WorldWideScience

Sample records for absorption fine structures

  1. Generalized Ramsauer-Townsend effect in extended x-ray-absorption fine structure

    International Nuclear Information System (INIS)

    Theoretical backscattering amplitude and phase functions, B(k) and phi(k), used in extended x-ray-absorption fine structure (EXAFS) studies show strong features in their k dependence which can be identified as a ''generalized Ramsauer-Townsend effect.'' This effect is studied in detail for elements with atomic number 78≤Z≤90

  2. Ab initio self-consistent x-ray absorption fine structure analysis for metalloproteins.

    Science.gov (United States)

    Dimakis, Nicholas; Bunker, Grant

    2006-12-01

    X-ray absorption fine structure is a powerful tool for probing the structures of metals in proteins in both crystalline and noncrystalline environments. Until recently, a fundamental problem in biological XAFS has been that ad hoc assumptions must be made concerning the vibrational properties of the amino acid residues that are coordinated to the metal to fit the data. Here, an automatic procedure for accurate structural determination of active sites of metalloproteins is presented. It is based on direct multiple-scattering simulation of experimental X-ray absorption fine structure spectra combining electron multiple scattering calculations with density functional theory calculations of vibrational modes of amino acid residues and the genetic algorithm differential evolution to determine a global minimum in the space of fitting parameters. Structure determination of the metalloprotein active site is obtained through a self-consistent iterative procedure with only minimal initial information.

  3. Photoconductivity measurement of polymers by x-ray absorption fine structure

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Photoconductivity spectra measurement of polymers at x-ray energies around the Zn and Co K edges,shows obvious x-ray absorption fine structure oscillations.The photoconductivity spectra obtained for gapped and sandwiched electrode geometric samples,indicate that the shape of photoconductivity spectrum depends on the electrode configuration of the samples.The thickness of the conduction layer can be estimated from the photoconductivity spectrum.

  4. Atomic calculations and search for variation of the fine-structure constant in quasar absorption spectra

    Science.gov (United States)

    Dzuba, V. A.; Flambaum, V. V.

    A brief review of the search for variation of the fine structure constant in quasar absorption spectra is presented. Special consideration is given to the role of atomic calculations in the analysis of the observed data. A range of methods which allow to perform calculations for atoms or ions with different electron structure and which cover practically all periodic table of elements is discussed. Critical compilation of the results of the calculations as well as a review of the most recent results of the analysis are presented.

  5. Atomic calculations and search for variation of the fine structure constant in quasar absorption spectra

    CERN Document Server

    Dzuba, V A

    2008-01-01

    A brief review of the search for variation of the fine structure constant in quasar absorption spectra is presented. Special consideration is given to the role of atomic calculations in the analysis of the observed data. A range of methods which allow to perform calculations for atoms or ions with different electron structure and which cover practically all periodic table of elements is discussed. Critical compilation of the results of the calculations as well as a review of the most recent results of the analysis are presented.

  6. Fine Structure of the R Absorption Lines of Cr3+ in Antiferromagnetic Dysprosium Aluminum Garnet

    Science.gov (United States)

    Aoyagi, Kiyoshi; Kajiura, Masako; Sugano, Satoru

    1981-11-01

    The absorption spectrum of a Cr3+ ion in an antiferromagnetic disprosium aluminum garnet with the Néel temperature TN of 2.5 K, is measured in the red region between 1.7 K and 4.2 K. It is shown that the fine structure of the R1 and R2 lines at 1.7 K can be explained by using an effective Hamiltonian for the t2g3 2E excited state of Cr3+ in the surrounding of the ordered Dy3+ spins. The gross feature of the observed temperature dependence of the fine structure is shown to be reproduced by assuming appropriate exchange interactions of Cr3+ with Dy3+.

  7. A new analysis of fine-structure constant measurements and modelling errors from quasar absorption lines

    OpenAIRE

    Wilczynska, Michael R.; Webb, John K.; King, Julian A.; Murphy, Michael T.; Bainbridge, Matthew B.; Flambaum, Victor V.

    2015-01-01

    We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of $0.4 \\leq z_{abs} \\leq 2.3$ observed on the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of $\\Delta\\alpha/\\alpha=\\left(0.22\\pm0.23\\right)\\times10^{-5...

  8. Extended X-ray absorption fine structure investigation of nitrogen stabilized expanded austenite

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny;

    2010-01-01

    the N atoms remaining in the solid state after H2-reduction are trapped by Cr atoms. Quantitative interpretation in terms of the local distortions around Cr atoms and their N coordination number reveals that no Cr–N clusters or CrN platelets are present.......As-delivered austenitic stainless steel and nitrogen stabilized expanded austenite, both fully nitrided and denitrided (in H2), were investigated with Cr, Fe and Ni extended X-ray absorption fine structure. The data shows pronounced short-range ordering of Cr and N. For the denitrided specimen...

  9. A new analysis of fine-structure constant measurements and modelling errors from quasar absorption lines

    Science.gov (United States)

    Wilczynska, Michael R.; Webb, John K.; King, Julian A.; Murphy, Michael T.; Bainbridge, Matthew B.; Flambaum, Victor V.

    2015-12-01

    We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of 0.4 ≤ zabs ≤ 2.3 observed on the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of Δα/α = (0.22 ± 0.23) × 10-5, consistent with the dipole variation reported in Webb et al. and King et al. This paper also examines modelling methodologies and systematic effects. In particular, we focus on the consequences of fitting quasar absorption systems with too few absorbing components and of selectively fitting only the stronger components in an absorption complex. We show that using insufficient continuum regions around an absorption complex causes a significant increase in the scatter of a sample of Δα/α measurements, thus unnecessarily reducing the overall precision. We further show that fitting absorption systems with too few velocity components also results in a significant increase in the scatter of Δα/α measurements, and in addition causes Δα/α error estimates to be systematically underestimated. These results thus identify some of the potential pitfalls in analysis techniques and provide a guide for future analyses.

  10. Single shot near edge x-ray absorption fine structure spectroscopy in the laboratory

    Science.gov (United States)

    Mantouvalou, I.; Witte, K.; Martyanov, W.; Jonas, A.; Grötzsch, D.; Streeck, C.; Löchel, H.; Rudolph, I.; Erko, A.; Stiel, H.; Kanngießer, B.

    2016-05-01

    With the help of adapted off-axis reflection zone plates, near edge X-ray absorption fine structure spectra at the C and N K-absorption edge have been recorded using a single 1.2 ns long soft X-ray pulse. The transmission experiments were performed with a laser-produced plasma source in the laboratory rendering time resolved measurements feasible independent on large scale facilities. A resolving power of E/ΔE ˜ 950 at the respective edges could be demonstrated. A comparison of single shot spectra with those collected with longer measuring time proves that all features of the used reference samples (silicon nitrate and polyimide) can be resolved in 1.2 ns. Hence, investigations of radiation sensitive biological specimen become possible due to the high efficiency of the optical elements enabling low dose experiments.

  11. A new analysis of fine-structure constant measurements and modelling errors from quasar absorption lines

    CERN Document Server

    Wilczynska, Michael R; King, Julian A; Murphy, Michael T; Bainbridge, Matthew B; Flambaum, Victor V

    2015-01-01

    We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of $0.4 \\leq z_{abs} \\leq 2.3$ observed on the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of $\\Delta\\alpha/\\alpha=\\left(0.22\\pm0.23\\right)\\times10^{-5}$, consistent with the dipole variation reported in Webb et al. and King et al. This paper also examines modelling methodologies and systematic effects. In particular we focus on the consequences of fitting quasar absorption systems with too few absorbing components and of selectively fitting only the stronger components in an absorption complex. We show that using insufficient continuum regions around an absorption complex causes a significant increase in the scatter of a sample of $\\Delta\\alpha/\\alpha$ measurements, th...

  12. Possible evidence for a variable fine structure constant from QSO absorption lines motivations, analysis and results

    CERN Document Server

    Murphy, M T; Flambaum, V V; Dzuba, V A; Churchill, C W; Prochaska, J X; Barrow, John D; Wolfe, A M

    2001-01-01

    An experimental search for variation in the fundamental coupling constants is strongly motivated by modern high-energy physics theories. Comparison of quasar absorption line spectra with laboratory spectra provides a sensitive probe for variability of the fine structure constant, alpha, over cosmological time-scales. We have previously developed and applied a new method providing an order of magnitude gain in precision over previous optical astrophysical constraints. Here we extend that work by including new quasar spectra of damped Lyman-alpha absorption systems. We also re-analyse our previous lower redshift data and confirm our initial results. The constraints on alpha come from simultaneous fitting of absorption lines of subsets of the following species: Mg I, Mg II, Al II, Al III, Si II, Cr II, Fe II, Ni II and Zn II. We present a detailed description of our methods and results based on an analysis of 49 quasar absorption systems (towards 28 QSOs) covering the redshift range 0.5 < z < 3.5. There is...

  13. X-ray absorption fine structure of aged, Pu-doped glass and ceramic waste forms

    Science.gov (United States)

    Hess, N. J.; Weber, W. J.; Conradson, S. D.

    1998-04-01

    X-ray absorption spectroscopic (XAS) studies were performed on three compositionally identical, Pu-doped, borosilicate glasses prepared 15 years ago at different α-activities by varying the 239Pu/ 238Pu isotopic ratio. The resulting α-activities ranged from 1.9×10 7 to 4.2×10 9 Bq/g and have current, accumulated doses between 8.8×10 15 to 1.9×10 18 α-decays/g. Two ceramic, polycrystalline zircon (ZrSiO 4) samples prepared 16 years ago with 10.0 wt% Pu was also investigated. Varying the 239Pu/ 238Pu isotopic ratio in these samples resulted in α-activities of 2.5×10 8 and 5.6×10 10 Bq/g and current, accumulated doses of 1.2×10 17 and 2.8×10 19 α-decays/g. The multicomponent composition of the waste forms permitted XAS investigations at six absorption edges for the borosilicate glass and at three absorption edges for the polycrystalline zircons. For both waste forms, analysis of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectra indicates that the local environment around the cations exhibits different degrees of disorder as a result of the accumulated α-decay dose. In general, cations with short cation-oxygen bonds show little effect from self-radiation whereas cations with long cation-oxygen bonds show a greater degree of disorder with accumulated α-decay dose.

  14. High-sensitivity x-ray absorption fine structure investigation of arsenic shallow implant in silicon

    International Nuclear Information System (INIS)

    High-sensitivity fluorescence-yield x-ray absorption fine structure spectroscopy (XAFS) has been investigated to characterize the local structure around arsenic shallow implant in silicon. Fluorescence-yield XAFS experiments were performed using a high-brilliance synchrotron radiation beam from an in-vacuum-type undulator in a third-generation light source. In addition to investigating the efficiency of high-brilliance undulator x-rays during the fluorescence-yield XAFS measurements, we compared the analytical performance of both the wavelength dispersive spectrometer (WDS) and the energy dispersive spectrometer (EDS) based on the silicon drift detector (SDD). It was confirmed that the WDS reduces the influence of scattering background due to the high spectral resolution. Another advantage of the WDS is high counting rate measurements. It was found that fluorescence-yield XAFS using undulator x-rays combined with the WDS permits superior sensitivity measurements.

  15. Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra

    CERN Document Server

    Murphy, M T; Flambaum, V V

    2003-01-01

    [Abridged] We previously presented evidence for a varying fine-structure constant, alpha, in two independent samples of Keck/HIRES QSO spectra. Here we present a detailed many-multiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2absorption clouds. Assuming that da/a=0 at z_abs=0, the da...

  16. Possible evidence for a variable fine-structure constant from QSO absorption lines: systematic errors

    Science.gov (United States)

    Murphy, M. T.; Webb, J. K.; Flambaum, V. V.; Churchill, C. W.; Prochaska, J. X.

    2001-11-01

    Comparison of quasar (QSO) absorption spectra with laboratory spectra allows us to probe possible variations in the fundamental constants over cosmological time-scales. In a companion paper we present an analysis of Keck/HIRES spectra and report possible evidence suggesting that the fine-structure constant, α, may have been smaller in the past: [formmu2]Δα/α=(-0.72+/-0.18)×10-5 over the redshift range [formmu3]0.5

  17. Possible evidence for a variable fine structure constant from QSO absorption lines systematic errors

    CERN Document Server

    Murphy, M T; Flambaum, V V; Churchill, C W; Prochaska, J X

    2001-01-01

    Comparison of quasar absorption spectra with laboratory spectra allow us to probe possible variations in the fundamental constants over cosmological time-scales. In a companion paper we present an analysis of Keck/HIRES spectra and report possible evidence suggesting that the fine structure constant, alpha, may have been smaller in the past: da/a = (-0.72 +/- 0.18) * 10^{-5} over the redshift range 0.5 < z < 3.5. In this paper we describe a comprehensive investigation into possible systematic effects. Most of these do not significantly influence our results. When we correct for those which do produce a significant systematic effect in the data, the deviation of da/a from zero becomes more significant. We are lead increasingly to the interpretation that alpha was slightly smaller in the past.

  18. Extended x-ray absorption fine structure investigation of annealed carbon expanded austenite

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas L.; Somers, Marcel A. J.;

    2012-01-01

    Carbon expanded austenite synthesized through carburizing of austenitic stainless steel powder at 380°C was annealed at 470°C and investigated with extended X-ray absorption fine structure (EXAFS) and synchrotron powder diffraction (SPD). SPD showed that the samples consisted of carbon expanded......-carburized in a temperature regime around 470°C. The surface zone is converted into carbon expanded austenite; the high interstitial content of carbon dissolved in the surface results in highly favorable materials properties. In the present article the local atomic environment of (annealed) carbon expanded austenite...... was investigated with EXAFS. Copyright © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim....

  19. Near-Edge X-ray Absorption Fine Structure Spectroscopy of Diamondoid Thiol Monolayers on Gold

    Energy Technology Data Exchange (ETDEWEB)

    Willey, T M; Fabbri, J; Lee, J I; Schreiner, P; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J; Carlson, B; Vance, A L; Yang, W; Terminello, L J; van Buuren, T; Melosh, N

    2007-11-27

    Diamondoids, hydrocarbon molecules with cubic-diamond-cage structures, have unique properties with potential value for nanotechnology. The availability and ability to selectively functionalize this special class of nanodiamond materials opens new possibilities for surface-modification, for high-efficiency field emitters in molecular electronics, as seed crystals for diamond growth, or as robust mechanical coatings. The properties of self-assembled monolayers (SAMs) of diamondoids are thus of fundamental interest for a variety of emerging applications. This paper presents the effects of thiol substitution position and polymantane order on diamondoid SAMs on gold using near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS). A framework to determine both molecular tilt and twist through NEXAFS is presented and reveals highly ordered diamondoid SAMs, with the molecular orientation controlled by the thiol location. C 1s and S 2p binding energies are lower in adamantane thiol than alkane thiols on gold by 0.67 {+-} 0.05 eV and 0.16 {+-} 0.04 eV respectively. These binding energies vary with diamondoid monolayer structure and thiol substitution position, consistent with different amounts of steric strain and electronic interaction with the substrate. This work demonstrates control over the assembly, in particular the orientational and electronic structure, providing a flexible design of surface properties with this exciting new class of diamond clusters.

  20. Constraining the Variation of the Fine-structure Constant with Observations of Narrow Quasar Absorption Lines

    Science.gov (United States)

    Songaila, A.; Cowie, L. L.

    2014-10-01

    The unequivocal demonstration of temporal or spatial variability in a fundamental constant of nature would be of enormous significance. Recent attempts to measure the variability of the fine-structure constant α over cosmological time, using high-resolution spectra of high-redshift quasars observed with 10 m class telescopes, have produced conflicting results. We use the many multiplet (MM) method with Mg II and Fe II lines on very high signal-to-noise, high-resolution (R = 72, 000) Keck HIRES spectra of eight narrow quasar absorption systems. We consider both systematic uncertainties in spectrograph wavelength calibration and also velocity offsets introduced by complex velocity structure in even apparently simple and weak narrow lines and analyze their effect on claimed variations in α. We find no significant change in α, Δα/α = (0.43 ± 0.34) × 10-5, in the redshift range z = 0.7-1.5, where this includes both statistical and systematic errors. We also show that the scatter in measurements of Δα/α arising from absorption line structure can be considerably larger than assigned statistical errors even for apparently simple and narrow absorption systems. We find a null result of Δα/α = (- 0.59 ± 0.55) × 10-5 in a system at z = 1.7382 using lines of Cr II, Zn II, and Mn II, whereas using Cr II and Zn II lines in a system at z = 1.6614 we find a systematic velocity trend that, if interpreted as a shift in α, would correspond to Δα/α = (1.88 ± 0.47) × 10-5, where both results include both statistical and systematic errors. This latter result is almost certainly caused by varying ionic abundances in subcomponents of the line: using Mn II, Ni II, and Cr II in the analysis changes the result to Δα/α = (- 0.47 ± 0.53) × 10-5. Combining the Mg II and Fe II results with estimates based on Mn II, Ni II, and Cr II gives Δα/α = (- 0.01 ± 0.26) × 10-5. We conclude that spectroscopic measurements of quasar absorption lines are not yet capable of

  1. Constraining the variation of the fine-structure constant with observations of narrow quasar absorption lines

    Energy Technology Data Exchange (ETDEWEB)

    Songaila, A.; Cowie, L. L., E-mail: acowie@ifa.hawaii.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2014-10-01

    The unequivocal demonstration of temporal or spatial variability in a fundamental constant of nature would be of enormous significance. Recent attempts to measure the variability of the fine-structure constant α over cosmological time, using high-resolution spectra of high-redshift quasars observed with 10 m class telescopes, have produced conflicting results. We use the many multiplet (MM) method with Mg II and Fe II lines on very high signal-to-noise, high-resolution (R = 72, 000) Keck HIRES spectra of eight narrow quasar absorption systems. We consider both systematic uncertainties in spectrograph wavelength calibration and also velocity offsets introduced by complex velocity structure in even apparently simple and weak narrow lines and analyze their effect on claimed variations in α. We find no significant change in α, Δα/α = (0.43 ± 0.34) × 10{sup –5}, in the redshift range z = 0.7-1.5, where this includes both statistical and systematic errors. We also show that the scatter in measurements of Δα/α arising from absorption line structure can be considerably larger than assigned statistical errors even for apparently simple and narrow absorption systems. We find a null result of Δα/α = (– 0.59 ± 0.55) × 10{sup –5} in a system at z = 1.7382 using lines of Cr II, Zn II, and Mn II, whereas using Cr II and Zn II lines in a system at z = 1.6614 we find a systematic velocity trend that, if interpreted as a shift in α, would correspond to Δα/α = (1.88 ± 0.47) × 10{sup –5}, where both results include both statistical and systematic errors. This latter result is almost certainly caused by varying ionic abundances in subcomponents of the line: using Mn II, Ni II, and Cr II in the analysis changes the result to Δα/α = (– 0.47 ± 0.53) × 10{sup –5}. Combining the Mg II and Fe II results with estimates based on Mn II, Ni II, and Cr II gives Δα/α = (– 0.01 ± 0.26) × 10{sup –5}. We conclude that spectroscopic measurements of

  2. Constraining the variation of the fine-structure constant with observations of narrow quasar absorption lines

    International Nuclear Information System (INIS)

    The unequivocal demonstration of temporal or spatial variability in a fundamental constant of nature would be of enormous significance. Recent attempts to measure the variability of the fine-structure constant α over cosmological time, using high-resolution spectra of high-redshift quasars observed with 10 m class telescopes, have produced conflicting results. We use the many multiplet (MM) method with Mg II and Fe II lines on very high signal-to-noise, high-resolution (R = 72, 000) Keck HIRES spectra of eight narrow quasar absorption systems. We consider both systematic uncertainties in spectrograph wavelength calibration and also velocity offsets introduced by complex velocity structure in even apparently simple and weak narrow lines and analyze their effect on claimed variations in α. We find no significant change in α, Δα/α = (0.43 ± 0.34) × 10–5, in the redshift range z = 0.7-1.5, where this includes both statistical and systematic errors. We also show that the scatter in measurements of Δα/α arising from absorption line structure can be considerably larger than assigned statistical errors even for apparently simple and narrow absorption systems. We find a null result of Δα/α = (– 0.59 ± 0.55) × 10–5 in a system at z = 1.7382 using lines of Cr II, Zn II, and Mn II, whereas using Cr II and Zn II lines in a system at z = 1.6614 we find a systematic velocity trend that, if interpreted as a shift in α, would correspond to Δα/α = (1.88 ± 0.47) × 10–5, where both results include both statistical and systematic errors. This latter result is almost certainly caused by varying ionic abundances in subcomponents of the line: using Mn II, Ni II, and Cr II in the analysis changes the result to Δα/α = (– 0.47 ± 0.53) × 10–5. Combining the Mg II and Fe II results with estimates based on Mn II, Ni II, and Cr II gives Δα/α = (– 0.01 ± 0.26) × 10–5. We conclude that spectroscopic measurements of quasar absorption lines are not yet

  3. Development of a two-dimensional imaging system of X-ray absorption fine structure.

    Science.gov (United States)

    Katayama, Misaki; Sumiwaka, Koichi; Hayashi, Kazuhiro; Ozutsumi, Kazuhiko; Ohta, Toshiaki; Inada, Yasuhiro

    2012-09-01

    A two-dimensional imaging system of X-ray absorption fine structure (XAFS) has been developed at beamline BL-4 of the Synchrotron Radiation Center of Ritsumeikan University. The system mainly consists of an ionization chamber for I(0) measurement, a sample stage, and a two-dimensional complementary metal oxide semiconductor (CMOS) image sensor for measuring the transmitted X-ray intensity. The X-ray energy shift in the vertical direction, which originates from the vertical divergence of the X-ray beam on the monochromator surface, is corrected by considering the geometrical configuration of the monochromator. This energy correction improves the energy resolution of the XAFS spectrum because each pixel in the CMOS detector has a very small vertical acceptance of ∼0.5 µrad. A data analysis system has also been developed to automatically determine the energy of the absorption edge. This allows the chemical species to be mapped based on the XANES feature over a wide area of 4.8 mm (H) × 3.6 mm (V) with a resolution of 10 µm × 10 µm. The system has been applied to the chemical state mapping of the Mn species in a LiMn(2)O(4) cathode. The heterogeneous distribution of the Mn oxidation state is demonstrated and is considered to relate to the slow delocalization of Li(+)-defect sites in the spinel crystal structure. The two-dimensional-imaging XAFS system is expected to be a powerful tool for analyzing the spatial distributions of chemical species in many heterogeneous materials such as battery electrodes. PMID:22898951

  4. Does the fine structure constant vary? A third quasar absorption sample consistent with varying alpha

    CERN Document Server

    Webb, J K; Flambaum, V V; Curran, S J

    2003-01-01

    We report preliminary results from a third sample of quasar absorption line spectra from the Keck telescope which has been studied to search for any possible variation of the fine structure constant, alpha. This third sample, which is larger than the sum of the two previously published samples, shows the same effect, and also gives, as do the previous two samples, a significant result. The combined sample yields a highly significant effect, da/a = (alpha_z - alpha_0)/alpha_0 = -0.57 +/- 0.10 x 10^{-5}, averaged over the redshift range 0.2 < z < 3.7. We include a brief discussion of small-scale kinematic structure in quasar absorbing clouds. However, kinematics are unlikely to impact significantly on the averaged non-zero da/a above, and we have so far been unable to identify any systematic effect which can explain it. New measurements of quasar spectra obtained using independent instrumentation and telescopes are required to properly check the Keck results.

  5. Molecular characterization of brominated persistent pollutants using extended X-ray absorption fine structure (EXAFS) spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bergknut, Magnus; Skyllberg, Ulf [Swedish University of Agricultural Sciences (SLU), Department of Forest Ecology and Management, Umeaa (Sweden); Persson, Per [Umeaa University, Department of Chemistry, Umeaa (Sweden)

    2008-02-15

    X-ray absorption fine structure (EXAFS) spectroscopy spectra were collected for three brominated persistent pollutants: 6-bromo-2,4,5-trichlorophenol (BrTriClP), pentabromophenol (PentaBrP) and 3,3',5,5'-tetrabromobisphenol A (TBBA). The substances were selected to be symmetrical (BrTriClP and TBBA) or asymmetrical (PentaBrP) with respect to the atomic Br positions and to differ in the number of bromine and other halide atoms, as well as their relative positions. The asymmetrical PentaBrP was modelled with special detail as not all bromine atoms have identical coordination environments. The studied substances displayed unique EXAFS spectra, which could be used to determine the molecular structure in fair detail. We conclude that EXAFS spectroscopy is a suitable technique for molecular characterization of the comparatively complex molecules within the class of compounds of brominated organic persistent pollutants. A detailed understanding of the EXAFS spectra of the pure compounds opens up possibilities to study the interactions with soil and sediment matrices by means of EXAFS spectroscopy. (orig.)

  6. Constraining the Variation of the Fine Structure Constant with Observations of Narrow Quasar Absorption Lines

    CERN Document Server

    Songaila, A

    2014-01-01

    The unequivocal demonstration of temporal or spatial variability in a fundamental constant of nature would be of enormous significance. Recent attempts to measure the variability of the fine structure constant, alpha, over cosmological time, using high resolution spectra of high redshift quasars observed with 10m class telescopes, have produced conflicting results. We used the Many Multiplet (MM) method with Mg II and Fe II lines on very high signal-to-noise, high resolution (R = 72,000) Keck HIRES spectra of eight narrow quasar absorption systems and show, using careful wavelength calibrations, that the systematic wavelength errors are too large for previous observations to have had the sensitivity to detect such variation using this technique. We find no significant change in alpha, Delta(alpha)/alpha =(0.00 +/- 0.24) x 10^(-5), in the redshift range z=0.7-1.5. We also show that the scatter in measurements of Delta(alpha)/alpha arising from line selection can be considerably larger than assigned statistical...

  7. Local structure of NiAl compounds investigated by extended X-ray absorption fine-structure spectroscopy.

    Science.gov (United States)

    Tian, J S; Han, G M; Wei, H; Jin, T; Dargusch, M S

    2012-07-01

    The local structures of pure NiAl and Ti-, Co-doped NiAl compounds have been obtained utilizing extended X-ray absorption fine-structure (EXAFS) spectroscopy. The results provide experimental evidence that Ni antisite defects exist in the Ni-rich NiAl compounds. The site preference of Ti and Co has been confirmed. Ti occupies the Al sublattice, while Co occupies the Ni sublattice. The structure parameters obtained by EXAFS were consistent with the X-ray diffraction results. Owing to the precipitation of α-Cr, the local structure of NiAl-Cr has not been obtained, making the site preference of Cr unclear. PMID:22713881

  8. Atomic Transition Frequencies, Isotope Shifts, and Sensitivity to Variation of the Fine Structure Constant for Studies of Quasar Absorption Spectra

    Science.gov (United States)

    Berengut, J. C.; Dzuba, V. A.; Flambaum, V. V.; King, J. A.; Kozlov, M. G.; Murphy, M. T.; Webb, J. K.

    Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental "constants" in the Universe. A change in the fine structure constant, α = {e}2/hslash c , could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that α varies spatially (61). That is, in one direction on the sky α seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger.

  9. A surface extended X-ray absorption fine structure study of tellurium adsorbed onto Si(100)

    Science.gov (United States)

    Burgess, S. R.; Cowie, B. C. C.; Wilks, S. P.; Dunstan, P. R.; Dunscombe, C. J.; Williams, R. H.

    1996-09-01

    The adsorption of tellurium on Si(100) has been studied using surface extended X-ray adsorption fine structure (SEXAFS) and X-ray standing wave spectroscopy (XSW). This particular system is of interest due to its potential applicability in the surfactant aided growth of CdHgTeCdTeSi(100) based infra-red detectors. The Te/Si(100) structure was generated by depositing a thick layer (˜ 100 Å) of CdTe onto a clean Si (2 × 1) double domain surface, and annealing the sample to 350°C. This resulted is a ˜ 1 ML Te terminated surface where the (2 × 1) reconstruction was lost in favour of a (1 × 1) symmetry. X-ray absorption of the Te L 3 edge ( E = 4341 eV), with a photon energy range of 4440-4700 eV, was probed using a total yield detection scheme. The SEXAFS results indicated that the Te atoms sat in 2-fold bridge sites directly above a fourth layer Si atom. The corresponding bond length was measured to be 2.52 ± 0.05 Å. The XSW measurements of the (400) reflection gave a coherent position of 1.63 ± 0.03 Å and a coherent fraction of 0.65. This is consistent with the breaking of the SiSi dimers and thus could be an example of the phenomena of adsorbate-induced dereconstruction of the surface. These results are compared with those of Bennet et al. who examined a similar system using soft X-ray photoemission (SXPS) and the STM study of Yoshikawa et al.

  10. Fine structures in the optical absorption spectra of photochemical silver in silver halides? A call for further research

    OpenAIRE

    Georgiev, Mladen

    2007-01-01

    A survey is presented of the work done so far to check earlier claims that a fine structure may be observed to occur under certain circumstances in the impurity spectral range of the optical absorption spectra of silver halides following photostimulation in the intrinsic range. This structure, associated with the photochemical formation of silver specks, has been questioned over the years. We now weigh carefully the experimental evidence on the silver halides against a background of similar d...

  11. Influence of the geometric structure on the V L3 near edge X-ray absorption fine structure from vanadium phosphorus oxide catalysts

    OpenAIRE

    Hävecker, M.; Knop-Gericke, A.; Mayer, R; Fait, M.; Bluhm, H.; Schlögl, R.

    2002-01-01

    We present the V L3 near edge X-ray absorption fine structure (NEXAFS) of a vanadium phosphorus oxide (VPO) catalyst. The spectrum is related to the V3d-O2p hybridised unoccupied states. The overall peak position at the V L3-absorption edge is determined by the formal oxidation state of the absorbing vanadium atom. Details of the absorption fine structure are influenced by the geometric structure of the compound. Empirically we found a linear relationship between the energy position of severa...

  12. Influence of the geometric structure on the V L3 near edge X-ray absorption fine structure from vanadium phosphorus oxide catalysts

    OpenAIRE

    Hävecker, Michael; Knop-Gericke, Axel; Mayer, Ralf W.; Fait, Martin; Bluhm, Hendrik; Schlögl, Robert

    2002-01-01

    We present the V L3 near edge X-ray absorption fine structure (NEXAFS) of a vanadium phosphorus oxide (VPO) catalyst. The spectrum is related to the V3d-O2p hybridised unoccupied states. The overall peak position at the V L3-absorption edge is determined by the formal oxidation state of the absorbing vanadium atom. Details of the absorption fine structure are influenced by the geometric structure of the compound. Empirically we found a linear relationship between the energy position of severa...

  13. Determining Orientational Structure of Diamondoid Thiols Attached to Silver Using Near Edge X-ray Absorption Fine Structure Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Willey, T M; Lee, J I; Fabbri, J D; Wang, D; Nielsen, M; Randel, J C; Schreiner, P R; Fokin, A A; Tkachenko, B A; Fokina, N A; Dahl, J P; Carlson, R K; Terminello, L J; Melosh, N A; van Buuren, T

    2008-10-07

    Near-edge x-ray absorption fine structure spectroscopy (NEXAFS) is a powerful tool for determination of molecular orientation in self-assembled monolayers and other surface-attached molecules. A general framework for using NEXAFS to simultaneously determine molecular tilt and twist of rigid molecules attached to surfaces is presented. This framework is applied to self-assembled monolayers of higher diamondoid, hydrocarbon molecules with cubic-diamond-cage structures. Diamondoid monolayers chemisorbed on metal substrates are known to exhibit interesting electronic and surface properties. This work compares molecular orientation in monolayers prepared on silver substrates using two different thiol positional isomers of [121]tetramantane, and thiols derived from two different pentamantane structural isomers, [1212]pentamantane and [1(2,3)4]pentamantane. The observed differences in monolayer structure demonstrate the utility and limitations of NEXAFS spectroscopy and the framework. The results also demonstrate the ability to control diamondoid assembly, in particular the molecular orientational structure, providing a flexible platform for the modification of surface properties with this exciting new class of nanodiamond materials.

  14. Displacive phase-transition of cuprite Ag2O revealed by extended x-ray absorption fine structure

    Science.gov (United States)

    Sanson, Andrea

    2016-08-01

    The low-temperature phase-transition of silver oxide (Ag2O) has been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy as a function of temperature. The thermal evolution of the local structure around Ag atoms has been determined. In particular, below the phase-transition temperature at ∼35 K, a progressive splitting of the Ag-Ag next-nearest-neighbor distances is observed. This definitely supports the idea that the phase-transition of Ag2O is due to displacive disorder of the Ag atoms.

  15. Determination of hexavalent chromium in plastic certified reference materials by X-ray absorption fine structure analysis

    Science.gov (United States)

    Ohata, Masaki; Matsubayashi, Nobuyuki

    X-ray absorption fine structure (XAFS) analysis with transmission mode was used to determine the percentages of hexavalent chromium {Cr(VI)} in total Cr in plastic certified reference materials (CRMs). Cr-K edge X-ray absorption near-edge structure (XANES) spectra were observed and the normalized pre-edge peaks of the spectrum where absorption data was summed was acquired for the determination of Cr(VI). Examination of different number of data point and range of photon energy for summed absorption of the pre-edge peak resulted in reproducible absorption data, though the measurements were carried out at different beam time and beam line. The concentrations of Cr(VI) in the plastic CRMs were also estimated from both the certified value of total Cr and the determined percentage of Cr(VI). The analytical procedure and the estimated concentrations can be useful for the determination of Cr(VI) in plastics with respect to RoHS (restriction of the use of hazardous substances in electrical and electronics equipment) directive.

  16. Determination of hexavalent chromium in plastic certified reference materials by X-ray absorption fine structure analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ohata, Masaki, E-mail: m-oohata@aist.go.jp [Inorganic Standard Section, Inorganic Analytical Chemistry Division, National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST) (Japan); Matsubayashi, Nobuyuki [Super-Spectroscopy System Research Group, Research Institute of Instrumentation Frontier (RIIF), National Institute of Advanced Industrial Science and Technology (AIST) (Japan)

    2014-03-01

    X-ray absorption fine structure (XAFS) analysis with transmission mode was used to determine the percentages of hexavalent chromium {Cr(VI)} in total Cr in plastic certified reference materials (CRMs). Cr-K edge X-ray absorption near-edge structure (XANES) spectra were observed and the normalized pre-edge peaks of the spectrum where absorption data was summed was acquired for the determination of Cr(VI). Examination of different number of data point and range of photon energy for summed absorption of the pre-edge peak resulted in reproducible absorption data, though the measurements were carried out at different beam time and beam line. The concentrations of Cr(VI) in the plastic CRMs were also estimated from both the certified value of total Cr and the determined percentage of Cr(VI). The analytical procedure and the estimated concentrations can be useful for the determination of Cr(VI) in plastics with respect to RoHS (restriction of the use of hazardous substances in electrical and electronics equipment) directive.

  17. Time-variability of the fine-structure constant expected from the Oklo constraint and the QSO absorption lines

    CERN Document Server

    Fujii, Y

    2003-01-01

    The data from the QSO absorption lines indicating a nonzero time-variability of the fine-structure constant has been re-analyzed on the basis of a "damped-oscillator" fit, as motivated by the same type of behavior of a scalar field, dilaton, which mimics a cosmological constant to understand the accelerating universe. We find nearly as good fit to the latest data as the simple weighted mean. In this way, we offer a way to fit the more stringent result from the Oklo phenomenon, as well.

  18. Time-variability of the fine-structure constant expected from the Oklo constraint and the QSO absorption lines

    Science.gov (United States)

    Fujii, Yasunori

    2003-10-01

    The data from the QSO absorption lines indicating a nonzero time-variability of the fine-structure constant has been re-analyzed on the basis of a ``damped-oscillator'' fit, as motivated by the same type of behavior of a scalar field, dilaton, which mimics a cosmological constant to understand the accelerating universe. We find nearly as good fit to the latest data as the simple weighted mean. In this way, we offer a way to fit the more stringent result from the Oklo phenomenon, as well.

  19. 100-picosecond time-resolved X-ray absorption fine structure of FeII(1,10-phenanthroline)3

    International Nuclear Information System (INIS)

    Studying photo-induced molecular dynamics in liquid with sub-nanosecond time-resolution and sub-Angstrom spatial resolution gives information for understanding fundamental chemical process in the photo-induced cooperative phenomena of molecular systems and also for developing new materials and devices. Here, we present time-resolved X-ray absorption fine structure on the spin-crossover complex FeII tris-(1,10-phenanthroline) dissolved in aqueous solution. We utilized femtosecond laser at 400nm pulse for excitation and 100ps X-ray pulse for probe.

  20. 100-picosecond time-resolved X-ray absorption fine structure of FeII(1,10-phenanthroline)3

    Science.gov (United States)

    Sato, Tokushi; Nozawa, Shunsuke; Ichiyanagi, Kouhei; Tomita, Ayana; Ichikawa, Hirohiko; Chollet, Matthieu; Fujii, Hiroshi; Adachi, Shin-ichi; Koshihara, Shin-ya

    2009-02-01

    Studying photo-induced molecular dynamics in liquid with sub-nanosecond time-resolution and sub-Angstrom spatial resolution gives information for understanding fundamental chemical process in the photo-induced cooperative phenomena of molecular systems and also for developing new materials and devices. Here, we present time-resolved X-ray absorption fine structure on the spin-crossover complex FeII tris-(1,10-phenanthroline) dissolved in aqueous solution. We utilized femtosecond laser at 400nm pulse for excitation and 100ps X-ray pulse for probe.

  1. PREFACE: The 15th International Conference on X-ray Absorption Fine Structure (XAFS15)

    Science.gov (United States)

    Wu, Z. Y.

    2013-04-01

    The 15th International Conference on X-ray Absorption Fine Structure (XAFS15) was held on 22-28 July 2012 in Beijing, P. R. China. About 340 scientists from 34 countries attended this important international event. Main hall Figure 1. Main hall of XAFS15. The rapidly increasing application of XAFS to the study of a large variety of materials and the operation of the new SR source led to the first meeting of XAFS users in 1981 in England. Following that a further 14 International Conferences have been held. Comparing a breakdown of attendees according to their national origin, it is clear that participation is spreading to include attendees from more and more countries every year. The strategy of development in China of science and education is increasing quickly thanks to the large investment in scientific and technological research and infrastructure. There are three Synchrotron Radiation facilities in mainland China, Hefei Light Source (HLS) in the National Natural Science Foundation of China (NSRL), Beijing Synchrotron Radiation Facility (BSRF) in the Institute of High Energy Physics, and Shanghai Synchrotron Radiation Facility (SSRF) in the Shanghai Institute of Applied Physics. More than 10000 users and over 5000 proposals run at these facilities. Among them, many teams from the USA, Japan, German, Italy, Russia, and other countries. More than 3000 manuscript were published in SCI journals, including (incomplete) Science (7), Nature (10), Nature Series (7), PNAS (3), JACS (12), Angew. Chem. Int. Ed. (15), Nano Lett. (2), etc. In XAFS15, the participants contributed 18 plenary invited talks, 16 parallel invited talks, 136 oral presentations, 12 special talks, and 219 poster presentations. Wide communication was promoted in the conference halls, the classical banquet restaurant, and the Great Wall. Parallel hallCommunicationPoster room Figure 2. Parallel hallFigure 3. CommunicationFigure 4. Poster room This volume contains 136 invited and contributed papers

  2. Further constraints on variation of the fine-structure constant from alkali-doublet QSO absorption lines

    Science.gov (United States)

    Murphy, M. T.; Webb, J. K.; Flambaum, V. V.; Prochaska, J. X.; Wolfe, A. M.

    2001-11-01

    Comparison of quasar (QSO) absorption-line spectra with laboratory spectra provides a precise probe for variability of the fine-structure constant, α, over cosmological time-scales. We constrain variation in α in 21 Keck/HIRES Siiv absorption systems using the alkali-doublet (AD) method in which changes in α are related to changes in the doublet spacing. The precision obtained with the AD method has been increased by a factor of 3: Δα/α=(-0.5+/-1.3)×10-5. We also analyse potential systematic errors in this result. Finally, we compare the AD method with the many-multiplet method, which has achieved an order of magnitude greater precision, and we discuss the future of the AD method.

  3. A comparison of fine structures in high-resolution x-ray-absorption spectra of various condensed organic molecules.

    Science.gov (United States)

    Schoell, A; Zou, Y; Huebner, D; Urquhart, S G; Schmidt, Th; Fink, R; Umbach, E

    2005-07-22

    We report on a high-resolution C-K and O-K near-edge x-ray-absorption fine-structure (NEXAFS) study of large aromatic molecules in condensed thin films, namely, anhydrides 1,4,5,8-naphthalene-tetracarboxylic acid dianhydride, 3,4,9,10-perylene-tetracarboxylic acid dianhydride, benzoperylene-(1,2)-dicarboxylic acid anhydride, and 1,8-naphthalene-dicarboxylic acid anhydride and the quinoic acenaphthenequinone. Due to the high-energy resolution of the third-generation synchrotron source BESSY II we observe large differences in the NEXAFS fine structures even for very similar molecules, resulting in a wealth of new information. The rich fine structure can unambiguously be assigned to the coupling of electronic transitions to vibronic excitations. Backed by ab initio calculations we present a detailed analysis of the spectra that allows the complete interpretation of the near-edge features. It also yields information on the vibronic properties in the electronically excited state as well as on the response of the electronic system upon core excitation. The strong differences in the electron-vibron coupling for different molecules are discussed. PMID:16095371

  4. Interpretation of the pre-edge X-ray absorption fine structures in MnO

    Institute of Scientific and Technical Information of China (English)

    LI Shu-Jun; HU Rong; HU Tian-Dou; XIE Ya-Ning; ZHANG Jing; TAO Ye; WU Zi-Yu

    2003-01-01

    The weak pre-edge features in the Mn K-edge X-ray absorption near-edge structure (XANES) spectrumof manganese monoxide (MnO) were investigated by comparing experimental data with dipolar and quadrupolarcross-section calculations in the framework of multiple-scattering theory. We assign the first pre-edge feature to a di-rect quadrupolar transition from Is core state to 3d molecular orbitals of the central atom, e.g., the lowest in energy,due to the more effective attraction of the core hole. The second peak in this region arises unambiguously from thehybridization between p-orbitals of the central atom with higher-shell metal octahedral orbitals.

  5. Fine structures in the optical absorption spectra of photochemical silver in silver halides? A call for further research

    CERN Document Server

    Georgiev, Mladen

    2007-01-01

    A survey is presented of the work done so far to check earlier claims that a fine structure may be observed to occur under certain circumstances in the impurity spectral range of the optical absorption spectra of silver halides following photostimulation in the intrinsic range. This structure, associated with the photochemical formation of silver specks, has been questioned over the years. We now weigh carefully the experimental evidence on the silver halides against a background of similar data on the alkali halides, where competing processes run slower. We come to the conclusion that present day advances in experimental techniques may be quite adequate for providing a solid experimental basis to solve the problem unambiguously.

  6. Atomic transition frequencies, isotope shifts, and sensitivity to variation of the fine structure constant for studies of quasar absorption spectra

    CERN Document Server

    Berengut, J C; Flambaum, V V; King, J A; Kozlov, M G; Murphy, M T; Webb, J K

    2010-01-01

    Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental "constants" in the Universe. A change in the fine structure constant, alpha, could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that alpha varies spatially. That is, in one direction on the sky alpha seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger. To continue this study we need accurate laboratory measurements of atomic transition frequencies. The aim of this paper is to provide a compilation of transitions of importance to the search for alpha variation. They are E1 transitions to the ground state in several different atoms and ions, with wavelengths ranging from around 900 - 6000 A, and require an accuracy of better than 10^{-4} A. We discuss isotope shift measurements that are...

  7. On variations in the fine-structure constant and limits on AGB pollution of quasar absorption systems

    CERN Document Server

    Fenner, Y; Gibson, B K

    2005-01-01

    At redshifts z_abs < 2, quasar absorption-line constraints on space-time variations in the fine-structure constant, alpha, rely on the comparison of MgII and FeII transition wavelengths. One potentially important uncertainty is the relative abundance of Mg isotopes in the absorbers which, if different from solar, can cause spurious shifts in the measured wavelengths and, therefore, alpha. Here we explore chemical evolution models with enhanced populations of intermediate-mass (IM) stars which, in their asymptotic giant branch (AGB) phase, are thought to be the dominant factories for heavy Mg isotopes at the low metallicities typical of quasar absorption systems. By design, these models partially explain recent Keck/HIRES evidence for a smaller alpha in z_abs < 2 absorption clouds than on Earth. However, such models also over-produce N, violating observed abundance trends in high-z_abs damped Lyman-alpha systems (DLAs). Our results do not support the recent claim of Ashenfelter, Mathews & Olive (2004...

  8. Laboratory-based recording of holographic fine structure in X-ray absorption anisotropy using polycapillary optics

    Energy Technology Data Exchange (ETDEWEB)

    Dabrowski, K.M. [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland); Korecki, P., E-mail: pawel.korecki@uj.edu.pl [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Holographic fine structures in X-ray absorption recorded using a tabletop setup. Black-Right-Pointing-Pointer Setup based on polycapillary collimating optics and an HOPG crystal. Black-Right-Pointing-Pointer Demonstration of element sensitivity by detection of X-ray fluorescence. Black-Right-Pointing-Pointer Potential of laboratory-based experiments for heavily doped crystals and thin films. - Abstract: A tabletop setup composed of a collimating polycapillary optics and a highly oriented pyrolytic graphite monochromator (HOPG) was characterized and used for recording two-dimensional maps of X-ray absorption anisotropy (XAA). XAA originates from interference of X-rays directly inside the sample. Depending on experimental conditions, fine structures in XAA can be interpreted in terms of X-ray holograms or X-ray standing waves and can be used for an element selective atomic-resolved structural analysis. The implementation of polycapillary optics resulted in a two-order of magnitude gain in the radiant intensity (photons/s/solid angle) as compared to a system without optics and enabled efficient recording of XAA with a resolution of 0.15 Degree-Sign for Mo K{alpha} radiation. Element sensitivity was demonstrated by acquisition of distinct XAA signals for Ga and As atoms in a GaAs (1 1 1) wafer by using X-ray fluorescence as a secondary signal. These results indicate the possibility of performing laboratory-based XAA experiments for heavily doped single crystals or thin films. So far, because of the weak holographic modulation of XAA, such experiments could be only performed using synchrotron radiation.

  9. Quick extended x-ray absorption fine structure instrument with millisecond time scale, optimized for in situ applications.

    Science.gov (United States)

    Khalid, S; Caliebe, W; Siddons, P; So, I; Clay, B; Lenhard, T; Hanson, J; Wang, Q; Frenkel, A I; Marinkovic, N; Hould, N; Ginder-Vogel, M; Landrot, G L; Sparks, D L; Ganjoo, A

    2010-01-01

    In order to learn about in situ structural changes in materials at subseconds time scale, we have further refined the techniques of quick extended x-ray absorption fine structure (QEXAFS) and quick x-ray absorption near edge structure (XANES) spectroscopies at beamline X18B at the National Synchrotron Light Source. The channel cut Si (111) monochromator oscillation is driven through a tangential arm at 5 Hz, using a cam, dc motor, pulley, and belt system. The rubber belt between the motor and the cam damps the mechanical noise. EXAFS scan taken in 100 ms is comparable to standard data. The angle and the angular range of the monochromator can be changed to collect a full EXAFS or XANES spectrum in the energy range 4.7-40.0 KeV. The data are recorded in ascending and descending order of energy, on the fly, without any loss of beam time. The QEXAFS mechanical system is outside the vacuum system, and therefore changing the mode of operation from conventional to QEXAFS takes only a few minutes. This instrument allows the acquisition of time resolved data in a variety of systems relevant to electrochemical, photochemical, catalytic, materials, and environmental sciences.

  10. Artificial intelligence applied to the automatic analysis of absorption spectra. Objective measurement of the fine structure constant

    CERN Document Server

    Bainbridge, Matthew B

    2016-01-01

    A new and fully-automated method is presented for the analysis of high-resolution absorption spectra (GVPFIT). The method has broad application but here we apply it specifically to the problem of measuring the fine structure constant at high redshift. For this we need objectivity and reproducibility. GVPFIT is also motivated by the importance of obtaining a large statistical sample of measurements of $\\Delta\\alpha/\\alpha$. Interactive analyses are both time consuming and complex and automation makes obtaining a large sample feasible. Three numerical methods are unified into one artificial intelligence process: a genetic algorithm that emulates the Darwinian processes of reproduction, mutation and selection, non-linear least-squares with parameter constraints (VPFIT), and Bayesian model averaging. In contrast to previous methodologies, which relied on a particular solution as being the most likely model, GVPFIT plus Bayesian model averaging derives results from a large set of models, and helps overcome systema...

  11. Zinc cysteine active sites of metalloproteins: a density functional theory and x-ray absorption fine structure study.

    Science.gov (United States)

    Dimakis, Nicholas; Farooqi, Mohammed Junaid; Garza, Emily Sofia; Bunker, Grant

    2008-03-21

    Density functional theory (DFT) and x-ray absorption fine structure (XAFS) spectroscopy are complementary tools for the biophysical study of active sites in metalloproteins. DFT is used to compute XAFS multiple scattering Debye Waller factors, which are then employed in genetic algorithm-based fitting process to obtain a global fit to the XAFS in the space of fitting parameters. Zn-Cys sites, which serve important functions as transcriptional switches in Zn finger proteins and matrix metalloproteinases, previously have proven intractable by this method; here these limitations are removed. In this work we evaluate optimal DFT nonlocal functionals and basis sets for determining optimal geometries and vibrational densities of states of mixed ligation Zn(His)(4-n)(Cys)(n) sites. Theoretical results are compared to experimental XAFS measurements and Raman spectra from the literature and tabulated for use.

  12. Methods of Determining Lead Speciation in Fly Ash by X-ray Absorption Fine-Structure Spectroscopy and a Sequential Extraction Procedure

    OpenAIRE

    Funatsuki, Atsushi; Takaoka, Masaki; Oshita, Kazuyuki; Takeda, Nobuo

    2012-01-01

    Understanding the chemical state of lead in fly ash generated from a waste thermal treatment is important, since the toxicity and solubility of the element depends on its chemical state. This study identified three potential methods for obtaining quantitative information regarding the chemical state of lead in fly ash: X-ray absorption near edge structure (XANES) analysis, extended X-ray absorption fine structure (EXAFS) analysis, and the sequential extraction procedure. The result of this pr...

  13. High-precision limit on variation in the fine-structure constant from a single quasar absorption system

    CERN Document Server

    Kotuš, Srđan M; Carswell, Robert F

    2016-01-01

    The brightest southern quasar above redshift $z=1$, HE 0515$-$4414, with its strong intervening metal absorption-line system at $z_{abs}=1.1508$, provides a unique opportunity to precisely measure or limit relative variations in the fine-structure constant ($\\Delta\\alpha/\\alpha$). A variation of just $\\sim$3 parts per million (ppm) would produce detectable velocity shifts between its many strong metal transitions. Using new and archival observations from the Ultraviolet and Visual Echelle Spectrograph (UVES) we obtain an extremely high signal-to-noise ratio spectrum (peaking at S/N $\\approx250$ pix$^{-1}$). This provides the most precise measurement of $\\Delta\\alpha/\\alpha$ from a single absorption system to date, $\\Delta\\alpha/\\alpha=-1.42\\pm0.55_{\\rm stat}\\pm0.65_{\\rm sys}$ ppm, comparable with the precision from previous, large samples of $\\sim$150 absorbers. The largest systematic error in all (but one) previous similar measurements, including the large samples, was long-range distortions in the wavelengt...

  14. Oxygen K-edge extended x-ray-absorption fine-structure studies of molecules containing oxygen and carbon atoms

    International Nuclear Information System (INIS)

    The absorption spectra of a group of selected molecules containing O: C bonds, carbon monoxide, carbon dioxide, carbonyl sulfide, acetone, ethanol, diethylether, tetrahydrofuran, and dioxane, have been recorded in a transmission mode in the energy region from 500 to 1000 eV. Earlier observation of extended x-ray-absorption fine structure (EXAFS) in some of these molecules is confirmed. A systematic analysis of the EXAFS spectra is performed. The results in both phase and amplitude show disagreement with the single-electron single-scattering theory with plane-wave approximation. The measured phase is systematically lower than the theory of Teo and Lee [J. Am. Chem. Soc. 101, 2815 (1979)] by about 0.7--1.5 rad, which may be significant in determining interatomic distances. The EXAFS amplitude function in the molecules containing oxygen-carbon single bonds also shows an appreciable deviation (decrease) in the first-neighbor backscattering from that predicted by theory and an increase in the second-neighbor backscattering at high-k values

  15. Precise limits on cosmological variability of the fine-structure constant with zinc and chromium quasar absorption lines

    Science.gov (United States)

    Murphy, Michael T.; Malec, Adrian L.; Prochaska, J. Xavier

    2016-09-01

    The strongest transitions of Zn and Cr II are the most sensitive to relative variations in the fine-structure constant (Δα/α) among the transitions commonly observed in quasar absorption spectra. They also lie within just 40 Å of each other (rest frame), so they are resistant to the main systematic error affecting most previous measurements of Δα/α: long-range distortions of the wavelength calibration. While Zn and Cr II absorption is normally very weak in quasar spectra, we obtained high signal-to-noise, high-resolution echelle spectra from the Keck and Very Large Telescopes of nine rare systems where it is strong enough to constrain Δα/α from these species alone. These provide 12 independent measurements (three quasars were observed with both telescopes) at redshifts 1.0-2.4, 11 of which pass stringent reliability criteria. These 11 are all consistent with Δα/α = 0 within their individual uncertainties of 3.5-13 parts per million (ppm), with a weighted mean Δα/α = 0.4 ± 1.4stat ± 0.9sys ppm (1σ statistical and systematic uncertainties), indicating no significant cosmological variations in α. This is the first statistical sample of absorbers that is resistant to long-range calibration distortions (at the repeated across echelle orders of individual spectra.

  16. Precise limits on cosmological variability of the fine-structure constant with zinc and chromium quasar absorption lines

    CERN Document Server

    Murphy, Michael T; Prochaska, J Xavier

    2016-01-01

    The strongest transitions of Zn and CrII are the most sensitive to relative variations in the fine-structure constant ($\\Delta\\alpha/\\alpha$) among the transitions commonly observed in quasar absorption spectra. They also lie within just 40 \\AA\\ of each other (rest frame), so they are resistant to the main systematic error affecting most previous measurements of $\\Delta\\alpha/\\alpha$: long-range distortions of the wavelength calibration. While Zn and CrII absorption is normally very weak in quasar spectra, we obtained high signal-to-noise, high-resolution echelle spectra from the Keck and Very Large Telescopes of 9 rare systems where it is strong enough to constrain $\\Delta\\alpha/\\alpha$ from these species alone. These provide 12 independent measurements (3 quasars were observed with both telescopes) at redshifts 1.0--2.4, 11 of which pass stringent reliability criteria. These 11 are all consistent with $\\Delta\\alpha/\\alpha=0$ within their individual uncertainties of 3.5--13 parts per million (ppm), with a we...

  17. Sulfur X-ray absorption fine structure in porous Li–S cathode films measured under argon atmospheric conditions

    Energy Technology Data Exchange (ETDEWEB)

    Müller, Matthias, E-mail: matthias.mueller@ptb.de [Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin (Germany); Choudhury, Soumyadip [Leibniz-Institut für Polymerforschung, Hohe Strasse 6, 01069 Dresden (Germany); Technische Universität Dresden, Physical Chemistry of Polymeric Materials ,01062 Dresden (Germany); Gruber, Katharina [VARTA Micro Innovation GmbH, Stremayrgasse 9, 8010 Graz (Austria); Cruz, Valene B. [Universität Ulm, Institut für Elektrochemie, 89069 Ulm (Germany); Helmholtz-Institut Ulm (HIU), 89069 Ulm (Germany); Fuchsbichler, Bernd [VARTA Micro Innovation GmbH, Stremayrgasse 9, 8010 Graz (Austria); Jacob, Timo [Universität Ulm, Institut für Elektrochemie, 89069 Ulm (Germany); Helmholtz-Institut Ulm (HIU), 89069 Ulm (Germany); Koller, Stefan [VARTA Micro Innovation GmbH, Stremayrgasse 9, 8010 Graz (Austria); Stamm, Manfred [Leibniz-Institut für Polymerforschung, Hohe Strasse 6, 01069 Dresden (Germany); Technische Universität Dresden, Physical Chemistry of Polymeric Materials ,01062 Dresden (Germany); Ionov, Leonid [Leibniz-Institut für Polymerforschung, Hohe Strasse 6, 01069 Dresden (Germany); Beckhoff, Burkhard [Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin (Germany)

    2014-04-01

    In this paper we present the first results for the characterization of highly porous cathode materials with pore sizes below 1 μm for Lithium Sulfur (Li–S) batteries by Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. A novel cathode material of porous carbon films fabricated with colloidal array templates has been investigated. In addition, an electrochemical characterization has been performed aiming on an improved correlation of physical and chemical parameters with the electrochemical performance. The performed NEXAFS measurements of cathode materials allowed for a chemical speciation of the sulfur content inside the cathode material. The aim of the presented investigation was to evaluate the potential of the NEXAFS technique to characterize sulfur in novel battery material. The long term goal for the characterization of the battery materials is the sensitive identification of undesired side reactions, such as the polysulfide shuttle, which takes place during charging and discharging of the battery. The main drawback associated with the investigation of these materials is the fact that NEXAFS measurements can usually only be performed ex situ due to the limited in situ instrumentation being available. For Li–S batteries this problem is more pronounced because of the low photon energies needed to study the sulfur K absorption edge at 2472 eV. We employed 1 μm thick Si{sub 3}N{sub 4} windows to construct sealed argon cells for NEXAFS measurements under ultra high vacuum (UHV) conditions as a first step towards in situ measurements. The cells keep the sample under argon atmosphere at any time and the X-ray beam passes mainly through vacuum which enables the detection of the low energy X-ray emission of sulfur. Using these argon cells we found indications for the presence of lithium polysulfides in the cathode films whereas the correlations to the offline electrochemical results remain somewhat ambiguous. As a consequence of these findings one

  18. Extended X-ray absorption fine structure of the [Fe]-hydrogenase Hmd active site

    Energy Technology Data Exchange (ETDEWEB)

    Salomone-Stagni, Marco; Meyer-Klaucke, Wolfram [European Molecular Biology Laboratory (EMBL), Outstation Hamburg, Notkestr. 85, 22603 Hamburg (Germany); Vogt, Sonja; Shima, Seigo, E-mail: wolfram@embl-hamburg.d [Max-Planck-Institut fuer terrestrische Mikrobiologie, Karl-von-Frisch-Strasse, D-35043 Marburg (Germany)

    2009-11-15

    Hydrogenases are enzymes that catalyze the reversible oxidation of molecular hydrogen. Although their structure and catalytic mechanism are of considerable applied interest as models for the development of efficient catalysts for hydrogen fueled processes, the understanding of how hydrogenases react with H{sub 2} is only in its infancy. Two of the three known types of hydrogenases are iron-sulfur proteins that contain a dinuclear metal center, either [NiFe] or [FeFe]. In contrast, [Fe]-hydrogenase is the only mononuclear hydrogenase and thus a perfect system for studying the structural and electronic determinants of these enzymes. Here we summarize recent improvements in modeling based on the EXAFS signal and the geometric structure of this metalloenzyme in its as isolated or reconstituted form. The individual contributions to the EXAFS resulting in two different structural models are presented and discussed. Inspired by the new crystal structure, we show an advanced EXAFS model for the enzyme from Methanothermobacter marburgensis.

  19. Near-edge X-ray absorption fine-structure spectroscopy of naphthalene diimide-thiophene co-polymers

    International Nuclear Information System (INIS)

    Near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy is an important tool for probing the structure of conjugated polymer films used in organic electronic devices. High-performance conjugated polymers are often donor-acceptor co-polymers which feature a repeat unit with multiple functional groups. To facilitate better application of NEXAFS spectroscopy to the study of such materials, improved understanding of the observed NEXAFS spectral features is required. In order to examine how the NEXAFS spectrum of a donor-acceptor co-polymer relates to the properties of the sub-units, a series of naphthalene diimide-thiophene-based co-polymers have been studied where the nature and length of the donor co-monomer has been systematically varied. The spectra of these materials are compared with that of a thiophene homopolymer and naphthalene diimide monomer enabling peak assignment and the influence of inter-unit electronic coupling to be assessed. We find that while it is possible to attribute peaks within the π* manifold as arising primarily due to the naphthalene diimide or thiophene sub-units, very similar dichroism of these peaks is observed indicating that it may not be possible to separately probe the molecular orientation of the separate sub-units with carbon K-edge NEXAFS spectroscopy

  20. Water formation reaction on Pt(111): Near edge x-ray absorption fine structure experiments and kinetic Monte Carlo simulations

    International Nuclear Information System (INIS)

    The catalytic water formation reaction was investigated by the energy dispersive near-edge x-ray absorption fine structure (dispersive NEXAFS) spectroscopy. An oxygen covered Pt(111) surface with the (2x2) structure was exposed to gaseous hydrogen (5.0x10-9 Torr) at constant surface temperatures (120-140 K). O K-edge NEXAFS spectra were measured during the reaction with a time interval of 35 s. Quantitative analyses of the spectra provided the coverage changes of the adsorbed species (O, OH, and H2O). The reaction is composed of three steps, which are characterized by an induction period (I), fast increase in coverage of OH and H2O with consuming O (II), and slow conversion of OH to H2O after the complete consumption of O (III). It was also found that the maximum OH coverage becomes smaller at a higher temperature. The kinetic Monte Carlo simulation has reproduced the three characteristic reaction steps; in the first step OH domains are created through two-dimensional aggregation of H2O (I), after the nucleation process the second step sets in where the OH domains propagate by the autocatalytic cycle until they contact with each other (II), and finally the merged OH domains convert to H2O (III). The reaction diffusion method was also applied to this system. It explained the reaction behavior in a wide surface area

  1. The structure of liquid semiconductors, superionic conductors and glasses by neutron scattering, X-ray diffraction and extended X-ray absorption fine structure

    CERN Document Server

    Buchanan, P

    2001-01-01

    NDIS technique alone. The structure of liquid FeTe sub 2 was determined at the total structure factor level using neutron diffraction in order to estimate the effect of chalcogenide ion size on the structure. The results demonstrate the feasibility of the additional structural determination techniques for disordered materials made possible through the development of third generation X-ray synchrotron sources. A study of the applicability of modern X-ray and neutron scattering techniques to the study of the structure of liquid semiconductors and glasses has been made. The results demonstrate how neutron scattering with isotopic substitution (NDIS), anomalous X-ray scattering and Extended X-ray Absorption Fine Structure (EXAFS) can be successfully used to elucidate the structure of materials that cannot be studied by NDIS alone. The local coordination structure of Ag sub 2 Se in its room temperature, superionic and liquid phases has been determined using the EXAFS technique. This EXAFS data have been combined w...

  2. Time-Resolved Pump-Probe X-ray Absorption Fine Structure Spectroscopy of Gaq3

    OpenAIRE

    Dicke, Benjamin

    2014-01-01

    Gallium(tris-8-hydroxyquinoline) (Gaq3) belongs to a class of metal organic compounds, usedas electron transport layer and emissive layer in organic light emitting diodes. Many researchactivities have concentrated on the optical and electronic properties, especially of the homologuemolecule aluminum(tris-8-hydroxyquinoline) (Alq3). Knowledge of the first excited state S1structure of these molecules could provide deeper insight into the processes involved into the operationof electronic device...

  3. Reply to open-quote open-quote Comment on open-quote x-ray-absorption fine structure in embedded atoms close-quote close-quote close-quote

    International Nuclear Information System (INIS)

    We respond to the previous Comment concerning the evidence for a weak oscillatory structure in the atomic background absorption cross section in x-ray-absorption fine structure (XAFS). We show that improved background calculations which suppress muffin-tin discontinuities still exhibit fine structure comparable to that observed. copyright 1996 The American Physical Society

  4. Formation mechanism of Ge nanocrystals embedded in SiO2 studied by fluorescence x-ray absorption fine structure

    Institute of Scientific and Technical Information of China (English)

    Yan Wen-Sheng; Li Zhong-Rui; Sun Zhi-Hu; Pan Zhi-Yun; Wei Shi-Qiang

    2007-01-01

    This paper reports that the Ge nanocrystals embedded in SiO2 matrix are grown on Si(100) and quartz-glass substrates, and the formation mechanism is systematically studied by using fluorescence x-ray absorption fine structure (XAFS). It is found that the formation of Ge nanocrystals strongly depends on the properties of substrate materials. In the as-prepared samples with Ge molar content of 60%, Ge atoms exist in amorphous Ge (about 36%) and GeO2 (about 24%) phases. At the annealing temperature of 1073 K, on the quartz-glass substrate Ge nanocrystals are generated from crystallization of amorphous Ge, rather than from the direct decomposition of GeO2 in the as-deposited sample.However, on the Si(100) substrate, the Ge nanocrystals are generated partly from crystallization of amorphous Ge, and partly from GeO2 phases through the permutation reaction with Si substrate. Quantitative analysis reveals that about 10% of GeO2 in the as-prepared sample are permuted with Si wafer to form Ge nanocrystals.

