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Sample records for adsorption fine structure

  1. Mechanism of Pb Adsorption to Fatty Acid Langmuir Monolayers Studied by X-ray Absorption Fine Structure Spectroscopy

    SciTech Connect

    Boyanov, M.I.; Kmetko, J.; Shibata, T.; Datta, A.; Dutta, P.; Bunker, B.A.

    2010-09-30

    The local atomic environment of lead (Pb) adsorbed to a CH{sub 3}(CH{sub 2}){sub 19}COOH Langmuir monolayer was investigated in situ using grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy at the Pb L{sub III} edge. Measurements were performed at pH 6.5 of the 10{sup -5} M PbCl{sub 2} solution subphase, a condition under which grazing incidence diffraction (GID) revealed a large-area commensurate superstructure underneath the close-packed organic monolayer. The XAFS results indicate covalent binding of the Pb cations to the carboxyl headgroups, and the observed Pb-Pb coordination suggests that the metal is adsorbed as a hydrolysis polymer, rather than as individual Pb{sup 2+} ions. The data are consistent with a bidentate chelating mechanism and a one Pb atom to one carboxyl headgroup binding stoichiometry. We discuss how this adsorption model can explain the peculiarities observed with Pb in previous metal-Langmuir monolayer studies. A systematic study of lead perchlorate and lead acetate aqueous solutions is presented and used in the analysis. XAFS multiple scattering effects from alignment of the Pb-C-C atoms in the lead acetate solutions are reported.

  2. Adsorption and stability of malonic acid on rutile TiO2 (110), studied by near edge X-ray absorption fine structure and photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Syres, Karen L.; Thomas, Andrew G.; Graham, Darren M.; Spencer, Ben F.; Flavell, Wendy R.; Jackman, Mark J.; Dhanak, Vinod R.

    2014-08-01

    The adsorption of malonic acid on rutile TiO2 (110) has been studied using photoelectron spectroscopy and C K-edge, near edge X-ray fine structure spectroscopy (NEXAFS). Analysis of the O 1s and Ti 2p spectra suggest that the molecule adsorbs dissociatively in a doubly-bidentate adsorption geometry as malonate. The data are unable to distinguish between a chelating bonding mode with the backbone of the molecule lying along the [001] azimuth or a bridging geometry along the direction. Work carried out on a wiggler beamline suggests that the molecule is unstable under irradiation by high-flux synchrotron radiation from this type of insertion device.

  3. Adsorption site and structure determination of c(2x2) N{sub 2}/Ni(100) using angle-resolved photoemission extended fine structure

    SciTech Connect

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A.

    1997-04-01

    The authors have determined the atomic spatial structure of c(2x2) N2Ni(100) with Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) from the nitrogen 1s core level using monochromatized x-rays from beamline 6.1 at SSRL and beamline 9.3.2 at the ALS. The chemically shifted N 1s peak intensities were summed together to obtain ARPEFS curves for both nitrogen atoms in the molecule. They used a new, highly-optimized program based on the Rehr-Albers scattering matrix formalism to find the adsorption site and to quantitatively determine the bond-lengths. The nitrogen molecule stands upright at an atop site, with a N-Ni bond length of 2.25(1) {angstrom}, a N-N bond length of 1.10(7) {angstrom}, and a first layer Ni-Ni spacing of 1.76(4) {angstrom}. The shake-up peak shows an identical ARPEFS diffraction pattern, confirming its intrinsic nature and supporting a previous use of this feature to decompose the peak into contributions from the chemically inequivalent nitrogen atoms. Comparison to a previously published theoretical treatment of N-N-Ni and experimental structures of analogous adsorbate systems demonstrates the importance of adsorbate-adsorbate interactions in weakly chemisorbed systems.

  4. Adsorption site and structure determination of c(2 × 2) N2/Ni(100) using angle-resolved photoemission extended fine structure

    NASA Astrophysics Data System (ADS)

    Moler, Edward J.; Kellar, Scot A.; Huff, W. R. A.; Hussain, Zahid; Zheng, Yu; Hudson, Eric A.; Chen, Yufeng; Shirley, David A.

    1997-01-01

    We have determined the atomic spatial structure of c(2 × 2) N2/Ni(100) with angle-resolved photoemission extended fine structure using the nitrogen 1s core level. The chemically shifted N 1s peak intensities were summed to obtain ARPEFS curves for both nitrogen atoms in the molecule. We used a new, highly optimized program based on the Rehr-Albers scattering matrix formalism to find the adsorption site and to determine the bond lengths quantitatively. The nitrogen molecule stands upright at an atop site, with a NNi bond length of 2.25(1) Å, a NN bond length of 1.10(7) Å, and a first layer NiNi spacing of 1.76(4) Å. The shake-up peak shows an identical ARPEFS diffraction pattern, confirming its intrinsic nature and supporting a previous use of this feature to decompose the peak into contributions from the chemically inequivalent nitrogen atoms. Comparison to a previously published theoretical treatment of NNNi and experimental structures of analogous adsorbate systems demonstrates the importance of adsorbate-adsorbate interactions in weakly chemisorbed systems.

  5. Low-temperature adsorption of H2S on Ni(001) studied by near-edge- and surface-extended-x-ray-absorption fine structure

    NASA Astrophysics Data System (ADS)

    McGrath, R.; MacDowell, A. A.; Hashizume, T.; Sette, F.; Citrin, P. H.

    1989-11-01

    The adsorption of H2S on Ni(001) has been studied with surface-extended x-ray-absorption fine structure and near-edge x-ray-absorption fine structure (NEXAFS) using the AT&T Bell Laboratories X15B beamline at the National Synchrotron Light Source. At 95 K and full saturation coverage, ~0.45 monolayer (ML) of S atoms in fourfold-hollow sites are produced, characteristic of room-temperature adsorption, accompanied by ~0.05 ML of oriented molecular H2S. Both these atomic and molecular chemisorbed species are buried under ~0.9 ML of disordered physisorbed H2S. No evidence for HS is found. Above 190 K the two molecular H2S phases desorb, leaving only dissociated S. These findings differ from previously reported interpretations of data obtained with high-resolution electron-energy-loss spectroscopy. They also exemplify the utility of NEXAFS for identifying and quantifying atomic and molecular surface species even when their difference involves only H and the two species coexist.

  6. Insights from arsenate adsorption on rutile (110): grazing-incidence X-ray absorption fine structure spectroscopy and DFT+U study.

    PubMed

    Yan, Li; Hu, Shan; Duan, Jinming; Jing, Chuanyong

    2014-07-03

    Insights into the bonding of As(V) at the metal oxide/aqueous interface can further our understanding of its fate and transport in the environment. The motivation of this work is to explore the interfacial configuration of As(V) on single crystal rutile (110) using grazing-incidence X-ray absorption fine structure spectroscopy (GI-XAFS) and planewave density functional calculations with on-site repulsion (DFT+U). In contrast to the commonly considered corner-sharing bidentate binuclear structure, tetrahedral As(V) binds as an edge/corner-sharing tridentate binuclear complex on rutile (110), as evidenced by observation of three As-Ti distances at 2.83, 3.36, and 4.05 Å. In agreement with the GI-XAFS analysis, our DFT+U calculations for this configuration resulted in the lowest adsorption energy among five possible alternatives. In addition, the electron density difference further demonstrated the transfer of charge between surface Ti atoms and O atoms in AsO4. This charge transfer consequently induced the formation of a chemical bond, which is also confirmed by the partial density of states analysis. Our results may shed new light on coupling the GI-XAFS and DFT approaches to explore molecular-scale adsorption mechanisms on single crystal surfaces.

  7. Experimental study of germanium adsorption on goethite and germanium coprecipitation with iron hydroxide: X-ray absorption fine structure and macroscopic characterization

    NASA Astrophysics Data System (ADS)

    Pokrovsky, O. S.; Pokrovski, G. S.; Schott, J.; Galy, A.

    2006-07-01

    Adsorption of germanium on goethite was studied at 25 °C in batch reactors as a function of pH (1-12), germanium concentration in solution (10 -7 to 0.002 M) and solid/solution ratio (1.8-17 g/L). The maximal surface site density determined via Ge adsorption experiments at pH from 6 to 10 is equal to 2.5 ± 0.1 μmol/m 2. The percentage of adsorbed Ge increases with pH at pH < 9, reaches a maximum at pH ˜ 9 and slightly decreases when pH is further increased to 11. These results allowed generation of a 2-p K Surface Complexation Model (SCM) which implies a constant capacitance of the electric double layer and postulates the presence of two Ge complexes, >FeO-Ge(OH)30 and >FeO-GeO(OH)2-, at the goethite-solution interface. Coprecipitation of Ge with iron oxy(hydr)oxides formed during Fe(II) oxidation by atmospheric oxygen or by Fe(III) hydrolysis in neutral solutions led to high Ge incorporations in solid with maximal Ge/Fe molar ratio close to 0.5. The molar Ge/Fe ratio in precipitated solid is proportional to that in the initial solution according to the equation (Ge/Fe) solid = k × (Ge/Fe) solution with 0.7 ⩽ k ⩽ 1.0. The structure of adsorbed and coprecipitated Ge complexes was further characterized using XAFS spectroscopy. In agreement with previous data on oxyanions adsorption on goethite, bi-dentate bi-nuclear surface complexes composed of tetrahedrally coordinated Ge attached to the corners of two adjacent Fe octahedra represent the dominant contribution to the EXAFS signal. Coprecipitated samples with Ge/Fe molar ratios >0.1, and samples not aged in solution (<1 day) having intermediate Ge/Fe ratios (0.01-0.1) show 4 ± 0.3 oxygen atoms at 1.76 ± 0.01 Å around Ge. Samples less concentrated in Ge (0.001 < Ge/Fe < 0.10) and aged longer times in solution (up to 280 days) exhibit a splitting of the first atomic shell with Ge in both tetrahedral ( R = 1.77 ± 0.02 Å) and octahedral ( R = 1.92 ± 0.03 Å) coordination with oxygen. In these samples

  8. Fine structure in krypton excimer

    SciTech Connect

    Hemici, M.; Saoudi, R.; Descroix, E.; Audouard, E.; Laporte, P. ); Spiegelmann, F. )

    1995-04-01

    By using laser reduced fluorescence techniques, molecular absorption from the first relaxed excited excimer states of krypton is obtained in the 960--990-nm wavelength range. Five bands are observed and analyzed by comparison with an [ital ab] [ital initio] calculated spectrum. The fine structure is thus evidenced.

  9. Fine structures at pore boundary

    NASA Astrophysics Data System (ADS)

    Bharti, L.; Quintero Noda, C.; Joshi, C.; Rakesh, S.; Pandya, A.

    2016-10-01

    We present high resolution observations of fine structures at pore boundaries. The inner part of granules towards umbra show dark striations which evolve into a filamentary structure with dark core and `Y' shape at the head of the filaments. These filaments migrate into the umbra similar to penumbral filaments. These filaments show higher temperature, lower magnetic field strength and more inclined field compared to the background umbra. The optical depth stratification of physical quantities suggests their similarity with penumbral filaments. However, line-of-sight velocity pattern is different from penumbral filaments where they show downflows in the deeper layers of the atmosphere while the higher layers show upflows. These observations show filamentation in a simple magnetic configuration.

  10. Fine Structure in Solar Flares.

    PubMed

    Warren

    2000-06-20

    We present observations of several large two-ribbon flares observed with both the Transition Region and Coronal Explorer (TRACE) and the soft X-ray telescope on Yohkoh. The high spatial resolution TRACE observations show that solar flare plasma is generally not confined to a single loop or even a few isolated loops but to a multitude of fine coronal structures. These observations also suggest that the high-temperature flare plasma generally appears diffuse while the cooler ( less, similar2 MK) postflare plasma is looplike. We conjecture that the diffuse appearance of the high-temperature flare emission seen with TRACE is due to a combination of the emission measure structure of these flares and the instrumental temperature response and does not reflect fundamental differences in plasma morphology at the different temperatures.

  11. Adsorption of alkenyl succinic anhydride from solutions in carbon tetrachloride on a fine magnetite surface

    NASA Astrophysics Data System (ADS)

    Balmasova, O. V.; Ramazanova, A. G.; Korolev, V. V.

    2016-06-01

    The adsorption of alkenyl succinic anhydride from a solution in carbon tetrachloride on a fine magnetite surface at a temperature of 298.15 K is studied using fine magnetite, which forms the basis of magnetic fluids, as the adsorbent. An adsorption isotherm is recorded and interpreted in terms of the theory of the volume filling of micropores (TVFM). Adsorption process parameters are calculated on the basis of the isotherm. It is shown that at low equilibrium concentrations, the experimental adsorption isotherm is linear in the TVFM equation coordinates.

  12. Fine Structure of Plasmaspheric Hiss

    NASA Astrophysics Data System (ADS)

    Summers, D.; Omura, Y.; Nakamura, S.; Kletzing, C.

    2014-12-01

    Plasmaspheric hiss plays a key role in controlling the structure and dynamics of Earth's radiation belts.The quiet time slot region between the inner and outer belts can be explained as a steady-state balance between earthward radial diffusion and pitch-angle scattering loss of energetic electrons to the atmosphere induced by plasmaspheric hiss. Plasmaspheric hiss can also induce gradual precipitation loss of MeV electrons from the outer radiation belt. Plasmaspheric hiss has been widely regarded as a broadband,structureless,incoherent emission. Here, by examining burst-mode vector waveform data from the EMFISIS instrument on the Van Allen Probes mission,we show that plasmaspheric hiss is a coherent emission with complex fine structure. Specifically, plasmaspheric hiss appears as discrete rising tone and falling tone elements. By means of waveform analysis we identify typical amplitudes,phase profiles,and sweep rates of the rising and falling tone elements. The new observations reported here can be expected to fuel a re-examination of the properties of plasmaspheric hiss, including a further re-analysis of the generation mechanism for hiss.

  13. Adsorption of oxygen on W/100/ - Adsorption kinetics and structure

    NASA Technical Reports Server (NTRS)

    Bauer, E.; Poppa, H.; Viswanath, Y.

    1976-01-01

    The adsorption of oxygen on W(100) single-crystal surfaces is studied by Auger electron spectroscopy (AES), flash desorption, low-energy electron diffraction (LEED), and retarding-field work-function measurements. The AES results reveal stepwise changes in the sticking coefficients in the coverage range 0 to 1 and activated adsorption at higher coverages. Upon room-temperature adsorption, a series of complex LEED patterns is observed. In layers adsorbed at 1050 K and cooled to room temperature, the p(2 x 1) structure is the first ordered structure observed. This structure shows a reversible order-disorder transition between 700 and 1000 K and is characterized by a work function which is lower than that of the clean surface. Heating room-temperature adsorbates changes their structure irreversibly. At temperatures below 750 K, some new structures are observed.

  14. THE FINE STRUCTURE OF DIPLOCOCCUS PNEUMONIAE

    PubMed Central

    Tomasz, Alexander; Jamieson, James D.; Ottolenghi, Elena

    1964-01-01

    The fine structure of an unencapsulated strain of Diplococcus pneumoniae is described. A striking feature of these bacteria is an intracytoplasmic membrane system which appears to be an extension of septa of dividing bacteria. The possible function of these structures and their relationship to the plasma membrane and other types of intracytoplasmic membranes found in pneumococcus is discussed. PMID:14203390

  15. Fine-Grained Auditory Discrimination: Factor Structures.

    ERIC Educational Resources Information Center

    Elliott, Lois L.; Hammer, Michael A.

    1993-01-01

    This study, with 161 children with and without language learning problems, tested the hypothesis that as children's language development matures, factor-analytic structural changes occur that are associated with measurements of fine-grained auditory discrimination, receptive vocabulary, receptive language, speech production, and 3 performance…

  16. THE FINE STRUCTURE OF THE RAT CEREBELLUM

    PubMed Central

    Herndon, Robert M.

    1964-01-01

    This paper describes the fine structure of the granule cells, stellate neurons, astrocytes, Bergmann glia, oligodendrocytes, and microglia of the rat cerebellum after fixation by perfusion with buffered 1 per cent osmium tetroxide. Criteria are given for differentiating the various cell types, and the findings are correlated with previous light microscope and electron microscope studies of the cerebellum. PMID:14222815

  17. THE FINE STRUCTURE OF THE PURKINJE CELL

    PubMed Central

    Herndon, Robert M.

    1963-01-01

    This paper describes the fine structure of the Purkinje cell of the rat cerebellum after fixation by perfusion with 1 per cent buffered osmium tetroxide. Structures described include a large Golgi apparatus, abundant Nissl substance, mitochondria, multivesicular bodies, osmiophilic granules, axodendritic and axosomatic synapses, the nucleus, the nucleolus, and the nucleolar body. A new and possibly unique relationship between mitochondria and subsurface cisterns is described. Possible functional correlations are discussed. PMID:13953993

  18. Breakthrough adsorption study of migratory nickel in fine-grained soil.

    PubMed

    Ghosh, S; Mukherjee, S N; Kumar, Sunil; Chakraborty, P; Fan, Maohong

    2007-09-01

    The present study was conducted to evaluate the breakthrough curve for nickel adsorption in fine-grained soil from a nearby ash pond site of a thermal power plant. Nickel was found to be the major polluting solute in the ash sluicing wastewater. The adsorption of nickel by vertical soil column batch test and horizontal migration test was carried out in the laboratory. Field investigation was conducted also, by installing test wells around the ash pond site. Experimental results showed a good adsorptive capacity of soil for nickel ions. The breakthrough curves showed a reasonable fitting with a one-dimensional mathematical model. The breakthrough curves yielded from field test results showed good agreement with a two-dimensional mathematical model.

  19. Universal fine structure of nematic hedgehogs

    NASA Astrophysics Data System (ADS)

    Kralj, Samo; Virga, Epifanio G.

    2001-02-01

    We study in a Landau-de Gennes approach the biaxial structure of a nematic point defect with topological charge M = + 1. We aim to illuminate the role of the confining boundaries in determining the fine structure of the defect. We show that there are different regimes associated with different values of the ratio between the typical size R of the region in space occupied by the material and the biaxial correlation length ξb. For R/ξb>20 the core structure is already qualitatively universal, that is, independent of the confining geometry, while also for R/ξb>200 any quantitative difference is unlikely to be detected.

  20. Ultraviolet observations of solar fine structure.

    PubMed

    Dere, K P; Bartoe, J D; Brueckner, G E; Cook, J W; Socker, D G

    1987-11-27

    The High Resolution Telescope and Spectrograph was flown on the Spacelab-2 shuttle mission to perform extended observations of the solar chromosphere and transition zone at high spatial and temporal resolution. Ultraviolet spectroheliograms show the temporal development of macrospicules at the solar limb. The C IV transition zone emission is produced in discrete emission elements that must be composed of exceedingly fine (less than 70 kilometers) subresolution structures.

  1. Recovering the fine structures in solar images

    NASA Technical Reports Server (NTRS)

    Karovska, Margarita; Habbal, S. R.; Golub, L.; Deluca, E.; Hudson, Hugh S.

    1994-01-01

    Several examples of the capability of the blind iterative deconvolution (BID) technique to recover the real point spread function, when limited a priori information is available about its characteristics. To demonstrate the potential of image post-processing for probing the fine scale and temporal variability of the solar atmosphere, the BID technique is applied to different samples of solar observations from space. The BID technique was originally proposed for correction of the effects of atmospheric turbulence on optical images. The processed images provide a detailed view of the spatial structure of the solar atmosphere at different heights in regions with different large-scale magnetic field structures.

  2. Internal Fine Structure of Ellerman Bombs

    NASA Astrophysics Data System (ADS)

    Hashimoto, Yuki; Kitai, Reizaburo; Ichimoto, Kiyoshi; Ueno, Satoru; Nagata, Shin'ichi; Ishii, Takako T.; Hagino, Masaoki; Komori, Hiroyuki; Nishida, Keisuke; Matsumoto, Takuma; Otsuji, Kenichi; Nakamura, Tahei; Kawate, Tomoko; Watanabe, Hiroko; Shibata, Kazunari

    2010-08-01

    We conducted coordinated observations of Ellerman bombs (EBs) between Hinode Satellite and Hida Observatory (HOP12). CaII H broad-band filter images of NOAA 10966 on 2007 August 9 and 10 were obtained with the Solar Optical Telescope (SOT) aboard the Hinode Satellite, and many bright points were observed. We identified a total of 4 bright points as EBs, and studied the temporal variation of their morphological fine structures and spectroscopic characteristics. With high-resolution CaII H images of SOT, we found that the EBs, thus far thought of as single bright features, are composed of a few of fine subcomponents. Also, by using Stokes I/V filtergrams with Hinode/SOT, and CaII H spectroheliograms with Hida/Domeless Solar Telescope (DST), our observation showed: (1) The mean duration, the mean width, the mean length, and the mean aspect ratio of the subcomponents were 390 s, 170 km, 450 km, and 2.7, respectively. (2) Subcomponents started to appear on the magnetic neutral lines, and extended their lengths from the original locations. (3) When the CaII H line of EBs showed the characteristic blue asymmetry, they are associated with the appearance or re-brightening of subcomponents. Summarizing our results, we obtained an observational view that elementary magnetic reconnections take place one by one successively and intermittently in EBs, and that their manifestation is the fine subcomponents of the EB phenomena.

  3. Molecular Eigensolution Symmetry Analysis and Fine Structure

    PubMed Central

    Harter, William G.; Mitchell, Justin C.

    2013-01-01

    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. PMID:23344041

  4. Surface area, porosity and water adsorption properties of fine volcanic ash particles

    NASA Astrophysics Data System (ADS)

    Delmelle, Pierre; Villiéras, Frédéric; Pelletier, Manuel

    2005-02-01

    Our understanding on how ash particles in volcanic plumes react with coexisting gases and aerosols is still rudimentary, despite the importance of these reactions in influencing the chemistry and dynamics of a plume. In this study, six samples of fine ash (<100 μm) from different volcanoes were measured for their specific surface area, as, porosity and water adsorption properties with the aim to provide insights into the capacity of silicate ash particles to react with gases, including water vapour. To do so, we performed high-resolution nitrogen and water vapour adsorption/desorption experiments at 77 K and 303 K, respectively. The nitrogen data indicated as values in the range 1.1 2.1 m2/g, except in one case where a as of 10 m2/g was measured. This high value is attributed to incorporation of hydrothermal phases, such as clay minerals, in the ash surface composition. The data also revealed that the ash samples are essentially non-porous, or have a porosity dominated by macropores with widths >500 Å. All the specimens had similar pore size distributions, with a small peak centered around 50 Å. These findings suggest that fine ash particles have relatively undifferentiated surface textures, irrespective of the chemical composition and eruption type. Adsorption isotherms for water vapour revealed that the capacity of the ash samples for water adsorption is systematically larger than predicted from the nitrogen adsorption as values. Enhanced reactivity of the ash surface towards water may result from (i) hydration of bulk ash constituents; (ii) hydration of surface compounds; and/or (iii) hydroxylation of the surface of the ash. The later mechanism may lead to irreversible retention of water. Based on these experiments, we predict that volcanic ash is covered by a complete monolayer of water under ambient atmospheric conditions. In addition, capillary condensation within ash pores should allow for deposition of condensed water on to ash particles before water

  5. Angle-resolved photoemission extended fine structure

    SciTech Connect

    Barton, J.J.

    1985-03-01

    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.

  6. Revisit to diffraction anomalous fine structure

    PubMed Central

    Kawaguchi, T.; Fukuda, K.; Tokuda, K.; Shimada, K.; Ichitsubo, T.; Oishi, M.; Mizuki, J.; Matsubara, E.

    2014-01-01

    The diffraction anomalous fine structure (DAFS) method that is a spectroscopic analysis combined with resonant X-ray diffraction enables the determination of the valence state and local structure of a selected element at a specific crystalline site and/or phase. This method has been improved by using a polycrystalline sample, channel-cut monochromator optics with an undulator synchrotron radiation source, an area detector and direct determination of resonant terms with a logarithmic dispersion relation. This study makes the DAFS method more convenient and saves a large amount of measurement time in comparison with the conventional DAFS method with a single crystal. The improved DAFS method has been applied to some model samples, Ni foil and Fe3O4 powder, to demonstrate the validity of the measurement and the analysis of the present DAFS method. PMID:25343791

  7. Solar Prominence Fine Structure and Dynamics

    NASA Astrophysics Data System (ADS)

    Berger, Thomas

    2014-01-01

    We review recent observational and theoretical results on the fine structure and dynamics of solar prominences, beginning with an overview of prominence classifications, the proposal of possible new ``funnel prominence'' classification, and a discussion of the recent ``solar tornado'' findings. We then focus on quiescent prominences to review formation, down-flow dynamics, and the ``prominence bubble'' phenomena. We show new observations of the prominence bubble Rayleigh-Taylor instability triggered by a Kelvin-Helmholtz shear flow instability occurring along the bubble boundary. Finally we review recent studies on plasma composition of bubbles, emphasizing that differential emission measure (DEM) analysis offers a more quantitative analysis than photometric comparisons. In conclusion, we discuss the relation of prominences to coronal magnetic flux ropes, proposing that prominences can be understood as partially ionized condensations of plasma forming the return flow of a general magneto-thermal convection in the corona.

  8. Study of the local distortions of the perovskite system La{sub 1-x}Sr{sub x}CoO{sub 3} (0 {ge} x {ge} 0.35) using the extended x-ray adsorption fine structure technique.

    SciTech Connect

    Jiang, Y.; Bridges, F.; Sundaram, N.; Belanger, D. P.; Anderson, I. E.; Mitchell, J. F.; Zheng, H.; Univ. of California at Santa Cruz

    2009-01-01

    We present a temperature-dependent extended x-ray absorption fine structure (EXAFS)/x-ray absorption near edge structure (XANES) investigation of La{sub 1-x}Sr{sub x}CoO{sub 3} (LSCO) over a wide doping concentration range (0 {le} x {le} 0.35). Five of the samples are nanoparticles (x = 0.15, 0.20, 0.25, 0.30, and 0.35) and four are bulk powders (x = 0, 0.15, 0.20, and 0.30). From the EXAFS analysis, we find that the Co-O bonds are well ordered for both bulk and nanoparticle materials and there is no clear evidence for a Jahn-Teller (JT) distortion in the LSCO system (either static or dynamic). The distortion of the Co-O bond with increasing T, parameterized by the width of the pair distribution function (PDF), {sigma} (T), can easily be modeled using a correlated Debye model with a high correlated Debye temperature {approx} 800 K. There is also no evidence for a step in plots of {sigma}{sup 2} vs T. In addition, the very small nonthermal contribution to {sigma}{sup 2} for the Co-O (PDF), {sigma}{sup 2} static, sets an upper limit on the extent of any Jahn-Teller distortion at low T. These experiments are inconsistent with the existence of a significant fraction of Co sites with an intermediate spin (IS) state, for which there is a JT active e{sub g} electron on the Co atoms. We cannot, however, exclude the possibility of a tiny fraction of sites having a JT distortion or some other (non-JT active) means of producing an IS state. The bulk samples are well ordered out to at least the third neighbors (Co-Co) while the nanoparticles show increased disorder and a reduction in coordination for Co-Co. XANES data are also presented, and, for both bulk and nanoparticle samples, there is essentially no edge shift with increasing Sr concentration. Bond-valence sums also indicate no change in effective Co valence. These results indicate that when holes are introduced via Sr doping, they have little Co(3d) character and the Co configuration remains close to 3d{sup 6}; we argue

  9. Beta environmental fine structure characterization of defects

    NASA Astrophysics Data System (ADS)

    Benedek, G.; Fiorini, E.; Giuliani, A.; Milani, P.; Monfardini, A.; Nucciotti, A.; Prandoni, M. L.; Sancrotti, M.

    1999-04-01

    The fine structure of beta emission (BEFS) due to the interference with the scattered waves from neighboring atoms, analogous to EXAFS, is known to produce oscillations in the Kurie plot. Here we suggest the use of BEFS for characterizing the lattice environment of β-emitting defects located at a distance from the crystal surface not exceeding the mean free path of β-electrons. Examples of defective structures in semiconductors whose atomic arrangement could be conveniently studied with BEFS are tritium-passivated dangling bonds, β-radioactive ions implanted in the crystal lattice or segregated at extended defects such as dislocations, grain boundaries or radiation damage. Also 14C-doped diamond-like materials and other exotic carbon forms, as well as the atomic environment of ions in metal alloys could be good candidate for BEFS. In this work we have calculated the fractional BEFS modulation for 187Re in its ordinary hcp crystal lattice for which experimental data by Cosulich et al. are available. The good correspondence between theory and experiment permits to conclude that BEFS experiments at low temperature are accessible to the present bolometric detection techniques and can provide an expedient method, as compared to EXAFS, for an accurate structural assessment of extended defects in solids.

  10. The fine structure of developing elastic cartilage.

    PubMed Central

    Cox, R W; Peacock, M A

    1977-01-01

    The fine structure of the elastic cartilage of the pinna has been examined in young rabbits aged from 1 day to 1108 days. Changes associated with growth and development are related not only to age but also to the actual situation in the pinna. In the midline, progressive changes are seen from the tip to the base. The changes in the chondroblasts with time are compared with those described in hyaline cartilage. Structures occur that, except for the presence of crystals, are apparently morphologically identical with the matrix vesicles of calcifying cartilage. These matrix vesicles, however, become very prominent with age, and aggregations of them appear to be released into the intercellular tissue from vacuoles at the periphery of the chondroblasts. There is no obvious association with calcification. Occasional single cilia, desmosomes and giant mitochondria are seen. Elastica is present at birth, and eventually every cell is separated from its neighbours by a partial investment of elastica. The quantity of matrix seems to increase with time, and with distance from the tip of the ear. This is accompanied by a marked increase in cell size with time. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 PMID:870470

  11. Fine Structure and Function in Stentor polymorphus

    PubMed Central

    Randall, J. T.; Jackson, Sylvia Fitton

    1958-01-01

    The fine structure of the ciliate Stentor has been studied by means of the electron microscope and the results have been correlated with observations made on the living organism by means of light microscopy; special reference has been made to structural features which may be responsible for contraction and extension in Stentor. Descriptions have been given of the structure of the macronucleus, the vacuolated cytoplasm, mitochondria and the pellicle; a detailed study has also been made of the adoral membranelles. About 250 membranelles encircle the peristomal cap and each is composed of 3 rows of cilia, with 20 to 25 cilia in each row; a fibrillar root system connected with the membranelles depends into the endoplasm for about 20 µ and each is essentially in the shape of a fan, the terminal ends of each root bifurcating to connect to neighbouring roots. The membranelles thus form a cohesive unit and this morphological arrangement may have a bearing on the motion and coordination of the whole system. Two structural features extending throughout the length of the animal have been identified per cortical stripe in the body wall of Stentor; first, km fibres lying just beneath the pellicle are composed of stacks of fibrillar sheets and are identical with the birefringent fibres observed in the living animal. The individual fibrils of the sheets are in turn connected to the kinetosomes of the body cilia; thus the km fibres are homologous to kinetodesmata. Secondly, M bands lie beneath the km fibres and form an interconnected system in contact with the surrounding vacuolated cytoplasm; the thickness of the M bands is greatest at the base of a contracted animal. The contractile and extensile properties of these organelles have been discussed in the light of experimental results and theoretical considerations. PMID:13610947

  12. Fine structure and function in Stentor polymorphous.

    PubMed

    RANDALL, J T; JACKSON, S F

    1958-11-25

    The fine structure of the ciliate Stentor has been studied by means of the electron microscope and the results have been correlated with observations made on the living organism by means of light microscopy; special reference has been made to structural features which may be responsible for contraction and extension in Stentor. Descriptions have been given of the structure of the macronucleus, the vacuolated cytoplasm, mitochondria and the pellicle; a detailed study has also been made of the adoral membranelles. About 250 membranelles encircle the peristomal cap and each is composed of 3 rows of cilia, with 20 to 25 cilia in each row; a fibrillar root system connected with the membranelles depends into the endoplasm for about 20 micro and each is essentially in the shape of a fan, the terminal ends of each root bifurcating to connect to neighbouring roots. The membranelles thus form a cohesive unit and this morphological arrangement may have a bearing on the motion and coordination of the whole system. Two structural features extending throughout the length of the animal have been identified per cortical stripe in the body wall of Stentor; first, km fibres lying just beneath the pellicle are composed of stacks of fibrillar sheets and are identical with the birefringent fibres observed in the living animal. The individual fibrils of the sheets are in turn connected to the kinetosomes of the body cilia; thus the km fibres are homologous to kinetodesmata. Secondly, M bands lie beneath the km fibres and form an interconnected system in contact with the surrounding vacuolated cytoplasm; the thickness of the M bands is greatest at the base of a contracted animal. The contractile and extensile properties of these organelles have been discussed in the light of experimental results and theoretical considerations.

  13. Analysis of Diffraction Anomalous Fine Structure

    NASA Astrophysics Data System (ADS)

    Cross, Julie Olmsted

    This thesis presents a systematic study of the application of DAFS to determine site-specific local structural and chemical information in complex materials, and the first application of state-of-the-art theoretical XAFS calculations using the computer program scFEFF to model DAFS data. In addition, the iterative dispersion analysis method, first suggested by Pickering, et al., has been generalized to accommodate the off-resonance anomalous scattering from heavy atoms in the unit cell. The generalized algorithm scKKFIT was applied to DAFS data from eight (00 l) reflections of the high-T _{c} superconductor YBa _2Cu_3O_ {6.8} to obtain the weighted complex resonant scattering amplitudes Delta f_{ rm w}(Q, E). The fine-structure functions chi_{rm w}(Q, E) isolated from the Delta f_{ rm w}(Q, E) are linear combinations of the individual site fine structure functions chi _{rm w}(Q, E) = Sigma_{i}W_{i,{ bf Q}}chi_{i}(E) from the two inequivalent Cu sites, added together according to the structure factor for the Cu sublattice. The chi_{rm w}(Q, E) were fit en masse using the XAFS analysis program scFEFFIT under a set of constraints on the coefficients W _{i,{bf Q}} based on the structure factor for kinematic scattering. The W_{i,{bf Q}} determined by scFEFFIT were used to obtain the fully separated complex resonant scattering amplitudes Delta f(E) for the two Cu sites. The theoretical connection between DAFS and XAFS is used to justify the application of state-of-the-art theoretical XAFS calculations to DAFS analysis. The polarization dependence of DAFS is described in terms of individual virtual photoelectron scattering paths in the Rehr-Albers separable curved-wave formalism. Polarization is shown to be an important factor in all DAFS experiments. Three experimental constraints are found necessary for obtaining site-separated Delta f(E) from DAFS data by linear inversion of the W_{i, {bf Q}} matrix and scKKFIT isolated Delta f_{rm w }(Q, E): (1) The diffraction must be

  14. Fine Collimator Grids Using Silicon Metering Structure

    NASA Technical Reports Server (NTRS)

    Eberhard, Carol

    1998-01-01

    The project Fine Collimator Grids Using Silicon Metering Structure was managed by Dr. Carol Eberhard of the Electromagnetic Systems & Technology Department (Space & Technology Division) of TRW who also wrote this final report. The KOH chemical etching of the silicon wafers was primarily done by Dr. Simon Prussin of the Electrical Engineering Department of UCLA at the laboratory on campus. Moshe Sergant of the Superconductor Electronics Technology Department (Electronics Systems & Technology Division) of TRW and Dr. Prussin were instrumental in developing the low temperature silicon etching processes. Moshe Sergant and George G. Pinneo of the Microelectronics Production Department (Electronics Systems & Technology Division) of TRW were instrumental in developing the processes for filling the slots etched in the silicon wafers with metal-filled materials. Their work was carried out in the laboratories at the Space Park facility. Moshe Sergant is also responsible for the impressive array of Scanning Electron Microscope images with which the various processes were monitored. Many others also contributed their time and expertise to the project. I wish to thank them all.

  15. Cosmological constant, fine structure constant and beyond

    NASA Astrophysics Data System (ADS)

    Wei, Hao; Zou, Xiao-Bo; Li, Hong-Yu; Xue, Dong-Ze

    2017-01-01

    In the present work, we consider the cosmological constant model Λ ∝ α ^{-6}, which is well motivated from three independent approaches. As is well known, the hint of varying fine structure constant α was found in 1998. If Λ ∝ α ^{-6} is right, it means that the cosmological constant Λ should also be varying. Here, we try to develop a suitable framework to model this varying cosmological constant Λ ∝ α ^{-6}, in which we view it from an interacting vacuum energy perspective. Then we consider the observational constraints on these models by using the 293 Δ α /α data from the absorption systems in the spectra of distant quasars. We find that the model parameters can be tightly constrained to the very narrow ranges of O(10^{-5}) typically. On the other hand, we can also view the varying cosmological constant model Λ ∝ α ^{-6} from another perspective, namely it can be equivalent to a model containing "dark energy" and "warm dark matter", but there is no interaction between them. We find that this is also fully consistent with the observational constraints on warm dark matter.

  16. Fine velocity structures collisional dissipation in plasmas

    NASA Astrophysics Data System (ADS)

    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

  17. Fine Structure of Solar Acoustic Oscillations Due to Rotation

    NASA Technical Reports Server (NTRS)

    Goode, P. R.; Dziembowski, W.

    1984-01-01

    The nature of the fine structure of high order, low degree five minute period solar oscillations following from various postulated forms of spherical rotation is predicted. The first and second order effects of rotation are included.

  18. The fine-structure constant before quantum mechanics

    NASA Astrophysics Data System (ADS)

    Kragh, Helge

    2003-03-01

    This paper focuses on the early history of the fine-structure constant, largely the period until 1925. Contrary to what is generally assumed, speculations concerning the interdependence of the elementary electric charge and Planck's constant predated Arnold Sommerfeld's 1916 discussion of the dimensionless constant. This paper pays particular attention to a little known work from 1914 in which G N Lewis and E Q Adams derived what is effectively a numerical expression for the fine-structure constant.

  19. Spectropolarimetry of fine magnetized structures in the upper solar atmosphere

    NASA Astrophysics Data System (ADS)

    Schad, Thomas Anthony

    2013-12-01

    One of the earliest indications of magnetic fields acting in the solar atmosphere came at the beginning of the 20th century when George Hale noted a "decided definiteness of structure" in photographs within the Hydrogen Balmer-alpha line core. Fine structure both in the chromosphere and in the corona result from processes that are not well understood but accepted as a consequence of the solar magnetic field. Our knowledge of this field is lacking, and until recently, the assumed relationship between fine thermal structure and the magnetic field remained untested. Here, spectropolarimetric diagnostics of fine structures in the solar chromosphere and cool corona are advanced using the infrared He I triplet at 1083 nm. Precise calibration procedures are developed for the Facility Infrared Spectropolarimeter (FIRS), recently commissioned at the Dunn Solar Telescope. Together with high-order adaptive optics, we simultaneously map fine structures while obtaining a polarimetric sensitivity of up to 2 x 10--4 of the incoming intensity. These instrument improvements result in the first maps of the He I polarized signatures within an active region superpenumbra, where Hale first recognized fine-structuring. Selective absorption and emission processes due to non-equilibrium optical pumping are recognized. Our interpretation, using advanced inversions of the He I triplet, provides confirmation of Hale's initial suspicion---the fine structures of the solar chromosphere are visual markers for the magnetic field. Yet, the fine chromospheric thermal structure is not matched by an equivalently fine magnetic structure. Our ability to measure this field suggests the utility of the He I triplet as an inner boundary condition for the inner heliospheric magnetic field. In the corona itself, we infer the vector properties of a catastrophically-cooled coronal loop, uniting space-based and ground-based instrumentation. We determine how fine loops are anchored in the photosphere via a

  20. Phonons on the clean metal surfaces and in adsorption structures

    NASA Astrophysics Data System (ADS)

    Rusina, Galina G.; Chulkov, Evgenii V.

    2013-06-01

    The state-of-the-art studies of the vibrational dynamics of clean metal surfaces and metal surface structures formed upon the sub-monolayer adsorption of the atoms of various elements are considered. A brief historical survey of the milestones of investigations of surface phonons is presented. The results of studies of the atomic structure and vibration characteristics of surfaces with low and high Miller indices and adsorption structures are analyzed. It is demonstrated that vicinal surfaces of FCC metals tend to exhibit specific vibrational modes located on the step and polarized along the step. Irrespective of the type and position of adsorption or the substrate structure, the phonon spectra of sub-monolayer adsorption structures always tend to display two modes for combined translational displacements of adatoms and for coupled vibrations of substrate atoms and adatoms polarized in the direction normal to the surface. The bibliography includes 202 references.

  1. The Fine Structure of YCuO

    SciTech Connect

    Van Tendeloo, G.; Garlea, O.; Darie, C.; Bougerol-Chaillout, C.; Bordet, P.

    2001-02-01

    YCuO{sub 2} delafossite crystallizes into two stacking variants; hexagonal 2H or rhombohedral 3R, depending on the preparation conditions. The structure of the fully oxygenated material YCuO{sub 2.50} has been determined as orthorhombic (a{sub o}=6.1961 {angstrom}; b{sub o}=11.2158 {angstrom}; c{sub o}=7.1505 {angstrom}; space group Pnma). The structure is based on the hexagonal 2H structure (a{sub o}=a{sub H}{radical}3; b{sub o}=c{sub H}; c{sub o}=2a{sub H}). Upon incomplete oxidation, a different YCuO{sub Z} phase with ideal composition YCuO{sub 2.33} and lattice parameters a{sub H}{radical}3, a{sub H}{radical}3, c{sub H} is also formed. Diffraction patterns are often very complex because of the presence of planar defects and intergrowth of both phases. Under electron beam irradiation, oxygen is released from the structure and one phase gradually transforms into the other.

  2. Fine Structure of APLYSIA Statocyst Receptor Cells

    DTIC Science & Technology

    1974-08-01

    receptors. Cold Spring Harbor Symp. Quant. Biol. 30:133-145, 1965. 5. Flock, A. Sensory transduction in hair cells. In: Handbook of Sensory...and Lundquist, P.-G. Structural basis for directional sen- sitivity in cochlear and vestibular sensory receptors. Cold Spring Harbor Symp

  3. A Newtonian Explanation of the Hydrogen Fine Structure

    NASA Astrophysics Data System (ADS)

    Fisher, Paul; Espinosa, James; Woodyard, James

    2010-10-01

    The Hydrogen spectrum as seen by low dispersion spectrometers is correctly described by a classical theory founded on Ritz's magnetic model. With increasingly powerful instruments, individual lines are split into smaller groupings that are three orders of magnitude smaller. Arnold Sommerfeld was the first to develop a theory based on the mass variation of the electron to correctly describe this ``fine'' structure. A few years later, Vannevar Bush pointed out that Weber's force law could be used instead of Einstein's theory of relativity. We will utilize this line of approach to present a purely classical theory of the fine structure of the Hydrogen atom. Ritz's theory of electromagnetism replaces Weber's law; we will summarize all the other atomic physics experiments that our classical theory already describes correctly. Finally we will show how this fine structure theory logically paves the way for an explanation of the linear Stark effect.

  4. 3D WHOLE-PROMINENCE FINE STRUCTURE MODELING

    SciTech Connect

    Gunár, Stanislav; Mackay, Duncan H.

    2015-04-20

    We present the first 3D whole-prominence fine structure model. The model combines a 3D magnetic field configuration of an entire prominence obtained from nonlinear force-free field simulations, with a detailed description of the prominence plasma. The plasma is located in magnetic dips in hydrostatic equilibrium and is distributed along multiple fine structures within the 3D magnetic model. Through the use of a novel radiative transfer visualization technique for the Hα line such plasma-loaded magnetic field model produces synthetic images of the modeled prominence comparable with high-resolution observations. This allows us for the first time to use a single technique to consistently study, in both emission on the limb and absorption against the solar disk, the fine structures of prominences/filaments produced by a magnetic field model.

  5. Advances in Nanocarbon Metals: Fine Structure

    DTIC Science & Technology

    2015-03-01

    SUPPLEMENTARY NOTES 14. ABSTRACT This study is an investigation of the structure and some properties of silver, copper, and aluminum alloy covetics...Covetics can incorporate large amounts of carbon (C) in a nanoscale form to alter physical and mechanical properties of the base metal or alloy ...and properties can be obtained. 15. SUBJECT TERMS covetic, nanocarbon silver, aluminum , copper 16. SECURITY CLASSIFICATION OF: 17. LIMITATION

  6. Farber's disease: a fine structural study.

    PubMed

    Abenoza, P; Sibley, R K

    1987-01-01

    A 1-week-old baby boy presented with hepatosplenomegaly, coarse facial features, and cloudy corneas. A metabolic storage disease was considered and he underwent cutaneous and liver biopsy. By light microscopy the skin was normal. Kupffer cells were enlarged and had foamy cytoplasm. Ultrastructural examination of skin and liver demonstrated features compatible with Farber's disease: curvilinear and "banana" bodies, zebra-like structures, and concentric lamellar bodies. A deficiency of lysosomal acid ceramidase was subsequently demonstrated in cultured fibroblasts and in liver tissue corroborating the ultrastructural findings.

  7. Fine Structure of Ectothiorhodospira mobilis Pelsh1

    PubMed Central

    Remsen, C. C.; Watson, S. W.; Waterbury, J. B.; Trüper, H. G.

    1968-01-01

    The cell wall structure, arrangement of photosynthetic membranes, and the attachment of flagella of Ectothiorhodospira mobilis strain 8112 were examined by using freeze-etching and conventional electron microscopic techniques. The outer coat of the multilayered cell wall is comprised of 50 A repeating subunits, arranged in a regular array. The photosynthetic membranes, which originate from and are attached to the plasma membrane, are arranged in a more complex pattern than previously seen in other bacteria. The tuft of flagella in E. mobilis is inserted into a polar organelle. The relationship of this organelle to the polar membrane and the mechanism of attachment of the flagella to the polar organelle is discussed. Images PMID:5669908

  8. Characterization of Fine Structure in Sprites

    NASA Astrophysics Data System (ADS)

    Gerken, E. A.; Inan, U. S.

    2001-12-01

    During the summer months of 1998-2000, Stanford University fielded campaigns to telescopically image sprites. The campaigns were conducted at Langmuir Laboratory (operated by New Mexico Institute of Mining and Technology) in Socorro NM and Yucca Ridge Observatory in Fort Collins CO. The experiment consisted of two intensified CCD cameras, two photometers, and crossed magnetic loop VLF antennas. One camera was mounted on a 16in diameter, 72in focal length Newtonian telescope with a field of view of 0.72x0.9 degrees and the other had a 50mm lens with a field of view of 9x12 degrees. Similarly one photometer was mounted on an 8in diameter, 1200mm focal length Newtonian telescope with a circular field of view of 1 degree and the second was red-filtered and had a wider field of view of 3x6 degrees. All four instruments were mounted on the same platform and were aligned. Video data was stored on VHS tapes with the photometer signals recorded on the audio channels. GPS video time-stamping and IRIG-B code were used for timing. Data from these campaigns reveal streamer structures within sprites ranging from 25m to 200m in width. Streamer morphologies are diverse ranging from single columns to multiply-forked structures to chains of beads. Faint downward branching is observed prior to some large sprite events. Streamers are seen to develop on time scales from less than 17ms to over 100ms. Streamer sizes and velocities are compared to existing models and charge moments for associated sferics are presented.

  9. Fine structure of the FMR-1 locus

    SciTech Connect

    Nelson, D.L.; Eichler, E.E.; Richards, S.; Gibbs, R.A.

    1994-07-15

    The fragile X syndrome is due to a CGG triplet expansion in the first exon of FMR-1, resulting in hypermethylation and extinction of gene expression. To further understanding of the gene`s involvement in the syndrome, we have determined the physical structure of this locus. A high resolution restriction map of cosmids from the region has been prepared encompassing approximately 50 kb. Using exon-exon PCR and restriction analysis, the FMR-1 gene has been determined to consist of 17 exons spanning 38 kb of Xq27.3. Each intron-exon boundary has been sequenced. In general, the splice donors and acceptors located in the 5{prime} portion of the gene demonstrate greater adherence to consensus than those in the 3{prime} end, providing a possible explanation for the finding of alternative splicing in FMR-1. Sequence analysis of the region immediately flanking the CGG triplet repeat demonstrated both tetranucleotide and dinucleotide repeats. Additional sequence is being obtained from the overlapping cosmids spanning the gene, and extending 20 kb proximal and approximately 30 kb distal as part of a larger project to determine sequence on the megabase scale in the Xq27.3-q28 region. These sequences are being characterized from normal and affected individuals to assess polymorphisms and the role (if any) of peculiar sequences in the generation of fragile X CGG instability. The elucidation of the structure and composition of the FMR-1 gene as well as its flanking region will enhance detection of other mutations possible in fragile X phenocopy individuals.

  10. Strained spiral vortex model for turbulent fine structure

    NASA Technical Reports Server (NTRS)

    Lundgren, T. S.

    1982-01-01

    A model for the intermittent fine structure of high Reynolds number turbulence is proposed. The model consists of slender axially strained spiral vortex solutions of the Navier-Stokes equation. The tightening of the spiral turns by the differential rotation of the induced swirling velocity produces a cascade of velocity fluctuations to smaller scale. The Kolmogorov energy spectrum is a result of this model.

  11. Temporal Fine Structure and Applications to Cochlear Implants

    ERIC Educational Resources Information Center

    Li, Xing

    2013-01-01

    Complex broadband sounds are decomposed by the auditory filters into a series of relatively narrowband signals, each of which conveys information about the sound by time-varying features. The slow changes in the overall amplitude constitute envelope, while the more rapid events, such as zero crossings, constitute temporal fine structure (TFS).…

  12. The origin of the distortion product otoacoustic emission fine structure

    NASA Astrophysics Data System (ADS)

    Piskorski, Pawel

    Distortion-product otoacoustic emissions (DPOAEs) are sounds detected in the ear canal which are generated by the nonlinear processes in the inner ear (cochlea) in response to the external stimulation of two or more tones (primaries). Their generation region in the cochlea can be systematically changed by varying the primary frequencies, and they are currently being evaluated for possible clinical use in screening for hearing defects. The phase and amplitude of various orders of DPOAEs of frequencies, f/sb [dp]=f1-n(f2-f1),/ (n=1,2,/...), were measured in human subjects for two- tone stimuli of frequencies f1 and f2 (>f1). A number of experimental paradigms (fixed primary ratio f2/f1, fixed f1, fixed f2, and fixed f/sb [dp]) were used to investigate the nature of peaks and valleys (fine structure) of DPOAEs in their phase and amplitude dependence on the primary frequencies. This fine structure must be taken into account in any potential clinical applications of DPOAEs. The experimental results largely support a model in which the fine structure stems from interference at the base of the cochlea between distortion product (DP) components coming from the primary DPOAE source region (around the f2 tonotopic place) and components coming from the DP tonotopic place (via reflection of an apically moving DP wave). The spectral periodicity of the fine structures for several orders of apical DPOAEs corresponds to a tonotopic displacement of about 0.4 mm along the basilar membrane (BM) (0.4 bark). In agreement with the reaction model, this spectral spacing is also characteristic of synchronous evoked and spontaneous otoacoustic emission spectra as well as the microstructure of the hearing threshold. Approximate analytic expressions for the mechanisms which are responsible for the fine structure are used to interpret the data.

  13. Fine structures in the light diffraction pattern of striated muscle.

    PubMed

    Leung, A F

    1984-10-01

    Single skeletal muscle fibres of frog were illuminated with a He-Ne, argon-ion or rhodamine 6G dye laser. The fine structures lying within the diffraction columns moved parallel to the fibre axis without changing their pattern when either the wavelength or the incident angle of the laser beam was varied, or when the fibre was stretched slightly. However, their pattern remained nearly constant when the fibre was submerged in hypotonic or hypertonic solution. As the illumination of about 1 mm or 0.1 mm width scanned along the length of the fibre, new structures emerged while others faded away giving rise to the notion that the diffraction columns were moving in the direction of the scan. A decrease in the illumination width caused the structures lying on the periphery of the diffraction column to disappear and the width of the remaining structures to increase. Measurements rule out the existence of large diffraction planes in these muscles. In addition, they indicate that the fine structures come from the diffraction of the whole rather than independent components of the illuminated volume. The origin of the fine structures is explained by two diffraction models.

  14. Assigning {gamma} deformation from fine structure in exotic nuclei

    SciTech Connect

    Ferreira, L. S.; Maglione, E.; Arumugam, P.

    2011-10-28

    The nonadiabatic quasiparticle model for triaxial shapes is used to perform calculations for decay of {sup 141}Ho, the only known odd-Z even-N deformed nucleus for which fine structure in proton emission from both ground and isomeric states has been observed. All experimental data corresponding to this unique case namely, the rotational spectra of parent and daughter nuclei, decay widths and branching ratios for ground and isomeric states, could be well explained with a strong triaxial deformation {gamma}{approx}20. The recent experimental observation of fine structure decay from the isomeric state, can be explained only with an assignment of I{sup {pi}} = 3/2{sup +} as the decaying state, in contradiction with the previous assignment, of I{sup {pi}} 1/2{sup +}, based on adiabatic calculations. This study reveals that proton emission measurements could be a precise tool to probe triaxial deformations and other structural properties of exotic nuclei beyond the proton dripline.

  15. Variations in the fine-structure constant constraining gravity theories

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    In this paper, we investigate how the fine-structure constant, α, locally varies in the presence of a static and spherically symmetric gravitational source. The procedure consists in calculating the solution and the energy eigenvalues of a massive scalar field around that source, considering the weak-field regime. From this result, we obtain expressions for a spatially variable fine-structure constant by considering suitable modifications in the involved parameters admitting some scenarios of semi-classical and quantum gravities. Constraints on free parameters of the approached theories are calculated from astrophysical observations of the emission spectra of a white dwarf. Such constraints are finally compared with those obtained in the literature.

  16. Fine Structure of Dark Energy and New Physics

    DOE PAGES

    Jejjala, Vishnu; Kavic, Michael; Minic, Djordje

    2007-01-01

    Following our recent work on the cosmological constant problem, in this letter we make a specific proposal regarding the fine structure (i.e., the spectrum) of dark energy. The proposal is motivated by a deep analogy between the blackbody radiation problem, which led to the development of quantum theory, and the cosmological constant problem, for which we have recently argued calls for a conceptual extension of the quantum theory. We argue that the fine structure of dark energy is governed by a Wien distribution, indicating its dual quantum and classical nature. We discuss observational consequences of such a picture of darkmore » energy and constrain the distribution function.« less

  17. Analysis of fine structure in the nuclear continuum

    SciTech Connect

    Shevchenko, A.; Kalmykov, Y.; Neumann-Cosel, P. von; Ponomarev, V. Yu.; Richter, A.; Wambach, J.; Carter, J.; Usman, I.; Cooper, G. R. J.; Fearick, R. W.

    2008-02-15

    Fine structure has been shown to be a general phenomenon of nuclear giant resonances of different multipolarities over a wide mass range. In this article we assess various techniques that have been proposed to extract quantitative information from the fine structure in terms of characteristic scales. These include the so-called local scaling dimension, the entropy index method, Fourier analysis, and continuous and discrete wavelet transforms. As an example, results on the isoscalar giant quadrupole resonance in {sup 208}Pb from high-energy-resolution inelastic proton scattering and calculations with the quasiparticle-phonon model are analyzed. Wavelet analysis, both continuous and discrete, of the spectra is shown to be a powerful tool to extract the magnitude and localization of characteristic scales.

  18. Classification of surface structures on fine metallic wires

    NASA Astrophysics Data System (ADS)

    Bernabeu, E.; Sanchez-Brea, L. M.; Siegmann, P.; Martinez-Antón, J. C.; Gomez-Pedrero, J. A.; Wilkening, G.; Koenders, L.; Müller, F.; Hildebrand, M.; Hermann, H.

    2001-08-01

    In this report a classification of the main surface structures found on fine metallic wires is carried out (between ˜20 and 500 μm in diameter). For this, we have analyzed a series of wires of different metallic materials, diameters and production environments by scanning electron microscopy, atomic force microscopy, and confocal microscopy. A description and the images of the structures is given and, in addition, a nomenclature to be used by manufacturers, customers and researches is proposed. With this information the surface quality of fine metallic wires may be improved in a fabrication level. One of the objectives of this catalogue of defects is to serve as a basis for measuring the quality of the surface of the wires during the production process and the development of a measuring device for that purpose.

  19. Fine-scale human genetic structure in Western France

    PubMed Central

    Karakachoff, Matilde; Duforet-Frebourg, Nicolas; Simonet, Floriane; Le Scouarnec, Solena; Pellen, Nadine; Lecointe, Simon; Charpentier, Eric; Gros, Françoise; Cauchi, Stéphane; Froguel, Philippe; Copin, Nane; Balkau, B; Ducimetière, P; Eschwège;, E; Alhenc-Gelas, F; Girault, A; Fumeron, F; Marre, M; Roussel, R; Bonnet, F; Cauchi, S; Froguel, P; Cogneau, J; Born, C; Caces, E; Cailleau, M; Lantieri, O; Moreau, J G; Rakotozafy, F; Tichet, J; Le Tourneau, Thierry; Probst, Vincent; Le Marec, Hervé; Molinaro, Sabrina; Balkau, Beverley; Redon, Richard; Schott, Jean-Jacques; Blum, Michael GB; Dina, Christian

    2015-01-01

    The difficulties arising from association analysis with rare variants underline the importance of suitable reference population cohorts, which integrate detailed spatial information. We analyzed a sample of 1684 individuals from Western France, who were genotyped at genome-wide level, from two cohorts D.E.S.I.R and CavsGen. We found that fine-scale population structure occurs at the scale of Western France, with distinct admixture proportions for individuals originating from the Brittany Region and the Vendée Department. Genetic differentiation increases with distance at a high rate in these two parts of Northwestern France and linkage disequilibrium is higher in Brittany suggesting a lower effective population size. When looking for genomic regions informative about Breton origin, we found two prominent associated regions that include the lactase region and the HLA complex. For both the lactase and the HLA regions, there is a low differentiation between Bretons and Irish, and this is also found at the genome-wide level. At a more refined scale, and within the Pays de la Loire Region, we also found evidence of fine-scale population structure, although principal component analysis showed that individuals from different departments cannot be confidently discriminated. Because of the evidence for fine-scale genetic structure in Western France, we anticipate that rare and geographically localized variants will be identified in future full-sequence analyses. PMID:25182131

  20. Fine structure of the exciton electroabsorption in semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Monozon, B. S.; Schmelcher, P.

    2017-02-01

    Wannier-Mott excitons in a semiconductor layered superlattice (SL) are investigated analytically for the case that the period of the superlattice is much smaller than the 2D exciton Bohr radius. Additionally we assume the presence of a longitudinal external static electric field directed parallel to the SL axis. The exciton states and the optical absorption coefficient are derived in the tight-binding and adiabatic approximations. Strong and weak electric fields providing spatially localized and extended electron and hole states, respectively, are studied. The dependencies of the exciton states and the exciton absorption spectrum on the SL parameters and the electric field strength are presented in an explicit form. We focus on the fine structure of the ground quasi-2D exciton level formed by the series of closely spaced energy levels adjacent from the high frequencies. These levels are related to the adiabatically slow relative exciton longitudinal motion governed by the potential formed by the in-plane exciton state. It is shown that the external electric fields compress the fine structure energy levels, decrease the intensities of the corresponding optical peaks and increase the exciton binding energy. A possible experimental study of the fine structure of the exciton electroabsorption is discussed.

  1. Fine-scale human genetic structure in Western France.

    PubMed

    Karakachoff, Matilde; Duforet-Frebourg, Nicolas; Simonet, Floriane; Le Scouarnec, Solena; Pellen, Nadine; Lecointe, Simon; Charpentier, Eric; Gros, Françoise; Cauchi, Stéphane; Froguel, Philippe; Copin, Nane; Le Tourneau, Thierry; Probst, Vincent; Le Marec, Hervé; Molinaro, Sabrina; Balkau, Beverley; Redon, Richard; Schott, Jean-Jacques; Blum, Michael Gb; Dina, Christian

    2015-06-01

    The difficulties arising from association analysis with rare variants underline the importance of suitable reference population cohorts, which integrate detailed spatial information. We analyzed a sample of 1684 individuals from Western France, who were genotyped at genome-wide level, from two cohorts D.E.S.I.R and CavsGen. We found that fine-scale population structure occurs at the scale of Western France, with distinct admixture proportions for individuals originating from the Brittany Region and the Vendée Department. Genetic differentiation increases with distance at a high rate in these two parts of Northwestern France and linkage disequilibrium is higher in Brittany suggesting a lower effective population size. When looking for genomic regions informative about Breton origin, we found two prominent associated regions that include the lactase region and the HLA complex. For both the lactase and the HLA regions, there is a low differentiation between Bretons and Irish, and this is also found at the genome-wide level. At a more refined scale, and within the Pays de la Loire Region, we also found evidence of fine-scale population structure, although principal component analysis showed that individuals from different departments cannot be confidently discriminated. Because of the evidence for fine-scale genetic structure in Western France, we anticipate that rare and geographically localized variants will be identified in future full-sequence analyses.

  2. Solar chromospheric fine scale structures: dynamics and energetics

    NASA Astrophysics Data System (ADS)

    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.

  3. Exploring the fine structure at the limb in coronal holes

    NASA Technical Reports Server (NTRS)

    Karovska, Magarita; Blundell, Solon F.; Habbal, Shadia Rifai

    1994-01-01

    The fine structure of the solar limb in coronal holes is explored at temperatures ranging from 10(exp 4) to 10(exp 6) K. An image enhancement algorithm orignally developed for solar eclipse observations is applied to a number of simultaneous multiwavelength observations made with the Harvard Extreme Ultraviolet Spectrometer experiment on Skylab. The enhanced images reveal the presence of filamentary structures above the limb with a characteristic separation of approximately 10 to 15 sec . Some of the structures extend from the solar limb into the corona to at least 4 min above the solar limb. The brightness of these structures changes as a function of height above the limb. The brightest emission is associated with spiculelike structures in the proximity of the limb. The emission characteristic of high-temperature plasma is not cospatial with the emission at lower temperatures, indicating the presence of different temperature plasmas in the field of view.

  4. Extended X-ray absorption fine structure of bimetallic nanoparticles

    PubMed Central

    2011-01-01

    Summary Electronic and magnetic properties strongly depend on the structure of the material, especially on the crystal symmetry and chemical environment. In nanoparticles, the break of symmetry at the surface may yield different physical properties with respect to the corresponding bulk material. A useful tool to investigate the electronic structure, magnetic behaviour and local crystallographic structure is X-ray absorption spectroscopy. In this review, recent developments in the field of extended X-ray absorption fine structure measurements and in the analysis methods for structural investigations of bimetallic nanoparticles are highlighted. The standard analysis based on Fourier transforms is compared to the relatively new field of wavelet transforms that have the potential to outperform traditional analysis, especially in bimetallic alloys. As an example, the lattice expansion and inhomogeneous alloying found in FePt nanoparticles is presented, and this is discussed below in terms of the influence of employed density functional theory calculations on the magnetic properties. PMID:21977436

  5. Fine-Scale Filamentary Structure in Coronal Streamers

    NASA Technical Reports Server (NTRS)

    Woo, Richard; Armstrong, John W.; Bird, Michael K.; Paetzold, Martin

    1995-01-01

    Doppler scintillation measurements of a coronal streamer lasting several solar rotations have been conducted by Ulysses in 1991 over a heliocentric distance range of 14-77 R(sub 0). By showing that the solar corona is filamentary, and that Doppler frequency is the radio counterpart of white-light eclipse pictures processed to enhance spatial gradients, it is demonstrated that Doppler scintillation measurements provide the high spatial resolution that has long eluded white-light coronagraph measurements. The region of enhanced scintillation, spanning an angular extent of 1.8 deg in heliographic longitude, coincides with the radially expanding streamer stalk and represents filamentary structure with scale sizes at least as small as 340 km (0.5 sec) when extrapolated to the Sun. Within the stalk of the streamer, the fine-scale structure corresponding to scale sizes in the range of 20-340 km at the Sun and associated with closed magnetic fields amounts to a few percent of the mean density, while outside the stalk, the fine-scale structure associated with open fields is an order of magnitude lower. Clustering of filamentary structure that takes place within the stalk of the streamer is suggestive of multiple current sheets. Comparison with ISEE 3 in situ plasma measurements shows that significant evolution resulting from dynamic interaction with increasing heliocentric distance takes place by the time streamers reach Earth orbit.

  6. Extended x-ray absorption fine structure studies of hemoglobin

    SciTech Connect

    Shulman, R.G.

    1987-02-01

    Results of extended x-ray absorption fine structure (EXAFS) studies of the iron atom in deoxygenated hemoglobin are reviewed. It is shown that the iron-porphinato nitrogen distance has been determined to be 2.06 +/- 0.01 A by two independent investigations. Difficulties experienced in using this distance to calculate the iron's distance above the plane by triangulation are shown to be due to ignoring differences between ferrous and ferric hemes. It is concluded that the iron is 0.2 +/- 0.1/0.2 A above the plane of the nitrogens as originally shown.

