WorldWideScience

Sample records for surface spin-flip rate

  1. Measurement of spin-flip probabilities for ultracold neutrons interacting with nickel phosphorus coated surfaces

    CERN Document Server

    Tang, Z; Brandt, A; Callahan, N B; Clayton, S M; Currie, S A; Ito, T M; Makela, M; Masuda, Y; Morris, C L; Pattie, R; Ramsey, J C; Salvat, D J; Saunders, A; Young, A R

    2015-01-01

    We report a measurement of the spin-flip probabilities for ultracold neutrons interacting with surfaces coated with nickel phosphorus. For 50 $\\mu$m thick nickel phosphorus coated on stainless steel, the spin-flip probability per bounce was found to be $\\beta_{\\rm NiP\\;on\\;SS} = (3.3^{+1.8}_{-5.6}) \\times 10^{-6}$. For 50 $\\mu$m thick nickel phosphorus coated on aluminum, the spin-flip probability per bounce was found to be $\\beta_{\\rm NiP\\;on\\;Al} = (3.6^{+2.1}_{-5.9}) \\times 10^{-6}$. For the copper guide used as reference, the spin flip probability per bounce was found to be $\\beta_{\\rm Cu} = (6.7^{+5.0}_{-2.5}) \\times 10^{-6}$. Nickel phosphorus coated stainless steel or aluminum provides a solution when UCN guides that have a high Fermi potential and are low-cost, mechanically robust, and non-depolarizing are needed.

  2. Heating rate and spin flip lifetime due to near field noise in layered superconducting atom chips

    CERN Document Server

    Fermani, Rachele; Zhang, Bo; Lim, Michael J; Dumke, Rainer

    2009-01-01

    We theoretically investigate the heating rate and spin flip lifetimes due to near field noise for atoms trapped close to layered superconducting structures. In particular, we compare the case of a gold layer deposited above a superconductor with the case of a bare superconductor. We study a niobium-based and a YBCO-based chip. For both niobium and YBCO chips at a temperature of 4.2 K, we find that the deposition of the gold layer can have a significant impact on the heating rate and spin flip lifetime, as a result of the increase of the near field noise. At a chip temperature of 77 K, this effect is less pronounced for the YBCO chip.

  3. Spin flipping a stored polarized proton beam

    Science.gov (United States)

    Caussyn, D. D.; Derbenev, Ya. S.; Ellison, T. J.; Lee, S. Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; Stephenson, E. J.; von Przewoski, B.; Blinov, B. B.; Chu, C. M.; Courant, E. D.; Crandell, D. A.; Kaufman, W. A.; Krisch, A. D.; Nurushev, T. S.; Phelps, R. A.; Ratner, L. G.; Wong, V. K.; Ohmori, C.

    1994-11-01

    We recently studied the spin flipping of a vertically polarized, stored 139-MeV proton beam. To flip the spin, we induced an rf depolarizing resonance by sweeping our rf solenoid magnet's frequency through the resonance frequency. With multiple spin flips, we found a polarization loss of 0.0000+/-0.0005 per spin flip under the best conditions; this loss increased significantly for small changes in the conditions. Minimizing the depolarization during each spin flip is especially important because frequent spin flipping could significantly reduce the systematic errors in stored polarized-beam experiments.

  4. Magnetic polaron and Fermi surface effects on the ESR spin-flip scattering of EuB6 above TC≈15 K

    Science.gov (United States)

    Urbano, R. R.; Pagliuso, P. G.; Rettori, C.; Oseroff, S. B.; Sarrao, J. L.; Schlottmann, P.; Fisk, Z.

    2004-12-01

    The spin-flip scattering (SFS) between conduction and Eu4f7 ( S7/28) electrons in the paramagnetic phase of EuB6 ( T⩾TC≈15 K) is studied by electron spin resonance (ESR) and magneto-resistance (MR) experiments. The observed Dysonian resonance suggests a metallic environment for the Eu ions. ESR at high field, H≅12.05 kG ( ν≅33.9 GHz), shows an anisotropic line width with cubic symmetry. ESR at low-field, 1.46 kG (4.1 GHz) and 3.35 kG (9.5 GHz), shows broader line width and smaller anisotropy than at higher field. The narrowing and anisotropy of the line width at high fields are indicative of a homogeneous resonance where the line width is mainly governed by the SFS mechanism due to the exchange interaction between Eu4f7 and conduction electrons. Besides the negative MR, we found an anisotropic MR with cubic symmetry. These results are interpreted in terms of magnetic polaron and Fermi surface effects.

  5. Magnetic polaron and Fermi surface effects on the ESR spin-flip scattering of EuB6 above TC{approx}15K

    Energy Technology Data Exchange (ETDEWEB)

    Urbano, R.R. [Instituto de Fisica ' Gleb Wataghin' , Universidade Estadual de Campinas, Cidade Universitaria ' Zaferino Vaz' , UNICAMP, CP 6165, Campinas 13083-970 (Brazil)]. E-mail: urbano@ifi.unicamp.br; Pagliuso, P.G. [Instituto de Fisica ' Gleb Wataghin' , Universidade Estadual de Campinas, Cidade Universitaria ' Zaferino Vaz' , UNICAMP, CP 6165, Campinas 13083-970 (Brazil); Rettori, C. [Instituto de Fisica ' Gleb Wataghin' , Universidade Estadual de Campinas, Cidade Universitaria ' Zaferino Vaz' , UNICAMP, CP 6165, Campinas 13083-970 (Brazil); Oseroff, S.B. [San Diego State University, San Diego, CA 92182 (United States); Sarrao, J.L. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Schlottmann, P. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 2310 (United States); Fisk, Z. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 2310 (United States)

    2004-12-31

    The spin-flip scattering (SFS) between conduction and Eu2+4f7 (S7/28) electrons in the paramagnetic phase of EuB6 (T>=TC{approx}15K) is studied by electron spin resonance (ESR) and magneto-resistance (MR) experiments. The observed Dysonian resonance suggests a metallic environment for the Eu2+ ions. ESR at high field, H-bar 12.05kG ({nu}-bar 33.9GHz), shows an anisotropic line width with cubic symmetry. ESR at low-field, 1.46kG (4.1GHz) and 3.35kG (9.5GHz), shows broader line width and smaller anisotropy than at higher field. The narrowing and anisotropy of the line width at high fields are indicative of a homogeneous resonance where the line width is mainly governed by the SFS mechanism due to the exchange interaction between Eu2+ 4f7 and conduction electrons. Besides the negative MR, we found an anisotropic MR with cubic symmetry. These results are interpreted in terms of magnetic polaron and Fermi surface effects.

  6. Spin-flip, tensor equation-of-motion configuration interaction with a density-functional correction: A spin-complete method for exploring excited-state potential energy surfaces

    Science.gov (United States)

    Zhang, Xing; Herbert, John M.

    2015-12-01

    We revisit the formalism of the spin-adapted, spin-flip (SA-SF) configuration-interaction singles (CIS) method based on a tensor equation-of-motion formalism that affords proper spin eigenstates without sacrificing single-reference simplicity. Matrix elements for SA-SF-CIS are then modified in a manner similar to collinear spin-flip time-dependent density functional theory (SF-TDDFT), to include a DFT exchange-correlation correction. The performance of this method, which we call SA-SF-DFT, is evaluated numerically and we find that it systematically improves the energies of electronic states that exhibit significant spin contamination within the conventional SF-TDDFT approach. The new method cures the state assignment problem that plagues geometry optimizations and ab initio molecular dynamics simulations using traditional SF-TDDFT, without sacrificing computational efficiency, and furthermore provides correct topology at conical intersections, including those that involve the ground state, unlike conventional TDDFT. As such, SA-SF-DFT appears to be a promising method for generating excited-state potential energy surfaces at DFT cost.

  7. Spin-flip processes and radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers

    Science.gov (United States)

    Slobodeniuk, A. O.; Basko, D. M.

    2016-09-01

    We perform a theoretical study of radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers. This decay necessarily involves an electronic spin flip. The intrinsic decay mechanism due to interband spin-flip dipole moment perpendicular to the monolayer plane, gives a rate about 100-1000 times smaller than that of bright excitons. However, we find that this mechanism also introduces an energy splitting due to a local field effect, and the whole oscillator strength is contained in the higher-energy component, while the lowest-energy state remains dark and needs an extrinsic spin-flip mechanism for the decay. Rashba effect due to a perpendicular electric field or a dielectric substrate, gives a negligible radiative decay rate (about 107 times slower than that of bright excitons). Spin flip due to Zeeman effect in a sufficiently strong in-plane magnetic field can give a decay rate comparable to that due to the intrinsic interband spin-flip dipole.

  8. Spin flips in generic black hole binaries

    CERN Document Server

    Lousto, Carlos O

    2015-01-01

    We study the spin dynamics of individual black holes in a binary system. In particular we focus on the polar precession of spins and the possibility of a complete flip of spins with respect to the orbital plane. We perform a full numerical simulation that displays these characteristics. We evolve equal mass binary spinning black holes for $t=20,000M$ from an initial proper separation of $d=25M$ down to merger after 48.5 orbits. We compute the gravitational radiation from this system and compare it to 3.5 post-Newtonian generated waveforms finding close agreement. We then further use 3.5 post-Newtonian evolutions to show the extension of this spin {flip-flop} phenomenon to unequal mass binaries. We also provide analytic expressions to approximate the maximum {flip-flop} angle and frequency in terms of the binary spins and mass ratio parameters at a given orbital radius. Finally we discuss the effect this spin {flip-flop} would have on accreting matter and other potential observational effects.

  9. Polarizing a stored proton beam by spin flip?

    CERN Document Server

    Oellers, D; Barsov, S; Bechstedt, U; Benati, P; Bertelli, S; Chiladze, D; Ciullo, G; Contalbrigo, M; Dalpiaz, P F; Dietrich, J; Dolfus, N; Dymov, S; Engels, R; Erven, W; Garishvili, A; Gebel, R; Goslawski, P; Grigoryev, K; Hadamek, H; Kacharava, A; Khoukaz, A; Kulikov, A; Langenberg, G; Lehrach, A; Lenisa, P; Lomidze, N; Lorentz, B; Macharashvili, G; Maier, R; Martin, S; Merzliakov, S; Meshkov, I N; Meyer, H O; Mielke, M; Mikirtychiants, M; Mikirtychiants, S; Nass, A; Nekipelov, M; Nikolaev, N N; Nioradze, M; d'Orsaneo, G; Papenbrock, M; Prasuhn, D; Rathmann, F; Sarkadi, J; Schleichert, R; Smirnov, A; Seyfarth, H; Sowinski, J; Spoelgen, D; Stancari, G; Stancari, M; Statera, M; Steffens, E; Stein, H J; Stockhorst, H; Straatmann, H; Ströher, H; Tabidze, M; Tagliente, G; Engblom, P Thoerngren; Trusov, S; Vasilyev, A; Weidemann, Chr; Welsch, D; Wieder, P; Wüstner, P; Zupranski, P

    2009-01-01

    We discuss polarizing a proton beam in a storage ring, either by selective removal or by spin flip of the stored ions. Prompted by recent, conflicting calculations, we have carried out a measurement of the spin flip cross section in low-energy electron-proton scattering. The experiment uses the cooling electron beam at COSY as an electron target. The measured cross sections are too small for making spin flip a viable tool in polarizing a stored beam. This invalidates a recent proposal to use co-moving polarized positrons to polarize a stored antiproton beam.

  10. Spin-flip noise in a multiterminal spin valve

    OpenAIRE

    Belzig, Wolfgang; Zareyan, Malek

    2004-01-01

    We study shot noise and cross-correlations in a four terminal spin-valve geometry using a Boltzmann-Langevin approach. The Fano factor (shot noise to current ratio) depends on the magnetic configuration of the leads and the spin-flip processes in the normal metal. In a four-terminal geometry, spin-flip processes are particularly prominent in the cross-correlations between terminals with opposite magnetization.

  11. Antidamping spin-orbit torque driven by spin-flip reflection mechanism on the surface of a topological insulator: A time-dependent nonequilibrium Green function approach

    Science.gov (United States)

    Mahfouzi, Farzad; Nikolić, Branislav K.; Kioussis, Nicholas

    2016-03-01

    Motivated by recent experiments observing spin-orbit torque (SOT) acting on the magnetization m ⃗ of a ferromagnetic (F) overlayer on the surface of a three-dimensional topological insulator (TI), we investigate the origin of the SOT and the magnetization dynamics in such systems. We predict that lateral F/TI bilayers of finite length, sandwiched between two normal metal leads, will generate a large anti-damping-like SOT per very low charge current injected parallel to the interface. The large values of anti-damping-like SOT are spatially localized around the transverse edges of the F overlayer. Our analysis is based on adiabatic expansion (to first order in ∂ m ⃗/∂ t ) of time-dependent nonequilibrium Green functions (NEGFs), describing electrons pushed out of equilibrium both by the applied bias voltage and by the slow variation of a classical degree of freedom [such as m ⃗(t ) ]. From it we extract formulas for spin torque and charge pumping, which show that they are reciprocal effects to each other, as well as Gilbert damping in the presence of SO coupling. The NEGF-based formula for SOT naturally splits into four components, determined by their behavior (even or odd) under the time and bias voltage reversal. Their complex angular dependence is delineated and employed within Landau-Lifshitz-Gilbert simulations of magnetization dynamics in order to demonstrate capability of the predicted SOT to efficiently switch m ⃗ of a perpendicularly magnetized F overlayer.

  12. Spin flip of multiqubit states in discrete phase space

    Science.gov (United States)

    Srinivasan, K.; Raghavan, G.

    2017-02-01

    Time reversal and spin flip are discrete symmetry operations of substantial importance to quantum information and quantum computation. Spin flip arises in the context of separability, quantification of entanglement and the construction of universal NOT gates. The present work investigates the relationship between the quantum state of a multiqubit system represented by the discrete Wigner function (DWFs) and its spin-flipped counterpart. The two are shown to be related through a Hadamard matrix that is independent of the choice of the quantum net used for the tomographic reconstruction of the DWF. These results are of interest to cases involving the direct tomographic reconstruction of the DWF from experimental data, and in the analysis of entanglement related properties purely in terms of the DWF.

  13. Polarizing a stored proton beam by spin-flip?

    Energy Technology Data Exchange (ETDEWEB)

    Oellers, Dieter Gerd Christian

    2010-04-15

    The present thesis discusses the extraction of the electron-proton spin-flip cross-section. The experimental setup, the data analysis and the results are pictured in detail. The proton is described by a QCD-based parton model. In leading twist three functions are needed. The quark distribution, the helicity distribution and the transversity distribution. While the first two are well-known, the transversity distribution is largely unknown. A self-sufficient measurement of the transversity is possible in double polarized proton-antiproton scattering. This rises the need of a polarized antiproton beam. So far spin filtering is the only tested method to produce a polarized proton beam, which may be capable to hold also for antiprotons. In-situ polarization build-up of a stored beam either by selective removal or by spin-flip of a spin-(1)/(2) beam is mathematically described. A high spin-flip cross-section would create an effective method to produce a polarized antiproton beam by polarized positrons. Prompted by conflicting calculations, a measurement of the spin-flip cross-section in low-energy electron-proton scattering was carried out. This experiment uses the electron beam of the electron cooler at COSY as an electron target. The depolarization of the stored proton beam is detected. An overview of the experiment is followed by detailed descriptions of the cycle setup, of the electron target and the ANKE silicon tracking telescopes acting as a beam polarimeter. Elastic protondeuteron scattering is the analyzing reaction. The event selection is depicted and the beam polarization is calculated. Upper limits of the two electron-proton spin-flip cross-sections {sigma} {sub parallel} and {sigma} {sub perpendicular} {sub to} are deduced using the likelihood method. (orig.)

  14. Neutron spin-flip scattering of nanocrystalline cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Honecker, D; Doebrich, F; Michels, A [Laboratory for the Physics of Advanced Materials, University of Luxembourg, 162A Avenue de la Faiencerie, L-1511 Luxembourg (Luxembourg); Dewhurst, C D; Wiedenmann, A, E-mail: andreas.michels@uni.l [Institut Laue-Langevin, 6 Rue Jules Horowitz, BP 156, F-38042 Grenoble Cedex 9 (France)

    2011-01-12

    We report results of longitudinal (one-dimensional) neutron polarization analysis on polycrystalline bulk Co with an average crystallite size of D = 10 nm. The spin-flip small-angle neutron scattering (SANS) data are analyzed in the approach-to-saturation regime within the framework of micromagnetic theory. In particular, we provide a closed-form expression for the spin-flip SANS cross section d{Sigma}{sup {+-}-+}/d{Omega}. From the data analysis, we find a room-temperature value of A = (2.6 {+-} 0.1) x 10{sup -11} J m{sup -1} for the exchange-stiffness constant, which agrees well with earlier data.

  15. Spin flips and quantum information for anti-parallel spins

    CERN Document Server

    Gisin, Nicolas

    1999-01-01

    We consider two different ways to encode quantum information, by parallel or anti-parallel pairs of spins. We find that there is more information in the anti-parallel ones. This purely quantum mechanical effect is due to entanglement, not of the states but occuring in the course of the measuring process. We also introduce a range of quantum information processing machines, such as spin-flip and anti-cloning.

  16. Supermassive black hole spin-flip during the inspiral

    Energy Technology Data Exchange (ETDEWEB)

    Gergely, Laszlo A [Department of Theoretical Physics, University of Szeged (Hungary); Biermann, Peter L [MPI for Radioastronomy, Bonn (Germany); Caramete, Laurentiu I, E-mail: gergely@physx.u-szeged.h, E-mail: plbiermann@mpifr-bonn.mpg.d, E-mail: lcaramete@gmail.co [Institute for Space Sciences, Bucharest (Romania)

    2010-10-07

    During post-Newtonian evolution of a compact binary, a mass ratio {nu} different from 1 provides a second small parameter, which can lead to unexpected results. We present a statistics of supermassive black hole candidates, which enables us first to derive their mass distribution, and then to establish a logarithmically even probability in {nu} of the mass ratios at their encounter. In the mass ratio range {nu} in (1/30, 1/3) of supermassive black hole mergers representing 40% of all possible cases, the combined effect of spin-orbit precession and gravitational radiation leads to a spin-flip of the dominant spin during the inspiral phase of the merger. This provides a mechanism for explaining a large set of observations on X-shaped radio galaxies. In another 40% with mass ratios {nu} in (1/30, 1/1000) a spin-flip never occurs, while in the remaining 20% of mergers with mass ratios {nu} in (1/3, 1) it may occur during the plunge. We analyze the magnitude of the spin-flip angle occurring during the inspiral as a function of the mass ratio and original relative orientation of the spin and orbital angular momentum. We also derive a formula for the final spin at the end of the inspiral in this mass ratio range.

  17. Supermassive black hole spin-flip during the inspiral

    CERN Document Server

    Gergely, László Á; Caramete, Laurenţiu I

    2010-01-01

    During post-Newtonian evolution of a compact binary, a mass ratio different from one provides a second small parameter, which can lead to unexpected results. We present a statistics of supermassive black hole candidates, which enables us first to derive their mass distribution, then to establish a logarithmically even probability of the mass ratios at their encounter. In the mass ratio range (1/30,1/3) of supermassive black hole mergers representing 40% of all possible cases, the combined effect of spin-orbit precession and gravitational radiation leads to a spin-flip of the dominant spin during the inspiral phase of the merger. This provides a mechanism for explaining a large set of observations on X-shaped radio galaxies. In another 40%, with mass ratios (1/30,1/1000) a spin-flip never happens, while in the remaining 20% of mergers with mass ratios (1/3,1) it may occur during the plunge. We analyze the magnitude of the spin-flip angle occurring during the inspiral as function of the mass ratio and original ...

  18. The role of spin-flipping terms in hadronic transitions of $\\Upsilon(4S)$

    CERN Document Server

    Segovia, Jorge; Entem, David R

    2015-01-01

    Recent experimental data on the $\\Upsilon(4S)\\to\\Upsilon(1S)\\eta$ and $\\Upsilon(4S)\\to h_{b}(1P)\\eta$ processes seem to contradict the naive expectation that hadronic transitions with spin-flipping terms should be suppressed with respect those without spin-flip. We analyze these transitions using the QCD Multipole Expansion (QCDME) approach and within a constituent quark model framework that has been applied successfully to the heavy-quark sectors during the last years. The QCDME formalism requires the computation of hybrid intermediate states which has been performed in a natural, parameter-free extension of our constituent quark model based on the Quark Confining String (QCS) scheme. We show that i) the M1-M1 contribution in the decay rate of the $\\Upsilon(4S)\\to\\Upsilon(1S)\\eta$ is important and its supression until now is not justified; ii) the role played by the $L=0$ hybrid states, which enter in the calculation of the M1-M1 contribution, explains the enhancement in the $\\Upsilon(4S)\\to\\Upsilon(1S)\\eta$...

  19. Spin flipping in ring-coupled-cluster-doubles theory

    DEFF Research Database (Denmark)

    Klopper, Wim; M. Teale, Andrew; Coriani, Sonia

    2011-01-01

    We report a critical analysis and comparison of a variety of random-phase-approximation (RPA) based approaches to determine the electronic ground-state energy. Interrelations between RPA variants are examined by numerical examples with particular attention paid to the role of spin-flipped excitat......We report a critical analysis and comparison of a variety of random-phase-approximation (RPA) based approaches to determine the electronic ground-state energy. Interrelations between RPA variants are examined by numerical examples with particular attention paid to the role of spin...

  20. Spin-polarized free electron beam interaction with radiation and superradiant spin-flip radiative emission

    Directory of Open Access Journals (Sweden)

    A. Gover

    2006-06-01

    Full Text Available The problems of spin-polarized free-electron beam interaction with electromagnetic wave at electron-spin resonance conditions in a magnetic field and of superradiant spin-flip radiative emission are analyzed in the framework of a comprehensive classical model. The spontaneous emission of spin-flip radiation from electron beams is very weak. We show that the detectivity of electron spin resonant spin-flip and combined spin-flip/cyclotron-resonance-emission radiation can be substantially enhanced by operating with ultrashort spin-polarized electron beam bunches under conditions of superradiant (coherent emission. The proposed radiative spin-state modulation and the spin-flip radiative emission schemes can be used for control and noninvasive diagnostics of polarized electron/positron beams. Such schemes are of relevance in important scattering experiments off nucleons in nuclear physics and off magnetic targets in condensed matter physics.

  1. Superfluidity enhanced by spin-flip tunnelling in the presence of a magnetic field

    Science.gov (United States)

    Zheng, Jun-Hui; Wang, Daw-Wei; Juzeliūnas, Gediminas

    2016-01-01

    It is well-known that when the magnetic field is stronger than a critical value, the spin imbalance can break the Cooper pairs of electrons and hence hinder the superconductivity in a spin-singlet channel. In a bilayer system of ultra-cold Fermi gases, however, we demonstrate that the critical value of the magnetic field at zero temperature can be significantly increased by including a spin-flip tunnelling, which opens a gap in the spin-triplet channel near the Fermi surface and hence reduces the influence of the effective magnetic field on the superfluidity. The phase transition also changes from first order to second order when the tunnelling exceeds a critical value. Considering a realistic experiment, this mechanism can be implemented by applying an intralayer Raman coupling between the spin states with a phase difference between the two layers. PMID:27633848

  2. From spin flip excitations to the spin susceptibility enhancement of a two-dimensional electron gas.

    Science.gov (United States)

    Perez, F; Aku-leh, C; Richards, D; Jusserand, B; Smith, L C; Wolverson, D; Karczewski, G

    2007-07-13

    The g-factor enhancement of the spin-polarized two-dimensional electron gas was measured directly over a wide range of spin polarizations, using spin flip resonant Raman scattering spectroscopy on two-dimensional electron gases embedded in Cd(1-x)Mn(x)Te semimagnetic quantum wells. At zero Raman transferred momentum, the single-particle spin flip excitation, energy Z*, coexists in the Raman spectrum with the spin flip wave of energy Z, the bare giant Zeeman splitting. We compare the measured g-factor enhancement with recent spin-susceptibility enhancement theories and deduce the spin-polarization dependence of the mass renormalization.

  3. Spin flipping a stored vertically polarized proton beam with an RF solenoid

    Science.gov (United States)

    Phelps, R. A.; Blinov, B. B.; Chu, C. M.; Courant, E. D.; Crandell, D. A.; Kaufman, W. A.; Krisch, A. D.; Nurushev, T. S.; Ratner, L. G.; Wong, V. K.; Caussyn, D. D.; Derbenev, Ya. S.; Ellison, T. J. P.; Lee, S. Y.; Rinckel, T.; Schwandt, P.; Sperisen, F.; Stephenson, E. J.; Przewoski, B. von; Ohmori, C.

    1995-09-01

    A recent experiment in the IUCF cooler ring studied the spin flip of a stored vertically polarized 139 MeV proton beam. This spin flip was accomplished by using an RF solenoid to induce an artificial depolarizing resonance in the ring, and then varying the solenoid's frequency through this resonance value to induce spin flip. We found a polarization loss after multiple spin flips of about 0.00±0.05% per flip and also losses for very long flip times. This device will be useful for reducing systematic errors in polarized beam-internal target scattering asymmetry experiments by enabling experimenters to perform frequent beam polarization reversals in the course of the experiment.

  4. Analysis of spin flip data in rings with nearly full Siberian Snakes

    Energy Technology Data Exchange (ETDEWEB)

    Mane, S.R. [Convergent Computing Inc., P.O. Box 561, Shoreham, NY 11786 (United States)], E-mail: srmane@optonline.net

    2009-04-01

    I calculate theoretical values to fit experimental measurements of spin flip resonance widths in rings with nearly full strength Siberian Snakes. Some measurements were made using an rf solenoid, and others using vertical field rf dipoles. In particular, the staff of the MIT-Bates Linear Accelerator Laboratory kindly made available to me additional unpublished data for the spin flipping of stored polarized electrons at 850 MeV using a vertical field rf dipole spin flipper.

  5. Spin-Flip Process through Double Quantum Dots Coupled to Ferromagnetic Leads

    Institute of Scientific and Technical Information of China (English)

    YAN Cong-Hua; WU Shao-Quan; HUANG Rui; SUN Wei-Li

    2006-01-01

    @@ We investigate the spin-flip process through double quantum dots coupled to two ferromagnetic leads in series.By means of the slave-boson mean-field approximation, we calculate the density of states in the Kondo regime for two different configurations of the leads. It is found that transport shows some remarkable properties depending on the spin-flip strength. These effects may be useful in exploiting the role of electronic correlation in spintronics.

  6. Spin-flip Raman scattering in low-dimensional semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Debus, Joerg

    2012-07-01

    The challenges for achieving novel spin effects or improving existent spin phenomena are based on interaction, namely interactions between carriers themselves as well as a carrier and a second system, such as the nuclear spin or phonon system leading to a scattering process and thus to spin decoherence. By means of the resonant spin-flip Raman scattering technique fundamental spin interactions of carriers confined in low-dimensional semiconductors, their dependence on the local structure symmetry as well as the type and excitation state of the carrier complex are characterized. It is shown that the scattering processes of the electron, hole, and exciton spins depend on the symmetry of the crystal lattice, quantum confinement potential, and magnetic field confinement. The studies outline problems of the semiconductor spintronics, but also ways to identify and monitor them, and present a novel quantum dot structure providing a long exciton lifetime and temperature-robust longitudinal spin relaxation time thus making a step toward the realization of spin-based applications.

  7. The spin-flip extended single excitation configuration interaction method

    Science.gov (United States)

    Casanova, David; Head-Gordon, Martin

    2008-08-01

    An extension of the spin-flip single excitation configuration interaction (SF-CIS) method is introduced. The extension, abbreviated as SF-XCIS, includes all configurations in which no more than one virtual level of the high spin triplet reference becomes occupied and no more than one doubly occupied level becomes vacant. The number of such configurations is quadratic with molecule size, and the method is implemented in a direct algorithm whose cost scales in the same way with molecule size as CIS itself, thus permitting applications to large systems. Starting from a spin restricted triplet determinant, SF-XCIS yields spin-pure singlet, triplet, and quintet states, and treats both half-occupied reference orbitals in a fully balanced way to allow application to strongly correlated problems. Tests on bond dissociation in the HF molecule, the torsional potential of ethylene, and excited states of polyenes show encouraging improvements using SF-XCIS compared to SF-CIS and a previously suggested extension, the spin-complete CIS model.

  8. Spin transport and spin-flip scattering in magnetic multilayer structures

    Science.gov (United States)

    Garzon, Samir

    2006-03-01

    The existence of spin-flip scattering at the interface between ferromagnetic (F) and nonmagnetic (N) layers of magnetoresistive F/N/F structures can significantly reduce the size of the magnetoresistance, limiting the sensitivity and increasing the power consumption of F/N/F devices such as GMR magnetic field sensors, magnetic read heads, and MRAM's [1]. Detecting and measuring the degree of spin flip scattering in F/N/F structures can allow further optimization in such devices as well as increase the understanding of interfacial spin transport. Our nonlocal spin injection and detection experiments on mesoscopic Co-Al2O3-Cu-Al2O3-Co spin valves provide evidence for the existence of interfacial spin-flip scattering in magnetoresistive devices [2]. By extending the conventional picture of spin-dependent interfacial resistances (R, R) to include two additional spin-flip scattering channels (R,R) [3] we have shown that the nonlocal resistance contains information about both the degree of spin polarization and the degree of spin-flip scattering at the F/N interface. The magnitudes of R and R depend on the relative orientation of the detector magnetization and the nonequilibrium magnetization in the normal metal. We have observed that the difference in spin-flip scattering between up and down channels vanishes at low temperatures, but for T>100K it increases nonlinearly with temperature. Further evidence for the presence of interfacial spin-flip scattering can be obtained from noise measurements, which are extremely sensitive to the microscopic transport details. [1] Spin Dependent Transport in Magnetic Nanostructures, edited by S. Maekawa and T. Shinjo (Taylor & Francis, New York, 2002). [2] S. Garzon, I. Zuti'c, and R. A. Webb, Phys. Rev. Lett. 94, 176601 (2005). [3] E. I. Rashba, Eur. Phys. J. B 29, 513 (2002).

  9. Analytic derivative couplings for spin-flip configuration interaction singles and spin-flip time-dependent density functional theory.

    Science.gov (United States)

    Zhang, Xing; Herbert, John M

    2014-08-14

    We revisit the calculation of analytic derivative couplings for configuration interaction singles (CIS), and derive and implement these couplings for its spin-flip variant for the first time. Our algorithm is closely related to the CIS analytic energy gradient algorithm and should be straightforward to implement in any quantum chemistry code that has CIS analytic energy gradients. The additional cost of evaluating the derivative couplings is small in comparison to the cost of evaluating the gradients for the two electronic states in question. Incorporation of an exchange-correlation term provides an ad hoc extension of this formalism to time-dependent density functional theory within the Tamm-Dancoff approximation, without the need to invoke quadratic response theory or evaluate third derivatives of the exchange-correlation functional. Application to several different conical intersections in ethylene demonstrates that minimum-energy crossing points along conical seams can be located at substantially reduced cost when analytic derivative couplings are employed, as compared to use of a branching-plane updating algorithm that does not require these couplings. Application to H3 near its D(3h) geometry demonstrates that correct topology is obtained in the vicinity of a conical intersection involving a degenerate ground state.

  10. Magnetic soft mode behaviour investigated via multi-spin flip Raman spectroscopy on near surface Cd{sub 1-x}Mn{sub x}Te/Cd{sub 1-y}Mg{sub y}Te quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Kehl, Christian

    2011-03-28

    The main motivation for this thesis was the experimental confirmation of the theoretically predicted magnetic soft mode and the analysis of its dependence on the hole-concentration and external B-field, as well as its disappearance with increasing sample temperature. For that purpose, CdMnTe/CdMgTe QWs (Mn: 0.6%, 1.0%) positioned close to the sample surface (13-19 nm) were investigated in an in-plane applied external magnetic field (up to 4.5 T in Voigt-geometry) via a two-colour experiment i.e. using two light sources. This allows the spin excitation of Mn-ions by simultaneously tuning the hole-concentration towards the ferromagnetic phase transition by photo-generated carriers. Thus, one tuneable laser is responsible for resonant below-barrier excitation as a probe for Multi-SF Raman scattering. The other laser excites photo-generated carriers from above barrier (2.41 eV) for tuning the hole concentration in the QW. Positioning the QW close to the sample surface causes a surface-induced p-doping of the QW (intrinsic hole concentration in the QW) and enables the active tuning of the hole concentration by photo-generated carriers due to different tunnelling behaviour of electrons and holes from the QW to the surface. The Mn-g-factor was decreased by quasi-continuously increasing the above-barrier illumination, while the below-barrier excitation was kept at a constant low power. This results in a Mn-g-factor reduction starting from its atomic value g=2.01 to lowest evaluated Mn-g-factor in this thesis g=1.77. This is a magnetic softening of 12%. Apart from the general magnetic soft mode behaviour at low temperatures, one of the main experimental results in this thesis is the confirmation of the theoretical prediction that the magnetic soft mode behaviour in the external B-field does not only depend on the carrier concentration but also on the B-field strength itself. An additional aspect is the temperature dependence of the magnetic soft mode. The Mn

  11. Large deviation principle for one-dimensional random walk in dynamic random environment: attractive spin-flips and simple symmetric exclusion

    CERN Document Server

    Avena, L; Redig, F

    2009-01-01

    Consider a one-dimensional shift-invariant attractive spin-flip system in equilibrium, constituting a dynamic random environment, together with a nearest-neighbor random walk that on occupied sites has a local drift to the right but on vacant sites has a local drift to the left. In previous work we proved a law of large numbers for dynamic random environments satisfying a space-time mixing property called cone-mixing. If an attractive spin-flip system has a finite average coupling time at the origin for two copies starting from the all-occupied and the all-vacant configuration, respectively, then it is cone-mixing. In the present paper we prove a large deviation principle for the empirical speed of the random walk, both quenched and annealed, and exhibit some properties of the associated rate functions. Under an exponential space-time mixing condition for the spin-flip system, which is stronger than cone-mixing, the two rate functions have a unique zero, i.e., the slow-down phenomenon known to be possible in ...

  12. Spin wave and spin flip in hexagonal LuMnO3 single crystal

    Science.gov (United States)

    Chen, Xiang-Bai; Guo, Peng-Cheng; Huyen, Nguyen Thi; Kim, Seung; Yang, In-Sang; Wang, Xueyun; Cheong, Sang-Wook

    2017-03-01

    Manipulation and control of spin wave and spin flip are crucial for future developments of magnonic and spintronic devices. We present that the spin wave in hexagonal LuMnO3 single crystal can be selectively excited with laser polarization perpendicular to the c-axis of hexagonal LuMnO3 and photon energy ˜1.8 eV. The selective excitation of spin wave also suggests that the spin flip can be selectively controlled in hexagonal manganites. In addition, a microscopic model of the spin wave generation correlated with the four-spin-flip in hexagonal manganites is suggested to account for the line-shape of the observed spin wave.

  13. Spin-flip reflection at the normal metal-spin superconductor interface

    Science.gov (United States)

    Lv, Peng; Guo, Ai-Min; Li, Huaiyu; Liu, Chunxiao; Xie, X. C.; Sun, Qing-Feng

    2017-03-01

    We study spin transport through a normal metal-spin superconductor junction. A spin-flip reflection is demonstrated at the interface, where a spin-up electron incident from the normal metal can be reflected as a spin-down electron and the spin 2 ×ℏ /2 will be injected into the spin superconductor. When the (spin) voltage is smaller than the gap of the spin superconductor, the spin-flip reflection determines the transport properties of the junction. We consider both graphene-based (linear-dispersion-relation) and quadratic-dispersion-relation normal metal-spin superconductor junctions in detail. For the two-dimensional graphene-based junction, the spin-flip reflected electron can be along the specular direction (retro-direction) when the incident and reflected electron locates in the same band (different bands). A perfect spin-flip reflection can occur when the incident electron is normal to the interface, and the reflection coefficient is slightly suppressed for the oblique incident case. As a comparison, for the one-dimensional quadratic-dispersion-relation junction, the spin-flip reflection coefficient can reach 1 at certain incident energies. In addition, both the charge current and the spin current under a charge (spin) voltage are studied. The spin conductance is proportional to the spin-flip reflection coefficient when the spin voltage is less than the gap of the spin superconductor. These results will help us get a better understanding of spin transport through the normal metal-spin superconductor junction.

  14. Spin-flip process through double quantum dots coupled to two half-metallic ferromagnetic leads

    Institute of Scientific and Technical Information of China (English)

    Yan Cong-Hua; Wu Shao-Quan; Huang Rui; Sun Wei-Li

    2008-01-01

    We investigate the spin-flip process through double quantum dots coupled to two half-metallic ferromagnetic leads in series.By means of the slave-boson mean-field approximation,we calculate the density of states in the Kondo regime for two different configurations of the leads.It is found that the transport shows some remarkable properties depending on the spin-flip strength.These effects may be useful in exploiting the role of electronic correlation in spintronics.

  15. Deuteron spin-flip resonance widths and the spin response function

    Directory of Open Access Journals (Sweden)

    S. R. Mane

    2007-11-01

    Full Text Available The spin response function is used to analyze the spin-flip resonance widths of stored polarized deuteron beams. It is found, using simple model assumptions, that the contribution of the vertical betatron oscillations (for an rf radial dipole field spin-flipper reduces the resonance width by an amount in good agreement with recent measurements. It is also noted that, for spin-flip measurements with an rf-solenoid spin flipper, the spin response formalism also yields an answer consistent with experimental data.

  16. Rf Depolarizing Resonances In The Presence Of A Full Siberian Snake And Full Snake Spin-flipping

    CERN Document Server

    Blinov, B B

    2000-01-01

    Frequent polarization reversals, or spin-flips, of a stored polarized beam in high energy scattering asymmetry experiments may greatly reduce systematic errors of spin asymmetry measurements. A spin-flipping technique is being developed by using rf magnets running at a frequency close to the spin precession frequency, thereby creating spin-depolarizing resonances; the spin can then be flipped by ramping the rf magnet's frequency through the resonance. We studied, at the Indiana University Cyclotron Facility Cooler Ring, properties of such rf depolarizing resonances in the presence of a nearly-full Siberian snake and their possible application for spin- flipping. By using an rf-solenoid magnet, we reached a 98.7 ± 1% efficiency of spin-flipping. However, an rf-dipole magnet is more practical at high energies; hence, studies of spin-flipping by an rf-dipole are underway at IUCF.

  17. Spin Flips - II. Evolution of dark matter halo spin orientation, and its correlation with major mergers

    CERN Document Server

    Bett, Philip E

    2015-01-01

    We expand our previous study on the relationship between changes in the orientation of the angular momentum vector of dark matter haloes ("spin flips") and changes in their mass (Bett & Frenk 2012), to cover the full range of halo masses in a simulation cube of length 100 $h^{-1}$ Mpc. Since strong disturbances to a halo (such as might be indicated by a large change in the spin direction) are likely also to disturb the galaxy evolving within, spin flips could be a mechanism for galaxy morphological transformation without involving major mergers. We find that 35% of haloes have, at some point in their lifetimes, had a spin flip of at least $45\\deg$ that does not coincide with a major merger. Over 75% of large spin flips coincide with non-major mergers; only a quarter coincide with major mergers. We find a similar picture for changes to the inner-halo spin orientation, although here there is an increased likelihood of a flip occurring. Changes in halo angular momentum orientation, and other such measures of...

  18. Spin flip by RF-field at storage rings with siberian snakes

    Energy Technology Data Exchange (ETDEWEB)

    Koop, I.; Shatunov, Y. [Budker Institute for Nuclear Physics, Novosibirsk, 630090 (Russia)

    1995-09-01

    The beam dynamics and optics of spin flipping polarized beams with an RF field in storage rings with Siberian Snakes is discussed. The dispersion relations are determined and depolarization of the beams are discussed. (AIP) {copyright} {ital 1995 American Institute of Physics.}

  19. Double-spin-flip resonance of rhodium nuclei at positive and negative spin temperatures

    DEFF Research Database (Denmark)

    Tuoriniemi, J.T.; Knuuttila, T.A.; Lefmann, K.

    2000-01-01

    Sensitive SQUID-NMR measurements were used to study the mutual interactions in the highly polarized nuclear-spin system of rhodium metal. The dipolar coupling gives rise to a weak double-spin-flip resonance. The observed frequency shifts allow deducing separately the dipolarlike contribution...

  20. Computational quantum chemistry for single Heisenberg spin couplings made simple: just one spin flip required.

    Science.gov (United States)

    Mayhall, Nicholas J; Head-Gordon, Martin

    2014-10-07

    We highlight a simple strategy for computing the magnetic coupling constants, J, for a complex containing two multiradical centers. On the assumption that the system follows Heisenberg Hamiltonian physics, J is obtained from a spin-flip electronic structure calculation where only a single electron is excited (and spin-flipped), from the single reference with maximum Ŝz, M, to the M - 1 manifold, regardless of the number of unpaired electrons, 2M, on the radical centers. In an active space picture involving 2M orbitals, only one β electron is required, together with only one α hole. While this observation is extremely simple, the reduction in the number of essential configurations from exponential in M to only linear provides dramatic computational benefits. This (M, M - 1) strategy for evaluating J is an unambiguous, spin-pure, wave function theory counterpart of the various projected broken symmetry density functional theory schemes, and likewise gives explicit energies for each possible spin-state that enable evaluation of properties. The approach is illustrated on five complexes with varying numbers of unpaired electrons, for which one spin-flip calculations are used to compute J. Some implications for further development of spin-flip methods are discussed.

  1. Computational quantum chemistry for single Heisenberg spin couplings made simple: Just one spin flip required

    Energy Technology Data Exchange (ETDEWEB)

    Mayhall, Nicholas J.; Head-Gordon, Martin, E-mail: mhg@cchem.berkeley.edu [Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2014-10-07

    We highlight a simple strategy for computing the magnetic coupling constants, J, for a complex containing two multiradical centers. On the assumption that the system follows Heisenberg Hamiltonian physics, J is obtained from a spin-flip electronic structure calculation where only a single electron is excited (and spin-flipped), from the single reference with maximum S{sup ^}{sub z}, M, to the M − 1 manifold, regardless of the number of unpaired electrons, 2M, on the radical centers. In an active space picture involving 2M orbitals, only one β electron is required, together with only one α hole. While this observation is extremely simple, the reduction in the number of essential configurations from exponential in M to only linear provides dramatic computational benefits. This (M, M − 1) strategy for evaluating J is an unambiguous, spin-pure, wave function theory counterpart of the various projected broken symmetry density functional theory schemes, and likewise gives explicit energies for each possible spin-state that enable evaluation of properties. The approach is illustrated on five complexes with varying numbers of unpaired electrons, for which one spin-flip calculations are used to compute J. Some implications for further development of spin-flip methods are discussed.

  2. Spin-flip-Raman studies of semimagnetic II-VI heterostructures; Spin-flip-Raman-Untersuchungen an semimagnetischen II-VI-Halbleiter-Quantentroegen und Volumenproben

    Energy Technology Data Exchange (ETDEWEB)

    Lentze, Michael

    2009-03-18

    In the present doctoral thesis, spin flip Raman studies of semimagnetic (Zn,Mn)Se samples were in the focus of interest. Quantum wells as well as bulk-like materials were investigated. The main goal was a better understanding of the exchange interaction behaviour of heavily n-doped semimagnetic samples. The influence of doping on the exchange interaction is of special relevance with regard to spintronics applications. Several series of high quality MBE-grown (Zn,Mn)Se-samples samples were available. (orig.)

  3. Spin flip loss in magnetic confinement of ultracold neutrons for neutron lifetime experiments

    CERN Document Server

    Steyerl, A; Kaufman, C; Müller, G; Malik, S S

    2016-01-01

    We analyze the spin flip loss for ultracold neutrons in magnetic bottles of the type used in experiments aiming at a precise measurement of the neutron lifetime, extending the one-dimensional field model used previously by Steyerl $\\textit{et al.}$ [Phys.Rev.C $\\mathbf{86}$, 065501 (2012)] to two dimensions for cylindrical multipole fields. We also develop a general analysis applicable to three dimensions. Here we apply it to multipole fields and to the bowl-type field configuration used for the Los Alamos UCN$\\tau$ experiment. In all cases considered the spin flip loss calculated exceeds the Majorana estimate by many orders of magnitude but can be suppressed sufficiently by applying a holding field of appropriate magnitude to allow high-precision neutron lifetime measurements, provided other possible sources of systematic error are under control.

  4. Spin-Flip of Polaron in Polymers with a Magnetic Impurity

    Institute of Scientific and Technical Information of China (English)

    CHEN Mei-Juan; YAN Yong-Hong; WU Chang-Qin

    2007-01-01

    Using a nonadiabatic evolution method, we investigate the spin-nip process ofpolaron in polymers with a magnetic impurity. Our results show that when the spin orientation of this impurity is fixed to be perpendicular to the spin ofpolaron (θ=π/2), the magnetic impurity causes a spin-flip process. The probability of the spin-Sip increases with the increase of exchange integral J up to about 0.35 eV and then decreases with the increase of J. In the case J is fixed while the spin orientation is adjustable, we find the probability of the spin-flip varies with the impurity orientation and reaches a maximum value at θ=π/2.

  5. Spin Flips versus Spin Transport in Nonthermal Electrons Excited by Ultrashort Optical Pulses in Transition Metals

    Science.gov (United States)

    Shokeen, V.; Sanchez Piaia, M.; Bigot, J.-Y.; Müller, T.; Elliott, P.; Dewhurst, J. K.; Sharma, S.; Gross, E. K. U.

    2017-09-01

    A joint theoretical and experimental investigation is performed to understand the underlying physics of laser-induced demagnetization in Ni and Co films with varying thicknesses excited by 10 fs optical pulses. Experimentally, the dynamics of spins is studied by determining the time-dependent amplitude of the Voigt vector, retrieved from a full set of magnetic and nonmagnetic quantities performed on both sides of films, with absolute time reference. Theoretically, ab initio calculations are performed using time-dependent density functional theory. Overall, we demonstrate that spin-orbit induced spin flips are the most significant contributors with superdiffusive spin transport, which assumes only that the transport of majority spins without spin flips induced by scattering does not apply in Ni. In Co it plays a significant role during the first ˜20 fs only. Our study highlights the material dependent nature of the demagnetization during the process of thermalization of nonequilibrium spins.

  6. Entangling atomic spins with a Rydberg-dressed spin-flip blockade

    Science.gov (United States)

    Jau, Y.-Y.; Hankin, A. M.; Keating, T.; Deutsch, I. H.; Biedermann, G. W.

    2016-01-01

    Controlling the quantum entanglement between parts of a many-body system is key to unlocking the power of quantum technologies such as quantum computation, high-precision sensing, and the simulation of many-body physics. The spin degrees of freedom of ultracold neutral atoms in their ground electronic state provide a natural platform for such applications thanks to their long coherence times and the ability to control them with magneto-optical fields. However, the creation of strong coherent coupling between spins has been challenging. Here we demonstrate a strong and tunable Rydberg-dressed interaction between spins of individually trapped caesium atoms with energy shifts of order 1 MHz in units of Planck’s constant. This interaction leads to a ground-state spin-flip blockade, whereby simultaneous hyperfine spin flips of two atoms are inhibited owing to their mutual interaction. We employ this spin-flip blockade to rapidly produce single-step Bell-state entanglement between two atoms with a fidelity >=81(2)%.

  7. Triggering of spin-flipping-modulated exchange bias in FeCo nanoparticles by electronic excitation

    Science.gov (United States)

    Sarker, Debalaya; Bhattacharya, Saswata; Srivastava, Pankaj; Ghosh, Santanu

    2016-12-01

    The exchange coupling between ferromagnetic (FM)-antiferromagnetic (AF) interfaces is a key element of modern spintronic devices. We here introduce a new way of triggering exchange bias (EB) in swift heavy ion (SHI) irradiated FeCo-SiO2 films, which is a manifestation of spin-flipping at high irradiation fluence. The elongation of FeCo nanoparticles (NPs) in SiO2 matrix gives rise to perpendicular magnetic anisotropy at intermediate fluence. However, a clear shift in hysteresis loop is evident at the highest fluence. This reveals the existence of an AF exchange pinning domain in the NPs, which is identified not to be oxide shell from XANES analysis. Thermal spike calculations along with first-principles based simulations under the framework of density functional theory (DFT) demonstrate that spin flipping of 3d valence electrons is responsible for formation of these AF domains inside the FM NPs. EXAFS experiments at Fe and Co K-edges further unravel that spin-flipping in highest fluence irradiated film results in reduced bond lengths. The results highlight the possibility of miniaturization of magnetic storage devices by using irradiated NPs instead of conventionally used FM-AF multilayers.

  8. Dynamic neutron scattering on incoherent systems using efficient resonance spin flip techniques

    Energy Technology Data Exchange (ETDEWEB)

    Häussler, Wolfgang [Heinz Maier-Leibnitz Zentrum, Technische Universität München, D-85748 Garching, Germany and Physik-Department E21, Technische Universität München, D-85748 Garching (Germany); Kredler, Lukas [Physik-Department E21, Technische Universität München, D-85748 Garching (Germany)

    2014-05-15

    We have performed numerical ray-tracing Monte-Carlo-simulations of incoherent dynamic neutron scattering experiments. We intend to optimize the efficiency of incoherent measurements depending on the fraction of neutrons scattered without and with spin flip at the sample. In addition to conventional spin echo, we have numerically and experimentally studied oscillating intensity techniques. The results point out the advantages of these different spin echo variants and are an important prerequisite for neutron resonance spin echo instruments like RESEDA (FRM II, Munich), to choose the most efficient technique depending on the scattering vector range and the properties of the sample system under study.

  9. Spin-Flip Process of Polarons in Conjugated Polymers with Magnetic Impurities

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hui; ZHANG Xu-Ming; AN Zhong; CHEN Yu-Guang; WU Chang-Qin

    2009-01-01

    Being driven by an external electric field,a polaron carrying both spin 1/2 and charge ±e moves at a constant speed in a polymer chain.When the polaron passes through a specific site,which couples to a magnetic impurity via spin-exchange interactions,its spin undergoes a spin-flip process if it is antiparallel to the impurity spin.Our numerical simulation shows that (a) a swap-like operation is performed between the polaron and impurity during the scattering process (b) polarons might be good candidates to be information carriers in the molecular scale.

  10. Density matrix based time-dependent configuration interaction approach to ultrafast spin-flip dynamics

    CERN Document Server

    Wang, H; Kühn, O

    2016-01-01

    Recent developments in attosecond spectroscopy yield access to the correlated motion of electrons on their intrinsic time scales. Spin-flip dynamics is usually considered in the context of valence electronic states, where spin-orbit coupling is weak and processes related to the electron spin are usually driven by nuclear motion. However, for core-excited states, where the core hole has a nonzero angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a much shorter time scale. Using density matrix based time-dependent restricted active space configuration interaction including spin-orbit coupling, we address an unprecedentedly short spin-crossover for the example of L-edge (2p$\\rightarrow$3d) excited states of a prototypical Fe(II) complex. This process occurs on a time scale, which is faster than that of Auger decay ($\\sim$4\\,fs) treated here explicitly. Modest variations of carrier frequency and pulse duration can lead to substantial changes in the spin-state yield, suggesting its cont...

  11. Spin-flip dynamics of the Curie-Weiss model : Loss of Gibbsianness with possibly broken symmetry

    NARCIS (Netherlands)

    Kulske, Christof; Le Ny, Arnaud

    2007-01-01

    We study the conditional probabilities of the Curie-Weiss Ising model in vanishing external field under a symmetric independent stochastic spin-flip dynamics and discuss their set of points of discontinuity (bad points). We exhibit a complete analysis of the transition between Gibbsian and non-Gibbs

  12. Ultrafast spin-flip dynamics in transition metal complexes triggered by soft X-ray light

    CERN Document Server

    Wang, Huihui; Aziz, Saadullah G; Kühn, O

    2016-01-01

    Recent advances in attosecond physics provide access to the correlated motion of valence and core electrons on their intrinsic timescales. For valence excitations, processes related to the electron spin are usually driven by nuclear motion. For core-excited states, where the core hole has a nonzero angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a much shorter time scale. Here, unprecedented short spin-crossover driven by spin-orbit coupling is demonstrated for L-edge (2p$\\rightarrow$3d) excited states of a prototypical Fe(II) complex. It occurs on a time scale, which is faster than the core hole lifetime of about 4~fs. A detailed analysis of such phenomena will

  13. Theoretical study on phase conjugation in weakly injected vertical-cavity surface-emitting lasers

    Institute of Scientific and Technical Information of China (English)

    Zhang Wei-Li; Pan Wei; Luo Bin; Li Xiao-Feng; Zou Xi-Hua; Wang Meng-Yao

    2008-01-01

    This paper gives a detailed theoretical investigation on phase conjugation induced by nearly degenerate fourwave mixing in single mode vertical-cavity surface-emitting lasers (VCSELs) with~weak optical injection.Considering VCSELs that can work in linearly polarized or elliptically polarized states,it derives the theoretical expression of the conjugated field by small signal analysis based on the vectoral rate equations--the spin-flip model.For linearly polarized state,VCSELs show similar conjugate spectra to edge-emitting semiconductor lasers.For the eUiptically polarized state,dichroism and birefringence parameters as well as the spin-flip rate can change the conjugate spectra.Especially,when frequency detuning of the probe and pump waves is between the positive and negative relaxation oscillation frequency,changes are evident.For specific values of parameters,conjugate efficiency between 20 dB to 40 dB are obtained.

  14. Nitrogen nuclear spin flips in nitroxide spin probes of different sizes in glassy o-terphenyl: Possible relation with α- and β-relaxations

    Science.gov (United States)

    Isaev, N. P.; Dzuba, S. A.

    2011-09-01

    The pulsed electron-electron double resonance (ELDOR) technique was employed to study nitroxide spin probes of three different sizes dissolved in glassy o-terphenyl. A microwave pulse applied to the central hyperfine structure (hfs) component of the nitroxide electron paramagnetic resonance spectrum was followed by two echo-detecting pulses of different microwave frequency to probe the magnetization transfer (MT) to the low-field hfs component. The MT between hfs components is readily related to flips in the nitrogen nuclear spin, which in turn are induced by molecular motion. The MT on the time scale of tens of microseconds was observed over a wide temperature range, including temperatures near and well below the glass transition. For a bulky nitroxide, it was found that MT rates approach dielectric α (primary) relaxation frequencies reported for o-terphenyl in the literature. For small nitroxides, MT rates were found to match the frequencies of dielectric β (secondary) Johari-Goldstein relaxation. The most probable motional mechanism inducing the nitrogen nuclear spin flips is large-angle angular jumps, between some orientations of unequal occupation probabilities. The pulsed ELDOR of nitroxide spin probes may provide additional insight into the nature of Johari-Goldstein relaxation in glassy media and may serve as a tool for studying this relaxation in substances consisting of non-rigid molecules (such as branched polymers) and in heterogeneous and non-polar systems (such as a core of biological membranes).

  15. Optimizing minimum free-energy crossing points in solution: linear-response free energy/spin-flip density functional theory approach.

    Science.gov (United States)

    Minezawa, Noriyuki

    2014-10-28

    Examining photochemical processes in solution requires understanding the solvent effects on the potential energy profiles near conical intersections (CIs). For that purpose, the CI point in solution is determined as the crossing between nonequilibrium free energy surfaces. In this work, the nonequilibrium free energy is described using the combined method of linear-response free energy and collinear spin-flip time-dependent density functional theory. The proposed approach reveals the solvent effects on the CI geometries of stilbene in an acetonitrile solution and those of thymine in water. Polar acetonitrile decreases the energy difference between the twisted minimum and twisted-pyramidalized CI of stilbene. For thymine in water, the hydrogen bond formation stabilizes significantly the CI puckered at the carbonyl carbon atom. The result is consistent with the recent simulation showing that the reaction path via this geometry is open in water. Therefore, the present method is a promising way of identifying the free-energy crossing points that play an essential role in photochemistry of solvated molecules.

  16. Relation between magnetization and Faraday angles produced by ultrafast spin-flip processes within the three-level Λ-type system

    Energy Technology Data Exchange (ETDEWEB)

    Hinschberger, Y. [Departamento de Física e Astronomia, Instituto de Física dos Materiais da Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Lavoine, J. P. [Departement of Ultrafast Optics and Nanophotonics, Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504, CNRS, Université de Strasbourg, 23, Rue du Loess, BP 43, 67034 Strasbourg-Cedex 2 (France)

    2015-08-07

    Ultrafast magneto-optical (MO) experiments constitute a powerful tool to explore the magnetization dynamics of diverse materials. Over the last decade, there have been many theoretical and experimental developments on this subject. However, the relation between the magnetization dynamics and the transient MO response still remains unclear. In this work, we calculate the magnetization of a material, as well as the magneto-optical rotation and ellipticity angles measured in a single-beam experiment. Then, we compare the magnetization to the MO response. The magnetic material is modeled by a three-level Λ-type system, which represents a simple model to describe MO effects induced by an ultrafast laser pulse. Our calculations use the density matrix formalism, while the dynamics of the system is obtained by solving the Lindblad equation taking into account population relaxation and dephasing processes. Furthermore, we consider the Faraday rotation of the optical waves that simultaneously causes spin-flip. We show that the Faraday angles remain proportional to the magnetization only if the system has reached the equilibrium-state, and that this proportionality is directly related to the population and coherence decay rates. For the non-equilibrium situation, the previous proportionality relation is no longer valid. We show that our model is able to interpret some recent experimental results obtained in a single-pulse experiment. We further show that, after a critical pulse duration, the decrease of the ellipticity as a function of the absorbed energy is a characteristic of the system.

  17. Achieving a high magnetization in sub-nanostructured magnetite films by spin-flipping of tetrahedral Fe3. cations

    Institute of Scientific and Technical Information of China (English)

    Tun Seng Herng[1,2; Wen Xiao[1; Sock Mui Poh[2,3; Feizhou He[5; Ronny Sutarto[5; Xiaojian Zhu[6; Runwei Li[6; Xinmao Yin[2,3,4; Caozheng Diao[2; Yang Yang[1; Xuelian Huang[1; Xiaojiang Yu[2; Yuan Ping Feng[4; AndrivoRusydi[2,3,4; Jun Ding[1

    2015-01-01

    Magnetite Fe304 (ferrite) has attracted considerable interest for its exceptional physical properties: It is predicted to be a semimetallic ferromagnetic with a high Curie temperature, it displays a metal-insulator transition, and has potential oxide-electronics applications. Here, we fabricate a high-magnetization (〉 1 Tesla) high-resistance (-0.1 Ωcm) sub-nanostructured (grain size 〈 3 nm) Fe304 film via grain-size control and nano-engineering. We report a new phenomenon of spin- flipping of the valence-spin tetrahedral FeB* in the sub-nanostructured Fe304 film, which produces the high magnetization. Using soft X-ray magnetic circular dichroism and soft X-ray absorption, both at the Fe L3,2- and O K-edges, and supported by first-principles and charge-transfer multiple calculations, we observe an anomalous enhancement of double exchange, accompanied by a suppression of the superexchange interactions because of the spin-flipping mechanism via oxygen at the grain boundaries. Our result may open avenues for developing spin- manipulated giant magnetic Fe304-based compounds via nano-grain size control.

  18. Mechanisms of spin-flipping and metal-insulator transition in nano-Fe3O4

    Science.gov (United States)

    Dito Fauzi, Angga; Aziz Majidi, Muhammad; Rusydi, Andrivo

    2017-04-01

    Fe3O4 is a half-metallic ferrimagnet with {{T}\\text{C}}∼ 860 K exhibiting metal-insulator transition (MIT) at  ∼120 K. In bulk form, the saturation magnetization is 0.6 Tesla (∼471 emu cm‑3). A recent experimental study has shown that the saturation magnetization of nano-Fe3O4 thin films can achieve up to  ∼760 emu cm‑3, attributed to spin-flipping of Fe ions at tetrahedral sites assisted by oxygen vacancies (V O). Such a system has shown to have higher MIT temperature (∼150 K). The spin-flipping is a new phenomenon in Fe3O4, while the MIT is a long-standing one. Here, we propose a model and calculations to investigate the mechanisms of both phenomena. Our results show that, for the system without V O, the ferrimagnetic configuration is energetically favorable. Remakably, upon inclusion of V O, the ground-state configuration switches into ferromagnetic. As for the MIT, by proposing temperature dependences of some hopping integrals in the model, we demonstrate that the system without and with V O undergo the MIT in slightly different ways, leading to higher MIT temperature for the system with V O, in agreement with the experimental data. Our results also show that the MIT in both systems occur concomitantly with the redistribution of electrons among the three Fe ions in each Fe3O4 formula unit. As such temperature dependences of hopping integrals may arise due to dynamic Jahn–Teller effects, our phenomenological theory may provide a way to reconcile existing theories relating the MIT to the structural transition and the charge ordering.

  19. Adapting algebraic diagrammatic construction schemes for the polarization propagator to problems with multi-reference electronic ground states exploiting the spin-flip ansatz

    Science.gov (United States)

    Lefrancois, Daniel; Wormit, Michael; Dreuw, Andreas

    2015-09-01

    For the investigation of molecular systems with electronic ground states exhibiting multi-reference character, a spin-flip (SF) version of the algebraic diagrammatic construction (ADC) scheme for the polarization propagator up to third order perturbation theory (SF-ADC(3)) is derived via the intermediate state representation and implemented into our existing ADC computer program adcman. The accuracy of these new SF-ADC(n) approaches is tested on typical situations, in which the ground state acquires multi-reference character, like bond breaking of H2 and HF, the torsional motion of ethylene, and the excited states of rectangular and square-planar cyclobutadiene. Overall, the results of SF-ADC(n) reveal an accurate description of these systems in comparison with standard multi-reference methods. Thus, the spin-flip versions of ADC are easy-to-use methods for the calculation of "few-reference" systems, which possess a stable single-reference triplet ground state.

  20. Computational Quantum Chemistry for Multiple-Site Heisenberg Spin Couplings Made Simple: Still Only One Spin-Flip Required.

    Science.gov (United States)

    Mayhall, Nicholas J; Head-Gordon, Martin

    2015-05-21

    We provide a simple procedure for using inexpensive ab initio calculations to compute exchange coupling constants, J(AB), for multiradical molecules containing both an arbitrary number of radical sites and an arbitrary number of unpaired electrons. For a system comprised of 2M unpaired electrons, one needs only to compute states having the Ŝ(z) quantum number M - 1. Conveniently, these are precisely the states that are accessed by the family of single spin-flip methods. Building an effective Hamiltonian with these states allows one to extract all of the J(AB) constants in the molecule. Unlike approaches based on density functional theory, this procedure relies on neither spin-contaminated states nor nonunique spin-projection formulas. A key benefit is that it is possible to obtain completely spin-pure exchange coupling constants with inexpensive ab initio calculations. A couple of examples are provided to illustrate the approach, including a 4-nickel cubane complex and a 6-chromium horseshoe complex with 18 entangled electrons.

  1. Improved CUDA programs for GPU computing of Swendsen-Wang multi-cluster spin flip algorithm: 2D and 3D Ising, Potts, and XY models

    Science.gov (United States)

    Komura, Yukihiro; Okabe, Yutaka

    2016-03-01

    We present new versions of sample CUDA programs for the GPU computing of the Swendsen-Wang multi-cluster spin flip algorithm. In this update, we add the method of GPU-based cluster-labeling algorithm without the use of conventional iteration (Komura, 2015) to those programs. For high-precision calculations, we also add a random-number generator in the cuRAND library. Moreover, we fix several bugs and remove the extra usage of shared memory in the kernel functions.

  2. Spin-flip scattering and band structure mismatch effect on transport of pure spin across ferromagnetic semimetal/metal material interfaces

    Science.gov (United States)

    Pasanai, K.

    2016-03-01

    The tunneling conductance spectra of a ferromagnetic semimetal/metal junction, where there were electrons and holes with the same spin directions as the essential conducting particle, was theoretically studied based on a scattering approach in a ballistic regime. The main area of interest was to perform a high spin polarization by considering the effect of the interfacial scattering at the interface that was composed of normal and spin-flip scattering, the particle effective mass mismatch on the reflection and transmission probabilities, and spin polarization of conductance. It was found that the spin polarization of conductance decreased with increasing spin-flip scattering. Interestingly, the normal scattering can cause the spin polarization of the conductance to reach a maximum value in the presence of both kinds of scattering. When the particle effective mass mismatch was considered, the spin polarization of conductance was large when the electron effective mass in the valence band was smaller than that in the conduction band. However, in this calculation, the results of a ferromagnetic semimetal/metal junction behaved similarly to those of a ferromagnetic metal/metal junction.

  3. Adapting algebraic diagrammatic construction schemes for the polarization propagator to problems with multi-reference electronic ground states exploiting the spin-flip ansatz

    Energy Technology Data Exchange (ETDEWEB)

    Lefrancois, Daniel; Wormit, Michael; Dreuw, Andreas, E-mail: dreuw@uni-heidelberg.de [Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer Feld 368, 69120 Heidelberg (Germany)

    2015-09-28

    For the investigation of molecular systems with electronic ground states exhibiting multi-reference character, a spin-flip (SF) version of the algebraic diagrammatic construction (ADC) scheme for the polarization propagator up to third order perturbation theory (SF-ADC(3)) is derived via the intermediate state representation and implemented into our existing ADC computer program adcman. The accuracy of these new SF-ADC(n) approaches is tested on typical situations, in which the ground state acquires multi-reference character, like bond breaking of H{sub 2} and HF, the torsional motion of ethylene, and the excited states of rectangular and square-planar cyclobutadiene. Overall, the results of SF-ADC(n) reveal an accurate description of these systems in comparison with standard multi-reference methods. Thus, the spin-flip versions of ADC are easy-to-use methods for the calculation of “few-reference” systems, which possess a stable single-reference triplet ground state.

  4. Dark-bright exciton spin-flip rates of quantum dots determined by a modified local density of optical states

    DEFF Research Database (Denmark)

    Lodahl, Peter; Johansen, Jeppe; Julsgaard, Brian;

    2009-01-01

    This work investigates the influence of dark excitons on the radiative dynamics of semiconductor quantum dots (QDs). Dark excitons have total angular momentum of 2 and contribute to the fine structure of the exciton ground state. As opposed to bright excitons that have total angular momentum 1...

  5. Accurate adiabatic singlet-triplet gaps in atoms and molecules employing the third-order spin-flip algebraic diagrammatic construction scheme for the polarization propagator

    Science.gov (United States)

    Lefrancois, Daniel; Rehn, Dirk R.; Dreuw, Andreas

    2016-08-01

    For the calculation of adiabatic singlet-triplet gaps (STG) in diradicaloid systems the spin-flip (SF) variant of the algebraic diagrammatic construction (ADC) scheme for the polarization propagator in third order perturbation theory (SF-ADC(3)) has been applied. Due to the methodology of the SF approach the singlet and triplet states are treated on an equal footing since they are part of the same determinant subspace. This leads to a systematically more accurate description of, e.g., diradicaloid systems than with the corresponding non-SF single-reference methods. Furthermore, using analytical excited state gradients at ADC(3) level, geometry optimizations of the singlet and triplet states were performed leading to a fully consistent description of the systems, leading to only small errors in the calculated STGs ranging between 0.6 and 2.4 kcal/mol with respect to experimental references.

  6. CUDA programs for GPU computing of Swendsen-Wang multi-cluster spin flip algorithm: 2D and 3D Ising, Potts, and XY models

    CERN Document Server

    Komura, Yukihiro

    2014-01-01

    We present sample CUDA programs for the GPU computing of the Swendsen-Wang multi-cluster spin flip algorithm. We deal with the classical spin models; the Ising model, the $q$-state Potts model, and the classical XY model. As for the lattice, both the 2D (square) lattice and the 3D (simple cubic) lattice are treated. We already reported the idea of the GPU implementation for 2D models [Comput. Phys. Commun. 183 (2012) 1155-1161]. We here explain the details of sample programs, and discuss the performance of the present GPU implementation for the 3D Ising and XY models. We also show the calculated results of the moment ratio for these models, and discuss phase transitions.

  7. Valence excitation energies of alkenes, carbonyl compounds, and azabenzenes by time-dependent density functional theory: Linear response of the ground state compared to collinear and noncollinear spin-flip TDDFT with the Tamm-Dancoff approximation

    Science.gov (United States)

    Isegawa, Miho; Truhlar, Donald G.

    2013-04-01

    Time-dependent density functional theory (TDDFT) holds great promise for studying photochemistry because of its affordable cost for large systems and for repeated calculations as required for direct dynamics. The chief obstacle is uncertain accuracy. There have been many validation studies, but there are also many formulations, and there have been few studies where several formulations were applied systematically to the same problems. Another issue, when TDDFT is applied with only a single exchange-correlation functional, is that errors in the functional may mask successes or failures of the formulation. Here, to try to sort out some of the issues, we apply eight formulations of adiabatic TDDFT to the first valence excitations of ten molecules with 18 density functionals of diverse types. The formulations examined are linear response from the ground state (LR-TDDFT), linear response from the ground state with the Tamm-Dancoff approximation (TDDFT-TDA), the original collinear spin-flip approximation with the Tamm-Dancoff (TD) approximation (SF1-TDDFT-TDA), the original noncollinear spin-flip approximation with the TDA approximation (SF1-NC-TDDFT-TDA), combined self-consistent-field (SCF) and collinear spin-flip calculations in the original spin-projected form (SF2-TDDFT-TDA) or non-spin-projected (NSF2-TDDFT-TDA), and combined SCF and noncollinear spin-flip calculations (SF2-NC-TDDFT-TDA and NSF2-NC-TDDFT-TDA). Comparing LR-TDDFT to TDDFT-TDA, we observed that the excitation energy is raised by the TDA; this brings the excitation energies underestimated by full linear response closer to experiment, but sometimes it makes the results worse. For ethylene and butadiene, the excitation energies are underestimated by LR-TDDFT, and the error becomes smaller making the TDA. Neither SF1-TDDFT-TDA nor SF2-TDDFT-TDA provides a lower mean unsigned error than LR-TDDFT or TDDFT-TDA. The comparison between collinear and noncollinear kernels shows that the noncollinear kernel

  8. Development of a 3He nuclear spin flip system on an in-situ SEOP 3He spin filter and demonstration for a neutron reflectometer and magnetic imaging technique

    Science.gov (United States)

    Hayashida, H.; Oku, T.; Kira, H.; Sakai, K.; Hiroi, K.; Ino, T.; Shinohara, T.; Imagawa, T.; Ohkawara, M.; Ohoyama, K.; Kakurai, K.; Takeda, M.; Yamazaki, D.; Oikawa, K.; Harada, M.; Miyata, N.; Akutsu, K.; Mizusawa, M.; Parker, J. D.; Matsumoto, Y.; Zhang, S.; Suzuki, J.; Soyama, K.; Aizawa, K.; Arai, M.