  5. Investigation of copper(I) oxide quantum dots by near edge X-ray absorption fine structure spectroscopy

    International Nuclear Information System (INIS)

    Copper(I) oxide quantum dots (OQDs) were grown in various thicknesses on different SrTiO3(001) surfaces and were investigated by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The experimental growth conditions for the OQDs were optimized to obtain Cu2O as the major phase. The OQDs grown on clean SrTiO3(001) surfaces at 825 K and higher with p(O-2) of 9.0 x 10(-7) Torr or greater contain mostly CuO, contrasting to OQDs grown at 800 K with p(O-2) of similar to 7.0 x10(-7) Torr that contain primarily Cu2O. Furthermore, there is a strong interaction between the SrTiO3(001) surface and the first few monolayers of the OQDs, which induces the formation of Cu(II). However, this interaction is mitigated with increasing thickness of OQDs, resulting in the exclusive formation of Cu2O in the top most layers. The influence of the SrTiO3(001) substrate on the formation of OQDs can be minimized by modifying the substrate surface using chemical treatment and/or energetic Au2+ ion-beam irradiation. Examination of the photochemical properties of these OQDs shows that prolonged soft X-ray irradiation under vacuum reduces Cu(II), which is present as a minor impurity in the Cu(I)OQDs

  6. Local and electronic strictures of Al90FexCe10-x (x = 3, 5, 7) alloys. The analysis of near fine structure of X-ray absorption

    International Nuclear Information System (INIS)

    One obtained near fine structure of X-ray absorption Al90FexCe10-x (x = 3, 5, 7) beyond iron K-boundary. One carried out theoretical analysis of these data by method of the total multiple scattering. Comparison of the experimental data with the theoretical results enables to choose the best model of the local structure around iron atoms. The best accord with the experiment is achieved for FeAl6 model at reduction of interatomic distance by 4%. As the dipole matrix element of probability of transition for iron K-boundary is not the function varying abruptly with the energy, the near fine structure of absorption X-ray spectrum beyond iron K-boundary represents the density of iron free p-states within Al90FexCe10-x alloy conductivity range

  7. Fine structure of the CCl3 UV absorption spectrum and CCl3 kinetics

    DEFF Research Database (Denmark)

    Ellermann, T.

    1992-01-01

    The UV gas-phase spectrum of CCl3 was recorded in the range 220-300 nm using pulse radiolysis of CHCl3/SF6 or CCl4/Ar gas mixtures. The UV spectrum exhibits a pronounced vibrational fine structure which is assigned to transition into the (C2A1'(3s)) Rydberg state. The vibronic progression has a...

  8. High resolution spectrometer for extended x-ray absorption fine structure measurements in the 6 keV to 15 keV energy range

    Science.gov (United States)

    Seely, J. F.; Hudson, L. T.; Henins, Albert; Feldman, U.

    2016-11-01

    A Cauchois transmission-crystal spectrometer has been developed with high crystal resolving power in the 6 keV-15 keV energy range and sufficient sensitivity to record single-shot spectra from the Lawrence Livermore National Laboratory (LLNL) Titan laser and other comparable or more energetic lasers. The spectrometer capabilities were tested by recording the W L transitions from a laboratory source and the extended x-ray absorption fine structure (EXAFS) spectrum through a Cu foil.

  9. Comment on "Limits on the Time Variation of the Electromagnetic Fine-Structure Constant in the Low Energy Limit from Absorption Lines in the Spectra of Distant Quasars"

    CERN Document Server

    Murphy, Michael T; Flambaum, Victor V

    2007-01-01

    In their Letter [Phys. Rev. Lett. 92, 121302 (2004)] (also [Astron. Astrophys. 417, 853 (2004)]), Srianand et al. analysed optical spectra of heavy-element species in 23 absorption systems along background quasar sight-lines, reporting limits on relative variations in the fine-structure constant: da/a=(-0.06+/-0.06) x 10^{-5}. Here we demonstrate basic flaws in their analysis, using the same data and absorption profile fits, which led to spurious values of da/a and significantly underestimated uncertainties. We conclude that these data and fits offer no stringent test of previous evidence for a varying alpha.

  10. Extended x-ray--absorption fine structure of small Cu and Ni clusters: Binding-energy and bond-length changes with cluster size

    Energy Technology Data Exchange (ETDEWEB)

    Apai, G.; Hamilton, J.F.; Stohr, J.; Thompson, A.

    1979-07-09

    Extended x-ray--absorption fine-structure measurements have been made on metal clusters of Cu and Ni which were formed by vapor deposition on amorphous carbon substrates. Small clusters of both elements show a substantial contraction of the nearest-neighbor metal-metal distance and an increase in binding energy for the onset of the K absorption edge. The results are explained by the increasing surface-to-volume ratio as the cluster size decreases resulting in a more free-atom--like configuration of the metal atoms.

  11. In-situ structural investigation of non-stoichiometric HfO{sub 2-x} films using quick-scanning extended X-ray absorption fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Milias, E-mail: milias.liu@pc.rwth-aachen.de [Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen (Germany); JARA — Fundamentals of Future Information Technologies (Germany); Leichtweiß, Thomas; Janek, Jürgen [Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, 35392 Giessen (Germany); Martin, Manfred [Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen (Germany); JARA — Fundamentals of Future Information Technologies (Germany)

    2013-07-31

    In this work, we report our results on the synthesis and structural characterization of hafnium oxide thin films prepared by means of pulsed laser deposition. During the deposition, different gas atmospheres (O{sub 2,} Ar, Ar/H{sub 2}) were used. Electron probe micro analysis and X-ray photoelectron spectroscopy measurements show that films deposited in Ar or Ar/H{sub 2} are oxygen deficient, while films deposited in O{sub 2} are stoichiometric. X-ray diffraction data confirm that the as-prepared films are amorphous and form the monoclinic HfO{sub 2} phase during annealing. In-situ quick-scanning extended X-ray absorption fine structure measurements carried out at elevated temperatures up to 440 °C showed an increase in the Hf–Hf order. From the time-resolved data the crystallization kinetics are extracted and analyzed using the Avrami model. - Highlights: • Thin films of HfO{sub 2-x} were deposited by pulsed laser deposition on glass substrates. • Different gas atmospheres (O{sub 2}, Ar, Ar/H{sub 2}) were used to control the stoichiometry. • Films deposited under reducing conditions are highly non-stoichiometric. • As-prepared films are amorphous but crystallize upon heating up to 440 °C. • Time resolved in-situ X-ray absorption spectroscopy analysis of crystallization.

  12. A combined fit of total scattering and extended x-ray absorption fine structure data for local-structure determination in crystalline materials

    Energy Technology Data Exchange (ETDEWEB)

    Proffen, Thomas E [Los Alamos National Laboratory; Krayzman, Victor [NIST; Levin, Igor [NIST; Tucker, Matt [ISIS, UK

    2009-01-01

    Reverse Monte Carlo (RMC) refinements of local structure using a simultaneous fit of X-ray/neutron total scattering and extended X-ray absorption fine structure (EXAFS) data were developed to incorporate an explicit treatment of both single- and multiple-scattering contributions to EXAFS. The refinement algorithm, implemented as an extension to the public domain computer software RMCProfile, enables accurate modeling of EXAFS over distances encompassing several coordination shells around the absorbing species. The approach was first tested on Ni, which exhibits extensive multiple scattering in EXAFS, and then applied to perovskite-like SrAl{sub 1/2}Nb{sub 1/2}O{sub 3}. This compound crystal1izes with a cubic double-perovskite structure but presents a challenge for local-structure determination using a total pair-distribution function (PDF) alone because of overlapping peaks of the constituent partial PDFs (e.g. Al-O and Nb-O or Sr-O and O-O). The results obtained here suggest that the combined use of the total scattering and EXAFS data provides sufficient constraints for RMC refinements to recover fine details of local structure in complex perovskites. Among other results, it was found that the probability density distribution for Sr in SrAl{sub 1/2}Nb{sub 1/2}O{sub 3} adopts T{sub d} point-group symmetry for the Sr sites, determined by the ordered arrangement of Al and Nb, as opposed to a spherical distribution commonly assumed in traditional Rietveld refinements.

  13. The structure of the homogeneous oxidation catalyst, Mn(II)-Br(-I)x, in supercritical water: An x-ray absorption fine structure study

    International Nuclear Information System (INIS)

    Extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) spectroscopies were used to probe the first-shell coordination structure of Mn(II) and Br(-I) ion pairs in supercritical water. This work was performed to clarify why solutions of MnBr2 in supercritical water are known to effectively catalyze the aerobic oxidative synthesis of terephthalic acid from p-xylene. The Mn and Br K-edge spectra were collected at the bending magnet beamline (sector 20) at the Advanced Photon Source, Argonne. The first-shell coordination structure about the Mn(II) ion changes from octahedral at ambient conditions to tetrahedral at supercritical conditions. Under supercritical conditions, the measured bond distances of Mn-OH2 and Mn-Br are 2.11 and 2.46 ?, respectively. Direct contact ion pairs form with about 2 Br(-I) ions present in the first coordination shell of the Mn(II) ion. The structure of dissolved MnBr2, below 1.0 m, changes from essentially [Mn(II)(H2O)6]+2 to [Mn(II)(H2O)2(Br)2] in supercritical water (scH2O). When an excess of a Br(-I) ion is added, the bromide coordination increases and the number of water molecules decreases. The results show that the initial MnBr2 catalyst in scH2O is tetrahedral with two Mn-Br contact ion pairs. The presence of the acetate anion deactivates the catalyst by formation of insoluble MnO

  14. Effects of alloying elements on the electronic structure and ductility of NiAl compounds investigated by X-ray absorption fine structure

    Science.gov (United States)

    Tian, J. S.; Han, G. M.; Wei, H.; Zheng, Q.; Jin, T.; Sun, X. F.; Hu, Z. Q.

    2013-06-01

    The Ni L3,2-edge spectra of the pure Ni, pure NiAl and alloying-element-doped NiAl compounds were obtained by synchrotron radiation X-ray absorption fine structure (XAFS). Due to orbital hybridization effect, directional covalent-type bonds formed and decreased the ductility during forming NiAl. Combining the XAFS spectra analysis and electronegativity comparison, the effects of alloying elements on the electronic structure and then the ductility of the NiAl compounds were obtained. The results showed that Cr, Co, Mo, Ru and W doping could be beneficial to the ductility by both weakening the directional bonds along the direction and enhancing the d-d interactions of the transition metals-Ni atom pair, namely by the transition from covalent bonds to metallic bonds which was beneficial for dislocation to migrate. The results agreed well with the available experimental data and other theoretical results, proving that the model linking the electronic structure and ductility is reliable and can be used as guidance for alloy design.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1985-03-04

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

  16. 100-picosecond time-resolved X-ray absorption fine structure of Fe{sup II}(1,10-phenanthroline){sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Tokushi; Tomita, Ayana; Koshihara, Shin-ya [Department of Materials Science, Tokyo Institute of Technology (Japan); Nozawa, Shunsuke; Ichiyanagi, Kouhei; Ichikawa, Hirohiko; Adachi, Shin-ichi [Non-Equilibrium Dynamics Project, ERATO, JST (Japan); Chollet, Matthieu [Advanced Photon Source, Argonne, Chicago (United States); Fujii, Hiroshi, E-mail: skoshi@cms.titech.ac.j [Institute for Molecular Science, National Institutes of Natural Sciences (Japan)

    2009-02-01

    Studying photo-induced molecular dynamics in liquid with sub-nanosecond time-resolution and sub-Angstrom spatial resolution gives information for understanding fundamental chemical process in the photo-induced cooperative phenomena of molecular systems and also for developing new materials and devices. Here, we present time-resolved X-ray absorption fine structure on the spin-crossover complex Fe{sup II} tris-(1,10-phenanthroline) dissolved in aqueous solution. We utilized femtosecond laser at 400nm pulse for excitation and 100ps X-ray pulse for probe.

  17. Optical and mechanical design of the extended x-ray absorption fine structure (EXAFS) beam-line at Indus-II synchrotron source

    International Nuclear Information System (INIS)

    An extended x-ray absorption fine structure (EXAFS) beam line for x-ray absorption studies using energy dispersive geometry and position sensitive detector is being designed for the INDUS-II Synchrotron source. The beam line would be used for doing x-ray absorption experiments involving measurements of fme structures above the absorption edge of different species of atoms in a material The results of the above experiments would lead to the determination of different important structural parameters of materials viz.. inter-atomic distance. co-ordination number, degree of disorder and radial distribution function etc. The optical design of the beam line has been completed based on the working principle that a single crystal bent in the shape of an ellipse by a crystal bender would act as a dispersing as well as focusing element. The mechanical design of the beam line including the crystal bender has also been completed and discussed here. Calculations have been done to detennine the temperature profile on the different components of the beam line under exposure to synchrotron radiation and proper cooling channels have been designed to bring down the heat load on the components. (author)

  18. Application of x-ray absorption fine structure (XAFS) to local-order analysis in Fe-Cr maghemite-like materials

    Energy Technology Data Exchange (ETDEWEB)

    Montero-Cabrera, M. E., E-mail: elena.montero@cimav.edu.mx; Fuentes-Cobas, L. E.; Macías-Ríos, E. [Centro de Investigación en Materiales Avanzados, Chihuahua, 31136, México (Mexico); Fuentes-Montero, M. E. [Universidad Autónoma de Chihuahua, Chihuahua, 31000, México (Mexico)

    2015-07-23

    The maghemite-like oxide system γ-Fe{sub 2-x}Cr{sub x}O{sub 3} (x=0.75, 1 and 1.25) was studied by X-ray absorption fine structure (XAFS) and by synchrotron radiation X-ray diffraction (XRD). Measurements were performed at the Stanford Synchrotron Radiation Lightsource at room temperature, at beamlines 2-1, 2-3 and 4-3. High-resolution XRD patterns were processed by means of the Rietveld method. In cases of atoms being neighbors in the Periodic Table, the order/disorder degree of the considered solutions is indiscernible by “normal” (absence of “anomalous scattering”) diffraction experiments. Thus, maghemite-like materials were investigated by XAFS in both Fe and Cr K-edges to clarify, via short-range structure characterization, the local ordering of the investigated system. Athena and Artemis graphic user interfaces for IFEFFIT and FEFF8.4 codes were employed for XAFS spectra interpretation. Pre-edge decomposition and theoretical modeling of X-ray absorption near edge structure (XANES) transitions were performed. By analysis of the Cr K-edge XANES, it has been confirmed that Cr is located in an octahedral environment. Fitting of the extended X-ray absorption fine structure (EXAFS) spectra was performed under the consideration that the central atom of Fe is allowed to occupy octa- and tetrahedral positions, while Cr occupies only octahedral ones. Coordination number of neighboring atoms, interatomic distances and their quadratic deviation average were determined for x=1, by fitting simultaneously the EXAFS spectra of both Fe and Cr K-edges. The results of fitting the experimental spectra with theoretical standards showed that the cation vacancies tend to follow a regular pattern within the structure of the iron-chromium maghemite (FeCrO{sub 3})

  19. Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction

    Science.gov (United States)

    Boccato, Silvia; Sanson, Andrea; Kantor, Innokenty; Mathon, Olivier; Dyadkin, Vadim; Chernyshov, Dmitry; Carnera, Alberto; Pascarelli, Sakura

    2016-09-01

    The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe–Fe bonds, was found by EXAFS.

  20. Thermal and magnetic anomalies of α-iron: an exploration by extended x-ray absorption fine structure spectroscopy and synchrotron x-ray diffraction.

    Science.gov (United States)

    Boccato, Silvia; Sanson, Andrea; Kantor, Innokenty; Mathon, Olivier; Dyadkin, Vadim; Chernyshov, Dmitry; Carnera, Alberto; Pascarelli, Sakura

    2016-09-01

    The local structure and dynamics of α-iron have been investigated by extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray diffraction (XRD) in order to shed light on some thermal and magnetic anomalies observed in the last decades. The quantitative EXAFS analysis of the first two coordination shells reveals a peculiar local vibrational dynamics of α-iron: the second neighbor distance exhibits anharmonicity and vibrational anisotropy larger than the first neighbor distance. We search for possible distortions of the bcc structure to justify the unexplained magnetostriction anomalies of α-iron and provide a value for the maximum dislocation of the central Fe atom. No thermal anomalies have been detected from the current XRD data. On the contrary, an intriguing thermal anomaly at about 150 K, ascribed to a stiffening of the Fe-Fe bonds, was found by EXAFS. PMID:27385480

  1. Absolute determination of charge-coupled device quantum detection efficiency using Si K-edge x-ray absorption fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, J; Steel, A B

    2012-05-06

    We report a method to determine the quantum detection efficiency and the absorbing layers on a front-illuminated charge-coupled device (CCD). The CCD under study, as part of a crystal spectrometer, measures intense continuum x-ray emission from a picosecond laser-produced plasma and spectrally resolves the Si K-edge x-ray absorption fine structure features due to the electrode gate structure of the device. The CCD response across the Si K-edge shows a large discontinuity as well as a number of oscillations that are identified individually and uniquely from Si, SiO{sub 2}, and Si{sub 3}N{sub 4} layers. From the spectral analysis of the structure and K-edge discontinuity, the active layer thickness and the different absorbing layers thickness can be determined precisely. A precise CCD detection model from 0.2-10 keV can be deduced from this highly sensitive technique.

  2. An X-ray Absorption Fine Structure study of Au adsorbed onto the non-metabolizing cells of two soil bacterial species

    Science.gov (United States)

    Song, Zhen; Kenney, Janice P. L.; Fein, Jeremy B.; Bunker, Bruce A.

    2012-06-01

    Gram-positive and Gram-negative bacterial cells can remove Au from Au(III)-chloride solutions, and the extent of removal is strongly pH dependent. In order to determine the removal mechanisms, X-ray Absorption Fine Structure (XAFS) spectroscopy experiments were conducted on non-metabolizing biomass of Bacillus subtilis and Pseudomonas putida with fixed Au(III) concentrations over a range of bacterial concentrations and pH values. X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) data on both bacterial species indicate that more than 90% of the Au atoms on the bacterial cell walls were reduced to Au(I). In contrast to what has been observed for Au(III) interaction with metabolizing bacterial cells, no Au(0) or Au-Au nearest neighbors were observed in our experimental systems. All of the removed Au was present as adsorbed bacterial surface complexes. For both species, the XAFS data suggest that although Au-chloride-hydroxide aqueous complexes dominate the speciation of Au in solution, Au on the bacterial cell wall is characterized predominantly by binding of Au atoms to sulfhydryl functional groups and amine and/or carboxyl functional groups, and the relative importance of the sulfhydryl groups increases with increasing pH and with decreasing Au loading. The XAFS data for both microorganism species suggest that adsorption is the first step in the formation of Au nanoparticles by bacteria, and the results enhance our ability to account for the behavior of Au in bacteria-bearing geologic systems.

  3. An X-ray Absorption Fine Structure study of Au adsorbed onto the non-metabolizing cells of two soil bacterial species

    Energy Technology Data Exchange (ETDEWEB)

    Song, Zhen; Kenney, Janice P.L.; Fein, Jeremy B.; Bunker, Bruce A. (Notre)

    2015-02-09

    Gram-positive and Gram-negative bacterial cells can remove Au from Au(III)-chloride solutions, and the extent of removal is strongly pH dependent. In order to determine the removal mechanisms, X-ray Absorption Fine Structure (XAFS) spectroscopy experiments were conducted on non-metabolizing biomass of Bacillus subtilis and Pseudomonas putida with fixed Au(III) concentrations over a range of bacterial concentrations and pH values. X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) data on both bacterial species indicate that more than 90% of the Au atoms on the bacterial cell walls were reduced to Au(I). In contrast to what has been observed for Au(III) interaction with metabolizing bacterial cells, no Au(0) or Au-Au nearest neighbors were observed in our experimental systems. All of the removed Au was present as adsorbed bacterial surface complexes. For both species, the XAFS data suggest that although Au-chloride-hydroxide aqueous complexes dominate the speciation of Au in solution, Au on the bacterial cell wall is characterized predominantly by binding of Au atoms to sulfhydryl functional groups and amine and/or carboxyl functional groups, and the relative importance of the sulfhydryl groups increases with increasing pH and with decreasing Au loading. The XAFS data for both microorganism species suggest that adsorption is the first step in the formation of Au nanoparticles by bacteria, and the results enhance our ability to account for the behavior of Au in bacteria-bearing geologic systems.

  4. Local structure of Fe-doped In{sub 2}O{sub 3} films investigated by X-ray absorption fine structure spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    An, Yukai; Wang, Shiqi; Feng, Deqiang; Liu, Jiwen [Key Laboratory of Display Materials and Photoelectric Devices, Ministry of Education, Tianjin (China); Tianjin Key Laboratory for Photoelectric Materials and Devices, Tianjin (China); Tianjin University of Technology, School of Material Science and Engineering, Tianjin (China); Wu, Zhonghua [Chinese Academy of Sciences, Beijing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics, Beijing (China)

    2014-06-15

    (In{sub 1-x}Fe{sub x}){sub 2}O{sub 3} (x = 0.07, 0.09, 0.16, 0.22, 0.31) films were deposited on Si(100) substrates by RF-magnetron sputtering technique. The influence of Fe doping on the local structure of films was investigated by X-ray absorption spectroscopy (XAS) at Fe K-edge and L-edge. For the (In{sub 1-x}Fe{sub x}){sub 2}O{sub 3} films with x = 0.07, 0.09 and 0.16, Fe ions dissolve into In{sub 2}O{sub 3} and substitute for In{sup 3+} sites with a mixed-valence state (Fe{sup 2+}/Fe{sup 3+}) of Fe ions. However, a secondary phase of Fe metal clusters is formed in the (In{sub 1-x}Fe{sub x}){sub 2}O{sub 3} films with x = 0.22 and 0.31. The qualitative analyses of Fe-K edge extended X-ray absorption fine structure (EXAFS) reveal that the Fe-O bond length shortens and the corresponding Debye-Waller factor (α{sup 2}) increases with the increase of Fe concentration, indicating the relaxation of oxygen environment of Fe ions upon substitution. The anomalously large structural disorder and very short Fe-O distance are also observed in the films with high Fe concentration. Linear combination fittings at Fe L-edge further confirm the coexistence of Fe{sup 2+} and Fe{sup 3+} with a ratio of ∝3:2 (Fe{sup 2+}: Fe{sup 3+}) for the (In{sub 1-x}Fe{sub x}){sub 2}O{sub 3} film with x = 0.16. However, a significant fraction (∝40 at%) of the Fe metal clusters is found in the (In{sub 1-x}Fe{sub x}){sub 2}O{sub 3} film with x = 0.31. (orig.)

  5. Extended x-ray absorption fine structure measurements on radio frequency magnetron sputtered HfO2 thin films deposited with different oxygen partial pressures.

    Science.gov (United States)

    Maidul Haque, S; Nayak, C; Bhattacharyya, Dibyendu; Jha, S N; Sahoo, N K

    2016-03-20

    Two sets of HfO2 thin film have been deposited by the radio frequency magnetron sputtering technique at various oxygen partial pressures, one set without any substrate bias and another set with a 50 W pulsed dc substrate bias. The films have been characterized by extended x-ray absorption fine structure (EXAFS) measurements at the Hf L3 edge, and the structural information obtained from analysis of the EXAFS data has been used to explain the macroscopic behavior of the refractive index obtained from spectroscopic ellipsometry measurements. It has been observed that the variation of refractive index with oxygen partial pressure depends on the Hf-Hf bond length for the set of films deposited without substrate bias, while for the other set of films deposited with pulsed dc substrate bias, it depends on the oxygen coordination of the nearest neighbor shell surrounding Hf sites.

  6. Studies of Mn/GaAs digital alloys using x-ray absorption fine structure and x-ray diffraction methods

    Science.gov (United States)

    Soo, Y. L.; Kioseoglou, G.; Kim, S.; Chen, X.; Luo, H.; Kao, Y. H.; Sasaki, Y.; Liu, X.; Furdyna, J. K.

    2002-04-01

    Local structure and effective chemical valency of Mn atoms in Mn/GaAs digital alloys have been investigated using the x-ray absorption fine structure techniques. The samples were prepared by molecular-beam epitaxy with different thickness of GaAs layers separating the nominal Mn monolayers. Lattice constants of the digital alloys are found by x-ray diffraction to increase linearly in a very narrow range (about 0.3%) with the Mn/GaAs ratio in the samples. Our data show that Mn atoms in the nominal Mn monolayers actually combine with GaAs to form (Ga, Mn)As alloys with Mn atoms substituting for the Ga sites in GaAs. This result clearly rules out the possibility of dominant MnAs formation.

  7. Portable ultrahigh-vacuum sample storage system for polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Yoshihide, E-mail: e0827@mosk.tytlabs.co.jp; Nishimura, Yusaku F.; Suzuki, Ryo; Beniya, Atsushi; Isomura, Noritake [Toyota Central R& D Labs., Inc., Yokomichi 41-1, Nagakute, Aichi 480-1192 (Japan); Uehara, Hiromitsu; Asakura, Kiyotaka; Takakusagi, Satoru [Catalysis Research Center, Hokkaido University, Kita 21-10, Sapporo, Hokkaido 001-0021 (Japan); Nimura, Tomoyuki [AVC Co., Ltd., Inada 1450-6, Hitachinaka, Ibaraki 312-0061 (Japan)

    2016-03-15

    A portable ultrahigh-vacuum sample storage system was designed and built to investigate the detailed geometric structures of mass-selected metal clusters on oxide substrates by polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS). This ultrahigh-vacuum (UHV) sample storage system provides the handover of samples between two different sample manipulating systems. The sample storage system is adaptable for public transportation, facilitating experiments using air-sensitive samples in synchrotron radiation or other quantum beam facilities. The samples were transferred by the developed portable UHV transfer system via a public transportation at a distance over 400 km. The performance of the transfer system was demonstrated by a successful PTRF-XAFS study of Pt{sub 4} clusters deposited on a TiO{sub 2}(110) surface.

  8. Composition analysis of a polymer electrolyte membrane fuel cell microporous layer using scanning transmission X-ray microscopy and near edge X-ray absorption fine structure analysis

    Science.gov (United States)

    George, Michael G.; Wang, Jian; Banerjee, Rupak; Bazylak, Aimy

    2016-03-01

    The novel application of scanning transmission X-ray microscopy (STXM) to the microporous layer (MPL) of a polymer electrolyte membrane fuel cell is investigated. A spatially resolved chemical component distribution map is obtained for the MPL of a commercially available SGL 25 BC sample. This is achieved with near edge X-ray absorption fine structure spectroscopic analysis. Prior to analysis the sample is embedded in non-reactive epoxy and ultra-microtomed to a thickness of 100 nm. Polytetrafluoroethylene (PTFE), carbon particle agglomerates, and supporting epoxy resin distributions are identified and reconstructed for a scanning area of 6 μm × 6 μm. It is observed that the spatial distribution of PTFE is strongly correlated to the carbon particle agglomerations. Additionally, agglomerate structures of PTFE are identified, possibly indicating the presence of a unique mesostructure in the MPL. STXM analysis is presented as a useful technique for the investigation of chemical species distributions in the MPL.

  9. Searching for variations in the fine-structure constant and the proton-to-electron mass ratio using quasar absorption lines

    CERN Document Server

    King, Julian A

    2012-01-01

    (abridged) Quasar absorption lines provide a precise test of the assumed constancy of the fundamental constants of physics. We have investigated potential changes in the fine-structure constant, alpha, and the proton-to-electron mass ratio, mu. The many-multiplet method allows one to use optical fine-structure transitions to constrain (Delta alpha)/alpha at better than the 10^(-5) level. We present a new analysis of 154 quasar absorbers with 0.2 1.6 sub-samples independently yield consistent estimates of the dipole direction, which suggests that the effect is not caused by telescope systematics. We consider a number of systematic effects and show that they are unable to explain the observed dipole effect. We have used spectra of the quasars Q0405-443, Q0347-383 and Q0528-250 from VLT/UVES to investigate the absorbers at z=2.595, 3.025 and 2.811 in these spectra respectively. We find that (Delta mu)/mu=(10.1 +/- 6.6) x 10^(-6), (8.2 +/- 7.5) x 10^(-6) and (-1.4 +/- 3.9) x 10^(-6) in these absorbers respectivel...

  10. Atheoretical study of the oxygen K-edge near-edge X-ray absorption fine structure of N2O/Ir(110)

    Institute of Scientific and Technical Information of China (English)

    Wu Tai-Quan; Zhu Ping; Wang Xin-Yan; Luo Hong-Lei

    2012-01-01

    A multiple-scattering cluster method is employed to calculate the oxygen K-edge near-edge X-ray absorption fine structure of N2O/Ir(ll0) and its monolayer.Two peaks and one weak resonance appear in both cases.The selfconsistent field DV-Xα calculations of the peaks and resonance show that the physical origin of the pre-cdge peak x is different from those of the main peak 1 and the other weak resonance σl.This setup is intrinsic to the N2O monolayer,owing to the interaction between the neighbouring molecular chains in the monolayer and partly to the adsorbed atomic oxygen,according to both the theoretical and experimental data.

  11. Study of Synchrotron Radiation Near-Edge X-Ray Absorption Fine-Structure of Amorphous Hydrogenated Carbon Films at Various Thicknesses

    Directory of Open Access Journals (Sweden)

    Sarayut Tunmee

    2015-01-01

    Full Text Available The compositions and bonding states of the amorphous hydrogenated carbon films at various thicknesses were evaluated via near-edge X-ray absorption fine-structure (NEXAFS and elastic recoil detection analysis combined with Rutherford backscattering spectrometry. The absolute carbon sp2 contents were determined to decrease to 65% from 73%, while the hydrogen contents increase from 26 to 33 at.% as the film thickness increases. In addition, as the film thickness increases, the π⁎ (C=C, σ⁎ (C–H, σ⁎ (C=C, and σ⁎ (C≡C bonding states were found to increase, whereas the π⁎ (C≡C and σ⁎ (C–C bonding states were observed to decrease in the NEXAFS spectra. Consequently, the film thickness is a key factor to evaluate the composition and bonding state of the films.

  12. Near-edge X-ray absorption fine structure study of disordering in Gd2(Ti1-yZry)2O7 pyrochlores.

    Science.gov (United States)

    Nachimuthu, Ponnusamy; Thevuthasan, Suntharampillai; Adams, Evan M; Weber, William J; Begg, Bruce D; Mun, Bongjin S; Shuh, David K; Lindle, Dennis W; Gullikson, Eric M; Perera, Rupert C C

    2005-02-01

    Disorder in Gd2(Ti(1-y)Zry)2O7 pyrochlores, for y = 0.0-1.0, is investigated by Ti 2p and O 1s near-edge X-ray absorption fine structure spectroscopy. Ti(4+) ions are found to occupy octahedral sites in Gd2Ti2O7 with a tetragonal distortion induced by vacant oxygen sites. As Zr substitutes for Ti, the tetragonal distortion decreases, and Zr coordination increases from 6 to 8. The migration of oxygen ions from 48f or 8b sites to vacant 8a sites compensate for the increased Zr coordination, thereby reducing the number of vacant 8a sites, which further reduces the tetragonal distortion and introduces more disorder around Ti. This is evidence for simultaneous cation disorder with anion migration.

  13. Liquid crystal alignment on ion-beam-treated polyimide with a long alkyl side chain: near edge X-ray absorption fine structure spectroscopy analysis.

    Science.gov (United States)

    Seo, Joo-Hong; Hwang, Soo Won; Song, Dong Han; Shin, Jae Hoon; Yoon, Tae-Hoon; Kim, Jae Chang; Yi, Mi Hye

    2009-02-19

    Liquid crystal alignment on ion-beam-treated polyimides with a long alkyl side chain was investigated using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The long alkyl side chains and the asymmetric distribution and orientational order of the pi-bonds of the polyimide surface can be determined by analyzing the angular dependent resonance intensities of the NEXAFS measurements. Herein, we demonstrate that the pretilt angle of the LC cell made by our method decreases as more long alkyl side chains are destroyed. Additionally, the tilt direction of the LC molecules can be determined from the asymmetric distribution of pi-bonds of the polyimide created by the ion beam irradiation. PMID:19161281

  14. Particle Formation from Pulsed Laser Irradiation of SootAggregates studied with scanning mobility particle sizer, transmissionelectron microscope and near-edge x-ray absorption fine structure.

    Energy Technology Data Exchange (ETDEWEB)

    Michelsen, Hope A.; Tivanski, Alexei V.; Gilles, Mary K.; vanPoppel, Laura H.; Dansson, Mark A.; Buseck, Peter R.; Buseck, Peter R.

    2007-02-20

    We investigated the physical and chemical changes induced in soot aggregates exposed to laser radiation using a scanning mobility particle sizer, a transmission electron microscope, and a scanning transmission x-ray microscope to perform near-edge x-ray absorption fine structure spectroscopy. Laser-induced nanoparticle production was observed at fluences above 0.12 J/cm(2) at 532 nm and 0.22 J/cm(2) at 1064 nm. Our results indicate that new particle formation proceeds via (1) vaporization of small carbon clusters by thermal or photolytic mechanisms, followed by homogeneous nucleation, (2) heterogeneous nucleation of vaporized carbon clusters onto material ablated from primary particles, or (3) both processes.

  15. Multiple-Scattering of Near-Edge x-ray Absorption Fine Structure of Sulphur-Passivated InP(100) Surface

    Institute of Scientific and Technical Information of China (English)

    曹松; 唐景昌; 沈少来; 陈更生; 马丹

    2003-01-01

    We use the multiple-scattering cluster method to calculate the sulphur 1s near-edge x-ray absorption fine structure (NEXAFS) of S-passivated InP(100) surface. The physical origins of the resonances in the NEXAFS have been unveiled. It is shown that the most important resonance is attributed to the photoelectron scattering between the central sulphur and the nearest indium atoms. The studies show that two S-S dimers with the bond lengths of 2.05 A and 3.05 A coexist in the surface, meanwhile the bridge and antibridge site adsorption of single S could not be ruled out. We support the scanning tunnelling microscopy result that the S-passivated InP(100) surface exhibits significant disorder.

  16. Coupled-cluster response theory for near-edge x-ray-absorption fine structure of atoms and molecules

    DEFF Research Database (Denmark)

    Coriani, Sonia; Christiansen, Ove; Fransson, Thomas;

    2012-01-01

    response function, the near K-edge x-ray absorption spectra of neon, water, and carbon monoxide are determined and compared with experiment. Results at the CCSD level show relative peak intensities in good agreement with experiment with discrepancies in transition energies due to incomplete treatment...

  17. Microstructures of Fe77-xNixCu1Nb2P14B6 Soft Magnetic AlloysStudied by X-Ray Absorption Fine Structure

    Institute of Scientific and Technical Information of China (English)

    YIN Shi-Long; BIAN Qing; WEI Shi-Qiang

    2000-01-01

    Local structures of the mechanically alloyed Fe77-xNixCu1Nb2P14B6 soft magnetic materials have been in vestigated by x-ray absorption fine structure. The results show that mechanical alloying (MA) can drive the Fe77-xNixCu1Nb2P14B6 powder mixture to produce amorphous alloy when the atomic concentration of Fe ele ment is about and over 40%. On the contrary, the MA Fe77-xNixCu1Nb2P14B6 is a solid solution with an fcc-like structure in the region of lower Fe atomic concentration (< 22%), preserving a medium-range order around Ni and Fe atoms. Moreover, we have found that the local structure geometry of Fe atom is similar to that of Ni atom for all the MA Fer7-xNixCu1 Nb2P14B6 samples. It indicates that the local structures of Fe and Ni atoms in a Fe77-xNixCu1 Nb2P14B6 sample only depend on the x value of element Ni after ball milling.

  18. Extended X-ray absorption fine structure studies of impulsive-type hardening in the heavily Be-doped ZnSe ternaries

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Shabina; Singh, Pankaja [Barkatullah University, Bhopal (India); Mazher, Javed [Addis Ababa University, Addis Ababa (Ethiopia)

    2014-02-15

    Inherently soft zinc-selenides have been hardened through beryllium doping. High-quality stoichiometric ternaries of Be{sub x}Zn{sub 1-x}Se have been synthesized by using the Bridgeman technique. State-of-art X-ray absorption spectroscopy is performed by varying the concentration of the cationic dopant, Be, from 6% to 55% in the host ZnSe. Extended X-ray absorption fine structure analyses are carried out to study the next-neighbor and next nearest neighbor atomic positions, nature of the substitutional doping, extent of bond length homogeneity, the presence of involuntary contrast among path distances, and the crossover from a soft to a hard character of the ternary with increasing Be concentration. Our results indicate the presence of a non-regular impulsive hardening in the ternary with a disparity at the lower and the higher Be-doping levels, which are discussed vis-a-vis self-accommodation of substitutional dopants in the host lattice.

  19. Synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure study on oxidative etching of diamond-like carbon films by hyperthermal atomic oxygen

    International Nuclear Information System (INIS)

    Surface structural changes of a hydrogenated diamond-like carbon (DLC) film exposed to a hyperthermal atomic oxygen beam were investigated by Rutherford backscattering spectroscopy (RBS), synchrotron radiation photoelectron spectroscopy (SR-PES), and near-edge X-ray absorption fine structure (NEXAFS). It was confirmed that the DLC surface was oxidized and etched by high-energy collisions of atomic oxygen. RBS and real-time mass-loss data showed a linear relationship between etching and atomic oxygen fluence. SR-PES data suggested that the oxide layer was restricted to the topmost surface of the DLC film. NEXAFS data were interpreted to mean that the sp2 structure at the DLC surface was selectively etched by collisions with hyperthermal atomic oxygen, and an sp3-rich region remained at the topmost DLC surface. The formation of an sp3-rich layer at the DLC surface led to surface roughening and a reduced erosion yield relative to the pristine DLC surface.

  20. Searching for variations in the fine-structure constant and the proton-to-electron mass ratio using quasar absorption lines

    Science.gov (United States)

    King, Julian A.

    2012-02-01

    (abridged) Quasar absorption lines provide a precise test of the assumed constancy of the fundamental constants of physics. We have investigated potential changes in the fine-structure constant, alpha, and the proton-to-electron mass ratio, mu. The many-multiplet method allows one to use optical fine-structure transitions to constrain (Delta alpha)/alpha at better than the 10^(-5) level. We present a new analysis of 154 quasar absorbers with 0.2 1.6 sub-samples independently yield consistent estimates of the dipole direction, which suggests that the effect is not caused by telescope systematics. We consider a number of systematic effects and show that they are unable to explain the observed dipole effect. We have used spectra of the quasars Q0405-443, Q0347-383 and Q0528-250 from VLT/UVES to investigate the absorbers at z=2.595, 3.025 and 2.811 in these spectra respectively. We find that (Delta mu)/mu=(10.1 +/- 6.6) x 10^(-6), (8.2 +/- 7.5) x 10^(-6) and (-1.4 +/- 3.9) x 10^(-6) in these absorbers respectively. A second spectrum of Q0528-250 provides an additional constraint of (Delta mu)/mu=(0.2 +/- 3.2_stat +/- 1.9_sys) x 10^(-6). The weighted mean of these values yields (Delta mu)/mu=(1.7 +/- 2.4) x 10^(-6), the most precise constraint on evolution in mu at z>1.

  1. The Core/Shell Structure of CdSe/ZnS Quantum Dots Characterized by X-Ray Absorption Fine Spectroscopy

    Directory of Open Access Journals (Sweden)

    Huijing Wei

    2015-01-01

    Full Text Available Understanding the chemical and physical properties of core/shell nanocrystal quantum dots (QDs is key for their use in light-emission applications. In this paper, a single-step injection-free scalable synthetic method is applied to prepare high-quality core/shell QDs with emission wavelengths of 544 nm, 601 nm, and 634 nm. X-ray absorption fine structure spectra are used to determine the core/shell structure of CdSe/ZnS quantum dots. Moreover, theoretical XANES spectra calculated by FEFF.8.20 are used to determine the structure of Se and S compounds. The QD samples displayed nearly spherical shapes with diameters of approximately 3.4 ± 0.5 nm (634 nm, 4.5 ± 0.4 nm (601 nm, and 5.5 ± 0.5 nm (544 nm. With XANES results and MS calculations, it is indicated that sphalerite ZnS capped with organic sulfur ligands should be the shell structure. Wurtzite CdSe is the main core structure with a Cd-Se bond length of 2.3 Å without phase shift. This means that different emission wavelengths are only due to the crystal size with single-step injection-free synthesis. Therefore, single-step injection-free synthesis could generate a nearly ideal core/shell structure of CdSe/ZnS QDs capped with an organic sulfur ligand.

  2. Limits on the time variation of the electromagnetic fine-structure constant in the low energy limit from absorption lines in the spectra of distant quasars

    CERN Document Server

    Srianand, R; Petitjean, P; Aracil, B; Srianand, Raghunathan; Chand, Hum; Petitjean, Patrick; Aracil, Bastien

    2004-01-01

    Most of the successful physical theories rely on the constancy of few fundamental quantities (such as the speed of light, $c$, the fine-structure constant, \\alpha, the proton to electron mass ratio, \\mu, etc), and constraining the possible time variations of these fundamental quantities is an important step toward a complete physical theory. Time variation of \\alpha can be accurately probed using absorption lines seen in the spectra of distant quasars. Here, we present the results of a detailed many-multiplet analysis performed on a new sample of Mg II systems observed in high quality quasar spectra obtained using the Very Large Telescope. The weighted mean value of the variation in \\alpha derived from our analysis over the redshift range 0.4

  3. Extended X- ray absorption fine structure study at the K-edge of copper in mixed ligand complexes having benzimidazole as one of the ligands

    Science.gov (United States)

    Hinge, V. K.; Joshi, S. K.; Nitin Nair, N.; Singh Verma, Vikram; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

    2014-09-01

    Extended X-ray absorption fine structure (EXAFS) spectra have been studied at the K-edge of copper in some of its biologically important complexes, viz., [Cu(BzImH)4X2] and [Cu(BzIm)2], where X= Cl, Br, 1/2SO4, ClO4, NO3, and BzIm = Benzimidazolato anion. The spectra have been recorded using a bent crystal 0.4 m Cauchois-type transmission spectrograph. The positions of EXAFS maxima and minima have been used to determine the bond lengths in the complexes with the help of three different methods, namely, Levy's, Lytle's and Lytle, Sayers and Stern's (L.S.S.) methods. The phase uncorrected bond lengths have also been determined from Fourier transforms of the experimental spectra. The results obtained from these methods have been discussed and it has been found that the results obtained by L.S.S. method are comparable with the results obtained by Fourier transformation method and that these two methods give phase uncorrected bond lengths.

  4. Assignment of near-edge x-ray absorption fine structure spectra of metalloporphyrins by means of time-dependent density-functional calculations

    Science.gov (United States)

    Schmidt, Norman; Fink, Rainer; Hieringer, Wolfgang

    2010-08-01

    The C 1s and N 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of three prototype tetraphenyl porphyrin (TPP) molecules are discussed in the framework of a combined experimental and theoretical study. We employ time-dependent density-functional theory (TDDFT) to compute the NEXAFS spectra of the open- and closed-shell metalloporphyrins CoTPP and ZnTPP as well as the free-base 2HTPP in realistic nonplanar conformations. Using Becke's well-known half-and-half hybrid functional, the computed core excitation spectra are mostly in good agreement with the experimental data in the low-energy region below the appropriate ionization threshold. To make these calculations feasible, we apply a new, simple scheme based on TDDFT using a modified single-particle input spectrum. This scheme is very easy to implement in standard codes and allows one to compute core excitation spectra at a similar cost as ordinary UV/vis spectra even for larger molecules. We employ these calculations for a detailed assignment of the NEXAFS spectra including subtle shifts in certain peaks of the N 1s spectra, which depend on the central coordination of the TPP ligand. We furthermore assign the observed NEXAFS resonances to the individual molecular subunits of the investigated TPP molecules.

  5. Near edge X-ray absorption fine structure study for optimization of hard diamond-like carbon film formation with Ar cluster ion beam

    CERN Document Server

    Kitagawa, T; Kanda, K; Shimizugawa, Y; Toyoda, N; Matsui, S; Yamada, I; Tsubakino, H; Matsuo, J

    2003-01-01

    Diamond-like carbon (DLC) film deposited using C sub 6 sub 0 vapor with simultaneous irradiation of an Ar cluster ion beam was characterized by a near edge X-ray absorption fine structure (NEXAFS), in order to optimize the hard DLC film deposition conditions. Contents of sp sup 2 orbitals in the films, which were estimated from NEXAFS spectra, are 30% lower than that of a conventional DLC film deposited by a RF plasma method. Those contents were obtained under the flux ratio of the C sub 6 sub 0 molecules to the Ar cluster ions to range from 1 to 20, at 5keV of Ar cluster ion acceleration energy. Average hardness of the films was 50 GPa under these flux ratios. This hardness was three times higher than that of a conventional DLC film. Furthermore, the lowest sp sup 2 content and above-mentioned high hardness were obtained at room temperature of the substrate when the depositions were performed in the range of the substrate temperature from room temperature to 250degC. (author)

  6. Silver speciation in liver of marine mammals by synchrotron X-ray absorption fine structure and X-ray fluorescence spectroscopies.

    Science.gov (United States)

    Nakazawa, Emiko; Ikemoto, Tokutaka; Hokura, Akiko; Terada, Yasuko; Kunito, Takashi; Yamamoto, Takahito; Yamada, Tadasu K; Rosas, Fernando C W; Fillmann, Gilberto; Tanabe, Shinsuke; Nakai, Izumi

    2011-06-01

    The chemical form of Ag in the livers of five species of marine mammals was examined using X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectroscopies. The XAFS analysis suggested that Ag(2)Se was present in the livers of the Franciscana dolphin (Pontoporia blainvillei), Dall's porpoise (Phocoenoides dalli), and Baird's beaked whale (Berardius bairdii), whereas Ag(2)S was present in the livers of the striped dolphin (Stenella coeruleoalba) and pygmy killer whale (Feresa attenuata). XRF spectroscopy results revealed that the distribution patterns of Ag and Se in a thin section of the liver of the Franciscana dolphin were the same; this also implied that Ag was associated with Se in the liver. Thus, the interaction of Ag with Se or S may offer significant protection against the toxicity of Ag in marine mammals. The formation of either Ag(2)Se or Ag(2)S might depend on the Hg levels in the liver. Ag(2)Se was observed in liver samples with relatively high Ag/Hg ratio, whereas liver samples with low Ag/Hg ratio contained Ag(2)S. PMID:21491037

  7. Study of the chemical environment of cerium in low silica calcium aluminosilicate glasses by extended X-ray absorption fine structure (EXAFS)

    International Nuclear Information System (INIS)

    Full text. Currently, great attention has been given to rare earth doped optical glasses. These elements by having the 4f shell partially filled exhibit a wealth of sharp fluorescent transitions representing almost every region of the visible and near-infrared portions of the electromagnetic spectrum, being of interest in photonics, when embedded in the glass matrix. In addition cerium oxide possess high hardness and stability to high temperatures, and it has been used in industry in different ways such as catalysts, fuel and solar cells, ultraviolet radiation filters, oxygen sensors and in the polishing of materials. In this context, cerium doped low silica calcium aluminosilicate (LSCA) glasses are considered good candidates for solid state laser active medium due to their good mechanical, optical and thermal properties. Recently it was shown that LSCA glasses doped with cerium oxide is a source of emitting white light, which is of technological applications interest. However it is known that increasing the dopant concentration in the glass matrix, an interaction of rare earth ions takes place leading to a closer proximity between the rare earth ions, and thus a reduction in their quantum efficiency. In this work, the local structure of Cerium in LSCA glasses was characterized by Extended X-Ray Absorption Fine Structure Spectroscopy (EXAFS). The EXAFS and XANES measurements were performed in the Ce LIII-edge at the XAS beam line of LNLS facility (Campinas, Brazil) at room temperature. Structural parameters, coordination numbers (N), interatomic distance (R) and degree of disorder (σ2) were obtained from least squares fitting

  8. Communication: Coordination structure of bromide ions associated with hexyltrimethylammonium cations at liquid/liquid interfaces under potentiostatic control as studied by total-reflection X-ray absorption fine structure.

    Science.gov (United States)

    Nagatani, Hirohisa; Harada, Makoto; Tanida, Hajime; Sakae, Hiroki; Imura, Hisanori

    2014-03-14

    Total-reflection X-ray absorption fine structure (TR-XAFS) technique was applied for the first time to an interface between two immiscible electrolyte solutions under potentiostatic control. The hydration structure of bromide ions was investigated at polarized 2-octanone/water interfaces. TR-XAFS spectra at Br K-edge measured in the presence of hexyltrimethylammonium bromide (C6TAB) were slightly modified depending on the Galvani potential difference (Δ(o)(w)φ). The extended X-ray absorption fine structure analysis exposed hydration structure changes of bromide ions at the polarized interface. The coordination structure of bromide ions at the interface could be analyzed as compared with bromide ions dissolved in aqueous solution and Br(-)-exchanged resin having quaternary ammonium groups. The results indicated that bromide ions were associated with C6TA(+) at the polarized interface. The relative contribution of ion association form of bromide ions with quaternary ammonium groups was enhanced at a potential close to the ion transfer of C6TA(+), where the interfacial concentration of C6TA(+) is increased as a function of Δ(o)(w)φ.

  9. Characterizing phosphorus speciation of Chesapeake Bay sediments using chemical extraction, 31P NMR, and X-ray absorption fine structure spectroscopy.

    Science.gov (United States)

    Li, Wei; Joshi, Sunendra R; Hou, Guangjin; Burdige, David J; Sparks, Donald L; Jaisi, Deb P

    2015-01-01

    Nutrient contamination has been one of the lingering issues in the Chesapeake Bay because the bay restoration is complicated by temporally and seasonally variable nutrient sources and complex interaction between imported and regenerated nutrients. Differential reactivity of sedimentary phosphorus (P) pools in response to imposed biogeochemical conditions can record past sediment history and therefore a detailed sediment P speciation may provide information on P cycling particularly the stability of a P pool and the formation of one pool at the expense of another. This study examined sediment P speciation from three sites in the Chesapeake Bay: (i) a North site in the upstream bay, (ii) a middle site in the central bay dominated by seasonally hypoxic bottom water, and (iii) a South site at the bay-ocean boundary using a combination of sequential P extraction (SEDEX) and spectroscopic techniques, including (31)P NMR, P X-ray absorption near edge structure spectroscopy (XANES), and Fe extended X-ray absorption fine structure (EXAFS). Results from sequential P extraction reveal that sediment P is composed predominantly of ferric Fe-bound P and authigenic P, which was further confirmed by solid-state (31)P NMR, XANES, and EXAFS analyses. Additionally, solution (31)P NMR results show that the sediments from the middle site contain high amounts of organic P such as monoesters and diesters, compared to the other two sites, but that these compounds rapidly decrease with sediment depth indicating remineralized P could have precipitated as authigenic P. Fe EXAFS enabled to identify the changes in Fe mineral composition and P sinks in response to imposed redox condition in the middle site sediments. The presence of lepidocrocite, vermiculite, and Fe smectite in the middle site sediments indicates that some ferric Fe minerals can still be present along with pyrite and vivianite, and that ferric Fe-bound P pool can be a major P sink in anoxic sediments. These results provide

  10. Systematic Oxidation of Polystyrene by Ultraviolet-Ozone, Characterized by Near-Edge X-ray Absorption Fine Structure and Contact Angle

    Energy Technology Data Exchange (ETDEWEB)

    Klein,R.; Fischer, D.; Lenhart, J.

    2008-01-01

    The process of implanting oxygen in polystyrene (PS) via exposure to ultraviolet-ozone (UV-O) was systematically investigated using the characterization technique of near-edge X-ray absorption fine structure (NEXAFS). Samples of PS exposed to UV-O for 10-300 s and washed with isopropanol were analyzed using the carbon and oxygen K-edge NEXAFS partial electron yields, using various retarding bias voltages to depth-profile the oxygen penetration into the surface. Evaluation of reference polymers provided a scale to quantify the oxygen concentration implanted by UV-O treatment. We find that ozone initially reacts with the double bonds on the phenyl rings, forming carbonyl groups, but within 1 min of exposure, the ratio of double to single oxygen bonds stabilizes at a lower value. Oxygen penetrates the film with relative ease, creating a fairly uniform distribution of oxygen within at least the first 4 nm (the effective depth probed by NEXAFS here). Before oxygen accumulates in large concentrations, however, it preferentially degrades the uppermost layer of the film by removing oxygenated low-molecular-weight oligomers. The failure to accumulate high concentrations of oxygen is seen in the nearly constant carbon edge jump, the low concentration of oxygen even at 5 min exposure (58% of that in poly(4-acetoxystyrene), the polymer with the most similarities to UV-O-treated PS), and the relatively high contact angles. At 5 min exposure the oxygen concentration contains ca. 7 atomic % oxygen. The oxygen species that are implanted consist predominantly of single O-C bonds and double OC bonds but also include a small fraction of O-H. UV-O treatment leads a plateau after 2 min exposure in the water contact angle hysteresis, at a value of 67 {+-} 2, due primarily to chemical heterogeneity. Annealing above Tg allows oxygenated species to move short distances away from the surface but not diffuse further than 1-2 nm.

  11. Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge{sub 1−x}Sn{sub x} films

    Energy Technology Data Exchange (ETDEWEB)

    Gencarelli, F., E-mail: federica.gencarelli@imec.be; Heyns, M. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Department of Metallurgy and Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Grandjean, D. [Laboratory for Solid State Physics and Magnetism, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Shimura, Y.; Vandervorst, W. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Vincent, B.; Loo, R. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Banerjee, D. [Dutch-Belgian Beamline (DUBBLE), ESRF - The European Synchrotron, CS 40220, 38043 Grenoble (France); Vantomme, A.; Temst, K. [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2015-03-07

    We present an extended X-ray absorption fine structure investigation of the local environment of Sn atoms in strained and relaxed Ge{sub 1−x}Sn{sub x} layers with different compositions. We show that the preferred configuration for the incorporation of Sn atoms in these Ge{sub 1−x}Sn{sub x} layers is that of a α-Sn defect, with each Sn atom covalently bonded to four Ge atoms in a classic tetrahedral configuration. Sn interstitials, Sn-split vacancy complexes, or Sn dimers, if present at all, are not expected to involve more than 2.5% of the total Sn atoms. This finding, along with a relative increase of Sn atoms in the second atomic shell around a central Sn atom in Ge{sub 1−x}Sn{sub x} layers with increasing Sn concentrations, suggests that the investigated materials are homogeneous random substitutional alloys. Within the accuracy of the measurements, the degree of strain relaxation of the Ge{sub 1−x}Sn{sub x} layers does not have a significant impact on the local atomic surrounding of the Sn atoms. Finally, the calculated topological rigidity parameter a** = 0.69 ± 0.29 indicates that the strain due to alloying in Ge{sub 1−x}Sn{sub x} is accommodated via bond stretching and bond bending, with a slight predominance of the latter, in agreement with ab initio calculations reported in literature.

  12. Impacts of chemical amendment and plant growth on lead speciation and enzyme activities in a shooting range soil: an x-ray absorption fine structure investigation.

    Science.gov (United States)

    Hashimoto, Yohey; Matsufuru, Hiroki; Takaoka, Masaki; Tanida, Hajime; Sato, Takeshi

    2009-01-01

    In situ chemical immobilization is a practical remediation technology for metal-contaminated soils because of its capability to reduce cost and environmental impacts. We assessed the immobilization effects of poultry waste amendment and plant growth (Panicum maximum Jacq.) on Pb speciation and enzyme activities in shooting range soils. Soil contaminated with Pb was obtained from the top 20 cm of a shooting range. To evaluate Pb mobility in the soil profile treated with plants and immobilizing amendment, we used large columns filled with Pb-contaminated soil (0-20 cm, surface soils) and non-contaminated soil (20-75 cm, subsurface soils). The column study demonstrated that the amendment reduced the toxicity characteristic leaching procedure-extractable Pb in the surface soil by 90% of the Control soil. Lead mobility from the surface to subsurface profiles was significantly attenuated by plant growth but was promoted by the amendment without plant application. The extended X-ray absorption fine structure analysis revealed that the amendment reduced the proportion of PbCO(3) and Pb-organic complexes and transformed them into a more geochemically stable species of Pb(5)(PO(4))(3)Cl with 30 to 35% of the total Pb species. Applications of plant and amendment increased activities of dehydrogenase and phosphatase in the surface soil with 2.7- and 1.1-fold greater than those in Control, respectively. The use of amendments in combination with plant growth may have potential as an integrated remediation strategy that enables Pb immobilization and soil biological restoration in shooting range soils. PMID:19465717

  13. Incomplete transformations of Pb to pyromorphite by phosphate-induced immobilization investigated by X-ray absorption fine structure (XAFS) spectroscopy.

    Science.gov (United States)

    Hashimoto, Yohey; Takaoka, Masaki; Oshita, Kazuyuki; Tanida, Hajime

    2009-07-01

    For an accurate assessment of immobilization technologies, it is necessary to illustrate the transformation of target metal species into their final products. The present study employed extended X-ray absorption fine structure (EXAFS) spectroscopy combined with linear combination fitting (LCF) to determine Pb species and their proportions in contaminated soils treated with phosphate amendments. Lead contaminated soils collected from a shooting range were separately treated with calcium phosphate (CP), hydroxyapatite synthesized from ceramic waste (CHA), and incinerated poultry litter (PW). Soils were incubated at 32% water content for 7 and 380 d. The EXAFS-LCF analysis illustrated that Pb speciation in the control soil included organically-complexed phases (Pb(org), 32%), PbO (22%), PbCO(3) (28%), and Pb(3)(CO(3))(2)(OH)(2) (8%). As the incubation period increased, the proportion of chloropyromorphite [Pb(5)(PO(4))(3)Cl] increased from 20% to 27% in CHA and from 19% to 31% in CP soils. The spectra of PW-amended soils were reproduced adequately with a combination of Pb(org), PbO, and chloropyromorphite in the proportion of about 20%, 45%, and 23%, respectively. The effectiveness of amendments on Pb immobilization as indicated by the chloropyromorphite proportion was in the order of CP (31%)>CHA (27%)>PW (23%) after 380 d of incubation. Our study indicates that about 70% of Pb species was not immobilized as a form of chloropyromorphite, and the additional supply of phosphate amendment scarcely promoted chloropyromorphite formation. The EXAFS-LCF approach illustrated that organically-complexed Pb was persistent in all amended soils, suggesting that an enriched soil organic carbon may be an inhibitory factor for pyromorphite transformations. PMID:19467557

  14. Surface complexation and precipitate geometry for aqueous Zn(II) sorption on ferrihydrite I: X-ray absorption extended fine structure spectroscopy analysis

    Science.gov (United States)

    Waychunas, G.A.; Fuller, C.C.; Davis, J.A.

    2002-01-01

    "Two-line" ferrihydrite samples precipitated and then exposed to a range of aqueous Zn solutions (10-5 to 10-3 M), and also coprecipitated in similar Zn solutions (pH 6.5), have been examined by Zn and Fe K-edge X-ray absorption spectroscopy. Typical Zn complexes on the surface have Zn-O distances of 1.97(0.2) A?? and coordination numbers of about 4.0(0.5), consistent with tetrahedral oxygen coordination. This contrasts with Zn-O distances of 2.11(.02) A?? and coordination numbers of 6 to 7 in the aqueous Zn solutions used in sample preparation. X-ray absorption extended fine structure spectroscopy (EXAFS) fits to the second shell of cation neighbors indicate as many as 4 Zn-Fe neighbors at 3.44(.04) A?? in coprecipitated samples, and about two Zn-Fe neighbors at the same distance in adsorption samples. In both sets of samples, the fitted coordination number of second shell cations decreases as sorption density increases, indicating changes in the number and type of available complexing sites or the onset of competitive precipitation processes. Comparison of our results with the possible geometries for surface complexes and precipitates suggests that the Zn sorption complexes are inner sphere and at lowest adsorption densities are bidentate, sharing apical oxygens with adjacent edge-sharing Fe(O,OH)6 octahedra. Coprecipitation samples have complexes with similar geometry, but these are polydentate, sharing apices with more than two adjacent edge-sharing Fe(O,OH)6 polyhedra. The results are inconsistent with Zn entering the ferrihydrite structure (i.e., solid solution formation) or formation of other Zn-Fe precipitates. The fitted Zn-Fe coordination numbers drop with increasing Zn density with a minimum of about 0.8(.2) at Zn/(Zn + Fe) of 0.08 or more. This change appears to be attributable to the onset of precipitation of zinc hydroxide polymers with mainly tetrahedral Zn coordination. At the highest loadings studied, the nature of the complexes changes further

  15. Apparatus for In Situ X-Ray Absorption Fine Structure Studies on Catalytic Systems in the Energy Range 1000 eV

    NARCIS (Netherlands)

    Koningsberger, D.C.; Eerden, A.M.J. van der; Bokhoven, J.A. van; Smith, A.D.

    2000-01-01

    A new apparatus for in situ x-ray absoprtion fine structure measurements in the medium energy range of 1000–3500 eV has been developed. Measurements can be performed in a gaseous environment (max. pressure 1 bar) at temperatures ranging from 80 to 750 K. Pre-treatments can be performed at 5 bar and

  16. Antimony(III) complexing with O-bearing organic ligands in aqueous solution: An X-ray absorption fine structure spectroscopy and solubility study

    Science.gov (United States)

    Tella, Marie; Pokrovski, Gleb S.

    2009-01-01

    The stability and structure of aqueous complexes formed by trivalent antimony (Sb III) with carboxylic acids (acetic, adipic, malonic, lactic, oxalic, tartaric, and citric acid), phenols (catechol), and amino acids (glycine) having O- and N-functional groups (carboxyl, alcoholic hydroxyl, phenolic hydroxyl and amine) typical of natural organic matter, were determined at 20 and 60 °C from solubility and X-ray absorption fine structure (XAFS) spectroscopy measurements. In organic-free aqueous solutions and in the presence of acetic, adipic, malonic acids and glycine, both spectroscopic and solubility data are consistent with the dominant formation of Sb III hydroxide species, Sb(OH)3-nn+,Sb(OH)30andSb(OH)4-, at strongly acid, acid-to-neutral and basic pH, respectively, demonstrating negligible complexing with mono-functional organic ligands (acetic) or those having non adjacent carboxylic groups (adipic, malonic). In contrast, in the presence of poly-functional carboxylic and hydroxy-carboxylic acids and catechol, Sb III forms stable 1:1 and 1:2 complexes with the studied organic ligands over a wide pH range typical of natural waters (3 cycle. Stability constants for these species, generated from Sb 2O 3 (rhomb.) solubility experiments, were used to model Sb complexing with natural humic acids possessing the same functional groups as those investigated in this study. Our predictions show that in an aqueous solution of pH between 2 and 10, containing 1 μg/L of Sb and 5 mg/L of dissolved organic carbon (DOC), up to 35% of total dissolved Sb binds to aqueous organic matter via carboxylic and hydroxy-carboxylic groups. This amount of complexed Sb for typical natural DOC concentrations is in agreement with that estimated from dialysis experiments performed with commercial humic acid in our work and those available in the literature for a range of standardized IHSS humic acids. Our results imply that a significant part of Sb is likely to be bound with humic acids via

  17. Extended X-ray absorption fine structure studies of Zn2Fe2 hybrid hemoglobins: absence of heme bond length changes in half-ligated species.

    Science.gov (United States)

    Simolo, K; Korszun, Z R; Stucky, G; Moffat, K; McLendon, G; Bunker, G

    1986-07-01

    Metal hybrid hemoglobins, in which Zn(II) replaces Fe(II), have been structurally characterized by extended X-ray absorption structure (EXAFS) studies. Since Zn and Fe have very different K absorption edge energies, the structures of the ligated (Fe) and unligated (Zn) sites could be examined independently within a single molecule that mimics an intermediate ligation state. The observed EXAFS spectra and associated structural parameters are compared among the ligand free (alpha Zn)2(beta Zn)2, half-ligated (alpha FeCO)2(beta Zn)2 and (alpha Zn)2(beta FeCO)2, and fully ligated (alpha FeCO)2(beta FeCO)2 systems.

  18. In situ Fe K-edge X-ray absorption fine structure of a pyrite electrode in a Li/polyethylene oxide (LiClO{sub 4})/FeS{sub 2} battery environment

    Energy Technology Data Exchange (ETDEWEB)

    Totir, D.; Bae, I.T.; Hu, Y.; Scherson, D.A. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Chemistry; Antonio, M.R. [Argonne National Lab., IL (United States). Chemistry Div.

