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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 of dopamine on rutile TiO2 (110): a photoemission and near-edge X-ray absorption fine structure study.

    PubMed

    Jackman, Mark J; Syres, Karen L; Cant, David J H; Hardman, Samantha J O; Thomas, Andrew G

    2014-07-29

    Synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) techniques have been used to study the adsorption of dopamine on a rutile TiO2 (110) single crystal. Photoemission results suggest that dopamine bonds through the oxygen molecules in a bidentate fashion. From the data, it is ambiguous whether the oxygens bond to the same 5-fold coordinated surface titanium atom or bridges across two, although based on the bonding of pyrocatechol on rutile TiO2 (110), it is likely that the dopamine bridges two titanium atoms. Using the searchlight effect, the carbon K-edge near-edge X-ray absorption fine structure NEXAFS spectra recorded for dopamine on rutile TiO2 (110) show the phenyl ring to be oriented at 78° ± 5° from the surface and twisted 11 ± 10° relative to the (001) direction.

  3. Adsorption of dopamine on rutile TiO2 (110): a photoemission and near-edge X-ray absorption fine structure study.

    PubMed

    Jackman, Mark J; Syres, Karen L; Cant, David J H; Hardman, Samantha J O; Thomas, Andrew G

    2014-07-29

    Synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) techniques have been used to study the adsorption of dopamine on a rutile TiO2 (110) single crystal. Photoemission results suggest that dopamine bonds through the oxygen molecules in a bidentate fashion. From the data, it is ambiguous whether the oxygens bond to the same 5-fold coordinated surface titanium atom or bridges across two, although based on the bonding of pyrocatechol on rutile TiO2 (110), it is likely that the dopamine bridges two titanium atoms. Using the searchlight effect, the carbon K-edge near-edge X-ray absorption fine structure NEXAFS spectra recorded for dopamine on rutile TiO2 (110) show the phenyl ring to be oriented at 78° ± 5° from the surface and twisted 11 ± 10° relative to the (001) direction. PMID:25003716

  4. 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.

  5. 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.

  6. 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.

  7. New fine structure cooling rate

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.

    1976-01-01

    One of the dominant electron cooling processes in the ionosphere is caused by electron impact induced fine structure transitions among the ground state levels of atomic oxygen. This fine structure cooling rate is based on theoretical cross sections. Recent advances in the numerical cross section determinations to include polarization effects and more accurate representations of the atomic target result in new lower values. These cross sections are employed in this paper to derive a new fine structure cooling rate which is between 40% and 60% of the currently used rate. A new generalized formula is presented for the cooling rate (from which the fine structure cooling rate is derived), valid for arbitrary mass and temperature difference of the colliding particles and arbitrary inelastic energy difference.

  8. 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

  9. Catalyst Chemical State during CO Oxidation Reaction on Cu(111) Studied with Ambient-Pressure X-ray Photoelectron Spectroscopy and Near Edge X-ray Adsorption Fine Structure Spectroscopy.

    PubMed

    Eren, Baran; Heine, Christian; Bluhm, Hendrik; Somorjai, Gabor A; Salmeron, Miquel

    2015-09-01

    The chemical structure of a Cu(111) model catalyst during the CO oxidation reaction in the CO+O2 pressure range of 10-300 mTorr at 298-413 K was studied in situ using surface sensitive X-ray photoelectron and adsorption spectroscopy techniques [X-ray photoelectron spectroscopy (XPS) and near edge X-ray adsorption fine structure spectroscopy (NEXAFS)]. For O2:CO partial pressure ratios below 1:3, the surface is covered by chemisorbed O and by a thin (∼1 nm) Cu2O layer, which covers completely the surface for ratios above 1:3 between 333 and 413 K. The Cu2O film increases in thickness and exceeds the escape depth (∼3-4 nm) of the XPS and NEXAFS photoelectrons used for analysis at 413 K. No CuO formation was detected under the reaction conditions used in this work. The main reaction intermediate was found to be CO2(δ-), with a coverage that correlates with the amount of Cu2O, suggesting that this phase is the most active for CO oxidation.

  10. 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.

  11. 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.

  12. 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.

  13. Fine structure of cluster decays

    SciTech Connect

    Dumitrescu, O.

    1994-03-01

    Within the one level {ital R}-matrix approach, expressions are derived for the hindrance factors of cluster radioactive decays in which {ital y} {ital the} {ital shell} {ital model} {ital with} {ital effective} {ital residual} {ital interactions} [{ital e}.{ital g}.,{ital thelar} in the Michigan State University version for nearly spherical nuclei, or the enlarged superfluid model (ESM) recently proposed for deformed nuclei]. The exterior wave functions are calculated from a cluster-nucleus double-folding model potential obtained with the M3Y interaction. As examples of the cluster decay fine structure we analyzed the particular cases of {alpha} decay of {sup 241}Am and {sup 243}Cm, {sup 14}C decay of {sup 223}Ra, and {sup 34}Si decay of {sup 243}Cm. Good agreement with the experimental data is obtained.

  14. Probing the orientation of electrostatically immobilized Protein G B1 by time-of-flight secondary ion spectrometry, sum frequency generation, and near-edge X-ray adsorption fine structure spectroscopy.

    PubMed

    Baio, Joe E; Weidner, Tobias; Baugh, Loren; Gamble, Lara J; Stayton, Patrick S; Castner, David G

    2012-01-31

    To fully develop techniques that provide an accurate description of protein structure at a surface, we must start with a relatively simple model system before moving to increasingly complex systems. In this study, X-ray photoelectron spectroscopy (XPS), sum frequency generation spectroscopy (SFG), near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to probe the orientation of Protein G B1 (6 kDa) immobilized onto both amine (NH(3)(+)) and carboxyl (COO(-)) functionalized gold. Previously, we have shown that we could successfully control orientation of a similar Protein G fragment via a cysteine-maleimide bond. In this investigation, to induce opposite end-on orientations, a charge distribution was created within the Protein G B1 fragment by first substituting specific negatively charged amino acids with neutral amino acids and then immobilizing the protein onto two oppositely charged self-assembled monolayer (SAM) surfaces (NH(3)(+) and COO(-)). Protein coverage, on both surfaces, was monitored by the change in the atomic % N, as determined by XPS. Spectral features within the SFG spectra, acquired for the protein adsorbed onto a NH(3)(+)-SAM surface, indicates that this electrostatic interaction does induce the protein to form an oriented monolayer on the SAM substrate. This corresponded to the polarization dependence of the spectral feature related to the NEXAFS N(1s)-to-π* transition of the β-sheet peptide bonds within the protein layer. ToF-SIMS data demonstrated a clear separation between the two samples based on the intensity differences of secondary ions stemming from amino acids located asymmetrically within Protein G B1 (methionine: 62 and 105 m/z; tyrosine: 107 and 137 m/z; leucine: 86 m/z). For a more quantitative examination of orientation, we developed a ratio comparing the sum of the intensities of secondary-ions stemming from the amino acid residues at either end

  15. Adsorption of antimony onto iron oxyhydroxides: adsorption behavior and surface structure.

    PubMed

    Guo, Xuejun; Wu, Zhijun; He, Mengchang; Meng, Xiaoguang; Jin, Xin; Qiu, Nan; Zhang, Jing

    2014-07-15

    Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl3, was oxidized into Sb(V) probably due to the involvement of O2 in the long duration of sample preservation. Only one Sb-Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0-1.9 attributed to bidentate mononuclear edge-sharing ((2)E) between Sb and HFO.

  16. Surface properties of coal fines in water. 1. Electrokinetics and surfactant adsorption

    SciTech Connect

    Ayub, A.L.; Al Taweel, A.M.; Kwak, J.C.T.

    1985-01-01

    The adsorption of phenol, p-nitrophenol, the nonionic surfactant Triton X-100 (a commercial mixture of octylphenol poly ethoxylates) and the cationic surfactant dodecyltrimethyl ammonium bromide (DTAB) from aqueous solution on coal fines from a coal washing plant has been studied. Adsorbate solution concentrations range from 0-8 x 10/sup -4/ m. For the cationic and nonionic surfactants both adsorption isotherms and electrokinetic isotherms were determined. The adsorption of phenol, but not of Triton X-100 and DTAB, is found to increase with time for periods up to three hundred h. For short contract times (less than thirty h.), the amount of Triton X-100 adsorbed is about three times higher than the amount of phenol adsorbed at the same solution concentration. The electrokinetic data show that the zeta potential of the coal is not affected by the adsorption of Triton X-100. On the other hand, adsorption of the cationic surfactant strongly influences the zeta potential. For negatively charged coal, i.e., at higher solution pH (iep of the coal used is 5.3), the adsorption of cationic surfactant leads to charge reversal at a typical free surfactant concentration often well below 10/sup -4/ molal. 20 references.

  17. 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. PMID:17744366

  18. Structure and Elongation of fine Ladies’ Hosiery

    NASA Astrophysics Data System (ADS)

    Lozo, M.; Vrljicak, Z.

    2016-07-01

    On a sock-knitting machine with diameter of cylindrical needle bed 100 mm (4e") that knitted with 400 needles, samples of fine women's hosiery were made from four PA filament yarns in counts 20 dtex f 20, 30 dtex f 34, 40 dtex f 40 and 60 dtex f 60. Each type of yarns was used to make hosiery samples with four loop sinking depths of unit values in a computer program 400, 550, 700 and 850. For all the samples, parameters of yarn structure were analyzed and elongation properties of knitted fabric were measured. During the elongation of knitted fabric, areas of knitted fabric elasticity, beginning of permanent deformation and elongation at break were measured. Elongation of knitted fabric in the wale direction, i.e. transverse hosiery elongation and elongation of knitted fabric in the course direction, or longitudinal direction of hosiery were measured. Yarn fineness and loop sinking depth significantly influence the elongation properties of hosiery.

  19. Cryogels: morphological, structural and adsorption characterisation.

    PubMed

    Gun'ko, Vladimir M; Savina, Irina N; Mikhalovsky, Sergey V

    2013-01-01

    Experimental results on polymer, protein, and composite cryogels and data treatment methods used for morphological, textural, structural, adsorption and diffusion characterisation of the materials are analysed and compared. Treatment of microscopic images with specific software gives quantitative structural information on both native cryogels and freeze-dried materials that is useful to analyse the drying effects on their structure. A combination of cryoporometry, relaxometry, thermoporometry, small angle X-ray scattering (SAXS), equilibrium and kinetic adsorption of low and high-molecular weight compounds, diffusion breakthrough of macromolecules within macroporous cryogel membranes, studying interactions of cells with cryogels provides a consistent and comprehensive picture of textural, structural and adsorption properties of a variety of cryogels. This analysis allows us to establish certain regularities in the cryogel properties related to narrow (diameter 0.4100 μm) with boundary sizes within modified life science pore classification. Particular attention is paid to water bound in cryogels in native superhydrated or freeze-dried states. At least, five states of water - free unbound, weakly bound (changes in the Gibbs free energy-ΔG<0.5-0.8 kJ/mol) and strongly bound (-ΔG>0.8 kJ/mol), and weakly associated (chemical shift of the proton resonance δ(H)=1-2 ppm) and strongly associated (δ(H)=3-6 ppm) waters can be distinguished in hydrated cryogels using (1)H NMR, DSC, TSDC, TG and other methods. Different software for image treatment or developed to analyse the data obtained with the adsorption, diffusion, SAXS, cryoporometry and thermoporometry methods and based on regularisation algorithms is analysed and used for the quantitative morphological, structural and adsorption characterisation of individual and composite cryogels, including polymers

  20. The mechanism of hydrogen sulfide adsorption on fine rubber particle media (FRPM).

    PubMed

    Wang, Ning; Park, Jaeyoung; Ellis, Timothy G

    2013-09-15

    A commercial rubber waste product, fine rubber particle media (FRPM), was found to adsorb hydrogen sulfide (H₂S) at 0.12 mg H₂S/g FRPM of adsorption capacity. Since FRPM seems to be an attractive alternative to treat H₂S owing to its economic advantages as well as its physicochemical characteristics, several analyses were conducted to investigate fundamental information, surface properties, and breakthrough characteristics of FRPM as adsorbent. The physical properties of FRPM including composition and surface chemistry were investigated to compare its performance with commonly available commercial H₂S adsorbents such as activated carbon and assess the possible adsorption mechanism. The specific surface area of FRPM was less than 1% of activated carbon. FRPM does not have enough surface area supporting a pure physical adsorption of H₂S because it is particulate in nature with limited porosity. The adsorption of FRPM to remove H₂S was complex mechanism and involved a combination of zinc compounds and carbon black.

  1. 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.

  2. Magnetic tension of sunspot fine structures

    NASA Astrophysics Data System (ADS)

    Venkatakrishnan, P.; Tiwari, Sanjiv Kumar

    2010-06-01

    Context. The equilibrium structure of sunspots depends critically on its magnetic topology and is dominated by magnetic forces. Tension force is one component of the Lorentz force, which balances the gradient of magnetic pressure in force-free configurations. Aims: We employ the tension term of the Lorentz force to clarify the structure of sunspot features like penumbral filaments, umbral light bridges, and outer penumbral fine structures. Methods: We computed the vertical component of the tension term of Lorentz force over two active regions, NOAA AR 10933 and NOAA AR 10930 observed on 5 January 2007 and 12 December 2006, respectively. The former is a simple active region while the latter is a complex one with highly sheared polarity inversion line (PIL). We obtained the vector magnetograms from Hinode(SOT/SP). Results: We find an inhomogeneous distribution of tension with both positive and negative signs in various features of the sunspots. The existence of positive tension at locations of lower field strength and higher inclination is compatible with the uncombed model of the penumbral structure. Positive tension is also seen in umbral light bridges, which could be indication of uncombed structure of the light bridge. Likewise, the upwardly directed tension associated with bipolar regions in the penumbra could be a direct confirmation of the sea serpent model of penumbral structures. Upwardly directed tension at the PIL of AR 10930 seems to be related to flux emergence. The magnitude of the tension force is greater than the force of gravity in some places, implying a nearly force-free configuration for these sunspot features. Conclusions: From our study, magnetic tension emerges as a useful diagnostic of the local equilibrium of the sunspot fine structures. Figures A.1-A.3 are only available in electronic form at http://www.aanda.org

  3. The fine structure constant and habitable planets

    NASA Astrophysics Data System (ADS)

    Sandora, McCullen

    2016-08-01

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

  4. The fine structure constant and habitable planets

    NASA Astrophysics Data System (ADS)

    Sandora, McCullen

    2016-08-01

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

  5. 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

  6. 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.

  7. Sheath over a finely structured divertor plate

    SciTech Connect

    Cohen, R. H., LLNL

    1998-05-15

    The surface of a divertor plate typically has fine structure. Depending on the material - and the duration of exposure to the plasma, the characteristic size of the surface imperfections may vary over a broad range. In this paper, we consider the case where these structures have scale h that is much smaller than the ion gyroradius {rho}{sub i} but greater than the electron gyroradius {rho}{sub e}. The magnetic field intersects the divertor plate at a shallow angle {alpha}<fine surface structures and strongly tilted magnetic field, gives rise to many interesting new phenomena in the sheath. We consider only the plasma part of the problem: given the presence of some structure, what are the consequences in terms of the plasma properties in the vicinity of the surface? We are not addressing the issue of what process has caused the appearance of the structure. However, once the plasma part of the problem is solved, on could return to the analysis of the wall erosion problem, based on the solution obtained. For the environment of the divertor region of a medium-size tokamak (plasma density n{approximately}4x10{sup 13} cm{sup -3}, plasma temperature T{approximately}50 eV, the magnetic field strength B{approximately} 2T), one has: {rho}{sub i} {approximately}500 {micro}m (hydrogen), {rho}{sub e}{approximately}10 {micro}m. We, therefore, are going to analyze the scales of imperfections in the range 10 {micro}m

  8. Magnetic fine structure of solar coronal loops

    NASA Technical Reports Server (NTRS)

    Van Ballegooijen, A. A.

    1988-01-01

    A numerical simulation of the effect of a random photospheric flow on the magnetic structure of a coronal loop is presented. An initially uniform field embedded in a perfectly conducting plasma is assumed, extending between two flat parallel plates representing the solar photosphere at both ends of the loop. The field is perturbed by a sequence of randomly phased, sinusoidal flow patterns applied at one of the boundary plates, and the corresponding sequence of force-free fields is determined. It is found that the electric currents generated by these flows develop a fine structure on a scale significantly smaller than the wavelength of the velocity patterns. This suggests that magnetic energy is transferred to smaller scale via a cascade process.

  9. Fine structure in deformed proton emitters.

    SciTech Connect

    Sonzogni, A. A.; Davids, C. N.; Woods, P. J.; Seweryniak, D.; Carpenter, M. P.; Ressler, J. J.; Schwartz, J.; Uusitalo, J.; Walters, W. B.

    1999-12-07

    In a recent experiment to study the proton radioactivity of the highly deformed {sup 131}Eu nucleus, two proton lines were detected. The higher energy one was assigned to the ground-state to ground-state decay, while the lower energy, to the ground-state to the 2{sup +} state decay. This constitutes the first observation of fine structure in proton radioactivity. With these four measured quantities, proton energies, half-life and branching ratio, it is possible to determine the Nilsson configuration of the ground state of the proton emitting nucleus as well as the 2{sup +} energy and nuclear deformation of the daughter nucleus. These results will be presented and discussed.

  10. 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.

  11. FINE STRUCTURE OF BRUCELLA SUIS SPHEROPLASTS

    PubMed Central

    Hines, William D.; Freeman, Bob A.; Pearson, Gary R.

    1964-01-01

    Hines, William D. (University of Chicago, Chicago, Ill.), Bob A. Freeman, and Gary R. Pearson. Fine structure of Brucella suis spheroplasts. J. Bacteriol. 87:1492–1498. 1964.—Spheroplasts of Brucella suis, prepared by treatment with penicillin and glycine, and normal cells were sectioned and studied by electron microscopy. These spheroplasts differed from the normal cell in that they were greatly expanded and coccoid in shape. The cell wall and cytoplasmic membrane were more easily demonstrated in the spheroplasts. The cell wall and cytoplasmic membrane of normal cells appeared structureless, but in the spheroplasts both were shown to consist of two dark layers sandwiching a lighter layer. The cytoplasm of the spheroplasts was more dilute than that of normal cells and, in the case of glycine-induced spheroplasts, tended to aggregate. Images PMID:14188733

  12. Cell fine structure and function - Past and present

    NASA Technical Reports Server (NTRS)

    Fernandez-Moran, H.

    1970-01-01

    Electron microscopic studies of nerve membrane fine structure, discussing cell membrane multienzyme and macromolecular energy and information transduction, protein synthesis and nucleic acids interrelations

  13. 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

  14. Fine structures in decametric noise storms: possible mechanisms.

    NASA Astrophysics Data System (ADS)

    Melrose, D. B.

    The properties and existing theories for three types of fine structure observed in solar decametric storms are reviewed. The types are stria bursts, including split pair bursts, triple bursts and type IIIb bursts, drift pair (DP) bursts and S bursts.

  15. Fine thermal structure of a coronal active region.

    PubMed

    Reale, Fabio; Parenti, Susanna; Reeves, Kathy K; Weber, Mark; Bobra, Monica G; Barbera, Marco; Kano, Ryouhei; Narukage, Noriyuki; Shimojo, Masumi; Sakao, Taro; Peres, Giovanni; Golub, Leon

    2007-12-01

    The determination of the fine thermal structure of the solar corona is fundamental to constraining the coronal heating mechanisms. The Hinode X-ray Telescope collected images of the solar corona in different passbands, thus providing temperature diagnostics through energy ratios. By combining different filters to optimize the signal-to-noise ratio, we observed a coronal active region in five filters, revealing a highly thermally structured corona: very fine structures in the core of the region and on a larger scale further away. We observed continuous thermal distribution along the coronal loops, as well as entangled structures, and variations of thermal structuring along the line of sight.

  16. 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

  17. Double-sided F and Cl adsorptions on graphene at various atomic ratios: Geometric, orientation and electronic structure aspects

    NASA Astrophysics Data System (ADS)

    Widjaja, Hantarto; Jiang, Zhong-Tao; Altarawneh, Mohammednoor; Yin, Chun-Yang; Goh, Bee-Min; Mondinos, Nicholas; Amri, Amun; Dlugogorski, Bogdan Z.

    2016-06-01

    Elemental adsorption on graphene offers an effective procedure in fine-tuning electronic and mechanical properties of graphene. The effects of dopants depend on adsorption site, the degree of coverage as well as on the configuration of the deployed supercell. In this contribution, the density functional theory (DFT) calculations were performed to investigate the electronic structures of F and Cl adsorption (double-sided, top site) on graphene in terms of adsorption orientation, atomic ratios, i.e., from C:F/Cl = 18:2 to C:F/Cl = 2:2. Despite being members of the halogens group, F- and Cl-adsorbed on graphene show contrasting trends. F is adsorbed to graphene more strongly than Cl. F favours full and 25% adsorption coverage, while Cl favours 25% coverage. Both F and Cl cases open band gap (at Fermi energy) at certain atomic concentration coverage, but none creates magnetization.

  18. Structure and adsorption properties of a porous cooper hexacyanoferrate polymorph

    NASA Astrophysics Data System (ADS)

    Roque-Malherbe, R.; Carballo, E.; Polanco, R.; Lugo, F.; Lozano, C.

    2015-11-01

    The key questions addressed here were: the structure elucidation and the investigation of the adsorption space and framework expansion effect of a Cu(II) hexacyanoferrate (III) polymorph (labeled Cu-PBA-I). The structural analysis was performed with a broad set of characterization methods. Additionally, a low and high pressure carbon dioxide adsorption investigation was performed, assuming, to comprehend the adsorption experiments, that the adsorbent plus the adsorbed phase were a solid solution. We concluded: that the Cu-PBA-I presented the following composition, K1/4 Cu (II)[ Fe (III)(CN)6 ] 3 / 4⋄1/4 nH2 O , exhibited an antiferromagnetic behavior and displayed a thermally stable I 4 bar m 2 space group lattice in the degassed state. Moreover, the low pressure adsorption study allowed the calculation of the micropore volume, W=0.09 cm3/g and the isosteric heat of adsorption, qiso=19 kJ/mol; further, the high pressure adsorption data revealed an extremely high adsorption capacity owing to a framework expansion effect. Finally, the DRIFTS spectrum of adsorbed CO2 displayed peaks corresponding to carbon dioxide physically adsorbed and interacting with electron accepting Lewis acid sites. Hence, was produced an excellent adsorbent which combine porosity and anti-ferromagnetism, antagonist properties rarely found together.

  19. Fine crystal structure of porous corundum ceramics

    NASA Astrophysics Data System (ADS)

    Grigoriev, M. V.; Kulkov, S. N.

    2011-05-01

    The microstructure of corundum ceramics based on powders with a varying grain size has been investigated. Both commercial alumina powders and those fabricated by denitration of aluminum salts in a high-frequency discharge plasma were used. An increase in the plasma-chemical Al2O3 powder content in the sample was found to change the pore structure of the corundum ceramics from a high-porosity ceramic skeleton with a well-developed system of channel-forming pores to ceramics with isolated pores. The change in the pore structure was observed for 50% porosity and caused an increase in the level of crystal lattice microdistortions. An increase in the sintering temperature from 1200 to 1650°C is shown to be responsible for a two-fold increase in the average crystallite size and for annealing of lattice defects along grain boundaries.

  20. Surfaces of Microparticles in Colloids: Structure and Molecular Adsorption Kinetics

    NASA Astrophysics Data System (ADS)

    Dai, Hai-Lung

    2002-03-01

    Surfaces of micron and sub-micron size particles in liquid solution are probed by second harmonic generation (SHG) facilitated with femtosecond laser pulses. The particles probed include inorganic objects such as carbon black and color pigments, polymeric species like polystyrene beads, and biological systems such as blood cells and ecoli. In the experiments, dye molecules are first adsorbed onto the particle surface to allow generation of second harmonics upon light irradiation. Competition for adsorption between these surface dye molecules and the molecules of interest in the solution is then monitored by the SHG signal to reveal the molecular adsorption kinetics and surface structure. Specifically, surfactant adsorption on polymer surfaces, the structure of carbon black surface, and protein adsorption on biological surfaces, monitored by this technique, will be discussed.

  1. The Fine Structure of Some Retinal Photoreceptors

    PubMed Central

    Moody, M. F.; Robertson, J. D.

    1960-01-01

    An electron microscope study has been made of octopus and amphibian photoreceptors, after fixing with KMnO4 and embedding in araldite. What has previously been seen as a single dense stratum bounding the tubular compartments (octopus) or the double membrane discs (rods and cones), now shows a double structure. We interpret this as showing that these tubules and discs have similar bounding surfaces, which are probably directly related to the cell membrane. This is confirmed by the finding that the tubules and discs are (at least occasionally) continuous with the cell membrane. PMID:14423794

  2. Probing the pore wall structure of nanoporous carbons using adsorption.

    PubMed

    Nguyen, Thanh X; Bhatia, Suresh K

    2004-04-27

    Hitherto, adsorption has been traditionally used to study only the porous structure in disordered materials, while the structure of the solid phase skeleton has been probed by crystallographic methods such as X-ray diffraction. Here we show that for carbons density functional theory, suitably adapted to consider heterogeneity of the pore walls, can be reliably used to probe features of the solid structure hitherto accessibly only approximately even by crystallographic methods. We investigate a range of carbons and determine pore wall thickness distributions using argon adsorption, with results corroborated by X-ray diffraction.

  3. 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).…

  4. Structural Determinants for Protein adsorption/non-adsorption to Silica Surface

    PubMed Central

    Mathé, Christelle; Devineau, Stéphanie; Aude, Jean-Christophe; Lagniel, Gilles; Chédin, Stéphane; Legros, Véronique; Mathon, Marie-Hélène; Renault, Jean-Philippe; Pin, Serge; Boulard, Yves; Labarre, Jean

    2013-01-01

    The understanding of the mechanisms involved in the interaction of proteins with inorganic surfaces is of major interest in both fundamental research and applications such as nanotechnology. However, despite intense research, the mechanisms and the structural determinants of protein/surface interactions are still unclear. We developed a strategy consisting in identifying, in a mixture of hundreds of soluble proteins, those proteins that are adsorbed on the surface and those that are not. If the two protein subsets are large enough, their statistical comparative analysis must reveal the physicochemical determinants relevant for adsorption versus non-adsorption. This methodology was tested with silica nanoparticles. We found that the adsorbed proteins contain a higher number of charged amino acids, particularly arginine, which is consistent with involvement of this basic amino acid in electrostatic interactions with silica. The analysis also identified a marked bias toward low aromatic amino acid content (phenylalanine, tryptophan, tyrosine and histidine) in adsorbed proteins. Structural analyses and molecular dynamics simulations of proteins from the two groups indicate that non-adsorbed proteins have twice as many π-π interactions and higher structural rigidity. The data are consistent with the notion that adsorption is correlated with the flexibility of the protein and with its ability to spread on the surface. Our findings led us to propose a refined model of protein adsorption. PMID:24282583

  5. The Fine-Structure Constant and Wavelength Calibration

    NASA Astrophysics Data System (ADS)

    Whitmore, Jonathan

    The fine-structure constant is a fundamental constant of the universe--and widely thought to have an unchanging value. However, the past decade has witnessed a controversy unfold over the claimed detection that the fine-structure constant had a different value in the distant past. These astrophysical measurements were made with spectrographs at the world's largest optical telescopes. The spectrographs make precise measurements of the wavelength spacing of absorption lines in the metals in the gas between the quasar background source and our telescopes on Earth. The wavelength spacing gives a snapshot of the atomic physics at the time of the interaction. Whether the fine-structure constant has changed is determined by comparing the atomic physics in the distant past with the atomic physics of today. We present our contribution to the discussion by analyzing three nights data taken with the HIRES instrument (High Resolution Echelle Spectrograph) on the Keck telescope. We provide an independent measurement on the fine-structure constant from the Damped Lyman alpha system at a redshift of z =2.309 (10.8 billion years ago) quasar PHL957. We developed a new method for calibrating the wavelength scale of a quasar exposure to a much higher precision than previously achieved. In our subsequent analysis, we discovered unexpected wavelength calibration errors that has not been taken into account in the previously reported measurements. After characterizing the wavelength miscalibrations on the Keck-HIRES instrument, we obtained several nights of data from the main competing instrument, the VLT (Very Large Telescope) with UVES (Ultraviolet and Visual Echelle Spectrograph). We applied our new wavelength calibration method and uncovered similar in nature systematic errors as found on Keck-HIRES. Finally, we make a detailed Monte Carlo exploration of the effects that these miscalibrations have on making precision fine-structure constant measurements.

  6. 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.

  7. Efferent Modulation of Stimulus Frequency Otoacoustic Emission Fine Structure

    PubMed Central

    Zhao, Wei; Dewey, James B.; Boothalingam, Sriram; Dhar, Sumitrajit

    2015-01-01

    Otoacoustic emissions, sounds generated in the inner ear, have become a convenient non-invasive tool to examine the efferent modulation of cochlear mechanics. Activation of the medial olivocochlear (MOC) efferents has been shown to alter the magnitude of these emissions. When the effects of efferent activation on the detailed spectral structures of these emissions have been examined, a shift of the spectral patterns toward higher frequencies has been reported for distortion product and spontaneous otoacoustic emissions. Stimulus frequency otoacoustic emissions (SFOAEs) have been proposed as the preferred emission type in the study of efferent modulation due to the simplicity of their production leading to the possibility of clearer interpretation of results. The effects of efferent activation on the complex spectral patterns of SFOAEs have not been examined to the best of our knowledge. We have examined the effects of activating the MOC efferents using broadband noise in normal-hearing humans. The detailed spectral structure of SFOAEs, known as fine structure, was recorded with and without contralateral acoustic stimulation. Results indicate that SFOAEs are reduced in magnitude and their fine structure pushed to higher frequencies by contralateral acoustic stimulation. These changes are similar to those observed in distortion product or spontaneous otoacoustic emissions and behavioral hearing thresholds. Taken together with observations made about magnitude and phase changes in otoacoustic emissions and hearing thresholds upon contralateral acoustic stimulation, all changes in otoacoustic emission and hearing threshold fine structure appear to be driven by a common set of mechanisms. Specifically, frequency shifts in fine structure patterns appear to be linked to changes in SFOAE phase due to contralateral acoustic stimulation. PMID:26696843

  8. Molecular structure-adsorption study on current textile dyes.

    PubMed

    Örücü, E; Tugcu, G; Saçan, M T

    2014-01-01

    This study was performed to investigate the adsorption of a diverse set of textile dyes onto granulated activated carbon (GAC). The adsorption experiments were carried out in a batch system. The Langmuir and Freundlich isotherm models were applied to experimental data and the isotherm constants were calculated for 33 anthraquinone and azo dyes. The adsorption equilibrium data fitted more adequately to the Langmuir isotherm model than the Freundlich isotherm model. Added to a qualitative analysis of experimental results, multiple linear regression (MLR), support vector regression (SVR) and back propagation neural network (BPNN) methods were used to develop quantitative structure-property relationship (QSPR) models with the novel adsorption data. The data were divided randomly into training and test sets. The predictive ability of all models was evaluated using the test set. Descriptors were selected with a genetic algorithm (GA) using QSARINS software. Results related to QSPR models on the adsorption capacity of GAC showed that molecular structure of dyes was represented by ionization potential based on two-dimensional topological distances, chromophoric features and a property filter index. Comparison of the performance of the models demonstrated the superiority of the BPNN over GA-MLR and SVR models. PMID:25529487

  9. Fine structure of the solar transition region - Observations and interpretation

    NASA Technical Reports Server (NTRS)

    Cook, J. W.; Brueckner, G. E.

    1991-01-01

    An evaluation is conducted of recent high spatial resolution observations of the solar transition region and temperature minimum, in the form of UV spectra and spectroheliographs from both sounding rockets and the Spacelab 2 flights of the High Resolution Telescope and Spectrograph (HRTS). Attention is given to the solar atmosphere structure implications of the HRST's observational results. The inclusion of fine structure in conjectures concerning the transition region affects the plausibility of 1D average models of the solar atmosphere, as well as the determination of temperature gradients, possible nonradiative-heating mechanisms, and the comparison of transition region structures with corresponding observations of the photosphere and corona.

  10. Fine structure constant and quantized optical transparency of plasmonic nanoarrays.

    PubMed

    Kravets, V G; Schedin, F; Grigorenko, A N

    2012-01-01

    Optics is renowned for displaying quantum phenomena. Indeed, studies of emission and absorption lines, the photoelectric effect and blackbody radiation helped to build the foundations of quantum mechanics. Nevertheless, it came as a surprise that the visible transparency of suspended graphene is determined solely by the fine structure constant, as this kind of universality had been previously reserved only for quantized resistance and flux quanta in superconductors. Here we describe a plasmonic system in which relative optical transparency is determined solely by the fine structure constant. The system consists of a regular array of gold nanoparticles fabricated on a thin metallic sublayer. We show that its relative transparency can be quantized in the near-infrared, which we attribute to the quantized contact resistance between the nanoparticles and the metallic sublayer. Our results open new possibilities in the exploration of universal dynamic conductance in plasmonic nanooptics.

  11. 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.

  12. Relative fine-structure intensities in two-photon excitation

    NASA Technical Reports Server (NTRS)

    Crosley, D. R.; Bischel, W. K.

    1984-01-01

    A discrepancy is pointed out between experimental determinations of the relative intensities for different fine-structure components of the two-photon transitions 2p3P 3p3P in oxygen and 2p3 4S0 - 2p2 3p4D0 in nitrogen, which agreed well with calculations involving a single virtual intermediate level, and a two-photon selection rule dJ not equal to one, derived in a purely theoretical and erroneous treatment of these transitions. Five other experiments are also briefly examined, with the conclusion that relative fine-structure intensities in two-photon transitions are well understood as straightforward extensions of angular momentum coupling in single-photon cases, in accordance with allowed dJ = 0, + or -1, and + or -2 transitions.

  13. 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.

  14. 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

  15. 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

  16. Deeper Probing of the Fine-structure Constant

    NASA Astrophysics Data System (ADS)

    Goradia, Shantilal

    2008-10-01

    In our earlier attempt in [1] to derive fine-structure constant, one subtle reason why the natural logarithm of the age of the universe in Planck times comes out to be slightly greater than the reciprocal of the fine structure constant is that the variable W in Boltzmann's expression should be the age of the universe in Planck times divided by the bit depth for our specific application. Since we cannot decode the nature's bit depth, we cannot come up with the expected value of ALPHA. For an assumed bit depth of 10, the reciprocal of ALPHA goes down by ln10 (2.3) without having a significant impact on the order of magnitude of the baud rate (baud rate = bits per second/bit depth = 10^43 (Planck time/second)/10 = 10^42). Use of terms and equations from informatics in both of author's interrelated abstracts this meeting is meant to engage a wider audience simply. [1] Goradia, Shantilal ``What is Fine-structure Constant?'' http://www.arXiv.org/pdf/physics/0210040v3.

  17. 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.

  18. Fine structure of coupled optical modes in photonic molecules

    NASA Astrophysics Data System (ADS)

    Rakovich, Y. P.; Donegan, J. F.; Gerlach, M.; Bradley, A. L.; Connolly, T. M.; Boland, J. J.; Gaponik, N.; Rogach, A.

    2004-11-01

    We report on the coherent coupling of whispering gallery modes (WGM) in a photonic molecule formed from two melamine-formaldehyde spherical microcavities with a thin shell of CdTe nanocrystals. Utilizing a microporous polymer structure to orient the photonic molecule, we have excited the photonic molecule both on and off axis. This controllable geometry has allowed the observation of an off-axis fine structure that consists of very sharp peaks resulting from the removal of the WGM degeneracy with respect to the azimuthal quantum number m . The mode splittings are in very good agreement with theory.

  19. Fine structure of coupled optical modes in photonic molecules

    SciTech Connect

    Rakovich, Y.P.; Donegan, J.F.; Gerlach, M.; Bradley, A.L.; Connolly, T.M.; Boland, J.J.; Gaponik, N.; Rogach, A.

    2004-11-01

    We report on the coherent coupling of whispering gallery modes (WGM) in a photonic molecule formed from two melamine-formaldehyde spherical microcavities with a thin shell of CdTe nanocrystals. Utilizing a microporous polymer structure to orient the photonic molecule, we have excited the photonic molecule both on and off axis. This controllable geometry has allowed the observation of an off-axis fine structure that consists of very sharp peaks resulting from the removal of the WGM degeneracy with respect to the azimuthal quantum number m. The mode splittings are in very good agreement with theory.