    2016-04-01

    We have been developing a 3He neutron spin filter (NSF) using the spin exchange optical pumping (SEOP) technique. The 3He NSF provides a high-energy polarized neutron beam with large beam size. Moreover the 3He NSF can work as a π-flipper for a polarized neutron beam by flipping the 3He nuclear spin using a nuclear magnetic resonance (NMR) technique. For NMR with the in-situ SEOP technique, the polarization of the laser must be reversed simultaneously because a non-reversed laser reduces the polarization of the spin-flipped 3He. To change the polarity of the laser, a half-wavelength plate was installed. The rotation angle of the half-wavelength plate was optimized, and a polarization of 97% was obtained for the circularly polarized laser. The 3He polarization reached 70% and was stable over one week. A demonstration of the 3He nuclear spin flip system was performed at the polarized neutron reflectometer SHARAKU (BL17) and NOBORU (BL10) at J-PARC. Off-specular measurement from a magnetic Fe/Cr thin film and magnetic imaging of a magnetic steel sheet were performed at BL17 and BL10, respectively.

  9. Eberhard Widmann (Stefan Meyer Institute, Vienna) and Silke Federmann (Ph.D. Student from Vienna in the CERN-Austrian Ph.D. program) together with a microwave cavity developed by Silke at CERN. The cavity will be used for the first time to look for spin-flip transitions of antihydrogen atoms later this year.

    CERN Multimedia

    Maximilien Brice

    2011-01-01

    Eberhard Widmann (Stefan Meyer Institute, Vienna) and Silke Federmann (Ph.D. Student from Vienna in the CERN-Austrian Ph.D. program) together with a microwave cavity developed by Silke at CERN. The cavity will be used for the first time to look for spin-flip transitions of antihydrogen atoms later this year.

  10. Screened Thermonuclear Reaction Rates on Magnetar Surfaces

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-Lin; LUO Zhi-Quan; LIU Jing-Jing; LAI Xiang-Jun

    2008-01-01

    Improving Salpeter's method, we discuss the effect of superstrong magnetic fields (such as those of magnetars) on thermonuclear reaction rates. These most interesting reactions, including the hydrogen burning by the CNO cycle and the helium burning by the triple alpha reaction, are investigated as examples on the magnetar surfaces. The obtained result shows that the superstrong magnetic fields can increase the thermonuclear reaction rates by many orders of magnitude. The enhancement may have significant influence for further study research of the magnetars, especially for the x-ray luminosity observation and the evolution of magnetars.

  11. Static polarizabilities for excited states within the spin-conserving and spin-flipping equation-of-motion coupled-cluster singles and doubles formalism: Theory, implementation, and benchmarks.

    Science.gov (United States)

    Nanda, Kaushik D; Krylov, Anna I

    2016-11-28

    We present the theory and implementation for calculating static polarizabilities within the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) framework for electronically excited states and its spin-flip variant. We evaluate the second derivatives of the EOM-CCSD Lagrangian with respect to electric-field perturbations. The relaxation of reference molecular orbitals is not included. In our approach, the wave function amplitudes satisfy the 2n + 1 rule and the amplitude-response Lagrange multipliers satisfy the 2n + 2 rule. The new implementation is validated against finite-field and CCSD response-theory calculations of the excited-state polarizabilities of pyrimidine and s-tetrazine. We use the new method to compute static polarizabilities of different types of electronic states (valence, charge-transfer, singlets, and triplets) in open- and closed-shell systems (uracil, p-nitroaniline, methylene, and p-benzyne). We also present an alternative approach for calculating excited-state static polarizabilities as expectation values by using the EOM-CCSD wave functions and energies in the polarizability expression for an exact state. We find that this computationally less demanding approach may show differences up to ∼30% relative to the excited-state polarizabilities computed using the analytic-derivative formalism.

  12. Effect of the diradical character on static polarizabilities and two-photon absorption cross sections: A closer look with spin-flip equation-of-motion coupled-cluster singles and doubles method

    Science.gov (United States)

    Nanda, Kaushik D.; Krylov, Anna I.

    2017-06-01

    We present static polarizabilities and two-photon absorption (2PA) cross sections for the low-lying electronic states of prototypical diradicals such as benzynes and analogues of m-xylylene and p-quinodimethane computed with the spin-flip equation-of-motion coupled-cluster singles and doubles (EOM-SF-CCSD) method. The static polarizabilities were calculated as analytic second derivatives of the EOM energies, and the 2PA cross sections were calculated using the expectation-value approach. We explain the trends in the nonlinear responses of the SF target states by constructing few-states models based on truncated sum-over-states expressions for these nonlinear properties. By using a Huckel-type treatment of the frontier molecular orbitals that host the unpaired electrons, we rationalize the trends in the dipole interactions between the SF target states relevant in the few-states models. We demonstrate the correlation between the nonlinear responses of these electronic states and the diradical character.

  13. Static polarizabilities for excited states within the spin-conserving and spin-flipping equation-of-motion coupled-cluster singles and doubles formalism: Theory, implementation, and benchmarks

    Science.gov (United States)

    Nanda, Kaushik D.; Krylov, Anna I.

    2016-11-01

    We present the theory and implementation for calculating static polarizabilities within the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) framework for electronically excited states and its spin-flip variant. We evaluate the second derivatives of the EOM-CCSD Lagrangian with respect to electric-field perturbations. The relaxation of reference molecular orbitals is not included. In our approach, the wave function amplitudes satisfy the 2n + 1 rule and the amplitude-response Lagrange multipliers satisfy the 2n + 2 rule. The new implementation is validated against finite-field and CCSD response-theory calculations of the excited-state polarizabilities of pyrimidine and s-tetrazine. We use the new method to compute static polarizabilities of different types of electronic states (valence, charge-transfer, singlets, and triplets) in open- and closed-shell systems (uracil, p-nitroaniline, methylene, and p-benzyne). We also present an alternative approach for calculating excited-state static polarizabilities as expectation values by using the EOM-CCSD wave functions and energies in the polarizability expression for an exact state. We find that this computationally less demanding approach may show differences up to ˜30 % relative to the excited-state polarizabilities computed using the analytic-derivative formalism.

  14. Using a non-spin flip model to rationalize the irregular patterns observed in the activation of the C-H and Si-H bonds of small molecules by CpMCO (M = Co, Rh) complexes.

    Science.gov (United States)

    Castro, Guadalupe; Colmenares, Fernando

    2017-09-20

    The activation of the C-H and Si-H bonds of CH(CH3)3 and SiH(CH3)3 molecules by organometallic compounds CpMCO (M = Co, Rh) has been investigated through DFT and CASSCF-MRMP2 calculations. In particular, we have analyzed the pathways joining the lowest-lying triplet and singlet states of the reactants with the products arising from the insertion of the metal atom into the C-H or Si-H bonds of the organic molecules. Channels connecting the reactants with the inserted structure Cp(CO)H-M-C(CH3)3 through the oxidative addition of the C-H bond of the organic molecule to the metal fragment were found only for the reaction CpRhCO + CH(CH3)3. However, inserted structures could also be obtained for the interactions of SiH(CH3)3 with CpCoCO and CpRhCO by two sequential reactions involving the formation and rebounding of the radical fragments Cp(CO)H-M + Si(CH3)3. According to this two-step reaction scheme, the complex CpCoCO is unable to activate the C-H bond of the CH(CH3)3 molecule due to the high energy at which the radical fragments Cp(CO)H-M + C(CH3)3 are located. The picture attained for these interactions is consistent with the available experimental data for this kind of reaction and allows rationalization of the differences in the reactivity patterns determined for them without using spin-flip models, as has been proposed in previous studies.

  15. Spin relaxation and the Elliott-Yafet parameter in W(001) ultrathin films: Surface states, anisotropy, and oscillation effects

    Science.gov (United States)

    Long, Nguyen H.; Mavropoulos, Phivos; Zimmermann, Bernd; Heers, Swantje; Bauer, David S. G.; Blügel, Stefan; Mokrousov, Yuriy

    2013-06-01

    Using first-principles methods based on density-functional theory, we investigate the spin relaxation in W(001) ultrathin films. Within the framework of the Elliott-Yafet theory, we calculate the spin mixing of the Bloch states and we explicitly consider spin-flip scattering off self-adatoms. At small film thicknesses, we find an oscillatory behavior of the spin-mixing parameter and relaxation rate as a function of the film thickness, which we trace back to surface-state properties. We also analyze the Rashba effect experienced by the surface states and discuss its influence on the spin relaxation. Finally, we calculate the anisotropy of the spin-relaxation rate with respect to the polarization direction of the excited spin population relative to the crystallographic axes of the film. We find that the spin-relaxation rate can increase by as much as 27% when the spin polarization is directed out of plane, compared to the case when it is in plane. Our calculations are based on the multiple-scattering formalism of the Korringa-Kohn-Rostoker Green-function method.

  16. Spin flipping in rings with Siberian Snakes

    Energy Technology Data Exchange (ETDEWEB)

    Mane, S.R. [Convergent Computing Inc., P.O. Box 561, Shoreham, NY 11786 (United States)], E-mail: srmane@optonline.net

    2009-07-01

    I display numerical spin tracking simulations for spin flippers in model storage rings with full or nearly full Siberian Snakes. In many cases, the results differ from the predictions using the Froissart-Stora formula.

  17. Properties of water surface discharge at different pulse repetition rates

    Energy Technology Data Exchange (ETDEWEB)

    Ruma,; Yoshihara, K. [Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555 (Japan); Hosseini, S. H. R., E-mail: hosseini@kumamoto-u.ac.jp; Sakugawa, T.; Akiyama, H. [Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555 (Japan); Institute of Pulsed Power Science, Kumamoto University, Kumamoto 860-8555 (Japan); Akiyama, M. [Department of Electrical and Electronic Engineering, Kagoshima University, Kagoshima 890-0065 (Japan); Lukeš, P. [Institute of Plasma Physics, AS CR, Prague, Prague 18200 (Czech Republic)

    2014-09-28

    The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000 Hz, with 0.5 J per pulse energy output at 25 kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H₂O₂) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H₂O₂ and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications.

  18. Rate and extent of aqueous perchlorate removal by iron surfaces.

    Science.gov (United States)

    Moore, Angela M; De Leon, Corinne H; Young, Thomas M

    2003-07-15

    The rate and extent of perchlorate reduction on several types of iron metal was studied in batch and column reactors. Mass balances performed on the batch experiments indicate that perchlorate is initially sorbed to the iron surface, followed by a reduction to chloride. Perchlorate removal was proportional to the iron dosage in the batch reactors, with up to 66% removal in 336 h in the highest dosage system (1.25 g mL(-1)). Surface-normalized reaction rates among three commercial sources of iron filings were similar for acid-washed samples. The most significant perchlorate removal occurred in solutions with slightly acidic or near-neutral initial pH values. Surface mediation of the reaction is supported by the absence of reduction in batch experiments with soluble Fe2+ and also by the similarity in specific reaction rate constants (kSA) determined for three different iron types. Elevated soluble chloride concentrations significantly inhibited perchlorate reduction, and lower removal rates were observed for iron samples with higher amounts of background chloride contamination. Perchlorate reduction was not observed on electrolytic sources of iron or on a mixed-phase oxide (Fe3O4), suggesting that the reactive iron phase is neither pure zerovalent iron nor the mixed oxide alone. A mixed valence iron hydr(oxide) coating or a sorbed Fe2+ surface complex represent the most likely sites for the reaction. The observed reaction rates are too slow for immediate use in remediation system design, but the findings may provide a basis for future development of cost-effective abiotic perchlorate removal techniques.

  19. Auger neutralization rates of multiply charged ions near metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Nedeljkovic, N.N.; Janev, R.K.; Lazur, V.Y.

    1988-08-15

    Transition rates for the Auger neutralization processes of multiply charged ions on metal surfaces are calculated in closed analytical form. The core potential of a multiply charged ion is represented by a pseudopotential, which accounts for the electron screening effects and allows transition to the pure Coulomb case (fully stripped ions). The relative importance of various neutralization channels in slow-ion--surface collisions is discussed for the examples of He/sup 2+/+Mo(100) and C/sup 3+/+Mo(100) collisional systems.

  20. Dropwise condensation rate of water breath figures on polymer surfaces having similar surface free energies

    Science.gov (United States)

    Ucar, Ikrime O.; Erbil, H. Yildirim

    2012-10-01

    This study investigates the effect of surface roughness, wettability, water contact angle hysteresis (CAH) and wetting hysteresis (WH) of polymeric substrates to the water drop condensation rate. We used five polyolefin coatings whose surface free energies were in a close range of 30-37 mJ/m2 but having different surface roughness and CAH. The formation of water breath figures was monitored at a temperature just below the dew point. The initial number of the condensed droplets per unit area (N0) and droplet surface coverage were determined during the early stage of drop condensation where the droplet coalescence was negligible. It was found that the mean drop diameter of condensed droplets on these polymer surfaces grow according to a power law with exponent 1/3 of time, similar to the previous reports given in the literature. It was determined that surface roughness and corresponding CAH and WH properties of polymers have important effects on the number of nucleation sites and growth rate of the condensed water droplets. N0 values and the surface coverage increased with the increase in surface roughness, CAH and WH of the polymer surfaces. The total condensed water drop volume also increased with the increase in surface roughness in accordance with the increase of the number of nucleated droplets.

  1. Toward understanding the rates of reactions at mineral surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Casey, W.H. [Univ. of California Davis, CA (United States). Dept. of Land, Air and Water Resources and Dept. of Geology; Ludwig, C. [EAWAG, Swiss Federal Institute for Environmental Science and Technolgy, Dubendorf (Switzerland). Dept. of Resources and Waste management; Holmen, B. [Univ. of California Davis, CA (United States). Dept. of Land, Air and Water Resources

    1998-12-31

    Environmental geo chemists are commonly called upon to make predictions over long scales of time and distance. In many cases, these predictions involve disequilibrium reactions, such as the decomposition of ozone-depleting gases or the migration rates of groundwater contaminants. These groundwater contaminants interact with mineral surfaces in a complicated fashion that is not understood quantitatively. However, in a real sense, mineral dissolution studies are to the aqueous geo chemists what Escherichia coli are to microbiologists: an inexpensive model system to map out important kinetic relations that can then be extended qualitatively to other settings. This chapter explains that is enormously useful to draw analogies between reactions at mineral surfaces and at dissolved metal-ligand complexes. In this approach, the reactivities of bond between a metal and a water molecule or ligand in the inner-coordination-sphere of the dissolved complex are proxies for bonds between a metal and oxygen at the mineral surface, which cannot be studied directly.

  2. Enzyme surface rigidity tunes the temperature dependence of catalytic rates.

    Science.gov (United States)

    Isaksen, Geir Villy; Åqvist, Johan; Brandsdal, Bjørn Olav

    2016-07-12

    The structural origin of enzyme adaptation to low temperature, allowing efficient catalysis of chemical reactions even near the freezing point of water, remains a fundamental puzzle in biocatalysis. A remarkable universal fingerprint shared by all cold-active enzymes is a reduction of the activation enthalpy accompanied by a more negative entropy, which alleviates the exponential decrease in chemical reaction rates caused by lowering of the temperature. Herein, we explore the role of protein surface mobility in determining this enthalpy-entropy balance. The effects of modifying surface rigidity in cold- and warm-active trypsins are demonstrated here by calculation of high-precision Arrhenius plots and thermodynamic activation parameters for the peptide hydrolysis reaction, using extensive computer simulations. The protein surface flexibility is systematically varied by applying positional restraints, causing the remarkable effect of turning the cold-active trypsin into a variant with mesophilic characteristics without changing the amino acid sequence. Furthermore, we show that just restraining a key surface loop causes the same effect as a point mutation in that loop between the cold- and warm-active trypsin. Importantly, changes in the activation enthalpy-entropy balance of up to 10 kcal/mol are almost perfectly balanced at room temperature, whereas they yield significantly higher rates at low temperatures for the cold-adapted enzyme.

  3. Production rates of cosmogenic nuclei on the lunar surface

    Science.gov (United States)

    Dong, Tie-Kuang; Yun, Su-Jun; Ma, Tao; Chang, Jin; Dong, Wu-Dong; Zhang, Xiao-Ping; Li, Guo-Long; Ren, Zhong-Zhou

    2014-07-01

    A physical model for Geant4-based simulation of the galactic cosmic ray (GCR) particles' interaction with the lunar surface matter has been developed to investigate the production rates of cosmogenic nuclei. In this model the GCRs, mainly very high energy protons and α particles, bombard the surface of the Moon and produce many secondary particles, such as protons and neutrons. The energies of protons and neutrons at different depths are recorded and saved as ROOT files, and the analytical expressions for the differential proton and neutron fluxes are obtained through the best-fit procedure using ROOT software. To test the validity of this model, we calculate the production rates of the long-lived nuclei 10Be and 26Al in the Apollo 15 long drill core by combining the above differential fluxes and the newly evaluated spallation reaction cross sections. Our numerical results show that the theoretical production rates agree quite well with the measured data, which means that this model works well. Therefore, it can be expected that this model can be used to investigate the cosmogenic nuclei in future lunar samples returned by the Chinese lunar exploration program and can be extended to study other objects, such as meteorites and the Earth's atmosphere.

  4. Cosmogenic Nuclei Production Rate on the Lunar Surface

    CERN Document Server

    Dong, Tie-Kuang; Ma, Tao; Chang, Jin; Dong, Wu-Dong; Zhang, Xiao-Ping; Li, Guo-Long; Ren, Zhong-Zhou

    2013-01-01

    A physical model of Geant4-based simulation of galactic cosmic ray (GCR) particles interaction with the lunar surface matter has been developed to investigate the production rate of cosmogenic nuclei. In this model the GCRs, mainly very high energy protons and $\\alpha$ particles, bombard the surface of the Moon and produce many secondary particles such as protons and neutrons. The energies of proton and neutron at different depths are recorded and saved into ROOT files, and the analytical expressions for the differential proton and neutron fluxes are obtained through the best-fit procedure under the ROOT software. To test the validity of this model, we calculate the production rates of long-lived nuclei $^{10}$Be and $^{26}$Al in the Apollo 15 long drill core by combining the above differential fluxes and the newly evaluated spallation reaction cross sections. Numerical results show that the theoretical production rates agree quite well with the measured data. It means that this model works well. Therefore, i...

  5. Indexing Glomerular Filtration Rate to Body Surface Area

    DEFF Research Database (Denmark)

    Redal-Baigorri, Belén; Rasmussen, Knud; Heaf, James Goya

    2014-01-01

    BACKGROUND: Kidney function is mostly expressed in terms of glomerular filtration rate (GFR). A common feature is the expression as ml/min per 1.73 m(2) , which represents the adjustment of the individual kidney function to a standard body surface area (BSA) to allow comparison between individuals....... We investigated the impact of indexing GFR to BSA in cancer patients, as this BSA indexation might affect the reported individual kidney function. METHODS: Cross-sectional study of 895 adults who had their kidney function measured with (51) chrome ethylene diamine tetraacetic acid. Mean values of BSA...

  6. CONVERSION RATES OF SURFACE HOx RADICALS IN BEIJING CITY

    Institute of Scientific and Technical Information of China (English)

    REN Xin-rong; WANG Li-xin; WANG Hui-xiang; MIAO Guo-fang

    2004-01-01

    Surface OH radical concentration in Beijing City was measured by impregnated filter trapping technique-high performance liquid chromatography (IFT-HPLC). The observed concentration of OH radical showed obvious diurnal and seasonal variations, with maximum readings at noon or afternoon, ~80×106OH/cm3 in summer and ~20×106-40×106OH/cm3 in fall. On the basis of measured data, the reaction rates related to the photochemical process of Hox (OH+HO2) were derived and characteristics of atmospheric chemical processes in the city were analyzed. The results showed that conversion rates of atmospheric OH and HO2 in the summer of Beijing City were air of the city mainly originated from the photolysis of the gaseous HNO2, and the main sink of OH were the photochemical reactions with VOCs, NO2, HCHO and CO. It was different from the clean area.

  7. Controlling Surface Roughness to Enhance Mass Flow Rates in Nanochannels

    Science.gov (United States)

    Zimon, Malgorzata; Emerson, David; Reese, Jason

    2012-11-01

    A very active field of research in fluid mechanics and material science is predicting the behavior of Newtonian fluids flowing over porous media with different wettabilities. Opposite effects have been observed: some state that wall roughness always suppresses fluid-slip, whereas others show that for some cases roughness may reduce the surface friction. In this work, MD simulations were carried out to further investigate physical mechanisms for liquid slip, and factors affecting it. A rough wall was formed by either periodically spaced rectangular protrusions or was represented by a cosine wave. The MD simulations were conducted to study Poiseuille and Couette flow of liquid argon in a nanochannel with hydrophilic kryptonian walls. The effect of wall roughness and interface wettability on the streaming velocity, and the slip-length at the walls, is observed to be significant. Our results show a dependency of mass flow rate on the type of flow and topography of the channel walls. For a fixed magnitude of the driving force, an increase in the mass flow rate, compared to the smooth surface, was observed for the wavy roughness, whereas the opposite effect was observed for Couette flow where a higher slip was obtained for rectangular gaps. The study is funded in the UK by the Engineering and Physical Sciences Research Council.

  8. Optimal mutation rates in dynamic environments: The eigen model

    Science.gov (United States)

    Ancliff, Mark; Park, Jeong-Man

    2011-03-01

    We consider the Eigen quasispecies model with a dynamic environment. For an environment with sharp-peak fitness in which the most-fit sequence moves by k spin-flips each period T we find an asymptotic stationary state in which the quasispecies population changes regularly according to the regular environmental change. From this stationary state we estimate the maximum and the minimum mutation rates for a quasispecies to survive under the changing environment and calculate the optimum mutation rate that maximizes the population growth. Interestingly we find that the optimum mutation rate in the Eigen model is lower than that in the Crow-Kimura model, and at their optimum mutation rates the corresponding mean fitness in the Eigen model is lower than that in the Crow-Kimura model, suggesting that the mutation process which occurs in parallel to the replication process as in the Crow-Kimura model gives an adaptive advantage under changing environment.

  9. Optimization of Surface Acoustic Wave-Based Rate Sensors

    Directory of Open Access Journals (Sweden)

    Fangqian Xu

    2015-10-01

    Full Text Available The optimization of an surface acoustic wave (SAW-based rate sensor incorporating metallic dot arrays was performed by using the approach of partial-wave analysis in layered media. The optimal sensor chip designs, including the material choice of piezoelectric crystals and metallic dots, dot thickness, and sensor operation frequency were determined theoretically. The theoretical predictions were confirmed experimentally by using the developed SAW sensor composed of differential delay line-oscillators and a metallic dot array deposited along the acoustic wave propagation path of the SAW delay lines. A significant improvement in sensor sensitivity was achieved in the case of 128° YX LiNbO3, and a thicker Au dot array, and low operation frequency were used to structure the sensor.

  10. The water outgassing rate of internal surfaces of vacuum systems

    Science.gov (United States)

    Rozanov, L. N.

    2016-07-01

    On the basis of experimental adsorption isotherm the ratio between the real and geometrical surfaces was calculated and the amount of gas required to form a monolayer was defined. Simultaneous usage of Henry and Frendlih equations allowed to determine the dependence of the heat of adsorption on the logarithm of the absorbed gas amount A mathematical model of pumping of the vacuum systems with adsorbing walls is presented. This model uses the parameters of the vacuum system and the dependence of the adsorption heat on the amount of the adsorbed gas .The conditions of the existence of regular pumping regime are discussed. The structure database vacuum adsorption properties of materials was proposed. The experimental data on the determination of the adsorption outgassing rate were released.

  11. Analysis of reaction rates of single molecules on metal surfaces

    Science.gov (United States)

    Ueba, H.

    2017-10-01

    The experimental results of the action spectra i.e., reaction rate R(V) as a function of a bias voltage V are analyzed for rotation of a single CCH (D) molecule on a Cu (100) surface [5] and hopping of a single H(D)2O molecule on Pd(111) surface [6]. In the former system it is identified that rotation occurs if enough energy stored in the C-H (D) in-plane bending (IPB) mode excited by tunneling electron is transferred to the C-H (D) out of plane bending (OPB) mode (reaction coordinate mode) via the anharmonic mode coupling in a single electron process. The calculated R(V) shows an excellent agreement with the experimental results except at the low bias voltages below V ≃ 60 mV where no experimental data is available for the nonlinear current I dependence of R(I). A reproduction of the experimental R(V) at the higher voltage region allows us to determine the vibrational density of states of the C-H IPB mode and its coupling rate to the C-H (D) OPB mode as well as the inelastic tunneling current to excite IPB mode. A change of a conductance upon excitation of the C-H IPB mode enables us to evaluate the electron-vibration coupling strength inducing the rotation motion of CCH molecule. In the latter system investigated at a high temperature of about 40 K, the constant R(V) due to thermal hopping followed by the rapid increase is satisfactory explained by anharmonic inter-mode coupling between the scissor mode excited by tunneling electrons and the frustrated translation mode for H(D)2O molecule on Pd(111).

  12. The production rate of cosmogenic deuterium at the Moon's surface

    Science.gov (United States)

    Füri, Evelyn; Deloule, Etienne; Trappitsch, Reto

    2017-09-01

    The hydrogen (D/H) isotope ratio is a key tracer for the source of planetary water. However, secondary processes such as solar wind implantation and cosmic ray induced spallation reactions have modified the primordial D/H signature of 'water' in all rocks and soils recovered on the Moon. Here, we re-evaluate the production rate of cosmogenic deuterium (D) at the Moon's surface through ion microprobe analyses of hydrogen isotopes in olivines from eight Apollo 12 and 15 mare basalts. These in situ measurements are complemented by CO2 laser extraction-static mass spectrometry analyses of cosmogenic noble gas nuclides (3He, 21Ne, 38Ar). Cosmic ray exposure (CRE) ages of the mare basalts, derived from their cosmogenic 21Ne content, range from 60 to 422 Ma. These CRE ages are 35% higher, on average, than the published values for the same samples. The amount of D detected in the olivines increases linearly with increasing CRE ages, consistent with a production rate of (2.17 ± 0.11) ×10-12 mol(g rock)-1 Ma-1. This value is more than twice as high as previous estimates for the production of D by galactic cosmic rays, indicating that for water-poor lunar samples, i.e., samples with water concentrations ≤50 ppm, corrected D/H ratios have been severely overestimated.

  13. Maximum, minimum, and optimal mutation rates in dynamic environments

    Science.gov (United States)

    Ancliff, Mark; Park, Jeong-Man

    2009-12-01

    We analyze the dynamics of the parallel mutation-selection quasispecies model with a changing environment. For an environment with the sharp-peak fitness function in which the most fit sequence changes by k spin flips every period T , we find analytical expressions for the minimum and maximum mutation rates for which a quasispecies can survive, valid in the limit of large sequence size. We find an asymptotic solution in which the quasispecies population changes periodically according to the periodic environmental change. In this state we compute the mutation rate that gives the optimal mean fitness over a period. We find that the optimal mutation rate per genome, k/T , is independent of genome size, a relationship which is observed across broad groups of real organisms.

  14. Surface roughness and removal rate in magnetorheological finishing of a subsurface damage free surface

    Institute of Scientific and Technical Information of China (English)

    CHENG Haobo; WANG Yingwei; FENG Zhijing; CHENG Kai

    2005-01-01

    Based on computer-controlled optical surfacing, a new technique called magnetorheological finishing (MRF), is presented. The new technique combines the features of conventional loose abrasive machining with a wheel shaped polishing tool. The tool incorporates a host of features and has unprecedented fabricating versatility. The pre-polishing and fine polishing processes can be performed only by adjusting different parameters. The material removal function is studied theoretically and the results of simulation present a Gaussian distribution feature. Based on the established theoretical model, material removal rate experiments involving a parabolic mirror are designed and carried out to determine the effect of controllable parameters on size of the gap between the workpiece and the polishing wheel,rotating speed of the polishing wheel, concentration of volume fraction of non-magnetic particles and polishing time. Further experiments are carried out on the surface microstructure of the workpiece, the final surface roughness with an initial value of 10.98 nm reaches 1.22 nm root mean square (RMS) after 20 min of polishing. The subsurface damage experiment and the atomic force microscopy (AFM)measurement on the polished surface can also verify the feasibility of the MRF technique.

  15. Rate of evolution of the specific surface area of surface snow layers.

    Science.gov (United States)

    Cabanes, Axel; Legagneux, Loïc; Dominé, Florent

    2003-02-15

    The snowpack can impact atmospheric chemistry by exchanging adsorbed or dissolved gases with the atmosphere. Modeling this impact requires the knowledge of the specific surface area (SSA) of snow and its variations with time. We have therefore measured the evolution of the SSA of eight recent surface snow layers in the Arctic and the French Alps, using CH4 adsorption at liquid nitrogen temperature (77 K). The SSA of fresh snow layers was found to decrease with time, from initial values in the range 613-1540 cm2/g to values as low as 257 cm2/g after 6 days. This is explained by snow metamorphism, which causes modifications in crystal shapes, here essentially crystal rounding and the disappearance of microstructures. A parametrization of the rate of SSA decrease is proposed. We fit the SSA decrease to an exponential law and find that the time constant alpha(exp) (day(-1)) depends on temperature according to alpha(exp) = 76.6 exp (-1708/7), with Tin kelvin. Our parametrization predicts that the SSA of a snow layer evolving at -40 degrees C will decrease by a factor of 2 after 14 days, while a similar decrease at -1 degrees C will only require 5 days. Wind was found to increase the rate of SSA decrease, but insufficient data did not allow a parametrization of this effect.

  16. Inelastic quasiparticle lifetimes of the Shockley surface state band on Ni(111)

    Energy Technology Data Exchange (ETDEWEB)

    Braun, Kai-Felix [Ohio University, Nanoscale and Quantum Phenomena Institute, Physics and Astronomy Department, Athens, OH (United States); Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Hla, Saw-Wai [Ohio University, Nanoscale and Quantum Phenomena Institute, Physics and Astronomy Department, Athens, OH (United States); Samango GmbH, Darmstadt (Germany)

    2010-03-15

    We present a study of the low-energy quasiparticle lifetimes of the Shockley surface state on the Ni(111) surface with scanning tunnelling spectroscopy. By measuring the coherence length of the decaying standing wave pattern at straight step edges electron and hole lifetimes have been determined. The values of the lifetime measured on this ferromagnetic surface show to be considerable smaller than the values obtained from noble metal surfaces. This is explained by differences in the electron density of states at the Fermi energy but has to include substantial spin-flip scattering. Furthermore hole lifetimes appear to be larger than electron lifetimes with the same excitation energy. Although only results for the majority spin component are presented, a spin-dependent selfenergy is expected. (orig.)

  17. Transport Rate of Surface Erosion by the Hydrodynamics

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The coherence and exposure degree are used in analyzing initiation of slope sediment.The initial ve- locity is built by using a critical roiling model.A transport rate formula of slope erosion is established using the Meyer-Peter model.The formula is tested by experiment and agrees well but the errors are big when the flow discharge and rain intensity are smaller.

  18. Continuous Rating for Diggability Assessment in Surface Mines

    Science.gov (United States)

    IPHAR, Melih

    2016-10-01

    The rocks can be loosened either by drilling-blasting or direct excavation using powerful machines in opencast mining operations. The economics of rock excavation is considered for each method to be applied. If blasting operation is not preferred and also the geological structures and rock mass properties in site are convenient (favourable ground conditions) for ripping or direct excavation method by mining machines, the next step is to determine which machine or excavator should be selected for the excavation purposes. Many researchers have proposed several diggability or excavatability assessment methods for deciding on excavator type to be used in the field. Most of these systems are generally based on assigning a rating for the parameters having importance in rock excavation process. However, the sharp transitions between the two adjacent classes for a given parameter can lead to some uncertainties. In this paper, it has been proposed that varying rating should be assigned for a given parameter called as “continuous rating” instead of giving constant rating for a given class.

  19. Effects of mass flow rate and droplet velocity on surface heat flux during cryogen spray cooling

    Energy Technology Data Exchange (ETDEWEB)

    Karapetian, Emil [Department of Chemical Engineering and Material Sciences, University of California, Irvine, CA (United States); Aguilar, Guillermo [Department of Biomedical Engineering, University of California, Irvine, CA (United States); Kimel, Sol [Beckman Laser Institute, University of California, Irvine, CA (United States); Lavernia, Enrique J [Department of Chemical Engineering and Material Sciences, University of California, Irvine, CA (United States); Nelson, J Stuart [Department of Biomedical Engineering, University of California, Irvine, CA (United States)

    2003-01-07

    Cryogen spray cooling (CSC) is used to protect the epidermis during dermatologic laser surgery. To date, the relative influence of the fundamental spray parameters on surface cooling remains incompletely understood. This study explores the effects of mass flow rate and average droplet velocity on the surface heat flux during CSC. It is shown that the effect of mass flow rate on the surface heat flux is much more important compared to that of droplet velocity. However, for fully atomized sprays with small flow rates, droplet velocity can make a substantial difference in the surface heat flux. (note)

  20. Effect of surface orientation on dissolution rates and topography of CaF2

    Science.gov (United States)

    Godinho, J. R. A.; Piazolo, S.; Evins, L. Z.

    2012-06-01

    This paper reports how during dissolution differences in surface chemistry affect the evolution of topography of CaF2 pellets with a microstructure similar to UO2 spent nuclear fuel. 3D confocal profilometry and atomic force microscopy were used to quantify retreat rates and analyze topography changes on surfaces with different orientations as dissolution proceeds up to 468 h. A NaClO4 (0.05 M) solution with pH 3.6 which was far from equilibrium relative to CaF2 was used. Measured dissolution rates depend directly on the orientation of the exposed planes. The {1 1 1} is the most stable plane with a dissolution rate of (1.2 ± 0.8) × 10-9 mol m-2 s-1, and {1 1 2} the least stable plane with a dissolution rate 33 times faster that {1 1 1}. Surfaces that expose both Ca and F atoms in the same plane dissolve faster. Dissolution rates were found to be correlated to surface orientation which is characterized by a specific surface chemistry and therefore related to surface energy. It is proposed that every surface is characterized by the relative proportions of the three reference planes {1 1 1}, {1 0 0} and {1 1 0}, and by the high energy sites at their interceptions. Based on the different dissolution rates observed we propose a dissolution model to explain changes of topography during dissolution. Surfaces with slower dissolution rate, and inferred lower surface energy, tend to form while dissolution proceeds leading to an increase of roughness and surface area. This adjustment of the surface suggests that dissolution rates during early stages of dissolution are different from the later stages. The time-dependency of this dynamic system needs to be taken into consideration when predicting long-term dissolution rates.

  1. Heat and mass transfer rates during flow of dissociated hydrogen gas over graphite surface

    Science.gov (United States)

    Nema, V. K.; Sharma, O. P.

    1986-01-01

    To improve upon the performance of chemical rockets, the nuclear reactor has been applied to a rocket propulsion system using hydrogen gas as working fluid and a graphite-composite forming a part of the structure. Under the boundary layer approximation, theoretical predictions of skin friction coefficient, surface heat transfer rate and surface regression rate have been made for laminar/turbulent dissociated hydrogen gas flowing over a flat graphite surface. The external stream is assumed to be frozen. The analysis is restricted to Mach numbers low enough to deal with the situation of only surface-reaction between hydrogen and graphite. Empirical correlations of displacement thickness, local skin friction coefficient, local Nusselt number and local non-dimensional heat transfer rate have been obtained. The magnitude of the surface regression rate is found low enough to ensure the use of graphite as a linear or a component of the system over an extended period without loss of performance.

  2. Surface reaction rate and probability of ozone and alpha-terpineol on glass, polyvinyl chloride, and latex paint surfaces.

    Science.gov (United States)

    Shu, Shi; Morrison, Glenn C

    2011-05-15

    Ozone can react homogeneously with unsaturated organic compounds in buildings to generate undesirable products. However, these reactions can also occur on indoor surfaces, especially for low-volatility organics. Conversion rates of ozone with α-terpineol, a representative low-volatility compound, were quantified on surfaces that mimic indoor substrates. Rates were measured for α-terpineol adsorbed to beads of glass, polyvinylchloride (PVC), and dry latex paint, in a plug flow reactor. A newly defined second-order surface reaction rate coefficient, k(2), was derived from the flow reactor model. The value of k(2) ranged from 0.68 × 10(-14) cm(4)s(-1)molecule(-1) for α-terpineol adsorbed to PVC to 3.17 × 10(-14) cm(4)s(-1)molecule(-1) for glass, but was insensitive to relative humidity. Further, k(2) is only weakly influenced by the adsorbed mass but instead appears to be more strongly related to the interfacial activity α-terpineol. The minimum reaction probability ranged from 3.79 × 10(-6) for glass at 20% RH to 6.75 × 10(-5) for PVC at 50% RH. The combination of high equilibrium surface coverage and high reactivity for α-terpineol suggests that surface conversion rates are fast enough to compete with or even overwhelm other removal mechanisms in buildings such as gas-phase conversion and air exchange.

  3. Micro Wire Electro Discharge Grinding: Optimization of Material Removal Rate and Surface Roughness

    Science.gov (United States)

    Yeakub Ali, Mohammad; Rahman, Mohamed Abd; Nordin, Rosmarina

    2017-03-01

    This paper presents the analysis and modelling of material removal rate (MRR) and surface roughness (Ra) by micro wire electro discharge grinding (micro-WEDG) with control parameter of gap voltage, feed rate, and spindle speed. The data were analyzed and empirical models are developed. The optimized values of MRR and Ra are 0.051 mm3/min and 0.25 μm respectively with 110 V gap voltage, 38 μm/s feed rate, and 1315 rpm spindle speed. The analysis showed that gap voltage has significant effect on material removal rate while spindle speed has significant effect on surface roughness.

  4. Size dependence of surface thermodynamic properties of nanoparticles and its determination method by reaction rate constant

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wenjiao; Xue, Yongqiang, E-mail: xyqlw@126.com; Cui, Zixiang

    2016-08-15

    Surface thermodynamic properties are the fundamental properties of nanomaterials, and these properties depend on the size of nanoparticles. In this paper, relations of molar surface thermodynamic properties and surface heat capacity at constant pressure of nanoparticles with particle size were derived theoretically, and the method of obtaining the surface thermodynamic properties by reaction rate constant was put forward. The reaction of nano-MgO with sodium bisulfate solution was taken as a research system. The influence regularities of the particle size on the surface thermodynamic properties were discussed theoretically and experimentally, which show that the experimental regularities are in accordance with the corresponding theoretical relations. With the decreasing of nanoparticle size, the molar surface thermodynamic properties increase, while the surface heat capacity decreases (the absolute value increases). In addition, the surface thermodynamic properties are linearly related to the reciprocal of nanoparticle diameter, respectively.

  5. The effect of heating rate on the surface chemistry of NiTi.

    Science.gov (United States)

    Undisz, Andreas; Hanke, Robert; Freiberg, Katharina E; Hoffmann, Volker; Rettenmayr, Markus

    2014-11-01

    The impact of the heating rate on the Ni content at the surface of the oxide layer of biomedical NiTi is explored. Heat treatment emulating common shape-setting procedures was performed by means of conventional and inductive heating for similar annealing time and temperature, applying various heating rates from ~0.25 K s(-1) to 250 K s(-1). A glow discharge optical emission spectroscopy method was established and employed to evaluate concentration profiles of Ni, Ti and O in the near-surface region at high resolution. The Ni content at the surface of the differently treated samples varies significantly, with maximum surface Ni concentrations of ~20 at.% at the lowest and ~1.5 at.% at the highest heating rate, i.e. the total amount of Ni contained in the surface region of the oxide layer decreases by >15 times. Consequently, the heating rate is a determinant for the biomedical characteristics of NiTi, especially since Ni available at the surface of the oxide layer may affect the hemocompatibility and be released promptly after surgical application of a respective implant. Furthermore, apparently contradictory results presented in the literature reporting surface Ni concentrations of ~3 at.% to >20 at.% after heat treatment are consistently explained considering the ascertained effect of the heating rate.

  6. Experimental Test of“Parity-Time Asymmetry”in Electron Spin-Flip Raman Scattering of the N+H…O Hydrogen Bond in Chiral Alanine Crystals%“宇称-时间不对称”的实验探索:手性丙氨酸单晶NH…O氢键的电子自旋翻转相变的不对称拉曼散射

    Institute of Scientific and Technical Information of China (English)

    王文清; 龚; 沈新春; 张玉凤

    2013-01-01

      手性丙氨酸单晶的极性N+H…O氢键在~270 K的自发对称性破缺,可用变温拉曼振动光谱在b(cc)b几何条件下在线测定.由于其对手性的灵敏度,可以测定D-和L-丙氨酸的N+H…O氢键在电子自旋翻转相变时的微小能差.晶体定向能量的正/负,在于电子自旋的上/下转向,取决于原子内在磁场的方向.变温拉曼振动光谱可以观察到:在D-和L-丙氨酸单晶之间,拉曼散射光子的波数位移方向相反,散射光子的不对称度约为1/3.由于自旋是轴矢量,样品必须是单晶,沿轴向测定.多晶粉末不能观察到相变.与次甲基(Cα-H)在260 K的自旋翻转相变,用变温拉曼振动光谱在c(aa)c几何条件下的相对测量结果接近一致.本实验提供了一条证明真实手性和“宇称-时间(PT)不对称”的新线索.%Spontaneous symmetry breaking of the N+H…O bond in chiral alanine crystals around 270 K was detected in situ by Raman vibrational scattering with b(cc)b geometry. An electron spin-flip transition of the N+H…O mode in D-/L-alanine was observed by the scattering of light with left/right orientation and its spin projection antiparal el to the direction of propagation. It is an internal magnetic field originated from the spin-orbit interaction. An obvious Raman wavenumber shift with opposite in sign and roughly one third of the asymmetry (A) of the scattered photon between D-and L-alanine crystals was observed. This shift was not seen in polycrystal ine powder measurements because spin is an axial vector. An electron spin-flip transition of the methyne (Cα-H) mode around 260 K was shown to be approximative coincidence by examining the temperature-dependent relative intensity of asymmetric Raman scattering with c(aa)c geometry. This article provides evidence for the true chirality and parity-time (PT) asymmetry in molecular clusters of D-and L-alanine crystals.

  7. The effect of surface cover on infiltration rate in steep forest plantations

    Science.gov (United States)

    Hiraoka, M.; Onda, Y.; Kato, H.; Ito, S.; Mizugaki, S.

    2007-12-01

    The Japanese cypress (Hinoki; Chamaecyparis obtusa) is a major commercial tree species in Japan, and without thinning of high-density stands, canopy closure prevents development of understory vegetation. Therefore there is a concern for overlandflow and sediment yield due to infiltration rate lowering from steep hillslopes of Japanese cypress plantation. We developed a light-weight rainfall simulator based on the design of Meyer and Harmon (1979). A flat fan Veejet 80150 spraying nozzle (Spraying systems Co., USA) is mounted on the manifold at 2.13 m high from the plot surface. The nozzle oscillates so that the spray fans swept across the targeting 1m x 1m plot. The Veejet 80150 spraying nozzle produces large raindrops larger than 2 mm in diameter, and can simulate the high raindrop kinetic energy of natural storm. A targeted rainfall rate is 180 mm/h. Total 25 sprinkling experiments have been conducted on 35-degree hillslopes with varying surface cover. We obtained the minimum infiltration rate of 14 mm/h where the surface cover is very little. The infiltration rates were plotted against the total understory vegetation and dry weight of total surface cover including litter. The infiltration rate increased with the increasing total surface cover, and higher regression coefficient is obtained for the case of the total surface cover. These results will contribute to the future modeling studies of overlandflow occurrences for the catchment scales.

  8. Wear rate and surface coating optimization of coconut coir-based polymer using fuzzy logic

    Indian Academy of Sciences (India)

    SRINIVASAN S P; RAAJARAJAN L

    2017-03-01

    The use of fuzzy logic for modeling surface parameters of coconut coir-based composite is the focus of this research paper. Natural fiber–polymer composite has been developed by combining coconut coir as a stimulator and polyester as a fixative. This sturdy material is resistant to scratches in the coating process on the surface layer of composite material. The specimen of this composite material is fabricated by different coir fiber and resin content. A polyurethane coating is also applied with varied thickness to give better wear rate and surface coating properties. A fuzzy logic approach is adopted to invent the optimal wear rate and surface coating using coating thickness and fiber content properties. The results indicate the best combinations of coatingthickness and its surface roughness of the sandwiches. MATLAB 7 is used in this work.

  9. Fuzzy prediction and experimental verification of road surface cleaning rate by pure waterjets

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The cleaning parameters affecting cleaning rate using pure waterjets to clean road surface was researched. A mathematical model for predicting cleaning rate was established using fuzzy mathematical method. A fuzzy rule base characterizing the relationship between input and output parameters was built through experiments. The prediction of cleaning rate was achieved under the condition of given input parameters by rule-based fuzzy reasoning. The prediction results were analyzed through experimental verification.

  10. Decay rates of large-l Rydberg states of multiply charged ions approaching solid surfaces

    Science.gov (United States)

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

    2008-07-01

    We investigate the ionization of large-l multiply charged Rydberg ions approaching solid surfaces within the framework of decay model and applying the etalon equation method. The radial coordinate rho of the active electron is treated as a variational parameter and therefore the parabolic symmetry is preserved in this procedure. The complex eigenenergies are calculated from which the energy terms and the ionization rates are derived. We find that the large-l Rydberg states decay at approximately the same ion-surface distances as the low-l states oriented toward the vacuum and considerably closer to the surface comparing to the low-l states oriented towards the surface.

  11. Effect of surface chemistry on the rate of osseointegration of sintered porous-surfaced Ti-6Al-4V implants.

    Science.gov (United States)

    Taché, Alex; Gan, Lu; Deporter, Douglas; Pilliar, Robert M

    2004-01-01

    The effect of adding a thin sol-gel-formed calcium phosphate (CaP) coating to sintered porous-surfaced titanium alloy (Ti-6Al-4V) implants on rates of initial bone ingrowth was investigated. Control implants (as manufactured) and similar implants with sol-gel CaP coatings were randomly placed in distal femoral rabbit condyles (1 implant/leg). After healing for 6, 9, 12, and 16 days, 8 of 10 rabbits in each time group were assessed for maximum implant pullout force (N) and interface stiffness (N/mm). Selected extracted implants also were examined by secondary electron imaging to characterize affected surfaces. The implants of the remaining 2 rabbits in each group were examined by backscattered scanning electron microscopy (BSEM). Significantly greater pullout forces and interface stiffness were found for CaP-coated implants at 6 and 9 days. At 6 days, BSEM revealed bone ingrowth on CaP-coated implants but not on control implants. Secondary electron imaging and BSEM observations also suggested greater bone ingrowth with CaP-coated porous implants at 9, 12, and 16 days. Sol-gel-formed CaP surface films significantly enhance rates of bone ingrowth into sintered porous-surfaced implants. This surface treatment may have a number of clinical benefits, including shortening the period prior to functional loading of such implants and improving treatment outcomes in situations of poor bone quality and/or quantity. (More than 50 references).

  12. Surface supersaturation in flow-rate modulation epitaxy of GaN

    Science.gov (United States)

    Akasaka, Tetsuya; Lin, Chia-Hung; Yamamoto, Hideki; Kumakura, Kazuhide

    2017-06-01

    Hillocks on N-face GaN (000 1 bar) films are effectively eliminated by group-III-source flow-rate modulation epitaxy (FME), wherein the flow-rate of group-III sources are sequentially modulated under a constant supply of NH3. A hillock-free smooth surface obtained by group-III-source FME is attributed to the enhancement of step-flow growth. We found that a hillock originates from a micropipe and grows by spiral growth around the micropipe. The spiral growth rate rapidly decreases with decreasing the degree of surface supersaturation σ, while the step-flow growth rate decreases linearly. For group-III-source FME, wherein σ is lower than conventional continuous growth, the spiral growth rate could be lower than the step-flow growth one so that the formation of hillocks is suppressed.

  13. Direct Measurement of Surface Dissolution Rates in Potential Nuclear Waste Forms: The Example of Pyrochlore.

    Science.gov (United States)

    Fischer, Cornelius; Finkeldei, Sarah; Brandt, Felix; Bosbach, Dirk; Luttge, Andreas

    2015-08-19

    The long-term stability of ceramic materials that are considered as potential nuclear waste forms is governed by heterogeneous surface reactivity. Thus, instead of a mean rate, the identification of one or more dominant contributors to the overall dissolution rate is the key to predict the stability of waste forms quantitatively. Direct surface measurements by vertical scanning interferometry (VSI) and their analysis via material flux maps and resulting dissolution rate spectra provide data about dominant rate contributors and their variability over time. Using pyrochlore (Nd2Zr2O7) pellet dissolution under acidic conditions as an example, we demonstrate the identification and quantification of dissolution rate contributors, based on VSI data and rate spectrum analysis. Heterogeneous surface alteration of pyrochlore varies by a factor of about 5 and additional material loss by chemo-mechanical grain pull-out within the uppermost grain layer. We identified four different rate contributors that are responsible for the observed dissolution rate range of single grains. Our new concept offers the opportunity to increase our mechanistic understanding and to predict quantitatively the alteration of ceramic waste forms.

  14. Material Removal Rate, Electrode Wear Rate, and Surface Roughness Evaluation in Die Sinking EDM with Hollow Tool through Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Teepu Sultan

    2014-01-01

    Full Text Available Electrical discharge machining is one of the earliest nontraditional machining, extensively used in industry for processing of parts having unusual profiles with reasonable precision. In the present work, an attempt has been made to model material removal rate, electrode wear rate, and surface roughness through response surface methodology in a die sinking EDM process. The optimization was performed in two steps using one factor at a time for preliminary evaluation and a Box-Behnken design involving three variables with three levels for determination of the critical experimental conditions. Pulse on time, pulse off time, and peak current were changed during the tests, while a copper electrode having tubular cross section was employed to machine through holes on EN 353 steel alloy workpiece. The results of analysis of variance indicated that the proposed mathematical models obtained can adequately describe the performances within the limits of factors being studied. The experimental and predicted values were in a good agreement. Surface topography is revealed with the help of scanning electron microscope micrographs.

  15. Effects of surface orientation, fluid chemistry and mechanical polishing on the variability of dolomite dissolution rates

    Science.gov (United States)

    Saldi, Giuseppe D.; Voltolini, Marco; Knauss, Kevin G.

    2017-06-01

    Recent studies of carbonate surface reactivity have underscored the fundamental variability of dissolution rates and the heterogeneous distribution of the reaction over the mineral surface due to the inhomogeneous distribution of surface energy. Dolomite dissolution rates relative to different cleavage planes (r-planes) and surfaces cut approximately perpendicular to the c-axis (c-planes) were studied at 50 °C as a function of pH (3.4 ≤ pH ≤ 9.0) and solution composition by vertical scanning interferometry (VSI) and atomic force microscopy (AFM), with the aim of providing an estimate of the intrinsic rate variation of dolomite single crystals and describing the surface reaction distribution and the rate controlling mechanisms. Surface normal retreat rates measured under acidic conditions increased linearly with time and were not visibly affected by the parallel increase of surface roughness. Mean total dissolution rates of r-planes decreased by over 200 times from pH 3.4 to pH 9.0 and CO32--rich solutions, whereas corresponding rate variations spanned over 3 orders of magnitude when also c-plane rate distributions were included in the analysis. At acid to near neutral pH, c-planes dissolved ∼ three times faster than the adjoining r-planes but slower at basic pH and high total carbon concentration, displaying a distinctive morphologic evolution in these two regimes. The comparison of polished and unpolished crystals showed that polished cleavage planes dissolved about three times faster than the unpolished counterpart at near neutral to basic conditions, whereas no significant difference in reactivity was observed at pH topography over the course of the reaction, the evolution of the entire crystal morphology depends also on the reactivity of edge and corner regions, whose contribution to measured rates is not generally taken into account by laboratory experiments. The study of time-dependent mineral morphology and reactivity requires an integrated approach

  16. The effect of surface cover and soil devastation on infiltration rate in steep forest plantations

    Science.gov (United States)

    Onda, Y.; Hiraoka, M.; Kato, H.; Gomi, T.; Miyata, S.; Mizugaki, S.

    2008-12-01

    The Japanese cypress (Hinoki; Chamaecyparis obtusa) is a major commercial tree species in Japan, and without thinning of high-density stands, canopy closure prevents development of understory vegetation. Therefore there is a concern for overlandflow and sediment yield due to infiltration rate lowering. We developed a light-weight rainfall simulator based on the design of Meyer and Harmon (1979). A flat fan Veejet 80150 spraying nozzle (Spraying systems Co., USA) is mounted on the manifold at 2.13 m high from the plot surface. The nozzle oscillates so that the spray fan sweeps across the targeting 1 m x 1 m plot. The Veejet 80150 spraying nozzle produces large raindrops larger than 2 mm in diameter, and can simulate the high raindrop kinetic energy of natural throughfall. A targeted rainfall rate is 180 mm/h. About 30 sprinkling experiments have been conducted on 35-degree hillslopes with varying surface cover in 5 locations in Japan. We obtained the minimum infiltration rate of 14 mm/h where the surface cover is very little. The infiltration rates were plotted against the total understory vegetation and dry weight of total surface cover including litter. The infiltration rate increased with the increasing total surface cover, and generally higher regression coefficient was found for the case of the total surface cover. In some cases, high infiltration rates were obtained where surface cover is low. Two possible explanations can be made; 1) surface soil (especially fine particles) has been washed away, where soil is mostly composed of gravel and the percentage of fine fraction is low, or 2) because of long-term soil loss by raindrop detachment, remaining soil looks like "ghanging"h between exposed fine root networks of Japanese cypress, where soil bulk density is significantly lower than other site. Therefore the infiltration rate in the devastated Japanese cypress plantations is not only controlled by loss of surface vegetation by low light condition, but soil

  17. Adsorption rate of phenol from aqueous solution onto organobentonite: surface diffusion and kinetic models.

    Science.gov (United States)

    Ocampo-Perez, Raul; Leyva-Ramos, Roberto; Mendoza-Barron, Jovita; Guerrero-Coronado, Rosa M

    2011-12-01

    The concentration decay curves for the adsorption of phenol on organobentonite were obtained in an agitated tank batch adsorber. The experimental adsorption rate data were interpreted with diffusional models as well as first-order, second-order and Langmuir kinetic models. The surface diffusion model adjusted the data quite well, revealing that the overall rate of adsorption was controlled by surface diffusion. Furthermore, the surface diffusion coefficient increased raising the mass of phenol adsorbed at equilibrium and was independent of the particle diameter in the range 0.042-0.0126 cm. It was demonstrated that the overall rate of adsorption was essentially not affected by the external mass transfer. The second-order and the Langmuir kinetic models fitted the experimental data quite well; however, the kinetic constants of both models varied without any physical meaning while increasing the particle size and the mass of phenol adsorbed at equilibrium. Copyright © 2011 Elsevier Inc. All rights reserved.

  18. Effects of Asymmetrical Micro Electrode Surface Topography to AC Electroosmosis flow Rate

    CERN Document Server

    Hong-Yuan, Jiang; Zhen-Xiu, Hou; Yu-Kun, Ren; Yong-Jun, Sun

    2010-01-01

    AC Electroosmosis (ACEO) has many advantages such as low power consumption, non-moving parts, and easy to integrate etc., so it is widely used for low concentration microfluid manipulation in low frequency range. Classical ACEO theory assumes that electric double layer (EDL) is the main cause of electric field induced flow, and gives electric-flow field coupling equations for ACEO flow rate. But the calculation data usually are tens times faster than the experimental velocities. In this paper, electrode surface topography is included to solve ACEO flow rate. With electrode surface roughness as the characteristic parameter, equivalent EDL model is set up to modify the classical EDL model. The relationship between flow rate and electrode surface roughness is studied. Experiment results agree with the simulation very well, proving the feasibility of equivalent EDL model.

  19. Carbon Surface Layers on a High-Rate LiFePO4

    Energy Technology Data Exchange (ETDEWEB)

    Gabrisch, Heike; Wilcox, James D.; Doeff, Marca M.

    2005-09-06

    Transmission electron microscopy (TEM) was used to image particles of a high-rate LiFePO4 sample containing a small amount of in situ carbon. The particle morphology is highly irregular, with a wide size distribution. Nevertheless, coatings, varying from about 5-10 nm in thickness, could readily be detected on surfaces of particles as well as on edges of agglomerates. Elemental mapping using Energy Filtered TEM (EFTEM) indicates that these very thin surface layers are composed of carbon. These observations have important implications for the design of high-rate LiFePO4 materials in which, ideally, a minimal amount of carbon coating is used.

  20. Estimating spatially distributed monthly evapotranspiration rates by linear transformations of MODIS daytime land surface temperature data

    Directory of Open Access Journals (Sweden)

    J. Szilagyi

    2009-05-01

    Full Text Available Under simplifying conditions catchment-scale vapor pressure at the drying land surface can be calculated as a function of its watershed-representative temperature (<Ts> by the wet-surface equation (WSE, similar to the wet-bulb equation in meteorology for calculating the dry-bulb thermometer vapor pressure of the Complementary Relationship of evaporation. The corresponding watershed ET rate, , is obtained from the Bowen ratio with the help of air temperature, humidity and percent possible sunshine data. The resulting (<Ts>, pair together with the wet-environment surface temperature (<Tws> and ET rate (ETw, obtained by the Priestley-Taylor equation, define a linear transformation on a monthly basis by which spatially distributed ET rates can be estimated as a sole function of MODIS daytime land surface temperature, Ts, values within the watershed. The linear transformation preserves the mean which is highly desirable. <Tws>, in the lack of significant open water surfaces within the study watershed (Elkhorn, Nebraska, was obtained as the mean of the smallest MODIS Ts values each month. The resulting period-averaged (2000–2007 catchment-scale ET rate of 624 mm/yr is very close to the water-balance derived ET rate of about 617 mm/yr. The latter is a somewhat uncertain value due to the effects of (a observed groundwater depletion of about 1m over the study period caused by extensive irrigation, and; (b the uncertain rate of net regional groundwater supply toward the watershed. The spatially distributed ET rates correspond well with soil/aquifer properties and the resulting land use type (i.e. rangeland versus center-pivot irrigated crops.

  1. The role of advanced reactive surface area characterization in improving predictions of mineral reaction rates

    Science.gov (United States)

    Beckingham, L. E.; Zhang, S.; Mitnick, E.; Cole, D. R.; Yang, L.; Anovitz, L. M.; Sheets, J.; Swift, A.; Kneafsey, T. J.; Landrot, G.; Mito, S.; Xue, Z.; Steefel, C. I.; DePaolo, D. J.; Ajo Franklin, J. B.

    2014-12-01

    Geologic sequestration of CO2 in deep sedimentary formations is a promising means of mitigating carbon emissions from coal-fired power plants but the long-term fate of injected CO2 is challenging to predict. Reactive transport models are used to gain insight over long times but rely on laboratory determined mineral reaction rates that have been difficult to extrapolate to field systems. This, in part, is due to a lack of understanding of mineral reactive surface area. Many models use an arbitrary approximation of reactive surface area, applying orders of magnitude scaling factors to measured BET or geometric surface areas. Recently, a few more sophisticated approaches have used 2D and 3D image analyses to determine mineral-specific reactive surface areas that account for the accessibility of minerals. However, the ability of these advanced surface area estimates to improve predictions of mineral reaction rates has yet to be determined. In this study, we fuse X-ray microCT, SEM QEMSCAN, XRD, SANS, and SEM-FIB analysis to determine mineral-specific accessible reactive surface areas for a core sample from the Nagaoka pilot CO2 injection site (Japan). This sample is primarily quartz, plagioclase, smectite, K-feldspar, and pyroxene. SEM imaging shows abundant smectite cement and grain coatings that decrease the fluid accessibility of other minerals. However, analysis of FIB-SEM images reveals that smectite nano-pores are well connected such that access to underlying minerals is not occluded by smectite coatings. Mineral-specific accessible surfaces are determined, accounting for the connectivity of the pore space with and without connected smectite nano-pores. The large-scale impact of variations in accessibility and dissolution rates are then determined through continuum scale modeling using grid-cell specific information on accessible surface areas. This approach will be compared with a traditional continuum scale model using mineral abundances and common surface area

  2. Effect of Heating Rates on the Formable Oxide Scale on a C-Steel Surface

    Institute of Scientific and Technical Information of China (English)

    A.A.El-Meligi

    2004-01-01

    Oxide scale formation on a C-steel surface has been investigated using linear heating rates ranging from 0.1℃/min to 10℃/min at high temperatures. The studies on the oxide scale formation at high temperature (650℃) at slower heating rate (0.1℃/min) shows that the kinetic regime is linear. X-ray diffraction measurements revealed that the scale constituents are significantly influenced by the heating rate. The adherence of the scale was improved by using slower heating rate (0.1℃/min-≤650℃),while above such degree the scale was susceptible to cracking and flaking out of the alloy surface. In fact, the development of oxide growth stresses can cause considerable scale cracking. As well, variation of the crystallite sizes under the aforementioned conditions might affect the scale stacking to the alloy surface. The secondary electron detector images of the oxide scale shows that the scale was imperfectly smooth and there were a number of voids and defects in the scale skin, especially at fast heating rate. This observation could be attributed to defects of the as-received alloy. In general, slower heating rate reduced the defects of the scale and improved its adherence.

  3. The nucleation rate surfaces design over diagram of phase equilibria and their applications for computational chemistry

    Science.gov (United States)

    Anisimov, M. P.

    2016-12-01

    One can find in scientific literature a pretty fresh idea of the nucleation rate surfaces design over the diagrams of phase equilibria. That idea looks like profitable for the nucleation theory development and for various practical applications where predictions of theory have no high enough accuracy for today. The common thermodynamics has no real ability to predict parameters of the first order phase transition. Nucleation experiment can be provided in very local nucleation conditions even the nucleation takes place from the critical line (in two-component case) down to the absolute zero temperature limit and from zero nucleation rates at phase equilibria up to the spinodal conditions. Theory predictions have low reliability as a rule. The computational chemistry has chance to make solution of that problem easier when a set of the used axiomatic statements will adapt enough progressive assumptions [1]. Semiempirical design of the nucleation rate surfaces over diagrams of phase equilibria have a potential ability to provide a reasonable quality information on nucleation rate for each channel of nucleation. Consideration and using of the nucleation rate surface topologies to optimize synthesis of a given phase of the target material can be available when data base on nucleation rates over diagrams of phase equilibria will be created.

  4. Prediction of material removal rate and surface roughness for wire electrical discharge machining of nickel using response surface methodology

    Directory of Open Access Journals (Sweden)

    Thangam Chinnadurai

    2016-12-01

    Full Text Available This study focuses on investigating the effects of process parameters, namely, Peak current (Ip, Pulse on time (Ton, Pulse off time (Toff, Water pressure (Wp, Wire feed rate (Wf, Wire tension (Wt, Servo voltage (Sv and Servo feed setting (Sfs, on the Material Removal Rate (MRR and Surface Roughness (SR for Wire electrical discharge machining (Wire-EDM of nickel using Taguchi method. Response Surface Methodology (RSM is adopted to evolve mathematical relationships between the wire cutting process parameters and the output variables of the weld joint to determine the welding input parameters that lead to the desired optimal wire cutting quality. Besides, using response surface plots, the interaction effects of process parameters on the responses are analyzed and discussed. The statistical software Mini-tab is used to establish the design and to obtain the regression equations. The developed mathematical models are tested by analysis-of-variance (ANOVA method to check their appropriateness and suitability. Finally, a comparison is made between measured and calculated results, which are in good agreement. This indicates that the developed models can predict the responses accurately and precisely within the limits of cutting parameter being used.

  5. The effect of loading rate on ductile fracture toughness and fracture surface roughness

    DEFF Research Database (Denmark)

    Osovski, S.; Srivastava, Akhilesh Kumar; Ponson, L.

    2015-01-01

    The variation of ductile crack growth resistance and fracture surface roughness with loading rate is modeled under mode I plane strain, small scale yielding conditions. Three-dimensional calculations are carried out using an elastic-viscoplastic constitutive relation for a progressively cavitatin...

  6. Is there a link between blastomere contact surfaces of day 3 embryos and live birth rate?

    Directory of Open Access Journals (Sweden)

    Paternot Goedele

    2012-09-01

    Full Text Available Abstract Background Cell-cell communication and adhesion are essential for the compaction process of early stage embryos. The aim of this study was to develop a non-invasive objective calculation system of embryo compaction in order to test the hypothesis that embryos with a larger mean contact surface result in a higher live birth rate compared to embryos with a lower mean contact surface. Methods Multilevel images of 474 embryos transferred on day 3 were evaluated by the Cellify software. This software calculates the contact surfaces between the blastomeres. The primary outcome of this study was live birth. An ideal range of contact surface was determined and the positive and negative predictive value, the sensitivity, the specificity and the area under the curve for this new characteristic were calculated. Results In total, 115 (24% transferred embryos resulted in a live birth. Selection of an embryo for transfer on its mean contact surface could predict live birth with a high sensitivity (80% and high negative predicting value (83% but with a low positive predictive value (27%, a low specificity (31% and low area under the ROC curve (0.56. The mean contact surface of embryos cultured in a single medium was significantly higher compared to the mean contact surface of embryos cultured in a sequential medium (p = 0.0003. Conclusions Neither the mean contact surface nor the number of contact surfaces of a day 3 embryo had an additional value in the prediction of live birth. The type of culture medium, however, had an impact on the contact surface of an embryo. Embryos cultured in a single medium had a significant larger contact surface compared to embryos cultured in the sequential medium.

  7. Thermodynamics of a dry atmosphere at different surface exchange rates and rotation speeds

    CERN Document Server

    Pascale, Salvatore; Lucarini, Valerio; Wang, Yixiong

    2012-01-01

    We study the combined effect of the rotation speed {\\Omega} and of the surface exchange rate - quantified by a surface turbulent relaxation timescale {\\tau} - on the dissipative properties of an Earth-like dry atmosphere. The rotation speed {\\Omega} is varied between one tenth and eight times that of the Earth {\\Omega} \\approx 7.29\\cdot10-5 rad-1 and {\\tau} from 45 minutes to 500 days. We study the circulation regimes induced by such parametric variations through two key dimensionless parameters, the thermal Rossby number Ro and the frictional dimensionless number Ff. An extensive analysis is performed by using nonequilibrium thermodynamics diagnostic tools such as material entropy production, efficiency, meridional heat transport and kinetic energy dissipation. The thermal dissipation associated with the sensible heat flux is found to depend mainly on the surface properties and to be almost independent from the rotation rate, whereas the dissipation of kinetic energy depends in a nontrivial way on both. Slow...

  8. Effect of surface structure of kaolinite on aggregation, settling rate, and bed density.

    Science.gov (United States)

    Du, Jianhua; Morris, Gayle; Pushkarova, Rada A; Smart, Roger St C

    2010-08-17

    The flocculation and solid/liquid separation of four well-characterized kaolinites (2 well, 2 poorly crystallized) have been studied for comparison of surface structure (SEM), aggregate structure during flocculation (cryo-SEM), settling rate, and bed density (with raking). It is shown that major differences in these properties are largely due to crystallinity and consequent surface structure of the extensive (larger dimension "basal") face. Well-crystallized kaolinites, with higher Hinckley indices and lower aspect ratios, have relatively smooth, flat basal surfaces and thicker edge planes promoting both effective initial bridging flocculation (largely edge-edge) and structural rearrangement to face-face during the raking process. This results in faster settling rates and more compact bed structures. Poorly crystallized kaolinites, with low Hinckley indices and high aspect ratios, exhibit ragged, stepped structures of the extensive face with a high proportion of nanosized islands forming cascade-like steps (i.e., multiple edges) contributing up to 30% of the specific surface area and providing flocculant adsorption sites (hydroxyl groups) across this extensive face. This leads to bridging flocculation taking place on both edge and extensive ("basal") planes, producing low-density edge-face structures during flocculation which leads to slow settling rates and poor bed densities. In particular, the complex surface morphology of the poorly crystallized kaolinites resists the transformation of edge-face structures to dense face-face structures under shear force introduced by raking. This results in low sediment density for poorly crystallized kaolinites. The studies suggest that the main influence on settling rates and bed densities of kaolinites in mineral tailings is likely to be related to the crystallinity and surface morphology of the kaolinite. They also suggest that interpretation of kaolinite behavior based on models of a flat (001) basal plane and edge sites

  9. Size dependence of volume and surface nucleation rates for homogeneous freezing of supercooled water droplets

    Directory of Open Access Journals (Sweden)

    T. Kuhn

    2009-10-01

    Full Text Available We investigated the relative roles of volume and surface nucleation in the freezing of water droplets. Nucleation experiments were carried out in a cryogenic laminar aerosol flow tube using supercooled liquid water aerosols with radii between about 1 and 3 μ m. Temperature- and size-dependent values of volume- and surface-based homogeneous nucleation rate between 234.8 and 236.2 K are derived with help of a microphysical model from aerosol compositions and size distributions based on infrared extinction measurements in the aerosol flow tube. The results show that the contribution from nucleation at the droplet surface increases with decreasing droplet radius and dominates over nucleation in the bulk droplet volume for droplets with radii smaller than approximately 5 μm. This is interpreted in terms of a lowered free energy of ice germ formation in the surface-based process and has implications for the parameterization of homogeneous ice nucleation in numerical models.

  10. Evaluation of Finite-Rate GasSurface Interaction Models for a Carbon Based Ablator

    Science.gov (United States)

    Chen, Yih-Kanq; Goekcen, Tahir

    2015-01-01

    Two sets of finite-rate gas-surface interaction model between air and the carbon surface are studied. The first set is an engineering model with one-way chemical reactions, and the second set is a more detailed model with two-way chemical reactions. These two proposed models intend to cover the carbon surface ablation conditions including the low temperature rate-controlled oxidation, the mid-temperature diffusion-controlled oxidation, and the high temperature sublimation. The prediction of carbon surface recession is achieved by coupling a material thermal response code and a Navier-Stokes flow code. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and Ablation Program, which predicts charring material thermal response and shape change on hypersonic space vehicles. The flow code solves the reacting full Navier-Stokes equations using Data Parallel Line Relaxation method. Recession analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities with heat fluxes ranging from 45 to 1100 wcm2 are performed and compared with data for model validation. The ablating material used in these arc-jet tests is Phenolic Impregnated Carbon Ablator. Additionally, computational predictions of surface recession and shape change are in good agreement with measurement for arc-jet conditions of Small Probe Reentry Investigation for Thermal Protection System Engineering.

  11. Micrometeorological Measurements of Air-Surface Exchange Rates of PBTs in the Great Lakes Region

    Science.gov (United States)

    Tobias, D. E.; Perlinger, J. A.; Morrow, P.

