this surface-enhanced electrochemiluminescence (SEECL) system, AuNPs work as the LSPR source to improve the ECL intensity and Ru@SiO 2 NPs are used as ECL luminophores. In the phosphate buffer solution (PBS), the evident anodic ECL of Ru@SiO 2 on the above working electrode is observed in the presence of the template molecule fumonisin B 1 (FB 1 ), which could act as the coreactant of Ru@SiO 2 NPs due to the amino group of FB 1 . When the template molecules were eluted from the MIP, little coreactant was left, resulting in an apparent decrease of ECL signal. After the MIP-ECL sensor was incubated in FB 1 solution, the template molecules rebound to the MIP surface, leading to the enhancement of ECL signal again. On the basis of these results, a facile MIP-ECL sensor has been successfully fabricated, which exhibited a linear range from 0.001 to 100ngmL -1 with a detection limit of 0.35pgmL -1 for FB 1 . Moreover, the proposed MIP-ECL sensor displayed an excellent application in real samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Radial Mixing and Ru-Mo Isotope Systematics Under Different Accretion Scenarios

NASA Astrophysics Data System (ADS)

Fischer, R. A.; Nimmo, F.; O'Brien, D. P.

2017-12-01

The Ru-Mo isotopic compositions of inner Solar System bodies may reflect the provenance of accreted material and how it evolved with time, both of which are controlled by the accretion scenario these bodies experienced. Here we use a total of 116 N-body simulations of terrestrial planet accretion, run in the Eccentric Jupiter and Saturn (EJS), Circular Jupiter and Saturn (CJS), and Grand Tack scenarios, to model the Ru-Mo anomalies of Earth, Mars, and Theia analogues. This model starts by applying an initial step function in Ru-Mo isotopic composition, with compositions reflecting those in meteorites, and traces compositional evolution as planets accrete. The mass-weighted provenance of the resulting planets reveals more radial mixing in Grand Tack simulations than in EJS/CJS simulations, and more efficient mixing among late-accreted material than during the main phase of accretion in EJS/CJS simulations. We find that an extensive homogenous inner disk region is required to reproduce Earth's observed Ru-Mo composition. EJS/CJS simulations require a homogeneous reservoir in the inner disk extending to ≥3-4 AU (≥74-98% of initial mass) to reproduce Earth's composition, while Grand Tack simulations require a homogeneous reservoir extending to ≥3-10 AU (≥97-99% of initial mass), and likely to ≥7-10 AU. In the Grand Tack model, Jupiter's initial location (the most likely location for a discontinuity in isotopic composition) is 3.5 AU; however, this step location has only a 33% likelihood of producing an Earth with the correct Ru-Mo isotopic signature for the most plausible model conditions. Our results give the testable predictions that Mars has zero Ru anomaly and small or zero Mo anomaly, and the Moon has zero Mo anomaly. These predictions are insensitive to wide variations in parameter choices.

Particle size dependence of CO tolerance of anode PtRu catalysts for polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Yamanaka, Toshiro; Takeguchi, Tatsuya; Wang, Guoxiong; Muhamad, Ernee Noryana; Ueda, Wataru

An anode catalyst for a polymer electrolyte fuel cell must be CO-tolerant, that is, it must have the function of hydrogen oxidation in the presence of CO, because hydrogen fuel gas generated by the steam reforming process of natural gas contains a small amount of CO. In the present study, PtRu/C catalysts were prepared with control of the degree of Pt-Ru alloying and the size of PtRu particles. This control has become possible by a new method of heat treatment at the final step in the preparation of catalysts. The CO tolerances of PtRu/C catalysts with the same degree of Pt-Ru alloying and with different average sizes of PtRu particles were thus compared. Polarization curves were obtained with pure H 2 and CO/H 2 (CO concentrations of 500-2040 ppm). It was found that the CO tolerance of highly dispersed PtRu/C (high dispersion (HD)) with small PtRu particles was much higher than that of poorly dispersed PtRu/C (low dispersion (LD)) with large metal particles. The CO tolerance of PtRu/C (HD) was higher than that of any commercial PtRu/C. The high CO tolerance of PtRu/C (HD) is thought to be due to efficient concerted functions of Pt, Ru, and their alloy.

The disruption of multiplanet systems through resonance with a binary orbit.

PubMed

Touma, Jihad R; Sridhar, S

2015-08-27

Most exoplanetary systems in binary stars are of S-type, and consist of one or more planets orbiting a primary star with a wide binary stellar companion. Planetary eccentricities and mutual inclinations can be large, perhaps forced gravitationally by the binary companion. Earlier work on single planet systems appealed to the Kozai-Lidov instability wherein a sufficiently inclined binary orbit excites large-amplitude oscillations in the planet's eccentricity and inclination. The instability, however, can be quenched by many agents that induce fast orbital precession, including mutual gravitational forces in a multiplanet system. Here we report that orbital precession, which inhibits Kozai-Lidov cycling in a multiplanet system, can become fast enough to resonate with the orbital motion of a distant binary companion. Resonant binary forcing results in dramatic outcomes ranging from the excitation of large planetary eccentricities and mutual inclinations to total disruption. Processes such as planetary migration can bring an initially non-resonant system into resonance. As it does not require special physical or initial conditions, binary resonant driving is generic and may have altered the architecture of many multiplanet systems. It can also weaken the multiplanet occurrence rate in wide binaries, and affect planet formation in close binaries.

IMPACT OF Ce DOPING ON THE MAGNETIC AND TRANSPORT PROPERTIES OF Y1-xCexSr2Ru0.9Cu2.1O7.9; x = 0.05 AND 0.1

NASA Astrophysics Data System (ADS)

Balamurugan, S.

2012-11-01

The magnetic and transport properties of lightly Ce doped, Y1-xCexSr2Ru0.9Cu2.1 O7.9(x = 0.05 and 0.1) samples have been studied and their results are compared with the pristine rutheno-cuprate, YSr2Ru0.9Cu2.1O7.9. The electron doping due to Ce4+ for Y3+ ion impacts on the physical properties of the present system. The tetragonal stabilized samples exhibit magneto superconducting properties under zero field cooled condition (H = 10 Oe) and the diamagnetic onset transition, Td shift slightly towards higher temperature with the increase of "x". Weak antiferromagnetic like hysteresis curves are seen for these samples at 2 K in the magnetic field strength up to ±10 kOe and the magnetization moment, M(μB/Ru) decreases with increase of "x". While the magnetic property of the present system is due to canted Ru moments, the superconducting signal originates from CuO2 plane. Through electrical resistivity measurements we observe that none of the samples exhibit bulk superconductivity down to 2 K. However the x = 0.05 sample reveals lowest resistivity in the entire temperature range than x = 0 and 0.1 samples. The isothermal magnetoresistance, MR(H) measured at different temperatures vary with tuning of "x". While x = 0.1 doped sample shows lower -MR( 8%), the pristine sample exhibits maximum -MR(45%) at 2 K under ±90 kOe field condition.

Ultrasensitive electrochemiluminescent aptasensor for ochratoxin A detection with the loop-mediated isothermal amplification.

PubMed

Yuan, Yali; Wei, Shiqiang; Liu, Guangpeng; Xie, Shunbi; Chai, Yaqin; Yuan, Ruo

2014-02-06

In this study, we for the first time presented an efficient, accurate, rapid, simple and ultrasensitive detection system for small molecule ochratoxin A (OTA) by using the integration of loop-mediated isothermal amplification (LAMP) technique and subsequently direct readout of LAMP amplicons with a signal-on electrochemiluminescent (ECL) system. Firstly, the dsDNA composed by OTA aptamer and its capture DNA were immobilized on the electrode. After the target recognition, the OTA aptamer bond with target OTA and subsequently left off the electrode, which effectively decreased the immobilization amount of OTA aptamer on electrode. Then, the remaining OTA aptamers on the electrode served as inner primer to initiate the LAMP reaction. Interestingly, the LAMP amplification was detected by monitoring the intercalation of DNA-binding Ru(phen)3(2+) ECL indictors into newly formed amplicons with a set of integrated electrodes. The ECL indictor Ru(phen)3(2+) binding to amplicons caused the reduction of the ECL intensity due to the slow diffusion of Ru(phen)3(2+)-amplicons complex to the electrode surface. Therefore, the presence of more OTA was expected to lead to the release of more OTA aptamer, which meant less OTA aptamer remained on electrode for producing LAMP amplicons, resulting in less Ru(phen)3(2+) interlaced into the formed amplicons within a fixed Ru(phen)3(2+) amount with an obviously increased ECL signal input. As a result, a detection limit as low as 10 fM for OTA was achieved. The aptasensor also has good reproducibility and stability. Copyright © 2013 Elsevier B.V. All rights reserved.

The effect of coating patterns with spinel-based investment on the castability and porosity of titanium cast into three phosphate-bonded investments.

PubMed

Pieralini, Anelise R F; Benjamin, Camila M; Ribeiro, Ricardo Faria; Scaf, Gulnara; Adabo, Gelson Luis

2010-10-01

This study evaluated the effect of pattern coating with spinel-based investment Rematitan Ultra (RU) on the castability and internal porosity of commercially pure (CP) titanium invested into phosphate-bonded investments. The apparent porosity of the investment was also measured. Square patterns (15 × 15 × 0.3 mm(3)) were either coated with RU, or not and invested into the phosphate-bonded investments: Rematitan Plus (RP), Rema Exakt (RE), Castorit Super C (CA), and RU (control group). The castings were made in an Ar-arc vacuum-pressure machine. The castability area (mm(2) ) was measured by an image-analysis system (n = 10). For internal porosity, the casting (12 × 12 × 2 mm(3) ) was studied by the X-ray method, and the projected porous area percentage was measured by an image-analysis system (n = 10). The apparent porosity of the investment (n = 10) was measured in accordance with the ASTM C373-88 standard. Analysis of variance (One-way ANOVA) of castability was significant, and the Tukey test indicated that RU had the highest mean but the investing technique with coating increased the castability for all phosphate-bonded investments. The analysis of the internal porosity of the cast by the nonparametric test demonstrated that the RP, RE, and CA with coating and RP without coating did not differ from the control group (RU), while the CA and RE casts without coating were more porous. The one-way ANOVA of apparent porosity of the investment was significant, and the Tukey test showed that the means of RU (36.10%) and CA (37.22%) were higher than those of RP (25.91%) and RE (26.02%). Pattern coating with spinel-based material prior to phosphate-bonded investments can influence the castability and the internal porosity of CP Ti. © 2010 by The American College of Prosthodontists.

Light-Induced Activation of a Molybdenum Oxotransferase Model within a Ru(II)-Mo(VI) Dyad.

PubMed

Ducrot, Aurélien B; Coulson, Ben A; Perutz, Robin N; Duhme-Klair, Anne-Kathrin

2016-12-19

Nature uses molybdenum-containing enzymes to catalyze oxygen atom transfer (OAT) from water to organic substrates. In these enzymes, the two electrons that are released during the reaction are rapidly removed, one at a time, by spatially separated electron transfer units. Inspired by this design, a Ru(II)-Mo(VI) dyad was synthesized and characterized, with the aim of accelerating the rate-determining step in the cis-dioxo molybdenum-catalyzed OAT cycle, the transfer of an oxo ligand to triphenyl phosphine, via a photo-oxidation process. The dyad consists of a photoactive bis(bipyridyl)-phenanthroline ruthenium moiety that is covalently linked to a bioinspired cis-dioxo molybdenum thiosemicarbazone complex. The quantum yield and luminescence lifetimes of the dyad [Ru(bpy) 2 (L 2 )MoO 2 (solv)] 2+ were determined. The major component of the luminescence decay in MeCN solution (τ = 1149 ± 2 ns, 67%) corresponds closely to the lifetime of excited [Ru(bpy) 2 (phen-NH 2 )] 2+ , while the minor component (τ = 320 ± 1 ns, 31%) matches that of [Ru(bpy) 2 (H 2 -L 2 )] 2+ . In addition, the (spectro)electrochemical properties of the system were investigated. Catalytic tests showed that the dyad-catalyzed OAT from dimethyl sulfoxide to triphenyl phosphine proceeds significantly faster upon irradiation with visible light than in the dark. Methylviologen acts as a mediator in the photoredox cycle, but it is regenerated and hence only required in stoichiometric amounts with respect to the catalyst rather than sacrificial amounts. It is proposed that oxidative quenching of the photoexcited Ru unit, followed by intramolecular electron transfer, leads to the production of a reactive one-electron oxidized catalyst, which is not accessible by electrochemical methods. A significant, but less pronounced, rate enhancement was observed when an analogous bimolecular system was tested, indicating that intramolecular electron transfer between the photosensitizer and the catalytic center is more efficient than intermolecular electron transfer between the separate components.

Additive effects of growth promoting technologies on performance of grazing steers and economics of the wheat pasture enterprise.

PubMed

Beck, P; Hess, T; Hubbell, D; Hufstedler, G D; Fieser, B; Caldwell, J

2014-03-01

This research was designed to evaluate the effect of monensin (Elanco Animal Health, Greenfield, IN) supplementation via mineral or pressed protein block with or without a growth-promoting implant on performance of steers grazing wheat pasture in Arkansas over 2 yr. Preconditioned steers (n = 360, BW = 238 ± 5.1 kg) grazed 15 1.6-ha wheat pastures in the fall (n = 60 steers each fall, stocking rate of 2.5 steers/ha) or 30 0.8-ha wheat pastures in the spring (n = 120 steers each spring, stocking rate of 5 steers/ha). Steers in each pasture were given free-choice access to nonmedicated mineral (CNTRL; MoorMan's WeatherMaster Range Minerals A 646AAA; ADM Alliance Nutrition, Inc., Quincy, IL), or were supplemented with monensin (Elanco Animal Health, Greenfield, IN) via mineral containing 1.78 g monensin/kg (RMIN; MoorMan's Grower Mineral RU-1620 590AR; ADM Alliance Nutrition, Inc.), or pressed protein block containing 0.33 g monensin/kg (RBLCK; MoorMan's Mintrate Blonde Block RU; ADM Alliance Nutrition, Inc.). Additionally, one-half of the steers in each pasture were implanted (IMPL) with 40 mg trenbolone acetate and 8 mg estradiol (Component TE-G with Tylan; Elanco Animal Health). There was no interaction (P ≥ 0.71) between supplement treatment and growth-promoting implants, and ADG for RMIN and RBLCK were increased (P < 0.01) over CNTRL by 0.07 to 0.09 kg/d, respectively. Implanting steers with Component TE-G increased (P < 0.01) ADG by 0.14 kg/d. The combination of these growth-promoting technologies are a cost-effective means of increasing beef production by 22% without increasing level of supplementation or pasture acreage. Utilizing ionophores and implants together for wheat pasture stocker cattle decreased cost of gain by 26%. Utilizing both IMPL and monensin increased net return by $30 to $54/steer for RMIN or $18 to $43/steer for RBLCK compared with UNIMPL CNTRL at Low and High values of BW gain, respectively.

Unipro UGENE: a unified bioinformatics toolkit.

PubMed

Okonechnikov, Konstantin; Golosova, Olga; Fursov, Mikhail

2012-04-15

Unipro UGENE is a multiplatform open-source software with the main goal of assisting molecular biologists without much expertise in bioinformatics to manage, analyze and visualize their data. UGENE integrates widely used bioinformatics tools within a common user interface. The toolkit supports multiple biological data formats and allows the retrieval of data from remote data sources. It provides visualization modules for biological objects such as annotated genome sequences, Next Generation Sequencing (NGS) assembly data, multiple sequence alignments, phylogenetic trees and 3D structures. Most of the integrated algorithms are tuned for maximum performance by the usage of multithreading and special processor instructions. UGENE includes a visual environment for creating reusable workflows that can be launched on local resources or in a High Performance Computing (HPC) environment. UGENE is written in C++ using the Qt framework. The built-in plugin system and structured UGENE API make it possible to extend the toolkit with new functionality. UGENE binaries are freely available for MS Windows, Linux and Mac OS X at http://ugene.unipro.ru/download.html. UGENE code is licensed under the GPLv2; the information about the code licensing and copyright of integrated tools can be found in the LICENSE.3rd_party file provided with the source bundle.

A New Class of Ternary Compound for Lithium-Ion Battery: from Composite to Solid Solution.

PubMed

Wang, Jiali; Wu, Hailong; Cui, Yanhua; Liu, Shengzhou; Tian, Xiaoqing; Cui, Yixiu; Liu, Xiaojiang; Yang, Yin

2018-02-14

Searching for high-performance cathode materials is a crucial task to develop advanced lithium-ion batteries (LIBs) with high-energy densities for electrical vehicles (EVs). As a promising lithium-rich material, Li 2 MnO 3 delivers high capacity over 200 mAh g -1 but suffers from poor structural stability and electronic conductivity. Replacing Mn 4+ ions by relatively larger Sn 4+ ions is regarded as a possible strategy to improve structural stability and thus cycling performance of Li 2 MnO 3 material. However, large difference in ionic radii of Mn 4+ and Sn 4+ ions leads to phase separation of Li 2 MnO 3 and Li 2 SnO 3 during high-temperature synthesis. To prepare solid-solution phase of Li 2 MnO 3 -Li 2 SnO 3 , a buffer agent of Ru 4+ , whose ionic radius is in between that of Mn 4+ and Sn 4+ ions, is introduced to assist the formation of a single solid-solution phase. The results show that the Li 2 RuO 3 -Li 2 MnO 3 -Li 2 SnO 3 ternary system evolves from mixed composite phases into a single solid-solution phase with increasing Ru content. Meanwhile, discharge capacity of this ternary system shows significantly increase at the transformation point which is ascribed to the improvement of Li + /e - transportation kinetics and anionic redox chemistry for solid-solution phase. The role of Mn/Sn molar ratio of Li 2 RuO 3 -Li 2 MnO 3 -Li 2 SnO 3 ternary system has also been studied. It is revealed that higher Sn content benefits cycling stability of the system because Sn 4+ ions with larger sizes could partially block the migration of Mn 4+ and Ru 4+ from transition metal layer to Li layer, thus suppressing structural transformation of the system from layered-to-spinel phase. These findings may enable a new route for exploring ternary or even quaternary lithium-rich cathode materials for LIBs.

Terrestrial Planet Formation in Binary Star Systems

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Quintana, Elisa V.; Chambers, John; Duncan, Martin J.; Adams, Fred

2003-01-01

Most stars reside in multiple star systems; however, virtually all models of planetary growth have assumed an isolated single star. Numerical simulations of the collapse of molecular cloud cores to form binary stars suggest that disks will form within such systems. Observations indirectly suggest disk material around one or both components within young binary star systems. If planets form at the right places within such circumstellar disks, they can remain in stable orbits within the binary star systems for eons. We are simulating the late stages of growth of terrestrial planets within binary star systems, using a new, ultrafast, symplectic integrator that we have developed for this purpose. We show that the late stages of terrestrial planet formation can indeed take place in a wide variety of binary systems and we have begun to delineate the range of parameter space for which this statement is true. Results of our initial simulations of planetary growth around each star in the alpha Centauri system and other 'wide' binary systems, as well as around both stars in very close binary systems, will be presented.

When ruthenia met titania: Achieving extraordinary catalytic activity at low temperature by nanostructuring of oxides

DOE PAGES

Graciani, J.; Stacchiola, D.; Yang, F.; ...

2015-09-09

Nanostructured RuO x/TiO 2(110) catalysts have a remarkable catalytic activity for CO oxidation at temperatures in the range of 350–375 K. Furthermore, the RuO 2(110) surface has no activity. The state-of-the-art DFT calculations indicate that the main reasons for such an impressive improvement in the catalytic activity are: (i) a decrease of the diffusion barrier of adsorbed O atoms by around 40%, from 1.07 eV in RuO 2(110) to 0.66 eV in RuO x/TiO 2(110), which explains the shift of the activity to lower temperatures and (ii) a lowering of the barrier by 20% for the association of adsorbed COmore » and O species to give CO 2 (the main barrier for the CO oxidation reaction) passing from around 0.7 eV in RuO 2(110) to 0.55 eV in RuO x/TiO 2(110). We show that the catalytic properties of ruthenia are strongly modified when supported as nanostructures on titania, attaining higher activity at temperatures 100 K lower than that needed for pure ruthenia. As in other systems consisting of ceria nanostructures supported on titania, nanostructured ruthenia shows strongly modified properties compared to the pure oxide, consolidating the fact that the nanostructuring of oxides is a main way to attain higher catalytic activity at lower temperatures.« less

Substituent-directed structural and physicochemical controls of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

PubMed

Chang, Ho-Chol; Mochizuki, Katsunori; Kitagawa, Susumu

2005-05-30

A family of diruthenium complexes with ligand-unsupported Ru-Ru bonds has been systematically synthesized, and their crystal structures and physical properties have been examined. A simple, useful reaction between Ru2(OAc)4Cl (OAc- = acetate) and catechol derivatives in the presence of bases afforded a variety of diruthenium complexes, generally formulated as [Na(n){Ru2(R4Cat)4}] (n = 2 or 3; R4 = -F4, -Cl4, -Br4, -H4, -3,5-di-t-Bu, and -3,6-di-t-Bu; Cat(2-) = catecholate). The most characteristic feature of the complexes is the formation of short ligand-unsupported Ru-Ru bonds (2.140-2.273 A). These comprehensive studies were carried out to evaluate the effects of the oxidation states and the substituents governing the molecular structures and physicochemical properties. The Ru-Ru bond distances, rotational conformations, and bending structures of the complexes were successfully varied. The results presented in this manuscript clearly demonstrate that the complexes with ligand-unsupported Ru-Ru bonds can sensitively respond to redox reactions and ligand substituents on the basis of the greater degree of freedom in their molecular structures.

Heterobimetallic Nitrido Complexes of Group 8 Metalloporphyrins.