    1996-12-31

    Electronic and structural properties of materials generated by the reduction and subsequent oxidation of pyrite in a lithium-based solid polymer electrolyte have been examined by in situ fluorescence Fe K-edge X-ray absorption fine structure (XAFS) in a FeS{sub 2}/Li battery environment. The XAFS results obtained are consistent with the formation of metallic iron as one of the products of the full (4-electron) discharge, in agreement with information reported in other laboratories. Extended X-ray absorption fine structure (EXAFS) data reveal that a subsequent 2-electron or 4-electron recharge generates a species with a Fe-S bond distance identical to that of pyrite, d(Fe-S) = 2.259 {angstrom}, with no other clearly detectable interactions due to more distant atoms. Based on the similarities between the metrical parameters and other features in the X-ray absorption near edge structure (XANES), the ferrous sites in these species appear to be tetrahedrally coordinated, as in chalcopyrite (CuFeS{sub 2}), for which d(Fe-S) is 2.257 {angstrom}, and, thus, different than in Li{sub 2} FeS{sub 2}, a material that exhibits longer Fe-S distances.

  19. Fine structure constant variation or spacetime anisotropy?

    International Nuclear Information System (INIS)

    Recent observations on the quasar absorption spectra supply evidence for the variation of the fine structure constant α. In this paper, we propose another interpretation of the observational data on the quasar absorption spectra: a scenario with spacetime inhomogeneity and anisotropy. Maybe the spacetime is characterized by the Finsler geometry instead of the Riemann one. The Finsler geometry admits fewer symmetries than the Riemann geometry does. We investigate the Finslerian geodesic equations in the Randers spacetime (a special Finsler spacetime). It is found that the cosmological redshift in this spacetime deviates from the one in general relativity. The modification term to the redshift could be generally revealed as a monopole plus dipole function of spacetime locations and directions. We suggest that this modification corresponds to the spatial monopole and dipole of α variation in the quasar absorption spectra. (orig.)

  20. Structural Study of Cu-Deficient Cu2(1-x)ZnSnSe4 Solar Cell Materials by X-ray Diffraction and X-ray Absorption Fine Structure

    Science.gov (United States)

    Gao, Feng; Yamazoe, Seiji; Maeda, Tsuyoshi; Wada, Takahiro

    2012-10-01

    Cu-poor Cu2(1-x)ZnSnSe4 powders were prepared from elemental powders. The crystal structure of Cu-poor Cu2(1-x)ZnSnSe4 was examined by X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) analyses. Kesterite-type Cu2(1-x)ZnSnSe4 could be prepared in the range of 0≤x ≤0.0750. The lattice parameters were refined by the Rietveld analysis of X-ray diffraction data. The lattice constants a and c decreased with a decrease in the Cu/(Zn+Sn) ratio. However, there was little change in c/a value. On the other hand, the position of the Se atom (u parameters) changed considerably. The XAFS study showed that the local structure of Sn in Cu2ZnSnSe4 (CZTSe) changed with a decrease in Cu/(Zn+Sn) ratio and the local structural changes in Cu, Zn, or Se could not be clearly observed. These local structural changes around Sn are due to the disordering of Cu, Zn, and Sn atoms. The diffuse reflectance spectra showed that the band gap of Cu2ZnSnSe4 is 0.98 eV and that the band gaps do not depend on Cu/(Zn+Sn) ratio in the range of 0≤x ≤0.0750.

  1. Surface atomic structures of Fe2O3 nanoparticles coated with cetyltrimethyl ammonium bromide and sodium dodecyl benzene sulphonate:an extended x-ray absorption fine-structure study

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Fe2O3 nanoparticles coated with sodium dodecyl benzene sulphonate(DBS)or cetyltrimethyl ammonium bromide(CTAB) were prepared by using a microemulsion method in the system water/toluene.The nanoparticles were characterized by means of transmission electron microscopy and average particle sizes of 5.0nm and 6.0nm were found for DBS-modified and CTAB-modified nanoparticles respectively.The local atomic structures of these iron(Ⅲ) oxide nanoparticles were probed by using the extended x-ray absorption fine-structure technique.Fe K absorption spectra were collected at beam line 4W1B of Beijing Synchrotron Radiation Facility.A structureal model was proposed for describing their atomic structures.The Fe-O bond length at the surface of DBS-coated Fe2O3 nanoparticles was found to be similar to that in bulk Fe2O3.but there was about 0.04A expansion for the CTAB-coated Fe2O3 nanoparticles.On the basis of the model proposed in this paper,the thicknesses of the surface layers were estimated to be 0.5nm and 0.7nm.respectively,for the DBS-coated and CTAB-coated Fe2O3 nanoparticles.The anharmonicity of the atomic vibration and the asymmetry of atom-pair distribution were found to be larger at the surface of the nanoparticles than in the bulk material,while the Debye-Waller factors are almost the same for the surface and the core parts of the nanoparticles.It can be concluded that the atomic structure of the nanoparticle surface is ordered.but the atom-pari distribution is asymmetric.

  2. Observations of substorm fine structure

    Directory of Open Access Journals (Sweden)

    L. L. Lazutin

    Full Text Available Particle and magnetic field measurements on the CRRES satellite were used, together with geosynchronous satellites and ground-based observations, to investigate the fine structure of a magnetospheric substorm on February 9, 1991. Using the variations in the electron fluxes, the substorm activity was divided into several intensifications lasting about 3–15 minutes each. The two main features of the data were: (1 the intensifications showed internal fine structure in the time scale of about 2 minutes or less. We call these shorter periods activations. Energetic electrons and protons at the closest geosynchronous spacecraft (1990 095 were found to have comparable activation structure. (2 The energetic (>69 keV proton injections were delayed with respect to electron injections, and actually coincided in time with the end of the intensifications and partial returns to locally more stretched field line configuration. We propose that the energetic protons could be able to control the dynamics of the system locally be quenching the ongoing intensification and possibly preparing the final large-scale poleward movement of the activity. It was also shown that these protons originated from the same intensification as the preceeding electrons. Therefore, the substorm instability responsible for the intensifications could introduce a negative feedback loop into the system, creating the observed fine structure with the intensification time scales.

    Key words. Magnetospheric Physics (Storms and substorms.

  3. Local structures of mechanically alloyed Fe100—xCux solid soulutions studied by X—ray absorption fine structure

    Institute of Scientific and Technical Information of China (English)

    WenshengYan; YuzhiLi; 等

    2001-01-01

    The local structures of the immiscible Fe100-xCux alloys(x=0,10,20,40,60,80and100)produced by mechanical alloying have been investigated by XAFS.For the Fe100-xCux(x≥40) solid solutions,the local structures around Fe atoms change from bcc structure to fcc one and the Cu atoms maintain the original coordination geometry after milling for 160 hours.On the contrary,the local structures around Cu atoms in both of Fe80Cu20 and Fe90 Cu10 alloys appear a transition from fcc to bcc structure.We found that the Debye-waller factor σof fcc Fe-Cu phase is larger than that of bcc F-Cu phase,and the σ(0.099A°)around Fe atoms is larger than that (0.089A°) of Cu in the Fe100-xCux(x≥40)solid solutions,This suggests that the mechanically alloyed Fe100-xCux supersaturated solid solution is not a homogeneous alloy,and consists of Fe-rich and Cu-rich regions for various compositions.A possible mechanism for bcc-to-fcc and fcc-to-bcc changes in Fe100-xCux solid solutions is discussed in relation to the interdiffusion and transition induced by the ball milling.

  4. Determining biological fine structure by differential absorption of soft x-rays. [Ultrastructural studies of nerve fibers using scanning electron microscopy without need for staining or osmication

    Energy Technology Data Exchange (ETDEWEB)

    Panessa-Warren, Barbara J.; Warren, John B.

    1979-06-01

    The use of soft x-ray contact microscopy in examining histochemically treated human tissue embedded in plastic and exposed as unstained thin sections is demonstrated. When our preliminary data revealed that we could clearly image not only the histochemical reaction product, but the unstained biological fine structure of the surrounding tissues, we decided to test our hypothesis further and see if we could image unstained biological molecular aggregates as well. For this part of the investigation, we chose to examine hydrated proteoglycan aggregates. Proteoglycans are an essential component of the organic matrix of cartilage, and play a primary role in the retention and maintenance of extracellular water. To avoid any artifacts due to the introduction of exogeneous materials, and examine the proteoglycan aggregates in their hydrated, natural configuration, we made contact x-ray images of isolated proteoglycan aggregates in water.

  5. Structural characterization of Bi2Te3 and Sb2Te3 as a function of temperature using neutron powder diffraction and extended X-ray absorption fine structure techniques

    International Nuclear Information System (INIS)

    The structure of Bi2Te3 (Seebeck coefficient Standard Reference Material (SRM™ 3451)) and the related phase Sb2Te3 have been characterized as a function of temperature using the neutron powder diffraction (NPD) and the extended X-ray absorption fine structure (EXAFS) techniques. The neutron structural studies were carried out from 20 K to 300 K for Bi2Te3 and from 10 K to 298 K for Sb2Te3. The EXAFS technique for studying the local structure of the two compounds was conducted from 19 K to 298 K. Bi2Te3 and Sb2Te3 are isostructural, with a space group of R3¯m. The structure consists of repeated quintuple layers of atoms, Te2-M-Te1-M-Te2 (where M = Bi or Sb) stacking along the c-axis of the unit cell. EXAFS was used to examine the bond distances and static and thermal disorders for the first three shells of Bi2Te3 and Sb2Te3 as a function of temperature. The temperature dependencies of thermal disorders were analyzed using the Debye and Einstein models for lattice vibrations. The Debye and Einstein temperatures for the first two shells of Bi2Te3 are similar to those of Sb2Te3 within the uncertainty in the data. However, the Debye and Einstein temperatures for the third shell of Bi-Bi are significantly lower than those of the third shell of Sb-Sb. The Einstein temperature for the third shell is consistent with a soft phonon mode in both Bi2Te3 and Sb2Te3. The lower Einstein temperature of Bi-Bi relative to Sb-Sb is consistent with the lower value of thermal conductivity of Bi2Te3 relative to Sb2Te3

  6. Study on accumulation mechanism of cadmium in rice (oriza sativa L.) by micro-XRF imaging and x-ray absorption fine structure analysis utilizing synchrotron radiation

    International Nuclear Information System (INIS)

    This paper reports on the distribution of Cd and essential elements in the stems of rice plants, 'Nipponbare' and 'Milyang 23', measured by synchrotron radiation micro-XRF imaging. X-ray absorption near edge structure (XANES) analysis was applied to estimate the chemical forms of Cd in the roots, stems and leaves, aiming to reveal the mechanisms of Cd transport in rice. The results show that the Cd concentration of 'Nipponbare' was found to be higher than that of 'Milyang 23' at the root, although there was no significant difference between these two cultivars at the shoot. In addition, the distribution of Cd and the essential elements inside the plant were clearly revealed by micro-XRF imaging. It was found that Cd was also localized to the bundle. The Cd K-edge XANES analysis indicated that Cd was bound to sulfur in the root for both rice plants. Furthermore, the content of Cd combining with S (Cd-S) in the stem of 'Nipponbare' became 1.5 times higher after exposing to Cd for a long time, while only a slight change in the stem of 'Milyang 23' was found. In contrast with the stem, the leaf of 'Nipponbare' contained a lower Cd-S content than that of the control after a long-term exposure, while that of 'Milyang 23' became higher. In conclusion, the difference in the chemical form of Cd at the shoots affected the different accumulation behaviors of Cd between 'Nipponbare' and 'Milyang 23'. (author)

  7. Probing cation antisite disorder in Gd2 Ti2 O7 pyrochlore by site-specific near-edge x-ray-absorption fine structure and x-ray photoelectron spectroscopy

    Science.gov (United States)

    Nachimuthu, P.; Thevuthasan, S.; Engelhard, M. H.; Weber, W. J.; Shuh, D. K.; Hamdan, N. M.; Mun, B. S.; Adams, E. M.; McCready, D. E.; Shutthanandan, V.; Lindle, D. W.; Balakrishnan, G.; Paul, D. M.; Gullikson, E. M.; Perera, R. C. C.; Lian, J.; Wang, L. M.; Ewing, R. C.

    2004-09-01

    Disorder in Gd2Ti2O7 is investigated by near-edge x-ray-absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy (XPS). NEXAFS shows Ti4+ ions occupy octahedral sites with a tetragonal distortion induced by vacant oxygen sites. O1s XPS spectra obtained with a charge neutralization system from Gd2Ti2O7(100) and the Gd2Ti2O7 pyrochlore used by Chen [Phys. Rev. Lett. 88, 105901 (2002)], both yielded a single peak, unlike the previous result on the latter that found two peaks. The current results give no evidence for an anisotropic distribution of Ti and O. The extra features reported in the aforementioned communication resulted from charging effects and incomplete surface cleaning. Thus, a result confirming the direct observation of simultaneous cation-anion antisite disordering and lending credence to the split vacancy model has been clarified.

  8. Structural characterization of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} as a function of temperature using neutron powder diffraction and extended X-ray absorption fine structure techniques

    Energy Technology Data Exchange (ETDEWEB)

    Mansour, A. N. [Naval Surface Warfare Center, Carderock Division, West Bethesda, Maryland 20817 (United States); Wong-Ng, W. [Materials Measurement Science Division National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Huang, Q. [Center for Neutron Research National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Tang, W. [Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018 (China); Thompson, A.; Sharp, J. [Marlow Industries, Inc Dallas, Texas 75238 (United States)

    2014-08-28

    The structure of Bi{sub 2}Te{sub 3} (Seebeck coefficient Standard Reference Material (SRM™ 3451)) and the related phase Sb{sub 2}Te{sub 3} have been characterized as a function of temperature using the neutron powder diffraction (NPD) and the extended X-ray absorption fine structure (EXAFS) techniques. The neutron structural studies were carried out from 20 K to 300 K for Bi{sub 2}Te{sub 3} and from 10 K to 298 K for Sb{sub 2}Te{sub 3}. The EXAFS technique for studying the local structure of the two compounds was conducted from 19 K to 298 K. Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} are isostructural, with a space group of R3{sup ¯}m. The structure consists of repeated quintuple layers of atoms, Te2-M-Te1-M-Te2 (where M = Bi or Sb) stacking along the c-axis of the unit cell. EXAFS was used to examine the bond distances and static and thermal disorders for the first three shells of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} as a function of temperature. The temperature dependencies of thermal disorders were analyzed using the Debye and Einstein models for lattice vibrations. The Debye and Einstein temperatures for the first two shells of Bi{sub 2}Te{sub 3} are similar to those of Sb{sub 2}Te{sub 3} within the uncertainty in the data. However, the Debye and Einstein temperatures for the third shell of Bi-Bi are significantly lower than those of the third shell of Sb-Sb. The Einstein temperature for the third shell is consistent with a soft phonon mode in both Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3}. The lower Einstein temperature of Bi-Bi relative to Sb-Sb is consistent with the lower value of thermal conductivity of Bi{sub 2}Te{sub 3} relative to Sb{sub 2}Te{sub 3}.

  9. Limits on the temporal variation of the fine structure constant, quark masses and strong interaction from quasar absorption spectra and atomic clock experiments

    CERN Document Server

    Flambaum, V V; Thomas, A W; Young, R D

    2004-01-01

    We perform calculations of the dependence of nuclear magnetic moments on quark masses and obtain limits on the variation of $(m_q/\\Lambda_{QCD})$ from recent measurements of hydrogen hyperfine (21 cm) and molecular rotational transitions in quasar absorption systems, atomic clock experiments with hyperfine transitions in H, Rb, Cs, Yb$^+$, Hg$^+$ and optical transition in Hg$^+$. Experiments with Cd$^+$, deuterium/hydrogen, molecular SF$_6$ and Zeeman transitions in $^3$He/Xe are also discussed.

  10. Limits on the time variation of the electromagnetic fine-structure constant in the low energy limit from absorption lines in the spectra of distant quasars

    International Nuclear Information System (INIS)

    We present the results of a detailed many-multiplet analysis performed on a new sample of Mg ii systems observed in high quality quasar spectra obtained using the Very Large Telescope. The weighted mean value of the variation in α derived from our analysis over the redshift range 0.4≤z≤2.3 is Δα/α=(-0.06±0.06)x10-5. The median redshift of our sample (z≅1.55) corresponds to a look-back time of 9.7 Gyr in the most favored cosmological model today. This gives a 3σ limit, -2.5x10-16≤(Δα/αΔt)≤+1.2x10-16 yr-1, for the time variation of α, that forms the strongest constraint obtained based on high redshift quasar absorption line systems

  11. Near-edge x-ray absorption fine-structure study of ion-beam-induced phase transformation in Gd2(Ti1-yZry)2O7

    Science.gov (United States)

    Nachimuthu, P.; Thevuthasan, S.; Shutthanandan, V.; Adams, E. M.; Weber, W. J.; Begg, B. D.; Shuh, D. K.; Lindle, D. W.; Gullikson, E. M.; Perera, R. C. C.

    2005-02-01

    The structural and electronic properties of Gd2(Ti1-yZry)2O7 (y =0-1) pyrochlores following a 2.0-MeV Au2+ ion-beam irradiation (˜5.0×1014Au2+/cm2) have been investigated by Ti2p and O1s near-edge x-ray absorption fine structure (NEXAFS). The irradiation of Gd2(Ti1-yZry)2O7 leads to the phase transformation from the ordered pyrochlore structure (Fd3m) to the defect fluorite structure (Fm3m) regardless of Zr concentration. Irradiated Gd2(Ti1-yZry)2O7 with y ⩽0.5 are amorphous, although significant short-range order is present. Contrasting to this behavior, compositions with y ⩾0.75 retain crystallinity in the defect fluorite structure following irradiation. The local structures of Zr4+ in the irradiated Gd2(Ti1-yZry)2O7 with y ⩾0.75 determined by NEXAFS are the same as in the cubic fluorite-structured yttria-stabilized zirconia (Y -ZrO2), thereby providing conclusive evidence for the phase transformation. The TiO6 octahedra present in Gd2(Ti1-yZry)2O7 are completely modified by ion-beam irradiation to TiOx polyhedra, and the Ti coordination is increased to eight with longer Ti -O bond distances. The similarity between cation sites and the degree of disorder in Gd2Zr2O7 facilitate the rearrangement and relaxation of Gd, Zr, and O ions/defects. This inhibits amorphization during the ion-beam-induced phase transition to the radiation-resistant defect fluorite structure, which is in contrast to the ordered Gd2Ti2O7.

  12. A theoretical and experimental study of the near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectra (XPS) of nucleobases: Thymine and adenine

    Energy Technology Data Exchange (ETDEWEB)

    Plekan, O. [Sincrotrone Trieste, Area Science Park, I-34012 Basovizza, Trieste (Italy); Feyer, V. [CNR-IMIP, Montelibretti, Rome I-00016 (Italy); Richter, R. [Sincrotrone Trieste, Area Science Park, I-34012 Basovizza, Trieste (Italy); Coreno, M. [CNR-IMIP, Montelibretti, Rome I-00016 (Italy); De Simone, M. [Laboratorio Nazionale TASC, INFM-CNR, 34012 Trieste (Italy); Prince, K.C. [Sincrotrone Trieste, Area Science Park, I-34012 Basovizza, Trieste (Italy); Laboratorio Nazionale TASC, INFM-CNR, 34012 Trieste (Italy); Trofimov, A.B. [Laboratory of Quantum Chemistry, Irkutsk State University, Karl Marx str. 1, 664003 Irkutsk (Russian Federation); Gromov, E.V. [Laboratory of Quantum Chemistry, Irkutsk State University, Karl Marx str. 1, 664003 Irkutsk (Russian Federation); Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany); Zaytseva, I.L. [Laboratory of Quantum Chemistry, Irkutsk State University, Karl Marx str. 1, 664003 Irkutsk (Russian Federation); Schirmer, J. [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany)], E-mail: Jochen.Schirmer@pci.uni-heidelberg.de

    2008-05-23

    The core level electron excitation and ionization spectra of thymine and adenine have been investigated by photoabsorption and photoemission spectroscopy, and the results interpreted by means of ab initio calculations using the second-order algebraic-diagrammatic construction (ADC(2)) method for the polarization propagator and the fourth-order ADC method (ADC(4)) for the one-particle Green's function. The photoabsorption spectra are dominated by transitions from core levels to unoccupied {pi} states, but also show clear structures due to Rydberg transitions. The calculated spectra are in good agreement with the experimental results, and many of the observed structures are assigned.

  13. Was the fine-structure constant variable over cosmological time?

    International Nuclear Information System (INIS)

    Cosmological variation of the fine-structure constant (α) dependent on the redshifts of quasars. Using the emission (absorption) systems in the spectra of distant quasars, we investigate the effects of the cosmology variability in the value of the fine-structure constant (α) dependent on the redshifts of quasars during the evolution of Universe. We obtain optical spectra of fine-structure transitions in [Ne-III], [Ne-V], [O-III], [O-I], and [S-II] multiplets from a sample of 14 Seyfert 1.5 galaxies in the low-z range. 0.035 2(t)/α2(0) = (0.999965 ± 0.00005529). (authors)

  14. Cosmological Constant, Fine Structure Constant and Beyond

    CERN Document Server

    Wei, Hao; Li, Hong-Yu; Xue, Dong-Ze

    2016-01-01

    In this work, we consider the cosmological constant model $\\Lambda\\propto\\alpha^{-6}$, which is well motivated from three independent approaches. As is well known, the evidence of varying fine structure constant $\\alpha$ was found in 1998. If $\\Lambda\\propto\\alpha^{-6}$ is right, it means that the cosmological constant $\\Lambda$ should be also varying. In this work, we try to develop a suitable framework to model this varying cosmological constant $\\Lambda\\propto\\alpha^{-6}$, in which we view it from an interacting vacuum energy perspective. We propose two types of models to describe the evolutions of $\\Lambda$ and $\\alpha$. Then, we consider the observational constraints on these models, by using the 293 $\\Delta\\alpha/\\alpha$ data from the absorption systems in the spectra of distant quasars, and the data of type Ia supernovae (SNIa), cosmic microwave background (CMB), baryon acoustic oscillation (BAO). We find that the model parameters can be tightly constrained to the narrow ranges of ${\\cal O}(10^{-5})$ t...

  15. X-ray absorption fine structure evidence for amorphous zinc sulfide as a major zinc species in suspended matter from the Seine River downstream of Paris, Ile-de-France, France.

    Science.gov (United States)

    Priadi, Cindy; Le Pape, Pierre; Morin, Guillaume; Ayrault, Sophie; Maillot, Fabien; Juillot, Farid; Hochreutener, Rebecca; Llorens, Isabelle; Testemale, Denis; Proux, Olivier; Brown, Gordon E

    2012-04-01

    Zinc is one of the most widespread trace metals (TMs) in Earth surface environments and is the most concentrated TM in the downstream section of the Seine River (France) due to significant anthropogenic input from the Paris conurbation. In order to better identify the sources and cycling processes of Zn in this River basin, we investigated seasonal and spatial variations of Zn speciation in suspended particulate matter (SPM) in the oxic water column of the Seine River from upstream to downstream of Paris using synchrotron-based extend X-ray absorption fine structure (EXAFS) spectroscopy at the Zn K-edge. First-neighbor contributions to the EXAFS were analyzed in SPM samples, dried and stored under a dry nitrogen atmosphere or under an ambient oxygenated atmosphere. We found a sulfur first coordination environment around Zn (in the form of amorphous zinc sulfide) in the raw SPM samples stored under dry nitrogen vs an oxygen first coordination environment around Zn in the samples stored in an oxygenated atmosphere. These findings are supported by scanning electron microscopy and energy dispersive X-ray spectrometry observations. Linear combination fitting of the EXAFS data for SPM samples, using a large set of EXAFS spectra of Zn model compounds, indicates dramatic changes in the Zn speciation from upstream to downstream of Paris, with amorphous ZnS particles becoming dominant dowstream. In contrast, Zn species associated with calcite (either adsorbed or incorporated in the structure) are dominant upstream. Other Zn species representing about half of the Zn pool in the SPM consist of Zn-sorbed on iron oxyhydroxides (ferrihydrite and goethite) and, to a lesser extent, Zn-Al layered double hydroxides, Zn incorporated in dioctahedral layers of clay minerals and Zn sorbed to amorphous silica. Our results highlight the importance of preserving the oxidation state in TM speciation studies when sampling suspended matter, even in an oxic water column.

  16. Effect of Iron(II) on Arsenic Sequestration by δ-MnO2: Desorption Studies Using Stirred-Flow Experiments and X-Ray Absorption Fine-Structure Spectroscopy.

    Science.gov (United States)

    Wu, Yun; Li, Wei; Sparks, Donald L

    2015-11-17

    Arsenic (As) mobility in the environment is greatly affected by its oxidation state and the degree to which it is sorbed on metal oxide surfaces. Manganese (Mn) and iron (Fe) oxides are ubiquitous solids in terrestrial systems and have high sorptive capacities for many trace metals, including As. Although numerous studies have studied the effects of As adsorption and desorption onto Fe and Mn oxides individually, the fate of As within mixed systems representative of natural environments has not been resolved. In this research, As(III) was initially reacted with a poorly crystalline phyllomanganate (δ-MnO2) in the presence of Fe(II) prior to desorption. This initial reaction resulted in the sorption of both As(III) and As(V) on mixed Fe/Mn-oxides surfaces. A desorption study was carried out using two environmentally significant ions, phosphate (PO4(3-)) and calcium (Ca(2+)). Both a stirred-flow technique and X-ray absorption fine-structure spectroscopy (XAFS) analysis were used to investigate As desorption behavior. Results showed that when As(III)/Fe(II) = 1:1 in the initial reaction, only As(V) was desorbed, agreeing with a previous study showing that As(III) is not associated with the Fe/Mn-oxides. When As(III)/Fe(II) = 1:10 in the initial reaction, both As(III) and As(V) can be desorbed from the Fe/Mn-oxide surface, and more As(III) is desorbed than As(V). Neither of the desorbents used in this study completely removed As(III) or As(V) from the Fe/Mn-oxides surface. However, the As desorption fraction decreases with increasing Fe(II) concentration in the initial reactions.

  17. Combined time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure spectroscopy study on the complexation of trivalent actinides with chloride at T = 25-200 °C.

    Science.gov (United States)

    Skerencak-Frech, Andrej; Fröhlich, Daniel R; Rothe, Jörg; Dardenne, Kathy; Panak, Petra J

    2014-01-21

    The complexation of trivalent actinides (An(III)) with chloride is studied in the temperature range from 25 to 200 °C by spectroscopic methods. Time-resolved laser fluorescence spectroscopy (TRLFS) is applied to determine the thermodynamic data of Cm(III)-Cl(-) complexes, while extended X-ray absorption fine structure spectroscopy (EXAFS) is used to determine the structural data of the respective Am(III) complexes. The experiments are performed in a custom-built high-temperature cell which is modified for the respective spectroscopic technique. The TRLFS results show that at 25 °C the speciation is dominated mainly by the Cm(3+) aquo ion. Only a minor fraction of the CmCl(2+) complex is present in solution. As the temperature increases, the fraction of this species decreases further. Simultaneously, the fraction of the CmCl2(+) complex increases strongly with the temperature. Also, the CmCl3 complex is formed to a minor extent at T > 160 °C. The conditional stability constant log β'2 is determined as a function of the temperature and extrapolated to zero ionic strength with the specific ion interaction theory approach. The log β°2(T) values increase by more than 3 orders of magnitude in the studied temperature range. The temperature dependency of log β°2 is fitted by the extended van't Hoff equation to determine ΔrH°m, ΔrS°m, and ΔrC°p,m. The EXAFS results support these findings. The results confirm the absence of americium(III) chloride complexes at T = 25 and 90 °C ([Am(III)] = 10(-3) m, [Cl(-)] = 3.0 m), and the spectra are described by 9-10 oxygen atoms at a distance of 2.44-2.48 Å. At T = 200 °C two chloride ligands are present in the inner coordination sphere of Am(III) at a distance of 2.78 Å.

  18. Habitable sphere and fine structure constant

    CERN Document Server

    Kozlovskii, Miroslaw P; Kozlowski, Miroslaw; Marciak-Kozlowska, Janina

    2005-01-01

    Future space missions, TPF and Darwin will focus on searches of signatures of life on extrasolar planets. In this paper we look for model independ definition of the habitable zone. It will be shown that the radius of the habitable sphere depends only on the constants of the Nature. Key words: Habitable sphere, fine structure constant.

  19. Structural sound absorption in liquid metals

    International Nuclear Information System (INIS)

    Present article is devoted to structural sound absorption in liquid metals. The study of sound absorption in liquid metals shown that in all studied objects the structural absorption of sound was observed. The mechanism of structural relaxation in molten metal was revealed.

  20. Extended X-ray absorption fine structure studies of Zn/sub 2/Fe/sub 2/ hybrid hemoglobins: absence of heme bond length changes in half-ligated species

    Energy Technology Data Exchange (ETDEWEB)

    Simolo, K.; Korszun, Z.R.; Stucky, G.; Moffat, K.; McLendon, G.

    1986-07-01

    Metal hybrid hemoglobins, in which Zn(II) replaces Fe(II), have been structurally characterized by extended X-ray absorption structure (EAFS) studies. Since Zn and Fe have very different K absorption edge energies, the structures of the ligated (Fe) and unligated (Zn) sites could be examined independently within a single molecule that mimics an intermediate ligation state. The observed EXAFS spectra and associated structural parameters are compared among the ligand free (..cap alpha..Zn)/sub 2/(..beta..Zn)/sub 2/, half-ligated (..cap alpha..FeCO)/sub 2/(..beta..Zn)/sub 2/ and (..cap alpha..Zn)/sub 2/(..beta..FeCO)/sub 2/, and fully ligated (..cap alpha..FeCO)/sub 2/(..beta..FeCO)/sub 2/ systems.

  1. Microwave non-resonant absorption in fine cobalt ferrite particles

    Energy Technology Data Exchange (ETDEWEB)

    Mata-Zamora, M.E. [Depto. Investigacion Aplicada, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, 04510 (Mexico)]. E-mail: memzamora@yahoo.com.mx; Montiel, H. [Depto. Investigacion Aplicada, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, 04510 (Mexico); Alvarez, G. [Depto. Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, 04510 (Mexico); Saniger, J.M. [Depto. Investigacion Aplicada, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, 04510 (Mexico); Zamorano, R. [Escuela Superior de Fisica y Matematicas, IPN, 07738 (Mexico); Valenzuela, R. [Depto. Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, 04510 (Mexico)

    2007-09-15

    Cobalt ferrite particles of average crystallite size of 11 nm were obtained by a sol-gel process at 400 deg. C . The powders were annealed at temperatures of 500, 600, 700 and 800 deg. C in air. Derivative microwave power absorption (dP/dH) measurements were carried out as a function of magnetic field (H {sub DC}) at X band (9.4 GHz), in the field range -80-796 kA/m for all annealed temperatures. In order to compare the response of saturation magnetization measurements with high frequency measurements, we calculated the areas inside both the magnetization (A {sub M}) and the absorption hysteresis loops (A {sub LFS}). The dependence of these areas as a function of crystallite size is remarkably similar in both experiments.

  2. Gravitational Interactions and Fine-Structure Constant

    CERN Document Server

    Jentschura, U D; Nandori, I

    2015-01-01

    Electromagnetic and gravitational central-field problems are studied with relativistic quantum mechanics on curved space-time backgrounds. Corrections to the transition current are identified. Analogies of the gravitational and electromagnetic spectra suggest the definition of a gravitational fine-structure constant. The electromagnetic and gravitational coupling constants enter the Einstein-Hilbert-Maxwell Lagrangian. We postulate that the variational principle holds with regard to a global dilation transformation of the space-time coordinates. The variation suggests is consistent with a functional relationship of the form alpha_QED being proportional to alpha_G^(1/2), where alpha_QED is the electrodynamic fine-structure constant, and alpha_G its gravitational analogue.

  3. Effect of fine structure on precise diagnostics

    International Nuclear Information System (INIS)

    Nowadays, in order to do effective spectroscopy, several experimental conditions force us to describe very precisely the emitter atom. For example, in a tokamak, the cold peripheral plasma emits intense spectral line from hydrogen isotopes broadened by Zeeman and Doppler effect. Under such conditions of low temperatures, we have to take care if fine structure modifies and/or broadens the spectrum. Moreover, under some conditions encountered in Motional Stark effect spectroscopy, asymmetries in the observed spectra could be explained by fine structure effects. Our team has developed since several years a numerical code able to calculate line shape emitted by any kind of atoms perturbed by electric and magnetic fields. This permits to us to explore very large conditions of plasmas. In this poster we will investigate the effect of fine structure on the spectroscopy of deuterium in tokamak edge plasma conditions, as well as in the case of Motional Stark effect. We will consider a wide range of temperatures varying from a few eV to 104 eV, and magnetic field between 0 to 5 Teslas. (author)

  4. Variation of the fine structure constant

    CERN Document Server

    Lipovka, Anton A

    2016-01-01

    In present paper we evaluate the fine structure constant variation which should take place as the Universe is expanded and its curvature is changed adiabatically. This changing of the fine structure constant is attributed to the energy lost by physical system (consist of baryonic component and electromagnetic field) due to expansion of our Universe. Obtained ratio (d alpha)/alpha = 1. 10{-18} (per second) is only five times smaller than actually reported experimental limit on this value. For this reason this variation can probably be measured within a couple of years. To argue the correctness of our approach we calculate the Planck constant as adiabatic invariant of electromagnetic field, from geometry of our Universe in the framework of the pseudo- Riemannian geometry. Finally we discuss the double clock experiment based on Al+ and Hg+ clocks carried out by T. Rosenband et al. (Science 2008). We show that in this particular case there is an error in method and this way the fine structure constant variation c...

  5. Further Evidence for Cosmological Evolution of the Fine Structure Constant

    Energy Technology Data Exchange (ETDEWEB)

    Webb, J. K.; Murphy, M. T.; Flambaum, V. V.; Dzuba, V. A.; Barrow, J. D.; Churchill, C. W.; Prochaska, J. X.; Wolfe, A. M.

    2001-08-27

    We describe the results of a search for time variability of the fine structure constant {alpha} using absorption systems in the spectra of distant quasars. Three large optical data sets and two 21 cm and mm absorption systems provide four independent samples, spanning {approx}23% to 87% of the age of the universe. Each sample yields a smaller {alpha} in the past and the optical sample shows a 4{sigma} deviation: {Delta}{alpha}/{alpha}=-0.72{+-}0.18 x 10{sup -5} over the redshift range 0.5

  6. Further Evidence for Cosmological Evolution of the Fine Structure Constant

    CERN Document Server

    Webb, J K; Flambaum, V V; Dzuba, V A; Barrow, John D; Churchill, C W; Prochaska, J X; Wolfe, A M

    2001-01-01

    We summarise the results of a search for time variability of the fine structure constant, alpha, using absorption systems in the spectra of distant quasars. Three large optical datasets and two 21cm/mm absorption systems provide four independent samples, spanning approximately 23% to 87% of the age of the universe. Each sample yields a negative Delta(alpha)/alpha (smaller alpha in the past) and the whole optical sample shows a 4-sigma deviation: Delta(alpha)/alpha = -0.72 +/- 0.18 x 10^{-5} over the redshift range 0.5 < z < 3.5. A comprehensive search for systematic effects reveals none which can explain our results. The only potentially significant systematic effects push Delta(alpha)/alpha towards positive values, i.e. our results would become more significant were we to correct for them.

  7. Fine-structure constant variability surprises for laboratory atomic spectroscopy and cosmological evolution of quasar spectra

    CERN Document Server

    Bekenstein, J D

    2003-01-01

    Calculation of the Dirac hydrogen atom spectrum in the framework of dynamical fine structure constant (alpha) variability discloses a small departure in the laboratory from Sommerfeld's formula for the fine structure shifts, possibly measurable today. And for a distant object in the universe, the wavelength shift of a spectral line specifically ascribable to cosmological alpha variation is found to depend differently on the quantum numbers than in the conventional view. This last result clashes with the conventional wisdom that an atom's spectrum can change with cosmological time only through evolution of the alpha parameter in the energy eigenvalue formula, and thus impacts on the Webb group's analysis of fine structure intervals in quasar absorption lines (which has been claimed to disclose cosmological alpha evolution). In particular, analyzing together a mix of quasar absorption lines from different fine structure multiplets can bias estimates of cosmological alpha variability.

  8. The fine structure constant and habitable planets

    Science.gov (United States)

    Sandora, McCullen

    2016-08-01

    We use the existence of habitable planets to impose anthropic requirements on the fine structure constant, α. To this effect, we present two considerations that restrict its value to be very near the one observed. The first, that the end product of stellar fusion is iron and not one of its neighboring elements, restricts α‑1 to be 145± 50. The second, that radiogenic heat in the Earth's interior remains adequately productive for billions of years, restricts it to be 145±9. A connection with the grand unified theory window is discussed, effectively providing a route to probe ultra-high energy physics with upcoming advances in planetary science.

  9. The Fine Structure Constant and Habitable Planets

    CERN Document Server

    Sandora, McCullen

    2016-01-01

    We use the existence of habitable planets to impose anthropic requirements on the fine structure constant, $\\alpha$. To this effect, we present two considerations that restrict its value to be very near the one observed. The first, that the end product of stellar fusion is iron and not one of its neighboring elements, restricts $\\alpha^{-1}$ to be $145\\pm 50$. The second, that radiogenic heat in the Earth's interior remains adequately productive for billions of years, restricts it to be $145\\pm9$. A connection with the grand unified theory window is discussed, effectively providing a route to probe ultra-high energy physics with upcoming advances in planetary science.

  10. The fine structure constant and habitable planets

    Science.gov (United States)

    Sandora, McCullen

    2016-08-01

    We use the existence of habitable planets to impose anthropic requirements on the fine structure constant, α. To this effect, we present two considerations that restrict its value to be very near the one observed. The first, that the end product of stellar fusion is iron and not one of its neighboring elements, restricts α-1 to be 145± 50. The second, that radiogenic heat in the Earth's interior remains adequately productive for billions of years, restricts it to be 145±9. A connection with the grand unified theory window is discussed, effectively providing a route to probe ultra-high energy physics with upcoming advances in planetary science.

  11. The fine structure of the ionosphere

    DEFF Research Database (Denmark)

    D'Angelo, N.; Michelsen, Poul

    1967-01-01

    We consider in this note the excitation of ion-acoustic waves by vertical gradients of density in the ionosphere. The conclusion is reached that the fine structure of the ionosphere is probably affected by the resulting instability, as comparison with observations seems to indicate. Recently, Liu......' is its height gradients, and nu is the ion-neutral collision frequency. We have examined the stability of the ionosphere against growth of low-frequency quasielectrostatic waves, taking into account the compressibility of the plasma....

  12. Fine Structure Constant: Theme With Variations

    CERN Document Server

    Bezerra, V B; Muniz, C R; Tahim, M O; Vieira, H S

    2016-01-01

    In this paper, we study the spatial variation of the fine structure constant $\\alpha$ due to the presence of a static and spherically symmetric gravitational source. The procedure consists of calculating the solution including the energy eigenvalues of a massive scalar field around that source, considering the weak-field regimen, which yields the gravitational analog of the atomic Bohr levels. From this result, we obtain several values for the effective $\\alpha$ by considering some scenarios of semi-classical and quantum gravities. Constraints on the parameters of the involved theories are calculated from astrophysical observations of the white dwarf emission spectra. Such constraints are compared with those ones obtained in the literature.

  13. Molecular Eigensolution Symmetry Analysis and Fine Structure

    Directory of Open Access Journals (Sweden)

    William G. Harter

    2013-01-01

    Full Text Available Spectra of high-symmetry molecules contain fine and superfine level cluster structure related to J-tunneling between hills and valleys on rovibronic energy surfaces (RES. Such graphic visualizations help disentangle multi-level dynamics, selection rules, and state mixing effects including widespread violation of nuclear spin symmetry species. A review of RES analysis compares it to that of potential energy surfaces (PES used in Born-Oppenheimer approximations. Both take advantage of adiabatic coupling in order to visualize Hamiltonian eigensolutions. RES of symmetric and D2 asymmetric top rank-2-tensor Hamiltonians are compared with Oh spherical top rank-4-tensor fine-structure clusters of 6-fold and 8-fold tunneling multiplets. Then extreme 12-fold and 24-fold multiplets are analyzed by RES plots of higher rank tensor Hamiltonians. Such extreme clustering is rare in fundamental bands but prevalent in hot bands, and analysis of its superfine structure requires more efficient labeling and a more powerful group theory. This is introduced using elementary examples involving two groups of order-6 (C6 and D3~C3v, then applied to families of Oh clusters in SF6 spectra and to extreme clusters.

  14. Angle-resolved photoemission extended fine structure

    International Nuclear Information System (INIS)

    Measurements of the Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) from the S(1s) core level of a c(2 x 2)S/Ni(001) are analyzed to determine the spacing between the S overlayer and the first and second Ni layers. ARPEFS is a type of photoelectron diffraction measurement in which the photoelectron kinetic energy is swept typically from 100 to 600 eV. By using this wide range of intermediate energies we add high precision and theoretical simplification to the advantages of the photoelectron diffraction technique for determining surface structures. We report developments in the theory of photoelectron scattering in the intermediate energy range, measurement of the experimental photoemission spectra, their reduction to ARPEFS, and the surface structure determination from the ARPEFS by combined Fourier and multiple-scattering analyses. 202 refs., 67 figs., 2 tabs

  15. Magnetic Tension of Sunspot Fine Structures

    CERN Document Server

    Venkatakrishnan, P

    2010-01-01

    The equilibrium structure of sunspots depends critically on its magnetic topology and is dominated by magnetic forces. Tension force is one component of the Lorentz force which balances the gradient of magnetic pressure in force-free configurations. We employ the tension term of the Lorentz force to clarify the structure of sunspot features like penumbral filaments, umbral light bridges and outer penumbral fine structures. We compute vertical component of tension term of Lorentz force over two active regions namely NOAA AR 10933 and NOAA AR 10930 observed on 05 January 2007 and 12 December 2006 respectively. The former is a simple while latter is a complex active region with highly sheared polarity inversion line (PIL). The vector magnetograms used are obtained from Hinode(SOT/SP). We find an inhomogeneous distribution of tension with both positive and negative signs in various features of the sunspots. The existence of positive tension at locations of lower field strength and higher inclination is compatible...

  16. The fine structure constant and numerical alchemy

    CERN Document Server

    Dattoli, Giuseppe

    2010-01-01

    We comment on past and more recent efforts to derive a formula yielding the fine structure constant in terms of integers and transcendent numbers. We analyse these "exoteric" attitudes and describe the myths regarding {\\alpha}, which seems to have very ancient roots, tracing back to Cabbala and to medieval alchemic conceptions. We discuss the obsession for this constant developed by Pauli and the cultural "environment" in which such an "obsession" grew. We also derive a simple formula for {\\alpha} in terms of two numbers {\\pi} and 137 only. The formula we propose reproduces the experimental values up to the last significant digit, it has not any physical motivation and is the result of an alchemic combination of numbers. We make a comparison with other existing formulae, discuss the relevant limits of validity by comparison with the experimental values and discuss a criterion to recover a physical meaning, if existing, from their mathematical properties.

  17. Varying fine-structure and gravitational constants

    International Nuclear Information System (INIS)

    A simple relation between the time-dependent fine-structure and gravitational constants of alpha/alpha2 approx G/G is derived from the hypothesis that both of these fundamental constants are related to the more fundamental length scale of nature as in he unified pregauge and pregeometric theory of all fundamental forces. From the latest observation of alpha/alpha = (-1.91 ± 0.54) centre dot 10-15yr-1 by Webb et al., it leads to the prediction of G/G = (-0.154 ± 0.044) centre dot 10-12yr-1, which is not only consistent with the most precise limit of G/G = (-0.6 ± 2.0) centre dot 10-12yr-1 by Thorsett but also feasible for future experimental tests

  18. Characterization of the Cu(Π) and Zn(Π) binding to the Amyloid-β short peptides by both the Extended X-ray Absorption Fine Structure and the Synchrotron Radiation Circular Dichroism spectroscopy

    Science.gov (United States)

    Zhang, Zhiyin; Sun, Shuaishuai; Xu, Jianhua; Zhang, Jing; Huang, Yan; Zhang, Bingbing; Tao, Ye

    2013-04-01

    Alzheimer's disease (AD) is a progressive and devastating neurodegenerative pathology, clinically characterized by dementia, cognitive impairment, personality disorders and memory loss. It is generally accepted that, misfolding of Aβ peptides is the key element in pathogenesis and the secondary structure of Aβ can be changed to major β-strand with reasons unknown yet. Many studies have shown that the misfolding may be linked with some biometals, mainly copper and zinc ions. To characterize interactions of Aβ and metal ions, we utilized both the extended X-ray fine structure spectroscopy (EXAFS) and the synchrotron radiation circular dichroism spectroscopy (SRCD). Aβ (13-22), Aβ (13-21), Aβ (E22G) and Aβ(HH-AA) were selected to study the mechanism of copper and zinc binding to Aβ. We found that Cu interaction with H13 and H14 residues led to the disappearance of the PPΠ, while the Cu binding E22 residue caused a remarkable conformation change to β-sheet enrichment. The Zn ion, in contrast, made little effect on the conformation and it coordinated to only one histidine (H residue) or not.

  19. Time Variation of the Fine Structure Constant Driven by Quintessence

    CERN Document Server

    Anchordoqui, L A; Anchordoqui, Luis; Goldberg, Haim

    2003-01-01

    There are indications from the study of quasar absorption spectra that the fine structure constant $\\alpha$ may have been measurably smaller for redshifts $z>2.$ Analyses of other data ($^{149}$Sm fission rate for the Oklo natural reactor, variation of $^{187}$Re $\\beta$-decay rate in meteorite studies, atomic clock measurements) which probe variations of $\\alpha$ in the more recent past imply much smaller deviations from its present value. In this work we tie the variation of $\\alpha$ to the evolution of the quintessence field proposed by Albrecht and Skordis, and show that agreement with all these data, as well as consistency with WMAP observations, can be achieved for a range of parameters. Some definite predictions follow for upcoming space missions searching for violations of the equivalence principle.

  20. Time variation of the fine structure constant driven by quintessence

    Science.gov (United States)

    Anchordoqui, Luis; Goldberg, Haim

    2003-10-01

    There are indications from the study of quasar absorption spectra that the fine structure constant α may have been measurably smaller for redshifts z>2. Analyses of other data (149Sm fission rate for the Oklo natural reactor, variation of 187Re β-decay rate in meteorite studies, atomic clock measurements) which probe variations of α in the more recent past imply much smaller deviations from its present value. In this work we tie the variation of α to the evolution of the quintessence field proposed by Albrecht and Skordis, and show that agreement with all these data, as well as consistency with Wilkinson Microwave Anisotropy Probe observations, can be achieved for a range of parameters. Some definite predictions follow for upcoming space missions searching for violations of the equivalence principle.

  1. Fine structure of charge exchange lines observed in laboratory plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Ida, K.; Nishimura, S. [National Inst. for Fusion Science, Nagoya (Japan); Kondo, K.

    1997-01-01

    The influence of the fine structure of charge exchange lines appears only at the plasma edge or in the recombining phase where the ion temperature is low enough. The observed spectra in Li III and C VI are consistent with the sum of fine-structure components populated by statistical weights (assuming complete l-mixing) not by direct charge exchange cross sections. Some discrepancy was observed in the intensity ratio of fine-structure components between the observation and calculation for C VI in the recombining phase. The fine-structure of charge exchange lines gives an apparent Doppler shift in plasma rotation velocity measurement using charge exchange spectroscopy. (author)

  2. Implications of a Time-Varying Fine Structure Constant

    CERN Document Server

    Alfonso-Faus, A

    2002-01-01

    Much work has been done after the possibility of a fine structure constant being time-varying. It has been taken as an indication of a time-varying speed of light. Here we prove that this is not the case. We prove that the speed of light may or may not vary with time, independently of the fine structure constant being constant or not. Time variations of the speed of light, if present, have to be derived by some other means and not from the fine structure constant. No implications based on the possible variations of the fine structure constant can be imposed on the speed of light.

  3. An Einstein-Cartan Fine Structure Constant Definition

    Directory of Open Access Journals (Sweden)

    Stone R. A. Jr.

    2010-01-01

    Full Text Available The fine structure constant definition given in Stone R.A. Jr. Progress in Physics, 2010, v.1, 11-13 is compared to an Einstein-Cartan fine structure constant definition. It is shown that the Einstein-Cartan definition produces the correct pure theory value, just not the measure value. To produce the measured value, the pure theory Einstein-Cartan fine structure constant requires only the new variables and spin coupling of the fine structure constant definition in [1].

  4. Fine velocity structures collisional dissipation in plasmas

    Science.gov (United States)

    Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi

    2016-04-01

    In a weakly collisional plasma, such as the solar wind, collisions are usually considered far too weak to produce any significant effect on the plasma dynamics [1]. However, the estimation of collisionality is often based on the restrictive assumption that the particle velocity distribution function (VDF) shape is close to Maxwellian [2]. On the other hand, in situ spacecraft measurements in the solar wind [3], as well as kinetic numerical experiments [4], indicate that marked non-Maxwellian features develop in the three-dimensional VDFs, (temperature anisotropies, generation of particle beams, ring-like modulations etc.) as a result of the kinetic turbulent cascade of energy towards short spatial scales. Therefore, since collisional effects are proportional to the velocity gradients of the VDF, the collisionless hypothesis may fail locally in velocity space. Here, the existence of several characteristic times during the collisional relaxation of fine velocity structures is investigated by means of Eulerian numerical simulations of a spatially homogeneous force-free weakly collisional plasma. The effect of smoothing out velocity gradients on the evolution of global quantities, such as temperature and entropy, is discussed, suggesting that plasma collisionality can increase locally due to the velocity space deformation of the particle velocity distribution. In particular, by means of Eulerian simulations of collisional relaxation of a spatially homogeneous force-free plasma, in which collisions among particles of the same species are modeled through the complete Landau operator, we show that the system entropy growth occurs over several time scales, inversely proportional to the steepness of the velocity gradients in the VDF. We report clear evidences that fine velocity structures are dissipated by collisions in a time much shorter than global non-Maxwellian features, like, for example, temperature anisotropies. Moreover we indicate that, if small-scale structures

  5. The Fine Structure Lines of Hydrogen in HII Regions

    CERN Document Server

    Dennison, B; Minter, A H; Dennison, Brian; Minter, Anthony H.

    2005-01-01

    The 2s_{1/2} state of hydrogen is metastable and overpopulated in HII regions. In addition, the 2p states may be pumped by ambient Lyman-alpha radiation. Fine structure transitions between these states may be observable in HII regions at 1.1 GHz (2s_{1/2}-2p_{1/2}) and/or 9.9 GHz (2s_{1/2}-2p_{3/2}), although the details of absorption versus emission are determined by the relative populations of the 2s and 2p states. The n=2 level populations are solved with a parameterization that allows for Lyman-alpha pumping of the 2p states. The density of Lyman-alpha photons is set by their creation rate, easily determined from the recombination rate, and their removal rate. Here we suggest that the dominant removal mechanism of Lyman-alpha radiation in HII regions is absorption by dust. This circumvents the need to solve the Lyman-alpha transfer problem, and provides an upper limit to the rate at which the 2p states are populated by Lyman-alpha photons. In virtually all cases of interest, the 2p states are predominantl...

  6. Local Fine Structural Insight into Mechanism of Electrochemical Passivation of Titanium.

    Science.gov (United States)

    Wang, Lu; Yu, Hongying; Wang, Ke; Xu, Haisong; Wang, Shaoyang; Sun, Dongbai

    2016-07-20

    Electrochemically formed passive film on titanium in 1.0 M H2SO4 solution and its thickness, composition, chemical state, and local fine structure are examined by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure. AES analysis reveals that the thickness and composition of oxide film are proportional to the reciprocal of current density in potentiodynamic polarization. XPS depth profiles of the chemical states of titanium exhibit the coexistence of various valences cations in the surface. Quantitative X-ray absorption near edge structure analysis of the local electronic structure of the topmost surface (∼5.0 nm) shows that the ratio of [TiO2]/[Ti2O3] is consistent with that of passivation/dissolution of electrochemical activity. Theoretical calculation and analysis of extended X-ray absorption fine structure spectra at Ti K-edge indicate that both the structures of passivation and dissolution are distorted caused by the appearance of two different sites of Ti-O and Ti-Ti. And the bound water in the topmost surface plays a vital role in structural disorder confirmed by XPS. Overall, the increase of average Ti-O coordination causes the electrochemical passivation, and the dissolution is due to the decrease of average Ti-Ti coordination. The structural variations of passivation in coordination number and interatomic distance are in good agreement with the prediction of point defect model. PMID:27355902

  7. A five dimensional model of varying effective gravitational and fine structure constants

    Science.gov (United States)

    Mbelek, J. P.; Lachièze-Rey, M.

    2003-01-01

    We explore the possibility that the reported time variation of the fine structure constant alpha is due to a coupling between electromagnetism and gravitation. We predict such a coupling from a very simple effective theory of physical interactions, under the form of an improved version of the Kaluza-Klein theory. We show that it precisely leads to a variation of the effective fine structure constant with cosmic conditions, and thus with cosmic time. The comparison with the recent data from distant quasars absorption line spectra gives a good agreement; moreover, this may reconcile the claimed results on alpha with the upper limit from the Oklo naturel Uranium fission reactor.

  8. Intestinal absorption of specific structured triacylglycerols

    DEFF Research Database (Denmark)

    Mu, Huiling; Høy, Carl-Erik

    2001-01-01

    To clarify the intestinal absorption pathway of medium-chain fatty acids from MMM-type structured triaclyglycerols containing both medium- and long-chain fatty acids, we studied the lymphatic transport of 1,3-dioctanoyl-2-linoleoyl-sn- glycerol (8:0/18:2/8:0), 1,3-didecanoyl-2-linoleoyl...... activated into CoA, and reacylated into triacylglycerols in the enterocyte, The hydrolysis of MLM-type STAG is predominantly partial hydrolysis, whereas part of the STAG can also be hydrolyzed to free glycerol and free fatty acids. - Mu, H., and CE. Hoy. Intestinal absorption of specific structured...

  9. Atomic fine structure in a space of constant curvature

    Energy Technology Data Exchange (ETDEWEB)

    Bessis, N.; Bessis, G.; Shamseddine, R. (Lyon-1 Univ., 69 - Villeurbanne (France))

    1982-10-01

    As a contribution to a tentative formulation of atomic physics in a curved space, the determination of atomic fine structure energies in a space of constant curvature is investigated. Starting from the Dirac equation in a curved space-time, the analogue of the Pauli equation in a general coordinate system is derived. The theoretical curvature induced shifts and splittings of the fine structure energy levels are put in evidence and examined for the particular case of the hydrogenic n=2 levels.

  10. Fundamental Nature of the Fine-Structure Constant

    OpenAIRE

    Sherbon, Michael A.

    2014-01-01

    Arnold Sommerfeld introduced the fine-structure constant that determines the strength of the electromagnetic interaction. Following Sommerfeld, Wolfgang Pauli left several clues to calculating the fine-structure constant with his research on Johannes Kepler's view of nature and Pythagorean geometry. The Laplace limit of Kepler's equation in classical mechanics, the Bohr-Sommerfeld model of the hydrogen atom and Julian Schwinger's research enable a calculation of the electron magne...

  11. Atomic fine structure in a space of constant curvature

    International Nuclear Information System (INIS)

    As a contribution to a tentative formulation of atomic physics in a curved space, the determination of atomic fine structure energies in a space of constant curvature is investigated. Starting from the Dirac equation in a curved space-time, the analogue of the Pauli equation in a general coordinate system is derived. The theoretical curvature induced shifts and splittings of the fine structure energy levels are put in evidence and examined for the particular case of the hydrogenic n=2 levels. (author)

  12. Radiation Absorption Mechanism in Nonvolatile MNOS Structure

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The γ-ray radiation will speed up the discharge of the stored charge in nonvolatile MNOS structure. The radiation absorption mechanism to enhance the discharge is discussed. A direct radiation emission model from the interface traps distributing both in energy level and in space is given. The theoretical results based on this model are in good agreement with experimental measurement.

  13. Fine defective structure of silicon carbide powders obtained from different starting materials

    Directory of Open Access Journals (Sweden)

    Tomila T.V.

    2006-01-01

    Full Text Available The fine defective structure of silicon carbide powders obtained from silicic acid-saccharose, aerosil-saccharose, aerosil-carbon black, and hydrated cellulose-silicic acid gel systems was investigated. The relation between IR absorption characteristics and the microstructure of SiC particles obtained from different starting materials was established. The numerical relationship between the lattice parameter a and the frequency νTO is presented.

  14. Fine defective structure of silicon carbide powders obtained from different starting materials

    OpenAIRE

    Tomila T.V.; Vlasova M.V.; Kakazey M.G.; Vyshnyakova K.L.; Ragulya A.V.; Pereselentseva L.N.

    2006-01-01

    The fine defective structure of silicon carbide powders obtained from silicic acid-saccharose, aerosil-saccharose, aerosil-carbon black, and hydrated cellulose-silicic acid gel systems was investigated. The relation between IR absorption characteristics and the microstructure of SiC particles obtained from different starting materials was established. The numerical relationship between the lattice parameter a and the frequency νTO is presented.

  15. Re/Os Constraint on the Time Variability of the Fine-Structure Constant

    Science.gov (United States)

    Fujii, Yasunori; Iwamoto, Akira

    2003-12-01

    We argue that the accuracy by which the isochron parameters of the decay 187Re→187Os are determined by dating iron meteorites may constrain the possible time dependence of the decay rate and hence of the fine-structure constant α, not directly but only in a model-dependent manner. From this point of view, some of the attempts to analyze the Oklo constraint and the results of the quasistellar-object absorption lines are reexamined.

  16. Re/Os constraint on the time-variability of the fine-structure constant

    CERN Document Server

    Fujii, Y; Fujii, Yasunori; Iwamoto, Akira

    2003-01-01

    We argue that the accuracy by which the isochron parameters of the decay $^{187}{\\rm Re}\\to ^{187}{\\rm Os}$ are determined by dating iron meteorites may not directly constrain the possible time-dependence of the decay rate and hence of the fine-structure constant $\\alpha$. From this point of view, some of the attempts to analyze the Oklo constraint and the results of the QSO absorption lines are re-examined.

  17. Intestinal absorption of specific structured triacylglycerols

    DEFF Research Database (Denmark)

    Mu, Huiling; Høy, Carl-Erik

    2001-01-01

    To clarify the intestinal absorption pathway of medium-chain fatty acids from MMM-type structured triaclyglycerols containing both medium- and long-chain fatty acids, we studied the lymphatic transport of 1,3-dioctanoyl-2-linoleoyl-sn- glycerol (8:0/18:2/8:0), 1,3-didecanoyl-2-linoleoyl...... and activated into CoA, and reacylated into triacylglycerols in the enterocyte, The hydrolysis of MLM-type STAG is predominantly partial hydrolysis, whereas part of the STAG can also be hydrolyzed to free glycerol and free fatty acids. - Mu, H., and CE. Hoy. Intestinal absorption of specific structured......-sn-glycerol (10:0/18:2/10:0), and 1,3-didodecanoyl-2-linoleoyl-sn-glycerol (12:0/18:2/12:0) in a rat model. Safflower oil was used in the absorption study in order to compare the absorption of medium- chain fatty acids and long-chain fatty acids, The triacylglycerol species of lymph Lipids were separated...

  18. Chemical evolution of Mg isotopes versus the time variation of the fine structure constant

    International Nuclear Information System (INIS)

    We show that the synthesis of Mg25,26 at the base of the convective envelope in low-metallicity asymptotic giant branch stars can produce the isotopic ratios needed to explain the low-z subset (with z<1.8) of the many-multiplet data from quasar absorption systems without invoking a time variation of the fine structure constant. This is supported by observations of high abundances of the neutron-rich Mg isotopes in metal-poor globular-cluster stars. We conclude that the quasar absorption spectra may be providing interesting information on the nucleosynthetic history of such systems

  19. Fine Structure of Regenerated Silk Fibroin Solids

    Institute of Scientific and Technical Information of China (English)

    LI Ming-zhong; WU Zheng-yu; Norihiko Minoura; YAN Hao-jing

    2002-01-01

    The fibronin solids (membrane and gel) were prepared from regenerated silk fibroin solution in different ways. The structure of the fibroin solids and its change during storage were studied. The results indicated that the structure of fibroin membraneair-dried at 30℃ or freeze dried at a freezing temperature of - 20 - - 4℃ was the coexistence of amporphous and silk I structure. The amorphous region could partly be transformed into silk I structure under room temperature and humidity. The structure of porous silk fibroin membrane was the coexistence of amorphous and small part of silk Ⅱ, if the aqueous fibroin was freeze dried within the temperature range of - 80℃ to - 20℃, and the amorphous partly transformed into silk I during storage. Thestructure of fibroin gel naturally forming when kept at room temperature was coexistent of amorphous and silk Ⅱ. The content of Gly and ala was high in the surface membrane of aqueous fibroin and its structure was mostly silk I and silk Ⅱ with high crystallinity.

  20. A new method to determine the density and water absorption of fine recycled aggregates

    Directory of Open Access Journals (Sweden)

    Fernando Rodrigues

    2013-01-01

    Full Text Available The construction industry keeps on demanding huge quantities of natural resources, mainly minerals for mortars and concrete production. The depletion of many quarries and environmental concerns about reducing the dumping of construction and demolition waste in quarries have led to an increase in the procuring and use of recycled aggregates from this type of waste. If they are to be incorporated in concrete and mortars it is essential to know their properties to guarantee the adequate performance of the end products, in both mechanical and durability-related terms. Existing regulated tests were developed for natural aggregates, however, and several problems arise when they are applied to recycled aggregates, especially fine recycled aggregates (FRA. This paper describes the main problems encountered with these tests and proposes an alternative method to determine the density and water absorption of FRA that removes them. The use of sodium hexametaphosphate solutions in the water absorption test has proven to improve its efficiency, minimizing cohesion between particles and helping to release entrained air.

  1. Residence time and pH effects on the bonding configuration of orthophosphate surface complexes at the goethite/water interface as examined by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy.

    Science.gov (United States)

    Abdala, Dalton Belchior; Northrup, Paul Andrew; Vicentin, Flávio César; Sparks, Donald Lewis

    2015-03-15

    Identifying the mechanisms by which P is bound to soils and soil constituents is ultimately important as they provide information on the stability of bound species and their reactivity in the environment. EXAFS studies were carried out to provide information on how the local chemical environment of sorbed P changes as an effect of pH and time. Goethite was reacted with orthophosphate at a P concentration of 0.8mmolL(-1) P at pH 3.0, 4.5 and 6.0. The residence time effect on the mechanisms of P sorption on goethite was also evaluated for two different reaction times, 5 and 18days, on goethite suspensions reacted at pH 4.5. The objective of this study was to understand how P sorption mechanisms change over a wide pH range when subjected to P concentrations above the P saturation ratio of goethite. Phosphorus K-edge EXAFS spectra were collected at 2150eV in fluorescence mode and the structural parameters were obtained through the fits of sorption data using Artemis. The monodentate surface complex was shown to be the predominant mechanism by which P sorbs at the goethite surface under the experimental conditions. The lack of a discrete Fe-P shell and the presence of highly disordered structures, particularly, at R-space ⩾3.5 suggested the formation of P surface precipitates at the goethite/water interface. PMID:25514644

  2. Helium 23P Fine Structure Measurement in a Discharge Cell

    Science.gov (United States)

    Zelevinsky, T.; Farkas, D.; Gabrielse, G.

    2005-12-01

    A precise measurement of helium 23P fine structure was carried out in a discharge cell using Doppler-free laser spectroscopy. It is the only known experiment to directly measure all three fine structure intervals at a 1 kHz level of accuracy. The 23P1 - 23P2 interval value agrees with other experiments but disagrees with theoretical predictions of two-electron QED. When this disagreement is resolved, the 23P0 - 23P1 interval measurement reported here will allow a determination of the fine structure constant to 14 parts in 109, surpassing the precision of the well known QED-independent quantum Hall effect and Josephson effect determinations. The discharge cell is shown to be advantageous in the study and correction of systematic frequency shifts related to light pressure, and the use of the cell ensures that the possible systematic errors are substantially different from those reported in other experiments.

  3. Fine structure of helium and light helium-like ions

    OpenAIRE

    Pachucki, Krzysztof; Yerokhin, Vladimir A.

    2010-01-01

    Calculational results are presented for the fine-structure splitting of the 2^3P state of helium and helium-like ions with the nuclear charge Z up to 10. Theoretical predictions are in agreement with the latest experimental results for the helium fine-structure intervals as well as with the most of the experimental data available for light helium-like ions. Comparing the theoretical value of the 2^3P_0-2^3P_1 interval in helium with the experimental result [T. Zelevinsky et al. Phys. Rev. Let...

  4. Spectral fine structure effects on material and doppler reactivity worth

    International Nuclear Information System (INIS)

    New formulations concerning the fine structure effects on the reactivity worth of resonances are developed and conclusions are derived following the extension to more general types of perturbations which include: the removal of resonance material at finite temperatures and the temperature variation of part of the resonance material. It is concluded that the flux method can overpredict the reactivity worth of resonance materials more than anticipated. Calculations on the Doppler worth were carried out; the results can be useful for asessing the contribution of the fine structure effects to the large discrepancy that exists between the calculated and measured small sample Doppler worths. (B.G.)