  20. Oxygen on Ni(111): A multiple-scattering analysis of the near-edge x-ray-absorption fine structure

    NASA Astrophysics Data System (ADS)

    Pedio, M.; Becker, L.; Hillert, B.; D'addato, S.; Haase, J.

    1990-04-01

    Oxygen chemisorption and oxide formation on a Ni(111) surface have been monitored by using the near-edge x-ray-absorption fine-structure technique. The adsorption site of oxygen in the p(2×2) and (√3 × √3 )R30° superstructures has been determined by a multiple-scattering analysis. In both structures the oxygen occupies a threefold-coordinated fcc site with a nearest-neighbor O-Ni bond length of 1.85+/-0.05 Å on a Ni(111) surface relaxed outwards by ~0.15 Å.

  1. 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.

  2. 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.

  3. 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.

  4. Numerical models of sunspot formation and fine structure.

    PubMed

    Rempel, Matthias

    2012-07-13

    Sunspots are central to our understanding of solar (and stellar) magnetism in many respects. On the large scale, they link the magnetic field observable in the photosphere to the dynamo processes operating in the solar interior. Properly interpreting the constraints that sunspots impose on the dynamo process requires a detailed understanding of the processes involved in their formation, dynamical evolution and decay. On the small scale, they give an insight into how convective energy transport interacts with the magnetic field over a wide range of field strengths and inclination angles, leading to sunspot fine structure observed in the form of umbral dots and penumbral filaments. Over the past decade, substantial progress has been made on both observational and theoretical sides. Advanced ground- and space-based observations have resolved, for the first time, the details of umbral dots and penumbral filaments and discovered similarities in their substructures. Numerical models have advanced to the degree that simulations of entire sunspots with sufficient resolution to resolve sunspot fine structure are feasible. A combination of improved helioseismic inversion techniques with seismic forward modelling provides new views on the subsurface structure of sunspots. In this review, we summarize recent progress, with particular focus on numerical modelling. PMID:22665895

  5. 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.

  6. Structural study of Fe (II) adsorption on hematite (1102)

    SciTech Connect

    Tanwar, K.S.; Petitto, S.C.; Ghose, S.K.; Eng, P.J.; Trainor, T.P.

    2008-07-15

    The structure of {alpha}-Fe{sub 2}O{sub 3}(1{bar 1}02) reacted with Fe(II) under anoxic conditions was studied using crystal truncation rod (CTR) diffraction. The CTR results show the crystalline termination of {alpha}-Fe{sub 2}O{sub 3}(1{bar 1}02) is modified due to adsorption of Fe(II) at crystallographic lattice sites. In addition, the binding sites for adsorbed Fe are similar for all studied conditions: reaction for 2 h at pH 5.0, for 34 d at pH 5.0, and for 5.5 h at pH 7.0. The occupancy of adsorbed Fe increases with both reaction time and pH, which is consistent with typical cation adsorption behavior on iron (hydr)oxide surfaces. The metal-oxygen bond lengths of the (ordered) surface Fe atoms are characteristic of Fe(III), which provides indirect evidence for oxidation of adsorbed Fe(II) and is consistent with recent studies indicating that Fe(III)-hydroxides are effective oxidants for dissolved ferrous iron. Grazing-incidence X-ray diffraction measurements indicate that no crystalline surface reaction products formed during the course of Fe(II) reaction. Overall, the structural characterization of the Fe(II) adsorption reaction results in an enhanced understanding of how reduced iron affects the structure, stability and reactivity of hematite.

  7. Adsorption of copper to different biogenic oyster shell structures

    NASA Astrophysics Data System (ADS)

    Wu, Qiong; Chen, Jie; Clark, Malcolm; Yu, Yan

    2014-08-01

    The removal of copper from solution by oyster shell powder was investigated for potential wastewater treatment uses. In particular, adsorption behavior differences between the prismatic (PP) and nacreous (NP) shell layers, and how this affects copper removal, were investigated. Experimental results indicated that copper adsorption was highly pH-dependent with optimal copper removal at pH 5.5, where the powdered whole raw shell (RP) removed up to 99.9% of the copper within 24 h at a 10 mg/L initial copper concentration. Langmuir and Freundlich models were used to analyze the isotherm PP, NP and RP data. These results showed a strong homogeneous Langmuir model for low initial copper concentrations (5-30 mg/L) to both RP and PP layer, while strong agreement with a heterogeneous Freundlich model for high initial copper concentrations (30-200 mg/L); nevertheless, a homogeneous Langmuir model provided the best fit for the more dense NP layer across the initial concentration range (5-200 mg/L). The distribution coefficient (Kd) value of PP layer for each initial concentration investigated was substantially higher than the NP layer and it was also found that the PP layer dominated the adsorption process with an adsorption capacity of 8.9 mg/g, while the adsorption capacity of the NP layer was 2.6 mg/g. These differences are believed to be because of the more porous structure of the PP layer, which was confirmed by scanning electron microscopy, infrared spectroscopy, energy-dispersive X-ray spectroscopy, and thermogravimetry-differential thermal analyses.

  8. 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.

  9. 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.

  10. Fine structure of Bodo curvifilus Griessmann (Kinetoplastida: Bodonidae).

    PubMed

    Burzell, L A

    1975-02-01

    Bodo curvifilus Griessmann conforms in its fine structure to the criteria proposed for the genus Bodo, including the presence of subpellicular microtubules, a single large kinetoplast-mitochondrion, emergence of the 2 heterodynamic flagella from a subapical flagellar pocket, and the presence of a paraxial rod associated with the axoneme of each flagellum. B. curvifilus possesses cytoplasmic bodies which resemble endosymbiotic bacteria. These are similar to those found in Bodo saltans. Bodo curvifilus can be distinguished ultrastructurally from Bodo caudatus and B. saltans by the presence in B. curvifilus of a hitherto unreported structure, "the microtubular prism," consisting of a bundle of 19 microtubules. In cross section, 15 of these microtubules form a cross-linked prismatic array. This microtubular bundle originates near the flagellar pocket and extends for several micrometers into the body of the organism where it follows the periphery of the cell and the long finger-like projections of the kinetoplast-mitochondrion.

  11. Adsorption structure of water molecules on the Be(0001) surface

    SciTech Connect

    Yang, Yu; Li, Yanfang; Wang, Shuangxi; Zhang, Ping

    2014-06-07

    By using density functional theory calculations, we systematically investigate the adsorption of water molecules at different coverages on the Be(0001) surface. The coverage dependence of the prototype water structures and energetics for water adlayer growth are systematically studied. The structures, energetics, and electronic properties are calculated and compared with other available studies. Through our systematic investigations, we find that water molecules form clusters or chains on the Be(0001) surface at low coverages. When increasing the water coverage, water molecules tend to form a 2 × 2 hexagonal network on the Be(0001) surface.

  12. Structural phases of adsorption for flexible polymers on nanocylinder surfaces.

    PubMed

    Gross, Jonathan; Vogel, Thomas; Bachmann, Michael

    2015-11-11

    By means of generalized-ensemble Monte Carlo simulations, we investigate the thermodynamic behavior of a flexible, elastic polymer model in the presence of an attractive nanocylinder. We systematically identify the structural phases that are formed by competing monomer-monomer and monomer-substrate interactions. The influence of the relative surface attraction strength on the structural phases in the hyperphase diagram, parameterized by cylinder radius and temperature, is discussed as well. In the limiting case of the infinitely large cylinder radius, our results coincide with previous outcomes of studies of polymer adsorption on planar substrates.

  13. 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. PMID:26760054

  14. 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.

  15. Collisional Relaxation of Fine Velocity Structures in Plasmas.

    PubMed

    Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi

    2016-04-01

    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 locally increase due to velocity space deformations of the particle velocity distribution function. These results support the idea that high-resolution measurements of the particle velocity distribution function are crucial for an accurate description of weakly collisional systems, such as the solar wind, in order to answer relevant scientific questions, related, for example, to particle heating and energization. PMID:27104713

  16. Fine structure in the cluster decay of radium isotopes

    NASA Astrophysics Data System (ADS)

    Santhosh, K. P.

    2010-01-01

    Half-life times for 14C cluster emission from various radium isotopes are computed taking interacting potential as the sum of Coulomb and proximity potentials. The half-life time values are compared with experimental data and with the values reported by Poenaru et al using the analytical super-asymmetric fission model (ASAFM). The lowest half-life time for 222Ra stresses the role of the doubly magic 208Pb daughter in the exotic decay process. It is found that neutron excess in the parent nucleus slows down the exotic decay process. The high hindrance factor (HF) of the 14C branch to the ground state (9/2+) and the low HF to the first excited state (11/2+) of the 209Pb daughter are in good agreement with the experimental result. The fine structure from 223Ra gives direct evidence of the presence of a spherical component in the deformed parent nucleus.

  17. FOURIER ANALYSIS OF EXTENDED FINE STRUCTURE WITH AUTOREGRESSIVE PREDICTION

    SciTech Connect

    Barton, J.; Shirley, D.A.

    1985-01-01

    Autoregressive prediction is adapted to double the resolution of Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) Fourier transforms. Even with the optimal taper (weighting function), the commonly used taper-and-transform Fourier method has limited resolution: it assumes the signal is zero beyond the limits of the measurement. By seeking the Fourier spectrum of an infinite extent oscillation consistent with the measurements but otherwise having maximum entropy, the errors caused by finite data range can be reduced. Our procedure developed to implement this concept applies autoregressive prediction to extrapolate the signal to an extent controlled by a taper width. Difficulties encountered when processing actual ARPEFS data are discussed. A key feature of this approach is the ability to convert improved measurements (signal-to-noise or point density) into improved Fourier resolution.

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

    NASA Astrophysics Data System (ADS)

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

    2001-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Anchordoqui, Luis; Goldberg, Haim

    2003-10-01

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

  20. Nonlinear Electrodynamics Analysis Of The Fine Structure Constant

    NASA Astrophysics Data System (ADS)

    Mbelek, Jean Paul

    2010-10-01

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

  1. Collisional Relaxation of Fine Velocity Structures in Plasmas

    NASA Astrophysics Data System (ADS)

    Pezzi, Oreste; Valentini, Francesco; Veltri, Pierluigi

    2016-04-01

    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 locally increase due to velocity space deformations of the particle velocity distribution function. These results support the idea that high-resolution measurements of the particle velocity distribution function are crucial for an accurate description of weakly collisional systems, such as the solar wind, in order to answer relevant scientific questions, related, for example, to particle heating and energization.

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

    NASA Astrophysics Data System (ADS)

    Fujii, Yasunori

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

  3. 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.

  4. 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.

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

    PubMed

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

    2008-07-01

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

  6. Structural studies of molecular and metallic overlayers using angle- resolved photoemission extended fine structure

    SciTech Connect

    Huang, Z.

    1992-10-01

    Angle-resolved photoemission extended fine structure (ARPEFS) was used to study molecular and metallic overlayers on metal surfaces through analysis of p2mg(2[times]1)CO/Ni(110) and the p(2[times]2)K/Ni(111) adsorption. For the dense p2mg(2[times]1)CO/Ni(110) surface layer, photoemission intensities from C 1s level were measured in three directions at photoelectron kinetic energies 60-400 eV. Using multiple-scattering spherical-wave (MSSW) modeling, it was found that CO molecules are adsorbed on short-bridge sites, with adjacent CO along the [110] direction displaced alternatively in opposite directions towards the [001] azimuths to form a zigzag chain geometry. The tilt angle is 16[plus minus]2[degree] from the surface normal for the direction linking the C atom and the center of the Ni bridge. The carbon C-Ni interatomic distance was determined to be 1.94[plus minus]0.02[Angstrom]. The first- to second-layer spacing of Ni is 1.27[plus minus]0.04[Angstrom], up from 1.10[Angstrom] for the clean Ni(110) surface, but close to the 1.25[Angstrom] Ni interlayer spacing in the bulk. The C-O bond length and tilt angle were varied within small ranges (1.10--1.20[Angstrom] and 15--23[degrees]) in our MSSW simulations. Best agreement between experiment and simulations was achieved at 1.16[Angstrom] and 19[degrees]. This yields an O-O distance of 2.95[Angstrom] for the two nearest CO molecules, (van der Waals' radius [approximately] 1.5 [Angstrom] for oxygen). Two different partial-wave phase-shifts were used in MSSW, and structural results from both are in very good agreement. For the p(2[times]2)K/Ni(111) overlayer, ARPEFS [chi](k) curves from K 1s level measured along [111] and [771] at 130K showed that the K atoms are preferentially adsorbed on the atop sites, in agreement with a LEED study of the same system.

  7. Structural studies of molecular and metallic overlayers using angle- resolved photoemission extended fine structure

    SciTech Connect

    Huang, Z.

    1992-10-01

    Angle-resolved photoemission extended fine structure (ARPEFS) was used to study molecular and metallic overlayers on metal surfaces through analysis of p2mg(2{times}1)CO/Ni(110) and the p(2{times}2)K/Ni(111) adsorption. For the dense p2mg(2{times}1)CO/Ni(110) surface layer, photoemission intensities from C 1s level were measured in three directions at photoelectron kinetic energies 60-400 eV. Using multiple-scattering spherical-wave (MSSW) modeling, it was found that CO molecules are adsorbed on short-bridge sites, with adjacent CO along the [110] direction displaced alternatively in opposite directions towards the [001] azimuths to form a zigzag chain geometry. The tilt angle is 16{plus_minus}2{degree} from the surface normal for the direction linking the C atom and the center of the Ni bridge. The carbon C-Ni interatomic distance was determined to be 1.94{plus_minus}0.02{Angstrom}. The first- to second-layer spacing of Ni is 1.27{plus_minus}0.04{Angstrom}, up from 1.10{Angstrom} for the clean Ni(110) surface, but close to the 1.25{Angstrom} Ni interlayer spacing in the bulk. The C-O bond length and tilt angle were varied within small ranges (1.10--1.20{Angstrom} and 15--23{degrees}) in our MSSW simulations. Best agreement between experiment and simulations was achieved at 1.16{Angstrom} and 19{degrees}. This yields an O-O distance of 2.95{Angstrom} for the two nearest CO molecules, (van der Waals` radius {approximately} 1.5 {Angstrom} for oxygen). Two different partial-wave phase-shifts were used in MSSW, and structural results from both are in very good agreement. For the p(2{times}2)K/Ni(111) overlayer, ARPEFS {chi}(k) curves from K 1s level measured along [111] and [771] at 130K showed that the K atoms are preferentially adsorbed on the atop sites, in agreement with a LEED study of the same system.

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

    NASA Astrophysics Data System (ADS)

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

    1996-09-01

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

  9. 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.

  10. Observations on the Fine Structure of the Turtle Atrium

    PubMed Central

    Fawcett, Don W.; Selby, Cecily C.

    1958-01-01

    The general fine structure of the atrial musculature of the turtle heart is described, including; the nature of the sarcolemma; the cross-banded structure of the myofibrils; the character of the sarcoplasm, and the form and disposition of its organelles. An abundant granular component of the sarcoplasm in this species is tentatively identified as a particulate form of glycogen. The myocardium is composed of individual cells joined end to end at primitive intercalated discs, and side to side at sites of cohesion that resemble the desmosomes of epithelia. Transitional forms are found between desmosomes and intercalated discs. Both consist of a thickened area of the cell membrane with an accumulation of dense material in the subjacent cytoplasm. This dense amorphous component is often continuous with the Z substance of the myofibrils and may be of the same composition. The observations reported reemphasize the basic similarity between desmosomes and terminal bars of epithelia and intercalated discs of cardiac muscle. Numerous unmyelinated nerves are found beneath the endocardium. Some of these occupy recesses in the surface of Schwann cells; others are naked axons. No specialized nerve endings are found. Axons passing near the sarcolemma contain synaptic vesicles, and it is believed that this degree of proximity is sufficient to constitute a functioning myoneural junction. PMID:13502430

  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. Fine structure of the Mn acceptor in GaAs

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Holanda, R. F. L.; Busti, V. C.; Colaço, L. R.; Alcaniz, J. S.; Landau, S. J.

    2016-08-01

    As is well known, measurements of the Sunyaev-Zeldovich effect can be combined with observations of the X-ray surface brightness of galaxy clusters to estimate the angular diameter distance to these structures. In this paper, we show that this technique depends on the fine structure constant, α. Therefore, if α is a time-dependent quantity, e.g., α = α0phi(z), where phi is a function of redshift, we argue that current data do not provide the real angular diameter distance, DA(z), to the cluster, but instead DAdata(z) = phi(z)2 DA(z). We use this result to derive constraints on a possible variation of α for a class of dilaton runaway models considering a sample of 25 measurements of DAdata(z) in redshift range 0.023 < z < 0.784 and estimates of DA(z) from current type Ia supernovae observations. We find no significant indication of variation of α with the present data.

  14. Can Temporal Fine Structure and Temporal Envelope be Considered Independently for Pitch Perception?

    PubMed

    Grimault, Nicolas

    2016-01-01

    In psychoacoustics, works on pitch perception attempt to distinguish between envelope and fine structure cues that are generally viewed as independent and separated using a Hilbert transform. To empirically distinguish between envelope and fine structure cues in pitch perception experiments, a dedicated signal has been proposed. This signal is an unresolved harmonic complex tones with all harmonics shifted by the same amount of Hz. As the frequency distance between adjacent components is regular and identical than in the original harmonic complex tone, such a signal has the same envelope but a different fine structure. So, any perceptual difference between these signals is interpreted as a fine structure based percept. Here, as illustrated by very basic simulations, I suggest that this orthogonal point of view that is generally admitted could be a conceptual error. In fact, neither the fine structure nor the envelope is required to be fully encoded to explain pitch perception. Sufficient information is conveyed by the peaks in the fine structure that are located nearby a maximum of the envelope. Envelope and fine structure could then be in perpetual interaction and the pitch would be conveyed by "the fine structure under envelope". Moreover, as the temporal delay between peaks of interest is rather longer than the delay between two adjacent peaks of the fine structure, such a mechanism would be much less constrained by the phase locking limitation of the auditory system. Several data from the literature are discussed from this new conceptual point of view. PMID:27080676

  15. fine structure of 410km discontinuity beneath the Southern Europe

    NASA Astrophysics Data System (ADS)

    Wan, K.; Wan, X.; Ni, S.

    2005-12-01

    In the distance range of 10-14 degrees, P waves from the topside reflection off the 410km discontinuity are very sensitive to the fine structure of the discontinuity. We analyzed 49 broadband seismograms from an earthquake ( May 18, 1998) in Italy (Mw 5.8) , recorded by Orfeus and SZGRF networks. Distances between the source and the stations were from 9° to 19°, and provided a detailed look at the 410km structure. On the other hand, the azimuth of these records were in a narrow range from 334° and 356°, so the differences in azimuth may have little effects on the waveforms. From our observation, P410 phase has little change in amplitude when the distance decreases from 15° to about 11.5°. However, an abrupt termination was observed from distance 11° to 10.5°. These features cannot be explained with PREM model. We calculated several groups of models with F-K method and compared their synthetic seismograms with the observed one. These models are: 1) two-step sharp jump models, with different thickness; 2) linear models; 3) linear-sharp jump models[Tim Melbourne, Don Helmberger, Journal of Geophysical Research, 1998]; 4) models calculated from a mineralogical model[Gaherty, Wang, Geophysical research letters, 1999]; Features in the observed waveform can be well modeled with model 3 and 4 while only parts of them fitted to model 1 or 2. But when we calculated with a less detailed model, seismograms of model 4 should have more noise than model 3. In conclusion, the structure of 410km discontinuity can be considered as a linear-sharp velocity jump, which is consistent with mineralogical models.

  16. Structural studies of amorphous titanium diboride thin films by extended x-ray-absorption fine-structure and extended electron-energy-loss fine-structure techniques

    NASA Astrophysics Data System (ADS)

    Kaloyeros, Alain E.; Hoffman, Mark P.; Williams, Wendell S.; Greene, Alex E.; McMillan, Joyce A.

    1988-10-01

    The local atomic structure of amorphous titanium diboride thin films, prepared by electron-beam vaporization (EBV) of the crystalline compound onto liquid-nitrogen-cooled substrates, was studied using extended x-ray-absorption fine-structure (EXAFS) and extended energy-loss fine-structure (EXELFS) techniques. From a comparison of the extended fine-structure spectra of the amorphous films with corresponding spectra of crystalline titanium diboride, accurate information was derived on the nature of the local structure, or short-range order, and on the coordination numbers, interatomic distances, and nanostructural atomic disorder in amorphous TiB2. A relaxation of the interatomic spacing and a reduction of coordination number for the nearest-neighbor atoms was inferred for the amorphous state. Local prismatic coordination with random 90° rotations about prismatic planes is proposed as a likely atomic structure consistent with the data for the amorphous form. Finally, EXAFS and EXELFS were employed to examine in detail the structural changes induced in amorphous TiB2 by variations in the EBV deposition parameters, and to determine a set of optimized parameters for the EBV deposition of a TiB2 stable amorphous phase.

  17. 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

  18. Speech identification based on temporal fine structure cues

    PubMed Central

    Sheft, Stanley; Ardoint, Marine; Lorenzi, Christian

    2008-01-01

    The contribution of temporal fine structure (TFS) cues to consonant identification was assessed in normal-hearing listeners with two speech-processing schemes designed to remove temporal envelope (E) cues. Stimuli were processed vowel-consonant-vowel speech tokens. Derived from the analytic signal, carrier signals were extracted from the output of a bank of analysis filters. The “PM” and “FM” processing schemes estimated a phase- and frequency-modulation function, respectively, of each carrier signal and applied them to a sinusoidal carrier at the analysis-filter center frequency. In the FM scheme, processed signals were further restricted to the analysis-filter bandwidth. A third scheme retaining only E cues from each band was used for comparison. Stimuli processed with the PM and FM schemes were found to be highly intelligible (50–80% correct identification) over a variety of experimental conditions designed to affect the putative reconstruction of E cues subsequent to peripheral auditory filtering. Analysis of confusions between consonants showed that the contribution of TFS cues was greater for place than manner of articulation, whereas the converse was observed for E cues. Taken together, these results indicate that TFS cues convey important phonetic information that is not solely a consequence of E reconstruction. PMID:18646999

  19. Fine structure of seminiferous tubules in antarctic seals.

    PubMed

    Sinha, A A; Erickson, A W; Seal, U S

    1977-03-01

    The fine structure of seminiferous tubules from 5 crabeater, 2 leopard and 2 Ross seals showed that during the nonbreeding season the tubules were essentially similar in possessing spermatogenic and Sertoli cells. However, the tubules of leopard and Ross seals had more primary and secondary spermatocytes and spermatids than the crabeater seals. In general, the tubules were devoid of spermatozoa. The spermatids showed stages of maturation such as Golgi phase of acrosome formation, acrosomal cap formation and condensation of nuclei. Some spermatids degenerated in tubules. Both maturing and degenerating spermatids were closely associated with Sertoli cells. Junctional complexes with plaques of filaments were observed between Sertoli cells and the spermatogenic cells. Sertoli cells, irregular and polygonal, contained highly convoluted nuclei, strands of rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi complexes, small mitochondria, variable amounts of lipid droplets, lysosomes, lipofuscin granules and highly plicated plasma membranes. In brief, the spermatogenic activity had practically ceased in the testes and the animals probably secreted low levels of testosterone during the nonbreeding season. PMID:844074

  20. Consonant identification using temporal fine structure and recovered envelope cuesa)

    PubMed Central

    Swaminathan, Jayaganesh; Reed, Charlotte M.; Desloge, Joseph G.; Braida, Louis D.; Delhorne, Lorraine A.

    2014-01-01

    The contribution of recovered envelopes (RENVs) to the utilization of temporal-fine structure (TFS) speech cues was examined in normal-hearing listeners. Consonant identification experiments used speech stimuli processed to present TFS or RENV cues. Experiment 1 examined the effects of exposure and presentation order using 16-band TFS speech and 40-band RENV speech recovered from 16-band TFS speech. Prior exposure to TFS speech aided in the reception of RENV speech. Performance on the two conditions was similar (∼50%-correct) for experienced listeners as was the pattern of consonant confusions. Experiment 2 examined the effect of varying the number of RENV bands recovered from 16-band TFS speech. Mean identification scores decreased as the number of RENV bands decreased from 40 to 8 and were only slightly above chance levels for 16 and 8 bands. Experiment 3 examined the effect of varying the number of bands in the TFS speech from which 40-band RENV speech was constructed. Performance fell from 85%- to 31%-correct as the number of TFS bands increased from 1 to 32. Overall, these results suggest that the interpretation of previous studies that have used TFS speech may have been confounded with the presence of RENVs. PMID:25235005

  1. 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. PMID:14154485

  2. 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.

  3. 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.

  4. [Adsorption of Cu on Core-shell Structured Magnetic Particles: Relationship Between Adsorption Performance and Surface Properties].

    PubMed

    Li, Qiu-mei; Chen, Jing; Li, Hai-ning; Zhang, Xiao-lei; Zhang, Gao-sheng

    2015-12-01

    In order to reveal the relationship between the adsorption performance of adsorbents and their compositions, structure, and surface properties, the core-shell structured Fe₃O₄/MnO2 and Fe-Mn/Mn₂2 magnetic particles were systematically characterized using multiple techniques and their Cu adsorption behaviors as well as mechanism were also investigated in details. It was found that both Fe₃O4 and Fe-Mn had spinel structure and no obvious crystalline phase change was observed after coating with MnO₂. The introduction of Mn might improve the affinity between the core and the shell, and therefore enhanced the amount and distribution uniformity of the MnO₂ coated. Consequently, Fe-Mn/MnO₂ exhibited a higher BET specific surface area and a lower isoelectric point. The results of sorption experiments showed that Fe-Mn had a higher maximal Cu adsorption capacity of 33.7 mg · g⁻¹ at pH 5.5, compared with 17.5 mg · g⁻¹ of Fe₃O4. After coating, the maximal adsorption capacity of Fe-Mn/MnO₂ was increased to 58.2 mg · g⁻¹, which was 2.6 times as high as that of Fe₃O₄/MnO₂ and outperformed the majority of magnetic adsorbents reported in literature. In addition, a specific adsorption of Cu occurred at the surface of Fe₃O₄/MnO₂ or Fe-Mn/MnO₂ through the formation of inner-sphere complexes. In conclusion, the adsorption performance of the magnetic particles was positively related to their compositions, structure, and surface properties. PMID:27011990

  5. [Adsorption of Cu on Core-shell Structured Magnetic Particles: Relationship Between Adsorption Performance and Surface Properties].

    PubMed

    Li, Qiu-mei; Chen, Jing; Li, Hai-ning; Zhang, Xiao-lei; Zhang, Gao-sheng

    2015-12-01

    In order to reveal the relationship between the adsorption performance of adsorbents and their compositions, structure, and surface properties, the core-shell structured Fe₃O₄/MnO2 and Fe-Mn/Mn₂2 magnetic particles were systematically characterized using multiple techniques and their Cu adsorption behaviors as well as mechanism were also investigated in details. It was found that both Fe₃O4 and Fe-Mn had spinel structure and no obvious crystalline phase change was observed after coating with MnO₂. The introduction of Mn might improve the affinity between the core and the shell, and therefore enhanced the amount and distribution uniformity of the MnO₂ coated. Consequently, Fe-Mn/MnO₂ exhibited a higher BET specific surface area and a lower isoelectric point. The results of sorption experiments showed that Fe-Mn had a higher maximal Cu adsorption capacity of 33.7 mg · g⁻¹ at pH 5.5, compared with 17.5 mg · g⁻¹ of Fe₃O4. After coating, the maximal adsorption capacity of Fe-Mn/MnO₂ was increased to 58.2 mg · g⁻¹, which was 2.6 times as high as that of Fe₃O₄/MnO₂ and outperformed the majority of magnetic adsorbents reported in literature. In addition, a specific adsorption of Cu occurred at the surface of Fe₃O₄/MnO₂ or Fe-Mn/MnO₂ through the formation of inner-sphere complexes. In conclusion, the adsorption performance of the magnetic particles was positively related to their compositions, structure, and surface properties.

  6. 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.

  7. Phosphate adsorption on aluminum-coordinated functionalized macroporous–mesoporous silica: Surface structure and adsorption behavior

    SciTech Connect

    Huang, Weiya; Li, Dan; Zhu, Yi; Xu, Kai; Li, Jianqiang; Han, Boping; Zhang, Yuanming

    2013-12-15

    Graphical abstract: - Highlights: • Al-coordinated functionalized macroporous–mesoporous silica for phosphate removal. • It had the maximum adsorption capacity of 23.59 mg P/g. • Over 95% of the final adsorption capacity reached in the first 1 min. - Abstract: In this study, Al(III)-coordinated diamino-functionalized macroporous–mesoporous silica was synthesized and characterized by X-ray diffraction, N{sub 2} adsorption–desorption, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy. Because of well-defined and interconnecting macroporous–mesoporous networks, the resulting adsorbent (MM-SBA) exhibited a significantly better phosphate adsorption performance and faster removal rate, as compared with the mesoporous adsorbent (M-SBA). Based on the Freundlich and Langmuir models, the phosphate adsorption capacity and the maximum adsorption capacity of MM-SBA were 7.99 mg P/g and 23.59 mg P/g, respectively. In the kinetic study of MM-SBA, over 95% of its final adsorption capacity reached in the first 1 min; whereas that of M-SBA was less than 79%.

  8. 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.

  9. 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.

  10. 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.

  11. 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}.

  12. 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

  13. 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.

  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. Fine-structure enhancement — assessment of a simple method to resolve overlapping bands in spectra

    NASA Astrophysics Data System (ADS)

    Barth, Andreas

    2000-05-01

    A simple mathematical procedure — fine-structure enhancement — has been assessed on its ability to resolve overlapping bands in spectra. Its advantages and limitations have been explored using synthetic and experimental spectra. Fine-structure enhancement involves smoothing the original spectrum, multiplying the smoothed spectrum with a weighting factor and subtracting this spectrum from the original spectrum. As a result, the fine-structure of the original spectrum is enhanced in the processed spectrum and bands that overlap in the original spectrum appear as distinct bands in the processed spectrum. To be resolved by fine-structure enhancement, Lorentzian lines have to be separated by more than their quarter width at half maximum, Gaussian lines by more than their half width at half maximum. A comparison of fine-structure enhancement and Fourier self-deconvolution shows that Fourier self-deconvolution has in theory a higher potential to resolve overlapping bands. However, this depends crucially on the correct choice of the parameters. In practice, when parameters commonly used are chosen for Fourier self-deconvolution, fine-structure enhancement leads to similar results. This is demonstrated at the example of the infrared absorbance spectrum of the protein papain, where the amide I band components could be resolved similarly with both methods. Thus, fine-structure enhancement seems to be a simple alternative to Fourier self-deconvolution that does not require specialised software.

  16. Compensation of logarithmic corrections in calculating the fine structure of levels in hydrogen-like atoms

    SciTech Connect

    Boikova, N. A. Tyukhtyaev, Yu. N.; Faustov, R. N.

    2011-01-15

    Special features of the quasipotential approach to calculating logarithmic (in the fine-structure constant) contributions to the fine splitting of energy levels in hydrogen-like atoms are analyzed. The boundaries of the region of applicability of the Fell technique are indicated, and the order of corrections beyond this region is estimated.

  17. Molecular dynamics simulation study on controlling the adsorption behavior of polyethylene by fine tuning the surface nanodecoration of graphite.

    PubMed

    Wang, Xiao-Lin; Lu, Zhong-Yuan; Li, Ze-Sheng; Sun, Chia-Chung

    2007-01-16

    Molecular dynamics simulations are applied to study the adsorption of polyethylene with different chain lengths on patterned graphite surfaces that contain nanoscale protrusions. The influence of the nanostructure on the strong attractive interaction inherently in the hydrophobic polyethylene and hydrophobic graphite system is investigated by modifying the top surface area and the height and the shape of the protrusions. The results are analyzed in terms of the chain configuration, the adsorption energy, the global orientational order parameter, and the normalized surface-chain contacting pair number in the first adsorption layer. When the size of the protrusion increases, the adsorption energy, the order parameter, and the normalized surface-chain contacting pair number decrease at a fixed chain length. When the size of the protrusion is fixed, the average adsorption energy per monomer and the order parameter decrease with increasing chain length because of the stronger intramolecular interactions between the monomers. Changing the protrusion shape in a suitable way will effectively reduce the strong surface-chain interaction.

  18. 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.

  19. 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

  20. New fine structure cooling rate. [electron impact transitions in the ionosphere

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.

    1976-01-01

    One of the dominant electron cooling processes in the ionosphere is caused by electron impact induced fine structure transitions among the ground state levels of atomic oxygen. This fine structure cooling rate is based on theoretical cross sections. Recent advances in the numerical cross section determinations to include polarization effects and more accurate representations of the atomic target result in new lower values. These cross sections are employed in this paper to derive a new fine structure cooling rate which is between 40% and 60% of the currently used rate. A new generalized formula is presented for the cooling rate (from which the fine structure cooling rate is derived), valid for arbitrary mass and temperature difference of the colliding particles and arbitrary inelastic energy difference.

  1. Selective homopolymer adsorption on structured surfaces as a model for pattern recognition.

    PubMed

    Gemünden, Patrick; Behringer, Hans

    2013-01-14

    Homopolymer adsorption onto chemically structured periodic surfaces and its potential for pattern recognition is investigated using Monte Carlo simulations. To analyze the surface-induced selective adsorption on a fundamental geometric level polymer chains are represented by freely jointed chains with a fixed bond length whose monomers are attracted by the sites of regular lattice patterns. The structural properties of the adsorbed low-temperature state are comprehensively discussed for different lattices by looking at the radius of gyration and the inter bond angle distributions. These observables show a non-trivial dependence on the commensurability of characteristic lengths given by the lattice constant and by the bond length. Reasons for this behavior are given by exploiting geometric and entropic arguments. The findings are examined in the context of pattern recognition by polymer adsorption. Furthermore, the adsorption transition is discussed briefly. For certain incommensurable situations the adsorption occurs in two steps due to entropic restrictions.

  2. 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.

  3. Effects of Al(3+) doping on the structure and properties of goethite and its adsorption behavior towards phosphate.

    PubMed

    Li, Wei; Wang, Longjun; Liu, Fan; Liang, Xiaoliang; Feng, Xionghan; Tan, Wenfeng; Zheng, Lirong; Yin, Hui

    2016-07-01

    Al substitution in goethite is common in soils, and has strong influence on the structure and physicochemical properties of goethite. In this research, a series of Al-doped goethites were synthesized, and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The adsorption behavior of these samples towards PO4(3-) was also investigated. Characterization results demonstrated that increasing Al content in goethite led to a reduction in crystallinity, increase in specific surface area (SSA), and morphology change from needle-like to granular. Rietveld structure refinement revealed that the lattice parameter a remained almost constant and b slightly decreased, but c was significantly reduced, and the calculated crystal density increased. EXAFS analysis demonstrated that the Fe(Al)-O distance in the structure of the doped goethites was almost the same, but the Fe-Fe(Al) distance decreased with increasing Al content. Surface analysis showed that, with increasing Al content, the content of OH groups on the mineral surface increased. The adsorption of phosphate per unit mass of Al-doped goethite increased, while adsorption per unit area decreased owing to the decrease of the relative proportion of (110) facets in the total surface area of the minerals. The results of this research facilitate better understanding of the effect of Al substitution on the structure and properties of goethite and the cycling of phosphate in the environment. PMID:27372115

  4. Effects of Al(3+) doping on the structure and properties of goethite and its adsorption behavior towards phosphate.

    PubMed

    Li, Wei; Wang, Longjun; Liu, Fan; Liang, Xiaoliang; Feng, Xionghan; Tan, Wenfeng; Zheng, Lirong; Yin, Hui

    2016-07-01

    Al substitution in goethite is common in soils, and has strong influence on the structure and physicochemical properties of goethite. In this research, a series of Al-doped goethites were synthesized, and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The adsorption behavior of these samples towards PO4(3-) was also investigated. Characterization results demonstrated that increasing Al content in goethite led to a reduction in crystallinity, increase in specific surface area (SSA), and morphology change from needle-like to granular. Rietveld structure refinement revealed that the lattice parameter a remained almost constant and b slightly decreased, but c was significantly reduced, and the calculated crystal density increased. EXAFS analysis demonstrated that the Fe(Al)-O distance in the structure of the doped goethites was almost the same, but the Fe-Fe(Al) distance decreased with increasing Al content. Surface analysis showed that, with increasing Al content, the content of OH groups on the mineral surface increased. The adsorption of phosphate per unit mass of Al-doped goethite increased, while adsorption per unit area decreased owing to the decrease of the relative proportion of (110) facets in the total surface area of the minerals. The results of this research facilitate better understanding of the effect of Al substitution on the structure and properties of goethite and the cycling of phosphate in the environment.