    2002-12-01

    The fate of persistent bioaccumulative toxic chemicals (PBTs) in the environment is controlled by their exchange with various aquatic and terrestrial surfaces. Many of the PBTs are semivolatile and present in the atmosphere almost entirely in the vapor phase. The rate of exchange of these vapor phase chemicals can be predicted from physicochemical properties of the chemical and the surface and the meteorological conditions during the exchange. However, field studies of the uptake of the PBTs are extremely limited or nonexistent making it difficult to evaluate the modeled transfer velocities. This presentation describes a novel method to directly measure air-surface exchange rates of PBTs above aquatic and terrestrial surfaces by the micrometeorological technique known as the modified Bowen ratio approach. Simultaneous measurements of the air temperature, water vapor content, windspeed, and the chemical species concentration at two heights above the surface are required to derive the transfer velocity of the chemical. Advanced techniques that minimize the number of sample preparation steps are required to make the two concentration measurements with adequate relative accuracy. To accomplish this task, ambient air is sampled with a multicapillary column and the analytes are directly desorbed into a high-resolution gas chromatograph for quantitation. This presentation will summarize preliminary measurements made in the near-shore region of Upper Michigan's Keweenaw Peninsula on Lake Superior during the summer of 2001 and 2002.

  12. The effect of corrosion induced surface morphology changes on ultrasonically monitored corrosion rates

    Science.gov (United States)

    Gajdacsi, Attila; Cegla, Frederic

    2016-11-01

    Corrosion rates obtained by very frequent (daily) measurements with permanently installed ultrasonic sensors have been shown to be highly inaccurate when changes in surface morphology lead to ultrasonic signal distortion. In this paper the accuracy of ultrasonically estimated corrosion rates (mean wall thickness loss) by means of standard signal processing methods (peak to peak—P2P, first arrival—FA, cross correlation—XC) was investigated and a novel thickness extraction algorithm (adaptive cross-correlation—AXC) is presented. All of the algorithms were tested on simulated ultrasonic data that was obtained by modelling the surface geometry evolution coupled with a fast ultrasonic signal simulator based on the distributed point source method. The performance of each algorithm could then be determined by comparing the actual known mean thickness losses of the simulated surfaces to the values that each algorithm returned. The results showed that AXC is the best of the investigated processing algorithms. For spatially random thickness loss 90% of AXC estimated thickness trends were within -10 to +25% of the actual mean loss rate (e.g. 0.75-1.1 mm year-1 would be measured for a 1 mm year-1 actual mean loss rate). The other algorithms (P2P, FA, XC) exhibited error distributions that were 5-10 times larger. All algorithms performed worse in scenarios where wall loss was not distributed randomly in space (spatially correlated thickness loss occured) and where the overall rms of the surface was either growing or declining. However, on these surfaces AXC also outperformed the other algorithms and showed almost an order of magnitude improvement compared to them.

  13. Probing long-lived dark excitons in self-assembled quantum dots

    DEFF Research Database (Denmark)

    Johansen, Jeppe; Julsgaard, Brian; Stobbe, Søren;

    2010-01-01

    size. The energy dependence is compared to a recent model from the literature, in which the spin flip is due to the combined action of short-range exchange interaction and acoustic phonons. We furthermore observe a pronounced enhancement of the spin-flip rate close to semiconductor-air interfaces......-resolved spontaneous emission measurements in a modified local density of optical states to unambiguously record the spin-flip rate. Pronounced variations in the spin-flip rate with the quantum dot emission energy are observed demonstrating that the exciton storage time can be extended by controlling the quantum dot...

  14. Surface loss rate of H and N radicals in H2/N2 plasma etching process

    Science.gov (United States)

    Moon, Chang Sung; Takeda, Keigo; Hayashi, Toshio; Takashima, Seigo; Sekine, Makoto; Setsuhara, Yuichi; Shiratani, Masaharu; Hori, Masaru

    2008-10-01

    As ULSI devices are down to nano-scale size, there have been many efforts to develop low dielectric constant (low-k) materials and establish the plasma etching technology. Especially, the interaction between the plasma and the surface has an enormous influence on characterizing the etching process. However, the reactions in contact with solid surface such as substrate and wall are very complicated and moreover, at present, there are many interactions unknown and they are not fully understood yet. In this study, surface loss probabilities of H, N radicals on stainless steel and organic low-k film surfaces are investigated by vacuum ultraviolet absorption spectroscopy (VUVAS) technique. The changes of H, N radical densities are quantitatively measured in H2/N2 plasma afterglow and the loss rates on each surface are evaluated. It is expected that the development of plasma etching process can be advanced by understanding the reaction of radicals with the surface during organic low-k etching process.

  15. Relationship between Spreading Rate and Wetting Behaviour of Oil on Surface of Surfactant Solution

    Institute of Scientific and Technical Information of China (English)

    YE Xi; CHENG Yang; HUANG Xue-Dong; MA Hong-Ru

    2007-01-01

    @@ We report a systematic investigation of the spreading of a polydimethylsiloxane oil layer on flat surfaces of solution containing anionic surfactant of sodium dodecylsulfate. The experiment reveals that different wetting behaviours of the oil follow different spreading rates. In the case of complete wetting, it obeys a 0. 75 power law, while in the pseudopartial wetting it follows a non-power law. The results can well be explained by a new simple theory of spreading. The theory further predicts that for a complete wetting state there exists another spreading rate.

  16. The surface-forming energy release rate based fracture criterion for elastic-plastic crack propagation

    Science.gov (United States)

    Xiao, Si; Wang, He-Ling; Liu, Bin; Hwang, Keh-Chih

    2015-11-01

    The J-integral based criterion is widely used in elastic-plastic fracture mechanics. However, it is not rigorously applicable when plastic unloading appears during crack propagation. One difficulty is that the energy density with plastic unloading in the J-integral cannot be defined unambiguously. In this paper, we alternatively start from the analysis on the power balance, and propose a surface-forming energy release rate (ERR), which represents the energy available for separating the crack surfaces during the crack propagation and excludes the loading-mode-dependent plastic dissipation. Therefore the surface-forming ERR based fracture criterion has wider applicability, including elastic-plastic crack propagation problems. Several formulae are derived for calculating the surface-forming ERR. From the most concise formula, it is interesting to note that the surface-forming ERR can be computed using only the stress and deformation of the current moment, and the definition of the energy density or work density is avoided. When an infinitesimal contour is chosen, the expression can be further simplified. For any fracture behaviors, the surface-forming ERR is proven to be path-independent, and the path-independence of its constituent term, so-called Js-integral, is also investigated. The physical meanings and applicability of the proposed surface-forming ERR, traditional ERR, Js-integral and J-integral are compared and discussed. Besides, we give an interpretation of Rice paradox by comparing the cohesive fracture model and the surface-forming ERR based fracture criterion.

  17. Neural-estimator for the surface emission rate of atmospheric gases

    CERN Document Server

    Paes, F F

    2009-01-01

    The emission rate of minority atmospheric gases is inferred by a new approach based on neural networks. The neural network applied is the multi-layer perceptron with backpropagation algorithm for learning. The identification of these surface fluxes is an inverse problem. A comparison between the new neural-inversion and regularized inverse solution id performed. The results obtained from the neural networks are significantly better. In addition, the inversion with the neural netwroks is fster than regularized approaches, after training.

  18. Rate of evaporation from the free surface of a heated liquid

    Science.gov (United States)

    Örvös, M.; Szabó, V.; Poós, T.

    2016-11-01

    A method and an experimental setup are developed for determining the intensity of evaporation from the free surface of water. During the measurement, the ambient air velocity and the water temperature can be varied. The mass and temperature of water, as well as the temperature, pressure, and humidity of the ambient air are measured as functions of time. The evaporation rates are calculated from the measured and recorded data in the cases of natural and forced convection.

  19. Characterization of MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces

    Directory of Open Access Journals (Sweden)

    Venkatakrishnan Krishnan

    2011-01-01

    Full Text Available Abstract In this study, MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces under ambient condition were characterized by scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction analysis (XRD, and X-ray photoelectron spectroscopy (XPS. The radiation fluence used was 0.5 J/cm2 at a pulse repetition rate of 25 MHz with 1 ms interaction time. SEM analysis of the irradiated surfaces showed self-assembled intermingled weblike nanofibrous structure in and around the laser-irradiated spots. Further TEM investigation on this nanostructure revealed that the nanofibrous structure is formed due to aggregation of Au-Si/Si nanoparticles. The XRD peaks at 32.2°, 39.7°, and 62.5° were identified as (200, (211, and (321 reflections, respectively, corresponding to gold silicide. In addition, the observed chemical shift of Au 4f and Si 2p lines in XPS spectrum of the irradiated surface illustrated the presence of gold silicide at the irradiated surface. The generation of Si/Au-Si alloy fibrous nanoparticles aggregate is explained by the nucleation and subsequent condensation of vapor in the plasma plume during irradiation and expulsion of molten material due to high plasma pressure.

  20. The effect of loading rate on ductile fracture toughness and fracture surface roughness

    Science.gov (United States)

    Osovski, S.; Srivastava, A.; Ponson, L.; Bouchaud, E.; Tvergaard, V.; Ravi-Chandar, K.; Needleman, A.

    2015-03-01

    The variation of ductile crack growth resistance and fracture surface roughness with loading rate is modeled under mode I plane strain, small scale yielding conditions. Three-dimensional calculations are carried out using an elastic-viscoplastic constitutive relation for a progressively cavitating solid with two populations of void nucleating second phase particles. Larger inclusions that result in void nucleation at an early stage are modeled as discrete void nucleation sites while smaller particles that require large strains to nucleate voids are homogeneously distributed. The calculations are carried out for two values of density of the larger inclusions, 3.6% and 7.1%, and for prescribed loading rates K˙˙I ranging from 1 ×105 MPa√{ m }s-1 to 5 ×107 MPa√{ m }s-1. The ductile fracture mode is found to undergo a transition from one that can be regarded as growth of a dominant main crack at the lower loading rates to one dominated by damage nucleation and micro-cracking ahead of the main crack at the higher loading rates. The values of JIC, the tearing modulus, TR, the total plastic dissipation and the plastic dissipation in the fracture process region are all found to increase with increasing loading rate. However, the ratio of plastic dissipation in the fracture process region to total plastic dissipation decreases with increasing prescribed loading rate. The fracture surfaces are found to display two self-affine regimes, with a Hurst exponent β ≈ 0.60 at small length scales and with β ≈ 0.45 at larger length scales. The multi-fractal spectra indicate multi-affine behavior in most cases but a range of loading rates and length scales exhibiting mono-affine behavior is also found. Parameters characterizing the fracture surface statistics, including the length scale at which a transition from a power law tail to an exponential tail occurs, are related to the mode of crack growth/damage accumulation. A linear relation is found between the values of JIC

  1. Differences in rates of decrease of environmental radiation dose rates by ground surface property in Fukushima City after the Fukushima Daiichi nuclear power plant accident.

    Science.gov (United States)

    Kakamu, Takeyasu; Kanda, Hideyuki; Tsuji, Masayoshi; Kobayashi, Daisuke; Miyake, Masao; Hayakawa, Takehito; Katsuda, Shin-ichiro; Mori, Yayoi; Okouchi, Toshiyasu; Hazama, Akihiro; Fukushima, Tetsuhito

    2013-01-01

    After the Great East Japan Earthquake on 11 March 2011, the environmental radiation dose in Fukushima City increased. On 11 April, 1 mo after the earthquake, the environmental radiation dose rate at various surfaces in the same area differed greatly by surface property. Environmental radiation measurements continue in order to determine the estimated time to 50% reduction in environmental radiation dose rates by surface property in order to make suggestions for decontamination in Fukushima. The measurements were carried out from 11 April to 11 November 2011. Forty-eight (48) measurement points were selected, including four kinds of ground surface properties: grass (13), soil (5), artificial turf (7), and asphalt (23). Environmental radiation dose rate was measured at heights of 100 cm above the ground surface. Time to 50% reduction of environmental radiation dose rates was estimated for each ground surface property. Radiation dose rates on 11 November had decreased significantly compared with those on 11 April for all surface properties. Artificial turf showed the longest time to 50% reduction (544.32 d, standard error: 96.86), and soil showed the shortest (213.20 d, standard error: 35.88). The authors found the environmental radiation dose rate on artificial materials to have a longer 50% reduction time than that on natural materials. These results contribute to determining an order of priority for decontamination after nuclear disasters.

  2. Size dependence of volume and surface nucleation rates for homogeneous freezing of supercooled water droplets

    Directory of Open Access Journals (Sweden)

    T. Kuhn

    2011-03-01

    Full Text Available The relative roles of volume and surface nucleation were investigated for the homogeneous freezing of pure water droplets. Experiments were carried out in a cryogenic laminar aerosol flow tube using supercooled water aerosols with maximum volume densities at radii between 1 and 3 μm. Temperature- and size-dependent values of volume- and surface-based homogeneous nucleation rates between 234.8 and 236.2 K were derived using a microphysical model and aerosol phase compositions and size distributions determined from infrared extinction measurements in the flow tube. The results show that the contribution from nucleation at the droplet surface increases with decreasing droplet radius and dominates over nucleation in the bulk droplet volume for droplets with radii smaller than approximately 5 μm. This is interpreted in terms of a lowered free energy of ice germ formation in the surface-based process. The implications of surface nucleation for the parameterization of homogeneous ice nucleation in numerical models are considered.

  3. Complex Wind-Induced Variations of Surface Snow Accumulation Rates over East Antarctica

    Science.gov (United States)

    Das, I.; Scambos, T. A.; Koenig, L.; van den Broeke, M.; Lenaerts, J.

    2015-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. Using airborne radar, lidar and thresholds of surface slope, modeled surface mass balance (SMB) and wind fields, we have predicted continent-wide distribution of wind-scour zones over Antarctica. These zones are located over relatively steep ice surfaces formed by ice flow over bedrock topography. Near-surface winds accelerate over these steeper slopes and erode and sublimate the snow. This results in numerous localized regions (typically ≤ 200 km2) with reduced or negative surface accumulation. Although small zones of re-deposition occur at the base of the steeper slope areas, the redeposited mass is small relative to the ablation loss. Total losses from wind-scour and wind-glaze areas amounts to tens of gigatons annually. Near the coast, winds often blow significant amounts of surface snow from these zones into the ocean. Large uncertainties remain in SMB estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss or redistribution over the wind-scour zones. In this study, we also use Operation IceBridge's snow radar data to provide evidence for a gradual ablation of ~16-18 m of firn (~200 years of accumulation) from wind-scour zones over the upper Recovery Ice Stream catchment. The maximum ablation rates observed in this region are ~ -54 kg m-2 a-1 (-54 mm water equivalent a-1). Our airborne radio echo-sounding analysis show snow redeposition downslope of the wind-scour zones is <10% of the cumulative mass loss. Our study shows that the local mass loss is dominated by sublimation to water vapor rather than wind-transport of snow.

  4. Radon and Thoron Exhalation Rates from Surface Soil of Bangka - Belitung Islands, Indonesia

    Directory of Open Access Journals (Sweden)

    Syarbaini Syarbaini

    2015-03-01

    Full Text Available DOI:10.17014/ijog.2.1.35-42Radon and thoron exhalation rate from soil is one of the most important factors that can influence the radioactivity level in the environment. Radon and thoron gases are produced by the decay of the radioactive elements those are radium and thorium in the soil, where its concentration depends on the soil conditions and the local geological background. In this paper, the results of radon and thoron exhalation rate measurements from surface soil of Bangka Belitung Islands at thirty six measurement sites are presented. Exhalation rates of radon and thoron were measured by using an accumulation chamber equipped with a solid-state alpha particle detector. Furthermore, the correlations between radon and thoron exhalation rates with their parent nuclide (226Ra and 232Th concentrations in collected soil samples from the same locations were also evaluated. The result of the measurement shows that mostly the distribution of radon and thoron is similar to 226Ra and 232Th, eventhough it was not a good correlation between radon and thoron exhalation rate with their parent activity concentrations (226Ra and 232Th due to the environmental factors that can influence the radon and thoron mobilities in the soil. In comparison to a world average, Bangka Belitung Islands have the 222Rn and 220Rn exhalation rates higher than the world average value for the regions with normal background radiation.

  5. Near-surface air temperature lapse rates in Xinjiang, northwestern China

    Science.gov (United States)

    Du, Mingxia; Zhang, Mingjun; Wang, Shengjie; Zhu, Xiaofan; Che, Yanjun

    2017-01-01

    Lapse rates of near-surface (2 m) air temperature are important parameters in hydrologic and climate simulations, especially for the mountainous areas without enough in-situ observations. In Xinjiang, northwestern China, the elevations range from higher than 7000 m to lower than sea level, but the existing long-term meteorological measurements are limited and distributed unevenly. To calculate lapse rates in Xinjiang, the daily data of near-surface air temperature (T min, T ave, and T max) were measured by automatic weather stations from 2012 to 2014. All the in situ observation stations were gridded into a network of 1.5° (latitude) by 1.5° (longitude), and the spatial distribution and the daily, monthly, seasonal variations of lapse rates for T min, T ave, and T max in Xinjiang are analyzed. The Urumqi River Basin has been considered as a case to study the influence of elevation, aspect, and the wet and dry air conditions to the T min, T ave, and T max lapse rates. Results show that (1) the lapse rates for T min, T ave, and T max vary spatially during the observation period. The spatial diversity of T min lapse rates is larger than that of T ave, and that of T max is the smallest. For each season, T max lapse rates have more negative values than T ave lapse rates which are steeper than T min lapse rates. The weakest spatial diversity usually appears in July throughout a year. (2) The comparison for the three subregions (North, Middle, and South region) exhibits that lapse rates have similar day-to-day and month-to-month characteristics which present shallower values in winter months and steeper values in summer months. The T ave lapse rates in North region are shallower than those in Middle and South region, and the steepest T ave lapse rates of the three regions all appear in April. T min lapse rates are shallower than T max lapse rates. The maximum medians of T min and T max lapse rates for each grid in the three regions all appear in January, whereas the

  6. Surface activity distribution measurements and establishment of a dose rate map inside the destroyed Chernobyl reactor

    Energy Technology Data Exchange (ETDEWEB)

    Chesnokov, A.V.; Fedin, V.I.; Gulyaev, A.A. [RECOM Ltd., Moscow (Russian Federation)] [and others

    1999-02-01

    A Gamma Locator designed for contamination survey inside the reactor hall of the 4th unit of Chernobyl NNP has been developed. The device consists of a detector head and a remote control computer connected by a 150 m long cable. The detector head (dimensions: 500 mm by 500 mm by 400 mm; weight: about 40 kg) is a collimated scintillation gamma detector (the collimation angle is 10 deg.). It is installed on a scanning unit and was placed inside the reactor hall. The Gamma Locator scans all surfaces of the reactor hall with angular steps ({<=} 1 deg. vertically as well as horizontally) and the particle fluence from the corresponding direction is recorded. The distance between the device head and the measured surface is instantaneously registered by a laser distance gauge. Inside the collimator there is a small CCD camera which makes it possible to obtain a visible image of the measured surface. The effective surface activity levels are presented in colour on the screen of the control computer. The gamma detector essentially consists of a CsI(TI) scintillator crystal ({phi} 8 mm in diameter, 2.5 mm in thickness) and a Si photodiode. The detector energy resolution is about 8% for radiation from {sup 137}Cs. The exposure dose rate distribution in the reactor hall is estimated from the measured effective surface activities ({sup 137}Cs is the main gamma emitting isotope inside the reactor hall). The results of dose rate calculations are presented in colour superposed on a drawing of the reactor hall. (au) 1 tab., 28 ills., 16 refs.

  7. Platelets interact with tissue factor immobilized on surfaces: effects of shear rate.

    Science.gov (United States)

    Tonda, R; Lopez-Vilchez, I; Navalon, F; Pino, M; Hernandez, M R; Escolar, G; Galan, A M

    2008-01-01

    While procoagulant activities of Tissue Factor (TF) have been widely investigated, its possible pro-adhesive properties towards platelets have not been studied in detail. We explored the interaction of platelets with human Tissue Factor (hTF) firmly adsorbed on a synthetic surface of polyvinilidene difluoride (PVDF) using different shear rates. For studies at 250 and 600 s(-1), TF firmly adsorbed was exposed to flowing anticoagulated blood in flat perfusion devices. Deposition of platelets and fibrin were evaluated by morphometric, immunocytochemical and ultrastructural methods. Prothrombin fragment 1 + 2 (F1 + 2) levels were also measured. Experiments at 5000 s(-1), were performed on the Platelet Function Analyzer (PFA-100) with experimental cartridges with collagen (COL) or collagen-hTF (COL + TF). Haemostatic effect of recombinant activated FVIIa (rFVIIa) was assessed in the same experimental settings. Platelet deposition on hTF reached 19.8 +/- 1.3% and 26.1 +/- 3.4% of the total surface, at 250 and 600 s(-1), respectively. Fibrin formation was significantly higher at 250 s(-1) than at 600 s(-1) (P hTF (154.09 +/- 14.69 s vs. 191.45 +/- 16.09 s COL alone; P hTF is an adhesive substrate for platelets and suggest that the von Willebrand factor could mediate these interactions. At low and intermediate shear rates, rFVIIa enhanced the procoagulant action of hTF, but this effect was not observed at very high shear rates.

  8. Rainfall timing and poultry litter application rate effects on phosphorus loss in surface runoff.

    Science.gov (United States)

    Schroeder, P D; Radcliffe, D E; Cabrera, M L

    2004-01-01

    Phosphorus (P) in runoff from pastures amended with poultry litter may be a significant contributor to eutrophication of lakes and streams in Georgia and other areas in the southeastern United States. The objectives of this research were to determine the effects of litter application rate and initial runoff timing on the long-term loss of P in runoff from surface-applied poultry litter and to develop equations that predict P loss in runoff under these conditions. Litter application rates of 2, 7, and 13 Mg ha(-1), and three rainfall scenarios applied to 1- x 2-m plots in a 3 x 3 randomized complete block design with three replications. The rainfall scenarios included (i) sufficient rainfall to produce runoff immediately after litter application; (ii) no rainfall for 30 d after litter application; and (iii) small rainfall events every 7 d (5 min at 75 mm h(-1)) for 30 d. Phosphorus loss was greatest from the high litter rate and immediate runoff treatments. Nonlinear regression equations based on the small plot study produced fairly accurate (r(2) = 0.52-0.62) prediction of P concentrations in runoff water from larger (0.75 ha) fields over a 2-yr period. Predicted P concentrations were closest to observed values for events that occurred shortly after litter application, and the relative error in predictions increased with time after litter application. In addition, previously developed equations relating soil test P levels to runoff P concentrations were ineffective in the presence of surface-applied litter.

  9. Escaping the correction for body surface area when calculating glomerular filtration rate in children

    Energy Technology Data Exchange (ETDEWEB)

    Piepsz, Amy; Tondeur, Marianne [CHU St. Pierre, Department of Radioisotopes, Brussels (Belgium); Ham, Hamphrey [University Hospital Ghent, Department of Nuclear Medicine, Ghent (Belgium)

    2008-09-15

    {sup 51}Cr ethylene diamine tetraacetic acid ({sup 51}Cr EDTA) clearance is nowadays considered as an accurate and reproducible method for measuring glomerular filtration rate (GFR) in children. Normal values in function of age, corrected for body surface area, have been recently updated. However, much criticism has been expressed about the validity of body surface area correction. The aim of the present paper was to present the normal GFR values, not corrected for body surface area, with the associated percentile curves. For that purpose, the same patients as in the previous paper were selected, namely those with no recent urinary tract infection, having a normal left to right {sup 99m}Tc MAG3 uptake ratio and a normal kidney morphology on the early parenchymal images. A single blood sample method was used for {sup 51}Cr EDTA clearance measurement. Clearance values, not corrected for body surface area, increased progressively up to the adolescence. The percentile curves were determined and allow, for a single patient, to estimate accurately the level of non-corrected clearance and the evolution with time, whatever the age. (orig.)

  10. Effect of Surface Microstructure on the Temperature sensitivity of Burning Rate of Ammonium Perchlorate

    Directory of Open Access Journals (Sweden)

    K. Kishore

    1997-04-01

    Full Text Available Considering Vielle's law and the new thermodynamic model which the authors have developed recently the true dependence of temperature sensitivity of burning rate of ammonium perchlorate (AP on pressure is resolved and experimentally verified for bellet burning. The value of decreases with pressure steeply in regime I' (below 20 atm, but gently in regime I (above 20 atm. The value of powder AP has been determined and it is observed that (powder > (pellet, which clearly suggests that of is innuenced by the surface temperature sensitive parameter and hence by the surface/subsurface microstructure. In powder burning, the buoyant lifting of the particles into the gas phase occurs, Which constitutes the so-called 'free board region' (FER extending just above the true surface. Consequent to the decomposition of AP particles in FER, the condensed phase heat release gets curtailed and (powder becomes larger. A general relationship for in terms of density and surface temperature is suggested, which is applicable to both pellet and powder AP.

  11. Effects of surface cracks and strain rate on the tensile behavior of Balmoral Red granite

    Directory of Open Access Journals (Sweden)

    Mardoukhi Ahmad

    2015-01-01

    Full Text Available This paper presents an experimental procedure for studying the effects of surface cracks on the mechanical behavior of Balmoral Red granite under dynamic and quasi-static loading. Three different thermal shocks were applied on the surface of the Brazilian Disc test samples by keeping a flame torch at a fixed distance from the sample surface for 10, 30, and 60 seconds. Microscopy clearly shows that the number of the surface cracks increases with the duration of the thermal shock. After the thermal shock, the Brazilian Disc tests were performed using a servohydraulic materials testing machine and a compression Split Hopkinson Pressure Bar (SHPB device. The results show that the tensile strength of the rock decreases and the rate sensitivity of the rock increases as more cracks are introduced to the structure. The DIC analysis of the Brazilian disc tests shows that the fracture of the sample initiates at the center of the samples or slightly closer to the incident bar contact point. This is followed by crushing of the samples at both contact points with the stress bars.

  12. Dosimetric perturbations of a lead shield for surface and interstitial high-dose-rate brachytherapy.

    Science.gov (United States)

    Candela-Juan, Cristian; Granero, Domingo; Vijande, Javier; Ballester, Facundo; Perez-Calatayud, Jose; Rivard, Mark J

    2014-06-01

    In surface and interstitial high-dose-rate brachytherapy with either (60)Co, (192)Ir, or (169)Yb sources, some radiosensitive organs near the surface may be exposed to high absorbed doses. This may be reduced by covering the implants with a lead shield on the body surface, which results in dosimetric perturbations. Monte Carlo simulations in Geant4 were performed for the three radionuclides placed at a single dwell position. Four different shield thicknesses (0, 3, 6, and 10 mm) and three different source depths (0, 5, and 10 mm) in water were considered, with the lead shield placed at the phantom surface. Backscatter dose enhancement and transmission data were obtained for the lead shields. Results were corrected to account for a realistic clinical case with multiple dwell positions. The range of the high backscatter dose enhancement in water is 3 mm for (60)Co and 1 mm for both (192)Ir and (169)Yb. Transmission data for (60)Co and (192)Ir are smaller than those reported by Papagiannis et al (2008 Med. Phys. 35 4898-4906) for brachytherapy facility shielding; for (169)Yb, the difference is negligible. In conclusion, the backscatter overdose produced by the lead shield can be avoided by just adding a few millimetres of bolus. Transmission data provided in this work as a function of lead thickness can be used to estimate healthy organ equivalent dose saving. Use of a lead shield is justified.

  13. 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

  14. Theoretical Standard Model Rates of Proton to Neutron Conversions Near Metallic Hydride Surfaces

    CERN Document Server

    Widom, A

    2006-01-01

    The process of radiation induced electron capture by protons or deuterons producing new ultra low momentum neutrons and neutrinos may be theoretically described within the standard field theoretical model of electroweak interactions. For protons or deuterons in the neighborhoods of surfaces of condensed matter metallic hydride cathodes, such conversions are determined in part by the collective plasma modes of the participating charged particles, e.g. electrons and protons. The radiation energy required for such low energy nuclear reactions may be supplied by the applied voltage required to push a strong charged current across a metallic hydride surface employed as a cathode within a chemical cell. The electroweak rates of the resulting ultra low momentum neutron production are computed from these considerations.

  15. A Finite-Rate Gas-Surface Interaction Model Informed by Fundamental Computational Chemistry Simulations

    Science.gov (United States)

    2013-03-31

    oxygen interactions with a specific crystalline polymorph of SiO2 (called β- cristobalite ). Computer images of this crystal lattice are shown in Fig...2. The choice of β- cristobalite is motivated by experimental studies from Balat-Pichelin et al. [15,22,23] where silicon-carbide (SiC) surfaces were...conclusion that the measured loss rates correspond to β- cristobalite was based on the fact that for polymorph diagrams of SiO2, β- cristobalite is most stable

  16. A Surface Heat Disturbance Method for Measuring Local TIssue Blood Perfusion Rate

    Institute of Scientific and Technical Information of China (English)

    PengJianshu; TianYongquan

    1996-01-01

    A non-damage method for measuring local tissue blood perfusion rate by surface heat disturbance and its two special embodiments for realizing this measurement are presented in this paper,In the derivation of mathematical model,the Pennes equation is used,and two parameters which are very diffcult to be known-the arterial blood temperature Ta and the metabolic heat generation rate qm,have been eliminated.So if has provided a feasible basis for application.In this paper,the performance and the adaptable condition of the measurement method and its structure peculiarities are discussed over a wide variety of parameters.Moreover,the effectiveness of the measurement method has been demonstrated by means of the quantitative measurement of tissue in vitro,the comparative measurement of animal under artificial perfusion and the dependence measurement in human body.

  17. Solute transport predicts scaling of surface reaction rates in porous media: Applications to silicate weathering

    CERN Document Server

    Hunt, Allen G; Ghanbarian, Behzad

    2013-01-01

    We apply our theory of conservative solute transport, based on concepts from percolation theory, directly and without modification to reactive solute transport. This theory has previously been shown to predict the observed range of dispersivity values for conservative solute transport over ten orders of magnitude of length scale. We now show that the temporal dependence derived for the solute velocity accurately predicts the time-dependence for the weathering of silicate minerals over nine orders of magnitude of time scale, while its predicted length dependence agrees with data obtained for reaction rates over five orders of magnitude of length scale. In both cases, it is possible to unify lab and field results. Thus, net reaction rates appear to be limited by solute transport velocities. We suggest the possible relevance of our results to landscape evolution of the earth's terrestrial surface.

  18. Ab Initio Calculation of Rate Constants for Molecule–Surface Reactions with Chemical Accuracy

    Science.gov (United States)

    Piccini, GiovanniMaria; Alessio, Maristella

    2016-01-01

    Abstract The ab initio prediction of reaction rate constants for systems with hundreds of atoms with an accuracy that is comparable to experiment is a challenge for computational quantum chemistry. We present a divide‐and‐conquer strategy that departs from the potential energy surfaces obtained by standard density functional theory with inclusion of dispersion. The energies of the reactant and transition structures are refined by wavefunction‐type calculations for the reaction site. Thermal effects and entropies are calculated from vibrational partition functions, and the anharmonic frequencies are calculated separately for each vibrational mode. This method is applied to a key reaction of an industrially relevant catalytic process, the methylation of small alkenes over zeolites. The calculated reaction rate constants (free energies), pre‐exponential factors (entropies), and enthalpy barriers show that our computational strategy yields results that agree with experiment within chemical accuracy limits (less than one order of magnitude). PMID:27008460

  19. Enhanced Sensitivity of Surface Acoustic Wave-Based Rate Sensors Incorporating Metallic Dot Arrays

    Directory of Open Access Journals (Sweden)

    Wen Wang

    2014-02-01

    Full Text Available A new surface acoustic wave (SAW-based rate sensor pattern incorporating metallic dot arrays was developed in this paper. Two parallel SAW delay lines with a reverse direction and an operation frequency of 80 MHz on a same X-112°Y LiTaO3 wafer are fabricated as the feedback of two SAW oscillators, and mixed oscillation frequency was used to characterize the external rotation. To enhance the Coriolis force effect acting on the SAW propagation, a copper (Cu dot array was deposited along the SAW propagation path of the SAW devices. The approach of partial-wave analysis in layered media was referred to analyze the response mechanisms of the SAW based rate sensor, resulting in determination of the optimal design parameters. To improve the frequency stability of the oscillator, the single phase unidirectional transducers (SPUDTs and combed transducer were used to form the SAW device to minimize the insertion loss and accomplish the single mode selection, respectively. Excellent long-term (measured in hours frequency stability of 0.1 ppm/h was obtained. Using the rate table with high precision, the performance of the developed SAW rate sensor was evaluated experimentally; satisfactory detection sensitivity (16.7 Hz∙deg∙s−1 and good linearity were observed.

  20. Enhanced sensitivity of surface acoustic wave-based rate sensors incorporating metallic dot arrays.

    Science.gov (United States)

    Wang, Wen; Shao, Xiuting; Liu, Xinlu; Liu, Jiuling; He, Shitang

    2014-02-26

    A new surface acoustic wave (SAW)-based rate sensor pattern incorporating metallic dot arrays was developed in this paper. Two parallel SAW delay lines with a reverse direction and an operation frequency of 80 MHz on a same X-112°Y LiTaO3 wafer are fabricated as the feedback of two SAW oscillators, and mixed oscillation frequency was used to characterize the external rotation. To enhance the Coriolis force effect acting on the SAW propagation, a copper (Cu) dot array was deposited along the SAW propagation path of the SAW devices. The approach of partial-wave analysis in layered media was referred to analyze the response mechanisms of the SAW based rate sensor, resulting in determination of the optimal design parameters. To improve the frequency stability of the oscillator, the single phase unidirectional transducers (SPUDTs) and combed transducer were used to form the SAW device to minimize the insertion loss and accomplish the single mode selection, respectively. Excellent long-term (measured in hours) frequency stability of 0.1 ppm/h was obtained. Using the rate table with high precision, the performance of the developed SAW rate sensor was evaluated experimentally; satisfactory detection sensitivity (16.7 Hz∙deg∙s(-1)) and good linearity were observed.

  1. Distinct global warming rates tied to multiple ocean surface temperature changes

    Science.gov (United States)

    Yao, Shuai-Lei; Luo, Jing-Jia; Huang, Gang; Wang, Pengfei

    2017-07-01

    The globally averaged surface temperature has shown distinct multi-decadal fluctuations since 1900, characterized by two weak slowdowns in the mid-twentieth century and early twenty-first century and two strong accelerations in the early and late twentieth century. While the recent global warming (GW) hiatus has been particularly ascribed to the eastern Pacific cooling, causes of the cooling in the mid-twentieth century and distinct intensity differences between the slowdowns and accelerations remain unclear. Here, our model experiments with multiple ocean sea surface temperature (SST) forcing reveal that, although the Pacific SSTs play essential roles in the GW rates, SST changes in other basins also exert vital influences. The mid-twentieth-century cooling results from the SST cooling in the tropical Pacific and Atlantic, which is partly offset by the Southern Ocean warming. During the recent hiatus, the tropical Pacific-induced strong cooling is largely compensated by warming effects of other oceans. In contrast, during the acceleration periods, ubiquitous SST warming across all the oceans acts jointly to exaggerate the GW. Multi-model simulations with separated radiative forcing suggest diverse causes of the SST changes in multiple oceans during the GW acceleration and slowdown periods. Our results highlight the importance of multiple oceans on the multi-decadal GW rates.

  2. The surface quality of AWJ cut parts as a function of abrasive material reusing rate

    Science.gov (United States)

    Schnakovszky, C.; Herghelegiu, E.; Radu, M. C.; Tampu, N. C.

    2015-11-01

    Abrasive water jet cutting (AWJ) has been extensively used during the last years to process a large variety of materials since it offers important advantages as a good quality of the processed surface, without heat affected zones, low environmental impact (no emission of dust or other compounds that endanger the health of the user), small induced mechanical stresses etc. The main disadvantage is the high cost of processing (cost of equipment and consumables). In view of this, the effects of reusing the abrasive material on the quality of processed surface are investigated in this paper. Two steel materials were used: OL 37 (S 235) with large applicability in machine building industry and 2P armor steel used in the arms industry. The reusing rate of the garnet abrasive material was: 0%, 20%, 40%, 60%, 80% and 100%. The quality of processed surface was quantified by the following parameters: width at the jet inlet (Li), width at the jet outlet (Lo), inclination angle (α), deviation from perpendicularity (u) and roughness (Ra).

  3. Surface Wind Vector and Rain Rate Observation Capability of Future Hurricane Imaging Radiometer (HIRAD)

    Science.gov (United States)

    Miller, Timothy; Atlas, Robert; Bailey, M. C.; Black, Peter; El-Nimri, Salem; Hood, Robbie; James, Mark; Johnson, James; Jones, Linwood; Ruf, Christopher; Uhlhorn, Eric

    2009-01-01

    The Hurricane Imaging Radiometer (HIRAD) is the next-generation Stepped Frequency Microwave Radiometer (SFMR), and it will offer the capability of simultaneous wide-swath observations of both extreme ocean surface wind vector and strong precipitation from either aircraft (including UAS) or satellite platforms. HIRAD will be a compact, lightweight, low-power instrument with no moving parts that will produce valid wind observations under hurricane conditions when existing microwave sensors (radiometers or scatterometers) are hindered by precipitation. The SFMR i s a proven aircraft remote sensing system for simultaneously observing extreme ocean surface wind speeds and rain rates, including those of major hurricane intensity. The proposed HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer technology. The first version of the instrument will be a single polarization system for wind speed and rain rate, with a dual-polarization system to follow for wind vector capability. This sensor will operate over 4-7 GHz (C-band frequencies) where the required tropical cyclone remote sensing physics has been validated by both SFMR and WindSat radiometers. HIRAD incorporates a unique, technologically advanced array antenna and several other technologies successfully demonstrated by NASA s Instrument Incubator Program. A brassboard (laboratory) version of the instrument has been completed and successfully tested in a test chamber. Development of the aircraft instrument is underway, with flight testing planned for the fall of 2009. Preliminary Observing System Simulation Experiments (OSSEs) show that HIRAD will have a significant positive impact on surface wind analyses as either a new aircraft or satellite sensor. New off-nadir data collected in 2008 by SFMR that affirms the ability of this measurement technique to obtain wind speed data at non-zero incidence angle will

  4. Heteroepitaxial growth of cadmium carbonate at dolomite and calcite surfaces: Mechanisms and rates

    Science.gov (United States)

    Callagon, Erika Blanca R.; Lee, Sang Soo; Eng, Peter J.; Laanait, Nouamane; Sturchio, Neil C.; Nagy, Kathryn L.; Fenter, Paul

    2017-05-01

    The systematic variation of rates and the mechanism of cadmium uptake on the (1 0 4) surface of dolomite (CaMg(CO3)2) were investigated using in situ and ex situ atomic force microscopy (AFM), ex situ specular X-ray reflectivity (XR), and ex situ X-ray fluorescence (XRF). Selected experiments were performed on the calcite (CaCO3) (1 0 4) surface for comparison. Aqueous solutions of CdCl2, CaCl2, and NaHCO3, undersaturated with respect to calcite and supersaturated with respect to otavite (CdCO3) and the (CdxCa1-x)CO3 solid solution, were reacted with dolomite surfaces for minutes to days. Calcite substrates were reacted with solutions containing 1-50 μM CdCl2, and with no added Ca or CO3. Thin carbonate films following the Stranski-Krastanov growth mode were observed on both substrates. Specular XR and XRF revealed the formation of nm-thick Cd-rich carbonate films that were structurally ordered with respect to the dolomite (1 0 4) plane. Epitaxial films adopted the calcite crystal structure with a d104-spacing (3.00 Å) larger than those of pure dolomite (2.88 Å) and otavite (2.95 Å) indicating either a solid solution with x ≈ 0.5, or a strained Cd-rich carbonate with a composition near that of otavite. The growth rate r of this phase increases with the initial supersaturation of the solution with respect to the solid solution, βmax , and follows the empirical relationship, as determined from XRF measurements, given by:

  5. Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden-Popper phases?

    Science.gov (United States)

    Tomkiewicz, Alex C; Tamimi, Mazin A; Huq, Ashfia; McIntosh, Steven

    2015-01-01

    The possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of three Ruddlesden-Popper phases, general form A(n-1)A(2)'B(n)O(3n+1), A(n-1)A(2)'B(n)X(3n+1); LaSrCo(0.5)Fe(0.5)O(4-δ) (n = 1), La(0.3)Sr(2.7)CoFeO(7-δ) (n = 2) and LaSr3Co(1.5)Fe(1.5)O(10-δ) (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. This is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. We conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.

  6. Engineering of surface microstructure transformations using high rate severe plastic deformation in machining

    Science.gov (United States)

    Abolghasem, Sepideh

    Engineering surface structures especially at the nanometer length-scales can enable fundamentally new multifunctional property combinations, including tunable physical, mechanical, electrochemical and biological responses. Emerging manufacturing paradigms involving Severe Plastic Deformation (SPD), for manipulating final microstructure of the surfaces are unfortunately limited by poorly elucidated process-structure-performance linkages, which are characterized by three central variables of plasticity: strain, strain-rate and temperature that determine the resulting Ultrafine Grained (UFG) microstructure. The challenge of UFG surface engineering, design and manufacturing can be overcome if and only if the mappings between the central variables and the final microstructure are delineated. The objective of the proposed document is to first envision a phase-space, whose axes are parameterized in terms of the central variables of SPD. Then, each point can correspond to a unique microstructure, characterized by its location on this map. If the parametrization and the population of the datasets are accurately defined, then the mapping is bijective where: i) realizing microstructure designs can be reduced to simply one of tuning process parameters falling within the map s desired subspaces. And, inversely, ii) microstructure prediction is directly possible by merely relating the measured/calculated thermomechanics at each point in the deformation zone to the corresponding spot on the maps. However, the analytic approach to establish this map first requires extensive datasets, where the microstructures are accurately measured for a known set of strain, strain-rate and temperature of applied SPD. Although such datasets do not exist, even after the empirical data is accumulated, there is a lack of formalized statistical outlines in relating microstructural characteristic to the process parameters in order to build the mapping framework. Addressing these gaps has led to this

  7. Response surface modelling of tool electrode wear rate and material removal rate in micro electrical discharge machining of Inconel 718

    DEFF Research Database (Denmark)

    Puthumana, Govindan

    2017-01-01

    conductivity and high strength causing it extremely difficult tomachine. Micro-Electrical Discharge Machining (Micro-EDM) is a non-conventional method that has a potential toovercome these restrictions for machining of Inconel 718. Response Surface Method (RSM) was used for modelling thetool Electrode Wear...

  8. Size distribution of Parkfield’s microearthquakes reflects changes in surface creep rate

    Science.gov (United States)

    Tormann, Theresa; Wiemer, Stefan; Metzger, Sabrina; Michael, Andrew J.; Hardebeck, Jeanne L.

    2013-01-01

    The nucleation area of the series of M6 events in Parkfield has been shown to be characterized by low b-values throughout the seismic cycle. Since low b-values represent high differential stresses, the asperity structure seems to be always stably stressed and even unaffected by the latest main shock in 2004. However, because fault loading rates and applied shear stress vary with time, some degree of temporal variability of the b-value within stable blocks is to be expected. We discuss in this study adequate techniques and uncertainty treatment for a detailed analysis of the temporal evolution of b-values. We show that the derived signal for the Parkfield asperity correlates with changes in surface creep, suggesting a sensitive time resolution of the b-value stress meter, and confirming near-critical loading conditions within the Parkfield asperity.

  9. Measurement of surface emission flux rates for volatile organic compounds at Technical Area 54

    Energy Technology Data Exchange (ETDEWEB)

    Trujillo, V.; Morgenstern, M.; Krier, D. [Los Alamos National Lab., NM (United States); Gilkeson, R. [Weirich and Associates, Albuquerque, NM (United States)

    1998-06-01

    The survey described in this report was conducted to estimate the mass of volatile organic compounds venting to the atmosphere from active and inactive waste disposal sites at Technical Area 54. A large number of nonintrusive passive sample collection devices were placed on the ground surface for 72 hours to characterize an area of approximately 150 acres. Results provided an indication of the boundary location of the known volatile organic plume, plume constituents, and isolated high concentration areas. The data from this survey enhanced existing data from a limited number of monitor wells currently used for plume surveillance. Results indicate that the estimated mass emission to the atmosphere is orders of magnitude lower than what is considered a small flux rate at a spill site or a Resource Conservation and Recovery Act landfill and is far below the threshold limit established by the State of New Mexico as an air quality concern.

  10. Active Faults of the Northwest Himalaya: Pattern, Rate, and Timing of Surface Rupturing Earthquakes

    Science.gov (United States)

    Yule, J.; Madden, C.; Gavillot, Y.; Hebeler, A.; Meigs, A.; Hussein, A.; Malik, M.; Bhat, M.; Kausar, A.; Ramzan, S.; Sayab, M.; Yeats, R. S.

    2012-12-01

    The 2005 Kashmir earthquake (Mw 7.6) is the only Himalayan earthquake to rupture the surface since the 15th to 16th century A.D. when >Mw 8.5 earthquakes ruptured the Himalayan Frontal thrust (HFT) in the central Himalaya. Megathrust-type earthquakes like these seem to relieve a majority of the accumulated interseismic strain and concentrate permanent strain across a narrow width at the deformation front (faults within the orogen appear to accommodate little strain). The 2005 within-plate rupture in Kashmir may be a clue that a different seismotectonic model applies to the northwest Himalaya where active deformation occurs on faults distributed more than 120 km across the orogen. An asymmetric anticline marks the deformation front in Kashmir where the HFT is inferred to be blind, though ~20 m-high escarpments suggest that unrecognized thrust fault(s) may reach the surface locally. Folded river terraces and dip data also suggest that this frontal fold contains a SW-dipping back thrust. In Pakistan the Salt Range thrust system (SRT) defines the thrust front. New mapping and preliminary OSL dates from deformed Holocene sediments exposed along the westernmost SRT reveal that the fault slips at 1-7 mm/yr and last ruptured within the last several thousand years. Within the orogenic wedge to the north of the deformation front, active shortening occurs along a system of surface-rupturing reverse faults, extending from the Balakot-Bagh fault (source of the 2005 Kashmir earthquake) to the Reasi fault (RF) in Indian Kashmir to the southeast. One strand of the RF displaces a 350 m-high, 80 ± 6 ka (preliminary OSL age) fluvial terrace, yielding a minimum shortening rate of 3-5 mm/yr. Trenches excavated across the RF nearby reveal a distinct angular unconformity that likely formed during a surface rupture ~4500 yrs BP. Farther north, three northeast-dipping reverse faults cut Quaternary terraces on the southwest side of the Kashmir Valley. Trenches expose evidence for at least

  11. Cell surface structures influence lung clearance rate of systemically infused mesenchymal stromal cells.

    Science.gov (United States)

    Nystedt, Johanna; Anderson, Heidi; Tikkanen, Jonne; Pietilä, Mika; Hirvonen, Tia; Takalo, Reijo; Heiskanen, Annamari; Satomaa, Tero; Natunen, Suvi; Lehtonen, Siri; Hakkarainen, Tanja; Korhonen, Matti; Laitinen, Saara; Valmu, Leena; Lehenkari, Petri

    2013-02-01

    The promising clinical effects of mesenchymal stromal/stem cells (MSCs) rely especially on paracrine and nonimmunogenic mechanisms. Delivery routes are essential for the efficacy of cell therapy and systemic delivery by infusion is the obvious goal for many forms of MSC therapy. Lung adhesion of MSCs might, however, be a major obstacle yet to overcome. Current knowledge does not allow us to make sound conclusions whether MSC lung entrapment is harmful or beneficial, and thus we wanted to explore MSC lung adhesion in greater detail. We found a striking difference in the lung clearance rate of systemically infused MSCs derived from two different clinical sources, namely bone marrow (BM-MSCs) and umbilical cord blood (UCB-MSCs). The BM-MSCs and UCB-MSCs used in this study differed in cell size, but our results also indicated other mechanisms behind the lung adherence. A detailed analysis of the cell surface profiles revealed differences in the expression of relevant adhesion molecules. The UCB-MSCs had higher expression levels of α4 integrin (CD49d, VLA-4), α6 integrin (CD49f, VLA-6), and the hepatocyte growth factor receptor (c-Met) and a higher general fucosylation level. Strikingly, the level of CD49d and CD49f expression could be functionally linked with the lung clearance rate. Additionally, we saw a possible link between MSC lung adherence and higher fibronectin expression and we show that the expression of fibronectin increases with MSC culture confluence. Future studies should aim at developing methods of transiently modifying the cell surface structures in order to improve the delivery of therapeutic cells.

  12. Comparing OSL and CN techniques for dating fluvial terraces and estimating surface process rates in Pamir

    Science.gov (United States)

    Fuchs, Margret; Gloaguen, Richard; Pohl, Eric; Sulaymonova, Vasila; Merchel, Silke; Rugel, Georg

    2014-05-01

    The quantification of surface process rates is crucial for understanding the topographic evolution of high mountains. Spatial and temporal variations in fluvial incision and basin-wide erosion enable to decipher the role of tectonic and climatic drivers. The Pamir is peculiar in both aspects because of its location at the western end of the India-Asia collision zone, and its position at the edge of two atmospheric circulation systems, the Westerlies and the Indian Summer Monsoon. The architecture of the Panj river network indicates prominent variations across the main tectonic structures of the Pamir. The trunk stream, deflects from the predominantly westward river orientation and cuts across the southern and central Pamir domes before doubling back to the west and leaving the orogen. Optically stimulated luminescence (OSL) dating of fluvial terraces reveals short-term sedimentation along the trunk stream during the last ~25 kyr. The agreement of OSL results to new exposure ages based on the cosmogenic nuclide (CN) 10Be confirms accurate terrace age modelling and treatment of incomplete bleaching. The consistent terrace sedimentation and exposure ages suggest also fast terrace abandonment and rapid onset of incision. Considerable differences in terrace heights reflect high spatial variations of fluvial incision, independent of time interval, change in rock type or catchment increase. Highest rates of (5.9 ± 1.1) mm/yr to (10.0 ± 2.0) mm/yr describe the fluvial dynamic across the Shakhdara Dome and that related to the Darvaz Fault Zone. Lower rates of (3.9 ± 0.6) mm/yr to (4.5 ± 0.7) mm/yr indicate a transient stage north of the Yazgulom Dome. Fluvial incision decreases to rates ranging from (1.7 ± 0.3) mm/yr to (3.9 ± 0.7) mm/yr in graded river reaches associated to southern dome boundaries. The pattern agrees to the interpretation of successive upstream river captures across the southern and central Pamir domes inferred from morphometric analyses of river

  13. Determination of surface dose rate of indigenous (32)P patch brachytherapy source by experimental and Monte Carlo methods.

    Science.gov (United States)

    Kumar, Sudhir; Srinivasan, P; Sharma, S D; Saxena, Sanjay Kumar; Bakshi, A K; Dash, Ashutosh; Babu, D A R; Sharma, D N

    2015-09-01

    Isotope production and Application Division of Bhabha Atomic Research Center developed (32)P patch sources for treatment of superficial tumors. Surface dose rate of a newly developed (32)P patch source of nominal diameter 25 mm was measured experimentally using standard extrapolation ionization chamber and Gafchromic EBT film. Monte Carlo model of the (32)P patch source along with the extrapolation chamber was also developed to estimate the surface dose rates from these sources. The surface dose rates to tissue (cGy/min) measured using extrapolation chamber and radiochromic films are 82.03±4.18 (k=2) and 79.13±2.53 (k=2) respectively. The two values of the surface dose rates measured using the two independent experimental methods are in good agreement to each other within a variation of 3.5%. The surface dose rate to tissue (cGy/min) estimated using the MCNP Monte Carlo code works out to be 77.78±1.16 (k=2). The maximum deviation between the surface dose rates to tissue obtained by Monte Carlo and the extrapolation chamber method is 5.2% whereas the difference between the surface dose rates obtained by radiochromic film measurement and the Monte Carlo simulation is 1.7%. The three values of the surface dose rates of the (32)P patch source obtained by three independent methods are in good agreement to one another within the uncertainties associated with their measurements and calculation. This work has demonstrated that MCNP based electron transport simulations are accurate enough for determining the dosimetry parameters of the indigenously developed (32)P patch sources for contact brachytherapy applications.

  14. In situ synchrotron IR study relating temperature and heating rate to surface functional group changes in biomass.

    Science.gov (United States)

    Kirtania, Kawnish; Tanner, Joanne; Kabir, Kazi Bayzid; Rajendran, Sharmen; Bhattacharya, Sankar

    2014-01-01

    Three types of woody biomass were investigated under pyrolysis condition to observe the change in the surface functional groups by Fourier transform infrared (FTIR) technique with increasing temperature under two different (5 and 150°C/min) heating rates. The experiments were carried out in situ in the infrared microscopy beamline (IRM) of the Australian Synchrotron. The capability of the beamline made it possible to focus on single particles to obtain low noise measurements without mixing with KBr. At lower heating rate, the surface functional groups were completely removed by 550°C. In case of higher heating rate, a delay was observed in losing the functional groups. Even at a high temperature, significant number of functional groups was retained after the higher heating rate experiments. This implies that at considerably high heating rates typical of industrial reactors, more functional groups will remain on the surface.

  15. Trends in CO Oxidation Rates for Metal Nanoparticles and Close-Packed, Stepped, and Kinked Surfaces

    DEFF Research Database (Denmark)

    Jiang, Tao; Mowbray, Duncan; Dobrin, Sergey;

    2009-01-01

    Using density functional theory calculations, we study trends in the CO oxidation activity for different metals and surfaces. Specifically, we show how the activity of (111) close-packed surfaces, (211) stepped surfaces, (532) kinked surfaces, 55 atom cuboctahedral clusters, and 12 atom cluster...

  16. Effect of surface-plasmon polaritons on spontaneous emission and intermolecular energy-transfer rates in multilayered geometries

    NARCIS (Netherlands)

    Marocico, C. A.; Knoester, J.

    2011-01-01

    We use a Green's tensor method to investigate the spontaneous emission rate of a molecule and the energy-transfer rate between molecules placed in two types of layered geometries: a slab geometry and a planar waveguide. We focus especially on the role played by surface-plasmon polaritons in

  17. Differences in Rate and Direction of Shifts between Phytoplankton Size Structure and Sea Surface Temperature

    Directory of Open Access Journals (Sweden)

    Hisatomo Waga

    2017-03-01

    Full Text Available Species distributions are changing with various rates and directions in response to recent global warming. The velocity of sea surface temperature (SST has been used to predict species migration and persistence as an expectation of how species track their thermal niches; however, several studies have found that evidence for species shifts has deviated from the velocity of SST. This study investigated whether estimation of the velocity of shifts in phytoplankton size structure using remote sensing data could contribute to better prediction of species shifts. A chlorophyll-a (Chla size distribution (CSD model was developed by quantifying the relationships between the size structure of the phytoplankton community and the spectral features of the phytoplankton absorption coefficient (aph(λ, based on the principal component analysis approach. Model validation demonstrated that the exponent of CSD (hereafter, CSD slope, which can describe the synoptic size structure of a phytoplankton community, was derived successfully with a relative root mean square error of 18.5%. The median velocity of CSD slope across the ocean was 485.2 km·decade−1, broadly similar to Chla (531.5 km·decade−1. These values were twice the velocity of SST, and the directions of shifts in CSD slope and Chla were quite different from that of SST. Because Chla is generally covariant with the size structure of a phytoplankton community, we believe that spatiotemporal changes in Chla can explain the variations of phytoplankton size structure. Obvious differences in both rate and direction of shifts were found between the phytoplankton size structure and SST, implying that shifts of phytoplankton size structure could be a powerful tool for assessing the distributional shifts of marine species. Our results will contribute to generate global and regional maps of expected species shifts in response to environmental forcing.

  18. Cold collisions of SH- with He: Potential energy surface and rate coefficients

    Science.gov (United States)

    Bop, C. T.; Trabelsi, T.; Hammami, K.; Mogren Al Mogren, M.; Lique, F.; Hochlaf, M.

    2017-09-01

    Collisional energy transfer under cold conditions is of great importance from the fundamental and applicative point of view. Here, we investigate low temperature collisions of the SH- anion with He. We have generated a three-dimensional potential energy surface (PES) for the SH-(X1Σ+)-He(1S) van der Waals complex. The ab initio multi-dimensional interaction PES was computed using the explicitly correlated coupled cluster approach with simple, double, and perturbative triple excitation in conjunction with the augmented-correlation consistent-polarized valence triple zeta Gaussian basis set. The PES presents two minima located at linear geometries. Then, the PES was averaged over the ground vibrational wave function of the SH- molecule and the resulting two-dimensional PES was incorporated into exact quantum mechanical close coupling calculations to study the collisional excitation of SH- by He. We have computed inelastic cross sections among the 11 first rotational levels of SH- for energies up to 2500 cm-1. (De-)excitation rate coefficients were deduced for temperatures ranging from 1 to 300 K by thermally averaging the cross sections. We also performed calculations using the new PES for a fixed internuclear SH- distance. Both sets of results were found to be in reasonable agreement despite differences existing at low temperatures confirming that accurate predictions require the consideration of all internal degrees of freedom in the case of molecular hydrides. The rate coefficients presented here may be useful in interpreting future experimental work on the SH- negative ion colliding with He as those recently done for the OH--He collisional system as well as for possible astrophysical applications in case SH- would be detected in the interstellar medium.

  19. Adhesive-Bonded Composite Joint Analysis with Delaminated Surface Ply Using Strain-Energy Release Rate

    Science.gov (United States)

    Chadegani, Alireza; Yang, Chihdar; Smeltzer, Stanley S. III

    2012-01-01

    This paper presents an analytical model to determine the strain energy release rate due to an interlaminar crack of the surface ply in adhesively bonded composite joints subjected to axial tension. Single-lap shear-joint standard test specimen geometry with thick bondline is followed for model development. The field equations are formulated by using the first-order shear-deformation theory in laminated plates together with kinematics relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. The system of second-order differential equations is solved to using the symbolic computation tool Maple 9.52 to provide displacements fields. The equivalent forces at the tip of the prescribed interlaminar crack are obtained based on interlaminar stress distributions. The strain energy release rate of the crack is then determined by using the crack closure method. Finite element analyses using the J integral as well as the crack closure method are performed to verify the developed analytical model. It has been shown that the results using the analytical method correlate well with the results from the finite element analyses. An attempt is made to predict the failure loads of the joints based on limited test data from the literature. The effectiveness of the inclusion of bondline thickness is justified when compared with the results obtained from the previous model in which a thin bondline and uniform adhesive stresses through the bondline thickness are assumed.

  20. Short-term inactivation rates of selected Gram-positive and Gram-negative bacteria attached to metal oxide mineral surfaces: role of solution and surface chemistry.

    Science.gov (United States)

    Asadishad, Bahareh; Ghoshal, Subhasis; Tufenkji, Nathalie

    2013-06-04

    Metal oxides such as ferric or aluminum oxides can play an important role in the retention of bacteria in granular aquatic environments; however, their role in bacterial inactivation is not well understood. Herein, we examined the role of water chemistry and surface chemistry on the short-term inactivation rates of three bacteria when adhered to surfaces. To evaluate the role of water chemistry on the inactivation of attached bacteria, the loss in membrane integrity of bacteria attached to an iron oxide (Fe2O3) surface was measured over a range of water ionic strengths of either monovalent or divalent salts in the absence of a growth substrate. The influence of surface chemistry on the inactivation of attached bacteria was examined by measuring the loss in membrane integrity of cells attached to three surfaces (SiO2, Fe2O3, and Al2O3) at a specific water chemistry (10 mM KCl). Bacteria were allowed to attach onto the SiO2 or metal oxide coated slides mounted in a parallel-plate flow cell, and their inactivation rate (loss in membrane integrity) was measured directly without removing the cells from the surface and without disturbing the system. X-ray photoelectron spectroscopy analysis revealed a high correlation between the amounts of C-metal or O-metal bonds and the corresponding bacterial inactivation rates for each surface. Finally, for all three surfaces, a consistent increase in inactivation rate was observed with the type of bacterium in the order: Enterococcus faecalis, Escherichia coli O157:H7, and Escherichia coli D21f2.

  1. Effects of scaffold surface morphology on cell adhesion and survival rate in vitreous cryopreservation of tenocyte-scaffold constructs

    Science.gov (United States)

    Wang, Zhi; Qing, Quan; Chen, Xi; Liu, Cheng-Jun; Luo, Jing-Cong; Hu, Jin-Lian; Qin, Ting-Wu

    2016-12-01

    The purpose of this study was to investigate the effects of scaffold surface morphology on cell adhesion and survival rate in vitreous cryopreservation of tenocyte-scaffold constructs. Tenocytes were obtained from tail tendons of rats. Polydimethylsiloxane (PDMS) was used to fabricate three types of scaffolds with varying surface morphological characteristics, i.e., smooth, micro-grooved, and porous surfaces, respectively. The tenocytes were seeded on the surfaces of the scaffolds to form tenocyte-scaffold constructs. The constructs were cryopreserved in a vitreous cryoprotectant (CPA) with a multi-step protocol. The cell adhesion to scaffolds was observed with electronic scanning microscopy (SEM). The elongation index of the living tenocytes and ratio of live/dead cell number were examined based on a live/dead dual fluorescent staining technique, and the survival rate of tenocytes was studied with flow cytometry (FC). The results showed the shapes of tenocytes varied between the different groups: flat or polygonal (on smooth surface), spindle (on micro-grooved surface), and spindle or ellipse (on porous surface). After thawing, the porous surface got the most living tenocytes and a higher survival rate, suggesting its potential application for vitreous cryopreservation of engineered tendon constructs.

  2. Mechanisms of high-regularity periodic structuring of silicon surface by sub-MHz repetition rate ultrashort laser pulses

    Science.gov (United States)

    Gnilitskyi, Iaroslav; Gruzdev, Vitaly; Bulgakova, Nadezhda M.; Mocek, Tomáš; Orazi, Leonardo

    2016-10-01

    Silicon is one of the most abundant materials which is used in many areas of modern research and technology. A variety of those applications require surface nanopatterning with minimum structure defects. However, the high-quality nanostructuring of large areas of silicon surface at industrially acceptable speed is still a challenge. Here, we report a rapid formation of highly regular laser-induced periodic surface structures (HR-LIPSS) in the regime of strong ablation by infrared femtosecond laser pulses at sub-MHz repetition rate. Parameters of the laser-surface interactions and obtained experimental results suggest an important role of electrostatically assisted bond softening in initiating the HR-LIPSS formation.

  3. Heart rate variability and surface electromyography of trained cyclists at different cadences

    Directory of Open Access Journals (Sweden)

    Bruno Saraiva

    2016-06-01

    Full Text Available The heart rate variability (HRV and surface electromyography (sEMG are important tools in the evaluation of cardiac autonomic system and neuromuscular parameters, respectively. The aim of the study was to evaluate the behavior of HRV and sEMG of the vastus lateralis in two exercise protocols on a cycle ergometer at 60 and 80 rpm. Eight healthy men cyclists who have trained for at least two years were evaluated. Reduction was observed followed by stabilization of RMSSD and SDNN indices of HRV (p<0.05 along with increases in the amplitude of the sEMG signal (p<0.05 in both protocols. Significant correlations were observed between the responses of HRV and sEMG in the cadence of 60 rpm (RMSSD and sEMG: r = -0.42, p=0.03; SDNN and sEMG: r = -0.45, p=0.01 and 80 rpm (RMSSD and sEMG: r = -0.47, p=0.02; SDNN and sEMG: r = -0.49, p=0.01, yet no difference was observed for these variables between the two protocols. We concluded that the parasympathetic cardiac responses and sEMG are independent of cadences applied at the same power output.

  4. Deuterium recycling rate constants derived from plasma implantation/desorption shots in a martensitic steel surface

    Energy Technology Data Exchange (ETDEWEB)

    Sedano, L.A. [CIEMAT/DIAE, Madrid (Spain); European Commission/JRC, H-Materials Interaction Sector, Ispra (Italy); Esteban, G.A. [UPV-EHU/ETSIIT, D. Nuc. Eng. and Fluid Mec., Bilbao (Spain); Perujo, A. [European Commission/JRC, H-Materials Interaction Sector, Ispra (Italy)

    2001-12-04

    The recombination (K{sub 2}) and dissociation rate constants (K{sub 1}) are essential magnitudes for the tracking of tritium at the first wall (FW) of fusion reactors (FR). This paper presents our plasma implantation/recycling test, the modelling of the experiment and the results obtained for K{sub 2} and K{sub 1} in the case of a deuterium (D{sub 3}{sup +}/D{sub 2}{sup +}) plasma in the martensitic steel DIN 1.4914 (MANET). Once parasitic contributions were accounted, the D{sub 2} release from the target was seen to be surface limited. The values obtained for K{sub 1} and K{sub 2} show low dispersion on impinging flux and ion energies. For K{sub 1} a roughly constant value of 7 x 10{sup -6} mol Pa{sup -1} m{sup -2} s{sup -1} is derived. The obtained K{sub 2} is written as: K{sub 2} = 2.414 exp (-1571/RT) (m{sup 4} mol{sup -1} s{sup -1}), with R = 8.314 J mol{sup -1} K{sup -1}. Our activation energies agree with those existing in the literature derived from permeation experiments. High reflection coefficients are derived, which are in good agreement with the classical theory of ion scattering at low energy. (orig.)

  5. Impact of surface curvature on dose delivery in intraoperative high-dose-rate brachytherapy.

    Science.gov (United States)

    Oh, Moonseong; Wang, Zhou; Malhotra, Harish K; Jaggernauth, Wainwright; Podgorsak, Matthew B

    2009-01-01

    In intraoperative high-dose-rate (IOHDR) brachytherapy, a 2-dimensional (2D) geometry is typically used for treatment planning. The assumption of planar geometry may cause serious errors in dose delivery for target surfaces that are, in reality, curved. A study to evaluate the magnitude of these errors in clinical practice was undertaken. Cylindrical phantoms with 6 radii (range: 1.35-12.5 cm) were used to simulate curved treatment geometries. Treatment plans were developed for various planar geometries and were delivered to the cylindrical phantoms using catheters inserted into Freiburg applicators of varying dimension. Dose distributions were measured using radiographic film. In comparison to the treatment plan (for a planar geometry), the doses delivered to prescription points were higher on the concave side of the geometry, up to 15% for the phantom with the smallest radius. On the convex side of the applicator, delivered doses were up to 10% lower for small treated areas (5 catheters). Our measurements have shown inaccuracy in dose delivery when the original planar treatment plan is delivered with a curved applicator. Dose delivery errors arising from the use of planar treatment plans with curved applicators may be significant.

  6. A Krebs Cycle Component Limits Caspase Activation Rate through Mitochondrial Surface Restriction of CRL Activation.

    Science.gov (United States)

    Aram, Lior; Braun, Tslil; Braverman, Carmel; Kaplan, Yosef; Ravid, Liat; Levin-Zaidman, Smadar; Arama, Eli

    2016-04-04

    How cells avoid excessive caspase activity and unwanted cell death during apoptotic caspase-mediated removal of large cellular structures is poorly understood. We investigate caspase-mediated extrusion of spermatid cytoplasmic contents in Drosophila during spermatid individualization. We show that a Krebs cycle component, the ATP-specific form of the succinyl-CoA synthetase β subunit (A-Sβ), binds to and activates the Cullin-3-based ubiquitin ligase (CRL3) complex required for caspase activation in spermatids. In vitro and in vivo evidence suggests that this interaction occurs on the mitochondrial surface, thereby limiting the source of CRL3 complex activation to the vicinity of this organelle and reducing the potential rate of caspase activation by at least 60%. Domain swapping between A-Sβ and the GTP-specific SCSβ (G-Sβ), which functions redundantly in the Krebs cycle, show that the metabolic and structural roles of A-Sβ in spermatids can be uncoupled, highlighting a moonlighting function of this Krebs cycle component in CRL activation.

  7. Comparative Evaluation of Frictional Properties, Load Deflection Rate and Surface Characteristics of Different Coloured TMA Archwires - An Invitro Study.

    Science.gov (United States)

    Aloysius, Arul Pradeep; Vijayalakshmi, Devaki; Deepika; Soundararajan, Nagachandran Kandasamy; Manohar, Vijaykumar Neelam; Khan, Nayeemullah

    2015-12-01

    During tooth movement the success of sliding mechanics is dependent upon various factors which include frictional resistance at bracket-archwire interface, surface roughness of archwire materials and elastic properties of archwires. Ion implantation techniques reduce the frictional force and allow better tooth movement clinically. The main objective of this study was to evaluate and compare the frictional properties, load deflection rate and surface characteristics of Honey dew and Purple coloured (Ion implanted) TMA wires with uncoated TMA wires. Fifteen archwire samples were divided into three groups comprising of five samples in each group namely, Group I - Uncoated TMA wires (Control), Group II - Purple coloured TMA wires and Group III- Honey dew TMA wires. Friction and load deflection rate testing were performed with the Instron Universal testing machine and the surface characteristics of the wires were evaluated before and after sliding using Scanning Electron Microscope. The mean frictional characteristics and surface roughness for Honey dew TMA wires was lesser than Purple coloured TMA wires which was statistically significant. Both the coloured TMA wires showed low frictional characteristics and less surface roughness than uncoated TMA wires (the control). The mean load deflection rate was low for both coloured ion implanted TMA wires when compared to uncoated TMA wires which was statistically significant. Coloured ion implanted TMA wires, especially Honey dew TMA wires have low friction, low load deflection rate and improved surface finish. Hence they can be used in frictionless as well as sliding mechanics, where uncoated TMA wires are inefficient.

  8. Influence of deposition rate on PL spectrum and surface morphology of ZnO nanolayers deposited on Si (100) substrate

    Indian Academy of Sciences (India)

    A Zendehnam; M Mirzaee; S Miri

    2014-04-01

    Zinc oxide (ZnO) thin films were deposited on Si (100) substrate through sputtering of zinc by DC magnetron, followed by thermal oxidation. Different deposition rates were used in coating films with 100 nm thickness (0.6–4.5 nm/s). Photoluminescence spectra of the produced samples were obtained and it was found that the violet emission peak intensity increases with deposition rate. Scanning electron microscopy (SEM) micrograph and atomic force microscopy (AFM) images for the zinc oxide films were obtained. Morphological changes due to various deposition rate are discussed in the light of changes observed in the ZnO crystals. Low coating rates produced smooth surface with small grains while higher deposition rates increased the surface roughness and larger grain size. AFM and SEM results are in good agreement and support the PL results.

