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Sample records for na2o cao k2o

  1. Effect of nitridation on the aqueous dissolution of Na2O-K2O-CaO-P2O5 metaphosphate glasses.

    PubMed

    Riguidel, Quentin; Muoz, Francisco

    2011-06-01

    The use of oxynitride glasses is presented as an alternative for the preparation of bioresorbable phosphate glasses with a controlled dissolution rate. This work describes the design of oxynitride phosphate glasses within the systems of composition (50-x)Na(2)OxCaO50P(2)O(5) and (25-(x/2))Na(2)O(25-(x/2))K(2)OxCaO50P(2)O(5) (x=5, 10, 15, 20 mol.%) throughout the processing parameters of the ammonolysis reaction and the glass composition. Mixed-alkali sodium-potassium phosphate glasses with low CaO contents present the best characteristics for nitridation. The dissolution rate has been determined by immersion of glass samples in water, at constant temperature of 37 C, and has been discussed as a function of both modifiers composition and nitrogen content incorporated in the glasses through ammonolysis. All oxynitride glass compositions dissolve congruently and their dissolution rate decreases by more than three orders of magnitude for the highest nitrogen contents. However, it has been demonstrated that nitrogen contents as low as 2-3 wt.% (i.e. a 0.2N/P ratio) are sufficient to decrease the dissolution rate by one order of magnitude with respect to the pure oxide glasses. Novel oxynitride phosphate glasses with a controlled and congruent dissolution are proposed for future applications in biodegradable composite materials, tissue engineering or host matrices for the controlled release of drugs. PMID:21440095

  2. Melt densities for leucogranites and granitic pegmatites: Partial molar volumes for SiO 2, Al 2O 3, Na 2O, K 2O, Li 2O, Rb 2O, Cs 2O, MgO, CaO, SrO, BaO, B 2O 3, P 2O 5, F 2O -1, TiO 2, Nb 2O 5, Ta 2O 5, and WO 3

    NASA Astrophysics Data System (ADS)

    Knoche, R.; Dingwell, D. B.; Webb, S. L.

    1995-11-01

    The densities and thermal expansivities of thirty-eight haplogranitic silicate melts have been experimentally determined. The compositions represent the additions of approximately 5, 10, and 20 wt% of selected oxide components Al 2O 3, Na 2O, K 2O, Li 2O, Rb 2O, Cs 2O, MgO, CaO, SrO, BaO, TiO 2, Nb 2O 5, Ta 2O 5, and WO 3 to a base melt of haplogranitic (HPG8) composition. The densities of melts have been obtained by a combination of scanning dilatometry and room temperature Archimedean density determinations together with scanning calorimetry. The thermal expansivities were obtained by a combination of scanning calorimetry and scanning dilatometry. The results of the density and expansivity determinations for the melts are fit to a multicomponent linear least squares regression of molar volume vs. molar composition. The resulting partial molar volumes of the molten oxides are reported for a reference temperature of 750C. The multicomponent linear least squares regression yields a description of the database with a root mean squared deviation of 0.3%. The fit to these new partial molar volume data includes our previous data for B 2O 3, P 2O 5, and F 2O -1-bearing haplogranitic melts. The partial molar volumes of the oxides vary from 10.53 0.29 cm 3 mole -1 for MgO to 69.09 1.82 cm 3 mol -1 for P 2O 5. Compared on the basis of one oxygen per mole they range from 10.53 0.29 cm 3 mol -1 (MgO) to 55.38 1.69 cm 3 mol -1 (Cs 2O). The present data, taken together with an estimate of the partial molar volume of water in these melts (13.1 1.3 cm 3 mol -1) are recommended to be used to calculate the low pressure densities of leucogranitic and pegmatitic melts.

  3. Effects of Substitution of K2O for Na2O on the Bioactivity of CaO-Na2O-SiO2-P2O5 glasses

    NASA Astrophysics Data System (ADS)

    Kim, Taehee; Hwang, Chawon; Gwoo, Donggun; Park, Hoyyul; Ryu, Bong-Ki

    2012-10-01

    The compositional dependences of bioactivity, thermal properties, atomic structure, and surface morphology have been investigated in the CaO-Na2O-SiO2-P2O5 system; this system is known as a bioglass. 45S5 Bioglass® is known to be a general and highly bioactive material. However, the bioactivity of this glassy material is expected to be improved by modifying the alkali-metal composition. Thermal properties, density, and molar volume were measured to investigate the structural packing. FT-IR spectra and X-ray diffraction were used to confirm the structures of these glasses. The morphology was examined using field emission electron microscopy, and the formation of a Ca-P layer was studied using an energy-dispersive system. This study shows that the tendency to form a calcium phosphate layer is increased with the substitution of K2O for Na2O.

  4. Synthesis of (Na2O,PbO)-Nb2O5, (Na2O,BaO)-Nb2O5, and (K2O,SrO)-Nb2O5 thin films using sol-gel method

    SciTech Connect

    Peng, Fei; Li, Dongsheng

    2010-09-01

    Homogeneous pore free Ba2NaNb5O15, KSr2Nb5O15, and 2•Na2O-PbO-6•Nb2O5 thin films were fabricated on sapphire substrates using the sol-gel technique. By controlling the gelation and coating process, thickness of thin films fabricated was controllable from ~40 nm to ~10 μm. Synthesized thin films possessed highly preferred orientated microstructure. Another advantage of this method is the subsequent heat treatment temperature dramatically decreased compared with other methods. This increases stoichiometry control and makes the large scale fabrication more feasible and efficient.

  5. Compositional dependence of bioactivity of glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2.

    PubMed

    Brink, M; Turunen, T; Happonen, R P; Yli-Urpo, A

    1997-10-01

    The bioactivity, i.e., bone-bonding ability, of 26 glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2 was studied in vivo. This investigation of bioactivity was performed to establish the compositional dependence of bioactivity, and enabled a model to be developed that describes the relation between reactions in vivo and glass composition. Reactions in vivo were investigated by inserting glass implants into rabbit tibia for 8 weeks. The glasses and the surrounding tissue were examined using scanning electron microscopy (SEM), light microscopy, and energy-dispersive X-ray analysis (EDXA). For most of the glasses containing < 59 mol % SiO2, SEM and EDXA showed two distinct layers at the glass surface after implantation, one silica-rich and another containing calcium phosphate. The build-up of these layers in vivo was taken as a sign of bioactivity. The in vivo experiments showed that glasses in the investigated system are bioactive when they contain 14-30 mol % alkali oxides, 14-30 mol % alkaline earth oxides, and < 59 mol % SiO2. Glasses containing potassium and magnesium bonded to bone in a similar way as bioactive glasses developed so far. PMID:9335356

  6. Orange Peel Oxidative Gasification on Ni Catalysts Promoted with CaO, CeO2 or K2O.

    PubMed

    Vargas, G; Zapata, B; Valenzuela, M A; Alfaro, S

    2015-09-01

    Orange peel can be considered as an attractive raw material to be gasified for hydrogen or syngas production. In this work, the catalytic evaluation of several silica-supported nickel catalysts in the oxidative degradation of waste orange peel is reported. It was found that the catalytic gasification with the K2O-Ni/silica catalyst produces more hydrogen than the non-catalytic route at 600 degrees C. Surprisingly, a significant amount of ethene was obtained with the CeO2-Ni/silica catalyst, which was explained in terms of an oxidative dehydrogenation reaction of ethane formed during biomass or tar decomposition. PMID:26716225

  7. Nucleation and crystallization of Na2O-2CaO-3SiO2 glass by differential thermal analysis

    NASA Technical Reports Server (NTRS)

    Xu, Xiaojie J.; Ray, Chandra S.; Day, Delbert E.

    1991-01-01

    DTA is presently used to characterize the nucleation and crystallization processes of the Na2O-2CaO-3SiO2 glass. A nucleation rate-temperaturelike curve is obtained by plotting either the reciprocal of the temperature corresponding to the crystallization peak maximum, or the height of the crystallization peak, as a function of nucleation temperature. The nucleation-temperature range for this glass composition, 550-650 C, and the maximum nucleation temperature of 600 + or - 5 C, are found to be in excellent agreement with those associated with the classical nucleation technique, followed by isothermal crystallization. It is noted that when most of the nucleation occurs during the DTA measurements, a modified Kissinger equation must be used to calculate the crystallization energy.

