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Sample records for pt111 vicinal surfaces

  1. Double stripe reconstruction of the Pt(111) surface

    Indian Academy of Sciences (India)

    Raghani Pushpa; Shobhana Narasimhan

    2003-01-01

    We have studied the reconstruction of the Pt(111) surface theoretically, using a 2D generalization of the Frenkel–Kontorova model. The parameters in the model are obtained by performing ab initio density functional theory calculations. The Pt(111) surface does not reconstruct under normal conditions but experiments have shown that there are two ways to induce the reconstruction: by increasing the temperature, or by depositing adatoms on the surface. The basic motif of this reconstruction is a `double stripe’ with an increased surface density and alternating hcp and fcc domains, arranged to form a honeycomb pattern with a very large repeat distance of 100–300 Å. In this paper, we have studied the `double stripe’ reconstruction of the Pt(111) surface. In agreement with experiment, we find that it is favourable for the surface to reconstruct in the presence of adatoms, but not otherwise.

  2. Adsorption and coupling of 4-aminophenol on Pt(111) surfaces

    Science.gov (United States)

    Otero-Irurueta, G.; Martínez, J. I.; Bueno, R. A.; Palomares, F. J.; Salavagione, H. J.; Singh, M. K.; Méndez, J.; Ellis, G. J.; López, M. F.; Martín-Gago, J. A.

    2016-04-01

    We have deposited 4-aminophenol on Pt(111) surfaces in ultra-high vacuum and studied the strength of its adsorption through a combination of STM, LEED, XPS and ab initio calculations. Although an ordered (2√3 × 2√3)R30° phase appears, we have observed that molecule-substrate interaction dominates the adsorption geometry and properties of the system. At RT the high catalytic activity of Pt induces aminophenol to lose the H atom from the hydroxyl group, and a proportion of the molecules lose the complete hydroxyl group. After annealing above 420 K, all deposited aminophenol molecules have lost the OH moiety and some hydrogen atoms from the amino groups. At this temperature, short single-molecule oligomer chains can be observed. These chains are the product of a new reaction that proceeds via the coupling of radical species that is favored by surface diffusion.

  3. Reforming of oxygenates for H2 production: correlating reactivity of ethylene glycol and ethanol on Pt(111) and Ni/Pt(111) with surface d-band center.

    Science.gov (United States)

    Skoplyak, Orest; Barteau, Mark A; Chen, Jingguang G

    2006-02-02

    The dehydrogenation and decarbonylation of ethylene glycol and ethanol were studied using temperature programmed desorption (TPD) on Pt(111) and Ni/Pt(111) bimetallic surfaces, as probe reactions for the reforming of oxygenates for the production of H2 for fuel cells. Ethylene glycol reacted via dehydrogenation to form CO and H2, corresponding to the desired reforming reaction, and via total decomposition to produce C(ad), O(ad), and H2. Ethanol reacted by three reaction pathways, dehydrogenation, decarbonylation, and total decomposition, producing CO, H2, CH4, C(ad), and O(ad). Surfaces prepared by deposition of a monolayer of Ni on Pt(111) at 300 K, designated Ni-Pt-Pt(111), displayed increased reforming activity compared to Pt(111), subsurface monolayer Pt-Ni-Pt(111), and thick Ni/Pt(111). Reforming activity was correlated with the d-band center of the surfaces and displayed a linear trend for both ethylene glycol and ethanol, with activity increasing as the surface d-band center moved closer to the Fermi level. This trend was opposite to that previously observed for hydrogenation reactions, where increased activity occurred on subsurface monolayers as the d-band center shifted away from the Fermi level. Extrapolation of the correlation between activity and the surface d-band center of bimetallic systems may provide useful predictions for the selection and rational design of bimetallic catalysts for the reforming of oxygenates.

  4. Structure Determination of Au on Pt(111 Surface: LEED, STM and DFT Study

    Directory of Open Access Journals (Sweden)

    Katarzyna Krupski

    2015-05-01

    Full Text Available Low-energy electron diffraction (LEED, scanning tunneling microscopy (STM and density functional theory (DFT calculations have been used to investigate the atomic and electronic structure of gold deposited (between 0.8 and 1.0 monolayer on the Pt(111 face in ultrahigh vacuum at room temperature. The analysis of LEED and STM measurements indicates two-dimensional growth of the first Au monolayer. Change of the measured surface lattice constant equal to 2.80 Å after Au adsorption was not observed. Based on DFT, the distance between the nearest atoms in the case of bare Pt(111 and Au/Pt(111 surface is equal to 2.83 Å, which gives 1% difference in comparison with STM values. The first and second interlayer spacing of the clean Pt(111 surface are expanded by +0.87% and contracted by −0.43%, respectively. The adsorption energy of the Au atom on the Pt(111 surface is dependent on the adsorption position, and there is a preference for a hollow fcc site. For the Au/Pt(111 surface, the top interlayer spacing is expanded by +2.16% with respect to the ideal bulk value. Changes in the electronic properties of the Au/Pt(111 system below the Fermi level connected to the interaction of Au atoms with Pt(111 surface are observed.

  5. Surface electrochemistry of CO on Pt(111): Anion Effects

    Energy Technology Data Exchange (ETDEWEB)

    Markovic, N.M.; Lucas, C.A.; Rodes, A.; Stamenkovic, V.; Ross, P.N.

    2001-07-30

    In-situ studies of CO adsorption by surface x-ray scattering (SXS) and Fourier transform infrared (FTIR) spectroscopy techniques are used to create the link between the macroscopic kinetic rates of CO oxidation and the microscopic level of understanding the structure/site occupancy of CO on Pt(111). A remarkable difference in activity was observed between alkaline and acid solutions. In alkaline solution the oxidation of CO proceeds at low overpotential (<0.2 V) by the surface reaction between the adsorbed CO and OH, the latter forming selectively in the hydrogen underpotential potential region at defect sites. In acid solution these sites are blocked by specific adsorption of anions, and consequently in a solution containing Br{sup -} the ignition potential is shifted positively by 0.6 V. Anions of supporting electrolytes also have dramatic effects on both the potential range of stability and the domain size of the p(2x2)-3CO structure which is formed at 0.05 V. The stability/domain size of this structure increases from KOH (ca. 30 {angstrom} between 0.05 < E < 0.3V), to HClO{sub 4} (ca. 140 {angstrom} between 0.05 < E < 0.6V) to HClO{sub 4} + Br{sup -} (ca 350 {angstrom} between 0.05 < E < 0.8V). The larger the ordered domains of the p(2x2)-CO{sub ad} structure are, the less active the surface is towards CO oxidation.

  6. Electrochemical properties of CO{sub x}/Pt(111) model catalyst surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wadayama, T.; Todoroki, N.; Yoshida, H.; Yamada, Y. [Tohoku Univ., Sendai (Japan). Dept. of Materials Science

    2010-07-01

    Oxygen reduction reaction (ORR) activities for clean Pt(111) and Co-deposited Pt(111) (CO{sub x}/Pt(111)) model catalyst surfaces fabricated by molecular beam epitaxy (MBE) were evaluated. Low-energy electron diffration (LEED) and infrared reflection absorption spectroscopy (IRRAS) was used to investigate the CO{sub x}/Pt(111) surface structures. 1.0-L-carbon monoxide (CO) exposure to the clean Pt(111) at 323 K yielded linear-bonded and bridge-bonded CO-PT bands at 2092 and 1850 cm{sup -1}. 0.3nm-thick-Co deposition onto the clean Pt(111) at 343 K brought about small hexagons of satellites on a LEED pattern and a main IR band ascribable to Co-CO bonds is located at 2000 cm{sup -1}. In contrast, at 823-K-Co deposition, a LEED pattern is almost identical as that for the clean Pt(111): an absorbed CO band at 2080 cm{sup -1} dominated IR spectrum for the 1.0-L-CO exposed surface. The results suggest that the Co deposition at 823 K generates a Pt-enriched outermost surface (Pt-skin) formed through surface segregation of the substrate Pt atoms. A linear-sweep voltammetry (LSV) curve was recorded for the Co/Pt(111)-skin in O{sub 2}-saturated HCIO{sub 4}. Specific ORR activity for the Pt-skin is 10-times higher than that for the clean Pt(111). (orig.)

  7. Oxidation of formic acid on the Pt(111) surface in the gas phase.

    Science.gov (United States)

    Gao, Wang; Keith, John A; Anton, Josef; Jacob, Timo

    2010-09-28

    Formic acid (HCOOH) oxidation on Pt(111) under gas-phase conditions is a benchmark heterogeneous catalysis reaction used to probe electro-catalytic HCOOH conversion in fuel cells, itself an important reaction in energy conversion. We used density functional theory (DFT) calculations to elucidate the fundamental oxidation mechanisms of HCOOH in the gas phase, determining the relative strengths of chemical interactions between HCOOH oxidation intermediates and the Pt(111) surface. We focused on investigating how water and adsorption coverage affects reaction intermediate structures and transition states. Our results show that adsorbed HCOO is a reactive intermediate in gas phase, and co-adsorbed water plays a key role in HCOOH oxidation influencing the structure of reaction intermediates and reaction barriers on Pt(111). The simulations show the preferred catalytic pathway is qualitatively dependent on surface coverage. These results provide a conceptual basis to better interpret its complicated experimental reaction kinetics.

  8. Controlled FCC/on-top binding of H/Pt(111) using surface stress

    Science.gov (United States)

    Shuttleworth, I. G.

    2016-08-01

    The preferred binding site of H/Pt(111) has been shown to be change from the on-top to FCC as the Pt(111) surface goes approximately from a state of compressive to tensile strain. A chemical analysis of the system has shown that for both FCC and on-top bound cases the H ssbnd Pt s and H ssbnd Pt d interactions have a similar importance in determining the preferred binding position. It has been seen that FCC-bound H forms a distinct state below the Pt d-band, whereas the on-top bound H does not.

  9. Vibrational properties of the Pt(111)- p(2 × 2)-K surface superstructure

    Science.gov (United States)

    Rusina, G. G.; Eremeev, S. V.; Borisova, S. D.; Chulkov, E. V.

    2008-08-01

    The vibrational spectra of the Pt(111)- p(2 × 2)-K ordered surface superstructure formed on the platinum surface upon adsorption of 0.25 potassium monolayer are calculated using the interatomic interaction potentials obtained within the tight-binding approximation. The surface relaxation, the dispersion of surface phonons, the local density of surface vibrational states, and the polarization of vibrational modes of adatoms and substrate atoms are discussed. The theoretical results are in good agreement with the recently obtained experimental data.

  10. A first-principle calculation of sulfur oxidation on metallic Ni(111) and Pt(111), and bimetallic Ni@Pt(111) and Pt@Ni(111) surfaces.

    Science.gov (United States)

    Yeh, Chen-Hao; Ho, Jia-Jen

    2012-09-17

    Sulfur, a pollutant known to poison fuel-cell electrodes, generally comes from S-containing species such as hydrogen sulfide (H(2)S). The S-containing species become adsorbed on a metal electrode and leave atomic S strongly bound to the metal surface. This surface sulfur is completely removed typically by oxidation with O(2) into gaseous SO(2). According to our DFT calculations, the oxidation of sulfur at 0.25 ML surface sulfur coverage on pure Pt(111) and Ni(111) metal surfaces is exothermic. The barriers to the formation of SO(2) are 0.41 and 1.07 eV, respectively. Various metals combined to form bimetallic surfaces are reported to tune the catalytic capabilities toward some reactions. Our results show that it is more difficult to remove surface sulfur from a Ni@Pt(111) surface with reaction barrier 1.86 eV for SO(2) formation than from a Pt@Ni(111) surface (0.13 eV). This result is in good agreement with the statement that bimetallic surfaces could demonstrate more or less activity than to pure metal surfaces by comparing electronic and structural effects. Furthermore, by calculating the reaction free energies we found that the sulfur oxidation reaction on the Pt@Ni(111) surface exhibits the best spontaneity of SO(2) desorption at either room temperature or high temperatures.

  11. Electronic effects of surface oxygen on the bonding of NO to Pt(111)

    Energy Technology Data Exchange (ETDEWEB)

    Bartram, M.E.; Koel, B.E. (Univ. of Colorado, Boulder (United States)); Carter, E.A. (Univ. of California, Los Angeles (United States))

    1989-01-01

    Changes in the bonding of NO on Pt(111) induced by the coadsorption of high coverages of oxygen atoms have been studied with temperature programmed desorption (TPD), vibrational spectroscopy using high resolution electron energy loss spectroscopy (HREELS), and ultraviolet photoelectron spectroscopy (UPS). Modification of the electronic structure of surface Pt atoms by the strongly electron-withdrawing adsorbed oxygen atoms alters the relative stabilities of NO adsorption sites and the nature of the Pt-NO bond. Coadsorption of 0.25 ML (monolayers) of O{sub (a)} destabilizes the two-fold bridge site for NO adsorption that is energetically preferred on clean Pt(111) and causes preferential NO adsorption in the atop site initially. For this oxygen coverage, some population of the bridge site occurs at the highest NO coverages, but occupation of this site can be eliminated completely by preadsorption of 0.75 ML of oxygen. This high coverage of coadsorbed oxygen now induces a further change in the nature of the NO chemisorption bond for NO adsorbed in atop sties, forming bent NO rather than the linear NO species formed on clean Pt(111). The saturation coverage of bent NO is 0.15 ML on this 0.75 ML oxygen-precovered surface and the heat of adsorption is only 1-2 kcal/mol less than linear NO adsorbed in atop sites on clean Pt(111). By using the HREELS and UPS data to identify these three chemically distinct forms of NO{sub (a)}, the authors are able rationalize their formation (and subsequent properties) in different electron environments by correlating bonding configurations with the charge-transfer capabilities of the Pt substrate. Finally, they note that despite the presence of large excesses of O{sub (a)}, NO is never oxidized to form NO{sub 2}.

  12. Lignin-derived oxygenate reforming on a bimetallic surface: The reaction of benzaldehyde on Zn/Pt(111)

    Science.gov (United States)

    Shi, Daming; Vohs, John M.

    2016-08-01

    Temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) were used to characterize the adsorption and reaction of benzaldehyde (C6H5CHO) on hydrogen-covered Pt(111) and Zn-modified Pt(111) surfaces. Benzaldehyde was found to interact with Pt(111) via both the phenyl ring and carbonyl of the aldehyde group. This bonding configuration facilitates unselective decomposition of the benzaldehyde to produce CO, H2, and small hydrocarbon fragments at relatively low temperatures. On the other hand, benzaldehyde was found to bond to Zn-decorated Pt(111) surface exclusively via the carbonyl group in an η2(C, O) configuration, with the phenyl ring tilted away from the surface. This configuration weakens Csbnd O bond in the carbonyl facilitating its cleavage and helps prevent hydrogenation of the phenyl ring.

  13. Surface termination of CePt5/Pt (111 ): The key to chemical inertness

    Science.gov (United States)

    Praetorius, C.; Zinner, M.; Held, G.; Fauth, K.

    2015-11-01

    The surface termination of CePt5/Pt (111 ) is determined experimentally by LEED-IV. In accordance with recent theoretical predictions, a dense Pt terminated surface is being found. Whereas the CePt5 volume lattice comprises Pt kagome layers, additional Pt atoms occupy the associated hole positions at the surface. This finding provides a natural explanation for the remarkable inertness of the CePt5 intermetallic. Implications of the structural relaxations determined by LEED-IV analysis are discussed with regard to observations by scanning tunneling microscopy and electron spectroscopies.

  14. RKKY-like contributions to the magnetic anisotropy energy: 3 d adatoms on Pt(111) surface

    Science.gov (United States)

    Bouhassoune, Mohammmed; Dias, Manuel dos Santos; Zimmermann, Bernd; Dederichs, Peter H.; Lounis, Samir

    2016-09-01

    The magnetic anisotropy energy defines the energy barrier that stabilizes a magnetic moment. Utilizing density-functional-theory-based simulations and analytical formulations, we establish that this barrier is strongly modified by long-range contributions very similar to Friedel oscillations and Rudermann-Kittel-Kasuya-Yosida interactions. Thus, oscillations are expected and observed, with different decaying factors and highly anisotropic in realistic materials, which can switch nontrivially the sign of the magnetic anisotropy energy. This behavior is general, and for illustration we address the transition-metal adatoms, Cr, Mn, Fe, and Co deposited on a Pt(111) surface. We explain, in particular, the mechanisms leading to the strong site dependence of the magnetic anisotropy energy observed for Fe adatoms on a Pt(111) surface as revealed previously via first-principles-based simulations and inelastic scanning tunneling spectroscopy [A. A. Khajetoorians et al., Phys. Rev. Lett. 111, 157204 (2013), 10.1103/PhysRevLett.111.157204]. The same mechanisms are probably active for the site dependence of the magnetic anisotropy energy obtained for Fe adatoms on Pd or Rh(111) surfaces and for Co adatoms on a Rh(111) surface [P. Blonski et al., Phys. Rev. B 81, 104426 (2010), 10.1103/PhysRevB.81.104426].

  15. Adsorption and decomposition of cyclohexanone (C6H10O) on Pt(111) and the (2 × 2) and (√3 × √3)r30°-Sn/Pt(111) surface alloys.

    Science.gov (United States)

    Kim, Jooho; Welch, Lindsey A; Olivas, Amelia; Podkolzin, Simon G; Koel, Bruce E

    2010-11-02

    Adsorption and decomposition of cyclohexanone (C(6)H(10)O) on Pt(111) and on two ordered Pt-Sn surface alloys, (2 × 2)-Sn/Pt(111) and (√3 × √3)R30°-Sn/Pt(111), formed by vapor deposition of Sn on the Pt(111) single crystal surface were studied with TPD, HREELS, AES, LEED, and DFT calculations with vibrational analyses. Saturation coverage of C(6)H(10)O was found to be 0.25 ML, independent of the Sn surface concentration. The Pt(111) surface was reactive toward cyclohexanone, with the adsorption in the monolayer being about 70% irreversible. C(6)H(10)O decomposed to yield CO, H(2)O, H(2), and CH(4). Some C-O bond breaking occurred, yielding H(2)O and leaving some carbon on the surface after TPD. HREELS data showed that cyclohexanone decomposition in the monolayer began by 200 K. Intermediates from cyclohexanone decomposition were also relatively unstable on Pt(111), since coadsorbed CO and H were formed below 250 K. Surface Sn allowed for some cyclohexanone to adsorb reversibly. C(6)H(10)O dissociated on the (2 × 2) surface to form CO and H(2)O at low coverages, and methane and H(2) in smaller amounts than on Pt(111). Adsorption of cyclohexanone on (√3 × √3)R30°-Sn/Pt(111) at 90 K was mostly reversible. DFT calculations suggest that C(6)H(10)O adsorbs on Pt(111) in two configurations: by bonding weakly through oxygen to an atop Pt site and more strongly through simultaneously oxygen and carbon of the carbonyl to a bridged Pt-Pt site. In contrast, on alloy surfaces, C(6)H(10)O bonds preferentially to Sn. The presence of Sn, furthermore, is predicted to make the formation of the strongly bound C(6)H(10)O species bonding through O and C, which is a likely decomposition precursor, thermodynamically unfavorable. Alloying with Sn, thus, is shown to moderate adsorptive and reactive activity of Pt(111).

  16. Theoretical Study of CO Adsorption on Ni(111), Pt(111) and Pt/Ni(111) Surfaces

    Science.gov (United States)

    Cabeza, G. F.; Castellani, N. J.; Légaré, P.

    CO adsorption on a pseudomorphic Pt overlayer supported by Ni(111) has been studied with the use of extended Huckel calculations. Experimental information on the pure Pt(111) and Ni(111) single crystals was employed to select a consistent parameter set for our bimetallic system. This gives a good description of the chemisorption bond changes between the various systems considered in our study. The CO chemisorption energy on Pt/Ni(111) was found to be lowered in comparison with Pt(111) and Ni(111), in good agreement with experimental data on Pt-rich Pt-Ni surface alloys. This observation could be justified by the electronic changes of the Pt states (valence band broadening and decreasing density at the Fermi level). Indeed, they induce, in comparison with the pure substrates, a repulsion between Pt and CO although the 2π* population of the chemisorbed molecule increases. This points to the necessity of going beyond arguments based on an analysis of the 5σ donation and 2π* backdonation for a complete description of the chemisorption bond.

  17. Reversible Vertical Manipulations of Single Pt Adatom on Pt(111)Surface with a Triple-Apex Tip

    Institute of Scientific and Technical Information of China (English)

    XIE Yi-Qun; LIU Qing-Wei; ZHANG Peng; LI Yu-Fen; GAN Fu-Xi; ZHUANG Jun

    2008-01-01

    @@ With a triple-apex tip,we investigate theoretically the vertical manipulation of single Pt adatom on the Pt(111)surface.The adatom adsorbed on the fcc site of the flat Pt(111)surface can be transferred vertically to the tip by adjusting the tip height properly.Moreover,based on the strong vertical trapping ability and the relatively weak lateral trapping ability of the tip,we propose a simple method to realize a reversible vertical manipulation of the Pt adatom from the highly coordinated sites,the kink and the step sites,of the stepped Pt(111)surface.All the vertical manjpulations are completed using only the atomic force between the tip and the adatom,without the electric field.

  18. Molecular Precursors-Induced Surface Reconstruction at Graphene/Pt(111) Interfaces

    CERN Document Server

    Wang, Qian; Shi, Xingqiang

    2015-01-01

    Inspired by experimental observations of Pt(111) surfaces reconstruction at the Pt/graphene (Gr) interfaces with ordered vacancy networks in the outermost Pt layer, the mechanism of the surface reconstruction is investigated by van-der-Waals-corrected density functional theory in combination with particle-swarm optimization algorithm and ab initio atomistic thermodynamics. Our global structural search finds a more stable reconstructed (Rec) structure than that was reported before. With correction for vacancy formation energy, we demonstrate that the experimental observed surface reconstruction occurred at the earlier stages of graphene formation: 1) reconstruction occurred when C60 adsorption (before decomposition to form graphene) for C60 as a molecular precursor, or 2) reconstruction occurred when there were (partial) hydrogens retain in the adsorbed carbon structures for C2H4 and C60H30 as precursors. The reason can be attributed to that the energy gain, from the strengthened Pt-C bonding for C of C60 or f...

  19. Microcanonical unimolecular rate theory at surfaces. I. Dissociative chemisorption of methane on Pt(111)

    Science.gov (United States)

    Bukoski, A.; Blumling, D.; Harrison, I.

    2003-01-01

    A model of gas-surface reactivity is developed based on the ideas that (a) adsorbate chemistry is a local phenomenon, (b) the active system energy of an adsorbed molecule and a few immediately adjacent surface atoms suffices to fix microcanonical rate constants for surface kinetic processes such as desorption and dissociation, and (c) energy exchange between the local adsorbate-surface complexes and the surrounding substrate can be modeled via a Master equation to describe the system/heat reservoir coupling. The resulting microcanonical unimolecular rate theory (MURT) for analyzing and predicting both thermal equilibrium and nonequilibrium kinetics for surface reactions is applied to the dissociative chemisorption of methane on Pt(111). Energy exchange due to phonon-mediated energy transfer between the local adsorbate-surface complexes and the surface is explored and estimated to be insignificant for the reactive experimental conditions investigated here. Simulations of experimental molecular beam data indicate that the apparent threshold energy for CH4 dissociative chemisorption on Pt(111) is E0=0.61 eV (over a C-H stretch reaction coordinate), the local adsorbate-surface complex includes three surface oscillators, and the pooled energy from 16 active degrees of freedom is available to help surmount the dissociation barrier. For nonequilibrium molecular beam experiments, predictions are made for the initial methane dissociative sticking coefficient as a function of isotope, normal translational energy, molecular beam nozzle temperature, and surface temperature. MURT analysis of the thermal programmed desorption of CH4 physisorbed on Pt(111) finds the physisorption well depth is 0.16 eV. Thermal equilibrium dissociative sticking coefficients for methane on Pt(111) are predicted for the temperature range from 250-2000 K. Tolman relations for the activation energy under thermal equilibrium conditions and for a variety of "effective activation energies" under

  20. Interaction of CO with PtxAg1-x/Pt(111) surface alloys: More than dilution by Ag atoms

    Science.gov (United States)

    Schüttler, K. M.; Mancera, L. A.; Diemant, T.; Groß, A.; Behm, R. J.

    2016-08-01

    We have investigated CO adsorption on structurally well-defined PtxAg1-x/Pt(111) surface alloys, combining temperature-programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRRAS) as well as density functional theory (DFT) based calculations. This is part of a systematic approach including previous studies of CO adsorption on closely related Pt(111)- and Pd(111)-based surface alloys. Following changes in the adsorption properties with increasing Ag content and correlating them with structural changes allow us to assign desorption features to specific adsorption sites/ensembles identified in previous scanning tunneling microscopy (STM) measurements, and thus to identify and separate contributions from different effects such as geometric ensemble effects and electronic ligand/strain effects. DFT calculations give further insight into the nature of the metal-CO bond on these bimetallic sites. Most prominently, the growth of a new CO desorption feature at higher temperature (~ 550 K) in the TPD spectra of Ag-rich surface alloys, which is unique for the group of Pt(111)- and Pd(111)-based surface alloys, is attributed to CO adsorption on Pt atoms surrounded by a Ag-rich neighborhood. Adsorption on these sites manifests in an IR band down-shifted to significantly lower wave number. Systematic comparison of the present results with previous findings for CO adsorption on the related Pt(111)- and Pd(111)-based surface alloys gains a detailed insight into general trends in the adsorption behavior of bimetallic surfaces.

  1. Alloy formation and chemisorption at Zn/Pt(111) bimetallic surfaces using alkali ISS, XPD, and TPD.

    Science.gov (United States)

    Ho, Chih-Sung; Martono, Eddie; Banerjee, Santanu; Roszell, John; Vohs, John; Koel, Bruce E

    2013-11-21

    Alloy formation and chemisorption at bimetallic surfaces formed by vapor-depositing Zn on a Pt(111) single crystal were investigated primarily by using X-ray photoelectron diffraction (XPD), X-ray photoelectron spectroscopy (XPS), low-energy alkali ion scattering spectroscopy (ALISS), low electron energy diffraction (LEED), and temperature programmed desorption (TPD). A wide range of conditions were investigated to explore whether deposition and annealing of Zn films could produce well-defined, ordered alloy surfaces, similar to those encountered for Sn/Pt(111) surface alloys. These attempts were unsuccessful, although weak, diffuse (2 × 2) spots were observed under special conditions. The particular PtZn bimetallic alloy created by annealing one monolayer of Zn on Pt(111) at 600 K, which has a Zn composition in the surface layer of about 5 at. %, was investigated in detail by using XPD and ALISS. Only a diffuse (1 × 1) pattern was observed from this surface by LEED, suggesting that no long-range, ordered alloy structure was formed. Zn atoms were substitutionally incorporated into the Pt(111) crystal to form a near-surface alloy in which Zn atoms were found to reside primarily in the topmost and second layers. The alloyed Zn atoms in the topmost layer are coplanar with the Pt atoms in the surface layer, without any "buckling" of Zn, that is, displacement in the vertical direction. This result is expected because of the similar size of Pt and Zn, based on previous studies of bimetallic Pt alloys. Zn atoms desorb upon heating rather than diffusing deep into the bulk of the Pt crystal. Temperature programmed desorption (TPD) measurements show that both CO and NO have lower desorption energies on the PtZn alloy surface compared to that on the clean Pt(111) surface.

  2. Ab-initio study of the coadsorption of Li and H on Pt(001), Pt(110) and Pt(111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Saad, Farida [Laboratoire de Physique et Chimie Quantique, Faculte des Sciences, Universite Mouloud Mammeri, 15000 Tizi-Ouzou (Algeria); Zemirli, Mourad, E-mail: zemirlimourad@mail.ummto.dz [Laboratoire de Physique et Chimie Quantique, Faculte des Sciences, Universite Mouloud Mammeri, 15000 Tizi-Ouzou (Algeria); Benakki, Mouloud; Bouarab, Said [Laboratoire de Physique et Chimie Quantique, Faculte des Sciences, Universite Mouloud Mammeri, 15000 Tizi-Ouzou (Algeria)

    2012-02-15

    The coadsorption of Li and H atoms on Pt(001), Pt(110) and Pt(111) surfaces is studied using density functional theory with generalised gradient approximation. In all calculations Li, H and the two topmost layers of the metal were allowed to relax. At coverage of 0.25 mono-layer in a p(2 Multiplication-Sign 2) unit cell, lithium adsorption at the hollow site for the three surfaces is favoured over top and bridge sites. The most favoured adsorption sites for H atom on the Pt(001) and Pt(110) surfaces are the top and bridge sites, while on Pt(111) surface the fcc site appears to be slightly favoured over the hcp site. The coadsorption of Li and atomic hydrogen shows that the interaction between the two adsorbates is stabilising when they are far from each other. The analysis of Li, H and Pt local density of states shows that Li strongly interacts with the Pt surfaces.

  3. Surface spectroscopy of CO/Pt(111) with high harmonics in the XUV

    Energy Technology Data Exchange (ETDEWEB)

    Haarlammert, Thorben; Wegner, Sebastian; Tsilimis, Grigorius; Zacharias, Helmut [Physikalisches Institut, Westfaelische Wilhelms-Universitaet, Muenster (Germany); Golovin, Alexander [Institute of Physics, St. Petersburg State University (Russian Federation)

    2008-07-01

    We report on the generation of high harmonic radiation in the photon energy range up to 100 eV with up to 10 kHz repetition rate, based on the conversion of femtosecond Ti:sapphire radiation in rare gases. The fundamental laser is based on a single stage, multiple pass ampli-fication of a cavity-dumped oscillator. Output pulse energies of 1 mJ and pulse durations of les than 30 fs at adjustable repetition rates up to 10 kHz are achieved. The generated High Harmonics are separated by a toroidal grating and directed to the surface. A time-of-flight detector with multiple anodes registers the kinetic energies of emitted photoelectrons. The angular distributions of photoelectrons emitted form CO/Pt(111) under s-polarized excitations have been measured for a variety of initial photon energies. Different from gas phase results a significant intensity of photoelectrons are emitted also in the normal direction, i.e., in the direction of the C-O chemical bond. A first theoretical investigation supports qualitatively the observed angular distributions.

  4. Study of high coverages of atomic oxygen on the Pt(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Parker, D.H.; Bartram, M.E.; Koel, B.E. (Univ. of Colorado, Boulder (United States))

    1989-01-01

    Atomic oxygen coverages of up to 0.75 monolayer (ML) may be adsorbed cleanly on Pt(111) surfaces under UHV conditions by exposure to NO{sub 2} at 400 K. The authors have studied this adsorbed oxygen layer by using AES, LEED, UPS, HREELS, TPD, and work function ({Delta}{phi}) measurements. The (2{times}2)-O structure formed at {theta}{sub o} = 0.25 ML is still apparent at {theta}{sub o} = 0.60 ML and a faint (2{times}2) pattern persists even up to {theta}{sub o} = 0.75 ML.AES and {Delta}{phi} measurements show no evidence for chemically distinct species in the adlayer as a function of oxygen coverage. HREELS spectra clearly rule out the presence of molecular oxygen and oxide species over the range of oxygen coverage studied. UPS also shows no shift in binding energy of the oxygen-derived peak as the coverage is increased. These spectroscopic probes indicate that all oxygen is present as atomic oxygen with no indication of oxide formation or molecular oxygen at any coverage. Multiple O{sub 2} desorption peaks observed in TPD are interpreted as arising largely from kinetic effects rather than a result of multiple, distinctly different chemical species, even though large changes in the Pt-O bond energy are determined from the TPD data. The activation energy for O{sub 2} desorption reflects the sum of the heat of dissociative adsorption of O{sub 2} and the activation energy for O{sub 2} desorption reflects the sum of the heat of dissociative adsorption of O{sub 2} and the activation energy for O{sub 2} dissociation. The structure in the O{sub 2} TPD spectrum is due to large changes in the activation energy for O{sub 2} desorption resulting from increases in the barrier to dissociative O{sub 2} chemisorption and decreases in the Pt-O bond energy.

  5. Modification of the surface electronic and chemical properties of Pt(111) by subsurface 3d transition metals

    DEFF Research Database (Denmark)

    Kitchin, J. R.; Nørskov, Jens Kehlet; Barteau, M. A.;

    2004-01-01

    The modification of the electronic and chemical properties of Pt(111) surfaces by subsurface 3d transition metals was studied using density-functional theory. In each case investigated, the Pt surface d-band was broadened and lowered in energy by interactions with the subsurface 3d metals......, resulting in weaker dissociative adsorption energies of hydrogen and oxygen on these surfaces. The magnitude of the decrease in adsorption energy was largest for the early 3d transition metals and smallest for the late 3d transition metals. In some cases, dissociative adsorption was calculated...

  6. Oxidation mechanism of formic acid on the bismuth adatom-modified Pt(111) surface.

    Science.gov (United States)

    Perales-Rondón, Juan Victor; Ferre-Vilaplana, Adolfo; Feliu, Juan M; Herrero, Enrique

    2014-09-24

    In order to improve catalytic processes, elucidation of reaction mechanisms is essential. Here, supported by a combination of experimental and computational results, the oxidation mechanism of formic acid on Pt(111) electrodes modified by the incorporation of bismuth adatoms is revealed. In the proposed model, formic acid is first physisorbed on bismuth and then deprotonated and chemisorbed in formate form, also on bismuth, from which configuration the C-H bond is cleaved, on a neighbor Pt site, yielding CO2. It was found computationally that the activation energy for the C-H bond cleavage step is negligible, which was also verified experimentally.

  7. Faraday efficiency and mechanism of electrochemical surface reactions: CO2 reduction and H2 formation on Pt(111).

    Science.gov (United States)

    Hussain, Javed; Jónsson, Hannes; Skúlason, Egill

    2016-12-22

    An atomic scale model of the electrical double layer is used to calculate the mechanism and rate of electrochemical reduction of CO2 as well as H2 formation at a Pt(111) electrode. The water layer contains solvated protons and the electrode has excess electrons at the surface. Density functional theory within the generalized gradient approximation is used to describe the electronic structure while the mechanism and activation energy of the various elementary reactions is obtained by calculating minimum energy paths using the nudged elastic band method. The applied electrical potential is deduced from the calculated work function. The optimal reaction mechanism for CO2 reduction to either methane or methanol is found and the estimated rate compared with that of the competing reaction, H2 formation. When the free energy of only the intermediates and reactants is taken into account, not the activation energy, Pt(111) would seem to be a good electrocatalyst for CO2 reduction, significantly better than Cu(111). This, however, contradicts experimental findings. Detailed calculations reported here show that the activation energy for CO2 reduction is high for both Heyrovsky and Tafel mechanisms on Pt(111) in the relevant range of applied potential. The rate-limiting step of the Heyrovsky mechanism, *COOH + H(+) + e(-) → *CO + H2O, is estimated to have an activation energy of 0.95 eV at -0.9 V vs. standard hydrogen electrode. Under the same conditions, the activation energy for H2 formation is estimated to be only 0.5 eV. This explains why attempts to reduce CO2 using platinum electrodes have produced only H2. A comparison is made with analogous results for Cu(111) [J. Hussain et al., Procedia Comput. Sci., 2015, 51, 1865] where a reaction mechanism with low activation energy for CO2 electroreduction to methane was identified. The difference between the two electrocatalysts is discussed.

  8. The CO/Pt(111) Puzzle

    Energy Technology Data Exchange (ETDEWEB)

    FEIBELMAN,PETER J.; HAMMER,B.; NORSHOV,J.K.; WAGNER,F.; SCHEFFLER,M.; STUMPF,R.; DUMESIC,J.; WATWE,R.

    2000-07-12

    Notwithstanding half a dozen theoretical publications, well-converged density-functional calculations, whether based on a local or generalized-gradient exchange-correlation potential, whether all-electron or employing pseudopotentials underestimate CO's preference for low-coordination binding sites on Pt(111) and vicinals to it. For example, they imply that CO should prefer hollow- to atop-site adsorption on Pt(111), in apparent contradiction to a host of low temperature experimental studies.

  9. Time-resolved measurements of laser-induced diffusion of CO molecules on stepped Pt(111)-surfaces; Zeitaufgeloeste Untersuchung der laser-induzierten Diffusion von CO-Molekuelen auf gestuften Pt(111)-Oberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Lawrenz, M.

    2007-10-30

    In the present work the dynamics of CO-molecules on a stepped Pt(111)-surface induced by fs-laser pulses at low temperatures was studied by using laser spectroscopy. In the first part of the work, the laser-induced diffusion for the CO/Pt(111)-system could be demonstrated and modelled successfully for step diffusion. At first, the diffusion of CO-molecules from the step sites to the terrace sites on the surface was traced. The experimentally discovered energy transfer time of 500 fs for this process confirms the assumption of an electronically induced process. In the following it was explained how the experimental results were modelled. A friction coefficient which depends on the electron temperature yields a consistent model, whereas for the understanding of the fluence dependence and time-resolved measurements parallel the same set of parameters was used. Furthermore, the analysis was extended to the CO-terrace diffusion. Small coverages of CO were adsorbed to the terraces and the diffusion was detected as the temporal evolution of the occupation of the step sites acting as traps for the diffusing molecules. The additional performed two-pulse correlation measurements also indicate an electronically induced process. At the substrate temperature of 40 K the cross-correlation - where an energy transfer time of 1.8 ps was extracted - suggests also an electronically induced energy transfer mechanism. Diffusion experiments were performed for different substrate temperatures. (orig.)

  10. Interaction of oxygen and carbon monoxide with Pt(111) at intermediate pressure and temperature : revisiting the fruit fly of surface science

    NARCIS (Netherlands)

    Bashlakov, Dmytro

    2014-01-01

    This thesis uses the surface science approach to address questions regarding the interaction of oxygen with platinum and its subsequent reaction with carbon monoxide. A Pt(111) single crystal surface is used as a model for the catalyst. Chapter 1 provides an overview of the literature on the

  11. Catalytically Triggered Energy Release from Strained Organic Molecules: The Surface Chemistry of Quadricyclane and Norbornadiene on Pt(111).

    Science.gov (United States)

    Bauer, Udo; Mohr, Susanne; Döpper, Tibor; Bachmann, Philipp; Späth, Florian; Düll, Fabian; Schwarz, Matthias; Brummel, Olaf; Fromm, Lukas; Pinkert, Ute; Görling, Andreas; Hirsch, Andreas; Bachmann, Julien; Steinrück, Hans-Peter; Libuda, Jörg; Papp, Christian

    2017-01-31

    We have investigated the surface chemistry of the polycyclic valence-isomer pair norbornadiene (NBD) and quadricyclane (QC) on Pt(111). The NBD/QC system is considered to be a prototype for energy storage in strained organic compounds. By using a multimethod approach, including UV photoelectron, high-resolution X-ray photoelectron, and IR reflection-absorption spectroscopic analysis and DFT calculations, we could unambiguously identify and differentiate between the two molecules in the multilayer phase, which implies that the energy-loaded QC molecule is stable in this state. Upon adsorption in the (sub)monolayer regime, the different spectroscopies yielded identical spectra for NBD and QC at 125 and 160 K, when multilayer desorption takes place. This behavior is explained by a rapid cycloreversion of QC to NBD upon contact with the Pt surface. The NBD adsorbs in a η(2) :η(1) geometry with an agostic Pt-H interaction of the bridgehead CH2 subunit and the surface. Strong spectral changes are observed between 190 and 220 K because the hydrogen atom that forms the agostic bond is broke. This reaction yields a norbornadienyl intermediate species that is stable up to approximately 380 K. At higher temperatures, the molecule dehydrogenates and decomposes into smaller carbonaceous fragments.

  12. Model electrochemical interfaces in ultra-high vacuum: solvent-induced surface potential profiles on Pt(111) from work-function measurements and infrared Stark effects

    Science.gov (United States)

    Kizhakevariam, Naushad; Villegas, Ignacio; Weaver, Michael J.

    1995-08-01

    The influence of various solvents upon the interfacial-potential profile on Pt(111) has been investigated by means of work-function changes and infrared frequency Stark shifts attending sequential-molecular dosing in ultra-high vacuum (UHV) at a suitably low temperature (ca. 100 K) with the primary objective of assessing the role of surface solvation in related electrochemical systems. The solvents examined — dichloromethane, benzene, acetone, acetonitrile, methanol, and ammonia — span a range of polarity and other solvating properties. These species were dosed onto both clean and CO-saturated Pt(111), the Stark shifts being evaluated for the CO stretching mode of terminally co-ordinated carbon monoxide. Marked decreases (≥ 1 eV) in the work function, Φ, and hence in the surface potential, φ, are observed on the addition of most solvents onto clean Pt(111). Milder yet still substantial Φ decreases are also observed for solvent dosage upon CO-saturated Pt(111). These latter Φ changes correlate approximately with the observed vCO frequency downshifts, suggesting that the latter property is also sensitive to the solvent-induced electrostatic interfacial field. The functional form of both the Φ decreases and the corresponding vCO frequency downshifts induced by solvent dosage provide insight into the dosage-dependent potential profile and its relationship to both the monolayer and multilayer solvent structure. The present findings are also briefly compared with corresponding vtCO - Φ data obtained for potassium atom dosing, where the surface potential is altered instead by varying the surface electronic charge in the presence of a given solvent. The underlying factors responsible for the surprisingly large solvent-induced surface potential shifts are discussed in detail, and the likely importance of the surface electronic charge distribution as well as solvent dipole orientation and adsorbate-metal charge sharing is pointed out.

  13. The Electrochemical Development of Pt(111 Stepped Surfaces and Its Influence on Methanol Electrooxidation

    Directory of Open Access Journals (Sweden)

    E. Teliz

    2011-01-01

    Full Text Available The progress in the preparation of new electrode surfaces by electrochemical treatments exhibiting high faradaic efficiencies towards industrial electrocatalytic processes has gained more attention in today's scientific community. Most of the papers report new catalysts dispersed on different substrates, but some fundamental studies required for electrochemical and physical characterizations are sometimes forgotten. In this paper, we make a full staging of two electrochemical treatments that can be conducted to enhance the electrocatalytic activity of platinum surfaces, such as, electrofacetting through square wave potential programs and constant cathodic polarizations in the net hydrogen evolution region. The cathodic treatment applied at −2 V clearly develops (111 stepped planes similarly to the electrofacetting performed after applying the square wave program between 1.40 V and 0.70 V at 2.5 kHz. The X-ray diffraction patterns of both surfaces as well as on other electrofacetted platinum electrodes are obtained for comparison purposes. Moreover, the electrocatalytic activity towards methanol electrooxidation also exhibits equivalent coulombic efficiencies and 200% higher than on polycrystalline platinum as demonstrated by linear sweep voltammetry and potentiostatic current decays.

  14. Adsorption of halide anions at the Pt(111)-solution interface studied by {bold {ital in situ}} surface x-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, C.A.; Markovic, N.M.; Ross, P.N. [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)

    1997-03-01

    In this paper we present x-ray scattering results of iodide, bromide, and chloride adsorption onto the Pt(111) surface in solution. Iodide forms two commensurate adlayer structures, a ({radical}(7){times}{radical}(7))R19.1{degree} phase and a hexagonal (3{times}3) phase, which coexist on the Pt surface. Formation of the (3{times}3) phase appears to be kinetically limited, whereas the {radical}(7) phase shows a hysteretic effect as a function of the electrode potential, associated with an order-disorder transition. Bromide forms a series of high-order commensurate structures on Pt(111) that are poorly ordered unless the size of the unit cell is small. No ordered structures for chloride adsorption are observed and specular x-ray reflectivity results suggest that the chloride coverage at low potential is too small to form a close-packed monolayer on the surface. The differences between the structures formed by the adsorbed anions, and the differences between results for Pt(111) and Au(111), are discussed in terms of the strength of the metal-halide interaction. {copyright} {ital 1997} {ital The American Physical Society}

  15. Vibrational states of the Pt(111)- $ ≤ft( {sqrt {3} × sqrt {3} } right) $ R30°-K surface structure

    Science.gov (United States)

    Rusina, G. G.; Borisov, S. D.; Eremeev, S. V.; Chulkov, E. V.

    2010-09-01

    Vibrational spectrum of the ordered Pt(111)- left( {sqrt {3} × sqrt {3} } right) R30°- K surface superstructure formed on the platinum surface with adsorption of 1/3 ML potassium is calculated with the use of the interatomic interaction potentials obtained in the strong bond approximation. Relaxation of the surface, dispersion of the surface phonons, local density of vibrational states, and polarization of phonon modes of adatoms and atoms of the substrate are discussed in the work. The theoretical results obtained agree well with the available experimental data.

  16. Molecular orientation and lattice ordering of C60 molecules on the polar FeO/Pt(111) surface

    Science.gov (United States)

    Qin, Zhihui; Liu, Cunding; Chen, Jian; Guo, Qinmin; Yu, Yinghui; Cao, Gengyu

    2012-01-01

    C60 molecules assemble into close packing layer under the domination of the intermolecular interaction when deposited onto Pt(111)-supported FeO layer kept at 400 K. From corresponding high resolution scanning tunneling microscopy (STM) image, a kind of C60 molecular orientational ordering stabilized by the intermolecular interaction is revealed as C60/FeO(111)-(√133 × √133) R17.5° structure and determined from the commensurability between the C60 nearest-neighbor distance and the lattice of the underlying oxygen layer. Moreover, due to the inhomogeneously distributed work function of the underlying FeO layer, the C60 molecular electronic state is periodically modulated resulting in a bright-dim STM contrast. In addition, one coincidence lattice ordering is determined as 8 × 8 superstructure with respect to the C60 primitive cell, which overlays a 3 × 3 moiré cell of the underlying FeO layer.

  17. 离子液体中Au(111)和Pt(111)表面Ge欠电位沉积的现场STM研究%Underpotential Deposition of Germanium on Au(111) and Pt(111) Surfaces in Ionic Liquids

    Institute of Scientific and Technical Information of China (English)

    谢旭芬; 颜佳伟; 梁景洪; 李纪军; 张梦; 毛秉伟

    2014-01-01

    本文研究BMIPF6离子液体中Au(111)和Pt(111)表面Ge的电沉积行为.循环伏安法测试结果表明,在含0.1 mol· LlGeCL的BMIPF6溶液Au(111)和Pt(111)表面均有两个与Ge沉积过程相关的还原峰.第一个还原峰包含了Ge4+还原成Ge2+及Ge的欠电位沉积,第二个还原峰对应Ge的本体沉积.现场扫描隧道显微镜研究结果表明,Ge在Au(111)和Pt(11 1)表面均有两层欠电位沉积.第一层欠电位沉积厚度平均约为0.25 nm、形貌平整、带有缝隙的亚单层结构.第二层欠电位沉积形貌相对粗糙的点状团簇结构.该欠电位沉积过程伴随表面合金化.

  18. Resonant core spectroscopies of the charge transfer interactions between C60 and the surfaces of Au(111), Ag(111), Cu(111) and Pt(111)

    Science.gov (United States)

    Gibson, Andrew J.; Temperton, Robert H.; Handrup, Karsten; O'Shea, James N.

    2017-03-01

    Charge transfer interactions between C60 and the metal surfaces of Ag(111), Cu(111), Au(111) and Pt(111) have been studied using synchrotron-based photoemission, resonant photoemission and X-ray absorption spectroscopies. By placing the X-ray absorption and valence band spectra on a common binding energy scale, the energetic overlap of the unoccupied molecular orbitals with the density of states of the underlying metal surface have been assessed in the context of possible charge transfer pathways. Resonant photoemission and resonant Auger data, measuring the valence region as a function of photon energy for C60 adsorbed on Au(111) reveals three constant high kinetic energy features associated with Auger-like core-hole decay involving an electron transferred from the surface to the LUMO of the molecule and electrons from the three highest occupied molecular orbitals, respectively and in the presence of ultra-fast charge transfer of the originally photoexcited molecule to the surface. Data for the C60/Ag(111) surface reveals an additional Auger-like feature arising from a core-hole decay process involving more than one electron transferred from the surface into the LUMO. An analysis of the relative abundance of these core-hole decay channels estimates that on average 2.4 ± 0.3 electrons are transferred from the Ag(111) surface into the LUMO. A core-hole clock analysis has also been applied to assess the charge transfer coupling in the other direction, from the molecule to the Au(111) and Ag(111) surfaces. Resonant photoemission and resonant Auger data for C60 molecules adsorbed on the Pt(111) and Cu(111) surfaces are shown to exhibit no super-Auger features, which is attributed to the strong modification of the unoccupied molecular orbitals arising from stronger chemical coupling of the molecule to the surface.

  19. The screening effects of the screened exchange hybrid functional in surface systems: A case study on the CO/Pt(111) problem

    Science.gov (United States)

    Li, H.; Gillen, R.; Robertson, J.

    2016-06-01

    The screened exchange (sX) hybrid functional has been widely used in computational material science. Although it has widely been studied in bulk systems, less is known about its functional behavior in surface systems which are crucial to many technologies such as materials synthesis and nano-electronic devices. Assessing the screening dependent functional behaviors in the surface systems is therefore important for its application in such systems. In this work, we investigate the screening effects of the sX in CO adsorption on Pt(111) surface. The differences between the sX and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functionals, and the effects of screening parameters are studied. The screening has two effects: first, the HOMO-LUMO gap is screening dependent. This affects the site preference most significantly. In this work, atop adsorption of CO/Pt(111) is predicted by the hybrid functionals with screened exchange potential. The sX(1.44) gives the largest HOMO-LUMO gap for the isolated CO molecule. The adsorption energy difference between the atop and fcc site is also the largest by the sX(1.44) which is explained by the reduced metal d states to the CO 2π* state back-donation, with stronger effect for the fcc adsorption than for the atop adsorption; second, the adsorption energy is screening dependent. This can be seen by comparing the sX(2.38) and HSE06 which have different screening strengths. They show similar surface band structures for the CO adsorption but different adsorption energies, which is explained by the stronger CO 5σ state to the metal d states donation or the effectively screened Pauli repulsion. This work underlines the screening strength as a main difference between sX and HSE06, as well as an important hybrid functional parameter for surface calculation.

  20. Study of surface chemistry and microstructure of TiO2 nanostructures on Pt(111)/Si wafer and FTO glass substrates: a comparative approach

    Science.gov (United States)

    Roy Moulik, Samik; Ghatak, Ankita; Ghosh, Barnali

    2016-09-01

    We report, the kinetically controlled growth of the (002)-oriented TiO2 nanorods on fluorine-doped tin oxide (FTO) coated glass substrate via a cost effective hydrothermal synthesis route of binary oxides. In addition to this, the nanoflowered like growth of TiO2 nanorods using cubic structure Pt(111)/SiO2/Si substrate has also been demonstrated. Tuning of shape, crystallographic structure issues has been discussed by controlling the surface chemistry of the substrate on which the nanostructures were grown. The crystallographic structural aspects of the grown nanorods was confirmed both on ensemble and single nanowire level using spatially resolved tools and techniques. Growth mechanism for different shape, size and crystallographic structure depending on the surface chemistry of the substrate has been proposed. Understanding of growth of oriented TiO2 nanorods and interaction mechanism is quite promising and encouraging for designing optoelectronic and photocatalytic devices to enhanced electron transport and lower exciton recombination rates.

  1. Ethylene hydrogenation catalysis on Pt(111) single-crystal surfaces studied by using mass spectrometry and in situ infrared absorption spectroscopy

    Science.gov (United States)

    Tillekaratne, Aashani; Simonovis, Juan Pablo; Zaera, Francisco

    2016-10-01

    The catalytic hydrogenation of ethylene promoted by a Pt(111) single crystal was studied by using a ultrahigh-vacuum surface-science instrument equipped with a so-called high-pressure cell. Kinetic data were acquired continuously during the catalytic conversion of atmospheric-pressure mixtures of ethylene and hydrogen by using mass spectrometry while simultaneously characterizing the surface species in operando mode by reflection-absorption infrared spectroscopy (RAIRS). Many observations reported in previous studies of this system were corroborated, including the presence of adsorbed alkylidyne intermediates during the reaction and the zero-order dependence of the rate of hydrogenation on the pressure of ethylene. In addition, the high quality of the kinetic data, which could be recorded continuously versus time and processed to calculate time-dependent turnover frequencies (TOFs), afforded a more detailed analysis of the mechanism. Specifically, deuterium labeling could be used to estimate the extent of isotope scrambling reached with mixed-isotope-substituted reactants (C2H4 + D2 and C2D4 + H2). Perhaps the most important new observation from this work is that, although extensive H-D exchange takes place on ethylene before being fully converted to ethane, the average stoichiometry of the final product retains the expected stoichiometry of the gas mixture, that is, four regular hydrogen atoms and two deuteriums per ethane molecule in the case of the experiments with C2H4 + D2. This means that no hydrogen atoms are removed from the surface via their inter-recombination to produce X2 (X = H or D). It is concluded that, under catalytic conditions, hydrogen surface recombination is much slower than ethylene hydrogenation and H-D exchange.

  2. Co on Pt(111) studied by spin-polarized scanning tunneling microscopy and spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Meier, F.K.

    2006-07-01

    In this thesis the electronic properties of the bare Pt(111) surface, the structural, electronic, and magnetic properties of monolayer and double-layer high Co nanostructures as well as the spin-averaged electronic structure of single Co atoms on Pt(111) were studied by low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS). The experiments on the bare Pt(111) surface and on single Co atoms have been performed in an STM facility operating at temperatures of down to 0.3 K and at magnetic fields of up to 14 T under ultra-high vacuum conditions. The facility has been taken into operation within the time period of this thesis and its specifications were tested by STS measurements. These characterization measurements show a very high stability of the tunneling junction and an energy resolution of about 100 {mu}eV, which is close to the thermal limit. The investigation of the electronic structure of the bare Pt(111) surface reveals the existence of an unoccupied surface state. By a comparison of the measured dispersion to first-principles electronic structure calculations the state is assigned to an sp-derived surface band at the lower boundary of the projected bulk band gap. The surface state exhibits a strong spin-orbit coupling induced spin splitting. The close vicinity to the bulk bands leads to a strong linear contribution to the dispersion and thus to a deviant appearance in the density of states in comparison to the surface states of the (111) surfaces of noble metals. A detailed study of Co monolayer and double-layer nanostructures on the Pt(111) surface shows that both kinds of nanostructures exhibit a highly inhomogeneous electronic structure which changes at the scale of only a few Aa due to a strong stacking dependence with respect to the Pt(111) substrate. With the help of first principles calculations the different spectroscopic appearance for Co atoms within the Co monolayer is assigned to a stacking dependent hybridization of Co states

  3. Metallization of cyanide-modified Pt(111) electrodes with copper

    DEFF Research Database (Denmark)

    Escribano, Maria Escudero; Wildi, Christopher; Mwanda, Jonathan A.

    2016-01-01

    The reduction of Cu2+ ions irreversibly attached to the surface of a cyanide-modified Pt(111) electrode via non-covalent or weakly covalent interactions with the N atom of adsorbed cyanide was studied using cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM). Both CV and STM...... provide evidence that the reduction of irreversibly adsorbed Cu2+ to Cu in Cu2+-free sulfuric acid solutions does not result in the stripping of the cyanide adlayer. This strongly suggests that the reduction process results in the metallization of the cyanide adlayer on Pt(111), yielding a platinum-cyanide...

  4. The Pt(111)/Electrolyte Interface under Oxygen Reduction Reaction Conditions

    DEFF Research Database (Denmark)

    Bondarenko, A.S.; Stephens, Ifan; Hansen, Heine Anton;

    2011-01-01

    between the adsorbate and Pt surface atoms (0.45−1.15 V vs RHE). An equivalent electric circuit is proposed to model the Pt(111)/electrolyte interface under ORR conditions within the selected potential window. This equivalent circuit reflects three processes with different time constants, which occur...... simultaneously during the ORR at Pt(111). Density functional theory (DFT) calculations were used to correlate and interpret the results of the measurements. The calculations indicate that the coadsorption of ClO4* and Cl* with OH* is unlikely. Our analysis suggests that the two-dimensional (2D) structures formed...

  5. Pyrrole Hydrogenation over Rh(111) and Pt(111) Single-Crystal Surfaces and Hydrogenation Promotion Mediated by 1-Methylpyrrole: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

    Energy Technology Data Exchange (ETDEWEB)

    Kliewer, Christopher J.; Bieri, Marco; Somorjai, Gabor A.

    2008-03-04

    Sum-frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to study the adsorption and hydrogenation of pyrrole over both Pt(111) and Rh(111) single-crystal surfaces at Torr pressures (3 Torr pyrrole, 30 Torr H{sub 2}) to form pyrrolidine and the minor product butylamine. Over Pt(111) at 298 K it was found that pyrrole adsorbs in an upright geometry cleaving the N-H bond to bind through the nitrogen evidenced by SFG data. Over Rh(111) at 298 K pyrrole adsorbs in a tilted geometry relative to the surface through the p-aromatic system. A pyrroline surface reaction intermediate, which was not detected in the gas phase, was seen by SFG during the hydrogenation over both surfaces. Significant enhancement of the reaction rate was achieved over both metal surfaces by adsorbing 1-methylpyrrole before reaction. SFG vibrational spectroscopic results indicate that reaction promotion is achieved by weakening the bonding between the N-containing products and the metal surface because of lateral interactions on the surface between 1-methylpyrrole and the reaction species, reducing the desorption energy of the products. It was found that the ring-opening product butylamine was a reaction poison over both surfaces, but this effect can be minimized by treating the catalyst surfaces with 1-methylpyrrole before reaction. The reaction rate was not enhanced with elevated temperatures, and SFG suggests desorption of pyrrole at elevated temperatures.

  6. Underpotential Deposition of Silver on Pt(111). Part 1. Concentration Dependence

    Science.gov (United States)

    1990-01-01

    AD-A236 692 Underpotential Deposition of Silver on Pt(111): Part I. Concentration Dependence r T ~.J.F. Rodriguez, D.L. Taylor and H.D. Abruhla* EL...dependence of the underpotential deposition of silver on well-defined Pt(111) electrodes. Electrochemical as well as ultra high vacuum surface...silver are deposited at underpotentials but the stability of the second layer is a strong function of the silver ion concentration in solution. When

  7. Correlação entre a estrutura atômica superficial e o processo de adsorção-dessorção reversível de hidrogênio em eletrodos monocristalinos Pt(111, Pt(100 e Pt(110 The correlation between the atomic surface structure and the reversible adsorption-desorption of hydrogen on single crystal Pt (111, Pt (100 and Pt (110 electrodes

    Directory of Open Access Journals (Sweden)

    Valderi Pacheco dos Santos

    2001-12-01

    Full Text Available Platinum is widely used as electrode in electrocatalytic processes, however the use of polycrystalline electrodes introduces a series of variables in the electrochemical system due to the aleatory contribution of all the crystallographic orientations with different surface packing of atoms. Single crystal platinum electrodes of low Miller index present surface structure of high regularity and serve as model to establish a correlation among the macroscopic and microscopic properties of the electrochemical interface. Therefore, the main aim of this work is the study of the voltammetric profiles of the reversible adsorption-desorption of hydrogen on Pt(100, Pt(110 and Pt(111, in order to correlate the electrochemical properties of each different orientation with the surface atomic structure.

  8. Interaction of gas phase atomic hydrogen with Pt(111): Direct evidence for the formation of bulk hydrogen species

    Institute of Scientific and Technical Information of China (English)

    JIANG ZhiQuan; HUANG WeiXin; BAO XinHe

    2007-01-01

    Employing hot tungsten filament to thermal dissociate molecular hydrogen, we generated gas phase atomic hydrogen under ultra-high vacuum (UHV) conditions and investigated its interaction with Pt(111) surface. Thermal desorption spectroscopy (TDS) results demonstrate that adsorption of molecular hydrogen on Pt(111) forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species. Bulk Had species is more thermal-unstable than surface Had species on Pt(111), suggesting that bulk Had species is more energetic. This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions.

  9. Complete wetting of Pt(111) by nanoscale liquid water films

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.; Smith, R. Scott; Kay, Bruce D.; Kimmel, Gregory A.

    2016-02-04

    The melting and wetting of nanoscale crystalline ice films on Pt(111) that are transiently heated above the melting point using nanosecond laser pulses are studied with infrared refection absorption spectroscopy (IRAS) and Kr temperature programmed desorption (TPD). The as-grown crystalline ice films consist of isolated nanoscale ice crystallites embedded in a hydrophobic water monolayer. Upon heating above the melting point, these ice crystallites rapidly melt to form nanoscale droplets of liquid water. Rapid cooling of the system to cryogenic temperatures after each laser pulse quenches the water films and allows them to be interrogated with IRAS, Kr TPD and other ultrahigh vacuum surface science techniques. With each successive heat pulse, these liquid drops spread across the surface until it is entirely covered with multilayer water films after several pulses. These results, which show that nanoscale water films completely wet Pt(111), are in contrast to molecular dynamics simulations predicting partial wetting of nanoscale water drops on a hydrophobic water monolayer. The results provide valuable new insights into the wetting characteristics of nanoscale water films on a clean, well-characterized single crystal surface.

  10. Atomic Structure Control of Silica Thin Films on Pt(111)

    KAUST Repository

    Crampton, Andrew S

    2015-05-27

    Metal oxide thin films grown on metal single crystals are commonly used to model heterogeneous catalyst supports. The structure and properties of thin silicon dioxide films grown on metal single crystals have only recently been thoroughly characterized and their spectral properties well established. We report the successful growth of a three- dimensional, vitreous silicon dioxide thin film on the Pt(111) surface and reproduce the closed bilayer structure previously reported. The confirmation of the three dimensional nature of the film is unequivocally shown by the infrared absorption band at 1252 cm−1. Temperature programmed desorption was used to show that this three-dimensional thin film covers the Pt(111) surface to such an extent that its application as a catalyst support for clusters/nanoparticles is possible. The growth of a three-dimensional film was seen to be directly correlated with the amount of oxygen present on the surface after the silicon evaporation process. This excess of oxygen is tentatively attributed to atomic oxygen being generated in the evaporator. The identification of atomic oxygen as a necessary building block for the formation of a three-dimensional thin film opens up new possibilities for thin film growth on metal supports, whereby simply changing the type of oxygen enables thin films with different atomic structures to be synthesized. This is a novel approach to tune the synthesis parameters of thin films to grow a specific structure and expands the options for modeling common amorphous silica supports under ultra high vacuum conditions.

  11. A density-functional theory study of electrochemical adsorption of sulfuric acid anions on Pt(111).

    Science.gov (United States)

    Santana, Juan A; Cabrera, Carlos R; Ishikawa, Yasuyuki

    2010-08-28

    A density-functional theory study of the electrochemical adsorption of sulfuric acid anions was conducted at the Pt(111)/electrolyte interface over a wide range of electrode potential, including the anomalous region of the hydrogen voltammogram of this electrode. We focus on the precise nature of the binding species and their bonding to the surface, identifying the adsorbed species as a function of electrode potential. In particular, the origin of anomalous or so-called "butterfly" feature in this voltammogram between +0.30 and +0.50 V vs. the reference hydrogen electrode and the nature of the adsorbed species on the Pt(111) surface in this potential range were explicated.

  12. Catalytic reaction energetics by single crystal adsorption calorimetry: hydrocarbons on Pt(111).

    Science.gov (United States)

    Lytken, Ole; Lew, Wanda; Campbell, Charles T

    2008-10-01

    Single crystal adsorption calorimetry provides essential information about the energetics of surface reactions on well-defined surfaces where the adsorbed reaction products can be clearly identified. In this tutorial review, we cover the essentials of that technique, with emphasis on our lab's recent advances in sensitivity and temperature range, and demonstrate what can be achieved through a review of selected example studies concerning adsorption and dehydrogenation of hydrocarbons on Pt(111). A fairly complete reaction enthalpy diagram is presented for the dehydrogenation of cyclohexane to benzene on Pt(111).