  5. Coherent perfect absorption in photonic structures

    CERN Document Server

    Baldacci, Lorenzo; Tredicucci, Alessandro

    2016-01-01

    The ability to drive a system with an external input is a fundamental aspect of light-matter interaction. The coherent perfect absorption (CPA) phenomenon extends to the general multibeam interference phenomenology the well known critical coupling concepts. This interferometric control of absorption can be employed to reach full delivery of optical energy to nanoscale systems such as plasmonic nanoparticles, and multi-port interference can be used to enhance the absorption of a nanoscale device when it is embedded in a strongly scattering system, with potential applications to nanoscale sensing. Here we review the two-port CPA in reference to photonic structures which can resonantly couple to the external fields. A revised two-port theory of CPA is illustrated, which relies on the Scattering Matrix formalism and is valid for all linear two-port systems with reciprocity. Through a semiclassical approach, treating two-port critical coupling conditions in a non-perturbative regime, it is demonstrated that the st...

  6. Binding energy and fine structure of the He- ion

    Institute of Scientific and Technical Information of China (English)

    ZHUO; Lin; ZHU; Jing-jing; GOU; Bing-cong

    2007-01-01

    The variational method using a multiconfiguration wavefunction is carried out on the core-excited state 1s2s2p 4P0 for helium negative ion, including mass polarization and relativistic corrections. Binding energy and fine structure are reported. The results are compared with other theoretical and experimental date in the literature.

  7. The Fine Structure of Equity-Index Option Dynamics

    DEFF Research Database (Denmark)

    Andersen, Torben G.; Bondarenko, Oleg; Todorov, Viktor;

    We analyze the high-frequency dynamics of S&P 500 equity-index option prices by constructing an assortment of implied volatility measures. This allows us to infer the underlying fine structure behind the innovations in the latent state variables driving the movements of the volatility surface. In...

  8. Mathematical description of SO/sub 2/ absorption in an aqueous suspension of finely powdered limestone

    Energy Technology Data Exchange (ETDEWEB)

    Biba, V.; Hrncir, J.; Vejvoda, J.

    1978-01-01

    A mathematical model has been proposed that characterizes the course of SO/sub 2/ absorption in a bubble reactor filled by a suspension of finely powdered limestone. The agreement between the experimental results and the calculated course of the output SO/sub 2/ concentration shows that the model represents a useful basis for the description of the studied process. However, as the model has been so far verified only on one sample at a single temperature and for only one grain composition, the results obtained can be considered only as the first step in the modelling of the process. Experiments performed under different condition of temperature, grain composition and with different types of limestone, and/or some further additions to the reaction scheme involved (e.g., the dissociation of carbonates) are needed to make the model more accurate. The results so far obtained represent thus a contribution to the approximation of the fundamental theory of processes that take place in the wet limestone technology of desulphurization of combustion gases.

  9. The local structure and optical absorption characteristic investigation on Fe doped TiO2 nanoparticles

    CERN Document Server

    Zhao, Tianxing; Huang, Junheng; He, Jinfu; Liu, Qinghua; Pan, Zhiyun; Wu, Ziyu

    2014-01-01

    The local structures and optical absorption characteristic of Fe doped TiO2 nanoparticles synthesized by the sol-gel method were characterized by X-ray Diffraction (XRD), X-ray absorption fine structure spectroscopy (XAFS) and UV-Vis absorption spectroscopy (UV-Vis). XRD patterns show that all Fe-doped TiO2 samples have the characteristic anatase structure. Accurate Fe and Ti K-edge EXAFS analysis further reveal that all Fe atoms replace Ti atoms in the anatase lattice. The analysis of UV-Vis data shows a red shift to the visible range. According to the above results, we claim that substitutional Fe atoms lead to the formation of structural defects and new intermediate energy levels appear, narrowing the band gap and extending the optical absorption edge towards the visible region.

  10. Precision Measurements: Testing the Time Variation of the Fine Structure Constant

    Science.gov (United States)

    Lamoreaux, Steve

    2004-05-01

    Often, precision measurements from diverse fields can be used to learn new facts about the universe. The usual definition of "precision" is based on improvements over previous measurements. A review of the present state of knowledge regarding the possible time variation of the fine structure constant α will be presented; "precise" data from natural phenomena, which include an apparent shift in the red-shift-scaled fine structure in the absorption spectra of quasar light, and the isotopic abundances in the fission products of a prehistoric natural reactor in Oklo, Gabon. Prospects to improve the accuracy for the constancy of α with laboratory experiments will be discussed. Our two experimental investigations currently being developed are based on optical spectroscopy of trapped ions and on radiofrequency spectroscopy of an atomic dysprosium beam. A sensitivity of dotα/α≈ 10-18/yr is anticipated. Because this accuracy exceeds that by which the second is defined, these measurements will necessarily be differential.

  11. Markov Chain Monte Carlo methods applied to measuring the fine structure constant from quasar spectroscopy

    Science.gov (United States)

    King, Julian; Mortlock, Daniel; Webb, John; Murphy, Michael

    2010-11-01

    Recent attempts to constrain cosmological variation in the fine structure constant, α, using quasar absorption lines have yielded two statistical samples which initially appear to be inconsistent. One of these samples was subsequently demonstrated to not pass consistency tests; it appears that the optimisation algorithm used to fit the model to the spectra failed. Nevertheless, the results of the other hinge on the robustness of the spectral fitting program VPFIT, which has been tested through simulation but not through direct exploration of the likelihood function. We present the application of Markov Chain Monte Carlo (MCMC) methods to this problem, and demonstrate that VPFIT produces similar values and uncertainties for Δα/α, the fractional change in the fine structure constant, as our MCMC algorithm, and thus that VPFIT is reliable.

  12. Markov Chain Monte Carlo methods applied to measuring the fine structure constant from quasar spectroscopy

    CERN Document Server

    King, Julian A; Webb, John K; Murphy, Michael T

    2009-01-01

    Recent attempts to constrain cosmological variation in the fine structure constant, alpha, using quasar absorption lines have yielded two statistical samples which initially appear to be inconsistent. One of these samples was subsequently demonstrated to not pass consistency tests; it appears that the optimisation algorithm used to fit the model to the spectra failed. Nevertheless, the results of the other hinge on the robustness of the spectral fitting program VPFIT, which has been tested through simulation but not through direct exploration of the likelihood function. We present the application of Markov Chain Monte Carlo (MCMC) methods to this problem, and demonstrate that VPFIT produces similar values and uncertainties for (Delta alpha)/(alpha), the fractional change in the fine structure constant, as our MCMC algorithm, and thus that VPFIT is reliable.

  13. How strongly does dating meteorites constrain the time-dependence of the fine-structure constant?

    CERN Document Server

    Fujii, Y; Fujii, Yasunori; Iwamoto, Akira

    2005-01-01

    We review our argument on the nature of the so-called meteorite constraint on the possible time-dependence of the fine-structure constant, emphasizing that dating meteorites at the present time is different in principle from searching directly for the traces in the past, as in the Oklo phenomenon and the QSO absorption lines. In the related literature, we still find some arguments not necessarily consistent with this difference to be taken properly into account. This does not imply that any of the model-dependent approaches are useless in practice, though we cannot help guessing that dating meteorites is no match for the Oklo and the QSO in probing time-dependence of the fine-structure constant, at this moment. Some of the relevance to the QSO data particularly in terms of the scalar field will be discussed.

  14. A five dimensional model of varying effective gravitational and fine structure constants

    CERN Document Server

    Mbelek, J P

    2003-01-01

    We explore the possibility that the reported time variation of the fine structure constant $\\alpha$ is due to a coupling between electromagnetism and gravitation. We consider the coupling predicted by a very simple {\\sl effective} theory of physical interactions, under the form of an improved version of the Kaluza-Klein theory. We show that it is precisely expressed by a variation of the effective fine structure constant with cosmic conditions, and thus with cosmic time. We compare the predicted variation with the recent data from distant quasars absorption line spectra: we find a good agreement, which moreover reconcile the claimed results on $\\alpha$ with the upper limit from the Oklo naturel Uranium fission reactor.

  15. How Strongly does Dating Meteorites Constrain the Time-Dependence of the Fine-Structure Constant?

    Science.gov (United States)

    Fujii, Yasunori; Iwamoto, Akira

    We review our argument on the nature of the so-called meteorite constraint on the possible time-dependence of the fine-structure constant, emphasizing that dating meteorites at the present time is different in principle from searching directly for the traces in the past, as in the Oklo phenomenon and the QSO absorption lines. In the related literature, we still find some arguments not necessarily consistent with this difference to be taken properly into account. It does not immediately follow that any model-dependent approaches are useless in practice, though we cannot help suspecting that dating meteorites is no match for the Oklo and the QSO in probing the time-variability of the fine-structure constant, at this moment. Some of the relevance to the QSO data particularly in terms of the scalar field will be discussed.

  16. Constraints on field theoretical models for variation of the fine structure constant

    Science.gov (United States)

    Steinhardt, Charles L.

    2005-02-01

    Recent theoretical ideas and observational claims suggest that the fine structure constant α may be variable. We examine a spectrum of models in which α is a function of a scalar field. Specifically, we consider three scenarios: oscillating α, monotonic time variation of α, and time-independent α that is spatially varying. We examine the constraints imposed upon these theories by cosmological observations, particle detector experiments, and “fifth force” experiments. These constraints are very strong on models involving oscillation but cannot compete with bounds from the Oklo subnuclear reactor on models with monotonic timelike variation of α. One particular model with spatial variation is consistent with all current experimental and observational measurements, including those from two seemingly conflicting measurements of the fine structure constant using the many multiplet method on absorption lines.

  17. Electron excitation rates among fine structure levels in O III

    International Nuclear Information System (INIS)

    Electron collision strengths have been calculated for 146 transitions among the fine-structure levels in O III using a suitable transformation of LS coupling reactance matrix elements computed with the R-matrix method. These have been obtained at a fine energy grid in an energy region below 5.16 Ry and are found to be varying with electron energy, exhibiting a complicated resonance structure in almost the entire energy range. These have been averaged over a Maxwellian distribution of electron energies to get the effective collision strengths which are very simply related to the excitation and the de-excitation rate coefficients. The results are tabulated in a temperature region below 60,000 K. These are the first extensive results in the literature and are believed to be highly useful for astrophysical plasma diagnostics

  18. Topological quantization in units of the fine structure constant

    OpenAIRE

    Maciejko, Joseph; Qi, Xiao-Liang; Drew, H. Dennis; Zhang, Shou-Cheng

    2010-01-01

    Fundamental topological phenomena in condensed matter physics are associated with a quantized electromagnetic response in units of fundamental constants. Recently, it has been predicted theoretically that the time-reversal invariant topological insulator in three dimensions exhibits a topological magnetoelectric effect quantized in units of the fine structure constant $\\alpha=e^2/\\hbar c$. In this work, we propose an optical experiment to directly measure this topological quantization phenome...

  19. Photoreceptor fine structure in the bobtail goanna (Tiliqua rugosa)

    OpenAIRE

    Braekevelt, Charlie R.

    1989-01-01

    The fine structure of the retinal photoreceptors has been studied by light and electron microscopy in the bobtail goanna (Tiliqua rugosa) an Australian diurna1 lizard. The photoreceptors in this species are readily divisible into rods or cones based on morphological criteria. Single cones are the dominate cell type with a cone:rod ratio of about 80: 1. No multiple photoreceptors were present nor was a photoreceptor mosiac observed. Cones are large cells with a ...

  20. Subcortical representation of speech fine structure relates to reading ability

    OpenAIRE

    Hornickel, Jane; Anderson, Samira; Skoe, Erika; Yi, Han-Gyol; Kraus, Nina

    2012-01-01

    Impaired perception of consonants by poor readers is reflected in poor subcortical encoding of speech timing and harmonics. We assessed auditory brainstem representation of higher harmonics within a consonant-vowel formant transition to identify relationships between speech fine structure and reading. Responses were analyzed in three ways: a single stimulus polarity, adding responses to inverted polarities (emphasizing low harmonics), and subtracting responses to inverted polarities (emphasiz...

  1. Quintessential Nature of the Fine-Structure Constant

    OpenAIRE

    Sherbon, Michael A.

    2015-01-01

    7 pages International audience An introduction is given to the geometry and harmonics of the Golden Apex in the Great Pyramid, with the metaphysical and mathematical determination of the fine-structure constant of electromagnetic interactions. Newton's gravitational constant is also presented in harmonic form and other fundamental physical constants are then found related to the quintessential geometry of the Golden Apex in the Great Pyramid.

  2. Relativistic corrections in atoms and space-time variation of the fine structure constant

    Energy Technology Data Exchange (ETDEWEB)

    Dzuba, V.A.; Flambaum, V.V.; Murphy, M.T.; Webb, J.K. [School of Physics, Univ. of New South Wales, Sydney, NSW (Australia)

    2001-07-01

    Comparison of quasar absorption line spectra with laboratory spectra provides the best probe for variability of the fine structure constant, {alpha}=e{sup 2}/{Dirac_h}c, over cosmological time-scales. We have demonstrated that high sensitivity to the variation of a can be obtained from a comparison of the spectra of heavy and light atoms and have obtained an order of magnitude gain in precision over previous methods. Our new data hint that a was smaller at earlier epochs. Careful searches have so far not revealed any spurious e.ect that can explain the observations.

  3. Oklo Constraint on the Time-Variabilityof the Fine-Structure Constant

    Science.gov (United States)

    Fujii, Yasunori

    The Oklo phenomenon, natural fission reactors which had taken place in Gabon about 2 billion years ago, provides one of the most stringent constraints on the possible time-variability of the fine-structure constant . We first review briefly what it is and how reliable it is in constraining . We then compare the result with a more recent result on the nonzero change of obtained from the observation of the QSO absorption lines. We suggest a possible way to make these results consistent with each other in terms of the behavior of a scalar field which is expected to be responsible for the acceleration of the universe.

  4. Solar chromospheric fine scale structures: dynamics and energetics

    Science.gov (United States)

    Tziotziou, K.

    2012-01-01

    The solar chromosphere is a very inhomogeneous and dynamic layer of the solar atmosphere that exhibits several phenomena on a wide range of spatial and temporal scales. High-resolution and long-duration observations, employing mostly lines, such as Halpha, the Ca II infrared lines and the Ca II H and K lines, obtained both from ground-based telescope facilities (e.g. DST, VTT, THEMIS, SST, DOT), as well as state-of-the-art satellites (e.g. SOHO, TRACE, HINODE) reveal an incredibly rich, dynamic and highly structured chromospheric environment. What is known in literature as the chromospheric fine-scale structure mainly consists of small fibrilar-like features that connect various parts of quiet/active regions or span across the chromospheric network cell interiors, showing a large diversity of both physical and dynamic characteristics. The highly dynamic, fine-scale chromospheric structures are mostly governed by flows which reflect the complex geometry and dynamics of the local magnetic field and play an important role in the propagation and dissipation of waves. A comprehensive study of these structures requires deep understanding of the physical processes involved and investigation of their intricate link with structures/processes at lower photospheric levels. Furthermore, due to their large number present on the solar surface, it is essential to investigate their impact on the mass and energy transport to higher atmospheric layers through processes such as magnetic reconnection and propagation of waves. The in-depth study of all aforementioned characteristics and processes, with the further addition of non-LTE physics, as well as the use of three-dimensional numerical simulations poses a fascinating challenge for both theory and numerical modeling of chromospheric fine-scale structures.

  5. The fine structure of capillaries and small arteries.

    Science.gov (United States)

    MOORE, D H; RUSKA, H

    1957-05-25

    Details of capillary endothelia of the mammalian heart are described and compared with capillaries of other organs and tissues. Continuous invagination and pinching off of the plasma membrane to form small vesicles which move across the cytoplasm are suggested as constituting a means of active and selective transmission through capillary walls (12). This might be designated as cytopempsis (transmission by cell). The fine structure of the different layers in the walls of small heart arteries is demonstrated. Endothelial protrusions extend through windows of the elestica interna to make direct contact with smooth muscle plasma membranes. The elastica interna appears to vary greatly in both thickness and density, and probably restricts filtration, diffusion, and osmosis to such an extent that windows and the transport mechanisms described (cytopempsis) are necessary for the functional integrity of the smooth muscle layer. The contractile material consists of very fine, poorly oriented filaments. PMID:13438930

  6. Study of the inner structure of fine coal filter cake

    Energy Technology Data Exchange (ETDEWEB)

    Shi Chang-sheng; Xie Guang-yuan; Zhang Yue-qiu [China University of Mining & Technology, Xuzhou (China). School of Environmental Sciences and Spatial Informatics

    2006-07-01

    The dewatering of fine coal in coal processing is very important. Based on the theories of dewatering, the inner structure of the filter cake was analyzed using the scanning-electron microscope. The porosity, the maximal diameter of voids and the average area of voids were analyzed in detail. Genuine causes influencing final moisture of the cake were identified. The results show that the porosity of the filter cake increased from 3.87 % to 15.46 % with the increasing of size of fine coal from 0.045 mm to 0.5 mm, and the average area of the void increased from 2.14{mu}m{sup 2} to 8.24 {mu}m{sup 2}. 8 refs., 8 figs., 5 tabs.

  7. The fine structure of the Saturnian ring system

    International Nuclear Information System (INIS)

    A dust disc within a planetary magnetosphere constitutes a novel type of dust-ring current. Such an azimuthal current carrying dust disc is subject to the dusty plasma analog of the well known finite-resistivity 'tearing' mode instability in regular plasma current sheets, at long wavelengths. It is proposed that the presently observed fine ringlet structure of the Saturnian ring system is a relic of this process operating at cosmogonic times and breaking up the initial proto-ring (which may be regarded as an admixture of fine dust and plasma) into an ensemble of thin ringlets. It is shown that this instability developes at a rate that is many orders of magnitude faster than any other known instability, when the disc thickness reaches a value that is comparable to its present observed value. (Auth.)

  8. The fine structure line deficit in S 140

    CERN Document Server

    Ossenkopf, Volker; Okada, Yoko; Mookerjea, Bhaswati; van der Tak, Floris F S; Simon, Robert; Pütz, Patrick; Güsten, Rolf

    2015-01-01

    We try to understand the gas heating and cooling in the S 140 star forming region by spatially and spectrally resolving the distribution of the main cooling lines with GREAT/SOFIA. We mapped the fine structure lines of [OI] (63 {\\mu}m) and [CII] (158 {\\mu}m) and the rotational transitions of CO 13-12 and 16-15 with GREAT/SOFIA and analyzed the spatial and velocity structure to assign the emission to individual heating sources. We measure the optical depth of the [CII] line and perform radiative transfer computations for all observed transitions. By comparing the line intensities with the far-infrared continuum we can assess the total cooling budget and measure the gas heating efficiency. The main emission of fine structure lines in S 140 stems from a 8.3'' region close to the infrared source IRS 2 that is not prominent at any other wavelength. It can be explained by a photon-dominated region (PDR) structure around the embedded cluster if we assume that the [OI] line intensity is reduced by a factor seven due ...

  9. Structural transformation of finely dispersed, various rank anthracite during graphitization

    Energy Technology Data Exchange (ETDEWEB)

    Chuparova, L.D.; Yurkovskii, I.M.; Ivanov, V.P.; Kirilin, N.S.

    1987-09-01

    Investigates effect of dispersity, rank and petrographic composition on structural transformation of anthracite during high temperature treatment (1600-2500 C). Discusses tests made on 3 types of vitrainized anthracite (low, medium and high degree of metamorphism) obtained from Donbass mines and on samples of fusainized anthracite from the Gorlovsk basin. Establishes that vitrainized high and medium metamorphic grade anthracite might have components that do not graphitize. States that fine comminution of anthracite results in transformation of componental composition and that the effect of mineral additives on anthracite graphitization rises with increase in degree of comminution. 3 refs.

  10. Topological Quantization in Units of the Fine Structure Constant

    Energy Technology Data Exchange (ETDEWEB)

    Maciejko, Joseph; /Stanford U., Phys. Dept. /Stanford U., Materials Sci. Dept. /SLAC; Qi, Xiao-Liang; /Station Q, UCSB /Stanford U., Phys. Dept. /Stanford U., Materials Sci. Dept. /SLAC; Drew, H.Dennis; /Maryland U.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept. /Stanford U., Materials Sci. Dept. /SLAC

    2011-11-11

    Fundamental topological phenomena in condensed matter physics are associated with a quantized electromagnetic response in units of fundamental constants. Recently, it has been predicted theoretically that the time-reversal invariant topological insulator in three dimensions exhibits a topological magnetoelectric effect quantized in units of the fine structure constant {alpha} = e{sup 2}/{h_bar}c. In this Letter, we propose an optical experiment to directly measure this topological quantization phenomenon, independent of material details. Our proposal also provides a way to measure the half-quantized Hall conductances on the two surfaces of the topological insulator independently of each other.

  11. Distortion product otoacoustic emission fine structure of symphony orchestra musicians

    DEFF Research Database (Denmark)

    Reuter, Karen; Hammershøi, Dorte

    Otoacoustic emissions (OAE) are sounds produced by the healthy inner ear. They can be measured as low-level signals in the ear canal and are used to monitor the functioning of outer hair cells.Several studies indicate that OAE might be a more sensitive measure to detect early noise-induced hearing...... losses than puretone audiometry. The distortion product otoacoustic emission (DPOAE) fine structure is obtained when the ear is stimulated by dual tone stimuli using a high frequency resolution. It is characterized by quasi-periodic variations across frequency, as it can be observed in the hearing...

  12. Distortion product otoacoustic emission fine structure of symphony orchestra musicians

    DEFF Research Database (Denmark)

    Reuter, Karen; Hammershøi, Dorte

    2006-01-01

    Otoacoustic emissions (OAE) are sounds produced by the healthy inner ear. They can be measured as low-level signals in the ear canal and are used to monitor the functioning of outer hair cells. Many studies indicate that OAE might be a more sensitive measure to detect early noise-induced haring...... losses than pure-tone audiometry. The distortion product otoacoustic emission (DPOAE) fine structure is obtained when the ear is stiumulated by dual tone stimuli using a high frequency resolution. It is characterized by quasi-periodic variations across frequency, as it can be observed in the hearing...

  13. A simple cosmology with a varying fine structure constant

    International Nuclear Information System (INIS)

    We investigate the cosmological consequences of a theory in which the electric charge e can vary. In this theory the fine structure 'constant', α, remains almost constant in the radiation era, undergoes a small increase in the matter era, but approaches a constant value when the universe starts accelerating because of a positive cosmological constant. This model satisfies geonuclear, nucleosynthesis, and cosmic microwave background constraints on time variation in α , while fitting the observed accelerating Universe and evidence for small α variations in quasar spectra. It also places specific restrictions on the nature of the dark matter. Further tests, involving stellar spectra and Eoetvoes experiments, are proposed

  14. Urban, Forest, and Agricultural AIS Data: Fine Spectral Structure

    Science.gov (United States)

    Vanderbilt, V. C.

    1985-01-01

    Spectra acquired by the Airborne Imaging Spectrometer (AIS) near Lafayette, IN, Ely, MN, and over the Stanford University campus, CA were analyzed for fine spectral structure using two techniques: the ratio of radiance of a ground target to the radiance of a standard and also the correlation coefficient of radiances at adjacent wavelengths. The results show ramp like features in the ratios. These features are due to the biochemical composition of the leaf and to the optical scattering properties of its cuticle. The size and shape of the ramps vary with ground cover.

  15. Emission wavelength tuning of fluorescence by fine structural control of optical metamaterials with Fano resonance

    Science.gov (United States)

    Moritake, Y.; Kanamori, Y.; Hane, K.

    2016-09-01

    We demonstrated fine emission wavelength tuning of quantum dot (QD) fluorescence by fine structural control of optical metamaterials with Fano resonance. An asymmetric-double-bar (ADB), which was composed of only two bars with slightly different bar lengths, was used to obtain Fano resonance in the optical region. By changing the short bar length of ADB structures with high dimensional accuracy in the order of 10 nm, resonant wavelengths of Fano resonance were controlled from 1296 to 1416 nm. Fluorescence of QDs embedded in a polymer layer on ADB metamaterials were modified due to coupling to Fano resonance and fine tuning from 1350 to 1376 nm was observed. Wavelength tuning of modified fluorescence was reproduced by analysis using absorption peaks of Fano resonance. Tuning range of modified fluorescence became narrow, which was interpreted by a simple Gaussian model and resulted from comparable FWHM in QD fluorescence and Fano resonant peaks. The results will help the design and fabrication of metamaterial devices with fluorophores such as light sources and biomarkers.

  16. Emission wavelength tuning of fluorescence by fine structural control of optical metamaterials with Fano resonance.

    Science.gov (United States)

    Moritake, Y; Kanamori, Y; Hane, K

    2016-09-13

    We demonstrated fine emission wavelength tuning of quantum dot (QD) fluorescence by fine structural control of optical metamaterials with Fano resonance. An asymmetric-double-bar (ADB), which was composed of only two bars with slightly different bar lengths, was used to obtain Fano resonance in the optical region. By changing the short bar length of ADB structures with high dimensional accuracy in the order of 10 nm, resonant wavelengths of Fano resonance were controlled from 1296 to 1416 nm. Fluorescence of QDs embedded in a polymer layer on ADB metamaterials were modified due to coupling to Fano resonance and fine tuning from 1350 to 1376 nm was observed. Wavelength tuning of modified fluorescence was reproduced by analysis using absorption peaks of Fano resonance. Tuning range of modified fluorescence became narrow, which was interpreted by a simple Gaussian model and resulted from comparable FWHM in QD fluorescence and Fano resonant peaks. The results will help the design and fabrication of metamaterial devices with fluorophores such as light sources and biomarkers.

  17. Atomic structure of Mn-rich nanocolumns probed by x-ray absorption spectroscopy

    Science.gov (United States)

    Rovezzi, M.; Devillers, T.; Arras, E.; d'Acapito, F.; Barski, A.; Jamet, M.; Pochet, P.

    2008-06-01

    In this letter, we have used the extended x-ray-absorption fine-structure (EXAFS) technique to investigate the structure of Mn-rich self-organized nanocolumns grown by low temperature molecular beam epitaxy. The EXAFS analysis has shown that Mn-rich nanocolumns exhibit a complex local structure that cannot be described by a simple substitutional model. Additional interatomic distances had to be considered in the EXAFS model which are in excellent agreement with the structure of a Ge-3Mn building block tetrahedron of Ge3Mn5.

  18. Effect of fine solid particles on absorption rate of gaseous CO2

    Institute of Scientific and Technical Information of China (English)

    Sumin LU; Youguang MA; Shuhua SHEN; Chunying ZHU

    2008-01-01

    The influence of the properties of solid particles in slurry on the absorption of CO2 in the slurry was inves-tigated in a stirred thermostatic reactor. The absorption experiments were carried out in three different slurries con-sisting of water, cyclohexane and soybean oil, respectively, and three kinds of solid particles (active carbon, active alu-mina and silica gel) were incorporated into each of the above mentioned slurries separately. The experimental results show that the active carbon particles could enhance the absorption rate of gaseous CO2 in the aqueous slurry, while in the cyclohexane slurry, active carbon particles indi-cated no the absorption enhancement effect. However, it was observed that the active alumina and silica gel particles could enhance the absorption rate of CO2 in the cyclohex-ane slurry. These phenomena indicate that the solid part-icles, which could enhance the gaseous CO2 absorption rate, should possess two properties simultaneously, i.e. they rejected the solvent and had higher adsorption capacity for the solute. The experimental results also show that, as for those solid particles which could enhance the gas absorption rate, the enhancement increased quickly with the increase of solid concentration in slurry at first, and then reached a constant value gradually. It was also found that the enhancement factor was related to the coverage fraction of solid particles on the gas-liquid interface, and due to the reduction of surface fraction with increasing stirred speed, the enhancement factor decreased.

  19. QED Based Calculation of the Fine Structure Constant

    Energy Technology Data Exchange (ETDEWEB)

    Lestone, John Paul [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-10-13

    Quantum electrodynamics is complex and its associated mathematics can appear overwhelming for those not trained in this field. Here, semi-classical approaches are used to obtain a more intuitive feel for what causes electrostatics, and the anomalous magnetic moment of the electron. These intuitive arguments lead to a possible answer to the question of the nature of charge. Virtual photons, with a reduced wavelength of λ, are assumed to interact with isolated electrons with a cross section of πλ2. This interaction is assumed to generate time-reversed virtual photons that are capable of seeking out and interacting with other electrons. This exchange of virtual photons between particles is assumed to generate and define the strength of electromagnetism. With the inclusion of near-field effects the model presented here gives a fine structure constant of ~1/137 and an anomalous magnetic moment of the electron of ~0.00116. These calculations support the possibility that near-field corrections are the key to understanding the numerical value of the dimensionless fine structure constant.

  20. Black Holes and Quantum Theory: The Fine Structure Constant Connection

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2006-10-01

    Full Text Available The new dynamical theory of space is further confirmed by showing that the effective “black hole” masses M BH in 19 spherical star systems, from globular clusters to galaxies, with masses M , satisfy the prediction that M BH = α 2 M , where α is the fine structure constant. As well the necessary and unique generalisations of the Schr ̈ odinger and Dirac equations permit the first derivation of gravity from a deeper theory, showing that gravity is a quantum effect of quantum matter interacting with the dynamical space. As well the necessary generalisation of Maxwell’s equations displays the observed light bending effects. Finally it is shown from the generalised Dirac equation where the spacetime mathematical formalism, and the accompanying geodesic prescription for matter trajectories, comes from. The new theory of space is non-local and we see many parallels between this and quantum theory, in addition to the fine structure constant manifesting in both, so supporting the argument that space is a quantum foam system, as implied by the deeper information-theoretic theory known as Process Physics. The spatial dynamics also provides an explanation for the “dark matter” effect and as well the non-locality of the dynamics provides a mechanism for generating the uniformity of the universe, so explaining the cosmological horizon problem.

  1. Clusters of galaxies and variation of the fine structure constant

    CERN Document Server

    Galli, Silvia

    2012-01-01

    We propose a new method to probe for variations in the fine structure constant alpha using clusters of galaxies, opening up a window on a new redshift range for such constraints. Hot clusters shine in the X-ray mainly due to bremsstrahlung, while they leave an imprint on the CMB frequency spectrum through the Sunyaev-Zel'dovich effect. These two physical processes can be characterized by the integrated Comptonization parameter Y_SZ DA^2 and its X-ray counterpart, the Y_X parameter. The ratio of these two quantities is expected to be constant from numerical simulations and current observations. We show that this fact can be exploited to constrain alpha, as the ratio of the two parameters depends on the fine structure constant as alpha^{3.5}. We determine current constraints from a combination of Planck SZ and XMM-Newton data, testing different models of variation of alpha. When fitting for a constant value of alpha, we find that current constraints are at the 1% level, comparable with current CMB constraints. ...

  2. Herschel Galactic plane survey of [NII] fine structure emission

    CERN Document Server

    Goldsmith, Paul F; Langer, William D; Pineda, Jorge L

    2015-01-01

    We present the first large scale high angular resolution survey of ionized nitrogen in the Galactic Plane through emission of its two fine structure transitions ([NII]) at 122 $\\mu$m and 205 $\\mu$m. The observations were largely obtained with the PACS instrument onboard the Herschel Space Observatory. The lines-of-sight were in the Galactic plane, following those of the Herschel OTKP project GOT C+. Both lines are reliably detected at the 10$^{-8}$ - 10$^{-7}$ $W$m$^{-2}$sr$^{-1}$ level over the range -60$^{o}$ $\\leq$ $l$ $\\leq$ 60$^{o}$. The $rms$ of the intensity among the 25 PACS spaxels of a given pointing is typically less than one third of the mean intensity, showing that the emission is extended. [NII] is produced in gas in which hydrogen is ionized, and collisional excitation is by electrons. The ratio of the two fine structure transitions provides a direct measurement of the electron density, yielding $n(e)$ largely in the range 10 to 50 cm$^{-3}$ with an average value of 29 cm$^{-3}$ and N$^+$ colum...

  3. Surface structure of CdSe Nanorods revealed by combined X-rayabsorption fine structure measurements and ab-initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Aruguete, Deborah A.; Marcus, Matthew A.; Li, Liang-shi; Williamson, Andrew; Fakra, Sirine; Gygi, Francois; Galli, Giulia; Alivisatos, A. Paul

    2006-01-27

    We report orientation-specific, surface-sensitive structural characterization of colloidal CdSe nanorods with extended X-ray absorption fine structure spectroscopy and ab-initio density functional theory calculations. Our measurements of crystallographically-aligned CdSe nanorods show that they have reconstructed Cd-rich surfaces. They exhibit orientation-dependent changes in interatomic distances which are qualitatively reproduced by our calculations. These calculations reveal that the measured interatomic distance anisotropy originates from the nanorod surface.

  4. Structural studies using X-ray absorption and scattering techniques

    International Nuclear Information System (INIS)

    The thesis presents extended X-ray absorption fine structure, EXAFS, and large angle X-ray scattering, LAXS, techniques; instrumentation, data collection and reduction, and applications. These techniques have been used to determine the structures of magnesium halides and organomagnesium halides in diethyl ether and tetrahydrofuran solution. The iodides were used for the LAXS measurements and Br K edge EXAFS data were collected for the corresponding bromides. Two different complexes are present in the diethyl ether solution of magnesium iodide; a polymeric chain-type structure where magnesium is tetrahedrally coordinated, as well as dimeric complex with octahedrally coordinated magnesium. Solvated MgI+ is the dominating species in tetrahydrofuran solution. The organomagnesium halides are present in diethyl ether solution as both solvated monomeric and dimeric complexes. Magnesium coordinates a halide ion, an alkyl or aryl group and four solvent molecules octahedrally in the monomeric complex. In the dimeric complex magnesium is octahedrally coordinated by two bridging halide ions, an alkyl or aryl group and three solvent molecules. The distribution of monomeric and dimeric complexes in various solutions are given by a dimerisation constant, Kdl. The results indicate that the Schlenk equilibrium is present in these solutions, however, in an extended form. In diethyl ether solution, where MgX2 does not dissociate, no MgX2 complex and thereby no Schlenk equilibrium has been observed. In tetrahydrofuran solution MgI2 has dissociated into mainly MgI+ and I-. This indicates that the concentration of MgI2 is low and that the Schlenk equilibrium should be expanded even further to include the dissociation equilibrium of the magnesium halide. In the thesis Fe K edge EXAFS data collected for the semireduced form of protein A of methane monooxygenase from Methylococcus capsulatus, are also presented. (139 refs.)

  5. Thermally detected optical absorption in sophisticated nitride structures

    Energy Technology Data Exchange (ETDEWEB)

    Vasson, A.; Leymarie, J. [LASMEA-UMR 6602 CNRS-UBP, 63177 Aubiere Cedex (France); Shubina, T.V. [Ioffe Physico-Technical Institute, RAS, St. Petersburg 194021 (Russian Federation)

    2005-02-01

    The thermally detected optical absorption (TDOA) is applied to elucidate peculiarities of absorption in nitride structures of unusual morphology like GaN nanocolumns or InN layers with various imperfections. A study of GaN structures permits us to establish position of an absorption edge in TDOA spectra. We demonstrate that the absorption edge is different in GaN regions of opposite polarities. In InN with metallic In inclusions, this technique enable separation of InN interband absorption and extinction related to the Mie resonances, if the latter are below the principal absorption edge. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Shell structure of pancakes and the absorption spectra of quasars

    International Nuclear Information System (INIS)

    The formation of the absorption lines of atomic hydrogen in the spectra of distant quasars is considered. A model is constructed of the formation of shells of a pancake formed in the adiabatic picture of the generation of the large-scale structure of the universe. It is shown that the absorption lines can form doublets and the equivalent widths of the corresponding lines are calculated. The physical conditions corresponding to the observed heavy-element absorption spectra are discussed

  7. Fine-structure energy levels and lifetimes in Br XXIV

    Energy Technology Data Exchange (ETDEWEB)

    Tayal, Vikas; Gupta, G P [Department of Physics, SD (Postgraduate) College, Muzaffarnagar, UP (India)

    2005-11-28

    We have performed large-scale CIV3 calculations of excitation energies from the ground state for 48 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the (1s{sup 2}2s{sup 2}2p{sup 6})3s{sup 2}({sup 1}S), 3s3p({sup 1,3}P{sup o}), 3s3d({sup 1,3}D), 3s4s({sup 1,3}S), 3s4p({sup 1,3}P{sup o}), 3s4d({sup 1,3}D), 3s4f({sup 1,3}F{sup o}), 3p{sup 2}({sup 1}S, {sup 3}P, {sup 1}D), 3p3d({sup 1,3}P{sup o}, {sup 1,3}D{sup o}, {sup 1,3}F{sup o}), 3p4s({sup 1,3}P{sup o}) and 3d{sup 2}({sup 1}S, {sup 3}P, {sup 1}D) states of Br XXIV. These states are represented by extensive configuration-interaction (CI) wavefunctions obtained using the CIV3 computer code of Hibbert. The relativistic effects in intermediate coupling are incorporated by means of the Breit-Pauli Hamiltonian which consists of the non-relativistic term plus the one-body mass correction, Darwin term, and spin-orbit, spin-other-orbit and spin-spin operators. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made so that the energy splittings are as close as possible to the experimental values. Our calculated excitation energies, including their ordering, are in excellent agreement with the available experimental results except that the levels {sup 1}D{sub 2} and {sup 3}P{sub 2} belonging to the same configuration 3p{sup 2} interchanged their positions compared to the experiment. This interchange in our calculation is discussed and explained through eigenvector compositions of the two levels. From our radiative decay rates, we have calculated radiative lifetimes of some fine-structure levels. Our calculated lifetimes of the levels 3s3p({sup 3}P{sub 1}) and 3s3p({sup 1}P{sub 1}) are found to be in good agreement with the experimental and other theoretical results. In this calculation we also predict new data for several fine-structure levels where no other theoretical and experimental

  8. Nonlinear Electrodynamics Analysis Of The Fine Structure Constant

    Science.gov (United States)

    Mbelek, Jean Paul

    2010-10-01

    It has been claimed that during the late time history of our universe, the fine structure constant, α, has been increasing [1],[2]. However, other teams has claimed a discordant result [3],[4]. Also, the current precision of laboratory tests is not sufficient to either comfort or reject any of these astronomical observations. Here we suggest that a nonlinear electrodynamics (NLED) interaction of photons with the weak local background magnetic fields of a gas cloud absorber can reconcile the null result of refs.[3] and [4] with the negative variation found by refs. [2] and [1] and also to find a bridge with the positive variation found later by Levshakov et al.. [5]-[7]. Moreover, NLED photon propagation in a vacuum permeated by a background magnetic field is actually in full agreement with constraints from Oklo natural reactor data.

  9. Measurement of the Running of the Fine-Structure Constant

    CERN Document Server

    Acciarri, M; Adriani, O; Aguilar-Benítez, M; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Ambrosi, G; Anderhub, H; Andreev, V P; Angelescu, T; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Baksay, L; Balandras, A; Ball, R C; Banerjee, S; Banerjee, Sw; Barczyk, A; Barillère, R; Barone, L; Bartalini, P; Basile, M; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Bhattacharya, S; Biasini, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böhm, A; Boldizsar, L; Borgia, B; Bourilkov, D; Bourquin, Maurice; Braccini, S; Branson, J G; Brigljevic, V; Brochu, F; Buffini, A; Buijs, A; Burger, J D; Burger, W J; Button, A M; Cai, X D; Campanelli, M; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Castellini, G; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada-Canales, M; Cesaroni, F; Chamizo-Llatas, M; Chang, Y H; Chaturvedi, U K; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, Luisa; Cindolo, F; Civinini, C; Clare, I; Clare, R; Coignet, G; Colijn, A P; Colino, N; Costantini, S; Cotorobai, F; Cozzoni, B; de la Cruz, B; Csilling, Akos; Cucciarelli, S; Dai, T S; van Dalen, J A; D'Alessandro, R; De Asmundis, R; Déglon, P L; Degré, A; Deiters, K; Della Volpe, D; Denes, P; De Notaristefani, F; De Salvo, A; Diemoz, M; Van Dierendonck, D N; Di Lodovico, F; Dionisi, C; Dittmar, Michael; Dominguez, A; Doria, A; Dova, M T; Duchesneau, D; Dufournaud, D; Duinker, P; Durán, I; El-Mamouni, H; Engler, A; Eppling, F J; Erné, F C; Extermann, Pierre; Fabre, M; Faccini, R; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, Marta; Ferguson, T; Ferroni, F; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisk, I; Forconi, G; Fredj, L; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gau, S S; Gentile, S; Gheordanescu, N; Giagu, S; Gong, Z F; Grenier, G; Grimm, O; Grünewald, M W; Guida, M; van Gulik, R; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hasan, A; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hidas, P; Hirschfelder, J; Hirstius, A; Hofer, H; Holzner, G; Hoorani, H; Hou, S R; Iashvili, I; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Khan, R A; Kaur, M; Kienzle-Focacci, M N; Kim, D; Kim, D H; Kim, J K; Kim, S C; Kirkby, Jasper; Kiss, D; Kittel, E W; Klimentov, A; König, A C; Kopp, A; Koutsenko, V F; Kräber, M H; Krämer, R W; Krenz, W; Krüger, A; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lassila-Perini, K M; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Lee, H J; Le Goff, J M; Leiste, R; Leonardi, E; Levchenko, P M; Li Chuan; Likhoded, S A; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lü, Y S; Lübelsmeyer, K; Luci, C; Luckey, D; Lugnier, L; Luminari, L; Lustermann, W; Ma Wen Gan; Maity, M; Malgeri, L; Malinin, A; Maña, C; Mangeol, D J J; Marchesini, P A; Marian, G; Martin, J P; Marzano, F; Massaro, G G G; Mazumdar, K; McNeil, R R; Mele, S; Merola, L; Meschini, M; Metzger, W J; Von der Mey, M; Mihul, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Molnár, P; Monteleoni, B; Moulik, T; Muanza, G S; Muheim, F; Muijs, A J M; Musy, M; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Niessen, T; Nisati, A; Nowak, H; Oh, Yu D; Organtini, G; Oulianov, A; Palomares, C; Pandoulas, D; Paoletti, S; Paolucci, P; Paramatti, R; Park, H K; Park, I H; Pascale, G; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pieri, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Postema, H; Pothier, J; Produit, N; Prokofev, D; Prokofiev, D O; Quartieri, J; Rahal-Callot, G; Rahaman, M A; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Raspereza, A V; Raven, G; Razis, P A; Ren, D; Rescigno, M; Reucroft, S; Van Rhee, T; Riemann, S; Riles, K; Robohm, A; Rodin, J; Roe, B P; Romero, L; Rosca, A; Rosier-Lees, S; Rubio, Juan Antonio; Ruschmeier, D; Rykaczewski, H; Saremi, S; Sarkar, S; Salicio, J; Sánchez, E; Sanders, M P; Sarakinos, M E; Schäfer, C; Shchegelskii, V; Schmidt-Kärst, S; Schmitz, D; Schopper, Herwig Franz; Schotanus, D J; Schwering, G; Sciacca, C; Sciarrino, D; Seganti, A; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A V; Siedenburg, T; Son, D; Smith, B; Spillantini, P; Steuer, M; Stickland, D P; Stone, A; Stone, H; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Suter, H; Swain, J D; Szillási, Z; Sztaricskai, T; Tang, X W; Tauscher, Ludwig; Taylor, L; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tung, K L; Uchida, Y; Ulbricht, J; Valente, E; Vesztergombi, G; Vetlitskii, I; Vicinanza, D; Viertel, Gert M; Villa, S; Vivargent, M; Vlachos, S; Vodopyanov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Vorvolakos, A; Wadhwa, M; Wallraff, W; Wang, M; Wang, X L; Wang, Z M; Weber, A; Weber, M; Wienemann, P; Wilkens, H; Wu, S X; Wynhoff, S; Xia, L; Xu, Z Z; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Ye, J B; Yeh, S C; Zalite, A; Zalite, Yu; Zhang, Z P; Zhu, G Y; Zhu, R Y; Zichichi, A; Zilizi, G; Zöller, M

    2000-01-01

    Small-angle Bhabha scattering data recorded at the Z resonance and large-angleBhabha scattering data recorded at $\\sqrt{s} = 189$ \\textrm{Ge\\kern -0.1em V} bythe L3 detector at LEP are used to measure the running of the effective fine-structure constant for spacelike momentum transfers. The results are\\begin{eqnarray*} \\alpha^{-1}(-2.1 \\mathrm{Ge\\kern -0.1em V}^{2}) - \\alpha^{-1}(-6.25 \\mathrm{Ge\\kern -0.1em V}^{2}) & = & 0.78 \\pm 0.26 \\\\ \\alpha^{-1}(-12.25 \\mathrm{Ge\\kern -0.1em V}^{2}) - \\alpha^{-1}(-3434 \\mathrm{Ge\\kern -0.1em V}^{2}) & = & 3.80 \\pm 1.29, \\\\\\end{eqnarray*}in agreement with theoretical predictions.

  10. Varying Fine Structure Constant and Black Hole Physics

    CERN Document Server

    Das, S; Das, Saurya; Kunstatter, Gabor

    2003-01-01

    Recent astrophysical observations suggest that the fine structure constant $\\alpha=e^2/\\hbar c$ may be slowly increasing with time. This may be due to an increase of $e$ or a decrease of $c$, or both. In this article, we argue from model independent considerations that this variation should be considered adiabatic. Then, we examine in detail the consequences of such an adiabatic variation in the context of a specific model of quantized charged black holes. We find that the second law of black hole thermodynamics is obeyed, regardless of the origin of the variation, and that interesting constraints arise on the charge and mass of black holes. Finally, we estimate the work done on a black hole of mass $M$ due to the $\\alpha$ variation.

  11. Atomic Clocks and Variations of the FIne Structure Constant

    Science.gov (United States)

    Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    1995-01-01

    We describe a new test for possible variations of the fine structure constant alpha by comparisons of rates between clocks based on hyperfine transitions in alkali atoms with different atomic number Z. H-maser, Cs, and Hg(+) clocks have a different dependence on alpha via relativistic contributions of order (Z-alpha)(sup 2). Recent H-maser vs Hg(+) clock comparison data improve laboratory limits on a time variation by 100-fold to give dot-alpha less than or equal to 3.7 x 10(exp -14)/yr. Future laser cooled clocks (Be(+), Rb, Cs, Hg(+), etc.), when compared, will yield the most sensitive of all tests for dot-alpha/alpha.

  12. Varying Fine-Structure Constant and the Cosmological Constant Problem

    CERN Document Server

    Fujii, Y

    2003-01-01

    We start with a brief account of the latest analysis of the Oklo phenomenon providing the still most stringent constraint on time-variability of the fine- structure constant $\\alpha$. Comparing this with the recent result from the measurement of distant QSO's appears to indicate a non-uniform time-dependence, which we argue to be related to another recent finding of the accelerating universe. This view is implemented in terms of the scalar-tensor theory, applied specifically to the small but nonzero cosmological constant. Our detailed calculation shows that these two phenomena can be understood in terms of a common origin, a particular behavior of the scalar field, dilaton. We also sketch how this theoretical approach makes it appropriate to revisit non- Newtonian gravity featuring small violation of Weak Equivalence Principle at medium distances.

  13. Varying Fine-Structure Constant and the Cosmological Constant Problem

    Science.gov (United States)

    Fujii, Yasunori

    We start with a brief account of the latest analysis of the Oklo phenomenon providing the still most stringent constraint on time variability of the fine-structure constant α. Comparing this with the recent result from the measurement of distant QSO's appears to indicate a non-uniform time-dependence, which we argue to be related to another recent finding of the accelerating universe. This view is implemented in terms of the scalar-tensor theory, applied specifically to the small but nonzero cosmological constant. Our detailed calculation shows that these two phenomena can be understood in terms of a common origin, a particular behavior of the scalar field, dilaton. We also sketch how this theoretical approach makes it appropriate to revisit non-Newtonian gravity featuring small violation of Weak Equivalence Principle at medium distances.

  14. Fine-structure constant constraints on dark energy

    CERN Document Server

    Martins, C J A P

    2015-01-01

    We use astrophysical and atomic clock tests of the stability of the fine-structure constant $\\alpha$, together with Type Ia supernova and Hubble parameter data, to constrain the simplest class of dynamical dark energy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling, $\\zeta$, to the electromagnetic sector) the $\\alpha$ variation. We show how current data tightly constrains a combination of $\\zeta$ and the dark energy equation of state $w_0$. At the $95\\%$ confidence level and marginalizing over $w_0$ we find $|\\zeta|<5\\times10^{-6}$, with the atomic clock tests dominating the constraints. The forthcoming generation of high-resolution ultra-stable spectrographs will enable significantly tighter constraints.

  15. Behavioral Measures of Monaural Temporal Fine Structure Processing

    DEFF Research Database (Denmark)

    Santurette, Sébastien; Dau, Torsten

    Deficits in temporal fine structure (TFS) processing found in hearing-impaired listeners have been shown to correlate poorly to audibility and frequency selectivity, despite adverse effects on speech perception in noise. This underlines the need for an independent measure of TFS processing when...... characterizing hearing impairment. Estimating the acuity of monaural TFS processing in humans however remains a challenge. One suggested measure is based on the ability of listeners to detect a pitch shift between harmonic (H) and inharmonic (I) complex tones with unresolved components (e.g. Moore et al., JASA...... and spectral resolution, for the low pitch evoked by high-frequency complex tones. The aim was to estimate the efficiency of monaural TFS cues as a function of the stimulus center frequency Fc and its ratio N to the stimulus envelope repetition rate. A pitch-matching paradigm was used, such that changes...

  16. A heterogeneity test for fine-scale genetic structure.

    Science.gov (United States)

    Smouse, Peter E; Peakall, Rod; Gonzales, Eva

    2008-07-01

    For organisms with limited vagility and/or occupying patchy habitats, we often encounter nonrandom patterns of genetic affinity over relatively small spatial scales, labelled fine-scale genetic structure. Both the extent and decay rate of that pattern can be expected to depend on numerous interesting demographic, ecological, historical, and mating system factors, and it would be useful to be able to compare different situations. There is, however, no heterogeneity test currently available for fine-scale genetic structure that would provide us with any guidance on whether the differences we encounter are statistically credible. Here, we develop a general nonparametric heterogeneity test, elaborating on standard autocorrelation methods for pairs of individuals. We first develop a 'pooled within-population' correlogram, where the distance classes (lags) can be defined as functions of distance. Using that pooled correlogram as our null-hypothesis reference frame, we then develop a heterogeneity test of the autocorrelations among different populations, lag-by-lag. From these single-lag tests, we construct an analogous test of heterogeneity for multilag correlograms. We illustrate with a pair of biological examples, one involving the Australian bush rat, the other involving toadshade trillium. The Australian bush rat has limited vagility, and sometimes occupies patchy habitat. We show that the autocorrelation pattern diverges somewhat between continuous and patchy habitat types. For toadshade trillium, clonal replication in Piedmont populations substantially increases autocorrelation for short lags, but clonal replication is less pronounced in mountain populations. Removal of clonal replicates reduces the autocorrelation for short lags and reverses the sign of the difference between mountain and Piedmont correlograms.

  17. Neon Fine-Structure Line Emission By X-ray Irradiated Protoplanetary Disks

    CERN Document Server

    Glassgold, A E; Igea, J; Glassgold, Alfred E.; Najita, Joan R.; Igea, Javier

    2006-01-01

    Using a thermal-chemical model for the generic T-Tauri disk of D'Alessio et al. (1999), we estimate the strength of the fine-structure emission lines of NeII and NeIII at 12.81 and 15.55 microns that arise from the warm atmosphere of the disk exposed to hard stellar X-rays. The Ne ions are produced by the absorption of keV X-rays from the K shell of neutral Ne, followed by the Auger ejection of several additional electrons. The recombination cascade of the Ne ions is slow because of weak charge transfer with atomic hydrogen in the case of Ne2+ and by essentially no charge transfer for Ne+. For a distance of 140pc, the 12.81 micron line of Ne II has a flux of 1e-14 erg/cm2s, which should be observable with the Spitzer Infrared Spectrometer and suitable ground based instrumentation. The detection of these fine-structure lines would clearly demonstrate the effects of X-rays on the physical and chemical properties of the disks of young stellar objects and provide a diagnostic of the warm gas in protoplanetary dis...

  18. Fine structure of a resonantly excited p -shell exciton in a CdTe quantum dot

    Science.gov (United States)

    Smoleński, T.; Kazimierczuk, T.; Goryca, M.; Wojnar, P.; Kossacki, P.

    2016-05-01

    We present a polarization-resolved photoluminescence excitation study of the absorption spectrum of a p -shell neutral exciton in a single CdTe/ZnTe quantum dot. We find that the fine structure of the p -shell exciton is completely analogous to the fine structure of the s -shell exciton, including the selection rules and the effects of a magnetic field applied in Faraday and Voigt configurations. The energy spectrum of the p -shell exciton is found to be well described by introducing respective isotropic and anisotropic constants of the exchange interaction between a p -shell electron and a p -shell hole. The typical values of these exchange constants averaged over several randomly selected quantum dots yield δ0p p=(0.92 ±0.16 ) meV and δ1p p=(0.58 ±0.25 ) meV. Additionally, we demonstrate that the nonresonant relaxation of the p -shell exciton conserves the exciton spin to a very high degree for both bright and dark exciton configurations.

  19. Constraints on a possible variation of the fine structure constant from galaxy cluster data

    Science.gov (United States)

    Holanda, R. F. L.; Landau, S. J.; Alcaniz, J. S.; Sánchez G., I. E.; Busti, V. C.

    2016-05-01

    We propose a new method to probe a possible time evolution of the fine structure constant α from X-ray and Sunyaev-Zel'dovich measurements of the gas mass fraction (fgas) in galaxy clusters. Taking into account a direct relation between variations of α and violations of the distance-duality relation, we discuss constraints on α for a class of dilaton runaway models. Although not yet competitive with bounds from high-z quasar absorption systems, our constraints, considering a sample of 29 measurements of fgas, in the redshift interval 0.14 intermediate redshifts. Furthermore, current and planned surveys will provide a larger amount of data and thus allow to improve the limits on α variation obtained in the present analysis.

  20. FINE STRUCTURES AND OVERLYING LOOPS OF CONFINED SOLAR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuhong; Zhang, Jun [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Xiang, Yongyuan, E-mail: shuhongyang@nao.cas.cn [Fuxian Solar Observatory, Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China)

    2014-10-01

    Using the Hα observations from the New Vacuum Solar Telescope at the Fuxian Solar Observatory, we focus on the fine structures of three confined flares and the issue why all the three flares are confined instead of eruptive. All the three confined flares take place successively at the same location and have similar morphologies, so can be termed homologous confined flares. In the simultaneous images obtained by the Solar Dynamics Observatory, many large-scale coronal loops above the confined flares are clearly observed in multi-wavelengths. At the pre-flare stage, two dipoles emerge near the negative sunspot, and the dipolar patches are connected by small loops appearing as arch-shaped Hα fibrils. There exists a reconnection between the small loops, and thus the Hα fibrils change their configuration. The reconnection also occurs between a set of emerging Hα fibrils and a set of pre-existing large loops, which are rooted in the negative sunspot, a nearby positive patch, and some remote positive faculae, forming a typical three-legged structure. During the flare processes, the overlying loops, some of which are tracked by activated dark materials, do not break out. These direct observations may illustrate the physical mechanism of confined flares, i.e., magnetic reconnection between the emerging loops and the pre-existing loops triggers flares and the overlying loops prevent the flares from being eruptive.

  1. Fine structure of the Mn acceptor in GaAs

    Science.gov (United States)

    Krainov, I. V.; Debus, J.; Averkiev, N. S.; Dimitriev, G. S.; Sapega, V. F.; Lähderanta, E.

    2016-06-01

    We reveal the electronic level structure of the Mn acceptor, which consists of a valence-band hole bound to an Mn2 + ion, in presence of applied uniaxial stress and an external magnetic field in bulk GaAs. Resonant spin-flip Raman scattering is used to measure the g factor of the AMn0 center in the ground and excited states with the total angular momenta F =1 and F =2 and characterize the optical selection rules of the spin-flip transitions between these Mn-acceptor states. We determine the random stress fields near the Mn acceptor, the constant of the antiferromagnetic exchange interaction between the valence-band holes and the electrons of the inner Mn2 + shell as well as the deformation potential for the exchange energy. The p -d exchange energy, in particular, decreases significantly with increasing compressive stress. By combining the experimental Raman study with the developed theoretical model on the scattering efficiency, in which also the random local and external uniaxial stresses and magnetic field are considered, the fine structure of the Mn acceptor is determined in full detail.

  2. Galaxy clusters, type Ia supernovae and the fine structure constant

    CERN Document Server

    Holanda, R F L; Colaço, L R; Alcaniz, J S; Landau, S J

    2016-01-01

    As is well known, measurements of the Sunyaev-Zeldovich effect can be combined with observations of the X-ray surface brightness of galaxy clusters to estimate the angular diameter distance to these structures. In this paper, we show that this technique depends on the fine structure constant, $\\alpha$. Therefore, if $\\alpha$ is a time-dependent quantity, e.g., $\\alpha=\\alpha_0 \\phi(z)$, where $\\phi$ is a function of redshift, we argue that current data do not provide the real angular diameter distance, $D_{\\rm{A}}(z)$, to the cluster but instead $D_A^{data}(z) = \\phi(z)^2 D_{\\rm{A}}(z)$. We use this result to derive constraints on a possible variation of $\\alpha$ for a class of dilaton runaway models considering a sample of 25 measurements of $D_A^{data}(z)$ in redshift range $0.023 < z < 0.784$ and estimates of $D_{\\rm{A}}(z)$ from current type Ia supernovae observations. We find no significant indication of variation of $\\alpha$ with the present data.

  3. Quasi-static energy absorption of hollow microlattice structures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, YL; Schaedler, TA; Jacobsen, AJ; Chen, X

    2014-12-01

    We present a comprehensive modeling and numerical study focusing on the energy quasi-static crushing behavior and energy absorption characteristics of hollow tube microlattice structures. The peak stress and effective plateau stress of the hollow microlattice structures are deduced for different geometrical parameters which gives volume and mass densities of energy absorption, D-v and D-m, scale with the relative density, (rho) over bar, as D-v similar to (rho) over bar (1) (5) and D-m similar to (rho) over bar (0 5), respectively, fitting very well to the experimental results of both 60 degrees inclined and 90 degrees predominately microlattices. Then the strategies for energy absorption enhancement are proposed for the engineering design of microlattice structures. By introducing a gradient in the thickness or radius of the lattice members, the buckle propagation can be modulated resulting in an increase in energy absorption density that can exceed 40%. Liquid filler is another approach to improve energy absorption by strengthening the microtruss via circumference expansion, and the gain may be over 100% in terms of volume density. Insight into the correlations between microlattice architecture and energy absorption performance combined with the high degree of architecture control paves the way for designing high performance microlattice structures for a range of impact and impulse mitigation applications for vehicles and structures. (C) 2014 Elsevier Ltd. All rights reserved.

  4. Guided fine needle absorption biopsy in the diagnosis of cysts in maritime workers.

    Science.gov (United States)

    Bartelik, W; Jaremin, B; Smolińska, D; Głombiowski, P

    Cysts in the organs of the abdominal cavity revealed in ultrasonographic examinations in patients with none or with unclear clinical symptoms cause diagnostic and fitness for work assessment problems. The aim of the study was to evaluate the usefulness of ultrasonography of cysts, combined with biochemical, bacteriological, cytological examinations and analysis of markers CEA and AFP of the fluid collected with fine needle aspiration biopsy (FAB). The study material examined were maritime workers who were submitted to these examinations for diagnostic purposes and/or previous to issue of certificate of health for work at sea. Examinations results provided support for usefulness of the method discussed in diagnosis and differentiation of inflammatory and neoplastic processes with simple cysts. This was crucial for final diagnosis, for decision about treatment and recognizing fitness for work at sea. It was concluded that the method FAB is safe both in hospital as well as in ambulatory conditions. PMID:7580347

  5. Bumblebee Homing: The Fine Structure of Head Turning Movements.

    Directory of Open Access Journals (Sweden)

    Norbert Boeddeker

    Full Text Available Changes in flight direction in flying insects are largely due to roll, yaw and pitch rotations of their body. Head orientation is stabilized for most of the time by counter rotation. Here, we use high-speed video to analyse head- and body-movements of the bumblebee Bombus terrestris while approaching and departing from a food source located between three landmarks in an indoor flight-arena. The flight paths consist of almost straight flight segments that are interspersed with rapid turns. These short and fast yaw turns ("saccades" are usually accompanied by even faster head yaw turns that change gaze direction. Since a large part of image rotation is thereby reduced to brief instants of time, this behavioural pattern facilitates depth perception from visual motion parallax during the intersaccadic intervals. The detailed analysis of the fine structure of the bees' head turning movements shows that the time course of single head saccades is very stereotypical. We find a consistent relationship between the duration, peak velocity and amplitude of saccadic head movements, which in its main characteristics resembles the so-called "saccadic main sequence" in humans. The fact that bumblebee head saccades are highly stereotyped as in humans, may hint at a common principle, where fast and precise motor control is used to reliably reduce the time during which the retinal images moves.

  6. Absorption lines and the radio structure of quasars

    International Nuclear Information System (INIS)

    High angular resolution radio observations at lambda6cm of 20 quasars are presented, all but two of which have been selected from a sample used by previous authors for a survey of absorption lines. The additional two, 1246-057 and 1333 + 286, are quasars with broad absorption lines and appear to be radio quiet. The radio structures for the entire sample of 66 sources of the previous authors are summarized and an investigation is made of whether the radio structure might provide clues on understanding the origin of the absorption lines in the range Zsub(em)-Zsub(ab) approx. 3000-18000 kms-1. The frequency of occurrence of absorption lines appears to be similar for both radio and optically selected quasars. (author)

  7. Electronic structure and optic absorption of phosphorene under strain

    Science.gov (United States)

    Duan, Houjian; Yang, Mou; Wang, Ruiqiang

    2016-07-01

    We studied the electronic structure and optic absorption of phosphorene (monolayer of black phosphorus) under strain. Strain was found to be a powerful tool for the band structure engineering. The in-plane strain in armchair or zigzag direction changes the effective mass components along both directions, while the vertical strain only has significant effect on the effective mass in the armchair direction. The band gap is narrowed by compressive in-plane strain and tensile vertical strain. Under certain strain configurations, the gap is closed and the energy band evolves to the semi-Dirac type: the dispersion is linear in the armchair direction and is gapless quadratic in the zigzag direction. The band-edge optic absorption is completely polarized along the armchair direction, and the polarization rate is reduced when the photon energy increases. Strain not only changes the absorption edge (the smallest photon energy for electron transition), but also the absorption polarization.

  8. Transient Intersubband Optical Absorption in Double Quantum Well Structure

    Institute of Scientific and Technical Information of China (English)

    WU Bin-He

    2005-01-01

    The microscopic equations of motion including many-body effects are derived to study the intersubband polarization in the double quantum well structure induced by an ultrafast pumping infrared light. Based on the selfconsistent field theory, the transient probe absorption coefficient is calculated. These calculations are beyond the previous steady-state assumption. Transient probe absorption spectra are calculated under different pumping intensity and various pump probe delay.

  9. Fine structure of Pn velocity beneath Sichuan-Yunnan region

    Institute of Scientific and Technical Information of China (English)

    黄金莉; 宋晓东; 汪素云

    2003-01-01

    We use 23298 Pn arrival-time data from Chinese national and provincial earthquake bulletins to invert fine structure of Pn velocity and anisotropy at the top of the mantle beneath the Sichuan-Yunnan and its adjacent region. The results suggest that the Pn velocity in this region shows significant lateral variation; the Pn velocity varies from 7.7 to 8.3 km/s. The Pn-velocity variation correlates well with the tectonic activity and heat flow of the region. Low Pn velocity is observed in southwest Yunnan , Tengchong volcano area, and the Panxi tectonic area. These areas have very active seismicity and tectonic activity with high surface heat flow. On the other hand, high Pn velocity is observed in some stable regions, such as the central region of the Yangtze Platform; the most pronounced high velocity area is located in the Sichuan Basin, south of Chengdu. Pn anisotropy shows a complex pattern of regional deformation. The Pn fast direction shows a prominent clockwise rotation pattern from east of the Tibetan block to the Sichuan-Yunnan diamond block to southwest Yunnan, which may be related to southeastward escape of the Tibetan Plateau material due to the collision of the Indian Plate to the Eurasia Plate. Thus there appears to be strong correlation between the crustal deformation and the upper mantle structure in the region. The delay times of events and stations show that the crust thickness decreases from the Tibetan Plateau to eastern China, which is consistent with the results from deep seismic sounding.