  8. First Measurements of Time-Dependent Nucleation as a Function of Composition in Na2O.2CaO.3SiO2 Glasses

    NASA Technical Reports Server (NTRS)

    Kelton, K. F.; Narayan, K. Lakshmi

    1996-01-01

    The first measurements in any system of the composition dependence of the time-dependent nucleation rate are presented Nucleation rates of the stoichiometric crystalline phase, Na2O.2CaO.3SiO2, from quenched glasses made with different SiO2 concentrations were determined as a function of temperature and glass composition. A strong compositional dependence of the nucleation rates and a weak dependence for the induction times are observed. Using measured values of the liquidus temperatures and growth velocities as a function of glass composition, these data are shown to be consistent with predictions from the classical theory of nucleation, assuming a composition-dependent interfacial energy.

  9. Crystallization Behavior and Microstructure of Silica-Free 5K2O-45CaO-50P2O5 Bioglass

    NASA Astrophysics Data System (ADS)

    Wang, Moo-Chin; Lai, You-Cheng; Shih, Wei-Jen; Shih, Ping-Yu; Chen, Guo-Ju; Li, Wang-Long

    2010-02-01

    The crystallization behavior and microstructure of silica-free 5K2O-45CaO-50P2O5 (KCP) bioglass have been studied using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning election microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The activation energy for the KCP bioglass crystallization is found to be 337.4 kJ/mol using a nonisothermal method. The crystalline phases of the glass surface determined by XRD are KCa(PO3)3, 4CaO·3P2O5, and β-Ca(PO3)2 when the KCP bioglass is crystallized at 903 K for 4 hours. The crystalline phase of the powder samples determined by XRD is β-Ca(PO3)2 when silica-free KCP glasses crystallized at 873 to 1073 K for 8 hours. Crystallization starts at the surface of the KCP bioglass and then proceeds toward the interior of the glass matrix. The morphology of β-Ca(PO3)2 is a fibrillar shape 20 to 180 nm in length and 17 to 20 nm in diameter, with an aspect ratio ranging from 1.0 to 10.6.

  10. Oscillatory Zoning in Plagioclase: Effect of P, T And Partial Molal Volumes of Na2O And CaO In The Melt

    NASA Astrophysics Data System (ADS)

    Kilinc, A.; Ustunisik, G.

    2009-05-01

    In many explosively erupting volcanoes geophysical evidence suggests pooling of magma in multiple magma chambers within the crust before eruption. We evaluated the effect of adiabatic uprise of magma followed by isobaric crystallization on plagioclase zoning using the Melts software. A basaltic andesite, parental magma for the explosively erupting Erciyes Volcano in central Turkey, has been used as the starting composition in the calculations. In our multiple magma chamber model, basaltic andesite magma moves adiabatically from 2 kb to a shallower magma chamber at 1.5 kb pressure where it crystallizes isobarically and then moves adiabatically again from 1.5 kb to a magma chamber at 1 kb where it crystallizes isobarically before erupting. In our simulations, the An content of plagioclase increases in the adiabatic uprise steps and decreases in the isobaric steps. The net result of this calculation shows that oscillatory zoning is developed. Increase and decrease in the An content of plagioclase during adiabatic and isobaric steps, respectively is explained by the effect of pressure on the partial molal volumes of Na2O and CaO in the melt.

  11. A Structural Molar Volume Model for Oxide Melts Part II: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Ternary and Multicomponent Systems

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

    2016-04-01

    A structural molar volume model based on the silicate tetrahedral Q-species has been developed to accurately predict the molar volume of molten oxides. In this study, the molar volumes of ternary and multicomponent melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system are reviewed and compared with the predicted molar volumes from the newly developed structural model. The model can accurately predict the molar volumes using binary model parameters without any ternary or multicomponent parameters. The nonlinear behavior in the molar volume of silicate melts is well predicted by the present model.

  12. A Structural Molar Volume Model for Oxide Melts Part II: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 MeltsTernary and Multicomponent Systems

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

    2015-12-01

    A structural molar volume model based on the silicate tetrahedral Q-species has been developed to accurately predict the molar volume of molten oxides. In this study, the molar volumes of ternary and multicomponent melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system are reviewed and compared with the predicted molar volumes from the newly developed structural model. The model can accurately predict the molar volumes using binary model parameters without any ternary or multicomponent parameters. The nonlinear behavior in the molar volume of silicate melts is well predicted by the present model.

  13. Raman and infrared spectroscopy study on structure and microstructure of glass-ceramic materials from SiO2-Al2O3-Na2O-K2O-CaO system modified by variable molar ratio of SiO2/Al2O3

    NASA Astrophysics Data System (ADS)

    Partyka, Janusz; Le?niak, Magdalena

    2016-01-01

    This paper is focused on the effect of the molar ratio of SiO2/Al2O3 on the microstructure and structure of the internal aluminium-silicon-oxide lattice of the glass-ceramic materials from the SiO2-Al2O3-Na2O-K2O-CaO system. In order to examine the real composition of the obtained samples, a chemical analysis was performed. Following the heat-treatment procedure, pseudowollastonite, anorthite and the vitreous phase were identified. In order to determine the microstructure, research using the scanning electron microscope (SEM) with EDS was done. For the inner structural study, X-ray diffraction (XRD), Raman spectroscopy as well as MIR and FIR spectroscopy were performed.

  14. Raman and infrared spectroscopy study on structure and microstructure of glass-ceramic materials from SiO2-Al2O3-Na2O-K2O-CaO system modified by variable molar ratio of SiO2/Al2O3.

    PubMed

    Partyka, Janusz; Le?niak, Magdalena

    2016-01-01

    This paper is focused on the effect of the molar ratio of SiO2/Al2O3 on the microstructure and structure of the internal aluminium-silicon-oxide lattice of the glass-ceramic materials from the SiO2-Al2O3-Na2O-K2O-CaO system. In order to examine the real composition of the obtained samples, a chemical analysis was performed. Following the heat-treatment procedure, pseudowollastonite, anorthite and the vitreous phase were identified. In order to determine the microstructure, research using the scanning electron microscope (SEM) with EDS was done. For the inner structural study, X-ray diffraction (XRD), Raman spectroscopy as well as MIR and FIR spectroscopy were performed. PMID:26196934

  15. A Structural Molar Volume Model for Oxide Melts Part I: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Binary Systems

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

    2016-04-01

    A structural molar volume model was developed to accurately reproduce the molar volume of molten oxides. As the non-linearity of molar volume is related to the change in structure of molten oxides, the silicate tetrahedral Q-species, calculated from the modified quasichemical model with an optimized thermodynamic database, were used as basic structural units in the present model. Experimental molar volume data for unary and binary melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system were critically evaluated. The molar volumes of unary oxide components and binary Q-species, which are model parameters of the present structural model, were determined to accurately reproduce the experimental data across the entire binary composition in a wide range of temperatures. The non-linear behavior of molar volume and thermal expansivity of binary melt depending on SiO2 content are well reproduced by the present model.

  16. A Structural Molar Volume Model for Oxide Melts Part I: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 MeltsBinary Systems

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

    2015-12-01

    A structural molar volume model was developed to accurately reproduce the molar volume of molten oxides. As the non-linearity of molar volume is related to the change in structure of molten oxides, the silicate tetrahedral Q-species, calculated from the modified quasichemical model with an optimized thermodynamic database, were used as basic structural units in the present model. Experimental molar volume data for unary and binary melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system were critically evaluated. The molar volumes of unary oxide components and binary Q-species, which are model parameters of the present structural model, were determined to accurately reproduce the experimental data across the entire binary composition in a wide range of temperatures. The non-linear behavior of molar volume and thermal expansivity of binary melt depending on SiO2 content are well reproduced by the present model.

  17. Sol-gel synthesis of quaternary (P2O5)55-(CaO)25-(Na2O)(20-x)-(TiO2) x bioresorbable glasses for bone tissue engineering applications (x = 0, 5, 10, or 15).