  13. Comparative Analysis of Cobalt Oxide Nanoisland Stability and Edge Structures on Three Related Noble Metal Surfaces: Au (111), Pt (111) and Ag (111)

    DEFF Research Database (Denmark)

    Fester, Jakob; Bajdich, Michal; Walton, Alexander

    2017-01-01

    Metal oxide nanostructures and thin films grown on metallic substrates have attracted strong attention as model catalysts and as interesting inverse catalyst systems in their own right. In this study, we investigate the role of metal support in the growth and stabilization of cobalt oxide...... nanostructures on the three related (111) surfaces of Au, Pt and Ag, as investigated by means of high-resolution scanning tunneling microscopy and DFT calculations. All three substrates promote the growth of crystalline CoOx (x = 1−2) islands under oxidative conditions, but we find several noteworthy differences...... for water dissociation....

  14. CO oxidation on Pt(111) at near ambient pressures

    Energy Technology Data Exchange (ETDEWEB)

    Krick Calderón, S.; Grabau, M.; Kress, B.; Papp, C. [Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen (Germany); Óvári, L. [MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Rerrich Béla tér 1, 6720 Szeged (Hungary); Steinrück, H.-P. [Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen (Germany); Erlangen Catalysis Resource Center, Egerlandstr. 3, 91058 Erlangen (Germany)

    2016-01-28

    The oxidation of CO on Pt(111) was investigated simultaneously by near ambient pressure X-ray photoelectron spectroscopy and online gas analysis. Different CO:O{sub 2} reaction mixtures at total pressures of up to 1 mbar were used in continuous flow mode to obtain an understanding of the surface chemistry. By temperature-programmed and by isothermal measurements, the onset temperature of the reaction was determined for the different reactant mixtures. Highest turnover frequencies were found for the stoichiometric mixture. At elevated temperatures, the reaction becomes diffusion-limited in both temperature-programmed and isothermal measurements. In the highly active regime, no adsorbates were detected on the surface; it is therefore concluded that the catalyst surface is in a metallic state, within the detection limits of the experiment, under the applied conditions. Minor bulk impurities such as silicon were observed to influence the reaction up to total inhibition by formation of non-platinum oxides.

  15. Cyclic voltammograms for H on Pt(111) and Pt(100) from first principles

    DEFF Research Database (Denmark)

    Karlberg, Gustav; Jaramillo, Thomas; Skulason, Egill;

    2007-01-01

    Cyclic voltammetry is a fundamental experimental method for characterizing electrochemical surfaces. Despite its wide use, a way to quantitatively and directly relate cyclic voltammetry to ab initio calculations has been lacking. We derive the cyclic voltammogram for H on Pt(111) and Pt(100), based...

  16. Some reflections on the understanding of the oxygen reduction reaction at Pt(111

    Directory of Open Access Journals (Sweden)

    Ana M. Gómez-Marín

    2013-12-01

    Full Text Available The oxygen reduction reaction (ORR is a pivotal process in electrochemistry. Unfortunately, after decades of intensive research, a fundamental knowledge about its reaction mechanism is still lacking. In this paper, a global and critical view on the most important experimental and theoretical results regarding the ORR on Pt(111 and its vicinal surfaces, in both acidic and alkaline media, is taken. Phenomena such as the ORR surface structure sensitivity and the lack of a reduction current at high potentials are discussed in the light of the surface oxidation and disordering processes and the possible relevance of the hydrogen peroxide reduction and oxidation reactions in the ORR mechanism. The necessity to build precise and realistic reaction models, which are deducted from reliable experimental results that need to be carefully taken under strict working conditions is shown. Therefore, progress in the understanding of this important reaction on a molecular level, and the choice of the right approach for the design of the electrocatalysts for fuel-cell cathodes is only possible through a cooperative approach between theory and experiments.

  17. Interaction of gas phase atomic hydrogen with Pt(111):Direct evidence for the formation of bulk hydrogen species

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Employing hot tungsten filament to thermal dissociate molecular hydrogen,we generated gas phase atomic hydrogen under ultra-high vacuum(UHV)conditions and investigated its interaction with Pt(111) surface.Thermal desorption spectroscopy(TDS)results demonstrate that adsorption of molecular hy- drogen on Pt(111)forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species.Bulk Had species is more thermal-unstable than surface Had species on Pt(111),suggesting that bulk Had species is more energetic.This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions.

  18. HCOOH decomposition on Pt(111): A DFT study

    Science.gov (United States)

    Scaranto, Jessica; Mavrikakis, Manos

    2016-06-01

    Formic acid (HCOOH) decomposition on transition metal surfaces is important for hydrogen production and for its electro-oxidation in direct HCOOH fuel cells. HCOOH can decompose through dehydrogenation leading to formation of CO2 and H2 or dehydration leading to CO and H2O; because CO can poison metal surfaces, dehydrogenation is typically the desirable decomposition path. Here we report a mechanistic analysis of HCOOH decomposition on Pt(111), obtained from a plane wave density functional theory (DFT-PW91) study. We analyzed the dehydrogenation mechanism by considering the two possible pathways involving the formate (HCOO) or the carboxyl (COOH) intermediate. We also considered several possible dehydration paths leading to CO formation. We studied HCOO and COOH decomposition both on the clean surface and in the presence of other relevant co-adsorbates. The results suggest that COOH formation is energetically more difficult than HCOO formation. In contrast, COOH dehydrogenation is easier than HCOO decomposition. We found that CO2 is the main product through both pathways and that CO is produced mainly through the dehydroxylation of the COOH intermediate.

  19. Underpotential deposition of hydrogen on benzene-modified Pt(111) in aqueous H2SO4.

    Science.gov (United States)

    Jerkiewicz, Gregory; DeBlois, Martin; Radovic-Hrapovic, Zorana; Tessier, Jean-Pierre; Perreault, Frédéric; Lessard, Jean

    2005-04-12

    The Pt(111) electrode is modified by an overlayer of C6H6 (ads) upon its cycling in the 0.05-0.80 V range in aq H2SO4 + 1 mM C6H6. The C6H6 (ads) overlayer significantly changes the underpotential-deposited H (H(UPD)) and anion adsorption, and cyclic-voltammetry (CV) profiles show a sharp cathodic peak and an asymmetric anodic one in the 0.05-0.80 V potential range. The C6H6 (ads) layer blocks the (bi)sulfate adsorption but facilitates the adsorption of one monolayer of H(UPD). Cycling of the benzene-modified Pt(111) in benzene-free aq 0.05 H2SO4 from 0.05 to 0.80 V results in a partial desorption of C6H6 (ads) and in a partial recovery of the CV profile characteristic of an unmodified Pt(111). The peak potential of the cathodic and anodic feature is independent of the scan rate, s (10 0 to 0 kJ mol(-1) at theta(H(UPD) --> 1. The nonzero values of delta Delta G degrees testify that the adsorbing and desorbing H(UPD) adatoms interact with an energetically different substrate. The lateral interactions changed from repulsive (omega = 29 kJ mol(-1) at theta(H(UPD) --> 0) to attractive (omega = -28 kJ mol(-1) at theta(H(UPD) --> 1) as the H(UPD) coverage increases. The values of delta S degrees(ads)(H(UPD)) increase from 19 to 56 J K(-1) mol(-1), while those of delta S degrees(des)(H(UPD)) decrease from 45 to -30 J K(-1) mol(-1) with an increase of H(UPD) coverage. The values of delta H degrees(des)(H(UPD)) and delta H degrees(des)(H(UPD)) vary from 0 to 27 kJ mol(-1). The Pt(111)-H(UPD) surface bond energy at the benzene-modified Pt(111) electrode falls in the 191-218 kJ mol(-1) range and is weaker than in the case of the unmodified Pt(111) electrode in the same electrolyte.

  20. Sublattice Localized Electronic States in Atomically Resolved Graphene-Pt(111) Edge-Boundaries

    OpenAIRE

    Merino-Mateo, Pablo; Pinardi, Anna Lisa; Méndez, Javier; López, María Francisca; Pérez, Rubén; Martín-Gago, José A.

    2014-01-01

    Understanding the connection of graphene with metal surfaces is a necessary step for developing atomically precise graphene-based technology. Combining high-resolution STM experiments and DFT calculations, we have unambiguously unveiled the atomic structure of the boundary between a graphene zigzag edge and a Pt(111) step. The graphene edges minimize their strain by inducing a 3-fold edge-reconstruction on the metal side. We show the existence of an unoccupied electronic state that is mostly ...

  1. Density Functional Theory Calculations and Analysis of Reaction Pathways for Reduction of Nitric Oxide by Hydrogen on Pt(111)

    Energy Technology Data Exchange (ETDEWEB)

    Farberow, Carrie A.; Dumesic, James A.; Mavrikakis, Manos

    2014-10-03

    Reaction pathways are explored for low temperature (e.g., 400 K) reduction of nitric oxide by hydrogen on Pt(111). First-principles electronic structure calculations based on periodic, self-consistent density functional theory(DFT-GGA, PW91) are employed to obtain thermodynamic and kinetic parameters for proposed reaction schemes on Pt(111). The surface of Pt(111) during NO reduction by H₂ at low temperatures is predicted to operate at a high NO coverage, and this environment is explicitly taken into account in the DFT calculations. Maximum rate analyses are performed to assess the most likely reaction mechanisms leading to formation of N₂O, the major product observed experimentally at low temperatures. The results of these analyses suggest that the reaction most likely proceeds via the addition of at least two H atoms to adsorbed NO, followed by cleavage of the N-O bond.

  2. Direct Visualization of Catalytically Active Sites at the FeO-Pt(111) Interface

    Energy Technology Data Exchange (ETDEWEB)

    Kudernatsch, Wilhelmine; Peng, Guowen; Zeuthen, Helene; Bai, Yunhai; Merte, L. R.; Lammich, Lutz; Besenbacher, Fleming; Mavrikakis, Manos; Wendt, Stefen

    2015-08-25

    Within the area of surface science, one of the “holy grails” is to directly visualize a chemical reaction at the atomic scale. Whereas this goal has been reached by high-resolution scanning tunneling microscopy (STM) in a number of cases for reactions occurring at flat surfaces, such a direct view is often inhibited for reaction occurring at steps and interfaces. Here we have studied the CO oxidation reaction at the interface between ultrathin FeO islands and a Pt(111) support by in situ STM and density functional theory (DFT) calculations. Time-lapsed STM imaging on this inverse model catalyst in O2 and CO environments revealed catalytic activity occurring at the FeO-Pt(111) interface and directly showed that the Fe-edges host the catalytically most active sites for the CO oxidation reaction. This is an important result since previous evidence for the catalytic activity of the FeO-Pt(111) interface is essentially based on averaging techniques in conjunction with DFT calculations. The presented STM results are in accord with DFTþU calculations, in which we compare possible CO oxidation pathways on oxidized Fe-edges and O-edges. We found that the CO oxidation reaction is more favorable on the oxidized Fe-edges, both thermodynamically and kinetically.

  3. Direct Visualization of Catalytically Active Sites at the FeO-Pt(111) Interface.

    Science.gov (United States)

    Kudernatsch, Wilhelmine; Peng, Guowen; Zeuthen, Helene; Bai, Yunhai; Merte, Lindsay R; Lammich, Lutz; Besenbacher, Flemming; Mavrikakis, Manos; Wendt, Stefan

    2015-08-25

    Within the area of surface science, one of the "holy grails" is to directly visualize a chemical reaction at the atomic scale. Whereas this goal has been reached by high-resolution scanning tunneling microscopy (STM) in a number of cases for reactions occurring at flat surfaces, such a direct view is often inhibited for reaction occurring at steps and interfaces. Here we have studied the CO oxidation reaction at the interface between ultrathin FeO islands and a Pt(111) support by in situ STM and density functional theory (DFT) calculations. Time-lapsed STM imaging on this inverse model catalyst in O2 and CO environments revealed catalytic activity occurring at the FeO-Pt(111) interface and directly showed that the Fe-edges host the catalytically most active sites for the CO oxidation reaction. This is an important result since previous evidence for the catalytic activity of the FeO-Pt(111) interface is essentially based on averaging techniques in conjunction with DFT calculations. The presented STM results are in accord with DFT+U calculations, in which we compare possible CO oxidation pathways on oxidized Fe-edges and O-edges. We found that the CO oxidation reaction is more favorable on the oxidized Fe-edges, both thermodynamically and kinetically.

  4. Adsorption, mobility, and dimerization of benzaldehyde on Pt(111)

    DEFF Research Database (Denmark)

    Rasmussen, Anton Michael Havelund; Hammer, Bjørk

    2012-01-01

    Building on results for the adsorption of benzene on Pt(111), the adsorption of benzaldehyde is investigated using density functional theory. Benzaldehyde is found to chemisorb preferentially with its aromatic ring in the flat-lying bridge geometry that is also preferred for benzene. Across the i...

  5. Calorimetric measurement of adsorption and adhesion energies of Cu on Pt(111)

    Science.gov (United States)

    James, Trevor E.; Hemmingson, Stephanie L.; Sellers, Jason R. V.; Campbell, Charles T.

    2017-03-01

    The adsorption energies of submonolayer amounts of one metal on the surface of another metal have been measured for decades by temperature programmed desorption. However, that method fails for metals that alloy. We report here the first measurement of the adsorption energy for any such metal-on-metal combination that forms a bulk alloy. The adsorption and interfacial energetics of vapor deposited Cu onto Pt(111) at 300 K has been studied using single crystal adsorption calorimetry (SCAC) and X-ray photoelectron spectroscopy (XPS). The Cu grows as 2D pseudomorphic islands in the first layer and its heat of adsorption decreased linearly from 358 to 339 kJ/mol. This is attributed to increasing lattice strain with island size, associated with the small lattice mismatch (8%). It adsorbs 2 kJ/mol more weakly in the 2nd layer than above 3 ML, where it reaches the bulk heat of sublimation of Cu(solid), 337 kJ/mol. The adhesion energy of multilayer Cu onto Pt(111) is 3.76 J/m2. The extra stability of the first Cu monolayer compared to bulk Cu measured here is 12 kJ/mol, compared to a difference of 83 kJ/mol for underpotential deposition of Cu on a Pt(111) electrode, with the difference attributed to stronger bonding of Cu to the solvent and double layer compared to Pt.

  6. Are Vicinal Metal Surfaces Stable?

    DEFF Research Database (Denmark)

    Frenken, J. W. M.; Stoltze, Per

    1999-01-01

    We use effective medium theory to demonstrate that the energies of many metal surfaces are lowered when these surfaces are replaced by facets with lower-index orientations. This implies that the low-temperature equilibrium shapes of many metal crystals should be heavily faceted. The predicted ins...

  7. Infrared spectroscopy of physisorbed and chemisorbed N-2 in the Pt(111)(3x3)N-2 structure

    DEFF Research Database (Denmark)

    Gustafsson, K.; Karlberg, Gustav; Andersson, Sven

    2007-01-01

    Using infrared spectroscopy and low electron energy diffraction, we have investigated the adsorption of N-2, at 30 K, on the Pt(111) and the Pt(111)(1x1)H surfaces. At monolayer coverage, N-2 orders in commensurate (3x3) structures on both surfaces, and we propose that the unit cells contain four...... molecules in each case. The infrared spectra reveal that N-2 exclusively physisorbs on the Pt(111)(1x1)H surface, while both physisorbed and chemisorbed N-2 is detected on the Pt(111) surface. Physisorbed N-2 is the majority species in the latter case, and the two adsorption states show an almost identical...... uptake behavior, which indicates that they are intrinsic constituents of the growing (3x3) N-2 islands. An analysis of the infrared absorbance data, based on a simple scaling concept suggested by density functional theory calculations, supports a model in which the (3x3) unit cell contains one...

  8. Hydrogen-induced Kondo effect for Co/Pt(111)

    Energy Technology Data Exchange (ETDEWEB)

    Dubout, Quentin; Calleja Mitja, Fabian; Etzkorn, Markus; Lehnert, Anne; Claude, Laurent; Gambardella, Pietro; Brune, Harald [Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland)

    2011-07-01

    We present 0.4 K Scanning Tunneling Spectroscopy (STS) results on hydrogenated Co adatoms on Pt(111). Molecular H dosage creates two Co-H adsorption complexes with comparable abundance. Type I displays very large (40 %) inelastic conductance steps that originate from vibrations, as evidenced by their shift when substituting H by D. Type II displays smaller (5 %) conductance steps at higher energies, again due to H vibrations, together with a large conductance peak at the Fermi level. This feature is attributed to the Kondo effect. Its splitting in magnetic fields up to 8 Tesla identifies the Co-H complex as a S = 1/2 system, whereas clean Co/Pt(111) has a spin of 1 and shows no Kondo effect. H-adsorption has been reported to quench the Kondo effect, here we show that it can produce it.

  9. Spectroscopy of the conformational disorder in molecular films: Tetracosane and squalane on Pt(111)

    Science.gov (United States)

    Fuhrmann, D.; Graham, A. P.

    2004-02-01

    The spectroscopic investigation of the molecular vibrations of adsorbed branched and unbranched alkane molecules using helium atom scattering (HAS) provides evidence for the thermal formation of gauche defects in tetracosane (C24H50) monolayers above 200 K. HAS results for the vibration of tetracosane molecules perpendicular to the Pt(111) surface reveal a strong frequency decrease and peak broadening above the transition temperature which can be related to a reduction of the force holding the molecules to the surface. This reduction of the force is interpreted as being due to the thermal formation of gauche defects within the tetracosane molecules.

  10. Tuning the Activity of Pt(111) for Oxygen Electroreduction by Subsurface Alloying

    DEFF Research Database (Denmark)

    Stephens, Ifan; Bondarenko, A.S.; Perez-Alonso, F.J.

    2011-01-01

    To enable the development of low temperature fuel cells, significant improvements are required to the efficiency of the Pt electrocatalysts at the cathode, where oxygen reduction takes place. Herein, we study the effect of subsurface solute metals on the reactivity of Pt, using a Cu/Pt(111) near......-surface alloy. Our investigations incorporate electrochemical measurements, ultrahigh vacuum experiments, and density functional theory. Changes to the OH binding energy, ΔEOH, were monitored in situ and adjusted continuously through the subsurface Cu coverage. The incorporation of submonolayer quantities of Cu...

  11. Enhancement in Ethanol Electrooxidation by SnO(x) Nanoislands Grown on Pt(111): Effect of Oxide-Metal Interface Sites

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, W.P.; Axnanda, S.; White, M.G.; Adzic, R.R.; Hrbek, J.

    2011-08-25

    An integrated surface science and electrochemistry approach has been used to prepare and characterize SnO{sub x}/Pt(111) model catalysts and evaluate their electrochemical activity for the ethanol oxidation reaction (EOR). Nanoislands of SnO{sub x} are deposited onto the Pt(111) by reactive layer assisted deposition in which Sn metal is vapor deposited onto a Pt(111) surface precovered by NO{sub 2}. X-ray photoelectron spectroscopy (XPS) shows that the SnO{sub x} islands are highly reduced with Sn{sup 2+} being the dominant chemical species. After exposing the SnO{sub x}/Pt(111) surface to H{sub 2}O or an electrolyte solution, XPS provides evidence for a significant amount of H{sub 2}O/OH adsorbed on the reduced SnO{sub x} surfaces. Electrochemical testing reveals that the catalytic performance of Pt(111) toward ethanol electrooxidation is significantly enhanced with SnO{sub x} islands added onto the surface. The enhanced EOR activity is tentatively attributed to the efficient removal of CO{sub ads}-like poisoning species at Pt sites by oxygen-containing species that are readily formed on the SnO{sub x} nanoislands. Moreover, the strong dependence of the EOR activity on SnO{sub x} coverage provides experimental evidence for the importance of SnO{sub x}-Pt interface sites in the EOR.

  12. Controlling the Adsorption of Aromatic Compounds on Pt(111) with Oxygenate Substituents: From DFT to Simple Molecular Descriptors.

    Science.gov (United States)

    Réocreux, Romain; Huynh, Minh; Michel, Carine; Sautet, Philippe

    2016-06-01

    Aromatic chemistry on metallic surfaces is involved in many processes within the contexts of biomass valorization, pollutant degradation, or corrosion protection. Albeit theoretically and experimentally challenging, knowing the structure and the stability of aromatic compounds on such surfaces is essential to understand their properties. To gain insights on this topic, we performed periodic ab initio calculations on Pt(111) to determine a set of simple molecular descriptors that predict both the stability and the structure of aromatic adsorbates substituted with alkyl and alkoxy (or hydroxy) groups. While the van der Waals (vdW) interaction is controlled by the molecular weight and the deformation energy by both the nature and the relative position of the substituents to the surface, the chemical bonding can be correlated to the Hard and Soft Acids and Bases (HSAB) interaction energy. This work gives general insights on the interaction of aromatic compounds with the Pt(111) surface.

  13. Step- vs. kink-formation energies on Pt(111)

    Energy Technology Data Exchange (ETDEWEB)

    FEIBELMAN,PETER J.

    2000-05-01

    Ab-initio kink-formation energies are about 0.25 and 0.18 eV on the (100)- and (111)-microfacet steps of Pt(111), while the sum of the step-formation energies is 0.75 eV/atom. These results imply a specific ratio of formation energies for the two step types, namely 1.14, in excellent agreement with experiment. If kink-formation costs the same energy on the two step types, an inference recently drawn from scanning probe observations of step wandering, this ratio ought to be 1.

  14. Methanol Adsorption and Reaction on Samaria Thin Films on Pt(111

    Directory of Open Access Journals (Sweden)

    Jin-Hao Jhang

    2015-09-01

    Full Text Available We investigated the adsorption and reaction of methanol on continuous and discontinuous films of samarium oxide (SmOx grown on Pt(111 in ultrahigh vacuum. The methanol decomposition was studied by temperature programmed desorption (TPD and infrared reflection absorption spectroscopy (IRRAS, while structural changes of the oxide surface were monitored by low-energy electron diffraction (LEED. Methanol dehydrogenates to adsorbed methoxy species on both the continuous and discontinuous SmOx films, eventually leading to the desorption of CO and H2 which desorbs at temperatures in the range 400–600 K. Small quantities of CO2 are also detected mainly on as-prepared Sm2O3 thin films, but the production of CO2 is limited during repeated TPD runs. The discontinuous film exhibits the highest reactivity compared to the continuous film and the Pt(111 substrate. The reactivity of methanol on reduced and reoxidized films was also investigated, revealing how SmOx structures influence the chemical behavior. Over repeated TPD experiments, a SmOx structural/chemical equilibrium condition is found which can be approached either from oxidized or reduced films. We also observed hydrogen absence in TPD which indicates that hydrogen is stored either in SmOx films or as OH groups on the SmOx surfaces.

  15. PtxGd alloy formation on Pt(111): Preparation and structural characterization

    Science.gov (United States)

    Ulrikkeholm, Elisabeth T.; Pedersen, Anders F.; Vej-Hansen, Ulrik G.; Escudero-Escribano, Maria; Stephens, Ifan E. L.; Friebel, Daniel; Mehta, Apurva; Schiøtz, Jakob; Feidenhansl', Robert K.; Nilsson, Anders; Chorkendorff, Ib

    2016-10-01

    PtxGd single crystals have been prepared in ultra high vacuum (UHV). This alloy shows promising catalytic properties for the oxygen reduction reaction. The samples were prepared by using vacuum deposition of a thick layer of Gd on a sputter cleaned Pt(111) single crystal, resulting in a ∼63 nm thick alloy layer. Subsequently the surfaces were characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), ion scattering spectroscopy (ISS) and temperature programmed desorption (TPD) of CO. A Pt terminated alloy was observed upon annealing the sample to 600 ∘C. The LEED and synchrotron XRD experiments have shown that a slightly compressed (2 × 2) alloy appear. The alloy film followed the orientation of the Pt(111) substrate half the time, otherwise it was rotated by 30∘. The TPD spectra show a well-defined peak shifted down 200 ∘C in temperature. The crystal structure of the alloy was investigated using ex-situ X-ray diffraction experiments, which revealed an in-plane compression and a complicated stacking sequence. The crystallites in the crystal are very small, and a high degree of twinning by merohedry was observed.

  16. Study of underpotential deposited Cu layers on Pt(111) and their stability against CO and CO2 in perchloric acid

    DEFF Research Database (Denmark)

    Schlaup, Christian Georg; Horch, Sebastian

    2013-01-01

    The underpotential deposition (UPD) of copper on a Pt(111) electrode and the influence of gas coadsorbates, i.e. CO and CO2, on the thus deposited copper layer were studied in a 0.1 M HClO4 electrolyte by means of EC-STM. By UPD, an atomically flat Cu layer is formed, which exhibits a pseudomorphic...... (1 × 1) structure. However, it contains several point defects due to which its total coverage is less than a monolayer, in agreement with the measured charge density in the CV curves. Upon exposure to a CO-saturated solution the pseudomorphic structure collapses to a coalescent structure with many...... vacancy islands. This phase transition is induced by the preferential binding of CO to the Pt(111) surface. In contrast, CO2, which binds stronger to copper, does not affect the pseudomorphic structure of the Cu layer....

  17. Work function mediated by deposition of ultrathin polar FeO on Pt(111)

    Science.gov (United States)

    Lu, Shuangzan; Qin, Zhihui; Guo, Qinmin; Cao, Gengyu

    2017-01-01

    Significant work function changes from bare Pt(111) surface to 1 monolayer and 2 monolayers of ultrathin iron oxide (FeO) films on it are investigated by means of scanning tunneling microscopy/spectroscopy (STM/STS). With FeO layer-by-layer growth, a continuous reduction of the work function along with the surface vacuum level (VL) shifting is observed. We found that the compression of the electron spill-out at the metal-oxide interface and the substantial reconstruction of 2 ML FeO film, respectively, make major contributions to the first and the second reductions of the work function. The rectifying effect in FeO films is also observed, which is attributed to the downward shift of band alignment imposed by the total change in surface dipole. Our work shows that the polar oxide films play an important role to adjust surface electronic structures for enhancing device functionality.

  18. Theoretical elucidation of the competitive electro-oxidation mechanisms of formic acid on Pt(111).

    Science.gov (United States)

    Gao, Wang; Keith, John A; Anton, Josef; Jacob, Timo

    2010-12-29

    The mechanisms of formic acid (HCOOH) oxidation on Pt(111) under electrochemical conditions have been studied using density functional theory and then compared with the analogous gas-phase reaction. Results show that HCOOH oxidation under a water-covered surface behaves substantially differently than in the gas phase or using a solvation model involving only a few water molecules. Using these models, we evaluated the detailed reaction process, including energies and geometric structures of intermediates and transition states under the influence of different solvation models and electrode potentials. Our calculations indicate that this potential-dependent electrochemical oxidation proceeds via a multipath mechanism (involving both the adsorbed HCOOH and HCOO intermediates), a result succinctly rationalizing conflicting experimental observations. Moreover, this study highlights how subtle changes in electrochemical reaction environments can influence (electro)catalysis.

  19. Comparative study of vibrations in submonolayer structures of potassium on Pt(111)

    Science.gov (United States)

    Rusina, G. G.; Eremeev, S. V.; Borisova, S. D.; Chulkov, E. V.

    2012-03-01

    We present results of a comparative study of the vibrational spectrum and local density of phonon states in ordered p(2 × 2) and (\\sqrt{3}\\times \\sqrt{3}){R}30^{\\circ} structures formed by potassium atoms on the Pt(111) surface. The calculations were performed with tight-binding interatomic interaction potentials. It was found that the mode associated with vertical displacements of K adatoms has an energy of about 20 meV in both K structures. The strength and energy of this mode slightly decreases with increasing coverage. This result is in good agreement with available experimental data. As in time-resolved second harmonic generation measurements, we observed low frequency modes for both structures considered, which are caused by the interaction of potassium with the second layer of the substrate.

  20. Controlling the spin of co atoms on pt(111) by hydrogen adsorption.

    Science.gov (United States)

    Dubout, Q; Donati, F; Wäckerlin, C; Calleja, F; Etzkorn, M; Lehnert, A; Claude, L; Gambardella, P; Brune, H

    2015-03-13

    We investigate the effect of H adsorption on the magnetic properties of individual Co atoms on Pt(111) with scanning tunneling microscopy. For pristine Co atoms, we detect no inelastic features in the tunnel spectra. Conversely, CoH and CoH2 show a number of low-energy vibrational features in their differential conductance identified by isotope substitution. Only the fcc-adsorbed species present conductance steps of magnetic origin, with a field splitting identifying their effective spin as Seff=2 for CoH and 3/2 for CoH2. The exposure to H2 and desorption through tunnel electrons allow the reversible control of the spin in half-integer steps. Because of the presence of the surface, the hydrogen-induced spin increase is opposite to the spin sequence of CoHn molecules in the gas phase.

  1. Simulating Linear Sweep Voltammetry from First-Principles: Application to Electrochemical Oxidation of Water on Pt(111) and Pt3Ni(111)

    DEFF Research Database (Denmark)

    Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Rossmeisl, Jan

    2012-01-01

    Cyclic voltammetry is a fundamental experimental method for characterizing adsorbates on electrochemical surfaces. We present a model for the electrochemical solid–liquid interface, and we simulate the linear sweep voltammogram of the electrochemical oxidation of H2O on Pt(111) and Pt3Ni(111...

  2. The Effects of Organic Adsorbates on the Underpotential Deposition of Silver on Pt(111) Electrodes

    Science.gov (United States)

    1993-01-01

    CV) The Effects of Organic Adsorbates on the Underpotential Deposition W.0 of Silver on Pt(111) Electrodes _• D. L. Taylor and H. D. Abruxla* D TIC...to determine the effects of competing organic adsorbates on the underpotential deposition of silver on Pt(111). The adsorbates studied are known to...hcis )n appive tor pubic release and sal Its distribution is unlimited. fu .. 93-12456 INTRODUCTION The process of underpotential deposition (UPD) of

  3. A comparative study of the photodissociation of physisorbed O{sub 2} on Pt(111) and graphite

    Energy Technology Data Exchange (ETDEWEB)

    Siller, L.; Bennett, R.A.; Palmer, R.E. [Nanoscale Physics Research Laboratory, School of Physics and Space Research, University of Birmingham, Birmingham B15 2TT (United Kingdom); Bennett, S.L. [Physical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ (United Kingdom); CLRC, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Crabtree, H.M.; Foord, J.S. [Physical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ (United Kingdom); Wilkes, J. [Physical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ (United Kingdom); School of Applied Sciences, University of Huddersfield, Huddersfield HD1 3DH (United Kingdom); Lamont, C.L.A. [School of Applied Sciences, University of Huddersfield, Huddersfield HD1 3DH (United Kingdom); MacDonald, M.A. [CLRC, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom)

    1997-07-07

    A comparative study of photodesorption from physisorbed oxygen layers on (highly oriented pyrolytic) graphite and Pt(111) surfaces has been carried out using continuously tuneable synchrotron radiation in the energy range 13 - 35 eV. The photodesorption of both O{sup +} and O{sup -} species is detected. Through monitoring the ion yields as a function of the photon energy and coverage we have proposed a new mechanism for photodesorption of O{sup -} ions induced by inelastic scattering and attachment of photoelectrons originating from the adsorbate layer in the photon energy region between 25 and 30 eV. (author)

  4. Methane dissociation on Pt(111): Searching for a specific reaction parameter density functional

    Energy Technology Data Exchange (ETDEWEB)

    Nattino, Francesco, E-mail: f.nattino@chem.leidenuniv.nl; Migliorini, Davide; Kroes, Geert-Jan [Leiden Institute of Chemistry, Leiden University, Gorlaeus Laboratories, P.O. Box 9502, 2300 RA Leiden (Netherlands); Bonfanti, Matteo [Dipartimento di Chimica, Università degli Studi di Milano, via Golgi 19, 20133 Milano (Italy)

    2016-01-28

    The theoretical description of methane dissociating on metal surfaces is a current frontier in the field of gas-surface dynamics. Dynamical models that aim at achieving a highly accurate description of this reaction rely on potential energy surfaces based on density functional theory calculations at the generalized gradient approximation. We focus here on the effect that the exchange-correlation functional has on the reactivity of methane on a metal surface, using CHD{sub 3} + Pt(111) as a test case. We present new ab initio molecular dynamics calculations performed with various density functionals, looking also at functionals that account for the van der Waals (vdW) interaction. While searching for a semi-empirical specific reaction parameter density functional for this system, we find that the use of a weighted average of the PBE and the RPBE exchange functionals together with a vdW-corrected correlation functional leads to an improved agreement with quantum state-resolved experimental data for the sticking probability, compared to previous PBE calculations. With this semi-empirical density functional, we have also investigated the surface temperature dependence of the methane dissociation reaction and the influence of the rotational alignment on the reactivity, and compared our results with experiments.

  5. Insight into the Reaction Mechanisms of Methanol on PtRu/Pt(111): A Density Functional Study

    Science.gov (United States)

    Ding, Qiuyue; Xu, Wenbin; Sang, Pengpeng; Xu, Jing; Zhao, Lianming; He, Xiaoli; Guo, Wenyue

    2016-04-01

    Periodic DFT calculations have been performed to systematically investigate the mechanisms of methanol decomposition and oxidation on the PtRu/Pt(111) surface. Geometries and energies for the primary species involved are analyzed and the reaction network has been mapped out. The calculation shows that among three initial Csbnd H, Osbnd H, and Csbnd O bond scissions of methanol, the Osbnd H bond scission is found to be the most favorable and bears a lower energy barrier than the desorption of methanol. The decomposition of CH3O occurs via the path CH3O → CH2O → CHO → CO with the limiting step of the first dehydrogenation. Although the oxidation of CO is hindered by a high barrier, the CHO oxidation to CHOOH could occur facilely. Further decomposition of formic acid to CO2 and/or CO could occur via four possible pathways, that is, initial Csbnd H, Osbnd H, and Csbnd O bond activations as well as simultaneous activation of Csbnd H and Csbnd O bonds, where the first pathway, HCOOH → COOH → CO2, is the most favorable from a kinetic point of view. Compared to that on Pt(111), methanol on PtRu/Pt(111) prefers to decomposition rather than desorption and then oxidation via the favorable non-CO path with a lower rate-determining energy barrier of CH3O → CH2O for the whole reaction, which indicates that PtRu alloy can improved tolerance toward CO poisoning compared with pure Pt.

  6. Making channeling visible: keV noble gas ion trails on Pt(111)

    Energy Technology Data Exchange (ETDEWEB)

    Redinger, A; Standop, S; Michely, T [II Physikalisches Institut, Universitaet zu Koeln, D-50937 Koeln (Germany); Rosandi, Y; Urbassek, H M, E-mail: urbassek@rhrk.uni-kl.de [Fachbereich Physik und Forschungszentrum OPTIMAS, Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany)

    2011-01-15

    The impact of argon and xenon noble gas ions on Pt(111) in grazing incidence geometry are studied through direct comparison of scanning tunneling microscopy images and molecular dynamics simulations. The energy range investigated is 1-15 keV and the angles of incidence with respect to the surface normal are between 78.5{sup 0} and 88{sup 0}. The focus of the paper is on events where ions gently enter the crystal at steps and are guided in channels between the top most layers of the crystal. The trajectories of the subsurface channeled ions are visible as trails of surface damage. The mechanism of trail formation is analyzed using simulations and analytical theory. Significant differences between Xe{sup +} and Ar{sup +} projectiles in damage, in the onset energy of subsurface channeling as well as in ion energy dependence of trail length and appearance are traced back to the projectile and ion energy dependence of the stopping force. The asymmetry of damage production with respect to the ion trajectory direction is explained through the details of the channel shape and subchannel structure as calculated from the continuum approximation of the channel potential. Measured and simulated channel switching in directions normal and parallel to the surface as well as an increase of ions entering into channels from the perfect surface with increasing angles of incidence are discussed.

  7. Angle resolved photoelectron distribution of the 1{pi} resonance of CO/Pt(111)

    Energy Technology Data Exchange (ETDEWEB)

    Haarlammert, Thorben; Wegner, Sebastian; Tsilimis, Grigorius; Zacharias, Helmut [Physikalisches Institut, Westfaelische Wilhelms Universitaet, Muenster (Germany); Golovin, Alexander [Institute of Physics, St. Petersburg State University (Russian Federation)

    2009-07-01

    The CO 1{pi} level of a c(4 x 2)-2CO/Pt(111) reconstruction shows a significant resonance when varying the photon energy between h{nu}=23 eV and h{nu}=48 e V. This resonance has not been observed in gas phase measurements or on the Pt(1 10) surface. To investigate the photoelectron distribution of the 1{pi} level high harmonic radiaton has been used. By conversion in rare gases like argon, neon, or helium photon energies of up to 100 eV have been generated at repetition r ates of up to 10 kHz. The single harmonics have been separated and focused by a toroidal grating and directed to the sample surface. A time-of-flight detector with multiple anodes registers the kinetic energies of the emitted photoelectrons and enables the simultaneous detection of multiple emission angles. The angular distributions of photoelectrons emitted from the CO 1{pi} level have been measured for a variety of initial photon energies. Further the angular distributions of the CO 1{pi} level photoelectrons emitted from a CO-Pt{sub 7} cluster have been calculated using the MSX{alpha}-Method which shows good agreement with the ex perimental data.

  8. Step bunching on the vicinal GaN(0001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Ramana Murty, M. V.; Fini, P.; Stephenson, G. B.; Thompson, Carol; Eastman, J. A.; Munkholm, A.; Auciello, O.; Jothilingam, R.; DenBaars, S. P.; Speck, J. S.

    2000-10-15

    Nominally 2{sup o} vicinal GaN(0001) surfaces exhibit monolayer-height steps at 990{sup o}C in the metal-organic chemical vapor deposition environment. Real-time x-ray scattering observations at 715--990{sup o}C indicate that there is a tendency for step bunching during growth. Below 850{sup o}C, step bunches nucleated during growth remain and coarsen after growth, while above 850{sup o}C, the surface reverts to monolayer-height steps after growth. Surfaces vicinal toward the {l_brace}1{bar 1}00{r_brace} and the {l_brace}11{bar 2}0{r_brace} planes exhibit similar behavior. We suggest a simple equilibrium surface orientational phase diagram for vicinal GaN(0001) that is consistent with these observations.

  9. On the mechanism of the direct pathway for formic acid oxidation at a Pt(111) electrode.

    Science.gov (United States)

    Xu, Jie; Yuan, Daofu; Yang, Fan; Mei, Dong; Zhang, Zunbiao; Chen, Yan-Xia

    2013-03-28

    In order determine whether formate is a reaction intermediate of the direct pathway for formic acid oxidation at a Pt electrode, formic acid (HCOOH) oxidation at a Pt(111) electrode has been studied by normal and fast scan voltammetry in 0.1 M HClO4 solutions with different HCOOH concentrations. The relationship between the HCOOH oxidation current density (j(ox)) and formate coverage (θ(formate)) is quantitatively analyzed. The kinetic simulation reveals that the previously proposed formate pathway, with decomposition of the bridge-bonded formate (HCOO(B)) as a rate determining step (rds), cannot be the main pathway responsible for the majority of the current for HCOOH oxidation. Instead, a kinetic model based on a mechanism with formic acid adsorption [structure: see text], along with simultaneous C-H bond activation as the rds for the direct pathway, explains the measured data well. It was found for the relatively slow rate of formic acid oxidation, that adsorption-desorption of the formate is faster, which competes for the surface sites for formic acid oxidation.

  10. Revealing the active intermediates in the oxidation of formic acid on Au and Pt(111).

    Science.gov (United States)

    Gao, Wang; Song, Er Hong; Jiang, Qing; Jacob, Timo

    2014-08-25

    The mechanisms of formic acid (HCOOH) oxidation on Au(111) under gas-phase and electrochemical conditions was studied by using density functional theory and then compared with the analogous processes on Pt(111). Our results demonstrate that a mechanism involving a single intermediate molecule is preferred on both Au and Pt(111). Furthermore, under gas-phase conditions, HCOOH oxidation proceeds through the same mechanism (formate pathway) on Au and Pt(111), whereas under electrochemical conditions, it can take place through significantly different mechanisms (formate and/or direct pathways), depending on the applied electrode potential. Our calculations help to rationalize conflicting experimental explanations and are crucial for understanding the mechanism of this fundamental (electro-)catalytic process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Tuning Aryl−CH···O Intermolecular Interactions on Pt(111)

    DEFF Research Database (Denmark)

    Demers-Carpentier, Vincent; Laliberte, Marc-André; Pan, Yunxiang

    2011-01-01

    Scanning tunneling microscopy (STM) data are reported for the room-temperature adsorption of 2,2,2-trifluoroacetophenone (TFAP), 2,2,2-trifluorovinylbenzene (TFVB), octafluoroacetophenone (OFAP), and methyl benzoate (MB) on Pt(111). The objective of the study is to establish the role of aryl−CH··...

  12. Tuning Aryl−CH···O Intermolecular Interactions on Pt(111)

    DEFF Research Database (Denmark)

    Demers-Carpentier, Vincent; Laliberte, Marc-André; Pan, Yunxiang

    2010-01-01

    Scanning tunneling microscopy (STM) data are reported for the room-temperature adsorption of 2,2,2-trifluoroacetophenone (TFAP), 2,2,2-trifluorovinylbenzene (TFVB), octafluoroacetophenone (OFAP), and methyl benzoate (MB) on Pt(111). The objective of the study is to establish the role of aryl−CH··...

  13. Guaiacol hydrodeoxygenation mechanism on Pt(111): Insights from density functional theory and linear free energy relations

    Science.gov (United States)

    In this study density functional theory (DFT) was used to study the adsorption of guaiacol and its initial hydrodeoxygenation (HDO) reactions on Pt(111). Previously reported Brønsted–Evans–Polanyi (BEP) correlations for small open chain molecules are found to be inadequate in estimating the reaction...

  14. Tuning Aryl−CH···O Intermolecular Interactions on Pt(111)

    DEFF Research Database (Denmark)

    Demers-Carpentier, Vincent; Laliberte, Marc-André; Pan, Yunxiang

    2010-01-01

    Scanning tunneling microscopy (STM) data are reported for the room-temperature adsorption of 2,2,2-trifluoroacetophenone (TFAP), 2,2,2-trifluorovinylbenzene (TFVB), octafluoroacetophenone (OFAP), and methyl benzoate (MB) on Pt(111). The objective of the study is to establish the role of aryl−CH··...

  15. Electrooxidation of CO and H{sub 2}/CO mixtures on Pt(111) in acid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Markovic, N.M.; Grgur, B.N.; Ross, P.N. [Lawrence Berkeley National Lab., CA (United States). Materials Sciences Div.; Lucas, C.A. [Univ. of Liverpool (United Kingdom)

    1999-01-21

    Electrocatalysis of CO oxidation and the interfacial structure of the CO adlayer (CO{sub ad}) on the Pt(111) surface in 0.5 M H{sub 2}SO{sub 4} were examined by using the rotating disk electrode method in combination with in situ surface X-ray diffraction measurements. The results presented here elucidate the roles played by two different forms of CO{sub ad}: one which is oxidized at lower overpotentials, in the so-called preoxidation region, the authors characterize as a weakly adsorbed state (CO{sub ad,w}), and a strongly adsorbed state (CO{sub ad,s}) which is oxidized at higher overpotentials. The CO{sub ad,w} state forms at saturation coverage by adsorption at E < 0.15 V and assumes a compressed p(2 x 2) structure containing 3 CO molecules in the unit cell (0.75 CO/Pt). The authors propose that oxidative removal of CO{sub ad.w} is accompanied by simultaneous relaxation of the CO adlayer, and that the remaining CO{sub ad} ({approx}0.6 CO/Pt) assumes a new bonding state which they identify as CO{sub ad,s}. The CO{sub ad,s} state is present in a structure lacking long-range order. Despite the reduced coverage by CO{sub ad}, H{sub 2} electrooxidation is still completely poisoned at potentials below 0.6 V. The electrooxidation of CO in solution is proposed to occur via the CO{sub ad,w} state at 0.6--0.8 V, and via the CO{sub ad,s} at higher potentials.

  16. Scanning Tunneling Microscopy Measurements of the Full Cycle of a Heterogeneous Asymmetric Hydrogenation Reaction on Chirally Modified Pt(111)

    DEFF Research Database (Denmark)

    Demers-Carpentier, Vincent; Goubert, Guillaume; Masini, Federico

    2012-01-01

    -(1-naphthyl)ethylamine, ((R)-NEA), as the modifier. On the nonmodified surface, introduction of H2 at a background pressure of ∼1 × 10–6 mbar leads to the rapid break-up of TFAP dimer structures followed by the gradual removal of all TFAP-related images. During the latter step, some monomers display an extra...... protrusion compared to TFAP in dimer structures. They are attributed to a half-hydrogenated intermediate. The introduction of H2 to a mixture of (R)-NEA and TFAP on Pt(111) leads to the removal of TFAP without any change in the population of the modifier, as required for an efficient chirally modified...

  17. Electronic density functional theory in the grand canonical ensemble, electrochemistry, and the underpotential deposition of Cu/Pt(111)

    Science.gov (United States)

    Sundararaman, Ravishankar; Weaver, Kendra; Arias, Tomas

    2012-02-01

    The study of electrochemical systems within electronic density functional theory requires the handling of non-neutral electronic systems in the plane-wave basis in order to accurately describe charged metallic surfaces; this can be accomplished in joint density functional theory by adding an electrolyte with Debye screening ootnotetextK. L. Weaver and T. A. Arias (under preparation). This capability opens up the opportunity to work in the grand canonical ensemble at fixed chemical potential μ for the electrons, which corresponds directly to the experimental setting in electrochemistry. We present efficient techniques for electronic density functional calculations at fixed μ, and demonstrate the improvement in predictive power over conventional neutral calculations using the underpotential deposition of Cu/Pt(111) as an example: for the first time, we calculate absolute voltages for electrochemical processes in excellent agreement with experiment, instead of voltage shifts alone.

  18. Adsorption and Accommodation of Xe on Pt(111)

    Science.gov (United States)

    1992-05-25

    atoms on metal surfaces.15. 16 15 May 1992 -7- Acknowledgments The authors would like to thank Dan Auerbach, Mark Cardillo, Milton Cole, Roald ...Phys. Rev. Lett. 66, 1998 (1991). 15. S. C. Wang and G. Ehrlich, J. Chem. Phys. 94, 4071 (1991). 16. D. E. Sanders and A. E. DePristo, Surf. Sci. 254

  19. Density functional theory studies of the adsorption of ethylene and oxygen on Pt(111) and Pt3Sn(111)

    DEFF Research Database (Denmark)

    Watwe, R.M.; Cortright, R.D.; Mavrikakis, Manos

    2001-01-01

    of pi -bonded ethylene, di-sigma -bonded ethylene, and ethylidyne species are weaker on Pt3Sn(111) than on Pt(111) by 21, 31, and 50 kJ/mol, respectively. Hence, the electronic effect of Sn on the adsorption of ethylene depends on the type of adsorption site, with adsorption on three-fold site weakened......Density functional theory, employing periodic slab calculations, was used to investigate the interactions of ethylene and oxygen with Pt(111) and Pt3Sn(111). The predicted energetics and structures of adsorbed species on Pt(111) are in good agreement with experimental data. The binding energies...

  20. Electric-field-modulated nonvolatile resistance switching in VO₂/PMN-PT(111) heterostructures.

    Science.gov (United States)

    Zhi, Bowen; Gao, Guanyin; Xu, Haoran; Chen, Feng; Tan, Xuelian; Chen, Pingfan; Wang, Lingfei; Wu, Wenbin

    2014-04-09

    The electric-field-modulated resistance switching in VO2 thin films grown on piezoelectric (111)-0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (PMN-PT) substrates has been investigated. Large relative change in resistance (10.7%) was observed in VO2/PMN-PT(111) hererostructures at room temperature. For a substrate with a given polarization direction, stable resistive states of VO2 films can be realized even when the applied electric fields are removed from the heterostructures. By sweeping electric fields across the heterostructure appropriately, multiple resistive states can be achieved. These stable resistive states result from the different stable remnant strain states of substrate, which is related to the rearrangements of ferroelectric domain structures in PMN-PT(111) substrate. The resistance switching tuned by electric field in our work may have potential applications for novel electronic devices.

  1. Energetics of methanol and formic acid oxidation on Pt(111): Mechanistic insights from adsorption calorimetry

    Science.gov (United States)

    Silbaugh, Trent L.; Karp, Eric M.; Campbell, Charles T.

    2016-08-01

    The catalytic and electrocatalytic oxidation and reforming of methanol and formic acid have received intense interest due to potential use in direct fuel cells and as prototype models for understanding electrocatalysis. Consequently, the reaction energy diagram (energies of all the adsorbed intermediates and activation energies of all the elementary steps) have been estimated for these reactions on Pt(111) by density functional theory (DFT) in several studies. However, no experimental measurement of these energy diagrams have been reported, nor is there a consensus on the mechanisms. Here, we use energies of key intermediates on Pt(111) from single crystal adsorption calorimetry (SCAC) and temperature programmed desorption (TPD) to build a combined energy diagram for these reactions. It suggests a new pathway involving monodentate formate as a key intermediate, with bidentate formate only being a spectator species that slows the rate. This helps reconcile conflicting proposed mechanisms.

  2. Atomic Aggregation Processes in the Early Stages of Pt/Pt(111) Growth

    Institute of Scientific and Technical Information of China (English)

    ZHUANG Guo-Ce; ZHU Xiao-Bin; WANG Wei

    2000-01-01

    The atomic aggregation processes in the early stages of Pt/Pt(111) growth are studied by using kinetic Monte Carlo simulations. Our results show that the average neighbor coordination number of the atoms in a cluster is a function of temperature, agreeing well with the experiment observations of scanning tunneling microscopy. The influence of diffusion barriers of various atomic processes on the morphology of islands is also studied. Different morphologies of the islands (dendritic, fractal, or compact islands) are found.

  3. Interaction of carbon dioxide with Cu overlayers on Pt(111)

    DEFF Research Database (Denmark)

    Schumacher, N.; Andersson, Klas Jerker; Grabow, L.C.

    2008-01-01

    Experimental and theoretical studies on the interaction of carbon dioxide with pseudomorphic and rough copper layers deposited on a platinum (111) single crystal are reported. Evidence for carbon dioxide dissociation and carbonate formation is presented and the relevance to methanol synthesis......) reveals a broad high temperature desorption state for CO2 with peak maximum around 450 K. X-ray photoelectron spectroscopy (XPS) shows that approximately one third of the oxygen accumulated on the surface upon CO2 exposure remains after TPD, indicative of carbonate formation via CO2 dissociation supplying...... O-ads and then facile CO2 + O-ads association, as well as subsequent decomposition at higher temperatures. Density functional theory studies of stepped Cu and Cu/Pt slabs reproduce vibrational frequencies of the carbonate, suggesting a nearly flat tridentate configuration at steps/defect sites....

  4. Tip-Dependent Scanning Tunneling Microscopy Imaging of Ultrathin FeO Films on Pt(111)

    DEFF Research Database (Denmark)

    Merte, Lindsay Richard; Grabow, Lars C.; Peng, Guowen

    2011-01-01

    High-resolution scanning tunneling microscope (STM) images of moiré-structured FeO films on Pt(111) were obtained in a number of different tip-dependent imaging modes. For the first time, the STM images are distinguished and interpreted unambiguously with the help of distinct oxygen-vacancy dislo......High-resolution scanning tunneling microscope (STM) images of moiré-structured FeO films on Pt(111) were obtained in a number of different tip-dependent imaging modes. For the first time, the STM images are distinguished and interpreted unambiguously with the help of distinct oxygen......-vacancy dislocation loops in the FeO moiré structure. The experimental STM results are compared with the results of electronic structure calculations within the DFT+U scheme for a realistic (sqrt(91)xsqrt(91)R5.2 moiré unit cell supported on Pt(111) as well as with the results from previous studies. We find that one...... on the specific tip apex state and likely result from specific tip-sample chemical interactions. From the present STM results we show that several of the previously published conclusions for the FeO system have to be revisited....

  5. Probing adsorption phenomena on a single crystal Pt-alloy surface under oxygen reduction reaction conditions

    DEFF Research Database (Denmark)

    Bondarenko, Alexander S.; Stephens, Ifan E.L.; Bech, Lone;

    2012-01-01

    The adsorption dynamics of *OH and *O species at Pt(111) and Cu/Pt(111) near-surface alloy (NSA) surfaces in oxygen-free and O2-saturated 0.1M HClO4 was investigated. Subsurface Cu modifies the electronic structure at the Pt(111) surface resulting in weaker bonding to adsorbates like *OH, *H or *...

  6. Na-induced bonding and bond-length changes for CO on Pt(111): A near-edge x-ray-absorption fine-structure study

    Energy Technology Data Exchange (ETDEWEB)

    Sette, F.; Stoehr, J.; Kollin, E.B.; Dwyer, D.J.; Gland, J.L.; Robbins, J.L.; Johnson, A.L.

    1985-03-04

    Near-edge x-ray absorption fine-structure studies above the C and O K edges for CO on Pt(111) reveal a 4-eV shift of the sigma shape resonance when Na(0.2 monolayer) is coabsorbed. This allows determination of a Na-induced (0.12 +- 0.03)-A expansion of the C-O bond. Na does not affect the vertical molecular orientation on the surface. Reduction and broadening of the 1s..-->..2..pi..( resonance and the CO bond lengthening in the presence of Na signifies substantially increased metal to CO backbonding.

  7. Electrodeposition of copper on a Pt(111) electrode in sulfuric acid containing poly(ethylene glycol) and chloride ions as probed by in situ STM.

    Science.gov (United States)

    Fu, YunLin; Pao, Te; Chen, Sih-Zih; Yau, ShuehLin; Dow, Wei-Ping; Lee, Yuh-Lang

    2012-07-03

    This study employed real-time in situ STM imaging to examine the adsorption of PEG molecules on Pt(111) modified by a monolayer of copper adatoms and the subsequent bulk Cu deposition in 1 M H(2)SO(4) + 1 mM CuSO(4)+ 1 mM KCl + 88 μM PEG. At the end of Cu underpotential deposition (~0.35 V vs Ag/AgCl), a highly ordered Pt(111)-(√3 × √7)-Cu + HSO(4)(-) structure was observed in 1 M H(2)SO(4) + 1 mM CuSO(4). This adlattice restructured upon the introduction of poly(ethylene glycol) (PEG, molecular weight 200) and chloride anions. At the onset potential for bulk Cu deposition (~0 V), a Pt(111)-(√3 × √3)R30°-Cu + Cl(-) structure was imaged with a tunneling current of 0.5 nA and a bias voltage of 100 mV. Lowering the tunneling current to 0.2 nA yielded a (4 × 4) structure, presumably because of adsorbed PEG200 molecules. The subsequent nucleation and deposition processes of Cu in solution containing PEG and Cl(-) were examined, revealing the nucleation of 2- to 3-nm-wide CuCl clusters on an atomically smooth Pt(111) surface at overpotentials of less than 50 mV. With larger overpotential (η > 150 mV), Cu deposition seemed to bypass the production of CuCl species, leading to layered Cu deposition, starting preferentially at step defects, followed by lateral growth to cover the entire Pt electrode surface. These processes were observed with both PEG200 and 4000, although the former tended to produce more CuCl nanoclusters. Raising [H(2)SO(4)] to 1 M substantiates the suppressing effect of PEG on Cu deposition. This STM study provided atomic- or molecular-level insight into the effect of PEG additives on the deposition of Cu.

  8. Water adsorption on graphene/Pt(111 at room temperature: A vibrational investigation

    Directory of Open Access Journals (Sweden)

    A. Politano

    2011-12-01

    Full Text Available Water interaction with quasi-freestanding graphene deposited on Pt(111 has been investigated by using vibrational spectroscopy. Loss measurements show that water molecules dosed at room temperature can dissociate giving rise to C-H bonds. The formation of the C-H bonds strongly attenuates the optical phonons of the graphene sheet. On the other hand, at 100 K water has been found to adsorb only in molecular state. Present findings should be taken into account in engineering graphene-based devices which should work at atmospheric pressure and at room temperature.

  9. Electrochemical deposition of copper onto Pt(111) in the presence of (bi)sulfate anions

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, C.A. [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)]|[Department of Physics, University of Liverpool, Oliver Lodge Laboratory, Liverpool, L69 7ZE (United Kingdom); Markovic, N.M.; Ross, P.N. [Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)

    1997-08-01

    Using {ital in situ} x-ray diffraction we have studied the underpotential deposition (UPD) of copper onto a Pt(111) electrode in sulfuric acid. Deposition occurs in a two-stage process; close to a full monolayer of Cu being preceded by a ({radical}(3){times}{radical}(3))R30{degree} structure that consists of both Cu and (bi)sulfate anions and is similar to the structure observed on the Au(111) electrode. Utilizing anomalous scattering methods we can accurately determine the Cu coverage during UPD and propose structural models based on crystal truncation rod measurements. {copyright} {ital 1997} {ital The American Physical Society}

  10. Mechanisms of pattern formation in grazing-incidence ion bombardment of Pt(111)

    OpenAIRE

    Hansen, H; Redinger, A.; Messlinger, S.; Stoian, G.; Rosandi, Y.; Urbassek, H. M.; Linke, U.; Michely, T.

    2006-01-01

    Ripple patterns forming on Pt(111) due to 5 keV Ar+ grazing-incidence ion bombardment were investigated by scanning tunneling microscopy in a broad temperature range from 100 to 720 K and for ion fluences up to 3x10(20) ions/m(2). A detailed morphological analysis together with molecular dynamics simulations of single ion impacts allow us to develop atomic scale models for the formation of these patterns. The large difference in step edge versus terrace damage is shown to be crucial for rippl...

  11. In-situ spectroscopic monitoring of the ambient pressure hydrogenation of C2 to ethane on Pt(111)

    Science.gov (United States)

    Krooswyk, Joel D.; Kruppe, Christopher M.; Trenary, Michael

    2016-10-01

    The hydrogenation of C2 molecules formed on the Pt(111) surface through acetylene exposure at 750 K was monitored in-situ with reflection absorption infrared spectroscopy (RAIRS) in the presence of up to 10 Torr of H2. The coverage of post-reaction surface carbon was measured with Auger electron spectroscopy. The RAIR spectra show that C2 is hydrogenated to an ethylidyne intermediate. The hydrogenation of ethylidyne was also monitored at 400 K for H2(g) pressures of 1.0 × 10- 2 to 10 Torr. At H2(g) pressures greater than 1.0 Torr, ethylidyne is completely hydrogenated. In an attempt to probe the nature of the C2 adsorption sites, RAIR spectra of coadsorbed CO were obtained. It is found that while C2 does not block CO adsorption, the spectra indicate that the surface carbon is free of hydrogen. In contrast, ethylidyne blocks CO adsorption sites. In the presence of coadsorbed CO, complete hydrogenation of ethylidyne occurs at 450 K versus 400 K in the absence of CO.

  12. Coadsorption of ethylene and potassium on Pt(111). 1. Formation of a. pi. -bonded state of ethylene

    Energy Technology Data Exchange (ETDEWEB)

    Windham, R.G.; Bartram, M.E.; Koel, B.E.

    1988-05-19

    High resolution electron energy spectroscopy (HREELS), temperature-programmed desorption (TPD), and ultraviolet photoelectron spectroscopy (UPS) have been combined to study the effect of preadsorbed potassium on the adsorption of ethylene on the platinum(111) single-crystal surface. Addition of potassium increases the relative amount of reversible ethylene adsorption at 100 K/. Upon coadsorption with potassium, the authors also observe a new low-temperature ethylene desorption state at 150 K, with E/sub d/ = 5-9 kcal mol/sup -1/, which is about one-half the binding energy of ethylene adsorbed on clean Pt(111). The origin of this new desorption state is the formation of a weakly interacting ethylene species, which is only slightly distorted from the gas-phase hybridization, as determined primarily by vibrational spectroscopy. An explanation is given for these effects in which the increased charge density at the platinum surface due to coadsorbed potassium inhibits the strong sigma-donation of adsorbed ethylene to platinum and greatly reduces the chemisorption bond strength.

  13. A LEEM/micro-LEED investigation of phase transformations in TiOx/Pt(111) ultrathin films.

    Science.gov (United States)

    Agnoli, Stefano; Menteş, T Onur; Niño, Miguel A; Locatelli, Andrea; Granozzi, Gaetano

    2009-05-21

    A combined use of low energy electron microscopy (LEEM) and microprobe LEED (micro-LEED) allows the in-situ observation of dynamical processes at the TiOx/Pt(111) interface. The transformations between different surface-stabilized phases are investigated in the case of room temperature TiOx reactive deposition with subsequent post-annealing. For a coverage of 0.6 MLeq, UHV annealing to 400 degrees C leads to the formation of the zigzag-like z-TiO1.33 layer. At higher temperatures a rotated z-TiO1.33 phase is observed, its lateral distribution being strongly influenced by surface morphology. Concurrently, the z-TiO1.33 layer partially transforms into a kagomé-like TiO1.5 structure. The resulting oxygen enrichment of the interface is interpreted by invoking Ti interdiffusion into the substrate. At a coverage of 0.45 MLeq, UHV annealing at 500 degrees C transforms the z-TiO1.33 layer into a different zigzag-like z'-TiO1.25 layer. Post-annealing in oxygen of the reduced phases or direct reactive deposition at high temperature both produce the rect-TiO2 stoichiometric phase, showing characteristic needle-like domains aligned according to the rect-TiO2 unit cell orientation.

  14. Oxygen reduction on a Pt(111) catalyst in HT-PEM fuel cells by density functional theory

    Science.gov (United States)

    Sun, Hong; Li, Jie; Almheiri, Saif; Xiao, Jianyu

    2017-08-01

    The oxygen reduction reaction plays an important role in the performance of high-temperature proton exchange membrane (HT-PEM) fuel cells. In this study, a molecular dynamics model, which is based on the density functional theory and couples the system's energy, the exchange-correlation energy functional, the charge density distribution function, and the simplified Kohn-Sham equation, was developed to simulate the oxygen reduction reaction on a Pt(111) surface. Additionally, an electrochemical reaction system on the basis of a four-electron reaction mechanism was also developed for this simulation. The reaction path of the oxygen reduction reaction, the product structure of each reaction step and the system's energy were simulated. It is found that the first step reaction of the first hydrogen ion with the oxygen molecule is the controlling step of the overall reaction. Increasing the operating temperature speeds up the first step reaction rate and slightly decreases its reaction energy barrier. Our results provide insight into the working principles of HT-PEM fuel cells.

  15. Oxygen reduction on a Pt(111 catalyst in HT-PEM fuel cells by density functional theory

    Directory of Open Access Journals (Sweden)

    Hong Sun

    2017-08-01

    Full Text Available The oxygen reduction reaction plays an important role in the performance of high-temperature proton exchange membrane (HT-PEM fuel cells. In this study, a molecular dynamics model, which is based on the density functional theory and couples the system’s energy, the exchange-correlation energy functional, the charge density distribution function, and the simplified Kohn–Sham equation, was developed to simulate the oxygen reduction reaction on a Pt(111 surface. Additionally, an electrochemical reaction system on the basis of a four-electron reaction mechanism was also developed for this simulation. The reaction path of the oxygen reduction reaction, the product structure of each reaction step and the system’s energy were simulated. It is found that the first step reaction of the first hydrogen ion with the oxygen molecule is the controlling step of the overall reaction. Increasing the operating temperature speeds up the first step reaction rate and slightly decreases its reaction energy barrier. Our results provide insight into the working principles of HT-PEM fuel cells.

