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Sample records for resolved energy dispersive

  1. Opportunities for Time Resolved Studies at the ID24 Energy Dispersive XAS Beamline of the ESRF

    SciTech Connect

    Mathon, O.; Aquilanti, G.; Guilera, G.; Labiche, J.-C.; Linden, P. van der; Newton, M. A.; Ponchut, C.; Trapananti, A.; Pascarelli, S.

    2007-01-19

    ID24 is the energy dispersive beamline of the European Synchrotron Radiation Facility dedicated to X-ray Absorption Spectroscopy (XAS). Thanks to the parallel acquisition mode that allows data in a large energy range to be collected simultaneously, XAS using dispersive optics is particularly suited for the study of time dependent processes. The techniques that can be used to study such systems vary according to the timescale of the phenomena under investigation. They take advantage of the temporal structure of the synchrotron radiation in case of time resolution of the order of the intrinsic duration of the x-ray pulse (100 ps), while for time scales above 100 {mu}s or below 100 ps, the x-ray beam can be considered continuous and the time resolution is determined by the different detection systems.

  2. In situ energy-dispersive x-ray diffraction system for time-resolved thin-film growth studies

    NASA Astrophysics Data System (ADS)

    Ellmer, K.; Mientus, R.; Weiß, V.; Rossner, H.

    2003-03-01

    Energy-dispersive x-ray diffraction (EDXRD) with synchrotron light can be used for in situ-structural analysis during polycrystalline thin-film growth, due to its fast data collection and the fixed diffraction angle. An in situ deposition and analysis set-up for the investigation of nucleation and growth of thin films during magnetron sputtering was constructed and installed at the synchrotron radiation source Hamburger Synchrotronstrahlungs Labor (Hamburg). The polychromatic synchrotron beam passes the sputtering chamber through Kapton windows and hits the substrate with the growing film. The diffracted beam, observed under a fixed diffraction angle of between 1° and 10° was energy-analysed by a high-purity germanium detector. The measurement time for a single XRD spectrum can be as short as 10 s for a beam line at a bending magnet, which allows a time-resolved monitoring of film growth. The performance of the in situ EDXRD set-up is demonstrated for the growth of zinc oxide and tin-doped indium oxide films prepared by reactive magnetron sputtering from ceramic and metallic targets. From the position and the width of the diffraction lines the internal mechanical strain and the grain size of the growing films can be derived. The prospects for thin-film growth investigations using such an instrument are assessed.

  3. Time-resolved and energy-dispersed spin excitation in ferromagnets and clusters under influence of femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Hartenstein, T.; Lefkidis, G.; Hübner, W.; Zhang, G. P.; Bai, Y.

    2009-04-01

    When an ultrafast laser impinges a magnetic material, it excites charge and then, via spin-orbit-coupling, spin. This holds great promise for the future magnetic storage. However, the coupling of the two dynamics is far from clear, which hampers the experimental effort in femtosecond magnetism. Since not every excitation induces the same spin excitation, a clear understanding of the correlation between charge and spin is crucial. In this paper we investigate in a complete first-principles manner the energy dispersion of the spin-moment change in ferromagnetic Ni and the effect of the distance between the magnetic centers upon the spin localization and local-spin-flip times in metallic chains. Thus we establish the missing link between the spin-momentum change and the density-of-states change, and derive rules-of-thumb for localized spin manipulation.

  4. Spatially resolved energy dispersive x-ray spectroscopic method for in-situ evaluation of mechanical properties during the growth of a C - Pt composite nanowire

    NASA Astrophysics Data System (ADS)

    Banerjee, Amit; Banerjee, S. S.

    2014-05-01

    A core-shell type C-Pt composite nanowire is fabricated using focused ion and electron beam induced chemical vapor deposition techniques. Using information from spatially resolved energy dispersive x-ray spectra, we detect the resonance vibration in the C-Pt composite nanowire. We use this method to measure the Young's moduli of the constituents (C, Pt) of the composite nanowire and also estimate the density of the FEB CVD grown Pt shell surrounding the C core. By measuring the resonance characteristics of the composite nanowire we estimate a Pt shell growth rate of ˜0.9 nms-1. The study is analyzed to suggest that the Pt shell growth mechanism is primarily governed by the sticking coefficient of the organometallic vapor on the C nanowire core.

  5. Spatially resolved energy dispersive x-ray spectroscopic method for in-situ evaluation of mechanical properties during the growth of a C - Pt composite nanowire

    SciTech Connect

    Banerjee, Amit; Banerjee, S. S.

    2014-05-15

    A core-shell type C-Pt composite nanowire is fabricated using focused ion and electron beam induced chemical vapor deposition techniques. Using information from spatially resolved energy dispersive x-ray spectra, we detect the resonance vibration in the C-Pt composite nanowire. We use this method to measure the Young's moduli of the constituents (C, Pt) of the composite nanowire and also estimate the density of the FEB CVD grown Pt shell surrounding the C core. By measuring the resonance characteristics of the composite nanowire we estimate a Pt shell growth rate of ∼0.9 nms{sup −1}. The study is analyzed to suggest that the Pt shell growth mechanism is primarily governed by the sticking coefficient of the organometallic vapor on the C nanowire core.

  6. Microsecond time-resolved energy-dispersive EXAFS measurement and its application to film the thermolysis of (NH4)2[PtCl6

    NASA Astrophysics Data System (ADS)

    Kong, Qingyu; Baudelet, Francois; Han, Jun; Chagnot, Sebastien; Barthe, Laurent; Headspith, Jon; Goldsbrough, Roger; Picca, Frederic E.; Spalla, Olivier

    2012-12-01

    Microsecond (μs) time-resolved extended X-ray absorption fine structure spectroscopy (EXAFS) has been developed using an energy-dispersive EXAFS (EDE) setup equipped with a silicon Quantum Detector ULTRA. The feasibility was investigated with a prototypical thermally driven redox reaction, the thermal decomposition of (NH4)2[PtCl6]. EXAFS data were collected with snapshots every 60 μs during the course of the thermolysis reaction, then averaged for 100 times along the reaction to get better signal to noise ratio which reduces the time resolution to 6 millisecond (ms). Our results provide direct structural evidence of cis-PtCl2(NH3)2 as the intermediate, together with continuous electronic and geometric structure dynamics of the reactant, intermediate and final product during the course of the thermolysis of (NH4)2[PtCl6]. The thermal effect on EXAFS signals at high temperatures is considered in the data analysis, which is essential to follow the reaction process correctly. This method could also be applied to other reaction dynamics.

  7. Microsecond time-resolved energy-dispersive EXAFS measurement and its application to film the thermolysis of (NH4)2[PtCl6

    PubMed Central

    Kong, Qingyu; Baudelet, Francois; Han, Jun; Chagnot, Sebastien; Barthe, Laurent; Headspith, Jon; Goldsbrough, Roger; Picca, Frederic E.; Spalla, Olivier

    2012-01-01

    Microsecond (μs) time-resolved extended X-ray absorption fine structure spectroscopy (EXAFS) has been developed using an energy-dispersive EXAFS (EDE) setup equipped with a silicon Quantum Detector ULTRA. The feasibility was investigated with a prototypical thermally driven redox reaction, the thermal decomposition of (NH4)2[PtCl6]. EXAFS data were collected with snapshots every 60 μs during the course of the thermolysis reaction, then averaged for 100 times along the reaction to get better signal to noise ratio which reduces the time resolution to 6 millisecond (ms). Our results provide direct structural evidence of cis-PtCl2(NH3)2 as the intermediate, together with continuous electronic and geometric structure dynamics of the reactant, intermediate and final product during the course of the thermolysis of (NH4)2[PtCl6]. The thermal effect on EXAFS signals at high temperatures is considered in the data analysis, which is essential to follow the reaction process correctly. This method could also be applied to other reaction dynamics. PMID:23264880

  8. Evaluation study of building-resolved urban dispersion models

    SciTech Connect

    Flaherty, Julia E.; Allwine, K Jerry; Brown, Mike J.; Coirier, WIlliam J.; Ericson, Shawn C.; Hansen, Olav R.; Huber, Alan H.; Kim, Sura; Leach, Martin J.; Mirocha, Jeff D.; Newsom, Rob K.; Patnaik, Gopal; Senocak, Inanc

    2007-09-10

    For effective emergency response and recovery planning, it is critically important that building-resolved urban dispersion models be evaluated using field data. Several full-physics computational fluid dynamics (CFD) models and semi-empirical building-resolved (SEB) models are being advanced and applied to simulating flow and dispersion in urban areas. To obtain an estimate of the current state-of-readiness of these classes of models, the Department of Homeland Security (DHS) funded a study to compare five CFD models and one SEB model with tracer data from the extensive Midtown Manhattan field study (MID05) conducted during August 2005 as part of the DHS Urban Dispersion Program (UDP; Allwine and Flaherty 2007). Six days of tracer and meteorological experiments were conducted over an approximately 2-km-by-2-km area in Midtown Manhattan just south of Central Park in New York City. A subset of these data was used for model evaluations. The study was conducted such that an evaluation team, independent of the six modeling teams, provided all the input data (e.g., building data, meteorological data and tracer release rates) and run conditions for each of four experimental periods simulated. Tracer concentration data for two of the four experimental periods were provided to the modeling teams for their own evaluation of their respective models to ensure proper setup and operation. Tracer data were not provided for the second two experimental periods to provide for an independent evaluation of the models. The tracer concentrations resulting from the model simulations were provided to the evaluation team in a standard format for consistency in inter-comparing model results. An overview of the model evaluation approach will be given followed by a discussion on the qualitative comparison of the respective models with the field data. Future model developments efforts needed to address modeling gaps identified from this study will also be discussed.

  9. Time-resolved energy-dispersive diffraction from X-FEL spontaneous emission: a proposal for sub-picosecond pumps & probe structural investigations

    NASA Astrophysics Data System (ADS)

    Rossi Albertini, Valerio; Paci, Barbara; Perfetti, Paolo

    2004-11-01

    The forthcoming generation of X-ray machines, based on Free Electron Laser (X-FEL) technology, should provide ultra-short pulses that may be used to probe the real-time structural evolution of a system activated by an optical laser pump. Unfortunately, the sub-picosecond synchronization of the pump and probe pulses produced by two independent sources is, at present, one of the main obstacles that needs to be overcome. Here we propose a new approach for carrying out time-resolved diffraction studies of evolving systems, which aims to bypass the synchronization problem.

  10. Anomalous lattice expansion in yttria stabilized zirconia under simultaneous applied electric and thermal fields: A time-resolved in situ energy dispersive x-ray diffractometry study with an ultrahigh energy synchrotron probe

    SciTech Connect

    Akdogan, E. K.; Savkl Latin-Small-Letter-Dotless-I y Latin-Small-Letter-Dotless-I ld Latin-Small-Letter-Dotless-I z, I.; Bicer, H.; Paxton, W.; Toksoy, F.; Tsakalakos, T.; Zhong, Z.

    2013-06-21

    Nonisothermal densification in 8% yttria doped zirconia (8YSZ) particulate matter of 250 nm median particle size was studied under 215 V/cm dc electric field and 9 Degree-Sign C/min heating rate, using time-resolved in-situ high temperature energy dispersive x-ray diffractometry with a polychromatic 200 keV synchrotron probe. Densification occurred in the 876-905 Degree-Sign C range, which resulted in 97% of the theoretical density. No local melting at particle-particle contacts was observed in scanning electron micrographs, implying densification was due to solid state mass transport processes. The maximum current draw at 905 Degree-Sign C was 3 A, corresponding to instantaneous absorbed power density of 570 W/cm{sup 3}. Densification of 8YSZ was accompanied by anomalous elastic volume expansions of the unit cell by 0.45% and 2.80% at 847 Degree-Sign C and 905 Degree-Sign C, respectively. The anomalous expansion at 905 Degree-Sign C at which maximum densification was observed is characterized by three stages: (I) linear stage, (II) anomalous stage, and (III) anelastic recovery stage. The densification in stage I (184 s) and II (15 s) was completed in 199 s, while anelastic relaxation in stage III lasted 130 s. The residual strains ({epsilon}) at room temperature, as computed from tetragonal (112) and (211) reflections, are {epsilon}{sub (112)} = 0.05% and {epsilon}{sub (211)} = 0.13%, respectively. Time dependence of (211) and (112) peak widths ({beta}) show a decrease with both exhibiting a singularity at 905 Degree-Sign C. An anisotropy in (112) and (211) peak widths of {l_brace} {beta}{sub (112)}/{beta}{sub (211)}{r_brace} = (3:1) magnitude was observed. No phase transformation occurred at 905 Degree-Sign C as verified from diffraction spectra on both sides of the singularity, i.e., the unit cell symmetry remains tetragonal. We attribute the reduction in densification temperature and time to ultrafast ambipolar diffusion of species arising from the

  11. Development of dispersive XAFS system for analysis of time-resolved spatial distribution of electrode reaction.

    PubMed

    Katayama, Misaki; Miyahara, Ryota; Watanabe, Toshiki; Yamagishi, Hirona; Yamashita, Shohei; Kizaki, Terue; Sugawara, Yoshimi; Inada, Yasuhiro

    2015-09-01

    Apparatus for a technique based on the dispersive optics of X-ray absorption fine structure (XAFS) has been developed at beamline BL-5 of the Synchrotron Radiation Center of Ritsumeikan University. The vertical axis of the cross section of the synchrotron light is used to disperse the X-ray energy using a cylindrical polychromator and the horizontal axis is used for the spatially resolved analysis with a pixel array detector. The vertically dispersive XAFS (VDXAFS) instrument was designed to analyze the dynamic changeover of the inhomogeneous electrode reaction of secondary batteries. The line-shaped X-ray beam is transmitted through the electrode sample, and then the dispersed transmitted X-rays are detected by a two-dimensional detector. An array of XAFS spectra in the linear footprint of the transmitted X-ray on the sample is obtained with the time resolution of the repetition frequency of the detector. Sequential measurements of the space-resolved XAFS data are possible with the VDXAFS instrument. The time and spatial resolutions of the VDXAFS instrument depend on the flux density of the available X-ray beam and the size of the light source, and they were estimated as 1 s and 100 µm, respectively. The electrode reaction of the LiFePO4 lithium ion battery was analyzed during the constant current charging process and during the charging process after potential jumping. PMID:26289274

  12. The Time-resolved and Extreme-conditions XAS (TEXAS) facility at the European Synchrotron Radiation Facility: the energy-dispersive X-ray absorption spectroscopy beamline ID24.

    PubMed

    Pascarelli, S; Mathon, O; Mairs, T; Kantor, I; Agostini, G; Strohm, C; Pasternak, S; Perrin, F; Berruyer, G; Chappelet, P; Clavel, C; Dominguez, M C

    2016-01-01

    The European Synchrotron Radiation Facility has recently made available to the user community a facility totally dedicated to Time-resolved and Extreme-conditions X-ray Absorption Spectroscopy--TEXAS. Based on an upgrade of the former energy-dispersive XAS beamline ID24, it provides a unique experimental tool combining unprecedented brilliance (up to 10(14) photons s(-1) on a 4 µm × 4 µm FWHM spot) and detection speed for a full EXAFS spectrum (100 ps per spectrum). The science mission includes studies of processes down to the nanosecond timescale, and investigations of matter at extreme pressure (500 GPa), temperature (10000 K) and magnetic field (30 T). The core activities of the beamline are centered on new experiments dedicated to the investigation of extreme states of matter that can be maintained only for very short periods of time. Here the infrastructure, optical scheme, detection systems and sample environments used to enable the mission-critical performance are described, and examples of first results on the investigation of the electronic and local structure in melts at pressure and temperature conditions relevant to the Earth's interior and in laser-shocked matter are given. PMID:26698085

  13. DNS of fully resolved spherical particles dispersed in isotropic turbulence

    NASA Astrophysics Data System (ADS)

    Lucci, Francesco; Ferrante, Antonino; Elghobashi, Said

    2008-11-01

    Our DNS study concerns the interactions between decaying isotropic turbulence and solid spherical particles with diameter, d, larger than the Kolmogorov length scale, η. We employ an Immersed Boundary method similar to that of Uhlmann (JCP, 2005) to resolve the flow around 6400 spherical particles with a volume fraction of φv=0.1. The monosize particles have a diameter, d = 16 ηo. Our simulations, with 256^3 mesh points and Reλ0= 75, cover a range of 38 <=τp/τKo<=149, for the ratio of the particle response time to the initial Kolmogorov time scale. A Lagrangian approach is used to compute the frequency spectrum of the turbulence kinetic energy (TKE) of the fluid phase. The effects of varying τp/τKo on the spectrum and the decay rate of TKE are discussed. The effects of the formation of the particle boundary layer on the viscous dissipation rate of TKE are also discussed.

  14. Energy-Resolved Positron Annihilation in Flight in Solid Targets

    NASA Astrophysics Data System (ADS)

    Weber, M. H.; Hunt, A. W.; Golovchenko, J. A.; Lynn, K. G.

    1999-11-01

    Energy-resolved two-quantum annihilation in flight of positrons with energies ranging from 10 to 71.6 keV was observed. An energy-dispersive two-detector coincidence system was used to observe the sum and difference energies of the γ rays from annihilating positron-electron pairs. For positrons penetrating carbon foils the c/v dependence of the annihilation cross section is confirmed. Spectra obtained from gold-coated carbon foils show evidence of in-flight annihilation with gold M-shell electrons.

  15. Energy resolved X-ray grating interferometry

    SciTech Connect

    Thuering, T.; Stampanoni, M.; Barber, W. C.; Iwanczyk, J. S.; Seo, Y.; Alhassen, F.

    2013-05-13

    Although compatible with polychromatic radiation, the sensitivity in X-ray phase contrast imaging with a grating interferometer is strongly dependent on the X-ray spectrum. We used an energy resolving detector to quantitatively investigate the dependency of the noise from the spectral bandwidth and to consequently optimize the system-by selecting the best energy band matching the experimental conditions-with respect to sensitivity maximization and, eventually, dose. Further, since theoretical calculations of the spectrum are usually limited due to non-ideal conditions, an energy resolving detector accurately quantifies the spectral changes induced by the interferometer including flux reduction and beam hardening.

  16. Origin of the quasiparticle dispersion kinks in Bi-2212 determined from angle-resolved inelastic electron scattering

    NASA Astrophysics Data System (ADS)

    Vig, Sean; Kogar, Anshul; Mishra, Vivek; Norman, Mike; Gu, Genda; Abbamonte, Peter

    2015-03-01

    The kink features in the low energy quasiparticle dispersion in cuprate superconductors have been extensively studied using angle-resolved photoemission spectroscopy (ARPES). The existence of these kinks is a signature of a renormalization of the fermionic quasiparticles due to coupling to some bosonic collective mode at a scale related to the kink energy. In this talk, I will present angle-resolved inelastic electron scattering studies of the bosonic collective excitations in optimally doped Bi2Sr2CaCu2O8+δ. Performing a 2D momentum parameterization of these modes, we reconstruct the complete dynamical susceptibility, χ (q , ω) , which we use to perform a one-loop self energy correction to the quasiparticle dispersion. The result reproduces well the dispersion observed with ARPES, indicating that these excitations are the origin of the observed kinks. I will discuss the implications of our study for phonon vs. spin fluctuation interpretation of these effects. This work was supported as part of the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science.

  17. Time-Resolved Dispersive XAFS Instrument at NW2A Beamline of PF-AR

    NASA Astrophysics Data System (ADS)

    Inada, Y.; Suzuki, A.; Niwa, Y.; Nomura, M.

    2007-01-01

    The configuration and performance of the time-resolved dispersive XAFS (DXAFS) instrument, which has been constructed at the NW2A beamline of PF-AR (KEK), are presented. The DXAFS instrument is mainly composed of a polychromator part, a position control part for sample, and a linear detector part. The Bragg- and Laue-type polychromator crystal (Si(111) or Si(311)) is bent using the holder with fixed bending radius, in which the thermostated water is circulated to prevent the temperature change of crystal due to the heat load. The photodiode array (PDA) with and without phosphor screen is used as the linear X-ray detector, and the minimum exposure time is 2 ms for the 1024-element PDA. The phosphor screen on the PDA detector prevents the damage of the chip especially for high energy X-rays but the existence reduces the energy resolution because of the scattering of the visible light converted on the phosphor. The DXAFS instrument was applied to the mechanistic study of the reduction processes of Cu supported on MFI zeolite, and the intermediate Cu(I) states have been successfully observed during the reduction from Cu(II) to Cu(0).

  18. Electromagnetic energy momentum in dispersive media

    SciTech Connect

    Philbin, T. G.

    2011-01-15

    The standard derivations of electromagnetic energy and momentum in media take Maxwell's equations as the starting point. It is well known that for dispersive media this approach does not directly yield exact expressions for the energy and momentum densities. Although Maxwell's equations fully describe electromagnetic fields, the general approach to conserved quantities in field theory is not based on the field equations, but rather on the action. Here an action principle for macroscopic electromagnetism in dispersive, lossless media is used to derive the exact conserved energy-momentum tensor. The time-averaged energy density reduces to Brillouin's simple formula when the fields are monochromatic. The time-averaged momentum density for monochromatic fields corresponds to the familiar Minkowski expression DxB, but for general fields in dispersive media the momentum density does not have the Minkowski value. The results are unaffected by the debate over momentum balance in light-matter interactions.

  19. Instrumentation for time-resolved dispersive studies at Advanced Photon Source beamline 1-BM

    SciTech Connect

    Brauer, S.; Rodricks, B.

    1996-07-01

    We describe progress in optics and instrumentation at beamline 1-BM, designed in part for time-resolved dispersive x-ray absorption fine structure (XAFS) measurements. The key optical element is a horizontally focusing curved-crystal monochromator that invokes a 4-point bending scheme and a liquid-metal cooling bath. The device has been designed for dispersive studies in the 5-24 keV range, with a horizontal focal spot size of {le}100 micrometers FWHM. To minimize thermal distortions and thermal equilibration time, the 355 {times} 32 {times} 0.8 mm crystal is nearly half submerged in a bath of Ga-In-Sn-Zn alloy, which thermally couples the crystal to the water-cooled Cu frame, while permitting the required crystal bending. Harmonic rejection, focusing schemes and the novel spectrometer positioning system will be described. For microsecond-resolution time-resolved studies, a fast CCD streak camera detector has been developed. Results from commissioning tests of the instrumentation are described. 11 refs., 4 figs.

  20. DISPERSION ANALYSIS OF RADIATION/THERMAL FRONTS WITH FULL RESOLVED SPECTRAL OPACITY VARIATION.

    SciTech Connect

    L. AUER; R. LOWRIE

    2000-12-01

    The radiation transport and linearized thermal energy equations have been analyzed to find the temporal dependence of the component modes in a radiation/thermal front. The fully resolved spectral variation of the opacity as a function of energy, as well as the exact time and angular dependence, is treated in this work. As we are able to study arbitrarily complicated opacity spectra, we stress the importance of the new results as a check on the effect of using opacity averages.

  1. Spatially Resolving Ocean Color and Sediment Dispersion in River Plumes, Coastal Systems, and Continental Shelf Waters

    NASA Technical Reports Server (NTRS)

    Aurin, Dirk Alexander; Mannino, Antonio; Franz, Bryan

    2013-01-01

    Satellite remote sensing of ocean color in dynamic coastal, inland, and nearshorewaters is impeded by high variability in optical constituents, demands specialized atmospheric correction, and is limited by instrument sensitivity. To accurately detect dispersion of bio-optical properties, remote sensors require ample signal-to-noise ratio (SNR) to sense small variations in ocean color without saturating over bright pixels, an atmospheric correction that can accommodate significantwater-leaving radiance in the near infrared (NIR), and spatial and temporal resolution that coincides with the scales of variability in the environment. Several current and historic space-borne sensors have met these requirements with success in the open ocean, but are not optimized for highly red-reflective and heterogeneous waters such as those found near river outflows or in the presence of sediment resuspension. Here we apply analytical approaches for determining optimal spatial resolution, dominant spatial scales of variability ("patches"), and proportions of patch variability that can be resolved from four river plumes around the world between 2008 and 2011. An offshore region in the Sargasso Sea is analyzed for comparison. A method is presented for processing Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua and Terra imagery including cloud detection, stray lightmasking, faulty detector avoidance, and dynamic aerosol correction using short-wave- and near-infrared wavebands in extremely turbid regions which pose distinct optical and technical challenges. Results showthat a pixel size of approx. 520 mor smaller is generally required to resolve spatial heterogeneity in ocean color and total suspended materials in river plumes. Optimal pixel size increases with distance from shore to approx. 630 m in nearshore regions, approx 750 m on the continental shelf, and approx. 1350 m in the open ocean. Greater than 90% of the optical variability within plume regions is resolvable with

  2. Intermolecular energy-band dispersion in PTCDA multilayers

    NASA Astrophysics Data System (ADS)

    Yamane, Hiroyuki; Kera, Satoshi; Okudaira, Koji K.; Yoshimura, Daisuke; Seki, Kazuhiko; Ueno, Nobuo

    2003-07-01

    The electronic structure of a well-oriented perylene-3,4,9,10-tetracarboxylic acid-dianhydride multilayer prepared on MoS2 single crystal surface were studied by angle-resolved ultraviolet photoemission spectroscopy using synchrotron radiation. From the photon energy dependence of normal emission spectra, we observed an intermolecular energy-band dispersion of about 0.2 eV for the highest occupied molecular orbital (HOMO) band of single π character. The observed energy-band dispersion showed a cosine curve, which originates from the intermolecular π-π interaction. Analyses using the tight-binding model gave that the transfer integral of about 0.05 eV for the π-π interaction, the effective mass of HOMO hole m*h=5.28m0, and the hole mobility μh>3.8 cm2/V s. This is the first observation of the intermolecular energy-band dispersion of a conventional single-component organic semiconductor only with the weak intermolecular van der Waals interaction.

  3. Characterization of Ultrafast Laser Pulses using a Low-dispersion Frequency Resolved Optical Grating Spectrometer

    NASA Astrophysics Data System (ADS)

    Whitelock, Hope; Bishop, Michael; Khosravi, Soroush; Obaid, Razib; Berrah, Nora

    2016-05-01

    A low dispersion frequency-resolved optical gating (FROG) spectrometer was designed to characterize ultrashort (<50 femtosecond) laser pulses from a commercial regenerative amplifier, optical parametric amplifier, and a home-built non-colinear optical parametric amplifier. This instrument splits a laser pulse into two replicas with a 90:10 intensity ratio using a thin pellicle beam-splitter and then recombines the pulses in a birefringent medium. The instrument detects a wavelength-sensitive change in polarization of the weak probe pulse in the presence of the stronger pump pulse inside the birefringent medium. Scanning the time delay between the two pulses and acquiring spectra allows for characterization of the frequency and time content of ultrafast laser pulses, that is needed for interpretation of experimental results obtained from these ultrafast laser systems. Funded by the DoE-BES, Grant No. DE-SC0012376.

  4. Ecological succession as an energy dispersal process.

    PubMed

    Würtz, Peter; Annila, Arto

    2010-04-01

    Ecological succession is described by the 2nd law of thermodynamics. According to the universal law of the maximal energy dispersal, an ecosystem evolves toward a stationary state in its surroundings by consuming free energy via diverse mechanisms. Species are the mechanisms that conduct energy down along gradients between repositories of energy which consist of populations at various thermodynamic levels. The salient characteristics of succession, growing biomass production, increasing species richness and shifting distributions of species are found as consequences of the universal quest to diminish energy density differences in least time. The analysis reveals that during succession the ecosystem's energy transduction network, i.e., the food web organizes increasingly more effective in the free energy reduction by acquiring new, more effective and abandoning old, less effective species of energy transduction. The number of species does not necessarily peak at the climax state that corresponds to the maximum-entropy partition of species maximizing consumption of free energy. According to the theory of evolution by natural selection founded on statistical physics of open systems, ecological succession is one among many other evolutionary processes. PMID:20097257

  5. Concept of proton radiography using energy resolved dose measurement

    NASA Astrophysics Data System (ADS)

    Bentefour, El H.; Schnuerer, Roland; Lu, Hsiao-Ming

    2016-08-01

    Energy resolved dosimetry offers a potential path to single detector based proton imaging using scanned proton beams. This is because energy resolved dose functions encrypt the radiological depth at which the measurements are made. When a set of predetermined proton beams ‘proton imaging field’ are used to deliver a well determined dose distribution in a specific volume, then, at any given depth x of this volume, the behavior of the dose against the energies of the proton imaging field is unique and characterizes the depth x. This concept applies directly to proton therapy scanning delivery methods (pencil beam scanning and uniform scanning) and it can be extended to the proton therapy passive delivery methods (single and double scattering) if the delivery of the irradiation is time-controlled with a known time-energy relationship. To derive the water equivalent path length (WEPL) from the energy resolved dose measurement, one may proceed in two different ways. A first method is by matching the measured energy resolved dose function to a pre-established calibration database of the behavior of the energy resolved dose in water, measured over the entire range of radiological depths with at least 1 mm spatial resolution. This calibration database can also be made specific to the patient if computed using the patient x-CT data. A second method to determine the WEPL is by using the empirical relationships between the WEPL and the integral dose or the depth at 80% of the proximal fall off of the energy resolved dose functions in water. In this note, we establish the evidence of the fundamental relationship between the energy resolved dose and the WEPL at the depth of the measurement. Then, we illustrate this relationship with experimental data and discuss its imaging dynamic range for 230 MeV protons.

  6. Concept of proton radiography using energy resolved dose measurement.

    PubMed

    Bentefour, El H; Schnuerer, Roland; Lu, Hsiao-Ming

    2016-08-21

    Energy resolved dosimetry offers a potential path to single detector based proton imaging using scanned proton beams. This is because energy resolved dose functions encrypt the radiological depth at which the measurements are made. When a set of predetermined proton beams 'proton imaging field' are used to deliver a well determined dose distribution in a specific volume, then, at any given depth x of this volume, the behavior of the dose against the energies of the proton imaging field is unique and characterizes the depth x. This concept applies directly to proton therapy scanning delivery methods (pencil beam scanning and uniform scanning) and it can be extended to the proton therapy passive delivery methods (single and double scattering) if the delivery of the irradiation is time-controlled with a known time-energy relationship. To derive the water equivalent path length (WEPL) from the energy resolved dose measurement, one may proceed in two different ways. A first method is by matching the measured energy resolved dose function to a pre-established calibration database of the behavior of the energy resolved dose in water, measured over the entire range of radiological depths with at least 1 mm spatial resolution. This calibration database can also be made specific to the patient if computed using the patient x-CT data. A second method to determine the WEPL is by using the empirical relationships between the WEPL and the integral dose or the depth at 80% of the proximal fall off of the energy resolved dose functions in water. In this note, we establish the evidence of the fundamental relationship between the energy resolved dose and the WEPL at the depth of the measurement. Then, we illustrate this relationship with experimental data and discuss its imaging dynamic range for 230 MeV protons. PMID:27435446

  7. Building-Resolved CFD Simulations for Greenhouse Gas Transport and Dispersion over Washington DC / Baltimore

    NASA Astrophysics Data System (ADS)

    Prasad, K.; Lopez-Coto, I.; Ghosh, S.; Mueller, K.; Whetstone, J. R.

    2015-12-01

    The North-East Corridor project aims to use a top-down inversion methodology to quantify sources of Greenhouse Gas (GHG) emissions over urban domains such as Washington DC / Baltimore with high spatial and temporal resolution. Atmospheric transport of tracer gases from an emission source to a tower mounted receptor are usually conducted using the Weather Research and Forecasting (WRF) model. For such simulations, WRF employs a parameterized turbulence model and does not resolve the fine scale dynamics generated by the flow around buildings and communities comprising a large city. The NIST Fire Dynamics Simulator (FDS) is a computational fluid dynamics model that utilizes large eddy simulation methods to model flow around buildings at length scales much smaller than is practical with WRF. FDS has the potential to evaluate the impact of complex urban topography on near-field dispersion and mixing difficult to simulate with a mesoscale atmospheric model. Such capabilities may be important in determining urban GHG emissions using atmospheric measurements. A methodology has been developed to run FDS as a sub-grid scale model within a WRF simulation. The coupling is based on nudging the FDS flow field towards that computed by WRF, and is currently limited to one way coupling performed in an off-line mode. Using the coupled WRF / FDS model, NIST will investigate the effects of the urban canopy at horizontal resolutions of 10-20 m in a domain of 12 x 12 km. The coupled WRF-FDS simulations will be used to calculate the dispersion of tracer gases in the North-East Corridor and to evaluate the upwind areas that contribute to tower observations, referred to in the inversion community as influence functions. Results of this study will provide guidance regarding the importance of explicit simulations of urban atmospheric turbulence in obtaining accurate estimates of greenhouse gas emissions and transport.

  8. Momentum and energy dependence of the anomalous high-energy dispersion in the electronic structure of high temperature superconductors.

    PubMed

    Inosov, D S; Fink, J; Kordyuk, A A; Borisenko, S V; Zabolotnyy, V B; Schuster, R; Knupfer, M; Büchner, B; Follath, R; Dürr, H A; Eberhardt, W; Hinkov, V; Keimer, B; Berger, H

    2007-12-01

    Using high-resolution angle-resolved photoemission spectroscopy we have studied the momentum and photon energy dependence of the anomalous high-energy dispersion, termed waterfalls, between the Fermi level and 1 eV binding energy in several high-T_{c} superconductors. We observe strong changes of the dispersion between different Brillouin zones and a strong dependence on the photon energy around 75 eV, which we associate with the resonant photoemission at the Cu3p-->3d_{x;{2}-y;{2}} edge. We conclude that the high-energy "waterfall" dispersion results from a strong suppression of the photoemission intensity at the center of the Brillouin zone due to matrix element effects and is, therefore, not an intrinsic feature of the spectral function. This indicates that the new high-energy scale in the electronic structure of cuprates derived from the waterfall-like dispersion may be incorrect. PMID:18233401

  9. Momentum and Energy Dependence of the Anomalous High-Energy Dispersion in the Electronic Structure of High Temperature Superconductors

    NASA Astrophysics Data System (ADS)

    Inosov, D. S.; Fink, J.; Kordyuk, A. A.; Borisenko, S. V.; Zabolotnyy, V. B.; Schuster, R.; Knupfer, M.; Büchner, B.; Follath, R.; Dürr, H. A.; Eberhardt, W.; Hinkov, V.; Keimer, B.; Berger, H.

    2007-12-01

    Using high-resolution angle-resolved photoemission spectroscopy we have studied the momentum and photon energy dependence of the anomalous high-energy dispersion, termed waterfalls, between the Fermi level and 1 eV binding energy in several high-Tc superconductors. We observe strong changes of the dispersion between different Brillouin zones and a strong dependence on the photon energy around 75 eV, which we associate with the resonant photoemission at the Cu3p→3dx2-y2 edge. We conclude that the high-energy “waterfall” dispersion results from a strong suppression of the photoemission intensity at the center of the Brillouin zone due to matrix element effects and is, therefore, not an intrinsic feature of the spectral function. This indicates that the new high-energy scale in the electronic structure of cuprates derived from the waterfall-like dispersion may be incorrect.

  10. Coupling of WRF and Building-resolved CFD Simulations for Greenhouse Gas Transport and Dispersion

    NASA Astrophysics Data System (ADS)

    Prasad, K.; Hu, H.; McDermott, R.; Lopez-Coto, I.; Davis, K. J.; Whetstone, J. R.; Lauvaux, T.

    2014-12-01

    The Indianapolis Flux Experiment (INFLUX) aims to use a top-down inversion methodology to quantify sources of Greenhouse Gas (GHG) emissions over an urban domain with high spatial and temporal resolution. Atmospheric transport of tracer gases from an emission source to a tower mounted receptor are usually conducted using the Weather Research and Forecasting (WRF) model. WRF is used extensively in the atmospheric community to simulate mesoscale atmospheric transport. For such simulations, WRF employs a parameterized turbulence model and does not resolve the fine scale dynamics that are generated by the flow around buildings and communities that are part of a large city. Since the model domain includes the city of Indianapolis, much of the flow of interest is over an urban topography. The NIST Fire Dynamics Simulator (FDS) is a computational fluid dynamics model to perform large eddy simulations of flow around buildings, but it has not been nested within a larger-scale atmospheric transport model such as WRF. FDS has the potential to evaluate the impact of complex urban topography on near-field dispersion and mixing that cannot be simulated with a mesoscale atmospheric model, and which may be important to determining urban GHG emissions using atmospheric measurements. A methodology has been developed to run FDS as a sub-grid scale model within a WRF simulation. The coupling is based on nudging the FDS flow field towards the one computed by WRF, and is currently limited to one way coupling performed in an off-line mode. Using the coupled WRF / FDS model, NIST will investigate the effects of the urban canopy at horizontal resolutions of 2-10 m. The coupled WRF-FDS simulations will be used to calculate the dispersion of tracer gases in an urban domain and to evaluate the upwind areas that contribute to tower observations, referred to in the inversion community as influence functions. Predicted mixing ratios will be compared with tower measurements and WRF simulations

  11. Low Energy Lorentz Violation from Modified Dispersion at High Energies.

    PubMed

    Husain, Viqar; Louko, Jorma

    2016-02-12

    Many quantum theories of gravity propose Lorentz-violating dispersion relations of the form ω=|k|f(|k|/M⋆), with recovery of approximate Lorentz invariance at energy scales much below M⋆. We show that a quantum field with this dispersion predicts drastic low energy Lorentz violation in atoms modeled as Unruh-DeWitt detectors, for any f that dips below unity somewhere. As an example, we show that polymer quantization motivated by loop quantum gravity predicts such Lorentz violation below current ion collider rapidities. PMID:26918976

  12. Correlation energy and dispersion interaction in the ab initio potential energy curve of the neon dimer

    SciTech Connect

    Bytautas, L.; Ruedenberg, K.

    2008-06-06

    A close approximation to the empirical potential energy curve of the neon dimer is obtained by coupled-cluster singles plus doubles plus noniterative triples calculations by using nonaugmented correlation-consistent basis sets without counterpoise corrections and complementing them by three-term extrapolations to the complete basis set limit. The potential energy is resolved into a self-consistent-field Hartree-Fock contribution and a correlation contribution. The latter is shown to decay in the long-range region in accordance with the empirical dispersion expansion.

  13. Correlation energy and dispersion interaction in the ab initio potential energy curve of the neon dimer.

    PubMed

    Bytautas, Laimutis; Ruedenberg, Klaus

    2008-06-01

    A close approximation to the empirical potential energy curve of the neon dimer is obtained by coupled-cluster singles plus doubles plus noniterative triples calculations by using nonaugmented correlation-consistent basis sets without counterpoise corrections and complementing them by three-term extrapolations to the complete basis set limit. The potential energy is resolved into a self-consistent-field Hartree-Fock contribution and a correlation contribution. The latter is shown to decay in the long-range region in accordance with the empirical dispersion expansion. PMID:18537423

  14. Source Inversion for contaminant plume dispersion in urban environments using building-resolving simulations

    SciTech Connect

    Chow, F K; Kosovic, B; Chan, S T

    2005-11-04

    Flow in urban environments is complicated by the presence of buildings, which divert the flow into often unexpected directions. Contaminants released at ground level are easily lofted above tall ({approx} 100 m) buildings and channeled through urban canyons that are perpendicular to the wind direction (see e.g., IOP 9 in Chan, 2005). The path of wind and scalars in urban environments is difficult to predict even with building-resolving computational fluid dynamics codes, due to the uncertainty in the synoptic wind and boundary conditions and other errors in the models. Given the difficulties due to the complexity of urban flows, solving an inverse problem becomes quite challenging. That is, given measurements of concentration at sensors scattered throughout a city, is it possible to detect the source of the contaminant? The ability to locate a source and determine its characteristics in a complex environment is necessary for emergency response for accidental or intentional releases of contaminants in densely-populated urban areas. The goal of this work is to demonstrate a robust statistical inversion procedure that performs well even under the complex flow conditions and uncertainty present in urban environments. Much work has previously focused on direct inversion procedures, where an inverse solution is obtained using an adjoint advection-diffusion equation. The exact direct inversion approaches are strictly limited to processes governed by linear equations. In addition, they assume the system is steady-state and that the equations are linear (Enting, 2002). In addition to adjoint models, optimization techniques are also employed to obtain solutions to inverse problems. These techniques often give only a single best answer, or assume a Gaussian distribution to account for uncertainties. General dispersion related inverse problems, however, often include non-linear processes (e.g., dispersion of chemically reacting substances) or are characterized by non

  15. Single Hit Energy-resolved Laue Diffraction

    SciTech Connect

    Patel, Shamim; Suggit, Matthew J.; Stubley, Paul G.; Ciricosta, Orlando; Wark, Justin S.; Higginbotham, Andrew; Hawreliak, James A.; Collins, Gilbert W.; Eggert, Jon H.; Comley, Andrew J.; Foster, John M.

    2015-05-15

    In situ white light Laue diffraction has been successfully used to interrogate the structure of single crystal materials undergoing rapid (nanosecond) dynamic compression up to megabar pressures. However, information on strain state accessible via this technique is limited, reducing its applicability for a range of applications. We present an extension to the existing Laue diffraction platform in which we record the photon energy of a subset of diffraction peaks. This allows for a measurement of the longitudinal and transverse strains in situ during compression. Consequently, we demonstrate measurement of volumetric compression of the unit cell, in addition to the limited aspect ratio information accessible in conventional white light Laue. We present preliminary results for silicon, where only an elastic strain is observed. VISAR measurements show the presence of a two wave structure and measurements show that material downstream of the second wave does not contribute to the observed diffraction peaks, supporting the idea that this material may be highly disordered, or has undergone large scale rotation.

  16. Deconstructing time-resolved optical rotatory dispersion kinetic measurements of cytochrome c folding: from molten globule to the native state.

    PubMed

    Chen, Eefei; Kliger, David S

    2012-01-01

    The far-UV time-resolved optical rotatory dispersion (TRORD) technique has contributed significantly to our understanding of nanosecond secondary structure kinetics in protein folding and function reactions. For reduced cytochrome c, protein folding kinetics have been probed largely from the unfolded to the native state. Here we provide details about sample preparation and the TRORD apparatus and measurements for studying folding from a partly unfolded state to the native secondary structure conformation of reduced cytochrome c. PMID:22760330

  17. Energy resolving CT systems using Medipix2 and MHSP detectors

    NASA Astrophysics Data System (ADS)

    Carramate, L. F. N. D.; Nachtrab, F.; Firsching, M.; Silva, A. L. M.; da Silva, A. M.; Veloso, J. F. C. A.; Uhlmann, N.

    2013-03-01

    Energy resolved imaging has been possible with a newest generation of radiation detectors with photon counting and spectroscopic capabilities. This innovation gives the possibility to enhance the image quality by applying techniques using the energy information. In this work two X-ray Computed Tomography (CT) Systems were assembled with two different energy resolving detectors: Medipix2 and MicroHole & Strip Plate (MHSP). These detectors have the aforesaid characteristics and showed a good performance for X-ray imaging. The Energy Weighting Technique (EWT) and Basis Material Decomposition (BMD) techniques were applied with good results. An improvement of 31% in the CNR was achieved by applying the EWT in the MHSP data and, using Medipix2, two basis materials (Carbon based and Aluminium) were decomposed successfully with densities close to the real values.

  18. Linear dispersion-diffusion analysis and its application to under-resolved turbulence simulations using discontinuous Galerkin spectral/hp methods

    NASA Astrophysics Data System (ADS)

    Moura, R. C.; Sherwin, S. J.; Peiró, J.

    2015-10-01

    We investigate the potential of linear dispersion-diffusion analysis in providing direct guidelines for turbulence simulations through the under-resolved DNS (sometimes called implicit LES) approach via spectral/hp methods. The discontinuous Galerkin (DG) formulation is assessed in particular as a representative of these methods. We revisit the eigensolutions technique as applied to linear advection and suggest a new perspective to the role of multiple numerical modes, peculiar to spectral/hp methods. From this new perspective, "secondary" eigenmodes are seen to replicate the propagation behaviour of a "primary" mode, so that DG's propagation characteristics can be obtained directly from the dispersion-diffusion curves of the primary mode. Numerical dissipation is then appraised from these primary eigencurves and its effect over poorly-resolved scales is quantified. Within this scenario, a simple criterion is proposed to estimate DG's effective resolution in terms of the largest wavenumber it can accurately resolve in a given hp approximation space, also allowing us to present points per wavelength estimates typically used in spectral and finite difference methods. Although strictly valid for linear advection, the devised criterion is tested against (1D) Burgers turbulence and found to predict with good accuracy the beginning of the dissipation range on the energy spectra of under-resolved simulations. The analysis of these test cases through the proposed methodology clarifies why and how the DG formulation can be used for under-resolved turbulence simulations without explicit subgrid-scale modelling. In particular, when dealing with communication limited hardware which forces one to consider the performance for a fixed number of degrees of freedom, the use of higher polynomial orders along with moderately coarser meshes is shown to be the best way to translate available degrees of freedom into resolution power.

  19. Complete momentum and energy resolved TOF electron spectrometerfor time-resolved photoemission spectroscopy

    SciTech Connect

    Hussain, Zahid; Lebedev, G.; Tremsin, A.; Siegmund, O.; Chen, Y.; Shen, Z.X.; Hussain, Z.

    2007-08-12

    Over the last decade, high-resolution Angle-Resolved Photoemission Spectroscopy (ARPES) has emerged as a tool of choice for studying the electronic structure of solids, in particular, strongly correlated complex materials such as cuprate superconductors. In this paper we present the design of a novel time-of-flight based electron analyzer with capability of 2D in momentum space (kx and ky) and all energies (calculated from time of flight) in the third dimension. This analyzer will utilize an improved version of a 2D delay linedetector capable of imaging with<35 mm (700x700 pixels) spatial resolution and better than 120 ps FWHM timing resolution. Electron optics concepts and optimization procedure are considered for achieving an energy resolution less than 1 meV and an angular resolution better than 0.11.

  20. X-ray characterization by energy-resolved powder diffraction

    NASA Astrophysics Data System (ADS)

    Cheung, G.; Hooker, S. M.

    2016-08-01

    A method for single-shot, nondestructive characterization of broadband x-ray beams, based on energy-resolved powder diffraction, is described. Monte-Carlo simulations are used to simulate data for x-ray beams in the keV range with parameters similar to those generated by betatron oscillations in a laser-driven plasma accelerator. The retrieved x-ray spectra are found to be in excellent agreement with those of the input beams for realistic numbers of incident photons. It is demonstrated that the angular divergence of the x rays can be deduced from the deviation of the detected photons from the Debye-Scherrer rings which would be produced by a parallel beam. It is shown that the angular divergence can be measured as a function of the photon energy, yielding the angularly resolved spectrum of the input x-ray beam.

  1. Resolving high energy emission of jets using strong gravitational lensing

    NASA Astrophysics Data System (ADS)

    Barnacka, Anna

    2014-11-01

    Chandra observations of M87 in 2004 uncovered an outburst originating in distant knot along the jet hundreds of parsecs from the core. This discovery challenges our understanding of the origin of high energy flares. Current technology is inadequate to resolve jets at distances greater than M87, or observed at higher energies. We propose to use gravitationally lensed jets to investigate the structure of more distant sources. Photons emitted at different sites cross the lens plane at different distances, thus magnification ratios and time delays differ between the mirage images. Monitoring of flares from lensed jets reveals the origin of the emission. With detectors like Chandra, lensed systems are a tool for resolving the structure of the jets and for investigating their cosmic evolution.

  2. Using dense locality sampling resolves the subtle genetic population structure of the dispersive fish species Plecoglossus altivelis.

    PubMed

    Takeshima, Hirohiko; Iguchi, Kei'ichiro; Hashiguchi, Yasuyuki; Nishida, Mutsumi

    2016-07-01

    In dispersive species with continuous distributions, genetic differentiation between local populations is often absent or subtle and thus difficult to detect. To incorporate such subtle differentiation into management plans, it may be essential to analyse many samples from many localities using adequate numbers of high-resolution genetic markers. Here, we evaluated the usefulness of dense locality sampling in resolving genetic population structure in the ayu (Plecoglossus altivelis), a dispersive fish important in Japanese inland fisheries. Genetic variability in, and differentiation between, ayu populations around the Japan-Ryukyu Archipelago were investigated in 4746 individuals collected from 120 localities by genotyping 12 microsatellite markers. These individuals represented the two subspecies of ayu, namely the Ryukyuan subspecies (Plecoglossus altivelis ryukyuensis) and both amphidromous and landlocked forms of the nominotypical subspecies (P. a. altivelis) along the archipelago. We successfully detected an absence of genetic differentiation within the landlocked form and subtle but significant differentiation and clear geographic patterns of genetic variation among populations of the amphidromous form, which had been considered genetically homogeneous. This suggests that dense locality sampling effectively resolves subtle differences in genetic population structure, reducing stochastic deviation in the detection of genetic differentiation and geographic patterns in local populations of this dispersive species. Resampling analyses based on empirical data sets clearly demonstrate the effectiveness of increasing the number of locality samples for stable and reliable estimations of genetic fixation indices. The genetic population structure observed within the amphidromous form provides useful information for identifying management or conservation units in ayu. PMID:27085501

  3. Resolving precipitation induced water content profiles by inversion of dispersive GPR data: A numerical study

    NASA Astrophysics Data System (ADS)

    Mangel, Adam R.; Moysey, Stephen M. J.; van der Kruk, Jan

    2015-06-01

    Surface-based ground-penetrating radar (GPR) measurements have significant potential for monitoring dynamic hydrologic processes at multiple scales in time and space. At early times during infiltration into a soil, the zone above the wetting front may act as a low-velocity waveguide that traps GPR waves, thereby causing dispersion and making interpretation of the data using standard methods difficult. In this work, we show that the dispersion is dependent upon the distribution of water within the waveguide, which is controlled by soil hydrologic properties. Simulations of infiltration were performed by varying the n-parameter of the Mualem-van Genuchten equation using HYDRUS-1D; the associated GPR data were simulated to evaluate the influence of dispersion. We observed a notable decrease in wave dispersion as the sharpness of the wetting front profile decreased. Given the sensitivity of the dispersion effect to the wetting front profile, we also evaluated whether the water content distribution can be determined through inversion of the dispersive GPR data. We found that a global grid search combined with the simplex algorithm was able to estimate the average water content when the wetted zone is divided into 2 layers. This approach was incapable, however, of representing the gradational nature of the water content distribution behind the wetting front. In contrast, the shuffled complex evolution algorithm was able to constrain a piece-wise linear function to closely match the shallow gradational water content profile. In both the layered and piece-wise linear case, the sensitivity of the dispersive data dropped sharply below the wetting front, which in this case was around 20 cm, i.e., twice the average wavelength, for a 900 MHz GPR survey. This study demonstrates that dispersive GPR data has significant potential for capturing the early-time dynamics of infiltration that cannot be obtained with standard GPR analysis approaches.

  4. Inverting GPR Dispersion Curves to Resolve Water Content Profiles of Precipitation Induced Low-Velocity Waveguides

    NASA Astrophysics Data System (ADS)

    Mangel, A. R.; Moysey, S. M.; Van Der Kruk, J.

    2014-12-01

    Surface-based ground-penetrating radar (GPR) measurements have significant potential for monitoring dynamic hydrologic processes at multiple scales in time and space. At early times during infiltration into a soil, the zone behind the wetting front may act as a low-velocity waveguide that causes dispersion of GPR waves, thereby making interpretation of the data using standard methods difficult. In this work, we show that the dispersion is dependent upon the distribution of water within the waveguide, which is controlled by soil hydrologic properties. Simulations of infiltration were performed by varying the n-parameter of the Mualem-van Genuchten equation using HYDRUS-1D; the associated GPR data were simulated to evaluate the influence of dispersion. We observed a notable decrease in the "shingling" effect in the GPR data associated with wave dispersion as the sharpness of the wetting front profile decreased. Given the sensitivity of the dispersion effect to the wetting front profile, we also evaluated whether the water content distribution can be determined through inversion of the dispersive GPR data. We found that a global grid search combined with the simplex algorithm was able to estimate the average water content when the wetted zone is divided into 1-2 effective layers. This approach was incapable, however, of representing the gradational nature of the water content distribution behind the wetting front. In contrast, the shuffled complex evolution algorithm was able to constrain a piece-wise linear function to closely match the shallow gradational water content profile. In both the layered and piece-wise linear case, the sensitivity of the dispersive data dropped sharply below the wetting front, which in this case was around 20 cm for a 1000MHz GPR survey. This study demonstrates that dispersive GPR data has significant potential for capturing the early-time dynamics of infiltration that cannot be obtained with standard GPR analysis approaches.

  5. Angle resolved electron energy loss spectroscopy on graphite

    NASA Astrophysics Data System (ADS)

    Diebold, U.; Preisinger, A.; Schattschneider, P.; Varga, P.

    We report on angle resolved electron energy loss spectroscopy (EELS) in reflection mode with low primary energy on a graphite single crystal. Measurements with primary electron energy of 175 eV have been performed in off-Bragg-reflex geometry in two different directions within the (0001) surface plane of the graphite single crystal. In addition, EELS measurements in specular reflection mode with different primary energies and angles of incidence were done in order to distinguish between surface and bulk plasmon losses. The energy losses and the transferred momenta of the losses have been analyzed. The results are compared with the loss functions for bulk and surface excitations calculated from the dielectric function ɛ(ω, q) obtained from TEELS-data (EELS in transmission mode) [Springer Tracts Mod. Phys. 54 (1970) 77].

  6. Optimal ''image-based'' weighting for energy-resolved CT

    SciTech Connect

    Schmidt, Taly Gilat

    2009-07-15

    This paper investigates a method of reconstructing images from energy-resolved CT data with negligible beam-hardening artifacts and improved contrast-to-nosie ratio (CNR) compared to conventional energy-weighting methods. Conceptually, the investigated method first reconstructs separate images from each energy bin. The final image is a linear combination of the energy-bin images, with the weights chosen to maximize the CNR in the final image. The optimal weight of a particular energy-bin image is derived to be proportional to the contrast-to-noise-variance ratio in that image. The investigated weighting method is referred to as ''image-based'' weighting, although, as will be described, the weights can be calculated and the energy-bin data combined prior to reconstruction. The performance of optimal image-based energy weighting with respect to CNR and beam-hardening artifacts was investigated through simulations and compared to that of energy integrating, photon counting, and previously studied optimal ''projection-based'' energy weighting. Two acquisitions were simulated: dedicated breast CT and a conventional thorax scan. The energy-resolving detector was simulated with five energy bins. Four methods of estimating the optimal weights were investigated, including task-specific and task-independent methods and methods that require a single reconstruction versus multiple reconstructions. Results demonstrated that optimal image-based weighting improved the CNR compared to energy-integrating weighting by factors of 1.15-1.6 depending on the task. Compared to photon-counting weighting, the CNR improvement ranged from 1.0 to 1.3. The CNR improvement factors were comparable to those of projection-based optimal energy weighting. The beam-hardening cupping artifact increased from 5.2% for energy-integrating weighting to 12.8% for optimal projection-based weighting, while optimal image-based weighting reduced the cupping to 0.6%. Overall, optimal image-based energy weighting

  7. Visible/Infrared Imaging Spectroscopy and Energy-Resolving Detectors

    NASA Astrophysics Data System (ADS)

    Eisenhauer, Frank; Raab, Walfried

    2015-08-01

    Imaging spectroscopy has seen rapid progress over the past 25 years, leading to breakthroughs in many fields of astronomy that would not have been otherwise possible. This review overviews the visible/infrared imaging spectroscopy techniques as well as energy-resolving detectors. We introduce the working principle of scanning Fabry-Perot and Fourier transform spectrometers and explain the most common integral field concepts based on mirror slicers, lenslet arrays, and fibers. The main advantage of integral field spectrographs is the simultaneous measurement of spatial and spectral information. Although Fabry-Perot and Fourier transform spectrometers can provide a larger field of view, it is ultimately the higher sensitivity of integral field units that make them the technique of choice. This is arguably the case for image slicers, which make the most efficient use of the available detector pixels and have equal or higher transmission than lenslet arrays and fiber integral field units, respectively. We also address the more specific issues of large étendue operation, focal ratio degradation, anamorphic magnification, and diffraction-limited operation. This review also covers the emerging technology of energy-resolving detectors, which promise very simple and efficient instrument designs. These energy-resolving detectors are based on superconducting thin film technology and exploit either the very small superconducting energy to count the number of quasi-particles excited in the absorption of the photon or the extremely steep phase transition between the normal- and superconducting phase to measure a temperature increase. We have put special emphasis on an overview of the underlying physical phenomena as well as on the recent technological progress and astronomical path finder experiments.

  8. The Dark Energy Survey: Prospects for resolved stellar populations

    SciTech Connect

    Rossetto, Bruno M.; Santiago, Basílio X.; Girardi, Léo; Camargo, Julio I. B.; Balbinot, Eduardo; da Costa, Luiz N.; Yanny, Brian; Maia, Marcio A. G.; Makler, Martin; Ogando, Ricardo L. C.; Pellegrini, Paulo S.; Ramos, Beatriz; de Simoni, Fernando; Armstrong, R.; Bertin, E.; Desai, S.; Kuropatkin, N.; Lin, H.; Mohr, J. J.; Tucker, D. L.

    2011-05-06

    Wide angle and deep surveys, regardless of their primary purpose, always sample a large number of stars in the Galaxy and in its satellite system. We here make a forecast of the expected stellar sample resulting from the Dark Energy Survey and the perspectives that it will open for studies of Galactic structure and resolved stellar populations in general. An estimated 1.2 x 108 stars will be sampled in DES grizY filters in the southern equatorial hemisphere. This roughly corresponds to 20% of all DES sources. Most of these stars belong to the stellar thick disk and halo of the Galaxy.

  9. A continuum solvent model of the multipolar dispersion solvation energy.

    PubMed

    Duignan, Timothy T; Parsons, Drew F; Ninham, Barry W

    2013-08-15

    The dispersion energy is an important contribution to the total solvation energies of ions and neutral molecules. Here, we present a new continuum model calculation of these energies, based on macroscopic quantum electrodynamics. The model uses the frequency dependent multipole polarizabilities of molecules in order to accurately calculate the dispersion interaction of a solute particle with surrounding water molecules. It includes the dipole, quadrupole, and octupole moment contributions. The water is modeled via a bulk dielectric susceptibility with a spherical cavity occupied by the solute. The model invokes damping functions to account for solute-solvent wave function overlap. The assumptions made are very similar to those used in the Born model. This provides consistency and additivity of electrostatic and dispersion (quantum mechanical) interactions. The energy increases in magnitude with cation size, but decreases slightly with size for the highly polarizable anions. The higher order multipole moments are essential, making up more than 50% of the dispersion solvation energy of the fluoride ion. This method provides an accurate and simple way of calculating the notoriously problematic dispersion contribution to the solvation energy. The result establishes the importance of using accurate calculations of the dispersion energy for the modeling of solvation. PMID:23837890

  10. Site-specific intermolecular valence-band dispersion in α-phase crystalline films of cobalt phthalocyanine studied by angle-resolved photoemission spectroscopy

    SciTech Connect

    Yamane, Hiroyuki; Kosugi, Nobuhiro

    2014-12-14

    The valence band structure of α-phase crystalline films of cobalt phthalocyanine (CoPc) grown on Au(111) is investigated by using angle-resolved photoemission spectroscopy (ARPES) with synchrotron radiation. The photo-induced change in the ARPES peaks is noticed in shape and energy of the highest occupied molecular orbital (HOMO, C 2p) and HOMO-1 (Co 3d) of CoPc, and is misleading the interpretation of the electronic properties of CoPc films. From the damage-free normal-emission ARPES measurement, the clear valence-band dispersion has been first observed, showing that orbital-specific behaviors are attributable to the interplay of the intermolecular π-π and π-d interactions. The HOMO band dispersion of 0.1 eV gives the lower limit of the hole mobility for α-CoPc of 28.9 cm{sup 2} V{sup −1} s{sup −1} at 15 K. The non-dispersive character of the split HOMO-1 bands indicates that the localization of the spin state is a possible origin of the antiferromagnetism.

  11. Energy-resolved computed tomography: first experimental results

    NASA Astrophysics Data System (ADS)

    Shikhaliev, Polad M.

    2008-10-01

    First experimental results with energy-resolved computed tomography (CT) are reported. The contrast-to-noise ratio (CNR) in CT has been improved with x-ray energy weighting for the first time. Further, x-ray energy weighting improved the CNR in material decomposition CT when applied to CT projections prior to dual-energy subtraction. The existing CT systems use an energy (charge) integrating x-ray detector that provides a signal proportional to the energy of the x-ray photon. Thus, the x-ray photons with lower energies are scored less than those with higher energies. This underestimates contribution of lower energy photons that would provide higher contrast. The highest CNR can be achieved if the x-ray photons are scored by a factor that would increase as the x-ray energy decreases. This could be performed by detecting each x-ray photon separately and measuring its energy. The energy selective CT data could then be saved, and any weighting factor could be applied digitally to a detected x-ray photon. The CT system includes a photon counting detector with linear arrays of pixels made from cadmium zinc telluride (CZT) semiconductor. A cylindrical phantom with 10.2 cm diameter made from tissue-equivalent material was used for CT imaging. The phantom included contrast elements representing calcifications, iodine, adipose and glandular tissue. The x-ray tube voltage was 120 kVp. The energy selective CT data were acquired, and used to generate energy-weighted and material-selective CT images. The energy-weighted and material decomposition CT images were generated using a single CT scan at a fixed x-ray tube voltage. For material decomposition the x-ray spectrum was digitally spilt into low- and high-energy parts and dual-energy subtraction was applied. The x-ray energy weighting resulted in CNR improvement of calcifications and iodine by a factor of 1.40 and 1.63, respectively, as compared to conventional charge integrating CT. The x-ray energy weighting was also applied

  12. Nitrogenase FeMoco investigated by spatially resolved anomalous dispersion refinement

    PubMed Central

    Spatzal, Thomas; Schlesier, Julia; Burger, Eva-Maria; Sippel, Daniel; Zhang, Limei; Andrade, Susana L.A.; Rees, Douglas C.; Einsle, Oliver

    2016-01-01

    The [Mo:7Fe:9S:C] iron-molybdenum cofactor (FeMoco) of nitrogenase is the largest known metal cluster and catalyses the 6-electron reduction of dinitrogen to ammonium in biological nitrogen fixation. Only recently its atomic structure was clarified, while its reactivity and electronic structure remain under debate. Here we show that for its resting S=3/2 state the common iron oxidation state assignments must be reconsidered. By a spatially resolved refinement of the anomalous scattering contributions of the 7 Fe atoms of FeMoco, we conclude that three irons (Fe1/3/7) are more reduced than the other four (Fe2/4/5/6). Our data are in agreement with the recently revised oxidation state assignment for the molybdenum ion, providing the first spatially resolved picture of the resting-state electron distribution within FeMoco. This might provide the long-sought experimental basis for a generally accepted theoretical description of the cluster that is in line with available spectroscopic and functional data. PMID:26973151

  13. Encapsulated Energy Transfer Cassettes with Extremely Well Resolved Fluorescent Outputs

    PubMed Central

    Ueno, Yuichiro; Jose, Jiney; Loudet, Aurore; Pérez-Bolívar, César; Anzenbacher, Pavel; Burgess, Kevin

    2010-01-01

    This paper concerns the development of water-compatible fluorescent imaging-probes with tunable photonic properties that can be excited at a single wavelength. Bichromophoric cassettes 1a – 1c consisting of a BODIPY donor and a cyanine acceptor were prepared using a simple synthetic route, and their photophysical properties were investigated. Upon excitation of the BODIPY moiety at 488 nm the excitation energy is transferred through an acetylene bridge to the cyanine dye acceptor, which emits light at approximately 600, 700, and 800 nm, ie with remarkable dispersions. This effect is facilitated by efficient energy transfer that gives a ‘quasi-Stokes’ shift of between 86 – 290 nm opening a huge spectral window for imaging. The emissive properties of the cassettes depend on the energy transfer (ET) mechanism: the faster the transfer, the more efficient it is. Measurements of rates of energy transfer indicate that a through-bond energy transfer takes place in the cassettes 1a and 1b that is two orders of magnitude faster than the classical through-space, Förster, energy transfer (in the case of cassette 1c, however, both mechanisms are possible, and the rate measurements do not allow us to discern between them). Thus the cassettes 1a – 1c are well suited for multiplexing experiments in biotechnological methods that involve a single laser-excitation source. However, for widespread application of these probes their solubility in aqueous media must be improved. Consequently, the probes were encapsulated in calcium phosphate/silicate nanoparticles (diameter ca 22 nm) that are freely dispersible in water. This encapsulation process resulted in only minor changes in the photophysical properties of the cassettes. The system based on cassette 1a was chosen to probe how effectively these nanoparticles could be used to deliver the dyes into cells. Encapsulated cassette 1a permeated Clone 9 rat liver cells where it localized in the mitochondria and fluoresced through

  14. Electromagnetic energy flux vector for a dispersive linear medium.

    PubMed

    Crenshaw, Michael E; Akozbek, Neset

    2006-05-01

    The electromagnetic energy flux vector in a dispersive linear medium is derived from energy conservation and microscopic quantum electrodynamics and is found to be of the Umov form as the product of an electromagnetic energy density and a velocity vector. PMID:16803063

  15. Crossing statistic: Bayesian interpretation, model selection and resolving dark energy parametrization problem

    SciTech Connect

    Shafieloo, Arman

    2012-05-01

    By introducing Crossing functions and hyper-parameters I show that the Bayesian interpretation of the Crossing Statistics [1] can be used trivially for the purpose of model selection among cosmological models. In this approach to falsify a cosmological model there is no need to compare it with other models or assume any particular form of parametrization for the cosmological quantities like luminosity distance, Hubble parameter or equation of state of dark energy. Instead, hyper-parameters of Crossing functions perform as discriminators between correct and wrong models. Using this approach one can falsify any assumed cosmological model without putting priors on the underlying actual model of the universe and its parameters, hence the issue of dark energy parametrization is resolved. It will be also shown that the sensitivity of the method to the intrinsic dispersion of the data is small that is another important characteristic of the method in testing cosmological models dealing with data with high uncertainties.

  16. Single atom identification by energy dispersive x-ray spectroscopy

    SciTech Connect

    Lovejoy, T. C.; Dellby, N.; Krivanek, O. L.; Ramasse, Q. M.; Falke, M.; Kaeppel, A.; Terborg, R.; Zan, R.

    2012-04-09

    Using aberration-corrected scanning transmission electron microscope and energy dispersive x-ray spectroscopy, single, isolated impurity atoms of silicon and platinum in monolayer and multilayer graphene are identified. Simultaneously acquired electron energy loss spectra confirm the elemental identification. Contamination difficulties are overcome by employing near-UHV sample conditions. Signal intensities agree within a factor of two with standardless estimates.

  17. Imaging the Formation of High-Energy Dispersion Anomalies in the Actinide UCoGa5

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy; Durakiewicz, Tomasz; Zhu, Jian-Xin; Joyce, John J.; Sarrao, John L.; Graf, Matthias J.

    2012-10-01

    We use angle-resolved photoemission spectroscopy to image the emergence of substantial dispersion and spectral-weight anomalies in the electronic renormalization of the actinide compound UCoGa5 that was presumed to belong to a conventional Fermi-liquid family. Kinks or abrupt breaks in the slope of the quasiparticle dispersion are detected both at low (approximately 130 meV) and high (approximately 1 eV) binding energies below the Fermi energy, ruling out any significant contribution of phonons. We perform numerical calculations to demonstrate that the anomalies are adequately described by coupling between itinerant fermions and spin fluctuations arising from the particle-hole continuum of the spin-orbit-split 5f states of uranium. These anomalies resemble the “waterfall” phenomenon of the high-temperature copper-oxide superconductors, suggesting that spin fluctuations are a generic route toward multiform electronic phases in correlated materials as different as high-temperature superconductors and actinides.

  18. Dispersal

    USGS Publications Warehouse

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  19. Modern electron microscopy resolved in space, energy and time

    NASA Astrophysics Data System (ADS)

    Carbone, F.

    2011-06-01

    Recent pioneering experiments combining ultrafast lasers with electron-based technology demonstrated the possibility to obtain real-time information about chemical bonds and their dynamics during reactions and phase transformation. These techniques have been successfully applied to several states of matter including gases, liquids, solids and biological samples showing a unique versatility thanks to the high sensitivity of electrons to tiny amounts of material and their low radiation damage. A very powerful tool, the time-resolved Transmission Electron Microscope (TEM), is capable of delivering information on the structure of ordered and disordered matter through diffraction and imaging, with a spatial resolution down to the atomic limit (10-10 m); the same apparatus can distinguish dynamical phenomena happening on the time-scales between fs and ms, with a dynamic range of 12 orders of magnitude. At the same time, spectroscopic information can be obtained from the loss of kinetic energy of electrons interacting with specimens in the range of interband transitions and plasmons in solids, or charge transfers in molecules, all the way up to the atomic core levels with the same time-resolution. In this contribution, we focus on the recent advances in fs Electron Energy Loss Spectroscopy (FEELS), discussing the main results and their implications for future studies.

  20. Vacuum field energy and spontaneous emission in anomalously dispersive cavities

    SciTech Connect

    Bradshaw, Douglas H.; Di Rosa, Michael D.

    2011-05-15

    Anomalously dispersive cavities, particularly white-light cavities, may have larger bandwidth to finesse ratios than their normally dispersive counterparts. Partly for this reason, they have been proposed for use in laser interferometer gravitational-wave observatory (LIGO)-like gravity-wave detectors and in ring-laser gyroscopes. In this paper we analyze the quantum noise associated with anomalously dispersive cavity modes. The vacuum field energy associated with a particular cavity mode is proportional to the cavity-averaged group velocity of that mode. For anomalously dispersive cavities with group index values between 1 and 0, this means that the total vacuum field energy associated with a particular cavity mode must exceed ({h_bar}/2{pi}){omega}/2. For white-light cavities in particular, the group index approaches zero and the vacuum field energy of a particular spatial mode may be significantly enhanced. We predict enhanced spontaneous emission rates into anomalously dispersive cavity modes and broadened laser linewidths when the linewidth of intracavity emitters is broader than the cavity linewidth.

  1. Integrated assessment of dispersed energy resources deployment

    SciTech Connect

    Marnay, Chris; Blanco, Raquel; Hamachi, Kristina S.; Kawaan, Cornelia P.; Osborn, Julie G.; Rubio, F. Javier

    2000-06-01

    The goal of this work is to create an integrated framework for forecasting the adoption of distributed energy resources (DER), both by electricity customers and by the various institutions within the industry itself, and for evaluating the effect of this adoption on the power system, particularly on the overall reliability and quality of electrical service to the end user. This effort and follow on contributions are intended to anticipate and explore possible patterns of DER deployment, thereby guiding technical work on microgrids towards the key technical problems. An early example of this process addressed is the question of possible DER adopting customer disconnection. A deployment scenario in which many customers disconnect from their distribution company (disco) entirely leads to a quite different set of technical problems than a scenario in which customers self generate a significant share or all of their on-site electricity requirements and additionally buy and sell energy and ancillary services (AS) locally and/or into wider markets. The exploratory work in this study suggests that the economics under which customers disconnect entirely are unlikely.

  2. Pulsed Magnetic Fields for an XAS Energy Dispersive Beamline

    SciTech Connect

    Linden, Peter van der; Mathon, Olivier; Neisius, Thomas

    2007-01-19

    Pulsed magnetic fields constitute an attractive alternative to superconducting magnets for many x-ray techniques. The ESRF ID24 energy dispersive beamline was used for pulsed magnetic field room temperature XMCD measurements on GdCo3. The signal has been measured up to a magnetic field of 5.5 Tesla without signs of deterioration.