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

    PubMed Central

    2010-01-01

    Background A widely used method to find conserved secondary structure in RNA is to first construct a multiple sequence alignment, and then fold the alignment, optimizing a score based on thermodynamics and covariance. This method works best around 75% sequence similarity. However, in a "twilight zone" below 55% similarity, the sequence alignment tends to obscure the covariance signal used in the second phase. Therefore, while the overall shape of the consensus structure may still be found, the degree of conservation cannot be estimated reliably. Results Based on a combination of available methods, we present a method named planACstar for improving structure conservation in structural alignments in the twilight zone. After constructing a consensus structure by alignment folding, planACstar abandons the original sequence alignment, refolds the sequences individually, but consistent with the consensus, aligns the structures, irrespective of sequence, by a pure structure alignment method, and derives an improved sequence alignment from the alignment of structures, to be re-submitted to alignment folding, etc.. This circle may be iterated as long as structural conservation improves, but normally, one step suffices. Conclusions Employing the tools ClustalW, RNAalifold, and RNAforester, we find that for sequences with 30-55% sequence identity, structural conservation can be improved by 10% on average, with a large variation, measured in terms of RNAalifold's own criterion, the structure conservation index. PMID:20433706

  6. Composition and structural effects on the adsorption of ionic liquids onto activated carbon.

    PubMed

    Lemus, Jesús; Neves, Catarina M S S; Marques, Carlos F C; Freire, Mara G; Coutinho, João A P; Palomar, Jose

    2013-09-01

    The applications and variety of ionic liquids (ILs) have increased during the last few years, and their use at a large scale will require their removal/recovery from wastewater streams. Adsorption on activated carbons (ACs) has been recently proposed for this aim and this work presents a systematic analysis of the influence of the IL chemical structures (cation side chain, head group, anion type and the presence of functional groups) on their adsorption onto commercial AC from water solution. Here, the adsorption of 21 new ILs, which include imidazolium-, pyridinium-, pyrrolidinium-, piperidinium-, phosphonium- and ammonium-based cations and different hydrophobic and hydrophilic anions, has been experimentally measured. This contribution allows an expansion of the range of IL compounds studied in previous works, and permits a better understanding of the influence of the IL structures through the adsorption on AC. In addition, the COSMO-RS method was used to analyze the measured adsorption isotherms, allowing the understanding of the role of the cationic and anionic structures in the adsorption process, in terms of the different interactions between the IL compound and AC surface/water solvent. The results of this work provide new insights for the development of adsorption as an effective operation to remove/recover ILs with very different chemical nature from water solution.

  7. 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.

  8. Surface Structural Ion Adsorption Modeling of Competitive Binding of Oxyanions by Metal (Hydr)oxides.

    PubMed

    Hiemstra; Van Riemsdijk WH

    1999-02-01

    Spectroscopy has provided a progressive flow of information concerning the binding mechanism(s) of ions and their surface-complex structure. An important challenge in surface complexation models (SCM) is to connect the molecular microscopic reality to macroscopic adsorption phenomena. This is important because SCM alone provide insufficient insight in the binding mechanisms, and moreover, it is a priori not obvious that SCM, which describe the pH dependent adsorption correctly in simple systems, will predict the ion interaction under multicomponent conditions. This study elucidates the primary factor controlling the adsorption process by analysing the adsorption and competition of PO4, AsO4, and SeO3. We 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, we show that the commonly used 2pK 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 dependency 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

  9. Adsorption of hydrogen sulfide onto activated carbon fibers: effect of pore structure and surface chemistry.

    PubMed

    Feng, Wenguo; Kwon, Seokjoon; Borguet, Eric; Vidic, Radisav

    2005-12-15

    To understand the nature of H2S adsorption onto carbon surfaces under dry and anoxic conditions, the effects of carbon pore structure and surface chemistry were studied using activated carbon fibers (ACFs) with different pore structures and surface areas. Surface pretreatments, including oxidation and heattreatment, were conducted before adsorption/desorption tests in a fixed-bed reactor. Raw ACFs with higher surface area showed greater adsorption and retention of sulfur, and heat treatment further enhanced adsorption and retention of sulfur. The retained amount of hydrogen sulfide correlated well with the amount of basic functional groups on the carbon surface, while the desorbed amount reflected the effect of pore structure. Temperature-programmed desorption (TPD) and thermal gravimetric analysis (TGA) showed that the retained sulfurous compounds were strongly bonded to the carbon surface. In addition, surface chemistry of the sorbent might determine the predominant form of adsorbate on the surface. PMID:16475362

  10. Adsorption of hydrogen sulfide onto activated carbon fibers: effect of pore structure and surface chemistry.

    PubMed

    Feng, Wenguo; Kwon, Seokjoon; Borguet, Eric; Vidic, Radisav

    2005-12-15

    To understand the nature of H2S adsorption onto carbon surfaces under dry and anoxic conditions, the effects of carbon pore structure and surface chemistry were studied using activated carbon fibers (ACFs) with different pore structures and surface areas. Surface pretreatments, including oxidation and heattreatment, were conducted before adsorption/desorption tests in a fixed-bed reactor. Raw ACFs with higher surface area showed greater adsorption and retention of sulfur, and heat treatment further enhanced adsorption and retention of sulfur. The retained amount of hydrogen sulfide correlated well with the amount of basic functional groups on the carbon surface, while the desorbed amount reflected the effect of pore structure. Temperature-programmed desorption (TPD) and thermal gravimetric analysis (TGA) showed that the retained sulfurous compounds were strongly bonded to the carbon surface. In addition, surface chemistry of the sorbent might determine the predominant form of adsorbate on the surface.

  11. Phosphate adsorption on aluminum-impregnated mesoporous silicates: surface structure and behavior of adsorbents.

    PubMed

    Shin, Eun Woo; Han, James S; Jang, Min; Min, Soo-Hong; Park, Jae Kwang; Rowell, Roger M

    2004-02-01

    Phosphorus from excess fertilizers and detergents ends up washing into lakes, creeks, and rivers. This overabundance of phosphorus causes excessive aquatic plant and algae growth and depletes the dissolved oxygen supply in the water. In this study, aluminum-impregnated mesoporous adsorbents were tested for their ability to remove phosphate from water. The surface structure of the materials was investigated with X-ray diffraction (XRD), a N2 adsorption-desorption technique, Fourier transform-infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS) to understand the effect of surface properties on the adsorption behavior of phosphate. The mesoporous materials were loaded with Al components by reaction with surface silanol groups. In the adsorption test, the Al-impregnated mesoporous materials showed fast adsorption kinetics as well as high adsorption capacities, compared with activated alumina. The uniform mesopores of the Al-impregnated mesoporous materials caused the diffusion rate in the adsorption process to increase, which in turn caused the fast adsorption kinetics. High phosphate adsorption capacities of the Al-impregnated mesoporous materials were attributed to not only the increase of surface hydroxyl density on Al oxide due to well-dispersed impregnation of Al components but also the decrease in stoichiometry of surface hydroxyl ions to phosphate by the formation of monodentate surface complexes. PMID:14968882

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

    PubMed

    Germann, Matthias; Willitsch, Stefan

    2016-07-28

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

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

    PubMed

    Germann, Matthias; Willitsch, Stefan

    2016-07-28

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

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

    NASA Astrophysics Data System (ADS)

    Germann, Matthias; Willitsch, Stefan

    2016-07-01

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

  15. The fine-scale genetic structure of the British population.

    PubMed

    Leslie, Stephen; Winney, Bruce; Hellenthal, Garrett; 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

    2015-03-19

    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 single nucleotide polymorphism (SNP) data from a carefully chosen geographically diverse sample of 2,039 individuals from the United Kingdom. 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 southeastern England from Anglo-Saxon migrations to be under half, and identify the regions not carrying genetic material from these migrations. We suggest significant pre-Roman but post-Mesolithic movement into southeastern England from continental Europe, and show that in non-Saxon parts of the United Kingdom, there exist genetically differentiated subgroups rather than a general 'Celtic' population.

  16. 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

  17. The fine-scale genetic structure of the British population.

    PubMed

    Leslie, Stephen; Winney, Bruce; Hellenthal, Garrett; 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

    2015-03-19

    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 single nucleotide polymorphism (SNP) data from a carefully chosen geographically diverse sample of 2,039 individuals from the United Kingdom. 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 southeastern England from Anglo-Saxon migrations to be under half, and identify the regions not carrying genetic material from these migrations. We suggest significant pre-Roman but post-Mesolithic movement into southeastern England from continental Europe, and show that in non-Saxon parts of the United Kingdom, there exist genetically differentiated subgroups rather than a general 'Celtic' population. PMID:25788095

  18. An action-based fine-grained access control mechanism for structured documents and its application.

    PubMed

    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.

  19. 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

  20. The fine structure of Meissner's touch corpuscles of human fingers.

    PubMed

    CAUNA, N; ROSS, L L

    1960-10-01

    Thin slices of the finger pads of six individuals were fixed in buffered 1 per cent osmic acid, embedded in deaerated, nitrogenated methacrylate, and cut into thin sections for electron microscopic study. Before embedding, the slices were trimmed so as to include several digital tactile corpuscles. Some thin sections were stained in 10 per cent aqueous phosphotungstic acid solution. The principal part of Meissner's corpuscle is made up of flattened laminar cells stretching across the corpuscle in irregular layers. The perinuclear cytoplasm of these cells contains numerous small mitochondria, a sparse granular endoplasmic reticulum, and a large number of small vesicles. Nerve fibers enter the side or base of the corpuscle, lose their myelin sheaths, and follow a meandering course between the laminar cell plates. The nerve endings enter into a close appositional relationship with the flattened portions of the laminar cells. In some areas the apposed axolemma and cell membranes are slightly thickened with small vesicles located along the cell membrane or on both surfaces. These regions are interpreted as synapses. The most prominent feature of the nerve endings is an extraordinary accumulation of small mitochondria which vary in size and internal density. The nerve endings also contain vacuoles, groups of dense concentric membranes, and small dense vesicles of irregular distribution. The laminar cells are separated from one another by a dense intercellular substance of uniform thickness which also envelops the entire corpuscle. This material contains randomly oriented collagen fibers and fine fibrils bound together by a dense material at nodal points recurring at regular intervals of approximately 120 mmicro. These findings are discussed in relation to the problems of the function of Meissner's corpuscle, neural material loss and replacement, and the presence of synapses.

  1. Effects of composition and structure of alginates on adsorption of divalent metals

    NASA Astrophysics Data System (ADS)

    Nai-Yu, Zheng; Yan-Xia, Zhang; Xiao, Fan; Li-Jun, Han

    1994-03-01

    Results of a series of experiments (on the adsorption of divalent metal ions by dried alginic acid, Na and Ca alginates of different composition and block structure) conducted in this systematic study of the effects of the composition and structure of alginates on the static adsorption equilibrium of divalent metal ions indicate that the properties of alginate adsorption to divalent metal ions are highly different, depending not only on the cations used, but also on the form and structure of the alginates. There is close correlation between the adsorption properties and the structure of the alginates. The selectivity coefficient of Na alginate for Cd-Sr ion exchange tends to increase with the increase of the M/G ratio in alginate, whereas the adsorption capacity of Ca alginate for Cu2+ ion decrease with the increase of the G-block or the average length of the G-block(bar N_G ) and the total adsorption capacity of alginic acid is found to vary in the same order as the F MM(diad frequency) in alginate in the mixed solution of Sr2+, Ba2+ and Cd2+.

  2. Aged nano-structured platinum based catalyst: effect of chemical treatment on adsorption and catalytic activity.

    PubMed

    Shim, Wang Geun; Nahm, Seung Won; Park, Hyuk Ryeol; Yun, Hyung Sun; Seo, Seong Gyu; Kim, Sang Chai

    2011-02-01

    To examine the effect of chemical treatment on the adsorption and catalytic activity of nanostructured platinum based catalyst, the aged commercial Pt/AC catalyst was pretreated with sulfuric acid (H2SO4) and a cleaning agent (Hexane). Several reliable methods such as nitrogen adsorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma (ICP) were employed to characterize the aged Pt/AC catalyst and its chemically pretreated Pt/AC catalysts. The catalytic and adsorption activities of nano-structured heterogeneous Pt/AC catalyst were investigated on the basis of toluene oxidation and adsorption isotherm data. In addition, the adsorption isotherms of toluene were used to calculate the adsorption energy distribution functions for the parent catalyst and its pre-treated nano-structured Pt/AC catalysts. It was found that sulfuric acid aqueous treatment can enhance the catalytic performance of aged Pt/AC catalyst toward catalytic oxidation of toluene. It was also shown that a comparative analysis of the energy distribution functions for nano-structured Pt/AC catalysts as well as the pore size distribution provides valuable information about their structural and energetic heterogeneity.

  3. 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.

  4. Fine structure on flat surfaces of quasicrystalline Al-Pd-Mn

    NASA Astrophysics Data System (ADS)

    Shen, Z.; Stoldt, C. R.; Jenks, C. J.; Lograsso, T. A.; Thiel, P. A.

    1999-12-01

    We have analyzed the fine structure revealed by scanning tunneling microscopy for a flat (within 0.8 Å) fivefold surface of i-Al-Pd-Mn. Even though features in the image appear to be arranged randomly, self-similar features are separated by distinct distances. The distribution of such distances is compatible with the separations between pseudo-Mackay icosahedra tangent to the topmost layer, and with separations between other cluster-based units. We propose that the fine structure is due to electronic structure imposed by the clusters.

  5. [Ultraviolet spectroscopic study on the fine structures in the solar polar hole].

    PubMed

    Zhang, Min; Wang, Dong; Liu, Guo-Hong

    2014-07-01

    Fine structures in the south solar polar coronal hole were observed by N IV line of SOHO/SUMER spectrograph. The scales of the fine structures range spatially range from 1 arcsec to several arcsecs, temporally from 1 min to several minutes, and parts of them are in strip shape along the slit direction. The line-of-sight velocity of them is up to tens of km x s(-1) with red and blue shift intercrossed occasionally, which appear periodically as long as 100 minutes in some regions. Part of the fine structures can be clearly observed at the Ne V III line with higher formation temperature in the same spectral window. The time and location of some fine structures with high velocity in the Ne V III spectrum are almost the same as that in N IV spectrum, but they are extended and diffused in the Ne V III spectrum. Some fine structures have non-Gaussian profiles with the line-of-sight Doppler velocities up to 150 km x s(-1) in the N IV blue/red wings, which is similar with the explosive events in the transition region. In the past, explosive events are small-scale dynamic phenomena often observed in the quiet-sun (QS) region, while their properties in coronal holes (CHs) remain unclear. Here, we find the EE-like events with strong dynamics in the south solar polar coronal hole by N IV line of SOHO/SUMER spectrograph.

  6. 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.

  7. Fine structural dependence of ultraviolet reflections in the King Penguin beak horn.

    PubMed

    Dresp, Birgitta; Langley, Keith

    2006-03-01

    The visual perception of many birds extends into the near-ultraviolet (UV) spectrum and ultraviolet is used by some to communicate. The beak horn of the King Penguin (Aptenodytes patagonicus) intensely reflects in the ultraviolet and this appears to be implicated in partner choice. In a preliminary study, we recently demonstrated that this ultraviolet reflectance has a structural basis, resulting from crystal-like photonic structures, capable of reflecting in the near-UV. The present study attempted to define the origin of the photonic elements that produce the UV reflectance and to better understand how the UV signal is optimized by their fine structure. Using light and electron microscopic analysis combined with new spectrophotometric data, we describe here in detail the fine structure of the entire King Penguin beak horn in addition to that of its photonic crystals. The data obtained reveal a one-dimensional structural periodicity within this tissue and demonstrate a direct relationship between its fine structure and its function. In addition, they suggest how the photonic structures are produced and how they are stabilized. The measured lattice dimensions of the photonic crystals, together with morphological data on its composition, permit predictions of the wavelength of reflected light. These correlate well with experimentally observed values. The way the UV signal is optimized by the fine structure of the beak tissue is discussed with regard to its putative biological role. PMID:16470837

  8. Development and validation of pore structure models for adsorption in activated carbons

    SciTech Connect

    Davies, G.M.; Seaton, N.A.

    1999-09-14

    Predicting adsorption over a range of operating conditions and the improvement of the adsorbent itself are two important aspects that arise in the industrial application of adsorption. Both of these aspects can be addressed using molecular simulation techniques in conjunction with an appropriate model of the internal structure of the adsorbent. The internal structure of activated carbons is particularly difficult to model due to the fact that the structure is only locally crystalline and that most of the void volumes within the structure have length scales comparable to small molecules. This paper presents a systematic method to develop suitable models of the internal structure that are based on networks of regularly shaped model pores. Important aspects that are addressed include the realism and consistency of the resulting models. The method is illustrated using the adsorption of pure methane and ethane, and binary mixtures of these components, over a wide range of operating conditions onto four activated carbons.

  9. Fine structure of subauroral electric field and electron content

    NASA Astrophysics Data System (ADS)

    Makarevich, Roman A.; Bristow, W. A.

    2014-05-01

    Small-scale structure of the plasma convection and electron content within the subauroral polarization stream (SAPS) is investigated. We present ionospheric observations during the main phase of the geomagnetic storm on 17 March 2013, during which a sequence of intense, highly localized, and fast-moving electric field (EF) structures within SAPS was observed by the Super Dual Auroral Radar Network Christmas Valley West (CVW) radar. The CVW EF measurements at 60 s resolution are analyzed in context of coincident GPS measurements of the total electron content (TEC) at 30 s resolution. The strong and narrow feature of the subauroral ion drift (SAID) was observed poleward of the TEC trough, with a TEC enhancement (peak) seen in the SAPS (SAID) region. The SAPS wave activity commenced ~2 h (15 min) after first appearance of SAPS (SAID). The SAPS structures appeared near the poleward edge of the trough, propagated westward, and merged with SAID near TEC peak. The propagation velocity was comparable with convection velocity within each EF structure. The SAPS TEC exhibited a general decrease toward the end of the period. On a smaller time scale, TEC exhibited a small but appreciable decrease within EF structures. The wavelet spectra of EF and TEC showed similar variations, with wave period of ~5 min period near onset and increasing to 8-10 min toward the end of the period with significant wave activity. A scenario is discussed, in which the SAPS wave activity may modify the ionospheric conductance and TEC at small scales, with large-scale magnetosphere-ionosphere feedback acting to continuously deplete TEC where/when such activity does not occur.

  10. 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 ...

  11. Fine Level Set Structure of Flat Isometric Immersions

    NASA Astrophysics Data System (ADS)

    Hornung, Peter

    2011-03-01

    A result by Pogorelov asserts that C 1 isometric immersions u of a bounded domain {S subset mathbb R^2} into {mathbb {R}^3} whose normal takes values in a set of zero area enjoy the following regularity property: the gradient {f := nabla u} is `developable' in the sense that the nondegenerate level sets of f consist of straight line segments intersecting the boundary of S at both endpoints. Motivated by applications in nonlinear elasticity, we study the level set structure of such f when S is an arbitrary bounded Lipschitz domain. We show that f can be approximated by uniformly bounded maps with a simplified level set structure. We also show that the domain S can be decomposed (up to a controlled remainder) into finitely many subdomains, each of which admits a global line of curvature parametrization.

  12. CONSTRAINTS ON SPATIAL VARIATIONS IN THE FINE-STRUCTURE CONSTANT FROM PLANCK

    SciTech Connect

    O'Bryan, Jon; Smidt, Joseph; De Bernardis, Francesco; Cooray, Asantha

    2015-01-01

    We use the cosmic microwave background (CMB) anisotropy data from Planck to constrain the spatial fluctuations of the fine-structure constant α at a redshift of 1100. We use a quadratic estimator to measure the four-point correlation function of the CMB temperature anisotropies and extract the angular power spectrum fine-structure constant spatial variations projected along the line of sight at the last scattering surface. At tens of degree angular scales and above, we constrain the fractional rms fluctuations of the fine-structure constant to be (δα/α){sub rms} < 3.4 × 10{sup –3} at the 68% confidence level. We find no evidence for a spatially varying α at a redshift of 10{sup 3}.

  13. Laplace defect spectroscopy for recognition of deep-level fine structures

    NASA Astrophysics Data System (ADS)

    Kang, Junyong; Zhan, Huahan; Huang, Qi/sheng

    2000-03-01

    A Laplace defect spectrometer (LDS) was investigated for use in decomposition of non-exponential transients. The system was tested by measuring known multi-exponential transients generated by RC circuits and applied to the study of non-exponential transients resulting from electron emission from Sn-related DX centers and hole emission from Fe-related deep acceptors. The non-exponential transients were investigated under different conditions and related to the alloy random effect. Their LDS spectra exhibited several well-resolved sharp peaks that were assigned to the fine structures of the two DX centers and the Fe-related deep acceptors, respectively, after comparison with DLTS observations. The activation energies of the fine structures were determined by linear fitting of the slopes of temperature dependences of electron and hole emission rates. The results show that the LDS is useful for investigation of deep-level fine structures.

  14. 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.

  15. Titanium local structure in tektite probed by X-ray absorption fine structure spectroscopy.

    PubMed

    Wang, Ling; Yoshiasa, Akira; Okube, Maki; Takeda, Takashi

    2011-11-01

    The local structure of titanium in tektites from six strewn fields was studied by Ti K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) in order to provide quantitative data on Ti-O distance and Ti coordination number. The titanium in tektites possessed different coordination environment types. XANES spectra patterns revealed resemblance to high-temperature TiO(2)-SiO(2) glass and TiO(2) anatase. All samples showed that the valence of Ti is 4+. Based on the Ti-O distances, coordination numbers and radial distribution function determined by EXAFS analyses, the tektites were classified into three types: type I, Ti occupies a four-coordinated tetrahedral site with Ti-O distances of 1.84-1.79 Å; type II, Ti occupies a five-coordinated trigonal bipyramidal or tetragonal pyramidal site with Ti-O distances of 1.92-1.89 Å; type III, Ti occupies a six-coordinated octahedral site with Ti-O distances of 2.00-1.96 Å. Although Ti occupies the TiO(6) octahedral site in most titanium minerals under ambient conditions, some tektites have four- and five-coordinated Ti. This study indicated that the local structure of Ti might change in impact events and the following stages.

  16. Titanium local structure in tektite probed by X-ray absorption fine structure spectroscopy.

    PubMed

    Wang, Ling; Yoshiasa, Akira; Okube, Maki; Takeda, Takashi

    2011-11-01

    The local structure of titanium in tektites from six strewn fields was studied by Ti K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) in order to provide quantitative data on Ti-O distance and Ti coordination number. The titanium in tektites possessed different coordination environment types. XANES spectra patterns revealed resemblance to high-temperature TiO(2)-SiO(2) glass and TiO(2) anatase. All samples showed that the valence of Ti is 4+. Based on the Ti-O distances, coordination numbers and radial distribution function determined by EXAFS analyses, the tektites were classified into three types: type I, Ti occupies a four-coordinated tetrahedral site with Ti-O distances of 1.84-1.79 Å; type II, Ti occupies a five-coordinated trigonal bipyramidal or tetragonal pyramidal site with Ti-O distances of 1.92-1.89 Å; type III, Ti occupies a six-coordinated octahedral site with Ti-O distances of 2.00-1.96 Å. Although Ti occupies the TiO(6) octahedral site in most titanium minerals under ambient conditions, some tektites have four- and five-coordinated Ti. This study indicated that the local structure of Ti might change in impact events and the following stages. PMID:21997913

  17. Fine Structure of Fossilized Bacteria in Volyn Kerite

    NASA Astrophysics Data System (ADS)

    Gorlenko, V. M.; Zhmur, S. I.; Duda, V. I.; Suzina, N. E.; Osipov, G. A.; Dmitriev, V. V.

    2000-12-01

    Ultrathin sectioning and cryofracture of fibrous kerite, sampled from 1.8-1.75 billion year old Volyn sediments (Ukraine), revealed in bacteria-like bodies the presence of structures similar to sheath, cell wall, periplasm, cytoplasm, septum, membranes, intramembrane particles, poly-β-hydroxybutyrate inclusions. On the strength of these data and also the fatty acid profiles of these microfossils, we concluded that fibrous kerites are biogenic formations, namely fossilized bacterial mats.

  18. Fine structure of adhesive devices of Strepsiptera (Insecta).

    PubMed

    Pohl, Hans; Beutel, Rolf G

    2004-01-01

    Legs and other body parts of males, females and first instar larvae of almost all recognised families of Strepsiptera (Insecta) were examined. Descriptions of tibial, tarsal and pretarsal adhesive structures for each family are presented. These and attachment devices not associated with the legs are discussed. Strepsiptera evolved two strictly different types of tarsal attachment structures: hairy surfaces in the males and smooth flexible pads in the first instar larvae. Additional adhesive devices are present in several subgroups: mushroom-shaped microtrichia on the maxillary palp of males of Bohartillidae and acute pointed tibiae, or tarsal segments of males in different families. First instar larvae have evolved adhesive hairs on the ventral side of the body and on the podomeres. Specialised adhesive hairs are absent in the groundplan of adult males of Strepsiptera, but have evolved with the adoption of permanent endoparasitism of females. The most elaborate attachment structures, both in males and first instar larvae, are present in parasites of fast flying hymenopteran hosts (Aculeata). PMID:18089021

  19. 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.

  20. Modeling fine-scale soil surface structure using geostatistics

    NASA Astrophysics Data System (ADS)

    Croft, H.; Anderson, K.; Brazier, R. E.; Kuhn, N. J.

    2013-04-01

    There is widespread recognition that spatially distributed information on soil surface roughness (SSR) is required for hydrological and geomorphological applications. Such information is necessary to describe variability in soil structure, which is highly heterogeneous in time and space, to parameterize hydrology and erosion models and to understand the temporal evolution of the soil surface in response to rainfall. This paper demonstrates how results from semivariogram analysis can quantify key elements of SSR for such applications. Three soil types (silt, silt loam, and silty clay) were used to show how different types of structural variance in SSR evolve during simulated rainfall events. All three soil types were progressively degraded using artificial rainfall to produce a series of roughness states. A calibrated laser profiling instrument was used to measure SSR over a 10 cm × 10 cm spatial extent, at a 2 mm resolution. These data were geostatistically analyzed in the context of aggregate breakdown and soil crusting. The results show that such processes are represented by a quantifiable decrease in sill variance, from 7.81 (control) to 0.94 (after 60 min of rainfall). Soil surface features such as soil cracks, tillage lines and erosional areas were quantified by local maxima in semivariance at a given length scale. This research demonstrates that semivariogram analysis can retrieve spatiotemporal variations in soil surface condition; in order to provide information on hydrological pathways. Consequently, geostatistically derived SSR shows strong potential for inclusion as spatial information in hydrology and erosion models to represent complex surface processes at different soil structural scales.

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

    PubMed

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

    2008-06-13

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

  2. Coupled-channels study of fine structure in the {alpha} decay of platinum isotopes

    SciTech Connect

    Ni Dongdong; Ren Zhongzhou

    2011-09-15

    The fine structure observed in the {alpha} decay of deformed platinum isotopes is investigated using the recently developed five-channel formalism, based on the coupled-channel Schroedinger equation with outgoing wave boundary conditions. The internal effect of daughter states is taken into account in dealing with the interaction matrix and the {alpha}-cluster formation. The available experimental data concerning {alpha}-decay half-lives and fine structures are reproduced. Some predictions are made especially for the {alpha} decay of neutron-rich isotopes, which could guide future experiments.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    Mbelek, J. P.; Lachièze-Rey, M.

    2003-01-01

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

  5. Effect of water structure on adsorption of thermosensitive polymer hydrogel in salt solutions

    SciTech Connect

    Nakano, Yoshio; Seida, Yoshimi

    1996-12-31

    Effects of temperature and additive salt on an adsorption property of thermosensitive polymer hydrogel were studied in terms of (1) phase transition temperature of the gel, (2) hydration structure of network of the gel in the various salt solutions, and (3) structure of water in the solutions. The adsorption properties of the gel were correlated fairly well with the phase transition temperature of the gel and the structure of water both on the network of the gel and in the bulk solution. 2 refs., 5 figs.

  6. Structural Properties and Phase Transition of Na Adsorption on Monolayer MoS2.

    PubMed

    He, Hai; Lu, Pengfei; Wu, Liyuan; Zhang, Chunfang; Song, Yuxin; Guan, Pengfei; Wang, Shumin

    2016-12-01

    First-principles calculations are performed to investigate the structural stability of Na adsorption on 1H and 1T phases of monolayer MoS2. Our results demonstrate that it is likely to make the stability of distorted 1T phase of MoS2 over the 1H phase through adsorption of Na atoms. The type of distortion depends on the concentration of adsorbed Na atoms and changes from zigzag-like to diamond-like with the increasing of adsorbed Na atom concentrations. Our calculations show that the phase transition from 1H-MoS2 to 1T-MoS2 can be obtained by Na adsorption. We also calculate the electrochemical properties of Na adsorption on MoS2 monolayer. These results indicate that MoS2 is one of potential negative electrodes for Na-ion batteries. PMID:27416903

  7. Structural Properties and Phase Transition of Na Adsorption on Monolayer MoS2

    NASA Astrophysics Data System (ADS)

    He, Hai; Lu, Pengfei; Wu, Liyuan; Zhang, Chunfang; Song, Yuxin; Guan, Pengfei; Wang, Shumin

    2016-07-01

    First-principles calculations are performed to investigate the structural stability of Na adsorption on 1H and 1T phases of monolayer MoS2. Our results demonstrate that it is likely to make the stability of distorted 1T phase of MoS2 over the 1H phase through adsorption of Na atoms. The type of distortion depends on the concentration of adsorbed Na atoms and changes from zigzag-like to diamond-like with the increasing of adsorbed Na atom concentrations. Our calculations show that the phase transition from 1H-MoS2 to 1T-MoS2 can be obtained by Na adsorption. We also calculate the electrochemical properties of Na adsorption on MoS2 monolayer. These results indicate that MoS2 is one of potential negative electrodes for Na-ion batteries.

  8. Structural Properties and Phase Transition of Na Adsorption on Monolayer MoS2.

    PubMed

    He, Hai; Lu, Pengfei; Wu, Liyuan; Zhang, Chunfang; Song, Yuxin; Guan, Pengfei; Wang, Shumin

    2016-12-01

    First-principles calculations are performed to investigate the structural stability of Na adsorption on 1H and 1T phases of monolayer MoS2. Our results demonstrate that it is likely to make the stability of distorted 1T phase of MoS2 over the 1H phase through adsorption of Na atoms. The type of distortion depends on the concentration of adsorbed Na atoms and changes from zigzag-like to diamond-like with the increasing of adsorbed Na atom concentrations. Our calculations show that the phase transition from 1H-MoS2 to 1T-MoS2 can be obtained by Na adsorption. We also calculate the electrochemical properties of Na adsorption on MoS2 monolayer. These results indicate that MoS2 is one of potential negative electrodes for Na-ion batteries.

  9. Role of catechol structure in the adsorption and transformation reactions of L-DOPA in soils.

    PubMed

    Furubayashi, Akihiro; Hiradate, Syuntaro; Fujii, Yoshiharu

    2007-02-01

    3-(3',4'-Dihydroxyphenyl)-L-alanine (L-DOPA), which is synthesized in velvet bean (Mucuna pruriens), inhibits plant growth. The concentration of L-DOPA in soil is reduced by adsorption and transformation reactions, which can result in the reduction of its plant-growth-inhibitory activity. To determine which part of the L-DOPA structure is involved in the adsorption and soil transformation reactions, we compared the kinetics of L-DOPA disappearance in a volcanic ash soil with that of L-phenylalanine (3-phenyl-L-alanine) and L-tyrosine (3-(4'-hydroxyphenyl)-L-alanine), compounds that are similar in structure to L-DOPA but do not have a catechol (o-dihydroxybenzene) moiety. L-Phenylalanine and L-tyrosine were not adsorbed and transformed in the soil at equilibrium pH values between 4 and 7. These results suggest that the adsorption and transformation reactions of L-DOPA in the soil involve the catechol moiety and not the amino and carboxylic acid groups, which are common to all three compounds. Like L-DOPA, (+)-catechin, another allelochemical that contains a catechol moiety, underwent adsorption and soil transformation reactions. Thus, we concluded that the concentrations of allelochemicals bearing a catechol moiety in soils will decrease rapidly owing to adsorption and transformation reactions, and this decrease will be faster in soils with a high pH value or high adsorption ability. Owing to this decrease in concentration, allelopathic phenomena may not occur.

  10. Fine structure of the jet from Cygnus A

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The superfine structure of the bipolar outflow from the radio galaxy Cygnus A has been investigated at a wavelength of 2 cm. The surrounding thermal plasma inflows onto the disk and is transferred in a spiral to the center, with the plasma velocity and temperature increasing to relativistic values. The rotating bipolar outflow carries away an excess angular momentum as it is accumulated. The high-velocity central flow is surrounded by parallel chains of components, the tangential directions of the low-velocity flows. Rotation collimates the flow; ring currents, a longitudinal magnetic field, are generated in it. The size of the high-velocity jet exceeds the size of the counterjet by a factor of 3.5 due to the velocity difference: the acceleration of the flow moving along the field and its decelerationwhenmoving in a direction opposite to the magnetic field of the system. The observed features are typical of objects with active nuclei.

  11. Ab initio X-Ray Absorption Fine Structure Cumulants

    NASA Astrophysics Data System (ADS)

    Vila, F.; Rehr, J. J.; Rossner, H. H.; Krappe, H. J.

    2006-03-01

    Theoretical calculations of vibrational effects in x-ray absorption spectra typically employ semi-phenomenological models, e.g. empirical force constants or correlated Debye or Einstein models. Instead we introduce an efficient and generally applicable ab initio approach based on electronic structure calculations of the dynamical matrix together with the Lanczos recursion algorithm [1] and relations between the cumulants. The approach yields 1) the thermal expansion coefficients (first cumulant of the vibrational distribution function); 2) correlated Debye-Waller factors (second cumulants) and 3) anharmonic contributions (third cumulants). Results are presented for crystalline (Cu, Au, Ge, GaAs) and molecular (GeCl4, C6H6) systems. Our results for the Debye-Waller factors agree well with experiment. [1]H.J. Krappe and H.H. Rossner, Phys. Rev. B70, 104102 (2004).

  12. 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.

  13. Fine structure of the spermatozoon of the strepsipteran Xenos moutoni.

    PubMed

    Mazzini, M; Carcupino, M; Kathirithamby, J

    1991-01-01

    Spermatozoa of Xenos moutoni De Buysson belonging to the order Strepsiptera (Insecta) were examined by electron microscopy. The spermatozoon was seen to have an elongated head and a tail containing a 9+9+2 axoneme and two mitochondrial derivatives of equal size. The pear-shaped acrosome is characterised by a mono-layered structure and terminates anteriorly forming two pyramidal evaginations. The nucleus exhibits an external portion of dense chromatin and an internal one of uncondensed material. The latter occupies a central position at the base and becomes progressively peripheral at the apex. The tail is long and in its final portion the axoneme loses its elements progressively. These results have been compared with the ultrastructure of the spermatozoa of Coleoptera which have been considered as a sister group of Strepsiptera. PMID:18621157

  14. Fine Structure of Extracellular Polysaccharide of Erwinia amylovora†

    PubMed Central

    Politis, D. J.; Goodman, R. N.