  16. Adlayer of hydroquinone on Pt(111) in solution and in a vacuum studied by STM and LEED.

    Science.gov (United States)

    Inukai, Junji; Wakisaka, Mitsuru; Yamagishi, Masaoki; Itaya, Kingo

    2004-08-31

    Hydroquinone (HQ) adlayers were formed on Pt(111) in HF solution and in a vacuum. By using scanning tunneling microscopy (STM) in solution, it was revealed that HQ formed an ordered structure on Pt(111) with a strong attractive interaction between two adjacent hydroxyl groups in neighboring HQ molecules. After the sample was transferred into a vacuum, low-energy electron diffraction (LEED) measurement was performed, which showed that the (2.56 x 2.56)R16 degrees incommensurate structure of the HQ adlayer was formed in solution. The HQ adlayer on Pt(111) was formed also by vapor deposition, and the identical (2.56 x 2.56)R16 degrees adlayer structure was found by LEED and STM in a vacuum.

  17. The role of the cationic Pt sites in the adsorption properties of water and ethanol on the Pt4/Pt(111) and Pt4/CeO2(111) substrates: A density functional theory investigation

    Science.gov (United States)

    Seminovski, Yohanna; Tereshchuk, Polina; Kiejna, Adam; Da Silva, Juarez L. F.

    2016-09-01

    Finite site platinum particles, Ptn, supported on reduced or unreduced cerium oxide surfaces, i.e., CeO2-x(111) ( 0 CeO2-x has been improved in the last years; however, the identification of the active sites on the Ptn/CeO2-x(111) substrates is still far from complete. In this work, we applied density functional theory based calculations with the addition of the on-site Coulomb interactions (DFT+U) for the investigation of the active sites and the role of the Pt oxidation state on the adsorption properties of water and ethanol (probe molecules) on four selected substrates, namely, Pt(111), Pt4/Pt(111), CeO2(111), and Pt4/CeO2(111). Our results show that water and ethanol preferentially bind in the cationic sites of the base of the tetrahedron Pt4 cluster instead of the anionic lower-coordinated Pt atoms located on the cluster-top or in the surface Ce (cationic) and O (anionic) sites. The presence of the Pt4 cluster contributes to increase the adsorption energy of both molecules on Pt(111) and CeO2(111) surfaces; however, its magnitude increases less for the case of Pt4/CeO2(111). Thus, the cationic Pt sites play a crucial role in the adsorption properties of water and ethanol. Both water and ethanol bind to on-top sites via the O atom and adopt parallel and perpendicular configurations on the Pt(111) and CeO2(111) substrates, respectively, while their orientation is changed once the Pt4 cluster is involved, favoring H binding with the surface sites.

  18. Pyridine on flat Pt(111) and stepped Pt(355)—An in situ HRXPS investigation of adsorption and thermal evolution

    Energy Technology Data Exchange (ETDEWEB)

    Wöckel, Claudia; Eilert, Andrè; Welke, Martin; Schöppke, Matthias; Denecke, Reinhard, E-mail: denecke@uni-leipzig.de [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstraße 2, 04103 Leipzig (Germany); Steinrück, Hans-Peter [Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen (Germany)

    2016-01-07

    We investigated the adsorption and reaction of pyridine on flat Pt(111) and stepped Pt(355) surfaces via high-resolution in situ x-ray photoelectron spectroscopy. The surfaces were exposed to pyridine at temperatures between 112 and 300 K while simultaneously recording XP spectra. Subsequently, the crystals were annealed and the temperature dependencies of the N 1s and C 1s core levels were studied again in a continuous and quantitative way. Various surface species were found, namely, physisorbed, flat-lying and end-on pyridine, α-pyridyl species on the terraces and on the steps and several unidentified high temperature species. We were able to show an influence of the steps of Pt(355) by pre-adsorbing silver next to the step, which selectively suppresses the step adsorption.

  19. Enhanced creation of dispersive monolayer phonons in Xe/Pt(111) by inelastic helium atom scattering at low energies

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Bruch, Ludwig Walter

    2007-01-01

    Conditions likely to lead to enhanced inelastic atomic scattering that creates shear horizontal (SH) and longitudinal acoustic (LA) monolayer phonons are identified, specifically examining the inelastic scattering of He-4 atoms by a monolayer solid of Xe/Pt(111) at incident energies of 2-25 meV. ...

  20. The decoration of vicinal copper polycrystalline surface by Antimony

    CSIR Research Space (South Africa)

    Ndlovu, GF

    2011-07-01

    Full Text Available An Ultra-high Vacuum Variable Temperature Scanning Tunnelling Microscope was used to study the growth mechanism of Antimony on vicinal Cu polycrystalline samples. The STM data after deposition of 0.3 ML Sb at 300°C showed localization of Sb atoms...

  1. Following the molecular motion of near-resonant excited CO on Pt(111): A simulated x-ray photoelectron diffraction study based on molecular dynamics calculations

    Science.gov (United States)

    Greif, Michael; Nagy, Tibor; Soloviov, Maksym; Castiglioni, Luca; Hengsberger, Matthias; Meuwly, Markus; Osterwalder, Jürg

    2015-01-01

    A THz-pump and x-ray-probe experiment is simulated where x-ray photoelectron diffraction (XPD) patterns record the coherent vibrational motion of carbon monoxide molecules adsorbed on a Pt(111) surface. Using molecular dynamics simulations, the excitation of frustrated wagging-type motion of the CO molecules by a few-cycle pulse of 2 THz radiation is calculated. From the atomic coordinates, the time-resolved XPD patterns of the C 1s core level photoelectrons are generated. Due to the direct structural information in these data provided by the forward scattering maximum along the carbon-oxygen direction, the sequence of these patterns represents the equivalent of a molecular movie. PMID:26798798

  2. Following the molecular motion of near-resonant excited CO on Pt(111: A simulated x-ray photoelectron diffraction study based on molecular dynamics calculations

    Directory of Open Access Journals (Sweden)

    Michael Greif

    2015-05-01

    Full Text Available A THz-pump and x-ray-probe experiment is simulated where x-ray photoelectron diffraction (XPD patterns record the coherent vibrational motion of carbon monoxide molecules adsorbed on a Pt(111 surface. Using molecular dynamics simulations, the excitation of frustrated wagging-type motion of the CO molecules by a few-cycle pulse of 2 THz radiation is calculated. From the atomic coordinates, the time-resolved XPD patterns of the C 1s core level photoelectrons are generated. Due to the direct structural information in these data provided by the forward scattering maximum along the carbon-oxygen direction, the sequence of these patterns represents the equivalent of a molecular movie.

  3. Nanoscale patterning, macroscopic reconstruction, and enhanced surface stress by organic adsorption on vicinal surfaces

    Science.gov (United States)

    Pollinger, Florian; Schmitt, Stefan; Sander, Dirk; Tian, Zhen; Kirschner, Jürgen; Vrdoljak, Pavo; Stadler, Christoph; Maier, Florian; Marchetto, Helder; Schmidt, Thomas; Schöll, Achim; Umbach, Eberhard

    2017-01-01

    Self-organization is a promising method within the framework of bottom-up architectures to generate nanostructures in an efficient way. The present work demonstrates that self-organization on the length scale of a few to several tens of nanometers can be achieved by a proper combination of a large (organic) molecule and a vicinal metal surface if the local bonding of the molecule on steps is significantly stronger than that on low-index surfaces. In this case thermal annealing may lead to large mass transport of the subjacent substrate atoms such that nanometer-wide and micrometer-long molecular stripes or other patterns are being formed on high-index planes. The formation of these patterns can be controlled by the initial surface orientation and adsorbate coverage. The patterns arrange self-organized in regular arrays by repulsive mechanical interactions over long distances accompanied by a significant enhancement of surface stress. We demonstrate this effect using the planar organic molecule PTCDA as adsorbate and Ag(10 8 7) and Ag(775) surfaces as substrate. The patterns are directly observed by STM, the formation of vicinal surfaces is monitored by high-resolution electron diffraction, the microscopic surface morphology changes are followed by spectro-microscopy, and the macroscopic changes of surface stress are measured by a cantilever bending method. The in situ combination of these complementary techniques provides compelling evidence for elastic interaction and a significant stress contribution to long-range order and nanopattern formation.

  4. Island Shape-Induced Transition from 2D to 3D Growth for Pt/Pt(111)

    DEFF Research Database (Denmark)

    Jacobsen, Joachim; Jacobsen, Karsten Wedel; Stoltze, Per

    1995-01-01

    We present a kinetic Monte Carlo simulation of the growth of Pt on Pt(111) capable of describing the experimentally observed temperature dependence of the island shapes and the growth mode. We show that the transition from a 2D growth mode at low temperatures to a 3D mode at higher temperatures...... is closely related to the disappearance of kink sites and the appearance of the triangular islands observed in the 3D growth regime....

  5. Formation and sintering of Pt nanopartictes on vicinal rutile TiO2 surfaces

    DEFF Research Database (Denmark)

    Rieboldt, Felix; Helveg, S.; Bechstein, Ralf;

    2014-01-01

    By means of scanning tunnelling microscopy (STM) the nucleation, growth and sintering of platinum nanoparticles (Pt NP's) was studied on vicinal and flat rutile titanium dioxide (TiO2) surfaces. Utilising physical vapour deposition, the nucleation of Pt NP's on TiO2 surfaces at room temperature (RT...

  6. CO adsorption and dissociation on Pt(111) and Ni(111) surfaces

    DEFF Research Database (Denmark)

    Morikawa, Y.; Mortensen, Jens Jørgen; Hammer, Bjørk

    1997-01-01

    CO adsorption and dissociation processes have been studied using first-principles total energy and force calculations. The adsorption energies, atomic structures and vibrational modes of molecularly chemisorbed states are well reproduced in the present calculations. We have examined several...

  7. Revised potentiometric-surface map, Yucca Mountain and vicinity, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Ervin, E.M.; Luckey, R.R.; Burkhardt, D.J.

    1994-12-01

    The revised potentiometric-surface map presented in this report updates earlier maps of the Yucca Mountain area using mainly 1988 average water levels. Because of refinements in the corrections to the water-level measurements, these water levels have increased accuracy and precision over older values. The small-gradient area to the southeast of Yucca Mountain is contoured with a 0.25-meter interval and ranges in water-level altitude from 728.5 to 73 1.0 meters. Other areas with different water levels, to the north and west of Yucca Mountain, are illustrated with shaded patterns. The potentiometric surface can be divided into three regions: (1) A small-gradient area to the southeast of Yucca Mountain, which may be explained by flow through high-transmissivity rocks or low ground-water flux through the area; (2) A moderate-gradient area, on the western side of Yucca Mountain, where the water-level altitude ranges from 775 to 780 meters, and appears to be impeded by the Solitario Canyon Fault and a splay of that fault; and (3) A large-gradient area, to the north-northeast of Yucca Mountain, where water level altitude ranges from 738 to 1,035 meters, possibly as a result of a semi-perched groundwater system. Water levels from wells at Yucca Mountain were examined for yearly trends using linear least-squares regression. Data from five wells exhibited trends which were statistically significant, but some of those may be a result of slow equilibration of the water level from drilling in less permeable rocks. Adjustments for temperature and density changes in the deep wells with long fluid columns were attempted, but some of the adjusted data did not fit the surrounding data and, thus, were not used.

  8. Revised potentiometric-surface map, Yucca Mountain and vicinity, Nevada

    Science.gov (United States)

    Ervin, E.M.; Luckey, R.R.; Burkhardt, D.J.

    1993-01-01

    The revised potentiometric-surface map presented in this report updates earlier maps of the Yucca Mountain area using mainly 1988 average water levels. Because of refinements in the corrections to the water-level measurements, these water levels have increased accuracy and precision over older values. The small-gradient area to the southeast of Yucca Mountain is contoured with a 0.25-meter interval and ranges in water-level altitude from 728.5 to 731.0 meters. Other areas with different water levels, to the north and west of Yucca Mountain, are illustrated with shaded patterns. The potentiometric surface can be divided into three regions: 1) A small-gradient area to the southeast of Yucca Mountain, which may be explained by flow through high-transmissivity rocks or low ground-water flux through the area; 2) A moderate-gradient area, on the western side of Yucca Mountain, where the water-level altitude ranges from 775 to 780 meters, and appears to be impeded by the Solitario Canyon Fault and a splay of that fault; and 3) A large-gradient area, to the north-northeast of Yucca Mountain, where water level altitude ranges from 738 to 1,035 meters, possibly as a result of a semi-perched groundwater system. Water levels from wells at Yucca Mountain were examined for yearly trends (1986-89) using linear least-squares regression. Data from five wells exhibited trends which were statistically significant, but some of those may be a result of slow equilibration of the water level from drilling in less permeable rocks. Adjustments for temperature and density changes in the deep wells with long fluid columns were attempted, but some of the adjusted data did not fit the surrounding data and, thus, were not used.

  9. Buckling of reconstruction elements of the edges of triple steps on vicinal Si(111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhachuk, R. A., E-mail: zhachuk@gmail.com [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Coutinho, J. [University of Aveiro, Campus Santiago, I3N, Department of Physics (Portugal); Rayson, M. J. [University of Surrey, Department of Chemistry (United Kingdom); Briddon, P. R. [Newcastle University, School of Electrical, Electronic and Computer Engineering (United Kingdom)

    2015-04-15

    The structure of steps with a height of three (111) interplanar distances on vicinal Si(111) surfaces has been analyzed through density functional theory calculations. It has been shown that several stable atomic configurations are possible depending on the buckling of the reconstruction elements of edges of the steps on the surface. It has been found that the direction of the buckling of reconstruction elements in the ground state of the surface is determined by the Coulomb interaction with their nearest atomic environment.

  10. Surface Science in an MOCVD Environment: Arsenic on Vicinal Ge(100)

    Energy Technology Data Exchange (ETDEWEB)

    McMahon, W. E.; Olson, J. M.

    1998-11-01

    Scanning tunneling microscope (STM) images of arsine-exposed vicinal Ge(100) surfaces show that most As/Ge steps are reconstructed, and that a variety of different step structures exist. The entire family of reconstructed As/Ge steps can be divided into two types, which we have chosen to call ''single-row'' steps and ''double-row'' steps. In this paper we propose a model for a double-row step created by annealing a vicinal Ge(100) substrate under an arsine flux in a metal-organic chemical vapor deposition (MOCVD) chamber.

  11. 吡啶吸附对Pt(111)电极上Cu欠电位沉积的影响%INFLUENCE OF PYRIDINE ADSORPTION ON Cu UNDERPOTENTIAL DEPOSITION ON Pt(111)

    Institute of Scientific and Technical Information of China (English)

    王红森

    2002-01-01

    应用循环伏安法(CV)研究了溶液pH值和吡啶吸附对Pt(111)上Cu欠电位沉积(upd)的影响.结果发现,溶液pH值对Cu的upd的峰电位和形状有明显的影响.在0.5 mol*L-1 H2SO4+CuSO4溶液中吡啶的加入抑制了Cu的upd,而在0.1 mol*L-1 K2SO4+CuSO4(pH=5.2)溶液中,吡啶的加入却催化了Cu的upd.这一现象应该与吡啶环上氮原子的质子化而导致的吡啶吸附取向的变化有关.

  12. CHARACTERISTICS OF FATIGUE SURFACE MICROCRACK GROWTH IN VICINAL INCLUSION FOR POWDER METALLURGY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    WangXishu; LiYongqiang

    2003-01-01

    Inclusion flaw is one of the worst flaws of powder metallurgy. The inclusion flaw plays an important role in the failure of high temperature turbine materials in aircraft components and automotive parts, especially fatigue failure. In this paper, an experimental investigation of fatigue microcrack propagation in the vicinal inclusion were carried out by the servo-hydraulic fatigue test system with scanning electron microscope (SEM). It has been found from the SEM images that the fatigue surface microcrack occurs in the matrix and inclusion. According to the SEM images, the characteristics of fatigue crack initiation and growth in vicinal inclusion for powder metallurgy alloys are analyzed in detail. The effect of the geometrical shape and material type of surface inclusions on the cracking is also discussed with the finite element method (FEM).

  13. The interaction of water and hydrogen with nickel surfaces

    NARCIS (Netherlands)

    Shan, Junjun

    2009-01-01

    As nickel and platinum are in the same group of the periodic table, the Ni(111) and Pt(111) surfaces may be expected to show similar interaction with water and hydrogen. However in this thesis, we show these interactions for Ni(111) are quite different from those of Pt(111). Moreover, our results

  14. The interaction of water and hydrogen with nickel surfaces

    NARCIS (Netherlands)

    Shan, Junjun

    2009-01-01

    As nickel and platinum are in the same group of the periodic table, the Ni(111) and Pt(111) surfaces may be expected to show similar interaction with water and hydrogen. However in this thesis, we show these interactions for Ni(111) are quite different from those of Pt(111). Moreover, our results sh

  15. Linear in-plane magnetoconductance and spin susceptibility of a 2D electron gas on a vicinal silicon surface

    OpenAIRE

    Proskuryakov, Y. Y.; Kvon, Z. D.; Savchenko, A. K.

    2003-01-01

    In this work we have studied the parallel magnetoresistance of a 2DEG near a vicinal silicon surface. An unusual, linear magnetoconductance is observed in the fields up to $B = 15$ T, which we explain by the effect of spin olarization on impurity scattering. This linear magnetoresistance shows strong anomalies near the boundaries of the minigap in the electron spectrum of the vicinal system.

  16. Comparison of the microstructure and magnetic properties of strontium hexaferrite films deposited on Al2O3(0001), Si(100)/Pt(111) and Si(100) substrates by pulsed laser technique

    Science.gov (United States)

    Masoudpanah, S. M.; Seyyed Ebrahimi, S. A.; Ong, C. K.

    2014-01-01

    Strontium hexaferrite SrFe12O19 (SrM) films have been deposited on Al2O3(0001), Si(100)/Pt(111) and Si(100) substrates. The (001) oriented SrFe12O19 films deposited on the Al2O3(0001) and Si(100)/Pt(111) substrates have been confirmed by X-ray diffraction patterns. Higher coercivity in perpendicular direction rather than in-plane direction of the SrM/Al2O3(0001) and SrM/Pt(111) films showed that the films had perpendicular magnetic anisotropy. The (001) orientation and similar microstructure and magnetic properties of the SrM/Al2O3(0001) and SrM/Pt(111) films show the Al2O3(0001) substrate can be replaced by the Si(100)/Pt(111) substrate.

  17. The oxygen reduction reaction mechanism on Pt(111) from density functional theory calculations

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Skulason, Egill; Siahrostami, Samira;

    2010-01-01

    We study the oxygen reduction reaction (ORR) mechanism on a Pt(1 1 1) surface using density functional theory calculations We find that at low overpotentials the surface is covered with a half dissociated water layer We estimate the barrier for proton transfer to this surface and the barrier for ...

  18. Optical characterization of gold chains and steps on the vicinal Si(557) surface: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Hogan, Conor [Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, via Fosso del Cavaliere 100, 00133 Rome (Italy); Department of Physics and European Theoretical Spectroscopy Facility (ETSF), University of Rome ' ' Tor Vergata' ' , Via della Ricerca Scientifica 1, 00133 Rome (Italy); McAlinden, Niall; McGilp, John F. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland)

    2012-06-15

    We present a joint experimental-theoretical study of the reflectance anisotropy of clean and gold-covered Si(557), a vicinal surface of Si(111) upon which gold forms quasi-one-dimensional (1D) chains parallel to the steps. By means of first-principles calculations, we analyse the close relationship between the various surface structural motifs and the optical properties. Good agreement is found between experimental and computed spectra of single-step models of both clean and Au-adsorbed surfaces. Spectral fingerprints of monoatomic gold chains and silicon step edges are identified. The role of spin-orbit coupling (SOC) on the surface optical properties is examined, and found to have little effect. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Ag on a Ni vicinal surface: Coupling Stranski-Krastanov and "magic" heteroepitaxial growth

    Science.gov (United States)

    Bellec, Amandine; Garreau, Yves; Creuze, Jérôme; Vlad, Alina; Picca, Frederic; Sauvage-Simkin, Michèle; Coati, Alessandro

    2017-08-01

    Using vicinal surfaces as a template for heteroepitaxial growth offers a unique possibility to control the orientation and the crystallinity of the grown layer. The study presented here focuses on the growth of Ag on a carefully chosen Ni(11 9 9) substrate. Ag adopts a Stranski-Krastanov growth mode with a slightly constrained wetting layer limited to two monolayers on which well crystallized islands grow. The specific orientation of the Ni substrate leads to Ag(7 9 9) orientation for the Ag thin film and it prevents the formation of twin and stacking fault.

  20. Step-Flow Growth on Vicinal GaAs Surfaces by Migration-Enhanced Epitaxy

    Science.gov (United States)

    Yamaguchi, Hiroshi; Horikoshi, Yoshiji

    1989-08-01

    The mechanism of step-flow growth on vicinal GaAs substrates during migration-enhanced epitaxy are studied using the reflection high-energy electron diffraction technique. Results show that the low As pressure during migration-enhanced epitaxy growth accelerates step-flow growth. In addition, it is also shown that monolayer terraces composed of surface Ga atoms are formed from step edges during the Ga deposition process. A GaAs/AlAs tilted superlattice is established using this growth technique. X-ray diffraction measurement and transmission electron microscopy observations show that the fabricated structure has periodic composition modulation along the axis tilted from the substrate azimuth.

  1. Group V adsorbate structures on vicinal Ge(001) surfaces determined from the optical spectrum

    Science.gov (United States)

    Banerjee, S.; Patterson, C. H.; McGilp, J. F.

    2017-06-01

    Vicinal Ge(001) is the standard substrate for the fabrication of high-performance solar cells by metal-organic vapour phase epitaxy, where growth of the III-V material on single domain Ge surfaces, with a single dimer orientation, minimizes the formation of anti-phase domain defects. Reflectance anisotropy spectroscopy has proved to be a powerful and sensitive optical probe of such anisotropic surface structures, but moving beyond fingerprinting to atomic structure determination from the optical spectra has been held back by the high computational cost. It is shown that an empirical, local-orbital-based hybrid density functional theory approach produces very good agreement between the theory and the experiment for (2 × 1)-As and (2 × 1)-Sb structures grown on vicinal Ge(001). These results, when taken together with previous work on Si interfaces, show that this computationally efficient approach is likely to prove to be an important general technique for determining the structure of anisotropic semiconductor surfaces and interfaces by comparing the experimental and calculated optical spectrum.

  2. Nanostructured sapphire vicinal surfaces as templates for the growth of self-organized oxide nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Thune, E., E-mail: elsa.thune@unilim.fr [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France); Boulle, A. [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France); Babonneau, D.; Pailloux, F. [Laboratoire de Physique des Materiaux (PHYMAT), UMR CNRS 6630, Universite de Poitiers, Boulevard Marie et Pierre Curie - Teleport 2, BP 30179, F-86962 Futuroscope - Chasseneuil Cedex (France); Hamd, W.; Guinebretiere, R. [Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface (SPCTS), UMR CNRS 6638, ENSCI, 47-73 Avenue Albert Thomas, F-87065 Limoges Cedex (France)

    2009-11-15

    Vicinal substrates of sapphire with miscut angle of 10 deg. from the (0 0 1) planes towards the [1 1 0] direction have been annealed in air in the range from 1000 to 1500 deg. C. The behaviour of these surfaces has been characterized as a function of the temperature and the thermal treatment time by Atomic Force Microscopy observations. A thermal treatment at 1250 deg. C allows to stabilize a surface made of periodically spaced nanosized step-bunches. Such stepped surfaces were used as template to grow self-patterned epitaxial oxide nanoparticles by thermal annealing of yttria-stabilized zirconia thin films produced by sol-gel dip-coating. Grazing Incidence Small Angle X-ray Scattering and High-Resolution Transmission Electron Microscopy were used to study the morphology of the nanoparticles and their epitaxial relationships with the substrate.

  3. Surface and subsurface microgravity data in the vicinity of Sanford Underground Research Facility, Lead, South Dakota

    Science.gov (United States)

    Kennedy, Jeffrey R.; Koth, Karl R.; Carruth, Rob

    2015-01-01

    Absolute gravity data were collected at 32 stations in the vicinity of the Sanford Underground Research Facility from 2007 through 2014 for the purpose of monitoring groundwater storage change during dewatering of the former Homestake gold mine in the Black Hills of South Dakota, the largest and deepest underground mine in North America. Eight underground stations are at depths from 300 feet below land surface to 4,850 feet below land surface. Surface stations were located using Global Positioning System observations, and subsurface stations were located on the basis of maps constructed from survey measurements made while the mine was in operation. Gravity varies widely at many stations; however, no consistent temporal trends are present across all stations during the 7-year period of data collection.

  4. Vibrational states on vicinal surfaces of Al, Ag, Cu and Pd

    Science.gov (United States)

    Sklyadneva, I. Yu.; Rusina, G. G.; Chulkov, E. V.

    1998-10-01

    We present the calculation of vibrational modes and lattice relaxation for the (110), (211), (311), (511), (331) and (221) surfaces of Al, Ag, Cu and Pd. The surface phonon frequencies and polarizations are obtained for relaxed and unrelaxed surfaces using embedded atom model potentials. On all surfaces studied step-localized vibrational modes and surface states localized on terrace atoms are found. It is shown that as the terrace width increases so does the number of surface phonons. It is found that interlayer relaxation leads to a shift in the frequencies of the surface states and to a change in the number and localization. In particular, it may cause the appearance or disappearance of step modes. It is shown that the character of relaxation on vicinal surfaces is determined by the number of atoms on a terrace. A comparison of the results with the available experimental data for the Al(221), Cu(211), and Cu(511) surfaces indicates that there is a good agreement with the experimental data.

  5. Magnetic circular dichroism in near-threshold photoemission from an ultrathin Co/Pt(111) film at variable work function

    Energy Technology Data Exchange (ETDEWEB)

    Hild, Kerstin; Schoenhense, Gerd; Elmers, Hans-Joachim [Institute of Physics, Johannes Gutenberg University, Mainz (Germany); Nakagawa, Takeshi; Yokoyama, Toshihiko [Institute for Molecular Science, Graduate University for Advanced Studies, Okazaki (Japan); Tarafder, Kartick; Oppeneer, Peter [Department of Physics and Materials Science, Uppsala University (Sweden)

    2011-07-01

    In order to disentangle the magnetic dichroism effect of the two excitation steps in a two-photon photoemission process (2PPE) we compare measurements at different work function for the same Co/Pt(111) sample. The work function {phi} is adjusted by Cs adsorption and the photon energy h{nu} by a tunable Ti:Sa femtosecond laser. For one-photon photoemission (1PPE) at h{nu} = 3 eV we measure an asymmetry of 6.2%. A 2PPE process at the same photon energy yields a value of 8.3%. This suggests the first step to be the major asymmetry creating process. A considerably larger asymmetry (17 %) is observed for 2PPE at h{nu} = 1.5 eV. The results are explained by interband transitions deviating from the direction of observation {gamma}-L. These MCD experiments suggest a paradigm shift from the classical model of photoemission that exclusively considers k parallel conserving emission processes.

  6. Tuning coercive force by adjusting electric potential in solution processed Co/Pt(111) and the mechanism involved

    Science.gov (United States)

    Chang, Cheng-Hsun-Tony; Kuo, Wei-Hsu; Chang, Yu-Chieh; Tsay, Jyh-Shen; Yau, Shueh-Lin

    2017-03-01

    A combination of a solution process and the control of the electric potential for magnetism represents a new approach to operating spintronic devices with a highly controlled efficiency and lower power consumption with reduced production cost. As a paradigmatic example, we investigated Co/Pt(111) in the Bloch-wall regime. The depression in coercive force was detected by applying a negative electric potential in an electrolytic solution. The reversible control of coercive force by varying the electric potential within few hundred millivolts is demonstrated. By changing the electric potential in ferromagnetic layers with smaller thicknesses, the efficiency for controlling the tunable coercive force becomes higher. Assuming that the pinning domains are independent of the applied electric potential, an electric potential tuning-magnetic anisotropy energy model was derived and provided insights into our knowledge of the relation between the electric potential tuning coercive force and the thickness of the ferromagnetic layer. Based on the fact that the coercive force can be tuned by changing the electric potential using a solution process, we developed a novel concept of electric-potential-tuned magnetic recording, resulting in a stable recording media with a high degree of writing ability.

  7. Comparison of the microstructure and magnetic properties of strontium hexaferrite films deposited on Al{sub 2}O{sub 3}(0001), Si(100)/Pt(111) and Si(100) substrates by pulsed laser technique

    Energy Technology Data Exchange (ETDEWEB)

    Masoudpanah, S.M. [Center of Excellence for Magnetic Materials, School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); School of Materials Science and Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Seyyed Ebrahimi, S.A., E-mail: saseyyed@ut.ac.ir [Center of Excellence for Magnetic Materials, School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Ong, C.K. [Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore)

    2014-01-15

    Strontium hexaferrite SrFe{sub 12}O{sub 19} (SrM) films have been deposited on Al{sub 2}O{sub 3}(0001), Si(100)/Pt(111) and Si(100) substrates. The (001) oriented SrFe{sub 12}O{sub 19} films deposited on the Al{sub 2}O{sub 3}(0001) and Si(100)/Pt(111) substrates have been confirmed by X-ray diffraction patterns. Higher coercivity in perpendicular direction rather than in-plane direction of the SrM/Al{sub 2}O{sub 3}(0001) and SrM/Pt(111) films showed that the films had perpendicular magnetic anisotropy. The (001) orientation and similar microstructure and magnetic properties of the SrM/Al{sub 2}O{sub 3}(0001) and SrM/Pt(111) films show the Al{sub 2}O{sub 3}(0001) substrate can be replaced by the Si(100)/Pt(111) substrate. - Highlights: • The SrFe{sub 12}O{sub 19} film deposited on different Si(100), Si(100)/Pt(111) and Al{sub 2}O{sub 3}(0001) substrates by PLD. • The SrM/Pt(111) and SrM/Al{sub 2}O{sub 3}(0001) films showed the c-axis perpendicular orientation. • The SrM/Al{sub 2}O{sub 3}(0001) films exhibited more perpendicular magnetic anisotropy than SrM/Pt(111) films. • The Al{sub 2}O{sub 3}(0001) substrate can be replaced by the Si(100)/Pt(111) substrate.

  8. Step density waves on growing vicinal crystal surfaces - Theory and experiment

    Science.gov (United States)

    Ranguelov, Bogdan; Müller, Pierre; Metois, Jean-Jacques; Stoyanov, Stoyan

    2017-01-01

    The Burton, Cabrera and Frank (BCF) theory plays a key conceptual role in understanding and modeling the crystal growth of vicinal surfaces. In BCF theory the adatom concentration on a vicinal surface obeys to a diffusion equation, generally solved within quasi-static approximation where the adatom concentration at a given distance x from a step has a steady state value n (x) . Recently, we show that going beyond this approximation (Ranguelov and Stoyanov, 2007) [6], for fast surface diffusion and slow attachment/detachment kinetics of adatoms at the steps, a train of fast-moving steps is unstable against the formation of steps density waves. More precisely, the step density waves are generated if the step velocity exceeds a critical value related to the strength of the step-step repulsion. This theoretical treatment corresponds to the case when the time to reach a steady state concentration of adatoms on a given terrace is comparable to the time for a non-negligible change of the step configuration leading to a terrace adatom concentration n (x , t) that depends not only on the terrace width, but also on its "past width". This formation of step density waves originates from the high velocity of step motion and has nothing to do with usual kinetic instabilities of step bunching induced by Ehrlich-Schwoebel effect, surface electromigration and/or the impact of impurities on the step rate. The so-predicted formation of step density waves is illustrated by numerical integration of the equations for step motion. In order to complete our previous theoretical treatment of the non-stationary BCF problem, we perform an in-situ reflection electron microscopy experiment at specific temperature interval and direction of the heating current, in which, for the first time, the step density waves instability is evidenced on Si(111) surface during highest possible Si adatoms deposition rates.

  9. Understanding the Oxygen Reduction Reaction on a Y/Pt(111) Single Crystal

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese; Johansson, Tobias Peter; Malacrida, Paolo;

    2014-01-01

    using electrochemical measurements, low energy electron diffraction, ion scattering spectroscopy, angle resolved X-ray photoelectron spectroscopy, temperature programmed desorption of CO, and synchrotron based X-ray absorption spectroscopy and surface sensitive X-ray diffraction. These measurements were...... that it showed exceptional activity for the ORR [1]. Later studies also revealed that Pt5Y, prepared in the same manner also showed similar high activity, as shown in Figure (a) below. However, our X-ray photoelectron spectroscopy measurements revealed that the structure formed under reaction conditions...... in Figure A. Since there is no Y in the first few atomic layers, we attribute the high activity to the compressive strain exerted onto the surface by the alloy bulk. [1] J. Greeley, I.E.L. Stephens, A.S. Bondarenko, T.P. Johansson, H.A. Hansen, T.F. Jaramillo, J. Rossmeisl, I. Chorkendorff, J.K. Nørskov...

  10. Narrowing of terrace-width distributions during growth on vicinal surfaces

    Science.gov (United States)

    Hamouda, A. BH.; Pimpinelli, A.; Einstein, T. L.

    2009-10-01

    We present analytic and numerical results for the steady-state, non-equilibrium terrace-width distribution (TWD) of steps during growth on vicinal surfaces. Kinetic Monte Carlo shows that the TWD narrows progressively with increasing flux until the model breaks down. The narrowing corresponds to kinetic repulsion between moving steps, due to the intrinsic asymmetry of the adatom diffusion current on a growing surface. With a 1-dimensional (1D) model, from a Burton-Cabrera-Frank approach, we make contact with previous work, in which the attachment asymmetry can also be due to electromigration or to asymmetry in attachment rates; we deduce an expression for the narrowing via a Fokker-Planck analysis. We illustrate how Ehrlich-Schwoebel barriers (although inducing an instability in 2D) also lead to such asymmetry and narrowing.

  11. PTCDA induced faceting of a vicinal Ag(111) surface: an in-situ LEEM study

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Thomas; Marchetto, Helder; Sala, Alessandro; Freund, Hajo [Fritz-Haber-Institut, Abt. CP, 14195 Berlin (Germany); Pollinger, Florian; Schmitt, Stefan; Maier, Florian C.; Reinert, Friedrich T. [Universitaet Wuerzburg, EP II, 97074 Wuerzburg (Germany); Umbach, Eberhard [Universitaet Wuerzburg, EP II, 97074 Wuerzburg (Germany); Forschungszentrum Karlsruhe, 76021 Karlsruhe (Germany)

    2009-07-01

    Adsorption of organic molecules on vicinal metal surfaces is known to promote faceting and self-organized ordering on mesoscopic scales. In the temperature range between 400 K and 620 K the adsorption of PTCDA on a Ag(10 8 7) surface has been studied in-situ and in real-time by LEEM (low energy electron microscopy) and LEED, using the SMART microscope. The deposition of one organic layer leads to grating-like structures. The direct observation reveals a two-step process: first, facets with an angle of ca. 25 inclination are formed with (111) orientated areas in between, whereas only the facets are covered by PTCDA. In a second step the bare (111) areas are covered by PTCDA, forming a complete monolayer. The temperature dependence of the structure sizes and the influence of inhomogeneity in the initial substrate step density are discussed.

  12. PtxGd alloy formation on Pt(111): Preparation and structural characterization

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese; Pedersen, Anders Filsøe; Vej-Hansen, Ulrik Grønbjerg

    2016-01-01

    thick alloy layer. Subsequently the surfaces were characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), ion scattering spectroscopy (ISS) and temperature programmed desorption (TPD) of CO. A Pt terminated alloy was observed upon annealing the sample to 600...... (ring operator)C in temperature. The crystal structure of the alloy was investigated using ex-situ X-ray diffraction experiments, which revealed an in-plane compression and a complicated stacking sequence. The crystallites in the crystal are very small, and a high degree of twinning by merohedry...

  13. Influence of step faceting on the enantiospecific decomposition of aspartic acid on chiral Cu surfaces vicinal to Cu{111}.

    Science.gov (United States)

    Reinicker, A D; Therrien, A J; Lawton, T J; Ali, R; Sykes, E C H; Gellman, A J

    2016-09-13

    On surfaces vicinal to Cu{111}, l-aspartic acid (l-Asp) adsorption causes steps to facet enantiospecifically into {310}(R) and {320}(S) steps. l-Asp has its highest heat of adsortion on surfaces that naturally expose the {310}(R) or {320}(S) steps but decomposes preferentially on the {310}(R) steps.

  14. Simulation of Nanowires on Metal Vicinal Surfaces: Effect of Growth Parameters and Energetic Barriers

    Science.gov (United States)

    Hamouda, Ajmi B. H.; Blel, Sonia; Einstein, T. L.

    2012-02-01

    Growing one-dimensional metal structures is an important task in the investigation of the electronic and magnetic properties of new devices. We used kinetic Monte-Carlo (kMC) method to simulate the formation of nanowires of several metallic and non-metallic adatoms on Cu and Pt vicinal surfaces. We found that mono-atomic chains form on step-edges due to energetic barriers (the so-called Ehrlich-shwoebel and exchange barriers) on step-edge. Creation of perfect wires is found to depend on growth parameters and binding energies. We measure the filling ratio of nanowires for different chemical species in a wide range of temperature and flux. Perfect wires were obtained at lower deposition rate for all tested adatoms, however we notice different temperature ranges. Our results were compared with experimental ones [Gambardella et al., Surf. Sci.449, 93-103 (2000), PRB 61, 2254-2262, (2000)]. We review the role of impurities in nanostructuring of surfaces [Hamouda et al., Phys. Rev. B 83, 035423, (2011)] and discuss the effect of their energetic barriers on the obtained quality of nanowires. Our work provides experimentalists with optimum growth parameters for the creation of a uniform distribution of wires on surfaces.

  15. Infrared spectroscopy of one-dimensional metallic nanostructures on silicon vicinal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hoang, Chung Vu

    2010-06-23

    Vicinal silicon(111) surfaces are used as templates for the growth of lead nanowires as well as gold and indium atom chains. The morphology of the Au atom chains was studied by use of Scanning Tunneling Microscopy (STM) and Reflection High Energy Electron Diffraction (RHEED). The In chains were investigated by infrared spectroscopy with the electrical field component of the IR light polarized either parallel or perpendicular to the wires. It is shown that at room temperature, In atom-chains display a plasmonic absorption feature along the chain but not in the perpendicular direction. Furthermore, upon cooling down to liquid nitrogen temperature, a metal to insulator transition is observed. A structural distortion is also confirmed by RHEED. As for the result of Pb nanowires, by means of infrared spectroscopy, it is now possible to control the average length of parallel nanowire arrays by monitoring four experimental parameters that influence on the nucleation density; namely: Pb coverage, evaporation rate, substrate temperature and the surface itself. The system shows an enhancement of the absorption at the antenna frequency in the low temperature regime. This scenario is assigned to the reduction of electron-phonon scattering due to low temperature. (orig.)

  16. Localized surface plasmon mediated energy transfer in the vicinity of core-shell nanoparticle

    Science.gov (United States)

    Shishodia, Manmohan Singh; Juneja, Soniya

    2016-05-01

    Multipole spectral expansion based theory of energy transfer interactions between a donor and an acceptor molecule in the vicinity of a core-shell (nanoshell or core@shell) based plasmonic nanostructure is developed. In view of the diverse applications and rich plasmonic features such as tuning capability of surface plasmon (SP) frequencies, greater sensitivity to the change of dielectric environment, controllable redirection of electromagnetic radiation, closed form expressions for Energy Transfer Rate Enhancement Factor (ETREF) near core-shell particle are reported. The dependence of ETREF on different parameters is established through fitting equations, perceived to be of key importance for developing appropriate designs. The theoretical approach developed in the present work is capable of treating higher order multipoles, which, in turn, are also shown to play a crucial role in the present context. Moreover, closed form expressions derived in the present work can directly be used as formula, e.g., for designing SP based biosensors and estimating energy exchange between proteins and excitonic interactions in quantum dots.

  17. Localized surface plasmon mediated energy transfer in the vicinity of core-shell nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Shishodia, Manmohan Singh, E-mail: manmohan@gbu.ac.in; Juneja, Soniya [Department of Applied Physics, School of Vocational Studies and Applied Sciences, Gautam Buddha University, Greater Noida 201308 (India)

    2016-05-28

    Multipole spectral expansion based theory of energy transfer interactions between a donor and an acceptor molecule in the vicinity of a core-shell (nanoshell or core@shell) based plasmonic nanostructure is developed. In view of the diverse applications and rich plasmonic features such as tuning capability of surface plasmon (SP) frequencies, greater sensitivity to the change of dielectric environment, controllable redirection of electromagnetic radiation, closed form expressions for Energy Transfer Rate Enhancement Factor (ETREF) near core-shell particle are reported. The dependence of ETREF on different parameters is established through fitting equations, perceived to be of key importance for developing appropriate designs. The theoretical approach developed in the present work is capable of treating higher order multipoles, which, in turn, are also shown to play a crucial role in the present context. Moreover, closed form expressions derived in the present work can directly be used as formula, e.g., for designing SP based biosensors and estimating energy exchange between proteins and excitonic interactions in quantum dots.

  18. Dispersion of inorganic contaminants in surface water in the vicinity of Potchefstroom

    Science.gov (United States)

    Manyatshe, A.; Fosso-Kankeu, E.; van der Berg, D.; Lemmer, N.; Waanders, F.; Tutu, H.

    2017-08-01

    Potchefstroom and the neighbouring cities rely mostly on the Mooi River and Vaal River for their water needs. These rivers flow through the gold mining areas and farms, and are therefore likely to be contaminated with substantial amounts of inorganic pollutants. Water was collected along the rivers network, streams, canals and dams in Potchefstroom and the vicinity. The samples were characterized for geochemical parameters, metals and anions concentrations. The results showed high concentrations of potentially toxic elements such as As (4.53 mg/L - 5.74 mg/L), Cd (0.25 mg/L - 0.7 mg/L), Pb (1.14 mg/L - 5.13 mg/L) and U (0.04 mg/L - 0.11 mg/L) which were predominantly found around the mining areas. Elevated concentrations of anions such SO42- and CN- were detected around mining areas while NO3- was dominant near farms. The relatively high levels of anions and metals in the surface water made it unfit for domestic or agricultural use. The study showed that contaminants in mining and agricultural facilities were potentially mobilised, thus impacting the nearby water systems.

  19. Double layer effects in electrocatalysis: the oxygen reduction reaction and ethanol oxidation reaction on Au(111), Pt(111) and Ir(111) in alkaline media containing Na and Li cations.

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Pietro P.; Strmcnik, Dusan; Jirkovsky, Jakub S.; Connell, Justin G.; Stamenkovic, Vojislav; Markovic, Nenad

    2016-03-15

    Oxygen reduction and ethanol oxidation reactions were studied on Au(111), Pt(111) and Ir(111) in alkaline solutions containing sodium and/or lithium cations. By keeping the same (111) surface orientation and exploring oxophilicity trends and non-covalent interactions between OHad and alkali metal cations (AMCn+), we were able to gain deep insights into the multiple roles that OHad plays in these important electrocatalytic reactions. Cyclic voltammetry experiments revealed that OHad formation initiates at distinct electrode potentials, governed by the oxophilicity of the specific metal surface, with further OHad adlayer stabilization by non-covalent alkali-cation interactions and affecting the formation of a “true oxide” layer at higher electrode potentials. Although OHad is a simple spectator for the ORR, it promotes the ethanol oxidation reaction (EOR) at lower potentials and act as spectator at high OHad coverages. By changing the alkali metal cation at the interface (Li+) on more oxophilic surfaces, it was possible to promote the EOR even more, relative to Na+, without changing the product distribution for the reaction. This cation effect suggests that OHad---Li+(H2O)x clusters can stabilize the ethoxide adlayer, thus improving the EOR activity. Our results indicate the importance of the entire electrochemical interface in determining the electrocatalytic activity during reaction.

  20. CO Chemisorption at Metal Surfaces and Overlayers

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Morikawa, Y.; Nørskov, Jens Kehlet

    1996-01-01

    A database of ab initio calculations of the chemisorption energy of CO over Ni(111), Cu(111), Ru(0001), Pd(111), Ag(111), Pt(111), Au(111), Cu3Pt(111), and some metallic overlayer structures is presented. The trends can be reproduced with a simple model describing the interaction between the meta...... d states and the CO 2 pi* and 5 sigma states, renormalized by the metal sp continuum. Our model rationalizes the results by Rodriguez and Goodman [Science 257, 897 (1992)] showing a strong correlation between the CO chemisorption energy and the surface core level shift.......A database of ab initio calculations of the chemisorption energy of CO over Ni(111), Cu(111), Ru(0001), Pd(111), Ag(111), Pt(111), Au(111), Cu3Pt(111), and some metallic overlayer structures is presented. The trends can be reproduced with a simple model describing the interaction between the metal...

  1. Non-covalent interactions in water electrolysis: influence on the activity of Pt(111) and iridium oxide catalysts in acidic media.

    Science.gov (United States)

    Ganassin, Alberto; Colic, Viktor; Tymoczko, Jakub; Bandarenka, Aliaksandr S; Schuhmann, Wolfgang

    2015-04-07

    Electrolyte components, which are typically not considered to be directly involved in catalytic processes at solid-liquid electrified interfaces, often demonstrate a significant or even drastic influence on the activity, stability and selectivity of electrocatalysts. While there has been certain progress in the understanding of these electrolyte effects, lack of experimental data for various important systems frequently complicates the rational design of new active materials. Modern proton-exchange membrane (PEM) electrolyzers utilize Pt- and Ir-based electrocatalysts, which are among the very few materials that are both active and stable under the extreme conditions of water splitting. We use model Pt(111) and Ir-oxide films grown on Ir(111) electrodes and explore the effect of alkali metal cations and sulfate-anions on the hydrogen evolution and the oxygen evolution reactions in acidic media. We demonstrate that sulfate anions decrease the activity of Ir-oxide towards the oxygen evolution reaction while Rb(+) drastically promotes hydrogen evolution reaction at the Pt(111) electrodes as compared to the reference HClO4 electrolytes. Issues related to the activity benchmarking for these catalysts are discussed.

  2. In situ STM imaging of bis-3-sodiumsulfopropyl-disulfide molecules adsorbed on copper film electrodeposited on Pt(111) single crystal electrode.

    Science.gov (United States)

    Tu, HsinLing; Yen, PoYu; Chen, Sihzih; Yau, ShuehLin; Dow, Wei-Ping; Lee, Yuh-Lang

    2011-06-07

    The adsorption of bis-3-sodiumsulfopropyldi-sulfide (SPS) on metal electrodes in chloride-containing media has been intensively studied to unveil its accelerating effect on Cu electrodeposition. Molecular resolution scanning tunneling microscopy (STM) imaging technique was used in this study to explore the adsorption and decomposition of SPS molecules concurring with the electrodeposition of copper on an ordered Pt(111) electrode in 0.1 M HClO(4) + 1 mM Cu(ClO(4))(2) + 1 mM KCl. Depending on the potential of Pt(111), SPS molecules could react, adsorb, and decompose at chloride-capped Cu films. A submonolayer of Cu adatoms classified as the underpotential deposition (UPD) layer at 0.4 V (vs Ag/AgCl) was completely displaced by SPS molecules, possibly occurring via RSSR (SPS) + Cl-Cu-Pt → RS(-)-Pt(+) + RS(-) (MPS) + Cu(2+) + Cl(-), where MPS is 3-mercaptopropanesulfonate. By contrast, at 0.2 V, where a full monolayer of Cu was presumed to be deposited, SPS molecules were adsorbed in local (4 × 4) structures at the lower ends of step ledges. Bulk Cu deposition driven by a small overpotential (η deposit at the very beginning (deposit, the chloride adlayer was still adsorbed to afford SPS admolecules arranged in a unique 1D striped phase. SPS molecules could decompose into MPS upon further Cu deposition, as a (2 × 2)-MPS structure was observed with prolonged in situ STM imaging. It was possible to visualize either SPS admolecules in the upper plane or chloride adlayer sitting underneath upon switching the imaging conditions. Overall, this study established a MPS molecular film adsorbed to the chloride adlayer sitting atop the Cu deposit.

  3. General aspects of surface alloy formation

    Energy Technology Data Exchange (ETDEWEB)

    Bergbreiter, Andreas; Engstfeld, Albert K.; Roetter, Ralf T.; Hoster, Harry E.; Behm, R. Juergen [Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm (Germany); Berko, Andras

    2010-07-01

    Surface confined alloys are excellent model systems for studies of structure-property relationships of bimetallic surfaces. They are formed by deposition of a guest metal B onto a substrate A, followed by annealing to a temperature, where place exchange between adatoms and atoms from the underlying surface layer becomes possible and diffusion into the bulk is sufficiently slow. We exemplarily confirmed by scanning tunneling microscopy and Auger electron spectroscopy for PtRu/Ru(0001), PdRu/Ru(0001), AuPt/Pt(111), AgPt/Pt(111), and AgPd/Pd(111), surface alloys are obtained for systems where metal B has a negative surface segregation energy within metal A. By exchanging A and B, however, AB surface alloys are most likely overgrown by metal B, which we demonstrate for RuPt/Pt(111) in comparison to PtRu/Ru(0001).

  4. Magnetic transport apparatus for the production of ultracold atomic gases in the vicinity of a dielectric surface

    CERN Document Server

    Haendel, S; Wiles, T P; Hopkins, S A; Cornish, S L

    2011-01-01

    We present an apparatus designed for studies of atom-surface interactions using quantum degenerate gases of $^{85}$Rb and $^{87}$Rb in the vicinity of a room temperature dielectric surface. The surface to be investigated is a super-polished face of a glass Dove prism mounted in a glass cell under ultra-high vacuum (UHV). To maintain excellent optical access to the region surrounding the surface magnetic transport is used to deliver ultracold atoms from a separate vacuum chamber housing the magneto-optical trap (MOT). We present a detailed description of the vacuum apparatus highlighting the novel design features; a low profile MOT chamber and the inclusion of an obstacle in the transport path. We report the characterization and optimization of the magnetic transport around the obstacle, achieving transport efficiencies of 70% with negligible heating. Finally we demonstrate the loading of a hybrid optical-magnetic trap with $^{87}$Rb and the creation of Bose-Einstein condensates via forced evaporative cooling ...

  5. Bridging the pressure gap: In situ atomic-level investigations of model platinum catalyst surfaces under reaction conditions by scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    McIntyre, B.J.

    1994-05-01

    Results of this thesis show that STM measurements can provide information about the surfaces and their adsorbates. Stability of Pt(110) under high pressures of H2, O2, and CO was studied (Chap. 4). In situ UHV and high vacuum experiments were carried out for sulfur on Pt(111) (Chap.5). STM studies of CO/S/Pt(111) in high CO pressures showed that the Pt substrate undergoes a stacking-fault-domain reconstruction involving periodic transitions from fcc to hcp stacking of top-layer atoms (Chap.6). In Chap.7, the stability of propylene on Pt(111) and the decomposition products were studied in situ with the HPSTM. Finally, in Chap.8, results are presented which show how the Pt tip of the HPSTM was used to locally rehydrogenate and oxidize carbonaceous clusters deposited on the Pt(111) surface; the Pt tip acted as a catalyst after activation by short voltage pulses.

  6. Scanning tunneling microscopy of monoatomic gold chains on vicinal Si(335) surface: experimental and theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Krawiec, M.; Kwapinski, T.; Jalochowski, M. [Institute of Physics and Nanotechnology Center, M. Curie-Sklodowska University, pl. M. Curie-Sklodowskiej 1, 20-031 Lublin (Poland)

    2005-02-01

    We study electronic and topographic properties of the Si(335) surface, containing Au wires parallel to the steps. We use scanning tunneling microscopy (STM) supplemented by reflection of high energy electron diffraction (RHEED) technique. The STM data show the space and voltage dependent oscillations of the distance between STM tip and the surface which can be explained within one band tight binding Hubbard model. We calculate the STM current using nonequilibrium Keldysh Green function formalism. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Control of F\\"orster energy transfer in vicinity of metallic surfaces and hyperbolic metamaterials

    CERN Document Server

    Tumkur, Thejaswi U; Bonner, Carl E; Poddubny, Alexander N; Narimanov, Evgenii E; Noginov, Mikhail A

    2015-01-01

    Optical cavities, plasmonic structures, photonic band crystals, interfaces, as well as, generally speaking, any photonic media with homogeneous or spatially inhomogeneous dielectric permittivity (including metamaterials) have local densities of photonic states, which are different from that in vacuum. These modified density of states environments are known to control both the rate and angular distribution of spontaneous emission. In the present study, we ask the question whether the proximity to metallic and metamaterial surfaces can affect other physical phenomena of fundamental and practical importance. We show that the same substrates and the same nonlocal dielectric environments that boost spontaneous emission, also inhibit F\\"orster energy transfer between donor and acceptor molecules doped into a thin polymeric film. This finding correlates with the fact that in dielectric media, the rate of spontaneous emission is proportional to the index of refraction n, while the rate of the donor-acceptor energy tr...

  8. One-dimensional model of interacting-step fluctuations on vicinal surfaces: Analytical formulas and kinetic Monte-Carlo simulations

    Science.gov (United States)

    Patrone, Paul; Einstein, T. L.; Margetis, Dionisios

    2011-03-01

    We study a 1+1D, stochastic, Burton-Cabrera-Frank (BCF) model of interacting steps fluctuating on a vicinal crystal. The step energy accounts for entropic and nearest-neighbor elastic-dipole interactions. Our goal is to formulate and validate a self-consistent mean-field (MF) formalism to approximately solve the system of coupled, nonlinear stochastic differential equations (SDEs) governing fluctuations in surface motion. We derive formulas for the time-dependent terrace width distribution (TWD) and its steady-state limit. By comparison with kinetic Monte-Carlo simulations, we show that our MF formalism improves upon models in which step interactions are linearized. We also indicate how fitting parameters of our steady state MF TWD may be used to determine the mass transport regime and step interaction energy of certain experimental systems. PP and TLE supported by NSF MRSEC under Grant DMR 05-20471 at U. of Maryland; DM supported by NSF under Grant DMS 08-47587.

  9. One-dimensional model of interacting-step fluctuations on vicinal surfaces: Analytical formulas and kinetic Monte Carlo simulations

    Science.gov (United States)

    Patrone, Paul N.; Einstein, T. L.; Margetis, Dionisios

    2010-12-01

    We study analytically and numerically a one-dimensional model of interacting line defects (steps) fluctuating on a vicinal crystal. Our goal is to formulate and validate analytical techniques for approximately solving systems of coupled nonlinear stochastic differential equations (SDEs) governing fluctuations in surface motion. In our analytical approach, the starting point is the Burton-Cabrera-Frank (BCF) model by which step motion is driven by diffusion of adsorbed atoms on terraces and atom attachment-detachment at steps. The step energy accounts for entropic and nearest-neighbor elastic-dipole interactions. By including Gaussian white noise to the equations of motion for terrace widths, we formulate large systems of SDEs under different choices of diffusion coefficients for the noise. We simplify this description via (i) perturbation theory and linearization of the step interactions and, alternatively, (ii) a mean-field (MF) approximation whereby widths of adjacent terraces are replaced by a self-consistent field but nonlinearities in step interactions are retained. We derive simplified formulas for the time-dependent terrace-width distribution (TWD) and its steady-state limit. Our MF analytical predictions for the TWD compare favorably with kinetic Monte Carlo simulations under the addition of a suitably conservative white noise in the BCF equations.

  10. Clumped isotopes in near-surface atmospheric CO2 over land, coast and ocean in Taiwan and its vicinity

    Science.gov (United States)

    Hussain Laskar, Amzad; Liang, Mao-Chang

    2016-09-01

    Molecules containing two rare isotopes (e.g., 13C18O16O in CO2), called clumped isotopes, in atmospheric CO2 are powerful tools to provide an alternative way to independently constrain the sources of CO2 in the atmosphere because of their unique physical and chemical properties. We presented clumped isotope data (Δ47) in near-surface atmospheric CO2 from urban, suburban, ocean, coast, high mountain ( ˜ 3.2 km a.s.l.) and forest in Taiwan and its vicinity. The primary goal of the study was to use the unique Δ47 signature in atmospheric CO2 to show the extents of its deviations from thermodynamic equilibrium due to different processes such as photosynthesis, respiration and local anthropogenic emissions, which the commonly used tracers such as δ13C and δ18O cannot provide. We also explored the potential of Δ47 to identify/quantify the contribution of CO2 from various sources. Atmospheric CO2 over ocean was found to be in thermodynamic equilibrium with the surrounding surface sea water. Respired CO2 was also in close thermodynamic equilibrium at ambient air temperature. In contrast, photosynthetic activity result in significant deviation in Δ47 values from that expected thermodynamically. The disequilibrium could be a consequence of kinetic effects associated with the diffusion of CO2 in and out of the leaf stomata. We observed that δ18O and Δ47 do not vary similarly when photosynthesis was involved unlike simple water-CO2 exchange. Additionally we obtained Δ47 values of car exhaust CO2 that were significantly lower than the atmospheric CO2 but higher than that expected at the combustion temperature. In urban and suburban regions, the Δ47 values were found to be lower than the thermodynamic equilibrium values at the ambient temperature, suggesting contributions from local combustion emission.

  11. Measurement and scaling of air-surface mercury exchange from substrates in the vicinity of two Nevada gold mines.

    Science.gov (United States)

    Miller, Matthieu B; Gustin, Mae S; Eckley, Chris S

    2011-09-01

    The state of Nevada has extensive mineral resources, and is the largest producer of gold in the USA as well as fourth in world gold production. Mercury (Hg) is often present in the hydrothermal systems that produce gold deposits, and can be found in elevated concentrations in gold ore. As a result, mining of gold ore in Nevada has been shown to release Hg to the atmosphere from point and non-point sources. This project focused on measurement of air-soil Hg exchange associated with undisturbed soils and bedrock outcrops in the vicinity of two large gold mines. Field and laboratory data collected were used to identify the important variables controlling Hg flux from these surfaces, and to estimate a net flux from the areas adjacent to the active mines as well as that occurring from the mined area pre-disturbance. Mean daily flux by substrate type ranged from 9 ng m(-2) day(-1) to 140 ng m(-2) day(-1). Periods of net deposition of elemental Hg were observed when air masses originating from a mine site moved over sampling locations. Based on these observations and measured soil Hg concentrations we suggest that emissions from point and non-point sources at the mines are a source of Hg to the surrounding substrates with the amount deposited not being of an environmental concern but of interest mainly with respect to the cycling of atmospheric elemental Hg. Observations indicate that while some component of the deposited Hg is sequestered in the soil, this Hg is gradually released back to the atmosphere over time. Estimated pre-disturbance emissions from the current mine footprints based on field data were 0.1 and 1.7 kg yr(-1), compared to that estimated for the current non-point mining sources of 19 and 109 kg yr(-1), respectively.

  12. Pits on the Surfaces of Epitaxial c-Axis YBa2Cu3O7-δ Thin Films Grown on Vicinal SrTiO3 Substrates

    Institute of Scientific and Technical Information of China (English)

    胡文斐; 李林; 赵新杰; 刘维; 陈莺飞; 王天生; 邱祥冈

    2001-01-01

    The reoccurrence of pits has been found on the surfaces of c-axis YBa2CusO7-δ (YBCO) films grown epitaxially on 10℃ vicinal SrTiOs substrates by pulsed laser deposition. They are always associated with films with a stepterrace structure, while polycrystalline films have no pits. Pit formation is attributed to the large interfacial stress induced by vicinal substrate and oxygen deficiency of the YBCO film during the tetragonal-to-orthorhombic (TO) phase transition, which cannot be released by forming twins, and leads to rupturing of the film surface. By reducing the oxidation partial pressure for the T-O phase transition to 80 Pa, no pits were formed, and the YBCO film is superconducting at 60K.

  13. Modification of platinum surfaces by spontaneous deposition: Methanol oxidation electrocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    MacDonald, J.P.; Gualtieri, B.; Runga, N.; Teliz, E.; Zinola, C.F. [Fundamental Electrochemistry Laboratory, School of Sciences, Universidad de la Republica, Igua Street No. 4225, CP 11400, Montevideo (Uruguay)

    2008-12-15

    The presence of a second metal on platinum surfaces affects the performance of methanol oxidation. However, most of the electrocatalytic reactions are studied by using electrochemically deposited platinum alloys, but in the case of spontaneous deposition the situation is not so clear since the surface distribution, stability and morphology are usually not well documented. The formation of surface decorated samples on mono- and poly-crystalline platinum is followed by electrochemical and spectroscopic techniques and analysis of their performance towards methanol adsorption and oxidation compared with that on pure platinum. Pt/Sn and Pt/Ru are of special interest because of their well-known performance in methanol fuel cells. Methanol oxidation on Pt(111)/Ru, Pt(111)/Sn and Pt(111) shows that ruthenium is the only one able to promote the reaction since the simultaneous dissolution of tin occurs and competes with the process of interest. The in situ infrared spectroscopy is used to compare methanol oxidation on Pt(111)/Ru and Pt(111) in acid media using p-polarized light. The formation of bridge bound carbon monoxide is inhibited in the presence of ruthenium ad-species, whereas on Pt(111) the three adsorption configurations are observed. Linear sweep polarization curves and Tafel slopes (calculated from steady state potentiostatic plots) for methanol oxidation are compared on polycrystalline surfaces modified by tin or ruthenium at different coverages. There is almost no change in the Tafel slopes due to the presence of the foreign metal except for Pt/Ru, where a 0.09 V decade{sup -1} slope was calculated below 0.55 V due to hydroxyl adsorbates on ruthenium islands. The anodic stripping of methanol residues on the three surfaces indicates a lower amount of carbon monoxide-type adsorbates on Pt/Ru, and the simultaneous tin dissolution process leading to residues oxidation on Pt/Sn electrodes. (author)

  14. Plasma parameters in the vicinity of the quartz window of a low pressure surface wave discharge produced in O2

    DEFF Research Database (Denmark)

    Nakao, S.; Stamate, Eugen; Sugai, H.

    2007-01-01

    Plasma parameters in the vicinity of the dielectric window of a low density, microwave discharge produced in 0, at 915 N/FHz are investigated by a spherical probe and optical emission spectroscopy while the microwave field distribution is measured by a spectrum analyzer. The electron energy...

  15. Structure dependence of Pt surface activated ammonia oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Santen, R A van; Offermans, W K [Schuit Institute of Catalysis, Laboratory of Inorganic Chemistry and Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Ricart, J M; Novell-Leruth, G [Department of Chemical Physics and Inorganic Chemistry, University Rovira I Virgili, C/ Marcel.lI Domingo s/n, 43007 Tarragona (Spain); Perez-RamIrez, J [Institute of Chemical Research of Catalonia (ICIQ) and Catalan, Institution for Research and Advanced Studies (ICREA), Avinguda Paisos Catalans 16, 43007, Tarragona (Spain)], E-mail: r.a.v.santen@tue.nl

    2008-06-01

    Computational advances that enable the prediction of the structures and the energies of surface reaction intermediates are providing essential information to the formulation of theories of surface chemical reactivity. In this contribution this is illustrated for the activation of ammonia by coadsorbed oxygen and hydroxyl on the Pt(111), Pt(100), and Pt(211) surfaces.

  16. Dependence on surface pH and surface substrate concentration of activity of microsome-bound arylsulfatase C and the surface charge density in the vicinity of the enzyme.