    PubMed

    Foroutan, Farzad; Walters, Nick J; Owens, Gareth J; Mordan, Nicola J; Kim, Hae-Won; de Leeuw, Nora H; Knowles, Jonathan C

    2015-08-01

    In the present study, we report a new and facile sol-gel synthesis of phosphate-based glasses with the general formula of (P2O5)55-(CaO)25-(Na2O)(20-x)-(TiO2) x , where x = 0, 5, 10 or 15, for bone tissue engineering applications. The sol-gel synthesis method allows greater control over glass morphology at relatively low processing temperature (200 C) in comparison with phosphate-based melt-derived glasses (~1000 C). The glasses were analyzed using several characterization techniques, including x-ray diffraction (XRD), (31)P magic angle spinning nuclear magnetic resonance ((31)P MAS-NMR), Fourier transform infrared (FTIR) spectroscopy and energy-dispersive x-ray (EDX) spectroscopy, which confirmed the amorphous and glassy nature of the prepared samples. Degradation was assessed by measuring the ion release and pH change of the storage medium. Cytocompatibility was also confirmed by culturing osteoblast-like osteosarcoma cell line MG-63 on the glass microparticles over a seven-day period. Cell attachment to the particles was imaged using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results revealed the potential of phosphate-based sol-gel derived glasses containing 5 or 10 mol% TiO2, with high surface area, ideal dissolution rate for cell attachment and easily metabolized dissolution products, for bone tissue engineering applications. PMID:26306553

  18. K2O-rich trapped melt in olivine in the Nakhla meteorite: Implications for petrogenesis of nakhlites and evolution of the Martian mantle

    NASA Astrophysics Data System (ADS)

    Goodrich, Cyrena Anne; Treiman, Allan H.; Filiberto, Justin; Gross, Juliane; Jercinovic, Michael

    2013-12-01

    We used new analytical and theoretical methods to determine the major and minor element compositions of the primary trapped liquid (PTLs) represented by melt inclusions in olivine and augite in the Martian clinopyroxenite, Nakhla, for comparison with previously proposed compositions for the Nakhla (or nakhlite) parent magma. We particularly focused on obtaining accurate K2O contents, and on testing whether high K2O contents and K2O/Na2O ratios obtained in previous studies of melt inclusions in olivine in Nakhla could have been due to unrepresentative sampling, systematic errors arising from electron microprobe techniques, late alteration of the inclusions, and/or boundary layer effects. Based on analyses of 35 melt inclusions in olivine cores, the PTL in olivine, PTLoliv, contained (by wt) approximately 47% SiO2, 6.3% Al2O3, 9.6% CaO, 1.8% K2O, and 0.9% Na2O, with K2O/Na2O = 2.0. We infer that the high K2O content of PTLoliv is not due to boundary layer effects and represents a real property of the melt from which the host olivine crystallized. This melt was cosaturated with olivine and augite. Its mg# is model-dependent and is constrained only to be ≥19 (equilibrium Fo = 40). Based on analyses of 91 melt inclusions in augite cores, the PTL in augite, PTLaug, contained (by wt) 53-54% SiO2, 7-8% Al2O3, 0.8-1.1% K2O, and 1.1-1.4% Na2O, with K2O/Na2O = 0.7-0.8. This K2O content and K2O/Na2O ratio are significantly higher than inferred in studies of melt inclusions in augite in Nakhla by experimental rehomogenization. PTLaug was saturated only with augite, and in equilibrium with augite cores of mg# 62. PTLaug represents the Nakhla parent magma, and does not evolve to PTLoliv by fractional crystallization. We therefore conclude that olivine cores in Nakhla (and, by extension, other nakhlites) are xenocrystic. We propose that PTLoliv and PTLaug were generated from the same source region. PTLoliv was generated first and emplaced to form olivine-rich cumulate rocks. Shortly thereafter, PTLaug was generated and ascended through these olivine-rich cumulates, incorporating fragments of wallrock that became the xenocrystic olivine cores in Nakhla. The Nakhla (nakhlite) mantle source region was pyroxenitic with some olivine, and could have become enriched in K relative to Na via metasomatism. A high degree of melting of this source produced the silica-poor, alkali-rich magma PTLoliv. Further ascension and decompression of the source led to generation of the silica-rich, relatively alkali-poor magma PTLaug. Potassium-rich magmas like those involved in the formation of the nakhlites represent an important part of the diversity of Martian igneous rocks.

  19. Sol-gel Synthesis and Electrospraying of Biodegradable (P2O5)55-(CaO)30-(Na2O)15 Glass Nanospheres as a Transient Contrast Agent for Ultrasound Stem Cell Imaging

    PubMed Central

    Gambhir, Sanjiv S.; Vermesh, Ophir; Kim, Hae-Won; Knowles, Jonathan C.

    2015-01-01

    Ultrasound imaging is a powerful tool in medicine because of the millisecond temporal resolution and sub-millimeter spatial resolution of acoustic imaging. However, the current generation of acoustic contrast agents is primarily limited to vascular targets due to their large size. Nano-size particles have the potential to be used as a contrast agent for ultrasound molecular imaging. Silica-based nanoparticles have shown promise here, however their slow degradation rate may limit their applications as a contrast agent. Phosphate-based glasses are an attractive alternative with controllable degradation rate and easily metabolized degradation components in the body. In this study, biodegradable P2O5-CaO-Na2O phosphate-based glass nanospheres (PGNs) were synthesized and characterized as contrast agents for ultrasound imaging. The structure of the PGNs was characterised using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), 31P nuclear magnetic resonance (31P MAS-NMR), and Fourier transform infrared (FTIR) spectroscopy. The SEM images indicated a spherical shape with a diameter size range of 200-500 nm. The XRD, 31P NMR and FTIR results revealed the amorphous and glassy nature of PGNs that consisted of mainly Q1 and Q2 phosphate units. We used this contrast to label mesenchymal stem cells and determined in vitro and in vivo detection limits of 5 and 9 μg/mL, respectively. Cell counts down to 4000 could be measured with ultrasound imaging with no cytoxicity at doses needed for imaging. Importantly, ion release studies confirmed these PGNs biodegrade into aqueous media with degradation products that can be easily metabolized in the body. PMID:25625373

  20. Na 2O solubility in CaO-MgO-SiO 2 melts

    NASA Astrophysics Data System (ADS)

    Mathieu, R.; Libourel, G.; Deloule, E.; Tissandier, L.; Rapin, C.; Podor, R.

    2011-01-01

    The sodium solubility in silicate melts in the CaO-MgO-SiO 2 (CMS) system at 1400 C has been measured by using a closed thermochemical reactor designed to control alkali metal activity. In this reactor, Na (g) evaporation from a Na 2O- xSiO 2 melt imposes an alkali metal vapor pressure in equilibrium with the molten silicate samples. Because of equilibrium conditions in the reactor, the activity of sodium-metal oxide in the molten samples is the same as that of the source, i.e., aNa 2O (sample) = aNa 2O (source). This design also allows to determine the sodium oxide activity coefficient in the samples. Thirty-three different CMS compositions were studied. The results show that the amount of sodium entering from the gas phase (i.e., Na 2O solubility) is strongly sensitive to silica content of the melt and, to a lesser extent, the relative amounts of CaO and MgO. Despite the large range of tested melt compositions (0 < CaO and MgO < 40; 40 < SiO 2 < 100; in wt%), we found that Na 2O solubility is conveniently modeled as a linear function of the optical basicity ( ?) calculated on a Na-free basis melt composition. In our experiments, ?Na 2O (sample) ranges from 7 10 -7 to 5 10 -6, indicating a strongly non-ideal behavior of Na 2O solubility in the studied CMS melts (?Na 2O (sample) ? 1). In addition to showing the effect of sodium on phase relationships in the CMS system, this Na 2O solubility study brings valuable new constraints on how melt structure controls the solubility of Na in the CMS silicate melts. Our results suggest that Na 2O addition causes depolymerization of the melt by preferential breaking of Si-O-Si bonds of the most polymerized tetrahedral sites, mainly Q 4.