  3. Identification of position isomers by energy-resolved mass spectrometry.

    PubMed

    Menachery, Sunil Paul M; Laprévote, Olivier; Nguyen, Thao P; Aravind, Usha K; Gopinathan, Pramod; Aravindakumar, Charuvila T

    2015-07-01

    This study reports an energy-resolved mass spectrometric (ERMS) strategy for the characterization of position isomers derived from the reaction of hydroxyl radicals ((●)OH) with diphenhydramine (DPH) that are usually hard to differentiate by other methods. The isomer analogues formed by (●)OH attack on the side chain of DPH are identified with the help of a specific fragment ion peak (m/z 88) in the collision-induced dissociation (CID) spectrum of the protonated molecule. In the negative ion mode, the breakdown curves of the deprotonated molecules show an order of stability (supported by density functional theory (DFT) calculations) ortho > meta > para of the positional isomers formed by the hydroxylation of the aromatic ring. The gas phase stability of the deprotonated molecules [M - H](-) towards the benzylic cleavage depends mainly on the formation of intramolecular hydrogen bonds and of the mesomeric effect of the phenol hydroxyl. The [M - H](-) molecules of ortho and meta isomers result a peak at m/z 183 with notably different intensities because of the presence/absence of an intramolecular hydrogen bonding between the OH group and C9 protons. The ERMS approach discussed in this report might be an effective replacement for the conventional methods that requires very costly and time-consuming separation/purification methods along with the use of multi-spectroscopic methods. PMID:26349650

  4. Energy Dispersive X-ray Tomography for 3D Elemental Mapping of Individual Nanoparticles.

    PubMed

    Slater, Thomas J A; Lewis, Edward A; Haigh, Sarah J

    2016-01-01

    Energy dispersive X-ray spectroscopy within the scanning transmission electron microscope (STEM) provides accurate elemental analysis with high spatial resolution, and is even capable of providing atomically resolved elemental maps. In this technique, a highly focused electron beam is incident upon a thin sample and the energy of emitted X-rays is measured in order to determine the atomic species of material within the beam path. This elementally sensitive spectroscopy technique can be extended to three dimensional tomographic imaging by acquiring multiple spectrum images with the sample tilted along an axis perpendicular to the electron beam direction. Elemental distributions within single nanoparticles are often important for determining their optical, catalytic and magnetic properties. Techniques such as X-ray tomography and slice and view energy dispersive X-ray mapping in the scanning electron microscope provide elementally sensitive three dimensional imaging but are typically limited to spatial resolutions of > 20 nm. Atom probe tomography provides near atomic resolution but preparing nanoparticle samples for atom probe analysis is often challenging. Thus, elementally sensitive techniques applied within the scanning transmission electron microscope are uniquely placed to study elemental distributions within nanoparticles of dimensions 10-100 nm. Here, energy dispersive X-ray (EDX) spectroscopy within the STEM is applied to investigate the distribution of elements in single AgAu nanoparticles. The surface segregation of both Ag and Au, at different nanoparticle compositions, has been observed. PMID:27403838

  5. Imaging ultrasonic dispersive guided wave energy in long bones using linear radon transform.

    PubMed

    Tran, Tho N H T; Nguyen, Kim-Cuong T; Sacchi, Mauricio D; Le, Lawrence H

    2014-11-01

    Multichannel analysis of dispersive ultrasonic energy requires a reliable mapping of the data from the time-distance (t-x) domain to the frequency-wavenumber (f-k) or frequency-phase velocity (f-c) domain. The mapping is usually performed with the classic 2-D Fourier transform (FT) with a subsequent substitution and interpolation via c = 2πf/k. The extracted dispersion trajectories of the guided modes lack the resolution in the transformed plane to discriminate wave modes. The resolving power associated with the FT is closely linked to the aperture of the recorded data. Here, we present a linear Radon transform (RT) to image the dispersive energies of the recorded ultrasound wave fields. The RT is posed as an inverse problem, which allows implementation of the regularization strategy to enhance the focusing power. We choose a Cauchy regularization for the high-resolution RT. Three forms of Radon transform: adjoint, damped least-squares, and high-resolution are described, and are compared with respect to robustness using simulated and cervine bone data. The RT also depends on the data aperture, but not as severely as does the FT. With the RT, the resolution of the dispersion panel could be improved up to around 300% over that of the FT. Among the Radon solutions, the high-resolution RT delineated the guided wave energy with much better imaging resolution (at least 110%) than the other two forms. The Radon operator can also accommodate unevenly spaced records. The results of the study suggest that the high-resolution RT is a valuable imaging tool to extract dispersive guided wave energies under limited aperture. PMID:25282483

  6. Continuous energy diffraction spectroscopy: A new d-space matching technique for energy dispersive synchrotron radiation diffraction

    NASA Astrophysics Data System (ADS)

    Lee, P. L.; Beno, M. A.; Knapp, G. S.; Jennings, G.

    1994-07-01

    In this article, a new technique, continuous energy diffraction spectroscopy (CEDS) is described, for diffraction experiments using a synchrotron energy dispersive polychromatic beamline. This type of beamline uses a curved crystal monochromator (polychromator) to focus a range of x-ray energies (bandwidth ˜1 keV) into a narrow (100-120 μm) line image. With a sample at this image point, using an 2D detector, we are able to measure diffracted intensities for the entire energy range of the incident beam simultaneously with limited or no motion of the sample. This method allows the collection of anomalous scattering and diffraction anomalous fine structure (DAFS) data faster and more accurately than with conventional methods. Because of the speed with which these types of diffraction experiments can be done, this method creates new options for time resolved diffraction experiments and provides new data collection strategies.

  7. Pulse propagation, dispersion, and energy in magnetic materials.

    PubMed

    Scalora, Michael; D'Aguanno, Giuseppe; Mattiucci, Nadia; Akozbek, Neset; Bloemer, Mark J; Centini, Marco; Sibilia, Concita; Bertolotti, Mario

    2005-12-01

    We discuss pulse propagation effects in generic, electrically and magnetically dispersive media that may display large material discontinuities, such as a surface boundary. Using the known basic constitutive relations between the fields, and an explicit Taylor expansion to describe the dielectric susceptibility and magnetic permeability, we derive expressions for energy density and energy dissipation rates, and equations of motion for the coupled electric and magnetic fields. We then solve the equations of motion in the presence of a single interface, and find that in addition to the now-established negative refraction process an energy exchange occurs between the electric and magnetic fields as the pulse traverses the boundary. PMID:16486072

  8. Inverse energy dispersion of energetic ions observed in the magnetosheath

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Sibeck, D. G.; Hwang, K.-J.; Wang, Y.; Silveira, M. V. D.; Fok, M.-C.; Mauk, B. H.; Cohen, I. J.; Ruohoniemi, J. M.; Kitamura, N.; Burch, J. L.; Giles, B. L.; Torbert, R. B.; Russell, C. T.; Lester, M.

    2016-07-01

    We present a case study of energetic ions observed by the Energetic Particle Detector (EPD) on the Magnetospheric Multiscale spacecraft in the magnetosheath just outside the subsolar magnetopause that occurred at 1000 UT on 8 December 2015. As the magnetopause receded inward, the EPD observed a burst of energetic (˜50-1000 keV) proton, helium, and oxygen ions that exhibited an inverse dispersion, with the lowest energy ions appearing first. The prolonged interval of fast antisunward flow observed in the magnetosheath and transient increases in the H components of global ground magnetograms demonstrate that the burst appeared at a time when the magnetosphere was rapidly compressed. We attribute the inverse energy dispersion to the leakage along reconnected magnetic field lines of betatron-accelerated energetic ions in the magnetosheath, and a burst of reconnection has an extent of about 1.5 RE using combined Super Dual Auroral Radar Network radar and EPD observations.

  9. Electromagnetic energy dispersion in a 5D universe

    SciTech Connect

    Hartnett, John G.

    2010-06-15

    Electromagnetism is analyzed in a 5D expanding universe. Compared to the usual 4D description of electrodynamics it can be viewed as adding effective charge and current densities to the universe that are static in time. These lead to effective polarization and magnetization of the vacuum, which is most significant at high redshift. Electromagnetic waves propagate but group and phase velocities are dispersive. This introduces a new energy scale to the cosmos. And as a result electromagnetic waves propagate with superluminal speeds but no energy is transmitted faster than the canonical speed of light c.

  10. Electromagnetic energy dispersion in a 5D universe

    NASA Astrophysics Data System (ADS)

    Hartnett, John G.

    2010-06-01

    Electromagnetism is analyzed in a 5D expanding universe. Compared to the usual 4D description of electrodynamics it can be viewed as adding effective charge and current densities to the universe that are static in time. These lead to effective polarization and magnetization of the vacuum, which is most significant at high redshift. Electromagnetic waves propagate but group and phase velocities are dispersive. This introduces a new energy scale to the cosmos. And as a result electromagnetic waves propagate with superluminal speeds but no energy is transmitted faster than the canonical speed of light c.

  11. Energy dispersive photon counting detectors for breast imaging

    NASA Astrophysics Data System (ADS)

    Barber, William C.; Wessel, Jan C.; Malakhov, Nail; Wawrzyniak, Gregor; Hartsough, Neal E.; Gandhi, Thulasidharan; Nygard, Einar; Iwanczyk, Jan S.

    2013-09-01

    We report on our efforts toward the development of silicon (Si) strip detectors for energy-resolved clinical breast imaging. Typically, x-ray integrating detectors based on scintillating cesium iodide CsI(Tl) or amorphous selenium (a- Se) are used in most commercial systems. Recently, mammography instrumentation has been introduced based on photon counting silicon Si strip detectors. Mammography requires high flux from the x-ray generator, therefore, in order to achieve energy resolved single photon counting, a high output count rate (OCR) for the detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel, provided that the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions. We present our methods and results from the optimization of prototype detectors based on Si strip structures. We describe the detector optimization and the development of ASIC readout electronics that provide the required spatial resolution, low noise, high count rate capabilities and minimal power consumption.

  12. Energy Dispersive Spectrometry and Quantitative Analysis Short Course. Introduction to X-ray Energy Dispersive Spectrometry and Quantitative Analysis

    NASA Technical Reports Server (NTRS)

    Carpenter, Paul; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    This course will cover practical applications of the energy-dispersive spectrometer (EDS) to x-ray microanalysis. Topics covered will include detector technology, advances in pulse processing, resolution and performance monitoring, detector modeling, peak deconvolution and fitting, qualitative and quantitative analysis, compositional mapping, and standards. An emphasis will be placed on use of the EDS for quantitative analysis, with discussion of typical problems encountered in the analysis of a wide range of materials and sample geometries.

  13. A universal high energy anomaly in angle resolved photoemissionspectra of high temperature superconductors -- possible evidence ofspinon and holon branches

    SciTech Connect

    Graf, J.; Gweon, G.-H.; McElroy, K.; Zhou, S.Y.; Jozwiak, C.; Rotenberg, E.; Bill, A.; Sasagawa, T.; Eisaki, H.; Uchida, S.; Takagi,H.; Lee, D.-H.; Lanzara A.

    2006-12-19

    A universal high energy anomaly in the single particlespectral function is reported in three different families of hightemperature superconductors by using angle-resolved photoemissionspectroscopy. As we follow the dispersing peak of the spectral functionfrom the Fermi energy to the valence band complex, we find dispersionanomalies marked by two distinctive high energy scales, E_1 approx 0.38eV and E_2 approx 0.8 eV. E_1 marks the energy above which the dispersionsplits into two branches. One is a continuation of the near parabolicdispersion, albeit with reduced spectral weight, and reaches the bottomof the band at the Gamma point at approx 0.5 eV. The other is given by apeak in the momentum space, nearly independent of energy between E_1 andE_2. Above E_2, a band-like dispersion re-emerges. We conjecture thatthese two energies mark the disintegration of the low energyquasiparticles into a spinon and holon branch in the high T_c cuprates.

  14. Energy-entropy dispersion relation in DNA sequences

    NASA Astrophysics Data System (ADS)

    Nowak, H.; Haeussler, P.

    2013-10-01

    For a number of virus- and bacterium genomes we use the concept of block entropy from information theory and compare it with the corresponding configurational energy, defined via the ionization energies of the nucleotides and a hopping term for their interactions in the sense of a tight-binding model. Additionally to the four-letter alphabet of the nucleotides we discuss a reduction to a two-letter alphabet. We find a well defined relation between block entropy and block energy for a not too large block length which can be interpreted as a generalized dispersion relation for all genome sequences. The relation can be used to look for enhanced interactions between virus and bacterium genomes. Well known examples for virus-virus and virus-bacterium interactions are analyzed along this line.

  15. Bose gas with generalized dispersion relation plus an energy gap

    NASA Astrophysics Data System (ADS)

    Solis, M. A.; Martinez, J. G.; Garcia, J.

    We report the critical temperature, the condensed fraction, the internal energy and the specific heat for a d-dimensional Bose gas with a generalized dispersion relation plus an energy gap, i.e., ɛ =ɛ0 for k = 0 and ɛ =ɛ0 + Δ +csks , for k > 0 , where ℏk is the particle momentum, ɛ0 the lowest particle energy, cs a constant with dimension of energy multiplied by a length to the power s > 0 . When Δ > 0 , a Bose-Einstein critical temperature Tc ≠ 0 exists for any d / s >= 0 at which the internal energy shows a peak and the specific heat shows a jump. The critical temperature and the specific heat jump increase as functions of the gap but they decrease as functions of d / s . Thermodynamic properties are ɛ0 independent since this is just a reference energy. For Δ = 0 we recover the results reported in Ref. [1]. V. C. Aguilera-Navarro, M. de Llano y M. A. Solís, Eur. J. Phys. 20, 177 (1999). We acknowledge partial support from Grants PAPIIT IN111613 and CONACyT 221030.

  16. In situ energy dispersive x-ray reflectometry measurements on organic solar cells upon working

    NASA Astrophysics Data System (ADS)

    Paci, B.; Generosi, A.; Albertini, V. Rossi; Perfetti, P.; de Bettignies, R.; Firon, M.; Leroy, J.; Sentein, C.

    2005-11-01

    The change in the morphology of plastic solar cells was studied by means of time-resolved energy dispersive x-ray reflectivity (XRR). This unconventional application of the XRR technique allowed the follow up of in situ morphological evolution of an organic photovoltaic device upon working. The study consisted of three steps: A preliminary set of XRR measurements on various samples representing the intermediate stages of cell construction, which provided accurate data regarding the electronic densities of the different layers; the verification of the morphological stability of the device under ambient condition; a real-time collection of XRR patterns, both in the dark and during 15h in artificial light conditions which allowed the changes in the system morphology at the electrode-active layer interface to be monitored. In this way, a progressive thickening of this interface, responsible for a reduction in the performances of the device, was observed directly.

  17. Note: A new angle-resolved proton energy spectrometer

    SciTech Connect

    Zheng, Y.; Su, L. N.; Liu, M.; Liu, B. C.; Shen, Z. W.; Fan, H. T.; Li, Y. T.; Chen, L. M.; Lu, X.; Ma, J. L.; Wang, W. M.; Wang, Z. H.; Wei, Z. Y.; Zhang, J.

    2013-09-15

    In typical laser-driven proton acceleration experiments Thomson parabola proton spectrometers are used to measure the proton spectra with very small acceptance angle in specific directions. Stacks composed of CR-39 nuclear track detectors, imaging plates, or radiochromic films are used to measure the angular distributions of the proton beams, respectively. In this paper, a new proton spectrometer, which can measure the spectra and angular distributions simultaneously, has been designed. Proton acceleration experiments performed on the Xtreme light III laser system demonstrates that the spectrometer can give angle-resolved spectra with a large acceptance angle. This will be conductive to revealing the acceleration mechanisms, optimization, and applications of laser-driven proton beams.

  18. Specific Energies for the Collisional Dispersion of Gravitational Aggregates

    NASA Astrophysics Data System (ADS)

    Campo Bagatin, Adriano; Davo, M.; Richardson, D. C.

    2009-09-01

    One of the most interesting problems in planetology is the one concerning the internal structure of asteroids and comets. Despite of the available experimental results about the fragmentation of cohesive bodies the size of a soccer ball, and the theoretical and numerical studies extending these results to larger objects, little is known about the response to collisions by objects that formed by the gravitational re-accumulation following shattering events. We are developing a systematic study of the effects of collisions on rocky and icy gravitational aggregates (GA) between 100 m and 100 km in size, under different conditions (mass and texture of targets and projectiles, impact angle, momentum of collision, rotation of target). The study is based on a numerical model of the N-body problem (PKDGRAV code). We present our results on the dependence of the threshold specific energy for the dispersion of targets (Q*D) as a function of their mass, obtaining the corresponding scaling law. All GA are made up by the same number of particles. We have chosen 7 different targets, scaling a factor of 3 in mass and we performed a number of head-on collisions on each target mass with different projectile masses. In this way, we are able to relate the impact energy with the fraction of mass reaccumulated after impacts (f_R), and derive the threshold specific energy for dispersion, Q*_D, by interpolating the corresponding fitted linear relationship. As the result of every single collision partly depends on impact location, a number of collisions is performed with a same target and projectile, changing the direction of impact (not the impact angle). We take the average and standard deviation of the corresponding mass fraction of each set of collisions. Finally a power law relationship between Q*_D and size is derived. The main results of this study are presented.

  19. Time-resolved study on dynamic chemical state conversion of SiO2-supported Co species by means of dispersive XAFS technique

    NASA Astrophysics Data System (ADS)

    Chotiwan, S.; Tomiga, H.; Yamashita, S.; Katayama, M.; Inada, Y.

    2016-05-01

    The chemical state conversion of the Co species supported on SiO2 was investigated using the in-situ and the time-resolved XAFS techniques. The supported Co3O4 species was finally reduced to metallic Co with the stable intermediate state of CoO for both the temperature-programmed and time-course processes. The oxidation of Co0 traced the reverse route to Co3O4, whereas the relative stability of the Co3O4 species to the CoO intermediate under the oxidative environment diminished the composition of CoO. The time-resolved measurement for the oxidation reaction showed an additional intermediate at the early stage of the CoO intermediate formation suggesting the Co0 particle dispersion.

  20. Resolving shifting patterns of muscle energy use in swimming fish.

    PubMed

    Gerry, Shannon P; Ellerby, David J

    2014-01-01

    Muscle metabolism dominates the energy costs of locomotion. Although in vivo measures of muscle strain, activity and force can indicate mechanical function, similar muscle-level measures of energy use are challenging to obtain. Without this information locomotor systems are essentially a black box in terms of the distribution of metabolic energy. Although in situ measurements of muscle metabolism are not practical in multiple muscles, the rate of blood flow to skeletal muscle tissue can be used as a proxy for aerobic metabolism, allowing the cost of particular muscle functions to be estimated. Axial, undulatory swimming is one of the most common modes of vertebrate locomotion. In fish, segmented myotomal muscles are the primary power source, driving undulations of the body axis that transfer momentum to the water. Multiple fins and the associated fin muscles also contribute to thrust production, and stabilization and control of the swimming trajectory. We have used blood flow tracers in swimming rainbow trout (Oncorhynchus mykiss) to estimate the regional distribution of energy use across the myotomal and fin muscle groups to reveal the functional distribution of metabolic energy use within a swimming animal for the first time. Energy use by the myotomal muscle increased with speed to meet thrust requirements, particularly in posterior myotomes where muscle power outputs are greatest. At low speeds, there was high fin muscle energy use, consistent with active stability control. As speed increased, and fins were adducted, overall fin muscle energy use declined, except in the caudal fin muscles where active fin stiffening is required to maintain power transfer to the wake. The present data were obtained under steady-state conditions which rarely apply in natural, physical environments. This approach also has potential to reveal the mechanical factors that underlie changes in locomotor cost associated with movement through unsteady flow regimes. PMID:25165858

  1. Resolving Shifting Patterns of Muscle Energy Use in Swimming Fish

    PubMed Central

    Gerry, Shannon P.; Ellerby, David J.

    2014-01-01

    Muscle metabolism dominates the energy costs of locomotion. Although in vivo measures of muscle strain, activity and force can indicate mechanical function, similar muscle-level measures of energy use are challenging to obtain. Without this information locomotor systems are essentially a black box in terms of the distribution of metabolic energy. Although in situ measurements of muscle metabolism are not practical in multiple muscles, the rate of blood flow to skeletal muscle tissue can be used as a proxy for aerobic metabolism, allowing the cost of particular muscle functions to be estimated. Axial, undulatory swimming is one of the most common modes of vertebrate locomotion. In fish, segmented myotomal muscles are the primary power source, driving undulations of the body axis that transfer momentum to the water. Multiple fins and the associated fin muscles also contribute to thrust production, and stabilization and control of the swimming trajectory. We have used blood flow tracers in swimming rainbow trout (Oncorhynchus mykiss) to estimate the regional distribution of energy use across the myotomal and fin muscle groups to reveal the functional distribution of metabolic energy use within a swimming animal for the first time. Energy use by the myotomal muscle increased with speed to meet thrust requirements, particularly in posterior myotomes where muscle power outputs are greatest. At low speeds, there was high fin muscle energy use, consistent with active stability control. As speed increased, and fins were adducted, overall fin muscle energy use declined, except in the caudal fin muscles where active fin stiffening is required to maintain power transfer to the wake. The present data were obtained under steady-state conditions which rarely apply in natural, physical environments. This approach also has potential to reveal the mechanical factors that underlie changes in locomotor cost associated with movement through unsteady flow regimes. PMID:25165858

  2. Microcalorimeter-type energy dispersive X-ray spectrometer for a transmission electron microscope.

    PubMed

    Hara, Toru; Tanaka, Keiichi; Maehata, Keisuke; Mitsuda, Kazuhisa; Yamasaki, Noriko Y; Ohsaki, Mitsuaki; Watanabe, Katsuaki; Yu, Xiuzhen; Ito, Takuji; Yamanaka, Yoshihiro

    2010-01-01

    A new energy dispersive X-ray spectrometer (EDS) with a microcalorimeter detector equipped with a transmission electron microscope (TEM) has been developed for high- accuracy compositional analysis in the nanoscale. A superconducting transition-edge-sensor-type microcalorimeter is applied as the detector. A cryogen-free cooling system, which consists of a mechanical and a dilution refrigerator, is selected to achieve long-term temperature stability. In order to mount these detector and refrigerators on a TEM, the cooling system is specially designed such that these two refrigerators are separated. Also, the detector position and arrangement are carefully designed to avoid adverse affects between the superconductor detector and the TEM lens system. Using the developed EDS system, at present, an energy resolution of 21.92 eV full-width-at-half maximum has been achieved at the Cr K alpha line. This value is about seven times better than that of the current typical commercial Si(Li) detector, which is usually around 140 eV. The developed microcalorimeter EDS system can measure a wide energy range, 1-20 keV, at one time with this high energy resolution that can resolve peaks from most of the elements. Although several further developments will be needed to enable practical use, highly accurate compositional analysis with high energy resolution will be realized by this microcalorimeter EDS system. PMID:19717388

  3. Photon backscattering tissue characterization by energy dispersive spectroscopy evaluations.

    PubMed

    Tartari, A; Casnati, E; Fernandez, J E; Felsteiner, J; Baraldi, C

    1994-02-01

    Techniques for in vivo tissue characterization based on scattered photons have usually been confined to evaluating coherent and Compton peaks. However, information can also be obtained from the energy analysis of the Compton scattered distribution. This paper looks at the extension of a technique validated by the authors for characterizing tissues composed of low-atomic-number elements. To this end, an EDXRS (energy dispersive x-ray spectrometry) computer simulation procedure was performed and applied to test the validity of a figure of merit able to characterize binary compounds. This figure of merit is based on the photon fluence values in a restricted energy interval of the measured distribution of incoherently scattered photons. After careful experimental tests with 59.54 keV incident photons at scattering angles down to 60degrees, the simulation procedure was applied to quasi-monochromatic and polychromatic high-radiance sources. The results show that the characterization by the figure of merit, which operates satisfactorily with monochromatic sources, is unsatisfactory in the latter cases, which seem to favour a different parameter for compound characterization. PMID:15552121

  4. Inter-phase heat transfer and energy coupling in turbulent dispersed multiphase flows

    NASA Astrophysics Data System (ADS)

    Ling, Y.; Balachandar, S.; Parmar, M.

    2016-03-01

    The present paper addresses important fundamental issues of inter-phase heat transfer and energy coupling in turbulent dispersed multiphase flows through scaling analysis. In typical point-particle or two-fluid approaches, the fluid motion and convective heat transfer at the particle scale are not resolved and the momentum and energy coupling between fluid and particles are provided by proper closure models. By examining the kinetic energy transfer due to the coupling forces from the macroscale to microscale fluid motion, closure models are obtained for the contributions of the coupling forces to the energy coupling. Due to the inviscid origin of the added-mass force, its contribution to the microscale kinetic energy does not contribute to dissipative transfer to fluid internal energy as was done by the quasi-steady force. Time scale analysis shows that when the particle is larger than a critical diameter, the diffusive-unsteady kernel decays at a time scale that is smaller than the Kolmogorov time scale. As a result, the computationally costly Basset-like integral form of diffusive-unsteady heat transfer can be simplified to a non-integral form. Conventionally, the fluid-to-particle volumetric heat capacity ratio is used to evaluate the relative importance of the unsteady heat transfer to the energy balance of the particles. Therefore, for gas-particle flows, where the fluid-to-particle volumetric heat capacity ratio is small, unsteady heat transfer is usually ignored. However, the present scaling analysis shows that for small fluid-to-particle volumetric heat capacity ratio, the importance of the unsteady heat transfer actually depends on the ratio between the particle size and the Kolmogorov scale. Furthermore, the particle mass loading multiplied by the heat capacity ratio is usually used to estimate the importance of the thermal two-way coupling effect. Through scaling argument, improved estimates are established for the energy coupling parameters of each

  5. Imaging Dispersive Energy Analyzer (IDEA) for Ionosphere-Thermosphere Measurements

    NASA Astrophysics Data System (ADS)

    Syrstad, E. A.; Fenn, D.; Watson, M.; Schicker, S.; Smith, B.

    2011-12-01

    We present a new instrument concept for in situ satellite-based measurement of ion drifts / neutral winds, temperature, density, and composition. The Imaging Dispersive Energy Analyzer (IDEA) combines high-throughput dispersive energy analysis with 2-D imaging ion detection to provide complete characterization of the velocity distribution of a charged particle stream. The IDEA deflector operates at a small (<15 V) d.c. potential, with no voltage scanning necessary. All ions transmitted through the entrance collimator are deflected according to kinetic energy and detected by a microchannel plate (MCP) / imaging anode system (100% duty cycle). This produces a characteristic detector image from which the critical atmospheric parameters can be retrieved. Major species are separated by their mean kinetic energies according to the spacecraft velocity (e.g., 4.7 eV for O and 8.2 eV for N2). Spatial distributions are fit by maximal-likelihood routines, with centroid positions yielding each component of the neutral wind / ion drift velocity (assuming knowledge of the spacecraft pointing vector), and temperature determined from distribution width. The IDEA deflector consists of resistive glass side plates to propagate a linear potential gradient between copper end plates. The exit plane is a semi-transparent gate with parallel wires, with each wire at a unique voltage according to vertical position and contact point with the resistive glass. This design yields an 'ideal' electrostatic deflector, with no fringing or perturbed fields, in a very compact geometry. Thus, ions follow predictable trajectories, and straightforward data analysis produces highly accurate measurements of the ion velocity distribution function. Two recently proposed instrument suites, the Ion Drifts, Electric Fields, and Temperature (IDEFT) sensor and the Total Thermosphere Sensor (TTS), use orthogonally-oriented IDEA analyzers and a shared imaging detector to characterize the ionosphere and

  6. Spectrally resolved white light interferometry to measure material dispersion over a wide spectral band in a single acquisition.

    PubMed

    Arosa, Yago; Lago, Elena López; Varela, Luis Miguel; de la Fuente, Raúl

    2016-07-25

    In this paper we apply spectrally resolved white light interferometry to measure refractive and group index over a wide spectral band from 400 to 1000 nm. The output of a Michelson interferometer is spectrally decomposed by a homemade prism spectrometer with a high resolution camera. The group index is determined directly from the phase extracted from the spectral interferogram while the refractive index is estimated once its value at a given wavelength is known. PMID:27464179

  7. An online, energy-resolving beam profile detector for laser-driven proton beams.

    PubMed

    Metzkes, J; Zeil, K; Kraft, S D; Karsch, L; Sobiella, M; Rehwald, M; Obst, L; Schlenvoigt, H-P; Schramm, U

    2016-08-01

    In this paper, a scintillator-based online beam profile detector for the characterization of laser-driven proton beams is presented. Using a pixelated matrix with varying absorber thicknesses, the proton beam is spatially resolved in two dimensions and simultaneously energy-resolved. A thin plastic scintillator placed behind the absorber and read out by a CCD camera is used as the active detector material. The spatial detector resolution reaches down to ∼4 mm and the detector can resolve proton beam profiles for up to 9 proton threshold energies. With these detector design parameters, the spatial characteristics of the proton distribution and its cut-off energy can be analyzed online and on-shot under vacuum conditions. The paper discusses the detector design, its characterization and calibration at a conventional proton source, as well as the first detector application at a laser-driven proton source. PMID:27587116

  8. Energy-resolved positron annihilation rates for molecules

    SciTech Connect

    Barnes, L. D.; Young, J. A.; Surko, C. M.

    2006-07-15

    The development of high resolution positron beams has enabled measurements of annihilation rates for molecules as a function of incident positron energy. Vibrational Feshbach resonances in these spectra provide evidence for the existence of positron-molecule bound states. In this paper we present further studies of this phenomenon. Evidence is presented for positronically excited bound states (i.e., in addition to the ground state) in C{sub 12}H{sub 26} and C{sub 14}H{sub 30}. Measurements of the annihilation spectra of the halomethanes, CH{sub 3}F, CH{sub 3}Cl, and CH{sub 3}Br, exhibit strong resonances that vary significantly with the substituted halogen. Annihilation spectra for linear alkanes and ring molecules are compared. Annihilation spectra and infrared absorption spectra are compared for a number of molecules. Finally, annihilation rate measurements are presented for a variety of molecules at energies {>=}0.5 eV (i.e., above the vibrational resonances). These provide a measure of the annihilation rates in the absence of vibrational resonances.

  9. Measuring Performance of Energy-Dispersive X-ray Systems.

    PubMed

    Statham

    1998-11-01

    : As Si(Li) detector technology has matured, many of the fundamental problems have been addressed in the competition among manufacturers and there is now an expectation, implied by many textbooks, that all energy-dispersive X-ray (EDX) detectors are made and will perform in the same way. Although there has been some convergence in Si(Li) systems and these are still the most common, manufacturing recipes still differ and there are many alternative EDX devices, such as microcalorimeters and room temperature detectors, that have both advantages and disadvantages over Si(Li). Rather than emphasizing differences in technologies, performance measures should reveal benefits relevant to the intended application. The instrument is inevitably going to be a "black box" of integrated components; this article reviews some of the methods that have been applied and introduces some new techniques that can be used to assess performance without resorting to complex software or sophisticated mathematical algorithms. Sensitivity, resolution, artefacts, and stability are discussed with particular application to compositional analysis using electron beam excitation of X-rays in the 100-eV to 10-keV energy region. PMID:10087283

  10. Material separation in x-ray CT with energy resolved photon-counting detectors

    SciTech Connect

    Wang Xiaolan; Meier, Dirk; Taguchi, Katsuyuki; Wagenaar, Douglas J.; Patt, Bradley E.; Frey, Eric C.

    2011-03-15

    Purpose: The objective of the study was to demonstrate that, in x-ray computed tomography (CT), more than two types of materials can be effectively separated with the use of an energy resolved photon-counting detector and classification methodology. Specifically, this applies to the case when contrast agents that contain K-absorption edges in the energy range of interest are present in the object. This separation is enabled via the use of recently developed energy resolved photon-counting detectors with multiple thresholds, which allow simultaneous measurements of the x-ray attenuation at multiple energies. Methods: To demonstrate this capability, we performed simulations and physical experiments using a six-threshold energy resolved photon-counting detector. We imaged mouse-sized cylindrical phantoms filled with several soft-tissue-like and bone-like materials and with iodine-based and gadolinium-based contrast agents. The linear attenuation coefficients were reconstructed for each material in each energy window and were visualized as scatter plots between pairs of energy windows. For comparison, a dual-kVp CT was also simulated using the same phantom materials. In this case, the linear attenuation coefficients at the lower kVp were plotted against those at the higher kVp. Results: In both the simulations and the physical experiments, the contrast agents were easily separable from other soft-tissue-like and bone-like materials, thanks to the availability of the attenuation coefficient measurements at more than two energies provided by the energy resolved photon-counting detector. In the simulations, the amount of separation was observed to be proportional to the concentration of the contrast agents; however, this was not observed in the physical experiments due to limitations of the real detector system. We used the angle between pairs of attenuation coefficient vectors in either the 5-D space (for non-contrast-agent materials using energy resolved photon

  11. Resolving the 180-degree ambiguity in vector magnetic field measurements: The 'minimum' energy solution

    NASA Technical Reports Server (NTRS)

    Metcalf, Thomas R.

    1994-01-01

    I present a robust algorithm that resolves the 180-deg ambiguity in measurements of the solar vector magnetic field. The technique simultaneously minimizes both the divergence of the magnetic field and the electric current density using a simulated annealing algorithm. This results in the field orientation with approximately minimum free energy. The technique is well-founded physically and is simple to implement.

  12. MicroCT with energy-resolved photon-counting detectors

    NASA Astrophysics Data System (ADS)

    Wang, X.; Meier, D.; Mikkelsen, S.; Maehlum, G. E.; Wagenaar, D. J.; Tsui, B. M. W.; Patt, B. E.; Frey, E. C.

    2011-05-01

    The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with K-absorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences.

  13. MicroCT with energy-resolved photon-counting detectors.

    PubMed

    Wang, X; Meier, D; Mikkelsen, S; Maehlum, G E; Wagenaar, D J; Tsui, B M W; Patt, B E; Frey, E C

    2011-05-01

    The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with K-absorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences. PMID:21464527

  14. The SLcam: a full-field energy dispersive X-ray camera

    NASA Astrophysics Data System (ADS)

    Bjeoumikhov, A.; Buzanich, G.; Langhoff, N.; Ordavo, I.; Radtke, M.; Reinholz, U.; Riesemeier, H.; Scharf, O.; Soltau, H.; Wedell, R.

    2012-11-01

    The color X-ray camera (SLcam®) is a full-field single photon imager. As stand-alone camera, it is applicable for energy and space-resolved X-ray detection measurements. The exchangeable poly-capillary optics in front of a beryllium entrance window conducts X-ray photons from the probe to distinguished energy dispersive pixels on a pnCCD. The dedicated software enables the acquisition and the online processing of the spectral data for all 69696 pixels, leading to a real-time visualization of the element distribution in a sample. No scanning system is employed. A first elemental composition image of the sample is visible within minutes while statistics is improving in the course of time. Straight poly-capillary optics allows for 1:1 imaging with a space resolution of 50 μm and no limited depth of sharpness, ideal to map uneven objects. Using conically shaped optics, a magnification of 6 times was achieved with a space resolution of 10 μm. We present a measurement with a laboratory source showing the camera capability to perform fast full-field X-ray Fluorescence (FF-XRF) imaging with an easy, portable and modular setup.

  15. The role of x-ray Swank factor in energy-resolving photon-counting imaging

    SciTech Connect

    Tanguay, Jesse; Kim, Ho Kyung; Cunningham, Ian. A.

    2010-12-15

    Purpose: Energy-resolved x-ray imaging has the potential to improve contrast-to-noise ratio by measuring the energy of each interacting photon and applying optimal weighting factors. The success of energy-resolving photon-counting (EPC) detectors relies on the ability of an x-ray detector to accurately measure the energy of each interacting photon. However, the escape of characteristic emissions and Compton scatter degrades spectral information. This article makes the theoretical connection between accuracy and imprecision in energy measurements with the x-ray Swank factor for a-Se, Si, CdZnTe, and HgI{sub 2}-based detectors. Methods: For a detector that implements adaptive binning to sum all elements in which x-ray energy is deposited for a single interaction, energy imprecision is shown to depend on the Swank factor for a large element with x rays incident at the center. The response function for each converter material is determined using Monte Carlo methods and used to determine energy accuracy, Swank factor, and relative energy imprecision in photon-energy measurements. Results: For each material, at energies below the respective K edges, accuracy is close to unity and imprecision is only a few percent. Above the K-edge energies, characteristic emission results in a drop in accuracy and precision that depends on escape probability. In Si, and to some extent a-Se, Compton-scatter escape also degrades energy precision with increasing energy. The influence of converter thickness on energy accuracy and imprecision is modest for low-Z materials but becomes important when using high-Z materials at energies greater than the K-edge energies. Conclusions: Accuracy and precision in energy measurements by EPC detectors are determined largely by the energy-dependent x-ray Swank factor. Modest decreases in the Swank factor (5%-15%) result in large increases in relative imprecision (30%-40%).

  16. Spin polarized energy-resolved photoemission from Ni(111) using synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Gudat, W.; Kisker, E.; Kuhlmann, E.; Campagna, M.

    1981-03-01

    We report on the first energy-resolved (retarding field mode) spin polarized photoemission measurement from a Ni(111) single crystal using synchrotron radiation from the ACO storage ring at LURE(ORSAY) It is shown that exchange effects can be detected for electron states well below the Fermi energy and that spin polarized, constant-initial-state spectroscopy of ferromagnets using synchrotron radiation is feasible.

  17. Vibrationally resolved electron-nuclear energy sharing in above-threshold multiphoton dissociation of CO

    NASA Astrophysics Data System (ADS)

    Sun, Xufei; Li, Min; Shao, Yun; Liu, Ming-Ming; Xie, Xiguo; Deng, Yongkai; Wu, Chengyin; Gong, Qihuang; Liu, Yunquan

    2016-07-01

    We study the photon energy sharing between the photoelectron and the nuclei in the process of above-threshold multiphoton dissociative ionization of CO molecules by measuring the joint energy spectra. The experimental observation shows that the electron-nuclear energy sharing strongly depends on the vibrational state. The experimental observation shows that both the energy deposited to the nuclei of C O+ and the emitted photoelectron decrease with increasing the vibrational level. Through studying the vibrationally resolved nuclear kinetic energy release and photoelectron energy spectra at different laser intensities, for each vibrational level of C O+ , the nuclei always tend to take the same amount of energy in every vibrational level regardless of the laser intensity, while the energy deposited to the photoelectron varies with respect to the laser intensity because of the ponderomotive shifted energy and the distinct dissociative ionization mechanisms.

  18. Optimal conditions for high-fidelity dispersive readout of a qubit with a photon-number-resolving detector

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrii

    2016-03-01

    We determine the optimal parameters for a simple and efficient scheme of dispersive readout of a qubit. Depending on the qubit state (ground or excited), the resonance of a cavity is shifted either to the red or to the blue side. Qubit state is inferred by detecting the photon number transmitted through the cavity. It turns out that this kind of detection provides better measurement fidelity than the detection of the presence or absence of photons only. We show that radiating the cavity on either of the frequencies it shifts to results in a suboptimal measurement. The optimal frequency of the probe photons is determined, as well as the optimal ratio of the shift to the resonator leakage. It is shown that to maximize the fidelity of a long-lasting measurement, it is sufficient to use the parameters optimizing the signal-to-noise ratio in the photon count. One can reach 99% fidelity for a single-shot measurement in various physical realizations of the scheme.

  19. Energy-scaling characteristics of solitons in strongly dispersion-managed fibers

    NASA Astrophysics Data System (ADS)

    Smith, N. J.; Doran, N. J.; Knox, F. M.; Forysiak, W.

    1996-12-01

    We present an empirical scaling law that models the increased energy required for launching a soliton into an optical system with sections of both normal and anomalous dispersion fiber. It is shown that the inclusion of periodic attenuation and amplification can be handled as separate problems, provided that the interval between optical amplifiers is substantially different from the period of the dispersion map. These concepts are illustrated by reference to an example system comprising dispersion-shifted fiber combined with anomalous standard fiber.

  20. An edge-on charge-transfer design for energy-resolved x-ray detection

    NASA Astrophysics Data System (ADS)

    Shi, Zaifeng; Yang, Haoyu; Cong, Wenxiang; Wang, Ge

    2016-06-01

    As an x-ray beam goes through the human body, it will collect important information via interaction with tissues. Since this interaction is energy-sensitive, the state-of-the-art spectral CT technologies provide higher quality images of biological tissues with x-ray energy information (or spectral information). With existing energy-integrating technologies, a large fraction of energy information is ignored in the x-ray detection process. Although the recently proposed photon-counting technology promises to achieve higher image quality at a lower radiation dose, it suffers from limitations in counting rate, performance uniformity, and fabrication cost. In this paper, we focus on an alternative approach to resolve the energy distribution of transmitted x-ray photons. First, we analyze the x-ray attenuation in a silicon substrate and describe a linear approximation model for x-ray detection. Then, we design an edge-on architecture based on the proposed energy-resolving model. In our design, the x-ray-photon-induced charges are transferred sequentially resembling the working process of a CCD camera. Finally, we numerically evaluate the linear approximation of x-ray attenuation and derive the energy distribution of x-ray photons. Our simulation results show that the proposed energy-sensing approach is feasible and has the potential to complement the photon-counting technology.

  1. An edge-on charge-transfer design for energy-resolved x-ray detection.

    PubMed

    Shi, Zaifeng; Yang, Haoyu; Cong, Wenxiang; Wang, Ge

    2016-06-01

    As an x-ray beam goes through the human body, it will collect important information via interaction with tissues. Since this interaction is energy-sensitive, the state-of-the-art spectral CT technologies provide higher quality images of biological tissues with x-ray energy information (or spectral information). With existing energy-integrating technologies, a large fraction of energy information is ignored in the x-ray detection process. Although the recently proposed photon-counting technology promises to achieve higher image quality at a lower radiation dose, it suffers from limitations in counting rate, performance uniformity, and fabrication cost. In this paper, we focus on an alternative approach to resolve the energy distribution of transmitted x-ray photons. First, we analyze the x-ray attenuation in a silicon substrate and describe a linear approximation model for x-ray detection. Then, we design an edge-on architecture based on the proposed energy-resolving model. In our design, the x-ray-photon-induced charges are transferred sequentially resembling the working process of a CCD camera. Finally, we numerically evaluate the linear approximation of x-ray attenuation and derive the energy distribution of x-ray photons. Our simulation results show that the proposed energy-sensing approach is feasible and has the potential to complement the photon-counting technology. PMID:27192190

  2. Time-resolved energy spectrum measurement of a linear induction accelerator with the magnetic analyzer

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Jiang, Xiao-Guo; Yang, Guo-Jun; Chen, Si-Fu; Zhang, Zhuo; Wei, Tao; Li, Jin

    2015-01-01

    We recently set up a time-resolved optical beam diagnostic system. Using this system, we measured the high current electron beam energy in the accelerator under construction. This paper introduces the principle of the diagnostic system, describes the setup, and shows the results. A bending beam line was designed using an existing magnetic analyzer with a 300 mm-bending radius and a 60° bending angle at hard-edge approximation. Calculations show that the magnitude of the beam energy is about 18 MeV, and the energy spread is within 2%. Our results agree well with the initial estimates deduced from the diode voltage approach.

  3. Monochromated, spatially resolved electron energy-loss spectroscopic measurements of gold nanoparticles in the plasmon range.

    PubMed

    Schaffer, B; Riegler, K; Kothleitner, G; Grogger, W; Hofer, F

    2009-02-01

    Gold nanoparticles show optical properties different from bulk material due to resonance phenomena which depend on local structure and geometry. Electron energy-loss spectrometry (EELS) in scanning transmission electron microscopy (STEM) allows the spatially resolved measurement of these properties at a resolution of few nanometers. In this work, the first monochromated measurements of gold nanoparticles (spheres, rods and triangles) are presented. Due to the improved energy resolution of about 0.2 eV, surface plasmon excitations at energies below 1 eV could be accurately measured from raw experimental data. PMID:18722779

  4. Dispersion-Energy-Driven Wagner–Meerwein Rearrangements in Oligosilanes

    PubMed Central

    2016-01-01

    The installation of structural complex oligosilanes from linear starting materials by Lewis acid induced skeletal rearrangement reactions was studied under stable ion conditions. The produced cations were fully characterized by multinuclear NMR spectroscopy at low temperature, and the reaction course was studied by substitution experiments. The results of density functional theory calculations indicate the decisive role of attractive dispersion forces between neighboring trimethylsilyl groups for product formation in these rearrangement reactions. These attractive dispersion interactions control the course of Wagner–Meerwein rearrangements in oligosilanes, in contrast to the classical rearrangement in hydrocarbon systems, which are dominated by electronic substituent effects such as resonance and hyperconjugation. PMID:27195490

  5. Dispersion-Energy-Driven Wagner-Meerwein Rearrangements in Oligosilanes.

    PubMed

    Albers, Lena; Rathjen, Saskia; Baumgartner, Judith; Marschner, Christoph; Müller, Thomas

    2016-06-01

    The installation of structural complex oligosilanes from linear starting materials by Lewis acid induced skeletal rearrangement reactions was studied under stable ion conditions. The produced cations were fully characterized by multinuclear NMR spectroscopy at low temperature, and the reaction course was studied by substitution experiments. The results of density functional theory calculations indicate the decisive role of attractive dispersion forces between neighboring trimethylsilyl groups for product formation in these rearrangement reactions. These attractive dispersion interactions control the course of Wagner-Meerwein rearrangements in oligosilanes, in contrast to the classical rearrangement in hydrocarbon systems, which are dominated by electronic substituent effects such as resonance and hyperconjugation. PMID:27195490

  6. Rayleigh-wave dispersive energy imaging using a high-resolution linear radon transform

    USGS Publications Warehouse

    Luo, Y.; Xia, J.; Miller, R.D.; Xu, Y.; Liu, J.; Liu, Q.

    2008-01-01

    Multichannel Analysis of Surface Waves (MASW) analysis is an efficient tool to obtain the vertical shear-wave profile. One of the key steps in the MASW method is to generate an image of dispersive energy in the frequency-velocity domain, so dispersion curves can be determined by picking peaks of dispersion energy. In this paper, we propose to image Rayleigh-wave dispersive energy by high-resolution linear Radon transform (LRT). The shot gather is first transformed along the time direction to the frequency domain and then the Rayleigh-wave dispersive energy can be imaged by high-resolution LRT using a weighted preconditioned conjugate gradient algorithm. Synthetic data with a set of linear events are presented to show the process of generating dispersive energy. Results of synthetic and real-world examples demonstrate that, compared with the slant stacking algorithm, high-resolution LRT can improve the resolution of images of dispersion energy by more than 50%. ?? Birkhaueser 2008.

  7. Focal construct geometry for high intensity energy dispersive x-ray diffraction based on x-ray capillary optics.

    PubMed

    Li, Fangzuo; Liu, Zhiguo; Sun, Tianxi; Jiang, Bowen; Zhu, Yu

    2016-03-14

    We presented a focal construct geometry (FCG) method for high intensity energy dispersive X-ray diffraction by utilizing a home-made ellipsoidal single-bounce capillary (ESBC) and a polycapillary parallel X-ray lens (PPXRL). The ESBC was employed to focus the X-rays from a conventional laboratory source into a small focal spot and to produce an annular X-ray beam in the far-field. Additionally, diffracted polychromatic X-rays were confocally collected by the PPXRL attached to a stationary energy-resolved detector. Our FCG method based on ESBC and PPXRL had achieved relatively high intensity diffraction peaks and effectively narrowed the diffraction peak width which was helpful in improving the potential d-spacing resolution for material phase analysis. PMID:26979685

  8. Focal construct geometry for high intensity energy dispersive x-ray diffraction based on x-ray capillary optics

    NASA Astrophysics Data System (ADS)

    Li, Fangzuo; Liu, Zhiguo; Sun, Tianxi; Jiang, Bowen; Zhu, Yu

    2016-03-01

    We presented a focal construct geometry (FCG) method for high intensity energy dispersive X-ray diffraction by utilizing a home-made ellipsoidal single-bounce capillary (ESBC) and a polycapillary parallel X-ray lens (PPXRL). The ESBC was employed to focus the X-rays from a conventional laboratory source into a small focal spot and to produce an annular X-ray beam in the far-field. Additionally, diffracted polychromatic X-rays were confocally collected by the PPXRL attached to a stationary energy-resolved detector. Our FCG method based on ESBC and PPXRL had achieved relatively high intensity diffraction peaks and effectively narrowed the diffraction peak width which was helpful in improving the potential d-spacing resolution for material phase analysis.

  9. Two types of ion energy dispersions observed in the nightside auroral regions during geomagnetically disturbed periods

    NASA Astrophysics Data System (ADS)

    Hirahara, M.; Mukai, T.; Nagai, T.; Kaya, N.; Hayakawa, H.; Fukunishi, H.

    1996-04-01

    The Akebono satellite has observed two types of energy dispersion signatures of discrete ion precipitation event in the nightside auroral regions during active geomagnetic conditions. The charged particle experiments and electric and magnetic field detectors on board Akebono provide us with essential clues to characterize the source regions and acceleration and/or injection processes associated with these two types of ion signatures. The magnetic field data obtained simultaneously by the geosynchronous GOES 6 and 7 satellites and the ground magnetograms are useful to examine their relationships with geomagnetic activity. Mass composition data and pitch angle distributions show that different sources and processes should be attributed to two types (Types I and II) of energy dispersion phenomena. Type I consists of multiple bouncing ion clusters constituted by H+. These H+ clusters tend to be detected at the expansion phase of substorms and have characteristic multiple energy-dispersed signatures. Type II consists of O+ energy dispersion(s), which is often observed at the recovery phase. It is reasonable to consider that the H+ clusters of Type I are accelerated by dipolarization at the equator, are injected in the field-aligned direction, and bounce on closed field lines after the substorm onset. We interpret these multiple energy dispersion events as mainly due to the time-of-flight (TOF) effect, although the convection may influence the energy-dispersed traces. Based of the TOF model, we estimate the source distance to be 20-30 RE along the field lines. On the other hand, the O+ energy dispersion of Type II is a consequence of reprecipitation of terrestrial ions ejected as an upward flowing ion (UFI) beam from the upper ionosphere by a parallel electrostatic potential difference. The O+ energy dispersion is induced by the E×B drift during the field-aligned transport from the source region to the observation point.

  10. High-Energy Anomaly in the Angle-Resolved Photoemission Spectra of Nd2-xCexCuO4: Evidence for a Matrix Element Effect

    NASA Astrophysics Data System (ADS)

    Rienks, E. D. L.; ńrrälä, M.; Lindroos, M.; Roth, F.; Tabis, W.; Yu, G.; Greven, M.; Fink, J.

    2014-09-01

    We use polarization-dependent angle-resolved photoemission spectroscopy (ARPES) to study the high-energy anomaly (HEA) in the dispersion of Nd2-xCexCuO4, x =0.123. We find that at particular photon energies the anomalous, waterfall-like dispersion gives way to a broad, continuous band. This suggests that the HEA is a matrix element effect: it arises due to a suppression of the intensity of the broadened quasiparticle band in a narrow momentum range. We confirm this interpretation experimentally, by showing that the HEA appears when the matrix element is suppressed deliberately by changing the light polarization. Calculations of the matrix element using atomic wave functions and simulation of the ARPES intensity with one-step model calculations provide further evidence for this scenario. The possibility to detect the full quasiparticle dispersion further allows us to extract the high-energy self-energy function near the center and at the edge of the Brillouin zone.

  11. High-energy anomaly in the angle-resolved photoemission spectra of Nd(2-x)Ce(x)CuO₄: evidence for a matrix element effect.

    PubMed

    Rienks, E D L; Ärrälä, M; Lindroos, M; Roth, F; Tabis, W; Yu, G; Greven, M; Fink, J

    2014-09-26

    We use polarization-dependent angle-resolved photoemission spectroscopy (ARPES) to study the high-energy anomaly (HEA) in the dispersion of Nd(2-x)Ce(x)CuO₄, x=0.123. We find that at particular photon energies the anomalous, waterfall-like dispersion gives way to a broad, continuous band. This suggests that the HEA is a matrix element effect: it arises due to a suppression of the intensity of the broadened quasiparticle band in a narrow momentum range. We confirm this interpretation experimentally, by showing that the HEA appears when the matrix element is suppressed deliberately by changing the light polarization. Calculations of the matrix element using atomic wave functions and simulation of the ARPES intensity with one-step model calculations provide further evidence for this scenario. The possibility to detect the full quasiparticle dispersion further allows us to extract the high-energy self-energy function near the center and at the edge of the Brillouin zone. PMID:25302914

  12. Unusual energy dispersion at the proton isotropy boundary: a statistical study

    NASA Astrophysics Data System (ADS)

    Chernyaeva, Sonya; Angelopoulos, Vassilis; Sergeev, Viktor; Chernyaev, Ivan

    The regular appearance of equatorward boundary of the isotropic proton precipitation (isotropy boundary, IB) is interpreted as a manifestation of the boundary between adiabatic and non-adiabatic particle motion regimes. Accordingly, the energy dependence of IB latitude (energy dispersion, with lower latitude IB observed for higher energy protons in case of normal dispersion) carries the information about the real magnetic field gradients (or, sporadic appearance of other scattering mechanism, in case of anomalous dispersion). In this study we investigate statistically the IB energy dispersion of the >30 and >80 keV energetic protons using data from low-altitude polar satellites NOAA-19 and -18 in September 2009, when two spacecraft follow each other along the same orbit. We found that the events with normal dispersion at proton energies of 30 to 80 keV protons constitute less than 20% of the total number of events (regardless of geomagnetic activity). In other cases (80%) we see either the coincidence of the proton IB at different energies (within 0.2(°) ), or the precipitation pattern is complicated by the presence of isolated precipitation structures equatorward of the IB. In small amount of cases the anomalous (inverse) energy dispersion was also observed, suggesting the presence of different precipitation mechanisms. To help discriminate between current sheet scattering and other mechanisms we also obtained the average relationship between empirical ratios of trapped and precipitated proton fluxes at different energies near the IB for cases of normal dispersion. The near coincidence of the proton IBs can be observed in the case of sharp magnetic field Bz gradients (Bz jumps), whose amplitude should be about 60% of the Bz background value. Their existence is tested by considering magnetic field observations at radial passes of THEMIS spacecraft near the IB observation meridian in the near magnetosphere, supported by adaptive modeling and other relevant

  13. Time, Energy, and Spatially Resolved TEM Investigations of Defectsin InGaN

    SciTech Connect

    Jinschek, J.R.; Kisielowski, C.

    2005-10-01

    A novel sample preparation technique is reported to fabricate electron transparent samples from devices utilizing a FIB process with a successive wet etching step. The high quality of the obtained samples allows for band gap--and chemical composition measurements of In{sub x}Ga{sub 1-x}N quantum wells where electron beam induced damage can be controlled and shown to be negligible. The results reveal indium enrichment in nanoclusters and defects that cause fluctuations of the band gap energy and can be measured by low loss Electron Energy Spectroscopy with nm resolution. Comparing our time, energy, and spatially resolved measurements of band gap energies, chemical composition, and their related fluctuations with literature data, we find quantitative agreement if the band gap energy of InN is 1.5-2 eV.

  14. The Dosepix detector—an energy-resolving photon-counting pixel detector for spectrometric measurements

    NASA Astrophysics Data System (ADS)

    Zang, A.; Anton, G.; Ballabriga, R.; Bisello, F.; Campbell, M.; Celi, J. C.; Fauler, A.; Fiederle, M.; Jensch, M.; Kochanski, N.; Llopart, X.; Michel, N.; Mollenhauer, U.; Ritter, I.; Tennert, F.; Wölfel, S.; Wong, W.; Michel, T.

    2015-04-01

    The Dosepix detector is a hybrid photon-counting pixel detector based on ideas of the Medipix and Timepix detector family. 1 mm thick cadmium telluride and 300 μm thick silicon were used as sensor material. The pixel matrix of the Dosepix consists of 16 x 16 square pixels with 12 rows of (200 μm)2 and 4 rows of (55 μm)2 sensitive area for the silicon sensor layer and 16 rows of pixels with 220 μm pixel pitch for CdTe. Besides digital energy integration and photon-counting mode, a novel concept of energy binning is included in the pixel electronics, allowing energy-resolved measurements in 16 energy bins within one acquisition. The possibilities of this detector concept range from applications in personal dosimetry and energy-resolved imaging to quality assurance of medical X-ray sources by analysis of the emitted photon spectrum. In this contribution the Dosepix detector, its response to X-rays as well as spectrum measurements with Si and CdTe sensor layer are presented. Furthermore, a first evaluation was carried out to use the Dosepix detector as a kVp-meter, that means to determine the applied acceleration voltage from measured X-ray tubes spectra.

  15. Dispersion of heavy ion deposited energy in nanometric electronic devices: Experimental measurements and simulation possibilities

    NASA Astrophysics Data System (ADS)

    Raine, M.; Gaillardin, M.; Paillet, P.; Duhamel, O.; Martinez, M.; Bernard, H.

    2015-12-01

    The dispersion of heavy ion deposited energy is explored in nanometric electronic devices. Experimental data are reported, in a large thin SOI diode and in a SOI FinFET device, showing larger distributions of collected charge in the nanometric volume device. Geant4 simulations are then presented, using two different modeling approaches. Both of them seem suitable to evaluate the dispersion of deposited energy induced by heavy ion beams in advanced electronic devices with nanometric dimensions.

  16. Development and characterization of a time-, position- and energy-resolved x-ray diagnostic for PBFA II target experiments

    SciTech Connect

    Derzon, M.S.; Filuk, A.B.; Pantuso, J.; Dukart, R.J.; Olsen, R.; Barber, T.; Bernard, M.

    1992-12-31

    A time-, position- and energy-resolved soft x-ray (100--500 eV) diagnostic is being developed for PBFA II target experiments. The diagnostic provides measurements of hydrodynamic motion and thermal gradients in light-ion fusion targets. A slit-image of the source is imprinted onto thin sheets (20{mu}m) of organic scintillator to create a one-dimensional image. The scintillator light is then proximity-coupled to a linear array of fiber-optics that transports the light to a streak camera that is operated without an intensifier. The streak camera output is recorded on a charge-coupled-device (CCD) camera. We are characterizing the spatial and temporal resolutions of the systems. This is done by collecting data from as many as 90 individual fibers and correcting for variations in throughput and the effects of spatial resolution to roughly 5% standard deviation in their relative throughput. Spatial resolution of these systems at the source is approximately 0.4 mm. Timing resolution is nominally 2 ns and it is limited primarily by the scintillator response and dispersion in the 50-m-long fiber array. We describe the measurement techniques and the results of the characterization.

  17. Electron self-energy of high temperature superconductors as revealed by angle-resolved photoemission.

    SciTech Connect

    Ding, H.; Norman, M. R.; Randeria, M.

    1997-12-05

    In this paper, we review some of the work our group has done in the past few years to obtain the electron self-energy of high temperature superconductors by analysis of angle-resolved photoemission data. We focus on three examples which have revealed: (1) a d-wave superconducting gap, (2) a collective mode in the superconducting state, and (3) pairing correlations in the pseudogap phase. In each case, although a novel result is obtained which captures the essence of the data, the conventional physics used leads to an incomplete picture. This indicates that new physics needs to be developed to obtain a proper understanding of these materials.

  18. Investigation of dissimilar metal welds by energy-resolved neutron imaging

    PubMed Central

    Tremsin, Anton S.; Ganguly, Supriyo; Meco, Sonia M.; Pardal, Goncalo R.; Shinohara, Takenao; Feller, W. Bruce

    2016-01-01

    A nondestructive study of the internal structure and compositional gradient of dissimilar metal-alloy welds through energy-resolved neutron imaging is described in this paper. The ability of neutrons to penetrate thick metal objects (up to several cm) provides a unique possibility to examine samples which are opaque to other conventional techniques. The presence of Bragg edges in the measured neutron transmission spectra can be used to characterize the internal residual strain within the samples and some microstructural features, e.g. texture within the grains, while neutron resonance absorption provides the possibility to map the degree of uniformity in mixing of the participating alloys and intermetallic formation within the welds. In addition, voids and other defects can be revealed by the variation of neutron attenuation across the samples. This paper demonstrates the potential of neutron energy-resolved imaging to measure all these characteristics simultaneously in a single experiment with sub-mm spatial resolution. Two dissimilar alloy welds are used in this study: Al autogenously laser welded to steel, and Ti gas metal arc welded (GMAW) to stainless steel using Cu as a filler alloy. The cold metal transfer variant of the GMAW process was used in joining the Ti to the stainless steel in order to minimize the heat input. The distributions of the lattice parameter and texture variation in these welds as well as the presence of voids and defects in the melt region are mapped across the welds. The depth of the thermal front in the Al–steel weld is clearly resolved and could be used to optimize the welding process. A highly textured structure is revealed in the Ti to stainless steel joint where copper was used as a filler wire. The limited diffusion of Ti into the weld region is also verified by the resonance absorption. PMID:27504075

  19. Noise suppression for energy-resolved CT using similarity-based non-local filtration

    NASA Astrophysics Data System (ADS)

    Harms, Joe; Wang, Tonghe; Petrongolo, Michael; Zhu, Lei

    2016-03-01

    In energy-resolved CT, images are reconstructed independently at different energy levels, resulting in images with different qualities but the same structures. We propose a similarity-based non-local filtration method to extract structural information from these images for noise suppression. For each pixel, we calculate its similarity to other pixels based on CT number. The calculation is repeated on each image at different energy levels and similarity values are averaged to generate a similarity matrix. Noise suppression is achieved by multiplying the image vector by the similarity matrix. Multiple scans on a tabletop CT system are used to simulate 6-channel energy-resolved CT, with energies ranging from 75 to 125 kVp. Phantom studies show that the proposed method improves average contrast-to-noise ratio (CNR) of seven materials on the 75 kVp image by a factor of 22. Compared with averaging CT images for noise suppression, our method achieves a higher CNR and reduces the CT number error of iodine solutions from 16.5% to 3.5% and the overall image root of mean-square error (RMSE) from 3.58% to 0.93%. On the phantom with line-pair structures, our algorithm reduces noise standard deviation (STD) by a factor of 23 while maintaining 7 lp/cm spatial resolution. Additionally, anthropomorphic head phantom studies show noise STD reduction by a factor or 26 with no loss of spatial resolution. The noise suppression achieved by the similarity-based method is clinically attractive, especially for CNRs of iodine in contrast-enhanced CT.

  20. Finessing the fracture energy barrier in ballistic seed dispersal.

    PubMed

    Deegan, Robert D

    2012-04-01

    Fracture is a highly dissipative process in which much of the stored elastic energy is consumed in the creation of new surfaces. Surprisingly, many plants use fracture to launch their seeds despite its seemingly prohibitive energy cost. Here we use Impatiens glandulifera as model case to study the impact of fracture on a plant's throwing capacity. I. glandulifera launches its seeds with speeds up to 4 m/s using cracks to trigger an explosive release of stored elastic energy. We find that the seed pod is optimally designed to minimize the cost of fracture. These characteristics may account for its success at invading Europe and North America. PMID:22431608

  1. Finessing the fracture energy barrier in ballistic seed dispersal

    PubMed Central

    Deegan, Robert D.

    2012-01-01

    Fracture is a highly dissipative process in which much of the stored elastic energy is consumed in the creation of new surfaces. Surprisingly, many plants use fracture to launch their seeds despite its seemingly prohibitive energy cost. Here we use Impatiens glandulifera as model case to study the impact of fracture on a plant’s throwing capacity. I. glandulifera launches its seeds with speeds up to 4 m/s using cracks to trigger an explosive release of stored elastic energy. We find that the seed pod is optimally designed to minimize the cost of fracture. These characteristics may account for its success at invading Europe and North America. PMID:22431608

  2. The calculation of surface orbital energies for specific types of active sites on dispersed metal catalysts

    SciTech Connect

    Augustine, R.L.; Lahanas, K.M.; Cole, F.

    1992-11-01

    An angular overlap calculation has been used to determine the s, p, and d orbital energy levels of the different types of surface sites present on dispersed metal catalysts. These data can permit a Frontier Molecular Orbital treatment of specific site activities as long as the surface orbital availability for overlap with adsorbed substrates is considered along with its energy value and symmetry.

  3. The calculation of surface orbital energies for specific types of active sites on dispersed metal catalysts

    SciTech Connect

    Augustine, R.L.; Lahanas, K.M.; Cole, F.

    1992-01-01

    An angular overlap calculation has been used to determine the s, p, and d orbital energy levels of the different types of surface sites present on dispersed metal catalysts. These data can permit a Frontier Molecular Orbital treatment of specific site activities as long as the surface orbital availability for overlap with adsorbed substrates is considered along with its energy value and symmetry.

  4. On an energy-latitude dispersion pattern of ion precipitation potentially associated with magnetospheric EMIC waves

    NASA Astrophysics Data System (ADS)

    Liang, Jun; Donovan, E.; Ni, B.; Yue, C.; Jiang, F.; Angelopoulos, V.

    2014-10-01

    Ion precipitation mechanisms are usually energy dependent and contingent upon magnetospheric/ionospheric locations. Therefore, the pattern of energy-latitude dependence of ion precipitation boundaries seen by low Earth orbit satellites can be implicative of the mechanism(s) underlying the precipitation. The pitch angle scattering of ions led by the field line curvature, a well-recognized mechanism of ion precipitation in the central plasma sheet (CPS), leads to one common pattern of energy-latitude dispersion, in that the ion precipitation flux diminishes at higher (lower) latitudes for protons with lower (higher) energies. In this study, we introduce one other systematically existing pattern of energy-latitude dispersion of ion precipitation, in that the lower energy ion precipitation extends to lower latitude than the higher-energy ion precipitation. Via investigating such a "reversed" energy-latitude dispersion pattern, we explore possible mechanisms of ion precipitation other than the field line curvature scattering. We demonstrate via theories and simulations that the H-band electromagnetic ion cyclotron (EMIC) wave is capable of preferentially scattering keV protons in the CPS and potentially leads to the reversed energy-latitude dispersion of proton precipitation. We then present detailed event analyses and provide support to a linkage between the EMIC waves in the equatorial CPS and ion precipitation events with reversed energy-latitude dispersion. We also discuss the role of ion acceleration in the topside ionosphere which, together with the CPS ion population, may result in a variety of energy-latitude distributions of the overall ion precipitation.

  5. Evaluating Chemical Dispersant Efficacy In An Experimental Wave Tank: 1, Dispersant Effectiveness As A Function Of Energy Dissipation Rate

    EPA Science Inventory

    Numerous laboratory test systems have been developed for the comparison of efficacy between various chemical oil dispersant formulations. However, for the assessment of chemical dispersant effectiveness under realistic sea state, test protocols are required to produce hydrodynam...

  6. Novel energy resolving x-ray pinhole camera on Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Pablant, N. A.; Delgado-Aparicio, L.; Bitter, M.; Brandstetter, S.; Eikenberry, E.; Ellis, R.; Hill, K. W.; Hofer, P.; Schneebeli, M.

    2012-10-01

    A new energy resolving x-ray pinhole camera has been recently installed on Alcator C-Mod. This diagnostic is capable of 1D or 2D imaging with a spatial resolution of ≈1 cm, an energy resolution of ≈1 keV in the range of 3.5-15 keV and a maximum time resolution of 5 ms. A novel use of a Pilatus 2 hybrid-pixel x-ray detector [P. Kraft et al., J. Synchrotron Rad. 16, 368 (2009), 10.1107/S0909049509009911] is employed in which the lower energy threshold of individual pixels is adjusted, allowing regions of a single detector to be sensitive to different x-ray energy ranges. Development of this new detector calibration technique was done as a collaboration between PPPL and Dectris Ltd. The calibration procedure is described, and the energy resolution of the detector is characterized. Initial data from this installation on Alcator C-Mod is presented. This diagnostic provides line-integrated measurements of impurity emission which can be used to determine impurity concentrations as well as the electron energy distribution.

  7. Characterization of a hybrid energy-resolving photon-counting detector

    NASA Astrophysics Data System (ADS)

    Zang, A.; Pelzer, G.; Anton, G.; Ballabriga Sune, R.; Bisello, F.; Campbell, M.; Fauler, A.; Fiederle, M.; Llopart Cudie, X.; Ritter, I.; Tennert, F.; Wölfel, S.; Wong, W. S.; Michel, T.

    2014-03-01

    Photon-counting detectors in medical x-ray imaging provide a higher dose efficiency than integrating detectors. Even further possibilities for imaging applications arise, if the energy of each photon counted is measured, as for example K-edge-imaging or optimizing image quality by applying energy weighting factors. In this contribution, we show results of the characterization of the Dosepix detector. This hybrid photon- counting pixel detector allows energy resolved measurements with a novel concept of energy binning included in the pixel electronics. Based on ideas of the Medipix detector family, it provides three different modes of operation: An integration mode, a photon-counting mode, and an energy-binning mode. In energy-binning mode, it is possible to set 16 energy thresholds in each pixel individually to derive a binned energy spectrum in every pixel in one acquisition. The hybrid setup allows using different sensor materials. For the measurements 300 μm Si and 1 mm CdTe were used. The detector matrix consists of 16 x 16 square pixels for CdTe (16 x 12 for Si) with a pixel pitch of 220 μm. The Dosepix was originally intended for applications in the field of radiation measurement. Therefore it is not optimized towards medical imaging. The detector concept itself still promises potential as an imaging detector. We present spectra measured in one single pixel as well as in the whole pixel matrix in energy-binning mode with a conventional x-ray tube. In addition, results concerning the count rate linearity for the different sensor materials are shown as well as measurements regarding energy resolution.

  8. Energy dissipation in matrix-isolated silver atoms: A time-resolved fluorescence study

    NASA Astrophysics Data System (ADS)

    Wiggenhauser, H.; Schroeder, W.; Kolb, D. M.

    1988-03-01

    The fluorescence from optically excited Ag atoms in Ar, Kr, and Xe matrices has been investigated in a time-resolved synchrotron-radiation study. A detailed energy dissipation model could be established from a systematic analysis of rise and decay times of all the observed fluorescence bands after pulsed excitation into the Ag (4d105p)2P1/2,3/2 levels, and by setting time windows between the excitation pulses in emission and emission-yield spectroscopy. Although the overall wavelength dependence of the decay time follows the λ3 law, the decay time is independent of λ within a given emission band. Finally, the role of energy transfer between Ag atoms and dimers for the evaluation of decay times is briefly addressed.

  9. Dynamics of chemical bonding mapped by energy-resolved 4D electron microscopy.

    PubMed

    Carbone, Fabrizio; Kwon, Oh-Hoon; Zewail, Ahmed H

    2009-07-10

    Chemical bonding dynamics are fundamental to the understanding of properties and behavior of materials and molecules. Here, we demonstrate the potential of time-resolved, femtosecond electron energy loss spectroscopy (EELS) for mapping electronic structural changes in the course of nuclear motions. For graphite, it is found that changes of milli-electron volts in the energy range of up to 50 electron volts reveal the compression and expansion of layers on the subpicometer scale (for surface and bulk atoms). These nonequilibrium structural features are correlated with the direction of change from sp2 [two-dimensional (2D) graphene] to sp3 (3D-diamond) electronic hybridization, and the results are compared with theoretical charge-density calculations. The reported femtosecond time resolution of four-dimensional (4D) electron microscopy represents an advance of 10 orders of magnitude over that of conventional EELS methods. PMID:19589997

  10. Deterministic and stochastic algorithms for resolving the flow fields in ducts and networks using energy minimization

    NASA Astrophysics Data System (ADS)

    Sochi, Taha

    2016-09-01

    Several deterministic and stochastic multi-variable global optimization algorithms (Conjugate Gradient, Nelder-Mead, Quasi-Newton and global) are investigated in conjunction with energy minimization principle to resolve the pressure and volumetric flow rate fields in single ducts and networks of interconnected ducts. The algorithms are tested with seven types of fluid: Newtonian, power law, Bingham, Herschel-Bulkley, Ellis, Ree-Eyring and Casson. The results obtained from all those algorithms for all these types of fluid agree very well with the analytically derived solutions as obtained from the traditional methods which are based on the conservation principles and fluid constitutive relations. The results confirm and generalize the findings of our previous investigations that the energy minimization principle is at the heart of the flow dynamics systems. The investigation also enriches the methods of computational fluid dynamics for solving the flow fields in tubes and networks for various types of Newtonian and non-Newtonian fluids.

  11. A tunable low-energy photon source for high-resolution angle-resolved photoemission spectroscopy

    SciTech Connect

    Harter, John W.; Monkman, Eric J.; Shai, Daniel E.; Nie Yuefeng; Uchida, Masaki; Burganov, Bulat; Chatterjee, Shouvik; King, Philip D. C.; Shen, Kyle M.

    2012-11-15

    We describe a tunable low-energy photon source consisting of a laser-driven xenon plasma lamp coupled to a Czerny-Turner monochromator. The combined tunability, brightness, and narrow spectral bandwidth make this light source useful in laboratory-based high-resolution photoemission spectroscopy experiments. The source supplies photons with energies up to {approx}7 eV, delivering under typical conditions >10{sup 12} ph/s within a 10 meV spectral bandwidth, which is comparable to helium plasma lamps and many synchrotron beamlines. We first describe the lamp and monochromator system and then characterize its output, with attention to those parameters which are of interest for photoemission experiments. Finally, we present angle-resolved photoemission spectroscopy data using the light source and compare its performance to a conventional helium plasma lamp.

  12. Non-pairwise additivity of the leading-order dispersion energy

    SciTech Connect

    Hollett, Joshua W.