    Science.gov (United States)

    Masamoto, K

    1984-03-01

    Dependence on the salt concentration of the activity of microsome-bound arylsulfatase C [EC 3.1.6.1] from rat liver was examined. The activity increased with increasing salt concentration in the reaction medium in the whole pH range tested. This effect can be explained by the dependence of the reaction rate on the surface pH and the surface concentration of the ionic substrate. The dependence on salt concentration of the activity of the microsome-bound arylsulfatase C and the pH-dependences of Vmax and Km of the enzyme were used for the estimation of pH at the microsomal surface. The two values of the surface pH (surface potential) and the salt concentration were applied to the Gouy-Chapman equation. The value of -0.39 +/- 0.08 X 10(-3) elementary charge/A2 was obtained as the surface charge density in the vicinity of the microsome-bound arylsulfatase C. This was smaller than the over-all value for microsomes (-1.08 +/- 0.04 X 10(-3) elementary charge/A2; Masamoto, K. (1982) J. Biochem. 92, 365-371). This suggests that the anion concentration in the vicinity of the enzyme on microsomes is lower than that in the bulk aqueous phase and is higher than the average value at the microsomal surface when the salt concentration is low.

  17. Thermal Stability and Growth Behavior of Erbium Silicide Nanowires Self-Assembled on a Vicinal Si(001) Surface

    Institute of Scientific and Technical Information of China (English)

    DING Tao; SONG Jun-Qiang; LI Juan; CAI Qun

    2011-01-01

    Erbium silicide nanowires are self-assembled on vicinal Si(Ool) substrates after electron beam evaporation and post annealing at 63(fC In-situ scanning tunneling microscopy investigations manifest that the nanowires will successively shrink and transform into a nanoisland with annealing prolonged. Meanwhile, a structural transition from hexagonal AIB2 phase to tetragonal ThSi'2 phase is revealed with high-resolution transmission electron microscopy. It is also found that the nanowires gradually expand to embed into the substrates during the growth process, which has much influence on the shape instability of nanowires. Additionally, a multiple deposition-annealing treatment is given as a novel growth method to strengthen the controlled fabrication of nanowires.%@@ Erbium silicide nanowires are self-assembled on vicinal Si(001) substrates after electron beam evaporation and post annealing at 630℃ In-situ scanning tunneling microscopy investigations manifest that the nanowires will successively shrink and transform into a nanoisland with annealing prolonged.Meanwhile, a structural transition from hexagonal AlB phase to tetragonal ThSi phase is revealed with high-resolution transmission electron microscopy.It is also found that the nanowires gradually expand to embed into the substrates during the growth process, which has much influence on the shape instability of nanowires.Additionally, a multiple deposition- annealing treatment is given as a novel growth method to strengthen the controlled fabrication of nanowires.

  18. Measurement of OH (X2Σ) in immediate vicinity of dielectric surface under pulsed dielectric barrier discharge at atmospheric pressure using two geometries of laser-induced fluorescence

    Science.gov (United States)

    Teramoto, Yoshiyuki; Kim, Hyun-Ha; Ogata, Atsushi; Negishi, Nobuaki

    2014-04-01

    The behavior of the ground state OH radical was studied in humid air using pulsed surface dielectric barrier discharge. The validity of OH measurement in immediate vicinity of the dielectric surface was discussed using two geometries of laser-induced fluorescence (LIF) measurement, and surface distribution and temporal profiles of OH were examined. A comparison of parallel- and perpendicular-LIF techniques for OH measurement revealed that OH was mostly produced in a region several tens of μm above the dielectric surface. The surface distribution profile of OH agreed well with that of N2(C), and in both cases, the total production generated by a discharge pulse was proportional to the discharge energy. The OH local density in surface streamer channels was estimated to be 1.3 × 1015 cm-3 according to the decay rate of OH, which was similar to that in corona discharge. Additionally, the local density of OH remained constant regardless of discharge energies. These results indicate that the yield of OH increased with the discharge energy owing to expansion of the surface streamer region, increase in streamer radius or thickness or the number of branches, whereas the local density of OH in the streamer channel remained constant regardless of discharge energy.

  19. Ice thickness, internal layers, and surface and subglacial topography in the vicinity of Chinese Antarctic Taishan station in Princess Elizabeth Land, East Antarctica

    Institute of Scientific and Technical Information of China (English)

    Tang Xue-Yuan; Guo Jing-Xue; Sun Bo; Wang Tian-Tian; Cui Xiang-Bin

    2016-01-01

    We present the results of two ground-based radio-echo-sounding (RES) and GPS surveys performed in the vicinity of new Chinese Taishan station, Princess Elizabeth Land, East Antarctica, obtained in two austral summers during CHINARE 21 (2004/2005) and CHINARE 29 (2012/2013). The radar surveys measured ice thickness and internal layers using 60- and 150-MHz radar systems, and GPS measurements showed smooth surface slopes around the station with altitudes of 2607–2636 m above sea level (a.s.l.). Radar profiles indicate an average ice thickness of 1900 m, with a maximum of 1949 m and a minimum of 1856 m, within a square area measuring approximately 2 km × 2 km in the vicinity of the station. The ice thickness beneath the station site is 1870 m. The subglacial landscape beneath the station is quiet sharp and ranges from 662 to 770 m a.s.l., revealing part of a mountainous topography. The ice volume in the grid is estimated to be 7.6 km3. Along a 60-MHz radar profi le with a length of 17.6 km at the region covering the station site, some disturbed internal layers are identifi ed and traced; the geometry of internal layers within the englacial stratigraphy may imply a complex depositional process in the area.

  20. PCDD/F contamination on surface soil in the vicinity of a hazardous waste incinerator: is it possible a different trend?

    Science.gov (United States)

    Korucu, Mahmut Kemal

    2017-01-01

    This study is the first to investigate the contamination of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) on surface soils in the vicinity of the first hazardous waste incinerator of Turkey. In the study, 24 soil samples were taken from a 1625-m-radius circle whose center is the stack of the incinerator. This process was repeated 1 year later. Since the acquired average PCDD/F concentrations of the two sampling campaigns (0.05 and 0.02 ng WHO-toxic equivalent (TEQ)/kg) were meaningfully low compared to the related literatures, a new sampling campaign was carried out to control this inconsistency, but this time in a foreign laboratory (0.56 ng WHO-TEQ/kg). In the same period, eight gas samples were taken from the stack under different operational conditions of the facility. According to the evaluations of the findings, the geographical-meteorological data of the study area and the specific operational conditions of the facility corroborate the concentrations of the first and the second soil samplings rather than the third one. The major underlying reason for the inconsistency of the soil concentrations may be the fact that the data analysis procedures used by the laboratories are different. The author suggests a hypothesis which argues that the soils in the vicinity of a hazardous waste incinerator may have significantly lower concentration levels than in related literatures.

  1. CO2 Electroreduction on Well-Defined Bimetallic Surfaces

    DEFF Research Database (Denmark)

    Varela Gasque, Ana Sofia; Schlaup, Christian Georg; Jovanov, Zarko P.

    2013-01-01

    We have studied the electrochemical reduction of CO2 on Cu overlayers on Pt(111) and Pt(211) surfaces. These systems were chosen to investigate the effect of strain on the catalytic activity of Cu surfaces and to obtain information about the role of steps in this process. The selectivity toward h...

  2. Harmonically-Interacting Step Approach to the Relaxation Process of Vicinal Surface. II. The Relaxation Process Induced by the Step-Edge Diffusion

    Science.gov (United States)

    Yamamoto, Takao

    1999-09-01

    The relaxation processes of vicinal surface induced by the diffusion of adatoms along the step edge are analyzed by the Ginzburg-Landau-Langevin equation based on the harmonically-interacting step (HIS) picture.By the equation, the time evolutions of the step deformation width and the step fluctuation width are analyzed.For the relaxation process induced by the infinite-length step-edge diffusion, these quantities show the “universal” scaling behaviors.However, both of the universality and the scaling behavior disappear for the finite-length diffusion.To verify the results quantitatively, we performed the Monte-Carlo calculations for the solid-on-solid step terrace-step-kink model.The results from the Monte-Carlo calculations agree with the analytic results from the HIS picture very well.

  3. Influence of Group-III-metal and Ag adsorption on the Ge growth on Si(111) and its vicinal surface

    Energy Technology Data Exchange (ETDEWEB)

    Speckmann, Moritz

    2011-12-15

    In the framework of this thesis the surfactant-mediated heteroepitaxial growth of Ge on different Si surfaces has been investigated by means of low-energy electron microscopy, low-energy electron diffraction, spot-profile analysing low-energy electron diffraction, X-ray standing waves, grazing-incidence X-ray diffraction, x-ray photoemission electron microscopy, X-ray photoemission spectroscopy, scanning tunneling microscopy, scanning electron microscopy, transmission electron microscopy, and density functional theory calculations. As surfactants gallium, indium, and silver were used. The adsorption of Ga or In on the intrinsically faceted Si(112) surface leads to a smoothing of the surface and the formation of (N x 1) reconstructions, where a mixture of building blocks of different sizes is always present. For both adsorbates the overall periodicity on the surface is strongly dependent on the deposition temperature and the coverage. For the experimental conditions chosen here, the periodicities are in the range of 5.2{<=}N{<=}6.5 and 3.4{<=}N{<=}3.7 for Ga and In, respectively. The (N x 1) unit cells of Ga/Si(112) and In/Si(112) are found to consist of adsorbate atoms on terrace and step-edge sites, forming two atomic chains along the [110] direction. In the Ga-induced structures two Ga-vacancies per unit cell (one in the terrace and one in the step-edge site) are found and a continuous vacancy line on the surface is formed. In the In/Si(112) structure only one vacancy per unit cell in the step-edge site exists and, thus, a continuous adsorbate chain on the terrace sites is present. The adsorption of Ga or In on Si(112) strongly influences the subsequent Ge growth. Ge deposition on the Ga-terminated Si(112) surface leads to the formation of Ge nanowires, which are elongated along the Ga chains and reach lengths of up to 2000 nm for a growth temperature of 600 C. On In-covered Si(112), both small dash-like Ge islands and triangularly shaped islands are found, where

  4. Survival Of Large-l Rydberg States Of Highly Charged Ions In The Vicinity Of Metal Surfaces

    Science.gov (United States)

    Mirkovic, M. A.; Nedeljkovic, N. N.; Božanic, D. K.

    2010-07-01

    The probabilities for ionization of large-l multiply charged Rydberg ions approaching metallic surfaces at thermal velocities in the normal incidence geometry were calculated. The ionization process was treated within the framework of decay model using the appropriate etalon equation method for solving the complex energy eigenvalue problem. It is shown that, in contrast to corresponding low-l states, the large-l Rydberg states exhibit non-zero survival probabilities.

  5. Phase diagrams for surface alloys

    DEFF Research Database (Denmark)

    Christensen, Asbjørn; Ruban, Andrei; Stoltze, Per

    1997-01-01

    is based on density-functional calculations using the coherent-potential approximation and on effective-medium theory. We give self-consistent density-functional results for the segregation energy and surface mixing energy for all combinations of the transition and noble metals. Finally we discuss...... in detail the cases Ag/Cu(100), Pt/Cu(111), Ag/Pt(111), Co/Cu(111), Fe/Cu(111), and Pd/Cu(110) in connection with available experimental results....

  6. Surface core-level shifts for Pt single-crystal surfaces

    Science.gov (United States)

    Baetzold, R. C.; Apai, G.; Shustorovich, E.; Jaeger, R.

    1982-10-01

    The (111) and (110) surfaces of Pt, clean, oxidized, and covered by CO, have been investigated for surface 4f core-level binding-energy shifts. For the (111) face the surface Pt4f72 core level was shifted by 0.40+/-0.05 eV to lower binding energy relative to the bulk peak. On the (110)-(1×2) reconstructed surface similarly shifted peaks at 0.21+/-0.05 and 0.55+/-0.05 eV were observed. Chemisorbed carbon monoxide shifts the Pt(111) surface-related core level by 1.3 eV to higher binding energy. Formation of subsurface oxygen did not produce changes in the Pt(111)4f72 core-level binding energies. The results obtained are explained and their possible implications are discussed.

  7. Photogrammetrical deformation measurements at structures located in the vicinity of surface mine slopes, and forecasting of expected deformation values

    Energy Technology Data Exchange (ETDEWEB)

    Wedekind, O. (Ingenieurschule fuer Geodaesie und Kartographie, Dresden (German Democratic Republic))

    1990-02-01

    Discusses measurement of equipment stability in brown coal surface mines. A long conveyor belt system installed parallel to the spoil bank slope and a spoil belt conveyor bridge were surveyed for movements of position. Photogrammetrical measuring instrument was the UMK 10/1318 unit of Carl Zeiss Jena; for data analysis the Stecometer G and the TEBIT program systems were used. Measurement results are provided. Forecasting possible future movement of belt conveyor supports was further carried out using a mathematical collocation model and the empirical Moeser auto-covariance function of the bell shaped cosinus type. Results of mathematical forecasting are compared to repeated measurements carried out after 6 months, proving suitability of the mathematical method. 3 refs.

  8. [Impact of polymetallic mine (Zn, Pb, Cu) residues on surface water, sediments and soils at the vicinity (Marrakech, Morocco)].

    Science.gov (United States)

    El Adnani, M; Rodriguez-Maroto, J M; Sbai, M L; Loukili Idrissi, L; Nejmeddine, A

    2007-09-01

    Metal sulphide tailings present a potential risk for the environment because of their natural oxidability which leads to the production of acid mine drainage. The prospected site close to Marrakech includes zinc, lead and copper sulphide deposits. This site is located in an agricultural area near the Tensift River which is used for irrigation. In addition to the tailing leachates, underground mine waters are also discharged into the river. This represents a potential risk for the environment and human health. The aim of this study was to assess the tailings impact on surface water, sediments and soil qualities. Chemical analysis of surface water and sediments collected downstream of the mine revealed that, water and sediments present high concentrations of major ions and heavy metals. The analysis also revealed spatial as well as temporal changes in the chemical properties of the studied water and sediments. These changes are attributed to the rising phenomena. The soil near the mine presents high content of sulphate. Its Zn, Pb, Cu and Fe contents are respectively 38, 15, 11 and 1.6 times higher than non contaminated soils located far away from the site. The soil irrigated with underground mine waters shows concentrations of SO4(2-), Cu, Zn, Fe, Cd and Pb which are respectively 4, 10, 28, 2, 9 and 12 times higher than soils which are not irrigated with this mine water. This study also showed that there has been a change in the physicochemical characteristics of water and sediments in the sampling points downstream of the mine before its closure and after its activity renewal.

  9. Occupied and unoccupied electronic states on vicinal Si(111) surfaces decorated with monoatomic gold chains; Besetzte und unbesetzte elektronische Zustaende vizinaler Si(111)-Oberflaechen mit atomaren Goldketten

    Energy Technology Data Exchange (ETDEWEB)

    Biedermann, Kerstin

    2012-07-12

    In this work, the occupied and unoccupied electronic states of vicinal Si(111)-Au surfaces were investigated. The research focused on amending the experimental electronic band structure by two-photon photoemission and laser-based photoemission and bringing it in line with theoretical band structure calculations. This work dealt with the Si(553)-Au, the Si(111)-(5x2)-Au and the Si(557)-Au surface. Angle-resolved UV-photoelectron spectroscopy gave access to the occupied part of the band structure and thus to the energetic position, the dispersion and the symmetry of the occupied states. Bichromatic two-photon photoemission, however, revealed information about the energetics and, in addition, about the dynamics of unoccupied states on a femtosecond timescale. Notably, the selective polarization of the laser pulses allowed for distinguishing and classifying many of the states with respect to their symmetry. All three surfaces exhibited both surface and bulk states in the occupied part of the band structure. They could be clearly identified and separated from surface contributions by means of tight-binding calculations of the bulk band structure of silicon and by comparison to each other. An added similarity of these surfaces are the one-dimensional Rashba-split gold states, which definitely show dispersion along the chains but not perpendicular to them. All surfaces exhibit states which can easily be assigned to the gold chains. Additional features, however, cannot be attributed clearly to the characteristics of the complex surface reconstruction in all cases. An assignment to surface states was only successfully accomplished for Si(553)-Au. The primary emphasis of this photoemission study was on the Si(553)-Au surface, which shows the smallest defect density in comparison to the other surfaces and hence exhibits the sharpest peaks in the experimental spectra. In accordance with ab-initio band structure calculations this surface also displays, in addition to one

  10. Confronting vicinity of the surface water and sea shore in a shallow glaciogenic aquifer in southern Finland

    Directory of Open Access Journals (Sweden)

    S. Luoma

    2014-07-01

    Full Text Available The chemical characterization of groundwater in shallow, unconfined, low-lying coastal aquifer in Santala, southern Finland was identified by utilising the integrations of multivariate statistical approaches; principal component analysis (PCA and hierarchical cluster analysis (HCA, with the stable isotope δ2H and δ18O, hydrogeochemistry and field monitoring data. HCA classified groundwater samples into 6 distinct groups that reveal the factors controlling temporal and spatial variations of groundwater geochemistry such as geology, anthropogenic sources from human activities, climate and surface water. High temporal variation of groundwater chemistry corresponds directly to precipitation. With increase in precipitation, KMnO4 consumption, EC, alkalinity and Ca concentrations also increase in most wells, while Fe, Al, Mn and SO4 are occasionally increased during spring after the snowmelt in specific geologic condition. The continued increase of NO3 and metals concentrations in groundwater indicates the potential contamination risk to aquifer. Stable isotopes of δ18O and δ2H indicate groundwater recharges directly from the meteoric water with insignificant contribution from lake water, and no seawater intrusion into the aquifer. Groundwater geochemistry suggests local seawater intrusion being temporary able to take place in the sulphate reduction zone along the fresh and seawater mixed zone in the low-lying coastal area but contribution of seawater was very low. The influence of lake water can be observed from the increases of KMnO4 consumption in wells nearby the lake.

  11. Chromium speciation and fractionation in ground and surface waters in the vicinity of chromite ore processing residue disposal sites.

    Science.gov (United States)

    Farmer, John G; Thomas, Rhodri P; Graham, Margaret C; Geelhoed, Jeanine S; Lumsdon, David G; Paterson, Edward

    2002-04-01

    Chromium concentrations of up to 91 mg l(-1) were found by ICP-OES for ground water from nine boreholes at four landfill sites in an area of S.E. Glasgow/S. Lanarkshire where high-lime chromite ore processing residue (COPR) from a local chemical works had been deposited from 1830 to 1968. Surface water concentrations of up to 6.7 mg l(-1) in a local tributary stream fell to 0.11 mg l(-1) in the River Clyde. Two independent techniques of complexation/colorimetry and speciated isotope dilution mass spectrometry (SIDMS) showed that Cr was predominantly (>90%) in hexavalent form (CrVI) as CrO4(2-), as anticipated at the high pH (7.5-12.5) of the sites. Some differences between the implied and directly determined concentrations of dissolved CrIII, however, appeared related to the total organic carbon (TOC) content. This was most significant for the ground water from one borehole that had the highest TOC concentration of 300 mg l(-1) and at which ultrafiltration produced significant decreases in Cr concentration with decreasing size fractions, e.g. complex. This showed for the main Cr-containing fraction, 100 kDa-0.45 microm, that the Cr was associated with a dark brown band characteristic of organic (humic) matter. Comparison of gel electrophoresis and FTIR results for ultrafilter retentates of ground water from this borehole with those for a borehole at another site where CrVI predominated suggested the influence of carboxylate groups, both in reducing CrVI and in forming soluble CrIII-humic complexes. The implications of this for remediation strategies (especially those based on the addition of organic matter) designed to reduce highly mobile and carcinogenic Cr(VI)O4(2-) to the much less harmful CrIII as insoluble Cr(OH)3 are discussed.

  12. Geologic evaluation of six nonwelded tuff sites in the vicinity of Yucca Mountain, Nevada for a surface-based test facility for the Yucca Mountain Project

    Energy Technology Data Exchange (ETDEWEB)

    Broxton, D.E.; Chipera, S.J.; Byers, F.M. Jr. [Los Alamos National Lab., NM (United States); Rautman, C.A. [Sandia National Labs., Albuquerque, NM (United States)

    1993-10-01

    Outcrops of nonwelded tuff at six locations in the vicinity of Yucca Mountain, Nevada, were examined to determine their suitability for hosting a surface-based test facility for the Yucca Mountain Project. Investigators will use this facility to test equipment and procedures for the Exploratory Studies Facility and to conduct site characterization field experiments. The outcrops investigated contain rocks that include or are similar to the tuffaceous beds of Calico Hills, an important geologic and hydrologic barrier between the potential repository and the water table. The tuffaceous beds of Calico Hills at the site of the potential repository consist of both vitric and zeolitic tuffs, thus three of the outcrops examined are vitric tuffs and three are zeolitic tuffs. New data were collected to determine the lithology, chemistry, mineralogy, and modal petrography of the outcrops. Some preliminary data on hydrologic properties are also presented. Evaluation of suitability of the six sites is based on a comparison of their geologic characteristics to those found in the tuffaceous beds of Calico Hills within the exploration block.

  13. Nanowires and nanoneedles nucleation on vicinal substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xu, E-mail: zhangxubetter@gmail.com [Henan Key Laboratory of Laser and Opto-electric Information Technology, School of Information Engineering, Zhengzhou University, Zhengzhou 450052 (China); Xie, Dan; Huang, Genling [Zhengzhou Railway Vocational and Technical College, Zhengzhou 450052 (China); Sun, Xiao-Hong [Henan Key Laboratory of Laser and Opto-electric Information Technology, School of Information Engineering, Zhengzhou University, Zhengzhou 450052 (China)

    2015-01-01

    An analytic stress-driven nucleation model of nanowires (NWs) and nanoneedles (NNs) growing on a mismatched vicinal substrate is proposed. It is demonstrated that the formation enthalpy of NWs and NNs is a function of three independent variables, the base radius, aspect ratio and miscut angle of the vicinal surface. Theoretical analysis shows that the minimum nucleation barrier of an island decreases with increment of substrate misorientation, which means the nucleation of islands on a vicinal substrate is more favorable than that on a flat substrate.

  14. Structure of the lithosphere-asthenosphere system in the vicinity of the Tristan da Cunha hot spot as seen by surface waves

    Science.gov (United States)

    Bonadio, Raffaele; Geissler, Wolfram H.; Ravenna, Matteo; Lebedev, Sergei; Celli, Nicolas L.; Jokat, Wilfried; Jegen, Marion; Sens-Schönfelder, Christoph; Baba, Kiyoshi

    2017-04-01

    Tristan da Cunha is a volcanic island located above a hotspot in the South Atlantic. The deep mantle plume origin of the hotspot volcanism at the island is supported by anomalous geochemical data (Rohde et al., 2013 [1]) and global seismological evidences (French and Romanovicz, 2015 [2]). However, until recently, due to lack of local geophysical data in the South Atlantic and especially around Tristan da Cunha, the existence of a plume has not yet been confirmed. Therefore, an Ocean Bottom Seismometer experiment was carried out in 2012 and 2013 in the vicinity of the archipelago, with the aim of obtaining geophysical data that may help to get some more detailed insights into the structure of the upper mantle, possibly confirming the existence of a plume. In this work we study the shear wave velocity structure of the lithosphere-asthenosphere system beneath the Island. Rayleigh surface wave phase velocity dispersion curves have been obtained using a recent powerful implementation of the inter-station cross-correlation method (Meier et al., 2004 [3]; Soomro et al., 2016 [4]). The measured dispersion curves are used to invert for the 1D shear wave velocity structure beneath the study area and to obtain phase velocity tomographic maps. Our results show a pronounced low shear wave velocity anomaly between 70 and 120 km depth beneath the area; the lid shows high velocity, suggesting a cold, depleted and dehydrated shallow lithosphere, while the deeper lithosphere shows a velocity structure similar to young or rejuvenated Pacific oceanic lithosphere (Laske et al., 2011 [5]; Goes et al., 2012 [6]). Below the base of the lithosphere, shear wave velocities appear to be low, suggesting thermal effects and partial melting (as confirmed by petrological data). Decreasing velocities within the lithosphere south-westward reflect probably a thermal imprint of an underlying mantle plume. References [1] J.K. Rohde, P. van den Bogaard, K. Hoernle, F. Hauff, R. Werner, Evidence for an

  15. Kinetics of gas phase formic acid decomposition on platinum single crystal and polycrystalline surfaces

    Science.gov (United States)

    Detwiler, Michael D.; Milligan, Cory A.; Zemlyanov, Dmitry Y.; Delgass, W. Nicholas; Ribeiro, Fabio H.

    2016-06-01

    Formic acid dehydrogenation turnover rates (TORs) were measured on Pt(111), Pt(100), and polycrystalline Pt foil surfaces at a total pressure of 800 Torr between 413 and 513 K in a batch reactor connected to an ultra-high vacuum (UHV) system. The TORs, apparent activation energies, and reaction orders are not sensitive to the structure of the Pt surface, within the precision of the measurements. CO introduced into the batch reactor depressed the formic acid dehydrogenation TOR and increased the reaction's apparent activation energies on Pt(111) and Pt(100), consistent with behavior predicted by the Temkin equation. Two reaction mechanisms were explored which explain the formic acid decomposition mechanism on Pt, both of which include dissociative adsorption of formic acid, rate limiting formate decomposition, and quasi-equilibrated hydrogen recombination and CO adsorption. No evidence was found that catalytic supports used in previous studies altered the reaction kinetics or mechanism.

  16. Adsorbate-induced facetting reconstruction and self-organized domain patterning of vicinal Ag(111) surfaces; Adsorbatinduzierte richtungsabhaengige Facettierung und selbstorganisierte Domaenen-Musterbildung auf vizinalen Ag(111)-Oberflaechen

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Stefan

    2007-02-05

    This thesis investigates structural aspects of adsorbate-induced facetting of vicinal Ag(111) surfaces. It is mainly based on scanning tunneling microscope (STM) and low energy electron diffraction (LEED) experiments performed under UHV conditions. The planar dye-molecule perylene-3,4,9,10-tetracarboxilicacid-dianhydride (PTCDA) adsorbs preferentially at the step edges of the 8.5 Ag(111) vicinal surfaces used in the experiments. It causes a facetting reconstruction by the formation of (111) terraces and facets with a high step density. Moreover, two distinct preferential inclinations of facets were observed, which can only be explained by the selective influence of the adsorbate superstructure. In terms of thermodynamics, the facetting reconstruction can be described as an orientational phase separation, adapted to the constraints of planar surfaces. This concept is capable of explaining the local facetting phenomena. The formalism used predicts an important role of nucleation kinetics. This aspect is taken into account by introducing an additional phase of mobile molecules (2D molecular gas), which cannot be measured directly. Furthermore, strong arguments for the appearance of a critical island size for the PTCDA/ Ag(111) superstructure were found. This work presents structural information of all stable superstructures of PTCDA on vicinal Ag(111) surfaces. Altogether 16 such superstructures were found, 3 of which had been observed and published before. Density and commensurability were found to systematically depend on the step-structure. The two preferred inclinations of facets are related to two characteristic types of domain boundaries of the herringbone superstructure to the adjacent (111)-terrace. On the (111) terraces, small islands of metastable superstructures were found. Facets and (111) terraces form a regular grating-like domain pattern with a variable structural width of 5 to 75 nm. STM measurements show direct evidence for a long-range interaction

  17. Surface spectators and their role in relationships between activity and selectivity of the oxygen reduction reaction in acid environments.

    Energy Technology Data Exchange (ETDEWEB)

    Ciapina, Eduardo G.; Lopes, Pietro P.; Subbaraman, Ram; Ticianelli, Edson A.; Stamenkovic, Vojislav; Strmcnik, Dusan; Markovic, Nenad M.

    2015-11-01

    We use the rotating ring disk (RRDE) method to study activity-selectivity relationships for the oxygen reduction reaction (ORR) on Pt(111) modified by various surface coverages of adsorbed CNad (ΘCNad). The results demonstrate that small variations in ΘCNad have dramatic effect on the ORR activity and peroxide production, resulting in “volcano-like” dependence with an optimal surface coverage of ΘCNad = 0.3 ML. These relationships can be simply explained by balancing electronic and ensemble effects of co-adsorbed CNad and adsorbed spectator species from the supporting electrolytes, without the need for intermediate adsorption energy arguments. Although this study has focused on the Pt(111)-CNad/H2SO4 interface, the results and insight gained here are invaluable for controlling another dimension in the properties of electrochemical interfaces.

  18. Surface structures from low energy electron diffraction: Atoms, small molecules and an ordered ice film on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Materer, N.F.

    1995-09-01

    We investigated the surface bonding of various adsorbates (0, S, C{sub 2}H{sub 3} and NO) along with the resulting relaxation of the Pt(111) surface using low energy electron diffiraction (LEED). LEED experiments have been performed on these ordered overlayers along with theoretical structural analysis using automated tensor LEED (ATLEED). The resulting surface structures of these ordered overlayers exhibit similar adsorbate-induced relaxations. In all cases the adsorbate occupies the fcc hollow site and induces an approximately 0.1 A buckling of the metal surface. The three metal atoms directly bonded to the adsorbate are ``pulled`` out of the surface and the metal atom that is not bound to the adsorbate is `pushed`` inward. In order to understand the reliability of such details, we have carried out a comprehensive study of various non-structural parameters used in a LEED computation. We also studied the adsorption of water on the Pt(lll) surface. We ordered an ultra thin ice film on this surface. The film`s surface is found to be the (0001) face of hexagonal ice. This surface is apparently terminated by a full-bilayer, in which the uppermost water molecules have large vibrational amplitudes even at temperatures as low as 90 K. We examined two other metal surfaces besides Pt(111): Ni(111) and Fe(lll). On Ni(111), we have studied the surface under a high coverage of NO. On both Ni(111) and Pt(111) NO molecules occupy the hollow sites and the N-0 bond distances are practically identical. The challenging sample preparation of an Fe(111) surface has been investigated and a successful procedure has been obtained. The small interlayer spacing found on Fe(111) required special treatment in the LEED calculations. A new ATLEED program has been developed to handle this surface.

  19. Laser-assisted photoelectric effect from surfaces.

    Science.gov (United States)

    Miaja-Avila, L; Lei, C; Aeschlimann, M; Gland, J L; Murnane, M M; Kapteyn, H C; Saathoff, G

    2006-09-15

    We report the first observation of the laser-assisted photoelectric effect from a solid surface. By illuminating a Pt(111) sample simultaneously with ultrashort 1.6 eV and 42 eV pulses, we observe sidebands in the extreme ultraviolet photoemission spectrum. The magnitude of these sidebands as a function of time delay between the laser and extreme ultraviolet pulses represents a cross-correlation measurement of the extreme ultraviolet pulse. This effect promises to be useful to extend extreme ultraviolet pulse duration measurements to higher photon energies, as well as opening up femtosecond-to-attosecond time-scale electron dynamics in solid and surface-adsorbate systems.

  20. Studies of thin films and surfaces with optical harmonic generation and electron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wilk, Dieter Emre [Univ. of California, Berkeley, CA (United States)

    1996-01-01

    Optical second harmonic generation (SHG) and sum frequency generation (SFG) were used to study C60 thin solid films (low energy ED forbidden electronic excitations), and electron spectroscopy was used to study organic overlayers (xylenes) on Pt(111). Theory of SHG from a thin film is described in terms of surface and bulk contributions as well as local and nonlocal contributions to the optical nonlinearities. (1)In situ SHG data on C60 films during UHV film growth can be described in terms of only nonlocal contributions to both surface and bulk nonlinear susceptibilities. Microscopic origin of SHG response is discussed in terms of electric quadrupole and ED transitions of C60. (2)Adsorption and thermal decomposition of ortho- and para-xylene on Pt(111) is studied using HREELS, LEED, AES, and thermal desorption spectroscopy. We have observed preferential decomposition of the methyl groups which leads to distinct decomposition pathways for ortho- and para-xylene on Pt(111).

  1. Volgograd and vicinity: a Landsat view

    Science.gov (United States)

    Dando, William A.; Johnson, Gary E.

    1981-01-01

    Many diverse features can be discerned on the Landsat image of Volgograd and vicinity. Some of these features have resulted directly from man's alteration of the land surface in accordance with Stalin's and Khrushchev's plans for control of climate and for development in Volgograd and the surrounding area. Landsat images such as the one in this example provide the opportunity to inventory and assess man's imprint upon the land on a regional basis from a unique perspective.

  2. First-principles investigation of methanethiol adsorption and dissociation mechanisms on the high-Miller-index vicinal surface Cu(4 1 0).

    Science.gov (United States)

    Raouafi, Faycal; Seydou, Mahamadou; Lassoued, Karima; Taleb, Abdelhafed; Diawara, Boubakar

    2016-05-05

    In this work, we present detailed investigations of methanethiol adsorption on a Cu(4 1 0) surface within the framework of the self-consistent first-principles calculations as implemented in the Vienna ab initio simulation package (VASP). In particular, the adsorption sites, the surface coverage rate and electronic properties have been determined and compared to experimental values. The results indicate that the favorable adsorption site in the case of low coverage rate is a bridge on the step followed by the hollow site on the terrace. The adsorption significantly affects the outermost layer of the surface mainly for a higher coverage rate in a (2 × 2) supercell. The nature of the chemisorption process on the surface is analyzed by means of the density of states which, combined with charge density difference and atomic charge calculations, confirms the ionic character of the S-Cu bond. The specific effect of the presence of steps is highlighted by comparing the adsorption on the (1 0 0) terrace to the adsorption on the extended Cu(1 0 0) surface. Compared to the flat Cu(1 0 0), it is found here that while the stability is almost the same at p(2 × 2) coverage, the CH3S/Cu(4 1 0) becomes more stable than CH3S/Cu(1 0 0) at c(2 × 2) coverage with 0.30 eV per molecule. The mechanism of methanethiol dissociation is explored by the nudged elastic band method and demonstrates that the most favorable path is dissociation followed by migration of hydrogen from the step to its most stable position (hollow on the terrace) with energy barriers less than 0.5 eV.

  3. Surface channelling in grazing-incidence ion bombardment of a stepped surface

    Energy Technology Data Exchange (ETDEWEB)

    Rosandi, Yudi [Fachbereich Physik, Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany); Urbassek, Herbert M. [Fachbereich Physik, Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany)]. E-mail: urbassek@rhrk.uni-kl.de

    2007-03-15

    Using molecular-dynamics simulation, the impact of a 5keV Ar atom at 83 deg. incidence angle towards the surface normal onto a stepped Pt(111) surface is investigated. The projectile impinges with a [11-bar2] azimuth on a B step. The channelling of trajectories below the upper terrace is characterized in terms of the distribution of channelling lengths and the energy loss of channelled projectiles. The influence of target temperature is studied by simulating targets at 0K and at 550K.

  4. Influence of beryllium cations on the electrochemical oxidation of methanol on stepped platinum surfaces in alkaline solution

    Science.gov (United States)

    García, Gonzalo; Stoffelsma, Chantal; Rodriguez, Paramaconi; Koper, Marc T. M.

    2015-01-01

    The role of beryllium on the oxidation of methanol on Pt stepped surfaces (Pt[(n-1) (111)x(110)]) orientation-Pt(553) with n = 5, Pt(554) n = 10, Pt(151514) n = 30), Pt(111) and Pt(110) single crystals in alkaline media was studied by cyclic voltammetry and Fourier transform infrared spectroscopy (FTIRS). The results suggest that under the conditions of the experiment, the methanol oxidation reaction follows a direct pathway with formaldehyde and formate as reaction intermediates. The combination of OHads and beryllium blocks the adsorption and oxidation of methanol on Pt(111), but appears to promote the complete oxidation of methanol to carbon dioxide/carbonate on Pt(110).

  5. Chemical reactions on solid surfaces using molecular beam techniques

    Science.gov (United States)

    Palmer, R. L.

    1980-07-01

    Thermal energy molecular beams have been used to study chemical interactions with metal surfaces. Chemisorption of simple molecules such as H2, O2, CH4, C2Hx and CO was investigated on single and polycrystalline surfaces of Pt, Ni, Co, and Ag. Kinetic parameters and reaction mechanisms were determined for model catalytic reactions including CO and C2Hx oxidation and methanation from H2/CO mixtures. Chemical reactions of NOx with CO and D2 on Pt(111) and other surfaces have been surveyed and the kinetics of NO and O2 chemisorption have been measured. The theory of adsorption/desorption kinetics is reviewed and certain deficiencies identified.

  6. Surfaces and interfaces governing the OMVPE growth of APD-free GaP on AsH3-cleaned vicinal Si(100)

    Energy Technology Data Exchange (ETDEWEB)

    McMahon, William E.; Warren, Emily L.; Kibbler, Alan E.; France, Ryan M.; Norman, Andrew G.; Reedy, Robert C.; Olson, Jerry M.; Tamboli, Adele C.; Stradins, Paul

    2016-10-01

    Direct growth of GaP on Si enables the integration of III-V and Si optoelectronic devices for a wide variety of applications, and has therefore been the subject of much research for many decades. Most of this effort has been directed toward overcoming the two main technical challenges: 1) removing atmospheric oxygen and carbon contamination and 2) establishing the conditions needed for 'APD-free' III-V epitaxy (i.e., without antiphase domains). We have developed an OMVPE process for APD-free GaP growth on Si which overcomes both challenges by using AsH3 to clean and prepare the Si surface in situ at a relatively low temperature. This process is based upon a very brief 'AsH3-cleaning' step which simultaneously removes atmospheric contamination (thereby eliminating the need for Si regrowth) and creates a single-domain As-terminated Si surface. Here we discuss the key process steps using results from a suite of analysis tools.

  7. Sources of coal-mine drainage and their effects on surface-water chemistry in the Claybank Creek basin and vicinity, north-central Missouri, 1983-84

    Science.gov (United States)

    Blevins, Dale W.

    1989-01-01

    Eighteen sources of drainage related to past coal-mining activity were identified in the Claybank Creek, Missouri, study area, and eight of them were considered large enough to have detectable effects on receiving streams. However, only three sources (two coal-waste sites and one spring draining an underground mine) significantly affected the chemistry of water in receiving streams. Coal wastes in the Claybank Creek basin contributed large quantities of acid drainage to receiving streams during storm runoff. The pH of coal-waste runoff ranged from 2.1 to 2.8. At these small pH values, concentrations of some dissolved metals and dissolved sulfate were a few to several hundred times larger than Federal and State water-quality standards established for these constituents. Effects of acid storm runoff were detected near the mouth of North Fork Claybank Creek where the pH during a small storm was 3.9. Coal wastes in the streambeds and seepage from coal wastes also had significant effects on receiving streams during base flows. The receiving waters had pH values between 2.8 and 3.5, and concentrations of some dissolved metals and dissolved sulfate were a few to several hundred times larger than Federal and State water-quality standards. Most underground mines in the North Fork Claybank Creek basin seem to be hydraulically connected, and about 80 percent of their discharge surfaced at one site. Drainage from the underground mines contributed most of the dissolved constituents in North Fork Claybank Creek during dry weather. Underground-mine water always had a pH near 5.9 and was well-buffered. It had a dissolved-sulfate concentration of about 2,400 milligrams per liter, dissolved-manganese concentrations ranging from 4.0 to 5.3 milligrams per liter, and large concentrations of ferrous iron. Iron was in the ferrous state because of reducing conditions in the mines. When underground-mine drainage reached the ground surface, the ferrous iron was oxidized and precipitated to

  8. Hydrogeochemistry and quality of surface water and groundwater in the vicinity of Lake Monoun, West Cameroon: approach from multivariate statistical analysis and stable isotopic characterization.

    Science.gov (United States)

    Kamtchueng, Brice T; Fantong, Wilson Y; Wirmvem, Mengnjo J; Tiodjio, Rosine E; Takounjou, Alain F; Ndam Ngoupayou, Jules R; Kusakabe, Minoru; Zhang, Jing; Ohba, Takeshi; Tanyileke, Gregory; Hell, Joseph V; Ueda, Akira

    2016-09-01

    With the use of conventional hydrogeochemical techniques, multivariate statistical analysis, and stable isotope approaches, this paper investigates for the first time surface water and groundwater from the surrounding areas of Lake Monoun (LM), West Cameroon. The results reveal that waters are generally slightly acidic to neutral. The relative abundance of major dissolved species are Ca(2+) > Mg(2+) > Na(+) > K(+) for cations and HCO3 (-) ≫ NO3 (-) > Cl(-) > SO4 (2-) for anions. The main water type is Ca-Mg-HCO3. Observed salinity is related to water-rock interaction, ion exchange process, and anthropogenic activities. Nitrate and chloride have been identified as the most common pollutants. These pollutants are attributed to the chlorination of wells and leaching from pit latrines and refuse dumps. The stable isotopic compositions in the investigated water sources suggest evidence of evaporation before recharge. Four major groups of waters were identified by salinity and NO3 concentrations using the Q-mode hierarchical cluster analysis (HCA). Consistent with the isotopic results, group 1 represents fresh unpolluted water occurring near the recharge zone in the general flow regime; groups 2 and 3 are mixed water whose composition is controlled by both weathering of rock-forming minerals and anthropogenic activities; group 4 represents water under high vulnerability of anthropogenic pollution. Moreover, the isotopic results and the HCA showed that the CO2-rich bottom water of LM belongs to an isolated hydrological system within the Foumbot plain. Except for some springs, groundwater water in the area is inappropriate for drinking and domestic purposes but good to excellent for irrigation.

  9. Structure of the lithosphere-asthenosphere system in the vicinity of the Tristan da Cunha hot spot as seen by surface waves

    Science.gov (United States)

    Geissler, Wolfram; Bonadio, Raffaele; Lebedev, Sergei; Jokat, Wilfried; Jegen, Marion; Baba, Kiyoshi; Sens-Schönfelder, Christoph

    2016-04-01

    According to classical plume theory, the Tristan da Cunha hotspot is thought to have played a major role in the rifting of the South Atlantic margins and the creation of the aseismic Walvis Ridge by impinging at the base of the continental lithosphere shortly before or during the breakup of the South Atlantic margins. However, Tristan da Cunha is enigmatic as it cannot be clearly identified as a hot spot but may also be classified as a more shallow type of anomaly that may actually have been caused by the opening of the South Atlantic. The equivocal character of Tristan da Cunha is largely due to a lack of geophysical and petrological data in this region. We therefore staged a multi-disciplinary geophysical study of the region by acquiring passive marine electromagnetic and seismic data, and bathymetric data within the framework of the SPP1375 South Atlantic Margin Processes and Links with onshore Evolution (SAMPLE) funded by the German Science foundation. The experiment included two ship expeditions onboard the German R/V MARIA S. MERIAN in 2012 and 2013. In our contribution we will present first results on the shear wave velocity structure of the lithosphere-asthenosphere system. We applied the classical two-station method; Rayleigh wave dispersion curves are determined by cross-correlation of seismograms from a pair of station. We measured interstation phase velocities of (earthquake-excited) fundamental-mode surface waves in a period range of 10 to 60 s. The selection of acceptable phase-velocity measurements in the frequency domain had to be done manually for each event. We present phase-velocity maps for the study area. Furthermore, we present 1D shear wave velocity models inverted from the highest-quality observations.

  10. Impact assessment of ionizing radiation on human and non-human biota from the vicinity of a near-surface radioactive waste repository.

    Science.gov (United States)

    Nedveckaite, T; Gudelis, A; Vives i Batlle, J

    2013-05-01

    This work describes the radiological assessment of the near-surface Maisiagala radioactive waste repository (Lithuania) over the period 2005-2012, with focus on water pathways and special emphasis on tritium. The study includes an assessment of the effect of post-closure upgrading, the durability of which is greater than 30 years. Both human and terrestrial non-human biota are considered, with local low-intensity forestry and small farms being the area of concern. The radiological exposure was evaluated using the RESRAD-OFFSITE, RESRAD-BIOTA and ERICA codes in combination with long-term data from a dedicated environmental monitoring programme. All measurements were performed at the Lithuanian Institute of Physics as part of this project. It is determined that, after repository upgrading, radiological exposure to humans are significantly lower than the human dose constraint of 0.2 mSv/year valid in the Republic of Lithuania. Likewise, for non-human biota, dose rates are below the ERICA/PROTECT screening levels. The potential annual effective inhalation dose that could be incurred by the highest-exposed human individual (which is due to tritiated water vapour airborne release over the most exposed area) does not exceed 0.1 μSv. Tritium-labelled drinking water appears to be the main pathway for human impact, representing about 83 % of the exposure. Annual committed effective dose (CED) values for members of the public consuming birch sap as medical practice are calculated to be several orders of magnitude below the CEDs for the same location associated with drinking of well water. The data presented here indicate that upper soil-layer samples may not provide a good indication of potential exposure to terrestrial deep-rooted trees, as demonstrated by an investigation of stratified (3)H in soil moisture, expressed on a wet soil mass basis, in an area with subsurface contamination.

  11. Surface step terrace tuned microstructures and dielectric properties of highly epitaxial CaCu3Ti4O12 thin films on vicinal LaAlO3 substrates

    Science.gov (United States)

    Yao, Guang; Gao, Min; Ji, Yanda; Liang, Weizheng; Gao, Lei; Zheng, Shengliang; Wang, You; Pang, Bin; Chen, Y. B.; Zeng, Huizhong; Li, Handong; Wang, Zhiming; Liu, Jingsong; Chen, Chonglin; Lin, Yuan

    2016-10-01

    Controllable interfacial strain can manipulate the physical properties of epitaxial films and help understand the physical nature of the correlation between the properties and the atomic microstructures. By using a proper design of vicinal single-crystal substrate, the interface strain in epitaxial thin films can be well controlled by adjusting the miscut angle via a surface-step-terrace matching growth mode. Here, we demonstrate that LaAlO3 (LAO) substrates with various miscut angles of 1.0°, 2.75°, and 5.0° were used to tune the dielectric properties of epitaxial CaCu3Ti4O12 (CCTO) thin films. A model of coexistent compressive and tensile strained domains is proposed to understand the epitaxial nature. Our findings on the self-tuning of the compressive and tensile strained domain ratio along the interface depending on the miscut angle and the stress relaxation mechanism under this growth mode will open a new avenue to achieve CCTO films with high dielectric constant and low dielectric loss, which is critical for the design and integration of advanced heterostructures for high performance capacitance device applications.

  12. Effect of strain on surface diffusion and nucleation

    DEFF Research Database (Denmark)

    Brune, Harald; Bromann, Karsten; Röder, Holger;

    1995-01-01

    The influence of strain on diffusion and nucleation has been studied by means of scanning tunneling microscopy and effective-medium theory for Ag self-diffusion on strained and unstrained (111) surfaces. Experimentally, the diffusion barrier is observed to be substantially lower on a pseudomorphic...... Ag monolayer on Pt(111), 60 meV, compared to that on Ag(111), 97 meV. The calculations show that this strong effect is due to the 4.2% compressive strain of the Ag monolayer on Pt. It is shown that in general isotropic two-dimensional strain as well as its relief via dislocations have a drastic...

  13. Insight into chemoselectivity of nitroarene hydrogenation: A DFT-D3 study of nitroarene adsorption on metal surfaces under the realistic reaction conditions

    Science.gov (United States)

    Zhang, Lidong; Cao, Xiao-Ming; Hu, P.

    2017-01-01

    The adsorption of nitrobenzene and 4-nitrostyrene on the Pt(111) and the Au(111) surfaces under the general reaction condition of nitroarene catalytic hydrogenation is investigated utilizing periodic density functional theory calculations with the Grimme's empirical three-body dispersion correction to understand the influence of adsorption configurations on chemoselectivity of nitroarene compound hydrogenation. It is found that at the low coverage both nitrobenzene and 4-nitrostyrene tend to adsorb paralleling to the Pt(111) and the Au(111) surfaces. Based on the crystal orbital Hamilton population analysis, it is found that the chemical bonding between nitro group and Pt(111) surface is weak. The adsorption configurations of nitrobenzene and 4-nitrostyrene are determined by the chemisorption strength of phenyl group and vinyl group. Under the reaction condition, the 1/9 ML nitrobenzene and 4/9 ML hydrogen atom can be coadsorbed while the 1/6 ML 4-nitrostyrene and 1/3 ML hydrogen atom can be coadsorbed on Pt(111). With the increase of the coverage, nitrobenzene still remains its paralleled adsorption configuration while the adsorption configuration of 4-nitrostyrene is switched to the tilted adsorption configuration through vinyl group without the chemisorption of phenyl and nitro group on Pt(111). In addition, the competitive adsorption with hydrogen will not change the adsorption configuration of nitrobenzene and 4-nitrostyrene under the reaction condition. On Au(111), the physical adsorption strength determines the adsorption configuration. The paralleled adsorption with the shortest average distance between the adsorbate and Au(111) surface is preferred. At the paralleled adsorption configuration, the chemoselectivities of the hydrogenation on these functional groups are similar if only in terms of geometric configuration. However, the hydrogenation on nitro group encounters the problem of steric hindrance at the tilted adsorption configuration through vinyl

  14. Seismicity of Afghanistan and vicinity

    Science.gov (United States)

    Dewey, James W.

    2006-01-01

    This publication describes the seismicity of Afghanistan and vicinity and is intended for use in seismic hazard studies of that nation. Included are digital files with information on earthquakes that have been recorded in Afghanistan and vicinity through mid-December 2004. Chapter A provides an overview of the seismicity and tectonics of Afghanistan and defines the earthquake parameters included in the 'Summary Catalog' and the 'Summary of Macroseismic Effects.' Chapter B summarizes compilation of the 'Master Catalog' and 'Sub-Threshold Catalog' and documents their formats. The 'Summary Catalog' itself is presented as a comma-delimited ASCII file, the 'Summary of Macroseismic Effects' is presented as an html file, and the 'Master Catalog' and 'Sub-Threshold Catalog' are presented as flat ASCII files. Finally, this report includes as separate plates a digital image of a map of epicenters of earthquakes occurring since 1964 (Plate 1) and a representation of areas of damage or strong shaking from selected past earthquakes in Afghanistan and vicinity (Plate 2).

  15. Cooperativity in Surface Bonding and Hydrogen Bonding of Water and Hydroxyl at Metal Surfaces

    DEFF Research Database (Denmark)

    Schiros, T.; Ogasawara, H.; Naslund, L. A.;

    2010-01-01

    of the mixed phase at metal surfaces. The surface bonding can be considered to be similar to accepting a hydrogen bond, and we can thereby apply general cooperativity rules developed for hydrogen-bonded systems. This provides a simple understanding of why water molecules become more strongly bonded...... to the surface upon hydrogen bonding to OH and why the OH surface bonding is instead weakened through hydrogen bonding to water. We extend the application of this simple model to other observed cooperativity effects for pure water adsorption systems and H3O+ on metal surfaces.......We examine the balance of surface bonding and hydrogen bonding in the mixed OH + H2O overlayer on Pt(111), Cu(111), and Cu(110) via density functional theory calculations. We find that there is a cooperativity effect between surface bonding and hydrogen bonding that underlies the stability...

  16. Kinetics and thermodynamics of H2O dissociation and CO oxidation on the Pt/WC (0001) surface: A density functional theory study

    Science.gov (United States)

    Liang, Yuanyuan; Chen, Litao; Ma, Chun'an

    2017-02-01

    Adsorptions of H2O and CO on the Pt/WC(0001) [pseudomorphic platinum monolayer on WC(0001)] surface have been studied with periodical slab model by PW91 approach of GGA within the framework of density functional theory (DFT). The reaction pathways and mechanisms of H2O dissociation and CO oxidation are also investigated. For a comparison, similar calculation scheme are performed on the Pt (111) surface as well. The adsorption energies of H2O and CO on both concerned surfaces suggest that H2O binds preferentially on the Pt/WC (0001) surface, while CO prefers the metal surface Pt (111), agreeing well with the experimental observation that the tungsten carbides based material is less susceptible to CO poisoning than platinum. The activation energies for the stepwise H2O dehydrogenation reaction show that the progress of H2O dissociation is similar on the two surfaces; and coincidentally the oxidation of CO by surface hydroxyl is much more likely to occur than that by surface oxygen which comes up with the H2O dissociation. Although the activation barrier of H2O dissociation on the Pt/WC (0001) is similar to that on Pt (111), the key oxidant OH specials which play a key role in turning over surface carbon monoxide to carbon dioxide prefer the Pt/WC(0001) surface, and the improved CO oxidation reaction progress confirms that the Pt/WC surface is more CO-tolerant than the pure Pt. According to the electronic structure analysis we find that the increased CO tolerance is ascribed to the downshift of Pt d-band center because of the charge transfer from WC support to the coating surface.

  17. Electrode surface studies by LEED-Auger

    Science.gov (United States)

    Ogrady, W. E.; Woo, M. Y. C.; Hagans, P. L.; Yeager, E.

    1977-01-01

    The role the electronic and geometric structures of the metal surface play in electrochemical surface reactions remains as yet an unknown factor. In order to investigate these surface contributions to electrochemical reactions, a low-energy-electron diffraction (LEED) and an Auger electron spectrometer (AES) have been combined with an electrochemical thin-layer cell. The surface to be studied electrochemically is first characterized by LEED-AES and then transferred into a second chamber where it becomes part of the electrochemical thin-layer cell. Electrochemical reactions are then run on this surface. The sample may then be transferred back to the LEED-AES chamber for further characterization. Data on Pt (111) will be presented.

  18. Correlating Structure and Oxygen Reduction Activity on Y/Pt(111) and Gd/Pt(111) Single Crystals

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese; Pedersen, Anders Filsøe; Johansson, Tobias Peter

    2015-01-01

    Polymer Electrolyte Membrane Fuel Cells (PEMFC) hold promise as a zero-emission source of power, particularly suitable for automotive vehicles. However, the high loading of Pt required to catalyse the Oxygen Reduction Reaction (ORR) at the PEMFC cathode prevents the commercialisation of this tech...

  19. Dissociative adsorption of methane on surface oxide structures of Pd-Pt alloys

    CERN Document Server

    Dianat, Arezoo; Ciacchi, Lucio Colombi; Pompe, Wolfgang; Cuniberti, Gianaurelio; Bobeth, Manfred; 10.1021/jp905689t

    2010-01-01

    The dissociative adsorption of methane on variously oxidized Pd, Pt and Pd-Pt surfaces is investigated using density-functional theory, as a step towards understanding the combustion of methane on these materials. For Pd-Pt alloys, models of surface oxide structures are built on the basis of known oxides on Pd and Pt. The methane adsorption energy presents large variations depending on the oxide structure and composition. Adsorption is endothermic on the bare Pd(111) metal surface as well as on stable thin layer oxide structures such as the ($\\sqrt{5}\\times\\sqrt{5}$) surface oxide on Pd(100) and the PtO$_2$-like oxide on Pt(111). Instead, large adsorption energies are obtained for the (100) surface of bulk PdO, for metastable mixed Pd$_{1-x}$Pt$_x$O$_{4/3}$ oxide layers on Pt(100), and for Pd-Pt(111) surfaces covered with one oxygen monolayer. In the latter case, we find a net thermodynamic preference for a direct conversion of methane to methanol, which remains adsorbed on the oxidized metal substrates via w...

  20. Extending the range of low energy electron diffraction (LEED) surface structure determination: Co-adsorbed molecules, incommensurate overlayers and alloy surface order studied by new video and electron counting LEED techniques

    Energy Technology Data Exchange (ETDEWEB)

    Ogletree, D.F.

    1986-11-01

    LEED multiple scattering theory is briefly summarized, and aspects of electron scattering with particular significance to experimental measurements such as electron beam coherence, instrument response and phonon scattering are analyzed. Diffuse LEED experiments are discussed. New techniques that enhance the power of LEED are described, including a real-time video image digitizer applied to LEED intensity measurements, along with computer programs to generate I-V curves. The first electron counting LEED detector using a ''wedge and strip'' position sensitive anode and digital electronics is described. This instrument uses picoampere incident beam currents, and its sensitivity is limited only by statistics and counting times. Structural results on new classes of surface systems are presented. The structure of the c(4 x 2) phase of carbon monoxide adsorbed on Pt(111) has been determined, showing that carbon monoxide molecules adsorb in both top and bridge sites, 1.85 +- 0.10 A and 1.55 +- 0.10 A above the metal surface, respectively. The structure of an incommensurate graphite overlayer on Pt(111) is analyzed. The graphite layer is 3.70 +- 0.05 A above the metal surface, with intercalated carbon atoms located 1.25 +- 0.10 A above hollow sites supporting it. The (2..sqrt..3 x 4)-rectangular phase of benzene and carbon monoxide coadsorbed on Pt(111) is analyzed. Benzene molecules adsorb in bridge sites parallel to and 2.10 +- 0.10 A above the surface. The carbon ring is expanded, with an average C-C bond length of 1.72 +- 0.15 A. The carbon monoxide molecules also adsorb in bridge sites. The structure of the (..sqrt..3 x ..sqrt..3) reconstruction on the (111) face of the ..cap alpha..-CuAl alloy has been determined.

  1. Electrolysis of water on (oxidized) metal surfaces

    DEFF Research Database (Denmark)

    Rossmeisl, Jan; Logadottir, Ashildur; Nørskov, Jens Kehlet

    2005-01-01

    directly from the electronic structure calculations. We consider electrodes of Pt(111) and Au(111) in detail and then discuss trends for a series of different metals. We show that the difficult step in the water splitting process is the formation of superoxy-type (OOH) species on the surface...... by the splitting of a water molecule on top an adsorbed oxygen atom. One conclusion is that this is only possible on metal surfaces that are (partly) oxidized. We show that the binding energies of the different intermediates are linearly correlated for a number of metals. In a simple analysis, where the linear...... relations are assumed to be obeyed exactly, this leads to a universal relationship between the catalytic rate and the oxygen binding energy. Finally, we conclude that for systems obeying these relations, there is a limit to how good a water splitting catalyst an oxidized metal surface can become. (c) 2005...

  2. Surface Pourbaix diagrams and oxygen reduction activity of Pt, Ag and Ni(111) surfaces studied by DFT

    DEFF Research Database (Denmark)

    Hansen, Heine Anton; Rossmeisl, Jan; Nørskov, Jens Kehlet

    2008-01-01

    (ORR) on the different surface structures and calculate the free energy of the intermediates. We estimate their catalytic activity for ORR by determining the highest potential at which all ORR reaction steps reduce the free energy. We obtain self-consistency in the sense that the surface is stable...... but not in acidic PEM fuel cells. Based on density functional theory calculations we investigate the electrochemically most stable surface structures as a function of pH and electrostatic potential for Pt(111), Ag(111) and Ni(111), and we construct surface Pourbaix diagrams. We study the oxygen reduction reaction...... of the reactive surface. Oxygen absorbed on the surface shifts the reactivity towards the weak binding region, which in turn increases the activity. The oxidation state of the surface and the ORR potential are constant versus the reversible hydrogen electrode (RHE). The dissolution potential in acidic solution...

  3. Anisotropic Surface State Mediated RKKY Interaction Between Adatoms on a Hexagonal Lattice

    Science.gov (United States)

    Einstein, Theodore; Patrone, Paul

    2012-02-01

    Motivated by recent numerical studies of Ag on Pt(111), we derive a far-field expression for the RKKY interaction mediated by surface states on a (111) FCC surface, considering the effect of anisotropy in the Fermi edge. The main contribution to the interaction comes from electrons whose Fermi velocity vF is parallel to the vector R connecting the interacting adatoms; we show that in general, the corresponding Fermi wave-vector kF is not parallel to R. The interaction is oscillatory; the amplitude and wavelength of oscillations have angular dependence arising from the anisotropy of the surface state band structure. The wavelength, in particular, is determined by the component of the aforementioned kF that is parallel to R. Our analysis is easily generalized to other systems. For Ag on Pt(111), our results indicate that the RKKY interaction between pairs of adatoms should be nearly isotropic and so cannot account for the anisotropy found in the studies motivating our work.

  4. Anisotropic surface-state-mediated RKKY interaction between adatoms on a hexagonal lattice

    Science.gov (United States)

    Patrone, Paul N.; Einstein, T. L.

    2012-01-01

    Motivated by recent numerical studies of Ag on Pt(111), we derive an expression for the RKKY interaction mediated by surface states, considering the effect of anisotropy in the Fermi edge. Our analysis is based on a stationary phase approximation. The main contribution to the interaction comes from electrons whose Fermi velocity vF is parallel to the vector R connecting the interacting adatoms; we show that, in general, the corresponding Fermi wave vector kF is not parallel to R. The interaction is oscillatory; the amplitude and wavelength of oscillations have angular dependence arising from the anisotropy of the surface-state band structure. The wavelength, in particular, is determined by the projection of this kF (corresponding to vF) onto the direction of R. Our analysis is easily generalized to other systems. For Ag on Pt(111), our results indicate that the RKKY interaction between pairs of adatoms should be nearly isotropic and so cannot account for the anisotropy found in the studies motivating our work. However, for metals with surface-state dispersions similar to Be(101¯0), we show that the RKKY interaction should have considerable anisotropy.

  5. Computational studies of experimentally observed structures of sulfur on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Alfonso, Dominic

    2011-09-01

    First-principles electronic structure calculations were carried out to examine the experimentally observed structures of sulfur on close packed surfaces of a number of important metals - Ag(111), Cu(111), Ni(111), Pt(111), Rh(111), Re(0001) and Ru(0001). At low coverages ({le} 1/3 ML), the prediction is consistent with the typical pattern of preferred sulfur occupancy of threefold hollow sites, notably the fcc site on the (111) surfaces and the hcp site on the (0001) surfaces. Theoretical confirmation for the existence of pure sulfur overlayer phases on Pt(111), Rh(111), Re(0001) and Ru(0001) at higher coverages (> 1/3 ML) was provided. For the ({radical}7 x {radical}7) phase seen on Ag(111), the most preferred structure identified for adsorbed S trimer consists of an S atom on the top site bonded to two S atoms situated on the nearest neighbor off-bridge site positions. Among the different densely packed mixed sulfur-metal overlayer models suggested for the ({radical}7 x {radical}7) phase on Cu(111), the structure which consists of metal and S atoms in a hexagonal-like arrangement on the top substrate was found to be the most energetically favorable. For the (5{radical}3 x 2) phase on Ni(111), the calculations confirm the existence of clock-reconstructed top layer metal atoms onto which sulfur atoms are adsorbed.

  6. Synthesis and decomposition of ammonia on transition metal surfaces: bond-order-conservation-Morse-potential analysis

    Science.gov (United States)

    Shustorovich, Evgeny; Bell, Alexis T.

    1991-12-01

    The mechanism of ammonia synthesis and decomposition on transition metal surfaces has been analyzed using the BOC-MP (bond-order-conservation-Morse-potential) method. The analysis is based on calculations of the heats of chemisorption, Q, for all adsorbed species and activation barriers, Δ E∗, for all elementary reactions believed to be involved in the reaction N 2 + H 2 NH 3 over Pt(111), Ru(001), Fe(110), Re(001). The relevant experimental values of Q and Δ E∗ agree well with the BOC-MP estimates. It is shown that along the periodic series Pt, Ru, Fe, Re, the dissociation activation barriers decrease but the recombination and desorption barriers increase. In particular, we find that on all the surfaces the largest activation barrier corresponds to the recombinative desorption 2N s → N 2. This step is projected to be the rate-determining process for ammonia decomposition, and Pt is projected to be the most efficient catalyst. For the dissociation N 2 → 2N s, we find that the activation barrier sharply increases in the order Re ⩽ Fe ≪ Pt, which makes Pt surfaces incapable of catalyzing ammonia synthesis. These and other BOC-MP projections are in agreement with the results of mechanistic studies on Pt(111), Ru(001) and Fe(110).

  7. Contours--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the bathymetric contours for several seafloor maps of the Drakes Bay and Vicinity map area, California. The vector data file is...