  1. A new sol-gel process for producing Na(2)O-containing bioactive glass ceramics.

    PubMed

    Chen, Qi-Zhi; Li, Yuan; Jin, Li-Yu; Quinn, Julian M W; Komesaroff, Paul A

    2010-10-01

    The sol-gel process of producing SiO(2)-CaO bioactive glasses is well established, but problems remain with the poor mechanical properties of the amorphous form and the bioinertness of its crystalline counterpart. These properties may be improved by incorporating Na(2)O into bioactive glasses, which can result in the formation of a hard yet biodegradable crystalline phase from bioactive glasses when sintered. However, production of Na(2)O-containing bioactive glasses by sol-gel methods has proved to be difficult. This work reports a new sol-gel process for the production of Na(2)O-containing bioactive glass ceramics, potentially enabling their use as medical implantation materials. Fine powders of 45S5 (a Na(2)O-containing composition) glass ceramic have for the first time been successfully synthesized using the sol-gel technique in aqueous solution under ambient conditions, with the mean particle size being approximately 5 microm. A comparative study of sol-gel derived S70C30 (a Na(2)O-free composition) and 45S5 glass ceramic materials revealed that the latter possesses a number of features desirable in biomaterials used for bone tissue engineering, including (i) the crystalline phase Na(2)Ca(2)Si(3)O(9) that couples good mechanical strength with satisfactory biodegradability, (ii) formation of hydroxyapatite, which may promote good bone bonding and (iii) cytocompatibility. In contrast, the sol-gel derived S70C30 glass ceramic consisted of a virtually inert crystalline phase CaSiO(3). Moreover, amorphous S70C30 largely transited to CaCO(3) with minor hydroxyapatite when immersed in simulated body fluid under standard tissue culture conditions. In conclusion, sol-gel derived Na(2)O-containing glass ceramics have significant advantages over related Na(2)O-free materials, having a greatly improved combination of mechanical capability and biological absorbability. PMID:20447473

  2. Effects of sodium and potassium ions on a novel SeO2-B2O3-SiO2-P2O5-CaO bioactive system

    NASA Astrophysics Data System (ADS)

    Trandafir, D. L.; Ponta, O.; Ciceo-Lucacel, R.; Simon, V.

    2015-01-01

    The study is focused on Na2O and/or K2O influence on a new sol-gel derived SeO2-B2O3-SiO2-P2O5-CaO bioactive system. The structural changes induced by Na2O and/or K2O addition were correlated with the samples behavior in simulated biological media. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the structure and the type of the chemical bonds. The morphology of the samples was characterized through scanning electron microscopy (SEM). XRD results pointed out a prevalent vitreous structure with an incipient hydroxyapatite (HA) crystalline phase. FTIR results revealed a complex network consisting of silicate, phosphate and borate units, as well as the development of both A- and B-type of carbonate-substituted HA. The bioactivity of the samples was tested in vitro following the evolution of the apatite layers self-assembled on the samples surface in simulated body fluid. Their biocompatibility was investigated after samples surface functionalization with protein. The results indicate that sodium and potassium addition improves the biocompatibility by enhancement of protein adherence on samples surface and without to prevent the samples bioactivity.

  3. Distribution of anomalously high K2O volcanic rocks in Arizona: metasomatism at the Picacho Peak detachment fault.

    USGS Publications Warehouse

    Brooks, W.E.

    1986-01-01

    Metasomatized Tertiary lavas with anomalously high K2O and lower Na2O content are distributed within the NW-trending extensional terrain of SW Arizona. These rocks are common near core-complex-related detachment faults at Picacho Peak and the Harcuvar Mountains and in listric-faulted terrain at the Vulture Mountains. These rocks are also enriched in Zr but depleted in MgO. Fine-grained, euhedral orthoclase (adularia) is the dominant K-mineral; other secondary introduced minerals are quartz and calcite. Spatial association of metasomatism with the detachment faults suggests that detachment provided a conduit for hydrothermal fluids that altered the initial chemistry of the Tertiary volcanics and charged the upper plate rocks with mineralizing fluids that carried Zr and Ba, along with Au, Ag and Cu during detachment 17-18 m.y. ago.-L.C.H.

  4. Flower-like Na2O nanotip synthesis via femtosecond laser ablation of glass

    PubMed Central

    2012-01-01

    The current state-of-the-art in nanotip synthesis relies on techniques that utilize elaborate precursor chemicals, catalysts, or vacuum conditions, and any combination thereof. To realize their ultimate potential, synthesized nanotips require simpler fabrication techniques that allow for control over their final nano-morphology. We present a unique, dry, catalyst-free, and ambient condition method for creating densely clustered, flower-like, sodium oxide (Na2O) nanotips with controllable tip widths. Femtosecond laser ablation of a soda-lime glass substrate at a megahertz repetition rate, with nitrogen flow, was employed to generate nanotips with base and head widths as small as 100 and 20 nm respectively, and lengths as long as 10 μm. Control of the nanotip widths was demonstrated via laser dwell time with longer dwell times producing denser clusters of thinner nanotips. Energy dispersive X-ray analysis reveals that nanotip composition is Na2O. A new formation mechanism is proposed, involving an electrostatic effect between ionized nitrogen and polar Na2O. The synthesized nanotips may potentially be used in antibacterial and hydrogen storage applications. PMID:22809176

  5. Phase Equilibria Studies in the SiO2-K2O-CaO System

    NASA Astrophysics Data System (ADS)

    Chen, Mao; Hou, Xinmei; Chen, Junhong; Zhao, Baojun

    2016-02-01

    Phase equilibria in the SiO2-K2O-CaO system have been experimentally investigated in the SiO2-rich area. High-temperature equilibration, rapid quenching, and electron probe X-ray microanalysis (EPMA) techniques have been used in this study. K2O may vaporize during EPMA measurements causing significant uncertainties. In the present study, optimum EPMA operating conditions have been determined in order to accurately measure K2O concentrations in the quenched samples. The compositions of all phases present in the quenched sample were measured using EPMA with optimum operating parameters. The following primary phase fields were identified in the composition range investigated: SiO2, CaO·SiO2, 2CaO·SiO2, K2O·2CaO·2SiO2, and K2O·6CaO·4SiO2. The isotherms between 1273 K and 1473 K (1000 °C and 1200 °C) in these primary phase fields have been determined. The presence of the compounds K2O·2CaO·2SiO2 and K2O·6CaO·4SiO2 has been confirmed.

  6. Glass transition temperature and conductivity in Li2O and Na2O doped borophosphate glasses

    NASA Astrophysics Data System (ADS)

    Ashwajeet, J. S.; Sankarappa, T.; Ramanna, R.; Sujatha, T.; Awasthi, A. M.

    2015-08-01

    Two alkali doped Borophosphate glasses in the composition, (B2O3)0.2. (P2O5)0.3. (Na2O)(0.5-x). (Li2O)x, where x = 0.05 to 0.50 were prepared by standard melt quenching method at 1200K. Non-crystalline nature was confirmed by XRD studies. Room temperature density was measured by Archimedes principle. DC conductivity in the temperature range from 300K to 575K has been measured. Samples were DSC studied in the temperature range from 423K to 673K and glass transition temperature was determined. Glass transition temperature passed through minima for Li2O con.2centration between 0.25 and 0.30 mole fractions. Activation energy of conduction has been determined by analyzing temperature variation of conductivity determining Arrhenius law. Conductivity passed through minimum and activation passed through maximum for Li2O content from 0.25 to 0.30 mole fractions. Glass transition temperature passed through minimum for the same range of Li2O content. These results revealed mixed alkali effect taking place in these glasses. It is for the first time borophosphate glasses doped with Li2O and Na2O have been studied for density and dc conductivity and, the mixed alkali effect (MAE) has been observed.

  7. Dynamics of the hot metal dephosphorization with Na2O slags

    NASA Astrophysics Data System (ADS)

    Pak, J. J.; Fruehan, R. J.

    1987-12-01

    Dephosphorization reaction of hot metal by Na2CO3 has been studied experimentally to determine the reaction mechanism and thermodynamics. Most of the experiments were carried out at 1300 °C using Fe-Csat.-Si-P-S alloys. The results indicate that the CO2 gas released from Na2CO3 is important in the dephosphorization reaction as an oxidizer and increasing mass transfer by stirring the slag and metal. As the initial Si content in hot metal is increased, the degree of dephosphorization decreases significantly and the rephosphorization takes place earlier. The primary reason for the rephosphorization is that the activity of PO2.5 increases in the slag because of the evaporation of Na2O from the slag. The loss of Na2O increases the activity coefficient of PO2.5 and decreases the slag volume. At the later stage of Na2CO3 treatment, the reactions reach equilibrium with respect to phosphorus and sulfur, and the oxygen potential, P o2, at the slag-metal interface is determined by the C-CO equilibrium ( a c=1 and 1 atm CO). The presence of sulfur in the metal increases the rate of the dephosphorization because of the electrochemical nature of the reaction; sulfur transfer to the slag accepts the electrons from phosphorus transfer.