PubMed

Cheung, Wai-Man; Chiu, Wai-Hang; de Vere-Tucker, Matthew; Sung, Herman H-Y; Williams, Ian D; Leung, Wa-Hung

2017-05-15

Heterobimetallic nitrido porphyrin complexes with the [(L)(por)M-N-M'(L OEt )Cl 2 ] formula {por 2- = 5,10,15,20-tetraphenylporphyrin (TPP 2- ) or 5,10,15,20-tetra(p-tolyl)porphyrin (TTP 2- ) dianion; L OEt - = [Co(η 5 -C 5 H 5 ){P(O)(OEt) 2 } 3 ] - ; M = Fe, Ru, or Os; M' = Ru or Os; L = H 2 O or pyridine} have been synthesized, and their electrochemistry has been studied. Treatment of trans-[Fe(TPP)(py) 2 ] (py = pyridine) with Ru(VI) nitride [Ru(L OEt )(N)Cl 2 ] (1) afforded Fe/Ru μ-nitrido complex [(py)(TPP)Fe(μ-N)Ru(L OEt )Cl 2 ] (2). Similarly, Fe/Os analogue [(py)(TPP)Fe(μ-N)Os(L OEt )Cl 2 ] (3) was obtained from trans-[Fe(TPP)(py) 2 ] and [Os(L OEt )(N)Cl 2 ]. However, no reaction was found between trans-[Fe(TPP)(py) 2 ] and [Re(L OEt )(N)Cl(PPh 3 )]. Treatment of trans-[M(TPP)(CO)(EtOH)] with 1 afforded μ-nitrido complexes [(H 2 O)(TPP)M(μ-N)Ru(L OEt )Cl 2 ] [M = Ru (4a) or Os (5)]. TTP analogue [(H 2 O)(TTP)Ru(μ-N)Ru(L OEt )Cl 2 ] (4b) was prepared similarly from trans-[Ru(TTP)(CO)(EtOH)] and 1. Reaction of [(H 2 O)(por)M(μ-N)M(L OEt )Cl 2 ] with pyridine gave adducts [(py)(por)M(μ-N)Ru(L OEt )Cl 2 ] [por = TTP, and M = Ru (6); por = TPP, and M = Os (7)]. The diamagnetism and short (por)M-N(nitride) distances in 2 [Fe-N, 1.683(3) Å] and 4b [Ru-N, 1.743(3) Å] are indicative of the M IV ═N═M' IV bonding description. The cyclic voltammograms of the Fe/Ru (2) and Ru/Ru (4b) complexes in CH 2 Cl 2 displayed oxidation couples at approximately +0.29 and +0.35 V versus Fc +/0 (Fc = ferrocene) that are tentatively ascribed to the oxidation of the {L OEt Ru} and {Ru(TTP)} moieties, respectively, whereas the Fe/Os (3) and Os/Ru (5) complexes exhibited Os-centered oxidation at approximately -0.06 and +0.05 V versus Fc +/0 , respectively. The crystal structures of 2 and 4b have been determined.

Fractionation of the platinum-group elments and Re during crystallization of basalt in Kilauea Iki Lava Lake, Hawaii

USGS Publications Warehouse

Pitcher, L.; Helz, R.T.; Walker, R.J.; Piccoli, P.

2009-01-01

Kilauea Iki lava lake formed during the 1959 summit eruption of Kilauea Volcano, then crystallized and differentiated over a period of 35??years. It offers an opportunity to evaluate the fractionation behavior of trace elements in a uniquely well-documented basaltic system. A suite of 14 core samples recovered from 1967 to 1981 has been analyzed for 5 platinum-group elements (PGE: Ir, Os, Ru, Pt, Pd), plus Re. These samples have MgO ranging from 2.4 to 26.9??wt.%, with temperatures prior to quench ranging from 1140????C to ambient (110????C). Five eruption samples were also analyzed. Osmium and Ru concentrations vary by nearly four orders of magnitude (0.0006-1.40??ppb for Os and 0.0006-2.01??ppb for Ru) and are positively correlated with MgO content. These elements behaved compatibly during crystallization, mostly likely being concentrated in trace phases (alloy or sulfide) present in olivine phenocrysts or included chromite. Iridium also correlates positively with MgO, although less strongly than Os and Ru. The somewhat poorer correlation for Ir, compared with Os and Ru, may reflect variable loss of Ir as volatile IrF6 in some of the most magnesian samples. Rhenium is negatively correlated with MgO, behaving as an incompatible trace element. Its behavior in the lava lake is complicated by apparent volatile loss of Re, as suggested by a decrease in Re concentration with time of quenching for lake samples vs. eruption samples. Platinum and Pd concentrations are negatively, albeit weakly, correlated with MgO, so these elements were modestly incompatible during crystallization of the major silicate phases. Palladium contents peaked before precipitation of immiscible sulfide liquid, however, and decline sharply in the most differentiated samples. In contrast, Pt appears to have been unaffected by sulfide precipitation. Microprobe data confirm that Pd entered the sulfide liquid before Re, and that Pt is not strongly chalcophile in this system. Occasional high Pt values in both eruption and lava lake samples suggest the presence of unevenly distributed, unidentified Pt-rich trace phases in some Kilauea Iki materials. Estimated mineral (olivine + chromite)/melt D values for Os, Ir, Ru and Pt for equilibrium crystallization for samples from ~ 7 to 27??wt.% MgO are 26, 8.2, 19 and 0.55, respectively. These Os, Ir and Ru estimates are somewhat higher than previous estimates for similar systems. If fractional crystallization is instead assumed, D values are much more similar. Results confirm many prior observations in other mafic systems that olivine (together with included phases) has a major effect on absolute and relative abundances of Re and the PGE. The relatively linear correlations between these elements and MgO potentially permit accurate estimation of the concentrations of these elements in the primary melts of comparable systems, especially in instances where the MgO content of the primary melt is well constrained. ?? 2008 Elsevier B.V.

Equilibrium points and associated periodic orbits in the gravity of binary asteroid systems: (66391) 1999 KW4 as an example

NASA Astrophysics Data System (ADS)

Shi, Yu; Wang, Yue; Xu, Shijie

2018-04-01

The motion of a massless particle in the gravity of a binary asteroid system, referred as the restricted full three-body problem (RF3BP), is fundamental, not only for the evolution of the binary system, but also for the design of relevant space missions. In this paper, equilibrium points and associated periodic orbit families in the gravity of a binary system are investigated, with the binary (66391) 1999 KW4 as an example. The polyhedron shape model is used to describe irregular shapes and corresponding gravity fields of the primary and secondary of (66391) 1999 KW4, which is more accurate than the ellipsoid shape model in previous studies and provides a high-fidelity representation of the gravitational environment. Both of the synchronous and non-synchronous states of the binary system are considered. For the synchronous binary system, the equilibrium points and their stability are determined, and periodic orbit families emanating from each equilibrium point are generated by using the shooting (multiple shooting) method and the homotopy method, where the homotopy function connects the circular restricted three-body problem and RF3BP. In the non-synchronous binary system, trajectories of equivalent equilibrium points are calculated, and the associated periodic orbits are obtained by using the homotopy method, where the homotopy function connects the synchronous and non-synchronous systems. Although only the binary (66391) 1999 KW4 is considered, our methods will also be well applicable to other binary systems with polyhedron shape data. Our results on equilibrium points and associated periodic orbits provide general insights into the dynamical environment and orbital behaviors in proximity of small binary asteroids and enable the trajectory design and mission operations in future binary system explorations.

Bipyrimidine ruthenium(II) arene complexes: structure, reactivity and cytotoxicity.

PubMed

Betanzos-Lara, Soledad; Novakova, Olga; Deeth, Robert J; Pizarro, Ana M; Clarkson, Guy J; Liskova, Barbora; Brabec, Viktor; Sadler, Peter J; Habtemariam, Abraha

2012-10-01

The synthesis and characterization of complexes [(η(6)-arene)Ru(N,N')X][PF(6)], where arene is para-cymene (p-cym), biphenyl (bip), ethyl benzoate (etb), hexamethylbenzene (hmb), indane (ind) or 1,2,3,4-tetrahydronaphthalene (thn), N,N' is 2,2'-bipyrimidine (bpm) and X is Cl, Br or I, are reported, including the X-ray crystal structures of [(η(6)-p-cym)Ru(bpm)I][PF(6)], [(η(6)-bip)Ru(bpm)Cl][PF(6)], [(η(6)-bip)Ru(bpm)I][PF(6)] and [(η(6)-etb)Ru(bpm)Cl][PF(6)]. Complexes in which N,N' is 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione or 4,7-diphenyl-1,10-phenanthroline (bathophen) were studied for comparison. The Ru(II) arene complexes undergo ligand-exchange reactions in aqueous solution at 310 K; their half-lives for hydrolysis range from 14 to 715 min. Density functional theory calculations on [(η(6)-p-cym)Ru(bpm)Cl][PF(6)], [(η(6)-p-cym)Ru(bpm)Br][PF(6)], [(η(6)-p-cym)Ru(bpm)I][PF(6)], [(η(6)-bip)Ru(bpm)Cl][PF(6)], [(η(6)-bip)Ru(bpm)Br][PF(6)] and [(η(6)-bip)Ru(bpm)I][PF(6)] suggest that aquation occurs via an associative pathway and that the reaction is thermodynamically favourable when the leaving ligand is I > Br ≈ Cl. pK (a)* values for the aqua adducts of the complexes range from 6.9 to 7.32. A binding preference for 9-ethylguanine (9-EtG) compared with 9-ethyladenine (9-EtA) was observed for [(η(6)-p-cym)Ru(bpm)Cl][PF(6)], [(η(6)-hmb)Ru(bpm)Cl](+), [(η(6)-ind)Ru(bpm)Cl](+), [(η(6)-thn)Ru(bpm)Cl](+), [(η(6)-p-cym)Ru(phen)Cl](+) and [(η(6)-p-cym)Ru(bathophen)Cl](+) in aqueous solution at 310 K. The X-ray crystal structure of the guanine complex [(η(6)-p-cym)Ru(bpm)(9-EtG-N7)][PF(6)](2) shows multiple hydrogen bonding. Density functional theory calculations show that the 9-EtG adducts of all complexes are thermodynamically preferred compared with those of 9-EtA. However, the bmp complexes are inactive towards A2780 human ovarian cancer cells. Calf thymus DNA interactions for [(η(6)-p-cym)Ru(bpm)Cl][PF(6)] and [(η(6)-p-cym)Ru(phen)Cl][PF(6)] consist of weak coordinative, intercalative and monofunctional coordination. Binding to biomolecules such as glutathione may play a role in deactivating the bpm complexes.

Probing the formation mechanism and chemical states of carbon-supported Pt-Ru nanoparticles by in situ X-ray absorption spectroscopy.

PubMed

Hwang, Bing Joe; Chen, Ching-Hsiang; Sarma, Loka Subramanyam; Chen, Jiun-Ming; Wang, Guo-Rung; Tang, Mau-Tsu; Liu, Din-Goa; Lee, Jyh-Fu

2006-04-06

The understanding of the formation mechanism of nanoparticles is essential for the successful particle design and scaling-up process. This paper reports findings of an X-ray absorption spectroscopy (XAS) investigation, comprised of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions, to understand the mechanism of the carbon-supported Pt-Ru nanoparticles (NPs) formation process. We have utilized Watanabe's colloidal reduction method to synthesize Pt-Ru/C NPs. We slightly modified the Watanabe method by introducing a mixing and heat treatment step of Pt and Ru oxidic species at 100 degrees C for 8 h with a view to enhance the mixing efficiency of the precursor species, thereby one can achieve improved homogeneity and atomic distribution in the resultant Pt-Ru/C NPs. During the reduction process, in situ XAS measurements allowed us to follow the evolution of Pt and Ru environments and their chemical states. The Pt LIII-edge XAS indicates that when H2PtCl6 is treated with NaHSO3, the platinum compound is found to be reduced to a Pt(II) form corresponding to the anionic complex [Pt(SO3)4]6-. Further oxidation of this anionic complex with hydrogen peroxide forms dispersed [Pt(OH)6]2- species. Analysis of Ru K-edge XAS results confirms the reduction of RuIIICl3 to [RuII(OH)4]2- species upon addition of NaHSO3. Addition of hydrogen peroxide to [RuII(OH)4]2- causes dehydrogenation and forms RuOx species. Mixing of [Pt(OH)6]2- and RuOx species and heat treatment at 100 degrees C for 8 h produced a colloidal sol containing both Pt and Ru metallic as well as ionic contributions. The reduction of this colloidal mixture at 300 degrees C in hydrogen atmosphere for 2 h forms Pt-Ru nanoparticles as indicated by the presence of Pt and Ru atoms in the first coordination shell. Determination of the alloying extent or atomic distribution of Pt and Ru atoms in the resulting Pt-Ru/C NPs reveals that the alloying extent of Ru (JRu) is greater than that of the alloying extent of Pt (JPt). The XAS results support the Pt-rich core and Ru-rich shell structure with a considerable amount of segregation in the Pt region and with less segregation in the Ru region for the obtained Pt-Ru/C NPs.

Investigation of the Vortex States of Sr2RuO4-Ru Eutectic Microplates Using DC-SQUIDs

NASA Astrophysics Data System (ADS)

Sakuma, Daisuke; Nago, Yusuke; Ishiguro, Ryosuke; Kashiwaya, Satoshi; Nomura, Shintaro; Kono, Kimitoshi; Maeno, Yoshiteru; Takayanagi, Hideaki

2017-11-01

We investigated the magnetic properties of a Sr2RuO4-Ru eutectic microplate containing a single Ru-inclusion using micrometer-sized DC-SQUIDs (direct-current superconducting quantum interference devices). A phase frustration at the interface between chiral p-wave superconducting Sr2RuO4 and s-wave superconducting Ru is expected to cause novel magnetic vortex states such as the spontaneous Ru-center vortex under zero magnetic field [as reported by H. Kaneyasu and M. Sigrist, J. Phys. Soc. Jpn. 79, 053706 (2010)]. Our experimental results show no positive evidence for such a spontaneous vortex state. However, in an applied field, an abrupt change in the magnetic flux distribution was observed at a superconducting transition of Ru. The flux distribution is clarified by comparing our experimental results with electromagnetic field simulations in our sample geometry. We discuss the transition of the vortex states and the superconducting coupling at the Sr2RuO4/Ru interface.

The Impact of Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Dupuy, Trent; Mann, Andrew; Huber, Daniel

2018-01-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion. We now update these results with multi-epoch imaging to reject non-comoving background stars and securely identify even the least massive stellar companions, as well as tracing out the orbital motion of stellar companions. These results are beginning to reveal not just the fraction of binaries that do not host planets, but also potential explanations for planet survival even in some very close, dynamically active binary systems.

Pharmacological profile of the aerial parts of Rubus ulmifolius Schott.

PubMed

Ali, Niaz; Shaoib, Mohammad; Shah, Syed Wadood Ali; Shah, Ismail; Shuaib, Muhammad

2017-01-19

As aerial parts of Rubus ulmifolius contains phytochemicals like flavonoids and tannins. And whereas flavonoids and tannins have antioxidant and antipyretic activity, hence, current work is carried out to screen crude methanolic extract of aerial parts of Rubus ulmifolius (Ru.Cr) and crude flavonoids rich extract of Rubus ulmifolius (Ru.F) for possible antioxidant and antipyretic activity. Ru.Cr and Ru.F are also tested for brine shrimps lethality bioassay. Ru.F is tested for the first time for possible antioxidant and antipyretic activity. Preliminary phytochemical screening of Ru.Cr and Ru.F was performed as it provides rapid finger printing for targeting a pharmacological activity. Acute toxicity and Brine shrimps' cytotoxicity studies of Ru.Cr and Ru.F were performed to determine its safe dose range. Antioxidant and antipyretic studies were also performed as per reported procedures. Ru.Cr tested positive for presence of tannins, alkaloids, flavonoids and steroids. Ru.Cr is safe up to 6 g/kg following oral doses for acute toxicity study. Ru.Cr is safe up to 75 μg/kg (p.o), LC 50 for Ru.Cr and Ru.F are 16.7 ± 1.4 μg/ml 10.6 ± 1.8 μg/ml, respectively (n = 3). Both Ru.Cr and Ru.F demonstrated comparable antioxidant activity using vitamin C as standard (p ≤ 0.05). In test dose of 300 mg of Ru.Cr, rectal temperature was reduced by 74% (p ≤ 0.05) on 4 th hour of the administration. More, Ru.F produced 72% reduction in pyrexia (p ≤ 0.05) on 4 th hour of administration of paracetamol in Westar rats. The current work confirms that aerial parts of Rubus ulmifolius contain flavonoids that are safe up to 6 g/kg (p.o). Crude methanolic extract and flavonoids rich fraction of Rubus ulmifolius have significant antioxidant and antipyretic activity. Further work is required to isolate the pharmacologically active substances for relatively safe and effective antipyretics and antioxidants.

Synthesis of Ruthenium Carbonyl Complexes with Phosphine or Substituted Cp Ligands, and Their Activity in the Catalytic Deoxygenation of 1,2-Propanediol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Prasenjit; Fagan, Paul J.; Marshall, William J.

2009-07-20

A ruthenium hydride with a bulky substituted Cp ligand, (CpiPr4)Ru(CO)2H (CpiPr4 = C5(i-C3H7)4H) was prepared from the reaction of Ru3(CO)12 with 1,2,3,4-tetraisopropylcyclopentadiene. The molecular structure of (CpiPr4)Ru(CO)2H was determined by x-ray crystallography. The ruthenium hydride complex (C5Bz5)Ru(CO)2H (Bz = CH2Ph) was similarly prepared. The Ru-Ru bonded dimer, [(1,2,3-trimethylindenyl)Ru(CO)2]2, was produced from the reaction of 1,2,3-trimethylindene with Ru3(CO)12, and protonation of this dimer with HOTf gives {[(1,2,3-trimethylindenyl)Ru(CO)2]2(μ H)}+OTf –. A series of ruthenium hydride complexes CpRu(CO)(L)H [L = P(OPh)3, PCy3, PMe3, P(p C6H4F)3] were prepared by reaction of Cp(CO)2RuH with added L. Protonation of (CpiPr4)Ru(CO)2H, Cp*Ru(CO)2H or CpRu(CO)[P(OPh)3]H by HOTf 80more » °C led to equilibria with the cationic dihydrogen complexes, but H2 was released at higher temperatures. Protonation of CpRu[P(OPh)3]2H with HOTf gave an observable dihydrogen complex, {CpRu[P(OPh)3]2(η2 H2)}+OTf – that was converted at -20 °C to the dihydride complex {CpRu[P(OPh)3]2(H)2}+OTf –. These Ru complexes serve as catalyst precursors for the catalytic deoxygenation of 1,2-propanediol to give n-propanol. The catalytic reactions were carried out in sulfolane solvent with added HOTf under H2 (750 psi) at 110 °C. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. Pacific Northwest National Laboratory is operated by Battelle for DOE.« less

Hydrocarbon oxidation by beta-halogenated dioxoruthenium(VI) porphyrin complexes: effect of reduction potential (RuVI/V) and C-H bond-dissociation energy on rate constants.

PubMed

Che, Chi-Ming; Zhang, Jun-Long; Zhang, Rui; Huang, Jie-Sheng; Lai, Tat-Shing; Tsui, Wai-Man; Zhou, Xiang-Ge; Zhou, Zhong-Yuan; Zhu, Nianyong; Chang, Chi Kwong

2005-11-18

beta-Halogenated dioxoruthenium(VI) porphyrin complexes [Ru(VI)(F(28)-tpp)O(2)] [F(28)-tpp=2,3,7,8,12,13, 17,18-octafluoro-5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato(2-)] and [Ru(VI)(beta-Br(8)-tmp)O(2)] [beta-Br(8)-tmp=2,3,7,8,12,13,17,18-octabromo-5,10,15,20- tetrakis(2,4,6-trimethylphenyl)porphyrinato(2-)] were prepared from reactions of [Ru(II)(por)(CO)] [por=porphyrinato(2-)] with m-chloroperoxybenzoic acid in CH(2)Cl(2). Reactions of [Ru(VI)(por)O(2)] with excess PPh(3) in CH(2)Cl(2) gave [Ru(II)(F(20)-tpp)(PPh(3))(2)] [F(20)-tpp=5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato(2-)] and [Ru(II)(F(28)-tpp)(PPh(3))(2)]. The structures of [Ru(II)(por)(CO)(H(2)O)] and [Ru(II)(por)(PPh(3))(2)] (por=F(20)-tpp, F(28)-tpp) were determined by X-ray crystallography, revealing the effect of beta-fluorination of the porphyrin ligand on the coordination of axial ligands to ruthenium atom. The X-ray crystal structure of [Ru(VI)(F(20)-tpp)O(2)] shows a Ru=O bond length of 1.718(3) A. Electrochemical reduction of [Ru(VI)(por)O(2)] (Ru(VI) to Ru(V)) is irreversible or quasi-reversible, with the E(p,c)(Ru(VI/V)) spanning -0.31 to -1.15 V versus Cp(2)Fe(+/0). Kinetic studies were performed for the reactions of various [Ru(VI)(por)O(2)], including [Ru(VI)(F(28)-tpp)O(2)] and [Ru(VI)(beta-Br(8)-tmp)O(2)], with para-substituted styrenes p-X-C(6)H(4)CH=CH(2) (X=H, F, Cl, Me, MeO), cis- and trans-beta-methylstyrene, cyclohexene, norbornene, ethylbenzene, cumene, 9,10-dihydroanthracene, xanthene, and fluorene. The second-order rate constants (k(2)) obtained for the hydrocarbon oxidations by [Ru(VI)(F(28)-tpp)O(2)] are up to 28-fold larger than by [Ru(VI)(F(20)-tpp)O(2)]. Dual-parameter Hammett correlation implies that the styrene oxidation by [Ru(VI)(F(28)-tpp)O(2)] should involve rate-limiting generation of a benzylic radical intermediate, and the spin delocalization effect is more important than the polar effect. The k(2) values for the oxidation of styrene and ethylbenzene by [Ru(VI)(por)O(2)] increase with E(p,c)(Ru(VI/V)), and there is a linear correlation between log k(2) and E(p,c)(Ru(VI/V)). The small slope (approximately 2 V(-1)) of the log k(2) versus E(p,c)(Ru(VI/V)) plot suggests that the extent of charge transfer is small in the rate-determining step of the hydrocarbon oxidations. The rate constants correlate well with the C-H bond dissociation energies, in favor of a hydrogen-atom abstraction mechanism.

Isonitrile-functionalized ruthenium nanoparticles: intraparticle charge delocalization through Ru=C=N interfacial bonds

NASA Astrophysics Data System (ADS)

Zhang, Fengqi; Huang, Lin; Zou, Jiasui; Yang, Jun; Kang, Xiongwu; Chen, Shaowei

2017-09-01

Ruthenium nanoparticles (2.06 ± 0.46 nm in diameter) stabilized by 1-hexyl-4-isocyanobenzene (CNBH), denoted as RuCNBH, were prepared by the self-assembly of isonitrile molecules onto the surface of "bare" Ru colloids by virtue of the formation of Ru=C=N- interfacial bonds. FTIR measurements showed that the stretching vibration of the terminal -N≡C bonds at 2119 cm-1 for the monomeric ligands disappeared and concurrently three new bands at 2115, 2043, and 1944 cm-1 emerged with RuCNBH nanoparticles, which was ascribed to the transformation of -N≡C to Ru=C=N- by back donation of Ru-d electrons to the π* orbital of the organic ligands. Metathesis reaction of RuCNBH with vinyl derivatives further corroborated the nature of the Ru=C interfacial bonds. When 1-isocyanopyrene (CNPy) was bounded onto the Ru nanoparticles surface through Ru=C=N interfacial bond (denoted as RuCNPy), the emission maximum was found to red-shift by 27 nm, as compared to that of the CNPy monomers, along with a reduced fluorescence lifetime, due to intraparticle charge delocalization that arose from the conjugated Ru=C=N- interfacial bonds. The results of this study further underline the significance of metal-organic interfacial bonds in the control of intraparticle charge-transfer dynamics and the optical and electronic properties of metal nanoparticles. [Figure not available: see fulltext.