    2015-02-28

    The leading-order (i.e., dipole-dipole) dispersion energy is calculated for one-dimensional (1D) and two-dimensional (2D) infinite lattices, and an infinite 1D array of infinitely long lines, of doubly occupied locally harmonic wells. The dispersion energy is decomposed into pairwise and non-pairwise additive components. By varying the force constant and separation of the wells, the non-pairwise additive contribution to the dispersion energy is shown to depend on the overlap of density between neighboring wells. As well separation is increased, the non-pairwise additivity of the dispersion energy decays. The different rates of decay for 1D and 2D lattices of wells is explained in terms of a Jacobian effect that influences the number of nearest neighbors. For an array of infinitely long lines of wells spaced 5 bohrs apart, and an inter-well spacing of 3 bohrs within a line, the non-pairwise additive component of the leading-order dispersion energy is −0.11 kJ mol{sup −1} well{sup −1}, which is 7% of the total. The polarizability of the wells and the density overlap between them are small in comparison to that of the atomic densities that arise from the molecular density partitioning used in post-density-functional theory (DFT) damped dispersion corrections, or DFT-D methods. Therefore, the nonadditivity of the leading-order dispersion observed here is a conservative estimate of that in molecular clusters.

  13. Energy- and time-resolved detection of prompt gamma-rays for proton range verification

    NASA Astrophysics Data System (ADS)

    Verburg, Joost M.; Riley, Kent; Bortfeld, Thomas; Seco, Joao

    2013-10-01

    In this work, we present experimental results of a novel prompt gamma-ray detector for proton beam range verification. The detection system features an actively shielded cerium-doped lanthanum(III) bromide scintillator, coupled to a digital data acquisition system. The acquisition was synchronized to the cyclotron radio frequency to separate the prompt gamma-ray signals from the later-arriving neutron-induced background. We designed the detector to provide a high energy resolution and an effective reduction of background events, enabling discrete proton-induced prompt gamma lines to be resolved. Measuring discrete prompt gamma lines has several benefits for range verification. As the discrete energies correspond to specific nuclear transitions, the magnitudes of the different gamma lines have unique correlations with the proton energy and can be directly related to nuclear reaction cross sections. The quantification of discrete gamma lines also enables elemental analysis of tissue in the beam path, providing a better prediction of prompt gamma-ray yields. We present the results of experiments in which a water phantom was irradiated with proton pencil-beams in a clinical proton therapy gantry. A slit collimator was used to collimate the prompt gamma-rays, and measurements were performed at 27 positions along the path of proton beams with ranges of 9, 16 and 23 g cm-2 in water. The magnitudes of discrete gamma lines at 4.44, 5.2 and 6.13 MeV were quantified. The prompt gamma lines were found to be clearly resolved in dimensions of energy and time, and had a reproducible correlation with the proton depth-dose curve. We conclude that the measurement of discrete prompt gamma-rays for in vivo range verification of clinical proton beams is feasible, and plan to further study methods and detector designs for clinical use.

  14. Energy dispersive spectroscopy using synchrotron radiation: Intensity considerations

    NASA Astrophysics Data System (ADS)

    Skelton, E. F.; Elam, W. T.; Qadri, S. B.; Webb, A. W.; Schiferl, D.

    Detailed considerations are given to the reliability of energy dependent integrated intensity data collected from the pressure cavity of a diamond-anvil pressure cell illuminated with heterochromatic radiation from a synchrotron storage ring. It is demonstrated that at least in one run, the electron beam current cannot be used to correct for energy-intensity variations of the incident beam. Rather there appears to be an additional linear relationship between the decay of the synchrotron beam and the magnitude of the background intensity.

  15. Energy dispersive spectroscopy using synchrotron radiation: Intensity considerations

    NASA Astrophysics Data System (ADS)

    Skelton, E. F.; Elam, W. T.; Qadri, S. B.; Webb, A. W.; Schiferl, D.

    1986-05-01

    Detailed considerations are given to the reliability of energy dependent integrated intensity data collected from the pressure cavity of a diamond-anvil pressure cell illuminated with heterochromatic radiation from a synchrotron storage ring. It is demonstrated that, at least in one run, the electron beam current cannot be used to correct for energy-intensity variations of the incident beam. Rather, there appears to be an additional linear relationship between the decay of the synchrotron beam and the magnitude of the background intensity.

  16. Quantitative material decomposition using spectral computed tomography with an energy-resolved photon-counting detector

    NASA Astrophysics Data System (ADS)

    Lee, Seungwan; Choi, Yu-Na; Kim, Hee-Joung

    2014-09-01

    Dual-energy computed tomography (CT) techniques have been used to decompose materials and characterize tissues according to their physical and chemical compositions. However, these techniques are hampered by the limitations of conventional x-ray detectors operated in charge integrating mode. Energy-resolved photon-counting detectors provide spectral information from polychromatic x-rays using multiple energy thresholds. These detectors allow simultaneous acquisition of data in different energy ranges without spectral overlap, resulting in more efficient material decomposition and quantification for dual-energy CT. In this study, a pre-reconstruction dual-energy CT technique based on volume conservation was proposed for three-material decomposition. The technique was combined with iterative reconstruction algorithms by using a ray-driven projector in order to improve the quality of decomposition images and reduce radiation dose. A spectral CT system equipped with a CZT-based photon-counting detector was used to implement the proposed dual-energy CT technique. We obtained dual-energy images of calibration and three-material phantoms consisting of low atomic number materials from the optimal energy bins determined by Monte Carlo simulations. The material decomposition process was accomplished by both the proposed and post-reconstruction dual-energy CT techniques. Linear regression and normalized root-mean-square error (NRMSE) analyses were performed to evaluate the quantitative accuracy of decomposition images. The calibration accuracy of the proposed dual-energy CT technique was higher than that of the post-reconstruction dual-energy CT technique, with fitted slopes of 0.97-1.01 and NRMSEs of 0.20-4.50% for all basis materials. In the three-material phantom study, the proposed dual-energy CT technique decreased the NRMSEs of measured volume fractions by factors of 0.17-0.28 compared to the post-reconstruction dual-energy CT technique. It was concluded that the

  17. Quantitative material decomposition using spectral computed tomography with an energy-resolved photon-counting detector.

    PubMed

    Lee, Seungwan; Choi, Yu-Na; Kim, Hee-Joung

    2014-09-21

    Dual-energy computed tomography (CT) techniques have been used to decompose materials and characterize tissues according to their physical and chemical compositions. However, these techniques are hampered by the limitations of conventional x-ray detectors operated in charge integrating mode. Energy-resolved photon-counting detectors provide spectral information from polychromatic x-rays using multiple energy thresholds. These detectors allow simultaneous acquisition of data in different energy ranges without spectral overlap, resulting in more efficient material decomposition and quantification for dual-energy CT. In this study, a pre-reconstruction dual-energy CT technique based on volume conservation was proposed for three-material decomposition. The technique was combined with iterative reconstruction algorithms by using a ray-driven projector in order to improve the quality of decomposition images and reduce radiation dose. A spectral CT system equipped with a CZT-based photon-counting detector was used to implement the proposed dual-energy CT technique. We obtained dual-energy images of calibration and three-material phantoms consisting of low atomic number materials from the optimal energy bins determined by Monte Carlo simulations. The material decomposition process was accomplished by both the proposed and post-reconstruction dual-energy CT techniques. Linear regression and normalized root-mean-square error (NRMSE) analyses were performed to evaluate the quantitative accuracy of decomposition images. The calibration accuracy of the proposed dual-energy CT technique was higher than that of the post-reconstruction dual-energy CT technique, with fitted slopes of 0.97-1.01 and NRMSEs of 0.20-4.50% for all basis materials. In the three-material phantom study, the proposed dual-energy CT technique decreased the NRMSEs of measured volume fractions by factors of 0.17-0.28 compared to the post-reconstruction dual-energy CT technique. It was concluded that the

  18. Toward Femtosecond Time-Resolved Studies of Solvent-Solute Energy Transfer in Doped Helium Nanodroplets

    NASA Astrophysics Data System (ADS)

    Bacellar, C.; Ziemkiewicz, M. P.; Leone, S. R.; Neumark, D. M.; Gessner, O.

    2015-05-01

    Superfluid helium nanodroplets provide a unique cryogenic matrix for high resolution spectroscopy and ultracold chemistry applications. With increasing photon energy and, in particular, in the increasingly important Extreme Ultraviolet (EUV) regime, the droplets become optically dense and, therefore, participate in the EUV-induced dynamics. Energy- and charge-transfer mechanisms between the host droplets and dopant atoms, however, are poorly understood. Static energy domain measurements of helium droplets doped with noble gas atoms (Xe, Kr) indicate that Penning ionization due to energy transfer from the excited droplet to dopant atoms may be a significant relaxation channel. We have set up a femtosecond time-resolved photoelectron imaging experiment to probe these dynamics directly in the time-domain. Droplets containing 104 to 106 helium atoms and a small percentage (<10-4) of dopant atoms (Xe, Kr, Ne) are excited to the 1s2p Rydberg band by 21.6 eV photons produced by high harmonic generation (HHG). Transiently populated states are probed by 1.6 eV photons, generating time-dependent photoelectron kinetic energy distributions, which are monitored by velocity map imaging (VMI). The results will provide new information about the dynamic timescales and the different relaxation channels, giving access to a more complete physical picture of solvent-solute interactions in the superfluid environment. Prospects and challenges of the novel experiment as well as preliminary experimental results will be discussed.

  19. An empirical method for correcting the detector spectral response in energy-resolved CT

    NASA Astrophysics Data System (ADS)

    Schmidt, Taly Gilat

    2012-03-01

    Energy-resolving photon-counting detectors have the potential for improved material decomposition compared to dual-kVp approaches. However, material decomposition accuracy is limited by the nonideal spectral response of the detectors. This work proposes an empirical method for correcting the nonideal spectral response, including spectrum-tailing effects. Unlike previous correction methods which relied on synchrotron measurements, the proposed method can be performed on the scanner. The proposed method estimates a spectral-response matrix by performing x-ray projection measurements through a range of known thicknesses of two or more calibration materials. Once estimated, the spectral-response matrix is incorporated into conventional material decomposition algorithms. A simulation study investigated preliminary feasibility of the proposed method. The spectral-response matrix was estimated using simulated projection measurements through PMMA, aluminum, and gadolinium. An energy-resolved acquisition of a thorax phantom with gadolinium in the blood pool was simulated assuming a five-bin detector with realistic spectral response. Energy-bin data was decomposed into Compton, photoelectric, and gadolinium basis projections with and without the proposed correction method. Basis images were reconstructed by filtered backprojection. Results demonstrated that the nonideal spectral response reduced the ability to distinguish gadolinium from materials such as bone, while images reconstructed with the proposed correction method successfully depicted the contrast agent. The proposed correction method reduced errors from 9% to 0.6% in the Compton image, 90% to 0.6% in the photoelectric image and from 40% to 6% in the gadolinium image when using a three-material calibration. Overall, results support feasibility of the proposed spectral-response correction method.

  20. Concepts for design of an energy management system incorporating dispersed storage and generation

    NASA Technical Reports Server (NTRS)

    Kirkham, H.; Koerner, T.; Nightingale, D.

    1981-01-01

    New forms of generation based on renewable resources must be managed as part of existing power systems in order to be utilized with maximum effectiveness. Many of these generators are by their very nature dispersed or small, so that they will be connected to the distribution part of the power system. This situation poses new questions of control and protection, and the intermittent nature of some of the energy sources poses problems of scheduling and dispatch. Under the assumption that the general objectives of energy management will remain unchanged, the impact of dispersed storage and generation on some of the specific functions of power system control and its hardware are discussed.

  1. Time-Resolved Tandem Faraday Cup for High Energy TNSA Particles

    NASA Astrophysics Data System (ADS)

    Padalino, Stephen; Simone, Angela; Turner, Ethan; Ginnane, Mary Kate; Dubois, Natalie; Sangster, Craig; Regan, Sean

    2014-10-01

    MTW and OMEGA EP Lasers at LLE utilize ultra-intense laser light to produce bursts of high-energy ions through Target Normal Sheath Acceleration (TNSA). A Time Resolved Tandem Faraday Cup (TFC) is being designed to collect and differentiate protons and alphas from heavy ions produced during TNSA. The TFC will be comprised of a replaceable thickness absorber capable of stopping a range of user-selectable heavy ions. Ions heavier than alphas emitted from the TNSA plasma will stop within the primary TFC, while less massive particles will continue through and deposit their remaining charge in the secondary TFC. The time-resolved beam current generated in each cup will be measured on a fast storage scope in multiple channels. Secondary electrons released from the impact of heavy ions with the cups will be suppressed by magnetic and electrostatic fields. A charge-exchange foil at the TFC entrance will modify the charge state distribution of the heavy ions produced by the plasma to a known distribution. Using the known distribution and the time of flight of the heavy ions, the total heavy ion current can be determined. Ultimately the TFC will be used to normalize a variety of nuclear physics cross sections and stopping power measurements. Funded in part by a LLE contract through the DOE.

  2. Glucose Starvation-Induced Dispersal of Pseudomonas aeruginosa Biofilms Is cAMP and Energy Dependent

    PubMed Central

    Huynh, Tran T.; McDougald, Diane; Klebensberger, Janosch; Al Qarni, Budoor; Barraud, Nicolas; Rice, Scott A.; Kjelleberg, Staffan; Schleheck, David

    2012-01-01

    Carbon starvation has been shown to induce a massive dispersal event in biofilms of the opportunistic pathogen Pseudomonas aeruginosa; however, the molecular pathways controlling this dispersal response remain unknown. We quantified changes in the proteome of P. aeruginosa PAO1 biofilm and planktonic cells during glucose starvation by differential peptide-fingerprint mass-spectrometry (iTRAQ). In addition, we monitored dispersal photometrically, as a decrease in turbidity/opacity of biofilms pre-grown and starved in continuous flow-cells, in order to evaluate treatments (e.g. inhibitors CCCP, arsenate, chloramphenicol, L-serine hydroxamate) and key mutants altered in biofilm development and dispersal (e.g. nirS, vfr, bdlA, rpoS, lasRrhlR, Pf4-bacteriophage and cyaA). In wild-type biofilms, dispersal started within five minutes of glucose starvation, was maximal after 2 h, and up to 60% of the original biomass had dispersed after 24 h of starvation. The changes in protein synthesis were generally not more than two fold and indicated that more than 100 proteins belonging to various classes, including carbon and energy metabolism, stress adaptation, and motility, were differentially expressed. For the different treatments, only the proton-ionophore CCCP or arsenate, an inhibitor of ATP synthesis, prevented dispersal of the biofilms. For the different mutants tested, only cyaA, the synthase of the intracellular second messenger cAMP, failed to disperse; complementation of the cyaA mutation restored the wild-type phenotype. Hence, the pathway for carbon starvation-induced biofilm dispersal in P. aeruginosa PAO1 involves ATP production via direct ATP synthesis and proton-motive force dependent step(s) and is mediated through cAMP, which is likely to control the activity of proteins involved in remodeling biofilm cells in preparation for planktonic survival. PMID:22905180

  3. Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

    PubMed Central

    Barber, W. C.; Wessel, J. C.; Nygard, E.; Iwanczyk, J. S.

    2014-01-01

    We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

  4. Energy dispersive CdTe and CdZnTe detectors for spectral clinical CT and NDT applications

    NASA Astrophysics Data System (ADS)

    Barber, W. C.; Wessel, J. C.; Nygard, E.; Iwanczyk, J. S.

    2015-06-01

    We are developing room temperature compound semiconductor detectors for applications in energy-resolved high-flux single x-ray photon-counting spectral computed tomography (CT), including functional imaging with nanoparticle contrast agents for medical applications and non-destructive testing (NDT) for security applications. Energy-resolved photon-counting can provide reduced patient dose through optimal energy weighting for a particular imaging task in CT, functional contrast enhancement through spectroscopic imaging of metal nanoparticles in CT, and compositional analysis through multiple basis function material decomposition in CT and NDT. These applications produce high input count rates from an x-ray generator delivered to the detector. Therefore, in order to achieve energy-resolved single photon counting in these applications, a high output count rate (OCR) for an energy-dispersive detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) compound semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel provided the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions, and at a sufficiently high detective quantum efficiency (DQE). We have developed high-flux energy-resolved photon-counting x-ray imaging array sensors using pixellated CdTe and CdZnTe semiconductors optimized for clinical CT and security NDT. We have also fabricated high

  5. Time-resolved energy dynamics after single electron injection into an interacting helical liquid

    NASA Astrophysics Data System (ADS)

    Calzona, Alessio; Acciai, Matteo; Carrega, Matteo; Cavaliere, Fabio; Sassetti, Maura

    2016-07-01

    The possibility of injecting a single electron into ballistic conductors is at the basis of the new field of electron quantum optics. Here, we consider a single electron injection into the helical edge channels of a topological insulator. Their counterpropagating nature and the unavoidable presence of electron-electron interactions dramatically affect the time evolution of the single wave packet. Modeling the injection process from a mesoscopic capacitor in the presence of nonlocal tunneling, we focus on the time-resolved charge and energy packet dynamics. Both quantities split up into counterpropagating contributions whose profiles are strongly affected by the interaction strength. In addition, stronger signatures are found for the injected energy, which is also affected by the finite width of the tunneling region, in contrast to what happens for the charge. Indeed, the energy flow can be controlled by tuning the injection parameters, and we demonstrate that, in the presence of nonlocal tunneling, it is possible to achieve a situation in which charge and energy flow in opposite directions.

  6. Energy transfer in Anabaena variabilis filaments under nitrogen depletion, studied by time-resolved fluorescence.

    PubMed

    Onishi, Aya; Aikawa, Shimpei; Kondo, Akihiko; Akimoto, Seiji

    2015-08-01

    Some filamentous cyanobacteria (including Anabaena) differentiate into heterocysts under nitrogen-depleted conditions. During differentiation, the phycobiliproteins and photosystem II in the heterocysts are gradually degraded. Nitrogen depletion induces changes in the pigment composition of both vegetative cells and heterocysts, which affect the excitation energy transfer processes. To investigate the changes in excitation energy transfer processes of Anabaena variabilis filaments grown in standard medium (BG11) and a nitrogen-free medium (BG110), we measured their steady-state absorption spectra, steady-state fluorescence spectra, and time-resolved fluorescence spectra (TRFS) at 77 K. TRFS were measured with a picosecond time-correlated single photon counting system. The pigment compositions of the filaments grown in BG110 changed throughout the growth period; the relative phycocyanin levels monotonically decreased, whereas the relative carotenoid (Car) levels decreased and then recovered to their initial value (at day 0), with formation of lower-energy Cars. Nitrogen starvation also altered the fluorescence kinetics of PSI; the fluorescence maximum of TRFS immediately after excitation occurred at 735, 740, and 730 nm after 4, 8, and 15 days growth in BG110, respectively. Based on these results, we discuss the excitation energy transfer dynamics of A. variabilis filaments under the nitrogen-depleted condition throughout the growth period. PMID:25596847

  7. Energy resolved electrochemical impedance spectroscopy for electronic structure mapping in organic semiconductors

    SciTech Connect

    Nádaždy, V. Gmucová, K.; Schauer, F.

    2014-10-06

    We introduce an energy resolved electrochemical impedance spectroscopy method to map the electronic density of states (DOS) in organic semiconductor materials. The method consists in measurement of the charge transfer resistance of a semiconductor/electrolyte interface at a frequency where the redox reactions determine the real component of the impedance. The charge transfer resistance value provides direct information about the electronic DOS at the energy given by the electrochemical potential of the electrolyte, which can be adjusted using an external voltage. A simple theory for experimental data evaluation is proposed, along with an explanation of the corresponding experimental conditions. The method allows mapping over unprecedentedly wide energy and DOS ranges. Also, important DOS parameters can be determined directly from the raw experimental data without the lengthy analysis required in other techniques. The potential of the proposed method is illustrated by tracing weak bond defect states induced by ultraviolet treatment above the highest occupied molecular orbital in a prototypical σ-conjugated polymer, poly[methyl(phenyl)silylene]. The results agree well with those of our previous DOS reconstruction by post-transient space-charge-limited-current spectroscopy, which was, however, limited to a narrow energy range. In addition, good agreement of the DOS values measured on two common π-conjugated organic polymer semiconductors, polyphenylene vinylene and poly(3-hexylthiophene), with the rather rare previously published data demonstrate the accuracy of the proposed method.

  8. Quantification of surface amorphous content using dispersive surface energy: the concept of effective amorphous surface area.

    PubMed

    Brum, Jeffrey; Burnett, Daniel

    2011-09-01

    We investigate the use of dispersive surface energy in quantifying surface amorphous content, and the concept of effective amorphous surface area is introduced. An equation is introduced employing the linear combination of surface area normalized square root dispersive surface energy terms. This equation is effective in generating calibration curves when crystalline and amorphous references are used. Inverse gas chromatography is used to generate dispersive surface energy values. Two systems are investigated, and in both cases surface energy data collected for physical mixture samples comprised of amorphous and crystalline references fits the predicted response with good accuracy. Surface amorphous content of processed lactose samples is quantified using the calibration curve, and interpreted within the context of effective amorphous surface area. Data for bulk amorphous content is also utilized to generate a thorough picture of how disorder is distributed throughout the particle. An approach to quantifying surface amorphous content using dispersive surface energy is presented. Quantification is achieved by equating results to an effective amorphous surface area based on reference crystalline, and amorphous materials. PMID:21725707

  9. Time-resolved Förster-resonance-energy-transfer DNA assay on an active CMOS microarray

    PubMed Central

    Schwartz, David Eric; Gong, Ping; Shepard, Kenneth L.

    2008-01-01

    We present an active oligonucleotide microarray platform for time-resolved Förster resonance energy transfer (TR-FRET) assays. In these assays, immobilized probe is labeled with a donor fluorophore and analyte target is labeled with a fluorescence quencher. Changes in the fluorescence decay lifetime of the donor are measured to determine the extent of hybridization. In this work, we demonstrate that TR-FRET assays have reduced sensitivity to variances in probe surface density compared with standard fluorescence-based microarray assays. Use of an active array substrate, fabricated in a standard complementary metal-oxide-semiconductor (CMOS) process, provides the additional benefits of reduced system complexity and cost. The array consists of 4096 independent single-photon avalanche diode (SPAD) pixel sites and features on-chip time-to-digital conversion. We demonstrate the functionality of our system by measuring a DNA target concentration series using TR-FRET with semiconductor quantum dot donors. PMID:18515059

  10. Investigation of energy transfer mechanisms between Bi(2+) and Tm(3+) by time-resolved spectrum.

    PubMed

    Li, Yang; Sharafudeen, Kaniyarakkal; Dong, Guoping; Ma, Zhijun; Qiu, Jianrong

    2013-11-01

    Here, we report for the first time the optical properties of Bi(2+) and Tm(3+) co-doped germanate glasses and elucidate the potential of this material as substrates to improve the performance of CdTe solar cell. A strong emission peak at 800nm is observed under the excitation of 450-700nm in this material. The energy transfer processes from the transitions of Bi(2+) [(2)P3/2(1)→(2)P1/2]: Tm(3+) [(3)H6→(3)H4] are investigated by time-resolved luminescence spectroscopy. A cover glass exhibiting an ultra-broadband response spectrum covering the entire solar visible wavelength region is suggested to enhance the conversion efficiency of CdTe solar cells significantly. PMID:23850790

  11. First Mass-resolved Measurement of High-Energy Cosmic-Ray Antiprotons.

    PubMed

    Bergström; Boezio; Carlson; Francke; Grinstein; Khalchukov; Suffert; Hof; Kremer; Menn; Simon; Stephens; Ambriola; Bellotti; Cafagna; Ciacio; Circella; De Marzo C; Finetti; Papini; Piccardi; Spillantini; Bartalucci; Ricci; Casolino; De Pascale MP; Morselli; Picozza; Sparvoli; Bonvicini; Schiavon; Vacchi; Zampa; Mitchell; Ormes; Streitmatter; Bravar; Stochaj

    2000-05-10

    We report new results for the cosmic-ray antiproton-to-proton ratio from 3 to 50 GeV at the top of the atmosphere. These results represent the first measurements, on an event-by-event basis, of mass-resolved antiprotons above 18 GeV. The results were obtained with the NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas-RICH (Ring-Imaging Cerenkov) counter and a silicon-tungsten imaging calorimeter. The RICH detector was the first ever flown that is capable of identifying charge-one particles at energies above 5 GeV. The spectrometer was flown on 1998 May 28-29 from Fort Sumner, New Mexico. The measured p&d1;/p ratio is in agreement with a pure secondary interstellar production. PMID:10813676

  12. Energy calibration of energy-resolved photon-counting pixel detectors using laboratory polychromatic x-ray beams

    NASA Astrophysics Data System (ADS)

    Youn, Hanbean; Han, Jong Chul; Kam, Soohwa; Yun, Seungman; Kim, Ho Kyung

    2014-10-01

    Recently, photon-counting detectors capable of resolving incident x-ray photon energies have been considered for use in spectral x-ray imaging applications. For reliable use of energy-resolved photon-counting detectors (ERPCDs), energy calibration is an essential procedure prior to their use because variations in responses from each pixel of the ERPCD for incident photons, even at the same energy, are inevitable. Energy calibration can be performed using a variety of methods. In all of these methods, the photon spectra with well-defined peak energies are recorded. Every pixel should be calibrated on its own. In this study, we suggest the use of a conventional polychromatic x-ray source (that is typically used in laboratories) for energy calibration. The energy calibration procedure mainly includes the determination of the peak energies in the spectra, flood-field irradiation, determination of peak channels, and determination of calibration curves (i.e., the slopes and intercepts of linear polynomials). We applied a calibration algorithm to a CdTe ERPCD comprised of 128×128 pixels with a pitch of 0.35 mm using highly attenuated polychromatic x-ray beams to reduce the pulse pile-up effect, and to obtain a narrow-shaped spectrum due to beam hardening. The averaged relative error in calibration curves obtained from 16,384 pixels was about 0.56% for 59.6 keV photons from an Americium radioisotope. This pixel-by-pixel energy calibration enhanced the signal- and contrast-to-noise ratios in images, respectively, by a factor of ~5 and 3 due to improvement in image homogeneity, compared to those obtained without energy calibration. One secondary finding of this study was that the x-ray photon spectra obtained using a common algorithm for computing x-ray spectra reasonably described the peaks in the measured spectra, which implies easier peak detection without the direct measurement of spectra using a separate spectrometer. The proposed method will be a useful alternative to

  13. Energy-resolved CT imaging with a photon-counting silicon-strip detector

    NASA Astrophysics Data System (ADS)

    Persson, Mats; Huber, Ben; Karlsson, Staffan; Liu, Xuejin; Chen, Han; Xu, Cheng; Yveborg, Moa; Bornefalk, Hans; Danielsson, Mats

    2014-03-01

    Photon-counting detectors are promising candidates for use in the next generation of x-ray CT scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose, and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility. However, it is sometimes claimed to be unsuitable for use in computed tomography because of its low absorption efficiency and high fraction of Compton scatter. The purpose of this work is to demonstrate that high-quality energy-resolved CT images can nonetheless be acquired with clinically realistic exposure parameters using a photon-counting silicon-strip detector with eight energy thresholds developed in our group. We use a single detector module, consisting of a linear array of 50 0.5 × 0.4 mm detector elements, to image a phantom in a table-top lab setup. The phantom consists of a plastic cylinder with circular inserts containing water, fat and aqueous solutions of calcium, iodine and gadolinium, in different concentrations. We use basis material decomposition to obtain water, calcium, iodine and gadolinium basis images and demonstrate that these basis images can be used to separate the different materials in the inserts. We also show results showing that the detector has potential for quantitative measurements of substance concentrations.

  14. Energy-resolved CT imaging with a photon-counting silicon-strip detector

    NASA Astrophysics Data System (ADS)

    Persson, Mats; Huber, Ben; Karlsson, Staffan; Liu, Xuejin; Chen, Han; Xu, Cheng; Yveborg, Moa; Bornefalk, Hans; Danielsson, Mats

    2014-11-01

    Photon-counting detectors are promising candidates for use in the next generation of x-ray computed tomography (CT) scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility. However, it is sometimes overlooked for CT applications because of its low absorption efficiency and high fraction of Compton scatter. The purpose of this work is to demonstrate that silicon is a feasible material for CT detectors by showing energy-resolved CT images acquired with an 80 kVp x-ray tube spectrum using a photon-counting silicon-strip detector with eight energy thresholds developed in our group. We use a single detector module, consisting of a linear array of 50 0.5 × 0.4 mm detector elements, to image a phantom in a table-top lab setup. The phantom consists of a plastic cylinder with circular inserts containing water, fat and aqueous solutions of calcium, iodine and gadolinium, in different concentrations. By using basis material decomposition we obtain water, calcium, iodine and gadolinium basis images and demonstrate that these basis images can be used to separate the different materials in the inserts. We also show results showing that the detector has potential for quantitative measurements of substance concentrations.

  15. X-ray photo-emission and energy dispersive spectroscopy of HA coated titanium

    SciTech Connect

    Drummond, J.L.; Steinberg, A.D.; Krauss, A.R.

    1997-08-01

    The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (x-ray photo-emission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls, 30 minutes and 3 hours aged specimens in distilled water or 0.2M sodium phosphate buffer (pH 7.2) at room temperature. Each x-ray photo-emission cycle consisted of 3 scans followed by argon sputtering for 10 minutes for a total of usually 20 cycles, corresponding to a sampling depth of {approximately} 1500 {angstrom}. The energy dispersive spectroscopy analysis was on a 110 by 90 {mu}m area for 500 sec. Scanning electron microscopy examination showed crystal formation (3P{sub 2}O{sub 5}*2CAO*?H{sub 2}O by energy dispersive spectroscopy analysis) on the HA coating for the specimens aged in sodium phosphate buffer. The x-ray photo-emission results indicated the oxidation effect of water on the titanium (as TiO{sub 2}) and the effect of the buffer to increase the surface concentration of phosphorous. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis. The crystal growth was only observed for the sodium phosphate buffer specimens and only on the HA surface.

  16. Rossby wave energy dispersion from tropical cyclone in zonal basic flows

    NASA Astrophysics Data System (ADS)

    Shi, Wenli; Fei, Jianfang; Huang, Xiaogang; Liu, Yudi; Ma, Zhanhong; Yang, Lu

    2016-04-01

    This study investigates tropical cyclone energy dispersion under horizontally sheared flows using a nonlinear barotropic model. In addition to common patterns, unusual features of Rossby wave trains are also found in flows with constant vorticity and vorticity gradients. In terms of the direction of the energy dispersion, the wave train can rotate clockwise and elongate southwestward under anticyclonic circulation (ASH), which contributes to the reenhancement of the tropical cyclone (TC). The wave train even splits into two obvious wavelike trains in flows with a southward vorticity gradient (WSH). Energy dispersed from TCs varies over time, and variations in the intensity of the wave train components typically occur in two stages. Wave-activity flux diagnosis and ray tracing calculations are extended to the frame that moves along with the TC to reveal the concrete progress of wave propagation. The direction of the wave-activity flux is primarily determined by the combination of the basic flow and the TC velocity. Along the flux, the distribution of pseudomomentum effectively illustrates the development of wave trains, particularly the rotation and split of wave propagation. Ray tracing involves the quantitative tracing of wave features along rays, which effectively coincide with the wave train regimes. Flows of a constant shear (parabolic meridional variation) produce linear (nonlinear) wave number variations. For the split wave trains, the real and complex wave number waves move along divergent trajectories and are responsible for different energy dispersion ducts.

  17. Analysis of tincal ore waste by energy dispersive X-ray fluorescence (EDXRF) Technique

    NASA Astrophysics Data System (ADS)

    Kalfa, Orhan Murat; Üstündağ, Zafer; Özkırım, Ilknur; Kagan Kadıoğlu, Yusuf

    2007-01-01

    Etibank Borax Plant is located in Kırka-Eskişehir, Turkey. The borax waste from this plant was analyzed by means of energy dispersive X-ray fluorescence (EDXRF). The standard addition method was used for the determination of the concentration of Al, Fe, Zn, Sn, and Ba. The results are presented and discussed in this paper.

  18. Energy-Dispersive X-Ray Fluorescence Spectrometry: A Long Overdue Addition to the Chemistry Curriculum

    ERIC Educational Resources Information Center

    Palmer, Peter T.

    2011-01-01

    Portable Energy-Dispersive X-Ray Fluorescence (XRF) analyzers have undergone significant improvements over the past decade. Salient advantages of XRF for elemental analysis include minimal sample preparation, multielement analysis capabilities, detection limits in the low parts per million (ppm) range, and analysis times on the order of 1 min.…

  19. The relative effect of behaviour in larval dispersal in a low energy embayment

    NASA Astrophysics Data System (ADS)

    Daigle, Rémi M.; Chassé, Joël; Metaxas, Anna

    2016-05-01

    This study examined the relative importance of tidal phase, larval behaviour, release site, depth layer, and vertical swimming velocity on mean in-sea dispersal distance, retention, distance from shore, and population connectivity. Using a biophysical model, we simulated larval dispersal of marine benthic invertebrates for 6 taxonomic groups representing different combinations of swimming speed, and depth preference in St. George's Bay, NS, Canada, a shallow bay with low energy (e.g. lack of estuarine circulation). The biophysical model was run over a period of 3 months, from Jul to Sep, representing the period when larvae of the targeted species were present, and at each of 3 years. Overall, release site had the strongest effect of all factors on the dispersal metrics. Although less important than release site in our system, vertical distribution and swim speed had a significant effect which would likely be more pronounced in high (i.e. with features such as estuarine circulation or internal waves) than low energy environments. Retention and distance from shore were more responsive to our manipulations than dispersal distance, both in terms of the number of ecologically significant effects and the magnitudes of their effect size. These findings allow for the prioritization of biophysical model parameters and improved simulations of larval dispersal.

  20. Spatially and momentum resolved energy electron loss spectra from an ultra-thin PrNiO{sub 3} layer

    SciTech Connect

    Kinyanjui, M. K. Kaiser, U.; Benner, G.; Pavia, G.; Boucher, F.; Habermeier, H.-U.; Keimer, B.

    2015-05-18

    We present an experimental approach which allows for the acquisition of spectra from ultra-thin films at high spatial, momentum, and energy resolutions. Spatially and momentum (q) resolved electron energy loss spectra have been obtained from a 12 nm ultra-thin PrNiO{sub 3} layer using a nano-beam electron diffraction based approach which enabled the acquisition of momentum resolved spectra from individual, differently oriented nano-domains and at different positions of the PrNiO{sub 3} thin layer. The spatial and wavelength dependence of the spectral excitations are obtained and characterized after the analysis of the experimental spectra using calculated dielectric and energy loss functions. The presented approach makes a contribution towards obtaining momentum-resolved spectra from nanostructures, thin film, heterostructures, surfaces, and interfaces.

  1. Time-Resolved Tandem Faraday Cup Development for High Energy TNSA Particles

    NASA Astrophysics Data System (ADS)

    Padalino, S.; Simone, A.; Turner, E.; Ginnane, M. K.; Glisic, M.; Kousar, B.; Smith, A.; Sangster, C.; Regan, S.

    2015-11-01

    MTW and OMEGA EP Lasers at LLE utilize ultra-intense laser light to produce high-energy ion pulses through Target Normal Sheath Acceleration (TNSA). A Time Resolved Tandem Faraday Cup (TRTF) was designed and built to collect and differentiate protons from heavy ions (HI) produced during TNSA. The TRTF includes a replaceable thickness absorber capable of stopping a range of user-selectable HI emitted from TNSA plasma. HI stop within the primary cup, while less massive particles continue through and deposit their remaining charge in the secondary cup, releasing secondary electrons in the process. The time-resolved beam current generated in each cup will be measured on a fast storage scope in multiple channels. A charge-exchange foil at the TRTF entrance modifies the charge state distribution of HI to a known distribution. Using this distribution and the time of flight of the HI, the total HI current can be determined. Initial tests of the TRTF have been made using a proton beam produced by SUNY Geneseo's 1.7 MV Pelletron accelerator. A substantial reduction in secondary electron production, from 70% of the proton beam current at 2MeV down to 0.7%, was achieved by installing a pair of dipole magnet deflectors which successfully returned the electrons to the cups in the TRTF. Ultimately the TRTF will be used to normalize a variety of nuclear physics cross sections and stopping power measurements. Based in part upon work supported by a DOE NNSA Award#DE-NA0001944.

  2. The 20 element HgI2 energy dispersive x ray array detector system

    NASA Astrophysics Data System (ADS)

    Iwanczyk, J. A.; Dorri, N.; Wang, M.; Szczebiot, R. W.; Dabrowski, A. J.; Hedman, B.; Hodgson, K. O.; Patt, B. E.

    1991-11-01

    This paper describes recent progress in the development of HgI2 energy dispersive x-ray detector arrays and associated miniaturized processing electronics for synchrotron radiation research applications. The experimental results with a 20 element array detector were obtained under realistic synchrotron beam conditions at SSRL. An energy resolution of 250 eV (FWHM) at 5.9 keV (Mn-K(sub a)) was achieved. Energy resolution and throughput measurements versus input count rate and energy of incoming radiation have been measured. Extended X-ray Absorption Fine Structure (EXAFS) spectra were taken from diluted samples simulating proteins with nickel.

  3. Spatially resolving the very high energy emission from MGRO J2019+37 with VERITAS

    SciTech Connect

    Aliu, E.; Errando, M.; Aune, T.; Behera, B.; Chen, X.; Federici, S.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Bouvier, A.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dumm, J.; Dwarkadas, V. V.; Falcone, A. E-mail: nahee@uchicago.edu; and others

    2014-06-10

    We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended (∼2°) unidentified Milagro source is located toward the rich star formation region Cygnus-X. MGRO J2019+37 is resolved into two VERITAS sources. The faint, point-like source VER J2016+371 overlaps CTB 87, a filled-center remnant (SNR) with no evidence of a supernova remnant shell at the present time. Its spectrum is well fit in the 0.65-10 TeV energy range by a power-law model with photon index 2.3 ± 0.4. VER J2019+378 is a bright extended (∼1°) source that likely accounts for the bulk of the Milagro emission and is notably coincident with PSR J2021+3651 and the star formation region Sh 2–104. Its spectrum in the range 1-30 TeV is well fit with a power-law model of photon index 1.75 ± 0.3, among the hardest values measured in the VHE band, comparable to that observed near Vela-X. We explore the unusual spectrum and morphology in the radio and X-ray bands to constrain possible emission mechanisms for this source.

  4. Position and energy-resolved particle detection using phonon-mediated microwave kinetic inductance detectors

    SciTech Connect

    Moore, D. C.; Golwala, S. R.; Cornell, B.; Bumble, B.; Day, P. K.; LeDuc, H. G.; Zmuidzinas, J.

    2012-06-04

    We demonstrate position and energy-resolved phonon-mediated detection of particle interactions in a silicon substrate instrumented with an array of microwave kinetic inductance detectors (MKIDs). The relative magnitude and delay of the signal received in each sensor allow the location of the interaction to be determined with < or approx. 1mm resolution at 30 keV. Using this position information, variations in the detector response with position can be removed, and an energy resolution of {sigma}{sub E} = 0.55 keV at 30 keV was measured. Since MKIDs can be fabricated from a single deposited film and are naturally multiplexed in the frequency domain, this technology can be extended to provide highly pixelized athermal phonon sensors for {approx}1 kg scale detector elements. Such high-resolution, massive particle detectors would be applicable to rare-event searches such as the direct detection of dark matter, neutrinoless double-beta decay, or coherent neutrino-nucleus scattering.

  5. Feasibility of using energy-resolving detectors in differential phase-contrast imaging

    NASA Astrophysics Data System (ADS)

    Baturin, Pavlo

    2016-03-01

    In a common clinical setting, conventional absorption-based imaging provides relatively good contrast between bonelike and soft-tissue materials. The reliability of material differentiation, however, is hampered when materials with similar absorption properties are scanned. This problem can be addressed by utilizing a spectral imaging technique whereby multiple X-ray measurements are taken at different beam conditions. In this work, we discuss the possibility of using a spectral imaging approach in a grating-based, differential-phase contrast-imaging (DPCI) modality. Two approaches, dual exposure with a conventional flat-panel detector (FPD) and a single exposure with a photon-counting energy-resolving detector (PCD), were reviewed. The feasibility of a single-exposure DPCI and a two-bin PCD setup was assessed quantitatively by a least-squares minimization algorithm applied to an X-ray diffraction pattern. It was shown that a two-peak-shaped X-ray spectrum can allow PCDs to be placed unambiguously at single Talbot distances making it possible to simultaneously detect photons in each energy bin with comparable efficiencies. The results of this work can help build a bridge between two rapidly developing imaging modalities, X-ray spectral imaging and X-ray DPCI.

  6. Energy release in the solar corona from spatially resolved magnetic braids.

    PubMed

    Cirtain, J W; Golub, L; Winebarger, A R; De Pontieu, B; Kobayashi, K; Moore, R L; Walsh, R W; Korreck, K E; Weber, M; McCauley, P; Title, A; Kuzin, S; DeForest, C E

    2013-01-24

    It is now apparent that there are at least two heating mechanisms in the Sun's outer atmosphere, or corona. Wave heating may be the prevalent mechanism in quiet solar periods and may contribute to heating the corona to 1,500,000 K (refs 1-3). The active corona needs additional heating to reach 2,000,000-4,000,000 K; this heat has been theoretically proposed to come from the reconnection and unravelling of magnetic 'braids'. Evidence favouring that process has been inferred, but has not been generally accepted because observations are sparse and, in general, the braided magnetic strands that are thought to have an angular width of about 0.2 arc seconds have not been resolved. Fine-scale braiding has been seen in the chromosphere but not, until now, in the corona. Here we report observations, at a resolution of 0.2 arc seconds, of magnetic braids in a coronal active region that are reconnecting, relaxing and dissipating sufficient energy to heat the structures to about 4,000,000 K. Although our 5-minute observations cannot unambiguously identify the field reconnection and subsequent relaxation as the dominant heating mechanism throughout active regions, the energy available from the observed field relaxation in our example is ample for the observed heating. PMID:23344359

  7. Low-energy phonon dispersion in LaFe4Sb12

    NASA Astrophysics Data System (ADS)

    Leithe-Jasper, Andreas; Boehm, Martin; Mutka, Hannu; Koza, Michael M.

    We studied the vibrational dynamics of a single crystal of LaFe4Sb12 by three-axis inelastic neutron spectroscopy. The dispersion of phonons with wave vectors q along [ xx 0 ] and [ xxx ] directions in the energy range of eigenmodes with high amplitudes of lanthanum vibrations, i.e., at ℏω < 12 meV is identified. Symmetry-avoided anticrossing dispersion of phonons is established in both monitored directions and distinct eigenstates at high-symmetry points and at the Brillouin-zone center are discriminated. The experimentally derived phonon dispersion and intensities are compared with and backed up by ab initio lattice dynamics calculations. results of the computer model match well with the experimental data.

  8. Diffraction applications using the energy dispersive beamline, X6A, at NSLS

    NASA Astrophysics Data System (ADS)

    Lee, P. L.; Beno, M. A.; Knapp, G. S.; Jennings, G.; Ogata, C. M.

    1994-08-01

    The energy dispersive beamline X6A, at the National Synchrotron Light Source (NSLS) employs a curved crystal monochromator (polychromator) which focuses a range (approximately 1 keV) of x-ray energies into a narrow (100-120 micron) line image. Although this beamline was constructed primarily for time dependent EXAFS experiments, the authors have begun to explore the use of this instrument for energy dispersive diffraction experiments with different types of sample including macromolecular crystals. The tunability (E = 6.5 keV to 21 keV) and flexibility ((Delta)E = 100-1,000 eV) of the instrument makes the beamline ideal as a test bed for the application of polychromatic single crystal diffraction techniques to different chemical or biological materials.

  9. Low-energy dispersion of dynamic charge stripes in La1.75Sr0.25NiO4 observed with inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Zhong, Ruidan; Tranquada, John; Gu, Genda; Reznik, Dmitry; Winn, Barry

    The dynamic stripe correlations have been the subject of intense research, owing to the possible links with high-Tc superconductivity. In light of a recently published, direct observation of charge-stripe fluctuations in La2-xSrxNiO4 using inelastic neutron scattering, we did a follow-up neutron experiment on a x=0.25 sample to characterize the low-energy dispersion of these dynamic charge stripes using the HYSPEC instrument at the Spallation Neutron Source. The scattering signals are collected in the vicinity of a charge-order peak with a large wave vector (4.4, 3, 0), where dynamic spin-stripe correlations are negligible. Mapping the low-energy charge-stripe fluctuations in a wide temperature range, we observe a finite dispersion along the stripe-modulation direction at T >=160K where the charge stripes become disordered, while the steep dispersion in the orthogonal direction is not resolved. Work at BNL supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-SC00112704.

  10. Ocular dispersion

    NASA Astrophysics Data System (ADS)

    Hammer, Daniel X.; Noojin, Gary D.; Thomas, Robert J.; Stolarski, David J.; Rockwell, Benjamin A.; Welch, Ashley J.

    1999-06-01

    Spectrally resolved white-light interferometry (SRWLI) was used to measure the wavelength dependence of refractive index (i.e., dispersion) for various ocular components. The accuracy of the technique was assessed by measurement of fused silica and water, the refractive indices of which have been measured at several different wavelengths. The dispersion of bovine and rabbit aqueous and vitreous humor was measured from 400 to 1100 nm. Also, the dispersion was measured from 400 to 700 nm for aqueous and vitreous humor extracted from goat and rhesus monkey eyes. For the humors, the dispersion did not deviate significantly from water. In an additional experiment, the dispersion of aqueous and vitreous humor that had aged up to a month was compared to freshly harvested material. No difference was found between the fresh and aged media. An unsuccessful attempt was also made to use the technique for dispersion measurement of bovine cornea and lens. Future refinement may allow measurement of the dispersion of cornea and lens across the entire visible and near-infrared wavelength band. The principles of white- light interferometry including image analysis, measurement accuracy, and limitations of the technique, are discussed. In addition, alternate techniques and previous measurements of ocular dispersion are reviewed.

  11. Application of high-resolution linear Radon transform for Rayleigh-wave dispersive energy imaging and mode separating

    USGS Publications Warehouse

    Luo, Y.; Xia, J.; Miller, R.D.; Liu, J.; Xu, Y.; Liu, Q.

    2008-01-01

    Multichannel Analysis of Surface Waves (MASW) analysis is an efficient tool to obtain the vertical shear-wave profile. One of the key steps in the MASW method is to generate an image of dispersive energy in the frequency-velocity domain, so dispersion curves can be determined by picking peaks of dispersion energy. In this paper, we image Rayleigh-wave dispersive energy and separate multimodes from a multichannel record by high-resolution linear Radon transform (LRT). We first introduce Rayleigh-wave dispersive energy imaging by high-resolution LRT. We then show the process of Rayleigh-wave mode separation. Results of synthetic and real-world examples demonstrate that (1) compared with slant stacking algorithm, high-resolution LRT can improve the resolution of images of dispersion energy by more than 50% (2) high-resolution LRT can successfully separate multimode dispersive energy of Rayleigh waves with high resolution; and (3) multimode separation and reconstruction expand frequency ranges of higher mode dispersive energy, which not only increases the investigation depth but also provides a means to accurately determine cut-off frequencies.

  12. Time-domain electromagnetic energy in a frequency-dispersive left-handed medium

    SciTech Connect

    Cui Tiejun; Kong Jinau

    2004-11-15

    From Maxwell's equations and the Poynting theorem, the time-domain electric and magnetic energy densities are generally defined in the frequency-dispersive media based on the conservation of energy. As a consequence, a general definition of electric and magnetic energy is proposed. Comparing with existing formulations of electric and magnetic energy in frequency-dispersive media, the new definition is more reasonable and is valid in any case. Using the new definition and staring from the equation of motion, we have shown rigorously that the total energy density and the individual electric and magnetic energy densities are always positive in a realistic artificial left-handed medium (LHM) [R. A. Shelby, D. R. Smith, and S. Schultz, Science 292, 77 (2001)], which obeys actually the Lorentz medium model, although such a LHM has negative permittivity and negative permeability simultaneously in a certain frequency range. We have also shown that the conservation of energy is not violated in LHM. The earlier conclusions can be easily extended to the Drude medium model and the cold plasma medium model. Through an exact analysis of a one-dimensional transient current source radiating in LHM, numerical results are given to demonstrate that the work done by source, the power flowing outwards a surface, and the electric and magnetic energy stored in a volume are all positive in the time domain.

  13. Computing dispersive, polarizable, and electrostatic shifts of excitation energy in supramolecular systems: PTCDI crystal.

    PubMed

    Megow, Jörg

    2016-09-01

    The gas-to-crystal-shift denotes the shift of electronic excitation energies, i.e., the difference between ground and excited state energies, for a molecule transferred from the gas to the bulk phase. The contributions to the gas-to-crystal-shift comprise electrostatic as well as inductive polarization and dispersive energy shifts of the molecular excitation energies due to interaction with environmental molecules. For the example of 3,4,9,10-perylene-tetracarboxylic-diimide (PTCDI) bulk, the contributions to the gas-to-crystal shift are investigated. In the present work, electrostatic interaction is calculated via Coulomb interaction of partial charges while inductive and dispersive interactions are obtained using respective sum over states expressions. The coupling of higher transition densities for the first 4500 excited states of PTCDI was computed using transition partial charges based on an atomistic model of PTCDI bulk obtained from molecular dynamics simulations. As a result it is concluded that for the investigated model system of a PTCDI crystal, the gas to crystal shift is dominated by dispersive interaction. PMID:27608991

  14. Clausius-Clapeyron Scaling of Convective Available Potential Energy (CAPE) in Cloud-Resolving Simulations

    NASA Astrophysics Data System (ADS)

    Seeley, J.; Romps, D. M.

    2015-12-01

    Recent work by Singh and O'Gorman has produced a theory for convective available potential energy (CAPE) in radiative-convective equilibrium. In this model, the atmosphere deviates from a moist adiabat—and, therefore, has positive CAPE—because entrainment causes evaporative cooling in cloud updrafts, thereby steepening their lapse rate. This has led to the proposal that CAPE increases with global warming because the strength of evaporative cooling scales according to the Clausius-Clapeyron (CC) relation. However, CAPE could also change due to changes in cloud buoyancy and changes in the entrainment rate, both of which could vary with global warming. To test the relative importance of changes in CAPE due to CC scaling of evaporative cooling, changes in cloud buoyancy, and changes in the entrainment rate, we subject a cloud-resolving model to a suite of natural (and unnatural) forcings. We find that CAPE changes are primarily driven by changes in the strength of evaporative cooling; the effect of changes in the entrainment rate and cloud buoyancy are comparatively small. This builds support for CC scaling of CAPE.

  15. Production and destruction of eddy kinetic energy in forced submesoscale eddy-resolving simulations

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sonaljit; Ramachandran, Sanjiv; Tandon, Amit; Mahadevan, Amala

    2016-09-01

    We study the production and dissipation of the eddy kinetic energy (EKE) in a submesoscale eddy field forced with downfront winds using the Process Study Ocean Model (PSOM) with a horizontal grid resolution of 0.5 km. We simulate an idealized 100 m deep mixed-layer front initially in geostrophic balance with a jet in a domain that permits eddies within a range of O(1 km-100 km). The vertical eddy viscosities and the dissipation are parameterized using four different subgrid vertical mixing parameterizations: the k - ɛ , the KPP, and two different constant eddy viscosity and diffusivity profiles with a magnitude of O(10-2m2s-1) in the mixed layer. Our study shows that strong vertical eddy viscosities near the surface reduce the parameterized dissipation, whereas strong vertical eddy diffusivities reduce the lateral buoyancy gradients and consequently the rate of restratification by mixed-layer instabilities (MLI). Our simulations show that near the surface, the spatial variability of the dissipation along the periphery of the eddies depends on the relative alignment of the ageostrophic and geostrophic shear. Analysis of the resolved EKE budgets in the frontal region from the simulations show important similarities between the vertical structure of the EKE budget produced by the k - ɛ and KPP parameterizations, and earlier LES studies. Such an agreement is absent in the simulations using constant eddy-viscosity parameterizations.

  16. A homogeneous time-resolved fluorescence resonance energy transfer assay for phosphatidylserine exposure on apoptotic cells.

    PubMed

    Gasser, Jean-Philippe; Hehl, Michaela; Millward, Thomas A

    2009-01-01

    A simple, "mix-and-measure" microplate assay for phosphatidylserine (PtdSer) exposure on the surface of apoptotic cells is described. The assay exploits the fact that annexin V, a protein with high affinity and specificity for PtdSer, forms trimers and higher order oligomers on binding to membranes containing PtdSer. The transition from soluble monomer to cell-bound oligomer is detected using time-resolved fluorescence resonance energy transfer from europium chelate-labeled annexin V to Cy5-labeled annexin V. PtdSer detection is achieved by a single addition of a reagent mix containing labeled annexins and calcium ions directly to cell cultures in a 96-well plate, followed by a brief incubation before fluorescence measurement. The assay can be used to quantify PtdSer exposure on both suspension cells and adherent cells in situ. This method is simpler and faster than existing annexin V binding assays based on flow cytometry or microscopy, and it yields precise data with Z' values of 0.6-0.7. PMID:18835236

  17. Resolving Key Uncertainties in Subsurface Energy Recovery: One Role of In Situ Experimentation and URLs (Invited)

    NASA Astrophysics Data System (ADS)

    Elsworth, D.

    2013-12-01

    Significant uncertainties remain and influence the recovery of energy from the subsurface. These uncertainties include the fate and transport of long-lived radioactive wastes that result from the generation of nuclear power and have been the focus of an active network of international underground research laboratories dating back at least 35 years. However, other nascent carbon-free energy technologies including conventional and EGS geothermal methods, carbon-neutral methods such as carbon capture and sequestration and the utilization of reduced-carbon resources such as unconventional gas reservoirs offer significant challenges in their effective deployment. We illustrate the important role that in situ experiments may play in resolving behaviors at extended length- and time-scales for issues related to chemical-mechanical interactions. Significantly, these include the evolution of transport and mechanical characteristics of stress-sensitive fractured media and their influence of the long-term behavior of the system. Importantly, these interests typically relate to either creating reservoirs (hydroshearing in EGS reservoirs, artificial fractures in shales and coals) or maintaining seals at depth where the permeating fluids may include mixed brines, CO2, methane and other hydrocarbons. Critical questions relate to the interaction of these various fluid mixtures and compositions with the fractured substrate. Important needs are in understanding the roles of key processes (transmission, dissolution, precipitation, sorption and dynamic stressing) on the modification of effective stresses and their influence on the evolution of permeability, strength and induced seismicity on the resulting development of either wanted or unwanted fluid pathways. In situ experimentation has already contributed to addressing some crucial issues of these complex interactions at field scale. Important contributions are noted in understanding the fate and transport of long-lived wastes

  18. Energy-latitude dispersion patterns near the isotropy boundaries of energetic protons

    NASA Astrophysics Data System (ADS)

    Sergeev, V. A.; Chernyaeva, S. A.; Apatenkov, S. V.; Ganushkina, N. Y.; Dubyagin, S. V.

    2015-08-01

    Non-adiabatic motion of plasma sheet protons causes pitch-angle scattering and isotropic precipitation to the ionosphere, which forms the proton auroral oval. This mechanism related to current sheet scattering (CSS) provides a specific energy-latitude dispersion pattern near the equatorward boundary of proton isotropic precipitation (isotropy boundary, IB), with precipitation sharply decreasing at higher (lower) latitude for protons with lower (higher) energy. However, this boundary maps to the inner magnetosphere, where wave-induced scattering may provide different dispersion patterns as recently demonstrated by Liang et al. (2014). Motivated by the potential usage of the IBs for the magnetotail monitoring as well as by the need to better understand the mechanisms forming the proton IB, we investigate statistically the details of particle flux patterns near the proton IB using NOAA-POES polar spacecraft observations made during September 2009. By comparing precipitated-to-trapped flux ratio (J0/J90) at >30 and >80 keV proton energies, we found a relatively small number of simple CSS-type dispersion events (only 31 %). The clear reversed (wave-induced) dispersion patterns were very rare (5 %). The most frequent pattern had nearly coinciding IBs at two energies (63 %). The structured precipitation with multiple IBs was very frequent (60 %), that is, with two or more significant J0/J90 dropouts. The average latitudinal width of multiple IB structures was about 1°. Investigation of dozens of paired auroral zone crossings of POES satellites showed that the IB pattern is stable on a timescale of less than 2 min (a few proton bounce periods) but can evolve on a longer (several minutes) scale, suggesting temporal changes in some mesoscale structures in the equatorial magnetosphere. We discuss the possible role of CSS-related and wave-induced mechanisms and their possible coupling to interpret the emerging complicated patterns of proton isotropy boundaries.

  19. Scanning electron microscope/energy dispersive x ray analysis of impact residues in LDEF tray clamps

    NASA Technical Reports Server (NTRS)

    Bernhard, Ronald P.; Durin, Christian; Zolensky, Michael E.

    1993-01-01

    Detailed optical scanning of tray clamps is being conducted in the Facility for the Optical Inspection of Large Surfaces at JSC to locate and document impacts as small as 40 microns in diameter. Residues from selected impacts are then being characterized by Scanning Electron Microscopy/Energy Dispersive X-ray Analysis at CNES. Results from this analysis will be the initial step to classifying projectile residues into specific sources.

  20. Generating an image of dispersive energy by frequency decomposition and slant stacking

    USGS Publications Warehouse

    Xia, J.; Xu, Y.; Miller, R.D.

    2007-01-01

    We present a new algorithm for calculating an image of dispersive energy in the frequency-velocity (f-v) domain. The frequency decomposition is first applied to a shot gather in the offset-time domain to stretch impulsive data into pseudo-vibroseis data or frequency-swept data. Because there is a deterministic relationship between frequency and time in a sweep used in the frequency decomposition, the first step theoretically completes the transform from time to frequency. The slant stacking is then performed on the frequency-swept data to complete the transform from offset to velocity. This simple two-step algorithm generates an image of dispersive energy in the f-v domain. The straightforward transform only uses offset information of data so that this algorithm can be applied to data acquired with arbitrary geophone-acquisition geometry. Examples of synthetic and real-world data demonstrate that this algorithm generates accurate images of dispersive energy of the fundamental as well as higher modes. ?? Birkha??user Verlag, Basel, 2007.

  1. Conceptual understanding of climate change with a globally resolved energy balance model

    NASA Astrophysics Data System (ADS)

    Dommenget, Dietmar; Flöter, Janine

    2011-12-01

    The future climate change projections are essentially based on coupled general circulation model (CGCM) simulations, which give a distinct global warming pattern with arctic winter amplification, an equilibrium land-sea warming contrast and an inter-hemispheric warming gradient. While these simulations are the most important tool of the Intergovernmental Panel on Climate Change (IPCC) predictions, the conceptual understanding of these predicted structures of climate change and the causes of their uncertainties is very difficult to reach if only based on these highly complex CGCM simulations. In the study presented here we will introduce a very simple, globally resolved energy balance (GREB) model, which is capable of simulating the main characteristics of global warming. The model shall give a bridge between the strongly simplified energy balance models and the fully coupled 4-dimensional complex CGCMs. It provides a fast tool for the conceptual understanding and development of hypotheses for climate change studies, which shall build a basis or starting point for more detailed studies of observations and CGCM simulations. It is based on the surface energy balance by very simple representations of solar and thermal radiation, the atmospheric hydrological cycle, sensible turbulent heat flux, transport by the mean atmospheric circulation and heat exchange with the deeper ocean. Despite some limitations in the representations of the basic processes, the models climate sensitivity and the spatial structure of the warming pattern are within the uncertainties of the IPCC models simulations. It is capable of simulating aspects of the arctic winter amplification, the equilibrium land-sea warming contrast and the inter-hemispheric warming gradient with good agreement to the IPCC models in amplitude and structure. The results give some insight into the understanding of the land-sea contrast and the polar amplification. The GREB model suggests that the regional inhomogeneous

  2. The influence of the directional energy distribution on the nonlinear dispersion relation in a random gravity wave field

    NASA Technical Reports Server (NTRS)

    Huang, N. E.; Tung, C.-C.

    1977-01-01

    The influence of the directional distribution of wave energy on the dispersion relation is calculated numerically using various directional wave spectrum models. The results indicate that the dispersion relation varies both as a function of the directional energy distribution and the direction of propagation of the wave component under consideration. Furthermore, both the mean deviation and the random scatter from the linear approximation increase as the energy spreading decreases. Limited observational data are compared with the theoretical results. The agreement is favorable.

  3. Direct Imaging of Transient Fano Resonances in N2 Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J. J.; Kornilov, Oleg

    2016-04-01

    Autoionizing Rydberg states of molecular N2 are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14 ±1 fs , while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance.

  4. Direct Imaging of Transient Fano Resonances in N_{2} Using Time-, Energy-, and Angular-Resolved Photoelectron Spectroscopy.

    PubMed

    Eckstein, Martin; Yang, Chung-Hsin; Frassetto, Fabio; Poletto, Luca; Sansone, Giuseppe; Vrakking, Marc J J; Kornilov, Oleg

    2016-04-22

    Autoionizing Rydberg states of molecular N_{2} are studied using time-, energy-, and angular-resolved photoelectron spectroscopy. A femtosecond extreme ultraviolet pulse with a photon energy of 17.5 eV excites the resonance and a subsequent IR pulse ionizes the molecule before the autoionization takes place. The angular-resolved photoelectron spectra depend on pump-probe time delay and allow for the distinguishing of two electronic states contributing to the resonance. The lifetime of one of the contributions is determined to be 14±1  fs, while the lifetime of the other appears to be significantly shorter than the time resolution of the experiment. These observations suggest that the Rydberg states in this energy region are influenced by the effect of interference stabilization and merge into a complex resonance. PMID:27152799

  5. Application of decision tree algorithm for identification of rock forming minerals using energy dispersive spectrometry

    NASA Astrophysics Data System (ADS)

    Akkaş, Efe; Çubukçu, H. Evren; Artuner, Harun

    2014-05-01

    Rapid and automated mineral identification is compulsory in certain applications concerning natural rocks. Among all microscopic and spectrometric methods, energy dispersive X-ray spectrometers (EDS) integrated with scanning electron microscopes produce rapid information with reliable chemical data. Although obtaining elemental data with EDS analyses is fast and easy by the help of improving technology, it is rather challenging to perform accurate and rapid identification considering the large quantity of minerals in a rock sample with varying dimensions ranging between nanometer to centimeter. Furthermore, the physical properties of the specimen (roughness, thickness, electrical conductivity, position in the instrument etc.) and the incident electron beam (accelerating voltage, beam current, spot size etc.) control the produced characteristic X-ray, which in turn affect the elemental analyses. In order to minimize the effects of these physical constraints and develop an automated mineral identification system, a rule induction paradigm has been applied to energy dispersive spectral data. Decision tree classifiers divide training data sets into subclasses using generated rules or decisions and thereby it produces classification or recognition associated with these data sets. A number of thinsections prepared from rock samples with suitable mineralogy have been investigated and a preliminary 12 distinct mineral groups (olivine, orthopyroxene, clinopyroxene, apatite, amphibole, plagioclase, K- feldspar, zircon, magnetite, titanomagnetite, biotite, quartz), comprised mostly of silicates and oxides, have been selected. Energy dispersive spectral data for each group, consisting of 240 reference and 200 test analyses, have been acquired under various, non-standard, physical and electrical conditions. The reference X-Ray data have been used to assign the spectral distribution of elements to the specified mineral groups. Consequently, the test data have been analyzed using

  6. Resolving issues at the Department of Energy/Oak Ridge Operations Facilities

    SciTech Connect

    Row, T.H.; Adams, W.D.

    1988-01-01

    Waste management, like many other issues, has experienced major milestones. In 1971, the Calvert Cliff's decision resulted in an entirely different approach to the consideration of environmental impact analysis in reactor siting. The accidents at Three Mile Island and Chernobyl have had profound effects on nuclear power plant design. The high-level waste repository program has had many similar experiences that have modified the course of events. The management of radioactive, hazardous chemical and mixed waste in all of the facilities of the Oak Ridge Operations (ORO) Office of the Department of Energy (DOE) took on an entirely different meaning in 1984. On April 13, 1984, Federal Judge Robert Taylor said that DOE should proceed 'with all deliberate speed' to bring the Y-12 plant into compliance with the Resource Conservation and Recovery Act and the Clean Water Act. This decision resulted from a suit brought by the Legal Environmental Assistance Foundation (LEAF) and grew out of a continuing revelation of mercury spills and other problems related to the Oak Ridge plants of DOE. In this same time frame, other events occurred in Oak Ridge that would set the stage for major changes, to provide the supporting environment that allowed a very different and successful approach to resolving waste management issues at the DOE/ORO Facilities. This is the origin of the Oak Ridge Model which was recently adopted as the DOE Model. The concept is to assure that all stakeholders in waste management decisions have the opportunity to be participants from the first step. A discussion of many of the elements that have contributed to the success of the Model follows.

  7. A Monte Carlo simulation study of the effect of energy windows in computed tomography images based on an energy-resolved photon counting detector

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Wan; Choi, Yu-Na; Cho, Hyo-Min; Lee, Young-Jin; Ryu, Hyun-Ju; Kim, Hee-Joung

    2012-08-01

    The energy-resolved photon counting detector provides the spectral information that can be used to generate images. The novel imaging methods, including the K-edge imaging, projection-based energy weighting imaging and image-based energy weighting imaging, are based on the energy-resolved photon counting detector and can be realized by using various energy windows or energy bins. The location and width of the energy windows or energy bins are important because these techniques generate an image using the spectral information defined by the energy windows or energy bins. In this study, the reconstructed images acquired with K-edge imaging, projection-based energy weighting imaging and image-based energy weighting imaging were simulated using the Monte Carlo simulation. The effect of energy windows or energy bins was investigated with respect to the contrast, coefficient-of-variation (COV) and contrast-to-noise ratio (CNR). The three images were compared with respect to the CNR. We modeled the x-ray computed tomography system based on the CdTe energy-resolved photon counting detector and polymethylmethacrylate phantom, which have iodine, gadolinium and blood. To acquire K-edge images, the lower energy thresholds were fixed at K-edge absorption energy of iodine and gadolinium and the energy window widths were increased from 1 to 25 bins. The energy weighting factors optimized for iodine, gadolinium and blood were calculated from 5, 10, 15, 19 and 33 energy bins. We assigned the calculated energy weighting factors to the images acquired at each energy bin. In K-edge images, the contrast and COV decreased, when the energy window width was increased. The CNR increased as a function of the energy window width and decreased above the specific energy window width. When the number of energy bins was increased from 5 to 15, the contrast increased in the projection-based energy weighting images. There is a little difference in the contrast, when the number of energy bin is

  8. SU-E-I-77: A Noise Reduction Technique for Energy-Resolved Photon-Counting Detectors

    SciTech Connect

    Lam Ng, A; Ding, H; Cho, H; Molloi, S

    2014-06-01

    Purpose: Finding the optimal energy threshold setting for an energy-resolved photon-counting detector has an important impact on the maximization of contrast-to-noise-ratio (CNR). We introduce a noise reduction method to enhance CNR by reducing the noise in each energy bin without altering the average gray levels in the projection and image domains. Methods: We simulated a four bin energy-resolved photon-counting detector based on Si with a 10 mm depth of interaction. TASMIP algorithm was used to simulate a spectrum of 65 kVp with 2.7 mm Al filter. A 13 mm PMMA phantom with hydroxyapatite and iodine at different concentrations (100, 200 and 300 mg/ml for HA, and 2, 4, and 8 mg/ml for Iodine) was used. Projection-based and Image-based energy weighting methods were used to generate weighted images. A reference low noise image was used for noise reduction purposes. A Gaussian-like weighting function which computes the similarity between pixels of interest was calculated from the reference image and implemented on a pixel by pixel basis for the noisy images. Results: CNR improvement compared to different methods (Charge-Integrated, Photon-Counting and Energy-Weighting) and after noise reduction was highly task-dependent. The CNR improvement with respect to the Charge-Integrated CNR for hydroxyapatite and iodine were 1.8 and 1.5, respectively. In each of the energy bins, the noise was reduced by approximately factor of two without altering their respective average gray levels. Conclusion: The proposed noise reduction technique for energy-resolved photon-counting detectors can significantly reduce image noise. This technique can be used as a compliment to the current energy-weighting methods in CNR optimization.

  9. The elastic modulus correction term in creep activation energies Applied to oxide dispersion strengthened superalloy

    NASA Technical Reports Server (NTRS)

    Malu, M.; Tien, J. K.

    1975-01-01

    The effect of elastic modulus and the temperature dependence of elastic modulus on creep activation energies for an oxide dispersion strengthened nickel-base superalloy are investigated. This superalloy is commercially known as Inconel Alloy MA 753, strengthened both by gamma-prime precipitates and by yttria particles. It is shown that at intermediate temperatures, say below 1500 F, where elastic modulus is weakly dependent on temperature, the modulus correction term to creep activation energy is small. Accordingly, modulus corrections are insignificant for the superalloy considered, which shows high apparent creep activation energies at this temperature. On the contrary, at very high temperatures, the elastic modulus correction term can be significant, thus reducing the creep activation energy to that of vacancy self-diffusion. In order to obtain high-temperature creep resistance, a high-value elastic modulus with a weak dependence on temperature is required.

  10. Energy Efficienct Processes for Making Tackifier Dispersions used to make Pressure Sensitive Adhesives

    SciTech Connect

    Rakesh Gupta

    2006-07-26

    The primary objective of this project was to develop an energy efficient, environmentally friendly and low cost process (compared to the current process) for making tackifier dispersions that are used to make pressure-sensitive adhesives. These adhesives are employed in applications such as self-adhesive postage stamps and disposable diapers and are made by combining the tackifier dispersion with a natural or synthetic rubber latex. The current process for tackifier dispersion manufacture begins by melting a (plastic) resin and adding water to it in order to form a water-in-oil emulsion. This is then converted to an oil-in-water emulsion by phase inversion in the presence of continuous stirring. The resulting emulsion is the tackifier dispersion, but it is not concentrated and the remaining excess water has to be transported and removed. The main barrier that has to be overcome in the development of commercial quality tackifier dispersions is the inability to directly emulsify resin in water due to the very low viscosity of water as compared to the viscosity of the molten resin. In the present research, a number of solutions were proposed to overcome this barrier, and these included use of different mixer types to directly form the emulsion from the molten resin but without going through a phase inversion, the idea of forming a solid resin-in-water suspension having the correct size and size distribution but without melting of the resin, and the development of techniques of making a colloidal powder of the resin that could be dispersed in water just prior to use. Progress was made on each of these approaches, and each was found to be feasible. The most appealing solution, though, is the last one, since it does not require melting of the resin. Also, the powder can be shipped in dry form and then mixed with water in any proportion depending on the needs of the process. This research was conducted at Argonne National Laboratory, and it was determined the new process

  11. Low-energy neutron direct capture by 12C in a dispersive optical potential

    NASA Astrophysics Data System (ADS)

    Kitazawa, H.; Go, K.; Igashira, M.

    1998-01-01

    A dispersive optical potential for the interaction between low-energy neutrons and 12C nuclei is derived from a dispersion relation based on the Feshbach generalized optical model. The potential reproduces completely neutron total cross sections below 1.0 MeV and substantially reproduces the energy of the 3090 keV(1/2+) level in 13C which is of nearly pure 2s1/2 single-particle character. It is found that direct-capture model calculations with this potential explain quite successfully the observed off-resonance capture transitions to the ground (1/2-), 3090 keV(1/2+), 3685 keV(3/2-), and 3854 keV(5/2+) levels in 13C at neutron energies of 20-600 keV. Special emphasis is laid on the fact that in these model analyses, account should be taken of the spatial nonlocality of the neutron-nucleus interaction potential, in particular for negative energies.

  12. Low-energy neutron direct capture by {sup 12}C in a dispersive optical potential

    SciTech Connect

    Kitazawa, H.; Go, K.; Igashira, M.