  9. 比热和直流磁化率证明N+H…O-氢键的电子自旋翻转在D-和L-丙氨酸单晶中的不对称相变%Heat Capacity and DC-Magnetic Susceptibility Evidence for the Asymmetry of Electron Spin-Flip Phase Transition of N+H…O- Bond in Chiral Alanine Crystal

    Institute of Scientific and Technical Information of China (English)

    王文清; 沈新春; 吴季兰; 龚; 申国华; 赵洪凯

    2012-01-01

    With a view to understanding the argument of phase-transition mechanisms of D- and L-alanine at around 270 K,the temperature dependence of heat capacity measurements was investigated,for single crystals,ground powders,and polycrystalline products,using differential scanning calorimetry (DSC).The Cp (heat capacity under constant pressure) values of D- and L-alanine were calibrated with standard sapphire by the triple-curve method; these values coincide with the standard Cp values in the literature.Endothermic transition peaks were observed at Tc=272.02 K,ΔH=1.87 J· mol-1 and Tc=271.85 K,ΔH=1.46 J·mol-1 for D- and L- alanine,respectively,and Tc=273.59 K,ΔH=1.75 J·mol-1 and Tc=273.76 K,ΔH=1.57 J·mol-1 for the reference crystals D- and L-valine,respectively.The energy differences of 0.41 J· mol-1 for D-and L-alanine and 0.18 J · mol-1 for D- and L-valine,which were observed from pre-aligned molecules in the single crystals and vanished in the ground powders and polycrystalline products,show that the phase transition is related to the crystal lattice.Neutron diffraction results exclude the possibility of a D→L configuration change,and show that the hydrogen bonds run antiparallel to the c-axis in the D- and L-crystals.Polarized Raman vibrational spectroscopy shows that the transition mechanism may be related to the electronic orbital angular momentum and magnetic dipole moments of N+H … O- in the crystals.External magnetic fields,H=+1,-1 T,were applied parallel to the c(z)-axis of the D- and L-alanine crystalline lattices,respectively.The DC-magnetic susceptibilities show electron spin-flip transitions at around 270 K in D- and L-alanine.The spin is “up” or “down” relative to the direction of N+H… O- bond along the c(z)-axis.Based on spin rigidity and magnetic anisotropy,the results help to explain the discrepancies among heat capacity and magnetic susceptibility data for single crystals and polycrystalline powders of D- and L-alanine.%为了

  10. Angular Gamma Dose Rate Distribution at the Surface of Injected Ducted Concrete Shield

    Science.gov (United States)

    Sayed Ahmed, Fikria M.; Abboud, Aida

    The shielding problems that arise due to the irregular penetrations such as neutral beam injection ducts should be treated carefully to aid in the shield design. The present work was undertaken to describe the effects arising due to radiation streaming through the neutral beam injector ducts (NBID) on the angular distribution of the total gamma ray doses at the outer surface of illmenite concrete shield ( = 4.6g/cm3). The shield is pierced with NBID of different diameters and lengths.The measurements were performed using a collimated beam of both gamma rays and neutrons emitted from one of the horizontal channels of the ET-RR-1 reactor. The measurements were carried out using 7LiF teflon thermoliminescent dosimeters. Generally the obtained data reveal that the presence of the total dose increase at the centerline of NBID and which in turn tends to decrease with the increase of scattered angle. An empirical formula describing the differential dose rate ratio is predicted. The experimental data obtained reveal good agreement with the calculated ones.Translated AbstractDie radiale Verteilung der -Dosisrate auf der Oberfläuche einer durchlöcherten BetonabschirmungAbschirmprobleme, die ihren Ursprung in irregulärem Durchlaßvermögen haben, sollten sorgfältig untersucht werden, um die Konstruktion von Abschirmungen zu unterstützen. In der vorliegenden Arbeit wird versucht, den Effekt von ausgetretener Strahlung (nach dem Mechanismus der neutralen Strahlinjektordurchführung NBID) auf die radiale Verteilung der totalen y- Strahlendosis auf der äußeren Oberfläche einer Illmenitbetonabschirmung ( = 4,6 g/cm3) aufzuzeigen. Der Schild ist mit NBID's verschiedener Längen und Durchmesser versehen. Die experimentellen Werte stimmen gut mit berechneten überein. Eine empirische Formel für die radiale Verteilung wird angegeben.

  11. Influence of radiant energy exchange on the determination of convective heat transfer rates to Orbiter leeside surfaces during entry

    Science.gov (United States)

    Throckmorton, D. A.

    1982-01-01

    Temperatures measured at the aerodynamic surface of the Orbiter's thermal protection system (TPS), and calorimeter measurements, are used to determine heating rates to the TPS surface during atmospheric entry. On the Orbiter leeside, where convective heating rates are low, it is possible that a significant portion of the total energy input may result from solar radiation, and for the wing, cross radiation from the hot (relatively) Orbiter fuselage. In order to account for the potential impact of these sources, values of solar- and cross-radiation heat transfer are computed, based upon vehicle trajectory and attitude information and measured surface temperatures. Leeside heat-transfer data from the STS-2 mission are presented, and the significance of solar radiation and fuselage-to-wing cross-radiation contributions to total energy input to Orbiter leeside surfaces is assessed.

  12. Dissolution rates and surface chemistry of feldspar glass and crystal. Final technical report, June 15, 1995 - August 14, 2001

    Energy Technology Data Exchange (ETDEWEB)

    Brantley, S.; Pantano, C.

    2002-06-11

    Final report summarizing the completed work of the project entitled 'Dissolution of Feldspar in the Field and Laboratory.' One of the highly debated questions today in low-temperature geochemical kinetics centers upon the rate and mechanism of dissolution of feldspar, the most common mineral in the crust. In this project, the mechanisms of feldspar dissolution were investigated by emphasizing experiments with feldspar glass and crystal while comparing surface and solution chemistry. Specifically, laboratory work focused on the structure of altered surface layers on feldspars, the rate of dissolution of feldspar crystal and glass, and the presence of porosity and surface coatings on feldspars. In a complementary field project, the use of Sr concentrations and isotopic ratios were used to calculate feldspar dissolution rates.

  13. Determination of q=1 surface by the variation of pellet ablation rate on the HL-1M

    Institute of Scientific and Technical Information of China (English)

    Dong Jia-Fu; Qin Yun-Wen; Shi Bing-Ren; Li Wei; Luo Jun-Lin; Liu Yi; Fu Bing-Zhong; Dong Yun-Bo; Xiao Zheng-Gui; Zheng Yin-Jia

    2004-01-01

    Strong drop of Hα emission has been observed on the HL-1M tokamak by means of a detector array while a pellet crosses the q=1 surface. In this article, the q=1 surface has been determined precisely by the interval and the shape of the Hα emission striations on the pellet trajectory due to the variation of pellet ablation rate. The q-profile and current density distribution at the plasma centre region have been calculated according to the pellet ablation rate and the magnetic shear feature.

  14. Surface activation of polyethylene with an argon atmospheric pressure plasma jet: Influence of applied power and flow rate

    Science.gov (United States)

    Van Deynse, A.; Cools, P.; Leys, C.; De Geyter, N.; Morent, R.

    2015-02-01

    Atmospheric pressure plasma technology offers attractive perspectives to alter the surface properties of polymers. Within this context, the surface modification of polyethylene (LDPE) by an argon atmospheric pressure plasma jet (APPJ) is profoundly investigated in this work. The influence of two different parameters (applied power and argon flow rate) on the plasma jet characteristics and the LDPE surface properties is examined in detail. In a first step, the APPJ is electrically and visually characterized and visual inspection of the afterglow clearly shows that mainly a variation in argon flow rate can result in a changing afterglow length. A maximum afterglow length is obtained at an argon flow rate of 1-1.25 slm, while higher gas flows result in turbulence leading to a shorter afterglow. Secondly, the surface modification of LDPE is examined using different analyzing techniques namely water contact angle (WCA) measurements for the wettability, X-ray photoelectron spectroscopy (XPS) for the chemical composition and atomic force microscopy (AFM) for the surface morphology determination. WCA measurements show that by increasing the applied power the wettability of the LDPE increases. Increasing the argon flow rate up to 1.25 slm gives a decrease in WCA value or in other words an increased wettability. From 1.25 slm on, an increase in argon flow rate during plasma treatment decreases the LDPE wettability as can be concluded from the increased WCA values. An increased wettability can be explained by the incorporation of oxygen moieties. By increasing the discharge power, the concentrations of all oxygen containing groups such as Csbnd O, Cdbnd O and Osbnd Cdbnd O increase. Increasing the flow rate up to 1.25 slm results mainly in an increase in Osbnd Cdbnd O groups. However, from a flow rate of 1.25 slm on, the concentration of all oxygen groups again decreases. Based on these results, the appropriate settings for an efficient plasma treatment can easily be selected.

  15. Chemical rate model for the surface pyrolysis of tetrakis(dimethylamido)titanium to form titanium nitride films

    Science.gov (United States)

    Toprac, Anthony J.; Iacoponi, John A.; Littau, Karl A.

    1998-09-01

    A chemical kinetic rate model for the deposition of titanium nitride films from the surface reaction of tetrakis(dimethyl-amido)titanium (TDMAT) was developed. Without ammonia addition, TDMAT forms a titanium nitride film by pyrolyzing on the hot substrate surface. Experimental data from the applied materials 5000 deposition tool was modeled using a CSTR formulation. With the parameters of the surface reaction model regressed to fit portions of the experimental results, reasonably accurate model predictions over the entire domain of experimental data were obtained.

  16. Effect of high sedimentation rates on surface sediment dynamics and mangrove growth in the Porong River, Indonesia.

    Science.gov (United States)

    Sidik, Frida; Neil, David; Lovelock, Catherine E

    2016-06-15

    Large quantities of mud from the LUSI (Lumpur Sidoarjo) volcano in northeastern Java have been channeled to the sea causing high rates of sediment delivery to the mouth of the Porong River, which has a cover of natural and planted mangroves. This study investigated how the high rates of sediment delivery affected vertical accretion, surface elevation change and the growth of Avicennia sp., the dominant mangrove species in the region. During our observations in 2010-2011 (4-5years after the initial volcanic eruption), very high rates of sedimentation in the forests at the mouth of the river gave rise to high vertical accretion of over 10cmy(-1). The high sedimentation rates not only resulted in reduced growth of Avicennia sp. mangrove trees at the two study sites at the Porong River mouth, but also gave rise to high soil surface elevation gains.

  17. Kinetic model of II-VI(001) semiconductor surfaces : Growth rates in atomic layer epitaxy

    NARCIS (Netherlands)

    Volkmann, T; Ahr, M; Biehl, M

    2004-01-01

    We present a zinc-blende lattice gas model of II-VI(001) surfaces, which is investigated by means of kinetic Monte Carlo simulations. Anisotropic effective interactions between surface metal atoms allow for the description of, e.g., the sublimation of CdTe(001), including the reconstruction of Cd-te

  18. Research on the effect of coverage rate on the surface quality in laser direct writing process

    Science.gov (United States)

    Pan, Xuetao; Tu, Dawei

    2017-07-01

    Direct writing technique is usually used in femtosecond laser two-photon micromachining. The size of the scanning step is an important factor affecting the surface quality and machining efficiency of micro devices. According to the mechanism of two-photon polymerization, combining the distribution function of light intensity and the free radical concentration theory, we establish the mathematical model of coverage of solidification unit, then analyze the effect of coverage on the machining quality and efficiency. Using the principle of exposure equivalence, we also obtained the analytic expressions of the relationship among the surface quality characteristic parameters of microdevices and the scanning step, and carried out the numerical simulation and experiment. The results show that the scanning step has little influence on the surface quality of the line when it is much smaller than the size of the solidification unit. However, with increasing scanning step, the smoothness of line surface is reduced rapidly, and the surface quality becomes much worse.

  19. Hot electron mediated desorption rates calculated from excited state potential energy surfaces

    CERN Document Server

    Olsen, Thomas; Schiøtz, Jakob

    2008-01-01

    We present a model for Desorption Induce by (Multiple) Electronic Transitions (DIET/DIMET) based on potential energy surfaces calculated with the Delta Self-Consistent Field extension of Density Functional Theory. We calculate potential energy surfaces of CO and NO molecules adsorbed on various transition metal surfaces, and show that classical nuclear dynamics does not suffice for propagation in the excited state. We present a simple Hamiltonian describing the system, with parameters obtained from the excited state potential energy surface, and show that this model can describe desorption dynamics in both the DIET and DIMET regime, and reproduce the power law behavior observed experimentally. We observe that the internal stretch degree of freedom in the molecules is crucial for the energy transfer between the hot electrons and the molecule when the coupling to the surface is strong.

  20. Grain-Size Based Additivity Models for Scaling Multi-rate Uranyl Surface Complexation in Subsurface Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoying; Liu, Chongxuan; Hu, Bill X.; Hu, Qinhong

    2016-07-31

    The additivity model assumed that field-scale reaction properties in a sediment including surface area, reactive site concentration, and reaction rate can be predicted from field-scale grain-size distribution by linearly adding reaction properties estimated in laboratory for individual grain-size fractions. This study evaluated the additivity model in scaling mass transfer-limited, multi-rate uranyl (U(VI)) surface complexation reactions in a contaminated sediment. Experimental data of rate-limited U(VI) desorption in a stirred flow-cell reactor were used to estimate the statistical properties of the rate constants for individual grain-size fractions, which were then used to predict rate-limited U(VI) desorption in the composite sediment. The result indicated that the additivity model with respect to the rate of U(VI) desorption provided a good prediction of U(VI) desorption in the composite sediment. However, the rate constants were not directly scalable using the additivity model. An approximate additivity model for directly scaling rate constants was subsequently proposed and evaluated. The result found that the approximate model provided a good prediction of the experimental results within statistical uncertainty. This study also found that a gravel-size fraction (2 to 8 mm), which is often ignored in modeling U(VI) sorption and desorption, is statistically significant to the U(VI) desorption in the sediment.

  1. Soil erosion rates from mixed soil and gravel surfaces in a wind tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Ligotke, M.W.; Klopfer, D.C.

    1990-08-01

    Protective barriers have been identified as integral components of plans to isolate defense waste on the Hanford Site. The use of natural materials to construct protective barriers over waste site is being considered. Design requirements for protective barriers include preventing exposure of buried waste, and restricting penetration or percolation of surface waters through the waste zone. Studies were initiated to evaluate the effects of wind erosion on candidate protective barrier surfaces. A wind tunnel was used to provide controlled erosive stresses and to investigate the erosive effects of wind forces on proposed surface layers for protective barriers. Mixed soil and gravel surfaces were prepared and tested for resistance to wind erosion at the Pacific Northwest Laboratory Aerosol Wind Tunnel Research Facility. These tests were performed to investigate surface deflation caused by suspension of soil from various surface layer configurations and to provide a comparison of the relative resistance of the different surfaces to wind erosion. Planning, testing, and analyzing phases of this wind erosion project were coordinated with other tasks supporting the development of protective barriers. These tasks include climate-change predictions, field studies and modeling efforts. This report provides results of measurements of deflation caused by wind forces over level surfaces. Section 2.0 reviews surface layer characteristics and previous relevant studies on wind erosion, describes effects of erosion, and discusses wind tunnel modeling. Materials and methods of the wind tunnel tests are discussed in Section 3.0. Results and discussion are presented in Section 4.0, and conclusions and recommendations Section 5.0. 53 refs., 29 figs., 7 tabs.

  2. Experimental study of the surface thermal signature of gravity currents: application to the assessment of lava flow effusion rate

    Science.gov (United States)

    Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

    2011-12-01

    During an effusive volcanic eruption, the crisis management is mainly based on the prediction of lava flows advance and its velocity. As the spreading of lava flows is mainly controlled by its rheology and the eruptive mass flux, the key question is how to evaluate them during the eruption (rather than afterwards.) A relationship between the heat flux lost by the lava at its surface and the eruption rate is likely to exist, based on the first-order argument that higher eruption rates should correspond to larger power radiated by a lava flow. The semi-empirical formula developed by Harris and co-workers (e.g. Harris et al., Bull. Volc. 2007) is currently used to estimate lava flow rate from satellite surveys yielding the surface temperatures and area of the lava flow field. However, this approach is derived from a static thermal budget of the lava flow and does not explicitly model the time-evolution of the surface thermal signal. Here we propose laboratory experiments and theoretical studies of the cooling of a viscous axisymmetric gravity current fed at constant flux rate. We first consider the isoviscous case, for which the spreading is well-know. The experiments using silicon oil and the theoretical model both reveal the establishment of a steady surface thermal structure after a transient time. The steady state is a balance between surface cooling and heat advection in the flow. The radiated heat flux in the steady regime, a few days for a basaltic lava flow, depends mainly on the effusion rate rather than on the viscosity. In this regime, one thermal survey of the radiated power could provide a consistent estimate of the flow rate if the external cooling conditions (wind) are reasonably well constrained. We continue to investigate the relationship between the thermal radiated heat flux and the effusion rate by using in the experiments fluids with temperature-dependent viscosity (glucose syrup) or undergoing solidification while cooling (PEG wax). We observe a

  3. SU-E-T-165: Characterization of Dose Distributions in High-Dose-Rate Surface Brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Buzurovic, I; Hansen, J; Bhagwat, M; O’Farrell, D; Damato, A; Friesen, S; Devlin, P; Cormack, R [Dana-Farber/Brigham and Women’s Cancer Center, Harvard Medical School, Boston, MA (United States)

    2015-06-15

    Purpose: To characterize dose distributions in high-dose-rate(HDR) surface brachytherapy using an Ir-125 source for different geometries, field sizes and topology of the clinical targets(CT). To investigate the depth doses at the central axis(CAX), edges of the treatment fields(E), and lateral dose distributions(L) present when using flap applicators in skin cancer treatments. Methods: When malignancies diagnosed on the skin are treated, various geometries of the CT require proper adaptation of the flap or custom-made applicators to the treatment site. Consequently, the dose at the depth on CAX and field edges changes with variation of the curvatures and size of the applicators. To assess the dose distributions, we created a total of 10 treatment plans(TP) for 10×10 and 20×20 field sizes(FS) with a step size of 1cm. The geometry of the applicators was: planar(PA), curved to 30(CA30) and 60(CA60) degrees with respect to the CAX, half-cylinder(HC), and cylindrical shape(CS). One additional TP was created in which the applicators were positioned to form a dome shape(DS) with a diameter of 16cm. This TP was used to emulate treatment of the average sized scalp. All TPs were optimized to deliver a prescription dose at 8mm equidistantly from the planes containing the dwell positions. This optimization is equivalent to the clinical arrangement since the SSD for the flap applicators is 5mm and the prescription depth is 3mm in the majority of clinical cases. Results: The depths (in mm) of the isodose lines were: FS(10×10):PA[90%(9.1CAX,8.0E,7.6L),50%(28.3CAX,20E,17.3L), 25%(51.1CAX,40E,27L)],CA30[90%(10.3CAX,8.2E,7.9L),50%(32.1CAX, 16.2E,15.8L),25%(61.3CAX,36.7E,31.8L)],CA60[90%(12.2CAX,6.1E,6.3L ),50%(47CAX,14E,16.6L),25%(70.8CAX,31.9E,35.4L)],HC[90%(11.1CA X,6.3E,7.3L),50%(38.3CAX,14.6E,16.1L),25%(66.2CAX,33.8E,34.2L)];FS (20×20):PA[90%(11.1CAX,9.0E,7.0L),50%(34.4CAX,21.9E,15.3L),25%(7 0.4CAX,50.9E,34.8L)],CA30[90%(10.9CAX,7.5E,7.1L),50%(38.8CAX,16. 7E,15.4L),25

  4. Effect of Deposition Rate on Structure and Surface Morphology of Thin Evaporated Al Films on Dielectrics and Semiconductors

    Directory of Open Access Journals (Sweden)

    Kirill BORDO

    2012-12-01

    Full Text Available Aluminum (Al films with thickness of 100 nm were grown on unheated glass, silicon and mica substrates by electron beam evaporation. The deposition rates were adjusted in the range between 0.1 nm/s and 2 nm/s, the pressure in the vac­uum chamber during deposition was lower than 1·10–3 Pa. The structure and surface morphology of the as-deposited Al films were studied using scanning electron microscopy (SEM and atomic force microscopy (AFM. SEM imaging of the films showed that the mean grain size of thin Al films on all of the substrates increased from 20 nm – 30 nm to 50 nm – 70 nm with increase of the deposition rate. Quantitative AFM characterization showed that for all substrates the root mean square surface roughness increases monotonically with increasing the deposition rate from 0.1 nm/s to 2 nm/s. The observed effects of the deposition rate on the grain size and surface roughness are explained by the fundamental characteristics of the island growth mode, the influence of the background gases and the surface morphology of the bare substrates.DOI: http://dx.doi.org/10.5755/j01.ms.18.4.3088

  5. Exchange interactions of CaMnO3 in the bulk and at the surface

    CERN Document Server

    Keshavarz, Samara; Rodrigues, Debora; Pereiro, Manuel; Di Marco, Igor; Autieri, Carmine; Nordstrom, Lars; Solovyev, Igor; Sanyal, Biplab; Eriksson, Olle

    2016-01-01

    In this work, we present electronic and magnetic properties of CaMnO3 (CMO) as obtained from ab initio calculations. We identify the preferable magnetic order by means of density functional theory plus Hubbard U calculations and extract the effective exchange parameters (Jij's) using the magnetic force theorem. We find that the effects of geometrical relaxation at the surface as well as the change of crystal field are very strong and are able to influence the lower energy magnetic configuration. In particular, our analysis reveals that the exchange interaction between the Mn atoms belonging to the surface and the subsurface layers is very sensitive to the structural changes. An earlier study [A. Filippetti and W.E. Pickett, Phys. Rev. Lett. 83, 4184 (1999)] suggested that this coupling is ferromagnetic and gives rise to the spin flip process on the surface of CMO. In our work we confirm their finding for an unrelaxed geometry, but once the structural relaxations are taken into account, this exchange coupling ...

  6. Mixing times of monotone surfaces and SOS interfaces: a mean curvature approach

    CERN Document Server

    Caputo, Pietro; Toninelli, Fabio Lucio

    2011-01-01

    We consider stochastic spin-flip dynamics for: (i) monotone discrete surfaces in Z^3 with planar boundary height and (ii) the one-dimensional discrete Solid-on-Solid (SOS) model confined to a box. In both cases we show almost optimal bounds O(L^2polylog(L)) for the mixing time of the chain, where L is the natural size of the system. The dynamics at a macroscopic scale should be described by a deterministic mean curvature motion such that each point of the surface feels a drift which tends to minimize the local surface tension. Inspired by this heuristics, our approach consists in bounding the dynamics with an auxiliary one which, with very high probability, follows quite closely the deterministic mean curvature evolution. Key technical ingredients are monotonicity, coupling and an argument due to D.B. Wilson in the framework of lozenge tiling Markov Chains. Our approach works equally well for both models despite the fact that their equilibrium maximal height fluctuations occur on very different scales (logari...

  7. Soil erosion rates from mixed soil and gravel surfaces in a wind tunnel: A preliminary report

    Energy Technology Data Exchange (ETDEWEB)

    Ligotke, M.W.

    1988-12-01

    Tests of wind erosion were performed in a controlled-environment wind tunnel to support the development of natural-material protective barriers for long-term isolation of radioactive waste. Barrier performance standards currently being developed for internal and external barrier performance are expected to mandate a surface layer that is resistant to wind erosion. The purpose of this study was to initiate a series of tests to determine suitable soil and gravel mixtures for such a barrier and to test worst-case surface layer conditions under the influence of high wind speeds. Six mixed soil and gravel surfaces were prepared, weathered to represent natural wind-blown desert areas, and subjected to controlled wind erosion forces in a wind tunnel. The applied erosive forces, including surface shear forces, were characterized to provide a means of relating wind tunnel results with actual field conditions. Soil particle losses from the surfaces caused by suspension, saltation, and surface creep were monitored by aerosol sample probes and mass balance measurements. 23 refs., 22 figs., 3 tabs.

  8. A Comparative Analysis of Surface Roughness and Material Removal Rate in Milling Operation of AISI 410 Steel And Aluminium 6061

    Directory of Open Access Journals (Sweden)

    Gaurav Kumar,

    2014-06-01

    Full Text Available Surface roughness is an important measure of product quality since it greatly influences the performance of Mechanical parts as well as production cost. Roughness plays an extensive role in demonstrating how the object will interface with the environment. The main purpose of this paper is to analyse the comparative study of Surface Roughness and Material Removal Rate (MRR of Aluminium 6061and AISI 410 Steel. In the present paper three parameters were taken to check whether quality lies within desired tolerance level. Surface roughness and MRR were taken using three different parameters of CNC machining including spindle speed, feed rate and depth of cut. Optimization of surface roughness of aluminium 6061 and AISI 410 Steel were done using Response Surface Methodology. Response Surface Methodology is an adequate channel in which response variable can be optimized by taking several experimental runs. This paper aims to obtain an optimal setting of three milling parameters by using Carbide cutting tool in end milling operation of AISI 410 steel and Aluminium Alloy 6061 taken as specimen.

  9. Surface activation of polyethylene with an argon atmospheric pressure plasma jet: Influence of applied power and flow rate

    Energy Technology Data Exchange (ETDEWEB)

    Van Deynse, A., E-mail: Annick.VanDeynse@ugent.be [Department Industrial Technology and Construction, Faculty of Engineering & Architecture, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent (Belgium); Cools, P., E-mail: Pieter.Cools@ugent.be [Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering & Architecture, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent (Belgium); Leys, C., E-mail: Christophe.Leys@ugent.be [Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering & Architecture, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent (Belgium); De Geyter, N., E-mail: Nathalie.DeGeyter@ugent.be [Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering & Architecture, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent (Belgium); Morent, R., E-mail: Rino.Morent@ugent.be [Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering & Architecture, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent (Belgium)

    2015-02-15

    Highlights: • Surface modification of polyethylene by an argon atmospheric pressure plasma jet. • Investigation of the influence of the applied power and argon flow rate. • Turbulence in the gas flow leads to a shorter afterglow. • Turbulence in the gas flow results in a lower wettability of the polyethylene. • Increasing the applied power increases the wettability of the polyethylene. - Abstract: Atmospheric pressure plasma technology offers attractive perspectives to alter the surface properties of polymers. Within this context, the surface modification of polyethylene (LDPE) by an argon atmospheric pressure plasma jet (APPJ) is profoundly investigated in this work. The influence of two different parameters (applied power and argon flow rate) on the plasma jet characteristics and the LDPE surface properties is examined in detail. In a first step, the APPJ is electrically and visually characterized and visual inspection of the afterglow clearly shows that mainly a variation in argon flow rate can result in a changing afterglow length. A maximum afterglow length is obtained at an argon flow rate of 1–1.25 slm, while higher gas flows result in turbulence leading to a shorter afterglow. Secondly, the surface modification of LDPE is examined using different analyzing techniques namely water contact angle (WCA) measurements for the wettability, X-ray photoelectron spectroscopy (XPS) for the chemical composition and atomic force microscopy (AFM) for the surface morphology determination. WCA measurements show that by increasing the applied power the wettability of the LDPE increases. Increasing the argon flow rate up to 1.25 slm gives a decrease in WCA value or in other words an increased wettability. From 1.25 slm on, an increase in argon flow rate during plasma treatment decreases the LDPE wettability as can be concluded from the increased WCA values. An increased wettability can be explained by the incorporation of oxygen moieties. By increasing the

  10. Damping rates of surface plasmons for particles of size from nano- to micrometers; reduction of the nonradiative decay

    CERN Document Server

    Kolwas, Krystyna

    2012-01-01

    Damping rates of multipolar, localized surface plasmons (SP) of gold and silver nanospheres of radii up to $1000nm$ were found with the tools of classical electrodynamics. The significant increase in damping rates followed by noteworthy decrease for larger particles takes place along with substantial red-shift of plasmon resonance frequencies as a function of particle size. We also introduced interface damping into our modeling, which substantially modifies the plasmon damping rates of smaller particles. We demonstrate unexpected reduction of the multipolar SP damping rates in certain size ranges. This effect can be explained by the suppression of the nonradiative decay channel as a result of the lost competition with the radiative channel. We show that experimental dipole damping rates [H. Baida, et al., Nano Lett. 9(10) (2009) 3463, and C. S\\"onnichsen, et al., Phys. Rev. Lett. 88 (2002) 077402], and the resulting resonance quality factors can be described in a consistent and straightforward way within our ...

  11. Grain-Size Based Additivity Models for Scaling Multi-rate Uranyl Surface Complexation in Subsurface Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoying; Liu, Chongxuan; Hu, Bill X.; Hu, Qinhong

    2016-07-01

    This study statistically analyzed a grain-size based additivity model that has been proposed to scale reaction rates and parameters from laboratory to field. The additivity model assumed that reaction properties in a sediment including surface area, reactive site concentration, reaction rate, and extent can be predicted from field-scale grain size distribution by linearly adding reaction properties for individual grain size fractions. This study focused on the statistical analysis of the additivity model with respect to reaction rate constants using multi-rate uranyl (U(VI)) surface complexation reactions in a contaminated sediment as an example. Experimental data of rate-limited U(VI) desorption in a stirred flow-cell reactor were used to estimate the statistical properties of multi-rate parameters for individual grain size fractions. The statistical properties of the rate constants for the individual grain size fractions were then used to analyze the statistical properties of the additivity model to predict rate-limited U(VI) desorption in the composite sediment, and to evaluate the relative importance of individual grain size fractions to the overall U(VI) desorption. The result indicated that the additivity model provided a good prediction of the U(VI) desorption in the composite sediment. However, the rate constants were not directly scalable using the additivity model, and U(VI) desorption in individual grain size fractions have to be simulated in order to apply the additivity model. An approximate additivity model for directly scaling rate constants was subsequently proposed and evaluated. The result found that the approximate model provided a good prediction of the experimental results within statistical uncertainty. This study also found that a gravel size fraction (2-8mm), which is often ignored in modeling U(VI) sorption and desorption, is statistically significant to the U(VI) desorption in the sediment.

  12. Hydrogen sulphide removal from corroding concrete: comparison between surface removal rates and biomass activity.

    Science.gov (United States)

    Jensen, H S; Nielsen, A H; Lens, P N L; Hvitved-Jacobsen, T; Vollertsen, J

    2009-11-01

    Corrosion of concrete sewer pipes caused by hydrogen sulphide is a problem in many sewer networks. The mechanisms of production and fate of hydrogen sulphide in the sewer biofilms and wastewater as well as its release to the sewer atmosphere are largely understood. In contrast, the mechanisms of the uptake of hydrogen sulphide on the concrete surfaces and subsequent concrete corrosion are basically unknown. To shed light on these mechanisms, the uptake of hydrogen sulphide from a sewer gas phase was compared to the biological hydrogen sulphide removal potential of the concrete corrosion products. The results showed that both microbial degradation at and sorption to the concrete surfaces were important for the uptake of hydrogen sulphide on the concrete surfaces.

  13. Compositional variability across Mercury's surface revealed by MESSENGER measurements of variations in thermal neutron count rates

    Science.gov (United States)

    Peplowski, P. N.; Lawrence, D. J.; Goldsten, J. O.; Nittler, L. R.; Solomon, S. C.

    2013-12-01

    Measurements by MESSENGER's Gamma-Ray and Neutron Spectrometer (GRNS) have revealed variations in the flux of thermal neutrons across Mercury's northern hemisphere. These variations are interpreted to originate from spatial variations in surface elemental composition. In particular, the measurements are sensitive to the near-surface abundances of elements that absorb thermal neutrons, including major rock-forming elements such as Fe and Ti, minor elements such as Mn and Cl, and rare-earth elements such as Gd and Sm. We have constructed a map of thermal neutron variability across the surface and compared it with known variations in elemental composition and with the distribution of geologic units. Development of the map included the derivation of the macroscopic thermal neutron absorption cross section across the surface, a quantity whose value and variability provides useful constraints on the formation and geochemical evolution of Mercury's crust. Finally, by combining the thermal neutron measurements with previously reported elemental measurements from the GRNS and MESSENGER's X-Ray Spectrometer, we have derived constraints on the abundances of neutron-absorbing elements, including previously unreported limits for some minor and rare-earth elements.

  14. Fermi surfaces, spin-mixing parameter, and colossal anisotropy of spin relaxation in transition metals from ab initio theory

    Science.gov (United States)

    Zimmermann, Bernd; Mavropoulos, Phivos; Long, Nguyen H.; Gerhorst, Christian-Roman; Blügel, Stefan; Mokrousov, Yuriy

    2016-04-01

    The Fermi surfaces and Elliott-Yafet spin-mixing parameter (EYP) of several elemental metals are studied by ab initio calculations. We focus first on the anisotropy of the EYP as a function of the direction of the spin-quantization axis [B. Zimmermann et al., Phys. Rev. Lett. 109, 236603 (2012), 10.1103/PhysRevLett.109.236603]. We analyze in detail the origin of the gigantic anisotropy in 5 d hcp metals as compared to 5 d cubic metals by band structure calculations and discuss the stability of our results against an applied magnetic field. We further present calculations of light (4 d and 3 d ) hcp crystals, where we find a huge increase of the EYP anisotropy, reaching colossal values as large as 6000 % in hcp Ti. We attribute these findings to the reduced strength of spin-orbit coupling, which promotes the anisotropic spin-flip hot loops at the Fermi surface. In order to conduct these investigations, we developed an adapted tetrahedron-based method for the precise calculation of Fermi surfaces of complicated shape and accurate Fermi-surface integrals within the full-potential relativistic Korringa-Kohn-Rostoker Green function method.

  15. False negative rate and other performance measures of a sponge-wipe surface sampling method for low contaminant concentrations.

    Energy Technology Data Exchange (ETDEWEB)

    Einfeld, Wayne; Krauter, Paula A.; Boucher, Raymond M.; Tezak, Mathew; Amidan, Brett G. (Pacific Northwest National Laboratory, Richland, WA); Piepel, Greg F. (Pacific Northwest National Laboratory, Richland, WA)

    2011-05-01

    Recovery of spores from environmental surfaces is known to vary due to sampling methodology, techniques, spore size and characteristics, surface materials, and environmental conditions. A series of tests were performed to evaluate a new, validated sponge-wipe method. Specific factors evaluated were the effects of contaminant concentrations and surface materials on recovery efficiency (RE), false negative rate (FNR), limit of detection (LOD) - and the uncertainties of these quantities. Ceramic tile and stainless steel had the highest mean RE values (48.9 and 48.1%, respectively). Faux leather, vinyl tile, and painted wood had mean RE values of 30.3, 25.6, and 25.5, respectively, while plastic had the lowest mean RE (9.8%). Results show a roughly linear dependence of surface roughness on RE, where the smoothest surfaces have the highest mean RE values. REs were not influenced by the low spore concentrations tested (3 x 10{sup -3} to 1.86 CFU/cm{sup 2}). The FNR data were consistent with RE data, showing a trend of smoother surfaces resulting in higher REs and lower FNRs. Stainless steel generally had the lowest mean FNR (0.123) and plastic had the highest mean FNR (0.479). The LOD{sub 90} varied with surface material, from 0.015 CFU/cm{sup 2} on stainless steel up to 0.039 on plastic. Selecting sampling locations on the basis of surface roughness and using roughness to interpret spore recovery data can improve sampling. Further, FNR values, calculated as a function of concentration and surface material, can be used pre-sampling to calculate the numbers of samples for statistical sampling plans with desired performance, and post-sampling to calculate the confidence in characterization and clearance decisions.

  16. Collective non-equilibrium dynamics at surfaces and the spatio-temporal edge

    Science.gov (United States)

    Marcuzzi, M.; Gambassi, A.; Pleimling, M.

    2012-11-01

    Symmetries represent a fundamental constraint for physical systems and relevant new phenomena often emerge as a consequence of their breaking. An important example is provided by space- and time-translational invariance in statistical systems, which hold at a coarse-grained scale in equilibrium and are broken by spatial and temporal boundaries, the former being implemented by surfaces —unavoidable in real samples— the latter by some initial condition for the dynamics which causes a non-equilibrium evolution. While the separate effects of these two boundaries are well understood, we demonstrate here that additional, unexpected features arise upon approaching the effective edge formed by their intersection. For this purpose, we focus on the classical semi-infinite Ising model with spin-flip dynamics evolving out of equilibrium at its critical point. Considering both subcritical and critical values of the coupling among surface spins, we present numerical evidence of a scaling regime with universal features which emerges upon approaching the spatio-temporal edge and we rationalise these findings within a field-theoretical approach.

  17. Development of Copper Corrosion Products and Relation between Surface Appearance and Corrosion Rate

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Tran Thi Ngoc; Binh, Nguyen Thi Thanh [Vietnam National University, Ho Chi Minh (Viet Nam); Tru, Nguyen Nhi [Vietnam Institute for Tropical Technology and Environmental Protection, Ho Chi Minh (Viet Nam); Yoshino, Tsujino [Osaka Prefecture, Osaka (Japan); Yasuki, Maeda [Osaka Prefecture University, Osaka (Japan)

    2008-04-15

    Copper was exposed unsheltered and sheltered in four humid tropical sites, representing urban, urban-industrial, urban-marine and rural environments. The corrosion rates and the sequence of corrosion product formation are presented and discussed in relation with climatic and atmospheric pollution parameters. Chemical compositions of corrosion products were found to depend on environments and duration of exposure. In all environments, cuprite was the predominating corrosion product that formed first and continuously increased during the exposure. Among the sulphur-containing corrosion products, posnjakite and brochantite were more frequently found and the first formed earlier. Nantokite was the most common chlorine-containing products for most cases, except the high-chloride environment, where atacamite was detected instead. The corrosion rate of copper was well indicated by the colour of patina. The red-purple colour corresponded to the high corrosion rate and the greenish grey colour corresponded to the low corrosion rate. Corrosion rate of sheltered copper in urban-marine environment increased with the exposure time.

  18. Enhancement of muonium emission rate from silica aerogel with a laser ablated surface

    CERN Document Server

    Beer, G A; Hirota, S; Ishida, K; Iwasaki, M; Kanda, S; Kawai, H; Kawamura, N; Kitamura, R; Lee, S; Marshall, W Lee G M; Mibe, T; Miyake, Y; Okada, S; Olchanski, K; Olin, A; Oishi, Y; Onishi, H; Otani, M; Saito, N; Shimomura, K; Strasser, P; Tabata, M; Tomono, D; Ueno, K; Yokoyama, K; Won, E

    2014-01-01

    Emission of muonium ($\\mu^+e^-$) atoms from a laser-processed aerogel surface into vacuum was studied for the first time. Laser ablation was used to create hole-like regions with diameter of about 270$~\\mu$m in a triangular pattern with hole separation in the range of 300--500$~\\mu$m. The emission probability for the laser-processed aerogel sample is at least eight times higher than for a uniform one.

  19. Bacterial growth on surfaces: Automated image analysis for quantification of growth rate-related parameters

    DEFF Research Database (Denmark)

    Møller, S.; Sternberg, Claus; Poulsen, L. K.

    1995-01-01

    species-specific hybridizations with fluorescence-labelled ribosomal probes to estimate the single-cell concentration of RNA. By automated analysis of digitized images of stained cells, we determined four independent growth rate-related parameters: cellular RNA and DNA contents, cell volume......, and the frequency of dividing cells in a cell population. These parameters were used to compare physiological states of liquid-suspended and surfacegrowing Pseudomonas putida KT2442 in chemostat cultures. The major finding is that the correlation between substrate availability and cellular growth rate found...

  20. Dependence of the residual surface resistance of SRF cavities on the cooling rate through $T_\\mathrm{c}$

    CERN Document Server

    Romanenko, A; Melnychuk, O; Sergatskov, D A

    2014-01-01

    We report a strong effect of the cooling rate through $T_\\mathrm{c}$ on the amount of trapped external magnetic flux in superconducting niobium cavities. The effect is similar for all surface treatments including electropolishing with and without 120$^\\circ$C baking, and nitrogen doping. Direct magnetic field measurements on the cavity walls show that the effect stems from changes in the flux trapping efficiency at different cooling rates. Slow cooling leads to almost complete flux trapping and higher residual resistance while fast cooling leads to the much more efficient flux expulsion and lower residual resistance.

  1. Rates and patterns of surface deformation from laser scanning following the South Napa earthquake, California

    Science.gov (United States)

    DeLong, Stephen B.; Lienkaemper, James J.; Pickering, Alexandra J; Avdievitch, Nikita N.

    2015-01-01

    The A.D. 2014 M6.0 South Napa earthquake, despite its moderate magnitude, caused significant damage to the Napa Valley in northern California (USA). Surface rupture occurred along several mapped and unmapped faults. Field observations following the earthquake indicated that the magnitude of postseismic surface slip was likely to approach or exceed the maximum coseismic surface slip and as such presented ongoing hazard to infrastructure. Using a laser scanner, we monitored postseismic deformation in three dimensions through time along 0.5 km of the main surface rupture. A key component of this study is the demonstration of proper alignment of repeat surveys using point cloud–based methods that minimize error imposed by both local survey errors and global navigation satellite system georeferencing errors. Using solid modeling of natural and cultural features, we quantify dextral postseismic displacement at several hundred points near the main fault trace. We also quantify total dextral displacement of initially straight cultural features. Total dextral displacement from both coseismic displacement and the first 2.5 d of postseismic displacement ranges from 0.22 to 0.29 m. This range increased to 0.33–0.42 m at 59 d post-earthquake. Furthermore, we estimate up to 0.15 m of vertical deformation during the first 2.5 d post-earthquake, which then increased by ∼0.02 m at 59 d post-earthquake. This vertical deformation is not expressed as a distinct step or scarp at the fault trace but rather as a broad up-to-the-west zone of increasing elevation change spanning the fault trace over several tens of meters, challenging common notions about fault scarp development in strike-slip systems. Integrating these analyses provides three-dimensional mapping of surface deformation and identifies spatial variability in slip along the main fault trace that we attribute to distributed slip via subtle block rotation. These results indicate the benefits of laser scanner surveys along

  2. The relation between surface star formation rate density and spiral arms in NGC 5236 (M83)

    CERN Document Server

    Silva-Villa, Esteban

    2011-01-01

    For a long time the consensus has been that star formation rates are higher in the interior of spiral arms in galaxies, compared to inter-arm regions. However, recent studies have found that the star formation inside the arms is not more efficient than elsewhere in the galaxy. Previous studies have based their conclusion mainly on integrated light. We use resolved stellar populations to investigate the star formation rates throughout the nearby spiral galaxy NGC 5236. We aim to investigate how the star formation rate varies in the spiral arms compared to the inter-arm regions, using optical space-based observations of NGC 5236. Using ground-based H\\alpha images we traced regions of recent star formation, and reconstructed the arms of the galaxy. Using HST/ACS images we estimate star formation histories by means of the synthetic CMD method. Arms based on H\\alpha images showed to follow the regions where stellar crowding is higher. Star formation rates for individual arms over the fields covered were estimated ...

  3. Bacterial growth on surfaces: Automated image analysis for quantification of growth rate-related parameters

    DEFF Research Database (Denmark)

    Møller, S.; Sternberg, Claus; Poulsen, L. K.

    1995-01-01

    A fast routine method for estimating bacterial cell growth rates by using the metachromatic dye acridine orange is described. The method allows simultaneous estimates of cellular RNA and DNA contents of single cells. Acridine orange staining can be used as a nonspecific supplement to quantitative...

  4. Elementary stage rate coefficients of heterogeneous catalytic recombination of dissociated air on thermal protective surfaces from ab initio approach

    Science.gov (United States)

    Buchachenko, A. A.; Kroupnov, A. A.; Kovalev, V. L.

    2015-08-01

    Elementary stage rate coefficients of the full system of kinetic equations describing heterogeneous catalytic recombination of the dissociated air on the surfaces of thermal protective ceramic coatings of β-cristobalite and α-Al2O3 are determined using the quantum-mechanical calculations within the framework of cluster models and literature data. Both the impact and associative recombination processes of adsorbed oxygen and nitrogen atoms are taken into account.

  5. Modelling and analysis of material removal rate and surface roughness in wire-cut EDM of armour materials

    Directory of Open Access Journals (Sweden)

    Ravindranadh Bobbili

    2015-12-01

    Full Text Available The current work presents a comparative study of wire electrical discharge machining (WEDM of armour materials such as aluminium alloy 7017 and rolled homogeneous armour (RHA steel using buckingham pi theorem to model the input variables and thermo-physical characteristics of WEDM on material removal rate (MRR and surface roughness (Ra of Al 7017 and RHA steel. The parameters of the model such as pulse-on time, flushing pressure, input power, thermal diffusivity and latent heat of vaporization have been determined through design of experiment methodology. Wear rate of brass wire increases with rise in input energy in machining Al 7017. The dependence of thermo-physical properties and machining variables on mechanism of MRR and Ra has been described by performing scanning electron microscope (SEM study. The rise in pulse-on time from 0.85μs to 1.25μs causes improvement in MRR and deterioration of surface finish. The machined surface has revealed that craters are found on the machined surface. The propensity of formation of craters increases during WEDM with a higher current and larger pulse-on time.

  6. Soil surface organic layers in Arctic Alaska: Spatial distribution, rates of formation, and microclimatic effects

    Science.gov (United States)

    Baughman, Carson A.; Mann, Daniel H.; Verbyla, David L.; Kunz, Michael L.

    2015-06-01

    Organic layers of living and dead vegetation cover the ground surface in many permafrost landscapes and play important roles in ecosystem processes. These soil surface organic layers (SSOLs) store large amounts of carbon and buffer the underlying permafrost and its contained carbon from changes in aboveground climate. Understanding the dynamics of SSOLs is a prerequisite for predicting how permafrost and carbon stocks will respond to warming climate. Here we ask three questions about SSOLs in a representative area of the Arctic Foothills region of northern Alaska: (1) What environmental factors control the thickness of SSOLs and the carbon they store? (2) How long do SSOLs take to develop on newly stabilized point bars? (3) How do SSOLs affect temperature in the underlying ground? Results show that SSOL thickness and distribution correlate with elevation, drainage area, vegetation productivity, and incoming solar radiation. A multiple regression model based on these correlations can simulate spatial distribution of SSOLs and estimate the organic carbon stored there. SSOLs develop within a few decades after a new, sandy, geomorphic surface stabilizes but require 500-700 years to reach steady state thickness. Mature SSOLs lower the growing season temperature and mean annual temperature of the underlying mineral soil by 8 and 3°C, respectively. We suggest that the proximate effects of warming climate on permafrost landscapes now covered by SSOLs will occur indirectly via climate's effects on the frequency, extent, and severity of disturbances like fires and landslides that disrupt the SSOLs and interfere with their protection of the underlying permafrost.

  7. Soil surface organic layers in Arctic Alaska: spatial distribution, rates of formation, and microclimatic effects

    Science.gov (United States)

    Baughman, Carson A.; Mann, Daniel H.; Verbyla, David L.; Kunz, Michael L.

    2015-01-01

    Organic layers of living and dead vegetation cover the ground surface in many permafrost landscapes and play important roles in ecosystem processes. These soil surface organic layers (SSOLs) store large amounts of carbon and buffer the underlying permafrost and its contained carbon from changes in aboveground climate. Understanding the dynamics of SSOLs is a prerequisite for predicting how permafrost and carbon stocks will respond to warming climate. Here we ask three questions about SSOLs in a representative area of the Arctic Foothills region of northern Alaska: (1) What environmental factors control the thickness of SSOLs and the carbon they store? (2) How long do SSOLs take to develop on newly stabilized point bars? (3) How do SSOLs affect temperature in the underlying ground? Results show that SSOL thickness and distribution correlate with elevation, drainage area, vegetation productivity, and incoming solar radiation. A multiple regression model based on these correlations can simulate spatial distribution of SSOLs and estimate the organic carbon stored there. SSOLs develop within a few decades after a new, sandy, geomorphic surface stabilizes but require 500–700 years to reach steady state thickness. Mature SSOLs lower the growing season temperature and mean annual temperature of the underlying mineral soil by 8 and 3°C, respectively. We suggest that the proximate effects of warming climate on permafrost landscapes now covered by SSOLs will occur indirectly via climate's effects on the frequency, extent, and severity of disturbances like fires and landslides that disrupt the SSOLs and interfere with their protection of the underlying permafrost.

  8. In-situ buildup of cosmogenic isotopes at the earth`s surface: measurement of erosion rates and exposure times

    Energy Technology Data Exchange (ETDEWEB)

    Fifield, L.K.; Allan, G.L.; Stone, J.O.H.; Evans, J.M.; Cresswell, R.G.; Ophel, T.R. [Australian National Univ., Canberra, ACT (Australia)

    1993-12-31

    Cosmic rays produce a number of nuclides in rocks that can be used to determine the geomorphic history of surfaces. The most useful are the radioactive isotopes {sup 10}Be (t{sub 1/2} = 1.5Ma), {sup 26}Al (0.7Ma) and {sup 36}Cl (0.3Ma). Within the top 2m of the surface, these are produced principally by fast neutrons. At greater depths, production is dominated by the capture of negative muons. Measurements of a single nuclide produced in situ can be used to determine total exposure times or erosion rates. The use of multiple nuclides with different half-lives makes it possible to determine more complex histories, such as exposures interrupted by periods of burial. At the ANU, all three of the isotopes above are being used to study a variety of problems in geomorphology and paleoclimatology, although to date, most of the work has concentrated on {sup 36}Cl. The accumulation of cosmogenic {sup 36}Cl in calcite (CaCO{sub 3}) provides a means of measuring erosion rates on limestone surfaces. Sensitivity is achieved over a wide range of erosion rates due to the high production rate of {sup 36}Cl in calcite (typically greater than 30 atoms/g/yr) and a detection limit of ca. 5000 atoms/g attainable with the ANU AMS system. The method is simplified by the predominance of Ca reactions (principally spallation) over other sources of {sup 36}Cl in calcite, and the ease of sample preparation. This presentation discuss the results of measurements of {sup 36}Cl in calcite from limestone samples from Australia and Papua New Guinea. Erosion rates derived from these measurements range from 3 microns per year (Australia) to over 200 microns per year in the New Guinea highlands. 3 refs.

  9. Extraction of fetal heart rate from maternal surface ECG with provisions for multiple pregnancies.

    Science.gov (United States)

    Fanelli, A; Signorini, M G; Heldt, T

    2012-01-01

    Twin pregnancies carry an inherently higher risk than singleton pregnancies due to the increased chances of uterine growth restriction. It is thus desirable to monitor the wellbeing of the fetuses during gestation to detect potentially harmful conditions. The detection of fetal heart rate from the maternal abdominal ECG represents one possible approach for noninvasive and continuous fetal monitoring. Here, we propose a new algorithm for the extraction of twin fetal heart rate signals from maternal abdominal ECG recordings. The algorithm detects the fetal QRS complexes and converts the QRS onset series into a binary signal that is then recursively scanned to separate the contributions from the two fetuses. The algorithm was tested on synthetic singleton and twin abdominal recordings. It achieved an average sensitivity and accuracy for QRS complex detection of 97.5% and 93.6%, respectively.

  10. From the surface to the deep critical zone: Linking soil carbon, fluid saturation and weathering rate

    Science.gov (United States)

    Druhan, Jennifer; Lawrence, Corey; Oster, Jessica; Rempe, Daniella; Dietrich, William

    2017-04-01

    Shallow soils from a wide range of ecosystems demonstrate a clear and consistent relationship between effective fluid saturation and the rate at which organic carbon is converted to CO2. While the underlying mechanisms contributing to this dependence are diverse, a consistent pattern of maximum CO2 production at intermediate soil moisture supports a generalized functional relationship, which may be incorporated into a quantitative reactive transport framework. A key result of this model development is a prediction of the extent to which the inorganic carbon content of water in biologically active soils varies as a function of hydrologic parameters (i.e. moisture content and residence time), and in turn influences weathering reactions. Deeper in the CZ, the consistency of this relationship and the influence of hydrologically - regulated CO2 production on the rates of water - rock interaction are largely unknown. Here, we use a novel reactive transport model incorporating this functional relationship to consider how variations in the reactive potential of water entering the vadose zone influences subsurface weathering rates. We leverage two examples of variably saturated natural systems to consider (1) CO2 production and associated weathering potential regulated by seasonal hydrologic shifts and (2) the preservation of soil carbon signatures in the deep CZ over millennial timescales. First, at the Eel River CZ Observatory in Northern California, USA, a novel Vadose Zone Monitoring System (VMS) installed in a 14 - 20 m thick unsaturated section offers an unprecedented view into the physical, chemical and biological behavior of the depth profile separating soils from groundwater. Based on soil moisture, gas and fluid phase samples, we demonstrate a predictive relationship between seasonal hydrologic variations and the location and magnitude of geochemical weathering rates. Second, an environmental monitoring project in the Blue Springs Cave, Sparta, TN, USA, provides

  11. A simple small scale method to determine the re-suspension rate for non-fixed surface contamination

    Energy Technology Data Exchange (ETDEWEB)

    Nolte, O.; Koch, W. [Fraunhofer ITEM, Hanover (Germany); Lange, F.; Martens, R. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Cologne (Germany)

    2004-07-01

    In the frame of the Co-ordinated Research Program of IAEA ''Radiological aspects of package and conveyance non-fixed contamination'' it has been identified that there is a lack of knowledge concerning the airborne release from surfaces with non-fixed contamination of radioactive materials during normal transport conditions. This has a direct effect on the models and parameters underlying the non-fixed contamination limits for packages and conveyances. We have developed a simple and practicable methodology to investigate the suspension of non-fixed particle bound contamination from surfaces due to effects such as wind and vibration affecting packages during normal transport conditions. This method is based on the formation of a defined contamination layer on small test surfaces by bringing them into either liquid or airborne suspensions of surrogate particles. A time and particle size resolved detection technique covering the particle size range between 1 and 100 {mu}m is employed to measure the particle resuspension rate from the test surface exposed to controlled hydrodynamic and/or vibrational forces inside a narrow flow channel (4 mm channel height). All particles suspended from the test surface and incorporated into the airflow are size classified and counted by a clean room particle counter.

  12. Why is the Bay of Bengal experiencing a reduced rate of sea surface warming?

    Digital Repository Service at National Institute of Oceanography (India)

    DeMello, J.R.; PrasannaKumar, S.

    . RupaKumar et al. (2002) was the first to show that the Indian Ocean was warming at the rate of 0.5 °C per 100 years, based on the analysis of SST data during 1904 to 1994. Subsequently, Prasanna Kumar et al. (2009) showed that the Arabian Sea... is experiencing a secular warming and a regional climate shift after mid-1990 based on analysis of SST data during 1960 to 2005. However, no such studies on long term variability are available in the case of the BoB. It is in this context that in the present...

  13. Hydrolysis of VX on Concrete: Rate of Degradation by Direct Surface Interrogation using an Ion Trap Secondary Ion Mass Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Groenewold, Gary Steven; Appelhans, Anthony David; Gresham, Garold Linn; Olson, John Eric; Rowland, B.; Williams, j.; Jeffery, M. T.

    2002-09-01

    The nerve agent VX (O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate) is lethal at very low levels of exposure, which can occur by dermal contact with contaminated surfaces. Hence, behavior of VX in contact with common urban or industrial surfaces is a subject of acute interest. In the present study, VX was found to undergo complete degradation when in contact with concrete surfaces. The degradation was directly interrogated at submonolayer concentrations by periodically performing secondary ion mass spectrometry (SIMS) analyses after exposure of the concrete to VX. The abundance of the [VX + H]+ ion in the SIMS spectra was observed to decrease in an exponential fashion, consistent with first-order or pseudo-first-order behavior. This phenomenon enabled the rate constant to be determined at 0.005 min-1 at 25 C, which corresponds to a half-life of about 3 h on the concrete surface. The decrease in [VX + H]+ was accompanied by an increase in the abundance of the principal degradation product diisopropylaminoethanethiol (DESH), which arises by cleavage of the P-S bond. Degradation to form DESH is accompanied by the formation of ethyl methylphosphonic acid, which is observable only in the negative ion spectrum. A second degradation product was also implicated, which corresponded to a diisopropylvinylamine isomer (perhaps N,N-diisopropyl aziridinium) that arose via cleavage of the S-C bond. No evidence was observed for the formation of the toxic S-2-diisopropylaminoethyl methylphosphonothioic acid. The degradation rate constants were measured at four different temperatures (24-50 C), which resulted in a linear Arrhenius relationship and an activation energy of 52 kJ mol-1. This value agrees with previous values observed for VX hydrolysis in alkaline solutions, which suggests that the degradation of submonolayer VX is dominated by alkaline hydrolysis within the adventitious water film on the concrete surface.

  14. A Feasibility Study for Measuring Accurate Chest Compression Depth and Rate on Soft Surfaces Using Two Accelerometers and Spectral Analysis

    Directory of Open Access Journals (Sweden)

    Sofía Ruiz de Gauna

    2016-01-01

    Full Text Available Background. Cardiopulmonary resuscitation (CPR feedback devices are being increasingly used. However, current accelerometer-based devices overestimate chest displacement when CPR is performed on soft surfaces, which may lead to insufficient compression depth. Aim. To assess the performance of a new algorithm for measuring compression depth and rate based on two accelerometers in a simulated resuscitation scenario. Materials and Methods. Compressions were provided to a manikin on two mattresses, foam and sprung, with and without a backboard. One accelerometer was placed on the chest and the second at the manikin’s back. Chest displacement and mattress displacement were calculated from the spectral analysis of the corresponding acceleration every 2 seconds and subtracted to compute the actual sternal-spinal displacement. Compression rate was obtained from the chest acceleration. Results. Median unsigned error in depth was 2.1 mm (4.4%. Error was 2.4 mm in the foam and 1.7 mm in the sprung mattress (p<0.001. Error was 3.1/2.0 mm and 1.8/1.6 mm with/without backboard for foam and sprung, respectively (p<0.001. Median error in rate was 0.9 cpm (1.0%, with no significant differences between test conditions. Conclusion. The system provided accurate feedback on chest compression depth and rate on soft surfaces. Our solution compensated mattress displacement, avoiding overestimation of compression depth when CPR is performed on soft surfaces.

  15. Stability and bifurcation analysis of spin-polarized vertical-cavity surface-emitting lasers

    Science.gov (United States)

    Li, Nianqiang; Susanto, H.; Cemlyn, B. R.; Henning, I. D.; Adams, M. J.

    2017-07-01

    A detailed stability and bifurcation analysis of spin-polarized vertical-cavity surface-emitting lasers (VCSELs) is presented. We consider both steady-state and dynamical regimes. In the case of steady-state operation, we carry out a small-signal (asymptotic) stability analysis of the steady-state solutions for a representative set of spin-VCSEL parameters. Compared with full numerical simulation, we show this produces surprisingly accurate results over the whole range of pump ellipticity, and spin-VCSEL bias up to 1.5 times the threshold. We then combine direct numerical integration of the extended spin-flip model and standard continuation technique to examine the underlying dynamics. We find that the spin VCSEL undergoes a period-doubling or quasiperiodic route to chaos as either the pump magnitude or polarization ellipticity is varied. Moreover, we find that different dynamical states can coexist in a finite interval of pump intensity, and observe a hysteresis loop whose width is tunable via the pump polarization. Finally we report a comparison of stability maps in the plane of the pump polarization against pump magnitude produced by categorizing the dynamic output of a spin VCSEL from time-domain simulations, against supercritical bifurcation curves obtained by the standard continuation package auto. This helps us better understand the underlying dynamics of the spin VCSELs.

  16. Spin flipping in rings with Siberian Snakes II: Simulations with localized orbit excursions

    Energy Technology Data Exchange (ETDEWEB)

    Mane, S.R., E-mail: srmane001@gmail.com [Convergent Computing Inc., P.O. Box 561, Shoreham, NY 11786 (United States)

    2012-07-21

    A new program EILMS is used to perform spin tracking simulations, for spin flippers in model rings with full strength Siberian Snakes, at a spin tune of 1/2 . EILMS employs canonical variables and symplectic-unitary integrators for all beamline elements. In particular, tracking studies are presented for a new design of a spin flipper proposed for stored polarized proton beams in RHIC. The induced coherent vertical betatron oscillations are localized within the flipper system. Points of detail which require further study are elucidated.

  17. Comment on “Full spin flipping in the presence of full Siberian Snake”

    Directory of Open Access Journals (Sweden)

    S. R. Mane

    2009-09-01

    Full Text Available Bai and Roser {Phys. Rev. ST Accel. Beams 11, 091001 (2008PRABFM1098-440210.1103/PhysRevSTAB.11.091001 [Phys. Rev. ST Accel. Beams 12, 019901(E (2009]PRABFM1098-440210.1103/PhysRevSTAB.12.019901} have published an idea for a design of a spin flipper, consisting of two radial field rf dipoles with correlated phases, to operate with full strength Siberian Snakes, at a spin tune of 1/2. Some details of their design analysis are oversimplified.

  18. Why do galactic spins flip in the cosmic web? A Theory of Tidal Torques near saddles

    CERN Document Server

    Pichon, Christophe; Pogosyan, Dmitry; Dubois, Yohan; Desjacques, Vincent; Devriendt, Julien

    2014-01-01

    Filaments of the cosmic web drive spin acquisition of disc galaxies. The point process of filament-type saddle represent best this environment and can be used to revisit the Tidal Torque Theory in the context of an anisotropic peak (saddle) background split. The constrained misalignment between the tidal tensor and the Hessian of the density field generated in the vicinity of filament saddle points simply explains the corresponding transverse and longitudinal point-reflection symmetric geometry of spin distribution. It predicts in particular an azimuthal orientation of the spins of more massive galaxies and spin alignment with the filament for less massive galaxies. Its scale dependence also allows us to relate the transition mass corresponding to the alignment of dark matter halos spin relative to the direction of their neighboring filament to this geometry, and to predict accordingly it s scaling with the mass of non linearity, as was measured in simulations.

  19. Super-long life time for 2D cyclotron spin-flip excitons.

    Science.gov (United States)

    Kulik, L V; Gorbunov, A V; Zhuravlev, A S; Timofeev, V B; Dickmann, S; Kukushkin, I V

    2015-05-19

    An experimental technique for the indirect manipulation and detection of electron spins entangled in two-dimensional magnetoexcitons has been developed. The kinetics of the spin relaxation has been investigated. Photoexcited spin-magnetoexcitons were found to exhibit extremely slow relaxation in specific quantum Hall systems, fabricated in high mobility GaAs/AlGaAs structures; namely, the relaxation time reaches values over one hundred microseconds. A qualitative explanation of this spin-relaxation kinetics is presented. Its temperature and magnetic field dependencies are discussed within the available theoretical framework.

  20. Super-long life time for 2D cyclotron spin-flip excitons

    OpenAIRE

    Kulik, L. V.; Gorbunov, A. V.; Zhuravlev, A. S.; Timofeev, V. B.; Dickmann, S.; Kukushkin, I. V.

    2015-01-01

    An experimental technique for the indirect manipulation and detection of electron spins entangled in two-dimensional magnetoexcitons has been developed. The kinetics of the spin relaxation has been investigated. Photoexcited spin-magnetoexcitons were found to exhibit extremely slow relaxation in specific quantum Hall systems, fabricated in high mobility GaAs/AlGaAs structures, namely, the relaxation time reaches values over one hundred microseconds. A qualitative explanation of this spin-rela...

  1. Why do galactic spins flip in the cosmic web? A Theory of Tidal Torques near saddles

    Science.gov (United States)

    Pichon, Christophe; Codis, Sandrine; Pogosyan, Dmitry; Dubois, Yohan; Desjacques, Vincent; Devriendt, Julien

    2016-10-01

    Filaments of the cosmic web drive spin acquisition of disc galaxies. The point process of filament-type saddle represent best this environment and can be used to revisit the Tidal Torque Theory in the context of an anisotropic peak (saddle) background split. The constrained misalignment between the tidal tensor and the Hessian of the density field generated in the vicinity of filament saddle points simply explains the corresponding transverse and longitudinal point-reflection symmetric geometry of spin distribution. It predicts in particular an azimuthal orientation of the spins of more massive galaxies and spin alignment with the filament for less massive galaxies. Its scale dependence also allows us to relate the transition mass corresponding to the alignment of dark matter halos' spin relative to the direction of their neighboring filament to this geometry, and to predict accordingly it's scaling with the mass of non linearity, as was measured in simulations.

  2. Spin flip of neutrinos with magnetic moment in core-collapse supernova

    CERN Document Server

    Lychkovskiy, Oleg

    2009-01-01

    Neutrino with magnetic moment can experience a chirality flip while scattering off charged particles. This effect may lead to important consequences for the dynamics and the neutrino signal of the core-collapse supernova. It is known that if neutrino is a Dirac fermion, then nu_L->nu_R transition induced by the chirality flip leads to the emission of sterile right-handed neutrinos. The typical energies of these neutrinos are rather high, E ~ (100-200)MeV. Neutrino spin precession in the magnetic field either inside the collapsing star or in the interstellar space may lead to the backward transition, nu_R->nu_L. Both possibilities are known to be interesting. In the former case high-energy neutrinos can deliver additional energy to the supernova envelope, which can help the supernova to explode. In the latter case high-energy neutrinos may be detected simultaneously with the "normal" supernova neutrino signal, which would be a smoking gun for the Dirac neutrino magnetic moment. We report the results of the cal...

  3. Optimization of Material Removal Rate & Surface Roughness in Dry Turning of Medium Carbon Steel En19 by Using Taguchi Method

    Directory of Open Access Journals (Sweden)

    Ch. Maheswara Rao

    2015-10-01

    Full Text Available Optimization of machining parameters is valuable to maintain the accuracy of the components and to minimize the cost of machining. Surface finish is an important measure for the quality of the machined parts. The present work is an experimental investigation to study the effect of machining parameters on Material Removal Rate and Surface Roughness in dry turning of medium carbon steel EN19. Taguchi’s single objective optimization method was used to find the effect of input parameters on the responses. The experiments were conducted as per Taguchi’s L9 Orthogonal Array on CNC lathe under dry conditions. Cutting parameters of speed, feed and depth of cut were taken as inputs and machining was done by PVD TiAlN tool. Regression models for the responses were prepared by using MINITAB-16 software. Analysis of variance (ANOVA was used to find the influence of machining parameters on the responses. From the ANOVA results, it is clear that speed has high influence followed by feed and depth of cut has very low influence in achieving the optimum values for both Material Removal Rate and Surface Roughness. Finally, experimental and Regression values of responses were compared. From the results, it is found that both the values are close to each other hence, the regression models prepared were more accurate and adequate. Percentage of errors between experimental and regression values were calculated and they found in the range of ±0.20.

  4. Surface deformation associated with the 2013 Mw7.7 Balochistan earthquake: Geologic slip rates may significantly underestimate strain release

    Science.gov (United States)

    Gold, Ryan; Reitman, Nadine; Briggs, Richard; Barnhart, William; Hayes, Gavin

    2015-04-01

    The 24 September 2013 Mw7.7 Balochistan, Pakistan earthquake ruptured a ~200 km-long stretch of the 60° ± 15° northwest-dipping Hoshab fault in southern Pakistan. The earthquake is notable because it produced the second-largest lateral surface displacement observed for a continental strike-slip earthquake. Surface displacements and geodetic and teleseismic inversions indicate that peak slip occurred within the upper 0-3 km of the crust. To explore along-strike and fault-perpendicular surface deformation patterns, we remotely mapped the surface trace of the rupture and measured its surface deformation using high-resolution (0.5 m) pre- and post-event satellite imagery. Post-event images were collected 7-114 days following the earthquake, so our analysis captures the sum of both the coseismic and post-seismic (e.g., after slip) deformation. We document peak left-lateral offset of ~15 m using 289 near-field (±10 m from fault) laterally offset piercing points, such as streams, terrace risers, and roads. We characterize off-fault deformation by measuring the medium- (±200 m from fault) and far-field (±10 km from fault) displacement using manual (242 measurements) and automated image cross-correlation methods. Off-fault peak lateral displacement values (medium- and far-field) are ~16 m and commonly exceed the on-fault displacement magnitudes. Our observations suggest that coseismic surface displacement typically increases with distance away from the surface trace of the fault; however, the majority of surface displacement is within 100 m of the primary fault trace and is most localized on sections of the rupture exhibiting narrow (<5 m) zones of observable surface deformation. Furthermore, the near-field displacement measurements account for, on average, only 73% of the total coseismic displacement field and the pattern is highly heterogeneous. This analysis highlights the importance of identifying paleoseismic field study sites (e.g. trenches) that span fault

  5. Generalized Temporal Acceleration Scheme for Kinetic Monte Carlo Simulations of Surface Catalytic Processes by Scaling the Rates of Fast Reactions.

    Science.gov (United States)

    Dybeck, Eric Christopher; Plaisance, Craig Patrick; Neurock, Matthew

    2017-02-14

    A novel algorithm has been developed to achieve temporal acceleration during kinetic Monte Carlo (KMC) simulations of surface catalytic processes. This algorithm allows for the direct simulation of reaction networks containing kinetic processes occurring on vastly disparate timescales which computationally overburden standard KMC methods. Previously developed methods for temporal acceleration in KMC have been designed for specific systems and often require a priori information from the user such as identifying the fast and slow processes. In the approach presented herein, quasi-equilibrated processes are identified automatically based on previous executions of the forward and reverse reactions. Temporal acceleration is achieved by automatically scaling the intrinsic rate constants of the quasi-equilibrated processes, bringing their rates closer to the timescales of the slow kinetically relevant non-equilibrated processes. All reactions are still simulated directly, although with modified rate constants. Abrupt changes in the underlying dynamics of the reaction network are identified during the simulation and the reaction rate constants are rescaled accordingly. The algorithm has been utilized here to model the Fischer-Tropsch synthesis reaction over ruthenium nanoparticles. This reaction network has multiple timescale-disparate processes which would be intractable to simulate without the aid of temporal acceleration. The accelerated simulations are found to give reaction rates and selectivities indistinguishable from those calculated by an equivalent mean-field kinetic model. The computational savings of the algorithm can span many orders of magnitude in realistic systems and the computational cost is not limited by the magnitude of the timescale disparity in the system processes. Furthermore, the algorithm has been designed in a generic fashion and can easily be applied to other surface catalytic processes of interest.

  6. Nutrients interaction investigation to improve Monascus purpureus FTC5391 growth rate using Response Surface Methodology and Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Mohamad, R.

    2013-01-01

    Full Text Available Aims: Two vital factors, certain environmental conditions and nutrients as a source of energy are entailed for successful growth and reproduction of microorganisms. Manipulation of nutritional requirement is the simplest and most effectual strategy to stimulate and enhance the activity of microorganisms. Methodology and Results: In this study, response surface methodology (RSM and artificial neural network (ANN were employed to optimize the carbon and nitrogen sources in order to improve growth rate of Monascus purpureus FTC5391,a new local isolate. The best models for optimization of growth rate were a multilayer full feed-forward incremental back propagation network, and a modified response surface model using backward elimination. The optimum condition for cell mass production was: sucrose 2.5%, yeast extract 0.045%, casamino acid 0.275%, sodium nitrate 0.48%, potato starch 0.045%, dextrose 1%, potassium nitrate 0.57%. The experimental cell mass production using this optimal condition was 21 mg/plate/12days, which was 2.2-fold higher than the standard condition (sucrose 5%, yeast extract 0.15%, casamino acid 0.25%, sodium nitrate 0.3%, potato starch 0.2%, dextrose 1%, potassium nitrate 0.3%. Conclusion, significance and impact of study: The results of RSM and ANN showed that all carbon and nitrogen sources tested had significant effect on growth rate (P-value < 0.05. In addition the use of RSM and ANN alongside each other provided a proper growth prediction model.