Two-electron oxidation of deoxyguanosine by a Ru(III) complex without involving oxygen molecules through disproportionation.

PubMed

Choi, Sunhee; Ryu, DaWeon; DellaRocca, Joseph G; Wolf, Matthew W; Bogart, Justin A

2011-07-18

Among the many mechanisms for the oxidation of guanine derivatives (G) assisted by transition metals, Ru(III) and Pt(IV) metal ions share basically the same principle. Both Ru(III)- and Pt(IV)-bound G have highly positively polarized C8-H's that are susceptible to deprotonation by OH(-), and both undergo two-electron redox reactions. The main difference is that, unlike Pt(IV), Ru(III) is thought to require O(2) to undergo such a reaction. In this study, however, we report that [Ru(III)(NH(3))(5)(dGuo)] (dGuo = deoxyguanosine) yields cyclic-5'-O-C8-dGuo (a two-electron G oxidized product, cyclic-dGuo) without O(2). In the presence of O(2), 8-oxo-dGuo and cyclic-dGuo were observed. Both [Ru(II)(NH(3))(5)(dGuo)] and cyclic-dGuo were produced from [Ru(III)(NH(3))(5)(dGuo)] accelerated by [OH(-)]. We propose that [Ru(III)(NH(3))(5)(dGuo)] disproportionates to [Ru(II)(NH(3))(5)(dGuo)] and [Ru(IV)(NH(3))(4)(NH(2)(-))(dGuo)], followed by a 5'-OH attack on C8 in [Ru(IV)(NH(3))(4)(NH(2)(-))(dGuo)] to initiate an intramolecular two-electron transfer from dGuo to Ru(IV), generating cyclic-dGuo and Ru(II) without involving O(2).

Measurement of electrons from heavy-flavour hadron decays in p-Pb collisions at √{sNN} = 5.02TeV

NASA Astrophysics Data System (ADS)

Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahn, S. U.; Aiola, S.; Akindinov, A.; Alam, S. N.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Almaraz, J. R. M.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; Andrei, C.; Andronic, A.; Anguelov, V.; Anielski, J.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Arnaldi, R.; Arnold, O. W.; Arsene, I. C.; Arslandok, M.; Audurier, B.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Baldisseri, A.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Barth, K.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Belmont, R.; Belmont-Moreno, E.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biswas, R.; Biswas, S.; Bjelogrlic, S.; Blair, J. T.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Bossú, F.; Botta, E.; Böttger, S.; Bourjau, C.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Butt, J. B.; Buxton, J. T.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Carnesecchi, F.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Cerkala, J.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Cho, S.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; De, S.; De Caro, A.; de Cataldo, G.; de Conti, C.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; Deisting, A.; Deloff, A.; Dénes, E.; Deplano, C.; Dhankher, P.; Di Bari, D.; Di Mauro, A.; Di Nezza, P.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Drozhzhova, T.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Engel, H.; Epple, E.; Erazmus, B.; Erdemir, I.; Erhardt, F.; Espagnon, B.; Estienne, M.; Esumi, S.; Eum, J.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabbietti, L.; Fabris, D.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Feuillard, V. J. G.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Fleck, M. G.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Gasik, P.; Gauger, E. F.; Germain, M.; Gheata, A.; Gheata, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-Dziadus, E.; Glässel, P.; Goméz Coral, D. M.; Gomez Ramirez, A.; Gonzalez, V.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Grachov, O. A.; Graczykowski, L. K.; Graham, K. L.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Gronefeld, J. M.; Grosse-Oetringhaus, J. F.; Grossiord, J.-Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gunji, T.; Gupta, A.; Gupta, R.; Haake, R.; Haaland, Ø.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Harris, J. W.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Heide, M.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Hess, B. A.; Hetland, K. F.; Hillemanns, H.; Hippolyte, B.; Hosokawa, R.; Hristov, P.; Huang, M.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Inaba, M.; Ippolitov, M.; Irfan, M.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jacobs, P. M.; Jadhav, M. B.; Jadlovska, S.; Jadlovsky, J.; Jahnke, C.; Jakubowska, M. J.; Jang, H. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jung, H.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kamin, J.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karayan, L.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Mohisin Khan, M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, D. W.; Kim, D. J.; Kim, D.; Kim, H.; Kim, J. S.; Kim, M.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-Bösing, C.; Klewin, S.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobayashi, T.; Kobdaj, C.; Kofarago, M.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kopcik, M.; Kour, M.; Kouzinopoulos, C.; Kovalenko, O.; Kovalenko, V.; Kowalski, M.; Koyithatta Meethaleveedu, G.; Králik, I.; Kravčáková, A.; Kretz, M.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kuhn, C.; Kuijer, P. G.; Kumar, A.; Kumar, J.; Kumar, L.; Kumar, S.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; Ladron de Guevara, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lea, R.; Leardini, L.; Lee, G. R.; Lee, S.; Lehas, F.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; León Monzón, I.; León Vargas, H.; Leoncino, M.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loginov, V.; Loizides, C.; Lopez, X.; López Torres, E.; Lowe, A.; Luettig, P.; Lunardon, M.; Luparello, G.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manko, V.; Manso, F.; Manzari, V.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martin, N. A.; Martin Blanco, J.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martinez Pedreira, M.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzoni, M. A.; Mcdonald, D.; Meddi, F.; Melikyan, Y.; Menchaca-Rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Miake, Y.; Mieskolainen, M. M.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Minervini, L. M.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Moreira De Godoy, D. A.; Moreno, L. A. P.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Mulligan, J. D.; Munhoz, M. G.; Munzer, R. H.; Murray, S.; Musa, L.; Musinsky, J.; Naik, B.; Nair, R.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; Natal da Luz, H.; Nattrass, C.; Nayak, K.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Nellen, L.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Noris, J. C. C.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Ohlson, A.; Okatan, A.; Okubo, T.; Olah, L.; Oleniacz, J.; Oliveira Da Silva, A. C.; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Orava, R.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Pachmayer, Y.; Pagano, P.; Paić, G.; Pal, S. K.; Pan, J.; Pandey, A. K.; Papcun, P.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Paticchio, V.; Patra, R. N.; Paul, B.; Pei, H.; Peitzmann, T.; Pereira Da Costa, H.; Pereira De Oliveira Filho, E.; Peresunko, D.; Pérez Lara, C. E.; Perez Lezama, E.; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, J.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Rami, F.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Read, K. F.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Revol, J.-P.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Rocco, E.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Romita, R.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Šándor, L.; Sandoval, A.; Sano, M.; Sarkar, D.; Scapparone, E.; Scarlassara, F.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schuchmann, S.; Schukraft, J.; Schulc, M.; Schuster, T.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Šefčík, M.; Seger, J. E.; Sekiguchi, Y.; Sekihata, D.; Selyuzhenkov, I.; Senosi, K.; Senyukov, S.; Serradilla, E.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shangaraev, A.; Sharma, A.; Sharma, M.; Sharma, M.; Sharma, N.; Shigaki, K.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singha, S.; Singhal, V.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Søgaard, C.; Song, J.; Song, M.; Song, Z.; Soramel, F.; Sorensen, S.; Sozzi, F.; Spacek, M.; Spiriti, E.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Stachel, J.; Stan, I.; Stefanek, G.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Suljic, M.; Sultanov, R.; Šumbera, M.; Szabo, A.; Szanto de Toledo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Tabassam, U.; Takahashi, J.; Tambave, G. J.; Tanaka, N.; Tangaro, M. A.; Tarhini, M.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thäder, J.; Thomas, D.; Tieulent, R.; Timmins, A. R.; Toia, A.; Trogolo, S.; Trombetta, G.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vajzer, M.; Vala, M.; Valencia Palomo, L.; Vallero, S.; Van Der Maarel, J.; Van Hoorne, J. W.; van Leeuwen, M.; Vanat, T.; Vande Vyvre, P.; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Vechernin, V.; Veen, A. M.; Veldhoen, M.; Velure, A.; Venaruzzo, M.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Villatoro Tello, A.; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Vislavicius, V.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Vyushin, A.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Watanabe, D.; Watanabe, Y.; Weber, M.; Weber, S. G.; Weiser, D. F.; Wessels, J. P.; Westerhoff, U.; Whitehead, A. M.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, G.; Wilkinson, J.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yaldo, C. G.; Yang, H.; Yang, P.; Yano, S.; Yasar, C.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yoon, J. H.; Yurchenko, V.; Yushmanov, I.; Zaborowska, A.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zaporozhets, S.; Zardoshti, N.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhang, C.; Zhang, Z.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zyzak, M.

2016-03-01

The production of electrons from heavy-flavour hadron decays was measured as a function of transverse momentum (pT) in minimum-bias p-Pb collisions at √{sNN} = 5.02 TeV using the ALICE detector at the LHC. The measurement covers the pT interval 0.5

Measurement of electrons from heavy-flavour hadron decays in p–Pb collisions at s NN = 5.02 TeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adam, J.; Adamová, D.; Aggarwal, M. M.

2015-12-31

We measured the production of electrons from heavy-flavour hadron decays as a function of transverse momentum (p T) in minimum-bias p-Pb collisions at √s NN = 5.02 TeV using the ALICE detector at the LHC. Our measurement covers the p T interval 0.5 < p T < 12 GeV/c and the rapidity range -1.065 < y cms < 0.135 in the centre-of-mass reference frame. The contribution of electrons from background sources was subtracted using an invariant mass approach. The nuclear modification factor R-pPb was calculated by comparing the p T-differential invariant cross section in p-Pb collisions to a pp referencemore » at the same centre-of-mass energy, which was obtained by interpolating measurements at √s = 2.76 TeV and √= 7 TeV. The R pPb is consistent with unity within uncertainties of about 25%, which become larger for p T below 1 GeV/c. Furthermore, these measurements show that heavy-flavour production is consistent with binary scaling, so that a suppression in the high-p T yield in Pb-Pb collisions has to be attributed to effects induced by the hot medium produced in the final state. The data in p-Pb collisions are described by recent model calculations that include cold nuclear matter effects.« less

Biochemistry of metalocenes. The organ distribution of hydroxyacetyl (/sup 103/Ru)ruthenocene and its glucuronide in mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, A.J.; Macha, J.; Wenzel, M.

1980-01-01

Hydroxyacetyl(/sup 103/Ru)ruthenocene and its o-glucuronide were prepared in vitro by incubation of acetyl(/sup 103/Ru)ruthenocene with rat-liver homogenate, NADPH, and UDP-glucuronate. The factors affecting hydroxylation and glucuronidation in vitro were optimized for acetylruthenocene. Hydroxyacetyl(/sup 103/Ru)ruthenocene glucuronide showed no affinity for the adrenal glands, but after iv administration of hydroxyacetyl(/sup 103/Ru)ruthenocene there was a distinct accumulation of Ru-103 in adrenals, similar to that found after administration of acetyl(/sup 103/Ru)ruthenocene.

Pulsars in binary systems: probing binary stellar evolution and general relativity.

PubMed

Stairs, Ingrid H

2004-04-23

Radio pulsars in binary orbits often have short millisecond spin periods as a result of mass transfer from their companion stars. They therefore act as very precise, stable, moving clocks that allow us to investigate a large set of otherwise inaccessible astrophysical problems. The orbital parameters derived from high-precision binary pulsar timing provide constraints on binary evolution, characteristics of the binary pulsar population, and the masses of neutron stars with different mass-transfer histories. These binary systems also test gravitational theories, setting strong limits on deviations from general relativity. Surveys for new pulsars yield new binary systems that increase our understanding of all these fields and may open up whole new areas of physics, as most spectacularly evidenced by the recent discovery of an extremely relativistic double-pulsar system.

Polarizing beam splitter of deep-etched triangular-groove fused-silica gratings.

PubMed

Zheng, Jiangjun; Zhou, Changhe; Feng, Jijun; Wang, Bo

2008-07-15

We investigated the use of a deep-etched fused-silica grating with triangular-shaped grooves as a highly efficient polarizing beam splitter (PBS). A triangular-groove PBS grating is designed at a wavelength of 1550 nm to be used in optical communication. When it is illuminated in Littrow mounting, the transmitted TE- and TM-polarized waves are mainly diffracted in the minus-first and zeroth orders, respectively. The design condition is based on the average differences of the grating mode indices, which is verified by using rigorous coupled-wave analysis. The designed PBS grating is highly efficient over the C+L band range for both TE and TM polarizations (>97.68%). It is shown that such a triangular-groove PBS grating can exhibit a higher diffraction efficiency, a larger extinction ratio, and less reflection loss than the binary-phase fused-silica PBS grating.

BOREAS TE-18 Biomass Density Image of the SSA

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Knapp, David

2000-01-01

The BOREAS TE-18 team focused its efforts on using remotely sensed data to characterize the successional and disturbance dynamics of the boreal forest for use in carbon modeling. This biomass density image covers almost the entire BOREAS SSA. The pixels for which biomass density is computed include areas, that are in conifer land cover classes only. The biomass density values represent the amount of overstory biomass (i.e., tree biomass only) per unit area. It is derived from a Landsat-5 TM image collected on 02-Sep-1994. The technique that was used to create this image is very similar to the technique that was as used to create the physical classification of the SSA. The data are provided in a binary image file format. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

BOREAS TE-18 Landsat TM Physical Classification Image of the NSA

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Knapp, David

2000-01-01

The BOREAS TE-18 team focused its efforts on using remotely sensed data to characterize the successional and disturbance dynamics of the boreal forest for use in carbon modeling. The objective of this classification is to provide the BOREAS investigators with a data product that characterizes the land cover of the NSA. A Landsat-5 TM image from 21-Jun-1995 was used to derive the classification. A technique was implemented that uses reflectances of various land cover types along with a geometric optical canopy model to produce spectral trajectories. These trajectories are used in a way that is similar to training data to classify the image into the different land cover classes. The data are provided in a binary, image file format. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

BOREAS TE-18 Landsat TM Physical Classification Image of the SSA

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Knapp, David

2000-01-01

The BOREAS TE-18 team focused its efforts on using remotely sensed data to characterize the successional and disturbance dynamics of the boreal forest for use in carbon modeling. The objective of this classification is to provide the BOREAS investigators with a data product that characterizes the land cover of the SSA. A Landsat-5 TM image from 02-Sep-1994 was used to derive the classification. A technique was implemented that uses reflectances of various land cover types along with a geometric optical canopy model to produce spectral trajectories. These trajectories are used as training data to classify the image into the different land cover classes. These data are provided in a binary image file format. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

BOREAS TE-18 Landsat TM Maximum Likelihood Classification Image of the SSA

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Knapp, David

2000-01-01

The BOREAS TE-18 team focused its efforts on using remotely sensed data to characterize the successional and disturbance dynamics of the boreal forest for use in carbon modeling. The objective of this classification is to provide the BOREAS investigators with a data product that characterizes the land cover of the SSA. A Landsat-5 TM image from 02-Sep- 1994 was used to derive the classification. A technique was implemented that uses reflectances of various land cover types along with a geometric optical canopy model to produce spectral trajectories. These trajectories are used as training data to classify the image into the different land cover classes. These data are provided in a binary image file format. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Center (DAAC).

Numerical modeling of Bridgman growth of PbSnTe in a magnetic field

NASA Technical Reports Server (NTRS)

Yao, Minwu; Chait, Arnon; Fripp, Archibald L.; Debnam, William J.

1995-01-01

In this work we study heat and mass transport, fluid motion, and solid/liquid phase change in the process of steady Bridgman growth of Pb(.8)Sn(.2)Te (LTT) in an axially-imposed uniform magnetic field under terrestrial and microgravity conditions. In particular, this research is concerned with the interrelationships among segregation, buoyancy-driven convection, and magnetic damping in the LTT melt. The main objectives are to provide a quantitative understanding of the complex transport phenomena during solidification of the nondilute binary of LTT, to provide estimates of the strength of magnetic field required to achieve the desired diffusion-dominated growth, and to assess the role of magnetic damping for space and earth based control of the buoyancy-induced convection. The problem was solved by using FIDAP and numerical results for both vertical and horizontal growth configurations with respect to the acceleration of gravity vector are presented.

Positively selected amino acid replacements within the RuBisCO enzyme of oak trees are associated with ecological adaptations.

PubMed

Hermida-Carrera, Carmen; Fares, Mario A; Fernández, Ángel; Gil-Pelegrín, Eustaquio; Kapralov, Maxim V; Mir, Arnau; Molins, Arántzazu; Peguero-Pina, José Javier; Rocha, Jairo; Sancho-Knapik, Domingo; Galmés, Jeroni

2017-01-01

Phylogenetic analysis by maximum likelihood (PAML) has become the standard approach to study positive selection at the molecular level, but other methods may provide complementary ways to identify amino acid replacements associated with particular conditions. Here, we compare results of the decision tree (DT) model method with ones of PAML using the key photosynthetic enzyme RuBisCO as a model system to study molecular adaptation to particular ecological conditions in oaks (Quercus). We sequenced the chloroplast rbcL gene encoding RuBisCO large subunit in 158 Quercus species, covering about a third of the global genus diversity. It has been hypothesized that RuBisCO has evolved differentially depending on the environmental conditions and leaf traits governing internal gas diffusion patterns. Here, we show, using PAML, that amino acid replacements at the residue positions 95, 145, 251, 262 and 328 of the RuBisCO large subunit have been the subject of positive selection along particular Quercus lineages associated with the leaf traits and climate characteristics. In parallel, the DT model identified amino acid replacements at sites 95, 219, 262 and 328 being associated with the leaf traits and climate characteristics, exhibiting partial overlap with the results obtained using PAML.

Nanoscale structural and electronic characterization of α-RuCl3 layered compound

NASA Astrophysics Data System (ADS)

Ziatdinov, Maxim; Maksov, Artem; Banerjee, Arnab; Zhou, Wu; Berlijn, Tom; Yan, Jiaqiang; Nagler, Stephen; Mandrus, David; Baddorf, Arthur; Kalinin, Sergei

The exceptional interplay of spin-orbit effects, Coulomb interaction, and electron-lattice coupling is expected to produce an elaborate phase space of α-RuCl3 layered compound, which to date remains largely unexplored. Here we employ a combination of scanning transmission electron microscopy (STEM) and scanning tunneling microscopy (STM) for detailed evaluation of the system's microscopic structural and electronic orders with a sub-nanometer precision. The STM and STEM measurements are further supported by neutron scattering, X-Ray diffraction, density functional theory (DFT), and multivariate statistical analysis. Our results show a trigonal distortion of Cl octahedral ligand cage along the C3 symmetry axes in each RuCl3 layer. The lattice distortion is limited mainly to the Cl subsystem leaving the Ru honeycomb lattice nearly intact. The STM topographic and spectroscopic characterization reveals an intra unit cell electronic symmetry breaking in a spin-orbit coupled Mott insulating phase on the Cl-terminated surface of α-RuCl3. The associated long-range charge order (CO) pattern is linked to a surface component of Cl cage distortion. We finally discuss a fine structure of CO and its potential relation to variations of average unit cell geometries found in multivariate analysis of STEM data. The research was sponsored by the U.S. Department of Energy.

Positively selected amino acid replacements within the RuBisCO enzyme of oak trees are associated with ecological adaptations

PubMed Central

Hermida-Carrera, Carmen; Fares, Mario A.; Fernández, Ángel; Gil-Pelegrín, Eustaquio; Kapralov, Maxim V.; Mir, Arnau; Molins, Arántzazu; Peguero-Pina, José Javier; Rocha, Jairo; Sancho-Knapik, Domingo

2017-01-01

Phylogenetic analysis by maximum likelihood (PAML) has become the standard approach to study positive selection at the molecular level, but other methods may provide complementary ways to identify amino acid replacements associated with particular conditions. Here, we compare results of the decision tree (DT) model method with ones of PAML using the key photosynthetic enzyme RuBisCO as a model system to study molecular adaptation to particular ecological conditions in oaks (Quercus). We sequenced the chloroplast rbcL gene encoding RuBisCO large subunit in 158 Quercus species, covering about a third of the global genus diversity. It has been hypothesized that RuBisCO has evolved differentially depending on the environmental conditions and leaf traits governing internal gas diffusion patterns. Here, we show, using PAML, that amino acid replacements at the residue positions 95, 145, 251, 262 and 328 of the RuBisCO large subunit have been the subject of positive selection along particular Quercus lineages associated with the leaf traits and climate characteristics. In parallel, the DT model identified amino acid replacements at sites 95, 219, 262 and 328 being associated with the leaf traits and climate characteristics, exhibiting partial overlap with the results obtained using PAML. PMID:28859145

Preparation of Ru-doped SnO2-supported Pt catalysts and their electrocatalytic properties for methanol oxidation.

PubMed

Pang, H L; Zhang, X H; Zhong, X X; Liu, B; Wei, X G; Kuang, Y F; Chen, J H

2008-03-01

Ru-doped SnO2 nanoparticles were prepared by chemical precipitation and calcinations at 823 K. Due to high stability in diluted acidic solution, Ru-doped SnO2 nanoparticles were selected as the catalyst support and second catalyst for methanol electrooxidation. The micrograph, elemental composition, and structure of the Ru-doped SnO2 nanoparticles were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, respectively. The electrocatalytic properties of the Ru-doped SnO2-supported Pt catalyst (Pt/Ru-doped SnO2) for methanol oxidation have been investigated by cyclic voltammetry. Under the same loading mass of Pt, the Pt/Ru-doped SnO2 catalyst shows better electrocatalytic performance than the Pt/SnO2 catalyst and the best atomic ratio of Ru to Sn in Ru-doped SnO2 is 1/75. Additionally, the Pt/Ru-doped SnO2 catalyst possesses good long-term cycle stability.

Crystal structure, oxidation state and magnetism of Sr{sub x}La{sub 2−x}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} (x=1, 1.5)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lü, Minfeng, E-mail: m.f.lv@ciac.jl.cn; Deng, Xiaolong; Waerenborgh, João C.