  8. Dielectric Properties of Niobate Glass Ceramics of PbO-SrO-Na2O-Nb2O5-SiO2 System with Partial Substitution of K+ for Na+

    NASA Astrophysics Data System (ADS)

    Zhou, Hao; Zhang, Qingmeng; Tang, Qun; Cui, Hang; Xu, Yaohua; Lin, Chenguang; Du, Jun

    2015-12-01

    Substitution of K2O for Na2O content was performed for ferroelectric glass ceramics in the PbO-SrO-Na2O-Nb2O5-SiO2 system, in which a conventional melt quenching method was adopted for the parent glass production in order to investigate its effect on the crystallization process and associated dielectric properties. Phase identification combined with differential thermal analysis results show that the crystalline phase was compressed by the substitution of potassium ions. The hysteresis loop results demonstrate that by increasing the substitution of K+ for Na+, the maximal polarization was decreased while both the remanent polarization and coercive electric field increase. It is also noted that increasing the content of K+ could also reduce the dielectric constant of the glass ceramic system; the dielectric constant demonstrated a decrease from 775 to 299, meanwhile, the dielectric loss increased from 0.013 to 0.021 when 50 mol.% Na+ was replaced by K+. Additionally, leakage current results show that as more sodium ions are replaced by potassium ions, the leakage current increased and the resistivity decreased.

  9. Boron Removal from Silicon by CaO-Na2O-SiO2 Ternary Slag

    NASA Astrophysics Data System (ADS)

    Safarian, Jafar; Tranell, Gabriella; Tangstad, Merete

    2015-06-01

    Boron removal from silicon is an important issue for solar-grade silicon feedstock production. In the present study, the removal of B from liquid silicon by a CaO-Na2O-SiO2 slag is studied and it is shown that B can be rapidly removed from silicon within short refining times. Based on mass balance and chemical analysis of the reacted silicon and slag, it is indicated that the kinetics of B removal is dependent on the Na2O in the slag, the main reactive agent for B removal from the system. The transported B into the slag is gasified at the slag-gas interface through sodium metaborate evaporation, which is a rate controlling reaction for B transport to the gas phase. It is indicated that B removal rate by CaO-Na2O-SiO2 slag is considerably higher than that by CaO-SiO2 slags. It is proposed that boron oxide (B2O3) is better embedded in the structure of CaO-SiO2 slags than Na2O-containing slags.

  10. The nitrogen reaction between carbon saturated Iron and Na2O-SiO2 Slag: Part 1. Thermodynamics

    NASA Astrophysics Data System (ADS)

    Tsukihashi, F.; Fruehan, R. J.

    1986-09-01

    The nitrogen partition ratio between Na2O-SiO2 slags and carbon saturated iron was measured for slags containing from 0.4 to 0.55 mole fraction of Na2O and the temperature range 1200 to 1350 C. The nitrogen is dissolved in the slag as the cyanide ion (CN-) and the partition ratio is proportional to the oxygen pressure to the -1/4 power as predicted for CN- dissolution. The oxygen pressure for carbon saturated iron silicon alloys is controlled by the Si (metal)-SiO2 (slag) equilibrium. The nitrogen partition ratio and the cyanide capacity increase with Na2O content and temperature. Calculations indicate that Na2O-SiO2 slags will absorb three times more nitrogen than CaO-Al2O3 slags at the same basicity and temperature. Based on thermodynamic calculations it is estimated that for a typical Na2CO3 hot metal treatment, half of the nitrogen in the metal could possibly be removed.

  11. Physicochemical properties of Cs borosilicate glasses containing CaO

    NASA Astrophysics Data System (ADS)

    Banerjee, D.; Sudarsan, V.; Joseph, A.; Singh, I. J.; Nuwad, J.; Pillai, C. G. S.; Wattal, P. K.; Das, D.

    2011-06-01

    A series of Cs-borosilicate glasses of general formula (mol%): 17.5Na 2O-2.5Cs 2O-45SiO 2-(35- x)B 2O 3- xCaO, where x varies from 0 to 10, were prepared by conventional melt quenching technique. Physicochemical properties like glass transition temperature, extent of volatilization loss of Cs and chemical durability of these glasses have been investigated in detail. Based on the Tg values obtained from DSC studies, it is confirmed that the glass network remains unaffected with increase in CaO content in the glass at the expense of B 2O 3. Cs loss as function of duration of heating revealed that the Cs evaporation follows diffusion controlled mechanism and the extent of loss increases with the increase of CaO incorporation in glass. Chemical durability of the glasses has been found to improve significantly with in the increase of CaO content in glass and this has been attributed to the formation of Ca and Si rich layer at the outer surface of the glass, as inferred from SEM with EDX analysis.

  12. Investigation of SiO2:Na2O ratio as a corrosion inhibitor for metal alloys

    NASA Astrophysics Data System (ADS)

    Mohamad, N.; Othman, N. K.; Jalar, A.

    2013-11-01

    The silicate is one of the potential compounds used as a corrosion inhibitor for metal alloys. The mixture between silica and sodium hydroxide (NaOH) succeeded to produce the silicate product. The formulation of a silicate product normally variable depended by the different ratio of SiO2:Na2O. This research utilized the agriculture waste product of paddy using its rice husk. In this study, the amorphous silica content in rice husk ash was used after rice husk burnt in a muffle furnace at a certain temperature. The X-ray diffraction (XRD) analysis was done to determine the existence of amorphous phase of silica in the rice husk ash. There are several studies that recognized rice husk as an alternative source that obtained high silica content. The X-ray fluorescence (XRF) analysis was carried out to clarify the percentage amount of Si and O elements, which referred the silica compound in rice husk ash. The preparation of sodium silicate formulation were differ based on the SiO2:Na2O ratio (SiO2:Na2O ratio = 1.00, 2.00 and 3.00). These silicate based corrosion inhibitors were tested on several testing samples, which were copper (99.9%), aluminum alloy (AA 6061) and carbon steel (SAE 1045). The purpose of this study is to determine the appropriate SiO2:Na2O ratio and understand how this SiO2:Na2O ratio can affect the corrosion rate of each metal alloys immersed in acidic medium. In order to investigate this study, weight loss test was conducted in 0.5 M hydrochloric acid (HCl) for 24 hours at room temperature.

  13. FT-IR and thermoluminescence investigation of P2O5-BaO-K2O glass system

    NASA Astrophysics Data System (ADS)

    Ivascu, C.; Timar-Gabor, A.; Cozar, O.

    2013-11-01

    The 0.5P2O5ṡxBaOṡ(0.5-x)K2O glass system (0≤x≤0.5mol%) is investigated by FT-IR and thermoluminescence as a possible dosimetic material. FT-IR spectra show structural network modifications with the composition variations of the studied glasses. The predominant absorption bands are characterized by two broad peaks near 500 cm-1, two weak peaks around 740 cm-1 and three peaks in the 900-1270 cm-1 region. The shift in the position of the band assigned to asymmetric stretching of PO2- group, υas(PO2-) modes from ˜1100 cm-1 to 1085 cm-1 and the decrease in its relative intensity with the increasing of K2O content shows a network modifier role of this oxide.. Luminescence investigations show that by adding modifier oxides in the phosphate glass a dose dependent TL signals result upon irradiation. Thus P2O5-BaO-K2O glass system is a possible candidate material for dosimetry in the dose 0 - 50 Gy range.

  14. Thermal/Aqueous: on the H2O-Na2O Competition/Cooperation in Carbonaceous Chondrites (Kaba-L., NIPR Statistics V.)

    NASA Astrophysics Data System (ADS)

    Lukcs, B.; Brczi, Sz.

    1999-03-01

    In aqueous/thermal metamorphism, during hydration and dehydration process of carbonaceous chondrites H2O and Na2O cooperates/competes in the nonterrestrial environment, which can be seen in composition of Kaba and Antarctic (NIPR data) chondrites.