  10. ANALYSIS OF THE ABSORPTION CAPACITY OF STRUCTURAL FUNDS IN ROMANIA

    Directory of Open Access Journals (Sweden)

    BOLDEA BOGDAN ION

    2012-11-01

    Full Text Available In this article, we intend to realize an analysis of the absorption capacity of the Structural Funds in Romania, which is a crucial issue in the context of the regional development and the discretionary fiscal policy. We consider that the Structural Funds are the only free resource that can develop the national economy of Romania and also the roumanian society.

  11. Optimization of extraordinary optical absorption in plasmonic and dielectric structures

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard; Sigmund, Ole

    2013-01-01

    Extraordinary optical absorption (EOA) can be obtained by plasmonic surface structuring. However, studies that compare the performance of these plasmonic devices with similar structured dielectric devices are rarely found in the literature. In this work we show different methods to enhance the EO...

  12. Fine structure and optical properties of biological polarizers in crustaceans and cephalopods

    Science.gov (United States)

    Chiou, Tsyr-Huei; Caldwell, Roy L.; Hanlon, Roger T.; Cronin, Thomas W.

    2008-04-01

    The lighting of the underwater environment is constantly changing due to attenuation by water, scattering by suspended particles, as well as the refraction and reflection caused by the surface waves. These factors pose a great challenge for marine animals which communicate through visual signals, especially those based on color. To escape this problem, certain cephalopod mollusks and stomatopod crustaceans utilize the polarization properties of light. While the mechanisms behind the polarization vision of these two animal groups are similar, several distinctive types of polarizers (i.e. the structure producing the signal) have been found in these animals. To gain a better knowledge of how these polarizers function, we studied the relationships between fine structures and optical properties of four types of polarizers found in cephalopods and stomatopods. Although all the polarizers share a somewhat similar spectral range, around 450- 550 nm, the reflectance properties of the signals and the mechanisms used to produce them have dramatic differences. In cephalopods, stack-plates polarizers produce the polarization patterns found on the arms and around their eyes. In stomatopods, we have found one type of beam-splitting polarizer based on photonic structures and two absorptive polarizer types based on dichroic molecules. These stomatopod polarizers may be found on various appendages, and on the cuticle covering dorsal or lateral sides of the animal. Since the efficiencies of all these polarizer types are somewhat sensitive to the change of illumination and viewing angle, how these animals compensate with different behaviors or fine structural features of the polarizer also varies.

  13. Size-resolved measurements of brown carbon and estimates of their contribution to ambient fine particle light absorption based on water and methanol extracts

    Science.gov (United States)

    Liu, J.; Bergin, M.; Guo, H.; King, L.; Kotra, N.; Edgerton, E.; Weber, R. J.

    2013-07-01

    Light absorbing organic carbon, often termed brown carbon, has the potential to significantly contribute to the visible light absorption budget, particularly at shorter wavelengths. Currently, the relative contributions of particulate brown carbon to light absorption, as well as the sources of brown carbon are poorly understood. With this in mind field measurements were made at both urban (Atlanta), and rural (Yorkville) sites in Georgia. Measurements in Atlanta were made at both a central site and a road side site adjacent to a main highway near the city center. Fine particle brown carbon optical absorption is estimated based on Mie calculations using direct size resolved measurements of chromophores in filter extracts. Size-resolved atmospheric aerosol samples were collected using a cascade impactor and analyzed for water-soluble organic carbon (WSOC), organic and elemental carbon (OC and EC), and solution light absorption spectra of water and methanol extracts. Methanol extracts were more light-absorbing than water extracts for all size ranges and wavelengths. Absorption refractive indices of the organic extracts were calculated from solution measurements for a range of wavelengths and used with Mie theory to predict the light absorption by fine particles comprised of these components, under the assumption that brown carbon and other aerosol components were externally mixed. For all three sites, chromophores were predominately in the accumulation mode with an aerodynamic mean diameter of 0.5 μm, an optically effective size range resulting in predicted particle light absorption being a factor of 2 higher than bulk solution absorption. Fine particle absorption was also measured with a Multi-Angle Absorption Photometer (MAAP) and seven-wavelength Aethalometer. Scattering-corrected aethalometer and MAAP absorption were in good agreement at 670 nm and Mie-estimated absorption based on size-resolved EC data were within 30% of these optical instruments. When applied

  14. Size-resolved measurements of brown carbon and estimates of their contribution to ambient fine particle light absorption based on water and methanol extracts

    Directory of Open Access Journals (Sweden)

    J. Liu

    2013-07-01

    Full Text Available Light absorbing organic carbon, often termed brown carbon, has the potential to significantly contribute to the visible light absorption budget, particularly at shorter wavelengths. Currently, the relative contributions of particulate brown carbon to light absorption, as well as the sources of brown carbon are poorly understood. With this in mind field measurements were made at both urban (Atlanta, and rural (Yorkville sites in Georgia. Measurements in Atlanta were made at both a central site and a road side site adjacent to a main highway near the city center. Fine particle brown carbon optical absorption is estimated based on Mie calculations using direct size resolved measurements of chromophores in filter extracts. Size-resolved atmospheric aerosol samples were collected using a cascade impactor and analyzed for water-soluble organic carbon (WSOC, organic and elemental carbon (OC and EC, and solution light absorption spectra of water and methanol extracts. Methanol extracts were more light-absorbing than water extracts for all size ranges and wavelengths. Absorption refractive indices of the organic extracts were calculated from solution measurements for a range of wavelengths and used with Mie theory to predict the light absorption by fine particles comprised of these components, under the assumption that brown carbon and other aerosol components were externally mixed. For all three sites, chromophores were predominately in the accumulation mode with an aerodynamic mean diameter of 0.5 μm, an optically effective size range resulting in predicted particle light absorption being a factor of 2 higher than bulk solution absorption. Fine particle absorption was also measured with a Multi-Angle Absorption Photometer (MAAP and seven-wavelength Aethalometer. Scattering-corrected aethalometer and MAAP absorption were in good agreement at 670 nm and Mie-estimated absorption based on size-resolved EC data were within 30% of these optical instruments

  15. METHODS OF RECEIVING OF FINE-GRAINED STRUCTURE OF CASTINGS AT CRYSTALLIZATION

    Directory of Open Access Journals (Sweden)

    N. K. Tolochko

    2012-01-01

    Full Text Available The article deals with methods for fine-grained structure of ingots during crystallization depending on the used foundry technologies. It is shown that by using modern scientific and technological advances may improve the traditional and the development of new casting processes, providing production of cast parts with over fine-grained structure and enhanced properties.

  16. Interstellar dust grain composition from high-resolution X-ray absorption edge structure

    Science.gov (United States)

    Corrales, Lia

    2016-06-01

    X-ray light is sufficient to excite electrons from n=1 (K-shell) and n=2 (L-shell) energy levels of neutral interstellar metals, causing a sharp increase in the absorption cross-section. Near the ionization energy, the shape of the photoelectric absorption edge depends strongly on whether the atom is isolated or bound in molecules or minerals (dust). With high resolution X-ray spectroscopy, we can directly measure the state of metals and the mineral composition of dust in the interstellar medium. In addition, the scattering contribution to the X-ray extinction cross-section can be used to gauge grain size, shape, and filling factor. In order to fully take advantage of major advances in high resolution X-ray spectroscopy, lab measurements of X-ray absorption fine structure (XAFS) from suspected interstellar minerals are required. Optical constants derived from the absorption measurements can be used with Mie scattering or anomalous diffraction theory in order to model the full extinction cross-sections from the interstellar medium. Much like quasar spectra are used to probe other intergalactic gas, absorption spectroscopy of Galactic X-ray binaries and bright stars will yield key insights to the mineralogy and evolution of dust grains in the Milky Way.

  17. X-ray absorption spectroscopy: EXAFS and XANES - A versatile tool to study the atomic and electronic structure of materials

    International Nuclear Information System (INIS)

    X-ray absorption spectroscopy (XAS) had been an essential tool to gather spectroscopic information about atomic energy level structure in the early decades of this century. The correct interpretation of the oscillatory structure in the x-ray absorption cross-section above the absorption edge has transformed XAS from a spectroscopic tool to a structural technique. EXAFS (Extended X-ray Absorption Fine Structure) yields information about the interatomic distances, near neighbor coordination numbers, and lattice dynamics. XANES (X-ray Absorption Near Edge Structure), on the other hand, gives information about the valence state, energy bandwidth and bond angles. Today, there are about 50 experimental stations in various synchrotrons around the world dedicated to collecting x-ray absorption data from the bulk and surfaces of solids and liquids. In this chapter, they will give the basic principles of XAS, explain the information content of essentially two different aspects of the absorption process leading to EXAFS and XANES, and discuss the source and sample limitations

  18. Astronomical constraints on the cosmic evolution of the fine structure constant and possible quantum dimensions

    NARCIS (Netherlands)

    Carilli, CL; Menten, KM; Stocke, JT; Perlman, E; Vermeulen, R; Briggs, F; de Bruyn, AG; Conway, J; Moore, CP

    2000-01-01

    We present measurements of absorption by the 21 cm hyperfine transition of neutral hydrogen toward radio sources at substantial look-back times. These data are used in combination with observations of rotational transitions of common interstellar molecules to set limits on the evolution of the fine

  19. Dynamic energy absorption characteristics of hollow microlattice structures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, YL; Schaedler, TA; Chen, X

    2014-10-01

    Hollow microlattice structures are promising candidates for advanced energy absorption and their characteristics under dynamic crushing are explored. The energy absorption can be significantly enhanced by inertial stabilization, shock wave effect and strain rate hardening effect. In this paper we combine theoretical analysis and comprehensive finite element method simulation to decouple the three effects, and then obtain a simple model to predict the overall dynamic effects of hollow microlattice structures. Inertial stabilization originates from the suppression of sudden crushing of the microlattice and its contribution scales with the crushing speed, v. Shock wave effect comes from the discontinuity across the plastic shock wave front during dynamic loading and its contribution scales with e. The strain rate effect increases the effective yield strength upon dynamic deformation and increases the energy absorption density. A mechanism map is established that illustrates the dominance of these three dynamic effects at a range of crushing speeds. Compared with quasi-static loading, the energy absorption capacity a dynamic loading of 250 m/s can be enhanced by an order of magnitude. The study may shed useful insight on designing and optimizing the energy absorption performance of hollow microlattice structures under various dynamic loads. (C) 2014 Elsevier Ltd. All rights reserved.

  20. Absorption-reduced waveguide structure for efficient terahertz generation

    Energy Technology Data Exchange (ETDEWEB)

    Pálfalvi, L., E-mail: palfalvi@fizika.ttk.pte.hu [Institute of Physics, University of Pécs, Ifjúság ú. 6, 7624 Pécs (Hungary); Fülöp, J. A. [MTA-PTE High-Field Terahertz Research Group, Ifjúság ú. 6, 7624 Pécs (Hungary); Szentágothai Research Centre, University of Pécs, Ifjúság ú. 20, 7624 Pécs (Hungary); Hebling, J. [Institute of Physics, University of Pécs, Ifjúság ú. 6, 7624 Pécs (Hungary); MTA-PTE High-Field Terahertz Research Group, Ifjúság ú. 6, 7624 Pécs (Hungary); Szentágothai Research Centre, University of Pécs, Ifjúság ú. 20, 7624 Pécs (Hungary)

    2015-12-07

    An absorption-reduced planar waveguide structure is proposed for increasing the efficiency of terahertz (THz) pulse generation by optical rectification of femtosecond laser pulses with tilted-pulse-front in highly nonlinear materials with large absorption coefficient. The structure functions as waveguide both for the optical pump and the generated THz radiation. Most of the THz power propagates inside the cladding with low THz absorption, thereby reducing losses and leading to the enhancement of the THz generation efficiency by up to more than one order of magnitude, as compared with a bulk medium. Such a source can be suitable for highly efficient THz pulse generation pumped by low-energy (nJ-μJ) pulses at high (MHz) repetition rates delivered by compact fiber lasers.

  1. Energy absorption characteristics of nano-composite conical structures

    Science.gov (United States)

    Silva, F.; Sachse, S.; Njuguna, J.

    2012-09-01

    The effect of the filler material on the energy absorption capabilities of polyamide 6 composite structures is studied in details in the present paper. The axial dynamic and quasi-static collapse of conical structures was conducted using a high energy drop tower, as well as Instron 5500R electro-mechanical testing machine. The impact event was recorded using a high-speed camera and the fracture surface was investigated using scanning electron microscopy (SEM). The obtained results indicate an important influence of filler material on the energy absorption capabilities of the polymer composites. A significant increase in specific energy absorption (SEA) is observed in polyamide 6 (PA6) reinforced with nano-silica particles (SiO2) and glass-spheres (GS), whereas addition of montmorillonite (MMT) did not change the SEA parameter.

  2. Simple surface structure determination from Fourier transforms of angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Y. [Pennsylvania State Univ., University Park, PA (United States)]|[Lawrence Berkeley Lab., CA (United States); Shirley, D.A. [Pennsylvania State Univ., University Park, PA (United States)

    1995-02-01

    The authors show by Fourier analyses of experimental data, with no further treatment, that the positions of all the strong peaks in Fourier transforms of angle-resolved photoemission extended fine structure (ARPEFS) from adsorbed surfaces can be explicitly predicted from a trial structure with an accuracy of about {+-} 0.3 {angstrom} based on a single-scattering cluster model together with the concept of a strong backscattering cone, and without any additional analysis. This characteristic of ARPEFS Fourier transforms can be developed as a simple method for determining the structures of adsorbed surfaces to an accuracy of about {+-} 0.1 {angstrom}.

  3. Fine Resolution Termohaline Structure Of The Yuctatan Coastal Sea

    Science.gov (United States)

    Marino-Tapia, I.; Enriquez-Ortiz, C.; Capurro, L.; Euan-Avila, J.

    2007-05-01

    In the Yucatan peninsula there are a variety processes that drastically affect the thermohaline structure of the coastal seas. Some of these include hyperhaline lagoons that export salt to the ocean, upwelling events that propagate to the coast, persistent submarine groundwater discharges, and very high evaporation rates caused by the intense solar radiation. On July 2006 a fine resolution oceanographic campaign was performed on the Yucatan coast to study the detailed structure of thermohaline processes and currents from the shore to the 10 m isobath. A total of sixty nine transects that cover the entire northern stretch of the Yucatan coast were made. The transects extend seven kilometers in the offshore direction and have an alongshore spacing of 5 km. The temperature and salinity characteristics of the water column were monitored with a SEABIRD SBE 19 CTD performing profiles every 500 m along each transect. Ocean currents were measures along the same transect using a 1.5 MHz Acoustic Doppler Profiler (Sontek). The results clearly show the effects of coastal lagoons on the adjoining sea, with net salt export associated with hyperhaline lagoons (e.g. Ria Lagartos) or more estuarine influence of lagoons such as Celestun, where groundwater discharges play the role of rivers on the estuary. An assessment of this influence on the coastal ocean will be presented. It is well known the meteor impact at the end of the Cretacic era at Chicxulub, Yucatan, generated a crater with multiple rings which is evident from horizontal gravity gradients of the Yucatan mainland, and that associated with the outer ring there is a high concentration of cenotes (sinkholes) (Pope et al. 1991; Hildebrand, et al. 1995). It has also been shown that groundwater flows along this cenote ring towards the ocean, and the zones where the ring intersects the coast (Celestun and Dzilam Bravo) have impressive geologic features known as `submarine water springs' where freshwater springs as a fountain

  4. STRUCTURAL FUNDS ABSORPTION GROWTH BY IMPROVING THEIR MANAGEMENT

    Directory of Open Access Journals (Sweden)

    Pautu Sorina

    2012-12-01

    Full Text Available Grant project management is now a trend in the institutions of various types in Romania due to the opportunities offered by the EU through structural Instruments. Absorbing European funds is a challenge for Romania. The Managing Authority for Structural Instruments, together with the subordinated institutions present deficiencies in their coordination and implementation, the effect being a slow process of absorption of structural and cohesion funds. Taking action to enhance absorption of Structural and Cohesion Funds was done later; some measures are neither effective nor efficient. One of the major problems in implementing the Structural Funds is the continuous change of their national legislation. Therefore it is necessary to take measures to increase the absorption of structural funds and also the national adoption of a stable legal framework applicable to Structural Funds, guides of the applicant and clearly established project calls, without any latest changes, creating a transparent system of project proposals assessment and results communication of assessments to their beneficiaries, the payments required by the reimbursement requests within 45 days specified in the contract and not just their validation, terms compliance in approval notifications and addenda to the contract funding, proper training of the personnel from the intermediate organizations and linking information provided by their staff.

  5. Relative importance of temporal envelope and fine structure in lexical-tone perception (L)

    Science.gov (United States)

    Xu, Li; Pfingst, Bryan E.

    2003-12-01

    The relative importance of temporal envelope and fine structure in speech and music perception was investigated by Smith et al. [Nature (London) 416, 87-90 (2002)] using ``auditory chimera'' in which the envelope from one sound was paired with the fine structure of another. Smith et al. found that, when 4 to 16 frequency bands were used, recognition of English speech was dominated by the envelope, whereas recognition of melody was dominated by the fine structure. In the present study, Mandarin Chinese monosyllables were divided into 4, 8, or 16 frequency bands and the fine structure and envelope of one tone pattern were exchanged with those of another tone pattern of the same monosyllable. Five normal-hearing native Mandarin Chinese speakers completed a four-alternative forced-choice tone-identification task. In the vast majority of trials, subjects based their identification of the monosyllables on the fine structure rather than the envelope. Thus, the relative importance of envelope and fine structure for lexical-tone perception resembled that for melody recognition rather than that for English speech recognition. Delivering fine-structure information in cochlear implant stimulation could be particularly beneficial for lexical-tone perception.

  6. Theoretical Study of Relativistic Retardation Effects: the Abnormal Fine Structure of O Ⅱ

    Institute of Scientific and Technical Information of China (English)

    CHEN Shao-Hao; HAN Xiao-Ying; WANG Xiao-Lu; LI Ji

    2007-01-01

    Using multi-configuration Dirac-Fock and relativistic configuration interaction methods with high-order corrections, we report our precise calculation results of the fine-structure energy levels of the ground-state configuration of OⅡ(1s22s22p3). Our calculated fine-structure splittings of 2D3/2,5/2 and 2P1/2,3/2 are abnormal. We elucidate that the transverse (Breit) interaction, i.e. relativistic retardation effect, plays an important role for the abnormal fine-structure splittings. Our calculation results are in good agreement with experimental measurements.

  7. On the origin of fine structure in the photoluminescence spectra of the β-sialon:Eu2+ green phosphor

    Directory of Open Access Journals (Sweden)

    Kohsei Takahashi, Ken-ichi Yoshimura, Masamichi Harada, Yoshitaka Tomomura, Takashi Takeda, Rong-Jun Xie and Naoto Hirosaki

    2012-01-01

    Full Text Available The photoluminescence (PL and PL excitation (PLE spectra of Si6−zAlzOzN8−z (β-sialon:Eu2+ phosphors with small z values (z=0.025–0.24 were studied at room temperature and 6 K. The PL and PLE spectra exhibit fine structure with the PL lines being as sharp as 45–55 nm even at room temperature; this fine structure was enhanced by decreasing the z value. These results can be used for expanding the color gamut of liquid crystal displays, particularly in the blue–green region. From low-temperature measurements, the fine PLE structure was ascribed to discrete energy levels of 7FJ states. The 4f65d excited states of Eu2+ are considered to be localized near the 4f orbital. This is because the bonding of Eu2+ with surrounding atoms is ionic rather than covalent. Lattice phonon absorptions were also observed in the PLE spectrum, revealing that the optically active Eu2+ ions are located in the β-sialon crystal. The PL spectrum of the sample with the smallest z value (0.025 consists of a sharp zero-phonon line and lattice phonon replicas, which results in a sharp and asymmetric spectral shape.

  8. Distortion product otoacoustic emission fine structure as an early hearing loss predictor

    DEFF Research Database (Denmark)

    Reuter, Karen; Hammershøi, Dorte

    2006-01-01

    Otoacoustic emissions (OAEs) are a promising method to monitor early noise-induced hearing losses. When distortion product otoacoustic emissions (DPOAEs) are obtained with a high-frequency resolution, a ripple structure across frequency can be seen, called DPOAE fine structure. In this study DPOAE...... fine structures are obtained from 74 normal-hearing humans using primary levels of L1/L2=65/45 dB. The subjects belong to groups with different ages and exposure histories. A classification algorithm is developed, which quantifies the fine structure by the parameter's ripple place, ripple width, ripple...... and vary from subject to subject within groups. The results do not indicate that the DPOAE fine structure alters with the state of hearing, as it is suggested in the literature. The data analysis is still in process at this stage.  ...

  9. Effects of fine structure of absorption sp ectrum and spin-singlet on zero-field-splitting parameters for BaCrSi4O10 and AgGaSe2:Cr2+%BaCrSi4O10与AgGaSe2:Cr2+吸收光谱的精细结构及自旋单态对零场分裂参量的影响∗

    Institute of Scientific and Technical Information of China (English)

    谭晓明; 赵刚; 张迪

    2016-01-01

    The compounds doped with or containing Cr2+ ions are extensively used as optoelectronic and nonlinear optical materials, because they have special optical, magnetic and electric properties. These properties are very closely related to the absorption spectra and zero-field-splitting. The studies of the absorption spectra and zero-field-splitting are very important for realizing the doped microscopic mechanism and understanding the interaction between impurity ions and host crystals, and they may be useful to material designers. The concept of the standard basis adapted to the double group chain is adopted in the strong-field scheme by the crystal field theory. This concept emphasizes the standardization of the basis of the whole 3d4 configuration space including all spin states. Thus, the basis functions can be constructed according to each irreducible representation of the double group and each basis function has a certain expression. Each standard basis adapted to the double group chain can be built from the former by a linear transformation, which forms a basis chain. Thus, the complete energy matrix including spin singlet is constructed for Cr2+ ion in tetragonal symmetry environment in the strong-field-representation by the crystal field theory. The fine structures of absorption spectra and the spin-singlet contributions to zero-field-splitting parameters for BaCrSi4O10 and AgGaSe2:Cr2+ are studied by diagonalizing the complete energy matrix. The fine structures for the two systems and the zero-field-splitting parameters for BaCrSi4O10 are given theoretically for the first time. The fine structures are assigned by the irreducible representation of the group. The results show that the spin-singlet contribution to D is negligible, but the contributions to a and F are important. The contributions arise from the interaction of the spin quintuplets with both spin triplets and spin singlets via spin-orbit coupling. However, the selection rule of spin-orbit coupling

  10. Size-resolved measurements of brown carbon in water and methanol extracts and estimates of their contribution to ambient fine-particle light absorption

    Science.gov (United States)

    Liu, J.; Bergin, M.; Guo, H.; King, L.; Kotra, N.; Edgerton, E.; Weber, R. J.

    2013-12-01

    Light absorbing organic carbon, often called brown carbon, has the potential to significantly contribute to the visible light-absorption budget, particularly at shorter wavelengths. Currently, the relative contributions of particulate brown carbon to light absorption, as well as the sources of brown carbon, are poorly understood. With this in mind size-resolved direct measurements of brown carbon were made at both urban (Atlanta), and rural (Yorkville) sites in Georgia. Measurements in Atlanta were made at both a representative urban site and a road-side site adjacent to a main highway. Fine particle absorption was measured with a multi-angle absorption photometer (MAAP) and seven-wavelength Aethalometer, and brown carbon absorption was estimated based on Mie calculations using direct size-resolved measurements of chromophores in solvents. Size-resolved samples were collected using a cascade impactor and analyzed for water-soluble organic carbon (WSOC), organic and elemental carbon (OC and EC), and solution light-absorption spectra of water and methanol extracts. Methanol extracts were more light-absorbing than water extracts for all size ranges and wavelengths. Absorption refractive indices of the organic extracts were calculated from solution measurements for a range of wavelengths and used with Mie theory to predict the light absorption by fine particles comprised of these components, under the assumption that brown carbon and other aerosol components were externally mixed. For all three sites, chromophores were predominately in the accumulation mode with an aerodynamic mean diameter of 0.5 μm, an optically effective size range resulting in predicted particle light absorption being a factor of 2 higher than bulk solution absorption. Mie-predicted brown carbon absorption at 350 nm contributed a significant fraction (20 to 40%) relative to total light absorption, with the highest contributions at the rural site where organic to elemental carbon ratios were

  11. Triple-layer Absorptive Structures for Shock Wave Blast Protection

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Triple-layer absorptive structure is designed to reinforce a missile silo against shock wave blasts. An energy-absorbing layer and a cushion layer overlay the circular silo cover made of reinforced concrete. The dynamic stress analysis is performed by ABAQUS/Explicit. The mesoscopic structure of the energy absorbing layer is designed as an assembly of ductile tubes containing crushable cellular ceramics. Combined mesoscopic and macroscopic simulations indicate that the structure can enhance the survivability of a missile silo against blast waves.

  12. Does over-exposure modify the fine structure of distortion product otoacoustic emissions?

    DEFF Research Database (Denmark)

    Reuter, Karen; Hammershøi, Dorte

    2008-01-01

    It is investigated, whether the pattern of distortion product otoacoustic emission (DPOAE) fine structure (quasi-periodic variations across frequency) is altered by an acoustical over-exposure. DPOAE fine structures are determined in 16 normal-hearing humans using a high frequency-resolution and ......It is investigated, whether the pattern of distortion product otoacoustic emission (DPOAE) fine structure (quasi-periodic variations across frequency) is altered by an acoustical over-exposure. DPOAE fine structures are determined in 16 normal-hearing humans using a high frequency......-resolution and primary levels of L1/L2=65/45 dB. DPOAEs are measured both before and after the subjects are monaurally exposed to a 1 kHz tone lasting for 3 min at an equivalent threshold sound pressure level of 105.5 dB. After the exposure the DPOAE levels are shifted to lower values and recover to the initial levels...

  13. The influence of high-energy ion implantation on Al alloys fine structure and microhardness

    International Nuclear Information System (INIS)

    The microhardness and fine structure of Al alloys (D16 and Al Mn), implanted with 245 MeV krypton ions to doses of 1013 and 1014 cm-2 have been investigated. The implantation results in the un hardening of dispersion hardening D16 alloy and the hardening of thermally unharden able Al Mn alloy. The change in fine structure parameters of Al matrix of implanted alloys is in good agreement with the change in their microhardness

  14. Fine structure of phonon replicas in a tunnel spectrum of a GaAs quantum well

    OpenAIRE

    Krishtop, V. G.; Popov, V. G.; Henini, M.; Krupko, Yu.; Portal, J. -C.

    2014-01-01

    A fine structure of phonon replicas in the current-voltage characteristic of a resonant-tunneling diode has been investigated experimentally. A detailed study of the diode I-V curves in magnetic fields of different orientations has allowed to determine the origin of the features in the fine structure. The voltage positions of the features are shown to coincide with calculated that in the frame of two models: LO-phonon assisted tunneling and resonant tunneling of polarons.

  15. Fine structure and development of the collar enamel in gars ,Lepisosteus oculatus ,Actinopterygii

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The fine structure of collar enamel and the cells constituting the enamel organ during amelogenesis in Lepisosteus oculatus was observed by light,scanning electron and transmission electron microscopy.In the enamel,slender crystals were arranged perpendicular to the surface and the stripes that were parallel to the surface were observed,suggesting that the enamel in Lepisosteus shares common morphological features with that in sarcopterygian fish and amphibians.Ameloblasts containing developed Golgi apparatus,rough endoplasmic reticulum (rER) and secretory granules were found in the secretory stage.In the maturation stage,a ruffled border was not seen at the distal end of the ameloblasts,while many mitochondria and lysosome-like granules were obvious in the distal cytoplasm.The enamel organ consisted of the outer dental epithelial cells,stratum reticulum cells and ameloblasts,but there was no stratum intermedium.It is likely that the ameloblasts have less absorptive function in comparison with the inner dental epithelial cells facing cap enameloid.

  16. Non-linear electrodynamics and the variation of the fine structure constant

    Science.gov (United States)

    Mbelek, Jean Paul; Mosquera Cuesta, Herman J.

    2008-09-01

    It has been claimed that during the late-time history of our Universe, the fine structure constant of electromagnetism, α, has been increasing. The conclusion is achieved after looking at the separation between lines of ions like CIV, MgII, SiII, FeII, among others in the absorption spectra of very distant quasars, and comparing them with their counterparts obtained in the laboratory. However, in the meantime, other teams have claimed either a null result or a decreasing α with respect to the cosmic time. Also, the current precision of laboratory tests does not allow one to either comfort or reject any of these astronomical observations. Here, we suggest that as photons are the sidereal messengers, a non-linear electrodynamics (NLED) description of the interaction of photons with the weak local background magnetic fields of a gas cloud absorber around the emitting quasar can reconcile the Chand et al. and Levshakov et al. findings with the negative variation found by Murphy et al. and Webb et al., and also to find a bridge with the positive variation argued more recently by Levshakov et al. We also show that NLED photon propagation in a vacuum permeated by a background magnetic field presents a full agreement with constraints from Oklo natural reactor data. Finally, we show that NLED may render a null result only in a narrow range of the local background magnetic field which should be the case of both the claims by Chand et al. and by Srianand et al.

  17. Impact of instrumental systematic errors on fine-structure constant measurements with quasar spectra

    Science.gov (United States)

    Whitmore, Jonathan B.; Murphy, Michael T.

    2015-02-01

    We present a new `supercalibration' technique for measuring systematic distortions in the wavelength scales of high-resolution spectrographs. By comparing spectra of `solar twin' stars or asteroids with a reference laboratory solar spectrum, distortions in the standard thorium-argon calibration can be tracked with ˜10 m s-1 precision over the entire optical wavelength range on scales of both echelle orders (˜50-100 Å) and entire spectrographs arms (˜1000-3000 Å). Using archival spectra from the past 20 yr, we have probed the supercalibration history of the Very Large Telescope-Ultraviolet and Visible Echelle Spectrograph (VLT-UVES) and Keck-High Resolution Echelle Spectrograph (HIRES) spectrographs. We find that systematic errors in their wavelength scales are ubiquitous and substantial, with long-range distortions varying between typically ±200 m s-1 per 1000 Å. We apply a simple model of these distortions to simulated spectra that characterize the large UVES and HIRES quasar samples which previously indicated possible evidence for cosmological variations in the fine-structure constant, α. The spurious deviations in α produced by the model closely match important aspects of the VLT-UVES quasar results at all redshifts and partially explain the HIRES results, though not self-consistently at all redshifts. That is, the apparent ubiquity, size and general characteristics of the distortions are capable of significantly weakening the evidence for variations in α from quasar absorption lines.

  18. Calibration issues in estimating variability of the fine structure constant (alpha) with cosmic time

    CERN Document Server

    Centurión, Miriam; Levshakov, Sergei

    2009-01-01

    Laser Comb Wavelength calibration shows that the ThAr one is locally unreliable with possible deviations of up to 100 m/s within one order range, while delivering an overall 1 m/s accuracy (Wilken et al 2009). Such deviation corresponds to delta alpha/alpha ~ 7E-6 for a FeII-MgII pair. Comparison of line shifts among the 5 FeII lines, with almost identical sensitivity to fine structure constant changes, offers a clean way to directly test the presence of possible local wavelength calibration errors of whatever origin. We analyzed 5 absorption systems, with zabs ranging from 1.15 to 2.19 towards 3 bright QSOs. The results show that while some lines are aligned within 20 m/s, others reveal large deviations reaching 200 m/s or higher and corresponding to a delta alpha/alpha > 1E-5 level. The origin of these deviations is not clearly identified but could be related to the adaptation of wavelength calibration to CCD manufacturing irregularities. These results suggest that to draw conclusions from delta alpha/alpha...

  19. Accelerating universe and the time-dependent fine-structure constant

    Science.gov (United States)

    Fujii, Yasunori

    2010-11-01

    I start with assuming a gravitational scalar field as the dark-energy supposed to be responsible for the accelerating universe. Also from the point of view of unification, a scalar field implies a time-variability of certain “constants” in Nature. In this context I once derived a relation for the time-variability of the fine-structure constant α: Δα/α =ζ Ƶ(α/π) Δσ, where ζ and Ƶ are the constants of the order one, while σ on the right-hand side is the scalar field in action in the accelerating universe. I use the reduced Planckian units with c=ℏ =MP(=(8π G)-1/2)=1. I then compared the dynamics of the accelerating universe, on one hand, and Δα/α derived from the analyses of QSO absorption lines, Oklo phenomenon, also different atomic clocks in the laboratories, on the other hand. I am here going to discuss the theoretical background of the relation, based on the scalar-tensor theory invented first by Jordan in 1955.

  20. Cosmological variation of the fine structure constant from an ultralight scalar field: The effects of mass

    Science.gov (United States)

    Gardner, Carl L.

    2003-08-01

    Cosmological variation of the fine structure constant α due to the evolution of a spatially homogeneous ultralight scalar field (m˜H0) during the matter and Λ dominated eras is analyzed. Agreement of Δα/α with the value suggested by recent observations of quasar absorption lines is obtained by adjusting a single parameter, the coupling of the scalar field to matter. Asymptotically α(t) in this model goes to a constant value α¯≈α0 in the early radiation and the late Λ dominated eras. The coupling of the scalar field to (nonrelativistic) matter drives α slightly away from α¯ in the epochs when the density of matter is important. Simultaneous agreement with the more restrictive bounds on the variation |Δα/α| from the Oklo natural fission reactor and from meteorite samples can be achieved if the mass of the scalar field is on the order of 0.5 0.6 HΛ, where HΛ=Ω1/2ΛH0. Depending on the scalar field mass, α may be slightly smaller or larger than α0 at the times of big bang nucleosynthesis, the emission of the cosmic microwave background, the formation of early solar system meteorites, and the Oklo reactor. The effects on the evolution of α due to nonzero mass for the scalar field are emphasized. An order of magnitude improvement in the laboratory technique could lead to a detection of (α˙/α)0.

  1. Time variation of the fine structure constant α from realistic models of Oklo reactors.

    Science.gov (United States)

    Gould, C. R.; Sharapov, E. I.; Lamoreaux, S. K.

    2006-11-01

    The topic of whether the fundamental constants of nature vary with time has been a subject of great interest since Dirac originally proposed the possibility that GN˜1/tuniverse. Recent observations of absorption spectra lines from distant quasars appeared to indicate a possible increase in the fine structure constant α over ten billion years. Contrarily, analyses of the time evolution of α from Oklo natural nuclear reactor data have yielded inconsistent results, some indicating a decrease over two billion years while others indicated no change. We have used known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Reactors RZ2 and RZ10 were modeled with MCNP and the resulting neutron spectra were used to calculate the change in the ^149Sm capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. Our study resolves the contradictory situation with previous Oklo α-results. Our suggested 2 σ bound on a possible time variation of α over two billion years is stringent: -0.11 <=δαα <=0.24, in units of 10-7, but model dependent in that it assumes only α has varied over time.

  2. Metalloprotein active site structure determination: synergy between X-ray absorption spectroscopy and X-ray crystallography.

    Science.gov (United States)

    Cotelesage, Julien J H; Pushie, M Jake; Grochulski, Pawel; Pickering, Ingrid J; George, Graham N

    2012-10-01

    Structures of metalloprotein active sites derived from X-ray crystallography frequently contain chemical anomalies such as unexpected atomic geometries or elongated bond-lengths. Such anomalies are expected from the known errors inherent in macromolecular crystallography (ca. 0.1-0.2Å) and from the lack of appropriate restraints for metal sites which are often without precedent in the small molecule structure literature. Here we review the potential of X-ray absorption spectroscopy to provide information and perspective which could aid in improving the accuracy of metalloprotein crystal structure solutions. We also review the potential problem areas in analysis of the extended X-ray absorption fine structure (EXAFS) and discuss the use of density functional theory as another possible source of geometrical restraints for crystal structure analysis of metalloprotein active sites.

  3. Model galactic coronae: Ionization structure and absorption-line spectra

    International Nuclear Information System (INIS)

    We describe a general model for a gaseous galactic corona, and demonstrate that it is in harmony with a variety of observational and theoretical constraints. We then compute the ionization equilibria of H, He, C, N, O, Si, and S atoms in the corona and determine the strengths of resonance absorption lines arising therein. To this end, we obtain approximate cross sections for ionization of the heavy-element ions by photons of energy E/sub γ/< or =100 eV.We use our results first to discuss the expected absorption spectrum of our Galaxy's corona. Subsequently, we discuss in detail the relevance of our computed equilibria to the suggestion that galactic coronae produce some redshift systems in quasar absorption spectra. Because our model coronae are not isothermal, the ionization structure existing along various lines of sight through them is not in accord with the concept of ''reasonable ionization equilibrium'': a concept assumed to be valid in most analyses of quasar spectra. However, our calculations indicate that typically one well-established redshift system in each quasar absorption spectrum could arise in the corona of an intervening galaxy. This is the number expected from statistical arguments if quasar redshifts are fully cosmological in origin

  4. Solvation structure of the halides from x-ray absorption spectroscopy

    Science.gov (United States)

    Antalek, Matthew; Pace, Elisabetta; Hedman, Britt; Hodgson, Keith O.; Chillemi, Giovanni; Benfatto, Maurizio; Sarangi, Ritimukta; Frank, Patrick

    2016-07-01

    Three-dimensional models for the aqueous solvation structures of chloride, bromide, and iodide are reported. K-edge extended X-ray absorption fine structure (EXAFS) and Minuit X-ray absorption near edge (MXAN) analyses found well-defined single shell solvation spheres for bromide and iodide. However, dissolved chloride proved structurally distinct, with two solvation shells needed to explain its strikingly different X-ray absorption near edge structure (XANES) spectrum. Final solvation models were as follows: iodide, 8 water molecules at 3.60 ± 0.13 Å and bromide, 8 water molecules at 3.40 ± 0.14 Å, while chloride solvation included 7 water molecules at 3.15 ± 0.10 Å, and a second shell of 7 water molecules at 4.14 ± 0.30 Å. Each of the three derived solvation shells is approximately uniformly disposed about the halides, with no global asymmetry. Time-dependent density functional theory calculations simulating the chloride XANES spectra following from alternative solvation spheres revealed surprising sensitivity of the electronic state to 6-, 7-, or 8-coordination, implying a strongly bounded phase space for the correct structure during an MXAN fit. MXAN analysis further showed that the asymmetric solvation predicted from molecular dynamics simulations using halide polarization can play no significant part in bulk solvation. Classical molecular dynamics used to explore chloride solvation found a 7-water solvation shell at 3.12 (-0.04/+0.3) Å, supporting the experimental result. These experiments provide the first fully three-dimensional structures presenting to atomic resolution the aqueous solvation spheres of the larger halide ions.

  5. Structure- and dose-absorption relationships of coffee polyphenols.

    Science.gov (United States)

    Erk, Thomas; Hauser, Johanna; Williamson, Gary; Renouf, Mathieu; Steiling, Heike; Dionisi, Fabiola; Richling, Elke

    2014-01-01

    Chlorogenic acids (CGAs) from coffee have biological effects related to human health. Thus, specific data on their bioavailability in the upper gastrointestinal tract are of high interest, since some molecules are absorbed here and so are not metabolized by colonic microflora. Up to now, no data on structure-absorption relationships for CGAs have been published, despite this being the most consumed group of polyphenols in the western diet. To address this gap, we performed ex vivo absorption experiments with pig jejunal mucosa using the Ussing chamber model (a model simulating the mucosa and its luminal/apical side). The main coffee polyphenols, caffeoylquinic acid (CQA), feruloylquinic acid (FQA), caffeic acid (CA), dicaffeoylquinic acid (diCQA), and D-(-)-quinic acid (QA), were incubated in individual experiments equivalent to gut lumen physiologically achievable concentrations (0.2-3.5 mM). Identification and quantification were performed with HPLC-diode array detection and HPLC-MS/MS. Additionally, the presence of ABC-efflux transporters was determined by Western blot analysis. The percentages of initially applied CGAs that were absorbed through the jejunal pig mucosa were, in increasing order: diCQA, trace; CQA, ≈ 1%; CA, ≈ 1.5%; FQA, ≈ 2%; and QA, ≈ 4%. No differences were observed within the CGA subgroups. Dose-absorption experiments with 5-CQA suggested a passive diffusion (nonsaturable absorption and a linear dose-flux relationship) and its secretion was affected by NaN3 , indicating an active efflux. The ABC-efflux transporters MDR 1 and MRP 2 were identified in pig jejunal mucosa for the first time. We conclude that active efflux plays a significant role in CGA bioavailability and, further, that the mechanism of CGA absorption in the jejunum is governed by their physicochemical properties.

  6. Fine-tuning structural RNA alignments in the twilight zone

    Directory of Open Access Journals (Sweden)

    Schirmer Stefanie

    2010-04-01

    Full Text Available Abstract Background A widely used method to find conserved secondary structure in RNA is to first construct a multiple sequence alignment, and then fold the alignment, optimizing a score based on thermodynamics and covariance. This method works best around 75% sequence similarity. However, in a "twilight zone" below 55% similarity, the sequence alignment tends to obscure the covariance signal used in the second phase. Therefore, while the overall shape of the consensus structure may still be found, the degree of conservation cannot be estimated reliably. Results Based on a combination of available methods, we present a method named planACstar for improving structure conservation in structural alignments in the twilight zone. After constructing a consensus structure by alignment folding, planACstar abandons the original sequence alignment, refolds the sequences individually, but consistent with the consensus, aligns the structures, irrespective of sequence, by a pure structure alignment method, and derives an improved sequence alignment from the alignment of structures, to be re-submitted to alignment folding, etc.. This circle may be iterated as long as structural conservation improves, but normally, one step suffices. Conclusions Employing the tools ClustalW, RNAalifold, and RNAforester, we find that for sequences with 30-55% sequence identity, structural conservation can be improved by 10% on average, with a large variation, measured in terms of RNAalifold's own criterion, the structure conservation index.

  7. Insight into the structure of Pd/ZrO2 during the total oxidation of methane using combined in situ XRD, X.-ray absorption and Raman spectroscopy

    DEFF Research Database (Denmark)

    Grunwaldt, Jan-Dierk; van Vegten, Niels; Baiker, Alfons;

    2009-01-01

    The structure of palladium during the total combustion of methane has been studied by a combination of the complementary in situ techniques X-ray absorption spectroscopy, Raman spectroscopy and X-ray diffraction. The study demonstrates that finely dispersed and oxidized palladium is most active f...

  8. Fine- and hyperfine-structure effects in molecular photoionization: I. General theory and direct photoionization

    CERN Document Server

    Germann, Matthias

    2016-01-01

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O$_2$ (reported by H. Palm and F. Merkt, Phys. Rev. Lett. 81, 1385 (1998)) and are used for predicting hyperfine populations of molecular ions produced by photoionization.

  9. Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization.

    Science.gov (United States)

    Germann, Matthias; Willitsch, Stefan

    2016-07-28

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization. PMID:27475368

  10. Different Structures of PVA Nanofibrous Membrane for Sound Absorption Application

    Directory of Open Access Journals (Sweden)

    Jana Mohrova

    2012-01-01

    Full Text Available The thin nanofibrous layer has different properties in the field of sound absorption in comparison with porous fibrous material which works on a principle of friction of air particles in contact with walls of pores. In case of the thin nanofibrous layer, which represents a sound absorber here, the energy of sonic waves is absorbed by the principle of membrane resonance. The structure of the membrane can play an important role in the process of converting the sonic energy to a different energy type. The vibration system acts differently depending on the presence of smooth fibers in the structure, amount of partly merged fibers, or structure of polymer foil as extreme. Polyvinyl alcohol (PVA was used as a polymer because of its good water solubility. It is possible to influence the structure of nanofibrous layer during the production process thanks to this property of polyvinyl alcohol.

  11. An Action-Based Fine-Grained Access Control Mechanism for Structured Documents and Its Application

    Directory of Open Access Journals (Sweden)

    Mang Su

    2014-01-01

    Full Text Available This paper presents an action-based fine-grained access control mechanism for structured documents. Firstly, we define a describing model for structured documents and analyze the application scenarios. The describing model could support the permission management on chapters, pages, sections, words, and pictures of structured documents. Secondly, based on the action-based access control (ABAC model, we propose a fine-grained control protocol for structured documents by introducing temporal state and environmental state. The protocol covering different stages from document creation, to permission specification and usage control are given by using the Z-notation. Finally, we give the implementation of our mechanism and make the comparisons between the existing methods and our mechanism. The result shows that our mechanism could provide the better solution of fine-grained access control for structured documents in complicated networks. Moreover, it is more flexible and practical.

  12. Microstructure evolution and mechanical properties of eutectoid steel with ultrafine or fine (ferrite+cementite) structure

    International Nuclear Information System (INIS)

    Eutectoid steel with the ultrafine or fine-grained ferrite (α)+cementite (θ) particles structure was formed by hot deformation of undercooled austenite at 0.1 s−1 or 5 s−1 at 650 °C using a Gleeble 1500 hot simulator and subsequent annealing. The microstructural evolution of fine (α+θ) structure was investigated by means of a scanning electronic microscope, electron backscattered diffraction and transmission electron microscope, and the mechanical properties of fine (α+θ) steel were analyzed in comparison with that of ultrafine (α+θ) steel. The results show that only dynamic transformation of undercooled austenite into proeutectoid ferrite occurs during hot deformation at 650 °C at 5 s−1. During water quenching, lamellar pearlite with small colony sizes is formed and the average size of pearlite colonies decreases with increasing the strain. By subsequent annealing at 650 °C for 30 min, the spheroidization of lamellar pearlite takes place, resulting in the formation of fine (α+θ) structure consisting of ferrite matrix with the average size of about 4.9 μm and fine cementite particles mainly within ferrite grains. In comparison with ultrafine (α+θ) steel consisting of ferrite matrix with the average size of about 1.8 μm and relatively large cementite particles mostly located at grain boundaries, the yield strength, tensile strength, uniform elongation, total elongation and work-hardening capability of fine (α+θ) steel improve markedly

  13. Program package for semi-empirical analysis of the fine- and hyperfine structure of complex atoms

    International Nuclear Information System (INIS)

    The experimental work combined with semi-empirical calculations is a very efficient tool for the investigations of the fine- and hyperfine structure of the complex atoms. We present a set of programs for the analysis of the fine- and hyperfine structure. The input data for the calculations are: the fine structure energy levels, the gJ-factors and the hyperfine structure (hfs) A and B constants of experimentally observed levels. The programs are used for the analysis of electron systems containing any number of configurations up to four open shells. In the energy matrix generated, all kinds of electrostatic, magnetic and correlated electrostatic and magnetic interaction, up to second order perturbation theory, were included. As a result, we obtain predicted energy values for all the levels of the system considered, their exact spectroscopic description and also gJ-factors and hfs A and B constants

  14. The fine structure of niobium condensates deposited from ion-atomic fluxes in helium atmosphere

    International Nuclear Information System (INIS)

    Helium gas influence on the structural characteristics of niobium coatings deposited by low-energy metallic Nb ion-stoic fluxes in He atmosphere is investigated. It is shown that He implantation in Nb films during condensation is accompanied with the decreasing of the mean size of condensate grains. At the same time, He atoms modify no physical processes of the fine structure formation. Using thermodesorption spectroscopy we have determined that He atoms mainly belong to vacancy/vacancy-solute complexes in Nb coatings. Our conclusion is that such complexes play a dominant role in formation of the fine structure of vacuum coatings deposited from ion-atomic fluxes

  15. Energy absorption characteristics of lightweight structural member by stacking conditions

    Science.gov (United States)

    Choi, Juho; Yang, Yongjun; Hwang, Woochae; Pyeon, Seokbeom; Min, Hanki; Yeo, Ingoo; Yang, Inyoung

    2012-04-01

    The recent trend in vehicle design is aimed at improving crash safety and environmental-friendliness. To solve these issues, the needs for lighter vehicle to limit exhaust gas and improve fuel economy has been requested for environmental-friendliness. Automobile design should be made for reduced weight once the safety of vehicle is maintained. In this study, composite structural members were manufactured using carbon fiber reinforced plastic (CFRP) which are representative lightweight structural materials. Carbon fiber has been researched as alternative to metals for lightweight vehicle and better fuel economy. CFRP is an anisotropic material which is the most widely adapted lightweight structural member because of their inherent design flexibility and high specific strength and stiffness. Also, variation of CFRP interface number is important to increase the energy absorption capacity. In this study, one type of circular shaped composite tube was used, combined with reinforcing foam. The stacking condition was selected to investigate the effect of the fiber orientation angle and interface number. The crashworthy behavior of circular composite material tubes subjected to static axial compression under same conditions is reported. The axial static collapse tests were carried out for each section member. The collapse modes and the energy absorption capability of the members were analyzed.

  16. Fine structures in the atmosphere above a sunspot umbra

    CERN Document Server

    Bharti, L; Solanki, S K

    2013-01-01

    We present simultaneous photospheric and chromospheric observations of the trailing sunspot in NOAA 10904, obtained with the Swedish Solar Telescope (SST) La Palma, Canary Islands. Time series of high resolution \\ion{Ca}{ii}\\,$H$ images show transient jet-like structures in sunspot umbrae are elongated, which we call umbral microjets. These jets are directed roughly parallel to nearby penumbral microjets, suggesting that they are aligned with the background magnetic field. In general, first a bright dot-like structure appears, from which a jet later emerges, although some jets appear without an associated chromospheric dot. Bright photospheric umbral dots are associated with umbral microjets arising in the outer umbra. Nevertheless, a one-to-one correspondence between jet-like events and underlying umbral dots is not seen. They are typically less than 1\\arcsec ~long and less than 0\\farcs3 wide. The typical lifetime of umbral microjets is around one minute. The brightness of these structures increases from the...

  17. Fine structure characterization of zero-valent iron nanoparticles for decontamination of nitrites and nitrates in wastewater and groundwater

    Directory of Open Access Journals (Sweden)

    Kuen-Song Lin et al

    2008-01-01

    Full Text Available The main objectives of the present study were to investigate the chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization. This work also exemplifies the utilization of field emission-scanning electron microscope (FE–SEM, transmission electron microscopy (TEM, and x-ray diffraction (XRD to reveal the speciation and possible reaction pathway in a very complex adsorption and redox reaction process. Experimentally, ZVIN of this study was prepared by sodium borohydride reduction method at room temperature and ambient pressure. The morphology of as-synthesized ZVIN shows that the nearly ball and ultrafine particles ranged of 20–50 nm were observed with FE–SEM or TEM analysis. The kinetic model of nitrites or nitrates reductive reaction by ZVIN is proposed as a pseudo first-order kinetic equation. The nitrite and nitrate removal efficiencies using ZVIN were found 65–83% and 51–68%, respectively, based on three different initial concentrations. Based on the XRD pattern analyses, it is found that the quantitative relationship between nitrite and Fe(III or Fe(II is similar to the one between nitrate and Fe(III in the ZVIN study. The possible reason is due to the faster nitrite reduction by ZVIN. In fact, the occurrence of the relative faster nitrite reductive reaction suggested that the passivation of the ZVIN have a significant contribution to iron corrosion. The extended x-ray absorption fine structure (EXAFS or x-ray absorption near edge structure (XANES spectra show that the nitrites or nitrates reduce to N2 or NH3 while oxidizing the ZVIN to Fe2O3 or Fe3O4 electrochemically. It is also very clear that decontamination of nitrate or nitrite species in groundwater via the in-situ remediation with a ZVIN permeable reactive barrier would be environmentally attractive.

  18. Romania's road to Euro zone. From structural balance to structural balance corrected for absorption

    Directory of Open Access Journals (Sweden)

    Aura-Gabriela SOCOL

    2013-02-01

    Full Text Available The sovereign-debt crisis in the European Union has determined the necessity to reform the signal indicators for the analysis of the public finances' sustainability. In this context, many of the developing/emerging countries consider that the informational value provided by the structural budget balance indicator is insufficient, especially during the periods characterized by absorption. The present study suggests the transition from classical structural budget balance (CAB in the structural balance corrected for absorption (CAAB and supports the use of an improved indicator of the structural budget balance with a superior informational relevance for the macro-economic policies decision makers. Based on the economic literature we will demonstrate that the structural budget balance indicator should be improved, in order to also take into consideration the deviation of the current account balance from its sustainable level, particularly in the stage of the economic cycle characterized by high absorption.

  19. Distortion product otoacoustic emission fine-structure: An insight into the ear asymmetries

    Directory of Open Access Journals (Sweden)

    Bhamini Sharma

    2014-01-01

    Full Text Available Context: Use of distortion product otoacoustic emission (DPOAE as a measure of hearing sensitivity is common in clinical practice. However, use of a more informative DPOAE fine-structure has been limited due to non-reliability of DPOAE fine-structure. Aim: The current study was aimed at testing the interaural differences between the DPOAE fine-structure across three age groups. Settings and Design: Acoustically treated room with a calibrated dual channel audiometer (Orbiter 922 along with TDH-39 headphones and B-71 bone vibrator. GSI Tympstar was used for tympanometry and acoustic reflex measurements while ′ILO V6′ OAE analyzer was used for recording of DPOAE and DPOAE fine-structure. Material and Methods : A total of 98 subjects with normal peripheral hearing sensitivity were tested for DPOAE fine-structure. The three age groups consisted of young (8-18 years; n = 50, middle aged (30-40 years; n = 30, and elderly (50-60 years; n = 18. DPOAE fine-structure was studied at 8 points per octave on a total of 25 frequencies from 1000 to 8000 Hz. Statistical Analysis Used: Repeated measure analysis of variance. Results: There was a significant difference (P < 0.05 in the amplitudes at frequencies between 2000 and 3000 Hz. This was evident irrespective of the age groups. There was also a decrease in DPOAE amplitude in elderly group. Conclusions: Interaural asymmetry can be attributed as a reason to these findings and it occurred mostly in the speech perception frequencies. Reduced amplitude of DPAOE in the elderly group can be attributed to presbycusis.

  20. Fine structure of the pygmy dipole resonance in (136)Xe.

    Science.gov (United States)

    Savran, D; Fritzsche, M; Hasper, J; Lindenberg, K; Müller, S; Ponomarev, V Yu; Sonnabend, K; Zilges, A

    2008-06-13

    The photoresponse of the semimagic N=82 nucleus (136)Xe was measured up to the neutron separation energy S(n) using the (gamma, gamma') reaction. A concentration of strong dipole excitations is observed well below S(n) showing a fragmented resonancelike structure. Microscopic calculations in the quasiparticle phonon model including complex configurations of up to three phonons agree well with the experimental data in the total integrated strength, in the shape and the fragmentation of the resonance, which allows us to draw conclusions on the damping mechanism of the pygmy dipole resonance.

  1. British Industries Collaborative Exponential Programme, Vol. III: Fine structure experiments, miscellaneous exponential experiments

    International Nuclear Information System (INIS)

    The results are given of measurements of neutron flux fine structure in graphite lattices containing a wide range of uranium metal and uranium oxide fuel elements. In the ease of the metal fuel elements the observed fine structure parameters are correlated with theory. The remainder of the volume deals largely with investigations carried out in the BICEP exponential stacks. These include measurements of neutron diffusion area in graphite, and of buckling and flux distribution in an assembly containing a superlattice of empty channels. A correlation with theory of measurements of migration area asymmetry in uranium-graphite lattices is also given. (author)

  2. Precision Measurement of the Three 23PJ Helium Fine Structure Intervals

    Science.gov (United States)

    Zelevinsky, T.; Farkas, D.; Gabrielse, G.

    2005-11-01

    The three 23P fine structure intervals of He4 are measured at an improved accuracy that is sufficient to test two-electron QED theory and to determine the fine structure constant α to 14 parts in 109. The more accurate determination of α, to a precision higher than attained with the quantum Hall and Josephson effects, awaits the reconciliation of two inconsistent theoretical calculations now being compared term by term. A low pressure helium discharge presents experimental uncertainties quite different than for earlier measurements and allows direct measurements of light pressure shifts.

  3. Fine structure of flare ribbons and evolution of electric currents

    CERN Document Server

    Sharykin, I N

    2014-01-01

    Emission of solar flares across the electromagnetic spectrum is often observed in the form of two expanding ribbons. The standard flare model explains the flare ribbons as footpoints of magnetic arcades, emitting due to interaction of energetic particles with the chromospheric plasma. However, the physics of this interaction and properties of the accelerated particles are still unknown. We present results of multiwavelength observations of C2.1 flare of August 15, 2013, observed with New Solar Telescope (NST) of Big Bear Solar Observatory, Solar Dynamics Observatory (SDO), GOES and FERMI spacecraft. The observations reveal previously unresolved sub-arcsecond structure of the flare ribbons in regions of strong magnetic field consisting from numerous small-scale bright knots. We observe red-blue asymmetry of H alpha flare ribbons with a width as small as 100 km. We discuss the relationship between the ribbons and vertical electric currents estimated from vector magnetograms, and show that Joule heating can be r...

  4. Improved community structure detection using a modified fine tuning strategy

    CERN Document Server

    Sun, Yudong; Josic, Kresimir; Bassler, Kevin E

    2009-01-01

    The community structure of a complex network can be determined by finding the partitioning of its nodes that maximizes modularity. Many of the proposed algorithms for doing this work by recursively bisecting the network. We show that this unduely constrains their results, leading to a bias in the size of the communities they find and limiting their effectivness. To solve this problem, we propose adding a step to the existing algorithms that does not increase the order of their computational complexity. We show that, if this step is combined with a commonly used method, the identified constraint and resulting bias are removed, and its ability to find the optimal partitioning is improved. The effectiveness of this combined algorithm is also demonstrated by using it on real-world example networks. For a number of these examples, it achieves the best results of any known algorithm.

  5. New Limit on the Spatial and Temporal Variations of the Fine-Structure Constant Using High Redshifts of Quasar Spectra

    Science.gov (United States)

    Le, T. D.

    2015-03-01

    Highly precise measurements on the light from distant quasars can served as a powerful tool to test the possible spatial and temporal variations of the fine-structure constant α = e 2 /c during the evolution of the Universe. Here we set a limit on the possible cosmological space-time variations of α by comparing transitions in the absorption lines of the SiIV doublet observed in the early Universe with those mesured in the laboratory. The weighted mean value of the α-variation derived from our analysis over the redshift range 2.0 ≤ cps≤ 3.7 is Δα/α (-0.53 ± 0.72) ×10-5. This result improves the constraint on Δα/α by a factor of ~ seven compared to the published results in the literature.

  6. Design of Far-Red Sensitizing Squaraine Dyes Aiming Towards the Fine Tuning of Dye Molecular Structure.

    Science.gov (United States)

    Morimoto, Takuya; Fujikawa, Naotaka; Ogomi, Yuhei; Pandey, Shyam S; Ma, Tingli; Hayase, Shuzi

    2016-04-01

    Model squaraine dyes having sharp and narrow absorptions mainly in the far-red wavelength region has been logically designed, synthesized and used for their application as sensitizer in the dyesensitized solar cells (DSSC). In order to have fine control on energetics, dyes having same mother core and alkyl chain length varying only in molecular symmetry and position of substituent were designed. It has been found that even keeping all other structural factor constant, only positional variation of substituent leads to not only in the variation of energetics by 0.1 eV but affects the photovoltaic characteristics also. Optimum concentration of dye de-aggregating agent was found to be 100 times with respect to the sensitizing dye concentration. Amongst dyes utilized in this work best performance was obtained for unsymmetrical dye SQ-40 giving a photoconversion efficiency of 4.01% under simulated solar irradiation at global AM 1.5. PMID:27451618

  7. FINE STRUCTURE OF FLARE RIBBONS AND EVOLUTION OF ELECTRIC CURRENTS

    International Nuclear Information System (INIS)

    Emission of solar flares across the electromagnetic spectrum is often observed in the form of two expanding ribbons. The standard flare model explains flare ribbons as footpoints of magnetic arcades, emitting due to interaction of energetic particles with the chromospheric plasma. However, the physics of this interaction and properties of the accelerated particles are still unknown. We present results of multiwavelength observations of the C2.1 flare of 2013 August 15, observed with the New Solar Telescope of the Big Bear Solar Observatory, and the Solar Dynamics Observatory, GOES, and Fermi spacecraft. The observations reveal previously unresolved sub-arcsecond structure of flare ribbons in regions of strong magnetic field consisting from numerous small-scale bright knots. We observe a red-blue asymmetry of Hα flare ribbons with a width as small as ∼100 km. We discuss the relationship between the ribbons and vertical electric currents estimated from vector magnetograms, and show that Joule heating can be responsible for energization of Hα knots in the ribbons

  8. Application of X-ray Absorption Spectroscopy to the study of nuclear structural materials

    Science.gov (United States)

    Liu, Shanshan

    One of key technologies for the next generation nuclear systems are advanced materials, including high temperature structural materials, fast neutron resistance core materials and so on. Local structure determination in these systems, which often are crystallographically intractable, is critical to gaining an understanding of their properties. In this thesis, X-ray Absorption Spectroscopy (XAS), including Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES), is used to examine the geometric and electronic structure of nuclear structural materials under varying conditions. The thesis is divided into two main sections. The first examines the structural analysis of nanostructured ferritic alloys (NFA) which are dispersion strengthened by an ultra high density of Y-Ti-O enriched nano-features, resulting in remarkable high temperature creep strength and radiation damage resistance. Titanium and Yttrium K-edge XAS shows commercial alloys MA957 and J12YWT more closely resemble the as received Fe-14Cr-3W-0.4Ti (wt. %) powders, and mechanically alloyed (MA) powders with 0.25Y2O3 (wt. %). It shows that a significant fraction of substitutional Ti remains dissolved in the (BCC) ferrite matrix. In contrast, annealed powders and hot isostatic press (HIP) consolidated alloys show high temperature heat treatments shift the Y and Ti to more oxidized states that are consistent with combinations of Y2Ti2O7 and, especially, TiO. The second section describes corrosion studies of Pb with 316L stainless steel, molybdenum and spinet (MgAl2O4) at high temperature by XAS. The corrosion of fuel cladding and structural materials by liquid lead at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. The results of ex-situ studies show that a Mo substrate retained a smooth and less corroded surface than 316L stainless steel sample at elevated temperature. In

  9. Fine structure of bat deep posterior lingual glands (von Ebner's)

    Science.gov (United States)

    Azzali, G; Gatti, R; Bucci, G; Orlandini, G

    1989-10-01

    We studied the morphology and ultrastructure of the bat (Pipistrellus k.k. and Rhinolophus f.e.) deep posterior lingual glands (Ebner's glands) during hibernation, summer and after stimulation with pilocarpine. Ebner's glands are formed by serous tubulo-alveolar adenomeres and by an excretory system organized in intercalated ducts, long excretory ducts and a main excretory duct. The latter opens in the vallum which surrounds the circumvallate papillae and in the groove of the foliate papillae. The secretory cells, which lack basal folds, show abundant and dense granules (PAS+, Alcian blue -), microvilli (scarce during hibernation), a Golgi apparatus (well developed during summer and after stimulation with pilocarpine), a large nucleus and RER cisternae stacked at the basal pole. Centrioles, lipid droplets, heterogeneous bodies (in content and density, probably lipofuscin bodies), lysosomal multivesicular bodies and large, dense granules with a microcrystalline structure were also encountered. The lateral membranes of adjacent cells are joined by desmosomes; their interdigitations are neither numerous nor prominent during summer. Microfilaments, often gathered in small bundles, lie in the lateral, peripheral cytoplasm without any relation with desmosomes. In summer and particularly after stimulation with pilocarpine, the apical pole of the secretory cells is characterized by many long microvilli, pedunculated hyaloplasmic protrusions and secretory granules. During hibernation the lumen is filled with secretory material. Myoepithelial cells are arranged among secretory cells or between them and the basal lamina. The short intercalated ducts show similarities with the analogous ducts of the parotid gland. Striated ducts are absent. Excretory ducts are endowed with: a) an inner layer of cuboidal cells characterized by poorly developed cytoplasmic organelles, rare dense granules and a few small microvilli; b) an outer layer of basal cells lying on the basal lamina

  10. Control of single quantum dot emission characteristics and fine structure by lateral electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Ulrich, S.M.; Hafenbrak, R.; Michler, P. [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, Universiaet Stuttgart (Germany); Vogel, M.M. [Institut fuer Halbleiteroptik und Funktionelle Grenzflaechen, Universiaet Stuttgart (Germany); Institut fuer Strahlwerkzeuge, Universitaet Stuttgart (Germany); Wang, L. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Rastelli, A.; Schmidt, O.G. [Insitute for Integrative Nanosciences, IFW Dresden (Germany)

    2009-02-15

    The spontaneous emission characteristics of individual self-assembled (In,Ga)As/GaAs quantum dots have been investigated under the application of a tunable electric field in the lateral growth plane. For the neutral excitonic and bi-excitonic as well as a singly-charged (trionic) QD carrier configuration, similar quantum-confined Stark effects could be observed, thus enabling a direct and comparative determination of corresponding polarizability values {alpha}. In addition we have applied a refined detection technique of high-resolution Fabry-Perot interferometry on single QDs to investigate the anisotropy-induced excitonic fine structure and to monitor its tunability under a lateral electric field. Whereas most quantum dots reveal an oscillatory-type modulation and partial reduction in fine structure under the applied field, we also demonstrate the case of a selected QD where the initial fine structure could even be reversibly tuned down to zero. This fine structure tunability of single QDs represents an essential prerequisite for the realization of individually controlled entangled photon sources in the future. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Fine-structure energy levels, oscillator strengths and lifetimes in Cu XVIII

    International Nuclear Information System (INIS)

    We have performed large-scale CIV3 (Configuration Interaction Version 3) calculations of excitation energies from ground states for 141 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the levels of the (1s22s22p6) 3l2, 3l3l' and 3l4l configurations of Cu XVIII. These states are represented by very extensive configuration-interaction (CI) wavefunctions obtained using the CIV3 computer code of Hibbert. The important relativistic effects are included through the Breit-Pauli approximation. In order to keep our calculated energy splittings as close as possible to the experimental values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. Since mixing among several fine-structure levels is found to be very strong, it becomes difficult to identify these uniquely. Our excitation energies, including their ordering, are in excellent agreement (better than 1.0%) with the available experimental results. From our calculated radiative decay rates, we have also calculated radiative lifetimes of the fine-structure levels. Our calculated oscillator strengths and radiative decay rates are found to be in good agreement with other theoretical results, while the lifetimes agree very well with the experimental values (wherever available). In this calculation, we also predict new data for several fine-structure levels where no other theoretical and experimental results are available.