2014-03-15

Sr{sub x}La{sub 2−x}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} (x=1, 1.5) oxides with K{sub 2}NiF{sub 4}-type structure were prepared by solid state reaction and characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, magnetic and electrical resistivity measurements. The SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4} phase was obtained for the first time with a negligible amount of impurities. The octahedral Cu/RuO{sub 6} units are more elongated in SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4} than in Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} indicating a greater extent of static Jahn–Teller distortion. XPS suggests that mixed ion pairs Ru{sup 5+}/Ru{sup 4+}↔Cu{sup +}/Cu{sup 2+} are present in SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4}, whilemore » Ru remains as Ru{sup 5+} and Cu as Cu{sup 2+} in Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4}. Both samples show spin-glass behavior, which can be explained by competition between ferromagnetic and antiferromagnetic superexchange interactions. The negative Weiss temperature estimated for SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4}, −318 K, is significantly lower than −11.5 K deduced for Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} which may be related to the higher static Jahn–Teller distortion in the former oxide. -- Graphical abstract: SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4} with K{sub 2}NiF{sub 4}-type structure show a larger static Jahn–Teller distortion than Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4}, which may be related to stronger antiferromagnetic superexchange interactions. Highlights: • SrLaCu{sub 0.5}Ru{sub 0.5}O{sub 4} (I) larger Jahn–Teller (J–T) distortion than Sr{sub 1.5}La{sub 0.5}Cu{sub 0.5}Ru{sub 0.5}O{sub 4} (II). • Octahedral Cu/RuO{sub 6} units are more elongated in I than in II. • Mixed ion pairs Ru{sup 5+}/Ru{sup 4+}↔Cu{sup +}/Cu{sup 2+} are present in I, while Ru remains as Ru{sup 5+} and Cu as Cu{sup 2+} in II. • Negative Weiss temperature of I significantly lower, consistent with higher J–T distortion.« less

Thermal kinetics and short range order parameters of Se80X20 (X = Te, Sb) binary glasses

NASA Astrophysics Data System (ADS)

Moharram, A. H.; Abu El-Oyoun, M.; Abdel-Baset, A. M.

2014-06-01

Bulk Se80Te20 and Se80Sb20 glasses were prepared using the melt-quench technique. Differential scanning calorimetry (DSC) curves measured at different heating rates (5 K/min≤ α≤50 K/min) and X-ray diffraction (XRD) are used to characterize the as-quenched specimens. Based on the obtained results, the activation energy of glass transition and the activation energy of crystallization ( E g, E c) of the Se80Te20 glass are (137.5, 105.1 kJ/mol) higher than the corresponding values of the Se80Sb20 glass (106.8, 71.2 kJ/mol). An integer n value ( n=2) of the Se80Te20 glass indicates that only one crystallization mechanism is occurring while a non-integer exponent ( n=1.79) in the Se80Sb20 glass means that two mechanisms are working simultaneously during the amorphous-crystalline transformations. The total structure factor, S( K), indicates the presence of the short-range order (SRO) and the absence of the medium-range order (MRO) inside the as-quenched alloys. In an opposite way to the activation energies, the values of the first peak position and the total coordination number ( r 1, η 1), obtained from a Gaussian fit of the radial distribution function, of the Se80Te20 glass are (2.42 nm, 1.99 atom) lower than the corresponding values (2.55 nm, 2.36 atom) of the Se80Sb20 specimens.

Increasing the Efficiency of a Thermoelectric Generator Using an Evaporative Cooling System

NASA Astrophysics Data System (ADS)

Boonyasri, M.; Jamradloedluk, J.; Lertsatitthanakorn, C.; Therdyothin, A.; Soponronnarit, S.

2017-05-01

A system for reducing heat from the cold side of a thermoelectric (TE) power generator, based on the principle of evaporative cooling, is presented. An evaporative cooling system could increase the conversion efficiency of a TE generator. To this end, two sets of TE generators were constructed. Both TE generators were composed of five TE power modules. The cold and hot sides of the TE modules were fixed to rectangular fin heat sinks. The hot side heat sinks were inserted in a hot gas duct. The cold side of one set was cooled by the cooling air from a counter flow evaporative cooling system, whereas the other set was cooled by the parallel flow evaporative cooling system. The counter flow pattern had better performance than the parallel flow pattern. A comparison between the TE generator with and without an evaporative cooling system was made. Experimental results show that the power output increased by using the evaporative cooling system. This can significantly increase the TE conversion efficiency. The evaporative cooling system increased the power output of the TE generator from 22.9 W of ambient air flowing through the heat sinks to 28.6 W at the hot gas temperature of 350°C (an increase of about 24.8%). The present study shows the promising potential of using TE generators with evaporative cooling for waste heat recovery.

Long-Term Monitoring Of The High-Energy γ-Ray Emission From Ls I +61°303 And Ls 5039

DOE PAGES

Hadasch, D.; Torres, D. F.; Tanaka, T.; ...

2012-03-22

The Fermi Large Area Telescope (LAT) reported the first definitive GeV detections of the binaries LS I +61°303 and LS 5039 in the first year after its launch in 2008 June. These detections were unambiguous as a consequence of the reduced positional uncertainty and the detection of modulated γ-ray emission on the corresponding orbital periods. An analysis of new data from the LAT, comprising 30 months of observations, identifies a change in the γ-ray behavior of LS I +61°303. An increase in flux is detected in 2009 March and a steady decline in the orbital flux modulation is observed. Significantmore » emission up to 30 GeV is detected by the LAT; prior data sets led to upper limits only. Contemporaneous TeV observations no longer detected the source, or found it—in one orbit—close to periastron, far from the phases at which the source previously appeared at TeV energies. The detailed numerical simulations and models that exist within the literature do not predict or explain many of these features now observed at GeV and TeV energies. New ideas and models are needed to fully explain and understand this behavior. A detailed phase-resolved analysis of the spectral characterization of LS I +61°303 in the GeV regime ascribes a power law with an exponential cutoff spectrum along each analyzed portion of the system's orbit. The on-source exposure of LS 5039 is also substantially increased with respect to our prior publication. In this case, whereas the general γ-ray properties remain consistent, the increased statistics of the current data set allows for a deeper investigation of its orbital and spectral evolution.« less

Reactivity of Silanes with ( tBuPONOP)Ruthenium Dichloride: Facile Synthesis of Chloro-Silyl Ruthenium Compounds and Formic Acid Decomposition

DOE PAGES

Anderson, Nickolas H.; Boncella, James M.; Tondreau, Aaron M.

2017-08-15

The coordination of tBuPONOP ( tBuPONOP=2,6-bis(ditert-butylphosphinito)pyridine) to different ruthenium starting materials, to generate ( tBuPONOP)RuCl 2, was investigated in this paper. The resultant ( tBuPONOP)RuCl 2 reactivity with three different silanes was then investigated and contrasted dramatically with the reactivity of ( iPrPONOP)RuCl 2(DMSO) ( iPrPONOP=2,6-bis(diisopropylphosphinito)pyridine) with the same silanes. The 16-electron species ( tBuPONOP)Ru(H)Cl was produced from the reaction of triethylsilane with ( tBuPONOP)RuCl 2. Reactions of ( tBuPONOP)RuCl 2 with both phenylsilane or diphenylsilane afforded the 16-electron hydrido-silyl species ( tBuPONOP)Ru(H)(PhSiCl 2) and ( tBuPONOP)Ru(H)(Ph 2SiCl), respectively. Reactions of all three of these complexes with silver triflate affordedmore » the simple salt metathesis products of ( tBuPONOP)Ru(H)(OTf), ( tBuPONOP)Ru(H)(PhSiCl(OTf)), and ( tBuPONOP)Ru(H)(Ph 2Si(OTf)). Formic acid dehydrogenation was performed in the presence of triethylamine (TEA), and each species proved competent for gas-pressure generation of CO 2 and H 2. Finally, the hydride species ( tBuPONOP)Ru(H)Cl, ( tBuPONOP)Ru(H)(OTf), and ( tBuPONOP)Ru(H)(PhSiCl 2) exhibited faster catalytic activity than the other compounds tested.« less

Ruthenium chalcogenonitrosyl and bridged nitrido complexes containing chelating sulfur and oxygen ligands.

PubMed

Ng, Ho-Yuen; Cheung, Wai-Man; Kwan Huang, Enrique; Wong, Kang-Long; Sung, Herman H-Y; Williams, Ian D; Leung, Wa-Hung

2015-11-14

Ruthenium thio- and seleno-nitrosyl complexes containing chelating sulfur and oxygen ligands have been synthesised and their de-chalcogenation reactions have been studied. The reaction of mer-[Ru(N)Cl3(AsPh3)2] with elemental sulfur and selenium in tetrahydrofuran at reflux afforded the chalcogenonitrosyl complexes mer-[Ru(NX)Cl3(AsPh3)2] [X = S (1), Se (2)]. Treatment of 1 with KN(R2PS)2 afforded trans-[Ru(NS)Cl{N(R2PS)2}2] [R = Ph (3), Pr(i) (4), Bu(t) (5)]. Alternatively, the thionitrosyl complex 5 was obtained from [Bu(n)4N][Ru(N)Cl4] and KN(Bu(t)2PS)2, presumably via sulfur atom transfer from [N(Bu(t)2PS)2](-) to the nitride. Reactions of 1 and 2 with NaLOEt (LOEt(-) = [Co(η(5)-C5H5){P(O)(LOEt)2}3](-)) gave [Ru(NX)LOEtCl2] (X = S (8), Se (9)). Treatment of [Bu(n)4N][Ru(N)Cl4] with KN(R2PS)2 produced Ru(IV)-Ru(IV)μ-nitrido complexes [Ru2(μ-N){N(R2PS)2}4Cl] [R = Ph (6), Pr(i) (7)]. Reactions of 3 and 9 with PPh3 afforded 6 and [Ru(NPPh3)LOEtCl2], respectively. The desulfurisation of 5 with [Ni(cod)2] (cod = 1,5-cyclooctadiene) gave the mixed valance Ru(III)-Ru(IV)μ-nitrido complex [Ru2(μ-N){N(Bu(t)2PS)2}4] (10) that was oxidised by [Cp2Fe](PF6) to give the Ru(IV)-Ru(IV) complex [Ru2(μ-N){N(Bu(t)2PS)2}4](PF6) ([10]PF6). The crystal structures of 1, 2, 3, 7, 9 and 10 have been determined.

Anode materials for lithium ion batteries

DOEpatents

Abouimrane, Ali; Amine, Khalil

2015-06-09

A composite material has general Formula (1-x)J-(x)Q wherein: J is a metal carbon alloy of formula Sn.sub.zSi.sub.z'Met.sub.wMet'.sub.w'C.sub.t; Q is a metal oxide of formula A.sub..gamma.M.sub..alpha.M'.sub..alpha.'O.sub..beta.; A is Li, Na, or K; M, M', Met, and Met' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; 0

Observation of New Neutron-rich Isotopes among Fission Fragments from In-flight Fission of 345 MeV/nucleon 238U: Search for New Isotopes Conducted Concurrently with Decay Measurement Campaigns

NASA Astrophysics Data System (ADS)

Shimizu, Yohei; Kubo, Toshiyuki; Fukuda, Naoki; Inabe, Naohito; Kameda, Daisuke; Sato, Hiromi; Suzuki, Hiroshi; Takeda, Hiroyuki; Yoshida, Koichi; Lorusso, Giuseppe; Watanabe, Hiroshi; Simpson, Gary S.; Jungclaus, Andrea; Baba, Hidetada; Browne, Frank; Doornenbal, Pieter; Gey, Guillaunme; Isobe, Tadaaki; Li, Zhihuan; Nishimura, Shunji; Söderström, Pär-Anders; Sumikama, Toshiyuki; Taprogge, Jan; Vajta, Zsolt; Wu, Jin; Xu, Zhengyu; Odahara, Atsuko; Yagi, Ayumi; Nishibata, Hiroki; Lozeva, Radomira; Moon, Changbum; Jung, HyoSoon

2018-01-01

The search for new isotopes using the in-flight fission of a 238U beam has been conducted concurrently with decay measurements, during the so-called EURICA campaigns, at the RIKEN Nishina Center RI Beam Factory. Fission fragments were analyzed and identified in flight using the BigRIPS separator. We have identified the following 36 new neutron-rich isotopes: 104Rb, 113Zr, 116Nb, 118,119Mo, 121,122Tc, 125Ru, 127,128Rh, 129,130,131Pd, 132Ag, 134Cd, 136,137In, 139,140Sn, 141,142Sb, 144,145Te, 146,147I, 149,150Xe, 149,150,151Cs, 153,154Ba, and 154,155,156,157La.

VERITAS Observations of the Nova in V407 Cygni

NASA Technical Reports Server (NTRS)

Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.;

Metal-Organic-Framework-Derived Yolk-Shell-Structured Cobalt-Based Bimetallic Oxide Polyhedron with High Activity for Electrocatalytic Oxygen Evolution.

PubMed

Yu, Zhou; Bai, Yu; Liu, Yuxuan; Zhang, Shimin; Chen, Dandan; Zhang, Naiqing; Sun, Kening

2017-09-20

The development of inexpensive, efficient, and environmentally friendly catalysts for oxygen evolution reaction (OER) is of great significant for green energy utilization. Herein, binary metal oxides (M x Co 3-x O 4 , M = Zn, Ni, and Cu) with yolk-shell polyhedron (YSP) structure were fabricated by facile pyrolysis of bimetallic zeolitic imidazolate frameworks (MCo-ZIFs). Benefiting from the synergistic effects of metal ions and the unique yolk-shell structure, M x Co 3-x O 4 YSP displays good OER catalytic activity in alkaline media. Impressively, Zn x Co 3-x O 4 YSP shows a comparable overpotential of 337 mV at 10 mA cm -2 to commercial RuO 2 and exhibits superior long-term durability. The high activity and good stability reveals its promising application.

Computation provides chemical insight into the diverse hydride NMR chemical shifts of [Ru(NHC)4(L)H]0/+ species (NHC = N-heterocyclic carbene; L = vacant, H2, N2, CO, MeCN, O2, P4, SO2, H-, F- and Cl-) and their [Ru(R2PCH2CH2PR2)2(L)H]+ congeners.

PubMed

Häller, L Jonas L; Mas-Marzá, Elena; Cybulski, Mateusz K; Sanguramath, Rajashekharayya A; Macgregor, Stuart A; Mahon, Mary F; Raynaud, Christophe; Russell, Christopher A; Whittlesey, Michael K

2017-02-28

Relativistic density functional theory calculations, both with and without the effects of spin-orbit coupling, have been employed to model hydride NMR chemical shifts for a series of [Ru(NHC) 4 (L)H] 0/+ species (NHC = N-heterocyclic carbene; L = vacant, H 2 , N 2 , CO, MeCN, O 2 , P 4 , SO 2 , H - , F - and Cl - ), as well as selected phosphine analogues [Ru(R 2 PCH 2 CH 2 PR 2 ) 2 (L)H] + (R = i Pr, Cy; L = vacant, O 2 ). Inclusion of spin-orbit coupling provides good agreement with the experimental data. For the NHC systems large variations in hydride chemical shift are shown to arise from the paramagnetic term, with high net shielding (L = vacant, Cl - , F - ) being reinforced by the contribution from spin-orbit coupling. Natural chemical shift analysis highlights the major orbital contributions to the paramagnetic term and rationalizes trends via changes in the energies of the occupied Ru d π orbitals and the unoccupied σ* Ru-H orbital. In [Ru(NHC) 4 (η 2 -O 2 )H] + a δ-interaction with the O 2 ligand results in a low-lying LUMO of d π character. As a result this orbital can no longer contribute to the paramagnetic shielding, but instead provides additional deshielding via overlap with the remaining (occupied) d π orbital under the L z angular momentum operator. These two effects account for the unusual hydride chemical shift of +4.8 ppm observed experimentally for this species. Calculations reproduce hydride chemical shift data observed for [Ru( i Pr 2 PCH 2 CH 2 P i Pr 2 ) 2 (η 2 -O 2 )H] + (δ = -6.2 ppm) and [Ru(R 2 PCH 2 CH 2 PR 2 ) 2 H] + (ca. -32 ppm, R = i Pr, Cy). For the latter, the presence of a weak agostic interaction trans to the hydride ligand is significant, as in its absence (R = Me) calculations predict a chemical shift of -41 ppm, similar to the [Ru(NHC) 4 H] + analogues. Depending on the strength of the agostic interaction a variation of up to 18 ppm in hydride chemical shift is possible and this factor (that is not necessarily readily detected experimentally) can aid in the interpretation of hydride chemical shift data for nominally unsaturated hydride-containing species. The synthesis and crystallographic characterization of the BAr F 4 - salts of [Ru(IMe 4 ) 4 (L)H] + (IMe 4 = 1,3,4,5-tetramethylimidazol-2-ylidene; L = P 4 , SO 2 ; Ar F = 3,5-(CF 3 ) 2 C 6 H 3 ) and [Ru(IMe 4 ) 4 (Cl)H] are also reported.

The Photosynthetic Cycle

DOE R&D Accomplishments Database

Calvin, Melvin

1955-03-21

A cyclic sequence of transformations, including the carboxylation of RuDP (ribulose diphosphate) and its re-formation, has been deduced as the route for the creation of reduced carbon compounds in photosynthetic organisms. With the demonstration of RuDP as substrate for the carboxylation in a cell-free system, each of the reactions has now been carried out independently in vitro. Further purification of this last enzyme system has confirmed the deduction that the carboxylation of RuDP leads directly to the two molecules of PGA (phosphoglyceric acid) involving an internal dismutation and suggesting the name "carboxydismutase" for the enzyme. As a consequence of this knowledge of each of the steps in the photosynthetic CO{sub 2} reduction cycle, it is possible to define the reagent requirements to maintain it. The net requirement for the reduction of one molecule of CO{sub 2} is four equivalents of [H]and three molecules of ATP (adenine triphosphate). These must ultimately be supplied by the photochemical reaction. Some possible ways in which this may be accomplished are discussed.

Enhancement of high dielectric permittivity in CaCu3Ti4O12/RuO2 composites in the vicinity of the percolation threshold

NASA Astrophysics Data System (ADS)

Mukherjee, Rupam; Lawes, Gavin; Nadgorny, Boris

2014-08-01

We observe the large enhancement in the dielectric permittivity near the percolation threshold in a composite nanoparticle system consisting of metallic RuO2 grains embedded into CaCu3Ti4O12 (CCTO) matrix and annealed at 1100 °C. To understand the nature of the dielectric response, we prepared CCTO by using standard solid state and sol-gel processes, with the relative permittivity found to be on the order of 103-104 at 10 kHz. For RuO2/CCTO composites, an increase in the real part of the dielectric permittivity by approximately an order of magnitude is observed in the vicinity of the percolation threshold, with moderate losses at room temperature. The critical exponent of dielectric permittivity and conductivity of these composites are lower than universal value (0.8-1). In these composite systems, both Maxwell-Wagner and percolation effects have been found responsible for the enhancement of dielectric permittivity.

Investigation of excited state, reductive quenching, and intramolecular electron transfer of Ru(II)–Re(I) supramolecular photocatalysts for CO 2 reduction using time-resolved IR measurements

DOE PAGES

Koike, Kazuhide; Grills, David C.; Tamaki, Yusuke; ...

2018-02-14

Supramolecular photocatalysts in which Ru(II) photosensitizer and Re(I) catalyst units are connected to each other by an ethylene linker are among the best known, most effective and durable photocatalytic systems for CO 2 reduction. In this paper we report, for the first time, time-resolved infrared (TRIR) spectra of three of these binuclear complexes to uncover why the catalysts function so efficiently. Selective excitation of the Ru unit with a 532 nm laser pulse induces slow intramolecular electron transfer from the 3MLCT excited state of the Ru unit to the Re unit, with rate constants of (1.0–1.1) × 10 4 smore » -1 as a major component and (3.5–4.3) × 10 6 s -1 as a minor component, in acetonitrile. The produced charge-separated state has a long lifetime, with charge recombination rate constants of only (6.5–8.4) × 10 4 s -1. Thus, although it has a large driving force (-ΔG 0 CR ~ 2.6 eV), this process is in the Marcus inverted region. On the other hand, in the presence of 1-benzyl-1,4-dihydronicotinamide (BNAH), reductive quenching of the excited Ru unit proceeds much faster (k q[BNAH (0.2 M)] = (3.5–3.8) × 10 6 s -1) than the abovementioned intramolecular oxidative quenching, producing the one-electron-reduced species (OERS) of the Ru unit. Nanosecond TRIR data clearly show that intramolecular electron transfer from the OERS of the Ru unit to the Re unit (k ET > 2 × 10 7 s -1) is much faster than from the excited state of the Ru unit, and that it is also faster than the reductive quenching process of the excited Ru unit by BNAH. To measure the exact value of k ET, picosecond TRIR spectroscopy and a stronger reductant were used. Thus, in the case of the binuclear complex with tri(p-fluorophenyl)phosphine ligands (RuRe(FPh)), for which intramolecular electron transfer is expected to be the fastest among the three binuclear complexes, in the presence of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH), k ET was measured as k ET = (1.4 ± 0.1) × 10 9 s -1. This clearly shows that intramolecular electron transfer in these RuRe binuclear supramolecular photocatalysts is not the rate-determining process in the photocatalytic reduction of CO 2, which is one of the main reasons why they work so efficiently.« less

Investigation of excited state, reductive quenching, and intramolecular electron transfer of Ru(II)–Re(I) supramolecular photocatalysts for CO 2 reduction using time-resolved IR measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koike, Kazuhide; Grills, David C.; Tamaki, Yusuke

Supramolecular photocatalysts in which Ru(II) photosensitizer and Re(I) catalyst units are connected to each other by an ethylene linker are among the best known, most effective and durable photocatalytic systems for CO 2 reduction. In this paper we report, for the first time, time-resolved infrared (TRIR) spectra of three of these binuclear complexes to uncover why the catalysts function so efficiently. Selective excitation of the Ru unit with a 532 nm laser pulse induces slow intramolecular electron transfer from the 3MLCT excited state of the Ru unit to the Re unit, with rate constants of (1.0–1.1) × 10 4 smore » -1 as a major component and (3.5–4.3) × 10 6 s -1 as a minor component, in acetonitrile. The produced charge-separated state has a long lifetime, with charge recombination rate constants of only (6.5–8.4) × 10 4 s -1. Thus, although it has a large driving force (-ΔG 0 CR ~ 2.6 eV), this process is in the Marcus inverted region. On the other hand, in the presence of 1-benzyl-1,4-dihydronicotinamide (BNAH), reductive quenching of the excited Ru unit proceeds much faster (k q[BNAH (0.2 M)] = (3.5–3.8) × 10 6 s -1) than the abovementioned intramolecular oxidative quenching, producing the one-electron-reduced species (OERS) of the Ru unit. Nanosecond TRIR data clearly show that intramolecular electron transfer from the OERS of the Ru unit to the Re unit (k ET > 2 × 10 7 s -1) is much faster than from the excited state of the Ru unit, and that it is also faster than the reductive quenching process of the excited Ru unit by BNAH. To measure the exact value of k ET, picosecond TRIR spectroscopy and a stronger reductant were used. Thus, in the case of the binuclear complex with tri(p-fluorophenyl)phosphine ligands (RuRe(FPh)), for which intramolecular electron transfer is expected to be the fastest among the three binuclear complexes, in the presence of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH), k ET was measured as k ET = (1.4 ± 0.1) × 10 9 s -1. This clearly shows that intramolecular electron transfer in these RuRe binuclear supramolecular photocatalysts is not the rate-determining process in the photocatalytic reduction of CO 2, which is one of the main reasons why they work so efficiently.« less

Multiple Pathways for Benzyl Alcohol Oxidation by Ru V =O 3+ and Ru IV =O 2+

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul, Amit; Hull, Jonathan F.; Norris, Michael R.