  7. A simple cosmology with a varying fine structure constant.

    PubMed

    Sandvik, Håvard Bunes; Barrow, John D; Magueijo, João

    2002-01-21

    We investigate the cosmological consequences of a theory in which the electric charge e can vary. In this theory the fine structure "constant," alpha, 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 alpha, while fitting the observed accelerating Universe and evidence for small alpha variations in quasar spectra. It also places specific restrictions on the nature of the dark matter. Further tests, involving stellar spectra and Eötvös experiments, are proposed.

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

    NASA Technical Reports Server (NTRS)

    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.

  9. New Tests for Variations of the Fine Structure Constant

    NASA Technical Reports Server (NTRS)

    Prestage, John D.

    1995-01-01

    We describe a new test for possible variations of the fine structure constant, by comparisons of rates between clocks based on hyperfine transitions in alkali atomos with different atomic number Z. H- maser, Cs and Hg+ clocks have a different dependence on ia relativistic contributions of order (Z. Recent H-maser vs Hg+ clock comparison data improves laboratory limits on a time variation by 100-fold to giveFuture laser cooled clocks (Be+, Rb, Cs, Hg+, etc.), when compared, will yield the most senstive of all tests for.

  10. Topological Quantization in Units of the Fine Structure Constant

    SciTech Connect

    Maciejko, Joseph; Qi, Xiao-Liang; Drew, H.Dennis; 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. Thermal stability analysis of the fine structure of solar prominences

    NASA Technical Reports Server (NTRS)

    Demoulin, Pascal; Malherbe, Jean-Marie; Schmieder, Brigitte; Raadu, Mickael A.

    1986-01-01

    The linear thermal stability of a 2D periodic structure (alternatively hot and cold) in a uniform magnetic field is analyzed. The energy equation includes wave heating (assumed proportional to density), radiative cooling and both conduction parallel and orthogonal to magnetic lines. The equilibrium is perturbed at constant gas pressure. With parallel conduction only, it is found to be unstable when the length scale 1// is greater than 45 Mn. In that case, orthogonal conduction becomes important and stabilizes the structure when the length scale is smaller than 5 km. On the other hand, when the length scale is greater than 5 km, the thermal equilibrium is unstable, and the corresponding time scale is about 10,000 s: this result may be compared to observations showing that the lifetime of the fine structure of solar prominences is about one hour; consequently, our computations suggest that the size of the unresolved threads could be of the order of 10 km only.

  12. Search for fine scale structures in high latitude solar wind

    NASA Technical Reports Server (NTRS)

    Livi, S.; Parenti, S.; Poletto, G.

    1995-01-01

    About 25 years ago, E. Parker suggested that, as a consequence of the inhomogeneous structure of the corona, the solar wind might consist of adjacent structures with different physical conditions. Since that suggestion was made, the solar wind plasma characteristics have been measured in situ through many experiments, but little has been done to check whether the solar wind shows any evidence for fine scale structures, and, in the affirmative, how far from the Sun these structures persist. A previous work on this subject, by Thieme, Marsch and Schwenn (1990), based on Helios data, lead these authors to claim that the solar wind, between 0.3 and 1 AU, is inhomogeneous on a scale consistent with the hypothesis that the plume-interplume plasmas, at those distances, still retain their identity. In this work we present preliminary results from an investigation of the solar wind fine structure from Ulysses high latitude observations. To this end, we have analyzed data over several months, during 1994, at times well after Ulysses's last encounter with the Heliospheric Current Sheet, when the spacecraft was at latitudes above 50 degrees. These data refer to high speed wind coming from southern polar coronal holes and are best suited for plume-interplume identification. We have performed a power spectra analysis of typical plasma parameters, to test whether the wind plasma consist of two distinct plasma populations. We also examined data to check whether there is any evidence for an horizontal pressure balance over the hypothesized distinct structures. Our results are discussed and compared with previous findings.

  13. Vertical fine structure observations in the eastern equatorial Pacific

    SciTech Connect

    Hayes, S.P.

    1981-11-20

    Measurements of vertical displacement and horizontal velocity finestructure near the equator at 110/sup 0/W in the eastern Pacific Ocean are reported. Profiles were scaled to a constant Bruent-Vaeisaelae frequency ocean (N/sub 0/ = 1 cph) in accordance with a WKBJ approximation. A total of 57 CTD casts between 3/sup 0/N and 3/sup 0/S taken during five cruises in 1979 were analyzed. Results show an equatorial enhancement of vertical displacement is similar variance for vertical wavelengths longer than 50 sdbar (stretched decibars). This enhancement is similar to that which has been reported at 125/sup 0/W and 179/sup 0/E. Difference between locations can be accounted for by the observed temporal variability at 110/sup 0/W. Coherence between vertical displacement profiles separated in time by dealys of 2 hours to 120 hour indicate that the high wave number structures were largely associated with time scales of 4 days and less. Meridionally, vertical structures longer than 300 sdbar were coherent within 50 km of the equator. We interpret this vertical displacement fine structure enhancement as high wave number equatorially trapped inertial-gravity waves. The velocity fine structure measurements in July 1979 also indicate equatorially enhanced horizontal kinetic energy for vertical wave lengths longer than 100 sdbar. The velocity structures persisted over the 56 hour of measurement and appeared to have longer time scales than the vertical displacements. Meridional energy measurement and appeared to have longer time scales than the vertical displacements. Meridional energy exceeded zonal energy; however, the two components were coherent. We interpret these velocity structures as inertial-gravity waves which were produced off the equator and are propagating through the equatorial region.

  14. Metal adsorption by agricultural biosorbents: Adsorption isotherm, kinetic and biosorbents chemical structures.

    PubMed

    Sadeek, Sadeek A; Negm, Nabel A; Hefni, Hassan H H; Wahab, Mostafa M Abdel

    2015-11-01

    Biosorption of Cu(II), Co(II) and Fe(III) ions from aqueous solutions by rice husk, palm leaf and water hyacinth was investigated as a function of initial pH, initial heavy metal ions concentration and treatment time. The adsorption process was examined by two adsorption isotherms: Langmuir and Freundlich isotherms. The experimental data of biosorption process were analyzed using pseudo-first order, pseudo-second order kinetic models. The equilibrium biosorption isotherms showed that the three studied biosorbents possess high affinity and sorption capacity for Cu(II), Co(II) and Fe(III) ions. Rice husk showed more efficiency than palm leaf and water hyacinth. Adsorption of Cu(II) and Co(II) was more efficient in alkaline medium (pH 9) than neutral medium due to the high solubility of metal ion complexes. The metal removal efficiency of each biosorbent was correlated to its chemical structure. DTA studies showed formation of metal complex between the biosorbents and the metal ions. The obtained results showed that the tested biosorbents are efficient and alternate low-cost biosorbent for removal of heavy metal ions from aqueous media.

  15. QED Based Calculation of the Fine Structure Constant

    SciTech Connect

    Lestone, John Paul

    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.

  16. SOLAR RADIO BURSTS WITH SPECTRAL FINE STRUCTURES IN PREFLARES

    SciTech Connect

    Zhang, Yin; Tan, Baolin; Huang, Jing; Tan, Chengming; Karlický, Marian; Mészárosová, Hana; Simões, Paulo J.A.

    2015-01-20

    Good observations of preflare activities are important for us to understand the origin and triggering mechanism of solar flares, and to predict the occurrence of solar flares. This work presents the characteristics of microwave spectral fine structures as preflare activities of four solar flares observed by the Ondřejov radio spectrograph in the frequency range of 0.8-2.0 GHz. We found that these microwave bursts which occurred 1-4 minutes before the onset of flares have spectral fine structures with relatively weak intensities and very short timescales. They include microwave quasi-periodic pulsations with very short periods of 0.1-0.3 s and dot bursts with millisecond timescales and narrow frequency bandwidths. Accompanying these microwave bursts are filament motions, plasma ejection or loop brightening in the EUV imaging observations, and non-thermal hard X-ray emission enhancements observed by RHESSI. These facts may reveal certain independent, non-thermal energy releasing processes and particle acceleration before the onset of solar flares. They may help us to understand the nature of solar flares and to predict their occurrence.

  17. Fine structure in the cluster decays of the translead nuclei

    SciTech Connect

    Dumitrescu, O. |; Cioaca, C.

    1995-06-01

    Within the one level {ital R}-matrix approach several hindrance factors for the radioactive decays in which are emitted {sup 4}He, {sup 14}C, and {sup 20}O atomic nuclei are calculated. The interior wave functions are supposed to be given by the recently proposed enlarged superfluid model, an extension of the JINR-Dubna`s quasiparticle phonon nuclear model. The spectroscopic factors are expanded in terms of products of cluster overlaps and intrinsic overlap integrals. The cluster overlaps are equivalents of the generalized coefficients of fractional parentage, while for the intrinsic overlap integrals we construct a model, which is an extension of the usual models for simple particle decay such as deuteron, triton, and {alpha} decay. The exterior wave functions are calculated from a cluster-nucleus double-folding model potential obtained with the {ital M}3{ital Y} interaction. As examples of the cluster decay fine structure we analyzed the particular cases of {alpha} decay of {sup 255}Fm, {sup 14}C decay of {sup 223}Ra and {sup 20}O decay of {sup 229}Th and {sup 255}Fm. A relatively good agreement with the experimental data is obtained especially in the case of the {alpha}-decay fine structure.

  18. The effect of boron oxide on the composition, structure, and adsorptivity of glass surfaces

    NASA Astrophysics Data System (ADS)

    Schaut, Robert A.

    Boron oxide has been added to commercial silicate glasses for many years to aid in lowering melting temperatures, lowering thermal expansion, and controlling chemical durability. The fact that simple borate glasses have rather high thermal expansion and low chemical durability attests to the unique influence of boron oxide additions upon the properties of silicate glasses. However, the impact of boron oxide additions upon surface properties of multicomponent borosilicates such as adsorption and reactivity is not yet well understood. In particular, the presence of multiple coordination states for boron is expected to introduce adsorption sites with different acidic or basic behavior, but their existence is yet unproven. To investigate these effects, multicomponent sodium aluminosilicate glasses have been prepared with varying sodium and boron concentrations and drawn into moderately high-surface-area continuous filament fibers. A relatively new technique, boron K-edge Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is applied to study the local boron coordination at fracture and melt-derived fiber surfaces of these glasses. This structural information is combined with surface compositional information by X-ray Photoelectron Spectroscopy (XPS) to characterize the local atomic structure of boron at the as-formed glass surface. Finally, this information is used to interpret the adsorptivity of these as-formed and leached surfaces toward short-chain alcohol molecules through a new Inverse Gas Chromatography---Temperature Programmed Desorption (IGC-TPD) experiment. The results clearly show that boron additions to alkali-free glass surfaces introduce a unique adsorption site which is not present on boron-free glass surfaces and is easily removed by leaching in acidic solutions.

  19. Simulations of glass surfaces structure, water adsorption, and bond rupture

    NASA Astrophysics Data System (ADS)

    Garofalini, Stephen H.

    1990-12-01

    Molecular dynamics simulations of the structure of silica glass surfaces formed in a perfect vacuum as well as in the presence of a water vapor show the type, location, and concentration of specific features formed in the surface. A bond rupture mechanism which causes silanol formation far removed from the original reaction site is observed. The 3-membered ring is proposed as a site for H adsorption in the glass.

  20. The fine scale structures of airflow over Bergen

    NASA Astrophysics Data System (ADS)

    Ólafsson, Haraldur; Rugaard Furevik, Birgitte; Asle Olseth, Jan; Edvard Grov, Ole

    2015-04-01

    A large network of automatic weather stations is operated in the the complex terrain of Bergen City and its surroundings. This so-called Bergen School of Meteorology network is used to explore the fine scale structures of the atmosphere in a föhn case and evaluate how numerical simulations perform in reproducing the details of the flow. In general, the vertical profile is well reproduced, as well as many details in the wind field, as long as the resolution permits adequate representation of the topography. The intermittent nature of the flow remains however a problem. A step towards better local forecasts may lie in predicting not only the fundamental parameters such as wind and temperature, but their local temporal variability as well.

  1. Atomic Clocks and Variations of the FIne Structure Constant

    NASA Technical Reports Server (NTRS)

    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.

  2. HERSCHEL GALACTIC PLANE SURVEY OF [N ii] FINE STRUCTURE EMISSION

    SciTech Connect

    Goldsmith, Paul F.; Yıldız, Umut A.; Langer, William D.; Pineda, Jorge L.

    2015-12-01

    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 ([N ii]) at 122 and 205 μm. 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{sup −8}–10{sup −7} Wm{sup −2} sr{sup −1} level over the range –60° ≤ l ≤ 60°. 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. [N ii] 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 10–50 cm{sup −3} with an average value of 29 cm{sup −3} and N{sup +} column densities 10{sup 16}–10{sup 17} cm{sup −2}. [N ii] emission is highly correlated with that of [C ii], and we calculate that between 1/3 and 1/2 of the [C ii] emission is associated with the ionized gas. The relatively high electron densities indicate that the source of the [N ii] emission is not the warm ionized medium (WIM), which has electron densities more than 100 times smaller. Possible origins of the observed [N ii] include the ionized surfaces of dense atomic and molecular clouds, the extended low-density envelopes of H ii regions, and low-filling factor high-density fluctuations of the WIM.

  3. Herschel Galactic Plane Survey of [NII] Fine Structure Emission

    NASA Astrophysics Data System (ADS)

    Goldsmith, Paul F.; Yıldız, Umut A.; Langer, William D.; Pineda, Jorge L.

    2015-12-01

    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 ([N ii]) at 122 and 205 μm. 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 Wm-2 sr-1 level over the range -60° ≤ l ≤ 60°. 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. [N ii] 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 10-50 cm-3 with an average value of 29 cm-3 and N+ column densities 1016-1017 cm-2. [N ii] emission is highly correlated with that of [C ii], and we calculate that between 1/3 and 1/2 of the [C ii] emission is associated with the ionized gas. The relatively high electron densities indicate that the source of the [N ii] emission is not the warm ionized medium (WIM), which has electron densities more than 100 times smaller. Possible origins of the observed [N ii] include the ionized surfaces of dense atomic and molecular clouds, the extended low-density envelopes of H ii regions, and low-filling factor high-density fluctuations of the WIM.

  4. Structural changes caused by H 2 adsorption on the Si(111)7 × 7 surface

    NASA Astrophysics Data System (ADS)

    Wolff, S. H.; Wagner, S.; Gibson, J. M.; Loretto, D.; Robinson, I. K.; Bean, J. C.

    1990-12-01

    Structural changes caused by the adsorption of molecular hydrogen adsorption onto the Si(111)7 × 7 surface reconstruction are quantified using the first structure parameter refinement on transmission electron diffraction (TED) data. We find that initial adsorption of molecular hydrogen onto the Si(111)7 × 7 surface causes a preferential decrease in the occupancy of the center adatoms. Further adsorption of hydrogen results in the breaking of the dimer bonds and the removal of the corner adatoms.

  5. THE FINE STRUCTURE OF STREPTOMYCES VIOLACEORUBER (S. COELICOLOR)

    PubMed Central

    Glauert, Audrey M.; Hopwood, David A.

    1961-01-01

    A study of thin sections of hyphae of Streptomyces violaceoruber in the electron microscope showed that the structure of the walls and the mode of formation of cross-walls are similar to those of Gram-positive bacteria. A beaded structure was seen in some regions of the wall, and the significance of this observation is discussed in relation to previous studies of the fine structure of bacterial cell walls. Elements of the intracytoplasmic membrane system appear to be involved in the process of cross-wall formation. The walls of the hyphae of the aerial mycelium divide into two layers before the spores are formed, and only the inner component of the wall grows inwards to form the cross-walls and so delimit the spores. The outer component remains intact for a time and acts as a sheath around the developing spores. Finally the sheath breaks and the spores are liberated. This process is contrasted with the formation of endospores in eubacteria. When the spores germinate, the walls of the germ tubes are continuous with those of the spores. PMID:13705984

  6. Shear rheology of mixed protein adsorption layers vs their structure studied by surface force measurements.

    PubMed

    Danov, Krassimir D; Kralchevsky, Peter A; Radulova, Gergana M; Basheva, Elka S; Stoyanov, Simeon D; Pelan, Eddie G

    2015-08-01

    The hydrophobins are proteins that form the most rigid adsorption layers at liquid interfaces in comparison with all other investigated proteins. The mixing of hydrophobin HFBII with other conventional proteins is expected to reduce the surface shear elasticity and viscosity, E(sh) and η(sh), proportional to the fraction of the conventional protein. However, the experiments show that the effect of mixing can be rather different depending on the nature of the additive. If the additive is a globular protein, like β-lactoglobulin and ovalbumin, the surface rigidity is preserved, and even enhanced. The experiments with separate foam films indicate that this is due to the formation of a bilayer structure at the air/water interface. The more hydrophobic HFBII forms the upper layer adjacent to the air phase, whereas the conventional globular protein forms the lower layer that faces the water phase. Thus, the elastic network formed by the adsorbed hydrophobin remains intact, and even reinforced by the adjacent layer of globular protein. In contrast, the addition of the disordered protein β-casein leads to softening of the HFBII adsorption layer. Similar (an even stronger) effect is produced by the nonionic surfactant Tween 20. This can be explained with the penetration of the hydrophobic tails of β-casein and Tween 20 between the HFBII molecules at the interface, which breaks the integrity of the hydrophobin interfacial elastic network. The analyzed experimental data for the surface shear rheology of various protein adsorption layers comply with a viscoelastic thixotropic model, which allows one to determine E(sh) and η(sh) from the measured storage and loss moduli, G' and G″. The results could contribute for quantitative characterization and deeper understanding of the factors that control the surface rigidity of protein adsorption layers with potential application for the creation of stable foams and emulsions with fine bubbles or droplets.

  7. Hierarchical Porous Zeolite Structures for Pressure Swing Adsorption Applications.

    PubMed

    Besser, Benjamin; Tajiri, Henrique Akira; Mikolajczyk, Gerd; Möllmer, Jens; Schumacher, Thomas C; Odenbach, Stefan; Gläser, Roger; Kroll, Stephen; Rezwan, Kurosch

    2016-02-10

    Porous adsorbents with hierarchical structured macropores ranging from 1 to 100 μm are prepared using a combination of freeze casting and additional sacrificial templating of polyurethane foams, with a zeolite 13X powder serving as adsorbent. The pore system of the prepared monoliths features micropores assigned to the zeolite 13X particle framework, interparticular pores of ∼1-2 μm, lamellar pores derived from freeze casting of ∼10 μm, and an interconnected pore network obtained from the sacrificial templates ranging from around 100 to 200 μm with a total porosity of 71%. Gas permeation measurements show an increase in intrinsic permeability by a factor of 14 for monoliths prepared with an additional sacrificial templated foam compared to monoliths solely providing freeze casting pores. Cyclic CO2 adsorption and desorption tests where pressure swings between 8 and 140 kPa reveal constant working capacities over multiple cycles. Furthermore, the monoliths feature a high volumetric working capacity of ∼1.34 mmol/cm(3) which is competitive to packed beds made of commercially available zeolite 13X beads (∼1.28 mmol/cm(3)). Combined with the faster CO2 uptake showing an adsorption of 50% within 5-8 s (beads ∼10 s), the monoliths show great potential for pressure swing adsorption applications, where high volumetric working capacities, fast uptakes, and low pressure drops are needed for a high system performance.

  8. Damping of Magnetohydrodynamic Waves in Solar Prominence Fine Structures

    NASA Astrophysics Data System (ADS)

    Soler, Roberto

    2010-05-01

    High-resolution observations of solar filaments and prominences reveal that these large-scale coronal structures are formed by a myriad of long and thin ribbons, here called threads, which are piled up to form the prominence body. Evidences suggest that these fine structures are magnetic flux tubes anchored in the solar photosphere, which are partially filled with the cool and dense prominence material. Individual and collective oscillations of prominence and filament fine structures are frequently reported by means of oscillatory variations in Doppler signals and spectral line intensity. Common features of these observations are that the reported oscillatory periods are usually in a narrow range between 2 and 10 minutes, that the velocity amplitudes are smaller than ˜3 km/s, and that the oscillations seem to be strongly damped after a few periods. Typically, the ratio of the damping time, tD, to the period, P, is tD/P < 10. While the oscillations have been interpreted in the context of the magnetohydrodynamic (MHD) theory, i.e., in terms of the MHD normal modes supported by the filament thread body and/or propagating MHD waves, the mechanism or mechanisms responsible for the damping are not well-known and a comparative study between different damping mechanisms is needed. In this Thesis, we study the efficiency of several physical mechanisms for the damping of MHD oscillations in prominence fine structures. Both individual and collective oscillations of threads are analyzed. We model a filament thread as a straight cylindrical magnetic flux tube with prominence conditions, embedded in a magnetized environment representing the solar coronal medium. The basic MHD equations are applied to the model and contain non-ideal terms accounting for effects as, e.g., non-adiabatic mechanisms, magnetic diffusion, ion-neutral collisions, etc., that may be of relevance in prominence plasmas and whose role on the damping of the oscillations is assessed. Our method combines

  9. Fine structure of the nucleus of the galaxy NGC 1275

    NASA Astrophysics Data System (ADS)

    Matveyenko, L. I.; Seleznev, S. V.

    2016-04-01

    The fine structure of the nucleus of the Seyfert galaxy NGC 1275 was investigated in 2005-2010 at a wavelength of 2 cm with a resolution as high as 50 μas. The structure consists of two parallel identical systems, eastern and western, spaced 0.5 pc apart in the plane of the sky. Each of them contains an ejector and a bipolar outflow. There are extended regions, lobes, at the extension of the bipolar outflows in the -10° and 170° directions at distances of 5 pc northward and 6.5 pc southward of the active zone. The observed difference between the jet and counterjet sizes by a factor of ~3 and between the distances to the lobes by a factor of 0.8 is determined by the difference between their velocities and by the change of sign of the outflow acceleration in the period of silence. The high-velocity bipolar outflows are surrounded by three pairs of low-velocity components. The diameters of the low-velocity coaxial outflows and the third component are Ø1 ≈ 0.3 pc, Ø2 ≈ 0.8 pc, and Ø3 ≈ 1.4 pc at the detection limit. The outer low-velocity components of the outflows encompass both high-velocity outflows. The velocities of the outflows and their brightness temperatures increase exponentially as the center of the high-velocity outflows is approached. The brightness temperatures of the high-velocity outflows at the ejector exit are T b > 1012 K. The spectral line velocities in the nuclear region differ by ~600 km s-1 due to the velocity difference between the two systems. In the case of Keplerian motion, the revolution period is ~5 × 103 yr, and the mass of the central massive bodies, black holes, is M ≈ 107M⊙. The fine structure suggests a vortical nature of the formation. In the case under consideration, two parallel vortices spaced ~0.5 pc apart and shifted by ~0.5 pc relative to each other were formed. The surrounding material inflows onto the disk of each system, is transferred in a spiral to the center, and is ejected in the -10° and 170

  10. Fine-scale genetic structuring on Manacus manacus leks.

    PubMed

    Shorey, L; Piertney, S; Stone, J; Höglund, J

    2000-11-16

    Leks have traditionally been considered as arenas where males compete to attract females and secure matings. Thus, direct fitness benefits mediated through competition between males to fertilize females have been considered to be the primary force driving the evolution of lekking behaviour. Inclusive fitness benefits mediated through kin selection may also be involved in lek formation and evolution, but to date this theory has been largely ignored. According to kin-selection theory, both reproducing and non-reproducing males may gain indirect inclusive fitness benefits. If females are attracted to larger leks, non-reproducing males add attractiveness to a lek, and therefore, in a genetically structured population, boost the reproductive success of kin. Theory predicts that the attractiveness of leks is plastic, and that males establish themselves on a lek in which the top male, in terms of reproductive success, is a close relative. Here we show that in white-bearded manakins (Manacus manacus), for which larger leks are more attractive to females and so secure the maximum number of matings, there is extraordinary fine-scale genetic structure, with leks being composed of clusters of related kin. We propose that males establish themselves where they find relatives to such an extent that they form groups within leks, and that such behaviour is consistent with kin-selection theory to maximize reproductive success of the group.

  11. FINE STRUCTURES AND OVERLYING LOOPS OF CONFINED SOLAR FLARES

    SciTech Connect

    Yang, Shuhong; Zhang, Jun; Xiang, Yongyuan

    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.

  12. Varying fine structure 'constant' and charged black holes

    SciTech Connect

    Bekenstein, Jacob D.; Schiffer, Marcelo

    2009-12-15

    Speculation that the fine-structure constant {alpha} varies in spacetime has a long history. We derive, in 4-D general relativity and in isotropic coordinates, the solution for a charged spherical black hole according to the framework for dynamical {alpha} J. D. Bekenstein, Phys. Rev. D 25, 1527 (1982).. This solution coincides with a previously known one-parameter extension of the dilatonic black hole family. Among the notable properties of varying-{alpha} charged black holes are adherence to a 'no hair' principle, the absence of the inner (Cauchy) horizon of the Reissner-Nordstroem black holes, the nonexistence of precisely extremal black holes, and the appearance of naked singularities in an analytic extension of the relevant metric. The exteriors of almost extremal electrically (magnetically) charged black holes have simple structures which makes their influence on applied magnetic (electric) fields transparent. We rederive the thermodynamic functions of the modified black holes; the otherwise difficult calculation of the electric potential is done by a shortcut. We confirm that variability of {alpha} in the wake of expansion of the universe does not threaten the generalized second law.

  13. Waves and Fine Structure in Expanding Laser-Produced Plasmas

    NASA Astrophysics Data System (ADS)

    Collette, Andrew; Gekelman, Walter

    2009-11-01

    The behavior of expanding dense plasmas has long been a topic of interest in space plasma research, particularly in the case of expansion within a magnetized background. Previous laser-plasma experiments at the UCLA Large Plasma Device have observed the creation of strong (δBB > 50%) diamagnetic cavities, along with large-scale wave activity and hints of fine-scale structure. A new series of experiments conducted recently at the LaPD performs direct measurement of the fields inside the expanding plasma via a novel 2D probe drive system. This system combines small-scale (0.5mm-1mm) magnetic and electric field probes with high-accuracy vacuum ceramic motors, to allow measurement of the plasma volume over a 2000-point grid at 1mm resolution. The data reveal both coherent high-amplitude waves associated with the formation of these magnetic features, and complicated small-scale structure in both the magnetic field and floating potential. In addition, we will present correlation techniques using multiple independent B and E field probes. This reveals behavior of turbulent, non-phase-locked phenomena. Both the case of a single expanding plasma and two colliding plasmas were studied.

  14. Fine structure behaviour of VVER-1000 RPV materials under irradiation

    NASA Astrophysics Data System (ADS)

    Gurovich, B. A.; Kuleshova, E. A.; Shtrombakh, Ya. I.; Erak, D. Yu.; Chernobaeva, A. A.; Zabusov, O. O.

    2009-06-01

    Changes in the fine structure and mechanical properties of the base metal (BM) and weld metal (WM) of VVER-1000 pressure vessels during accumulation of neutron dose in the range of fluences ˜(3.2-15) × 10 23 m -2 ( E > 0.5 MeV) at 290 °C are studied using methods of transmission electron microscopy, fractographic analysis, and Auger electron spectroscopy. A correlation was found between the changes of mechanical properties and the micro- and nano-structures of the studied steels. Accumulation of neutron dose considerably raises the strength characteristics and transition temperature of VVER-1000 pressure vessel steels. The rate of changes in the mechanical properties of the weld metal is significantly higher than that of the base metal. The slower growth of strength characteristics and transition temperature shift of the base metal under irradiation as compared with the weld metal is due to the slower growth of the density of radiation defects and radiation-induced precipitates. The level of intergranular embrittlement under irradiation in the weld metal is not higher then in the base metal in spite of the higher content of nickel.

  15. PDR modeling of the LWS fine-structure lines in ultraluminous galaxies

    NASA Technical Reports Server (NTRS)

    Luhman, M. L.; Satyapal, S.; Fischer, J.; Wolfire, M. G.

    1997-01-01

    The observations performed onboard the Infrared Space Observatory (ISO) long wavelength spectrometer (LWS) on the fine structure lines in ultraluminous galaxies are reported on. The C II 158 micrometer, the O I 63 and 146 micrometer fine structure lines were detected. These lines were compared to the results of the revised theoretical models of extragalactic photodissociation regions (PDRs). The PDR origin of the fine structure lines and the physical properties of the PDR component are discussed.

  16. A Simple Model for Fine Structure Transitions in Alkali-Metal Noble-Gas Collisions

    DTIC Science & Technology

    2015-03-01

    fine- structure transition rates of the alkali atoms . The integration of this integral is primarily performed nu- merically, using an adaptive Romberg...Previous work on the fine structure transitions of alkali atoms as they collide with noble gas atoms includes a full quantum mechanical calculation of...adiabaticity in alkali atom fine structure mixing”. SPIE LASE, 896207–896207. International Society for Optics and Photonics, 2014. 4. Griffiths, David J

  17. Fine structure analysis of Salmonella typhimurium glutamate synthase genes.

    PubMed Central

    Madonna, M J; Fuchs, R L; Brenchley, J E

    1985-01-01

    Glutamate synthase activity is required for the growth of Salmonella typhimurium on media containing a growth-rate-limiting nitrogen source. Mutations that alter glutamate synthase activity had been identified in the gltB gene, but it was not known which of the two nonidentical subunits of the enzyme was altered. To examine the gene-protein relationship of the glt region, two nonsense mutations were identified and used to demonstrate that gltB encodes the large subunit of the enzyme. Six strains with independent Mu cts d1 (lac bla) insertions were isolated, from which a collection of deletion mutations was obtained. The deletions were transduced with the nonsense mutations and 38 other glt point mutations to construct a fine-structure genetic map. Chromosome mobilization studies, mediated by Hfr derivatives of Mu cts d1 lysogens, showed that gltB is transcribed in a clockwise direction, as shown in the S. typhimurium linkage map. Studies of the polar effects of three Mu cts d1 insertions indicated that the gene for the small subunit maps clockwise to gltB and that the two genes are cotranscribed to form a glt operon. Images PMID:3881392

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

    PubMed Central

    Boeddeker, Norbert; Mertes, Marcel; Dittmar, Laura; Egelhaaf, Martin

    2015-01-01

    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. PMID:26352836

  19. FINE STRUCTURE OF THE EYE OF A CHAETOGNATH.

    PubMed

    EAKIN, R M; WESTFALL, J A

    1964-04-01

    Electron microscopy reveals a star-like pigment cell at the center of the eye of the arrow-worm, Sagitta scrippsae. Between the arms of the pigment cell are clusters of photoreceptor cell processes, each process consisting of: (1) a tubular segment containing longitudinally arranged microtubules about 500 A in diameter and 20 micro in length; (2) a remarkable conical body, composed of cords and large granules, situated at the base of the tubular segment; and (3) a connecting piece which, like that of rods and cones, connects the process with the sensory cell proper and through which runs a fibrillar apparatus consisting of nine peripheral double tubules. Beneath the connecting piece lies a typical centriole with a striated rootlet. The receptor cell process is deeply recessed into the sensory cell which may possess a corona of microvilli at its inner surface. A nerve fiber arises from the outer end of the cell and passes into the optic nerve. Additional features are some supporting cells, an external layer of flattened epithelial cells, and an over-all investment of basement membrane and thick fibrous capsule. The fine structure and function of these elements of the eye are discussed in relation to earlier studies with the light microscope. The ciliary nature of the photoreceptor cell process in S. scrippsae points to a probable evolutionary relationship of chaetognaths to echinoderms and chordates.

  20. THE FINE STRUCTURE OF VON EBNER'S GLAND OF THE RAT

    PubMed Central

    Hand, Arthur R.

    1970-01-01

    The fine structure of von Ebner's gland was studied in untreated rats and rats stimulated to secrete by fasting-refeeding or injection of pilocarpine. Cytological features were similar to those reported for pancreas and parotid gland. Abundant granular endoplasmic reticulum filled the basal portion of the cell, a well-developed Golgi complex was located in the vicinity of the nucleus, and the apical portion of the cell was filled with dense secretory granules. Dense heterogeneous bodies resembling lysosomes were closely associated with the Golgi complex. Coated vesicles were seen in the Golgi region and also in continuity with the cell membrane. Granule discharge occurred by fusion of the granule membrane with the cell membrane at the secretory surface. Successive fusion of adjacent granules to the previously fused granule formed a connected string of granules in the apical cytoplasm. Myoepithelial cells were present within the basement membrane, and nerve processes were seen adjacent to acinar and myoepithelial cells. Duct cells resembled the intercalated duct cells of the major salivary glands. PMID:5411078

  1. Hymenolepis nana: the fine structure of the embryonic envelopes.

    PubMed

    Fairweather, I; Threadgold, L T

    1981-06-01

    The fine structure of the envelopes surrounding hatched and unhatched oncospheres of Hymenolepis nana has been investigated by transmission and scanning electron microscopy (SEM), together with light microscope histochemical observations of JB-4 embedded material. The oncosphere is surrounded by 3 layers--the capsule, the outer envelope and the inner envelope, the latter giving rise to the embryophore and the 'oncospheral membrane'. An additional layer--the polar filament layer--lies between the 'oncospheral membrane' and the oncosphere. Shell material is deposited on the capsule as a thin layer. It is secreted by the outer envelope, which degenerates once shell formation is complete. The uterus may also contribute to shell formation. The embryophore forms a thin incomplete and peripheral layer within the inner envelope. In the basal region of this envelope, partial development of an 'oncospheral membrane' takes place, but it does not become detached as a separate layer. The polar filaments, which are characteristic of the oncosphere of H. nana, are derived from the epithelial covering of the oncosphere itself, which delaminates to form a separate polar filament layer. The filaments arise from knob-like projections at opposite poles of this layer. The design of the embryonic envelopes in H. nana show a number of modifications from the basic cyclophyllidean pattern, and these can be related to the demands of its 'direct' life-cycle.

  2. THE FINE STRUCTURE OF THE ELECTRIC ORGAN OF TORPEDO MARMORATA

    PubMed Central

    Sheridan, Michael N.

    1965-01-01

    The fine structure of the electric organ of the fish Torpedo marmorata has been examined after osmium tetroxide or potassium permanganate fixation, acetone dehydration, and Araldite embedment. This organ consists of stacks of electroplaques which possess a dorsal noninnervated and a ventral richly innervated surface. Both surfaces are covered with a thin basement membrane. A tubular membranous network whose lumen is continuous with the extracellular space occupies the dorsal third of the electroplaque. Nerve endings, separated from the ventral surface of the electroplaque by a thin basement membrane, contain synaptic vesicles (diameter 300 to 1200 A), mitochondria, and electron-opaque granules (diameter 300 A). Projections from the nerve endings occupy the lumina of the finger-like invaginations of the ventral surface. The cytoplasm of the electroplaques contains the usual organelles. A "cellular cuff" surrounds most of the nerve fibers in the intercellular space, and is separated from the nerve fibre and its Schwann cell by a space containing connective tissue fibrils. The connective tissue fibrils and fibroblasts in the intercellular space are primarily associated with the dorsal surface of the electroplaque. PMID:14286287

  3. Fine structure genetic analysis of a beta-globin promoter.

    PubMed

    Myers, R M; Tilly, K; Maniatis, T

    1986-05-02

    A novel procedure for saturation mutagenesis of cloned DNA was used to obtain more than 100 single base substitutions within the promoter of the mouse beta-major globin gene. The effects of these promoter substitutions on transcription were determined by transfecting the cloned mutant genes into HeLa cells on plasmids containing an SV40 transcription enhancer, and measuring the levels of correctly initiated beta-globin transcripts after 2 days. Mutations in three regions of the promoter resulted in a significant decrease in the level of transcription: (i) the CACCC box, located between -87 and -95, (ii) the CCAAT box, located between -72 and -77, and (iii) the TATA box, located between -26 and -30 relative to the start site of transcription. In contrast, two different mutations in nucleotides immediately upstream from the CCAAT box resulted in a 3- to 3.5-fold increase in transcription. With two minor exceptions, single base substitutions in all other regions of the promoter had no effect on transcription. These results precisely delineate the cis-acting sequences required for accurate and efficient initiation of beta-globin transcription, and they establish a general approach for the fine structure genetic analysis of eukaryotic regulatory sequences.

  4. Fine structure of A and M antigens from Brucella biovars.

    PubMed

    Meikle, P J; Perry, M B; Cherwonogrodzky, J W; Bundle, D R

    1989-09-01

    Brucella A and M epitopes were found on single O-polysaccharide chains of all biotype strains of this species. Lipopolysaccharides from the type and reference strains of five of the six Brucella species, B. abortus, B. melitensis, B. suis, B. canis, and B. neotomae, were extracted and purified. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in conjunction with silver staining and immunoblotting developed by monoclonal antibodies, showed bands characteristic of A, M, or mixed A and M antigens. The A antigen previously described as an exclusively alpha 1,2-linked homopolymer of 4,6-dideoxy-4-formamido-D-mannopyranose was shown by 1H and 13C nuclear magnetic resonance spectroscopy to possess a fine structure consistent with the low-frequency occurrence of alpha 1, 3-linked 4,6-dideoxy-4-formamido-D-mannopyranose residues. This feature was previously attributed only to the M antigen, which is also a homopolymer of the same sugar. B. melitensis biotype 3 and B. suis biotype 4 lipopolysaccharides showed characteristics of mixed A and M antigens. Immunoabsorption of these O polysaccharides on a column of immobilized A-antigen-specific monoclonal antibody enriched polymer chains with A-antigen characteristics but did not eliminate M epitopes. Composite A- and M-antigen characteristics resulted from O polysaccharides in which the frequency of alpha 1,3 linkages, and hence, M-antigen characteristics, varied. All biotypes assigned as A+ M- expressed one or two alpha 1,3-linked residues per polysaccharide O chain. M antigens (M+ A-) also possessed a unique M epitope as well as a tetrasaccharide determinant common to A-antigen structures. B. canis and B. abortus 45/20, both rough strains, expressed low-molecular-weight A antigen.

  5. Fine structure of the 2003 geomagnetic jerk near China

    NASA Astrophysics Data System (ADS)

    Ou, J.; Du, A.

    2015-12-01

    The 2003 jerk has an abrupt change in the geomagnetic secular variation (SV), and was recognized as a local phenomenon of internal origin from the satellite observations (Olsen and Mandea, 2007). Notable strength of the 2003 jerk is located near China. The temporal and spatial features at this area are important to resolve the Earth's core fluid flow dynamics at local scale (e.g. Wardinski et al., 2008). We investigate the temporal-spatial development of the 2003 jerk in more detail near China with the ground-based observations and CHAOS-3 core field model. We select the data in the international geomagnetic quiet days to calculate the monthly means. In order to reduce the influence of the external field, we adopt a function comprising the terms associated with the indices of the geomagnetic activity, and the terms of the periodic signals on the observatory monthly means data (Stewart and Whaler, 1992). We then use an empirical AR-2 model to represent the internal field signals in the observatory data. The extreme detection is applied to identify the jerk in the SV time series. The onset time and the strength of the 2003 jerk are obtained through the detection for geomagnetic field component, X, Y and Z. The maximum of the strength of the 2003 jerk is located under the Indian mainland. The onset time of this jerk propagates approximately southeastward. Two jerks in 2001 and 2003 for the Z component are further compared and they are confirmed as independent processes. We suggest the jerk in 2001 identical to the well known 1999 jerk in Europe (Mandea et al., 2000). Our results reveal the fine structures of the 2003 jerk that corroborate the conclusions in previous studies. The larger scale time-spatial structure given by the AR-2 model constructed from ground observatory data (monthly values) is consistent with the results from the CHAOS-3 model. This structure can be applied for further inversion of the local core surface fluid flow motions.

  6. SEISMOLOGY OF STANDING KINK OSCILLATIONS OF SOLAR PROMINENCE FINE STRUCTURES

    SciTech Connect

    Soler, R.; Arregui, I.; Oliver, R.; Ballester, J. L.

    2010-10-20

    We investigate standing kink magnetohydrodynamic (MHD) oscillations in a prominence fine structure modeled as a straight and cylindrical magnetic tube only partially filled with the prominence material and with its ends fixed at two rigid walls representing the solar photosphere. The prominence plasma is partially ionized and a transverse inhomogeneous transitional layer is included between the prominence thread and the coronal medium. Thus, ion-neutral collisions and resonant absorption are the damping mechanisms considered. Approximate analytical expressions of the period, the damping time, and their ratio are derived for the fundamental mode in the thin tube and thin boundary approximations. We find that the dominant damping mechanism is resonant absorption, which provides damping ratios in agreement with the observations, whereas ion-neutral collisions are irrelevant for damping. The values of the damping ratio are independent of both the prominence thread length and its position within the magnetic tube, and coincide with the values for a tube fully filled with the prominence plasma. The implications of our results in the context of the MHD seismology technique are discussed, pointing out that the reported short-period (2-10 minutes) and short-wavelength (700-8000 km) thread oscillations may not be consistent with a standing mode interpretation and could be related to propagating waves. Finally, we show that the inversion of some prominence physical parameters, e.g., Alfven speed, magnetic field strength, transverse inhomogeneity length scale, etc., is possible using observationally determined values of the period and damping time of the oscillations along with the analytical approximations of these quantities.

  7. A New Physical Meaning of Sommerfeld Fine Structure Constant

    NASA Astrophysics Data System (ADS)

    Sohrab, Siavash

    2015-04-01

    Identifying physical space or Casimir vacuum as a compressible tachyon fluid, Planck compressible ether, leads to stochastic definitions of Planck h = mk <λk > c and Boltzmann k = mk <νk > c constants, finite photon mass mk = (hk/c3)1/2 , amu = mk c2 = (hkc)1/2 , and modified Avogadro-Loschmidt number No = 1/(hkc)1/2 = 6.03766 x1023 mole-1 . Thus, Lorentz-FitzGerald contractions now result from compressibility of physical space and become causal (Pauli) in accordance with Poincaré-Lorentz dynamic theory of relativity as opposed to Einstein kinematic theory of relativity. At thermodynamic equilibrium he = me <λe > ve = hk = mk <λk > c = h, Compton wavelength can be expressed as λc = h/me c = (ve /c)h <λe > /(me <λe > ve) = αλe . Hence, Sommerfeld fine structure constant α is identified as the ratio of electron to photon speeds α = e2/(2ɛo hc) = ve/c = 1/137.036. The mean thermal speed of electron at equilibrium with photon gas is ve = 2.187640x106 m/s and its de Broglie wavelength is λe = 3.3250x10-10 m. Also, electron kinetic energy for oscillations in two directions < x + > and < x- > or ɛe = hνe = me ve2= kTe results in electron temperature Te = 3.15690x105 K.

  8. Fine structure of high-power microwave-induced resistance oscillations

    NASA Astrophysics Data System (ADS)

    Shi, Q.; Zudov, M. A.; Dmitriev, I. A.; Baldwin, K. Â. W.; Pfeiffer, L. Â. N.; West, K. Â. W.

    2017-01-01

    We report on observation of a fine structure of microwave-induced resistance oscillations in an ultraclean two-dimensional electron gas. This fine structure is manifested by multiple secondary sharp extrema, residing beside the primary ones, which emerge at high radiation power. Theoretical considerations reveal that this fine structure originates from multiphoton-assisted scattering off short-range impurities. Unique properties of the fine structure allow us to access all experimental parameters, including microwave power, and to separate different contributions to photoresistance. Furthermore, we show that the fine structure offers a convenient means to quantitatively assess the correlation properties of the disorder potential in high-quality systems, allowing separation of short- and long-range disorder contributions to the electron mobility.

  9. Beyond carbon nanotubes: adsorptions on and electronic structures of silicon nanotubes.

    PubMed

    Chen, Haoliang; Ray, Asok K

    2014-02-01

    In this paper, we have reviewed some of the recent theoretical studies on the electronic and structural properties of silicon nanotubes from single-walled to double-walled nanostructures, primarily focusing on the studies performed by the present authors. The studies so far have not indicated any metallic behavior in both single-walled and double-walled silicon nanotubes. Atomic and molecular adsorptions of elements including hydrogen, oxygen and alkali metals on single-walled silicon nanotubes are also reviewed and new results presented in detail. A systematic study of molecular adsorption and co-adsorptions of hydrogen and oxygen molecules in zigzag silicon nanotube (SiNT) has been performed using hybrid density functional theory. For adsorption of two hydrogen molecules in SiNT (10, 0), the original diatomic molecular structure was maintained after adsorption. The most preferred final site for hydrogen molecules is the on-top site. For adsorption of two oxygen molecules, the most preferred sites are bridge sites, which are the parallel or zigzag bridge sites. Complete dissociation, partial dissociation and non-dissociation were observed for adsorption of two oxygen molecules. Peroxide structure and Si-O-O structures have also been observed in adsorption of two oxygen molecules with smaller adsorption energies rather than complete dissociation. For the co-adsorption of one hydrogen molecule and one oxygen molecule, the hydrogen molecule is slightly polarized, and a suppression effect on HOMO-LUMO gap was observed.

  10. THE FINE STRUCTURE OF CORTICAL COMPONENTS OF PARAMECIUM MULTIMICRONUCLEATUM

    PubMed Central

    Sedar, Albert W.; Porter, Keith R.

    1955-01-01

    additional fiber system, the infraciliary lattice system, which is separate and distinct from the kinetodesmal system. This system consists of a fibrous network of irregular polygons and runs roughly parallel to the surface of the animal. Mitochondria have a fine structure similar in general features to that described for a number of mammalian cell types, but different in certain details. The structures corresponding to cristae mitochondriales appear as finger-like projections or microvilli extending into the matrix of the organelle from the inner membrane of the paired mitochondrial membrane. The cortical cytoplasm contains also a particulate component and a system of vesicles respectively comparable to the nucleoprotein particles and to the endoplasmic reticulum described in various metazoan cell types. An accessory kinetosome has been observed in oblique sections of a number of non-dividing specimens slightly removed from the ciliary kinetosome and on the same meridional line as the cilia and trichocysts. Its position corresponds to the location of the kinetosome of the newly formed cilium in animals selected as being in the approaching fission stage of the life cycle. PMID:13278368

  11. Fine Resolution Termohaline Structure Of The Yuctatan Coastal Sea

    NASA Astrophysics Data System (ADS)

    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

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

    SciTech Connect

    Zheng, Y. |; Shirley, D.A.

    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}.

  13. CRYOGENIC ADSORPTION OF HYDROGEN ISOTOPES OVER NANO-STRUCTURED MATERIALS

    SciTech Connect

    Xiao, S.; Heung, L.

    2010-10-07

    Porous materials such as zeolites, activated carbon, silica gels, alumina and a number of industrial catalysts are compared and ranked for hydrogen and deuterium adsorption at liquid nitrogen temperature. All samples show higher D{sub 2} adsorption than that of H{sub 2}, in which a HY sample has the greatest isotopic effect while 13X has the highest hydrogen uptake capacity. Material's moisture content has significant impact to its hydrogen uptake. A material without adequate drying could result in complete loss of its adsorption capacity. Even though some materials present higher H{sub 2} adsorption capacity at full pressure, their adsorption at low vapor pressure may not be as good as others. Adsorption capacity in a dynamic system is much less than in a static system. A sharp desorption is also expected in case of temperature upset.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Influences of the adsorption of different elements on the electronic structures of a tin sulfide monolayer.

    PubMed

    Li, Yang; Xia, Congxin; Du, Juan; Xiong, Wenqi; Li, Xueping; Wei, Shuyi

    2017-02-15

    Based on first-principles calculations, we investigated the adsorption energy, structural parameters, and electronic and magnetic properties for the adsorption of different atoms, including light metals, hydrogen, oxygen, and 3D transition metals (TM) adatoms, on a tin sulfide (SnS) monolayer. The results showed that Li- and Al-atom adsorption can effectively induce n-type carriers, whereas O atom adsorption can produce p-type doping in the SnS monolayer. In addition, except for Ni atoms, the other adatoms can induce magnetism in the SnS monolayer. Moreover, for Fe- and Co-atom adsorption, the occupied and unoccupied states belong to the same spin-channel. These results indicate that surface adsorption is an effective method to tune the electronic structures of the SnS monolayer.

  16. On the 1s24d Fine Structures of B III and Ne VIII

    NASA Astrophysics Data System (ADS)

    Wang, Zhiwen; Z, W. Wang; Kwong, T. Chung; Zhu, Xiaowei

    1995-01-01

    The fine structure of lithium-like 1s24d states in the literature behaves irregularly as a function of Z. The fine structures of the B III and Ne VIII fall well below the isoelectronic curve. The term energies of these two systems in the data tables also give worse agreement with the theoretical prediction. In this work, we show that the reason for this unusual situation is caused by a misidentification in the original spectra. When the correct identifications are made, the fine structures of both systems fall on the isoelectronic curve and the agreement between theory and experiment is excellent.

  17. Fine-scale structure in the far-infrared Milky-Way

    NASA Technical Reports Server (NTRS)

    Waller, William H.; Wall, William F.; Reach, William T.; Varosi, Frank; Ebert, Rick; Laughlin, Gaylin; Boulanger, Francois

    1995-01-01

    This final report summarizes the work performed and which falls into five broad categories: (1) generation of a new data product (mosaics of the far-infrared emission in the Milky Way); (2) acquisition of associated data products at other wavelengths; (3) spatial filtering of the far-infrared mosaics and resulting images of the FIR fine-scale structure; (4) evaluation of the spatially filtered data; (5) characterization of the FIR fine-scale structure in terms of its spatial statistics; and (6) identification of interstellar counterparts to the FIR fine-scale structure.

  18. Measurement of the lithium 10p fine structure interval and absolute energy

    SciTech Connect

    Oxley, Paul; Collins, Patrick

    2010-02-15

    We report a measurement of the fine structure interval of the {sup 7}Li 10p atomic state with a precision significantly better than previous measurements of fine structure intervals of Rydberg {sup 7}Li p states. Our result of 74.97(74) MHz provides an experimental value for the only n=10 fine structure interval which is yet to be calculated. We also report a measurement of the absolute energy of the 10p state and its quantum defect, which are, respectively, 42379.498(23)cm{sup -1} and 0.04694(10). These results are in good agreement with recent calculations.

  19. Magnetic diffusion instability and the fine structures of soler active region

    NASA Astrophysics Data System (ADS)

    Zhou, Dao-qi; Qian, Jing-kui; Ai, Guo-xiang

    1990-03-01

    Continuous observations over five days with the magnetic field telescope at Huairou yielded some clear characteristics of the fine structures in sunspot active regions. Starting from magnetic diffusivity being a function of temperature and using the induction equation we investigated the cause of the fine structures. Using linear perturbation of the MHD equations we found the instability mode. This gives rise to inhomogeneous structures in the originally smooth magnetic field and is the cause of the fine structures. Our observed fibrilles are about 1.5″ to 3.0″, or 1000 to 2000km in size, whereas, with certain typical values of sunspot parameters the theoretical lower limit for the fine structures is about 220km, in agreement with some observational estimates.

  20. Adsorption structure and bonding of trimesic acid on Cu(100)

    NASA Astrophysics Data System (ADS)

    Kanninen, L.; Jokinen, N.; Ali-Löytty, H.; Jussila, P.; Lahtonen, K.; Hirsimäki, M.; Valden, M.; Kuzmin, M.; Pärna, R.; Nõmmiste, E.

    2011-12-01

    Combining scanning tunneling microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy using synchrotron radiation, we have studied the adsorption and growth of trimesic acid (TMA, 1,3,5-benzenetricarboxylic acid, C6H3(COOH)3) on Cu(100) in a wide range of coverages (from submonolayer to multilayer ones) at room temperature and after subsequent annealing. A series of coverage-dependent TMA structures, transitions between these structures, and their properties are characterized, demonstrating the interplay between the bonding, orientation, and deprotonation reaction of adsorbed species. In particular, it is shown that the degree of deprotonation in TMA overlayers depends on the amount of deposited molecules non-monotonously, and that such behavior is well consistent with the formation mechanism proposed for the TMA/Cu(100) system. The results provide a good platform for further understanding of non-covalent interactions and self-assembly phenomena underlying the growth of supramolecular nanoassemblies of aromatic carboxylic (benzenecarboxylic) acids on metallic substrates.

  1. Arsenate adsorption structures on aluminum oxide and phyllosilicate mineral surfaces in smelter-impacted soils.

    PubMed

    Beaulieu, Brett T; Savage, Kaye S

    2005-05-15

    A clearer understanding of arsenic (As) retention and transport in forest soils impacted by copper smelter emissions may reduce risks to human health and provide insight into As behavior in the vadose zone. On Vashon-Maury Island in Puget Sound, As is predominantly associated with the fine (< 63 microm) fraction of surficial soils. X-ray diffraction of oriented samples from the < 2 microm size fraction indicate that clinochlore isthe dominant phyllosilicate. X-ray absorption spectroscopy (XAS) was employed to examine As oxidation state and local coordination environment in impacted soil samples. Arsenic is present as As(V) in tetrahedral coordination with oxygen, associated with aluminum (Al) octahedra in bidentate binuclear (bridging) structures with As-Al distances of 3.15 - 3.16 angstroms. Including multiple scattering (MS) paths derived from the arsenate tetrahedron in esperanzaite significantly improved the match between XAS fine structure (EXAFS) data and models generated from theoretical phase and amplitude functions. The data are interpreted to indicate arsenate adsorption onto poorly crystalline aluminum oxyhydroxides and/or the edges of clinochlore interlayer hydroxyl sheets with constrained geometries causing MS to be important This implies that As initially released from the smelter as particulate As(III) and As(V) oxides was oxidized, dissolved, and adsorbed onto soil minerals and colloids; no evidence for relic arsenic oxide was observed. Physical transport of arsenic oxide particles and As adsorbed on soil colloids may account for limited downward migration of As within the soil column. The oxidizing and mildly acidic pH conditions in the upper vadose zone promote stable sorption complexes; barring substantial changes in soil chemistry, As is not expected to experience significant mobilization.

  2. Fine structural characterization of microbodies and Woronin bodies in Trichophyton mentagrophytes.

    PubMed

    Vannini, G L; Mares, D

    1975-08-15

    Microbodies and Woronin bodies, organelles surrounded by a single unit membrane, were identified in the hyphal cells of Trichophyton mentagrophytes by employing a fixative containing TAPO. The fine structure of the organelles is described and their possible significance discussed.

  3. Impaired perception of temporal fine structure and musical timbre in cochlear implant users.

    PubMed

    Heng, Joseph; Cantarero, Gabriela; Elhilali, Mounya; Limb, Charles J

    2011-10-01

    Cochlear implant (CI) users demonstrate severe limitations in perceiving musical timbre, a psychoacoustic feature of sound responsible for 'tone color' and one's ability to identify a musical instrument. The reasons for this limitation remain poorly understood. In this study, we sought to examine the relative contributions of temporal envelope and fine structure for timbre judgments, in light of the fact that speech processing strategies employed by CI systems typically employ envelope extraction algorithms. We synthesized "instrumental chimeras" that systematically combined variable amounts of envelope and fine structure in 25% increments from two different source instruments with either sustained or percussive envelopes. CI users and normal hearing (NH) subjects were presented with 150 chimeras and asked to determine which instrument the chimera more closely resembled in a single-interval two-alternative forced choice task. By combining instruments with similar and dissimilar envelopes, we controlled the valence of envelope for timbre identification and compensated for envelope reconstruction from fine structure information. Our results show that NH subjects utilize envelope and fine structure interchangeably, whereas CI subjects demonstrate overwhelming reliance on temporal envelope. When chimeras were created from dissimilar envelope instrument pairs, NH subjects utilized a combination of envelope (p = 0.008) and fine structure information (p = 0.009) to make timbre judgments. In contrast, CI users utilized envelope information almost exclusively to make timbre judgments (p < 0.001) and ignored fine structure information (p = 0.908). Interestingly, when the value of envelope as a cue was reduced, both NH subjects and CI users utilized fine structure information to make timbre judgments (p < 0.001), although the effect was quite weak in CI users. Our findings confirm that impairments in fine structure processing underlie poor perception of musical timbre in CI

  4. Path integral formalism for the spectral line shape in plasmas: Lyman-{alpha} with fine structure

    SciTech Connect

    Bedida, N.; Meftah, M. T.; Boland, D.; Stamm, R.

    2008-10-22

    We examine in this work the expression of the dipolar autocorrelation function for an emitter in the plasma using the path integrals formalism. The results for Lyman alpha lines with fine structure are retrieved in a compact formula. The expression of the dipolar autocorrelation function takes into account the ions dynamics and the fine structure effects. The electron's effect is represented by the impact operator {phi}{sub e} in the final formula.

  5. Characterization of Tight Gas Reservoir Pore Structure Using USANS/SANS and Gas Adsorption Analysis

    SciTech Connect

    Clarkson, Christopher R; He, Lilin; Agamalian, Michael; Melnichenko, Yuri B; Mastalerz, Maria; Bustin, Mark; Radlinski, Andrzej Pawell; Blach, Tomasz P

    2012-01-01

    Small-angle and ultra-small-angle neutron scattering (SANS and USANS) measurements were performed on samples from the Triassic Montney tight gas reservoir in Western Canada in order to determine the applicability of these techniques for characterizing the full pore size spectrum and to gain insight into the nature of the pore structure and its control on permeability. The subject tight gas reservoir consists of a finely laminated siltstone sequence; extensive cementation and moderate clay content are the primary causes of low permeability. SANS/USANS experiments run at ambient pressure and temperature conditions on lithologically-diverse sub-samples of three core plugs demonstrated that a broad pore size distribution could be interpreted from the data. Two interpretation methods were used to evaluate total porosity, pore size distribution and surface area and the results were compared to independent estimates derived from helium porosimetry (connected porosity) and low-pressure N{sub 2} and CO{sub 2} adsorption (accessible surface area and pore size distribution). The pore structure of the three samples as interpreted from SANS/USANS is fairly uniform, with small differences in the small-pore range (< 2000 {angstrom}), possibly related to differences in degree of cementation, and mineralogy, in particular clay content. Total porosity interpreted from USANS/SANS is similar to (but systematically higher than) helium porosities measured on the whole core plug. Both methods were used to estimate the percentage of open porosity expressed here as a ratio of connected porosity, as established from helium adsorption, to the total porosity, as estimated from SANS/USANS techniques. Open porosity appears to control permeability (determined using pressure and pulse-decay techniques), with the highest permeability sample also having the highest percentage of open porosity. Surface area, as calculated from low-pressure N{sub 2} and CO{sub 2} adsorption, is significantly less

  6. Globular Clusters as Tracers of Fine Structure in the Dramatic Shell Galaxy NGC 474

    NASA Astrophysics Data System (ADS)

    Lim, Sungsoon; Peng, Eric W.; Duc, Pierre-Alain; Fensch, Jérémy; Durrell, Patrick R.; Harris, William E.; Cuillandre, Jean-Charles; Gwyn, Stephen; Lançon, Ariane; Sánchez-Janssen, Rúben

    2017-02-01

    Globular clusters (GCs) are some of the most visible tracers of the merging and accretion histories of galaxy halos. Metal-poor GCs, in particular, are thought to arrive in massive galaxies largely through dry, minor merging events, but it is rare to see a direct connection between GCs and visible stellar streams. NGC 474 is a post-merger early-type galaxy with dramatic fine structures made of concentric shells and radial streams that have been more clearly revealed by deep imaging. We present a study of GCs in NGC 474 to better establish the relationship between merger-induced fine structure and the GC system. We find that many GCs are superimposed on visible streams and shells, and about 35% of GCs outside 3{R}{{e},{galaxy}} are located in regions of fine structure. The spatial correlation between GCs and fine structure is significant at the 99.9% level, which shows that this correlation is not coincidental. The colors of GCs on fine structures are mostly blue, and we also find an intermediate-color population that is dominant in the central region and that will likely passively evolve to have colors consistent with a traditional metal-rich GC population. The association of the blue GCs with fine structures is direct confirmation that many metal-poor GCs are accreted onto massive galaxy halos through merging events and that the progenitors of these mergers are sub-{L}\\star galaxies.

  7. Effects of contralateral acoustic stimulation on spontaneous otoacoustic emissions and hearing threshold fine structure.

    PubMed

    Dewey, James B; Lee, Jungmee; Dhar, Sumitrajit

    2014-12-01

    Medial olivocochlear (MOC) influence on cochlear mechanics can be noninvasively, albeit indirectly, explored via the effects of contralateral acoustic stimulation (CAS) on otoacoustic emissions. CAS-mediated effects are particularly pronounced for spontaneous otoacoustic emissions (SOAEs), which are typically reduced in amplitude and shifted upward in frequency by CAS. We investigated whether similar frequency shifts and magnitude reductions were observed behaviorally in the fine structure of pure-tone hearing thresholds, a phenomenon thought to share a common underlying mechanism with SOAEs. In normal-hearing listeners, fine-resolution thresholds were obtained over a narrow frequency range centered on the frequency of an SOAE, both in the absence and presence of 60-dB SPL broadband CAS. While CAS shifted threshold fine structure patterns and SOAEs upward in frequency by a comparable amount, little reduction in the presence or depth of fine structure was observed at frequencies near those of SOAEs. In fact, CAS typically improved thresholds, particularly at threshold minima, and increased fine structure depth when reductions in the amplitude of the associated SOAE were less than 10 dB. Additional measurements made at frequencies distant from SOAEs, or near SOAEs that were more dramatically reduced in amplitude by the CAS, revealed that CAS tended to elevate thresholds and reduce threshold fine structure depth. The results suggest that threshold fine structure is sensitive to MOC-mediated changes in cochlear gain, but that SOAEs complicate the interpretation of threshold measurements at nearby frequencies, perhaps due to masking or other interference effects. Both threshold fine structure and SOAEs may be significant sources of intersubject and intrasubject variability in psychoacoustic investigations of MOC function.

  8. The fine scale genetic structure of the British population

    PubMed Central

    Davison, Dan; Boumertit, Abdelhamid; Day, Tammy; Hutnik, Katarzyna; Royrvik, Ellen C; Cunliffe, Barry; Lawson, Daniel J; Falush, Daniel; Freeman, Colin; Pirinen, Matti; Myers, Simon; Robinson, Mark; Donnelly, Peter; Bodmer, Walter

    2015-01-01

    Summary Fine-scale genetic variation between human populations is interesting as a signature of historical demographic events and because of its potential for confounding disease studies. We use haplotype-based statistical methods to analyse genome-wide SNP data from a carefully chosen geographically diverse sample of 2,039 individuals from the United Kingdom (UK). This reveals a rich and detailed pattern of genetic differentiation with remarkable concordance between genetic clusters and geography. The regional genetic differentiation and differing patterns of shared ancestry with 6,209 individuals from across Europe carry clear signals of historical demographic events. We estimate the genetic contribution to SE England from Anglo-Saxon migrations to be under half, identify the regions not carrying genetic material from these migrations, suggest significant pre-Roman but post-Mesolithic movement into SE England from the Continent, and show that in non-Saxon parts of the UK there exist genetically differentiated subgroups rather than a general “Celtic” population. PMID:25788095

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

    PubMed Central

    Su, Mang; Li, Fenghua; Tang, Zhi; Yu, Yinyan; Zhou, Bo

    2014-01-01

    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. PMID:25136651

  10. Quantifying envelope and fine-structure coding in auditory nerve responses to chimaeric speech.

    PubMed

    Heinz, Michael G; Swaminathan, Jayaganesh

    2009-09-01

    Any sound can be separated mathematically into a slowly varying envelope and rapidly varying fine-structure component. This property has motivated numerous perceptual studies to understand the relative importance of each component for speech and music perception. Specialized acoustic stimuli, such as auditory chimaeras with the envelope of one sound and fine structure of another have been used to separate the perceptual roles for envelope and fine structure. Cochlear narrowband filtering limits the ability to isolate fine structure from envelope; however, envelope recovery from fine structure has been difficult to evaluate physiologically. To evaluate envelope recovery at the output of the cochlea, neural cross-correlation coefficients were developed that quantify the similarity between two sets of spike-train responses. Shuffled auto- and cross-correlogram analyses were used to compute separate correlations for responses to envelope and fine structure based on both model and recorded spike trains from auditory nerve fibers. Previous correlogram analyses were extended to isolate envelope coding more effectively in auditory nerve fibers with low center frequencies, which are particularly important for speech coding. Recovered speech envelopes were present in both model and recorded responses to one- and 16-band speech fine-structure chimaeras and were significantly greater for the one-band case, consistent with perceptual studies. Model predictions suggest that cochlear recovered envelopes are reduced following sensorineural hearing loss due to broadened tuning associated with outer-hair cell dysfunction. In addition to the within-fiber cross-stimulus cases considered here, these neural cross-correlation coefficients can also be used to evaluate spatiotemporal coding by applying them to cross-fiber within-stimulus conditions. Thus, these neural metrics can be used to quantitatively evaluate a wide range of perceptually significant temporal coding issues relevant to

  11. Relations between structural parameters and adsorption characterization of templated nanoporous materials with cubic symmetry

    SciTech Connect

    Ravikovitch, P.I.; Neimark, A.V.