    1998-01-01

    A dispersive optical potential for the interaction between low-energy neutrons and {sup 12}C nuclei is derived from a dispersion relation based on the Feshbach generalized optical model. The potential reproduces completely neutron total cross sections below 1.0 MeV and substantially reproduces the energy of the 3090keV(1/2{sup +}) level in {sup 13}C which is of nearly pure 2s{sub 1/2} single-particle character. It is found that direct-capture model calculations with this potential explain quite successfully the observed off-resonance capture transitions to the ground (1/2{sup {minus}}), 3090keV(1/2{sup +}), 3685keV(3/2{sup {minus}}), and 3854keV(5/2{sup +}) levels in {sup 13}C at neutron energies of 20{endash}600 keV. Special emphasis is laid on the fact that in these model analyses, account should be taken of the spatial nonlocality of the neutron-nucleus interaction potential, in particular for negative energies. {copyright} {ital 1998} {ital The American Physical Society}

  13. Determination of selenium in biological samples with an energy-dispersive X-ray fluorescence spectrometer.

    PubMed

    Li, Xiaoli; Yu, Zhaoshui

    2016-05-01

    Selenium is both a nutrient and a toxin. Selenium-especially organic selenium-is a core component of human nutrition. Thus, it is very important to measure selenium in biological samples. The limited sensitivity of conventional XRF hampers its widespread use in biological samples. Here, we describe the use of high-energy (100kV, 600W) linearly polarized beam energy-dispersive X-Ray fluorescence spectroscopy (EDXRF) in tandem with a three-dimensional optics design to determine 0.1-5.1μgg(-1) levels of selenium in biological samples. The effects of various experimental parameters such as applied voltage, acquisition time, secondary target and various filters were thoroughly investigated. The detection limit of selenium in biological samples via high-energy (100kV, 600W) linearly polarized beam energy-dispersive X-ray fluorescence spectroscopy was decreased by one order of magnitude versus conventional XRF (Paltridge et al., 2012) and found to be 0.1μg/g. To the best of our knowledge, this is the first report to describe EDXRF measurements of Se in biological samples with important implications for the nutrition and analytical chemistry communities. PMID:26922394

  14. The velocity dispersion profile of NGC 6388 from resolved-star spectroscopy: No evidence of a central cusp and new constraints on the black hole mass

    SciTech Connect

    Lanzoni, B.; Mucciarelli, A.; Ferraro, F. R.; Miocchi, P.; Dalessandro, E.; Pallanca, C.; Massari, D.; Valenti, E.

    2013-06-01

    By combining high spatial resolution and wide-field spectroscopy performed, respectively, with SINFONI and FLAMES at the ESO/VLT we measured the radial velocities of more than 600 stars in the direction of NGC 6388, a Galactic globular cluster which is suspected to host an intermediate-mass black hole. Approximately 55% of the observed targets turned out to be cluster members. The cluster velocity dispersion has been derived from the radial velocity of individual stars: 52 measurements in the innermost 2'', and 276 stars located between 18'' and 600''. The velocity dispersion profile shows a central value of ∼13 km s{sup –1}, a flat behavior out to ∼60'' and a decreasing trend outward. The comparison with spherical and isotropic models shows that the observed density and velocity dispersion profiles are inconsistent with the presence of a central black hole more massive than ∼2000 M {sub ☉}. These findings are at odds with recent results obtained from integrated light spectra, showing a velocity dispersion profile with a steep central cusp of 23-25 km s{sup –1} at r < 2'' and suggesting the presence of a black hole with a mass of ∼1.7 × 10{sup 4} M {sub ☉}. We also found some evidence of systemic rotation with amplitude A {sub rot} ∼ 8 km s{sup –1} in the innermost 2'' (0.13 pc), decreasing to A {sub rot} = 3.2 km s{sup –1} at 18'' < r < 160''.

  15. Characterization of high energy Xe ion irradiation effects in single crystal molybdenum with depth-resolved synchrotron microbeam diffraction

    NASA Astrophysics Data System (ADS)

    Yun, Di; Miao, Yinbin; Xu, Ruqing; Mei, Zhigang; Mo, Kun; Mohamed, Walid; Ye, Bei; Pellin, Michael J.; Yacout, Abdellatif M.

    2016-04-01

    Microbeam X-ray diffraction experiments were conducted at beam line 34-ID of the Advanced Photon Source (APS) on fission fragment energy Xe heavy ion irradiated single crystal Molybdenum (Mo). Lattice strain measurements were obtained with a depth resolution of 0.7 μm, which is critical in resolving the peculiar heterogeneity of irradiation damage associated with heavy ion irradiation. Q-space diffraction peak shift measurements were correlated with lattice strain induced by the ion irradiations. Transmission electron microscopy (TEM) characterizations were performed on the as-irradiated materials as well. Nanometer sized Xe bubble microstructures were observed via TEM. Molecular Dynamics (MD) simulations were performed to help interpret the lattice strain measurement results from the experiment. This study showed that the irradiation effects by fission fragment energy Xe ion irradiations can be collaboratively understood with the depth resolved X-ray diffraction and TEM measurements under the assistance of MD simulations.

  16. Low energy x-ray spectra measured with a mercuric iodide energy dispersive spectrometer in a scanning electron microscope

    SciTech Connect

    Iwanczyk, J.S.; Dabrowski, A.J.; Huth, G.C.; Bradley, J.G.; Conley, J.M.; Albee, A.L.

    1985-01-01

    A mercuric iodide energy dispersive x-ray spectrometer, with Peltier cooling provided for the detector and input field effect transistor, has been developed and tested in a scanning electron microscope. X-ray spectra were obtained with the 15 keV electron beam. An energy resolution of 225 eV (FWHM) for Mn-K/sub ..cap alpha../ at 5.9 keV and 195 eV (FWHM) for Mg-K line at 1.25 keV has been measured. Overall system noise level was 175 eV (FWHM). The detector system characterization with a carbon target demonstrated good energy sensitivity at low energies and lack of significant spectral artifacts at higher energies. 16 refs., 5 figs.

  17. Low energy X-ray spectra measured with a mercuric iodide energy dispersive spectrometer in a scanning electron microscope

    NASA Technical Reports Server (NTRS)

    Iwanczyk, J. S.; Dabrowski, A. J.; Huth, G. C.; Bradley, J. G.; Conley, J. M.

    1986-01-01

    A mercuric iodide energy dispersive X-ray spectrometer, with Peltier cooling provided for the detector and input field effect transistor, has been developed and tested in a scanning electron microscope. X-ray spectra were obtained with the 15 keV electron beam. An energy resolution of 225 eV (FWHM) for Mn-K(alpha) at 5.9 keV and 195 eV (FWHM) for the Mg-K line at 1.25 keV has been measured. Overall system noise level was 175 eV (FWHM). The detector system characterization with a carbon target demonstrated good energy sensitivity at low energies and lack of significant spectral artifacts at higher energies.

  18. Decoupling the contribution of dispersive and acid-base components of surface energy on the cohesion of pharmaceutical powders.

    PubMed

    Shah, Umang V; Olusanmi, Dolapo; Narang, Ajit S; Hussain, Munir A; Tobyn, Michael J; Heng, Jerry Y Y

    2014-11-20

    This study reports an experimental approach to determine the contribution from two different components of surface energy on cohesion. A method to tailor the surface chemistry of mefenamic acid via silanization is established and the role of surface energy on cohesion is investigated. Silanization was used as a method to functionalize mefenamic acid surfaces with four different functional end groups resulting in an ascending order of the dispersive component of surface energy. Furthermore, four haloalkane functional end groups were grafted on to the surface of mefenamic acid, resulting in varying levels of acid-base component of surface energy, while maintaining constant dispersive component of surface energy. A proportional increase in cohesion was observed with increases in both dispersive as well as acid-base components of surface energy. Contributions from dispersive and acid-base surface energy on cohesion were determined using an iterative approach. Due to the contribution from acid-base surface energy, cohesion was found to increase ∼11.7× compared to the contribution from dispersive surface energy. Here, we provide an approach to deconvolute the contribution from two different components of surface energy on cohesion, which has the potential of predicting powder flow behavior and ultimately controlling powder cohesion. PMID:25223493

  19. Influence of gravity level and interfacial energies on dispersion-forming tendencies in hypermonotectic Cu-Pb-Al alloys

    NASA Technical Reports Server (NTRS)

    Andrews, J. B.; Curreri, P. A.; Sandlin, A. C.

    1988-01-01

    Results on the nondirectional solidification of several hypermonotectic Cu-Pb-Al alloys were obtained aboard NASA's KC-135 zero-gravity aircraft in order to determine the influence of interfacial energies and gravity levels on dispersion-forming tendencies. The Al content was systematially varied in the alloys. The dispersion-forming ability is correlated with gravity level during solidification, the interfacial energy between the immiscible phases, and the tendency for the minority immiscible phase to wet the walls of the crucible.

  20. Energy Dispersive X-Ray and Electrochemical Impedance Spectroscopies for Performance and Corrosion Analysis of PEMWEs

    NASA Astrophysics Data System (ADS)

    Steen, S. M., Iii; Zhang, F.-Y.

    2014-11-01

    Proton exchange membrane water electrolyzers (PEMWEs) are a promising energy storage technology due to their high efficiency, compact design, and ability to be used in a renewable energy system. Before they are able to make a large commercial impact, there are several hurdles facing the technology today. Two powerful techniques for both in-situ and ex- situ characterizations to improve upon their performance and better understand their corrosion are electrochemical impedance spectroscopy and energy dispersive x-ray spectroscopy, respectively. In this paper, the authors use both methods in order to characterize the anode gas diffusion layer (GDL) in a PEMWE cell and better understand the corrosion that occurs in the oxygen electrode during electrolysis.

  1. High-energy femtosecond Yb-doped dispersion compensation free fiber laser.

    PubMed

    Ortaç, B; Schmidt, O; Schreiber, T; Limpert, J; Tünnermann, A; Hideur, A

    2007-08-20

    We report on a mode-locked high energy fiber laser operating in the dispersion compensation free regime. The sigma cavity is constructed with a saturable absorber mirror and short-length large-mode-area photonic crystal fiber. The laser generates positively-chirped pulses with an energy of 265 nJ at a repetition rate of 10.18 MHz in a stable and self-starting operation. The pulses are compressible down to 400 fs leading to a peak power of 500 kW. Numerical simulations accurately reflect the experimental results and reveal the mechanisms for self consistent intracavity pulse evolution. With this performance mode-locked fiber lasers can compete with state-of-the-art bulk femtosecond oscillators for the first time and pulse energy scaling beyond the muJ-level appears to be feasible. PMID:19547427

  2. New software to model energy dispersive X-ray diffraction in polycrystalline materials

    NASA Astrophysics Data System (ADS)

    Ghammraoui, B.; Tabary, J.; Pouget, S.; Paulus, C.; Moulin, V.; Verger, L.; Duvauchelle, Ph.

    2012-02-01

    Detection of illicit materials, such as explosives or drugs, within mixed samples is a major issue, both for general security and as part of forensic analyses. In this paper, we describe a new code simulating energy dispersive X-ray diffraction patterns in polycrystalline materials. This program, SinFullscat, models diffraction of any object in any diffractometer system taking all physical phenomena, including amorphous background, into account. Many system parameters can be tuned: geometry, collimators (slit and cylindrical), sample properties, X-ray source and detector energy resolution. Good agreement between simulations and experimental data was obtained. Simulations using explosive materials indicated that parameters such as the diffraction angle or the energy resolution of the detector have a significant impact on the diffraction signature of the material inspected. This software will be a convenient tool to test many diffractometer configurations, providing information on the one that best restores the spectral diffraction signature of the materials of interest.

  3. Determination of carrier yields for neutron activation analysis using energy dispersive X-ray spectrometry

    USGS Publications Warehouse

    Johnson, R.G.; Wandless, G.A.

    1984-01-01

    A new method is described for determining carrier yield in the radiochemical neutron activation analysis of rare-earth elements in silicate rocks by group separation. The method involves the determination of the rare-earth elements present in the carrier by means of energy-dispersive X-ray fluorescence analysis, eliminating the need to re-irradiate samples in a nuclear reactor after the gamma ray analysis is complete. Results from the analysis of USGS standards AGV-1 and BCR-1 compare favorably with those obtained using the conventional method. ?? 1984 Akade??miai Kiado??.

  4. Distinction between entrance and exit wounds by energy dispersive X-ray fluorescence spectrometry.

    PubMed

    Tanaka, Naoko; Kinoshita, Hiroshi; Takakura, Ayaka; Jamal, Mostofa; Ito, Asuka; Kumihashi, Mitsuru; Tsutsui, Kunihiko; Kimura, Shoji; Ameno, Kiyoshi

    2016-09-01

    We investigated gunshot wounds in two autopsy cases using energy dispersive X-ray spectrometry (EDX). Lead and copper were detected in the entrance wound of one case and lead, antimony, and copper were detected in that of the other case. In the exit wounds of both cases, lead, antimony, and copper were below detection limits. These findings indicate that the detection of metallic elements, such as lead, antimony, and copper, which are found in bullets, may be useful for differentiating entrance from exit wounds using EDX. PMID:27591531

  5. Energy transfer between rhodamine 3B and oxazine 4 in synthetic-saponite dispersions and films.

    PubMed

    Czímerová, A; Iyi, N; Bujdák, J

    2007-02-15

    The objective of this study was the investigation of energy transfer between the laser dyes rhodamine 3B (R3B) and oxazine 4 (Ox4) adsorbed on the surface of synthetic Sumecton saponite (Sum). The process of energy transfer was studied for both saponite dispersions and oriented solid films. The electronic properties, luminescence, and the energy transfer process were described by UV-vis absorption and fluorescence spectroscopy. For the efficiency of the energy transfer process, the concentrations of energy donor and acceptor components on a clay mineral surface were found to be essential. A side reaction of the molecular assembly formation reduced both the luminescence and energy-transfer yields, mainly due to fluorescence quenching. The quenching was more problematic for the solid film specimens, where an appropriate modification of the inorganic host with hydrophobic alkylammonium cations was used to achieve a higher luminescence. Due to the higher tendency of Ox4 to form nonluminescent aggregates at higher concentrations, the lowering of the Ox4 concentration further improved the luminescent properties of the films. In this case, the energy transfer occurring in the solid film from R3B to Ox4 was clearly proven. PMID:17118384

  6. Gamma-to-electron magnetic spectrometer (GEMS): An energy-resolved γ-ray diagnostic for the National Ignition Facilitya)

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Herrmann, H. W.; Hilsabeck, T. J.; Moy, K.; Stoeffl, W.; Mack, J. M.; Young, C. S.; Wu, W.; Barlow, D. B.; Schillig, J. B.; Sims, J. R.; Lopez, F. E.; Mares, D.; Oertel, J. A.; Hayes-Sterbenz, A. C.

    2012-10-01

    The gamma-to-electron magnetic spectrometer, having better than 5% energy resolution, is proposed to resolve γ-rays in the range of Eo ± 20% in single shot, where Eo is the central energy and is tunable from 2 to 25 MeV. Gamma-rays from inertial confinement fusion implosions interact with a thin Compton converter (e.g., beryllium) located at approximately 300 cm from the target chamber center (TCC). Scattered electrons out of the Compton converter enter an electromagnet placed outside the NIF chamber (approximately 600 cm from TCC) where energy selection takes place. The electromagnet provides tunable Eo over a broad range in a compact manner. Energy resolved electrons are measured by an array of quartz Cherenkov converters coupled to photomultipliers. Given 100 detectable electrons in the energy bins of interest, 3 × 1014 minimum deuterium/tritium (DT) neutrons will be required to measure the 4.44 MeV 12C γ-rays assuming 200 mg/cm2 plastic ablator areal density and 3 × 1015 minimum DT neutrons to measure the 16.75 MeV DT γ-ray line.

  7. Gamma-to-electron magnetic spectrometer (GEMS): An energy-resolved {gamma}-ray diagnostic for the National Ignition Facility

    SciTech Connect

    Kim, Y.; Herrmann, H. W.; Mack, J. M.; Young, C. S.; Barlow, D. B.; Schillig, J. B.; Sims, J. R. Jr.; Lopez, F. E.; Mares, D.; Oertel, J. A.; Hayes-Sterbenz, A. C.; Hilsabeck, T. J.; Wu, W.; Moy, K.; Stoeffl, W.

    2012-10-15

    The gamma-to-electron magnetic spectrometer, having better than 5% energy resolution, is proposed to resolve {gamma}-rays in the range of E{sub o}{+-} 20% in single shot, where E{sub o} is the central energy and is tunable from 2 to 25 MeV. Gamma-rays from inertial confinement fusion implosions interact with a thin Compton converter (e.g., beryllium) located at approximately 300 cm from the target chamber center (TCC). Scattered electrons out of the Compton converter enter an electromagnet placed outside the NIF chamber (approximately 600 cm from TCC) where energy selection takes place. The electromagnet provides tunable E{sub o} over a broad range in a compact manner. Energy resolved electrons are measured by an array of quartz Cherenkov converters coupled to photomultipliers. Given 100 detectable electrons in the energy bins of interest, 3 Multiplication-Sign 10{sup 14} minimum deuterium/tritium (DT) neutrons will be required to measure the 4.44 MeV {sup 12}C {gamma}-rays assuming 200 mg/cm{sup 2} plastic ablator areal density and 3 Multiplication-Sign 10{sup 15} minimum DT neutrons to measure the 16.75 MeV DT {gamma}-ray line.

  8. Alternating magnetic field energy absorption in the dispersion of iron oxide nanoparticles in a viscous medium

    NASA Astrophysics Data System (ADS)

    Smolkova, Ilona S.; Kazantseva, Natalia E.; Babayan, Vladimir; Smolka, Petr; Parmar, Harshida; Vilcakova, Jarmila; Schneeweiss, Oldrich; Pizurova, Nadezda

    2015-01-01

    Magnetic iron oxide nanoparticles were obtained by a coprecipitation method in a controlled growth process leading to the formation of uniform highly crystalline nanoparticles with average size of 13 nm, which corresponds to the superparamagnetic state. Nanoparticles obtained are a mixture of single-phase nanoparticles of magnetite and maghemite as well as nanoparticles of non-stoichiometric magnetite. The subsequent annealing of nanoparticles at 300 °C in air during 6 h leads to the full transformation to maghemite. It results in reduced value of the saturation magnetization (from 56 emu g-1 to 48 emu g-1) but does not affect the heating ability of nanoparticles. A 2-7 wt% dispersion of as-prepared and annealed nanoparticles in glycerol provides high heating rate in alternating magnetic fields allowed for application in magnetic hyperthermia; however the value of specific loss power does not exceed 30 W g-1. This feature of heat output is explained by the combined effect of magnetic interparticle interactions and the properties of the carrier medium. Nanoparticles coalesce during the synthesis and form aggregates showing ferromagnetic-like behavior with magnetization hysteresis, distinct sextets on Mössbauer spectrum, blocking temperature well about room temperature, which accounts for the higher energy barrier for magnetization reversal. At the same time, low specific heat capacity of glycerol intensifies heat transfer in the magnetic dispersion. However, high viscosity of glycerol limits the specific loss power value, since predominantly the Neel relaxation accounts for the absorption of AC magnetic field energy.

  9. Quantitative energy-dispersive x-ray diffraction for identification of counterfeit medicines: a preliminary study

    NASA Astrophysics Data System (ADS)

    Crews, Chiaki C. E.; O'Flynn, Daniel; Sidebottom, Aiden; Speller, Robert D.

    2015-06-01

    The prevalence of counterfeit and substandard medicines has been growing rapidly over the past decade, and fast, nondestructive techniques for their detection are urgently needed to counter this trend. In this study, energy-dispersive X-ray diffraction (EDXRD) combined with chemometrics was assessed for its effectiveness in quantitative analysis of compressed powder mixtures. Although EDXRD produces lower-resolution diffraction patterns than angular-dispersive X-ray diffraction (ADXRD), it is of interest for this application as it carries the advantage of allowing the analysis of tablets within their packaging, due to the higher energy X-rays used. A series of caffeine, paracetamol and microcrystalline cellulose mixtures were prepared with compositions between 0 - 100 weight% in 20 weight% steps (22 samples in total, including a centroid mixture), and were pressed into tablets. EDXRD spectra were collected in triplicate, and a principal component analysis (PCA) separated these into their correct positions in the ternary mixture design. A partial least-squares (PLS) regression model calibrated using this training set was validated using both segmented cross-validation, and with a test set of six samples (mixtures in 8:1:1 and 5⅓:2⅓:2⅓ ratios) - the latter giving a root-mean square error of prediction (RMSEP) of 1.30, 2.25 and 2.03 weight% for caffeine, paracetamol and cellulose respectively. These initial results are promising, with RMSEP values on a par with those reported in the ADXRD literature.

  10. Practical applications of energy dispersive X-ray microanalysis in diagnostic oral pathology

    SciTech Connect

    Daley, T.D.; Gibson, D. )

    1990-03-01

    Energy dispersive X-ray microanalysis is a powerful tool that can reveal the presence and relative quantities of elements in minute particles in biologic materials. Although this technique has been used in some aspects of dental research, it has rarely been applied to diagnostic oral pathology. The purpose of this paper is to inform practicing dentists and oral specialists about the diagnostic potential of this procedure by presenting three case reports. The first case involved the identification of flakes of a metallic material claimed by a 14-year-old girl to appear periodically between her mandibular molars. In the second case, a periodontist was spared a lawsuit when a freely mobile mass in the antrum of his patient was found to be a calcium-phosphorus compound not related to the periodontal packing that had been used. The third case involved the differential diagnosis of amalgam tattoo and graphite tattoo in a pigmented lesion of the hard palate mucosa. The results of the analyses were significant and indicate a role for this technique in the assessment of selected cases. Potential for wider use of energy dispersive X-ray microanalysis in diagnostic oral pathology exists as research progresses.

  11. X-ray coherent scattering form factors of tissues, water and plastics using energy dispersion

    NASA Astrophysics Data System (ADS)

    King, B. W.; Landheer, K. A.; Johns, P. C.

    2011-07-01

    A key requirement for the development of the field of medical x-ray scatter imaging is accurate characterization of the differential scattering cross sections of tissues and phantom materials. The coherent x-ray scattering form factors of five tissues (fat, muscle, liver, kidney, and bone) obtained from butcher shops, four plastics (polyethylene, polystyrene, lexan (polycarbonate), nylon), and water have been measured using an energy-dispersive technique. The energy-dispersive technique has several improvements over traditional diffractometer measurements. Most notably, the form factor is measured on an absolute scale with no need for scaling factors. Form factors are reported in terms of the quantity x = λ-1sin (θ/2) over the range 0.363-9.25 nm-1. The coherent form factors of muscle, liver, and kidney resemble those of water, while fat has a narrower peak at lower x, and bone is more structured. The linear attenuation coefficients of the ten materials have also been measured over the range 30-110 keV and parameterized using the dual-material approach with the basis functions being the linear attenuation coefficients of polymethylmethacrylate and aluminum.

  12. Coulomb Interaction Effect in Weyl Fermions with Tilted Energy Dispersion in Two Dimensions.

    PubMed

    Isobe, Hiroki; Nagaosa, Naoto

    2016-03-18

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α-(BEDT-TTF)_{2}I_{3} and three-dimensional WTe_{2}. The Coulomb interaction between electrons modifies the velocities in an essential way in the low-energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the speed of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions. PMID:27035318

  13. Unified dispersive approach to real and virtual photon-photon scattering at low energy

    NASA Astrophysics Data System (ADS)

    Moussallam, B.

    2013-09-01

    Previous representations of pion-pair production amplitudes by two real photons at low energy, which combine dispersion theoretical constraints with elastic unitarity, chiral symmetry and soft-photon constraints are generalised to the case where one photon is virtual. The constructed amplitudes display explicitly the dependence on the ππ phase-shifts, on pion form factors and on pion polarisabilities. They apply both for space-like and time-like virtualities despite the apparent overlap of the left- and right-hand cuts, by implementing a definition of resonance exchange amplitudes complying with analyticity and consistent limiting prescriptions for the energy variables. Applications are made to the pion generalised polarisabilies, to vector-meson radiative decays, and to the σγ electromagnetic form factor. Finally, an evaluation of the contribution of γππ states in the hadronic vacuum polarisation to the muon g-2 is given, which should be less model dependent than previous estimates.

  14. Superconducting Detector System for High-Resolution Energy-Dispersive Soft X-Ray Spectroscopy

    SciTech Connect

    Friedrich, S; Niedermayr, T; Drury, O; Funk, T; Frank, M; Labov, S E; Cramer, S

    2001-02-21

    Synchrotron-based soft x-ray spectroscopy is often limited by detector performance. Grating spectrometers have the resolution, but lack the efficiency for the analysis of dilute samples. Semiconducting Si(Li) or Ge detectors are efficient, but often lack the resolution to separate weak signals from strong nearby lines in multi-element samples. Superconducting tunnel junctions (STJs) operated at temperatures below 1 K can be used as high-resolution high-efficiency x-ray detectors. They combine high energy resolution around 10 eV FWHM with the broad band efficiency of energy-dispersive detectors. We have designed a two-stage adiabatic demagnetization refrigerator (ADR) to operate STJ detectors in x-ray fluorescence measurements at beam line 4 of the ALS. We demonstrate the capabilities of such a detector system for fluorescence analysis of dilute metal sites in proteins and inorganic model compounds.

  15. Coulomb Interaction Effect in Weyl Fermions with Tilted Energy Dispersion in Two Dimensions

    NASA Astrophysics Data System (ADS)

    Isobe, Hiroki; Nagaosa, Naoto

    2016-03-01

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α -(BEDT -TTF )2I3 and three-dimensional WTe2 . The Coulomb interaction between electrons modifies the velocities in an essential way in the low-energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the speed of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions.

  16. Better Resolved Low Frequency Dispersions by the Apt Use of Kramers-Kronig Relations, Differential Operators, and All-In-1 Modeling.

    PubMed

    van Turnhout, J

    2016-01-01

    The dielectric spectra of colloidal systems often contain a typical low frequency dispersion, which usually remains unnoticed, because of the presence of strong conduction losses. The KK relations offer a means for converting ε' into ε″ data. This allows us to calculate conduction free ε″ spectra in which the l.f. dispersion will show up undisturbed. This interconversion can be done on line with a moving frame of logarithmically spaced ε' data. The coefficients of the conversion frames were obtained by kernel matching and by using symbolic differential operators. Logarithmic derivatives and differences of ε' and ε″ provide another option for conduction free data analysis. These difference-based functions actually derived from approximations to the distribution function, have the additional advantage of improving the resolution power of dielectric studies. A high resolution is important because of the rich relaxation structure of colloidal suspensions. The development of all-in-1 modeling facilitates the conduction free and high resolution data analysis. This mathematical tool allows the apart-together fitting of multiple data and multiple model functions. It proved also useful to go around the KK conversion altogether. This was achieved by the combined approximating ε' and ε″ data with a complex rational fractional power function. The all-in-1 minimization turned out to be also highly useful for the dielectric modeling of a suspension with the complex dipolar coefficient. It guarantees a secure correction for the electrode polarization, so that the modeling with the help of the differences ε' and ε″ can zoom in on the genuine colloidal relaxations. PMID:27242997

  17. Determination of time- and height-resolved volcanic ash emissions and their use for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption

    NASA Astrophysics Data System (ADS)

    Stohl, A.; Prata, A. J.; Eckhardt, S.; Clarisse, L.; Durant, A.; Henne, S.; Kristiansen, N. I.; Minikin, A.; Schumann, U.; Seibert, P.; Stebel, K.; Thomas, H. E.; Thorsteinsson, T.; Tørseth, K.; Weinzierl, B.

    2011-05-01

    The April-May, 2010 volcanic eruptions of Eyjafjallajökull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that large improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3 ± 4.2 Tg for particles in the size range of 2.8-28 μm diameter. We evaluate the results of our model results with a posteriori ash emissions using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "Normal" flying zone in up to 14 % (6-16 %), 2 % (1-3 %) and 7 % (4-11 %), respectively, of the European area. For a limit of 2 mg m-3 only two episodes with fractions of 1.5 % (0.2-2.8 %) and 0.9 % (0.1-1.6 %) occurred, while the current "No-Fly" zone criterion of 4 mg m-3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.

  18. Better resolved low frequency dispersions by the apt use of Kramers-Kronig relations, differential operators and all-in-1 modelling

    NASA Astrophysics Data System (ADS)

    Turnhout, Jan

    2016-05-01

    The dielectric spectra of colloidal systems often contain a typical low frequency dispersion, which usually remains unnoticed, because of the presence of strong conduction losses. The KK relations offer a means for converting ɛ' into ɛ'' data. This allows us to calculate conduction free ɛ'' spectra in which the l.f. dispersion will show up undisturbed. This interconversion can be done on line with a moving frame of logarithmically spaced ɛ' data. The coefficients of the conversion frames were obtained by kernel matching and by using symbolic differential operators. Logarithmic derivatives and differences of ɛ' and ɛ'' provide another option for conduction free data analysis. These difference-based functions actually derived from approximations to the distribution function, have the additional advantage of improving the resolution power of dielectric studies. A high resolution is important because of the rich relaxation structure of colloidal suspensions. The development of all-in-1 modelling facilitates the conduction free and high resolution data analysis. This mathematical tool allows the apart-together fitting of multiple data and multiple model functions. It proved also useful to go around the KK conversion altogether. This was achieved by the combined approximating ɛ' and ɛ'' data with a complex rational fractional power function. The all-in-1 minimization turned out to be also highly useful for the dielectric modelling of a suspension with the complex dipolar coefficient. It guarantees a secure correction for the electrode polarization, so that the modelling with the help of the differences ɛ' and ɛ'' can zoom in on the genuine colloidal relaxations.

  19. Better Resolved Low Frequency Dispersions by the Apt Use of Kramers-Kronig Relations, Differential Operators, and All-In-1 Modeling

    PubMed Central

    van Turnhout, J.

    2016-01-01

    The dielectric spectra of colloidal systems often contain a typical low frequency dispersion, which usually remains unnoticed, because of the presence of strong conduction losses. The KK relations offer a means for converting ε′ into ε″ data. This allows us to calculate conduction free ε″ spectra in which the l.f. dispersion will show up undisturbed. This interconversion can be done on line with a moving frame of logarithmically spaced ε′ data. The coefficients of the conversion frames were obtained by kernel matching and by using symbolic differential operators. Logarithmic derivatives and differences of ε′ and ε″ provide another option for conduction free data analysis. These difference-based functions actually derived from approximations to the distribution function, have the additional advantage of improving the resolution power of dielectric studies. A high resolution is important because of the rich relaxation structure of colloidal suspensions. The development of all-in-1 modeling facilitates the conduction free and high resolution data analysis. This mathematical tool allows the apart-together fitting of multiple data and multiple model functions. It proved also useful to go around the KK conversion altogether. This was achieved by the combined approximating ε′ and ε″ data with a complex rational fractional power function. The all-in-1 minimization turned out to be also highly useful for the dielectric modeling of a suspension with the complex dipolar coefficient. It guarantees a secure correction for the electrode polarization, so that the modeling with the help of the differences ε′ and ε″ can zoom in on the genuine colloidal relaxations. PMID:27242997

  20. Construction and operation of parallel electric and magnetic field spectrometers for mass/energy resolved multi-ion charge exchange diagnostics on the Tokamak Fusion Test Reactor

    SciTech Connect

    Medley, S.S.; Roquemore, A.L.

    1998-07-01

    A novel charge exchange spectrometer using a dee-shaped region of parallel electric and magnetic fields was developed at the Princeton Plasma Physics Laboratory for neutral particle diagnostics on the Tokamak Fusion Test Reactor (TFTR). The E{parallel}B spectrometer has an energy range of 0.5{le}Athinsp(amu)Ethinsp(keV){le}600 and provides mass-resolved energy spectra of H{sup +}, D{sup +}, and T{sup +} (or {sup 3}He{sup +}) ion species simultaneously during a single discharge. The detector plane exhibits parallel rows of analyzed ions, each row containing the energy dispersed ions of a given mass-to-charge ratio. The detector consists of a large area microchannel plate (MCP) which is provided with three rectangular, semicontinuous active area strips, one coinciding with each of the mass rows for detection of H{sup +}, D{sup +}, and T{sup +} (or {sup 3}He{sup +}) and each mass row has 75 energy channels. To suppress spurious signals attending operation of the plate in the magnetic fringe field of the spectrometer, the MCP was housed in a double-walled iron shield with a wire mesh ion entrance window. Using an accelerator neutron generator, the MCP neutron detection efficiency was measured to be 1.7{times}10{sup {minus}3} and 6.4{times}10{sup {minus}3}thinspcounts/neutron/cm{sup 2} for 2.5 MeV-DD and 14 MeV-DT neutrons, respectively. The design and calibration of the spectrometer are described in detail, including the effect of MCP exposure to tritium, and results obtained during high performance D{endash}D operation on TFTR are presented to illustrate the performance of the E{parallel}B spectrometer. The spectrometers were not used during D{endash}T plasma operation due to the cost of providing the required radiation shielding. {copyright} {ital 1998 American Institute of Physics.}

  1. The H + OCS hot atom reaction - CO state distributions and translational energy from time-resolved infrared absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Nickolaisen, Scott L.; Cartland, Harry E.

    1993-01-01

    Time-resolved infrared diode laser spectroscopy has been used to probe CO internal and translational excitation from the reaction of hot H atoms with OCS. Product distributions should be strongly biased toward the maximum 1.4 eV collision energy obtained from 278 nm pulsed photolysis of HI. Rotations and vibrations are both colder than predicted by statistical density of states theory, as evidenced by large positive surprisal parameters. The bias against rotation is stronger than that against vibration, with measurable population as high as v = 4. The average CO internal excitation is 1920/cm, accounting for only 13 percent of the available energy. Of the energy balance, time-resolved sub-Doppler line shape measurements show that more than 38 percent appears as relative translation of the separating CO and SH fragments. Studies of the relaxation kinetics indicate that some rotational energy transfer occurs on the time scale of our measurements, but the distributions do not relax sufficiently to alter our conclusions. Vibrational distributions are nascent, though vibrational relaxation of excited CO is unusually fast in the OCS bath, with rates approaching 3 percent of gas kinetic for v = 1.

  2. Determination of time- and height-resolved volcanic ash emissions for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption

    NASA Astrophysics Data System (ADS)

    Stohl, A.; Prata, A. J.; Eckhardt, S.; Clarisse, L.; Durant, A.; Henne, S.; Kristiansen, N. I.; Minikin, A.; Schumann, U.; Seibert, P.; Stebel, K.; Thomas, H. E.; Thorsteinsson, T.; Tørseth, K.; Weinzierl, B.

    2011-02-01

    The April-May 2010 volcanic eruptions of Eyjafjallajökull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that dramatic improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3 ± 4.2 Tg for particles in the size range of 2.8-28 μm diameter and extrapolate this to a total ash emission of 11.9 ± 5.9 Tg for the size range of 0.25-250 μm. We evaluate the results of our a posteriori model using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "normal" flying zone in up to 14% (6-16%), 2% (1-3%) and 7% (4-11%), respectively, of the European area. For a limit of 2 mg m-3 only two episodes with fractions of 1.5% (0.2-2.8%) and 0.9% (0.1-1.6%) occurred, while the current "no-fly" zone criterion of 4 mg m-3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.

  3. Energy-dispersive X-ray diffraction using an annular beam.

    PubMed

    Dicken, A J; Evans, J P O; Rogers, K D; Greenwood, C; Godber, S X; Prokopiou, D; Stone, N; Clement, J G; Lyburn, I; Martin, R M; Zioupos, P

    2015-05-18

    We demonstrate material phase identification by measuring polychromatic diffraction spots from samples at least 20 mm in diameter and up to 10 mm thick with an energy resolving point detector. Within our method an annular X-ray beam in the form of a conical shell is incident with its symmetry axis normal to an extended polycrystalline sample. The detector is configured to receive diffracted flux transmitted through the sample and is positioned on the symmetry axis of the annular beam. We present the experiment data from a range of different materials and demonstrate the acquisition of useful data with sub-second collection times of 0.5 s; equating to 0.15 mAs. Our technique should be highly relevant in fields that demand rapid analytical methods such as medicine, security screening and non-destructive testing. PMID:26074592

  4. The Role of Energy Dispersion in the Genesis and Life Cycle of African Easterly Waves

    NASA Astrophysics Data System (ADS)

    Diaz, Michael

    This dissertation uses energy dispersion and wave packet concepts to provide a better conceptual model of the genesis and life cycle of African Easterly Waves and to better understand the instability of the African Easterly Jet (AEJ). The existence of an upstream (eastward) group velocity for AEWs is shown based on single-point lag regressions using gridded reanalysis data from 1990 to 2010. The eastward energy dispersion is consistent with the direction of ageostrophic geopotential flux vectors. A local eddy kinetic energy (EKE) budget reveals that, early in the life cycle of AEWs, growth rate due to geopotential flux convergence exceeds baroclinic and barotropic growth rates. Later in the life cycle, EKE decay due to geopotential flux divergence cancels or exceeds baroclinic and barotropic growth. A potential vorticity (PV) budget is used to diagnose tendencies related to group propagation. Although both upstream and downstream group speeds are possible because of the reversal in the mean meridional PV gradient, upstream propagation associated with the positive poleward PV gradient dominates wave packet evolution. Analogous to the concept of downstream development of midlatitude baroclinic waves, new AEWs develop preferentially upstream of the older ones, thus providing a mechanism for seeding new waves. The usefulness of upstream development as a genesis mechanism for AEWs is demonstrated by performing a case study of the AEW which ultimately produced hurricane Alberto (2000). The case study uses the ERA-interim reanalysis combined with surface observations and TRMM data. Using a local EKE budget, we attribute its genesis to energy dispersion from a preceding AEW. After genesis, baroclinic and barotropic conversion dominated the energetics of this AEW. Some strengths and weaknesses of upstream development as a paradigm for AEW genesis are discussed with respect to other potential mechanisms. The stability of the AEJ is examined applying the concept of absolute

  5. Surface energy changes and their relationship with the dispersibility of salmeterol xinafoate powders for inhalation after storage at high RH.

    PubMed

    Das, Shyamal; Larson, Ian; Young, Paul; Stewart, Peter

    2009-11-01

    This study investigated the relationship between surface energy of micronized lactose, coarse lactose and salmeterol xinafoate and dispersibility from a mixture after storage at 75% RH. Surface energies, dispersibility, morphology, and the presence of amorphous domains were determined by inverse gas chromatography, twin stage impinger, scanning electron microscope and dynamic vapour sorption, respectively. The fine particle fraction of mixture decreased significantly in 4 weeks (P<0.05), reaching a static level in 3 months. Amorphous content was not detected in the micronized lactose, coarse lactose and salmeterol xinafoate. After conditioning stored samples at 75% RH for 2h, dispersive surface energy of both micronized and coarse lactose significantly decreased (P<0.05), while the polar surface energy of all significantly increased (P<0.05) resulting in significant increase in total surface energy after storage. After conditioning stored samples at 0% RH for 2h, no significant difference was observed in any surface energy parameter. This study concluded that the total surface energy increased during storage at high RH due to the adhered surface moisture. The mechanism of decreased dispersibility was related to increased capillary/solid bridging interactions and to possible increased interaction of contiguous particles due to increased polar surface energy. PMID:19732829

  6. Influence of argon and oxygen on charge-state-resolved ion energy distributions of filtered aluminum arcs

    NASA Astrophysics Data System (ADS)

    Rosén, Johanna; Anders, André; Mráz, Stanislav; Atiser, Adil; Schneider, Jochen M.

    2006-06-01

    The charge-state-resolved ion energy distributions (IEDs) in filtered aluminum vacuum arc plasmas were measured and analyzed at different oxygen and argon pressures in the range of 0.5-8.0 mTorr. A significant reduction of the ion energy was detected as the pressure was increased, most pronounced in an argon environment and for the higher charge states. The corresponding average charge state decreased from 1.87 to 1.0 with increasing pressure. The IEDs of all metal ions in oxygen were fitted with shifted Maxwellian distributions. The results show that it is possible to obtain a plasma composition with a narrow charge-state distribution as well as a narrow IED. These data may enable tailoring thin film properties through selecting growth conditions that are characterized by predefined charge state and energy distributions.

  7. Characterization of spatially resolved high resolution x-ray spectrometers for high energy density physics and light source experiments

    SciTech Connect

    Hill, K. W. Bitter, M.; Delgado-Aparacio, L.; Efthimion, P.; Pablant, N. A.; Lu, J.; Beiersdorfer, P.; Chen, H.; Magee, E.

    2014-11-15

    A high resolution 1D imaging x-ray spectrometer concept comprising a spherically bent crystal and a 2D pixelated detector is being optimized for diagnostics of small sources such as high energy density physics (HEDP) and synchrotron radiation or x-ray free electron laser experiments. This instrument is used on tokamak experiments for Doppler measurements of ion temperature and plasma flow velocity profiles. Laboratory measurements demonstrate a resolving power, E/ΔE of order 10 000 and spatial resolution better than 10 μm. Initial tests of the high resolution instrument on HEDP plasmas are being performed.

  8. An Overview of High-Resolution, Non-Dispersive, Imaging Spectrometers for High-Energy Photons

    NASA Technical Reports Server (NTRS)

    Kilbourne, Caroline

    2010-01-01

    High-resolution x-ray spectroscopy has become a powerful tool for studying the evolving universe. The grating spectrometers on the XMM and Chandra satellites initiated a new era in x-ray astronomy. Despite their successes, there is still need for instrumentation that can provide higher spectral resolution with high throughput in the Fe-K band and for extended sources. What is needed is a non-dispersive imaging spectrometer - essentially a 14-bit x-ray color camera. And a requirement for a nondispersive spectrometer designed to provide eV-scale spectral resolution is a temperature below 0.1 K. The required spectral resolution and the constraints of thermodynamics and engineering dictate the temperature regime nearly independently of the details of the sensor or the read-out technology. Low-temperature spectrometers can be divided into two classes - - equilibrium and non-equilibrium. In the equilibrium devices, or calorimeters, the energy is deposited in an isolated thermal mass and the resulting increase in temperature is measured. In the non-equilibrium devices, the absorbed energy produces quantized excitations that are counted to determine the energy. The two approaches have different strong points, and within each class a variety of optimizations have been pursued. I will present the basic fundamentals of operation and the details of the most successful device designs to date. I will also discuss how the measurement priorities (resolution, energy band, count rate) influence the optimal choice of detector technology.

  9. Time-resolved photoemission apparatus achieving sub-20-meV energy resolution and high stability

    SciTech Connect

    Ishida, Y.; Togashi, T.; Yamamoto, K.; Tanaka, M.; Kiss, T.; Otsu, T.; Kobayashi, Y.; Shin, S.

    2014-12-15

    The paper describes a time- and angle-resolved photoemission apparatus consisting of a hemispherical analyzer and a pulsed laser source. We demonstrate 1.48-eV pump and 5.92-eV probe measurements at the ⩾10.5-meV and ⩾240-fs resolutions by use of fairly monochromatic 170-fs pulses delivered from a regeneratively amplified Ti:sapphire laser system operating typically at 250 kHz. The apparatus is capable to resolve the optically filled superconducting peak in the unoccupied states of a cuprate superconductor, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ}. A dataset recorded on Bi(111) surface is also presented. Technical descriptions include the followings: A simple procedure to fine-tune the spatio-temporal overlap of the pump-and-probe beams and their diameters; achieving a long-term stability of the system that enables a normalization-free dataset acquisition; changing the repetition rate by utilizing acoustic optical modulator and frequency-division circuit.

  10. Size-resolved global emission inventory of primary particulate matter from energy-related combustion sources

    NASA Astrophysics Data System (ADS)

    Winijkul, E.; Yan, F.; Lu, Z.; Streets, D. G.; Bond, T. C.; Zhao, Y.

    2015-04-01

    Current emission inventories provide information about the mass emissions of different chemical species from different emitting sources without information concerning the size distribution of primary particulate matter (PM). The size distribution information, however, is an important input into chemical transport models that determine the fate of PM and its impacts on climate and public health. At present, models usually make rather rudimentary assumptions about the size distribution of primary PM emissions in their model inputs. In this study, we develop a global and regional, size-resolved, mass emission inventory of primary PM emissions from source-specific combustion components of the residential, industrial, power, and transportation sectors for the year 2010. Uncertainties in the emission profiles are also provided. The global size-resolved PM emissions show a distribution with a single peak and the majority of the mass of particles in size ranges smaller than 1 μm. The PM size distributions for different sectors and world regions vary considerably, due to the different combustion characteristics. Typically, the sizes of particles decrease in the order: power sector > industrial sector > residential sector > transportation sector. Three emission scenarios are applied to the baseline distributions to study the likely changes in size distribution of emissions as clean technologies are implemented.

  11. ENERGY-DEPENDENT LIGHT CURVES AND PHASE-RESOLVED SPECTRA OF HIGH-ENERGY GAMMA-RAYS FROM THE CRAB PULSAR

    SciTech Connect

    Li, X.; Zhang, L.

    2010-12-20

    Energy-dependent light curves and phase-resolved spectra of high-energy {gamma}-ray emission from the Crab pulsar have been detected recently by the Fermi Large Area Telescope (LAT). Within the framework of a two-pole, three-dimensional outer gap model, we calculate the energy-dependent light curves and phase-resolved spectra in the inertial observer's frame. Our results show that (1) the observed {gamma}-ray properties from both Fermi LAT and MAGIC can be reproduced well in this model; (2) the first peak of the light curves in the energy region less than {approx}10 GeV comes from the sum of emissions from both the north and south poles, and the second peak comes only from the emission from the south pole; however, the relative contribution of the two poles to the first peak changes with increasing {gamma}-ray energy, and the light curve in the energy region greater than {approx}20 GeV comes completely from the emission of the south pole; and (3) {gamma}-rays in the energy region greater than 100 MeV are produced through inverse Compton scattering from secondary pairs and the survival curvature photons, where the latter dominate over {gamma}-ray emission in the energy region greater than several GeV.

  12. Communication: A combined periodic density functional and incremental wave-function-based approach for the dispersion-accounting time-resolved dynamics of {sup 4}He nanodroplets on surfaces: {sup 4}He/graphene

    SciTech Connect

    Lara-Castells, María Pilar de; Stoll, Hermann; Civalleri, Bartolomeo; Causà, Mauro; Voloshina, Elena; Mitrushchenkov, Alexander O.; Pi, Martí

    2014-10-21

    In this work we propose a general strategy to calculate accurate He–surface interaction potentials. It extends the dispersionless density functional approach recently developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] to adsorbate-surface interactions by including periodic boundary conditions. We also introduce a scheme to parametrize the dispersion interaction by calculating two- and three-body dispersion terms at coupled cluster singles and doubles and perturbative triples (CCSD(T)) level via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. The performance of the composite approach is tested on {sup 4}He/graphene by determining the energies of the low-lying selective adsorption states, finding an excellent agreement with the best available theoretical data. Second, the capability of the approach to describe dispersionless correlation effects realistically is used to extract dispersion effects in time-dependent density functional simulations on the collision of {sup 4}He droplets with a single graphene sheet. It is found that dispersion effects play a key role in the fast spreading of the {sup 4}He nanodroplet, the evaporation-like process of helium atoms, and the formation of solid-like helium structures. These characteristics are expected to be quite general and highly relevant to explain experimental measurements with the newly developed helium droplet mediated deposition technique.

  13. Energy dispersive-EXAFS of Pd nucleation at a liquid/liquid interface

    NASA Astrophysics Data System (ADS)

    Chang, S.-Y.; Booth, S. G.; Uehara, A.; Mosselmans, J. F. W.; Cibin, G.; Pham, V.-T.; Nataf, L.; Dryfe, R. A. W.; Schroeder, S. L. M.

    2016-05-01

    Energy dispersive extended X-ray absorption fine structure (EDE) has been applied to Pd nanoparticle nucleation at a liquid/liquid interface under control over the interfacial potential and thereby the driving force for nucleation. Preliminary analysis focusing on Pd K edge-step height determination shows that under supersaturated conditions the concentration of Pd near the interface fluctuate over a period of several hours, likely due to the continuous formation and dissolution of sub-critical nuclei. Open circuit potential measurements conducted ex-situ in a liquid/liquid electrochemical cell support this view, showing that the fluctuations in Pd concentration are also visible as variations in potential across the liquid/liquid interface. By decreasing the interfacial potential through inclusion of a common ion (tetraethylammonium, TEA+) the Pd nanoparticle growth rate could be slowed down, resulting in a smooth nucleation process. Eventually, when the TEA+ ions reached an equilibrium potential, Pd nucleation and particle growth were inhibited.

  14. Soil characterization by energy dispersive X-ray fluorescence: sampling strategy for in situ analysis.

    PubMed

    Custo, Graciela; Boeykens, Susana; Dawidowski, L; Fox, L; Gómez, D; Luna, F; Vázquez, Cristina

    2005-07-01

    This work describes a sampling strategy that will allow the use of portable EDXRF (energy dispersive X-ray fluorescence) instruments for "in situ" soil analysis. The methodology covers a general approach to planning field investigations for any type of environmental studies and it was applied for a soil characterization study in the zone of Campana, Argentina, by evaluating data coming from an EDXRF spectrometer with a radioisotope excitation source. Simulating non-treated sampled as "in situ" samples and a soil characterization for Campana area was intended. "In situ" EDXRF methodology is a powerful analytical modality with the advantage of providing data immediately, allowing a fast general screening of the soil composition. PMID:16038489

  15. Energy dispersive x-ray diffraction of charge density waves via chemical filtering

    SciTech Connect

    Feng Yejun; Somayazulu, M. S.; Jaramillo, R.; Rosenbaum, T.F.; Isaacs, E.D.; Hu Jingzhu; Mao Hokwang

    2005-06-15

    Pressure tuning of phase transitions is a powerful tool in condensed matter physics, permitting high-resolution studies while preserving fundamental symmetries. At the highest pressures, energy dispersive x-ray diffraction (EDXD) has been a critical method for geometrically confined diamond anvil cell experiments. We develop a chemical filter technique complementary to EDXD that permits the study of satellite peaks as weak as 10{sup -4} of the crystal Bragg diffraction. In particular, we map out the temperature dependence of the incommensurate charge density wave diffraction from single-crystal, elemental chromium. This technique provides the potential for future GPa pressure studies of many-body effects in a broad range of solid state systems.

  16. Nano-sized Lithium Manganese Oxide Dispersed on Carbon Nanotubes for Energy Storage Applications

    SciTech Connect

    Bak, S.B.

    2009-08-01

    Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200 C for 30 min using MnO{sub 2}-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4 mAh/g at a 1.6 C-rate, and is maintained at 99.1 mAh/g even at a 16 C-rate. The initial specific capacity is also maintained up to the 50th cycle to give 97% capacity retention. The LMO/CNT nanocomposite shows excellent power performance and good structural reversibility as an electrode material in energy storage systems, such as lithium-ion batteries and electrochemical capacitors. This synthetic strategy opens a new avenue for the effective and facile synthesis of lithium transition metal oxide/CNT nanocomposite.

  17. Characterization of small noble metal electrodes by voltammetry and energy dispersive x ray analysis

    NASA Astrophysics Data System (ADS)

    Strein, Timothy G.; Ewing, Andrew G.

    1993-01-01

    Construction and characterization of platinum and gold electrodes with total structural diameters of 1-2 micrometers is described. These small voltammetric probes have been constructed by direct electroreduction of noble metals onto the tips of etched carbon fiber microdisk electrodes. Voltammetry, electron microscopy, energy-dispersive x-ray analysis, and pulsed amperometric detection have been used to characterize these electrodes. Dopamine concentrations have been determined over a range of 10(exp -4) to 10(exp -3) M in the biological buffer system which contains 25 mM glucose, a compound known to adsorb strongly to electrodes. Amperometric monitoring at a constant potential with these small results in signal decay of 20% to 40% in a ten minute experiment. Pulsed amperometric detection minimizes electrode fouling, resulting in 5% or less signal decay over the same ten minute period.

  18. Evaluation on determination of iodine in coal by energy dispersive X-ray fluorescence

    USGS Publications Warehouse

    Wang, B.; Jackson, J.C.; Palmer, C.; Zheng, B.; Finkelman, R.B.

    2005-01-01

    A quick and inexpensive method of relative high iodine determination from coal samples was evaluated. Energy dispersive X-ray fluorescence (EDXRF) provided a detection limit of about 14 ppm (3 times of standard deviations of the blank sample), without any complex sample preparation. An analytical relative standard deviation of 16% was readily attainable for coal samples. Under optimum conditions, coal samples with iodine concentrations higher than 5 ppm can be determined using this EDXRF method. For the time being, due to the general iodine concentrations of coal samples lower than 5 ppm, except for some high iodine content coal, this method can not effectively been used for iodine determination. More work needed to meet the requirement of determination of iodine from coal samples for this method. Copyright ?? 2005 by The Geochemical Society of Japan.

  19. Compositional analysis of Ceramic Glaze by Laser Induced Breakdown Spectroscopy and Energy Dispersive X-Ray

    NASA Astrophysics Data System (ADS)

    Khedr, A.; Abdel-kareem, O.; Elnabi, S. H.; Harith, M. A.

    2011-09-01

    Laser induced breakdown spectroscopy (LIBS) has been applied for the analysis of Egyptian Islamic glaze ceramic sample. The sample dating back to Fatimid period (969-1169AD), and collected from Al-Fustat excavation store in Cairo. The analysis of contaminated pottery sample has been performed to draw mapping for the elemental compositions by LIBS technique. LIBS measurements have been done by the fundamental wavelength (1064 nm) of Nd: YAG laser for the elemental analysis and performing the cleaning processes of the pottery sample. In addition, complementary analyses were carried out by scanning electron microscopy linked with energy dispersive X-ray microanalysis (SEM/EDX) to obtain verification of chemical results. The morphological surfaces before and after cleaning has been done by Optical Microscopy (OM).

  20. Quantitative atomic resolution elemental mapping via absolute-scale energy dispersive X-ray spectroscopy.

    PubMed

    Chen, Z; Weyland, M; Sang, X; Xu, W; Dycus, J H; LeBeau, J M; D'Alfonso, A J; Allen, L J; Findlay, S D

    2016-09-01

    Quantitative agreement on an absolute scale is demonstrated between experiment and simulation for two-dimensional, atomic-resolution elemental mapping via energy dispersive X-ray spectroscopy. This requires all experimental parameters to be carefully characterized. The agreement is good, but some discrepancies remain. The most likely contributing factors are identified and discussed. Previous predictions that increasing the probe forming aperture helps to suppress the channelling enhancement in the average signal are confirmed experimentally. It is emphasized that simple column-by-column analysis requires a choice of sample thickness that compromises between being thick enough to yield a good signal-to-noise ratio while being thin enough that the overwhelming majority of the EDX signal derives from the column on which the probe is placed, despite strong electron scattering effects. PMID:27258645

  1. Development of an energy dispersive spectrometer for a transmission electron microscope utilizing a TES microcalorimeter array

    NASA Astrophysics Data System (ADS)

    Tanaka, Keiichi; Mitsuda, Kazuhisa; Hara, Tom; Maehata, Keisuke; Yamasaki, Noriko Y.; Odawara, Akikazu; Nagata, Atsushi; Watanabe, Katsuaki; Takei, Yoh

    2009-12-01

    A high-energy-resolution energy dispersive spectrometer (EDS) utilizing a TES (transition edge sensor) microcalorimeter array is developed for a transmission electron microscope (TEM). The goals of the development are (1) an energy range of 0.3-10 keV, (2) an energy resolution of FWHM <10 eV, (3) a maximum counting rate of 3 kcps, and (4) a cryogen-free cooling system. We adopted a dilution refrigerator (DR) pre-cooled by a Gifford-McMahon (GM) refrigerator to cool the TES microcalorimeter to ˜100 mK. In order to avoid micro phonics of GM fridge to propagate to the TEM, pressurized He gas is circulated between the DR and the GM to reject heat from the DR. The GM is mechanically well isolated from the TEM. In oder to obtain 3 kcps counting rate, we utilize a ten pixel TES array and read out the signals in parallel wtih ten analog signal channels from cryogenic to room temperature electronics. One of the pixels can be always irradiated by a radio isotope for energy calibration. As the first step, we have attached a single pixel TES system cooled by the cryogen-free cooling system to the TEM and obtained an energy resolution of 8 eV at 1.8 keV without degrading the spatial resolution of the TEM at a 2 Å level. A ten pixel TES system is also being developed from the front-end detector assembly to the room temperature digital electronics. We describe the signal processing system and packaging of the detector assembly.

  2. UV-curable low surface energy fluorinated polycarbonate-based polyurethane dispersion.

    PubMed

    Hwang, Hyeon-Deuk; Kim, Hyun-Joong

    2011-10-15

    UV-curable low surface energy fluorinated polycarbonate-based polyurethane dispersions were synthesized by incorporating a hydroxy-terminated perfluoropolyether (PFPE) into the soft segment of polyurethane. The effects of the PFPE content on the UV-curing behavior, physical, surface, thermal properties and refractive index were investigated. The UV-curing behavior was analyzed by photo-differential scanning calorimetry. The surface free energy of the UV-cured film, which is related to the water or oil repellency, was calculated from contact angle measurements using the Lewis acid-base three liquids method. The surface free energy decreased significantly with increasing fluorine concentration because PFPE in the soft segment was tailored to the surface and produced a UV-cured film with a hydrophobic fluorine enriched surface, as confirmed by X-ray photoelectron spectroscopy. With increasing the fluorine content, the refractive indices of UV-cured films decreased. However, the UV-curing rate and final conversion was decreased with increasing contents of PFPE, which resulted in the decrease of the glass transition temperature (T(g)), crosslink density, tensile strength and surface hardness. PMID:21788027

  3. Lattice vibrations in the Frenkel-Kontorova model. I. Phonon dispersion, number density, and energy

    DOE PAGESBeta

    Meng, Qingping; Wu, Lijun; Welch, David O.; Zhu, Yimei

    2015-06-17

    We studied the lattice vibrations of two inter-penetrating atomic sublattices via the Frenkel-Kontorova (FK) model of a linear chain of harmonically interacting atoms subjected to an on-site potential, using the technique of thermodynamic Green's functions based on quantum field-theoretical methods. General expressions were deduced for the phonon frequency-wave-vector dispersion relations, number density, and energy of the FK model system. In addition, as the application of the theory, we investigated in detail cases of linear chains with various periods of the on-site potential of the FK model. Some unusual but interesting features for different amplitudes of the on-site potential of themore » FK model are discussed. In the commensurate structure, the phonon spectrum always starts at a finite frequency, and the gaps of the spectrum are true ones with a zero density of modes. In the incommensurate structure, the phonon spectrum starts from zero frequency, but at a non-zero wave vector; there are some modes inside these gap regions, but their density is very low. In our approximation, the energy of a higher-order commensurate state of the one-dimensional system at a finite temperature may become indefinitely close to the energy of an incommensurate state. This finding implies that the higher-order incommensurate-commensurate transitions are continuous ones and that the phase transition may exhibit a “devil's staircase” behavior at a finite temperature.« less

  4. Lattice vibrations in the Frenkel-Kontorova model. I. Phonon dispersion, number density, and energy

    NASA Astrophysics Data System (ADS)

    Meng, Qingping; Wu, Lijun; Welch, David O.; Zhu, Yimei

    2015-06-01

    We studied the lattice vibrations of two interpenetrating atomic sublattices via the Frenkel-Kontorova (FK) model of a linear chain of harmonically interacting atoms subjected to an on-site potential using the technique of thermodynamic Green's functions based on quantum field-theoretical methods. General expressions were deduced for the phonon frequency-wave-vector dispersion relations, number density, and energy of the FK model system. As the application of the theory, we investigated in detail cases of linear chains with various periods of the on-site potential of the FK model. Some unusual but interesting features for different amplitudes of the on-site potential of the FK model are discussed. In the commensurate structure, the phonon spectrum always starts at a finite frequency, and the gaps of the spectrum are true ones with a zero density of modes. In the incommensurate structure, the phonon spectrum starts from zero frequency, but at a nonzero wave vector; there are some modes inside these gap regions, but their density is very low. In our approximation, the energy of a higher-order commensurate state of the one-dimensional system at a finite temperature may become indefinitely close to the energy of an incommensurate state. This finding implies that the higher-order incommensurate-commensurate transitions are continuous ones and that the phase transition may exhibit a "devil's staircase" behavior at a finite temperature.

  5. Lattice vibrations in the Frenkel-Kontorova model. I. Phonon dispersion, number density, and energy

    SciTech Connect

    Meng, Qingping; Wu, Lijun; Welch, David O.; Zhu, Yimei

    2015-06-17

    We studied the lattice vibrations of two inter-penetrating atomic sublattices via the Frenkel-Kontorova (FK) model of a linear chain of harmonically interacting atoms subjected to an on-site potential, using the technique of thermodynamic Green's functions based on quantum field-theoretical methods. General expressions were deduced for the phonon frequency-wave-vector dispersion relations, number density, and energy of the FK model system. In addition, as the application of the theory, we investigated in detail cases of linear chains with various periods of the on-site potential of the FK model. Some unusual but interesting features for different amplitudes of the on-site potential of the FK model are discussed. In the commensurate structure, the phonon spectrum always starts at a finite frequency, and the gaps of the spectrum are true ones with a zero density of modes. In the incommensurate structure, the phonon spectrum starts from zero frequency, but at a non-zero wave vector; there are some modes inside these gap regions, but their density is very low. In our approximation, the energy of a higher-order commensurate state of the one-dimensional system at a finite temperature may become indefinitely close to the energy of an incommensurate state. This finding implies that the higher-order incommensurate-commensurate transitions are continuous ones and that the phase transition may exhibit a “devil's staircase” behavior at a finite temperature.

  6. Identifying and Resolving Issues in EnergyPlus and DOE-2 Window Heat Transfer Calculations

    SciTech Connect

    Booten, C.; Kruis, N.; Christensen, C.

    2012-08-01

    Issues in building energy software accuracy are often identified by comparative, analytical, and empirical testing as delineated in the BESTEST methodology. As described in this report, window-related discrepancies in heating energy predictions were identified through comparative testing of EnergyPlus and DOE-2. Multiple causes for discrepancies were identified, and software fixes are recommended to better align the models with the intended algorithms and underlying test data.

  7. Towards hybrid pixel detectors for energy-dispersive or soft X-ray photon science.

    PubMed

    Jungmann-Smith, J H; Bergamaschi, A; Brückner, M; Cartier, S; Dinapoli, R; Greiffenberg, D; Huthwelker, T; Maliakal, D; Mayilyan, D; Medjoubi, K; Mezza, D; Mozzanica, A; Ramilli, M; Ruder, Ch; Schädler, L; Schmitt, B; Shi, X; Tinti, G

    2016-03-01

    JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications at free-electron lasers and synchrotron light sources. The JUNGFRAU 0.4 prototype presented here is specifically geared towards low-noise performance and hence soft X-ray detection. The design, geometry and readout architecture of JUNGFRAU 0.4 correspond to those of other JUNGFRAU pixel detectors, which are charge-integrating detectors with 75 µm × 75 µm pixels. Main characteristics of JUNGFRAU 0.4 are its fixed gain and r.m.s. noise of as low as 27 e(-) electronic noise charge (<100 eV) with no active cooling. The 48 × 48 pixels JUNGFRAU 0.4 prototype can be combined with a charge-sharing suppression mask directly placed on the sensor, which keeps photons from hitting the charge-sharing regions of the pixels. The mask consists of a 150 µm tungsten sheet, in which 28 µm-diameter holes are laser-drilled. The mask is aligned with the pixels. The noise and gain characterization, and single-photon detection as low as 1.2 keV are shown. The performance of JUNGFRAU 0.4 without the mask and also in the charge-sharing suppression configuration (with the mask, with a `software mask' or a `cluster finding' algorithm) is tested, compared and evaluated, in particular with respect to the removal of the charge-sharing contribution in the spectra, the detection efficiency and the photon rate capability. Energy-dispersive and imaging experiments with fluorescence X-ray irradiation from an X-ray tube and a synchrotron light source are successfully demonstrated with an r.m.s. energy resolution of 20% (no mask) and 14% (with the mask) at 1.2 keV and of 5% at 13.3 keV. The performance evaluation of the JUNGFRAU 0.4 prototype suggests that this detection system could be the starting point for a future detector development effort for either applications in the soft X-ray energy regime or for an energy-dispersive

  8. Energy-resolved neutron SEU measurements from 22 to 160 MeV

    SciTech Connect

    Johansson, K.; Dyreklev, P.; Granbom, B.; Olsson, N.; Blomgren, J.; Renberg, P.U.

    1998-12-01

    The energy dependence of the neutron- induced single-event upset (NSEU) cross section for Static RAMs have been measured, using quasi-monoenergetic neutrons of five different energies from 22 to 160 MeV. The measured SEU cross sections were corrected for the low-energy neutron tail by an iterative folding procedure. A clear energy dependence has been found. The SEU rate has been compared both with results from testing with a neutron spallation spectrum up to 800 MeV and the measured SEU rate from In-Flight experiments at 10 km.

  9. Development of a Schottky CdTe Medipix3RX hybrid photon counting detector with spatial and energy resolving capabilities

    NASA Astrophysics Data System (ADS)

    Gimenez, E. N.; Astromskas, V.; Horswell, I.; Omar, D.; Spiers, J.; Tartoni, N.

    2016-07-01

    A multichip CdTe-Medipix3RX detector system was developed in order to bring the advantages of photon-counting detectors to applications in the hard X-ray range of energies. The detector head consisted of 2×2 Medipix3RX ASICs bump-bonded to a 28 mm×28 mm e- collection Schottky contact CdTe sensor. Schottky CdTe sensors undergo performance degrading polarization which increases with temperature, flux and the longer the HV is applied. Keeping the temperature stable and periodically refreshing the high voltage bias supply was used to minimize the polarization and achieve a stable and reproducible detector response. This leads to good quality images and successful results on the energy resolving capabilities of the system.

  10. Digital performance improvements of a CdTe pixel detector for high flux energy-resolved X-ray imaging

    NASA Astrophysics Data System (ADS)

    Abbene, L.; Gerardi, G.; Principato, F.

    2015-03-01

    Photon counting detectors with energy resolving capabilities are desired for high flux X-ray imaging. In this work, we present the performance of a pixelated Schottky Al/p-CdTe/Pt detector (4×4) coupled to a custom-designed digital readout electronics for high flux measurements. The detector (4×4×2 mm3) has an anode layout based on an array of 16 pixels with a geometric pitch of 1 mm (pixel size of 0.6 mm). The 4-channel readout electronics is able to continuously digitize and process the signals from each pixel, performing multi-parameter analysis (event arrival time, pulse shape, pulse height, pulse time width, etc.) even at high fluxes and at different throughput and energy resolution conditions. The spectroscopic response of the system to monochromatic X-ray sources, at both low and high rates, is presented with particular attention to the mitigation of some typical spectral distortions (pile-up, baseline shifts and charge sharing). At a photon counting rate of 520 kcps/pixel, the system exhibits an energy resolution (FWHM at 59.5 keV) of 4.6%, 7.1% and 9% at throughputs of 0.9%, 16% and 82%, respectively. Measurements of Ag-target X-ray spectra also show the ability of the system to perform accurate estimation of the input counting rate up to 1.1 Mcps/pixel. The aim of this work is to point out, beside the appealing properties of CdTe detectors, the benefits of the digital approach in the development of high-performance energy resolved photon counting (ERPC) systems for high flux X-ray imaging.

  11. TOF Electron Energy Analyzer for Spin and Angular Resolved Photoemission Spectroscopy

    SciTech Connect

    Lebedev, Gennadi; Jozwiak, Chris; Andresen, Nord; Lanzara, Alessandra; Hussain, Zahid

    2008-07-09

    Current pulsed laser and synchrotron x-ray sources provide new opportunities for Time-Of- Flight (TOF) based photoemission spectroscopy to increase photoelectron energy resolution and efficiency compared to current standard techniques. The principals of photoelectron timing front formation, temporal aberration minimization, and optimization of electron beam transmission are presented. We have developed these concepts into a high resolution Electron Optical Scheme (EOS) of a TOF Electron Energy Analyzer (TOF-EEA) for photoemission spectroscopy. The EOS of the analyzer includes an electrostatic objective lens, three columns of transport lenses and a 90 degree energy band pass filter (BPF). The analyzer has two modes of operation: Spectrometer Mode (SM) with straight passage of electrons through the EOS undeflected by the BPF, allowing the entire spectrum to be measured, and Monochromator Mode (MM) in which the BPF defines a certain energy window inside the scope of the electron energy spectrum.

  12. Non-diffusive ignition of a gaseous reactive mixture following time-resolved, spatially distributed energy deposition

    NASA Astrophysics Data System (ADS)

    Kassoy, D. R.

    2014-01-01

    Systematic asymptotic methods are applied to the compressible conservation and state equations for a reactive gas, including transport terms, to develop a rational thermomechanical formulation for the ignition of a chemical reaction following time-resolved, spatially distributed thermal energy addition from an external source into a finite volume of gas. A multi-parameter asymptotic analysis is developed for a wide range of energy deposition levels relative to the initial internal energy in the volume when the heating timescale is short compared to the characteristic acoustic timescale of the volume. Below a quantitatively defined threshold for energy addition, a nearly constant volume heating process occurs, with a small but finite internal gas expansion Mach number. Very little added thermal energy is converted to kinetic energy. The gas expelled from the boundary of the hot, high-pressure spot is the source of mechanical disturbances (acoustic and shock waves) that propagate away into the neighbouring unheated gas. When the energy addition reaches the threshold value, the heating process is fully compressible with a substantial internal gas expansion Mach number, the source of blast waves propagating into the unheated environmental gas. This case corresponds to an extremely large non-dimensional hot-spot temperature and pressure. If the former is sufficiently large, a high activation energy chemical reaction is initiated on the short heating timescale. This phenomenon is in contrast to that for more modest levels of energy addition, where a thermal explosion occurs only after the familiar extended ignition delay period for a classical high activation reaction. Transport effects, modulated by an asymptotically small Knudsen number, are shown to be negligible unless a local gradient in temperature, concentration or velocity is exceptionally large.

  13. Fast GPU-based absolute intensity determination for energy-dispersive X-ray Laue diffraction

    NASA Astrophysics Data System (ADS)

    Alghabi, F.; Send, S.; Schipper, U.; Abboud, A.; Pietsch, U.; Kolb, A.

    2016-01-01

    This paper presents a novel method for fast determination of absolute intensities in the sites of Laue spots generated by a tetragonal hen egg-white lysozyme crystal after exposure to white synchrotron radiation during an energy-dispersive X-ray Laue diffraction experiment. The Laue spots are taken by means of an energy-dispersive X-ray 2D pnCCD detector. Current pnCCD detectors have a spatial resolution of 384 × 384 pixels of size 75 × 75 μm2 each and operate at a maximum of 400 Hz. Future devices are going to have higher spatial resolution and frame rates. The proposed method runs on a computer equipped with multiple Graphics Processing Units (GPUs) which provide fast and parallel processing capabilities. Accordingly, our GPU-based algorithm exploits these capabilities to further analyse the Laue spots of the sample. The main contribution of the paper is therefore an alternative algorithm for determining absolute intensities of Laue spots which are themselves computed from a sequence of pnCCD frames. Moreover, a new method for integrating spectral peak intensities and improved background correction, a different way of calculating mean count rate of the background signal and also a new method for n-dimensional Poisson fitting are presented.We present a comparison of the quality of results from the GPU-based algorithm with the quality of results from a prior (base) algorithm running on CPU. This comparison shows that our algorithm is able to produce results with at least the same quality as the base algorithm. Furthermore, the GPU-based algorithm is able to speed up one of the most time-consuming parts of the base algorithm, which is n-dimensional Poisson fitting, by a factor of more than 3. Also, the entire procedure of extracting Laue spots' positions, energies and absolute intensities from a raw dataset of pnCCD frames is accelerated by a factor of more than 3.

  14. Rainbows in energy- and angle-resolved ion scattering from surfaces

    SciTech Connect

    Tenner, A.D.; Gillen, K.T.; Horn, T.C.M.; Los, J.; Kleyn, A.W.

    1984-06-11

    The angular and energy distributions of K/sup +/ ions scattered at normal incidence with an initial energy of 35 eV on a W(110) surface were measured for various crystal orientations. The complex distributions show rainbows, which are due to both to extrema in the deflection functions for the two scattering angles as well as to an extremum in the final energy as a function of the impact parameter. With use of computer simulations with a nonadditive model potential all observed structures can be explained.

  15. Time-resolved soft-x-ray studies of energy transport in layered and planar laser-driven targets

    SciTech Connect

    Stradling, G.L.

    1982-04-19

    New low-energy x-ray diagnostic techniques are used to explore energy-transport processes in laser heated plasmas. Streak cameras are used to provide 15-psec time-resolution measurements of subkeV x-ray emission. A very thin (50 ..mu..g/cm/sup 2/) carbon substrate provides a low-energy x-ray transparent window to the transmission photocathode of this soft x-ray streak camera. Active differential vacuum pumping of the instrument is required. The use of high-sensitivity, low secondary-electron energy-spread CsI photocathodes in x-ray streak cameras is also described. Significant increases in sensitivity with only a small and intermittant decrease in dynamic range were observed. These coherent, complementary advances in subkeV, time-resolved x-ray diagnostic capability are applied to energy-transport investigations of 1.06-..mu..m laser plasmas. Both solid disk targets of a variety of Z's as well as Be-on-Al layered-disk targets were irradiated with 700-psec laser pulses of selected intensity between 3 x 10/sup 14/ W/cm/sup 2/ and 1 x 10/sup 15/ W/cm/sup 2/.