2011-02-21

Significant rate enhancements are found for benzyl alcohol oxidation by the RuV=O3+ form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH2)]2+ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to RuIV=O2+ and for the RuIV=O2+ form with added bases due to a new pathway, concerted hydride proton transfer (HPT).

Multiple Pathways for Benzyl Alcohol Oxidation by Ru V=O 3+ and Ru IV=O 2+

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul, Amit; Hull, Jonathan F.; Norris, Michael R.

2011-01-20

Significant rate enhancements are found for benzyl alcohol oxidation by the Ru V=O 3+ form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH 2)] 2+ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to Ru IV=O 2+ and for the Ru IV=O 2+ form with added bases due to a new pathway, concerted hydride proton transfer (HPT).

Atomistic Modeling of RuAl and (RuNi) Al Alloys

NASA Technical Reports Server (NTRS)

Gargano, Pablo; Mosca, Hugo; Bozzolo, Guillermo; Noebe, Ronald D.; Gray, Hugh R. (Technical Monitor)

2002-01-01

Atomistic modeling of RuAl and RuAlNi alloys, using the BFS (Bozzolo-Ferrante-Smith) method for alloys is performed. The lattice parameter and energy of formation of B2 RuAl as a function of stoichiometry and the lattice parameter of (Ru(sub 50-x)Ni(sub x)Al(sub 50)) alloys as a function of Ni concentration are computed. BFS based Monte Carlo simulations indicate that compositions close to Ru25Ni25Al50 are single phase with no obvious evidence of a miscibility gap and separation of the individual B2 phases.

Micrometer FX/DLX: A Pedagogic Compiler

DTIC Science & Technology

1992-03-01

delimited by double-quotes L E Literal = Integer-Numeral U Boolean-literal U String-literal E::= L ’I (lambda (1*) EB) (Eo E*) (let ((I E)*) EB) (letrec...except VAL, ATEMP, and RETADR) are saved in this activation frame. Arguments to the procedure are evaluated and placed in registers ARGO, ARGi , etc. By...ENV) "ENV") ((ru FP) "FP11) ((u ru SP) ’Isp") Us u ARGO) "ARGO") ru ARGI ) *"ARG1**) ((ru ARG2) "LRG2") ((ru ARG3) "ARG3") Us~ ru ARG4) "ARG4’) ((x ru

Vapour phase growth and characterization of II-VI mixed crystals

NASA Astrophysics Data System (ADS)

Reddy, D. R.; Reddy, B. K.

1992-02-01

All II-VI semiconductors with melting temperatures well above 1000 degree(s)C and with appreciable congruent vaporization well below their melting temperatures leave little scope for any growth technique except for the slow but efficient vaporphase growth method. Theoretical flaw in diffusion models of vapor phase growth was corrected by Factor and Garrett by incorporating the flow velocity term which otherwise would lead to segregation of constituents. An additional degree of freedom arising from the presence of two components was well utilized to finely control the stoichiometry in binaries. In mixed II-VI systems the components are either three or four, depending on whether the system is a ternary or a quaternary. The added degrees of freedom make it very difficult to control stoichiometry. However, Igaki et al. demonstrated the feasibility of control of stoichiometry in CdSxSe1-x. In this paper, a self-sealing vaporphase growth technique used for both ternary and quaternary system is described. The systems studied are CdSxSe1-x, (ZnSe)x(CdTe)1-x and (ZnTe)x(CdSe)1-x. Results on growth mechanism, miscibility, structure, band gap variation, conductivity type variation with 'x' and transport properties are presented in a comparative way and discussed. CdSxSe1-x system in the entire 'X' has the same crystal structure and type of conductivity. The second system has the same zincblend structure but the type of conductivity is very sensitive to thermal treatment. In the last system both structure and types of conductivity are different. The discontinuities in properties associated with this divergent end compound are presented and discussed. Among the physical properties/parameters studied crystal structure, bandgap and nature of conductivity are tailorable, and magnitudes of conductivity and dielectric properties are very difficult to control in the crystals grown by this vapor phase method.

Ru-core/Cu-shell bimetallic nanoparticles with controlled size formed in one-pot synthesis.

PubMed

Helgadottir, I; Freychet, G; Arquillière, P; Maret, M; Gergaud, P; Haumesser, P H; Santini, C C

2014-12-21

Suspensions of bimetallic nanoparticles (NPs) of Ru and Cu have been synthesized by simultaneous decomposition of two organometallic compounds in an ionic liquid. These suspensions have been characterized by Anomalous Small-Angle X-ray Scattering (ASAXS) at energies slightly below the Ru K-edge. It is found that the NPs adopt a Ru-core, a Cu-shell structure, with a constant Ru core diameter of 1.9 nm for all Ru : Cu compositions, while the Cu shell thickness increases with Cu content up to 0.9 nm. The formation of RuCuNPs thus proceeds through rapid decomposition of the Ru precursor into RuNPs of constant size followed by the reaction of the Cu precursor and agglomeration as a Cu shell. Thus, the different decomposition kinetics of precursors make possible the elaboration of core-shell NPs composed of two metals without chemical affinity.

Ferromagnetism and Ru-Ru distance in SrRuO3 thin film grown on SrTiO3 (111) substrate

PubMed Central

2014-01-01

Epitaxial SrRuO3 thin films were grown on both (100) and (111) SrTiO3 substrates with atomically flat surfaces that are required to grow high-quality films of materials under debate. The following notable differences were observed in the (111)-oriented SrRuO3 films: (1) slightly different growth mode, (2) approximately 10 K higher ferromagnetic transition temperature, and (3) better conducting behavior with higher relative resistivity ratio, than (100)c-oriented SrRuO3 films. Together with the reported results on SrRuO3 thin films grown on (110) SrTiO3 substrate, the different physical properties were discussed newly in terms of the Ru-Ru nearest neighbor distance instead of the famous tolerance factor. PACS 75.70.Ak; 75.60.Ej; 81.15.Fg PMID:24393495

Direct methanol fuel cell with extended reaction zone anode: PtRu and PtRuMo supported on graphite felt

NASA Astrophysics Data System (ADS)

Bauer, Alex; Gyenge, Előd L.; Oloman, Colin W.

Pressed graphite felt (thickness ∼350 μm) with electrodeposited PtRu (43 g m -2, 1.4:1 atomic ratio) or PtRuMo (52 g m -2, 1:1:0.3 atomic ratio) nanoparticle catalysts was investigated as an anode for direct methanol fuel cells. At temperatures above 333 K the fuel cell performance of the PtRuMo catalyst was superior compared to PtRu. The power density was 2200 W m -2 with PtRuMo at 5500 A m -2 and 353 K while under the same conditions PtRu yielded 1925 W m -2. However, the degradation rate of the Mo containing catalyst formulation was higher. Compared to conventional gas diffusion electrodes with comparable PtRu catalyst composition and load, the graphite felt anodes gave higher power densities mainly due to the extended reaction zone for methanol oxidation.

Electronically highly cubic conditions for Ru in α -RuCl3

NASA Astrophysics Data System (ADS)

Agrestini, S.; Kuo, C.-Y.; Ko, K.-T.; Hu, Z.; Kasinathan, D.; Vasili, H. B.; Herrero-Martin, J.; Valvidares, S. M.; Pellegrin, E.; Jang, L.-Y.; Henschel, A.; Schmidt, M.; Tanaka, A.; Tjeng, L. H.

2017-10-01

We studied the local Ru 4 d electronic structure of α -RuCl3 by means of polarization-dependent x-ray absorption spectroscopy at the Ru L2 ,3 edges. We observed a vanishingly small linear dichroism indicating that electronically the Ru 4 d local symmetry is highly cubic. Using full multiplet cluster calculations we were able to reproduce the spectra excellently and to extract that the trigonal splitting of the t2 g orbitals is -12 ±10 meV, i.e., negligible as compared to the Ru 4 d spin-orbit coupling constant. Consistent with our magnetic circular dichroism measurements, we found that the ratio of the orbital and spin moments is 2.0, the value expected for a Jeff=1/2 ground state. We have thus shown that as far as the Ru 4 d local properties are concerned, α -RuCl3 is an ideal candidate for the realization of Kitaev physics.

Synthesis, Electrochemistry, and Excited-State Properties of Three Ru(II) Quaterpyridine Complexes

DOE PAGES

Rudd, Jennifer A.; Brennaman, M. Kyle; Michaux, Katherine E.; ...

2016-03-09

The complexes [Ru(qpy)LL']2+ (qpy = 2,2':6',2'':6'',2''-quaterpyridine), with 1: L = acetonitrile, L'= chloride; 2: L = L'= acetonitrile; and 3: L = L'= vinylpyridine, have been prepared from [Ru(qpy) (Cl)2]. Their absorption spectra in CH3CN exhibit broad metal-to-ligand charge transfer (MLCT) absorptions arising from overlapping 1A1 → 1MLCT transitions. Photoluminescence is not observed at room temperature, but all three are weakly emissive in 4:1 ethanol/methanol glasses at 77 K with broad, featureless emissions observed between 600 and 1000 nm consistent with MLCT phosphorescence. Cyclic voltammograms in CH3CN reveal the expected RuIII/II redox couples. In 0.1 M trifluoroacetic acid (TFA), 1more » and 2 undergo aquation to give [RuII(qpy)(OH2)2]2+, as evidenced by the appearance of waves for the couples [RuIII(qpy)(OH2)2]3+/[RuII(qpy)(OH2)2]2+, [RuIV(qpy)(O)(OH2)]2+/[RuIII(qpy)(OH2)2]3+, and [RuVI(qpy)(O)2]2+/[RuIV(qpy)(O)(OH2)]2+ in cyclic voltammograms.« less

Comparative reactivity of TpRu(L)(NCMe)Ph (L = CO or PMe3): impact of ancillary ligand l on activation of carbon-hydrogen bonds including catalytic hydroarylation and hydrovinylation/oligomerization of ethylene.

PubMed

Foley, Nicholas A; Lail, Marty; Lee, John P; Gunnoe, T Brent; Cundari, Thomas R; Petersen, Jeffrey L

2007-05-30

Complexes of the type TpRu(L)(NCMe)R [L = CO or PMe3; R = Ph or Me; Tp = hydridotris(pyrazolyl)borate] initiate C-H activation of benzene. Kinetic studies, isotopic labeling, and other experimental evidence suggest that the mechanism of benzene C-H activation involves reversible dissociation of acetonitrile, reversible benzene coordination, and rate-determining C-H activation of coordinated benzene. TpRu(PMe3)(NCMe)Ph initiates C-D activation of C6D6 at rates that are approximately 2-3 times more rapid than that for TpRu(CO)(NCMe)Ph (depending on substrate concentration); however, the catalytic hydrophenylation of ethylene using TpRu(PMe3)(NCMe)Ph is substantially less efficient than catalysis with TpRu(CO)(NCMe)Ph. For TpRu(PMe3)(NCMe)Ph, C-H activation of ethylene, to ultimately produce TpRu(PMe3)(eta3-C4H7), is found to kinetically compete with catalytic ethylene hydrophenylation. In THF solutions containing ethylene, TpRu(PMe3)(NCMe)Ph and TpRu(CO)(NCMe)Ph separately convert to TpRu(L)(eta3-C4H7) (L = PMe3 or CO, respectively) via initial Ru-mediated ethylene C-H activation. Heating mesitylene solutions of TpRu(L)(eta3-C4H7) under ethylene pressure results in the catalytic production of butenes (i.e., ethylene hydrovinylation) and hexenes.

Simulating Ru L3-edge X-ray Absorption Spectroscopy with Time-Dependent Density Functional Theory: Model Complexes and Electron Localization in Mixed-Valence Metal Dimers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Kuiken, Benjamin E.; Valiev, Marat; Daifuku, Stephanie L.

2013-05-01

Ruthenium L2,3-edge X-ray absorption (XA) spectroscopy probes transitions from core 2p orbitals to the 4d levels of the atom and is a powerful tool for interrogating the local electronic and molecular structure around the metal atom. However, a molecular-level interpretation of the Ru L2,3-edge spectral lineshapes is often complicated by spin–orbit coupling (SOC) and multiplet effects. In this study, we develop spin-free time-dependent density functional theory (TDDFT) as a viable and predictive tool to simulate the Ru L3-edge spectra. We successfully simulate and analyze the ground state Ru L3-edge XA spectra of a series of RuII and RuIII complexes: [Ru(NH3)6]2+/3+,more » [Ru(CN)6]4-/3-, [RuCl6]4-/3-, and the ground (1A1) and photoexcited (3MLCT) transient states of [Ru(bpy)3]2+ and Ru(dcbpy)2(NCS)2 (termed N3). The TDDFT simulations reproduce all the experimentally observed features in Ru L3-edge XA spectra. The advantage of using TDDFT to assign complicated Ru L3-edge spectra is illustrated by its ability to identify ligand specific charge transfer features in complex molecules. We conclude that the B3LYP functional is the most reliable functional for accurately predicting the location of charge transfer features in these spectra. Experimental and simulated Ru L3-edge XA spectra are presented for the transition metal mixed-valence dimers [(NC)5MII-CN-RuIII(NH3)5]- (where M = Fe or Ru) dissolved in water. We explore the spectral signatures of electron delocalization in Ru L3-edge XA spectroscopy and our simulations reveal that the inclusion of explicit solvent molecules is crucial for reproducing the experimentally determined valencies, highlighting the importance of the role of the solvent in transition metal charge transfer chemistry.« less

Performance Analysis and Discussion on the Thermoelectric Element Footprint for PV-TE Maximum Power Generation

NASA Astrophysics Data System (ADS)

Li, Guiqiang; Zhao, Xudong; Jin, Yi; Chen, Xiao; Ji, Jie; Shittu, Samson

2018-06-01

Geometrical optimisation is a valuable way to improve the efficiency of a thermoelectric element (TE). In a hybrid photovoltaic-thermoelectric (PV-TE) system, the photovoltaic (PV) and thermoelectric (TE) components have a relatively complex relationship; their individual effects mean that geometrical optimisation of the TE element alone may not be sufficient to optimize the entire PV-TE hybrid system. In this paper, we introduce a parametric optimisation of the geometry of the thermoelectric element footprint for a PV-TE system. A uni-couple TE model was built for the PV-TE using the finite element method and temperature-dependent thermoelectric material properties. Two types of PV cells were investigated in this paper and the performance of PV-TE with different lengths of TE elements and different footprint areas was analysed. The outcome showed that no matter the TE element's length and the footprint areas, the maximum power output occurs when A n /A p = 1. This finding is useful, as it provides a reference whenever PV-TE optimisation is investigated.

Structural and electronic properties of Cu2Q and CuQ (Q = O, S, Se, and Te) studied by first-principles calculations

NASA Astrophysics Data System (ADS)

Zhao, Ting; Wang, Yu-An; Zhao, Zong-Yan; Liu, Qiang; Liu, Qing-Ju

2018-01-01

In order to explore the similarity, difference, and tendency of binary copper-based chalcogenides, the crystal structure, electronic structure, and optical properties of eight compounds of Cu2Q and CuQ (Q = O, S, Se, and Te) have been calculated by density functional theory with HSE06 method. According to the calculated results, the electronic structure and optical properties of Cu2Q and CuQ present certain similarities and tendencies, with the increase of atomic number of Q elements: the interactions between Cu-Q, Cu-Cu, and Q-Q are gradually enhancing; the value of band gap is gradually decreasing, due to the down-shifting of Cu-4p states; the covalent feature of Cu atoms is gradually strengthening, while their ionic feature is gradually weakening; the absorption coefficient in the visible-light region is also increasing. On the other hand, some differences can be found, owing to the different crystal structure and component, for example: CuO presents the characteristics of multi-band gap, which is very favorable to absorb infrared-light; the electron transfer in CuQ is stronger than that in Cu2Q; the absorption peaks and intensity are very strong in the ultraviolet-light region and infrared-light region. The findings in the present work will help to understand the underlying physical mechanism of binary copper-based chalcogenides, and available to design novel copper-based chalcogenides photo-electronics materials and devices.

Structural and electronic properties of monolayer group III monochalcogenides

NASA Astrophysics Data System (ADS)

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

2017-03-01

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

The role of the non-magnetic material in spin pumping and magnetization dynamics in NiFe and CoFeB multilayer systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruiz-Calaforra, A., E-mail: ruiz@physik.uni-kl.de; Brächer, T.; Lauer, V.

2015-04-28

We present a study of the effective magnetization M{sub eff} and the effective damping parameter α{sub eff} by means of ferromagnetic resonance spectroscopy on the ferromagnetic (FM) materials Ni{sub 81}Fe{sub 19} (NiFe) and Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB) in FM/Pt, FM/NM, and FM/NM/Pt systems with the non-magnetic (NM) materials Ru, Cr, Al, and MgO. Moreover, for NiFe layer systems, the influence of interface effects is studied by way of thickness dependent measurements of M{sub eff} and α{sub eff}. Additionally, spin pumping in NiFe/NM/Pt is investigated by means of inverse spin Hall effect (ISHE) measurements. We observe a large dependence ofmore » M{sub eff} and α{sub eff} of the NiFe films on the adjacent NM layer. While Cr and Al do not induce a large change in the magnetic properties, Ru, Pt, and MgO affect M{sub eff} and α{sub eff} in different degrees. In particular, NiFe/Ru and NiFe/Ru/Pt systems show a large perpendicular surface anisotropy and a significant enhancement of the damping. In contrast, the magnetic properties of CoFeB films do not have a large influence of the NM adjacent material and only CoFeB/Pt systems present an enhancement of α{sub eff}. However, this enhancement is much more pronounced in NiFe/Pt. By the introduction of the NM spacer material, this enhancement is reduced. Furthermore, a difference in symmetry between NiFe/NM/Pt and NiFe/NM systems in the output voltage signal from the ISHE measurements reveals the presence of spin pumping into the Pt layer in all-metallic NiFe/NM/Pt and NiFe/Pt systems.« less

Ru-decorated Pt surfaces as model fuel cell electrocatalysts for CO electrooxidation.

PubMed

Maillard, F; Lu, G-Q; Wieckowski, A; Stimming, U

2005-09-01

This feature article concerns Pt surfaces modified (decorated) by ruthenium as model fuel cell electrocatalysts for electrooxidation processes. This work reveals the role of ruthenium promoters in enhancing electrocatalytic activity toward organic fuels for fuel cells, and it particularly concerns the methanol decomposition product, surface CO. A special focus is on surface mobility of the CO as it is catalytically oxidized to CO(2). Different methods used to prepare Ru-decorated Pt single crystal surfaces as well as Ru-decorated Pt nanoparticles are reviewed, and the methods of characterization and testing of their activity are discussed. The focus is on the origin of peak splitting involved in the voltammetric electrooxidation of CO on Ru-decorated Pt surfaces, and on the interpretative consequences of the splitting for single crystal and nanoparticle Pt/Ru bimetallic surfaces. Apparently, screening through the literature allows formulating several models of the CO stripping reaction, and the validity of these models is discussed. Major efforts are made in this article to compare the results reported by the Urbana-Champaign group and the Munich group, but also by other groups. As electrocatalysis is progressively more and more driven by theory, our review of the experimental findings may serve to summarize the state of the art and clarify the roads ahead. Future studies will deal with highly dispersed and reactive nanoscale surfaces and other more advanced catalytic materials for fuel cell catalysis and related energy applications. It is expected that the metal/metal and metal/substrate interactions will be increasingly investigated on atomic and electronic levels, with likewise increasing participation of theory, and the structure and reactivity of various monolayer catalytic systems involving more than two metals (that is ternary and quaternary systems) will be interrogated.

The Gd-Co-Al system at 870/1070 K as a representative of the rare earth-Co-Al family and new rare-earth cobalt aluminides: Crystal structure and magnetic properties

NASA Astrophysics Data System (ADS)

Morozkin, A. V.; Garshev, A. V.; Knotko, A. V.; Yapaskurt, V. O.; Mozharivskyj, Y.; Yuan, Fang; Yao, Jinlei; Nirmala, R.; Quezado, S.; Malik, S. K.

2018-05-01

The Gd-Co-Al system has been investigated at 870/1070 K by X-ray and elemental EDS analyses. The existence of the known compounds Gd2Co3Al9 (Y2Co3Ga9-type), Gd3Co4.5Al11.5 (Gd3Co4.6Al11) (Gd3Ru4Al12-type), Gd3Co6-7.4Al3-1.6 (CeNi3-type), GdCo1.15-0.65Al0.85-1.35 (MgZn2-type), Gd2Co2Al (Mo2NiB2-type) and Gd3Co3.5-3.25Al0.5-0.75 (W3CoB3-type) has been confirmed at 870/1070 K. Structure types have been determined for Gd2Co6Al19 (U2Co6Al19-type), Gd7Co6Al7 (Pr7Co6Al7-type), Gd6Co2-2.21Al1-0.79 (Ho6Co2Ga-type) and Gd14Co3.2Al2.8 (Gd14Co2.58Al3.42 at 970 K) (Lu14Co3In3-type). The structures of Gd6Co2Al, Gd6Co2.21Al0.79 and Gd14Co2.58Al3.42 flux-grown at 970 K have been refined from the single crystal X-ray diffraction data. Additionally, new ternary compounds Gd2Co5.7-5.3Al1.3-1.7 (Er2Co7-type) and Gd58Co20Al22 (unknown type structure) have been identified. Quasi-binary solid solutions were detected for Gd2Co17, GdCo5, Gd2Co7, GdCo3, GdCo2 and GdAl2 at 870/1070 K, while no appreciable solubility was observed for the other binary compounds in the Gd-Co-Al system. Magnetic properties of the Gd2Co3Al9, Gd3Co4.6Al11, Gd7Co6Al7, Gd6Co2.2Al0.8 and Gd14Co2.58Al3.42 compounds have been studied and are presented in this work. Gd6Co2.2Al0.8, Gd3Co4.6Al11, Gd7Co6Al7 and Gd14Co2.58Al3.42 order ferromagnetically, while Gd2Co3Al9 displays antiferromagnetic transition. Additionally, {Y, Sm, Tb - Tm}2Co6Al19 (U2Co6Al19-type), Yb2Co3Al9 (Y2Co3Ga9-type), {Y, Sm, Tm, Yb}3Co4.6Al11 (Gd3Ru4Al12-type) and Tb7Co6Al7 (Pr7Co6Al7-type) compounds have been synthesized and investigated.