  8. Habitat--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the habitat map of the seafloor of the Drakes Bay and Vicinity map area, California. The vector data file is included in...

  9. Contours--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents bathymetric contours for several seafloor maps of the Monterey Canyon and Vicinity map area, California. The raster data file is...

  10. Bathymetry--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the bathymetry and shaded-relief maps of Drakes Bay and Vicinity, California (raster data file is included in...

  11. Habitat--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the habitat map of the seafloor of the Monterey Canyon and Vicinity map area, California. The vector data file is included in...

  12. Habitat--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the habitat map of the seafloor of the Monterey Canyon and Vicinity map area, California. The vector data file is included in...

  13. Contours--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents bathymetric contours for several seafloor maps of the Monterey Canyon and Vicinity map area, California. The raster data file is...

  14. Structural sensitivity studies of ethylene hydrogenation on platinum and rhodium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Quinlan, M.A. [California Univ., Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States)

    1996-01-01

    The catalytic hydrogenation of ethylene and hydrogen on the well characterized surfaces of the noble metals platinum and rhodium has been studied for the purposes of determining the relative activity of these two substrates as well as the degree of structure sensitivity. The Pt(111) and the Rh(755) single crystal surfaces,as well as Pt and Rh foils, were employed as substrates to study the effect of surface step structure on reactivity. In addition, vibrational spectroscopy studies were performed for ethylene adsorption on the stepped Rh(755) surface. The catalytic reaction were obtained using a combined ultrahigh vacuum chamber coupled with an atmospheric pressure reaction chamber that functioned as a batch reactor. Samples could be prepared using standard surface science techniques and characterized for surface composition and geometry using Auger Electron Spectroscopy and Low Energy Electron Diffraction. A comparison of the reactivity of Rh(111) with the results from this study on Rh(755) allows a direct determination of the effect of step structure on ethylene hydrogenation activity. Structure sensitivity is expected to exhibit orders of magnitude differences in rate as surface orientation is varied. In this case, no significant differences were found, confirming the structure insensitivity of this reaction over this metal. The turnover frequency of the Rh(111) surface, 5 {times} 10{sup 1} s{sup {minus}1}, is in relatively good agreement with the turnover frequency of 9 {times} 10{sup 1} s{sup {minus}1} measured for the Rh(755) surface. Rate measurements made on the Pt(111) surface and the Pt foil are in excellent agreement, both measuring 3 {times} 10{sup 2} s{sup minus}1. Likewise, it is concluded that no strong structure sensitivity for the platinum surfaces exists. High Resolution Electron Energy Loss Spectroscopy studies of adsorbed ethylene on the Rh(755) surface compare favorably with the ethylidyne spectra obtained on the Rh(111) and Rh(100) surfaces.

  15. Benzene and Its Derivatives Adsorbed on Metal Surfaces: A Bag Full of Surprises

    Science.gov (United States)

    Liu, Wei; Scheffler, Matthias; Tkatchenko, Alexandre

    2014-03-01

    The study of molecule/metal interfaces is important for fundamental and applied surface science, and the electronic properties of these interfaces can be tuned by controlling their geometries. In this regard, a particular challenge for electronic structure theory is to reliably model the structure and stability of such hybrid interfaces. Here, we demonstrate that our DFT+vdWsurf method is able to describe 25 systems [e.g., benzene on Au(111) and Pt(111), thiophene/Ag(111), and DIP/Ag(111)] with an accuracy of 0.1 Å in adsorption heights and 0.1 eV in binding energies wrt. reliable experimental data. In addition, our DFT+vdWsurf calculations lead to a few peculiar findings: (1) The vdW energy can contribute more to the binding of covalently bonded systems than it does in physisorbed interfaces; (2) the binding energies of similar molecules can be identical, despite significantly different adsorption heights; (3) the physically bound (precursor) state for aromatics on Pt(111) can be prominently stabilized and long-lived, making it potentially useful in molecular switches.

  16. Effects of van der Waals density functional corrections on trends in furfural adsorption and hydrogenation on close-packed transition metal surfaces

    Science.gov (United States)

    Liu, Bin; Cheng, Lei; Curtiss, Larry; Greeley, Jeffrey

    2014-04-01

    The hydrogenation of furfural to furfuryl alcohol on Pd(111), Cu(111) and Pt(111) is studied with both standard Density Functional Theory (DFT)-GGA functionals and with van der Waals-corrected density functionals. VdW-DF functionals, including optPBE, optB88, optB86b, and Grimme's method, are used to optimize the adsorption configurations of furfural, furfuryl alcohol, and related intermediates resulting from hydrogenation of furfural, and the results are compared to corresponding values determined with GGA functionals, including PW91 and PBE. On Pd(111) and Pt(111), the adsorption geometries of the intermediates are not noticeably different between the two classes of functionals, while on Cu(111), modest changes are seen in both the perpendicular distance and the orientation of the aromatic ring with respect to the planar surface. In general, the binding energies increase substantially in magnitude as a result of van der Waals contributions on all metals. In contrast, however, dispersion effects on the kinetics of hydrogenation are relatively small. It is found that activation barriers are not significantly affected by the inclusion of dispersion effects, and a Brønsted-Evans-Polanyi relationship developed solely from PW91 calculations on Pd(111) is capable of describing corresponding results on Cu(111) and Pt(111), even when the dispersion effects are included. Finally, the reaction energies and barriers derived from the dispersion-corrected and pure GGA calculations are used to plot simple potential energy profiles for furfural hydrogenation to furfuryl alcohol on the three considered metals, and an approximately constant downshift of the energetics due to the dispersion corrections is observed.

  17. Effects of van der Waals Density Functional Corrections on Trends in Furfural Adsorption and Hydrogenation on Close-Packed Transition Metal Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bin; Cheng, Lei; Curtiss, Larry A.; Greeley, Jeffrey P.

    2014-04-01

    The hydrogenation of furfural to furfuryl alcohol on Pd(111), Cu(111) and Pt(111) is studied with both standard Density Functional Theory (DFT)-GGA functionals and with van der Waals-corrected density functionals. VdWDF functionals, including optPBE, optB88, optB86b, and Grimme's method, are used to optimize the adsorption configurations of furfural, furfuryl alcohol, and related intermediates resulting from hydrogenation of furfural, and the results are compared to corresponding values determined with GGA functionals, including PW91 and PBE. On Pd(111) and Pt(111), the adsorption geometries of the intermediates are not noticeably different between the two classes of functionals, while on Cu(111), modest changes are seen in both the erpendicular distance and the orientation of the aromatic ringwith respect to the planar surface. In general, the binding energies increase substantially in magnitude as a result of van derWaals contributions on all metals. In contrast, however, dispersion effects on the kinetics of hydrogenation are relatively small. It is found that activation barriers are not significantly affected by the inclusion of dispersion effects, and a Brønsted–Evans–Polanyi relationship developed solely fromPW91 calculations on Pd(111) is capable of describing corresponding results on Cu(111) and Pt(111), even when the dispersion effects are included. Finally, the reaction energies and barriers derived from the dispersion-corrected and pure GGA calculations are used to plot simple potential energy profiles for furfural hydrogenation to furfuryl alcohol on the three considered metals, and an approximately constant downshift of the energetics due to the dispersion corrections is observed.

  18. Narrowing of Terrace-width Distributions During Growth on Vicinals

    Science.gov (United States)

    Hamouda, Ajmi Bh.; Pimpinelli, A.; Einstein, T. L.

    2009-03-01

    Using kinetic Monte Carlo simulations for a generic minimal SOS model of vicinal surfaces, we compute the terrace-width distributions (TWDs) as a function of incident flux during homoepitaxial growth. We show that the distribution narrows markedly, U.B.P.-Clermont 2 as though there were a flux-dependent repulsion between steps, until the step picture fails at high flux. Using a Fokker-Planck approach, we analyze the evolution and saturation of this narrowing. We compare with a 1D model and with our simulations for narrowing due to an Ehrlich-Schwoebel barrier.

  19. The structures and dynamics of atomic and molecular adsorbates on metal surfaces by scanning tunneling microscopy and low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Hyungsuk Alexander [Univ. of California, Berkeley, CA (United States)

    1996-12-01

    Studies of surface structure and dynamics of atoms and molecules on metal surfaces are presented. My research has focused on understanding the nature of adsorbate-adsorbate and adsorbate-substrate interactions through surface studies of coverage dependency and coadsorption using both scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The effect of adsorbate coverage on the surface structures of sulfur on Pt(111) and Rh(111) was examined. On Pt(111), sulfur forms p(2x2) at 0.25 ML of sulfur, which transforms into a more compressed (√3x√3)R30° at 0.33 ML. On both structures, it was found that sulfur adsorbs only in fcc sites. When the coverage of sulfur exceeds 0.33 ML, it formed more complex c(√3x7)rect structure with 3 sulfur atoms per unit cell. In this structure, two different adsorption sites for sulfur atoms were observed - two on fcc sites and one on hcp site within the unit cell.

  20. Catalytic enantioselective synthesis of vicinal dialkyl arrays

    NARCIS (Netherlands)

    van Zijl, Anthoni W.; Szymanski, Wiktor; Lopez, Ferrnando; Minnaard, Adriaan J.; Feringa, Ben L.

    2008-01-01

    With a consecutive "asymmetric allylic alkylation (AAA)/cross-metathesis (CM)/conjugate addition (CA)" protocol it is possible to synthesize either stereoisomer of compounds containing a vicinal dialkyl array with excellent stereoselectivity. The versatility of this protocol in natural product synth

  1. The Role of Substrate Electrons in the Wetting of a Metal Surface

    Energy Technology Data Exchange (ETDEWEB)

    Schiros, T.; Takahashi, O.; Andersson, K.J.; Ostrom, H.; Pettersson, L.G.M.; Nilsson, A.; Ogasawara, H.; /SLAC

    2012-04-18

    We address how the electronic and geometric structures of metal surfaces determine water-metal bonding by affecting the balance between Pauli repulsion and electrostatic attraction. We show how the rigid d-electrons and the softer s-electrons utilize different mechanisms for the redistribution of charge that enables surface wetting. On open d-shell Pt(111), the ligand field of water alters the distribution of metal d-electrons to reduce the repulsion. The closed-shell Cu d{sup 10} configuration of isostructural Cu(111), however, does not afford this mechanism, resulting in a hydrophobic surface and three-dimensional ice cluster formation. On the geometrically corrugated Cu(110) surface, however, charge depletion involving the mobile sp-electrons at atomic rows reduces the exchange repulsion sufficiently such that formation of a two-dimensional wetting layer is still favored in spite of the d{sup 10} electronic configuration.

  2. Biotic, temporal and spatial variability of tritium concentrations in transpirate samples collected in the vicinity of a near-surface low-level nuclear waste disposal site and nearby research reactor.

    Science.gov (United States)

    Twining, J R; Hughes, C E; Harrison, J J; Hankin, S; Crawford, J; Johansen, M; Dyer, L

    2011-06-01

    The results of a 21 month sampling program measuring tritium in tree transpirate with respect to local sources are reported. The aim was to assess the potential of tree transpirate to indicate the presence of sub-surface seepage plumes. Transpirate gathered from trees near low-level nuclear waste disposal trenches contained activity concentrations of (3)H that were significantly higher (up to ∼700 Bq L(-1)) than local background levels (0-10 Bq L(-1)). The effects of the waste source declined rapidly with distance to be at background levels within 10s of metres. A research reactor 1.6 km south of the site contributed significant (p nuclear waste site.

  3. Vicinal light inspection of translucent materials

    Science.gov (United States)

    Burns, Geroge R.; Yang, Pin

    2010-01-19

    The present invention includes methods and apparatus for inspecting vicinally illuminated non-patterned areas of translucent materials. An initial image of the material is received. A second image is received following a relative translation between the material being inspected and a device generating the images. Each vicinally illuminated image includes a portion having optimal illumination, that can be extracted and stored in a composite image of the non-patterned area. The composite image includes aligned portions of the extracted image portions, and provides a composite having optimal illumination over a non-patterned area of the material to be inspected. The composite image can be processed by enhancement and object detection algorithms, to determine the presence of, and characterize any inhomogeneities present in the material.

  4. Quantifying Mapping Orbit Performance in the Vicinity of Primitive Bodies

    Science.gov (United States)

    Pavlak, Thomas A.; Broschart, Stephen B.; Lantoine, Gregory

    2015-01-01

    Predicting and quantifying the capability of mapping orbits in the vicinity of primitive bodies is challenging given the complex orbit geometries that exist and the irregular shape of the bodies themselves. This paper employs various quantitative metrics to characterize the performance and relative effectiveness of various types of mapping orbits including terminator, quasi-terminator, hovering, pingpong, and conic-like trajectories. Metrics of interest include surface area coverage, lighting conditions, and the variety of viewing angles achieved. The metrics discussed in this investigation are intended to enable mission designers and project stakeholders to better characterize candidate mapping orbits during preliminary mission formulation activities.The goal of this investigation is to understand the trade space associated with carrying out remotesensing campaigns at small primitive bodies in the context of a robotic space mission. Specifically,this study seeks to understand the surface viewing geometries, ranges, etc. that are available fromseveral commonly proposed mapping orbits architectures.

  5. Surfactant-modified diffusion on transition-metal surfaces (reprinted with the addition of the appendices)

    Energy Technology Data Exchange (ETDEWEB)

    FEIBELMAN,PETER J.; KELLOGG,GARY LEE

    2000-03-01

    Wanting to convert surface impurities from a nuisance to a systematically applicable nano-fabrication tool, the authors have sought to understand how such impurities affect self-diffusion on transition-metal surfaces. Their field-ion microscope experiments reveal that in the presence of surface hydrogen, self-diffusion on Rh(100) is promoted, while on Pt(100), not only is it inhibited, but its mechanism changes. First-principles calculations aimed at learning how oxygen fosters perfect layerwise growth on a growing Pt(111) crystal contradict the idea in the literature that it does so by directly promoting transport over Pt island boundaries. The discovery that its real effect is to burn off adventitious adsorbed carbon monoxide demonstrates the predictive value of state-of-the-art calculation methods.

  6. Neurobiochemical changes in the vicinity of a nanostructured neural implant

    Science.gov (United States)

    Bérces, Zsófia; Tóth, Kinga; Márton, Gergely; Pál, Ildikó; Kováts-Megyesi, Bálint; Fekete, Zoltán; Ulbert, István; Pongrácz, Anita

    2016-01-01

    Neural interface technologies including recording and stimulation electrodes are currently in the early phase of clinical trials aiming to help patients with spinal cord injuries, degenerative disorders, strokes interrupting descending motor pathways, or limb amputations. Their lifetime is of key importance; however, it is limited by the foreign body response of the tissue causing the loss of neurons and a reactive astrogliosis around the implant surface. Improving the biocompatibility of implant surfaces, especially promoting neuronal attachment and regeneration is therefore essential. In our work, bioactive properties of implanted black polySi nanostructured surfaces (520–800 nm long nanopillars with a diameter of 150–200 nm) were investigated and compared to microstructured Si surfaces in eight-week-long in vivo experiments. Glial encapsulation and local neuronal cell loss were characterised using GFAP and NeuN immunostaining respectively, followed by systematic image analysis. Regarding the severity of gliosis, no significant difference was observed in the vicinity of the different implant surfaces, however, the number of surviving neurons close to the nanostructured surface was higher than that of the microstructured ones. Our results imply that the functionality of implanted microelectrodes covered by Si nanopillars may lead to improved long-term recordings. PMID:27775024

  7. Neurobiochemical changes in the vicinity of a nanostructured neural implant

    Science.gov (United States)

    Bérces, Zsófia; Tóth, Kinga; Márton, Gergely; Pál, Ildikó; Kováts-Megyesi, Bálint; Fekete, Zoltán; Ulbert, István; Pongrácz, Anita

    2016-10-01

    Neural interface technologies including recording and stimulation electrodes are currently in the early phase of clinical trials aiming to help patients with spinal cord injuries, degenerative disorders, strokes interrupting descending motor pathways, or limb amputations. Their lifetime is of key importance; however, it is limited by the foreign body response of the tissue causing the loss of neurons and a reactive astrogliosis around the implant surface. Improving the biocompatibility of implant surfaces, especially promoting neuronal attachment and regeneration is therefore essential. In our work, bioactive properties of implanted black polySi nanostructured surfaces (520–800 nm long nanopillars with a diameter of 150–200 nm) were investigated and compared to microstructured Si surfaces in eight-week-long in vivo experiments. Glial encapsulation and local neuronal cell loss were characterised using GFAP and NeuN immunostaining respectively, followed by systematic image analysis. Regarding the severity of gliosis, no significant difference was observed in the vicinity of the different implant surfaces, however, the number of surviving neurons close to the nanostructured surface was higher than that of the microstructured ones. Our results imply that the functionality of implanted microelectrodes covered by Si nanopillars may lead to improved long-term recordings.

  8. Influence of vicinal sapphire substrate on the properties of N-polar GaN films grown by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Zhiyu; Zhang, Jincheng, E-mail: jchzhang@xidian.edu.cn; Xu, Shengrui; Chen, Zhibin; Yang, Shuangyong; Tian, Kun; Hao, Yue [Key Lab of Wide Band-Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi' an, Shaanxi 710071 (China); Su, Xujun [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215123 (China); Shi, Xuefang [School of Advanced Materials and Nanotechnology, Xidian University, Xi' an, Shaanxi 710071 (China)

    2014-08-25

    The influence of vicinal sapphire substrates on the growth of N-polar GaN films by metal-organic chemical vapor deposition is investigated. Smooth GaN films without hexagonal surface feature are obtained on vicinal substrate. Transmission electron microscope results reveal that basal-plane stacking faults are formed in GaN on vicinal substrate, leading to a reduction in threading dislocation density. Furthermore, it has been found that there is a weaker yellow luminescence in GaN on vicinal substrate than that on (0001) substrate, which might be explained by the different trends of the carbon impurity incorporation.

  9. Surface vacancy channels through ion channeling

    Energy Technology Data Exchange (ETDEWEB)

    Redinger, Alex; Standop, Sebastian; Michely, Thomas [II. Physikalisches Institut, Universitaet Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany); Rosandi, Yudi; Urbassek, Herbert M. [Fachbereich Physik, Technische Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse, D-67663 Kaiserslautern (Germany)

    2009-07-01

    Damage patterns of single ion impacts on Pt(111) have been studied by scanning tunneling microscopy (STM) and molecular dynamics simulations (MD). Low temperature experiments, where surface diffusion is absent, have been performed for argon and xenon ions with energies between 1 keV and 15 keV at an angle of incidence of 86 {sup circle} measured with respect to the surface normal. Ions hitting preexisting illuminated step edges penetrate into the crystal and are guided in open crystallographic directions, one or more layers underneath the surface (subsurface channeling). In the case of argon channeling the resulting surface damage consists of adatom and vacancy pairs aligned in ion beam direction. After xenon channeling thin surface vacancy trenches along the ion trajectories - surface vacancy channels - are observed. They result from very efficient sputtering and adatom production along the ion trajectory. This phenomena is well reproduced in molecular dynamics simulations of single ion impacts at 0 K. The damage patterns of Argon and Xenon impacts can be traced back to the different energy losses of the particles in the channel. Channeling distances exceeding 1000 A for 15 keV xenon impacts are observed.

  10. Study of GRBs Hosts Galaxies Vicinity Properties

    Science.gov (United States)

    Bernal, S.; Vasquez, N.; Hoyle, F.

    2017-07-01

    The study of GRBs host galaxies and its vicinity could provide constrains on the progenitor and an opportunity to use these violent explosions to characterize the nature of the highredshift universe. Studies of GRB host galaxies reveal a population of starforming galaxies with great diversity, spanning a wide range of masses, star formation rate, and redshifts. In order to study the galactic ambient of GRBs we used the S. Savaglio catalog from 2015 where 245 GRBs are listed with RA-Dec position and z. We choose 22 GRBs Hosts galaxies from Savaglio catalog and SDSS DR12, with z range 0work we provide characteristics on the regions for future works related with highredsift universe that using the GRBs.

  11. Undergraduate Laboratory for Surface Science

    Science.gov (United States)

    Okumura, Mitchio; Beauchamp, Jesse L.; Dickert, Jeffrey M.; Essy, Blair R.; Claypool, Christopher L.

    1996-02-01

    Surface science has developed into a multidisciplinary field of research with applications ranging from heterogeneous catalysis to semiconductor etching (1). Aspects of surface chemistry are now included in physical chemistry textbooks (2) and undergraduate curricula (3), but the perceived cost and complexity of equipment has deterred the introduction of surface science methods in undergraduate laboratories (4). Efforts to expose chemistry undergraduates to state-of-the-art surface instrumentation have just begun (5). To provide our undergraduates with hands-on experience in using standard techniques for characterizing surface morphology, adsorbates, kinetics, and reaction mechanisms, we have developed a set of surface science experiments for our physical chemistry laboratory sequence. The centerpiece of the laboratory is an ultrahigh vacuum (UHV) chamber for studies of single crystal surfaces. This instrument, shown in the figure, has surface analysis capabilities including low energy electron diffraction (LEED), Auger spectroscopy, and temperature-programmed desorption (TPD). The laboratory exercises involve experiments on the well-studied Pt(111) surface. Students prepare a previously mounted single crystal sample by sputtering it with an argon ion gun and heating it under O2. Electron diffraction patterns from the cleaned surface are then obtained with a reverse view LEED apparatus (Princeton Instruments). Images are captured by a charge-coupled device (CCD) camera interfaced to a personal computer for easy downloading and subsequent analysis. Although the LEED images from a Pt(111) surface can be readily interpreted using simple diffraction arguments, this lab provides an excellent context for introducing Miller indices and reciprocal lattices (6). The surface chemical composition can be investigated by Auger spectroscopy, using the LEED apparatus as a simple energy analyzer. The temperature programmed desorption experiment, which is nearly complete, will be

  12. Effect of van der Waals interactions on the chemisorption and physisorption of phenol and phenoxy on metal surfaces

    Science.gov (United States)

    Peköz, Rengin; Donadio, Davide

    2016-09-01

    The adsorption of phenol and phenoxy on the (111) surface of Au and Pt has been investigated by density functional theory calculations with the conventional PBE functional and three different non-local van der Waals (vdW) exchange and correlation functionals. It is found that both phenol and phenoxy on Au(111) are physisorbed. In contrast, phenol on Pt(111) presents an adsorption energy profile with a stable chemisorption state and a weakly metastable physisorbed precursor. While the use of vdW functionals is essential to determine the correct binding energy of both chemisorption and physisorption states, the relative stability and existence of an energy barrier between them depend on the semi-local approximations in the functionals. The first dissociation mechanism of phenol, yielding phenoxy and atomic hydrogen, has been also investigated, and the reaction and activation energies of the resulting phenoxy on the flat surfaces of Au and Pt were discussed.

  13. Formation of the BiAg2 surface alloy on lattice-mismatched interfaces

    Science.gov (United States)

    Abd El-Fattah, Z. M.; Lutz, P.; Piquero-Zulaica, I.; Lobo-Checa, J.; Schiller, F.; Bentmann, H.; Ortega, J. E.; Reinert, F.

    2016-10-01

    We report on the growth of a monolayer-thick BiAg2 surface alloy on thin Ag films grown on Pt(111) and Cu(111). Using low energy electron diffraction (LEED), angle resolved photoemission spectroscopy (ARPES), and scanning tunneling microscopy (STM) we show that the surface structure of the 1/3 ML Bi/x -ML Ag/Pt(111) system (x ≥2 ) is strongly affected by the annealing temperature required to form the alloy. As judged from the characteristic (√{3 }×√{3 } )R 30∘ LEED pattern, the BiAg2 alloy is partially formed at room temperature. A gentle, gradual increase in the annealing temperatures successively results in the formation of a pure BiAg2 phase, a combination of that phase with a (2 ×2 ) superstructure, and finally the pure (2 ×2 ) phase, which persists at higher annealing temperatures. These results complement recent work reporting the (2 ×2 ) as a predominant phase, and attributing the absence of BiAg2 alloy to the strained Ag/Pt interface. Likewise, we show that the growth of the BiAg2 alloy on similarly lattice-mismatched 1 and 2 ML Ag-Cu(111) interfaces also requires a low annealing temperature, whilst higher temperatures result in BiAg2 clustering and the formation of a BiCu2 alloy. The demonstration that the BiAg2 alloy can be formed on thin Ag films on different substrates presenting a strained interface has the prospect of serving as bases for technologically relevant systems, such as Rashba alloys interfaced with magnetic and semiconductor substrates.

  14. Stereoselective microbial dehalorespiration with vicinal dichlorinated alkanes.

    Science.gov (United States)

    De Wildeman, Stefaan; Diekert, Gabriele; Van Langenhove, Herman; Verstraete, Willy

    2003-09-01

    The suspected carcinogen 1,2-dichloroethane (1,2-DCA) is the most abundant chlorinated C(2) groundwater pollutant on earth. However, a reductive in situ detoxification technology for this compound does not exist. Although anaerobic dehalorespiring bacteria are known to catalyze several dechlorination steps in the reductive-degradation pathway of chlorinated ethenes and ethanes, no appropriate isolates that selectively and metabolically convert them into completely dechlorinated end products in defined growth media have been reported. Here we report on the isolation of Desulfitobacterium dichloroeliminans strain DCA1, a nutritionally defined anaerobic dehalorespiring bacterium that selectively converts 1,2-dichloroethane and all possible vicinal dichloropropanes and -butanes into completely dechlorinated end products. Menaquinone was identified as an essential cofactor for growth of strain DCA1 in pure culture. Strain DCA1 converts chiral chlorosubstrates, revealing the presence of a stereoselective dehalogenase that exclusively catalyzes an energy-conserving anti mechanistic dichloroelimination. Unlike any known dehalorespiring isolate, strain DCA1 does not carry out reductive hydrogenolysis reactions but rather exclusively dichloroeliminates its substrates. This unique dehalorespiratory biochemistry has shown promising application possibilities for bioremediation purposes and fine-chemical synthesis.

  15. Toroidal surfaces compared with spherocylindrical surfaces

    Science.gov (United States)

    Malacara-Doblado, Daniel; Malacara-Hernandez, Daniel; Garcia-Marquez, Jorge L.

    1995-08-01

    Toroidal and sphero-cylindrical optical surfaces are two different kinds of surfaces (Menchaca and Malacara, 1986), but they are almost identical in the vicinity of the optical axis. The separation between these two surfaces increases when the distance to the optical axis increases. In this work the separation between these two surfaces outside of the central region is analytically studied.

  16. The flow gradients in the vicinity of a shock wave for a thermodynamically imperfect gas

    Science.gov (United States)

    Uskov, V. N.; Mostovykh, P. S.

    2016-11-01

    Supersonic rotational planar and axisymmetric flows of a non-viscous, non-heat-conductive gas with arbitrary thermodynamic properties in the vicinity of a steady shock wave are studied. The differential equations describing the gas flow upstream and downstream of the discontinuity surface and the dynamic compatibility conditions at this discontinuity are used. The gas flow non-uniformity in the shock vicinity is described by the spatial derivatives of the gasdynamic parameters at a point on the shock surface. The parameters are the gas pressure, density, and velocity vector. The derivatives with respect to the directions of the streamline and normal to it, and of the shock surface and normal to it, are considered. Spatial derivatives of all gasdynamic parameters are expressed through the flow non-isobaric factor along the streamline, the streamline curvature, and the flow vorticity and non-isoenthalpy factors. An algorithm for determining these factors of the gas flow downstream of a shock wave is developed. Example calculations of these factors for imperfect oxygen and thermodynamically perfect gas are presented. The influence coefficients of the upstream flow factors on the downstream flow factors are calculated. The gas flow in the vicinity of the shock is described by the isolines of gasdynamic parameters. Uniform planar and axisymmetric flows at different distances from the axis of symmetry are examined; the isobars, isopycnics, isotachs and isoclines are used to characterize the downstream flow behind a curved shock in an imperfect gas.

  17. Desorption Kinetics of Ar, Kr, Xe, N2, O2, CO, Methane, Ethane, and Propane from Graphene and Amorphous Solid Water Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Smith, R. Scott; May, Robert A.; Kay, Bruce D.

    2016-03-03

    The desorption kinetics for Ar, Kr, Xe, N2, O2, CO, methane, ethane, and propane from grapheme covered Pt(111) and amorphous solid water (ASW) surfaces are investigated using temperature programmed desorption (TPD). The TPD spectra for all of the adsorbates from graphene have well-resolved first, second, third, and multi- layer desorption peaks. The alignment of the leading edges is consistent the zero-order desorption for all of the adsorbates. An Arrhenius analysis is used to obtain desorption energies and prefactors for desorption from graphene for all of the adsorbates. In contrast, the leading desorption edges for the adsorbates from ASW do not align (for coverages < 2 ML). The non-alignment of TPD leading edges suggests that there are multiple desorption binding sites on the ASW surface. Inversion analysis is used to obtain the coverage dependent desorption energies and prefactors for desorption from ASW for all of the adsorbates.

  18. Aerial survey of sea otters in the Cordova vicinity

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The movement of significantly large numbers of sea otters into the Cordova vicinity has generated a local storm of protest concerning the ability of sea otters to...

  19. Faults--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the faults for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included in...

  20. Faults--Drakes Bay and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data of faults for the geologic and geomorphologic map of the Drakes Bay and Vicinity map area, California. The vector data file is...

  1. Faults--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the faults for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included in...

  2. Folds--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the folds for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included in...

  3. Folds--Drakes Bay and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data of folds for the geologic and geomorphologic map of the Drakes Bay and Vicinity map area, California. The vector data file is...

  4. Paleoshorelines--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the paleoshorelines for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is...

  5. Backscatter A [8101]--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity map area, California. Backscatter data are provided as separate grids...

  6. BackscatterC [7125]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  7. Lexical consciousness-raising in the vicinity of target vocabulary

    Directory of Open Access Journals (Sweden)

    Hadi, Farjami

    2013-01-01

    Full Text Available This study compared the effectiveness of three techniques for teaching English vocabulary to Persian native speakers: a traditional procedure, the classical cloze procedure, and an innovative procedure, which is dubbed here as vicinity technique, based on incidental learning, noticing and consciousness-raising. To do the comparison, 51 students, registered at a private language institute, were randomly assigned to three groups and were taught 40 vocabulary items in five sessions in the three procedures. To evaluate the vocabulary gain in the three conditions, immediate and delayed post-tests were administered and the obtained data were analyzed using ANOVA. The results revealed that the vicinity technique was more effective than the traditional procedure; both in immediate and delayed evaluations. It was also revealed that, although there was no significant difference between the vicinity technique and the classical cloze technique in short-term, the vicinity technique was more effective than the classical cloze one for long-term retention.

  8. Folds--Drakes Bay and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data of folds for the geologic and geomorphologic map of the Drakes Bay and Vicinity map area, California. The vector data file is...

  9. Faults--Drakes Bay and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data of faults for the geologic and geomorphologic map of the Drakes Bay and Vicinity map area, California. The vector data file is...

  10. Backscatter B [Swath]--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity map area, California. Backscatter data are provided as separate grids...

  11. Paleoshorelines--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the paleoshorelines for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is...

  12. BackscatterB [EM300]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  13. Faults--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the faults for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included...

  14. Folds--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the folds for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included in...

  15. Backscatter C [7125]--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity map area, California. Backscatter data are provided as separate grids...

  16. BackscatterC [7125]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  17. BackscatterB [EM300]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  18. Backscatter A [8101]--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity map area, California. Backscatter data are provided as separate grids...

  19. Backscatter C [7125]--Drakes Bay and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Drakes bay and Vicinity map area, California. Backscatter data are provided as separate grids...

  20. MAJOR OIL PLAYS IN UTAH AND VICINITY

    Energy Technology Data Exchange (ETDEWEB)

    Thomas C. Chidsey; Craig D. Morgan; Kevin McClure; Grant C. Willis

    2003-09-01

    Arizona. Outcrop analogs are found in the stratigraphically equivalent Navajo Sandstone of southern Utah which displays large-scale dunal cross-strata with excellent reservoir properties and interdunal features such as oases, wadi, and playa lithofacies with poor reservoir properties. Hydrocarbons in the Paradox Formation are stratigraphically trapped in carbonate buildups (or phylloid-algal mounds). Similar carbonate buildups are exposed in the Paradox along the San Juan River of southeastern Utah. Reservoir-quality porosity may develop in the types of facies associated with buildups such as troughs, detrital wedges, and fans, identified from these outcrops. When combined with subsurface geological and production data, these outcrop analogs can improve (1) development drilling and production strategies such as horizontal drilling, (2) reservoir-simulation models, (3) reserve calculations, and (4) design and implementation of secondary/tertiary oil recovery programs and other best practices used in the oil fields of Utah and vicinity. During this quarter, technology transfer activities consisted of exhibiting the project plans, objectives, and products at a booth at the 2003 annual convention of the American Association of Petroleum Geologists. The project home page was updated on the Utah Geological Survey Internet web site.

  1. Theoretical investigation of water formation on Rh and Pt Surfaces

    Science.gov (United States)

    Wilke, Steffen; Natoli, Vincent; Cohen, Morrel H.

    2000-06-01

    Catalytic water formation from adsorbed H and O adatoms is a fundamental reaction step in a variety of technologically important reactions involving organic molecules. In particular, the water-formation rate determines the selectivity of the catalytic partial oxidation of methane to syngas. In this report we present a theoretical investigation of the potential-energy diagram for water formation from adsorbed O and H species on Rh(111) and Pt(111) surfaces. The study is based on accurate first-principles calculations applying density-functional theory. Our results are compared to the potential-energy diagram for this reaction inferred from experimental data by Hickman and Schmidt [AIChE. J. 39, 1164 (1993)]. The calculations essentially reproduce the scheme of Hickman and Schmidt for water formation on Rh(111) with the important difference that the OH molecule is significantly more stable than assumed by Hickman and Schmidt. On Pt(111) surfaces, however, the calculations predict a barrier to OH formation very similar to that found on Rh(111). In particular, the calculated barrier to OH formation of about 20 kcal/mol seems to contradict the small 2.5 kcal/mol barrier assumed in the Hickman-Schmidt scheme and the observed large rate of water formation on Pt. A possible explanation for the apparent discrepancy between the large calculated barrier for OH formation on Pt and the experimentally observed rapid formation of water even at low temperatures is that the active sites for water formation on Pt are at "defect" sites and not on the ideally flat terraces. A similar conclusion has been reached by Verheij and co-workers [Surf. Sci. 371, 100 (1997); Chem. Phys. Lett. 174, 449 (1990); Surf. Sci. 272, 276 (1991)], who did detailed experimental work on water formation on Pt surfaces. Analyzing our results, we develop an explicit picture of the interaction processes governing the formation of OH groups. This picture rationalizes the calculated weak dependence of OH

  2. Kinetics and mechanism of the oxidation of some vicinal and non-vicinal diols by tetrabutylammonium tribromide

    Indian Academy of Sciences (India)

    Jaya Gosain; Pradeep K Sharma

    2003-04-01

    Kinetics of oxidation of five vicinal and four non-vicinal diols, and two of their monoethers, by tetrabutylammonium tribromide (TBATB) has been studied. The vicinal diols yield products arising out of glycol-bond fission, while the non-vicinal diols produce the hydroxycarbonyl compounds. The reaction is first-order with respect to TBATB. Michaelis-Menten type kinetics is observed with respect to diols. The reaction fails to induce the polymerization of acrylonitrile. There is no effect of tetrabutylammonium chloride on the reaction rate. The proposed reactive oxidizing species is the tribromide ion. The effect of solvent composition indicates that the rate increases with increase in the polarity of the solvent. The oxidation of [1,1,2,2-2H4] ethanediol shows the absence of any primary kinetic isotope effect. Values of solvent isotope effect, (H2O)/(D2O), at 288 K for the oxidation of ethanediol, propane-1,3-diol and 3-methoxybutan-1-ol are 3.41, 0.98 and 1.02 respectively. A mechanism involving a glycol-bond fission has been proposed for the oxidation of vicinal diols. Non-vicinal diols are oxidised by a hydride-transfer mechanism, as they are monohydric alcohols.

  3. Major Oil Plays in Utah and Vicinity

    Energy Technology Data Exchange (ETDEWEB)

    Thomas C. Chidsey; Craig D. Morgan; Kevin McClure; Douglas A. Sprinkel; Roger L. Bon; Hellmut H. Doelling

    2003-12-31

    fractured and sealed by overlying argillaceous and non-fractured units. The best outcrop analogs for Twin Creek reservoirs are found at Devils Slide and near the town of Peoa, Utah, where fractures in dense, homogeneous non-porous limestone beds are in contact with the basal siltstone units (containing sealed fractures) of the overlying units. The shallow marine, Mississippian Leadville Limestone is a major oil and gas reservoir in the Paradox Basin of Utah and Colorado. Hydrocarbons are produced from basement-involved, northwest-trending structural traps with closure on both anticlines and faults. Excellent outcrops of Leadville-equivalent rocks are found along the south flank of the Uinta Mountains, Utah. For example, like the Leadville, the Mississippian Madison Limestone contains zones of solution breccia, fractures, and facies variations. When combined with subsurface geological and production data, these outcrop analogs can improve (1) development drilling and production strategies such as horizontal drilling, (2) reservoir-simulation models, (3) reserve calculations, and (4) design and implementation of secondary/tertiary oil recovery programs and other best practices used in the oil fields of Utah and vicinity. In the southern Green River Formation play of the Uinta Basin, optimal drilling, development, and production practices consist of: (1) owning drilling rigs and frac holding tanks; (2) perforating sandstone beds with more than 8 percent neutron porosity and stimulate with separate fracture treatments; (3) placing completed wells on primary production using artificial lift; (4) converting wells relatively soon to secondary waterflooding maintaining reservoir pressure above the bubble point to maximize oil recovery; (5) developing waterflood units using an alternating injector--producer pattern on 40-acre (16-ha) spacing; and (6) recompleting producing wells by perforating all beds that are productive in the waterflood unit. As part of technology transfer

  4. NO2 uptake under practically relevant conditions on BaO/Pt(111)

    Energy Technology Data Exchange (ETDEWEB)

    Mudiyanselage, Kumudu; Szanyi, János

    2012-02-01

    The formation of nitrites and nitrates (Ba(NOx)2) under practically relevant conditions (PNO2 up to 1.0 Torr and T = 500 K) and their thermal decomposition on BaO (>20 monolayer equivalent (MLE))/Pt(1 1 1) were studied using temperature programmed desorption (TPD), infrared reflection absorption (IRA), and Xray photoelectron (XP) spectroscopies. The exposure of BaO to 1.0 × 10-8 Torr NO2 at 500 K leads to the formation of a Ba(NOx)2 layer with small, disordered crystalline nitrate clusters. Under these conditions (PNO2 = 1.0 × 10-8 Torr and T = 500 K) only the top portion of the BaO layer converts to Ba(NOx)2 and the nitrites in this Ba(NOx)2 layer stay without converting completely to nitrates even after 100 min of NO2 exposure. In the thermal decomposition of Ba(NOx)2, first nitrites decompose, releasing NO and then the decomposition of nitrates occurs via two pathways releasing NO2 and NO + O2. At 500 K and PNO2 ≥ 1.0 × 10-7 Torr, first NO2 reacts with BaO to form small disordered crystalline Ba(NO3)2 particles and then these particles agglomerate to form large, well-ordered (bulk-like) crystalline nitrates as the NO2 exposure increases. The thermal decomposition of these well-ordered, bulk-like crystalline nitrate aggregates occurs in two steps releasing NO2 and NO + O2 in each step in two different temperature regions. NO2 pressure ≥1.0 × 10-5 Torr is required for the complete oxidation of initially formed nitrites to nitrates and the full nitration of the BaO layer at 500 K sample temperature. We gratefully acknowledge the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle Memorial Institute under contract number DE-AC05-76RL01830.

  5. Formate stability and carbonate hydrogenation on strained Cu overlayers on Pt(111)

    DEFF Research Database (Denmark)

    Schumacher, Nana Maria Pii; Andersson, Klas Jerker; Nerlov, Jesper

    2008-01-01

    to previous results obtained for supported, and lattice-strained, Cu nanoparticles. The hydrogenation of carbonate produced by 0.3 bar CO2 exposure at room temperature was monitored with XPS and TPD showing a significant loss of carbonate when subjected to 0.2 bar H2 at room temperature. However, the presence...

  6. Reaction dynamics of small molecules at metal surfaces

    CERN Document Server

    Samson, P A

    1999-01-01

    directed angular distributions suggest the influence of a trapping mechanism, recombining molecules scattering through a molecularly adsorbed state, with a transition state of large d sub N sub N responsible for the product vibrational excitation. Although N sub 2 dissociation on Fe(100) forms a simple overlayer structure, on Fe(110), molecular chemisorption does not occur at or above room temperature and the sticking is extremely small (approx 10 sup - sup 6 to 10 sup - sup 7). Activated nitrogen bombardment can be used to prepare a 'surface nitride' with a structure related to the geometry of bulk Fe sub 4 N. Scanning tunnelling microscopy yields atomic scale features that cannot be explained by simple overlayers. It is proposed that the uppermost iron layer reconstructs to generate quasi-octahedral sites between the top two layers, with sub-surface nitrogen in these sites forming a model for the 'surface nitride' structure. The dissociation-desorption dynamics of D sub 2 upon the Sn/Pt(111) surface alloy a...

  7. Anomalous state of a 2DEG in vicinal Si MOSFET in high magnetic fields

    OpenAIRE

    Kvon, Z. D.; Proskuryakov, Y. Y.; Savchenko, A. K.

    2003-01-01

    We report the observation of an anomalous state of a 2D electron gas near a vicinal surface of a silicon MOSFET in high magnetic fields. It is characterised by unusual behaviour of the conductivities $\\sigma_{xx}$ and $\\sigma_{xy}$, which can be described as a collapse of the Zeeman spin splitting accompanied by a large peak in $\\sigma_{xx}$ and an anomalous peak in $ \\sigma_{xy}$. It occurs at densities corresponding to the position of the Fermi level above the onset of the superlattice mini...

  8. Comments on "the cause of crustal deformation in the vicinity of Zhangbei earthquake area"

    Institute of Scientific and Technical Information of China (English)

    WANG Chao; ZHANG Hong; SHAN Xinjian

    2004-01-01

    @@ In the comments "the cause of crustal deformation in the vicinity of Zhangbei earthquake area" (hereafter referred to as "Cause"), the authors propose a new seismic focal mechanism of Zhangbei-Shangyi earthquake occurring on Jan. 10, 1998, which opposes our D-InSAR model[1,2]. They assume that the displacement measured by D-InSAR is not the surface representation of seismic fault movement at the northwestern terminus of the Zhangjiakou-Penglai fault zone, but resulted from volcano activation caused by the movement of thermal matter beneath the displacement field. However, this assumption requires concrete evidence and further research.

  9. Surface Chemistry of Aromatic Reactants on Pt- and Mo-Modified Pt Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, Allison M.; Mark, Lesli; Rasmussen, Mathew J.; Hensley, Jesse E.; Medlin, J. Will

    2016-11-01

    Supported catalysts containing an oxophilic metal such as Mo and a noble metal such as Pt have shown promising activity and selectivity for deoxygenation of biomass-derived compounds. Here, we report that PtMo catalysts also promote hydrogenolysis of the model compound benzyl alcohol, while decarbonylation is most prevalent over unmodified Pt. A combination of single crystal surface science studies, density functional theory (DFT) calculations, and vapor phase upgrading experiments using supported catalysts was carried out to better understand the mechanism by which Mo promotes deoxygenation. Molybdenum was deposited in submonolayer quantities on a Pt(111) surface and reduced at high temperature. Temperature-programmed desorption (TPD) experiments using benzyl alcohol as a reactant showed greatly enhanced yields of the deoxygenation product toluene at moderate Mo coverages. To understand how the interaction of the aromatic group with the surface influenced this reactivity, we investigated the adsorption of toluene as a probe molecule. We found that the addition of Mo to Pt(111) resulted in a significant decrease in toluene decomposition. DFT calculations indicated that this decrease was consistent with decreased aromatic adsorption strengths that accompany incorporation of Mo into the Pt subsurface. The weaker aromatic-surface interaction on Pt/Mo surfaces led to a tilted adsorption geometry for benzyl alcohol, which presumably promotes hydrogenolysis to produce toluene instead of decarbonylation to produce benzene and CO. Alumina-supported Pt and PtMo catalysts were also tested for benzyl alcohol deoxygenation. PtMo catalysts had a higher rate of toluene production and lower rates of benzene and benzaldehyde production. Additionally, when benzaldehyde was used as the reactant to measure decarbonylation activity the mass-normalized rate of benzene production was 2.5 times higher on Pt than PtMo. Overall, the results of TPD, DFT, and supported catalyst experiments

  10. Decomposition and reduction of NO on transition metal surfaces: bond order conservation Morse potential analysis

    Science.gov (United States)

    Shustorovich, Evgeny; Bell, Alexis T.

    1993-05-01

    Periodic trends in the decomposition of NO and its reduction to N 2 and NH 3 by CO and H 2 on transition metal surfaces have been analyzed theoretically using the bond order conservation Morse potential (BOCMP) method. The analysis is based on calculations of the energetics, the reaction enthalpies ΔH and activation barriers ΔH ∗, of elementary steps thought to comprise the mechanisms of the NO transformations. As the periodic series, the close-packed surfaces Pt(111), Rh(111), Ru(001), and Re(001) were chosen. The calculated heats of chemisorption Q of NH 3, NH 2, NH, NO, H 2O and OH are in good agreement with experiment. The activation barriers for dissociation of NO from a chemisorbed state, ΔE NOs∗ were found to decrease in the order Pt > Rh > Ru > Re. For reasonable values of QN and QO, in the zero-coverage extreme these activation barriers were calculated to be much smaller than the relevant heats of chemisorption QNO, so that dissociation of No upon heating is projected for all the surfaces studied with the possible exception of Pt(111). The presence of adsorbed N S and O S atoms may dramatically increase the values of ΔE NOS∗, for example, from 7-9 to 24-27 kcal/mol for Rh(100) and Rh(100)c(2 × 2)O,N, respectively. This sensitiv the values of ΔE NOs∗ to NO S coverage may explain the diversity of experimental results obtained for different coverages (exposu and temperatures even for the same single crystal face. The anisotropy of the values of QX(X = NO, N, O) for different surfaces and possible reconstructions of these surfaces also contribute to the balance between dissociation and desorption of NO. Of the two channels for recombinative desorption of N 2, 2N S→ N 2,g and N S + NO S→ N 2,g + O S, the latter has the smaller activati barrier. Because the N 2 formation barriers rapidly increase in the order Pt ˜ Rh ≪ Ru ≪ Re, Rh or Rh-Pt surfaces are projected to be the most efficient catalysts for NO reduction by CO (to N 2 and CO 2

  11. Classical stochastic theory for the sticking probability of atoms scattered on surfaces.

    Science.gov (United States)

    Pollak, Eli

    2011-06-30

    A stochastic theory is formulated for the sticking probability of a projectile scattered from a surface. The theory is then explored by applying it to a generalized Langevin equation model of the scattering dynamics. The theory succeeds in describing the known features of trapping on surfaces. At low energies sticking will occur only if there is an attractive interaction between the projectile and the surface. The probability of sticking at low energies is greater the lower the temperature and the deeper the attractive well of the particle as it approaches the surface. The sticking probability in the absence of horizontal friction tends to be lower as the stiffness of the surface increases. However, in the presence of horizontal friction, increased stiffness may lead to an increase in the sticking coefficient. A cos(2)(θ(i)) scaling is found only in the absence of corrugation and horizontal friction. The theory is then applied successfully to describe experimentally measured sticking probabilities for the scattering of Xe on a Pt(111) surface.

  12. Laboratory modelling of resonant wave-current interaction in the vicinity wind farm masts

    Science.gov (United States)

    Gunnoo, Hans; Abcha, Nizar; Garcia-Hermosa, Maria-Isabel; Ezersky, Alexander

    2015-04-01

    In the nearest future, by 2020, about 4% of electricity in Europe will be supplied by sea stations operating from renewable sources: ocean thermal energy, wave and tidal energy, wind farms. By now the wind stations located in the coastal zone, provide the most part of electricity in different European countries. Meanwhile, effects of wind farms on the environment are not sufficiently studied. We report results of laboratory simulations aimed at investigation of hydrodynamic fields arising in the vicinity of wind farm masts under the action of currents and surface waves. The main attention is paid to modeling the resonance effects when the amplitude of velocity pulsations in the vicinity of the masts under the joint action of currents and harmonic waves demonstrate significant growth. This resonance can lead to an increase in Reynolds stress on the bottom, intensification of sediment transport and sound generation. The experiments are performed in the 17 meters hydrodynamical channel of laboratory Morphodynamique Continentale et Côtière UMR CNRS 6143. Mast are modeled by vertical cylinder placed in a steady flow. Behind the cylinder turbulent Karman vortex street occurs. Results are obtained in interval of Reynolds numbers Re=103 - 104(Re=Ud/v, where U is the velocity of the flow, d is diameter of the cylinder, ν is cinematic viscosity). Harmonic surface waves of small amplitude propagating upstream are excited by computer controlled wave maker. In the absence of surface waves, turbulent Karman street with averaged frequency f is observed. It is revealed experimentally that harmonic surface waves with a frequencies closed to 2f can synchronize vortex shedding and increase the amplitude of velocity fluctuations in the wake of the cylinder. Map of regimes is found on the parameter plane amplitude of the surface wave - wave frequency. In order to distinguish the synchronization regimes, we defined phase of oscillations using the Hilbert transform technique. We

  13. Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy.

    Science.gov (United States)

    Chen, Li; Ueta, Hirokazu; Bisson, Régis; Beck, Rainer D

    2013-05-01

    We report the design and characterization of a new molecular-beam/surface-science apparatus for quantum state-resolved studies of gas/surface reaction dynamics combining optical state-specific reactant preparation in a molecular beam by rapid adiabatic passage with detection of surface-bound reaction products by reflection absorption infrared spectroscopy (RAIRS). RAIRS is a non-invasive infrared spectroscopic detection technique that enables online monitoring of the buildup of reaction products on the target surface during reactant deposition by a molecular beam. The product uptake rate obtained by calibrated RAIRS detection yields the coverage dependent state-resolved reaction probability S(θ). Furthermore, the infrared absorption spectra of the adsorbed products obtained by the RAIRS technique provide structural information, which help to identify nascent reaction products, investigate reaction pathways, and determine branching ratios for different pathways of a chemisorption reaction. Measurements of the dissociative chemisorption of methane on Pt(111) with this new apparatus are presented to illustrate the utility of RAIRS detection for highly detailed studies of chemical reactions at the gas/surface interface.

  14. Thermodynamic model of coherent island formation on vicinal substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xu, E-mail: zhangxubetter@gmail.com; Sun, Xiao-Hong [Henan Key Laboratory of Laser and Opto-electric Information Technology, School of Information Engineering, Zhengzhou University, Zhengzhou 450052 (China); Yu, Yanguang [School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, Northfields Ave, Wollongong, New South Wales 2522 (Australia); Ren, Xiaomin [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

    2014-04-28

    A thermodynamic model has been proposed to address the formation of coherent island on the vicinal substrate. The morphological transition from square based island to elongated based one with various substrate misorientations is described. The initial stage of nucleation and growth process of islands in Stranski–Krastanow system is studied by taking into account the elastic deformations and the change of energy in the case of two-dimensional growth mode. The theoretical analysis shows the minimum nucleation barrier of island is on the decrease with increment of substrate misorientation, which means the nucleation of island on vicinal substrate is more favorable than that on flat substrate. By using the fitting data of experimental results done by Persichetti et al., [Phys. Rev. Lett. 104, 036104 (2010) and Phys. Rev. B 82, 121309(R) (2010)], we provide a meaningful explanation of the experimental observations.

  15. Identification of probable groundwater paths in the Amargosa Desert vicinity

    Energy Technology Data Exchange (ETDEWEB)

    Al-Qudah, Omar, E-mail: omal@miners.utep.edu [Environmental Science and Engineering, University of Texas at El Paso, 500 W University Ave, El Paso, TX 79968 (United States); Woocay, Arturo [Division de Estudios de Posgrado e Investigacion, Instituto Tecnologico de Ciudad Juarez, Ave. Tecnologico 1340, Ciudad Juarez, CHIH 32500 (Mexico)] [Environmental Science and Engineering, Civil Engineering Department, University of Texas at El Paso, 500 W University Ave, El Paso, TX 79968 (United States); Walton, John [Environmental Science and Engineering, Civil Engineering Department, University of Texas at El Paso, 500 W University Ave, El Paso, TX 79968 (United States)

    2011-04-15

    Research highlights: {yields} PHREEQC, PCFA and clustering determine groundwater chemical signatures and groups. {yields} Hydro-chemical signatures and groups denote surface runoff infiltration and flow-paths. {yields} Chemical signatures obtained at infiltration regions change slightly along flow-paths. {yields} Identified flow-paths are the traces of the Amargosa River and Forty mile Wash. {yields} A third possible flow-path is the trace of Gravity Fault, Rock Valley and Death Valley. - Abstract: In this study, the hydrogeochemical program PHREEQC was used to determine the chemical speciation and mineral saturation indices (SIs) of groundwater in the vicinity of the proposed high-level nuclear waste repository at Yucca Mountain, Nevada (USA). In turn, these data were used to interpret the origin and recharge mode of groundwater, to elucidate the mechanisms of flow and transport, and to determine potential sources of groundwater contamination. PHREEQC was run to determine aqueous dissolved species and minerals that would be in equilibrium with the study area's groundwater. Selected major ions, associated SI, F{sup -} and Ca/Na ion exchange were then examined using the multivariate statistical methods of principal component factor analysis and k-means cluster analysis. Analysis of dissolved ion concentrations, SIs, and Ca/Na ion exchange allows simultaneous consideration of arithmetic (raw concentrations) and logarithmic (SI, ion exchange) variables that describe the hydrochemical system and, therefore, can provide further insight into the system's behavior. The analysis indicates that the dominant processes and reactions responsible for the hydrochemical evolution in the system are (1) evaporative concentration prior to infiltration, (2) carbonate equilibrium, (3) silicate weathering reactions, (4) limited mixing with saline water, (5) dissolution/precipitation of calcite, dolomite and fluorite, and (6) ion exchange. Principal component factor analysis

  16. Light slowdown in the vicinity of cross-over resonances

    CERN Document Server

    Perdian, M; Zaremba, J; Zielinska-Kaniasty, S

    2004-01-01

    Pulse propagation is considered in an inhomogeneously broadened medium of three-level atoms in a V-configuration, dressed by a counter-propagating pump pulse. A significant signal slowdown is demonstrated in this of the three frequency windows of a reduced absorption and a steep normal dispersion, which is due to a cross-over resonance. Particular properties of the group index in the vicinity of such a resonance are demonstrated in the case of closely spaced upper levels.

  17. Land subsidence and problems affecting land use at Edwards Air Force Base and vicinity, California, 1990

    Science.gov (United States)

    Blodgett, James C.; Williams, J. S.

    Land subsidence in Antelope Valley, which includes Edwards Air Force Base, was first reported in the 1950's; by 1967, about 200 square miles of Antelope Valley were affected by as much as 2 feet of subsidence. The purpose of the report is to present the results to date of recent studies done by the U.S. Geological Survey, in cooperation with the U.S. Department of the Air Force, to determine the cause and areal extent of land subsidence and surface deformation on Rogers Lakebed and vicinity, and the effects of surface deformation on runways used for aircraft landings at Edwards AFB in southern California. Because of the time-related effects of land subsidence, several years of data collection will be needed to establish subsidence trends and evaluate those factors causing land subsidence.

  18. Modelling of plasma behaviour in the vicinity of intensive impurity sources

    Science.gov (United States)

    Tokar, Mikhail Z.; Ding, Rui; Koltunov, Mikhail

    2010-07-01

    Plasma behaviour in the vicinity of strong sources of impurities is considered by taking into account quasi-neutrality, Coulomb collisions of background particles with impurity ions, radiation losses and sinks of charged particles to bounding material surfaces. If several ion species are present in the plasma the generalized Bohm criterion requires that a certain function of the main ion velocity changes its sign when moving along the magnetic field from the distant plasma through the impurity source to the surface. This allows us to formulate the 'regularity' conditions for the motion equation of the main ions and a numerical approach to find the only physical solution without singularities is elaborated. Calculations of plasma parameters in the shadow of a limiter, through which impurities are injected, have been done for the conditions of impurity seeding experiments in the tokamak TEXTOR.

  19. Vibrations of alkali metal overlayers on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rusina, G G; Eremeev, S V; Borisova, S D [Institute of Strength Physics and Materials Science SB RAS, 634021, Tomsk (Russian Federation); Echenique, P M; Chulkov, E V [Donostia International Physics Center (DIPC), 20018 San Sebastian/Donostia, Basque Country (Spain); Benedek, G [Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, 20125 Milano (Italy)], E-mail: rusina@ispms.tsc.ru

    2008-06-04

    We review the current progress in the understanding of vibrations of alkalis adsorbed on metal surfaces. The analysis of alkali vibrations was made on the basis of available theoretical and experimental results. We also include in this discussion our recent calculations of vibrations in K/Pt(111) and Li(Na)/Cu(001) systems. The dependence of alkali adlayer localized modes on atomic mass, adsorption position and coverage as well as the dependence of vertical vibration frequency on the substrate orientation is discussed. The square root of atomic mass dependence of the vertical vibration energy has been confirmed by using computational data for alkalis on the Al(111) and Cu(001) substrates. We have confirmed that in a wide range of submonolayer coverages the stretch mode energy remains nearly constant while the energy of in-plane polarized modes increases with the increase of alkali coverage. It was shown that the spectrum of both stretch and in-plane vibrations can be very sensitive to the adsorption position of alkali atoms and substrate orientation.

  20. Vibrations of alkali metal overlayers on metal surfaces

    Science.gov (United States)

    Rusina, G. G.; Eremeev, S. V.; Echenique, P. M.; Benedek, G.; Borisova, S. D.; Chulkov, E. V.

    2008-06-01

    We review the current progress in the understanding of vibrations of alkalis adsorbed on metal surfaces. The analysis of alkali vibrations was made on the basis of available theoretical and experimental results. We also include in this discussion our recent calculations of vibrations in K/Pt(111) and Li(Na)/Cu(001) systems. The dependence of alkali adlayer localized modes on atomic mass, adsorption position and coverage as well as the dependence of vertical vibration frequency on the substrate orientation is discussed. The square root of atomic mass dependence of the vertical vibration energy has been confirmed by using computational data for alkalis on the Al(111) and Cu(001) substrates. We have confirmed that in a wide range of submonolayer coverages the stretch mode energy remains nearly constant while the energy of in-plane polarized modes increases with the increase of alkali coverage. It was shown that the spectrum of both stretch and in-plane vibrations can be very sensitive to the adsorption position of alkali atoms and substrate orientation.

  1. Identification of surface species by vibrational normal mode analysis. A DFT study

    Science.gov (United States)

    Zhao, Zhi-Jian; Genest, Alexander; Rösch, Notker

    2017-10-01

    Infrared spectroscopy is an important experimental tool for identifying molecular species adsorbed on a metal surface that can be used in situ. Often vibrational modes in such IR spectra of surface species are assigned and identified by comparison with vibrational spectra of related (molecular) compounds of known structure, e. g., an organometallic cluster analogue. To check the validity of this strategy, we carried out a computational study where we compared the normal modes of three C2Hx species (x = 3, 4) in two types of systems, as adsorbates on the Pt(111) surface and as ligands in an organometallic cluster compound. The results of our DFT calculations reproduce the experimental observed frequencies with deviations of at most 50 cm-1. However, the frequencies of the C2Hx species in both types of systems have to be interpreted with due caution if the coordination mode is unknown. The comparative identification strategy works satisfactorily when the coordination mode of the molecular species (ethylidyne) is similar on the surface and in the metal cluster. However, large shifts are encountered when the molecular species (vinyl) exhibits different coordination modes on both types of substrates.

  2. Horizontal Electric Field in the Vicinity of Structures Hit by Lightning

    Directory of Open Access Journals (Sweden)

    Celio Fonseca Barbosa

    2016-09-01

    Full Text Available The horizontal electric field at the ground surface in the vicinity of structures hit by lightning flashes is relevant to the safety of human beings and livestock; it determines the touch and step voltages around the structure. This paper uses an approximate analytical formula for calculating the horizontal electric field, which was adapted to take into account the effect of the structure foundation. The input for the calculation is the current waveform at the base of the structure, and the results agree well with those obtained by other authors using the finite-difference time-domain (FDTD method. The approximate formula is applied to calculate touch and step voltages in the vicinity of a structure and the results show that the use of the direct current (DC approximation to calculate touch and step voltages may lead to significant errors; especially for fast-rising currents and relatively good-conducting soils. This means that DC approximation could be used for positive first stroke and poor-conducting ground (ρ ≥ 1000 Ω∙m, but cannot be used for subsequent strokes and good-conducting ground (ρ ≤ 100 Ω∙m. Moreover, step voltages differ more from the DC approximation than the touch voltages.

  3. Ground-Water Temperature Data, Nevada Test Site and Vicinity, Nye, Clark, and Lincoln Counties, Nevada, 2000-2006.

    Energy Technology Data Exchange (ETDEWEB)

    Steven R. Reiner

    2007-08-07

    Ground-water temperature data were collected by the U.S. Geological Survey in wells at and in the vicinity of the Nevada Test Site during the years 2000–2006. Periodic ground-water temperatures were collected in 166 wells. In general, periodic ground-water temperatures were measured annually in each well at 5 and 55 feet below the water surface. Ground-water temperature profiles were collected in 73 wells. Temperatures were measured at multiple depths below the water surface to produce these profiles. Databases were constructed to present the ground-water temperature data.

  4. Ground-Water Temperature Data, Nevada Test Site and Vicinity, Nye, Clark, and Lincoln Counties, Nevada, 2000-2006

    Science.gov (United States)

    Reiner, Steven R.

    2007-01-01

    Ground-water temperature data were collected by the U.S. Geological Survey in wells at and in the vicinity of the Nevada Test Site during the years 2000-2006. Periodic ground-water temperatures were collected in 166 wells. In general, periodic ground-water temperatures were measured annually in each well at 5 and 55 feet below the water surface. Ground-water temperature profiles were collected in 73 wells. Temperatures were measured at multiple depths below the water surface to produce these profiles. Databases were constructed to present the ground-water temperature data.

  5. Laser pointing in the vicinity of jet engine plumes

    Science.gov (United States)

    Schleijpen, Ric H. M. A.

    2009-09-01

    Target tracking and laser-based pointing from airborne platforms can be degraded significantly by the propagation environment around an airborne platform including zones of severe turbulence generated by rotor downwash and engine exhausts. This is the topic of the EDA study group ERG 108.019 on "Laser beam propagation and imaging through severe environments". This paper reports on experiments on optical propagation in the vicinity of a plume of a scaled down jet engine, performed by this co-operation group. The group is also working on methods for estimating the extent of the turbulence effects on the tracking and pointing performance under these conditions.

  6. Scheme Transformations in the Vicinity of an Infrared Fixed Point

    DEFF Research Database (Denmark)

    Ryttov, Thomas; Shrock, Robert

    2012-01-01

    We analyze the effect of scheme transformations in the vicinity of an exact or approximate infrared fixed point in an asymptotically free gauge theory with fermions. We show that there is far less freedom in carrying out such scheme transformations in this case than at an ultraviolet fixed point....... We construct a transformation from the $\\bar{MS}$ scheme to a scheme with a vanishing three-loop term in the $\\beta$ function and use this to assess the scheme dependence of an infrared fixed point in SU($N$) theories with fermions. Implications for the anomalous dimension of the fermion bilinear...