    2000-03-21

    A systematic approach is proposed to structural characterization of templated nanoporous materials with cubic symmetry by gas adsorption. The authors hypothesize that regular structures of these materials can be described in terms of triply periodic minimal surfaces (TPMS), similarly to bicontinuous mesophases observed in oil-water, lipid, block copolymer, and other amphiphilic systems. The authors relate topological characteristics of TPMS to the pore structure parameters evaluated from adsorption measurements, such as the specific surface area, pore volume, mean pore size, and also pore wall thickness. The relations obtained can be used for discrimination of possible TPMS morphologies. The method developed is used for characterization of newly synthesized MCM-48 mesoporous materials by low-temperature nitrogen adsorption. They show that adsorption data fully support the minimal gyroid model of MCM-48 structure (Ia3d space group) established earlier by the X-ray diffraction (XRD) and transmission electron microscopy studies. The mean pore size of MCM-48 can be accurately described by the hydraulic diameter calculated from the capillary condensation region of nitrogen adsorption isotherms by the nonlocal density functional theory method. Moreover, the adsorption method allows one to estimate the pore wall thickness, which cannot be done by XRD. For a series of high-quality MCM-48 materials reported recently in the literature, the calculated mean wall thickness varied from 0.8 to 1.2 nm. The adsorption method developed is recommended as a complement to X-ray diffraction and electron microscopy techniques for characterization of nanoporous materials.

  12. Structure and hydrogen adsorption properties in low density nanoporous carbons from simulations

    SciTech Connect

    Peng, L.; Morris, James R

    2012-01-01

    We systematically model the hydrogen adsorption in nanoporous carbons over a wide range of carbon bulk densities (0.6 - 2.4 g/cm3) by using tight binding molecular dynamics simulations for the carbon structures and thermodynamics calculations of the hydrogen adsorption. The resulting structures are in good agreement with the experimental data of ultra-microporous carbon (UMC), a wood-based activated carbon, as indicated by comparisons of the microstructure at atomic level, pair distribution function, and pore size distribution. The hydrogen adsorption calculations in carbon structures demonstrate both a promising hydrogen storage capacity (excess uptake of 1.33 wt% at 298K and 5 MPa, for carbon structures at the lower range of densities) and a reasonable heat of adsorption (12-22 kJ/mol). This work demonstrates that increasing the heat of adsorption does not necessarily increase the hydrogen uptake. In fact, the available adsorption volume is as important as the isosteric heat of adsorption for hydrogen storage in nanoporous carbons.

  13. Local structure studies of some cobalt (II) complexes using extended X-ray absorption fine structure

    NASA Astrophysics Data System (ADS)

    Mishra, Ashutosh; Ninama, Samrath; Trivedi, Apurva

    2014-09-01

    Extended X-ray Absorption Fine Structure (EXAFS) analysis of Cobalt (II) complex as a ligand of 2 -methyl-3-[(bis-aniline(R) phenyl]-3H-l,5 benzodiazepine for finding local structure using conventional method .The Co(II) complexes were prepared by chemical root method. The EXAFS spectra were recorded at Cobalt K-edge i.e.; 7709 eV using Dispersive EXFAS beam line at 2.5GeV Indus-2 Synchrotron Radiation Source(SRS) at RRCAT, Indore, India. The recorded EXAFS data were analysed using the computer software Athena for determine the nearest neighbouring distances (bond lengths) of these complexes with conventional methods and it compared with Fourier transform(FT) analysis. The Fourier Transform convert EXAFS data signal into r-space or k-space. This is useful for visualizing the major contributions to the EXAFS spectrum.

  14. Influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays.

    PubMed

    Sánchez-Martín, M J; Dorado, M C; del Hoyo, C; Rodríguez-Cruz, M S

    2008-01-15

    Adsorption of three surfactants of different nature, Triton X-100 (TX100) (non-ionic), sodium dodecylsulphate (SDS) (anionic) and octadecyltrimethylammonium bromide (ODTMA) (cationic) by four layered (montmorillonite, illite, muscovite and kaolinite) and two non-layered (sepiolite and palygorskite) clay minerals was studied. The objective was to improve the understanding of surfactant behaviour in soils for the possible use of these compounds in remediation technologies of contaminated soils by toxic organic compounds. Adsorption isotherms were obtained using surfactant concentrations higher and lower than the critical micelle concentration (cmc). These isotherms showed different adsorption stages of the surfactants by the clay minerals, and were classified in different subgroups of the L-, S- or H-types. An increase in the adsorption of SDS and ODTMA by all clay minerals is observed up to the cmc of the surfactant in the equilibrium solution is reached. However, there was further TX100 adsorption when the equilibrium concentration was well above the cmc. Adsorption constants from Langmuir and Freundlich equations (TX100 and ODTMA) or Freundlich equation (SDS) were used to compare adsorption of different surfactants by clay minerals studied. These constants indicated the surfactant adsorption by clay minerals followed this order ODTMA>TX100>SDS. The adsorption of TX100 and ODTMA was higher by montmorillonite and illite, and the adsorption of SDS was found to be higher by kaolinite and sepiolite. Results obtained show the influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays, and they indicate the interest to consider the soil mineralogical composition when one surfactant have to be selected in order to establish more efficient strategies for the remediation of soils and water contaminated by toxic organic pollutants.

  15. Structural properties and adsorption capacity of holocellulose aerogels synthesized from an alkali hydroxide-urea solution

    NASA Astrophysics Data System (ADS)

    Kwon, Gu-Joong; Kim, Dae-Young; Hwang, Jae-Hyun; Kang, Joo-Hyon

    2014-05-01

    A tulip tree was used to synthesize a holocellulose aerogel from an aqueous alkali hydroxide-urea solution with the substitution of an organic solvent followed by freeze-drying. For comparison, the synthesized holocellulose aerogels were divided into two groups according to the source of the hydrogel, an upper suspended layer and a bottom concentrated layer of the centrifuged solution of cellulose and NaOH/urea solvents. We investigated the effects of the temperature of the pre-cooled NaOH/urea solution ( i.e., dissolution temperature) on the pore structure and the adsorption capacity of the holocellulose aerogel. A nano-fibrillar network structure of the holocellulose aerogel was observed, with little morphological difference in pore structure for different dissolution temperatures. Both micropores and mesopores were observed in the holocellulose aerogel. The specific surface area of the holocellulose aerogel was generally greater at lower dissolution temperatures. In a series of adsorption tests using methylene blue, the holocellulose aerogel showed the greatest adsorption capacity at the lowest dissolution temperature tested (-2°C). However, the dissolution temperature generally had little effect on the adsorption capacity. The holocellulose aerogel produced from the upper suspended layer of the centrifuged hydrogel solution showed a greater porosity and adsorption capacity than the one produced from the bottom concentrated layer. Overall, the aerogel made by utilizing a delignified tulip tree display a high surface area and a high adsorption property, indicating its possible application in eco-friendly adsorption materials.

  16. A note on chromospheric fine structure at active region polarity boundaries.

    NASA Technical Reports Server (NTRS)

    Prata, S. W.

    1971-01-01

    High resolution H-alpha filtergrams from Big Bear Solar Observatory reveal that some filamentary features in active regions have fine structure and hence magnetic field transverse to the gross structure and the zero longitudinal field line. These features are distinct from the usual active region filament, in which fine structure, magnetic field, and filament are all parallel to the zero longitudinal field line. The latter occur on boundaries between regions of weaker fields, while the former occur at boundaries between regions of stronger field.

  17. Modification of DPOAE Fine Structure Stemming from Changes in Outer and Middle Ear Function

    NASA Astrophysics Data System (ADS)

    Long, Glenis R.; Henin, Simon; Thompson, Suzanne

    2011-11-01

    High resolution DPOAE fine structure was evaluated when the output impedance of the cochlea was modified by: (1) Changes in outer ear volume, due to accumulation of cerumen, which does not modify input impedance. (2) Manipulation of middle ear pressure and scarring of the tympanic membrane (which modify both input and output impedance). At high primary levels a wider and deeper DPOAE structure combined with (and sometimes dominated) DPOAE level fine structure. The group delay was also modified, sometimes giving rise to negative group delay. The data can be modeled by assuming that the increased impedance at the oval widow produces reflections back into the cochlea which can be re-reflected.

  18. Remarkable proanthocyanidin adsorption properties of monastrell pomace cell wall material highlight its potential use as an alternative fining agent in red wine production.

    PubMed

    Bautista-Ortín, Ana Belén; Ruiz-García, Yolanda; Marín, Fátima; Molero, Noelia; Apolinar-Valiente, Rafael; Gómez-Plaza, Encarna

    2015-01-21

    The existence of interactions between the polysaccharides of vegetal cell walls and proanthocyanins makes this cell wall material an interesting option for its use as a fining agent to reduce the level of proanthocyanins in wines. Pomace wastes from the winery are widely available and a source of cell wall material, and the identification of varieties whose pomace cell walls present high proanthocyanin binding capacity and of processing methods that could enhance their adsorption properties could be of great interest. This study compared the proanthocyanin adsorption properties of pomace cell wall material from three different grape varieties (Monastrell, Cabernet Sauvignon, and Syrah), and the results were compared with those obtained using fresh grape cell walls. Also, the effect of the vinification method has been studied. Analysis of the proanthocyanidins in the solution after reaction with the cell wall material, using phloroglucinolysis and size exclusion chromatography, provided quantitative and qualitative information on the adsorbed and nonadsorbed compounds. A highlight of this study was the observation that Monastrell pomace cell wall material showed a strong affinity for proanthocyanidins, with values similar to that obtained for fresh grapes cell walls, and a preferential binding of high molecular mass proanthocyanidins, so these pomace cell walls could be used in wines to reduce astringency. The use of maceration enzymes during vinification had little effect on the retention capacity of the pomace cell walls obtained from this vinification, although an increase in the retention of low molecular mass proanthocyanidins was observed, and this might have implications for wine sensory properties.

  19. Structural characteristics of activated carbons and ibuprofen adsorption affected by bovine serum albumin.

    PubMed

    Melillo, M; Gun'ko, V M; Tennison, S R; Mikhalovska, L I; Phillips, G J; Davies, J G; Lloyd, A W; Kozynchenko, O P; Malik, D J; Streat, M; Mikhalovsky, S V

    2004-03-30

    Structural characteristics of a series of MAST carbons were studied using scanning electron microscopy images and the nitrogen adsorption isotherms analyzed with several models of pores and different adsorption equations. A developed model of pores as a mixture of gaps between spherical nanoparticles and slitlike pores was found appropriate for MAST carbons. Adsorption of ibuprofen [2-(4-isobutylphenyl)propionic acid] on activated carbons possessing different pore size distributions in protein-free and bovine serum albumin (BSA)-containing aqueous solutions reveals the importance of the contribution of mesopores to the total porosity of adsorbents. The influence of the mesoporosity increases when considering the removal of the drug from the protein-containing solution. Cellulose-coated microporous carbon Norit RBX adsorbs significantly smaller amounts of ibuprofen than uncoated micro/mesoporous MAST carbons whose adsorption capability increases with increasing mesoporosity and specific surface area, burnoff dependent variable. A similar effect of broad pores is observed on adsorption of fibrinogen on the same carbons. Analysis of the ibuprofen adsorption data using Langmuir and D'Arcy-Watt equations as the kernel of the Fredholm integral equation shows that the nonuniformity of ibuprofen adsorption complexes diminishes with the presence of BSA. This effect may be explained by a partial adsorption of ibuprofen onto protein molecules immobilized on carbon particles and blocking of a portion of narrow pores.

  20. Fine structure of bone in dinosaurs, birds and mammals.

    PubMed

    Rensberger, J M; Watabe, M

    2000-08-10

    After observation of detailed structural evidence for the origin of birds from dinosaurs, and in light of evidence that dinosaur bone tissue resembles the histology in mammals, the histology of bone has become one of the focal points in discussions of the physiology of dinosaurs and Mesozoic birds. Most of this microstructural information has focused on features related to the vascular organization and the amount of remodelled bone around vascular canals. However, the finer structures have received less attention, although differences in such structures have been observed among modern vertebrates. Here we present evidence that canaliculi--the submicrometre-sized channels that interconnect bone cells and vascular canals--and the collagen fibre bundles in bone are differently organized among certain dinosaur lineages. Ornithomimid dinosaurs are more like birds than mammals in these features. In canalicular structure, and to some extent in fibre bundle arrangement, ornithischian dinosaurs are more like mammals. These differences in both canalicular and lamellar structure are probably linked to differences in the process and rate of bone formation.

  1. Competitive adsorption of dyes and heavy metals on zeolitic structures.

    PubMed

    Hernández-Montoya, V; Pérez-Cruz, M A; Mendoza-Castillo, D I; Moreno-Virgen, M R; Bonilla-Petriciolet, A

    2013-02-15

    The adsorption of Acid blue 25, basic blue 9, basic violet 3, Pb(2+), Ni(2+), Zn(2+) and Cd(2+) ions has been studied in single and dye-metal binary solutions using two mineral materials: Clinoptilolite (CL) and ER (Erionite). These zeolites were characterized by FT-IR spectroscopy; potentiometric titration and nitrogen adsorption isotherms at 77 K to obtain their textural parameters. Results indicated that ER has an acidic character and a high specific surface (401 m(2) g(-1)) in contrast with the zeolite CL (21 m(2) g(-1)). Surprisingly, the removal of dyes was very similar for the two zeolites and they showed a considerable selectivity by the basic dyes in comparison with the acid dyes. In the case of heavy metals, ER was more effective in the adsorption process showing a selectivity of: Pb(2+) > Ni(2+) > Zn(2+) > Cd(2+). In the multicomponent adsorption experiments an antagonistic effect was observed in the removal of basic dyes and heavy metals. Particularly, the adsorbed amount of basic violet 3 decreased more significantly when the heavy metals are presents in contrast with the basic blue 9.

  2. Laser structuring of ultra-fine circuit lines in printed circuit boards: Laser structuring, neodymium-doped yttrium aluminium garnet laser, fine circuit lines

    NASA Astrophysics Data System (ADS)

    Zhang, Bin

    Laser structuring technique emerged in recent years for the need of fabricating fine circuit lines and spaces in printed circuit board. Most of the previous work only introduced laser structuring as a new method in the fabrication of fine circuit lines and mentioned that the width of circuit line can be reduced under 50 pin or helox with this technique. Laser structuring technique will have a prosperous future only when the relationship between process parameters and fabrication results are deeply understood. This study focuses on the control, prediction and optimization of circuit geometry by studying relations between the process parameters and fabrication results in laser structuring technology. The effects of laser parameters (Frequency-tripled Nd:YAG laser) on the geometry of circuits were carried out by experiments and analyzed by mathematical method. The geometry of circuit space can efficiently be controlled by investigating the main factors that influence the characteristic parameters of circuit space with Taguchi methodology. ANN was firstly used in the study of laser structuring technique. With ANN models, the optimization of process parameters in laser writing step can be realized and the 2-D cross-sectional profile of circuit space can be calculated with the combination of ANN model and mathematical method. At last, the final circuit lines and circuit spaces fabricated were tested using the quality and reliability tests---electrical open/short test, peel test and surface insulation resistance test (SIR test). The minimum widths of circuit lines and circuit spaces with good quality and reliability fabricated by laser structuring were 25 mum and 45 mum respectively. The project is significant for both applied and academic fields. This study contributes to the understanding of the laser structuring technology and is of benefit in the fabrication of very fine line circuits in advanced printed circuit board industry.

  3. A simulation for gravity fine structure recovery from high-low GRAVSAT SST data

    NASA Technical Reports Server (NTRS)

    Estes, R. H.; Lancaster, E. R.

    1976-01-01

    Covariance error analysis techniques were applied to investigate estimation strategies for the high-low SST mission for accurate local recovery of gravitational fine structure, considering the aliasing effects of unsolved for parameters. Surface density blocks of 5 deg x 5 deg and 2 1/2 deg x 2 1/2 deg resolution were utilized to represent the high order geopotential with the drag-free GRAVSAT configured in a nearly circular polar orbit at 250 km. altitude. GEOPAUSE and geosynchronous satellites were considered as high relay spacecraft. It is demonstrated that knowledge of gravitational fine structure can be significantly improved at 5 deg x 5 deg resolution using SST data from a high-low configuration with reasonably accurate orbits for the low GRAVSAT. The gravity fine structure recoverability of the high-low SST mission is compared with the low-low configuration and shown to be superior.

  4. Excited-state energies and fine structure of highly charged lithiumlike ions

    NASA Astrophysics Data System (ADS)

    Li, Jin-ying; Ding, Da-jun; Wang, Zhi-wen

    2013-10-01

    The full-core-plus-correlation method (FCPC) is extended to calculate the energies and fine structures of 1s2nd and 1s2nf (n≤5) states for the lithiumlike systems with high nuclear charge from Z = 41 to 50. In calculating energy, the higher-order relativistic contribution is estimated under a hydrogenic approximation. The nonrelativistic energies and wave functions are calculated by the Rayleigh-Ritz method. The mass polarization and the relativistic corrections including the kinetic energy correction, the Darwin term, the electron-electron contact term, and the orbit-orbit interaction are calculated perturbatively as the first-order correction. The quantum-electrodynamics contributions to the energy and to the fine-structure splitting are estimated by using the effective nuclear charge formula. The excited energies, the fine structures, and other relevant term energies are given and compared with the data available in the literature.

  5. Acid natural clinoptilolite: structural properties against adsorption/separation of n-paraffins.

    PubMed

    Rivera, Aramis; Farías, Tania; de Ménorval, Louis Charles; Autié-Castro, Giselle; Yee-Madeira, Hernany; Contreras, José Luis; Autié-Pérez, Miguel

    2011-08-01

    The employment of an acid natural clinoptilolite (AZH-1) in the adsorption and separation of n-paraffins has been evaluated. Natural clinoptilolite, NZ, was the raw material used to prepare the sodium-exchanged clinoptilolite (AZ) starting from which the AZH-1 sample was obtained by acid treatment. The structural stability of the samples after the applied treatments was demonstrated. The nitrogen adsorption experiments indicated that the acid sample has a homogeneous porous distribution and a considerable increase in the micropore volume with respect to NZ and AZ. The employment of the inverse gas chromatography at infinite dilution (IGCID) allowed studying the adsorption and separation of n-paraffin mixtures on AZH-1. It was also confirmed that the diffusion on AZH-1 took place in an unblocked structure through the A channel of ten members with minimal interactions. The IGCID results demonstrated the capacities of the acid Cuban natural zeolite in the adsorption and separation of n-paraffin mixtures.

  6. Adsorption and desorption performance of benzene over hierarchically structured carbon-silica aerogel composites.

    PubMed

    Dou, Baojuan; Li, Jinjun; Wang, Yufei; Wang, Hailin; Ma, Chunyan; Hao, Zhengping

    2011-11-30

    Hierarchically structured carbon-silica aerogel (CSA) composites were synthesized from cheap water glass precursors and granulated activated carbon via a post-synthesis surface modification with trimethylchlorosilane (TMCS) and a low-cost ambient pressure drying procedure. The resultant CSA composites possess micro/mesoporous structure and hydrophobic surface. The adsorption and desorption performance of benzene on carbon-silica aerogel composite (CSA-2) under static and dynamic conditions were investigated, comparing with pure silica aerogel (CSA-0) and microporous activated carbon (AC). It was found that CSA-2 has high affinity towards aromatic molecules and fast adsorption kinetics. Excellent performance of dynamic adsorption and desorption observed on CSA-2 is related to its higher adsorption capacity than CSA-0 and less mass transfer resistance than AC, arising from the well-developed microporosity and open foam mesostructure in the CSA composites.

  7. THE FINE STRUCTURE OF TWO UNUSUAL STALKED BACTERIA

    PubMed Central

    Pate, Jack L.; Ordal, Erling J.

    1965-01-01

    Two strains of bacteria that produce slender appendages (pseudostalks) from their lateral surfaces were studied using the electron microscope. The pseudostalks were shown to be extensions of the cytoplasm and peripheral membranes of the cell proper. Both strains of bacteria produce holdfasts at the poles of the cells by the means of which attachment can take place. The pseudostalks are not involved in the attachment of cells. No specialized intracytoplasmic structures are present at the point of juncture of pseudostalk and cell. A discussion of the possible functions of the pseudostalks, based on the electron microscope findings, is presented. PMID:5857250

  8. Transition wavelengths and fine structure for the doublet states of Be/sup +/

    SciTech Connect

    Davis, B.F.; Chung, K.T.

    1984-05-01

    Seventeen bound and core-excited states of Be/sup +/ are calculated using configuration-interaction wave functions. Relativistic and mass-polarization correction are included. The relativistic corrections considered are correction to the kinetic energy, Darwin term, contact terms, and retardation effect. The fine structure is calculated by using spin-orbit and spin-other-orbit operators. The wavelengths computed for the transitions from the core-excited states improve the agreement between theory and experiment. The lifetimes for these states are also calculated. Our calculated transition wavelengths and fine structures for the bound states agree well in most cases with the experimental data tabulated by Bashkin and Stoner.

  9. Enhancement of speech intelligibility in reverberant rooms: role of amplitude envelope and temporal fine structure.

    PubMed

    Srinivasan, Nirmal Kumar; Zahorik, Pavel

    2014-06-01

    The temporal envelope and fine structure of speech make distinct contributions to the perception of speech in normal-hearing listeners, and are differentially affected by room reverberation. Previous work has demonstrated enhanced speech intelligibility in reverberant rooms when prior exposure to the room was provided. Here, the relative contributions of envelope and fine structure cues to this intelligibility enhancement were tested using an open-set speech corpus and virtual auditory space techniques to independently manipulate the speech cues within a simulated room. Intelligibility enhancement was observed only when the envelope was reverberant, indicating that the enhancement is envelope-based.

  10. Progress towards a precision measurement of the n=2 triplet P fine structure of atomic helium

    NASA Astrophysics Data System (ADS)

    Kato, K.; Fitzakerley, D. W.; George, M. C.; Vutha, A. C.; Storry, C. H.; Hessels, E. A.

    2016-05-01

    We report progress on the measurement of the J = 1 to J = 2 23 P fine-structure interval of atomic helium. The measurement uses a liquid-nitrogen-cooled DC discharge source of metastable helium and the atomic beam is laser cooled in the transverse directions. The atoms are excited to 23 P by a 1083-nm diode laser, and the fine-structure transition is driven by microwaves using the frequency-offset separated oscillatory fields technique. The transition is detected by further laser excitation to a Rydberg state, followed by Stark ionization. This work is supported by NSERC, CRC.

  11. Arsenate Adsorption On Ruthenium Oxides: A Spectroscopic And Kinetic Investigation

    EPA Science Inventory

    Arsenate adsorption on amorphous (RuO2•1.1H2O) and crystalline (RuO2) ruthenium oxides was evaluated using spectroscopic and kinetic methods to elucidate the adsorption mechanism. Extended X-ray absorption fine structure spectroscopy (EXAFS) was ...

  12. Structural characteristics of modified activated carbons and adsorption of explosives.

    PubMed

    Tomaszewski, W; Gun'ko, V M; Skubiszewska-Zieba, J; Leboda, R

    2003-10-15

    Several series of activated carbons prepared by catalytic and noncatalytic gasification and subsequent deposition of pyrocarbon by pyrolysis of methylene chloride or n-amyl alcohol were studied by FTIR, chromatography, and adsorption methods using nitrogen and probe organics (explosives). The relationships between the textural characteristics of carbon samples and the recovery rates (eta) of explosives on solid-phase extraction (SPE) using different solvents for their elution after adsorption were analyzed using experimental and quantum chemical calculation results. The eta values for nitrate esters, cyclic nitroamines, and nitroaromatics only partially correlate with different adsorbent parameters (characterizing microporosity, mesoporosity, pore size distributions, etc.), polarity of eluting solvents, or characteristics of probe molecules, since there are many factors strongly affecting the recovery rates. Some of the synthesized carbons provide higher eta values than those for such commercial adsorbents as Hypercarb and Envicarb.

  13. Adsorption of fibrinogen on a biomedical-grade stainless steel 316LVM surface: a PM-IRRAS study of the adsorption thermodynamics, kinetics and secondary structure changes.

    PubMed

    Desroches, Marie-Josee; Omanovic, Sasha

    2008-05-14

    Polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) was employed to investigate the interaction of serum protein fibrinogen with a biomedical-grade 316LVM stainless steel surface, in terms of the adsorption thermodynamics, kinetics and secondary structure changes of the protein. Apparent Gibbs energy of adsorption values indicated a highly spontaneous and strong adsorption of fibrinogen onto the surface. The kinetics of fibrinogen adsorption were successfully modeled using a pseudo first-order kinetic model. Deconvolution of the amide I bands indicated that the adsorption of fibrinogen on 316LVM results in significant changes in the protein's secondary structure that occur predominantly within the first minute of adsorption. Among the investigated structures, the alpha-helix structure undergoes the smallest changes, while the beta-sheet and beta-turns structures undergo significant changes. It was shown that lateral interactions between the adsorbed molecules do not play a role in controlling the secondary structure changes. An increase in temperature induced changes in the secondary structure of the protein, characterized by a loss of the alpha-helical content and its transformation into the beta-turns structure.

  14. Development of Internal Fine Structure in Stretched Rubber Vulcanizates

    SciTech Connect

    M Tosaka; S Toki; J Che; L Rong; B Hsiao

    2011-12-31

    Small-angle X-ray scattering (SAXS) pattern and tensile stress during relaxation of stretched rubber vulcanizates (synthetic polyisoprene) were measured simultaneously at room temperature and at 0 C. The samples were quickly stretched to the prefixed strain and then allowed to relax for 1 h. In every SAXS pattern, the intensity distribution was elongated along the equator, indicating the formation of structures elongated in the stretching direction. The so-called two-spots pattern corresponding to the long period of stacked lamellar crystals did not appear even when the critical strain to induce crystallization was exceeded. On the other hand, even below the critical strain, additional development of equatorial streaks was detected in the differential SAXS patterns. This result suggests the growth of the density fluctuation elongated in the stretching direction, which is not directly related to strain-induced crystallization.

  15. FINE STRUCTURE AND PIGMENT CONVERSION IN ISOLATED ETIOLATED PROPLASTIDS

    PubMed Central

    Klein, Shimon; Poljakoff-Mayber, A.

    1961-01-01

    Proplastids containing a prolamellar body were isolated from leaves of etiolated bean plants. The isolation methods do not necessarily lead to destruction of their submicroscopic structure and most of the isolated proplastids show well preserved outer membranes, lamellar strands, and the prolamellar body. Morphological intactness of the proplastids varies; certain leaf fractions contain single prolamellar bodies as well as proplastids. Since pellets after centrifugation between 350 g and 1000 to 3000 g contain intact proplastids and, as was shown by quantitative experiments, the same fractions show photoconversion of protochlorophyll to chlorophyll, it is supposed that the isolated particles probably retain many of the properties which are characteristic of them in situ. Isolated proplastids may thus be a valuable tool in investigations on the development of the photosynthetic apparatus. PMID:14456780

  16. Fine structure of olfactory sensilla in myriapods and arachnids.

    PubMed

    Tichy, H; Barth, F G

    1992-09-01

    Structural features of various types of olfactory sensilla are reviewed. 1) Sensilla basiconica which differ in form and size are found on the antennae of centipedes and millipedes. Their walls show longitudinal slits or grooves that either open into the sensillum lumen or do not penetrate the cuticle. In other such sensilla the outer surface is pierced by pores and the inner surface grooved and pocketed. These sensilla are innervated by one to six sensory cells. Their unbranched outer dendritic segments extend to the tip of the sensillum. The sensory cells are surrounded by two or three sheath cells which terminate at the sensillum base or form a continuous tube around the entire length of the outer dendritic segments. 2) Temporal organs of centipedes are located between the insertion of the antenna and the ocelli. These sensilla consist of a shallow cuticular ring with a central sensory plate made up by a layer of unperforated cuticle or a capsule with a mushroom-shaped structure inside formed by fibrous-looking cuticle. A dozen sensory cells with unbranched outer dendritic segments innervate each sensillum. They extend toward the sensory cuticle and pass just below it. Numerous sheath cell processes run parallel to the outer dendritic segments up to the sensory cuticle. 3) Thread-like flagella of Pauropoda are found on the antennae. They possess a flexible unperforated cuticular wall. These sensilla contain nine sensory cells surrounded by several sheath cells which form a continuous cytoplasmic tube around the outer dendritic segments. 4) Single-walled sensilla with numerous plugged pores penetrating the cuticular wall occur on the tarsus of the first leg in ticks. Each sensillum is innervated by 4-15 sensory cells. Three sheath cells terminate in the base of the sensillum. 5) Double-walled sensilla with spoke canals are found on the first tarsus of ticks. Their shaft is longitudinally grooved. Pore canals lead inward from the bottom of the grooves and open

  17. Fine structure of the sensilla of Peripatopsis moseleyi (Onychophora).

    PubMed

    Storch, V; Ruhberg, H

    1977-02-14

    Three types of sensilla occurring on the lips and on the antennae of Peripatopsis moseleyi have been investigated by scanning and transmission electron microscopy. On the lips sensory spines can be found which contain numerous cilia originating from bipolar receptor cells. They reach the tip of the spine where the cuticle is modified. The perikarya of the sensory cells, a large supporting cell with a complicated surface and a second type of receptor, form a bud-like structure and are surrounded by a layer of collagen fibrils. The second receptor cell bears apical stereocilia as well as a kinocilium which are directed towards the centre of the animal -- thus the cell appears to be turned upside down. The sensilla of the antennae are 1) sensory bristles containing two or three kinds of receptor cells, one of which bears an apical cilium and one kind of supportive cell and 2) sensory bulbs located within furrows consisting of receptor cells with branched cilia and two kinds of supportive cells which are covered by a modified thin cuticle. According to the electron microscopical findings the sensory spines on the lips are presumably chemoreceptors. The sensory bristles on the antennae can be regarded as mechanoreceptors and the sensory bulbs as chemoreceptors.

  18. The fine structure of endothelium of large arteries.

    PubMed

    BUCK, R C

    1958-03-25

    Endothelium of large arteries from several species was studied in thin sections with the electron microscope. Before sacrifice, some animals received an intravenous injection of colloidal thorium dioxide which was visualized in the sections. Surface replicas were prepared by carbon evaporation on either frozen-dried endothelium or on endothelium dried by sublimation of naphthalene with which the tissue had been impregnated. Cell boundaries, stained with silver, were observed in sections and also from the surface by stripping off the inner part of the endothelium. In addition to the usual cytoplasmic organelles, the endothelial cells showed certain characteristic features, namely, large invaginated pockets communicating with the arterial lumen, numerous much smaller vesicular structures immediately under the plasma membrane and apparently also communicating with the lumen, and inclusions, into which injected thorium particles were incorporated. Intercellular boundaries appeared as regular double membranes in thin sections, and they were outlined by a double row of silver granules after silver staining. No evidence was obtained of permeation of intracellular spaces by colloidal thorium.

  19. Golgi, Cajal, and the Fine Structure of the Nervous System

    PubMed Central

    Peters, Alan

    2012-01-01

    Towards the middle of the twentieth century, neuroanatomy was on the decline. It was revived by the development of two new methods. One was the Nauta-Gygax method, which selectively stained nerve fibers that had been caused to degenerate by experimental lesions. This allowed connections between various parts of the nervous system to be better determined. The second was electron microscopy, which allowed the structure of neurons and the synapses between them to be examined in detail, and eventually this led to a revival of the Golgi impregnation methods. This occurred in the 1970s because of the desire of electron microscopists to determine the origins of the neuronal profiles they encountered in electron micrographs of various parts of the central nervous system. Eventually this led to the development of Golgi/EM techniques, whereby individual impregnated neurons could first be characterized by light microscopy and then thin sectioned for detailed analyses. Examining the axon terminals of such impregnated neurons, especially those in the cerebral cortex, for the first time revealed details of intercellular connections and allowed neuronal circuits to be postulated. However, Golgi/EM had only a brief, but fruitful existence. It was soon superceded by intracellular filling techniques, which allowed the added dimension that the physiological properties of identified neurons could also be determined. PMID:17270274

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

    SciTech Connect

    Sharykin, I. N.; Kosovichev, A. G.

    2014-06-10

    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 H{sub α} 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 H{sub α} knots in the ribbons.

  1. Fine-scaled human genetic structure revealed by SNP microarrays.

    PubMed

    Xing, Jinchuan; Watkins, W Scott; Witherspoon, David J; Zhang, Yuhua; Guthery, Stephen L; Thara, Rangaswamy; Mowry, Bryan J; Bulayeva, Kazima; Weiss, Robert B; Jorde, Lynn B

    2009-05-01

    We report an analysis of more than 240,000 loci genotyped using the Affymetrix SNP microarray in 554 individuals from 27 worldwide populations in Africa, Asia, and Europe. To provide a more extensive and complete sampling of human genetic variation, we have included caste and tribal samples from two states in South India, Daghestanis from eastern Europe, and the Iban from Malaysia. Consistent with observations made by Charles Darwin, our results highlight shared variation among human populations and demonstrate that much genetic variation is geographically continuous. At the same time, principal components analyses reveal discernible genetic differentiation among almost all identified populations in our sample, and in most cases, individuals can be clearly assigned to defined populations on the basis of SNP genotypes. All individuals are accurately classified into continental groups using a model-based clustering algorithm, but between closely related populations, genetic and self-classifications conflict for some individuals. The 250K data permitted high-level resolution of genetic variation among Indian caste and tribal populations and between highland and lowland Daghestani populations. In particular, upper-caste individuals from Tamil Nadu and Andhra Pradesh form one defined group, lower-caste individuals from these two states form another, and the tribal Irula samples form a third. Our results emphasize the correlation of genetic and geographic distances and highlight other elements, including social factors that have contributed to population structure.

  2. Surface structural ion adsorption modeling of competitive binding of oxyanions by metal (hydr)oxides

    SciTech Connect

    Hiemstra, T.; Riemsdijk, W.H. van

    1999-02-01

    An important challenge in surface complexation models (SCM) is to connect the molecular microscopic reality to macroscopic adsorption phenomena. This study elucidates the primary factor controlling the adsorption process by analyzing the adsorption and competition of PO{sub 4}, AsO{sub 4}, and SeO{sub 3}. The authors show that the structure of the surface-complex acting in the dominant electrostatic field can be ascertained as the primary controlling adsorption factor. The surface species of arsenate are identical with those of phosphate and the adsorption behavior is very similar. On the basis of the selenite adsorption, The authors show that the commonly used 1pK models are incapable to incorporate in the adsorption modeling the correct bidentate binding mechanism found by spectroscopy. The use of the bidentate mechanism leads to a proton-oxyanion ratio and corresponding pH dependence that are too large. The inappropriate intrinsic charge attribution to the primary surface groups and the condensation of the inner sphere surface complex to a point charge are responsible for this behavior of commonly used 2pK models. Both key factors are differently defined in the charge distributed multi-site complexation (CD-MUSIC) model and are based in this model on a surface structural approach. The CD-MUSIC model can successfully describe the macroscopic adsorption phenomena using the surface speciation and binding mechanisms as found by spectroscopy. The model is also able to predict the anion competition well. The charge distribution in the interface is in agreement with the observed structure of surface complexes.

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

    PubMed

    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

  4. Adsorption dynamics for the system hydrogen/palladium and its relation to the surface electronic structure

    NASA Astrophysics Data System (ADS)

    Resch, Ch.; Berger, H. F.; Rendulic, K. D.; Bertel, E.

    1994-09-01

    We have determined differential sticking coefficients for a monoenergetic nozzle beam of hydrogen on Pd(111) and Pd(110). In particular the energy dependence and the angular variation of the initial sticking coefficient were measured. The results indicate that adsorption of hydrogen on palladium occurs in parallel processes through a direct path with an activation barrier of perhaps 50 meV or less and a precursor path. There is relatively little difference in the adsorption properties of the (111) and the (110) plane. The appearance of a molecular precursor on the (111) plane can be related to the electronic structure of palladium, in particular to the absence of occupied Shockley surface states, as compared to Ni (111) and Pt (111). Pre-adsorbed potassium on a (110) plane acts as an inhibitor to adsorption. Different inhibiting mechanisms are observed for the direct adsorption path and the precursor path. At high potassium coverage the precursor path is completely suppressed.

  5. Fine structure of the subradular organ of Lepidochitona cinereus (L), (Mollusca, Polyplacophora).

    PubMed

    Boyle, P R

    1975-10-13

    Electron microscopy of the subradular organ of the chiton Lepidochitona cinereus (L) reveals at least three cell types, microvillous, ciliated and mucus-secreting, situated in a single epithelium. The base of the epithelium is abundantly innervated and supplied with muscle cells. The fine structure is consistent with a chemosensory function for the subradular organ.

  6. Site-specific ionisation edge fine-structure of Rutile in the electron microscope.

    PubMed

    Hetaba, Walid; Löffler, Stefan; Willinger, Marc-Georg; Schuster, Manfred Erwin; Schlögl, Robert; Schattschneider, Peter

    2014-08-01

    Combined Bloch-wave and density functional theory simulations are performed to investigate the effects of different channelling conditions on the fine-structure of electron energy-loss spectra. The simulated spectra compare well with experiments. Furthermore, we demonstrate that using this technique, the site-specific investigation of atomic orbitals is possible. This opens new possibilities for chemical analyses.

  7. Fine-scale population structure, inbreeding risk and avoidance in a wild insect population.

    PubMed

    Bretman, Amanda; Rodríguez-Muñoz, Rolando; Walling, Craig; Slate, Jon; Tregenza, Tom

    2011-07-01

    The ecological and evolutionary importance of fine-scale genetic structure within populations is increasingly appreciated. However, available data are largely restricted to wild vertebrates and eusocial insects. In addition, there is the expectation that most insects tend to have such large- and high-density populations and are so mobile that they are unlikely to face inbreeding risks through fine-scale population structuring. This has made the growing body of evidence for inbreeding avoidance in insects and its implication in mating systems evolution somewhat enigmatic. We present a 4-year study of a natural population of field crickets. Using detailed video monitoring combined with genotyping, we track the movement of all adults within the population and investigate genetic structure at a fine scale. We find some evidence for relatives being found in closer proximity, both across generations and within a single breeding season. Whilst incestuous matings are not avoided, population inbreeding is low, suggesting that mating is close to random and the limited fine-scale structure does not create significant inbreeding risk. Hence, there is little evidence for selective pressures associated with the evolution of inbreeding avoidance mechanisms in a closely related species.

  8. Photoionization modeling of the LWS fine-structure lines in IR bright galaxies

    NASA Technical Reports Server (NTRS)

    Satyapal, S.; Luhman, M. L.; Fischer, J.; Greenhouse, M. A.; Wolfire, M. G.

    1997-01-01

    The long wavelength spectrometer (LWS) fine structure line spectra from infrared luminous galaxies were modeled using stellar evolutionary synthesis models combined with photoionization and photodissociation region models. The calculations were carried out by using the computational code CLOUDY. Starburst and active galactic nuclei models are presented. The effects of dust in the ionized region are examined.

  9. Accuracy of mapping the Earth's gravity field fine structure with a spaceborne gravity gradiometer mission

    NASA Technical Reports Server (NTRS)

    Kahn, W. D.

    1984-01-01

    The spaceborne gravity gradiometer is a potential sensor for mapping the fine structure of the Earth's gravity field. Error analyses were performed to investigate the accuracy of the determination of the Earth's gravity field from a gravity field satellite mission. The orbital height of the spacecraft is the dominating parameter as far as gravity field resolution and accuracies are concerned.

  10. Comment on ``Interpretation of the fine structure in the 14C radioactive decay of 223'

    NASA Astrophysics Data System (ADS)

    Hussonnois, M.; Le Du, J. F.; Brillard, L.; Ardisson, G.

    1991-12-01

    Priority of our interpretation of the fine structure in the 14C radioactive decay of 223Ra is asserted. It seems that the deformation parameter values, used in the framework of ARM to interpret properties of both 223Ra ground and excited states, partly allow for the qualitative interpretation of the experimental hindrance factors to the 209Pb states.

  11. Synthesis, structural elucidation and carbon dioxide adsorption on Zn (II) hexacyanoferrate (II) Prussian blue analogue

    NASA Astrophysics Data System (ADS)

    Roque-Malherbe, R.; Lugo, F.; Polanco, R.

    2016-11-01

    In the course of the last years hexacyanoferrates have been widely studied; even though, the adsorption properties of Zn (II) hexacyanoferrate(II) (labelled here Zn-HII) have not been thoroughly considered. In addition, soft porous crystals, i.e., adsorbents that display structural flexibility have been, as well, extensively studied, however this property has not been reported for Zn (II) hexacyanoferrate(II). In this regard, the key questions addressed here were the synthesis and structural characterization of Zn-HII together with the investigation of their low (up to 1 bar) and high pressure (up to 30 bar) adsorption properties, to found if these materials show structural flexibility. Then, to attain the anticipated goals, structural characterizations were made with: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) and thermo-gravimetric analysis (TGA), simultaneously, with the investigation of the adsorption of carbon dioxide. As a result of the research process we concluded that the Zn-HII displayed Fm3 barm space group framework. Besides, the carbon dioxide adsorption investigation demonstrated the presence of the framework expansion effect together with an extremely high adsorption heat, properties that could be useful for the use of Zn(II) hexacyanoferrate(II) as an excellent adsorbent.

  12. Mechanical properties of 15%Mn steel with fine lamellar structure consisting of ferrite and austenite phases

    NASA Astrophysics Data System (ADS)

    Ueji, R.; Okitsu, Y.; Nakamura, T.; Takagi, Y.; Tanaka, Y.

    2010-07-01

    New steel with fine lamellar structure consisting of austenite and ferrite was developed. 15mass%Mn-3%Al-3%Si steel sheet was used in this study. First of all, the effect of the cooling rate on the microstructure was examined. The cooling at the slower speed of 100 deg/hour created the dual phase structure consisting of both austenite and ferrite. The additional rolling developed the fine lamellar duplex structure. Improvement of both the tensile strength and elongation was achieved by rolling. The strength increases furthermore by the rolling up to larger reduction. The 90% rolled sheet shows high tensile strength around 1000MPa with large elongation (15%-20%). These results indicate that the multi-phased structure with controlled lamellar morphology is beneficial for the management of both high strength and large ductility.

  13. On velocity gradient dynamics and fine-scale structure: experiments support DNS and models

    NASA Astrophysics Data System (ADS)

    Lawson, John; Dawson, James

    2015-11-01

    The fine scales of turbulence are embodied by statistics of velocity gradients. In solving exact equations for their evolution, the challenge is to specify how the pressure Hessian acts. This is determined by the footprints that ``structures'' of enstrophy and strain leave in conditional average pressure fields. We use direct and approximate conditional averaging methods to extract this structure from different turbulence datasets: a direct numerical simulation and a unique scanning tomography experiment in a ``French washing machine''. Direct comparisons between simulation and experiment show the structure and resulting dynamics are in excellent, quantitative agreement. This evidence supports existing modelling approaches and provides insights towards their refinement. Moreover, it demonstrates the dynamical significance and the reproducibility of fine-scale structure.

  14. HRTS observations of the fine structure and dynamics of the solar chromosphere and transition zone

    NASA Technical Reports Server (NTRS)

    Dere, K. P.

    1983-01-01

    Arc-second UV observations of the Sun by the NRL High Resolution Telescope and Spectrograph (HRTS) have led to the discovery of dynamic fine structures such as 400 km/s coronal jets and chromospheric jets (spicules) and have provided new information about the structure and dynamics of the transition zone. These observations are reviewed and their relevance to the origin of the solar wind is discussed.

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

    PubMed

    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.

  16. Exciton fine structure and spin relaxation in semiconductor colloidal quantum dots.

    PubMed

    Kim, Jeongho; Wong, Cathy Y; Scholes, Gregory D

    2009-08-18

    Quantum dots (QDs) have discrete quantum states isolated from the environment, making QDs well suited for quantum information processing. In semiconductor QDs, the electron spins can be coherently oriented by photoexcitation using circularly polarized light, creating optical orientation. The optically induced spin orientation could serve as a unit for data storage and processing. Carrier spin orientation is also envisioned to be a key component in a related, though parallel, field of semiconductor spintronics. However, the oriented spin population rapidly loses its coherence by interaction with the environment, thereby erasing the prepared information. Since long-lasting spin orientation is desirable in both areas of investigation, spin relaxation is the central focus of investigation for optimization of device performance. In this Account, we discuss a topic peripherally related to these emerging areas of investigation: exciton fine structure relaxation (EFSR). The radiationless transition occurring in the exciton fine structure not only highlights a novel aspect of QD exciton relaxation but also has implications for carrier spin relaxation in QDs. We focus on examining the EFSR in connection with optical spin orientation and subsequent ultrafast relaxation of electron and hole spin densities in the framework of the exciton fine structure basis. Despite its significance, the study of exciton fine structure in colloidal QDs has been hampered by the experimental challenge arising from inhomogeneous line broadening that obscures the details of closely spaced fine structure states in the frequency domain. In this Account, we show that spin relaxation occurring in the fine structure of CdSe QDs can be probed by a time-domain nonlinear polarization spectroscopy, circumventing the obstacles confronted in the frequency-domain spectroscopy. In particular, by combining polarization sequences of multiple optical pulses with the unique optical selection rules of

  17. Adsorption characteristics of bovine serum albumin onto alumina with a specific crystalline structure.

    PubMed

    Kawashita, Masakazu; Hayashi, Junpei; Li, Zhixia; Miyazaki, Toshiki; Hashimoto, Masami; Hihara, Hiroki; Kanetaka, Hiroyasu

    2014-02-01

    Bone cement containing alumina particles with a specific crystalline structure exhibits the ability to bond with bone. These particles (AL-P) are mainly composed of delta-type alumina (δ-Al2O3). It is likely that some of the proteins present in the body environment are adsorbed onto the cement and influence the expression of its bioactivity. However, the effect that this adsorption of proteins has on the bone-bonding mechanism of bone cement has not yet been elucidated. In this study, we investigated the characteristics of the adsorption of bovine serum albumin (BSA) onto AL-P and compared them with those of its adsorption onto hydroxyapatite (HA), which also exhibits bone-bonding ability, as well as with those of adsorption onto alpha-type alumina (α-Al2O3), which does not bond with bone. The adsorption characteristics of BSA onto AL-P were very different from those onto α-Al2O3 but quite similar to those onto HA. It is speculated that BSA is adsorbed onto AL-P and HA by interionic interactions, while it is adsorbed onto α-Al2O3 by electrostatic attraction. The results suggest that the specific adsorption of albumin onto implant materials might play a role in the expression of the bone-bonding abilities of the materials.

  18. Correlation between oxygen adsorption energy and electronic structure of transition metal macrocyclic complexes

    SciTech Connect

    Liu, Kexi; Lei, Yinkai; Wang, Guofeng

    2013-11-28

    Oxygen adsorption energy is directly relevant to the catalytic activity of electrocatalysts for oxygen reduction reaction (ORR). In this study, we established the correlation between the O{sub 2} adsorption energy and the electronic structure of transition metal macrocyclic complexes which exhibit activity for ORR. To this end, we have predicted the molecular and electronic structures of a series of transition metal macrocyclic complexes with planar N{sub 4} chelation, as well as the molecular and electronic structures for the O{sub 2} adsorption on these macrocyclic molecules, using the density functional theory calculation method. We found that the calculated adsorption energy of O{sub 2} on the transition metal macrocyclic complexes was linearly related to the average position (relative to the lowest unoccupied molecular orbital of the macrocyclic complexes) of the non-bonding d orbitals (d{sub z{sup 2}}, d{sub xy}, d{sub xz}, and d{sub yz}) which belong to the central transition metal atom. Importantly, our results suggest that varying the energy level of the non-bonding d orbitals through changing the central transition metal atom and/or peripheral ligand groups could be an effective way to tuning their O{sub 2} adsorption energy for enhancing the ORR activity of transition metal macrocyclic complex catalysts.

  19. Adsorption performance of salicylic acid on a novel resin with distinctive double pore structure.

    PubMed

    Xiao, Guqing; Wen, Ruiming; Liu, Aijiao; He, Guowen; Wu, Dan

    2017-05-05

    Two approaches were used to synthesize two resins with different pore structures. In one way, the CH2Cl groups in macroporous chloromethylated polystyrene resin were transformed to methylene bridges, and achieved a hypercrosslinked resin with plentiful micropores (denoted GQ-06). In the other way, 50% of the CH2Cl groups in chloromethylated polystyrene resin was used to produce micropores, while the residual 50% of the CH2Cl groups was reacted with 2-aminopyridine, and prepared another resin with double pore structure of hypercrosslinked resin and macroporous resin (denoted GQ-11). The adsorption of salicylic acid (SA) on GQ-11 was investigated using GQ-06 as the reference adsorbent. The effect of pH on the adsorption of SA on GQ-06 was consistent with the dissociation curve of SA. The maximum adsorption capacity of SA on GQ-11 was observed at the solution pH of 2.64. The greater adsorption rate of SA on GQ-11 than that of GQ-06 was attributed to its double pore structure. The multifunctional adsorption mechanism of anion exchange and hydrophobic interaction resulted in the larger equilibrium capacity of SA on GQ-11 than that of GQ-06. GQ-06 and GQ-11 could be regenerated by absolute alcohol and 80% of alcohol -0.5mol/L of sodium hydroxide aqueous solution, respectively.

  20. Correlation between oxygen adsorption energy and electronic structure of transition metal macrocyclic complexes.

    PubMed

    Liu, Kexi; Lei, Yinkai; Wang, Guofeng

    2013-11-28

    Oxygen adsorption energy is directly relevant to the catalytic activity of electrocatalysts for oxygen reduction reaction (ORR). In this study, we established the correlation between the O2 adsorption energy and the electronic structure of transition metal macrocyclic complexes which exhibit activity for ORR. To this end, we have predicted the molecular and electronic structures of a series of transition metal macrocyclic complexes with planar N4 chelation, as well as the molecular and electronic structures for the O2 adsorption on these macrocyclic molecules, using the density functional theory calculation method. We found that the calculated adsorption energy of O2 on the transition metal macrocyclic complexes was linearly related to the average position (relative to the lowest unoccupied molecular orbital of the macrocyclic complexes) of the non-bonding d orbitals (d(z(2)), d(xy), d(xz), and d(yz)) which belong to the central transition metal atom. Importantly, our results suggest that varying the energy level of the non-bonding d orbitals through changing the central transition metal atom and/or peripheral ligand groups could be an effective way to tuning their O2 adsorption energy for enhancing the ORR activity of transition metal macrocyclic complex catalysts.

  1. Chemical Reaction and Adsorption Structure on Metal Surfaces of the Platinum Group

    NASA Astrophysics Data System (ADS)

    Murata, Yoshitada

    Professor Ertl was awarded the chemistry Nobel Prize. One of his remarkable works is imaging of surface non-linear processes for CO oxidation on Pt(110). The mechanism for this pattern formation is briefly discussed. We studied previously laser-induced desorption (LID) from NO on Pt(111) extensively. However, the experimental results could not be explained until the adsorption structure of Pt(111)-NO was elucidated consistently in 2002 by the experimental and the theoretical investigation. For Pt(111)-CO at low coverage, on the other hand, the most stable adsorption structure obtained from the ab initio calculations is in contradiction to that confirmed by the experimental studies.

  2. Fine structure zonal flow excitation by beta-induced Alfvén eigenmode

    NASA Astrophysics Data System (ADS)

    Qiu, Zhiyong; Chen, Liu; Zonca, Fulvio

    2016-10-01

    Nonlinear excitation of low frequency zonal structure (LFZS) by beta-induced Alfvén 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.

  3. The fine-structure intervals of (N-14)+ by far-infrared laser magnetic resonance

    NASA Technical Reports Server (NTRS)

    Brown, John M.; Varberg, Thomas D.; Evenson, Kenneth M.; Cooksy, Andrew L.

    1994-01-01

    The far-infrared laser magnetic resonance spectra associated with both fine-structure transitions in (N-14)+ in its ground P-3 state have been recorded. This is the first laboratory observation of the J = 1 left arrow 0 transition and its frequency has been determined two orders of magnitude more accurately than previously. The remeasurement of the J = 2 left arrow 1 spectrum revealed a small error in the previous laboratory measurements. The fine-structure splittings (free of hyperfine interactions) determined in this work are (delta)E(sub 10) = 1461.13190 (61) GHz, (delta)E(sub 21) = 2459.38006 (37) GHz. Zero-field transition frequencies which include the effects of hyperfine structure have also been calculated. Refined values for the hyperfine constants and the g(sub J) factors have been obtained.

  4. Fine-structure deletion map of the Escherichia coli L-arabinose operon.

    PubMed

    Schleif, R

    1972-11-01

    A fine-structure deletion map of the L-arabinose operon of E. coli was constructed by mapping deletion endpoints against point mutations. Of 350 independent deletions with average endpoint separation of ten nucleotides, 51 ended in the control region between the C and B genes, and the rest ended in the structural genes A, B, C, and D. If deletion endpoints are randomly distributed, the C and B genes are separated by about 510 nucleotides. Deletion endpoints and locations of point mutations in fact do appear randomly interspersed in the C and B genes, but no point mutations were found in the control region between them. Deletions were isolated with the aid of a heat-inducible lambda phage inserted into leucine genes adjacent to the arabinose genes. A high-capacity mating technique was developed for rapidly generating fine structure maps from many deletions and point mutations.

  5. Kinetics of the water adsorption driven structural transformationof ZnS nanoparticles

    SciTech Connect

    Goodell, C.M.; Gilbert, B.; Weigand, S.J.; Banfield, J.F.

    2007-08-01

    Nanoparticles of certain materials can respond structurally to changes in their surface environments. We have previously shown that methanol, water adsorption, and aggregation-disaggregation can change the structure of 3 nm diameter zinc sulfide (ZnS). However, in prior observations of water-driven structure change, aggregation may also have taken place. Therefore, we investigated the structural consequences of water adsorption alone on anhydrous nanoparticles that were dried to minimize changes in aggregation. Using simultaneously collected small- and wide-angle x-ray scattering (SAXS/WAXS) data, we show that water vapor adsorption alone drives a structural transformation in ZnS nanoparticles in the temperature range 22-40 C. The transition kinetics are strongly temperature dependent, with an activation energy of 58.1 {+-} 9.8 kJ/mol, consistent with atom displacement rather than bond breaking. At 50 C, aggregate restructuring occurred, increasing the transition kinetics beyond the rate expected for water adsorption alone. The observation of isosbestic points in the WAXS data suggests that the particles do not transform continuously between the initial and final structural state but rather undergo an abrupt change from a less ordered to a more ordered state.

  6. Formulating the bonding contribution equation in heterogeneous catalysis: a quantitative description between the surface structure and adsorption energy.

    PubMed

    Wang, Ziyun; Hu, P

    2017-02-15

    The relation between the surface structure and adsorption energy of adsorbates is of great importance in heterogeneous catalysis. Based on density functional theory calculations, we propose an explicit equation with three chemically meaningful terms, namely the bonding contribution equation, to quantitatively account for the surface structures and the adsorption energies. Successful predictions of oxygen adsorption energies on complex alloy surfaces containing up to 4 components are demonstrated, and the generality of this equation is also tested using different surface sizes and other adsorbates. This work may not only offer a powerful tool to understand the structure-adsorption relation, but may also be used to inversely design novel catalysts.

  7. Effect of bisulfite treatment on composition, structure, enzymatic hydrolysis and cellulase adsorption profiles of sugarcane bagasse.

    PubMed

    Liu, Z J; Lan, T Q; Li, H; Gao, X; Zhang, H

    2017-01-01

    The effect of sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL) on composition, structure, enzymatic hydrolysis and cellulase adsorption profiles of sugarcane bagasse (SCB) was investigated. SPORL gave a higher SCB hydrolysis yield (85.33%) compared to dilute acid pretreatment (DA) (64.39%). The SEM pictures showed that SPORL SCB structure became more disordered and looser, suggesting SPORL SCB was more accessible to cellulase. The zeta potential of SPORL SCB suspension (-21.89mV) was significantly different from that of DA SCB (-12.87mV), which demonstrated the lignin in SPORL SCB was more hydrophilic. With regard to cellulase adsorption profiles, SPORL SCB had a lower non-productive adsorption (14.87mg/glignin) and a higher productive adsorption (37.67 mg/gcarbohydrate) compared with DA SCB (17.05mg/glignin; 25.79mg/gcarbohydrate). These results indicated that SPORL SCB had better accessibility to cellulase and the higher productive cellulase adsorption of SPORL SCB had improved hydrolysis.

  8. FINE-SCALE STRUCTURES OF FLUX ROPES TRACKED BY ERUPTING MATERIAL

    SciTech Connect

    Li Ting; Zhang Jun E-mail: zjun@nao.cas.cn

    2013-06-20

    We present Solar Dynamics Observatory observations of two flux ropes tracked out by material from a surge and a failed filament eruption on 2012 July 29 and August 4, respectively. For the first event, the interaction between the erupting surge and a loop-shaped filament in the east seems to 'peel off' the filament and add bright mass into the flux rope body. The second event is associated with a C-class flare that occurs several minutes before the filament activation. The two flux ropes are, respectively, composed of 85 {+-} 12 and 102 {+-} 15 fine-scale structures, with an average width of about 1.''6. Our observations show that two extreme ends of the flux rope are rooted in opposite polarity fields and each end is composed of multiple footpoints (FPs) of fine-scale structures. The FPs of the fine-scale structures are located at network magnetic fields, with magnetic fluxes from 5.6 Multiplication-Sign 10{sup 18} Mx to 8.6 Multiplication-Sign 10{sup 19} Mx. Moreover, almost half of the FPs show converging motion of smaller magnetic structures over 10 hr before the appearance of the flux rope. By calculating the magnetic fields of the FPs, we deduce that the two flux ropes occupy at least 4.3 Multiplication-Sign 10{sup 20} Mx and 7.6 Multiplication-Sign 10{sup 20} Mx magnetic fluxes, respectively.

  9. Fine scale genetic structure in the wild ancestor of maize (Zea mays ssp. parviglumis).

    PubMed

    Van Heerwaarden, Joost; Ross-Ibarra, Jeffrey; Doebley, John; Glaubitz, Jeffrey C; González, Jose De Jesús Sánchez; Gaut, Brandon S; Eguiarte, Luis E

    2010-03-01

    Analysis of fine scale genetic structure in continuous populations of outcrossing plant species has traditionally been limited by the availability of sufficient markers. We used a set of 468 SNPs to characterize fine-scale genetic structure within and between two dense stands of the wild ancestor of maize, teosinte (Zea mays ssp. parviglumis). Our analyses confirmed that teosinte is highly outcrossing and showed little population structure over short distances. We found that the two populations were clearly genetically differentiated, although the actual level of differentiation was low. Spatial autocorrelation of relatedness was observed within both sites but was somewhat stronger in one of the populations. Using principal component analysis, we found evidence for significant local differentiation in the population with stronger spatial autocorrelation. This differentiation was associated with pronounced shifts in the first two principal components along the field. These shifts corresponded to changes in allele frequencies, potentially due to local topographical features. There was little evidence for selection at individual loci as a contributing factor to differentiation. Our results demonstrate that significant local differentiation may, but need not, co-occur with spatial autocorrelation of relatedness. The present study represents one of the most detailed analyses of local genetic structure to date and provides a benchmark for future studies dealing with fine scale patterns of genetic diversity in natural plant populations.

  10. Automatic detection and extraction of ultra-fine bright structure observed with new vacuum solar telescope

    NASA Astrophysics Data System (ADS)

    Deng, Linhua

    2017-02-01

    Solar magnetic structures exhibit a wealth of different spatial and temporal scales. Presently, solar magnetic element is believed to be the ultra-fine magnetic structure in the lower solar atmospheric layer, and the diffraction limit of the largest-aperture solar telescope (New Vacuum Solar Telescope; NVST) of China is close to the spatial scale of magnetic element. This implies that modern solar observations have entered the era of high resolution better than 0.2 arc-second. Since the year of 2011, the NVST have successfully established and obtained huge observational data. Moreover, the ultra-fine magnetic structure rooted in the dark inter-graunlar lanes can be easily resolved. Studies on the observational characteristics and physical mechanism of magnetic bright points is one of the most important aspects in the field of solar physics, so it is very important to determine the statistical and physical parameters of magnetic bright points with the feature extraction techniques and numerical analysis approaches. For identifying such ultra-fine magnetic structure, an automatically and effectively detection algorithm, employed the Laplacian transform and the morphological dilation technique, is proposed and examined. Then, the statistical parameters such as the typical diameter, the area distribution, the eccentricity, and the intensity contrast are obtained. And finally, the scientific meaning for investigating the physical parameters of magnetic bright points are discussed, especially for understanding the physical processes of solar magnetic energy transferred from the photosphere to the corona.

  11. Influence of the pore structure and surface chemical properties of activated carbon on the adsorption of mercury from aqueous solutions.

    PubMed

    Lu, Xincheng; Jiang, Jianchun; Sun, Kang; Wang, Jinbiao; Zhang, Yanping

    2014-01-15

    Reactivation and chemical modification were used to obtain modified activated carbons with different pore structure and surface chemical properties. The samples were characterized by nitrogen absorption-desorption, Fourier transform infrared spectroscopy and the Bothem method. Using mercury chloride as the target pollutant, the Hg(2+) adsorption ability of samples was investigated. The results show that the Hg(2+) adsorption capacity of samples increased significantly with increases in micropores and acidic functional groups and that the adsorption process was exothermic. Different models and thermodynamic parameters were evaluated to establish the mechanisms. It was concluded that the adsorption occurred through a monolayer mechanism by a two-speed process involving both rapid adsorption and slow adsorption. The adsorption rate was determined by chemical reaction.

  12. Fine structure in plasma waves and radiation near the plasma frequency in Earth's foreshock

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1994-01-01

    Novel observations are presented of intrunsic fine structure in the frequency spectrum of electomagnetic (EM) radiation and plasma waves near the electron plasma frequency f(sub p) during a period of unusually high interplanetary magnetic field strength. Measured using the wideband receiver on the International Sun-Earth Explorer (ISEE) 1 spacecraft, fine-structured emissions are observed both in the solar wind and the foreshock, The fine structure is shown to correspond to emissions spaced above f(sub p) near half harmonies of the electon cyclotron frequency f(sub ce), i.e., near f(sub p) + nf(sub ce)/2. These appear to be the first space physics observations of emissions spaced by f(sub ce)/2. Indirect but strong arguments are used to discriminate between EM and electrostatic (ES) signals, to identify whether ISEE 1 is in the solar wind or the foreshock, and to determine the relative frequencies of the emissions and the local f(sub p). The data are consistent with generation of the ES and EM emissions in the foreshock, with subsequent propagation of the EM emissions into the solar wind. It remains possible that some emissions currently identified as ES have significant EM character. The ES and EM emisions often merge into one another with minimal changes in frequency, arguing that their source regions and generation mechanisms are related and imposing significant constraints on theories. The f(sub ce)/2 ES and EM fine structures observed may be intrinsic to the emission mechanisms or to superposition of two series of signals with f(sub ce) spacing that differ in starting frequency by f(sub ce)/2. Present theories for nonlinear wave coupling processes, cyclotron maser emission, and other linear instability processes are all unable to explain multiple EM and/or ES components spaced by approximately f(sub ce)/2 above f(sub p) for f(sub p)/f(sub ce) much greater than 1 and typical for shock beams parameters. Suitable avenues for further theoretical research are

  13. X-ray absorption fine structure study of heavily P doped (111) and (001) diamond

    NASA Astrophysics Data System (ADS)

    Shikata, Shinichi; Yamaguchi, Koji; Fujiwara, Akihiko; Tamenori, Yusuke; Yahiro, Jumpei; Kunisu, Masahiro; Yamada, Takatoshi

    2017-02-01

    X-ray absorption fine structure (XANES) measurements were carried out for P doped (111) and (001) diamond films, and the results were compared with those from simulations. For the (111) spectrum, the main strong peak observed at 2147.0 eV and three broad peaks centered at 2150 eV, 2157 eV, and 2165 eV were observed. The assignment with the estimation by the simulation of the XANES peaks showed the interstitial sites additional to the substitutional site. The Extended X-ray Absorption Fine Structure (EXAFS) result of the P doped (111) diamond showed that the first and second neighboring peaks are observed at 1.21 A and 2.0 A, respectively. The assignment with the estimation by the simulation of the EXAFS peaks also showed the interstitial sites additional to the substitutional site. Overall, P in diamonds presumably has dopant sites in both the substitutional and interstitial sites.

  14. Relation Between Basophilia and Fine Structure of Cytoplasm in the Fungus Allomyces macrogynus Em

    PubMed Central

    Blondel, Benigna; Turian, Gilbert

    1960-01-01

    In a fungus, Allomyces macrogynus Em., staining tests have revealed changes in the location of cytoplasmic basophilia following different phases of the developmental cycle. These variations in location were used to observe which fine structures correspond to basophile and non-basophile areas of the cytoplasm. Hyphae, gametangia, zygotes, and plants were fixed at various developmental stages in OsO4, pH 6.1, and embedded in vestopal. Sections were examined in the electron microscope. Comparison of basophile and non-basophile cytoplasms leads to the conclusion that cytoplasmic particles of 150 to 200 A in diameter are responsible for basophilia. The possibility of these particles being ribosomes is discussed and confirmed. The present paper also describes some observations on the fine structure of other cellular components of this fungus, such as nuclei, mitochondria, various granules, and flagella. PMID:13801597

  15. Fine structure of a biexciton in a single quantum dot with a magnetic impurity

    NASA Astrophysics Data System (ADS)

    Trojnar, Anna H.; Korkusinski, Marek; Mendes, Udson C.; Goryca, Mateusz; Koperski, Maciej; Smolenski, Tomasz; Kossacki, Piotr; Wojnar, Piotr; Hawrylak, Pawel

    2013-05-01

    We show theoretically and experimentally that the ground state of a biexciton in a CdTe self-assembled quantum dot with a magnetic Mn impurity exhibits a fine structure due to electron-electron Coulomb and electron-Mn exchange interactions. Results of exact diagonalization of the microscopic biexciton-manganese-ion model predict a pattern of three pairs of states in the ground-state manifold, each pair labeled by the projection of Mn spin. We show that the fine structure determines the ordering of the biexciton emission maxima and can be derived from the biexciton and exciton emission spectra. Theoretical predictions are successfully compared with measured biexciton and exciton emission spectra of a single CdTe dot with a Mn ion in its center.