    1980-01-01

    Virulent E9 and avirulent E8 strains of Erwinia amylovora were shown by means of light, transmission, and scanning microscopy to be, respectively, encapsulated and unencapsulated. Difficulty was encountered in stabilizing the fibrillar-appearing capsular extracellular polysaccharide. We suggest that the ephemeral nature of extracellular polysaccharide is due to the collapse of its extended structure upon dehydration. This occurs when bacteria are prepared for either transmission or scanning electron microscopy. The electron micrographs support our previous biochemical and immunological studies contending that the capsule is composed of tightly bound and loosely held components. The preparation of bacteria in freeze-dried colonies has permitted us to observe and explain the fluidity of the encapsulated strain. We suggest that this fluidity is a reflection of the loosely held extracellular polysaccharide or slime. Images PMID:16345638

  15. THE FINE STRUCTURE OF TESTICULAR INTERSTITIAL CELLS IN GUINEA PIGS

    PubMed Central

    Christensen, A. Kent

    1965-01-01

    In guinea pig testes perfused with either glutaraldehyde or osmium tetroxide fixative, the cytoplasm of the interstitial cells contains an exceptionally abundant agranular endoplasmic reticulum. The reticulum in central regions of the cell is a network of interconnected tubules, but in extensive peripheral areas the reticulum is commonly organized into closely packed, flattened cisternae which are fenestrated. Occasional small patches of the granular reticulum occur in the cytoplasm and connect freely with the agranular reticulum. The mitochondria have a dense matrix and contain cristae and some tubules. The Golgi complex is disperse and shows no evidence of secretory material. The cytoplasm also contains lipid droplets. Lipofuscin pigment granules are probably polymorphic residual bodies and contain three components: (1) a dense material which at high magnification shows a 75-A periodicity; (2) a medium-sized lipid droplet; and (3) a cap-like structure. In glutaraldehyde-perfused testis the interstitial cell cytoplasm appears to have the same density from cell to cell, and the agranular reticulum is tubular or cisternal but not in the form of empty vesicles. Thus the "dark" and "light" cells and the vesicular agranular reticulum sometimes encountered in other fixations may be artifacts. Biochemical results from other laboratories, correlated with the present findings, indicate that the membranes of the agranular endoplasmic reticulum in guinea pig interstitial cells are the site of at least two enzymes of androgen biosynthesis, the 17-hydroxylase and the 17-desmolase. PMID:19866687

  16. 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. PMID:19411602

  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. 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.

  19. 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.

  20. 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 Fm 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.

  1. Delay between the Circularly Polarized Components in Fine Structures during Solar Type IV Events

    NASA Astrophysics Data System (ADS)

    Chernov, G. P.; Zlobec, P.

    1995-08-01

    We analyzed intermediately polarized (20 80%) fine structures (pulsations, sudden reductions, fiber bursts and zebras) that were recorded in type IV events. The mean polarization degree was practically the same for all the fine structures recorded in an interval lasting a few minutes and it was similar to the polarization of the continuum. A detailed analysis during the evolution of single structures reveals changes in polarization (in particular an ‘undulation’ at flux density minima) even stronger than 20%. They were caused by a delay, up to 0.1 s, between the two circularly polarized components. The weaker polarimetric component was delayed in 2 sets and the stronger one in 1 set. In the event of April 24, 1985 different types of fine structures were sporadically detected in more than one hour long time interval. Short delays of the stronger or of the weaker component were sometimes observed. The events characterized by fine structures are generally totally polarized in the ordinary mode. We assume that this holds also for the phenomena studied here. The observed intermediate polarization therefore requires a depolarization due to propagation effects. We discuss the mode coupling and the reflection of the original radio signal that could also generate the delay of the weaker and the stronger component respectively. The possibility of polarization variation due to the change of the angle between the direction of the propagation and the magnetic field in a quasi-transversal region and in a low intensity magnetic field in a current sheet is also given.

  2. Spike-like Bursts as Fine Structure of Zebras

    NASA Astrophysics Data System (ADS)

    Zlobec, P.; Karlický, M.

    2007-12-01

    We studied the characteristics of the zebra-associated spike-like bursts that were recorded with high time resolution at 1420 MHz in four intervals (from 12:45 to 12:48 UT) during 5 August 2003. Our detailed analysis is based on the selection of more than 500 such spike-like bursts and it is, at least to our knowledge, the first study devoted to such short-lived bursts. Their characteristics are different from those pertinent to “normal” spike bursts, as presented in the paper by Güdel and Benz ( Astron. Astrophys. 231, 202, 1990); in particular, their duration (about 7.4 ms at half power) is shorter, so they should be members of the SSS (super short structures) family (Magdalenić et al., Astrophys. J. 642, L77, 2006). The bursts were generally strongly R-polarized; however, during the decaying part of interval I a low R-polarized and L-polarized bursts were also present. This change of polarization shows a trend that resembles the peculiar form of the zebra lines in the spectral dominion (“V” like). A global statistical analysis on the bursts observed in the two polarimetric channels shows that the highest cross-correlation coefficient (about 0.5) was pertinent to interval I. The zebras and the bursts can be interpreted by the same double plasma resonance process as proposed by Bárta and Karlický ( Astron. Astrophys. 379, 1045, 2001) and Karlický et al. ( Astron. Astrophys. 375, 638, 2001); in particular, the spikes are generated by the interruption of this process by assumed turbulence (density or magnetic field variations). This process should be present in the region close to the reconnection site ( e.g., in the plasma reconnection outflows) where the density and the magnetic field vary strongly.

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

    PubMed

    Dimakis, Nicholas; Bunker, Grant

    2006-12-01

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

  5. Revealing the Fine Structures of the Lithosphere Asthenosphere Boundary

    NASA Astrophysics Data System (ADS)

    Olugboji, Tolulope Morayo

    to the generation of the observed fabric. A contrast with normal oceans lends further evidence that this hypothesized origin for crustal anisotropy is a distinct feature of ocean-islands, separate from the formation of normal ocean crust/plates. Anisotropic structures are also observed at the LAB and may be due to changes in plate motion through time, hotspot activity or both.

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

    PubMed

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

    2016-07-20

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

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Liu, Kexi; Lei, Yinkai; Wang, Guofeng

    2013-11-01

    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 dyz) 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.

  10. 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.

  11. 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.

  12. Fine-structured TiO2 ceramic patterns on the ceramic surface fabricated by replication

    NASA Astrophysics Data System (ADS)

    Kim, H. D.; Nakayama, T.; Hong, B. J.; Imaki, K.; Yoshimura, T.; Suzuki, T.; Suematsu, H.; Lee, S. W.; Fu, Z.; Niihara, K.

    2011-03-01

    The ability to fabricate high precision micro- to nanoscale structure in a wide variety of materials is of crucial importance for the advancement of microtechnology, nanotechnology and nanoscience. Also, the ability to create micrometer and sub-micrometer architecture for functional ceramics is a prerequisite of exploring the rich field of ceramic nanotechnology. In this work we fabricated three-dimensional oxide ceramic materials with fine-structure over multiple length scales by combining replication patterning technique, polyvinyl alcohol (PVA), oxide ceramic material (TiO2) nano-sized particles. Our study is based on the idea that PVA can be easily detached from a mold by peeling. We confirmed that micron and sub-micron-sized fine-structured oxide ceramic patterns containing nano-sized pores could be fabricated using this procedure. The results presented demonstrate the compositional and structural diversities that are possible with a facile approach and simple method.

  13. Study on the electronic structure and hydrogen adsorption by transition metal decorated single wall carbon nanotubes.

    PubMed

    Modak, P; Chakraborty, Brahmananda; Banerjee, S

    2012-05-01

    The ground state geometry and electronic structure of various 4d transition metal (TM) atom (Y, Zr, Nb and Mo) decorated single wall carbon nanotubes (SWCNTs) are obtained using density functional theory and the projector augmented wave (PAW) method. We found a systematic change in the adsorption site of the transition metal atom with increasing number of d electrons. We also predicted that Y and Zr decorated SWCNTs are metallic whereas Nb and Mo decorated SWCNTs are semiconducting. From detailed electronic structure and Bader charge analysis we found that the systematic variation of the adsorption site with the number of d electrons is related to the decreasing amount of charge transfer from the TM atom to the SWCNT along the 4d series. We have also studied the hydrogen adsorption capabilities of these decorated SWCNTs to understand the role of transition metal d electrons in binding the hydrogen molecules to the system. We found that metallic SWCNT + TM systems are better hydrogen adsorbers. We showed that the hydrogen adsorption by a TM decorated SWCNT will be maximum when all the adsorptions are physisorption and that the retention of magnetism by the system is crucial for physisorption.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Identical Binding Energies and Work Functions for Distinct Adsorption Structures: Olympicenes on the Cu(111) Surface.

    PubMed

    Liu, Wei; Schuler, Bruno; Xu, Yong; Moll, Nikolaj; Meyer, Gerhard; Gross, Leo; Tkatchenko, Alexandre

    2016-03-17

    Reliability is one of the major concerns and challenges in designing organic/inorganic interfaces for (opto)electronic applications. Even small structural differences for molecules on substrates can result in a significant variation in the interface functionality, due to the strong correlation between geometry, stability, and electronic structure. Here, we employed state-of-the-art first-principles calculations with van der Waals interactions, in combination with atomic force microscopy experiments, to explore the interaction mechanism for three structurally related olympicene molecules adsorbed on the Cu(111) surface. The substitution of a single atom in the olympicene molecule switches the nature of adsorption from predominantly physisorptive character [olympicene on Cu(111)], to an intermediate state [olympicene-derived ketone on Cu(111)], then to chemisorptive character [olympicene radical on Cu(111)]. Despite the remarkable difference in adsorption structures (by up to 0.9 Å in adsorption height) and different nature of bonding, the olympicene, its ketone, and its radical derivatives have essentially identical binding energies and work functions upon interaction with the metal substrate. Our findings suggest that the stability and work functions of molecular adsorbates could be rendered insensitive to their adsorption structures, which could be a useful property for (opto)electronic applications. PMID:26928143

  16. 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.

  17. 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.

  18. 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

  19. X-ray absorption fine structure determination of pH-dependent U-bacterial cell wall interactions

    NASA Astrophysics Data System (ADS)

    Kelly, S. D.; Kemner, K. M.; Fein, J. B.; Fowle, D. A.; Boyanov, M. I.; Bunker, B. A.; Yee, N.

    2002-11-01

    X-ray absorption fine structure (XAFS) measurements was used at the U L3-edge to directly determine the pH dependence of the cell wall functional groups responsible for the absorption of aqueous UO 22+ to Bacillus subtilis from pH 1.67 to 4.80. Surface complexation modeling can be used to predict metal distributions in water-rock systems, and it has been used to quantify bacterial adsorption of metal cations. However, successful application of these models requires a detailed knowledge not only of the type of bacterial surface site involved in metal adsorption/desorption, but also of the binding geometry. Previous acid-base titrations of B. subtilis cells suggested that three surface functional group types are important on the cell wall; these groups have been postulated to correspond to carboxyl, phosphoryl, and hydroxyl sites. When the U(VI) adsorption to B. subtilis is measured, observed is a significant pH-independent absorption at low pH values (<3.0), ascribed to an interaction between the uranyl cation and a neutrally charged phosphoryl group on the cell wall. The present study provides independent quantitative constraints on the types of sites involved in uranyl binding to B. subtilis from pH 1.67 to 4.80. The XAFS results indicate that at extremely low pH (pH 1.67) UO 22+ binds exclusively to phosphoryl functional groups on the cell wall, with an average distance between the U atom and the P atom of 3.64 ± 0.01 Å. This U-P distance indicates an inner-sphere complex with an oxygen atom shared between the UO 22+ and the phosphoryl ligand. The P signal at extremely low pH value is consistent with the UO 22+ binding to a protonated phosphoryl group, as previously ascribed. With increasing pH (3.22 and 4.80), UO 22+ binds increasingly to bacterial surface carboxyl functional groups, with an average distance between the U atom and the C atom of 2.89 ± 0.02 Å. This U-C distance indicates an inner-sphere complex with two oxygen atoms shared between the UO 22

  20. Adsorption of monomers on microspherical structures of thermal heterocomplex molecules from amino ACIDS

    NASA Astrophysics Data System (ADS)

    Honda, Hajime; Sakurazawa, Shigeru; Dekikimura, H.; Imai, Eiichi; Matsuno, Koichiro

    1995-10-01

    The surface of a microspherical structure formed in the aqueous suspension of thermal heterocomplex molecules made by heating aspartic acid and proline can adsorb basic amino acids such as histidine, lysine and arginine. It can also adsorb adenine, cytosine, adenosine and cytidine. Electrostatic interactions acting between those monomers to be adsorbed and the adsorbing surface are responsible for the adsorption.

  1. 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.

  2. CO adsorption on small Aun (n = 1-4) structures supported on hematite. I. Adsorption on iron terminated α-Fe2O3 (0001) surface

    NASA Astrophysics Data System (ADS)

    Pabisiak, Tomasz; Winiarski, Maciej J.; Kiejna, Adam

    2016-01-01

    This is the first of two papers dealing with the adsorption of Au and formation of Aun nanostructures (n = 1-4) on hematite (0001) surface and adsorption of CO thereon. The stoichiometric Fe-terminated (0001) surface of hematite was investigated using density functional theory in the generalized gradient approximation of Perdew-Burke-Ernzerhof (PBE) form with Hubbard correction U, accounting for strong electron correlations (PBE+U). The structural, energetic, and electronic properties of the systems studied were examined for vertical and flattened configurations of Aun nanostructures adsorbed on the hematite surfaces. The flattened ones, which can be viewed as bilayer-like structures, were found energetically more favored than vertical ones. For both classes of structures the adsorption binding energy increases with the number of Au atoms in a structure. The adsorption of Aun induces charge rearrangement at the Aun/oxide contact which is reflected in work function changes. In most considered cases Aun adsorption increases the work function. A detailed analysis of the bonding electron charge is presented and the corresponding electron charge rearrangements at the contacts were quantified by a Bader charge analyses. The interaction of a CO molecule with the Aun nanostructures supported on α-Fe2O3 (0001) and the oxide support was studied. It is found that the CO adsorption binding to the hematite supported Aun structures is more than twice as strong as to the bare hematite surface. Analysis of the Bader charges on the atoms showed that in each case CO binds to the most positively charged (cationic) atom of the Aun structure. Changes in the electronic structure of the Aun species and of the oxide support, and their consequences for the interactions with CO, are discussed.

  3. 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.

  4. 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.

  5. Molecular Adsorption Changes the Quantum Structure of Oxide-Supported Gold Nanoparticles: Chemisorption versus Physisorption

    NASA Astrophysics Data System (ADS)

    Stiehler, Christian; Calaza, Florencia; Schneider, Wolf-Dieter; Nilius, Niklas; Freund, Hans-Joachim

    2015-07-01

    STM conductance spectroscopy and mapping has been used to analyze the impact of molecular adsorption on the quantized electronic structure of individual metal nanoparticles. For this purpose, isophorone and CO2 , as prototype molecules for physisorptive and chemisorptive binding, were dosed onto monolayer Au islands grown on MgO thin films. The molecules attach exclusively to the metal-oxide boundary, while the interior of the islands remains pristine. The Au quantum well states are perturbed due to the adsorption process and increase their mutual energy spacing in the CO2 case but move together in isophorone-covered islands. The shifts disclose the nature of the molecule-Au interaction, which relies on electron exchange for the CO2 ligands but on dispersive forces for the organic species. Our experiments reveal how molecular adsorption affects individual quantum systems, a topic of utmost relevance for heterogeneous catalysis.

  6. Molecular Adsorption Changes the Quantum Structure of Oxide-Supported Gold Nanoparticles: Chemisorption versus Physisorption.

    PubMed

    Stiehler, Christian; Calaza, Florencia; Schneider, Wolf-Dieter; Nilius, Niklas; Freund, Hans-Joachim

    2015-07-17

    STM conductance spectroscopy and mapping has been used to analyze the impact of molecular adsorption on the quantized electronic structure of individual metal nanoparticles. For this purpose, isophorone and CO2, as prototype molecules for physisorptive and chemisorptive binding, were dosed onto monolayer Au islands grown on MgO thin films. The molecules attach exclusively to the metal-oxide boundary, while the interior of the islands remains pristine. The Au quantum well states are perturbed due to the adsorption process and increase their mutual energy spacing in the CO2 case but move together in isophorone-covered islands. The shifts disclose the nature of the molecule-Au interaction, which relies on electron exchange for the CO2 ligands but on dispersive forces for the organic species. Our experiments reveal how molecular adsorption affects individual quantum systems, a topic of utmost relevance for heterogeneous catalysis. PMID:26230817

  7. Effect of Yeast Cell Morphology, Cell Wall Physical Structure and Chemical Composition on Patulin Adsorption.

    PubMed

    Luo, Ying; Wang, Jianguo; Liu, Bin; Wang, Zhouli; Yuan, Yahong; Yue, Tianli

    2015-01-01

    The capability of yeast to adsorb patulin in fruit juice can aid in substantially reducing the patulin toxic effect on human health. This study aimed to investigate the capability of yeast cell morphology and cell wall internal structure and composition to adsorb patulin. To compare different yeast cell morphologies, cell wall internal structure and composition, scanning electron microscope, transmission electron microscope and ion chromatography were used. The results indicated that patulin adsorption capability of yeast was influenced by cell surface areas, volume, and cell wall thickness, as well as 1,3-β-glucan content. Among these factors, cell wall thickness and 1,3-β-glucan content serve significant functions. The investigation revealed that patulin adsorption capability was mainly affected by the three-dimensional network structure of the cell wall composed of 1,3-β-glucan. Finally, patulin adsorption in commercial kiwi fruit juice was investigated, and the results indicated that yeast cells could adsorb patulin from commercial kiwi fruit juice efficiently. This study can potentially simulate in vitro cell walls to enhance patulin adsorption capability and successfully apply to fruit juice industry. PMID:26295574

  8. Adsorption of heavy metal ions by hierarchically structured magnetite-carbonaceous spheres.

    PubMed

    Gong, Jingming; Wang, Xiaoqing; Shao, Xiulan; Yuan, Shuang; Yang, Chenlin; Hu, Xianluo

    2012-11-15

    Magnetically driven separation technology has received considerable attention in recent decade for its great potential application. In this work, hierarchically structured magnetite-carbonaceous microspheres (Fe(3)O(4)-C MSs) have been synthesized for the adsorption of heavy metal ions from aqueous solution. Each sphere contains numerous unique rattle-type structured magnetic particles, realizing the integration of rattle-type building unit into microspheres. The as-prepared composites with high BET surface area, hierarchical as well as mesoporous structures, exhibit an excellent adsorption capacity for heavy metal ions and a convenient separation procedure with the help of an external magnet. It was found that the maximum adsorption capacity of the composite toward Pb(2+) was ∼126mgg(-1), displaying a high efficiency for the removal of heavy metal ions. The Freundlich adsorption isotherm was applicable to describe the removal processes. Kinetics of the Pb(2+) removal was found to follow pseudo-second-order rate equation. The as-prepared composite of Fe(3)O(4)-C MSs as well as Pb(2+)-adsorbed composite were carefully examined by scanning electron microscopy (SEM), Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR), nitrogen sorption measurements, and X-ray photoelectron spectroscopy (XPS). Based on the characterization results, a possible mechanism of Pb(2+) removal with the composite of Fe(3)O(4)-C MSs was proposed.

  9. Effect of Yeast Cell Morphology, Cell Wall Physical Structure and Chemical Composition on Patulin Adsorption

    PubMed Central

    Luo, Ying; Wang, Jianguo; Liu, Bin; Wang, Zhouli; Yuan, Yahong; Yue, Tianli

    2015-01-01

    The capability of yeast to adsorb patulin in fruit juice can aid in substantially reducing the patulin toxic effect on human health. This study aimed to investigate the capability of yeast cell morphology and cell wall internal structure and composition to adsorb patulin. To compare different yeast cell morphologies, cell wall internal structure and composition, scanning electron microscope, transmission electron microscope and ion chromatography were used. The results indicated that patulin adsorption capability of yeast was influenced by cell surface areas, volume, and cell wall thickness, as well as 1,3-β-glucan content. Among these factors, cell wall thickness and 1,3-β-glucan content serve significant functions. The investigation revealed that patulin adsorption capability was mainly affected by the three-dimensional network structure of the cell wall composed of 1,3-β-glucan. Finally, patulin adsorption in commercial kiwi fruit juice was investigated, and the results indicated that yeast cells could adsorb patulin from commercial kiwi fruit juice efficiently. This study can potentially simulate in vitro cell walls to enhance patulin adsorption capability and successfully apply to fruit juice industry. PMID:26295574

  10. Adsorption of gold subnano-structures on a magnetite(111) surface and their interaction with CO.

    PubMed

    Pabisiak, Tomasz; Winiarski, Maciej J; Ossowski, Tomasz; Kiejna, Adam

    2016-07-21

    Gold deposited on iron oxide surfaces can catalyze the oxidation of carbon monoxide. The adsorption of gold subnano-structures on the Fe-rich termination of the magnetite(111) surface has been investigated using density functional theory. The structural, energetic, and electronic properties of gold/magnetite systems have been examined for vertical and flattened configurations of adsorbed Aun (n = 1-4) species. Single gold adatoms strongly bonded to the iron atoms of the Fe3O4(111) surface appear to be negatively charged, and consequently increase the work function. For a more stable class of larger, flattened Aun structures the adsorption binding energy per adatom is substantially increased. The structures exhibit a net positive charge, with the Au atoms binding with the oxide having distinctly cationic character. A charge transfer from the larger gold structures to the substrate is consistent with the lowering of the work function. The bonding of a CO molecule to a Au monomer on the Fe3O4(111) surface has been found nearly as strong as that to the iron site of the bare Fe-terminated surface. However, CO bonding to larger, oxide supported Aun structures is distinctly stronger than that to the bare oxide surface. Upon CO adsorption all Aun structures are cationic and CO shows a tendency to bind to the most cationic atom of the Aun cluster.

  11. Adsorption of gold subnano-structures on a magnetite(111) surface and their interaction with CO.

    PubMed

    Pabisiak, Tomasz; Winiarski, Maciej J; Ossowski, Tomasz; Kiejna, Adam

    2016-07-21

    Gold deposited on iron oxide surfaces can catalyze the oxidation of carbon monoxide. The adsorption of gold subnano-structures on the Fe-rich termination of the magnetite(111) surface has been investigated using density functional theory. The structural, energetic, and electronic properties of gold/magnetite systems have been examined for vertical and flattened configurations of adsorbed Aun (n = 1-4) species. Single gold adatoms strongly bonded to the iron atoms of the Fe3O4(111) surface appear to be negatively charged, and consequently increase the work function. For a more stable class of larger, flattened Aun structures the adsorption binding energy per adatom is substantially increased. The structures exhibit a net positive charge, with the Au atoms binding with the oxide having distinctly cationic character. A charge transfer from the larger gold structures to the substrate is consistent with the lowering of the work function. The bonding of a CO molecule to a Au monomer on the Fe3O4(111) surface has been found nearly as strong as that to the iron site of the bare Fe-terminated surface. However, CO bonding to larger, oxide supported Aun structures is distinctly stronger than that to the bare oxide surface. Upon CO adsorption all Aun structures are cationic and CO shows a tendency to bind to the most cationic atom of the Aun cluster. PMID:27332962

  12. 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.

  13. 21-cm radiation: a new probe of variation in the fine-structure constant.

    PubMed

    Khatri, Rishi; Wandelt, Benjamin D

    2007-03-16

    We investigate the effect of variation in the value of the fine-structure constant (alpha) at high redshifts (recombination > z > 30) on the absorption of the cosmic microwave background (CMB) at 21 cm hyperfine transition of the neutral atomic hydrogen. We find that the 21 cm signal is very sensitive to the variations in alpha and it is so far the only probe of the fine-structure constant in this redshift range. A change in the value of alpha by 1% changes the mean brightness temperature decrement of the CMB due to 21 cm absorption by >5% over the redshift range z < 50. There is an effect of similar magnitude on the amplitude of the fluctuations in the brightness temperature. The redshift of maximum absorption also changes by approximately 5%.

  14. Magnetic fields, plasma densities, and plasma beta parameters estimated from high-frequency zebra fine structures

    NASA Astrophysics Data System (ADS)

    Karlický, M.; Jiricka, K.

    2002-10-01

    Using the recent model of the radio zebra fine structures (Ledenev et al. 2001) the magnetic fields, plasma densities, and plasma beta parameters are estimated from high-frequency zebra fine structures. It was found that in the flare radio source of high-frequency (1-2 GHz) zebras the densities and magnetic fields vary in the intervals of (1-4)×1010 cm-3 and 40-230 G, respectively. Assuming then the flare temperature as about of 107K, the plasma beta parameters in the zebra radio sources are in the 0.05-0.81 interval. Thus the plasma pressure effects in such radio sources, especially in those with many zebra lines, are not negligible.

  15. 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.

  16. 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

  17. Fine structure of alpha decay to rotational states of heavy nuclei

    SciTech Connect

    Wang, Y. Z.; Dong, J. M.; Peng, B. B.; Zhang, H. F.

    2010-06-15

    To gain a better insight into alpha-decay fine structure, we calculate the relative intensities of alpha decay to 2{sup +} and 4{sup +} rotational states in the framework of the generalized liquid drop model (GLDM) and improved Royer's formula. The calculated relative intensities of alpha decay to 2{sup +} states are in good agreement with the experimental data. For the relative intensities of alpha decay to 4{sup +} states, a good agreement with experimental data is achieved for Th and U isotopes. The formula we obtain is useful for the analysis of experimental data of alpha-decay fine structure. In addition, some predicted relative intensities which are still not measured are provided for future experiments.

  18. 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.

  19. Interpretation of the fine structure in the sup 14 C radioactive decay of sup 223 Ra

    SciTech Connect

    Sheline, R.K. ); Ragnarsson, I. )

    1991-03-01

    The experimental hindrance factors determined from the fine structure in the {sup 14}C decay of {sup 223}Ra are strikingly similar to the hindrance factors observed in the alpha decay of odd-{ital A} reflection-asymmetric deformed nuclei in spite of the deformed to spherical shape which occurs in the {sup 14}C decay. Calculations of the overlap between the reflection-asymmetric ground state of {sup 223}Ra and the spherical shell-model orbitals of {sup 209}Pb involved in the {sup 14}C decay are consistent with the experimental hindrance factors from the {sup 14}C fine structure except that the {ital j}{sub 15/2} orbital is more strongly populated experimentally than the calculations suggest.

  20. 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

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

    NASA Astrophysics Data System (ADS)

    Lamoreaux, Steve

    2004-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Parker, Richard

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Fujii, Yasunori; Iwamoto, Akira

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

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

    NASA Astrophysics Data System (ADS)

    Steinhardt, Charles L.

    2005-02-01

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

  6. 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.

  7. 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.

  8. Type IIIb bursts and their fine structure in frequency band 18-30 MHz

    NASA Astrophysics Data System (ADS)

    Melnik, V. N.; Rucker, H. O.; Konovalenko, A. A.; Shevchuk, N. V.; Abranin, E. P.; Dorovskyy, V. V.; Lecacheux, A.

    2010-01-01

    This paper deals with Type IIIb bursts, which were observed in the frequency band from 18 to 30 MHz. These bursts have fine frequency structures contrary to usual Type III bursts. The main properties of Type IIIb bursts such as number of striae in a burst, their frequency drift rates, durations, frequency widths of stria, emission fluxes are presented. It is also shown that parameters of stria bursts depend on the position of active areas on the solar disk.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Fujii, Yasunori; Iwamoto, Akira

    2003-12-01

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

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

    PubMed

    Fujii, Yasunori; Iwamoto, Akira

    2003-12-31

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

  12. 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.

  13. Fine structures in the broadened line of distributed feedback lasers under high-speed direct modulation

    SciTech Connect

    Yoshikuni, Y.; Matsuoka, T.; Motosugi, G.; Yamanaka, N.

    1984-10-15

    Precise observation of the single longitudinal mode spectrum for distributed feeedback lasers revealed fine structures when the spectrum was broadened by high-speed modulation. A dynamic simulation can explain reasonably the above behavior if the model takes into account the carrier density modulation enhanced by the relaxation oscillation. In this letter, experimental results where both modulation depth and speed were varied are described along with a calculated result.

  14. 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.

  15. 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.

  16. Characterizing HII regions in High-z ULIRGs with far infrared fine structure lines

    NASA Astrophysics Data System (ADS)

    Brisbin, Drew; Ferkinhoff, Carl; Stacey, Gordon J.; Parshley, Stephen; Hailey-Dunsheath, Steve; Lamarche, Cody

    2015-01-01

    The nature of star-forming ULIRGs in the early Universe remains mysterious. Is their star formation fueled predominantly through cold flow accretion, or through major mergers? What fraction of the sources have AGN, and what is the stellar mass function powering the HII regions? Of particular importance to these questions is the characterization of the ionized gas properties, and the coupling with the cooler photodissociation region (PDR) gas. To address these issues we have undertaken a mini-survey of several z~1-2 luminous galaxies observed in multiple ionized oxygen far infrared fine structure lines. These fine structure lines allow us to constrain the density and radiation field of the ionized gas and test for the presence of harder AGN powered radiation. Coupled with previous data including the [CII] and [OI] fine structure lines emanating from PDR gas, we will also test the ability to simultaneously model both PDR and HII gas components. This survey, modest in extent, offers an illustrative snapshot of the diversity of systems in the early Universe.

  17. 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.

  18. 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.

  19. 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

  20. Studying the Variation of the Fine-Structure Constant Using Emission-Line Multiplets

    NASA Astrophysics Data System (ADS)

    Grupe, Dirk; Pradhan, Anil K.; Frank, Stephan

    2005-08-01

    As an extension of the method by Bahcall and coworkers to investigate the time dependence of the fine-structure constant, we describe an approach based on new observations of forbidden-line multiplets from different ionic species. We obtain optical spectra of fine-structure transitions in [Ne III], [Ne V], [O III], [O I], and [S II] multiplets from a sample of 14 Seyfert 1.5 galaxies in the low-z range 0.035fine-structure constant. The approach can be further extended and generalized to a ``many-multiplet emission-line method'' analogous in principle to the corresponding method using absorption lines. With that aim, we note that the theoretical limits on emission-line ratios of selected ions are precisely known and provide well-constrained selection criteria. We also discuss several other forbidden and allowed lines that may constitute the basis for a more rigorous study using high-resolution instruments on the next generation of 8 m class telescopes. Based on observations obtained at MDM Observatory, Arizona.

  1. Fine structure of the alloy-broadened thermal emission spectra from DX centers in GaAlAs

    NASA Astrophysics Data System (ADS)

    Calleja, E.; Gomez, A.; Muñoz, E.; Cámara, P.

    1988-05-01

    Deep level transient spectroscopy in Si- and Sn-doped GaAlAs reveals a fine structure of the DX center thermal emission spectra under adequate filling pulse and sampling window times. This structure is reproducible in samples with Al mode fractions near 30% but it is not detectable in samples with 85% Al content. All resolved peaks of this fine structure have the same thermal emission energy but quite different capture cross section (σ∞n). This fact indicates that the origin of the fine structure and of the nonexponential behavior of the thermal emission processes is the discrete broadening of σ∞n due to the alloy effect.

  2. Fine-Scale Structure of the Moho From Receiver Functions: Effects of a Deforming Crust

    NASA Astrophysics Data System (ADS)

    Zandt, G.; Gilbert, H.; Ozacar, A.; Owens, T. J.

    2004-12-01

    Andrija Mohorovicic, a Croatian seismologist, is credited with the first estimation in 1906 of crustal thickness using the critically refracted phase Pn. The crust-mantle boundary has become commonly known as the Moho and its depth, structure, formation, and evolution remains an important research topic in seismology, petrology, and tectonics. Other seismic phases sensitive to Moho depth and structure are the converted phases Ps and Sp, and the associated 2p1s and 1p2s reverberation phases that are isolated in receiver function waveforms. With sufficient station coverage, multiple receiver functions can be migrated and stacked into cross-sections of the crust. Crustal cross-sections from tectonically active regions reveal dramatic variations in amplitude and frequency content of Moho phases that we associate with fine-scale structure, and possibly anisotropy at the crust-mantle boundary. The Moho amplitude or "brightness" is a measure of the crust-mantle impedance contrast, thickness and structure within the crust-mantle boundary, and effects of scattering from 3D structure. Processes directly related to these Moho structures include crustal thickening, crustal extension, crustal flow, delamination or convective removal, and eclogitization. Therefore, the fine-scale seismological structure of the Moho is an important constraint in regional tectonic reconstructions. Examples of receiver function crustal images and their tectonic implications from the western US, South American Andes, and the Tibetan plateau will be reviewed.

  3. 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. PMID:25552343

  4. Adsorption of α-Synuclein on Lipid Bilayers: Modulating the Structure and Stability of Protein Assemblies

    PubMed Central

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

    2010-01-01

    The interaction of α-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 α-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 α-synuclein must target a broad range of potentially toxic, membrane-bound assemblies. PMID:20187615

  5. 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. PMID:23165918

  6. Adsorption induced transitions in soft porous crystals: An osmotic potential approach to multistability and intermediate structures

    NASA Astrophysics Data System (ADS)

    Bousquet, David; Coudert, François-Xavier; Fossati, Alexandre G. J.; Neimark, Alexander V.; Fuchs, Alain H.; Boutin, Anne

    2013-05-01

    Soft porous crystals are flexible metal-organic frameworks that respond to physical stimuli (temperature, pressure, and gas adsorption) by large changes in their structure and unit cell volume. We propose here a thermodynamic treatment, based on the osmotic ensemble, of the interplay between guest adsorption and host deformation, where the bare host material can undergo elastic deformation, as well as structural transitions between metastable phases in the case of a multistable material. We show that in addition to structural transitions between metastable phases of bistable or multistable host frameworks, a new guest-stabilized host phase can be created when the size of the adsorbate is larger than the empty material's pore size. We then confront the findings of our approach with experimental data for systems exhibiting phenomena such as gate opening and breathing.

  7. Quad-plane stereoscopic PIV for fine-scale structure measurements in turbulence

    NASA Astrophysics Data System (ADS)

    Naka, Y.; Tomita, K.; Shimura, M.; Fukushima, N.; Tanahashi, M.; Miyauchi, T.

    2016-05-01

    The fine-scale structure in turbulence is investigated by quad-plane stereoscopic particle image velocimetry (QPSPIV). The quad-plane consists of two each of different polarizations and wavelengths, and it provides three velocity components at four independent parallel planes. Measurements have been undertaken in the developed region of a turbulent round jet with a spatial resolution sufficient to capture the small-scale structures. The advantage of the QPSPIV is presented in terms of the spectral response in the evaluation of the out-of-plane velocity gradient. The full velocity gradient tensor is computed with a fourth-order finite difference scheme in the out-of-plane direction as well as the in-plane directions. The turbulence quantities, such as the vorticity components, the energy dissipation rate and the second and third invariants of the velocity gradient tensor, are computed according to their faithful definitions. The coherent fine-scale eddies are extracted from the present QPSPIV data. The probability density functions of the diameter and the maximum azimuthal velocity of the extracted eddies exhibit their peak at approximately 8η and 1.5u_k, respectively, where η and u_k are the Kolmogorov length and velocity. These values agree well with the data in the literature. The phase-averaged distributions of turbulence quantities around the coherent fine-scale eddy indicate an apparent elliptic feature around the axis. Furthermore, the state of the strain rate exerting the eddy is quantified from the phase-averaged distributions of eigenvalues of the strain rate tensor and the alignment of the corresponding eigenvectors against the axis. The present study gives a solid experimental support of the coherent fine-scale structures in turbulence, and the technique can be applied to various flow fields and to the higher Reynolds number condition.

  8. 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.

  9. Measurements of photon interference X-ray absorption fine structure (piXAFS).

    PubMed

    Tröger, L; Kappen, P; Nishino, Y; Haack, N; Materlik, G

    2001-03-01

    Experimental data are presented which demonstrate the existence of a fine structure in extended X-ray absorption spectra due to interference effects in the initial photon state (piXAFS). Interference occurs between the incident electromagnetic wave and its coherently scattered waves from neighboring atoms. Using fine platinum and tungsten powders as well as polycrystalline platinum foil, piXAFS was measured in high-precision absorption experiments at beamline X1 at HASYLAB/DESY over a wide energy range. piXAFS is observed below and above absorption-edge positions in both transmission and total-electron-yield detection. Based on experimental data it is shown that piXAFS is sensitive to geometric atomic structure. Fourier-transformed piXAFS data carry information, comparable with that of EXAFS, about the short-range-order structure of the sample. Sharp structures occur in piXAFS when a Bragg backscattering condition of the incident X-rays is fulfilled. They allow precise measurement of long-range-order structural information. Measured data are compared with simulations based on piXAFS theory. Although piXAFS structures are similarly observed in two detection techniques, the importance of scattering off the sample for the measurements needs to be investigated further. Disentangling piXAFS, multielectron photoexcitations and atomic XAFS in high-precision measurements close to absorption edges poses a challenge for future studies.