  12. MULTIPLET FINE-STRUCTURE IN THE PHOTOEMISSION OF THE GADOLINIUM AND TERBIUM 5P LEVELS

    NARCIS (Netherlands)

    THOLE, BT; WANG, XD; HARMON, BN; LI, DQ; DOWBEN, PA

    1993-01-01

    Fine structure is observed in the photoemission of the gadolinium and terbium 5p levels. The 5p levels are split into multiplets due to spin-orbit splitting and to Coulomb and exchange interactions with the f shell. The calculated theoretical spectra are in good agreement with the experimental resul

  13. Temporal integration near threshold fine structure - The role of cochlear processing

    DEFF Research Database (Denmark)

    Epp, Bastian; Mauermann, Manfred; Verhey, Jesko L.

    The hearing thresholds of normal hearing listeners often show quasi-periodic variations when measured with a high frequency resolution. This hearing threshold fine structure is related to other frequency specific variations in the perception of sound such as loudness and amplitude modulated tones...

  14. The Ecosphere and the Value of the Electromagnetic Fine Structure Constant

    OpenAIRE

    Kozlowski, M.; Marciak-Kozlowska, J.

    2003-01-01

    Following the coincidence A x atomic year ~ Earth year (s), (A = Avogardo number, atomic year=a_B/alpha c, a_B=Bohr radius, alpha= fine structure constant, c=light velocity) and considering the "niche" for alpha, i.e. 180^{-1}

  15. The Fine Structures of Three Symmetric Latin Squares with Even Orders

    Institute of Scientific and Technical Information of China (English)

    Er Qiang FENG; Yan Xun CHANG

    2011-01-01

    Denote by SFin(v) the set of all integer pairs (t, s) for which there exist three symmetric Latin squares of order v on the same set having fine structure (t, s). We completely determine the set SFin(2n) for any integer n ≥ 5.

  16. The role of adiabaticity in alkali atom-fine structure mixing

    Science.gov (United States)

    Eshel, Ben; Weeks, David E.; Perram, Glen P.

    2014-02-01

    Fine-structure mixing cross-sections for the alkalis in collisions with the rare gases are reviewed. Included in the review are all the rare gases in collisions with all of the first excited state of the alkalis, the second excited state for K, Rb and Cs and the third excited state for Rb and Cs. The cross-sections are converted to probabilities for energy transfer using a quantum-defect calculated cross-section and are then presented as a function of adiabaticity. The data shows a clear decreasing trend with adiabaticity but secondary factors prevent the probabilities from decreasing as quickly as expected. Polarizability is introduced as a proxy for the secondary influences on the data as it increases with both rare gas partner and alkali excited state. The polarizability is shown to cause the probability of fine structure transition to be higher than expected. An empirical model is introduced and fit to the data. Future work will develop a model using time-independent perturbation theory in order to further develop a physical rational for the dependence of fine structure cross sections on adiabaticity and to further understand the secondary influences on the probability for fine structure transition.

  17. Fine-structure energy levels, oscillator strengths and lifetimes in Co-XV

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, G.P. [S. D. (Postgraduate) College, Muzaffarnagar, 251 001, India, affiliated to Chowdhary Charan Singh Univ., Dept. of Physics, Meerut (India); Msezane, A.Z. [Clark Atlanta Univ., Dept. of Physics and Center for Theoretical Studies of Physical Systems, Atlanta, Georgia (United States)

    2008-09-15

    The study of Al-like spectra of ions of the elements of the iron group has received a great deal of attention because they are of particular interest in controlled thermonuclear fusion. Excitation energies from ground state for 97 fine-structure levels as well as oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the fine-structure levels of the terms belonging to the (1s{sup 2}2s{sup 2}2p{sup 6})3s{sup 2}3p,3s3p{sup 2},3s{sup 2}3d, 3p{sup 3}, 3s3p3d, 3p{sup 2}3d, 3s3d{sup 2},3s{sup 2}4s,3s{sup 2}4p,3s{sup 2}4d,3s{sup 2}4f, and 3s3p4s configurations of Co XV are calculated, using extensive configuration-interaction (CI) wave functions, obtained with the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are included through the Breit-Pauli approximation via spin-orbit, spin-other-orbit, spin-spin, Darwin and mass correction terms. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made. Our calculated excitation energies, including their ordering, are in excellent agreement with the experimental results and the experimentally compiled energy values of the National Institute for Standards and Technology (NIST) wherever available. The mixing among several fine-structure levels is found to be very strong, with most of the strongly mixed levels belonging to the (1s{sup 2}2s{sup 2}2p{sup 6})3p{sup 2}3d and 3s3d{sup 2} configurations. The strong mixing among several fine-structure levels makes it very difficult to identify them uniquely. Perhaps, that may be the reason for the lack of both experimental and theoretical results for these levels. We believe that our extensive calculated values can guide experimentalists in identifying the fine-structure levels in their future work. From our radiative decay rates we have also calculated radiative lifetimes of some fine-structure levels. In this calculation we also predict new data for

  18. Fine-structure energy levels, oscillator strengths and lifetimes in Co-XV

    International Nuclear Information System (INIS)

    The study of Al-like spectra of ions of the elements of the iron group has received a great deal of attention because they are of particular interest in controlled thermonuclear fusion. Excitation energies from ground state for 97 fine-structure levels as well as oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the fine-structure levels of the terms belonging to the (1s22s22p6)3s23p,3s3p2,3s23d, 3p3, 3s3p3d, 3p23d, 3s3d2,3s24s,3s24p,3s24d,3s24f, and 3s3p4s configurations of Co XV are calculated, using extensive configuration-interaction (CI) wave functions, obtained with the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are included through the Breit-Pauli approximation via spin-orbit, spin-other-orbit, spin-spin, Darwin and mass correction terms. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made. Our calculated excitation energies, including their ordering, are in excellent agreement with the experimental results and the experimentally compiled energy values of the National Institute for Standards and Technology (NIST) wherever available. The mixing among several fine-structure levels is found to be very strong, with most of the strongly mixed levels belonging to the (1s22s22p6)3p23d and 3s3d2 configurations. The strong mixing among several fine-structure levels makes it very difficult to identify them uniquely. Perhaps, that may be the reason for the lack of both experimental and theoretical results for these levels. We believe that our extensive calculated values can guide experimentalists in identifying the fine-structure levels in their future work. From our radiative decay rates we have also calculated radiative lifetimes of some fine-structure levels. In this calculation we also predict new data for several fine-structure levels where no other theoretical and/or experimental results are available. (authors)

  19. Fine-structure energy levels, oscillator strengths and lifetimes in Cu XVI

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, G P [Department of Physics, S D (Postgraduate) College, Muzaffarnagar-251 001 (Affiliated to Chowdhary Charan Singh University, Meerut-250 004) (India); Msezane, A Z, E-mail: g_p_gupta1@yahoo.co.in [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta, GA 30314 (United States)

    2011-05-01

    We have performed large-scale CIV3 calculations of excitation energies from ground state for 69 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the fine-structure levels of the terms belonging to the (1s{sup 2}2s{sup 2}2p{sup 6})3s{sup 2}3p{sup 2}, 3s3p{sup 3}, 3p{sup 4}, 3s{sup 2}3p3d, 3s{sup 2}3p4s, 3s{sup 2}3p4p, 3s{sup 2}3p4d, and 3s{sup 2}3p4f configurations of Cu XVI. These states are represented by very extensive configuration-interaction (CI) wave functions obtained with the computer code CIV3 of Hibbert. The important relativistic effects in intermediate coupling are incorporated by means of the Breit-Pauli Hamiltonian. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made so that the energy splittings are as close as possible to the energy values of those from the National Institute for Standards and Technology. The mixing among several fine-structure levels is found to be very strong. From our radiative decay rates we have also calculated radiative lifetimes of the fine-structure levels. Our calculated lifetime for the high spin level 3s3p{sup 3}({sup 5}S{sub 2}) is found to be in excellent agreement with the experimental value of Trabert et al (1988 J. Opt. Soc. Am. B 5 2173). In this calculation, we also predict new data for several fine-structure levels where no other theoretical and/or experimental results are available.

  20. Fine-structure energy levels, oscillator strengths and lifetimes in Cu XVI

    International Nuclear Information System (INIS)

    We have performed large-scale CIV3 calculations of excitation energies from ground state for 69 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the fine-structure levels of the terms belonging to the (1s22s22p6)3s23p2, 3s3p3, 3p4, 3s23p3d, 3s23p4s, 3s23p4p, 3s23p4d, and 3s23p4f configurations of Cu XVI. These states are represented by very extensive configuration-interaction (CI) wave functions obtained with the computer code CIV3 of Hibbert. The important relativistic effects in intermediate coupling are incorporated by means of the Breit-Pauli Hamiltonian. Small adjustments to the diagonal elements of the Hamiltonian matrices have been made so that the energy splittings are as close as possible to the energy values of those from the National Institute for Standards and Technology. The mixing among several fine-structure levels is found to be very strong. From our radiative decay rates we have also calculated radiative lifetimes of the fine-structure levels. Our calculated lifetime for the high spin level 3s3p3(5S2) is found to be in excellent agreement with the experimental value of Trabert et al (1988 J. Opt. Soc. Am. B 5 2173). In this calculation, we also predict new data for several fine-structure levels where no other theoretical and/or experimental results are available.

  1. Identification of three critical regions within mouse interleukin 2 by fine structural deletion analysis.

    OpenAIRE

    Zurawski, S M; Zurawski, G

    1988-01-01

    We have analyzed structure--function relationships of the protein hormone murine interleukin 2 by fine structural deletion mapping. A total of 130 deletion mutant proteins, together with some substitution and insertion mutant proteins, was expressed in Escherichia coli and analyzed for their ability to sustain the proliferation of a cloned murine T cell line. This analysis has permitted a functional map of the protein to be drawn and classifies five segments of the protein, which together con...

  2. Determining the velocity fine structure by a laser anemometer with fixed orientation

    Energy Technology Data Exchange (ETDEWEB)

    Kristensen, Leif; Kirkegaard, P.; Mikkelsen, Torben

    2011-02-15

    We have studied the velocity structure functions and spectra which can be determined by a CW-laser anemometer and a (pulsed) lidar anemometer. We have found useful theoretical expressions for both types of anemometers and compared their filtering of the along-beam turbulent velocity. The purpose has been to establish a basis for remote determining of turbulence fine-structure in terms of the rate of dissipation of specific kinetic energy in the atmospheric boundary layer. (Author)

  3. Scattering pulse of label free fine structure cells to determine the size scale of scattering structures

    Science.gov (United States)

    Zhang, Lu; Chen, Xingyu; Zhang, Zhenxi; Chen, Wei; Zhao, Hong; Zhao, Xin; Li, Kaixing; Yuan, Li

    2016-04-01

    Scattering pulse is sensitive to the morphology and components of each single label-free cell. The most direct detection result, label free cell's scattering pulse is studied in this paper as a novel trait to recognize large malignant cells from small normal cells. A set of intrinsic scattering pulse calculation method is figured out, which combines both hydraulic focusing theory and small particle's scattering principle. Based on the scattering detection angle ranges of widely used flow cytometry, the scattering pulses formed by cell scattering energy in forward scattering angle 2°-5° and side scattering angle 80°-110° are discussed. Combining the analysis of cell's illuminating light energy, the peak, area, and full width at half maximum (FWHM) of label free cells' scattering pulses for fine structure cells with diameter 1-20 μm are studied to extract the interrelations of scattering pulse's features and cell's morphology. The theoretical and experimental results show that cell's diameter and FWHM of its scattering pulse agree with approximate linear distribution; the peak and area of scattering pulse do not always increase with cell's diameter becoming larger, but when cell's diameter is less than about 16 μm the monotone increasing relation of scattering pulse peak or area with cell's diameter can be obtained. This relationship between the features of scattering pulse and cell's size is potentially a useful but very simple criterion to distinguishing malignant and normal cells by their sizes and morphologies in label free cells clinical examinations.

  4. Les structures fines de l'\\'{e}lectromagn\\'{e}tisme classique et de la relativit\\'{e} restreinte (The fine structures of Classical Electromagnetism and Special Relativity)

    CERN Document Server

    Pierseaux, Y; Pierseaux, Yves; Rousseaux, Germain

    2006-01-01

    One of us (Y.P.) has shown the existence of a longitudinal component in the propagation of light waves on the basis of the kinematics underlying Poincar\\'{e}'s ellipse. We show how this statement agrees with the electromagnetic theory. We recall that the second of us supports the existence of a "fine structure" of Electromagnetism that is, the co-existence of two theories, one based on the fields (Heaviside-Hertz) and the other on the potentials (Riemann-Lorenz). The existence of two different kinematics (the "fine structure" of Special Relativity : Einstein or Poincar\\'{e}) corresponds to these two formulations of Classical Electromagnetism. With this goal in mind, we prove the relativistic covariance of the Helmholtz decomposition of the vector potential. This one translates into a generalized compensation for all directions of propagation, on the basis of the tangent to Poincar\\'{e}'s ellipse, between the scalar potential and the longitudinal component of the vector potential. The adoption by Poincar\\'{e} ...

  5. Quasar absorption spectra and the structure of the universe

    International Nuclear Information System (INIS)

    Analysis of the spacing between absorption-line systems in quasar spectra and comparison against deep optical survey data for the separation between superclusters of galaxies indicates that the absorption originates in the superclusters. Supported by analogous data on the absorbing gas in the galactic and Magellanic Cloud halos, this inference sharpens theoretical conclusions as to the properties of superclusters. The problem of the unidentified quasar absorption lines is discussed

  6. Quasar absorption spectra and the structure of the universe

    Energy Technology Data Exchange (ETDEWEB)

    Doroshkevich, A.G.

    1984-03-01

    Analysis of the spacing between absorption-line systems in quasar spectra and comparison against deep optical survey data for the separation between superclusters of galaxies indicates that the absorption originates in the superclusters. Supported by analogous data on the absorbing gas in the galactic and Magellanic Cloud halos, this inference sharpens theoretical conclusions as to the properties of superclusters. The problem of the unidentified quasar absorption lines is discussed.

  7. The Fine-structure Constant as a Probe of Chemical Evolution and AGB Nucleosynthesis in Damped Lyman-alpha Systems

    CERN Document Server

    Ashenfelter, T P; Olive, Keith A; Ashenfelter, Timothy P.; Mathews, Grant J.; Olive, Keith A.

    2004-01-01

    Evidence from a large sample of quasar absorption-line spectra in damped Lyman-alpha systems has suggested a possible time variation of the fine structure constant alpha. The most statistically significant portion of this sample involves the comparison of Mg and Fe wavelength shifts using the many-multiplet (MM) method. However, the sensitivity of this method to the abundance of heavy isotopes, especially Mg, is enough to imitate an apparent variation in alpha in the redshift range 0.5 < z < 1.8. We implement recent yields of intermediate mass (IM) stars into a chemical evolution model and show that the ensuing isotope distribution of Mg can account for the observed variation in alpha. As such, these observations of quasar absorption spectra can be used to probe the nucleosynthetic history of low-metallicity damped Lyman-$\\alpha$ systems in the redshift range 0.5 < z < 1.8. This analysis, in conjunction with other abundance measurements of low-metallicity systems, reinforces the mounting evidence ...

  8. Fine Structure Zonal Flow Excitation by Beta-induced Alfven Eigenmode

    CERN Document Server

    Qiu, Zhiyong; Zonca, Fulvio

    2016-01-01

    Nonlinear excitation of low frequency zonal structure (LFZS) by beta-induced Alfven eigenmode (BAE) is investigated using nonlinear gyrokinetic theory. It is found that electrostatic zonal flow (ZF), rather than zonal current, is preferentially excited by finite amplitude BAE. In addition to the well-known meso-scale radial envelope structure, ZF is also found to exhibit fine radial structure due to the localization of BAE with respect to mode rational surfaces. Specifically, the zonal electric field has an even mode structure at the rational surface where radial envelope peaks.

  9. Electronic fine structure and recombination dynamics in single InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Seguin, R.

    2008-01-28

    In the work at hand single InAs/GaAs quantum dots (QDs) are examined via cathodoluminescence spectroscopy. A thorough analysis of the spectra leads to an unambiguous assignment of the lines to the decay of specific excitonic complexes. A special aspect of the Coulomb interaction, the exchange interaction, gives rise to a fine structure in the initial and final states of an excitonic decay. This leads to a fine structure in the emission spectra that again is unique for every excitonic complex. The exchange interaction is discussed in great detail in this work.QDs of different sizes are investigated and the influence on the electronic properties is monitored. Additionally, the structure is modified ex situ by a thermal annealing process. The changes of the spectra under different annealing temperatures are traced. Finally, recombination dynamics of different excitonic complexes are examined by performing time-resolved cathodoluminescence spectroscopy. (orig.)

  10. Electronic fine structure and recombination dynamics in single InAs quantum dots

    International Nuclear Information System (INIS)

    In the work at hand single InAs/GaAs quantum dots (QDs) are examined via cathodoluminescence spectroscopy. A thorough analysis of the spectra leads to an unambiguous assignment of the lines to the decay of specific excitonic complexes. A special aspect of the Coulomb interaction, the exchange interaction, gives rise to a fine structure in the initial and final states of an excitonic decay. This leads to a fine structure in the emission spectra that again is unique for every excitonic complex. The exchange interaction is discussed in great detail in this work.QDs of different sizes are investigated and the influence on the electronic properties is monitored. Additionally, the structure is modified ex situ by a thermal annealing process. The changes of the spectra under different annealing temperatures are traced. Finally, recombination dynamics of different excitonic complexes are examined by performing time-resolved cathodoluminescence spectroscopy. (orig.)

  11. Structural characterization of bismuth molybdates by x-ray absorption spectroscopy and powder neutron diffraction profile analysis

    Energy Technology Data Exchange (ETDEWEB)

    Antonio, M.R.; Teller, R.G.; Sandstorm, D.R.; Mehicic, M.; Brazdil, J.F.

    1988-05-19

    By use of synchrotron radiation, high-quality X-ray absorption data have been recorded for three bismuth molybdate phases with the general composition Bi/sub 2/O/sub 3/ x nMoO/sub 3/, for n = 3 (..cap alpha..-phase) n = 2 (..beta..-phase), and n = 1 (..gamma..-phase). The results of these bismuth L/sub 3/-edge and molybdenum K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) studies provide structural insights about the local environments of the Bi/sup 3 +/ and Mo/sup 6 +/ ions. Also, the structure of ..beta..-Bi/sub 2/O/sub 3/ x 2MoO/sub 3/ was investigated by the use of time-of-flight powder neutron diffraction. The profile analysis of the neutron data for ..beta..-bismuth molybdate (monoclinic, P2/sub 1//n, a = 11.9515 (4) A, b = 10.7993 (4) A, c = 11.8805 (4) A, ..beta.. = 90.142 (5)/sup 0/, and Z = 8) revealed that the bismuth and molybdenum cations are present in a fluorite-like sublattice.

  12. Diffraction Anomalous Fine Structure study and atomistic simulation of Ge/Si nanoislands

    Energy Technology Data Exchange (ETDEWEB)

    Katcho, N.A. [Instituto de Quimica Fisica Rocasolano, IQFR-CSIC, c. Serrano 119, 28006 Madrid (Spain); ICMA, Dep. Fisica de la Materia Condensada, CSIC-Universidad de Zaragoza (Spain); Richard, M.-I. [Aix-Marseille Universite, IM2NP-CNRS, Faculte des Sciences et Techniques, F-13397 Marseille Cedex (France); Proietti, M.G., E-mail: proietti@unizar.es [ICMA, Dep. Fisica de la Materia Condensada, CSIC-Universidad de Zaragoza (Spain); Renevier, H., E-mail: hubert.renevier@grenoble-inp.fr [LMGP, Grenoble INP - Minatec, Grenoble (France); Leclere, C. [LMGP, Grenoble INP - Minatec, Grenoble (France); Favre-Nicolin, V. [CEA-UJF, INAC, SP2M, Grenoble (France); Zhang, J.J.; Bauer, G. [Institut fuer Halbleiter - und Festkoerperphysik, Johannes Kepler Universitaet Linz (Austria)

    2012-08-01

    We applied Grazing Incidence Diffraction Anomalous Fine Structure to the study of the structure of Ge dome-shaped nanoislands, grown by Molecular Beam Epitaxy on Si (0 0 1) substrates at a temperature of 650 Degree-Sign C. We determined the vertical composition of the islands showing the presence of a strong Ge/Si intermixing that is nearly constant from bottom to top. In particular, an abrupt change is found at the substrate interface where the composition switches from pure Si to Ge{sub 0.6}Si{sub 0.4}. The analysis of the Diffraction Anomalous Fine Structure oscillations of the spectra is crucial to obtain the true composition profile. We performed atomistic simulations to investigate the role of the strained substrate underneath the dome on the diffraction results and to quantify the resolution of our method. Anomalous Diffraction spectra and Diffraction Anomalous Fine Structure oscillations have been simulated for a real size and real shape cluster including faceting, giving a more detailed data interpretation and understanding of the Ge-Si intermixing mechanism.

  13. Complete study of excitonic fine-structure splitting in GaN/AlN quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Hoenig, Gerald; Winkelnkemper, Momme; Schliwa, Andrei; Hoffmann, Axel; Bimberg, Dieter [Institut fuer Festkoerperphysik, Technische Universitaet Berlin (Germany); Kindel, Christian [Institut fuer Festkoerperphysik, Technische Universitaet Berlin (Germany); Research Center for Advanced Science and Technology, University of Tokyo (Japan); Kako, Satoshi [Institute for Nano Quantum Information Electronics, University of Tokyo (Japan); Kawano, Takeshi; Oishi, Hiroaki [Research Center for Advanced Science and Technology, University of Tokyo (Japan); Arakawa, Yasuhiko [Research Center for Advanced Science and Technology, University of Tokyo (Japan); Institute for Nano Quantum Information Electronics, University of Tokyo (Japan); Institute of Industrial Science, University of Tokyo, Komaba, Meguro, Tokyo (Japan)

    2010-07-01

    A detailed understanding of the excitonic fine structure in quantum dots (QDs) is indispensable for their use in quantum cryptography devices. While the fine structure in As-based QDs has been studied extensively, there is a lack of such investigations for N-based QDs, which might operate at room temperature. We present the first complete study of excitonic fine-structure splitting (FSS) in GaN/AlN QDs. Our experimental studies reveal a huge FSS of up to 7 meV with a strong dependence on the emission energy inverse to that in As-based QDs. Our theoretical studies, performed with a configuration-interaction method based on realistic 8-band-k.p Hartree-Fock states, confirm the experimental results and identify the origin of FSS as lattice strain induced. Based on our results it is possible to induce a strain gradient (by micro mechanic techniques or structuring methods), which will reduce the FSS to zero for the emission of entangled photon pairs.

  14. Lower bound on the value of the fine-structure constant

    CERN Document Server

    Hod, Shahar

    2010-01-01

    Recently, we have proposed the existence of a universal relation between the maximal electric charge and total mass of any weakly self-gravitating object: $Z\\leq Z^*={\\alpha}^{-1/3}A^{2/3}$, where $Z$ is the number of protons, $A$ is the total baryon (mass) number, and $\\alpha=e^2/\\hbar c$ is the fine-structure constant. Motivated by this novel bound, we explore the $(Z,A)$-relation of atomic nuclei as deduced from the Weizs\\"acker semi-empirical mass formula. It is shown that {\\it all} nuclei, including the meta-stable maximally charged ones, conform to the upper bound. Moreover, we suggest that the new charge-mass bound places an interesting constraint on the value of the fine-structure constant: $\\alpha\\gtrsim 1/323$.

  15. Special Features of Polarization-Induced Relaxation in Structurally Disordered Finely Dispersed Systems

    Science.gov (United States)

    Shcherbachenko, L. A.; Tanaev, A. B.; Bezrukova, Ya. V.; Ezhova, L. I.; Baryshnikov, D. S.; Marchuk, S. D.; Berezovskii, P. P.

    2015-04-01

    Dielectric characteristics of finely dispersed hydrated natural coal from the Krasnoyarsk Strip Mine are measured in wide ranges of external measuring electric field frequencies, environmental temperatures, and humidities. The frequency, temperature, and concentration dispersions of the dielectric permittivity are revealed for the examined structures. An analysis of the results obtained demonstrates that a cluster layer of the polar aqueous matrix characterized by rigid fixing of water molecules is formed at the interphase boundaries of the examined system. It is demonstrated that this layer plays the role of the potential barrier that complicates transitions for both free water molecules and surface active dispersed coals oriented by the electric field. This layer can increase the electric strength of the examined disordered finely dispersed structures.

  16. Changes in the fine structure of stochastic distributions as a consequence of space-time fluctuations

    CERN Document Server

    Shnoll, S E

    2006-01-01

    Earlier we showed that the fine structure of the spectrum of amplitude variations in the results of measurements of the processes of different nature (in other words, the fine structure of the dispersion of results or the pattern of the corresponding histograms) is subject to macroscopic fluctuations, changing regularly with time. These changes indicate that the dispersion of results that remains after all artifacts are excluded inevitably accompanies any measurements and reflects very basic features of our world. In our research, we have come to the conclusion that this dispersion of results is the effect of space-time fluctuations, which, in their turn, are caused by the movement of the measured object in an anisotropic gravitational field. Among other things, this conclusion means that the examination of the detailed pattern of distributions obtained from the results of measurement of the dynamics of processes of different nature discovers laws, which cannot be revealed with traditional methods for the ana...

  17. Number Archetypes and “Background” Control Theory Concerning the Fine Structure Constant

    Directory of Open Access Journals (Sweden)

    Péter Várlaki

    2008-05-01

    Full Text Available In this paper we analyze in detail the central role of number ‘137’, the so-calledFine Structure Constant in the collaboration of Pauli and Jung. First, we present the fascinationor the obsession of Pauli for the interpretation of number ‘137’. Second, we treat thespontaneous messages originating from unconscious concerning number ‘137’ in the wellknowndreams of Pauli. We restrict our investigations to the dreams containing the especiallyimportant formulae of Fine Structure Constant (4π3 + π2 + π, and also that containingthe so-called background models of mathematical control systems. Third, we shortlymention four of the numerous synchronicities arising during the Pauli–Jung collaboration.

  18. Topological map of the Hofstadter butterfly: Fine structure of Chern numbers and Van Hove singularities

    Science.gov (United States)

    Naumis, Gerardo G.

    2016-04-01

    The Hofstadter butterfly is a quantum fractal with a highly complex nested set of gaps, where each gap represents a quantum Hall state whose quantized conductivity is characterized by topological invariants known as the Chern numbers. Here we obtain simple rules to determine the Chern numbers at all scales in the butterfly fractal and lay out a very detailed topological map of the butterfly by using a method used to describe quasicrystals: the cut and projection method. Our study reveals the existence of a set of critical points that separates orderly patterns of both positive and negative Cherns that appear as a fine structure in the butterfly. This fine structure can be understood as a small tilting of the projection subspace in the cut and projection method and by using a Chern meeting formula. Finally, we prove that the critical points are identified with the Van Hove singularities that exist at every band center in the butterfly landscape.

  19. Measuring the fine structure constant with Bragg diffraction and Bloch oscillations

    Science.gov (United States)

    Yu, Chenghui; Estey, Brian; Parker, Richard; Dudley, Jordan; Müller, Holger

    2016-05-01

    We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations. In this new scheme, we have achieved a resolution of δα / α =0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We have suppressed many systematic effects known in most atom interferometers with Raman beam splitters such as light shift, Zeeman effect shift as well as vibration. We have also simulated multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implemented spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics.

  20. Measuring h /mCs and the Fine Structure Constant with Bragg Diffraction and Bloch Oscillations

    Science.gov (United States)

    Parker, Richard

    2016-05-01

    We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations. In this new scheme, we have achieved a resolution of δα / α =0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We suppress many systematic effects, e.g., Zeeman shifts and effects from Earth's gravity and vibrations, use Bloch oscillations to increase the signal and reduce the diffraction phase, simulate multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implement spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics.

  1. Fusion reaction yield in focused discharges with variable energy and plasma fine structure

    International Nuclear Information System (INIS)

    The same linear correlation between the distribution parameters (ΔT and Max ΔV) of the radial current density J between electrodes and the fusion reaction yield per pulse, Y, in the plasma focus (PF) pinch was quantitatively determined from different PF machines. Contact prints of current-sheath fragments (CSF) ejected from the pinch are obtained from 2.5-MeV-D+ ions. CSF's show the same submillimetric fine structure of the pinch. (author) 3 refs., 2 tabs

  2. Fine Structure of Hydrogen Bond in Cholic Acid Revealed by 2DIR Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on cryogenic FT-IR spectroscopic studies of hydrogen bonds in cholic acid, two-dimensional FT-IR spectroscopy was applied to enhance our understanding of the hydrogen bonds of cholic acid. Fine spectral structures were revealed by asynchronous 2D FT-IR spectra. The co-relationship among various bands was discussed according to the synchronous 2D FT-IR spectrum.

  3. Fine-structure energy levels, oscillator strengths and lifetimes in Mn XIII

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, G P [Department of Physics, S. D. Postgraduate College - Affiliated to Chowdhary Charan Singh University, Meerut-250 004, Muzaffarnagar-251 001 (India); Msezane, A Z [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta, GA 30314 (United States)

    2007-09-15

    We have performed large scale CIV3 calculations of excitation energies from ground state for 98 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the fine-structure levels of the terms belonging to the (1s{sup 2}2s{sup 2} 2p{sup 6})3s{sup 2} 3p, 3s3p{sup 2}, 3s{sup 2}3d, 3p{sup 3}, 3s3p3d, 3p{sup 2} 3d, 3s3d{sup 2}, 3s{sup 2} 4s, 3s{sup 2} 4p, 3s{sup 2}4d, 3s{sup 2} 4f and 3s3p4s configurations of Al-like manganese. These states are represented by very extensive configuration-interaction (CI) wavefunctions obtained with the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are incorporated by means of the Breit-Pauli Hamiltonian. In order to keep our calculated energy splittings as close as possible to the experimental values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. Our calculated excitation energies, including their ordering, are in excellent agreement with the available experimental results. From our radiative decay rates, we have also calculated radiative lifetimes of some fine-structure levels. Differences between our calculated lifetimes and those of Froese Fisher et al (2006 At. Data Nucl. Data Tables 92 607) for several fine-structure levels are discussed.

  4. Fine-structure energy levels, oscillator strengths and lifetimes in Cu XVIII

    Energy Technology Data Exchange (ETDEWEB)

    Tayal, Vikas [Department of Physics, Dronacharya College of Engineering (Affiliated to Uttar Pradesh Technical University, Lucknow), Greater Noida (UP), 201 308 (India); Gupta, G P [Department of Physics, S D (Postgraduate) College (Affiliated with Choudhary Charan Singh University, Meerut), Muzaffarnagar - UP, 251 001 (India)], E-mail: tayalvikas11@rediffmail.com

    2009-11-15

    We have performed large-scale CIV3 (Configuration Interaction Version 3) calculations of excitation energies from ground states for 141 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the levels of the (1s{sup 2}2s{sup 2}2p{sup 6}) 3l{sup 2}, 3l3l' and 3l4l configurations of Cu XVIII. These states are represented by very extensive configuration-interaction (CI) wavefunctions obtained using the CIV3 computer code of Hibbert. The important relativistic effects are included through the Breit-Pauli approximation. In order to keep our calculated energy splittings as close as possible to the experimental values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. Since mixing among several fine-structure levels is found to be very strong, it becomes difficult to identify these uniquely. Our excitation energies, including their ordering, are in excellent agreement (better than 1.0%) with the available experimental results. From our calculated radiative decay rates, we have also calculated radiative lifetimes of the fine-structure levels. Our calculated oscillator strengths and radiative decay rates are found to be in good agreement with other theoretical results, while the lifetimes agree very well with the experimental values (wherever available). In this calculation, we also predict new data for several fine-structure levels where no other theoretical and experimental results are available.

  5. Fine structure DPOAEs in normal hearing consanguineous parents of congenitally hearing impaired siblings (probable carriers

    Directory of Open Access Journals (Sweden)

    Megha Sasidharan

    2013-01-01

    Full Text Available Background: This study examines the concealed phenotypic variations in carriers of non-syndromic recessive hearing loss, using fine structure distortion product otoacoustic emissions (DPOAEs. As genetic tests were not feasible to validate the recessive trait in the participants, an inclusion criterion was followed, where in normal hearing parents with two or more hearing-impaired children and a positive consanguinity were assumed to be probable carriers. Materials and Methods: The amplitude of fine structure DPOAEs from 27 ears of probable carriers was compared with 62 normal control ears. The primaries were presented at 65/55dBSPL, maintaining a frequency ratio of 1.2, covering 20 points per octave across 1-4 kHz. A comparison between the octaves 1-2 kHz and 2-4 kHz was also made in all the participants to observe if the deviant functioning of the hair cells predominated the higher or the lower frequencies. Results: The overall fine structure amplitude was significantly reduced in the probable carrier group across the frequencies. There was a significant difference between 1-2 kHz and 2-4 kHz in both non-carriers and probable carriers. The higher frequencies had a lower amplitude and the lower frequencies had a higher amplitude. The probable carrier group had a relatively significant amplitude reduction in the higher octave when compared to the control group. Conclusion: Carriers of hearing loss do exhibit subtle functional changes in the ear, in spite of having a normal hearing sensitivity. This study throws light on the scope of fine structure emissions to emerge as a very good diagnostic tool in the field of audiology.

  6. Atomic oxygen fine-structure splittings with tunable far-infrared spectroscopy

    Science.gov (United States)

    Zink, Lyndon R.; Evenson, Kenneth M.; Matsushima, Fusakazu; Nelis, Thomas; Robinson, Ruth L.

    1991-01-01

    Fine-structure splittings of atomic oxygen (O-16) in the ground state have been accurately measured using a tunable far-infrared spectrometer. The 3P0-3pl splitting is 2,060,069.09 (10) MHz, and the 3Pl-3P2 splitting is 4,744,777.49 (16) MHz. These frequencies are important for measuring atomic oxygen concentration in earth's atmosphere and the interstellar medium.

  7. INJECTION-BASED STABILIZATION OF PERVIOUS SOILS, CONCRETE AND MASONRY STRUCTURES USING PARTICULARLY FINELY DISPERSED BINDERS

    OpenAIRE

    Kharchenko Igor Yakovlevich; Bazhenov Marat Ildarovich

    2012-01-01

    The authors consider the problem of maintenance of buildings and structures of architectural merit. Expedient resolution of this problem consists in the application of a mineral hydraulic binder that has a particularly fine, gradually and smoothly changing granulometric composition and explicit and steady chemical and mineral composition. The above binder is recovered as a result of the air separation of Portland cement. The above binder comprises Portland clinker, furnace slag, ...

  8. Energies, fine structures and transition wavelengths of the core-excited states in Be * ions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The fine structures of doubly excited resonances of lithium-like beryllium are calculated using the saddle-point and saddle-point complex-rotation methods. A restricted variational method is used to obtain a more accurate value for the nonrelativistic energy. Relativistic and mass polarization corrections to the resonance energy are included. Transition wavelengths are also calculated and compared with other theories and experimental results.

  9. Cosmological implications in electrodynamics due to variations of the fine structure constant

    CERN Document Server

    Martínez-Ledesma, J L

    2002-01-01

    Astronomical observations are strongly suggesting that the fine structure constant varies cosmologically. We present an analysis on the consequences that this variations might induce on the electromagnetic field as a whole. We show that under this circumstances the electrodynamics in vacuum of the universe are described by two fields, the ``standard'' Maxwell's field and a new scalar field. We provide a generalized Lorentz force which can be used to test our results experimentally.

  10. Structural studies of molecular and metallic overlayers using angle- resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Z.

    1992-10-01

    Angle-resolved photoemission extended fine structure (ARPEFS) was used to study molecular and metallic overlayers on metal surfaces through analysis of p2mg(2[times]1)CO/Ni(110) and the p(2[times]2)K/Ni(111) adsorption. For the dense p2mg(2[times]1)CO/Ni(110) surface layer, photoemission intensities from C 1s level were measured in three directions at photoelectron kinetic energies 60-400 eV. Using multiple-scattering spherical-wave (MSSW) modeling, it was found that CO molecules are adsorbed on short-bridge sites, with adjacent CO along the [110] direction displaced alternatively in opposite directions towards the [001] azimuths to form a zigzag chain geometry. The tilt angle is 16[plus minus]2[degree] from the surface normal for the direction linking the C atom and the center of the Ni bridge. The carbon C-Ni interatomic distance was determined to be 1.94[plus minus]0.02[Angstrom]. The first- to second-layer spacing of Ni is 1.27[plus minus]0.04[Angstrom], up from 1.10[Angstrom] for the clean Ni(110) surface, but close to the 1.25[Angstrom] Ni interlayer spacing in the bulk. The C-O bond length and tilt angle were varied within small ranges (1.10--1.20[Angstrom] and 15--23[degrees]) in our MSSW simulations. Best agreement between experiment and simulations was achieved at 1.16[Angstrom] and 19[degrees]. This yields an O-O distance of 2.95[Angstrom] for the two nearest CO molecules, (van der Waals' radius [approximately] 1.5 [Angstrom] for oxygen). Two different partial-wave phase-shifts were used in MSSW, and structural results from both are in very good agreement. For the p(2[times]2)K/Ni(111) overlayer, ARPEFS [chi](k) curves from K 1s level measured along [111] and [771] at 130K showed that the K atoms are preferentially adsorbed on the atop sites, in agreement with a LEED study of the same system.

  11. Structural studies of molecular and metallic overlayers using angle- resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Z.

    1992-10-01

    Angle-resolved photoemission extended fine structure (ARPEFS) was used to study molecular and metallic overlayers on metal surfaces through analysis of p2mg(2{times}1)CO/Ni(110) and the p(2{times}2)K/Ni(111) adsorption. For the dense p2mg(2{times}1)CO/Ni(110) surface layer, photoemission intensities from C 1s level were measured in three directions at photoelectron kinetic energies 60-400 eV. Using multiple-scattering spherical-wave (MSSW) modeling, it was found that CO molecules are adsorbed on short-bridge sites, with adjacent CO along the [110] direction displaced alternatively in opposite directions towards the [001] azimuths to form a zigzag chain geometry. The tilt angle is 16{plus_minus}2{degree} from the surface normal for the direction linking the C atom and the center of the Ni bridge. The carbon C-Ni interatomic distance was determined to be 1.94{plus_minus}0.02{Angstrom}. The first- to second-layer spacing of Ni is 1.27{plus_minus}0.04{Angstrom}, up from 1.10{Angstrom} for the clean Ni(110) surface, but close to the 1.25{Angstrom} Ni interlayer spacing in the bulk. The C-O bond length and tilt angle were varied within small ranges (1.10--1.20{Angstrom} and 15--23{degrees}) in our MSSW simulations. Best agreement between experiment and simulations was achieved at 1.16{Angstrom} and 19{degrees}. This yields an O-O distance of 2.95{Angstrom} for the two nearest CO molecules, (van der Waals` radius {approximately} 1.5 {Angstrom} for oxygen). Two different partial-wave phase-shifts were used in MSSW, and structural results from both are in very good agreement. For the p(2{times}2)K/Ni(111) overlayer, ARPEFS {chi}(k) curves from K 1s level measured along [111] and [771] at 130K showed that the K atoms are preferentially adsorbed on the atop sites, in agreement with a LEED study of the same system.

  12. Absorption spectra of quasars and the structure of the Universe

    International Nuclear Information System (INIS)

    The analysis of the distribution of the distances between the systems of absorption lines in the quasars' spectra and the comparison of this distribution with the distribution of the distances between superclusters in the deep optical surveys are carried out. It is shown that the systems of absorption lines are connected with superclusters of galaxies. The comparison of the absorbing gas parameters with the data for coronae of the Galaxy and of the Magellanic Clouds confirms this connection and permits to revise conclusions of the theory on the properties of superclusters. The problem of unidentified absorption lines in the quasars spectra is discussed

  13. Correlation effects on fine-structure energy levels, oscillator strengths and lifetimes in Ca VII

    Energy Technology Data Exchange (ETDEWEB)

    Tayal, Vikas [Department of Physics, Dronacharya College of Engineering, Greater Noida (UP) (Affiliated to Uttar Pradesh Technical University, Lucknow) (India); Gupta, G P [Department of Physics, S. D. (Postgraduate) College, Muzaffarnagar (UP), Affiliated to Choudhary Charan Singh University, Meerut - 250 004 (India); Sharma, M K [Department of Physics, Krishna Institute of Engineering and Technology, Ghaziabad (UP) (Affiliated to Uttar Pradesh Technical University, Lucknow) (India)

    2009-11-01

    Energy levels, oscillator strengths, and transition probabilities for transitions among the fine-structure levels of the terms belonging to the 3s{sup 2}3p{sup 2}, 3s3p{sup 3}, 3s{sup 2}3p3d, 3p{sup 4}, 3s{sup 2}3p4s, 3s{sup 2}3p4p, 3s{sup 2}3p4d, and 3s{sup 2}3p4f configurations of Si-like Calcium are calculated using extensive configuration-interaction (CI) wave functions obtained with the CIV3 computer code of Hibbert. The relativistic effects in intermediate coupling are incorporated by means of the Breit-Pauli Hamiltonian. The energy splitting of 70 fine-structure levels, oscillator strengths and transition probabilities for electric-dipole-allowed and intercombination transitions and, also the lifetimes of fine-structure levels are presented and compared with available experimental and other theoretical results.

  14. Fine-structure energy levels, radiative rates and lifetimes in Fe XIII

    International Nuclear Information System (INIS)

    Energy levels and radiative rates for transition among the fine-structure levels of the terms belonging to the 3s23p2, 3s3p3,3s23p3d, 3p4, 3s3p23d, 3s23d2, 3p23d2, 3p33d, 3s3p3d2, 3s23p4s, 3s23p4p, 3s23p4d, 3s23p4f and 3s3p24s configurations of Si-like Iron are calculated through the CIV3 computer code using extensive configuration-interaction (CI) wavefunctions. The important relativistic effects are included through the Breit-Pauli approximation. The energy splitting of 390 fine-structure levels, oscillator strengths and radiative rates for electric-dipole-allowed and intercombination transitions and, also the lifetimes of fine-structure levels are presented and compared with available experimental and other theoretical results.

  15. Strong limit on the spatial and temporal variations of the fine-structure constant

    Science.gov (United States)

    Le, T. D.

    2016-10-01

    Observed spectra of quasars provide a powerful tool to test the possible spatial and temporal variations of the fine-structure constant α = e 2/ћc over the history of the Universe. It is demonstrated that high sensitivity to the variation of α can be obtained from a comparison of the spectra of quasars and laboratories. We reported a new constraint on the variation of the fine-structure constant based on the analysis of the optical spectra of the fine-structure transitions in [NeIII], [NeV], [OIII], [OI] and [SII] multiplets from 14 Seyfert 1.5 galaxies. The weighted mean value of the α-variation derived from our analysis over the redshift range 0.035 < z < 0.281 Δα/α= (4.50 +/- 5.53) \\times 10-5. This result presents strong limit improvements on the constraint on Δα/α compared to the published in the literature

  16. Multipoint MMS observations of fine-scale SAPS structure in the inner magnetosphere

    Science.gov (United States)

    Erickson, P. J.; Matsui, H.; Foster, J. C.; Torbert, R. B.; Ergun, R. E.; Khotyaintsev, Yu. V.; Lindqvist, P.-A.; Argall, M. R.; Farrugia, C. J.; Paulson, K. W.; Strangeway, R. J.; Magnes, W.

    2016-07-01

    We present detailed observations of dynamic, fine-scale inner magnetosphere-ionosphere coupling at ˜3.9 RE in the Region 2 Birkeland field-aligned current (FAC). We find that observed electrodynamic spatial/temporal scales are primarily characteristic of magnetically mapped ionospheric structure. On 15 September 2015, conjugate Magnetospheric Multiscale (MMS) spacecraft and Millstone Hill radar observations show plasmasphere boundary region subauroral polarization stream (SAPS) electric fields at L = 4.0-4.2 near 21 MLT. MMS observations reveal high-altitude ˜1 mV/m fine-scale radial and azimuthal electric field perturbations over ≤0.15 L with high spatial coherence over ≥2-3 min and show outward motion within a broader FAC of ˜0.12 μA/m2. Our analysis shows that MMS electric field fluctuations are most likely reflective of SAPS ionospheric structure at scales of ˜22 km and with ionospheric closure of small-scale filamentary FAC perturbations. The results highlight the ionosphere's importance in regulating fine-scale magnetosphere-ionosphere structure.

  17. Bloch oscillations of ultracold atoms and measurement of the fine structure constant; Oscillations de Bloch d'atomes ultrafroids et mesure de la constante de structure fine

    Energy Technology Data Exchange (ETDEWEB)

    Clade, P

    2005-10-15

    From a measurement of the recoil velocity of an atom absorbing a photon, it is possible to deduce a determination of the ratio h/m between the Planck constant and the mass of the atoms and then to deduce a value of the fine structure constant alpha. To do this measurement, we use the technique of Bloch oscillations, which allows us to transfer a large number of recoils to atoms. A velocity sensor, based on velocity selective Raman transition, enables us to measure the momentum transferred to the atoms. A measurement with a statistical uncertainty of 4.4 10{sup -9}, in conjunction with a careful study of systematic effects (5 10{sup -9}), has led us to a determination of alpha with an uncertainty of 6.7 10{sup -9}: {alpha}{sup -1}(Rb) = 137.03599878 (91). This uncertainty is similar to the uncertainty of the best determinations of alpha based on atom interferometry. (author)

  18. X-ray Absorption Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

    This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

  19. Fine-scale spatial genetic structure of eight tropical tree species as analysed by RAPDs.

    Science.gov (United States)

    Degen, B; Caron, H; Bandou, E; Maggia, L; Chevallier, M H; Leveau, A; Kremer, A

    2001-10-01

    The fine-scale spatial genetic structure of eight tropical tree species (Chrysophyllum sanguinolentum, Carapa procera, Dicorynia guianensis, Eperua grandiflora, Moronobea coccinea, Symphonia globulifera, Virola michelii, Vouacapoua americana) was studied in populations that were part of a silvicultural trial in French Guiana. The species analysed have different spatial distribution, sexual system, pollen and seed dispersal agents, flowering phenology and environmental demands. The spatial position of trees and a RAPD data set for each species were combined using a multivariate genetic distance method to estimate spatial genetic structure. A significant spatial genetic structure was found for four of the eight species. In contrast to most observations in temperate forests, where spatial structure is not usually detected at distances greater than 50 m, significant genetic structure was found at distances up to 300 m. The relationships between spatial genetic structure and life history characteristics are discussed. PMID:11737299

  20. Quad-plane stereoscopic PIV for fine-scale structure measurements in turbulence

    Science.gov (United States)

    Naka, Y.; Tomita, K.; Shimura, M.; Fukushima, N.; Tanahashi, M.; Miyauchi, T.

    2016-05-01

    The fine-scale structure in turbulence is investigated by quad-plane stereoscopic particle image velocimetry (QPSPIV). The quad-plane consists of two each of different polarizations and wavelengths, and it provides three velocity components at four independent parallel planes. Measurements have been undertaken in the developed region of a turbulent round jet with a spatial resolution sufficient to capture the small-scale structures. The advantage of the QPSPIV is presented in terms of the spectral response in the evaluation of the out-of-plane velocity gradient. The full velocity gradient tensor is computed with a fourth-order finite difference scheme in the out-of-plane direction as well as the in-plane directions. The turbulence quantities, such as the vorticity components, the energy dissipation rate and the second and third invariants of the velocity gradient tensor, are computed according to their faithful definitions. The coherent fine-scale eddies are extracted from the present QPSPIV data. The probability density functions of the diameter and the maximum azimuthal velocity of the extracted eddies exhibit their peak at approximately 8η and 1.5u_k, respectively, where η and u_k are the Kolmogorov length and velocity. These values agree well with the data in the literature. The phase-averaged distributions of turbulence quantities around the coherent fine-scale eddy indicate an apparent elliptic feature around the axis. Furthermore, the state of the strain rate exerting the eddy is quantified from the phase-averaged distributions of eigenvalues of the strain rate tensor and the alignment of the corresponding eigenvectors against the axis. The present study gives a solid experimental support of the coherent fine-scale structures in turbulence, and the technique can be applied to various flow fields and to the higher Reynolds number condition.

  1. Fine structure of 25 extragalactic radio sources. [interferometric observations of quasars

    Science.gov (United States)

    Wittels, J. J.; Knight, C. A.; Shapiro, I. I.; Hinteregger, H. F.; Rogers, A. E. E.; Whitney, A. R.; Clark, T. A.; Hutton, L. K.; Marandino, G. E.; Niell, A. E.

    1975-01-01

    Interferometric observations taken at 7.8 GHz (gamma approximately = 3.8 cm) with five pairings of antennae of 25 extragalactic radio sources between April, 1972 and May, 1973 are reported. These sources exhibit a broad variety of fine structure from very simple to complex. The total flux and the correlated flux of some of the sources underwent large changes in a few weeks, while the structure and total power of others remained constant during the entire period of observation. Some aspects of the data processing and a discussion of errors are presented. Numerous figures are provided and explained. The individual radio sources are described in detail.

  2. Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

    NARCIS (Netherlands)

    De Hoop, A.T.; Jiang, L.

    2009-01-01

    The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwell's equations numerically to b

  3. Electronic structure and optical properties of CdS{sub x}Se{sub 1−x} solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, M. W. [DESY (Deutsches Elektronen-Synchrotron), FS-PEX, Notkestrasse 85, 22607 Hamburg (Germany); Yiu, Y. M., E-mail: yyiu@uwo.ca; Sham, T. K. [Department of Chemistry, University of Western Ontario, London, ON N6A5B7 (Canada); Ward, M. J. [Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, NY 14853 (United States); Liu, L. [Institute of Functional Nano and Soft Materials (FUNSOM) and Soochow University-Western University Center for Synchrotron Radiation Research, Soochow University, Suzhou, Jiangsu, 215123 (China); Hu, Y. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK S7N2V3 (Canada); Zapien, J. A. [Center Of Super-Diamond and Advanced Films (COSDAF) and Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China); Liu, Yingkai [Institute of Physics and Electronic Information, Yunnan Normal University, Kunming, Yunnan, 650500 (China)

    2014-11-21

    The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS{sub x}Se{sub 1−x} solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed.

  4. Chemical speciation of Fe and Ni in residual oil fly ash fine particulate matter using X-ray absorption spectroscopy.

    Science.gov (United States)

    Pattanaik, Sidhartha; Huggins, Frank E; Huffman, Gerald P

    2012-12-01

    Epidemiological studies have linked residual oil fly ash fine particulate matter with aerodynamic diameter tube boiler (FTB) and a refractory line combustor (RLC). The study reveals that only Fe(2)(SO(4))(3)·nH(2)O is present in RLC PM(2.5) while Fe(2)(SO(4))(3)·nH(2)O predominates in FTB PM(2.5) with inclusion of varying amounts of nickel ferrite. The finding that RLC PM(2.5) is more bioavailable and hence more toxic than FTB PM(2.5) is significant. The reduction of toxicity of FTB PM(2.5) is due to the immobilization of a portion of Fe and Ni in the formation of an insoluble NiFe(2)O(4). This may explain the variation of toxicity from exposure to different ROFA PM(2.5). Additionally, the speciation data are sought for developing emission inventories for source apportionment study and understanding the mechanism of PM formation.

  5. Search for cosmological variation of the fine-structure constant using relativistic energy shifts in Ge II, Sn II, and Pb II

    International Nuclear Information System (INIS)

    The sensitivity of atomic transition frequencies to variation of the fine structure constant α=e2/(ℎ/2π)c increases proportional to Z2 where Z is the nuclear charge. Recently several lines of heavy ions Ge II, Sn II, and Pb II have been detected in quasar absorption spectra. We have performed accurate many-body calculations of the α2 dependence of transition frequencies (q coefficients) for these atoms and found an order-of-magnitude increase in sensitivity in comparison with atomic transitions which were previously used to search for temporal and spatial variation of α in quasar absorption systems. An interesting feature in Pb II is a highly nonlinear dependence on α2 due to the level pseudocrossings

  6. Accurate Electron Affinity of Iron and Fine Structures of Negative Iron ions

    Science.gov (United States)

    Chen, Xiaolin; Luo, Zhihong; Li, Jiaming; Ning, Chuangang

    2016-05-01

    Ionization potential (IP) is defined as the amount of energy required to remove the most loosely bound electron of an atom, while electron affinity (EA) is defined as the amount of energy released when an electron is attached to a neutral atom. Both IP and EA are critical for understanding chemical properties of an element. In contrast to accurate IPs and structures of neutral atoms, EAs and structures of negative ions are relatively unexplored, especially for the transition metal anions. Here, we report the accurate EA value of Fe and fine structures of Fe‑ using the slow electron velocity imaging method. These measurements yield a very accurate EA value of Fe, 1235.93(28) cm‑1 or 153.236(34) meV. The fine structures of Fe‑ were also successfully resolved. The present work provides a reliable benchmark for theoretical calculations, and also paves the way for improving the EA measurements of other transition metal atoms to the sub cm‑1 accuracy.

  7. Structural changes in fine-grained high-temperature steels under the influence of temperature stress

    International Nuclear Information System (INIS)

    Fine-grained high-temperature steels have gained great importance as materials for reactor pressure vessels. Alloying with small additions of carbide-forming elements does not only preserve the fine grain but also helps to achieve a certain retention of hardness which improves the high-temperature strength of these steels. During welding, a narrow zone of the basic material is heated over the transition temperature. The result is a coarse-grained, austenitic structure. In order to find out whether such structural changes caused by welding may damage the material during heat treatment or operation, the mechanical properties of some types of structures were tested with regard to their strength, their notched bar impact strength, and their creep rupture strength, and the findings were interpreted with the aid of scans of the surfaces of fracture and electron microscope pictures of the microstructure. The results show that the toughness of the structure of a heat influence region of the steels investigated would decrease further at operating temperatures above 2000C and below the appropriate tempering temperature if the additional heat treatment in the tempering temperature region after welding were omitted. The toughness of the heat influence region is increased by annealing to such a degree that it almost reaches that of the basic material. (GSCH)

  8. Indirect estimation of absorption properties for fine aerosol particles using AATSR observations: a case study of wildfires in Russia in 2010

    Science.gov (United States)

    Rodriguez, E.; Kolmonen, P.; Virtanen, T. H.; Sogacheva, L.; Sundstrom, A.-M.; de Leeuw, G.

    2015-08-01

    The Advanced Along-Track Scanning Radiometer (AATSR) on board the ENVISAT satellite is used to study aerosol properties. The retrieval of aerosol properties from satellite data is based on the optimized fit of simulated and measured reflectances at the top of the atmosphere (TOA). The simulations are made using a radiative transfer model with a variety of representative aerosol properties. The retrieval process utilizes a combination of four aerosol components, each of which is defined by their (lognormal) size distribution and a complex refractive index: a weakly and a strongly absorbing fine-mode component, coarse mode sea salt aerosol and coarse mode desert dust aerosol). These components are externally mixed to provide the aerosol model which in turn is used to calculate the aerosol optical depth (AOD). In the AATSR aerosol retrieval algorithm, the mixing of these components is decided by minimizing the error function given by the sum of the differences between measured and calculated path radiances at 3-4 wavelengths, where the path radiances are varied by varying the aerosol component mixing ratios. The continuous variation of the fine-mode components allows for the continuous variation of the fine-mode aerosol absorption. Assuming that the correct aerosol model (i.e. the correct mixing fractions of the four components) is selected during the retrieval process, also other aerosol properties could be computed such as the single scattering albedo (SSA). Implications of this assumption regarding the ratio of the weakly/strongly absorbing fine-mode fraction are investigated in this paper by evaluating the validity of the SSA thus obtained. The SSA is indirectly estimated for aerosol plumes with moderate-to-high AOD resulting from wildfires in Russia in the summer of 2010. Together with the AOD, the SSA provides the aerosol absorbing optical depth (AAOD). The results are compared with AERONET data, i.e. AOD level 2.0 and SSA and AAOD inversion products. The RMSE

  9. Lack of sex-biased dispersal promotes fine-scale genetic structure in alpine ungulates

    Science.gov (United States)

    Roffler, Gretchen H.; Talbot, Sandra L.; Luikart, Gordon; Sage, George K.; Pilgrim, Kristy L.; Adams, Layne G.; Schwartz, Michael K.

    2014-01-01

    Identifying patterns of fine-scale genetic structure in natural populations can advance understanding of critical ecological processes such as dispersal and gene flow across heterogeneous landscapes. Alpine ungulates generally exhibit high levels of genetic structure due to female philopatry and patchy configuration of mountain habitats. We assessed the spatial scale of genetic structure and the amount of gene flow in 301 Dall’s sheep (Ovis dalli dalli) at the landscape level using 15 nuclear microsatellites and 473 base pairs of the mitochondrial (mtDNA) control region. Dall’s sheep exhibited significant genetic structure within contiguous mountain ranges, but mtDNA structure occurred at a broader geographic scale than nuclear DNA within the study area, and mtDNA structure for other North American mountain sheep populations. No evidence of male-mediated gene flow or greater philopatry of females was observed; there was little difference between markers with different modes of inheritance (pairwise nuclear DNA F ST = 0.004–0.325; mtDNA F ST = 0.009–0.544), and males were no more likely than females to be recent immigrants. Historical patterns based on mtDNA indicate separate northern and southern lineages and a pattern of expansion following regional glacial retreat. Boundaries of genetic clusters aligned geographically with prominent mountain ranges, icefields, and major river valleys based on Bayesian and hierarchical modeling of microsatellite and mtDNA data. Our results suggest that fine-scale genetic structure in Dall’s sheep is influenced by limited dispersal, and structure may be weaker in populations occurring near ancestral levels of density and distribution in continuous habitats compared to other alpine ungulates that have experienced declines and marked habitat fragmentation.

  10. Boron carbide: Consistency of components, lattice parameters, fine structure and chemical composition makes the complex structure reasonable

    Science.gov (United States)

    Werheit, Helmut

    2016-10-01

    The complex, highly distorted structure of boron carbide is composed of B12 and B11C icosahedra and CBC, CBB and B□B linear elements, whose concentration depends on the chemical composition each. These concentrations are shown to be consistent with lattice parameters, fine structure data and chemical composition. The respective impacts on lattice parameters are estimated and discussed. Considering the contributions of the different structural components to the energy of the overall structure makes the structure and its variation within the homogeneity range reasonable; in particular that of B4.3C representing the carbon-rich limit of the homogeneity range. Replacing in B4.3C virtually the B□B components by CBC yields the hypothetical moderately distorted B4.0C (structure formula (B11C)CBC). The reduction of lattice parameters related is compatible with recently reported uncommonly prepared single crystals, whose compositions deviate from B4.3C.

  11. INFLUENCE OF FINE-DISPERSED BORON CARBIDE ON THE STRUCTURE AND CHARACTERISTICS OF IRON-BORON ALLOY

    Directory of Open Access Journals (Sweden)

    N. F. Nevar

    2010-01-01

    Full Text Available The influence of boron carbide as fine-dispersed material input into the melt on structure morphology, founding, technological and exploitation characterisstics of cast iron-boron material is shown.

  12. A Note on Transfinite M Theory and the Fine Structure Constant

    CERN Document Server

    Castro, C

    2001-01-01

    In this short note, using notions from $p$-Adic QFT and $p$-branes, we derive the transfinite M $theoretical$ corrections $(\\alpha_M)^{-1} = 100 + 61 \\phi$ to El Naschie's inverse fine structure constant value $(\\alpha_{HS})^{-1}= 100 + 60\\phi$ which was based on a transfinite Heterotic string theory ormalism . $\\phi$ is the Golden Mean $0.6180339...$. Our results are consistent with recent Astrophysical observations of he Boomerang and Maxima experiments, with previous results based on the four dimensional gravitational conformal anomaly calculations and with an enhanced hierarchy of the number of lines on Del Pezzo surfaces.

  13. Tuning Photoluminescence Energy and Fine Structure Splitting in Single Quantum Dots by Uniaxial Stress

    Institute of Scientific and Technical Information of China (English)

    DOU Xiu-Ming; SUN Bao-Quan; WANG Bao-Rui; MA Shan-Shan; ZHOU Rong; HUANG She-Song; NI Hai-Qiao; NIU Zhi-Chuan

    2008-01-01

    @@ We report a photoluminescence (PL) energy red-shift of single quantum dots(QDs)by applying an in-plane compressive uniaxial stress along the[110]direction at a liquid nitrogen temperature.Uniaxial stress has an effect not only on the confinement potential in the growth direction which results in the PL shift,but also on the cylindrical symmetry of QDs which can be reflected by the change of the full width at half maximum of PL peak.This implies that uniaxial stress has an important role in tuning PL energy and fine structure splitting of QDs.

  14. Anisotropic Beam Model for the Spectral Observations of Radio Burst Fine Structures on 1998 April 15

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A fine structure consisting of three almost equidistant frequency bands was observed in the high frequency part of a solar burst on 1998 April 15 by the spectrometer of Beijing Astronomical Observatory in the range 2.6-3.8 GHz. A model for this event based on beam-anisotropic instability in the solar corona is presented. Longitudinal plasma waves are excited at cyclotron resonance and then transformed into radio emission at their second harmonic. The model is in accordance with the observations if we suppose a magnetic field strength in the region of emission generation of about 200 G.

  15. Time Variation of the Fine Structure Constant in the Spacetime of a Cosmic Domain Wall

    Science.gov (United States)

    Campanelli, L.; Cea, P.; Tedesco, L.

    The gravitational field produced by a domain wall acts as a medium with spacetime-dependent permittivity ɛ. Therefore, the fine structure constant α=e2/4πɛ will be a time-dependent function at fixed position. The most stringent constraint on the time-variation of α comes from the natural reactor Oklo and gives |˙ α /α | < few × 10-17 yr-1. This limit constrains the tension of a cosmic domain wall to be less than σ ≲ 10-2 MeV3, and then represents the most severe limit on the energy density of a cosmic wall stretching our Universe.

  16. Time Variation of the Fine Structure Constant in the Spacetime of a Domain Wall

    CERN Document Server

    Campanelli, L; Tedesco, L

    2005-01-01

    The gravitational field produced by a domain wall acts as a medium with spacetime-dependent permittivity \\epsilon. Therefore, the fine structure constant \\alpha = e^2/4 \\pi \\epsilon will be a time-dependent function at fixed position. The most stringent constraint on the time-variation of \\alpha comes from the natural reactor Oklo and gives |\\dot{\\alpha}/\\alpha| < few 10^{-17} yr^{-1}. This limit constrains the tension of a cosmic domain wall to be less than \\sigma \\lesssim 10^{-2} MeV^3, and then represents the most severe limit on the energy density of a cosmic wall stretching our Universe.

  17. Fusion reaction yield in focused discharges with variable energy and plasma fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Bortolotti, A.; Brzosko, J.S.; Chiara, P. De; Kilic, H.; Mezzetti, F.; Nardi, V.; Powell, C.; Wang, J. [Stevens Inst. of Tech., Hoboken, NJ (United States)]|[Ferrara Univ. (Italy)

    1992-12-31

    The same linear correlation between the distribution parameters ({Delta}T and Max {Delta}V) of the radial current density J between electrodes and the fusion reaction yield per pulse, Y, in the plasma focus (PF) pinch was quantitatively determined from different PF machines. Contact prints of current-sheath fragments (CSF) ejected from the pinch are obtained from 2.5-MeV-D{sup +} ions. CSF`s show the same submillimetric fine structure of the pinch. (author) 3 refs., 2 tabs.