  16. Solar Cycle Fine Structure and Surface Rotation from Ca II K-Line Time Series Data

    NASA Technical Reports Server (NTRS)

    Scargle, Jeff; Keil, Steve; Worden, Pete

    2011-01-01

    Analysis of three and a half decades of data from the NSO/AFRL/Sac Peak K-line monitoring program yields evidence for four components to the variation: (a) the solar cycle, with considerable fine structure and a quasi-periodicity of 122.4 days; (b) a stochastic process, faster than (a) and largely independent of it, (c) a quasi-periodic signal due to rotational modulation, and of course (d) observational errors (shown to be quite small). Correlation and power spectrum analyses elucidate periodic and aperiodic variation of these chromospheric parameters. Time-frequency analysis is especially useful for extracting information about differential rotation, and in particular elucidates the connection between its behavior and fine structure of the solar cycle on approximately one-year time scales. These results further suggest that similar analyses will be useful at detecting and characterizing differential rotation in stars from stellar light-curves such as those being produced at NASA's Kepler observatory.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Lanthanide ion probes of structure in biology. Environmentally sensitive fine structure in laser-induced terbium(III) luminescence.

    PubMed

    Sudnick, D R; Horrocks, W D

    1979-05-23

    The 488 nm line of the CW argon ion laser provides a convenient visible source for the direct excitation of the emissive 5D4 state of the Tb(III) ion. Room temperature emission spectra of Tb(III) in a variety of environments have been examined under relatively high resolution. The samples studied include structurally well-characterized crystalline solids, model chelate complexes in solution and Tb(III) bound to the enzyme thermolysin and the protein parvalbumin. The fine structure in the emissions is caused by ligand field splittings of both ground and excited state J manifolds. These spectra provide signatures sensitive to the immediate coordination environment of the Tb(III) ion. Solid state/solution state structural comparisons are made. The emission fine structure reveal differences between the EF side calcium-binding sites of parvalbumin and the calcium site 1 of thermolysin.

  20. MCDHF calculations of isotope shifts of even-parity fine-structure levels in neutral osmium

    NASA Astrophysics Data System (ADS)

    Palmeri, P.; Quinet, P.; Bouazza, S.

    2016-12-01

    Ab initio multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations have been carried out in order to determine the isotope shifts of all the fine-structure levels belonging to the even-parity configurations (5d+6s)8 in neutral osmium, Os I. The theoretical predictions have been compared to laser spectroscopy measurements available in the literature showing a good agreement between theory and experiment.

  1. Enhanced effect of temporal variation of the fine-structure constant in diatomic molecules

    SciTech Connect

    Flambaum, V. V.

    2006-03-15

    We show that the relative effect of variation of the fine-structure constant in microwave transitions between very close and narrow rotational-hyperfine levels may be enhanced 2-3 orders of magnitude in diatomic molecules with unpaired electrons like LaS, LaO, LuS, LuO, YbF, and similar molecular ions. The enhancement is result of cancellation between the hyperfine and rotational intervals.

  2. Cosmological variation of the fine-structure constant versus a new interaction

    SciTech Connect

    Angstmann, E.J.; Flambaum, V.V.; Karshenboim, S.G.

    2004-10-01

    We show that using the modified form of the Dirac Hamiltonian as suggested by Bekenstein does not affect the analysis of QSO data pertaining to a measurement of {alpha} variation. We obtain the present time limit on Bekenstein's parameter, tan{sup 2} {chi}=(0.2{+-}0.7)x10{sup -6}, from the measurement of the hydrogen 2p fine structure using a value of {alpha} obtained from different experiments.

  3. Atomic oxygen fine-structure splittings with tunable far-infrared spectroscopy

    NASA Technical Reports Server (NTRS)

    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.

  4. The 16th International Conference on X-ray Absorption Fine Structure (XAFS16)

    NASA Astrophysics Data System (ADS)

    Grunwaldt, J.-D.; Hagelstein, M.; Rothe, J.

    2016-05-01

    This preface of the proceedings volume of the 16th International Conference on X- ray Absorption Fine Structure (XAFS16) gives a glance on the five days of cutting-edge X-ray science which were held in Karlsruhe, Germany, August 23 - 28, 2015. In addition, several satellite meetings took place in Hamburg, Berlin and Stuttgart, a Sino-German workshop, three data analysis tutorials as well as special symposia on industrial catalysis and XFELs were held at the conference venue.

  5. Changes in adsorption and optical properties of liquid crystal langmuir films at structural phase transition

    NASA Astrophysics Data System (ADS)

    Zaitsev, V. B.; Levshin, N. L.; Khlybov, S. V.; Yudin, S. G.

    2012-12-01

    The adsorption isotherms of water molecules, absorption spectra, and spectra of diffuse scattering and polarization of reflected light are studied for ultrathin Langmuir films prepared based on liquid crystals. A structural phase transition near 70°C is detected. Some specific features of the reflection spectra at the phase transition temperature are found. Suggestions are made regarding the nature of the phase transition.

  6. Structural, electronic and adsorption properties of Rh(111)/Mo(110) bimetallic catalyst: A DFT study

    NASA Astrophysics Data System (ADS)

    Palotás, K.; Bakó, I.; Bugyi, L.

    2016-12-01

    Geometric and electronic characterizations of one monolayer rhodium with Nishiyama-Wassermann (NW) structure on Mo(110) substrate have been performed by density functional theory (DFT) calculations. In the NW structure the Rh atoms form a wavy structure propagating along the [001] direction, characterized by an amplitude of 0.26 Å in the [110] direction and by 0.10 Å in the [110] direction of the Mo(110) substrate. Strain and ligand effects operating in the rhodium film are distinguished and found to be manifested in the downward shift of the d-band center of the electron density of states (DOS) by 0.11 eV and 0.18 eV, respectively. The shift in the d-band center of Rh DOS predicts a decrease in the surface reactivity toward CO adsorption, which has been verified by detailed calculations of bond energies of CO located at on-top, bridge and hollow adsorption sites. The CO adsorption energies are decreased by about 35% compared to those reported for pure Rh(111), offering novel catalytic pathways for the molecule. An in-depth analysis of the charge transfer and the partial DOS characters upon CO adsorption on the NW-structured Rh(111)/Mo(110) bimetallic catalyst and on the pure Rh(111) surface sheds light on the bonding mechanism of CO and on the governing factors determining its lowered bond energy on the bimetallic surface.

  7. STRUCTURAL EFFECTS ON THE HIGH TEMPERATURE ADSORPTION OF CO2 ON A SYNTHETIC HYDROTALCITE

    EPA Science Inventory

    Hydrotalcite-like compounds (HTlcs) are solid sorbents that may potentially be used for high temperature separation and capture of CO2. The high-temperature adsorption of CO2 on Mg-Al-CO3 HTlc is affected by structural changes that take place upo...

  8. Adsorption on molecularly imprinted polymers of structural analogues of a template. Single-component adsorption isotherm data

    SciTech Connect

    Kim, Hyunjung; Guiochon, Georges A

    2005-10-01

    The equilibrium adsorption isotherms on two otherwise identical polymers, one imprinted with Fmoc-L-tryptophan (Fmoc-L-Trp) (MIP), the other nonimprinted (NIP), of compounds that are structural analogues of the template were acquired by frontal analysis (FA) in an acetonitrile/acetic acid (99/1 v/v) mobile phase, over a wide concentration range (from 0.005 to 50 mM). These analogues were Fmoc-L-tyrosine, Fmoc-L-serine, Fmoc-L-phenyalanine, Fmoc-glycine (Fmoc-Gly), Fmoc-L-tryptophan pentafluorophenyl ester (Fmoc-L-Trp(OPfp)), and their antipodes. These substrates have different numbers of functional groups able to interact with the 4-vinylpyridine groups of the polymer. For a given number of the functional groups, these substrates have different hydrophobicities of their side groups (as indicated by their partition coefficients (log P{sub ow}) in the octanol-water system (e.g., from 4.74 for Fmoc-Trp to 2.53 for Fmoc-Gly)). Statistical results from the fitting of the FA data to Langmuirian isotherm models, the calculation of the affinity energy distribution, and the comparison of calculated and experimental band profiles show that all these sets of FA data are best accounted for by a tri-Langmuir isotherm model, except for the data of Fmoc-L-Trp(OPfp) that are best modeled by a simple Langmuir isotherm. So, all compounds but Fmoc-L-Trp(OPfp) find three different types of adsorption sites on both the MIP and the NIP. The properties of these different types of sites were studied systematically. The results show that the affinity of the structural analogues for the NIP is controlled mostly by the number of the functional groups on the substrates and somewhat by the hydrophobicity of their side groups. These two factors control also the MIP affinity toward the enantiomers of the structural analogues that have a stereochemistry different from that of the template. In contrast, the affinity of the highest affinity sites of the MIP toward the enantiomers of these

  9. Selective Adsorption of CO2 from Light Gas Mixtures Using a Structurally Dynamic Porous Coordination Polymer**

    SciTech Connect

    Kristi L. Kauffman, Jeffrey T. Culp, Andrew J. Allen, Laura Espinal, Winnie Wong-Ng, Thomas D. Brown, Angela Goodman, Mark P. Bernardo, Russel J. Pancoast, Danielle Chirdon, Christopher Matranga*

    2010-01-01

    The selective adsorption of CO{sub 2} from mixtures with N{sub 2}, CH{sub 4}, and N{sub 2}O in a dynamic porous coordination polymer (see monomer structure) was evaluated by ATR-FTIR spectroscopy, GC, and SANS. All three techniques indicate highly selective adsorption of CO{sub 2} from CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} mixtures at 30 C, with no selectivity observed for the CO{sub 2}/N{sub 2}O system.

  10. Current Work to Improve Precision in Measurements of Helium Fine Structure

    NASA Astrophysics Data System (ADS)

    Hassan Rezaeian, Nima; Shiner, Davis

    2013-05-01

    With the recent improvement on the 23P Helium fine structure calculation by Pachucki and the quest for finding the most precise value for α, spectroscopic measurement of the helium atom has a great advantage to find this primary constant. Distinctively, the 32 GHz atomic fine structure of 23P J2 to J0 interval with uncertainty of 100Hz leads a factor of three better than the best current value of α and an impulsion to the theory to evaluate the largest term of order mα8 is our ambition. This measurement not only tests the quantum electrodynamics, but also establishes the fine structure constant α with uncertainty of 1.6 ppb. The electron g-factor measurement of α, even though, is by far more accurate at 0.37 ppb, our end result would be a examination to the best alternative atom recoil measurements with different approach. To reach on this level of accuracy, we implement our frequency selector with precision better than 1 to 100 along with laser cooling mechanism to enhance the signal to noise ratio by increasing the signal strength. This work is supported by NSF grant.

  11. Current Work to Improve Precision in Measurements of Helium Fine Structure

    NASA Astrophysics Data System (ADS)

    Hassan Rezaeian, Nima; Shiner, David

    2013-06-01

    With the recent improvement on the 23P Helium fine structure calculation by Pachucki and the quest for finding the most precise value for α, spectroscopic measurement of the helium atom has a great advantage to find this primary constant. Distinctively, the 32 GHz atomic fine structure of 23P J2 to J0 interval with uncertainty of 100Hz leads a factor of three better than the best current value of α and an impulsion to the theory to evaluate the largest term of order mα8 is our ambition. This measurement not only tests the quantum electrodynamics, but also establishes the fine structure constant α with uncertainty of 1.6 ppb. The electron g-factor measurement of α, even though, is by far more accurate at 0.37 ppb, our end result would be a examination to the best alternative atom recoil measurements with different approach. To reach on this level of accuracy, we implement our frequency selector with precision better than 1 to 100 along with laser cooling mechanism to enhance the signal to noise ratio by increasing the signal strength. This work is supported by NSF grant.

  12. Exciton fine structure and spin/valley dynamics in nanosystems (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Glazov, Mikhail M.

    2015-09-01

    In my invited talk the fine structure of neutral and charged excitons for GaAs/AlGaAs quantum dots (QDs) grown on (111) plane as well for transition metal dichalcogenides (TMDCs) monolayers will be discussed. These, at first glance, different systems posses similar trigonal symmetry, which makes exciton fine structure and spin dynamics unusual compared with standard low-dimensional semiconductors. The effects of long-range exchange interaction induced mixing of excitons in two valleys of TMDCs and of magneto-induced mixing of bright and dark excitonic states in trigonal QDs are predicted and confirmed experimentally. Manifestations of excitonic spin/valley dynamics in photoluminescence, pump-probe Kerr rotation and spin noise are discussed. The presentation will be based on the following references: [1] G. Sallen, B. Urbaszek, M. M. Glazov, et al., Dark-Bright Mixing of Interband Transitions in Symmetric Semiconductor Quantum Dots, Phys. Rev. Lett. 107, 166604 (2011). [2] L. Bouet, M. Vidal, T. Mano, N. Ha, T. Kuroda, M. V. Durnev, M. M. Glazov, et al., Charge tuning in [111] grown GaAs droplet quantum dots, Appl. Phys. Lett. 105, 082111 (2014). [3] M. M. Glazov, et al., Exciton fine structure and spin decoherence in monolayers of transition metal dichalcogenides Phys. Rev. B 89, 201302(R) (2014). [4] C. R. Zhu, K. Zhang, M. Glazov, et al., Exciton valley dynamics probed by Kerr rotation in WSe2 monolayers, Phys. Rev. B 90, 161302(R) (2014).

  13. Effective collision strengths for fine-structure transitions in Si VII

    SciTech Connect

    Sossah, A. M.; Tayal, S. S.

    2014-05-20

    The effective collision strengths for electron-impact excitation of fine-structure transitions in Si VII are calculated as a function of electron temperature in the range 5000-2,000,000 K. The B-spline Breit-Pauli R-matrix method has been used to calculate collision strengths by electron impact. The target wave functions have been obtained using the multi-configuration Hartree-Fock method with term-dependent non-orthogonal orbitals. The 92 fine-structure levels belonging to the 46 LS states of 2s {sup 2}2p {sup 4}, 2s2p {sup 5}, 2p {sup 6}, 2s {sup 2}2p {sup 3}3s, 2s {sup 2}2p {sup 3}3p, 2s {sup 2}2p {sup 3}3d, and 2s2p {sup 4}3s configurations are included in our calculations of oscillator strengths and collision strengths. There are 4186 possible fine-structure allowed and forbidden transitions among the 92 levels. The present excitation energies, oscillator strengths, and collision strengths have been compared with previous theoretical results and available experimental data. Generally, a good agreement is found with the 6 LS-state close-coupling approximation results of Butler and Zeippen and the 44 LS-state distorted wave calculation of Bhatia and Landi.

  14. Multipoint MMS observations of fine-scale SAPS structure in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    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.

  15. Helium induced fine structure in the electronic spectra of anthracene derivatives doped into superfluid helium nanodroplets

    SciTech Connect

    Pentlehner, D.; Slenczka, A.

    2015-01-07

    Electronic spectra of organic molecules doped into superfluid helium nanodroplets show characteristic features induced by the helium environment. Besides a solvent induced shift of the electronic transition frequency, in many cases, a spectral fine structure can be resolved for electronic and vibronic transitions which goes beyond the expected feature of a zero phonon line accompanied by a phonon wing as known from matrix isolation spectroscopy. The spectral shape of the zero phonon line and the helium induced phonon wing depends strongly on the dopant species. Phonon wings, for example, are reported ranging from single or multiple sharp transitions to broad (Δν > 100 cm{sup −1}) diffuse signals. Despite the large number of example spectra in the literature, a quantitative understanding of the helium induced fine structure of the zero phonon line and the phonon wing is missing. Our approach is a systematic investigation of related molecular compounds, which may help to shed light on this key feature of microsolvation in superfluid helium droplets. This paper is part of a comparative study of the helium induced fine structure observed in electronic spectra of anthracene derivatives with particular emphasis on a spectrally sharp multiplet splitting at the electronic origin. In addition to previously discussed species, 9-cyanoanthracene and 9-chloroanthracene will be presented in this study for the first time.

  16. Atomistic theory of excitonic fine structure in InAs/InP nanowire quantum dot molecules

    NASA Astrophysics Data System (ADS)

    Świderski, M.; Zieliński, M.

    2017-03-01

    Nanowire quantum dots have peculiar electronic and optical properties. In this work we use atomistic tight binding to study excitonic spectra of artificial molecules formed by a double nanowire quantum dot. We demonstrate a key role of atomistic symmetry and nanowire substrate orientation rather than cylindrical shape symmetry of a nanowire and a molecule. In particular for [001 ] nanowire orientation we observe a nonvanishing bright exciton splitting for a quasimolecule formed by two cylindrical quantum dots of different heights. This effect is due to interdot coupling that effectively reduces the overall symmetry, whereas single uncoupled [001 ] quantum dots have zero fine structure splitting. We found that the same double quantum dot system grown on [111 ] nanowire reveals no excitonic fine structure for all considered quantum dot distances and individual quantum dot heights. Further we demonstrate a pronounced, by several orders of magnitude, increase of the dark exciton optical activity in a quantum dot molecule as compared to a single quantum dot. For [111 ] systems we also show spontaneous localization of single particle states in one of nominally identical quantum dots forming a molecule, which is mediated by strain and origins from the lack of the vertical inversion symmetry in [111 ] nanostructures of overall C3 v symmetry. Finally, we study lowering of symmetry due to alloy randomness that triggers nonzero excitonic fine structure and the dark exciton optical activity in realistic nanowire quantum dot molecules of intermixed composition.

  17. Strong limit on the spatial and temporal variations of the fine-structure constant

    NASA Astrophysics Data System (ADS)

    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

  18. Adsorptive characterization of the ZIF-68 metal-organic framework: a complex structure with amphiphilic properties.

    PubMed

    Van der Perre, Stijn; Van Assche, Tom; Bozbiyik, Belgin; Lannoeye, Jeroen; De Vos, Dirk E; Baron, Gino V; Denayer, Joeri F M

    2014-07-22

    In this experimental study, the adsorption behavior of the ZIF-68 heterolinked zeolitic imidazolate framework has been explored. Vapor phase adsorption isotherms of linear C1-C6 alcohols, C6 alkane isomers, aromatics (benzene, toluene, xylene isomers, 1,3,5-trimethylbenzene, and 1,3,5-triisopropylbenzene), and polar adsorbates (water, acetonitrile, and acetone) are reported and discussed. The complex pore structure of ZIF-68, with two one-dimensional channels, each with a different polarity, displays an overall hydrophobic character. Its two-pore system results in S-shaped isotherms for small polar adsorbates (small alcohols, acetone, and acetonitrile), while longer alcohols and nonpolar molecules, such as aromatics and C6 alkane isomers, lead to type I adsorption isotherms. Bulky molecules, with a kinetic diameter significantly larger than the pore windows, are adsorbed in large amounts, which gave reason to think that this ZIF-68 material has a certain degree of framework flexibility to enlarge the free aperture of the channels. Besides, diffusion coefficients from vapor phase uptake and infrared experiments point to a different adsorption mechanism for polar and nonpolar adsorbates. Liquid phase adsorption experiments demonstrated the separation of alcohol mixtures (ethanol/1-butanol) at low concentration from water, with a clear preference for 1-butanol.

  19. Adsorption of mixed cationic-nonionic surfactant and its effect on bentonite structure.

    PubMed

    Zhang, Yaxin; Zhao, Yan; Zhu, Yong; Wu, Huayong; Wang, Hongtao; Lu, Wenjing

    2012-01-01

    The adsorption of cationic-nonionic mixed surfactant onto bentonite and its effect on bentonite structure were investigated. The objective was to improve the understanding of surfactant behavior on clay mineral for its possible use in remediation technologies of soil and groundwater contaminated by toxic organic compounds. The cationic surfactant used was hexadecylpyridinium bromide (HDPB), and the nonionic surfactant was Triton X-100 (TX100). Adsorption of TX100 was enhanced significantly by the addition of HDPB, but this enhancement decreased with an increase in the fraction of the cationic surfactant. Part of HDPB was replaced by TX100 which decreased the adsorption of HDPB. However, the total adsorbed amount of the mixed surfactant was still increased substantially, indicating the synergistic effect between the cationic and nonionic surfactants. The surfactant-modified bentonite was characterized by Brunauer-Emmett-Teller specific surface area measurement, Fourier transform infrared spectroscopy, and thermogravimetric-derivative thermogravimetric/differential thermal analyses. Surfactant intercalation was found to decrease the bentonite specific surface area, pore volume, and surface roughness and irregularities, as calculated by nitrogen adsorption-desorption isotherms. The co-adsorption of the cationic and nonionic surfactants increased the ordering conformation of the adsorbed surfactants on bentonite, but decreased the thermal stability of the organobentonite system.

  20. Molecular dynamics simulations of H2 adsorption in tetramethyl ammonium lithium phthalocyanine crystalline structures.

    PubMed

    Lamonte, Kevin; Gómez Gualdrón, Diego A; Cabrales-Navarro, Fredy A; Scanlon, Lawrence G; Sandi, Giselle; Feld, William; Balbuena, Perla B

    2008-12-11

    Tetramethyl ammonium lithium phthalocyanine is explored as a potential material for storage of molecular hydrogen. Density functional theory calculations are used to investigate the molecular structure and the dimer conformation. Additional scans performed to determine the interactions of a H2 molecule located at various distances from the molecular sites are used to generate a simple force field including dipole-induced-dipole interactions. This force field is employed in molecular dynamics simulations to calculate adsorption isotherms at various pressures. The regions of strongest adsorption are quantified as functions of temperature, pressure, and separation between molecules in the adsorbent phase, and compared to the regions of strongest binding energy as given by the proposed force field. It is found that the total adsorption could not be predicted only from the spatial distribution of the strongest binding energies; the available volume is the other contributing factor even if the volume includes regions of much lower binding energy. The results suggest that the complex anion is primarily involved in the adsorption process with molecular hydrogen, whereas the cation serves to provide access for hydrogen adsorption in both sides of the anion molecular plane, and spacing between the planes.

  1. Quantitative structure property relationships for the adsorption of pharmaceuticals onto activated carbon.

    PubMed

    Dickenson, E R V; Drewes, J E

    2010-01-01

    Isotherms were determined for the adsorption of five pharmaceutical residues, primidone, carbamazepine, ibuprofen, naproxen and diclofenac, to Calgon Filtrasorb 300 powdered activated carbon (PAC). The sorption behavior was examined in ultra-pure and wastewater effluent organic matter (EfOM) matrices, where more sorption was observed in the ultra-pure water for PAC doses greater than 10 mg/L suggesting the presence of EfOM hinders the sorption of the pharmaceuticals to the PAC. Adsorption behaviors were described by the Freundlich isotherm model. Quantitative structure property relationships (QSPRs) in the form of polyparameter linear solvation energy relationships were developed for simulating the Freundlich adsorption capacity in both ultra-pure and EfOM matrices. The significant 3D-based descriptors for the QSPRs were the molar volume, polarizability and hydrogen-bond donor parameters.

  2. Evolution of ultramicroporous adsorptive structure in poly(furfuryl alcohol)-derived carbogenic molecular sieves

    SciTech Connect

    Mariwala, R.K.; Foley, H.C. )

    1994-03-01

    The genesis of the adsorptive structure of carbogenic molecular sieves (CMS) derived from poly(furfuryl alcohol) (PFA) was investigated as a function of the synthesis temperature (from 400 to 1200 C) and soak time (from 0 to 8 h). The apparent CO[sub 2] adsorption capacity of these materials maximizes at 93 mg/g with a final synthesis temperature of 800 C. The maximum adsorption capacity is obtained from the 24-h CO[sub 2] uptake of 93 mg/g at a relative pressure of 0.015 and at T = 295 K. [sup 13]C CP-MAS NMR spectra of the carbon produced at lower synthesis temperature and short soak times shows a resonance that is reminiscent of the PFA precursor. At higher synthesis temperatures and longer soak times, the NMR spectra display resonances attributable only to aromatic microdomains.

  3. [Structural changes of aged biochar and the influence on phenanthrene adsorption].

    PubMed

    Tang, Wei; Guo, Yue; Wu, Jing-Gui; Huang, Zhao-Qin; Dai, Jing-Yu

    2014-07-01

    Biochars prepared by pyrolysis of rice husk at 350 degrees C and 550 degrees C were incubated in the lucifugal thermostat for 300 d. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Scanning Electron Microscopy (SEM), and Nuclear Magnetic Resonance (NMR) techniques were applied to explore the structural change before and after incubation. It was found that the oxygen content was increased after incubation, suggesting the formation of oxygen-containing functional groups. Incubation of the biochars also enhanced their nonlinear adsorption of phenanthrene. Structural change subjected to incubation was in fact affected by the pyrolysis temperatures at which the biochars were synthesized. Increase of polarity and decrease of aromaticity were found for biochars prepared at 350 degrees C. In contrast, incubation of biochars prepared at 550 degrees C resulted in increased aliphatic contents and aromaticity, as well as decrease of carboxyl group. The adsorption capacity of phenanthrene predicted by Langmuir model was 3.57 and 2.35 mg x g(-1) for new and aged biochar with lower pyrolysis temperature, respectively. It was assumed that change of the surface structure of the biochars due to aging inhibited the adsorption. On the contrary, aging of biochares prepared at 550 degrees C resulted in enhanced adsorption capacity of phenanthrene from 0.42 to 4.17 mg x (-1), which was probably correlated to the partition effect due to enhanced aromaticity. The data obtained in this research suggested that aging of biochars potentially affected the fate of the pollutants in environment.

  4. Hydrophobic core/hydrophilic shell structured mesoporous silica nanospheres: enhanced adsorption of organic compounds from water.

    PubMed

    Li, Shuru; Jiao, Xuan; Yang, Hengquan

    2013-01-29

    Inspired by the structure features of micelle, we attempt to synthesize a novel functionalized mesoporous silica nanosphere consisting of a hydrophobic core and a hydrophilic shell. The obtained solid materials were structurally confirmed by N(2) sorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Their compositions were characterized by Fourier transfer infrared spectroscopy (FT-IR), solid state NMR, X-ray photoelectron spectroscopy (XPS), and elemental analysis. Its fundamental properties such as dispersibility in water or organic phase, wettability, and adsorption ability toward hydrophobic organics in water were investigated. It was revealed that these important properties could be facilely adjusted through varying structure and composition. In particular, these materials showed much better adsorption ability toward hydrophobic organic molecules in water than conventional monofunctionalized mesoporous materials, owing to possessing the hydrophobic/hydrophilic domain-segregated and hierarchically functionalized mesoporous structures. The intriguing properties would make mesoporous materials more accessible to many important applications, especially in aqueous systems.

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

    PubMed Central

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

    2016-01-01

    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. PMID:27622503

  6. A cascade interpretation of Lundgren's stretched spiral vortex model for turbulent fine structure

    NASA Astrophysics Data System (ADS)

    Gilbert, Andrew D.

    1993-11-01

    Lundgren's [Phys. Fluids 25, 2193 (1982)] model for turbulent fine structure comprises coherent vortices which wind up vorticity variations into spiral structures; simultaneously the vortices are stretched axially by a background strain field. The model predicts a k-5/3 energy spectrum and is remarkably robust to the form of the coherent vortices and the form of the vorticity variations. To understand this the present article introduces a simple cascade argument which illuminates how the dynamical processes of vortex stretching and reduction of scale conspire to give this Kolmogorov spectrum. Some generalizations are considered.

  7. X-Ray Absorption Fine Structure Study for Fe60Ni40 Alloy

    SciTech Connect

    Yang, Dong-Seok; Oh, Kyuseung; Na, Wonkyung; Kim, Nayoung; Yoo, Yong-Goo; Min, Seung-Gi; Yu, Seong-Cho

    2007-02-02

    Fe60Ni40 alloys were fabricated by the mechanical alloying process with process periods of 1, 2, 4, 6, 12 and 24 hours, respectively. The formation of alloy and the structural evolution of the alloy were examined by X-ray diffraction and extended X-ray absorption fine structure methods. With increase of alloying time the BCC phase of iron was changed significantly during the mechanical alloying process. The alloying was activated in about 6 hours and completed in about 24 hours.

  8. Tailoring the exciton fine structure of cadmium selenide nanocrystals with shape anisotropy and magnetic field.

    PubMed

    Sinito, Chiara; Fernée, Mark J; Goupalov, Serguei V; Mulvaney, Paul; Tamarat, Philippe; Lounis, Brahim

    2014-11-25

    We use nominally spheroidal CdSe nanocrystals with a zinc blende crystal structure to study how shape perturbations lift the energy degeneracies of the band-edge exciton. Nanocrystals with a low degree of symmetry exhibit splitting of both upper and lower bright state degeneracies due to valence band mixing combined with the isotropic exchange interaction, allowing active control of the level splitting with a magnetic field. Asymmetry-induced splitting of the bright states is used to reveal the entire 8-state band-edge fine structure, enabling complete comparison with band-edge exciton models.

  9. New determination of the fine structure constant from the electron value and QED.

    PubMed

    Gabrielse, G; Hanneke, D; Kinoshita, T; Nio, M; Odom, B

    2006-07-21

    Quantum electrodynamics (QED) predicts a relationship between the dimensionless magnetic moment of the electron (g) and the fine structure constant (alpha). A new measurement of g using a one-electron quantum cyclotron, together with a QED calculation involving 891 eighth-order Feynman diagrams, determine alpha(-1)=137.035 999 710 (96) [0.70 ppb]. The uncertainties are 10 times smaller than those of nearest rival methods that include atom-recoil measurements. Comparisons of measured and calculated g test QED most stringently, and set a limit on internal electron structure.

  10. Structural characterization of poorly-crystalline scorodite, iron(III)-arsenate co-precipitates and uranium mill neutralized raffinate solids using X-ray absorption fine structure spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, N.; Jiang, D. T.; Cutler, J.; Kotzer, T.; Jia, Y. F.; Demopoulos, G. P.; Rowson, J. W.

    2009-06-01

    X-ray absorption fine structure (XAFS) is used to characterize the mineralogy of the iron(III)-arsenate(V) precipitates produced during the raffinate (aqueous effluent) neutralization process at the McClean Lake uranium mill in northern Saskatchewan, Canada. To facilitate the structural characterization of the precipitated solids derived from the neutralized raffinate, a set of reference compounds were synthesized and analyzed. The reference compounds include crystalline scorodite, poorly-crystalline scorodite, iron(III)-arsenate co-precipitates obtained under different pH conditions, and arsenate-adsorbed on goethite. The poorly-crystalline scorodite (prepared at pH 4 with Fe/As = 1) has similar As local structure as that of crystalline scorodite. Both As and Fe K-edge XAFS of poorly-crystalline scorodite yield consistent results on As-Fe (or Fe-As) shell. From As K-edge analysis the As-Fe shell has an inter-atomic distance of 3.33 ± 0.02 Å and coordination number of 3.2; while from Fe K-edge analysis the Fe-As distance and coordination number are 3.31 ± 0.02 Å and 3.8, respectively. These are in contrast with the typical arsenate adsorption on bidentate binuclear sites on goethite surfaces, where the As-Fe distance is 3.26 ± 0.03 Å and coordination number is close to 2. A similar local structure identified in the poorly-crystalline scorodite is also found in co-precipitation solids (Fe(III)/As(V) = 3) when precipitated at the same pH (pH = 4): As-Fe distance 3.30 ± 0.03 Å and coordination number 3.9; while at pH = 8 the co-precipitate has As-Fe distance of 3.27 ± 0.03 Å and coordination number about 2, resembling more closely the adsorption case. The As local structure in the two neutralized raffinate solid series (precipitated at pH values up to 7) closely resembles that in the poorly-crystalline scorodite. All of the raffinate solids have the same As-Fe inter-atomic distance as that in the poorly-crystalline scorodite, and a systematic decrease in the

  11. The Effect of Quantum-Mechanical Interference on Precise Measurements of the n = 2 Triplet P Fine Structure of Helium

    SciTech Connect

    Marsman, A.; Horbatsch, M.; Hessels, E. A.

    2015-09-15

    For many decades, improvements in both theory and experiment of the fine structure of the n = 2 triplet P levels of helium have allowed for an increasingly precise determination of the fine-structure constant. Recently, it has been observed that quantum-mechanical interference between neighboring resonances can cause significant shifts, even if such neighboring resonances are separated by thousands of natural widths. The shifts depend in detail on the experimental method used for the measurement, as well as the specific experimental parameters employed. Here, we review how these shifts apply for the most precise measurements of the helium 2{sup 3}P fine-structure intervals.

  12. Dispersal, Mating Events and Fine-Scale Genetic Structure in the Lesser Flat-Headed Bats

    PubMed Central

    Guo, Tingting; Flanders, Jon; Zhang, Shuyi

    2013-01-01

    Population genetic structure has important consequences in evolutionary processes and conservation genetics in animals. Fine-scale population genetic structure depends on the pattern of landscape, the permanent movement of individuals, and the dispersal of their genes during temporary mating events. The lesser flat-headed bat (Tylonycteris pachypus) is a nonmigratory Asian bat species that roosts in small groups within the internodes of bamboo stems and the habitats are fragmented. Our previous parentage analyses revealed considerable extra-group mating in this species. To assess the spatial limits and sex-biased nature of gene flow in the same population, we used 20 microsatellite loci and mtDNA sequencing of the ND2 gene to quantify genetic structure among 54 groups of adult flat-headed bats, at nine localities in South China. AMOVA and FST estimates revealed significant genetic differentiation among localities. Alternatively, the pairwise FST values among roosting groups appeared to be related to the incidence of associated extra-group breeding, suggesting the impact of mating events on fine-scale genetic structure. Global spatial autocorrelation analyses showed positive genetic correlation for up to 3 km, indicating the role of fragmented habitat and the specialized social organization as a barrier in the movement of individuals among bamboo forests. The male-biased dispersal pattern resulted in weaker spatial genetic structure between localities among males than among females, and fine-scale analyses supported that relatedness levels within internodes were higher among females than among males. Finally, only females were more related to their same sex roost mates than to individuals from neighbouring roosts, suggestive of natal philopatry in females. PMID:23349888

  13. Structural characterization and adsorption properties of pluronic F127 onto iron oxides magnetic nanoparticles.

    PubMed

    Dehvari, Khalilalrahman; Lin, Kuen-Song; Wang, Steven S S

    2014-03-01

    Superparamagnetic iron oxide nanoparticles coated with polymers have shown low toxicity and chemical stability in physiological condition, thereby can be used to deliver encapsulated drugs throughout the body by external magnetic fields. In this study, magnetic nanoparticles were synthesized thorough co-precipitation method and their interaction with Pluronic F127 block copolymer as well as adsorption properties of polymer onto nanoparticles were investigated. Adsorption measurement revealed different adsorption behaviors below and above the polymer's critical micelle concentration. The Freundlich isotherm was found to better describe the adsorption behavior of Pluronic F127 onto SIONPs particles below the block copolymer critical micelle concentration. At higher concentration, the adsorbed amount is likely to diminish due to interpenetration of the adsorbed macromolecular micelles and volume-excluded effects for block copolymers. Furthermore, magnetic nanocomposites with different concentration of polymers were prepared through hydrothermal method. The crystalline structure, morphology, pore structure, and magnetic properties of magnetic nanoparticles/nanocomposites products at different pH and polymer concentration were studied. Results showed that due to the hematite impurities, magnetic nanocomposites synthesized at higher pH have lower magnetization.

  14. Nanosheet-structured boron nitride spheres with a versatile adsorption capacity for water cleaning.

    PubMed

    Liu, Fei; Yu, Jie; Ji, Xixi; Qian, Muqi

    2015-01-28

    Here, we report the synthesis of nanosheet-structured boron nitride spheres (NSBNSs) by a catalyzing thermal evaporation method from solid B powders. The NSBNSs consist of radially oriented ultrathin nanosheets with the sheet edges oriented on the surface. Formation of this unique structure occurs only at a certain reaction temperature. The diameter from 4 μm to 700 nm and the nanosheet thickness from 9.1 to 3.1 nm of the NSBNSs can be well-controlled by appropriately changing the mass ratio of boron powders and catalyst. The NSBNSs possess versatile adsorption capacity, exhibiting excellent adsorption performance for oil, dyes, and heavy metal ions from water. The oil uptake reaches 7.8 times its own weight. The adsorption capacities for malachite green and methylene blue are 324 and 233 mg/g, while those for Cu(2+), Pb(2+), and Cd(2+) are 678.7, 536.7, and 107.0 mg/g, respectively. The adsorption capacities of the NSBNSs for Cu(2+) and Pb(2+) are higher or much higher than those of the adsorbents reported previously. These results demonstrate the great potential of NSBNSs for water treatment and cleaning.

  15. Microwave-Assisted Hydrothermal Rapid Synthesis of Calcium Phosphates: Structural Control and Application in Protein Adsorption

    PubMed Central

    Cai, Zhu-Yun; Peng, Fan; Zi, Yun-Peng; Chen, Feng; Qian, Qi-Rong

    2015-01-01

    Synthetic calcium phosphate (CaP)-based materials have attracted much attention in the biomedical field. In this study, we have investigated the effect of pH values on CaP nanostructures prepared using a microwave-assisted hydrothermal method. The hierarchical nanosheet-assembled hydroxyapatite (HAP) nanostructure was prepared under weak acidic conditions (pH 5), while the HAP nanorod was prepared under neutral (pH 7) and weak alkali (pH 9) condition. However, when the pH value increases to 11, a mixed product of HAP nanorod and tri-calcium phosphate nanoparticle was obtained. The results indicated that the pH value of the initial reaction solution played an important role in the phase and structure of the CaP. Furthermore, the protein adsorption and release performance of the as-prepared CaP nanostructures were investigated by using hemoglobin (Hb) as a model protein. The sample that was prepared at pH = 11 and consisted of mixed morphologies of nanorods and nanoprisms showed a higher Hb protein adsorption capacity than the sample prepared at pH 5, which could be explained by its smaller size and dispersed structure. The results revealed the relatively high protein adsorption capacity of the as-prepared CaP nanostructures, which show promise for applications in various biomedical fields such as drug delivery and protein adsorption.

  16. Predicting adsorption of aromatic compounds by carbon nanotubes based on quantitative structure property relationship principles

    NASA Astrophysics Data System (ADS)

    Rahimi-Nasrabadi, Mehdi; Akhoondi, Reza; Pourmortazavi, Seied Mahdi; Ahmadi, Farhad

    2015-11-01

    Quantitative structure property relationship (QSPR) models were developed to predict the adsorption of aromatic compounds by carbon nanotubes (CNTs). Five descriptors chosen by combining self-organizing map and stepwise multiple linear regression (MLR) techniques were used to connect the structure of the studied chemicals with their adsorption descriptor (K∞) using linear and nonlinear modeling techniques. Correlation coefficient (R2) of 0.99 and root-mean square error (RMSE) of 0.29 for multilayered perceptron neural network (MLP-NN) model are signs of the superiority of the developed nonlinear model over MLR model with R2 of 0.93 and RMSE of 0.36. The results of cross-validation test showed the reliability of MLP-NN to predict the K∞ values for the aromatic contaminants. Molar volume and hydrogen bond accepting ability were found to be the factors much influencing the adsorption of the compounds. The developed QSPR, as a neural network based model, could be used to predict the adsorption of organic compounds by CNTs.

  17. Groundwater Arsenic Adsorption on Granular TiO2: Integrating Atomic Structure, Filtration, and Health Impact.

    PubMed

    Hu, Shan; Shi, Qiantao; Jing, Chuanyong

    2015-08-18

    A pressing challenge in arsenic (As) adsorptive filtration is to decipher how the As atomic surface structure obtained in the laboratory can be used to accurately predict the field filtration cycle. The motivation of this study was therefore to integrate molecular level As adsorption mechanisms and capacities to predict effluent As from granular TiO2 columns in the field as well as its health impacts. Approximately 2,955 bed volumes of groundwater with an average of 542 μg/L As were filtered before the effluent As concentration exceeded 10 μg/L, corresponding to an adsorption capacity of 1.53 mg As/g TiO2. After regeneration, the TiO2 column could treat 2,563 bed volumes of groundwater, resulting in an As load of 1.36 mg/g TiO2. Column filtration and EXAFS results showed that among coexisting ions present in groundwater, only Ca(2+), Si(OH)4, and HCO3(-) would interfere with As adsorption. The compound effects of coexisting ions and molecular level structural information were incorporated in the PHREEQC program to satisfactorily predict the As breakthrough curves. The total urinary As concentration from four volunteers of local residences, ranging from 972 to 2,080 μg/L before groundwater treatment, decreased to the range 31.7-73.3 μg/L at the end of the experimental cycle (15-33 days).

  18. Adsorption of alpha-synuclein on lipid bilayers: modulating the structure and stability of protein assemblies.

    PubMed

    Haque, Farzin; Pandey, Anjan P; Cambrea, Lee R; Rochet, Jean-Christophe; Hovis, Jennifer S

    2010-03-25

    The interaction of alpha-synuclein with phospholipid membranes has been examined using supported lipid bilayers and epi-fluorescence microscopy. The membranes contained phosphatidylcholine (PC) and phosphatidic acid (PA), which mix at physiological pH. Upon protein adsorption, the lipids undergo fluid-fluid phase separation into PC-rich and PA-rich regions. The protein preferentially adsorbs to the PA-rich regions. The adsorption and subsequent aggregation of alpha-synuclein was probed by tuning several parameters: the charge on the lipids, the charge on the protein, and the screening environment. Conditions which promoted the greatest extent of adsorption resulted in structurally heterogeneous aggregates, while comparatively homogeneous aggregates were observed under conditions whereby adsorption did not occur as readily. Our observation that different alterations to the system lead to different degrees of aggregation and different aggregate structures poses a challenge for drug discovery. Namely, therapies aimed at neutralizing alpha-synuclein must target a broad range of potentially toxic, membrane-bound assemblies.

  19. Enhanced CO2 adsorption over polymeric amines supported on heteroatom-incorporated SBA-15 silica: impact of heteroatom type and loading on sorbent structure and adsorption performance.

    PubMed

    Kuwahara, Yasutaka; Kang, Dun-Yen; Copeland, John R; Bollini, Praveen; Sievers, Carsten; Kamegawa, Takashi; Yamashita, Hiromi; Jones, Christopher W

    2012-12-21

    Silica supported amine materials are promising compositions that can be used to effectively remove CO(2) from large stationary sources, such as flue gas generated from coal-fired power plants (ca. 10 % CO(2)) and potentially from ambient air (ca. 400 ppm CO(2)). The CO(2) adsorption characteristics of prototypical poly(ethyleneimine)-silica composite adsorbents can be significantly enhanced by altering the acid/base properties of the silica support by heteroatom incorporation into the silica matrix. In this study, an array of poly(ethyleneimine)-impregnated mesoporous silica SBA-15 materials containing heteroatoms (Al, Ti, Zr, and Ce) in their silica matrices are prepared and examined in adsorption experiments under conditions simulating flue gas (10 % CO(2) in Ar) and ambient air (400 ppm CO(2) in Ar) to assess the effects of heteroatom incorporation on the CO(2) adsorption properties. The structure of the composite adsorbents, including local information concerning the state of the incorporated heteroatoms and the overall surface properties of the silicate supports, are investigated in detail to draw a relationship between the adsorbent structure and CO(2) adsorption/desorption performance. The CO(2) adsorption/desorption kinetics are assessed by thermogravimetric analysis and in situ FT-IR measurements. These combined results, coupled with data on adsorbent regenerability, demonstrate a stabilizing effect of the heteroatoms on the poly(ethyleneimine), enhancing adsorbent capacity, adsorption kinetics, regenerability, and stability of the supported aminopolymers over continued cycling. It is suggested that the CO(2) adsorption performance of silica-aminopolymer composites may be further enhanced in the future by more precisely tuning the acid/base properties of the support.

  20. Adsorption structures and energetics of molecules on metal surfaces: Bridging experiment and theory

    NASA Astrophysics Data System (ADS)

    Maurer, Reinhard J.; Ruiz, Victor G.; Camarillo-Cisneros, Javier; Liu, Wei; Ferri, Nicola; Reuter, Karsten; Tkatchenko, Alexandre

    2016-05-01

    Adsorption geometry and stability of organic molecules on surfaces are key parameters that determine the observable properties and functions of hybrid inorganic/organic systems (HIOSs). Despite many recent advances in precise experimental characterization and improvements in first-principles electronic structure methods, reliable databases of structures and energetics for large adsorbed molecules are largely amiss. In this review, we present such a database for a range of molecules adsorbed on metal single-crystal surfaces. The systems we analyze include noble-gas atoms, conjugated aromatic molecules, carbon nanostructures, and heteroaromatic compounds adsorbed on five different metal surfaces. The overall objective is to establish a diverse benchmark dataset that enables an assessment of current and future electronic structure methods, and motivates further experimental studies that provide ever more reliable data. Specifically, the benchmark structures and energetics from experiment are here compared with the recently developed van der Waals (vdW) inclusive density-functional theory (DFT) method, DFT + vdWsurf. In comparison to 23 adsorption heights and 17 adsorption energies from experiment we find a mean average deviation of 0.06 Å and 0.16 eV, respectively. This confirms the DFT + vdWsurf method as an accurate and efficient approach to treat HIOSs. A detailed discussion identifies remaining challenges to be addressed in future development of electronic structure methods, for which the here presented benchmark database may serve as an important reference.

  1. Fine-Scale Genetic Structure and Reproductive Biology of the Blueberry Pathogen Monilinia vaccinii-corymbosi.

    PubMed

    Burchhardt, Kathleen M; Miller, Megan E; Cline, William O; Cubeta, Marc A

    2017-02-01

    The fungus Monilinia vaccinii-corymbosi, a pathogen of Vaccinium spp., requires asexual and sexual spore production to complete its life cycle. A recent study found population structuring of M. vaccinii-corymbosi over a broad spatial scale in the United States. In this study, we examined fine-scale genetic structuring, temporal dynamics, and reproductive biology within a 125-by-132-m blueberry plot from 2010 to 2012. In total, 395 isolates of M. vaccinii-corymbosi were sampled from infected shoots and fruit to examine their multilocus haplotype (MLH) using microsatellite markers. The MLH of 190 single-ascospore isolates from 21 apothecia was also determined. Little to no genetic differentiation and unrestricted gene flow were detected among four sampled time points and between infected tissue types. Discriminant analysis of principal components suggested genetic structuring within the field, with at least K = 3 genetically distinct clusters maintained over four sampled time points. Single-ascospore progeny from eight apothecia had identical MLH and at least two distinct MLH were detected from 13 apothecia. Tests for linkage disequilibrium suggested that genetically diverse ascospore progeny were the product of recombination. This study supports the idea that the fine-scale dynamics of M. vaccinii-corymbosi may be complex, with genetic structuring, inbreeding, and outcrossing detected in the study area.

  2. Accurate Electron Affinity of Iron and Fine Structures of Negative Iron ions

    PubMed Central

    Chen, Xiaolin; Luo, Zhihong; Li, Jiaming; Ning, Chuangang

    2016-01-01

    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. PMID:27138292

  3. Accurate Electron Affinity of Iron and Fine Structures of Negative Iron ions.

    PubMed

    Chen, Xiaolin; Luo, Zhihong; Li, Jiaming; Ning, Chuangang

    2016-05-03

    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.

  4. Coarse-fine vertical scanning based optical profiler for structured surface measurement with large step height

    NASA Astrophysics Data System (ADS)

    Zheng, Yi; Liu, Xiaojun; Lei, Zili; Li, Qian; Yang, Xiao; Chen, Liangzhou; Lu, Wenlong

    2015-02-01

    White light interference (WLI) optical profiler had been used widely for structured surface measurement. To achieve high measuring accuracy, piezoelectric ceramic (PZT) was usually used as the vertical scanning unit, which was normally less than 100um and only for small range structured surface measurement. With the development of advanced manufacturing technology, precision structured surfaces with large step height were appearing. To satisfy the measurement requirements of this kind of precision structured surfaces, WLI optical profiler with large range had to be developed. In this paper, an optical profiler was proposed, in which a coarse-fine vertical scanning system was adopted to expand its measurement range to 10mm while its resolution still at nanometer level.

  5. Confocal imaging reveals three-dimensional fine structure difference between ventral and dorsal nerve roots.

    PubMed

    Wu, Yuxiang; Sui, Tao; Cao, Xiaojian; Lv, Xiaohua; Zeng, Shaoqun; Sun, Peng

    2011-05-01

    Peripheral nerve injury repair is one of the most challenging problems in neurosurgery, partially due to lack of knowledge of three-dimensional (3-D) fine structure and organization of peripheral nerves. In this paper, we explored the structures of nerve fibers in ventral and dorsal nerves with a laser scanning confocal microscopy. Thick tissue staining results suggested that nerve fibers have a different 3-D structure in ventral and dorsal nerves, and reconstruction from serial sectioning images showed that in ventral nerves the nerve fibers travel in a winding form, while in dorsal nerves, the nerve fibers form in a parallel cable pattern. These structural differences could help surgeons to differentiate ventral and dorsal nerves in peripheral nerve injury repair, and also facilitate scientists to get a deeper understanding about nerve fiber organization.

  6. Confocal imaging reveals three-dimensional fine structure difference between ventral and dorsal nerve roots

    NASA Astrophysics Data System (ADS)

    Wu, Yuxiang; Sui, Tao; Cao, Xiaojian; Lv, Xiaohua; Zeng, Shaoqun; Sun, Peng

    2011-05-01

    Peripheral nerve injury repair is one of the most challenging problems in neurosurgery, partially due to lack of knowledge of three-dimensional (3-D) fine structure and organization of peripheral nerves. In this paper, we explored the structures of nerve fibers in ventral and dorsal nerves with a laser scanning confocal microscopy. Thick tissue staining results suggested that nerve fibers have a different 3-D structure in ventral and dorsal nerves, and reconstruction from serial sectioning images showed that in ventral nerves the nerve fibers travel in a winding form, while in dorsal nerves, the nerve fibers form in a parallel cable pattern. These structural differences could help surgeons to differentiate ventral and dorsal nerves in peripheral nerve injury repair, and also facilitate scientists to get a deeper understanding about nerve fiber organization.

  7. Lack of sex-biased dispersal promotes fine-scale genetic structure in alpine ungulates

    USGS Publications Warehouse

    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.

  8. Vibronic fine structure in high-resolution x-ray absorption spectra from ion-bombarded boron nitride nanotubes

    SciTech Connect

    Petravic, Mladen; Peter, Robert; Varasanec, Marijana; Li Luhua; Chen Ying; Cowie, Bruce C. C.

    2013-05-15

    The authors have applied high-resolution near-edge x-ray absorption fine structure measurements around the nitrogen K-edge to study the effects of ion-bombardment on near-surface properties of boron nitride nanotubes. A notable difference has been observed between surface sensitive partial electron yield (PEY) and bulk sensitive total electron yield (TEY) fine-structure measurements. The authors assign the PEY fine structure to the coupling of excited molecular vibrational modes to electronic transitions in NO molecules trapped just below the surface. Oxidation resistance of the boron nitride nanotubes is significantly reduced by low energy ion bombardment, as broken B-N bonds are replaced by N-O bonds involving oxygen present in the surface region. In contrast to the PEY spectra, the bulk sensitive TEY measurements on as-grown samples do not exhibit any fine structure while the ion-bombarded samples show a clear vibronic signature of molecular nitrogen.

  9. Water dissociative adsorption on NiO(111): Energetics and structure of the hydroxylated surface

    SciTech Connect

    Zhao, Wei; Bajdich, Michal; Carey, Spencer; Vojvodic, Aleksandra; Nørskov, Jens K.; Campbell, Charles T.

    2016-09-19

    The energetics of the reactions of water with metal oxide surfaces are of tremendous interest for catalysis, electrocatalysis, and geochemistry, yet the energy for the dissociative adsorption of water was only previously measured on one well-defined oxide surface, iron oxide. In the present paper, the enthalpy of the dissociative adsorption of water is measured on NiO(111)-2 × 2 at 300 K using single-crystal adsorption calorimetry. The differential heat of dissociative adsorption decreases with coverage from 170 to 117 kJ/mol in the first 0.25 ML of coverage. Water adsorbs molecularly on top of that, with a heat of ~92 kJ/mol. Density functional theory (DFT) calculations reproduce the measured energies well (all within 17 kJ/mol) and provide insight into the atomic-level structure of the surfaces studied experimentally. They show that the oxygen-terminated O-octo(2 × 2) structure is the most stable NiO(111)-2 × 2 termination and gives reaction energies with water that are more consistent with the calorimetry results than the metal-terminated surface. They show that water adsorbs dissociatively on this (2 × 2)-O-octo surface to produce a hydroxyl-covered surface with a heat of adsorption of 171 ± 5 kJ/mol in the low-coverage limit (very close to 170 kJ/mol experimentally) and an integral heat that decreases by 14 kJ/mol up to saturation (compared to ~30 kJ/mol experimentally). As a result, sensitivity of this reaction’s energy to choice of DFT method is tested using a variety of different exchange correlation functionals, including HSE06, and found to be quite weak.

  10. Water dissociative adsorption on NiO(111): Energetics and structure of the hydroxylated surface

    DOE PAGES

    Zhao, Wei; Bajdich, Michal; Carey, Spencer; ...

    2016-09-19

    The energetics of the reactions of water with metal oxide surfaces are of tremendous interest for catalysis, electrocatalysis, and geochemistry, yet the energy for the dissociative adsorption of water was only previously measured on one well-defined oxide surface, iron oxide. In the present paper, the enthalpy of the dissociative adsorption of water is measured on NiO(111)-2 × 2 at 300 K using single-crystal adsorption calorimetry. The differential heat of dissociative adsorption decreases with coverage from 170 to 117 kJ/mol in the first 0.25 ML of coverage. Water adsorbs molecularly on top of that, with a heat of ~92 kJ/mol. Densitymore » functional theory (DFT) calculations reproduce the measured energies well (all within 17 kJ/mol) and provide insight into the atomic-level structure of the surfaces studied experimentally. They show that the oxygen-terminated O-octo(2 × 2) structure is the most stable NiO(111)-2 × 2 termination and gives reaction energies with water that are more consistent with the calorimetry results than the metal-terminated surface. They show that water adsorbs dissociatively on this (2 × 2)-O-octo surface to produce a hydroxyl-covered surface with a heat of adsorption of 171 ± 5 kJ/mol in the low-coverage limit (very close to 170 kJ/mol experimentally) and an integral heat that decreases by 14 kJ/mol up to saturation (compared to ~30 kJ/mol experimentally). As a result, sensitivity of this reaction’s energy to choice of DFT method is tested using a variety of different exchange correlation functionals, including HSE06, and found to be quite weak.« less

  11. Global investigation of the fine structure of the isoscalar giant quadrupole resonance

    SciTech Connect

    Shevchenko, A.; Burda, O.; Kalmykov, Y.; Neumann-Cosel, P. von; Ponomarev, V. Yu.; Richter, A.; Wambach, J.; Carter, J.; Sideras-Haddad, E.; Cooper, G. R. J.; Fearick, R. W.; Foertsch, S. V.; Lawrie, J. J.; Neveling, R.; Smit, F. D.; Fujita, H.; Fujita, Y.; Lacroix, D.

    2009-04-15

    Fine structure in the region of the isoscalar giant quadrupole resonance (ISGQR) in {sup 58}Ni, {sup 89}Y, {sup 90}Zr, {sup 120}Sn, {sup 166}Er, and {sup 208}Pb has been observed in high-energy-resolution ({delta}E{sub 1/2}{approx_equal}35-50 keV) inelastic proton scattering measurements at E{sub 0}=200 MeV at iThemba LABS. Calculations of the corresponding quadrupole excitation strength functions performed within models based on the random-phase approximation (RPA) reveal similar fine structure when the mixing of one-particle one-hole states with two-particle two-hole states is taken into account. A detailed comparison of the experimental data is made with results from the quasiparticle-phonon model (QPM) and the extended time-dependent Hartree-Fock (ETDHF) method. For {sup 208}Pb, additional theoretical results from second RPA and the extended theory of finite Fermi systems (ETFFS) are discussed. A continuous wavelet analysis of the experimental and the calculated spectra is used to extract dominant scales characterizing the fine structure. Although the calculations agree with qualitative features of these scales, considerable differences are found between the model and experimental results and amongst different models. Within the framework of the QPM and ETDHF calculations it is possible to decompose the model spaces into subspaces approximately corresponding to different damping mechanisms. It is demonstrated that characteristic scales mainly arise from the collective coupling of the ISGQR to low-energy surface vibrations.

  12. Fine Structure in the Mm-Wavelength Spectra of the Active Region

    NASA Astrophysics Data System (ADS)

    Sawant, H. S.; Cecatto, J. R.

    1990-11-01

    RESUMEN. Faltan observaciones solares espectrosc6picas en la longitud de onda milimetrica. Hay sugerencias de que se puede superponer una fi na estructura en frecuencia a la componente-S de la regi6n solar activa, asi como a la componente del brote en las longitudes de onda milimetri- cas. Se ha desarrollado un receptor de alta sensibilidad de pasos de frecuencia que opera en el intervalo de 23-18 GHz con una resoluci6n de 1 GHz y resoluci6n de tiempo variable entre 1.2 y 96 sec, usando la an- tena de Itapetinga de 13.7-m para estudiar la estructura fina en frecuencia y tiempo. Discutimos el espectro en longitud de onda-mm en re- giones activas y su evoluci6n en el tiempo. El estudio de Ia evoluci6n en el tiempo de la regi6n activa en AR 5569 observada el 29 de junio de 1989, sugiere la existencia de estructuras finas como funci6n deltiempo. ABSTRACT. There is a lack of mm-wavelength spectroscopic solar observations. There are suggestions that a fine structure in frequency may be superimposed on the S-component of solar active region as well as on the burst component at inm-wavelengths. To study fine structure in frequency and time, a high sensitivity step frequency receiver operating in the frequency range 23-18 GHz with frequency resolution of 1 GHz and variable time resolution 1.2 to 96 sec, using 13.7 m diameter Itapetinga radome covered antenna, has been developed. Here, we discuss mm-wavelength spectra of active regions and their time evolution. Study of time evolution of an active region AR 5569 observed on 29th June, 1989 suggests existence of fine structures as a function of time. ( Ck : SUN-ACTIVITY - SUN-RADIO RADIATION

  13. 3D WHOLE-PROMINENCE FINE STRUCTURE MODELING. II. PROMINENCE EVOLUTION

    SciTech Connect

    Gunár, Stanislav; Mackay, Duncan H.

    2015-10-20

    We use the new three-dimensional (3D) whole-prominence fine structure model to study the evolution of prominences and their fine structures in response to changes in the underlying photospheric magnetic flux distribution. The applied model combines a detailed 3D prominence magnetic field configuration with a realistic description of the prominence plasma distributed along multiple fine structures. In addition, we utilize an approximate Hα visualization technique to study the evolution of the visible cool prominence plasma both in emission (prominence) and absorption (filament). We show that the initial magnetic field configuration of the modeled prominence is significantly disturbed by the changing position of a single polarity of a magnetic bipole as the bipole is advected toward the main body of the filament. This leads to the creation of a barb, which becomes the dominant feature visible in the synthetic Hα images of both the prominence and filament views. The evolution of the bipole also creates conditions that lead to the disappearance and reappearance of large portions of the main body. We also show that an arch-like region containing a dark void (a bubble) can be naturally produced in the synthetic prominence Hα images. While not visible in terms of the magnetic field lines, it is due to a lack of Hα emission from low-pressure, low-density plasma located in shallow magnetic dips lying along the lines of sight intersecting the dark void. In addition, a quasi-vertical small-scale feature consisting of short and deep dips, piled one above the other, is produced.

  14. Boron carbide: Consistency of components, lattice parameters, fine structure and chemical composition makes the complex structure reasonable

    NASA Astrophysics Data System (ADS)

    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.

  15. Fine-structure splittings in high-lying {sup 2}F states of rubidium via three-step laser spectroscopy

    SciTech Connect

    Brandenberger, J. R.; Malyshev, G. S.

    2010-03-15

    Three-step laser spectroscopy has been used to measure six additional fine-structure splittings in the n {sup 2}F states of {sup 87}Rb for 11{<=}n{<=}16. When combined with our previous measurements for 4{<=}n{<=}10, they constitute a continuous sequence of 13 measurements suitable for comparison to fine-structure calculations in heavy alkali-metal atoms where relativistic effects, core polarization, configuration mixing, and electron correlation are important.

  16. Fine-Scale Structure of Solar Polar Faculae and their relation to Magnetic Patches

    NASA Astrophysics Data System (ADS)

    Suematsu, Y.; Kaithakkal, A. J.

    2014-12-01

    The fine-scale structure and dynamics of solar polar faculae were studied using Hinode/SOT spectro-polarimetric and filtergraphic observations at polar regions. It is revealed that polar magnetic patches of large flux have substructures, with a few small faculae in the much larger patches. It was also found that faculae tend to have higher intrinsic magnetic field strengths compared with the non-facular regions inside the associated magnetic patches. G-band images reveal much thinner facular structures of close to 0.1 arcsec and the faculae appear as a cluster of thin tapered tube-like structures; individual size is about 0.2 x 0.5 arcsec, reaching the maximum closer mid-way to the limb, are likely projected on the limb-side neighboring granules with center-ward dark lanes. Typical lifetime of each facular elements is about five minutes, showing side-way motion during the life. Corresponding bright fine elongated structures are seen in Ca II H, although such structures are more numerous and therefore there does not always exist one-to-one correspondence of Ca II H bright structures with the G-band facular elements. In H-alpha and Na I D line wing, fibril structure emanating limb-ward from the faulae and Ca II H bright regions. Those facts imply that the polar faculae appear in the root of intense vertically-oriented thin magnetic flux tubes which are consistent with the result from the magnetic properties reduced from the spectro-polarimetry. Those results suggest that the Spruit's hot wall effect explains the appearance of faculae in intense vertically oriented flux tube whose formation is dynamically changing.

  17. On the fine-structure constant in a plasma model of the fluctuating vacuum substratum

    NASA Technical Reports Server (NTRS)

    Cragin, B. L.

    1986-01-01

    The existence of an intimate connection between the quivering motion of electrons and positrons (Zitterbewegung), predicted by the Dirac equation, and the zero-point fluctuations of the vacuum is suggested. The nature of the proposed connection is discussed quantitatively, and an approximate self-consistency relation is derived, supplying a purely mathematical expression that relates the dimensionless coupling strengths (fine-structure constants) alpha sub e and alpha sub g of electromagnetism and gravity. These considerations provide a tentative explanation for the heretofore puzzling number 1/alpha sub e of about 137.036 and suggest that attempts to unify gravity with the electroweak and strong interactions will ultimately prove successful.

  18. Sensitivity of ultracold-atom scattering experiments to variation of the fine-structure constant

    SciTech Connect

    Borschevsky, A.; Beloy, K.; Flambaum, V. V.; Schwerdtfeger, P.

    2011-05-15

    We present numerical calculations for cesium and mercury to estimate the sensitivity of the scattering length to the variation of the fine-structure constant {alpha}. The method used follows the ideas of Chin and Flambaum [Phys. Rev. Lett. 96, 230801 (2006)], where the sensitivity to the variation of the electron-to-proton mass ratio {beta} was considered. We demonstrate that for heavy systems, the sensitivity to the variation of {alpha} is of the same order of magnitude as to the variation of {beta}. Near narrow Feshbach resonances, the enhancement of the sensitivity may exceed nine orders of magnitude.

  19. The fine structure of muscle attachments in a spider (Latrodectus mactans, Fabr.).

    PubMed

    Smith, D S; Järlfors, U; Russell, F E

    1969-01-01

    The fine structure of a spider myo-apodeme junction is described, and discussed in terms of other arthropod muscle attachments. This is contrasted with the situation in the venom gland, equipped with muscle fibers that control expulsion of the secreted material. The latter involves a cell-free collagenous matrix, lying between the muscle cells and the sheath of the gland. As in other arthropods, skeletal fibers are attached to the apodeme cuticle via specialized epidermal cells, containing oriented microtubules. Interdigitations between these cells and muscle, basally, and cuticle, apically, are described. Extracellular tonofibrillae described elsewhere are inconspicuous in the apodeme cuticle.