  7. Adsorption of CO on Co(0001) and Pt Co(0001) surfaces: an experimental and theoretical study

    Science.gov (United States)

    Cabeza, G. F.; Légaré, P.; Castellani, N. J.

    2000-10-01

    CO adsorption on Co(0001) and Pt submonolayer deposits on Co(0001) at room temperature have been investigated by combining the surface techniques of low-energy electron diffraction and X-ray and UV photoelectron spectroscopy. The influence of bimetallic system formation on the CO adsorption was studied. CO is molecularly adsorbed on both surfaces. The saturation coverage under ultrahigh vacuum conditions corresponds to a well-ordered ( 3× 3)R30° structure in the presence of Pt. The CO uptake on Pt-Co(0001) was found to be lowered in comparison with Co(0001) as the platinum coverage increased between 0 to 0.6 ML. However, CO is adsorbed both on the Pt and Co areas. It is shown that CO is located in the top Pt sites, with an adsorption energy reduced by 38% with respect to the pure Pt(111) surface. This result is in good agreement with our theoretical results of CO chemisorption energy on a pseudomorphic Pt overlayer supported by Co(0001). A decreased Pt density of states at the Fermi level and a high binding energy shift of the d-band center in comparison with the pure metal was observed both experimentally and theoretically.

  8. Local thermal unpleasantness and discomfort prediction in the vicinity of thermoneutrality.

    Science.gov (United States)

    Pellerin, Nicolas; Deschuyteneer, Anne; Candas, Victor

    2004-09-01

    This work emphasizes a better understanding of the origin of human thermal discomfort under heterogeneous but steady environments, in subjects in the vicinity of physiological and sensory thermoneutrality. The knowledge of skin temperatures allows a psychophysiological study aiming at linking the body thermal state (local and global) to thermal sensation (perceptive and affective judgements). By using two driving simulators, 345 subjects were exposed to different thermal environments, modulated by factors such as the air distribution in the automotive cockpit or the clothing insulation (winter or summer). This work shows that consideration of the local thermal state is essential for the evaluation of thermal comfort in the case of non-uniform environments. Our experimental conditions point out that the overall sensation of discomfort is quantitative, with local unpleasantness needing to be felt for a certain number of body surfaces. A local origin is suggested for cold discomfort, in opposition to the global characteristics of warm discomfort.

  9. Health effects of living in the vicinity of the landfills

    Directory of Open Access Journals (Sweden)

    Katarzyna Lar

    2013-12-01

    Full Text Available Landfill sites are the easiest, the cheapest and the most common way of waste management and disposal. In the face of the increasing amount of waste, the dynamics of globalization and urbanization process, waste management is an important issue of ecological policy in highly developed countries. Landfill sites intensify environmental threats for the neighborhood and give rise to toxic substances which impair human health being released from the landfills. These are persistent organic pollutants (POPs, heavy metals and also biological gas, bioaerosols, bacteria and viruses. Scientists have conducted a lot of research to evaluate the impact of landfill sites on human health living in their vicinity. They found increased occurrence of congenital anomalies, increased risk of certain cancers and low birth weight of infants. The results of the studies didn’t deliver absolute proof of relation between the impact of landfill sites on the induction of cancer and other diseases. There is a necessity to conduct further research to evaluate the impact of landfill sites on people health living in the vicinity

  10. Drawdown distribution in the vicinity of nonvertical wells.

    Science.gov (United States)

    Williams, Dennis E

    2013-01-01

    Recent developments in subsurface intake systems for ocean desalination plants are considering use of angled wells (slant wells) completed in permeable materials beneath the ocean floor. Conventional drawdown equations for vertical or horizontal wells are inadequate to properly describe the drawdown distribution in the vicinity of slant wells. Using the principle of superposition combined with standard well hydraulics, universal drawdown equations (UDE) are presented which calculate the drawdown distribution in the vicinity of production wells with inclination angles ranging from 0° (horizontal wells) to 90° (vertical wells). The method is computationally simple and other than the normal assumptions for standard well equations, it only requires that the calculated drawdown represent the drawdown which would be measured in a fully penetrating observation well. Solutions using the UDE are developed for confined, unconfined and semi-confined (leaky) aquifers and compared with analytical equations for vertical and horizontal wells, and with a numerical model for slant wells. The UDE is also applied to pumping test data from the Dana Point slant well project in Southern California.

  11. High velocity vortex channeling in vicinal YBCO thin films.

    Science.gov (United States)

    Puica, I; Lang, W; Durrell, J H

    2012-09-01

    We report on electrical transport measurements at high current densities on optimally doped YBa2Cu3O7-δ thin films grown on vicinal SrTiO3 substrates. Data were collected by using a pulsed-current technique in a four-probe arrangement, allowing to extend the current-voltage characteristics to high supercritical current densities (up to 24 MA cm(-2)) and high electric fields (more than 20 V/cm), in the superconducting state at temperatures between 30 and 80 K. The electric measurements were performed on tracks perpendicular to the vicinal step direction, such that the current crossed between ab planes, under magnetic field rotated in the plane defined by the crystallographic c axis and the current density. At magnetic field orientation parallel to the cuprate layers, evidence for the sliding motion along the ab planes (vortex channeling) was found. The signature of vortex channeling appeared to get enhanced with increasing electric field, due to the peculiar depinning features in the kinked vortex range. They give rise to a current-voltage characteristics steeper than in the more off-plane rectilinear vortex orientations, in the electric field range below approximately 1 V/cm. Roughly above this value, the high vortex channeling velocities (up to 8.6 km/s) could be ascribed to the flux flow, although the signature of ohmic transport appeared to be altered by unavoidable macroscopic self-heating and hot-electron-like effects.

  12. Earthquakes in Arkansas and vicinity 1699-2010

    Science.gov (United States)

    Dart, Richard L.; Ausbrooks, Scott M.

    2011-01-01

    This map summarizes approximately 300 years of earthquake activity in Arkansas. It is one in a series of similar State earthquake history maps. Work on the Arkansas map was done in collaboration with the Arkansas Geological Survey. The earthquake data plotted on the map are from several sources: the Arkansas Geological Survey, the Center for Earthquake Research and Information, the National Center for Earthquake Engineering Research, and the Mississippi Department of Environmental Quality. In addition to earthquake locations, other materials presented include seismic hazard and isoseismal maps and related text. Earthquakes are a legitimate concern in Arkansas and parts of adjacent states. Arkansas has undergone a number of significant felt earthquakes since 1811. At least two of these events caused property damage: a magnitude 4.7 earthquake in 1931, and a magnitude 4.3 earthquake in 1967. The map shows all historical and instrumentally located earthquakes in Arkansas and vicinity between 1811 and 2010. The largest historic earthquake in the vicinity of the State was an intensity XI event, on December 16, 1811; the first earthquake in the New Madrid sequence. This violent event and the earthquakes that followed caused considerable damage to the then sparsely settled region.

  13. Earthquakes in Mississippi and vicinity 1811-2010

    Science.gov (United States)

    Dart, Richard L.; Bograd, Michael B.E.

    2011-01-01

    This map summarizes two centuries of earthquake activity in Mississippi. Work on the Mississippi map was done in collaboration with the Mississippi Department of Environmental Quality, Office of Geology. The earthquake data plotted on the map are from several sources: the Mississippi Department of Environmental Quality, the Center for Earthquake Research and Information, the National Center for Earthquake Engineering Research, and the Arkansas Geological Survey. In addition to earthquake locations, other materials include seismic hazard and isoseismal maps and related text. Earthquakes are a legitimate concern in Mississippi and parts of adjacent States. Mississippi has undergone a number of felt earthquakes since 1811. At least two of these events caused property damage: a magnitude 4.7 earthquake in 1931, and a magnitude 4.3 earthquake in 1967. The map shows all historical and instrumentally located earthquakes in Mississippi and vicinity between 1811 and 2010. The largest historic earthquake in the vicinity of the State was an intensity XI event, on December 16, 1811; the first earthquake in the New Madrid sequence. This violent event and the earthquakes that followed caused considerable damage to the then sparsely settled region.

  14. Quantum dynamics of STM and laser induced desorption of atoms and molecules from surfaces

    CERN Document Server

    Boendgen, G

    2001-01-01

    The manipulation of atoms and molecules at solid surfaces by electronic excitations with electrons (or holes) emitted from the tip of a scanning tunneling microscope (STM) or with laser radiation is both of applied and fundamental interest, e.g. for micro- and nanostructuring of materials, the clarification of elementary (catalytic) reaction mechanisms and for the question of how to treat the quantum dynamics of a laser or STM driven 'system' (the adsorbate) in contact with a dissipative (energy-withdrawing) 'bath' (the substrate). Desorption induced by electronic transitions (DIET) and its variant DIMET (M = multiple) are among the simplest possible 'reactions' of adsorbate-surface systems; usually involving extremely short-lived electronically excited intermediates. In this thesis, the ultra-short dynamics of directly (localised to the adsorbate-substrate complex) and indirectly (i.e., through the substrate) stimulated DIET and DIMET processes was studied for Si(100)-(2x1):H(D) and Pt(111):NO. Isotope effec...

  15. The structure and reactivity of adsorbates on stepped Rh and Pt surfaces investigated by LEED, HREELS, TPD, XPS and STM

    Energy Technology Data Exchange (ETDEWEB)

    Batteas, J.D. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Materials Science Div.

    1995-06-01

    Defects on surfaces such as steps play an important role in surface chemistry. In order to obtain an understanding of the influence of steps in surface chemical reactions, the structure and reactivity of small molecules (O{sub 2}, CO, H{sub 2}S, and C{sub 2}H{sub 4}) on atomically stepped surfaces of RH and Pt have been investigated. The detailed structures of CO and oxygen bonded to the Rh(110) surface were determined. The CO molecules bond near the short bridge sites with the CO molecular axis tilted approximately 24{degree} from the surface normal. Oxygen atoms are bound asymmetrically in the 3-fold fcc hollow-sites to the (111) facets of the steps. The interactions of CO and oxygen on the Rh(311) surface were examined. The reaction of CO with the ordered phases of O shows two distinct reaction channels, a low temperature reaction limited channel (200 K) and a high temperature diffusion limited channel (350 K). Models of the reaction geometry and dynamics are proposed. The thermal decomposition of ethylene was examined on the Rh(311) surface. The stable decomposition species (C{sub 2}H, CH and C{sub 2}) are formed near 300 K, approximately 100 K lower on the stepped Rh(311) than on the flatter Rh(111) surface. The formation of these species at lower temperatures is attributed to the stepped nature of the surface. Finally, in situ STM was used to examine surface structural changes of a stepped Pt(111) crystal under coadsorption of sulfur and CO. This is the first direct evidence for a new mechanism by which a surface covered with an unreactive, strongly chemisorbed overlayer can form new sites, for bonding and reactions to occur, by massive surface restructuring at the step edges. This new surface phenomenon answers some of the puzzles of metal surface catalysis and its implications are described. 278 refs.

  16. Geologic map of Yosemite National Park and vicinity, California

    Science.gov (United States)

    Huber, N.K.; Bateman, P.C.; Wahrhaftig, Clyde

    1989-01-01

    This digital map database represents the general distribution of bedrock and surficial deposits of the Yosemite National Park vicinity. It was produced directly from the file used to create the print version in 1989. The Yosemite National Park region is comprised of portions of 15 7.5 minute quadrangles. The original publication of the map in 1989 included the map, described map units and provided correlations, as well as a geologic summary and references, all on the same sheet. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:125,000 or smaller.

  17. Monitoring noise from aircraft operations in the vicinity of airports

    Science.gov (United States)

    Eldred, Kenneth Mck.

    This paper presents an overview of a proposed Society of Automotive Engineers Aerospace Recommended Practice (ARP4721) with this title. The ARP is intended to provide engineering methods for measuring the noise from aircraft operations in the vicinity of airports for a variety of potential users and purposes. It uses the A-weighted Sound Level (Slow) and quantities derived from its time history as the principal descriptor of aircraft noise. It represents an evolutionary growth from the airport noise monitoring experience over the past three decades. It is intended to cover both unattended multi-channel noise measurement systems used for routine monitoring and attended systems used for special monitoring or for other measurement purposes. It contains recommended methods for the acquisition of non-acoustical data and requirements for systems that acquire acoustical data and their processing. It provides information on temporal and spatial sampling with respect to sampling design and errors, and discusses several applications for its use in monitoring.

  18. Clock Synchronization and Navigation in the Vicinity of the Earth

    CERN Document Server

    Bahder, T B

    2004-01-01

    Clock synchronization is the backbone of applications such as high-accuracy satellite navigation, geolocation, space-based interferometry, and cryptographic communication systems. The high accuracy of synchronization needed over satellite-to-ground and satellite-to-satellite distances requires the use of general relativistic concepts. The role of geometrical optics and antenna phase center approximations are discussed in high accuracy work. The clock synchronization problem is explored from a general relativistic point of view, with emphasis on the local measurement process and the use of the tetrad formalism as the correct model of relativistic measurements. The treatment makes use of J. L. Synge's world function of space-time as a basic coordinate independent geometric concept. A metric is used for space-time in the vicinity of the Earth, where coordinate time is proper time on the geoid. The problem of satellite clock syntonization is analyzed by numerically integrating the geodesic equations of motion for...

  19. Local dark energy: HST evidence from the vicinity of the M 81/M 82 galaxy group

    CERN Document Server

    Chernin, A D; Kashibadze, O G; Makarov, D I; Teerikorpi, P; Valtonen, M J; Dolgachev, V P; Domozhilova, L M

    2007-01-01

    The Hubble Space Telescope observations of the nearby galaxy group M 81/M 82 and its vicinity indicate that the expansion outflow around the group is dominated by the antigravity of the dark energy background. The local density of dark energy in the area is estimated to be near the global dark energy density or perhaps exactly equal to it. This conclusion agrees with our previous results for the Local group vicinity and the vicinity of the Cen A/M 83 group.

  20. Growth mode transitions induced by hydrogen-assisted MBE on vicinal GaAs(110)

    Energy Technology Data Exchange (ETDEWEB)

    Tejedor, P. [Instituto de Ciencia de Materiales de Madrid (C.S.I.C)., Sor Juana Ines de la Cruz s/n, Cantoblanco, 28049 Madrid (Spain)]. E-mail: ptejedor@icmm.csic.es; Crespillo, M.L. [Instituto de Ciencia de Materiales de Madrid (C.S.I.C)., Sor Juana Ines de la Cruz s/n, Cantoblanco, 28049 Madrid (Spain); Joyce, B.A. [Imperial College of Science, Technology and Medicine, The Blackett Laboratory, London SW7 2BZ (United Kingdom)

    2006-07-15

    The homoepitaxial growth of GaAs by hydrogen-assisted molecular beam epitaxy (H-MBE) on (110) substrates vicinal to (111)A has been studied by reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM) for different kinetic regimes. When the GaAs growth rate is limited by the kinetics of adatom incorporation to steps, the presence of chemisorbed H on the surface after oxide removal promotes the incorporation of adatoms to steps from the lower terraces, leading to the formation of multiatomic step arrays or ridge patterns by a combination of step propagation and two-dimensional layer-by-layer growth. Supply of atomic H during epitaxy favours three-dimensional growth, leading to Ga-induced surface roughening or mound formation. At high temperatures, the Ga-As interactions at step edges are faster and stable growth of GaAs occurs by step propagation, leading to a faceted surface when H is used both during oxide removal and/or MBE growth.

  1. Lunar Infrared Spectrometer to Characterize the Hydration of Regolith in the Vicinity of a Lander

    Science.gov (United States)

    Ivanov, Andrey; Fedorova, Anna; Korablev, Oleg; Mantsevich, Sergey; Stepanov, Alexander; Kalinnikov, Yury

    Lunar Infrared Spectrometer (LIS) is an experiment onboard Luna-Globe (Luna 25) and Luna-Resurce (Luna 27) Russian surface missions. It is a pencil-beam spectrometer to be pointed by a robotic arm of the landing module, and is intended for study of the lunar surface composition in the vicinity of the lander. The instrument’s field of view (FOV) of 1(°) is co-aligned with the FOV (45(°) ) of a stereo TV camera. The spectrometer will provide measurements of selected surface areas in the spectral range of 1.15-3.3 mum. The spectral selection is provided by acousto-optic tunable filter (AOTF), which scans the spectral range sequentially. Electrical command of the AOTF allows selecting the spectral sampling, and permits a random access if needed. The spectral resolution is better than 25 cm (-1) . The instrument’s mass is 1.3 kg. The primary goal of the experiment is to detect the regolith hydration at 3mum, identifying its form from the shape of the spectrum, and to follow its changes during the day/shadow pattern. Also, LIS will allow to study the mineralogical composition from mineral signatures within the spectral range, and will serve for selection of samples to be analyzed by other instruments.

  2. Studies of the surface structures of molecular crystals and of adsorbed molecular monolayers on the (111) crystal faces of platinum and silver by low-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Firment, L.E.

    1977-01-01

    The structures of molecular crystal surfaces were investigated for the first time by the use of low-energy electron diffraction (LEED). The experimental results from a variety of molecular crystals were examined and compared as a first step towards understanding the properties of these surfaces on a microscopic level. The method of sample preparation employed, vapor deposition onto metal single-crystal substrates at low temperatures in ultrahigh vacuum, allowed concurrent study of the structures of adsorbed monolayers on metal surfaces and of the growth processes of molecular films on metal substrates. The systems investigated were ice, ammonia, naphthalene, benzene, the n-paraffins (C/sub 3/ to C/sub 8/), cyclohexane, trioxane, acetic acid, propionic acid, methanol, and methylamine adsorbed and condensed on both Pt(111) and Ag(111) surfaces. Electron-beam-induced damage of the molecular surfaces was observed after electron exposures of 10/sup -4/ A sec cm/sup -2/ at 20 eV. Aromatic molecular crystal samples were more resistant to damage than samples of saturated molecules. The quality and orientation of the grown molecular crystal films were influenced by substrate preparation and growth conditions. Forty ordered monolayer structures were observed. 110 figures, 22 tables, 162 references.

  3. Observation of Atomic Steps on Vicinal Si(111) Annealed in Hydrogen Gas Flow by Scanning Tunneling Microscopy

    Science.gov (United States)

    Kitahara, Kuninori; Ueda, Osamu

    1993-12-01

    The surface of vicinal Si(111) annealed in H2 flow was observed by equipping the chemical vapor deposition chamber with the scanning tunneling microscope. Samples were annealed at 1000°C for 10 min by passing an electric current under the H2 pressure of 7 Torr. Their surface morphology was compared with those annealed in ultrahigh vacuum (UHV) and in N2 flow at the same temperature. We found that the step motion during annealing in H2 was obviously smaller than that for annealing in UHV and N2. The multisteps formed during the annealing in UHV and N2 were not observed for H2 annealing except in the case of heating by direct current in the direction of lower to higher terraces. The mechanism of the interruption of the step motion is discussed from the viewpoint of the interaction between the surface and hydrogen.

  4. 33 CFR 165.701 - Vicinity, Kennedy Space Center, Merritt Island, Florida-security zone.

    Science.gov (United States)

    2010-07-01

    ... § 165.701 Vicinity, Kennedy Space Center, Merritt Island, Florida—security zone. (a) The water, land... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Vicinity, Kennedy Space Center, Merritt Island, Florida-security zone. 165.701 Section 165.701 Navigation and Navigable Waters COAST...

  5. Pregnancy outcome of women in the vicinity of nuclear power plants in Taiwan.

    Science.gov (United States)

    Wang, Shiow-Ing; Lee, Long-Teng; Zou, Ming-Lun; Fan, Chen-Wei; Yaung, Chin-Liang

    2010-03-01

    The purpose of the study was to investigate whether proximity to nuclear power plants may increase the risk of abnormal pregnant outcomes among the resident women. In this ecological study, data were used from the Health Services Birth Reports Database established by the Bureau of Health Promotion, National Department of Health, Taiwan, in 2001-2004. Chi-square-tests were carried out to investigate the "Plant-vicinity" and "Non plant-vicinity" group in terms of pregnancy outcome. Additionally, logistic regression was performed to investigate whether residence in the vicinity of a nuclear power plant was related to any abnormal pregnancy results. Based on data from 5,679 included subjects, no difference was observed between pregnancy outcomes of the "Plant-vicinity" and "Non plant-vicinity" groups. After accounting for possible confounders, the adjusted odds ratios were 1.20 (95% CI = 0.56-2.56) for stillbirth, 1.21 (95% CI = 0.95-1.53) for premature birth, 1.04 (95% CI = 0.79-1.37) for low birth weight, and 1.58 (95% CI = 0.85-2.93) for congenital deficiencies, respectively, when comparing the "Plant-vicinity" with the "Non plant-vicinity" group. The results of the study indicate that residence in the vicinity of a nuclear power plant is not a significant factor which will cause abnormal health situations during pregnancy.

  6. Transmission in the vicinity of the Dirac point in hexagonal Photonic Crystals

    CERN Document Server

    Diem, Marcus; Soukoulis, C M

    2008-01-01

    We use a scattering matrix approach to simulate the transmission through a hexagonal Photonic Crystal in the vicinity of the Dirac point. If the crystal is oriented so that the propagation direction perpendicular to the surface corresponds to the Gamma-K direction, no oblique transmission is possible for a very long (infinite) structure. For a finite structure with width, W, and length, L, the length dependence of the transmission is given by T_total = Gamma_0 W/L. For T_total all waves with a wavevector parallel to the surface, k_||=n 2pi/W, described by a channel number, n, must be considered. We show the transmission at the Dirac point follows the given scaling law and this scaling law is related to the behavior of the individual channels. This leads to the establishment of a criterion for the maximum length for this scaling behavior when the total transmission reaches a constant value. We also compare this scaling behavior to the results in other frequency regions.

  7. Seismicity of the Earth 1900-2007, Japan and Vicinity

    Science.gov (United States)

    Rhea, Susan; Tarr, Arthur C.; Hayes, Gavin P.; Villaseñor, Antonio; Benz, Harley

    2010-01-01

    This map shows details of Japan and vicinity not visible in an earlier publication, U.S. Geological Survey Scientific Investigations Map 3064. Japan and its island possessions lie across four major tectonic plates: Pacific plate, North America plate; Eurasia plate; and Philippine Sea plate. The Pacific plate is subducted into the mantle, beneath Hokkaido and northern Honshu, along the eastern margin of the Okhotsk microplate, a proposed subdivision of the North America plate (Bird, 2003). Farther south, the pacific plate is subducted beneath volcanic islands along the eastern margin of the Philippine Sea plate. This 2,200 km-long zone of subduction of the Pacific plate is responsible for the creation of the deep offshore Ogasawara and Japan trenches as well as parallel chains of islands and volcanoes, typical of the Circumpacific island arcs. Similarly, the Philippine Sea plate is itself subducting under the Eurasia plate along a zone, extending from Taiwan to southern Honshu, that comprises the Ryuku Islands and the Nansei-Shonto trench.

  8. Chemically traced blobs in the vicinity of a submarine canyon

    Science.gov (United States)

    Brogueira, M. J.; Cabeçadas, G.; Gonçalves, C.; Cabeçadas, P.

    2003-04-01

    A hydrographic cruise was carried out in May 2001 off southern Portugal, in the vicinity of Portimão canyon. This major topographic irregularity across the path of the Mediterranean undercurrent is known to induce water masses instability and to be a site of dipole formation. Two blobs of distinct water masses were revealed mainly through chemical tracers, namely dissolved oxygen and nutrients. One low-salinity blob, centred at ˜800 m depth, displayed high values of AOU (above 100 μmol/kg) and nutrients (NO_3 up to 14 μmol/kg, PO_4 up to 0.9 and Si(OH)_4 up to 11 μmol/kg), which are features of the Antarctic Intermediate Water (AAIW) present in the area. The deeper salty warm blob, extending from the MW outflow, corresponded to the relatively more oxygenated (AOU 77 μmol/kg) and nutrient-impoverished (NO_3 9 μmol/kg, PO_4 0.6 μmol/kg and Si(OH)_4 6 μmol/kg) saline Mediterranean Water. Further, the influence of this deeper blob expanding down (till 1800--2000 m) into the well-ventilated and nutrient-enriched North Atlantic Deep Water (NADW) was visible through nutrient patterns. The chemical data enabled the identification of the described blobs structure associated with this particular canyon located on the westward flow of MW into the North Atlantic.

  9. Dynamics of O2 Chemisorption on a Flat Platinum Surface Probed by an Alignment-Controlled O2 Beam.

    Science.gov (United States)

    Ueta, Hirokazu; Kurahashi, Mitsunori

    2017-04-03

    O2 adsorption on Pt surfaces is of great technological importance owing to its relevance to reactions for the purification of car exhaust gas and the oxygen reduction on fuel-cell electrodes. Although the O2 /Pt(111) system has been investigated intensively, questions still remain concerning the origin of the low O2 sticking probability and its unusual energy dependence. We herein clarify the alignment dependence of the initial sticking probability (S0 ) using the single spin-rotational state-selected [(J,M)=(2,2)] O2 beam. The results indicate that, at low translational energy (E0 ) conditions, direct activated chemisorption occurs only when the O2 axis is nearly parallel to the surface. At high energy conditions (E0 >0.5 eV), however, S0 for the parallel O2 decreases with increasing E0 while that of the perpendicular O2 increases, accounting for the nearly energy-independent O2 sticking probability determined previously by a non-state-resolved experiment. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. An Investigation of the Levels and Distribution of Selected Heavy Metals in Sediments and Plant Species within the Vicinity of Ex-Iron Mine in Bukit Besi

    Directory of Open Access Journals (Sweden)

    Ahmad A. Kutty

    2016-01-01

    Full Text Available An assessment of the abandoned mine impacts on the concentrations and distribution of heavy metals in surface sediments and plant species within the vicinity of an ex-iron mine in Malaysia was conducted. The sequential extraction method was used to extract anthropogenic metals in sediments. The results showed that metals in EFLE, AR, and OO fractions were higher than ambient concentrations which indicate that heavy metals have been loaded from ex-iron mining area into the surrounding aquatic environments. The metal accumulation in the four dominant plant species grown naturally within the vicinity of Bukit Besi ex-iron mining was investigated. Exceptional elevated concentrations of metal were found in plants and surface sediments. Several established criteria were applied to determine the hyperaccumulator plants. The results revealed that Melastoma malabathricum and Pityrogramma calomelanos are classified as Fe and Al hyperaccumulators, while Scirpus triqueter, Melastoma malabathricum, and Pityrogramma calomelanos were undoubtedly hyperaccumulator for Cd.

  11. Statistic characteristics and weather significance of infrared TBB during May―August in Beijing and its vicinity

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to meet the demand of nowcasting convective storms in Beijing, the climatological characteristics of convective storms in Beijing and its vicinity were analyzed based on the infrared (IR) temperature of black body (TBB) data during May―August of 1997―2004. The climatological probabilities, the diurnal cycle and the spatial distribution of convective storms are given respectively in this paper. The results show that the climatological characteristics of convective storms denoted by TBB≤-52℃ are consistent with those statistic studies based on the surface and lightning observations. Furthermore, the climatological characteristics of May and June are very different from those of July and August, showing that there are two types of convective storms in this region. One occurs in the transient polar air mass on the midlatitude continent during the late spring and early summer. This type of convection arises with thunder, strong wind gust and hail over the mountainous area in the northern part of this region from afternoon to nightfall, the other occurs with heavy rainfall in the warm and moist air mass over the North China Plain and vicinity of Bohai Sea. This study also shows that the long-term data of IR TBB observed by geostationary satellite can complement the temporal and spatial limitation of the weather radar and surface observations.

  12. Mantle plumes in the vicinity of subduction zones

    Science.gov (United States)

    Mériaux, C. A.; Mériaux, A.-S.; Schellart, W. P.; Duarte, J. C.; Duarte, S. S.; Chen, Z.

    2016-11-01

    We present three-dimensional deep-mantle laboratory models of a compositional plume within the vicinity of a buoyancy-driven subducting plate with a fixed trailing edge. We modelled front plumes (in the mantle wedge), rear plumes (beneath the subducting plate) and side plumes with slab/plume systems of buoyancy flux ratio spanning a range from 2 to 100 that overlaps the ratios in nature of 0.2-100. This study shows that 1) rising side and front plumes can be dragged over thousands of kilometres into the mantle wedge, 2) flattening of rear plumes in the trench-normal direction can be initiated 700 km away from the trench, and a plume material layer of lesser density and viscosity can ultimately almost entirely underlay a retreating slab after slab/plume impact, 3) while side and rear plumes are not tilted until they reach ∼600 km depth, front plumes can be tilted at increasing depths as their plume buoyancy is lessened, and rise at a slower rate when subjected to a slab-induced downwelling, 4) rear plumes whose buoyancy flux is close to that of a slab, can retard subduction until the slab is 600 km long, and 5) slab-plume interaction can lead to a diversity of spatial plume material distributions into the mantle wedge. We discuss natural slab/plume systems of the Cascadia/Bowie-Cobb, and Nazca/San Felix-Juan Fernandez systems on the basis of our experiments and each geodynamic context and assess the influence of slab downwelling at depths for the starting plumes of Java, Coral Sea and East Solomon. Overall, this study shows how slab/plume interactions can result in a variety of geological, geophysical and geochemical signatures.

  13. Genotoxicity of agricultural soils in the vicinity of industrial area.

    Science.gov (United States)

    Ansari, Mohd Ikram; Malik, Abdul

    2009-03-17

    Soil samples from agricultural fields (cultivated) in the vicinity of industrial area of Ghaziabad City (India) were collected. In this city, wastewater coming from both industrial and domestic sources and without any treatment is used to irrigate the food crops. This practice has been polluting the soil and pollutants might reach the food chain. Gas chromatographic analysis show the presence of certain organochlorine (DDE, DDT, dieldrin, aldrin and endosulfan) and organophosphorus (dimethoate, malathion, methylparathion and chlorpyrifos) pesticides in soil samples. Samples were extracted using different solvents, i.e. methanol, chloroform, acetonitrile, hexane and acetone (all were HPLC-grade, SRL, India), and the extracts were assayed for genotoxic potential using Ames Salmonella/microsome test, DNA repair defective mutants and bacteriophage lambda systems. TA98 and TA100 were found to be the most sensitive strains to all the soil extracts tested. Methanol extracts exhibited a maximum mutagenicity with TA98 strain {540 (-S9) and 638 (+S9) revertants/g of soil} and 938 (-S9) and 1008 (+S9) revertants/g of soil with TA100 strain. The damage in the DNA repair defective mutants was found maximum with methanolic extract followed by acetonitrile, chloroform, hexane and acetone at the dose level of 40 microl/ml culture after 6h of treatment. The survival was 25, 30, 32, 33 and 35% in polA strain after 6h of treatment when tested with wastewater irrigated soil extracts of methanol, acetonitrile, chloroform, hexane and acetone, respectively. A significant decrease in the plaque forming units of bacteriophage lambda was also observed when treated with 40 microl of test samples. Present results showed that methanolic extracts of soil were more toxic than other soil extracts. The soil is accumulating a large number of pollutants due to wastewater irrigation and this practice of accumulation has an impact on soil health.

  14. Ferroelastic strain control of multiple nonvolatile resistance tuning in SrRuO3/PMN-PT(111) multiferroic heterostructures

    Science.gov (United States)

    Zheng, Ming; Ni, Hao; Qi, Yaping; Huang, Weiyi; Zeng, Jiali; Gao, Ju

    2017-05-01

    The electric-field-tunable resistance switching in elastically coupled SrRuO3 thin films grown on (111)-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ferroelectric-crystal substrates has been investigated. During the ferroelectric poling process, the resistance evolution tracks the electric-field-induced in-plane strain of the film efficiently, revealing strain but not the electrostatic charge-mediated coupling mechanism. Using 109° and 71° ferroelastic domain switching of the substrate, multiple reversible and nonvolatile resistance states can be achieved at room temperature, which is closely related to the relative proportion of in-plane polarization vectors and induced distinct in-plane strain states after domain switching. Our findings provide an approach to elucidate electrically driven domain switching dynamics and design energy efficient, high-density spintronic memory devices.

  15. A Study of Bisulfate Adsorption on PT(111) Single Crystal Electrodes Using In-situ Fourier Transform Infrared Spectroscopy

    Science.gov (United States)

    1989-08-10

    for the S04 2 - anion are taken from IR data for aqueous solutions.8 The C3v symmetry group for the HS04 " anion is arrived at by treating the...hydroxyl moiety as a point mass 9 , and the peak positions are representative of HS04 " in aqueous solution and in crystal hydrates.9 ,l0 There are five...are the symmetric stretch of bisulfate, vs(HS0 4-), at -1050 cm 1 , the double degenerate asymmetric stretch of bisulfate, vas( HS04 ") and the triply

  16. Stereodirection of an α-ketoester at sub-molecular sites on chirally modified Pt(111): Heterogeneous asymmetric catalysis

    DEFF Research Database (Denmark)

    Demers-Carpentier, V.; Rasmussen, A.M.H.; Goubert, G.

    2013-01-01

    Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3,3,3-triflu......Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3...

  17. Laser controlled melting of pre-treated zirconia surface

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [ME Department, KFUPM, Dhahran 31261, (Saudi Arabia); Akhtar, S.S. [ME Department, KFUPM, Dhahran 31261, (Saudi Arabia); Karatas, C. [Engineering College, Hacettepe University, (Turkey)

    2011-05-15

    Laser treatment of pre-prepared zirconia surface is carried out. The pre-prepared surface, prior to laser treatment, consists of 50 {mu}m carbon film and 7% titanium carbide particles, which are imbedded in the carbon film. The microstructural and morphological changes in the laser treated surface layer are examined using optical and scanning electron microscopes, energy dispersive spectroscopy, and X-ray diffraction. The fracture toughness of the laser treated surface is measured and the residual stress formed at the surface vicinity is determined from the X-ray diffraction technique. It is found that the microhardness of the laser treated surface increased slightly due to the dense layer formed at the surface vicinity. However, the laser treatment process reduces the fracture toughness of the surface due to improved surface hardness and the residual stress formed in the surface vicinity.

  18. Local dark energy: HST evidence from the vicinity of the M81/M82 galaxy group

    Science.gov (United States)

    Chernin, A. D.; Karachentsev, I. D.; Kashibadze, O. G.; Makarov, D. I.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.

    2007-10-01

    The Hubble Space Telescope observations of the nearby galaxy group M81/M82 and its vicinity indicate that the dynamics of the expansion outflow around the group is dominated by the antigravity of the dark energy background. The local density of dark energy in the area is estimated to be near the global dark energy density or perhaps exactly equal to it. This conclusion agrees well with our previous results for the Local Group vicinity and the vicinity of the Cen A/M83 group.

  19. Uranium mill tailings remedial action program. Radiological survey of Shiprock vicinity property SH03, Shiprock, NM, July-November 1982

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, K F; Justus, A L; Sholeen, C M; Smith, W H; Wynveen, R A

    1984-04-01

    A comprehensive survey of the vicinity property designated as SH03 was conducted on an intermittent basis from July 26 to November 11, 1982. At the time of the survey, three structures were located on the property - a residential trailer, the main structure, and an old gas pump housing. The lands surrounding the structures were either sparsely covered with arid vegetation or paved. The assessment activities included determination of indoor and outdoor surface radiation levels, for both fixed and removable contamination, through direct instrument and smear (indoor only) surveys; measurement of ambient external penetrating radiation levels at 1-meter heights; and analyses of air, soil, and other material samples. No evidence of radioactive contamination was found inside the trailer. However, the results of the radiological assessment did indicate the occurrence of elevated levels of gamma, surface alpha, and radon daughter radioactivity within the main structure. The short-term radon daughter measurements exceeded the limit of 0.02 Working Level for average annual concentration including background. The assessment also indicated elevated levels of radioactivity in the outdoor environs, encompassing about 32,000 ft/sup 2/ of the grounds adjacent to and surrounding the main structure on the east, south, and west sides. The contamination appeared to be due to the presence of unprocessed uranium ore. Analysis of surface soil samples collected from the environs indicated radium concentrations in excess of the limit of 5 pCi/g above background specified in the EPA Standard. Subsurface soil sampling was not conducted, and thus the vertical extent of the radiological contamination is not known. Since the surface soil contamination levels exceeded the limits specified in the EPA Standard, remedial action for this vicinity site should be considered.

  20. Radionuclide Distribution in the Soil on the Stabatishkes Site in the Vicinity of the Ignalina NPP

    Directory of Open Access Journals (Sweden)

    Jevgenij Aliončik

    2011-02-01

    Full Text Available A near surface repository for low and intermediate-level short-lived radioactive waste will be built on the Stabatiškės site in the vicinity of Ignalina NPP during decommissioning works. The reservoir can also be used for the waste stored in the temporary repositories of the Ignalina NPP. Engineering and nature protective barriers are used in the repository for radioactive waste, however, radionuclides can spread into the environment, extend in the biosphere and cause (define the external power light exposure of the environment due to the natural and premature (prescheduled degradation of the engineering barriers of the repository. The properties of the soil (acidity, quantity of organic substances, humidity are being investigated for estimating the possible migration and dispersion of radionuclides. The activity of radionuclides in the soil is also estimated before building the repository. Natural and artificial radionuclides make the pollution of the soil, and therefore the accumulation and vertical migration of artificial (137Cs, 60Co and natural (226Ra, 232Th, 40K radionuclides are being researched in the soil on the Stabatiškės site.Article in Lithuanian

  1. Search for Compact Stellar Groups in the Vicinity of IRAS Sources

    CERN Document Server

    Azatyan, N M; Khachatryan, K G

    2016-01-01

    The results of a search for compact clusters in the vicinity of 19 IRAS sources based on data from the GPS UKIDSS and Spitzer GLIMPSE surveys are presented. Overall, clusters have been identified in 15 regions. Clusters are identified for the first time in 4 regions (IRAS 18151-1208, IRAS 18316-0602, 18517+0437, 19110+1045). In 5 regions (IRAS 05168+3634, 05358+3543, IRAS 18507+0121, IRAS 20188+3928, IRAS 20198+3716) the compact groups we have identified are substructures within more extended clusters. The radii of the identified groups and the surface star density are widely scattered with ranges of 0.3-2.7 pc and 4-1360 stars/pc^2, respectively. In 11 of the clusters, the IRAS sources are associated with a pair or even a group of YSOs. The groups identified in the near IR include representatives of a later evolutionary class II among the stellar objects associated with the IRAS sources.

  2. Escape from the vicinity of fractal basin boundaries of a star cluster

    CERN Document Server

    Ernst, Andreas; Spurzem, Rainer; Porth, Oliver

    2007-01-01

    The dissolution process of star clusters is rather intricate for theory. We investigate it in the context of chaotic dynamics. We use the simple Plummer model for the gravitational field of a star cluster and treat the tidal field of the Galaxy within the tidal approximation. That is, a linear approximation of tidal forces from the Galaxy based on epicyclic theory in a rotating reference frame. The Poincar\\'e surfaces of section reveal the effect of a Coriolis asymmetry. The system is non-hyperbolic which has important consequences for the dynamics. We calculated the basins of escape with respect to the Lagrangian points $L_1$ and $L_2$. The longest escape times have been measured for initial conditions in the vicinity of the fractal basin boundaries. Furthermore, we computed the chaotic saddle for the system and its stable and unstable manifolds. The chaotic saddle is a fractal structure in phase space which has the form of a Cantor set and introduces chaos into the system.

  3. The Relaxation of Vicinal (001) with ZigZag [110] Steps

    Science.gov (United States)

    Hawkins, Micah; Hamouda, Ajmi Bh; González-Cabrera, Diego Luis; Einstein, Theodore L.

    2012-02-01

    This talk presents a kinetic Monte Carlo study of the relaxation dynamics of [110] steps on a vicinal (001) simple cubic surface. This system is interesting because [110] steps have different elementary excitation energetics and favor step diffusion more than close-packed [100] steps. In this talk we show how this leads to relaxation dynamics showing greater fluctuations on a shorter time scale for [110] steps as well as 2-bond breaking processes being rate determining in contrast to 3-bond breaking processes for [100] steps. The existence of a steady state is shown via the convergence of terrace width distributions at times much longer than the relaxation time. In this time regime excellent fits to the modified generalized Wigner distribution (as well as to the Berry-Robnik model when steps can overlap) were obtained. Also, step-position correlation function data show diffusion-limited increase for small distances along the step as well as greater average step displacement for zigzag steps compared to straight steps for somewhat longer distances along the step. Work supported by NSF-MRSEC Grant DMR 05-20471 as well as a DOE-CMCSN Grant.

  4. Residual stress evaluation in the vicinity of ceramic coating interface using polychromatic X-ray method

    Energy Technology Data Exchange (ETDEWEB)

    Shibano, Jun-ichi; Ukai, Takayoshi; Tadano, Shigeru [Hokkaido Univ., Sapporo (Japan). Faculty of Engineering; Todoh, Masahiro

    1995-06-01

    This paper presents a polychromatic X-ray method for nondestructive evaluation of residual stress distributed in the vicinity of the interface between a ceramic coating layer and a substrate metal. Since the strain is assumed to be a linear function of the depth, the strain distribution along the depth direction can be obtained from the weighted mean strain equation calculated by considering the intensity of diffracted X-rays over the penetration depth. Therefore, the distribution along the depth direction of the residual stress was determined by the strain distributions in two directions: the vertical direction and the inclined direction to the surface. SUS316 coated with TiN by the PVD process was used as the specimen. The residual stress distributions in the coating layer and the substrate of the specimen were evaluated using this method. As a result, not only compressive residual stress in the coating layer but also the stress gradient in the substrate could be confirmed simultaneously and nondestructively. (author).

  5. Analytical Validation of a Continuum Model for Epitaxial Growth with Elasticity on Vicinal Surfaces

    Science.gov (United States)

    Dal Maso, G.; Fonseca, I.; Leoni, G.

    2014-06-01

    Within the context of heteroepitaxial growth of a film onto a substrate, terraces and steps self-organize according to misfit elasticity forces. Discrete models of this behavior were developed by Duport et al. (J Phys I 5:1317-1350, 1995) and Tersoff et al. (Phys Rev Lett 75:2730-2733, 1995). A continuum limit of these was in turn derived by Xiang (SIAM J Appl Math 63:241-258, 2002) (see also the work of Xiang and Weinan Phys Rev B 69:035409-1-035409-16, 2004; Xu and Xiang SIAM J Appl Math 69:1393-1414, 2009). In this paper we formulate a notion of weak solution to Xiang's continuum model in terms of a variational inequality that is satisfied by strong solutions. Then we prove the existence of a weak solution.

  6. Continuum Limit of a Mesoscopic Model with Elasticity of Step Motion on Vicinal Surfaces

    Science.gov (United States)

    Gao, Yuan; Liu, Jian-Guo; Lu, Jianfeng

    2016-12-01

    This work considers the rigorous derivation of continuum models of step motion starting from a mesoscopic Burton-Cabrera-Frank-type model following the Xiang's work (Xiang in SIAM J Appl Math 63(1):241-258, 2002). We prove that as the lattice parameter goes to zero, for a finite time interval, a modified discrete model converges to the strong solution of the limiting PDE with first-order convergence rate.

  7. Geologic Map of Lassen Volcanic National Park and Vicinity, California

    Science.gov (United States)

    Clynne, Michael A.; Muffler, L.J. Patrick

    2010-01-01

    The geologic map of Lassen Volcanic National Park (LVNP) and vicinity encompasses 1,905 km2 at the south end of the Cascade Range in Shasta, Lassen, Tehama, and Plumas Counties, northeastern California (fig. 1, sheet 3). The park includes 430 km2 of scenic volcanic features, glacially sculpted terrain, and the most spectacular array of thermal features in the Cascade Range. Interest in preserving the scenic wonders of the Lassen area as a national park arose in the early 1900s to protect it from commercial development and led to the establishment in 1907 of two small national monuments centered on Lassen Peak and Cinder Cone. The eruptions of Lassen Peak in 1914-15 were the first in the Cascade Range since widespread settling of the West in the late 1800s. Through the printed media, the eruptions aroused considerable public interest and inspired renewed efforts, which had languished since 1907, to establish a national park. In 1916, Lassen Volcanic National Park was established by combining the areas of the previously established national monuments and adjacent lands. The southernmost Cascade Range is bounded on the west by the Sacramento Valley and the Klamath Mountains, on the south by the Sierra Nevada, and on the east by the Basin and Range geologic provinces. Most of the map area is underlain by middle to late Pleistocene volcanic rocks; Holocene, early Pleistocene, and late Pliocene volcanic rocks (radiometric dating, photographs of geologic features, and links to related data or web sites. Data contained in the CD-ROM are also available on this Web site. The southernmost Cascade Range consists of a regional platform of basalt and basaltic andesite, with subordinate andesite and sparse dacite. Nested within these regional rocks are 'volcanic centers', defined as large, long-lived, composite, calc-alkaline edifices erupting the full range of compositions from basalt to rhyolite, but dominated by andesite and dacite. Volcanic centers are produced by the

  8. Ground-water resources in the vicinity of Cortland, Trumbull County, Ohio

    Science.gov (United States)

    Barton, G.J.; Wright, P.R.

    1997-01-01

    The city of Cortland lies on the southeast ern shoreline of the 12.3-square-mile Mosquito Creek Lake in Trumbull County, Ohio. Cortland relies upon public wells completed in the Cussewago Sandstone for potable water. The Cussewago Sandstone, the principal aquifer in the study area, is a subcrop of the glaciofluvial sediments in the lake; the unit dips gently towards the southeast. Thickness of the Cussewago Sandstone ranges from less than 20 feet in south-central Bazetta Township to 152 feet in Cortland. The Bedford Shale overlies and confines the Cussewago Sandstone and separates it hydraulically from the Berea Sandstone. The Bedford Shale and Berea Sandstone are not a prolific source of ground water. In places, the Bedford Shale was completely eroded away prior to deposition of the Berea Sandstone. Where the Bedford Shale is absent, such as at the City of Cortland North Well Field, the Berea Sandstone and Cussewago Sandstone are likely in hydraulic connection. Throughout most of the study area, the Cussewago Sandstone is a confined aquifer. Ground-water flow is to the east and southeast. Pumping at both Cortland well fields has created cones of depression in the potentiometric surface. These cones of depression cause a local reversal in ground-water flow immediately east of both well fields. The absence of detectable concentrations of tritium in water samples from wells completed in the Cussewago Sandstone at Cortland indicates that ground water predates the atmospheric nuclear testing of the 1950's. Ground water requires about 60 to 110 years to flow from the Cussewago Sandstone subcrop of the glaciofluvial sediments in the lake to the Cortland public-supply wells. A comparison of aquifer storage and pumpage in the study area shows that the Cussewago Sandstone receives adequate recharge to support current withdrawals by Cortland public-supply wells. In the immediate vicinity of Cortland- between Route 305 and the Bazetta-Mecca Town ship line and between the

  9. Analysis of the thermochemistry of C sub 2 hydrocarbons on transition metal surfaces using a refined BOC-MP approach

    Energy Technology Data Exchange (ETDEWEB)

    Bell, A.T. (Lawrence Berkeley Lab., CA (United States)); Shustorovich, E. (Eastman Kodak Co., Rochester, NY (United States))

    1990-01-01

    A refined version of the BOC-MP (bond-order-conservation Morse-potential) approach has been used to calculate the heats of adsorption and the activation barriers for dissociation and recombination of C{sub 2}H{sub x} species on transition metals surfaces, such as Fe/W(110), Ni(111), and Pt(111). The calculations reveal distinct periodic patterns of C{sub 2}H{sub x} transformations. In particular, it is found that most of the decomposition routes of ethylene and acetylene are strongly exothermic on Fe and W, but are mildly endothermic on Pt. Accordingly, the calculations predict that C-H and C-C bond cleavage from the gas phase occurs practically without activation on Fe and W, but with finite activation barriers on Ni and especially Pt. The conceivable pathways of C{sub 2}H{sub x} decompositions are discussed in detail. The projections of the refined BOC-MP approach are in much better agreement with experiment, as compared with the authors' previous calculations.

  10. Analysis of the thermochemistry of C 2 hydrocarbons on transition metal surfaces using a refined BOC-MP approach

    Science.gov (United States)

    Bell, Alexis T.; Shustorovich, Evgeny

    1990-09-01

    A refined version of the BOC-MP (bond-order-conservation Morse-potential) approach has been used to calculate the heats of adsorption and the activation barriers for dissociation and recombination of C 2H x species on transition metal surfaces, such as Fe/W(110), Ni(111), and Pt(111). The calculations reveal distinct periodic patterns of C 2H x transformations. In particular, it is found that most of the decomposition routes of ethylene and acetylene are strongly exothermic on Fe and W, but are mildly endothermic on Pt. Accordingly, the calculations predict that C-H and C-C bond cleavage from the gas phase occurs practically without activation on Fe and W, but with finite activation barriers on Ni and especially Pt. The conceivable pathways of C 2H x decompositions are discussed in detail. The projections of the refined BOC-MP approach are in much better agreement with experiment, as compared with our previous calculations.

  11. Surface spin-polarized currents generated in topological insulators by circularly polarized synchrotron radiation and their photoelectron spectroscopy indication

    Science.gov (United States)

    Shikin, A. M.; Klimovskikh, I. I.; Filyanina, M. V.; Rybkina, A. A.; Pudikov, D. A.; Kokh, K. A.; Tereshchenko, O. E.

    2016-08-01

    A new method for generating spin-polarized currents in topological insulators has been proposed and investigated. The method is associated with the spin-dependent asymmetry of the generation of holes at the Fermi level for branches of topological surface states with the opposite spin orientation under the circularly polarized synchrotron radiation. The result of the generation of holes is the formation of compensating spin-polarized currents, the value of which is determined by the concentration of the generated holes and depends on the specific features of the electronic and spin structures of the system. The indicator of the formed spin-polarized current can be a shift of the Fermi edge in the photoelectron spectra upon photoexcitation by synchrotron radiation with the opposite circular polarization. The topological insulators with different stoichiometric compositions (Bi1.5Sb0.5Te1.8Se1.2 and PbBi2Se2Te2) have been investigated. It has been found that there is a correlation in the shifts and generated spin-polarized currents with the specific features of the electronic spin structure. Investigations of the graphene/Pt(111) system have demonstrated the possibility of using this method for other systems with a spin-polarized electronic structure.

  12. Statistic characteristics of severe convective storm during Warm-Season in the Beijing-Tianjin region and its vicinity

    Institute of Scientific and Technical Information of China (English)

    HAN Lei; YU XiaoDing; ZHENG YongGuang; CHEN MingXuan; WANG HongQing; LIN YinJing

    2009-01-01

    This study analyzed the climatological characteristics of severe convective storms in the Beijing and Tianjin region and its vicinity based on the Doppler radar data of Tanggu during May-August of 2003-2007. The climatological characteristics, e.g. storm area, volume, top height, max reflectivity, life time and motion, are analyzed. The results include: 75% of all storms in the Beijing-Tianjin region last no more than 30 minutes, and most storms have a volume less than 400 km3; most storms move from southwest to northeast while the speed is between 10-30 km/h; the mean storm top height is about 6 km, but some strong convective storms can have a top height larger than 15 km; finally, storm area and volume have a similar geographical distribution character showing increasing trends from west to east. Compared with the statistic results based on the conventional surface meteorological observations, the results based on the radar data can present not only 3D spatial statistic results of convective storms (e.g., volume and top height), but also the quantitative climatological characteristics, such as the lifetime and speed distributions. These statistical results are useful for studying the climatic characteristics of convective storms in the Beijing-Tianjin region and its vicinity.

  13. Digital Geologic Map of Rocky Mountain National Park and Vicinity, Colorado (NPS, GRD, GRE, ROMO)

    Data.gov (United States)

    National Park Service, Department of the Interior — The Digital Geologic Map of Rocky Mountain National Park and Vicinity, Coloradois comprised of GIS data layers, two ancillary GIS tables, a Windows Help File with...

  14. Digital Geologic Map of Great Basin National Park and Vicinity, Nevada (NPS, GRD, GRE, GRBA)

    Data.gov (United States)

    National Park Service, Department of the Interior — The Digital Geologic Map of Great Basin National Park and Vicinity, Nevada is composed of GIS data layers, two ancillary GIS tables, a Windows Help File with...

  15. Efficient Debromination of Vicinal (, (-Dibromo Carboxylic Acid Derivatives with the Sm/HOAc System

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The α, β vicinal dibromo carboxylic acid and its derivatives were debrominated with Sm/HOAc system to afford the corresponding cinnamic acid and its derivatives in good yields under mild conditions.

  16. Geology and geomorphology--Drakes Bay and Vicinity Bay Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the geologic and geomorphic map of the Drakes Bay and Vicinity map area, California. The polygon shapefile is included in...

  17. Geology and geomorphology--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included in...

  18. BackscatterA [USGS SWATH]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  19. BackscatterD [CSUMB Swath]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  20. Geology and geomorphology--Drakes Bay and Vicinity Bay Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the geologic and geomorphic map of the Drakes Bay and Vicinity map area, California. The polygon shapefile is included in...

  1. Life in wind turbines vicinity, effects on health – a review

    Directory of Open Access Journals (Sweden)

    Krystyna Pawlas

    2012-12-01

    Full Text Available The paper presents a short review of scientific papers , and other sources concerning health effects of exposure to noise, infrasounds, electromagnetic radiation and mechanical hazards induced in dwellers living in vicinity of wind farm.

  2. Geology and geomorphology--Monterey Canyon and Vicinity Map Area, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the geologic and geomorphic map of Monterey Canyon and Vicinity, California. The vector data file is included in...

  3. Basalt microlapilli in deep sea sediments of Indian Ocean in the vicinity of Vityaz fracture zone

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.; Iyer, S.D.

    Two cores recovered from the flanks of Mid-India oceanic ridge in the vicinity of Vityaz fracture zone consist of discrete pyroclastic layers at various depths. These layers are composed of coarse-grained, angular basaltic microlapilli in which...

  4. 78 FR 13747 - Railroad Safety: Advisory Notice Related to Railroad Accidents in Vicinity of Underground Pipelines

    Science.gov (United States)

    2013-02-28

    ... Federal Railroad Administration Railroad Safety: Advisory Notice Related to Railroad Accidents in Vicinity of Underground Pipelines AGENCY: Federal Railroad Administration (FRA), Department of Transportation... National Transportation Safety Board (NTSB), FRA is issuing this Advisory Notice to inform railroads of the...

  5. BackscatterD [CSUMB Swath]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  6. BackscatterA [USGS SWATH]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for the acoustic-backscatter map of Monterey Canyon and Vicinity map area, California. Backscatter data are provided as separate...

  7. Treatments for reducing total vicine in Egyptian faba bean (Giza 2 variety).

    Science.gov (United States)

    Abd Allah, M A; Foda, Y H; Abu Salem, F M; Abd Allah, Z S

    1988-01-01

    The response of faba bean 'Vicia faba' (Giza 2 variety) towards soaking conditions differed greatly since the absorbed quantities of water (either by the whole or the decorticated forms) are a function of their chemical constituents. On the other hand, 28.45% of the total vicine (vicine & convicine) present in the whole faba bean samples was extracted after soaking for 72 h at room temperature. Subsequently, other soaking mediums, i.e., 0.5% sodium carbonate and/or 1% acetic acid were used in an attempt to increase the level of vicine elimination. Percentage removal of total vicine in whole faba bean was higher in the acidic (61.31%) than the alkaline (38.40%) medium under the conditions tested, i.e., at room temperature for 72 hours. The rates of vicine + convicine elimination in decorticated faba bean for the acidic acid and alkaline soaking media were 78.46 and 79.13%, respectively. The solubility ratio of total vicine relative to soaking solutions (H2O:Na2CO3:Acetic acid) was 1:1.35:2.16 in the whole broad bean and 1:2.41:2.39 in the decorticated samples. The residual amounts of total vicine (78.33% and 77.27%) present after stewing under normal and under pressure cooking conditions could be expected to be decreased to 30.33% for the former and 29.92% for the later after 72 h of soaking. Regression analysis was used to estimate the theoretical zero point of vicine elimination from faba bean through soaking in 1% acetic acid.

  8. An improved tropospheric NO2 retrieval for satellite observations in the vicinity of mountainous terrain

    Directory of Open Access Journals (Sweden)

    R. Dirksen

    2009-03-01

    Full Text Available We present an approach to reduce topography-related errors of vertical tropospheric columns (VTC of NO2 retrieved from the Ozone Monitoring Instrument (OMI in the vicinity of mountainous terrain. This is crucial for reliable estimates of air pollution levels over our particular area of interest, the Alpine region and the adjacent planes, where the operational OMI products exhibit significant biases due to the coarse resolution of surface parameters used in the retrieval. Our approach replaces the coarse-gridded surface pressures by accurate pixel-average values using a high-resolution topography data set, and scales the a priori NO2 profiles accordingly. NO2 VTC reprocessed in this way for the period 2006–2007 suggest that the current Dutch OMI NO2 product (DOMINO underestimates NO2 over the Po Valley in Italy and over the Swiss plateau by about 20% in winter and 5% in summer under clear-sky conditions (cloud radiance fraction <0.5. A sensitivity analysis shows that these seasonal differences are mainly due to the different a priori NO2 profile shapes and solar zenith angles in winter and summer. The comparison of NO2 columns from the original and the enhanced retrieval with corresponding columns deduced from ground-based in situ observations over the Swiss plateau and the Po Valley illustrates the promise of our new retrieval. It partially reduces the underestimation of the OMI VTCs at polluted sites in winter and fall and generally improves the agreement in terms of slope and correlation at rural stations. It does not solve, however, the issue that the OMI DOMINO product tends to overestimate very low columns observed at rural sites in spring and summer.

  9. Characterization of the hydrogeology and stress state in the vicinity of the homestake mine, Lead, SD

    Science.gov (United States)

    Ebenhack, Johnathan Foss

    changed the hydrology and stress state in the vicinity of the Homestake mine. Dewatering reduces the hydraulic head and changes the flow systems in the vicinity of the mine. Four major hydrogeologic zones are recognized: 1.) a Shallow Flow System in the upper few hundred meters that dominates recharge and discharge to streams, 2.) a Recharge Capture Zone where water that has entered the region as recharge since mining began is captured by the mine, 3.) a Storage Capture Zone where water from storage in the host rock around the mine is captured, and 4.) a Mine Workings Zone where rock has been removed. Water enters the system at the top of the Shallow Flow System and either discharges to the streams or flows downward and becomes recharge to the lower capture zones. The Recharge Capture Zone grows with time as regions of storage are depleted and new recharge enters, and eventually it is assumed that the entire capture zone for the mine will become the Recharge Capture Zone. Fluxes from the Shallow Flow System to the Recharge Capture Zone typically range from 1x10-9 to 4x10-9 m/s. The largest recharge fluxes from the Shallow Flow System to the Recharge Capture Zone occur above the shallowest portions of the mine. Recharge flux also occurs above areas adjacent to the mine, and when projected to the surface the Recharge Capture Zone creates a roughly elliptical shape that is 6 km x 3.6 km. The Storage Capture Zone extends out beyond and below the Recharge Capture Zone and when projected to the surface creates a roughly elliptical region that is approximately 8.3 km x 6.6 km and extends down to depths of almost 5 km. Hydraulic heads and flow paths have been affected beyond the Storage Capture Zone but this water had not reached the mine by 135 years and therefore these regions are not included in the capture zones. The model was calibrated using in-situ stress data at various points in the mine to improve its ability to estimate the stress state and mechanical deformation

  10. Water-gas shift reaction over gold nanoparticles dispersed on nanostructured CeOx-TiO2(110) surfaces: Effects of high ceria coverage

    Science.gov (United States)

    Grinter, D. C.; Park, J. B.; Agnoli, S.; Evans, J.; Hrbek, J.; Stacchiola, D. J.; Senanayake, S. D.; Rodriguez, J. A.

    2016-08-01

    Scanning tunnelling microscopy has been used to study the morphology of an overlayer of ceria in contact with a TiO2(110) substrate. Two types of domains were observed after ceria deposition. An ordered ceria film covered half of the surface and high-resolution imaging suggested a near-c(6 × 2) relationship to the underlying TiO2(110)-(1 × 1). The other half of the surface comprised CeOx nanoparticles and reconstructed TiOx supported on TiO2(110)-(1 × 1). Exposure to a small amount of gold resulted in the formation of isolated gold atoms and small clusters on the ordered ceria film and TiO2(110)-(1 × 1) areas, which exhibited significant sintering at 500 K and showed strong interaction between the sintered gold clusters and the domain boundaries of the ceria film. The Au/CeOx/TiO2(110) model system proved to be a good catalyst for the water-gas shift (WGS) exhibiting much higher turnover frequencies (TOFs) than Cu(111) and Pt(111) benchmarks, or the individual Au/TiO2(110) and Au/CeO2(111) systems. For Au/CeOx/TiO2(110) catalysts, there was a decrease in catalytic activity with increasing ceria coverage that correlates with a reduction in the concentration of Ce3 + formed during WGS reaction conditions.

  11. Element-specific study of epitaxial NiO/Ag/CoO/Fe films grown on vicinal Ag(001) using photoemission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Y.; Li, J.; Tan, A.; Jin, E.; Son, J.; Park, J. S.; Doran, A.; Young, A. T.; Scholl, A.; Arenholz, E.; Wu, J.; Hwang, C.; Zhao, H. W.; Qiu, Z. Q.

    2011-01-10

    NiO/Ag/CoO/Fe single crystalline films are grown epitaxially on a vicinal Ag(001) substrate using molecular beam epitaxy and investigated by photoemission electron microscopy. We find that after zero-field cooling, the in-plane Fe magnetization switches from parallel to perpendicular direction of the atomic steps of the vicinal surface at thinner CoO thickness but remains in its original direction parallel to the steps at thicker CoO thickness. CoO and NiO domain imaging result shows that both CoO/Fe and NiO/CoO spins are perpendicularly coupled, suggesting that the Fe magnetization switching may be associated with the rotatable-frozen spin transition of the CoO film.

  12. Dual-system Tectonics of the San Luis Range and Vicinity, Coastal Central California

    Science.gov (United States)

    Hamilton, D. H.

    2010-12-01

    topography; the rapidly uplifting San Luis Range represents the field of NE-SW compression driving a thrust—backthrust thrust fault wedge “popup” while the adjacent shear strike slip faulting associated with the plate boundary San Gregorio-Hosgri splay of the San Andreas fault system results in only minor surface deformation of the sea floor surface of late Quaternary marine planation. Interaction between the two tectonic systems occurs mainly along the SE shoreline of Estero Bay where NNW aligned strike slip faults intersect the uplifting San Luis Range thrust fault “popup” wedge, and along the recently identified Shoreline fault, against which the SSW-vergent leading edge of the San Luis Range thrust impinges at depths of 1-5 km. The latter structural relationship gives rise to locally pronounced west facing sea floor surface scarps along a fault with mostly or entirely horizontal strike slip motion. Overall the San Luis Range and vicinity constitutes an excellent full scale laboratory for observation of evidence of a variety of tectonic processes in action. The opportunity for studies of tectonism here arises not only from the geologically and topographically clearly exhibited effects of the two interacting tectonic fields (NNW shear; NE-SW compression) but also from the extensive baseline studies of the area conducted during the past 40 years.

  13. Submesoscale Dispersion in the Vicinity of the Deepwater Horizon Spill

    Science.gov (United States)

    Ozgokmen, T. M.