  15. Crystallization kinetics of bioactive glasses in the ZnO-Na2O-CaO-SiO2 system.

    PubMed

    Malavasi, Gianluca; Lusvardi, Gigliola; Pedone, Alfonso; Menziani, Maria Cristina; Dappiaggi, Monica; Gualtieri, Alessandro; Menabue, Ledi

    2007-08-30

    The crystallization kinetics of Na(2)O.CaO.2SiO(2) (x = 0) and 0.68ZnO.Na(2)O.CaO.2SiO(2) (x = 0.68, where x is the ZnO stoichiometric coefficient in the glass formula) bioactive glasses have been studied using both nonisothermal and isothermal methods. The results obtained from isothermal XRPD analyses have showed that the first glass crystallizes into the isochemical Na(2)CaSi(2)O(6) phase, whereas the Na(2)ZnSiO(4) crystalline phase is obtained from the Zn-rich glass, in addition to Na(2)CaSi(2)O(6). The activation energy (Ea) for the crystallization of the Na(2)O.CaO.2SiO(2) glass is 193 +/- 10 and 203 +/- 5 kJ/mol from the isothermal in situ XRPD and nonisothermal DSC experiments, respectively. The Avrami exponent n determined from the isothermal method is 1 at low temperature (530 degrees C), and its value increases linearly with temperature increase up to 2 at 607 degrees C. For the crystallization of Na(2)CaSi(2)O(6) from the Zn-containing glass, higher values of both the crystallization temperature (667 and 661 degrees C) and Ea (223 +/- 10 and 211 +/- 5 kJ/mol) have been found from the isothermal and nonisothermal methods, respectively. The Na(2)ZnSiO(4) crystalline phase crystallizes at lower temperature with respect to Na(2)CaSi(2)O(6), and the Ea value is 266 +/- 20 and 245 +/- 15 kJ/mol from the isothermal and nonisothermal methods, respectively. The results of this work show that the addition of Zn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass. In fact, it causes an increase of Ea for the Na diffusion process, determined using MD simulations, and consequently an overall increase of Ea for the crystallization process of Na(2)CaSi(2)O(6). Our results show good agreement between the Ea and n values obtained with the two different methods and confirm the reliability of the nonisothermal method applied to kinetic crystallization of glassy systems. This study allows the determination of the temperature stability field of the crystalline phases with the view of creating a different glass ceramic useful in the field of bioactive materials. PMID:17676823

  16. Critical Evaluation and Thermodynamic Optimization of the Na2O-FeO-Fe2O3 System

    NASA Astrophysics Data System (ADS)

    Moosavi-Khoonsari, Elmira; Jung, In-Ho

    2016-02-01

    A complete literature review, critical evaluation, and thermodynamic optimization of experimental phase diagrams and thermodynamic properties of the Na2O-FeO-Fe2O3 system were performed at 1 bar total pressure. A set of optimized model parameters obtained for all phases present in this system reproduces available and reliable thermodynamic properties and phase equilibria within experimental error limits from 298 K (25 °C) to above liquidus temperatures for all compositions and oxygen partial pressures from metallic saturation to 1 atm. The liquid phase was modeled based on the Modified Quasichemical Model by considering the possible formation of NaFeO2 associate in the liquid state. Complicated subsolidus phase relations depending on the oxygen partial pressure and temperature were elucidated, and discrepancies among experimental data were resolved.

  17. Studies on influence of aluminium ions on the bioactivity of B2O3-SiO2-P2O5-Na2O-CaO glass system by means of spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Mohini, G. Jagan; Krishnamacharyulu, N.; Sahaya Baskaran, G.; Rao, P. Venkateswara; Veeraiah, N.

    2013-12-01

    Bioactive multi component glasses of the composition of 27.4 B2O3-6.4 SiO2-2.5 P2O5-25.5 Na2O-(38.2 - x) CaO: x Al2O3 (x between 0 and 3.2) were synthesized, by melt quenching technique and their bioactivity was investigated as a function of Al2O3 concentration. Initially, optical absorption and infrared spectra were recorded and analyzed in order to have some pre-understanding over structural aspects of the glasses. For understanding the bioactivity, the samples were immersed in simulated body fluid (SBF) solution for prolonged times (∼30 days) and the weight loss measurements were carried out. The spectroscopic studies were repeated on the post immersed samples. From the comparison of the analysis of the spectroscopic data of both pre-immersed and post-immersed samples together with the information on variation of pH value of residual solution as a function of immersion time, it is concluded that the participation of aluminium ions in tetrahedral positions is hindrance for the formation of HA layer and for the bioactivity of the samples.

  18. Understanding the magnetic behavior of heat treated CaO-P2O5-Na2O-Fe2O3-SiO2 bioactive glass using electron paramagnetic resonance studies

    NASA Astrophysics Data System (ADS)

    Shankhwar, Nisha; Kothiyal, G. P.; Srinivasan, A.

    2014-09-01

    Bioactive glass of composition 41CaO-44SiO2-4P2O5-8Fe2O3-3Na2O has been heat treated in the temperature (TA) range of 750-1150 °C for time periods (tA) ranging from 1 h to 3 h to yield magnetic bioactive glass ceramics (MBCs). X-ray diffraction studies indicate the presence of bone mineral (hydroxyapatite and wollastonite) and magnetic (magnetite and α-hematite) phases in nanocrystalline form in the MBCs. Electron paramagnetic resonance (EPR) study was carried out to understand the variation in saturation magnetization and coercivity of the MBCs with TA and tA. These studies reveal the nature and amount of iron ions present in the MBCs and their interaction in the glassy oxide matrix as a function of annealing parameters. The deterioration in the magnetic properties of the glass heat treated above 1050 °C is attributed to the crystallization of the non-magnetic α-hematite phase. These results are expected to be useful in the application of these MBCs as thermoseeds in hyperthermia treatment of cancer.

  19. A semi-empirical thermodynamic formalism for high-pressure aqueous silicate solutions in the model system K2O-Na2O-CaO-MgO-Al2O3-SiO2-H2O-CO2, a first approach

    NASA Astrophysics Data System (ADS)

    Schertl, H.; Burchard, M.; Hertwig, A.; Maresch, W. V.

    2012-12-01

    The results of experimental solubility determinations in aqueous solutions at high pressures up to 5 GPa are often difficult to gauge with respect to precision and accuracy, because of the potential uncertainties inherent in the available experimental approaches. Existing models of aqueous silicate solutions at low pressures are either unsuitable for extrapolation beyond 0.5 to 1.0 GPa or involve polynomial fits in which the fit parameters lack direct physical meaning. An approach described by Gerya et al. [1,2], based on statistical thermodynamics, allows aqueous silicate solutions to be described as mixtures of fictive oxide "components" together with water molecules in both clustered and "gas-like", i.e. unassociated, states. Burchard et al. [3] presented a first data set for fluids in the system CaO-SiO2-H2O, using the statistical thermodynamic formulation of Gerya et al [1,2] and extending it to include charged fluid species such as Ca2+, Ca(OH)+, Ca(OH)2, OH- and H+. We have now further developed the data set of Burchard et al. [3] by including carbonic fluid species and extending the model system to include MgO and Al2O3. In addition, initial progress has been made in including potassium and sodium model species. Solid phase data were obtained by mathematical conversion of existing thermodynamic mineral data into the semi-empirical form. With this semi-empirical data set calculations for simple, "wet" silicate rocks are now possible. We present applications to suites of jadeitites and jadeite-lawsonite-quartz rocks from the Rio San Juan serpentinite mlanges of the northern Dominican Republic. These rocks have crystallized from high-pressure aqueous fluids in a long-lived intra-oceanic subduction-zone environment at various times and at different P-T conditions (Schertl et al. [4]). The fluid-rock interactions leading to these spectacular rocks are still poorly understood. [1] Gerya et al. (2004) Phys. Chem. Minerals 31, 429-455; [2] Gerya et al. (2005) Eur. J. Mineral. 17, 269-283; [3] Burchard et al. (2011) Eur. J. Mineral. 23, 409-424; Schertl et al. (2012) Eur. J. Mineral. 24, 199-216.

  20. NEAR-Solidus Phase Relationships in Metapelites to 1.0 GPa: Influence of K2O Content

    NASA Astrophysics Data System (ADS)

    Ferri, F.