Synthesis of Ruthenium Carbonyl Complexes with Phosphine or Substituted Cp Ligands, and Their Activity in the Catalytic Deoxygenation of 1,2-Propanediol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bullock, R.M.; Ghosh, P.; Fagan, P.J.

2009-07-20

A ruthenium hydride with a bulky tetra-substituted Cp ligand, (Cp{sup iPr{sub 4}})Ru(CO){sub 2}H (Cp{sup iPr{sub 4}} = C{sub 5}(i-C{sub 3}H{sub 7}){sub 4}H) was prepared from the reaction of Ru{sub 3}(CO){sub 12} with 1,2,3,4-tetraisopropylcyclopentadiene. The molecular structure of (Cp{sup iPr{sub 4}})Ru(CO){sub 2}H was determined by X-ray crystallography. The ruthenium hydride complex (C{sub 5}Bz{sub 5})Ru(CO){sub 2}H (Bz = CH{sub 2}Ph) was similarly prepared. The Ru-Ru bonded dimer, [(1,2,3-trimethylindenyl)Ru(CO){sub 2}]{sub 2}, was produced from the reaction of 1,2,3-trimethylindene with Ru{sub 3}(CO){sub 12}, and protonation of this dimer with HOTf gives {l_brace}[(1,2,3-trimethylindenyl)Ru(CO){sub 2}]{sub 2}-({mu}-H){r_brace}{sup +}OTf{sup -}. A series of ruthenium hydride complexes CpRu(CO)(L)H [Lmore » = P(OPh){sub 3}, PCy{sub 3}, PMe{sub 3}, P(p-C{sub 6}H{sub 4}F){sub 3}] were prepared by reaction of Cp(CO){sub 2}RuH with added L. Protonation of (Cp{sup iPr{sub 4}})Ru(CO){sub 2}H, Cp*Ru(CO){sub 2}H, or CpRu(CO)[P-(OPh){sub 3}]H by HOTf at -80 C led to equilibria with the cationic dihydrogen complexes, but H{sub 2} was released at higher temperatures. Protonation of CpRu[P(OPh){sub 3}]{sub 2}H with HOTf gave an observable dihydrogen complex, {l_brace}CpRu[P-(OPh){sub 3}]{sub 2}({eta}{sup 2}-H{sub 2}){r_brace}+OTf{sup -} that was converted at -20 C to the dihydride complex {l_brace}CpRu[P(OPh){sub 3}]{sub 2}(H){sub 2}{r_brace}{sup +}OTf{sup -}. These Ru complexes serve as catalyst precursors for the catalytic deoxygenation of 1,2-propanediol to give n-propanol. The catalytic reactions were carried out in sulfolane solvent with added HOTf under H{sub 2} (750 psi) at 110 C.« less

R144: a very massive binary likely ejected from R136 through a binary-binary encounter

NASA Astrophysics Data System (ADS)

Oh, Seungkyung; Kroupa, Pavel; Banerjee, Sambaran

2014-02-01

R144 is a recently confirmed very massive, spectroscopic binary which appears isolated from the core of the massive young star cluster R136. The dynamical ejection hypothesis as an origin for its location is claimed improbable by Sana et al. due to its binary nature and high mass. We demonstrate here by means of direct N-body calculations that a very massive binary system can be readily dynamically ejected from an R136-like cluster, through a close encounter with a very massive system. One out of four N-body cluster models produces a dynamically ejected very massive binary system with a mass comparable to R144. The system has a system mass of ≈355 M⊙ and is located at 36.8 pc from the centre of its parent cluster, moving away from the cluster with a velocity of 57 km s-1 at 2 Myr as a result of a binary-binary interaction. This implies that R144 could have been ejected from R136 through a strong encounter with another massive binary or single star. In addition, we discuss all massive binaries and single stars which are ejected dynamically from their parent cluster in the N-body models.

Tin-decorated ruthenium nanoparticles: a way to tune selectivity in hydrogenation reaction

NASA Astrophysics Data System (ADS)

Bonnefille, Eric; Novio, Fernando; Gutmann, Torsten; Poteau, Romuald; Lecante, Pierre; Jumas, Jean-Claude; Philippot, Karine; Chaudret, Bruno

2014-07-01

Two series of ruthenium nanoparticles stabilized either by a polymer (polyvinylpyrrolidone; Ru/PVP) or a ligand (bisdiphenylphosphinobutane; Ru/dppb) were reacted with tributyltin hydride [(n-C4H9)3SnH] leading to tin-decorated ruthenium nanoparticles, Ru/PVP/Sn and Ru/dppb/Sn. The Sn/Ru molar ratio was varied in order to study the influence of the surface tin content on the properties of these new nanoparticles, by comparison with Ru/PVP and Ru/dppb. Besides HRTEM and WAXS analyses, spectroscopic techniques (IR, NMR and Mössbauer) combined with theoretical calculations and a simple catalytic test (styrene hydrogenation) allowed us to evidence the formation of μ3-bridging ``SnR'' groups on the ruthenium surface as well as to rationalize their influence on surface chemistry and catalytic activity.Two series of ruthenium nanoparticles stabilized either by a polymer (polyvinylpyrrolidone; Ru/PVP) or a ligand (bisdiphenylphosphinobutane; Ru/dppb) were reacted with tributyltin hydride [(n-C4H9)3SnH] leading to tin-decorated ruthenium nanoparticles, Ru/PVP/Sn and Ru/dppb/Sn. The Sn/Ru molar ratio was varied in order to study the influence of the surface tin content on the properties of these new nanoparticles, by comparison with Ru/PVP and Ru/dppb. Besides HRTEM and WAXS analyses, spectroscopic techniques (IR, NMR and Mössbauer) combined with theoretical calculations and a simple catalytic test (styrene hydrogenation) allowed us to evidence the formation of μ3-bridging ``SnR'' groups on the ruthenium surface as well as to rationalize their influence on surface chemistry and catalytic activity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00791c

At the Borderline between Metal-Metal Mixed Valency and a Radical Bridge Situation: Four Charge States of a Diruthenium Complex with a Redox-Active Bis( mer-tridentate) Ligand.

PubMed

Mondal, Sudipta; Schwederski, Brigitte; Frey, Wolfgang; Fiedler, Jan; Záliš, Stanislav; Kaim, Wolfgang

2018-04-02

The complex ions [L 3 Ru(μ,η 3 :η 3 -BL)RuL 3 ] n+ (1 n+ , L 3 = 4,4',4″-tri- tert-butyl-2,6,2',6″-terpyridine and H 2 BL 2- = 1,2-bis(salicyloyl)hydrazide(2-)) were isolated with PF 6 - or ClO 4 - counterions ( n = 1) and as bis(hexafluorophosphate) ( n = 2). Structural, electrochemical, and spectroscopic characterization reveals the monocation as intermediate ( K c = 10 8.2 ) in the three-step reversible redox system 1 0/+/2+/3+ . The 1 + ion has the molecule-bridged (Ru- - -Ru 4.727 Å) ruthenium centers involved in five- and six-membered chelate rings, and it exhibits long-wavelength absorptions at λ max 2240, 1660, and 1530 nm (ε max = 1000, 3000, and 8000 M -1 cm -1 , respectively), which would be compatible with a Ru III Ru II mixed-valent situation or with a coordinated radical ion bridge. In fact, EPR and DFT analysis of 1 + reveals that the spin is equally distributed over the ligand bridge and over both metals. The oxidized paramagnetic ions 1 2+ and 1 3+ have been studied by 1 H NMR and EPR and by TD-DFT supported UV-vis-NIR and MIR (mid-IR) spectroelectrochemistry. The capacity of various kinds of bis( mer-tridentate) bridging ligands (π donors or π acceptors, cyclometalated or noncyclometalated) for mediating metal-metal interactions is discussed.

Novel and versatile solid-state chemiluminescence sensor based on TiO2-Ru(bpy)32+ nanoparticles for pharmaceutical drugs detection

NASA Astrophysics Data System (ADS)

Al-Hetlani, Entesar; Amin, Mohamed O.; Madkour, Metwally

2018-02-01

This work describes a novel and versatile solid-state chemiluminescence sensor for analyte detection using TiO2-Ru(bpy)32+-Ce(IV). Herein, we report the synthesis, characterization, optimization and application of a new type of hybrid nanoparticles (NPs). Mesoporous TiO2-Ru(bpy)32+ NPs were prepared using a modified sol-gel method by incorporating Ru(bpy)32+ into the initial reaction mixture at various concentrations. The resultant bright orange precipitate was characterized via transmission electron microscopy, N2 sorpometry, inductively coupled plasma-optical emission spectrometer (ICP-OES), Raman and UV-Vis spectroscopy techniques. The concentration of Ru(bpy)32+ complex in the NPs was quantified using ICP-OES, and its chemiluminescence (CL) response was measured and compared with the same concentration in the liquid phase using oxalate as model analyte. The results showed that this type of hybrid material exhibited a higher CL signal compared with the liquid phase due to the enlarged surface area of the hybrid NPs ( 149.6 m2/g). The amount of TiO2-Ru(bpy)32+ NPs and the effect of the analyte flow rate were also investigated to optimize the CL signal. The optimized system was further used to detect oxalate and two pharmaceutical drugs, namely, imipramine and promazine. The linear range for both drugs was 1-100 pm with limits of detection (LOD) of 0.1 and 0.5 pm, respectively. This approach is considered to be simple, low cost and facile and can be applied to a wide range of analytes.

Superlattice formation lifting degeneracy protected by nonsymmorphic symmetry through a metal-insulator transition in RuAs

NASA Astrophysics Data System (ADS)

Kotegawa, Hisashi; Takeda, Keiki; Kuwata, Yoshiki; Hayashi, Junichi; Tou, Hideki; Sugawara, Hitoshi; Sakurai, Takahiro; Ohta, Hitoshi; Harima, Hisatomo

2018-05-01

A single crystal of RuAs obtained with the Bi-flux method shows obvious successive metal-insulator transitions at TMI 1˜255 K and TMI 2˜195 K. The x-ray diffraction measurement reveals the formation of a superlattice of 3 ×3 ×3 of the original unit cell below TMI 2, accompanied by a change of the crystal system from the orthorhombic structure to the monoclinic one. Simple dimerization of the Ru ions is not seen in the ground state. The multiple As sites observed in the nuclear quadrupole resonance spectrum also demonstrate the formation of the superlattice in the ground state, which is clarified to be nonmagnetic. The divergence in 1 /T1 at TMI 1 shows that a symmetry lowering by the metal-insulator transition is accompanied by strong critical fluctuations of some degrees of freedom. Using the structural parameters in the insulating state, the first-principles calculation reproduces successfully the reasonable size of nuclear quadrupole frequencies νQ for the multiple As sites, ensuring the high validity of the structural parameters. The calculation also gives a remarkable suppression in the density of states near the Fermi level, although the gap opening is insufficient. A coupled modulation of the calculated Ru d -electron numbers and the crystal structure proposes the formation of a charge density wave in RuAs. Some lacking factors remain, but it is shown that a lifting of degeneracy protected by the nonsymmorphic symmetry through the superlattice formation is a key ingredient for the metal-insulator transition in RuAs.

Multiple Pathways for Benzyl Alcohol Oxidation by Ru V=O 3+ and Ru IV=O 2+

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul, Amit; Hull, Jonathan F.; Norris, Michael R.

2011-01-20

Significant rate enhancements are found for benzyl alcohol oxidation by the Ru V=O 3+ form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH 2)] 2+ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to Ru IV=O 2+ and for the Ru IV=O 2+ form with added bases due to a new pathway involving concerted hydride proton transfer (HPT).

Ru(III) catalyzed permanganate oxidation of aniline at environmentally relevant pH.

PubMed

Zhang, Jing; Zhang, Ying; Wang, Hui; Guan, Xiaohong

2014-07-01

Ru(III) was employed as catalyst for aniline oxidation by permanganate at environmentally relevant pH for the first time. Ru(III) could significantly improve the oxidation rate of aniline by 5-24 times with its concentration increasing from 2.5 to 15 μmol/L. The reaction of Ru(III) catalyzed permanganate oxidation of aniline was first-order with respect to aniline, permanganate and Ru(III), respectively. Thus the oxidation kinetics can be described by a third-order rate law. Aniline degradation by Ru(III) catalyzed permanganate oxidation was markedly influenced by pH, and the second-order rate constant (ktapp) decreased from 643.20 to 2.67 (mol/L)⁻¹sec⁻¹ with increasing pH from 4.0 to 9.0, which was possibly due to the decrease of permanganate oxidation potential with increasing pH. In both the uncatalytic and catalytic permanganate oxidation, six byproducts of aniline were identified in UPLC-MS/MS analysis. Ru(III), as an electron shuttle, was oxidized by permanganate to Ru(VI) and Ru(VII), which acted the co-oxidants for decomposition of aniline. Although Ru(III) could catalyze permanganate oxidation of aniline effectively, dosing homogeneous Ru(III) into water would lead to a second pollution. Therefore, efforts would be made to investigate the catalytic performance of supported Ru(III) toward permanganate oxidation in our future study. Copyright © 2014. Published by Elsevier B.V.

Tunable multifunctional topological insulators in ternary Heusler and related compounds

NASA Astrophysics Data System (ADS)

Felser, Claudia

2011-03-01

Recently the quantum spin Hall effect was theoretically predicted and experimentally realized in quantum wells based on the binary semiconductor HgTe. The quantum spin Hall state and topological insulators are new states of quantum matter interesting for both fundamental condensed-matter physics and material science. Many Heusler compounds with C1b structure are ternary semiconductors that are structurally and electronically related to the binary semiconductors. The diversity of Heusler materials opens wide possibilities for tuning the bandgap and setting the desired band inversion by choosing compounds with appropriate hybridization strength (by the lattice parameter) and magnitude of spin--orbit coupling (by the atomic charge). Based on first-principle calculations we demonstrate that around 50 Heusler compounds show band inversion similar to that of HgTe. The topological state in these zero-gap semiconductors can be created by applying strain or by designing an appropriate quantumwell structure, similar to the case of HgTe. Many of these ternary zero-gap semiconductors (LnAuPb, LnPdBi, LnPtSb and LnPtBi) contain the rare-earth element Ln, which can realize additional properties ranging from superconductivity (for example LaPtBi) to magnetism (for example GdPtBi) and heavy fermion behaviour (for example YbPtBi). These properties can open new research directions in realizing the quantized anomalous Hall effect and topological superconductors. Heusler compounds are similar to a stuffed diamond, correspondingly, it should be possible to find the ``high Z'' equivalent of graphene in a graphite-like structure with 18 valence electrons and with inverted bands. Indeed the ternary compounds, such as LiAuSe and KHgSb with a honeycomb structure of their Au-Se and Hg-Sb layers feature band inversion very similar to HgTe which is a strong precondition for existence of the topological surface states. These materials have a gap at the Fermi energy and are therefore candidates for 3D-topological insulators. Additionally they are centro-symmetric, therefore, it is possible to determine the parity of their wave functions, and hence, their topological character. Surprisingly, the compound KHgSb with the strong SOC is topologically trivial, whereas LiAuSe is found to be a topological non-trivial insulator.

SiO2 decoration dramatically enhanced the stability of PtRu electrocatalysts with undetectable deterioration in fuel cell performance.

PubMed

Yu, Xinxin; Xu, Zejun; Yang, Zehui; Xu, Sen; Zhang, Quan; Ling, Ying; Zhang, Yunfeng; Cai, Weiwei

2018-06-15

Prevention of Ru dissolution is essential for steady CO tolerance of anodic electrocatalysts in direct methanol fuel cells. Here, we demonstrate a facile way to stabilize Ru atoms by decorating commercial CB/PtRu with SiO 2 , which shows a six-fold higher stability and similar activity toward a methanol oxidation reaction leading to no discernible degradation in fuel cell performance compared to commercial CB/PtRu electrocatalysts. The higher stability and stable CO tolerance of SiO 2 -decorated electrocatalysts originate from the SiO 2 coating, since Ru atoms are partially ionized during SiO 2 decorating, resulting in difficulties in dissolution; while, in the case of commercial CB/PtRu, the dissolved Ru offers active sites for Pt coalescences and CO species resulting in the rapid decay of the electrochemical surface area and fuel cell performance. To the best of our knowledge, this is the first study about the stabilization of Ru atoms by SiO 2 . The highest stability is obtained for a PtRu electrocatalyst with negligible effect on the electrochemical properties.

Well-Defined Heterobimetallic Reactivity at Unsupported Ruthenium-Indium Bonds.

PubMed

Riddlestone, Ian M; Rajabi, Nasir A; Macgregor, Stuart A; Mahon, Mary F; Whittlesey, Michael K

2018-02-01

The hydride complex [Ru(IPr) 2 (CO)H][BAr F 4 ], 1, reacts with InMe 3 with loss of CH 4 to form [Ru(IPr) 2 (CO)(InMe)(Me)][BAr F 4 ], 4, featuring an unsupported Ru-In bond with unsaturated Ru and In centres. 4 reacts with H 2 to give [Ru(IPr) 2 (CO)(η 2 -H 2 )(InMe)(H)][BAr F 4 ], 5, while CO induces formation of the indyl complex [Ru(IPr) 2 (CO) 3 (InMe 2 )][BAr F 4 ], 7. These observations highlight the ability of Me to shuttle between Ru and In centres and are supported by DFT calculations on the mechanism of formation of 4 and its reactions with H 2 and CO. An analysis of Ru-In bonding in these species is also presented. Reaction of 1 with GaMe 3 also involves CH 4 loss but, in contrast to its In congener, sees IPr transfer from Ru to Ga to give a gallyl complex featuring an η 6 interaction of one aryl substituent with Ru. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

SiO2 decoration dramatically enhanced the stability of PtRu electrocatalysts with undetectable deterioration in fuel cell performance

NASA Astrophysics Data System (ADS)

Yu, Xinxin; Xu, Zejun; Yang, Zehui; Xu, Sen; Zhang, Quan; Ling, Ying; Zhang, Yunfeng; Cai, Weiwei

2018-06-01

Prevention of Ru dissolution is essential for steady CO tolerance of anodic electrocatalysts in direct methanol fuel cells. Here, we demonstrate a facile way to stabilize Ru atoms by decorating commercial CB/PtRu with SiO2, which shows a six-fold higher stability and similar activity toward a methanol oxidation reaction leading to no discernible degradation in fuel cell performance compared to commercial CB/PtRu electrocatalysts. The higher stability and stable CO tolerance of SiO2-decorated electrocatalysts originate from the SiO2 coating, since Ru atoms are partially ionized during SiO2 decorating, resulting in difficulties in dissolution; while, in the case of commercial CB/PtRu, the dissolved Ru offers active sites for Pt coalescences and CO species resulting in the rapid decay of the electrochemical surface area and fuel cell performance. To the best of our knowledge, this is the first study about the stabilization of Ru atoms by SiO2. The highest stability is obtained for a PtRu electrocatalyst with negligible effect on the electrochemical properties.

Ultrathin Cr added Ru film as a seedless Cu diffusion barrier for advanced Cu interconnects

NASA Astrophysics Data System (ADS)

Hsu, Kuo-Chung; Perng, Dung-Ching; Yeh, Jia-Bin; Wang, Yi-Chun

2012-07-01

A 5 nm thick Cr added Ru film has been extensively investigated as a seedless Cu diffusion barrier. High-resolution transmission electron microscopy micrograph, X-ray diffraction (XRD) pattern and Fourier transform-electron diffraction pattern reveal that a Cr contained Ru (RuCr) film has a glassy microstructure and is an amorphous-like film. XRD patterns and sheet resistance data show that the RuCr film is stable up to 650 °C, which is approximately a 200 °C improvement in thermal stability as compared to that of the pure Ru film. X-ray photoelectron spectroscopy depth profiles show that the RuCr film can successfully block Cu diffusion, even after a 30-min 650 °C annealing. The leakage current of the Cu/5 nm RuCr/porous SiOCH/Si stacked structure is about two orders of magnitude lower than that of a pristine Ru sample for electric field below 1 MV/cm. The RuCr film can be a promising Cu diffusion barrier for advanced Cu metallization.

Methyl-cyclopentadienyl Ruthenium Compounds with 2,2'-Bipyridine Derivatives Display Strong Anticancer Activity and Multidrug Resistance Potential.

PubMed

Côrte-Real, Leonor; Teixeira, Ricardo G; Gírio, Patrícia; Comsa, Elisabeta; Moreno, Alexis; Nasr, Rachad; Baubichon-Cortay, Hélène; Avecilla, Fernando; Marques, Fernanda; Robalo, M Paula; Mendes, Paulo; Ramalho, João P Prates; Garcia, M Helena; Falson, Pierre; Valente, Andreia

2018-04-16

New ruthenium methyl-cyclopentadienyl compounds bearing bipyridine derivatives with the general formula [Ru(η 5 -MeCp)(PPh 3 )(4,4'-R-2,2'-bpy)] + (Ru1, R = H; Ru2, R = CH 3 ; and Ru3, R = CH 2 OH) have been synthesized and characterized by spectroscopic and analytical techniques. Ru1 crystallized in the monoclinic P2 1 / c, Ru2 in the triclinic P1̅, and Ru3 in the monoclinic P2 1 / n space group. In all molecular structures, the ruthenium center adopts a "piano stool" distribution. Density functional theory calculations were performed for all complexes, and the results support spectroscopic data. Ru1 and Ru3 were poor substrates of the main multidrug resistance human pumps, ABCB1, ABCG2, ABCC1, and ABCC2, while Ru2 displayed inhibitory properties of ABCC1 and ABCC2 pumps. Importantly, all compounds displayed a very high cytotoxic profile for ovarian cancer cells (sensitive and resistant) that was much more pronounced than that observed with cisplatin, making them very promising anticancer agents.

The OGLE Collection of Variable Stars. Over 450 000 Eclipsing and Ellipsoidal Binary Systems Toward the Galactic Bulge

NASA Astrophysics Data System (ADS)

Soszyński, I.; Pawlak, M.; Pietrukowicz, P.; Udalski, A.; Szymański, M. K.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; Kozłowski, S.; Skowron, D. M.; Skowron, J.; Mróz, P.; Hamanowicz, A.