  20. Domain Dynamics in Piezoresponse Force Spectroscopy: Quantitative Deconvolution and Hysteresis Loop Fine Structure

    SciTech Connect

    Bdikin, Igor; Kholkin, Andrei; Morozovska, A. N.; Svechnikov, S. V.; Kim, S.-H.; Kalinin, Sergei V

    2008-01-01

    Domain dynamics in the Piezoresponse Force Spectroscopy (PFS) experiment is studied using the combination of local hysteresis loop acquisition with simultaneous domain imaging. The analytical theory for PFS signal from domain of arbitrary cross-section and length is developed for the analysis of experimental data on Pb(Zr,Ti)O3 polycrystalline films. The results suggest formation of oblate domain at early stage of the nucleation and growth, consistent with efficient screening of depolarization field. The fine structure of the hysteresis loop is shown to be related to the observed jumps in the domain geometry during domain wall propagation (nanoscale Barkhausen jumps), indicative of strong domain-defect interactions.

  1. The fine structure of the sperm of the round goby (Neogobius melanostomus)

    USGS Publications Warehouse

    Allen, Jeffrey D.; Walker, Glenn K.; Nichols, Susan J.; Sorenson, Dorothy

    2004-01-01

    The fine structural details of the spermatozoon of the round goby are presented for the first time in this study. Scanning and transmission electron microscopic examination of testis reveals an anacrosomal spermatozoon with a slightly elongate head and uniformly compacted chromatin. The midpiece contains a single, spherical mitochondrion. Two perpendicularly oriented centrioles lie in a deep, eccentric nuclear fossa with no regularly observed connection to the nucleus. The flagellum develops bilateral fins soon after emerging from the fossa; each extends approximately 1 A?m from the axoneme and persists nearly the length of the flagellum.

  2. Quantum field theory and classical optics: determining the fine structure constant

    NASA Astrophysics Data System (ADS)

    Leuchs, Gerd; Hawton, Margaret; Sánchez-Soto, Luis L.

    2017-01-01

    The properties of the vacuum are described by quantum physics including the response to external fields such as electromagnetic radiation. Of the two parameters that govern the details of the electromagnetic field dynamics in vacuum, one is fixed by the requirement of Lorentz invariance c = 1/\\sqrt {ε 0 μ 0 } . The other one, Z0 = \\sqrt {μ 0 /ε 0 } = 1/(cε 0 ) and its relation to the quantum vacuum, is discussed in this contribution. Deriving ε 0 from the properties of the quantum vacuum implies the derivation of the fine structure constant.

  3. Biology of Budding Bacteria III. Fine Structure of Rhodomicrobium and Hyphomicrobium spp

    PubMed Central

    Conti, S. F.; Hirsch, Peter

    1965-01-01

    Conti, S. F. (Dartmouth Medical School, Hanover, N.H.), and Peter Hirsch. Biology of budding bacteria. III. Fine structure of Rhodomicrobium and Hyphomicrobium spp. J. Bacteriol. 89:503–512. 1965.—The ultrastructure of 14 strains of hyphomicrobia, and of Rhodomicrobium vannielii, was investigated by means of electron microscopy of thin sections. The majority of the strains of hyphomicrobia possessed a well-developed internal membrane system, which appeared to be derived by invagination from the cytoplasmic membrane. The subcellular organization of the hyphomicrobia and R. vannielii was investigated. Images PMID:14255720

  4. Enhanced Laboratory Sensitivity to Variation of the Fine-Structure Constant using Highly Charged Ions

    SciTech Connect

    Berengut, J. C.; Dzuba, V. A.; Flambaum, V. V.

    2010-09-17

    We study atomic systems that are in the frequency range of optical atomic clocks and have enhanced sensitivity to potential time variation of the fine-structure constant {alpha}. The high sensitivity is due to coherent contributions from three factors: high nuclear charge Z, high ionization degree, and significant differences in the configuration composition of the states involved. Configuration crossing keeps the frequencies in the optical range despite the large ionization energies. We discuss a few promising examples that have the largest {alpha} sensitivities seen in atomic systems.

  5. Improved self-absorption correction for extended x-ray absorption fine-structure measurements

    SciTech Connect

    Booth, C.H.; Bridges, F.

    2003-06-04

    Extended x-ray absorption fine-structure (EXAFS) data collected in the fluorescence mode are susceptible to an apparent amplitude reduction due to the self-absorption of the fluorescing photon by the sample before it reaches a detector. Previous treatments have made the simplifying assumption that the effect of the EXAFS on the correction term is negligible, and that the samples are in the thick limit. We present a nearly exact treatment that can be applied for any sample thickness or concentration, and retains the EXAFS oscillations in the correction term.

  6. Ground-based and spaceborn observations of the type II burst with developed fine structure

    NASA Astrophysics Data System (ADS)

    Dorovskyy, V.; Melnik, V.; Konovalenko, A.; Brazhenko, A.; Rucker, H.; Stanislavskyy, A.; Panchenko, M.

    2012-09-01

    The combination of two huge ground-based radio telescopes (UTR-2 and URAN-2) operated in decameter wavelengths with three spatially separated spacecrafts (SOHO, STEREO-A and STEREO-B) equipped with white light coronagraphs, UV telescopes and decameter-hectometer band radio telescopes created a unique opportunity to investigate the high energy solar transients, such as CMEs and their manifestations in radio bands - type II bursts. In this paper we made detailed analysis of the powerful and complex event occurred on 7 June 2011 consisted of Halo-CME and type II burst with rich fine structure.

  7. Extended X-ray absorption fine structure (EXAFS) study of CaSO 4:Dy phosphors

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, D.; Bakshi, A. K.; Ciatto, G.; Aquilanti, G.; Pradhan, A. S.; Pascarelli, S.

    2006-03-01

    Extended X-ray absorption fine structure (EXAFS) measurements have been carried out on CaSO 4:Dy phosphors at the Dy L 3 edge with synchrotron radiation. The data have been analysed to find out the Dy-S and Dy-O bond lengths in the neighborhood of the Dy atoms. Measurements have been carried out over several samples thermally annealed for different cycles at 400 °C in air for 1 h and the change in bond lengths in samples with increasing number of annealing cycles have been studied by analyzing the EXAFS data.

  8. Fine structure of transient waves in a random medium: The correlation and spectral density functions

    NASA Technical Reports Server (NTRS)

    Wenzel, Alan R.

    1994-01-01

    This is essentially a progress report on a theoretical investigation of the propagation of transient waves in a random medium. The emphasis in this study is on applications to sonic-boom propagation, particularly as regards the effect of atmospheric turbulence on the sonic-boom waveform. The analysis is general, however, and is applicable to other types of waves besides sonic-boom waves. The phenomenon of primary concern in this investigation is the fine structure of the wave. A figure is used to illustrate what is meant by finestructure.

  9. Enhanced laboratory sensitivity to variation of the fine-structure constant using highly charged ions.

    PubMed

    Berengut, J C; Dzuba, V A; Flambaum, V V

    2010-09-17

    We study atomic systems that are in the frequency range of optical atomic clocks and have enhanced sensitivity to potential time variation of the fine-structure constant α. The high sensitivity is due to coherent contributions from three factors: high nuclear charge Z, high ionization degree, and significant differences in the configuration composition of the states involved. Configuration crossing keeps the frequencies in the optical range despite the large ionization energies. We discuss a few promising examples that have the largest α sensitivities seen in atomic systems.

  10. Deciphering Adsorption Structure on Insulators at the Atomic Scale

    SciTech Connect

    Thurmer, Konrad; Feibelman, Peter J.

    2014-09-01

    We applied Scanning Probe Microscopy and Density Functional Theory (DFT) to discover the basics of how adsorbates wet insulating substrates, addressing a key question in geochemistry. To allow experiments on insulating samples we added Atomic Force Microscopy (AFM) capability to our existing UHV Scanning Tunneling Microscope (STM). This was accomplished by integrating and debugging a commercial qPlus AFM upgrade. Examining up-to-40-nm-thick water films grown in vacuum we found that the exact nature of the growth spirals forming around dislocations determines what structure of ice, cubic or hexagonal, is formed at low temperature. DFT revealed that wetting of mica is controlled by how exactly a water layer wraps around (hydrates) the K+ ions that protrude from the mica surface. DFT also sheds light on the experimentally observed extreme sensitivity of the mica surface to preparation conditions: K atoms can easily be rinsed off by water flowing past the mica surface.

  11. Fine-scale population structure of blue whale wintering aggregations in the Gulf of California.

    PubMed

    Costa-Urrutia, Paula; Sanvito, Simona; Victoria-Cota, Nelva; Enríquez-Paredes, Luis; Gendron, Diane

    2013-01-01

    Population differentiation in environments without well-defined geographical barriers represents a challenge for wildlife management. Based on a comprehensive database of individual sighting records (1988-2009) of blue whales from the winter/calving Gulf of California, we assessed the fine-scale genetic and spatial structure of the population using individual-based approaches. Skin samples of 187 individuals were analyzed for nine microsatellite loci. A single population with no divergence among years and months and no isolation by distance (Rxy = 0.1-0.001, p>0.05) were found. We ran two bayesian clustering methods using Structure and Geneland softwares in two different ways: 1) a general analysis including all individuals in which a single cluster was identified with both softwares; 2) a specific analysis of females only in which two main clusters (Loreto Bay and northern areas, and San Jose-La Paz Bay area) were revealed by Geneland program. This study provides information indicating that blue whales wintering in the Gulf of California are part of a single population unit and showed a fine-scale structure among females, possibly associated with their high site fidelity, particularly when attending calves. It is likely that the loss of genetic variation is minimized by male mediated gene flow, which may reduce the genetic drift effect. Opportunities for kin selection may also influence calf survival and, in consequence, have a positive impact on population demography in this small and endangered population.

  12. Fine-Scale Population Structure of Blue Whale Wintering Aggregations in the Gulf of California

    PubMed Central

    Costa-Urrutia, Paula; Sanvito, Simona; Victoria-Cota, Nelva; Enríquez-Paredes, Luis; Gendron, Diane

    2013-01-01

    Population differentiation in environments without well-defined geographical barriers represents a challenge for wildlife management. Based on a comprehensive database of individual sighting records (1988–2009) of blue whales from the winter/calving Gulf of California, we assessed the fine-scale genetic and spatial structure of the population using individual-based approaches. Skin samples of 187 individuals were analyzed for nine microsatellite loci. A single population with no divergence among years and months and no isolation by distance (Rxy = 0.1–0.001, p>0.05) were found. We ran two Bayesian clustering methods using Structure and Geneland softwares in two different ways: 1) a general analysis including all individuals in which a single cluster was identified with both softwares; 2) a specific analysis of females only in which two main clusters (Loreto Bay and northern areas, and San Jose-La Paz Bay area) were revealed by Geneland program. This study provides information indicating that blue whales wintering in the Gulf of California are part of a single population unit and showed a fine-scale structure among females, possibly associated with their high site fidelity, particularly when attending calves. It is likely that the loss of genetic variation is minimized by male mediated gene flow, which may reduce the genetic drift effect. Opportunities for kin selection may also influence calf survival and, in consequence, have a positive impact on population demography in this small and endangered population. PMID:23505485

  13. Julius Edgar Lilienfeld Prize Talk: Measuring the Electron Magnetic Moment and the Fine Structure Constant

    NASA Astrophysics Data System (ADS)

    Gabrielse, Gerald

    2011-05-01

    The electron magnetic moment in Bohr magnetons has been measured to a precision of 3 parts in 1013. This measurement, with quantum electrodynamics (AED) theory, provides the most precise value of the fine structure constant. This measurement, with a value of the fine structure from other measurements, also tests QED and sets a limit on the internal structure of the electron. A one-electron quantum cyclotron is at the heart of the measurement -- an electron suspended in a magnetic field and cooled enough that its lowest cyclotron and spin quantum states can be deduced with quantum nondemolition (QND) measurements. A cylindrical Penning trap cavity inhibits spontaneous emission and feedback methods make the electron excite and sustain its own motion for detection. A new apparatus is being commissioned in pursuit of more precise measurements. Adapted methods are promising for observing a proton spin flip, which should make it possible to compare the antiproton and proton magnetic moments a million times more accurately than is currently possible.

  14. Position-sensitive change in the transition metal L-edge fine structures

    SciTech Connect

    Gulec, Ahmet; Phillips, Patrick J.; Klie, Robert F.

    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.

  15. Fine and Superfine Structure of the Decameter-Hectometer Type II Burst on 7 June 2011

    NASA Astrophysics Data System (ADS)

    Dorovskyy, V. V.; Melnik, V. N.; Konovalenko, A. A.; Brazhenko, A. I.; Panchenko, M.; Poedts, S.; Mykhaylov, V. A.

    2015-07-01

    The characteristics of a type II burst with a herringbone structure observed both with ground-based radio telescopes (UTR-2 and URAN-2) and space-borne spectrometers (STEREO-A and 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. 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 a wide frequency band (16 - 32 MHz). A second-order fine frequency structure of the herringbone sub-bursts was observed and studied for the first time. Using STEREO/COR1 and SOHO/LASCO-C2 images, we determined the direction and radial speed of the coronal mass ejection responsible for the studied type II burst. The possible location of the type II burst source on the flank of the shock was found.

  16. Features of sound propagation in the ocean with fine-structure inhomogeneities

    NASA Astrophysics Data System (ADS)

    Gostev, V. S.; Mikryukov, A. V.; Popov, O. E.

    2016-09-01

    We analyze the results of an experiment using an explosive sound source in the tropical part of the Indian Ocean. We consider the time structure of sound signals in geometric shadow zones to a distance of 270 km and the scheme of how the sound field in the shadow zone is formed by rays reflected from horizontally extended fine-structured sound velocity layers. From the results of calculation using a wave program that realizes the method of psuedodifferential parabolic equations, we analyze the influence of signal scattering by fine-structure sound velocity inhomogeneities on the sound field distribution in a waveguide. We show that the field formed by spots of light in each of the shadow zones is generated by a regular field and propagates in parallel to it, taking energy from the regular zone in the near field and in each subsequent convergence zone. This mechanism causes an additional decrease in the field in illuminated zones, which can be interpreted as additional attenuation of the regular sound field.

  17. A comparative study of distortion-product-otoacoustic-emission fine structure in human newborns and adults with normal hearing.

    PubMed

    Dhar, Sumitrajit; Abdala, Carolina

    2007-10-01

    Distortion product otoacoustic emissions (DPOAE) measured in human newborns are not adult-like. More than a decade of work from various investigators has created a well-developed body of evidence describing these differences but the putative anatomy or physiology has only been partially explained. Recently, Abdala and Keefe [J. Acoust. Soc. Am. 120, 3832-3842 (2006)] have identified outer and middle ear immaturities that at least partially describe the differences observed between newborn and adult input-output functions and suppression tuning curves. DPOAE fine structure characteristics and their maturation have not been examined to any extent in the literature. Fine structure characteristics in two groups of ten newborns and young adults with normal hearing sensitivity are compared here. Consistent with previous reports, the newborns show higher DPOAE levels; greater fine structure depth and wider fine structure spacing is also observed in the newborns. Differences in fine structure morphology are also observed between the two age groups. While some of these findings are attributable to an immature outer and middle ear system in the newborns, it is argued that some observed differences in fine structure characteristics might be due to remnant immaturities in passive motion of the basilar membrane in the newborn cochlea.

  18. Fine structure of the dogfish egg case: a unique collagenous material.

    PubMed

    Knight, D P; Hunt, S

    1976-01-01

    The fine structure of the dogfish egg case is described with special reference to the highly ordered, unique, collagen-containing fibrils. The outer layer of the case wall contains densely packed, amorphous granules, rich in tyrosine while approximately 98% of the thickness of the case is built up from orthogonally stacked laminae of closely packed, collagen-containing fibrils. These fibrils show a paracrystalline three-dimensional construction. A model for the structure of the B band of the fibril is proposed, based on appearances in transverse sections of different thickness and on two projection seen in longitudinal sections. The transverse projection of the unit cell appears to be a square lattice with sides approximately 110 A possibly containing a pseudocell with sides (see article). The structure of these fibrils is discussed in relation to those of rat tail tendon collagen.

  19. `Fingerprint' Fine Structure in the Solar Decametric Radio Spectrum Solar Physics

    NASA Astrophysics Data System (ADS)

    Zlotnik, E. Y.; Zaitsev, V. V.; Melnik, V. N.; Konovalenko, A. A.; Dorovskyy, V. V.

    2015-07-01

    We study a unique fine structure in the dynamic spectrum of the solar radio emission discovered by the UTR-2 radio telescope (Kharkiv, Ukraine) in the frequency band of 20 - 30 MHz. The structure was observed against the background of a broadband type IV radio burst and consisted of parallel drifting narrow bands of enhanced emission and absorption on the background emission. The observed structure differs from the widely known zebra pattern at meter and decimeter wavelengths by the opposite directions of the frequency drift within a single stripe at a given time. We show that the observed properties can be understood in the framework of the radiation mechanism by virtue of the double plasma resonance effect in a nonuniform coronal magnetic trap. We propose a source model providing the observed frequency drift of the stripes.

  20. Hemicellulose fine structure is affected differently during ripening of tomato lines with contrasted texture.

    PubMed

    Lahaye, Marc; Quemener, Bernard; Causse, Mathilde; Seymour, Graham B

    2012-11-01

    The impact of genetic and fruit ripening on hemicelluloses fine structure was studied in twelve near isogenic lines of tomato fruits harboring firmness QTL. The sugar composition and the MALDI-TOF MS oligosaccharides profile after glucanase hydrolysis of the cell walls were determined from all green and red fruits pericarp tissue. MS profiles showed two major series of oligomers attributed to xyloglucan (XG) and glucomannan (GM) with minor peaks for xylan and ions attributed to galacto-oligomers. The oligosaccharides MS intensity varied significantly with the fruit genetic and ripening status. Correlations between MS intensity indicated structural regulations of both XG and GM structures with genetics and ripening. These results point to a region on the tomato chromosome 9 controlling cell wall galactose metabolism.

  1. Observation of fine structures in laser-driven electron beams using coherent transition radiation.

    PubMed

    Glinec, Y; Faure, J; Norlin, A; Pukhov, A; Malka, V

    2007-05-11

    We have measured the coherent optical transition radiation emitted by an electron beam from laser-plasma interaction. The measurement of the spectrum of the radiation reveals fine structures of the electron beam in the range 400-1000 nm. These structures are reproduced using an electron distribution from a 3D particle-in-cell simulation and are attributed to microbunching of the electron bunch due to its interaction with the laser field. When the radiator is placed closer to the interaction point, spectral oscillations have also been recorded, signature of the interference of the radiation produced by two electron bunches delayed by 74 fs. The second electron bunch duration is shown to be ultrashort to match the intensity level of the radiation. Whereas transition radiation was used at longer wavelengths in order to estimate the electron bunch length, this study focuses on the ultrashort structures of the electron beam.

  2. Frequency-dependent fine structure in the frequency-following response: The byproduct of multiple generators.

    PubMed

    Tichko, Parker; Skoe, Erika

    2017-01-28

    The frequency-following response (FFR) is an auditory-evoked response recorded at the scalp that captures the spectrotemporal properties of tonal stimuli. Previous investigations report that the amplitude of the FFR fluctuates as a function of stimulus frequency, a phenomenon thought to reflect multiple neural generators phase-locking to the stimulus with different response latencies. When phase-locked responses are offset by different latencies, constructive and destructive phase interferences emerge in the volume-conducted signals, culminating in an attenuation or amplification of the scalp-recorded response in a frequency-specific manner. Borrowing from the literature on the audiogram and otoacoustic emissions (OAEs), we refer to this frequency-specific waxing and waning of the FFR amplitude as fine structure. While prior work on the human FFR was limited by small sets of stimulus frequencies, here, we provide the first systematic investigation of FFR fine structure using a broad stimulus set (90 + frequencies) that spanned the limits of human pitch perception. Consistent with predictions, the magnitude of the FFR response varied systematically as a function of stimulus frequency between 16.35 and 880 Hz. In our dataset, FFR high points (local maxima) emerged at ∼44, 87, 208, and 415 Hz with FFR valleys (local minima) emerging ∼62, 110, 311, and 448 Hz. To investigate whether these amplitude fluctuations are the result of multiple neural generators with distinct latencies, we created a theoretical model of the FFR that included six putative generators. Based on the extant literature on the sources of the FFR, our model adopted latencies characteristic of the cochlear microphonic (0 ms), cochlear nucleus (∼1.25 ms), superior olive (∼3.7 ms), and inferior colliculus (∼5 ms). In addition, we included two longer latency putative generators (∼13 ms, and ∼25 ms) reflective of the characteristic latencies of primary and non-primary auditory

  3. Fine Structure of Tibetan Kefir Grains and Their Yeast Distribution, Diversity, and Shift

    PubMed Central

    Lu, Man; Wang, Xingxing; Sun, Guowei; Qin, Bing; Xiao, Jinzhou; Yan, Shuling; Pan, Yingjie; Wang, Yongjie

    2014-01-01

    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 associations between S

  4. Kinetics of protein adsorption on gold nanoparticle with variable protein structure and nanoparticle size

    NASA Astrophysics Data System (ADS)

    Khan, S.; Gupta, A.; Verma, N. C.; Nandi, C. K.

    2015-10-01

    The spontaneous protein adsorption on nanomaterial surfaces and the formation of a protein corona around nanoparticles are poorly understood physical phenomena, with high biological relevance. The complexity arises mainly due to the poor knowledge of the structural orientation of the adsorbed proteins onto the nanoparticle surface and difficulties in correlating the protein nanoparticle interaction to the protein corona in real time scale. Here, we provide quantitative insights into the kinetics, number, and binding orientation of a few common blood proteins when they interact with citrate and cetyltriethylammoniumbromide stabilized spherical gold nanoparticles with variable sizes. The kinetics of the protein adsorption was studied experimentally by monitoring the change in hydrodynamic diameter and zeta potential of the nanoparticle-protein complex. To understand the competitive binding of human serum albumin and hemoglobin, time dependent fluorescence quenching was studied using dual fluorophore tags. We have performed molecular docking of three different proteins—human serum albumin, bovine serum albumin, and hemoglobin—on different nanoparticle surfaces to elucidate the possible structural orientation of the adsorbed protein. Our data show that the growth kinetics of a protein corona is exclusively dependent on both protein structure and surface chemistry of the nanoparticles. The study quantitatively suggests that a general physical law of protein adsorption is unlikely to exist as the interaction is unique and specific for a given pair.

  5. Modeling the structure and composition of nanoparticles by extended X-Ray absorption fine-structure spectroscopy

    SciTech Connect

    Frenkel, Anatoly I.; Yevick, Aaron; Cooper, Chana; Vasic, Relja

    2011-07-19

    Many metal clusters in the 1-nm size range are catalytically active, and their enhanced reactivity is often attributed to their size, structure, morphology, and details of alloying. Synchrotron sources provide a wide range of opportunities for studying catalysis. Among them, extended X-ray absorption fine-structure (EXAFS) spectroscopy is the premier method for investigating structure and composition of nanocatalysts. In this review, we summarize common methods of EXAFS analysis for geometric and compositional characterization of nanoparticles. We discuss several aspects of the experiments and analyses that are critical for reliably modeling EXAFS data. The most important are sample homogeneity, the width of the size and compositional distribution functions, and accounting for multiple-scattering contributions to EXAFS. We focus on the contribution of structural disorder and structural/compositional heterogeneity to the accuracy of three-dimensional modeling.

  6. The role of VL gene structural determinants in the fine specificity of anti-DNA antibodies.

    PubMed

    Singh, A K; Gangemi, R M; Barrett, K J

    1994-01-01

    To investigate the structural contribution of the light chain of anti-DNA antibodies to fine specificity, the VKappa genes of two monoclonal anti-DNA antibodies, termed H241 and H102, were cloned and sequenced. H102 and H241 are independently derived from MRL-lpr/lpr mice and differ in their fine specificity: H241 binds dsDNA and normal glomeruli in vitro and deposits in the kidney in vivo, whereas H102 binds only ssDNA and does not deposit in the kidney. Both are encoded by nearly identical VH genes but different N and D regions. Our previous results have demonstrated that the VH gene for H102 and H241 encodes eight other anti-DNA antibodies that also differed in fine specificity. This suggested that the gene product encoded by the VH 102/241 gene, may have intrinsic affinity for DNA, but is unlikely to determine fine specificity or nephritogenicity. In the present study we examined whether the VKappa gene might account for the difference in nephritogenicity. The complete nucleotide and deduced amino acid sequence of VK 102 and VK241 revealed that they are very dissimilar to each other (< 60% homology). VK 241 defined a new member of the VKappa gene family and was moderately homologous to two other VK genes encoding anti-DNA antibodies and to one VK gene encoding an anti-histone antibody all from lupus strains of mice. In addition, sequence diversity in the VK CDR1 region and position 96 of the CDR3 region was observed that may be of significance in determining fine specificity. VK 102 was highly homologous to two other VKappa genes, VKs17.2 and VK C8.5, both encoding anti-DNA antibodies and members of the VK20 gene family. It was striking that all three members of the VK 20 gene family code for DNA reactivity. This suggests that certain VKappa genes may also be used to repeatedly code for anti-DNA reactivity.

  7. Fine-Scale Genetic Structure Arises during Range Expansion of an Invasive Gecko

    PubMed Central

    Short, Kristen Harfmann; Petren, Kenneth

    2011-01-01

    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. PMID:22053186

  8. Study on the Coordination Structure of Pt Sorbed on Bacterial Cells Using X-Ray Absorption Fine Structure Spectroscopy

    PubMed Central

    Tanaka, Kazuya; Watanabe, Naoko

    2015-01-01

    Biosorption has been intensively investigated as a promising technology for the recovery of precious metals from solution. However, the detailed mechanism responsible for the biosorption of Pt on a biomass is not fully understood because of a lack of spectroscopic studies. We applied X-ray absorption fine structure spectroscopy to elucidate the coordination structure of Pt sorbed on bacterial cells. We examined the sorption of Pt(II) and Pt(IV) species on bacterial cells of Bacillus subtilis and Shewanella putrefaciens in NaCl solutions. X-ray absorption near-edge structure and extended X-ray absorption fine structure (EXAFS) of Pt-sorbed bacteria suggested that Pt(IV) was reduced to Pt(II) on the cell’s surface, even in the absence of an organic material as an exogenous electron donor. EXAFS spectra demonstrated that Pt sorbed on bacterial cells has a fourfold coordination of chlorine ions, similar to PtCl42-, which indicated that sorption on the protonated amine groups of the bacterial cells. This work clearly demonstrated the coordination structure of Pt sorbed on bacterial cells. The findings of this study will contribute to the understanding of Pt biosorption on biomass, and facilitate the development of recovery methods for rare metals using biosorbent materials. PMID:25996945

  9. Time variation of the fine structure constant in the early universe and the Bekenstein model

    NASA Astrophysics Data System (ADS)

    Mosquera, M. E.; Scóccola, C. G.; Landau, S. J.; Vucetich, H.

    2008-02-01

    Aims:We calculate the bounds on the variation in the fine structure constant at the time of primordial nucleosynthesis and at the time of neutral hydrogen formation. We used these bounds and other bounds from the late universe to test the Bekenstein model. Methods: We modified the Kawano code, CAMB, and CosmoMC to include the possible variation in the fine structure constant. We used observational primordial abundances of D, ^4He, and ^7Li, recent data from the cosmic microwave background, and the 2dFGRS power spectrum, to obtain bounds on the variation in α. We calculated a piecewise solution to the scalar field equation of the Bekenstein model in two different regimes: i) matter and radiation, ii) matter and cosmological constant. We match both solutions with the appropriate boundary conditions. We performed a statistical analysis, using the bounds obtained from the early universe and other bounds from the late universe to constrain the free parameters of the model. Results: Results are consistent with no variation in α for the early universe. Limits on α are inconsistent with the scale length of the theory l being larger than the Planck scale. Conclusions: In order to fit all observational and experimental data, the assumption l > Lp implied in Bekenstein's model has to be relaxed.

  10. Unexpected fine-scale population structure in a broadcast-spawning Antarctic marine mollusc.

    PubMed

    Hoffman, Joseph I; Clarke, Andy; Clark, Melody S; Fretwell, Peter; Peck, Lloyd S

    2012-01-01

    Several recent empirical studies have challenged the prevailing dogma that broadcast-spawning species exhibit little or no population genetic structure by documenting genetic discontinuities associated with large-scale oceanographic features. However, relatively few studies have explored patterns of genetic differentiation over fine spatial scales. Consequently, we used a hierarchical sampling design to investigate the basis of a weak but significant genetic difference previously reported between Antarctic limpets (Nacella concinna) sampled from Adelaide and Galindez Islands near the base of the Antarctic Peninsula. Three sites within Ryder Bay, Adelaide Island (Rothera Point, Leonie and Anchorage Islands) were each sub-sampled three times, yielding a total of 405 samples that were genotyped at 155 informative Amplified Fragment Length Polymorphisms (AFLPs). Contrary to our initial expectations, limpets from Anchorage Island were found to be subtly, but significantly distinct from those sampled from the other sites. This suggests that local processes may play an important role in generating fine-scale population structure even in species with excellent dispersal capabilities, and highlights the importance of sampling at multiple spatial scales in population genetic surveys.

  11. A Potential Link Between the Cosmological Constant and the Fine-structure Constant

    NASA Astrophysics Data System (ADS)

    Goradia, Shantilal

    2008-04-01

    The age of the universe, about 10^60 Planck times, makes the spherical radius (R) of its space 10^60 Planck lengths, as the light moves one Planck length per one Planck time. The fine-structure constant (α) closely equals the natural logarithm of the square root of the reciprocal of the cosmological constant (λ), making α ln (1/λ), where λ = 1/ R^2 as originally introduced by Einstein in equation number (14) in his 1917 paper: Cosmological Considerations on the General Theory of Relativity. This confirms the time-dependent variation of fine-structure constant in [1], but does not address the issue of dark energy. While [1] invokes negative entropy (-Q/T), so it also invokes dark energy simply. The problem still remains that no theory, as yet, combines the probabilistic aspect of quantum mechanics with gravity. In the meanwhile, we can link [1] with the quantum information theory as information links to entropy. [1] Goradia S. Preprint at (http://www.arxiv.org/physics/0210040 v3 (Jan 2007).

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Fine structure of the red luminescence band in undoped GaN

    SciTech Connect

    Reshchikov, M. A.; Usikov, A.; Helava, H.; Makarov, Yu.

    2014-01-20

    Many point defects in GaN responsible for broad photoluminescence (PL) bands remain unidentified. Their presence in thick GaN layers grown by hydride vapor phase epitaxy (HVPE) detrimentally affects the material quality and may hinder the use of GaN in high-power electronic devices. One of the main PL bands in HVPE-grown GaN is the red luminescence (RL) band with a maximum at 1.8 eV. We observed the fine structure of this band with a zero-phonon line (ZPL) at 2.36 eV, which may help to identify the related defect. The shift of the ZPL with excitation intensity and the temperature-related transformation of the RL band fine structure indicate that the RL band is caused by transitions from a shallow donor (at low temperature) or from the conduction band (above 50 K) to an unknown deep acceptor having an energy level 1.130 eV above the valence band.

  14. THE FINE STRUCTURE OF THE NUCLEOLUS DURING MITOSIS IN THE GRASSHOPPER NEUROBLAST CELL

    PubMed Central

    Stevens, Barbara J.

    1965-01-01

    The behavior of the nucleolus during mitosis was studied by electron microscopy in neuroblast cells of the grasshopper embryo, Chortophaga viridifasciata. Living neuroblast cells were observed in the light microscope, and their mitotic stages were identified and recorded. The cells were fixed and embedded; alternate thick and thin sections were made for light and electron microscopy. The interphase nucleolus consists of two fine structural components arranged in separate zones. Concentrations of 150 A granules form a dense peripheral zone, while the central regions are composed of a homogeneous background substance. Observations show that nucleolar dissolution in prophase occurs in two steps with a preliminary loss of the background substance followed by a dispersal of the granules. Nucleolar material reappears at anaphase as small clumps or layers at the chromosome surfaces. These later form into definite bodies, which disappear as the nucleolus grows in telophase. Evidence suggests both a collecting and a synthesizing role for the nucleolus-associated chromatin. The final, mature nucleolar form is produced by a rearrangement of the fine structural components and an increase in their mass. PMID:14326121

  15. The variation of the fine-structure constant from disformal couplings

    SciTech Connect

    De Bruck, Carsten van; Mifsud, Jurgen; Nunes, Nelson J. E-mail: jmifsud1@sheffield.ac.uk

    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.

  16. Infrared fine-structure line diagnostics of shrouded active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Voit, G. M.

    1993-01-01

    Far-infrared spectroscopy of celestial objects will improve dramatically in the coming decade, allowing astronomers to use fine-structure line emission to probe photoionized regions obscured in the optical band by thick clouds of dust. The ultraluminous far-IR galaxies revealed by IRAS, quasar-like in luminosity but smothered in molecular gas, probably conceal either immense starbursts or luminous active nuclei. In both scenarios, these objects ought to produce copious infrared fine-structure emission with several lines comparable to H(beta) in luminosity. This paper shows how these lines, if detected, can be used to determine the electron densities and far-IR obscurations of shrouded photoionized regions and to constrain the shape and ionization parameter of the ionizing spectra. The presence of (Ne V) emission in particular will distinguish shrouded AGN's from shrouded starbursts. Since all active galaxies photoionize at least some surrounding material, these diagnostics can also be applied to active galaxies in general and will aid in studying how an active nucleus interacts with the interstellar medium of its host galaxy.

  17. Retinular fine structure in compound eyes of diurnal and nocturnal sphingid moths.

    PubMed

    Eguchi, E

    1982-01-01

    Retinular fine structure has been compared in the superposition compound eyes of three sphingid moths, one nocturnal, Cechenena, and two diurnal, Cephonodes and Macroglossum. Cechenena and Cephonodes have tiered retinas with three kinds of retinular cells: two distal, six regular and one basal. The distal retinular cells in Cechenena are special in having a complex partially intracellular rhabdomere not present in Cephonodes. Macroglossum lacks the distal retinular cell. In Cephonodes a unique rhabdom type, formed by the six regular retinular cells in the middle region of the retinula, is divided into three separate longitudinal plates arranged closely parallel to one another. Their constituent microvilli are consequently all nearly unidirectional. The ratio of rhabdom volume to retinular cell volume in the two diurnal sphingids is 10-27%; this is about the same as that (25%) of skipper butterflies, but significantly smaller than in the nocturnal Cechenena (60%). In the diurnal sphingids retinular cell membranes show elongate meandering profiles with septate junctions between adjacent retinular cells. From the comparative fine structure of their eyes the diurnal sphingids and the skippers would appear to be phylogenetically closely related.

  18. On the mechanisms involved in the recovery of envelope information from temporal fine structure

    PubMed Central

    Apoux, Frédéric; Millman, Rebecca E.; Viemeister, Neal F.; Brown, Christopher A.; Bacon, Sid P.

    2011-01-01

    Three experiments were designed to provide psychophysical evidence for the existence of envelope information in the temporal fine structure (TFS) of stimuli that were originally amplitude modulated (AM). The original stimuli typically consisted of the sum of a sinusoidally AM tone and two unmodulated tones so that the envelope and TFS could be determined a priori. Experiment 1 showed that normal-hearing listeners not only perceive AM when presented with the Hilbert fine structure alone but AM detection thresholds are lower than those observed when presenting the original stimuli. Based on our analysis, envelope recovery resulted from the failure of the decomposition process to remove the spectral components related to the original envelope from the TFS and the introduction of spectral components related to the original envelope, suggesting that frequency- to amplitude-modulation conversion is not necessary to recover envelope information from TFS. Experiment 2 suggested that these spectral components interact in such a way that envelope fluctuations are minimized in the broadband TFS. Experiment 3 demonstrated that the modulation depth at the original carrier frequency is only slightly reduced compared to the depth of the original modulator. It also indicated that envelope recovery is not specific to the Hilbert decomposition. PMID:21786897

  19. Perceptual weighting of individual and concurrent cues for sentence intelligibility: Frequency, envelope, and fine structure

    PubMed Central

    Fogerty, Daniel

    2011-01-01

    The speech signal may be divided into frequency bands, each containing temporal properties of the envelope and fine structure. For maximal speech understanding, listeners must allocate their perceptual resources to the most informative acoustic properties. Understanding this perceptual weighting is essential for the design of assistive listening devices that need to preserve these important speech cues. This study measured the perceptual weighting of young normal-hearing listeners for the envelope and fine structure in each of three frequency bands for sentence materials. Perceptual weights were obtained under two listening contexts: (1) when each acoustic property was presented individually and (2) when multiple acoustic properties were available concurrently. The processing method was designed to vary the availability of each acoustic property independently by adding noise at different levels. Perceptual weights were determined by correlating a listener’s performance with the availability of each acoustic property on a trial-by-trial basis. Results demonstrated that weights were (1) equal when acoustic properties were presented individually and (2) biased toward envelope and mid-frequency information when multiple properties were available. Results suggest a complex interaction between the available acoustic properties and the listening context in determining how best to allocate perceptual resources when listening to speech in noise. PMID:21361454

  20. Fine structure of synaptic sites and circuits in mushroom bodies of insect brains.

    PubMed

    Schürmann, Friedrich-Wilhelm

    2016-09-01

    In the insect brain, mushroom bodies represent a prominent central neuropil for multisensory integration and, crucially, for learning and memory. For this reason, special attention has been focused on its small chemical synapses. Early studies on synaptic types and their distribution, using conventional electron microscopy, and recent publications have resolved basic features of synaptic circuits. More recent studies, using experimental methods for resolving neurons, such as immunocytochemistry, genetic labelling, high resolution confocal microscopy and more advanced electron microscopy, have revealed many new details about the fine structure and molecular contents of identifiable neurons of mushroom bodies and has led to more refined modelling of functional organisation. Synaptic circuitries have been described in most detail for the calyces. In contrast, the mushroom bodies' columnar peduncle and lobes have been explored to a lesser degree. In dissecting local microcircuits, the scientist is confronted with complex neuronal compartmentalisation and specific synaptic arrangements. This article reviews classical and modern studies on the fine structure of synapses and their networks in mushroom bodies across several insect species.

  1. [Spectrum characterization and fine structure of copper phthalocyanine-doped TiO2 microcavities].

    PubMed

    Liu, Cheng-lin; Zhang, Xin-yi; Zhong, Ju-hua; Zhu, Yi-hua; He, Bo; Wei, Shi-qiang

    2007-10-01

    Copper phthalocyanine-doped TiO2 microcavities were fabricated by chemistry method. Their spectrum characterization was studied by Fourier transform infrared (FTIR) and Raman spectroscopy, and their fine structure was analyzed by X-ray absorption fine structure (XAFS). The results show that there is interaction of copper phthalocyanine (CuPc) and TiO2 microcavities after TiO2 microcavities was doped with CuPc. For example, there is absorption at 900.76 cm(-1) in FTIR spectra, and the "red shift" of both OH vibration at 3392.75 cm(-1) and CH vibration at 2848.83 cm(-1). There exist definite peak shifts and intensity changes in infrared absorption in the C-C or C-N vibration in the planar phthalocyanine ring, the winding vibration of C-H inside and C-N outside plane of benzene ring. In Raman spectrum, there are 403.4, 592.1 and 679.1 cm(-1) characterized peaks of TiO2 in CuPc-doped TiO2 microcavities, but their wave-numbers show shifts to anatase TiO2. The vibration peaks at 1586.8 and 1525.6 cm(-1) show that there exists the composite material of CuPc and TiO2. These changes are related to the plane tropism of the molecule structure of copper phthalocyanine. XAFS showed tetrahedron TiO4 structure of Ti in TiO2 microcavities doped with copper phthalocyanine, and the changes of inner "medial distances" and the surface structure of TiO2 microcavities.

  2. Fine- and hyperfine structure investigations of even configuration system of atomic terbium

    NASA Astrophysics Data System (ADS)

    Stefanska, D.; Elantkowska, M.; Ruczkowski, J.; Furmann, B.

    2017-03-01

    In this work a parametric study of the fine structure (fs) and the hyperfine structure (hfs) for the even-parity configurations of atomic terbium (Tb I) is presented, based in considerable part on the new experimental results. Measurements on 134 spectral lines were performed by laser induced fluorescence (LIF) in a hollow cathode discharge lamp; on this basis, the hyperfine structure constants A and B were determined for 52 even-parity levels belonging to the configurations 4f85d6s2, 4f85d26s or 4f96s6p; in all the cases those levels were involved in the transitions investigated as the lower levels. For 40 levels the hfs was examined for the first time, and for the remaining 12 levels the new measurements supplement our earlier results. As a by-product, also preliminary values of the hfs constants for 84 odd-parity levels were determined (the investigations of the odd-parity levels system in the terbium atom are still in progress). This huge amount of new experimental data, supplemented by our earlier published results, were considered for the fine and hyperfine structure analysis. A multi-configuration fit of 7 configurations was performed, taking into account second-order of perturbation theory, including the effects of closed shell-open shell excitations. Predicted values of the level energies, as well as of magnetic dipole and electric quadrupole hyperfine structure constants A and B, are quoted in cases when no experimental values are available. By combining our experimental data with our own semi-empirical procedure it was possible to identify correctly the lower and upper level of the line 544.1440 nm measured by Childs with the use of the atomic-beam laser-rf double-resonance technique (Childs, J Opt Soc Am B 9;1992:191-6).

  3. Fine-scale population structure in a deep-sea teleost (orange roughy, Hoplostethus atlanticus)

    NASA Astrophysics Data System (ADS)

    Carlsson, Jens; Shephard, Samuel; Coughlan, James; Trueman, Clive N.; Rogan, Emer; Cross, Tom F.

    2011-06-01

    Microsatellite and otolith chemistry variability were analysed to assess fine scale genetic structure in the deep-sea teleost orange roughy ( Hoplostethus atlanticus). The Porcupine Bank located on the continental shelf west of Ireland, comprises a complex system of mounds and flat areas that are broken up by canyons. Orange roughy form spawning aggregations on mounds and flat areas, and were heavily fished until the resource was depleted. By analysing adults in spawning condition and juvenile orange roughy from six mounds and one flat area, shallow but significant genetic population structure was evident ( FST=0.0031, Dest across loci=0.0306 and G-test). Most of the structure was accounted for by inclusion of a sample from the flats (six of ten significant pairwise FST estimates and G-tests, and five of the highest Dest estimates included the flat sample). While the flat sample contributed most to the genetic structure, there was still significant (albeit weaker) structure among mound samples. The observed structure was supported by otolith analyses. Fish caught as late juveniles in either the flat or mound areas showed consistent differences in chemistry at the otolith core throughout the initial 10 years of growth, which could indicate site fidelity. We hypothesise that seafloor topographic structures (mounds and flats) may provide discrete spawning areas for orange roughy and that the limited gene flow between these spawning areas is insufficient to counteract genetic drift.

  4. Role of uniform pore structure and high positive charges in the arsenate adsorption performance of Al13-modified montmorillonite.

    PubMed

    Zhao, Shou; Feng, Chenghong; Huang, Xiangning; Li, Baohua; Niu, Junfeng; Shen, Zhenyao

    2012-02-15

    Four modified montmorillonite adsorbents with varied Al(13) contents (i.e., Na-Mont, AC-Mont, PAC(20)-Mont, and Al(13)-Mont) were synthesized and characterized by N(2) adsorption/desorption, X-ray diffraction, and Fourier-transform infrared analyses. The arsenate adsorption performance of the four adsorbents were also investigated to determine the role of intercalated Al(13), especially its high purity, high positive charge (+7), and special Keggin structure. With increased Al(13) content, the physicochemical properties (e.g., surface area, structural uniformity, basal spacing, and pore volume) and adsorption performance of the modified montmorillonites were significantly but disproportionately improved. The adsorption data well fitted the Freundlich and Redlich-Peterson isotherm model, whereas the kinetic data better correlated with the pseudo-second-order kinetic model. The arsenate sorption mechanism of the montmorillonites changed from physical to chemisorption after intercalation with Al(13). Increasing charges of the intercalated ions enhanced the arsenate adsorption kinetics, but had minimal effect on the structural changes of the montmorillonites. The uniform pore structure formed by intercalation with high-purity Al(13) greatly enhanced the pore diffusion and adsorption rate of arsenate, resulting in the high adsorption performance of Al(13)-Mont.

  5. Fine-scale density wave structure of Saturn's A and B rings: Theory and simulations

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny

    We examine the linear stability of the Saturnian ring disk of mutually gravitating and physically colliding particles with special emphasis on its fine-scale of the order of 100 m density wave structure, that is, almost regularly spaced, aligned cylindric density enhancements and optically-thin zones with the width and the spacing between them of roughly several tens particle diameters. We analyze the Jeans’ instabilities of gravity perturbations (e.g. those produced by a spontaneous disturbance) analytically by using the Navier-Stokes dynamical equations of a compressible fluid. For the first time in planetary ring dynamics, the theory is not restricted by any assumptions about the thickness of the system. We consider a simple model of the system consisting of a three-dimensional ring disk that is weakly inhomogeneous and whose structure is analyzed by making a horizontally local short-wave approximation. We demonstrate that the disk is Jeans-unstable and that gravity perturbations grow effectively within a few orbital periods. We find that self-gravitation plays a key role in the formation of the fine structure. The predictions of the theory are compared with observations of Saturn’s rings by the Cassini spacecraft and are found to be in good agreement. In particular, it appears very likely that some of the quasi-periodic microstructures observed in Saturn’s A and B rings - both axisymmetric and nonaxisymmetric ones - are manifestations of these effects. Thus, one can attribute the fine-scale structure observed in Saturn’s A and B rings in Cassini data to the development of free Lin-Shu type compression waves, or density waves -- normal modes -- developing in the plane of the system. From the well-developed theory of galactic spiral density waves, a free density wave is known to rotate in a rigid-body manner and to not be affected by differential rotation of the ring disk. We argue that the quasi-periodic density enhancements revealed in Cassini data are

  6. Effect of Fe(II)/Ce(III) dosage ratio on the structure and anion adsorptive removal of hydrothermally precipitated composites: Insights from EXAFS/XANES, XRD and FTIR.

    PubMed

    Chubar, Natalia; Gerda, Vasyl; Banerjee, Dipanjan; Yablokova, Ganna

    2017-02-01

    In this work, we present material chemistry in the hydrothermal synthesis of new complex structure materials based on various dosage ratios of Fe and Ce (1:0, 2:1, 1:1, 1:2, 0:1), characterize them by the relevant methods that allow characterization of both crystalline and amorphous phases and correlate their structure/surface properties with the adsorptive performance of the five toxic anions. The applied synthesis conditions resulted in the formation of different compounds of Fe and Ce components. The Fe-component was dominated by various phases of Fe hydrous oxides, whereas the Ce-component was composed of various phases of Ce carbonates. The presence of two metal salts in raw materials resulted in the formation of a mesoporous structure and averaged the surface area compared to one metal-based material. The surface of all Fe-Ce composites was abundant in Fe component phases. Two-metal systems showed stronger anion removal performance than one-metal materials. The best adsorption was demonstrated by Fe-Ce based materials that had low crystallinity, that were rich in phases and that exhibited surfaces were abundant in greater number of surface functional groups. Notably, Fe extended fine structures simulated by EXAFS in these better adsorbents were rich from oscillations from both heavy and light atoms. This work provides new insights on the structure of composite inorganic materials useful to develop their applications in adsorption and catalysis. It also presents new inorganic anion exchangers with very high removal potential to fluoride and arsenate.

  7. Glucose and Fluoxetine Induce Fine Structural Change in Human Serum Albumin

    PubMed Central

    Shahani, Minoo; Daneshi-Mehr, Fatemeh; Tadayon, Roya; Hoseinzade Salavati, Behrooz; Akbar Zadeh-Baghban, Ali-Reza; Zamanian, Abbas; Rezaei-Tavirani, Mostafa

    2013-01-01

    Human serum albumin has been used as a model protein for protein folding and ligand binding studies over many decades. Due to its long life period and high concentration in plasma, HSA is highly sensitive to glycation. It is reported that 175 mg/dL glucose concentration is a threshold of kidney activity for the beginning of excretion of glucose. pH denaturation of HSA in absence and presence of different concentrations of glucose is studied and based on the Pace two-state model, the findings are analyzed. In addition, florescence emission data of albumin range in the period of 300-500 nm was depicted. The amounts of free energy change and [D]1/2 parameters of unfolding in correspond to florescence date indicate that glucose induces fine structural change in human serum albumin. Results showed that 175 mg/dL glucose concentration is a critical point for albumin structural and functional alteration. PMID:24250587

  8. The fine structure of pulmonary contusion and the effect of various drugs.

    PubMed Central

    Casley-Smith, J. R.; Eckert, P.; Földi-Börcsök, E.

    1976-01-01

    The results of contusion were examined by electron and light microscopy in the lungs of rats. It was found that the results here were very similar to those elsewhere in the body, with a few minor modifications due to the unique structure of the lung. Densitometry of protein concentration and visual estimation of oedema were used to quantitate the effects on the injury. The benzo-pyrone drug Venalot had a considerable effect in reducing the protein concentration in the air spaces and the interstitial tissue, and of the oedema in the latter. Neither the proteinase inhibitor Trasylol nor the pectin-based plasma expander HAS had any significant effect on the fine structural alterations of pulmonary contusion. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 PMID:1087159

  9. THE FINE STRUCTURE OF STALKED BACTERIA BELONGING TO THE FAMILY CAULOBACTERACEAE.

    PubMed

    STOVEPOINDEXTER, J L; COHEN-BAZIRE, G

    1964-12-01

    The fine structure of a series of stalked bacteria belonging to the genera Caulobacter and Asticcacaulis has been examined in thin sections. The cell wall has the multilayered structure typical of many Gram-negative bacteria, and continues without interruption throughout the length of the stalk. The core of the stalk, continuous with the cytoplasmic region of the cell, is enclosed in an extension of the cell membrane, and contains a system of internal membranes: it is devoid of ribosomes and nucleoplasm. A membranous organelle occupies the juncture of stalk and cell, separating the ribosomal region from the core of the stalk. Typical mesosomes also occur in the cell, being particularly frequent at the plane of division. The secreted holdfast is located at the tip of the stalk in Caulobacter, and at the pole of the cell adjacent to the stalk in Asticcacaulis.

  10. THE FINE STRUCTURE OF STALKED BACTERIA BELONGING TO THE FAMILY CAULOBACTERACEAE

    PubMed Central

    Stove Poindexter, Jeanne L.; Cohen-Bazire, Germaine

    1964-01-01

    The fine structure of a series of stalked bacteria belonging to the genera Caulobacter and Asticcacaulis has been examined in thin sections. The cell wall has the multilayered structure typical of many Gram-negative bacteria, and continues without interruption throughout the length of the stalk. The core of the stalk, continuous with the cytoplasmic region of the cell, is enclosed in an extension of the cell membrane, and contains a system of internal membranes: it is devoid of ribosomes and nucleoplasm. A membranous organelle occupies the juncture of stalk and cell, separating the ribosomal region from the core of the stalk. Typical mesosomes also occur in the cell, being particularly frequent at the plane of division. The secreted holdfast is located at the tip of the stalk in Caulobacter, and at the pole of the cell adjacent to the stalk in Asticcacaulis. PMID:14245437

  11. Novel angular encoder for a quick-extended x-ray absorption fine structure monochromator

    SciTech Connect

    Stoetzel, J.; Luetzenkirchen-Hecht, D.; Frahm, R.; Fonda, E.; De Oliveira, N.; Briois, V.

    2008-08-15

    New concepts for time-resolved x-ray absorption spectroscopy using the quick-extended x-ray absorption fine structure (QEXAFS) method are presented. QEXAFS is a powerful tool to gain structural information about, e.g., fast chemical reactions or phase transitions on a subsecond scale. This can be achieved with a monochromator design that employs a channel-cut crystal on a cam driven tilt table for rapid angular oscillations of the Bragg angle. A new angular encoder system and a new data acquisition were described and characterized that were applied to a QEXAFS monochromator to get spectra with a directly measured accurate energy scale. New electronics were designed to allow a fast acquisition of the Bragg angle values and the absorption data during the measurements simultaneously.

  12. Systematics of fine structure in the α decay of deformed odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Ren, Zhongzhou; Ni, Dongdong

    2014-12-01

    We present a detailed analysis of the a-decay fine structure in 32 deformed odd-mass nuclei from Z = 93 to Z = 102. The α-decay half-lives are systematically calculated within the multichannel cluster model (MCCM), which turns out to well reproduce the experimental data and show the neutron deformed shell structure. The branching ratios for various daughter states are investigated in the MCCM and in the WKB barrier penetration approach, respectively. It is found that the MCCM results agree well with the experimental data, while the WKB results have relatively large deviations from the experimental data for the α transitions to the high-lying members of the rotational band.

  13. Fine and hyperfine structure of P-wave levels in muonic hydrogen

    SciTech Connect

    Martynenko, A. P.

    2008-01-15

    Corrections of order {alpha}{sup 5} and {alpha}{sup 6} are calculated for muonic hydrogen in the fine-structure interval {delta}E{sup fs} = E(2P{sub 3/2}) - E(2P{sub 1/2}) and in the hyperfine structure of the 2P{sub 1/2}-and 2P{sub 3/2}-wave energy levels. The resulting values of {delta}E{sup fs} = 8352.08 {mu}eV, {delta}E-tilde {sup hfs}(2P{sub 1/2}) = 7819.80 {mu}eV, and {delta}E-tilde {sup hfs}(2P{sub 3/2}) = 3248.03 {mu}eV provide reliable guidelines in performing a comparison with relevant experimental data and in more precisely extracting the experimental value of the (2P-2S) Lamb shift in the muonic-hydrogen atom.

  14. SANS and UV-vis spectroscopy studies of resultant structure from lysozyme adsorption on silica nanoparticles.

    PubMed

    Kumar, Sugam; Aswal, Vinod K; Kohlbrecher, Joachim

    2011-08-16

    The interaction of lysozyme protein (M.W. 14.7 kD) with two sizes of silica nanoparticles (16 and 25 nm) has been examined in aqueous solution using UV-vis spectroscopy and small-angle neutron scattering (SANS). The measurements were performed on fixed concentration (1 wt %) of nanoparticles and varying concentration of protein in the range 0 to 2 wt %. The adsorption isotherm as obtained using UV-vis spectroscopy suggests strong interaction of the two components and shows an exponential behavior. The saturation values of adsorption are found to be around 90 and 270 protein molecules per particle for 16 and 25 nm sized nanoparticles, respectively. The adsorption of protein on nanoparticles leads to the aggregation of particles and these structures have been studied by SANS. The aggregates are characterized by fractal structure coexisting with unaggregated particles at low protein concentrations and free proteins at higher protein concentrations. Further, contrast variation SANS measurements have been carried out to differentiate the adsorbed and free protein in these systems.

  15. Crystallographic structure of Ni-Co coating on the affinity adsorption of histidine-tagged protein.

    PubMed

    Chang, Yaw-Jen; Chen, Sheng-Zheng; Ho, Ching-Yuan

    2015-04-01

    The principle of immobilized metal affinity chromatography (IMAC) has been recently implemented for protein microarrays for the study of protein abundance and function. Ni-Co film fabricated by electrodeposition is a novel microarray surface in an alloy type for immobilizing histidine-tagged proteins based on IMAC. In this paper, the effects of crystallographic structures and surface properties of Ni-Co coatings, with and without the annealing process, on the immobilization of histidine-tagged proteins were systematically investigated. The experimental results reveal that the stronger hcp texture, due to a higher Co content, results in better affinity adsorption for histidine-tagged biotin. Nevertheless, the allotropic phase transformation from hcp to fcc, due to the annealing process, leads to the decrease of affinity adsorption. The wettability property and the surface roughness of Ni-Co coating are, however, not important factors. Obviously, the crystallographic structure of Ni-Co coating is the dominant factor for the specific affinity adsorption of histidine-tagged protein.

  16. Breed Locally, Disperse Globally: Fine-Scale Genetic Structure Despite Landscape-Scale Panmixia in a Fire-Specialist

    PubMed Central

    Pierson, Jennifer C.; Allendorf, Fred W.; Drapeau, Pierre; Schwartz, Michael K.

    2013-01-01

    An exciting advance in the understanding of metapopulation dynamics has been the investigation of how populations respond to ephemeral patches that go ‘extinct’ during the lifetime of an individual. Previous research has shown that this scenario leads to genetic homogenization across large spatial scales. However, little is known about fine-scale genetic structuring or how this changes over time in ephemeral patches. We predicted that species that specialize on ephemeral habitats will delay dispersal to exploit natal habitat patches while resources are plentiful and thus display fine-scale structure. To investigate this idea, we evaluated the effect of frequent colonization of ephemeral habitats on the fine-scale genetic structure of a fire specialist, the black-backed woodpecker (Picoides arcticus) and found a pattern of fine-scale genetic structure. We then tested for differences in spatial structure between sexes and detected a pattern consistent with male-biased dispersal. We also detected a temporal increase in relatedness among individuals within newly burned forest patches. Our results indicate that specialist species that outlive their ephemeral patches can accrue significant fine-scale spatial structure that does not necessarily affect spatial structure at larger scales. This highlights the importance of both spatial and temporal scale considerations in both sampling and data interpretation of molecular genetic results. PMID:23825646

  17. Breed locally, disperse globally: fine-scale genetic structure despite landscape-scale panmixia in a fire-specialist.

    PubMed

    Pierson, Jennifer C; Allendorf, Fred W; Drapeau, Pierre; Schwartz, Michael K

    2013-01-01

    An exciting advance in the understanding of metapopulation dynamics has been the investigation of how populations respond to ephemeral patches that go 'extinct' during the lifetime of an individual. Previous research has shown that this scenario leads to genetic homogenization across large spatial scales. However, little is known about fine-scale genetic structuring or how this changes over time in ephemeral patches. We predicted that species that specialize on ephemeral habitats will delay dispersal to exploit natal habitat patches while resources are plentiful and thus display fine-scale structure. To investigate this idea, we evaluated the effect of frequent colonization of ephemeral habitats on the fine-scale genetic structure of a fire specialist, the black-backed woodpecker (Picoides arcticus) and found a pattern of fine-scale genetic structure. We then tested for differences in spatial structure between sexes and detected a pattern consistent with male-biased dispersal. We also detected a temporal increase in relatedness among individuals within newly burned forest patches. Our results indicate that specialist species that outlive their ephemeral patches can accrue significant fine-scale spatial structure that does not necessarily affect spatial structure at larger scales. This highlights the importance of both spatial and temporal scale considerations in both sampling and data interpretation of molecular genetic results.

  18. Fine-scale spatial genetic structure and dispersal among spotted salamander (Ambystoma maculatum) breeding populations.

    PubMed

    Zamudio, Kelly R; Wieczorek, Ania M

    2007-01-01

    We examined fine-scale genetic variation among breeding aggregations of the spotted salamander (Ambystoma maculatum) to quantify dispersal, interpopulation connectivity and population genetic structure. Spotted salamanders rely on temporary ponds or wetlands for aggregate breeding. Adequate breeding sites are relatively isolated from one another and field studies suggest considerable adult site fidelity; therefore, we expected to find population structure and differentiation at small spatial scales. We used microsatellites to estimate population structure and dispersal among 29 breeding aggregations in Tompkins County, New York, USA, an area encompassing 1272 km(2). Bayesian and frequency-based analyses revealed fine-scale genetic structure with two genetically defined demes: the North deme included seven breeding ponds, and the South deme included 13 ponds. Nine ponds showed evidence of admixture between these two genetic pools. Bayesian assignment tests for detection of interpopulation dispersal indicate that immigration among ponds is common within demes, and that certain populations serve as sources of immigrants to neighbouring ponds. Likewise, spatial genetic correlation analyses showed that populations < or = 4.8 km distant from each other show significant genetic correlation that is not evident at higher scales. Within-population levels of relatedness are consistently larger than expected if mating were completely random across ponds, and in the case of a few ponds, within-population processes such as inbreeding or reproductive skew contribute significantly to differentiation from neighbouring ponds. Our data underscore the importance of these within-population processes as a source of genetic diversity across the landscape, despite considerable population connectivity. Our data further suggest that spotted salamander breeding groups behave as metapopulations, with population clusters as functional units, but sufficient migration among demes to allow for

  19. Fine spectral structures in Jovian decametric radio emission observed by ground-based radio telescope.

    NASA Astrophysics Data System (ADS)

    Panchenko, M.; Brazhenko, A. I.; Shaposhnikov, V. E.; Konovalenko, A. A.; Rucker, H. O.

    2014-04-01

    Jupiter with the largest planetary magnetosphere in the solar system emits intense coherent non-thermal radio emission in a wide frequency range. This emission is a result of a complicated interaction between the dynamic Jovian magnetosphere and energetic particles supplying the free energy from planetary rotation and the interaction between Jupiter and the Galilean moons. Decametric radio emission (DAM) is the strongest component of Jovian radiation observed in a frequency range from few MHz up to 40 MHz. This emission is generated via cyclotron maser mechanism in sources located along Jovian magnetic field lines. Depending on the time scales the Jovian DAMexhibits different complex spectral structures. We present the observations of the Jovian decametric radio emission using the large ground-based radio telescope URAN- 2 (Poltava, Ukraine) operated in the decametric frequency range. This telescope is one of the largest low frequency telescopes in Europe equipped with high performance digital radio spectrometers. The antenna array of URAN-2 consists of 512 crossed dipoles with an effective area of 28 000m2 and beam pattern size of 3.5 x 7 deg. (at 25 MHz). The instrument enables continuous observations of the Jovian radio during long period of times. Jovian DAM was observed continuously since Sep. 2012 (depending on Jupiter visibility) with relatively high time-frequency resolution (4 kHz - 100ms) in the broad frequency range (8-32MHz). We have detected a big amount of the fine spectral structures in the dynamic spectra of DAM such as trains of S-bursts, quasi-continuous narrowband emission, narrow-band splitting events and zebra stripe-like patterns. We analyzed mainly the fine structures associated with non-Io controlled DAM. We discuss how the observed narrowband structures which most probably are related to the propagation of the decametric radiation in the Jupiter's ionosphere can be used to study the plasma parameters in the inner Jovian magnetosphere.

  20. Adsorption-induced changes in ribonuclease A structure and enzymatic activity on solid surfaces.

    PubMed

    Wei, Yang; Thyparambil, Aby A; Wu, Yonnie; Latour, Robert A

    2014-12-16

    Ribonuclease A (RNase A) is a small globular enzyme that lyses RNA. The remarkable solution stability of its structure and enzymatic activity has led to its investigation to develop a new class of drugs for cancer chemotherapeutics. However, the successful clinical application of RNase A has been reported to be limited by insufficient stability and loss of enzymatic activity when it was coupled with a biomaterial carrier for drug delivery. The objective of this study was to characterize the structural stability and enzymatic activity of RNase A when it was adsorbed on different surface chemistries (represented by fused silica glass, high-density polyethylene, and poly(methyl-methacrylate)). Changes in protein structure were measured by circular dichroism, amino acid labeling with mass spectrometry, and in vitro assays of its enzymatic activity. Our results indicated that the process of adsorption caused RNase A to undergo a substantial degree of unfolding with significant differences in its adsorbed structure on each material surface. Adsorption caused RNase A to lose about 60% of its native-state enzymatic activity independent of the material on which it was adsorbed. These results indicate that the native-state structure of RNase A is greatly altered when it is adsorbed on a wide range of surface chemistries, especially at the catalytic site. Therefore, drug delivery systems must focus on retaining the native structure of RNase A in order to maintain a high level of enzymatic activity for applications such as antitumor chemotherapy.

  1. Synthesis, Structural, and Adsorption Properties and Thermal Stability of Nanohydroxyapatite/Polysaccharide Composites.

    PubMed

    Skwarek, Ewa; Goncharuk, Olena; Sternik, Dariusz; Janusz, Wladyslaw; Gdula, Karolina; Gun'ko, Vladimir M

    2017-12-01

    A series of composites based on nanohydroxyapatite (nHAp) and natural polysaccharides (PS) (nHAp/agar, nHAp/chitosan, nHAp/pectin FB300, nHAp/pectin APA103, nHAp/sodium alginate) was synthesized by liquid-phase two-step method and characterized using nitrogen adsorption-desorption, DSC, TG, FTIR spectroscopy, and SEM. The analysis of nitrogen adsorption-desorption data shows that composites with a nHAp: PS ratio of 4:1 exhibit a sufficiently high specific surface area from 49 to 82 m(2)/g. The incremental pore size distributions indicate mainly mesoporosity. The composites with the component ratio 1:1 preferably form a film-like structure, and the value of S BET varies from 0.3 to 43 m(2)/g depending on the nature of a polysaccharide. Adsorption of Sr(II) on the composites from the aqueous solutions has been studied. The thermal properties of polysaccharides alone and in nHAp/PS show the influence of nHAp, since there is a shift of characteristic DSC and DTG peaks. FTIR spectroscopy data confirm the presence of functional groups typical for nHAp as well as polysaccharides in composites. Structure and morphological characteristics of the composites are strongly dependent on the ratio of components, since nHAp/PS at 4:1 have relatively large S BET values and a good ability to adsorb metal ions. The comparison of the adsorption capacity with respect to Sr(II) of nHAp, polysaccharides, and composites shows that it of the latter is higher than that of nHAp (per 1 m(2) of surface).