  18. On the relationship between multi-channel envelope and temporal fine structure

    DEFF Research Database (Denmark)

    Søndergaard, Peter Lempel; Decorsiere, Remi Julien Blaise; Dau, Torsten

    2011-01-01

    The envelope of a signal is broadly defined as the slow changes in time of the signal, where as the temporal fine structure (TFS) are the fast changes in time, i.e. the carrier wave(s) of the signal. The focus of this paper is on envelope and TFS in multi-channel systems. We discuss the difference...... providing an increasingly better approximation to the auditory system. A corollary from these results is that it is not possible to generate a test signal containing contradictory information in its multi-channel envelope and TFS....

  19. Evolution of the fine-structure constant in runaway dilaton models

    CERN Document Server

    Martins, C J A P; Martinelli, M; Calabrese, E; Pandolfi, S

    2015-01-01

    We study the detailed evolution of the fine-structure constant $\\alpha$ in the string-inspired runaway dilaton class of models of Damour, Piazza and Veneziano. We provide constraints on this scenario using the most recent $\\alpha$ measurements and discuss ways to distinguish it from alternative models for varying $\\alpha$. For model parameters which saturate bounds from current observations, the redshift drift signal can differ considerably from that of the canonical $\\Lambda$CDM paradigm at high redshifts. Measurements of this signal by the forthcoming European Extremely Large Telescope (E-ELT), together with more sensitive $\\alpha$ measurements, will thus dramatically constrain these scenarios.

  20. Calculation of the fine structure of the level in Rydberg state of lithium

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The level shift and level formula of lithium atom in Rydberg states are achieved by means of the calculation of polarization of the atomic core (including the contribution of dipole moment, quadrupole moment and octupole moment);meanwhile, the effect of relativity theory, the orbital angular momentum L and the spin angular momentum S coupling (LS coupling), and high order correction of the effective potential are considered. The some fine structures (N=5~12,L=4~9,J=L±1/2) and the corresponding level intervals in Rydberg states can be calculated by the above-mentioned level formula and compared with correlated experimental data.

  1. Prospect of China's Auroral Fine-structure Imaging System (CAFIS) at Zhongshan station in Antarctica

    Institute of Scientific and Technical Information of China (English)

    LIU Shun-lin; HAN De-sheng; HU Hong-qiao; HUANG De-hong; ZHANG Bei-chen; YANG Hui-gen

    2008-01-01

    A new auroral imaging system is reported which is planned to be deployed at Zhongshan Station in Antarctica in the end of 2009. The system will focus on study of optical auroras in small scales and be called China' s Auroral Fine-structure Imaging System (CAFIS). The project of CAFIS is carried out by support of 'the tenth five-year plan for capacity building' of China. CAFIS will be a powerful groundbased platform for aurora observational experiments. Composing and advantages of CAFIS are introduced in this brief report. Some potential study topics involved CAFIS are also considered.

  2. Electron-impact fine-structure transitions in Cu XX from its ground state

    International Nuclear Information System (INIS)

    The R-matrix method is used to calculate collision strengths for electron-impact excitation of Cu XX from its ground state. Configuration interaction wavefunctions are used to represent the lowest 15 LS coupled states which are retained in the R-matrix expansion. Effective collisions strengths are calculated for transitions from the ground state to fine-structure levels of the excited states by employing a transformation of the LS coupled reactance matrices, and by assuming a Maxwellian distribution for the incident electron. This is the first detailed calculation on this ion in which the effects of exchange, channel couplings and short-range correlation effects are taken into account. (author)

  3. Fine-scale spatial genetic structure in a multi-oak-species (Quercus spp.) forest

    OpenAIRE

    Curtu AL; Craciunesc I; Enescu CM; Vidalis A; Sofletea N

    2015-01-01

    Patterns of fine-scale spatial distribution of multilocus genotypes can provide valuable insights into the biology of forest tree species. Here we tested for the existence of spatial genetic structure (SGS) in a four-oak-species forest with contrasting species abundances and hybridization rates. A total of 483 adult trees were mapped over 8.6 ha and genotyped using 10 highly polymorphic genomic regions. A weak but significant SGS was observed in each of the four oak species, with Quercus frai...

  4. Oklo Constraint on the Time-Variability of the Fine-Structure Constant

    CERN Document Server

    Fujii, Y

    2003-01-01

    The Oklo phenomenon, natural fission reactors which had taken place in Gabon about 2 billion years ago, porvides one of the most stringent constraints on the possible time-variability of the fine-structure constant $\\alpha$. We first review briefly what it is and how reliable it is in constraining $\\alpha$. We then compare the result with a more recent result on the nonzero change of $\\alpha$ obtained from the observation of the QSO absoorption lines. We suggest a possible way to make these results consistent with each other in terms of the behavior of a scalar field which is expected to be responsible for the accelaration of the universe.

  5. Variation of the fine-structure constant from the de Sitter invariant special relativity

    Institute of Scientific and Technical Information of China (English)

    CHEN Shao-Xia; XIAO Neng-Chao; YAN Mu-Lin

    2008-01-01

    We discuss the variation of the fine-structure constant,α.There are obvious discrepancies among the results of α-variation from recent Quasi-stellar observation experiments and from the Oklo uranium mine analysis.We use dS Sitter invariant Special Relativity (SRc,R) and Dirac large number hypothesis to discuss this puzzle,and present a possible solution to the disagreement.By means of the observational data and the discussions presented in this paper,we estimate the radius of the Universe in SRc,R which is about ~2(√5)×1011l.y.

  6. Time Evolution of the Fine Structure Constant in a Two-Field Quintessence Model

    CERN Document Server

    Bento, M C; Santos, N M C

    2004-01-01

    We examine the variation of the fine structure constant in the context of a two-field quintessence model. We find that, for solutions that lead to a transient late period of accelerated expansion, it is possible to fit the data arising from quasar spectra and comply with the bounds on the variation of $\\alpha$ from the Oklo reactor, meteorite analysis, atomic clock measurements, Cosmic Microwave Background Radiation and Big Bang Nucleosynthesis. That is more difficult if we consider solutions corresponding to a late period of permanent accelerated expansion.

  7. Time evolution of the fine structure constant in a two-field quintessence model

    Science.gov (United States)

    Bento, M. C.; Bertolami, O.; Santos, N. M.

    2004-11-01

    We examine the variation of the fine structure constant in the context of a two-field quintessence model. We find that, for solutions that lead to a transient late period of accelerated expansion, it is possible to fit the data arising from quasar spectra and comply with the bounds on the variation of α from the Oklo reactor, meteorite analysis, atomic clock measurements, cosmic microwave background radiation, and big bang nucleosynthesis. That is more difficult if we consider solutions corresponding to a late period of permanent accelerated expansion.

  8. Evolution of the fine-structure constant in runaway dilaton models

    Directory of Open Access Journals (Sweden)

    C.J.A.P. Martins

    2015-04-01

    Full Text Available We study the detailed evolution of the fine-structure constant α in the string-inspired runaway dilaton class of models of Damour, Piazza and Veneziano. We provide constraints on this scenario using the most recent α measurements and discuss ways to distinguish it from alternative models for varying α. For model parameters which saturate bounds from current observations, the redshift drift signal can differ considerably from that of the canonical ΛCDM paradigm at high redshifts. Measurements of this signal by the forthcoming European Extremely Large Telescope (E-ELT, together with more sensitive α measurements, will thus dramatically constrain these scenarios.

  9. Fine structure in 14C emission from 223Ra and 224Ra

    International Nuclear Information System (INIS)

    The measurement of the energy spectrum of 14C nuclei emitted in the spontaneous radioactivity of 223Ra and 224Ra has been carried out, using thin and intense sources (480 MBq for 223Ra and 3550 MBq for 224Ra). The sources were obtained by implanting mass-separated beams into Al and vitreous C catchers. The measurement was performed with a superconducting solenoidal spectrometer. Our discovery, previously reported, of fine structure in the energy spectrum of 14C emission from 223Ra, which is analogous to the one known for α emission, is confirmed. Only 13% of the branching ratio in 14C decay leads to the ground state of the residual nucleus, while 81% to the first excited state. For 14C emission from 224Ra, a lower limit of 2 for the hindrance factor has been measured for the transition to the first excited state in the residual nucleus. Also, a precise identification in Z with an ExΔE telescope has been performed for the radiation from the 223Ra source. Our measurements of fine structure in 14C emissions open this field to nuclear structure studies

  10. Position-sensitive change in the transition metal L-edge fine structures

    Energy Technology Data Exchange (ETDEWEB)

    Gulec, Ahmet; Phillips, Patrick J.; Klie, Robert F. [Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607 (United States)

    2015-10-05

    Studying the structure and composition of solid-state materials on the atomic scale has become nearly routine in transmission electron microscopy with the development of novel electron optics and electron sources. In particular, with spatial resolutions better than 0.1 nm and energy resolution smaller than 100 meV, the stoichiometry, bonding, and coordination can now be examined on similar scales. Aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy (EELS) have played a crucial role in identifying charge ordering, valence, and as spin state transitions in transition metal perovskite oxides. In this letter, we investigate the effects of ever-decreasing electron-probe sizes on the measured near-edge fine-structure of the transition metal core-loss edge using EELS. We find that for certain transition metal perovskites, the position of the electron probe with respect to the atomic column is crucial in determining the correct valence state. Several reasons for the observed position-sensitive EELS fine-structure are discussed.

  11. Microwave burst with fine spectral structures in a solar flare on 2011 August 9

    CERN Document Server

    Tan, Baolin; Liu, Yuying; 10.1051/eas/1255035

    2012-01-01

    On August 9, 2011, there was an X6.9 flare event occurred near the west limb of solar disk. From the observation obtained by the spectrometer of the Chinese Solar Broadband Radio Spectrometer in Huairou (SBRS/Huairou) around the flare, we find that this powerful flare has only a short-duration microwave burst of about only 5 minutes, and during the short-duration microwave burst, there are several kinds of fine structures on the spectrogram. These fine structures include very short-period pulsations, millisecond spike bursts, and type III bursts. The most interesting is that almost all of the pulses of very short-period pulsation (VSP) are structured by clusters of millisecond timescales of spike bursts or type III bursts. And there exists three different kinds of frequency drift rates in the VSP: the frequency drift rates with absolute value of about 55 - 130 MHz s^{-1} in the pulse groups, the frequency drift rates with absolute value of about 2.91 - 16.9 GHz s^{-1} on each individual pulse, and the frequen...

  12. Fine and superfine structure of Decameter-Hectometer type II burst on 2011 June 7

    CERN Document Server

    Dorovskyy, V V; Konovalenko, A A; Brazhenko, A I; Panchenko, M; Poedts, S; Mykhaylov, V A

    2015-01-01

    The characteristics of the type II bursts with herringbone structure observed both by ground based radio telescopes (UTR-2, URAN-2) and spaceborn spectrometers (STEREO A-B) are discussed. The burst was recorded on 7 June, 2011 in the frequency band 3--33~MHz. It was characterized by extremely rich fine structure. The statistical analysis of more than 300 herringbone sub-bursts constituting the burst was performed separately for the positively (reverse) and negatively (forward) drifting sub-bursts. The sense and the degree of circular polarization of the herringbone sub-bursts were measured in the respectively wide frequency band (16--32~MHz). A second order fine frequency structure of the herringbone sub-bursts was firstly observed and processed. Using STEREO COR1 (A,B) and SOHO LASCO C2 images the direction and radial speed of the CME responsible for the studied type II burst were determined. The possible location of the type II burst source on the flank of the shock was found.

  13. On the Evidence for Cosmic Variation of the Fine Structure Constant: A Bayesian Reanalysis of the Quasar Dataset

    CERN Document Server

    Cameron, Ewan

    2012-01-01

    We review the evidence behind recent claims of spatial variation in the fine structure constant deriving from observations on ground-based telescopes of ionic absorption lines in the light from distant quasars. To this end we expand upon previous non-Bayesian analyses limited by the assumptions of a strictly Normal and unbiased form for the "unexplained errors" of the benchmark quasar dataset. Through nested importance sampling and the method of power posteriors we evaluate and compare marginal likelihoods (or Bayes factors) for three competing hypotheses-(i) the strict null (no cosmic variation), (ii) the monopole null (a constant Earth-to-quasar offset only), and (iii) the monopole+dipole hypothesis (featuring a cosmic variation manifest to the Earth-bound observer as a North-South divergence)-under various alternative error terms. Our analysis reveals significant support for a skeptical interpretation in which the apparent dipole effect is driven solely by systematic errors of opposing sign inherent in mea...

  14. Cosmological Variation of the Fine Structure Constant from an Ultra-Light Scalar Field: The Effects of Mass

    CERN Document Server

    Gardner, C L

    2003-01-01

    Cosmological variation of the fine structure constant $\\alpha$ due to the evolution of a spatially homogeneous ultra-light scalar field ($m \\sim H_0$) during the matter and $\\Lambda$ dominated eras is analyzed. Agreement of $\\Delta \\alpha/\\alpha$ with the value suggested by recent observations of quasar absorption lines is obtained by adjusting a single parameter, the coupling of the scalar field to matter. Asymptotically $\\alpha(t)$ in this model goes to a constant value $\\bar{\\alpha} \\approx \\alpha_0$ in the early radiation and the late $\\Lambda$ dominated eras. The coupling of the scalar field to (nonrelativistic) matter drives $\\alpha$ slightly away from $\\bar{\\alpha}$ in the epochs when the density of matter is important. Simultaneous agreement with the more restrictive bounds on the variation $|\\Delta \\alpha/\\alpha|$ from the Oklo natural fission reactor and from meteorite samples can be achieved if the mass of the scalar field is on the order of 0.5--0.6 $\\bar{H}$, where $\\bar{H} = \\Omega_\\Lambda^{1/2}...

  15. The up-scattering treatment in the fine-structure self-shielding method in APOLLO3®

    International Nuclear Information System (INIS)

    The use of the exact elastic scattering in resonance domain introduces the neutron up-scattering which must be taken into account in the deterministic transport code. We present the newly implemented up-scattering treatment in the fine-structure self-shielding method of APOLLO3®. Two pin cell calculations have been carried out in order to evaluate the impact of the up-scattering treatment. The results are compared to those obtained by the Monte Carlo code TRIPOLI-4® with its newly implemented DBRC model. The comparison of k-eff values on the examples of single cell calculations shows a very good agreement between the APOLLO3® up-scattering treatment and the TRIPOLI-4® DBRC model, which is less than 30 pcm for UOX fuel and less than 110 pcm for MOX. Also, the differential effects of asymptotic versus exact kernel produced by APOLLO3® compared to TRIPOLI-4®, do not exceed 20 pcm for the UOX cell and 40 pcm for the MOX cell. A detailed comparison of the U238 absorption rates shows clearly the influences of the first four big resonances of U238 to the calculation results. (author)

  16. Magnetic properties and fine structure of Fe-Co alloys with vanadium and chromium additions

    Energy Technology Data Exchange (ETDEWEB)

    Dzhavadov, D.M.; Tyapkin, Yu.D. (Tsentral' nyj Nauchno-Issledovatel' skij Inst. Chernoj Metallurgii, Moscow (USSR))

    1982-11-01

    Magnetic properties of alloys iron-cobalt, iron-cobalt-vanadium, iron-cobalt-chromium have been investigated. Measurements of permeability, coercive force Hsub(c), B/sub 25/ and B/sub 100/ magnetic saturation on alloy samples on which electrical resistance previously is measured and fine crystalline structure is studied by the methods of transmission electron microscopy, diffusion scattering of X rays and electrons and NGR. Comparison of properties and structure makes possible to bind Hsub(c), B permeability values with such structure features as a long-range order of B2 type, short-range decomposition order and Cottrell clouds formation in vanadium containing alloys and a complex short-range order in chromium-containing alloys.

  17. Gaussian Beam Tunneling through a Gyrotropic-Nihility Finely-Stratified Structure

    CERN Document Server

    Tuz, Vladimir R

    2014-01-01

    The three-dimensional Gaussian beam transmission through a ferrite-semiconductor finely-stratified structure being under an action of an external static magnetic field in the Faraday geometry is considered. The beam field is represented by an angular continuous spectrum of plane waves. In the long-wavelength limit, the studied structure is described as a gyroelectromagnetic medium defined by the effective permittivity and effective permeability tensors. The investigations are carried out in the frequency band where the real parts of the on-diagonal elements of both effective permittivity and effective permeability tensors are close to zero while the off-diagonal ones are non-zero. In this frequency band the studied structure is referred to a gyrotropic-nihility medium. It is found out that a Gaussian beam keeps its parameters unchanged (beam width and shape) when passing through the layer of such a medium except of a portion of the absorbed energy.

  18. He I vector magnetic field maps of a sunspot and its superpenumbral fine-structure

    CERN Document Server

    Schad, T A; Lin, H; Tritschler, A

    2015-01-01

    Advanced inversions of high-resolution spectropolarimetric observations of the He I triplet at 1083 nm are used to generate unique maps of the chromospheric magnetic field vector across a sunspot and its superpenumbral canopy. The observations were acquired by the Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar Telescope (DST) on 29 January 2012. Multiple atmospheric models are employed in the inversions, as superpenumbral Stokes profiles are dominated by atomic-level polarization while sunspot profiles are Zeeman-dominated but also exhibit signatures perhaps induced by symmetry breaking effects of the radiation field incident on the chromospheric material. We derive the equilibrium magnetic structure of a sunspot in the chromosphere, and further show that the superpenumbral magnetic field does not appear finely structured, unlike the observed intensity structure. This suggests fibrils are not concentrations of magnetic flux but rather distinguished by individualized thermalization. We also dire...

  19. Structure and Mass Absorption of Hypothetical Terrestrial Black Holes

    OpenAIRE

    VanDevender, A. P.; VanDevender, J. Pace

    2011-01-01

    The prospect of mini black holes, either primordial or in planned experiments at the Large Hadron Collider, interacting with the earth motivate us to examine how they may be detected and the scope of their impact on the earth. We propose that the more massive of these objects may gravitationally bind matter without significant absorption. Since the wave functions of gravitationally bound atoms orbiting a black hole are analogous to those of electrons around a nucleus, we call such an object t...

  20. Linear optical absorption spectra of mesoscopic structures in intense THz fields: Free-particle properties

    DEFF Research Database (Denmark)

    Johnsen, Kristinn; Jauho, Antti-Pekka

    1998-01-01

    We theoretically study the effect of THz radiation on the linear optical absorption spectra of semiconductor structures. A general theoretical framework, based on nonequilibrium Green functions, is formulated and applied to the calculation of linear optical absorption spectrum for several nonequi...

  1. Fine structure of Tibetan kefir grains and their yeast distribution, diversity, and shift.

    Directory of Open Access Journals (Sweden)

    Man Lu

    Full Text Available Tibetan kefir grains (TKGs, a kind of natural starter for fermented milk in Tibet, China, host various microorganisms of lactic acid bacteria, yeasts, and occasionally acetic acid bacteria in a polysaccharide/protein matrix. In the present study, the fine structure of TKGs was studied to shed light on this unusual symbiosis with stereomicroscopy and thin sections. The results reveal that TKGs consist of numerous small grain units, which are characterized by a hollow globular structure with a diameter between 2.0 and 9.0 mm and a wall thickness of approximately 200 µm. A polyhedron-like net structure, formed mainly by the bacteria, was observed in the wall of the grain units, which has not been reported previously to our knowledge. Towards the inside of the grain unit, the polyhedron-like net structures became gradually larger in diameter and fewer in number. Such fine structures may play a crucial role in the stability of the grains. Subsequently, the distribution, diversity, and shift of yeasts in TKGs were investigated based on thin section, scanning electron microscopy, cloning and sequencing of D1/D2 of the 26S rRNA gene, real-time quantitative PCR, and in situ hybridization with specific fluorescence-labeled oligonucleotide probes. These show that (i yeasts appear to localize on the outer surface of the grains and grow normally together to form colonies embedded in the bacterial community; (ii the diversity of yeasts is relatively low on genus level with three dominant species--Saccharomyces cerevisiae, Kluyveromyces marxianus, and Yarrowia lipolytica; (iii S. cerevisiae is the stable predominant yeast species, while the composition of Kluyveromyces and Yarrowia are subject to change over time. Our results indicate that TKGs are relatively stable in structure, and culture conditions to some extent shape the microbial community and interaction in kefir grains. These findings pave the way for further study of the specific symbiotic

  2. Probing Warm Dense Matter electronic structure using X-ray absorption Near Edge Spectroscopy (XANES)

    Science.gov (United States)

    Benuzzi Mounaix, Alessandra

    2011-06-01

    The behavior and physical properties of warm dense matter, fundamental for various branches of physics including planetology and Inertial Confinement Fusion, are non trivial to simulate either theoretically, numerically or experimentally. Despite important progress obtained in the last decade on macroscopic characterization (e.g. equations of state), microscopic studies are today necessary to investigate finely the WDM structure changes, the phase transitions and to test physical hypothesis and approximations commonly used in calculations. In this work, highly compressed aluminum has been investigated with the aim of bringing information on the evolution of its electronic structure by using K-edge shift and XANES. The experiment was performed at LULI laboratory where we used one long pulse (500 ps, IL ~ 8 1013 W/cm2) to create a uniform shock and a second ps beam (IL ~ 1017 W/cm2) to generate an ultra-short broadband X-ray source near the Al K-edge. The spectra were registered by using two conical KAP Bragg crystals. The main target was designed to probe the Aluminum in reshocked conditions allowing us to probe and to test theories in an extreme regime up to now unexplored (ρ ~ 3 ρ0 and T ~ 8 eV). The hydrodynamical Al conditions were measured by using VISARs interferometers and self-emission diagnostics. By increasing the delay between the two beams, we have been able to observe the modification of absorption spectra for unloading Al conditions (ρ >= 0.5 g/cc), and to put in evidence the relocalization of the 3p valence electrons occurring in the metal-non metal transition. All data have been compared to ab initio and dense plasma calculations.

  3. Fine-scale genetic structure arises during range expansion of an invasive gecko.

    Directory of Open Access Journals (Sweden)

    Kristen Harfmann Short

    Full Text Available Processes of range expansion are increasingly important in light of current concerns about invasive species and range shifts due to climate change. Theoretical studies suggest that genetic structuring may occur during range expansion. Ephemeral genetic structure can have important evolutionary implications, such as propagating genetic changes along the wave front of expansion, yet few studies have shown evidence of such structure. We tested the hypothesis that genetic structure arises during range expansion in Hemidactylus mabouia, a nocturnal African gecko recently introduced to Florida, USA. Twelve highly variable microsatellite loci were used to screen 418 individuals collected from 43 locations from four sampling sites across Florida, representing a gradient from earlier (∼1990s to very recent colonization. We found earlier colonized locations had little detectable genetic structure and higher allelic richness than more recently colonized locations. Genetic structuring was pronounced among locations at spatial scales of tens to hundreds of meters near the leading edge of range expansion. Despite the rapid pace of range expansion in this introduced gecko, dispersal is limited among many suitable habitat patches. Fine-scale genetic structure is likely the result of founder effects during colonization of suitable habitat patches. It may be obscured over time and by scale-dependent modes of dispersal. Further studies are needed to determine if such genetic structure affects adaptation and trait evolution in range expansions and range shifts.

  4. Fine-scale population genetic structure in a fission-fusion society.

    Science.gov (United States)

    Archie, Elizabeth A; Maldonado, Jésus E; Hollister-Smith, Julie A; Poole, Joyce H; Moss, Cynthia J; Fleischer, Robert C; Alberts, Susan C

    2008-06-01

    Nonrandom patterns of mating and dispersal create fine-scale genetic structure in natural populations - especially of social mammals - with important evolutionary and conservation genetic consequences. Such structure is well-characterized for typical mammalian societies; that is, societies where social group composition is stable, dispersal is male-biased, and males form permanent breeding associations in just one or a few social groups over the course of their lives. However, genetic structure is not well understood for social mammals that differ from this pattern, including elephants. In elephant societies, social groups fission and fuse, and males never form permanent breeding associations with female groups. Here, we combine 33 years of behavioural observations with genetic information for 545 African elephants (Loxodonta africana), to investigate how mating and dispersal behaviours structure genetic variation between social groups and across age classes. We found that, like most social mammals, female matrilocality in elephants creates co-ancestry within core social groups and significant genetic differentiation between groups (Phi(ST) = 0.058). However, unlike typical social mammals, male elephants do not bias reproduction towards a limited subset of social groups, and instead breed randomly across the population. As a result, reproductively dominant males mediate gene flow between core groups, which creates cohorts of similar-aged paternal relatives across the population. Because poaching tends to eliminate the oldest elephants from populations, illegal hunting and poaching are likely to erode fine-scale genetic structure. We discuss our results and their evolutionary and conservation genetic implications in the context of other social mammals.

  5. Sensitivity to temporal fine structure and hearing-aid outcomes in older adults

    Directory of Open Access Journals (Sweden)

    Elvira ePerez Vallejos

    2014-02-01

    Full Text Available Objective: to investigate the effect of sensitivity to temporal fine structure on subjective measures of hearing aid outcome.Design: Prior to receiving hearing aids, participants completed a test to assess sensitivity to temporal fine structure (TFS, the Glasgow Hearing Aid Benefit Profile (GHABP, and the Speech, Spatial and Qualities of hearing (SSQ-A. Follow-up appointments, comprised the GHABP, the SSQ-B , and the International Outcome Inventory for Hearing Aid Outcomes (IOI-HA.Study sample: 75 adults were recruited from direct referral clinics. Results: Two thirds of participants were found to have good sensitivity to TFS; listeners with good sensitivity to TFS rated their hearing abilities higher at pre-fitting (SSQ-A than those with poor sensitivity to TFS. At follow-up, participants with good sensitivity to TFS showed a small improvement on SSQ-B over listeners with poor sensitivity to TFS. Conclusions: The clinical identification of a patient’s ability to process TFS information at an early stage in the treatment pathway could prove useful in managing expectations about hearing aid outcomes.

  6. Fine structure of uterus and non-functioning paruterine organ in Orthoskrjabinia junlanae (Cestoda, Cyclophyllidea).

    Science.gov (United States)

    Korneva, Janetta V; Kornienko, Svetlana A; Jones, Malcolm K

    2016-06-01

    Some cyclophyllidean cestodes provide protection for their eggs in the external environment by providing them with additional protective layers around the egg membranes. In attempting to examine such adaptations, the microanatomy and fine structure of the uterus of pregravid and gravid proglottids of the cyclophyllidean cestode Orthoskrjabinia junlanae, a parasite of mammals that inhabit a terrestrial but moist environment, were studied. In the initial stages of uterine development, developing embryos locate freely in the lumen of a saccate uterus that later partitions into chambers. Each chamber that forms encloses several embryos. The chambers are surrounded by muscle cells that synthesize extracellular matrix actively. The paruterine organs consist of stacks of flattened long outgrowths of muscular cells, interspersed with small lipid droplets. In the gravid proglottids, the size of paruterine organ increases and consists of flattened basal and small rounded apical parts separated by constrictions. The fine structure of the organ wall remains the same: sparse nuclei and stacks of flattened cytoplasmic outgrowths but internal invaginations or lumen in the paruterine organ are absent. Completely developed eggs remain localized in the uterus. Based on the comparative morpho-functional analysis of uterine and paruterine organs and uterine capsules in cestodes, we conclude that these non-functioning paruterine organ in O. junlanae is an example of an atavism. We postulate that the life cycle of the parasite, which infects mammals living in wet habitats, where threats of desiccation of parasite ova is reduced, has favoured a reversion to a more ancestral form of uterine development. PMID:26997340

  7. Oscillatory behavior of chromospheric fine structures in a network and a semi-active regions

    CERN Document Server

    Bostanci, Z F; Al, N

    2014-01-01

    In the present work, we study the periodicities of oscillations in dark fine structures using observations of a network and a semi-active region close to the solar disk center. We simultaneously obtained spatially high resolution time series of white light images and narrow band images in the H$\\alpha$ line using the 2D G\\"ottingen spectrometer, which were based on two Fabry-Perot interferometers and mounted in the VTT/Observatorio del Teide/Tenerife. During the observations, the H$\\alpha$ line was scanned at 18 wavelength positions with steps of 125 m\\AA. We computed series of Doppler and intensity images by subtraction and addition of the H$\\alpha$ $\\pm$ 0.3 \\AA\\ and $\\pm$ 0.7 \\AA\\ pairs, sampling the upper chromosphere and the upper photosphere, respectively. Then we obtained power, coherence and phase difference spectra by performing a wavelet analysis to the Doppler fluctuations. Here, we present comparative results of oscillatory properties of dark fine structures seen in a network and a semi-active reg...

  8. On the fine structure of the sunspot penumbrae. II. The nature of the Evershed flow

    CERN Document Server

    Borrero, J M; Solanki, S K; Collados, M

    2005-01-01

    We investigate the fine structure of the sunspot penumbra by means of a model that allows for a flux tube in horizontal pressure balance with the magnetic background atmosphere in which it is embedded. We apply this model to spectropolarimetric observations of two neutral iron lines at 1.56 $\\mu$m and invert several radial cuts in the penumbra of the same sunspot at two different heliocentric angles. In the inner part of the penumbra we find hot flux tubes that are somewhat inclined to the horizontal. They become gradually more horizontal and cooler with increasing radial distance. This is accompanied by an increase in the velocity of the plasma and a decrease of the gas pressure difference between flux tube and the background component. At large radial distances the flow speed exceeds the critical speed and evidence is found for the formation of a shock front. These results are in good agreement with simulations of the penumbral fine structure and provide strong support for the siphon flow as the physical me...

  9. Understanding Physical Conditions in High Redshift Galaxies through C I Fine Structure Lines: Data and Methodology

    CERN Document Server

    Jorgenson, Regina A; Prochaska, J Xavier

    2010-01-01

    We probe the physical conditions in high redshift galaxies, specifically, the Damped Lyman-alpha Systems (DLAs) using neutral carbon (CI) fine structure lines and molecular hydrogen (H2). We report five new detections of CI and analyze the CI in an additional 2 DLAs with previously published data. We also present one new detection of H2 in a DLA. We present a new method of analysis that simultaneously constrains \\emph{both} the volume density and the temperature of the gas, as opposed to previous studies that a priori assumed a gas temperature. We use only the column density of CI measured in the fine structure states and the assumption of ionization equilibrium in order to constrain the physical conditions in the gas. We present a sample of 11 CI velocity components in 6 DLAs and compare their properties to those derived by the global CII* technique. The resulting median values for this sample are: = 69 cm^{-3}, = 50 K, and = 3.86 cm^{-3} K, with standard deviations, sigma_{n(HI)} = 134 cm^{-3}, sigma_T =...

  10. Constraining spatial variations of the fine structure constant using clusters of galaxies and Planck data

    CERN Document Server

    de Martino, I; Ebeling, H; Kocevski, D

    2016-01-01

    We propose an improved methodology to constrain spatial variations of the fine structure constant using clusters of galaxies. We use the {\\it Planck} 2013 data to measure the thermal Sunyaev-Zeldovich effect at the location of 618 X-ray selected clusters. We then use a Monte Carlo Markov Chain algorithm to obtain the temperature of the Cosmic Microwave Background at the location of each galaxy cluster. When fitting three different phenomenological parameterizations allowing for monopole and dipole amplitudes in the value of the fine structure constant we improve the results of earlier analysis involving clusters and CMB power spectrum, and we also found that the best-fit direction of a hypothetical dipole is compatible with the direction of other known anomalies. Although the constraining power of our current datasets do not allow us to test the indications of a dipole obtained though high-resolution optical/UV spectroscopy, our results do highlight that clusters of galaxies will be a very powerful tool to pr...

  11. Fine structure of the topological defect core: Disclination in lyotropic chromonic liquid crystal

    Science.gov (United States)

    Zhou, Shuang; Shiyanovskii, Sergij; Park, Heung-Shik; Kim, Young-Ki; Hearn, Tristan; Reichel, Lothar; Lavrentovich, Oleg

    Topological defects represent an important concept in many branches of modern physics ranging from cosmology and optics to hard and soft matter. One of the most difficult problems is the fine structure of the so-called core region of defects, where the deformations of the order parameter are so strong that the phenomenological description valid in the far field becomes invalid. Experimental exploration of the fine core structure is usually hindered by the small size (atomic/molecular level) of the core, where optical or even electron microscopy techniques are invalid. In this work, we take advantage of the peculiar nature of the so-called lyotropic chromonic liquid crystals (LCLC) of a nematic type that carry disclinations with a core extending over macroscopic distances (tens of micrometers), large enough to explore their spatial variation by optical and electron microscopy. We demonstrate that the director and the scalar order parameter (associated with the degree of orientational order) show a profound change in the core region. In particular, as one approaches the center of the defect, the azimuthal dependency of the director field changes dramatically and the scalar order parameter shows a strong dependence on the strength of splay and bend deformations. This work is supported by NSF Grant DMS-1434185.

  12. The variation of the fine-structure constant from disformal couplings

    Science.gov (United States)

    van de Bruck, Carsten; Mifsud, Jurgen; Nunes, Nelson J.

    2015-12-01

    We study a theory in which the electromagnetic field is disformally coupled to a scalar field, in addition to a usual non-minimal electromagnetic coupling. We show that disformal couplings modify the expression for the fine-structure constant, α. As a result, the theory we consider can explain the non-zero reported variation in the evolution of α by purely considering disformal couplings. We also find that if matter and photons are coupled in the same way to the scalar field, disformal couplings itself do not lead to a variation of the fine-structure constant. A number of scenarios are discussed consistent with the current astrophysical, geochemical, laboratory and the cosmic microwave background radiation constraints on the cosmological evolution of α. The models presented are also consistent with the current type Ia supernovae constraints on the effective dark energy equation of state. We find that the Oklo bound in particular puts strong constraints on the model parameters. From our numerical results, we find that the introduction of a non-minimal electromagnetic coupling enhances the cosmological variation in α. Better constrained data is expected to be reported by ALMA and with the forthcoming generation of high-resolution ultra-stable spectrographs such as PEPSI, ESPRESSO, and ELT-HIRES. Furthermore, an expected increase in the sensitivity of molecular and nuclear clocks will put a more stringent constraint on the theory.

  13. The variation of the fine-structure constant from disformal couplings

    CERN Document Server

    van de Bruck, Carsten; Nunes, Nelson J

    2015-01-01

    We study a theory in which the electromagnetic field is disformally coupled to a scalar field, in addition to a usual non-minimal electromagnetic coupling. We show that disformal couplings modify the expression for the fine-structure constant, alpha. As a result, the theory we consider can explain the non-zero reported variation in the evolution of alpha by purely considering disformal couplings. We also find that if matter and photons are coupled in the same way to the scalar field, disformal couplings itself do not lead to a variation of the fine-structure constant. A number of scenarios are discussed consistent with the current astrophysical, geochemical, laboratory and the cosmic microwave background radiation constraints on the cosmological evolution of alpha. The models presented are also consistent with the current type Ia supernovae constraints on the effective dark energy equation of state. We find that the Oklo bound in particular puts strong constraints on the model parameters. From our numerical r...

  14. The Fine-Structure of the Net-Circular Polarization in a Sunspot Penumbra

    CERN Document Server

    Tritschler, A; Schlichenmaier, R; Hagenaar, H J

    2007-01-01

    We present novel evidence for a fine structure observed in the net-circular polarization (NCP) of a sunspot penumbra based on spectropolarimetric measurements utilizing the Zeeman sensitive FeI 630.2 nm line. For the first time we detect a filamentary organized fine structure of the NCP on spatial scales that are similar to the inhomogeneities found in the penumbral flow field. We also observe an additional property of the visible NCP, a zero-crossing of the NCP in the outer parts of the center-side penumbra, which has not been recognized before. In order to interprete the observations we solve the radiative transfer equations for polarized light in a model penumbra with embedded magnetic flux tubes. We demonstrate that the observed zero-crossing of the NCP can be explained by an increased magnetic field strength inside magnetic flux tubes in the outer penumbra combined with a decreased magnetic field strength in the background field. Our results strongly support the concept of the uncombed penumbra.

  15. MHD wave modes resolved in fine-scale chromospheric magnetic structures

    CERN Document Server

    Verth, G

    2015-01-01

    Within the last decade, due to significant improvements in the spatial and temporal resolution of chromospheric data, magnetohydrodynamic (MHD) wave studies in this fascinating region of the Sun's atmosphere have risen to the forefront of solar physics research. In this review we begin by reviewing the challenges and debates that have manifested in relation to MHD wave mode identification in fine-scale chromospheric magnetic structures, including spicules, fibrils and mottles. Next we go on to discuss how the process of accurately identifying MHD wave modes also has a crucial role to play in estimating their wave energy flux. This is of cardinal importance for estimating what the possible contribution of MHD waves is to solar atmospheric heating. Finally, we detail how such advances in chromospheric MHD wave studies have also allowed us, for the first time, to implement cutting-edge magnetoseismological techniques that provide new insight into the sub-resolution plasma structuring of the lower solar atmospher...

  16. Fine structures of organic photovoltaic thin films probed by frequency-shift electrostatic force microscopy

    Science.gov (United States)

    Araki, Kento; Ie, Yutaka; Aso, Yoshio; Matsumoto, Takuya

    2016-07-01

    The localized charge and electrostatic properties of organic photovoltaic thin films are predominating factors for controlling energy conversion efficiency. The surface potential and electrostatic structures of organic photovoltaic thin films were investigated by frequency shift mode Kelvin force microscopy (KFM) and electrostatic force microscopy (EFM). The KFM images of a poly[2-methoxy-5-(3‧,7‧-dimethyloctyloxy)-1,4-phenylene vinylene]/phenyl-C61-butyric-acid-methyl ester (PCBM) blend thin film reveals that the PCBM domains precipitate as the topmost layer on the thin films. We find fine structures that were not observed in the topography and KFM images. The bias dependence of the EFM images suggests that the EFM contrast reflects the field-induced polarization, indicating the presence of charge trapping sites.

  17. Fine structure in the cosmic ray spectrum: Further analysis and the next step

    Science.gov (United States)

    Erlykin, A. D.; Wolfendale, A. W.

    2012-01-01

    An analysis is made of the fine structure in the cosmic ray energy spectrum: new facets of present observations and their interpretation and the next step. It is argued that less than about 10% of the intensity of the helium 'peak' at the knee at ≈5 PeV is due to just a few sources (SNR) other than the single source. The apparent concavity in the rigidity spectra of protons and helium nuclei which have maximum curvature at about 200 GV is confirmed by a joint analysis of the PAMELA, CREAM and ATIC experiments. The spectra of heavier nuclei also show remarkable structure in the form of 'ankles' at several hundred GeV/nucleon. Possible mechanisms are discussed. The search for 'pulsar peaks' has not yet proved successful.

  18. Fine structure in the cosmic ray spectrum: Further analysis and the next step

    CERN Document Server

    Erlykin, A D

    2011-01-01

    An analysis is made of the fine structure in the cosmic ray energy spectrum: new facets of present observations and their interpretation and the next step. It is argued that less than about 10% of the intensity of the helium `peak' at the knee at $\\simeq 5PeV$ is due to just a few sources (SNR) other than the single source. The apparent concavity in the rigidity spectra of protons and helium nuclei which have maximum curvature at about 200 GV is confirmed by a joint analysis of the PAMELA, CREAM and ATIC experiments. The spectra of heavier nuclei also show remarkable structure in the form of `ankles' at several hundred GeV/nucleon. Possible mechanisms are discussed. The search for `pulsar peaks' has not yet proved successful.

  19. Phonon density of states of cadmium iodide deduced from the fine structure of the 3A2g → 1Eg electronic transition of nickel(2+) ion-doped cadmium iodide.

    NARCIS (Netherlands)

    Kuindersma, S. R.; Boudewijn, Pieter Reinder

    1978-01-01

    The absorption and MCD spectra of the 3A2g → 1Eg transition of CdI2:Ni2+ at ∼ 12,500 cm-1 were measured. The unusual vibronic fine structure is explained by the coupling of the phonons of the CdI2 lattice to the electronic states of Ni2+. The dispersion curves for the acoustical and optical branches

  20. Electron-Vibration Structure of Absorption Spectra of Resazurine

    Directory of Open Access Journals (Sweden)

    T.N. Sakun

    2011-01-01

    Full Text Available In the work the experimental and theoretical investigation of the spectral characteristics of a resazurin molecule are carried out. Comparison of results of experimental and theoretical researches has allowed showing, that the spectrum of absorption in the visible region is formed by quantum transitions between electronic states of the molecule, and also by the electron-vibration interaction. In the work the method of reception of theoretical results with the control of molecule symmetry is offered. It has allowed to receive the completely coordinated theoretical and experimental results both by position and by size of the extinction factor and to find out the nature of all quantum transitions and oscillatory frequencies. It is shown, that strips of absorption in the visible region of the spectrum are formed at participation of the totally symmetrical vibrations of the molecule among which the greatest participation stand out vibrations with frequencies in the region of 478 cm – 1, 1467 cm – 1, and also by group of oscillatory frequencies in the region of 1800-2000 cm – 1 which were less than found theoretically for the basic state of the molecule because the degree of loosening of the bonds that responsible for specified vibrations, increases at excitation of the molecule.

  1. Microsatellite analyses reveal fine-scale genetic structure in grey mouse lemurs (Microcebus murinus).

    Science.gov (United States)

    Fredsted, T; Pertoldi, C; Schierup, M H; Kappeler, P M

    2005-07-01

    Information on genetic structure can be used to complement direct inferences on social systems and behaviour. We studied the genetic structure of the solitary grey mouse lemur (Microcebus murinus), a small, nocturnal primate endemic to western Madagascar, with the aim of getting further insight on its breeding structure. Tissue samples from 167 grey mouse lemurs in an area covering 12.3 km2 in Kirindy Forest were obtained from trapping. The capture data indicated a noncontinuous distribution of individuals in the study area. Using 10 microsatellite markers, significant genetic differentiation in the study area was demonstrated and dispersal was found to be significantly male biased. Furthermore, we observed an overall excess of homozygotes in the total population (F(IT) = 0.131), which we interpret as caused by fine-scale structure with breeding occurring in small units. Evidence for a clumped distribution of identical homozygotes was found, supporting the notion that dispersal distance for breeding was shorter than that for foraging, i.e. the breeding neighbourhood size is smaller than the foraging neighbourhood size. In conclusion, we found a more complex population structure than what has been previously reported in studies performed on smaller spatial scales. The noncontinuous distribution of individuals and the effects of social variables on the genetic structure have implications for the interpretation of social organization and the planning of conservation activities that may apply to other solitary and endangered mammals as well.

  2. An X-ray absorption spectroscopy investigation of the local atomic structure in Cu-Ni-Si alloy after severe plastic deformation and ageing

    Science.gov (United States)

    Azzeddine, H.; Harfouche, M.; Hennet, L.; Thiaudiere, D.; Kawasaki, M.; Bradai, D.; Langdon, T. G.

    2015-08-01

    The local atomic structure of Cu-Ni-Si alloy after severe plastic deformation (SPD) processing and the decomposition of supersaturated solid solution upon annealing were investigated by means of X-ray absorption spectroscopy. The coordination number and interatomic distances were obtained by analyzing experimental extend X-ray absorption fine structure data collected at the Ni K-edge. Results indicate that the environment of Ni atoms in Cu-Ni-Si alloy is strongly influenced by the deformation process. Moreover, ageing at 973 K affects strongly the atomic structure around the Ni atoms in Cu-Ni-Si deformed by equal channel angular pressing and high pressure torsion. This influence is discussed in terms of changes and decomposition features of the Cu-Ni-Si solid solution.

  3. Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

    OpenAIRE

    De Hoop, A.T.; Jiang, L.

    2009-01-01

    The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwell's equations numerically to be practically inapplicable. To overcome this difficulty, an approximate method is proposed that models the interaction of the layer with an incident electromagnetic field via a boundary condition t...

  4. The Effects of Instrumental Elliptical Polarization on Stellar Point Spread Function Fine Structure

    Science.gov (United States)

    Carson, Joseph C.; Kern, Brian D.; Breckinridge, James B.; Trauger, John T.

    2005-01-01

    We present procedures and preliminary results from a study on the effects of instrumental polarization on the fine structure of the stellar point spread function (PSF). These effects are important to understand because the the aberration caused by instrumental polarization on an otherwise diffraction-limited will likely have have severe consequences for extreme high contrast imaging systems such as NASA's planned Terrestrial Planet Finder (TPF) mission and the proposed NASA Eclipse mission. The report here, describing our efforts to examine these effects, includes two parts: 1) a numerical analysis of the effect of metallic reflection, with some polarization-specific retardation, on a spherical wavefront; 2) an experimental approach for observing this effect, along with some preliminary laboratory results. While the experimental phase of this study requires more fine-tuning to produce meaningful results, the numerical analysis indicates that the inclusion of polarization-specific phase effects (retardation) results in a point spread function (PSF) aberration more severe than the amplitude (reflectivity) effects previously recorded in the literature.

  5. Radio Structures of Compact Quasars with Broad Absorption Lines

    Science.gov (United States)

    Kunert-Bajraszewska, Magdalena; Gawroński, Marcin P.

    2010-05-01

    Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is due to a geometrical effect and/or it is connected with the quasar evolution. Using the final release of FIRST survey combined with a catalog of BAL QSOs from SDSS/DR3, we have constructed a new sample of compact radio-loud BAL QSOs, which constitutes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis of the BAL QSOs radio morphology, orientation, and jet evolution using the European VLBI Network (EVN) at 1.6 GHz and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz.

  6. Outlier SNP markers reveal fine-scale genetic structuring across European hake populations (Merluccius merluccius).

    Science.gov (United States)

    Milano, Ilaria; Babbucci, Massimiliano; Cariani, Alessia; Atanassova, Miroslava; Bekkevold, Dorte; Carvalho, Gary R; Espiñeira, Montserrat; Fiorentino, Fabio; Garofalo, Germana; Geffen, Audrey J; Hansen, Jakob H; Helyar, Sarah J; Nielsen, Einar E; Ogden, Rob; Patarnello, Tomaso; Stagioni, Marco; Tinti, Fausto; Bargelloni, Luca

    2014-01-01

    Shallow population structure is generally reported for most marine fish and explained as a consequence of high dispersal, connectivity and large population size. Targeted gene analyses and more recently genome-wide studies have challenged such view, suggesting that adaptive divergence might occur even when neutral markers provide genetic homogeneity across populations. Here, 381 SNPs located in transcribed regions were used to assess large- and fine-scale population structure in the European hake (Merluccius merluccius), a widely distributed demersal species of high priority for the European fishery. Analysis of 850 individuals from 19 locations across the entire distribution range showed evidence for several outlier loci, with significantly higher resolving power. While 299 putatively neutral SNPs confirmed the genetic break between basins (F(CT) = 0.016) and weak differentiation within basins, outlier loci revealed a dramatic divergence between Atlantic and Mediterranean populations (F(CT) range 0.275-0.705) and fine-scale significant population structure. Outlier loci separated North Sea and Northern Portugal populations from all other Atlantic samples and revealed a strong differentiation among Western, Central and Eastern Mediterranean geographical samples. Significant correlation of allele frequencies at outlier loci with seawater surface temperature and salinity supported the hypothesis that populations might be adapted to local conditions. Such evidence highlights the importance of integrating information from neutral and adaptive evolutionary patterns towards a better assessment of genetic diversity. Accordingly, the generated outlier SNP data could be used for tackling illegal practices in hake fishing and commercialization as well as to develop explicit spatial models for defining management units and stock boundaries.

  7. Properties and Modeling of Unresolved Fine Structure Loops Observed in the Solar Transition Region by IRIS

    Science.gov (United States)

    Brooks, David H.; Reep, Jeffrey W.; Warren, Harry P.

    2016-08-01

    Recent observations from the Interface Region Imaging Spectrograph (IRIS) have discovered a new class of numerous low-lying dynamic loop structures, and it has been argued that they are the long-postulated unresolved fine structures (UFSs) that dominate the emission of the solar transition region. In this letter, we combine IRIS measurements of the properties of a sample of 108 UFSs (intensities, lengths, widths, lifetimes) with one-dimensional non-equilibrium ionization simulations, using the HYDRAD hydrodynamic model to examine whether the UFSs are now truly spatially resolved in the sense of being individual structures rather than being composed of multiple magnetic threads. We find that a simulation of an impulsively heated single strand can reproduce most of the observed properties, suggesting that the UFSs may be resolved, and the distribution of UFS widths implies that they are structured on a spatial scale of 133 km on average. Spatial scales of a few hundred kilometers appear to be typical for a range of chromospheric and coronal structures, and we conjecture that this could be an important clue for understanding the coronal heating process.

  8. Fine Structure ENA Sources Beyond the Termination Shock: Observational Constraints and Detection Limits

    Science.gov (United States)

    Demajistre, R.; Janzen, P. H.; Allegrini, F.; Dayeh, M. A.; McComas, D. J.; Schwadron, N.

    2015-12-01

    High spatial resolution maps from the IBEX mission (McComas et al, Science, 2009) suggest the presence of "fine structure" in the signal from beyond the termination shock. That is, areas of enhanced ENA emission that span less than a degree in the IBEX sky map. If confirmed, this would suggest very concentrated areas of emission from sources with scales of a few AU embedded in the outer heliosphere (or proportionally larger if they are located beyond the heliopause). This, in turn, would require the presence of unanticipated structures (plasma or neutral) beyond the termination shock for which the physics is poorly defined. It is therefore crucial to confirm the presence of these structures through careful analysis, or to establish the detection limits if the data taken to date is not sufficient for such a confirmation. In this work, we use 5 years worth of IBEX data to examine the statistical significance of these enhancements. We examine correlations in time, ENA energy and coincidence type for evidence of these small-scale spatial structures. Then, using the known spatial response of the IBEX instrument, establish the conditions under which such structure, if present, would be detectable. This detection threshold analysis is fully applicable future measurements, such as those planned for IMAP.

  9. Fine-structure energy levels and radiative decay rates in Al-like vanadium

    International Nuclear Information System (INIS)

    Large-scale calculations of excitation energies from ground state for 97 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the (1s22s22p6)3s23p(2P0), 3s3p2(2S,2P,2D,4P), 3s23d(2D), 3p3(4S0,2P0,2D0), 3s3p(3P0)3d(2P0,2D0,2F0,4P0,4D0,4F0), 3s3p(1P0)3d(2P0,2D0,2F0), 3p2(1S)3d(2D), 3p2(1D)3d(2S,2P,2D,2F,2G), 3p2(3P)3d(2P,2D,2F,4P,4D,4F), 3s3d2(2S,2P,2D,2F,2G,4P,4F), 3s24s(2S), 3s24p(2P0), 3s24d(2D), 3s24f(2F0), 3s3p(3P0)4s(2P0,4P0) and 3s3p(1P0)4s(2P0) states of V XI are performed using extensive configuration-interaction (CI) wavefunctions. The calculations used the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are incorporated by means of the Breit-Pauli Hamiltonian. In order to keep our calculated energy splittings as close as possible to the National Institute of Standard and Technology (NIST) values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. Our calculated excitation energies, including their ordering, are in excellent agreement with the available NIST results. From our radiative decay rates, we have also calculated radiative lifetimes of some fine-structure levels. Generally, very good agreement between our calculated lifetimes and those from sophisticated calculation is realized for many fine-structure levels. However, a few significant differences are noted and discussed.

  10. Role of defects in BiFeO₃ multiferroic films and their local electronic structure by x-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ravalia, Ashish; Vagadia, Megha; Solanki, P. S.; Shah, N. A.; Kuberkar, D. G., E-mail: dgkuberkar@rediffmail.com [Department of Physics, Saurashtra University, Rajkot 360 005 (India); Gautam, S.; Chae, K. H. [Nano Material Analysis Centre, Korean Institute of Science and Technology, Seoul 136-79 (Korea, Republic of); Asokan, K. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India)

    2014-10-21

    Present study reports the role of defects in the electrical transport in BiFeO₃ (BFO) multiferroic films and its local electronic structure investigated by near-edge X-ray absorption fine structure. Defects created by high energy 200 MeV Ag⁺¹⁵ ion irradiation with a fluence of ∼5 × 10¹¹ ions/cm² results in the increase in structural strain and reduction in the mobility of charge carriers and enhancement in resistive (I-V) and polarization (P-E) switching behaviour. At higher fluence of ∼5 × 10¹² ions/cm², there is a release in the structural strain due to local annealing effect, resulting in an increase in the mobility of charge carriers, which are released from oxygen vacancies and hence suppression in resistive and polarization switching. Near-edge X-ray absorption fine structure studies at Fe L₃,₂- and O K-edges show a significant change in the spectral features suggesting the modifications in the local electronic structure responsible for changes in the intrinsic magnetic moment and electrical transport properties of BFO.

  11. Atlas of fine structures of dynamic spectra of solar type IV-dm and some type II radio bursts

    International Nuclear Information System (INIS)

    The author presents an atlas of spectral fine structures of solar radio bursts of types IV and II around 1 m wavelength, as obtained with a multichannel spectrograph at Dwingeloo. The structures form largely a collection of observations of these events during late 1968 through 1974, thus covering almost entirely the declining branch of solar cycle 20. The spectrograph has an extra enhanced contrast output with properties quite different from those of the commonly used swept frequency spectrographs. The corresponding instrumental characteristics and effects are discussed. A classification of fine structures and an analysis of their statistical properties and of those of the pertinent radio events are also given. (Auth.)

  12. Observation of Fine Lung Structure by Ultrahigh-Resolution Optical Coherence Tomography Using 800, 1060, and 1300 nm Supercontinua

    Science.gov (United States)

    Ishida, Shutaro; Nishizawa, Norihiko; Kitatsuji, Masashi; Ohshima, Hiroyoshi; Hasegawa, Yoshinori; Matsushima, Miyoko; Kawabe, Tsutomu

    2012-04-01

    Cross-sectional imaging of isolated rat lungs was demonstrated by ultrahigh-resolution optical coherence tomography using supercontinua at 800, 1060, and 1300 nm wavelengths. The detailed structure of the trachea, including cartilage, mucosa, and annular ligaments, were observed clearly. In the imaging of visceral pleura and alveoli, when phosphate-buffered saline was instilled into the lung, the penetration depth of imaging was improved, and clear images of the fine structure of the lung, including alveoli, were observed owing to the index-matching effect. The wavelength dependence of the light source was discussed for the observation of fine structure and imaging contrast.

  13. Synchrotron X-ray absorption spectroscopy study of local structure transformation behavior in perovskite Ba(Ti,Zr)O3 system

    International Nuclear Information System (INIS)

    Highlights: • Synthesis, global structure was studied by XRD technique. • The local structure of the Ti ions in the Ba(Ti,Zr)O3 using XAS technique. • EXAFS and XANES analysis showed that Ti-displacement lead to the phase transition. • The results were confirmed by XANES simulation and EXAFS fitting. • This work deals with application of a novel Synchrotron. - Abstract: In this work, the change of the local atomic structure in BaTi1−xZrxO3 ceramics was investigated by synchrotron X-ray absorption spectroscopy technique. The X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectra at the Ti K-edge were measured and compared with simulated spectra. The results show that an increase of Zr content in Ba(Ti,Zr)O3 lattice structure affected significantly the phase transition behavior and the local structure surrounding the Ti absorbing atom. More importantly, the information on the locally determined structures and its relation to the phase transition characteristic from relaxor ferroelectric to polar clusters in Ba(Ti,Zr)O3 system were obtained and discussed

  14. Synchrotron X-ray absorption spectroscopy study of local structure transformation behavior in perovskite Ba(Ti,Zr)O{sub 3} system

    Energy Technology Data Exchange (ETDEWEB)

    Bootchanont, Atipong, E-mail: a.bootchanont@gmail.com [School of Physics, Institute of Science, Suranaree University of Technology, COE-NANOTEC-SUT on Advanced Functional Nanomaterials, Nakhon Ratchasima 30000 (Thailand); Jutimoosik, Jaru [School of Physics, Institute of Science, Suranaree University of Technology, COE-NANOTEC-SUT on Advanced Functional Nanomaterials, Nakhon Ratchasima 30000 (Thailand); Chandarak, Sujittra [Department of Materials Engineering, Faculty of Engineering and Architecture, Rajamangala University of Technology Isan, Nakhon Ratchasima 30000 (Thailand); Unruan, Muangjai [Department of Applied Physics, Faculty of Science and Liberal Arts, Rajamangala University of Technology Isan, Nakhon Ratchasima 30000 (Thailand); Kidkhunthod, Pinit; Klysubun, Wantana [Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); Rujirawat, Saroj; Yimnirun, Rattikorn [School of Physics, Institute of Science, Suranaree University of Technology, COE-NANOTEC-SUT on Advanced Functional Nanomaterials, Nakhon Ratchasima 30000 (Thailand); Guo, Ruyan; Bhalla, Amar [Department of Electrical and Computer Engineering, College of Engineering, University of Texas at San Antonio, TX 78249 (United States)

    2014-12-15

    Highlights: • Synthesis, global structure was studied by XRD technique. • The local structure of the Ti ions in the Ba(Ti,Zr)O{sub 3} using XAS technique. • EXAFS and XANES analysis showed that Ti-displacement lead to the phase transition. • The results were confirmed by XANES simulation and EXAFS fitting. • This work deals with application of a novel Synchrotron. - Abstract: In this work, the change of the local atomic structure in BaTi{sub 1−x}Zr{sub x}O{sub 3} ceramics was investigated by synchrotron X-ray absorption spectroscopy technique. The X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectra at the Ti K-edge were measured and compared with simulated spectra. The results show that an increase of Zr content in Ba(Ti,Zr)O{sub 3} lattice structure affected significantly the phase transition behavior and the local structure surrounding the Ti absorbing atom. More importantly, the information on the locally determined structures and its relation to the phase transition characteristic from relaxor ferroelectric to polar clusters in Ba(Ti,Zr)O{sub 3} system were obtained and discussed.

  15. Study on the improved structure of dye-sensitized solar cells for enhancing light absorption

    Institute of Scientific and Technical Information of China (English)

    LIU Yong; SHEN Hui; DENG Youjun

    2007-01-01

    The absorption coefncients of N719 or N3 dyes at the longer wavelength region (>600 nm)are not enough to catch photons efficiently,but the solar spectrum has a large photon flux in the wavelength region between 500 and 1,000 nm,so it is desirable to enhance the absorption of light by the dye-sensitized solar cells(DSSC)to achieve higher efficiencies.To solve this problem,an improved structure Of DSSC for enhancing light absorption is introduced in this paper, and I-V characteristics of DSSC are measured to illustrate the enhancement of the light absorption and efficiency.As a result,the improved DSSC exhibits higher light absorption and solar-to-electric conversion efficiency than traditional DSSC.

  16. Anomalous absorption of bulk shear sagittal acoustic waves in a layered structure with viscous fluid

    CERN Document Server

    Gramotnev, D K; Nieminen, T A; Gramotnev, Dmitri K.; Mather, Melissa L.; Nieminen, Timo A.

    2003-01-01

    It is demonstrated theoretically that the absorptivity of bulk shear sagittal waves by an ultra-thin layer of viscous fluid between two different elastic media has a strong maximum (in some cases as good as 100%) at an optimal layer thickness. This thickness is usually much smaller than the penetration depths and lengths of transverse and longitudinal waves in the fluid. The angular dependencies of the absorptivity are demonstrated to have significant and unusual structure near critical angles of incidence. The effect of non-Newtonian properties and non-uniformities of the fluid layer on the absorptivity is also investigated. In particular, it is shown that the absorption in a thin layer of viscous fluid is much more sensitive to non-zero relaxation time(s) in the fluid layer than the absorption at an isolated solid-fluid interface.

  17. Fine structure of inelastic electron scattering cross-section spectra for MN

    Science.gov (United States)

    Parshin, A. S.; Igumenov, A. Yu; Mikhlin, Yu L.; Pchelyakov, O. P.; Zhigalov, V. S.

    2016-04-01

    The comparative analysis of the reflection electron energy loss spectra and the inelastic electron scattering cross-section spectra for Mn was carried out. It is shown that inelastic electron scattering cross-section spectra have certain advantages in the study of the interaction of electrons with the substance as compared to the electron energy loss spectra. The inelastic electron scattering cross section spectra fine structure was analysed by fitting the experimental spectra using the 3 parameters Lorentzian-type formula of Tougaard. This method was used for the quantitative analysis of the contributions of various loss processes in the inelastic electron scattering cross section spectra, determination of the loss peaks energies and origin.

  18. Dust-cloud structures behind a shock wave moving over a deposited layer of fine particles

    Institute of Scientific and Technical Information of China (English)

    WANG Boyi; XIONG Yi; CHEN Qian; A.N. OSIPTSOV

    2005-01-01

    The present paper investigates dispersed-phase flow structures of a dust cloud induced by a normal shock wave moving at a constant speed over a flat surface deposited with fine particles. In the shock-fitted coordinates, the general equations of dusty-gas boundary layer flows are formulated within the framework of a multi-fluid model and parametric numerical studies of the carrier- and dispersedphase flow fields are performed. The problem associated with crossing particle trajectories and the formation of local particle accumulation regions are solved by using the full Lagrangian method for the dispersed phase. The basic features of the near-wall two-phase flow under consideration including the role of Saffman force in the particle entrainment and the development of discontinuities or singularities in the particle density profiles are discussed. The effects associated with account of the non-uniformity of particle size and the finiteness of the particle Knudsen numbers are studied in detail.

  19. Automated fine structure image analysis method for discrimination of diabetic retinopathy stage using conjunctival microvasculature images

    Science.gov (United States)

    Khansari, Maziyar M; O’Neill, William; Penn, Richard; Chau, Felix; Blair, Norman P; Shahidi, Mahnaz

    2016-01-01

    The conjunctiva is a densely vascularized mucus membrane covering the sclera of the eye with a unique advantage of accessibility for direct visualization and non-invasive imaging. The purpose of this study is to apply an automated quantitative method for discrimination of different stages of diabetic retinopathy (DR) using conjunctival microvasculature images. Fine structural analysis of conjunctival microvasculature images was performed by ordinary least square regression and Fisher linear discriminant analysis. Conjunctival images between groups of non-diabetic and diabetic subjects at different stages of DR were discriminated. The automated method’s discriminate rates were higher than those determined by human observers. The method allowed sensitive and rapid discrimination by assessment of conjunctival microvasculature images and can be potentially useful for DR screening and monitoring. PMID:27446692

  20. 3-Space In-Flow Theory of Gravity: Boreholes, Blackholes and the Fine Structure Constant

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2006-04-01

    Full Text Available A theory of 3-space explains the phenomenon of gravity as arising from the time-dependence and inhomogeneity of the differential flow of this 3-space. The emergent theory of gravity has two gravitational constants: G - Newton's constant, and a dimensionless constant alpha. Various experiments and astronomical observations have shown that alpha is the fine structure constant ~1/137. Here we analyse the Greenland Ice Shelf and Nevada Test Site borehole g anomalies, and confirm with increased precision this value of alpha. This and other successful tests of this theory of gravity, including the supermassive black holes in globular clusters and galaxies, and the "dark-matter" effect in spiral galaxies, shows the validity of this theory of gravity. This success implies that the non-relativistic Newtonian gravity was fundamentally flawed from the beginning, and that this flaw was inherited by the relativistic General Relativity theory of gravity.

  1. 3-Space In-Flow Theory of Gravity: Boreholes, Blackholes and the Fine Structure Constant

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2006-04-01

    Full Text Available A theory of 3-space explains the phenomenon of gravity as arising from the time-dependence and inhomogeneity of the differential flow of this 3-space. The emergent theory of gravity has two gravitational constants: GN — Newton’s constant, and a dimensionless constant α. Various experiments and astronomical observations have shown that α is the fine structure constant ≈ 1/137. Here we analyse the Greenland Ice Shelf and Nevada Test Site borehole g anomalies, and confirm with increased precision this value of α. This and other successful tests of this theory of gravity, including the supermassive black holes in globular clusters and galaxies, and the “dark-matter” effect in spiral galaxies, shows the validity of this theory of gravity. This success implies that the non-relativistic Newtonian gravity was fundamentally flawed from the beginning, and that this flaw was inherited by the relativistic General Relativity theory of gravity.

  2. Damping Properties vs. Structure Fineness of the High-zinc Aluminum Alloys

    Directory of Open Access Journals (Sweden)

    W.K. Krajewski

    2012-09-01

    Full Text Available The subject of this study is the presentation of relation between the degree of structure fineness and ultrasonic wave dampingcoefficient for the high-zinc aluminium alloys represented in this study by the sand mould cast alloy Al - 20 wt% Zn (AlZn20. Thestudied alloy was refined with a modifying (Al,Zn-Ti3 ternary master alloy, introducing Ti in the amount of 400 pm into metal. Based on the analysis of the initial and modified alloy macrostructure images and ultrasonic testing, it was found that the addition of (Al,Zn-Ti3 master alloy, alongside a significant fragmentation of grains, does not reduce the coefficient of ultrasonic waves with a frequency of 1 MHz.

  3. Representations of U(2∞ and the Value of the Fine Structure Constant

    Directory of Open Access Journals (Sweden)

    William H. Klink

    2005-12-01

    Full Text Available A relativistic quantum mechanics is formulated in which all of the interactions are in the four-momentum operator and Lorentz transformations are kinematic. Interactions are introduced through vertices, which are bilinear in fermion and antifermion creation and annihilation operators, and linear in boson creation and annihilation operators. The fermion-antifermion operators generate a unitary Lie algebra, whose representations are fixed by a first order Casimir operator (corresponding to baryon number or charge. Eigenvectors and eigenvalues of the four-momentum operator are analyzed and exact solutions in the strong coupling limit are sketched. A simple model shows how the fine structure constant might be determined for the QED vertex.