  16. High harmonic generation based time resolved ARPES at 30 eV with 50 meV energy resolution

    NASA Astrophysics Data System (ADS)

    Rohwer, Timm; Sie, Edbert J.; Mahmood, Fahad; Gedik, Nuh

    Angle-resolved photoelectron spectroscopy (ARPES) has emerged as a leading technique in identifying equilibrium properties of complex electronic systems as well as their correlated dynamics. By using femtosecond high harmonic generation (HHG) pulses, this technique can be extended to monitor ultrafast changes in the electronic structure in response to an optical excitation. However, the broad bandwidth of the HHG pulses has been a major experimental limitation. In this contribution, we combine the HHG source with an off-axis Czerny-Turner XUV monochromator and a three-dimensional ``ARTOF'' photoelectron detector to achieve an unrivaled overall energy resolution of 50 meV in multiple harmonic energies. Moreover, the use of a stack of different gratings enables us to fine control both the photon energy and time vs. energy resolution to its particular needs. The performance of our setup is demonstrated by studies on the transition metal dichalcogenide IrTe2 which undergoes a first-order structural transition and accompanied reconstruction of the band structure upon cooling without the characteristic opening of an energy gap.

  17. Phase evolution in carbide dispersion strengthened nanostructured copper composite by high energy ball milling

    SciTech Connect

    Hussain, Zuhailawati; Nur Hawadah, M. S.

    2012-09-06

    In this study, high-energy ball milling was applied to synthesis in situ nanostructured copper based composite reinforced with metal carbides. Cu, M (M=W or Ti) and graphite powder mixture were mechanically alloyed for various milling time in a planetary ball mill with composition of Cu-20vol%WC and Cu-20vol%TiC. Then the as-milled powder were compacted at 200 to 400 MPa and sintered in a vacuum furnace at 900 Degree-Sign C. The results of X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy analysis showed that formation of tungsten carbides (W{sub 2}C and WC phases) was observed after sintering of Cu-W-C mixture while TiC precipitated in as-milled powder of Cu-Ti-C composite after 5 h and become amorphous with longer milling. Mechanism of MA explained the cold welding and fracturing event during milling. Cu-W-C system shows fracturing event is more dominant at early stage of milling and W particle still existed after milling up to 60 h. While in Cu-Ti-C system, cold welding is more dominant and all Ti particles dissolved into Cu matrix.

  18. Phase evolution in carbide dispersion strengthened nanostructured copper composite by high energy ball milling

    NASA Astrophysics Data System (ADS)

    Hussain, Zuhailawati; Nur Hawadah, M. S.

    2012-09-01

    In this study, high-energy ball milling was applied to synthesis in situ nanostructured copper based composite reinforced with metal carbides. Cu, M (M=W or Ti) and graphite powder mixture were mechanically alloyed for various milling time in a planetary ball mill with composition of Cu-20vol%WC and Cu-20vol%TiC. Then the as-milled powder were compacted at 200 to 400 MPa and sintered in a vacuum furnace at 900°C. The results of X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy analysis showed that formation of tungsten carbides (W2C and WC phases) was observed after sintering of Cu-W-C mixture while TiC precipitated in as-milled powder of Cu-Ti-C composite after 5 h and become amorphous with longer milling. Mechanism of MA explained the cold welding and fracturing event during milling. Cu-W-C system shows fracturing event is more dominant at early stage of milling and W particle still existed after milling up to 60 h. While in Cu-Ti-C system, cold welding is more dominant and all Ti particles dissolved into Cu matrix.

  19. Binding of Transcription Factors Adapts to Resolve Information-Energy Tradeoff

    NASA Astrophysics Data System (ADS)

    Savir, Yonatan; Kagan, Jacob; Tlusty, Tsvi

    2016-03-01

    We examine the binding of transcription factors to DNA in terms of an information transfer problem. The input of the noisy channel is the biophysical signal of a factor bound to a DNA site, and the output is a distribution of probable DNA sequences at this site. This task involves an inherent tradeoff between the information gain and the energetics of the binding interaction—high binding energies provide higher information gain but hinder the dynamics of the system as factors are bound too tightly. We show that adaptation of the binding interaction towards increasing information transfer under a general energy constraint implies that the information gain per specific binding energy at each base-pair is maximized. We analyze hundreds of prokaryote and eukaryote transcription factors from various organisms to evaluate the discrimination energies. We find that, in accordance with our theoretical argument, binding energies nearly maximize the information gain per energy. This work suggests the adaptation of information gain as a generic design principle of molecular recognition systems.

  20. Persistent luminescence nanoprobe for biosensing and lifetime imaging of cell apoptosis via time-resolved fluorescence resonance energy transfer.

    PubMed

    Zhang, Lei; Lei, Jianping; Liu, Jintong; Ma, Fengjiao; Ju, Huangxian

    2015-10-01

    Time-resolved fluorescence technique can reduce the short-lived background luminescence and auto-fluorescence interference from cells and tissues by exerting the delay time between pulsed excitation light and signal acquisition. Here, we prepared persistent luminescence nanoparticles (PLNPs) to design a universal time-resolved fluorescence resonance energy transfer (TR-FRET) platform for biosensing, lifetime imaging of cell apoptosis and in situ lifetime quantification of intracellular caspase-3. Three kinds of PLNPs-based nanoprobes are assembled by covalently binding dye-labeled peptides or DNA to carboxyl-functionalized PLNPs for the efficient detection of caspase-3, microRNA and protein. The peptides-functionalized nanoprobe is also employed for fluorescence lifetime imaging to monitor cell apoptosis, which shows a dependence of cellular fluorescence lifetime on caspase-3 activity and thus leads to an in situ quantification method. This work provides a proof-of-concept for PLNPs-based TR-FRET analysis and demonstrates its potential in exploring dynamical information of life process. PMID:26232881

  1. Misidentification of major constituents by automatic qualitative energy dispersive X-ray microanalysis: a problem that threatens the credibility of the analytical community.

    PubMed

    Newbury, Dale E

    2005-12-01

    Automatic qualitative analysis for peak identification is a standard feature of virtually all modern computer-aided analysis software for energy dispersive X-ray spectrometry with electron excitation. Testing of recently installed systems from four different manufacturers has revealed the occasional occurrence of misidentification of peaks of major constituents whose concentrations exceeded 0.1 mass fraction (10 wt%). Test materials where peak identification failures were observed included ZnS, KBr, FeS2, tantalum-niobium alloy, NIST Standard Reference Material 482 (copper-gold alloy), Bi2Te3, uranium-rhodium alloys, platinum-chromium alloy, GaAs, and GaP. These misidentifications of major constituents were exacerbated when the incident beam energy was 10 keV or lower, which restricted or excluded the excitation of the high photon energy K- and L-shell X-rays where multiple peaks, for example, Kalpha (K-L2,3)-Kbeta (K-M2,3); Lalpha (L3-M4,5)-Lbeta (L2-M4)-Lgamma (L2-N4), are well resolved and amenable to identification with high confidence. These misidentifications are so severe as to properly qualify as blunders that present a serious challenge to the credibility of this critical analytical technique. Systematic testing of a peak identification system with a suite of diverse materials can reveal the specific elements and X-ray peaks where failures are likely to occur. PMID:17481333

  2. Misidentification of Major Constituents by Automatic Qualitative Energy Dispersive X-ray Microanalysis: A Problem that Threatens the Credibility of the Analytical Community

    NASA Astrophysics Data System (ADS)

    Newbury*, Dale E.

    2005-12-01

    Automatic qualitative analysis for peak identification is a standard feature of virtually all modern computer-aided analysis software for energy dispersive X-ray spectrometry with electron excitation. Testing of recently installed systems from four different manufacturers has revealed the occasional occurrence of misidentification of peaks of major constituents whose concentrations exceeded 0.1 mass fraction (10 wt%). Test materials where peak identification failures were observed included ZnS, KBr, FeS2, tantalum-niobium alloy, NIST Standard Reference Material 482 (copper gold alloy), Bi2Te3, uranium rhodium alloys, platinum chromium alloy, GaAs, and GaP. These misidentifications of major constituents were exacerbated when the incident beam energy was 10 keV or lower, which restricted or excluded the excitation of the high photon energy K- and L-shell X-rays where multiple peaks, for example, K[alpha] (K-L2,3) K[beta] (K-M2,3); L[alpha] (L3-M4,5) L[beta] (L2-M4) L[gamma] (L2-N4), are well resolved and amenable to identification with high confidence. These misidentifications are so severe as to properly qualify as blunders that present a serious challenge to the credibility of this critical analytical technique. Systematic testing of a peak identification system with a suite of diverse materials can reveal the specific elements and X-ray peaks where failures are likely to occur.

  3. CMOS-sensors for energy-resolved X-ray imaging

    NASA Astrophysics Data System (ADS)

    Doering, D.; Amar-Youcef, S.; Baudot, J.; Deveaux, M.; Dulinski, W.; Kachel, M.; Linnik, B.; Müntz, C.; Stroth, Joachim

    2016-01-01

    Due to their low noise, CMOS Monolithic Active Pixel Sensors are suited to sense X-rays with a few keV quantum energy, which is of interest for high resolution X-ray imaging. Moreover, the good energy resolution of the silicon sensors might be used to measure this quantum energy. Combining both features with the good spatial resolution of CMOS sensors opens the potential to build ``color sensitive" X-ray cameras. Taking such colored images is hampered by the need to operate the CMOS sensors in a single photon counting mode, which restricts the photon flux capability of the sensors. More importantly, the charge sharing between the pixels smears the potentially good energy resolution of the sensors. Based on our experience with CMOS sensors for charged particle tracking, we studied techniques to overcome the latter by means of an offline processing of the data obtained from a CMOS sensor prototype. We found that the energy resolution of the pixels can be recovered at the expense of reduced quantum efficiency. We will introduce the results of our study and discuss the feasibility of taking colored X-ray pictures with CMOS sensors.

  4. Resolving Anomalies in Predicting Electrokinetic Energy Conversion Efficiencies of Nanofluidic Devices

    PubMed Central

    Majumder, Sagardip; Dhar, Jayabrata; Chakraborty, Suman

    2015-01-01

    We devise a new approach for capturing complex interfacial interactions over reduced length scales, towards predicting electrokinetic energy conversion efficiencies of nanofluidic devices. By embedding several aspects of intermolecular interactions in continuum based formalism, we show that our simple theory becomes capable of representing complex interconnections between electro-mechanics and hydrodynamics over reduced length scales. The predictions from our model are supported by reported experimental data, and are in excellent quantitative agreement with molecular dynamics simulations. The present model, thus, may be employed to rationalize the discrepancies between low energy conversion efficiencies of nanofluidic channels that have been realized from experiments, and the impractically high energy conversion efficiencies that have been routinely predicted by the existing theories. PMID:26437925

  5. Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

    NASA Astrophysics Data System (ADS)

    Radu, L.; Mihailescu, I.; Radu, S.; Gazdaru, D.

    2007-09-01

    The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m 2 was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy.

  6. Time-resolved energy spectrum of the ion beam generated in the plasma focus

    SciTech Connect

    Kilic, H.

    1984-01-01

    A major feature of plasma focus devices in the acceleration of deuterons to energy values of several MeV with an externally applied voltage of only 15 kV on the electrodes. A plasma focus machine (49 ..mu..f, 15 kV, 5.5 kJ) was built and operated in six different pressure regimes (8-3 Torr, D/sub 2/ filling) to measure deuteron beam energies, beam emission time, and absolute beam intensity as a function of drilling pressure and of hard x-ray intensities. A Faraday cup used as an ion collector was placed in a differentially pumped chamber (10/sup -4/ 10/sup -5/ Torr) which was separated from the plasma focus chamber via a 150 /sup +/m diameter pinhole. The energy spectrum of the deuteron beam from a plasma focus discharge was determined with a new time-of-flight method and with a differential filter (2.5 ..mu..m - 750 ..mu..m, mylar filters) method in the energy interval 0.2 to 9 MeV. The ion time-of-flight method accounts for the time structure of the ion beam source on a nanosecond time scale. The new experimental results show that, in beam mode operation (3 - 4 Torr D/sub 2/), more than 10/sup 14/ deuterons with energy 0.2-0.5 MeV are accelerated in each discharge in the electrode axis (2.3 x 10/sup -4/ sr) with corresponding peak ion current approx. = 200 mA, and more than 10/sup 12/ deuterons are accelerated in the energy interval 0.5 - 9 MeV with a peak current of 10 mA. The ion beam acceleration mechanism is strongly dependent on the filling pressure of the discharge chamber. The deuteron beam intensity increases with hard x-ray intensity which fits a particle acceleration process in which the same field accelerates both ion and electron beams.

  7. Photosystem II Does Not Possess a Simple Excitation Energy Funnel: Time-Resolved Fluorescence Spectroscopy Meets Theory

    PubMed Central

    2013-01-01

    The experimentally obtained time-resolved fluorescence spectra of photosystem II (PS II) core complexes, purified from a thermophilic cyanobacterium Thermosynechococcus vulcanus, at 5–180 K are compared with simulations. Dynamic localization effects of excitons are treated implicitly by introducing exciton domains of strongly coupled pigments. Exciton relaxations within a domain and exciton transfers between domains are treated on the basis of Redfield theory and generalized Förster theory, respectively. The excitonic couplings between the pigments are calculated by a quantum chemical/electrostatic method (Poisson-TrEsp). Starting with previously published values, a refined set of site energies of the pigments is obtained through optimization cycles of the fits of stationary optical spectra of PS II. Satisfactorily agreement between the experimental and simulated spectra is obtained for the absorption spectrum including its temperature dependence and the linear dichroism spectrum of PS II core complexes (PS II-CC). Furthermore, the refined site energies well reproduce the temperature dependence of the time-resolved fluorescence spectrum of PS II-CC, which is characterized by the emergence of a 695 nm fluorescence peak upon cooling down to 77 K and the decrease of its relative intensity upon further cooling below 77 K. The blue shift of the fluorescence band upon cooling below 77 K is explained by the existence of two red-shifted chlorophyll pools emitting at around 685 and 695 nm. The former pool is assigned to Chl45 or Chl43 in CP43 (Chl numbering according to the nomenclature of Loll et al. Nature2005, 438, 1040) while the latter is assigned to Chl29 in CP47. The 695 nm emitting chlorophyll is suggested to attract excitations from the peripheral light-harvesting complexes and might also be involved in photoprotection. PMID:23537277

  8. Charge-state resolved energy spectra of swift 22Ne ions passing through thin carbon foils

    NASA Astrophysics Data System (ADS)

    Blazevic, A.; Bohlen, H. G.; von Oertzen, W.; Balashov, V. V.; Stysin, A. V.

    2006-04-01

    The method of coupled kinetic equations for a unified description of charge exchange and excitation of ions passing through matter is applied to calculate energy-loss spectra of swift 22Ne ions in carbon foils in the non-equilibrium regime. Good agreement is obtained for these calculations with the results of recent measurements, performed at the ISL-facility at the Hahn-Meitner Institute.

  9. Protein interaction quantified in vivo by spectrally resolved fluorescence resonance energy transfer

    PubMed Central

    2004-01-01

    We describe a fluorescence resonance energy transfer (FRET)-based method for finding in living cells the fraction of a protein population (αT) forming complexes, and the average number (n) of those protein molecules in each complex. The method relies both on sensitized acceptor emission and on donor de-quenching (by photobleaching of the acceptor molecules), coupled with full spectral analysis of the differential fluorescence signature, in order to quantify the donor/acceptor energy transfer. The approach and sensitivity limits are well suited for in vivo microscopic investigations. This is demonstrated using a scanning laser confocal microscope to study complex formation of the sterile 2 α-factor receptor protein (Ste2p), labelled with green, cyan, and yellow fluorescent proteins (GFP, CFP, and YFP respectively), in budding yeast Saccharomyces cerevisiae. A theoretical model is presented that relates the efficiency of energy transfer in protein populations (the apparent FRET efficiency, Eapp) to the energy transferred in a single donor/acceptor pair (E, the true FRET efficiency). We determined E by using a new method that relies on Eapp measurements for two donor/acceptor pairs, Ste2p–CFP/Ste2p–YFP and Ste2p–GFP/Ste2p–YFP. From Eapp and E we determined αT≈1 and n≈2 for Ste2 proteins. Since the Ste2p complexes are formed in the absence of the ligand in our experiments, we conclude that the α-factor pheromone is not necessary for dimerization. PMID:15352875

  10. EVALUATION OF MIXING ENERGY IN FLASKS USED FOR DISPERSANT EFFECTIVENESS TESTING

    EPA Science Inventory

    A U.S. Environmental Protection Agency (EPA) laboratory screening protocol for dispersant effectiveness consists of placing water, oil, and a dispersant in a flask and mixing the contents on an orbital shaker. Two flasks are being investigated, a simple Erlenmeyer (used in EPA's...

  11. Analysis of nuclear materials by energy dispersive x-ray fluorescence and spectral effects of alpha decay

    SciTech Connect

    Worley, Christopher G

    2009-01-01

    Energy dispersive X-ray fluorescence (EDXRF) spectra collected from alpha emitters are complicated by artifacts inherent to the alpha decay process, particularly when using portable instruments. For example, {sup 239}Pu EDXRF spectra exhibit a prominent uranium L X-ray emission peak series due to sample alpha decay rather than source-induced X-ray fluorescence. A portable EDXRF instrument was used to collect spectra from plutonium, americium, and a Pu-contaminated steel sample. The plutonium sample was also analyzed by wavelength dispersive XRF to demonstrate spectral differences observed when using these very different instruments.

  12. Elemental analysis of mining wastes by energy dispersive X-ray fluorescence (EDXRF)

    NASA Astrophysics Data System (ADS)

    Gonzalez-Fernandez, O.; Queralt, I.; Carvalho, M. L.; Garcia, G.

    2007-08-01

    An energy dispersive X-ray fluorescence (EDXRF) tri-axial geometry experimental spectrometer has been employed to determine the concentrations of 13 different elements (K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr and Pb) in mine wastes from different depths of two mine tailings from the Cartagena-La Union (Spain) mining district. The elements were determined and quantified using the fundamental parameters method. The concentrations of Cr, Ni, Cu, Zn and Pb were compared to the values from the European and Spanish legislation to evaluate the environmental risk and to classify the wastes as inert wastes or as wastes that have to be control land-filled. The results obtained demonstrate that these wastes can be considered as inert for the considered elements, apart from the concentration levels of Zn and Pb. Whilst Zn slightly overpasses the regulatory levels, Pb mean value exceeds three to six times the value to be considered as Class I potential land-filling material.

  13. An energy dispersive x-ray scattering and molecular dynamics study of liquid dimethyl carbonate

    NASA Astrophysics Data System (ADS)

    Gontrani, Lorenzo; Russina, Olga; Marincola, Flaminia Cesare; Caminiti, Ruggero

    2009-12-01

    In this work, we report on the first x-ray diffraction study on liquid dimethyl carbonate. Diffraction spectra were collected with an energy-dispersive instrument, whose wide Q-range allows the structure determination of weakly ordered systems (such as liquids). The structural correlation in this liquid ranges up to about 20 Å. The observed patterns are interpreted with a structural model derived from classical molecular dynamics simulations. The simulations were run using OPLS force field, only slightly modified to restrain bond distances to the experimental values. The model structure function and radial distribution functions, averaged among the productive trajectory frames, are in very good agreement with the corresponding experimental ones. Molecular dynamics results show that the deviations from C2v cis-cis structure, predicted by ab initio calculations and observed by electron diffraction in the gas phase, are small. By analyzing the intra- and intermolecular pair distribution functions, it was possible to assign the peaks of the experimental radial distribution function to specific structural correlations, and to compute the different average intermolecular coordination numbers. The intermolecular methyl-carbonyl oxygen distance is thoroughly discussed to assess the presence of weak C-H⋯ṡO hydrogen bonds.

  14. Energy Dispersive XAFS: Characterization of Electronically Excited States of Copper(I) Complexes

    PubMed Central

    2013-01-01

    Energy dispersive X-ray absorption spectroscopy (ED-XAS), in which the whole XAS spectrum is acquired simultaneously, has been applied to reduce the real-time for acquisition of spectra of photoinduced excited states by using a germanium microstrip detector gated around one X-ray bunch of the ESRF (100 ps). Cu K-edge XAS was used to investigate the MLCT states of [Cu(dmp)2]+ (dmp =2,9-dimethyl-1,10-phenanthroline) and [Cu(dbtmp)2]+ (dbtmp =2,9-di-n-butyl-3,4,7,8-tetramethyl-1,10-phenanthroline) with the excited states created by excitation at 450 nm (10 Hz). The decay of the longer lived complex with bulky ligands, was monitored for up to 100 ns. DFT calculations of the longer lived MLCT excited state of [Cu(dbp)2]+ (dbp =2,9-di-n-butyl-1,10-phenanthroline) with the bulkier diimine ligands, indicated that the excited state behaves as a Jahn–Teller distorted Cu(II) site, with the interligand dihedral angle changing from 83 to 60° as the tetrahedral coordination geometry flattens and a reduction in the Cu–N distance of 0.03 Å. PMID:23718738

  15. Micro-molding with ultrasonic vibration energy: new method to disperse nanoclays in polymer matrices.

    PubMed

    Planellas, Marc; Sacristán, Matías; Rey, Lorena; Olmo, Cristian; Aymamí, Joan; Casas, María T; del Valle, Luis J; Franco, Lourdes; Puiggalí, Jordi

    2014-07-01

    Ultrasound technology was proved as an efficient processing technique to obtain micro-molded specimens of polylactide (PLA) and polybutylene succinate (PBS), which were selected as examples of biodegradable polyesters widely employed in commodity and specialty applications. Operational parameters such as amplitude, molding force and processing time were successfully optimized to prepare samples with a decrease in the number average molecular weight lower than 6%. Ultrasonic waves also seemed an ideal energy source to provide effective disaggregation of clay silicate layers, and therefore exfoliated nanocomposites. X-ray diffraction patterns of nanocomposites prepared by direct micro-molding of PLA or PBS powder mixtures with natural montmorillonite or different organo-modified clays showed the disappearance of the 001 silicate reflection for specimens having up to 6 wt.% clay content. All electron micrographs revealed relatively homogeneous dispersion and sheet nanostructures oriented in the direction of the melt flow. Incorporation of clay particles during processing had practically no influence on PLA characteristics but enhanced PBS degradation when an organo-modifier was employed. This was in agreement with thermal stability data deduced from thermogravimetric analysis. Cold crystallization experiments directly performed on micro-molded PLA specimens pointed to a complex influence of clay particles reflected by the increase or decrease of the overall non-isothermal crystallization rate when compared to the neat polymer. In all cases, the addition of clay led to a clear decrease in the Avrami exponent. PMID:24457002

  16. High temperature monitoring of silicon carbide ceramics by confocal energy dispersive X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Li, Fangzuo; Liu, Zhiguo; Sun, Tianxi

    2016-04-01

    In the present work, we presented an alternative method for monitoring of the oxidation situation of silicon carbide (SiC) ceramics at various high temperatures in air by measuring the Compton-to-Rayleigh intensity ratios (ICo/IRa) and effective atomic numbers (Zeff) of SiC ceramics with the confocal energy dispersive X-ray fluorescence (EDXRF) spectrometer. A calibration curve of the relationship between ICo/IRa and Zeff was established by using a set of 8 SiC calibration samples. The sensitivity of this approach is so high that it can be easily distinguished samples of Zeff differing from each other by only 0.01. The linear relationship between the variation of Zeff and the variations of contents of C, Si and O of SiC ceramics were found, and the corresponding calculation model of the relationship between the ΔZ and the ΔCC, ΔCSi, and ΔCO were established. The variation of contents of components of the tested SiC ceramics after oxidation at high temperature was quantitatively calculated based on the model. It was shown that the results of contents of carbon, silicon and oxygen obtained by this method were in good agreement with the results obtained by XPS, giving values of relative deviation less than 1%. It was concluded that the practicality of this proposed method for monitoring of the oxidation situation of SiC ceramics at high temperatures was acceptable.

  17. Micro energy-dispersive x-ray fluorescence spectrometry study of dentin coating with nanobiomaterials

    NASA Astrophysics Data System (ADS)

    Soares, Luís. Eduardo Silva; Nahorny, Sídnei; Marciano, Fernanda Roberta; Zanin, Hudson; Lobo, Anderson de Oliveira

    2015-06-01

    New biomaterials such as multi-walled carbon nanotubes oxide/graphene oxide (MWCNTO/GO), nanohydroxyapatite (nHAp) and combination of them together or not to acidulated phosphate fluoride gel (F) have been tested as protective coating before root dentin erosion. Fourteen bovine teeth were cleaned, polished, divided into two parts (n=28) and assigned to seven groups: (Control) - without previous surface treatment; F treatment; nHAp; MWCNTO/GO; F+nHAp; F+MWCNTO/GO and F+MWCNTO/GO/nHAp composites. Each sample had two sites of pre-treatments: acid etched area and an area without treatment. After the biomaterials application, the samples were submitted to six cycles (demineralization: orange juice, 10 min; remineralization: artificial saliva, 1 h). Micro energy-dispersive X-ray fluorescence spectrometry (μ-EDXRF) mapping area analyses were performed after erosive cycling on both sites (n=84). μ-EDXRF mappings showed that artificial saliva and MWCNTO/GO/nHAp/F composite treatments produced lower dentin demineralization than in the other groups. Exposed dentin tubules allowed better interaction of nanobiomaterials than in smear layer covered dentin. Association of fluoride with other biomaterials had a positive influence on acid etched dentin. MWCNTO/GO/nHAp/F composite treatment resulted in levels of demineralization similar to the control group.

  18. Dispersed, decentralized and renewable energy sources: alternatives to national vulnerability and war. Final report, July 1979-December 1980

    SciTech Connect

    McCasker, J.; Clark, W.

    1980-12-01

    Section 1 and 2 of this report contain background information on centralized energy systems and the relationship between vulnerability of these systems, energy planning, and existing civil defense programs. Section 3 and 4 contain an extensive investigation, review and categorization of alternative approaches to centralized, vulnerable energy systems; a review of dispersed and renewable technologies which can be appropriately implemented at the local level; and matrices for evaluation of these technologies for emergency and crisis planning. Specific recommendations to FEMA are included on the use of localized energy approaches for emergency response and recovery situations.

  19. Förster resonance energy transfer rate in any dielectric nanophotonic medium with weak dispersion

    NASA Astrophysics Data System (ADS)

    Wubs, Martijn; Vos, Willem L.

    2016-05-01

    Motivated by the ongoing debate about nanophotonic control of Förster resonance energy transfer (FRET), notably by the local density of optical states (LDOS), we study FRET and spontaneous emission in arbitrary nanophotonic media with weak dispersion and weak absorption in the frequency overlap range of donor and acceptor. This system allows us to obtain the following two new insights. Firstly, we derive that the FRET rate only depends on the static part of the Green function. Hence, the FRET rate is independent of frequency, in contrast to spontaneous-emission rates and LDOS that are strongly frequency dependent in nanophotonic media. Therefore, the position-dependent FRET rate and the LDOS at the donor transition frequency are completely uncorrelated for any nondispersive medium. Secondly, we derive an exact expression for the FRET rate as a frequency integral of the imaginary part of the Green function. This leads to very accurate approximation for the FRET rate that features the LDOS that is integrated over a huge bandwidth ranging from zero frequency to far into the UV. We illustrate these general results for the analytic model system of a pair of ideal dipole emitters—donor and acceptor—in the vicinity of an ideal mirror. We find that the FRET rate is independent of the LDOS at the donor emission frequency. Moreover, we observe that the FRET rate hardly depends on the frequency-integrated LDOS. Nevertheless, the FRET is controlled between inhibition and 4×enhancement at distances close to the mirror, typically a few nm. Finally, we discuss the consequences of our results to applications of Förster resonance energy transfer, for instance in quantum information processing.

  20. Possibility of vibrationally resolved cross section measurements for low energy charge transfer in H + H2+

    NASA Astrophysics Data System (ADS)

    Guillen, C. I.; Strom, R. A.; Tobar, J. A.; Panchenko, D. I.; Andrianarijaona, V. M.

    2015-04-01

    Charge transfer (CT) in H + H2+--> H+ + H2 has fundamental implications because it involves the smallest atomic ion, atom, molecular ion, and molecule possible. The current merged-beam apparatus at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, can reliably create and access low collision energies; the existing ion-atom merged beams apparatus there is currently able to benchmark the CT of these fundamental systems at energies below 0.1eV/u (Phys. Rev. A 84, 062716, 2011). A strong contribution from vi = 2 is observed, however, the data analysis still suffers from the lack of information on the vibrational state distribution of H2+.We are exploring the possibility of inserting a three-dimensional imaging technique at the end station of the ORNL apparatus in order to measure the vibrational state distribution of H2+that are produced by the electron cyclotron resonance (ECR) ion source. Discussion of our initial design for the insertion of this technique in the aforementioned system will be presented here. Work supported by the National Science Foundation under Grant No. PHY-1068877.

  1. Optical constants and dispersion energy parameters of NiO thin films prepared by radio frequency magnetron sputtering technique

    NASA Astrophysics Data System (ADS)

    Usha, K. S.; Sivakumar, R.; Sanjeeviraja, C.

    2013-09-01

    In this paper, we report on rf power induced change in the structural and optical properties of nickel oxide (NiO) thin films deposited onto glass substrates by rf magnetron sputtering technique. The crystallinity of the film was found to increase with increasing rf power and the deposited film belong to cubic phase. The maximum optical transmittance of 95% was observed for the film deposited at 100 W. The slight shift in transmission threshold towards higher wavelength region with increasing rf power revealed the systematic reduction in optical energy band gap (3.93 to 3.12 eV) of the films. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal dispersion in the transparent region. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion parameters, dielectric constants, relaxation time, and optical non-linear susceptibility were evaluated. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.

  2. Adipocytokine Orosomucoid Integrates Inflammatory and Metabolic Signals to Preserve Energy Homeostasis by Resolving Immoderate Inflammation*

    PubMed Central

    Lee, Yun Sok; Choi, Jin Woo; Hwang, Injae; Lee, Joo Won; Lee, Jae Ho; Kim, A. Young; Huh, Jin Young; Koh, Young Jun; Koh, Gou Young; Son, Hee Jung; Masuzaki, Hiroaki; Hotta, Kikuko; Alfadda, Assim A.; Kim, Jae Bum

    2010-01-01

    Orosomucoid (ORM), also called α-1 acid glycoprotein, is an abundant plasma protein that is an immunomodulator induced by stressful conditions such as infections. In this study, we reveal that Orm is induced selectively in the adipose tissue of obese mice to suppress excess inflammation that otherwise disturbs energy homeostasis. Adipose Orm levels were elevated by metabolic signals, including insulin, high glucose, and free fatty acid, as well as by the proinflammatory cytokine tumor necrosis factor-α, which is found in increased levels in the adipose tissue of morbid obese subjects. In both adipocytes and macrophages, ORM suppressed proinflammatory gene expression and pathways such as NF-κB and mitogen-activated protein kinase signalings and reactive oxygen species generation. Concomitantly, ORM relieved hyperglycemia-induced insulin resistance as well as tumor necrosis factor-α-mediated lipolysis in adipocytes. Accordingly, ORM improved glucose and insulin tolerance in obese and diabetic db/db mice. Taken together, our results suggest that ORM integrates inflammatory and metabolic signals to modulate immune responses to protect adipose tissue from excessive inflammation and thereby from metabolic dysfunction. PMID:20442402

  3. Sequence-resolved free energy profiles of stress-bearing vimentin intermediate filaments.

    PubMed

    Ramm, Beatrice; Stigler, Johannes; Hinczewski, Michael; Thirumalai, D; Herrmann, Harald; Woehlke, Günther; Rief, Matthias

    2014-08-01

    Intermediate filaments (IFs) are key to the mechanical strength of metazoan cells. Their basic building blocks are dimeric coiled coils mediating hierarchical assembly of the full-length filaments. Here we use single-molecule force spectroscopy by optical tweezers to assess the folding and stability of coil 2B of the model IF protein vimentin. The coiled coil was unzipped from its N and C termini. When pulling from the C terminus, we observed that the coiled coil was resistant to force owing to the high stability of the C-terminal region. Pulling from the N terminus revealed that the N-terminal half is considerably less stable. The mechanical pulling assay is a unique tool to study and control seed formation and structure propagation of the coiled coil. We then used rigorous theory-based deconvolution for a model-free extraction of the energy landscape and local stability profiles. The data obtained from the two distinct pulling directions complement each other and reveal a tripartite stability of the coiled coil: a labile N-terminal half, followed by a medium stability section and a highly stable region at the far C-terminal end. The different stability regions provide important insight into the mechanics of IF assembly. PMID:25049381

  4. On the possibility of ephedrine detection: time-resolved fluorescence resonance energy transfer (FRET)-based approach.

    PubMed

    Varriale, Antonio; Marzullo, Vincenzo Manuel; Di Giovanni, Stefano; Scala, Andrea; Capo, Alessandro; Majoli, Adelia; Pennacchio, Angela; Staiano, Maria; D'Auria, Sabato

    2016-09-01

    Ephedrine is one of the main precursor compounds used in the illegal production of amphetamines and related drugs. Actually, conventional analytical methods such as high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and gas chromatography-mass spectrometry (GC-MS) are used for the detection of ephedrine; sadly, these methods require qualified personnel and are time-consuming and expensive. In order to overcome these problems, in recent years, different methods have been developed based on the surface plasmon resonance (SPR) and electrochemical method. In this work, we present a simple, rapid, and effective method to detect the presence of ephedrine in solution, based on competitive fluorescence resonance energy transfer (FRET) assay. The antibody anti-ephedrine and ephedrine derivative were produced and labeled respectively, with two different fluorescent probes (donor and acceptor). The change in FRET signal intensity between donor and acceptor ephedrine compounds gives the possibility of detecting ephedrine traces of at least 0.81 ± 0.04 ppm (LOD). Graphical abstract A new Time-resolved Fluorescence Resonance Energy Transfer (FRET) assay for ephedrine detection. PMID:27395357

  5. Laboratory implementation of edge illumination X-ray phase-contrast imaging with energy-resolved detectors

    NASA Astrophysics Data System (ADS)

    Diemoz, P. C.; Endrizzi, M.; Vittoria, F. A.; Hagen, C. K.; Kallon, G.; Basta, D.; Marenzana, M.; Delogu, P.; Vincenzi, A.; De Ruvo, L.; Spandre, G.; Brez, A.; Bellazzini, R.; Olivo, A.

    2015-03-01

    Edge illumination (EI) X-ray phase-contrast imaging (XPCI) has potential for applications in different fields of research, including materials science, non-destructive industrial testing, small-animal imaging, and medical imaging. One of its main advantages is the compatibility with laboratory equipment, in particular with conventional non-microfocal sources, which makes its exploitation in normal research laboratories possible. In this work, we demonstrate that the signal in laboratory implementations of EI can be correctly described with the use of the simplified geometrical optics. Besides enabling the derivation of simple expressions for the sensitivity and spatial resolution of a given EI setup, this model also highlights the EI's achromaticity. With the aim of improving image quality, as well as to take advantage of the fact that all energies in the spectrum contribute to the image contrast, we carried out EI acquisitions using a photon-counting energy-resolved detector. The obtained results demonstrate that this approach has great potential for future laboratory implementations of EI.

  6. Level sequence and splitting identification of closely spaced energy levels by angle-resolved analysis of fluorescence light

    NASA Astrophysics Data System (ADS)

    Wu, Z. W.; Volotka, A. V.; Surzhykov, A.; Dong, C. Z.; Fritzsche, S.

    2016-06-01

    The angular distribution and linear polarization of the fluorescence light following the resonant photoexcitation is investigated within the framework of density matrix and second-order perturbation theory. Emphasis has been placed on "signatures" for determining the level sequence and splitting of intermediate (partially) overlapping resonances, if analyzed as a function of photon energy of incident light. Detailed computations within the multiconfiguration Dirac-Fock method have been performed, especially for the 1 s22 s22 p63 s ,Ji=1 /2 +γ1→(1s22 s 2 p63 s ) 13 p3 /2,J =1 /2 ,3 /2 →1 s22 s22 p63 s ,Jf=1 /2 +γ2 photoexcitation and subsequent fluorescence emission of atomic sodium. A remarkably strong dependence of the angular distribution and linear polarization of the γ2 fluorescence emission is found upon the level sequence and splitting of the intermediate (1s22 s 2 p63 s ) 13 p3 /2,J =1 /2 ,3 /2 overlapping resonances owing to their finite lifetime (linewidth). We therefore suggest that accurate measurements of the angular distribution and linear polarization might help identify the sequence and small splittings of closely spaced energy levels, even if they cannot be spectroscopically resolved.

  7. How Consistent are Recent Variations in the Tropical Energy and Water Cycle Resolved by Satellite Measurements?

    NASA Technical Reports Server (NTRS)

    Robertson, F. R.; Lu, H.-I.

    2004-01-01

    One notable aspect of Earth's climate is that although the planet appears to be very close to radiative balance at top-of-atmosphere (TOA), the atmosphere itself and underlying surface are not. Profound exchanges of energy between the atmosphere and oceans, land and cryosphere occur over a range of time scales. Recent evidence from broadband satellite measurements suggests that even these TOA fluxes contain some detectable variations. Our ability to measure and reconstruct radiative fluxes at the surface and at the top of atmosphere is improving rapidly. One question is 'How consistent, physically, are these diverse remotely-sensed data sets'? The answer is of crucial importance to understanding climate processes, improving physical models, and improving remote sensing algorithms. In this work we will evaluate two recently released estimates of radiative fluxes, focusing primarily on surface estimates. The International Satellite Cloud Climatology Project 'FD' radiative flux profiles are available from mid-1983 to near present and have been constructed by driving the radiative transfer physics from the Goddard Institute for Space Studies (GISS) global model with ISCCP clouds and TOVS (TIROS Operational Vertical Sounder)thermodynamic profiles. Full and clear sky SW and LW fluxes are produced. A similar product from the NASA/GEWEX Surface Radiation Budget Project using different radiative flux codes and thermodynamics from the NASA/Goddard Earth Observing System (GEOS-1) assimilation model makes a similar calculation of surface fluxes. However this data set currently extends only through 1995. We also employ precipitation measurements from the Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measuring Mission (TRMM). Finally, ocean evaporation estimates from the Special Sensor Microwave Imager (SSM/I) are considered as well as derived evaporation from the NCAR/NCEP Reanalysis. Additional information is included in the original extended

  8. Analysis of energy dispersive x-ray diffraction profiles for material identification, imaging and system control

    NASA Astrophysics Data System (ADS)

    Cook, Emily Jane

    2008-12-01

    This thesis presents the analysis of low angle X-ray scatter measurements taken with an energy dispersive system for substance identification, imaging and system control. Diffraction measurements were made on illicit drugs, which have pseudo- crystalline structures and thus produce diffraction patterns comprising a se ries of sharp peaks. Though the diffraction profiles of each drug are visually characteristic, automated detection systems require a substance identification algorithm, and multivariate analysis was selected as suitable. The software was trained with measured diffraction data from 60 samples covering 7 illicit drugs and 5 common cutting agents, collected with a range of statistical qual ities and used to predict the content of 7 unknown samples. In all cases the constituents were identified correctly and the contents predicted to within 15%. Soft tissues exhibit broad peaks in their diffraction patterns. Diffraction data were collected from formalin fixed breast tissue samples and used to gen erate images. Maximum contrast between healthy and suspicious regions was achieved using momentum transfer windows 1.04-1.10 and 1.84-1.90 nm_1. The resulting images had an average contrast of 24.6% and 38.9% compared to the corresponding transmission X-ray images (18.3%). The data was used to simulate the feedback for an adaptive imaging system and the ratio of the aforementioned momentum transfer regions found to be an excellent pa rameter. Investigation into the effects of formalin fixation on human breast tissue and animal tissue equivalents indicated that fixation in standard 10% buffered formalin does not alter the diffraction profiles of tissue in the mo mentum transfer regions examined, though 100% unbuffered formalin affects the profile of porcine muscle tissue (a substitute for glandular and tumourous tissue), though fat is unaffected.

  9. Scanning electron microscope/energy dispersive x ray analysis of impact residues on LDEF tray clamps

    NASA Technical Reports Server (NTRS)

    Bernhard, Ronald P.; Durin, Christian; Zolensky, Michael E.

    1992-01-01

    To better understand the nature of particulates in low-Earth orbit (LEO), and their effects on spacecraft hardware, we are analyzing residues found in impacts on the Long Duration Exposure Facility (LDEF) tray clamps. LDEF experiment trays were held in place by 6 to 8 chromic-anodized aluminum (6061-T6) clamps that were fastened to the spacecraft frame using three stainless steel hex bolts. Each clamp exposed an area of approximately 58 sq cm (4.8 cm x 12.7 cm x .45 cm, minus the bolt coverage). Some 337 out of 774 LDEF tray clamps were archived at JSC and are available through the Meteoroid & Debris Special Investigation Group (M&D SIG). Optical scanning of clamps, starting with Bay/Row A01 and working toward H25, is being conducted at JSC to locate and document impacts as small as 40 microns. These impacts are then inspected by Scanning Electron Microscopy/Energy Dispersive X-ray Analysis (SEM/EDXA) to select those features which contain appreciable impact residue material. Based upon the composition of projectile remnants, and using criteria developed at JSC, we have made a preliminary discrimination between micrometeoroid and space debris residue-containing impact features. Presently, 13 impacts containing significant amounts of unmelted and semi-melted micrometeoritic residues were forwarded to Centre National d'Etudes Spatiales (CNES) in France. At the CNES facilities, the upgraded impacts were analyzed using a JEOL T330A SEM equipped with a NORAN Instruments, Voyager X-ray Analyzer. All residues were quantitatively characterized by composition (including oxygen and carbon) to help understand interplanetary dust as possibly being derived from comets and asteroids.

  10. Micro energy dispersive X-ray fluorescence analysis of polychrome lead-glazed Portuguese faiences

    NASA Astrophysics Data System (ADS)

    Guilherme, A.; Pessanha, S.; Carvalho, M. L.; dos Santos, J. M. F.; Coroado, J.

    2010-04-01

    Several glazed ceramic pieces, originally produced in Coimbra (Portugal), were submitted to elemental analysis, having as premise the pigment manufacture production recognition. Although having been produced in Coimbra, their location changed as time passed due to historical reasons. A recent exhibition in Coimbra brought together a great number of these pieces and in situ micro Energy Dispersive X-ray Fluorescence (µ-EDXRF) analyses were performed in order to achieve some chemical and physical data on the manufacture of faiences in Coimbra. A non-commercial µ-EDXRF equipment for in situ analysis was employed in this work, carrying some important improvements when compared to the conventional ones, namely, analyzing spot sizes of about 100 µm diameter. The combination of a capillary X-ray lens with a new generation of low power microfocus X-ray tube and a drift chamber detector enabled a portable unit for micro-XRF with a few tens of µm lateral resolution. The advantages in using a portable system emphasized with polycapillary optics enabled to distinguish proximal different pigmented areas, as well as the glaze itself. These first scientific results on the pigment analysis of the collection of faiences seem to point to a unique production center with own techniques and raw materials. This conclusion arose with identification of the blue pigments having in its constitution Mn, Fe Co and As and the yellows as a result of the combination between Pb and Sb. A statistical treatment was used to reveal groups of similarities on the pigments elemental profile.

  11. Energy resolved actinometry for simultaneous measurement of atomic oxygen densities and local mean electron energies in radio-frequency driven plasmas

    SciTech Connect

    Greb, Arthur Niemi, Kari; O'Connell, Deborah; Gans, Timo

    2014-12-08

    A diagnostic method for the simultaneous determination of atomic oxygen densities and mean electron energies is demonstrated for an atmospheric pressure radio-frequency plasma jet. The proposed method is based on phase resolved optical emission measurements of the direct and dissociative electron-impact excitation dynamics of three distinct emission lines, namely, Ar 750.4 nm, O 777.4 nm, and O 844.6 nm. The energy dependence of these lines serves as basis for analysis by taking into account two line ratios. In this frame, the method is highly adaptable with regard to pressure and gas composition. Results are benchmarked against independent numerical simulations and two-photon absorption laser-induced fluorescence experiments.

  12. Backscattered electron imaging and windowless energy dispersive x-ray microanalysis: a new technique for gallstone analysis

    SciTech Connect

    Kaufman, H.S.; Lillemoe, K.D.; Magnuson, T.H.; Frasca, P.; Pitt, H.A. )

    1990-12-01

    Scanning electron microscopy with or without conventional energy dispersive x-ray microanalysis is currently used to identify gallstone microstructure and inorganic composition. Organic calcium salts are among many biliary constituents thought to have a role in gallstone nidation and growth. However, current analytical techniques which identify these salts are destructive and compromise gallstone microstructural data. We have developed a new technique for gallstone analysis which provides simultaneous structural and compositional identification of calcium salts within gallstones. Backscattered electron imaging is used to localize calcium within cholesterol at minimum concentrations of 0.01%. Windowless energy dispersive x-ray microanalysis produces elemental spectra of gallstone calcium salts which are qualitatively and quantitatively different. These combined techniques provide simultaneous structural and compositional information obtained from intact gallstone cross-sections and have been used to identify calcium salts in gallstones obtained at cholecystectomy from 106 patients.

  13. Clinical applications of scanning electron microscopy and energy dispersive X-ray analysis in dermatology--an up-date

    SciTech Connect

    Forslind, B.

    1988-06-01

    Dermatological papers comprising scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis data published 1983 through 1986 in international journals are reviewed, as an update to our 1984 paper on Clinical applications of scanning electron microscopy and X-ray microanalysis in dermatology. The present paper not only deals with a review of recent publications in this area but also presents the application of microincineration to hair and cryosectioned freeze-dried skin specimens. Examples of the increased contrast obtained in hair cross sections are presented and a discussion on the feasibility of microincineration at analysis of hair and skin cross sections is given. Particle probe analysis (EDX: energy dispersive X-ray analysis and PMP: proton microprobe analysis) as applied to hair and skin samples are presented with stress put on the proton probe analysis. The complementarity of EDX and PMP is demonstrated and future applications are suggested. 75 references.

  14. DETERMINING NEUTRON STAR MASSES AND RADII USING ENERGY-RESOLVED WAVEFORMS OF X-RAY BURST OSCILLATIONS

    SciTech Connect

    Lo, Ka Ho; Lamb, Frederick K.; Miller, M. Coleman; Bhattacharyya, Sudip

    2013-10-10

    Simultaneous, precise measurements of the mass M and radius R of neutron stars can yield uniquely valuable information about the still uncertain properties of cold matter at several times the density of nuclear matter. One method that could be used to measure M and R is to analyze the energy-dependent waveforms of the X-ray flux oscillations seen during some thermonuclear bursts from some neutron stars. These oscillations are thought to be produced by X-ray emission from hotter regions on the surface of the star that are rotating at or near the spin frequency of the star. Here we explore how well M and R could be determined by generating and analyzing, using Bayesian techniques, synthetic energy-resolved X-ray data that we produce assuming a future space mission having 2-30 keV energy coverage and an effective area of 10 m{sup 2}, such as the proposed Large Observatory for X-Ray Timing or Advanced X-Ray Timing Array missions. We find that waveforms from hot spots within 10° of the rotation equator usually constrain both M and R with an uncertainty of about 10%, if there are 10{sup 6} total counts from the spot, whereas waveforms from spots within 20° of the rotation pole provide no useful constraints. The constraints we report can usually be achieved even if the burst oscillations vary with time and data from multiple bursts must be used to obtain 10{sup 6} counts from the hot spot. This is therefore a promising method to constrain M and R tightly enough to discriminate strongly between competing models of cold, high-density matter.

  15. R-matrix analysis of the 236U(n,γ) reaction in the resolved resonance energy region

    NASA Astrophysics Data System (ADS)

    Mezentseva, Zh.; Berthoumieux, E.; Borella, A.; Cennini, P.; Furman, W.; Goverdovski, A.; Gunsing, F.; Mengoni, A.; Schillebeeckx, P.; Wynants, R.

    2009-01-01

    The neutron capture cross section of 236U was measured in the neutron energy range from 1 eV to 10 keV by the neutron time-of-flight method at the GELINA white pulsed neutron source of the Institute for Reference Materials and Measurements (IRMM) in Geel (Belgium). The gamma rays originating from neutron capture events were detected by two C6D6-based liquid scintillators using the pulse height weighting technique. The weighting function has been derived from Monte-Carlo simulations of the detector response to monoenergetic gamma rays. The sample under investigation with a total amount of 338 mg of 236U was located in the neutron beam at a distance of 28.6 m from the source. The shape of the neutron flux was determined by a 10B neutron counter, placed approximately 60 cm upstream in the neutron beam line. The neutron capture yield in the resolved resonance region up to 1 keV has been derived from time-of-flight spectra.

  16. R-matrix analysis of the {sup 236}U(n,{gamma}) reaction in the resolved resonance energy region

    SciTech Connect

    Mezentseva, Zh.; Berthoumieux, E.; Gunsing, F.; Cennini, P.; Furman, W.; Goverdovski, A.; Mengoni, A.

    2009-01-28

    The neutron capture cross section of {sup 236}U was measured in the neutron energy range from 1 eV to 10 keV by the neutron time-of-flight method at the GELINA white pulsed neutron source of the Institute for Reference Materials and Measurements (IRMM) in Geel (Belgium). The gamma rays originating from neutron capture events were detected by two C{sub 6}D{sub 6}-based liquid scintillators using the pulse height weighting technique. The weighting function has been derived from Monte-Carlo simulations of the detector response to monoenergetic gamma rays.The sample under investigation with a total amount of 338 mg of {sup 236}U was located in the neutron beam at a distance of 28.6 m from the source. The shape of the neutron flux was determined by a {sup 10}B neutron counter, placed approximately 60 cm upstream in the neutron beam line.The neutron capture yield in the resolved resonance region up to 1 keV has been derived from time-of-flight spectra.

  17. Rapid Homogeneous Immunoassay Based on Time-Resolved Förster Resonance Energy Transfer for Serodiagnosis of Acute Hantavirus Infection

    PubMed Central

    Hepojoki, Satu; Hedman, Klaus; Vapalahti, Olli; Vaheri, Antti

    2014-01-01

    We recently introduced a homogeneous immunoassay based on time-resolved Förster resonance energy transfer (TR-FRET) elicited by fluorophore-labeled antigen and fluorophore-labeled protein L, bound by an immunoglobulin. As the first clinical application, we employ this approach (LFRET) in serodiagnosis of Puumala hantavirus (PUUV) infection. A reference panel containing serum from individuals with acute (n = 21) or past (n = 17) PUUV infection and from PUUV-seronegative individuals (n = 20) was used to define the parameters. The clinical assay performance was evaluated with a prospectively collected serum panel (panel 2; n = 153). Based on the results for panel 1, the threshold for positivity was set at a signal level that was 3-fold over background, while those with a signal <3-fold over the background level were considered PUUV seronegative. With panel 1, 20/21 acute- and 7/10 past-infection samples induced positive signals, compared to 0/20 seronegatives. With panel 2, a positive signal was obtained in 39/40 acute- and 4/10 past-infection samples, as opposed to 7/103 seronegatives. However, after IgG depletion, 58/61 acute-infection samples were LFRET positive, while all past-infection and seronegative samples were negative, corresponding to 100% specificity and 95% sensitivity in detection of acute PUUV infection. We demonstrate that the novel immunoassay is a promising tool for rapid serodiagnosis of acute Puumala virus infection. PMID:25520445

  18. Computer simulation of the distribution of hexane in a lipid bilayer: spatially resolved free energy, entropy, and enthalpy profiles.

    PubMed

    MacCallum, Justin L; Tieleman, D Peter

    2006-01-11

    The partitioning behavior of small molecules in lipid bilayers is important in a variety of areas including membrane protein folding and pharmacology. However, the inhomogeneous nature of lipid bilayers on a nanometer length scale complicates experimental studies of membrane partitioning. To gain more insight in the partitioning of a small molecule into the lipid bilayer, we have carried out atomistic computer simulations of hexane in a dioleoyl phosphatidylcholine model membrane. We have been able to obtain spatially resolved free energy, entropy, enthalpy, and heat capacity profiles based on umbrella sampling calculations at three different temperatures. In agreement with experiment, hexane partitions preferentially to the center of the bilayer. This process is driven almost entirely by a favorable entropy change, consistent with the hydrophobic effect. In contrast, partitioning to the densest region of the acyl chains is dominated by a favorable enthalpy change with a small entropy change, which is consistent with the "nonclassical" hydrophobic effect or "bilayer" effect. We explain the features of the entropy and enthalpy profiles in terms of density and free volume in the system. PMID:16390139

  19. Interannual modulation of eddy kinetic energy in the northeastern South China Sea as revealed by an eddy-resolving OGCM

    NASA Astrophysics Data System (ADS)

    Sun, Zhongbin; Zhang, Zhiwei; Zhao, Wei; Tian, Jiwei

    2016-05-01

    Interannual modulation of eddy kinetic energy (EKE) in the northeastern South China Sea (NE-SCS) is investigated based on outputs of an eddy-resolving oceanic general circulation model between 1980 and 2014. The EKE displays distinct interannual modulations with periods between 1.5 and 7 years. The maximum peak-to-trough amplitude of the interannual modulation occurred during period 2004-2005, which was about 1.5-fold the time-mean EKE level. Further analysis suggested that interannual variability of EKE in the NE-SCS is primarily modulated by the Luzon Strait transport (LST). During high-EKE years, the LST increases corresponding to a strengthened Kuroshio intrusion. The strengthened Kuroshio intrusion enhances the baroclinic instability of current in the NE-SCS and thus leads to a strong EKE. The reverse is true during low-EKE years when LST is smaller. Influences of ENSO and Pacific mesoscale eddies on the interannual modulation of LST are also discussed in this study.

  20. Resolving the High-energy Universe with Strong Gravitational Lensing: The Case of PKS 1830-211

    NASA Astrophysics Data System (ADS)

    Barnacka, Anna; Geller, Margaret J.; Dell'Antonio, Ian P.; Benbow, Wystan

    2015-08-01

    Gravitational lensing is a potentially powerful tool for elucidating the origin of gamma-ray emission from distant sources. Cosmic lenses magnify the emission from distant sources and produce time delays between mirage images. Gravitationally induced time delays depend on the position of the emitting regions in the source plane. The Fermi/LAT telescope continuously monitors the entire sky and detects gamma-ray flares, including those from gravitationally lensed blazars. Therefore, temporal resolution at gamma-ray energies can be used to measure these time delays, which, in turn, can be used to resolve the origin of the gamma-ray flares spatially. We provide a guide to the application and Monte Carlo simulation of three techniques for analyzing these unresolved light curves: the autocorrelation function, the double power spectrum, and the maximum peak method. We apply these methods to derive time delays from the gamma-ray light curve of the gravitationally lensed blazar PKS 1830-211. The result of temporal analysis combined with the properties of the lens from radio observations yield an improvement in spatial resolution at gamma-ray energies by a factor of 10,000. We analyze four active periods. For two of these periods the emission is consistent with origination from the core, and for the other two the data suggest that the emission region is displaced from the core by more than ˜1.5 kpc. For the core emission, the gamma-ray time delays, 23+/- 0.5 {days} and 19.7+/- 1.2 days, are consistent with the radio time delay of {26}-5+4 days.

  1. Time-resolved characterization and energy balance analysis of implosion core in shock-ignition experiments at OMEGA

    SciTech Connect

    Florido, R. Mancini, R. C.; Nagayama, T.; Tommasini, R.; Delettrez, J. A.; Regan, S. P.

    2014-10-15

    Time-resolved temperature and density conditions in the core of shock-ignition implosions have been determined for the first time. The diagnostic method relies on the observation, with a streaked crystal spectrometer, of the signature of an Ar tracer added to the deuterium gas fill. The data analysis confirms the importance of the shell attenuation effect previously noted on time-integrated spectroscopic measurements of thick-wall targets [R. Florido et al., Phys. Rev. E 83, 066408 (2011)]. This effect must be taken into account in order to obtain reliable results. The extracted temperature and density time-histories are representative of the state of the core during the implosion deceleration and burning phases. As a consequence of the ignitor shock launched by the sharp intensity spike at the end of the laser pulse, observed average core electron temperature and mass density reach T ∼ 1100 eV and ρ ∼ 2 g/cm{sup 3}; then temperature drops to T ∼ 920 eV while density rises to ρ ∼ 3.4 g/cm{sup 3} about the time of peak compression. Compared to 1D hydrodynamic simulations, the experiment shows similar maximum temperatures and smaller densities. Simulations do not reproduce all observations. Differences are noted in the heating dynamics driven by the ignitor shock and the optical depth time-history of the compressed shell. Time-histories of core conditions extracted from spectroscopy show that the implosion can be interpreted as a two-stage polytropic process. Furthermore, an energy balance analysis of implosion core suggests an increase in total energy greater than what 1D hydrodynamic simulations predict. This new methodology can be implemented in other ICF experiments to look into implosion dynamics and help to understand the underlying physics.

  2. Electron-probe quantitative energy-dispersive analysis of trace magnesium concentrations in Ag-Mg alloys

    SciTech Connect

    Marinenko, R.B.

    1996-12-31

    Internally oxidized Ag-Mg alloys are used as sheaths for high Tc superconductor wires because of their superior mechanical properties. The preparation and characteristics of these materials have been reported. Performance of the sheaths depends on the concentration of the magnesium which generally is less than 0.5 wt. percent. The purpose of this work was to determine whether electron probe microanalysis using energy dispersive spectrometry (EDS) could be used to quantitate three different Ag-Mg alloys. Quantitative EDS analysis can be difficult because the AgL escape peak occurs at the same energy (1.25 keV) as the Mg K{alpha} peak.

  3. EVALUATION OF MIXING ENERGY IN LABORATORY FLASKS USED FOR DISPERSANT EFFECTIVENESS TESTING

    EPA Science Inventory

    The evaluation of dispersant effectiveness used for oil spills is commonly done using tests conducted in laboratory flasks. The success of a test relies on replication of the conditions at sea. We used a hot wire anemometer to characterize the turbulence characteristics in the s...

  4. Comparison of quantitative k-edge empirical estimators using an energy-resolved photon-counting detector

    NASA Astrophysics Data System (ADS)

    Zimmerman, Kevin C.; Gilat Schmidt, Taly

    2016-03-01

    Using an energy-resolving photon counting detector, the amount of k-edge material in the x-ray path can be estimated using a process known as material decomposition. However, non-ideal effects within the detector make it difficult to accurately perform this decomposition. This work evaluated the k-edge material decomposition accuracy of two empirical estimators. A neural network estimator and a linearized maximum likelihood estimator with error look-up tables (A-table method) were evaluated through simulations and experiments. Each estimator was trained on system-specific calibration data rather than specific modeling of non-ideal detector effects or the x-ray source spectrum. Projections through a step-wedge calibration phantom consisting of different path lengths through PMMA, aluminum, and a k-edge material was used to train the estimators. The estimators were tested by decomposing data acquired through different path lengths of the basis materials. The estimators had similar performance in the chest phantom simulations with gadolinium. They estimated four of the five densities of gadolinium with less than 2mg/mL bias. The neural networks estimates demonstrated lower bias but higher variance than the A-table estimates in the iodine contrast agent simulations. The neural networks had an experimental variance lower than the CRLB indicating it is a biased estimator. In the experimental study, the k-edge material contribution was estimated with less than 14% bias for the neural network estimator and less than 41% bias for the A-table method.

  5. Identification of Pregnane X Receptor Ligands Using Time-Resolved Fluorescence Resonance Energy Transfer and Quantitative High-Throughput Screening

    PubMed Central

    Shukla, Sunita J.; Nguyen, Dac-Trung; MacArthur, Ryan; Simeonov, Anton; Frazee, William J.; Hallis, Tina M.; Marks, Bryan D.; Singh, Upinder; Eliason, Hildegard C.; Printen, John; Austin, Christopher P.; Inglese, James

    2009-01-01

    Abstract The human pregnane X nuclear receptor (PXR) is a xenobiotic-regulated receptor that is activated by a range of diverse chemicals, including antibiotics, antifungals, glucocorticoids, and herbal extracts. PXR has been characterized as an important receptor in the metabolism of xenobiotics due to induction of cytochrome P450 isozymes and activation by a large number of prescribed medications. Developing methodologies that can efficiently detect PXR ligands will be clinically beneficial to avoid potential drug–drug interactions. To facilitate the identification of PXR ligands, a time-resolved fluorescence resonance energy transfer (TR-FRET) assay was miniaturized to a 1,536-well microtiter plate format to employ quantitative high-throughput screening (qHTS). The optimized 1,536-well TR-FRET assay showed Z′-factors of ≥0.5. Seven- to 15-point concentration–response curves (CRCs) were generated for 8,280 compounds using both terbium and fluorescein emission data, resulting in the generation of 241,664 data points. The qHTS method allowed us to retrospectively examine single concentration screening datasets to assess the sensitivity and selectivity of the PXR assay at different compound screening concentrations. Furthermore, nonspecific assay artifacts such as concentration-based quenching of the terbium signal and compound fluorescence were identified through the examination of CRCs for specific emission channels. The CRC information was also used to define chemotypes associated with PXR ligands. This study demonstrates the feasibility of profiling thousands of compounds against PXR using the TR-FRET assay in a high-throughput format. PMID:19505231

  6. Full Genotyping of a Highly Polymorphic Human Gene Trait by Time-Resolved Fluorescence Resonance Energy Transfer

    PubMed Central

    Totè, Edoardo; Lamperti, Marco; Bondani, Maria; Salerno, Domenico; Cassina, Valeria; Nardo, Luca

    2014-01-01

    The ability of detecting the subtle variations occurring, among different individuals, within specific DNA sequences encompassed in highly polymorphic genes discloses new applications in genomics and diagnostics. DQB1 is a gene of the HLA-II DQ locus of the Human Leukocyte Antigens (HLA) system. The polymorphisms of the trait of the DQB1 gene including codons 52–57 modulate the susceptibility to a number of severe pathologies. Moreover, the donor-receiver tissue compatibility in bone marrow transplantations is routinely assessed through crossed genotyping of DQB and DQA. For the above reasons, the development of rapid, reliable and cost-effective typing technologies of DQB1 in general, and more specifically of the codons 52–57, is a relevant although challenging task. Quantitative assessment of the fluorescence resonance energy transfer (FRET) efficiency between chromophores labelling the opposite ends of gene-specific oligonucleotide probes has proven to be a powerful tool to type DNA polymorphisms with single-nucleotide resolution. The FRET efficiency can be most conveniently quantified by applying a time-resolved fluorescence analysis methodology, i.e. time-correlated single-photon counting, which allows working on very diluted template specimens and in the presence of fluorescent contaminants. Here we present a full in-vitro characterization of the fluorescence responses of two probes when hybridized to oligonucleotide mixtures mimicking all the possible genotypes of the codons 52–57 trait of DQB1 (8 homozygous and 28 heterozygous). We show that each genotype can be effectively tagged by the combination of the fluorescence decay constants extrapolated from the data obtained with such probes. PMID:25215592

  7. A Vinblastine Fluorescent Probe for Pregnane X Receptor in a Time-Resolved Fluorescence Resonance Energy Transfer Assay

    PubMed Central

    Lin, Wenwei; Chen, Taosheng

    2013-01-01

    The pregnane X receptor (PXR) regulates the metabolism and excretion of xenobiotics and endobiotics by regulating the expression of drug-metabolizing enzymes and transporters. The unique structure of PXR allows the binding of many drugs and drug leads to it, possibly causing undesired drug-drug interactions. Therefore, it is crucial to evaluate whether lead compounds bind to PXR. Fluorescence-based assays are preferred because of their sensitivity and non-radioactive nature. One fluorescent PXR probe is currently commercially available; however, because its chemical structure is not publicly disclosed, it is not optimal for studying ligand-PXR interactions. Here we report the characterization of BODIPY FL Vinblastine, generated by labeling vinblastine with the fluorophore 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY FL), as a high-affinity ligand for human PXR with a Kd value of 673 nM. We provide evidence that BODIPY FL Vinblastine is a unique chemical entity different from either vinblastine or the fluorophore 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene in its function as a high-affinity human PXR ligand. We describe a BODIPY FL Vinblastine-based human PXR Time-Resolved Fluorescence Resonance Energy Transfer assay, which was used to successfully test a panel of human PXR ligands. The BODIPY FL Vinblastine–based biochemical assay is suitable for high-throughput screening to evaluate whether lead compounds bind to PXR. PMID:24044991

  8. Rayleigh-wave dispersive energy imaging and mode separating by high-resolution linear Radon transform

    USGS Publications Warehouse

    Luo, Y.; Xu, Y.; Liu, Q.; Xia, J.

    2008-01-01

    In recent years, multichannel analysis of surface waves (MASW) has been increasingly used for obtaining vertical shear-wave velocity profiles within near-surface materials. MASW uses a multichannel recording approach to capture the time-variant, full-seismic wavefield where dispersive surface waves can be used to estimate near-surface S-wave velocity. The technique consists of (1) acquisition of broadband, high-frequency ground roll using a multichannel recording system; (2) efficient and accurate algorithms that allow the extraction and analysis of 1D Rayleigh-wave dispersion curves; (3) stable and efficient inversion algorithms for estimating S-wave velocity profiles; and (4) construction of the 2D S-wave velocity field map.

  9. A discussion of the dispersion curve of energy excitations in liquid 4He

    NASA Astrophysics Data System (ADS)

    Bogoyavlenskii, I. V.; Puchkov, A. V.; Skomorokhov, A. N.; Karnatsevich, L. V.

    2004-10-01

    An investigation of the dispersion of excitations in a quantum liquid, superfluid 4He, is carried out. An attempt is made to systematize the published experimental data that indicate a substantially different nature of excitations with wave vectors corresponding to different parts of the dispersion curve of liquid 4He. Neutron spectroscopy data are analyzed in relation to a certain physical hypothesis concerning the formation of such a spectrum, and it is found that the majority of the known experimental facts can be explained in framework of that hypothesis. Particular attention is paid to a comparison of the experimental data obtained on the DIN-2PI time-of-flight spectrometer (at the IBR-2 Reactor, Dubna) with the results obtained at foreign research centers.

  10. Influence of ultrasonic energy on dispersion of aggregates and released amounts of organic matter and polyvalent cations

    NASA Astrophysics Data System (ADS)

    Kaiser, M.; Kleber, M.; Berhe, A. A.

    2010-12-01

    Aggregates play important roles in soil carbon storage and stabilization. Identification of scale-dependent mechanisms of soil aggregate formation and stability is necessary to predict and eventually manage the flow of carbon through terrestrial ecosystems. Application of ultrasonic energy is a common tool to disperse soil aggregates. In this study, we used ultra sonic energy (100 to 2000 J cm-3) to determine the amount of polyvalent cations and organic matter involved in aggregation processes in three arable and three forest soils that varied in soil mineral composition. To determine the amount of organic matter and cations released after application of different amount of ultrasonic energy, we removed the coarse fraction (>250 µm). The remaining residue (<250 µm) was mixed with water and ultrasonically dispersed by application of 100, 200, 400, 500, 1000, 1500 and 2000 J cm-3 energy. After centrifugation the supernatant was filtered and the solid residue freeze dried before we analyzed the amounts of water-extracted organic carbon (OC), Fe, Al, Ca, Mn, and Mg in the filtrates. The extracted OM and solid residues were further characterized by Fourier Transformed Infra Red spectroscopy and Scanning Electron Microscopy. Our results show a linear increase in amount of dissolved OC with increasing amounts of ultra sonic energy up to 1500 J cm-3 indicating maximum dispersion of soil aggregates at this energy level independent from soil type or land use. In contrast to Mn, and Mg, the amounts of dissolved Ca, Fe, and Al increase with increasing ultra sonic energy up to 1500 J cm-3. At 1500 J cm-3, the absolute amounts of OC, Ca, Fe, and Al released were specific for each soil type, likely indicating differences in type of OM-mineral interactions involved in micro-scaled aggregation processes. The amounts of dissolved Fe, and Al released after an application of 1500 J cm-3 are not related to oxalate- and dithionite- extractable, or total Al content indicating less

  11. Probing Heterogeneous Chemistry of Individual Atmospheric Particles Using Scanning Electron Microscopy and Energy-Dispersive X-ray Analysis

    SciTech Connect

    Krueger, Brenda J.; Grassian, Vicki H.; Iedema, Martin J.; Cowin, James P.; Laskin, Alexander

    2003-10-01

    In this paper, we demonstrate the utility of single-particle analysis to investigate the chemistry of isolated, individual particles of atmospheric relevance such as NaCl, sea salt, CaCO3, and SiO2. A variety of state-of-th-art scanning electron microscopy techniques, including environmental scanning electon microscopy and computer-controlled scanning electron microscopy/energy-dispersive X-ray analysis, were utilized for monitoring and quantifying phase transitions of individual particles, morphology, and compositional changes of individual particles as they react with nitric acid.

  12. In situ multi-element analyses by energy-dispersive X-ray fluorescence on varnishes of historical violins

    NASA Astrophysics Data System (ADS)

    Echard, Jean-Philippe

    2004-10-01

    Varnishes of Italian violins and other historical stringed instruments have been analyzed by energy-dispersive X-ray fluorescence (EDXRF). The instruments whose varnishes were to be analyzed were chosen from the collection kept in Musée de la Musique in Paris. Direct analyses were performed on instrument varnishes, without any sampling and non-destructively, showing inorganic elements such as lead, mercury and iron that could be related to siccatives or pigments. Analytical results and their comparison with old formulae or traditional recipes of violin varnishes, as with the few previous analytical results, will be discussed.

  13. Determining the cohesive energy of coronene by dispersion-corrected DFT methods: Periodic boundary conditions vs. molecular pairs

    NASA Astrophysics Data System (ADS)

    Sancho-García, J. C.; Pérez-Jiménez, A. J.; Olivier, Y.

    2015-02-01

    We investigate the cohesive energy of crystalline coronene by the dispersion-corrected methods DFT-D2, DFT-D3, and DFT-NL. For that purpose, we first employ bulk periodic boundary conditions and carefully analyze next all the interacting pairs of molecules within the crystalline structure. Our calculations reveal the nature and importance of the binding forces in every molecular pair tackled and provide revised estimates of the effects of two- and three-body terms, leading to accurate results in close agreement with experimental (sublimation enthalpies) reference values.

  14. Multi-element analysis of pyrite ores using polarized energy-dispersive X-ray fluorescence spectrometry.

    PubMed

    Ustündağ, Zafer; Ustündağ, Ilknur; Kağan Kadioğlu, Yusuf

    2007-07-01

    X-ray fluorescence (XRF) spectrometry is used worldwide in geological material analysis. This study, applies polarized energy-dispersive X-ray fluorescence (PEDXRF) Spectrometer and compares in the samples of Rize-Cayeli and Mardin pyrite ores. The samples of pyrite ore were collected from the Rize and Mardin in Turkey. The prepared samples were analyzed using a PEDXRF spectrometer. The result of the analysis shows the presence of many elements including rare-earth elements (from Na to Th). The accuracy and precision of the technique for chemical analysis is demonstrated by analyzing USGS standards, GEOL, GBW 7109 and GBW-7309 sediment. PMID:17459714

  15. A new background subtraction method for energy dispersive X-ray fluorescence spectra using a cubic spline interpolation

    NASA Astrophysics Data System (ADS)

    Yi, Longtao; Liu, Zhiguo; Wang, Kai; Chen, Man; Peng, Shiqi; Zhao, Weigang; He, Jialin; Zhao, Guangcui

    2015-03-01

    A new method is presented to subtract the background from the energy dispersive X-ray fluorescence (EDXRF) spectrum using a cubic spline interpolation. To accurately obtain interpolation nodes, a smooth fitting and a set of discriminant formulations were adopted. From these interpolation nodes, the background is estimated by a calculated cubic spline function. The method has been tested on spectra measured from a coin and an oil painting using a confocal MXRF setup. In addition, the method has been tested on an existing sample spectrum. The result confirms that the method can properly subtract the background.

  16. Benzyne-functionalized graphene and graphite characterized by Raman spectroscopy and energy dispersive X-ray analysis

    PubMed Central

    Magedov, Igor V.; Frolova, Lilia V.; Ovezmyradov, Mekan; Bethke, Donald; Shaner, Eric A.; Kalugin, Nikolai G.

    2012-01-01

    The benzyne functionalization of chemical vapor deposition grown large area graphene and graphite was performed using a mixture of o-trimethylsilylphenyl triflate and cesium fluoride that react with the carbon surface. The reaction requires at least 2 days of treatment before the appearance of Raman and energy-dispersive X-ray spectral signatures that verify modification. Raman spectra of modified graphene and graphite show a rich structure of lines corresponding to C=C-C, C-H, and low frequency modes of surface-attached benzyne rings. PMID:23505324

  17. Dose-rate controlled energy dispersive x-ray spectroscopic mapping of the metallic components in a biohybrid nanosystem

    NASA Astrophysics Data System (ADS)

    Zhu, Yuanyuan; Munro, Catherine J.; Olszta, Matthew J.; Edwards, Danny J.; Braunschweig, Adam B.; Knecht, Marc R.; Browning, Nigel D.