  10. Rare Variation Facilitates Inferences of Fine-Scale Population Structure in Humans

    PubMed Central

    O’Connor, Timothy D.; Fu, Wenqing; Mychaleckyj, Josyf C.; Logsdon, Benjamin; Auer, Paul; Carlson, Christopher S.; Leal, Suzanne M.; Smith, Joshua D.; Rieder, Mark J.; Bamshad, Michael J.; Nickerson, Deborah A.; Akey, Joshua M.

    2015-01-01

    Understanding the genetic structure of human populations has important implications for the design and interpretation of disease mapping studies and reconstructing human evolutionary history. To date, inferences of human population structure have primarily been made with common variants. However, recent large-scale resequencing studies have shown an abundance of rare variation in humans, which may be particularly useful for making inferences of fine-scale population structure. To this end, we used an information theory framework and extensive coalescent simulations to rigorously quantify the informativeness of rare and common variation to detect signatures of fine-scale population structure. We show that rare variation affords unique insights into patterns of recent population structure. Furthermore, to empirically assess our theoretical findings, we analyzed high-coverage exome sequences in 6,515 European and African American individuals. As predicted, rare variants are more informative than common polymorphisms in revealing a distinct cluster of European–American individuals, and subsequent analyses demonstrate that these individuals are likely of Ashkenazi Jewish ancestry. Our results provide new insights into the population structure using rare variation, which will be an important factor to account for in rare variant association studies. PMID:25415970

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

    SciTech Connect

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

    2009-12-01

    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

  12. The fine structure of the axostyle and its associations with organelles in Trichomonads.

    PubMed

    Benchimol, M; Diniz, J A; Ribeiro, K

    2000-04-01

    The fine structure of the axostyle in the protists Tritrichomonas foetus and Monocercomonas sp is described using transmission electron microscopy after quick-freezing techniques and immunocytochemistry. The axostyle microtubules presents a lateral projection formed by two protofilaments in addition to the 13 protofilaments normally found in microtubules. The axostyle is associated with other cell structures such as hydrogenosomes, endoplasmic reticulum, sigmoid filaments and glycogen particles. The microtubules of the pelta-axostylar system are connected to each other by bridges regularly spaced with an interval of 9 nm. Labeling of the axostyle was observed after cell incubation with monoclonal antibodies recognizing alpha-tubulin and acetylated-tubulin.

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

    PubMed

    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

  14. 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

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

    PubMed

    Moritake, Y; Kanamori, Y; Hane, K

    2016-09-13

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  17. Fine Structure of the Eggshell of the Blow Fly, Lucilia cuprina

    PubMed Central

    Sukontason, Kabkaew L.; Bunchu, Nophawan; Chaiwong, Tarinee; Kuntalue, Budsabong; Sukontason, Kom

    2007-01-01

    The fine structure of the eggshell of blow fly, Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae), was examined using scanning and transmission electron microscopy. Eggs, 1.09±0.07 mm in length and 0.25±0.05 mm in width, bore a relatively wide plastron that extending along almost the entire length. The polygonal pattern of chorionic sculpture was indistinct. The ultrathin section indicated a multi-layered eggshell having an exochorion, outer endochorion, pillars, an inner endochorion, innermost chorionic layer, and a wax layer. This study provides new information about the fine morphology of blow flies eggs. A key to differentiate the eggs of forensically important flies in Thailand is given. PMID:20334590

  18. 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.

  19. Fine-scale spatial genetic structure of common and declining bumble bees across an agricultural landscape

    PubMed Central

    Dreier, Stephanie; Redhead, John W; Warren, Ian A; Bourke, Andrew F G; Heard, Matthew S; Jordan, William C; Sumner, Seirian; Wang, Jinliang; Carvell, Claire

    2014-01-01

    Land-use changes have threatened populations of many insect pollinators, including bumble bees. Patterns of dispersal and gene flow are key determinants of species' ability to respond to land-use change, but have been little investigated at a fine scale (<10 km) in bumble bees. Using microsatellite markers, we determined the fine-scale spatial genetic structure of populations of four common Bombus species (B. terrestris, B. lapidarius, B. pascuorum and B. hortorum) and one declining species (B. ruderatus) in an agricultural landscape in Southern England, UK. The study landscape contained sown flower patches representing agri-environment options for pollinators. We found that, as expected, the B. ruderatus population was characterized by relatively low heterozygosity, number of alleles and colony density. Across all species, inbreeding was absent or present but weak (FIS = 0.01–0.02). Using queen genotypes reconstructed from worker sibships and colony locations estimated from the positions of workers within these sibships, we found that significant isolation by distance was absent in B. lapidarius, B. hortorum and B. ruderatus. In B. terrestris and B. pascuorum, it was present but weak; for example, in these two species, expected relatedness of queens founding colonies 1 m apart was 0.02. These results show that bumble bee populations exhibit low levels of spatial genetic structure at fine spatial scales, most likely because of ongoing gene flow via widespread queen dispersal. In addition, the results demonstrate the potential for agri-environment scheme conservation measures to facilitate fine-scale gene flow by creating a more even distribution of suitable habitats across landscapes. PMID:24980963

  20. Fine-scale genetic structure in populations of the Chagas' disease vector Triatoma infestans (Hemiptera, Reduvidae).

    PubMed

    Pérez de Rosas, Alicia R; Segura, Elsa L; Fusco, Octavio; Guiñazú, Adolfo L Bareiro; García, Beatriz A

    2013-03-01

    Fine scale patterns of genetic structure and dispersal in Triatoma infestans populations from Argentina was analysed. A total of 314 insects from 22 domestic and peridomestic sites from the locality of San Martín (Capayán department, Catamarca province) were typed for 10 polymorphic microsatellite loci. The results confirm subdivision of T. infestans populations with restricted dispersal among sampling sites and suggest inbreeding and/or stratification within the different domestic and peridomestic structures. Spatial correlation analysis showed that the scale of structuring is approximately of 400 m, indicating that active dispersal would occur within this distance range. It was detected difference in scale of structuring among sexes, with females dispersing over greater distances than males. This study suggests that insecticide treatment and surveillance should be extended within a radius of 400 m around the infested area, which would help to reduce the probability of reinfestation by covering an area of active dispersal. The inferences made from fine-scale spatial genetic structure analyses of T. infestans populations has demonstrated to be important for community-wide control programs, providing a complementary approach to help improve vector control strategies.

  1. 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.

  2. Adsorption from the liquid phase on silica gels of various structural heterogeneity

    SciTech Connect

    Goworek, J.; Derylo-Marczewska, A.; Borowka, A.

    1999-08-31

    Competition of liquid components for silica gel surface was tested for binary liquid mixtures: methanol + benzene and 2-propanol + n-heptane. The adsorption isotherms were measured using silica gels for column chromatography Si-40 and Si-100 from Merck. On the basis of specific surface excess isotherms the surface layer capacities were calculated. Taking into account the properties of the bulk solutions, the influence of geometrical structure of silicas on the composition of the surface phase is discussed.

  3. [X-ray absorption fine structure (XAFS) study of the effects of pH on Pb(II) sorption by soil].

    PubMed

    Hu, Ning-Jing; Huang, Peng; Luo, Yong-Ming; Hu, Tian-Dou; Xie, Ya-Ning; Wu, Zi-Yu

    2010-12-01

    Combined batch sorption and in situ X-ray absorption fine structure (XAFS) provide direct assessment of the mechanisms for Pb(II) sorption at the soil-water interface under different pH conditions. The XAFS data indicated that the innersphere Pb sorption complex with ionic character (Pb4 (OH)4(4+)) dominated the Pb surface speciation, and the outer-sphere Pb sorption complex and the precipitation of calcium carbonate containing Pb(PbCaCO3) were also involved in the adsorption samples. Coordination number and radial distance of the first-shell Pb-O decreased from 0.172 7 to 0.166 6 nm and the percentage of inner-sphere complexes increased when the initial pH changed from 6.0 to 8.5, indicating that the mechanism of Pb(II) sorption by the soil was pH-dependent. PMID:21322254

  4. Free energy landscapes for the thermodynamic understanding of adsorption-induced deformations and structural transitions in porous materials

    NASA Astrophysics Data System (ADS)

    Bousquet, D.; Coudert, F.-X.; Boutin, A.

    2012-07-01

    Soft porous crystals are flexible metal-organic frameworks that respond to physical stimuli such as temperature, pressure, and gas adsorption by large changes in their structure and unit cell volume. While they have attracted a lot of interest, molecular simulation methods that directly couple adsorption and large structural deformations in an efficient manner are still lacking. We propose here a new Monte Carlo simulation method based on non-Boltzmann sampling in (guest loading, volume) space using the Wang-Landau algorithm, and show that it can be used to fully characterize the adsorption properties and the material's response to adsorption at thermodynamic equilibrium. We showcase this new method on a simple model of the MIL-53 family of breathing materials, demonstrating its potential and contrasting it with the pitfalls of direct, Boltzmann simulations. We furthermore propose an explanation for the hysteretic nature of adsorption in terms of free energy barriers between the two metastable host phases.

  5. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    Ionization potential (IP) is defined as the amount of energy required to remove the most loosely bound electron of an atom, while electron affinity (EA) is defined as the amount of energy released when an electron is attached to a neutral atom. Both IP and EA are critical for understanding chemical properties of an element. In contrast to accurate IPs and structures of neutral atoms, EAs and structures of negative ions are relatively unexplored, especially for the transition metal anions. Here, we report the accurate EA value of Fe and fine structures of Fe‑ using the slow electron velocity imaging method. These measurements yield a very accurate EA value of Fe, 1235.93(28) cm‑1 or 153.236(34) meV. The fine structures of Fe‑ were also successfully resolved. The present work provides a reliable benchmark for theoretical calculations, and also paves the way for improving the EA measurements of other transition metal atoms to the sub cm‑1 accuracy.

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

    PubMed

    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

  8. 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.

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

    PubMed

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

    2015-10-28

    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. PMID:26520545

  10. 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.

  11. 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.

  12. 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.

  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. 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.

  15. COLLISIONAL EXCITATION OF THE [C II] FINE STRUCTURE TRANSITION IN INTERSTELLAR CLOUDS

    SciTech Connect

    Goldsmith, Paul F.; Langer, William D.; Pineda, Jorge L.; Velusamy, T.

    2012-11-15

    We analyze the collisional excitation of the 158 {mu}m (1900.5 GHz) fine structure transition of ionized carbon in terms of line intensities produced by simple cloud models. The single C{sup +} fine structure transition is a very important coolant of the atomic interstellar medium (ISM) and of photon-dominated regions in which carbon is partially or completely in ionized form. The [C II] line is widely used as a tracer of star formation in the Milky Way and other galaxies. Excitation of the [C II] fine structure transition can be via collisions with hydrogen molecules, atoms, and electrons. Analysis of [C II] observations is complicated by the fact that it is difficult to determine the optical depth of the line. We discuss the excitation of the [C II] line, deriving analytic results for several limiting cases and carry out numerical solutions using a large velocity gradient model for a more inclusive analysis. For antenna temperatures up to 1/3 of the brightness temperature of the gas kinetic temperature, the antenna temperature is linearly proportional to the column density of C{sup +} irrespective of the optical depth of the transition. This is appropriately referred to as the effectively optically thin approximation. We review the critical densities for excitation of the [C II] line by various collision partners, briefly analyze C{sup +} absorption, and conclude with a discussion of C{sup +} cooling and how the considerations for line intensities affect the behavior of this important coolant of the ISM.

  16. 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

  17. 3D Whole-prominence Fine Structure Modeling. II. Prominence Evolution

    NASA Astrophysics Data System (ADS)

    Gunár, Stanislav; Mackay, Duncan H.

    2015-10-01

    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.

  18. Observation of a straight-line wind case caused by a gust front and its associated fine-scale structures

    NASA Astrophysics Data System (ADS)

    Quan, Wanqing; Xu, Xin; Wang, Yuan

    2014-12-01

    A straight-line wind case was observed in Tianjin on 13 June 2005, which was caused by a gust front from a squall line. Mesoscale analyses based on observations from in-situ surface stations, sounding, and in-situ radar as well as fine-scale analyses based on observation tower data were performed. The mesoscale characteristics of the gust front determined its shape and fine-scale internal structures. Based on the scale and wavelet analyses, the fine-scale structures within the gust front were distinguished from the classical mesoscale structures, and such fine-scale structures were associated with the distribution of straight-line wind zones. A series of cross-frontal fine-scale circulations at the lowest levels of the gust front was discovered, which caused a relatively weak wind zone within the frontal strong wind zone. The downdraft at the rear of the head region of the gust front was more intense than in the classical model, and similar to the microburst, a series of vertical vortices propagated from the rear region to the frontal region. In addition, strong tangential fine-scale instability was detected in the frontal region. Finally, a fine-scale gust front model with straight-line wind zones is presented.

  19. Study of microscopic structure of porous media - fine coal filter cakes

    SciTech Connect

    Kakwani, R.M.

    1983-01-01

    The macroscopic properties of the porous media, e.g., permeability, capillary pressure, relative permeability, depend upon the microscopic structure of the porous medium. In the coal preparation plants, the filtration and dewatering rates of the fine coal filter cakes are important in determining the final moisture content. The microscopic structure of the porous coal filter cakes plays an important role in these operations. Moreover, the two phase flow through the porous medium can be explained in detail by considering its pore structure. Hence, the development of a technique for the micro-structural analysis of unconsolidated coal filter cakes is investigated. The technique developed is also applicable to many consolidated porous media like sandstones, rocks, etc. Optical methods were utilized to study the micro-structure of fine coal cakes. The investigation of -32 mesh Pittsburgh seam coal cakes reveals a non-uniform structure at low solid concentration of 0.33 kg coal/kg water. An increase in the solid concentration in the slurry produces a more uniform structure with an increase in the filtration and dewatering rates. It was found that coal filter cakes are incompressible over the range of 28 to 67 kPa applied vacuum. An important aspect of this work was to provide quantitative information about the presence of air bubbles in the coal filter cakes. These air bubbles are evolved from the aerated slurry and they reduce the filtration rates. A linear correlation between the particle and pore size distribution of -32 mesh Pittsburgh coal was found.

  20. 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.

  1. Silicon 1s near edge X-ray absorption fine structure spectroscopy of functionalized silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Ritchie, A.; Cao, W.; Dasog, M.; Purkait, T. K.; Senger, C.; Hu, Y. F.; Xiao, Q. F.; Veinot, J. G. C.; Urquhart, S. G.

    2016-10-01

    Silicon 1s Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of silicon nanocrystals have been examined as a function of nanocrystal size (3-100 nm), varying surface functionalization (hydrogen or 1-pentyl termination), or embedded in oxide. The NEXAFS spectra are characterized as a function of nanocrystal size and surface functionalization. Clear spectroscopic evidence for long range order is observed silicon nanocrystals that are 5-8 nm in diameter or larger. Energy shifts in the silicon 1s NEXAFS spectra of covalently functionalized silicon nanocrystals with changing size are attributed to surface chemical shifts and not to quantum confinement effects.

  2. 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.

  3. 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.

  4. Origin of fine structure in si photoelectron spectra at silicon surfaces and interfaces.

    PubMed

    Yazyev, Oleg V; Pasquarello, Alfredo

    2006-04-21

    Using a first-principles approach, we investigate the origin of the fine structure in Si 2p photoelectron spectra at the Si(100)-(2 x 1) surface and at the Si(100)-SiO2 interface. Calculated and measured shifts show very good agreement for both systems. By using maximally localized Wannier functions, we clearly identify the shifts resulting from the electronegativity of second-neighbor atoms. The other shifts are then found to be proportional to the average bond-length variation around the Si atom. Hence, in combination with accurate modeling, photoelectron spectroscopy can provide a direct measure of the strain field at the atomic scale.

  5. Coupled-channels study of fine structure in the {alpha} decay of well deformed nuclei

    SciTech Connect

    Ni Dongdong; Ren Zhongzhou

    2011-06-15

    We formulate a theoretical model for the {alpha} decay of well-deformed even-even nuclei based on the coupled-channel Schroedinger equation. The {alpha}-decay half-lives and fine structures observed in {alpha} decay are well described by the five-channel microscopic calculations. Since the branching ratios to high-spin states are hard to understand in the traditional {alpha}-decay theories, this success could be important to interpret future observations of heavier nuclei. It is also found that the {alpha} transition to high-spin states is a powerful tool to probe the energy spectrum and deformation of daughter nuclei.

  6. 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.

  7. Thermal Expansion Behaviour of Silver Examined by Extended X-Ray Absorption Fine Structure Spectroscopy

    SciTech Connect

    Dubiel, M.; Chasse, A.; Haug, J.; Schneider, R.; Kruth, H.

    2007-02-02

    EXAFS (extended X-ray absorption fine structure) investigations are reported concerning the thermal expansion behaviour of silver in an extended range of temperature from 10 K to about 950 K measured in transmission mode. Both the ratio method and an EXAFS fitting procedure were applied to reveal the temperature dependence of EXAFS parameters. Models based on quantum and classical thermodynamic perturbation theory have been used to interpret experimental data and compared to XRD (X-ray diffraction) results of bulk silver material. The description of thermodynamic data of thermal expansion of silver in the complete range of temperature by EXAFS Spectroscopy was successful by first calculations using third order quantum perturbation theory.

  8. 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.

  9. 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.

  10. Surface extended x-ray absorption fine structure of low-Z absorbates using fluorescence detection

    SciTech Connect

    Stoehr, J.; Kollin, E.B.; Fischer, D.A.; Hastings, J.B.; Zaera, F.; Sette, F.

    1985-05-01

    Comparison of x-ray fluorescence yield (FY) and electron yield surface extended x-ray absorption fine structure spectra above the S K-edge for c(2 x 2) S on Ni(100) reveals an order of magnitude higher sensitivity of the FY technique. Using FY detection, thiophene (C/sub 4/H/sub 4/S) chemisorption on Ni(100) is studied with S coverages down to 0.08 monolayer. The molecule dissociates at temperatures as low as 100K by interaction with fourfold hollow Ni sites. Blocking of these sites by oxygen leaves the molecule intact.

  11. Time Variation of the Fine Structure Constant in the Spacetime of a Cosmic Domain Wall

    NASA Astrophysics Data System (ADS)

    Campanelli, L.; Cea, P.; Tedesco, L.

    The gravitational field produced by a domain wall acts as a medium with spacetime-dependent permittivity ɛ. Therefore, the fine structure constant α=e2/4πɛ will be a time-dependent function at fixed position. The most stringent constraint on the time-variation of α comes from the natural reactor Oklo and gives |˙ α /α | < few × 10-17 yr-1. This limit constrains the tension of a cosmic domain wall to be less than σ ≲ 10-2 MeV3, and then represents the most severe limit on the energy density of a cosmic wall stretching our Universe.

  12. 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.

  13. Electronic fine structure in the electron-hole plasma in SrB6

    PubMed

    Rodriguez; Weht; Pickett

    2000-04-24

    Electron-hole mixing-induced fine structure in alkaline earth hexaborides leads to lower energy (temperature) scales, and thus a stronger tendency toward an excitonic instability than in their doped counterparts (viz. Ca1-xLaxB6, x approximately 0.005), which are high-Curie-temperature, small-moment ferromagnets. Comparison of Fermi surfaces and spectral distributions with de Haas-van Alphen, optical, transport, and tunneling data indicates that SrB6 remains a fermionic semimetal down to (at least) 5 K, rather than forming an excitonic condensate. For the doped system the Curie temperature is higher than the degeneracy temperature.

  14. Time evolution of the fine structure constant in a two-field quintessence model

    NASA Astrophysics Data System (ADS)

    Bento, M. C.; Bertolami, O.; Santos, N. M.

    2004-11-01

    We examine the variation of the fine structure constant in the context of a two-field quintessence model. We find that, for solutions that lead to a transient late period of accelerated expansion, it is possible to fit the data arising from quasar spectra and comply with the bounds on the variation of α from the Oklo reactor, meteorite analysis, atomic clock measurements, cosmic microwave background radiation, and big bang nucleosynthesis. That is more difficult if we consider solutions corresponding to a late period of permanent accelerated expansion.

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

    NASA Astrophysics Data System (ADS)

    Fujii, Yasunori

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

  16. 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. PMID:23505485

  17. 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.

  18. 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

  19. 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.

  20. Fine structure in sup 14 C emission from sup 223 Ra and sup 224 Ra

    SciTech Connect

    Hourani, E.; Rosier, L.; Berrier-Ronsin, G.; Elayi, A.; Mueller, A.C.; Rappenecker, G.; Rotbard, G.; Renou, G.; Liebe, A.; Stab, L. ); Ravn, H.L. )

    1991-10-01

    The measurement of the energy spectrum of {sup 14}C nuclei emitted in the spontaneous radioactivity of {sup 223}Ra and {sup 224}Ra has been carried out, using thin and intense sources (480 MBq for {sup 223}Ra and 3550 MBq for {sup 224}Ra). The sources were obtained by implanting mass-separated beams into Al and vitreous C catchers. The measurement was performed with a superconducting solenoidal spectrometer. Our discovery, previously reported, of fine structure in the energy spectrum of {sup 14}C emission from {sup 223}Ra, which is analogous to the one known for {alpha} emission, is confirmed. Only 13% of the branching ratio in {sup 14}C decay leads to the ground state of the residual nucleus, while 81% to the first excited state. For {sup 14}C emission from {sup 224}Ra, a lower limit of 2 for the hindrance factor has been measured for the transition to the first excited state in the residual nucleus. Also, a precise identification in {ital Z} with an {ital E}{times}{Delta}{ital E} telescope has been performed for the radiation from the {sup 223}Ra source. Our measurements of fine structure in {sup 14}C emissions open this field to nuclear structure studies.

  1. 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.

  2. 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.

  3. 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. PMID:25731093

  4. Importance of structural and chemical heterogeneity of activated carbon surfaces for adsorption of dibenzothiophene

    SciTech Connect

    Ania, C.O.; Bandosz, T.J.

    2005-08-16

    The performance of various activated carbons obtained from different carbon precursors (i.e., plastic waste, coal, and wood) as adsorbents for the desulfurization of liquid hydrocarbon fuels was evaluated. To increase surface heterogeneity, the carbon surface was modified by oxidation with ammonium persulfate. The results showed the importance of activated carbon pore sizes and surface chemistry for the adsorption of dibenzothiophene (DBT) from liquid phase. Adsorption of DBT on activated carbons is governed by two types of contributions: physical and chemical interactions. The former include dispersive interactions in the microporous network of the carbons. While the volume of micropores governs the amount physisorbed, mesopores control the kinetics of the process. On the other hand, introduction of surface functional groups enhances the performance of the activated carbons as a result of specific interactions between the acidic centers of the carbon and the basic structure of DBT molecule as well as sulfur-sulfur interactions.

  5. Controlling the Adsorption of Carbon Monoxide on Platinum Clusters by Dopant-Induced Electronic Structure Modification.

    PubMed

    Ferrari, Piero; Molina, Luis M; Kaydashev, Vladimir E; Alonso, Julio A; Lievens, Peter; Janssens, Ewald

    2016-09-01

    A major drawback of state-of-the-art proton exchange membrane fuel cells is the CO poisoning of platinum catalysts. It is known that CO poisoning is reduced if platinum alloys are used, but the underlying mechanism therefore is still under debate. We study the influence of dopant atoms on the CO adsorption on small platinum clusters using mass spectrometry experiments and density functional calculations. A significant reduction in the reactivity for Nb- and Mo-doped clusters is attributed to electron transfer from those highly coordinated dopants to the Pt atoms and the concomitant lower CO binding energies. On the other hand Sn and Ag dopants have a lower Pt coordination and have a limited effect on the CO adsorption. Analysis of the density of states demonstrates a correlation of dopant-induced changes in the electronic structure with the enhanced tolerance to CO poisoning. PMID:27464653

  6. Adsorption-induced changes of the structure of the tethered chain layers in a simple fluid.

    PubMed

    Borówko, M; Sokołowski, S; Staszewski, T

    2014-06-21

    We use density functional theory to study the influence of fluid adsorption on the structure of grafted chain layer. The chains are modeled as freely jointed spheres. The chain segments and spherical molecules of the fluid interact via the Lennard-Jones potential. The fluid molecules are attracted by the substrate. We calculate the excess adsorption isotherms, the average height of tethered chains, and the force acting on selected segments of the chains. The parameters that were varied include the length of grafted chains, the grafting density, the parameters characterizing fluid-chain and fluid-surface interactions, the bulk fluid density, and temperature. We show that depending on the density of the bulk fluid the height of the bonded layer increases, remains constant, or decreases with increasing temperature.

  7. Prediction of activated carbon adsorption capacities for organic vapors using quantitative structure-activity relationship methods

    SciTech Connect

    Nirmalakhandan, N.N. ); Speece, R.E. )

    1993-08-01

    Quantitative structure-activity relationship (QSAR) methods were used to develop models to estimate and predict activated carbon adsorption capacities for organic vapors. Literature isothermal data from two sources for 22 organic contaminants on six different carbons were merged to form a training set of 75 data points. Two different QSAR approaches were evaluated: the molecular connectivity approach and the linear solvation energy relationship approach. The QSAR model developed in this study using the molecular connectivity approach was able to fit the experimental data with r = 0.96 and standard error of 0.09. The utility of the model was demonstrated by using predicted k values to calculate adsorption capacities of 12 chemicals on two different carbons and comparing them with experimentally determined values. 9 refs., 1 fig., 3 tabs.

  8. 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

  9. Structure and magnetic properties of Nd2Fe14B fine particles produced by spark erosion

    NASA Astrophysics Data System (ADS)

    Wan, H.; Berkowitz, A. E.

    1994-11-01

    At present Nd2Fe14B is the best permanent magnet because of its extremely high coercivity and energy product. Optimum properties of Nd2Fe14B magnets can be attained by producing single domain particles, and then aligning and compacting them. Due to the reactivity of the Nd constitutent, it is challenging to produce and handle a large amount of fine particles of this material. We have prepared fine particles of Nd2Fe14B by spark erosion with various dielectric media. Yield, size, size distribution, structure, and magnetic properties are discussed. The Nd2Fe14B particles were made by the sharker pot spark erosion method. Relaxation oscillators or a pulse generator were used to power the park erosion. Commercial Neomax 35 was employed as the primary material. The dielectric media were liquid Ar, Ar gas, and hydrocarbons, which provided an oxygen free environment. Structure and size were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and x-ray diffraction. Magnetic properties were measured by vibrating sample magnetometer (VSM) with temperatures in range of 4.2-1200 K. The particles produced in these three different dielectric media had different microstructures and crystal structures. The particles made in Ar gas were pure Nd2Fe14B phase. The particles made in liquid Ar were a mixture of amorphous and crystalline Nd2Fe14B, because the liquid Ar provided a much higher quench rate than Ar gas, which produced some amorphous Nd2Fe14B. Upon annealing, the amorphous particles became crystalline. The fine particles produced in hydrocarbons, such as pentane and dodecane, had more complex mixed phases, since the rare earth reacted with the hydrocarbons during the sparking process. The phases were NdC2, alpha-Fe, and amorphous and crystalline Nd2Fe14B. The effects of power parameters, such as voltage and capacitance, on particle size were investigated. Particle sizes from 20 nm to 50 microns were obtained.

  10. Electronic structures of hybrid graphene/boron nitride nanoribbons with hydrogen adsorption

    NASA Astrophysics Data System (ADS)

    Lee, Chi-Hsuan; Yang, Chih-Kai

    Electronic properties of hybrid graphene/boron nitride nanoribbons are investigated using density functional calculations. It is found that hydrogen adsorption on a graphene nanoribbon alters band structures drastically. Furthermore, H-vacancy chains and lines can effectively shape the conduction properties. Influences of edge atoms with nonzero magnetic moments and the interface between B and N are also prominent in the electronic structures. This work was supported by the Ministry of Science and Technology of the Republic of China under Grant Number MOST 104-2112-M-004-003.

  11. 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

  12. Fine-scale population genetic structure in a fission-fusion society.

    PubMed

    Archie, Elizabeth A; Maldonado, Jésus E; Hollister-Smith, Julie A; Poole, Joyce H; Moss, Cynthia J; Fleischer, Robert C; Alberts, Susan C

    2008-06-01

    Nonrandom patterns of mating and dispersal create fine-scale genetic structure in natural populations - especially of social mammals - with important evolutionary and conservation genetic consequences. Such structure is well-characterized for typical mammalian societies; that is, societies where social group composition is stable, dispersal is male-biased, and males form permanent breeding associations in just one or a few social groups over the course of their lives. However, genetic structure is not well understood for social mammals that differ from this pattern, including elephants. In elephant societies, social groups fission and fuse, and males never form permanent breeding associations with female groups. Here, we combine 33 years of behavioural observations with genetic information for 545 African elephants (Loxodonta africana), to investigate how mating and dispersal behaviours structure genetic variation between social groups and across age classes. We found that, like most social mammals, female matrilocality in elephants creates co-ancestry within core social groups and significant genetic differentiation between groups (Phi(ST) = 0.058). However, unlike typical social mammals, male elephants do not bias reproduction towards a limited subset of social groups, and instead breed randomly across the population. As a result, reproductively dominant males mediate gene flow between core groups, which creates cohorts of similar-aged paternal relatives across the population. Because poaching tends to eliminate the oldest elephants from populations, illegal hunting and poaching are likely to erode fine-scale genetic structure. We discuss our results and their evolutionary and conservation genetic implications in the context of other social mammals.

  13. Fine-scale population genetic structure in a fission-fusion society.

    PubMed

    Archie, Elizabeth A; Maldonado, Jésus E; Hollister-Smith, Julie A; Poole, Joyce H; Moss, Cynthia J; Fleischer, Robert C; Alberts, Susan C

    2008-06-01

    Nonrandom patterns of mating and dispersal create fine-scale genetic structure in natural populations - especially of social mammals - with important evolutionary and conservation genetic consequences. Such structure is well-characterized for typical mammalian societies; that is, societies where social group composition is stable, dispersal is male-biased, and males form permanent breeding associations in just one or a few social groups over the course of their lives. However, genetic structure is not well understood for social mammals that differ from this pattern, including elephants. In elephant societies, social groups fission and fuse, and males never form permanent breeding associations with female groups. Here, we combine 33 years of behavioural observations with genetic information for 545 African elephants (Loxodonta africana), to investigate how mating and dispersal behaviours structure genetic variation between social groups and across age classes. We found that, like most social mammals, female matrilocality in elephants creates co-ancestry within core social groups and significant genetic differentiation between groups (Phi(ST) = 0.058). However, unlike typical social mammals, male elephants do not bias reproduction towards a limited subset of social groups, and instead breed randomly across the population. As a result, reproductively dominant males mediate gene flow between core groups, which creates cohorts of similar-aged paternal relatives across the population. Because poaching tends to eliminate the oldest elephants from populations, illegal hunting and poaching are likely to erode fine-scale genetic structure. We discuss our results and their evolutionary and conservation genetic implications in the context of other social mammals. PMID:18466226

  14. [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.

  15. Fine structure of epithelial canal cells in petioles of Xanthium pensylvanicum

    SciTech Connect

    Maksymowych, R.; Ledbetter, M.C. Brookhaven National Lab., Upton, NY )

    1987-01-01

    Secretory canals were examined in petioles of Xanthium pensylvanicum (Cocklebur) grown under long day illumination to maintain vegetative growth. The fine structure of the canal and its epithelium was studied by electron microscopy of thin section cut transverse to the principal axis of petioles from leaves in an early stage of development. The canal proper is delimited by walls of epithelial cells which protrude into a scallop shaped cavity. In comparison to the surrounding parenchyma, the epithelial cells are smaller, cytoplasmically more dense, and less vacuolate. The epithelium contains pleomorphic starch-free plastids with planar thylakoids frequently stacked into grana; thus, the plastids are presumed photosynthetically active. Mitochondria are abundant and often dense. The cytoplasm is rich in free polysomes, and smooth endoplasmic reticulum predominates over the rough form. Spheroidal granules averaging about 530 nm in diameter are numerous in the epithelium and appear at lower concentration in neighboring cells. Many features of fine structure of the epithelial cells suggest that a high metabolic activity in present in this tissue during this early stage of development. A possible function of the canals is defense against insect predation and animal grazing.

  16. 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.

  17. 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.

  18. Electron affinity of arsenic and the fine structure of As- measured using infrared photodetachment threshold spectroscopy

    NASA Astrophysics Data System (ADS)

    Walter, C. W.; Gibson, N. D.; Field, R. L., III; Snedden, A. P.; Shapiro, J. Z.; Janczak, C. M.; Hanstorp, D.

    2009-07-01

    The binding energy and fine-structure splittings of the arsenic negative ion (As-) have been measured using infrared photodetachment threshold spectroscopy. The relative cross section for neutral atom production was measured with a crossed ion-beam-laser-beam apparatus over selected photon energy ranges between 630-810 meV. An s -wave threshold was observed due to the opening of the As-(4p4P32) to As(4p3S43/2) ground-state to ground-state transition, which yields the electron affinity of As to be 804.8(2) meV. s -wave thresholds were also observed for detachment from the J=1 and J=0 excited levels of As- , permitting accurate determination of the fine-structure splittings of 127.6(2) meV for P31-P32 and 164.3(10) meV for P30-P32 . The present values are consistent with previous measurements and substantially reduce the uncertainties.

  19. 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.

  20. Fine structure of uterus and non-functioning paruterine organ in Orthoskrjabinia junlanae (Cestoda, Cyclophyllidea).

    PubMed

    Korneva, Janetta V; Kornienko, Svetlana A; Jones, Malcolm K

    2016-06-01

    Some cyclophyllidean cestodes provide protection for their eggs in the external environment by providing them with additional protective layers around the egg membranes. In attempting to examine such adaptations, the microanatomy and fine structure of the uterus of pregravid and gravid proglottids of the cyclophyllidean cestode Orthoskrjabinia junlanae, a parasite of mammals that inhabit a terrestrial but moist environment, were studied. In the initial stages of uterine development, developing embryos locate freely in the lumen of a saccate uterus that later partitions into chambers. Each chamber that forms encloses several embryos. The chambers are surrounded by muscle cells that synthesize extracellular matrix actively. The paruterine organs consist of stacks of flattened long outgrowths of muscular cells, interspersed with small lipid droplets. In the gravid proglottids, the size of paruterine organ increases and consists of flattened basal and small rounded apical parts separated by constrictions. The fine structure of the organ wall remains the same: sparse nuclei and stacks of flattened cytoplasmic outgrowths but internal invaginations or lumen in the paruterine organ are absent. Completely developed eggs remain localized in the uterus. Based on the comparative morpho-functional analysis of uterine and paruterine organs and uterine capsules in cestodes, we conclude that these non-functioning paruterine organ in O. junlanae is an example of an atavism. We postulate that the life cycle of the parasite, which infects mammals living in wet habitats, where threats of desiccation of parasite ova is reduced, has favoured a reversion to a more ancestral form of uterine development. PMID:26997340

  1. 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.

  2. Atmospheric fine structure during GTE TRACE A: Relationships among ozone, carbon monoxide, and water vapor

    NASA Astrophysics Data System (ADS)

    Collins, James E.; Anderson, Bruce E.; Sachse, Glen W.; Barrick, John D. W.; Wade, Larry O.; Burney, Lewis G.; Hill, Gerald F.

    1996-10-01

    A major focus of the Global Tropospheric Experiment/Transport and Chemistry Near the Equator-Atlantic (GTE TRACE A) experiment was to determine whether the seasonal tropospheric ozone (O3) buildup over the tropical South Atlantic, observed by both satellites and sondes, is due to photochemical production of O3 from biomass burning effluents or from transport of O3 from the stratosphere. During this expedition, fast response in situ measurements were made of O3, carbon monoxide (CO), and dew point (DP) from aboard the NASA DC-8 aircraft. Numerous vertical profiles were obtained over Brazil, Africa, and the South Atlantic to determine the origin of the observed O3 enhancement. Fine structure in these data was examined by (1) investigating differences in the species concentration (5-s averages) and its 2 km vertical running mean during altitude profiles, (2) calculating Fishman-Seiler coefficients for all vertical profiles with altitude range greater than 3 km, and (3) calculating linear regressions between species across short time intervals (2.5 min) using time series data. The fine structure holds information about the recent history of an air mass and therefore can indicate the "source" of tropospheric O3 enhancement: either transport from the stratosphere (negative correlation with CO and DP) or from photochemistry in the troposphere (positive correlation with CO). All three methods indicate that within the tropical South Atlantic during the TRACE A experiment, net in situ photochemical production is significantly more important than transport from the stratosphere.