2016-12-01

We present a collection of 450 598 eclipsing and ellipsoidal binary systems detected in the OGLE fields toward the Galactic bulge. The collection consists of binary systems of all types: detached, semi-detached, and contact eclipsing binaries, RS CVn stars, cataclysmic variables, HW Vir binaries, double periodic variables, and even planetary transits. For all stars we provide the I- and V-band time-series photometry obtained during the OGLE-II, OGLE-III, and OGLE-IV surveys. We discuss methods used to identify binary systems in the OGLE data and present several objects of particular interest.

Determination of the axial rotation rate using apsidal motion for early-type eclipsing binaries

NASA Astrophysics Data System (ADS)

Khaliullin, Kh. F.; Khaliullina, A. I.

2007-11-01

Because the modern theory of stellar structure and evolution has a sound observational basis, we can consider that the apsidal parameters k2 computed in terms of this theory correctly reflect the radial density distribution in stars of different masses and spectral types. This allows us to address the problem of apsidal motion in close binary systems in a new way. Unlike the traditional approach, in this paper we use the observed apsidal periods Uobs to estimate the angular axial velocities of components, ωr, at fixed model values of k2. We use this approach to analyse the observational data for 28 eclipsing systems with known Uobs and early-type primaries (M >= 1.6 Msolar or Te >= 6000 K). We measure the age of the system in units of the synchronization time, t/tsyn. Our analysis yielded the following results. (i) There is a clear correlation between ωr/ωsyn and t/tsyn: the younger a star, the higher the angular velocity of its axial rotation in units of ωsyn, the angular velocity at pseudo-synchronization. This correlation is more significant and obvious if the synchronization time, tsyn, is computed in terms of the Zahn theory. (ii) This observational fact implies that the synchronization of early-type components in close binary systems continues on the main sequence. The synchronization times for the inner layers of the components (i.e. those that are responsible for apsidal motion) are about 1.6 and 3.1 dex longer than those predicted by the theories of Zahn and Tassoul, respectively. The average initial angular velocities (for the zero-age main sequence) are equal to ω0/ωsyn ~ 2.0. The dependence of the parameter E2 on stellar mass probably needs to be refined in the Zahn theory. (iii) Some components of the eclipsing systems of the sample studied show radially differential axial rotation. This is consistent with the Zahn theory, which predicts that the synchronization starts at the surface, where radiative damping of dynamical tides occurs, and develops toward the interior. Therefore, one would expect the inner parts of young double early-type stars to rotate faster than the outer parts.

Activation of H2 over the Ru-Zn Bond in the Transition Metal-Lewis Acid Heterobimetallic Species [Ru(IPr)2(CO)ZnEt](.).

PubMed

Riddlestone, Ian M; Rajabi, Nasir A; Lowe, John P; Mahon, Mary F; Macgregor, Stuart A; Whittlesey, Michael K

2016-09-07

Reaction of [Ru(IPr)2(CO)H]BAr(F)4 with ZnEt2 forms the heterobimetallic species [Ru(IPr)2(CO)ZnEt]BAr(F)4 (2), which features an unsupported Ru-Zn bond. 2 reacts with H2 to give [Ru(IPr)2(CO)(η(2)-H2)(H)2ZnEt]BAr(F)4 (3) and [Ru(IPr)2(CO)(H)2ZnEt]BAr(F)4 (4). DFT calculations indicate that H2 activation at 2 proceeds via oxidative cleavage at Ru with concomitant hydride transfer to Zn. 2 can also activate hydridic E-H bonds (E = B, Si), and computed mechanisms for the facile H/H exchange processes observed in 3 and 4 are presented.

Bimolecular Coupling as a Vector for Decomposition of Fast-Initiating Olefin Metathesis Catalysts.

PubMed

Bailey, Gwendolyn A; Foscato, Marco; Higman, Carolyn S; Day, Craig S; Jensen, Vidar R; Fogg, Deryn E

2018-06-06

The correlation between rapid initiation and rapid decomposition in olefin metathesis is probed for a series of fast-initiating, phosphine-free Ru catalysts: the Hoveyda catalyst HII, RuCl 2 (L)(═CHC 6 H 4 - o-O i Pr); the Grela catalyst nG (a derivative of HII with a nitro group para to O i Pr); the Piers catalyst PII, [RuCl 2 (L)(═CHPCy 3 )]OTf; the third-generation Grubbs catalyst GIII, RuCl 2 (L)(py) 2 (═CHPh); and dianiline catalyst DA, RuCl 2 (L)( o-dianiline)(═CHPh), in all of which L = H 2 IMes = N,N'-bis(mesityl)imidazolin-2-ylidene. Prior studies of ethylene metathesis have established that various Ru metathesis catalysts can decompose by β-elimination of propene from the metallacyclobutane intermediate RuCl 2 (H 2 IMes)(κ 2 -C 3 H 6 ), Ru-2. The present work demonstrates that in metathesis of terminal olefins, β-elimination yields only ca. 25-40% propenes for HII, nG, PII, or DA, and none for GIII. The discrepancy is attributed to competing decomposition via bimolecular coupling of methylidene intermediate RuCl 2 (H 2 IMes)(═CH 2 ), Ru-1. Direct evidence for methylidene coupling is presented, via the controlled decomposition of transiently stabilized adducts of Ru-1, RuCl 2 (H 2 IMes)L n (═CH 2 ) (L n = py n' ; n' = 1, 2, or o-dianiline). These adducts were synthesized by treating in situ-generated metallacyclobutane Ru-2 with pyridine or o-dianiline, and were isolated by precipitating at low temperature (-116 or -78 °C, respectively). On warming, both undergo methylidene coupling, liberating ethylene and forming RuCl 2 (H 2 IMes)L n . A mechanism is proposed based on kinetic studies and molecular-level computational analysis. Bimolecular coupling emerges as an important contributor to the instability of Ru-1, and a potentially major pathway for decomposition of fast-initiating, phosphine-free metathesis catalysts.

Improving geothermal power plants with a binary cycle

NASA Astrophysics Data System (ADS)

Tomarov, G. V.; Shipkov, A. A.; Sorokina, E. V.

2015-12-01

The recent development of binary geothermal technology is analyzed. General trends in the introduction of low-temperature geothermal sources are summarized. The use of single-phase low-temperature geothermal fluids in binary power plants proves possible and expedient. The benefits of power plants with a binary cycle in comparison with traditional systems are shown. The selection of the working fluid is considered, and the influence of the fluid's physicochemical properties on the design of the binary power plant is discussed. The design of binary power plants is based on the chemical composition and energy potential of the geothermal fluids and on the landscape and climatic conditions at the intended location. Experience in developing a prototype 2.5 MW Russian binary power unit at Pauzhetka geothermal power plant (Kamchatka) is outlined. Most binary systems are designed individually for a specific location. Means of improving the technology and equipment at binary geothermal power plants are identified. One option is the development of modular systems based on several binary systems that employ the heat from the working fluid at different temperatures.

Contact Binaries on Their Way Towards Merging

NASA Astrophysics Data System (ADS)

Gazeas, K.

2015-07-01

Contact binaries are the most frequently observed type of eclipsing star system. They are small, cool, low-mass binaries belonging to a relatively old stellar population. They follow certain empirical relationships that closely connect a number of physical parameters with each other, largely because of constraints coming from the Roche geometry. As a result, contact binaries provide an excellent test of stellar evolution, specifically for stellar merger scenarios. Observing campaigns by many authors have led to the cataloging of thousands of contact binaries and enabled statistical studies of many of their properties. A large number of contact binaries have been found to exhibit extraordinary behavior, requiring follow-up observations to study their peculiarities in detail. For example, a doubly-eclipsing quadruple system consisting of a contact binary and a detached binary is a highly constrained system offering an excellent laboratory to test evolutionary theories for binaries. A new observing project was initiated at the University of Athens in 2012 in order to investigate the possible lower limit for the orbital period of binary systems before coalescence, prior to merging.

Synthesis and Hydrodeoxygenation Properties of Ruthenium Phosphide Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowker, Richard H.; Smith, Mica C.; Pease, Melissa

2011-07-01

Ru2P/SiO2 and RuP/SiO2 catalysts were prepared by the temperature-programmed reduction (TPR) of uncalcined precursors containing hypophosphite ion (H2PO2-) as the phosphorus source. The Ru2P/SiO2 and RuP/SiO2 catalysts had small average particle sizes (~4 nm) and high CO chemisorption capacities (90-110 umol/g). The Ru phosphide catalysts exhibited similar or higher furan (C4H4O) hydrodeoxygenation (HDO) activities than did a Ru/SiO2 catalyst, and the phosphide catalysts favored C4 hydrocarbon products while the Ru metal catalyst produced primarily C3 hydrocarbons.

Dynamics of rotationally fissioned asteroids: Source of observed small asteroid systems

NASA Astrophysics Data System (ADS)

Jacobson, Seth A.; Scheeres, Daniel J.

2011-07-01

We present a model of near-Earth asteroid (NEA) rotational fission and ensuing dynamics that describes the creation of synchronous binaries and all other observed NEA systems including: doubly synchronous binaries, high- e binaries, ternary systems, and contact binaries. Our model only presupposes the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, "rubble pile" asteroid geophysics, and gravitational interactions. The YORP effect torques a "rubble pile" asteroid until the asteroid reaches its fission spin limit and the components enter orbit about each other (Scheeres, D.J. [2007]. Icarus 189, 370-385). Non-spherical gravitational potentials couple the spin states to the orbit state and chaotically drive the system towards the observed asteroid classes along two evolutionary tracks primarily distinguished by mass ratio. Related to this is a new binary process termed secondary fission - the secondary asteroid of the binary system is rotationally accelerated via gravitational torques until it fissions, thus creating a chaotic ternary system. The initially chaotic binary can be stabilized to create a synchronous binary by components of the fissioned secondary asteroid impacting the primary asteroid, solar gravitational perturbations, and mutual body tides. These results emphasize the importance of the initial component size distribution and configuration within the parent asteroid. NEAs may go through multiple binary cycles and many YORP-induced rotational fissions during their approximately 10 Myr lifetime in the inner Solar System. Rotational fission and the ensuing dynamics are responsible for all NEA systems including the most commonly observed synchronous binaries.

Close binary systems among very low-mass stars and brown dwarfs

NASA Astrophysics Data System (ADS)

Jeffries, R. D.; Maxted, P. F. L.

2005-12-01

Using Monte Carlo simulations and published radial velocity surveys we have constrained the frequency and separation (a) distribution of very low-mass star (VLM) and brown dwarf (BD) binary systems. We find that simple Gaussian extensions of the observed wide binary distribution, with a peak at 4 AU and 0.6<\\sigma_{\\log(a/AU)}<1.0, correctly reproduce the observed number of close binary systems, implying a close (a<2.6 AU) binary frequency of 17-30 % and overall frequency of 32-45 %. N-body models of the dynamical decay of unstable protostellar multiple systems are excluded with high confidence because they do not produce enough close binary VLMs/BDs. The large number of close binaries and high overall binary frequency are also completely inconsistent with published smoothed particle hydrodynamical modelling and argue against a dynamical origin for VLMs/BDs.

Spectroscopic and Photometric Analysis of the HW Vir Star PTF1 J011339.09+225739.1

NASA Astrophysics Data System (ADS)

Wolz, Maximilian; Kupfer, Thomas; Drechsel, Horst; Heber, Ulrich; Irrgang, Andreas; Hermes, J. J.; Bloemen, Steven; Levitan, David; Dhillon, Vik; Marsh, TomR.

2018-05-01

HW Vir systems are rare eclipsing binary systems including a subdwarf B star (sdB) with a faint companion, mostly M-dwarfs. Up to now, 19 HW Vir systems have been published, three of them with substellar companions. We report the spectroscopic as well as photometric observation of the eclipsing sdB binary PTF1 J011339.09+225739.1 (PTF1 J0113) in a close (a=0.722 ± 0.023 R⊙), short period (P = 0.0933731(3)d) orbit. A quantitative spectral analysis of the sdB yields Te.=29280 ± 720 K, log(g)=5.77 ± 0.09 dex, and log(y)=-2.32 ± 0.12. The circular orbital velocity of the sdB of K1=74.2 ± 1.7 km s-1 is derived from the radial velocity curve. Except for the strong reflection effect, no other light contribution of the companion could be detected. The light curves - recorded with ULTRACAM - were analyzed using the Wilson-Devinney code. We find an inclination angle of i=79.88 ± 0.18∘. Because our first attempts to determine q failed, we calculated large grids of synthetic lightcurves for several mass ratios. Because of degeneracy, good solutions for different mass ratios were found - the one at q = 0.24 is consistent with the sdB's canonical mass (MsdB = 0.47 M⊙). Accordingly, the mass of the companion is M2=0.112 ± 0.003 M⊙. The radii of the two components were also derived: RsdB=0.178 ± 0.006 R⊙ and R2 = 0.158 ± 0.009 R⊙. Thus, the results for the secondary are consistent with an M-dwarf as secondary

Progress towards an Optimization Methodology for Combustion-Driven Portable Thermoelectric Power Generation Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnan, Shankar; Karri, Naveen K.; Gogna, Pawan K.

2012-03-13

Enormous military and commercial interests exist in developing quiet, lightweight, and compact thermoelectric (TE) power generation systems. This paper investigates design integration and analysis of an advanced TE power generation system implementing JP-8 fueled combustion and thermal recuperation. Design and development of a portable TE power system using a JP-8 combustor as a high temperature heat source and optimal process flows depend on efficient heat generation, transfer, and recovery within the system are explored. Design optimization of the system required considering the combustion system efficiency and TE conversion efficiency simultaneously. The combustor performance and TE sub-system performance were coupled directlymore » through exhaust temperatures, fuel and air mass flow rates, heat exchanger performance, subsequent hot-side temperatures, and cold-side cooling techniques and temperatures. Systematic investigation of this system relied on accurate thermodynamic modeling of complex, high-temperature combustion processes concomitantly with detailed thermoelectric converter thermal/mechanical modeling. To this end, this work reports on design integration of systemlevel process flow simulations using commercial software CHEMCADTM with in-house thermoelectric converter and module optimization, and heat exchanger analyses using COMSOLTM software. High-performance, high-temperature TE materials and segmented TE element designs are incorporated in coupled design analyses to achieve predicted TE subsystem level conversion efficiencies exceeding 10%. These TE advances are integrated with a high performance microtechnology combustion reactor based on recent advances at the Pacific Northwest National Laboratory (PNNL). Predictions from this coupled simulation established a basis for optimal selection of fuel and air flow rates, thermoelectric module design and operating conditions, and microtechnology heat-exchanger design criteria. This paper will discuss this simulation process that leads directly to system efficiency power maps defining potentially available optimal system operating conditions and regimes. This coupled simulation approach enables pathways for integrated use of high-performance combustor components, high performance TE devices, and microtechnologies to produce a compact, lightweight, combustion driven TE power system prototype that operates on common fuels.« less

Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

NASA Astrophysics Data System (ADS)

Grabow, Lars C.; Yuan, Qiuyi; Doan, Hieu A.; Brankovic, Stanko R.

2015-10-01

A single layer, bi-metallic RuPt catalyst on Au(111) is synthesized using surface limited red-ox replacement of underpotentially deposited Cu and Pb monolayers though a two-step process. The resulting 2D RuPt monolayer nanoclusters have a unique core-edge structure with a Ru core and Pt at the edge along the perimeter. The activity of this catalyst is evaluated using CO monolayer oxidation as the probe reaction. Cyclic voltammetry demonstrates that the 2D RuPt core-edge catalyst morphology is significantly more active than either Pt or Ru monolayer catalysts. Density functional theory calculations in combination with infra-red spectroscopy data point towards oscillating variations (ripples) in the adsorption energy landscape along the radial direction of the Ru core as the origin of the observed behavior. Both, CO and OH experience a thermodynamic driving force for surface migration towards the Ru-Pt interface, where they adsorb most strongly and react rapidly. We propose that the complex interplay between epitaxial strain, ligand and finite size effects is responsible for the formation of the rippled RuPt monolayer cluster, which provides optimal conditions for a quasi-ideal bi-functional mechanism for CO oxidation, in which CO is adsorbed mainly on Pt, and Ru provides OH to the active Pt-Ru interface.

A new approach to synthesize supported ruthenium phosphides for hydrodesulfurization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Qingfang; Key Laboratory of Advanced Energy Materials Chemistry; Wang, Zhiqiang

2016-02-15

Highlights: • We bring out a new method to synthesize noble metal phosphides at low temperature. • Both RuP and Ru{sub 2}P were synthesized using triphenylphosphine as phosphorus sources. • Ru{sub 2}P was the better active phase for HDS than RuP and metal Ru. • RuP/SiO{sub 2} prepared by new method had better HDS activity to that by TPR method. - Abstract: Supported noble metal ruthenium phosphides were synthesized by one-step H{sub 2}-thermal treatment method using triphenylphosphine (TPP) as phosphorus sources at low temperatures. Two phosphides RuP and Ru{sub 2}P can be prepared by this method via varying the molarmore » ratio of metal salt and TPP. The as-prepared phosphides were characterized by X-ray powder diffraction (XRD), low-temperature N{sub 2} adsorption, CO chemisorption and transmission electronic microscopy (TEM). The supported ruthenium phosphides prepared by new method and conventional method together with contradistinctive metallic ruthenium were evaluated in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The catalytic results showed that metal-rich Ru{sub 2}P was the better active phase for HDS than RuP and metal Ru. Besides this, ruthenium phosphide catalyst prepared by new method exhibited superior HDS activity to that prepared by conventional method.« less

Formation and nitrile hydrogenation performance of Ru nanoparticles on a K-doped Al2O3 surface.

PubMed

Muratsugu, Satoshi; Kityakarn, Sutasinee; Wang, Fei; Ishiguro, Nozomu; Kamachi, Takashi; Yoshizawa, Kazunari; Sekizawa, Oki; Uruga, Tomoya; Tada, Mizuki

2015-10-14

Decarbonylation-promoted Ru nanoparticle formation from Ru3(CO)12 on a basic K-doped Al2O3 surface was investigated by in situ FT-IR and in situ XAFS. Supported Ru3(CO)12 clusters on K-doped Al2O3 were converted stepwise to Ru nanoparticles, which catalyzed the selective hydrogenation of nitriles to the corresponding primary amines via initial decarbonylation, the nucleation of the Ru cluster core, and the growth of metallic Ru nanoparticles on the surface. As a result, small Ru nanoparticles, with an average diameter of less than 2 nm, were formed on the support and acted as efficient catalysts for nitrile hydrogenation at 343 K under hydrogen at atmospheric pressure. The structure and catalytic performance of Ru catalysts depended strongly on the type of oxide support, and the K-doped Al2O3 support acted as a good oxide for the selective nitrile hydrogenation without basic additives like ammonia. The activation of nitriles on the modelled Ru catalyst was also investigated by DFT calculations, and the adsorption structure of a nitrene-like intermediate, which was favourable for high primary amine selectivity, was the most stable structure on Ru compared with other intermediate structures.

A new photoactive Ru(II)tris(2,2'-bipyridine) templated Zn(II) benzene-1,4-dicarboxylate metal organic framework: structure and photophysical properties.

PubMed

Whittington, Christi L; Wojtas, Lukasz; Gao, Wen-Yang; Ma, Shengqian; Larsen, Randy W

2015-03-28

It has now been demonstrated that Ru(ii)tris(2,2'-bipyridine) (RuBpy) can be utilized to template the formation of new metal organic framework (MOF) materials containing crystallographically resolved RuBpy clusters with unique photophysical properties. Two such materials, RWLC-1 and RWLC-2, have now been reported from our laboratory and are composed of RuBpy encapsulated in MOFs composed of Zn(ii) ions and 1,3,5-tris(4-carboxyphenyl)benzene ligands (C. L. Whittington, L. Wojtas and R. W. Larsen, Inorg. Chem., 2014, 53, 160-166). Here, a third RuBpy templated photoactive MOF is described (RWLC-3) that is derived from the reaction between Zn(ii) ions and 1,4-dicarboxybenzene in the presence of RuBpy. Single Crystal X-ray diffraction studies determined the position of RuBpy cations within the crystal lattice. The RWLC-3 structure is described as a 2-fold interpenetrated pillared honeycomb network (bnb) containing crystallographically resolved RuBpy clusters. The two bnb networks are weakly interconnected. The encapsulated RuBpy exhibits two emission decay lifetimes (τ-fast = 120 ns, τ-slow = 453 ns) and a bathochromic shift in the steady state emission spectrum relative to RuBpy in ethanol.

General synthesis of (salen)ruthenium(III) complexes via N...N coupling of (salen)ruthenium(VI) nitrides.

PubMed

Man, Wai-Lun; Kwong, Hoi-Ki; Lam, William W Y; Xiang, Jing; Wong, Tsz-Wing; Lam, Wing-Hong; Wong, Wing-Tak; Peng, Shie-Ming; Lau, Tai-Chu

2008-07-07

Reaction of [Ru (VI)(N)(L (1))(MeOH)] (+) (L (1) = N, N'-bis(salicylidene)- o-cyclohexylenediamine dianion) with excess pyridine in CH 3CN produces [Ru (III)(L (1))(py) 2] (+) and N 2. The proposed mechanism involves initial equilibrium formation of [Ru (VI)(N)(L (1))(py)] (+), which undergoes rapid N...N coupling to produce [(py)(L (1))Ru (III) N N-Ru (III)(L (1))(py)] (2+); this is followed by pyridine substituion to give the final product. This ligand-induced N...N coupling of Ru (VI)N is utilized in the preparation of a series of new ruthenium(III) salen complexes, [Ru (III)(L)(X) 2] (+/-) (L = salen ligand; X = H 2O, 1-MeIm, py, Me 2SO, PhNH 2, ( t )BuNH 2, Cl (-) or CN (-)). The structures of [Ru (III)(L (1))(NH 2Ph) 2](PF 6) ( 6), K[Ru (III)(L (1))(CN) 2] ( 9), [Ru (III)(L (2))(NCCH 3) 2][Au (I)(CN) 2] ( 11) (L (2) = N, N'-bis(salicylidene)- o-phenylenediamine dianion) and [N ( n )Bu 4][Ru (III)(L (3))Cl 2] ( 12) (L (3) = N, N'-bis(salicylidene)ethylenediamine dianion) have been determined by X-ray crystallography.

Comparison of physical and photophysical properties of monometallic and bimetallic ruthenium(II) complexes containing structurally altered diimine ligands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Macatangay, A.; Jackman, D.C.; Merkert, J.W.