    2016-08-01

    In this work, we showcase that through precise control of the electron dose rate, state-of-the-art large solid angle energy dispersive x-ray spectroscopy mapping in aberration-corrected scanning transmission electron microscope is capable of faithful and unambiguous chemical characterization of the Pt and Pd distribution in a peptide-mediated nanosystem. This low-dose-rate recording scheme adds another dimension of flexibility to the design of elemental mapping experiments, and holds significant potential for extending its application to a wide variety of beam sensitive hybrid nanostructures.

  18. Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

    SciTech Connect

    Bromberger, H. Liu, H.; Chávez-Cervantes, M.; Gierz, I.; Ermolov, A.; Belli, F.; Abdolvand, A.; Russell, P. St. J.; Travers, J. C.; Calegari, F.; Li, M. T.; Lin, C. T.; Cavalleri, A.

    2015-08-31

    A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi{sub 2}Se{sub 3} with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials.

  19. Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Bromberger, H.; Ermolov, A.; Belli, F.; Liu, H.; Calegari, F.; Chávez-Cervantes, M.; Li, M. T.; Lin, C. T.; Abdolvand, A.; Russell, P. St. J.; Cavalleri, A.; Travers, J. C.; Gierz, I.

    2015-08-01

    A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi2Se3 with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials.

  20. Calibration and energy resolution study of a high dispersive power Thomson Parabola Spectrometer with monochromatic proton beams

    NASA Astrophysics Data System (ADS)

    Schillaci, F.; Maggiore, M.; Velyhan, A.; Cirrone, G. A. P.; Cuttone, G.; Margarone, D.; Parasiliti Palumbo, G.; Pisciotta, P.; Rifuggiato, D.; Romano, F.; Russo, G.; Scuderi, V.; Stancampiano, C.; Tramontana, A.; Amato, A.; Caruso, G. F.; Salamone, S.

    2014-10-01

    A high energy resolution, high dispersive power Thomson Parabola Spectrometer has been developed at INFN-LNS in order to characterize laser-driven beams up to 30- 40 MeV for protons. This device has parallel electric and magnetic field to deflect particles of a certain charge-to-mass ratio onto parabolic traces on the detection plane. Calibration of the deflection sector is crucial for data analysis, namely energy determination of analysed beam, and to evaluate the effective energy limit and resolution. This work reports the study of monochromatic proton beams delivered by the TANDEM accelerator at LNS (Catania) in the energy range between 6 and 12.5 MeV analysed with our spectrometer which allows a precise characterization of the electric and magnetic deflections. Also the energy and the Q/A resolutions and the energy limits have been evaluated proposing a mathematical model that can be used for data analysis, for the experimental set up and for the device scalability for higher energy.

  1. Engineering Strategies and Methods for Avoiding Air-Quality Externalities: Dispersion Modeling, Home Energy Conservation, and Scenario Planning

    NASA Astrophysics Data System (ADS)

    Knox, Andrew James

    Energy conservation can improve air quality by reducing emissions from fuel combustion. The human health value retained through better air quality can then offset the cost of energy conservation. Through this thesis' innovative yet widely-accessible combination of air pollution dispersion modeling and atmospheric chemistry, it is estimated that the health value retained by avoiding emissions from Ontario's former coal-fired generating stations is 5.74/MWh (using an upper-bound value of 265,000 per year of life lost). This value is combined with energy modeling of homes in the first-ever assessment of the air-quality health benefits of low-energy buildings. It is shown that avoided health damages can equal 7% of additional construction costs of energy efficient buildings in Ontario. At 7%, health savings are a significant item in the cost analysis of efficient buildings. Looking to energy efficiency in the context of likely future low-resource natural gas scenarios, building efficient buildings today is shown to be more economically efficient than any building retrofit option. Considering future natural gas scarcity in the context of Ontario's Long-Term Energy Plan reveals that Ontario may be forced to return to coal-fired electricity. Projected coal use would result in externalities greater than $600 million/year; 80% more than air-quality externalities from Ontario's electricity in 1985. Radically aggressive investment in electricity conservation (75% reduction per capita by 2075) is one promising path forward that keeps air-quality externalities below 1985 levels. Non-health externalities are an additional concern, the quantification, and ultimately monetization, of which could be practical using emerging air pollution monitoring technologies. Energy, conservation, energy planning, and energy's externalities form a complex situation in which today's decisions are critical to a successful future. It is clear that reducing the demand for energy is essential and

  2. Investigation of the dispersion and the effective masses of excitons in bulk 2 H -MoS2 using transition electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Habenicht, Carsten; Knupfer, Martin; Büchner, Bernd

    2015-06-01

    We have investigated the electronic excitations in bulk 2 H -MoS2 using electron energy-loss spectroscopy. The electron energy-loss spectra in the Γ M and Γ K directions were measured for various momentum transfer values. The results allow the identification of the A1 and B1 exciton peaks and in particular their energy-momentum dispersion. The dispersions exhibit approximately quadratic upward trends and slight anisotropies in the Γ M and Γ K directions. The fitted energy-momentum transfer functions allow the estimation of the effective masses of the excitons which are in close proximity to predicted values.

  3. Oil dispersants

    SciTech Connect

    Flaherty, L.M.

    1989-01-01

    This book contains papers presented at a symposium of the American Society for Testing and Materials. The topics covered include: The effect of elastomers on the efficiency of oil spill dispersants; planning for dispersant use; field experience with dispersants for oil spills on land; and measurements on natural dispersion.

  4. Design and Performance of a TES X-ray Microcalorimeter Array for Energy Dispersive Spectroscopy on Scanning Transmission Electron Microscope

    NASA Astrophysics Data System (ADS)

    Muramatsu, Haruka; Nagayoshi, K.; Hayashi, T.; Sakai, K.; Yamamoto, R.; Mitsuda, K.; Yamasaki, N. Y.; Maehata, K.; Hara, T.

    2016-07-01

    We discuss the design and performance of a transition edge sensor (TES) X-ray microcalorimeter array for scanning transmission electron microscope (STEM)-energy dispersive X-ray spectroscopy (EDS). The TES X-ray microcalorimeter has better energy resolution compared to conventional silicon drift detector and STEM-EDS utilizing a TES detector makes it possible to map the distribution of elements on a specimen in addition to analyze the composition. The requirement for a TES detector is a high counting rate (>20 kcps), wide energy band (0.5-15 keV) and good energy resolution (<10 eV) full width at half maximum. The major improvement of this development is to increase the maximum counting rate. In order to accommodate the high counting rate, we adopted an 8 × 8 format, 64-pixel array and common biasing scheme for the readout method. We did all design and fabrication of the device in house. With the device we have fabricated most recently, the pulse decay time is 40 \\upmu s which is expected to achieve 50 kcps. For a single pixel, the measured energy resolution was 7.8 eV at 5.9 keV. This device satisfies the requirements of counting rate and energy resolution, although several issues remain where the performance must be confirmed.

  5. Design and Performance of a TES X-ray Microcalorimeter Array for Energy Dispersive Spectroscopy on Scanning Transmission Electron Microscope

    NASA Astrophysics Data System (ADS)

    Muramatsu, Haruka; Nagayoshi, K.; Hayashi, T.; Sakai, K.; Yamamoto, R.; Mitsuda, K.; Yamasaki, N. Y.; Maehata, K.; Hara, T.

    2016-02-01

    We discuss the design and performance of a transition edge sensor (TES) X-ray microcalorimeter array for scanning transmission electron microscope (STEM)-energy dispersive X-ray spectroscopy (EDS). The TES X-ray microcalorimeter has better energy resolution compared to conventional silicon drift detector and STEM-EDS utilizing a TES detector makes it possible to map the distribution of elements on a specimen in addition to analyze the composition. The requirement for a TES detector is a high counting rate (> 20 kcps), wide energy band (0.5-15 keV) and good energy resolution (< 10 eV) full width at half maximum. The major improvement of this development is to increase the maximum counting rate. In order to accommodate the high counting rate, we adopted an 8 × 8 format, 64-pixel array and common biasing scheme for the readout method. We did all design and fabrication of the device in house. With the device we have fabricated most recently, the pulse decay time is 40 \\upmu s which is expected to achieve 50 kcps. For a single pixel, the measured energy resolution was 7.8 eV at 5.9 keV. This device satisfies the requirements of counting rate and energy resolution, although several issues remain where the performance must be confirmed.

  6. Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation**

    PubMed Central

    Schomakers, Jasmin; Zehetner, Franz; Mentler, Axel; Ottner, Franz; Mayer, Herwig

    2016-01-01

    It has been increasingly recognized that soil organic matter stabilization is strongly controlled by physical binding within soil aggregates. It is therefore essential to measure soil aggregate stability reliably over a wide range of disruptive energies and different aggregate sizes. To this end, we tested high-accuracy ultrasonic dispersion in combination with subsequent sedimentation and X-ray attenuation. Three arable topsoils (notillage) from Central Europe were subjected to ultrasound at four different specific energy levels: 0.5, 6.7, 100 and 500 J cm−3, and the resulting suspensions were analyzed for aggregate size distribution by wet sieving (2 000-63 μm) and sedimentation/X-ray attenuation (63-2 μm). The combination of wet sieving and sedimentation technique allowed for a continuous analysis, at high resolution, of soil aggregate breakdown dynamics after defined energy inputs. Our results show that aggregate size distribution strongly varied with sonication energy input and soil type. The strongest effects were observed in the range of low specific energies (< 10 J cm−3), which previous studies have largely neglected. This shows that low ultrasonic energies are required to capture the full range of aggregate stability and release of soil organic matter upon aggregate breakdown. PMID:27099408

  7. Design and Performance of a TES X-ray Microcalorimeter Array for Energy Dispersive Spectroscopy on Scanning Transmission Electron Microscope

    NASA Astrophysics Data System (ADS)

    Muramatsu, Haruka; Nagayoshi, K.; Hayashi, T.; Sakai, K.; Yamamoto, R.; Mitsuda, K.; Yamasaki, N. Y.; Maehata, K.; Hara, T.

    2016-07-01

    We discuss the design and performance of a transition edge sensor (TES) X-ray microcalorimeter array for scanning transmission electron microscope (STEM)-energy dispersive X-ray spectroscopy (EDS). The TES X-ray microcalorimeter has better energy resolution compared to conventional silicon drift detector and STEM-EDS utilizing a TES detector makes it possible to map the distribution of elements on a specimen in addition to analyze the composition. The requirement for a TES detector is a high counting rate (>20 kcps), wide energy band (0.5-15 keV) and good energy resolution (<10 eV) full width at half maximum. The major improvement of this development is to increase the maximum counting rate. In order to accommodate the high counting rate, we adopted an 8 × 8 format, 64-pixel array and common biasing scheme for the readout method. We did all design and fabrication of the device in house. With the device we have fabricated most recently, the pulse decay time is 40 μs which is expected to achieve 50 kcps. For a single pixel, the measured energy resolution was 7.8 eV at 5.9 keV. This device satisfies the requirements of counting rate and energy resolution, although several issues remain where the performance must be confirmed.

  8. Portable energy dispersive X-ray fluorescence and X-ray diffraction and radiography system for archaeometry

    NASA Astrophysics Data System (ADS)

    Mendoza Cuevas, Ariadna; Perez Gravie, Homero

    2011-03-01

    Starting on a laboratory developed portable X-ray fluorescence (PXRF) spectrometer; three different analytical results can be performed: analysis of chemical elements, analysis of major chemical crystalline phase and structural analysis, which represents a contribution to a new, low cost development of portable X-ray analyzer; since these results are respectively obtained with independent equipments for X-ray fluorescence, X-ray diffraction and radiography. Detection limits of PXRF were characterized using standard reference materials for ceramics, glass, bronze and bones, which are the main materials requiring quantitative analysis in art and archeological objects. A setup for simultaneous energy dispersive X-ray fluorescence and diffraction (ED (XRF-XRD)) in the reflection mode has been tested for in situ and non-destructive analysis according to the requirements of art objects inspection. The system uses a single low power X-ray tube and an X-ray energy dispersive detector to measure X-ray diffraction spectrum at a fixed angle. Application to the identification of jadeite-jade mineral in archeological objects by XRD is presented. A local high resolution radiography image obtained with the same low power X-ray tube allows for studies in painting and archeological bones.

  9. Methodology toward 3D micro X-ray fluorescence imaging using an energy dispersive charge-coupled device detector.

    PubMed

    Garrevoet, Jan; Vekemans, Bart; Tack, Pieter; De Samber, Björn; Schmitz, Sylvia; Brenker, Frank E; Falkenberg, Gerald; Vincze, Laszlo

    2014-12-01

    A new three-dimensional (3D) micro X-ray fluorescence (μXRF) methodology based on a novel 2D energy dispersive CCD detector has been developed and evaluated at the P06 beamline of the Petra-III storage ring (DESY) in Hamburg, Germany. This method is based on the illumination of the investigated sample cross-section by a horizontally focused beam (vertical sheet beam) while fluorescent X-rays are detected perpendicularly to the sheet beam by a 2D energy dispersive (ED) CCD detector allowing the collection of 2D cross-sectional elemental images of a certain depth within the sample, limited only by signal self-absorption effects. 3D elemental information is obtained by a linear scan of the sample in the horizontal direction across the vertically oriented sheet beam and combining the detected cross-sectional images into a 3D elemental distribution data set. Results of the 3D μXRF analysis of mineral inclusions in natural deep Earth diamonds are presented to illustrate this new methodology. PMID:25346101

  10. One-loop omega-potential of quantum fields with ellipsoid constant-energy surface dispersion law

    NASA Astrophysics Data System (ADS)

    Kazinski, P. O.; Shipulya, M. A.

    2011-10-01

    Rapidly convergent expansions of a one-loop contribution to the partition function of quantum fields with ellipsoid constant-energy surface dispersion law are derived. The omega-potential is naturally decomposed into three parts: the quasiclassical contribution, the contribution from the branch cut of the dispersion law, and the oscillating part. The low- and high-temperature expansions of the quasiclassical part are obtained. An explicit expression and a relation of the contribution from the cut with the Casimir term and vacuum energy are established. The oscillating part is represented in the form of the Chowla-Selberg expansion of the Epstein zeta function. Various resummations of this expansion are considered. The general procedure developed is then applied to two models: massless particles in a box both at zero and nonzero chemical potential, and electrons in a thin metal film. Rapidly convergent expansions of the partition function and average particle number are obtained for these models. In particular, the oscillations of the chemical potential of conduction electrons in graphene and a thin metal film due to a variation of size of the crystal are described.

  11. Defining the contributions of permanent electrostatics, Pauli repulsion, and dispersion in density functional theory calculations of intermolecular interaction energies.

    PubMed

    Horn, Paul R; Mao, Yuezhi; Head-Gordon, Martin

    2016-03-21

    In energy decomposition analysis of Kohn-Sham density functional theory calculations, the so-called frozen (or pre-polarization) interaction energy contains contributions from permanent electrostatics, dispersion, and Pauli repulsion. The standard classical approach to separate them suffers from several well-known limitations. We introduce an alternative scheme that employs valid antisymmetric electronic wavefunctions throughout and is based on the identification of individual fragment contributions to the initial supersystem wavefunction as determined by an energetic optimality criterion. The density deformations identified with individual fragments upon formation of the initial supersystem wavefunction are analyzed along with the distance dependence of the new and classical terms for test cases that include the neon dimer, ammonia borane, water-Na(+), water-Cl(-), and the naphthalene dimer. PMID:27004862

  12. The effect of silica on polymorphic precipitation of calcium carbonate: an on-line energy-dispersive X-ray diffraction (EDXRD) study

    NASA Astrophysics Data System (ADS)

    Kellermeier, Matthias; Glaab, Fabian; Klein, Regina; Melero-García, Emilio; Kunz, Werner; García-Ruiz, Juan Manuel

    2013-07-01

    Calcium carbonate is the most abundant biomineral and a compound of great industrial importance. Its precipitation from solution has been studied extensively and was often shown to proceed via distinct intermediate phases, which undergo sequential transformations before eventually yielding the stable crystalline polymorph, calcite. In the present work, we have investigated the crystallisation of calcium carbonate in a time-resolved and non-invasive manner by means of energy-dispersive X-ray diffraction (EDXRD) using synchrotron radiation. In particular, the role of silica as a soluble additive during the crystallisation process was examined. Measurements were carried out at different temperatures (20, 50 and 80 °C) and various silica concentrations. Experiments conducted in the absence of silica reflect the continuous conversion of kinetically formed metastable polymorphs (vaterite and aragonite) to calcite and allow for quantifying the progress of transformation. Addition of silica induced remarkable changes in the temporal evolution of polymorphic fractions existing in the system. Essentially, the formation of calcite was found to be accelerated at 20 °C, whereas marked retardation or complete inhibition of phase transitions was observed at higher temperatures. These findings are explained in terms of a competition between the promotional effect of silica on calcite growth rates and kinetic stabilisation of vaterite and aragonite due to adsorption (or precipitation) of silica on their surfaces, along with temperature-dependent variations of silica condensation rates. Data collected at high silica concentrations indicate the presence of an amorphous phase over extended frames of time, suggesting that initially generated ACC particles are progressively stabilised by silica. Our results may have important implications for CaCO3 precipitation scenarios in both geochemical and industrial settings, where solution silicate is omnipresent, as well as for CO2

  13. Energy partitioning and impulse dispersion in the decorated, tapered, strongly nonlinear granular alignment: A system with many potential applications

    NASA Astrophysics Data System (ADS)

    Doney, Robert L.; Agui, Juan H.; Sen, Surajit

    2009-09-01

    Rapid absorption of impulses using light-weight, small, reusable systems is a challenging problem. An axially aligned set of progressively shrinking elastic spheres, a "tapered chain," has been shown to be a versatile and scalable shock absorber in earlier simulational, theoretical, and experimental works by several authors. We have recently shown (see R. L. Doney and S. Sen, Phys. Rev. Lett. 97, 155502 (2006)) that the shock absorption ability of a tapered chain can be dramatically enhanced by placing small interstitial grains between the regular grains in the tapered chain systems. Here we focus on a detailed study of the problem introduced in the above mentioned letter, present extensive dynamical simulations using parameters for a titanium-aluminum-vanadium alloy Ti6Al4V, derive attendant hard-sphere analyses based formulae to describe energy dispersion, and finally discuss some preliminary experimental results using systems with chrome spheres and small Nitinol interstitial grains to present the underlying nonlinear dynamics of this so-called decorated tapered granular alignment. We are specifically interested in small systems, comprised of several grains. This is because in real applications, mass and volume occupied must inevitably be minimized. Our conclusion is that the decorated tapered chain offers enhanced energy dispersion by locking in much of the input energy in the grains of the tapered chain rather than in the small interstitial grains. Thus, the present study offers insights into how the shock absorption capabilities of these systems can be pushed even further by improving energy absorption capabilities of the larger grains in the tapered chains. We envision that these scalable, decorated tapered chains may be used as shock absorbing components in body armor, armored vehicles, building applications and in perhaps even in applications in rehabilitation science.

  14. Complete description of ionization energy and electron affinity in organic solids: Determining contributions from electronic polarization, energy band dispersion, and molecular orientation

    NASA Astrophysics Data System (ADS)

    Yoshida, Hiroyuki; Yamada, Kazuto; Tsutsumi, Jun'ya; Sato, Naoki

    2015-08-01

    Ionization energy and electron affinity in organic solids are understood in terms of a single molecule perturbed by solid-state effects such as polarization energy, band dispersion, and molecular orientation as primary factors. However, no work has been done to determine the individual contributions experimentally. In this work, the electron affinities of thin films of pentacene and perfluoropentacene with different molecular orientations are determined to a precision of 0.1 eV using low-energy inverse photoemission spectroscopy. Based on the precisely determined electron affinities in the solid state together with the corresponding data of the ionization energies and other energy parameters, we quantitatively evaluate the contribution of these effects. It turns out that the bandwidth as well as the polarization energy contributes to the ionization energy and electron affinity in the solid state while the effect of the surface dipole is at most a few eV and does not vary with the molecular orientation. As a result, we conclude that the molecular orientation dependence of the ionization energy and electron affinity of organic solids originates from the orientation-dependent polarization energy in the film.

  15. A BOINC based, citizen-science project for pixel spectral energy distribution fitting of resolved galaxies in multi-wavelength surveys

    NASA Astrophysics Data System (ADS)

    Vinsen, Kevin; Thilker, David

    2013-11-01

    In this work we present our experience from the first year of theSkyNet Pan-STARRS1 Optical Galaxy Survey (POGS) project. This citizen-scientist driven research project uses the Berkeley Open Infrastructure for Network Computing (BOINC) middleware and thousands of Internet-connected computers to measure the resolved galactic structural properties of ˜100,000 low redshift galaxies. We are combining the spectral coverage of GALEX, Pan-STARRS1, SDSS, and WISE to generate a value-added, multi-wavelength UV-optical-NIR galaxy atlas for the nearby Universe. Specifically, we are measuring physical parameters (such as local stellar mass, star formation rate, and first-order star formation history) on a resolved pixel-by-pixel basis using spectral energy distribution (SED) fitting techniques in a distributed computing mode. Berkeley Open Infrastructure for Network Computing.

  16. Effect of x-ray energy dispersion in digital subtraction imaging at the iodine K-edge--A Monte Carlo study

    SciTech Connect

    Prino, F.; Ceballos, C.; Cabal, A.; Sarnelli, A.; Gambaccini, M.; Ramello, L.

    2008-01-15

    The effect of the energy dispersion of a quasi-monochromatic x-ray beam on the performance of a dual-energy x-ray imaging system is studied by means of Monte Carlo simulations using MCNPX (Monte Carlo N-Particle eXtended) version 2.6.0. In particular, the case of subtraction imaging at the iodine K-edge, suitable for angiographic imaging application, is investigated. The average energies of the two beams bracketing the iodine K-edge are set to the values of 31.2 and 35.6 keV corresponding to the ones obtained with a compact source based on a conventional x-ray tube and a mosaic crystal monochromator. The energy dispersion of the two beams is varied between 0 and 10 keV of full width at half-maximum (FWHM). The signal and signal-to-noise ratio produced in the simulated images by iodine-filled cavities (simulating patient vessels) drilled in a PMMA phantom are studied as a function of the x-ray energy dispersion. The obtained results show that, for the considered energy separation of 4.4 keV, no dramatic deterioration of the image quality is observed with increasing x-ray energy dispersion up to a FWHM of about 2.35 keV. The case of different beam energies is also investigated by means of fast simulations of the phantom absorption.

  17. High time resolution measurement of multiple electron precipitations with energy-time dispersion in high-latitude part of the cusp region

    NASA Astrophysics Data System (ADS)

    Tanaka, H.; Saito, Y.; Asamura, K.; Ishii, S.; Mukai, T.

    2005-07-01

    The SS-520-2 sounding rocket skimmed over the high-latitude part of the cusp region and observed fine-scale field-aligned electron precipitations in the vicinity of the inverted-V structures with the Low Energy Particle-Electron Spectrum Analyzer (LEP-ESA). There are at least two types of fine-scale electron precipitations, namely "edge-type electron bursts" and "multiple energy-time dispersions." Edge-type electron bursts were observed only at the edge of the inverted-V region, whereas multiple energy-time dispersions were observed separately from the inverted-V region as well as within or overlapping it. The latter was characterized by field-aligned precipitations with falling energies from ˜200 eV down to ˜20 eV at a repetition rate of 1-2 Hz. Source altitudes were estimated using the energy-time and pitch angle-time dispersions. As a result, we found that the source altitudes were distributed along the geomagnetic field at altitudes of several thousand kilometers, depending on the accelerated energies of electrons. Higher-energy electrons are generated at higher altitudes. The source temperature of the energy-time dispersion was much higher than that of ionospheric cold electrons. We suggest that electrons injected from the magnetosheath were accelerated by inertial Alfvén waves at altitudes of several thousands of kilometers.

  18. Improving radiation dose efficiency of X-ray differential phase contrast imaging using an energy-resolving grating interferometer and a novel rank constraint.

    PubMed

    Ge, Yongshuai; Zhang, Ran; Li, Ke; Chen, Guang-Hong

    2016-06-13

    In this paper, a novel method was developed to improve the radiation dose efficiency, viz., contrast to noise ratio normalized by dose (CNRD), of the grating-based X-ray differential phase contrast (DPC) imaging system that is integrated with an energy-resolving photon counting detector. The method exploits the low-dimensionality of the spatial-spectral DPC image matrix acquired from different energy windows. A low rank approximation of the spatial-spectral image matrix was developed to reduce image noise while retaining the DPC signal accuracy for every energy window. Numerical simulations and experimental phantom studies have been performed to validate the proposed method by showing noise reduction and CNRD improvement for each energy window. PMID:27410315

  19. Differences in excitation energy transfer of Arthrospira platensis cells grown in seawater medium and freshwater medium, probed by time-resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Arba, Muhammad; Aikawa, Shimpei; Niki, Kenta; Yokono, Makio; Kondo, Akihiko; Akimoto, Seiji

    2013-11-01

    Excitation energy transfer of Arthrospira platensis cells grown in f/2 medium (a high salinity medium) and SOT medium (a control) was investigated by steady-state and time-resolved spectroscopies. Growth in f/2 medium induced changes in absorption and fluorescence spectra as well as in the energy transfer pathways. Excitation energy captured by phycobilisome (PBS) was transferred directly to photosystem (PS) I, instead of being first transferred to an intermediate (PBS → PSII → PSI), as observed in SOT medium. The respiration rate increased while photosynthetic rate reduced in f/2 medium. Possible causes of the differences in light-harvesting and energy-transfer processes between the two media are discussed.

  20. The complexity of protein energy landscapes studied by solution NMR relaxation dispersion experiments

    PubMed Central

    Khirich, Gennady; Loria, J. Patrick

    2016-01-01

    The millisecond timescale motions in ribonuclease A (RNase A) were studied by solution NMR CPMG and off-resonance R1ρ relaxation dispersion experiments over a wide pH and temperature range. These experiments identify three separate protein regions termed Cluster 1, Cluster 2, and R33 whose motions are governed by distinct thermodynamic parameters. Moreover each of these regions has motions with different pH dependencies. Cluster 1 shows an increase in activation enthalpy and activation entropy as the pH is lowered, whereas Cluster two exhibits the opposite behavior. In contrast the activation enthalpy and entropy of R33 show no pH dependence. Compounding the differences, Δω values for Cluster 2 are characteristic of two-site conformational exchange yet similar analysis for Cluster 1 indicates that this region of the enzyme exhibits conformational fluctuations between a major conformer and a pH-dependent average of protonated and de-protonated minor conformers. PMID:25680027

  1. Influence of Dispersoids on Corrosion Behavior of Oxide Dispersion-Strengthened 18Cr Steels made by High-Energy Milling

    NASA Astrophysics Data System (ADS)

    Nagini, M.; Jyothirmayi, A.; Vijay, R.; Rao, Tata N.; Reddy, A. V.; Rajulapati, Koteswararao V.; Sundararajan, G.

    2016-02-01

    Corrosion behavior of 18Cr ferritic steel with and without yttria produced by high-energy milling followed by hot extrusion was studied in 3.5% NaCl solution using electrochemical and immersion techniques. The cyclic polarization study showed that pitting corrosion is predominant in all the materials. The pitting rate is higher in yttria dispersed steels and also increases with milling time. Impedance analysis revealed the formation of better corrosion resistance film on the surface of the steel without yttria. Potentiodynamic polarization studies indicated that the corrosion rate decreased up to 48 h of exposure time and increased beyond 48 h. The increase in corrosion rate beyond 48 h is due to the porous passive film. The corrosion behavior of all the materials in immersion studies followed the same trend as observed in electrochemical studies. Even though the corrosion rate of yttria dispersed 18Cr ferritic steel is less than that of the base material, the difference is marginal. The presence of dispersoids appears to promote nucleation of pits when compared to the steel without the dispersoids.

  2. RESOLVE Project

    NASA Technical Reports Server (NTRS)

    Parker, Ray; Coan, Mary; Cryderman, Kate; Captain, Janine

    2013-01-01

    The RESOLVE project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph - mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize component and integrated system performance. Testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments was done. Test procedures were developed to guide experimental tests and test reports to analyze and draw conclusions from the data. In addition, knowledge and experience was gained with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer, WDD, Sample Delivery System, and GC-MS in the vacuum chamber. This testing will provide hands-on exposure to a flight forward spaceflight subsystem, the processes associated with testing equipment in a vacuum chamber, and experience working in a laboratory setting. Examples of specific analysis conducted include: pneumatic analysis to calculate the WDD's efficiency at extracting water vapor from the gas stream to form condensation; thermal analysis of the conduction and radiation along a line connecting two thermal masses; and proportional-integral-derivative (PID) heater control analysis. Since LAVA is a scientific subsystem, the near-infrared spectrometer and GC-MS instruments will be tested during the ETU testing phase.

  3. Strong Energy-momentum Dispersion of Phonon Dressed Carriers in the Lightly Doped Band Insulator SrTiO3

    SciTech Connect

    Meevasana, Warawat

    2010-05-26

    Much progress has been made recently in the study of the effects of electron-phonon (el-ph) coupling in doped insulators using angle resolved photoemission (ARPES), yielding evidence for the dominant role of el-ph interactions in underdoped cuprates. As these studies have been limited to doped Mott insulators, the important question arises how this compares with doped band insulators where similar el-ph couplings should be at work. The archetypical case is the perovskite SrTiO{sub 3} (STO), well known for its giant dielectric constant of 10000 at low temperature, exceeding that of La{sub 2}CuO{sub 4} by a factor of 500. Based on this fact, it has been suggested that doped STO should be the archetypical bipolaron superconductor. Here we report an ARPES study from high-quality surfaces of lightly doped SrTiO{sub 3}. Comparing to lightly doped Mott insulators, we find the signatures of only moderate electron-phonon coupling: a dispersion anomaly associated with the low frequency optical phonon with a {lambda}{prime} {approx} 0.3 and an overall bandwidth renormalization suggesting an overall {lambda}{prime} {approx} 0.7 coming from the higher frequency phonons. Further, we find no clear signatures of the large pseudogap or small polaron phenomena. These findings demonstrate that a large dielectric constant itself is not a good indicator of el-ph coupling and highlight the unusually strong effects of the el-ph coupling in doped Mott insulators.

  4. Internal energy of HCl upon photolysis of 2-chloropropene at 193 nm investigated with time-resolved Fourier-transform spectroscopy and quasiclassical trajectories

    SciTech Connect

    Chang, C.-M.; Huang, Y.-H.; Liu, S.-Y.; Lee, Y.-P.; Pombar-Perez, Marta; Martinez-Nunez, Emilio; Vazquez, Saulo A.

    2008-12-14

    Following photodissociation of 2-chloropropene (H{sub 2}CCClCH{sub 3}) at 193 nm, vibration-rotationally resolved emission spectra of HCl ({upsilon}{<=}6) in the spectral region of 1900-2900 cm{sup -1} were recorded with a step-scan time-resolved Fourier-transform spectrometer. All vibrational levels show a small low-J component corresponding to {approx}400 K and a major high-J component corresponding to 7100-18 700 K with average rotational energy of 39{+-}{sub 3}{sup 11} kJ mol{sup -1}. The vibrational population of HCl is inverted at {upsilon}=2, and the average vibrational energy is 86{+-}5 kJ mol{sup -1}. Two possible channels of molecular elimination producing HCl+propyne or HCl+allene cannot be distinguished positively based on the observed internal energy distribution of HCl. The observed rotational distributions fit qualitatively with the distributions of both channels obtained with quasiclassical trajectories (QCTs), but the QCT calculations predict negligible populations for states at small J. The observed vibrational distribution agrees satisfactorily with the total QCT distribution obtained as a weighted sum of contributions from both four-center elimination channels. Internal energy distributions of HCl from 2-chloropropene and vinyl chloride are compared.

  5. Electron probe energy dispersive X-ray microanalysis (EDXA) in the investigation of fossil bone: the case of Java man.

    PubMed

    Bartsiokas, A; Day, M H

    1993-05-22

    Doubts about the attribution of the Trinil femur to Homo erectus on anatomical grounds have a long history. Here, for the first time, published stratigraphic information and chemical evidence based on the Ca/P ratios confirm that the anatomical doubts are justified. The Trinil femur apparently belongs to a more recent stratum above the 'fossil layer' (Hauptknochenschicht, HK) in which the Trinil calotte was found. It is concluded that the Trinil Femur I belongs to Homo sapiens, whereas the Trinil Femora II-V and the calotte belong to H. erectus. The chemical evidence derives from the use of electron probe energy dispersive X-ray microanalysis (EDXA), a technique that can be virtually non-destructive and therefore may be used on scarce fossil evidence. PMID:8391701

  6. Energy dispersive x-ray analysis of the cornea. Application to paraffin sections of normal and diseased corneas

    SciTech Connect

    Robinson, M.R.; Streeten, B.W.

    1984-11-01

    The distribution of chemical elements in the normal human cornea was studied by energy dispersive x-ray analysis and scanning electron microscopy of routinely prepared paraffin sections. Calcium, phosphorus, and sulfur were consistently present in quantities above background and varied in concentration regionally. Analysis of fresh-frozen tissue, an approximation of the in vivo state, gave a similar elemental profile to paraffin sections, except for the loss of diffusable electrolytes in the latter. After fixation, S was the most abundant element and was highest in Descemet's membrane. Corneas with granular, lattice, macular, and Fuchs endothelial dystrophies, band keratopathy, and spheroidal degeneration were also examined. Characteristic patterns of abnormal S and Ca distribution were found in each of the dystrophies. The relative proportions of Ca, P, and S gave diagnostic profiles for distinguishing band keratopathy and spheroidal degeneration.

  7. Energy dispersive X-ray spectroscopy analysis of Si sidewall surface etched by deep-reactive ion etching

    NASA Astrophysics Data System (ADS)

    Matsutani, Akihiro; Nishioka, Kunio; Sato, Mina

    2016-06-01

    We investigated the composition of a passivation film on a sidewall etched by deep-reactive ion etching (RIE) using SF6/O2 and C4F8 plasma, by energy-dispersive X-ray (EDX) spectroscopy. It was found that the compositions of carbon and fluorine in the passivation film on the etched sidewall depend on the width and depth of the etched trench. It is important to understand both the plasma behavior and the passivation film composition to carry out fabrication by deep-RIE. We consider that these results of the EDX analysis of an etched sidewall will be useful for understanding plasma behavior in order to optimize the process conditions of deep-RIE.

  8. Standardless Quantitative Electron-Excited X-ray Microanalysis by Energy-Dispersive Spectrometry: What Is Its Proper Role?

    PubMed

    Newbury

    1998-11-01

    : Electron beam X-ray microanalysis with semiconductor energy-dispersive spectrometry (EDS) performed with standards and calculated matrix corrections can yield quantitative results with a distribution such that 95% of analyses fall within +/-5% relative for major and minor constituents. Standardless methods substitute calculations for the standard intensities, based either on physical models of X-ray generation and propagation (first principles) or on mathematical fits to remotely measured standards (fitted standards). Error distributions have been measured for three different standardless analysis procedures with a suite of microanalysis standards including metal alloys, glasses, minerals, ceramics, and stoichiometric compounds. For the first-principles standardless procedure, the error distribution placed 95% of analyses within +/-50% relative, whereas for two commercial fitted standards procedures, the error distributions placed 95% of analyses within +/-25% relative. The implication of these error distributions for the accuracy of analytical results is considered, and recommendations for the use of standardless analysis are given. PMID:10087281

  9. Standardless Quantitative Electron-Excited X-ray Microanalysis by Energy-Dispersive Spectrometry: What Is Its Proper Role?

    NASA Astrophysics Data System (ADS)

    Newbury, Dale E.

    1998-11-01

    : Electron beam X-ray microanalysis with semiconductor energy-dispersive spectrometry (EDS) performed with standards and calculated matrix corrections can yield quantitative results with a distribution such that 95% of analyses fall within ±5% relative for major and minor constituents. Standardless methods substitute calculations for the standard intensities, based either on physical models of X-ray generation and propagation (first principles) or on mathematical fits to remotely measured standards (fitted standards). Error distributions have been measured for three different standardless analysis procedures with a suite of microanalysis standards including metal alloys, glasses, minerals, ceramics, and stoichiometric compounds. For the first-principles standardless procedure, the error distribution placed 95% of analyses within ±50% relative, whereas for two commercial fitted standards procedures, the error distributions placed 95% of analyses within ±25% relative. The implication of these error distributions for the accuracy of analytical results is considered, and recommendations for the use of standardless analysis are given.

  10. Sodium lauryl sulfate enhances nickel penetration through guinea-pig skin. Studies with energy dispersive X-ray microanalysis

    SciTech Connect

    Lindberg, M.; Sagstroem, S.R.; Roomans, G.M.; Forslind, B.

    1989-03-01

    The effect of sodium lauryl sulphate (SLS), a common ingredient of detergents, on the penetration of nickel through the stratum corneum in the guinea-pig skin model was studied with energy dispersive X-ray microanalysis (EDX) to evaluate the barrier-damaging properties of this common detergent. The EDX technique allows a simultaneous determination of physiologically important elements, e.g., Na, Mg, P, Cl, K, Ca and S in addition to Ni at each point of measurement in epidermal cell strata. Our results show that SLS reduces the barrier function to Ni-ion penetration of the stratum corneum. In addition we have shown that EDX allows analysis of the influence of different factors involved in nickel penetration through the skin by giving data on the physiological effects on the epidermal cells caused by the applied substances.

  11. Trace elemental analysis of school chalk using energy dispersive X-ray florescence spectroscopy (ED-XRF)

    SciTech Connect

    Maruthi, Y. A.; Das, N. Lakshmana; Ramprasad, S.; Ram, S. S.; Sudarshan, M.

    2015-08-28

    The present studies focus the quantitative analysis of elements in school chalk to ensure the safety of its use. The elements like Calcium (Ca), Aluminum (Al), Iron (Fe), Silicon (Si) and Chromium (Cr) were analyzed from settled chalk dust samples collected from five classrooms (CD-1) and also from another set of unused chalk samples collected from local market (CD-2) using Energy Dispersive X-Ray florescence(ED-XRF) spectroscopy. Presence of these elements in significant concentrations in school chalk confirmed that, it is an irritant and occupational hazard. It is suggested to use protective equipments like filtered mask for mouth, nose and chalk holders. This study also suggested using the advanced mode of techniques like Digital boards, marker boards and power point presentations to mitigate the occupational hazard for classroom chalk.

  12. Trace elemental analysis of school chalk using energy dispersive X-ray florescence spectroscopy (ED-XRF)

    NASA Astrophysics Data System (ADS)

    Maruthi, Y. A.; Das, N. Lakshmana; Ramprasad, S.; Ram, S. S.; Sudarshan, M.

    2015-08-01

    The present studies focus the quantitative analysis of elements in school chalk to ensure the safety of its use. The elements like Calcium (Ca), Aluminum (Al), Iron (Fe), Silicon (Si) and Chromium (Cr) were analyzed from settled chalk dust samples collected from five classrooms (CD-1) and also from another set of unused chalk samples collected from local market (CD-2) using Energy Dispersive X-Ray florescence(ED-XRF) spectroscopy. Presence of these elements in significant concentrations in school chalk confirmed that, it is an irritant and occupational hazard. It is suggested to use protective equipments like filtered mask for mouth, nose and chalk holders. This study also suggested using the advanced mode of techniques like Digital boards, marker boards and power point presentations to mitigate the occupational hazard for classroom chalk

  13. Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF)

    USGS Publications Warehouse

    Smith, Kevin T.; Balouet, Jean Christophe; Shortle, Walter C.; Chalot, Michel; Beaujard, François; Grudd, Håkan; Vroblesky, Don A.; Burkem, Joel G.

    2014-01-01

    Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to distinguish dendrochemical effects of internal processes from environmental contamination. Calcium, potassium, and zinc are three marker cations that illustrate the influence of these processes. We found changes in cation chemistry in tree rings potentially due to biomineralization, development of cracks or checks, heartwood/sapwood differentiation, intra-annual processes, and compartmentalization of infection. Distinguishing internal from external processes that affect dendrochemistry will enhance the value of EDXRF for both physiological and forensic investigations.

  14. Non-destructive analysis of didymium and praseodymium molybdate crystals using energy dispersive X-ray fluorescence technique

    NASA Astrophysics Data System (ADS)

    Bhat, C. K.; Joseph, Daisy; Pandita, Sanjay; Kotru, P. N.

    2016-08-01

    Analysis of didymium (Di) and praseodymium molybdate crystals were carried out using energy dispersive X-ray fluorescence (EDXRF). The assigned empirical chemical formulae of the composites were tested and verified by the EDXRF technique by estimating experimental major elemental concentration ratios. On the Basis of these ratios, the established formulae for some of the composite materials have been verified and suggestions made for their refinement. Non-destructive technique used in this analysis enables to retain the original crystal samples and makes rapid simultaneous scan of major elements such as La, Pr, Ned and Mo as well as impurities such as Ce. Absence of samarium(Sm) in the spectrum during analysis of didymium molybdate crystals indicated an incomplete growth of mixed rare earth single crystal. These crystals (e.g.,Di) are shown to be of modified stoichiometry with Ce as trace impurity.

  15. Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF).

    PubMed

    Smith, Kevin T; Balouet, Jean Christophe; Shortle, Walter C; Chalot, Michel; Beaujard, François; Grudd, Håkan; Vroblesky, Don A; Burken, Joel G

    2014-01-01

    Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to distinguish dendrochemical effects of internal processes from environmental contamination. Calcium, potassium, and zinc are three marker cations that illustrate the influence of these processes. We found changes in cation chemistry in tree rings potentially due to biomineralization, development of cracks or checks, heartwood/sapwood differentiation, intra-annual processes, and compartmentalization of infection. Distinguishing internal from external processes that affect dendrochemistry will enhance the value of EDXRF for both physiological and forensic investigations. PMID:24034830

  16. Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry.

    PubMed

    Newbury, Dale E; Ritchie, Nicholas W M

    2016-06-01

    Electron-excited X-ray microanalysis performed with scanning electron microscopy and energy-dispersive spectrometry (EDS) has been used to measure trace elemental constituents of complex multielement materials, where "trace" refers to constituents present at concentrations below 0.01 (mass fraction). High count spectra measured with silicon drift detector EDS were quantified using the standards/matrix correction protocol embedded in the NIST DTSA-II software engine. Robust quantitative analytical results for trace constituents were obtained from concentrations as low as 0.000500 (mass fraction), even in the presence of significant peak interferences from minor (concentration 0.01≤C≤0.1) and major (C>0.1) constituents. Limits of detection as low as 0.000200 were achieved in the absence of peak interference. PMID:27329308

  17. RESOLVE Project

    NASA Technical Reports Server (NTRS)

    Parker, Ray O.

    2012-01-01

    The RESOLVE project is a lunar prospecting mission whose primary goal is to characterize water and other volatiles in lunar regolith. The Lunar Advanced Volatiles Analysis (LAVA) subsystem is comprised of a fluid subsystem that transports flow to the gas chromatograph- mass spectrometer (GC-MS) instruments that characterize volatiles and the Water Droplet Demonstration (WDD) that will capture and display water condensation in the gas stream. The LAVA Engineering Test Unit (ETU) is undergoing risk reduction testing this summer and fall within a vacuum chamber to understand and characterize C!Jmponent and integrated system performance. Ray will be assisting with component testing of line heaters, printed circuit heaters, pressure transducers, temperature sensors, regulators, and valves in atmospheric and vacuum environments. He will be developing procedures to guide these tests and test reports to analyze and draw conclusions from the data. In addition, he will gain experience with preparing a vacuum chamber with fluid and electrical connections. Further testing will include integrated testing of the fluid subsystem with the gas supply system, near-infrared spectrometer, WDD, Sample Delivery System, and GC-MS in the vacuum chamber. This testing will provide hands-on exposure to a flight forward spaceflight subsystem, the processes associated with testing equipment in a vacuum chamber, and experience working in a laboratory setting. Examples of specific analysis Ray will conduct include: pneumatic analysis to calculate the WOO's efficiency at extracting water vapor from the gas stream to form condensation; thermal analysis of the conduction and radiation along a line connecting two thermal masses; and proportional-integral-derivative (PID) heater control analysis. In this Research and Technology environment, Ray will be asked to problem solve real-time as issues arise. Since LAVA is a scientific subsystem, Ray will be utilizing his chemical engineering background to

  18. Energy dispersive X-ray analysis of titanium dioxide nanoparticle distribution after intravenous and subcutaneous injection in mice.

    PubMed

    Patri, Anil; Umbreit, Thomas; Zheng, J; Nagashima, K; Goering, Peter; Francke-Carroll, Sabine; Gordon, Edward; Weaver, James; Miller, Terry; Sadrieh, Nakissa; McNeil, Scott; Stratmeyer, Mel

    2009-11-01

    In an effort to understand the disposition and toxicokinetics of nanoscale materials, we used EDS (energy dispersive X-ray spectroscopy) to detect and map the distribution of titanium dioxide (TiO2) in tissue sections from mice following either subcutaneous (s.c.) or intravenous (i.v.) injection. TiO2 nanoparticles were administered at a dose of 560 mg/kg (i.v.) or 5600 mg/kg (s.c.) to Balb/c female mice on two consecutive days. Tissues (liver, kidney, lung, heart, spleen, and brain) were examined by light microscopy, TEM (transmission electron microscopy), SEM (scanning electron microscopy), and EDS following necropsy one day after treatment. Particle agglomerates were detected by light microscopy in all tissues examined, EDS microanalysis was used to confirm that these tissues contained elemental titanium and oxygen. The TEM micrographs and EDS spectra of the aggregates were compared with in vitro measurements of TiO2 nanoparticle injection solution (i.e., in water). The nanoparticles were also characterized using dynamic light scattering in water, 10 mM NaCl, and phosphate buffered saline (PBS). In low ionic strength solvents (water and 10 mM NaCl), the TiO2 particles had average hydrodynamic diameters ranging from 114-122 nm. In PBS, however, the average diameter increases to 1-2 microm, likely due to aggregation analogous to that observed in tissue by TEM and EDS. This investigation demonstrates the suitability of energy dispersive X-ray spectroscopy (EDS) for detection of nanoparticle aggregates in tissues and shows that disposition of TiO2 nanoparticles depends on the route of administration (i.v. or s.c.). PMID:19626582

  19. Energy dispersive X-ray microanalysis, fluoride release, and antimicrobial properties of glass ionomer cements indicated for atraumatic restorative treatment

    PubMed Central

    Saxena, Sudhanshu; Tiwari, Sonia

    2016-01-01

    Aim: The aim of this study was to compare constituents of glass powder, fluoride release, and antimicrobial properties of new atraumatic restorative treatment material with zirconia fillers and conventional glass ionomer cement (GIC) type IX. Materials and Methods: Thisin vitro study comparing Zirconomer and Fuji IX was executed in three parts: (1) energy dispersive X-ray microanalysis of glass powders (2) analysis of fluoride release at 1st, 3rd, 7th, 15th, and 30th day, and (3) antimicrobial activity against Streptococcus mutans, Lactobacillus casei, and Candida albicans at 48 hours. Data was analyzed using unpaired t-test and two way analysis of variance followed by least significant difference post hoc test. A P value of < 0.05 was considered statistically significant. Results: Energy dispersive X-ray microanalysis revealed that, in both Zirconomer and Fuji IX glass powders, mean atomic percentage of oxygen was more than 50%. According to the weight percentage, zirconium in Zirconomer and silica in Fuji IX were the second main elements. Calcium, zinc, and zirconium were observed only in Zirconomer. At all the time intervals, statistically significant higher amount of fluoride release was observed with Zirconomer than Fuji IX. At 48 hours, mean ± standard deviation (SD) of zone of inhibition against Streptococcus mutans was 11.14 ± 0.77 mm and 8.51 ± 0.43 mm for Zirconomer and Fuji IX, respectively. Against Lactobacillus casei, it was 14.06 ± 0.71 mm for Zirconomer and 11.70 ± 0.39 mm for Fuji IX. No antifungal activity was observed against Candida albicans by Zirconomer and Fuji IX. Conclusion: Zirconomer had higher antibacterial activity against Streptococcus mutans and Lactobacillus casei, which may be attributed to its composition and higher fluoride release. However, it failed to show antifungal effect againstCandida albicans. PMID:27583226

  20. ENERGY-DISPERSIVE, X-RAY REFLECTIVITY DENSITY MEASUREMENTS OF POROUS SIO2 XEROGELS

    EPA Science Inventory

    X-ray reflectivity has been used to nondestructively measure the density of thin, porous, SiO2-based xerogels. Critical angle, defined by total external reflection, was measured for multiple x-ray energies to correct for sample misalignment error in me determination of the densit...

  1. Position sensitive and energy dispersive x-ray detector based on silicon strip detector technology

    NASA Astrophysics Data System (ADS)

    Wiącek, P.; Dąbrowski, W.; Fink, J.; Fiutowski, T.; Krane, H.-G.; Loyer, F.; Schwamberger, A.; Świentek, K.; Venanzi, C.

    2015-04-01

    A new position sensitive detector with a global energy resolution for the entire detector of about 380 eV FWHM for 8.04 keV line at ambient temperature is presented. The measured global energy resolution is defined by the energy spectra summed over all strips of the detector, and thus it includes electronic noise of the front-end electronics, charge sharing effects, matching of parameters across the channels and other system noise sources. The target energy resolution has been achieved by segmentation of the strips to reduce their capacitance and by careful optimization of the front-end electronics. The key design aspects and parameters of the detector are discussed briefly in the paper. Excellent noise and matching performance of the readout ASIC and negligible system noise allow us to operate the detector with a discrimination threshold as low as 1 keV and to measure fluorescence radiation lines of light elements, down to Al Kα of 1.49 keV, simultaneously with measurements of the diffraction patterns. The measurement results that demonstrate the spectrometric and count rate performance of the developed detector are presented and discussed in the paper.

  2. The effect of solar irradiation on the fading of nylon and polyester fabrics dyed with selected disperse dyestuffs on radiant energy basis.

    PubMed

    Imaizumi, A; Yoshizumi, K; Fujita, T

    2004-04-01

    Solar total, UVA and UVB irradiances were measured separately using three kinds of wavelength band detectors in Tokyo, Japan in November 1999. Characteristics of diurnal variations were examined: Total irradiance reached a maximum value of about 600 W m(-2) at around noon. The variation pattern of UVA irradiance was observed to be similar to the total irradiance. The energy level was about 4.65% of total irradiance. Diurnal variation of UVB was in the form of a steeper bell curve due to the absorption in the air mass. UVB energy to solar total irradiance was about 0.07%. Photodegradation characteristics of two disperse dyestuffs were investigated on the basis of solar radiant energy. A UVA fluorescent lamp was applied to examine the fading characteristics to find the wavelength dependency. As a result, nylon dyeings were less lightfast by a factor of about 6 and 13 for C I Disperse Blue 27 and C I Disperse Blue 165, respectively, compared with polyester on the radiant energy basis. Visible light, as well as UVA, radiation contribute to fading of C I Disperse Blue 165 whereas UVA mostly cause the fading of C I Disperse Blue 27. PMID:15214450

  3. Energy-dependent crossover from anisotropic to isotropic magnetic dispersion in lightly-doped La1.96Sr0.04CuO4

    SciTech Connect

    Matsuda, Masaaki; Granroth, Garrett E; Fujita, M.; Yamada, K.; Tranquada, John M.

    2013-01-01

    Inelastic neutron scattering experiments have been performed on lightly-doped La$_{1.96}$Sr$_{0.04}$CuO$_{4}$, which shows diagonal incommensurate spin correlations at low temperatures. We previously reported that this crystal, with a single orthorhombic domain, exhibits the ``hourglass" dispersion at low energies [Phys. Rev. Lett. 101, 197001 (2008)]. In this paper, we investigate in detail the energy evolution of the magnetic excitations up to 65 meV. It is found that the anisotropic excitations at low energies, dispersing only along the spin modulation direction, crossover to an isotropic, conical dispersion that resembles spin waves in the parent compound La$_2$CuO$_{4}$. The change from two-fold to full symmetry on crossing the waist of the hourglass reproduces behavior first identified in studies of underdoped YBa$_2$Cu$_3$O$_{6+x}$. We discuss the significance of these results.

  4. A Transition Edge Sensor Microcalorimeter System for the Energy Dispersive Spectroscopy Performed on a Scanning-Transmission Electron Microscope

    NASA Astrophysics Data System (ADS)

    Maehata, K.; Hara, T.; Mitsuda, K.; Hidaka, M.; Tanaka, K.; Yamanaka, Y.

    2015-11-01

    We are conducting the development of a transition edge sensor (TES) microcalorimeter system for energy-dispersive X-ray spectroscopy (EDS), performed using a scanning-transmission electron microscope (STEM). The operating temperature of the TES microcalorimeter was maintained using a compact dry 3 He-4 He dilution refrigerator. This was pre-cooled by a remote helium cooling loop system and a Gifford-McMahon cooler. These conditions allowed for high-resolution STEM imaging to be achieved. A single-pixel TES microcalorimeter with a polycapillary optic was selected to demonstrate the analytical operation of the EDS system in the STEM. For a Ti-It-Pt sample, an X-ray energy resolution of 8.6 eV full-width at half maximum (FWHM) was obtained at Ir M_{α 1} , Pt M_{α 1} , and Ir M_{β } . Using an electron device sample, element distribution maps of Si, Ti, and W were obtained using a Si K_{α 1} X-ray energy resolution of 9.7 eV FWHM.

  5. A Transition Edge Sensor Microcalorimeter System for the Energy Dispersive Spectroscopy Performed on a Scanning-Transmission Electron Microscope

    NASA Astrophysics Data System (ADS)

    Maehata, K.; Hara, T.; Mitsuda, K.; Hidaka, M.; Tanaka, K.; Yamanaka, Y.

    2016-07-01

    We are conducting the development of a transition edge sensor (TES) microcalorimeter system for energy-dispersive X-ray spectroscopy (EDS), performed using a scanning-transmission electron microscope (STEM). The operating temperature of the TES microcalorimeter was maintained using a compact dry 3He-4He dilution refrigerator. This was pre-cooled by a remote helium cooling loop system and a Gifford-McMahon cooler. These conditions allowed for high-resolution STEM imaging to be achieved. A single-pixel TES microcalorimeter with a polycapillary optic was selected to demonstrate the analytical operation of the EDS system in the STEM. For a Ti-It-Pt sample, an X-ray energy resolution of 8.6 eV full-width at half maximum (FWHM) was obtained at Ir M_{α 1}, Pt M_{α 1}, and Ir M_{β }. Using an electron device sample, element distribution maps of Si, Ti, and W were obtained using a Si K_{α 1} X-ray energy resolution of 9.7 eV FWHM.

  6. Mass and energy dispersive recoil spectrometry of MOCVD grown Al xGa 1- xAs

    NASA Astrophysics Data System (ADS)

    Walker, S. R.; Johnston, P. N.; Bubb, I. F.; Stannard, W. B.; Cohen, D. D.; Dytlewski, N.; Hult, M.; Whitlow, H. J.; Zaring, C.; Östling, M.; Andersson, M.

    1994-12-01

    Mass and energy dispersive Recoil Spectrometry (RS) has been employed to study stoichiometric variations in Al xGa 1- xAs layers. Quantitative determination of x is an important problem in the production of device materials which is not easily solved with standard techniques. Rutherford Backscattering Spectrometry (RBS) has been used extensively in semiconductor research but overlap of signals in the backscattered ion spectrum is an important limitation in the analysis of materials such as Al xGa 1- xAs which contain elements of low and similar masses. Particle Induced X-ray Emission (PIXE) analysis has good elemental resolution for this class of materials but provides little depth resolution. RS enables the determination of separate energy spectra for individual or small groups of isotopes. This allows it to be used in many situations where RBS is inappropriate. It employs a heavy ion beam to cause constituent nuclei to recoil from the target, and a Time of Flight and Energy (ToF- E) detector to detect these recoiling nuclei. Appropriate mass selection of the ToF- E data allows the determination of depth distributions for each element.

  7. Rotationally resolved vibrational spectra of AsH3 (+)X̃(2)A2 (″): Tunneling splittings studied by zero-kinetic-energy photoelectron spectroscopy.

    PubMed

    Sun, Wei; Dai, Zuyang; Wang, Jia; Mo, Yuxiang

    2016-06-21

    The rotationally resolved vibrational spectra of AsH3 (+)X̃(2)A2 (″) have been measured for the first time with vibrational energies up to 6000 cm(-1) above the ground state using the zero-kinetic-energy photoelectron method. The symmetric inversion vibrational energy levels (v2 (+)) and the corresponding rotational constants for v2 (+)=0-15 have been determined. The tunneling splittings of the inversion vibration energy levels have been observed and are 0.8 and 37.7 (±0.5) cm(-1) for the ground and the first excited vibrational states, respectively. The first adiabatic ionization energy for AsH3 was determined as 79 243.3 ± 1 cm(-1). The geometric parameters of AsH3 (+)X̃(2)A2 (″) as a function of inversion vibrational numbers have been determined, indicating that the geometric structure of the cation changes from near-planar to pyramidal with increasing inversion vibrational excitation. In addition to the experimental measurements, a two-dimensional theoretical calculation considering the two symmetric vibrational modes was performed to determine the energy levels of the symmetric inversion, which are in good agreement with the experimental results. The inversion vibrational energy levels of SbH3 (+)X̃(2)A2 (″) have also been calculated and are found to have much smaller energy splittings than those of AsH3 (+)X̃(2)A2 (″). PMID:27334168

  8. Rotationally resolved vibrational spectra of AsH3 + (" separators=" X ˜ 2 A2 ″) : Tunneling splittings studied by zero-kinetic-energy photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, Wei; Dai, Zuyang; Wang, Jia; Mo, Yuxiang

    2016-06-01

    The rotationally resolved vibrational spectra of AsH3 + (" separators=" X ˜ 2 A2 ″) have been measured for the first time with vibrational energies up to 6000 cm-1 above the ground state using the zero-kinetic-energy photoelectron method. The symmetric inversion vibrational energy levels ( v2 +) and the corresponding rotational constants for v2 + = 0 -15 have been determined. The tunneling splittings of the inversion vibration energy levels have been observed and are 0.8 and 37.7 (±0.5) cm-1 for the ground and the first excited vibrational states, respectively. The first adiabatic ionization energy for AsH3 was determined as 79 243.3 ± 1 cm-1. The geometric parameters of AsH3 + (" separators=" X ˜ 2 A2 ″) as a function of inversion vibrational numbers have been determined, indicating that the geometric structure of the cation changes from near-planar to pyramidal with increasing inversion vibrational excitation. In addition to the experimental measurements, a two-dimensional theoretical calculation considering the two symmetric vibrational modes was performed to determine the energy levels of the symmetric inversion, which are in good agreement with the experimental results. The inversion vibrational energy levels of SbH3 + (" separators=" X ˜ 2 A2 ″) have also been calculated and are found to have much smaller energy splittings than those of AsH3 + (" separators=" X ˜ 2 A2 ″) .

  9. Theory of diamagnetism in the pseudogap phase of high-temperature superconductors: Implications from the self-energy of angle-resolved photoemission

    NASA Astrophysics Data System (ADS)

    Wulin, Dan; Levin, K.

    2012-11-01

    In this paper we apply the emerging-consensus understanding of the fermionic self-energy deduced from angle-resolved photoemisssion spectroscopy (ARPES) experiments to deduce the implications for orbital diamagnetism in the underdoped cuprates. Many theories using many different starting points have arrived at a broadened BCS-like form for the normal state self-energy associated with a d-wave excitation gap, as is compatible with ARPES data. Establishing consistency with the f-sum rules, we show how this self-energy, along with the constraint that there is no Meissner effect in the normal phase, are sufficient to deduce the orbital susceptibility. We conclude, moreover, that diamagnetism is large for a d-wave pseudogap. Our results should apply rather widely to many theories of the pseudogap, independent of the microscopic details.

  10. Angle-resolved intensity and energy distributions of positive and negative hydrogen ions released from tungsten surface by molecular hydrogen ion impact

    NASA Astrophysics Data System (ADS)

    Kato, S.; Tanaka, N.; Sasao, M.; Kisaki, M.; Tsumori, K.; Nishiura, M.; Matsumoto, Y.; Kenmotsu, T.; Wada, M.; Yamaoka, H.

    2015-08-01

    Hydrogen ion reflection properties have been investigated following the injection of H+, H2+ and H3+ ions onto a polycrystalline W surface. Angle- and energy-resolved intensity distributions of both scattered H+ and H- ions are measured by a magnetic momentum analyzer. We have detected atomic hydrogen ions reflected from the surface, while molecular hydrogen ions are unobserved within our detection limit. The reflected hydrogen ion energy is approximately less than one-third of the incident beam energy for H3+ ion injection and less than a half of that for H2+ ion injection. Other reflection properties are very similar to those of monoatomic H+ ion injection. Experimental results are compared to the classical trajectory simulations using the ACAT code based on the binary collision approximation.

  11. Time Resolved Spectroscopic Studies on a Novel Synthesized Photo-Switchable Organic Dyad and Its Nanocomposite Form in Order to Develop Light Energy Conversion Devices.

    PubMed

    Dutta Pal, Gopa; Paul, Abhijit; Yadav, Somnath; Bardhan, Munmun; De, Asish; Chowdhury, Joydeep; Jana, Aindrila; Ganguly, Tapan

    2015-08-01

    UV-vis absorption, steady state and time resolved spectroscopic investigations in pico and nanosecond time domain were made in the different environments on a novel synthesized dyad, 3-(2-methoxynaphthalen-1-yl)-1-(4-methoxyphenyl)prop-2-en-1-one (MNTMA) in its pristine form and when combined with gold (Au) nanoparticles i.e., in its nanocomposite structure. Both steady state and time resolved measurements coupled with the DFT calculations performed by using Gaussian 03 suit of software operated in the linux operating system show that though the dyad exhibits mainly the folded conformation in the ground state but on photoexcitation the nanocomposite form of dyad prefers to be in elongated structure in the excited state indicating its photoswitchable nature. Due to the predominancy of elongated isomeric form of the dyad in the excited state in presence of Au Nps, it appears that the dyad MNTMA may behave as a good light energy converter specially in its nanocomposite form. As larger charge separation rate (kcs ~ 4 x 10(8) s-1) is found relative to the rate associated with the energy wasting charge recombination processes (kcR ~ 3 x 10(5) s-1) in the nanocomposite form of the dyad, it demonstrates the suitability of constructing the efficient light energy conversion devices with Au-dyad hybrid nanomaterials. PMID:26369151

  12. Energy-resolved electron-yield XAS studies of nanoporous CoAlPO-18 and CoAlPO-34 catalysts.

    PubMed

    Martis, Vladimir; Martis, Martin; Lipp, John; Detollenaere, Dirk; Rayment, Trevor; Sankar, Gopinathan; Bras, Wim

    2014-07-01

    Energy-resolved electron-yield X-ray absorption spectroscopy is a promising technique for probing the near-surface structure of nanomaterials because of its ability to discriminate between the near-surface and bulk of materials. So far, the technique has only been used in model systems. Here, the local structural characterization of nanoporous cobalt-substituted aluminophosphates is reported and it is shown that the technique can be employed for the study of open-framework catalytically active systems. Evidence that the cobalt ions on the surface of the crystals react differently to those in the bulk is found. PMID:24971969

  13. Angle-resolved photoelectron spectroscopy of sequential three-photon triple ionization of neon at 90.5 eV photon energy

    SciTech Connect

    Rouzee, A.; Siu, W.; Huismans, Y.; Johnsson, P.; Gryzlova, E. V.; Fukuzawa, H.; Yamada, A.; Ueda, K.; Louis, E.; Bijkerk, F.; Holland, D. M. P.; Grum-Grzhimailo, A. N.; Kabachnik, N. M.; Vrakking, M. J. J.

    2011-03-15

    Multiple photoionization of neon atoms by a strong 13.7 nm (90.5 eV) laser pulse has been studied at the FLASH free electron laser in Hamburg. A velocity map imaging spectrometer was used to record angle-resolved photoelectron spectra on a single-shot basis. Analysis of the evolution of the spectra with the FEL pulse energy in combination with extensive theoretical calculations allows the ionization pathways that contribute to be assigned, revealing the occurrence of sequential three-photon triple ionization.

  14. Modified dispersion relations lead to a finite zero point gravitational energy

    SciTech Connect

    Garattini, Remo; Mandanici, Gianluca

    2011-04-15

    We compute the zero point energy in a spherically symmetric background distorted at high energy as predicted by Gravity's Rainbow. In this context we setup a Sturm-Liouville problem with the cosmological constant considered as the associated eigenvalue. The eigenvalue equation is a reformulation of the Wheeler-DeWitt equation. With the help of a canonical decomposition, we find that the relevant contribution to one loop is given by the graviton quantum fluctuations around the given background. By means of a variational approach based on Gaussian trial functionals, we find that the ordinary divergences can here be handled by an appropriate choice of the rainbow's functions, in contrast to what happens in other conventional approaches. A final discussion on the connection of our result with the observed cosmological constant is also reported.

  15. Free energy landscapes and volumes of coexisting phases for a colloidal dispersion

    NASA Astrophysics Data System (ADS)

    Lang, Trinh Hoa; Wang, G. F.; Lai, S. K.

    2010-01-01

    Treating the repulsive part of a pairwise potential by the hard-sphere form and its attractive part by the effective depletion potential form, we calculate using this model potential the colloidal domains of phase separation. Differing from the usual recipe of applying the thermodynamic conditions of equal pressure and equal chemical potential where the branches of coexisting phases are the ultimate target, we employ the free energy density minimization approach [G. F. Wang and S. K. Lai, Phys. Rev. E 70, 051402 (2004)] to crosshatch the domains of equilibrium phases, which consist of the gas, liquid, and solid homogeneous phases as well as the coexistence of these phases. This numerical procedure is attractive since it yields naturally the colloidal volume of space occupied by each of the coexisting phases. In this work, we first examine the change in structures of the fluid and solid free energy density landscapes with the effective polymer concentration. We show by explicit illustration the link between the free energy density landscapes and the development of both the metastable and stable coexisting phases. Then, attention is paid to the spatial volumes predicted at the triple point. It is found here that the volumes of spaces of the three coexisting phases at the triple point vary one dimensionally, whereas for the two coexisting phases, they are uniquely determined.

  16. Energy hyperspace for stacking interaction in AU/AU dinucleotide step: Dispersion-corrected density functional theory study.

    PubMed

    Mukherjee, Sanchita; Kailasam, Senthilkumar; Bansal, Manju; Bhattacharyya, Dhananjay

    2014-01-01

    Double helical structures of DNA and RNA are mostly determined by base pair stacking interactions, which give them the base sequence-directed features, such as small roll values for the purine-pyrimidine steps. Earlier attempts to characterize stacking interactions were mostly restricted to calculations on fiber diffraction geometries or optimized structure using ab initio calculations lacking variation in geometry to comment on rather unusual large roll values observed in AU/AU base pair step in crystal structures of RNA double helices. We have generated stacking energy hyperspace by modeling geometries with variations along the important degrees of freedom, roll, and slide, which were chosen via statistical analysis as maximally sequence dependent. Corresponding energy contours were constructed by several quantum chemical methods including dispersion corrections. This analysis established the most suitable methods for stacked base pair systems despite the limitation imparted by number of atom in a base pair step to employ very high level of theory. All the methods predict negative roll value and near-zero slide to be most favorable for the purine-pyrimidine steps, in agreement with Calladine's steric clash based rule. Successive base pairs in RNA are always linked by sugar-phosphate backbone with C3'-endo sugars and this demands C1'-C1' distance of about 5.4 Å along the chains. Consideration of an energy penalty term for deviation of C1'-C1' distance from the mean value, to the recent DFT-D functionals, specifically ωB97X-D appears to predict reliable energy contour for AU/AU step. Such distance-based penalty improves energy contours for the other purine-pyrimidine sequences also. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 107-120, 2014. PMID:23722519

  17. Experimental and Theoretical Determination of Dissociation Energies of Dispersion-Dominated Aromatic Molecular Complexes.

    PubMed

    Frey, Jann A; Holzer, Christof; Klopper, Wim; Leutwyler, Samuel

    2016-05-11

    The dissociation energy (D0) of an isolated and cold molecular complex in the gas-phase is a fundamental measure of the strength of the intermolecular interactions between its constituent moieties. Accurate D0 values are important for the understanding of intermolecular bonding, for benchmarking high-level theoretical calculations, and for the parametrization of force-field models used in fields ranging from crystallography to biochemistry. We review experimental and theoretical methods for determining gas-phase D0 values of M·S complexes, where M is a (hetero)aromatic molecule and S is a closed-shell "solvent" atom or molecule. The experimental methods discussed involve M-centered (S0 → S1) electronic excitation, which is often followed by ionization to the M(+)·S ion. The D0 is measured by depositing a defined amount of vibrational energy in the neutral ground state, giving M(‡)·S, the neutral S1 excited state, giving M*·S, or the M(+)·S ion ground state. The experimental methods and their relative advantages and disadvantages are discussed. Based on the electronic structure of M and S, we classify the M·S complexes as Type I, II, or III, and discuss characteristic properties of their respective potential energy surfaces that affect or hinder the determination of D0. Current theoretical approaches are reviewed, which comprise methods based on a Kohn-Sham reference determinant as well as wave function-based methods based on coupled-cluster theory. PMID:27055105

  18. Characterizing the Use of Ultrasonic Energy in Promoting Uniform Microstructural Dispersions in Immiscible Mixtures

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Fedoseyev, A. I.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Gravity driven separation and preferential wetting precludes uniform microstructural distributions during solidification processing of immiscible, liquid-liquid mixtures. Historically, it is, however, established that liquid/liquid suspensions can be established and maintained by utilizing ultrasound. Following a brief introduction the results of experiments on immiscible mixtures subjected to ultrasonic energy during solidification processing will be compared and evaluated in view of a recently developed mathematical model. The presentation continues by discussion of scaling the model to commercial viability and concludes with the implications of such processing in a microgravity environment.

  19. Characterizing the Use of Ultrasonic Energy in Promoting Uniform Microstructural Dispersions in Immiscible Mixtures

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Fedoseyev, A. I.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Gravity driven separation and preferential wetting precludes uniform microstructural distributions during solidification processing of immiscible, liquid-liquid mixtures. Historically, it is, however, established that liquid/liquid suspensions can be established and maintained by utilizing ultrasound. Following a brief introduction the results of experiments on immiscible mixtures subjected to ultrasonic energy during solidification processing will be compared and evaluated in view of a recently developed mathematical model. The presentation continues by discussion of scaling the model to commercial viability and concludes with the implications of such processing in a microgravity environment.

  20. High-Energy Magnon Dispersion and Multimagnon Continuum in La2CuO4

    NASA Astrophysics Data System (ADS)

    Headings, Neil; Hayden, Stephen; Coldea, Radu; Perring, Toby

    2009-03-01

    We report high-energy neutron scattering measurements of the magnetic excitations in the S=1/2 antiferromagnet La2CuO4. Measurements were made using the MAPS time-of-flight spectrometer at the ISIS spallation source. Previous measurements found evidence for higher order (cyclic) exchange couplings. We find evidence for significant corrections to linear spin-wave (SW) theory including these higher-order exchange constants. In particular, the intensity of the spin wave pole deviates strongly from that predicted by SW theory near the Q=(1/2,0) position. We also find evidence for a multi-magnon continuum.

  1. Modeling complex dispersed energy and clean water systems for the United States/Mexico border

    NASA Astrophysics Data System (ADS)

    Herrera, Hugo Francisco Lopez

    As world population grows, and its technology evolves, the demand for electricity inexorably increases. Until now most of this electricity has been produced via fossil fuels, non-renewable energy resources that are irreversibly deteriorating our environment. On the economical aspect it does not get any better. Let's not forget market rules, the higher the demand and lower the offer, the higher the price we will have to pay. Oil is an excellent example. Some countries try to solve this situation with Pharaohnic projects, i.e. investing absurd amounts of money in 'green electricity' building monstrous dams to power equally monstrous hydroelectric power plants. The only problem with this is that it is not green at all---it does have an enormous environmental impact---it is extremely complicated and expensive to implement. It is important to point out, that this research project does not try to solve world's thirst for electricity. It is rather aimed to help solve this problematic at a much lower scale---it should be considered as an extremely small step in the right direction. It focuses on satisfying the local electricity needs with renewable, non-contaminating and locally available resources. More concisely, this project focuses on the attainment and use of hydrogen as an alternate energy source in El Paso/Juarez region. Clean technology is nowadays available to produce hydrogen and oxygen, i.e. the photoelectrolysis process. Photovoltaic cells coupled with electrolytic devices can be used to produce hydrogen and oxygen in a sustainable manner. In this research, simulation models of hybrid systems were designed and developed. They were capable to compare, predict and evaluate different options for hydrogen generation. On the other hand, with the produced hydrogen from the electrolysis process it was possible to generate electricity through fuel cells. The main objectives of the proposed research were to define how to use the resources for the attainment of hydrogen

  2. Ultrafast potential energy surface softening of one-dimensional organic conductors revealed by picosecond time-resolved Laue crystallography.