  3. Unexpected Fine-Scale Population Structure in a Broadcast-Spawning Antarctic Marine Mollusc

    PubMed Central

    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. PMID:22403655

  4. 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

  5. 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

  6. Theoretical study of the adsorption of CHO radicals on hexagonal boron nitride sheet: Structural and electronic changes

    NASA Astrophysics Data System (ADS)

    Tian, Yu; Pan, Xiao-fan; Liu, Yue-jie; Zhao, Jing-xiang

    2014-03-01

    It is well known that pristine hexagonal boron nitride sheet (h-BN sheet) exhibits large insulating band gap, thus hindering its application to some extent. In this regard, surface chemisorption of certain groups on h-BN sheet is shown to be the most popular method to tune its band gap and thus modify its electronic properties. In the present work, we performed density functional theory (DFT) calculations to study the adsorption of CHO radicals with different coverages on h-BN sheet. Particular attention is paid to explore the effects of CHO adsorption on the geometrical structures and electronic properties of h-BN sheet. The results indicate that the adsorption of a single CHO radical on pristine h-BN sheet is very weak with a negligible adsorption energy (-0.09 eV). In contrast, upon adsorption of more CHO radicals on h-BN sheet, these adsorbates prefer to adsorb in pairs on the B and the nearest N atoms from both sides of h-BN sheet. An energy diagram of the average adsorption energy of CHO radicals on h-BN sheet as a function of its coverage indicates that up to 20 CHO radicals (40%) can be attached to h-BN sheet with the adsorption energy of -0.29 eV. More importantly, the adsorption of CHO radicals can induce certain impurity states within the band gap of h-BN sheet, thus reducing the band gap and enhancing its electrical conductivity.

  7. The Fine-Structure Lines of Hydrogen in H II Regions

    NASA Astrophysics Data System (ADS)

    Dennison, Brian; Turner, B. E.; Minter, Anthony H.

    2005-11-01

    The 2s1/2 state of hydrogen is metastable and overpopulated in H II regions. In addition, the 2p states may be pumped by ambient Lyα radiation. Fine-structure transitions between these states may be observable in H II regions at 1.1 GHz (2s1/2-2p1/2) and/or 9.9 GHz (2s1/2-2p3/2), although the details of absorption versus emission are determined by the relative populations of the 2s and 2p states. The n=2 level populations are solved with a parameterization that allows for Lyα pumping of the 2p states. The Lyα pumping rate has long been considered uncertain, as it involves solution of the difficult Lyα transfer problem. The density of Lyα photons is set by their creation rate, easily determined from the recombination rate, and their removal rate. Here we suggest that the dominant removal mechanism of Lyα radiation in H II regions is absorption by dust. This circumvents the need to solve the Lyα transfer problem and provides an upper limit to the rate at which the 2p states are populated by Lyα photons. In virtually all cases of interest, the 2p states are predominantly populated by recombination, rather than Lyα pumping. We then solve the radiative transfer problem for the fine-structure lines in the presence of free-free radiation. In the likely absence of Lyα pumping, the 2s1/2-->2p1/2 lines will appear in stimulated emission, and the 2s1/2-->2p3/2 lines in absorption. Because the final 2p states are short lived, these lines are dominated by intrinsic line width (99.8 MHz). In addition, each fine-structure line is a multiplet of three blended hyperfine transitions. Searching for the 9.9 GHz lines in high emission measure H II regions offers the best prospects for detection. The lines are predicted to be weak; in the best cases, line-to-continuum ratios of several tenths of a percent might be expected with line strengths of tens to a hundred mK with the Green Bank Telescope. Predicted line strengths, at both 1.1 and 9.9 GHz, are given for a number of H II

  8. Negative thermal expansion in CuCl: An extended x-ray absorption fine structure study

    SciTech Connect

    Vaccari, M.; Grisenti, R.; Fornasini, P.; Rocca, F.; Sanson, A.

    2007-05-01

    Extended x-ray absorption fine structure (EXAFS) has been measured from liquid helium to ambient temperature at the Cu K edge of copper chloride (CuCl) to investigate the local origin of negative thermal expansion. A quantitative analysis of the first coordination shell, performed by the cumulant method, reveals that the nearest-neighbor Cu-Cl interatomic distance undergoes a strong positive expansion, contrasting with the much weaker negative expansion of the crystallographic distance between average atomic positions below 100 K. The anisotropy of relative thermal vibrations, monitored by the ratio {gamma} between perpendicular and parallel mean square relative displacements, is considerably high, while the diffraction thermal factors are isotropic. The relative perpendicular vibrations measured by EXAFS are related to the tension mechanism and to the transverse acoustic modes, which are considered responsible for negative thermal expansion in zinc-blende structures.

  9. Fine structures of organic photovoltaic thin films probed by frequency-shift electrostatic force microscopy

    NASA Astrophysics Data System (ADS)

    Araki, Kento; Ie, Yutaka; Aso, Yoshio; Matsumoto, Takuya

    2016-07-01

    The localized charge and electrostatic properties of organic photovoltaic thin films are predominating factors for controlling energy conversion efficiency. The surface potential and electrostatic structures of organic photovoltaic thin films were investigated by frequency shift mode Kelvin force microscopy (KFM) and electrostatic force microscopy (EFM). The KFM images of a poly[2-methoxy-5-(3‧,7‧-dimethyloctyloxy)-1,4-phenylene vinylene]/phenyl-C61-butyric-acid-methyl ester (PCBM) blend thin film reveals that the PCBM domains precipitate as the topmost layer on the thin films. We find fine structures that were not observed in the topography and KFM images. The bias dependence of the EFM images suggests that the EFM contrast reflects the field-induced polarization, indicating the presence of charge trapping sites.

  10. Xe nanocrystals in Si studied by x-ray absorption fine structure spectroscopy

    SciTech Connect

    Faraci, Giuseppe; Pennisi, Agata R.; Zontone, Federico

    2007-07-15

    The structural configuration of Xe clusters, obtained by ion implantation in a Si matrix, has been investigated as a function of the temperature by x-ray absorption fine structure spectroscopy. In contrast with previous results, we demonstrate that an accurate analysis of the data, using high order cumulants, gives evidence of Xe fcc nanocrystals at low temperature, even in the as-implanted Si; expansion of the Xe lattice is always found as a function of the temperature, with no appreciable overpressure. We point out that a dramatic modification of these conclusions can be induced by an incorrect analysis using standard symmetrical pair distribution function G(r); for this reason, all the results were checked by x-ray diffraction measurements.

  11. 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

  12. Using networks to identify fine structural differences between functionally distinct protein states.

    PubMed

    Swint-Kruse, Liskin

    2004-08-31

    The vast increase in available data from the "-omics" revolution has enabled the fields of structural proteomics and structure prediction to make great progress in assigning realistic three-dimensional structures to each protein molecule. The challenge now lies in determining the fine structural details that endow unique functions to sequences that assume a common fold. Similar problems are encountered in understanding how distinct conformations contribute to different phases of a single protein's dynamic function. However, efforts are hampered by the complexity of these large, three-dimensional molecules. To overcome this limitation, structural data have been recast as two-dimensional networks. This analysis greatly reduces visual complexity but retains information about individual residues. Such diagrams are very useful for comparing multiple structures, including (1) homologous proteins, (2) time points throughout a dynamics simulation, and (3) functionally different conformations of a given protein. Enhanced structural examination results in new functional hypotheses to test experimentally. Here, network representations were key to discerning a difference between unliganded and inducer-bound lactose repressor protein (LacI), which were previously presumed to be identical structures. Further, the interface of unliganded LacI was surprisingly similar to that of the K84L variant and various structures generated by molecular dynamics simulations. Apo-LacI appears to be poised to adopt the conformation of either the DNA- or inducer-bound structures, and the K84L mutation appears to freeze the structure partway through the conformational transition. Additional examination of the effector binding pocket results in specific hypotheses about how inducer, anti-inducer, and neutral sugars exert their effects on repressor function. PMID:15323549

  13. 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.

  14. Adsorptive capacity and evolution of the pore structure of alumina on reaction with gaseous hydrogen fluoride.

    PubMed

    McIntosh, Grant J; Agbenyegah, Gordon E K; Hyland, Margaret M; Metson, James B

    2015-05-19

    Brunauer-Emmet-Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding, that porosity changes are attributed not to monolayer uptake but more reasonably to pore length attenuation. The model assumes nothing specific regarding the Al2O3-HF system and is therefore likely general to adsorbate/adsorbent phenomena.

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

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

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

  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. Adsorption and structural fractionation of dissolved organic matter (DOM) by soil mineral surfaces

    NASA Astrophysics Data System (ADS)

    Avneri, Shani; Polubesova, Tamara; Chefetz, Benny

    2015-04-01

    Dissolved organic matter (DOM) represents a small but highly reactive fraction of the soil organic matter (SOM). One of the important processes affecting the fate of DOM in soils is its interactions with mineral phases. Adsorptive fractionation of DOM by soils and minerals has been observed previously, however detailed changes in composition of DOM due to its interactions with mineral soils were not yet elucidated. In this research the adsorption and physico-chemical fractionation of DOM by soil poor with organic matter and rich with iron oxides and clay fraction was investigated. The changes in DOM structural composition were studied using separation with polymeric resins. The following fractions were obtained: hydrophobic acid (HoA), hydrophobic neutral (HoN), hydrophilic acid (HiA), hydrophilic base (HiB), and hydrophilic neutral (HiN). Two types of DOM were studied: DOM extracted from composted biosolids (compost DOM) and DOM from Suwanee River (SRNOM). Sorption affinity of DOM to soil mineral surfaces was source and chemistry dependent. SRNOM, which was characterized by higher content of aromatic and carboxylic groups demonstrated higher affinity to the studied soil than compost DOM. For both DOM samples preferential adsorption of HoA by soil (50-85% from adsorbed carbon) was observed. Desorption of both DOM types demonstrated significant hysteresis (up to 90-100% of dissolved organic carbon was retained by the soil after 3 cycles of desorption stages). This suggests that DOM desorption behavior was affected by HoA dominant adsorption to the soil mineral fraction, and not by DOM source. Results of this study indicate that interactions of different types of DOM with mineral soil may result in similar changes in composition and properties of DOM both in the supernatant as well as in the adsorbed phase. The change in DOM composition due to its interaction with soil minerals may influence the interactions of pollutants with DOM and soil particle surfaces.

  18. Microsatellite analyses reveal fine-scale genetic structure in grey mouse lemurs (Microcebus murinus).

    PubMed

    Fredsted, T; Pertoldi, C; Schierup, M H; Kappeler, P M

    2005-07-01

    Information on genetic structure can be used to complement direct inferences on social systems and behaviour. We studied the genetic structure of the solitary grey mouse lemur (Microcebus murinus), a small, nocturnal primate endemic to western Madagascar, with the aim of getting further insight on its breeding structure. Tissue samples from 167 grey mouse lemurs in an area covering 12.3 km2 in Kirindy Forest were obtained from trapping. The capture data indicated a noncontinuous distribution of individuals in the study area. Using 10 microsatellite markers, significant genetic differentiation in the study area was demonstrated and dispersal was found to be significantly male biased. Furthermore, we observed an overall excess of homozygotes in the total population (F(IT) = 0.131), which we interpret as caused by fine-scale structure with breeding occurring in small units. Evidence for a clumped distribution of identical homozygotes was found, supporting the notion that dispersal distance for breeding was shorter than that for foraging, i.e. the breeding neighbourhood size is smaller than the foraging neighbourhood size. In conclusion, we found a more complex population structure than what has been previously reported in studies performed on smaller spatial scales. The noncontinuous distribution of individuals and the effects of social variables on the genetic structure have implications for the interpretation of social organization and the planning of conservation activities that may apply to other solitary and endangered mammals as well.

  19. Fine structures and switching of electrical conductivity in labyrinth silver films on sapphire

    NASA Astrophysics Data System (ADS)

    Vartanyan, T. A.; Gladskikh, I. A.; Leonov, N. B.; Przhibel'skii, S. G.

    2014-04-01

    Changes in electrical resistance of silver films were measured in the range from 1013 to 103 Ω during thermal deposition on sapphire in a high vacuum, after the deposition over time, and under an applied voltage. The dependences of the electrical resistance of the films on their thickness and deposition rate were determined. It was established that, with an increase in the film thickness from 2 to 10 nm during the deposition at rates of 0.6 and 0.1 Å/s, the resistance decreases by 7.5 and 4 orders of magnitude, respectively. The measured dependences of the resistance on the deposition time were found to be close to exponential. The room-temperature resistance of 10-nm-thick films deposited at different rates changed spontaneously by 3-4 orders of magnitude in different ways: the resistance of the slowly deposited films spontaneously increased, whereas in the rapidly deposited films, it spontaneously decreased. After fine annealing, the steady-state resistance changed also differently: it increased by 2 orders of magnitude in the former case and by 9 orders of magnitude in the latter case. Under voltages above 5 V, the resistance of the rapidly deposited films abruptly decreased from ˜1012 to ˜106 Ω, and these films became ohmic. After fine annealing, they became again high-ohmic. Under voltages above 5 V, the high-ohmic films thus obtained became again low-ohmic. This cycle of electrical conductivity switching was reproduced many times. The observed phenomena were explained in the framework of the hypothesis of the formation of fine metastable structures in channels of labyrinth films, namely, protrusions and bridges that bring together the boundaries of islands and connect them into conducting clusters, respectively.

  20. 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.

  1. Mechanical properties and structural evolution during deformation of fine grain magnesium and aluminum alloys

    NASA Astrophysics Data System (ADS)

    Yang, Qi

    Grain refinement improves the formability and the strength of wrought Mg and Al alloys. Ultrafine grain Mg is produced by a new process for severe plastic deformation, called Alternate Biaxial Reverse Corrugation (ABRC). Fine grain structure in Al is produced by creating a new composition capable of precipitating dispersed intermetallics in the alloy. Slip and twinning subdivide an initial bimodal grain structure of Mg alloy during processing. Dynamic recovery and recrystallization lead to the formation of nearly uniform ultrafine microstructure of average grain size 1.4mum, containing many submicron grains. In Mg, twinning causes grain refinement in the early stages, but it is inhibited when grain size becomes finer. A strong basal texture is created after several corrugation and flattening steps, but eventually weakened as grain size becomes finer. Grain rotation and possible dynamic recrystallization are believed to cause a drop in the intensity of basal texture. At room temperature, grain refinement causes a considerable increase in strain rate sensitivity of flow stress (m) leading to the enhancement of post-uniform elongation. Yield strength increases, and becomes more isotropic due to the inhibition of twinning in fine grain Mg alloy, compared to coarse grain alloy. Normal anisotropy ratio (R value) for fine grain Mg at room temperature is higher than that for coarse grain alloy. At warm temperatures, formability is significantly increased due to an increase in strain rate sensitivity of flow stress and diffuse quasistable flow in fine grain Mg, as compared with coarse grain alloy. At 200°C and strain rates below 2x10-4s-1, the fine grain alloy demonstrates a high rate of strain hardening up to a true strain of 0.6 in addition to its high strain rate sensitivity (m ˜ 0.4-0.5), leading to a high elongation of 300-400%. There is competition between dynamic grain growth and grain refinement during straining at warm temperature. Mg exhibits isotropic

  2. 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.

  3. Morphology and fine structure of Acipenser persicus (Acipenseridae, Chondrostei) spermatozoon: Inter-species comparison in Acipenseriformes.

    PubMed

    Hatef, Azadeh; Alavi, Sayyed Mohammad Hadi; Noveiri, Shahrouz Baradaran; Poorbagher, Hadi; Alipour, Ali Reza; Pourkazemi, Mohammad; Linhart, Otomar

    2011-01-01

    This study describes morphology and fine structure of the Persian sturgeon (Acipenser persicus) (Acipenseridae, Chondrostei) spermatozoon. The results show that the spermatozoon of A. persicus is differentiated into an elongated head (length: mean±SD: 7.1±0.5μm) with an acrosome (length: 1.2±0.2μm), a cylindrical midpiece (length: 1.8±0.5μm), a flagellum (length: 50.3±5.9μm) and a total length of 59.2±6.2μm. Ten posterolateral projections (PLPs) arise from the posterior edge of the acrosome and there were 3 endonuclear canals that traversed the nucleus from the acrosomal end to the basal nuclear fossa region. Three to six mitochondria were in peripheral midpiece and the proximal and distal centrioles were located near to "implantation fossa" and basement of the flagellum. The axoneme has a typical eukaryotic structure composed of 9 peripheral microtubules and a central pair of single microtubule surrounded by the plasma membrane. Lateral fins were observed along the flagellum. The fins started and ended at 0.5-1μm from midpiece and at 4-6μm from the end of flagellum. There were significant differences in the size of almost all measured morphological parameters between males and flagellar, midpiece and nucleus characters were more isolated parameters that can be considered for detecting inter-individual variations. This study showed that sperm morphology and fine structure are similar among sturgeon species, but the dimensions of the parameters may differ. PMID:21144681

  4. Outlier SNP markers reveal fine-scale genetic structuring across European hake populations (Merluccius merluccius).

    PubMed

    Milano, Ilaria; Babbucci, Massimiliano; Cariani, Alessia; Atanassova, Miroslava; Bekkevold, Dorte; Carvalho, Gary R; Espiñeira, Montserrat; Fiorentino, Fabio; Garofalo, Germana; Geffen, Audrey J; Hansen, Jakob H; Helyar, Sarah J; Nielsen, Einar E; Ogden, Rob; Patarnello, Tomaso; Stagioni, Marco; Tinti, Fausto; Bargelloni, Luca

    2014-01-01

    Shallow population structure is generally reported for most marine fish and explained as a consequence of high dispersal, connectivity and large population size. Targeted gene analyses and more recently genome-wide studies have challenged such view, suggesting that adaptive divergence might occur even when neutral markers provide genetic homogeneity across populations. Here, 381 SNPs located in transcribed regions were used to assess large- and fine-scale population structure in the European hake (Merluccius merluccius), a widely distributed demersal species of high priority for the European fishery. Analysis of 850 individuals from 19 locations across the entire distribution range showed evidence for several outlier loci, with significantly higher resolving power. While 299 putatively neutral SNPs confirmed the genetic break between basins (F(CT) = 0.016) and weak differentiation within basins, outlier loci revealed a dramatic divergence between Atlantic and Mediterranean populations (F(CT) range 0.275-0.705) and fine-scale significant population structure. Outlier loci separated North Sea and Northern Portugal populations from all other Atlantic samples and revealed a strong differentiation among Western, Central and Eastern Mediterranean geographical samples. Significant correlation of allele frequencies at outlier loci with seawater surface temperature and salinity supported the hypothesis that populations might be adapted to local conditions. Such evidence highlights the importance of integrating information from neutral and adaptive evolutionary patterns towards a better assessment of genetic diversity. Accordingly, the generated outlier SNP data could be used for tackling illegal practices in hake fishing and commercialization as well as to develop explicit spatial models for defining management units and stock boundaries.

  5. Fine Structure ENA Sources Beyond the Termination Shock: Observational Constraints and Detection Limits

    NASA Astrophysics Data System (ADS)

    Demajistre, R.; Janzen, P. H.; Allegrini, F.; Dayeh, M. A.; McComas, D. J.; Schwadron, N.

    2015-12-01

    High spatial resolution maps from the IBEX mission (McComas et al, Science, 2009) suggest the presence of "fine structure" in the signal from beyond the termination shock. That is, areas of enhanced ENA emission that span less than a degree in the IBEX sky map. If confirmed, this would suggest very concentrated areas of emission from sources with scales of a few AU embedded in the outer heliosphere (or proportionally larger if they are located beyond the heliopause). This, in turn, would require the presence of unanticipated structures (plasma or neutral) beyond the termination shock for which the physics is poorly defined. It is therefore crucial to confirm the presence of these structures through careful analysis, or to establish the detection limits if the data taken to date is not sufficient for such a confirmation. In this work, we use 5 years worth of IBEX data to examine the statistical significance of these enhancements. We examine correlations in time, ENA energy and coincidence type for evidence of these small-scale spatial structures. Then, using the known spatial response of the IBEX instrument, establish the conditions under which such structure, if present, would be detectable. This detection threshold analysis is fully applicable future measurements, such as those planned for IMAP.

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

    PubMed

    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

  7. 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

  8. 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.

  9. Fine-scale community and genetic structure are tightly linked in species-rich grasslands

    PubMed Central

    Whitlock, Raj; Bilton, Mark C.; Grime, J. Phil; Burke, Terry

    2011-01-01

    Recent evidence indicates that grassland community structure and species diversity are influenced by genetic variation within species. We review what is known regarding the impact of intraspecific diversity on grassland community structure, using an ancient limestone pasture as a focal example. Two genotype-dependent effects appear to modify community structure in this system. First, the abundance of individual constituent species can depend upon the combined influence of direct genetic effects stemming from individuals within the population. Second, the outcome of localized interspecific interactions occurring within the community can depend on the genotypes of participating individuals (indicating indirect genetic effects). Only genotypic interactions are thought to be capable of allowing the long-term coexistence of both genotypes and species. We discuss the implications of these effects for the maintenance of diversity in grasslands. Next, we present new observations indicating that losses of genotypic diversity from each of two species can be predicted by the abundance of other coexisting species within experimental grassland communities. These results suggest genotype-specific responses to abundance in other coexisting species. We conclude that both direct and indirect genetic effects are likely to shape community structure and species coexistence in grasslands, implying tight linkage between fine-scale genetic and community structure. PMID:21444309

  10. 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.

  11. 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

  12. 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

  13. Relative contributions of temporal envelope and fine structure cues to lexical tone recognition in hearing-impaired listeners.

    PubMed

    Wang, Shuo; Xu, Li; Mannell, Robert

    2011-12-01

    It has been reported that normal-hearing Chinese speakers base their lexical tone recognition on fine structure regardless of temporal envelope cues. However, a few psychoacoustic and perceptual studies have demonstrated that listeners with sensorineural hearing impairment may have an impaired ability to use fine structure information, whereas their ability to use temporal envelope information is close to normal. The purpose of this study is to investigate the relative contributions of temporal envelope and fine structure cues to lexical tone recognition in normal-hearing and hearing-impaired native Mandarin Chinese speakers. Twenty-two normal-hearing subjects and 31 subjects with various degrees of sensorineural hearing loss participated in the study. Sixteen sets of Mandarin monosyllables with four tone patterns for each were processed through a "chimeric synthesizer" in which temporal envelope from a monosyllabic word of one tone was paired with fine structure from the same monosyllable of other tones. The chimeric tokens were generated in the three channel conditions (4, 8, and 16 channels). Results showed that differences in tone responses among the three channel conditions were minor. On average, 90.9%, 70.9%, 57.5%, and 38.2% of tone responses were consistent with fine structure for normal-hearing, moderate, moderate to severe, and severely hearing-impaired groups respectively, whereas 6.8%, 21.1%, 31.4%, and 44.7% of tone responses were consistent with temporal envelope cues for the above-mentioned groups. Tone responses that were consistent neither with temporal envelope nor fine structure had averages of 2.3%, 8.0%, 11.1%, and 17.1% for the above-mentioned groups of subjects. Pure-tone average thresholds were negatively correlated with tone responses that were consistent with fine structure, but were positively correlated with tone responses that were based on the temporal envelope cues. Consistent with the idea that the spectral resolvability is

  14. Adsorption of Te on Ge(001): Nearly Perfect Dereconstruction and Structural Phase Transition

    NASA Astrophysics Data System (ADS)

    Lyman, P. F.; Marasco, D. L.; Bedzyk, M. J.

    1998-03-01

    The (001) face of a diamond-structure semiconductor has two dangling bonds per surface atom. Therefore, the adsorption of 1 ML of a hexavalent group VI element could saturate all available surface bonds, resulting in a perfect (1×1) termination. This adsorbate-induced dereconstruction has previously been demonstrated for S/Ge(001) and, somewhat imperfectly, for Te/Si(001). Here we describe a study of the local structure and long-range order of Te/Ge(001) using x-ray standing waves (XSW) and LEED for annealing temperatures of 540 K and 670 K. At 540 K, Te exclusively occupied the expected bridge sites, forming a (1×1) local structure. Thus, the Te atoms caused a nearly perfect dereconstruction of the Ge(001) dimerized clean surface. The streaky (2×1) LEED pattern betrayed a small remaining pairing tendency. Upon annealing to 670 K, the Te exhibited a new and surprising behavior. A clear phase transition occurred, indicated both by a dramatic change in the LEED pattern to a streaky c(2×2), and decrease of the Te adsorption height by 0.07 ÅWe hypothesize that approximately half of the Te desorbed, and some of the Ge surface atoms redimerized; the remaining Te atoms occupy "cave" (or long bridge) sites, between two Ge dimers.

  15. Critical influence of adsorption geometry in the heterogeneous epoxidation of "allylic" alkenes: structure and reactivity of three phenylpropene isomers on Cu(111).

    PubMed

    Williams, Federico J; Cropley, Rachael L; Vaughan, Owain P H; Urquhart, Andrew J; Tikhov, Mintcho S; Kolczewski, Christine; Hermann, Klaus; Lambert, Richard M

    2005-12-01

    It has long been conjectured that the difficulty of heterogeneously epoxidizing higher alkenes such as propene is due to the presence in the molecule of "allylic" H atoms that are readily stripped off by the oxygenated surface of the metal catalyst resulting in combustion. Here, taking advantage of the intrinsically higher epoxidation selectivity of Cu over Ag under vacuum conditions, we have used three phenylpropene structural isomers to examine the correlation between adsorption geometry and oxidation chemistry. It is found that under comparable conditions alpha-methylstyrene, trans-methylstyrene, and allylbenzene behave very differently on the oxygenated Cu(111) surface: the first undergoes extensive epoxidation accompanied by relatively little decomposition of the alkene; the second leads to some epoxide formation and extensive alkene decomposition; and the third is almost inert with respect to both reaction pathways. This reactive behavior is understandable in terms of the corresponding molecular conformations determined by near-edge X-ray absorption fine structure spectroscopy and density functional theory calculations. The proximity to the surface of the C=C function and of the allylic H atoms is critically important in determining reaction selectivity. This demonstrates the importance of adsorption geometry and confirms that allylic H stripping is indeed a key process that limits epoxidation selectivity in such cases.

  16. Novel sandwich structure adsorptive membranes for removal of 4-nitrotoluene from water.

    PubMed

    Guo, Yuexin; Jia, Zhiqian

    2016-11-01

    Novel sandwich PES-SPES/PS-PDVB/PTFE adsorptive membranes were prepared by a filtration/immersion precipitation method and employed for the removal of 4-nitrotoluene from water. The static adsorption thermodynamics, kinetics, dynamic adsorption/desorption and membrane reusability were investigated. The results showed that the Freundlich model describes the adsorption isotherm satisfactorily. With increased PS-PDVB content, the maximum static adsorption capacity, partition coefficient, apparent adsorption rate constant, and dynamic adsorption capacity all significantly increased. The sandwich membranes showed much higher removal efficiency and adsorption capacity than those of mixed matrix membranes. With respect to dynamics adsorption/desorption, the sandwich membranes exhibited excellent reusability, with a removal efficiency greater than 95% even after five recycles. PMID:27322899

  17. Constraints on the Time Variation of the Fine Structure Constant by the 5-Year WMAP Data

    NASA Astrophysics Data System (ADS)

    Nakashima, M.; Nagata, R.; Yokoyama, J.

    2008-12-01

    The constraints on the time variation of the fine structure constant at recombination epoch relative to its present value, Δα/α ≡ (α_{rec} - α_{now})/α_{now}, are obtained from the analysis of the 5-year WMAP cosmic microwave background data. As a result of Markov-Chain Monte-Carlo analysis, it is found that, contrary to the analysis based on the previous WMAP data, the mean value of Δα/α = -0.0009 does not change significantly whether we use the Hubble Space Telescope (HST) measurement of the Hubble parameter as a prior or not. The resultant 95% confidence ranges of Δα/α are -0.028 < Δα/α < 0.026 with HST prior and -0.050 < Δα/α < 0.042 without HST prior.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Fine structure of spermatozoa in the common pandora (Pagellus erythrinus Linnaeus, 1758) (Perciformes, Sparidae).

    PubMed

    Maricchiolo, G; Genovese, L; Laurà, R; Micale, V; Muglia, U

    2004-10-01

    Scanning and transmission electron microscopy were used to investigate the fine structure of the sperm of the Sparid fish Pagellus erythrinus L. The spermatozoon of pandora has a spherical head lacking an acrosome, a cone-shaped midpiece and a long tail. The midpiece houses a single mitochondrion. The centriolar complex lies inside the nuclear fossa and is composed of a proximal and a distal centriole which are arranged at right angles to each other. The flagellum is inserted medio-laterally into the head, contains the conventional 9+2 axoneme and possesses one pair of lateral fins. On the basis of its ultrastructural organization, the pandora sperm can be regarded as an evolved form of the primitive spermatozoon found in Teleosts. According to the morphological classification proposed by Mattei (1970), the sperm of pandora belongs to a "type I" designation, like that of the other Sparid fish.

  5. Fine structure of DX(Sn) centers in AlxGa1-xAs

    NASA Astrophysics Data System (ADS)

    Zhan, H. H.; Kang, J. Y.; Wu, Z. Y.; Huang, Q. S.

    1998-09-01

    High resolution Laplace defect spectroscopy was used to study the fine structure of the electron emission process of DX(Sn) centers in AlxGa1-xAs (x=0.26,0.53). Two groups of peaks in the spectra of electron emission rates were found to correspond to two DX-like centers observed by deep level transient spectroscopy. The line splitting in both groups derives from the alloy disorder effect attributed to the different local configurations of Al and Ga atoms around two DX-like centers. Experimental evidence for the microscopic nature of two DX-like centers in Sn-doped AlGaAs is provided.

  6. 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).

  7. Fine structure of inelastic electron scattering cross-section spectra for MN

    NASA Astrophysics Data System (ADS)

    Parshin, A. S.; Igumenov, A. Yu; Mikhlin, Yu L.; Pchelyakov, O. P.; Zhigalov, V. S.

    2016-04-01

    The comparative analysis of the reflection electron energy loss spectra and the inelastic electron scattering cross-section spectra for Mn was carried out. It is shown that inelastic electron scattering cross-section spectra have certain advantages in the study of the interaction of electrons with the substance as compared to the electron energy loss spectra. The inelastic electron scattering cross section spectra fine structure was analysed by fitting the experimental spectra using the 3 parameters Lorentzian-type formula of Tougaard. This method was used for the quantitative analysis of the contributions of various loss processes in the inelastic electron scattering cross section spectra, determination of the loss peaks energies and origin.

  8. Strain-driven growth of GaAs(111) quantum dots with low fine structure splitting

    SciTech Connect

    Yerino, Christopher D.; Jung, Daehwan; Lee, Minjoo Larry; Simmonds, Paul J.; Liang, Baolai; Huffaker, Diana L.; Schneider, Christian; Unsleber, Sebastian; Vo, Minh; Kamp, Martin; Höfling, Sven

    2014-12-22

    Symmetric quantum dots (QDs) on (111)-oriented surfaces are promising candidates for generating polarization-entangled photons due to their low excitonic fine structure splitting (FSS). However, (111) QDs are difficult to grow. The conventional use of compressive strain to drive QD self-assembly fails to form 3D nanostructures on (111) surfaces. Instead, we demonstrate that (111) QDs self-assemble under tensile strain by growing GaAs QDs on an InP(111)A substrate. Tensile GaAs self-assembly produces a low density of QDs with a symmetric triangular morphology. Coherent, tensile QDs are observed without dislocations, and the QDs luminescence at room temperature. Single QD measurements reveal low FSS with a median value of 7.6 μeV, due to the high symmetry of the (111) QDs. Tensile self-assembly thus offers a simple route to symmetric (111) QDs for entangled photon emitters.

  9. 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.

  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 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).

  12. 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). PMID:11136034

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

    NASA Astrophysics Data System (ADS)

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

    2001-11-01

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

  14. Mechanical Behavior of Agave Americana L. Fibres: Correlation Between Fine Structure and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Msahli, S.; Chaabouni, Y.; Sakli, F.; Drean, J. Y.

    In this study, results of a mechanical behavior study of fibres extracted from the agave Americana L. plant, the most abundant variety in Tunisia, are presented. These results deal with the principal and mechanical characteristics of these fibres which are the elongation at break, the elasticity modulus and the rupture facture. These results permitted to situate these fibres, compared to the other textile fibres, as materials that can be used in technical applications such as reinforcing composites or geotextile. In order to understand the mechanical properties of these fibres, a correlation study between the properties already cited and the fine structure was done. The obtained results showed that the mechanical properties of agave Americana L. fibres are closely related to the individual fibers deformations and to the natural matrix (lignin and gums) that links these elementary fibres.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    We propose a new method to probe a possible time evolution of the fine structure constant α from X-ray and Sunyaev-Zel'dovich measurements of the gas mass fraction (fgas) in galaxy clusters. Taking into account a direct relation between variations of α and violations of the distance-duality relation, we discuss constraints on α for a class of dilaton runaway models. Although not yet competitive with bounds from high-z quasar absorption systems, our constraints, considering a sample of 29 measurements of fgas, in the redshift interval 0.14 < z < 0.89, provide an independent estimate of α variation at low and intermediate redshifts. Furthermore, current and planned surveys will provide a larger amount of data and thus allow to improve the limits on α variation obtained in the present analysis.

  16. Synchrotron x-ray fluorescence and extended x-ray absorption fine structure analysis

    SciTech Connect

    Chen, J.R.; Gordon, B.M.; Hanson, A.L.; Jones, K.W.; Kraner, H.W.; Chao, E.C.T.; Minkin, J.A.

    1984-01-01

    The advent of dedicated synchrotron radiation sources has led to a significant increase in activity in many areas of science dealing with the interaction of x-rays with matter. Synchrotron radiation provides intense, linearly polarized, naturally collimated, continuously tunable photon beams, which are used to determine not only the elemental composition of a complex, polyatomic, dilute material but also the chemical form of the elements with improved accuracy. Examples of the application of synchrotron radiation include experiments in synchrotron x-ray fluorescence (SXRF) analysis and extended x-ray absorption fine structure (EXAFS) analysis. New synchrotron radiation x-ray microprobes for elemental analysis in the parts per billion range are under construction at several laboratories. 76 references, 24 figures.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  18. Variation of the fine-structure constant from the de Sitter invariant special relativity

    NASA Astrophysics Data System (ADS)

    Chen, Shao-Xia; Xiao, Neng-Chao; Yan, Mu-Lin

    2008-08-01

    We discuss the variation of the fine-structure constant, α. There are obvious discrepancies among the results of α-variation from recent Quasi-stellar observation experiments and from the Oklo uranium mine analysis. We use dS Sitter invariant Special Relativity (Script SScript Rc,R) and Dirac large number hypothesis to discuss this puzzle, and present a possible solution to the disagreement. By means of the observational data and the discussions presented in this paper, we estimate the radius of the Universe in Script SScript Rc,R which is about ~2√5×1011l.y. Supported by National Natural Science Foundation of China (90403021) and PhD Program Funds of Education Ministry of China (20020358040)

  19. 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.

  20. 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.

  1. A simulation for gravity fine structure recovery from low-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 low-low SST mission for accurate local recovery of gravitational fine structure, considering the aliasing effects of unsolved for parameters. A 5 degree by 5 degree surface density block representation of the high order geopotential was utilized with the drag-free low-low GRAVSAT configuration in a circular polar orbit at 250 km altitude. Recovery of local sets of density blocks from long data arcs was found not to be feasible due to strong aliasing effects. The error analysis for the recovery of local sets of density blocks using independent short data arcs demonstrated that the estimation strategy of simultaneously estimating a local set of blocks covered by data and two "buffer layers" of blocks not covered by data greatly reduced aliasing errors.

  2. 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.

  3. Neutron induced damage in reactor pressure vessel steel: An X-ray absorption fine structure study

    NASA Astrophysics Data System (ADS)

    Kuri, G.; Cammelli, S.; Degueldre, C.; Bertsch, J.; Gavillet, D.