    2014-12-01

    Reliable forecasts for the dispersion of oceanic contamination are important for coastal ecosystems, society and the economy as evidenced by the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 and the Fukushima nuclear plant incident in the Pacific Ocean in 2011. Accurate prediction of pollutant pathways and concentrations at the ocean surface requires understanding ocean dynamics over a broad range of spatial scales. Fundamental questions concerning the structure of the velocity field at the submesoscales (100 meters to tens of kilometers, hours to days) remain unresolved due to a lack of synoptic measurements at these scales. Using high-frequency position data provided by the near-simultaneous release of hundreds of accurately tracked surface drifters, we study the structure of submesoscale surface velocity fluctuations in the Northern Gulf Mexico. Observed two-point statistics confirm the accuracy of classic turbulence scaling laws at 200m-50km scales and clearly indicate that dispersion at the submesoscales is local, driven predominantly by energetic submesoscale fluctuations. The results demonstrate the feasibility and utility of deploying large clusters of drifting instruments to provide synoptic observations of spatial variability of the ocean surface velocity field. Our findings allow quantification of the submesoscale-driven dispersion missing in current operational circulation models and satellite altimeter-derived velocity fields.

  14. Le profil SVP : sismique au voisinage du puits The Wvp (Well Vicinity Profiling Stack

    Directory of Open Access Journals (Sweden)

    Blondin E.

    2006-11-01

    Full Text Available L'augmentation de l'investigation latérale du PSV (profil sismique vertical et le calage de la sismique de surface au puits peuvent être améliorés en combinant un profil sismique réflexion de surface d'une mise en oeuvre particulière (à base réceptrice fixe appelé SVP (sismique au voisinage du puits et un profil sismique vertical. Dans cette mise en oeuvre combinée, la sonde n'est immobilisée que pour le temps d'acquisition du PSV. L'utilisation d'une base sismique réceptrice fixe rend la mise en oeuvre du profil SVP légère et peu onéreuse. Les résultats obtenus montrent que les résolutions verticales du profil SVP et du PSV sont équivalentes. L'investigation latérale de cette mise en oeuvre mixte est de plusieurs centaines de mètres quelle que soit la profondeur. Cette recherche méthodologique a été réalisée en collaboration avec Gaz de France. Increasing the lateral range of investigation of VSP (vertical seismic profiling and the calibration of surface seismic profiles with well geological horizons can be improved by combining a surface seismic profile having a specific implementation (with a fixed receiving base called WVP (well vicinity profiling and a vertical seismic profile. In this combined implementation, the drilling rig is immobilized only for the acquisition time of the VSP. The use of a fixed seismic receiving base makes the implementation of the WVP stack light and inexpensive. The results obtained show that the vertical resolutions of the WVP stack and of the VSP are the same. The lateral range of investigation of this mixed implementation is several hundred meters no matter what the depth may be. This methodological research was done in collaboration with Gaz de France.

  15. Optimal estimation of absolute geostrophic velocity field in vicinity of the Luzon Strait using variational data assimilation technique

    Institute of Scientific and Technical Information of China (English)

    兰健; 王东晓

    2002-01-01

    A P - vector method is opt'inized using the variational data assimilation technique (VDAT). The absolute geostrophic velocity fields in the vicinity of the Luzon Strait (LS) are calculated, the spatial structures and seasonal variations o{ the absolute geostrophic velocity field are investigated. Our results show that the Kuroshio enters the South China Sea (SCS) in the south and middle of the Luzon Strait and flows out in the north, so the Kuroshio makes a slight clockwise curve in the Luzon Strait, and the curve is strong in winter and weak in summer. During the winter, a westward current appears in the surface, and locates at the west of the Luzon Strait. It is the north part of a cyclonic gyre which exits in the northeast of the SCS; an anti-cyclonic gyre occurs on the intermediate level, and it exits in the northeast of the SCS, and an eastward current exits in the southeast of the anti-cyclonic gyre.

  16. NUMERICAL SIMULATION OF AN OSCILLATING FLOW PAST A CIRCULAR CYLINDER IN THE VICINITY OF A PLANE WALL

    Institute of Scientific and Technical Information of China (English)

    SHAH Syed Bilai Hussain; LU Xi-yun

    2008-01-01

    Oscillating flow around a circular cylinder in the vicinity of a plane wall was investigated by solving the two-dimensional incompressible Navier-Stokes equations with a finite element Galarkin residual method. The effect of the gap G/D between the cylinder surface and the wall on the flow behavior was studied. For the case of G/D ≤ 0.25, the periodicity in the flow is attributed to both the outer shear layer instability and the oscillating frequency. As G/D > 0.25, vortex shedding occurs and the periodicity in the flow is mainly due to the competition of the oscillating frequency and the vortex shedding frequency from an isolated stationary cylinder.

  17. Fourier transform photoelectron diffraction and its application to molecular orbitals and surface structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Xin [Pennsylvania State Univ., University Park, PA (United States)

    1998-11-30

    Photoemission intensities from the molecular orbitals of c(2x2)CO/Pt(111) over a wide photon energy range were measured and analyzed by the same methods developed for structural studies using core levels. The 4{sigma} orbital center of gravity is found to be concentrated between the C and O atoms, while that of the 5{sigma} orbital lies between the C atom and the Pt surface. The C 1s photoelectron diffraction was used to determine the adsorption geometry. The earlier ambiguity that multiple scattering is needed to correctly model a {chi} curve while single scattering is sufficient for understanding major peaks in the ARPEFS-FTS is clarified by studying the clean Ni(111) surface. In the normal emission case, several different combinations of scattering events have similar path length differences (PLDs), and can either cancel each other or enhance the corresponding FT peak. In the off-normal case the degeneracy is greatly reduced due to the lower degree of symmetry. In normal emission AR PEFS, up to third order multiple scattering is needed to describe fully both the {chi} curve and its FT spectrum. To improve the spectral resolution in the ARPEFS-FT analysis, several new spectral analysis methods are introduced. With both autocorrelation autoregression (ACAR) and autocorrelation eigenvector (ACE), we can produce a reliable power spectrum by following the order-closing procedure. The best spectra are usually obtained when the autocorrelation sequence is computed with lags up to half the data range. A simple way of determining surface adsorption sites is proposed as follows: First use a single scattering cluster for possible adsorption sites to construct the geometrical PLDs from the strong backscattering events; then compare these PLDs with those obtained from the ARPEFS-FT analysis of the experimental data. After the preferred adsorption site is determined, fine tune the interlayer distances according to the positional R-factor.

  18. Sea-Floor Character and Sedimentary Processes in the Vicinity of Woods Hole, Massachusetts

    Science.gov (United States)

    Poppe, Lawrence J.; McMullen, Katherine Y.; Foster, David S.; Blackwood, Dann S.; Williams, S. Jeffress; Ackerman, Seth D.; Barnum, Steven R.; Brennan, Rick T.

    2008-01-01

    Continuous-coverage multibeam bathymetric models and sidescan-sonar imagery have been verified with high-resolution seismic-reflection profiles, sediment sampling, and bottom photography. Together these data layers provide detailed base maps that yield topographic, compositional, and environmental perspectives of the sea floor in the vicinity of Woods Hole, an important harbor and major passage between the Elizabeth Islands and Cape Cod, Massachusetts. Tidally dominated high-energy environments within Woods Hole have prevented deposition of Holocene marine sediments, exposed underlying glacial drift of the Buzzards Bay moraine, and winnowed finer grained sediments, leaving lag deposits of boulders and gravel. These conditions have also enlarged and preserved depressions in the moraine surface that were originally kettle holes and formed ebb-tidal deltas at the entrances to passages. Fields of transverse and barchanoid sand waves dominate across the southern part of the study area in Vineyard Sound, where benthic environments are characterized by processes associated with coarse-bedload transport. Transverse sand waves dominate near shoals where sediment supply is greater and have asymmetries that indicate that the shoals are shaped and maintained by clockwise gyres of net sediment transport. Barchanoid sand waves, which are most common where Holocene sediments are thinner, commonly align into elongate fields that have smaller isolated waves concentrated at the eastern ends and that progressively widen and have waveforms that increase in amplitude, wavelength, and complexity westward. The northern, protected parts of the Little and Inner Harbors are characterized by muddy sediment and processes associated with deposition. A pockmark field in Little Harbor and the muddy, organic-rich sediments that form a scarp along the edge of Parker Flat are evidence for the presence of submerged marsh deposits formed during the Holocene rise in sea level.

  19. Observations of rapid aerosol optical depth enhancements in the vicinity of polluted cumulus clouds

    Science.gov (United States)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Arola, A.; Ferrare, R. A.; Hostetler, C. A.; Crumeyrolle, S. N.; Berkoff, T. A.; Welton, E. J.; Lolli, S.; Lyapustin, A.; Wang, Y.; Schafer, J. S.; Giles, D. M.; Anderson, B. E.; Thornhill, K. L.; Minnis, P.; Pickering, K. E.; Loughner, C. P.; Smirnov, A.; Sinyuk, A.

    2014-11-01

    During the July 2011 Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field experiment in Maryland, significant enhancements in Aerosol Robotic Network (AERONET) sun-sky radiometer measured aerosol optical depth (AOD) were observed in the immediate vicinity of non-precipitating cumulus clouds on some days. Both measured Ångström exponents and aerosol size distribution retrievals made before, during and after cumulus development often suggest little change in fine mode particle size; therefore, implying possible new particle formation in addition to cloud processing and humidification of existing particles. In addition to sun-sky radiometer measurements of large enhancements of fine mode AOD, lidar measurements made from both ground-based and aircraft-based instruments during the experiment also measured large increases in aerosol signal at altitudes associated with the presence of fair weather cumulus clouds. These data show modifications of the aerosol vertical profile as a result of the aerosol enhancements at and below cloud altitudes. The airborne lidar data were utilized to estimate the spatial extent of these aerosol enhancements, finding increased AOD, backscatter and extinction out to 2.5 km distance from the cloud edge. Furthermore, in situ measurements made from aircraft vertical profiles over an AERONET site during the experiment also showed large increases in aerosol scattering and aerosol volume after cloud formation as compared to before. The 15-year AERONET database of AOD measurements at the Goddard Space Flight Center (GSFC), Maryland site, was investigated in order to obtain a climatological perspective of this phenomenon of AOD enhancement. Analysis of the diurnal cycle of AOD in summer showed significant increases in AOD from morning to late afternoon, corresponding to the diurnal cycle of cumulus development.

  20. Seafloor Character and Processes in the Vicinity of Woods Hole, Massachusetts

    Science.gov (United States)

    Poppe, L. J.; McMullen, K. Y.; Williams, S.; Barnum, S. R.; Brennan, R. T.

    2009-12-01

    Continuous-coverage multibeam bathymetry and sidescan-sonar imagery have been verified with high-resolution seismic-reflection profiles, sediment sampling, and bottom photography. Together these data provide detailed base maps that yield topographic, compositional, and environmental perspectives of the seafloor in the vicinity of Woods Hole, an important harbor and major passage between the Elizabeth Islands and Cape Cod, Massachusetts. Tidally-dominated high-energy environments within Woods Hole have prevented deposition of Holocene sediments, exposed underlying glacial drift of the Buzzards Bay moraine, and winnowed finer grained sediments leaving lag deposits of boulders and gravel. Tidal currents have also enlarged and preserved depressions in the moraine surface that were originally kettle holes and formed ebb-tidal deltas at the entrances to passages. Fields of transverse and barchanoid sand waves dominate across the southern part of the study area in Vineyard Sound where benthic environments are characterized by processes associated with coarse bedload transport. Transverse sand waves dominate near shoals where sediment is available and have asymmetries indicating the shoals are shaped and maintained by clockwise gyres. Barchanoid sand waves, which are most common where Holocene sediments are thinner, commonly occur in elongate fields that have small isolated waves concentrated at their eastern ends and that progressively widen and have waveforms that increase in amplitude, wavelength, and morphological complexity westward, indicating net westward transport. The northern, lower energy parts of the Little and Great Harbors are characterized by muddy sediment and processes associated with deposition. A pockmark field in Little Harbor and the muddy organic-rich sediments that form a scarp along the eastern edge of Great Harbor are evidence for the presence of buried marsh deposits submerged during the Holocene rise in sea level.

  1. Lead poisoning of horses in the vicinity of a battery recycling plant

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, H.; Iribarren, I.; Olalla, M.J.; Cala, V. [Departamento de Quimica Agricola, Geologia y Geoquimica, Facultad de Ciencias, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

    2002-05-06

    The diagnosis of lead poisoning in horses living on farmland in the vicinity of a battery recycling plant was based on clinical signs as well as on laboratory findings. Chemical analysis of six surface soils (0-15 cm) and herbage samples taken at different distances to the recycling plant showed very high total lead levels in the closest sites to the facility and a clear decrease with distance. Total lead levels in soil samples ranged from 127 to 5657 mg kg{sup -1}, with more than 70% of lead extractable by EDTA in the most polluted soils. Lead levels in the aerial part of herbage samples were in the range of 113-4741 mg kg{sup -1}. A water washing pre-treatment of the vegetal samples considerably diminished the concentration of lead, suggesting that airborne lead particles from the facility emissions were fixed on the shoots. The analysis of samples taken from six dead horses showed lead concentrations, expressed as mg kg{sup -1} (d.w.), as follows: blood: 0.20-0.89; liver: 2.5-15; kidney: 1.70-6.75. Lead intake levels, estimated according to the ingestion rate of Grammineae forage, illustrates that the apported lead through the ingestion of vegetation growing in the closest sites to the recycling plant was approximately 99.5 mg Pb/kg body weight/day surpassing the fatal dosage for horses of 2.4 mg Pb/kg body weight/day reported by Hammond and Aronson, Ann NY Acad Sci, 1964; 111: 595-611.

  2. Submesoscale Dispersion in the Vicinity of the Deepwater Horizon Spill

    Science.gov (United States)

    2014-09-02

    dental oil spill into marine waters in history with some 4.4 million barrels released into the DeSoto Canyon of the northern Gulf of Mexico (GoM) from...surface dispersion in the DeSoto Canyon region remain unclear. The region lies between the mesoscale eddy-driven deep water GoM (7) and the wind- driven...during the period of July 20 to July 31, 2012; during the same season as the Fig. 1. Multiscale flows near the DwH and DeSoto Canyon region. (A

  3. Addressing water vaporization in the vicinity of an exploding wire

    Science.gov (United States)

    Grinenko, A.; Gurovich, V. Tz.; Krasik, Ya. E.; Dolinsky, Yu.

    2006-12-01

    The phase state of thin (˜1μm) layer of water adjacent to the surface of rapidly heated thin wire 100±50μm in radius is analyzed by computer hydrodynamic calculation. It is shown that when heating of a wire to a temperature of 420°C is achieved in less than ˜500ns, the trajectory of the phase state is contained in the liquid part of the phase diagram. This suggests additional proof of and an explanation for the absence of shunting plasma discharge in fast underwater electrical wire explosions.

  4. Cancer incidence in the vicinity of nuclear power plants in Taiwan: a population-based study.

    Science.gov (United States)

    Wang, Shiow-Ing; Yaung, Chih-Liang; Lee, Long-Teng; Chiou, Shang-Jyh

    2016-01-01

    Numerous antinuclear demonstrations reveal that the public is anxious about the potential health effects caused by nuclear power plants. The purpose of this study is to address the question "Is there a higher cancer incidence rate in the vicinity of nuclear power plants in Taiwan?" The Taiwan Cancer Registry database from 1979 to 2003 was used to compare the standardized incidence rate of the top four cancers with strong evidence for radiation risks between the "plant-vicinity" with those "non-plant-vicinity" groups. All cancer sites, five-leading cancers in Taiwan, and gender-specific cancers were also studied. We also adopted different observation time to compare the incidence rate of cancers between two groups to explore the impact of the observation period. The incidences of leukemia, thyroid, lung, and breast cancer were not significantly different between two groups, but cervix uteri cancer showed higher incidence rates in the plant-vicinity group. The incidence of cervical cancer was not consistently associated with the duration of plant operation, according to a multiyear period comparison. Although there was higher incidence in cervix cancer in the plant-vicinity group, our findings did not provide the crucial evidence that nuclear power plants were the causal factor for some cancers with strong evidence for radiation risks.

  5. Geology in the Vicinity of the TYBO and BENHAM Underground Nuclear Tests, Pahute Mesa, Nevada Test Site

    Energy Technology Data Exchange (ETDEWEB)

    L. B. Prothro

    2001-12-01

    Recent radiochemical evidence from groundwater characterization and monitoring wells in the vicinity of the TYBO and BENHAM underground nuclear tests in Area 20 of the Nevada Test Site, suggests that migration of radionuclides within groundwater beneath this portion of Area 20 may be more rapid than previously thought. In order to gain a better understanding of the hydrogeologic conditions in the TYBO-BENHAM area for more accurate flow and transport modeling, a reevaluation of the subsurface geologic environment in the vicinity of the two underground tests was conducted. Eight existing drill holes provided subsurface control for the area. These holes included groundwater characterization and monitoring wells, exploratory holes, and large-diameter emplacement holes used for underground nuclear weapons tests. Detailed and consistent geologic descriptions of these holes were produced by updating existing geologic descriptions with data from petrographic, chemical, and mineralogic analyses, and current stratigraphic concepts of the region. The updated descriptions, along with surface geologic data, were used to develop a detailed geologic model of the TYBO-BENHAM area. This model is represented by diagrams that correlate stratigraphic, lithologic, and alteration intervals between holes, and by isopach and structure maps and geologic cross sections. Regional data outside the TYBO-BENHAM area were included in the isopach and structure maps to better evaluate the geology of the TYBO-BENHAM area in a regional context. The geologic model was then evaluated with regard to groundwater flow and radionuclide migration to assess the model's implications for flow and transport modeling. Implications include: (1) confirmation of the general hydrogeology of the area described in previous studies; (2) the presence of two previously unrecognized buried faults that could act as zones of enhanced permeability within aquifers; and (3) secondary alteration within tuff confining

  6. Seismicity of the Earth 1900–2010 Himalaya and vicinity

    Science.gov (United States)

    Turner, Bethan; Jenkins, Jennifer; Turner, Rebecca; Parker, Amy; Sinclair, Alison; Davies, Sian; Hayes, Gavin P.; Villaseñor, Antonio; Dart, Rirchard L.; Tarr, Arthur C.; Furlong, Kevin P.; Benz, Harley M.

    2013-01-01

    Seismicity in the Himalaya region predominantly results from the collision of the India and Eurasia continental plates, which are converging at a relative rate of 40–50 mm/yr. Northward underthrusting of India beneath Eurasia generates numerous earthquakes and consequently makes this area one of the most seismically hazardous regions on Earth. The surface expression of the plate boundary is marked by the foothills of the north-south trending Sulaiman Range in the west, the Indo-Burmese Arc in the east, and the east-west trending Himalaya Front in the north of India. Along the western margin of the India plate, relative motions between India and Eurasia are accommodated by strike-slip, reverse, and oblique-slip faulting resulting in the complex Sulaiman Range fold and thrust belt, and the major translational Chaman Fault in Afghanistan. Beneath the Pamir‒Hindu Kush Mountains of northern Afghanistan, earthquakes occur to depths as great as 200 km as a result of remnant lithospheric subduction. Further north again, the Tian Shan is a seismically active intra-continental mountain belt defined by a series of east-west trending thrust faults thought to be related to the broad footprint of the India-Eurasia collision. Tectonics in northern India are dominated by motion along the Main Frontal Thrust and associated thrust faults of the India-Eurasia plate boundary, which have resulted in a series of large and devastating earthquakes in (and prior to) the 20th century. The Tibetan Plateau to the north of the main plate boundary is a broad region of uplift associated with the India-Eurasia collision, and is cut by a series of generally east-west trending strike-slip faults. These include the Kunlun, Haiyuan, and the Altyn Tagh faults, all of which are left-lateral structures, and the Kara-Koram right-lateral fault. Throughout the plateau, thrust faults accommodate the north-south compressional component of crustal shortening associated with the ongoing collision of India

  7. Anisotropy of the resistivity and critical current density of porous vicinal YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} films

    Energy Technology Data Exchange (ETDEWEB)

    Emergo, R L S; Wu, J Z [Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 (United States); Haugan, T J; Barnes, P N [Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433-7919 (United States)

    2008-08-15

    The anisotropy of electrical transport properties of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films containing high density nanopores grown on 5 deg., 10 deg. and 20 deg. vicinal substrates was investigated. For porous films in the normal state, the resistivity in the longitudinal direction is comparable to that of reference YBCO films without nanopores. In addition, the {rho}{sub c}/{rho}{sub ab} ratios derived from the resistivities in longitudinal and transverse directions of the porous samples fall in the same range as that of twinned single crystal YBCO. For the superconducting state, the pore surfaces provide strong magnetic pins to magnetic vortices, which leads to significantly increased critical current density J{sub c} along the longitudinal direction as compared to that of the reference YBCO films. This strong isotropic pore surface pinning also increased the J{sub c} along the transverse direction as compared to that of nonporous vicinal YBCO films. This result suggests that the effect of nanopores on the electronic structure of YBCO is minimal and the strong pore surface pinning may provide an effective way to enhance J{sub c} after optimization.

  8. 14 CFR 91.137 - Temporary flight restrictions in the vicinity of disaster/hazard areas.

    Science.gov (United States)

    2010-01-01

    ... vicinity of disaster/hazard areas. 91.137 Section 91.137 Aeronautics and Space FEDERAL AVIATION... disaster/hazard areas. (a) The Administrator will issue a Notice to Airmen (NOTAM) designating an area within which temporary flight restrictions apply and specifying the hazard or condition requiring...

  9. Preliminary assessment of the electromagnetic environment in the immediate vicinity of the ETA accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Cabayan, H.S.; Bogdan, E.; Zicker, J.; Wythe, D.; Burke, G.J.

    1980-04-01

    The electromagnetic fields in the immediate vicinity of the Experimental Test Accelerator (ETA) at the Lawrence Livermore Laboratory have been characterized. Various EM sensors that cover the frequency band from the very low frequencies up into the GHz region have been used. The report describes in detail the probes, the test set-up and the data processing techniques.

  10. Revised Hydrogeology for the Suprabasalt Aquifer System, 200-West Area and Vicinity, Hanford Site, Washington

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Bruce A.; Bjornstad, Bruce N.; Schalla, Ronald; Webber, William D.

    2002-05-14

    The primary objective of this study was to refine the conceptual groundwater flow model for the 200-West Area and vicinity. This is the second of two reports that combine to cover the 200 Area Plateau, an area that holds the largest inventory of radionuclide and chemical waste on the Hanford Site.

  11. Characterization Of Contaminant Migration Potential In The Vicinity Of An In-Place Sand Cap

    Science.gov (United States)

    This study characterized the chemical transport potential of polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs) in the vicinity of a sand cap placed in the nearshore zone of a tidal marine embayment. Groundwater seepage was investigated along the per...

  12. Acoustically induced shear stresses in the vicinity of microbubbles in tissue

    DEFF Research Database (Denmark)

    Lewin, Peter A.; Jensen, Leif Bjørnø

    1982-01-01

    The shear stresses in the vicinity of gaseous microbubbles in tissue irradiated by continuous and transient ultrasonic fields typical of those used in diagnostic practice have been calculated from a solution of the equation of motion of the bubble. The assumptions and limitations of the model have...

  13. Programmatic Environmental Report for remedial actions at UMTRA (Uranium Mill Tailings Remedial Action) Project vicinity properties

    Energy Technology Data Exchange (ETDEWEB)

    1985-03-01

    This Environmental Report (ER) examines the environmental consequences of implementing a remedial action that would remove radioactive uranium mill tailings and associated contaminated materials from 394 vicinity properties near 14 inactive uranium processing sites included in the Uranium Mill Tailings Remedial Action (UMTRA) Project pursuant to Public Law 95--604, the Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978. Vicinity properties are those properties in the vicinity of the UMTRA Project inactive mill sites, either public or private, that are believed to be contaminated by residual radioactive material originating from one of the 14 inactive uranium processing sites, and which have been designated under Section 102(a)(1) of UMTRCA. The principal hazard associated with the contaminated properties results from the production of radon, a radioactive decay product of the radium contained in the tailings. Radon, a radioactive gas, can diffuse through the contaminated material and be released into the atmosphere where it and its radioactive decay products may be inhaled by humans. A second radiation exposure pathway results from the emission of gamma radiation from uranium decay products contained in the tailings. Gamma radiation emitted from contaminated material delivers an external exposure to the whole body. If the concentration of radon and its decay products is high enough and the exposure time long enough, or if the exposure to direct gamma radiation is long enough, cancers (i.e., excess health effects) may develop in persons living and working at the vicinity properties. 3 refs., 7 tabs.

  14. Series Resistance Monitoring for Photovoltaic Modules in the Vicinity of MPP

    DEFF Research Database (Denmark)

    Sera, Dezso

    2010-01-01

    the time period with reduced power production. This paper focuses on the estimation of series resistance of flat silicone PV panels or arrays during operation, in the vicinity of their MPP. The method presented in this paper helps to detect failures by monitoring changes in the panel’s or array’s series...

  15. BathymetryA Hillshade [2m]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for 2-m and 5-m bathymetry and shaded-relief maps of Monterey Canyon and Vicinity, California. The raster data file is included in...

  16. BathymetryB [5m]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for 2-m and 5-m bathymetry and shaded-relief maps of Monterey Canyon and Vicinity, California. The raster data file is included in...

  17. BathymetryA [2m]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for 2-m and 5-m bathymetry and shaded-relief maps of Monterey Canyon and Vicinity, California. The raster data file is included in...

  18. Two new species of Ophidiasterid sea-stars from the vicinity of Diaoyudao, East China Sea

    Science.gov (United States)

    Liao, Yulin

    1985-06-01

    Two new species of the asteroid family Ophidiasteridae are described from two specimens collected by commercial fishery vessels of Qingdao from the vicinity of Diaoyudao (25°45'N, 123°15'E), East China Sea. Hacelia tuberculata sp. nov. shows affinities with H. tyloplax (H. L. Clark, 1914) and Linckia gracilis sp. nov. is related to L. laevigata (Linnaeus).

  19. Metallocene catalyzed synthesis of fungistatic vicinal aminoalcohols under solvent free conditions.

    Science.gov (United States)

    Mancilla, Gabriela; Durán-Patrón, Rosa M; Macías-Sánchez, Antonio J; Collado, Isidro G

    2010-11-15

    Group 4 and 5 metallocenes, Cp(2)TiCl(2), Cp(2)ZrCl(2) and Cp(2)VCl(2), have been evaluated as catalyst in the solvent free, room temperature, preparation of vicinal aminoalcohols. The regioselectivity of the reaction and the fungistatic activity of the prepared compounds against Botrytis cinerea and Colletotrichum gloeosporioides are discussed.

  20. BathymetryB Hillshade [5m]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for 2-m and 5-m bathymetry and shaded-relief maps of Monterey Canyon and Vicinity, California. The raster data file is included in...

  1. Measuring dose from radiotherapy treatments in the vicinity of a cardiac pacemaker.

    Science.gov (United States)

    Peet, Samuel C; Wilks, Rachael; Kairn, Tanya; Crowe, Scott B

    2016-12-01

    This study investigated the dose absorbed by tissues surrounding artificial cardiac pacemakers during external beam radiotherapy procedures. The usefulness of out-of-field reference data, treatment planning systems, and skin dose measurements to estimate the dose in the vicinity of a pacemaker was also examined. Measurements were performed by installing a pacemaker onto an anthropomorphic phantom, and using radiochromic film and optically stimulated luminescence dosimeters to measure the dose in the vicinity of the device during the delivery of square fields and clinical treatment plans. It was found that the dose delivered in the vicinity of the cardiac device was unevenly distributed both laterally and anteroposteriorly. As the device was moved distally from the square field, the dose dropped exponentially, in line with out-of-field reference data in the literature. Treatment planning systems were found to substantially underestimate the dose for volumetric modulated arc therapy, helical tomotherapy, and 3D conformal treatments. The skin dose was observed to be either greater or lesser than the dose received at the depth of the device, depending on the treatment site, and so care should be if skin dose measurements are to be used to estimate the dose to a pacemaker. Square field reference data may be used as an upper estimate of absorbed dose per monitor unit in the vicinity of a cardiac device for complex treatments involving multiple gantry angles. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  2. 77 FR 71493 - Amendment of VOR Federal Airway V-8 in the Vicinity of Rifle, CO

    Science.gov (United States)

    2012-12-03

    ... Vicinity of Rifle, CO AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule, technical... Rifle, CO, to correct the description contained in part 71 to ensure it matches the information... realigned over the Rifle, CO, VHF Omnidirectional Range/Distance Measuring Equipment (VOR/DME) navigation...

  3. Influence of the Canton Tower on the cloud-to-ground lightning in its vicinity

    Science.gov (United States)

    Zhang, Changxiu; Lu, Weitao; Chen, Luwen; Qi, Qi; Ma, Ying; Yao, Wen; Zhang, Yijun

    2017-06-01

    This paper analyzed the influence of the Canton Tower on cloud-to-ground lightning in its vicinity based on the data obtained by Lightning Location System (LLS) of the Guangdong Power Grid Corporation from 1999 to 2015. The LLS data obtained before (1999-2005) and after (2010-2015) the erection of the Canton Tower were compared. The flash/stroke density showed a significant increase in the immediate vicinity around the Canton Tower within a radius of 1 km and a clear decrease in the annular vicinity with a radius from 1 km to 4 km. The arithmetic mean and median LLS-inferred peak current of strokes that occurred in 1 km radius area around the Canton Tower exhibited a significant increase, while that of the strokes that occurred beyond 1 km did not show a clear change. The percentage of negative flashes (ratio of negative flashes to total flashes) showed a slight increase in the immediate vicinity around the Canton Tower, which could be caused by the upward lightning (often negative) initiated from the tower. Due to the existence of the Canton Tower, the lightning multiplicity presented a decreasing trend to some extent within 4 km radius around the tower compared with the arithmetic mean value within 10 km radius. It is speculated that the Canton Tower induced lots of upward flashes and attracted some downward flashes around it within several kilometers radius to itself.

  4. Revised Hydrogeology for the Suprabasalt Aquifer System, 200-East Area and Vicinity, Hanford Site, Washington

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Bruce A.; Bjornstad, Bruce N.; Schalla, Ronald; Webber, William D.

    2000-04-20

    This study supports the Hanford Groundwater/Vadose integration project objectives to better understand the risk of groundwater contamination and potential risk to the public via groundwater flow paths. The primary objective of this study was to refine the conceptual groundwater flow model for the 200-East Area and vicinity.

  5. BathymetryA Hillshade [2m]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for 2-m and 5-m bathymetry and shaded-relief maps of Monterey Canyon and Vicinity, California. The raster data file is included in...

  6. BathymetryB [5m]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for 2-m and 5-m bathymetry and shaded-relief maps of Monterey Canyon and Vicinity, California. The raster data file is included in...

  7. BathymetryB Hillshade [5m]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for 2-m and 5-m bathymetry and shaded-relief maps of Monterey Canyon and Vicinity, California. The raster data file is included in...

  8. BathymetryA [2m]--Monterey Canyon and Vicinity, California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents data for 2-m and 5-m bathymetry and shaded-relief maps of Monterey Canyon and Vicinity, California. The raster data file is included in...

  9. Electrical properties, texture, and microstructure of vicinal YBa2Cu3O7−δ thin films

    NARCIS (Netherlands)

    Pedarnig, J.D.; Rössler, R.; Delamare, M.P.; Lang, W.; Bäuerle, D.; Köhler, A.; Zandbergen, H.W.

    2002-01-01

    Vicinal YBa2Cu3O7−δ (YBCO) thin films of thickness h = 20–480 nm are grown by pulsed-laser deposition on 10° miscut (001) SrTiO3 substrates. The anisotropic resistivities, c-axis texture, and critical temperature drastically depend on the thickness of vicinal films. High-resolution electron microsco

  10. Climate Prediction of Tropical Cyclone Activity in the Vicinity of Taiwan Using the Multivariate Least Absolute Deviation Regression Method

    Directory of Open Access Journals (Sweden)

    Pao-Shin Chu

    2007-01-01

    Full Text Available In this study, a multivariate linear regression model is applied to predict the seasonal tropical cyclone (TC count in the vicinity of Taiwan using large-scale climate variables available from the preceding May. Here the season encompasses the five-month period from June through October, when typhoons are most active in the study domain. The model is based on the least absolute deviation so that regression estimates are more resistant (i.e., not unduly influenced by outliers than those derived from the ordinary least square method. Through lagged correlation analysis, five parameters (sea surface temperature, sea level pressure, precipitable water, low-level relative vorticity, and vertical wind shear in key locations of the tropical western North Pacific are identified as predictor datasets. Results from crossvalidation suggest that the statistical model is skillful in predicting TC activity, with a correlation coefficient of 0.63 for 1970 - 2003. If more recent data are included, the correlation coefficient reaches 0.69 for 1970 - 2006. Relative importance of each predictor variable is evaluated. For predicting higher than normal seasonal TC activity, warmer sea surface temperatures, a moist troposphere, and the presence of a low-level cyclonic circulation coupled with low-latitude westerlies in the Philippine Sea in the antecedent May appear to be important.

  11. Growth of InAs quantum dots on vicinal GaAs substrates by molecular beam epitaxy

    Science.gov (United States)

    Weir, Nicholas; Yao, Ruizhe; Lee, Chi-Sen; Guo, Wei

    2016-10-01

    Previous work shows the benefits of using vicinal substrates but there is currently a gap in the experimental studies of the effects under different MBE growth conditions. To fully realize controllable growth while using a vicinal substrate, we systematically explore and discuss the mechanism behind the dependence of the optical characteristics of MBE grown InAs QD ensembles with different growth parameters on a vicinal substrate. In addition, the potential improvement in optical quality with a vicinal substrate over an on-axis is demonstrated and an investigation into applying a two-step growth procedure on a vicinal substrate is conducted. Photoluminescence of the grown QD ensembles shows that increasing V/III ratio increased wavelength and decreased FWHM. Decreasing substrate temperature increased wavelength and FWHM. Utilizing the two-step growth method increased both wavelength and FWHM with increased interruption time.

  12. Antibacterial activity of the sponge Ircinia ramosa: Importance of its surface-associated bacteria

    Digital Repository Service at National Institute of Oceanography (India)

    Thakur, N.L.; Anil, A.C.

    Variations in the antibacterial activity of the sponge Ircinia ramosa were evaluated during two collection periods (January and May) against vicinity fouling bacteria (VFB) and sponge surface-associated bacteria (SAB). The density of fouling...

  13. MeV Ion Anisotropies in the Vicinity of Interplanetary Shocks

    Science.gov (United States)

    Richardson, I. G.; Cane, H. V.; von Rosenvinge, T. T.

    2007-05-01

    The anticipated signatures of interplanetary shock acceleration to be found in energetic ion anisotropies in the vicinity of interplanetary shocks include near-isotropic particle distributions consistent with of diffusive shock acceleration, "pancake" distributions indicative of shock drift acceleration, and flow reversals suggestive of a particle acceleration region passing by the observing spacecraft. In practice, while clear examples of these phenomena exist, more typically, particle anisotropies near interplanetary shocks show considerable variation in time and space, both in individual events and from event to event. We investigate the properties of MeV/n ions in the vicinity of a number of interplanetary shocks associated with the largest energetic particle events of solar cycle 23, and previous cycles, including their intensity-time profiles, anisotropies, and relationship with local solar wind structures, using observations from the IMP 8, ISEE-3, Helios 1 and 3 spacecraft. The aim is to help to understand the role of shocks in major solar energetic particle events.

  14. Sugar Sweetened Beverage Consumption among Primary School Students: Influence of the Schools' Vicinity

    Science.gov (United States)

    Morin, Pascale; Lalonde, Benoit; Florina Fratu, Ramona; Bisset, Sherri

    2016-01-01

    The purpose of the research was to explore the associations between the characteristics of schools' vicinity and the risk of sugar sweetened beverage (SSB) consumption in elementary students. Findings exposed an important variation in student's SSB consumption between schools. Schools with a lower socioeconomic status or in a densely built environment tend to have higher proportion of regular SSB drinkers. These characteristics of the school's vicinity partly explained the variation observed between them. We estimated that a student moving to a school with a higher proportion of SSB drinkers may increase his/her chances by 52% of becoming a daily consumer. Important changes in dietary preferences can occur when children are in contact with a new social environment. Findings also support the idea that dietary behaviors among children result from the complex interactions between biological, social, and environmental factors. PMID:27752265

  15. Anomalous rotational diffusion in the vicinity of the isotropic to nematic phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Jadzyn, Jan [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznan (Poland); Czechowski, Grzegorz [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznan (Poland); Dejardin, Jean-Louis [Groupe de Physique Statistique et Moleculaire, MEPS, Universite de Perpignan, 52, Avenue Paul Alduy, 66860 Perpignan Cedex (France); Ginovska, Margarita [University of Cyril and Methodius, Faculty of Electrical Engineering, PO Box 574, 91000 Skopje (Macedonia, The Former Yugoslav Republic of)

    2005-02-16

    Dielectric relaxation measurements are performed with very high accuracy on a liquid crystalline compound n-octylcyanobiphenyl (8CB) in the isotropic (I), nematic (N) and smectic A (S{sub A}) phases. The data obtained display an essential difference in the rotational diffusion process in the vicinity of the I-N phase transition in comparison to that taking place in the vicinity of the N-S{sub A} phase transition. Thus, for the I-N transition, anomalously slow diffusion (subdiffusion), characterized by an anomalous coefficient {alpha}<1, is observed, while normal Brownian rotational diffusion with {alpha}{approx}1 is found for the N-S{sub A} transition. It is also shown how the fractal parameter {alpha} is temperature dependent with an extremely sharp variation at the I-N transition point in the form of a lambda-like profile.

  16. Magnetostrictive hypersound generation by spiral magnets in the vicinity of magnetic field induced phase transition

    Science.gov (United States)

    Bychkov, Igor V.; Kuzmin, Dmitry A.; Kamantsev, Alexander P.; Koledov, Victor V.; Shavrov, Vladimir G.

    2016-11-01

    In present work we have investigated magnetostrictive ultrasound generation by spiral magnets in the vicinity of magnetic field induced phase transition from spiral to collinear state. We found that such magnets may generate transverse sound waves with the wavelength equal to the spiral period. We have examined two types of spiral magnetic structures: with inhomogeneous exchange and Dzyaloshinskii-Moriya interactions. Frequency of the waves from exchange-caused spiral magnetic structure may reach some THz, while in case of Dzyaloshinskii-Moriya interaction-caused spiral it may reach some GHz. These waves will be emitted like a sound pulses. Amplitude of the waves is strictly depends on the phase transition speed. Some aspects of microwaves to hypersound transformation by spiral magnets in the vicinity of phase transition have been investigated as well. Results of the work may be interesting for investigation of phase transition kinetics as well, as for various hypersound applications.

  17. Electric and magnetic field testing in vicinity of 110/x kV substations

    Directory of Open Access Journals (Sweden)

    Grbić Maja

    2016-01-01

    Full Text Available The levels of non-ionizing radiation (electric and magnetic fields at power frequency, which occur near 110/x kV substations are analyzed in this paper. The results of electric field strength and magnetic flux density measurements in the vicinity of three typical substations of the aforementioned voltage level are shown. With the purpose of estimating the exposure of the population to these fields, the obtained results were compared to the reference maximum levels set for increased sensitivity areas, which amount to 2 kV/m for electric field and 40 μT for magnetic flux density. The objective of the conducted analysis is to reach general conclusions on the levels of electric and magnetic fields, which may occur in the vicinity of the substations mentioned above, and evaluate their compliance with the national regulations on the population protection from non-ionizing radiation.

  18. An Analysis of Scheme Transformations in the Vicinity of an Infrared Fixed Point

    CERN Document Server

    Ryttov, Thomas A

    2012-01-01

    We give a detailed analysis of the effects of scheme transformations in the vicinity of an exact or approximate infrared fixed point in an asymptotically free gauge theory with fermions. We list necessary conditions that such transformations must obey and show that, although these can easily be satisfied in the vicinity of an ultraviolet fixed point, they constitute significant restrictions on scheme transformations at an infrared fixed point. We construct acceptable scheme transformations and use these to study the scheme-dependence of an infrared fixed point, making comparison with our previous three-loop and four-loop calculations of the location of this point in the $\\bar{MS}$ scheme. We also use an illustrative hypothetical exact $\\beta$ function to investigate how accurately analyses of finite-order series expansions probe an infrared fixed point and the effect of a scheme transformation on these. Some implications of our work are discussed.

  19. Sugar Sweetened Beverage Consumption among Primary School Students: Influence of the Schools’ Vicinity

    Directory of Open Access Journals (Sweden)

    Alexandre Lebel

    2016-01-01

    Full Text Available The purpose of the research was to explore the associations between the characteristics of schools’ vicinity and the risk of sugar sweetened beverage (SSB consumption in elementary students. Findings exposed an important variation in student’s SSB consumption between schools. Schools with a lower socioeconomic status or in a densely built environment tend to have higher proportion of regular SSB drinkers. These characteristics of the school’s vicinity partly explained the variation observed between them. We estimated that a student moving to a school with a higher proportion of SSB drinkers may increase his/her chances by 52% of becoming a daily consumer. Important changes in dietary preferences can occur when children are in contact with a new social environment. Findings also support the idea that dietary behaviors among children result from the complex interactions between biological, social, and environmental factors.

  20. An Analysis of Scheme Transformations in the Vicinity of an Infrared Fixed Point

    DEFF Research Database (Denmark)

    Ryttov, Thomas; Shrock, Robert

    2012-01-01

    We give a detailed analysis of the effects of scheme transformations in the vicinity of an exact or approximate infrared fixed point in an asymptotically free gauge theory with fermions. We list necessary conditions that such transformations must obey and show that, although these can easily...... be satisfied in the vicinity of an ultraviolet fixed point, they constitute significant restrictions on scheme transformations at an infrared fixed point. We construct acceptable scheme transformations and use these to study the scheme-dependence of an infrared fixed point, making comparison with our previous...... three-loop and four-loop calculations of the location of this point in the $\\bar{MS}$ scheme. We also use an illustrative hypothetical exact $\\beta$ function to investigate how accurately analyses of finite-order series expansions probe an infrared fixed point and the effect of a scheme transformation...

  1. Axially astigmatic surfaces: different types and their properties

    Science.gov (United States)

    Malacara-Doblado, Daniel; Malacara-Hernandez, Daniel; Garcia-Marquez, Jorge L.

    1996-12-01

    Axially astigmatic surfaces have different curvatures in orthogonal diameters. Toroidal and spherocylindrical optical surfaces are two mathematically different special cases of axially astigmatic surfaces as noted by Menchaca and Malacara (1986), but they are almost identical in the vicinity of the optical axis. The different between these two surfaces increases when the distance to the optical axis increases. We study the general properties of astigmatic surfaces and some special interesting cases.

  2. Retrogradation of Waxy Rice Starch Gel in the Vicinity of the Glass Transition Temperature

    OpenAIRE

    2013-01-01

    The retrogradation rate of waxy rice starch gel was investigated during storage at temperatures in the vicinity of the glass transition temperature of a maximally concentrated system (T g ′), as it was hypothesized that such temperatures might cause different effects on retrogradation. The T g ′ value of fully gelatinized waxy rice starch gel with 50% water content and the enthalpy of melting retrograded amylopectin in the gels were investigated using differential scanning calorimetry. Starch...

  3. Soil gas mapping in the vicinity of Nikola Tesla thermo power plant disposal field

    Directory of Open Access Journals (Sweden)

    Nikolić Jugoslav L.

    2010-01-01

    Full Text Available This paper presents the results of identification of natural ionizing irradiation in the vicinity of Nikola Tesla B power plant ash disposal field. The investigations have comprised the determination of natural gas (radon and thoron activities with a passive discriminative nuclear track detector (CR 39 in the air column of the depth of 80 cm in the soil. The determination of gamma dose rate has been given as well, including the corresponding GPS coordinates of 28 measuring points.

  4. Properties of velocity field in the vicinity of synthetic jet generator

    Science.gov (United States)

    Strzelczyk, P.; Gil, P.

    2016-10-01

    The paper presents the results of experimental investigation of velocity field in the vicinity of synthetic jet actuator as a function of Stokes number and for constant Reynolds number. A constant temperature hot-wire anemometer with tungsten-platinum coated single wire probe used for the velocity measurements. Synthetic jet flow visualization was presented, especially process of vortex ring development. Synthetic jet velocity profiles were compared with a solution to fully-developed pipe flow with an oscillating pressure gradient.

  5. Soil environmental assessments on schools built on or in the vicinity of past industrial facilities

    OpenAIRE

    Leprond, Hubert; Girardeau, Ingrid; Gilbert, Dominique; Blanc, Céline

    2013-01-01

    International audience; As part of French environmental framework (law of August 3, 2009), environmental assessments on establishments accommodating children and adolescents were involved by the French Ministry of Environment. Assessments are carried out on schools built on or in the vicinity of potentially contaminated sites by past industrial activities. They are framed by the circular of May 4, 2010 co-signed by the French Ministry of Sustainable Development, the French Ministry of Educati...

  6. Nuisance Caused by Aircraft Noise in the Vicinity of Tehran International Airport

    Directory of Open Access Journals (Sweden)

    Stan Frost

    1999-03-01

    Full Text Available Noise measurement and social questionnaire surveys in three residential areas around Mehrabad International Airport (Tehran, Iran were based upon randomly selected dwellings in each area. A total of 193 individuals responded and many are annoyed and dissatisfied with aircraft noise and in consequence they would like to move. Aircraft noise is the strongest negative environmental factor affecting the residents in the vicinity of Mehrabad Airport and it could be a hazard for their health.

  7. Micron-Sized Particles Detected in the Vicinity of Jupiter by the Voyager Plasma Wave Instruments

    Science.gov (United States)

    Tsintikidis, D.; Gurnett, D. A.; Kurth, W. S.; Granroth, L. J.

    1996-01-01

    Wideband waveform data obtained by the plasma wave instruments onboard the Voyager 1 and 2 spacecraft have been used to study micron-sized dust particles in the vicinity of Jupiter. The technique used was developed during the flybys of Saturn, Uranus, and Neptune, and makes use of the fact that a particle striking the spacecraft at 10-20 km/s causes a voltage pulse in the plasma wave receiver. The waveform of the voltage pulse is much different than the waveform of plasma waves and provides a highly reliable method of detecting micron-sized dust particles. Although the dust impact rate observed in the vicinity of Jupiter is much lower than the rates at Saturn, Uranus, and Neptune, the particles are easily detectable. Approximately 1200 48-second frames of wideband waveform data were examined in the vicinity of Jupiter. Dust impact signatures were found in approximately 20% of these frames. The peak impact rates are about 1 impact per second, and the peak number densities are about 10(exp -5) m(exp -3). Most of the impacts occurred near the equatorial plane at radial distances less than about 35 R(sub j) from Jupiter. Analysis of the detection threshold indicates that the particles have masses greater than 10(exp -11) g, which corresponds to particles with diameters of a few micrometers or larger.

  8. Magnetostrictive hypersound generation by spiral magnets in the vicinity of magnetic field induced phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Bychkov, Igor V. [Chelyabinsk State University, 129 Br. Kashirinykh Str., Chelyabinsk 454001 (Russian Federation); South Ural State University (National Research University), 76 Lenin Prospekt, Chelyabinsk 454080 (Russian Federation); Kuzmin, Dmitry A., E-mail: kuzminda@csu.ru [Chelyabinsk State University, 129 Br. Kashirinykh Str., Chelyabinsk 454001 (Russian Federation); South Ural State University (National Research University), 76 Lenin Prospekt, Chelyabinsk 454080 (Russian Federation); Kamantsev, Alexander P.; Koledov, Victor V.; Shavrov, Vladimir G. [Kotelnikov Institute of Radio-engineering and Electronics of RAS, Mokhovaya Street 11-7, Moscow 125009 (Russian Federation)

    2016-11-01

    In present work we have investigated magnetostrictive ultrasound generation by spiral magnets in the vicinity of magnetic field induced phase transition from spiral to collinear state. We found that such magnets may generate transverse sound waves with the wavelength equal to the spiral period. We have examined two types of spiral magnetic structures: with inhomogeneous exchange and Dzyaloshinskii–Moriya interactions. Frequency of the waves from exchange-caused spiral magnetic structure may reach some THz, while in case of Dzyaloshinskii–Moriya interaction-caused spiral it may reach some GHz. These waves will be emitted like a sound pulses. Amplitude of the waves is strictly depends on the phase transition speed. Some aspects of microwaves to hypersound transformation by spiral magnets in the vicinity of phase transition have been investigated as well. Results of the work may be interesting for investigation of phase transition kinetics as well, as for various hypersound applications. - Highlights: • Magnetostrictive ultrasound generation by spiral magnets at phase transition (PT) is studied. • Spiral magnets during PT may generate transverse sound with wavelength equal to spiral period. • Amplitude of the sound is strictly depends on the phase transition speed. • Microwave-to-sound transformation in the vicinity of PT is investigated as well.

  9. Principal facts for about 16,000 gravity stations in the Nevada test site and vicinity

    Science.gov (United States)

    Harris, R. N.; Ponce, D. A.; Oliver, H. W.; Healey, D. L.

    The Nevada Test Site (NTS) and vicinity includes portions of the Goldfield, Caliente, Death Valley, and Las Vegas. This report documents and consolidates previously published and recently compiled gravity data to establish a gravity data base of about 16,000 stations for the NTS and vicinity. While compiling data sets, redundant stations and stations having doubtful locations or gravity values were excluded. Details of compiling the gravity data sets are discussed in later sections. Where feasible, an accuracy code has been assigned to each station so that the accuracy or reliability of each station can be evaluated. This data base was used in preparing complete Bouguer and isostatic gravity maps of the NTS and vicinity. Since publication of the complete Bouguer gravity map, additional data were incorporated into the isostatic gravity map. Gravity data were compiled from five sources: 14,183 stations from the U.S. Geological Survey (USGS), 326 stations from Exploration Data Consultants (EDCON) of Denver, Colorado, 906 stations from the Los Alamos National Laboratory (LANL), 212 stations from the University of Texas at Dallas (UTD), and 48 stations from the Defense Mapping Agency (DMA). This investigation is an effort to study several areas for potential storage of high-level radioactive waste. Gravity stations established under YMP are shown. The objective of this gravity survey was to explore for the presence of plutons.

  10. A research for environmental problems in the vicinity of mining area. Investigation into the impact of metallic mining on the environment and solutions

    Energy Technology Data Exchange (ETDEWEB)

    Min, Jeong Sik; Cheong, Young Wook; Lee, Hyun Joo; Song, Duk Young [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)

    1995-12-01

    This study is focused on the impacts of metalliferous mines on the environment in the vicinity of the abandoned and active mines and establishment of abatements of mining environmental problems. Total number of metalliferous mines surveyed were 40 in which samples of waters, mine wastes and soil were taken. Water parameters such as the pH, Eh, TDS, conductivity, turbidity, dissolved oxygen and temperature were measured in the field. Elements such as As, Cd, Pb, Zn, Cu, Al, Mn, sulfate and cyanide were analyzed. Significant concentrations of heavy metals, mainly Cd, Zn, Cu, Fe, Mn and Al, were found in mine waters from adit and in leachates extracted from mine wastes. The mine waters flowing out from the Dalsung and Ilgwang mines were the typical acid mine drainage(AMD) contaminated by the heavy metals. Passive biological systems(Anoxic wetland) to treat AMD for metals were designed and monitored for effluents from the reactors with 4 types of composts, cow manure and limestones, Results showed that the mushroom compost with cow manure and limestone was the best substrates in metal removing efficiencies. Results from leaching of mine wastes showed that As, Cd and Cu were extracted from some of mine wastes. AMD from the mine waste dump of the Daduk mine was found. These mean that mine wastes can contaminate the soil, surface water and ground waters in vicinity of mines. Therefore cover systems or liner system for containments of mine wastes were suggested to preserve the environment. Cu and As concentrations in soils surveyed were below the heavy metal concentrations in soils of Korean standard preventing plant of the crops. However, most of the acid mine waters are drained untreated, and mine wastes with heavy metals are distributed near soil environment. Therefore efforts to reduce possibilities of soil contamination in the vicinity of mining areas is required. (author). 33 refs.

  11. Selective reflection technique as a probe to monitor the growth of a metallic thin film on dielectric surfaces

    CERN Document Server

    Martins, Weliton Soares; Chevrollier, Martine; de Silans, Thierry Passerat

    2013-01-01

    Controlling thin film formation is technologically challenging. The knowledge of physical properties of the film and of the atoms in the surface vicinity can help improve control over the film growth. We investigate the use of the well-established selective reflection technique to probe the thin film during its growth, simultaneously monitoring the film thickness, the atom-surface van der Waals interaction and the vapor properties in the surface vicinity.

  12. Hydrogeologic framework, groundwater movement, and water budget in the Puyallup River Watershed and vicinity, Pierce and King Counties, Washington

    Science.gov (United States)

    Welch, Wendy B.; Johnson, Kenneth H.; Savoca, Mark E.; Lane, Ron C.; Fasser, Elisabeth T.; Gendaszek, Andrew S.; Marshall, Cameron; Clothier, Burt G.; Knoedler, Eric N.

    2015-01-01

    This report presents information used to characterize the groundwater-flow system in the Puyallup River Watershed and vicinity, and includes descriptions of the geology and hydrogeologic framework; groundwater recharge and discharge; groundwater levels and flow directions; seasonal groundwater level fluctuations; interactions between aquifers and the surface-water system; and a water budget. The study area covers about 1,220 square miles in northern Pierce and southern King Counties, Washington; extends north to the Green River and Auburn Valley and southwest to the Puyallup River and adjacent uplands; and is bounded on the south and east by foothills of the Cascade Range and on the west by Puget Sound. The area is underlain by a northwest-thickening sequence of unconsolidated glacial and interglacial deposits, which overlie sedimentary and volcanic bedrock units that crop out in the foothills along the southern and eastern margin of the study area. Geologic units were grouped into 13 hydrogeologic units consisting of aquifers, confining units, and an underlying bedrock unit. A surficial hydrogeologic unit map was developed and used with well information from 1,012 drillers’ logs to construct 8 hydrogeologic sections, and unit extent and thickness maps.

  13. Remote sensing observations of the coherent and non-coherent ring structures in the vicinity of Lesser Antilles

    Directory of Open Access Journals (Sweden)

    R. C. Cruz Gómez

    2007-03-01

    Full Text Available The North Brazil Current Rings (NBCR penetration into the Caribbean Sea is being investigated by employing a merged altimeter-derived sea height anomaly (TOPEX/Poseidon, Jason-1 and ERS-1, 2, the ocean surface color data (SeaWiFS and Global Drifter Program information. Four strategies are being applied to process the data: (1 calculations of the Okubo-Weiss parameter for NBCR identification, (2 longitude-time plots (also known as Hovmöller diagrams, (3 two-dimensional Radon transforms and (4 two-dimensional Fourier transforms.

    A twofold NBCR structure has been detected in the region under investigation. The results have shown that NBC rings mainly propagate into the Caribbean Sea along two principal pathways (near 12° N and 17° N in the ring translation corridor. Thus, rings following the southern pathway in the fall-winter period can enter through very shallow southern straits as non-coherent structures. A different behavior is observed near the northern pathway (~17° N, where NBC rings are thought to have a coherent structure during their squeezing into the eastern Caribbean, i.e. conserving the principal characteristics of the incident rings. We attribute this difference in the rings' behavior to the vertical scales of the rings and to the bottom topography features in the vicinity of the Lesser Antilles.

  14. Review of the general geology and solid-phase geochemical studies in the vicinity of the Central Oklahoma aquifer

    Science.gov (United States)

    Mosier, Elwin L.; Bullock, John H.

    1988-01-01

    The Central Oklahoma aquifer is the principal source of ground water for municipal, industrial, and rural use in central Oklahoma. Ground water in the aquifer is contained in consolidated sedimentary rocks consisting of the Admire, Council Grove, and Chase Groups, Wellington Formation, and Garber Sandstone and in the unconsolidated Quaternary alluvium and terrace deposits that occur along the major stream systems in the study area. The Garber Sandstone and the Wellington Formation comprise the main flow system and, as such, the aquifer is often referred to as the 'Garber-Wellington aquifer.' The consolidated sedimentary rocks consist of interbedded lenticular sandstone, shale, and siltstone beds deposited in similar deltaic environments in early Permian time. Arsenic, chromium, and selenium are found in the ground water of the Central Oklahoma aquifer in concentrations that, in places, exceed the primary drinking-water standards of the Environmental Protection Agency. Gross-alpha concentrations also exceed the primary standards in some wells, and uranium concentrations are uncommonly high in places. As a prerequisite to a surface and subsurface solid-phase geochemical study, this report summarizes the general geology of the Central Oklahoma study area. Summaries of results from certain previously reported solid-phase geochemical studies that relate to the vicinity of the Central Oklahoma aquifer are also given; including a summary of the analytical results and distribution plots for arsenic, selenium, chromium, thorium, uranium, copper, and barium from the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) Program.

  15. Seismic depth conversion problems associated with the Mississippi Canyon in the vicinity of Ewing Bank Block 305 field, offshore Louisiana

    Energy Technology Data Exchange (ETDEWEB)

    Leveille, G.P. (Conoco Inc., New Orleans, LA (USA)); Sahai, K.S.; McDaniel, P.G.

    1990-05-01

    Ewing Bank Block 305 field is located on the outermost edge of the continental shelf, approximately 145 km south of New Orleans, Louisiana. The geology of the field is fairly typical of other fields found offshore of Louisiana, except there is a huge, partly filled, Pleistocene submarine canyon that overlies the field. This canyon, which is commonly referred to as the Mississippi Canyon, causes a large seismic depth conversion problem that makes it virtually impossible to correctly map the structure of the field using normally processed marine seismic data The Mississippi Canyon is a large erosional feature that was formed at the mouth of the ancestral Mississippi River during the last glacial sea level lowstand. In the vicinity of the field, the canyon is about 10 km wide and 1 km deep, which is approximately two-thirds the size of the Grand Canyon of the Colorado River, and is filled mostly with Holocene sediments. Because the sediments that fill the canyon are very young, their interval velocities are much lower than the interval velocities of the sediments that form the canyon walls. This creates abrupt near surface lateral velocity variations that distort the geometry of seismic reflectors such that the time geometries seen on seismic lines are not at all indicative of the structure of the subsurface. Using a model-based processing technique and available well control, the authors have been able to solve this difficult depth conversion problem and have gained a better understanding of the geology of this field.

  16. Stratigraphy and alteration, 15 shallow thermal gradient holes, Roosevelt Hot Springs KGRA and vicinity, Millard and Beaver Counties, Utah

    Energy Technology Data Exchange (ETDEWEB)

    Hulen, J.B.

    1978-09-01

    Fifteen shallow thermal gradient drill holes were recently completed by Geothermal Power Corporation (GPCR) in the vicinity of the Roosevelt Hot Springs KGRA. Five holes penetrated Tertiary granitic rocks and Precambrian gneiss east of the KGRA. Seven holes completed entirely in alluvium near the southwestern corner of the KGRA encountered a near-surface marker horizon of Pleistocene pumice and perlite. Maximum calculated alluvial sedimentation rates since initial deposition of this pumice and perlite range from 1 foot in 12,500 years to 1 foot in 2,300 years. Three holes east of the Mineral Mountains penetrated late Cenozoic basaltic andesite beneath a thin veneer of alluvium. All 15 GPCR drill holes appear to be peripheral to a central zone of anomalously high thermal gradient and low resisitivity delineated by previous investigations. GPCR-8 and -14, however, are characterized by high heat flow and relatively abundant manganese oxide mineralization, which may reflect a favorable hydrologic system controlling thermal fluid flow at depth. These holes thus seem most encouraging for discovery of a deeper high-temperature geothermal resource.

  17. Stimulated bacterioplankton growth and selection for certain bacterial taxa in the vicinity of the ctenophore Mnemiopsis leidyi.

    Science.gov (United States)

    Dinasquet, Julie; Granhag, Lena; Riemann, Lasse

    2012-01-01

    Episodic blooms of voracious gelatinous zooplankton, such as the ctenophore Mnemiopsis leidyi, affect pools of inorganic nutrients and dissolved organic carbon by intensive grazing activities and mucus release. This will potentially influence bacterioplankton activity and community composition, at least at local scales; however, available studies on this are scarce. In the present study we examined effects of M. leidyi on bacterioplankton growth and composition in incubation experiments. Moreover, we examined community composition of bacteria associated with the surface and gut of M. leidyi. High release of ammonium and high bacterial growth was observed in the treatments with M. leidyi relative to controls. Deep 454 pyrosequencing of 16 S rRNA genes showed specific bacterial communities in treatments with M. leidyi as well as specific communities associated with M. leidyi tissue and gut. In particular, members of Flavobacteriaceae were associated with M. leidyi. Our study shows that M. leidyi influences bacterioplankton activity and community composition in the vicinity of the jellyfish. In particular during temporary aggregations of jellyfish, these local zones of high bacterial growth may contribute significantly to the spatial heterogeneity of bacterioplankton activity and community composition in the sea.

  18. Magnesium, Potassium and Phosphorus in Available Forms in Luvisols in the Vicinity of Głogów Copper Smelter

    Science.gov (United States)

    Jaworska, H.; Dąbkowska-Naskręt, H.; Różański, S.

    2016-02-01

    Region near Głogów is characterized as industrial—agricultural area, intensively used. Presented study was undertaken to estimate the impact of agricultural land use and the vicinity of Głogów copper smelter on the contents of available forms of magnesium, phosphorus and potassium in selected profiles of Luvisols. The following analysis were performed: soil particle-size distribution, pH, organic carbon contents, CaCO3 contents. The contents of available forms of phosphorus and potassium were determined by Egner- Riehm method and that of magnesium using Schachtschabel's method. The results of the study showed that the contents of available P is medium (III class of abundance), very low in K (V class) and for available Mg very low (V class) to medium for surface horizons and very high (I class of abundance) in other soil horizons. The soils, in spite of the elevated copper content in humus horizons, according to IUNG, were classified as uncontaminated soils, therefore, can be used in plant production for all types of crops.

  19. Stimulated bacterioplankton growth and selection for certain bacterial taxa in the vicinity of the ctenophore Mnemiopsis leidyi

    Directory of Open Access Journals (Sweden)

    Julie eDinasquet

    2012-08-01

    Full Text Available Episodic blooms of voracious gelatinous zooplankton, such as the ctenophore Mnemiopsis leidyi, affect pools of inorganic nutrients and dissolved organic carbon by intensive grazing activities and mucus release. This will potentially influence bacterioplankton activity and community composition, at least at local scales; however, available studies on this are scarce. In the present study we examined effects of M. leidyi on bacterioplankton growth and composition in incubation experiments. Moreover, we examined community composition of bacteria associated with the surface and gut of M. leidyi. High release of ammonium and high bacterial growth was observed in the treatments with M. leidyi relative to controls. Deep 454 pyrosequencing of 16S rRNA genes showed specific bacterial communities in treatments with M. leidyi as well as specific communities associated with M. leidyi tissue and gut. In particular, members of Flavobacteriaceae were associated with M. leidyi. Our study shows that M. leidyi influences bacterioplankton activity and community composition in the vicinity of the jellyfish. In particular during temporary aggregations of jellyfish, these local zones of high bacterial growth may contribute significantly to the spatial heterogeneity of bacterioplankton activity and community composition in the sea.

  20. Habitat mapping using hyperspectral images in the vicinity of Hekla volcano in Iceland

    Science.gov (United States)

    Vilmundardóttir, Olga K.; Sigurmundsson, Friðþór S.; Pedersen, Gro B. M.; Falco, Nicola; Rustowicz, Rose; Gísladóttir, Guðrún; Benediktsson, Jón A.