    2003-04-01

    The transition from amphibolite to granulite facies conditions in metasediments at intermediate pressure is still poorly defined and contradictions persist in currently available petrogenetic grids. Phase relationships in metapelites are investigated on four synthetic compositions (M-P-H-L) in the model system K2O-CaO-FeO-MgO-Al2O3-SiO2-H2O. Experiments were carried out in a piston cylinder apparatus at pressures and temperatures up to 1.0 GPa and to 730^o, and in an internally heated pressure vessel at 0.8 GPa at temperatures up to 730^o. In order to monitor the effect of H2O saturation and fluid speciation, three different charges were loaded for each bulk composition, two at fluid saturated conditions and fO2 buffered by graphite, Ni-NiO and hematite-magnetite respectively. Experiments were characterized by XRD, BSE images and EMPA. All assemblages contain quartz and anorthite. Garnet + biotite staurolite + muscovite are stable in compositions M and P while orthoamphibole replaces muscovite in compositions H and L, where the K2O content is lower. Orthoamphibole is of gedrite type containing 2.0 a.p.f.u. (23 O) of Al at 650^o and 2.5 a.p.f.u. at 700^o . At 700^o and 1.0 GPa and 680^o and 0.8 GPa cordierite is also present in composition L. Garnet has grossular and pyrope fractions of 0.1 and 0.2 respectively all over the pressure-temperature range. In agreement with phase relations experimentally determined by Poli and Schmidt (2002), our results revealed that the stability field of staurolite + biotite and orthoamphibole + staurolite pairs extend to higher pressures and temperatures if compared with calculated equilibria in analogous systems (Worley and Powell, 1998; Gouwei et al., 1994). At near-solidus conditions a variety of hydrous phases may be directly involved in the production of melt through fluid present or fluid absent melting reactions. X. Gowei, T. M. Will and R. Powell, J. Metamorphic Geol., 12: 99-119, 1994 S. Poli &M. W. Schmidt, Annu. Rev. Earth Planet. Sci. 30:1-29, 2002 Worley &R. Powell, J. Metamorphic Geol., 16: 169-188, 1998

  1. Optical properties and glass-forming region of the K2O-Sm2O3-TeO2 glass system

    NASA Astrophysics Data System (ADS)

    Hong, K. S.; Cha, Y. J.; Ha, M. G.; Choi, S.; Kim, J. P.; Lee, B. S.; Jeong, E. D.; Kim, H. G.; Borse, P. H.

    2014-11-01

    The optical properties and the glass-forming region of the K2O-Sm2O3-TeO2 glass system are studied. In the K2O-Sm2O3-TeO2 system, only the 5K2O-5Sm2O3-90TeO2 composition gives a transparent glass. The refractive index, n, and the optical band-gap energy, E g , of the 5K2O-5Sm2O3-90TeO2 glass are n = 2.04 0.003 and E g = 3.2 eV, respectively. A single Sm2Te6O15 phase is found to be formed by a two-step thermal treatment process at 370 C for 5 h and 390 C for 5 h. This is the first report on the crystallization and the preparation of the K2O-Sm2O3-TeO2 glass system.

  2. Modification of the Structure of Ti-Bearing Mold Flux by the Simultaneous Addition of B2O3 and Na2O

    NASA Astrophysics Data System (ADS)

    Li, Zhongmin; Sun, Yongqi; Liu, Lili; Zhang, Zuotai

    2016-03-01

    The present paper mainly focused on how B2O3 and Na2O additions influenced the structure of the Ti-bearing fluoride-free mold flux and investigated how the boron-related units were affected by Na2O. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, 11B magic angle spinning-nuclear magnetic resonance (MAS-NMR), and X-ray photoelectron spectroscopy (XPS) were utilized to identify different structural units and to analyze the overall modification of the network by additives. It was found that BO3 was more abundant than BO4 in the flux. In addition, the addition of B2O3 and Na2O was proved to promote conversion from non-ring BO3 to tetrahedral BO4, and this was confirmed by FTIR and 11B MAS NMR analysis. BO3 was a two-dimensional structure unit and contributed to construct a less stable network. With increasing B2O3 content, degree of polymerization of the flux was increased as confirmed by increased fraction of Q 3 in Raman spectra and non-bridging oxygen in XPS. By contrast, the addition of Na2O, which is a strong network breaker, brought about more non-bridging oxygen by breaking the Si-O-Si linkage which was verified by XPS results. Consequently, a less polymerized network was observed by decreasing content of Q 3 from Raman spectra.

  3. Raman Spectroscopic Study of Nd-Doped 10Na(2)O-90TeO(2) Glasses

    SciTech Connect

    Li, Hong; Su, Yali; Sundaram, S. K.

    2001-11-01

    Tellurite glass systems have important commercial applications in optical communication due to its high refractive index, good infrared transmittance, and high optical nonlinearity. Previously, we studied optical absorption. A local Nd-O structural transition, in the vicinity of 1 mol% Nd2O3, was found; the asymmetry of Nd-O ligand field was at maximum whereas, the degree of Nd-O bond covalency was in a minimum according to the Judd-Ofelt theory derived intensity parameters of the oscillator strength. In this study, we report our investigation on the structural change in the host matrix, 10Na2O-90TeO2, as a function of Nd2O3 concentration using Raman spectroscopy technique. Over the Nd2O3 concentration region from 0.5 to 2.5 mol%, our Raman spectroscopic study showed that the addition of Nd into tellurite glass converts TeO4 trigonal bipyramid (tbp) units to TeO3 trigonal pyramid (tp) units, and possibly some terminal TeO3+1 polyhedra. The Nd effect on the speciation of tellurite structural groups is similar to that of other metal cations of monovalent, divalent, and trivalent. The previously observed Nd-O local structural transition was also found in the current study. A transition, near 1 mol% Nd2O3, was observed in the correlations, both band position and intensity, between two Raman stretching vibration bands near 600 and 730 cm-1. The low frequency band represents the stretching vibration mode of TeO4 tbp units and the high frequency band represnts the stretching vibration mode of TeO3 trigonal pyramid (tp) units. Therefore, the observed transition may suggest the formation of TeO3+1 polyhedron units in the glasses with Nd2O3 concentration greater than 1 mol%. Near 465 cm-1, the bending vibration band for Te-O-Te linkages showed a significant decrease for the glass with 2.5 mol% Nd2O3, suggesting a considerable breakage of the tellurite network.

  4. Effect of SiO2/Na2O mole ratio on the properties of foam geopolymers fabricated from circulating fluidized bed fly ash

    NASA Astrophysics Data System (ADS)

    Liu, Ze; Shao, Ning-ning; Huang, Tian-yong; Qin, Jun-feng; Wang, Dong-min; Yang, Yu

    2014-06-01

    Geopolymers are three-dimensional aluminosilicates formed in a short time at low temperature by geopolymerization. In this paper, alkali-activated foam geopolymers were fabricated from circulating fluidized bed fly ash (CFA), and the effect of SiO2/Na2O mole ratio (0.91-1.68) on their properties was studied. Geopolymerization products were characterized by mechanical testing, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The results show that SiO2/Na2O mole ratio plays an important role in the mechanical and morphological characteristics of geopolymers. Foam samples prepared in 28 d with a SiO2/Na2O mole ratio of 1.42 exhibit the greatest compressive strength of 2.52 MPa. Morphological analysis reveals that these foam geopolymers appear the relatively optimized pore structure and distribution, which are beneficial to the structure stability. Moreover, a combination of the Si/Al atomic ratio ranging between 1.47 and 1.94 with the Na/Al atomic ratio of about 1 produces the samples with high strength.

  5. Removal of Boron and Phosphorus from Silicon Using CaO-SiO2-Na2O-Al2O3 Flux

    NASA Astrophysics Data System (ADS)

    Li, Mark; Utigard, Torstein; Barati, Mansoor

    2014-01-01

    A combination of solvent refining and flux treatment was employed to remove boron and phosphorus from crude silicon to acceptable levels for solar applications. Metallurgical grade silicon (MG-Si) was alloyed with pure copper, and the alloy was subjected to refining by liquid CaO-SiO2-Na2O-Al2O3 slags at 1773 K (1500 °C). The distribution of B and P between the slags and the alloy was examined under a range of slag compositions, varying in CaO:SiO2 and SiO2:Al2O3 ratios and the amount of Na2O. The results showed that both basicity and oxygen potential have a strong influence on the distributions of B and P. With silica affecting both parameters in these slags, a critical P_{{{{O}}2 }} could be identified that yields the highest impurity pick-up. The addition of Na2O to the slag system was found to increase the distributions of boron and phosphorus. A thermodynamic evaluation of the system showed that alloying copper with MG-Si leads to substantial increase of boron distribution coefficient. The highest boron and phosphorus distribution coefficients are 47 and 1.1, respectively. Using these optimum slags to reduce boron and phosphorus in MG-Si to solar grade level, a slag mass about 0.3 times and 17 times mass of alloy would be required, respectively.