  7. Improving snow process modeling with satellite-based estimation of near-surface-air-temperature lapse rate

    Science.gov (United States)

    Wang, Lei; Sun, Litao; Shrestha, Maheswor; Li, Xiuping; Liu, Wenbin; Zhou, Jing; Yang, Kun; Lu, Hui; Chen, Deliang

    2016-10-01

    In distributed hydrological modeling, surface air temperature (Tair) is of great importance in simulating cold region processes, while the near-surface-air-temperature lapse rate (NLR) is crucial to prepare Tair (when interpolating Tair from site observations to model grids). In this study, a distributed biosphere hydrological model with improved snow physics (WEB-DHM-S) was rigorously evaluated in a typical cold, large river basin (e.g., the upper Yellow River basin), given a mean monthly NLRs. Based on the validated model, we have examined the influence of the NLR on the simulated snow processes and streamflows. We found that the NLR has a large effect on the simulated streamflows, with a maximum difference of greater than 24% among the various scenarios for NLRs considered. To supplement the insufficient number of monitoring sites for near-surface-air-temperature at developing/undeveloped mountain regions, the nighttime Moderate Resolution Imaging Spectroradiometer land surface temperature is used as an alternative to derive the approximate NLR at a finer spatial scale (e.g., at different elevation bands, different land covers, different aspects, and different snow conditions). Using satellite-based estimation of NLR, the modeling of snow processes has been greatly refined. Results show that both the determination of rainfall/snowfall and the snowpack process were significantly improved, contributing to a reduced summer evapotranspiration and thus an improved streamflow simulation.

  8. Formation of the prebiotic molecule NH$_2$CHO on astronomical amorphous solid water surfaces: accurate tunneling rate calculations

    CERN Document Server

    Song, Lei

    2016-01-01

    Investigating how formamide forms in the interstellar medium is a hot topic in astrochemistry, which can contribute to our understanding of the origin of life on Earth. We have constructed a QM/MM model to simulate the hydrogenation of isocyanic acid on amorphous solid water surfaces to form formamide. The binding energy of HNCO on the ASW surface varies significantly between different binding sites, we found values between $\\sim$0 and 100 kJ mol$^{-1}$. The barrier for the hydrogenation reaction is almost independent of the binding energy, though. We calculated tunneling rate constants of H + HNCO $\\rightarrow$ NH$_2$CO at temperatures down to 103 K combining QM/MM with instanton theory. Tunneling dominates the reaction at such low temperatures. The tunneling reaction is hardly accelerated by the amorphous solid water surface compared to the gas phase for this system, even though the activation energy of the surface reaction is lower than the one of the gas-phase reaction. Both the height and width of the ba...

  9. Periodic disruptions induced by high repetition rate femtosecond pulses on magnesium-oxide-doped lithium niobate surfaces

    Science.gov (United States)

    Zhang, Shuanggen; Kan, Hongli; Zhai, Kaili; Ma, Xiurong; Luo, Yiming; Hu, Minglie; Wang, Qingyue

    2017-02-01

    In this paper, we demonstrate the periodic disruption formation on magnesium-oxide-doped lithium niobate surfaces by a femtosecond fiber laser system with wavelength and repetition rate of 1040 nm and 52 MHz, respectively. Three main experimental conditions, laser average power, scanning speed, and orientation of sample were systematically studied. In particular, the ablation morphologies of periodic disruptions under different crystal orientations were specifically researched. The result shows that such disruptions consisting of a bamboo-like inner structure appears periodically for focusing on the surface of X-, Y- and Z-cut wafers, which are formed by a rapid quenching of the material. Meanwhile, due to the anisotropic property, the bamboo-like inner structures consist of a cavity only arise from X- and Z-cut orientation.

  10. Guidance proposal for using available DegT50 values for estimation of degradation rates of plant protection products in Dutch surface water and sediment

    NARCIS (Netherlands)

    Boesten, J.J.T.I.; Adriaanse, P.I.; Horst, ter M.M.S.; Tiktak, A.; Linden, van der A.M.A.

    2014-01-01

    The degradation rate of plant protection products and their transformation products in surface water and sediment may influence their concentrations in Dutch surface water. Therefore the estimation of these rates may be an important part of the assessment of the exposure of aquatic organisms. We

  11. 3D-printed surface mould applicator for high-dose-rate brachytherapy

    Science.gov (United States)

    Schumacher, Mark; Lasso, Andras; Cumming, Ian; Rankin, Adam; Falkson, Conrad B.; Schreiner, L. John; Joshi, Chandra; Fichtinger, Gabor

    2015-03-01

    In contemporary high-dose-rate brachytherapy treatment of superficial tumors, catheters are placed in a wax mould. The creation of current wax models is a difficult and time consuming proces.The irradiation plan can only be computed post-construction and requires a second CT scan. In case no satisfactory dose plan can be created, the mould is discarded and the process is repeated. The objective of this work was to develop an automated method to replace suboptimal wax moulding. We developed a method to design and manufacture moulds that guarantee to yield satisfactory dosimetry. A 3D-printed mould with channels for the catheters designed from the patient's CT and mounted on a patient-specific thermoplastic mesh mask. The mould planner was implemented as an open-source module in the 3D Slicer platform. Series of test moulds were created to accommodate standard brachytherapy catheters of 1.70mm diameter. A calibration object was used to conclude that tunnels with a diameter of 2.25mm, minimum 12mm radius of curvature, and 1.0mm open channel gave the best fit for this printer/catheter combination. Moulds were created from the CT scan of thermoplastic mesh masks of actual patients. The patient-specific moulds have been visually verified to fit on the thermoplastic meshes. The masks were visually shown to fit onto the thermoplastic meshes, next the resulting dosimetry will have to be compared with treatment plans and dosimetry achieved with conventional wax moulds in order to validate our 3D printed moulds.

  12. Stretch rate effects and flame surface densities in premixed turbulent combustion up to 1.25 MPa

    KAUST Repository

    Bagdanavicius, Audrius

    2015-11-01

    Independent research at two centres using a burner and an explosion bomb has revealed important aspects of turbulent premixed flame structure. Measurements at pressures and temperatures up to 1.25MPa and 673K in the two rigs were aimed at quantifying the influences of flame stretch rate and strain rate Markstein number, Masr , on both turbulent burning velocity and flame surface density. That on burning velocity is expressed through the stretch rate factor, Io , or probability of burning, Pb 0.5. These depend on Masr , but they grow in importance as the Karlovitz stretch factor, K, increases, and are evaluated from the associated burning velocity data. Planar laser tomography was employed to identify contours of reaction progress variable in both rigs. These enabled both an appropriate flame front for the measurement of the turbulent burning velocity to be identified, and flame surface densities, with the associated factors, to be evaluated. In the explosion measurements, these parameters were derived also from the flame surface area, the derived Pb 0.5 factor and the measured turbulent burning velocities. In the burner measurement they were calculated directly from the flame surface density, which was derived from the flame contours.A new overall correlation is derived for the Pb 0.5 factor, in terms of Masr at different K and this is discussed in the light of previous theoretical studies. The wrinkled flame surface area normalised by the area associated with the turbulent burning velocity measurement, and the ratio of turbulent to laminar burning velocity, ut /ul , are also evaluated. The higher the value of Pb0.5, the more effective is an increased flame wrinkling in increasing ut /ul A correlation of the product of k and the laminar flame thickness with Karlovitz stretch factor and Markstein number is explored using the present data and those

  13. Groundwater Recharge Rates and Surface Runoff Response to Land Use and Land Cover Changes in Semi-arid Environments

    Science.gov (United States)

    Owuor, Steven; Butterbach-Bahl, Klaus; Guzha, Alphonce; Rufino, Mariana; Pelster, David; Díaz-Pinés, Eugenio; Breuer, Lutz; Merbold, Lutz

    2017-04-01

    Conclusive evidence and understanding of the effects of land use and land cover (LULC) on both groundwater recharge and surface runoff is critical for effective management of water resources in semi-arid region as those heavily depend on groundwater resources. However, there is limited quantitative evidence on how changes to LULC in semi-arid tropical and subtropical regions affect the subsurface components of the hydrologic cycle, particularly groundwater recharge. In this study, we reviewed a total of 27 studies (2 modelling and 25 experimental), which reported on pre- and post-land use change groundwater recharge or surface runoff magnitude, and thus allowed to quantify the response of groundwater recharge rates and runoff to LULC. Restoration of bare land induces a decrease in groundwater recharge from 42 % of precipitation to between 6 and 12 % depending on the final LULC. If forests are cleared for rangelands, groundwater recharge increases by 7.8 ± 12.6 %, while conversion to cropland or grassland results in increases of 3.4 ± 2.5 and 4.4 ± 3.3 %, respectively. Rehabilitation of bare land to cropland results in surface runoff reductions of between 5.2 and 7.3 %. The conversion of forest vegetation to managed LULC shows an increase in surface runoff from 1 to 14.1 % depending on the final LULC. Surface runoff is reduced from 2.5 to 1.1 % when grassland is converted to forest vegetation. While there is general consistency in the results from the selected case studies, we conclude that there are few experimental studies that have been conducted in tropical and subtropical semi-arid regions, despite that many people rely heavily on groundwater for their livelihoods. Therefore, there is an urgent need to increase the body of quantitative evidence given the pressure of growing human population and climate change on water resources in the region.

  14. Gas surface density, star formation rate surface density, and the maximum mass of young star clusters in a disk galaxy. I. The flocculent galaxy M33

    CERN Document Server

    Gonzalez-Lopezlira, Rosa A; Kroupa, Pavel

    2012-01-01

    We analyze the relationship between maximum cluster mass, M_max, and surface densities of total gas (Sigma_gas), molecular gas (Sigma_H2) and star formation rate (Sigma_SFR) in the flocculent galaxy M33, using published gas data and a catalog of more than 600 young star clusters in its disk. By comparing the radial distributions of gas and most massive cluster masses, we find that M_max is proportional to Sigma_gas^4.7, M_max is proportional Sigma_H2^1.3, and M_max is proportional to Sigma_SFR^1.0. We rule out that these correlations result from the size of sample; hence, the change of the maximum cluster mass must be due to physical causes.

  15. GAS SURFACE DENSITY, STAR FORMATION RATE SURFACE DENSITY, AND THE MAXIMUM MASS OF YOUNG STAR CLUSTERS IN A DISK GALAXY. II. THE GRAND-DESIGN GALAXY M51

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Lopezlira, Rosa A. [On sabbatical leave from the Centro de Radioastronomia y Astrofisica, UNAM, Campus Morelia, Michoacan, C.P. 58089, Mexico. (Mexico); Pflamm-Altenburg, Jan; Kroupa, Pavel, E-mail: r.gonzalez@crya.unam.mx [Argelander Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany)

    2013-06-20

    We analyze the relationship between maximum cluster mass and surface densities of total gas ({Sigma}{sub gas}), molecular gas ({Sigma}{sub H{sub 2}}), neutral gas ({Sigma}{sub H{sub I}}), and star formation rate ({Sigma}{sub SFR}) in the grand-design galaxy M51, using published gas data and a catalog of masses, ages, and reddenings of more than 1800 star clusters in its disk, of which 223 are above the cluster mass distribution function completeness limit. By comparing the two-dimensional distribution of cluster masses and gas surface densities, we find for clusters older than 25 Myr that M{sub 3rd}{proportional_to}{Sigma}{sub H{sub I}{sup 0.4{+-}0.2}}, whereM{sub 3rd} is the median of the five most massive clusters. There is no correlation with{Sigma}{sub gas},{Sigma}{sub H2}, or{Sigma}{sub SFR}. For clusters younger than 10 Myr, M{sub 3rd}{proportional_to}{Sigma}{sub H{sub I}{sup 0.6{+-}0.1}} and M{sub 3rd}{proportional_to}{Sigma}{sub gas}{sup 0.5{+-}0.2}; there is no correlation with either {Sigma}{sub H{sub 2}} or{Sigma}{sub SFR}. The results could hardly be more different from those found for clusters younger than 25 Myr in M33. For the flocculent galaxy M33, there is no correlation between maximum cluster mass and neutral gas, but we have determined M{sub 3rd}{proportional_to}{Sigma}{sub gas}{sup 3.8{+-}0.3}, M{sub 3rd}{proportional_to}{Sigma}{sub H{sub 2}{sup 1.2{+-}0.1}}, and M{sub 3rd}{proportional_to}{Sigma}{sub SFR}{sup 0.9{+-}0.1}. For the older sample in M51, the lack of tight correlations is probably due to the combination of strong azimuthal variations in the surface densities of gas and star formation rate, and the cluster ages. These two facts mean that neither the azimuthal average of the surface densities at a given radius nor the surface densities at the present-day location of a stellar cluster represent the true surface densities at the place and time of cluster formation. In the case of the younger sample, even if the clusters have not yet

  16. Rate of bitumen film transfer from a quartz surface to an air bubble as observed by optical microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lelinski, D. [FFE Minerals USA Inc., Salt Lake City, UT (United States); Drelich, J. [Michigan Technological Univ., Houghton, MI (United States). Dept. of Materials Science and Engineering; Miller, J.D. [Utah Univ., Salt Lake City, UT (United States). Dept. of Metallurgical Engineering; Hupka, J. [Gdansk Univ. of Technology, Gdansk (Poland). Dept. of Chemical Technology

    2004-08-01

    Froth flotation is a separation process used to recover oil from oil sands. The two separation steps in froth flotation include the release of oil from mineral matter, and oil flotation from the slurry. During flotation, gas bubbles collide with and attach to oil droplets and to oily soil particles. The flotation of oil-in water emulsions in the absence of solids has been studied extensively. This study focused on liquid/liquid spreading. It was limited to simple systems involving pure single-component liquids. Multi-component oils were only used in a few experiments. In particular, this paper discussed the rate of high viscosity bitumen transfer from a bitumen-coated quartz slide to an air bubble surface that occurred in an aqueous alkaline solution. Bitumen spreading observations were recorded with a video camera attached to a stereoscopic microscope. The objective was to improve hot-water processing technology for bitumen recovery from Utah oil sands. The study showed that during bitumen spreading, a bulk layer followed the formation of thin bitumen films. The spreading velocity was one order of magnitude less than the velocity of the precursor film. The study provided a better understanding of the basic separation techniques encountered in the sequence of oil sand slurry digestion, aeration, gravity separation and flotation. It was concluded that a strong intermolecular attraction exists between the bitumen molecules. This interaction reduces the rate of bitumen spreading at the water surface. 33 refs., 2 tabs., 12 figs.

  17. Investigation of the rates of surface and bulk ROS-generating reactions using indigo dye as an indicator

    Science.gov (United States)

    Anderson, Carly; Clark, Douglas; Graves, David

    2014-10-01

    We present evidence for the existence of two distinct processes that contribute to the generation of reactive oxygen and nitrogen species (RONS) in liquids exposed to cold atmospheric plasma (CAP) in air. At the plasma-liquid interface, there exists a fast surface reaction zone where RONS from the gas phase interact with species in the liquid. RONS can also be produced by ``slow'' chemical reactions in the bulk liquid, even long after plasma exposure. To separate the effects of these processes, we used indigo dye as an indicator of ROS production; specifically generation of hydroxyl radical. The rate of indigo decolorization while in direct contact with CAP is compared with the expected rate of hydroxyl radical generation at the liquid surface. When added to aqueous solutions after CAP exposure, indigo dye reacts on a time scale consistent with the production of peroxynitrous acid, ONOOH, which is known to decompose to hydroxyl radical below a pH of 6.8. In this study, the CAP used was a air corona discharge plasma run in a positive streamer mode.

  18. Six-Year Survival and Early Failure Rate of 2918 Implants with Hydrophobic and Hydrophilic Enossal Surfaces

    Directory of Open Access Journals (Sweden)

    Olivier Le Gac

    2015-02-01

    Full Text Available The aim of this chart review was to obtain an objective, quantitative assessment of the clinical performance of an implant line used in an implantological office setting. Implants with hydrophilic (INICELL and hydrophobic (TST; both: Thommen Medical AG, Grenchen, Switzerland enossal surfaces were compared and the cumulative implant survival rate was calculated. The data of 1063 patients that received 2918 implants (1337 INICELL, 1581 TST was included. The average follow up time was 2.1 (1.1–5.4 years for INICELL and 4.5 (1.3–5.9 years for TST implants (Thommen Medical AG, Switzerland. In the reported period 7 implants with INICELL (0.5% and 23 TST implants (1.5% failed. This difference was statistically significant. The analysis of cases treated and followed up in a single implantological office for 6 years confirmed the very good clinical outcome that was achieved with both used implant lines. Within the limitations of this retrospective analysis, the overall early failure rate of the hydrophilic implants was significantly lower than that of hydrophobic implants. The use of hydrophilic implants allows the clinician to obtain less early failures, hence the interest of an up-to-date surface for the daily work of an implant practice.

  19. Using a Family of Dividing Surfaces Normal to the Minimum EnergyPath for Quantum Instanton Rate Constants

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yimin; Miller, Wlliam H.

    2006-02-22

    One of the outstanding issues in the quantum instanton (QI) theory (or any transition state-type theory) for thermal rate constants of chemical reactions is the choice of an appropriate ''dividing surface'' (DS) that separates reactants and products. (In the general version of the QI theory, there are actually two dividing surfaces involved.) This paper shows one simple and general way for choosing DS's for use in QI Theory, namely using the family of (hyper) planes normal to the minimum energy path (MEP) on the potential energy surface at various distances s along it. Here the reaction coordinate is not one of the dynamical coordinates of the system (which will in general be the Cartesian coordinates of the atoms), but rather simply a parameter which specifies the DS. It is also shown how this idea can be implemented for an N-atom system in 3d space in a way that preserves overall translational and rotational invariance. Numerical application to a simple system (the colliner H + H{sub 2} reaction) is presented to illustrate the procedure.

  20. Surface morphology, growth rate and quality of diamond films synthesized in hot filament CVD system under various methane concentrations

    Science.gov (United States)

    Ali, M.; Ürgen, M.

    2011-08-01

    Hot filament chemical vapor deposition (CVD) technique has been used to deposit diamond films on silicon substrate. In the present study, diamond films were grown at various vol.% CH 4 in H 2 from 0.5% to 3.5%, at substrate temperature and pressure of 850 °C and 80 torr, respectively. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were employed to analyze the properties of deposited films. The formation of methyl radicals as a function of vol.% CH 4 not only changes film morphology but also increase film growth rate. At low, intermediate and high vol.% CH 4, cluster, faceted cubes and pyramidal features growth, were dominant. By increasing vol.% CH 4 from 0.5% to 3.5%, as the growth rate improved from ˜0.25 μm/h to ˜2.0 μm/h. Raman studies features revealed high purity diamond films at intermediate range of vol.% CH 4 and grain density increased by increasing CH 4 concentration. The present study represents experimentally surface morphology, growth rate and quality of diamond films grown in hot filament CVD system at various CH 4 concentrations.

  1. Dynamic contact angle and spreading rate measurements for the characterization of the effect of dentin surface treatments.

    Science.gov (United States)

    Wege, Hartmut Alexander; Aguilar, José Arturo; Rodríguez-Valverde, Miguel Angel; Toledano, Manuel; Osorio, Raquel; Cabrerizo-Vílchez, Miguel Angel

    2003-07-01

    A new methodology capable of providing reliable and reproducible contact angle (theta) data has been employed to study the effect of clinical treatments grinding, acid etching, and deproteinization on medial dentin tissue. It is based on the application of the ADSA-CD algorithm to the determination of low-rate dynamic contact angles, obtained from slowly growing drops, and on contact angle measurement, as well as spreading behavior analysis, during the relaxation of the system (water on treated dentin) after initial drop growth. The theta data obtained were substantially more reproducible than those obtained with classical methods. A net effect of the treatment on theta was found, increasing dentin wettability: theta (polished) >theta (etched) >theta (deproteinized). The spreading rates correlate with the angles and are adequate for the dentin surface characterization. ANOVA and SNK tests show that for advancing contact angles the means corresponding to all treatments are significantly different. In the relaxing phase, mean angle and spreading rates on polished dentin differ significantly from those on etched and deproteinized dentin, but the latter do not differ significantly from each other.

  2. Actual laser removal of black soiling crust from siliceous sandstone by high pulse repetition rate equipment: effects on surface morphology

    Directory of Open Access Journals (Sweden)

    Iglesias-Campos, M. A.

    2016-03-01

    Full Text Available This research project studies the role of pulse repetition rate in laser removal of black soiling crust from siliceous sandstone, and specifically, how laser fluence correlates with high pulse repetition rates in cleaning practice. The aim is to define practical cleaning processes and determine simple techniques for evaluation based on end-users’ perspective (restorers. Spot and surface tests were made using a Q-switched Nd:YAG laser system with a wide range of pulse repetition rates (5–200 Hz, systematically analysed and compared by macrophotography, portable microscope, stereomicroscope with 3D visualizing and area roughness measurements, SEM imaging and spectrophotometry. The results allow the conclusion that for operation under high pulse repetition rates the average of total energy applied per spot on a treated surface should be attendant upon fluence values in order to provide a systematic and accurate description of an actual laser cleaning intervention.En este trabajo se estudia el papel de la frecuencia de repetición en la limpieza láser de costras de contaminación sobre una arenisca silícea, y concretamente, como se relaciona fluencia y frecuencias elevadas en una limpieza real. Se pretende definir un procedimiento práctico de limpieza y determinar técnicas sencillas de evaluación desde el punto de vista de los usuarios finales (restauradores. Para el estudio se realizaron diferentes ensayos en spot y en superficie mediante un equipo Q-switched Nd:YAG con un amplio rango de frecuencias (5–200 Hz, que se analizaron y compararon sistemáticamente mediante macrofotografía, microscopio portátil, estereomicroscopio con visualización 3D y mediciones de rugosidad en área, imágenes SEM y espectrofotometría. Los resultados permiten proponer que, al trabajar con altas frecuencias, la media de la energía total depositada por spot en la superficie debería acompañar los valores de fluencia para describir y comprender mejor una

  3. Macrophyte decomposition in a surface-flow ammonia-dominated constructed wetland: Rates associated with environmental and biotic variables

    Science.gov (United States)

    Thullen, J.S.; Nelson, S.M.; Cade, B.S.; Sartoris, J.J.

    2008-01-01

    Decomposition of senesced culm material of two bulrush species was studied in a surface-flow ammonia-dominated treatment wetland in southern California. Decomposition of the submerged culm material during summer months was relatively rapid (k = 0.037 day-1), but slowed under extended submergence (up to 245 days) and during fall and spring sampling periods (k = 0.009-0.014 day-1). Stepwise regression of seasonal data indicated that final water temperature and abundance of the culm-mining midge, Glyptotendipes, were significantly associated with culm decomposition. Glyptotendipes abundance, in turn, was correlated with water quality parameters such as conductivity and dissolved oxygen and ammonia concentrations. No differences were detected in decomposition rates between the bulrush species, Schoenoplectus californicus and Schoenoplectus acutus.

  4. Slicing up the San Francisco Bay Area: Block kinematics and fault slip rates from GPS-derived surface velocities

    Science.gov (United States)

    D'Alessio, M. A.; Johanson, I. A.; Bürgmann, R.; Schmidt, D. A.; Murray, M. H.

    2005-06-01

    Observations of surface deformation allow us to determine the kinematics of faults in the San Francisco Bay Area. We present the Bay Area velocity unification (B?V?, "bay view"), a compilation of over 200 horizontal surface velocities computed from campaign-style and continuous Global Positioning System (GPS) observations from 1993 to 2003. We interpret this interseismic velocity field using a three-dimensional block model to determine the relative contributions of block motion, elastic strain accumulation, and shallow aseismic creep. The total relative motion between the Pacific plate and the rigid Sierra Nevada/Great Valley (SNGV) microplate is 37.9 ± 0.6 mm yr-1 directed toward N30.4°W ± 0.8° at San Francisco (±2σ). Fault slip rates from our preferred model are typically within the error bounds of geologic estimates but provide a better fit to geodetic data (notable right-lateral slip rates in mm yr-1: San Gregorio fault, 2.4 ± 1.0; West Napa fault, 4.0 ± 3.0; zone of faulting along the eastern margin of the Coast Range, 5.4 ± 1.0; and Mount Diablo thrust, 3.9 ± 1.0 of reverse slip and 4.0 ± 0.2 of right-lateral strike slip). Slip on the northern Calaveras is partitioned between both the West Napa and Concord/Green Valley fault systems. The total convergence across the Bay Area is negligible. Poles of rotation for Bay Area blocks progress systematically from the North America-Pacific to North America-SNGV poles. The resulting present-day relative motion cannot explain the strike of most Bay Area faults, but fault strike does loosely correlate with inferred plate motions at the time each fault initiated.

  5. Spatial-temporal variation of near-surface temperature lapse rates over the Tianshan Mountains, central Asia

    Science.gov (United States)

    Shen, Yan-Jun; Shen, Yanjun; Goetz, Jason; Brenning, Alexander

    2016-12-01

    Adequate estimates of near-surface temperature lapse rate (γlocal) are needed to represent air temperature in remote mountain regions with sparse instrumental records such as the mountains of central Asia. To identify the spatial and temporal variations of γlocal in the Tianshan Mountains, long-term (1961-2011) daily maximum, mean, and minimum temperature (Tmax, Tmean, and Tmin) data from 17 weather stations and 1 year of temperature logger data were analyzed considering three subregions: northern slopes, Kaidu Basin, and southern slopes. Simple linear regression was performed to identify relationships between elevation and temperature, revealing spatial and seasonal variations in γlocal. The γlocal are higher on the southern slopes than the northern slopes due to topography and regional climate conditions. Seasonally, γlocal are more pronounced higher in the summer than in the winter months. The γlocal are generally higher for Tmax than Tmean and Tmin. The Kaidu Basin shows similar seasonal variability but with the highest γlocal for Tmean and Tmin occurring in the spring. Formation of γlocal patterns is associated with the interactions of climate factors in different subregions. Overall, annual mean γlocal for Tmax, Tmean, and Tmin in the study's subregions are lower than the standard atmospheric lapse rate (6.5°C km-1), which would therefore be an inadequate choice for representing the near-surface temperature conditions in this area. Our findings highlight the importance of spatial and temporal variations of γlocal in hydrometeorological research in the data-sparse Tianshan Mountains.

  6. Gas surface density, star formation rate surface density, and the maximum mass of young star clusters in a disk galaxy. II. The grand-design galaxy M51

    CERN Document Server

    Gonzalez-Lopezlira, Rosa A; Kroupa, Pavel

    2013-01-01

    We analyze the relationship between maximum cluster mass, and surface densities of total gas (Sigma_gas), molecular gas (Sigma_H_2), neutral gas (Sigma_HI) and star formation rate (Sigma_SFR) in the grand design galaxy M51, using published gas data and a catalog of masses, ages, and reddenings of more than 1800 star clusters in its disk, of which 223 are above the cluster mass distribution function completeness limit. We find for clusters older than 25 Myr that M_3rd, the median of the 5 most massive clusters, is proportional to Sigma_HI^0.4. There is no correlation with Sigma_gas, Sigma_H2, or Sigma_SFR. For clusters younger than 10 Myr, M_3rd is proportional to Sigma_HI^0.6, M_3rd is proportional to Sigma_gas^0.5; there is no correlation with either Sigma_H_2 or Sigma_SFR. The results could hardly be more different than those found for clusters younger than 25 Myr in M33. For the flocculent galaxy M33, there is no correlation between maximum cluster mass and neutral gas, but M_3rd is proportional to Sigma_g...

  7. Surface reconstruction and derivation of erosion rates over several glaciations (1 Ma) in an alpine setting (Sinks Canyon, Wyoming, USA)

    Science.gov (United States)

    Züst, Fabian; Dahms, Dennis; Purves, Ross; Egli, Markus

    2014-08-01

    At middle to high latitudes, many alpine valleys have been shaped by glaciers associated with periods of Pleistocene glaciation. Present glaciated valleys are characterised by broadened valley floors and U-shaped cross sections, continuously formed by glacial activity from initially V-shaped, fluvial cross sections. Sinks Canyon (Wind River Range, USA) is a glaciated valley characterised by a typical U-shaped cross section, containing till from several glacial advances over a range of at least 1 Ma. The morphostratigraphic records indicate a fourfold difference in ice surface elevation between the youngest and oldest glacial periods, which is not easily explained by the present-day valley topography. To assess possible evolution scenarios of Sinks Canyon, we modelled the palaeovalley topography using a geographic information system (GIS) filtering technique in combination with temporal reference points from relative and numerically dated glacial deposits. Ice thicknesses were calculated using the shallow ice approximation. In our model, the valley became shallower and the topography smoother with increasing years back in time. The results suggest that valley topography with ages between 640 and 1000 ka can clearly be distinguished from the present-day topography. Surfaces with ages of 130-200 ka (attributable to MIS 6; Bull Lake glaciation) still could be discerned from present-day topography, but with relatively high uncertainties. The method did not work for topography less than ~ 100 ka or older than ~ 1 Ma. Erosion depths were calculated using the differences between present-day elevation and the modelled surfaces. Calculated erosion rates were within the range of reference values for glacial erosion (0.001 to 1 mm a- 1). Glacial erosion appears to have removed 0.52 to 0.72 mm a- 1 of rock within a time frame of 1 Ma, assuming 200 ka of aggregated glacial flow. If the glacial occupation was longer or the impact of fluvial erosion was not negligible (as assumed

  8. An analysis of the contact phase of blood coagulation: effects of shear rate and surface are intertwined.

    Science.gov (United States)

    Gregory, K; Basmadjian, D

    1994-01-01

    This work analyzes, for the first time, the combined role of blood flow, protein transport and the reaction network of the contact phase up to the "common pathway" of the blood coagulation cascade. The model is comprised of a set of 20 dominant reactions with 11 components. Systems of ODEs reducible to 4 coupled equations describe rigorously the dynamic behavior, while systems of algebraic equations, reducible to a single polynomial equation, model the steady state concentrations of the coagulants. The analysis showed that there is never more than one stable steady state. This is in contrast to the analysis of common pathway that gives rise to multiple concentration states. It also revealed a general robustness of the system to changes in procoagulant concentrations, inhibition rates and most activation rate constants. The system is largely impervious to the level of activated Factor XII, given that a trace (non-zero) level is present. In contrast, the system displays a dual response to flow and surface activity: A change in either of these factors alone can promote, have no effect on, or (in the case of flow) impede the progress of coagulation, depending on the value of the other factor. Their effects must therefore be examined in unison. These results may help resolve contradictory findings attributed to one or the other factor alone.

  9. Is Mass-based Metabolism Rate Proportional to Surface Area in Plant Leaves? A Data Re-analysis

    Institute of Scientific and Technical Information of China (English)

    Dongmei Jin; Yiqiang Dai; Li Sun; Shucun Sun

    2008-01-01

    We re-analyzed two large published databases on leaf traits of plant species from seven different biomes, and determined the scaling relationship between leaf metabolism rate (mass-based photosynthesis capacity, Amass, and mass-based dark respiration, Rdmass) and specific leaf area (SLA) across biomes, using a standardized major axis (SMA) method. Overall pooled data produced a scaling exponent of 1.33 for the relationship between Amass and SLA, significantly larger than 1.0; and 1.04 between Rdmass and SLA. The scaling exponent of the relationship between Amass and SLA ranged between 1.23 (in tropical forest) and 1.66 (in alpine biome), and it was significantly larger in alpine (1.66) and grass/meadow (1.52) biomes than in tropical forest (1.23) and wetland (1.27). The exponent of the relationship between Rdmass and SLA, however,was much smaller in wetland (1.05) than in temperate forest (1.29) and tropical rainforest (1.65). In general, the predicated universal scaling relationship that the mass-based metabolism rate should be proportional to surface area in organisms is not applicable at the leaf-level in plants. Rather, the large slope difference of the relationship between leaf metabolism rate and SLA found among biomes indicates that the strength of the selective forces driving the scaling relationship is different among the biomes. The result basically suggests the importance of increasing SLA to plant carbon gain in stressful environments and to carbon loss in favorable habitats, and therefore has an important implication for survival strategies of plants in different biomes.

  10. Effect of liquid swine manure rate, incorporation, and timing of rainfall on phosphorus loss with surface runoff.

    Science.gov (United States)

    Allen, Brett L; Mallarino, Antonio P

    2008-01-01

    Excessive manure phosphorus (P) application increases risk of P loss from fields. This study assessed total runoff P (TPR), bioavailable P (BAP), and dissolved reactive P (DRP) concentrations and loads in surface runoff after liquid swine (Sus scrofa domesticus) manure application with or without incorporation into soil and different timing of rainfall. Four replicated manure P treatments were applied in 2002 and in 2003 to two Iowa soils testing low in P managed with corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotations. Total P applied each time was 0 to 80 kg P ha(-1) at one site and 0 to 108 kg P ha(-1) at the other. Simulated rainfall was applied within 24 h of P application or after 10 to 16 d and 5 to 6 mo. Nonincorporated manure P increased DRP, BAP, and TPR concentrations and loads linearly or exponentially for 24-h and 10- to 16-d runoff events. On average for the 24-h events, DRP, BAP, and TPR concentrations were 5.4, 4.7, and 2.2 times higher, respectively, for nonincorporated manure than for incorporated manure; P loads were 3.8, 7.7, and 3.6 times higher; and DRP and BAP concentrations were 54% of TPR for nonincorporated manure and 22 to 25% for incorporated manure. A 10- to 16-d rainfall delay resulted in DRP, BAP, and TPR concentrations that were 3.1, 2.7, and 1.1 times lower, respectively, than for 24-h events across all nonincorporated P rates, sites, and years, whereas runoff P loads were 3.8, 3.6, and 1.6 times lower, respectively. A 5- to 6-mo simulated rainfall delay reduced runoff P to levels similar to control plots. Incorporating swine manure when the probability of immediate rainfall is high reduces the risk of P loss in surface runoff; however, this benefit sharply decreases with time.

  11. Surface-Layer Similarity Functions for Dissipation Rate and Structure Parameters of Temperature and Humidity Based on Eleven Field Experiments

    Science.gov (United States)

    Kooijmans, Linda M. J.; Hartogensis, Oscar K.

    2016-09-01

    In the literature, no consensus can be found on the exact form of the universal funtions of Monin-Obukhov similarity theory (MOST) for the structure parameters of temperature, {C_T}^2, and humidity, {C_q}^2, and the dissipation rate of turbulent kinetic energy, ɛ. By combining 11 datasets and applying data treatment with spectral data filtering and error-weighted curve-fitting we first derived robust MOST functions of {C_T}^2, {C_q}^2 and ɛ that cover a large stability range for both unstable and stable conditions. Second, as all data were gathered with the same instrumentation and were processed in the same way—in contrast to earlier studies—we were able to investigate the similarity of MOST functions across different datasets by defining MOST functions for all datasets individually. For {C_T}^2 and ɛ we found no substantial differences in MOST functions for datasets over different surface types or moisture regimes. MOST functions of {C_q}^2 differ from that of {C_T}^2, but we could not relate these differences to turbulence parameters often associated with non-local effects. Furthermore, we showed that limited stability ranges and a limited number of data points are plausible reasons for variations of MOST functions in the literature. Last, we investigated the sensitivity of fluxes to the uncertainty of MOST functions. We provide an overview of the uncertainty range for MOST functions of {C_T}^2, {C_q}^2 and ɛ, and suggest their use in determining the uncertainty in surface fluxes.

  12. Land Surface Biophysical-Climate Impacts of Tropical Deforestation with Time-dependence: Sensitivity to Deforestation Rates

    Science.gov (United States)

    Castillo, C. G.; Gurney, K. R.

    2010-12-01

    Deforestation perturbs both biophysical and carbon feedbacks on climate. However, biophysical feedbacks operate at more temporally-immediate and spatially-focused scales, and thus may be sensitive to the actual rate at which deforestation occurs rather than just to the total forest cover loss. Most of previous modeling experiments have focused on equilibrium impacts of mass instantaneous replacement of trees; but, anthropogenic deforestation evolves in time and may result in transient climatic changes which holistic assessments of land cover change impacts must be able to characterize for mitigation and adaptation initiatives to be effective. This exploratory work therefore attempts to determine if there exists a time-dependence within biophysical-climate impacts of deforestation; specifically, if indeed the rates of deforestation affect terrestrial biophysics-climate feedbacks during the period of active deforestation as well as the post-deforestation period. Described here is a method for simulating annual tropical deforestation in the fully-coupled Community Climate System Model 3.0 (CCSM3) with the Dynamic Global Vegetation Model (DGVM) for testing biosphere-climate sensitivity to “preservation pathways.” We test two deforestation curves- one with a 10% annual tree population thinning (DFC10-PT10), and one with 1% (DFC1-PT10) - each with a preservation target of 10% tree cover. During the period of active deforestation, surface albedo, net radiation, latent heat flux and climate variables are compared for time-dependence and sensitivity to total tropical tree foliar projective cover across the tropical band, the Amazon Basin, Central Africa and Southeast Asia. The deforestation rates produce characteristic trends in biophysical variables with DFC10-PT10 resulting in rapid increase/decrease during the initial 10-30 years before a slow leveling off, while DFC1-PT10 exhibits more gradual changes. The deforestation rate is also found to have little effect on

  13. Generation of polarization-resolved wideband unpredictability-enhanced chaotic signals based on vertical-cavity surface-emitting lasers subject to chaotic optical injection.

    Science.gov (United States)

    Chen, Jian-Jun; Wu, Zheng-Mao; Tang, Xi; Deng, Tao; Fan, Li; Zhong, Zhu-Qiang; Xia, Guang-Qiong

    2015-03-23

    A system framework is proposed and analyzed for generating polarization-resolved wideband unpredictability-enhanced chaotic signals based on a slave vertical-cavity surface-emitting laser (S-VCSEL) driven by an injected optical chaos signal from a master VCSEL (M-VCSEL) under optical feedback. After calculating the time series outputs from the M-VCSEL under optical feedback and the S-VCSEL under chaotic optical injection by using the spin-flip model (SFM), the unpredictability degree (UD) is evaluated by permutation entropy (PE), and the bandwidth of the polarization-resolved outputs from the M-VCSEL and S-VCSEL are numerically investigated. The results show that, under suitable parameters, both the bandwidth and UD of two polarization components (PCs) outputs from the S-VCSEL can be enhanced significantly compared with that of the driving chaotic signals output from the M-VCSEL. By simulating the influences of the feedback and injection parameters on the bandwidth and UD of the polarization-resolved outputs from S-VCSEL, related operating parameters can be optimized.

  14. Spin-dependent quantum transport in nanoscaled geometries

    Science.gov (United States)

    Heremans, Jean J.

    2011-10-01

    We discuss experiments where the spin degree of freedom leads to quantum interference phenomena in the solid-state. Under spin-orbit interactions (SOI), spin rotation modifies weak-localization to weak anti-localization (WAL). WAL's sensitivity to spin- and phase coherence leads to its use in determining the spin coherence lengths Ls in materials, of importance moreover in spintronics. Using WAL we measure the dependence of Ls on the wire width w in narrow nanolithographic ballistic InSb wires, ballistic InAs wires, and diffusive Bi wires with surface states with Rashba-like SOI. In all three systems we find that Ls increases with decreasing w. While theory predicts the increase for diffusive wires with linear (Rashba) SOI, we experimentally conclude that the increase in Ls under dimensional confinement may be more universal, with consequences for various applications. Further, in mesoscopic ring geometries on an InAs/AlGaSb 2D electron system (2DES) we observe both Aharonov-Bohm oscillations due to spatial quantum interference, and Altshuler-Aronov-Spivak oscillations due to time-reversed paths. A transport formalism describing quantum coherent networks including ballistic transport and SOI allows a comparison of spin- and phase coherence lengths extracted for such spatial- and temporal-loop quantum interference phenomena. We further applied WAL to study the magnetic interactions between a 2DES at the surface of InAs and local magnetic moments on the surface from rare earth (RE) ions (Gd3+, Ho3+, and Sm3+). The magnetic spin-flip rate carries information about magnetic interactions. Results indicate that the heavy RE ions increase the SOI scattering rate and the spin-flip rate, the latter indicating magnetic interactions. Moreover Ho3+ on InAs yields a spin-flip rate with an unusual power 1/2 temperature dependence, possibly characteristic of a Kondo system. We acknowledge funding from DOE (DE-FG02-08ER46532).

  15. Effects of growth temperature modulated by HCl flow rate on the surface and crystal qualities of thick GaN by HVPE

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Lubing [Research Center for Wide-gap Semiconductors, State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Wu Jiejun, E-mail: wujiejun@opt.elec.mie-u.ac.jp [Research Center for Wide-gap Semiconductors, State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Xu Ke; Yang Zhijian; Zhang Guoyi [Research Center for Wide-gap Semiconductors, State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)

    2009-06-30

    We studied the influence of the growth temperature and HCl flow rate on the morphological evolution of crack-free thick GaN films by using a home-made horizontal hydride vapor phase epitaxy on sapphire substrates. Optical difference microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and cathodoluminescence (CL) were carried out to reveal the surface property of the GaN epilayer. It was found that the higher growth temperature is a key factor to obtain mirror, colorless and flat GaN surface. However, this key effect of temperature was modulated by HCl flow rate (HCl > 15 sccm). The surface RMS roughness was reduced from 206 to 2.51 nm for 10 {mu}m x 10 {mu}m scan area when GaN was grown at 1070 deg. C with HCl flow rate up to 30 sccm. These samples also reduced their (0 0 0 2) FWHM result from 1000 to 300 arcsec and showed a strong near-band-edge peak in CL spectra. Results indicated that growth temperature influence growth velocities on different crystalline planes, which will lead to the different morphologies obtained. High growth temperature can improve the lateral growth rate of vertical {l_brace}1 1 - 2 0{r_brace} facets and reduce the vertical growth rate of top {l_brace}0 0 0 1{r_brace} facet combined with higher HCl flow rate, which leads to completely coalescence of surface.

  16. Surface Passivation of MoO3 Nanorods by Atomic Layer Deposition Towards High Rate Durable Li Ion Battery Anodes

    KAUST Repository

    Ahmed, Bilal

    2015-06-03

    We demonstrate an effective strategy to overcome the degradation of MoO3 nanorod anodes in Lithium (Li) ion batteries at high rate cycling. This is achieved by conformal nanoscale surface passivation of the MoO3 nanorods by HfO2 using atomic layer deposition (ALD). At high current density such as 1500 mA/g, the specific capacity of HfO2 coated MoO3 electrodes is 68% higher than bare MoO3 electrodes after 50 charge/discharge cycles. After 50 charge/discharge cycles, HfO2 coated MoO3 electrodes exhibited specific capacity of 657 mAh/g, on the other hand, bare MoO3 showed only 460 mAh/g. Furthermore, we observed that HfO2 coated MoO3 electrodes tend to stabilize faster than bare MoO3 electrodes because nanoscale HfO2 layer prevents structural degradation of MoO3 nanorods. Additionally, the growth temperature of MoO3 nanorods and the effect of HfO2 layer thickness was studied and found to be important parameters for optimum battery performance. The growth temperature defines the microstructural features and HfO2 layer thickness defines the diffusion coefficient of Li–ions through the passivation layer to the active material. Furthermore, ex–situ HRTEM, X–ray photoelectron spectroscopy (XPS), Raman spectroscopy and X–ray diffraction was carried out to explain the capacity retention mechanism after HfO2 coating.

  17. Surface Passivation of MoO₃ Nanorods by Atomic Layer Deposition toward High Rate Durable Li Ion Battery Anodes.

    Science.gov (United States)

    Ahmed, B; Shahid, Muhammad; Nagaraju, D H; Anjum, D H; Hedhili, Mohamed N; Alshareef, H N

    2015-06-24

    We demonstrate an effective strategy to overcome the degradation of MoO3 nanorod anodes in lithium (Li) ion batteries at high-rate cycling. This is achieved by conformal nanoscale surface passivation of the MoO3 nanorods by HfO2 using atomic layer deposition (ALD). At high current density such as 1500 mA/g, the specific capacity of HfO2-coated MoO3 electrodes is 68% higher than that of bare MoO3 electrodes after 50 charge/discharge cycles. After 50 charge/discharge cycles, HfO2-coated MoO3 electrodes exhibited specific capacity of 657 mAh/g; on the other hand, bare MoO3 showed only 460 mAh/g. Furthermore, we observed that HfO2-coated MoO3 electrodes tend to stabilize faster than bare MoO3 electrodes because nanoscale HfO2 layer prevents structural degradation of MoO3 nanorods. Additionally, the growth temperature of MoO3 nanorods and the effect of HfO2 layer thickness was studied and found to be important parameters for optimum battery performance. The growth temperature defines the microstructural features and HfO2 layer thickness defines the diffusion coefficient of Li-ions through the passivation layer to the active material. Furthermore, ex situ high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction were carried out to explain the capacity retention mechanism after HfO2 coating.

  18. Investigation of Adsorption Rates of Pb, Cd, Cu, Co and Ni to Fresh-water Surface Coatings Developed in Nanhu Lake

    Institute of Scientific and Technical Information of China (English)

    DONG De-ming; ZHANG Jing-jing; LI Yu; ZHANG Jun-zhi; HUA Xiu-yi; YANG Fan

    2004-01-01

    The adsorption kinetics of five heavy metals onto the natural surface coatings, which were collected in the Nanhu Lake in Changchun, Jilin Province, China, were investigated for the purpose of giving some explanations for the mechanisms of heavy metal adsorption onto the surface coatings with initial metal ions of 5 μmol/L. The results show that firstly, the adsorption of heavy metals onto the surface coatings follows the first order kinetics; secondly, the double-constant rate equation is suitable to describing the adsorption of heavy metals selected onto the natural aquatic surface coatings, following the order KCu>KPb>KCo>KNi>KCd; thirdly, there is a significant correlation between the adsorption rate and the physical and chemical characteristics of heavy metals, such as E0, ΔfH0m, and ΔfG0m based on the linear regression analysis.

  19. Effects of interfacial interaction potential on the sublimation rates of TNT films on a silica surface examined by QCM and AFM techniques

    Science.gov (United States)

    Mu, R.; Ueda, A.; Liu, Y. C.; Wu, M.; Henderson, D. O.; Lareau, R. T.; Chamberlain, R. T.

    2003-04-01

    The study of 2,4,6-trinitrotoluene (TNT) sublimation rates from the bulk surface and a substrate surface have been evaluated quantitatively with both atomic force microscopy and quartz crystal microbalance (QCM) techniques. A first principle theoretical model is proposed, which allows obtaining three critical parameters, bulk sublimation rate, surface interaction potential, and the effective decay length, with no arbitrary parameters. The bulk sublimation rate predicted by the model is quantitatively confirmed by QCM experiments. The isothermal measurements with QCM showed that the sublimation activation energy of bulk TNT is 131 kJ/mol. More importantly, all results were obtained at one atmosphere and near room temperature. Thus, it should have direct impacts on explosive trace detection device applications.

  20. Multi-Objective Optimization ( Surface Roughness & Material Removal Rate of Aisi 202 Grade Stainless Steel in Cnc Turning Using Extended Taguchi Method And Grey Analysis

    Directory of Open Access Journals (Sweden)

    Er.Ankush Aggarwal

    2014-07-01

    Full Text Available The present study applied Taguchi method through a case study in straight turning of AISI 202 stainless steel bar on CNC Machine ( Mfd by ACE DESIGNERS using Titanium Carbide tool for the optimization of Material removal rate, Surface Roughness and tool wear process parameter.The study aimed at evaluating the best process environment which could simultaneously satisfy requirements of both quality as well as productivity with special emphasis on maximizing material removal rate and minimizing surface roughness and tool flank wear at various combination of cutting speed, feed, depth of cut. The predicted optimal setting ensured maximum MRR and minimum surface roughness and tool wear. Since optimum material removal rate is desired, so higher the better criteria of Taguchi signal to noise ratio is used for MRR – SNs = -10 log(Sy2 /n

  1. Hydrophobic Surfaces of Spacecraft Components Enhance the Aggregation of Microorganisms and May Lead to Higher Survival Rates on Mars

    Science.gov (United States)

    Schuerger, A. C.; Kern, R. G.

    2003-01-01

    In order to minimize the forward contamination of Mars, spacecraft are assembled under clean-room conditions that often require several procedures to clean and sterilize components. Surface characteristics of spacecraft materials may contribute to microbial survival by protecting spores from sterilizing agents, including UV irradiation on the surface of Mars. The primary objective of this study was to evaluate the effects of surface characteristics of several spacecraft materials on the survival of Bacillus subtilis spores under simulated Martian conditions.

  2. Long-term slip rate of the southern San Andreas Fault, from 10Be-26Al surface exposure dating of an offset alluvial fan

    Energy Technology Data Exchange (ETDEWEB)

    der Woerd, J v; Klinger, Y; Sieh, K; Tapponnier, P; Ryerson, F; M?riaux, A

    2006-01-13

    We determine the long-term slip rate of the southern San Andreas Fault in the southeastern Indio Hills using {sup 10}Be and {sup 26}Al isotopes to date an offset alluvial fan surface. Field mapping complemented with topographic data, air photos and satellite images allow to precisely determine piercing points across the fault zone that are used to measure an offset of 565 {+-} 80 m. A total of twenty-six quartz-rich cobbles from three different fan surfaces were collected and dated. The tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history, negligible prior exposure and erosion, and yield an age of 35.5 {+-} 2.5 ka. The long-term slip rate of the San Andreas Fault south of Biskra Palms is thus 15.9 {+-} 3.4 mm/yr. This rate is about 10 mm/yr slower than geological (0-14 ka) and short-term geodetic estimates for this part of the San Andreas Fault implying changes in slip rate or in faulting behavior. This result puts new constraints on the slip rate of the San Jacinto and on the Eastern California Shear Zone for the last 35 ka. Our study shows that more sites along the major faults of southern California need to be targeted to better constrain the slip-rates over different time scales.

  3. A One-Layer Satellite Surface Energy Balance for Estimating Evapotranspiration Rates and Crop Water Stress Indexes

    Directory of Open Access Journals (Sweden)

    Salvatore Barbagallo

    2009-01-01

    Full Text Available Daily evapotranspiration fluxes over the semi-arid Catania Plain area (Eastern Sicily, Italy were evaluated using remotely sensed data from Landsat Thematic Mapper TM5 images. A one-source parameterization of the surface sensible heat flux exchange using satellite surface temperature has been used. The transfer of sensible and latent heat is described by aerodynamic resistance and surface resistance. Required model inputs are brightness, temperature, fractional vegetation cover or leaf area index, albedo, crop height, roughness lengths, net radiation, air temperature, air humidity and wind speed. The aerodynamic resistance (rah is formulated on the basis of the Monin-Obukhov surface layer similarity theory and the surface resistance (rs is evaluated from the energy balance equation. The instantaneous surface flux values were converted into evaporative fraction (EF over the heterogeneous land surface to derive daily evapotranspiration values. Remote sensing-based assessments of crop water stress (CWSI were also made in order to identify local irrigation requirements. Evapotranspiration data and crop coefficient values obtained from the approach were compared with: (i data from the semi-empirical approach “Kc reflectance-based”, which integrates satellite data in the visible and NIR regions of the electromagnetic spectrum with ground-based measurements and (ii surface energy flux measurements collected from a micrometeorological tower located in the experiment area. The expected variability associated with ET flux measurements suggests that the approach-derived surface fluxes were in acceptable agreement with the observations.

  4. Oscillations in motor unit discharge are reflected in the low-frequency component of rectified surface EMG and the rate of change in force.

    Science.gov (United States)

    Yoshitake, Yasuhide; Shinohara, Minoru

    2013-11-01

    Common drive to a motor unit (MU) pool manifests as low-frequency oscillations in MU discharge rate, producing fluctuations in muscle force. The aim of the study was to examine the temporal correlation between instantaneous MU discharge rate and rectified EMG in low frequencies. Additionally, we attempted to examine whether there is a temporal correlation between the low-frequency oscillations in MU discharge rate and the first derivative of force (dF/dt). Healthy young subjects produced steady submaximal force with their right finger as a single task or while maintaining a pinch-grip force with the left hand as a dual task. Surface EMG and fine-wire MU potentials were recorded from the first dorsal interosseous muscle in the right hand. Surface EMG was band-pass filtered (5-1,000 Hz) and full-wave rectified. Rectified surface EMG and the instantaneous discharge rate of MUs were smoothed by a Hann-window of 400 ms duration (equivalent to 2 Hz low-pass filtering). In each of the identified MUs, the smoothed MU discharge rate was positively correlated with the rectified-and-smoothed EMG as confirmed by the distinct peak in cross-correlation function with greater values in the dual task compared with the single task. Additionally, the smoothed MU discharge rate was temporally correlated with dF/dt more than with force and with rectified-and-smoothed EMG. The results indicated that the low-frequency component of rectified surface EMG and the first derivative of force provide temporal information on the low-frequency oscillations in the MU discharge rate.

  5. Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers.

    Science.gov (United States)

    Erdoğan, Mutlu; Öktem, Bülent; Kalaycıoğlu, Hamit; Yavaş, Seydi; Mukhopadhyay, Pranab K; Eken, Koray; Ozgören, Kıvanç; Aykaç, Yaşar; Tazebay, Uygar H; Ilday, F Ömer

    2011-05-23

    We propose and demonstrate the use of short pulsed fiber lasers in surface texturing using MHz-repetition-rate, microjoule- and sub-microjoule-energy pulses. Texturing of titanium-based (Ti6Al4V) dental implant surfaces is achieved using femtosecond, picosecond and (for comparison) nanosecond pulses with the aim of controlling attachment of human cells onto the surface. Femtosecond and picosecond pulses yield similar results in the creation of micron-scale textures with greatly reduced or no thermal heat effects, whereas nanosecond pulses result in strong thermal effects. Various surface textures are created with excellent uniformity and repeatability on a desired portion of the surface. The effects of the surface texturing on the attachment and proliferation of cells are characterized under cell culture conditions. Our data indicate that picosecond-pulsed laser modification can be utilized effectively in low-cost laser surface engineering of medical implants, where different areas on the surface can be made cell-attachment friendly or hostile through the use of different patterns.

  6. Temperature dependent scattering rates at the fermi surface of optimally doped Bi(2)Sr(2)CaCu(2)O(8+delta)

    Science.gov (United States)

    Valla; Fedorov; Johnson; Li; Gu; Koshizuka

    2000-07-24

    For optimally doped Bi(2)Sr(2)CaCu(2)O(8+delta), scattering rates in the normal state are found to have a linear temperature dependence over most of the Fermi surface. In the immediate vicinity of the (pi, 0) point, the scattering rates are nearly constant in the normal state, consistent with models in which scattering at this point determines the c-axis transport. In the superconducting state, the scattering rates away from the nodal direction appear to level off and become temperature independent.

  7. Communication: Rigorous quantum dynamics of O + O2 exchange reactions on an ab initio potential energy surface substantiate the negative temperature dependence of rate coefficients.

    Science.gov (United States)

    Li, Yaqin; Sun, Zhigang; Jiang, Bin; Xie, Daiqian; Dawes, Richard; Guo, Hua

    2014-08-28

    The kinetics and dynamics of several O + O2 isotope exchange reactions have been investigated on a recently determined accurate global O3 potential energy surface using a time-dependent wave packet method. The agreement between calculated and measured rate coefficients is significantly improved over previous work. More importantly, the experimentally observed negative temperature dependence of the rate coefficients is for the first time rigorously reproduced theoretically. This negative temperature dependence can be attributed to the absence in the new potential energy surface of a submerged "reef" structure, which was present in all previous potential energy surfaces. In addition, contributions of rotational excited states of the diatomic reactant further accentuate the negative temperature dependence.

  8. Effects of Surface Inclination on the Vertical Loading Rates and Landing Pattern during the First Attempt of Barefoot Running in Habitual Shod Runners.

    Science.gov (United States)

    An, W; Rainbow, M J; Cheung, R T H

    2015-01-01

    Barefoot running has been proposed to reduce vertical loading rates, which is a risk factor of running injuries. Most of the previous studies evaluated runners on level surfaces. This study examined the effect of surface inclination on vertical loading rates and landing pattern during the first attempt of barefoot running among habitual shod runners. Twenty habitual shod runners were asked to run on treadmill at 8.0 km/h at three inclination angles (0°; +10°; -10°) with and without their usual running shoes. Vertical average rate (VALR) and instantaneous loading rate (VILR) were obtained by established methods. Landing pattern was decided using high-speed camera. VALR and VILR in shod condition were significantly higher (p barefoot condition (p > 0.382). There was no difference (p > 0.413) in the landing pattern among all surface inclinations. Only one runner demonstrated complete transition to non-heel strike landing in all slope conditions. Reducing heel strike ratio in barefoot running did not ensure a decrease in loading rates (p > 0.15). Conversely, non-heel strike landing, regardless of footwear condition, would result in a softer landing (p < 0.011).

  9. Effects of Surface Inclination on the Vertical Loading Rates and Landing Pattern during the First Attempt of Barefoot Running in Habitual Shod Runners

    Directory of Open Access Journals (Sweden)

    W. An

    2015-01-01

    Full Text Available Barefoot running has been proposed to reduce vertical loading rates, which is a risk factor of running injuries. Most of the previous studies evaluated runners on level surfaces. This study examined the effect of surface inclination on vertical loading rates and landing pattern during the first attempt of barefoot running among habitual shod runners. Twenty habitual shod runners were asked to run on treadmill at 8.0 km/h at three inclination angles (0°; +10°; −10° with and without their usual running shoes. Vertical average rate (VALR and instantaneous loading rate (VILR were obtained by established methods. Landing pattern was decided using high-speed camera. VALR and VILR in shod condition were significantly higher (p0.382. There was no difference (p>0.413 in the landing pattern among all surface inclinations. Only one runner demonstrated complete transition to non-heel strike landing in all slope conditions. Reducing heel strike ratio in barefoot running did not ensure a decrease in loading rates (p>0.15. Conversely, non-heel strike landing, regardless of footwear condition, would result in a softer landing (p<0.011.

  10. Shake-flask test for determination of biodegradation rates of 14C-labelled chemicals at low concentrations in surface water systems

    DEFF Research Database (Denmark)

    Ingerslev, F.; Nyholm, Niels

    2000-01-01

    A simple shake-flask surface water biodegradability die away test with C-14-labeled chemicals added to microgram per liter concentrations (usually 1-100 mu g/L) is described and evaluated. The aim was to provide information on biodegradation behavior and kinetic rates at environmental (low......) concentrations in surface water systems. The basic principle of measurement was to determine evolved CO2 indirectly from measurements of total organic activity in subsamples after stripping off their content of CO2, Used with surface water alone the test simulates a pelagic environment and amended with sediments...... regular reinoculation with freshly collected surface water could, however, overcome the problems of false-negative results. (C) 2000 Academic Press....

  11. Immunological network activation by low-dose rate irradiation. Analysis of cell populations and cell surface molecules in whole body irradiated mice

    Energy Technology Data Exchange (ETDEWEB)

    Ina, Yasuhiro; Sakai, Kazuo [Central Research Inst. of Electric Power Industry, Low Dose Radiation Research Center, Komae, Tokyo (Japan)

    2003-07-01

    The effects of low-dose rate whole body irradiation on biodefense and immunological systems were investigated using female C57BL/6 (B6) mice. These B6 mice were exposed continuously to {gamma}-rays from a {sup 137}Cs source in the long-term low-dose rate irradiation facility at CRIEPI for 0 - 12 weeks at a dose rate of 0.95 mGy/hr. In the bone marrow, thymus, spleen, lymph nodes, and peripheral blood of the irradiated mice, changes in cell populations and cell surface molecules were examined. The cell surface functional molecules (CD3, CD4, CD8, CD19, CD45R/B220, ICAM-1, Fas, NK-1.1, CXCR4, and CCR5), and activation molecules (THAM, CD28, CD40, CD44H, CD70, B7-1, B7-2, OX-40 antigen, CTLA-4, CD30 ligand, and CD40 ligand) were analyzed by flow cytometry. The percentage of CD4{sup +} T cells and cell surface CD8 molecule expressions on the CD8{sup +} T cells increased significantly to 120-130% after 3 weeks of the irradiation, compared to non-irradiated control mice. On the other hand, the percentage of CD45R/B220{sup +} CD40{sup +} B cells, which is one of the immunological markers of inflammation, infection, tumor, and autoimmune disease, decreased significantly to 80-90% between the 3rd to 5th week of irradiation. There was no significant difference in other cell population rates and cell surface molecule expression. Furthermore, abnormal T cells bearing mutated T cell receptors induced by high-dose rate irradiation were not observed throughout this study. These results suggest that low-dose rate irradiation activates the immunological status of the whole body. (author)

  12. Quartz dissolution. I - Negative crystal experiments and a rate law. II - Theory of rough and smooth surfaces

    Science.gov (United States)

    Gratz, Andrew J.; Bird, Peter

    1993-01-01

    The range of the measured quartz dissolution rates, as a function of temperature and pOH, extent of saturation, and ionic strength, is extended to cover a wider range of solution chemistries, using the negative crystal methodology of Gratz et al. (1990) to measure the dissolution rate. A simple rate law describing the quartz dissolution kinetics above the point of zero charge of quartz is derived for ionic strengths above 0.003 m. Measurements were performed on some defective crystals, and the mathematics of step motion was developed for quartz dissolution and was compared with rough-face behavior using two different models.

  13. Influence of wetting effect at the outer surface of the pipe on increase in leak rate - experimental results and discussion

    Energy Technology Data Exchange (ETDEWEB)

    Isozaki, Toshikuni; Shibata, Katsuyuki

    1997-04-01

    Experimental and computed results applicable to Leak Before Break analysis are presented. The specific area of investigation is the effect of the temperature distribution changes due to wetting of the test pipe near the crack on the increase in the crack opening area and leak rate. Two 12-inch straight pipes subjected to both internal pressure and thermal load, but not to bending load, are modelled. The leak rate was found to be very susceptible to the metal temperature of the piping. In leak rate tests, therefore, it is recommended that temperature distribution be measured precisely for a wide area.

  14. Using surface creep rate to infer fraction locked for sections of the San Andreas fault system in northern California from alignment array and GPS data

    Science.gov (United States)

    Lienkaemper, James J.; McFarland, Forrest S.; Simpson, Robert W.; Caskey, S. John

    2014-01-01

    Surface creep rate, observed along five branches of the dextral San Andreas fault system in northern California, varies considerably from one section to the next, indicating that so too may the depth at which the faults are locked. We model locking on 29 fault sections using each section’s mean long‐term creep rate and the consensus values of fault width and geologic slip rate. Surface creep rate observations from 111 short‐range alignment and trilateration arrays and 48 near‐fault, Global Positioning System station pairs are used to estimate depth of creep, assuming an elastic half‐space model and adjusting depth of creep iteratively by trial and error to match the creep observations along fault sections. Fault sections are delineated either by geometric discontinuities between them or by distinctly different creeping behaviors. We remove transient rate changes associated with five large (M≥5.5) regional earthquakes. Estimates of fraction locked, the ratio of moment accumulation rate to loading rate, on each section of the fault system provide a uniform means to inform source parameters relevant to seismic‐hazard assessment. From its mean creep rates, we infer the main branch (the San Andreas fault) ranges from only 20%±10% locked on its central creeping section to 99%–100% on the north coast. From mean accumulation rates, we infer that four urban faults appear to have accumulated enough seismic moment to produce major earthquakes: the northern Calaveras (M 6.8), Hayward (M 6.8), Rodgers Creek (M 7.1), and Green Valley (M 7.1). The latter three faults are nearing or past their mean recurrence interval.

  15. Evaluation of a new experimental test procedure to more accurately determine the surface infiltration rate of permeable pavement systems

    NARCIS (Netherlands)

    Lucke, T.; Boogaard, F.; Van den Ven, F.

    2014-01-01

    Permeable pavements are specifically designed to promote the infiltration of stormwater through the paving surface in order to reduce run-off volumes and to improve water quality by removing sediment and other pollutants. However, research has shown that permeable pavements can become clogged over

  16. Surface deformation versus eruption rates of the two Eyjafjallajökull 2010 eruptions; implications for the magma plumbing system and origin of melts

    Science.gov (United States)

    Pedersen, R.; Sigmundsson, F.; Hreinsdottir, S.; Arnadottir, T.; Hoskuldsson, A.; Gudmundsson, M. T.; Magnusson, E.

    2010-12-01

    Repeated geodetic measurements reveal how active volcanoes deform at the surface, and data inversion facilitates inferences about the related volume changes of underlying deformation sources. During an eruption, drainage from a shallow magma chamber can lead to direct correlation between magma flow rate and deformation rates, as observed previously in Iceland. In the simplest case, a constant scale factor relates magma flow rates, deformation rates on the surface, and inferred volume contraction of subsurface sources. The scale factor will depend on magma source geometry, compressibility of residing magma and rheological properties of the crustal rocks. During the two eruptions of the Eyjafjallajökull volcano, Iceland, in 2010 an entirely different behaviour was observed. This behaviour may be related to the rather unique plumbing system of this particular Icelandic volcano, which appears to have no shallow magma chamber. For the initial flank eruption, where olivine basalt were erupted during a period of about 3 weeks, the average eruption rate was comparable to the inferred flow rate during formation of a pre-eruptive network of intrusions. Detailed GPS and InSAR measurements have revealed a model for the subsurface magma plumbing system active prior to and during the events with multiple sills around 5 km depth. Such intrusions have occurred intermittently in this particular volcano for the past 18 years. During the subsequent explosive trachy-andesitic summit eruption, the relation between deformation rate and magma flow rate is more complex. A large discrepancy exists between the inferred erupted volume and the computed volume change based on the associated surface deformation. When recalculated to dense rock equivalent, the inferred volume change responsible for the main deformation is about one order of magnitude smaller than the sum of mapped erupted volumes. Furthermore, the spatial pattern of the deformation is complex, and not directly related to the

  17. The effect of pulse duration on the growth rate of laser-induced damage sites at 351 nm on fused silica surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Negres, R A; Norton, M A; Liao, Z M; Cross, D A; Bude, J D; Carr, C W

    2009-10-29

    Past work in the area of laser-induced damage growth has shown growth rates to be primarily dependent on the laser fluence and wavelength. More recent studies suggest that growth rate, similar to the damage initiation process, is affected by a number of additional parameters including pulse duration, pulse shape, site size, and internal structure. In this study, we focus on the effect of pulse duration on the growth rate of laser damage sites located on the exit surface of fused silica optics. Our results demonstrate, for the first time, a significant dependence of growth rate at 351 nm on pulse duration from 1 ns to 15 ns as {tau}{sup 0.3} for sites in the 50-100 {micro}m size range.

  18. Survey of Gamma Dose and Radon Exhalation Rate from Soil Surface of High Background Natural Radiation Areas in Ramsar, Iran

    Directory of Open Access Journals (Sweden)

    Rouhollah Dehghani

    2013-09-01

    Full Text Available Background: Radon is a radioactive gas and the second leading cause of death due to lung cancer after smoking. Ramsar is known for having the highest levels of natural background radiation on earth. Materials and Methods: In this research study, 50 stations of high radioactivity areas of Ramsar were selected in warm season of the year. Then gamma dose and radon exhalation rate were measured.Results: Results showed that gamma dose and radon exhalation rate were in the range of 51-7100 nSv/hr and 9-15370 mBq/m2s, respectively.Conclusion: Compare to the worldwide average 16 mBq/m2s, estimated average annual effective of Radon exhalation rate in the study area is too high.

  19. Synthesis of surface modified LiFePO{sub 4} cathode material via polyol technique for high rate lithium secondary battery

    Energy Technology Data Exchange (ETDEWEB)

    Sivakumar, M., E-mail: susiva73@yahoo.co.in; Muruganantham, R.; Subadevi, R.

    2015-05-15

    Highlights: • NiO coating on LiFePO{sub 4} via polyol technique may be the first attempt. • Surface coating using NiO on LiFePO{sub 4} did not affect its orthorhombic olivine structure. • Surface modification using NiO on LiFePO{sub 4} delivers the discharge capacity of 164 mAh g{sup −1} at 0.1 C rate. - Abstract: The NiO-coated LiFePO{sub 4} composite cathode materials were prepared by simple tailored polyol technique, which has orthorhombic olivine structure without NiO phase. It delivers the reverse capacity of 164 mAh g{sup −1} at 0.1 C at ambient temperature. The material exhibits stable reverse capacity for several cycles even for the higher C-rates. Increasing the rate, the reverse capacity is almost stable over several cycles. Furthermore, at a high rate viz., 10, 20 and 30 C, the discharge capacity has been observed for the optimized NiO-coated LFP as 135, 120 and 69 mAh g{sup −1}, which demonstrates the excellent rate performance that can be useful for high power lithium secondary battery.

  20. Investigation of Surface Roughness and Material Removal Rate (MRR on Tool Steel Using Brass and Copper Electrode for Electrical Discharge Grinding (EDG Process

    Directory of Open Access Journals (Sweden)

    M. Hafiz Helmi

    2009-09-01

    Full Text Available This paper presents the investigation on surface roughness and material removal rate (MRR of tool steel machined with brass and copper electrode for Electrical Discharge Grinding (EDG process. The machining parameter include pulse ON time, pulse OFF time, peak current and capacitance. Analysis of variance (ANOVA with Taguchi method is used to investigate the significant effect on the performance characteristic and the optimal cutting parameters of EDG. The result shows that, the surface roughness value when using of both tool materials are mostly influenced by pulse ON time and peak current. The capacitance parameter in both experiments was not giving any significant effect. The significant factors for the material removal rate due to the machining parameter are peak current parameter and ON time parameter but it also can increase the machining time

  1. Effect of Deposition Rate on Structure and Surface Morphology of Thin Evaporated Al Films on Dielectrics and Semiconductors

    DEFF Research Database (Denmark)

    Bordo, K.; Rubahn, H. G.

    2012-01-01

    Aluminum (Al) films with thickness of 100 nm were grown on unheated glass, silicon and mica substrates by electron beam evaporation. The deposition rates were adjusted in the range between 0.1 nm/s and 2 nm/s, the pressure in the vacuum chamber during deposition was lower than 1.10(-3) Pa...

  2. Effects of airflow and liquid temperature on ammonia mass transfer above an emission surface: Experimental study on emission rate

    DEFF Research Database (Denmark)

    Rong, Li; Nielsen, P V; Zhang, Guo-Qiang

    2009-01-01

    The present study performed a series of experiments in a wind tunnel to investigate the impact of velocity, turbulence intensity and liquid-air temperature difference on ammonia emission rates. Decreasing velocity, turbulence intensity and liquid temperature are shown to reduce the ammonia emissi...