  2. Synthesis, Structural, and Adsorption Properties and Thermal Stability of Nanohydroxyapatite/Polysaccharide Composites

    NASA Astrophysics Data System (ADS)

    Skwarek, Ewa; Goncharuk, Olena; Sternik, Dariusz; Janusz, Wladyslaw; Gdula, Karolina; Gun'ko, Vladimir M.

    2017-02-01

    A series of composites based on nanohydroxyapatite (nHAp) and natural polysaccharides (PS) (nHAp/agar, nHAp/chitosan, nHAp/pectin FB300, nHAp/pectin APA103, nHAp/sodium alginate) was synthesized by liquid-phase two-step method and characterized using nitrogen adsorption-desorption, DSC, TG, FTIR spectroscopy, and SEM. The analysis of nitrogen adsorption-desorption data shows that composites with a nHAp: PS ratio of 4:1 exhibit a sufficiently high specific surface area from 49 to 82 m2/g. The incremental pore size distributions indicate mainly mesoporosity. The composites with the component ratio 1:1 preferably form a film-like structure, and the value of S BET varies from 0.3 to 43 m2/g depending on the nature of a polysaccharide. Adsorption of Sr(II) on the composites from the aqueous solutions has been studied. The thermal properties of polysaccharides alone and in nHAp/PS show the influence of nHAp, since there is a shift of characteristic DSC and DTG peaks. FTIR spectroscopy data confirm the presence of functional groups typical for nHAp as well as polysaccharides in composites. Structure and morphological characteristics of the composites are strongly dependent on the ratio of components, since nHAp/PS at 4:1 have relatively large S BET values and a good ability to adsorb metal ions. The comparison of the adsorption capacity with respect to Sr(II) of nHAp, polysaccharides, and composites shows that it of the latter is higher than that of nHAp (per 1 m2 of surface).

  3. Study of structural irregularities of smectite clay systems by small-angle neutron scattering and adsorption

    NASA Astrophysics Data System (ADS)

    De Stefanis, A.; Tomlinson, A. A. G.; Steriotis, Th. A.; Charalambopoulou, G. Ch.; Keiderling, U.

    2007-04-01

    Small angle neutron scattering (SANS) and its contrast-matching variant are employed in order to determine structural properties (inter-pillar distances and mass/surface fractal dimensions of the clay layers and pillars) of a series of smectite natural clays (montmorillonite, beidellite, and bentonite) and their pillared and pillared/ion-exchanged analogues. Moreover, a comparative analysis with the adsorption data is carried out on the basis of a systematic study of the structural changes induced by a particular treatment or modification (e.g. pillaring) of the clay systems.

  4. Regulation of the demographic structure in isomorphic biphasic life cycles at the spatial fine scale.

    PubMed

    Vieira, Vasco Manuel Nobre de Carvalho da Silva; Mateus, Marcos Duarte

    2014-01-01

    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.

  5. The Effects of Instrumental Elliptical Polarization on Stellar Point Spread Function Fine Structure

    NASA Technical Reports Server (NTRS)

    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.

  6. On the quantitative method for measurement and analysis of the fine structure of Fraunhofer line profiles

    NASA Astrophysics Data System (ADS)

    Kuli-Zade, D. M.

    The methods of measurement and analysis of the fine structure of weak and moderate Fraunhofer line profiles are considered. The digital spectral materials were obtained using rapid scanning high dispersion and high resolution double monochromators. The methods of asymmetry coefficient, bisector method and new quantitative method pro- posed by the author are discussed. The new physical values of differential, integral, residual and relative asymmetries are first introduced. These quantitative values permit us to investigate the dependence of asymmetry on microscopic (atomic) and macro- scopic (photospheric) values. It is shown that the integral profile asymmetries grow appreciably with increase in line equivalent width. The average effective depths of the formation of used Fraunhofer lines in the photosphere of the Sun are determined. It is shown that with the increasing of the effective formation depths of the lines integral and residual asymmetries of the lines profiles noticeably decrease. It is in fine agree- ment with the results of intensity dependence of asymmetry. The above-mentioned methods are critically compared and the advantages of author's method are shown. The computer program of calculation of the line-profile asymmetry parameters has been worked out.

  7. The Effect of X-Ray Absorption Fine Structure in Soft X-ray Astronomical Telescopes

    NASA Astrophysics Data System (ADS)

    Owens, Alan; Denby, Michael; Wells, Alan; Keay, Adam; Graessle, Dale E.; Blake, Richard L.

    1997-02-01

    Recent in-orbit measurements by high resolution soft X-ray telescopes have revealed low-level fine structure in target spectra that cannot be attributed to a celestial source. Ultimately, this can be traced to the ability of the new high spectral resolution silicon detectors to resolve X-ray absorption fine structure (XAFS) produced in the various detection subsystems. Based on measurements taken at the Daresbury Synchrotron Radiation Source (SRS) and the National Synchrotron Light Source (NSLS), we have modeled the full-up response function of the Joint European X-ray Telescope (JET-X), taking into account edge structure generated in the detectors, filters, and mirrors. It is found that unfolding celestial source spectra using a response function in which the detailed edge shapes are calculated from standard absorption cross sections leads to the generation of spectral artifacts at every absorption edge. These in turn produce unacceptably high values of χ2 in model fits for total source fluxes above ~4 × 104 counts. For JET-X, this corresponds to a source strength of ~0.4 millicrab observed for 105 s. Statistically significant ``linelike'' features are introduced into the derived source spectra with amplitudes as great as 10% of the source flux. For JET-X, these features rise above the 3 σ level for integral source exposures above ~5 × 104 source counts. The largest deviations in the residuals arise near 0.5 keV and 2.2 keV and are attributed to XAFS produced in the oxide surface layers of the CCD and the gold reflective surface of the mirrors, respectively. These results are significant for data interpretation tasks with the ASCA, JET-X, XMM, and Advanced X-Ray Astrophysics Facility (AXAF) telescopes.

  8. Spiky Fine Structure of Type III-like Radio Bursts in Absorption

    NASA Astrophysics Data System (ADS)

    Chernov, G. P.; Yan, Y. H.; Tan, C. M.; Chen, B.; Fu, Q. J.

    2010-03-01

    An uncommon fine structure in the radio spectrum consisting of bursts in absorption was observed with the Chinese Solar Broadband Radiospectrometer (SBRS) in the frequency range of 2.6 - 3.8 GHz during an X3.4/4B flare on 13 December 2006 in active region NOAA 10930 (S05W33). Usual fine structures in emission such as spikes, zebra stripes, and drifting fibers were observed at the peak of every new flare brightening. Within an hour at the decay phase of the event we observed bursts consisting of spikes in absorption, which pulsated periodically in frequency. Their instantaneous frequency bandwidths were found to be in the 75 MHz range. Moreover, in the strongest Type III-like bursts in absorption, the spikes showed stripes of the zebra-pattern (ZP) that drifted to higher frequencies. All spikes had the duration as short as down to the limit of the instrument resolution of ≈8 ms. The TRACE 195 Å images indicate that the magnetic reconnection at this moment occurred in the western edge of the flare loop arcade. Taking into account the presence of the reverse-drifting bursts in emission, in the course of the restoration of the magnetic structures in the corona, the acceleration of the beams of fast particles must have occurred both upward and downward at different heights. The upward beams will be captured by the magnetic trap, where the loss-cone distribution of fast particles (responsible for the emission of continuum and ZP) were formed. An additional injection of fast particles will fill the loss-cone later, breaking the loss-cone distribution. Therefore, the generation of continuum will be quenched at these moments, which was evidenced by the formation of bursts in absorption.

  9. Inter-annual maintenance of the fine-scale genetic structure in a biennial plant.

    PubMed

    Valverde, Javier; Gómez, José María; García, Cristina; Sharbel, Timothy F; Jiménez, María Noelia; Perfectti, Francisco

    2016-11-24

    Within plant populations, space-restricted gene movement, together with environmental heterogeneity, can result in a spatial variation in gene frequencies. In biennial plants, inter-annual flowering migrants can homogenize gene frequencies between consecutive cohorts. However, the actual impact of these migrants on spatial genetic variation remains unexplored. Here, we used 10 nuclear microsatellite and one plastid genetic marker to characterize the spatial genetic structure within two consecutive cohorts in a population of the biennial plant Erysimum mediohispanicum (Brassicaceae). We explored the maintenance of this structure between consecutive flowering cohorts at different levels of complexity, and investigated landscape effects on gene flow. We found that cohorts were not genetically differentiated and showed a spatial genetic structure defined by a negative genetic-spatial correlation at fine scale that varied in intensity with compass directions. This spatial genetic structure was maintained when comparing plants from different cohorts. Additionally, genotypes were consistently associated with environmental factors such as light availability and soil composition, but to a lesser extent compared with the spatial autocorrelation. We conclude that inter-annual migrants, in combination with limited seed dispersal and environmental heterogeneity, play a major role in shaping and maintaining the spatial genetic structure among cohorts in this biennial plant.

  10. Inter-annual maintenance of the fine-scale genetic structure in a biennial plant

    PubMed Central

    Valverde, Javier; Gómez, José María; García, Cristina; Sharbel, Timothy F.; Jiménez, María Noelia; Perfectti, Francisco

    2016-01-01

    Within plant populations, space-restricted gene movement, together with environmental heterogeneity, can result in a spatial variation in gene frequencies. In biennial plants, inter-annual flowering migrants can homogenize gene frequencies between consecutive cohorts. However, the actual impact of these migrants on spatial genetic variation remains unexplored. Here, we used 10 nuclear microsatellite and one plastid genetic marker to characterize the spatial genetic structure within two consecutive cohorts in a population of the biennial plant Erysimum mediohispanicum (Brassicaceae). We explored the maintenance of this structure between consecutive flowering cohorts at different levels of complexity, and investigated landscape effects on gene flow. We found that cohorts were not genetically differentiated and showed a spatial genetic structure defined by a negative genetic-spatial correlation at fine scale that varied in intensity with compass directions. This spatial genetic structure was maintained when comparing plants from different cohorts. Additionally, genotypes were consistently associated with environmental factors such as light availability and soil composition, but to a lesser extent compared with the spatial autocorrelation. We conclude that inter-annual migrants, in combination with limited seed dispersal and environmental heterogeneity, play a major role in shaping and maintaining the spatial genetic structure among cohorts in this biennial plant. PMID:27883087

  11. Properties and Modeling of Unresolved Fine Structure Loops Observed in the Solar Transition Region by IRIS

    NASA Astrophysics Data System (ADS)

    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.

  12. Resolving Fine Cardiac Structures in Rats with High-Resolution Diffusion Tensor Imaging

    PubMed Central

    Teh, Irvin; McClymont, Darryl; Burton, Rebecca A. B.; Maguire, Mahon L.; Whittington, Hannah J.; Lygate, Craig A.; Kohl, Peter; Schneider, Jürgen E.

    2016-01-01

    Cardiac architecture is fundamental to cardiac function and can be assessed non-invasively with diffusion tensor imaging (DTI). Here, we aimed to overcome technical challenges in ex vivo DTI in order to extract fine anatomical details and to provide novel insights in the 3D structure of the heart. An integrated set of methods was implemented in ex vivo rat hearts, including dynamic receiver gain adjustment, gradient system scaling calibration, prospective adjustment of diffusion gradients, and interleaving of diffusion-weighted and non-diffusion-weighted scans. Together, these methods enhanced SNR and spatial resolution, minimised orientation bias in diffusion-weighting, and reduced temperature variation, enabling detection of tissue structures such as cell alignment in atria, valves and vessels at an unprecedented level of detail. Improved confidence in eigenvector reproducibility enabled tracking of myolaminar structures as a basis for segmentation of functional groups of cardiomyocytes. Ex vivo DTI facilitates acquisition of high quality structural data that complements readily available in vivo cardiac functional and anatomical MRI. The improvements presented here will facilitate next generation virtual models integrating micro-structural and electro-mechanical properties of the heart. PMID:27466029

  13. Reduced fine-scale spatial genetic structure in grazed populations of Dianthus carthusianorum.

    PubMed

    Rico, Y; Wagner, H H

    2016-11-01

    Strong spatial genetic structure in plant populations can increase homozygosity, reducing genetic diversity and adaptive potential. The strength of spatial genetic structure largely depends on rates of seed dispersal and pollen flow. Seeds without dispersal adaptations are likely to be dispersed over short distances within the vicinity of the mother plant, resulting in spatial clustering of related genotypes (fine-scale spatial genetic structure, hereafter spatial genetic structure (SGS)). However, primary seed dispersal by zoochory can promote effective dispersal, increasing the mixing of seeds and influencing SGS within plant populations. In this study, we investigated the effects of seed dispersal by rotational sheep grazing on the strength of SGS and genetic diversity using 11 nuclear microsatellites for 49 populations of the calcareous grassland forb Dianthus carthusianorum. Populations connected by rotational sheep grazing showed significantly weaker SGS and higher genetic diversity than populations in ungrazed grasslands. Independent of grazing treatment, small populations showed significantly stronger SGS and lower genetic diversity than larger populations, likely due to genetic drift. A lack of significant differences in the strength of SGS and genetic diversity between populations that were recently colonized and pre-existing populations suggested that populations colonized after the reintroduction of rotational sheep grazing were likely founded by colonists from diverse source populations. We conclude that dispersal by rotational sheep grazing has the potential to considerably reduce SGS within D. carthusianorum populations. Our study highlights the effectiveness of landscape management by rotational sheep grazing to importantly reduce genetic structure at local scales within restored plant populations.

  14. WAVELENGTH ACCURACY OF THE KECK HIRES SPECTROGRAPH AND MEASURING CHANGES IN THE FINE STRUCTURE CONSTANT

    SciTech Connect

    Griest, Kim; Whitmore, Jonathan B.; Wolfe, Arthur M.; Prochaska, J. Xavier; Howk, J. Christopher; Marcy, Geoffrey W. E-mail: jonathan.b.whitmore@gmail.co

    2010-01-01

    We report on an attempt to accurately wavelength calibrate four nights of data taken with the Keck HIRES spectrograph on QSO PHL957, for the purpose of determining whether the fine structure constant was different in the past. Using new software and techniques, we measured the redshifts of various Ni II, Fe II, Si II, etc. lines in a damped Lyalpha system at z = 2.309. Roughly half the data were taken through the Keck iodine cell which contains thousands of well calibrated iodine lines. Using these iodine exposures to calibrate the normal Th-Ar Keck data pipeline output, we found absolute wavelength offsets of 500 m s{sup -1} to 1000 m s{sup -1} with drifts of more than 500 m s{sup -1} over a single night, and drifts of nearly 2000 m s{sup -1} over several nights. These offsets correspond to an absolute redshift of uncertainty of about DELTAz approx 10{sup -5}(DELTAlambda approx 0.02 A), with daily drifts of around DELTAz approx 5 x 10{sup -6} (DELTAlambda approx 0.01 A), and multiday drifts of nearly DELTAz approx 2 x 10{sup -5}(approx0.04 A). The causes of the wavelength offsets are not known, but since claimed shifts in the fine structure constant would result in velocity shifts of less than 100 m s{sup -1}, this level of systematic uncertainty may make it difficult to use Keck HIRES data to constrain the change in the fine structure constant. Using our calibrated data, we applied both our own fitting software and standard fitting software to measure DELTAalpha/alpha, but discovered that we could obtain results ranging from significant detection of either sign, to strong null limits, depending upon which sets of lines and which fitting method were used. We thus speculate that the discrepant results on DELTAalpha/alpha reported in the literature may be due to random fluctuations coming from underestimated systematic errors in wavelength calibration and fitting procedure.

  15. Fine structure of the mineralized teeth of the chiton Acanthopleura echinata (Mollusca: Polyplacophora).

    PubMed

    Wealthall, Rosamund J; Brooker, Lesley R; Macey, David J; Griffin, Brendan J

    2005-08-01

    The major lateral teeth of the chiton Acanthopleura echinata are composite structures composed of three distinct mineral zones: a posterior layer of magnetite; a thin band of lepidocrocite just anterior to this; and apatite throughout the core and anterior regions of the cusp. Biomineralization in these teeth is a matrix-mediated process, in which the minerals are deposited around fibers, with the different biominerals described as occupying architecturally discrete compartments. In this study, a range of scanning electron microscopes was utilized to undertake a detailed in situ investigation of the fine structure of the major lateral teeth. The arrangement of the organic and biomineral components of the tooth is similar throughout the three zones, having no discrete borders between them, and with crystallites of each mineral phase extending into the adjacent mineral zone. Along the posterior surface of the tooth, the organic fibers are arranged in a series of fine parallel lines, but just within the periphery their appearance takes on a "fish scale"-like pattern, reflective of the cross section of a series of units that are overlaid, and offset from each other, in adjacent rows. The units are approximately 2 microm wide and 0.6 microm thick and comprise biomineral plates separated by organic fibers. Two types of subunits make up each "fish scale": one is elongate and curved and forms a trough, in which the other, rod-like unit, is nestled. Adjacent rod and trough units are aligned into large sheets that define the fracture plane of the tooth. The alignment of the plates of rod-trough units is complex and exhibits extreme spatial variation within the tooth cusp. Close to the posterior surface the plates are essentially horizontal and lie in a lateromedial plane, while anteriorly they are almost vertical and lie in the posteroanterior plane. An understanding of the fine structure of the mineralized teeth of chitons, and of the relationship between the organic and

  16. Postsynthetic Functionalization of Mg-MOF-74 with Tetraethylenepentamine: Structural Characterization and Enhanced CO2 Adsorption.

    PubMed

    Su, Xiao; Bromberg, Lev; Martis, Vladimir; Simeon, Fritz; Huq, Ashfia; Hatton, T Alan

    2017-03-15

    Postsynthetic functionalization of magnesium 2,5-dihydroxyterephthalate (Mg-MOF-74) with tetraethylenepentamine (TEPA) resulted in improved CO2 adsorption performance under dry and humid conditions. XPS, elemental analysis, and neutron powder diffraction studies indicated that TEPA was incorporated throughout the MOF particle, although it coordinated preferentially with the unsaturated metal sites located in the immediate proximity to the surface. Neutron and X-ray powder diffraction analyses showed that the MOF structure was preserved after amine incorporation, with slight changes in the lattice parameters. The adsorption capacity of the functionalized amino-Mg-MOF-74 (TEPA-MOF) for CO2 was as high as 26.9 wt % versus 23.4 wt % for the original MOF due to the extra binding sites provided by the multiunit amines. The degree of functionalization with the amines was found to be important in enhancing CO2 adsorption, as the optimal surface coverage improved performance and stability under both pure CO2 and CO2/H2O coadsorption, and with partially saturated surface coverage, optimal CO2 capacity could be achieved under both wet and dry conditions by a synergistic binding of CO2 to the amines as well as metal centers.

  17. Influence of solution structure on adsorption of metal-EDTA complexes onto iron oxides

    SciTech Connect

    Nowack, B.; Sigg, L.

    1995-12-01

    The adsorption characteristics of a variety of divalent and trivalent metal-EDTA complexes onto goethite ({alpha}-FeOOH) and amorphous Fe(OH){sub 3} were examined. Uncomplexed EDTA is adsorbed as a ligand-like binuclear complex at low pH and as a mononuclear complex at high pH. The complexes of the divalent metals Ca, Zn, Ni, Cu, Co(II), and Ph show all the same ligand-like adsorption behavior. They are characterized by a quinquedentate structure in solution. Their adsorption in function of pH can be described by a ternary surface complex. The bidentate Pd(II) EDTA is adsorbed much stronger, but also ligand-like. La(III) EDTA and Bi(III) EDTA are adsorbed very strongly over the whole pH-range. The sexidentate complex of Co(III) is at low pH weakly adsorbed outer-spherically. Fe(III) EDTA is weakly adsorbed over the whole pH-range. The mobility of EDTA complexes in an aquifer depends therefore on the pH and on the type of complex.

  18. Capturing the Local Adsorption Structures of Carbon Dioxide in Polyamine-Impregnated Mesoporous Silica Adsorbents.

    PubMed

    Huang, Shing-Jong; Hung, Chin-Te; Zheng, Anmin; Lin, Jen-Shan; Yang, Chun-Fei; Chang, Yu-Chi; Deng, Feng; Liu, Shang-Bin

    2014-09-18

    Interactions between amines and carbon dioxide (CO2) are essential to amine-functionalized solid adsorbents for carbon capture, and an in-depth knowledge of these interactions is crucial to adsorbent design and fabrication as well as adsorption/desorption processes. The local structures of CO2 adsorbed on a tetraethylenepentamine-impregnated mesoporous silica SBA-15 were investigated by solid-state (13)C{(14)N} S-RESPDOR MAS NMR technique and theoretical DFT calculations. Two types of adsorption species, namely, secondary and tertiary carbamates as well as distant ammonium groups were identified together with their relative concentrations and relevant (14)N quadrupolar parameters. Moreover, a dipolar coupling of 716 Hz was derived, corresponding to a (13)C-(14)N internuclear distance of 1.45 Å. These experimental data are in excellent agreement with results obtained from DFT calculations, revealing that the distribution of surface primary and secondary amines readily dictates the CO2 adsorption/desorption properties of the adsorbent.

  19. Effect of CO and H adsorption on the compositional structure of binary nanoalloys via DFT modeling

    NASA Astrophysics Data System (ADS)

    West, Paul S.; Johnston, Roy L.; Barcaro, Giovanni; Fortunelli, Alessandro

    2013-08-01

    A theoretical approach to investigate the influence of CO and H adsorption on the compositional structure or chemical ordering of binary metal nanoclusters is applied to selected representative pairs: AuPd, PdPt, CuPt and PdRh. The truncated octahedral (TO) 38-atom cluster is chosen as a model of small fcc nanoclusters because its high-symmetry allows a simpler analysis and a reduced computational effort. A number of CO and H ligands (ranging from 1 to 8) are adsorbed on atop sites at the centre of (111) facets of the cluster, and the corresponding energetics are analyzed in detail. A strong tendency to segregation inversion from AuPd shell/core to core/shell is found upon CO adsorption, qualitatively very similar even though more pronounced than that found for the PdRh pair (where Pd plays the role of Au and Rh that of Pd). This effect is still present, but quantitatively modest, in PdPt. The value of the CO binding energy decreases in the sequence: Rh > Pt > Pd > Au, and is scarcely affected by the presence of neighbouring hetero-species (minor electronic effect). A clear electronic effect is instead found in the CuPt case, in which the strengthening of Pt-CO bonds when Cu neighbours surround the interacting Pt atom brings Cu from the centres to the edges of (111) facets in Pt-rich clusters upon CO adsorption. H adsorption brings about qualitatively similar effects, although to a much smaller degree, so that a definite segregation inversion is only predicted for the AuPd pair. The predicted trends are found to be in good agreement with available experimental results.

  20. Impact of heavy hole-light hole coupling on the exciton fine structure in quantum dots

    NASA Astrophysics Data System (ADS)

    Tsitsishvili, E.

    2017-03-01

    We present analytical results which describe the properties of the exciton ground state in a single semiconductor quantum dot (QD). Calculations are performed within the Luttinger-Kohn and Bir-Pikus Hamiltonian theory. We show in an explicit form that an interplay of the exchange interaction and the heavy hole-light hole coupling, which is due to the in-plane asymmetries of the dot shape and the strain distribution, plays an essential role. For both the bright and dark exciton, this combined effect leads to a dependence of the fine structure splitting and polarizations on the main anisotropy axis direction relative to the dot orientation. Basing on the obtained analytical expressions, we discuss some special cases in details.

  1. The role of temporal fine structure in harmonic segregation through mistuning.

    PubMed

    Moore, Brian C J; Glasberg, Brian R

    2010-01-01

    Bernstein and Oxenham [(2008). J. Acoust. Soc. Am. 124, 1653-1667] measured thresholds for discriminating the fundamental frequency, F0, of a complex tone that was passed through a fixed bandpass filter. They found that performance worsened when the F0 was decreased so that only harmonics above the tenth were audible. However, performance in this case was improved by mistuning the odd harmonics by 3%. Bernstein and Oxenham considered whether the results could be explained in terms of temporal fine structure information available at the output of a single auditory filter and concluded that their results did not appear to be consistent with such an explanation. Here, it is argued that such cues could have led to the improvement in performance produced by mistuning the odd harmonics.

  2. Optimal Design for Nonperiodic Fine Grating Structure Controlled by Proximity Correction with Electron-Beam Lithography

    NASA Astrophysics Data System (ADS)

    Okano, Masato; Hirai, Yoshihiko; Kikuta, Hisao

    2007-02-01

    We describe a method for designing nonperiodic fine grating structures such as a small F-number diffractive cylindrical lens, to be fabricated by direct-writing electron-beam lithography. The design is based on a resist development simulator for estimating a proximity effect of electron dose and the finite difference time domain (FDTD) method for simulating an electromagnetic field. The surface profile and electron dose distribution are simultaneously optimized to obtain the high diffraction efficiency. For the design of a diffractive lens of 50 μm width and 25 μm focal length, the calculated diffraction efficiency is 49% for 650-nm-wavelength light, which is slightly lower than that of a diffractive lens profile optimized by electromagnetic analysis without restrictions on fabrication limits.

  3. Extended X-ray absorption fine structural studies of copper and nickel ferrites

    NASA Astrophysics Data System (ADS)

    Malviya, P. K.; Sharma, P.; Mishra, Ashutosh; Bhalse, D.

    2014-09-01

    The Cu-Ni ferrites with general formula Cu1-xNix Fe2O4 (where x=0.0, 0.05, 0.10, 0. 15, 0.20) were prepared by solid state root method. X-ray, K- absorption fine structural measurements were carried out. EXAFS spectra have been recorded at the K-edge of Fe using the dispersive EXAFS (DEXAFS) beam line at 2.5GeV Indus-2 synchrotron radiation source RRCAT, Indore, India. The EXAFS data have been analysed using the computer software Athena. These have been used to determine the bond lengths in these ferrites with the help of four different methods, namely, Levy's, Lytle's and Lytle, Sayers and Stern's (LSS) methods.

  4. Enhanced sensitivity to the fine-structure-constant variation in the Th IV atomic clock transition

    SciTech Connect

    Flambaum, V. V.; Porsev, S. G.

    2009-12-15

    Our calculations have shown that the 5f{sub 5/2}-7s{sub 1/2} 23 131 cm{sup -1} transition from the ground state in the ion Th{sup 3+} is very sensitive to the temporal variation of the fine-structure constant alpha=e{sup 2}/(Planck constant/2pi)c (q=-75 300 cm{sup -1}). The line is very narrow, the ion has been trapped and laser cooled, and the positive shifter line 5f{sub 5/2}-5f{sub 7/2} 4325 cm{sup -1} (q=+2900 cm{sup -1}) may be used as a reference. A comparison may also be made with a positive shifter in another atom or ion. This makes Th{sup 3+} a good candidate to search for the alpha variation.

  5. High resolution telescope and spectrograph observations of solar fine structure in the 1600 A region

    NASA Technical Reports Server (NTRS)

    Cook, J. W.; Brueckner, G. E.; Bartoe, J.-D. F.

    1983-01-01

    High spatial resolution spectroheliograms of the 1600 A region obtained during the HRTS rocket flight of 1978 February 13 are presented. The morphology, fine structure, and temporal behavior of emission bright points (BPs) in active and quiet regions are illustrated. In quiet regions, network elements persist as morphological units, although individual BPs may vary in intensity while usually lasting the flight duration. In cell centers, the BPs are highly variable on a 1 minute time scale. BPs in plages remain more constant in brightness over the observing sequence. BPs cover less than 4 percent of the quiet surface. The lifetime and degree of packing of BPs vary with the local strength of the magnetic field.

  6. New limit on the present temporal variation of the fine structure constant

    SciTech Connect

    Peik, E.; Lipphardt, B.; Schnatz, H.; Schneider, T.; Tamm, Chr.; Karshenboim, S.G.

    2005-05-05

    A comparison of different atomic frequency standards over time can be used to perform a measurement of the present value of the temporal derivative of the fine structure constant {alpha} in a model-independent way without assumptions on constancy or variability of other parameters. We have measured an optical transition frequency at 688 THz in Yb+ with a cesium atomic clock at two times separated by 2.8 years and find that a variation of this frequency can be excluded within a 1{sigma} relative uncertainty of 4.4{center_dot}10-15 yr-1. Combined with recently published values for the constancy of other transition frequencies this measurement provides a limit on the present variability of {alpha} at the level of 2.0{center_dot}10-15 yr-1. Constraints are also derived for the drift rates of other fundamental constants like the electron/proton mass ratio and the proton g-factor.

  7. Temporal structure of gas temperature fluctuations and ignition of fine particles

    NASA Astrophysics Data System (ADS)

    Derevich, I. V.; Galdina, D. D.

    2016-11-01

    The paper studies ignition of fine particles, i.e., irreversible growth of particle temperature from an exothermal heterogeneous reaction, with the rate approximated with the Arrhenius law. The particles are suspended in gas with fluctuating temperature, and heat transfer from the particle surface occurs according to the Newtonian law. The equations take into account the temporal structure of gas temperature fluctuations. Modern methods of functional analysis were applied for deriving a closed equation for the probability density function for the particle temperature distribution. The gas temperature fluctuations lessen the threshold for the particle ignition in the hot gas as compared with the deterministic variant. The equations for probability density function produce a closed system of conjugate equations for the average temperature and dispersion of particle temperature fluctuations. The results of simulation illustrate the phenomenon of self-speeding drift of particle temperature towards the temperature of ignition startup.

  8. The tardigrade cuticle. I. Fine structure and the distribution of lipids.

    PubMed

    Wright, J C

    1988-01-01

    Fine structure and lipid distribution are studied in cuticles of five tardigrade species using TEM and SEM. Double osmication using partitioning methods reveals a substantial lipid component in the intracuticle and in irregular granular regions within the procuticle. These results are substantiated by the loss of osmiophily following lipid extraction with chloroform and methanol. Other lipid components are revealed by osmication following unmasking of lipo-protein complexes with thymol. These occur in the outer epicuticle and in the trilaminar layer lying between the epi- and intracuticles. Anhydrous fixation of dehydrated tardigrades (tuns) reveals dense, superficial masses of osmiophilic material, apparently concentrated lumps of the surface mucopolysaccharide ('flocculent coat'). However, cryo-SEMs of tuns reveal similar dense aggregations which apparently exude from pores (not visible) and are removed by chloroform. These results suggest extruded lipids since the flocculent coat is unaffected by chloroform; likely functions of such lipids are discussed.

  9. Domain Dynamics in Piezoresponse Force Microscopy: Quantitative Deconvolution and Hysteresis Loop Fine Structure

    SciTech Connect

    Bdikin, Igor; Kholkin, Andrei; Morozovska, A. N.; Svechnikov, S. V.; Kim, S.-H.; Kalinin, Sergei V

    2008-01-01

    Domain dynamics in the Piezoresponse Force Spectroscopy (PFS) experiment is studied using the combination of local hysteresis loop acquisition with simultaneous domain imaging. The analytical theory for PFS signal from domain of arbitrary cross-section is developed and used for the analysis of experimental data on Pb(Zr,Ti)O3 polycrystalline films. The results suggest formation of oblate domain at early stage of the domain nucleation and growth, consistent with efficient screening of depolarization field within the material. The fine structure of the hysteresis loop is shown to be related to the observed jumps in the domain geometry during domain wall propagation (nanoscale Barkhausen jumps), indicative of strong domain-defect interactions.

  10. MHD Wave Modes Resolved in Fine-Scale Chromospheric Magnetic Structures

    NASA Astrophysics Data System (ADS)

    Verth, G.; Jess, D. B.

    2016-02-01

    Due to its complex and dynamic fine-scale structure, the chromosphere is a particularly challenging region of the Sun's atmosphere to understand. It is now widely accepted that to model chromospheric dynamics, even on a magnetohydrodynamic (MHD) scale, while also calculating spectral line emission, one must realistically include the effects of partial ionization and radiative transfer in a multi-fluid plasma under non-LTE conditions. Accurate quantification of MHD wave energetics must be founded on a precise identification of the actual wave mode being observed. This chapter focuses on MHD kink-mode identification, MHD sausage mode identification, and MHD torsional Alfvén wave identification. It then reviews progress in determining more accurate energy flux estimations of specific MHD wave modes observed in the chromosphere. The chapter finally examines how the discovery of these MHD wave modes has helped us advance the field of chromospheric magnetoseismology.

  11. Fine-structural changes in the midgut of old Drosophila melanogaster

    NASA Technical Reports Server (NTRS)

    Anton-Erxleben, F.; Miquel, J.; Philpott, D. E.

    1983-01-01

    Senescent fine-structural changes in the midgut of Drosophila melanogaster are investigated. A large number of midgut mitochondria in old flies exhibit nodular cristae and a tubular system located perpendicular to the normal cristae orientation. Anterior intestinal cells show a senescent accumulation of age pigment, either with a surrounding two-unit membrane or without any membrane. The predominant localization of enlarged mitochondria and pigment in the luminal gut region may be related to the polarized metabolism of the intestinal cells. Findings concur with previous observations of dense-body accumulations and support the theory that mitochondria are involved in the aging of fixed post-mitotic cells. Demonstrated by statistical analyses is that mitochondrial size increase is related to mitochondrial variation increase.

  12. The coefficient of bond thermal expansion measured by extended x-ray absorption fine structure.

    PubMed

    Fornasini, P; Grisenti, R

    2014-10-28

    The bond thermal expansion is in principle different from the lattice expansion and can be measured by correlation sensitive probes such as extended x-ray absorption fine structure (EXAFS) and diffuse scattering. The temperature dependence of the coefficient α(bond)(T) of bond thermal expansion has been obtained from EXAFS for CdTe and for Cu. A coefficient α(tens)(T) of negative expansion due to tension effects has been calculated from the comparison of bond and lattice expansions. Negative lattice expansion is present in temperature intervals where α(bond) prevails over α(tens); this real-space approach is complementary but not equivalent to the Grüneisen theory. The relevance of taking into account the asymmetry of the nearest-neighbours distribution of distances in order to get reliable bond expansion values and the physical meaning of the third cumulant are thoroughly discussed.

  13. Fine structure in RF spectra of lightning return stroke wave forms

    NASA Technical Reports Server (NTRS)

    Lanzerotti, L. J.; Thomson, D. J.; Maclennan, C. G.; Rinnert, K.; Krider, E. P.

    1988-01-01

    The power spectra of the wide-band (10 Hz to 100 kHz) magnetic-field signals for a number of lightning return strokes measured during a thunderstorm which occurred in Lindau in August, 1984 have been calculated. The RF magnetic field data are obtained with the engineering unit of the Galileo Jupiter Probe lightning experiment. Each return stroke data stream is passed through an adaptive filter designed to whiten its spectrum. The spectra of the magnetic field data definitely show fine structure, with two or three distinct peaks in the spectra of many of the waveforms. A peak at f of about 60-70 kHz is often seen in the power spectra of the waveform time segments preceding and following the rise-to-peak amplitude of the return stroke.

  14. New determination of the fine structure constant and test of the quantum electrodynamics.

    PubMed

    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.

  15. Engineering quantum dots for electrical control of the fine structure splitting

    NASA Astrophysics Data System (ADS)

    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.

  16. Gravity field fine structure estimation techniques for a spaceborne gravity gradiometer

    NASA Technical Reports Server (NTRS)

    Kahn, W. D.; Englar, T. S., Jr.

    1987-01-01

    Use of standard estimation techniques to recover geopotential fine structure from gradiometer data requires the adjustment of small subsets of parameters while constraining others to their a priori values in order to minimize the computational load. Here, gravitational anomalies are selected as a parametrization of the gravity field which permits such an approach. Techniques coupled with numerical results for a spaceborne gravity gradiometer mission simulation are described which demonstrate that if a satellite is in a polar/circular orbit at an altitude of 160 km, 1 deg mean free air gravity anomalies can be recovered to an accuracy of 0.4 mgal, where 1 mgal = 0.001 cm/sq s.

  17. Fine structural changes in the lateral vestibular nucleus of aging rats

    NASA Technical Reports Server (NTRS)

    Johnson, J. E., Jr.; Miquel, J.

    1974-01-01

    The fine structure of the lateral vestibular nucleus was investigated in Sprague-Dawley rats, that were sacrified at 4 weeks, 6-8 weeks, 6-8 months, and 18-20 months of age. In the neuronal perikaria, the following age-associated changes were seen with increasing frequency with advancing age: rodlike nuclear inclusions and nuclear membrane invaginations; cytoplasmic dense bodies with the characteristics of lipofuscin; and moderate disorganization of the granular endoplasmic reticulum. Dense bodies were also seen in glial cells. Rats 18 to 20 months old showed dendritic swellings, axonal degeneration, and an apparent increase in the number of axosomatic synaptic terminals containing flattened vesicles (presumed to be inhibitory in function).

  18. Infrared fine-structure line diagnostics of shrouded active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Voit, G. M.

    1992-01-01

    The ultraluminous far-IR galaxies revealed by IRAS, quasar-like in luminosity but smothered in molecular gas, probably conceal either immense starbursts or luminous active nuclei. In both scenarios, these objects ought to produce copious infrared fine-structure emission with several lines comparable to H-beta in luminosity. We show how these lines, if detected, can be used to determine the electron densities and far-IR obscurations of shrouded photoionized regions and to constrain the shape and ionization parameter of the ionizing spectra. The presence of Ne v emission in particular will distinguish shrouded AGNs from shrouded starbursts. Since all active galaxies photoionize at least some surrounding material, these diagnostics can also be applied to active galaxies in general and will aid in studying how an active nucleus interacts with the interstellar medium of its host galaxy.

  19. Automated fine structure image analysis method for discrimination of diabetic retinopathy stage using conjunctival microvasculature images

    PubMed Central

    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. Fine structure of the isoscalar giant quadrupole resonance in 28Si and 27Al

    NASA Astrophysics Data System (ADS)

    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.

  1. Highly charged ions for atomic clocks and search for variation of the fine structure constant

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    We review a number of highly charged ions which have optical transitions suitable for building extremely accurate atomic clocks. This includes ions from Hf 12+ to U 34+, which have the 4 f 12 configuration of valence electrons, the Ir 17+ ion, which has a hole in almost filled 4 f subshell, the Ho 14+, Cf 15+, Es 17+ and Es 16+ ions. Clock transitions in most of these ions are sensitive to variation of the fine structure constant, α (α = e2/hbar c). E.g., californium and einsteinium ions have largest known sensitivity to α-variation while holmium ion looks as the most suitable ion for experimental study. We study the spectra of the ions and their features relevant to the use as frequency standards.

  2. Half-lives and fine structure for the α decay of deformed even-even nuclei

    NASA Astrophysics Data System (ADS)

    Ni, DongDong; Ren, ZhongZhou

    2011-08-01

    The α-decay properties of well-deformed even-even nuclei are systematically calculated within the multichannel cluster model (MCCM). Instead of working in the WKB framework, the quasibound solution to the coupled Schrödinger equation is presented with outgoing wave boundary conditions, and the coupling potential is taken into full account in terms of the general quantum theories. The calculated α-decay half-lives are found to agree well with the experimental data with a mean factor of less than 2. The fine structure observed in α decay is also well reproduced by the four-channel microscopic calculation. Very strikingly, the MCCM can give relatively precise descriptions of the branching ratio to excited 4+ states, which is often overestimated in the usual WKB calculations. We expect it to be a significant development of theoretical models toward quantitative descriptions of α transitions to high-spin daughter states.

  3. Theoretical description of fine structure in the α decay of heavy odd-odd nuclei

    NASA Astrophysics Data System (ADS)

    Ni, Dongdong; Ren, Zhongzhou

    2013-02-01

    The newly developed multichannel cluster model (MCCM), based on the coupled-channel Schrödinger equation with outgoing wave boundary conditions, is extended to study the α-decay fine structure in heavy odd-odd nuclei. Calculations are performed for the α transitions to favored rotational bands where the unpaired nucleons remain unchanged. The simple WKB barrier penetration formula is also used to evaluate the branching ratios for various daughter states. It is found that the WKB formula seems to overestimate the branching ratios for the second and third members of the favored rotational band, while the MCCM gives a precise description of them without any adjustable parameters. Moreover, the experimental total α-decay half-lives are well reproduced within the MCCM.

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

    PubMed

    Carilli, C L; Menten, K M; Stocke, J T; Perlman, E; Vermeulen, R; Briggs, F; de Bruyn, A G; Conway, J; Moore, C P

    2000-12-25

    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 structure constant: alpha/ alpha<3.5x10(-15) yr(-1), to a look-back time of 4.8 Gyr. In the context of string theory, the limit on the secular evolution of the scale factor of the compact dimensions, R, is &Rdot/ R<10(-15) yr(-1). Including terrestrial and other astronomical measurements places 2sigma limits on slow oscillations of R from the present to the epoch of cosmic nucleosynthesis, just seconds after the big bang, of DeltaR /R<10(-5).

  5. Fine structure of all-particle energy spectrum in the knee region

    NASA Astrophysics Data System (ADS)

    Garyaka, A.; Martirosov, R.; Ter-Antonyan, S.; Babayan, H.; Erlykin, A.; Gallant, Y.; Jones, L.; Kempa, J.; Nikolskaya, N.; Pattison, B.; Procureur, J.; Sokhoyan, S.; Vardanyan, H.

    2013-02-01

    All-particle energy spectrum in the knee region obtained from extensive air shower (EAS) measurements (GAMMA experiment, 700 g/cm2, Armenia) is presented. Energies of primary particles in the range of 106-108 GeV were evaluated on the basis of observed shower parameters Nch,Nμ, s, θ and corresponding parameterisation of CORSIKA simulated database for SIBYLL interaction model. All shower detection and reconstruction uncertainties were included in the simulated showers for four kinds (H, He, O, Fe) of primary nuclei. The reliability of observed all-particle energy spectrum is investigated from viewpoint of methodical errors and statistical fluctuations. Observed fine structure of all-particle energy spectrum can be interpreted by the rigidity-dependent steepening Galactic diffuse nuclei flux and an additional iron component in the region of 70-80 PeV primary energies most likely originated from nearby pulsars.

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

    SciTech Connect

    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.

  7. Fine structure of the copulatory apparatus of the tapeworm Tetrabothrius erostris (Cestoda: Tetrabothriidea).

    PubMed

    Korneva, Janetta V; Jones, Malcolm K; Kuklin, Vadim V

    2015-05-01

    The organization and fine structure of the complex copulatory apparatus of Tetrabothrius erostris (Tetrabothriidea) is investigated by light and transmission electron microscopy. A diversity of microstructures was found on the surface of genital ducts. The apical surfaces of male gonadoducts possess tubular and blade-like microtriches that have specific structure in each section of the duct. The apical part of the tubular microtriches contains numerous constrictions in the proximal section of the sperm duct; blade-like microtriches of cirrus possess longitudinal striation in the apical part, and their basal part is reinforced with electron-dense strands. Two types of microtriches occur on the surface of cirrus, and their presence may be considered as systematic features. Prostate glands containing granules of medium electron density (up to 130 nm diameter) are localized in the cirrus sac. The genital atrium contains numerous non-ciliated receptors. Paramyosin-like fibers (up to 200 nm) were found in the muscle fibers surrounding the male atrium canal. Microtriches on the surface of the distal region of the male atrial canal are covered by a glycocalyx. Electron-dense, membrane-like structures (up to 40 nm) lie under the apical membrane of the genital atrium and vagina. These structures do not form a continuous layer; its edges turn down and sink into the apical invaginations of epithelium. Hypotheses on the possible ways of copulation in T. erostris based on the observed ultrastructure are discussed.

  8. Comparison of fine structures of electron cyclotron harmonic emissions in aurora

    NASA Astrophysics Data System (ADS)

    LaBelle, J.; Dundek, M.

    2015-10-01

    Recent discoveries of higher harmonic cyclotron emissions in aurora occurring under daylight conditions motivated the modification of radio receivers at South Pole Station, Antarctica, to measure fine structure of such emissions during two consecutive austral summers, 2013-2014 and 2014-2015. The experiment recorded 347 emission events over 376 days of observation. The seasonal distribution of these events reveals that successively higher harmonics require higher solar zenith angles for occurrence, as expected if they are generated at the matching condition fuh = Nfce, which for higher N requires higher electron densities which are associated with higher solar zenith angles. This result implies that generation of higher harmonics from lower harmonics via wave-wave processes explains only a minority of events. Detailed examination of 21 cases in which two harmonics occur simultaneously shows that in almost all events the higher harmonic comes from higher altitudes, and only for a small fraction of events is it plausible that the frequencies of the fine structures of the emissions are correlated and in exact integer ratio. This observation puts an upper bound of 15-20% on the fraction of emissions which can be explained by wave-wave interactions involving Z mode waves at fce and, combined with consideration of source altitudes, puts an upper bound of 75% on the fraction explained by coalescence of Z mode waves at 2fce. Taken together, these results suggest that the dominant mechanism for the higher harmonics is independent generation at the matching points fuh = Nfce and that the wave-wave interaction mechanisms explain a relatively small fraction of events.

  9. On the Visibility of Prominence Fine Structures at Radio Millimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Heinzel, P.; Berlicki, A.; Bárta, M.; Karlický, M.; Rudawy, P.

    2015-07-01

    Prominence temperatures have so far mainly been determined by analyzing spectral line shapes, which is difficult when the spectral lines are optically thick. The radio spectra in the millimeter range offer a unique possibility to measure the kinetic temperature. However, studies in the past used data with insufficient spatial resolution to resolve the prominence fine structures. The aim of this article is to predict the visibility of prominence fine structures in the submillimeter/millimeter (SMM) domain, to estimate their brightness temperatures at various wavelengths, and to demonstrate the feasibility and usefulness of future high-resolution radio observations of solar prominences with ALMA ( Atacama Large Millimeter-submillimeter Array). Our novel approach is the conversion of H coronagraphic images into microwave spectral images. We show that the spatial variations of the prominence brightness both in the H line and in the SMM domain predominantly depend on the line-of-sight emission measure of the cool plasma, which we derive from the integrated intensities of the observed H line. This relation also offers a new possibility to determine the SMM optical thickness from simultaneous H observations with high resolution. We also describe how we determine the prominence kinetic temperature from SMM spectral images. Finally, we apply the ALMA image-processing software Common Astronomy Software Applications (CASA) to our simulated images to assess what ALMA would detect at a resolution level that is similar to the coronagraphic H images used in this study. Our results can thus help in preparations of first ALMA prominence observations in the frame of science and technical verification tests.

  10. Fine-structure energy levels, radiative rates and lifetimes in Si-like nickel

    NASA Astrophysics Data System (ADS)

    Gupta, G. P.; Msezane, A. Z.

    2012-07-01

    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.

  11. Clonal growth and fine-scale genetic structure in tanoak (Notholithocarpus densiflorus: Fagaceae).

    PubMed

    Dodd, Richard S; Mayer, Wasima; Nettel, Alejandro; Afzal-Rafii, Zara

    2013-01-01

    The combination of sprouting and reproduction by seed can have important consequences on fine-scale spatial distribution of genetic structure (SGS). SGS is an important consideration for species' restoration because it determines the minimum distance among seed trees to maximize genetic diversity while not prejudicing locally adapted genotypes. Local environmental conditions can be expected to influence levels of clonal spread and SGS, particularly in the case of disturbance regimes such as fire. Here, we characterize fine-scale genetic structure and clonal spread in tanoak from drier upland sites and more mesic lowland woodlands. Clonal spread was a significant mode of stand development, but spread was limited on average to about 5-6 m. Gene dispersal was decomposed into clonal and sexual components. The latter varied according to whether it was estimated from all ramets with the clonal component removed or for a single ramet per genet. We used the difference in these 2 estimates of gene dispersal as a measure of the effect of clonality on effective population size in this species. Although upland sites had a greater number of ramets per genet, most of the other indices computed were not significantly different. However, they tended to show greater heterozygote excess and shorter gene dispersal distances than the lowland sites. The average distance among inferred sibships on upland sites was approximately at the scale of maximum clonal range. This was not the case on lowland sites, where sibs were more dispersed. We recommend minimum distances among seed trees to avoid selecting clones and to maximize genetic diversity for restoration.

  12. Comparison of Fine Structures of Electron Cyclotron Harmonic Emissions in Aurora

    NASA Astrophysics Data System (ADS)

    Labelle, J. W.; Dundek, M.

    2015-12-01

    Recent discoveries of emissions at four and five times the electron cyclotron frequency in aurora occuring under daylit conditions motivated the modification of radio receivers at South Pole Station, Antarctica, to measure fine structure of such emissions during two consecutive austral summers, 2013-4 and 2014-5. The experiment recorded 347 emission events over 376 days of observation. The seasonal distribution of these events revealed that successively higher harmonics require higher solar zenith angles for occurrence, as expected if they are generated at locations where the upper hybrid frequency matches the cyclotron harmonic, which for higher harmonics requires higher electron densities which are associated with higher solar zenith angles. Detailed examination of 21 cases in which two harmonics occur simultaneously showed that only rarely, about ten percent of the time, are the frequencies of the fine structures of the emissions in exact integer ratio (e.g., 3:2, 4:3, or 5:4 depending on which combination of harmonics is observed). In the remaining approximately ninety percent of the cases, the higher harmonic occurred at a lower ratio than the appropriate integer ratio, as expected if the harmonics are generated independently at their separate matching conditions in the bottomside ionosphere, where the upper hybrid frequency increases with altitude while the gyroharmonics decrease with altitude. (The bottomside is the most likely source of the emissions, since from there the mode converted Z-modes have access to ground-level.) Taken together, these results suggest that the dominant mechanism for the higher harmonics is independent generation at locations where the upper hybrid frequency matches each harmonic, i.e., at a separate source altitude for each harmonic. Generation of higher harmonics through coalescence of lower harmonic waves explains at most a small minority of events.

  13. Hydrogenic Lamb shift in iron Fe{sup 25+} and fine-structure Lamb shift

    SciTech Connect

    Chantler, C. T.; Laming, J. M.; Dietrich, D. D.; Hallett, W. A.; McDonald, R.; Silver, J. D.

    2007-10-15

    1s-2p Lyman {alpha} transitions in hydrogenic iron Fe{sup 25+} have been observed from a beam-foil source in fourth-order diffraction off ADP 101 and PET 002 crystals, simultaneously with the n=2 to n=4 Balmer {beta} transitions diffracted in first order. Calibration of the local dispersion relation of the spectrometer using Balmer {beta} lines provides measurements of Lyman {alpha} wavelengths. The approach of fitting the full two-dimensional dispersion relation, including other members of Balmer and Lyman series, limits random and systematic correlation of parameters, and reveals a major systematic due to dynamical diffraction depth penetration into a curved crystal. The development of a theory of x-ray diffraction from mosaic crystals was necessary for the accurate interpretation of the experimental data. Photographic theory was also developed in the process of this research. Several systematics are discussed and quantified for the first time for these medium-Z QED comparisons. 2s-1s and 4f-2p satellites are explicitly investigated, and a dominant systematic is uncovered, which is due to the variable location of spectral emission downstream of the beam-foil target. 1s-2p{sub 3/2}, 1s-2p{sub 1/2} iron Lamb shifts are measured to be 35 376{+-}1900 cm{sup -1} and 35 953{+-}1800 cm{sup -1}. These agree with but lie higher than theory. This represents a 5.7% measurement of the hydrogenic 1s-2p{sub 1/2} Lamb shift in iron. The technique also reports the iron 2p{sub 3/2}-2p{sub 1/2} fine structure as 171 108 cm{sup -1}{+-}180 cm{sup -1}, which represents a 51% measurement of the hydrogenic iron fine-structure Lamb shift, and reports measurements of secondary lines.

  14. Production of fine structures in type III solar radio bursts due to turbulent density profiles

    SciTech Connect

    Loi, Shyeh Tjing; Cairns, Iver H.; Li, Bo

    2014-07-20

    Magnetic reconnection events in the corona release energetic electron beams along open field lines, and the beams generate radio emission at multiples of the electron plasma frequency f{sub p} to produce type III solar radio bursts. Type III bursts often exhibit irregularities in the form of flux modulations with frequency and/or local temporal advances and delays, and a type IIIb burst represents the extreme case where a type III burst is fragmented into a chain of narrowband features called striae. Remote and in situ spacecraft measurements have shown that density turbulence is ubiquitous in the corona and solar wind, and often exhibits a Kolmogorov power spectrum. In this work, we numerically investigate the effects of one-dimensional macroscopic density turbulence (along the beam direction) on the behavior of type III bursts, and find that this turbulence produces stria-like fine structures in the dynamic spectra of both f{sub p} and 2 f{sub p} radiation. Spectral and temporal fine structures in the predicted type III emission are produced by variations in the scattering path lengths and group speeds of radio emission, and in the locations and sizes of emitting volumes. Moderate turbulence levels yield flux enhancements with much broader half-power bandwidths in f{sub p} than 2 f{sub p} emission, possibly explaining the often observed type IIIb-III harmonic pairs as being where intensifications in 2 f{sub p} radiation are not resolved observationally. Larger turbulence levels producing trough-peak regions in the plasma density profile may lead to broader, resolvable intensifications in 2 f{sub p} radiation, which may account for the type IIIb-IIIb pairs that are sometimes observed.

  15. Impact of biogenic amine molecular weight and structure on surfactant adsorption at the air-water interface.

    PubMed

    Penfold, Jeffrey; Thomas, Robert K; Li, Peixun

    2016-02-01

    The oligoamines, such as ethylenediamine to pentaethylenetetramine, and the aliphatic biogenic amines, such as putrescine, spermidine and spermine, strongly interact with anionic surfactants, such as sodium dodecylsulfate, SDS. It has been shown that this results in pronounced surfactant adsorption at the air-water interface and the transition from monolayer to multilayer adsorption which depends upon solution pH and oligoamine structure. In the neutron reflectivity, NR, and surface tension, ST, results presented here the role of the oligoamine structure on the adsorption of SDS is investigated more fully using a range of different biogenic amines. The effect of the extent of the intra-molecular spacing between amine groups on the adsorption has been extended by comparing results for cadavarine with putrescine and ethylenediamine. The impact of more complex biogenic amine structures on the adsorption has been investigated with the aromatic phenethylamine, and the heterocyclic amines histamine and melamine. The results provide an important insight into how surfactant adsorption at interfaces can be manipulated by the addition of biogenic amines, and into the role of solution pH and oligoamine structure in modifying the interaction between the surfactant and oligoamine. The results impact greatly upon potential applications and in understanding some of the important biological functions of biogenic amines.

  16. Local Structure Around Te in Heavily Doped GaAs:Te using X-Ray Absorption Fine Structure

    SciTech Connect

    Pietnoczka, A.; Bacewicz, R.; Slupinski, T.; Antonowicz, J.; Wei, Su-Huai

    2012-04-01

    The annealing of heavily doped GaAs:Te can significantly change the free electron concentration in a reversible manner. These changes of electrical properties are accompanied by the structural changes of GaAs:Te solid solution. We used X-ray Absorption Fine Structure at K-edge of tellurium to determine local changes around Te atoms for different states of the GaAs:Te crystals caused by the annealing corresponding to different electron concentrations. The best EXAFS fit for the samples with high electron concentration was obtained for the substitutional Te{sub As} model with elongated Te-Ga bonds (as compared to the As-Ga distance). For the samples in the low concentration state the best fit was for the pairs of Te atoms forming a rhombohedral symmetry double-DX centre, with the proportional admixture of the substitutional tellurium.

  17. Enhancing gas adsorption and separation capacity through ligand functionalization of microporous metal-organic framework structures.

    PubMed

    Zhao, Yonggang; Wu, Haohan; Emge, Thomas J; Gong, Qihan; Nijem, Nour; Chabal, Yves J; Kong, Lingzhu; Langreth, David C; Liu, Hui; Zeng, Heping; Li, Jing

    2011-04-26

    Hydroxyl- and amino- functionalized [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O leads to two new structures, [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O (BDC=terephthalic acid, TED=triethylenediamine, BDC-OH=2-hydroxylterephthalic acid, BDC-NH(2)=2-aminoterephthalic acid). Single-crystal X-ray diffraction and powder X-ray diffraction studies confirmed that the structures of both functionalized compounds are very similar to that of their parent structure. Compound [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O can be considered a 3D porous structure with three interlacing 1D channels, whereas both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O contain only 1D open channels as a result of functionalization of the BDC ligand by the OH and NH(2) groups. A notable decrease in surface area and pore size is thus observed in both compounds. Consequently, [Zn(BDC)(TED)(0.5)]·2DMF·0.2H(2)O takes up the highest amount of H(2) at low temperatures. Interestingly, however, both [Zn(BDC-OH)(TED)(0.5)]·1.5DMF·0.3H(2)O and [Zn(BDC-NH(2))(TED)(0.5)]·xDMF·yH(2)O show significant enhancement in CO(2) uptake at room temperature, suggesting that the strong interactions between CO(2) and the functionalized ligands, indicating that surface chemistry, rather than porosity, plays a more important role in CO(2) adsorption. A comparison of single-component CO(2), CH(4), CO, N(2), and O(2) adsorption isotherms demonstrates that the adsorption selectivity of CO(2) over other small gases is considerably enhanced through functionalization of the frameworks. Infrared absorption spectroscopic measurements and theoretical calculations are also carried out to assess the effect of functional groups on CO(2) and H(2) adsorption potentials.

  18. Fine fragmentation distribution from structural reactive material casings under explosive loading

    NASA Astrophysics Data System (ADS)

    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.

  19. Fine structure and functional comments of mouthparts in Platypus cylindrus (Col., Curculionidae: Platypodinae).

    PubMed

    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.

  20. He i Vector Magnetic Field Maps of a Sunspot and Its Superpenumbral Fine-Structure

    NASA Astrophysics Data System (ADS)

    Schad, T. A.; Penn, M. J.; Lin, H.; Tritschler, A.

    2015-06-01

    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 because superpenumbral Stokes profiles are dominated by atomic-level polarization, while sunspot profiles are Zeeman-dominated, but also exhibit signatures that might be 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 furthermore show that the superpenumbral magnetic field does not appear to be finely structured, unlike the observed intensity structure. This suggests that fibrils are not concentrations of magnetic flux, but are instead distinguished by individualized thermalization. We also directly compare our inverted values with a current-free extrapolation of the chromospheric field. With improved measurements in the future, the average shear angle between the inferred magnetic field and the potential field may offer a means to quantify the non-potentiality of the chromospheric magnetic field to study the onset of explosive solar phenomena.

  1. Manipulation of Optoelectronic Properties and Band Structure Engineering of Ultrathin Te Nanowires by Chemical Adsorption.

    PubMed

    Roy, Ahin; Amin, Kazi Rafsanjani; Tripathi, Shalini; Biswas, Sangram; Singh, Abhishek K; Bid, Aveek; Ravishankar, N

    2017-01-13

    Band structure engineering is a powerful technique both for the design of new semiconductor materials and for imparting new functionalities to existing ones. In this article, we present a novel and versatile technique to achieve this by surface adsorption on low dimensional systems. As a specific example, we demonstrate, through detailed experiments and ab initio simulations, the controlled modification of band structure in ultrathin Te nanowires due to NO2 adsorption. Measurements of the temperature dependence of resistivity of single ultrathin Te nanowire field-effect transistor (FET) devices exposed to increasing amounts of NO2 reveal a gradual transition from a semiconducting to a metallic state. Gradual quenching of vibrational Raman modes of Te with increasing concentration of NO2 supports the appearance of a metallic state in NO2 adsorbed Te. Ab initio simulations attribute these observations to the appearance of midgap states in NO2 adsorbed Te nanowires. Our results provide fundamental insights into the effects of ambient on the electronic structures of low-dimensional materials and can be exploited for designing novel chemical sensors.

  2. Tunable Porous Organic Crystals: Structural Scope and Adsorption Properties of Nanoporous Steroidal Ureas

    PubMed Central

    2013-01-01

    Previous work has shown that certain steroidal bis-(N-phenyl)ureas, derived from cholic acid, form crystals in the P61 space group with unusually wide unidimensional pores. A key feature of the nanoporous steroidal urea (NPSU) structure is that groups at either end of the steroid are directed into the channels and may in principle be altered without disturbing the crystal packing. Herein we report an expanded study of this system, which increases the structural variety of NPSUs and also examines their inclusion properties. Nineteen new NPSU crystal structures are described, to add to the six which were previously reported. The materials show wide variations in channel size, shape, and chemical nature. Minimum pore diameters vary from ∼0 up to 13.1 Å, while some of the interior surfaces are markedly corrugated. Several variants possess functional groups positioned in the channels with potential to interact with guest molecules. Inclusion studies were performed using a relatively accessible tris-(N-phenyl)urea. Solvent removal was possible without crystal degradation, and gas adsorption could be demonstrated. Organic molecules ranging from simple aromatics (e.g., aniline and chlorobenzene) to the much larger squalene (Mw = 411) could be adsorbed from the liquid state, while several dyes were taken up from solutions in ether. Some dyes gave dichroic complexes, implying alignment of the chromophores in the NPSU channels. Notably, these complexes were formed by direct adsorption rather than cocrystallization, emphasizing the unusually robust nature of these organic molecular hosts. PMID:24147834

  3. Fine-Scale Density Wave Structure of Saturn's Main Rings: A Hydrodynamic Theory

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny; Gedalin, Michael

    The theoretical studies of Maxwell (1859) have showed that the rings around Saturn could not be solid or liquid, but rather a swarm of millions of individual particles rotating in separate concentric orbits at different speeds. A modern very popular model of the particles in Saturn's rings is a smooth ice sphere, whose restitution coefficient is quite high (exceeding 0.63) and decreases as the collision velocity increases. In this work, the linear stability of the Saturnian ring disk of mutually gravitating and physically colliding particles is examined with special emphasis on its fine-scale of the order of 100 m density wave structure, that is, almost regularly spaced, aligned cylindric density enhancements and optically-thin zones with the width and the spacing between them of roughly several tens particle diameters. Jeans' instabilities of small-amplitude gravity perturbations (e.g., those produced by a spontaneous disturbance) are analyzed analytically through the use of Navier-Stokes dynamical equations of a compressible fluid. An essential feature of this study is that the theory is not restricted by any assumptions regarding the thickness of the system. The simple model of the system is considered: the ring disk is considered to be thin, a weakly spatially inhomogeneous, and its structure is considered in a horizontally local short-wave approximation. We show that the disk is probably unstable and gravity perturbations grow effectively within a few orbital periods; self-gravitation plays a key role in the formation of the fine-scale structure while particle collisions play a secondary role. The predictions of the theory are compared with recent observations of Saturn's rings by the Cassini spacecraft and are found to be in good agreement. Particulary, it appears very likely that some of the microstructures observed in Saturn's A and B rings -both axisymmetric and nonaxisymmetric ones -are manifestations of these effects produced by Jeans' gravitational

  4. Hall effect and fine structures in magnetic reconnection with high plasma {beta}

    SciTech Connect

    Jin, S.P.; Yang, H.A.; Wang, X.G.

    2005-04-15

    Magnetic reconnection with various plasma {beta} (the ratio of plasma pressure to the magnetic pressure) is studied numerically using a 2.5 dimensional Hall magnetohydrodynamics (MHD) code developed from a multistep implicit scheme. The initial state of the Hall MHD simulation is an equilibrium Harris sheet with L{sub c}=0.5d{sub i} (where L{sub c} is the half-width of the equilibrium current layer and d{sub i} is the ion inertial length) and a zero guide field (i.e., B{sub y0}=0 at t=0). Driven by a constant boundary inflow a quasisteady fast reconnection occurs in the plasma with a low uniform resistivity. The out-of-plane magnetic field component B{sub y} is then spontaneously generated and its quadrupolar structure is shown around the X point. It is demonstrated by the comparing studies that the reconnection dynamics is controlled by the Hall effect and the effect of scalar electron pressure gradient is negligible in the generalized Ohm's law. It is also found that the openness of the magnetic separatrix angle and associated quadrupolar B{sub y} structure is enlarged as {beta} increases. When {beta}>2.0 fine structures of B{sub y} contours with reversed sign emerge. The numerical results indicate that the variations in electron velocity V{sub e} are greater than those in ion velocity V{sub i} and the decoupling of electron and ion occurs in larger scale lengths than d{sub i} as {beta} increases. Clearly, the reserve current, which is associated with the relative motion between electrons and ions, generates the fine structures of B{sub y} contours in the outflow region. Then the corresponding profile of B{sub y} component exhibits a static whistler wave signature. Enhanced wave activities observed during a Cluster crossing of the high-{beta} exterior cusp region [Y. Khotyaintsev, A. Vaivads, Y. Ogawa, B. Popielawska, M. Andre, S. Buchert, P. Decreau, B. Lavraud, and H. Reme, Ann. Geophys. 22, 2403 (2004)] might be related to the Hall effects of magnetic

  5. Fine Structures and Kinematics of an Intriguing Chromospheric Jet Observed by Hinode Solar Optical Telescope

    NASA Astrophysics Data System (ADS)

    Liu, W.; Berger, T. E.; Title, A. M.; Tarbell, T. D.