  4. Automatic detection and high resolution fine structure analysis of conic X-ray diffraction lines

    Energy Technology Data Exchange (ETDEWEB)

    Bauch, J.; Henschel, F. [TU Dresden, Institut fuer Werkstoffwissenschaft, 01069 Dresden (Germany); Schulze, M. [TU Dresden, Institut fuer Photogrammetrie und Fernerkundung, 01069 Dresden (Germany)

    2011-05-15

    The presented method demonstrates a first step in the development of a high resolution ''Residual stress microscope'' and facilitates through the implementation of largely automated procedures a fast detection of diffraction lines in the form of conic sections. It has been implemented for, but is not exclusively used for the Kossel technique and the ''X-ray Rotation-Tilt Method'' (XRT). The resulting multifaceted evaluable data base of many X-ray diffraction radiographies can be used not only for the systematic analysis of anomalies in diffraction lines (reflection fine structure), but also for direct calculation and output of precision residual stress tensors. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Fine structure of the isoscalar giant quadrupole resonance in 28Si and 27Al

    Science.gov (United States)

    Usman, I. T.; Buthelezi, Z.; Carter, J.; Cooper, G. R. J.; Fearick, R. W.; Förtsch, S. V.; Fujita, H.; Fujita, Y.; von Neumann-Cosel, P.; Neveling, R.; Papakonstantinou, P.; Pysmenetska, I.; Richter, A.; Roth, R.; Sideras-Haddad, E.; Smit, F. D.

    2016-08-01

    The isoscalar giant quadrupole resonance in 28Si and 27Al has been investigated with high-energy-resolution proton inelastic scattering at Ep=200 MeV and at scattering angles close to the maximum of Δ L =2 angular distributions with the K600 magnetic spectrometer of iThemba LABS, South Africa. Characteristic scales are extracted from the observed fine structure with a wavelet analysis and compared for 28Si with random-phase approximation and second random phase approximation calculations with an interaction derived from the Argonne V18 potential by a unitary transformation. A recent extension of the method to deformed nuclei provides the best description of the data, suggesting the significance of Landau damping.

  6. The fine structure splitting of the level of lithium in Rydberg states

    Institute of Scientific and Technical Information of China (English)

    胡先权; 胡文江; 孔春阳

    2002-01-01

    The Hamiltonian of the four-body problem for a lithium atom is expanded in series. The level shift and levelformula of a lithium atom in Rydberg states are achieved by means of the calculation of polarization of the atomic core(including the contribution of dipole, quadrupole and octupole components). We also consider the effect of relativitytheory, the orbital angular momentum L and the spin angular momentum S coupling scheme (LS coupling) and high-order correction of the effective potential to the level shift. The fine structure splitting (N=5-12, L=4-9, J=L±l/2)and level intervals in B ydberg states have been calculated by the above-mentioned formula and compared with recentexperimental data.

  7. Bloch oscillations of ultracold atoms and measurement of the fine structure constant

    International Nuclear Information System (INIS)

    From a measurement of the recoil velocity of an atom absorbing a photon, it is possible to deduce a determination of the ratio h/m between the Planck constant and the mass of the atoms and then to deduce a value of the fine structure constant alpha. To do this measurement, we use the technique of Bloch oscillations, which allows us to transfer a large number of recoils to atoms. A velocity sensor, based on velocity selective Raman transition, enables us to measure the momentum transferred to the atoms. A measurement with a statistical uncertainty of 4.4 10-9, in conjunction with a careful study of systematic effects (5 10-9), has led us to a determination of alpha with an uncertainty of 6.7 10-9: α-1(Rb) = 137.03599878 (91). This uncertainty is similar to the uncertainty of the best determinations of alpha based on atom interferometry. (author)

  8. Fine structure cross sections from reactance matrices - a more versatile development of the program JAJOM

    International Nuclear Information System (INIS)

    Results from calculations with LS-coupled wave functions (reactance matrices and term coupling coefficients) are used to compute collision strengths for transitions between fine structure levels. The imput is carefully checked. The algebraic transformation uses Racah algebra, the coefficients are computed as required. An optional further transformation to allow for intermediate coupling in the target requires term coupling coefficients to be supplied by the user. The collision strength are computed using either of two formulae, corresponding to weak or strong coupling respectively. This version of JAJOM is very flexible. Using the prepocessor included with this deck machine dependent features, array lengths, and mode of operation are all inserted according to the user's requirements. (Auth.)

  9. The variation of the fine structure constant: testing the dipole model with thermonuclear supernovae

    CERN Document Server

    Kraiselburd, Lucila; Negrelli, Carolina; Berro, Enrique García

    2014-01-01

    The large-number hypothesis conjectures that fundamental constants may vary. Accordingly, the spacetime variation of fundamental constants has been an active subject of research for decades. Recently, using data obtained with large telescopes a phenomenological model in which the fine structure constant might vary spatially has been proposed. We test whether this hypothetical spatial variation of {\\alpha}, which follows a dipole law, is compatible with the data of distant thermonuclear supernovae. Unlike previous works, in our calculations we consider not only the variation of the luminosity distance when a varying {\\alpha} is adopted, but we also take into account the variation of the peak luminosity of Type Ia supernovae resulting from a variation of {\\alpha}. This is done using an empirical relation for the peak bolometric magnitude of thermonuclear supernovae that correctly reproduces the results of detailed numerical simulations. We find that there is no significant difference between the several phenome...

  10. Study on Fine Structure of Gas Atomized LaNi5-based Alloys

    Institute of Scientific and Technical Information of China (English)

    Hai JING; Hong GUO; Shuguang ZHANG; Zili MA; Shaoming ZHANG

    2003-01-01

    The fine structure of hydrogen storage alloy powders MINi4.3-xCoxMn0.4Al0.3(x=0.75, 0.45, 0.10; MI: La-rich mischmetal) prepared by rapidly solidifying gas atomization was investigated using a Rietveld analysis method. Two setsof CaCu5-type crystal constants were observed in the studied alloys and one set was larger than the other. Withdecreasing powder radius the solidification rate of powder increased, and so did the percentage of a particle partwith larger crystal constants. The reason why there were two sets of crystal constants might be the difference ofsolidification rate between the outside and inside of a particle.

  11. Fine structures in Fe3Al alloy layer of a new hot dip aluminized steel

    Indian Academy of Sciences (India)

    Li Yajiang; Wang Juan; Zhang Yonglan; X Holly

    2002-12-01

    The fine structure in the Fe–Al alloy layer of a new hot dip aluminized steel (HDA) was examined by means of X-ray diffractometry (XRD), electron diffraction technique, etc. The test results indicated that the Fe–Al alloy layer of the new aluminized steel mainly composed of Fe3Al, FeAl and -Fe (Al) solid solution. There was no brittle phase containing higher aluminum content, such as FeAl3 (59.18% Al) and Fe2Al7 (62.93% Al). The tiny cracks and embrittlement, formerly caused by these brittle phases in the conventional aluminum-coated steel, were effectively eliminated. There was no microscopic defect (such as tiny cracks, pores or loose layer) in the coating. This is favourable to resist high temperature oxidation and corrosion of the aluminized steel.

  12. Theory of the Lamb shift and Fine Structure in $\\boldsymbol{(\\mu{}^{4}\\mathrm{He})^{+}}$

    CERN Document Server

    Diepold, Marc; Franke, Beatrice; Antognini, Aldo; Kottmann, Franz; Pohl, Randolf

    2016-01-01

    An up to date review of the theoretical contributions to the $2S\\rightarrow{}2P$ Lamb shift and the fine structure of the $2P$-state in the $(\\mu^4\\mathrm{He})^+$ ion is given. This summary will serve as the basis for the extraction of the alpha particle charge radius from the muonic helium Lamb shift measurements at the Paul Scherrer Institute Switzerland. Individual theoretical contributions needed for a charge radius extraction were compared and compiled into a consistent summary using the already established framework we used for muonic hydrogen and deuterium. The influence of the alpha particle charge distribution on the elastic two-photon exchange is studied to rule out possible model dependencies of the energy levels on the electric form factor of the nucleus.

  13. New determination of the fine structure constant and test of the quantum electrodynamics.

    Science.gov (United States)

    Bouchendira, Rym; Cladé, Pierre; Guellati-Khélifa, Saïda; Nez, François; Biraben, François

    2011-02-25

    We report a new measurement of the ratio h/m(Rb) between the Planck constant and the mass of (87)Rb atom. A new value of the fine structure constant is deduced, α(-1)=137.035999037(91) with a relative uncertainty of 6.6×10(-10). Using this determination, we obtain a theoretical value of the electron anomaly a(e)=0.00115965218113(84), which is in agreement with the experimental measurement of Gabrielse [a(e)=0.00115965218073(28)]. The comparison of these values provides the most stringent test of the QED. Moreover, the precision is large enough to verify for the first time the muonic and hadronic contributions to this anomaly.

  14. Engineering quantum dots for electrical control of the fine structure splitting

    Science.gov (United States)

    Pooley, M. A.; Bennett, A. J.; Farrer, I.; Ritchie, D. A.; Shields, A. J.

    2013-07-01

    We have studied the variation in fine-structure splitting (FSS) under application of vertical electric field in a range of quantum dots grown by different methods. In each sample, we confirm that this energy splitting changes linearly over the field range we can access. We conclude that this linear tuning is a general feature of self-assembled quantum dots, observed under different growth conditions, emission wavelengths, and in different material systems. Statistical measurements of characteristic parameters such as emission energy, Stark shift, and FSS tuning are presented which may provide a guide for future attempts to increase the yield of quantum dots that can be tuned to a minimal value of FSS with vertical electric field.

  15. Mechanical Behavior of Agave Americana L. Fibres: Correlation Between Fine Structure and Mechanical Properties

    Science.gov (United States)

    Msahli, S.; Chaabouni, Y.; Sakli, F.; Drean, J. Y.

    In this study, results of a mechanical behavior study of fibres extracted from the agave Americana L. plant, the most abundant variety in Tunisia, are presented. These results deal with the principal and mechanical characteristics of these fibres which are the elongation at break, the elasticity modulus and the rupture facture. These results permitted to situate these fibres, compared to the other textile fibres, as materials that can be used in technical applications such as reinforcing composites or geotextile. In order to understand the mechanical properties of these fibres, a correlation study between the properties already cited and the fine structure was done. The obtained results showed that the mechanical properties of agave Americana L. fibres are closely related to the individual fibers deformations and to the natural matrix (lignin and gums) that links these elementary fibres.

  16. Constraints on the time variation of the fine structure constant by the 5-year WMAP data

    CERN Document Server

    Nakashima, Masahiro; Yokoyama, Jun'ichi

    2008-01-01

    The constraints on the time variation of the fine structure constant at recombination epoch relative to its present value, $\\Delta\\alpha/\\alpha \\equiv (\\alpha_{\\mathrm{rec}} - \\alpha_{\\mathrm{now}})/\\alpha_{\\mathrm{now}}$, are obtained from the analysis of the 5-year WMAP cosmic microwave background data. As a result of Markov-Chain Monte-Carlo analysis, it is found that, contrary to the analysis based on the previous WMAP data, the mean value of $\\Delta\\alpha/\\alpha=-0.0009$ does not change significantly whether we use the Hubble Space Telescope (HST) measurement of the Hubble parameter as a prior or not. The resultant 95% confidence ranges of $\\Delta\\alpha/\\alpha$ are $-0.028 < \\Delta\\alpha/\\alpha < 0.026$ with HST prior and $-0.050 < \\Delta\\alpha/\\alpha < 0.042$ without HST prior.

  17. Measurement of isotope shifts, fine and hyperfine structure splittings of the lithium D lines

    International Nuclear Information System (INIS)

    The lithium D lines were studied using a diode laser that was frequency modulated by an electro-optic modulator, to excite an atomic beam. The transmission of part of the laser beam through an etalon was monitored to correct for the nonlinearity of the laser scan. The results for the 6,7Li 2S1/2 and 2P1/2 hyperfine splittings agree very well with the best existing data while those for the D1 isotope shift and 6,7Li fine structure splittings disagree significantly from data obtained by a previous laser atomic beam experiment. Our result for the D1 isotope shift is very close to the latest value computed using Hylleraas variational theory. (authors)

  18. 3-Space In-Flow Theory of Gravity: Boreholes, Blackholes and the Fine Structure Constant

    CERN Document Server

    Cahill, R T

    2006-01-01

    A theory of 3-space explains the phenomenon of gravity as arising from the time-dependence and inhomogeneity of the differential flow of this 3-space. The emergent theory of gravity has two gravitational constants: G - Newton's constant, and a dimensionless constant - alpha. Various experiments and astronomical observations have shown that alpha is the fine structure constant 1/137. Here we analyse the Greenland Ice Shelf and Nevada Test Site borehole g anomalies, and confirm with increased precision this value of alpha. This and other successful tests of this theory of gravity, including the supermassive black holes in globular clusters and galaxies, and the `dark-matter' effect in spiral galaxies, demonstrates the validity of this theory of gravity. This success implies that Newtonian gravity was fundamentally flawed from the beginning.

  19. Variation of the fine-structure constant from the de Sitter invariant special relativity

    Science.gov (United States)

    Chen, Shao-Xia; Xiao, Neng-Chao; Yan, Mu-Lin

    2008-08-01

    We discuss the variation of the fine-structure constant, α. There are obvious discrepancies among the results of α-variation from recent Quasi-stellar observation experiments and from the Oklo uranium mine analysis. We use dS Sitter invariant Special Relativity (Script SScript Rc,R) and Dirac large number hypothesis to discuss this puzzle, and present a possible solution to the disagreement. By means of the observational data and the discussions presented in this paper, we estimate the radius of the Universe in Script SScript Rc,R which is about ~2√5×1011l.y. Supported by National Natural Science Foundation of China (90403021) and PhD Program Funds of Education Ministry of China (20020358040)

  20. The Young Modulus of Black Strings and the Fine Structure of Blackfolds

    CERN Document Server

    Armas, Jay; Harmark, Troels; Obers, Niels A

    2011-01-01

    We explore corrections in the blackfold approach, which is a worldvolume theory capturing the dynamics of thin black branes. The corrections probe the fine structure of the branes, going beyond the approximation in which they are infinitely thin, and account for the dipole moment of worldvolume stress-energy as well as the internal spin degrees of freedom. We show that the dipole correction is induced elastically by bending a black brane. We argue that the long-wavelength transport coefficient capturing this response is a relativistic generalization of the Young modulus of elastic materials and we compute it analytically. Using this we draw predictions for black rings in dimensions greater than six. Furthermore, we employ our corrected blackfold equations to various multi-spinning black hole configurations in the blackfold limit, finding perfect agreement with known analytic solutions.

  1. Properties and Modeling of Unresolved Fine Structure Loops Observed by IRIS

    CERN Document Server

    Brooks, David H; Warren, Harry P

    2016-01-01

    Recent observations from the Interface Region Imaging Spectrograph (IRIS) have discovered a new class of numerous low-lying dynamic loop structures, and it has been argued that they are the long-postulated unresolved fine structures (UFS) that dominate the emission of the solar transition region. In this letter, we combine IRIS measurements of the properties of a sample of 108 UFS (intensities, lengths, widths, lifetimes) with 1-D non-equilibrium ionization simulations using the HYDRAD hydrodynamic model to examine whether the UFS are now truly spatially resolved in the sense of being individual structures rather than composed of multiple magnetic threads. We find that a simulation of an impulsively heated single strand can reproduce most of the observed properties suggesting that the UFS may be resolved, and the distribution of UFS widths implies that they are structured on a spatial scale of 133km on average. Spatial scales of a few hundred km appear to be typical for a range of chromospheric and coronal st...

  2. Fine-structure energy levels, radiative rates and lifetimes in Si-like nickel

    International Nuclear Information System (INIS)

    Large scale CIV3 calculations of excitation energies from ground state as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the fine-structure levels of the terms belonging to the (1s22s22p6)3s23p2, 3s3p3, 3p4, 3s23p3d, 3s23p4s, 3s23p4p, 3s23p4d and 3s23p4f configurations of Ni XV, are performed using very extensive configuration-interaction wave functions. The relativistic effects in intermediate coupling are incorporated by means of the Breit-Pauli Hamiltonian. In order to keep our calculated energy splittings as close as possible to the National Institute of Standard and Technology (NIST) values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. Our calculated excitation energies, including their ordering, are in excellent agreement with the available NIST results. From our radiative decay rates we have also calculated radiative lifetimes of the fine-structure levels. It is noted that our calculated radiative rates show significant disagreement (23-30%) with those calculated by Ishikawa and Vilkas (2002 Phys. Scr. 65 219) for the transitions involving the 3s3p3(5S2) level. For this high spin level 3s3p3(5S2) our calculated lifetime is found to be in excellent agreement with the experimental value of Träbert et al (1989 Z. Phys. D 11 207). In this calculation, we also predict many additional new and accurate data for various optically allowed and intercombination transitions to complete the void in the existing data. (paper)

  3. Spectral fine structure of the atomic ground states based on full relativistic theory

    Institute of Scientific and Technical Information of China (English)

    Zhenghe Zhu; Yongjian Tang

    2011-01-01

    @@ We focus on the full relativistic quantum mechanical calculations from boron to fluorine atoms with electronic configuration of 1s22s22pn (n = 1, 2, 3, 4, and 5), where 1s22s2 is the closed shell and 2pn is the open shell. Their active electrons in the open shell occupy all the six spinors as far as possible.Therefore, we suggest a new rule called "maximum probability" for the full symmetry group relativistic theory. Furthermore, the spectral fine structure of the atomic ground states based on the full relativistic theory and their intervals of L-S splitting are all reasonable. It is impossible to calculate the L-S splitting through non-relativistic quantum mechanics. The relativistic effect of atomic mass is increased significantly by about 12 folds from boron atom to fluorine atom.%We focus on the full relativistic quantum mechanical calculations from boron to fluorine atoms with electronic configuration of 1s22s22pn (n = 1, 2, 3, 4, and 5), where 1s22s2 is the closed shell and 2pn is the open shell. Their active electrons in the open shell occupy all the six spinors as far as possible.Therefore, we suggest a new rule called "maximum probability" for the full symmetry group relativistic theory. Furthermore, the spectral fine structure of the atomic ground states based on the full relativistic theory and their intervals of L-S splitting are all reasonable. It is impossible to calculate the L-S splitting through non-relativistic quantum mechanics. The relativistic effect of atomic mass is increased significantly by about 12 folds from boron atom to fluorine atom.

  4. A study of fine structure of diffuse aurora with ALIS-FAST measurements

    Directory of Open Access Journals (Sweden)

    T. Sergienko

    2008-10-01

    Full Text Available We present results of an investigation of the fine structure of the night sector diffuse auroral zone, observed simultaneously with optical instruments (ALIS from the ground and the FAST electron spectrometer from space 16 February 1997. Both the optical and particle data show that the diffuse auroral zone consisted of two regions. The equatorward part of the diffuse aurora was occupied by a pattern of regular, parallel auroral stripes. The auroral stripes were significantly brighter than the background luminosity, had widths of approximately 5 km and moved southward with a velocity of about 100 m/s. The second region, located between the region with auroral stripes and the discrete auroral arcs to the north, was filled with weak and almost homogeneous luminosity, against which short-lived auroral rays and small patches appeared chaotically. From analysis of the electron differential fluxes corresponding to the different regions of the diffuse aurora and based on existing theories of the scattering process we conclude the following: Strong pitch angle diffusion by electron cyclotron harmonic waves (ECH of plasma sheet electrons in the energy range from a few hundred eV to 3–4 keV was responsible for the electron precipitation, that produced the background luminosity within the whole diffuse zone. The fine structure, represented by the auroral stripes, was created by precipitation of electrons above 3–4 keV as a result of pitch angle diffusion into the loss cone by whistler mode waves. A so called "internal gravity wave" (Safargaleev and Maltsev, 1986 may explain the formation of the regular spatial pattern formed by the auroral stripes in the equatorward part of the diffuse auroral zone.

  5. [Histochemical findings of and fine structural changes in motor endplates in diseases with neuromuscular transmission abnormalities].

    Science.gov (United States)

    Yoshimura, Toshiro; Motomura, Masakatsu; Tsujihata, Mitsuhiro

    2011-07-01

    We herein review the histochemical findings and fine structural changes of motor endplates associated with diseases causing neuromuscular transmission abnormalities. In anti-acetylcholine receptor (AChR) antibody-positive myasthenia gravis (MG), type 2 fiber atrophy is observed, and the motor endplates show a reduction in the nerve terminal area, simplification of the postsynaptic membrane, decreased number of acetylcholine receptors, and deposition of immune complexes. In anti-MuSK antibody-positive MG, the fine structure shows a decrease in the postsynaptic membrane length, but the secondary synaptic cleft is preserved. There is no decrease in the number of AChRs, and there are no deposits of immune complexes at the motor endplates. Patients with Lambert-Eaton myasthenic syndrome show type 2 fiber atrophy, their motor endplates show a decrease in both the mean postsynaptic area and postsynaptic membrane length in the brachial biceps muscle. Congenital myasthenic syndrome with episodic apnea is characterized only by small-sized synaptic vesicles; the postsynaptic area is preserved. In subjects with congenital myasthenic syndrome with acetylcholinesterase deficiency, quantitative electron microscopy reveals a significant decrease in the nerve terminal size and presynaptic membrane length; further, the Schwann cell processes extend into the primary synaptic cleft, and partially or completely occlude the presynaptic membrane. The postsynaptic folds are degenerated, and associated with pinocytotic vesicles and labyrinthine membranous networks. Patients with slow-channel congenital myasthenia syndrome show type 1 fiber predominance, and their junctional folds are typically degenerated with widened synaptic space and loss of AChRs. Patients with AChR deficiency syndrome caused by recessive mutations in AChR subunits also show type 1 fiber predominance, and while most junctional folds are normal, some are simplified and have smaller than normal endplates. Rapsin and Mu

  6. Cultural transmission of tool use combined with habitat specializations leads to fine-scale genetic structure in bottlenose dolphins

    NARCIS (Netherlands)

    Kopps, Anna M.; Ackermann, Corinne Y.; Sherwin, William B.; Allen, Simon J.; Bejder, Lars; Kruetzen, Michael

    2014-01-01

    Socially learned behaviours leading to genetic population structure have rarely been described outside humans. Here, we provide evidence of fine-scale genetic structure that has probably arisen based on socially transmitted behaviours in bottlenose dolphins (Tursiops sp.) in western Shark Bay, Weste

  7. Enhanced absorption of graphene strips with a multilayer subwavelength grating structure

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jin-Hua; Huang, Yong-Qing, E-mail: yqhuang@bupt.edu.cn; Duan, Xiao-Feng; Wang, Qi; Zhang, Xia; Wang, Jun; Ren, Xiao-Min [State Key Laboratory of Information Photonics and Optical Communications, Institute of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

    2014-12-01

    The optical absorption of graphene strips covered on a multilayer subwavelength grating (MSG) surface is theoretically investigated. The absorption of graphene strips with MSG is enhanced in the wavelength range of 1500 nm to 1600 nm by critical coupling, which is associated with the combined effects of a guided resonance of MSG and its photonic band gap effect. The critical coupling of the graphene strips can be controlled by adjusting the incident angle without changing the structural parameters of MSG. The absorption of graphene strips can also be tuned by varying key parameters, such as grating period, strip width, and incident angle.

  8. Study of UCI4 structure and absorption spectra

    International Nuclear Information System (INIS)

    The two halides ThCl4 and ThBr4, which are isomorphic at room temperature, have a comparable behaviour when the temperature is lowered. The resonance line of the halogen isotope is split into two lines at a temperature of 96 K for ThBr4 and 70 K for ThCl4. These data confirm the observation of a phase transition first detected by Raman Spectroscopy. Though UCl4 is isomorphic with ThCl4 and ThBr4 at room temperature, it behaves differently versus temperature. The experiments performed from 4,2K to room temperature showed there is only one site for the halogen. UCl4 does not present a phase transition. Once some informations have been gathered on the matrices, optical absorption spectra on ThCl4:U4+ and UCl4 monocristals have been recorded in the visible and infrared ranges at 4,2 K and at room temperature. These spectra have many vibronic lines. To give a first interpretation of the pure electronic lines of U4+-ThCl4 and UCl4 studies on U4+-ThBr4 have been used, in particular the zero phonon lines which correspond to a Dsub(2d) symmetry, have been selected in comparison with the work done on ThBr4:U4+. The energy levels in ThCl4:U4+ and UCl4 have been fitted to the electrostatic parameters F0, F2,F4, F6, the spin orbit parameter, the configuration interaction parameters α, β, γ and crystal field parameters B02, B04, B44, B06, B46

  9. Structures and properties of Fe-C fine particles prepared by AC arc discharge

    Science.gov (United States)

    Li, Jian; Liu, Cunye; Zhao, Baogang; Lin, Yaoqiang; Deng, Zhaojing

    1999-05-01

    Fe-C fine particles are produced by an alternating arc discharge between iron and carbon electrodes in an Ar gas atmosphere at pressures of 8, 14 and 18 kPa. The crystal structure, morphology and surface composition have been studied, respectively, by X-ray diffraction, transmission electron microscopy, selected area electron diffraction and X-ray photoelectron spectroscopy. Magnetic properties and Curie temperatures have also been determined by a vibrating sample magnetometer. Results show that the particles are of two different crystal structures, one is hexagonal FeC and the other is cubic iron. The iron particles have a multi-layered structure composed of an α-Fe core wrapped by Fe 3O 4, FeO and FeO(OH) shells. It is found that the compositions and the specific saturation magnetization of the Fe-C particles prepared in different pressures of Ar gas are not the same, but their Curie temperatures are all 580±5°C.

  10. Active region fine structure observed at 0.08 arcsec resolution

    CERN Document Server

    Schlichenmaier, R; Hoch, S; Soltau, D; Berkefeld, T; Schmidt, D; Schmidt, W; Denker, C; Balthasar, H; Hofmann, A; Strassmeier, K G; Staude, J; Feller, A; Lagg, A; Solanki, S K; Collados, M; Sigwarth, M; Volkmer, R; Waldmann, T; Kneer, F; Nicklas, H; Sobotka, M

    2016-01-01

    The various mechanisms of magneto-convective energy transport determines the structure of sunspots and active regions. We characterise the appearance of light bridges and other fine structure details and elaborate on their magneto-convective nature. We present speckle-reconstructed images taken with the broad band imager at the 1.5 m GREGOR telescope in the 486nm and 589nm bands. We estimate the spatial resolution from the noise characteristics of the image bursts and obtain 0.08" at 589nm. We describe structure details in individual best images as well as the temporal evolution of selected features. We find branched dark lanes extending along thin (~1") light bridges in sunspots at various heliocentric angles. In thick (~2") light bridges the branches are disconnected from the central lane and have a `Y' shape with a bright grain toward the umbra. The images reveal that light bridges exist on varying intensity levels and that their small-scale features evolve on time scales of minutes. Faint light bridges sh...

  11. Fine fragmentation distribution from structural reactive material casings under explosive loading

    Science.gov (United States)

    Wilson, William; Zhang, Fan; Kim, Kibong

    2015-06-01

    Structural reactive material (SRM) can be used for explosive casings to provide additional blast energy. SRM fragments can react either promptly or after impact with nearby structure. Better understanding of fine fragment distributions from SRM casings is important for optimization of initiation and reaction of the SRM fragments. Key to this is knowledge of the initial fragmentation character before it has been altered by early reaction or by subsequent impact with surrounding structure. The study must be conducted beyond critical charge diameter to minimize effects of the expansion wave on fragment sizes. The collection and analysis of fragment distribution down to 40 micron size from thick SRM casings are therefore investigated in a 1.18 m diameter, 2.1 m3 closed cylindrical chamber filled with artificially-made pure snow packed to density 0.35 g/cm3. The snow quenches early reaction of SRM fragments and soft-catches the fragments before impact with the chamber walls. A 100 g cylindrical C-4 explosive charge is used, packed in a 3.3 cm inner diameter SRM casing, with length-to-diameter ratio of L/d = 2, and casing-to-explosive mass ratio of M/C = 1.75. Three types of SRM are investigated, including a baseline of Aluminum 6061 for comparison. The cased charge is suspended in an argon filled cavity, 20 cm in diameter and 40 cm long, within the snow filed chamber.

  12. Fine structure and functional comments of mouthparts in Platypus cylindrus (Col., Curculionidae: Platypodinae).

    Science.gov (United States)

    Belhoucine, Latifa; Bouhraoua, Rachid T; Prats, Eva; Pulade-Villar, Juli

    2013-02-01

    Oak pinhole borer, Platypus cylindrus is seen in recent years as one of the biggest enemies directly involved in the observed decline of cork oak in Mediterranean forests with all the economic implications. As an ambrosia beetle, it has developed its effective drilling mouthpart enough to make tunnels in hardwood of the tree. The fine structural aspects of the mouthpart using the field emission scanning electron microscopy are analyzed about 23 adults collected in galleries of infested cork oak trees (Quercus suber) in a littoral forest of northwest Algeria. These adults are preserved in alcohol 70%, cleaned and coated with gold. The mouthparts of this beetle consist commonly of a labrum, a pair of mandibles, a pair of maxillae and the labium but with adapted structure to excavate galleries in the hardwood. In this role is also involved the first pair of legs. The function that present the different structures related to the construction of the tunnels is discussed. Both of maxillary and labial palpi direct the food to the mouth and hold it while the mandibles chew the food. The distal ends of these palpi are flattened and have shovel-like setae. Females have larger maxillary palpi than males and this is related to the particular biology of each sex.

  13. The Effect of Heat on Structural Characteristics and Water Absorption Behavior of Agave Fibers

    Science.gov (United States)

    Saikia, Dip

    2008-04-01

    The structural characteristics and water absorptions behavior agave fibers were investigated over a range of temperature by using XRD, IR, TG and gravimetric methods. Three distinct thermal processes were observed during heating the fiber in the temperature range 310-760 K in air, oxygen and nitrogen invariably. The cellulose structures of the fibers were unaffected on heating up to 450 K. The samples showed thermal decomposition processes beyond 500 K. Fibers displayed a two-stage diffusion behavior. The structural parameters and kinetic of water absorption of the fibers at specific temperatures were analyzed.

  14. Fine structure of the isoscalar giant quadrupole resonance from high-resolution inelastic proton scattering experiments

    International Nuclear Information System (INIS)

    In the present work the phenomenon of fine structure in the region of the isoscalar giant quadrupole resonance in a number of heavy and medium-heavy nuclei is systematically investigated for the first time. High energy-resolution inelastic proton scattering experiments were carried out in September-October 2001 and in October 2003 at the iThemba LABS cyclotron facility in South Africa with an incident proton energy of 200 MeV. The obtained data with the energy resolution of triangle E58Ni,89Y,90Zr,120Sn,142Nd,166Er,208Pb), thereby establishing the global character of this phenomenon. Fine structure can be described using characteristic energy scales, appearing as a result of the decay of collective modes towards the compound nucleus through a hierarchy of couplings to complex degrees of freedom. For the extraction of the characteristic energy scales from the spectra an entropy index method and a novel technique based on the wavelet analysis are utilized. The global analysis of available data shows the presence of three groups of scales, according to their values. To the first group belong the scales with the values around and below 100 keV, which were detected in all the nuclei studied. The second group contains intermediate scales in the range of 100 keV to 1 MeV. These scales show large variations depending on the nuclear structure of the nucleus. The largest scales above 1 MeV are classified to the third group, describing the global structure of the resonance (the width). The interpretation of the observed scales is realized via the comparison with microscopic model calculations including the coupling of the initial one-particle-one-hole excitations to more complex configurations. A qualitative agreement of the experimentally observed scales with those obtained from the theoretical predictions supports the suggestion of the origin of fine structure from the coupling to the two-particle-two-hole states. However, quantitatively, large deviations are observed for

  15. Observation of the fine structure for rovibronic spectral lines in visible part of emission spectra of $D_2$

    CERN Document Server

    Lavrov, B P; Zhukov, A S

    2011-01-01

    For the first time the fine structure of rovibronic spectral lines in visible part of emission spectra of $D_2$ molecule has been observed. Observed splitting in visible doublets is about 0.2 cm$^{-1}$ in good accordance with previous observations in the infrared part of the spectrum ($a^3\\Sigma_g^+ \\to c^3\\Pi_u$ electronic transition) by means of FTIR and laser spectroscopy. Relative intensities of the fine structure components are in agreement with our calculations of adiabatic line strengths for Hund's case "b" coupling scheme.

  16. Cluster model calculation of N near K-edge energy-loss fine structures in hexagonal GaN crystal

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A cluster model is used to calculate electron energy-loss fine structures in crystal. The multiple-scattering self-consistent-field method is employed in the calculation. Our theoretical results of N near K-edge energy loss fine structures in hexagonal GaN crystal are in good agreement with the experimental spectra. Future possible experiments in energy-filtered transmission electron microscopy (EFTEM) are discussed and proposed because our theoretical work can provide clear assignments for transmitted electrons with different energy losses.

  17. Fine-structure Constant, Anomalous Magnetic Moment, Relativity Factor and the Golden Ratio that Divides the Bohr Radius

    OpenAIRE

    Heyrovska, R.; Narayan, S

    2005-01-01

    Sommerfeld introduced the fine-structure constant into physics, while he was taking into account the relativistic effects in the theory of the hydrogen atom. Ever since, it has puzzled many scientists like Eddington, Dirac, Feynman and others. Here the mysterious fine-structure constant, alpha = (Compton wavelength/de Broglie wavelength) = 1/137.036 = 2.627/360 is interpreted based on the finding that it is close to 2.618/360 = 1/137.508, where the Compton wavelength for hydrogen is a distanc...

  18. Unresolved fine-scale structure in solar coronal loop-tops

    Energy Technology Data Exchange (ETDEWEB)

    Scullion, E.; Van der Voort, L. Rouppe; Wedemeyer, S. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway); Antolin, P., E-mail: scullie@tcd.ie [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2014-12-10

    New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer substructures within coronal loop cross-sections, in order to understand the nature of the solar corona. Here, we push this lower limit further to search for the finest coronal loop substructures, through taking advantage of the resolving power of the Swedish 1 m Solar Telescope/CRisp Imaging Spectro-Polarimeter (CRISP), together with co-observations from the Solar Dynamics Observatory/Atmospheric Image Assembly (AIA). High-resolution imaging of the chromospheric Hα 656.28 nm spectral line core and wings can, under certain circumstances, allow one to deduce the topology of the local magnetic environment of the solar atmosphere where its observed. Here, we study post-flare coronal loops, which become filled with evaporated chromosphere that rapidly condenses into chromospheric clumps of plasma (detectable in Hα) known as a coronal rain, to investigate their fine-scale structure. We identify, through analysis of three data sets, large-scale catastrophic cooling in coronal loop-tops and the existence of multi-thermal, multi-stranded substructures. Many cool strands even extend fully intact from loop-top to footpoint. We discover that coronal loop fine-scale strands can appear bunched with as many as eight parallel strands within an AIA coronal loop cross-section. The strand number density versus cross-sectional width distribution, as detected by CRISP within AIA-defined coronal loops, most likely peaks at well below 100 km, and currently, 69% of the substructure strands are statistically unresolved in AIA coronal loops.

  19. Regulation of the demographic structure in isomorphic biphasic life cycles at the spatial fine scale.

    Directory of Open Access Journals (Sweden)

    Vasco Manuel Nobre de Carvalho da Silva Vieira

    Full Text Available Isomorphic biphasic algal life cycles often occur in the environment at ploidy abundance ratios (Haploid:Diploid different from 1. Its spatial variability occurs within populations related to intertidal height and hydrodynamic stress, possibly reflecting the niche partitioning driven by their diverging adaptation to the environment argued necessary for their prevalence (evolutionary stability. Demographic models based in matrix algebra were developed to investigate which vital rates may efficiently generate an H:D variability at a fine spatial resolution. It was also taken into account time variation and type of life strategy. Ploidy dissimilarities in fecundity rates set an H:D spatial structure miss-fitting the ploidy fitness ratio. The same happened with ploidy dissimilarities in ramet growth whenever reproductive output dominated the population demography. Only through ploidy dissimilarities in looping rates (stasis, breakage and clonal growth did the life cycle respond to a spatially heterogeneous environment efficiently creating a niche partition. Marginal locations were more sensitive than central locations. Related results have been obtained experimentally and numerically for widely different life cycles from the plant and animal kingdoms. Spore dispersal smoothed the effects of ploidy dissimilarities in fertility and enhanced the effects of ploidy dissimilarities looping rates. Ploidy dissimilarities in spore dispersal could also create the necessary niche partition, both over the space and time dimensions, even in spatial homogeneous environments and without the need for conditional differentiation of the ramets. Fine scale spatial variability may be the key for the prevalence of isomorphic biphasic life cycles, which has been neglected so far.

  20. Syntheses and absorption-structure relationships of some new photosensitizer cyanine dyes

    Indian Academy of Sciences (India)

    H A Shindy; A I M Koraiem

    2002-04-01

    New biheterocyclic compound was synthesized as starting material to prepare new photosensitizers mono-, tri-, substituted tri-, azadimethine and mixed cyanine dyes. Absorption-structure relationship of the synthesized cyanine dyes were determined by studying their electronic spectral behaviour in ethanol. The structure of the compounds were identified by elemental analysis, IR and 1H NMR spectral data.

  1. Metapopulation structure and fine-scaled genetic structuring in crop-wild hybrid weed beets

    OpenAIRE

    Arnaud, J-F; Cuguen, J.; Fénart, S

    2011-01-01

    This study explores the microspatial and temporal genetic variation in crop-wild hybrid weed beets that emerged from the seed bank in a cultivated field surveyed over two successive years. We demonstrate the occurrence of demes highly genetically differentiated, kin-structured, characterized by moderate effective population sizes, differing in propensity for selfing, and arising from nonrandom genetic subsets of the seed bank. Only one deme identified in the first survey year significantly co...

  2. Rotational and Fine Structure of Pseudo-Jahn Molecules with C_1 Symmetry

    Science.gov (United States)

    Liu, Jinjun

    2016-06-01

    It has been found in our previous works that rotational and fine-structure analysis of spectra involving nearly degenerate electronic states may aid in interpretation and analysis of the vibronic structure, specifically in the case of pseudo-Jahn-Teller (pJT) molecules with C_s symmetry. The spectral analysis of pJT derivatives (isopropoxy and cyclohexoxy of a prototypical JT molecule (the methoxy radical) allowed for quantitative determination of various contributions to the energy separation between the nearly degenerate electronic states, including the relativistic spin-orbit (SO) effect, the electrostatic interaction, and their zero-point energy difference. These states are coupled by SO and Coriolis interactions, which can also be determined accurately in rotational and fine structure analysis. Most recently, the spectroscopic model for rotational analysis of pJT molecules has been extended for analysis of molecules with C_1 symmetry, i.e., no symmetry. This model includes the six independently determinable components of the spin-rotation (SR) tensor and the three components of the SO and Coriolis interactions. It has been employed to simulate and fit high-resolution laser-induced fluorescence (LIF) spectra of jet-cooled alkoxy radicals with C_1 symmetry, including the 2-hexoxy and the 2-pentoxy radicals, as well as previously recorded LIF spectrum of the trans-conformer (defined by its OCCC dihedral angle) of the 2-butoxy radical. Although the LIF spectra can be reproduced by using either the SR constants or SO and Coriolis constants, the latter simulation offers results that are physically more meaningful whereas the SR constants have to be regarded as effective constants. Furthermore, we will review the SO and Coriolis constants of alkoxy radicals that have been investigated, starting from the well-studied methoxy radical (CH_3O). J. Liu, D. Melnik, and T. A. Miller, J. Chem. Phys. 139, 094308 (2013) J. Liu and T. A. Miller, J. Phys. Chem. A 118, 11871

  3. Micro-X-ray absorption near edge structure spectroscopy investigations of baroque tin-amalgam mirrors at BESSY using a capillary focusing system

    Science.gov (United States)

    Bartoll, J.; Röhrs, S.; Erko, A.; Firsov, A.; Bjeoumikhov, A.; Langhoff, N.

    2004-10-01

    An elliptically shaped glass monocapillary with a spatial resolution of 5 μm has been used for the fine focusing of the pre-focused X-ray beam produced by the graded-crystal monochromator beamline, KMC-2. The flux density gain of 50 was experimentally measured. The microprobe has been used in the energy range of 3.5-15 keV. Micro-X-ray fluorescence analysis (μXFA) and micro-X-ray absorption near edge structure spectroscopy (μXANES) measurements on test samples and investigations of baroque tin-amalgam mirrors were done.

  4. Micro-X-ray absorption near edge structure spectroscopy investigations of baroque tin-amalgam mirrors at BESSY using a capillary focusing system

    Energy Technology Data Exchange (ETDEWEB)

    Bartoll, J. [Stiftung Preussische Schloesser und Gaerten, Postfach 601462, 14414 Potsdam (Germany); Roehrs, S. [Technische Universitaet Berlin, Institut fuer Chemie, Strasse des 17. Juni 135, 10623 Berlin (Germany); Erko, A. [Berliner Elektronenspeicherring-Gesellschaft fuer Synchrotronstrahlung (BESSY) mbH, Albert-Einstein Str. 15, 12489 Berlin (Germany)]. E-mail: erko@bessy.de; Firsov, A. [Berliner Elektronenspeicherring-Gesellschaft fuer Synchrotronstrahlung (BESSY) mbH, Albert-Einstein Str. 15, 12489 Berlin (Germany); Bjeoumikhov, A. [IfG-Institut fuer Geraetebau GmbH Rudower Chaussee, 29-31, 12489 Berlin (Germany); Langhoff, N. [IfG-Institut fuer Geraetebau GmbH Rudower Chaussee, 29-31, 12489 Berlin (Germany)

    2004-10-08

    An elliptically shaped glass monocapillary with a spatial resolution of 5 {mu}m has been used for the fine focusing of the pre-focused X-ray beam produced by the graded-crystal monochromator beamline, KMC-2. The flux density gain of 50 was experimentally measured. The microprobe has been used in the energy range of 3.5-15 keV. Micro-X-ray fluorescence analysis ({mu}XFA) and micro-X-ray absorption near edge structure spectroscopy ({mu}XANES) measurements on test samples and investigations of baroque tin-amalgam mirrors were done.

  5. Fine-scale genetic structure of grape phylloxera from the roots and leaves of Vitis.

    Science.gov (United States)

    Corrie, A M; Hoffmann, A A

    2004-02-01

    Patterns of variation at microsatellite loci suggest that root populations of the pest grape phylloxera (Daktulosphaira vitifoliae) are largely parthenogenetic in Australian vineyards. To investigate reproduction in leaf galling phylloxera and the association between these individuals and phylloxera on roots, we examined in detail genetic variation in phylloxera from a vineyard block. Some genotypes found on leaf galls within this block were not present on roots, whereas others spanned both zones. There was no evidence that genotypes on roots were the product of sexual reproduction in leaf galls. mtDNA variation was not associated with the location of the phylloxera clones. The spatial distribution of genotypes within a root population was further investigated by intensively sampling phylloxera from another vineyard block. Join-count spatial autocorrelation statistics were used to explore fine-scale spatial structure. Clones were nonrandomly distributed within the block and there was evidence that the distribution of clones followed rows. These findings suggest firstly that there is limited dispersal of root and leaf feeding phylloxera, and secondly that factors, other than vine host, are likely to be important and contribute to clonal structure within populations. PMID:14679391

  6. Fine resolution mapping of population age-structures for health and development applications.

    Science.gov (United States)

    Alegana, V A; Atkinson, P M; Pezzulo, C; Sorichetta, A; Weiss, D; Bird, T; Erbach-Schoenberg, E; Tatem, A J

    2015-04-01

    The age-group composition of populations varies considerably across the world, and obtaining accurate, spatially detailed estimates of numbers of children under 5 years is important in designing vaccination strategies, educational planning or maternal healthcare delivery. Traditionally, such estimates are derived from population censuses, but these can often be unreliable, outdated and of coarse resolution for resource-poor settings. Focusing on Nigeria, we use nationally representative household surveys and their cluster locations to predict the proportion of the under-five population in 1 × 1 km using a Bayesian hierarchical spatio-temporal model. Results showed that land cover, travel time to major settlements, night-time lights and vegetation index were good predictors and that accounting for fine-scale variation, rather than assuming a uniform proportion of under 5 year olds can result in significant differences in health metrics. The largest gaps in estimated bednet and vaccination coverage were in Kano, Katsina and Jigawa. Geolocated household surveys are a valuable resource for providing detailed, contemporary and regularly updated population age-structure data in the absence of recent census data. By combining these with covariate layers, age-structure maps of unprecedented detail can be produced to guide the targeting of interventions in resource-poor settings. PMID:25788540

  7. Mineralogical properties and internal structures of individual fine particles of Saharan dust

    Science.gov (United States)

    Jeong, Gi Young; Park, Mi Yeon; Kandler, Konrad; Nousiainen, Timo; Kemppinen, Osku

    2016-10-01

    Mineral dust interacts with incoming/outgoing radiation, gases, other aerosols, and clouds. The assessment of its optical and chemical impacts requires knowledge of the physical and chemical properties of bulk dust and single particles. Despite the existence of a large body of data from field measurements and laboratory analyses, the internal properties of single dust particles have not been defined precisely. Here, we report on the mineralogical organization and internal structures of individual fine ( common particle type was clay-rich agglomerate, dominated by illite-smectite series clay minerals with subordinate kaolinite. Submicron grains of iron (hydr)oxides (goethite and hematite) were commonly dispersed through the clay-rich particles. The median total volume of the iron (hydr)oxide grains included in the dust particles was estimated to be about 1.5 % vol. The average iron content of clay minerals, assuming 14 wt % H2O, was determined to be 5.0 wt %. Coarse mineral cores, several micrometers in size, were coated with thin layers of clay-rich agglomerate. Overall, the dust particles were roughly ellipsoidal, with an average axial ratio of 1.4 : 1.0 : 0.5. The mineralogical and structural properties of single Saharan dust particles provide a basis for the modeling of dust radiative properties. Major iron-bearing minerals, such as illite-smectite series clay minerals and iron (hydr)oxides, were commonly submicron- to nano-sized, possibly enhancing their biogeochemical availability to remote marine ecosystems lacking micronutrients.

  8. Electronic fine structure in the nickel carbide superconductor Th2NiC2

    Science.gov (United States)

    Quan, Y.; Pickett, W. E.

    2013-07-01

    The recently reported nickel carbide superconductor body centered tetragonal I4/mmm Th2NiC2 with Tc=8.5 K increasing to 11.2 K upon alloying Th with Sc is found to have very fine structure in its electronic spectrum, according to density functional based first-principles calculations. The filled Ni 3d band complex is hybridized with C 2p and Th character to and through the Fermi level (EF), and a sharply structured density of states arises only when spin-orbit coupling is included, which splits a zone-center degeneracy, leaving a very flat band edge lying at the Fermi level. The flat part of the band corresponds to an effective mass mz*→∞ with large and negative mx*=my*. Although the region over which the effective mass characterization applies is less than 1% of the zone volume, it supplies on the order of half the states at (or just above) the Fermi level. The observed increase of Tc by hole doping is accounted for if the reference as-synthesized sample is minutely hole doped, which decreases the Fermi level density of states and will provide some stabilization. In this scenario, electron doping will increase the Fermi level density of states and the superconducting critical temperature. Vibrational properties are presented, and enough coupling to the C-Ni-C stretch mode at 70 meV is obtained to imply that superconductivity is electron-phonon mediated.

  9. Polyphenols from Bee Pollen: Structure, Absorption, Metabolism and Biological Activity

    Directory of Open Access Journals (Sweden)

    Anna Rzepecka-Stojko

    2015-12-01

    Full Text Available Bee pollen constitutes a natural source of antioxidants such as phenolic acids and flavonoids, which are responsible for its biological activity. Research has indicated the correlation between dietary polyphenols and cardioprotective, hepatoprotective, anti-inflammatory, antibacterial, anticancerogenic, immunostimulating, antianaemic effects, as well as their beneficial influence on osseous tissue. The beneficial effects of bee pollen on health result from the presence of phenolic acids and flavonoids which possess anti-inflammatory properties, phytosterol and linolenic acid which play an anticancerogenic role, and polysaccharides which stimulate immunological activity. Polyphenols are absorbed in the alimentary tract, metabolised by CYP450 enzymes, and excreted with urine and faeces. Flavonoids and phenolic acids are characterised by high antioxidative potential, which is closely related to their chemical structure. The high antioxidant potential of phenolic acids is due to the presence and location of hydroxyl groups, a carboxyl group in the immediate vicinity of ortho-diphenolic substituents, and the ethylene group between the phenyl ring and the carboxyl group. As regards flavonoids, essential structural elements are hydroxyl groups at the C5 and C7 positions in the A ring, and at the C3′ and C4′ positions in the B ring, and a hydroxyl group at the C3 position in the C ring. Furthermore, both, the double bond between C2 and C3, and a ketone group at the C4 position in the C ring enhance the antioxidative potential of these compounds. Polyphenols have an ideal chemical structure for scavenging free radicals and for creating chelates with metal ions, which makes them effective antioxidants in vivo.

  10. Evidence for the distortion product frequency place as a source of distribution product otoacoustic emission (DPOAE) fine structure in humans. I. Fine structure and higher-order DPOAE as a function of the frequency ratio f2/f1

    NARCIS (Netherlands)

    Mauermann, M; Uppenkamp, S; van Hengel, PWJ; Kollmeier, B

    1999-01-01

    Critical experiments were performed in order to validate the two-source hypothesis of distortion product otoacoustic emissions (DPOAE) generation. Measurements of the spectral fine structure of DPOAE in response to stimulation with two sinusoids have been:performed with normal-hearing subjects. The

  11. Cultural transmission of tool use combined with habitat specializations leads to fine-scale genetic structure in bottlenose dolphins

    OpenAIRE

    Kopps, Anna M.; Ackermann, Corinne Y.; William B Sherwin; Simon J Allen; Bejder, Lars; Krützen, Michael

    2014-01-01

    Socially learned behaviours leading to genetic population structure have rarely been described outside humans. Here, we provide evidence of fine-scale genetic structure that has probably arisen based on socially transmitted behaviours in bottlenose dolphins (Tursiops sp.) in western Shark Bay, Western Australia. We argue that vertical social transmission in different habitats has led to significant geographical genetic structure of mitochondrial DNA (mtDNA) haplotypes. Dolphins with mtDNA hap...

  12. Metapopulation structure and fine-scaled genetic structuring in crop-wild hybrid weed beets.

    Science.gov (United States)

    Arnaud, J-F; Cuguen, J; Fénart, S

    2011-10-01

    This study explores the microspatial and temporal genetic variation in crop-wild hybrid weed beets that emerged from the seed bank in a cultivated field surveyed over two successive years. We demonstrate the occurrence of demes highly genetically differentiated, kin-structured, characterized by moderate effective population sizes, differing in propensity for selfing, and arising from nonrandom genetic subsets of the seed bank. Only one deme identified in the first survey year significantly contributed to the weed beets that emerged in the second year. Spatial structuring appears to be primarily due to gravity seed dispersal and limited pollen flow among weed beet demes. Within each genetic cluster identified by Bayesian assignments and multivariate analyses, F(IS) estimates and level of biparental inbreeding--revealed by progeny analyses--dropped to non-significant values. This suggests that random mating occurs at the scale of genetically distinct demes over a very short scale. Our results highlight the need to carefully depict genetic discontinuities in weed species, when attempting to describe their local genetic neighborhoods within which genetic drift and selective processes occur.

  13. Metapopulation structure and fine-scaled genetic structuring in crop-wild hybrid weed beets.

    Science.gov (United States)

    Arnaud, J-F; Cuguen, J; Fénart, S

    2011-10-01

    This study explores the microspatial and temporal genetic variation in crop-wild hybrid weed beets that emerged from the seed bank in a cultivated field surveyed over two successive years. We demonstrate the occurrence of demes highly genetically differentiated, kin-structured, characterized by moderate effective population sizes, differing in propensity for selfing, and arising from nonrandom genetic subsets of the seed bank. Only one deme identified in the first survey year significantly contributed to the weed beets that emerged in the second year. Spatial structuring appears to be primarily due to gravity seed dispersal and limited pollen flow among weed beet demes. Within each genetic cluster identified by Bayesian assignments and multivariate analyses, F(IS) estimates and level of biparental inbreeding--revealed by progeny analyses--dropped to non-significant values. This suggests that random mating occurs at the scale of genetically distinct demes over a very short scale. Our results highlight the need to carefully depict genetic discontinuities in weed species, when attempting to describe their local genetic neighborhoods within which genetic drift and selective processes occur. PMID:21448229

  14. FINE STRAND-LIKE STRUCTURE IN THE SOLAR CORONA FROM MAGNETOHYDRODYNAMIC TRANSVERSE OSCILLATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Antolin, P. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Yokoyama, T. [Department of Earth and Planetary Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Van Doorsselaere, T., E-mail: patrick.antolin@nao.ac.jp [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, Bus 2400, B-3001 Leuven (Belgium)

    2014-06-01

    Current analytical and numerical modeling suggest the existence of ubiquitous thin current sheets in the corona that could explain the observed heating requirements. On the other hand, new high resolution observations of the corona indicate that its magnetic field may tend to organize itself in fine strand-like structures of few hundred kilometers widths. The link between small structure in models and the observed widths of strand-like structure several orders of magnitude larger is still not clear. A popular theoretical scenario is the nanoflare model, in which each strand is the product of an ensemble of heating events. Here, we suggest an alternative mechanism for strand generation. Through forward modeling of three-dimensional MHD simulations we show that small amplitude transverse MHD waves can lead in a few periods time to strand-like structure in loops in EUV intensity images. Our model is based on previous numerical work showing that transverse MHD oscillations can lead to Kelvin-Helmholtz instabilities that deform the cross-sectional area of loops. While previous work has focused on large amplitude oscillations, here we show that the instability can occur even for low wave amplitudes for long and thin loops, matching those presently observed in the corona. We show that the vortices generated from the instability are velocity sheared regions with enhanced emissivity hosting current sheets. Strands result as a complex combination of the vortices and the line-of-sight angle, last for timescales of a period, and can be observed for spatial resolutions of a tenth of loop radius.

  15. Benthic biofilm structure controls the deposition-resuspension dynamics of fine clay particles

    Science.gov (United States)

    Hunter, W. R.; Roche, K. R.; Drummond, J. D.; Boano, F.; Packman, A. I.; Battin, T. J.

    2015-12-01

    In fluvial ecosystems the alternation of deposition and resuspension of particles represents an important pathway for the downstream translocation of microbes and organic matter. Such particles can originate from algae and microbes, the spontaneous auto-aggregation of organic macromolecules (e.g., "river sown"), terrestrial detritus (traditionally classified as "particulate organic matter"), and erosive mineral and organo-mineral particles. The transport and retention of particles in headwater streams is associated with biofilms, which are surface-attached microbial communities. Whilst biofilm-particle interactions have been studied in bulk, a mechanistic understanding of these processes is lacking. Parallel macroscale/microscale observations are required to unravel the complex feedbacks between biofilm structure, coverage and the dynamics of deposition and resuspension. We used recirculating flume mesocosms to test how changes in biofilm structure affected the deposition and resuspension of clay-sized (Biofilms were grown in replicate 3-m-long recirculating flumes over variable lengths of time (0, 14, 21, 28, and 35) days. Fixed doses of fluorescent clay-sized particles were introduced to each flume and their deposition was traced over 30 minutes. A flood event was then simulated via a step increase in flowrate to quantify particle resuspension. 3D Optical Coherence Tomography was used to determine roughness, areal coverage and height of biofilms in each flume. From these measurements we characterised particle deposition and resuspension rates, using continuous time random walk modelling techniques, which we then tested as responses to changes in biofilm coverage and structure under both base-flow and flood-flow scenarios. Our results suggest that biofilm structural complexity is a primary control upon the retention and downstream transport of fine particles in stream mesocosms.

  16. Acoustic contributions of a sound absorbing blanket placed in a double panel structure: Absorption Versus Transmission

    CERN Document Server

    Doutres, Olivier; 10.1121/1.3458845

    2010-01-01

    The objective of this paper is to propose a simple tool to estimate the absorption vs. transmission loss contributions of a multilayered blanket unbounded in a double panel structure and thus guide its optimization. The normal incidence airborne sound transmission loss of the double panel structure, without structure-borne connections, is written in terms of three main contributions; (i) sound transmission loss of the panels, (ii) sound transmission loss of the blanket and (iii) sound absorption due to multiple reflections inside the cavity. The method is applied to four different blankets frequently used in automotive and aeronautic applications: a non-symmetric multilayer made of a screen in sandwich between two porous layers and three symmetric porous layers having different pore geometries. It is shown that the absorption behavior of the blanket controls the acoustic behavior of the treatment at low and medium frequencies and its transmission loss at high frequencies. Acoustic treatment having poor sound ...

  17. Fine-structure energy levels and radiative decay rates in Al-like vanadium

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, G P [Department of Physics, S D (Postgraduate) College, Muzaffarnagar-251 001 (Affiliated to Chowdhary Charan Singh University, Meerut - 250 004) (India); Msezane, A Z [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta, GA 30314 (United States)], E-mail: g_p_gupta1@yahoo.co.in

    2010-04-15

    Large-scale calculations of excitation energies from ground state for 97 fine-structure levels as well as of oscillator strengths and radiative decay rates for all electric-dipole-allowed and intercombination transitions among the (1s{sup 2}2s{sup 2}2p{sup 6})3s{sup 2}3p({sup 2}P{sup 0}), 3s3p{sup 2}({sup 2}S,{sup 2}P,{sup 2}D,{sup 4}P), 3s{sup 2}3d({sup 2}D), 3p{sup 3}({sup 4}S{sup 0},{sup 2}P{sup 0},{sup 2}D{sup 0}), 3s3p({sup 3}P{sup 0})3d({sup 2}P{sup 0},{sup 2}D{sup 0},{sup 2}F{sup 0},{sup 4}P{sup 0},{sup 4}D{sup 0},{sup 4}F{sup 0}), 3s3p({sup 1}P{sup 0})3d({sup 2}P{sup 0},{sup 2}D{sup 0},{sup 2}F{sup 0}), 3p{sup 2}({sup 1}S)3d({sup 2}D), 3p{sup 2}({sup 1}D)3d({sup 2}S,{sup 2}P,{sup 2}D,{sup 2}F,{sup 2}G), 3p{sup 2}({sup 3}P)3d({sup 2}P,{sup 2}D,{sup 2}F,{sup 4}P,{sup 4}D,{sup 4}F), 3s3d{sup 2}({sup 2}S,{sup 2}P,{sup 2}D,{sup 2}F,{sup 2}G,{sup 4}P,{sup 4}F), 3s{sup 2}4s({sup 2}S), 3s{sup 2}4p({sup 2}P{sup 0}), 3s{sup 2}4d({sup 2}D), 3s{sup 2}4f({sup 2}F{sup 0}), 3s3p({sup 3}P{sup 0})4s({sup 2}P{sup 0},{sup 4}P{sup 0}) and 3s3p({sup 1}P{sup 0})4s({sup 2}P{sup 0}) states of V XI are performed using extensive configuration-interaction (CI) wavefunctions. The calculations used the CIV3 computer code of Hibbert. The important relativistic effects in intermediate coupling are incorporated by means of the Breit-Pauli Hamiltonian. In order to keep our calculated energy splittings as close as possible to the National Institute of Standard and Technology (NIST) values, we have made small adjustments to the diagonal elements of the Hamiltonian matrices. Our calculated excitation energies, including their ordering, are in excellent agreement with the available NIST results. From our radiative decay rates, we have also calculated radiative lifetimes of some fine-structure levels. Generally, very good agreement between our calculated lifetimes and those from sophisticated calculation is realized for many fine-structure levels. However, a few significant differences are

  18. Novel laboratory methods for determining the fine scale electrical resistivity structure of core

    Science.gov (United States)

    Haslam, E. P.; Gunn, D. A.; Jackson, P. D.; Lovell, M. A.; Aydin, A.; Prance, R. J.; Watson, P.

    2014-12-01

    High-resolution electrical resistivity measurements are made on saturated rocks using novel laboratory instrumentation and multiple electrical voltage measurements involving in principle a four-point electrode measurement but with a single, moving electrode. Flat, rectangular core samples are scanned by varying the electrode position over a range of hundreds of millimetres with an accuracy of a tenth of a millimetre. Two approaches are tested involving a contact electrode and a non-contact electrode arrangement. The first galvanic method uses balanced cycle switching of a floating direct current (DC) source to minimise charge polarisation effects masking the resistivity distribution related to fine scale structure. These contacting electrode measurements are made with high common mode noise rejection via differential amplification with respect to a reference point within the current flow path. A computer based multifunction data acquisition system logs the current through the sample and voltages along equipotentials from which the resistivity measurements are derived. Multiple measurements are combined to create images of the surface resistivity structure, with variable spatial resolution controlled by the electrode spacing. Fine scale sedimentary features and open fractures in saturated rocks are interpreted from the measurements with reference to established relationships between electrical resistivity and porosity. Our results successfully characterise grainfall lamination and sandflow cross-stratification in a brine saturated, dune bedded core sample representative of a southern North Sea reservoir sandstone, studied using the system in constant current, variable voltage mode. In contrast, in a low porosity marble, identification of open fracture porosity against a background very low matrix porosity is achieved using the constant voltage, variable current mode. This new system is limited by the diameter of the electrode that for practical reasons can only be

  19. Changes in the Fine Structure of Stochastic Distributions as a Consequence of Space-Time Fluctuations

    Directory of Open Access Journals (Sweden)

    Shnoll S. E.

    2006-04-01

    Full Text Available This is a survey of the fine structure stochastic distributions in measurements obtained by me over 50 years. It is shown: (1 The forms of the histograms obtained at each geographic point (at each given moment of time are similar with high probability, even if we register phenomena of completely different nature — from biochemical reactions to the noise in a gravitational antenna, or α-decay. (2 The forms of the histograms change with time. The iterations of the same form have the periods of the stellar day (1.436 min, the solar day (1.440 min, the calendar year (365 solar days, and the sidereal year (365 solar days plus 6 hours and 9 min. (3 At the same instants of the local time, at different geographic points, the forms of the histograms are the same, with high probability. (4 The forms of the histograms depend on the locations of the Moon and the Sun with respect to the horizon. (5 All the facts are proof of the dependance of the form of the histograms on the location of the measured objects with respect to stars, the Sun, and the Moon. (6 At the instants of New Moon and the maxima of solar eclipses there are specific forms of the histograms. (7 It is probable that the observed correlations are not connected to flow power changes (the changes of the gravity force — we did not find the appropriate periods in changes in histogram form. (8 A sharp anisotropy of space was discovered, registered by α-decay detectors armed with collimators. Observations at 54◦ North (the collimator was pointed at the Pole Star showed no day-long periods, as was also the case for observations at 82◦ North, near the Pole. Histograms obtained by observations with an Easterly-directed collimator were determined every 718 minutes (half stellar day and with observations using a Westerly-directed collimator. (9 Collimators rotating counter-clockwise, in parallel with the celestial equator, gave the probability of changes in histograms as the number of the

  20. Changes in the Fine Structure of Stochastic Distributions as a Consequence of Space-Time Fluctuations

    Directory of Open Access Journals (Sweden)

    Shnoll S. E.

    2006-04-01

    Full Text Available This is a survey of the fine structure stochastic distributions in measurements obtained by me over 50 years. It is shown: (1 The forms of the histograms obtained at each geographic point (at each given moment of time are similar with high probability, even if we register phenomena of completely different nature --- from biochemical reactions to the noise in a gravitational antenna, or alpha-decay. (2 The forms of the histograms change with time. The iterations of the same form have the periods of the stellar day (1.436 min, the solar day (1.440 min, the calendar year (365 solar days, and the sidereal year (365 solar days plus 6 hours and 9 min. (3 At the same instants of the local time, at different geographic points, the forms of the histograms are the same, with high probability. (4 The forms of the histograms depend on the locations of the Moon and the Sun with respect to the horizon. (5 All the facts are proof of the dependance of the form of the histograms on the location of the measured objects with respect to stars, the Sun, and the Moon. (6 At the instants of New Moon and the maxima of solar eclipses there are specific forms of the histograms. (7 It is probable that the observed correlations are not connected to flow power changes (the changes of the gravity force --- we did not find the appropriate periods in changes in histogram form. (8 A sharp anisotropy of space was discovered, registered by alpha-decay detectors armed with collimators. Observations at 54 North (the collimator was pointed at the Pole Star showed no day-long periods, as was also the case for observations at 82 North, near the Pole. Histograms obtained by observations with an Easterly-directed collimator were determined every 718 minutes (half stellar day and with observations using a Westerly-directed collimator. (9 Collimators rotating counter-clockwise, in parallel with the celestial equator, gave the probability of changes in histograms as the number of the