    2009-03-01

    The radiation damage produced in reactor pressure vessel (RPV) steels during neutron irradiation is a long-standing problem of considerable practical interest. In this study, an extended X-ray absorption fine structure (EXAFS) spectroscopy has been applied at Cu, Ni and Mn K-edges to systematically investigate neutron induced radiation damage to the metal-site bcc structure of RPV steels, irradiated with neutrons in the fluence range from 0.85 to 5.0 × 1019 cm-2. An overall similarity of Cu, Ni and Mn atomic environment in the iron matrix is observed. The radial distribution functions (RDFs), derived from EXAFS data have been found to evolve continuously as a function of neutron fluence describing the atomic-scale structural modifications in RPVs by neutron irradiations. From the pristine data, long range order beyond the first- and second-shell is apparent in the RDF spectra. In the irradiated specimens, all near-neighbour peaks are greatly reduced in magnitude, typical of damaged material. Prolonged annealing leads annihilation of point defects to give rise to an increase in the coordination numbers of near-neighbour atomic shells approaching values close to that of non-irradiated material, but does not suppress the formation of nano-sized Cu and/or Ni-rich-precipitates. Total amount of radiation damage under a given irradiation condition has been determined. The average structural parameters estimated from the EXAFS data are presented and discussed.

  4. Optimal fine-scale structures in compliance minimization for a uniaxial load

    PubMed Central

    Kohn, Robert V.; Wirth, Benedikt

    2014-01-01

    We consider the optimization of the topology and geometry of an elastic structure O⊂R2 subjected to a fixed boundary load, i.e. we aim to minimize a weighted sum of material volume Vol(O), structure perimeter Per(O) and structure compliance Comp(O) (which is the work done by the load). As a first simple and instructive case, this paper treats the situation of an imposed uniform uniaxial tension load in two dimensions. If the weight ε of the perimeter is small, optimal geometries exhibit very fine-scale structure which cannot be resolved by numerical optimization. Instead, we prove how the minimum energy scales in ε, which involves the construction of a family of near-optimal geometries and thus provides qualitative insights. The construction is based on a classical branching procedure with some features unique to compliance minimization. The proof of the energy scaling also requires an ansatz-independent lower bound, which we derive once via a classical convex duality argument (which is restricted to two dimensions and the uniaxial load) and once via a Fourier-based refinement of the Hashin–Shtrikman bounds for the effective elastic moduli of composite materials. We also highlight the close relation to and the differences from shape optimization with a scalar PDE-constraint and a link to the pattern formation observed in intermediate states of type-I superconductors. PMID:25294972

  5. Uniform Catalytic Site in Sn-beta Zeolite Determined using X-ray Absorption Fine Structure

    SciTech Connect

    Bare,S.; Kelly, S.; Sinkler, W.; Low, J.; Modica, F.; Valencia, S.; Corma, A.; Nemeth, L.

    2005-01-01

    The Sn silicate zeolite, Sn-{beta}, has been shown to be an efficient, selective heterogeneous catalyst for Baeyer-Villiger oxidations. Using primarily a multishell fit to extended X-ray absorption fine structure (EXAFS) data, we show that the Sn does not randomly insert into the {beta}-zeolite structure but rather occupies identical, specific, crystallographic sites. These sites are the T5/T6 sites in the six-membered rings. Moreover, the Sn is substituted in pairs on opposite sides of these six-membered rings. We believe that it is the specific, uniform crystallographic location of the Sn in the crystal structure that leads to sites with uniform catalytic activity, and consequently to the high chemical selectivity demonstrated for this catalyst. This manifests itself in the almost enzyme-like selectivity of this catalyst in Baeyer-Villiger oxidations. This uniform site distribution of the Sn suggests that there is likely a symbiotic relationship between the structure-directing agent in the zeolite synthesis and the Sn heteroatoms during the framework formation.

  6. 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.

  7. 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.

  8. 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.

  9. Neutral hydrogen associated with shells and other fine structure in NGC 2865: A dynamically young elliptical?

    NASA Technical Reports Server (NTRS)

    Schiminovich, D.; Van Gorkom, J. H.; Van Der Hulst, J. M.; Malin, D. F.

    1995-01-01

    We report the discovery of neutral hydrogen in a second elliptical galaxy with shells, NGC 2865. Very Large Array (VLA) images reveal an association between the neutral hydrogen (H I) and the fine structure (shells, tails, and loops) in the galaxy. Similar to what we previously observed in NGC 5128 (Centaurus A), most of the 6 x 10(exp 8)/h(exp 2) solar mass of cold gas is found in a broken ring in the outer regions of NGC 2865 (beyond 0.5D(sub 25)) and is displaced to the outside of the shells and loops. The measured velocities cover a range of 500 km/s around the systematic velocity. The velocity field of the outer H I has the same sense and magnitude (and line of nodes) as that of the stars in the elliptical body. Although NGC 2865 appears to be a relaxed elliptical galaxy, deep images, photometry, and spectroscopy suggest that the galaxy might be the recent (less than 7 Gyr) product of a major disk-disk merger -- a 'dynamically young elliptical.' Our H I data support this hypothesis. Nevertheless, the association between gas and stellar fine structure, with gas displaced outward from the stars in projected position, implies gas motions not predicted by any of the current merger scenarios. Using the H I ring and assuming nearly circular motion, we measure M/L(sub B) at large radii (4 x 0.5D(sub 25)). We find M/L(sub B) = 33 +/- 4 h, a factor of 5 greater than the value of M/L(sub B) found for the central regions, indicating the presence of a dark halo.

  10. 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.

  11. Production of Fine Structures in Type III Solar Radio Bursts Due to Turbulent Density Profiles

    NASA Astrophysics Data System (ADS)

    Loi, Shyeh Tjing; Cairns, Iver H.; Li, Bo

    2014-07-01

    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 fp 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 fp and 2 fp 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 fp than 2 fp emission, possibly explaining the often observed type IIIb-III harmonic pairs as being where intensifications in 2 fp 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 fp radiation, which may account for the type IIIb-IIIb pairs that are sometimes observed.

  12. Al2O3-ZrO2 Finely Structured Multilayer Architectures from Suspension Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Tingaud, Olivier; Montavon, Ghislain; Denoirjean, Alain; Coudert, Jean-François; Rat, Vincent; Fauchais, Pierre

    2010-01-01

    Suspension plasma spraying (SPS) is an alternative to conventional atmospheric plasma spraying (APS) aiming at manufacturing thinner layers (i.e., 10-100 μm) due to the specific size of the feedstock particles, from a few tens of nanometers to a few micrometers. The staking of lamellae and particles, which present a diameter ranging from 0.1 to 2.0 μm and an average thickness from 20 to 300 nm, permits to manufacture finely structured layers. Moreover, it appears as a versatile process able to manufacture different coating architectures according to the operating parameters (suspension properties, injection configuration, plasma properties, spray distance, torch scan velocity, scanning step, etc.). However, the different parameters controlling the properties of the coating, and their interdependences, are not yet fully identified. Thus, the aim of this paper is, on the one hand, to better understand the influence of operating parameters on the coating manufacturing mechanisms (in particular, the plasma gas mixture effect) and, on the other hand, to produce Al2O3-ZrO2 finely structured layers with large varieties of architectures. For this purpose, a simple theoretical model was used to describe the plasma torch operating conditions at the nozzle exit, based on experimental data (mass enthalpy, arc current intensity, thermophysical properties of plasma forming gases, etc.) and the influences of the spray parameters were determined by mean of the study of sizes and shapes of spray beads. The results enabled then to reach a better understanding of involved phenomena and their interactions on the final coating architectures permitting to manufacture several types of microstructures.

  13. Element- and Site-Specific Oxidation State and Cation Distribution in Manganese Ferrite Films by Diffraction Anomalous Fine Structure

    SciTech Connect

    Yang,A.; Chen, Z.; Geiler, A.; Zuo, X.; Haskel, D.; Kravtsov, E.; Vittoria, C.; Harris, V.

    2008-01-01

    Epitaxial manganese ferrite thin films were studied by x-ray diffraction anomalous fine structure to obtain element-specific and site-specific information on site occupancy, local structure, and valency. These properties were introduced to molecular field theory to reproduce thermomagnetization curves and determine superexchange energy, Neel temperature, and spin canting angle.

  14. First-principles study on the adsorption properties of phenylalanine on carbon graphitic structures

    NASA Astrophysics Data System (ADS)

    Kang, Seoung-Hun; Kwon, Dae-Gyeon; Park, Sora; Kwon, Young-Kyun

    2015-12-01

    Using ab-initio density functional theory, we investigate the binding properties of phenylalanine, an amino acid, on graphitic carbon structures, such as graphene, nanotubes, and their modified structures. We focus especially on the effect of the adsorbate on the geometrical and the electronic structures of the absorbents. The phenylalanine molecule is found to bind weakly on pristine graphitic structures with a binding energy of 40-70 meV and not to change the electronic configuration of the graphitic structures, implying that the phenylalanine molecule may not be detected on pristine graphitic structures. On the other hand, the phenylalanine molecule exhibits a substantial increase in its binding energy up to ~2.60 eV on the magnesium-decorated boron-doped graphitic structures. We discover that the Fermi level of the system, which was shifted below the Dirac point of the graphitic structures due to p-doping by boron substitution, can be completely restored to the Dirac point because of the amino acid adsorption. This behavior implies that such modified structures can be utilized to detect phenylalanine molecules.

  15. 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.

  16. Fine-scale structure along the transition from flat to normal subduction in central Mexico

    NASA Astrophysics Data System (ADS)

    Dougherty, S. L.; Clayton, R. W.; Helmberger, D. V.; Andrews, V. M.

    2010-12-01

    The fine-scale seismic structure of the central Mexico subduction zone, particularly the interface between the slab and overriding plate, is studied using shallow (~40-90 km) intraslab earthquakes of moderate magnitude (M4-7). Regional waveforms from the contemporaneous Middle America Subduction Experiment (MASE) and Mapping the Rivera Subduction Zone (MARS) seismic arrays are complicated and contain detailed information about the subduction zone structure. Identification of seismic phases, their arrival times, and any possible complexities in their waveshapes provide evidence of lateral variations in structure. Using the time separation between the direct P-wave and the sPn phase, we estimate the crustal thickness of the overriding plate to be 36 km near the coast, increasing to 44 km beneath the Trans-Mexican Volcanic Belt (TMVB). The detailed waveform information obtained is used to model the structure of the subducted plates, particularly in the Rivera-Cocos plate boundary region, where recent studies have shown evidence for possible slab tearing. Mapping of residual P-wave arrival times relative to the iasp91 model show a strong fast anomaly focused within and east of the Colima graben, south of the TMVB, in the Rivera-Cocos plate boundary region. This fast anomaly may be indicative of the shallow Cocos slab and its termination to the west may represent the Rivera-Cocos plate boundary. The lateral extent of a thin low velocity layer imaged atop the subducted Cocos plate in recent studies along the MASE array is also examined here using the combined MASE and MARS waveforms. Of particular interest is the region where the slab transitions from flat to normal dip angles, near the Orozco Fracture Zone. We use forward modeling of the 2D structure of the subducted Rivera and Cocos plates using a finite-difference algorithm in order to provide constraints on the thickness, velocity, and geometry of each slab’s shallow seismic structure in this region.

  17. The fine structure of the developing pelvic fin dermal skeleton in the trout Salmo gairdneri.

    PubMed

    Géraudie, J; Landis, W J

    1982-02-01

    The morphogenetic and ultrastructural features of the dermal skeleton in the pelvic fin bud of a teleost, the rainbow trout Salmo gairdneri, have been examined by light and electron microscopy. The principal structural components observed are lepidotrichia and actinotrichia. Lepidotrichia consist of two parallel and symmetrical bony demirays that form jointed segments within the fin. The demirays calcify in a proximodistal direction within the extracellular collagen network of the basal lamella belonging to the epidermal-dermal interface of the fin. Needle- and plate-like particles of a solid mineral phase appear to be associated with the collagen fibrils and with a fine, granular, interfibrillar material central to the demirays. Cellular processes and membrane-bound vesicles are absent from the regions of calcification. During fin growth, the bony, acellular lepidotrichia are separated from the epidermal-dermal interface by infiltrating mesenchymal cells in proximal fin regions; in distal areas, the lepidotrichia remain within the basal lamella. The actinotrichia are extensive unmineralized rods of elastoidin that occupy the distal margin of the fin and precede the differentiation of lepidotrichia. Once the lepidotrichia form, actinotrichia lie preferentially between their demirays. In some instances, structural interactions are suggested between actinotrichia and lepidotrichia. Considerations of embryologic and structural features of fin components fail to support the hypothesis that individual segments of lepidotrichia are modified scales in all fish. PMID:7072614

  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. 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.

  20. 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. PMID:23182681

  1. 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.

  2. 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

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  5. 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.

  6. Structural influence of graft and block polycations on the adsorption of BSA.

    PubMed

    Zhang, Li; Jin, Fengmin; Zhang, Tingbin; Zhang, Ling; Xing, Jinfeng

    2016-04-01

    Protein adsorption is considered as an important factor for the low transfection efficiency of polycations in vivo. In this study, two typical polycations of equal molecular weight with different structures were chosen to investigate their adsorption on bovine serum albumin (BSA), including the block copolymer named poly (N-vinylpyrrolidone)-b-poly (2-dimethylaminoethyl methacrylate) (PVP-b-PDMAEMA, i.e. PbP) and graft copolymer named PVP-g-PDMAEMA (PgP), respectively. Fluorescence spectroscopy was used to confirm the binding constants and binding sites between polycations and BSA in static state. The binding constants were 4.1×10(4)M(-1) vs 8.3×10(4)M(-1) and binding sites were 0.3 vs 1.1 for PbP and PgP, respectively, indicating PgP had stronger binding affinity with BSA. Surface plasmon resonance (SPR) was used to study the dynamical non-specific interaction between BSA and polycations as well as the polyplexes. The numbers of both PbP and PgP adsorbed on BSA increased with concentration of polycations increasing, and the number of PgP adsorbed on BSA is higher compared with PbP when their concentration is low. When their concentration is high, the number of PbP adsorbed on BSA is more than that of PgP. However, PgP/DNA polyplexes showed higher adsorption amount compared with PbP/DNA polyplexes at different N/P ratios.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. [Use of mercury porosimetry, assisted by nitrogen adsorption in the investigation of the pore structure of tablets].

    PubMed

    Szepes, Anikó; Kovács, József; Szabóné Revész, Piroska

    2006-01-01

    The microstructure of pharmaceutical solid dosage forms (porosity, pore volume-size distribution, specific surface area) can be investigated by different methods. Mercury porosimetry and nitrogen gas adsorption have been widely used to characterize the pore structure of tablets because these methods enable the determination of porosity and pore size distribution in one step. The two techniques are based on different physical interactions and cover specific ranges of pore size. Mercury porosimetry determines mesopores and macropores, whereas gas adsorption covers the micropore range. The aim of this study was to investigate the relationship between the compression force and the structure of tablets containing theophylline. The porosity parameters determined with mercury porosimetry and nitrogen adsorption were compared. The results indicated a good correlation between the applied compression forces and the porosity parameters of the tablets. The pore volume-size distributions, the pore size frequencies and the specific surface areas obtained with mercury porosimetry and nitrogen adsorption were not equal, which can be attributed to the different measurement ranges and to the complexity of the pore structures. Our results allow the conclusion that mercury porosimetry, assisted by nitrogen adsorption as a complementary technique, is an acceptable method to achieve a proper characterization of the internal structure of tablets. PMID:17094658

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

    SciTech Connect

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

    2008-10-07

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

  13. Fine structures of zeolite-Linde-L (LTL): surface structures, growth unit and defects.

    PubMed

    Ohsuna, Tetsu; Slater, Ben; Gao, Feifei; Yu, Jihong; Sakamoto, Yasahiro; Zhu, Gaugshan; Terasaki, Osamu; Vaughan, David E W; Qiu, Shilun; Catlow, C Richard A

    2004-10-11

    High-resolution electron microscopy (HREM) has been used to image the surface structure of nano- and micrometer-sized synthetic crystals of zeolite-Linde-L (LTL). Columnar holes and rotational, nano-sized, wheel-like defects were observed within the crystals, where the hole has a minimum size equal to that of the rotational defect. Predictions of surface structure from atomistic computer simulation concur with the observations from HREM and provide insight into the crystal growth mechanism of perfect and defective LTL. Analysis of the energetics of the formation of rotational defect structures reveals that the driving force for defect creation is thermodynamic and furthermore, the rotational defects could be created in high concentrations. Formation of a columnar hole is found to be slightly energetically unfavourable and therefore we speculate that the incidence of both rotational and nano-sized vacancy defects is strongly dependent on kinetic factors and reaction conditions. The morphology of nano- and microcrystalline LTL is contradistinct and we use insights from simulation to propose an explanation of the disparity in crystal shape.

  14. 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.

  15. Distorted Tonotopic Coding of Temporal Envelope and Fine Structure with Noise-Induced Hearing Loss

    PubMed Central

    Kale, Sushrut

    2016-01-01

    People with cochlear hearing loss have substantial difficulty understanding speech in real-world listening environments (e.g., restaurants), even with amplification from a modern digital hearing aid. Unfortunately, a disconnect remains between human perceptual studies implicating diminished sensitivity to fast acoustic temporal fine structure (TFS) and animal studies showing minimal changes in neural coding of TFS or slower envelope (ENV) structure. Here, we used general system-identification (Wiener kernel) analyses of chinchilla auditory nerve fiber responses to Gaussian noise to reveal pronounced distortions in tonotopic coding of TFS and ENV following permanent, noise-induced hearing loss. In basal fibers with characteristic frequencies (CFs) >1.5 kHz, hearing loss introduced robust nontonotopic coding (i.e., at the wrong cochlear place) of low-frequency TFS, while ENV responses typically remained at CF. As a consequence, the highest dominant frequency of TFS coding in response to Gaussian noise was 2.4 kHz in noise-overexposed fibers compared with 4.5 kHz in control fibers. Coding of ENV also became nontonotopic in more pronounced cases of cochlear damage. In apical fibers, more classical hearing-loss effects were observed, i.e., broadened tuning without a significant shift in best frequency. Because these distortions and dissociations of TFS/ENV disrupt tonotopicity, a fundamental principle of auditory processing necessary for robust signal coding in background noise, these results have important implications for understanding communication difficulties faced by people with hearing loss. Further, hearing aids may benefit from distinct amplification strategies for apical and basal cochlear regions to address fundamentally different coding deficits. SIGNIFICANCE STATEMENT Speech-perception problems associated with noise overexposure are pervasive in today's society, even with modern digital hearing aids. Unfortunately, the underlying physiological deficits in

  16. 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

  17. Fine structure of the retinal epithelial regions of the red kangaroo (Macropus rufus).

    PubMed

    Young, D L; Braekevelt, C R

    1993-06-01

    The fine structure of the retinal epithelium, Bruch's membrane, and choriocapillaris has been studied by electron microscopy in the red kangaroo (Macropus rufus). The retinal epithelium consists of a single layer of pigmented, squamous cells. The epithelial cells are joined laterally by tight junctions and throughout the retina, display numerous basal infoldings and apical processes that enclose photoreceptor outer segments. The retinal epithelial cells are rich in smooth endoplasmic reticulum and mitochondria. Polysomes are a constant feature and the cells contain few profiles of rough endoplasmic reticulum. Membrane bound phagosomes of outer segment discs are frequently seen. All cells examined contain spherical to oval shaped pigment granules. We find no evidence of a tapetum either in the retinal epithelium or the choroid. Wandering phagocytes are occasionally observed at the photoreceptor-retinal epithelial junction. The presence of these cells has been reported in lower vertebrates but less frequently in mammals. Bruch's membrane displays the typical pentalaminate structure described for most vertebrates. The endothelium of the choriocapillaris is very thin and is highly fenestrated facing Bruch's membrane with a few fenestrations also present on the side bordering the choroid.

  18. 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.

  19. 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.

  20. 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

  1. 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. PMID:27474727

  2. Extended X-ray Absorption Fine Structure (EXAFS) Analysis of Novel High Laser Media

    NASA Astrophysics Data System (ADS)

    Hemantha, Aranwela; Marasinghe, G. K.; Segre, Carlo; Brow, Richard

    2011-03-01

    Rare earth-doped phosphate glasses are useful for a variety of optical and optoelectronic applications including high energy/high power (~ 1015 watt) Lasers. Binary (R2 O3)x (P2 O5)1-x glasses can be prepared in the compositional range 0 <= x <= ~ 0.30 . Atomic-scale structure, especially the coordination environment of R3+ ions, play a major role in determining optical/physical characteristics. We have investigated the R3+ local environment of Praseodymium and Neodymium ultraphosphate and meta phosphate(REMP) glasses using extended X-ray absorption fine structure technique. For both Nd and Pr phosphate glasses, nearest neighbor (oxygen) coordination decreases with increasing RE concentration. For the first oxygen shell the RE-O distance ranges between 2.38-2.40 Å and 2.39-2.46 Å for Nd and Pr respectively. The second co-ordination shell around the RE ions consists of phosphorus ions, with RE-P distance about 3.4-3.5 Å and co-ordination numbers ranging from 1.5 to 3. There exists an Oxygen shell (third shell) about 4.1 Å from RE ion for both Nd and Pr phosphate glasses. Support was provided by the NSF (UND) and DoE (Argonne Natl. Lab).

  3. Fine scale structure of an Anticyclonic eddy off Cape Verde peninsula observed from Glider

    NASA Astrophysics Data System (ADS)

    Kolodziejczyk, Nicolas; Testor, Pierre; Lazar, Alban; Echevin, Vincent; Krahmann, Gerd; Faye, Saliou; Wade, Malik; Estrade, Philippe; Capet, Xavier; Brehmer, Patrice

    2015-04-01

    Measurements from a joint French and German Glider transect along 14.7°N between Dakar/Senegal and the Cape Verde archipelago during March-April 2014 are used to investigate the transversal structure of an anticyclonic eddy. The anticyclone is centered around 14.7°N-21.6°W with a maximum surface azimuthal velocity of about 0.25 m s-1 and is located in a frontal region separating warm off-shore cooler near-shore surface waters. At depth (below 100 m) the anticyclone presents lower temperature and salinity than the surrounding water masses, but an oxygenated core. The surface relative vorticity derived from AVISO altimetry suggests that the anticyclone was formed about around 12°N just off the continental shelf. At depth the anticyclonic core is associated with fine-scale vertical and horizontal structures. These features exhibits vertical density-compensated property gradient at scales between 5-100 m. The spectra of isopycnal salinity and oxygen variance roll off as k-3/5-k-2 in the horizontal wavenumber range 10-100 km (with substantial uncertainties on the exact spectral slope). Overall, the submesoscale features accompanying the eddy are compatible with tracer stirring. Speculations on the impact of such anticyclonic eddies on the ventilation of the North Atlantic Oxygen Minimum Zone are proposed.

  4. 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 timescales as short as 0.15 ms, 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 wave packets. 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.

  5. 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.

  6. Local structure of Titanium in natural glasses probed by X-ray absorption fine structure

    NASA Astrophysics Data System (ADS)

    Wang, L.; Yoshiasa, A.; Okube, M.; Nakatani, T.; Hayasaka, Y.; Isobe, H.

    2013-04-01

    Synchrotron radiation has been used to collect titanium K-edge absorption spectra of a suite of natural glasses (tektites, impact glasses, fault rocks and volcanic glasses). XANES and XAFS analysis provided the qualitative and quantitative information of Ti oxidation state, Ti-O distance and site geometry. Tektites possess four-, five-, six-coordinated Ti, whereas fault rock-pseudotachylite, volcanic glasses and impact glass only presented five- and six-coordinated Ti. This study indicated that different petrogenesis of natural glasses has different local structures of titanium.

  7. 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

    2009-05-01

    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.

  8. An ab-initio study of adsorption of gaseous molecules on doped graphene structures

    NASA Astrophysics Data System (ADS)

    Balangi, H. R.; Shokri, A. A.

    2015-11-01

    In this work, electronic properties of bare and doped graphene layers in the presence of N, B and a type of defective impurities are investigated under adsorption of CO, NO, NH3 and NO2 molecules on it's external surface. We use a fully self-consistent density function theory (DFT) based calculations as implemented in SIESTA package. The local-density approximation (LDA) is considered for the exchange-correlation function. Total density of state (TDOS), partial density of state (PDOS) and charge density calculations are also considered to elucidate the difference in the CO, NO, NH3 and NO2 gases detection mechanism of pristine and doped graphene structures. With regard to that the charge transfer is occurring between the graphene sheet and gaseous molecules, the NO2 and NH3 molecules are considered as the recipient and donor of electrons, respectively. We show that the states contributed by the adsorbed CO and NO molecules are quite localized near the center of original band gap and they suggest that the charge transport in such systems cannot be enhanced considerably, while NO2 and NH3 molecules adsorption acts as the acceptor and donor, respectively. Our results can serve as a base for developments in designing nano-electronic devices.

  9. Substrate-induced structures of bismuth adsorption on graphene: a first principles study.

    PubMed

    Lin, Shih-Yang; Chang, Shen-Lin; Chen, Hsin-Hsien; Su, Shu-Hsuan; Huang, Jung-Chun; Lin, Ming-Fa

    2016-07-28

    The geometric and electronic properties of Bi-adsorbed monolayer graphene, enriched by the strong effect of a substrate, are investigated by first-principles calculations. The six-layered substrate, corrugated buffer layer, and slightly deformed monolayer graphene are all simulated. Adatom arrangements are thoroughly studied by analyzing the ground-state energies, bismuth adsorption energies, and Bi-Bi interaction energies of different adatom heights, inter-adatom distance, adsorption sites, and hexagonal positions. A hexagonal array of Bi atoms is dominated by the interactions between the buffer layer and the monolayer graphene. An increase in temperature can overcome a ∼50 meV energy barrier and induce triangular and rectangular nanoclusters. The most stable and metastable structures agree with the scanning tunneling microscopy measurements. The density of states exhibits a finite value at the Fermi level, a dip at ∼-0.2 eV, and a peak at ∼-0.6 eV, as observed in the experimental measurements of the tunneling conductance. PMID:27354143

  10. Quantitative Prediction of Molecular Adsorption: Structure and Binding of Benzene on Coinage Metals.

    PubMed

    Liu, Wei; Maaß, Friedrich; Willenbockel, Martin; Bronner, Christopher; Schulze, Michael; Soubatch, Serguei; Tautz, F Stefan; Tegeder, Petra; Tkatchenko, Alexandre

    2015-07-17

    Interfaces between organic molecules and solid surfaces play a prominent role in heterogeneous catalysis, molecular sensors and switches, light-emitting diodes, and photovoltaics. The properties and the ensuing function of such hybrid interfaces often depend exponentially on molecular adsorption heights and binding strengths, calling for well-established benchmarks of these two quantities. Here we present systematic measurements that enable us to quantify the interaction of benzene with the Ag(111) coinage metal substrate with unprecedented accuracy (0.02 Å in the vertical adsorption height and 0.05 eV in the binding strength) by means of normal-incidence x-ray standing waves and temperature-programed desorption techniques. Based on these accurate experimental benchmarks for a prototypical molecule-solid interface, we demonstrate that recently developed first-principles calculations that explicitly account for the nonlocality of electronic exchange and correlation effects are able to determine the structure and stability of benzene on the Ag(111) surface within experimental error bars. Remarkably, such precise experiments and calculations demonstrate that despite different electronic properties of copper, silver, and gold, the binding strength of benzene is equal on the (111) surface of these three coinage metals. Our results suggest the existence of universal binding energy trends for aromatic molecules on surfaces. PMID:26230807

  11. Metapopulation structure and fine-scaled genetic structuring in crop-wild hybrid weed beets

    PubMed Central

    Arnaud, J-F; Cuguen, J; Fénart, S

    2011-01-01

    This study explores the microspatial and temporal genetic variation in crop-wild hybrid weed beets that emerged from the seed bank in a cultivated field surveyed over two successive years. We demonstrate the occurrence of demes highly genetically differentiated, kin-structured, characterized by moderate effective population sizes, differing in propensity for selfing, and arising from nonrandom genetic subsets of the seed bank. Only one deme identified in the first survey year significantly contributed to the weed beets that emerged in the second year. Spatial structuring appears to be primarily due to gravity seed dispersal and limited pollen flow among weed beet demes. Within each genetic cluster identified by Bayesian assignments and multivariate analyses, FIS estimates and level of biparental inbreeding—revealed by progeny analyses—dropped to non-significant values. This suggests that random mating occurs at the scale of genetically distinct demes over a very short scale. Our results highlight the need to carefully depict genetic discontinuities in weed species, when attempting to describe their local genetic neighborhoods within which genetic drift and selective processes occur. PMID:21448229

  12. Metapopulation structure and fine-scaled genetic structuring in crop-wild hybrid weed beets.

    PubMed

    Arnaud, J-F; Cuguen, J; Fénart, S

    2011-10-01

    This study explores the microspatial and temporal genetic variation in crop-wild hybrid weed beets that emerged from the seed bank in a cultivated field surveyed over two successive years. We demonstrate the occurrence of demes highly genetically differentiated, kin-structured, characterized by moderate effective population sizes, differing in propensity for selfing, and arising from nonrandom genetic subsets of the seed bank. Only one deme identified in the first survey year significantly contributed to the weed beets that emerged in the second year. Spatial structuring appears to be primarily due to gravity seed dispersal and limited pollen flow among weed beet demes. Within each genetic cluster identified by Bayesian assignments and multivariate analyses, F(IS) estimates and level of biparental inbreeding--revealed by progeny analyses--dropped to non-significant values. This suggests that random mating occurs at the scale of genetically distinct demes over a very short scale. Our results highlight the need to carefully depict genetic discontinuities in weed species, when attempting to describe their local genetic neighborhoods within which genetic drift and selective processes occur.

  13. Metapopulation structure and fine-scaled genetic structuring in crop-wild hybrid weed beets.

    PubMed

    Arnaud, J-F; Cuguen, J; Fénart, S

    2011-10-01

    This study explores the microspatial and temporal genetic variation in crop-wild hybrid weed beets that emerged from the seed bank in a cultivated field surveyed over two successive years. We demonstrate the occurrence of demes highly genetically differentiated, kin-structured, characterized by moderate effective population sizes, differing in propensity for selfing, and arising from nonrandom genetic subsets of the seed bank. Only one deme identified in the first survey year significantly contributed to the weed beets that emerged in the second year. Spatial structuring appears to be primarily due to gravity seed dispersal and limited pollen flow among weed beet demes. Within each genetic cluster identified by Bayesian assignments and multivariate analyses, F(IS) estimates and level of biparental inbreeding--revealed by progeny analyses--dropped to non-significant values. This suggests that random mating occurs at the scale of genetically distinct demes over a very short scale. Our results highlight the need to carefully depict genetic discontinuities in weed species, when attempting to describe their local genetic neighborhoods within which genetic drift and selective processes occur. PMID:21448229

  14. Radiation effects in water ice: A near-edge x-ray absorption fine structure study

    NASA Astrophysics Data System (ADS)

    Laffon, C.; Lacombe, S.; Bournel, F.; Parent, Ph.

    2006-11-01

    The changes in the structure and composition of vapor-deposited ice films irradiated at 20K with soft x-ray photons (3-900eV) and their subsequent evolution with temperatures between 20 and 150K 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 HO2 radicals, as well as the oxygen O2 and hydrogen peroxide H2O2 molecules in irradiated porous amorphous solid water (p-ASW) and crystalline (Icryst) ice films. The evolution of their concentrations with the temperature indicates that HO2, O2, and H2O2 result from a simple step reaction fuelled by OH, where O2 is a product of HO2 and HO2 a product of H2O2. The local order of ice is also modified, whatever the initial structure is. The crystalline ice Icryst becomes amorphous. The high-density amorphous phase (Iah ) of ice is observed after irradiation of the p-ASW film, whose initial structure is the normal low-density form of the amorphous ice (Ial). The phase Iah 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 Iavh—is obtained after warming at 50K the irradiated p-ASW ice. This phase is stable up to 90K and partially transforms into crystalline ice at 150K.

  15. 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. PMID:26352236

  16. 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.

  17. 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.

  18. 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.

  19. Periodicity extraction in the anuran auditory nerve. II: Phase and temporal fine structure.

    PubMed

    Simmons, A M; Reese, G; Ferragamo, M

    1993-06-01

    Discharge patterns of single eighth nerve fibers in the bullfrog, Rana catesbeiana, were analyzed in response to signals consisting of multiple harmonics of a common, low-amplitude fundamental frequency. The signals were chosen to reflect the frequency and amplitude spectrum of the bullfrog's species-specific advertisement call. The phase spectrum of the signals was manipulated to produce envelopes that varied in their shapes from impulselike (sharp) to noiselike (flattened). Peripheral responses to these signals were analyzed by computing the autocorrelation functions of the spike trains and their power spectra, as well as by constructing period histograms over the time intervals of the low-frequency harmonics. In response to a phase aligned signal with an impulsive envelope, most fibers, regardless of their characteristic frequencies or place of origin within the inner ear, synchronize to the fundamental frequency of the signal. The temporal patterns of fiber discharge to these stimuli are not typically captured by that stimulus harmonic closet to the fiber characteristic frequency, as would be expected from a spectral coding mechanism for periodicity extraction, but instead directly reflect the periodicity of the stimulus envelope. Changing the phase relations between the individual harmonics constituting the signal produces changes in temporal discharge patterns of some fibers by shifting predominant synchronization away from the fundamental frequency to the low-frequency spectral peak in the complex stimuli. The proportion of fibers whose firing is captured by the fundamental frequency decreases as the waveform envelope becomes less impulselike. Fiber characteristic frequency is not highly correlated with the harmonic number to which synchronization is strongest. The higher-harmonic spectral fine structure of the signals is not reflected in fiber temporal response, regardless of the shape of the stimulus envelope, even for those harmonics within the range of

  20. Recovery and fine structure variability of RGII sub-domains in wine (Vitis vinifera Merlot)

    PubMed Central

    Buffetto, F.; Ropartz, D.; Zhang, X. J.; Gilbert, H. J.; Guillon, F.; Ralet, M.-C.

    2014-01-01

    Background and Aims Rhamnogalacturonan II (RGII) is a structurally complex pectic sub-domain composed of more than 12 different sugars and 20 different linkages distributed in five side chains along a homogalacturonan backbone. Although RGII has long been described as highly conserved over plant evolution, recent studies have revealed variations in the structure of the polysaccharide. This study examines the fine structure variability of RGII in wine, focusing on the side chains A and B obtained after sequential mild acid hydrolysis. Specifically, this study aims to differentiate intrinsic structural variations in these RGII side chains from structural variations due to acid hydrolysis. Methods RGII from wine (Vitis vinifera Merlot) was sequentially hydrolysed with trifluoroacetic acid (TFA) and the hydrolysis products were separated by anion-exchange chromatography (AEC). AEC fractions or total hydrolysates were analysed by MALDI-TOF mass spectrometry. Key Results The optimal conditions to recover non-degraded side chain B, side chain A and RGII backbone were 0·1 m TFA at 40 °C for 16 h, 0·48 m TFA at 40 °C for 16 h (or 0·1 m TFA at 60 °C for 8 h) and 0·1 m TFA at 60 °C for 16 h, respectively. Side chain B was particularly prone to acid degradation. Side chain A and the RGII GalA backbone were partly degraded by 0·1 m TFA at 80 °C for 1–4 h. AEC allowed separation of side chain B, methyl-esterified side chain A and non-methyl-esterified side chain A. The structure of side chain A and the GalA backbone were highly variable. Conclusions Several modifications to the RGII structure of wine were identified. The observed dearabinosylation and deacetylation were primarily the consequence of acidic treatment, while variation in methyl-esterification, methyl-ether linkages and oxidation reflect natural diversity. The physiological significance of this variability, however, remains to be determined. PMID:24908680

  1. 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

  2. Fine-Scale Analysis Reveals Cryptic Landscape Genetic Structure in Desert Tortoises

    PubMed Central

    Latch, Emily K.; Boarman, William I.; Walde, Andrew; Fleischer, Robert C.

    2011-01-01

    Characterizing the effects of landscape features on genetic variation is essential for understanding how landscapes shape patterns of gene flow and spatial genetic structure of populations. Most landscape genetics studies have focused on patterns of gene flow at a regional scale. However, the genetic structure of populations at a local scale may be influenced by a unique suite of landscape variables that have little bearing on connectivity patterns observed at broader spatial scales. We investigated fine-scale spatial patterns of genetic variation and gene flow in relation to features of the landscape in desert tortoise (Gopherus agassizii), using 859 tortoises genotyped at 16 microsatellite loci with associated data on geographic location, sex, elevation, slope, and soil type, and spatial relationship to putative barriers (power lines, roads). We used spatially explicit and non-explicit Bayesian clustering algorithms to partition the sample into discrete clusters, and characterize the relationships between genetic distance and ecological variables to identify factors with the greatest influence on gene flow at a local scale. Desert tortoises exhibit weak genetic structure at a local scale, and we identified two subpopulations across the study area. Although genetic differentiation between the subpopulations was low, our landscape genetic analysis identified both natural (slope) and anthropogenic (roads) landscape variables that have significantly influenced gene flow within this local population. We show that desert tortoise movements at a local scale are influenced by features of the landscape, and that these features are different than those that influence gene flow at larger scales. Our findings are important for desert tortoise conservation and management, particularly in light of recent translocation efforts in the region. More generally, our results indicate that recent landscape changes can affect gene flow at a local scale and that their effects can be

  3. 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.