  3. Observations of C-Band Brightness Temperature and Ocean Surface Wind Speed and Rain Rate in Hurricanes Earl And Karl (2010)

    Science.gov (United States)

    Miller, Timothy; James, Mark; Roberts, Brent J.; Biswax, Sayak; Uhlhorn, Eric; Black, Peter; Linwood Jones, W.; Johnson, Jimmy; Farrar, Spencer; Sahawneh, Saleem

    2012-01-01

    Ocean surface emission is affected by: a) Sea surface temperature. b) Wind speed (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields wind speed and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface wind, temp and rain b) Advances understanding & prediction of hurricane intensity c) Expands Stepped Frequency Microwave Radiometer capabilities d) Uses synthetic thinned array and RFI mitigation technology of Lightweight Rain Radiometer (NASA Instrument Incubator) Passive Microwave C-Band Radiometer with Freq: 4, 5, 6 & 6.6 GHz: a) Version 1: H-pol for ocean wind speed, b) Version 2: dual ]pol for ocean wind vectors. Performance Characteristics: a) Earth Incidence angle: 0deg - 60deg, b) Spatial Resolution: 2-5 km, c) Swath: approx.70 km for 20 km altitude. Observational Goals: WS 10 - >85 m/s RR 5 - > 100 mm/hr.

  4. Neutralizing positive charges at the surface of a protein lowers its rate of amide hydrogen exchange without altering its structure or increasing its thermostability.

    Science.gov (United States)

    Shaw, Bryan F; Arthanari, Haribabu; Narovlyansky, Max; Durazo, Armando; Frueh, Dominique P; Pollastri, Michael P; Lee, Andrew; Bilgicer, Basar; Gygi, Steven P; Wagner, Gerhard; Whitesides, George M

    2010-12-15

    This paper combines two techniques--mass spectrometry and protein charge ladders--to examine the relationship between the surface charge and hydrophobicity of a representative globular protein (bovine carbonic anhydrase II; BCA II) and its rate of amide hydrogen-deuterium (H/D) exchange. Mass spectrometric analysis indicated that the sequential acetylation of surface lysine-ε-NH3(+) groups--a type of modification that increases the net negative charge and hydrophobicity of the surface of BCA II without affecting its secondary or tertiary structure--resulted in a linear decrease in the aggregate rate of amide H/D exchange at pD 7.4, 15 °C. According to analysis with MS, the acetylation of each additional lysine generated between 1.4 and 0.9 additional hydrogens that are protected from H/D exchange during the 2 h exchange experiment at 15 °C, pD 7.4. NMR spectroscopy demonstrated that none of the hydrogen atoms which became protected upon acetylation were located on the side chain of the acetylated lysine residues (i.e., lys-ε-NHCOCH3) but were instead located on amide NHCO moieties in the backbone. The decrease in rate of exchange associated with acetylation paralleled a decrease in thermostability: the most slowly exchanging rungs of the charge ladder were the least thermostable (as measured by differential scanning calorimetry). This observation--that faster rates of exchange are associated with slower rates of denaturation--is contrary to the usual assumptions in protein chemistry. The fact that the rates of H/D exchange were similar for perbutyrated BCA II (e.g., [lys-ε-NHCO(CH2)2CH3]18) and peracetylated BCA II (e.g., [lys-ε-NHCOCH3]18) suggests that the electrostatic charge is more important than the hydrophobicity of surface groups in determining the rate of H/D exchange. These electrostatic effects on the kinetics of H/D exchange could complicate (or aid) the interpretation of experiments in which H/D exchange methods are used to probe the structural

  5. Fidelity of δ18O as a proxy for sea surface temperature: Influence of variable coral growth rates on the coral Porites lutea from Hainan Island, China

    Science.gov (United States)

    Shimamura, Michiyo; Oba, Tadamichi; Xu, Guoqiang; Lu, Bingquan; Wang, Luejiang; Murayama, Masafumi; Toyoda, Kazuhiro; Winter, Amos

    2005-09-01

    The extremely high temporal resolution (nearly daily interval) measurement was conducted on the coral (Porites lutea) oxygen isotope compositions (δ18Oc) to examine the detailed relationship between δ18Oc and sea surface temperature (SST) and seawater oxygen isotope composition (δ18Ow) from Hainan Island, China. Although SST and sea surface salinity (SSS) or δ18Ow varied in a wide range at the studied site, the dynamic range of δ18Oc recorded in coral was much smaller than expected from SST and SSS (δ18Ow) changes. The extremely high (>30°C) and low (rates (the overall rate is 15 mm/year) varied by a factor of about 18 within one year, from very slow in winter to very fast in spring. Light availability could affect the extension rate of coral skeleton through the activity of photosynthesis of symbiont algae. Such cessation and acceleration of calcification cause a serious distortion of the δ18O profile, which makes it difficult to make a correlation between δ18O and SST. Because high and low extension rates correspond to low- and high-density bands, respectively, a detailed examination of the density structure may assist the correction for distortion of the δ18O profile.

  6. CT computer-optimized high-dose-rate brachytherapy with surface applicator technique for scar boost radiation after breast reconstruction surgery.

    Science.gov (United States)

    Stewart, Alexandra J; O'Farrell, Desmond A; Bellon, Jennifer R; Hansen, Jorgen L; Duggan, Catherine; Czerminska, Maria A; Cormack, Robert A; Devlin, Phillip M

    2005-01-01

    Immediate breast reconstruction has become increasingly prevalent after mastectomy for breast cancer. Postoperative scar boost radiation for the reconstructed breast presents many planning challenges due to the shape, size, and curvature of the scar. High-dose-rate (HDR) surface applicator brachytherapy is a novel and effective method of delivering scar boost radiation. Two cases, one with a saline implant and one with a transverse rectus abdominis musculocutaneous flap reconstruction, illustrate the method and advantages of HDR optimization of surface applicators. For 2 patients a mold of the breast was made with Aquaplast sheets. A reproducible system was used for arm positioning. Skin fiducials, including tattoos from external beam planning, were matched to fiducials on the mold. HDR catheters were sited on the mold at 1cm intervals, with the central catheter situated along the scar. Topographically, both scars demonstrated extreme curvature in both craniocaudal and mediolateral directions. A CT computer-optimized HDR plan was developed, with the reference dose prescribed at the skin surface. The dosimetry was compared to single-field and matched-field electron plans. This surface applicator technique provided a uniform skin dose of 100% to the entire clinical target volume (CTV) without hot spots in both patients. The patient position and surface applicator setup were consistently reproducible. The patients tolerated the treatment well with minimal skin erythema. In the single-field electron plan, skin dose was decreased to 50% at the periphery of the scar. Matching fields addressed this depth dose decrement, but resulted in large localized hot spots of more than 200% centrally in each field. CT computer-optimized HDR surface applicator brachytherapy provided a reproducible homogeneous method of treating highly curved scars on the reconstructed breast. Electron beam treatment would result in longer and more complex treatments yet still provide a less

  7. Relationship between coral growth rate and sea surface temperature in the northern part of South China Sea during the past 100 a

    Institute of Scientific and Technical Information of China (English)

    聂宝符; 陈特固; 梁美桃; 王有强; 钟晋梁; 朱袁智

    1997-01-01

    To research the relationship between coral growth rate and sea surface temperature ( Tss), 5 cores of living Porites lutea were collected from the Xisha Islands and the southern Hainan Island waters and measured. The results of the study show that there is an obviously positive correlation between the coral growth rates and the Tss records from the northern part of South China Sea. The annual growth rates of the five samples of Porites lutea during the past 100 a are in the range of 7-15 mm/a, and their mean value is 11 mm/a. The correlation coefficients between the coral growth rates and the Tss records from the waters during 1961-1993 are in the range of 0. 77-0.89. As a result, a thermometer of the coral growth rate is established. A hindcasting Tss in the waters from 1993 to 1961 has been obtained with an error of about 0.12-0.17℃ . Based upon the calculated result, the rising rate of Tss in the northern part of South China Sea during the past 100 a is 0. 20℃ , which is higher than that of the air

  8. New insights into saline water evaporation from porous media: Complex interaction between evaporation rates, precipitation, and surface temperature

    Science.gov (United States)

    Shokri-Kuehni, Salomé M. S.; Vetter, Thomas; Webb, Colin; Shokri, Nima

    2017-06-01

    Understanding salt transport and deposition patterns during evaporation from porous media is important in many engineering and hydrological processes such as soil salinization, ecosystem functioning, and land-atmosphere interaction. As evaporation proceeds, salt concentration increases until it exceeds solubility limits, locally, and crystals precipitate. The interplay between transport processes, crystallization, and evaporation influences where crystallization occurs. During early stages, the precipitated salt creates an evolving porous structure affecting the evaporation kinetics. We conducted a comprehensive series of experiments to investigate how the salt concentration and precipitation influence evaporation dynamics. Our results illustrate the contribution of the evolving salt crust to the evaporative mass losses. High-resolution thermal imaging enabled us to investigate the complex temperature dynamics at the surface of precipitated salt, providing further confirmation of salt crust contribution to the evaporation. We identify different phases of saline water evaporation from porous media with the corresponding dominant mechanisms in each phase and extend the physical understanding of such processes.

  9. Bayesian belief network for CO2 leak detection by near-surface flux rates for CO2 and perfluorocarbon (PFC) tracer

    Science.gov (United States)

    Yang, Y.; Small, M. J.; Ogretim, E.; Gray, D. D.; Bromhal, G. S.; Strazisar, B. R.; Wells, A. W.

    2010-12-01

    To incorporate the use of multiple geologic sequestration monitoring techniques, a Bayesian Belief Network (BBN) for leak detection inference is applied to integrate the information provided by different techniques deployed at a site. In this study, two monitoring methods, near-surface soil CO2 flux and perfluorocarbon (PFC) tracer concentration, are included in the BBN. First, possible near-surface flux rates for CO2 and PFC tracer as a function of distance from a leakage point are simulated by TOUGH2, given different leakage rates and permeabilities. Then, the natural near-surface CO2 flux and background PFC tracer concentration measured at the Zero Emission Research and Technology (ZERT) site are used to determine critical values for leak inference and to calculate the probabilities of leak detection given a monitoring network. A BBN of leak detection is established by combing the TOUGH2 simulations and the background characterization of near-surface CO2 flux and PFC tracer at the sequestration site. The results show a positive correlation between the detection abilities of PFC tracer and soil CO2 flux, but the PFC tracer is more sensitive for detecting a leak in most cases. The BBN of leak detection including both soil CO2 flux and PFC tracer concentration gives an integrated probability estimation of leak detection for different permeability and leakage rates for a given monitoring network. A BBN developed using the proposed methodology can be used to help site engineers and decision makers to evaluate leakage signals and the risk of undetected leakage, given a suite of monitoring techniques and site conditions.

  10. SU-E-T-232: Custom High-Dose-Rate Brachytherapy Surface Mold Applicators: The Importance Source to Skin Distance

    Energy Technology Data Exchange (ETDEWEB)

    Park, S; Demanes, J; Kamrava, M [UCLA School of Medicine, Los Angeles, CA (United States)

    2015-06-15

    Purpose: Surface mold applicators can be customized to fit irregular skin surfaces that are difficult to treat with other radiation therapy techniques. Optimal design of customized HDR skin brachytherapy is not well-established. We evaluated the impact of applicator thickness (source to skin distance) on target dosimetry. Methods: 27 patients had 34 treated sites: scalp 4, face 13, extremity 13, and torso 4. Custom applicators were constructed from 5–15 mm thick thermoplastic bolus molded over the skin lesion. A planar array of plastic brachytherapy catheters spaced 5–10 mm apart was affixed to the bolus. CT simulation was used to contour the target volume and to determine the prescription depth. Inverse planning simulated annealing followed by graphical optimization was used to plan and deliver 40–56 Gy in 8–16 fractions. Target coverage parameters (D90, Dmean, and V100) and dose uniformity (V110–200, D0.1cc, D1cc, and D2cc) were studied according to target depth (<5mm vs. ≥5mm) and applicator thickness (5–10mm vs. ≥10mm). Results: The average prescription depth was 4.2±1.5mm. The average bolus thickness was 9.2±2.4mm. The median CTV volume was 10.0 cc (0.2–212.4 cc). Similar target coverage was achieved with prescription depths of <5mm and ≥5mm (Dmean = 113.8% vs. 112.4% and D90 = 100.2% vs. 98.3%). The <5mm prescription depth plans were more uniform (D0.1cc = 131.8% vs. 151.8%). Bolus thickness <10mm vs. ≥10mm plans also had similar target coverage (Dmean = 118.2% vs. 110.7% and D90 = 100.1% vs. 99.0%). Applicators ≥10mm thick, however, provide more uniform target dosimetry (D0.1cc = 146.9% vs. 139.5%). Conclusion: Prescription depth is based upon the thickness of the lesion and upon the clinical needs of the patient. Applicators ≥10mm thick provide more dose uniformity than 5–10mm thick applicators. Applicator thickness is an important variable that should be considered during treatment planning to achieve optimal dose uniformity.

  11. Seasonal variation of meteorological variables and recent surface ablation / accumulation rates on Davies Dome and Whisky Glacier, James Ross Island, Antarctica

    Science.gov (United States)

    Láska, K.; Nývlt, D.; Engel, Z.; Budík, L.

    2012-04-01

    In this study, surface mass balance data of two glaciers on James Ross Island, Antarctica, and its spatial and temporal variations are evaluated using snow ablation stakes, ground-penetrating radar, and dGPS measurements. The investigated glaciers are located on the Ulu Peninsula, northern part of James Ross Island. Davies Dome is an ice dome, which originates on the surface of a flat volcanic mesa at elevations >400 m a.s.l. and terminates with a single 700 m wide outlet in the Whisky Bay. Davies Dome has an area of ~6.5 km2 and lies in the altitude range of 0-514 m a.s.l. Whisky Glacier is a cold-based land-terminating valley glacier surrounded by an extensive moraine ridges made of debris-covered ice. The glacier has an area of ~2.4 km2 and lies in the altitude range of 215-520 m a.s.l. Within several summer austral summers, extensive field programme were carried out on both glaciers including the operation of two automatic weather stations, field mapping and mass balance measurements. Each station was equipped with albedometer CM7B (Kipp-Zonen, Netherlands), air temperature and humidity sensor EMS33 (EMS, Czech Republic), propeller anemometer 05103 (Young, USA), and snow depth sensors (Judd, USA). In the period 2009-2011, high seasonal and interdiurnal variability of incoming solar radiation and near-surface air temperature was found as a result of changes in the circulation patterns and synoptic-scale weather systems moving in the Circumpolar Trough. High ablation and accumulation rates were recorded mainly in the spring and summer seasons (October-February), while negligible changes were found in winter (May-September). The effects of positive degree-day temperatures on the surface ablation rates were examined using a linear regression model. In this approach, near-surface air temperature maps on the glacier surfaces were derived from digital elevation model according to actual temperature lapse rates. Mass balance investigations started in 2006 on Davies

  12. Recovery Efficiency, False Negative Rate, and Limit of Detection Performance of a Validated Macrofoam-Swab Sampling Method with Low Surface Concentrations of Two Bacillus anthracis Surrogates

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hutchison, Janine R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Deatherage Kaiser, Brooke L [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Amidan, Brett G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sydor, Michael A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Barrett, Christopher A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-03-31

    The performance of a macrofoam-swab sampling method was evaluated using Bacillus anthracis Sterne (BAS) and Bacillus atrophaeus Nakamura (BG) spores applied at nine low target amounts (2-500 spores) to positive-control plates and test coupons (2 in. × 2 in.) of four surface materials (glass, stainless steel, vinyl tile, and plastic). Test results from cultured samples were used to evaluate the effects of surrogate, surface concentration, and surface material on recovery efficiency (RE), false negative rate (FNR), and limit of detection. For RE, surrogate and surface material had statistically significant effects, but concentration did not. Mean REs were the lowest for vinyl tile (50.8% with BAS, 40.2% with BG) and the highest for glass (92.8% with BAS, 71.4% with BG). FNR values ranged from 0 to 0.833 for BAS and 0 to 0.806 for BG, with values increasing as concentration decreased in the range tested (0.078 to 19.375 CFU/cm2, where CFU denotes ‘colony forming units’). Surface material also had a statistically significant effect. A FNR-concentration curve was fit for each combination of surrogate and surface material. For both surrogates, the FNR curves tended to be the lowest for glass and highest for vinyl title. The FNR curves for BG tended to be higher than for BAS at lower concentrations, especially for glass. Results using a modified Rapid Viability-Polymerase Chain Reaction (mRV-PCR) analysis method were also obtained. The mRV-PCR results and comparisons to the culture results will be discussed in a subsequent report.

  13. Optimization of Aeration and Agitation Rate for Lipid and Gamma Linolenic Acid Production by Cunninghamella bainieri 2A1 in Submerged Fermentation Using Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Normah Saad

    2014-01-01

    Full Text Available The locally isolated filamentous fungus Cunninghamella bainieri 2A1 was cultivated in a 5 L bioreactor to produce lipid and gamma-linolenic acid (GLA. The optimization was carried out using response surface methodology based on a central composite design. A statistical model, second-order polynomial model, was adjusted to the experimental data to evaluate the effect of key operating variables, including aeration rate and agitation speed on lipid production. Process analysis showed that linear and quadratic effect of agitation intensity significantly influenced lipid production process (P<0.01. The quadratic model also indicated that the interaction between aeration rate and agitation speed had a highly significant effect on lipid production (P<0.01. Experimental results showed that a lipid content of 38.71% was produced in optimum conditions using an airflow rate and agitation speed of 0.32 vvm and 599 rpm, respectively. Similar results revealed that 0.058 (g/g gamma-linolenic acid was produced in optimum conditions where 1.0 vvm aeration rate and 441.45 rpm agitation rate were used. The regression model confirmed that aeration and agitation were of prime importance for optimum production of lipid in the bioreactor.

  14. Plasma induced neutrino spin-flip in a supernova and new bounds on the neutrino magnetic moment

    CERN Document Server

    Kuznetsov, A V

    2007-01-01

    The neutrino chirality-flip process under the conditions of the supernova core is investigated in detail with the plasma polarization effects in the photon propagator taken into account in a more complete form than in earlier publications. It is shown in part that the contribution of the proton fraction of plasma is essential. New upper bounds on the neutrino magnetic moment are obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from the limit on the averaged time of the left-handed neutrino washing out. The best upper bound on the neutrino magnetic moment from SN1987A is improved by the factor of 3 to 7.

  15. Mesoscopic spin-flip transport through a hybrid system with a single molecular dot system applied with ac magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Chen Qiao, E-mail: cqhy1127@yahoo.com.c [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China); Liu Jin [Institute of Theoretical Physics, Chinese Academy of Science, Beijing 100190 (China); Wang Zhiyong [School of Optoelectronic Information, Chongqing University of Technology, Chongqing 400054 (China)

    2011-01-17

    We have investigated the current for the system of vibrating quantum dot irradiated with a rotating magnetic field and an oscillating magnetic field by nonequilibrium Green's function. The rotating magnetic field rotates with the angular frequency {omega}{sub r} around the z-axis with the tilt angle {theta}, and the time-oscillating magnetic field is located in the z-axis with the angular frequency {omega}. Different behaviors have been shown in the presence of electron-phonon interaction (EPI) which plays a significant role in the transport. The current displays asymmetric behavior as the source-drain bias eV=0, novel side peaks or shoulders can be found due to the phonon absorption and emission procedure, and the negative differential resistance becomes stronger as the parameter g increases. Furthermore, the strong EPI also destroys the quasiperiodic oscillations of current in the region {mu}{sub 0}B{sub 1}>2.5{Delta}. The electron transport properties are also significantly influenced by the linewidth function {Gamma}.

  16. Very low surface recombination velocity on p-type c-Si by high-rate plasma-deposited aluminum oxide

    Science.gov (United States)

    Saint-Cast, Pierre; Kania, Daniel; Hofmann, Marc; Benick, Jan; Rentsch, Jochen; Preu, Ralf

    2009-10-01

    Aluminum oxide layers can provide excellent passivation for lowly and highly doped p-type silicon surfaces. Fixed negative charges induce an accumulation layer at the p-type silicon interface, resulting in very effective field-effect passivation. This paper presents highly negatively charged (Qox=-2.1×1012 cm-2) aluminum oxide layers produced using an inline plasma-enhanced chemical vapor deposition system, leading to very low effective recombination velocities (˜10 cm s-1) on low-resistivity p-type substrates. A minimum static deposition rate (100 nm min-1) at least one order of magnitude higher than atomic layer deposition was achieved on a large carrier surfaces (˜1 m2) without significantly reducing the resultant passivation quality.

  17. Forcing Mechanisms for the Variations of Near-surface Temperature Lapse Rates along the Himalayas, Tibetan Plateau (HTP) and Their Surroundings

    Science.gov (United States)

    Kattel, D. B.; Yao, T.; Ullah, K.; Islam, G. M. T.

    2016-12-01

    This study investigates the monthly characteristics of near-surface temperature lapse rates (TLRs) (i.e., governed by surface energy balance) based on the 176 stations 30-year (1980 to 2010) dataset covering a wide range of topography, climatic regime and relief (4801 m) in the HTP and its surroundings. Empirical analysis based on techniques in thermodynamics and hydrostatic system were used to obtain the results. Steepest TLRs in summer is due to strong dry convection and shallowest in winter is due to inversion effect is the general pattern of TLR that reported in previous studies in other mountainous region. Result of this study reports a contrast variation of TLRs from general patterns, and suggest distinct forcing mechanisms in an annual cycle. Shallower lapse rate occurs in summer throughout the regions is due to strong heat exchange process within the boundary layer, corresponding to the warm and moist atmospheric conditions. There is a systematic differences of TLRs in winter between the northern and southern slopes the Himalayas. Steeper TLRs in winter on the northern slopes is due to intense cooling at higher elevations, corresponding to the continental dry and cold air surges, and considerable snow-temperature feedback. The differences in elevation and topography, as well as the distinct variation of turbulent heating and cooling, explain the contrast TLRs (shallower) values in winter on the southern slopes. Distinct diurnal variations of TLRs and its magnitudes between alpine, dry, humid and coastal regions is due to the variations of adiabatic mixing during the daytime in the boundary layer i.e., associated with the variations in net radiations, elevation, surface roughness and sea surface temperature. The findings of this study is useful to determine the temperature range for accurately modelling in various field such as hydrology, glaciology, ecology, forestry, agriculture, as well as inevitable for climate downscaling in complex mountainous terrain.

  18. Rate and style of ice stream retreat constrained by new surface-exposure ages: The Minch, NW Scotland

    Science.gov (United States)

    Bradwell, Tom; Small, David; Fabel, Derek; Dove, Dayton; Cofaigh, Colm O.; Clark, Chris; Consortium, Britice-Chrono

    2016-04-01

    Chronologically constrained studies of former ice-sheet extents and dynamics are important for understanding past cryospheric responses and modelling future ice-sheet and sea-level change. As part of the BRITICE-CHRONO project, we present new geomorphological and chronological data from a marine-terminating ice stream system in NW Europe that operated during the Late Weichselian Glaciation. A suite of 51 cosmogenic-nuclide exposure ages from ice sheet moraines and glacially transported boulders constrain the maximum extent of the ice sheet on the continental shelf (~28 ka BP) and its subsequent retreat, between ~27 and 16 ka BP, into a large marine embayment (ca. 7000 km2; the Minch, NW Scotland). Recently acquired swath bathymetry and acoustic sub-bottom profiler data reveal several large transverse grounding-zone wedges up to 40 m thick and 5 km wide with diagnostic acoustic-facies architecture. These seabed sediment wedges mark former quasi-stable positions of grounded marine-terminating ice-stream fronts; their size and thickness suggest long-lived stillstands of the order of centuries. Statistically significant clusters of exposure ages from glacial deposits on islands and intervening headlands shed important new light on the age of these marine grounding-zone wedges and, by inference, the rate and timing of Minch palaeo-ice stream retreat. We find strong evidence for episodic ice stream retreat on the continental shelf between ~28-24 ka BP, in the outer Minch between ~24-22 ka BP, and in the central Minch between 22-18.5 ka BP. In contrast, final ice stream deglaciation (probably rapid and uninterrupted - with the ice sheet margin at or close to the present-day coastline in NW Scotland by 16.1 ka BP. It is hoped that these results will form the empirical basis for future ice-sheet modelling of this dynamically sensitive sector of the British-Irish Ice Sheet.

  19. Optimization of aeration and agitation rate for lipid and gamma linolenic acid production by Cunninghamella bainieri 2A1 in submerged fermentation using response surface methodology.

    Science.gov (United States)

    Saad, Normah; Abdeshahian, Peyman; Kalil, Mohd Sahaid; Yusoff, Wan Mohtar Wan; Hamid, Aidil Abdul

    2014-01-01

    The locally isolated filamentous fungus Cunninghamella bainieri 2A1 was cultivated in a 5 L bioreactor to produce lipid and gamma-linolenic acid (GLA). The optimization was carried out using response surface methodology based on a central composite design. A statistical model, second-order polynomial model, was adjusted to the experimental data to evaluate the effect of key operating variables, including aeration rate and agitation speed on lipid production. Process analysis showed that linear and quadratic effect of agitation intensity significantly influenced lipid production process (P production (P production of lipid in the bioreactor.

  20. Coupling convectively driven atmospheric circulation to surface rotation: Evidence for active methane weather in the observed spin rate drift of Titan

    CERN Document Server

    Mitchell, Jonathan L

    2008-01-01

    A large drift in the rotation rate of Titan observed by Cassini provided the first evidence of a subsurface ocean isolating the massive core from the icy crust. Seasonal exchange of angular momentum between the surface and atmosphere accounts for the magnitude of the effect, but observations lag the expected signal by a few years. We argue this time lag is due to the presence of an active methane weather cycle in the atmosphere. An analytic model of the seasonal cycle of atmospheric angular momentum is developed and compared to time-dependent simulations of Titan's atmosphere with and without methane thermodynamics. The disappearance of clouds at the summer pole suggests the drift rate has already switched direction, signaling the change in season from solstice to equinox.

  1. Experimental Design for a Macrofoam-Swab Study Relating the Recovery Efficiency and False Negative Rate to Low Concentrations of Two Bacillus anthracis Surrogates on Four Surface Materials

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hutchison, Janine R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-12-05

    This report describes the experimental design for a laboratory study to quantify the recovery efficiencies and false negative rates of a validated, macrofoam-swab sampling method for low concentrations of Bacillus anthracis Sterne (BAS) and Bacillus atrophaeus (BG) spores on four surface materials (stainless steel, glass, vinyl tile, plastic light cover panel). Two analytical methods (culture and polymerase chain reaction) will be used. Only one previous study has investigated how the false negative rate depends on test factors. The surrogates BAS and BG have not been tested together in the same study previously. Hence, this study will provide for completing gaps in the available information on the performance of macrofoam-swab sampling at low concentrations.

  2. Corrigendum to "Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit".

    Science.gov (United States)

    El-Jaby, Samy

    2016-06-01

    A recent paper published in Life Sciences in Space Research (El-Jaby and Richardson, 2015) presented estimates of the secondary neutron ambient and effective dose equivalent rates, in air, from surface altitudes up to suborbital altitudes and low Earth orbit. These estimates were based on MCNPX (LANL, 2011) (Monte Carlo N-Particle eXtended) radiation transport simulations of galactic cosmic radiation passing through Earth's atmosphere. During a recent review of the input decks used for these simulations, a systematic error was discovered that is addressed here. After reassessment, the neutron ambient and effective dose equivalent rates estimated are found to be 10 to 15% different, though, the essence of the conclusions drawn remains unchanged.

  3. Simultaneous optimization of material removal rate and surface roughness for WEDM of WC-Co composite using grey relational analysis along with Taguchi method

    Directory of Open Access Journals (Sweden)

    Kamal Jangra

    2011-01-01

    Full Text Available In this paper, wire electrical discharge machining of WC-Co composite has been reported. Influence of taper angle, peak current, pulse-on time, pulse-off time, wire tension and dielectric flow rate were investigated for material removal rate (MRR and surface roughness (SR during intricate machining of a carbide block. In order to optimize MRR and SR simultaneously, grey relational analysis (GRA has been employed along with Taguchi method. Through GRA, grey relational grade is used as a performance index to determine the optimal setting of process parameters for multiple machining characteristics. Analysis of variance (ANOVA shows that the taper angle and pulse-on time are the most significant parameters affecting the multiple machining characteristics. Confirmatory results, proves the potential of GRA to optimize process parameters successfully for multi-machining characteristics.

  4. Impact of dust aerosols on the radiative budget, surface heat fluxes, heating rate profiles and convective activity over West Africa during March 2006

    Directory of Open Access Journals (Sweden)

    M. Mallet

    2009-09-01

    Full Text Available The present work analyses the effect of dust aerosols on the surface and top of atmosphere radiative budget, surface temperature, sensible heat fluxes, atmospheric heating rate and convective activity over West Africa. The study is focused on the regional impact of a major dust event over the period of 7–14 March 2006 through numerical simulations performed with the mesoscale, nonhydrostatic atmospheric model MesoNH. Due to its importance on radiative budgets, a specific attention has been paid to the representation of dust single scattering albedo (SSA in MesoNH by using inversions of the AErosol RObotic NETwork (AERONET. The radiative impacts are estimated using two parallel simulations, one including radiative effects of dust and the other without them. The simulations of dust aerosol impacts on the radiative budget indicate remarkable instantaneous (at midday decrease of surface shortwave (SW radiations over land, with regional (9°–17° N, 10° W–20° E mean of −137 W/m2 during the 9 to 12 March period. The surface dimming resulting from the presence of dust is shown to cause important reduction of both surface temperature (up to 4°C and sensible heat fluxes (up to 100 W/m2, which is consistent with experimental observations. At the top of the atmosphere, the SW cooling (regional mean of −12.0 W/m2 induced by mineral dust is shown to dominate the total net (shortwave + longwave effect. The maximum SW heating occurs within the dusty layer with values comprised between 4 and 7° K by day and LW effect results in a cooling of −0.10/−0.20° K by day. Finally, the simulations suggest the decrease of the convective available potential energy (CAPE over the region in the presence of mineral dust.

  5. High rate and high spatial resolution surface deformation monitoring of the Argentiere glacier from complementary remote sensing and geodetic data

    Science.gov (United States)

    Benoit, Lionel; Pham, Ha-Thai; Trouvé, Emmanuel; Vernier, Flavien; Moreau, Luc; Martin, Olivier; Thom, Christian; Briole, Pierre

    2014-05-01

    The Argentière glacier in the French Alps (Mont-Blanc massif) is a 10 km long glacier covering 19 km². Its flow on a large scale has been studied for over a hundred years by glaciologists, but the time and space fluctuations of its flow are still poorly documented. We selected a small area of the glacier, about 1 km upstream of the Lognan serac fall to measure the glacier flow with in-situ GPS measurements combined with time series of ground based pictures and time series of synthetic aperture radar images from the TerreSAR-X satellite. The experiment took place during two months between September and November 2013 with a network of thirteen single-frequency GPS receivers (eleven set up on the glacier and two on the nearby bedrock) deployed in the field with a sampling rate of 30s. Our data processing allows us to estimate epoch by epoch coordinates of each GPS site with a centimetric precision. The main interest of this approach is twofold : the monitoring of the temporal evolution of the flow and the providing of ground control points for the local and satellite remote sensing imagery. The average velocities of the stations is around 15 cm/day with peaks reaching 25cm/day lasting a few hours to one day after rainfalls or cooling periods. We explain these accelerations as the consequence of an increased basal water pressure. The strain tensor analysis shows a good consistency between the main strain axis and the orientation of the cracks on both sides of the glacier. However, available only at eleven points, the GPS data can not in any case give a picture of the overall deformation of the glacier. In order to map the glacier flow as a whole, including crevasse areas or serac falls, two automatic digital cameras were installed during the experiment on the bedrock on the shore of the glacier with acquisitions every three hours during day time. The processing of the stereo pairs produces maps in which the pixels coordinates (and their changes) are estimated with a

  6. New chemical approach to obtain dense layer phosphate-based ionic conductor coating on negative electrode material surface: Synthesis way, outgassing and improvement of C-rate capability

    Science.gov (United States)

    Fleutot, Benoit; Davoisne, Carine; Gachot, Grégory; Cavalaglio, Sébastien; Grugeon, Sylvie; Viallet, Virginie

    2017-04-01

    Li4Ti5O12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process, due to interfacial reactions between active material and electrolyte solution. In the same time, the electronic and ionic conductivity of pristine LTO is very poor and induces the use of nanoparticles which increase the outgassing phenomena. The coating of LTO particles could be a solution. For this the LTO spinel particles are modified with ionic conductor Li3PO4 coating using a spray-drying method. For the first time a homogeneous thin dense layer phosphate based conductor is obtained without nanoparticles, as a thin film material. It is so possible to study the influence of ionic conductor deposited on the negative electrode material on performances by the controlled layer thickness. This coating was characterized by XRD, SEM, XPS and TEM. The electrochemical performance of Li3PO4 coated Li4Ti5O12 is improved at high C-rate by the surface modification (improvement of 30 mAh g-1 at 5 C-rate compared to pristine LTO for 5 nm of coating), inducing by a modification of surface energy. An optimum coating thickness was studied. This type of coating allows a significant decrease of outgassing phenomena due the conformal coating and opens the way to a great number of studies and new technologies.

  7. Research on the Influence of Cutting Rates on Macrogeometry Deflections of Surfaces under Processing Complex form Products Made of Aluminium Aloys

    Directory of Open Access Journals (Sweden)

    Ieva Švagždytė

    2015-03-01

    Full Text Available The article reviews the influence of cutting rates on macrogeometry deflection of milling complex form products and turning an outside surface. For that purpose, one of the most popular aluminium alloys 6082 has been chosen. A ball nose mill of 8 mm in diameter has been milled employing CNC vertical centre HAAS MINI MILL and applying CNC lathe HAAS ST 20 for turning. Measurements have been carried out using coordinate measuring machine DEA micro-hite DCC, applying the probe sphere of 3mm in diameter and the probe equipped with a needle. A deviation of the surface profile from tangent to therophore parabola has been investigated. The determinants R2 of the obtained regressive equation have disclosed that the depth of the cut has the biggest influence on macrogeometry deflections, whereas feed rate has a slighter influence and cutting speed has no radical influence. For the turning process, the depth of the cut has the strongest influence on circularity while cilindrisity has been mainly affected by cutting speed.

  8. The use of microsensors to study the role of the loading rate and surface velocity on the growth and the composition of nitrifying biofilms.

    Science.gov (United States)

    Gonzalez, B C; Spinola, A L G; Lamon, A W; Araujo, J C; Campos, J R

    2011-01-01

    The good composition and activity of biofilms are very important for successful operation and control of fixed-film biological reactors employed in liquid effluents treatment. During the last decade, microsensors have been applied to study microbial ecology. These sensors could provide information regarding the microbial activity concerning nitrification and denitrification that occur inside biofilms. Other techniques of molecular biology, such as fluorescence in situ hybridization (FISH), have also contributed to this matter because their application aids in the identification of the bacterial populations that compose the biofilms. The focus of this paper was to study the loading rate and surface velocity to promote the development of nitrifying biofilms in three distinct flow cells that were employed in the post treatment of a synthetic wastewater simulating the effluent from a UASB (Upflow Anaerobic Sludge Blanket) reactor. Using the FISH technique, it was found that the population of ammonia-oxidizing-bacteria was greater than that of nitrite-oxidizing-bacteria; this was also supported by the lower production of nitrate determined by physicochemical and microsensor analyses. It was verified that the loading rate and surface velocity that promoted the greatest nitrogen removal were 0.25 g N-amon m(-2)biofilm day(-1) and 1 m h(-1), respectively.

  9. Radical ions with nearly degenerate ground state: correlation between the rate of spin-lattice relaxation and the structure of adiabatic potential energy surface.

    Science.gov (United States)

    Borovkov, V I; Beregovaya, I V; Shchegoleva, L N; Potashov, P A; Bagryansky, V A; Molin, Y N

    2012-09-14

    Paramagnetic spin-lattice relaxation (SLR) in radical cations (RCs) of the cycloalkane series in liquid solution was studied and analyzed from the point of view of the correlation between the relaxation rate and the structure of the adiabatic potential energy surface (PES) of the RCs. SLR rates in the RCs formed in x-ray irradiated n-hexane solutions of the cycloalkanes studied were measured with the method of time-resolved magnetic field effect in the recombination fluorescence of spin-correlated radical ion pairs. Temperature and, for some cycloalkanes, magnetic field dependences of the relaxation rate were determined. It was found that the conventional Redfield theory of the paramagnetic relaxation as applied to the results on cyclohexane RC, gave a value of about 0.2 ps for the correlation time of the perturbation together with an unrealistically high value of 0.1 T in field units for the matrix element of the relaxation transition. The PES structure was obtained with the DFT quantum-chemical calculations. It was found that for all of the cycloalkanes RCs considered, including low symmetric alkyl-substituted ones, the adiabatic PESes were surfaces of pseudorotation due to avoided crossing. In the RCs studied, a correlation between the SLR rate and the calculated barrier height to the pseudorotation was revealed. For RCs with a higher relaxation rate, the apparent activation energies for the SLR were similar to the calculated heights of the barrier. To rationalize the data obtained it was assumed that the vibronic states degeneracy, which is specific for Jahn-Teller active cyclohexane RC, was approximately kept in the RCs of substituted cycloalkanes for the vibronic states with the energies above and close to the barrier height to the pseudorotation. It was proposed that the effective spin-lattice relaxation in a radical with nearly degenerate low-lying vibronic states originated from stochastic crossings of the vibronic levels that occur due to fluctuations of

  10. A Review on Optimization of Process Parameters for Surface Roughness and Material Removal Rate for SS 410 Material During Turning Operation

    Directory of Open Access Journals (Sweden)

    Jitendra Thakkar

    2014-02-01

    Full Text Available In machining operations, the extents of significant influence of the process parameters like speed, feed, and depth of cut are different for different responses. Therefore, optimization of surface roughness is a multi-factor, multi-objective optimization problem. Therefore, to solve such a multi-objective optimization problem, it is felt necessary to identify the optimal parametric combination, following which all objectives could be optimized simultaneously. In this context, it is essential to convert all the objective functions into an equivalent single objective function or overall representative function to meet desired multi-quality features of the machined surface. The required multi-quality features may or may not be conflicting in nature. The representative single objective function, thus calculated, would be optimized finally. All experiment conduct on CNC turning machine on SS410 material. In the present work, Design of Experiment (DOE with full factorial design has been explored to produce 27 specimens on SS410 by straight turning operation. Material removal rate(MRR will be calculated from MRR equation and software available for it and then compare it. Collected data related to surface roughness have been utilized for optimization.

  11. Probing mechanistic photochemistry of glyoxal in the gas phase by ab initio calculations of potential-energy surfaces and adiabatic and nonadiabatic rates.

    Science.gov (United States)

    Li, Quan-Song; Zhang, Feng; Fang, Wei-Hai; Yu, Jian-Guo

    2006-02-07

    In the present work, the wavelength-dependent mechanistic photochemistry of glyoxal in the gas phase has been explored by ab initio calculations of potential-energy surfaces, surface crossing points, and adiabatic and nonadiabatic rates. The CHOCHO molecules in S1 by photoexcitation at 393-440 nm mainly decay to the ground state via internal conversion, which is followed by molecular eliminations to form CO, H2CO,H2, and HCOH. Upon photodissociation of CHOCHO at 350-390 nm, intersystem crossing to T1 followed by the C-C bond cleavage is the dominant process in this wavelength range, which is responsible for the formation of the CHO radicals. The C-C and C-H bond cleavages along the S1 pathway are energetically accessible upon photodissociation of CHOCHO at 290-310 nm, which can compete with the S1-->T1 intersystem crossing process. The present study predicts that the C-H bond cleavage on the S1 surface is probably a new photolysis pathway at high excitation energy, which has not been observed experimentally. In addition, the trans-cis isomerization is predicted to occur more easily in the ground state than in the excited states.

  12. The unimolecular reaction of t-BuNO on singlet and triplet surfaces: Spectroscopy, real-time rate measurements, and NO energy distributions

    Science.gov (United States)

    Noble, M.; Qian, C. X. W.; Reisler, H.; Wittig, C.

    1986-11-01

    The predissociation of jet-cooled (CH3)3CNO (t-BuNO) following laser excitation in the à 1A`←X˜ 1A' system has been studied in both the energy (frequency) and time domains. Unlike the smaller nitroso compounds whose predissociation has been already examined, unimolecular reaction is the rate determining step for predissociation near threshold. Consequently, it has been possible to separately measure radiationless transition rates and unimolecular reaction rates in real time. Dissociation on both the ground state (S0) and the first triplet state (T1) has been identified. At threshold, dissociation proceeds only on S0, with lifetimes >3.5 μs, but for E°≥650 cm-1, fast (<10 ns) predissociation via T1 becomes progressively the dominant dissociative route. Nascent NO photofragments have been characterized in detail using one-photon LIF. The rotational and spin-orbit distributions of NO following dissociation on S0 are statistical, depending only on E°. The NO derived from dissociation on the T1 surface is not at all statistical, consistent with a sizable (˜650 cm-1) exit channel barrier on this surface. Most notably, the [NO(2Π3/2)]/[NO(2Π1/2)] ratios are much smaller, and rotational distributions are colder than predicted by a statistical model. In order that some of the predissociating vibrational states could be assigned, the 1A`←1A' spectrum of t-BuNO has been analyzed and the electronic origin assigned as 13 911 cm-1. The ground state dissociation energy, D0, is found to be 13 930±30 cm-1, i.e., 39.8±0.1 kcal mol-1.

  13. Temperature and pressure dependent rate coefficients for the reaction of C2H4 + HO2 on the C2H4O2H potential energy surface.

    Science.gov (United States)

    Guo, JunJiang; Xu, JiaQi; Li, ZeRong; Tan, NingXin; Li, XiangYuan

    2015-04-02

    The potential energy surface (PES) for reaction C2H4 + HO2 was examined by using the quantum chemical methods. All rates were determined computationally using the CBS-QB3 composite method combined with conventional transition state theory(TST), variational transition-state theory (VTST) and Rice-Ramsberger-Kassel-Marcus/master-equation (RRKM/ME) theory. The geometries optimization and the vibrational frequency analysis of reactants, transition states, and products were performed at the B3LYP/CBSB7 level. The composite CBS-QB3 method was applied for energy calculations. The major product channel of reaction C2H4 + HO2 is the formation C2H4O2H via an OH(···)π complex with 3.7 kcal/mol binding energy which exhibits negative-temperature dependence. We further investigated the reactions related to this complex, which were ignored in previous studies. Thermochemical properties of the species involved in the reactions were determined using the CBS-QB3 method, and enthalpies of formation of species were compared with literature values. The calculated rate constants are in good agreement with those available from literature and given in modified Arrhenius equation form, which are serviceable in combustion modeling of hydrocarbons. Finally, in order to illustrate the effect for low-temperature ignition of our new rate constants, we have implemented them into the existing mechanisms, which can predict ethylene ignition in a shock tube with better performance.

  14. Laser melting treatment of Ni-P surface alloys on mild steel. Influence of initial coating thickness and laser scanning rate

    Directory of Open Access Journals (Sweden)

    García-Alonso, M. C.

    1997-08-01

    Full Text Available Different thickness Ni-P coatings deposited on mild steel are submitted to laser surface melting at different scanning rates. The microstructure of the alloys is characterized by optical and scanning electron microscopy and microprobe analysis. It is shown that both the initial coating thickness and the laser scanning rate have an influence on the shape, extent and size of the different structures resulting from the solidification process. Thus, when the laser scanning rate increases a progressive refinement of the structure takes place that could even totally block the dendritic growth produced during solidification for a high initial coating thickness.

    Recubrimientos de Ni-P, con distinto espesor, depositados sobre un acero microaleado fueron tratados con láser a diferentes velocidades de barrido. La microestructura, tanto del recubrimiento como del acero base, ha sido caracterizada por microscopía óptica y electrónica y por microanálisis. En el proceso de solidificación se han obtenido distintas estructuras que varían en cuanto a la forma, extensión y tamaño dependiendo del espesor inicial de recubrimiento y de la velocidad de barrido del haz láser. A medida que la velocidad del haz aumenta, se produce un refinamiento progresivo de la microestructura dendrítica y, en casos extremos de alto espesor de recubrimiento y velocidades grandes, este crecimiento dendrítico se bloquea.

  15. Evaluation and Optimization of Amino Acids Retention Rate of Japanese Scallop Powder with Different Food Additives in Spray-drying Process by Response Surface Method

    Directory of Open Access Journals (Sweden)

    Jianfeng Sun

    2014-01-01

    Full Text Available Spray-drying process for Japanese scallop powder can cause damage because of its heat-sensitive components such as amino acids. Therefore it is important for amino acids to be embedded with the appropriate food additives in spray-drying process. In this study, with Japanese scallop as the raw, Response Surface Method (RSM with three variables (the addition level of &beta-cyclodextrin, modified starch and CMC was used to investigate the effect of food additives on the amino acids retention rate in Japanese scallop powder in spray drying. The equation model to predict amino acids retention rate was reported. The results showed that the optimal addition level of &beta-cyclodextrin, modified starch and CMC were 25.55, 24.55 and 2.96%, respectively. And the amino acids retention rate was 56.75±0.64%. This model was testified to fit the actual situation preferably, therefore it can provide theoretical and practical basis for industrial production of Japanese scallop powder.

  16. Revealing Hidden Deformation Sources in New Zealand: a Novel Inversion of GPS Data for Non-Prescriptive Physics-Based Surface Forces and High-Precision Strain Rates

    Science.gov (United States)

    Dimitrova, L. L.; Haines, A. J.; Wallace, L. M.; Williams, C. A.

    2013-12-01

    Monitoring strain accumulation in active deformation zones is vital for studying and preparing for earthquake hazards. New Zealand straddles the complicated boundary between the obliquely converging Australian and Pacific plates. The motion is accommodated largely along the Alpine Fault in the south, through the Marlborough fault system and onto the Hikurangi trench in the north. In addition, a significant component of the motion is distributed on smaller, poorly characterized faults. Dimitrova et al. (2012) showed that the vertical derivatives of horizontal stress (VDoHS) rates are a substantially higher resolution expression of subsurface sources of ongoing deformation than the GPS velocities or GPS derived strain rates. We expand this method to solve the horizontal force balance equations for the VDoHS in 2-D to obtain the highest possible resolution picture of the surface deformation pattern in New Zealand. We invert GPS data from campaign GPS observations spanning from 1995 to 2012 for the VDoHS that best fit the GPS velocities, without prescribing sources or zones of deformation, while fully accounting for the physics of the problem. Using the VDoHS rates we identify (1) areas of deformation due to well-known active faults, (2) areas of poorly characterized deformation, e.g. deformation along faults without slip rate information mapped from palaeo-seismicity, (3) areas of previously unknown deformation, potentially on hidden faults, and (4) areas undergoing post-seismic deformation. The VDoHS are integrated to produce the highest resolution to-date maps of strain rates. We identify an area of extensional areal strain between the Alpine fault and the Main Divide of the central Southern Alps indicating possible gravitational collapse of the Southern Alps. Relationships between the VDoHS and strain rates allow us to calculate the variation in fault slip rate and locking depth for the identified faults, and we show selected results for the Alpine Fault and the

  17. Experimental Design for a Macrofoam Swab Study Relating the Recovery Efficiency and False Negative Rate to Low Concentrations of Two Bacillus anthracis Surrogates on Four Surface Materials

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F.; Hutchison, Janine R.

    2014-04-16

    This report describes the experimental design for a laboratory study to quantify the recovery efficiencies and false negative rates of a validated, macrofoam swab sampling method for low concentrations of Bacillus anthracis Sterne (BAS) and Bacillus atrophaeus (BG) spores on four surface materials (stainless steel, glass, vinyl tile, plastic light cover panel). Two analytical methods (plating/counting and polymerase chain reaction) will be used. Only one previous study has investigated false negative as a function of affecting test factors. The surrogates BAS and BG have not been tested together in the same study previously. Hence, this study will provide for completing gaps in the available information on the performance of macrofoam swab sampling at low concentrations.

  18. Hurricane Imaging Radiometer (HIRAD) Observations of Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate During NASA's GRIP and HS3 Campaigns

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

    2012-01-01

    HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain spatial resolution of approximately 2 km, out to roughly 30 km each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. The physical retrieval technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  19. Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit.

    Science.gov (United States)

    El-Jaby, Samy; Richardson, Richard B

    2015-07-01

    Occupational exposures from ionizing radiation are currently regulated for airline travel (Earth orbit (∼300-400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit.

  20. High speed inscription of uniform, large-area laser-induced periodic surface structures in Cr films using a high repetition rate fs laser.

    Science.gov (United States)

    Ruiz de la Cruz, A; Lahoz, R; Siegel, J; de la Fuente, G F; Solis, J

    2014-04-15

    We report on the fabrication of laser-induced periodic surface structures in Cr films upon high repetition rate fs laser irradiation (up to 1 MHz, 500 fs, 1030 nm), employing beam scanning. Highly regular large-area (9  cm2) gratings with a relative diffraction efficiency of 42% can be produced within less than 6 min. The ripple period at moderate and high fluences is 0.9 μm, with a small period of 0.5 μm appearing at lower energies. The role of the irradiation parameters on the characteristics of the laser-induced periodic surface structures (LIPSS) is studied and discussed in the frame of the models presently used. We have identified the polarization vector orientation with respect to the scan direction as a key parameter for the fabrication of high-quality, large-area LIPSS, which, for perpendicular orientation, allows the coherent extension of the sub-wavelength structure over macroscopic distances. The processing strategy is robust in terms of broad parameter windows and applicable to other materials featuring LIPSS.

  1. Radioactivity Distribution In Surface And Core Sediment Of The Central Part Of The Algerian Coast: An Estimation Of The Recent Sedimentation Rate

    Directory of Open Access Journals (Sweden)

    A. NOUREDDINE

    2012-12-01

    Full Text Available Sediment core samples and marine surface sediments of identical composition, mostly muddy, were collected using a Van Veen type grab and a box corer on board the M.S. Benyahia research vessel (ISMAL, along the Algerian littoral, between Algiers (36Ζ49.9 N/ 03Ζ 02.3 E and Cherchell (36Ζ 39.4 N/ 02Ζ 12.4 E, during a sampling cruise in September 1997. The samples were analysed to determine the activity concentration of natural radionuclides (uranium and thorium series and 40 K as well and artificial radionuclides ( 137 Cs and Pu isotopes, using a direct gamma spectrometry for gamma emitters and radiochemical separations and alpha spectrometry for alpha emitters. The horizontal and vertical distribution of the examined radionuclides were studied in the surface and core samples and an effort to estimate the sedimentation rate was attempted.The measured values range was: 17 - 26 Bq/Kg dry for uranium series radioisotopes, 18 – 32 Bq/Kg dry for thorium series radioisotopes, 311 - 690 Bq/Kg dry for 40 K, 0.4 - 11 Bq/Kg dry, for 137 Cs and 0.4 – 1.0 Bq/Kg dry for 239 + 240 Pu.

  2. False Negative Rates of a Macrofoam-Swab Sampling Method with Low Surface Concentrations of Two Bacillus anthracis Surrogates via Real-Time PCR

    Energy Technology Data Exchange (ETDEWEB)

    Hutchison, Janine R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Piepel, Gregory F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Amidan, Brett G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sydor, Michael A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kaiser, Brooke L.D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-06-01

    Surface sampling for Bacillus anthracis spores has traditionally relied on detection via bacterial cultivation methods. Although effective, this approach does not provide the level of organism specificity that can be gained through molecular techniques. False negative rates (FNR) and limits of detection (LOD) were determined for two B. anthracis surrogates with modified rapid viability-polymerase chain reaction (mRV-PCR) following macrofoam-swab sampling. This study was conducted in parallel with a previously reported study that analyzed spores using a plate-culture method. B. anthracis Sterne (BAS) or B. atrophaeus Nakamura (BG) spores were deposited onto four surface materials (glass, stainless steel, vinyl tile, and plastic) at nine target concentrations (2 to 500 spores/coupon; 0.078 to 19.375 colony-forming units [CFU] per cm2). Mean FNR values for mRV-PCR analysis ranged from 0 to 0.917 for BAS and 0 to 0.875 for BG and increased as spore concentration decreased (over the concentrations investigated) for each surface material. FNRs based on mRV-PCR data were not statistically different for BAS and BG, but were significantly lower for glass than for vinyl tile. FNRs also tended to be lower for the mRV-PCR method compared to the culture method. The mRV-PCR LOD95 was lowest for glass (0.429 CFU/cm2 with BAS and 0.341 CFU/cm2 with BG) and highest for vinyl tile (0.919 CFU/cm2 with BAS and 0.917 CFU/cm2 with BG). These mRV-PCR LOD95 values were lower than the culture values (BAS: 0.678 to 1.023 CFU/cm2 and BG: 0.820 to 1.489 CFU/cm2). The FNR and LOD95 values reported in this work provide guidance for environmental sampling of Bacillus spores at low concentrations.

  3. Doppler assessment of the ratio of the systolic to diastolic duration in normal children: relation to heart rate, age and body surface area.

    Science.gov (United States)

    Sarnari, Roberto; Kamal, Reema Yousef; Friedberg, Mark K; Silverman, Norman H

    2009-08-01

    It has been shown that the ratio of systolic duration to diastolic duration (S/D) is a valuable global index of ventricular dysfunction in pediatric dilated and restrictive cardiomyopathy and is also a valuable index of the ventricular function of single systemic right ventricles in children who have undergone palliation of hypoplastic left-heart syndrome. The purposes of this study were to establish normal values for the S/D ratio in children without heart disease and to investigate its variation with heart rate (HR), age, and body surface area. Of 752 children found to have functional murmurs by clinical means, 179 (24% of the total database) had trace holosystolic tricuspid regurgitation. These patients ranged in age from 0.02 months to 19 years. For this study, the diastolic interval was defined as the period of right ventricular filling (ie, the period between 2 tricuspid regurgitant jets) and the systolic interval as the remainder of the cardiac cycle corresponding to the duration of holosystolic tricuspid regurgitation, including the periods of isovolumic contraction and relaxation. The relations between the systolic and diastolic periods and their ratio (S/D ratio) and HR, age, and body surface area were evaluated using univariate and multivariate linear regression analysis. Patient's age ranged from 0.02 months to 19 years (mean, 70.18+/-65.12 months), body surface area from 0.11 to 2.51 m2 (mean, 0.85+/-0.55 m2), and HR from 50 to 156 beats/min (mean, 96.72+/-23.19 beats/min). The systolic period ranged from 208.5 to 467 ms (mean, 314.08+/-52.57 ms) and the diastolic period from 166.5 to 809 ms (mean, 341.34+/-129.61 ms), yielding a S/D ratio ranging from 0.397 to 1.62 (mean, 0.995+/-0.23). Systolic period duration showed a linear negative decrease with increasing HR (y=1.9228x+500.05, r=-0.85). Diastolic duration decreased in an exponential fashion as HR increased (y=130,679x(-1.3232), r=-0.88). The S/D ratio correlated positively with HR (y=-1

  4. Global Monitoring RSEM System for Crop Production by Incorporating Satellite-based Photosynthesis Rates and Anomaly Data of Sea Surface Temperature

    Science.gov (United States)

    Kaneko, D.; Sakuma, H.

    2014-12-01

    The first author has been developing RSEM crop-monitoring system using satellite-based assessment of photosynthesis, incorporating meteorological conditions. Crop production comprises of several stages and plural mechanisms based on leaf photosynthesis, surface energy balance, and the maturing of grains after fixation of CO2, along with water exchange through soil vegetation-atmosphere transfer. Grain production in prime countries appears to be randomly perturbed regionally and globally. Weather for crop plants reflects turbulent phenomena of convective and advection flows in atmosphere and surface boundary layer. It has been difficult for scientists to simulate and forecast weather correctly for sufficiently long terms to crop harvesting. However, severely poor harvests related to continental events must originate from a consistent mechanism of abnormal energetic flow in the atmosphere through both land and oceans. It should be remembered that oceans have more than 100 times of energy storage compared to atmosphere and ocean currents represent gigantic energy flows, strongly affecting climate. Anomalies of Sea Surface Temperature (SST), globally known as El Niño, Indian Ocean dipole, and Atlantic Niño etc., affect the seasonal climate on a continental scale. The authors aim to combine monitoring and seasonal forecasting, considering such mechanisms through land-ocean biosphere transfer. The present system produces assessments for all continents, specifically monitoring agricultural fields of main crops. Historical regions of poor and good harvests are compared with distributions of SST anomalies, which are provided by NASA GSFC. Those comparisons fairly suggest that the Worst harvest in 1993 and the Best in 1994 relate to the offshore distribution of low temperature anomalies and high gaps in ocean surface temperatures. However, high-temperature anomalies supported good harvests because of sufficient solar radiation for photosynthesis, and poor harvests because

  5. Ultrafast electron, lattice and spin dynamics on rare earth metal surfaces. Investigated with linear and nonlinear optical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Radu, I.E.

    2006-03-15

    This thesis presents the femtosecond laser-induced electron, lattice and spin dynamics on two representative rare-earth systems: The ferromagnetic gadolinium Gd(0001) and the paramagnetic yttrium Y(0001) metals. The employed investigation tools are the time-resolved linear reflectivity and second-harmonic generation, which provide complementary information about the bulk and surface/interface dynamics, respectively. The femtosecond laser excitation of the exchange-split surface state of Gd(0001) triggers simultaneously the coherent vibrational dynamics of the lattice and spin subsystems in the surface region at a frequency of 3 THz. The coherent optical phonon corresponds to the vibration of the topmost atomic layer against the underlying bulk along the normal direction to the surface. The coupling mechanism between phonons and magnons is attributed to the modulation of the exchange interaction J between neighbour atoms due to the coherent lattice vibration. This leads to an oscillatory motion of the magnetic moments having the same frequency as the lattice vibration. Thus these results reveal a new type of phonon-magnon coupling mediated by the modulation of the exchange interaction and not by the conventional spin-orbit interaction. Moreover, we show that coherent spin dynamics in the THz frequency domain is achievable, which is at least one order of magnitude faster than previously reported. The laser-induced (de)magnetization dynamics of the ferromagnetic Gd(0001) thin films have been studied. Upon photo-excitation, the nonlinear magneto-optics measurements performed in this work show a sudden drop in the spin polarization of the surface state by more than 50% in a <100 fs time interval. Under comparable experimental conditions, the time-resolved photoemission studies reveal a constant exchange splitting of the surface state. The ultrafast decrease of spin polarization can be explained by the quasi-elastic spin-flip scattering of the hot electrons among spin

  6. False Negative Rates of a Macrofoam-Swab Sampling Method with Low Surface Concentrations of Two Bacillus anthracis Surrogates via Real-Time PCR

    Energy Technology Data Exchange (ETDEWEB)

    Hutchison, Janine R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Piepel, Gregory F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Amidan, Brett G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sydor, Michael A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Deatherage Kaiser, Brooke L [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-05-01

    Surface sampling for Bacillus anthracis spores has traditionally relied on detection via bacterial cultivation methods. Although effective, this approach does not provide the level of organism specificity that can be gained through molecular techniques. False negative rates (FNR) and limits of detection (LOD) were determined for two B. anthracis surrogates with modified rapid viability-polymerase chain reaction (mRV-PCR) following macrofoam-swab sampling. This study was conducted in parallel with a previously reported study that analyzed spores using a plate-culture method. B. anthracis Sterne (BAS) or B. atrophaeus Nakamura (BG) spores were deposited onto four surface materials (glass, stainless steel, vinyl tile, and plastic) at nine target concentrations (2 to 500 spores/coupon; 0.078 to 19.375 colony-forming units [CFU] per cm²). Mean FNR values for mRV-PCR analysis ranged from 0 to 0.917 for BAS and 0 to 0.875 for BG and increased as spore concentration decreased (over the concentrations investigated) for each surface material. FNRs based on mRV-PCR data were not statistically different for BAS and BG, but were significantly lower for glass than for vinyl tile. FNRs also tended to be lower for the mRV-PCR method compared to the culture method. The mRV-PCR LOD₉₅ was lowest for glass (0.429 CFU/cm² with BAS and 0.341 CFU/cm² with BG) and highest for vinyl tile (0.919 CFU/cm² with BAS and 0.917 CFU/cm² with BG). These mRV-PCR LOD₉₅ values were lower than the culture values (BAS: 0.678 to 1.023 CFU/cm² and BG: 0.820 to 1.489 CFU/cm²). The FNR and LOD₉₅ values reported in this work provide guidance for environmental sampling of Bacillus spores at low concentrations.

  7. Radiation damage and associated phase change effect on photodesorption rates from ices—Lyα studies of the surface behavior of CO{sub 2}(ice)

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Chunqing; Yates, John T. Jr., E-mail: jty2n@virginia.edu [Department of Chemistry, University of Virginia, Charlottesville, VA 22904 (United States)

    2014-01-01

    Photodesorption from a crystalline film of CO{sub 2}(ice) at 75 K has been studied using Lyα (10.2 eV) radiation. We combine quantitative mass spectrometric studies of gases evolved and transmission IR studies of species trapped in the ice. Direct CO desorption is observed from the primary CO{sub 2} photodissociation process, which occurs promptly for CO{sub 2} molecules located on the outermost surface of the ice (Process I). As the fluence of Lyα radiation increases to ∼5.5 × 10{sup 17} photons cm{sup –2}, extensive damage to the crystalline ice occurs and photo-produced CO molecules from deeper regions (Process II) are found to desorb at a rapidly increasing rate, which becomes two orders of magnitude greater than Process I. It is postulated that deep radiation damage to produce an extensive amorphous phase of CO{sub 2} occurs in the 50 nm ice film and that CO (and CO{sub 2}) diffusive transport is strongly enhanced in the amorphous phase. Photodesorption in Process II is a combination of electronic and thermally activated processes. Radiation damage in crystalline CO{sub 2} ice has been monitored by its effects on the vibrational line shapes of CO{sub 2}(ice). Here the crystalline-to-amorphous phase transition has been correlated with the occurrence of efficient molecular transport over long distances through the amorphous phase of CO{sub 2}(ice). Future studies of the composition of the interstellar region, generated by photodesorption from ice layers on grains, will have to consider the significant effects of radiation damage on photodesorption rates.

  8. Improvements of a COMS Land Surface Temperature Retrieval Algorithm Based on the Temperature Lapse Rate and Water Vapor/Aerosol Effect

    Directory of Open Access Journals (Sweden)

    A-Ra Cho

    2015-02-01

    Full Text Available The National Meteorological Satellite Center in Korea retrieves land surface temperature (LST by applying the split-window LST algorithm (CSW_v1.0 to Communication, Ocean, and Meteorological Satellite (COMS data. Considerable errors were detected under conditions of high water vapor content or temperature lapse rates during validation with Moderate Resolution Imaging Spectroradiometer (MODIS LST because of the too simplified LST algorithm. In this study, six types of LST retrieval equations (CSW_v2.0 were developed to upgrade the CSW_v1.0. These methods were developed by classifying “dry,” “normal,” and “wet” cases for day and night and considering the relative sizes of brightness temperature difference (BTD values. Similar to CSW_v1.0, the LST retrieved by CSW_v2.0 had a correlation coefficient of 0.99 with the prescribed LST and a slightly larger bias of −0.03 K from 0.00K; the root mean square error (RMSE improved from 1.41 K to 1.39 K. In general, CSW_v2.0 improved the retrieval accuracy compared to CSW_v1.0, especially when the lapse rate was high (mid-day and dawn and the water vapor content was high. The spatial distributions of LST retrieved by CSW_v2.0 were found to be similar to the MODIS LST independently of the season, day/night, and geographic locations. The validation using one year’s MODIS LST data showed that CSW_v2.0 improved the retrieval accuracy of LST in terms of correlations (from 0.988 to 0.989, bias (from −1.009 K to 0.292 K, and RMSEs (from 2.613 K to 2.237 K.

  9. Surface stabilized GMR nanorods of silver coated CrO{sub 2} synthesized via a polymer complex at ambient pressure

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, S., E-mail: drsomnathbiswas@gmail.com [The LNM Institute of Information Technology, Jaipur-302031 (India); Singh, G.P. [Centre for Nanotechnology, Central University of Jharkhand, Ranchi-835205 (India); Ram, S. [Materials Science Centre, Indian Institute of Technology, Kharagpur-721302 (India); Fecht, H.-J. [Insitut für Micro-und Nanomaterialien, Universität Ulm, Albert Einstein Allee-47, Ulm, D-89081, and Forschungszentrum Karlsruhe, Institute of Nanotechnology, Karlsruhe, D-76021 (Germany)

    2013-08-15

    Stable anisotropic nanorods of surface modified CrO{sub 2} (∼18 nm diameter) with a correlated diamagnetic layer (2–3 nm thickness) of silver efficiently tailors useful magnetic and magnetoresistance (MR) properties. Essentially, it involves a core-shell structure that is developed by displacing part of Cr{sup 4+} ions by Ag atoms on the CrO{sub 2} surface (topotactic surface layer) via an etching reaction of a CrO{sub 2}-polymer complex with Ag{sup +} ions in hot water followed by heating the dried sample at 300–400 °C in air. The stable Ag-layer so obtained in the form of a shell protects CrO{sub 2} such that it no longer converts to Cr{sub 2}O{sub 3} in ambient pressure during the processing. X-ray diffractogram of the Rutile type tetragonal CrO{sub 2} structure (lattice parameters a=0.4429 nm and c=0.2950 nm) includes weak peaks of a minority phase of an fcc-Ag (a=0.4086 nm). The silver surface layer, which manifests itself in a doublet of the 3d{sub 5/2} and 3d{sub 3/2} X-ray photoelectron bands of binding energies 368.46 eV and 374.48 eV, respectively, suppresses almost all Cr bands to appear in a measurable intensity. The sample exhibits a distinctly enhanced MR-value, e.g., (−) 7.6% at 77 K, than reported values in compacted CrO{sub 2} powders or composites. Such a large MR-value in the Coulomb blockade regime (<100 K) arises not only due to the suppressed spin flipping at low temperature but also from a spin dependent co-tunneling through an interlinked structure of silver and silver coated CrO{sub 2} nanorods. - Highlights: • Synthesis and structural studies of a novel GMR material of Ag coated CrO{sub 2}. • Tailoring useful GMR property in CrO{sub 2} nanorods of controlled shape and anisotropy. • Enhanced GMR is explained in correlation to the surface structure of CrO{sub 2} nanorods.

  10. The study of temperature effect on the performance characteristics of the InGaN-based vertical cavity surface emitting laser (VCSEL) by solving the rate equations

    Science.gov (United States)

    Goharrizi, A. Zandi; Alahyarizadeh, Gh.

    2016-08-01

    The use of semiconductor lasers is beneficial in long-distance communications. Practical communication systems based on these lasers need high ambient temperature, with temperature changes between 40∘C and 85∘C. The study of the temperature-dependent response of these lasers is important to improve them. This study investigates the effect of temperature on InGaN-based vertical cavity surface emitting lasers (VCSEL). The active region in this structure includes a single quantum well (SQW). The rate equations of carriers and densities are numerically solved. The time variations of carrier density, photon density and output power (N, S and P) at 25∘C and the current injection of 0.04 A are obtained. Values obtained for threshold current and output power include 7 mA and 44 mW, respectively. The effect of temperature on the time variations of N, S and P from 10∘C to 35∘C is studied. Results show that these parameters decrease and the threshold current increases with an increase in temperature. Furthermore, the investigation of the effect of injection current on N, S and P shows that raising the injection current can increase these parameters. Moreover, an increase in the injection current reduces the time response.

  11. Medium optimization to improve the flocculation rate of a novel compound bioflocculant, CBF-256, using response surface methodology and flocculation characters.

    Science.gov (United States)

    Ren, Dunjian; Li, Hongyang; Pu, Yuewu; Yi, Lvyun

    2013-01-01

    A novel compound bioflocculant, CBF-256, was obtained using three bacterial strains, Bacillus sp., Enterobacter sp., and Aeromonas sp., which were screened from activated sludge of a printing and dyeing wastewater treatment plant. Response surface methodology was employed to optimize the fermentation medium dosage to improve the flocculation rate of CBF-256, which increased from 69.00% to 82.65%. In addition the yield of the compound bioflocculant increased from 2.31 g·L(-1) to 2.84 g·L(-1). The flocculating efficiency distribution of the components of the culture broth indicated that the supernatant was the most effective component in the flocculation process. Fourier transform infrared spectroscopy and scanning electron microscopy were used to analyze the fermentation medium and composite bacteria. The compound flocculants were produced easily, and during the flocculation process, all the flocculation ingredients settled down in the remaining sludge along with the bacteria screened from the activated sludge, without causing secondary pollution.

  12. Ground-based Pa$\\alpha$ Narrow-band Imaging of Local Luminous Infrared Galaxies I: Star Formation Rates and Surface Densities

    CERN Document Server

    Tateuchi, Ken; Motohara, Kentaro; Takahashi, Hidenori; Kato, Natsuko Mitani; Kitagawa, Yutaro; Todo, Soya; Toshikawa, Koji; Sako, Shigeyuki; Uchimoto, Yuka K; Ohsawa, Ryou; Asano, Kentaro; Ita, Yoshifusa; Kamizuka, Takafumi; Komugi, Shinya; Koshida, Shintaro; Manabe, Sho; Nakamura, Tomohiko; Nakashima, Asami; Okada, Kazushi; Takagi, Toshinobu; Tanabé, Toshihiko; Uchiyama, Mizuho; Aoki, Tsutomu; Doi, Mamoru; Handa, Toshihiro; Kawara, Kimiaki; Kohno, Kotaro; Minezaki, Takeo; Miyata, Takashi; Morokuma, Tomoki; Soyano, Takeo; Tamura, Yoichi; Tanaka, Masuo; Tarusawa, Ken'ichi; Yoshii, Yuzuru

    2014-01-01

    Luminous infrared galaxies (LIRGs) are enshrouded by a large amount of dust, produced by their active star formation, and it is difficult to measure their activity in the optical wavelength. We have carried out Pa$\\alpha$ narrow-band imaging observations of 38 nearby star-forming galaxies including 33 LIRGs listed in $IRAS$ RBGS catalog with the Atacama Near InfraRed camera (ANIR) on the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope (miniTAO). Star formation rates (SFRs) estimated from the Pa$\\alpha$ fluxes, corrected for dust extinction using the Balmer Decrement Method (typically $A_V$ $\\sim$ 4.3 mag), show a good correlation with those from the bolometric infrared luminosity of $IRAS$ data within a scatter of 0.27 dex. This suggests that the correction of dust extinction for Pa$\\alpha$ flux is sufficient in our sample. We measure the physical sizes and the surface density of infrared luminosities ($\\Sigma_{L(\\mathrm{IR})}$) and $SFR$ ($\\Sigma_{SFR}$) of star-forming region for individual ga...

  13. The effect of inductively-coupled-plasma reactive ion etching power on the etching rate and the surface roughness of a sapphire substrate.