    2009-12-01

    Transient, small-scale ejections of plasma from the lower atmosphere are common manifestations of solar activity. Hinode, with its superior resolutions, has spurred renewed interest in solar jets since its launch. Here we report a chromospheric jet lasting for more than 1 hr on 2007 February 9 observed by the Hinode Solar Optical Telescope (SOT) in unprecedented detail. SOT Ca II H passband observations at high resolution of 0.2 arcsecond and cadence of 8 s allowed us to investigate the fine structures and kinematics of the jet. The ejection occurred in three episodes, rather than continuously, with the amount and velocity of material decreasing with time. The upward velocities along the jet range from ~440 to ~30 km/s, while the downward velocities of the material falling back have much smaller values (mean: -60 km/s) and a narrower distribution. Some tracks in the space-time plot clearly show parabolic shapes and the inferred acceleration is a fraction of the solar gravitational acceleration. The jet consists of fine threads (0.5-2 arcsecond wide), which exhibit coherent, oscillatory transverse motions perpendicular to the jet axis and about a common equilibrium position. These motions propagate upward, with the maximum phase speed of ~740 km/s found at the leading front of the jet. The transverse oscillation velocities range from 150 to 30 km/s, amplitudes from 6 to 2 Mm, and periods from 250 to 550 s. The oscillations slow down with time and cease when the material starts to fall back. The falling material travels along almost straight lines in the original direction of ascent, showing no transverse motions. These observations are consistent with the models suggested by Shibata & Uchida (1985) and Canfield et al. (1996). In this scenario, the jet involves untwisting helical threads, which rotate about the axis of a single large cylinder and shed magnetic helicity into the upper atmosphere. Implications of this event in the context of multiwavelength data in H

  6. Effects of crystalline structures and surface functional groups on the adsorption of haloacetic acids by inorganic materials.

    PubMed

    Punyapalakul, Patiparn; Soonglerdsongpha, Suwat; Kanlayaprasit, Chutima; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha

    2009-11-15

    The effects of the crystalline structure and surface functional groups of porous inorganic materials on the adsorption of dichloroacetic acid (DCAA) were evaluated by using hexagonal mesoporous silicates (HMS), two surface functional group (3-aminopropyltriethoxy- and 3-mercaptopropyl-) modified HMSs, faujasite Y zeolite and activated alumina as adsorbents, and compared with powdered activated carbon (PAC). Selective adsorption of HAA(5) group was studied by comparing single and multiple-solute solution, including effect of common electrolytes in tap water. Adsorption capacities were significantly affected by the crystalline structure. Hydrogen bonding is suggested to be the most important attractive force. Decreasing the pH lower than the pH(zpc) increased the DCAA adsorption capacities of these adsorbents due to electrostatic interaction and hydrogen bonding caused by protonation of the hydronium ion. Adsorption capacities of HAA(5) on HMS did not relate to molecular structure of HAA(5). Common electrolytes did not affect the adsorption capacities and selectivity of HMS for HAA5, while they affected those of PAC.

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

    SciTech Connect

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

    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.

  8. Effects of ammonium hydroxide on the structure and gas adsorption of nanosized Zr-MOFs (UiO-66).

    PubMed

    Abid, Hussein Rasool; Ang, Ha Ming; Wang, Shaobin

    2012-05-21

    Several zirconium-based metal-organic frameworks (Zr-MOFs) have been synthesized using ammonium hydroxide as an additive in the synthesis process. Their physicochemical properties have been characterized by N(2) adsorption/desorption, XRD, SEM, FTIR, and TGA, and their application in CO(2) adsorption was evaluated. It was found that addition of ammonium hydroxide produced some effects on the structure and adsorption behavior of Zr-MOFs. The pore size and pore volume of Zr-MOFs were enhanced with the additive, however, specific surface area of Zr-MOFs was reduced. Using an ammonium hydroxide additive, the crystal size of Zr-MOF was reduced with increasing amount of the additive. All the samples presented strong thermal stability. Adsorption tests showed that capacity of CO(2) adsorption on the Zr-MOFs under standard conditions was reduced due to decreased micropore fractions. However, modified Zr-MOFs had significantly lower adsorption heat. The adsorption capacity of carbon dioxide was increased at high pressure, reaching 8.63 mmol g(-1) at 987 kPa for Zr-MOF-NH(4)-2.

  9. Effects of structural connectivity on fine scale population genetic structure of muskrat, Ondatra zibethicus.

    PubMed

    Laurence, Sophie; Smith, Matthew J; Schulte-Hostedde, Albrecht I

    2013-09-01

    In heterogeneous landscapes, physical barriers and loss of structural connectivity have been shown to reduce gene flow and therefore lead to population structuring. In this study, we assessed the influence of landscape features on population genetic structure and gene flow of a semiaquatic species, the muskrat. A total of 97 muskrats were sampled from three watersheds near Sudbury, Ontario, Canada. We estimated population genetic structure using 11 microsatellite loci and identified a single genetic cluster and no genetic differences were found among the watersheds as a result of high levels of gene flow. At finer scales, we assessed the correlation between individual pairwise genetic distances and Euclidean distance as well as different models of least cost path (LCP). We used a range of cost values for the landscape types in order to build our LCP models. We found a positive relationship between genetic distance and least cost distance when we considered roads as corridors for movements. Open landscapes and urban areas seemed to restrict but not prevent gene flow within the study area. Our study underlines the high-dispersal ability of generalist species in their use of landscape and highlights how landscape features often considered barriers to animal movements are corridors for other species.

  10. FINE STRUCTURAL OBSERVATIONS RELATING TO THE PRODUCTION OF COLOR BY THE IRIDOPHORES OF A LIZARD, ANOLIS CAROLINENSIS

    PubMed Central

    Rohrlich, Susannah T.; Porter, Keith R.

    1972-01-01

    This paper presents the results of light and electron microscopy done on iridophores in the dorsal skin of the lizard Anolis carolinensis. New fine-structural details are revealed, and their importance is discussed. Of some interest is the complex of filaments between crystalline sheets in the cell. It is proposed that this complex is involved in the arrangement of crystals into crystalline sheets, and that the crystal arrangement and spacing are critical for the production of the cells' blue-green color. Tyndall scattering and thin-film interference are discussed as possible explanations for iridophore color production in relation to the fine-structural data obtained. PMID:5013601

  11. Fine Structure of the Gamow-Teller Resonance in {sup 90}Nb and Level Density of 1{sup +} States

    SciTech Connect

    Kalmykov, Y.; Neumann-Cosel, P. von; Ponomarev, V.Yu.; Richter, A.; Shevchenko, A.; Wambach, J.; Adachi, T.; Fujita, Y.; Shimbara, Y.; Berg, G.P.A.; Fujita, K.; Hatanaka, K.; Kamiya, J.; Nakanishi, K.; Sakamoto, N.; Sakemi, Y.; Shimizu, Y.; Wakasa, T.; Fujita, H.; Smit, F.D.

    2006-01-13

    The fine structure of the Gamow-Teller resonance in a medium-heavy nucleus is observed for the first time in a high-resolution {sup 90}Zr({sup 3}He,t){sup 90}Nb experiment at the Research Center for Nuclear Physics, Osaka. Using a novel wavelet analysis technique, it is possible to extract characteristic energy scales and to quantify their relative importance for the generation of the fine structure. This method combined with the selectivity of the reaction permits an extraction of the level density of 1{sup +} states in {sup 90}Nb.

  12. Spatial structure determination of ({radical}3 x {radical}3)R30{degrees} and (1.5 x 1.5)R18{degrees}CO on Cu(111) using angle-resolved photoemission extended fine structure

    SciTech Connect

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A.

    1997-04-01

    The authors report a study of the spatial structure of ({radical}3 x {radical}3)R30{degrees} (low coverage) and (1.5 x 1.5)R18{degrees} (intermediate coverage) CO adsorbed on Cu(111), using the Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) technique at beamline 9.3.2 at the Advanced Light Source. The CO molecule adsorbs on an atop site for both adsorption phases. Full multiple-scattering spherical-wave (MSSW) calculations were used to extract the C-Cu. bond length and the first Cu-Cu layer spacing for each adsorption phase. The authors find that the C-Cu bond length remains unchanged with increasing coverage, but the 1st Cu-Cu layer spacing contracts at the intermediate coverage. They calculate the bending mode force constant in the (1.5 x 1.5)R18{degrees} phase to be K{sub {delta}} = 2.2 (1) x 10{sup {minus}12} dyne-cm/rad from their experimentally determined bond lengths combined with previously published infra-red absorption frequencies.

  13. Regulation of the Demographic Structure in Isomorphic Biphasic Life Cycles at the Spatial Fine Scale

    PubMed Central

    Vieira, Vasco Manuel Nobre de Carvalho da Silva; Mateus, Marcos Duarte

    2014-01-01

    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. PMID:24658603

  14. Unresolved Fine-scale Structure in Solar Coronal Loop-tops

    NASA Astrophysics Data System (ADS)

    Scullion, E.; Rouppe van der Voort, L.; Wedemeyer, S.; Antolin, P.

    2014-12-01

    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.

  15. Unresolved fine-scale structure in solar coronal loop-tops

    SciTech Connect

    Scullion, E.; Van der Voort, L. Rouppe; Wedemeyer, S.; Antolin, P.

    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.

  16. Fine-scale genetic structure of Triatoma infestans in the Argentine Chaco.

    PubMed

    Piccinali, Romina Valeria; Gürtler, Ricardo Esteban

    2015-08-01

    The patterns of genetic structure in natural populations provide essential information for the improvement of pest management strategies including those targeting arthropod vectors of human diseases. We analyzed the patterns of fine-scale genetic structure in Triatoma infestans in a well-defined rural area close to Pampa del Indio, in the Argentine Arid-Humid Chaco transition, where a longitudinal study on house infestation and wing geometric morphometry is being conducted since 2007. A total of 228 insects collected in 16 domestic and peridomestic sites from two rural communities was genotyped for 10 microsatellite loci and analyzed. We did not find departures from Hardy-Weinberg expectations in collection sites, with three exceptions probably due to null alleles and substructuring. Domestic sites were more variable than peridomestic sites suggesting the presence of older bug populations in domestic sites or higher effective population sizes. Significant genetic structure was detected using F-statistics, a discriminant analysis of principal components and Bayesian clustering algorithms in an area of only 6.32 km(2). Microsatellite markers detected population structuring at a finer geographic scale (180-6300 m) than a previous study based on wing geometric morphometry (>4000 m). The spatial distribution of genetic variability was more properly explained by a hierarchical island than by an isolation-by-distance model. This study illustrates that, despite more than a decade without vector control interventions enhancing differentiation, genetic structure can be detected in T. infestans populations, particularly applying spatial information. This supports the potential of genetic studies to provide key information for hypothesis testing of the origins of house reinfestation.

  17. Surface adsorption of lattice HP proteins: Thermodynamics and structural transitions using Wang-Landau sampling

    NASA Astrophysics Data System (ADS)

    Li, Ying Wai; Wüst, Thomas; Landau, David P.

    2012-12-01

    Wang-Landau sampling has been applied to investigate the thermodynamics and structural properties of a lattice hydrophobic-polar heteropolymer (the HP protein model) interacting with an attractive substrate. For simplicity, we consider a short HP sequence consisting of only 36 monomers interacting with a substrate which attracts all monomers in the sequence. The conformational “phase transitions” have been identified by a canonical analysis of the specific heat and suitable structural observables. Three major “transitions”, namely, adsorption, hydrophobic core formation and “flattening” of adsorbed structures, are observed. Depending on the surface attractive strength relative to the intra-protein attraction among the H monomers, these processes take place in different sequences upon cooling.

  18. Rotational and Fine Structure of Pseudo-Jahn Molecules with C_1 Symmetry

    NASA Astrophysics Data System (ADS)

    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

  19. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy for mapping nano-scale distribution of organic carbon forms in soil: Application to black carbon particles

    NASA Astrophysics Data System (ADS)

    Lehmann, Johannes; Liang, Biqing; Solomon, Dawit; Lerotic, Mirna; LuizãO, Flavio; Kinyangi, James; SchäFer, Thorsten; Wirick, Sue; Jacobsen, Chris

    2005-03-01

    Small-scale heterogeneity of organic carbon (C) forms in soils is poorly quantified since appropriate analytical techniques were not available up to now. Specifically, tools for the identification of functional groups on the surface of micrometer-sized black C particles were not available up to now. Scanning Transmission X-ray Microscopy (STXM) using synchrotron radiation was used in conjunction with Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy to investigate nano-scale distribution (50-nm resolution) of C forms in black C particles and compared to synchrotron-based FTIR spectroscopy. A new embedding technique was developed that did not build on a C-based embedding medium and did not pose the risk of heat damage to the sample. Elemental sulfur (S) was melted to 220°C until it polymerized and quenched with liquid N2 to obtain a very viscous plastic S in which the black C could be embedded until it hardened to a noncrystalline state and was ultrasectioned. Principal component and cluster analysis followed by singular value decomposition was able to resolve distinct areas in a black carbon particle. The core of the studied biomass-derived black C particles was highly aromatic even after thousands of years of exposure in soil and resembled the spectral characteristics of fresh charcoal. Surrounding this core and on the surface of the black C particle, however, much larger proportions of carboxylic and phenolic C forms were identified that were spatially and structurally distinct from the core of the particle. Cluster analysis provided evidence for both oxidation of the black C particle itself as well as adsorption of non-black C. NEXAFS spectroscopy has great potential to allow new insight into black C properties with important implications for biogeochemical cycles such as mineralization of black C in soils and sediments, and adsorption of C, nutrients, and pollutants as well as transport in the geosphere, hydrosphere, and atmosphere.

  20. Significant spatial aggregation and fine-scale genetic structure in the homosporous fern Cyrtomium falcatum (Dryopteridaceae).

    PubMed

    Chung, Mi Yoon; Chung, Myong Gi

    2013-08-01

    Spores of homosporous ferns are small, wind-borne and thus have the potential for long-distance dispersal. This common perception has led to a prediction of near-random spatial genetic structure within fern populations. Spore dispersal and spore bank studies, however, indicate that most spores fall close to the maternal plant (< 5 m), supporting a prediction of significant fine-scale genetic structure (FSGS) within populations. To determine which of these two hypotheses is more likely to occur in nature, we measured inbreeding and quantified the spatial distribution of individuals and allozyme-based genotypes using spatial autocorrelation methods within four populations of the fern Cyrtomium falcatum in southern South Korea. Inbreeding levels were low, and all populations exhibited significant aggregation of individuals and strong FSGS. The present results support the second hypothesis, and the substantial FSGS in C. falcatum could reflect the unique features of most homosporous ferns (outcrossing mating systems that lead a majority of spores to occur at short distances and a very limited dispersal distance of male gametes). Although fern spores are physically analogous to orchid seeds, the intensity of FSGS exhibited in C. falcatum is four times stronger than that in 16 terrestrial orchid species.

  1. Characterization of a bioactive polysaccharide from Ganoderma atrum: Re-elucidation of the fine structure.

    PubMed

    Zhang, Hui; Nie, Shaoping; Cui, Steve W; Xu, Ming; Ding, Huihuang; Xie, Mingyong

    2017-02-20

    The fine structure in terms of backbone and branch chain features of a bioactive polysaccharide from Ganoderma atrum (PSG-1) was re-elucidated systematically using high performance anion-exchange chromatography (HPAEC), methylation and GLC-MS analysis, and 1D & 2D NMR spectroscopy. Monosaccharide composition analysis revealed that PSG-1-F0.2 fraction mainly consisted of glucose (73.8%) and glucuronic acid (15.3%), with small amount of mannose (5.7%) and galactose (5.2%). Based on methylation, multistep partial acid hydrolysis and NMR study, were proposed to substitute at the O-6 position of β-(1→3)-glucan. The small amount of mannose and galactose residues were considered to be from the other fraction in PSG which was very difficult to be separated from PSG-1-F0.2. This revised structure as an acidic β-(1→3, 1→6)-glucan is considered to be more accurate than the previous proposal of PSG-1.

  2. Electronic fine structure in the nickel carbide superconductor Th2NiC2

    NASA Astrophysics Data System (ADS)

    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.

  3. Fine-Scale Human Population Structure in Southern Africa Reflects Ecogeographic Boundaries.

    PubMed

    Uren, Caitlin; Kim, Minju; Martin, Alicia R; Bobo, Dean; Gignoux, Christopher R; van Helden, Paul D; Möller, Marlo; Hoal, Eileen G; Henn, Brenna M

    2016-09-01

    Recent genetic studies have established that the KhoeSan populations of southern Africa are distinct from all other African populations and have remained largely isolated during human prehistory until ∼2000 years ago. Dozens of different KhoeSan groups exist, belonging to three different language families, but very little is known about their population history. We examine new genome-wide polymorphism data and whole mitochondrial genomes for >100 South Africans from the ≠Khomani San and Nama populations of the Northern Cape, analyzed in conjunction with 19 additional southern African populations. Our analyses reveal fine-scale population structure in and around the Kalahari Desert. Surprisingly, this structure does not always correspond to linguistic or subsistence categories as previously suggested, but rather reflects the role of geographic barriers and the ecology of the greater Kalahari Basin. Regardless of subsistence strategy, the indigenous Khoe-speaking Nama pastoralists and the N|u-speaking ≠Khomani (formerly hunter-gatherers) share ancestry with other Khoe-speaking forager populations that form a rim around the Kalahari Desert. We reconstruct earlier migration patterns and estimate that the southern Kalahari populations were among the last to experience gene flow from Bantu speakers, ∼14 generations ago. We conclude that local adoption of pastoralism, at least by the Nama, appears to have been primarily a cultural process with limited genetic impact from eastern Africa.

  4. Angle-resolved photoemission extended fine structure: Multiple layers of emitters and multiple initial states

    SciTech Connect

    Huff, W.R.A.; Kellar, S.A.; Moler, E.J. |; Chen, Y.; Wu, H.; Shirley, D.A.; Hussain, Z.

    1995-08-01

    Recently, angle-resolved photoemission extended fine structure (ARPEFS) has been applied to experimental systems involving multiple layers of emitters and non-s core-level photoemission in an effort to broaden the utility of the technique. Most of the previous systems have been comprised of atomic or molecular overlayers adsorbed onto a single-crystal, metal surface and the photoemission data were taken from an s atomic core-level in the overlayer. For such a system, the acquired ARPEFS data is dominated by the p{sub o} final state wave backscattering from the substrate atoms and is well understood. In this study, we investigate ARPEFS as a surface-region structure determination technique when applied to experimental systems comprised of multiple layers of photoemitters and arbitrary initial state core-level photoemission. Understanding the data acquired from multiple layers of photoemitters is useful for studying multilayer interfaces, ''buried'' surfaces, and clean crystals in ultra- high vacuum. The ability to apply ARPEFS to arbitrary initial state core-level photoemission obviously opens up many systems to analysis. Efforts have been ongoing to understand such data in depth. We present clean Cu(111) 3s, 3p, and 3d core-level, normal photoemission data taken on a high resolution soft x-ray beamline 9.3.2 at the Advanced Light Source in Berkeley, California and clean Ni(111) 3p normal photoemission data taken at the National Synchrotron Light Source in Upton, New York, USA.

  5. Extended x-ray absorption fine structure studies of IBS Fe--Tb alloy films

    SciTech Connect

    Harris, V.G.; Aylesworth, K.D.; Kim, K.H.; Elam, W.T.; Koon, N.C. )

    1991-11-15

    We have employed extended x-ray absorption fine structure (EXAFS) analysis to study the compositional dependence of the atomic structure in Fe--Tb alloy films. Fourier transforms of EXAFS data, relative to both the Fe {ital K} and the Tb {ital L}{sub III} absorption edges, provide information about the local atomic environments relative to each atom. Results indicate the Fe EXAFS data to be dominated by Fe--Fe correlations, and consists of contributions from two Fe atomic shells at radial distances near 2.47 and 2.66 A and a Tb shell near 2.91 A. The coordination number of the Fe shells are measured to increase, while radial distances decrease, with increased Fe content. The Tb EXAFS data was found to have an atomic shells of Fe and Tb at 2.91 and 3.47 A, respectively. Analysis suggests that the Fe shell is very disordered and is comprised of approximately 9.5 atoms while the Tb shell has {approx}3 atoms.

  6. The fine structure of Langmuir waves observed upstream of the bow shock at Venus

    NASA Technical Reports Server (NTRS)

    Hospodarsky, G. B.; Gurnett, D. A.; Kurth, W. S.; Kivelson, M. G.; Strangeway, R. J.; Bolton, S. J.

    1994-01-01

    Highly structured Langmuir waves, also known as electron plasma oscillations, have been observed in the foreshock of Venus using the plasma wave experiment on the Galileo spacecraft during the gravity assist flyby on February 10, 1990. The Galileo wideband sampling system provides digital electric field waveform measurements at sampling rates up to 201,600 samples per second, much higher than any previous instrument of this type. The main Langmuir wave emission band occurs near the local electron plasma frequency, which was approximately 43 kHz. The Langmuir waves are observed to shift above and below the plasma frequency, sometimes by as much as 20 kHz. The shifts in frequency are closely correlated with the downstream distance from the tangent field line, implying that the shifts are controlled by the electron beam velocity. Considerable fine structure is also evident, with time scales as short as 0.15 milliseconds, corresponding to spatial scales of a few tens of Debye lengths. The frequency spectrum often consists of beat-type waveforms, with beat frequencies ranging from 0.2 to 7 kHz, and in a few cases, isolated wavepackets. The peak electric field strengths are approximately 1 mV/m. These field strengths are too small for strongly nonlinear processes to be important. The beat-type waveforms are suggestive of a parametric decay process.

  7. Retinal pigment epithelial fine structure in the great blue heron (Ardea herodias).

    PubMed

    Braekevelt, C R; Young, D L

    1994-09-01

    The fine structure of the retinal epithelium (RPE), choriocapillaris and Bruch's membrane (complexus basalis) has been studied by light and electron microscopy in the great blue heron (Ardea herodias). In this species the RPE consists of a single layer of cuboidal cells which display numerous basal (scleral) infoldings and plentiful apical (vitreal) processes which surround photoreceptor outer segments. These epithelial cells are joined laterally by a series of tight junctions located in the mid to basal region. Within the epithelial cells, smooth endoplasmic reticulum is very abundant while rough ER is not. Mitochondria (some of which are ring-shaped) and polysomes are abundant. In light-adaptation the RPE nuclei are large vesicular and basally located while the melanosomes of these cells are almost exclusively located within the apical processes. Myeloid bodies are large and numerous and often show ribosomes on their outer surface. Bruch's membrane (complexus basalis) shows the typical pentalaminate structure noted in the majority of vertebrates except teleosts. The choriocapillary endothelium is very thin facing Bruch's membrane but is only moderately fenestrated. The majority of these fenestrations show a single-layered diaphragm but double-layered diaphragms are also noted.

  8. Supratentorial intracerebral epithelial (ependymal) cysts: review, case reports, and fine structure.

    PubMed Central

    Friede, R L; Yasargil, M G

    1977-01-01

    The paper concerns the rare supratentorial, intracerebral or convexity cysts in adults having a wall lined with an epithelium resembling ependyma. The clincopathological aspects of such cysts are reviewed from 15 published cases and two specimens of the authors which could be examined with the electronmicroscope. These cysts manifest at a median age of 46 years as progressive, space occupying lesions with a fairly rapid clinical course of about one to two years. Twelve of 17 cysts were located in the frontal lobes, most were unequivocally intracerebral and none communicated with the lateral ventricle. Microscopic examination of the cyst wall disclosed some variance in structure, the most common feature being a monolayer of ciliated cells sitting on a very thin collagen membrane. One of the present cases was unique in that the compression by the cyst had caused a shell of infarction in the encompassing tissue. The fine structure of the cysts is described and compared with that of potential host tissues from which such cysts may originate. It is concluded that the cysts arise from displaced segments of the wall of the neural tube which correspond to the sites from which the tela chorioidea forms. Images PMID:864476

  9. Fine scale mapping of the structure and composition of the Elkhorn Slough (California, USA) tidal plume

    NASA Astrophysics Data System (ADS)

    Fischer, Andrew M.; Ryan, John P.; Rienecker, Erich V.

    2017-01-01

    Fine scale mapping of the structure and composition of a tidal ebb plume from a highly modified coastal lagoon (Elkhorn Slough, California, USA) was conducted by combining in situ, observational data sets from surface underway mapping, autonomous underwater vehicle (AUV) profiles, drifter tracking and the analysis of plume structure indices. The results reveal a 6-m-deep, jet-like, sediment laden plume extending one km offshore at low tide, which becomes entrained in the prevailing nearshore circulation. The plume that exits the slough is significantly different from the water that enters the slough. The rapidly evolving discharge plume is associated with elevated and highly correlated (r = 0.93) concentrations of dissolved organic matter and nitrate. While dissolved constituents remain in the shallow plume and are transported northward with the prevailing current, sediment may settle quickly through the water column and can be transported southwestward with the littoral currents. This study illustrates the applications of AUVs, when coupled with additional datasets, for generating higher resolution observational snapshots of dynamic and ephemeral tidal plumes. The results provide unique perspective on small-scale dynamics of an estuarine plume and its influence on coastal ecology.

  10. Fine-Structure Branching in N 2 C 4 1 Sigma + U (0)

    NASA Astrophysics Data System (ADS)

    Shemansky, D. E.; Kanik, I.; Ajello, J. M.

    1995-10-01

    We report a quantitative measurement of the predissociation fraction in the N2c'41Σ+u-X1Σ+g (0, 0) band, with an experimental determination of rotational line strengths. The fine structure of the N2(c'4-X) (0, 0) band has been analyzed in optically thin laboratory emission spectra obtained from crossed electron and N2 beams. The distortion of the emission envelope from calculations based on constant rotational level radiative transition probabilities and a thermalized ground state source population has been used to obtain an estimated predissociation loss fraction of 0.15 + -0.045+0.01 for the N2 c'4 (0) level averaged over rotational structure at a neutral gas temperature of 300 K. The analysis has been aided by measurements at gas temperatures depressed over a range from 300 to 30 K. The predissociation rate is temperature dependent, caused by nonuniform predissociation at intermediate and high rotational levels. The coupling of the rotational branches, also measured quantitatively for N2 c'4 (0) for the first time in this experiment, is complicated by configuration mixing with the c3 1Πu and b1Πu states forcing strong departures from Hönl-London factors.

  11. Limited Dispersal and Significant Fine - Scale Genetic Structure in a Tropical Montane Parrot Species

    PubMed Central

    Klauke, Nadine; Schaefer, H. Martin; Bauer, Michael; Segelbacher, Gernot

    2016-01-01

    Tropical montane ecosystems are biodiversity hotspots harbouring many endemics that are confined to specific habitat types within narrow altitudinal ranges. While deforestation put these ecosystems under threat, we still lack knowledge about how heterogeneous environments like the montane tropics promote population connectivity and persistence. We investigated the fine-scale genetic structure of the two largest subpopulations of the endangered El Oro parakeet (Pyrrhura orcesi) endemic to the Ecuadorian Andes. Specifically, we assessed the genetic divergence between three sites separated by small geographic distances but characterized by a heterogeneous habitat structure. Although geographical distances between sites are small (3–17 km), we found genetic differentiation between all sites. Even though dispersal capacity is generally high in parrots, our findings indicate that dispersal is limited even on this small geographic scale. Individual genotype assignment revealed similar genetic divergence across a valley (~ 3 km distance) compared to a continuous mountain range (~ 13 km distance). Our findings suggest that geographic barriers promote genetic divergence even on small spatial scales in this endangered endemic species. These results may have important implications for many other threatened and endemic species, particularly given the upslope shift of species predicted from climate change. PMID:28033364

  12. Fine and hyperfine structure in three low-lying 3S+ states of molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Minaev, Boris; Loboda, Oleksandr; Rinkevicius, Zilvinas; Vahtras, Olav; Ågren, Hans

    The fine structure constant (electron spin-spin coupling) and the hyperfine structure parameters (electron-nuclear spin coupling, including spin-rotation and electron-nuclear quadrupole coupling) in the low-lying triplet states and of molecular hydrogen and deuterium are calculated using a recently developed technique with full configu-ration interaction and multiconfiguration self-consistent field wave functions. The second-order spin-orbit coupling contribution to the 3Σ+ states splitting is negligible, and the calculations therefore provide a good estimate of the zero-field splitting based only on the electron spin-spin coupling values. For the bound state a negligible zero-field splitting is found, in qualitative agreement with the e-a spectrum. The zero-field splitting parameter is considerable for the repulsive state (≃1 cm-1) and of intermediate size for the bound state. The isotropic hyperfine coupling constant is very large not only for the valence state (1580 MHz) but also for the Rydberg a and e triplet states (≃1400 MHz). The quadrupole coupling constants for the deuterium isotopes are negligible (0.04-0.07 MHz) for all studied triplet states. The electric dipole activity of the spin sublevels in the triplet-singlet transitions to the ground state is estimated by means of the quadratic response technique.

  13. DIRECT IMAGING OF FINE STRUCTURE IN THE CHROMOSPHERE OF A SUNSPOT UMBRA

    SciTech Connect

    Socas-Navarro, H.

    2009-05-10

    High-resolution imaging observations from the Hinode spacecraft in the Ca II H line are employed to study the dynamics of the chromosphere above a sunspot. We find that umbral flashes and other brightenings produced by the oscillation are extremely rich in fine structure, even beyond the resolving limit of our observations (0.''22). The umbra is tremendously dynamic to the point that our time cadence of 20 s does not suffice to resolve the fast lateral (probably apparent) motion of the emission source. Some bright elements in our data set move with horizontal propagation speeds of 30 km s{sup -1}. We have detected filamentary structures inside the umbra (some of which have a horizontal extension of {approx}1500 km) which, to our best knowledge, had not been reported before. The power spectra of the intensity fluctuations reveal a few distinct areas with different properties within the umbra that seem to correspond with the umbral cores that form it. Inside each one of these areas the dominant frequencies of the oscillation are coherent, but they vary considerably from one core to another.

  14. The morphology and fine structure of the giant interneurons of the wood cricket Nemobius sylvestris.

    PubMed

    Insausti, T C; Lazzari, C R; Casas, J

    2011-02-01

    The structural and ultrastructural characteristics of giant interneurons in the terminal abdominal ganglion of the cricket Nemobius sylvestris were investigated by means of cobalt and fluorescent dye backfilling and transmission electron microscopy. The projections of the 8 eight pairs of the biggest ascending interneurons (giant interneurons) are described in detail. The somata of all interneurons analyzed are located contralateral to their axons, which project to the posterior region of the terminal ganglion and arborise in the cercal glomerulus. Neuron 7-1a is an exception, because its arborisation is restricted to the anterior region of the ganglion. The fine structure of giant interneurons shows typical features of highly active cells. We observed striking indentations in the perineural layer, enabling the somata of the giant interneurons to be very close to the haemolymph. The cercal glomerulus exhibits a high diversity of synaptic contacts (i.e. axo-dendritic, axo-axonic, dendro-axonic, and dendro-dendritic), as well as areas of tight junctions. Electrical synapses seem to be present, as well as mixed synapses. The anatomical organization of the giant interneurons is finally discussed in terms of functional implications and on a comparative basis.

  15. Sorption mechanisms of zinc to calcium silicate hydrate: X-ray absorption fine structure (XAFS) investigation.

    PubMed

    Ziegler, F; Scheidegger, A M; Johnson, C A; Dähn, R; Wieland, E

    2001-04-01

    In this study, X-ray absorption fine structure (XAFS) spectroscopy has been used to further elucidate the binding mechanisms of Zn(II) to calcium silicate hydrate (C-S-H), the quantitatively most important cement mineral. Such knowledge is essential for the assessment of the longterm behavior of cement-stabilized waste materials. XAFS spectra of the Zn(II) equilibrated with C-S-H(I) for up to 28 days are best modeled by tetrahedral coordination of Zn(II) by four O atoms in the first atomic shell. Beyond the first coordination shell, data analysis of more highly concentrated samples suggests the presence of two distinct Zn distances and possibly the presence of an Si shell. On the basis of the comparison with a set of reference compounds, this coordination environment can be reasonably related to the structure of hemimorphite, a naturally occurring zinc silicate, and/or the presence of gamma-Zn(OH)2. At the lowest Zn uptake, the above fitting approach failed and data could be described best with a Zn-Si and a Zn-Ca shell. Previous work has been able to show that Zn(II) diffuses into the C-S-H(I) particles and does not form discrete precipitates, so the findings appear to confirm the incorporation of Zn(II) in the interlayer of C-S-H(I).

  16. Fine and hyperfine structure of P-wave levels in muonic hydrogen

    SciTech Connect

    Martynenko, A. P.

    2008-01-15

    Corrections of order {alpha}{sup 5} and {alpha}{sup 6} are calculated for muonic hydrogen in the fine-structure interval {Delta}E{sup fs} = E(2P{sub 3/2}) - E(2P{sub 1/2}) and in the hyperfine structure of the 2P{sub 1/2}-and 2P{sub 3/2}-wave energy levels. The resulting values of {Delta}E{sup fs} = 8352.08 Micro-Sign eV, {Delta}E-tilde {sup hfs}(2P{sub 1/2}) = 7819.80 Micro-Sign eV, and {Delta}E-tilde {sup hfs}(2P{sub 3/2}) = 3248.03 Micro-Sign eV provide reliable guidelines in performing a comparison with relevant experimental data and in more precisely extracting the experimental value of the (2P-2S) Lamb shift in the muonic-hydrogen atom.

  17. Fine-scale genetic structure of grape phylloxera from the roots and leaves of Vitis.

    PubMed

    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.

  18. Fine resolution mapping of population age-structures for health and development applications

    PubMed Central

    Alegana, V. A.; Atkinson, P. M.; Pezzulo, C.; Sorichetta, A.; Weiss, D.; Bird, T.; Erbach-Schoenberg, E.; Tatem, A. J.

    2015-01-01

    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

  19. On the adsorption properties of magnetic fluids: Impact of bulk structure

    NASA Astrophysics Data System (ADS)

    Kubovcikova, Martina; Gapon, Igor V.; Zavisova, Vlasta; Koneracka, Martina; Petrenko, Viktor I.; Soltwedel, Olaf; Almasy, László; Avdeev, Mikhail V.; Kopcansky, Peter

    2017-04-01

    Adsorption of nanoparticles from magnetic fluids (MFs) on solid surface (crystalline silicon) was studied by neutron reflectometry (NR) and related to the bulk structural organization of MFs concluded from small-angle neutron scattering (SANS). The initial aqueous MF with nanomagnetite (co-precipitation reaction) stabilized by sodium oleate and MF modified by a biocompatible polymer, poly(ethylene glycol) (PEG), were considered. Regarding the bulk structure it was confirmed in the SANS experiment that comparatively small and compact (size 30 nm) aggregates of nanoparticle in the initial sample transfer to large and developed (size>130 nm, fractal dimension 2.7) associates in the PEG modified MF. This reorganization in the aggregates correlates with the changes in the neutron reflectivity that showed that a single adsorption layer of individual nanoparticles on the oxidized silicon surface for the initial MF disappears after the PEG modification. It is concluded that all particles in the modified fluid are in the aggregates that are not adsorbed by silicon.

  20. Sum-frequency generation of acetate adsorption on Au and Pt surfaces: Molecular structure effects

    NASA Astrophysics Data System (ADS)

    Braunschweig, Björn; Mukherjee, Prabuddha; Kutz, Robert B.; Wieckowski, Andrzej; Dlott, Dana D.

    2010-12-01

    The reversible adsorption of acetate on polycrystalline Au and Pt surfaces was investigated with broadband sum-frequency generation (SFG) and cyclic voltammetry. Specifically adsorbed acetate as well as coadsorbed sulfuric acid anions are observed for the first time with SFG and give rise to dramatically different SFG intensities on Au and Pt surfaces. While similar coverages of acetate adlayers on Au and Pt surfaces are well established by previous studies, an identification of the interfacial molecular structure has been elusive. However, we have applied the high sensitivity of SFG for interfacial polar ordering to identify different acetate structures at Au and Pt surfaces in contact with HClO4 and H2SO4 electrolytes. Acetate competes with the formation of surface oxides and shifts the oxidation threshold of both Au and Pt electrodes anodically. Effects of the supporting electrolyte on the formation of acetate adlayers are revealed by comparing SFG spectra in HClO4 and H2SO4 solutions: Sulfuric acid anions modify the potential-dependent acetate adsorption, compete with adsorbed acetate on Au and coadsorb with acetate on Pt surfaces.

  1. The empirical Bayes estimators of fine-scale population structure in high gene flow species.

    PubMed

    Kitada, Shuichi; Nakamichi, Reiichiro; Kishino, Hirohisa

    2017-02-27

    An empirical Bayes (EB) pairwise FST estimator was previously introduced and evaluated for its performance by numerical simulation. In this study, we conducted coalescent simulations and generated genetic population structure mechanistically, and compared the performance of the EBFST with Nei's GST , Nei & Chesser's bias-corrected GST (GST _NC ), Weir & Cockerham's ϴ (ϴWC ),( and ϴ with finite sample correction (ϴWC _F ). We also introduced EB estimators for Hedrick' G'ST and Jost' D. We applied these estimators to publicly available SNP genotypes of Atlantic herring. We also examined the power to detect the environmental factors causing the population structure. Our coalescent simulations revealed that the finite sample correction of ϴWC is necessary to assess population structure using pairwise FST values. For microsatellite markers, EBFST performed the best among the present estimators regarding both bias and precision under high gene flow scenarios (FST >0.032). For 300 SNPs, EBFST had the highest precision in all cases, but the bias was negative and greater than those for GST_NC and (ϴWC_F ) in all cases. GST_NC and (ϴWC_F ) performed very similarly at all levels of FST . As the number of loci increased up to 10 000, the precision of GST_NC and ϴWC_F became slightly better than for EBFST for cases with FST >0.004, even though the size of the bias remained constant. The EB estimators described the fine-scale population structure of the herring, and revealed that ~56% of the genetic differentiation was caused by sea surface temperature and salinity. The R package FINEPOP for implementing all estimators used here is available on CRAN. This article is protected by copyright. All rights reserved.

  2. Radiation effects in water ice: a near-edge x-ray absorption fine structure study.

    PubMed

    Laffon, C; Lacombe, S; Bournel, F; Parent, Ph

    2006-11-28

    The changes in the structure and composition of vapor-deposited ice films irradiated at 20 K with soft x-ray photons (3-900 eV) and their subsequent evolution with temperatures between 20 and 150 K have been investigated by near-edge x-ray absorption fine structure spectroscopy (NEXAFS) at the oxygen K edge. We observe the hydroxyl OH, the atomic oxygen O, and the hydroperoxyl HO(2) radicals, as well as the oxygen O(2) and hydrogen peroxide H(2)O(2) molecules in irradiated porous amorphous solid water (p-ASW) and crystalline (I(cryst)) ice films. The evolution of their concentrations with the temperature indicates that HO(2), O(2), and H(2)O(2) result from a simple step reaction fuelled by OH, where O(2) is a product of HO(2) and HO(2) a product of H(2)O(2). The local order of ice is also modified, whatever the initial structure is. The crystalline ice I(cryst) becomes amorphous. The high-density amorphous phase (I(a)h) of ice is observed after irradiation of the p-ASW film, whose initial structure is the normal low-density form of the amorphous ice (I(a)l). The phase I(a)h is thus peculiar to irradiated ice and does not exist in the as-deposited ice films. A new "very high density" amorphous phase-we call I(a)vh-is obtained after warming at 50 K the irradiated p-ASW ice. This phase is stable up to 90 K and partially transforms into crystalline ice at 150 K.

  3. Benthic biofilm structure controls the deposition-resuspension dynamics of fine clay particles

    NASA Astrophysics Data System (ADS)

    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 (< 10 μm) particles. 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.

  4. Segmentation and Enhancement of Latent Fingerprints: A Coarse to Fine Ridge Structure Dictionary.

    PubMed

    Cao, Kai; Liu, Eryun; Jain, Anil K

    2014-09-01

    Latent fingerprint matching has played a critical role in identifying suspects and criminals. However, compared to rolled and plain fingerprint matching, latent identification accuracy is significantly lower due to complex background noise, poor ridge quality and overlapping structured noise in latent images. Accordingly, manual markup of various features (e.g., region of interest, singular points and minutiae) is typically necessary to extract reliable features from latents. To reduce this markup cost and to improve the consistency in feature markup, fully automatic and highly accurate ("lights-out" capability) latent matching algorithms are needed. In this paper, a dictionary-based approach is proposed for automatic latent segmentation and enhancement towards the goal of achieving "lights-out" latent identification systems. Given a latent fingerprint image, a total variation (TV) decomposition model with L1 fidelity regularization is used to remove piecewise-smooth background noise. The texture component image obtained from the decomposition of latent image is divided into overlapping patches. Ridge structure dictionary, which is learnt from a set of high quality ridge patches, is then used to restore ridge structure in these latent patches. The ridge quality of a patch, which is used for latent segmentation, is defined as the structural similarity between the patch and its reconstruction. Orientation and frequency fields, which are used for latent enhancement, are then extracted from the reconstructed patch. To balance robustness and accuracy, a coarse to fine strategy is proposed. Experimental results on two latent fingerprint databases (i.e., NIST SD27 and WVU DB) show that the proposed algorithm outperforms the state-of-the-art segmentation and enhancement algorithms and boosts the performance of a state-of-the-art commercial latent matcher.

  5. FINE STRAND-LIKE STRUCTURE IN THE SOLAR CORONA FROM MAGNETOHYDRODYNAMIC TRANSVERSE OSCILLATIONS

    SciTech Connect

    Antolin, P.; Yokoyama, T.; Van Doorsselaere, T.

    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.

  6. Extended x-ray absorption fine structure studies of the atomic structure of nanoparticles in different metallic matrices.

    PubMed

    Baker, S H; Roy, M; Gurman, S J; Binns, C

    2009-05-06

    It has been appreciated for some time that the novel properties of particles in the size range 1-10 nm are potentially exploitable in a range of applications. In order to ultimately produce commercial devices containing nanosized particles, it is necessary to develop controllable means of incorporating them into macroscopic samples. One way of doing this is to embed the nanoparticles in a matrix of a different material, by co-deposition for example, to form a nanocomposite film. The atomic structure of the embedded particles can be strongly influenced by the matrix. Since some of the key properties of materials, including magnetism, strongly depend on atomic structure, the ability to determine atomic structure in embedded nanoparticles is very important. This review focuses on nanoparticles, in particular magnetic nanoparticles, embedded in different metal matrices. Extended x-ray absorption fine structure (EXAFS) provides an excellent means of probing atomic structure in nanocomposite materials, and an overview of this technique is given. Its application in probing catalytic metal clusters is described briefly, before giving an account of the use of EXAFS in determining atomic structure in magnetic nanocomposite films. In particular, we focus on cluster-assembled films comprised of Fe and Co nanosized particles embedded in various metal matrices, and show how the crystal structure of the particles can be changed by appropriate choice of the matrix material. The work discussed here demonstrates that combining the results of structural and magnetic measurements, as well as theoretical calculations, can play a significant part in tailoring the properties of new magnetic cluster-assembled materials.

  7. Structural changes of methemoglobin after adsorption on bioactive glass, as a function of surface functionalization and salt concentration

    NASA Astrophysics Data System (ADS)

    Gruian, C.; Vulpoi, A.; Steinhoff, H.-J.; Simon, S.

    2012-05-01

    Functional protein adsorption at liquid-solid interfaces has been intensively studied in the last years, however it is difficult to evidence directly conformational changes of the protein which are likely to appear upon adsorption. Spin labeling in combination with Electron Paramagnetic Resonance (EPR) spectroscopy was applied in this study to investigate adsorption of horse methemoglobin to bioactive glass (BG) similar in composition with 45S5 Bioglass®. X-band cw-EPR spectra of spin labeled methemoglobin in solution were compared to those obtained after adsorption on bioactive glass surface (functionalized and non-functionalized with glutaraldehyde), to extract information of the structure and dynamics in the vicinity of position β-93. The concentration of methemoglobin adsorbed on BG substrate was determined from the intensity of cw-EPR spectra and correlated with images obtained by Scanning Electron Microscopy (SEM). Line shape analysis of the EPR spectra revealed that ionic strength does not induce significant conformational changes in the protein structure upon adsorption, however, the chemical treatment applied to the bioactive glass surface positively influences protein adsorption.

  8. Fine-tuning of prototype chicken galectins: structure of CG-2 and structure-activity correlations.

    PubMed

    Ruiz, Federico M; Fernández, Israel S; López-Merino, Lara; Lagartera, Laura; Kaltner, Herbert; Menéndez, Margarita; André, Sabine; Solís, Dolores; Gabius, Hans Joachim; Romero, Antonio

    2013-09-01

    The comparatively small number of members of the family of adhesion/growth-regulatory galectins in chicken predestines this system as an attractive model to study the divergence of these lectins after gene duplication. Expression profiling of the three homodimeric (prototype) chicken galectins (CG-1A, CG-1B and CG-2) has raised evidence of distinct functionalities, explaining the interest in a detailed crystallographic analysis of CG-2. As revealed here, marked differences are found in the ligand-binding site and in the contact pattern within the homodimer interface, underlying a characteristic orientation of the two subunits. Notably, a distinctive trimer of dimers that is unique in all galectin crystal structures reported to date forms the core unit of the crystallographic assembly. Combination with spectroscopic and thermodynamic measurements, and comparisons with CG-1A and CG-1B, identify differential changes in the circular-dichroism spectra in the presence of lactose, reflecting the far-reaching impact of the ligand on hydrodynamic behaviour, and inter-galectin differences in both the entropy and the enthalpy of binding. This structural information is a salient step to complete the analysis of the full set of galectins from this model organism.

  9. Structural analysis of ultrafast extended x-ray absorption fine structure with subpicometer spatial resolution: Application to spin crossover complexes

    SciTech Connect

    Gawelda, W.; Bressler, C.; Pham, V.-T.; Veen, R. M. van der; Chergui, M.; Grolimund, D.; Abela, R.

    2009-03-28

    We present a novel analysis of time-resolved extended x-ray absorption fine structure (EXAFS) spectra based on the fitting of the experimental transients obtained from optical pump/x-ray probe experiments. We apply it to the analysis of picosecond EXAFS data on aqueous [Fe{sup II}(bpy){sub 3}]{sup 2+}, which undergoes a light induced conversion from its low-spin (LS) ground state to the short-lived ({tau}{approx_equal}650 ps) excited high-spin (HS) state. A series of EXAFS spectra were simulated for a collection of possible HS structures from which the ground state fit spectrum was subtracted to generate transient difference absorption (TA) spectra. These are then compared with the experimental TA spectrum using a least-squares statistical analysis to derive the structural change. This approach reduces the number of required parameters by cancellation in the differences. It also delivers a unique solution for both the fractional population and the extracted excited state structure. We thus obtain a value of the Fe-N bond elongation in the HS state with subpicometer precision (0.203{+-}0.008 A)

  10. Structural analysis of ultrafast extended x-ray absorption fine structure with subpicometer spatial resolution: application to spin crossover complexes.

    PubMed

    Gawelda, W; Pham, V-T; van der Veen, R M; Grolimund, D; Abela, R; Chergui, M; Bressler, C

    2009-03-28

    We present a novel analysis of time-resolved extended x-ray absorption fine structure (EXAFS) spectra based on the fitting of the experimental transients obtained from optical pump/x-ray probe experiments. We apply it to the analysis of picosecond EXAFS data on aqueous [Fe(II)(bpy)(3)](2+), which undergoes a light induced conversion from its low-spin (LS) ground state to the short-lived (tau approximately 650 ps) excited high-spin (HS) state. A series of EXAFS spectra were simulated for a collection of possible HS structures from which the ground state fit spectrum was subtracted to generate transient difference absorption (TA) spectra. These are then compared with the experimental TA spectrum using a least-squares statistical analysis to derive the structural change. This approach reduces the number of required parameters by cancellation in the differences. It also delivers a unique solution for both the fractional population and the extracted excited state structure. We thus obtain a value of the Fe-N bond elongation in the HS state with subpicometer precision (0.203+/-0.008 A).

  11. Novel laboratory methods for determining the fine scale electrical resistivity structure of core

    NASA Astrophysics Data System (ADS)

    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

  12. Impact of the molecular structure and adsorption mode of D-π-A dye sensitizers with a pyridyl group in dye-sensitized solar cells on the adsorption equilibrium constant for dye-adsorption on TiO2 surface.

    PubMed

    Ooyama, Yousuke; Yamaguchi, Naoya; Ohshita, Joji; Harima, Yutaka

    2016-12-07

    D-π-A dyes NI-4 bearing a pyridyl group, YNI-1 bearing two pyridyl groups and YNI-2 bearing two thienylpyridyl groups as the anchoring group on the TiO2 surface have been developed as dye sensitizers for dye-sensitized solar cells (DSSCs), where NI-4 and YNI-2 can adsorb onto the TiO2 electrode through the formation of the coordinate bond between the pyridyl group of the dye and the Lewis acid site (exposed Ti(n+) cations) on the TiO2 surface, but YNI-1 is predominantly adsorbed on the TiO2 electrode through the formation of the hydrogen bond between the pyridyl group of the dye and the Brønsted acid sites (surface-bound hydroxyl groups, Ti-OH) on the TiO2 surface. The difference in the dye-adsorption mode among the three dyes on the TiO2 surface has been investigated from the adsorption equilibrium constant (Kad) based on the Langmuir adsorption isotherms. It was found that the Kad values of YNI-1 and YNI-2 are higher than that of NI-4, and more interestingly, the Kad value of YNI-2 is higher than that of YNI-1. This work demonstrates that that for the D-π-A dye sensitizers with the pyridyl group as the anchoring group to the TiO2 surface the number of pyridyl groups and the dye-adsorption mode on the TiO2 electrode as well as the molecular structure of the dye sensitizer affect the Kad value for the adsorption of the dye to the TiO2 electrode, that is, resulting in a difference in the Kad value among the D-π-A dye sensitizers NI-4, YNI-1 and YNI-2.

  13. Causes and consequences of fine-scale population structure in a critically endangered freshwater seal

    PubMed Central

    2014-01-01

    Background Small, genetically uniform populations may face an elevated risk of extinction due to reduced environmental adaptability and individual fitness. Fragmentation can intensify these genetic adversities and, therefore, dispersal and gene flow among subpopulations within an isolated population is often essential for maintaining its viability. Using microsatellite and mtDNA data, we examined genetic diversity, spatial differentiation, interregional gene flow, and effective population sizes in the critically endangered Saimaa ringed seal (Phoca hispida saimensis), which is endemic to the large but highly fragmented Lake Saimaa in southeastern Finland. Results Microsatellite diversity within the subspecies (HE = 0.36) ranks among the lowest thus far recorded within the order Pinnipedia, with signs of ongoing loss of individual heterozygosity, reflecting very low effective subpopulation sizes. Bayesian assignment analyses of the microsatellite data revealed clear genetic differentiation among the main breeding areas, but interregional structuring was substantially weaker in biparentally inherited microsatellites (FST = 0.107) than in maternally inherited mtDNA (FST = 0.444), indicating a sevenfold difference in the gene flow mediated by males versus females. Conclusions Genetic structuring in the population appears to arise from the joint effects of multiple factors, including small effective subpopulation sizes, a fragmented lacustrine habitat, and behavioural dispersal limitation. The fine-scale differentiation found in the landlocked Saimaa ringed seal is especially surprising when contrasted with marine ringed seals, which often exhibit near-panmixia among subpopulations separated by hundreds or even thousands of kilometres. Our results demonstrate that population structures of endangered animals cannot be predicted based on data on even closely related species or subspecies. PMID:25005257

  14. A New Multibeam Sonar Technique for Evaluating Fine-Scale Fish Behavior Near Hydroelectric Dam Guidance Structures

    SciTech Connect

    Johnson, Robert L.; Simmons, Mary Ann; Simmons, Carver S.; Blanton, Susan L.; Coutant, C.

    2002-03-07

    This book chapter describes a Dual-Head Multibeam Sonar (DHMS) system developed by Battelle and deployed at two dam sites on the Snake and Columbia rivers in Washington State to evaluate the fine-scale (structures intended to facilitate downstream fish passage.

  15. A tale of two pectins: Diverse fine structures can result from identical processive PME treatments on similar high DM subtrates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effects of a processive pectin-methylesterase treatment on two different pectins, both possessing a high degree of methylesterification, were investigated. While the starting samples were purportedly very similar in fine structure, and even though the sample-averaged degree of methylesterificati...

  16. Polygamy and an absence of fine-scale structure in Dendroctonus ponderosae (Hopk.) (Coleoptera: Curcilionidae) confirmed using molecular markers.

    PubMed

    Janes, J K; Roe, A D; Rice, A V; Gorrell, J C; Coltman, D W; Langor, D W; Sperling, F A H

    2016-01-01

    An understanding of mating systems and fine-scale spatial genetic structure is required to effectively manage forest pest species such as Dendroctonus ponderosae (mountain pine beetle). Here we used genome-wide single-nucleotide polymorphisms to assess the fine-scale genetic structure and mating system of D. ponderosae collected from a single stand in Alberta, Canada. Fine-scale spatial genetic structure was absent within the stand and the majority of genetic variation was best explained at the individual level. Relatedness estimates support previous reports of pre-emergence mating. Parentage assignment tests indicate that a polygamous mating system better explains the relationships among individuals within a gallery than the previously reported female monogamous/male polygynous system. Furthermore, there is some evidence to suggest that females may exploit the galleries of other females, at least under epidemic conditions. Our results suggest that current management models are likely to be effective across large geographic areas based on the absence of fine-scale genetic structure.

  17. Properties of the prominence magnetic field and plasma distributions as obtained from 3D whole-prominence fine structure modeling

    NASA Astrophysics Data System (ADS)

    Gunár, S.; Mackay, D. H.

    2016-07-01

    Aims: We analyze distributions of the magnetic field strength and prominence plasma (temperature, pressure, plasma β, and mass) using the 3D whole-prominence fine structure model. Methods: The model combines a 3D magnetic field configuration of an entire prominence, obtained from non-linear force-free field simulations, with a detailed semi-empirically derived description of the prominence plasma. The plasma is located in magnetic dips in hydrostatic equilibrium and is distributed along multiple fine structures within the 3D magnetic model. Results: We show that in the modeled prominence, the variations of the magnetic field strength and its orientation are insignificant on scales comparable to the smallest dimensions of the observed prominence fine structures. We also show the ability of the 3D whole-prominence fine structure model to reveal the distribution of the prominence plasma with respect to its temperature within the prominence volume. This provides new insights into the composition of the prominence-corona transition region. We further demonstrate that the values of the plasma β are small throughout the majority of the modeled prominences when realistic photospheric magnetic flux distributions and prominence plasma parameters are assumed. While this is generally true, we also find that in the region with the deepest magnetic dips, the plasma β may increase towards unity. Finally, we show that the mass of the modeled prominence plasma is in good agreement with the mass of observed non-eruptive prominences.

  18. Polygamy and an absence of fine-scale structure in Dendroctonus ponderosae (Hopk.) (Coleoptera: Curcilionidae) confirmed using molecular markers

    PubMed Central

    Janes, J K; Roe, A D; Rice, A V; Gorrell, J C; Coltman, D W; Langor, D W; Sperling, F A H

    2016-01-01

    An understanding of mating systems and fine-scale spatial genetic structure is required to effectively manage forest pest species such as Dendroctonus ponderosae (mountain pine beetle). Here we used genome-wide single-nucleotide polymorphisms to assess the fine-scale genetic structure and mating system of D. ponderosae collected from a single stand in Alberta, Canada. Fine-scale spatial genetic structure was absent within the stand and the majority of genetic variation was best explained at the individual level. Relatedness estimates support previous reports of pre-emergence mating. Parentage assignment tests indicate that a polygamous mating system better explains the relationships among individuals within a gallery than the previously reported female monogamous/male polygynous system. Furthermore, there is some evidence to suggest that females may exploit the galleries of other females, at least under epidemic conditions. Our results suggest that current management models are likely to be effective across large geographic areas based on the absence of fine-scale genetic structure. PMID:26286666

  19. Variation in beta-glucan fine structure, extractability, and flour slurry viscosity in oats due to genotype and environment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Effects of genotype and environment on oats on beta-glucan extractability,flour slurry viscosity, and beta-glucan polymer fine structure were tested. Certain environments had unpredictable catastrophic effects on slurry viscosity. Learning the cause of such viscosity loss should be of high priority ...

  20. Coal froth flotation: effects of reagent adsorption on the froth structure

    SciTech Connect

    Meryem Ozmak; Zeki Aktas

    2006-05-15

    The amount and quality of concentrate obtained from froth flotation of a coal are very important to determine the efficiency of the separation process. The shape and size of the bubbles in the froth directly affect the amount and purity of the concentrate overflowed during the froth flotation of the coal. The froth structure is significantly dependent on parameters such as the size of the solid particles, the surface properties of the particles, the chemical structure of surface active agents, the reagents adsorbed onto solid particles, and the reagents remaining in water. This work was performed to determine the relationship between the reagents adsorbed on the solid particles, froth structure, and froth flotation performance. The -53 {mu}m size fraction of a bituminous coal was used to perform froth flotation experiments. The froth flotation of the coal used was performed in the presence of two nonionic surfactants, Triton x-100 (poly(ethylene glycol) tert-octylphenyl ether) and MIBC (methyl isobutyl carbinol), and an anionic surfactant, SDS (sodium dodecyl sulfate). The results showed that the adsorption of a high amount of reagent on the particles decreased the ability of separation, thus a substantial amount of mineral particles overflowed along with the hydrophobic coal particles. The use of MIBC with Triton x-100 or SDS as mixture increased solid recovery, and it was concluded that MIBC selectively adsorbed on solids acting as collector as well as a frother. Reagent adsorption has a crucial effect on the froth structure, which is strongly related to flotation performance. 33 refs., 18 figs.

  1. Structures and H2 adsorption properties of porous scandium metal-organic frameworks.

    PubMed

    Ibarra, Ilich A; Lin, Xiang; Yang, Sihai; Blake, Alexander J; Walker, Gavin S; Barnett, Sarah A; Allan, David R; Champness, Neil R; Hubberstey, Peter; Schröder, Martin

    2010-12-10

    Two new three-dimensional Sc(III) metal-organic frameworks {[Sc(3)O(L(1))(3)(H(2)O)(3)]·Cl(0.5)(OH)(0.5)(DMF)(4)(H(2)O)(3)}(∞) (1) (H(2)L(1)=1,4-benzene-dicarboxylic acid) and {[Sc(3)O(L(2))(2)(H(2)O)(3)](OH)(H(2)O)(5)(DMF)}(∞) (2) (H(3)L(2)=1,3,5-tris(4-carboxyphenyl)benzene) have been synthesised and characterised. The structures of both 1 and 2 incorporate the trinuclear trigonal planar [Sc(3)(O)(O(2)CR)(6)] building block featuring three Sc(III) centres joined by a central μ(3)-O(2-) donor. Each Sc(III) centre is further bound by four oxygen donors from four different bridging carboxylate anions, and a molecule of water located trans to the μ(3)-O(2-) donor completes the six coordination at the metal centre. Frameworks 1 and 2 show high thermal stability with retention of crystallinity up to 350 °C. The desolvated materials 1a and 2a, in which the solvent has been removed from the pores but with water or hydroxide remaining coordinated to Sc(III), show BET surface areas based upon N(2) uptake of 634 and 1233 m(2) g(-1), respectively, and pore volumes calculated from the maximum N(2) adsorption of 0.25 cm(3) g(-1) and 0.62 cm(3) g(-1), respectively. At 20 bar and 78 K, the H(2) isotherms for desolvated 1a and 2a confirm 2.48 and 1.99 wt% total H(2) uptake, respectively. The isosteric heats of adsorption were estimated to be 5.25 and 2.59 kJ mol(-1) at zero surface coverage for 1a and 2a, respectively. Treatment of 2 with acetone followed by thermal desolvation in vacuo generated free metal coordination sites in a new material 2b. Framework 2b shows an enhanced BET surface area of 1511 m(2) g(-1) and a pore volume of 0.76 cm(3) g(-1), with improved H(2) uptake capacity and a higher heat of H(2) adsorption. At 20 bar, H(2) capacity increases from 1.99 wt% in 2a to 2.64 wt% for 2b, and the H(2) adsorption enthalpy rises markedly from 2.59 to 6.90 kJ mol(-1).

  2. Characteristics of the starch fine structure and pasting properties of waxy rice during storage.

    PubMed

    Huang, Yu-Chan; Lai, Hsi-Mei

    2014-01-01

    Two waxy rice (TNW1 and TCSW1, exhibiting high and low amylase activity, respectively), were stored at 4 and 17 °C (polished rice) and at room temperature (paddy rice) for 15 months. The fine structure of starch isolated from the aged rice and the pasting properties of starch and rice flour were studied. After storage, the percentage of short amylopectin (AP) chains increased in TNW1, and no uniform changing pattern was observed in the chain-length (CL) distribution of TCSW1. The viscosity of starch isolated from the aged rice increased as the storage temperature and duration increased. We hypothesised that this increase was due to the hydrolysis of AP by endogenous amylase and the generation of small clusters during storage, which caused the simple dissociation of AP and a high swelling degree of starch granules during gelatinisation. Factor analysis of the first two factors associated with the characteristics of viscograms and the CL of AP explained 72% of the total variation.

  3. Fine structure of the landers fault zone: Segmentation and the rupture process

    USGS Publications Warehouse

    Li, Y.-G.; Vidale, J.E.; Aki, K.; Marone, C.J.; Lee, W.H.K.

    1994-01-01

    Observations and modeling of 3- to 6-hertz seismic shear waves trapped within the fault zone of the 1992 Landers earthquake series allow the fine structure and continuity of the zone to be evaluated. The fault, to a depth of at least 12 kilometers, is marked by a zone 100 to 200 meters wide where shear velocity is reduced by 30 to 50 percent. This zone forms a seismic waveguide that extends along the southern 30 kilometers of the Landers rupture surface and ends at the fault bend about 18 kilometers north of the main shock epicenter. Another fault plane waveguide, disconnected from the first, exists along the northern rupture surface. These observations, in conjunction with surface slip, detailed seismicity patterns, and the progression of rupture along the fault, suggest that several simple rupture planes were involved in the Landers earthquake and that the inferred rupture front hesitated or slowed at the location where the rupture jumped from one to the next plane. Reduction in rupture velocity can tentatively be attributed to fault plane complexity, and variations in moment release can be attributed to variations in available energy.

  4. Fine structure of the entanglement entropy in the O(2) model

    NASA Astrophysics Data System (ADS)

    Yang, Li-Ping; Liu, Yuzhi; Zou, Haiyuan; Xie, Z. Y.; Meurice, Y.

    2016-01-01

    We compare two calculations of the particle density in the superfluid phase of the O(2) model with a chemical potential μ in 1+1 dimensions. The first relies on exact blocking formulas from the Tensor Renormalization Group (TRG) formulation of the transfer matrix. The second is a worm algorithm. We show that the particle number distributions obtained with the two methods agree well. We use the TRG method to calculate the thermal entropy and the entanglement entropy. We describe the particle density, the two entropies and the topology of the world lines as we increase μ to go across the superfluid phase between the first two Mott insulating phases. For a sufficiently large temporal size, this process reveals an interesting fine structure: the average particle number and the winding number of most of the world lines in the Euclidean time direction increase by one unit at a time. At each step, the thermal entropy develops a peak and the entanglement entropy increases until we reach half-filling and then decreases in a way that approximately mirrors the ascent. This suggests an approximate fermionic picture.

  5. Sensitivity to temporal fine structure and hearing-aid outcomes in older adults

    PubMed Central

    Perez, Elvira; McCormack, Abby; Edmonds, Barrie A.

    2014-01-01

    Objective: To investigate the effect of sensitivity to temporal fine structure (TFS) on subjective measures of hearing aid outcome. Design: Prior to receiving hearing aids, participants completed a test to assess sensitivity to TFS and two self-assessment questionnaires; the Glasgow Hearing Aid Benefit Profile (GHABP), and the Speech, Spatial and Qualities of hearing (SSQ-A). Follow-up appointments, comprised three self-assessment questionnaires; 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 smaller improvement on SSQ-B over listeners with poor sensitivity to TFS. Among the questionnaires, only the SSQ showed greater sensitivity to measure subjective differences between listeners with good and 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. PMID:24550769

  6. THE FINE STRUCTURE OF SYMPATHETIC NEURONS IN X-IRRADIATED FROGS

    PubMed Central

    Pick, Joseph

    1965-01-01

    The effects of whole body x-irradiation on the fine structure of sympathetic neurons were studied in 15 unanesthetized adult frogs (Rana pipiens), as seen at intervals ranging from 1 hour to 2 weeks after single exposures to 1000 r and 2000 r. Using standard procedures, the lumbar sympathetic ganglia of experimental and 20 control animals were prepared for electron microscope examination. Radiation produced conspicuous but irregular and variable deterioration, swelling, and clearing of neuronal lysosomes. These changes may have been due to an increased permeability of lysosomal membranes, causing the entry of fluid into lysosomes and their swelling and deterioration, but a pronounced escape of lysosomal enzymes into the cytoplasm was questionable. Less frequent were the dilatation and the parallel layering or complete fusion and tight packing of the rough-edged endoplasmic reticulum. The number of vacuoles, probably derived from Golgi cisternae, was somewhat increased. These vacuoles were conjectured to serve the "sequestration" of damaged cytoplasmic areas. Abnormal amounts of presumptive glycogen granules occupied some axons of myelinated and unmyelinated fibers, especially of presynaptic nerve fibers. This was assumed to be due to a decreased breakdown of glycogen and probably caused the interruption of the transmission of nerve impulses in presynaptic fibers. The maximal incidence of these alterations seemingly occurred 8 days after exposure to 1000 r, and 1 hour after x-irradiation with 2000 r. Signs of recovery appeared 2 weeks after exposure to 2000 r. PMID:5865928

  7. Dual-carrier processing to convey temporal fine structure cues: Implications for cochlear implants

    PubMed Central

    Apoux, Frédéric; Youngdahl, Carla L.; Yoho, Sarah E.; Healy, Eric W.