  4. Log spiral of revolution highly oriented pyrolytic graphite monochromator for fluorescence x-ray absorption edge fine structure

    SciTech Connect

    Pease, D. M.; Daniel, M.; Budnick, J. I.; Rhodes, T.; Hammes, M.; Potrepka, D. M.; Sills, K.; Nelson, C.; Heald, S. M.; Brewe, D. I.

    2000-09-01

    We have constructed an x-ray monochromator based on a log spiral of revolution covered with highly oriented pyrolytic graphite. Such a monochromator is used for obtaining x-ray absorption edge fine structure by the fluorescence method, and is particularly useful for measuring the fine structure of dilute element A in a concentrated matrix of element B, where B is to the left of A in the Periodic Table. Using the log spiral monochromator, we measure good Cr x-ray fine structure in an alloy of 1% Cr in a V matrix, whereas the corresponding spectrum is severely distorted by the V background if nonmonochromatized fluorescence is used. We also obtain excellent rejection of Mn fluorescence relative to Cr fluorescence in a Cr{sub 80}Mn{sub 20} alloy, and can tune the monochromator such that the entire Mn step height is significantly smaller than the Cr x-ray absorption edge fine structure oscillations for this system. (c) 2000 American Institute of Physics.

  5. 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.

  6. 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

  7. Discrimination of Speech Sounds Based upon Temporal Envelope versus Fine Structure Cues in 5- to 7-Year-Old Children

    ERIC Educational Resources Information Center

    Bertoncini, Josiane; Serniclaes, Willy; Lorenzi, Christian

    2009-01-01

    Purpose: To investigate the capacity of young children and adults with normal hearing to discriminate speech on the basis of either relatively slow (temporal envelope, E) or fast (temporal fine structure, TFS) auditory cues. Method: Vowel-consonant-vowel nonsense disyllables were processed to preserve either the E or the TFS information in 16…

  8. 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.

  9. Fine-scale observations of the structure and evolution of a tornadic cold front

    NASA Astrophysics Data System (ADS)

    Clark, Matt; Rosenberg, Phil; Parker, Doug

    2013-04-01

    On 29 November 2011 a strong cold front crossed the UK. An intense, narrow rain band accompanied the front over northern England, along which several small tornadoes developed. The vertical structure of the front was sampled as it approached the UK, using dropsondes and in-situ aircraft measurements, as part of the DIAbatic influences on Mesoscale structures in ExTratropical storms (DIAMET) field campaign. One-minute-resolution data from the Met Office's network of automatic weather stations (AWSs) were used to investigate the structure of the surface front as it crossed the UK. 'Time-to-space' conversion of the AWS data, using a system motion vector estimated from sequences of radar data, permitted a fine-scale analysis of the surface frontal structure and its variation in the along-front direction. On the 28th, operational Unified Model output and aircraft dropsondes showed two separate fronts in the eastern Atlantic Ocean. By the morning of the 29th, dropsondes south of Ireland presented some features consistent with kata (also known as 'split') fronts, with two distinct, but overlapping dry intrusions, each overrunning saturated air below. Each dry intrusion was associated with a local maximum in the cross-front wind component, with a forward-directed, front-relative flow of ~ 5 - 10 m/s. Radar data showed the presence of multiple, narrow rain bands over Ireland and western extremities of the UK early on the 29th, as the front moved within range of the UK radar network. Over Ireland, the merger of at least two separate rain bands was observed. The merged band intensified and accelerated eastwards, leading to a single, intense, bowing line segment over northern England, along which the tornadoes occurred. In contrast, over southern England, no merger occurred, and the frontal zone was characterised by multiple rain bands for the duration of the observation period. The surface data showed markedly different structure in the temperature, wind and pressure fields

  10. 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.

  11. Understanding gate adsorption behaviour of CO2 on elastic layer-structured metal-organic framework-11.

    PubMed

    Hiraide, Shotaro; Tanaka, Hideki; Miyahara, Minoru T

    2016-03-14

    We demonstrate that CO2 gate adsorption behaviour of elastic layer-structured metal-organic framework-11 (ELM-11: [Cu(BF4)2(4,4'-bipyridine)2]), which is a family of soft porous crystals (SPCs), can be described by a thermodynamic model by free energy analysis with the aid of an adsorption experiment and a molecular simulation. The structures of ELM-11 (closed structure) at 273 K after its evacuation and CO2-encapsulated ELM-11 (open structure) at 195-298 K were determined by the Rietveld analysis using in situ synchrotron X-ray powder diffraction data. We then performed grand canonical Monte Carlo (GCMC) simulations for CO2 adsorption on the open host framework structures of ELM-11 from the Rietveld analysis. The temperature dependence of the Helmholtz free energy change of host ΔF(host) from the closed structure to the open structure was obtained by the free energy analysis using the GCMC data. We show that there is a linear correlation between ΔF(host) and temperature, and thus, the internal energy and entropy changes of host, ΔU(host) and ΔS(host), respectively, can be obtained. The obtained ΔU(host) value is in good agreement with that obtained from the quantum chemical calculations using the closed and open host framework structures, which demonstrates that the thermodynamic model for gate adsorption is highly appropriate. Moreover, our result suggests that the gate adsorption pressure depends on not only the guest-host interaction and the internal energy change of host, but also the entropy change of host, which should be one of the key factors for the tailored synthesis of SPCs. PMID:26498489

  12. Structural Analysis of Freshwater-Cultured Pearls with Different Lusters Using the Extended X-Ray Absorption Fine Structure Technique

    NASA Astrophysics Data System (ADS)

    Monarumit, N.; Noirawee, N.; Phlayrahan, A.; Promdee, K.; Won-in, K.; Satitkune, S.

    2016-05-01

    The quality of freshwater-cultured pearls (Chamberlainia hainesiana) is determined by their luster, which is related to the content of the two CaCO3 mineral phases: aragonite and vaterite. The atomic structures of pearl samples were analyzed by the extended X-ray absorption fine structure (EXAFS) technique using synchrotron radiation to compare the atomic environment and atomic bonding around Ca atoms of high- and low-luster pearls. The Ca K-edge EXAFS spectra of the pearl samples were determined and interpreted in terms of the photoelectron wave number and the distance between Ca atoms and neighboring atoms. From the results, the wave oscillation of high-luster pearls is less than that of low-luster pearls. This indicates the presence of the aragonite phase in high-luster pearls and a combination of aragonite and vaterite phases in low-luster pearls, especially in the fi rst and second shells of Ca atoms. It can be concluded that the different lusters of freshwater-cultured pearls are related to the different CaCO3 phases in their structures.

  13. Propagation of whistler waves driven by fine structured ion beams in the magnetotail

    NASA Technical Reports Server (NTRS)

    Burinskaya, T.; Schriver, D.; Ashour-Abdalla, M.

    1994-01-01

    In a previous paper, which examined the propagation of low-frequency whistler waves generated by ion beams in the Earth's plasma sheet boundary layer (PSBL), it was found that whistler waves driven in the PSBL are focused toward the central plasma sheet due to the global magnetotail inhomogeneities; this finding may help explain the observations of magnetic noise bursts in the tail (Burinskaya et al., 1993). In this paper the same phenomenon is examined, but this time a much more realistic model is used for the ion beam in the PSBL. While the PSBL has been modeled as a solid, homogeneous ion beams with a width of one Earth radius, observations and theoretical considerations have shown that PSBL ion beams actually have a decreasing velocity profile toward the plasma sheet and that the density of the beams within the PSBL can vary locally. We consider again the propagation and generation of electromagnetic waves but in the presence of fine structured ion beams in the PSBL. Our results show that whistler waves, generated quasi-parallel to the background magnetic field, can be trapped locally within small spatial regions where the ion beam density is enhanced compared to the density of the adjacent PSBL region. Wave spectra and nonlinear saturation mechanisms are discussed.

  14. 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.

  15. 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.

  16. Plasma Resonance Surfaces in the Magnetic Field Reconnection and Radio Fine Structures

    NASA Astrophysics Data System (ADS)

    Karlický, Marian

    2003-02-01

    Using a 2-D MHD model, the magnetic field reconnection in the current sheet and corresponding plasma resonance lines (surfaces in 3-D), where the upper-hybrid frequency equals one of harmonics of the electron gyrofrequency, ωUH=(ωpe2+ωBe2)1/2=sωBe (ωUH, ωpe, and ωBe are the upper hybrid, electron plasma, and cyclotron frequencies, respectively, and s is the integer harmonic number) are computed. Then at selected times and positions in the magnetic reconnection the spatial and time spectra of upper hybrid frequencies along the resonance lines are calculated. These spectra are discussed from the point of view of radio fine structures as narrowband dm-spikes, zebras, and lace bursts. It is shown that not only turbulent plasma outflows, suggested in the paper by Bárta and Karlický (2001), but also perturbed zones near the reconnection slow-mode shocks can be locations of the narrowband dm-spikes (and/or continua). Sources of the lace bursts (i.e. bursts with irregular lines) can be located in the reconnection space, too. On the other hand, the zebras (bursts with regular separations of zebra lines) need to be generated out of strongly perturbed reconnection areas.

  17. Fine-structure collision strengths and line ratios for [Ne V] in infrared and optical sources

    NASA Astrophysics Data System (ADS)

    Dance, Michael; Palay, Ethan; Nahar, Sultana N.; Pradhan, Anil K.

    2013-10-01

    New collisions' strengths for the mid-infrared (mid-IR) and optical transitions in Ne V are presented. Breit-Pauli-R-Matrix calculations for electron impact excitation are carried out with fully resolved near-threshold resonances at very low energies. In particular, the fine-structure lines at 14 and 24 μm due to transitions among the ground state levels 1s22s22p3 3P0, 1, 2, and the optical/near-ultraviolet lines at 2973, 3346 and 3426 Å transitions among the 3P0, 1, 2, 1D2, 1S0 levels are described. Maxwellian-averaged collision strengths are tabulated for all forbidden transitions within the ground configuration. While some significant differences are found for both the far infrared and the optical transitions compared to previous results, computed line emissivity ratios are in good agreement, but change rapidly in the low temperature range Te < 10 000 K. An analysis of the 14/24 μm ratio in low-energy-density (LED) plasma conditions reveals considerable variation; the effective rate coefficient may be dominated by the very low energy behaviour rather than the Maxwellian-averaged collision strengths. Computed values suggest a possible solution to the anomalous mid-IR ratios found to be lower than theoretical limits observed from planetary nebulae and Seyfert galaxies. While such LED conditions may be present in infrared sources, they might be inconsistent with photoionization equilibrium models.

  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. Detectability of temporal changes in fine structures near the inner core boundary beneath the eastern hemisphere

    NASA Astrophysics Data System (ADS)

    Yu, W.

    2016-07-01

    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. dt(PKiKP) values are mostly within ±30 ms of one another, without systematic temporal dependence. Some observations of PKiKP coda waves have absolute time shifts of >50 ms relative to their main phases. The combination of temporal changes in PKiKP coda arrivals and negligible changes in PKiKP arrivals favors a smooth ICB with fine-scale structures in the upper inner core. dt(PKiKP) values are interpreted in the context of melting- or growth-induced ICB topography, based on dynamic models. Uncertainties in dt(PKiKP) prevent verification of ICB melting or growth on decadal time scales.

  20. 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.

  1. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  3. 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 } .

  4. Fine structure of the landers fault zone: segmentation and the rupture process.

    PubMed

    Li, Y G; Aki, K; Vidale, J E; Lee, W H; Marone, C J

    1994-07-15

    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.

  5. 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.

  6. The fine structure of the ocelli of Triatoma infestans (Hemiptera: Reduviidae).

    PubMed

    Insausti, T C; Lazzari, C R

    2002-12-01

    The morphology and fine structure of the ocelli of Triatoma infestans have been analyzed by means of light and electron microscopy. The two dorsal ocelli of this species are located behind the compound eyes, looking dorsally and frontally. Externally, the ocelli are marked by the corneal lenses virtually spherical in form and limited internally by a cuticular apodeme. The lens focuses the incoming rays beyond the retina. A single layer of corneagen cells lies below the cuticular lens. The corneagen cells and photoreceptors are arranged in a cup-like fashion beneath the cuticular lens. A distal retinal zone comprises the rhabdoms, which are laterally connected in an hexagonal meshwork. A middle retinal zone comprises the receptor cell segment free of rhabdom, and a proximal zone their axons. In the middle zone, the oviform nuclei and spheroids are located. Screening pigment granules are present within the retinal cell. Spherical mitochondria are homogeneously distributed in the cytoplasm of the cell body. In the axonal zone, mitochondria are found in the peripheral region. Axons from receptor cells extend into the ocellar neuropile at the base of the ocelli, to synapse with second order neurons. The large axons of second order neurons are bundled by glial cells. The ocellar plexus exhibits a high diversity of synaptic unions (i.e. axo-dendritic, axo-axonic, dendro-axonic, and dendro-dendritic).

  7. 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

    2013-08-01

    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.

  8. Fine structural analysis of the neuronal inclusions of frontotemporal lobar degeneration with TDP-43 proteinopathy.

    PubMed

    Thorpe, Julian R; Tang, Helen; Atherton, Joe; Cairns, Nigel J

    2008-12-01

    TAR DNA-binding protein of 43 kDa (TDP-43) is a major component of the pathological inclusions of frontotemporal lobar degeneration with TDP-43 proteinopathy, also called FTLD with ubiquitin-positive, tau-negative inclusions (FTLD-U), and motor neuron disease (MND). TDP-43 is predominantly expressed in the nucleus and regulates gene expression and splicing. In FTLD with TDP-43 proteinopathy, neuronal inclusions present variably as cytoplasmic inclusions (NCIs), dystrophic neurites (DNs), and intranuclear inclusions (NIIs), leading to a fourfold neuropathological classification correlating with genotype. There have been few fine structural studies of these inclusions. Thus, we undertook an immunoelectron microscopic study of FTLD with TDP-43 proteinopathy, including sporadic and familial cases with progranulin (GRN) mutation. TDP-43-immunoreactive inclusions comprised two components: granular and filamentous. Filament widths, expressed as mean (range) were: NCI, 9 nm (4-16 nm); DN, 10 nm (5-16 nm); NII, 18 nm (9-50 nm). Morphologically distinct inclusion components may reflect the process of TDP-43 aggregation and interaction with other proteins: determining these latter may contribute towards understanding the heterogeneous pathogenesis of FTLD with TDP-43 proteinopathy. PMID:18974920

  9. Preferred Compression Speed for Speech and Music and Its Relationship to Sensitivity to Temporal Fine Structure.

    PubMed

    Moore, Brian C J; 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

  10. 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.

  11. Excitonic fine structure and binding energies of excitonic complexes in single InAs quantum dashes

    NASA Astrophysics Data System (ADS)

    Mrowiński, P.; Zieliński, M.; Świderski, M.; Misiewicz, J.; Somers, A.; Reithmaier, J. P.; Höfling, S.; Sek, G.

    2016-09-01

    The fundamental electronic and optical properties of elongated InAs nanostructures embedded in quaternary InGaAlAs barrier are investigated by means of high-resolution optical spectroscopy and many-body atomistic tight-binding theory. These wire-like shaped, self-assembled nanostructures are known as quantum dashes and are typically formed during the molecular beam epitaxial growth on InP substrates. In this paper, we study properties of excitonic complexes confined in quantum dashes emitting in a broad spectral range from below 1.2 to 1.55 μm. We find peculiar trends for the biexciton and negative trion binding energies, with pronounced trion binding in smaller size quantum dashes. These experimental findings are then compared and qualitatively explained by atomistic theory. The theoretical analysis shows a fundamental role of correlation effects for the absolute values of excitonic binding energies. Eventually, we determine the bright exciton fine structure splitting (FSS), where both the experiment and theory predict a broad distribution of the splitting varying from below 50 to almost 180 μeV. We identify several key factors determining the FSS values in such nanostructures, including quantum dash size variation and composition fluctuations.

  12. Fine Structure of the Cone of Heterodera schachtii with Emphasis on Musculature and Fenestration

    PubMed Central

    Cordero C., D. A.; Baldwin, J. G.

    1991-01-01

    Fine structure of the posterior cone of monoxenically cultured Heterodera schachtii is examined. The cone is not evident at the end of the fourth molt, but as the female matures the cone elongates, vulval lips enlarge, and cuticular patterns on the lips are modified. Body wall cuticle (BW) of the cone includes layers A and B, but C is modified or replaced by a network of fibers which correspond to the semifenestrae. Vaginal lining is continuous with the BW and terminates at the cuticular underbridge near the uterus. Vaginal musculature includes 48 dilatores vaginae (DV) as well as a sphincter vaginae (SV). The DV include a contractile and noncontractile region with abundant actin and glycogen. A distinct anal depressor muscle is present. In the cyst, only bullae, the underbridge, vagina lining, and traces of the SV muscle persist. Detailed morphology of the cone of H. schachtii provides insight into characters which, when compared with other heteroderines, will be useful in phylogenetic analysis of Heteroderinae. PMID:19283101

  13. 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.

  14. Fine-scale Horizontal Structure of Arctic Mixed-Phase Clouds.

    SciTech Connect

    Rambukkange,M.; Verlinde, J.; Elorante, E.; Luke, E.; Kollias, P.; Shupe, M.

    2006-07-10

    Recent in situ observations in stratiform clouds suggest that mixed phase regimes, here defined as limited cloud volumes containing both liquid and solid water, are constrained to narrow layers (order 100 m) separating all-liquid and fully glaciated volumes (Hallett and Viddaurre, 2005). The Department of Energy Atmospheric Radiation Measurement Program's (DOE-ARM, Ackerman and Stokes, 2003) North Slope of Alaska (NSA) ARM Climate Research Facility (ACRF) recently started collecting routine measurement of radar Doppler velocity power spectra from the Millimeter Cloud Radar (MMCR). Shupe et al. (2004) showed that Doppler spectra has potential to separate the contributions to the total reflectivity of the liquid and solid water in the radar volume, and thus to investigate further Hallett and Viddaurre's findings. The Mixed-Phase Arctic Cloud Experiment (MPACE) was conducted along the NSA to investigate the properties of Arctic mixed phase clouds (Verlinde et al., 2006). We present surface based remote sensing data from MPACE to discuss the fine-scale structure of the mixed-phase clouds observed during this experiment.

  15. Restricted gene flow and fine-scale population structuring in tool using New Caledonian crows

    NASA Astrophysics Data System (ADS)

    Rutz, C.; Ryder, T. B.; Fleischer, R. C.

    2012-04-01

    New Caledonian crows Corvus moneduloides are the most prolific avian tool users. It has been suggested that some aspects of their complex tool use behaviour are under the influence of cultural processes, involving the social transmission—and perhaps even progressive refinement—of tool designs. Using microsatellite and mt-haplotype profiling of crows from three distinct habitats (dry forest, farmland and beachside habitat), we show that New Caledonian crow populations can exhibit significant fine-scale genetic structuring. Our finding that some sites of <10 km apart were highly differentiated demonstrates considerable potential for genetic and/or cultural isolation of crow groups. Restricted movement of birds between local populations at such small spatial scales, especially across habitat boundaries, illustrates how specific tool designs could be preserved over time, and how tool technologies of different crow groups could diverge due to drift and local selection pressures. Young New Caledonian crows have an unusually long juvenile dependency period, during which they acquire complex tool-related foraging skills. We suggest that the resulting delayed natal dispersal drives population-divergence patterns in this species. Our work provides essential context for future studies that examine the genetic makeup of crow populations across larger geographic areas, including localities with suspected cultural differences in crow tool technologies.

  16. 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.

  17. Plant growth in elevated CO2 alters mitochondrial number and chloroplast fine structure

    PubMed Central

    Griffin, Kevin L.; Anderson, O. Roger; Gastrich, Mary D.; Lewis, James D.; Lin, Guanghui; Schuster, William; Seemann, Jeffrey R.; Tissue, David T.; Turnbull, Matthew H.; Whitehead, David

    2001-01-01

    With increasing interest in the effects of elevated atmospheric CO2 on plant growth and the global carbon balance, there is a need for greater understanding of how plants respond to variations in atmospheric partial pressure of CO2. Our research shows that elevated CO2 produces significant fine structural changes in major cellular organelles that appear to be an important component of the metabolic responses of plants to this global change. Nine species (representing seven plant families) in several experimental facilities with different CO2-dosing technologies were examined. Growth in elevated CO2 increased numbers of mitochondria per unit cell area by 1.3–2.4 times the number in control plants grown in lower CO2 and produced a statistically significant increase in the amount of chloroplast stroma (nonappressed) thylakoid membranes compared with those in lower CO2 treatments. There was no observable change in size of the mitochondria. However, in contrast to the CO2 effect on mitochondrial number, elevated CO2 promoted a decrease in the rate of mass-based dark respiration. These changes may reflect a major shift in plant metabolism and energy balance that may help to explain enhanced plant productivity in response to elevated atmospheric CO2 concentrations. PMID:11226263

  18. 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

    2013-08-01

    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. PMID:23971546

  19. Relative contribution of target and masker temporal fine structure to the unmasking of consonants in noise

    PubMed Central

    Apoux, Frédéric; Healy, Eric W.

    2011-01-01

    The present study assessed the relative contribution of the “target” and “masker” temporal fine structure (TFS) when identifying consonants. Accordingly, the TFS of the target and that of the masker were manipulated simultaneously or independently. A 30 band vocoder was used to replace the original TFS of the stimuli with tones. Four masker types were used. They included a speech-shaped noise, a speech-shaped noise modulated by a speech envelope, a sentence, or a sentence played backward. When the TFS of the target and that of the masker were disrupted simultaneously, consonant recognition dropped significantly compared to the unprocessed condition for all masker types, except the speech-shaped noise. Disruption of only the target TFS led to a significant drop in performance with all masker types. In contrast, disruption of only the masker TFS had no effect on recognition. Overall, the present data are consistent with previous work showing that TFS information plays a significant role in speech recognition in noise, especially when the noise fluctuates over time. However, the present study indicates that listeners rely primarily on TFS information in the target and that the nature of the masker TFS has a very limited influence on the outcome of the unmasking process. PMID:22225058

  20. Small scale flux emergence, small flares, and the unresolved fine structure: modeling and observations

    NASA Astrophysics Data System (ADS)

    Haraldson Hansteen, Viggo H.

    2016-05-01

    The emergence of flux through the photosphere and into the outer solar atmosphere is known to produce dynamic events in the chromosphere and corona. In this talk we will describe three-dimensional (3d) magnetohydrodynamic simulations of magnetic flux emergence in a model that spans the convection zone and into the outer solar atmosphere with the Bifrost code. We will contrast this with models in which no flux emergence occurs. These are a ``realistic'' model, in the sense that the parameters and physical effects that control the atmosphere can be used to produce diagnostics that can be directly compared with observations. Thus we will also contrast the model predictions with with SST and IRIS observations of an emerging flux region. We discuss the evolution of the model and several synthetic observables. We discuss the model's possible relevance to the so called 'unresolved fine structure' observed in the solar transition region. Finally, we will report on developments to merge `deeper' models constructed from MURaM simulations with Bifrost models of the chromosphere and corona in flare relevant simulations.

  1. Fine-structure energy levels and autoionizing width calculations of magnesium-like Ni XVII

    NASA Astrophysics Data System (ADS)

    Liang, Liang; Gao, Wenjing; Zhou, Chao; Zhang, Ling

    2013-05-01

    We have calculated highly excited fine-structure energy levels and their autoionizing width of 3 pns 3 P 1 ( n = 11-26), 3 pns 1 P 1 ( n = 10-22), 3 pnd 3 D 1 ( n = 11-26), 3 pnd 3 P 1 ( n = 10-21), 3 pnd 1 P 1( n = 10-21), 3 dnp 3 D 1 ( n = 7-30), 3 dnp 3 P 1 ( n = 7-28), 3 dnp 1 P 1 ( n = 7-28), 3 dnf 3 D 1 ( n = 7, 9-27), 3 dnf 3 P 1 ( n = 7, 9-27), and 3 dnf 1 P 1 ( n = 7, 9-27) for magnesium-like Ni XVII. The calculations are based upon the relativistic Breit-Pauli R-matrix approximation combining with the QB method of Quigley-Berrington (L. Quigley, K. A. Berrington, Pelan J. Comput. Phys. Commun. 114, 225 (1998)). We have reported the many unpublished energy values and autoionizing width of the J = 1 odd states of magnesium-like Ni XVII.

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

    NASA Astrophysics Data System (ADS)

    Mbelek, Jean Paul; Mosquera Cuesta, Herman J.

    2008-09-01

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

  3. 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

  4. Limit on the Temporal Variation of the Fine-Structure Constant Using Atomic Dysprosium

    SciTech Connect

    Cingoez, A.; Lapierre, A.; Leefer, N.; Nguyen, A.-T.; Lamoreaux, S. K.; Torgerson, J. R.; Budker, D.

    2007-01-26

    Over 8 months, we monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These frequencies are sensitive to variation of the fine-structure constant ({alpha}) due to relativistic corrections of opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a rf electric-dipole transition between them. Our measurements show that the frequency variation of the 3.1-MHz transition in {sup 163}Dy and the 235-MHz transition in {sup 162}Dy are 9.0{+-}6.7 Hz/yr and -0.6{+-}6.5 Hz/yr, respectively. These results provide a rate of fractional variation of {alpha} of (-2.7{+-}2.6)x10{sup -15} yr{sup -1} (1{sigma}) without assumptions on constancy of other fundamental constants, indicating absence of significant variation at the present level of sensitivity.

  5. 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.

  6. 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.

  7. Fine structure of vesiculated nerve profiles in the human lumbar facet joint.

    PubMed Central

    Vandenabeele, F; Creemers, J; Lambrichts, I; Robberechts, W

    1995-01-01

    The ultrastructural features of vesiculated nerve profiles were examined within a perivascular plexus of unmyelinated nerve fibres around small arteries and arterioles in the posterior facet joint capsule. Such profiles were exclusively observed in the dense fibrous layer and the adjacent part of the subintimal layer. The ligamentum flavum lacked any type of innervation. The vesiculated nerve profiles were tentatively classified on the basis of the fine structural appearances of their vesicular content. Two major types of nerve profiles could readily be distinguished in the capsular tissue. Both displayed a variable number of mitochondria, neurotubules and neurofilaments. The first type, containing predominantly small vesicles with an electron-dense granule or core, was frequently encountered and considered to be adrenergic in function. Profiles similar in morphology were also observed in the synovial plical tissue. A second type of profile, found in the joint capsule, contained varying proportions of small agranular (clear) vesicles and mitochondria. Some of these profiles exhibited an accumulation of mitochondria and were considered to be sensory in function. Nerve profiles filled with predominantly small flattened vesicles were occasionally encountered. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:8586567

  8. 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

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Gardner, Carl L.

    2003-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Fujii, Yasunori

    2010-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-11-01

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

  13. Fine structure of the retinal pigment epithelium of the great horned owl (Bubo virginianus).

    PubMed

    Braekevelt, C R; Thorlakson, I J

    1993-01-01

    The fine structure of the retinal epithelium (RPE), choriocapillaries and Bruch's membrane (complexus basalis) has been studied by light and electron microscopy in the great horned owl (Bubo virginianus). The RPE consists of a single layer of cuboidal cells joined laterally in the mid to basal region by a series of tight junctions forming part of the blood-ocular barrier. Basally (sclerally) the epithelial cells show numerous deep infoldings while apically (vitreally) a wealth of microvillar processes interdigitate with the photoreceptor cells. Internally the RPE cells display a large vesicular nucleus, plentiful smooth endoplasmic reticulum (SER) and polysomes with only small scattered profiles of rough endoplasmic reticulum (RER). Numerous pleomorphic mitochondria are basally located. In the light-adapted state the melanosomes are located almost exclusively within the apical processes indicating retinomotor movements. Myeloid bodies are numerous and often show ribosomes on their outer surface. Bruch's membrane is typical of avian species in that it is pentalaminate and the lamina densa is displaced towards the choriocapillaris. The choriocapillaris itself is but minimally fenestrated facing Bruch's membrane. Most fenestrations present show a single layered diaphragm while others display a double-layered diaphragm. PMID:8443429

  14. 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.

  15. Dynamics of Femtosecond Laser Ablation Plume Studied With Ultrafast X-ray Absorption Fine Structure Imaging

    SciTech Connect

    Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi; Nakano, Hidetoshi

    2010-10-08

    We investigated the dynamic process of an expanding femtosecond laser ablation plume of aluminum generated in an irradiation intensity range of 10{sup 13}-10{sup 15} W/cm{sup 2} with the ultrafast x-ray absorption fine structure (XAFS) imaging technique. The XAFS spectra of the aluminum L{sub II,III} edge of the plume revealed that the plume consists of doubly and singly charged ions, neutral atoms, liquid particles, and possible atomic clusters. Scanning electron microscopy of deposited ablation particles confirmed that the liquid particles corresponds to the spherical nanoparticles with a size ranging from several tens nanometers to approximately 200 nm. The spatiotemporal evolution of the XAFS image of the plume shows the sequential appearance of each ablation particle from aluminum surface according to its ejection velocity. The result suggests that the photomechanical fragmentation process, which was theoretically proposed, is dominant mechanism for the nanoparticle ejection under the irradiation intensity far from the ablation threshold of aluminum. This study clearly demonstrates the potential of our technique for measuring the ultrafast dynamics of femtosecond laser ablation process.

  16. Detection of Acoustic Temporal Fine Structure by Cochlear Implant Listeners: Behavioral Results and Computational Modeling

    PubMed Central

    Imennov, Nikita S.; Won, Jong Ho; Drennan, Ward R.; Jameyson, Elyse; Rubinstein, Jay T.

    2013-01-01

    A test of within-channel detection of acoustic temporal fine structure (aTFS) cues is presented. Eight cochlear implant listeners (CI) were asked to discriminate between two Schroeder-phase (SP) complexes using a two-alternative, forced-choice task. Because differences between the acoustic stimuli are primarily constrained to their aTFS, successful discrimination reflects a combination of the subjects’ perception of and the strategy’s ability to deliver aTFS cues. Subjects were mapped with single-channel Continuous Interleaved Sampling (CIS) and Simultaneous Analog Stimulation (SAS) strategies. To compare within- and across- channel delivery of aTFS cues, a 16-channel clinical HiRes strategy was also fitted. Throughout testing, SAS consistently outperformed the CIS strategy (p ≤ 0.002). For SP stimuli with F0 =50 Hz, the highest discrimination scores were achieved with the HiRes encoding, followed by scores with the SAS and the CIS strategies, respectively. At 200 Hz, single-channel SAS performed better than HiRes (p = 0.022), demonstrating that under a more challenging testing condition, discrimination performance with a single-channel analog encoding can exceed that of a 16-channel pulsatile strategy. To better understand the intermediate steps of discrimination, a biophysical model was used to examine the neural discharges evoked by the SP stimuli. Discrimination estimates calculated from simulated neural responses successfully tracked the behavioral performance trends of single-channel CI listeners. PMID:23333260

  17. Multiply-Charged Positive Ion Polarizabilities from Rydberg Ion Fine Structure

    NASA Astrophysics Data System (ADS)

    Lundeen, Stephen R.; Wright, Laura E.; Snow, Erica L.

    2006-05-01

    Experimental methods originally developed for study of fine structure patterns in high-L Rydberg states of neutral atoms and molecules have recently been extended to allow study of similar states in Rydberg states of multiply-charged ions[1]. Initial studies, carried out in Rydberg states of Si^+ and Si^2+, led to determination of the polarizabilities of Na-like and Mg-like Silicon ions [2,3], but similar studies may be feasible in a wide range of systems. Continued studies are aimed at studying ions with higher charge, such as the closed shell ion Kr^6+, and eventually the Radon-like ions U^6+ and Th^4+. [1] S.R. Lundeen in Advances in Atomic, Molecular and Optical Physics, Vol. 52, edited by P.R. Berman and C.C. Lin, p. 161 [2] R.A. Komara, M.A. Gearba, S.R. Lundeen, C.W. Fehrenbach, Phys. Rev. A 67, 062502 (2003) [3] R.A. Komara, M.A. Gearba, C.W. Fehrenbach, and S.R. Lundeen, J. Phys. B, At. Mol. Opt. Phys. 28, 2787 (2005)

  18. Study of the Local Structure of II-Vi Ternary Alloys by Extended X-Ray Absorption Fine Structure

    NASA Astrophysics Data System (ADS)

    Pong, Way-Faung

    Bondlengths, Debye-Waller factors, and site occupancy in the diluted magnetic semiconductors Zn_ {rm 1 - x}Mn_{ rm x}Se and Hg_{ rm 1 - x}Mn_{rm x}Te, and the narrow-gap semiconductor Hg _{rm 1 - x}Cd _{rm x}Te have been measured using extended x-ray absorption fine structure (EXAFS). The nearest-neighbor bond lengths in all of these alloys are found to be constant as a function of alloy composition within the experimental uncertainty of 0.01A. Because the average cation-cation distance changes with Mn composition, these results necessarily imply distortion of the tetrahedral bond angles. In the case of Zn_{rm 1 - x}Mn_{rm x} Se, the anion sublattice is shown to suffer the largest distortion, but the cation sublattice also exhibits some relaxation. The repercussions of these results are discussed, in terms of the amount of cation and anion sublattice distortion at low temperature and its connection to the superexchange mechanism occurring between the Mn ^{+2} ions and mediated by the intervening anion in Zn_{rm 1 - x}Mn_{rm x} Se. From the NN bond length relaxation results shown in this study and those reported elsewhere for the III -V-based and II-VI-based ternary compounds and DMS alloys, it appears that substitution of Mn^{+2 } ions into II-VI-based compounds causes greater local distortion, in general, than otherwise observed when group II cations are substituted for one another. We believe that the tetrahedral bond weakening in DMS is due to MN 3d-orbital (t_2) and anion p-orbital hybridization in DMS, leaving fewer p-orbitals available for tetrahedral bonding. This leads to the weakening of the bond force constants alpha, beta, as well as the bond becoming more ionic as Mn^{+2} is substituted into the II-VI-based compounds. Finally, the experimentally extended electron energy loss fine structure (EXELFS) technique, with modulations in the differential inelastic electron scattering cross -section above an absorption core edge, has been used in recent years to

  19. 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. PMID:27244444

  20. Structural transitions of mechanically alloyed Fe 100- xCu x systems studied by X-ray absorption fine structure

    NASA Astrophysics Data System (ADS)

    Wei, Shiqiang; Yan, Wensheng; Li, Yuzhi; Liu, Wenhan; Fan, Jiangwei; Zhang, Xinyi

    2001-11-01

    The local structures of the immiscible Fe 100- xCu x alloys ( x=0, 10, 20, 40, 60, 80 and 100) produced by mechanical alloying have been investigated by X-ray absorption fine structure technique. For the Fe 100- xCu x solid solutions with x⩾40, the local environment around the Fe atoms changes from bcc to fcc structure and the Cu atoms maintain the original coordination geometry after milling for 160 h. In contrast, the local structures around the Cu atoms in both Fe 80Cu 20 and Fe 90Cu 10 alloys exhibit a transition from fcc to bcc structure. Furthermore, we found that the coordination numbers N in the first shell of the Fe and Cu atoms were largely deviated from the stoichiometric composition for the Fe 100- xCu x solid solutions with x⩾40. The Debye-waller factor σ of the fcc Fe-Cu phase is larger than that of the bcc Fe-Cu phase, and the σ (0.099 Å) around Fe atoms is larger than that around Cu atoms (0.089 Å) in the Fe 100- xCu x solid solutions with x⩾40. This indicates that the mechanically alloyed Fe 100- xCu x supersaturated solid solutions with x⩾40 is not a homogeneous alloy, but consists of fcc Fe-rich and fcc Cu-rich regions. However, In Fe 100- xCu x solid solutions with x⩽20, the Cu atoms were almost homogeneously solved into the bcc Fe-Cu phase. A possible mechanism for bcc-to-fcc and fcc-to-bcc changes in Fe 100- xCu x solid solutions is discussed in relation to the interdiffusion and the transition induced by the ball milling.