    Science.gov (United States)

    Chang, Chun-Ming; Shiao, Ming-Hua; Yang, Chin-Tien; Cheng, Chung-Ta; Hsueh, Wen-Jeng

    2014-10-01

    In this study, patterned sapphire substrates are fabricated using nanosphere lithography (NSL) and inductively-coupled-plasma reactive ion etching (ICP-RIE). Polystyrene nanospheres of approximately 600 nm diameter are self-assembled on c-plane sapphire substrates by spin-coating. The diameter of the polystyrene nanospheres is modified to adjust the etching mask pitch cycle using oxygen plasma in the ICP-RIE system. A nickel thin film mask of 100 nm thickness is deposited by electron-beam evaporation on a substrate covered with treated nanospheres. The sapphire substrate is then etched in an inductively coupled plasma system using BCl3/Ar gas, to fabricate a structure with a periodic sub-micron hole array with different sidewall intervals. The DC bias voltage, the sapphire etching rate, the surface roughness, are studied as a function of the ICP and the RF power. Different sub-micron hole arrays with spacing cycles of 89 nm, 139 nm and 167 nm are successfully fabricated on the sapphire substrate, using suitable etching parameters.

  14. Maintenance measures for preservation and recovery of permeable pavement surface infiltration rate--The effects of street sweeping, vacuum cleaning, high pressure washing, and milling.

    Science.gov (United States)

    Winston, Ryan J; Al-Rubaei, Ahmed M; Blecken, Godecke T; Viklander, Maria; Hunt, William F

    2016-03-15

    The surface infiltration rates (SIR) of permeable pavements decline with time as sediment and debris clog pore spaces. Effective maintenance techniques are needed to ensure the hydraulic functionality and water quality benefits of this stormwater control. Eight different small-scale and full-scale maintenance techniques aimed at recovering pavement permeability were evaluated at ten different permeable pavement sites in the USA and Sweden. Maintenance techniques included manual removal of the upper 2 cm of fill material, mechanical street sweeping, regenerative-air street sweeping, vacuum street sweeping, hand-held vacuuming, high pressure washing, and milling of porous asphalt. The removal of the upper 2 cm of clogging material did not significantly improve the SIR of concrete grid paves (CGP) and permeable interlocking concrete pavers (PICP) due to the inclusion of fines in the joint and bedding stone during construction, suggesting routine maintenance cannot overcome improper construction. For porous asphalt maintenance, industrial hand-held vacuum cleaning, pressure washing, and milling were increasingly successful at recovering the SIR. Milling to a depth of 2.5 cm nearly restored the SIR for a 21-year old porous asphalt pavement to like-new conditions. For PICP, street sweepers employing suction were shown to be preferable to mechanical sweepers; additionally, maintenance efforts may become more intensive over time to maintain a threshold SIR, as maintenance was not 100% effective at removing clogging material.

  15. Transitions between hyperfine-structure states of the 2s metastable muonic hydrogen in collision processes

    Energy Technology Data Exchange (ETDEWEB)

    Czaplinski, W.

    1992-12-31

    Hyperfine effects in the symmetric collisions of the 2s metastable muonic hydrogen with hydrogen atoms: (p{mu}){sub 2s} + H, (d{mu}){sub 2s} + D, (t{mu}){sub 2s} + t are presented. Elastic and spin-flip cross sections for the scattering of The 2s muonic atoms are calculated in the two-level approximation as a function of collision energy. The corresponding formulae are derived with inclusion of electron screening and Lamb-shift between 2s and 2p energy levels of the muonic atom. The obtained spin-flip cross sections are about two orders of magnitude higher than their ground state counterparts and are much more influenced by electron screening. The rates of the spin-flip transitions are also calculated and are found to be about three orders of magnitude higher than the decay rate of the 2s state. (author). 65 refs, 15 figs, 4 tabs.

  16. Four years of ozone measurements in the Central Amazon - Effects of increasing deforestation rates and different meteorological conditions on near surface concentrations

    Science.gov (United States)

    Wolff, Stefan; Tsokankunku, Anywhere; Pöhlker, Christopher; Saturno, Jorge; Walter, David; Ditas, Florian; Könemann, Tobias; Ganzeveld, Laurens; Yañez-Serrano, Ana Maria; Souza, Rodrigo; Trebs, Ivonne; Sörgel, Matthias

    2017-04-01

    The ATTO (Amazon Tall Tower Observatory) site (02°08'38.8''S, 58°59'59.5''W) is located in the remote Amazon rainforest, allowing atmospheric and forest studies away from nearby anthropogenic emission sources. Starting with continuous measurements of vertical mixing ratio profiles of H2O, CO2 and O3 in April 2012 at 8 heights between 0.05 m and 80 m above ground, the longest continuous record of near surface O3 in the Amazon rainforest was established. Black carbon (BC), CO and micrometeorological measurements are available for the same period. During intensive campaigns, NOx was measured as well using the same profile system, and, therefore several month of simultaneous NOx measurements are available. During a period of about four months also direct flux measurements of O3 are available. Here, we analyze the long term and seasonal variability of near surface O3 mixing ratios with respect to air pollution, deposition and transport. The Central Amazon is characterized by a clear seasonal precipitation pattern (ca. 350 mm around March and ca. 80 mm around September), correlating strongly with ozone mixing ratios. Since 2012 deforestation rates have increased again in the Amazon, leading to higher air pollution especially during the drier season in the last years. For several strong pollution events we compared the effects of long and short distance biomass burning on O3 and NOx mixing ratios using back trajectories and satellite data. By comparing O3 mixing ratios with solar radiation, Bowen ratio, several trace gases and aerosol loads (Volatile Organic Compounds, CO and BC), different correlation patterns throughout the year that are linked to the sources (transport of O3 and precursors) and sinks (stomatal uptake and chemical reactions) are investigated. For example, the last months of 2015 were strongly influenced by an extraordinary El Niño phenomenon, leading to much drier conditions and enhanced biomass burning in the Amazon, which prolonged the period of

  17. VARIATION IN EROSION/DEPOSITION RATES OVER THE LAST FIFTTY YEARS ON ALLUVIAL FAN SURFACES OF L. PLEISTOCENE-MID HOLOCENE AGE, ESTIMATIONS USING 137CS SOIL PROFILE DATA, AMARGOSA VALLEY, NEVADA

    Energy Technology Data Exchange (ETDEWEB)

    C. Harrington; R. Kelly; K.T. Ebert

    2005-08-26

    Variations in erosion and deposition for the last fifty years (based on estimates from 137Cs profiles) on surfaces (Late Pleistocene to Late Holocene in age) making up the Fortymile Wash alluvial fan south of Yucca Mountain, is a function of surface age and of desert pavement development or absence. For purposes of comparing erosion and deposition, the surfaces can be examined as three groups: (1) Late Pleistocene surfaces possess areas of desert pavement development with thin Av or sandy A horizons, formed by the trapping capabilities of the pavements. These zones of deposition are complemented by coppice dune formation on similar parts of the surface. Areas on the surface where no pavement development has occurred are erosional in nature with 0.0 +/- 0.0 cm to 1.5 +/- 0.5 cm of erosion occurring primarily by winds blowing across the surface. Overall these surfaces may show either a small net depositional gain or small erosional loss. (2) Early Holocene surfaces have no well-developed desert pavements, but may have residual gravel deposits in small areas on the surfaces. These surfaces show the most consistent erosional surface areas on which it ranges from 1.0 +/-.01 cm to 2.0+/- .01 cm. Fewer depositional forms are found on this age of surface so there is probably a net loss of 1.5 cm across these surfaces. (3) The Late Holocene surfaces show the greatest variability in erosion and deposition. Overbank deposition during floods cover many edges of these surfaces and coppice dune formation also creates depositional features. Erosion rates are highly variable and range from 0.0 +/- 0.0 to a maximum of 2.0+/-.01. Erosion occurs because of the lack of protection of the surface. However, the common areas of deposition probably result in the surface having a small net depositional gain across these surfaces. Thus, the interchannel surfaces of the Fortymile Wash fan show a variety of erosional styles as well as areas of deposition. The fan, therefore, is a dynamic

  18. Nutrient uptake rate as a function of cell size and surface transporter density: A Michaelis-like approximation to the model of Pasciak and Gavis

    Science.gov (United States)

    Armstrong, Robert A.

    2008-10-01

    Pasciak and Gavis were first to propose a model of nutrient uptake that includes both physical transport by diffusion and active biological transport across the cell membrane. While the Pasciak-Gavis model is not complicated mathematically (it can be expressed in closed form as a quadratic equation), its parameters are not so easily interpretable biologically as are the parameters of the Michaelis-Menten uptake model; this lack of transparency is probably the main reason the Pasciak-Gavis model has not been adopted by ecologically oriented modelers. Here I derive a Michaelis-like approximation to the Pasciak-Gavis model, and show how the parameters of the latter map to those of the Michaelis-like model. The derived approximation differs from a pure Michaelis-Menten model in a subtle but potentially critical way: in a pure Michaelis-Menten model, the half-saturation constant for nutrient uptake is independent of the density of transporter (or "porter") proteins on the cell surface, while in the Pasciak-Gavis model and its Michaelis-like approximation, the half-saturation constant does depend on the density of porter proteins. The Pasciak-Gavis model predicts a unique relationship between cell size, nutrient concentration in the medium, the half-saturation constant of porter-limited nutrient uptake, and the resulting rate of uptake; the Michaelis-like approximation preserves the most important feature of that relationship, the size at which porter limitation gives way to diffusion limitation. Finally I discuss the implications for community structure that are implied by the Pasciak-Gavis model and its Michaelis-like approximation.

  19. A Lithium Ion Highway by Surface Coordination Polymerization: In Situ Growth of Metal-Organic Framework Thin Layers on Metal Oxides for Exceptional Rate and Cycling Performance.

    Science.gov (United States)

    Han, Yuzhen; Yu, Danni; Zhou, Junwen; Xu, Peiyu; Qi, Pengfei; Wang, Qianyou; Li, Siwu; Fu, Xiaotao; Gao, Xing; Jiang, Chenghao; Feng, Xiao; Wang, Bo

    2017-08-25

    A thin layer of a highly porous metal-organic framework material, ZIF-8, is fabricated uniformly on the surface of nanostructured transition metal oxides (ZnO nanoflakes and MnO2 nanorods) to boost the transfer of lithium ions. The novel design and uniform microstructure of the MOF-coated TMOs (ZIF-8@TMOs) exhibit dramatically enhanced rate and cycling performance comparing to their pristine counterparts. The capacities of ZIF-8@ZnO (nanoflakes) and ZIF-8@MnO2 (nanorods) are 28 % and 31 % higher that of the pristine ones at the same current density. The nanorods of ZIF-8@MnO2 show a capacity of 1067 mAh g(-1) after 500 cycles at 1 Ag(-1) and without any fading. To further improve the conductivity and capacity, the ZIF-8-coated materials are pyrolyzed at 700 °C in an N2 atmosphere (ZIF-8@TMO-700 N). After pyrolysis, a much higher capacity improvement is achieved: ZIF-8@ZnO-700 N and ZIF-8@MnO2 -700 N have 54 % and 69 % capacity increases compared with the pristine TMOs, and at 1 Ag(-1) , the capacity of ZIF-8@MnO2 -700 N is 1060 mAh g(-1) after cycling for 300 cycles. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. GROUND-BASED Paα NARROW-BAND IMAGING OF LOCAL LUMINOUS INFRARED GALAXIES. I. STAR FORMATION RATES AND SURFACE DENSITIES

    Energy Technology Data Exchange (ETDEWEB)

    Tateuchi, Ken; Konishi, Masahiro; Motohara, Kentaro; Takahashi, Hidenori; Kato, Natsuko Mitani; Kitagawa, Yutaro; Todo, Soya; Toshikawa, Koji; Sako, Shigeyuki; Uchimoto, Yuka K.; Ohsawa, Ryou; Asano, Kentaro; Kamizuka, Takafumi; Nakamura, Tomohiko; Okada, Kazushi [Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Ita, Yoshifusa [Astronomical Institute, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Komugi, Shinya [Division of Liberal Arts, Kogakuin University, 2665-1, Hachioji, Tokyo 192-0015 (Japan); Koshida, Shintaro [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); Manabe, Sho [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan); Nakashima, Asami, E-mail: tateuchi@ioa.s.u-tokyo.ac.jp [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); and others

    2015-03-15

    Luminous infrared galaxies (LIRGs) are enshrouded by a large amount of dust produced by their active star formation, and it is difficult to measure their activity in optical wavelengths. We have carried out Paα narrow-band imaging observations of 38 nearby star forming galaxies including 33 LIRGs listed in the IRAS Revised Bright Galaxy Sample catalog with the Atacama Near InfraRed camera on the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope (miniTAO). Star formation rates (SFRs) estimated from the Paα fluxes, corrected for dust extinction using the Balmer decrement method (typically A{sub V} ∼ 4.3 mag), show a good correlation with those from the bolometric infrared luminosity of the IRAS data within a scatter of 0.27 dex. This suggests that the correction of dust extinction for the Paα flux is sufficient in our sample. We measure the physical sizes and surface densities of infrared luminosities (Σ{sub L(IR)}) and the SFR (Σ{sub SFR}) of star forming regions for individual galaxies, and we find that most of the galaxies follow a sequence of local ultra-luminous or luminous infrared galaxies (U/LIRGs) on the L(IR)-Σ{sub L(IR)} and SFR-Σ{sub SFR} plane. We confirm that a transition of the sequence from normal galaxies to U/LIRGs is seen at L(IR) = 8 × 10{sup 10} L {sub ☉}. Also, we find that there is a large scatter in physical size, different from normal galaxies or ULIRGs. Considering the fact that most U/LIRGs are merging or interacting galaxies, this scatter may be caused by strong external factors or differences in their merging stages.

  1. Monitoring the Growth Rate of HAp Crystal on the Surface of Ti/TiO_2 in SCS by a Quartz Crystal Microbalance

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    1 IntroductionCommercially pure titanium and some titanium alloys including Ti6Al4V have been widely used in the manufacture of dental and orthopaedic implants. Although bulk properties dictate the mechanical properties of biomaterials, tissue-biomaterial processes are surface phenomena and they are governed by surface properties. Moreover, bioactivity of titanium surfaces is not high enough to induce the direct growth of the bone tissue and good bone fixation takes several months. The application of hydrox...

  2. Hydrophobic Surfaces of Spacecraft Components Enhance the Aggregation of Microorganisms and May Lead to Higher Survival Rates of Bacteria on Mars Landers

    Science.gov (United States)

    Schuerger, Andrew C.; Kern, Roger G.

    2004-01-01

    In order to minimize the forward contamination of Mars, spacecraft are assembled under cleanroom conditions that require several procedures to clean and sterilize components. Surface characteristics of spacecraft materials may contribute to microbial survival on the surface of Mars by protecting spores from sterilizing agents, including UV irradiation. The primary objective of this study was to evaluate the effects of surface characteristics of several spacecraft materials on the survival of Bacillus subtilis spores under simulated Martian conditions.

  3. Method of constrained global optimization

    Energy Technology Data Exchange (ETDEWEB)

    Altschuler, E.L.; Williams, T.J.; Ratner, E.R.; Dowla, F.; Wooten, F. (Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States) Department of Applied Physics, Stanford University, Stanford, California 94305 (United States) Department of Applied Science, University of California, Davis/Livermore, P.O. Box 808, Livermore, California 94551 (United States))

    1994-04-25

    We present a new method for optimization: constrained global optimization (CGO). CGO iteratively uses a Glauber spin flip probability and the Metropolis algorithm. The spin flip probability allows changing only the values of variables contributing excessively to the function to be minimized. We illustrate CGO with two problems---Thomson's problem of finding the minimum-energy configuration of unit charges on a spherical surface, and a problem of assigning offices---for which CGO finds better minima than other methods. We think CGO will apply to a wide class of optimization problems.

  4. Spin-orbit enhanced demagnetization rate in Co/Pt-multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kuiper, K. C.; Schellekens, A. J.; Koopmans, B. [Department of Applied Physics, Center for NanoMaterials, Eindhoven University of Technology, P. O. Box 513, 5600 MB Eindhoven (Netherlands); Roth, T.; Schmitt, O.; Cinchetti, M.; Aeschlimann, M. [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Strasse 46, 67663 Kaiserslautern (Germany)

    2014-11-17

    In order to explore the role of enhanced spin-orbit interactions on the laser-induced ultrafast magnetization dynamics, we performed a comparative study on cobalt thin films and Co/Pt multilayers. We show that the presence of the Co/Pt interfaces gives rise to a three-fold faster demagnetization upon femtosecond laser heating. Experimental data for a wide range of laser fluences are analyzed using the Microscopic 3-Temperature Model. We find that the Elliott-Yafet spin-flip scattering in the multilayer structure is increased by at least a factor of four with respect to the elementary Co film.

  5. Communication: Rate coefficients of the H + CH{sub 4} → H{sub 2} + CH{sub 3} reaction from ring polymer molecular dynamics on a highly accurate potential energy surface

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Qingyong, E-mail: mengqingyong@dicp.ac.cn; Chen, Jun, E-mail: chenjun@dicp.ac.cn; Zhang, Dong H., E-mail: zhangdh@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics and Center for Theoretical and Computational Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, 116023 Dalian (China)

    2015-09-14

    The ring polymer molecular dynamics (RPMD) calculations are performed to calculate rate constants for the title reaction on the recently constructed potential energy surface based on permutation invariant polynomial (PIP) neural-network (NN) fitting [J. Li et al., J. Chem. Phys. 142, 204302 (2015)]. By inspecting convergence, 16 beads are used in computing free-energy barriers at 300 K ≤ T ≤ 1000 K, while different numbers of beads are used for transmission coefficients. The present RPMD rates are in excellent agreement with quantum rates computed on the same potential energy surface, as well as with the experimental measurements, demonstrating further that the RPMD is capable of producing accurate rates for polyatomic chemical reactions even at rather low temperatures.

  6. Evaluation of the contribution of contamination of radiotherapy room surfaces in the measure of exposure rate of radioiodine therapy patients; Avaliacao da contribuicao da contaminacao de superficies do quarto terapeutico na medida da taxa de exposicao de pacientes de radioiodoterapia

    Energy Technology Data Exchange (ETDEWEB)

    Campos, Rafael Ferreira

    2015-07-01

    The contamination of radiotherapy room surfaces is significant and the measures of patient exposure rate are held on the fourth dependencies, relevant questions are raised: the background radiation of the room stay high due to surface contamination, may interfere with the rate of patient exposure at the time of its release? The monitoring site is important to determine whether the patient will be released? The value of the deal activity and the clinical condition of the patient may increase the contamination, influencing the monitoring results? This paper aims to conduct a quantitative analysis of surface contamination of the contribution of therapeutic room at the time is monitored exposure rate from inpatient. Measurements were made regarding the hospitalization of 32 patients with different doses administered activity, age and of both genders. The measurements were performed in the therapeutic rooms at the hospital Brotherhood Santa Casa de Misericordia de Sao Paulo. Exposure rate measurements were performed at the center of the room at 1 meter of the patient on the day of its release. After his release and prior to decontamination, measurements were performed at predetermined landmarks within the therapeutic room. The results revealed that on average background radiation, high due to surface contamination contributes only 2% of the patient dose rate. It can be considered that even with influence of contamination of surfaces, this is insignificant to determine if the patient may or may not be released. This study suggests that the site in which monitoring occurs exposure rate of the patient should not be decisive for liberation thereof. (author)

  7. The Influence of Feed Rate on Surface Roughness of TIC–WC Carbide And Al2O3 Ceramics SAWN-OFF with Inner Edge of Diamond Disc

    Directory of Open Access Journals (Sweden)

    Raimundas Mikolaitis

    2011-02-01

    Full Text Available The paper presents results of measurements of surface roughness of titanium-tungsten carbide (T14K8 and aluminium oxide (Al2O3 ceramics surfaces sawn-off with inner edge of diamond disc. The cutting process was performed by cutting machine “АЛМАЗ-4” with 60/40 grain size disc. The dependence of average roughness Ra of the sawn-off surface on feed speed of the workpiece was established.Article in Lithuanian

  8. Spiral growth and dissolution models with rate constants related to the frequency of partial dehydration of cations and to the surface tension

    Science.gov (United States)

    Christoffersen, J.; Christoffersen, M. R.

    1988-01-01

    A rate expression is developed for spiral dissolution, similar to the Nielsen expression for spiral growth, with the rate constant expressed in terms of frequencies related to dehydration frequencies. These models for spiral growth and dissolution are applied to growth and dissolution of brushite, DCPD.

  9. SU-E-T-09: A Clinical Implementation and Optimized Dosimetry Study of Freiberg Flap Skin Surface Treatment in High Dose Rate Brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Syh, J; Syh, J; Patel, B; Wu, H; Durci, M [Willis-Knighton Medical Center, Shreveport, LA (United States)

    2015-06-15

    Purpose: This case study was designated to confirm the optimized plan was used to treat skin surface of left leg in three stages. 1. To evaluate dose distribution and plan quality by alternating of the source loading catheters pattern in flexible Freiberg Flap skin surface (FFSS) applicator. 2. To investigate any impact on Dose Volume Histogram (DVH) of large superficial surface target volume coverage. 3. To compare the dose distribution if it was treated with electron beam. Methods: The Freiburg Flap is a flexible mesh style surface mold for skin radiation or intraoperative surface treatments. The Freiburg Flap consists of multiple spheres that are attached to each other, holding and guiding up to 18 treatment catheters. The Freiburg Flap also ensures a constant distance of 5mm from the treatment catheter to the surface. Three treatment trials with individual planning optimization were employed: 18 channels, 9 channels of FF and 6 MeV electron beam. The comparisons were highlighted in target coverage, dose conformity and dose sparing of surrounding tissues. Results: The first 18 channels brachytherapy plan was generated with 18 catheters inside the skin-wrapped up flap (Figure 1A). A second 9 catheters plan was generated associated with the same calculation points which were assigned to match prescription for target coverage as 18 catheters plan (Figure 1B). The optimized inverse plan was employed to reduce the dose to adjacent structures such as tibia or fibula. The comparison of DVH’s was depicted on Figure 2. External beam of electron RT plan was depicted in Figure 3. Overcall comparisons among these three were illustrated in Conclusion: The 9-channel Freiburg flap flexible skin applicator offers a reasonably acceptable plan without compromising the coverage. Electron beam was discouraged to use to treat curved skin surface because of low target coverage and high dose in adjacent tissues.

  10. Tilt optimized flip uniformity (TOFU) RF pulse for uniform image contrast at low specific absorption rate levels in combination with a surface breast coil at 7 Tesla

    NARCIS (Netherlands)

    van Kalleveen, Irene M. L.; Boer, VO; Luijten, Peter R.|info:eu-repo/dai/nl/304821098; Klomp, DWJ|info:eu-repo/dai/nl/298206382

    2015-01-01

    Purpose: Going to ultrahigh field MRI (e. g., 7 Tesla [ T]), the nonuniformity of the B_1 field and the increased radiofrequency (RF) power deposition become challenging. While surface coils improve the power efficiency in B_1, its field remains nonuniform. In this work, an RF pulse was designed tha

  11. Fully Coriolis-coupled quantum studies of the H + O2 (upsilon i = 0-2, j i = 0,1) --> OH + O reaction on an accurate potential energy surface: integral cross sections and rate constants.

    Science.gov (United States)

    Lin, Shi Ying; Sun, Zhigang; Guo, Hua; Zhang, Dong Hui; Honvault, Pascal; Xie, Daiqian; Lee, Soo-Y

    2008-01-31

    We present accurate quantum calculations of the integral cross section and rate constant for the H + O2 --> OH + O combustion reaction on a recently developed ab initio potential energy surface using parallelized time-dependent and Chebyshev wavepacket methods. Partial wave contributions up to J = 70 were computed with full Coriolis coupling, which enabled us to obtain the initial state-specified integral cross sections up to 2.0 eV of the collision energy and thermal rate constants up to 3000 K. The integral cross sections show a large reaction threshold due to the quantum endothermicity of the reaction, and they monotonically increase with the collision energy. As a result, the temperature dependence of the rate constant is of the Arrhenius type. In addition, it was found that reactivity is enhanced by reactant vibrational excitation. The calculated thermal rate constant shows a significant improvement over that obtained on the DMBE IV potential, but it still underestimates the experimental consensus.

  12. Motor unit firing rates and synchronisation affect the fractal dimension of simulated surface electromyogram during isometric/isotonic contraction of vastus lateralis muscle.

    Science.gov (United States)

    Mesin, Luca; Dardanello, Davide; Rainoldi, Alberto; Boccia, Gennaro

    2016-12-01

    During fatiguing contractions, many adjustments in motor units behaviour occur: decrease in muscle fibre conduction velocity; increase in motor units synchronisation; modulation of motor units firing rate; increase in variability of motor units inter-spike interval. We simulated the influence of all these adjustments on synthetic EMG signals in isometric/isotonic conditions. The fractal dimension of the EMG signal was found mainly influenced by motor units firing behaviour, being affected by both firing rate and synchronisation level, and least affected by muscle fibre conduction velocity. None of the calculated EMG indices was able to discriminate between firing rate and motor units synchronisation. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

  13. Low temperature hydrogen reduction of high surface area anatase and anatase/β-TiO₂ for high-charging-rate batteries.

    Science.gov (United States)

    Ventosa, Edgar; Tymoczko, Anna; Xie, Kunpeng; Xia, Wei; Muhler, Martin; Schuhmann, Wolfgang

    2014-09-01

    There are several strategies to improve the electrochemical performance of TiO2 as negative electrode material for Li-ion batteries. Introducing oxygen vacancies through hydrogen reduction leads to an enhancement in electrical conductivity. However, this strategy does not improve the low lithium-ion mobility. Herein, we show that by decreasing the temperature of hydrogen annealing the improved lithium-ion mobility of high-surface-area TiO2 and β-TiO2 can be combined with the enhanced electrical conductivity of oxygen deficiencies. Annealing at only 275-300 °C in pure hydrogen atmosphere successfully creates oxygen vacancies in TiO2, as confirmed by UV/Vis spectroscopy, whereas the temperature is low enough to maintain a high specific surface area and prevent β-to-anatase phase transformation. The hydrogen reduction of high-surface-area anatase or anatase/β-TiO2 at these temperatures leads to improvements in the performance, achieving charge capacities of 142 or 152 mAh g(-1) at 10C, respectively.

  14. Improved performance of TiO2 in the selective photo-catalytic oxidation of cyclohexane by increasing the rate of desorption through surface silylation

    NARCIS (Netherlands)

    Almeida, Ana Rita; Carneiro, Joana T.; Moulijn, Jacob A.; Mul, Guido

    2010-01-01

    The effect of silylation on the performance of an anatase TiO2 catalyst in the selective photo-oxidation of cyclohexane was investigated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and an illuminated slurry reactor. The rate of cyclohexanone formation showed

  15. Mechanism of copper surface toxicity in Escherichia coli O157:H7 and Salmonella involves immediate membrane depolarization followed by slower rate of DNA destruction which differs from that observed for Gram-positive bacteria.

    Science.gov (United States)

    Warnes, S L; Caves, V; Keevil, C W

    2012-07-01

    We have reported previously that copper I and II ionic species, and superoxide but not Fenton reaction generated hydroxyl radicals, are important in the killing mechanism of pathogenic enterococci on copper surfaces. In this new work we determined if the mechanism was the same in non-pathogenic ancestral (K12) and laboratory (DH5α) strains, and a pathogenic strain (O157), of Escherichia coli. The pathogenic strain exhibited prolonged survival on stainless steel surfaces compared with the other E. coli strains but all died within 10 min on copper surfaces using a 'dry' inoculum protocol (with approximately 10(7)  cfu cm(-2) ) to mimic dry touch contamination. We observed immediate cytoplasmic membrane depolarization, not seen with enterococci or methicillin resistant Staphylococcus aureus, and loss of outer membrane integrity, inhibition of respiration and in situ generation of reactive oxygen species on copper and copper alloy surfaces that did not occur on stainless steel. Chelation of copper (I) and (II) ionic species still had the most significant impact on bacterial survival but protection by d-mannitol suggests hydroxyl radicals are involved in the killing mechanism. We also observed a much slower rate of DNA destruction on copper surfaces compared with previous results for enterococci. This may be due to protection of the nucleic acid by the periplasm and the extensive cell aggregation that we observed on copper surfaces. Similar results were obtained for Salmonella species but partial quenching by d-mannitol suggests radicals other than hydroxyl may be involved. The results indicate that copper biocidal surfaces are effective for Gram-positive and Gram-negative bacteria but bacterial morphology affects the mechanism of toxicity. These surfaces could not only help to prevent infection spread but also prevent horizontal gene transmission which is responsible for the evolution of virulent toxin producing and antibiotic resistant bacteria. © 2011

  16. Radioactivity Distribution In Surface And Core Sediment Of The Central Part Of The Algerian Coast: An Estimation Of The Recent Sedimentation Rate

    OpenAIRE

    2012-01-01

    Sediment core samples and marine surface sediments of identical composition, mostly muddy, were collected using a Van Veen type grab and a box corer on board the M.S. Benyahia research vessel (ISMAL), along the Algerian littoral, between Algiers (36Ζ49.9 N/ 03Ζ 02.3 E) and Cherchell (36Ζ 39.4 N/ 02Ζ 12.4 E), during a sampling cruise in September 1997. The samples were analysed to determine the activity concentration of natural radionuclides (uranium and thorium series and 40 K as well) and ar...

  17. Solar UV irradiation-induced production of N2O from plant surfaces - low emissions rates but all over the world

    DEFF Research Database (Denmark)

    Mikkelsen, Teis Nørgaard; Bruhn, Dan; Ambus, Per

    for the first time N2O emission from terrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurements to investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and without UV-screening. Further laboratory tests were conducted...... with a range of species to study the controls and possible loci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c. 20-50 nmol m-2 h-1, mostly due to the UV component. The emission rate is temperature dependent with a rather high activation energy...... emission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed....

  18. Facial recognition software success rates for the identification of 3D surface reconstructed facial images: implications for patient privacy and security.

    Science.gov (United States)

    Mazura, Jan C; Juluru, Krishna; Chen, Joseph J; Morgan, Tara A; John, Majnu; Siegel, Eliot L

    2012-06-01

    Image de-identification has focused on the removal of textual protected health information (PHI). Surface reconstructions of the face have the potential to reveal a subject's identity even when textual PHI is absent. This study assessed the ability of a computer application to match research subjects' 3D facial reconstructions with conventional photographs of their face. In a prospective study, 29 subjects underwent CT scans of the head and had frontal digital photographs of their face taken. Facial reconstructions of each CT dataset were generated on a 3D workstation. In phase 1, photographs of the 29 subjects undergoing CT scans were added to a digital directory and tested for recognition using facial recognition software. In phases 2-4, additional photographs were added in groups of 50 to increase the pool of possible matches and the test for recognition was repeated. As an internal control, photographs of all subjects were tested for recognition against an identical photograph. Of 3D reconstructions, 27.5% were matched correctly to corresponding photographs (95% upper CL, 40.1%). All study subject photographs were matched correctly to identical photographs (95% lower CL, 88.6%). Of 3D reconstructions, 96.6% were recognized simply as a face by the software (95% lower CL, 83.5%). Facial recognition software has the potential to recognize features on 3D CT surface reconstructions and match these with photographs, with implications for PHI.

  19. Experimental Design for a Sponge-Wipe Study to Relate the Recovery Efficiency and False Negative Rate to the Concentration of a Bacillus anthracis Surrogate for Six Surface Materials

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Amidan, Brett G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Krauter, Paula [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Einfeld, Wayne [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2010-12-16

    Two concerns were raised by the Government Accountability Office following the 2001 building contaminations via letters containing Bacillus anthracis (BA). These included the: 1) lack of validated sampling methods, and 2) need to use statistical sampling to quantify the confidence of no contamination when all samples have negative results. Critical to addressing these concerns is quantifying the probability of correct detection (PCD) (or equivalently the false negative rate FNR = 1 - PCD). The PCD/FNR may depend on the 1) method of contaminant deposition, 2) surface concentration of the contaminant, 3) surface material being sampled, 4) sample collection method, 5) sample storage/transportation conditions, 6) sample processing method, and 7) sample analytical method. A review of the literature found 17 laboratory studies that focused on swab, wipe, or vacuum samples collected from a variety of surface materials contaminated by BA or a surrogate, and used culture methods to determine the surface contaminant concentration. These studies quantified performance of the sampling and analysis methods in terms of recovery efficiency (RE) and not PCD/FNR (which left a major gap in available information). Quantifying the PCD/FNR under a variety of conditions is a key aspect of validating sample and analysis methods, and also for calculating the confidence in characterization or clearance decisions based on a statistical sampling plan. A laboratory study was planned to partially fill the gap in PCD/FNR results. This report documents the experimental design developed by Pacific Northwest National Laboratory and Sandia National Laboratories (SNL) for a sponge-wipe method. The study will investigate the effects on key response variables from six surface materials contaminated with eight surface concentrations of a BA surrogate (Bacillus atrophaeus). The key response variables include measures of the contamination on test coupons of surface materials tested, contamination

  20. Experimental Design for a Sponge-Wipe Study to Relate the Recovery Efficiency and False Negative Rate to the Concentration of a Bacillus anthracis Surrogate for Six Surface Materials

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, Gregory F.; Amidan, Brett G.; Krauter, Paula; Einfeld, Wayne

    2011-05-01

    Two concerns were raised by the Government Accountability Office following the 2001 building contaminations via letters containing Bacillus anthracis (BA). These included the: 1) lack of validated sampling methods, and 2) need to use statistical sampling to quantify the confidence of no contamination when all samples have negative results. Critical to addressing these concerns is quantifying the false negative rate (FNR). The FNR may depend on the 1) method of contaminant deposition, 2) surface concentration of the contaminant, 3) surface material being sampled, 4) sample collection method, 5) sample storage/transportation conditions, 6) sample processing method, and 7) sample analytical method. A review of the literature found 17 laboratory studies that focused on swab, wipe, or vacuum samples collected from a variety of surface materials contaminated by BA or a surrogate, and used culture methods to determine the surface contaminant concentration. These studies quantified performance of the sampling and analysis methods in terms of recovery efficiency (RE) and not FNR (which left a major gap in available information). Quantifying the FNR under a variety of conditions is a key aspect of validating sample and analysis methods, and also for calculating the confidence in characterization or clearance decisions based on a statistical sampling plan. A laboratory study was planned to partially fill the gap in FNR results. This report documents the experimental design developed by Pacific Northwest National Laboratory and Sandia National Laboratories (SNL) for a sponge-wipe method. The testing was performed by SNL and is now completed. The study investigated the effects on key response variables from six surface materials contaminated with eight surface concentrations of a BA surrogate (Bacillus atrophaeus). The key response variables include measures of the contamination on test coupons of surface materials tested, contamination recovered from coupons by sponge

  1. The influence of cutting speed and feed rate in surface integrity of aisi 1045//Influencia de la velocidad de corte y la velocidad de avance en la integridad superficial del acero aisi 1045

    Directory of Open Access Journals (Sweden)

    Mario Jacas-Cabrera

    2015-09-01

    Full Text Available El objetivo de esta investigación es el estudio de la influencia de la velocidad de corte y la velocidad de avance en la integridad superficial del acero AISI-1045, sometido a un proceso de torneado. Las probetas se sometieron a un tratamiento térmico de recocidos (81 HRB. En el trabajo se empleó un diseño experimental 32, con dos variables a tres niveles experimentales, para un total de nueve experimentos, los que fueron replicados. La integridad superficial fue evaluada con la medición de la rugosidad superficial, las tensiones residuales superficiales, la medición de dureza por nano–indentación y por el análisis de la de formación terciaria. Los resultados determinaron la gran influencia de la velocidad de avance en la rugosidad superficial. La medición de las tensiones residuales mostró la influencia de las variables de corte. Del análisis microestructural se observó la existencia de dos zonas de deformación determinándose que el espesor de la zona endurecida llegó a 50 µm. Palabras claves: integridad superficial, rugosidad superficial, nano-indentación; superficie deformada____________________________________________________________________________AbstractThe aim of this research is to study the influence of cutting speed and feed rate on surface integrity of AISI-1045 subjected to a turning process. The specimens were in annealed condition (81 HRB. A 32 factorial experiment design was employed using low, medium and high levels of the two variables in study, performing 9 experiments with a replica. The surfaces were evaluated through the measurements of surface roughness, surface residual stresses, nano-indentation hardness and analyzing the deformed layer. Results corroborated the great influence of feed rate on surface roughness. The results of the residual stresses have shown the influence of cutting speed as well as feed rate in the behavior of circumferential and axial stress respectively. From the analysis of the

  2. External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting.

    Science.gov (United States)

    Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

    2013-01-01

    For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13.

  3. A crossover adjustment for improving sea surface height mapping from in-situ high rate ship-borne GNSS data using PPP technique

    Science.gov (United States)

    Guo, Jinyun; Dong, Zhenghua; Tan, Zhengguang; Liu, Xin; Chen, Chuanfa; Hwang, Cheinway

    2016-08-01

    Ship-borne global navigation satellite system (GNSS) technique can overcome the weakness of satellite altimetry and tide gauge in measuring sea surface heights (SSHs) over coastal seas. Ship-borne GNSS technique can be used to calibrate SSHs determined by the satellite altimetry and tide gauge. The ship-borne GNSS data are processed with the single-epoch precise point positioning (PPP) method to estimate SSHs which are filtered by the Gaussian filter to weaken and/or remove effects of sea wind and wave field. Tidal corrections are also taken into consideration to improve SSHs. One crossover adjustment method is put forward to calculate the bias and drift along the ship route and assess the accuracy of SSHs. We processed the in-situ ship-borne GPS data over the offshore sea around Keelung to compute precisely SSHs with the single-epoch PPP. Statistical results of SSH differences of crossover points indicate that the root mean squares error of SSHs determined by the ship-borne GPS is up to level of 12.9 cm over the offshore sea ~30 km far away to land.

  4. False-negative rate, limit of detection and recovery efficiency performance of a validated macrofoam-swab sampling method for low surface concentrations of Bacillus anthracis Sterne and Bacillus atrophaeus spores

    Energy Technology Data Exchange (ETDEWEB)

    Piepel, G. F. [Applied Statistics and Computational Sciences, Pacific Northwest National Laboratory, Richland WA USA; Deatherage Kaiser, B. L. [Chemical and Biological Signature Science Group, Pacific Northwest National Laboratory, Richland WA USA; Amidan, B. G. [Applied Statistics and Computational Sciences, Pacific Northwest National Laboratory, Richland WA USA; Sydor, M. A. [Chemical and Biological Signature Science Group, Pacific Northwest National Laboratory, Richland WA USA; Barrett, C. A. [Analytical Chemistry of Nuclear Materials, Pacific Northwest National Laboratory, Richland WA USA; Hutchison, J. R. [Chemical and Biological Signature Science Group, Pacific Northwest National Laboratory, Richland WA USA

    2016-05-06

    The performance of a macrofoam-swab sampling method was evaluated using Bacillus anthracis Sterne (BAS) and Bacillus atrophaeus Nakamura (BG) spores applied at nine low target amounts (2-500 spores) to positive-control plates and test coupons (2 in × 2 in) of four surface materials (glass, stainless steel, vinyl tile, and plastic). Test results from cultured samples were used to evaluate the effects of surrogate, surface concentration, and surface material on recovery efficiency (RE), false negative rate (FNR), and limit of detection. For RE, surrogate and surface material had statistically significant effects, but concentration did not. Mean REs were the lowest for vinyl tile (50.8% with BAS and 40.2% with BG) and the highest for glass (92.8% with BAS and 71.4% with BG). FNR values ranged from 0 to 0.833 for BAS and 0 to 0.806 for BG; values increased as concentration decreased in the range tested (0.078 to 19.375 CFU/cm2). Surface material also had a statistically significant effect. A FNR-concentration curve was fit for each combination of surrogate and surface material. For both surrogates, the FNR curves tended to be the lowest for glass and highest for vinyl title. The FNR curves for BG tended to be higher than for BAS at lower concentrations, especially for glass. Results using a modified Rapid Viability-Polymerase Chain Reaction (mRV-PCR) analysis method were also obtained. The mRV-PCR results and comparisons to the culture results will be discussed in a subsequent article.

  5. Low temperature rate coefficients of the H + CH{sup +} → C{sup +} + H{sub 2} reaction: New potential energy surface and time-independent quantum scattering

    Energy Technology Data Exchange (ETDEWEB)

    Werfelli, Ghofran [Université de Bordeaux, Institut des Sciences Moléculaires, CNRS UMR 5255, 33405 Talence Cedex (France); Faculté des Sciences de Tunis, Université de Tunis El-Manar, Laboratoire de Physique de la Matière Condensée, 2092 Tunis (Tunisia); Halvick, Philippe; Stoecklin, Thierry [Université de Bordeaux, Institut des Sciences Moléculaires, CNRS UMR 5255, 33405 Talence Cedex (France); Honvault, Pascal [Université de Bourgogne Franche-Comté, Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS UMR 6303, 21078 Dijon Cedex (France); Université de Franche-Comté, UFR ST, 25030 Besançon Cedex (France); Kerkeni, Boutheïna [Faculté des Sciences de Tunis, Université de Tunis El-Manar, Laboratoire de Physique de la Matière Condensée, 2092 Tunis (Tunisia); Institut Supérieur des Arts Multimédia de la Manouba, Université de la Manouba, 2010 la Manouba (Tunisia)

    2015-09-21

    The observed abundances of the methylidyne cation, CH{sup +}, in diffuse molecular clouds can be two orders of magnitude higher than the prediction of the standard gas-phase models which, in turn, predict rather well the abundances of neutral CH. It is therefore necessary to investigate all the possible formation and destruction processes of CH{sup +} in the interstellar medium with the most abundant species H, H{sub 2}, and e{sup −}. In this work, we address the destruction process of CH{sup +} by hydrogen abstraction. We report a new calculation of the low temperature rate coefficients for the abstraction reaction, using accurate time-independent quantum scattering and a new high-level ab initio global potential energy surface including a realistic model of the long-range interaction between the reactants H and CH{sup +}. The calculated thermal rate coefficient is in good agreement with the experimental data in the range 50 K–800 K. However, at lower temperatures, the experimental rate coefficient takes exceedingly small values which are not reproduced by the calculated rate coefficient. Instead, the latter rate coefficient is close to the one given by the Langevin capture model, as expected for a reaction involving an ion and a neutral species. Several recent theoretical works have reported a seemingly good agreement with the experiment below 50 K, but an analysis of these works show that they are based on potential energy surfaces with incorrect long-range behavior. The experimental results were explained by a loss of reactivity of the lowest rotational states of the reactant; however, the quantum scattering calculations show the opposite, namely, a reactivity enhancement with rotational excitation.

  6. Non-adiabatic effects within a single thermally-averaged potential energy surface: Thermal expansion and reaction rates of small molecules

    CERN Document Server

    Alonso, J L; Clemente-Gallardo, J; Echenique, P; Mazo, J J; Polo, V; Rubio, A; Zueco, D

    2012-01-01

    At non-zero temperature and when a system has low-lying excited electronic states, the ground-state Born--Oppenheimer approximation breaks down and the low-lying electronic states are involved in any chemical process. In this work, we use a temperature-dependent effective potential for the nuclei which can accomodate the influence of an arbitrary number of electronic states in a simple way, while at the same time producing the correct Boltzmann equibrium distribution for the electronic part. With the help of this effective potential, we show that thermally-activated low-lying electronic states can have a significant effect in molecular properties for which electronic excitations are oftentimes ignored. We study the thermal expansion of the Manganese dimer, Mn$_2$, where we find that the average bond length experiences a change larger than the present experimental accuracy upon the inclusion of the excited states into the picture. We also show that, when these states are taken into account, reaction rate const...

  7. Numerical study of shear rate effect on unsteady flow separation from the surface of the square cylinder using structural bifurcation analysis

    Science.gov (United States)

    Ray, Rajendra K.; Kumar, Atendra

    2017-08-01

    In this paper, an incompressible two-dimensional shear flow past a square cylinder problem is investigated numerically using a higher order compact finite difference scheme. Simulations are presented for three sets of Reynolds numbers, 100, 200, and 500, with various shear parameter (K) values ranging from 0.0 to 0.4. The purpose of the present study is to elaborate the influence of shear rate on the vortex shedding phenomenon behind the square cylinder. The results presented here show that the vortex shedding phenomenon strongly depends on Re as well as K. The strength and size of vortices shed behind the cylinder vary as a function of Re and K. When K is larger than a critical value, the vortex shedding phenomenon has completely disappeared depending on the Reynolds number. Apart from the numerical study, a thorough theoretical investigation has been done by using a topology based structural bifurcation analysis for unsteady flow separations from the walls of the cylinder. Through this analysis, we study the exact locations of the bifurcation points associated with secondary and tertiary vortices with appropriate non-dimensional time of occurrence. To the best of our knowledge, this is the first time, a topological aspect based structural bifurcation analysis has been done to understand the vortex shedding phenomenon and flow separation for this problem.

  8. Mössbauer Study of Electronic Spin-Flip Processes in NH4 Fe(SO4)2 ·12H2O

    DEFF Research Database (Denmark)

    Mørup, Steen; Thrane., N.

    1971-01-01

    the spectra are also influenced by components of the hyperfine field fluctuating perpendicular to the applied-field direction, thereby inducing transitions between the nuclear sublevels. In the case of high applied fields, a simple model permits the determination of the spin-correlation time. In 5-kG applied...... fields, the spin-correlation time was found to decrease from 1.6±0.15 nsec at 85 K to 0.50±0.05 nsec at 245 K due to spin-lattice interactions. It is shown that these results cannot be compared with the values obtained by high-frequency susceptibility measurements....

  9. Revisiting 2D Lattice Based Spin Flip-Flop Ising Model: Magnetic Properties of a Thin Film and Its Temperature Dependence

    Science.gov (United States)

    Singh, Satya Pal

    2014-01-01

    This paper presents a brief review of Ising's work done in 1925 for one dimensional spin chain with periodic boundary condition. Ising observed that no phase transition occurred at finite temperature in one dimension. He erroneously generalized his views in higher dimensions but that was not true. In 1941 Kramer and Wannier obtained…

  10. Actin cytoskeleton organization, cell surface modification and invasion rate of 5 glioblastoma cell lines differing in PTEN and p53 status

    Energy Technology Data Exchange (ETDEWEB)

    Djuzenova, Cholpon S., E-mail: djuzenova_t@ukw.de [Department of Radiation Oncology, University Hospital, Josef-Schneider-Strasse 11, D-97080 Würzburg (Germany); Fiedler, Vanessa [Department of Radiation Oncology, University Hospital, Josef-Schneider-Strasse 11, D-97080 Würzburg (Germany); Memmel, Simon [Lehrstuhl für Biotechnologie und Biophysik, Universität Würzburg, Biozentrum Am Hubland, 97070 Würzburg (Germany); Katzer, Astrid; Hartmann, Susanne [Department of Radiation Oncology, University Hospital, Josef-Schneider-Strasse 11, D-97080 Würzburg (Germany); Krohne, Georg [Elektronenmikroskopie, Biozentrum, Universität Würzburg, Am Hubland, 97070 Würzburg (Germany); Zimmermann, Heiko [Hauptabteilung Biophysik and Kryotechnologie, Fraunhofer-Institut für Biomedizinische Technik, Lehrstuhl für Molekulare und Zelluläre Biotechnologie/Nanotechnologie, Universität des Saarlandes, Ensheimer Strasse 48, 66386 St. Ingbert (Germany); Scholz, Claus-Jürgen [Interdisciplinary Center for Clinical Research, University Hospital, Versbacher Strasse 7, 97078 Würzburg (Germany); Polat, Bülent; Flentje, Michael [Department of Radiation Oncology, University Hospital, Josef-Schneider-Strasse 11, D-97080 Würzburg (Germany); and others

    2015-01-15

    Glioblastoma cells exhibit highly invasive behavior whose mechanisms are not yet fully understood. The present study explores the relationship between the invasion capacity of 5 glioblastoma cell lines differing in p53 and PTEN status, expression of mTOR and several other marker proteins involved in cell invasion, actin cytoskeleton organization and cell morphology. We found that two glioblastoma lines mutated in both p53 and PTEN genes (U373-MG and SNB19) exhibited the highest invasion rates through the Matrigel or collagen matrix. In DK-MG (p53wt/PTENwt) and GaMG (p53mut/PTENwt) cells, F-actin mainly occurred in the numerous stress fibers spanning the cytoplasm, whereas U87-MG (p53wt/PTENmut), U373-MG and SNB19 (both p53mut/PTENmut) cells preferentially expressed F-actin in filopodia and lamellipodia. Scanning electron microscopy confirmed the abundant filopodia and lamellipodia in the PTEN mutated cell lines. Interestingly, the gene profiling analysis revealed two clusters of cell lines, corresponding to the most (U373-MG and SNB19, i.e. p53 and PTEN mutated cells) and less invasive phenotypes. The results of this study might shed new light on the mechanisms of glioblastoma invasion. - Highlights: • We examine 5 glioblastoma lines on the invasion capacity and actin cytoskeleton. • Glioblastoma cell lines mutated in both p53 and PTEN were the most invasive. • Less invasive cells showed much less lamellipodia, but more actin stress fibers. • A mechanism for the differences in tumor cell invasion is proposed.

  11. 考虑水迁移率动态变化改进土壤溶质地表流失模型%Modified model for solute loss from soil to surface runoff considering with dynamic water transfer rate

    Institute of Scientific and Technical Information of China (English)

    夏传安; 童菊秀

    2016-01-01

    Solute loss from soil into surface runoff water plays a significant role in agricultural non-point source pollution. Thus, studying the mathematical model of solute loss in runoff is important for forecasting and controlling fertilizer loss in farmland. Water transfer rate is taken as the function of soil erosion in this study, and water transfer rate is not a constant but an exponent function of time, which decreases with time and finally achieves an unchangeable value, residual water transfer rate. The soil erosion based model is modified and the numerical solution of solute concentration in surface runoff water is obtained through modifying the Hydrus-1D code. And, only the solute numerical model is modified for coupling the surface loss model which is discrete with the implicit difference method in Hydrus-1D code. Two groups of published experiment data are used to verify our modified model. The results show that the related coefficients (r), between forecasted results and observed data are no less than 0.81 in all cases. Moreover, both average value of absolute residual and root-mean-square error are remarkably smaller in all cases than the values published before, with the average decrease value of 35.42 and 60.77 mg/L, respectively, which suggests that the modified model in our study is much better than original model to predict solute transfer from soil into surface runoff water. Solute concentrations in both runoff and soil profile could be simulated well. This result suggests that the modified model characterizes the solute loss process in surface runoff or in underground drainage. The solute curve for the condition with or without ponding water can be simulated with the modified model by just setting the proper parameters. The sum of solute loss in runoff increases with the rainfall increasing and decreases with the time in the single experiment. Residual water transfer rate does not change with rainfall intensity. Under non-infiltration condition

  12. 基于聚类NASVD的CE2-GRS月表放射性元素Th计数率分布%Distribution of the Thorium Counting Rate on the Lunar Surface from CE2-GRS Based on Cluster NASVD

    Institute of Scientific and Technical Information of China (English)

    李晓丽; 葛良全; 杨佳; 熊盛青

    2015-01-01

    月表Th元素分布特征对于分析月表岩石成因及化学特征等提供了重要依据。为了减小嫦娥二号伽玛谱(CE2-GRS)噪声对获取Th元素分布特征的影响,提出了一种基于噪声调整的奇异值分解(NASVD)去噪算法。通过伽玛谱预处理、去噪、本底扣除及净峰面积求解等步骤,获得月表放射性元素Th计数率全月分布图。通过与国内外其他方法所获得的Th元素计数率分布图对比有较高的一致性。与传统伽玛谱去噪算法比较,聚类NASVD算法能有效地去除统计涨落噪声影响,提取出嫦娥二号伽玛谱中的特征峰信息。%The distribution of thorium on the lunar surface provides the important evidence for lunar evolution history. It is difficult to obtain the distribution of thorium on the lunar surface from CE2-GRS because of noise in the spectrum. The method for smoothing the spectrum is proposed which is based on cluster NASVD. The counting rate map of thorium on the lunar surface is achieved from CE2-GRS. Counting rate map of thorium gamma-rays shows a surface thorium distribution that is in general agreement with other measurement from LP-GRS and SLENE GRS which have better accuracy. It is more effectively to reduce the noise and get the weak information of characteristic peak used the method of cluster NASVD than other traditional methods for smoothing gamma-ray spectrum.

  13. Surface Water & Surface Drainage

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — This data set contains boundaries for all surface water and surface drainage for the state of New Mexico. It is in a vector digital data structure digitized from a...

  14. Effects of N2/O2 flow rate on the surface properties and biocompatibility of nano-structured TiOxNy thin films prepared by high vacuum magnetron sputtering

    Science.gov (United States)

    Saleem, Sehrish; Ahmad, R.; Ikhlaq, Uzma; Ayub, R.; Wei, Hong Jin; Rui Zhen, Xu; Peng, Hui Li; Abbas, Khizra; Chu, Paul K.

    2015-07-01

    NiTi shape memory alloys (SMA) have many biomedical applications due to their excellent mechanical and biocompatible properties. However, nickel in the alloy may cause allergic and toxic reactions, which limit some applications. In this work, titanium oxynitride films were deposited on NiTi samples by high vacuum magnetron sputtering for various nitrogen and oxygen gas flow rates. The x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) results reveal the presence of different phases in the titanium oxynitride thin films. Energy dispersive spectroscopy (EDS) elemental mapping of samples after immersion in simulated body fluids (SBF) shows that Ni is depleted from the surface and cell cultures corroborate the enhanced biocompatibility in vitro. Project supported by the Higher Education Commission, Hong Kong Research Grants Council (RGC) General Research Funds (GRF), China (Grant No. 112212) and the City University of Hong Kong Applied Research Grant (ARG), China (Grant No. 9667066).

  15. ESCIMO.spread – a spreadsheet-based point snow surface energy balance model to calculate hourly snow water equivalent and melt rates for historical and changing climate conditions

    Directory of Open Access Journals (Sweden)

    T. Marke

    2010-05-01

    Full Text Available This paper describes the spreadsheet-based point energy balance model ESCIMO.spread which simulates the energy and mass balance as well as melt rates of a snow surface. The model makes use of hourly recordings of temperature, precipitation, wind speed, relative humidity, global and longwave radiation. The effect of potential climate change on the seasonal evolution of the snow cover can be estimated by modifying the time series of observed temperature and precipitation by means of adjustable parameters. Model output is graphically visualized in hourly and daily diagrams. The results compare well with weekly measured snow water equivalent (SWE. The model is easily portable and adjustable, and runs particularly fast: hourly calculation of a one winter season is instantaneous on a standard computer. ESICMO.spread can be obtained from the authors on request (contact: ulrich.strasser@uni-graz.at.

  16. Rate Gyroscopic Wellbore Survey System

    Institute of Scientific and Technical Information of China (English)

    Sheng Limin

    1997-01-01

    @@ The rate gyroscopic wellbore survey system as a new type of survey instruments adopts the inertial-grade rate gyro and quartz flexible accelerometers to compose a gyrocompassing system, transiting data to surface instrument by single core cable. The azimuth, inclination and tool-face angle can be computed from these data by surface computer.

  17. 盾构掘进速度及非正常停机对地面沉降的影响%Influences of shield advance rate and abnormal machine halt on tunnelling-induced ground surface settlements

    Institute of Scientific and Technical Information of China (English)

    林存刚; 吴世明; 张忠苗; 刘俊伟; 李宗梁

    2012-01-01

    Shield tunnelling in soft soils inevitably disturbs the surrounding environment and induces ground surface settlements. The serviceability and safety of the structures in the vicinity can be jeopardized in case that excess settlements are observed. A comprehensive understanding of the influencing factors of shield tunnelling induced ground settlements and an accurate settlement prediction are of great importance for minimizing the environment impacts of shield tunnelling. Taking the load of the shield into account, the Mindlin's solution is introduced to calculate the additional stress in soils beneath the shield, and the layer-wise summation method is applied to calculate the final one-dimensional consolidation settlement. The duration of additional stress in soils relies on the shield advance rate and its halt time, and the corresponding consolidation settlement can be calculated using the Terzaghi's one-dimensional consolidation theory. Finally, the relationship between consolidation settlements and ground surface settlements is established by Peck equation. The theory is verified by in-situ monitored ground surface settlements in construction of Hangzhou Qing-chun Road cross-river tunnel in China. These studies show that the shield advance rate and machine halt duration have a significant impact on the ground surface settlements, and the increase in shield advance rate and decrease in machine halt duration favors the settlement control.%软土中盾构隧道施工不可避免地扰动周围地层,进而引起地面沉降,沉降过大时将危及邻近建(构)筑物的正常使用和结构安全.全面理解盾构隧道施工引起的地面沉降的影响因素及对沉降的准确预测,对于减少施工环境危害十分重要.考虑盾构压重后,引入Mindlin解计算盾构下卧土层中的附加应力,采用单向压缩分层总和法计算盾构下卧土层的总固结沉降,由盾构掘进速度及停机时间确定附加应力作用时间后,应用

  18. Loss Mechanism and Loss Rate of Zinc Acetate from the Surface of the Activated Carbon in the Reaction Process%醋酸锌自催化剂表面上的流失机理和流失速度

    Institute of Scientific and Technical Information of China (English)

    孙培勤; 乌云高娃; 刘大壮

    2001-01-01

    In the reaction process of synthesizing vinyl acetate,the loss of the active species Zn(OAc)2 from the surface of activated carbon results from Zn(OAc)2 sublimating of gas phase and the blocking inside micropores with condensation products.The sublimation mechanism is that the reaction product vinyl acetate acts with Zn(OAc)2 to produce a volatilizable complex,then sublimates to gas phase.The overall loss ratio(LR) can be described as the equation LR=1-exp(-kvt),which is extensive application of the sublimation rate equation,where v is the flow rate of gas stream,t is reaction time,and k is loss rate constant.%乙炔和醋酸合成醋酸乙烯的反应过程中,催化剂的失活,是由催化剂中的醋酸锌Zn (OAc)2从活性炭表面上升华到气相中以及被凝聚物堵在微孔内部而引起的.升华机理是反应产物与Zn (OAc)2作用生成挥发性络合物再升华到气相中去.总流失速度可用LR=1-exp (-kvt)来描述,这是升华速度方程式的应用推广.式中v为气流速度,t为反应时间,k为速度常数.

  19. Ratings Revisited

    DEFF Research Database (Denmark)

    Lai, Signe Sophus

    2015-01-01

    tværs af medier og platforme, forskudt i tid og on-demand. This article focuses on audience ratings, which have functioned as the central ‘currency’ informing the media trade. It discusses changes to the production and accuracy of audience ratings at a time when established standards are being...... consumption. It argues that current tracking systems cannot capture increasingly cross-media, time-shifted, mobile, and on-demand audience behavior....

  20. Variation in CO2 assimilation rate induced by simulated dew waters with different sources of hydroxyl radical (*OH) on the needle surfaces of Japanese red pine (Pinus densifora Sieb. et Zucc.).

    Science.gov (United States)

    Kobayashi, T; Natanani, N; Hirakawa, T; Suzuki, M; Miyake, T; Chiwa, M; Yuhara, T; Hashimoto, N; Inoue, K; Yamamura, K; Agus, N; Sinogaya, J R; Nakane, K; Kume, A; Arakaki, T; Sakugawa, H

    2002-01-01

    The hydroxyl radical (*OH) is generated in polluted dew on the needle surfaces of Japanese red pine (Pinus densiflora Sieb. et Zucc.). This free radical, which is a potent oxidant, is assumed to be a cause of ecophysiological disorders of declining trees on the urban-facing side of Mt. Gokurakuji, western Japan. Mists of *OH-generating N(III) (HNO2 and NO2-) and HOOH + Fe + oxalate solutions (50 and 100 microM, pH 5.1-5.4) simulating the dew water were applied to the foliage of pine seedlings grown in open-top chambers in the early morning. Needles treated with 100 microM N(III) tended to have a greater maximum CO2 assimilation rate (Amax), a greater stomatal conductance (g(s)) and a greater needle nitrogen content (Nneedle), suggesting that N(III) mist acts as a fertilizer rather than as a phytotoxin. On the other hand, needles treated with 100 microM HOOH + Fe + oxalate solution showed the smallest Amax, g(s), and Nneedle, suggesting that the combination of HOOH + Fe + oxalate caused a decrease in needle productivity. The effects of HOOH + Fe + oxalate mist on pine needles were very similar to the symptoms of declining trees at Mt. Gokurakuji.

  1. 我国孕妇乙肝表面抗原阳性率的Meta分析%Meta-analysis on the positive rate of hepatitis B surface antigen among pregnant women in China

    Institute of Scientific and Technical Information of China (English)

    石果; 张顺祥

    2013-01-01

    Objective To systematically evaluate the national positive rate of hepatitis B surface antigen (HB-sAg) among pregnant women in China by meta-analysis. Methods Publications regarding the positive rate of HBsAg among pregnant women between 2002 and 2012 were extracted from China National Knowledge Infra-structure (CNK1). Chinese science & technology journal database (VIP) , Wanfang database and PubMed, The Mcta positive rate was estimated using generic inverse variance model and the random effect model provid-ed by MetaAnalyst software. Results Thirty-five papers were retrieved with a total sample size of 224 029. The weighted positive rate was 7. 91 % (95% Cl: 7. 78%-8. 03%) estimated by generic inverse variance model and 7. 60% (95% CI: 6. 50%-8. 70%) by the random effect model provided by MetaAnalyst software. Be-cause of the heterogeneity of included studies, the result acquired by MetaAnalyst software was more accurate. Conclusions The result of the meta-analysis is almost consistent with the result of national epidemiological survey, indicating that Meta analysis is reliable, which provides key parameter for making strategies to prevent maternal-infantile transmission.%目的 采用Meta分析系统评价我国孕妇2002 2012年乙肝表面抗原(HBsAg)阳性率情况.方法 系统检索中国期刊全文数据库(CNKI)、维普中文科技期刊全文数据库和万方数据资源系统及PubMed中2002年1月至2012年1月发表的有关中国孕妇HBsAg阳性率的研究报道,分别用广义倒方差模型及MetaAnalyst3.13软件提供的随机效应模型估计孕妇HBsAg合并阳性率.结果 共纳入文献35篇,总样本量224029例,经广义倒方差模型加权合并后的阳性率为7.91% (95%CI:7.78%~8.03%),MetaAnalyst合并后的阳性率7.6% (95%CI:6.5%~8.7%),因纳入研究结果具有异质性,采用MetaAnalyst提供的随机效应模型获得的结果更为合适,即我国孕妇HBsAg阳性率加权合并值为7.60%,95

  2. The lowest-lying electronic singlet and triplet potential energy surfaces for the HNO-NOH system: energetics, unimolecular rate constants, tunneling and kinetic isotope effects for the isomerization and dissociation reactions.

    Science.gov (United States)

    Bozkaya, Uğur; Turney, Justin M; Yamaguchi, Yukio; Schaefer, Henry F

    2012-04-28

    The lowest-lying electronic singlet and triplet potential energy surfaces (PES) for the HNO-NOH system have been investigated employing high level ab initio quantum chemical methods. The reaction energies and barriers have been predicted for two isomerization and four dissociation reactions. Total energies are extrapolated to the complete basis set limit applying focal point analyses. Anharmonic zero-point vibrational energies, diagonal Born-Oppenheimer corrections, relativistic effects, and core correlation corrections are also taken into account. On the singlet PES, the (1)HNO → (1)NOH endothermicity including all corrections is predicted to be 42.23 ± 0.2 kcal mol(-1). For the barrierless decomposition of (1)HNO to H + NO, the dissociation energy is estimated to be 47.48 ± 0.2 kcal mol(-1). For (1)NOH → H + NO, the reaction endothermicity and barrier are 5.25 ± 0.2 and 7.88 ± 0.2 kcal mol(-1). On the triplet PES the reaction energy and barrier including all corrections are predicted to be 7.73 ± 0.2 and 39.31 ± 0.2 kcal mol(-1) for the isomerization reaction (3)HNO → (3)NOH. For the triplet dissociation reaction (to H + NO) the corresponding results are 29.03 ± 0.2 and 32.41 ± 0.2 kcal mol(-1). Analogous results are 21.30 ± 0.2 and 33.67 ± 0.2 kcal mol(-1) for the dissociation reaction of (3)NOH (to H + NO). Unimolecular rate constants for the isomerization and dissociation reactions were obtained utilizing kinetic modeling methods. The tunneling and kinetic isotope effects are also investigated for these reactions. The adiabatic singlet-triplet energy splittings are predicted to be 18.45 ± 0.2 and 16.05 ± 0.2 kcal mol(-1) for HNO and NOH, respectively. Kinetic analyses based on solution of simultaneous first-order ordinary-differential rate equations demonstrate that the singlet NOH molecule will be difficult to prepare at room temperature, while the triplet NOH molecule is viable with respect to isomerization and dissociation reactions up to

  3. 10-year survival rate and the incidence of peri-implant disease of 374 titanium dental implants with a SLA surface: a prospective cohort study in 177 fully and partially edentulous patients.

    Science.gov (United States)

    van Velzen, Frank J J; Ofec, Ronen; Schulten, Engelbert A J M; Ten Bruggenkate, Christiaan M

    2015-10-01

    This prospective cohort study evaluates the 10-year survival and incidence of peri-implant disease at implant and patient level of sandblasted, large grid, and acid-etched titanium dental implants (Straumann, soft tissue level, SLA surface) in fully and partially edentulous patients. Patients who had dental implant surgery in the period between November 1997 and June 2001, with a follow-up of at least 10 years, were investigated for clinical and radiological examination. Among the 506 inserted dental implants in 250 patients, 10-year data regarding the outcome of implants were available for 374 dental implants in 177 patients. In the current study, peri-implantitis was defined as advanced bone loss (≧1.5 mm. postloading) in combination with bleeding on probing. At 10-year follow-up, only one implant was lost (0.3%) 2 months after implant surgery due to insufficient osseointegration. The average bone loss at 10 year postloading was 0.52 mm. Advanced bone loss at 10-year follow-up was present in 35 dental implants (9.8%). Seven percent of the observed dental implants showed bleeding on probing in combination with advanced bone loss and 4.2% when setting the threshold for advanced bone loss at 2.0 mm. Advanced bone loss without bleeding on probing was present in 2.8% of all implants. In this prospective study, the 10-year survival rate at implant and patient level was 99.7% and 99.4%, respectively. Peri-implantitis was present in 7% of the observed dental implants according to the above-mentioned definition of peri-implantitis. This study shows that SLA implants offer predictable long-term results as support in the treatment of fully and partially edentulous patients. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  4. The application research on the qualification rate of the stem washing temperature by response surface methodology optimization%响应面分析法优化洗梗水温合格率的应用研究

    Institute of Scientific and Technical Information of China (English)

    张常记; 李刚; 蒲辉艳; 杨中; 袁丹宇; 候萱

    2015-01-01

    以洗梗水温的合格率为评价指标,通过单因素试验、运用响应面和绝对差值分析法,考察了液位计安装位置、液位计高低检测位置、补偿蒸汽阀门开启和关闭点对洗梗水温合格率的影响.结果表明:液位计的安装位置为34 cm,低位检测位置为28 cm,高位检测位置为38 cm 时,洗梗水温合格率的最大预测值为94.996%.当水温<47.5℃时,补偿蒸汽阀门开度为100%;随着水温的增加逐渐减少补偿蒸汽阀门开度,当水温>52.5℃时,关闭补偿蒸汽阀门.经对液位检测程序和补偿蒸汽阀门开启和关闭程序优化,YSG -8AF 型洗梗机 PID 控制程序实现了加水和增温的自动控制,洗梗水温合格率从79.85%提高到99.92%.%Through the single factor test,the response surface methodology and the absolute difference anal-ysis method,the effect of the factors such as mounting position of the liquid level meter,the high and low level detection position of the liquid level meter,the compensation steam valve opening and closing point were investigated based on the comprehensive evaluation which were guided by the qualification rate of the stem washing temperature.The results showed that:When the mounting position of the liquid level meter was 34 cm,the low level detection position was 28 cm,the high level detection position was 38 cm,the maximal prediction value of the qualification rate of the stem washing temperature was 94.996%.When the temperature was less than 47.5 ℃,the opening of the compensation steam valve was 100%,which was gradually reduced with the increase of the water temperature;when the water temperature was more than 52.5 ℃,the opening of the compensation steam valve was closed.Through the program optimization of the liquid level detection,the compensation steam valve opening and closing point,the PID control program of the stem washing machine of YSG-8AF realized the automatic

  5. Surface chemistry theory and applications

    CERN Document Server

    Bikerman, J J

    2013-01-01

    Surface Chemistry Theory and Applications focuses on liquid-gas, liquid-liquid, solid-gas, solid-liquid, and solid-solid surfaces. The book first offers information on liquid-gas surfaces, including surface tension, measurement of surface tension, rate of capillarity rise, capillary attraction, bubble pressure and pore size, and surface tension and temperature. The text then ponders on liquid-liquid and solid-gas surfaces. Discussions focus on surface energy of solids, surface roughness and cleanness, adsorption of gases and vapors, adsorption hysteresis, interfacial tension, and interfacial t

  6. Validity of the formalism of calculation in surface TG-43 brachytherapy high dose rate; Validez del formalismo de calculo del TG-43 en braquiterapia superficial con alta tase de dosis

    Energy Technology Data Exchange (ETDEWEB)

    Granero, D.; Perez-Calatayud, J.; Vijande, J.; Ballester, F.; Rivard, M. J.