1996-11-06

The physical and photophysical properties of a series of monometallic, [Ru(bpy){sub 2}(dmb)]{sup 2+}, [Ru(bpy){sub 2}(BPY)]{sup 2+}, [Ru(bpy)(Obpy)]{sup 2+} and [Ru(bpy){sub 2}(Obpy)] {sup 2+}, and bimetallic, [(Ru(bpy){sub 2}){sub 2}(BPY)]{sup 4+} and [(Ru(bpy){sub 2}){sub 2}(Obpy)]{sup 4+}, complexes are examined, where bpy is 2,2{prime}-bipyridine, dmb is 4,4{prime}-dimethyl-2,2{prime}-bipyridine, BPY is 1,2-bis(4-methyl-2,2{prime}-bipyridin-4{prime}-yl)ethane, and Obpy is 1,2-bis(2,2{prime}-bipyridin-6-yl)ethane. The complexes display metal-to-ligand charge transfer transitions in the 450 nmn region, intraligand {pi}{yields}{pi}* transitions at energies greater than 300 nm, a reversible oxidation of the ruthenium(II) center in the 1.25-1.40 V vs SSCE region, a series of three reductions associated with each coordinated ligand commencing at {minus}1.3 Vmore » and ending at {approximately}{minus}1.9 V, and emission from a {sup 3}MLCT state having energy maxima between 598 and 610 nm. The Ru{sup III}/Ru{sup II} oxidation of the two bimetallic complexes is a single, two one-electron process. Relative to [Ru(bpy){sub 2}(BPY)]{sup 2+}, the Ru{sup III}/Ru{sup II} potential for [Ru-(bpy){sub 2}(Obpy)]{sup 2+} increases from 1.24 to 1.35 V, the room temperature emission lifetime decreases from 740 to 3ns, and the emission quantum yield decreases from 0.078 to 0.000 23. Similarly, relative to [(Ru(bpy){sub 2}){sub 2}(BPY)]{sup 4+}, the Ru{sup III}/Ru{sup II} potential for [(Ru(bpy){sub 2}){sub 2}(Obpy)]{sup 4+} increases from 1.28 to 1.32 V, the room temperature emission lifetime decreases from 770 to 3 ns, and the room temperature emission quantum yield decreases from 0.079 to 0.000 26.« less

Structural and functional similarities between a ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO)-like protein from Bacillus subtilis and photosynthetic RuBisCO.

PubMed

Saito, Yohtaro; Ashida, Hiroki; Sakiyama, Tomoko; de Marsac, Nicole Tandeau; Danchin, Antoine; Sekowska, Agnieszka; Yokota, Akiho

2009-05-08

The sequences classified as genes for various ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (RuBisCO)-like proteins (RLPs) are widely distributed among bacteria, archaea, and eukaryota. In the phylogenic tree constructed with these sequences, RuBisCOs and RLPs are grouped into four separate clades, forms I-IV. In RuBisCO enzymes encoded by form I, II, and III sequences, 19 conserved amino acid residues are essential for CO(2) fixation; however, 1-11 of these 19 residues are substituted with other amino acids in form IV RLPs. Among form IV RLPs, the only enzymatic activity detected to date is a 2,3-diketo-5-methylthiopentyl 1-phosphate (DK-MTP-1-P) enolase reaction catalyzed by Bacillus subtilis, Microcystis aeruginosa, and Geobacillus kaustophilus form IV RLPs. RLPs from Rhodospirillum rubrum, Rhodopseudomonas palustris, Chlorobium tepidum, and Bordetella bronchiseptica were inactive in the enolase reaction. DK-MTP-1-P enolase activity of B. subtilis RLP required Mg(2+) for catalysis and, like RuBisCO, was stimulated by CO(2). Four residues that are essential for the enolization reaction of RuBisCO, Lys(175), Lys(201), Asp(203), and Glu(204), were conserved in RLPs and were essential for DK-MTP-1-P enolase catalysis. Lys(123), the residue conserved in DK-MTP-1-P enolases, was also essential for B. subtilis RLP enolase activity. Similarities between the active site structures of RuBisCO and B. subtilis RLP were examined by analyzing the effects of structural analogs of RuBP on DK-MTP-1-P enolase activity. A transition state analog for the RuBP carboxylation of RuBisCO was a competitive inhibitor in the DK-MTP-1-P enolase reaction with a K(i) value of 103 mum. RuBP and d-phosphoglyceric acid, the substrate and product, respectively, of RuBisCO, were weaker competitive inhibitors. These results suggest that the amino acid residues utilized in the B. subtilis RLP enolase reaction are the same as those utilized in the RuBisCO RuBP enolization reaction.

Particle size distribution of radioactive aerosols after the Fukushima and the Chernobyl accidents.

PubMed

Malá, Helena; Rulík, Petr; Bečková, Vera; Mihalík, Ján; Slezáková, Miriam

2013-12-01

Following the Fukushima accident, a series of aerosol samples were taken between 24th March and 13th April 2011 by cascade impactors in the Czech Republic to obtain the size distribution of (131)I, (134)Cs, (137)Cs, and (7)Be aerosols. All distributions could be considered monomodal. The arithmetic means of the activity median aerodynamic diameters (AMADs) for artificial radionuclides and for (7)Be were 0.43 and 0.41 μm with GDSs 3.6 and 3.0, respectively. The time course of the AMADs of (134)Cs, (137)Cs and (7)Be in the sampled period showed a slight decrease at a significance level of 0.05, whereas the AMAD pertaining to (131)I increased at a significance level of 0.1. Results obtained after the Fukushima accident were compared with results obtained after the Chernobyl accident. The radionuclides released during the Chernobyl accident for which we determined the AMAD fell into two categories: refractory radionuclides ((140)Ba, (140)La (141)Ce, (144)Ce, (95)Zr and (95)Nb) and volatile radionuclides ((134)Cs, (137)Cs, (103)Ru, (106)Ru, (131)I, and (132)Te). The AMAD of the refractory radionuclides was approximately 3 times higher than the AMAD of the volatile radionuclides; nevertheless, the size distributions for volatile radionuclides having a mean AMAD value of 0.51 μm were very close to the distributions after the Fukushima accident. Copyright © 2013 Elsevier Ltd. All rights reserved.

Syntheses, structural determinations of [Ru(ROCS2)2(PPh3)2](+/0) pairs, and kinetic analyses of thermal reactions involving transient trans-[Ru(iPrOCS2)2(PPh3)2] species (ROCS2(-) = ethyl- or isopropyldithiocarbonate and PPh3 = triphenylphosphine).

PubMed

Noda, Kyoko; Ohuchi, Yuko; Hashimoto, Akira; Fujiki, Masayuki; Itoh, Sumitaka; Iwatsuki, Satoshi; Noda, Toshiaki; Suzuki, Takayoshi; Kashiwabara, Kazuo; Takagi, Hideo D

2006-02-06

Controlled-potential electrochemical oxidation of cis-[Ru(ROCS2)2(PPh3)2] (R = Et, iPr) yielded corresponding Ru(III) complexes, and the crystal structures of cis-[Ru(ROCS2)2(PPh3)2] and trans-[Ru(ROCS2)2(PPh3)2](PF6) were determined. Both pairs of complexes exhibited almost identical coordination structures. The Ru-P distances in trans-[Ru(III)(ROCS2)2(PPh3)2](PF6) [2.436(3)-2.443(3) A] were significantly longer than those in cis-[Ru(II)(ROCS2)2(PPh3)2] [2.306(1)-2.315(2) A]: the smaller ionic radius of Ru(III) than that of Ru(II) stabilizes the trans conformation for the Ru(III) complex due to the steric requirement of bulky phosphine ligands while mutual trans influence by the phosphine ligands induces significant elongation of the Ru(III)-P bonds. Cyclic voltammograms of the cis-[Ru(ROCS2)2(PPh3)2] and trans-[Ru(ROCS2)2(PPh3)2]+ complexes in dichloromethane solution exhibited typical dual redox signals corresponding to the cis-[Ru(ROCS2)2(PPh3)2](+/0) (ca. +0.15 and +0.10 V vs ferrocenium/ferrocene couple for R = Et and iPr, respectively) and to trans-[Ru(ROCS2)2(PPh3)2](+/0) (-0.05 and -0.15 V vs ferrocenium/ferrocene for R = Et and iPr, respectively) couples. Analyses on the basis of the Nicholson and Shain's method revealed that the thermal disappearance rate of transient trans-[Ru(ROCS2)2(PPh3)2] was dependent on the concentration of PPh3 in the bulk: the rate constant for the intramolecular isomerization reaction of trans-[Ru(iPrOCS2)2(PPh3)2] was determined as 0.338 +/- 0.004 s(-1) at 298.3 K (deltaH* = 41.8 +/- 1.5 kJ mol(-1) and deltaS* = -114 +/- 7 J mol(-1) K(-1)), while the dissociation rate constant of coordinated PPh3 from the trans-[Ru(iPrOCS2)2(PPh3)2] species was estimated as 0.113 +/- 0.008 s(-1) at 298.3 K (deltaH* = 97.6 +/- 0.8 kJ mol(-1) and deltaS* = 64 +/- 3 J mol(-1) K(-1)), by monitoring the EC reaction (electrode reaction followed by chemical processes) at different concentrations of PPh3 in the bulk. It was found that the trans to cis isomerization reaction takes place via the partial dissociation of iPrOCS2(-) from Ru(II), contrary to the previous claim that it takes place by the twist mechanism.

Density functional theory calculations on transition metal atoms adsorbed on graphene monolayers

NASA Astrophysics Data System (ADS)

Dimakis, Nicholas; Flor, Fernando Antonio; Salgado, Andres; Adjibi, Kolade; Vargas, Sarah; Saenz, Justin

2017-11-01

Transition metal atom adsorption on graphene monolayers has been elucidated using periodic density functional theory under hybrid and generalized gradient approximation functionals. More specifically, we examined the adsorption of Cu, Fe, Zn, Ru, and Os on graphene monolayers by calculating, among others, the electronic density-of-states spectra of the adatom-graphene system and the overlap populations of the adatom with the nearest adsorbing graphene carbon atoms. These calculations reveal that Cu form primarily covalent bonds with graphene atoms via strong hybridization between the adatom orbitals and the sp band of the graphene substrate, whereas the interaction of the Ru and Os with graphene also contain ionic parts. Although the interaction of Fe with graphene atoms is mostly covalent, some charge transfer to graphene is also observed. The interaction of Zn with graphene is weak. Mulliken population analysis and charge contour maps are used to elucidate charge transfers between the adatom and the substrate. The adsorption strength is correlated with the metal adsorption energy and the height of the metal adatom from the graphene plane for the geometrically optimized adatom-graphene system. Our analysis shows that show that metal adsorption strength follows the adatom trend Ru ≈ Os > Fe > Cu > Zn, as verified by corresponding changes in the adsorption energies. The increased metal-carbon orbital overlap for the Ru relative to Os adatom is attributed to hybridization defects.

SIM Lite Detection of Habitable Planets in P-Type Binary-Planetary Systems

NASA Technical Reports Server (NTRS)

Pan, Xiaopei; Shao, Michael; Shaklan, Stuart; Goullioud, Renaud

2010-01-01

Close binary stars like spectroscopic binaries create a completely different environment than single stars for the evolution of a protoplanetary disk. Dynamical interactions between one star and protoplanets in such systems provide more challenges for theorists to model giant planet migration and formation of multiple planets. For habitable planets the majority of host stars are in binary star systems. So far only a small amount of Jupiter-size planets have been discovered in binary stars, whose minimum separations are 20 AU and the median value is about 1000 AU (because of difficulties in radial velocity measurements). The SIM Lite mission, a space-based astrometric observatory, has a unique capability to detect habitable planets in binary star systems. This work analyzed responses of the optical system to the field stop for companion stars and demonstrated that SIM Lite can observe exoplanets in visual binaries with small angular separations. In particular we investigated the issues for the search for terrestrial planets in P-type binary-planetary systems, where the planets move around both stars in a relatively distant orbit.

Efficient Synthesis of Ir-Polyoxometalate Cluster Using a Continuous Flow Apparatus and STM Investigation of Its Coassembly Behavior on HOPG Surface.

PubMed

Zhang, Junyong; Chang, Shaoqing; Suryanto, Bryan H R; Gong, Chunhua; Zeng, Xianghua; Zhao, Chuan; Zeng, Qingdao; Xie, Jingli

2016-06-06

Taking advantage of a continuous-flow apparatus, the iridium(III)-containing polytungstate cluster K12Na2H2[Ir2Cl8P2W20O72]·37H2O (1) was obtained in a reasonable yield (13% based on IrCl3·H2O). Compound 1 was characterized by Fourier transform IR, UV-visible, (31)P NMR, electrospray ionization mass spectrometry (ESI-MS), and thermogravimetric analysis measurements. (31)P NMR, ESI-MS, and elemental analysis all indicated 1 was a new polytungstate cluster compared with the reported K14[(IrCl4)KP2W20O72] compound. Intriguingly, the successful isolation of 1 relied on the custom-built flow apparatus, demonstrating the uniqueness of continuous-flow chemistry to achieve crystalline materials. The catalytic properties of 1 were assessed by investigating the activity on catalyzing the electro-oxidation of ruthenium tris-2,2'-bipyridine [Ru(bpy)3](2+/3+). The voltammetric behavior suggested a coupled catalytic behavior between [Ru(bpy)3](3+/2+) and 1. Furthermore, on the highly oriented pyrolytic graphite surface, 1,3,5-tris(10-carboxydecyloxy) benzene (TCDB) was used as the two-dimensional host network to coassemble cluster 1; the surface morphology was observed by scanning tunneling microscope technique. "S"-shape of 1 was observed, indicating that the cluster could be accommodated in the cavity formed by two TCDB host molecules, leading to a TCDB/cluster binary structure.

Ru sub 3 (CO) sub 12 and Mo (CO) sub 6 overlayers adsorbed on Ru(001) and Au/Ru and their interaction with electrons and photons: An infrared reflection--absorption study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malik, I.J.; Hrbek, J.

1991-05-01

We studied adsorbed Ru{sub 3}(CO){sub 12} and Mo (CO){sub 6} overlayers on Ru(001) and Au/Ru surfaces by infrared reflection--absorption spectroscopy (IRAS) and thermal desorption spectroscopy (TDS). We characterized the C--O stretching mode of both metal carbonyls (4 cm{sup {minus}1} FWHM) and a deformation mode of Mo (CO){sub 6} at 608 cm{sup {minus}1} with an unusually narrow FWHM of 1 cm{sup {minus}1}. Both IRAS and TDS data suggest adsorption and desorption of metal carbonyls as molecular species with a preferential orientation in the overlayers. We discuss annealing experiments of Ru{sub 3}(CO){sub 12}/Ru(001), the interaction of Ru{sub 3}(CO){sub 12} overlayers with electronsmore » of up to 100-eV energy, and the interaction of Mo (CO){sub 6} overlayers with 300-nm photons.« less

Measurement of excitation functions of helion-induced reactions on enriched Ru targets for production of medically important 103Pd and 101mRh and some other radionuclides.

PubMed

Skakun, Ye; Qaim, S M

2008-05-01

Excitation functions were determined by the stacked-foil and induced radioactivity measurement technique for the reactions (100)Ru(alpha,n)(103)Pd, (101)Ru(alpha,2n)(103)Pd, (101)Ru((3)He,n)(103)Pd, and (102)Ru((3)He,2n)(103)Pd, producing the therapeutic radionuclide (103)Pd, and for the reactions (101)Ru((3)He,x)(101 m)Rh(Cum) and (102)Ru((3)He,x)(101 m)Rh(Cum), producing the medically interesting radionuclide (101 m)Rh. Data were also measured for the reactions (101)Ru((3)He,pn+d)(102 m,g)Rh, (102)Ru((3)He,p2n+dn+t)(102 m,g)Rh, (101)Ru((3)He,x)(101 g)Rh(Cum), (102)Ru((3)He,x)(101 g)Rh(Cum), (101)Ru((3)He,3n)(101)Pd, (102)Ru((3)He,4n)(101)Pd, (101)Ru((3)He,4n)(100)Pd, and (101)Ru((3)He,p3n+d2n+tn)(100)Rh, producing other palladium and rhodium isotopes/isomers. The energy ranges covered were up to 25 MeV for alpha-particles and up to 34 MeV for (3)He ions. The radioactivity of the radionuclide (103)Pd induced in thin metallic foils of the enriched ruthenium isotopes was measured by high-resolution X-ray spectrometry and the radioactivities of other radionuclides by gamma-ray spectrometry. The integral thick target yields of the radionuclide (103)Pd calculated from the excitation functions of the first four of the above-named reactions amount to 960, 1050, 50, and 725 kBq/microAh, respectively, at the maximum investigated energies of the incident particles. The integral thick target yields of the radionuclide (101 m)Rh amount to 16.1 and 2.9 MBq/microAh for (101)Ru and (102)Ru targets, respectively, at 34 MeV energy of incident (3)He ions. The integral yields of the other observed radionuclides were also deduced from the excitation functions of the above-mentioned respective nuclear reactions. The excitation functions and integral yields of some rare reaction products were also determined. The experimental excitation functions of some reactions are compared with the predictions of nuclear model calculations. In general, good agreement was obtained.

Swift , XMM - Newton , and NuSTAR Observations of PSR J2032+4127/MT91 213

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, K. L.; Kong, A. K. H.; Tam, P. H. T.

2017-07-10

We report our recent Swift , NuSTAR , and XMM - Newton X-ray and Lijiang optical observations on PSR J2032+4127/MT91 213, the γ -ray binary candidate with a period of 45–50 years. The coming periastron of the system was predicted to be in 2017 November, around which high-energy flares from keV to TeV are expected. Recent studies with Chandra and Swift X-ray observations taken in 2015/2016 showed that its X-ray emission has been brighter by a factors of ∼10 than that before 2013, probably revealing some ongoing activities between the pulsar wind and the stellar wind. Our new Swift /XRTmore » lightcurve shows no strong evidence of a single vigorous brightening trend, but rather several strong X-ray flares on weekly to monthly timescales with a slowly brightening baseline, namely the low state. The NuSTAR and XMM - Newton observations taken during the flaring and the low states, respectively, show a denser environment and a softer power-law index during the flaring state, implying that the pulsar wind interacted with the stronger stellar winds of the companion to produce the flares. These precursors would be crucial in studying the predicted giant outburst from this extreme γ -ray binary during the periastron passage in late 2017.« less

Semiconductor-metal transition of Se in Ru-Se Catalyst Nanoparticles

NASA Astrophysics Data System (ADS)

Babu, P. K.; Lewera, Adam; Oldfield, Eric; Wieckowski, Andrzej

2009-03-01

Ru-Se composite nanoparticles are promising catalysts for the oxygen reduction reaction (ORR) in fuel cells. Though the role of Se in enhancing the chemical stability of Ru nanoparticles is well established, the microscopic nature of Ru-Se interaction was not clearly understood. We carried out a combined investigation of ^77Se NMR and XPS on Ru-Se nanoparticles and our results indicate that Se, a semiconductor in elemental form, becomes metallic when interacting with Ru. ^77Se spin-lattice relaxation rates are found to be proportional to T, the well-known Korringa behavior characteristic of metals. The NMR results are supported by the XPS binding energy shifts which suggest that a possible Ru->Se charge transfer could be responsible for the semiconductor->metal transition of Se which also makes Ru less susceptible to oxidation during ORR.

Initial and steady-state Ru growth by atomic layer deposition studied by in situ Angle Resolved X-ray Photoelectron Spectroscopy

NASA Astrophysics Data System (ADS)

Egorov, Konstantin V.; Lebedinskii, Yury Yu.; Soloviev, Anatoly A.; Chouprik, Anastasia A.; Azarov, Alexander Yu.; Markeev, Andrey M.

2017-10-01

The clear substrate-dependent growth and delayed film continuity are essential challenges of Ru atomic layer deposition (ALD) demanding adequate and versatile approaches for their study. Here, we report on the application of in situ Angle Resolved X-ray Phototelectron Spectroscopy (ARXPS) for investigation of initial and steady-state ALD growth of Ru using Ru(EtCp)2 and O2 as precursors. Using ARXPS surface analysis technique we determine such parameters of Ru ALD initial growth as incubation period, fractional coverage and the thickness of islands/film depending on the substrate chemical state, governed by the presence/absence of NH3/Ar plasma pretreatment. It was demonstrated that NH3/Ar plasma pretreatment allows to obtain the lowest incubation period (∼7 ALD cycles) resulting in a continuous ultrathin (∼20 Å) and smooth Ru films after 70 ALD cycles. In situ XPS at UHV was used at steady state Ru growth for analysis of half-cycle reactions that revealed formation of RuOx (x ≈ 2) layer with thickness of ∼8 Å after O2 pulse (first half-cycle). It was also shown that oxygen of RuOx layer combusts Ru(EtCp)2 ligands in the second half-cycle reaction and the observed Ru growth of ∼0.34 Å per cycle is in a good agreement with the amount of oxygen in the RuOx layer.

Radial mixing and Ru-Mo isotope systematics under different accretion scenarios

NASA Astrophysics Data System (ADS)

Fischer, Rebecca A.; Nimmo, Francis; O'Brien, David P.

2018-01-01

The Ru-Mo isotopic compositions of inner Solar System bodies may reflect the provenance of accreted material and how it evolved with time, both of which are controlled by the accretion scenario these bodies experienced. Here we use a total of 116 N-body simulations of terrestrial planet accretion, run in the Eccentric Jupiter and Saturn (EJS), Circular Jupiter and Saturn (CJS), and Grand Tack scenarios, to model the Ru-Mo anomalies of Earth, Mars, and Theia analogues. This model starts by applying an initial step function in Ru-Mo isotopic composition, with compositions reflecting those in meteorites, and traces compositional evolution as planets accrete. The mass-weighted provenance of the resulting planets reveals more radial mixing in Grand Tack simulations than in EJS/CJS simulations, and more efficient mixing among late-accreted material than during the main phase of accretion in EJS/CJS simulations. We find that an extensive homogeneous inner disk region is required to reproduce Earth's observed Ru-Mo composition. EJS/CJS simulations require a homogeneous reservoir in the inner disk extending to ≥3-4 AU (≥74-98% of initial mass) to reproduce Earth's composition, while Grand Tack simulations require a homogeneous reservoir extending to ≥3-10 AU (≥97-99% of initial mass), and likely to ≥6-10 AU. In the Grand Tack model, Jupiter's initial location (the most likely location for a discontinuity in isotopic composition) is ∼3.5 AU; however, this step location has only a 33% likelihood of producing an Earth with the correct Ru-Mo isotopic signature for the most plausible model conditions. Our results give the testable predictions that Mars has zero Ru anomaly and small or zero Mo anomaly, and the Moon has zero Mo anomaly. These predictions are insensitive to wide variations in parameter choices.