    2015-01-01

    Speech intelligibility in noise can be degraded by using vocoder processing to alter the temporal fine structure (TFS). Here it is argued that this degradation is not attributable to the loss of speech information potentially present in the TFS. Instead it is proposed that the degradation results from the loss of sound-source segregation information when two or more carriers (i.e., TFS) are substituted with only one as a consequence of vocoder processing. To demonstrate this segregation role, vocoder processing involving two carriers, one for the target and one for the background, was implemented. Because this approach does not preserve the speech TFS, it may be assumed that any improvement in intelligibility can only be a consequence of the preserved carrier duality and associated segregation cues. Three experiments were conducted using this “dual-carrier” approach. All experiments showed substantial sentence intelligibility in noise improvements compared to traditional single-carrier conditions. In several conditions, the improvement was so substantial that intelligibility approximated that for unprocessed speech in noise. A foreseeable and potentially promising implication for the dual-carrier approach involves implementation into cochlear implant speech processors, where it may provide the TFS cues necessary to segregate speech from noise. PMID:26428784

  8. Helical Motions of Fine-structure Prominence Threads Observed by Hinode and IRIS

    NASA Astrophysics Data System (ADS)

    Okamoto, Takenori J.; Liu, Wei; Tsuneta, Saku

    2016-11-01

    Fine-structure dynamics in solar prominences holds critical clues to understanding their physical nature of significant space-weather implications. We report evidence of rotational motions of horizontal helical threads in two active-region prominences observed by the Hinode and/or Interface Region Imaging Spectrograph satellites at high resolution. In the first event, we found transverse motions of brightening threads at speeds up to 55 km s-1 seen in the plane of the sky. Such motions appeared as sinusoidal space-time trajectories with a typical period of ˜390 s, which is consistent with plane-of-sky projections of rotational motions. Phase delays at different locations suggest the propagation of twists along the threads at phase speeds of 90-270 km s-1. At least 15 episodes of such motions occurred in two days, none associated with an eruption. For these episodes, the plane-of-sky speed is linearly correlated with the vertical travel distance, suggestive of a constant angular speed. In the second event, we found Doppler velocities of 30-40 km s-1 in opposite directions in the top and bottom portions of the prominence, comparable to the plane-of-sky speed. The moving threads have about twice broader line widths than stationary threads. These observations, when taken together, provide strong evidence for rotations of helical prominence threads, which were likely driven by unwinding twists triggered by magnetic reconnection between twisted prominence magnetic fields and ambient coronal fields.

  9. Atomic transition energies and the variation of the fine-structure constant {alpha}

    SciTech Connect

    Borschevsky, Anastasia; Eliav, Ephraim; Ishikawa, Yasuyuki; Kaldor, Uzi

    2006-12-15

    Relativistic energy shifts of atomic excitation energies, showing the dependence of these energies on the value of the fine-structure constant {alpha}, are needed to extract past changes in {alpha} from spectra of distant quasars. These shifts are calculated by the Fock-space coupled cluster method and its extrapolated intermediate Hamiltonian extension, which allow high-accuracy treatment of electron correlation. The accuracy of the method is tested by comparing 33 transition energies in heavy atoms (obtained with the laboratory {alpha}) with experiment; the average error is 258 cm{sup -1}, and the largest error is 711 cm{sup -1}. This may be compared with an average error of 432 cm{sup -1} and a maximum error of 2150 cm{sup -1} in the work of Dzuba et al., who reported most of the available energy shift calculations. The enhanced accuracy is due to more extensive inclusion of electron correlation. To obtain the energy shifts, we repeated the calculations with different values of {alpha} (within 0.1% of the current value). Our shifts differ by up to 30% from the values given by Dzuba et al., with an average difference of 9%. Based on the better quality of the present-day excitation energies, we believe the energy shifts reported here are more accurate than earlier work.

  10. New limits on variation of the fine-structure constant using atomic dysprosium.

    PubMed

    Leefer, N; Weber, C T M; Cingöz, A; Torgerson, J R; Budker, D

    2013-08-09

    We report on the spectroscopy of radio-frequency transitions between nearly degenerate, opposite-parity excited states in atomic dysprosium (Dy). Theoretical calculations predict that these states are very sensitive to variation of the fine-structure constant α owing to large relativistic corrections of opposite sign for the opposite-parity levels. The near degeneracy reduces the relative precision necessary to place constraints on variation of α, competitive with results obtained from the best atomic clocks in the world. Additionally, the existence of several abundant isotopes of Dy allows isotopic comparisons that suppress common-mode systematic errors. The frequencies of the 754-MHz transition in 164Dy and 235-MHz transition in 162Dy are measured over the span of two years. The linear variation of α is α·/α=(-5.8±6.9([1σ]))×10(-17)  yr(-1), consistent with zero. The same data are used to constrain the dimensionless parameter kα characterizing a possible coupling of α to a changing gravitational potential. We find that kα=(-5.5±5.2([1σ]))×10(-7), essentially consistent with zero and the best constraint to date.

  11. Fine structure and immunocytochemistry of a new chemosensory system in the Chiton larva (Mollusca: Polyplacophora).

    PubMed

    Haszprunar, Gerhard; Friedrich, Stefan; Wanninger, Andreas; Ruthensteiner, Bernhard

    2002-02-01

    Combined electron microscopy and immunocytochemistry of the larvae of several polyplacophoran species (Chiton olivaceus, Lepidochitona aff. corrugata, Mopalia muscosa) revealed a sensory system new to science, a so-called "ampullary system." The cells of the "ampullary system" are arranged in four symmetrically situated pairs lying dorsolaterally and ventrolaterally in the pretrochal part of the trochophore-like larva and they send axons into the cerebral commissure. They are lost at metamorphosis. The fine structure of these cells strongly resembles that of so-called "ampullary cells" known from various sensory organs of other molluscs, such as the apical complex of gastropod and bivalve larvae, osphradia of vetigastropods, and olfactory organs of cephalopods, and nuchal organs of certain polychaetes. The ampullary cells and their nerves are densely stained by anti-FMRF-amide fluorescence dyes, whereas antiserotonin staining is only weak. While cytological homology of the ampullary cells with those of other organs is probable, the ampullary system as a whole is regarded as a synapomorphy of the Polyplacophora or Chitonida.

  12. Preferred Compression Speed for Speech and Music and Its Relationship to Sensitivity to Temporal Fine Structure.

    PubMed

    Moore, Brian C J; Sęk, Aleksander

    2016-09-07

    Multichannel amplitude compression is widely used in hearing aids. The preferred compression speed varies across individuals. Moore (2008) suggested that reduced sensitivity to temporal fine structure (TFS) may be associated with preference for slow compression. This idea was tested using a simulated hearing aid. It was also assessed whether preferences for compression speed depend on the type of stimulus: speech or music. Twenty-two hearing-impaired subjects were tested, and the stimulated hearing aid was fitted individually using the CAM2A method. On each trial, a given segment of speech or music was presented twice. One segment was processed with fast compression and the other with slow compression, and the order was balanced across trials. The subject indicated which segment was preferred and by how much. On average, slow compression was preferred over fast compression, more so for music, but there were distinct individual differences, which were highly correlated for speech and music. Sensitivity to TFS was assessed using the difference limen for frequency at 2000 Hz and by two measures of sensitivity to interaural phase at low frequencies. The results for the difference limens for frequency, but not the measures of sensitivity to interaural phase, supported the suggestion that preference for compression speed is affected by sensitivity to TFS.

  13. Influence of dense quantum plasmas on fine-structure splitting of Lyman doublets of hydrogenic systems

    SciTech Connect

    De, Madhab Ray, Debasis

    2015-05-15

    Relativistic calculations are performed to study the effects of oscillatory quantum plasma screening on the fine-structure splitting between the components of Lyman-α and β line doublets of atomic hydrogen and hydrgen-like argon ion within dense quantum plasmas, where the effective two-body (electron–nucleus) interaction is modeled by the Shukla–Eliasson oscillatory exponential cosine screened-Coulomb potential. The numerical solutions of the radial Dirac equation for the quantum plasma-embedded atomic systems reveal that the oscillatory quantum screening effect suppresses the doublet (energy) splitting substantially and the suppression becomes more prominent at large quantum wave number k{sub q}. In the absence of the oscillatory cosine screening term, much larger amount of suppression is noticed at larger values of k{sub q}, and the corresponding results represent the screening effect of an exponential screened-Coulomb two-body interaction. The Z{sup 4} scaling of the Lyman doublet splitting in low-Z hydrogen isoelectronic series of ions in free space is violated in dense quantum plasma environments. The relativistic data for the doublet splitting in the zero screening (k{sub q} = 0) case are in very good agreement with the NIST reference data, with slight discrepancies (∼0.2%) arising from the neglect of the quantum electrodynamic effects.

  14. Preferred Compression Speed for Speech and Music and Its Relationship to Sensitivity to Temporal Fine Structure

    PubMed Central

    Sęk, Aleksander

    2016-01-01

    Multichannel amplitude compression is widely used in hearing aids. The preferred compression speed varies across individuals. Moore (2008) suggested that reduced sensitivity to temporal fine structure (TFS) may be associated with preference for slow compression. This idea was tested using a simulated hearing aid. It was also assessed whether preferences for compression speed depend on the type of stimulus: speech or music. Twenty-two hearing-impaired subjects were tested, and the stimulated hearing aid was fitted individually using the CAM2A method. On each trial, a given segment of speech or music was presented twice. One segment was processed with fast compression and the other with slow compression, and the order was balanced across trials. The subject indicated which segment was preferred and by how much. On average, slow compression was preferred over fast compression, more so for music, but there were distinct individual differences, which were highly correlated for speech and music. Sensitivity to TFS was assessed using the difference limen for frequency at 2000 Hz and by two measures of sensitivity to interaural phase at low frequencies. The results for the difference limens for frequency, but not the measures of sensitivity to interaural phase, supported the suggestion that preference for compression speed is affected by sensitivity to TFS. PMID:27604778

  15. Fine structure of extracellular fibers in primo-nodes and vessels.

    PubMed

    Jung, Jong Hyun; Sung, Baeckkyoung; Soh, Kwang-Sup

    2011-01-01

    To investigate the extracellular matrices in the primo-nodes (PNs) and vessels (PVs) (Bonghan corpuscles and ducts), fine structure of the fibers comprising the extracellular matrices was studied in relation to the diameter and the periodicity to identify the types of the fibers. Electron micrographs of the fibers from the previously published works on the PNs and PVs were analyzed by using MATLAB programming and ImageJ software. The extracellular fibrous components of the PNs and PVs could be classified generally into two groups--thin collagen fibrils and thick non-collagenous wavy bent fibers. The thick bent fibers were fibrin-like. The diameters of the thick bent fibers were 30-200 nm and they were highly bent. This group included organ surface PNs and lymphatic PNs/PVs. The diameters of the collagen fibrils were 30-70 nm. Organ surface, heart, and hypodermis PVs were categorized in this group. The periodicity of bent fibers in an organ surface PN was 16.1 +/- 0.2 (SE) nm, and the periodicity of collagen fibrils in the hypodermis PVs was 37.4 +/- 0.5 (SE) nm. Further investigations are required to reveal the physiological implications of the two types of fibers in the PNs and PVs.

  16. Nonlinear Schrödinger-Poisson definition of fine-structure-constant's value ~1/137

    NASA Astrophysics Data System (ADS)

    Reinisch, G.

    2010-06-01

    By numerically investigating the nonlinear Schrödinger-Poisson eigenstates of a condensed Bose gas of charged particles that is confined in a two-dimensional axisymmetric parabolic potential ½meω2r2 (e.g. quantum-dot helium), it is shown that the probability amplitude between two nonlinear—and hence non-orthogonal—eigenstates displays an interference pattern scaled (within 0.03 %) by graphic equation Since α = e2/hbarc ~ 1/137 is the fine structure constant, this stunning result—indeed velocity of light c does not enter the present non-relativistic model—is tentatively explained by the existence of a "nonlinear" bound state of the trapped particle-particle interaction Coulomb field whose energy cal E = half pi hbar omega defines the induced emission or absorption equilibrium processes between two appropriate chemical potentials. Besides, a non-decoherence quantum-classical transition with increasing nonlinearity is pointed out. As a possible experimental test for the present theory, the 0s2 → 1s2 nonlinear transition in an hbarω = 1.66meV GaAs quantum-dot helium is emphasized.

  17. Electromagnetic emissions and fine structures observed near main ionospheric trough during geomagnetic storms and their interactions

    NASA Astrophysics Data System (ADS)

    Przepiórka, Dorota; Marek, Michał; Matyjasiak, Barbara; Rothkaehl, Hanna

    2016-04-01

    Geomagnetic conditions triggered by the solar activity affect the ionosphere, its fine and global structures. Very intense magnetic storms substantially change the plasma density, concentration and circulation. Especially sensitive region is located near auroral oval, where most energy is deposited during geomagnetic storms. In this region and just below it, where the main ionospheric trough is located, we observe enhanced electromagnetic emissions in different frequency ranges. In particular the AKR-like (Auroral Kilometric Radiation) emissions are seen at frequencies of the order of hundreds of kHz in the ionosphere, just below the auroral oval. Analyzing spectrograms from DEMETER mission and comparing them with electron density measurements from DEMETER, we found that AKR-like emissions are seen near poleward wall of the main ionospheric trough, during geomagnetic storms. Main ionospheric trough is known as a turbulent region which properties change as the geomagnetic storm evolves. This work is an attempt to determine how the presence of the different emissions affect main ionospheric trough parameters such as location, width and depth. Data used in this study come from DEMETER and RELEC missions. This work was partly supported by NCN grant Rezonans 2012/07/B/ST9/04414.

  18. FINE STRUCTURAL ALTERATIONS OF INTERPHASE NUCLEI OF LYMPHOCYTES STIMULATED TO GROWTH ACTIVITY IN VITRO

    PubMed Central

    Tokuyasu, K.; Madden, S. C.; Zeldis, L. J.

    1968-01-01

    This report describes fine structural changes of interphase nuclei of human peripheral blood lymphocytes stimulated to growth by short-term culture with phytohemagglutinin. Chromatin is found highly labile, its changes accompanying the sequential increases of RNA and DNA synthesis which are known to occur in lymphocyte cultures. In "resting" lymphocytes, abundant condensed chromatin appears as a network of large and small aggregates. Early in the response to phytohemagglutinin, small aggregates disappear during increase of diffuse chromatin regions. Small aggregates soon reappear, probably resulting from disaggregation of large masses of condensed chromatin. Loosened and highly dispersed forms then appear prior to the formation of prophase chromosomes. The loosened state is found by radioautography to be most active in DNA synthesis. Small nucleoli of resting lymphocytes have concentric agranular, fibrillar, and granular zones with small amounts of intranucleolar chromatin. Enlarging interphase nucleoli change chiefly (1) by increase in amount of intranucleolar chromatin and alteration of its state of aggregation and (2) by increase in granular components in close association with fibrillar components. PMID:5699935

  19. Fine-grained parallelism accelerating for RNA secondary structure prediction with pseudoknots based on FPGA.

    PubMed

    Xia, Fei; Jin, Guoqing

    2014-06-01

    PKNOTS is a most famous benchmark program and has been widely used to predict RNA secondary structure including pseudoknots. It adopts the standard four-dimensional (4D) dynamic programming (DP) method and is the basis of many variants and improved algorithms. Unfortunately, the O(N(6)) computing requirements and complicated data dependency greatly limits the usefulness of PKNOTS package with the explosion in gene database size. In this paper, we present a fine-grained parallel PKNOTS package and prototype system for accelerating RNA folding application based on FPGA chip. We adopted a series of storage optimization strategies to resolve the "Memory Wall" problem. We aggressively exploit parallel computing strategies to improve computational efficiency. We also propose several methods that collectively reduce the storage requirements for FPGA on-chip memory. To the best of our knowledge, our design is the first FPGA implementation for accelerating 4D DP problem for RNA folding application including pseudoknots. The experimental results show a factor of more than 50x average speedup over the PKNOTS-1.08 software running on a PC platform with Intel Core2 Q9400 Quad CPU for input RNA sequences. However, the power consumption of our FPGA accelerator is only about 50% of the general-purpose micro-processors.

  20. Sensitivity of bilateral cochlear implant users to fine-structure and envelope interaural time differences.

    PubMed

    Noel, Victor A; Eddington, Donald K

    2013-04-01

    Bilateral cochlear implant users have poor sensitivity to interaural time differences (ITDs) of high-rate pulse trains, which precludes use of these stimuli to convey fine-structure ITD cues. However, previous reports of single-neuron recordings in cats demonstrated good ITD sensitivity to 1000 pulses-per-second (pps) pulses when the pulses were sinusoidally amplitude modulated. The ability of modulation to restore ITD sensitivity to high-rate pulses in humans was tested by measuring ITD thresholds for three conditions: ITD encoded in the modulated carrier pulses alone, in the envelope alone, and in the whole waveform. Five of six subjects were not sensitive to ITD in the 1000-pps carrier, even with modulation. One subject's 1000-pps carrier ITD sensitivity did significantly improve due to modulation. Sensitivity to ITD encoded in the envelope was also measured as a function of modulation frequency, including at frequencies from 4 to 16 Hz where much of the speech envelope's energy and information resides. Sensitivity was best at the modulation frequency of 100 Hz and degraded rapidly outside of a narrow range. These results provide little evidence to support encoding ITD in the carrier of current bilateral processors, and suggest envelope ITD sensitivity is poor for an important segment of the speech modulation spectrum.

  1. Fine structure analysis and sintering properties of Si-doped hydroxyapatite.

    PubMed

    Qiu, Z Y; Li, G; Zhang, Y Q; Liu, J; Hu, W; Ma, J; Zhang, S M

    2012-08-01

    Si-doped hydroxyapatite (Si-HA) has been intensively investigated as a promising bone biomaterial because of the biomineralization and bone formation benefit from silicon addition. In the current work, Si-HA samples were synthesized by the aqueous precipitation method. The sintering property of Si-HA was studied in terms of phase composition and transition, which was influenced by the Si doping percentage and sintering temperature. The results indicate that all the as-prepared and sintered low Si doping samples (Si% ≤ 1.6 wt%) possess HA phases; while the high Si doping samples (Si% ≥ 2 wt%) present amorphous phases as prepared, and largely or even completely transform to β-tricalcium phosphate (β-TCP) phase after sintering at 1250 °C. The Rietveld refinement on x-ray diffraction patterns was conducted to determine the particle sizes, microstrain factors and anisotropic distributions. According to the refined results, the calculated anisotropic particle sizes correspond to the observations made by transmission electron microscopy. The microstrains also present anisotropic distributions in all refinements. The accurate variation in the fine structure of Si-HA has been studied by the improved refinements after considering the anisotropic distribution.

  2. Detectability of temporal changes in fine structures near the inner core boundary beneath the eastern hemisphere

    NASA Astrophysics Data System (ADS)

    Yu, Wen-che

    2016-04-01

    The inner core boundary (ICB), where melting and solidification of the core occur, plays a crucial role in the dynamics of the Earth's interior. To probe temporal changes near the ICB beneath the eastern hemisphere, I analyze differential times of PKiKP (dt(PKiKP)), double differential times of PKiKP-PKPdf, and PKiKP coda waves from repeating earthquakes in the Southwest Pacific subduction zones. Most PKiKP differential times are within ±30 ms, comparable to inherent travel time uncertainties due to inter-event separations, and suggest no systematic changes as a function of calendar time. Double differential times measured between PKiKP codas and PKiKP main phases show promising temporal changes, with absolute values of time shifts of >50 ms for some observations. However, there are discrepancies among results from different seismographs in the same calendar time window. Negligible changes in PKiKP times, combined with changes in PKiKP coda wave times on 5 year timescales, favor a smooth inner core boundary with fine-scale structures present in the upper inner core. Differential times of PKiKP can be interpreted in the context of either melting based on translational convection, or growth based on thermochemical mantle-inner core coupling. Small dt(PKiKP) values with inherent uncertainties do not have sufficient resolution to distinguish the resultant longitudinal (melting) and latitudinal (growth) dependencies predicted on the basis of the two models on 5 year timescales.

  3. Elongation pattern and fine structure of the sheaths formed by Thiothrix nivea and Thiothrix fructosivorans.

    PubMed

    Kawasaki, Yuta; Endo, Tomoyuki; Fujiwara, Atsuo; Kondo, Keiko; Katahira, Masato; Nittami, Tadashi; Sato, Michio; Takeda, Minoru

    2017-02-01

    Thiothrix strains are filamentous sulfur-oxidizing bacteria common in activated sludge. Some of the members, including Thiothrix nivea and T. fructosivorans, are known to form a microtubular sheath that covers a line of cells. The sheaths are assemblages of [→4)-β-d-GlcN-(1→4)-β-d-Glc-(1→]n modified with unusual deoxy sugars. In an attempt to elucidate the sheath-forming mechanism, the patterns of sheath formation and cell proliferation were determined in this study. Prior to analysis, both sheaths were confirmed to be highly de-N-acetylated. Sheaths in viable filaments were N-biotinylated followed by cultivation and then fluorescently immunostained. Epifluorescence microscopy of the filaments revealed ubiquitous elongation of the sheaths. For visualization of the cell proliferation pattern, the cell membrane was fluorescently stained. The epifluorescence images demonstrated that cell proliferation also proceeds ubiquitously, suggesting that sheath elongation proceeds surrounding an elongating cell. In addition, the fine structure of the Thiothrix filaments was analyzed by transmission electron microscopy employing a freeze-substitution technique. The micrographs of freeze-substituted filaments showed that the sheaths were thin and single layered. In contrast, the sheaths in chemically fixed filaments appeared thick and multilayered. Treatment with glutaraldehyde probably caused deformation of the sheaths. Supporting this possibility, the sheaths were found to be deformed or solubilized by N-acetylation.

  4. Fine structure of Delia platura (Meigen) (Diptera: Anthomyiidae) revealed by scanning electron microscopy.

    PubMed

    Wang, Qi-Ke; Yang, Yan-Zhi; Liu, Mei-Qin; Zhang, Dong

    2014-08-01

    Delia platura (Meigen) is a phytophagous fly that can cause significant crop losses. To obtain a better understanding of the external morphology of this species, adult D. platura is studied using scanning electron microscopy. Organs or structures that are important for taxonomy, such as the compound eyes, spiracles, pulvilli, wings, and genitalia are highlighted to complement previous description based on light microscope. Mesothoracic and metathoracic spiracles of D. platura that provide efficiency in preventing entrance of fine materials or dust into the tracheal system are morphologically different. In addition, the elongate-oval pulvillus is densely covered with tenent setae with spoon-like tip, which can increase the number of contact points for attachment to a surface. Four types of sensilla are observed on the male genitalia of D. platura including: trichoid sensilla, chaetic sensilla, three subtypes of campaniform sensilla, and basiconic sensilla. Long bristles and microtrichiae are observed on the female genitalia of D. platura. The possible function of sensilla located in the genitalia of D. platura is discussed. Microsc. Res. Tech. 77:619-630, 2014. © 2014 Wiley Periodicals, Inc.

  5. Influence of dense quantum plasmas on fine-structure splitting of Lyman doublets of hydrogenic systems

    NASA Astrophysics Data System (ADS)

    De, Madhab; Ray, Debasis

    2015-05-01

    Relativistic calculations are performed to study the effects of oscillatory quantum plasma screening on the fine-structure splitting between the components of Lyman-α and β line doublets of atomic hydrogen and hydrgen-like argon ion within dense quantum plasmas, where the effective two-body (electron-nucleus) interaction is modeled by the Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential. The numerical solutions of the radial Dirac equation for the quantum plasma-embedded atomic systems reveal that the oscillatory quantum screening effect suppresses the doublet (energy) splitting substantially and the suppression becomes more prominent at large quantum wave number kq. In the absence of the oscillatory cosine screening term, much larger amount of suppression is noticed at larger values of kq, and the corresponding results represent the screening effect of an exponential screened-Coulomb two-body interaction. The Z4 scaling of the Lyman doublet splitting in low-Z hydrogen isoelectronic series of ions in free space is violated in dense quantum plasma environments. The relativistic data for the doublet splitting in the zero screening (kq = 0) case are in very good agreement with the NIST reference data, with slight discrepancies (˜0.2%) arising from the neglect of the quantum electrodynamic effects.

  6. Fine structure and synaptology of the nitrergic neurons in medial septum of the rat brain.

    PubMed

    Halasy, Katalin; Szőke, Balázs; Janzsó, Gergely

    2017-03-01

    The nitrergic neuron population and certain aspects of their connectivity (peptidergic inputs, co-localization with GABA, synaptic target distribution) were studied in the medial septum of the rat brain. The histochemical localization of NADPH diaphorase and immunohistochemical identification of nNOS at light and electron microscopic level was applied. Double-labeling experiments with galanin and leucine enkephalin, moreover the postembedding GABA immunogold staining was also carried out. NADPH diaphorase- and nNOS-immunopositive neurons could be identified inside the borders of medial septum. Out of their peptidergic inputs galanin- and leucine enkephaline-immunopositive varicose fibers were found in close apposition with nNOS-immunopositive neurons. Based on fine structural characteristics (large indented nucleus, thin cytoplasmic rim, lack of axosomatic synapses) the nitrergic neurons are suggested to be identical with the septal cholinergic nerve cells. Their boutons established asymmetrical synapses mainly on dendritic shafts and spines, some of which were also nNOS-immunopositive. A lower amount of nNOS-immunopositive boutons of presumably extrinsic origin were found to be GABAergic.

  7. The fine structure of electron irradiation induced EL2-like defects in n-GaAs

    NASA Astrophysics Data System (ADS)

    Tunhuma, S. M.; Auret, F. D.; Legodi, M. J.; Diale, M.

    2016-04-01

    Defects induced by electron irradiation in n-GaAs have been studied using deep level transient spectroscopy (DLTS) and Laplace DLTS (L-DLTS). The E0.83 (EL2) is the only defect observed prior to irradiation. Ru/n-GaAs Schottky diodes were irradiated with high energy electrons from a Sr-90 radionuclide up to a fluence of 2.45 × 1013 cm-2. The prominent electron irradiation induced defects, E0.04, E0.14, E0.38, and E0.63, were observed together with the metastable E0.17. Using L-DLTS, we observed the fine structure of a broad base EL2-like defect peak. This was found to be made up of the E0.75, E0.83, and E0.85 defects. Our study reveals that high energy electron irradiation increases the concentration of the E0.83 defect and introduces a family of defects with electronic properties similar to those of the EL2.

  8. A FINE-STRUCTURAL ANALYSIS OF THE FUSION OF MYOGENIC CELLS

    PubMed Central

    Lipton, Bruce H.; Konigsberg, Irwin R.

    1972-01-01

    The fusion of myogenic cells has been examined on the fine-structural level in muscle cell cultures of embryonic Japanese Coturnix quail. Cells, selected by light microscopy, were serially sectioned normal to their long axis. In this plane, oblique sections of cell membranes are rare and plasmalemmal profiles are more easily traced between adjacent cells. In seven cases, pairs of cells, apparently fixed in the process of fusion, are joined by a single cytoplasmic bridge. Since obliquely sectioned membranes often suggest cytoplasmic confluence, tilting stage analysis was employed to resolve cell membranes in suspect cases. In contrast to such artifacts of superposition, however, the observed intercommunicating pores are contained within a pair of culs-de-sac formed by the fused membranes of both cells. These blind pouches can be traced back between the cells to the external space. The confluent regions are clearly demarcated and they are not simply areas between vesicular profiles. The results of this analysis suggest that (a) at no time is there any loss of integrity of the cellular envelope, and (b) fusion is most probably initiated at single sites between pairs of cells, the pore enlarging, leaving first vestiges and eventually no trace of the original intervening membranes. PMID:4554365

  9. Fine structure of low-energy H(+) in the nightside auroral region

    NASA Technical Reports Server (NTRS)

    Liu, Chao; Perez, J. D.; Moore, T. E.; Chappell, C. R.; Slavin, J. A.

    1994-01-01

    Low-energy H(+) data with 6-s resolution from the retarding ion mass spectrometer instrument on Dynamics Explorer (DE) 1 have been analyzed to reveal the fine structure at middle altitudes of the nightside auroral region. A new method for deconvolving the energy-integrated count rate in the spin plane of the satellite has been used to derive the two-dimensional phase space density. A detailed analysis reveals an alternating conic-beam-conic pattern with the observed conics correlated with large earthward currents in the auroral region. The strong downward current (larger than 1 microamperes per sq m (equivalent value at ionosphere)) provides a free energy source for the perpendicular ion heating, that generates the ion conics with energies from several eV to tens of eV. The bowl shape distribution of the low-energy H(+) is caused by the extended perpendicular heating. The strong correlation between conics and large downward currents suggests that the current-driven electrostatic ion cyclotron wave is an appropriate candidate for the transverse heating mechanism.

  10. DISCOVERY OF FINELY STRUCTURED DYNAMIC SOLAR CORONA OBSERVED IN THE Hi-C TELESCOPE

    SciTech Connect

    Winebarger, Amy R.; Cirtain, Jonathan; Savage, Sabrina; Alexander, Caroline; Golub, Leon; DeLuca, Edward; Schuler, Timothy

    2014-05-20

    In the Summer of 2012, the High-resolution Coronal Imager (Hi-C) flew on board a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore examine how the intensity scales from AIA resolution to Hi-C resolution. For each low-resolution pixel, we calculate the standard deviation in the contributing high-resolution pixel intensities and compare that to the expected standard deviation calculated from the noise. If these numbers are approximately equal, the corona can be assumed to be smoothly varying, i.e., have no evidence of substructure in the Hi-C image to within Hi-C's ability to measure it given its throughput and readout noise. A standard deviation much larger than the noise value indicates the presence of substructure. We calculate these values for each low-resolution pixel for each frame of the Hi-C data. On average, 70% of the pixels in each Hi-C image show no evidence of substructure. The locations where substructure is prevalent is in the moss regions and in regions of sheared magnetic field. We also find that the level of substructure varies significantly over the roughly 160 s of the Hi-C data analyzed here. This result indicates that the finely structured corona is concentrated in regions of heating and is highly time dependent.

  11. Implication of Spatial and Temporal Variations of the Fine-Structure Constant

    NASA Astrophysics Data System (ADS)

    Feng, Sze-Shiang; Yan, Mu-Lin

    2016-02-01

    Temporal and spatial variations of fine-structure constant α ≡ e2/hbar c in cosmology have been reported in analysis of combination Keck and VLT data. This paper studies the variations based on consideration of basic spacetime symmetry in physics. Both laboratory α 0 and distant α z are deduced from relativistic spectrum equations of atoms (e.g., hydrogen atom) defined in inertial reference systems. When Einstein's Λ≠0, the metric of local inertial reference systems in SM of cosmology is Beltrami metric instead of Minkowski, and the basic spacetime symmetry has to be de Sitter (dS) group. The corresponding special relativity (SR) is dS-SR. A model based on dS-SR is suggested. Comparing the predictions on α-varying with the data, the parameters are determined. The best-fit dipole mode in α's spatial varying is reproduced by this dS-SR model. α-varyings in whole sky are also studied. The results are generally in agreement with the estimations of observations. The main conclusion is that the phenomenon of α-varying cosmologically with dipole mode dominating is due to the de Sitter (or anti de Sitter) spacetime symmetry with a Minkowski point in an extended special relativity called de Sitter invariant special relativity (dS-SR) developed by Dirac-Inönü-Wigner-Gürsey-Lee-Lu-Zou-Guo.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. All-Optical dc Nanotesla Magnetometry Using Silicon Vacancy Fine Structure in Isotopically Purified Silicon Carbide

    NASA Astrophysics Data System (ADS)

    Simin, D.; Soltamov, V. A.; Poshakinskiy, A. V.; Anisimov, A. N.; Babunts, R. A.; Tolmachev, D. O.; Mokhov, E. N.; Trupke, M.; Tarasenko, S. A.; Sperlich, A.; Baranov, P. G.; Dyakonov, V.; Astakhov, G. V.

    2016-07-01

    We uncover the fine structure of a silicon vacancy in isotopically purified silicon carbide (4H-28SiC) and reveal not yet considered terms in the spin Hamiltonian, originated from the trigonal pyramidal symmetry of this spin-3 /2 color center. These terms give rise to additional spin transitions, which would be otherwise forbidden, and lead to a level anticrossing in an external magnetic field. We observe a sharp variation of the photoluminescence intensity in the vicinity of this level anticrossing, which can be used for a purely all-optical sensing of the magnetic field. We achieve dc magnetic field sensitivity better than 100 nT /√{Hz } within a volume of 3 ×10-7m m3 at room temperature and demonstrate that this contactless method is robust at high temperatures up to at least 500 K. As our approach does not require application of radio-frequency fields, it is scalable to much larger volumes. For an optimized light-trapping waveguide of 3 mm3 , the projection noise limit is below 100 fT /√{Hz } .

  14. Sensitivity of bilateral cochlear implant users to fine-structure and envelope interaural time differencesa

    PubMed Central

    Noel, Victor A.; Eddington, Donald K.

    2013-01-01

    Bilateral cochlear implant users have poor sensitivity to interaural time differences (ITDs) of high-rate pulse trains, which precludes use of these stimuli to convey fine-structure ITD cues. However, previous reports of single-neuron recordings in cats demonstrated good ITD sensitivity to 1000 pulses-per-second (pps) pulses when the pulses were sinusoidally amplitude modulated. The ability of modulation to restore ITD sensitivity to high-rate pulses in humans was tested by measuring ITD thresholds for three conditions: ITD encoded in the modulated carrier pulses alone, in the envelope alone, and in the whole waveform. Five of six subjects were not sensitive to ITD in the 1000-pps carrier, even with modulation. One subject's 1000-pps carrier ITD sensitivity did significantly improve due to modulation. Sensitivity to ITD encoded in the envelope was also measured as a function of modulation frequency, including at frequencies from 4 to 16 Hz where much of the speech envelope's energy and information resides. Sensitivity was best at the modulation frequency of 100 Hz and degraded rapidly outside of a narrow range. These results provide little evidence to support encoding ITD in the carrier of current bilateral processors, and suggest envelope ITD sensitivity is poor for an important segment of the speech modulation spectrum. PMID:23556598

  15. Discovery of Finely Structured Dynamic Solar Corona Observed in the Hi-C Telescope

    NASA Technical Reports Server (NTRS)

    Winebarger, A.; Cirtain, J.; Golub, L.; DeLuca, E.; Savage, S.; Alexander, C.; Schuler, T.

    2014-01-01

    In the summer of 2012, the High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore examine how the intensity scales from AIA resolution to Hi-C resolution. For each low-resolution pixel, we calculate the standard deviation in the contributing high-resolution pixel intensities and compare that to the expected standard deviation calculated from the noise. If these numbers are approximately equal, the corona can be assumed to be smoothly varying, i.e. have no evidence of substructure in the Hi-C image to within Hi-C's ability to measure it given its throughput and readout noise. A standard deviation much larger than the noise value indicates the presence of substructure. We calculate these values for each low-resolution pixel for each frame of the Hi-C data. On average, 70 percent of the pixels in each Hi-C image show no evidence of substructure. The locations where substructure is prevalent is in the moss regions and in regions of sheared magnetic field. We also find that the level of substructure varies significantly over the roughly 160 s of the Hi-C data analyzed here. This result indicates that the finely structured corona is concentrated in regions of heating and is highly time dependent.

  16. ;Long-hissler; fine structure within auroral hiss: A review and synthesis

    NASA Astrophysics Data System (ADS)

    Kim, Howard F.; LaBelle, James; Spasojević, Maria

    2017-04-01

    One of the most prominent fine-structures of auroral hiss is the ;long-hissler;, defined here as a dispersed feature embedded within broadband auroral hiss emissions in the frequency range 1-40 kHz and lasting longer than 0.3 s. While theory is limited, there is evidence that hisslers can be used in remote sensing of density characteristics at altitudes of thousands of km. By applying an automatic threshold algorithm to VLF data collected at South Pole 2230-0130 UT daily during June-August 2014, 22 h of auroral hiss are identified on 49 of 93 days analyzed, for an occurrence rate of 9.7% during the applicable MLT interval. From manual inspection of these intervals, 414 groups (trains) of long hisslers are identified on 34 of the 49 days on which hiss occurred. Median lower (upper) frequency bounds of these features are 8 (22) kHz, median frequency-time slope is -10 kHz/s, and median hissler repetition time within a train (hissler period) is 1.2 s. Hissler period and frequency-time slope are inversely related. Data from previous studies are reviewed to provide a comprehensive description of the phenomenon. Contrary to some previous studies, subsequent long hissler features are found to commonly overlap in time, and no evidence is found for an inverse relationship between hissler train duration and geomagnetic activity.

  17. Influence of fine structure of lipid A on Limulus amebocyte lysate clotting and toxic activities.

    PubMed Central

    Takayama, K; Qureshi, N; Raetz, C R; Ribi, E; Peterson, J; Cantrell, J L; Pearson, F C; Wiggins, J; Johnson, A G

    1984-01-01

    We examined the relationship between the fine structure of lipid A and the toxicity of endotoxin or lipopolysaccharides as measured by the Limulus amebocyte lysate (LAL), rabbit pyrogenicity, chicken embryo lethal dose, and dermal Shwartzman reaction tests. Lipid A and lipid A-like compounds obtained from deep-rough mutants of Salmonella spp. and Escherichia coli had a wide range of structural variations. These compounds included native lipopolysaccharides, diphosphoryl and monophosphoryl lipid A's, and lipid X (a monosaccharide). The LAL test was positive for all lipids tested with lysates from Travenol Laboratories and from Associates of Cape Cod (2.9 X 10(3) to 2.6 X 10(7) endotoxin units per mg), except for O-deacylated and dephosphorylated lipid X, which were negative. The Mallinckrodt lysate gave negative tests for lipid X. In the rabbit pyrogenicity and chicken embryo lethal dose tests, only native lipopolysaccharide and diphosphoryl lipid A's were judged toxic. The Shwartzman reaction was positive for a specific purified diphosphoryl lipid A (thin-layer chromatography-3 fraction) but negative for the purified monophosphoryl lipid A (also a thin-layer chromatography-3 fraction). These results show that the LAL test is not a valid measure of all parameters of toxicity of a lipid A or lipid A-like compound and can yield false-positive results. However, these findings are not in conflict with the widespread use of the LAL assay for pyrogens in the pharmaceutical industry since a good correlation exists between LAL results and pyrogenicity when undegraded endotoxin is evaluated in parallel assays. Images PMID:6378795

  18. Composite fermions and the first-Landau-level fine structure of the fractional quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Haxton, W. C.; Haxton, Daniel J.

    2016-04-01

    A set of scalar operators, originally introduced in connection with an analytic first-Landau-level (FLL) construction of fractional quantum Hall (FQHE) wave functions for the sphere, are employed in a somewhat different way to generate explicit representations of both hierarchy states (e.g., the series of fillings ν =1 /3 , 2/5, 3/7,⋯) and their conjugates (ν =1 , 2/3, 3/5,⋯) as noninteracting quasielectrons filling fine-structure subshells within the FLL. This yields, for planar and spherical geometries, a quasielectron representation of the incompressible FLL state of filling p /(2 p +1 ) in a magnetic field of strength B that is algebraically identical to the IQHE state of filling ν =p in a magnetic field of strength B /(2 p +1 ) . The construction provides a precise definition of the quasielectron/composite fermion that differs in some respects from common descriptions: they are eigenstates of L ,Lz ; they and the FLL subshells they occupy carry a third index I that is associated with breaking of scalar pairs; they absorb in their internal wave functions one, not two, units of magnetic flux; and they share a common, simple structure as vector products of a spinor creating an electron and one creating magnetic flux. We argue that these properties are a consequence of the breaking of the degeneracy of noninteracting electrons within the FLL by the scale-invariant Coulomb potential. We discuss the sense in which the wave function construction supports basic ideas of both composite fermion and hierarchical descriptions of the FQHE. We describe symmetries of the quasielectrons in the ν =1 /2 limit, where a deep Fermi sea of quasielectrons forms, and the quasielectrons take on Majorana and pseudo-Dirac characters. Finally, we show that the wave functions can be viewed as fermionic excitations of the bosonic half-filled shell, producing at ν =1 /2 an operator that differs from but plays the same role as the Pfaffian.

  19. Cellular Organization of Normal Mouse Liver: A Histological, Quantitative Immunocytochemical, and Fine Structural Analysis

    PubMed Central

    Baratta, Janie L.; Ngo, Anthony; Lopez, Bryan; Kasabwalla, Natasha; Longmuir, Kenneth J.; Robertson, Richard T.

    2009-01-01

    The cellular organization of normal mouse liver was studied using light and electron microscopy and quantitative immunocytochemical techniques. The general histological organization of the mouse liver is similar to livers of other mammalian species, with a lobular organization based on the distributions of portal areas and central venules. The parenchymal hepatocytes were detected with immunocytochemical techniques to recognize albumin or biotin containing cells. The macrophage Kupffer cells were identified with F4-80 immunocytochemistry, Ito stellate cells were identified with GFAP immunocytochemistry, and endothelial cells were labeled with the CD-34 antibody. Kupffer cells were labeled with intravascularly administered fluorescently labeled latex microspheres of both large (0.5 μm) and small (0.03 μm) diameters, while endothelial cells were labeled only with small diameter microspheres. Neither hepatocytes nor Ito stellate cells were labeled by intravascularly administered latex microspheres. The principal fine structural features of hepatocytes and non-parenchymal cells of mouse liver are similar to those reported for rat. Counts of immunocytochemically labeled cells with stained nuclei indicated that hepatocytes constituted approximately 52% of all labeled cells, Kupffer cells about 18%, Ito cells about 8%, and endothelial cells about 22% of all labeled cells. Approximately 35% of the hepatocytes contained two nuclei; none of the Kupffer or Ito cells were double nucleated. The presence of canaliculi and a bile duct system appear similar to that reported for other mammalian species. The cellular organization of the mouse liver is quite similar to that of other mammalian species, confirming that the mouse presents a useful animal model for studies of liver structure and function. PMID:19255771

  20. Mineralogical properties and internal structures of individual fine particles of Saharan dust

    NASA Astrophysics Data System (ADS)

    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 ( < 5 µm) Saharan dust particles sampled at Tenerife, Canary Islands. The bulk of Tenerife dust was composed of clay minerals (81 %), followed by quartz (10 %), plagioclase (3 %), and K-feldspar (2 %). Cross-sectional slices of Saharan dust particles prepared by the focused ion beam technique were analyzed by transmission electron microscopy (TEM) to probe the particle interiors. TEM analysis showed that the most 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.

  1. Symmetry Breaking and Fine Structure Splitting in Zincblende Quantum Dots: Atomistic Simulations of Long-Range Strain and Piezoelectric Field

    NASA Astrophysics Data System (ADS)

    Ahmed, Shaikh; Usman, Muhammad; Heitzinger, Clemens; Rahman, Rajib; Schliwa, Andrei; Klimeck, Gerhard

    2007-04-01

    Electrons and holes captured in self-assembled quantum dots (QDs) are subject to symmetry breaking that cannot be represented in with continuum material representations. Atomistic calculations reveal symmetry lowering due to effects of strain and piezo-electric fields. These effects are fundamentally based on the crystal topology in the quantum dots. This work studies these two competing effects and demonstrates the fine structure splitting that has been demonstrated experimentally can be attributed to the underlying atomistic structure of the quantum dots.

  2. Effect of Crystal Structure Fineness for Charge Alloy AK6M2 on Its Flux Treatment Efficiency

    NASA Astrophysics Data System (ADS)

    Nikitin, K. V.; Nikitin, V. I.; Timoshkin, I. Yu.; Chikova, O. A.

    2016-09-01

    The effect of charge billet structure and form of fluxes on structure, density, and gas content of alloy AK6M2 (Al - Si - Cu system) is studied. Alloys prepared from finely crystalline charge billet have smaller phase component sizes, lower gas content, and increased solid state density, and use of coarsely crystalline charge billets for alloy preparation necessitates an increase in flux preparation consumption in the stage of alloy preparation for casting.

  3. Fine Crustal Structure in the Northwestern Iranian Plateau Revealed by Ambient Noise Tomography

    NASA Astrophysics Data System (ADS)

    Jiang, Mingming; Chen, Ling; Talebian, Morteza; Ghods, Abdolreza; Ai, Yinshuang; Sobouti, Farhad; He, Yumei; Motaghi, Khalil; Chen, Qi-Fu; Lyv, Yan; Xiao, Wenjiao

    2016-04-01

    Detailed information about the crustal and lithospheric structures is crucial for understanding the geodynamics processes of continental collision and subsequent mountain building. Being at the initial stage of continental collision, the Iranian Plateau has not been well studied due to the lack of high-resolution, robust images of the crustal and lithospheric structures. Along the Zagros Orogen in the NW part of the Iranian Plateau the Arabian Plate has collided with the Eurasian Plate since about 30 Ma ago, whereas in the Makran region to the southeast oceanic subduction underneath the Eurasian Plate is still an ongoing process. For better understanding the geodynamic processes from subduction to collision, we planned to deploy multiple dense seismic arrays sampling regions at different tectonic stages in the Iranian Plateau. Up to now, we have finished the first seismic array observation in NW Iran. Based on the high quality data recorded, we conduct ambient noise tomography to investigate the fine crustal structure of the area from the south of the Zagros to the coast of the Southern Caspian Sea. Our results revel a salient decoupling between the upper crust and lower crust in the Zagros. The upper crust is slow, likely due to the effects of thick sediments, and displays a consistent anisotropy pattern with a NW-SE fast shear-wave direction, which is proximately parallel to the strike of the Zagros Orogen. The middle to lower crust, on the other hand, shows low-to-high velocity variations with depth and anisotropic fabrics trending to NE-SW, which is perpendicular to the strike of the orogen. Combined with the imaging results from receiver functions, we suggest that the collision between the Arabian and Eurasian Plates has caused strong crustal deformation and localized thickening of the lower crust beneath the Zagros. We also find a high velocity anomaly in the lower crust beneath the Alborz Mountain, isolated from the low velocities beneath the central Iran

  4. Characterization of the micropore structure of activated carbons by adsorptions of nitrogen and some hydrocarbons

    SciTech Connect

    Guezel, F.

    1999-02-01

    In the present study the effects of the duration of carbonization and physical activation properties of activated carbon from vegetable materials were investigated. Peanut shells were used to obtain active carbon. These shells were activated chemically with ZnCl{sub 2} and/or CO{sub 2} for different times, and the micropore structures of these active carbons were studied by measuring the adsorption isotherms for nitrogen and some hydrocarbons such as benzene, n-butane, isobutane, 2,2-dimethylbutane, and isooctane. As the physical activation time was increased, the primary micropores, which were measured at 0.01 relative pressure, were reduced, and they were replaced by larger secondary and tertiary micropores which were measured at 0.15--0.01 and 0.30--0.15 relative pressures. The ratios of the mesopore volume to the micropore volume also increased as the duration of physical activation increased.

  5. Using Neutron Reflectometry to Discern the Structure of Fibrinogen Adsorption at the Stainless Steel/Aqueous Interface.

    PubMed

    Wood, Mary H; Browning, Kathryn L; Barker, Robert D; Clarke, Stuart M

    2016-06-23

    Neutron reflectometry has been successfully used to study adsorption on a stainless steel surface by means of depositing a thin steel film on silicon. The film was characterized using XPS (X-ray photoelectron spectroscopy), TOF-SIMS (time-of-flight secondary ion mass spectrometry), and GIXRD (grazing incidence X-ray diffraction), demonstrating the retention both of the austenitic phase and of the required composition for 316L stainless steel. The adsorption of fibrinogen from a physiologically-relevant solution onto the steel surface was studied using neutron reflectometry and QCM (quartz crystal microbalance) and compared to that on a deposited chromium oxide surface. It was found that the protein forms an irreversibly bound layer at low concentrations, with maximum protein concentration a distance of around 20 Å from the surface. Evidence for a further diffuse reversibly-bound layer forming at higher concentrations was also observed. Both the structure of the layer revealed by the neutron reflectometry data and the high water retention predicted by the QCM data suggest that there is a significant extent of protein unfolding upon adsorption. A lower extent of adsorption was seen on the chromium surfaces, although the adsorbed layer structures were similar, suggesting comparable adsorption mechanisms.

  6. Thymine adsorption on two-dimensional boron nitride structures: first-principles studies.

    PubMed

    Castro-Medina, J; García-Toral, D; López-Fuentes, M; Sánchez-Castillo, A; Torres-Morales, S; de la Garza, L Morales; Cocoletzi, Gregorio H

    2017-04-01

    First-principles total-energy calculations were performed to investigate the structural and electronic properties of thymine (T) adsorption on pristine and Al-doped two-dimensional hexagonal boron nitride (2D-hBN) surfaces. Periodic density functional theory, as developed in the PWscf code of the quantum espresso package, was applied. The pseudopotential theory was used to deal with electron-ion interactions. The generalized gradient approximation was applied to treat the exchange-correlation energies. Van der Waals interactions were incorporated in the calculations. Considering T as an elongated molecule and the interactions through one oxygen atom of the molecule ring, two geometries were explored in pristine and Al-doped systems: in (1) the ring side O interacts with B, and (2) the O at the molecule end interacting with the B. The pristine case yields (4 × 4-a), (5 × 5-b) and (6 × 6-b) as the ground states, , while the doped system shows (4 × 4-a), (5 × 5-a) and (6 × 6-a) as the ground states. Calculations of the adsorption energies indicate chemisorption. Doping enhances the surface reactivity, inducing larger binding energies. The total density of states (DOS) was calculated and interpreted with the aid of the projected DOS. Below the Fermi energy, the DOS graphs indicate that p orbitals make the largest contributions. Above the Fermi level, the DOS is formed mainly by -s and H-s orbitals. The DOS graphs indicate that the structures have non-semiconductor behavior.

  7. The adsorption of nicotine from aqueous solutions on different zeolite structures.

    PubMed

    Rakić, Vesna; Damjanović, Ljiljana; Rac, Vladislav; Stosić, Dusan; Dondur, Vera; Auroux, Aline

    2010-03-01

    The present work is focused on the adsorption of nicotine from aqueous solutions. Based on the data available in the literature, serious concern is claimed regarding the appearance of nicotine in ground, surface and municipal wastewaters. In order to investigate the possibility of abatement by adsorption, three different types of zeolites (BEA, MFI and HEU) have been applied as adsorbents. In addition, the adsorption was performed on activated carbon, a solid customarily used for removal of pollutants from water. The adsorption of nicotine was studied by isothermal microcalorimetry, which provided the heats evolved as a result of adsorption. The values of these heats revealed that the investigated solids are energetically heterogeneous for the adsorption of nicotine from aqueous solution. Additionally, the amounts of adsorbed pollutant were determined and presented in the form of adsorption isotherms. The obtained adsorption isotherms were interpreted using Langmuir, Freundlich, and Sips equations; the latter was found to express high level of agreement with experimental data of nicotine adsorption on the investigated solids. The possibilities to regenerate the adsorbents were examined by means of thermogravimetry coupled with mass spectrometry. From all obtained results, it was possible to distinguish zeolite BEA as a material which possesses the capacity for adsorption of nicotine comparable to that of activated carbon.

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

    SciTech Connect

    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{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

  9. Active region fine structure observed at 0.08 arcsec resolution

    NASA Astrophysics Data System (ADS)

    Schlichenmaier, R.; von der Lühe, O.; 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.

    2016-11-01

    Context. The various mechanisms of magneto-convective energy transport determine the structure of sunspots and active regions. Aims: We characterise the appearance of light bridges and other fine-structure details and elaborate on their magneto-convective nature. Methods: We present speckle-reconstructed images taken with the broad-band imager (BBI) at the 1.5 m GREGOR telescope in the 486 nm and 589 nm bands. We estimate the spatial resolution from the noise characteristics of the image bursts and obtain 0.08″ at 589 nm. We describe structure details in individual best images as well as the temporal evolution of selected features. Results: 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 timescales of minutes. Faint light bridges show dark lanes outlined by the surrounding bright features. Dark lanes are very common and are also found in the boundary of pores. They have a characteristic width of 0.1″ or smaller. Intergranular dark lanes of that width are seen in active region granulation. Conclusions: We interpret our images in the context of magneto-convective simulations and findings: while central dark lanes in thin light bridges are elevated and associated with a density increase above upflows, the dark lane branches correspond to locations of downflows and are depressed relative to the adjacent bright plasma. Thick light bridges with central dark lanes show no projection effect. They have a flat elevated plateau that falls off steeply at the umbral boundary. There, Y-shaped filaments form as they do in the inner penumbra. This indicates the presence of inclined magnetic fields, meaning that the umbral magnetic field is wrapped around

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

    NASA Astrophysics Data System (ADS)

    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

  11. Quiescent Prominences in the Era of ALMA: Simulated Observations Using the 3D Whole-prominence Fine Structure Model

    NASA Astrophysics Data System (ADS)

    Gunár, Stanislav; Heinzel, Petr; Mackay, Duncan H.; Anzer, Ulrich

    2016-12-01

    We use the detailed 3D whole-prominence fine structure model to produce the first simulated high-resolution ALMA observations of a modeled quiescent solar prominence. The maps of synthetic brightness temperature and optical thickness shown in the present paper are produced using a visualization method for synthesis of the submillimeter/millimeter radio continua. We have obtained the simulated observations of both the prominence at the limb and the filament on the disk at wavelengths covering a broad range that encompasses the full potential of ALMA. We demonstrate here extent to which the small-scale and large-scale prominence and filament structures will be visible in the ALMA observations spanning both the optically thin and thick regimes. We analyze the relationship between the brightness and kinetic temperature of the prominence plasma. We also illustrate the opportunities ALMA will provide for studying the thermal structure of the prominence plasma from the cores of the cool prominence fine structure to the prominence-corona transition region. In addition, we show that detailed 3D modeling of entire prominences with their numerous fine structures will be important for the correct interpretation of future ALMA observations of prominences.

  12. ISO-SWS observations of OMC-1: H_2 and fine structure lines

    NASA Astrophysics Data System (ADS)

    Rosenthal, D.; Bertoldi, F.; Drapatz, S.

    2000-04-01

    Using the Short-Wavelength-Spectrometer on the Infrared Space Observatory (ISO), we obtained near- and mid-infrared spectra toward the brightest H_2 emission peak of the Orion OMC-1 outflow. A wealth of emission and absorption features were detected, dominated by 56 H_2 ro-vibrational and pure rotational lines reaching from H_2 0-0 S(1) to 0-0 S(25). The spectra also show a number of H i recombination lines, atomic and ionic fine structure lines, and molecular lines of CO and H_2O. Between 6 and 12 μm the emission is dominated by PAH features. The extinction toward the molecular and atomic line emitting regions is estimated from relative line intensities, and it is found that the H_2 emission arises from within the OMC-1 cloud at an average K-band extinction of 1.0 mag, whereas the atomic hydrogen emission and much of the fine structure emission comes from the foreground H ii region and its bounding photodissociation front. H_2 1-0 S(1) emission of the OMC-1 outflow as seen with the NICMOS camera aboard the HST (Schultz et al. 1999). Overlaid are the various apertures of our ISO-SWS observations, which were centered on alpha_2000 . = 5h 35m 13.s 67, delta_2000 . = -5 degr 22 arcmin 8. arcsec 5, with an aperture of 14 arcsec x 20 arcsec for lambda < 12 μm, 14 arcsec x 27 arcsec at 12 to 27.5μm, 20 arcsec x 27 arcsec at 27.5 to 29μm, and 20 arcsec x 33 arcsec at 29 to 45.2μm. The total H_2 luminosity in the ISO-SWS aperture is estimated at (17 +/- 5) Lsun , and extrapolated to the entire outflow, (120 +/- 60) Lsun . The H_2 level column density distribution shows no signs of fluorescent excitation or a deviation from an ortho-to-para ratio of three. It shows an excitation temperature which increases from about 600 K for the lowest rotational and vibrational levels to about 3200 K at level energies E(v,J)/k > 14 000 K. No single steady state shock model can reproduce the observed H_2 excitation. The higher energy H_2 levels may be excited either thermally in non

  13. Multi-wavelength fine structure and mass flows in solar microflares

    NASA Astrophysics Data System (ADS)

    Berkebile-Stoiser, S.; Gömöry, P.; Veronig, A. M.; Rybák, J.; Sütterlin, P.

    2009-10-01

    Aims: We study the multi-wavelength characteristics at high spatial resolution, as well as chromospheric evaporation signatures of solar microflares. To this end, we analyze the fine structure and mass flow dynamics in the chromosphere, transition region and corona of three homologous microflares (GOES class finely structured chromospheric flare brightenings for all three events, loop-shaped fibrils of increased emission between Hα brightenings, as well as a similar feature in Ca ii. For all three events, a RHESSI X-ray source (3-8 keV, T ≳ 10 MK) is located in between two chromospheric brightenings situated in magnetic flux of opposite polarity. We find the flow dynamics associated with the events to be very complex. In the chromosphere and transition region, CDS observed downflows for the first (v ≲ 40 km s-1), and

  14. Titanium dioxide fine structures by RF magnetron sputter method deposited on an electron-beam resist mask

    NASA Astrophysics Data System (ADS)

    Hashiba, Hideomi; Miyazaki, Yuta; Matsushita, Sachiko

    2013-09-01

    Titanium dioxide (TiO2) has been draw attention for wide range of applications from photonic crystals for visible light range by its catalytic characteristics to tera-hertz range by its high refractive index. We present an experimental study of fabrication of fine structures of TiO2 with a ZEP electron beam resist mask followed by Ti sputter deposition techniques. A TiO2 thin layer of 150 nm thick was grown on an FTO glass substrate with a fine patterned ZEP resist mask by a conventional RF magnetron sputter method with Ti target. The deposition was carried out with argon-oxygen gases at a pressure of 5.0 x 10 -1 Pa in a chamber. During the deposition, ratio of Ar-O2 gas was kept to the ratio of 2:1 and the deposition ratio was around 0.5 Å/s to ensure enough oxygen to form TiO2 and low temperature to avoid deformation of fine pattern of the ZPU resist mask. Deposited TiO2 layers are white-transparent, amorphous, and those roughnesses are around 7 nm. Fabricated TiO2 PCs have wider TiO2 slabs of 112 nm width leaving periodic 410 x 410 nm2 air gaps. We also studied transformation of TiO2 layers and TiO2 fine structures by baking at 500 °C. XRD measurement for TiO2 shows that the amorphous TiO2 transforms to rutile and anatase forms by the baking while keeping the same profile of the fine structures. Our fabrication method can be one of a promising technique to optic devices on researches and industrial area.

  15. [Study on the fine structure of K-feldspar of Qichun granite].

    PubMed

    Du, Deng-Wen; Hong, Han-Lie; Fan, Kan; Wang, Chao-Wen; Yin, Ke

    2013-03-01

    Fine structure of K-feldspar from the Qichun granite was investigated using X-ray diffraction (XRD), Fourier infrared absorption spectroscopy (FTIR), and inductively coupled plasma mass spectrometry methods to understand the evolution of the granitic magmatism and its correlation to molybdenite mineralization. The XRD results showed that K-feldspar of the potassic alteration veins has higher ordering index and triclinicity and is namely microcline with triclinic symmetry. K-feldspar of the early cretaceous granite has relatively lower ordering index and has widening [131] peak and is locally triclinic ordering. K-feldspar of the late cretaceous granite has lowest ordering index and sharp [131] peak and is honiogeneously monoclinic. The FTIR results showed that the IR spectra of the Qichun K-feldspar are similar to that of orthoclase reported by Farmer (1974). The 640 cm-1 absorption band increases while the 540 cm-' absorption band decreases with increase in K-feldspar ordering index, also, the 1,010 cm-1 absorption band separates into 1,010 and 1,046 cm-1 absorption bands, with a change in the band shape from widening to sharp outline. The ICP-MS results suggested that K-feldspar of the early cretaceous granite has relatively higher metal elements and rare earth elements, and the granite exhibits better mineralization background, K-feldspar of the potassic alteration veins has markedly lower Sr and Ba, indicating that the alteration fluid originated from the granitic magmatism, and hence, potassic alteration is a good indicator for molybdenite exploration.

  16. Statistical Study of Auroral Kilometric Radiation Fine Structure Striations Observed by Polar

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Persoon, A. M.; Pickett, J. S.; Gurnett, D. A.

    2000-01-01

    We have conducted a statistical survey of a semirandom sample of the auroral kilometric radiation (AKR) data observed by the plasma wave instrument wideband receiver on board the Polar spacecraft. We have determined that AKR fine structure patterns with very narrowband, negative drifting striations occur in approximately 6% of the high-resolution wideband spectrograms when AKR is present. Positive sloping striations are also observed, but at a much lower rate. More than 8200 AKR stripes have been scaled. The stripes are predominantly found in the 40 to 215-kHz frequency range and have a frequency extent of about 4 kHz and a duration of usually less than 2 s. The majority of the stripes have drift rates between -8 and -2 kHz/s, with a peak in the distribution between -6 and -4 kHz/s. There is also a much smaller group of striations with positive drift rates of up to about 5 or 6 kHz/s. We have further investigated the change of drift rate with frequency. Almost all striations are observed in the lowest two frequency bands of the wideband receiver (f < 215 kHz). There is an increase in the statistical drift rate with increasing frequency. The statistical slope of the striations increases with frequency from about -4.4 kHz/s at 75 kHz to about -5.7 kHz/s at 170 kHz. This frequency dependence of the drift rate is consistent, under certain conditions, with a production mechanism stimulated by an upward propagating electromagnetic ion cyclotron wave, as had been suggested earlier. However, such a changing drift rate is also compatible with a stimulated source region that propagates upward along the magnetic field line at the velocity of an ion beam accelerated by a local, upward directed electric field, as is typically observed in the auroral region. An explanation for this association is not apparent at this time.

  17. Ultra-Fine Scale Spatially-Integrated Mapping of Habitat and Occupancy Using Structure-From-Motion

    PubMed Central

    McDowall, Philip; Lynch, Heather J.

    2017-01-01

    Organisms respond to and often simultaneously modify their environment. While these interactions are apparent at the landscape extent, the driving mechanisms often occur at very fine spatial scales. Structure-from-Motion (SfM), a computer vision technique, allows the simultaneous mapping of organisms and fine scale habitat, and will greatly improve our understanding of habitat suitability, ecophysiology, and the bi-directional relationship between geomorphology and habitat use. SfM can be used to create high-resolution (centimeter-scale) three-dimensional (3D) habitat models at low cost. These models can capture the abiotic conditions formed by terrain and simultaneously record the position of individual organisms within that terrain. While coloniality is common in seabird species, we have a poor understanding of the extent to which dense breeding aggregations are driven by fine-scale active aggregation or limited suitable habitat. We demonstrate the use of SfM for fine-scale habitat suitability by reconstructing the locations of nests in a gentoo penguin colony and fitting models that explicitly account for conspecific attraction. The resulting digital elevation models (DEMs) are used as covariates in an inhomogeneous hybrid point process model. We find that gentoo penguin nest site selection is a function of the topography of the landscape, but that nests are far more aggregated than would be expected based on terrain alone, suggesting a strong role of behavioral aggregation in driving coloniality in this species. This integrated mapping of organisms and fine scale habitat will greatly improve our understanding of fine-scale habitat suitability, ecophysiology, and the complex bi-directional relationship between geomorphology and habitat use. PMID:28076351

  18. Ultra-Fine Scale Spatially-Integrated Mapping of Habitat and Occupancy Using Structure-From-Motion.

    PubMed

    McDowall, Philip; Lynch, Heather J

    2017-01-01

    Organisms respond to and often simultaneously modify their environment. While these interactions are apparent at the landscape extent, the driving mechanisms often occur at very fine spatial scales. Structure-from-Motion (SfM), a computer vision technique, allows the simultaneous mapping of organisms and fine scale habitat, and will greatly improve our understanding of habitat suitability, ecophysiology, and the bi-directional relationship between geomorphology and habitat use. SfM can be used to create high-resolution (centimeter-scale) three-dimensional (3D) habitat models at low cost. These models can capture the abiotic conditions formed by terrain and simultaneously record the position of individual organisms within that terrain. While coloniality is common in seabird species, we have a poor understanding of the extent to which dense breeding aggregations are driven by fine-scale active aggregation or limited suitable habitat. We demonstrate the use of SfM for fine-scale habitat suitability by reconstructing the locations of nests in a gentoo penguin colony and fitting models that explicitly account for conspecific attraction. T