    PubMed

    Messerschmidt, Marc; Tschentscher, Thomas; Cammarata, Marco; Meents, Alke; Sager, Christian; Davaasambuu, Jav; Busse, Gerhard; Techert, Simone

    2010-07-29

    Time-resolved Laue crystallography has been employed to study the structural dynamics of a one-dimensional organic conductor (tetrathiafulvalene-p-chloranil) during photoexcitation in the regime of the neutral to ionic phase transition. Exciting this crystalline system with 800 nm 100 fs long optical pulses leads to ultrafast population of a structural intermediate as early as 50 ps after excitation with a lifetime of at least 10 ns. Starting from the neutral phase, this intermediate has been assigned as a precursor state toward the photoinduced population of the ionic phase. The observed intensity changes are significantly different from comparable equilibrium structures. The interpretation of this structural data is that the potential of this intermediate is being softened during its population in a dynamical process. The depopulation proceeds through thermal processes. PMID:20597517

  3. [Influence of the Experiment Energy Dispersive X-Ray Fluorescence Measurement of Uranium by Different Excitation Source].

    PubMed

    Xiong, Chao; Ge, Liang-quan; Liu, Duan; Zhang, Qing-xian; Gu, Yi; Luo, Yao-yao; Zhao, Jian-kun

    2016-03-01

    Aiming at the self-excitation effect on the interference of measurements which exist in the process of Energy dispersive X-ray fluorescence method for uranium measurement. To solve the problem of radioactive isotopes only used as excitation source in determination of uranium. Utilizing the micro X-ray tube to test Self-excitation effect to get a comparison of the results obtained by three different uranium ore samples--109 Cd, 241 Am and Mirco X-ray tube. The results showed that self-excitation effect produced the area measure of characteristic X-ray peak is less than 1% of active condition, also the interference of measurements can be negligible. Photoelectric effect cross-section excited by 109 Cd is higher, corresponding fluorescence yield is higher than excited by 241 Am as well due to characteristics X-ray energy of 109 Cd, 22.11 & 24.95 KeV adjacent to absorption edge energy of L(α), 21.75 KeV, based on the above, excitation efficiency by 109 Cd is higher than 241 Am; The fact that measurement error excited by 241 Am is significantly greater than by 109 Cd is mainly due to peak region overlap between L energy peaks of uranium and Scattering peak of 241 Am, 26.35 keV, These factors above caused the background of measured Spectrum higher; The error between the uranium content in ore samples which the X-ray tube as the excitation source and the chemical analysis results is within 10%. Conclusion: This paper come to the conclusion that the technical quality of uranium measurement used X-ray tube as excitation source is superior to that in radioactive source excitation mode. PMID:27400534

  4. Optimization of the K-edge imaging for vulnerable plaques using gold nanoparticles and energy-resolved photon counting detectors: a simulation study

    PubMed Central

    Alivov, Yahya; Baturin, Pavlo; Le, Huy Q.; Ducote, Justin; Molloi, Sabee

    2014-01-01

    We investigated the effect of different imaging parameters such as dose, beam energy, energy resolution, and number of energy bins on image quality of K-edge spectral computed tomography (CT) of gold nanoparticles (GNP) accumulated in an atherosclerotic plaque. Maximum likelihood technique was employed to estimate the concentration of GNP, which served as a targeted intravenous contrast material intended to detect the degree of plaque's inflammation. The simulations studies used a single slice parallel beam CT geometry with an X-ray beam energy ranging between 50 and 140 kVp. The synthetic phantoms included small (3 cm in diameter) cylinder and chest (33x24 cm2) phantom, where both phantoms contained tissue, calcium, and gold. In the simulation studies GNP quantification and background (calcium and tissue) suppression task were pursued. The X-ray detection sensor was represented by an energy resolved photon counting detector (e.g., CdZnTe) with adjustable energy bins. Both ideal and more realistic (12% FWHM energy resolution) implementations of photon counting detector were simulated. The simulations were performed for the CdZnTe detector with pixel pitch of 0.5-1 mm, which corresponds to the performance without significant charge sharing and cross-talk effects. The Rose model was employed to estimate the minimum detectable concentration of GNPs. A figure of merit (FOM) was used to optimize the X-ray beam energy (kVp) to achieve the highest signal-to-noise ratio (SNR) with respect to patient dose. As a result, the successful identification of gold and background suppression was demonstrated. The highest FOM was observed at 125 kVp X-ray beam energy. The minimum detectable GNP concentration was determined to be approximately 1.06 μmol/mL (0.21 mg/mL) for an ideal detector and about 2.5 μmol/mL (0.49 mg/mL) for more realistic (12% FWHM) detector. The studies show the optimal imaging parameters at lowest patient dose using an energy resolved photon counting detector

  5. Picosecond time-resolved emission studies. I. Real-time measurements of solvent-solute interactions. II. Kinetics of energy flow in a photosynthetic antenna system. [4-aminophthalimide

    SciTech Connect

    Yeh, S.W.

    1985-11-01

    Using a picosecond fluorimeter, the dynamics of solvation of electronically excited 4-aminophthalimide in a variety of solvents is measured. The solvation process is manifested by a time-dependent red shift in the emission spectrum in certain solvents. This red shift is time-resolved using a streak camera system. The time constant of the relaxation is found to correlate strongly with the longitudinal dielectric relaxation rate of the solvent. The correlation holds for changes in solvent, for isotopic substitution of a solvent, and for changes in temperature. Never before have direct measurements of excited-state solvation dynamics been shown to correlate with dielectric relaxation over such a wide range of experimental conditions. Emission from certain photosynthetic antenna complexes, phycobilisomes, and from the building blocks of phycobilisomes, phycobiliproteins, has also been studied using the streak camera system. Both the rising and filling portions of the time-resolved emission profiles of the fluorescing chromophores in these structures are studied. The rates of energy transfer between structural domains of the antenna complex and within the isolated biliprotein complexes are deduced from these studies. Comparison of emission profiles from a series of structurally distinct phycobilisomes isolated from three related strains of cyanobacteria have provided new insights into the correlation of the energy transfer function and macromolecular structure in these light-harvesting antenna systems. 133 refs., 58 figs., 14 tabs.

  6. Modification of energy-transfer processes in the cyanobacterium, Arthrospira platensis, to adapt to light conditions, probed by time-resolved fluorescence spectroscopy.

    PubMed

    Akimoto, Seiji; Yokono, Makio; Aikawa, Shimpei; Kondo, Akihiko

    2013-11-01

    In cyanobacteria, the interactions among pigment-protein complexes are modified in response to changes in light conditions. In the present study, we analyzed excitation energy transfer from the phycobilisome and photosystem II to photosystem I in the cyanobacterium Arthrospira (Spirulina) platensis. The cells were grown under lights with different spectral profiles and under different light intensities, and the energy-transfer characteristics were evaluated using steady-state absorption, steady-state fluorescence, and picosecond time-resolved fluorescence spectroscopy techniques. The fluorescence rise and decay curves were analyzed by global analysis to obtain fluorescence decay-associated spectra. The direct energy transfer from the phycobilisome to photosystem I and energy transfer from photosystem II to photosystem I were modified depending on the light quality, light quantity, and cultivation period. However, the total amount of energy transferred to photosystem I remained constant under the different growth conditions. We discuss the differences in energy-transfer processes under different cultivation and light conditions. PMID:23605291

  7. Molecular dispersion energy parameters for alkali and halide ions in aqueous solution.

    PubMed

    Reiser, S; Deublein, S; Vrabec, J; Hasse, H

    2014-01-28

    Thermodynamic properties of aqueous solutions containing alkali and halide ions are determined by molecular simulation. The following ions are studied: Li(+), Na(+), K(+), Rb(+), Cs(+), F(-), Cl(-), Br(-), and I(-). The employed ion force fields consist of one Lennard-Jones (LJ) site and one concentric point charge with a magnitude of ±1 e. The SPC/E model is used for water. The LJ size parameter of the ion models is taken from Deublein et al. [J. Chem. Phys. 136, 084501 (2012)], while the LJ energy parameter is determined in the present study based on experimental self-diffusion coefficient data of the alkali cations and the halide anions in aqueous solutions as well as the position of the first maximum of the radial distribution function of water around the ions. On the basis of these force field parameters, the electric conductivity, the hydration dynamics of water molecules around the ions, and the enthalpy of hydration is predicted. Considering a wide range of salinity, this study is conducted at temperatures of 293.15 and 298.15 K and a pressure of 1 bar. PMID:25669552

  8. Molecular dispersion energy parameters for alkali and halide ions in aqueous solution

    SciTech Connect

    Reiser, S.; Deublein, S.; Hasse, H.; Vrabec, J.

    2014-01-28

    Thermodynamic properties of aqueous solutions containing alkali and halide ions are determined by molecular simulation. The following ions are studied: Li{sup +}, Na{sup +}, K{sup +}, Rb{sup +}, Cs{sup +}, F{sup −}, Cl{sup −}, Br{sup −}, and I{sup −}. The employed ion force fields consist of one Lennard-Jones (LJ) site and one concentric point charge with a magnitude of ±1 e. The SPC/E model is used for water. The LJ size parameter of the ion models is taken from Deublein et al. [J. Chem. Phys. 136, 084501 (2012)], while the LJ energy parameter is determined in the present study based on experimental self-diffusion coefficient data of the alkali cations and the halide anions in aqueous solutions as well as the position of the first maximum of the radial distribution function of water around the ions. On the basis of these force field parameters, the electric conductivity, the hydration dynamics of water molecules around the ions, and the enthalpy of hydration is predicted. Considering a wide range of salinity, this study is conducted at temperatures of 293.15 and 298.15 K and a pressure of 1 bar.

  9. DIBENZYLAMMONIUM AND SODIUM DIBENZYLDITHIOCARBAMATES AS PRECIPITANTS FOR PRECONCENTRATION OF TRACE ELEMENTS IN WATER FOR ANALYSIS BY ENERGY DISPERSIVE X-RAY FLUORESCENCE

    EPA Science Inventory

    Precipitation with combined dibenzylammonium dibenzyldithiocarbamate and sodium dibenzyldithiocarbamate at pH 5.0 can be used to separate 22 trace elements from water. Membrane filtration on the precipitate yielded a thin sample, suitable for analysis by energy dispersive X-ray f...

  10. In-situ and operando characterization of batteries with energy-dispersive synchrotron x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Paxton, William Arthur

    Batteries play a pivotal role in the low-carbon society that is required to thwart the effects of climate change. Alternative low-carbon energy sources, such as wind and solar, are often intermittent and unreliable. Batteries are able capture their energy and deliver it later when it is needed. The implementation of battery systems in grid-level and transportation sectors is essential for efficient use of alternative energy sources. Scientists and engineers need better tools to analyze and measure the performance characteristics of batteries. One of the main hindrances in the progress of battery research is that the constituent electrode materials are inaccessible once an electrochemical cell is constructed. This leaves the researcher with a limited number of available feedback mechanisms to assess the cell's performance, e.g., current, voltage, and impedance. These data are limited in their ability to reveal the more-localized smaller-scale structural mechanisms on which the batteries' performance is so dependent. Energy-dispersive x-ray diffraction (EDXRD) is one of the few techniques that can internally probe a sealed battery. By analyzing the structural behavior of battery electrodes, one is able to gain insight to the physical properties on which the battery's performance is dependent. In this dissertation, EDXRD with ultrahigh energy synchrotron radiation is used to probe the electrodes of manufactured primary and secondary lithium batteries under in-situ and operando conditions. The technique is then applied to solve specific challenges facing lithium ion batteries. Diffraction spectra are collected from within a battery at 40 micrometer resolution. Peak-fitting is used to quantitatively estimate the abundance of lithiated and non-lithiated phases. Through mapping the distribution of phases within, structural changes are linked to the battery's galvanic response. A three-dimensional spatial analysis of lithium iron phosphate batteries suggests that evolution

  11. Velocity Dispersions Across Bulge Types

    SciTech Connect

    Fabricius, Maximilian; Bender, Ralf; Hopp, Ulrich; Saglia, Roberto; Drory, Niv; Fisher, David

    2010-06-08

    We present first results from a long-slit spectroscopic survey of bulge kinematics in local spiral galaxies. Our optical spectra were obtained at the Hobby-Eberly Telescope with the LRS spectrograph and have a velocity resolution of 45 km/s (sigma*), which allows us to resolve the velocity dispersions in the bulge regions of most objects in our sample. We find that the velocity dispersion profiles in morphological classical bulge galaxies are always centrally peaked while the velocity dispersion of morphologically disk-like bulges stays relatively flat towards the center--once strongly barred galaxies are discarded.

  12. Bulk substrate porosity verification by applying Monte Carlo modeling and Castaing's formula using energy-dispersive x-rays

    NASA Astrophysics Data System (ADS)

    Yung, Lai Chin; Fei, Cheong Choke; Mandeep, Jit Singh; Amin, Nowshad; Lai, Khin Wee

    2015-11-01

    The leadframe fabrication process normally involves additional thin-metal layer plating on the bulk copper substrate surface for wire bonding purposes. Silver, tin, and copper flakes are commonly adopted as plating materials. It is critical to assess the density of the plated metal layer, and in particular to look for porosity or voids underneath the layer, which may reduce the reliability during high-temperature stress. A fast, reliable inspection technique is needed to assess the porosity or void weakness. To this end, the characteristics of x-rays generated from bulk samples were examined using an energy-dispersive x-ray (EDX) detector to examine the porosity percentage. Monte Carlo modeling was integrated with Castaing's formula to verify the integrity of the experimental data. Samples with different porosity percentages were considered to test the correlation between the intensity of the collected x-ray signal and the material density. To further verify the integrity of the model, conventional cross-sectional samples were also taken to observe the porosity percentage using Image J software measurement. A breakthrough in bulk substrate assessment was achieved by applying EDX for the first time to nonelemental analysis. The experimental data showed that the EDX features were not only useful for elemental analysis, but also applicable to thin-film metal layer thickness measurement and bulk material density determination. A detailed experiment was conducted using EDX to assess the plating metal layer and bulk material porosity.

  13. Distribution of toxic elements in teeth treated with amalgam using μ-energy dispersive X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Guerra, M.; Ferreira, C.; Carvalho, M. L.; Santos, J. P.; Pessanha, S.

    2016-08-01

    Over the years, the presence of mercury in amalgam fillings has raised some safety concerns. Amalgam is one of the most commonly used tooth fillings and contains approximately 50% of elemental mercury and 50% of other metals, mostly silver, tin and copper. Amalgam can release small amounts of mercury vapor over time, and patients can absorb these vapors by inhaling or ingesting them. In this study, 10 human teeth treated with dental amalgam were analyzed using energy dispersive X-ray fluorescence (EDXRF) to study the diffusion of its constituents, Ag, Cu, Sn and Hg. The used EDXRF setup, makes use of a polycapillary lens to focus radiation up to 25 μm allowing the mapping of the elemental distribution in the samples. Quantification was performed using the inbuilt software based on the Fundamental Parameters method for bulk samples, considering a hydroxyapatite matrix. The teeth were longitudinally cut and each slice was scanned from the surface enamel to the inner region (dentin and pulp cavity). Mercury concentration profiles show strong levels of this element close to the amalgam region, decreasing significantly in the dentin, and increasing again up to 40,000 μg·g- 1 in the cavity were the pulp used to exist when the tooth was vital.

  14. Atomic-scale Chemical Imaging and Quantification of Metallic Alloy Structures by Energy-Dispersive X-ray Spectroscopy

    PubMed Central

    Lu, Ping; Zhou, Lin; Kramer, M. J.; Smith, David J.

    2014-01-01

    Determination of atomic-scale crystal structure for nanostructured intermetallic alloys, such as magnetic alloys containing Al, Ni, Co (alnico) and Fe, is crucial for understanding physical properties such as magnetism, but technically challenging due to the small interatomic distances and the similar atomic numbers. By applying energy-dispersive X-ray spectroscopy (EDS) mapping to the study of two intermetallic phases of an alnico alloy resulting from spinodal decomposition, we have determined atomic-scale chemical composition at individual lattice sites for the two phases: one is the B2 phase with Fe0.76Co0.24 -Fe0.40Co0.60 ordering and the other is the L21 phase with Ni0.48Co0.52 at A-sites, Al at BΙ-sites and Fe0.20Ti0.80 at BΙΙ-sites, respectively. The technique developed through this study represents a powerful real-space approach to investigate structure chemically at the atomic scale for a wide range of materials systems. PMID:24492747

  15. Determination of selenium at trace levels in geologic materials by energy-dispersive X-ray fluorescence spectrometry

    USGS Publications Warehouse

    Wahlberg, J.S.

    1981-01-01

    Low levels of selenium (0.1-500 ppm) in both organic and inorganic geologic materials can be semiquantitatively measured by isolating Se as a thin film for presentation to an energy-dispersive X-ray fluorescence spectrometer. Suitably pulverized samples are first digested by fusing with a mixture of Na2CO3 and Na2O2. The fusion cake is dissolved in distilled water, buffered with NH4Cl, and filtered to remove Si and the R2O3 group. A carrier solution of Na2TeO4, plus solid KI, hydrazine sulfate and Na2SO3, is added to the filtrate. The solution is then vacuum-filtered through a 0.45-??m pore-size filter disc. The filter, with the thin film of precipitate, is supported between two sheets of Mylar?? film for analysis. Good agreement is shown between data reported in this study and literature values reported by epithermal neutron-activation analysis and spectrofluorimetry. The method can be made quantitative by utilizing a secondary precipitation to assure complete recovery of the Se. The X-ray method offers fast turn-around time and a reasonably high production rate. ?? 1981.

  16. Scanning Electron Microscopy Findings With Energy-Dispersive X-ray Investigations of Cosmetically Tinted Contact Lenses

    PubMed Central

    Hotta, Fumika; Imai, Shoji; Miyamoto, Tatsuro; Mitamura-Aizawa, Sayaka; Mitamura, Yoshinori

    2015-01-01

    Objective: To investigate the surfaces and principal elements of the colorants of cosmetically tinted contact lenses (Cos-CLs). Methods: We analyzed the surfaces and principal elements of the colorants of five commercially available Cos-CLs using scanning electron microscopy with energy-dispersive x-ray analysis. Results: In two Cos-CLs, the anterior and posterior surfaces were smooth, and colorants were found inside the lens. One lens showed colorants located to a depth of 8 to 14 μm from the anterior side of the lens. In the other lens, colorants were found in the most superficial layer on the posterior surface, although a coated layer was observed. The colorants in the other three lenses were deposited on either lens surface. Although a print pattern was uniform in embedded type lenses, uneven patterns were apparent in dot-matrix design lenses. Colorants used in all lenses contained chlorine, iron, and titanium. In the magnified scanning electron microscopy images of a certain lens, chlorine is exuded and spread. Conclusions: Cosmetically tinted contact lenses have a wide variety of lens surfaces and colorants. Colorants may be deposited on the lens surface and consist of an element that has tissue toxicity. PMID:25799458

  17. Atomic-scale chemical imaging and quantification of metallic alloy structures by energy-dispersive X-ray spectroscopy.

    PubMed

    Lu, Ping; Zhou, Lin; Kramer, M J; Smith, David J

    2014-01-01

    Determination of atomic-scale crystal structure for nanostructured intermetallic alloys, such as magnetic alloys containing Al, Ni, Co (alnico) and Fe, is crucial for understanding physical properties such as magnetism, but technically challenging due to the small interatomic distances and the similar atomic numbers. By applying energy-dispersive X-ray spectroscopy (EDS) mapping to the study of two intermetallic phases of an alnico alloy resulting from spinodal decomposition, we have determined atomic-scale chemical composition at individual lattice sites for the two phases: one is the B2 phase with Fe0.76Co0.24 -Fe0.40Co0.60 ordering and the other is the L2(1) phase with Ni0.48Co0.52 at A-sites, Al at B(Ι)-sites and Fe0.20Ti0.80 at B(ΙΙ)-sites, respectively. The technique developed through this study represents a powerful real-space approach to investigate structure chemically at the atomic scale for a wide range of materials systems. PMID:24492747

  18. NASA Li/CF(x) cell problem analysis: Scanning electron microscopy with energy dispersive x ray spectrometry

    NASA Technical Reports Server (NTRS)

    Baker, John

    1991-01-01

    An analysis was made of Lithium/carbon fluoride cell parts for possible chloride contamination induced by exposure to thionyl chloride (SOCl2); various samples were submitted for analysis. Only a portion of the analysis which has been conducted is covered, herein, namely analysis by scanning electron microscopy with energy dispersive x ray spectrometry (SEM/EDS). A strip of nickel was exposed to SOCl2 vapors to observe variations in surface concentrations of sulfur and chlorine with time. By detecting chlorine one can not infer contamination by SOCl2 only that contamination is present. Six samples of stainless steel foil were analyzed for chlorine using EDS. Chlorine was not detected on background samples but was detected on the samples which had been handled including those which had been cleaned. Cell covers suspected of being contaminated while in storage and covers which were not exposed to the same storage conditions were analyzed for chlorine. Although no chlorine was found on the covers from cells, it was found on all stored covers. Results are presented with techniques shown for analysis and identification. Relevant photomicrographs are presented.

  19. Time-resolved investigation of ionization processes in the Dresden Electron Beam Ion Source

    SciTech Connect

    Zschornack, G.; Heller, R.; Kreller, M.; Landgraf, S.; Grossmann, F.; Kentsch, U.; Ovsyannikov, V.P.; Schmidt, M.; Ullmann, F.

    2006-03-15

    The emission of characteristic x-ray lines of iron and krypton ions was measured in dependence on the confinement time in an Electron Beam Ion Source, the DRESDEN EBIS. Primarily the measurement was focused on x-ray lines from dielectronic recombination (DR) processes. Due to the sharp resonant character of DR processes the formation of individual ion charge states can be observed at different electron energies (resonance energies) with time-resolved energy-dispersive x-ray spectroscopy. In the case of iron ions, experimentally observed resonance energies are compared to resonance energies calculated with the Flexible Atomic Code (FAC). Further, on outer-shell K{sub {alpha}} x-ray satellites of krypton ions are time-resolve analyzed to construct the evolution of the ionization of krypton ions in the electron beam.

  20. Nanosecond time-resolved FTIR emission spectroscopy: Monitoring the energy distribution of highly vibrationally excited molecules during collisional deactivation

    SciTech Connect

    Pibel, C.D.; Sirota, E.; Brenner, J.; Dai, H.

    1998-01-01

    The 10{sup {minus}8} second time resolution in infrared emission spectroscopy has been demonstrated using a Fourier Transform spectrometer paired with a fast HgCdTe detector. The rapid time response of this system has enabled us to measure, with subcollisional period time resolution, the emission spectrum of highly vibrationally excited NO{sub 2} molecules during collisional deactivation by room temperature NO{sub 2}. The greatly improved time resolution of the spectra allows the determination of N(E,t), the instantaneous energy distribution of the ensemble of excited molecules, with virtually no distortion due to collisional averaging. In addition, an improved procedure for extracting optimized N(E,t) from the spectral data makes no prior assumptions about the shape of the energy distribution. It is found that the distribution is well approximated as the sum of a Gaussian function at high vibrational energies and a population at low energies resulting from V{endash}V transfer to bath NO{sub 2} molecules. The observation of a Gaussian-like function for the highly excited molecules is consistent with the widely invoked assumption that the step-size function of energy transfer per collision is exponential. {copyright} {ital 1998 American Institute of Physics.}

  1. Proceedings of the Wind Energy and Birds/Bats Workshop: Understanding and Resolving Bird and Bat Impacts

    SciTech Connect

    Schwartz, Susan Savitt

    2004-09-01

    Most conservation groups support the development of wind energy in the US as an alternative to fossil and nuclear-fueled power plants to meet growing demand for electrical energy. However, concerns have surfaced over the potential threat to birds, bats, and other wildlife from the construction and operation of wind turbine facilities. Co-sponsored by the American Bird Conservancy (ABC) and the American Wind Energy Association (AWEA), the Wind Energy and Birds/Bats Workshop was convened to examine current research on the impacts of wind energy development on avian and bat species and to discuss the most effective ways to mitigate such impacts. On 18-19 May 2004, 82 representatives from government, non-government organizations, private business, and academia met to (1) review the status of the wind industry and current project development practices, including pre-development risk assessment and post-construction monitoring; (2) learn what is known about direct, indirect (habitat), and cumulative impacts on birds and bats from existing wind projects; about relevant aspects of bat and bird migration ecology; about offshore wind development experience in Europe; and about preventing, minimizing, and mitigating avian and bat impacts; (3) review wind development guidelines developed by the USFWS and the Washington State Department of Fish and Wildlife; and (4) identify topics needing further research and to discuss what can be done to ensure that research is both credible and accessible. These Workshop Proceedings include detailed summaries of the presentations made and the discussions that followed.

  2. A spatially resolved retarding field energy analyzer design suitable for uniformity analysis across the surface of a semiconductor wafer

    SciTech Connect

    Sharma, S.; Gahan, D. Hopkins, M. B.; Kechkar, S.; Daniels, S.

    2014-04-15

    A novel retarding field energy analyzer design capable of measuring the spatial uniformity of the ion energy and ion flux across the surface of a semiconductor wafer is presented. The design consists of 13 individual, compact-sized, analyzers, all of which are multiplexed and controlled by a single acquisition unit. The analyzers were tested to have less than 2% variability from unit to unit due to tight manufacturing tolerances. The main sensor assembly consists of a 300 mm disk to mimic a semiconductor wafer and the plasma sampling orifices of each sensor are flush with disk surface. This device is placed directly on top of the rf biased electrode, at the wafer location, in an industrial capacitively coupled plasma reactor without the need for any modification to the electrode structure. The ion energy distribution, average ion energy, and average ion flux were measured at the 13 locations over the surface of the powered electrode to determine the degree of spatial nonuniformity. The ion energy and ion flux are shown to vary by approximately 20% and 5%, respectively, across the surface of the electrode for the range of conditions investigated in this study.

  3. A spatially resolved retarding field energy analyzer design suitable for uniformity analysis across the surface of a semiconductor wafer.

    PubMed

    Sharma, S; Gahan, D; Kechkar, S; Daniels, S; Hopkins, M B

    2014-04-01

    A novel retarding field energy analyzer design capable of measuring the spatial uniformity of the ion energy and ion flux across the surface of a semiconductor wafer is presented. The design consists of 13 individual, compact-sized, analyzers, all of which are multiplexed and controlled by a single acquisition unit. The analyzers were tested to have less than 2% variability from unit to unit due to tight manufacturing tolerances. The main sensor assembly consists of a 300 mm disk to mimic a semiconductor wafer and the plasma sampling orifices of each sensor are flush with disk surface. This device is placed directly on top of the rf biased electrode, at the wafer location, in an industrial capacitively coupled plasma reactor without the need for any modification to the electrode structure. The ion energy distribution, average ion energy, and average ion flux were measured at the 13 locations over the surface of the powered electrode to determine the degree of spatial nonuniformity. The ion energy and ion flux are shown to vary by approximately 20% and 5%, respectively, across the surface of the electrode for the range of conditions investigated in this study. PMID:24784609

  4. Energy transfer in the primary stages of the photosynthetic process investigated by picosecond time resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Pellegrino, F.

    The fate of the absorbed light energy in the primary stages of the photosynthetic process was studied. In particular, the energy transfer in the accessory pigment complex consisting of carotenoids, Chl. a and Chl. b in higher green plants and phycobiliproteins in blue-green algae were investigated. These accessory pigments are responsible for the highly efficient transfer of the excitation energy to the photochemically active reaction center traps. The risetime, decay time, fluorescence depolarization, temperature and intensity dependence of the fluoresence emission from higher green plant and algal photosystems were directly measured. Excitation was provided by single picosecond laser pulses, as well as a train of pulses at 530 nm, within an intensity range of 10 to the 12th power to 10 to the 16th power photons/sq cm per pulse.

  5. Measurements of electron temperature profiles on Alcator C-Mod using a novel energy-resolving x-ray camera

    NASA Astrophysics Data System (ADS)

    Maddox, J.; Delgado, L.; Pablant, N.; Hill, K. W.; Bitter, M.; Efthimion, P.; Rice, J.

    2015-11-01

    The most common electron temperature diagnostics, Thomson Scattering (TS) and Electron Cyclotron Emission (ECE), both require large diagnostic footprints and expensive optics. Another electron temperature diagnostic is the Pulse-Height-Analysis (PHA) system, which derives the electron temperature from the x-ray bremsstrahlung continuum. However, the main disadvantage of the PHA method is poor temporal resolution of the Si(Li) diode detectors. This paper presents a novel x-ray pinhole camera, which uses a pixilated Pilatus detector that allows single photon counting at a rate 2MHz per pixel and the setting of energy thresholds. The detector configuration is optimized by Shannon-sampling theory, such that spatial profiles of the x-ray continuum intensity can be obtained simultaneously for different energies, in the range from 4 to 16 keV. The exponential-like dependence of the x-ray intensity with photon energies is compared with a model describing the Be filter, attenuation in air, and detector efficiency, as well as different sets of energy thresholds. Electron temperature measurements are compared with TS and ECE measurements. This work was supported by the US DOE Contract No.DE-AC02-09CH11466 and the DoE Summer Undergraduate Laboratory Internship (SULI) program.

  6. Long cavity and low repetition rate passively mode-locked fiber laser with high-energy right angle trapezoid shaped soliton in anomalous dispersion regime

    NASA Astrophysics Data System (ADS)

    Luo, Wenfeng; Lv, Shuyuan; Zhao, Xiaoxia; Qiao, Dun

    2015-05-01

    A long cavity passively mode locked fiber laser in the anomalous dispersion regime is reported. Nonlinear polarization rotation technique is employed to achieve the mode locking in our experiments. The output pulse from the fiber laser has the Gaussian profile spectrum and right angle trapezoid shape. Stable mode locking is achieved without using any dispersion-compensation components. The single pulse with an energy of 652 nJ and a repetition rate of 836 kHz at the pump power of approximately 500 mW is obtained and the duration of the output pulse increases linearly with the pump power. Different from the conventional low-energy soliton pulse, experimental results demonstrate that the passively mode locked fiber laser operating in the anomalous regime can also realize high energy pulse.

  7. Studies on the formation of polymeric nano-emulsions obtained via low-energy emulsification and their use as templates for drug delivery nanoparticle dispersions.

    PubMed

    Calderó, G; Montes, R; Llinàs, M; García-Celma, M J; Porras, M; Solans, C

    2016-09-01

    Ethylcellulose nanoparticles have been obtained from O/W nano-emulsions of the water/polyoxyethylene 10 oleyl ether/[ethyl acetate+4wt% ethylcellulose] system by low energy-energy emulsification at 25°C. Nano-emulsions with droplet sizes below 200nm and high kinetic stability were chosen for solubilising dexamethasone (DXM). Phase behaviour, conductivity and optical analysis studies of the system have evidenced for the first time that both, the polymer and the drug play a role on the structure of the aggregates formed along the emulsification path. Nano-emulsion formation may take place by both, phase inversion and self-emulsification. Spherical polymeric nanoparticles containing surfactant, showing sizes below 160nm have been obtained from the nano-emulsions by organic solvent evaporation. DXM loading in the nanoparticles was high (>90%). The release kinetics of nanoparticle dispersions with similar particle size and encapsulated DXM but different polymer to surfactant ratio were studied and compared to an aqueous DXM solution. Drug release from the nanoparticle dispersions was slower than from the aqueous solution. While the DXM solution showed a Fickian release pattern, the release behaviour from the nanoparticle dispersions was faster than that expected from a pure Fickian release. A coupled diffusion/relaxation model fitted the results very well, suggesting that polymer chains undergo conformational changes enhancing drug release. The contribution of diffusion and relaxation to drug transport in the nanoparticle dispersions depended on their composition and release time. Surfactant micelles present in the nanoparticle dispersion may exert a mild reservoir effect. The small particle size and the prolonged DXM release provided by the ethylcellulose nanoparticle dispersions make them suitable vehicles for controlled drug delivery applications. PMID:27341306

  8. Resolving Past Liabilities for Future Reduction in Greenhouse Gases; Nuclear Energy and the Outstanding Federal Liability of Spent Nuclear Fuel

    NASA Astrophysics Data System (ADS)

    Donohue, Jay

    This thesis will: (1) examine the current state of nuclear power in the U.S.; (2) provide a comparison of nuclear power to both existing alternative/renewable sources of energy as well as fossil fuels; (3) dissect Standard Contracts created pursuant to the National Waste Policy Act (NWPA), Congress' attempt to find a solution for Spent Nuclear Fuel (SNF), and the designation of Yucca Mountain as a repository; (4) the anticipated failure of Yucca Mountain; (5) explore WIPP as well as attempts to build a facility on Native American land in Utah; (6) examine reprocessing as a solution for SNF used by France and Japan; and, finally, (7) propose a solution to reduce GHG's by developing new nuclear energy plants with financial support from the U.S. government and a solution to build a storage facility for SNF through the sitting of a repository based on a "bottom-up" cooperative federalism approach.

  9. ACOUSTIC RECTIFICATION IN DISPERSIVE MEDIA

    SciTech Connect

    Cantrell, John H.

    2009-03-03

    It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

  10. Acoustic Rectification in Dispersive Media

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.

    2008-01-01

    It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

  11. A comparison of ab initio quantum-mechanical and experimental D0 binding energies of eleven H-bonded and eleven dispersion-bound complexes.

    PubMed

    Haldar, Susanta; Gnanasekaran, Ramachandran; Hobza, Pavel

    2015-10-28

    Dissociation energies (D0) of 11 H-bonded and 11 dispersion-bound complexes were calculated as the sum of interaction energies and the change of zero-point vibrational energies (ΔZPVE). The structures of H-bonded complexes were optimized at the RI-MP2/cc-pVTZ level, at which deformation and harmonic ΔZPVE energies were also calculated. The structures of dispersion-bound complexes were optimized at the DFT-D3 level, and harmonic ΔZPVE energies were determined at the same level as well. For comparison, CCSD(T)/CBS D0 energies were also evaluated for both types of complexes. The CCSD(T)/CBS interaction energy was constructed as the sum of MP2/CBS interaction energy, extrapolated from aug-cc-pVTZ and aug-cc-pVQZ basis sets, and ΔCCSD(T) correction, determined with the aug-cc-pVDZ basis set. The ΔZPVE energies were determined for all complexes at the harmonic level and for selected complexes, these energies were also calculated using second-order vibration perturbation (VPT2) theory. For H-bonded complexes, the harmonic CCSD(T)/CBS D0 energies were in better agreement with the experimental values (with a mean relative error (MRE) of 6.2%) than the RI-MP2/cc-pVTZ D0 (a MRE of 12.3%). The same trend was found for dispersion-bound complexes (6.2% (MRE) at CCSD(T)/CBS and 7.7% (MRE) at the DFT-D3 level). When the anharmonic ΔZPVE term was included instead of harmonic one, the agreement between theoretical and experimental D0 deteriorated for H-bonded as well as dispersion-bound complexes. Finally, the applicability of "diagonal approximation" for determining the anharmonic ΔZPVE was shown. For the phenolH2O complex, the ΔZPVE energy calculated at the VPT2 level and on the basis of "diagonal approximation" differed by less than 0.1 kcal mol(-1). PMID:26392236

  12. Electron Beam Induced Damage of NaNO3 Single Crystals: An Energy, Temperature, and Quantum State Resolved Study

    SciTech Connect

    Petrik, Nikolay G. ); Knutsen, Karen; Paparazzo, Ernesto; Lea, A Scott ); Camaioni, Donald M. ); Orlando, Thomas M. )

    1999-12-01

    Electron-beam induced damage of NaNO3 single crystal is examined using laser resonance enhanced multiphoton ionization detection of the neutral desorption products, post irradiation temperature programmed desorption (TPD), secondary electron emission microscopy (SEEM) and Auger electron spectroscopy (AES). The damage initially involves destruction of the nitrate group and production of O (3PJ) and NO (2II) fragments with non-thermal energy distributions. Specifically, the O (3PJ) J-state distribution measured at 100 eV incident electron energy is 5 : 1.5 : 0.25 for J= 2 : 1 :0, the NO (2II) vibrational state distribution is 1 : 0.56 : 0.35 : 0.40 : 0.23 for v= 0 :2 : 2 : 3 : 4, and the NO (2II 1/2,3/2) rotational distribution has a high population of the upper (2II 3/2) spin-orbit component. Thermalized NO, O2 and NO2 are also produced and released, though the latter is a minor product. Yields of thermalized NO and O2 exhibit similar temperature dependencies with activation energies of 0.010+- 0.004 and 0.1+- 0.03 eV. These values are close to well-known activation energies of NO2 creation in the NaNO3 crystals. We suggest that the formation and desorption of thermalized molecular products involve NO2 defect states and unimolecular dissociation of NO3 which is activated by lattice phonons and vibrons. A significant amount of O2 gas is also released in post-irradiation thermal cycling from 110-440 K with peaks at {approx}260 and {approx}340 K. We associate the post-irradiation TPD of O2 with reactions involving O atoms released during thermal decompositions of (NO2 ...O) and ONOO. The SEEM image shows damage features and the AES spectra indicate that the irradiated region is depleted in both nitrogen and oxygen relative to Na. The elemental composition shows Na2O as a final product of the NaNO3 radiation decomposition. The ESD cross section using 100 eV electrons is at least {approx}10 -16cm2.

  13. Energy-dispersive spectroscopy and electron backscatter diffraction analysis of isothermally aged SAF 2507 type superduplex stainless steel

    NASA Astrophysics Data System (ADS)

    Dobranszky, J.; Szabo, P. J.; Berecz, T.; Hrotko, V.; Portko, M.

    2004-10-01

    Due to thermal effects, several precipitation and segregation processes are known in duplex stainless steels. These microstructural changes influence both of the original phases, but in different ways. Isothermal ageing in a large range of temperature was performed on SAF 2507 type steel. The temperature range was 300-1000 °C, the ageing time was between 100 s and 24 h. This paper discusses the results of ageing at 900 °C. Microstructural changes were investigated by electron microscopy, energy-dispersive spectroscopy and electron backscattered diffraction analysis. This technique allowed the determination of the microstructure of the secondary austenite and sigma phase and their mutual orientation properties. Beside this, thermoelectric power measurements were also performed, which gave information about the kinetics of the precipitation process. Results showed that sigma-phase precipitation started right after 200 s in the case of annealed steel, and faster than 100 s in the cold-rolled state. After 5000 s, the delta-ferrite disappeared. Chemical composition of sigma phase was independent on the ageing time. A small decrease in nickel content was observed with a slight increase of Cr content. Small amount of chi phase had also been observed on the ferrite-ferrite boundaries, but later they changed into sigma phase. Similarly to sigma phase, chi phase showed significant phosphorus enrichment. During ageing, small chrome nitride precipitates developed, which amount increased in time, and some vanadium could be measured in them. The orientation relationship between austenite and sigma phase deviated from Nenno-orientationship with about 24°, and seems to form a [110]‖[310] relationship, which was characteristic right from the beginning of the process, and remains more or less constant.

  14. Characterization of the interfacial geomechanics in gas shales via integrated Raman spectroscopy, nanoindentation and energy dispersive X-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Ferralis, N.; Abedi, S.; Grossman, J. C.; Ulm, F.

    2012-12-01

    The geomechanical characterization of gas shales at the microscale is currently enabled by the use of grid-based nanoindentation techniques. However, the inability to probe the chemical and mineral heterogeneity of gas shales limits the identification of the geomechanical properties of individual components and phases within the probed region. The development of an integrated multiphysics approach that combines geomechanical and chemical information is crucial for the characterization of interfaces between phases, leading to the identification of regions with low yield strain. Here we present a comprehensive investigation where a spatially aligned coupled multiphysics analysis of gas shales is used to identify relevant the geomechanics of mineral and organic phases and their interfaces. This method uses grid-based nanondentation to extract the geomechanical information. Raman spectroscopy is used to identify the majority of inorganic components (calcite, quartz, anatase, pyrite, clay) as well as to characterize the diversity and maturity in the organic component (kerogen). Energy dispersive X-ray is used in combination with Raman to identify clay. With the use of clustering analysis statistical tools a correlation analysis over the full range of data (geomechanics and chemical data), we identify several mineral phases, and we clearly associate the mechanical properties (defined in terms of hardness, modulus and yield strain) with each phase. With this innovative multiphysics analysis we were able to identify interfacial phases between inorganic phases, with distinct hardness and yield strain. We find that regions between calcite-rich or quartz rich phases and clay-rich phases showed a lower than of that of the corresponding boundary phases. Hence this approach provides a viable method for the identification of the "weakest links" in gas shales with the highest probability of fracture.

  15. Effects of industrial noise on circumpulpar dentin - a field emission scanning electron microscopy and energy dispersive spectroscopy analysis

    PubMed Central

    Cavacas, Maria Alzira; Tavares, Vitor; Oliveira, Maria João; Oliveira, Pedro; Sezinando, Ana; Martins dos Santos, José

    2013-01-01

    Chronic exposure to Industrial Noise (IN), rich in Low Frequency Noise (LFN), causes systemic fibrotic transformation and sustained stress. Dental wear, significantly increased with exposure to LFN, affects the teeth particularly through the circumpulpar dentin. Our goal is to understand the consequences of IN exposure on the circumpulpar dentin of Wistar rats. 10 Wistar rats were exposed to IN for 4 months, according to an occupationally simulated time schedule and 10 animals were used as age-matched controls. The first and the second upper and lower molars of each animal were processed for observation by Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive Spectroscopy (EDS) analysis was performed. In exposed animals FESEM showed a 2.0 to 6.0 μm-dense mineral band between dentin and the pulp with no regular continuity with the tubules. This structure had a few tubules where the odontoblasts processes could be observed embedded within the band and collagen fibers were trapped inside. EDS analysis revealed that it was hydroxyapatite similar to dentin, with a higher carbon content. FESEM results show that the band may be tertiary reparative dentin formed by odontoblast-like cells, but the increased amount of carbon (EDS) could mean that it is sclerotic dentin. IN should be acknowledge as a strong stimulus, able to cause an injury to odontoblasts and to the formation of reparative tertiary dentin, in a process that may accelerate the aging of the teeth, either by direct impact of acoustic pressure pulsations or by increased stress and dental wear. PMID:24294356

  16. A semianalytic model to extract differential linear scattering coefficients of breast tissue from energy dispersive x-ray diffraction measurements

    SciTech Connect

    LeClair, Robert J.; Boileau, Michel M.; Wang Yinkun

    2006-04-15

    The goal of this work is to develop a technique to measure the x-ray diffraction signals of breast biopsy specimens. A biomedical x-ray diffraction technology capable of measuring such signals may prove to be of diagnostic use to the medical field. Energy dispersive x-ray diffraction measurements coupled with a semianalytical model were used to extract the differential linear scattering coefficients [{mu}{sub s}(x)] of breast tissues on absolute scales. The coefficients describe the probabilities of scatter events occurring per unit length of tissue per unit solid angle of detection. They are a function of the momentum transfer argument, x=sin({theta}/2)/{lambda}, where {theta}=scatter angle and {lambda}=incident wavelength. The technique was validated by using a 3 mm diameter 50 kV polychromatic x-ray beam incident on a 5 mm diameter 5 mm thick sample of water. Water was used because good x-ray diffraction data are available in the literature. The scatter profiles from 6 deg. to 15 deg. in increments of 1 deg. were measured with a 3 mmx3 mmx2 mm thick cadmium zinc telluride detector. A 2 mm diameter Pb aperture was placed on top of the detector. The target to detector distance was 29 cm and the duration of each measurement was 10 min. Ensemble averages of the results compare well with the gold standard data of A. H. Narten [''X-ray diffraction data on liquid water in the temperature range 4 deg. C-200 deg. C, ORNL Report No. 4578 (1970)]. An average 7.68% difference for which most of the discrepancies can be attributed to the background noise at low angles was obtained. The preliminary measurements of breast tissue are also encouraging.

  17. Gunshot residue testing in suicides: Part I: Analysis by scanning electron microscopy with energy-dispersive X-ray.

    PubMed

    Molina, D Kimberley; Martinez, Michael; Garcia, James; DiMaio, Vincent J M

    2007-09-01

    Several different methods can be employed to test for gunshot residue (GSR) on a deceased person's hands, including scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Each of these techniques has been extensively studied, especially on living individuals. The current studies (Part I and Part II) were designed to compare the use and utility of the different GSR testing techniques in a medical examiner setting. In Part I, the hands of deceased persons who died from undisputed suicidal handgun wounds were tested for GSR by SEM-EDX over a 4-year period. A total of 116 cases were studied and analyzed for caliber of weapon, proximity of wound, and results of GSR testing, including spatial deposition upon the hands. It was found that in only 50% of cases with a known self-inflicted gunshot wound was SEM-EDX positive for at least 1 specific particle for GSR. In 18% of the cases there was a discernible pattern (spatial distribution) of the particles on the hand such that the manner in which the weapon was held could be determined. Since only 50% of cases where the person is known to have fired a weapon immediately prior to death were positive for GSR by SEM-EDX, this test should not be relied upon to determine whether a deceased individual has discharged a firearm. Furthermore, in only 18% of cases was a discernible pattern present indicating how the firearm was held. The low sensitivity, along with the low percentage of cases with a discernible pattern, limits the usefulness of GSR test results by SEM-EDX in differentiating self-inflicted from non-self-inflicted wounds. PMID:17721163

  18. TIME-RESOLVED VIBRATIONAL SPECTROSCOPY

    SciTech Connect

    Andrei Tokmakoff, MIT; Paul Champion, Northeastern University; Edwin J. Heilweil, NIST; Keith A. Nelson, MIT; Larry Ziegler, Boston University

    2009-05-14

    This document contains the Proceedings from the 14th International Conference on Time-Resolved Vibrational Spectroscopy, which was held in Meredith, NH from May 9-14, 2009. The study of molecular dynamics in chemical reaction and biological processes using time-resolved spectroscopy plays an important role in our understanding of energy conversion, storage, and utilization problems. Fundamental studies of chemical reactivity, molecular rearrangements, and charge transport are broadly supported by the DOE’s Office of Science because of their role in the development of alternative energy sources, the understanding of biological energy conversion processes, the efficient utilization of existing energy resources, and the mitigation of reactive intermediates in radiation chemistry. In addition, time-resolved spectroscopy is central to all five of DOE’s grand challenges for fundamental energy science. The Time-Resolved Vibrational Spectroscopy conference is organized biennially to bring the leaders in this field from around the globe together with young scientists to discuss the most recent scientific and technological advances. The latest technology in ultrafast infrared, Raman, and terahertz spectroscopy and the scientific advances that these methods enable were covered. Particular emphasis was placed on new experimental methods used to probe molecular dynamics in liquids, solids, interfaces, nanostructured materials, and biomolecules.

  19. Time-resolved measurements of electron and energy transfer of rhodamine B monolayer on the surface of organic crystals

    NASA Astrophysics Data System (ADS)

    Nakashima, Nobuaki; Yoshihara, Keitaro; Willig, Frank

    1980-10-01

    Fluorescence decays of a monolayer of rhodamine B on single crystals of anthracene, phenanthrene, and naphthalene have been measured for the first time with a picosecond laser and a streak camera. The fluorescence decays were not single exponentials. Two different decay characteristics have been observed corresponding to an exo- and endo-energetic electron transfer reaction between excited dye and substrate. The short decay of 35±7 ps on an anthracene crystal is explained by the electron-transfer kinetics from anthracene to excited rhodamine B. In the cases of naphthalene and phenanthrene,the electron transfer reaction becomes endo-energetic and slower. The decays within several tens of picoseconds are analyzed in terms of two-dimensional Förster-type energy transfer to quencher sites where dyes are suggested to be in contact with each other. In connection to this phenomenon, the concentration quenching of the fluorescence of rhodamine B in aqueous solution was elucidated in terms of the Förster-type energy transfer to the nonfluorescent dimer leading to a nonexponential decay.

  20. Coordination-resolved local bond contraction and electron binding-energy entrapment of Si atomic clusters and solid skins

    SciTech Connect

    Bo, Maolin; Huang, Yongli; Zhang, Ting; Wang, Yan E-mail: ecqsun@ntu.edu.sg; Zhang, Xi; Li, Can; Sun, Chang Q. E-mail: ecqsun@ntu.edu.sg

    2014-04-14

    Consistency between x-ray photoelectron spectroscopy measurements and density-function theory calculations confirms our bond order-length-strength notation-incorporated tight-binding theory predictions on the quantum entrapment of Si solid skin and atomic clusters. It has been revealed that bond-order deficiency shortens and strengthens the Si-Si bond, which results in the local densification and quantum entrapment of the core and valence electrons. Unifying Si clusters and Si(001) and (111) skins, this mechanism has led to quantification of the 2p binding energy of 96.089 eV for an isolated Si atom, and their bulk shifts of 2.461 eV. Findings evidence the significance of atomic undercoordination that is of great importance to device performance.

  1. Reconstruction of Time-Resolved Neutron Energy Spectra in Z-Pinch Experiments Using Time-of-flight Method

    SciTech Connect

    Rezac, K.; Klir, D.; Kubes, P.; Kravarik, J.

    2009-01-21

    We present the reconstruction of neutron energy spectra from time-of-flight signals. This technique is useful in experiments with the time of neutron production in the range of about tens or hundreds of nanoseconds. The neutron signals were obtained by a common hard X-ray and neutron fast plastic scintillation detectors. The reconstruction is based on the Monte Carlo method which has been improved by simultaneous usage of neutron detectors placed on two opposite sides from the neutron source. Although the reconstruction from detectors placed on two opposite sides is more difficult and a little bit inaccurate (it followed from several presumptions during the inclusion of both sides of detection), there are some advantages. The most important advantage is smaller influence of scattered neutrons on the reconstruction. Finally, we describe the estimation of the error of this reconstruction.

  2. Simple energy balance model resolving the seasons and the continents - Application to the astronomical theory of the ice ages

    NASA Technical Reports Server (NTRS)

    North, G. R.; Short, D. A.; Mengel, J. G.

    1983-01-01

    An analysis is undertaken of the properties of a one-level seasonal energy balance climate model having explicit, two-dimensional land-sea geography, where land and sea surfaces are strictly distinguished by the local thermal inertia employed and transport is governed by a smooth, latitude-dependent diffusion mechanism. Solutions of the seasonal cycle for the cases of both ice feedback exclusion and inclusion yield good agreements with real data, using minimal turning of the adjustable parameters. Discontinuous icecap growth is noted for both a solar constant that is lower by a few percent and a change of orbital elements to favor cool Northern Hemisphere summers. This discontinuous sensitivity is discussed in the context of the Milankovitch theory of the ice ages, and the associated branch structure is shown to be analogous to the 'small ice cap' instability of simpler models.

  3. The TFTR E Parallel B Spectrometer for Mass and Energy Resolved Multi-Ion Charge Exchange Diagnostics

    SciTech Connect

    A.L. Roquemore; S.S. Medley

    1998-01-01

    The Charge Exchange Neutral Analyzer diagnostic for the Tokamak Fusion Test Reactor was designed to measure the energy distributions of both the thermal ions and the supra thermal populations arising from neutral-beam injection and ion cyclotron radio-frequency heating. These measurements yield the plasma ion temperature, as well as several other plasma parameters necessary to provide an understanding of the plasma condition and the performance of the auxiliary heating methods. For this application, a novel charge-exchange spectrometer using a dee-shaped region of parallel electric and magnetic fields was developed at the Princeton Plasma Physics Laboratory. The design and performance of this spectrometer is described in detail, including the effects of exposure of the microchannel plate detector to magnetic fields, neutrons, and tritium.

  4. State-Resolved Quantum Dynamics of Photodetachment of HCO2(-)/DCO2(-) on an Accurate Global Potential Energy Surface.

    PubMed

    Zou, Lindong; Li, Jun; Wang, Hui; Ma, Jianyi; Guo, Hua

    2015-07-16

    Full-dimensional quantum dynamics studies of the photodetachment of HCO2(-) and DCO2(-) are reported using a wave-packet method on an accurate global potential energy surface of the neutral HOCO/HCO2 system. The calculated photoelectron spectra reproduced both the positions and widths of the main HCO2 and DCO2 peaks observed in experiment. Specifically, both the (2)A1 and (2)B2 resonance peaks of the neutral radicals were identified in our simulations thanks to the adiabatic PES that captures both the (2)A1 and (2)B2 minima. The narrow widths and isotope effect of the lowest resonances are indicative of tunneling-facilitated predissociation. Furthermore, the dissociation product CO2 was found to be excited in both its symmetric stretching and bending modes, which are coupled via a strong Fermi resonance, but rotationally cold, in good agreement with the recent photoelectron-photodetachment coincidence experiments. PMID:25607218

  5. Energy dispersive X-ray fluorescence analysis of ancient coins: The case of Greek silver drachmae from the Emporion site in Spain

    NASA Astrophysics Data System (ADS)

    Pitarch, A.; Queralt, I.

    2010-05-01

    Greek colonizers arrived at the Iberian Peninsula at the beginning of the sixth century B.C. and founded a small colony known as Emporion in north-east Spain. By the fifth century B.C., this colony became a small polis with a well-organized administrative structure. In this context, the necessity of coinage was a fact and the first coins were minted [1]. Some of these coins were characterized by using energy dispersive X-ray fluorescence equipment. The analytical study focused on the elemental characterization of the coins minted from the fourth century to the first century B.C. and their compositional evolution during this period. The investigation has pointed out a very high fineness of the alloys throughout the time, with an average silver content around 98.32%, and the feasibility of energy dispersive X-ray fluorescence as a screening tool for the characterization of the alloys.

  6. High energy pulses generation with giant spectrum bandwidth and submegahertz repetition rate from a passively mode-locked Yb-doped fiber laser in all normal dispersion cavity

    NASA Astrophysics Data System (ADS)

    Lin, J.-H.; Wang, D.; Lin, K.-H.

    2011-01-01

    Robust passively mode-locked pulse generation with low pulse repetition rate and giant spectrum bandwidth in an all-fiber, all-normal-dispersion ytterbium-doped fiber laser has been experimentally demonstrated using nonlinear polarization evolution technique. The highest pulse energy over 20 nJ with spectrum bandwidth over 50 nm can be experimentally obtained at 175 mW pump power. The mode-locked pulses reveal broadened 3-dB pulsewidth about several nanosecond and widened pedestal in time trace that is resulted from enormous dispersion in laser cavity and gain dynamics. At certain mode-locking state, a spectrum gap around 1056 nm are observed between the three and four energy levels of Yb-doped fiber laser. By properly rotating the polarization controller, the gap can be eliminated due to four-wave mixing to produce more flattened spectrum output.

  7. Dispersive liquid-liquid microextraction using diethyldithiocarbamate as a chelating agent and the dried-spot technique for the determination of Fe, Co, Ni, Cu, Zn, Se and Pb by energy-dispersive X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Kocot, Karina; Zawisza, Beata; Sitko, Rafal

    2012-07-01

    Dispersive liquid-liquid microextraction (DLLME) using sodium diethyldithiocarbamate (DDTC) as a chelating agent was investigated for the simultaneous determination of iron, cobalt, nickel, copper, zinc, selenium and lead ions in water samples. The procedure was performed using 5 mL of the sample, 100 μL of a 0.5% solution of DDTC, 30 μL of carbon tetrachloride (extraction phase) and 500 μL of methanol (disperser solvent). The experiments showed that Fe, Co, Ni, Cu, Zn and Pb can be simultaneously extracted at a pH of 5 and that Se can be extracted at a pH of 2-3. The results were compared with those obtained using ammonium pyrrolidine dithiocarbamate as a chelating agent. For all analytes, a linear range was observed up to 0.4 μg mL- 1. If Fe and Zn are present in concentrations 10 times higher than those of the other analytes, then the linearity is observed up to 0.2 μg mL- 1. In the present study, the organic phase that contained preconcentrated elements was deposited onto a Millipore filter and measured using energy-dispersive X-ray fluorescence spectrometry. The obtained detection limits were 2.9, 1.5, 2.0, 2.3, 2.5, 2.0 and 3.9 ng mL- 1 for Fe, Co, Ni, Cu, Zn, Se and Pb, respectively. This combination of DLLME and the dried-spot technique is promising for multielement analyses using other spectroscopy techniques, such as laser ablation-inductively coupled plasma-mass spectrometry, laser-induced breakdown spectroscopy or total-reflection X-ray fluorescence spectrometry.

  8. Determination and speciation of trace and ultratrace selenium ions by energy-dispersive X-ray fluorescence spectrometry using graphene as solid adsorbent in dispersive micro-solid phase extraction.

    PubMed

    Kocot, Karina; Leardi, Riccardo; Walczak, Beata; Sitko, Rafal

    2015-03-01

    A dispersive micro-solid phase extraction (DMSPE) with graphene as a solid adsorbent and ammonium pyrrolidinedithiocarbamate (APDC) as a chelating agent was proposed for speciation and detemination of inorganic selenium by the energy-dispersive X-ray fluorescence spectrometry (EDXRF). In developed DMSPE, graphene particles are dispersed throughout the analyzed solution, therefore reaction between Se(IV)-APDC complexes and graphene nanoparticles occurs immediately. The concentration of Se(VI) is calculated as the difference between the concentration of selenite after and before prereduction of selenate. A central composite face-centered design with 3 center points was performed in order to optimize conditions and to study the effect of four variables (pH of the sample, concentration of APDC, concentration of Triton-X-100, and sample volume). The best results were obtained when suspension consisting of 200 µg of graphene nanosheets, 1.2 mg of APDC and 0.06 mg of Triton-X-100 was rapidly injected to the 50 mL of the analyzed solution. Under optimized conditions Se ions can be determined with a very good recovery (97.7±5.0% and 99.2±6.6% for Se(IV) and Se(VI), respectively) and precision (RSD=5.1-6.6%). Proposed DMSPE/EDXRF procedure allowed to obtain low detection limits (0.032 ng mL(-1)) and high enrichment factor (1013±15). The proposed methodology was successfully applied for the determination of Se in mineral, tap, lake and sea water samples as well as in biological materials (Lobster Hepatopancreas and Pig Kidney). PMID:25618680

  9. Amalgam tattoo: report of an unusual clinical presentation and the use of energy dispersive X-ray analysis as an aid to diagnosis

    SciTech Connect

    McGinnis, J.P. Jr.; Greer, J.L.; Daniels, D.S.

    1985-01-01

    An unusual appearing gingival amalgam pigmentation (amalgam tattoo) that completely surrounded the maxillary right first premolar in a 13-year-old boy is presented. Because of the wide distribution and apparent clinical progression of the discoloration, an excisional biopsy was performed. The histopathologic diagnosis of amalgam pigmentation was confirmed in paraffin sections by energy dispersive X-ray microanalysis. Silver, tin, and mercury were detected in the specimen.

  10. Coherent femtosecond low-energy single-electron pulses for time-resolved diffraction and imaging: A numerical study

    SciTech Connect

    Paarmann, A.; Mueller, M.; Ernstorfer, R.; Gulde, M.; Schaefer, S.; Schweda, S.; Maiti, M.; Ropers, C.; Xu, C.; Hohage, T.; Schenk, F.

    2012-12-01

    We numerically investigate the properties of coherent femtosecond single electron wave packets photoemitted from nanotips in view of their application in ultrafast electron diffraction and non-destructive imaging with low-energy electrons. For two different geometries, we analyze the temporal and spatial broadening during propagation from the needle emitter to an anode, identifying the experimental parameters and challenges for realizing femtosecond time resolution. The simple tip-anode geometry is most versatile and allows for electron pulses of several ten of femtosecond duration using a very compact experimental design, however, providing very limited control over the electron beam collimation. A more sophisticated geometry comprising a suppressor-extractor electrostatic unit and a lens, similar to typical field emission electron microscope optics, is also investigated, allowing full control over the beam parameters. Using such a design, we find {approx}230 fs pulses feasible in a focused electron beam. The main limitation to achieve sub-hundred femtosecond time resolution is the typical size of such a device, and we suggest the implementation of more compact electron optics for optimal performance.

  11. Time-resolved imaging of the microbunching instability and energy spread at the Linac Coherent Light Source

    NASA Astrophysics Data System (ADS)

    Ratner, D.; Behrens, C.; Ding, Y.; Huang, Z.; Marinelli, A.; Maxwell, T.; Zhou, F.

    2015-03-01

    The microbunching instability (MBI) is a well-known problem for high brightness electron beams and has been observed at accelerator facilities around the world. Free-electron lasers (FELs) are particularly susceptible to MBI, which can distort the longitudinal phase space and increase the beam's slice energy spread (SES). Past studies of MBI at the Linac Coherent Light Source (LCLS) relied on optical transition radiation to infer the existence of microbunching. With the development of the x-band transverse deflecting cavity (XTCAV), we can for the first time directly image the longitudinal phase space at the end of the accelerator and complete a comprehensive study of MBI, revealing both detailed MBI behavior as well as insights into mitigation schemes. The fine time resolution of the XTCAV also provides the first LCLS measurements of the final SES, a critical parameter for many advanced FEL schemes. Detailed MBI and SES measurements can aid in understanding MBI mechanisms, benchmarking simulation codes, and designing future high-brightness accelerators.

  12. Picosecond time-resolved fluorescence studies on excitation energy transfer in a histidine 117 mutant of the D2 protein of photosystem II in Synechocystis 6803.

    PubMed

    Vasil'ev, S; Bruce, D

    2000-11-21

    The role of the peripheral reaction center chlorophyll a molecule associated with His117 of the D2 polypeptide in photosystem II was investigated in Synechocystis sp. PCC 6803 using a combination of steady state, pump-probe, and picosecond time-resolved fluorescence spectroscopy. Data were obtained from intact cells and isolated thylakoid membranes of a control mutant and a D2-H117T mutant, both of which lacked photosystem I. Excitation energy transfer and trapping were investigated by analyzing the data with a kinetic model that used an exact numerical solution of the Pauli master equation, taking into account available photosystem II spectral and structural information. The results of our kinetic analysis revealed the observed difference in excited-state dynamics between the H117T mutant and the control to be consistent with a retardation of the rate of excitation energy transfer from the peripheral chlorophyll of D2 (Chl at His117) to the electron-transfer pigments and an increase of the rate constant for charge recombination in the H117T mutant. The kinetic model was able to account for the experimentally observed changes in absorption cross section and fluorescence decay kinetics between the control and mutant by invoking changes in only these two rate constants. The results rule out quenching of excitation by a chlorophyll cation radical as a mechanism responsible for the lower efficiency of excitation energy utilization in the H117T mutant. Our work also demonstrates the importance of the chlorophyll associated with His117 of the D2 protein for excitation energy transfer to the PSII electron-transfer pigments and for the effective stabilization of the primary radical pair. PMID:11087370

  13. A spectral-timing analysis of the kHz QPOs in 4U 1636-53: the frequency-energy resolved RMS spectrum

    NASA Astrophysics Data System (ADS)

    Ribeiro, Evandro M.; Mendez, Mariano; Zhang, Guo-Bao; De Avellar, Márcio G. B.

    2016-07-01

    Our understanding of quasi-periodic oscillations (QPO) has been further advanced in the last few years by the use of combined spectral and timing techniques, and it is now clear that QPO properties are closely related to the spectral state of the source in which they appear. In this work we used all the available RXTE observations of the neutron-star low-mass X-ray binary 4U~1636-53 to study the properties of the kilohertz QPO as a function of energy and frequency. By following the frequency evolution of the kHz QPOs we created frequency-resolved fractional RMS spectra. We also studied the connection between the frequency of the kHz QPOs and the parameters of the model that fits the X-ray energy spectrum. We show the dependence of the QPO properties in a multi-parameter space, and we discuss the implication of our results to the mechanism that produces the QPOs. Our results provide input to the next generation of spectral-timing models, which will help us understand the variability and the environment around the neutron star in these systems.

  14. From ab initio potential energy surfaces to state-resolved reactivities: X + H2O ↔ HX + OH [X = F, Cl, and O((3)P)] reactions.

    PubMed

    Li, Jun; Jiang, Bin; Song, Hongwei; Ma, Jianyi; Zhao, Bin; Dawes, Richard; Guo, Hua

    2015-05-21

    We survey the recent advances in theoretical understanding of quantum state resolved dynamics, using the title reactions as examples. It is shown that the progress was made possible by major developments in two areas. First, an accurate analytical representation of many high-level ab initio points over a large configuration space can now be made with high fidelity and the necessary permutation symmetry. The resulting full-dimensional global potential energy surfaces enable dynamical calculations using either quasi-classical trajectory or more importantly quantum mechanical methods. The second advance is the development of accurate and efficient quantum dynamical methods, which are necessary for providing a reliable treatment of quantum effects in reaction dynamics such as tunneling, resonances, and zero-point energy. The powerful combination of the two advances has allowed us to achieve a quantitatively accurate characterization of the reaction dynamics, which unveiled rich dynamical features such as steric steering, strong mode specificity, and bond selectivity. The dependence of reactivity on reactant modes can be rationalized by the recently proposed sudden vector projection model, which attributes the mode specificity and bond selectivity to the coupling of reactant modes with the reaction coordinate at the relevant transition state. The deeper insights provided by these theoretical studies have advanced our understanding of reaction dynamics to a new level. PMID:25886142

  15. MOCCA: A 4k-Pixel Molecule Camera for the Position- and Energy-Resolving Detection of Neutral Molecule Fragments at CSR

    NASA Astrophysics Data System (ADS)

    Gamer, L.; Schulz, D.; Enss, C.; Fleischmann, A.; Gastaldo, L.; Kempf, S.; Krantz, C.; Novotný, O.; Schwalm, D.; Wolf, A.

    2016-08-01

    We present the design of MOCCA, a large-area particle detector that is developed for the position- and energy-resolving detection of neutral molecule fragments produced in electron-ion interactions at the Cryogenic Storage Ring at the Max Planck Institute for Nuclear Physics in Heidelberg. The detector is based on metallic magnetic calorimeters and consists of 4096 particle absorbers covering a total detection area of 44.8 mathrm {mm} × 44.8 mathrm {mm}. Groups of four absorbers are thermally coupled to a common paramagnetic temperature sensor where the strength of the thermal link is different for each absorber. This allows attributing a detector event within this group to the corresponding absorber by discriminating the signal rise times. A novel readout scheme further allows reading out all 1024 temperature sensors that are arranged in a 32 × 32 square array using only 16+16 current-sensing superconducting quantum interference devices. Numerical calculations taking into account a simplified detector model predict an energy resolution of Δ E_mathrm {FWHM} le 80 mathrm {eV} for all pixels of this detector.

  16. Time resolved temperature switchable excitation energy transfer processes between CdSe/ZnS nanocrystals and phycobiliprotein antenna from Acaryochloris marina

    NASA Astrophysics Data System (ADS)

    Schmitt, F.-J.; Maksimov, E. G.; Suedmeyer, H.; Jeyasangar, V.; Theiss, C.; Paschenko, V. Z.; Eichler, H. J.; Renger, G.

    2011-04-01

    Hybrid systems were self-assembled in solution from surface treated CdSe/ZnS quantum dots (QDs) and isolated phycobiliprotein (PBP) complexes from the cyanobacterium Acaryochloris marina. The excitation energy transfer (EET) from the QDs to attached PBPs was analyzed by time correlated single photon counting and time integrated fluorescence measurements at different temperatures. It was found: The green emission of the QDs (3.3 nm diameter of the CdSe core) in solution at 530 nm becomes strongly quenched after addition of PBPs. The functional connection between QDs and PBPs via EET interrupts at temperatures below 273 K (0 °C) This temperature dependent effect is fully reversible EET from QDs to PBPs occurs with a time constant of about 140 ps and an efficiency of 85-90% for coupled QDs/PBP hybrid complexes. A model of the EET steps is presented which is based on data evaluation of the time integrated fluorescence emission and the time resolved measurement results via decay associated emission spectra (DAS). According to the theory of Förster Resonance Energy Tranfer (FRET) the average distance between the center of the QDs and the nearest neighbouring chromophore is estimated to be 3.2 nm.

  17. MOCCA: A 4k-Pixel Molecule Camera for the Position- and Energy-Resolving Detection of Neutral Molecule Fragments at CSR

    NASA Astrophysics Data System (ADS)

    Gamer, L.; Schulz, D.; Enss, C.; Fleischmann, A.; Gastaldo, L.; Kempf, S.; Krantz, C.; Novotný, O.; Schwalm, D.; Wolf, A.

    2016-01-01

    We present the design of MOCCA, a large-area particle detector that is developed for the position- and energy-resolving detection of neutral molecule fragments produced in electron-ion interactions at the Cryogenic Storage Ring at the Max Planck Institute for Nuclear Physics in Heidelberg. The detector is based on metallic magnetic calorimeters and consists of 4096 particle absorbers covering a total detection area of 44.8 {mm} × 44.8 {mm} . Groups of four absorbers are thermally coupled to a common paramagnetic temperature sensor where the strength of the thermal link is different for each absorber. This allows attributing a detector event within this group to the corresponding absorber by discriminating the signal rise times. A novel readout scheme further allows reading out all 1024 temperature sensors that are arranged in a 32 × 32 square array using only 16+16 current-sensing superconducting quantum interference devices. Numerical calculations taking into account a simplified detector model predict an energy resolution of Δ E_{FWHM} ≤ 80 {eV} for all pixels of this detector.

  18. Adjustable rheology of fumed silica dispersion in urethane prepolymers: Composition-dependent sol and gel behaviors and energy-mediated shear responses

    SciTech Connect

    Zheng, Zhong Song, Yihu Wang, Xiang Zheng, Qiang

    2015-07-15

    Variation of colloidal and interfacial interactions leads to a microstructural diversity in fumed silica dispersions exhibiting absolutely different sol- or gel-like rheological responses. In this study, fumed silicas with different surface areas (200–400 m{sup 2}/g) and surface characteristics (hydrophilic or hydrophobic) are dispersed into moisture-cured polyurethane. The microstructures investigated using transmission electron microscope are associated perfectly with three different rheological behaviors: (i) Sols with well-dispersed silica aggregates, (ii) weak gels with agglomerate-linked networks, and (iii) strong gels with concentrated networks of large agglomerates. Though sols and gels are well distinguished by shear thickening or sustained thinning response through steady shear flow test, it is interesting that the sols and weak gels exhibit a uniform modulus plateau-softening-hardening-softening response with increasing dynamic strain at frequency 10 rad s{sup −1} while the strong gels show a sustained softening beyond the linear regime. Furthermore, the onset of softening and hardening can be normalized: The two softening are isoenergetic at mechanical energies of 0.3 J m{sup −3} and 10 kJ m{sup −3}. On the other hand, the hardening is initiated by a critical strain of 60%. The mechanisms involved in the generation of the sol- and the gel-like dispersions and their structural evolutions during shear are thoroughly clarified in relation to the polyols, the characteristic and content of silica and the curing catalysts.

  19. Departures from the Energy-Biodiversity Relationship in South African Passerines: Are the Legacies of Past Climates Mediated by Behavioral Constraints on Dispersal?

    PubMed Central

    Péron, Guillaume; Altwegg, Res

    2015-01-01

    Legacies of paleoclimates in contemporary biodiversity patterns have mostly been investigated with global datasets, or with weakly dispersive organisms, and as a consequence been interpreted in terms of geographical or physical constraints. If paleoclimatic legacies also occurred at the regional scale in the distributions of vagile organisms within biomes, they would rather suggest behavioral constraints on dispersal, i.e., philopatric syndromes. We examined 1) the residuals of the regression between contemporary energy and passerine species richness in South African biomes and 2) phylogenetic dispersion of passerine assemblages, using occupancy models and quarter-degree resolution citizen science data. We found a northeast to southwest gradient within mesic biomes congruent with the location of Quaternary mesic refugia, overall suggesting that as distance from refugia increased, more clades were lacking from local assemblages. A similar but weaker pattern was detected in the arid Karoo Biomes. In mobile organisms such as birds, behavioral constraints on dispersal appear strong enough to influence species distributions thousands of years after historical range contractions. PMID:26208300

  20. Investigation of the quaternary structure of an ABC transporter in living cells using spectrally resolved resonance energy transfer

    NASA Astrophysics Data System (ADS)

    Singh, Deo Raj

    Forster resonance energy transfer (FRET) has become an important tool to study proteins inside living cells. It has been used to explore membrane protein folding and dynamics, determine stoichiometry and geometry of protein complexes, and measure the distance between two molecules. In this dissertation, we use a method based on FRET and optical micro-spectroscopy (OptiMiS) technology, developed in our lab, to probe the structure of dynamic (as opposed to static) protein complexes in living cells. We use this method to determine the association stoichiometry and quaternary structure of an ABC transporter in living cells. Specifically, the transporter we investigate originates from the pathogen Pseudomonas aeruginosa, which is a Gram-negative bacterium with several virulence factors, lipopolysaccharides being one of them. This pathogen coexpresses two unique forms of lipopolysaccharides on its surface, the A- and B-bands. The A-band polysaccharides, synthesized in the cytoplasm, are translocated into the periplasm through an ATP-binding-cassette (ABC) transporter consisting of a transmembranar protein, Wzm, and a nucleotide-binding protein, Wzt. In P. aeruginosa, all of the biochemical studies of A-band LPS are concentrated on the stages of the synthesis and ligation of polysaccharides (PSs), leaving the export stage involving ABC transporter unexplored. The mode of PS export through ABC transporters is still unknown. This difficulty is due to the lack of information about sub-unit composition and structure of this bi-component ABC transporter. Using the FRET-OptiMiS combination method developed by our lab, we found that Wzt forms a rhombus-shaped homo-tetramer which becomes a square upon co-expression with Wzm, and that Wzm forms a square-shaped homo-tetramer both in the presence and absence of Wzt. Based on these results, we propose a structural model for the double-tetramer complex formed by the bi-component ABC transporter in living cells. An understanding of the

  1. Determining Neutron Star Masses and Radii using Energy-resolved Waveforms of X-ray Burst Oscillations

    NASA Astrophysics Data System (ADS)

    Lamb, Frederick K.; Lo, K.; Miller, M. C.; Bhattacharyya, S.