    2013-07-01

    The purpose of this work is to evaluate the clinical implications and limitations in implant surface with a source of HDR very close or in contact with the surface of the skin, also studied the effect of bolus on the implant. The two available radionuclides have been studied commercially in HDR, Ir-192 and Co-60 units. (Author)

  7. Theoretical and exp erimental investigation on the narrow-linewidth photonic microwave generation based on parallel polarized optically injected 1550 nm vertical-cavity surface-emitting laser%基于平行偏振光注入的1550 nm波段垂直腔表面发射激光器获取窄线宽光子微波的理论和实验研究∗

    Institute of Scientific and Technical Information of China (English)

    孙波; 吴加贵; 王顺天; 吴正茂; 夏光琼

    2016-01-01

    Photonic microwave generation has attracted much attention in recent years due to its potential applications in various fields such as radio-over-fiber communication, signal processing and radar systems. So far, different photonic microwave generation schemes have been proposed and investigated, such as the optical heterodyne method based on the beat of two independent lasers with a certain wavelength difference, the external modulation method based on electro-optical modulator, the dual-mode beat method based on the monolithic dual-mode semiconductor lasers, and the optoelectronic microwave oscillator method based on optoelectronic feedback loops. These schemes have their own advantages and deficiencies. Unlike the above schemes, in this paper we propose an all optical scheme for generating high-quality microwave based on a 1550 nm vertical-cavity surface-emitting laser (1550 nm-VCSEL). For such a scheme, high frequency microwave can be obtained based on a 1550 nm-VCSEL subjected to external optical injection, where the polarization of the injected light is the same as that of the dominant mode of the free-running 1550 nm-VCSEL (named parallel-polarized optical injection) and its wavelength is adjusted to being close to the wavelength of the suppressed polarization mode of the free-running 1550 nm-VCSEL. With the aid of double optical feedback, the linewidth of the obtained microwave can be narrowed. In this work, firstly, the feasibility of microwave generation based on parallel-polarized optically injected 1550 nm-VCSEL is analyzed theoretically by using the spin-flip model. Next, a corresponding experimental system is constructed, and the performance of microwave generation is preliminarily investigated experi-mentally. The experimental results show that 30 GHz microwave signals could be obtained based on a parallel-polarized, optically injected 1550 nm-VCSEL under suitable injection parameters, but the linewidth of microwave signal is relatively wide (hundreds

  8. 山东济宁杨营煤矿工业广场新近系砂层水井回灌量分析%Yangying Coalmine Surface Installation Area Neogene Sand Layer Wells Recharge Rate Analysis in Jining, Shandong

    Institute of Scientific and Technical Information of China (English)

    田立强; 范士彦; 许京丰; 王红梅

    2015-01-01

    The Yangying coalmine is intended to use water-source heat pump air-conditioning system to substitute traditional heating and air-conditioning facilities. To satisfy water-source heat pump air-conditioning system outdoor ground source heat exchange design requirements, need to determine hydrostatic and hydrodynamic unpressurized recharging effects, number of pumping and recharging wells and intervals between them. Through Yangying coalmine surface installation area Neogene sand layer water-bearing characteris-tics and Neogene deep well pumping and recharging tests, carried out hydrostatic and hydrodynamic unpressurized recharging compari-son have found that the effect of hydrodynamic unpressurized recharging is better with larger recharge rate and recharging ratio can be 67%as high. Thus determined the total recharging wells layout:according to system required water amount, using proportion of pump-ing, recharging wells 1:2 or 2:3 to set well numbers, and interval between wells not less than 75m.%杨营煤矿拟采用水源热泵空调系统替代传统的取暖、空调设施.为满足水源热泵空调系统室外地能换热系统设计的需要,需确定静水和动水无压回灌的效果,抽水井、回灌井的数量和间距.通过对杨营煤矿工业广场新生界砂层含水特征及新近系深水井的抽水和回灌试验,进行了静水和动水无压回灌的比较,发现动水无压回灌的效果较好,回灌量较大,回灌比达67%,从而确定了实现全部回灌的井群布置方式:根据系统需水量大小,采用抽水井、回灌井为1:2或2:3的比例设置水井数量,井间距不小于75 m.

  9. Rates of Gravel Dispersion

    Science.gov (United States)

    Haschenburger, J. K.

    2010-12-01

    Sediment transfers in gravel-bed rivers involve the three-dimensional dispersion of mixed size sediment. From a kinematics standpoint, few studies are available to inform on the streamwise and vertical rates of sediment dispersion in natural channels. This research uses a gravel tracing program to quantify dispersion rates over 19 flood seasons. Empirical observations come from Carnation Creek, a small gravel-bed river with large woody debris located on the west coast of Vancouver Island, Canada. Frequent floods and the relatively limited armor layer facilitate streambed activity and relatively high bedload transport rates, typically under partial sediment transport conditions. Over 2500 magnetically tagged stones, ranging in size from 16 to 180 mm, were deployed on the bed surface between 1989 and 1992 in four generations. To quantify gravel dispersion over distances up to 2.6 km, observations are taken from 11 recoveries. Over 280 floods capable of moving bedload occurred during this period, with five exceeding the estimated bankfull discharge. Streamwise dispersion is quantified by virtual velocity, while dispersion into the streambed is quantified by a vertical burial rate. The temporal trend in streamwise dispersion rates is described by a power function. Initial virtual velocities decline rapidly from around 1.4 m/hr to approach an asymptote value of about 0.2 m/hr. The rapid change corresponds to a significant increase in the proportion of buried tracers due to vertical mixing. Initial burial rates reflect the magnitude of the first flood after tracer deployment and range from 0.07 to 0.46 cm/hr depending on tracer generation. Burial rates converge to about 0.06 cm/hr after the fourth flood season and then gradually decline to about 0.01 cm/hr. Thus, the rate of streamwise dispersion exceeds that of vertical dispersion by three orders of magnitude when the movement of sediment routinely activated by floods is considered.

  10. Driven spin transitions in fluorinated single- and bilayer-graphene quantum dots

    Science.gov (United States)

    Żebrowski, D. P.; Peeters, F. M.; Szafran, B.

    2017-06-01

    Spin transitions driven by a periodically varying electric potential in dilute fluorinated graphene quantum dots are investigated. Flakes of monolayer graphene as well as electrostatic electron traps induced in bilayer graphene are considered. The stationary states obtained within the tight-binding approach are used as the basis for description of the system dynamics. The dilute fluorination of the top layer lifts the valley degeneracy of the confined states and attenuates the orbital magnetic dipole moments due to current circulation within the flake. The spin-orbit coupling introduced by the surface deformation of the top layer induced by the adatoms allows the spin flips to be driven by the AC electric field. For the bilayer quantum dots the spin flip times is substantially shorter than the spin relaxation. Dynamical effects including many-photon and multilevel transitions are also discussed.

  11. Residual entropy and simulated annealing

    OpenAIRE

    Ettelaie, R.; Moore, M. A.

    1985-01-01

    Determining the residual entropy in the simulated annealing approach to optimization is shown to provide useful information on the true ground state energy. The one-dimensional Ising spin glass is studied to exemplify the procedure and in this case the residual entropy is related to the number of one-spin flip stable metastable states. The residual entropy decreases to zero only logarithmically slowly with the inverse cooling rate.

  12. Rate type isotach compaction of consolidated sandstone

    NARCIS (Netherlands)

    Waal, J.A. de; Thienen-Visser, K. van; Pruiksma, J.P.

    2015-01-01

    Laboratory experiments on samples from a consolidated sandstone reservoir are presented that demonstrate rate type compaction behaviour similar to that observed on unconsolidated sands and soils. Such rate type behaviour can have large consequences for reservoir compaction, surface subsidence and

  13. Comparative study of the surface layer density of liquid surfaces

    Science.gov (United States)

    Chacón, E.; Fernández, E. M.; Duque, D.; Delgado-Buscalioni, R.; Tarazona, P.

    2009-11-01

    Capillary wave fluctuations blur the inherent structure of liquid surfaces in computer simulations. The intrinsic sampling method subtracts capillary wave fluctuations and yields the intrinsic surface structure, leading to a generic picture of the liquid surface. The most relevant magnitude of the method is the surface layer density ns that may be consistently determined from different properties: the layering structure of the intrinsic density profiles, the turnover rate for surface layer particles, and the hydrodynamic damping rate of capillary waves. The good agreement among these procedures provides evidence for the physical consistency of the surface layering hypothesis, as an inherent physical property of the liquid surfaces. The dependence of the surface compactness, roughness, and exchange rate with temperature is analyzed for several molecular interaction models.

  14. Explosive Phase Transition in a Majority-Vote Model with Inertia

    CERN Document Server

    Chen, Hanshuang; Zhang, Haifeng; Li, Guofeng; Hou, Zhonghuai; Kurths, Jürgen

    2016-01-01

    We generalize the original majority-vote model by incorporating an inertia into the microscopic dynamics of the spin flipping, where the spin-flip probability of any individual depends not only on the states of its neighbors, but also on its own state. Surprisingly, the order-disorder phase transition is changed from a usual continuous type to a discontinuous or an explosive one when the inertia is above an appropriate level. A central feature of such an explosive transition is a strong hysteresis behavior as noise intensity goes forward and backward. Within the hysteresis region, a disordered phase and two symmetric ordered phases are coexisting and transition rates between these phases are numerically calculated by a rare-event sampling method. A mean-field theory is developed to analytically reveal the property of this phase transition.

  15. Calendar year 1993 groundwater quality report for the Bear Creek Hydrogeologic Regime, Y-12 Plant, Oak Ridge, Tennessee. 1993 groundwater and surface water quality data and calculated rate of contaminant migration, Part 1

    Energy Technology Data Exchange (ETDEWEB)

    1994-02-01

    This report contains groundwater and surface-water quality data obtained during the 1993 calendar year (CY) at several hazardous and non-hazardous waste-management facilities associated with the US Department of Energy (DOE) Y-12 Plant located on the DOE Oak ridge Reservation (ORR) southeast of Oak Ridge, Tennessee. These sites are located southwest of the Y-12 Plant complex within the Bear Creek Hydrogeologic Regime (Bear Creek Regime), which is one of three regimes defined for the purposes of groundwater and surface-water quality monitoring at the Y-12 Plant. The Environmental Management Department of the Y-12 Plant Health, Safety, Environment, and Accountability (HSEA) Organization manages the monitoring activities in each regime as part of the Y-12 Plant Groundwater Protection Program (GWPP). The annual groundwater and surface water report for the Bear Creek Regime is completed in two-parts; Part 1 (this report) containing the groundwater and surface-water quality data and Part 2 containing a detailed evaluation of the data. The primary purpose of this report is to serve as a reference for the groundwater and surface-water quality data obtained each year under the lead of the Y-12 Plant GWPP. However, because it contains information needed to comply with Resource Conservation and Recovery Act (RCRA) interim status assessment monitoring reporting requirements, this report is submitted to the Tennessee Department of Health and Environment (TDEC) by the RCRA reporting deadline.

  16. Anodized dental implant surface

    Directory of Open Access Journals (Sweden)

    Sunil Kumar Mishra

    2017-01-01

    Full Text Available Purpose: Anodized implants with moderately rough surface were introduced around 2000. Whether these implants enhanced biologic effect to improve the environment for better osseointegration was unclear. The purpose of this article was to review the literature available on anodized surface in terms of their clinical success rate and bone response in patients till now. Materials and Methods: A broad electronic search of MEDLINE and PubMed databases was performed. A focus was made on peer-reviewed dental journals. Only articles related to anodized implants were included. Both animal and human studies were included. Results: The initial search of articles resulted in 581 articles on anodized implants. The initial screening of titles and abstracts resulted in 112 full-text papers; 40 animal studies, 16 studies on cell adhesion and bacterial adhesion onto anodized surfaced implants, and 47 human studies were included. Nine studies, which do not fulfill the inclusion criteria, were excluded. Conclusions: The long-term studies on anodized surface implants do favor the surface, but in most of the studies, anodized surface is compared with that of machined surface, but not with other surfaces commercially available. Anodized surface in terms of clinical success rate in cases of compromised bone and immediately extracted sockets has shown favorable success.

  17. Anodized dental implant surface.

    Science.gov (United States)

    Mishra, Sunil Kumar; Kumar, Muktadar Anand; Chowdhary, Ramesh

    2017-01-01

    Anodized implants with moderately rough surface were introduced around 2000. Whether these implants enhanced biologic effect to improve the environment for better osseointegration was unclear. The purpose of this article was to review the literature available on anodized surface in terms of their clinical success rate and bone response in patients till now. A broad electronic search of MEDLINE and PubMed databases was performed. A focus was made on peer-reviewed dental journals. Only articles related to anodized implants were included. Both animal and human studies were included. The initial search of articles resulted in 581 articles on anodized implants. The initial screening of titles and abstracts resulted in 112 full-text papers; 40 animal studies, 16 studies on cell adhesion and bacterial adhesion onto anodized surfaced implants, and 47 human studies were included. Nine studies, which do not fulfill the inclusion criteria, were excluded. The long-term studies on anodized surface implants do favor the surface, but in most of the studies, anodized surface is compared with that of machined surface, but not with other surfaces commercially available. Anodized surface in terms of clinical success rate in cases of compromised bone and immediately extracted sockets has shown favorable success.

  18. 10-year survival rate and the incidence of peri-implant disease of 374 titanium dental implants with a SLA surface: a prospective cohort study in 177 fully and partially edentulous patients

    NARCIS (Netherlands)

    van Velzen, F.J.J.; Ofec, R.; Schulten, E.A.J.M.; ten Bruggenkate, C.M.

    2015-01-01

    Purpose This prospective cohort study evaluates the 10-year survival and incidence of peri-implant disease at implant and patient level of sandblasted, large grid, and acid-etched titanium dental implants (Straumann, soft tissue level, SLA surface) in fully and partially edentulous patients.

  19. Surface-active ionic liquids in micellar catalysis: impact of anion selection on reaction rates in nucleophilic substitutions† †Electronic supplementary information (ESI) available: Formulae for calculating aggregation parameters and fitting of kinetic constants and copies of NMR spectra. See DOI: 10.1039/c6cp00493h Click here for additional data file.

    Science.gov (United States)

    Cognigni, Alice; Gaertner, Peter; Zirbs, Ronald; Peterlik, Herwig; Prochazka, Katharina; Schröder, Christian

    2016-01-01

    A series of surface-active ionic liquids based on the 1-dodecyl-3-methylimidazolium cation and different anions such as halides and alkylsulfates was synthesized. The aggregation behavior of these ionic liquids in water was characterized by surface tension, conductivity measurements and UV-Vis spectroscopy in order to determine the critical micelle concentration (CMC) and to provide aggregation parameters. The determination of surface activity and aggregation properties of amphiphilic ionic liquids was accompanied by SAXS studies on selected surface-active ionic liquids. The application of these surface-active ionic liquids with different anions was tested in nucleophilic substitution reactions for the degradation of organophosphorus compounds. Kinetic studies via UV-Vis spectrophotometry showed a strong acceleration of the reaction in the micellar system compared to pure water. In addition, an influence of the anion was observed, resulting in a correlation between the anion binding to the micelle and the reaction rate constants, indicating that the careful choice of the surface-active ionic liquid can considerably affect the outcome of reactions. PMID:27121134

  20. Superamphiphobic Surfaces

    NARCIS (Netherlands)

    Cavalli, A.; Mugele, F.; Brutin, David

    2015-01-01

    This chapter discusses recent trends in the development, fabrication, and characterization of superamphiphobic surfaces. An amphiphobic surface repels both polar liquids, such as water, and nonpolar (oily) liquids, and has therefore useful technological application in microfluidics devices, protecti

  1. Rumble surfaces

    CSIR Research Space (South Africa)

    National Institute for Transport and Road

    1977-01-01

    Full Text Available Rumble surfaces are intermittent short lengths of coarse-textured road surfacings on which vehicle tyres produce a rumbling sound. used in conjunction with appropriate roadsigns and markings, they can reduce accidents on rural roads by alerting...

  2. Surface analysis.

    Science.gov (United States)

    Kinsella, T

    2006-10-01

    Surface analysis techniques are important tools to use in the verification of surface cleanliness and medical device functionality. How these techniques can be employed and some example applications are described.

  3. Exploring the critical dependence of adsorption of various dyes on the degradation rate using Ln{sup 3+}-TiO{sub 2} surface under UV/solar light

    Energy Technology Data Exchange (ETDEWEB)

    Devi, L. Gomathi, E-mail: gomatidevi_naik@yahoo.co.in [Department of Post Graduate Studies in Chemistry, Central College City Campus, Dr. Ambedkar Street, Bangalore University, Bangalore 560001 (India); Kumar, S. Girish [Department of Post Graduate Studies in Chemistry, Central College City Campus, Dr. Ambedkar Street, Bangalore University, Bangalore 560001 (India)

    2012-11-15

    Graphical abstract: The surface reactive acidic sites enhances on doping with rare earth ions which facilitates efficient adsorption of the dye molecules on the catalyst surface. In addition, the nature of the dopant, its concentration and electronic configuration additionally contributes to the overall efficiency. Highlights: Black-Right-Pointing-Pointer The degradation of structurally different anionic dyes under different pH conditions is reported. Black-Right-Pointing-Pointer Pre adsorption of pollutant on catalyst surface is vital for efficient photocatalysis. Black-Right-Pointing-Pointer Adsorption of dye on the catalyst surface depends on the substituent's attached to it. Black-Right-Pointing-Pointer The dopant with half filled electronic configuration served as shallow traps for charge carriers. - Abstract: The degradation of structurally different anionic dyes like Alizarin Red S (ARS) Amaranth (AR), Brilliant Yellow (BY), Congo Red (CR), Fast Red (FR), Methyl Orange (MO), and Methyl Red (MR) were carried out using Ln{sup 3+} (Ln{sup 3+} = La{sup 3+}, Ce{sup 3+} and Gd{sup 3+}) doped TiO{sub 2} at different pH conditions under UV/solar light. All the anionic dyes underwent rapid degradation at acidic pH, while resisted at alkaline conditions due to the adsorptive tendency of these dyes on the catalyst surface at different pH conditions. Gd{sup 3+} (0.15 mol%)-TiO{sub 2} exhibited better activity compared to other photocatalyst ascribed to half filled electronic configuration of Gd{sup 3+} ions. It is proposed that Ln{sup 3+} serves only as charge carrier traps under UV light, while it also act as visible light sensitizers under solar light. Irrespective of the catalyst and excitation source, the dye degradation followed the order: AR > FR > MO > MR > ARS > BY > CR. The results suggest that pre-adsorption of the pollutant is vital for efficient photocatalysis which is dependent on the nature of the substituent's group attached to the dye molecule.

  4. Surface Mediated Photocatalysis.

    Science.gov (United States)

    1987-12-01

    Bipolar Photoelectrodes," M.A. Fox, Nouv. J. Chim. 1987, II, 129. 4. "Effect of Cosolvent Additives on Relative Rates of Photooxidation on...Semiconductor Surfaces," D.D. Sackett, M.A. Fox, J. Phys. Org. Chem, 19_8, in press. 5. "Selectivity in the Semiconductor-Mediated Photooxidation of Polyols ...surfaced properties of the heteropolytungstates were varied. The conceptual mechanistic picture involved in the heteropolyoxo induced photooxidations

  5. Optical pumping and population transfer of nuclear-spin states of caesium atoms in high magnetic fields

    Institute of Scientific and Technical Information of China (English)

    Luo Jun; Sun Xian-Ping; Zeng Xi-Zhi; Zhan Ming-Sheng

    2007-01-01

    Nuclear-spin states of gaseous-state Cs atoms in the ground state are optically manipulated using a Ti:sapphire laser in a magnetic field of 1.516 T, in which optical coupling of the nuclear-spin states is achieved through hyperfine interactions between electrons and nuclei. The steady-state population distribution in the hyperfine Zeeman sublevels of the ground state is detected by using a tunable diode laser. Furthermore, the state population transfer among the of Cs in the ground state due to stochastic collisions between Cs atoms and buffer-gas molecules, is studied at different of the hyperfine interaction can strongly cause the state population transfer and spin-state interchange among the hyperfine Zeeman sublevels. The calculated results maybe explain the steady-state population in hyperfine Zeeman sublevels in terms of rates of optical-pumping, electron-spin flip, nuclear spin flip, and electron-nuclear spin flip-flop transitions among the hyperfine Zeeman sublevels of the ground state of Cs atoms. This method may be applied to the nuclear-spin-based solid-state quantum computation.

  6. Surface reconstructions

    CERN Document Server

    Fisher, David J

    2009-01-01

    It is well-known, even at the most elementary level of scientific knowledge, that free surfaces have properties which make them differ from the underlying bulk material. In the case of liquids, it is common knowledge - even among laymen - that the liquid surface acts as though it were a distinct skin-like material. At a slightly more advanced level, it is known that the liquid surface will seek to minimize its total surface energy by minimizing its surface area; thereby affecting its local vapor-pressure and adsorption behavior. In the case of solids too, it has long been known that different

  7. Surface chemistry

    CERN Document Server

    Desai, KR

    2008-01-01

    The surface Chemistry of a material as a whole is crucially dependent upon the Nature and type of surfaces exposed on crystallites. It is therefore vitally important to independently Study different, well - defined surfaces through surface analytical techniques. In addition to composition and structure of surface, the subject also provides information on dynamic light scattering, micro emulsions, colloid Stability control and nanostructures. The present book endeavour to bring before the reader that the understanding and exploitation of Solid state phenomena depended largely on the ability to

  8. Mapping the Cosmic Dawn

    Science.gov (United States)

    Furlanetto, Steven

    The following sections are included: * A Brief History of Our Universe: From Soup to Galaxies * The Hidden Cosmic Dawn * The Solution: Flipping Spins * The Spin-Flip Transition as an Astronomical Tool * Foiled!: Early Cosmology with the Spin-Flip Transition * Spin-Flip Radiation Holds the Key to Observing the Cosmic Dawn * The Spin-Flip Background: The First Stars * The Spin-Flip Background: The First Black Holes * The Spin-Flip Background: The Epoch of Reionization * FM Radio Antennae as Cosmic Observatories * Piles and Tiles of Antennae: Mapping the Spin-Flip Background * Mountains to Scale: Challenges to Observing the Spin-Flip Background * Sound and Fury, Signifying Statistics * An Explosion of Telescopes * Dreams for the Future * An Unfinished Story

  9. Glass dissolution rate measurement and calculation revisited

    Science.gov (United States)

    Fournier, Maxime; Ull, Aurélien; Nicoleau, Elodie; Inagaki, Yaohiro; Odorico, Michaël; Frugier, Pierre; Gin, Stéphane

    2016-08-01

    Aqueous dissolution rate measurements of nuclear glasses are a key step in the long-term behavior study of such waste forms. These rates are routinely normalized to the glass surface area in contact with solution, and experiments are very often carried out using crushed materials. Various methods have been implemented to determine the surface area of such glass powders, leading to differing values, with the notion of the reactive surface area of crushed glass remaining vague. In this study, around forty initial dissolution rate measurements were conducted following static and flow rate (SPFT, MCFT) measurement protocols at 90 °C, pH 10. The international reference glass (ISG), in the forms of powders with different particle sizes and polished monoliths, and soda-lime glass beads were examined. Although crushed glass grains clearly cannot be assimilated with spheres, it is when using the samples geometric surface (Sgeo) that the rates measured on powders are closest to those found for monoliths. Overestimation of the reactive surface when using the BET model (SBET) may be due to small physical features at the atomic scale-contributing to BET surface area but not to AFM surface area. Such features are very small compared with the thickness of water ingress in glass (a few hundred nanometers) and should not be considered in rate calculations. With a SBET/Sgeo ratio of 2.5 ± 0.2 for ISG powders, it is shown here that rates measured on powders and normalized to Sgeo should be divided by 1.3 and rates normalized to SBET should be multiplied by 1.9 in order to be compared with rates measured on a monolith. The use of glass beads indicates that the geometric surface gives a good estimation of glass reactive surface if sample geometry can be precisely described. Although data clearly shows the repeatability of measurements, results must be given with a high uncertainty of approximately ±25%.

  10. Spherical Surfaces

    DEFF Research Database (Denmark)

    Brander, David

    2015-01-01

    We study surfaces of constant positive Gauss curvature in Euclidean 3-space via the harmonicity of the Gauss map. Using the loop group representation, we solve the regular and the singular geometric Cauchy problems for these surfaces, and use these solutions to compute several new examples. We gi...

  11. Superhydrophobic surfaces

    Science.gov (United States)

    Wang, Evelyn N; McCarthy, Matthew; Enright, Ryan; Culver, James N; Gerasopoulos, Konstantinos; Ghodssi, Reza

    2015-03-24

    Surfaces having a hierarchical structure--having features of both microscale and nanoscale dimensions--can exhibit superhydrophobic properties and advantageous condensation and heat transfer properties. The hierarchical surfaces can be fabricated using biological nanostructures, such as viruses as a self-assembled nanoscale template.

  12. Rating Movies and Rating the Raters Who Rate Them

    OpenAIRE

    Zhou, Hua; Lange, Kenneth

    2009-01-01

    The movie distribution company Netflix has generated considerable buzz in the statistics community by offering a million dollar prize for improvements to its movie rating system. Among the statisticians and computer scientists who have disclosed their techniques, the emphasis has been on machine learning approaches. This article has the modest goal of discussing a simple model for movie rating and other forms of democratic rating. Because the model involves a large number of parameters, it is...

  13. Surface Protonics Promotes Catalysis

    Science.gov (United States)

    Manabe, R.; Okada, S.; Inagaki, R.; Oshima, K.; Ogo, S.; Sekine, Y.

    2016-12-01

    Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando-IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd-CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.

  14. Hemocompatibility of polymeric nanostructured surfaces.

    Science.gov (United States)

    Leszczak, Victoria; Smith, Barbara S; Popat, Ketul C

    2013-01-01

    Tissue integration is an important property when inducing transplant tolerance, however, the hemocompatibility of the biomaterial surface also plays an important role in the ultimate success of the implant. Therefore, in order to induce transplant tolerance, it is critical to understand the interaction of blood components with the material surfaces. In this study, we have investigated the adsorption of key blood serum proteins, in vitro adhesion and activation of platelets and clotting kinetics of whole blood on flat polycaprolactone (PCL) surfaces, nanowire (NW) surfaces and nanofiber (NF) surfaces. Previous studies have shown that polymeric nanostructured surfaces improve cell adhesion, proliferation and viability; however it is unclear how these polymeric nanostructured surfaces interact with the blood and its components. Protein adsorption results indicate that while there were no significant differences in total albumin (ALB) adsorption on PCL, NW and NF surfaces, NW surfaces had higher total fibrinogen (FIB) and immunoglobulin-G (IgG) adsorption compared to NF and PCL surfaces. In contrast, NF surfaces had higher surface FIB and IgG adsorption compared to PCL and NW surfaces. Platelet adhesion and viability studies show more adhesion and clustering of platelets on the NF surfaces as compared to PCL and NW surfaces. Platelet activation studies reveal that NW surfaces have the highest percentage of unactivated platelets, whereas NF surfaces have the highest percentage of fully activated platelets. Whole blood clotting results indicate that NW surfaces maintain an increased amount of free hemoglobin during the clotting process compared to PCL and NF surface, indicating less clotting and slower rate of clotting on their surfaces.

  15. Recent deformation rates on Venus

    Science.gov (United States)

    Grimm, Robert E.

    1994-11-01

    Constraints on the recent geological evolution of Venus may be provided by quantitative estimates of the rates of the principal resurfacing processes, volcanism and tectonism. This paper focuses on the latter, using impact craters as strain indicators. The total postimpact tectonic strain lies in the range 0.5-6.5%, which defines a recent mean strain rate of 10-18-10-17/s when divided by the mean surface age. Interpretation of the cratering record as one of pure production requires a decline in resurfacing rates at about 500 Ma (catastrophic resurfacing model). If distributed tectonic resurfacing contributed strongly before that time, as suggested by the widespread occurrence of tessera as inliers, the mean global strain rate must have been at least approximately 10-15/s, which is also typical of terrestrial active margins. Numerical calculations of the response of the lithosphere to inferred mantle convective forces were performed to test the hypothesis that a decrease in surface strain rate by at least two orders of magnitude could be caused by a steady decline in heat flow over the last billion years. Parameterized convection models predict that the mean global thermal gradient decreases by only about 5 K/km over this time; even with the exponential dependence of viscosity upon temperature, the surface strain rate drops by little more than one order of magnitude. Strongly unsteady cooling and very low thermal gradients today are necessary to satisfy the catastrophic model. An alternative, uniformitarian resurfacing hypothesis holds that Venus is resurfaced in quasi-random 'patches' several hundred kilometers in size that occur in response to changing mantle convection patterns.

  16. Surface boxplots

    KAUST Repository

    Genton, Marc G.

    2014-01-22

    In this paper, we introduce a surface boxplot as a tool for visualization and exploratory analysis of samples of images. First, we use the notion of volume depth to order the images viewed as surfaces. In particular, we define the median image. We use an exact and fast algorithm for the ranking of the images. This allows us to detect potential outlying images that often contain interesting features not present in most of the images. Second, we build a graphical tool to visualize the surface boxplot and its various characteristics. A graph and histogram of the volume depth values allow us to identify images of interest. The code is available in the supporting information of this paper. We apply our surface boxplot to a sample of brain images and to a sample of climate model outputs.

  17. Glass dissolution rate measurement and calculation revisited

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, Maxime, E-mail: maxime.fournier@cea.fr [CEA, DEN, DTCD, SECM, F-30207, Bagnols sur Cèze (France); Ull, Aurélien; Nicoleau, Elodie [CEA, DEN, DTCD, SECM, F-30207, Bagnols sur Cèze (France); Inagaki, Yaohiro [Department of Applied Quantum Physics & Nuclear Engineering, Kyushu University, Fukuoka, 819-0395 (Japan); Odorico, Michaël [ICSM-UMR5257 CEA/CNRS/UM2/ENSCM, Site de Marcoule, BP17171, F-30207, Bagnols sur Cèze (France); Frugier, Pierre; Gin, Stéphane [CEA, DEN, DTCD, SECM, F-30207, Bagnols sur Cèze (France)

    2016-08-01

    Aqueous dissolution rate measurements of nuclear glasses are a key step in the long-term behavior study of such waste forms. These rates are routinely normalized to the glass surface area in contact with solution, and experiments are very often carried out using crushed materials. Various methods have been implemented to determine the surface area of such glass powders, leading to differing values, with the notion of the reactive surface area of crushed glass remaining vague. In this study, around forty initial dissolution rate measurements were conducted following static and flow rate (SPFT, MCFT) measurement protocols at 90 °C, pH 10. The international reference glass (ISG), in the forms of powders with different particle sizes and polished monoliths, and soda-lime glass beads were examined. Although crushed glass grains clearly cannot be assimilated with spheres, it is when using the samples geometric surface (S{sub geo}) that the rates measured on powders are closest to those found for monoliths. Overestimation of the reactive surface when using the BET model (S{sub BET}) may be due to small physical features at the atomic scale—contributing to BET surface area but not to AFM surface area. Such features are very small compared with the thickness of water ingress in glass (a few hundred nanometers) and should not be considered in rate calculations. With a S{sub BET}/S{sub geo} ratio of 2.5 ± 0.2 for ISG powders, it is shown here that rates measured on powders and normalized to S{sub geo} should be divided by 1.3 and rates normalized to S{sub BET} should be multiplied by 1.9 in order to be compared with rates measured on a monolith. The use of glass beads indicates that the geometric surface gives a good estimation of glass reactive surface if sample geometry can be precisely described. Although data clearly shows the repeatability of measurements, results must be given with a high uncertainty of approximately ±25%. - Highlights: • Initial dissolution

  18. Surface phonons

    CERN Document Server

    Wette, Frederik

    1991-01-01

    In recent years substantial progress has been made in the detection of surface phonons owing to considerable improvements in inelastic rare gas scattering tech­ niques and electron energy loss spectroscopy. With these methods it has become possible to measure surface vibrations in a wide energy range for all wave vectors in the two-dimensional Brillouin zone and thus to deduce the complete surface phonon dispersion curves. Inelastic atomic beam scattering and electron energy loss spectroscopy have started to play a role in the study of surface phonons similar to the one played by inelastic neutron scattering in the investigation of bulk phonons in the last thirty years. Detailed comparison between experimen­ tal results and theoretical studies of inelastic surface scattering and of surface phonons has now become feasible. It is therefore possible to test and to improve the details of interaction models which have been worked out theoretically in the last few decades. At this point we felt that a concise, co...

  19. Role of surface temperature in fluorocarbon plasma-surface interactions

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Caleb T.; Overzet, Lawrence J.; Goeckner, Matthew J. [Department of Electrical Engineering, University of Texas at Dallas, PO Box 830688, Richardson, TX 75083 (United States)

    2012-07-15

    This article examines plasma-surface reaction channels and the effect of surface temperature on the magnitude of those channels. Neutral species CF{sub 4}, C{sub 2}F{sub 6}, and C{sub 3}F{sub 8} are produced on surfaces. The magnitude of the production channel increases with surface temperature for all species, but favors higher mass species as the temperature is elevated. Additionally, the production rate of CF{sub 2} increases by a factor of 5 as the surface temperature is raised from 25 Degree-Sign C to 200 Degree-Sign C. Fluorine density, on the other hand, does not change as a function of either surface temperature or position outside of the plasma glow. This indicates that fluorine addition in the gas-phase is not a dominant reaction. Heating reactors can result in higher densities of depositing radical species, resulting in increased deposition rates on cooled substrates. Finally, the sticking probability of the depositing free radical species does not change as a function of surface temperature. Instead, the surface temperature acts together with an etchant species (possibly fluorine) to elevate desorption rates on that surface at temperatures lower than those required for unassisted thermal desorption.

  20. Surface micropattern limits bacterial contamination

    OpenAIRE

    Mann, Ethan E.; Manna, Dipankar; Mettetal, Michael R; May, Rhea M.; Dannemiller, Elisa M; Chung, Kenneth K.; Brennan, Anthony B; Reddy, Shravanthi T

    2014-01-01

    Background Bacterial surface contamination contributes to transmission of nosocomial infections. Chemical cleansers used to control surface contamination are often toxic and incorrectly implemented. Additional non-toxic strategies should be combined with regular cleanings to mitigate risks of human error and further decrease rates of nosocomial infections. The Sharklet micropattern (MP), inspired by shark skin, is an effective tool for reducing bacterial load on surfaces without toxic additiv...

  1. Raters & Rating Scales.

    Science.gov (United States)

    Lopez, Winifred A.; Stone, Mark H.

    1998-01-01

    The first article in this section, "Rating Scales and Shared Meaning," by Winifred A. Lopez, discusses the analysis of rating scale data. The second article, "Rating Scale Categories: Dichotomy, Double Dichotomy, and the Number Two," by Mark H. Stone, argues that dichotomies in rating scales are more useful than multiple ratings. (SLD)

  2. Real Property Tax Rates

    Data.gov (United States)

    Montgomery County of Maryland — The Levy Year 2012 real property tax rate dataset reflects all the rates per $100 set each year by the County Council. These rates are applied to the assessed value...

  3. Calculating transient rates from surveys

    CERN Document Server

    Carbone, Dario; Wijers, Ralph A M J; Rowlinson, Antonia

    2016-01-01

    We have developed a method to determine the transient surface density and transient rate for any given survey, using Monte-Carlo simulations. This method allows us to determine the transient rate as a function of both the flux and the duration of the transients in the whole flux-duration plane rather than one or a few points as currently available methods do. It is applicable to every survey strategy that is monitoring the same part of the sky, regardless the instrument or wavelength of the survey, or the target sources. We have simulated both top-hat and Fast Rise Exponential Decay light curves, highlighting how the shape of the light curve might affect the detectability of transients. Another application for this method is to estimate the number of transients of a given kind that are expected to be detected by a survey, provided that their rate is known.

  4. Calculating transient rates from surveys

    Science.gov (United States)

    Carbone, D.; van der Horst, A. J.; Wijers, R. A. M. J.; Rowlinson, A.

    2017-03-01

    We have developed a method to determine the transient surface density and transient rate for any given survey, using Monte Carlo simulations. This method allows us to determine the transient rate as a function of both the flux and the duration of the transients in the whole flux-duration plane rather than one or a few points as currently available methods do. It is applicable to every survey strategy that is monitoring the same part of the sky, regardless the instrument or wavelength of the survey, or the target sources. We have simulated both top-hat and Fast Rise Exponential Decay light curves, highlighting how the shape of the light curve might affect the detectability of transients. Another application for this method is to estimate the number of transients of a given kind that are expected to be detected by a survey, provided that their rate is known.

  5. Surfacing Moves

    DEFF Research Database (Denmark)

    Lutz, Peter

    2013-01-01

    such as schedules, machines, and aging bodies. To this end, the article also experiments with ‘surfacing’ as an ethnographic heuristic for figuring these different ‘spatial-timings’. The article concludes that surfacing matters not only in senior home care but also in the field-desks of ethnographic analysis....

  6. Attack surfaces

    DEFF Research Database (Denmark)

    Gruschka, Nils; Jensen, Meiko

    2010-01-01

    The new paradigm of cloud computing poses severe security risks to its adopters. In order to cope with these risks, appropriate taxonomies and classification criteria for attacks on cloud computing are required. In this work-in-progress paper we present one such taxonomy based on the notion...... of attack surfaces of the cloud computing scenario participants. © 2010 IEEE....

  7. Surfacing Moves

    DEFF Research Database (Denmark)

    Lutz, Peter

    2013-01-01

    such as schedules, machines, and aging bodies. To this end, the article also experiments with ‘surfacing’ as an ethnographic heuristic for figuring these different ‘spatial-timings’. The article concludes that surfacing matters not only in senior home care but also in the field-desks of ethnographic analysis....

  8. Rating Movies and Rating the Raters Who Rate Them.

    Science.gov (United States)

    Zhou, Hua; Lange, Kenneth

    2009-11-01

    The movie distribution company Netflix has generated considerable buzz in the statistics community by offering a million dollar prize for improvements to its movie rating system. Among the statisticians and computer scientists who have disclosed their techniques, the emphasis has been on machine learning approaches. This article has the modest goal of discussing a simple model for movie rating and other forms of democratic rating. Because the model involves a large number of parameters, it is nontrivial to carry out maximum likelihood estimation. Here we derive a straightforward EM algorithm from the perspective of the more general MM algorithm. The algorithm is capable of finding the global maximum on a likelihood landscape littered with inferior modes. We apply two variants of the model to a dataset from the MovieLens archive and compare their results. Our model identifies quirky raters, redefines the raw rankings, and permits imputation of missing ratings. The model is intended to stimulate discussion and development of better theory rather than to win the prize. It has the added benefit of introducing readers to some of the issues connected with analyzing high-dimensional data.

  9. Surface charge migration and dc surface flashover of surface-modified epoxy-based insulators

    Science.gov (United States)

    Li, Chuanyang; Hu, Jun; Lin, Chuanjie; Zhang, Boya; Zhang, Guixin; He, Jinliang

    2017-02-01

    Epoxy-based model insulators were manufactured and fluorinated under a F2/N2 mixture (12.5% F2) at 50 °C and 0.1 MPa for 15 min and 60 min. Surface charge accumulation and decay behavior were studied with and without dc voltage application. The effect of direct fluorination on surface charge migration as well as on flashover voltage was verified. The obtained results show that the charge decay of epoxy-based insulators is a slow process, but the decay rate increases when an outer dc electric field is applied. The surface charge distribution is changed when a streamer is triggered on the insulator surface. The existence of heteropolarity surface charges can decrease the dc surface flashover voltage to some extent, while the surface flashover voltage is almost unchanged when charges of the same polarity accumulate on the insulator surface. The short time fluorinated insulator can modify the surface resistivity, and the rate of surface charge dissipation is greatly increased under a dc electric field.

  10. Interest rate derivatives

    DEFF Research Database (Denmark)

    Svenstrup, Mikkel

    This Ph.D. thesis consists of four self-contained essays on valuation of interest rate derivatives. In particular derivatives related to management of interest rate risk care are considered.......This Ph.D. thesis consists of four self-contained essays on valuation of interest rate derivatives. In particular derivatives related to management of interest rate risk care are considered....

  11. Effects of sedative music on anxiety, heart rates and skin-surface temperature in patients awaiting cardiac catheterization examination%镇静音乐对等待心导管检查患者焦虑水平与心率及皮肤温度的影响

    Institute of Scientific and Technical Information of China (English)

    周荣; 刘皇军; 金立军; 何小玲; 黄敏

    2012-01-01

    Objective To explore the effects of sedative music on-anxiety, heart rates and fingertip skin-surface temperature in patients awaiting cardiac catheterization examination. Methods Forty subjects scheduled for cardiac catheterization examination were commensurately and randomly assigned to two groups. The control group were given conventional care, while the music group additionally received sedative music: patients were asked to listen to their favorable music for 30 min with the music rhythm ranging from 40 to 60 beats/min. Results Heart rates and fingertip skin-surface temperature changed significantly at all time points after the intervention in both groups (P<0. 05,P<0. 01), with the changes being more noticeable in the music group (P<0. 05). Conclusion Sedative music applied to patients awaiting cardiac catheterization examination, can reduce anxiety and heart rates, and increase fingertip skin-surface temperature. It is a safe and effective intervention against anxiety.%目的 探讨镇静音乐对等待心导管检查患者焦虑水平、心率(HR)及指端皮肤温度(ST)的影响.方法 将40例行心导管检查的患者随机分为音乐组和对照组,各20例.对照组按常规护理;音乐组在此基础上采用镇静音乐疗法,即助患者从CD中选择自己喜欢的一种镇静音乐播放,音乐节奏为40~60次/min,持续30min.结果 两组干预后的HR与ST在每个时间点(T1~T6)均有明显改变(P<0.05,P<0.01),但音乐组效果更显著(P<0.05).结论 镇静音乐可显著降低等待心导管检查患者的焦虑水平,减慢HR及提高指端ST,是对抗焦虑安全、有效的干预措施.

  12. Describing Surfaces.

    Science.gov (United States)

    1985-01-01

    York. Do Carmo , Manfredo P, [1976], Differential Geometry of Curves and Surfaces, Prent- ice-Hall, Englewood Cliffs, NJ. Faugeras, 0. D., et. al, [1982...lightbulb. It is well-known (for exam~ple, do Carmo "" "..-’,.’.V .. .V...i ra I s ; ul ing-.. "’. Figure 11. The helicoid of a single blade. (Reproduced from [do Carmo 1976, Figure 2-27 Page 94]) where m and 1 are assumed

  13. Re-examining the Dissolution of Spent Fuel: A Comparison of Different Methods for Calculating Rates

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, B D; Stout, R B

    2004-04-09

    Dissolution rates for spent fuel have typically been reported in terms of a rate normalized to the surface area of the specimen. Recent evidence has shown that neither the geometric surface area nor that measured with BET accurately predicts the effective surface area of spent fuel. Dissolution rates calculated from results obtained by flowthrough tests were reexamined comparing the cumulative releases and surface area normalized rates. While initial surface area is important for comparison of different rates, it appears that normalizing to the surface area introduces unnecessary uncertainty compared to using cumulative or fractional release rates. Discrepancies in past data analyses are mitigated using this alternative method.

  14. Heart rate index

    DEFF Research Database (Denmark)

    Haedersdal, C; Pedersen, F H; Svendsen, J H

    1992-01-01

    The present study compares the variables assessed by standard exercise test with the left ventricular ejection fraction (LVEF) measured by multigated radionuclide angiocardiography (MUGA) in 77 patients early after myocardial infarction. The exercise test and MUGA were performed within two weeks...... after the myocardial infarction. A significant correlation (Spearman's correlation coefficient rs, p less than 0.05) was found between LVEF at rest and the following variables assessed at exercise test: 1) the heart rate at rest, 2) rise in heart rate, 3) ratio between maximal heart rate and heart rate...... at rest, 4) rise in systolic blood pressure, 5) rate pressure product at rest, 6) rise in rate pressure product, 7) ratio (rHR) between maximal rate pressure product and rate pressure product at rest, 8) total exercise time. The heart rate was corrected for effects caused by age (heart index (HR...

  15. The rating reliability calculator

    Directory of Open Access Journals (Sweden)

    Solomon David J

    2004-04-01

    Full Text Available Abstract Background Rating scales form an important means of gathering evaluation data. Since important decisions are often based on these evaluations, determining the reliability of rating data can be critical. Most commonly used methods of estimating reliability require a complete set of ratings i.e. every subject being rated must be rated by each judge. Over fifty years ago Ebel described an algorithm for estimating the reliability of ratings based on incomplete data. While his article has been widely cited over the years, software based on the algorithm is not readily available. This paper describes an easy-to-use Web-based utility for estimating the reliability of ratings based on incomplete data using Ebel's algorithm. Methods The program is available public use on our server and the source code is freely available under GNU General Public License. The utility is written in PHP, a common open source imbedded scripting language. The rating data can be entered in a convenient format on the user's personal computer that the program will upload to the server for calculating the reliability and other statistics describing the ratings. Results When the program is run it displays the reliability, number of subject rated, harmonic mean number of judges rating each subject, the mean and standard deviation of the averaged ratings per subject. The program also displays the mean, standard deviation and number of ratings for each subject rated. Additionally the program will estimate the reliability of an average of a number of ratings for each subject via the Spearman-Brown prophecy formula. Conclusion This simple web-based program provides a convenient means of estimating the reliability of rating data without the need to conduct special studies in order to provide complete rating data. I would welcome other researchers revising and enhancing the program.

  16. Rate Review Data

    Data.gov (United States)

    U.S. Department of Health & Human Services — As of September 1, 2011, the Affordable Care Act and rate review regulation require review of rate increases of 10 percent or more. A non-grandfathered health plan...

  17. Rating mutual funds

    DEFF Research Database (Denmark)

    Bechmann, Ken L.; Rangvid, Jesper

    obtained an annual risk-adjusted excess return that is approximately 3-4 percentage points higher per annum than if the funds with the highest costs had been invested in. We compare the atpRating with the Morningstar Rating. We show that one reason why the atpRating and the Morningstar Rating contain...... different information is that the returns Morningstar uses as inputs when rating funds are highly volatile whereas the costs the atpRating uses as inputs when rating funds are highly persistent. In other words, a fund that has low costs one year will most likely also have low costs the following year......, whereas the return of a fund in a certain year generally contains only little information about the future return that the fund will generate. Finally, we have information on the investments in different mutual funds made by a small subgroup of investors known to have been exposed to both the atpRating...

  18. Rating mutual funds

    DEFF Research Database (Denmark)

    Bechmann, Ken L.; Rangvid, Jesper

    2007-01-01

    obtained a risk-adjusted excess return that is approximately 3-4 percentage points higher per annum than if the funds with the highest costs had been invested in. We compare the atpRating with the Morningstar Rating. We show that one reason why the atpRating and the Morningstar Rating contain different...... information is that the returns Morningstar uses as inputs when rating funds are highly volatile whereas the costs the atpRating uses as inputs when rating funds are highly persistent. In other words, a fund that has low costs one year will most likely also have low costs the following year, whereas...... the return of a fund in a certain year generally contains only little information about the future return that the fund will generate. Finally, we have information on the investments in different mutual funds made by a small subgroup of investors known to have been exposed to both the atpRating...

  19. Glomerular filtration rate

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/007305.htm Glomerular filtration rate To use the sharing features on this page, please enable JavaScript. Glomerular filtration rate (GFR) is a test used to check ...

  20. Labor Force Participation Rate

    Data.gov (United States)

    City and County of Durham, North Carolina — This thematic map presents the labor force participation rate of working-age people in the United States in 2010. The 2010 Labor Force Participation Rate shows the...

  1. Fertility Clinic Success Rates

    Science.gov (United States)

    ... and Autism 2013 Assisted Reproductive Technology Fertility Clinic Success Rates Report Recommend on Facebook Tweet Share Compartir 2013 ART Fertility Clinic Success Rates Report [PDF - 1MB] Bookmarks and thumbnails are ...

  2. Understanding Interest Rate Volatility

    DEFF Research Database (Denmark)

    Volker, Desi

    This thesis is the result of my Ph.D. studies at the Department of Finance of the Copenhagen Business School. It consists of three essays covering topics related to the term structure of interest rates, monetary policy and interest rate volatility. The rst essay, \\Monetary Policy Uncertainty...... and Interest Rates", examines the role of monetary policy uncertainty on the term structure of interest rates. The second essay, \\A Regime-Switching A ne Term Structure Model with Stochastic Volatility" (co-authored with Sebastian Fux), investigates the ability of the class of regime switching models...... with and without stochastic volatility to capture the main stylized features of U.S. interest rates. The third essay, \\Variance Risk Premia in the Interest Rate Swap Market", investigates the time-series and cross-sectional properties of the compensation demanded for holding interest rate variance risk. The essays...

  3. Film boiling on vertical surfaces.

    Science.gov (United States)

    Suryanarayana, N. V.; Merte, H., Jr.

    1972-01-01

    Film boiling of a saturated liquid on a vertical surface is analyzed to determine the local heat-transfer rates as a function of height and heater-surface superheat. Experiments show that the laminar-flow model is inadequate. A turbulent-vapor-flow model is used, and the influence of the interfacial oscillations is incorporated on a semiempirical basis. Measurements of local film boiling were obtained with a transient technique using saturated liquid nitrogen.

  4. Interactive Display of Surfaces Using Subdivision Surfaces and Wavelets

    Energy Technology Data Exchange (ETDEWEB)

    Duchaineau, M A; Bertram, M; Porumbescu, S; Hamann, B; Joy, K I

    2001-10-03

    Complex surfaces and solids are produced by large-scale modeling and simulation activities in a variety of disciplines. Productive interaction with these simulations requires that these surfaces or solids be viewable at interactive rates--yet many of these surfaced solids can contain hundreds of millions of polygondpolyhedra. Interactive display of these objects requires compression techniques to minimize storage, and fast view-dependent triangulation techniques to drive the graphics hardware. In this paper, we review recent advances in subdivision-surface wavelet compression and optimization that can be used to provide a framework for both compression and triangulation. These techniques can be used to produce suitable approximations of complex surfaces of arbitrary topology, and can be used to determine suitable triangulations for display. The techniques can be used in a variety of applications in computer graphics, computer animation and visualization.

  5. Helical surface structures

    CERN Document Server

    Brandenburg, A; Brandenburg, Axel; Blackman, Eric G.

    2002-01-01

    Over the past few years there has been growing interest in helical magnetic field structures seen at the solar surface, in coronal mass ejections, as well as in the solar wind. Although there is a great deal of randomness in the data, on average the extended structures are mostly left-handed on the northern hemisphere and right-handed on the southern. Surface field structures are also classified as dextral (= right bearing) and sinistral (= left bearing) occurring preferentially in the northern and southern hemispheres respectively. Of particular interest here is a quantitative measurement of the associated emergence rates of helical structures, which translate to magnetic helicity fluxes. In this review, we give a brief survey of what has been found so far and what is expected based on models. Particular emphasis is put on the scale dependence of the associated fields and an attempt is made to estimate the helicity flux of the mean field vs. fluctuating field.

  6. Measuring zebrafish turning rate.

    Science.gov (United States)

    Mwaffo, Violet; Butail, Sachit; di Bernardo, Mario; Porfiri, Maurizio

    2015-06-01

    Zebrafish is becoming a popular animal model in preclinical research, and zebrafish turning rate has been proposed for the analysis of activity in several domains. The turning rate is often estimated from the trajectory of the fish centroid that is output by commercial or custom-made target tracking software run on overhead videos of fish swimming. However, the accuracy of such indirect methods with respect to the turning rate associated with changes in heading during zebrafish locomotion is largely untested. Here, we compare two indirect methods for the turning rate estimation using the centroid velocity or position data, with full shape tracking for three different video sampling rates. We use tracking data from the overhead video recorded at 60, 30, and 15 frames per second of zebrafish swimming in a shallow water tank. Statistical comparisons of absolute turning rate across methods and sampling rates indicate that, while indirect methods are indistinguishable from full shape tracking, the video sampling rate significantly influences the turning rate measurement. The results of this study can aid in the selection of the video capture frame rate, an experimental design parameter in zebrafish behavioral experiments where activity is an important measure.

  7. UV/Ozone Cleaning of Surfaces

    Science.gov (United States)

    1986-05-01

    clean surfaces under UV radiation maintained the surface cleanliness indefinitely. Duting the period 1974-1976, Vig et al.( 3 - 5 ) described a series of...probably no other device of which the performance is so critically dependent upon surface cleanliness . For example, the aging requirement for one 5 MHz...such a device changes the frequency by about one part in 106. The surface cleanliness must therefore be such that the rate of contamination transfer

  8. Supernova electron capture rates

    CERN Document Server

    Martínez-Pinedo, G

    1999-01-01

    We have calculated the Gamow-Teller strength distributions for the ground states and low lying states of several nuclei that play an important role in the precollapse evolution of supernova. The calculations reproduce the experimental GT distributions nicely. The GT distribution are used to calculate electron capture rates for typical presupernova conditions. The computed rates are noticeably smaller than the presently adopted rates. The possible implications for the supernova evolution are discussed.

  9. Long Maturity Forward Rates

    DEFF Research Database (Denmark)

    Christiansen, Charlotte

    2001-01-01

    The paper aims to improve the knowledge of the empirical properties of the long maturity region of the forward rate curve. Firstly, the theoretical negative correlation between the slope at the long end of the forward rate curve and the term structure variance is recovered empirically and found...... to be statistically significant. Secondly, the expectations hypothesis is analyzed for the long maturity region of the forward rate curve using "forward rate" regressions. The expectations hypothesis is numerically close to being accepted but is statistically rejected. The findings provide mixed support...

  10. Seeking Universal Credit Ratings

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Amid the EU’s ongoing sovereign debt crisis,the current international credit rating system has been accused of aggravating the world’s economic woes.Recently,Guan Jianzhong,Chairman of the Board and President of the Beijing-based Dagong Global Credit Rating Co.Ltd.,spoke to Beijing Review reporter Yu Yan about reforms in the current international credit rating system and Dagong’s role.Dagong is the first non-Western rating agency to assess the world’s sovereign credit and risks.

  11. Exchange rate regime choice

    Directory of Open Access Journals (Sweden)

    Beker Emilija

    2006-01-01

    Full Text Available The choice of an adequate exchange rate regime proves to be a highly sensitive field within which the economic authorities present and confirm themselves. The advantages and disadvantages of fixed and flexible exchange rate regimes, which have been quite relativized from the conventional point of view, together with simultaneous, but not synchronized effects of structural and external factors, remain permanently questioned throughout a complex process of exchange rate regime decision making. The paper reflects the attempt of critical identification of the key exchange rate performances with emphasis on continuous non-uniformity and (uncertainty of shelf life of a relevant choice.

  12. Reduced journal rates

    Science.gov (United States)

    Richman, Barbara T.

    The American Institute of Physics (AIP) offers reduced rates for subscriptions to its journals to individual members of affiliated societies, including AGU. The offer is limited to one subscription per person to each journal.Rates for 1985 for AGU members are listed below

  13. Surface imaging microscope

    Science.gov (United States)

    Rogala, Eric W.; Bankman, Isaac N.

    2008-04-01

    The three-dimensional shapes of microscopic objects are becoming increasingly important for battlespace CBRNE sensing. Potential applications of microscopic 3D shape observations include characterization of biological weapon particles and manufacturing of micromechanical components. Aerosol signatures of stand-off lidar systems, using elastic backscatter or polarization, are dictated by the aerosol particle shapes and sizes that must be well characterized in the lab. A low-cost, fast instrument for 3D surface shape microscopy will be a valuable point sensor for biological particle sensing applications. Both the cost and imaging durations of traditional techniques such as confocal microscopes, atomic force microscopes, and electron scanning microscopes are too high. We investigated the feasibility of a low-cost, fast interferometric technique for imaging the 3D surface shape of microscopic objects at frame rates limited only by the camera in the system. The system operates at two laser wavelengths producing two fringe images collected simultaneously by a digital camera, and a specialized algorithm we developed reconstructs the surface map of the microscopic object. The current implementation assembled to test the concept and develop the new 3D reconstruction algorithm has 0.25 micron resolution in the x and y directions, and about 0.1 micron accuracy in the z direction, as tested on a microscopic glass test object manufactured with etching techniques. We describe the interferometric instrument, present the reconstruction algorithm, and discuss further development.

  14. High Rate Performing Li-ion Battery

    Science.gov (United States)

    2015-02-09

    permeable to lithium ions and efficient in transferring the electrons into/from the LVP surface to the corresponding current collector. a) b) c) d) e...PO4)3/C for High Rate Lithium-ion Battery Applications”, Lee Hwang Sheng, Nail Suleimanov, Vishwanathan Ramar, Mangayarkarasi Murugan, Kuppan

  15. Surface texture metrology for high precision surfaces

    DEFF Research Database (Denmark)

    Hansen, Hans Nørgaard; Gasparin, Stefania; Tosello, Guido

    2010-01-01

    This paper introduces some of the challenges related to surface texture measurement of high precision surfaces. The paper is presenting two case studies related to polished tool surfaces and micro part surfaces. In both cases measuring instrumentation, measurement procedure and the measurement...

  16. Surface texture metrology for high precision surfaces

    DEFF Research Database (Denmark)

    Hansen, Hans Nørgaard; Gasparin, Stefania; Tosello, Guido

    2010-01-01

    This paper introduces some of the challenges related to surface texture measurement of high precision surfaces. The paper is presenting two case studies related to polished tool surfaces and micro part surfaces. In both cases measuring instrumentation, measurement procedure and the measurement re...

  17. 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.

  18. National ART Success Rates

    Science.gov (United States)

    ... ART and Birth Defects ART and Autism 2013 Assisted Reproductive Technology National Summary Report Recommend on Facebook Tweet Share ... live-birth rate? [PDF - 1.37MB] Section 2: ART Cycles using fresh nondonor eggs or embryos What ...

  19. Rate of Speed

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — Rate of spread was modeled using FlamMap, an interagency fire behavior mapping and analysis program that computes potential fire behavior characteristics. The tool...

  20. Rate of force development

    DEFF Research Database (Denmark)

    Maffiuletti, Nicola A; Aagaard, Per; Blazevich, Anthony J

    2016-01-01

    The evaluation of rate of force development during rapid contractions has recently become quite popular for characterising explosive strength of athletes, elderly individuals and patients. The main aims of this narrative review are to describe the neuromuscular determinants of rate of force...... development and to discuss various methodological considerations inherent to its evaluation for research and clinical purposes. Rate of force development (1) seems to be mainly determined by the capacity to produce maximal voluntary activation in the early phase of an explosive contraction (first 50-75 ms......), particularly as a result of increased motor unit discharge rate; (2) can be improved by both explosive-type and heavy-resistance strength training in different subject populations, mainly through an improvement in rapid muscle activation; (3) is quite difficult to evaluate in a valid and reliable way...

  1. Ventilation rates and health

    DEFF Research Database (Denmark)

    Sundell, Jan; Levin, H; Nazaroff, W W

    2011-01-01

    The scientific literature through 2005 on the effects of ventilation rates on health in indoor environments has been reviewed by a multidisciplinary group. The group judged 27 papers published in peer-reviewed scientific journals as providing sufficient information on both ventilation rates...... and health effects to inform the relationship. Consistency was found across multiple investigations and different epidemiologic designs for different populations. Multiple health endpoints show similar relationships with ventilation rate. There is biological plausibility for an association of health outcomes...... studies of the relationship between ventilation rates and health, especially in diverse climates, in locations with polluted outdoor air and in buildings other than offices. PRACTICAL IMPLICATIONS: Ventilation with outdoor air plays an important role influencing human exposures to indoor pollutants...

  2. Allegheny County Obesity Rates

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — Obesity rates for each Census Tract in Allegheny County were produced for the study “Developing small-area predictions for smoking and obesity prevalence in the...

  3. Allegheny County Smoking Rates

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — Smoking rates for each Census Tract in Allegheny County were produced for the study “Developing small-area predictions for smoking and obesity prevalence in the...

  4. Interest Rates and Inflation

    OpenAIRE

    Michael Coopersmith

    2011-01-01

    A relation between interest rates and inflation is presented using a two component economic model and a simple general principle. Preliminary results indicate a remarkable similarity to classical economic theories, in particular that of Wicksell.

  5. Litter Decomposition Rates, 2015

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set contains decomposition rates for litter of Salicornia pacifica, Distichlis spicata, and Deschampsia cespitosa buried at 7 tidal marsh sites in 2015....

  6. Debenture Interest Rates

    Data.gov (United States)

    Department of Housing and Urban Development — Interest rates to be paid on debentures issued with respect to a loan or mortgage insured by the Federal Housing Commissioner under the provisions of the National...

  7. Target Heart Rates

    Science.gov (United States)

    ... morning after you’ve had a good night’s sleep and before you get out of bed. According to the National Institute of Health, the average resting heart rate: for children 10 years and older, and adults ( ...

  8. Universal Sampling Rate Distortion

    OpenAIRE

    Boda, Vinay Praneeth; Narayan, Prakash

    2017-01-01

    We examine the coordinated and universal rate-efficient sampling of a subset of correlated discrete memoryless sources followed by lossy compression of the sampled sources. The goal is to reconstruct a predesignated subset of sources within a specified level of distortion. The combined sampling mechanism and rate distortion code are universal in that they are devised to perform robustly without exact knowledge of the underlying joint probability distribution of the sources. In Bayesian as wel...

  9. MODELING THE RATE-CONTROLLED SORPTION OF HEXAVALENT CHROMIUM.

    Science.gov (United States)

    Grove, D.B.; Stollenwerk, K.G.

    1985-01-01

    Sorption of chromium VI on the iron-oxide- and hydroxide-coated surface of alluvial material was numerically simulated with rate-controlled reactions. Reaction kinetics and diffusional processes, in the form of film, pore, and particle diffusion, were simulated and compared with experimental results. The use of empirically calculated rate coefficients for diffusion through the reacting surface was found to simulate experimental data; pore or particle diffusion is believed to be a possible rate-controlling mechanism. The use of rate equations to predict conservative transport and rate- and local-equilibrium-controlled reactions was shown to be feasible.

  10. Representing Quadric Surfaces Using NURBS Surfaces

    Institute of Scientific and Technical Information of China (English)

    秦开怀

    1997-01-01

    A method for representing quadrc surfaces using NURBS is presented.By means of the necessary and sufficient conditons for NURBS curves to precisely represent circular arcs and other conics,quadric surfaces can be represented by NURBS surfaces with fewer control vertices.The method can be used not only for NURBS surface representation of quadric surfaces,but also for rounding polyhedrons.Many examples are given in the paper.

  11. Heart Rate Monitors

    Science.gov (United States)

    1990-01-01

    Under a NASA grant, Dr. Robert M. Davis and Dr. William M. Portnoy came up with a new type of electrocardiographic electrode that would enable long term use on astronauts. Their invention was an insulated capacitive electrode constructed of a thin dielectric film. NASA subsequently licensed the electrode technology to Richard Charnitski, inventor of the VersaClimber, who founded Heart Rate, Inc., to further develop and manufacture personal heart monitors and to produce exercise machines using the technology for the physical fitness, medical and home markets. Same technology is on both the Home and Institutional Model VersaClimbers. On the Home Model an infrared heart beat transmitter is worn under exercise clothing. Transmitted heart rate is used to control the work intensity on the VersaClimber using the heart rate as the speedometer of the exercise. This offers advantages to a full range of users from the cardiac rehab patient to the high level physical conditioning of elite athletes. The company manufactures and markets five models of the 1*2*3 HEART RATE monitors that are used wherever people exercise to accurately monitor their heart rate. Company is developing a talking heart rate monitor that works with portable headset radios. A version of the heart beat transmitter will be available to the manufacturers of other aerobic exercise machines.

  12. Hydration rate of obsidian.

    Science.gov (United States)

    Friedman, I; Long, W

    1976-01-30

    The hydration rates of 12 obsidian samples of different chemical compositions were measured at temperatures from 95 degrees to 245 degrees C. An expression relating hydration rate to temperature was derived for each sample. The SiO(2) content and refractive index are related to the hydration rate, as are the CaO, MgO, and original water contents. With this information it is possible to calculate the hydration rate of a sample from its silica content, refractive index, or chemical index and a knowledge of the effective temperature at which the hydration occurred. The effective hydration temperature can be either measured or approximated from weather records. Rates have been calculated by both methods, and the results show that weather records can give a good approximation to the true EHT, particularly in tropical and subtropical climates. If one determines the EHT by any of the methods suggested, and also measures or knows the rate of hydration of the particular obsidian used, it should be possible to carry out absolute dating to +/- 10 percent of the true age over periods as short as several years and as long as millions of years.

  13. Interbank overnight rate determinants

    Directory of Open Access Journals (Sweden)

    Kožul Nataša

    2015-01-01

    Full Text Available Reserve requirement is a regulation of most world's central banks, whereby commercial banks must hold a certain fraction of customer deposits in reserves, either deposited at the central bank or in the bank vaults. While these reserves are calculated periodically, banks usually manage their books daily, which may result in reserve shortfall or surplus. This phenomenon has led to the emergence of the interbank market where banks transact with one another, trading interest rate instruments of various maturities. This paper focuses on the overnight interest rate, as it is assumed to be an indicator of the central bank's policy. Moreover, as the overnight rate is included in the yield curve construction, it implicitly influences the rates for all longer maturities. Finally, as an equilibrium in the reserve supply and demand, movements in the overnight interest rate reflect the dynamics in the interbank market. Here, the main interbank indices are described, before discussing some important features of the overnight rate, and the factors underlying its movements.

  14. Resistive Plate Chamber Efficiency & Rate Capability Analysis

    Science.gov (United States)

    Candocia, Max

    2012-10-01

    Bakelite-based resistive plate chambers (RPCs) are particle detectors commonly used in muon trigger systems for high-energy physics experiments. Bakelite RPCs combine fast response, sufficient position resolution and low cost, and they can be operated at instantaneous background rates up to approximately 1.5 kHz/cm^2. Current and future collider experiments will demand operation of trigger RPCs under background rates higher than what is currently achieved. The rate capability is related to the bulk and surface conductivities of the Bakelite material used for the plates bordering the active gas volume in the RPCs. At the LHC and RHIC, these surfaces are coated with linseed oil, which lowers the surface resistivity of the Bakelite, which, to a point, improves the rate capability of the detectors. We have doped our own plates with various concentrations of carbon black. Over the past year we have tested RPCs with Bakelite plates of different resistivity using cosmic ray muons and radioactive Fe55 sources to emulate different levels of background in the detector. Results on the RPC efficiencies at different background rates and for different Bakelite coatings will be presented.

  15. Impact of electron-impurity scattering on the spin relaxation time in graphene: a first-principles study.

    Science.gov (United States)

    Fedorov, Dmitry V; Gradhand, Martin; Ostanin, Sergey; Maznichenko, Igor V; Ernst, Arthur; Fabian, Jaroslav; Mertig, Ingrid

    2013-04-12

    The effect of electron-impurity scattering on momentum and spin relaxation times in graphene is studied by means of relativistic ab initio calculations. Assuming carbon and silicon adatoms as natural impurities in graphene, we are able to simulate fast spin relaxation observed experimentally. We investigate the dependence of the relaxation times on the impurity position and demonstrate that C or Si adatoms act as real-space spin hot spots inducing spin-flip rates about 5 orders of magnitude larger than those of in-plane impurities. This fact confirms the hypothesis that the adatom-induced spin-orbit coupling leads to fast spin relaxation in graphene.

  16. Pulsed Sisyphus scheme for laser cooling of atomic (anti)hydrogen.

    Science.gov (United States)

    Wu, Saijun; Brown, Roger C; Phillips, William D; Porto, J V

    2011-05-27

    We propose a laser cooling technique in which atoms are selectively excited to a dressed metastable state whose light shift and decay rate are spatially correlated for Sisyphus cooling. The case of cooling magnetically trapped (anti)hydrogen with the 1S-2S-3P transitions by using pulsed ultraviolet and continuous-wave visible lasers is numerically simulated. We find a number of appealing features including rapid three-dimensional cooling from ∼1 K to recoil-limited, millikelvin temperatures, as well as suppressed spin-flip loss and manageable photoionization loss. © 2011 American Physical Society

  17. Cooling rate calculations for silicate glasses.

    Science.gov (United States)

    Birnie, D. P., III; Dyar, M. D.

    1986-03-01

    Series solution calculations of cooling rates are applied to a variety of samples with different thermal properties, including an analog of an Apollo 15 green glass and a hypothetical silicate melt. Cooling rates for the well-studied green glass and a generalized silicate melt are tabulated for different sample sizes, equilibration temperatures and quench media. Results suggest that cooling rates are heavily dependent on sample size and quench medium and are less dependent on values of physical properties. Thus cooling histories for glasses from planetary surfaces can be estimated on the basis of size distributions alone. In addition, the variation of cooling rate with sample size and quench medium can be used to control quench rate.

  18. Modelling heart rate kinetics.

    Science.gov (United States)

    Zakynthinaki, Maria S

    2015-01-01

    The objective of the present study was to formulate a simple and at the same time effective mathematical model of heart rate kinetics in response to movement (exercise). Based on an existing model, a system of two coupled differential equations which give the rate of change of heart rate and the rate of change of exercise intensity is used. The modifications introduced to the existing model are justified and discussed in detail, while models of blood lactate accumulation in respect to time and exercise intensity are also presented. The main modification is that the proposed model has now only one parameter which reflects the overall cardiovascular condition of the individual. The time elapsed after the beginning of the exercise, the intensity of the exercise, as well as blood lactate are also taken into account. Application of the model provides information regarding the individual's cardiovascular condition and is able to detect possible changes in it, across the data recording periods. To demonstrate examples of successful numerical fit of the model, constant intensity experimental heart rate data sets of two individuals have been selected and numerical optimization was implemented. In addition, numerical simulations provided predictions for various exercise intensities and various cardiovascular condition levels. The proposed model can serve as a powerful tool for a complete means of heart rate analysis, not only in exercise physiology (for efficiently designing training sessions for healthy subjects) but also in the areas of cardiovascular health and rehabilitation (including application in population groups for which direct heart rate recordings at intense exercises are not possible or not allowed, such as elderly or pregnant women).

  19. Modelling heart rate kinetics.

    Directory of Open Access Journals (Sweden)

    Maria S Zakynthinaki

    Full Text Available The objective of the present study was to formulate a simple and at the same time effective mathematical model of heart rate kinetics in response to movement (exercise. Based on an existing model, a system of two coupled differential equations which give the rate of change of heart rate and the rate of change of exercise intensity is used. The modifications introduced to the existing model are justified and discussed in detail, while models of blood lactate accumulation in respect to time and exercise intensity are also presented. The main modification is that the proposed model has now only one parameter which reflects the overall cardiovascular condition of the individual. The time elapsed after the beginning of the exercise, the intensity of the exercise, as well as blood lactate are also taken into account. Application of the model provides information regarding the individual's cardiovascular condition and is able to detect possible changes in it, across the data recording periods. To demonstrate examples of successful numerical fit of the model, constant intensity experimental heart rate data sets of two individuals have been selected and numerical optimization was implemented. In addition, numerical simulations provided predictions for various exercise intensities and various cardiovascular condition levels. The proposed model can serve as a powerful tool for a complete means of heart rate analysis, not only in exercise physiology (for efficiently designing training sessions for healthy subjects but also in the areas of cardiovascular health and rehabilitation (including application in population groups for which direct heart rate recordings at intense exercises are not possible or not allowed, such as elderly or pregnant women.

  20. Modelling Heart Rate Kinetics

    Science.gov (United States)

    Zakynthinaki, Maria S.

    2015-01-01

    The objective of the present study was to formulate a simple and at the same time effective mathematical model of heart rate kinetics in response to movement (exercise). Based on an existing model, a system of two coupled differential equations which give the rate of change of heart rate and the rate of change of exercise intensity is used. The modifications introduced to the existing model are justified and discussed in detail, while models of blood lactate accumulation in respect to time and exercise intensity are also presented. The main modification is that the proposed model has now only one parameter which reflects the overall cardiovascular condition of the individual. The time elapsed after the beginning of the exercise, the intensity of the exercise, as well as blood lactate are also taken into account. Application of the model provides information regarding the individual’s cardiovascular condition and is able to detect possible changes in it, across the data recording periods. To demonstrate examples of successful numerical fit of the model, constant intensity experimental heart rate data sets of two individuals have been selected and numerical optimization was implemented. In addition, numerical simulations provided predictions for various exercise intensities and various cardiovascular condition levels. The proposed model can serve as a powerful tool for a complete means of heart rate analysis, not only in exercise physiology (for efficiently designing training sessions for healthy subjects) but also in the areas of cardiovascular health and rehabilitation (including application in population groups for which direct heart rate recordings at intense exercises are not possible or not allowed, such as elderly or pregnant women). PMID:25876164