    2016-04-01

    Hekla, one of the most active volcanoes in Iceland, has created a diverse volcanic landscape with lava flows, hyaloclastite and tephra fields. The variety of geological formations and different times of formation create diverse vegetation within Hekla's vicinity. The region is subjected to extensive loss of vegetation cover and soil erosion due to human utilization of woodlands and ongoing sheep grazing. The eolian activity and frequent tephra deposition has created vast areas of sparse vegetation cover. Over the 20th century, many activities have centered on preventing further loss of vegetated land and restoring ecosystems. The benefit of these activities is now noticeable in the increased vegetation and woodland cover although erosion is still active within the area. For mapping and monitoring this highly dynamic environment remote sensing techniques are extremely useful. One of the principal goals of the project 'Environmental Mapping and Monitoring of Iceland with Remote Sensing' (EMMIRS) is to use hyperspectral images and LiDAR data to classify and map the vegetation within the Hekla area. The data was collected in an aerial survey in summer 2015 by the Natural Environment Research Council (NERC), UK. The habitat type classification, currently being developed at the Icelandic Institute of Natural History and follows the structure of the EUNIS classification system, will be used for classifying the vegetation. The habitat map created by this new technique's outcome will be compared to the existent vegetation maps made by the conventional vegetation mapping method and the multispectral image classification techniques. In the field, vegetation cover, soil properties and spectral reflectance were measured within different habitat types. Special emphasis was on collecting data on vegetation and soil in the historical lavas from Hekla for assessing habitats forming over the millennia. A lava-chronosequence was established by measuring vegetation and soil in lavas

  1. Heavy metal contamination in the vicinity of an industrial area near Bucharest.

    Science.gov (United States)

    Velea, Teodor; Gherghe, Liliana; Predica, Vasile; Krebs, Rolf

    2009-08-01

    Heavy metals such as lead are well known to cause harmful health effects. Especially children are particularly susceptible to increased levels of lead in their blood. It is also a fact that lead concentration is increasing in the environment due to increased anthropogenic activity. The risk of heavy metal contamination is pronounced in the environment adjacent to large industrial complexes. In a combined case study, the environmental pollution by heavy metals was related to children's health in the vicinity of an industrial area located 4 km south-east from Bucharest about 2 km east from the nearest town-Pantelimon. This site includes companies processing different, nonferrous solid wastes for recovery of heavy metals and producing different nonferrous alloys and lead batteries. In this paper, mainly the results of environmental sampling and analyses are summarized. Water, soil, and atmospheric deposition samples were collected from different locations within 3 km from the industrial area. For comparison, samples were also taken from Bucharest. Water samples were filtered (pollution. Highest heavy metal concentrations were found in 10-20 cm soil depths. There were also decreasing heavy metal concentrations for atmospheric deposition with increasing distance to the industrial site. In surface and groundwater samples, traces of zinc, copper and lead were detected. The heavy metal concentrations in soil were increased in the study area, mostly under legal action limits in low-concern areas (e.g., 1,000 mg Pb/kg dry soil), but often above action limits for high-concern areas (100 mg Pb/kg dry soil) such as populated areas. The soluble lead concentrations in water samples indicate a need for monitoring and assessing water quality in more detail. The results for atmospheric deposition showed increased dust precipitation and heavy metal loads in the study area compared to Bucharest. However, based on mass flow balance calculations, the actual atmospheric deposition of

  2. Wetting failure of hydrophilic surfaces promoted by surface roughness

    Science.gov (United States)

    Zhao, Meng-Hua; Chen, Xiao-Peng; Wang, Qing

    2014-06-01

    Wetting failure is of vital importance to many physical phenomena, such as industrial coating and drop emission. Here we show when and how the surface roughness promotes the destabilization of a moving contact line on a hydrophilic surface. Beyond the balance of the driving force and viscous resistance where a stable wetting interface is sustained, wetting failure occurs and is modified by the roughness of the surface. The promoting effect arises only when the wetting velocity is high enough to create a gas-liquid-solid composite interface in the vicinity of the moving contact line, and it is a function of the intrinsic contact angle and proportion of solid tops. We propose a model to explain splashes of rough solid spheres impacting into liquids. It reveals a novel concept that dynamic wetting on hydrophilic rough surfaces can be similar to that on hydrophobic surfaces, and brings a new way to design surfaces with specific wetting properties.

  3. Digital Geologic Map of Bryce Canyon National Park and Vicinity, Utah (NPS, GRD, GRI, BRCA, BRCA digital map)

    Data.gov (United States)

    National Park Service, Department of the Interior — The Digital Geologic Map of Bryce Canyon National Park and Vicinity, Utah is composed of GIS data layers complete with ArcMap 9.3 layer (.LYR) files, two ancillary...

  4. Digital Geologic Map of Palo Alto Battlefield National Historic Site and vicinity, Texas (NPS, GRD, GRE, PAAL, PAAL digital map)

    Data.gov (United States)

    National Park Service, Department of the Interior — The Digital Geologic Map of Palo Alto Battlefield National Historic Site and vicinity, Texas is composed of GIS data layers complete with ArcMap 9.2 layer (.LYR)...

  5. Digital Geologic Map of the American Camp Unit and vicinity, Washington (NPS, GRD, GRE, SAJH, SJIS digital map)

    Data.gov (United States)

    National Park Service, Department of the Interior — The Digital Geologic Map of the American Camp Unit and vicinity, Washington is composed of GIS data layers complete with ArcMap 9.2 layer (.LYR) files, two ancillary...

  6. Toxicity of Water and Sediment Samples Collected in the Vicinity of the Mixed Waste Management Facility, 1995 and 1996

    Energy Technology Data Exchange (ETDEWEB)

    Specht, W.L. [Westinghouse Savannah River Company, AIKEN, SC (United States)

    1996-07-01

    Three rounds of toxicity tests were conducted on water collected from eleven locations in the vicinity of the Mixed Waste Management Facility and four reference locations between January 1995 and April 1996.

  7. Digital Geologic Map of San Juan Island National Historical Park and vicinity, Washington (NPS, GRD, GRE, SAJH, SAJH digital map)

    Data.gov (United States)

    National Park Service, Department of the Interior — The Digital Geologic Map of San Juan Island National Historical Park and vicinity, Washington is composed of GIS data layers complete with ArcMap 9.2 layer (.LYR)...

  8. Digital Geologic Map of Congaree National Park and Vicinity, South Carolina (NPS, GRD, GRI, CONG, CONG digital map)

    Data.gov (United States)

    National Park Service, Department of the Interior — The Digital Geologic Map of Congaree National Park and Vicinity, South Carolina is composed of GIS data layers complete with ArcMap 9.3 layer (.LYR) files, two...

  9. Asymmetric reduction of α-hydroxy aromatic ketones to chiral aryl vicinal diols using carrot enzymes system

    Institute of Scientific and Technical Information of China (English)

    Xiang Liu; Yi Wang; Hai Yan Gao; Jian He Xu

    2012-01-01

    Asymmetric reduction of α-hydroxy aromatic ketones was carried out by using carrot enzymes system,yielding corresponding chiral vicinal diols with special functional groups.The optimum reaction conditions were obtained after investigation of various influencing factors.Chiral aryl vicinal diols were produced with good yields and excellent enantiomeric excesses under appropriate conditions,Meanwhile,the steric factors and electronic effects of the substituents on the aromatic ring were shown to have an interesting influence on both yield and enantioselectivity.

  10. EDITORIAL: Focus on Advances in Surface and Interface Science 2008 FOCUS ON ADVANCES IN SURFACE AND INTERFACE SCIENCE 2008

    Science.gov (United States)

    Scheffler, Matthias; Schneider, Wolf-Dieter

    2008-12-01

    Iori, K Sakamoto, H Narita, A Kimura, M Taniguchi, S Qiao, K Hasegawa, K Shimada, H Namatame and S Blügel Activated associative desorption of C + O → CO from Ru(001) induced by femtosecond laser pulses S Wagner, H Öström, A Kaebe, M Krenz, M Wolf, A C Luntz and C Frischkorn Surface structure of Sn-doped In2O3 (111) thin films by STM Erie H Morales, Yunbin He, Mykola Vinnichenko, Bernard Delley and Ulrike Diebold Coulomb oscillations in three-layer graphene nanostructures J Güttinger, C Stampfer, F Molitor, D Graf, T Ihn and K Ensslin Adsorption processes of hydrogen molecules on SiC(001), Si(001) and C(001) surfaces Xiangyang Peng, Peter Krüger and Johannes Pollmann Fermi surface nesting in several transition metal dichalcogenides D S Inosov, V B Zabolotnyy, D V Evtushinsky, A A Kordyuk, B Büchner, R Follath, H Berger and S V Borisenko Probing molecule-surface interactions through ultra-fast adsorbate dynamics: propane/Pt(111) A P Jardine, H Hedgeland, D Ward, Y Xiaoqing, W Allison, J Ellis and G Alexandrowicz A novel method achieving ultra-high geometrical resolution in scanning tunnelling microscopy R Temirov, S Soubatch, O Neucheva, A C Lassise and F S Tautz

  11. Concentration of NOX in the vicinity of the power plants Vojany EVO 1 and EVO 2

    Directory of Open Access Journals (Sweden)

    Ján Brehuv

    2006-12-01

    Full Text Available The paper presents a calculation of the maximal concentration of nitrogen oxides in the vicinity of point sources (main chimneys of power plants Vojany EVO1 and EVO2. The wind velocity u10,M (7, at which the concentration on a given place in the surrounding of the pollution source attains a maximal value, is calculated. The relation (8 for a calculation of the place with the maximal concentration for a given class of air stability (Table 1 and 2 and for a given wind velocity is derived. According to equation (3 and Table 3, a thermal capacity of EVO1 and EVO2 is calculated, considering a flat country in the vicinity of the sources (x3 = 0 in relation (1. Subsequently, it is also considered that the wind direction has the direction joining the source and the place of concentration calculation (x2 = 0. The calculations of concentration are performed for the 5th class of air stability. As to this class, favourable conditions for the pollutants dispersion are there. Thus, the maximum concentration is in a relatively small distance from the source with a sharp concentration maximum. As to other classes of the air stability (Table 1 and 2, the maximum concentration is located in larger distances from the source, i.e. about 10 km, as it is considered in Table 4 and 5. The theoretical calculation of NOX concentration in the vicinity of the sources, EVO1 and EVO2, shows (Table 4 and 5 that it does not exceed the allowable limit of 150 µg.m-3.

  12. Major ionic compositions of fine particulate matter in an animal feeding operation facility and its vicinity.

    Science.gov (United States)

    Li, Qian-feng; Wang-Li, Lingjuan; Liu, Zifei; Jayanty, R K M; Shah, Sanjay B; Bloomfield, Peter

    2014-11-01

    Animal feeding operations (AFOs) produce particulate matter (PM) and gaseous pollutants. Investigation of the chemical composition of PM2.5 inside and in the local vicinity of AFOs can help to understand the impact of the AFO emissions on ambient secondary PM formation. This study was conducted on a commercial egg production farm in North Carolina. Samples of PM2.5 were collected from five stations, with one located in an egg production house and the otherfour located in the vicinity ofthe farm alongfour wind directions. The major ions of NH4+, Na+, K+, SO4(2-), Cl-, and NO3- were analyzed using ion chromatography (IC). In the house, the mostly abundant ions were SO4(2-), Cl-, and K+. At ambient stations, SO4(2-), and NH4+ were the two most abundant ions. In the house, NH4+, SO4(2-), and NO3- accounted for only 10% of the PM2.5 mass; at ambient locations, NH4+, SO4(2-), and NO3- accounted for 36-41% of the PM2.5 mass. In the house, NH4+ had small seasonal variations indicating that gas- phase NH3. was not the only major force driving its gas-particle partitioning. At the ambient stations, NH4+ had the highest concentrations in summer In the house, K+, Na+, and Cl- were highly correlated with each other In ambient locations, SO4(2-) and NH4+ had a strong correlation, whereas in the house, SO4(2-) and NH4+ had a very weak correlation. Ambient temperature and solar radiation were positively correlated with NH4+ and SO4(2-). This study suggests that secondary PM formation inside the animal house was not an important source of PM2.5. In the vicinity, NH3 emissions had greater impact on PM2.5 formation.

  13. Simulated effects of groundwater withdrawals from aquifers in Ocean County and vicinity, New Jersey

    Science.gov (United States)

    Cauller, Stephen J.; Voronin, Lois M.; Chepiga, Mary M.

    2016-10-21

    Rapid population growth since the 1930s in Ocean County and vicinity, New Jersey, has placed increasing demands upon the area’s freshwater resources. To examine effects of groundwater withdrawals, a three-dimensional groundwater-flow model was developed to simulate the groundwater-flow systems of five area aquifers: the unconfined Kirkwood-Cohansey aquifer system and Vincentown aquifer, and three confined aquifers— the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, and the Piney Point aquifer. The influence of withdrawals is evaluated by using transient groundwater-flow model simulations that incorporate three withdrawal schemes. These are (1) no-withdrawal conditions; (2) 2000–03 withdrawal conditions, using reported monthly withdrawals at all production wells from January 2000 through December 2003; and (3) maximum-allocation withdrawal conditions using the maximum withdrawal allowed by New Jersey Department of Environmental Protection permits at each well. Particle tracking analysis, using results from model simulations, delineated particle flow paths from production wells to the point of recharge, and estimated particle travel times.Compared with no-withdrawal conditions, 2000–03 withdrawal conditions reduced the amount of groundwater flow out of the Kirkwood-Cohansey aquifer system into streams, increased the net flow of water into other layers, reduced net flow into or out of storage, and reduced flow from the Kirkwood-Cohansey aquifer system to constant head cells.Freshwater discharging to the Barnegat Bay-Little Egg Harbor estuary from streams and groundwater is essential to maintaining the ecology of the bay. Examination of selected stress periods indicates that simulated base flow in streams flowing into the Barnegat Bay-Little Egg Harbor estuary is reduced by as much as 49 cubic feet per second for 2000 to 2003 withdrawal conditions when compared with no-withdrawal conditions.In the three confined aquifers, water levels during

  14. Series Resistance Monitoring for Photovoltaic Modules in the Vicinity of MPP

    DEFF Research Database (Denmark)

    Sera, Dezso

    2010-01-01

    Faults and performance deterioration issues related to increases of the series resistance in PV modules or arrays are one of the most common causes to decrease the energy yield of photovoltaic installations. Therefore, the early detection of such failure types is very important in order to minimize...... the time period with reduced power production. This paper focuses on the estimation of series resistance of flat silicone PV panels or arrays during operation, in the vicinity of their MPP. The method presented in this paper helps to detect failures by monitoring changes in the panel’s or array’s series...

  15. Electromagnetic fields in the vicinity of DECT cordless telephones and mobile phones

    Directory of Open Access Journals (Sweden)

    Paweł Mamrot

    2015-12-01

    Full Text Available Background: Mobile telephones belong to the most frequently used personal devices. In their surroundings they produce the electromagnetic field (EMF, in which exposure range there are not only users but also nearby bystanders. The aim of the investigations and EMF measurements in the vicinity of phones was to identify the electric field levels with regard to various working modes. Material and methods: Twelve sets of DECT (digital enhanced cordless telecommunications cordless phones (12 base units and 15 handsets, 21 mobile telephones produced by different manufactures, and 16 smartphones in various applications, (including multimedia in the conditions of daily use in living rooms were measured. Measurements were taken using the point method in predetermined distances of 0.05–1 m from the devices without the presence of users. Results: In the vicinity of DECT cordless phone handsets, electric field strength ranged from 0.26 to 2.30 V/m in the distance of 0.05 m – 0.18–0.26 V/m (1 m. In surroundings of DECT cordless telephones base units the values of EMF were from 1.78–5.44 V/m (0.05 m to 0.19– 0.41 V/m (1 m. In the vicinity of mobile phones working in GSM mode with voice transmission, the electric field strength ranged from 2.34–9.14 V/m (0.05 m to 0.18–0.47 V/m (1 m while in the vicinity of mobile phones working in WCDMA (Wideband Code Division Multiple Access mode the electric field strength ranged from 0.22–1.83 V/m (0.05 m to 0.18–0.20 V/m (1 m. Conclusions: The mean values of the electric field strength for each group of devices, mobile phones and DECT wireless phones sets do not exceed the reference value of 7 V/m, adopted as the limit for general public exposure. Med Pr 2015;66(6:803–814

  16. CART Raman Lidar Aerosol and Water Vapor Measurements in the Vicinity of Clouds

    Science.gov (United States)

    Clayton, Marian B.; Ferrare, Richard A.; Turner, David; Newsom, Rob; Sivaraman, Chitra

    2008-01-01

    Aerosol and water vapor profiles acquired by the Raman lidar instrument located at the Climate Research Facility (CRF) at Southern Great Plains (SGP) provide data necessary to investigate the atmospheric variability in the vicinity of clouds near the top of the planetary boundary layer (PBL). Recent CARL upgrades and modifications to the routine processing algorithms afforded the necessarily high temporal and vertical data resolutions for these investigations. CARL measurements are used to investigate the behavior of aerosol backscattering and extinction and their correlation with water vapor and relative humidity.

  17. Enhanced gamma radiation toward the rotation axis from the immediate vicinity of extremely rotating black holes

    OpenAIRE

    Song, Yoogeun; Pu, Hung-Yi; Hirotani, Kouichi; Matsushita, Satoki; Kong, Albert K. H.; Chang, Hsiang-Kuang

    2017-01-01

    We investigate the acceleration of electrons and positrons by magnetic-field-aligned electric fields in the polar funnel of an accreting black hole (BH). Applying the pulsar outer-gap theory to BH magnetospheres, we find that such a lepton accelerator arises in the immediate vicinity of the event horizon due to frame-dragging, and that their gamma-ray luminosity increases with decreasing accretion rate. Furthermore, we demonstrate that the gamma-ray flux is enhanced along the rotation axis by...

  18. DFT Study of the Molybdenum-Catalyzed Deoxydehydration of Vicinal Diols

    DEFF Research Database (Denmark)

    Lupp, Daniel; Christensen, Niels Johan; Dethlefsen, Johannes Rytter

    2015-01-01

    The mechanism of the molybdenum-catalyzed deoxydehydration (DODH) of vicinal diols has been investigated using density functional theory. The proposed catalytic cycle involves condensation of the diol with an MoVI oxo complex, oxidative cleavage of the diol resulting in an MoIV complex......, and extrusion of the alkene. We have compared the proposed pathway with several alternatives, and the results have been corroborated by comparison with the molybdenum- catalyzed sulfoxide reduction recently published by Sanz et al. and with experimental observations for the DODH itself. Improved understanding...... of the mechanism should expedite future optimization of molybdenum-catalyzed biomass transformations....

  19. AN EXACT ANALYTICAL SOLUTION FOR THE INTERSTELLAR MAGNETIC FIELD IN THE VICINITY OF THE HELIOSPHERE

    Energy Technology Data Exchange (ETDEWEB)

    Röken, Christian [Universität Regensburg, Fakultät für Mathematik, Regensburg (Germany); Kleimann, Jens; Fichtner, Horst, E-mail: christian.roeken@mathematik.uni-regensburg.de, E-mail: jk@tp4.rub.de, E-mail: hf@tp4.rub.de [Ruhr-Universität Bochum, Fakultät für Physik und Astronomie, Institut für Theoretische Physik IV, Bochum (Germany)

    2015-06-01

    An analytical representation of the interstellar magnetic field in the vicinity of the heliosphere is derived. The three-dimensional field structure close to the heliopause is calculated as a solution of the induction equation under the assumption that it is frozen into a prescribed plasma flow resembling the characteristic interaction of the solar wind with the local interstellar medium. The usefulness of this analytical solution as an approximation to self-consistent magnetic field configurations obtained numerically from the full MHD equations is illustrated by quantitative comparisons.

  20. Nonradical Zinc-Barbier Reaction for Diastereoselective Synthesis of Vicinal Amino Alcohols

    DEFF Research Database (Denmark)

    Keinicke, Lise Edelmann; Fristrup, Peter; Norrby, Per-Ola

    2005-01-01

    A new protocol for the synthesis of vicinal amino alcohols is described. The method employs a Barbier-type reaction between an imine and 3-benzoyloxyallyl bromide in the presence of zinc metal. The addition products are debenzoylated to afford amino alcohols in good yields and with diastereomeric...... ratios greater than 85:15 in favor of the anti isomer. A Hammett study has been performed which strongly indicates that the allylation does not follow a radical mechanism, but instead an organometallic reagent is formed which subsequently reacts with the imine. A computational study based...

  1. Investigation of the conductivity distribution in the vicinity of a cascade volcano

    Energy Technology Data Exchange (ETDEWEB)

    Mozley, E.C.

    1982-11-01

    Magnetotelluric and telluric data were acquired in the vicinity of Mount Hood Oregon as part of a multidisciplinary exploration program to evaluate the geothermal potential of this stratocone volcano. Eleven field components were acquired simultaneously over the frequency band of 50. to .001 hertz. These data consisted of one five component magnetotelluric base site, two sets of two component remote electric field measurements and one set of remote horizontal magnetic field measurements. The data were recorded digitally in the field and processed later using the remote electric and magnetic signals to obtain unbiased tensor impedance and geomagnetic transfer function (tipper) estimates.

  2. Geophysical characterization of mineral and energy resources at Yucca Mountain and vicinity, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Langenheim, V.E.; Oliver, H.W. [Geological Survey, Menlo Park, CA (United States); Hoover, D.B. [Geological Survey, Denver, CO (United States)

    1991-12-31

    This report was prepared for the Yucca Mountain Project (Department of Energy) as part of the study of the mineral and energy resource potential of the site (Activity 8.3.1.9.2.1.5) under the Human Interference part of the program. Most of the 1991 geophysical scoping activities in the Mineral Resources Study were involved with the acquisition and evaluation of existing data. This report presents an overview of how geophysical data (existing and planned) will aid in the evaluation of the potential for mineral and energy resource potential at Yucca Mountain and vicinity.

  3. Contribution to the knowledge of jumping spiders (Araneae: Salticidae from vicinity of Jagodina, Central Serbia

    Directory of Open Access Journals (Sweden)

    Stanković, B.

    2012-09-01

    Full Text Available During last 10 years, based on personal collectings, 21 species from 14 genera of Salticidae (Araneae are recorded from vicinity of Jagodina: Ballus chalybeius, Carrhotus xanthogramma, Evarcha arcuata, Evarcha falcata, Heliophanus auratus, Heliophanus cupreus, Heliophanus flavipes, Heliophanus kochii, Icius hamatus, Icius subinermis, Leptorchestes berolinensis, Macaroeris nidicolens, Marpissa muscosa, Marpissa nivoyi, Mendoza canestrinii, Pellenes tripunctatus, Phintella castriesiana, Phlegra fasciata, Pseudeuophrys erratica, Pseudeuophrys lanigera, Salticus scenicus. All those species are provided with habitat notes and global distribution. New records for the spider fauna of Serbia are Heliophanus kochii (Simon 1868, Icius subinermis (Simon, 1937, Marpissa nivoyi (Lucas, 1846 and Mendoza canestrinii (Ninni, 1868.

  4. X-ray diffraction and surface acoustic wave analysis of BST/Pt/TiO{sub 2}/SiO{sub 2}/Si thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mseddi, Souhir; Hedi Ben Ghozlen, Mohamed [Laboratoire de Physique des Materiaux, Faculte des Sciences de Sfax, Universite de Sfax, 3018 Sfax (Tunisia); Njeh, Anouar [Unite de Physique, Informatique et Matematiques, Faculte des Sciences de Gafsa, Universite de Gafsa, 2112 Gafsa (Tunisia); Schneider, Dieter [Fraunhofer-Institut fuer Material- und Strahltechnologie, Winterbergstrasse 28, 1277 Dresden (Germany); Fuess, Hartmut [Institute of Materials Science, University of Technology, Petersenstr.23, 64287 Darmstadt (Germany)

    2011-11-15

    High dielectric constant and electrostriction property of (Ba, Sr)Ti0{sub 3} (BST) thin films result in an increasing interest for dielectric devices and microwave acoustic resonator. Barium strontium titanate (Ba{sub 0.645}Sr{sub 0.355}TiO{sub 3}) films of about 300 nm thickness are grown on Pt(111)/TiO{sub 2}/SiO{sub 2}/Si(001) substrates by rf magnetron sputtering deposition techniques. X-ray diffraction is applied for the microstructural characterization. The BST films exhibit a cubic perovskite structure with a dense and smooth surface. A laser acoustic waves (LA-waves) technique is used to generate surface acoustic waves (SAW) propagating in the BST films. Young's modulus E and the Poisson ratio {nu} of TiO{sub 2,} Pt and BST films in different propagation directions are derived from the measured dispersion curves. Estimation of BST elastics constants are served in SAW studies. Impact of stratification process on SAW, propagating along [100] and [110] directions of silicon substrate, has been interpreted on the basis of ordinary differential equation (ODE) and stiffness matrix method (SMM). A good agreement is observed between experimental and calculated dispersion curves. The performed calculations are strongly related to the implemented crystallographic data of each layer. Dispersion curves are found to be sensitive to the SAW propagation direction and the stratification process for the explored frequency ranges 50-250 MHz, even though it corresponds to a wave length clearly higher than the whole films thickness.

  5. DFT study on the selective oxidation of vinyl chloride on different metal surfaces

    Institute of Scientific and Technical Information of China (English)

    Ruipeng Ren; Ruixin Xi; Xianyong Pang; Yongkang Lü

    2011-01-01

    Selective epoxidation of vinyl chloride on Ag(111),Pt(111)and Rh(I 11)with pre-adsorbed atomic oxygen has been studied by density functional theory(DFT)calculation with the periodic slab model.The reaction energies and activation energies of the epoxidation reaction are determined.Because of the asymmetry of vinyl chloride,three competitive reaction pathways are investigated.The results indicate that the most possible reaction pathway is pathway Ⅲ.Compared the activation energies of the epoxidation reaction on Ag(111),Pt(111)and Rh(111),it is obvious that the reaction via OMMC(3)on Ag(111)is the most possible process.However,the selectivity to the target product over Ag(111)is the lowest among the three metals.The results also indicate that the formation of chloroacetaldehyde is more favorable than that of chloroepoxide.

  6. Compositionally graded InGaN layers grown on vicinal N-face GaN substrates by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Hestroffer, Karine; Lund, Cory; Koksaldi, Onur; Li, Haoran; Schmidt, Gordon; Trippel, Max; Veit, Peter; Bertram, Frank; Lu, Ning; Wang, Qingxiao; Christen, Jürgen; Kim, Moon J.; Mishra, Umesh K.; Keller, Stacia

    2017-05-01

    This work reports on compositionally graded (0 0 0 1 bar) N-polar InxGa1-xN layers. The InGaN grades with different final In compositions xf up to 0.25 were grown by plasma-assisted molecular beam epitaxy on vicinal GaN base layers with a miscut angle of 4° towards the m-direction. When increasing xf the surface morphology evolved from an interlacing finger structure, attributed to the Ehrlich-Schwöbel effect, towards fully strain-relaxed columnar features. Regardless of the crystal morphology and the strain state each graded sample exhibited a bright photoluminescence signal at room temperature spanning the whole visible range. Cross-sectional nanoscale cathodoluminescence evidenced a red-shift of the luminesced signal from 420 to 580 nm along the grade and also showed strong lateral emission inhomogeneities.

  7. Representation of two-phase flow in the vicinity of the repository in the 1996 performance assessment for the Waste Isolation Pilot Plant

    Energy Technology Data Exchange (ETDEWEB)

    VAUGHN,PALMER; BEAN,J.E.; HELTON,JON CRAIG; LORD,MICHAEL E.; MACKINNON,ROBERT J.; SCHREIBER,JAMES D.

    2000-05-18

    The following topics related to the representation of two-phase (gas and brine) flow in the vicinity of the repository in the 1996 performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP) are discussed: (1) system of nonlinear partial differential equations used to model two-phase flow, (2) incorporation of repository shafts into model (3) creep closure of repository. (4) interbed fracturing, (5) gas generation (6) capillary action in waste, (7) borebole model (8) numerical solution and (9) gas and brine flow across specified boundaries. Two-phase flow calculations are a central part of the 1996 WIPP PA and supply results that are subsequently used in the calculation of releases to the surface at the time of a drilling intrusion (i.e., spallings, direct brine releases) and long-term releases due to radionuclide transport by flowing groundwater.

  8. Ash dust co-centration in the vicinity of the ash disposal site depending on the size of the pond (“Water Mirror”

    Directory of Open Access Journals (Sweden)

    Zoran Gršić

    2010-09-01

    Full Text Available Thermal power plants Nikola Tesla “A” and “B” are large sources of ash from their ashes/slag deposit sites. Total sizes of ashes/slag depots are 600ha and 382ha, with active cassettes having dimensions ∼200 ha and ∼130 ha. The active cassettes of the disposal sites are covered by rather large waste ponds, the sizes of vary depending on the working condition of a sluice system and on meteorological conditions. Modeling of ash lifting was attempted using results from the dust lifting research. The relation between sizes of ponds and air dust concentration in the vicinity of ash disposal sites was analyzed. As expected, greater sizes of dried disposal site surfaces in combination with stronger winds gave greater dust emission and greater air dust concentration.

  9. Terrace-Width Distributions (TWDs) of Touching Steps: Modification of the Fermion Analogy, with Implications for Measuring Step-Step Interactions on Vicinals

    Science.gov (United States)

    Einstein, T. L.; Sathiyanarayanan, Rajesh; Hamouda, Ajmi Bh.; Kim, Kwangmoo

    2010-03-01

    Using Monte Carlo simulations, we computefootnotetextRS, ABH, and TLE, Phys. Rev. B 80 (2009) 153415. the TWDs of surfaces in which steps can touch each other, forming multiple-atomic height steps, but cannot cross (no overhangs), and so inconsistent with the standard mapping to spinless fermions. Our numerical results show that the generalized Wigner distribution, with minor modifications at small step separations, gives a very good fit for TWDs of touching steps. (We also generate analytic results by generalizing results for extended fermions.footnotetextSiew-Ann Cheong and C.L. Henley, arXiv:0907.4228v1.) The interaction strength derived from the fit parameter indicates an effective attraction between steps, weakening the overall repulsion. The strength of this effective attraction decreases for larger mean-step separations and decreasing step-touching energies; describable via finite-size scaling. Hence, accurate extraction of the true repulsion strength requires multiple vicinalities.

  10. Map showing recent (1997-98 El Nino) and historical landslides, Crow Creek and vicinity, Alameda and Contra Costa Counties, California

    Science.gov (United States)

    Coe, Jeffrey A.; Godt, Jonathan; Tachker, Pierre

    2004-01-01

    This report documents the spatial distribution of 3,800 landslides caused by 1997-98 El Ni?o winter rainfall in the vicinity of Crow Creek in Alameda and Contra Costa Counties, California. The report also documents 558 historical (pre-1997-98) landslides. Landslides were mapped from 1:12,000-scale aerial photographs and classified as either debris flows or slides. Slides include rotational and translational slides, earth flows, and complex slope movements. Debris flows and slides from the 1997-98 winter modified 1 percent of the surface of the 148.6 km2 study area. Debris flows were scattered throughout the area, regardless of the type of underlying bedrock geology. Slides, however, were concentrated in a soft sandstone, conglomerate, and clayey group of rock units. Digital map files accompany the report.

  11. Pulsed-laser deposition of vicinal and c-axis oriented high temperature superconducting thin films

    CERN Document Server

    Rössler, R

    2000-01-01

    respect to the temperature, oxygen pressure and laser fluence. (Re,Hg)Ba sub 2 Ca sub ( n-1)Cu sub n O sub x films are synthesized on (001) and vicinal SrTiO sub 3 substrates in a two step process employing pulsed-laser deposition of Hg-free precursor films and Hg-vapour annealing in a sealed quartz tube. The sealed quartz tube technique is described in detail and the thermodynamics and the phase formation are discussed. The influence of the Hg-vapour pressure and the annealing temperature on the film properties are investigated. The influence of Hg-vapour annealing on Bi sub 2 Sr sub 2 CaCu sub 2 O sub x films is described. YBa sub 2 Cu sub 3 O sub x films with thicknesses 20 to 480 nm are deposited on vicinal SrTiO sub 3 substrates (10 degrees tilt angle). Variation of the resistivities and changes in the film morphology depending on film thickness are described. The influence of post-annealing treatments on the film properties is discussed. Pulsed-laser deposition (PLD) of high temperature superconducting ...

  12. Ground Motion Prediction for the Vicinity by Using the Microtremor Site-effect Correction

    Science.gov (United States)

    Lin, C. M.; Wen, K. L.; Kuo, C. H.

    2015-12-01

    This study develops a method analyzing the seismograms of a strong-motion station and the microtremor site effects (H/V ratios) around it to predict the ground motion of its vicinity. The Hsinchu Science Park (HSP) in Taiwan was chosen as our study site. The horizontal S-wave seismograms of the TCU017 strong-motion station, which locates at the center of the HSP, were convoluted by the difference of the microtremor H/V ratio between various sites to synthesize the seismograms of several strong-motion stations around the HSP. The comparisons between synthetic and observed seismograms show that this method of ground motion prediction for the vicinity is feasible for far-field earthquakes. However, the seismic source and attenuation effects make this method ineffectual for near-field earthquakes. Because the microtremor H/V ratios at about 200 sites, which are densely distributed in the HSP, were conducted, the seismic ground motion distributions of some historical earthquakes were synthesized by this study. The synthetic ground motion distributions ignore the seismic source and attenuation effects but still show notable variations in the HSP because of the seismic site effects.

  13. Neutron diffraction analysis of residual strain/stress distribution in the vicinity of high strength welds

    Directory of Open Access Journals (Sweden)

    Hamák I.

    2010-06-01

    Full Text Available Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible for defect occurrence during welding and they are also responsible for crack initiation and propagation at the either static or dynamic load. The significant effect of weld metal chemical composition as well as the effect of fatigue load and local plastic deformation on residual stress distribution and fatigue life have been recognized for high strength steels welds. The changes in residual stress distribution have then positive effect on cold cracking behavior and also on fatigue properties of the welds [1-3]. Several experimental methods, both destructive and non-destructive, such as hole drilling method, X-ray diffraction, neutron diffraction and others, have been used to examine residual stress distribution in all three significant orientations in the vicinity of the welds. The present contribution summarizes the results of neutron diffraction measurements of residual stress distribution in the vicinity of single-pass high-strength-steel welds having different chemical composition as well as the influence of fatigue load and local plastic deformation. It has been observed that the chemical composition of the weld metal has a significant influence on the stress distribution around the weld. Similarly, by aplying both cyclic load or pre-stress load on the specimens, stress relaxation was observed even in the region of approximately 40 mm far from the weld toe.

  14. Zinc, among a 'cocktail' of metal pollutants, is responsible for the absence of the terrestrial isopod Porcellio scaber from the vicinity of a primary smelting works.

    Science.gov (United States)

    Hopkin, S P; Hames, C A

    1994-03-01

    : Porcellio scaber Latreille (Crustacea: Isopoda) of one month in age were reared for a year on leaf litter of field maple (Acer campestre) contaminated in the laboratory with a range of concentrations of cadmium, copper, lead or zinc. The metals were applied topically to the leaves as nitrates. Growth and survival, numbers of live offspring produced by females that matured, and concentrations of metals in adult isopods at the end of the experiment were measured.'Critical concentrations' of metals in food at which all the isopods died before producing offspring were 100 μg Cd g(-1), 100 μg Cu g(-1), 2000 μg Pb g(-1) and 1000 μg Zn g(-1) (on a dry weight basis). The relative toxicities of the four metals in the laboratory were compared with concentrations of cadmium, copper, lead and zinc in surface leaf litter in the vicinity of a primary smelting works at Avonmouth, South West England. The results support the hypothesis that the absence of Porcellio scaber from sites in the immediate vicinity of the factory is due to zinc poisoning. Although cadmium is approximately ten times more toxic to isopods than zinc in the laboratory, zinc is most likely to be killing isopods in the field because its concentration is always at least 30 times higher than cadmium in Avonmouth leaf litter, and more than 100 times higher at most sites.Populations of Porcellio scaber survive in field sites where surface leaf litter contains up to 5000 μg Zn g(-1). This is at least five times higher than the 'critical concentration' in laboratory experiments. Thus, the methodology for assessing metal toxicity described in this paper, exaggerates the potential effects of metals to isopods in the field. Such differences between laboratory and field toxicities of metals should be taken into account when environmental protection levels for metals are being proposed for soil invertebrates based on ecotoxicological tests conducted in the laboratory.

  15. A preliminary summary of a seismic-refraction survey in the vicinity of the Tonto Forest Observatory, Arizona

    Science.gov (United States)

    Roller, J.C.; Jackson, W.H.; Warren, D.H.; Healy, J.H.

    1964-01-01

    The U.S. Geological Survey complete d a seismic-refraction survey in the vicinity of the Tonto Forest Seismological Observatory (T.F.S.O.) in April and May 1964. More than 1200 km of reversed profiles were surveyed to determine the crustal structure and crustal and upper mantle velocities in this area. The purpose of this work was to provide information on wave-propagation paths of seismic events recorded at T.F.S.O. and to improve the performance of the Observatory in locating and identifying these events. First arrivals indicate that the Mohorovicic discontinuity dips to the northeast by as much as 6 degrees under T.F.S.O., and may even be displaced vertically by as much as 5 km immediately north of the Observatory near the boundary of the Basin and Range a n d t he Colorado Plateau Provinces. A preliminary examination of the first arrivals indicates that the crust at T.F.S.O. is at least 30 km thick and is made up of at least two seismic layers. A thin veneer at the surface with a velocity of approximately 4 km/sec is underlain by a layer with a velocity of approximately 5.9 km/sec to 6.1 km/sec. An intermediate layer with velocity of 6.6 to 7.0 km/sec is probably present in the lower crust, but is not revealed by first arrivals. The velocity of seismic waves in the upper mantle is about 7.9 km/sec.

  16. Impact assessment of mine drainage water and municipal wastewater on the surface water in the vicinity of Bor

    Directory of Open Access Journals (Sweden)

    Gardić Vojka R.

    2015-01-01

    Full Text Available Mining and copper production in Bor, in the past hundred years, had a huge impact on the environment of town, but also in a wide region. In the area of Bor, in the zone of Mining and Smelting Company (RTB activity, over 29,000 ha of land under forests and fields is degraded. The area of degraded agricultural land in the Bor municipality is over 60% of total agricultural land. Wastewater, generated in the sites of RTB Bor, pollute the Bor River and Krivelj River, which still flow into the Timok River and Danube River. These pollutions are often presented by low pH value, increased content of heavy metal ions, suspended particles and fine particles of flotation tailings, which is deposited in the valleys of these rivers on the area of over 2000 hectares. During the decades of exploitation of ore from the open pit Bor at different locations ("Visoki Planir" - also called “Oštreljski planir”, "Severni planir" dump of ore body "H" (RTH gangue and tailings were delayed. The largest amount of tailings, about 150 million tons, was postponed on location Visoki planir. The effect of the mining waste and the impact of the whole process of processing copper ore to the final products on the environment, was conducted during the 4th study period of the project "Management of mining waste-tailing dump in the Bor region," supported by the Japan Society for the Promotion Science (Eng. Japan Society for the Promotion of Science and the Japan international cooperation Agency and the Ministry of environment, Mining and Spatial planning of the Republic of Serbia. Influence of season on the level of pollutants in soil and water, the impact on water quality in the river Timok and the River Danube, was conducted during first three periods of project. This paper presents the results of the third study period. The third period of research, which was conducted over a period of 17. 10. 2012 to 17. 01.2013 year, included a review of pollution sources and define their impact on the environment. The study included the following sources of pollution: mining waste and drainage water originating from the active mine (Bor pit , field 1 Krivelj large tailings, flotation tailings in Bor RTH, metallurgical water, as well as the drainage water from the flotation tailings, which are no longer in operation (field 2 flotation tailings Great Krivelj, drainage water from the old Bor flotation tailings, the old inactive landfill mine gangue (Saraka landfill, Veliki planir - tailings from the old Bor mine, landfill mine gangue from mine RTH and the city - urban waste water, which are discharged without treatment directly into the watercourse Bor River. Wastewater directly pollute Bor River and Krivalj River.

  17. Surface Wind Fields in the Vicinity of Meso-Convective Storms as Derived from Radar Observations: Non-Tornadic Storms.

    Science.gov (United States)

    1986-12-01

    and always providing an optimistic viewpoint. Mr. Charles Brenton, Practical Meteorologist, took my original meso-analyses and applied his 35+ years...generator level (Marshall, 1953; Gunn and Marshall, 1955; Langleben, 1956; Wexler and Atlas, 1959). In these previous cases, the shortest times between...Personal communication. Wexler , R., and D. Atlas, 1959: Precipitation generating cells. J. of Meteor., 16, 327-332. Zrnic, D., 1985: Personal

  18. Impact assessment of mine drainage water and municipal wastewater on the surface water in the vicinity of Bor

    OpenAIRE

    Gardić Vojka R.; Petrović Jelena V.; Đurđevac-Ignjatović Lidija V.; Kolaković Srđan R.; Vujović Svetlana R.

    2015-01-01

    Mining and copper production in Bor, in the past hundred years, had a huge impact on the environment of town, but also in a wide region. In the area of Bor, in the zone of Mining and Smelting Company (RTB) activity, over 29,000 ha of land under forests and fields is degraded. The area of degraded agricultural land in the Bor municipality is over 60% of total agricultural land. Wastewater, generated in the sites of RTB Bor, pollute the Bor River and Krivelj ...

  19. Lead and cadmium in mushrooms from the vicinity of two large emission sources in Slovenia

    Energy Technology Data Exchange (ETDEWEB)

    Petkovšek, Samar Al Sayegh, E-mail: samar.petkovsek@erico.si; Pokorny, Boštjan

    2013-01-15

    Cd and Pb contents were determined in 699 samples of fruiting bodies of 55 mushrooms species, collected in the period 2000–2007 in the vicinity of the largest Slovenian thermal power plant (the Šalek Valley) and near an abandoned lead smelter (the Upper Meža Valley). The present study is the first regarding lead and cadmium in mushrooms from those exposed areas. Therefore, there was a significant lack of prior data. Among 55 studied mushroom species 36 species are edible and important from an ecotoxicological perspective. However, the remaining non-edible species are important for bioindication and allowed us to compare our results with other studies carried out in other polluted areas in Europe. The highest contents of Cd were found in Agaricus arvensis Schff.: Fr. (117 mg/kg dw) and Agaricus silvicola L.: Fr. (67.9 mg/kg dw), while the highest contents of Pb were found in Macrolepiota procera (Scop.) Singer (53.8 mg/kg dw) and Lycoperdon perlatum Pers. (50 mg/kg dw), respectively. Considering the high contents of both metals in fruiting bodies of edible fungi, together with FAO/WHO directives on tolerable levels of weekly intake of Pb/Cd by humans, it is evident that consumption of some mushroom species originating from both study areas may pose a significant human health risk. A. arvensis Schff.: Fr., A. silvicola L.: Fr. and Cortinarius caperatus (Pers.) Fr. originating from the Šalek Valley, and Armillaria mellea Vahl. P. Kumm., Boletus edulis Bull., L. perlatum Pers., Leccinum versipelle (Fr. and Hök) Snell, and M. procera (Scop.) Singer originating from the Upper Meža Valley should not be consumed at all. Our findings are consistent with some other studies, which emphasized that mushrooms from heavily polluted areas, such as in the vicinity of smelters, accumulate extremely high amounts of metals, and should therefore be omitted from human consumption. - Highlights: ► The Pb contents were higher in saprophytic fungi in comparison with mycorrhizal

  20. EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary

    Directory of Open Access Journals (Sweden)

    A. T. Aikio

    2008-02-01

    Full Text Available The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromsø (66.6° cgmLat and Longyearbyen (75.2° cgmLat on 27 February 2004 by using the coordinated EISCAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB made zig-zag-type motion with amplitude of 2.5° cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL. The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992. The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm.

    During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4 RE mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H+ and O+ ions took place within the plasma sheet boundary layer (PSBL as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be further energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency fluctuations.

    The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2° during

  1. In-situ Studies of the Reactions of Bifunctional and Heterocyclic Molecules over Noble Metal Single Crystal and Nanoparticle Catalysts Studied with Kinetics and Sum-Frequency Generation Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kliewer, Christopher J. [Univ. of California, Berkeley, CA (United States)

    2009-06-30

    Sum frequency generation surface vibrational spectroscopy (SFG-VS) in combination with gas chromatography (GC) was used in-situ to monitor surface bound reaction intermediates and reaction selectivities for the hydrogenation reactions of pyrrole, furan, pyridine, acrolein, crotonaldehyde, and prenal over Pt(111), Pt(100), Rh(111), and platinum nanoparticles under Torr reactant pressures and temperatures of 300K to 450K. The focus of this work is the correlation between the SFG-VS observed surface bound reaction intermediates and adsorption modes with the reaction selectivity, and how this is affected by catalyst structure and temperature. Pyrrole hydrogenation was investigated over Pt(111) and Rh(111) single crystals at Torr pressures. It was found that pyrrole adsorbs to Pt(111) perpendicularly by cleaving the N-H bond and binding through the nitrogen. However, over Rh(111) pyrrole adsorbs in a tilted geometry binding through the {pi}-aromatic orbitals. A surface-bound pyrroline reaction intermediate was detected over both surfaces with SFG-VS. It was found that the ring-cracking product butylamine is a reaction poison over both surfaces studied. Furan hydrogenation was studied over Pt(111), Pt(100), 10 nm cubic platinum nanoparticles and 1 nm platinum nanoparticles. The product distribution was observed to be highly structure sensitive and the acquired SFG-VS spectra reflected this sensitivity. Pt(100) exhibited more ring-cracking to form butanol than Pt(111), while the nanoparticles yielded higher selectivities for the partially saturated ring dihydrofuran. Pyridine hydrogenation was investigated over Pt(111) and Pt(100). The α-pyridyl surface adsorption mode was observed with SFG-VS over both surfaces. 1,4-dihydropyridine was seen as a surface intermediate over Pt(100) but not Pt(111). Upon heating the surfaces to 350K, the adsorbed pyridine changes to a flat-lying adsorption mode. No evidence was found for the pyridinium cation. The hydrogenation of the

  2. Microscopic Raman spectroscopy in the vicinity of domain wall of (Na,K)NbO3 piezoelectrics

    Science.gov (United States)

    Taniguchi, Yuya; Kakimoto, Ken-ichi

    2015-10-01

    The domain walls of Mn-doped (Na,K)NbO3 (NKN) crystals and ceramics have been measured by spectroscopy methods. Microscopy-Raman and infrared (IR) spectroscopies were performed vertically to lamellar domain structures by line mapping. Regarding the crystals, large changes were confirmed in the vicinity of domain walls. Both the Raman shift and the peak intensity at approximately 600 cm-1, which include the symmetric stretching modes of the oxygen octahedron, were observed. Similar changes were also characterized for electrically polarized NKN ceramics. In addition, the permittivity of NKN crystals increased in the vicinity of the domain wall, which was measured by IR spectroscopy. These results were attributed to the changes in the oxygen octahedron structures due to local changes in spontaneous polarization directions in the vicinity of the domain walls.

  3. Predicting Reaction Mechanisms and Potentials in Acid and Base from Self-Consistent Quantum Theory: H(ads) and OH(ads) Deposition on the Pt(111) Electrode.

    Science.gov (United States)

    Zhao, Meng; Anderson, Alfred B

    2016-02-18

    It has been shown recently that when reactants and products are well modeled within a comprehensive self-consistent theory for the electrochemical interface, accurate predictions are possible for reversible potentials, Urev, in acid electrolyte for reactions such as reduction of H(+)(aq) to form under potential deposited H(ads) and oxidation of an OH bond of H2O(ads) to deposit OH(ads). Predictions are based on calculated Gibbs energies for the reactant and product being equal at the reversible potential, which is the potential at the crossing point for reaction and product Gibbs energies, plotted as functions of electrode potential. In this Letter, it is demonstrated that the same capability holds for these reactions in basic electrolyte. This demonstration opens up the opportunity for predictions of reversible potentials and mechanisms for other electrocatalytic reactions in base.

  4. First principles study of (Cd, Hg, In, Tl, Sn, Pb, As, Sb, Bi, Se) modified Pt(111), Pt(100) and Pt(211) electrodes as CO oxidation catalysts

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir

    2015-01-01

    CO oxidation is a prototype reaction for studying oxidation of small organic molecules. Certain adatom modified Pt electrodes have a large promotional effect on CO oxidation. However, the effect is often coverage dependent, and has a limited effect due to short lifetimes of the adatoms. The cover...

  5. Synchrotron Based Structural Investigations of Mass-Selected PtxGd Nanoparticles and a Gd/Pt(111) Single Crystal for Electrochemical Oxygen Reduction

    DEFF Research Database (Denmark)

    Pedersen, Anders Filsøe; Velazquez-Palenzuela, Amado Andres; Masini, Federico

    2015-01-01

    . 134, 16476–16479 (2012). 3. Velazquez-Palenzuela, A. et al. The enhanced activity of mass-selected PtxGd nanoparticles for oxygen electroreduction. J. Catal. [in press] (2015). doi:10.1016/j.jcat.2014.12.012 4. Perez-Alonso, F. J. et al. The Effect of Size on the Oxygen Electroreduction Activity...

  6. Temperature dependence of magnetic susceptibility in the vicinity of martensitic transformation in ferromagnetic shape memory alloys.

    Science.gov (United States)

    Zablotskii, V; Pérez-Landazábal, J I; Recarte, V; Gómez-Polo, C

    2010-08-11

    Temperature dependences of low-field quasistatic magnetic susceptibility in the vicinity of martensitic transitions in an NiFeGa alloy are studied both by experiment and analytically. Pronounced reversible jumps of the magnetic susceptibility were observed near the martensitic transition temperature. A general description of the temperature dependences of the susceptibility in ferromagnetic austenite and martensite phases and the susceptibility jump at the transition is suggested. As a result, the main factors governing the temperature dependences of the magnetic susceptibility in the magnetic shape memory alloys are revealed. The magnetic susceptibility jump value is found to be related to changes of: (i) magnetic anisotropy; (ii) magnetic domain wall geometrical constraints (those determined by the alignment and size of twin variants) and (iii) mean magnetic domain spacing.

  7. Nonlinear oscillations of compact stars in the vicinity of the maximum mass configuration

    CERN Document Server

    Brillante, Alessandro

    2015-01-01

    We solve the dynamical GR equations for the spherically symmetric evolution of compact stars in the vicinity of the maximum mass, for which instability sets in according to linear perturbation theory. The calculations are done with the analytical Zeldovich-like EOS P=a(rho-rho_0) and with the TM1 parametrisation of the RMF model. The initial configurations for the dynamical calculations are represented by spherical stars with equilibrium density profile, which are perturbed by either (i) an artificially added inward velocity field proportional to the radial coordinate, or (ii) a rarefaction corresponding to a static and expanded star. These configurations are evolved using a one-dimensional GR hydro code for ideal and barotropic fluids. Depending on the initial conditions we obtain either stable oscillations or the collapse to a black hole. The minimal amplitude of the perturbation, needed to trigger gravitational collapse is evaluated. The approximate independence of this energy on the type of perturbation i...

  8. Turbulent flow in a ribbed channel: Flow structures in the vicinity of a rib

    DEFF Research Database (Denmark)

    Wang, Lei; Salewski, Mirko; Sundén, Bengt

    2010-01-01

    PIV measurements are performed in a channel with periodic ribs on one wall. The emphasis of this study is to investigate the flow structures in the vicinity of a rib in terms of mean velocities, Reynolds stresses, probability density functions (PDF), and two-point correlations. The PDF distribution...... of u′ is bimodal in the separated shear layer downstream of the rib. The maximum Reynolds shear stresses occur at the leading edge of the rib. Based on quadrant analysis, it is found that ejection motions make a dominant contribution to the Reynolds shear stress in this region. Moreover, topology......-based visualization is applied to the separation bubble upstream of the rib. Salient critical points and limit cycles are extracted, which gives clues to the physical processes occurring in the flow....

  9. Energetic electron acceleration observed by MMS in the vicinity of an X-line crossing

    Science.gov (United States)

    Jaynes, A. N.; Turner, D. L.; Wilder, F. D.; Osmane, A.; Baker, D. N.; Blake, J. B.; Fennell, J. F.; Cohen, I. J.; Mauk, B. H.; Reeves, G. D.; Ergun, R. E.; Giles, B. L.; Gershman, D. J.; Torbert, R. B.; Burch, J. L.

    2016-07-01

    During the first months of observations, the Magnetospheric Multiscale Fly's Eye Energetic Particle Spectrometer instrument has observed several instances of electron acceleration up to >100 keV while in the vicinity of the dayside reconnection region. While particle acceleration associated with magnetic reconnection has been seen to occur up to these energies in the tail region, it had not yet been reported at the magnetopause. This study reports on observations of electron acceleration up to hundreds of keV that were recorded on 19 September 2015 around 1000 UT, in the midst of an X-line crossing. In the region surrounding the X-line, whistler-mode and broadband electrostatic waves were observed simultaneously with the appearance of highly energetic electrons which exhibited significant energization in the perpendicular direction. The mechanisms by which particles may be accelerated via reconnection-related processes are intrinsic to understanding particle dynamics among a wide range of spatial scales and plasma environments.

  10. A floristic survey of Yucca Mountain and vicinity, Nye County, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Niles, W.E.; Leary, P.J.; Holland, J.S.; Landau, F.H.

    1995-12-01

    A survey of the vascular flora of Yucca Mountain and vicinity, Nye County, Nevada, was conducted from March to June 1994, and from March to October 1995. An annotated checklist of recorded taxa was compiled. Voucher plant specimens were collected and accessioned into the Herbarium at the University of Nevada, Las Vegas. Collection data accompanying these specimens were entered into that herbarium`s electronic data base. Combined results from this survey and the works of other investigators reveal the presence of a total of 375 specific and intraspecific taxa within the area these allocated to 179 genera and 54 families. No taxon currently listed as threatened or endangered under the Endangered Species Act was encountered during this study. Several candidate species for listing under this Act were present, and distributional data for these were recorded. No change in the status of these candidate species is recommended as the result of this study.

  11. Turbulence study in the vicinity of piano key weir: relevance, instrumentation, parameters and methods

    Science.gov (United States)

    Tiwari, Harinarayan; Sharma, Nayan

    2017-05-01

    This research paper focuses on the need of turbulence, instruments reliable to capture turbulence, different turbulence parameters and some advance methodology which can decompose various turbulence structures at different levels near hydraulic structures. Small-scale turbulence research has valid prospects in open channel flow. The relevance of the study is amplified as we introduce any hydraulic structure in the channel which disturbs the natural flow and creates discontinuity. To recover this discontinuity, the piano key weir (PKW) might be used with sloped keys. Constraints of empirical results in the vicinity of PKW necessitate extensive laboratory experiments with fair and reliable instrumentation techniques. Acoustic Doppler velocimeter was established to be best suited within range of some limitations using principal component analysis. Wavelet analysis is proposed to decompose the underlying turbulence structure in a better way.

  12. Monitoring of radionuclides in the vicinities of Finnish nuclear power plants in 1993 and 1994

    Energy Technology Data Exchange (ETDEWEB)

    Klemola, S.; Ilus, E.; Ikaeheimonen, T.K

    1998-08-01

    Monitoring of radioactive substances around Finnish nuclear power plants continued in 1993-1994 in accordance with the regular programmes. Some 1000 samples are analysed annually from the terrestrial and aquatic environments of the two power plant sites. Trace amounts of activation products originating from airborne releases from the local power plants were detected in several air, deposition and soil samples. Discharged nuclides were more abundant in the aquatic environment, especially in samples of indicator organisms, sinking matter and sediments. However, the concentrations were so low that they did not significantly increase the radiation burden in the environment. The dominant artificial radionuclides in the vicinity of the power plants remained the cesium isotopes, especially {sup 137}Cs but also {sup 134}Cs, originating from the Chernobyl accident. (orig.) 14 refs.

  13. Lyman-alpha observations in the vicinity of Saturn with Copernicus

    Science.gov (United States)

    Barker, E.; Cazes, S.; Emerich, C.; Vidal-Madjar, A.; Owen, T.

    1980-01-01

    For the first time, high-resolution Ly-alpha observations of the Saturn vicinity were completed with the Princeton spectrometer on board the Copernicus satellite. They showed that near a minimum solar activity the emissions related to several sources are 250 + or - 50 rayleighs for the interplanetary medium in a near-downwind direction, less than 100 rayleighs for the rings, 200 + or - 100 rayleighs for a torus linked to the Titan orbit, and 1400 + or - 450 rayleighs for the disk of Saturn. These results induce some constraints through the corresponding theoretical evaluations: the B ring as the primary source of the atoms for the ring emissions; an efficient production mechanism for hydrogen atoms in the Titan torus; and a slightly larger eddy diffusion coefficient in the Saturn atmosphere than in the Jupiter atmosphere near solar minimum.

  14. Turbulence study in the vicinity of piano key weir: relevance, instrumentation, parameters and methods

    Science.gov (United States)

    Tiwari, Harinarayan; Sharma, Nayan

    2015-03-01

    This research paper focuses on the need of turbulence, instruments reliable to capture turbulence, different turbulence parameters and some advance methodology which can decompose various turbulence structures at different levels near hydraulic structures. Small-scale turbulence research has valid prospects in open channel flow. The relevance of the study is amplified as we introduce any hydraulic structure in the channel which disturbs the natural flow and creates discontinuity. To recover this discontinuity, the piano key weir (PKW) might be used with sloped keys. Constraints of empirical results in the vicinity of PKW necessitate extensive laboratory experiments with fair and reliable instrumentation techniques. Acoustic Doppler velocimeter was established to be best suited within range of some limitations using principal component analysis. Wavelet analysis is proposed to decompose the underlying turbulence structure in a better way.

  15. Crystal acceleration effect for cold neutrons in the vicinity of the Bragg resonance

    Directory of Open Access Journals (Sweden)

    Yulia P. Braginetz

    2016-03-01

    Full Text Available A new mechanism of neutron acceleration is studied experimentally in detail for cold neutrons passing through the accelerated perfect crystal with the energies close to the Bragg one. The effect arises due to the following reason. The crystal refraction index (neutron–crystal interaction potential for neutron in the vicinity of the Bragg resonance sharply depends on the parameter of deviation from the exact Bragg condition, i.e. on the crystal–neutron relative velocity. Therefore the neutrons enter into the accelerated crystal with one neutron–crystal interaction potential and exit with the other. Neutron kinetic energy cannot vary inside the crystal due to its homogeneity. So, after passage through such a crystal, neutrons will be accelerated or decelerated because of the different energy change at the entrance and exit crystal boundaries.

  16. Patterns of criticality in the recent seismic activity in the vicinity of Athens, Greece

    Science.gov (United States)

    Dologlou, Elizabeth

    2016-04-01

    New data from the Mw 5.4 earthquake on 17 November 2014 in the vicinity of Athens and its seismic electric signal (SES) precursor confirm patterns of criticality in the pre-seismic region during the last preparatory phase. In detail, the stress drop of the main shock and the lead time of the associated SES are interconnected through a power law with an exponent a = 0.327 falling in the range of critical exponents for fracture. We note that this exponent is derived from a large amount of data and successfully passes the z-score statistical test. This fact supports the hypothesis that upon the emission of the SES the pre-focal area enters a critical stage where nonlinear dynamic processes dominate.

  17. Applicability of n-vicinity method for calculation of free energy of Ising model

    Science.gov (United States)

    Kryzhanovsky, Boris; Litinskii, Leonid

    2017-02-01

    Here we apply the n-vicinity method of approximate calculation of the partition function to an Ising Model with the nearest neighbor interaction on D-dimensional hypercube lattice. We solve the equation of state for an arbitrary dimension D and analyze the behavior of the free energy. As expected, for large dimensions (D ≥ 3) the system demonstrates a phase transition of the second kind. In this case, we obtain a simple analytical expression for the critical value of the inverse temperature. When 3 ≤ D ≤ 7 this expression is in a very good agreement with the results of computer simulations. In the case of small dimensions (D = 1 , 2), there is a noticeable discrepancy with the known exact results.

  18. Degenerate optomechanical parametric oscillators: cooling in the vicinity of a critical point

    CERN Document Server

    Degenfeld-Schonburg, Peter; Hartmann, Michael J; Navarrete-Benlloch, Carlos

    2015-01-01

    Degenerate optomechanical parametric oscillators are optical resonators in which a mechanical degree of freedom is coupled to a cavity mode that is nonlinearly amplified via parametric down-conversion of an external pumping laser. Below a critical pumping power the down-converted field is purely quantum-mechanical, making the theoretical description of such systems very challenging. Here we introduce a theoretical approach that is capable of describing this regime, even at the critical point itself. We find that the down-converted field can induce significant mechanical cooling and identify the process responsible of this as a "cooling by heating" mechanism. Moreover, we show that, contrary to naive expectations and semi-classical predictions, cooling is not optimal at the critical point, where the photon number is largest. Our approach opens the possibility for analyzing further hybrid dissipative quantum systems in the vicinity of critical points.

  19. New evidence for prehistoric copper metallurgy in the vicinity of Bor

    Directory of Open Access Journals (Sweden)

    Kapuran Aleksandar

    2016-01-01

    Full Text Available The last three years of archaeological investigations at the site Ru`ana in Banjsko Polje, in the immediate vicinity of Bor, have provided new evidence regarding the role of non-ferrous metallurgy in the economy of the prehistoric communities of north-eastern Serbia. The remains of metallurgical furnaces and a large amount of metallic slags at two neighbouring sites in the mentioned settlement reveal that locations with many installations for the thermal processing of copper ore existed in the Bronze Age. We believe, judging by the finds of material culture, that metallurgical activities in this area also continued into the Iron Age and, possibly, into the 4th century AD. [Projekat Ministarstva nauke Republike Srbije, br. 177020: Archaeology of Serbia: Cultural identity, integration factors, technological processes and the role of the central Balkans in the development of European prehistory

  20. California State Waters Map Series--Hueneme Canyon and vicinity, California

    Science.gov (United States)

    Johnson, Samuel Y.; Dartnell, Peter; Cochrane, Guy R.; Golden, Nadine E.; Phillips, Eleyne L.; Ritchie, Andrew C.; Kvitek, Rikk G.; Greene, H. Gary; Krigsman, Lisa M.; Endris, Charles A.; Clahan, Kevin B.; Sliter, Ray W.; Wong, Florence L.; Yoklavich, Mary M.; Normark, William R.

    2012-01-01

    In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California's State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Hueneme Canyon and vicinity map area lies within the eastern Santa Barbara Channel region of the Southern California Bight. The area is part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation - at least 90° - since the early Miocene has been proposed for the Western Transverse Ranges, and the region is presently undergoing north-south shortening. This geologically complex region forms a major biogeographic transition zone, separating the cold-temperate Oregonian province north of Point Conception from the warm-temperate California province to the south. The map area, which is offshore of the Oxnard plain and west of and along the trend of the south flank of the Santa Monica Mountains, lies at the east end of the Santa Barbara littoral cell, characterized by west-to-east littoral transport of sediment derived mainly from coastal watersheds. The Hueneme Canyon and vicinity map area in California's State Waters is characterized by two major physiographic features: (1) the nearshore continental shelf, and (2) the Hueneme and Mugu Submarine Canyon system, which, in the map area, includes Hueneme Canyon and parts