    2013-04-01

    Precise, simultaneous measurements of the mass M and radius R of neutron stars can yield uniquely valuable information about the still uncertain properties of cold matter at several times the density of nuclear matter. We have used a Bayesian approach to explore how well M and R could be measured using data on X-ray burst oscillations obtained with a future space mission having 2-30 keV energy coverage and an effective area of 10 square meters, such as the proposed LOFT or AXTAR missions. We have done this by generating synthetic observed waveforms for a variety of neutron star and hot spot properties and then determining the joint likelihood distributions of the parameters in a standard fitted model, given each synthetic waveform. We assume that 1 million counts have been collected from the hot spot and that the total background contributes about the same number of counts. We find that if the hot spot is within 10 degrees of the rotation equator, both M and R can usually be determined with an uncertainty of about 10%. If instead the spot is within 20 degrees of the rotation pole, the uncertainties are so large that waveform measurements alone provide no useful constraints on M and R. Observation of an identifiable atomic line in the hot-spot emission always tightly constrains M/R; it can also tightly constrain M and R individually if the spot is within about 30 degrees of the rotation equator. These precisions can usually be achieved even if the burst oscillations vary with time and data from multiple bursts must be used to obtain 1 million counts from the hot spot. Independent knowledge of the observer's inclination can greatly reduce the uncertainties, as can independent information about the background. Knowledge of the star’s distance can also help, but not as much. Deviations of the actual shape of the hot spot, the actual spectrum of the emission, and the actual beaming function from those assumed in the fitted model increase the uncertainties, sometimes

  2. [Energy-dispersive x-ray fluorescence spectrometry--a forensic chemistry method for determination of shooting distance].

    PubMed

    Havel, J

    2003-10-01

    The article follows up the experiences Energo-dispersive X-ray fluorescence spectrometry (EDXRF) as the forensic necrochemical method as the tool for detection of metals (gunshot residues--GSR) in connection with gunshot-wounds of persons--authors: dipl. Ing. J. Havel and dipl. Ing. K. Zelenka and Energo-dispersive X-ray fluorescence spectrometry (EDXRF) as the forensic method as the tool for identification of inlets (gunshot--entries) and outlets (gunshot--exits)--author: dipl. Ing. J. Havel. PMID:14661530

  3. Elemental analysis of sunflower cataract in Wilson's disease: a study using scanning transmission electron microscopy and energy dispersive spectroscopy.

    PubMed

    Jang, Hyo Ju; Kim, Joon Mo; Choi, Chul Young

    2014-04-01

    Signature ophthalmic characteristics of Wilson's disease (WD) are regarded as diagnostically important manifestations of the disease. Previous studies have proved the common occurrence of copper accumulation in the liver of patients with WD. However, in the case of sunflower cataracts, one of the rare diagnostic signs of WD, no study has demonstrated copper accumulation in the lens capsules of sunflower cataracts in WD patients. To investigate the nanostructure and elemental composition of sunflower cataracts in WD, transmission electron microscopy (TEM) was done on the capsulorhexised anterior lens capsule of sunflower cataracts in WD in order to evaluate anatomical variation and elemental changes. We utilized energy dispersive X-ray spectroscopy (EDS) to investigate the elemental composition of the lens capsule using both point and mapping spectroscopy. Quantitative analysis was performed for relative comparison of the elements. TEM showed the presence of granular deposits of varying size (20-350 nm), appearing mainly in the posterior one third of the anterior capsule. The deposits appeared in linear patterns with scattered dots. There were no electron-dense particles in the epithelial cell layer of the lens. Copper and sulfur peaks were consistently revealed in electron-dense granular deposits. In contrast, copper and sulfur peaks were absent in other tissues, including granule-free lens capsules and epithelial tissue. Most copper was exclusively located in clusters of electron-dense particles, and the copper distribution overlapped with sulfur on mapping spectroscopy. Quantitative analysis presented inconsistent ratios of copper to sulfur in each electron-dense granule. The mean ratio of copper to sulfur was about 3.25 (with a range of 2.39-3.78). This is the first elemental analysis of single electron particles in sunflower cataracts using EDS in the ophthalmic area. Sunflower cataracts with WD are assumed to be the result of accumulation of heterogeneous

  4. Development of a compact electron ion coincidence analyzer using a coaxially symmetric mirror electron energy analyzer and a miniature polar-angle-resolved time-of-flight ion mass spectrometer with four concentric anodes

    SciTech Connect

    Kobayashi, Eiichi; Nambu, Akira; Mase, Kazuhiko; Isari, Kouji; Tanaka, Kenichiro; Mori, Masanobu; Okudaira, Koji K.; Ueno, Nobuo

    2009-04-15

    A compact electron ion coincidence (EICO) analyzer that uses a coaxially symmetric mirror electron energy analyzer and a miniature polar-angle-resolved time-of-flight ion mass spectrometer with four concentric anodes was developed for surface science and surface analysis. The apparatus is especially useful in the study of ion desorption stimulated by an Auger process because information on the mass, yield, desorption polar angle, and kinetic energy of ions can be obtained for the selected core-ionization-final-states or the selected Auger-final-states. The analyzer can be used also for analysis of the configuration of specific surface molecules because the desorption polar angles reflect the direction of surface bonds. The EICO analyzer was evaluated by measuring polar-angle-resolved-ion yield spectra and coincidence spectra of Auger-electron and polar-angle-resolved H{sup +} from condensed water.

  5. Combination of electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy to determine indium concentration in InGaN thin film structures

    NASA Astrophysics Data System (ADS)

    Wang, X.; Chauvat, M. P.; Ruterana, P.; Walther, T.

    2015-11-01

    We demonstrate a method to determine the indium concentration, x, of In x Ga1-x N thin films by combining plasmon excitation studies in electron energy-loss spectroscopy (EELS) with a novel way of quantification of the intensity of x-ray lines in energy-dispersive x-ray spectroscopy (EDXS). The plasmon peak in EELS of InGaN is relatively broad. We fitted a Lorentz function to the main plasmon peak to suppress noise and the influence from the neighboring Ga 3d transition in the spectrum, which improves the precision in the evaluation of the plasmon peak position. As the indium concentration of InGaN is difficult to control during high temperature growth due to partial In desorption, the nominal indium concentrations provided by the growers were not considered reliable. The indium concentration obtained from EDXS quantification using Oxford Instrument ISIS 300 x-ray standard quantification software often did not agree with the nominal indium concentration, and quantification using K and L lines was inconsistent. We therefore developed a self-consistent iterative procedure to determine the In content from thickness-dependent k-factors, as described in recent work submitted to Journal of Microscopy. When the plasmon peak position is plotted versus the indium concentration from EDXS we obtain a linear relationship over the whole compositional range, and the standard error from linear least-squares fitting shows that the indium concentration can be determined from the plasmon peak position to within Δx = ± 0.037 standard deviation.

  6. Dispersion Modeling.

    ERIC Educational Resources Information Center

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  7. Electron-excited energy dispersive X-ray spectrometry at high speed and at high resolution: silicon drift detectors and microcalorimeters.

    PubMed

    Newbury, Dale E

    2006-12-01

    Two recent developments in X-ray spectrometer technology provide dramatic improvements in analytical capabilities that impact the frontiers of electron microscopy. Silicon drift detectors (SDD) use the same physics as silicon (lithium) energy dispersive spectrometers [Si(Li) EDS] but differ in design: only 10% of the thickness of the Si(Li) EDS with an anode area below 0.1 mm2 and a complex rear surface electrode pattern that creates a lateral internal charge collection field. The SDD equals or betters the Si(Li) EDS in most measures of performance. For output versus input count rate, the SDD exceeds the Si(Li) EDS by a factor of 5 to 10 for the same resolution. This high throughput can benefit analytical measurements that are count limited, such as X-ray mapping and trace measurements. The microcalorimeter EDS determines the X-ray energy by measuring the temperature rise in a metal absorber. Operating at 100 mK, the microcalorimeter EDS achieves resolution of 2-5 eV over a photon energy range of 200 eV to 10 keV in energy dispersive operation, eliminating most peak interference situations and providing high peak-to-background to detect low fluorescence yield peaks. Chemical bonding effects on low energy (< 2 keV) peak shapes can be measured. PMID:19830945

  8. R-Matrix Analysis of the 236U(n,gamma) Reaction in theResolved Resonance Energy Region

    SciTech Connect

    Mezentseva, Zh.; Koehler, Paul Edward; Collaboration, n_TOF

    2008-01-01

    The neutron capture cross section of 236U was measured in the neutron energy range from 1 eV to 10 keV by the neutron time-of-flight method at the GELINA white pulsed neutron source of the Institute for Reference Materials and Measurements (IRMM) in Geel (Belgium). The gamma rays originating from neutron capture events were detected by two C6D6-based liquid scintillators using the pulse height weighting technique. The weighting function has been derived from Monte-Carlo simulations of the detector response to monoenergetic gamma rays. The sample under investigation with a total amount of 338 mg of 236U was located in the neutron beam at a distance of 28.6 m from the source. The shape of the neutron flux was determined by a 10B neutron counter, placed approximately 60 cm upstream in the neutron beam line. The neutron capture yield in the resolved resonance region up to 1 keV has been derived from time-of-flight spectra.

  9. Energy- and time-resolved measurements of fast ions emitted from plasma-focus discharges by means of a Thomson spectrometer

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, R.; Czaus, K.; Paduch, M.; Sadowski, M. J.; Skladnik-Sadowska, E.; Zaloga, D. R.; Zielinska, E.; Żebrowski, J.

    2015-09-01

    The paper presents results of time-resolved measurements of fast deuterons emitted from high-current discharges of the Plasma-Focus (PF) type. The measurements were performed in a modified PF-1000U facility which is operated at the IFPiLM in Warsaw, Poland. The device was equipped with a fast-acting gas valve placed inside the inner electrode and oriented along the z-axis. The valve could inject a small volume of a chosen gas in front of this electrode. The PF discharges were initiated at the initial deuterium pressure equal to 1.6 or 2 hPa, with or without the use of the gas-puffing. Such discharges emitted intense beams of accelerated primary ions and X-ray pulses as well as products of nuclear fusion reactions. The reported measurements of the fast ion beams were performed by means of a Thomson-type spectrometer located at a chosen distance at the z-axis and equipped with miniature scintillation detectors. These detectors were placed in different points upon the deuteron parabola which corresponded to determined energy values. The detectors configuration allowed us to determine instants of the ion emission (using a TOF technique) and to compare them with instants of the X-ray emission. The collected data provided important information about emission characteristics of the modified PF-1000U facility.

  10. Generation of high energy square-wave pulses in all anomalous dispersion Er:Yb passive mode locked fiber ring laser.

    PubMed

    Semaan, Georges; Ben Braham, Fatma; Salhi, Mohamed; Meng, Yichang; Bahloul, Faouzi; Sanchez, François

    2016-04-18

    We have experimentally demonstrated square pulses emission from a co-doped Er:Yb double-clad fiber laser operating in anomalous dispersion DSR regime using the nonlinear polarization evolution technique. Stable mode-locked pulses have a repetition rate of 373 kHz with 2.27 µJ energy per pulse under a pumping power of 30 W in cavity. With the increase of pump power, both the duration and the energy of the output square pulses broaden. The experimental results demonstrate that the passively mode-locked fiber laser operating in the anomalous regime can also realize a high-energy pulse, which is different from the conventional low-energy soliton pulse. PMID:27137277

  11. Fog dispersion

    NASA Technical Reports Server (NTRS)

    Frost, W.; Christensen, L. S.; Collins, F. G.; Camp, D. W.

    1980-01-01

    A study of economically viable techniques for dispersing warm fog at commercial airports is presented. Five fog dispersion techniques are examined: evaporation suppression, downwash, mixing, seeding with hygroscopic material, thermal techniques, and charged particle techniques. Thermal techniques, although effective, were found to be too expensive for routine airport operations, and detrimental to the environment. Seeding or helicopter downwash are practical for small-scale or temporary fog clearing, but are probably not useful for airport operations on a routine basis. Considerable disagreement exists on the capability of charged particle techniques, which stems from the fact that different assumptions and parameter values are used in the analytical models. Recommendations resulting from the review of this technique are listed, and include: experimental measurements of the parameters in question; a study to ascertain possible safety hazards, such as increased electrical activity or fuel ignition during refueling operations which could render charged particle techniques impractical; and a study of a single charged particle generator.

  12. New parallel wavelength-dispersive spectrometer based on scanning electron microscope.

    PubMed

    Erko, Alexei; Firsov, Alexander; Gubzhokov, Renat; Bjeoumikhov, Anjuar; Günther, Andreas; Langhoff, Norbert; Bretschneider, Mario; Höhn, Yvonne; Wedell, Reiner

    2014-07-14

    A new wavelength - dispersive X-ray spectrometer for scanning electron microscopy (SEM) has been developed. This spectrometer can cover an energy range from 50 eV to 1120 eV by using an array made of seventeen reflection zone plates. Soft X-ray emission spectra of simple elements of Li, Be, B, C, N, Ti, V, O, Cr, Mn, Fe, Co, Ni, Cu, Zn and Ga were measured. The overall energy resolving power on the order of E/ΔE ~80 to 160 has been demonstrated. Spectrometer with 200 reflection zone plates has been used as a multi-channel analyser in the energy range of 100 - 1000 eV for quasi - continuous spectra measurements. The predicted energy-resolving power on the order of E/ΔE = 50 has been achieved in the entire energy range. PMID:25090506

  13. History of Resistance Welding Oxide Dispersion Strengthened Cladding and other High Temperature Materials at Center for Advanced Energy Studies

    SciTech Connect

    Larry Zirker; Nathan Jerred; Dr. Indrajit Charit; James Cole

    2012-03-01

    Research proposal 08-1079, 'A Comparative Study of Welded ODS Cladding Materials for AFCI/GNEP,' was funded in 2008 under an Advanced Fuel Cycle Initiative (AFCI) Research and Development Funding Opportunity, number DE-PS07-08ID14906. Th proposal sought to conduct research on joining oxide dispersion strengthen (ODS) tubing material to a solid end plug. This document summarizes the scientific and technical progress achieved during the project, which ran from 2008 to 2011.

  14. Method for the determination of Pd-catalyst residues in active pharmaceutical ingredients by means of high-energy polarized-beam energy dispersive X-ray fluorescence.

    PubMed

    Marguí, E; Van Meel, K; Van Grieken, R; Buendía, A; Fontàs, C; Hidalgo, M; Queralt, I

    2009-02-15

    In medicinal chemistry, Pd is perhaps the most-widely utilized precious metal, as catalyst in reactions which represent key transformations toward the synthesis of new active pharmaceutical ingredients (APIs). The disadvantage of this metal-catalyzed chemistry is that expensive and toxic metal residues are invariably left bound to the desired product. Thus, stringent regulatory guidelines exist for the amount of residual Pd that a drug candidate is allowed to contain. In this work, a rapid and simple method for the determination of Pd in API samples by high-energy polarized-beam energy dispersive X-ray fluorescence spectrometry has been developed and validated according to the specification limits of current legislation (10 mg kg(-1) Pd) and the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH guidelines). Sample and calibration standards preparation includes a first step of homogenization and then, in a second step, the pressing of the powdered material into pellets without any chemical treatment. The use of several synthetic calibration standards made of cellulose to simulate the API matrix appears to be an effective means to obtain reliable calibration curves with a good spread of data points over the working range. With the use of the best measuring conditions, the limit of detection (0.11 mg kg(-1) Pd) as well as the limit of quantitation (0.37 mg kg(-1) Pd) achieved meet rigorous requirements. The repeatability of the XRF measurement appeared to be less than 2%, while the precision of the whole method was around 7%. Trueness was evaluated by analyzing spiked API samples at the level of the specification limit and calculating the recovery factor, which was better than 95%. To study the applicability of the developed methodology for the intended purpose, three batches of the studied API were analyzed for their Pd content, and the attained results were comparable to those obtained by the

  15. KISMET tungsten dispersal experiment

    SciTech Connect

    Wohletz, K.; Kunkle, T.; Hawkins, W.

    1996-12-01

    Results of the KISMET tungsten dispersal experiment indicate a relatively small degree of wall-rock contamination caused by this underground explosive experiment. Designed as an add-on to the KISMET test, which was performed in the U-1a.02 drift of the LYNER facility at Nevada Test Site on 1 March 1995, this experiment involved recovery and analysis of wall-rock samples affected by the high- explosive test. The chemical, high-explosive blast drove tungsten powder, placed around the test package as a plutonium analog, into the surrounding wall- rock alluvium. Sample analyses by an analytical digital electron microscope (ADEM) show tungsten dispersed in the rock as tiny (<10 {mu}m) particles, agglomerates, and coatings on alluvial clasts. Tungsten concentrations, measured by energy dispersive spectral analysis on the ADEM, indicate penetration depths less than 0.1 m and maximum concentrations of 1.5 wt % in the alluvium.

  16. Air parcel trajectory dispersion near the tropical tropopause

    NASA Astrophysics Data System (ADS)

    Bergman, John W.; Jensen, Eric J.; Pfister, Leonhard; Bui, Thaopaul V.

    2016-04-01

    Dispersion of backward air parcel trajectories that are initially tightly grouped near the tropical tropopause is examined using three ensemble approaches: "RANWIND," in which different ensemble members use identical resolved wind fluctuations but different realizations of stochastic, multifractal simulations of unresolved winds; "PERTLOC," in which members use identical resolved wind fields but initial locations are perturbed 2° in latitude and longitude; and a multimodel ensemble ("MULTIMODEL") that uses identical initial conditions but different resolved wind fields and/or trajectory formulations. Comparisons among the approaches distinguish, to some degree, physical dispersion from that due to data uncertainty and the impacts of unresolved wind fluctuations from those of resolved variability. Dispersion rates are robust properties of trajectories near the tropical tropopause. Horizontal dispersion rates are typically ~3°/d, which is large enough to spread parcels throughout the tropics within typical tropical tropopause layer transport times (30-60 days) and underscores the importance of averaging large collections of trajectories to obtain reliable parcel source and pathway distributions. Vertical dispersion rates away from convection are ~2-3 hPa/d. Dispersion is primarily carried out by the resolved flow, and the RANWIND approach provides a plausible representation of actual trajectory dispersion rates, while PERTLOC provides a reasonable and inexpensive alternative to RANWIND. In contrast, dispersion from the MULTIMODEL calculations is important because it reflects systematic differences in resolved wind fields from different reanalysis data sets.

  17. Dispersive optical potential from an analysis of neutron single-particle energies in the Ti, Cr, and Fe isotopes featuring 20 to 50 neutrons

    SciTech Connect

    Bespalova, O. V. Ermakova, T. A.; Klimochkina, A. A.; Romanovsky, E. A.; Spasskaya, T. I.

    2012-11-15

    Neutron single-particle energies in unstable Ti, Cr, and Fe isotopes containing 20 to 26 neutrons were evaluated on the basis of experimental proton energies in the mirror-symmetric nuclei. The neutron single-particle energies in the 20 Less-Than-Or-Slanted-Equal-To N Less-Than-Or-Slanted-Equal-To 50 Ti, Cr, and Fe isotopes were calculated on the basis of the mean-field model with a dispersive optical potential, and the results were compared with available experimental data and with the results of estimations and calculations based on the relativistic mean-field model and on the multiparticle shell model with the GXPF1 interaction.

  18. The ground states of iron(III) porphines: role of entropy-enthalpy compensation, Fermi correlation, dispersion, and zero-point energies.

    PubMed

    Kepp, Kasper P

    2011-10-01

    Porphyrins are much studied due to their biochemical relevance and many applications. The density functional TPSSh has previously accurately described the energy of close-lying electronic states of transition metal systems such as porphyrins. However, a recent study questioned this conclusion based on calculations of five iron(III) porphines. Here, we compute the geometries of 80 different electronic configurations and the free energies of the most stable configurations with the functionals TPSSh, TPSS, and B3LYP. Zero-point energies and entropy favor high-spin by ~4kJ/mol and 0-10kJ/mol, respectively. When these effects are included, and all electronic configurations are evaluated, TPSSh correctly predicts the spin of all the four difficult phenylporphine cases and is within the lower bound of uncertainty of any known theoretical method for the fifth, iron(III) chloroporphine. Dispersion computed with DFT-D3 favors low-spin by 3-53kJ/mol (TPSSh) or 4-15kJ/mol (B3LYP) due to the attractive r(-6) term and the shorter distances in low-spin. The very large and diverse corrections from TPSS and TPSSh seem less consistent with the similarity of the systems than when calculated from B3LYP. If the functional-specific corrections are used, B3LYP and TPSSh are of equal accuracy, and TPSS is much worse, whereas if the physically reasonable B3LYP-computed dispersion effect is used for all functionals, TPSSh is accurate for all systems. B3LYP is significantly more accurate when dispersion is added, confirming previous results. PMID:21855825

  19. Photosynthetic dioxygen formation studied by time-resolved delayed fluorescence measurements--method, rationale, and results on the activation energy of dioxygen formation.

    PubMed

    Buchta, Joachim; Grabolle, Markus; Dau, Holger

    2007-06-01

    The analysis of the time-resolved delayed fluorescence (DF) measurements represents an important tool to study quantitatively light-induced electron transfer as well as associated processes, e.g. proton movements, at the donor side of photosystem II (PSII). This method can provide, inter alia, insights in the functionally important inner-protein proton movements, which are hardly detectable by conventional spectroscopic approaches. The underlying rationale and experimental details of the method are described. The delayed emission of chlorophyll fluorescence of highly active PSII membrane particles was measured in the time domain from 10 mus to 60 ms after each flash of a train of nanosecond laser pulses. Focusing on the oxygen-formation step induced by the third flash, we find that the recently reported formation of an S4-intermediate prior to the onset of O-O bond formation [M. Haumann, P. Liebisch, C. Müller, M. Barra, M. Grabolle, H. Dau, Science 310, 1019-1021, 2006] is a multiphasic process, as anticipated for proton movements from the manganese complex of PSII to the aqueous bulk phase. The S4-formation involves three or more likely sequential steps; a tri-exponential fit yields time constants of 14, 65, and 200 mus (at 20 degrees C, pH 6.4). We determine that S4-formation is characterized by a sizable difference in Gibbs free energy of more than 90 meV (20 degrees C, pH 6.4). In the second part of the study, the temperature dependence (-2.7 to 27.5 degrees C) of the rate constant of dioxygen formation (600/s at 20 degrees C) was investigated by analysis of DF transients. If the activation energy is assumed to be temperature-independent, a value of 230 meV is determined. There are weak indications for a biphasicity in the Arrhenius plot, but clear-cut evidence for a temperature-dependent switch between two activation energies, which would point to the existence of two distinct rate-limiting steps, is not obtained. PMID:17543884

  20. Conformational dynamics and intersubunit energy transfer in wild-type and mutant lipoamide dehydrogenase from Azotobacter vinelandii. A multidimensional time-resolved polarized fluorescence study.

    PubMed Central

    Bastiaens, P I; van Hoek, A; Benen, J A; Brochon, J C; Visser, A J

    1992-01-01

    Time-resolved fluorescence and fluorescence anisotropy data surfaces of flavin adenine dinucleotide bound to lipoamide dehydrogenase from Azotobacter vinelandii in 80% glycerol have been obtained by variation of excitation energy and temperature between 203 and 303 K. The fluorescence kinetics of a deletion mutant lacking 14 COOH-terminal amino acids were compared with the wild-type enzyme to study a possible interaction of the COOH-terminal tail with the active site of the enzyme. The flavin adenine dinucleotide fluorescence in both proteins exhibits a bimodal lifetime distribution as recovered by the maximum entropy method of data analysis. The difference in standard enthalpy and entropy of associated conformational substates was retrieved from the fractional contributions of the two lifetime classes. Activation energies of thermal quenching were obtained that confirm that the isoalloxazines in the deletion mutant are solvent accessible in contrast to the wild-type enzyme. Red-edge spectroscopy in conjunction with variation of temperature provides the necessary experimental axes to interpret the fluorescence depolarization in terms of intersubunit energy transfer rather than reorientational dynamics of the flavins. The results can be explained by a compartmental model that describes the anisotropy decay of a binary, inhomogeneously broadened, homoenergy transfer system. By using this model in a global analysis of the fluorescence anisotropy decay surface, the distance between and relative orientation of the two isoalloxazine rings are elucidated. For the wild-type enzyme, this geometrical information is in agreement with crystallographic data of the A. vinelandii enzyme, whereas the mutual orientation of the subunits in the deletion mutant is slightly altered. In addition, the ambiguity in the direction of the emission transition moment in the isoalloxazine ring is solved. The anisotropy decay parameters also provide information on electronic and dipolar

  1. Relationship between dislocations and residual stresses in cold-drawn pearlitic steel analyzed by energy-dispersive X-ray diffraction

    SciTech Connect

    Sato, Shigeo; Wagatsuma, Kazuaki; Suzuki, Shigeru; Kumagai, Masayoshi; Imafuku, Muneyuki; Tashiro, Hitoshi; Kajiwara, Kentaro; Shobu, Takahiasa

    2013-09-15

    We analyzed the dislocation distribution of cold-drawn pearlitic-steel wire by using the line-profile analysis based on the energy dispersive X-ray diffraction (EDXD). Although this line-profile analysis requires a high resolution in reciprocal space, the resolution for EDXD is generally poor due to the energy resolution of the detector. Our analysis demonstrated that the resolution in the reciprocal space can be maximized at small scattering angles. Using the line-profile analysis based on the EDXD, the microstructural parameters such as the crystallite size and the dislocation density of the ferrite phase in the pearlitic steel were successfully analyzed. In addition, the distribution of the residual stress of the ferrite phase of a pearlitic steel wire was also analyzed using the EDXD measurement. - Highlights: • Energy dispersive X-ray diffraction is applied to the line-profile analysis. • Distribution of dislocations in ferrite in the pearlitic steel wire is analyzed. • Relationship between dislocations and residual stress is discussed.

  2. Higher-order electric multipole contributions to retarded non-additive three-body dispersion interaction energies between atoms: Equilateral triangle and collinear configurations

    SciTech Connect

    Salam, A.

    2013-12-28

    The theory of molecular quantum electrodynamics (QED) is used to calculate higher electric multipole contributions to the dispersion energy shift between three atoms or molecules arranged in a straight line or in an equilateral triangle configuration. As in two-body potentials, three-body dispersion interactions are viewed in the QED formalism to arise from exchange of virtual photons between coupled pairs of particles. By employing an interaction Hamiltonian that is quadratic in the electric displacement field means that third-order perturbation theory can be used to yield the energy shift for a particular combination of electric multipole polarizable species, with only six time-ordered diagrams needing to be summed over. Specific potentials evaluated include dipole-dipole-quadrupole (DDQ), dipole-quadrupole-quadrupole (DQQ), and dipole-dipole-octupole (DDO) terms. For the geometries of interest, near-zone limiting forms are found to exhibit an R{sup −11} dependence on separation distance for the DDQ interaction, and an R{sup −13} behaviour for DQQ and DDO shifts, agreeing with an earlier semi-classical computation. Retardation weakens the potential in each case by R{sup −1} in the far-zone. It is found that by decomposing the octupole moment into its irreducible components of weights-1 and -3 that the former contribution to the DDO potential may be taken to be a higher-order correction to the leading triple dipole energy shift.

  3. Matrix effects in the energy dispersive X-ray analysis of CaO-Al(2)O(3)-MgO inclusions in steel.

    PubMed

    Pistorius, Petrus Christiaan; Verma, Neerav

    2011-12-01

    Energy dispersive X-ray microanalysis of micron-sized inclusions in steel is of considerable industrial importance. Measured spectra and Monte Carlo simulations show a significant effect of the steel matrix on analysis of CaO-Al(2)O(3)-MgO inclusions: the steel matrix filters the softer (Al and Mg) characteristic X-rays, increasing the relative height of the Ca peak. Bulk matrix correction methods would not result in correct inclusion compositions, but operating at a lower acceleration voltage shifts the effect to smaller inclusion sizes. PMID:22051086

  4. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

    PubMed

    Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

    2014-12-01

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. PMID:25126753

  5. Study of dispersion of mass distribution of ultra-high energy cosmic rays using a surface array of muon and electromagnetic detectors

    NASA Astrophysics Data System (ADS)

    Vícha, Jakub; Trávníček, Petr; Nosek, Dalibor; Ebr, Jan

    2015-09-01

    We consider a hypothetical observatory of ultra-high energy cosmic rays consisting of two surface detector arrays that measure independently electromagnetic and muon signals induced by air showers. Using the constant intensity cut method, sets of events ordered according to each of both signal sizes are compared giving the number of matched events. Based on its dependence on the zenith angle, a parameter sensitive to the dispersion of the distribution of the logarithmic mass of cosmic rays is introduced. The results obtained using two post-LHC models of hadronic interactions are very similar and indicate a weak dependence on details of these interactions.

  6. Combination of Raman, Infrared, and X-Ray Energy-Dispersion Spectroscopies and X-Ray Diffraction to Study a Fossilization Process

    NASA Astrophysics Data System (ADS)

    de Sousa Filho, Francisco Eduardo; da Silva, João Hermínio; Feitosa Saraiva, Antônio Álamo; Brito, Deyvid Dennys S.; Viana, Bartolomeu Cruz; de Oliveira Abagaro, Bruno Tavares; de Tarso Cavalcante Freire, Paulo

    2011-12-01

    X-ray diffraction was combined with X-ray energy-dispersion, Fourier-transform infrared, and Raman spectroscopies to study the fossilization of a Cretaceous specimen of the plant Brachyphyllum castilhoi, a fossil from the Ipubi Formation, in the Araripe Sedimentary Basin, Northeastern Brazil. Among the possible fossilization processes, which could involve pyrite, silicon oxide, calcium oxide, or other minerals, we were able to single out pyritization as the central mechanism producing the fossil, more than 100 million years ago. In addition to expanding the knowledge of the Ipubi Formation, this study shows that, when combined with other experimental techniques, Raman spectroscopy is a valuable tool at the paleontologist's disposal.

  7. A CdZnTe array for the detection of explosives in baggage by energy-dispersive X-ray diffraction signatures at multiple scatter angles

    NASA Astrophysics Data System (ADS)

    Malden, Catharine H.; Speller, Robert. D.

    2000-07-01

    CdZnTe detectors were used to collect energy-dispersive diffraction spectra at a range of scatter angles, from sheets of explosives hidden in baggage. It is shown that the combined information from these `signatures' can be used to determine whether an explosive sample is present or not. The geometrical configuration of the collimation and the position of the baggage within the scanner must be taken into careful consideration when optimising the capabilities of such a system. The CdZnTe array lends itself well to the detection of explosives in baggage since multiple signals may be collected simultaneously providing more rapid detection than achieved using a single detector.

  8. Energy dispersive X-ray diffraction in the diamond anvil, high-pressure apparatus - Comparison of synchrotron and conventional X-ray sources

    NASA Technical Reports Server (NTRS)

    Spain, I. L.; Black, D. R.

    1985-01-01

    The use of both conventional fixed-anode X-ray sources and synchrotron radiation to carry out energy-dispersive X-ray diffraction experiments at high pressure in a diamond anvil cell, is discussed. The photon flux at the sample and at the detector for the two cases are compared and the results are presented in graphs. It is shown that synchrotron radiation experiments can be performed with nearly two orders of magnitude increase in data rate if superior detectors and detector electronics are available.

  9. SPATIALLY RESOLVING A STARBURST GALAXY AT HARD X-RAY ENERGIES: NuSTAR, CHANDRA, AND VLBA OBSERVATIONS OF NGC 253

    SciTech Connect

    Wik, D. R.; Lehmer, B. D.; Hornschemeier, A. E.; Yukita, M.; Ptak, A.; Venters, T.; Zhang, W. W.; Zezas, A.; Antoniou, V.; Argo, M. K.; Bechtol, K.; Boggs, S.; Craig, W.; Krivonos, R.; Christensen, F.; Hailey, C.; Harrison, F.; Maccarone, T. J.; Stern, D.

    2014-12-20

    Prior to the launch of NuSTAR, it was not feasible to spatially resolve the hard (E > 10 keV) emission from galaxies beyond the Local Group. The combined NuSTAR data set, comprised of three ∼165 ks observations, allows spatial characterization of the hard X-ray emission in the galaxy NGC 253 for the first time. As a follow up to our initial study of its nuclear region, we present the first results concerning the full galaxy from simultaneous NuSTAR, Chandra, and Very Long Baseline Array monitoring of the local starburst galaxy NGC 253. Above ∼10 keV, nearly all the emission is concentrated within 100'' of the galactic center, produced almost exclusively by three nuclear sources, an off-nuclear ultraluminous X-ray source (ULX), and a pulsar candidate that we identify for the first time in these observations. We detect 21 distinct sources in energy bands up to 25 keV, mostly consisting of intermediate state black hole X-ray binaries. The global X-ray emission of the galaxy—dominated by the off-nuclear ULX and nuclear sources, which are also likely ULXs—falls steeply (photon index ≳ 3) above 10 keV, consistent with other NuSTAR-observed ULXs, and no significant excess above the background is detected at E > 40 keV. We report upper limits on diffuse inverse Compton emission for a range of spatial models. For the most extended morphologies considered, these hard X-ray constraints disfavor a dominant inverse Compton component to explain the γ-ray emission detected with Fermi and H.E.S.S. If NGC 253 is typical of starburst galaxies at higher redshift, their contribution to the E > 10 keV cosmic X-ray background is <1%.

  10. Energy-resolved collision-induced dissociation of non-covalent ions: charge- and guest-dependence of decomplexation reaction efficiencies.

    PubMed

    Carroy, Glenn; Lemaur, Vincent; De Winter, Julien; Isaacs, Lyle; De Pauw, Edwin; Cornil, Jérôme; Gerbaux, Pascal

    2016-05-14

    Supramolecular chemistry, and especially host-guest chemistry, has been the subject of great interest in the past few decades leading to the synthesis of host cage molecules such as calixarenes, cyclodextrins and more recently cucurbiturils. Mass spectrometry methods are increasingly used to decipher at the molecular level the non-covalent interactions between the different associated molecules. The present article illustrates that the association between mass spectrometry and computational chemistry techniques proves very complementary to depict the gas-phase dissociation processes of ionic non-covalent complexes when subjected to collisional activation. The selected system associates a nor-seco-cucurbit[10]uril bitopic receptor with different amino compounds (adamantylamine, para-xylylenediamine, and para-phenylenediamine). When subjected to CID experiments, the ternary complexes undergo fragmentation via dissociation of non-covalently bound partners. Interestingly, depending on their charge state, the collisionally excited complexes can selectively expel either a neutral guest molecule or a protonated guest molecule. Moreover, based on energy-resolved CID experiments, it is possible to evaluate the guest molecule dependence on the gas phase dissociation efficiency. We observed that the relative order of gas phase dissociation is charge state dependent, with the adamantylamine-containing complexes being the weakest when triply charged and the strongest when doubly charged. The energetics of the gas-phase dissociation reactions have been estimated by density functional theory (DFT) calculations. We succeeded in theoretically rationalizing the experimental collision-induced dissociation results with a special emphasis on: (i) the charge state of the expelled guest molecule and (ii) the nature of the guest molecule. PMID:27086657

  11. Development and implementation of a miniaturized high-throughput time-resolved fluorescence energy transfer assay to identify small molecule inhibitors of polo-like kinase 1.

    PubMed

    Sharlow, Elizabeth R; Leimgruber, Stephanie; Shun, Tong Ying; Lazo, John S

    2007-12-01

    Polo-like kinase (Plk) 1 is a key enzyme involved in regulating the mammalian cell cycle that is also a validated anticancer drug target. Nonetheless, there are relatively few readily available potent and selective small molecule inhibitors of Plk1. To increase the availability of pharmacologically valuable Plk1 inhibitors, we describe herein the development, variability assessment, validation, and implementation of a 384-well automated, miniaturized high-throughput time-resolved fluorescence energy transfer screening assay designed to identify Plk1 kinase inhibitors. Using a small molecule library of pharmaceutically active compounds to gauge high-throughput assay robustness and reproducibility, we found nine general kinase inhibitors, including H-89, which was selected as the minimum control. We then interrogated a 97,101 compound library from the National Institutes of Health repository for small molecule inhibitors of Plk1 kinase activity. The initial primary hit rate in a single 10 microM concentration format was 0.21%. Hit compounds were subjected to concentration-response confirmation and interference assays. Identified in the screen were seven compounds with 50% inhibitory concentration (IC50) values below 1 microM, 20 compounds with IC50 values between 1 microM and 5 microM, and eight compounds with IC50 values between 5 and 10 microM, which could be assigned to seven distinct chemotype classes. Hit compounds were also examined for their ability to inhibit other kinases such as protein kinase D, focal adhesion kinase, rho-associated coiled coil protein kinase 2, c-jun NH2-terminal kinase 3, and protein kinase A via experimentation or data-mining. These compounds should be useful as probes for the biological activity of Plk1 and as leads for the development of new selective inhibitors of Plk1. PMID:18181689

  12. Dynamical observation of lithium insertion/extraction reaction during charge-discharge processes in Li-ion batteries by in situ spatially resolved electron energy-loss spectroscopy.

    PubMed

    Shimoyamada, Atsushi; Yamamoto, Kazuo; Yoshida, Ryuji; Kato, Takehisa; Iriyama, Yasutoshi; Hirayama, Tsukasa

    2015-12-01

    All-solid-state Li-ion batteries (LIBs) with solid electrolytes are expected to be the next generation devices to overcome serious issues facing conventional LIBs with liquid electrolytes. However, the large Li-ion transfer resistance at the electrode/solid-electrolyte interfaces causes low power density and prevents practical use. In-situ-formed negative electrodes prepared by decomposing the solid electrolyte Li(1+x+3z)Alx(Ti,Ge)(2-x)Si(3z)P(3-z)O12 (LASGTP) with an excess Li-ion insertion reaction are effective electrodes providing low Li-ion transfer resistance at the interfaces. Prior to our work, however, it had still been unclear how the negative electrodes were formed in the parent solid electrolytes. Here, we succeeded in dynamically visualizing the formation by in situ spatially resolved electron energy-loss spectroscopy in a transmission electron microscope mode (SR-TEM-EELS). The Li-ions were gradually inserted into the solid electrolyte region around 400 nm from the negative current-collector/solid-electrolyte interface in the charge process. Some of the ions were then extracted in the discharge process, and the rest were diffused such that the distribution was almost flat, resulting in the negative electrodes. The redox reaction of Ti(4+)/Ti(3+) in the solid electrolyte was also observed in situ during the Li insertion/extraction processes. The in situ SR-TEM-EELS revealed the mechanism of the electrochemical reaction in solid-state batteries. PMID:26337787

  13. Resolving the Pericenter

    NASA Astrophysics Data System (ADS)

    Wisdom, Jack

    2015-10-01

    The Wisdom-Holman mapping method and its variations have become a mainstay of research in solar system dynamics. But the method is not without its limitations. Rauch & Holman noted that at large eccentricities sufficiently small steps must be taken to resolve the pericenter. In this paper, I explore in more detail what it means to resolve the pericenter.

  14. Space-resolved extreme ultraviolet spectroscopy free of high-energy neutral particle noise in wavelength range of 10–130 Å on the large helical device

    SciTech Connect

    Huang, Xianli; Morita, Shigeru; Oishi, Tetsutarou; Goto, Motoshi; Dong, Chunfeng

    2014-04-15

    A flat-field space-resolved extreme ultraviolet (EUV) spectrometer system working in wavelength range of 10–130 Å has been constructed in the Large Helical Device (LHD) for profile measurements of bremsstrahlung continuum and line emissions of heavy impurities in the central column of plasmas, which are aimed at studies on Z{sub eff} and impurity transport, respectively. Until now, a large amount of spike noise caused by neutral particles with high energies (≤180 keV) originating in neutral beam injection has been observed in EUV spectroscopy on LHD. The new system has been developed with an aim to delete such a spike noise from the signal by installing a thin filter which can block the high-energy neutral particles entering the EUV spectrometer. Three filters of 11 μm thick beryllium (Be), 3.3 μm thick polypropylene (PP), and 0.5 μm thick polyethylene terephthalate (PET: polyester) have been examined to eliminate the spike noise. Although the 11 μm Be and 3.3 μm PP filters can fully delete the spike noise in wavelength range of λ ≤ 20 Å, the signal intensity is also reduced. The 0.5 μm PET filter, on the other hand, can maintain sufficient signal intensity for the measurement and the spike noise remained in the signal is acceptable. As a result, the bremsstrahlung profile is successfully measured without noise at 20 Å even in low-density discharges, e.g., 2.9 × 10{sup 13} cm{sup −3}, when the 0.5 μm PET filter is used. The iron n = 3–2 Lα transition array consisting of FeXVII to FeXXIV is also excellently observed with their radial profiles in wavelength range of 10–18 Å. Each transition in the Lα array can be accurately identified with its radial profile. As a typical example of the method a spectral line at 17.62 Å is identified as FeXVIII transition. Results on absolute intensity calibration of the spectrometer system, pulse height and noise count analyses of the spike noise between holographic and ruled gratings and wavelength

  15. Photoemission line-shapes and dispersion relations in the superconducting state of BISCO

    NASA Astrophysics Data System (ADS)

    Fedorov, A. V.; Chuang, Y.-D.; Gromko, A. D.; Sun, Z.; Douglas, J.; Koralek, J. D.; Dessau, D. S.; Aiura, Y.; Yamaguchi, Y.; Oka, K.; Ando, Yoichi

    2003-03-01

    Using high-resolution angle-resolved photoemission on BISCO we have studied the dispersion relations and photoemission line-shapes close to the Fermi level. Results taken near (p,0) points of the Brilloin zone indicate that traditional peak-dip-hump structure is largely due to the presence of bonding and anti-bonding bands. However, a separate much weaker peak and hump structure can be detected if the bilayer splitting is resolved properly. This true peak-dip hump lineshape develops in the superconducting state. At the same time, the dispersion relations show the kink" or mass enhancement with the true quasiparticles occurring within the kink energy. We will argue that "kinks" detected in the vicinity of (p,0) points and along the nodal direction are distinctly different in nature.

  16. Graphene on Ir(111) characterized by angle-resolved photoemission

    NASA Astrophysics Data System (ADS)

    Kralj, Marko; Pletikosić, Ivo; Petrović, Marin; Pervan, Petar; Milun, Milorad; N'Diaye, Alpha T.; Busse, Carsten; Michely, Thomas; Fujii, Jun; Vobornik, Ivana

    2011-08-01

    Angle-resolved photoelectron spectroscopy (ARPES) is extensively used to characterize the dependence of the electronic structure of graphene on Ir(111) on the preparation process. ARPES findings reveal that temperature-programmed growth alone or in combination with chemical vapor deposition leads to graphene displaying sharp electronic bands. The photoemission intensity of the Dirac cone is monitored as a function of the increasing graphene area. Electronic features of the moiré superstructure present in the system, namely, minigaps and replica bands are examined and used as robust features to evaluate graphene uniformity. The overall dispersion of the π band is analyzed. Finally, by the variation of photon energy, relative changes of the π and σ band intensities are demonstrated.

  17. High-resolving mass spectrographs and spectrometers

    NASA Astrophysics Data System (ADS)

    Wollnik, Hermann

    2015-11-01

    Discussed are different types of high resolving mass spectrographs and spectrometers. In detail outlined are (1) magnetic and electric sector field mass spectrographs, which are the oldest systems, (2) Penning Trap mass spectrographs and spectrometers, which have achieved very high mass-resolving powers, but are technically demanding (3) time-of-flight mass spectrographs using high energy ions passing through accelerator rings, which have also achieved very high mass-resolving powers and are equally technically demanding, (4) linear time-of-flight mass spectrographs, which have become the most versatile mass analyzers for low energy ions, while the even higher performing multi-pass systems have only started to be used, (5) orbitraps, which also have achieved remarkably high mass-resolving powers for low energy ions.

  18. Elucidating redox-level dispersion and local dielectric effects within electroactive molecular films.

    PubMed

    Bueno, Paulo R; Davis, Jason J

    2014-02-18

    The electron exchange between a redox-active molecular film and its underlying electrode can be cleanly tracked, in a frequency-resolved manner, through associated capacitive charging. If acquired data is treated with a classical (non quantum) model, mathematically equivalent to a Nernst distribution for one redox energy level, redox site coverage is both underestimated and environmentally variable. This physically unrealistic model fails to account for the energetic dispersion intrinsically related to the quantized characteristics of coupled redox and electrode states. If one maps this redox capacitive charging as a function of electrode potential one not only reproduces observations made by standard electroanalytical methods but additionally and directly resolves the spread of redox state energies the electrode is communicating with. In treating a population of surface-confined redox states as constituting a density of states, these analyses further resolve the effects of electrolyte dielectric on energetic spread in accordance with the electron-transfer models proposed by Marcus and others. These observations additionally underpin a directly (spectrally) resolved dispersion in electron-transfer kinetics. PMID:24392706

  19. Relative dispersion in the atmosphere

    NASA Astrophysics Data System (ADS)

    LaCasce, Joe; Graff, Lise; Guttu, Sigmund

    2014-05-01

    The relative dispersion of pairs of particles in flows is of central importance when describing environmental dispersion, for example of volcanic ash. Atmospheric relative dispersion was examined previously in two balloon experiments in the Southern Hemisphere (the EOLE and TWERLE experiments). In both cases, the dispersion at scales below 1000 km grew exponentially in time, indicating the kinetic energy spectrum is steep. Subsequent analyses suggested though that the dispersion had a power law dependence on time, implying a shallower kinetic energy spectrum. The results from studies employing synthetic particles advected by reanalysis winds are similarly inconsistent, with indications of exponential growth in some cases and power law growth in others. Here we use a different statistic---the probability density function (PDF) of pair displacements---to study dispersion the dispersion of large numbers of synthetic particles, advected by ERA-Interim reanalysis winds. The particles were deployed in the troposphere and stratosphere, both in the tropics and the extra-tropics. We examine the PDFs for the different deployments and compare them to analytical expressions derived for different turbulent inertial ranges. In line with the earlier balloon experiments, the results indicate exponential growth at the sub-deformation (1000 km) scales. At larger scales, the dispersion is anisotropic (predominantly zonal) and pair motion becomes decorrelated. Structure functions calculated from the wind data are in line with these conclusions.

  20. Dispersion-correcting potentials can significantly improve the bond dissociation enthalpies and noncovalent binding energies predicted by density-functional theory

    SciTech Connect

    DiLabio, Gino A.; Koleini, Mohammad

    2014-05-14

    Dispersion-correcting potentials (DCPs) are atom-centered Gaussian functions that are applied in a manner that is similar to effective core potentials. Previous work on DCPs has focussed on their use as a simple means of improving the ability of conventional density-functional theory methods to predict the binding energies of noncovalently bonded molecular dimers. We show in this work that DCPs developed for use with the LC-ωPBE functional along with 6-31+G(2d,2p) basis sets are capable of simultaneously improving predicted noncovalent binding energies of van der Waals dimer complexes and covalent bond dissociation enthalpies in molecules. Specifically, the DCPs developed herein for the C, H, N, and O atoms provide binding energies for a set of 66 noncovalently bonded molecular dimers (the “S66” set) with a mean absolute error (MAE) of 0.21 kcal/mol, which represents an improvement of more than a factor of 10 over unadorned LC-ωPBE/6-31+G(2d,2p) and almost a factor of two improvement over LC-ωPBE/6-31+G(2d,2p) used in conjunction with the “D3” pairwise dispersion energy corrections. In addition, the DCPs reduce the MAE of calculated X-H and X-Y (X,Y = C, H, N, O) bond dissociation enthalpies for a set of 40 species from 3.2 kcal/mol obtained with unadorned LC-ωPBE/6-31+G(2d,2p) to 1.6 kcal/mol. Our findings demonstrate that broad improvements to the performance of DFT methods may be achievable through the use of DCPs.

  1. Spatially resolved spectral-imaging device

    DOEpatents

    Bloom, Joshua Simon; Tyson, John Anthony

    2016-02-09

    A spatially resolved spectral device comprising a dispersive array to receive an incident light comprising a principal ray. The dispersive array comprising a plurality of dichroic layers, each of the plurality of dichroic layers disposed in a path of a direction of the principal ray. Each of the plurality of dichroic layers configured to at least one of reflect or transmit a different wavelength range of the incident light. The device further comprising a detection array operatively coupled with the dispersive array. The detection array comprising a photosensitive component including a plurality of detection pixels, each of the plurality of detection pixels having a light-receiving surface disposed parallel to the direction of the principal ray to detect a respective one of the different wavelength ranges of incident light reflected from a corresponding one of the plurality of dichroic layers.

  2. A new method for polychromatic X-ray μLaue diffraction on a Cu pillar using an energy-dispersive pn-junction charge-coupled device

    SciTech Connect

    Abboud, A.; Send, S.; Pashniak, N.; Pietsch, U.; Kirchlechner, C.; Micha, J. S.; Ulrich, O.; Keckes, J.

    2014-11-15

    μLaue diffraction with a polychromatic X-ray beam can be used to measure strain fields and crystal orientations of micro crystals. The hydrostatic strain tensor can be obtained once the energy profile of the reflections is measured. However, this remains a challenge both on the time scale and reproducibility of the beam position on the sample. In this review, we present a new approach to obtain the spatial and energy profiles of Laue spots by using a pn-junction charge-coupled device, an energy-dispersive area detector providing 3D resolution of incident X-rays. The morphology and energetic structure of various Bragg peaks from a single crystalline Cu micro-cantilever used as a test system were simultaneously acquired. The method facilitates the determination of the Laue spots’ energy spectra without filtering the white X-ray beam. The synchrotron experiment was performed at the BM32 beamline of ESRF using polychromatic X-rays in the energy range between 5 and 25 keV and a beam size of 0.5 μm × 0.5 μm. The feasibility test on the well known system demonstrates the capabilities of the approach and introduces the “3D detector method” as a promising tool for material investigations to separate bending and strain for technical materials.

  3. A new method for polychromatic X-ray μLaue diffraction on a Cu pillar using an energy-dispersive pn-junction charge-coupled device.

    PubMed

    Abboud, A; Kirchlechner, C; Send, S; Micha, J S; Ulrich, O; Pashniak, N; Strüder, L; Keckes, J; Pietsch, U

    2014-11-01

    μLaue diffraction with a polychromatic X-ray beam can be used to measure strain fields and crystal orientations of micro crystals. The hydrostatic strain tensor can be obtained once the energy profile of the reflections is measured. However, this remains a challenge both on the time scale and reproducibility of the beam position on the sample. In this review, we present a new approach to obtain the spatial and energy profiles of Laue spots by using a pn-junction charge-coupled device, an energy-dispersive area detector providing 3D resolution of incident X-rays. The morphology and energetic structure of various Bragg peaks from a single crystalline Cu micro-cantilever used as a test system were simultaneously acquired. The method facilitates the determination of the Laue spots' energy spectra without filtering the white X-ray beam. The synchrotron experiment was performed at the BM32 beamline of ESRF using polychromatic X-rays in the energy range between 5 and 25 keV and a beam size of 0.5 μm × 0.5 μm. The feasibility test on the well known system demonstrates the capabilities of the approach and introduces the "3D detector method" as a promising tool for material investigations to separate bending and strain for technical materials. PMID:25430118

  4. Development of a high resolution and high dispersion Thomson parabola

    NASA Astrophysics Data System (ADS)

    Jung, D.; Hörlein, R.; Kiefer, D.; Letzring, S.; Gautier, D. C.; Schramm, U.; Hübsch, C.; Öhm, R.; Albright, B. J.; Fernandez, J. C.; Habs, D.; Hegelich, B. M.

    2011-01-01

    Here, we report on the development of a novel high resolution and high dispersion Thomson parabola for simultaneously resolving protons and low-Z ions of more than 100 MeV/nucleon necessary to explore novel laser ion acceleration schemes. High electric and magnetic fields enable energy resolutions of ΔE/E < 5% at 100 MeV/nucleon and impede premature merging of different ion species at low energies on the detector plane. First results from laser driven ion acceleration experiments performed at the Trident Laser Facility demonstrate high resolution and superior species and charge state separation of this novel Thomson parabola for ion energies of more than 30 MeV/nucleon.

  5. Development of a high resolution and high dispersion Thomson parabola.

    PubMed

    Jung, D; Hörlein, R; Kiefer, D; Letzring, S; Gautier, D C; Schramm, U; Hübsch, C; Öhm, R; Albright, B J; Fernandez, J C; Habs, D; Hegelich, B M

    2011-01-01

    Here, we report on the development of a novel high resolution and high dispersion Thomson parabola for simultaneously resolving protons and low-Z ions of more than 100 MeV/nucleon necessary to explore novel laser ion acceleration schemes. High electric and magnetic fields enable energy resolutions of ΔE∕E < 5% at 100 MeV/nucleon and impede premature merging of different ion species at low energies on the detector plane. First results from laser driven ion acceleration experiments performed at the Trident Laser Facility demonstrate high resolution and superior species and charge state separation of this novel Thomson parabola for ion energies of more than 30 MeV/nucleon. PMID:21280824

  6. Blueshifted Flat Dispersion Relation of Exciton-Polariton Condensates in a CuBr Microcavity

    NASA Astrophysics Data System (ADS)

    Nakayama, Masaaki; Murakami, Katsuya; Kim, DaeGwi

    2016-05-01

    We have investigated cavity-polariton condensation effects on the dispersion relation of the lower polariton branch (LPB) at 77 K in a CuBr microcavity by angle-resolved photoluminescence (PL) spectroscopy. The intrinsic cavity-polariton dispersion relations were characterized by the analysis of the incident light angle (in-plane wave vector k∥) dependence of cavity-polariton energies obtained using angle-resolved reflectance spectroscopy. It was found that a blueshifted PL band appears with a threshold-like nature as a function of excitation power density. The in-plane wave vector dependence of the blueshifted PL energy exhibits a flat dispersion relation in the k∥ range from 0 to ˜4.4 µm-1, which is clearly separated from the intrinsic LPB because of the large blueshift of ˜15 meV. We show that the blueshifted flat dispersion relation is possibly explained by the theory for a diffusive Goldstone mode peculiar to nonequilibrium cavity-polariton condensation.

  7. Band Structure of Helimagnons in MnSi Resolved by Inelastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Kugler, M.; Brandl, G.; Waizner, J.; Janoschek, M.; Georgii, R.; Bauer, A.; Seemann, K.; Rosch, A.; Pfleiderer, C.; Böni, P.; Garst, M.

    2015-08-01

    A magnetic helix realizes a one-dimensional magnetic crystal with a period given by the pitch length λh . Its spin-wave excitations—the helimagnons—experience Bragg scattering off this periodicity, leading to gaps in the spectrum that inhibit their propagation along the pitch direction. Using high-resolution inelastic neutron scattering, the resulting band structure of helimagnons was resolved by preparing a single crystal of MnSi in a single magnetic-helix domain. At least five helimagnon bands could be identified that cover the crossover from flat bands at low energies with helimagnons basically localized along the pitch direction to dispersing bands at higher energies. In the low-energy limit, we find the helimagnon spectrum to be determined by a universal, parameter-free theory. Taking into account corrections to this low-energy theory, quantitative agreement is obtained in the entire energy range studied with the help of a single fitting parameter.

  8. Direct observation of the mass renormalization in SrVO3 by angle resolved photoemission spectroscopy

    SciTech Connect

    Yoshida, t.

    2010-05-03

    We have performed an angle-resolved photoemission study of the three-dimensional perovskite-type SrVO{sub 3}. Observed spectral weight distribution of the coherent part in the momentum space shows cylindrical Fermi surfaces consisting of the V 3d t{sub 2g} orbitals as predicted by local-density approximation (LDA) band-structure calculation. The observed energy dispersion shows a moderately enhanced effective mass compared to the LDA results, corresponding to the effective mass enhancement seen in the thermodynamic properties. Contributions from the bulk and surface electronic structures to the observed spectra are discussed based on model calculations.

  9. Effects of density functionals and dispersion interactions on geometries, bond energies and harmonic frequencies of Etbnd UX3 (E = N, P, CH; X = H, F, Cl)

    NASA Astrophysics Data System (ADS)

    Pandey, Krishna Kumar; Patidar, Pankaj; Patidar, Sunil Kumar; Vishwakarma, Ravi

    2014-12-01

    Quantum-chemical calculations have been performed to evaluate the geometries, bonding nature and harmonic frequencies of the compounds [Etbnd UX3] at DFT, DFT-D3, DFT-D3(BJ) and DFT-dDSc levels using different density functionals BP86, BLYP, PBE, revPBE, PW91, TPSS and M06-L. The stretching frequency of Utbnd N bond in [Ntbnd UF3] calculated with DFT/BLYP closely resembles with the experimental value. The performance of different density functionals for accurate Utbnd N vibrational frequencies follows the order BLYP > revPBE > BP86 > PW91 > TPSS > PBE > M06-L. The BLYP functional gives accurate value of the Utbnd E bond distances. The uranium atom in the studied compounds [Etbnd UX3] is positively charged. Upon going from [Etbnd UF3] to [Etbnd UCl3], the partial Hirshfeld charge on uranium atom decreases because of the lower electronegativity of chlorine compared to flourine. The Gopinathan-Jug bond order for Utbnd E bonds ranges from 2.90 to 3.29. The Utbnd E bond dissociation energies vary with different density functionals as M06-L < TPSS < BLYP < revPBE < BP86 < PBE ≈ PW91. The orbital interactions ΔEorb, in all studied compounds [Etbnd UX3] are larger than the electrostatic interaction ΔEelstat, which means the Utbnd N bonds in these compound have greater degree of covalent character (in the range 63.8-77.2%). The Usbnd E σ-bonding interaction is the dominant bonding interaction in the nitride and methylidyne complexes while it is weaker in [Ptbnd UX3]. The dispersion energy contributions to the total bond dissociation energies are rather small. Compared to the Grimme's D3(BJ) corrections, the Corminboeuf's dispersion corrections are larger with metaGGA functionals (TPSS, M06-L) while smaller with GGA functionals.

  10. Pulsing frequency induced change in optical constants and dispersion energy parameters of WO3 films grown by pulsed direct current magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Punitha, K.; Sivakumar, R.; Sanjeeviraja, C.

    2014-03-01

    In this work, we present the pulsing frequency induced change in the structural, optical, vibrational, and luminescence properties of tungsten oxide (WO3) thin films deposited on microscopic glass and fluorine doped tin oxide (SnO2:F) coated glass substrates by pulsed dc magnetron sputtering technique. The WO3 films deposited on SnO2:F substrate belongs to monoclinic phase. The pulsing frequency has a significant influence on the preferred orientation and crystallinity of WO3 film. The maximum optical transmittance of 85% was observed for the film and the slight shift in transmission threshold towards higher wavelength region with increasing pulsing frequency revealed the systematic reduction in optical energy band gap (3.78 to 3.13 eV) of the films. The refractive index (n) of films are found to decrease (1.832 to 1.333 at 550 nm) with increasing pulsing frequency and the average value of extinction coefficient (k) is in the order of 10-3. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (Ed) parameters, dielectric constants, plasma frequency, oscillator strength, and oscillator energy (Eo) of WO3 films were calculated and reported for the first time due to variation in pulsing frequency during deposition by pulsed dc magnetron sputtering. The Eo is change between 6.30 and 3.88 eV, while the Ed varies from 25.81 to 7.88 eV, with pulsing frequency. The Raman peak observed at 1095 cm-1 attributes the presence of W-O symmetric stretching vibration. The slight shift in photoluminescence band is attributed to the difference in excitons transition. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.

  11. Fabrication of electric papers of graphene nanosheet shelled cellulose fibres by dispersion and infiltration as flexible electrodes for energy storage

    NASA Astrophysics Data System (ADS)

    Kang, Yan-Ru; Li, Ya-Li; Hou, Feng; Wen, Yang-Yang; Su, Dong

    2012-05-01

    An electrically conductive and electrochemically active composite paper of graphene nanosheet (GNS) coated cellulose fibres was fabricated via a simple paper-making process of dispersing chemically synthesized GNS into a cellulose pulp, followed by infiltration. The GNS nanosheet was deposited onto the cellulose fibers, forming a coating, during infiltration. It forms a continuous network through a bridge of interconnected cellulose fibres at small GNS loadings (3.2 wt%). The GNS/cellulose paper is as flexible and mechanically tough as the pure cellulose paper. The electrical measurements show the composite paper has a sheet resistance of 1063 Ω □-1 and a conductivity of 11.6 S m-1. The application of the composite paper as a flexible double layer supercapacitor in an organic electrolyte (LiPF6) displays a high capacity of 252 F g-1 at a current density of 1 A g-1 with respect to GNS. Moreover, the paper can be used as the anode in a lithium battery, showing distinct charge and discharge performances. The simple process for synthesising the GNS functionalized cellulose papers is attractive for the development of high performance papers for electrical, electrochemical and multifunctional applications.An electrically conductive and electrochemically active composite paper of graphene nanosheet (GNS) coated cellulose fibres was fabricated via a simple paper-making process of dispersing chemically synthesized GNS into a cellulose pulp, followed by infiltration. The GNS nanosheet was deposited onto the cellulose fibers, forming a coating, during infiltration. It forms a continuous network through a bridge of interconnected cellulose fibres at small GNS loadings (3.2 wt%). The GNS/cellulose paper is as flexible and mechanically tough as the pure cellulose paper. The electrical measurements show the composite paper has a sheet resistance of 1063 Ω □-1 and a conductivity of 11.6 S m-1. The application of the composite paper as a flexible double layer supercapacitor

  12. Colloidal Dispersions

    NASA Astrophysics Data System (ADS)

    Russel, W. B.; Saville, D. A.; Schowalter, W. R.

    1992-03-01

    The book covers the physical side of colloid science from the individual forces acting between submicron particles suspended in a liquid through the resulting equilibrium and dynamic properties. The relevant forces include Brownian motion, electrostatic repulsion, dispersion attraction, both attraction and repulsion due to soluble polymer, and viscous forces due to relative motion between the particles and the liquid. The balance among Brownian motion and the interparticle forces decides the questions of stability and phase behavior. Imposition of external fields produces complex effects, i.e. electrokinetic phenomena (electric field), sedimentation (gravitational field), diffusion (concentration/chemical potential gradient), and non-Newtonian rheology (shear field). The treatment aims to impart a sound, quantitative understanding based on fundamental theory and experiments with well-characterized model systems. This broad grasp of the fundamentals lends insight and helps to develop the intuitive sense needed to isolate essential features of technological problems and design critical experiments. Some exposure to fluid mechanics, statistical mechanics, and electricity and magnetism is assumed, but each subject is reintroduced in a self-contained manner.

  13. Fabrication of electric papers of graphene nanosheet shelled cellulose fibres by dispersion and infiltration as flexible electrodes for energy storage.

    PubMed

    Kang, Yan-Ru; Li, Ya-Li; Hou, Feng; Wen, Yang-Yang; Su, Dong

    2012-05-21

    An electrically conductive and electrochemically active composite paper of graphene nanosheet (GNS) coated cellulose fibres was fabricated via a simple paper-making process of dispersing chemically synthesized GNS into a cellulose pulp, followed by infiltration. The GNS nanosheet was deposited onto the cellulose fibers, forming a coating, during infiltration. It forms a continuous network through a bridge of interconnected cellulose fibres at small GNS loadings (3.2 wt%). The GNS/cellulose paper is as flexible and mechanically tough as the pure cellulose paper. The electrical measurements show the composite paper has a sheet resistance of 1063 Ω□(-1) and a conductivity of 11.6 S m(-1). The application of the composite paper as a flexible double layer supercapacitor in an organic electrolyte (LiPF(6)) displays a high capacity of 252 F g(-1) at a current density of 1 A g(-1) with respect to GNS. Moreover, the paper can be used as the anode in a lithium battery, showing distinct charge and discharge performances. The simple process for synthesising the GNS functionalized cellulose papers is attractive for the development of high performance papers for electrical, electrochemical and multifunctional applications. PMID:22535335

  14. Rigorous quantitative elemental microanalysis by scanning electron microscopy/energy dispersive x-ray spectrometry (SEM/EDS) with spectrum processing by NIST DTSA-II

    NASA Astrophysics Data System (ADS)

    Newbury, Dale E.; Ritchie, Nicholas W. M.

    2014-09-01

    Quantitative electron-excited x-ray microanalysis by scanning electron microscopy/silicon drift detector energy dispersive x-ray spectrometry (SEM/SDD-EDS) is capable of achieving high accuracy and high precision equivalent to that of the high spectral resolution wavelength dispersive x-ray spectrometer even when severe peak interference occurs. The throughput of the SDD-EDS enables high count spectra to be measured that are stable in calibration and resolution (peak shape) across the full deadtime range. With this high spectral stability, multiple linear least squares peak fitting is successful for separating overlapping peaks and spectral background. Careful specimen preparation is necessary to remove topography on unknowns and standards. The standards-based matrix correction procedure embedded in the NIST DTSA-II software engine returns quantitative results supported by a complete error budget, including estimates of the uncertainties from measurement statistics and from the physical basis of the matrix corrections. NIST DTSA-II is available free for Java-platforms at: http://www.cstl.nist.gov/div837/837.02/epq/dtsa2/index.html).

  15. Fast elemental screening of soil and sediment profiles using small-spot energy-dispersive X-ray fluorescence: application to mining sediments geochemistry.

    PubMed

    Gonzalez-Fernandez, Oscar; Queralt, Ignacio

    2010-09-01

    Elemental analysis of different sediment cores originating from the Cartagena-La Union mining district in Spain was carried out by means of a programmable small-spot energy-dispersive X-ray fluorescence (EDXRF) spectrometer to study the distribution of heavy metals along soil profiles. Cores were obtained from upstream sediments of a mining creek, from the lowland sedimentation plain, and from a mining landfill dump (tailings pile). A programmable two-dimensional (2D) stage and a focal spot resolution of 600 μm allow us to obtain complete core mapping. Geochemical results were verified using a more powerful wavelength-dispersion X-ray fluorescence (WDXRF) technique. The data obtained was processed in order to study the statistical correlations within the elemental compositions. The results obtained allow us to observe the differential in-depth distribution of heavy metals among the sampled zones. Dump site cores exhibit a homogeneous distribution of heavy metals, whereas the alluvial plain core shows accumulation of heavy metals in the upper part. This approach can be useful for the fast screening of heavy metals in depositional environments around mining sites. PMID:20828442

  16. X-ray energy dispersive spectroscopy of uranium ore using a TES microcalorimeter mounted on a field-emission scanning electron microscope

    NASA Astrophysics Data System (ADS)

    Maehata, Keisuke; Idemitsu, Kazuya; Tanaka, Keiichi

    2011-08-01

    Energy dispersive spectroscopic measurements of uranium ore were conducted using a superconducting phase transition-edge-thermosensor (TES) microcalorimeter mounted on a field-emission scanning electron microscope (SEM) to demonstrate its potential for high-precision microanalysis. The effective solid angle for X-ray detection is found to be larger than 2 msr by precise adjustments in the X-ray polycapillary alignment. The observed detection signal pulses with decay time constant of 50 μs enable maximum count rates larger than 300 counts per second. The energy resolution was determined to be 14.6 eV FWHM at Al Kα X-ray energies of 1487 eV. Distinct peaks appear in the resulting X-ra y energy spectrum associated with U-Mα, U-Mβ and U-Mγ X-rays emitted by the uranium ore specimens. This spectrum includes weaker peaks corresponding to C-Kα, Fe-Lα, Cu-L and Sr L α1 X rays.

  17. Ionic Liquids as a Reference Material Candidate for the Quick Performance Check of Energy Dispersive X-ray Spectrometers for the Low Energy Range below 1 keV

    PubMed Central

    2016-01-01

    Ionic liquids (ILs) are proposed as simple and efficient test materials to evaluate the performance of energy dispersive X-ray spectrometers (EDS) in the low energy range below 1 keV. By only one measurement, C Kα, N Kα, O Kα, and F Kα X-ray lines can be excited. Additionally, the S Kα line at 2.3 keV and, particularly, the S L series at 149 eV complete the picture with X-ray lines offered by the selected ILs. The well-known (certifiable) elemental composition of the ILs selected in the present study can be used to check the accuracy of results produced with the available EDS quantification routines in the low energy range, simultaneously, for several low atomic number elements. A comparison with other reference materials in use for testing the performance of EDS in the low energy range is included. PMID:27336962

  18. Thickness measurement of semiconductor thin films by energy dispersive X-ray fluorescence benchtop instrumentation: Application to GaN epilayers grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Queralt, I.; Ibañez, J.; Marguí, E.; Pujol, J.

    2010-07-01

    The importance of thin films in modern high technology products, such as semiconductors, requires fast and non-destructive analysis. A methodology to determine the thickness of single layers with benchtop energy dispersive X-ray fluorescence (EDXRF) instrumentation is described and tested following analytical validation criteria. The experimental work was carried out on gallium nitride thin films epitaxially grown on sapphire substrate. The results of samples with layers in the range from 400 to 1000 nm exhibit a good correlation with the layer thickness determined by optical reflectance. Spectral data obtained using thin layered samples indicate the possibility to precisely evaluate layer thickness from 5 nm, with a low relative standard deviation (RSD < 2%) of the results. In view of the limits of optical reflectance for very thin layer determination, EDXRF analysis offers the potential for the thickness determination of such kind of samples.

  19. Characterization of Japanese color sticks by energy dispersive X-ray fluorescence, X-ray diffraction and Fourier transform infrared analysis

    NASA Astrophysics Data System (ADS)

    Manso, M.; Valadas, S.; Pessanha, S.; Guilherme, A.; Queralt, I.; Candeias, A. E.; Carvalho, M. L.

    2010-04-01

    This work comprises the use of energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) techniques for the study of the composition of twentieth century traditional Japanese color sticks. By using the combination of analytical techniques it was possible to obtain information on inorganic and organic pigments, binders and fillers present in the sticks. The colorant materials identified in the sticks were zinc and titanium white, chrome yellow, yellow and red ochre, vermillion, alizarin, indigo, Prussian and synthetic ultramarine blue. The results also showed that calcite and barite were used as inorganic mineral fillers while Arabic gum was the medium used. EDXRF offered great potential for such investigations since it allowed the identification of the elements present in the sample preserving its integrity. However, this information alone was not enough to clearly identify some of the materials in study and therefore it was necessary to use XRD and FTIR techniques.

  20. Effects of Pamidronate on Dental Enamel Formation Assessed by Light Microscopy, Energy-Dispersive X-Ray Analysis, Scanning Electron Microscopy, and Microhardness Testing.

    PubMed

    Soares, Ana P; do Espírito Santo, Renan F; Line, Sérgio R P; Pinto, Maria das G F; Santos, Pablo de M; Toralles, Maria Betania P; do Espírito Santo, Alexandre R

    2016-06-01

    The aim of the present work was to investigate birefringence and morphology of the secretory-stage enamel organic extracellular matrix (EOECM), and structural and mechanical properties of mature enamel of upper incisors from adult rats that had been treated with pamidronate disodium (0.5 mg/kg/week for 56 days), using transmitted polarizing and bright-field light microscopies (TPLM and BFLM), energy-dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM) and microhardness testing. BFLM showed no morphological changes of the EOECM in pamidronate and control groups, but TPLM revealed a statistically significant reduction in optical retardation values of birefringence brightness of pamidronate-treated rats when compared with control animals (p0.05). The present study indicates that pamidronate can affect birefringence of the secretory-stage EOECM, which does not seem to be associated with significant changes in morphological and/or mechanical properties of mature enamel. PMID:27212049