  6. Effect of Na2O and B2O3 on the Crystallization Behavior of Low Fluorine Mold Fluxes for Casting Medium Carbon Steels

    NASA Astrophysics Data System (ADS)

    Wei, Juan; Wang, Wanlin; Zhou, Lejun; Huang, Daoyuan; Zhao, Huan; Ma, Fanjun

    2014-04-01

    An investigation has been conducted to study the effect of Na2O and B2O3 on the crystallization behavior of low fluorine (F) mold powders for casting medium carbon (MC) steels in this article. The results of this study indicated that B2O3 tends to lower the crystallization temperature and increase crystallization incubation time of the low F powders; however, Na2O plays an opposite role compared with that of B2O3. The crystalline phase of Ca11Si4B2O22 was formed in Sample D2 [F = 3 pct, Na2O = 10 pct, B2O3 = 8 pct (in wt pct)], which exhibited the most similar crystallization behavior to that of cuspidine, such that Sample D2 showed closest crystallization kinetics to that of a conventional high-F mold slag for casting MC steels. The precipitated crystalline phases for all the samples have been analyzed and discussed in the article.

  7. Kinetics of Na2O and B2O3 Loss From CaO-SiO2-Al2O3 Slags

    NASA Astrophysics Data System (ADS)

    Li, Mark; Utigard, Torstein; Barati, Mansoor

    2015-02-01

    The present work was carried out to study the loss of Na2O and B2O3 from CaO-SiO2-Al2O3 slags containing high content of Al2O3 and Na2O in the temperature range of 1573 K to 1773 K (1300 °C to 1500 °C). The rate of loss was determined by monitoring the weight change of the slag melt by thermogravimetric analysis under isothermal conditions. As expected, the evaporation rate was found to increase with increasing the temperature. Higher basicity and larger B2O3 and Na2O concentrations were also found to increase the evaporation rate. The evaporation rate appears to be controlled by chemical reaction at the surface in the beginning, followed by a mixed reaction-mass transfer regime, and finally a liquid-phase mass transport step. The apparent activation energies for the evaporation reaction were calculated for different slag compositions.

  8. An ab initio method for the prediction of the lattice thermal transport properties of oxide systems: Case study of Li2O and K2O

    NASA Astrophysics Data System (ADS)

    Gheribi, Amen E.; Seifitokaldani, Ali; Wu, Pearson; Chartrand, Patrice

    2015-10-01

    A method for the prediction of the thermal transport properties of macroscopic and isotropic oxides systems, above the standard temperature of T =298.15 K , is presented. This method combines: (i) the kinetic theory, (ii) a thermodynamically self consistent method for the density of the lattice vibration energy, and (iii) the three-phonon umklapp processes for the description of the phonon-phonon scattering. The proposed approach is purely predictive, as no experimental data are required for the model parameterization; they are derived from ground sate electronic structure calculations. Case studies on Li2O and K2O are presented and discussed. The predicted thermal transport properties are found to be in excellent agreement with available experimental data. The thermal conductivity of K2O is found to differ from the thermal conductivity of Li2O by an order of magnitude. This difference is explained in terms of electron localization within the crystal.

  9. Silicate liquid immiscibility in magmas and in the system K2O-FeO-AI2O3-SiO2: an example of serendipity

    USGS Publications Warehouse

    Roedder, E.

    1978-01-01

    The concept of silicate liquid immiscibility was invoked early in the history of petrology to explain certain pairs of compositionally divergent rocks, but. as a result of papers by Greig (Am. J. Sci. 13, 1-44, 133-154) and Bowen (The Evolution of the Igneous Rocks), it fell into disfavor for many years. The discovery of immiscibility in geologically reasonable temperature ranges and compositions in experimental work on the system K2O-FeO-Al2O3-SiO2, and of evidence for immiscibility in a variety of lunar and terrestrial rocks, has reinstated the process. Phase equilibria in the high-silica corner of the tetrahedron representing the system K2O- FeO-Al2O3-SiO2 are presented, in the form of constant FeO sections through the tetrahedron, at 10% increments. Those sections, showing the tentative relationships of the primary phase volumes, are based on 5631 quenching runs on 519 compositions, made in metallic iron containers in pure nitrogen. Thirteen crystalline compounds are involved, of which at least six show two or more crystal modifica-tions. Two separate phase volumes, in each of which two immiscible liquids, one iron-rich and the other iron-poor, are present at the liquidus. One of these volumes is entirely within the quaternary system, astride the 1:1 K2O:Al2O3 plane. No quaternary compounds as such have been found, but evidence does point toward at least partial quaternary solid solution, with rapidly lowering liquidus temperatures, from K2O??Al2O3?? 2SiO2 ('potash nepheline', kalsilite. kaliophilite) to the isostructural compound K2O??FeO??3SiO2, and from K2O??Al2O3??4SiO2 (leucite) to the isostructural compound K2O??FeO??5SiO2, Both of these series apparently involve substitution, in tetrahedral coordination. of a ferrous iron and a silicon ion for two aluminum ions. Some of the 'impurities' found in analyses of the natural phases may reflect these substitutions. As a result of the geometry of the immiscibility volume located entirely within the quaternary system, compositions near it show a number of phase changes and large amounts of crystallization with small temperature changes, generally in the range 1100-1150 C. Similar low-temperature, high-alkali immiscibility was discovered in a few exploratory runs in the equivalent systems with Rb or Cs substituting for K. But not in those with Li or Na. A review of the compositions and general behavior of systems involving immiscibility, both stable and metastable, and of the evidence for natural immiscibility. indicates that it may be a much more common feature than generally thought. Several examples of natural immiscibility are detailed; most yield a felsic. alkali-aluminosilicate melt and a mafic melt. from a wide variety of generally basaltic parental magmas, both under- and over saturated. Unfortunately, the best line of evidence for immiscibility in terrestrial rocks, a sharply defined meniscus between two compositionally disparate glasses, is by its very nature self-destructing, since it is effectively eliminated by either crystallization or gravitative separation and coalescence into separate magmas. Verification of operation of the exosolutionor 'splitting' process on a large scale will probably require careful study of isotopic and trace element partitioning in both laboratory and field. ?? 1978.

  10. Phase diagram for a portion of the system Ce 2O 3?Na 2O?P 2O 5 rich in P 2O 5

    NASA Astrophysics Data System (ADS)

    Szczygie?, Irena; Znamierowska, Teresa

    1989-10-01

    The phase diagram for a portion of the ternary system Ce 2O 3?Na 2O?P 2O 5 rich in P 2O 5 has been worked out. The durability of two cerium phosphates, CeP 5O 14 and CeP 3O 9, was investigated and the melting point of CeP 5O 14 determined (1064C congruently). Phase diagrams of the two binary systems CeP 3O 9?CeP 5O 14 and NaCe(PO 3) 4?CeP 5O 14 are presented.

  11. CAOS: Code for Adaptive Optics Systems

    NASA Astrophysics Data System (ADS)

    Carbillet, M.; Verinaud, C.; Femenia, B.; Riccardi, A.; Fini, L.

    2011-06-01

    The CAOS "system" (where CAOS stands for Code for Adaptive Optics Systems) is properly said a Problem Solving Environment (PSE). It is essentially composed of a graphical programming interface (the CAOS Application Builder) which can load different packages (set of modules). Current publicly distributed packages are the Software Package CAOS (the original adaptive optics package), the Software Package AIRY (an image-reconstruction-oriented package - AIRY stands for Astronomical Image Restoration with interferometrY), the Software Package PAOLAC (a simple CAOS interface for the analytic IDL code PAOLA developed by Laurent Jolissaint - PAOLAC stands for PAOLA within Caos), and a couple of private packages (not publicly distributed but restricted to the corresponding consortia): SPHERE (especially developed for the VLT planet finder SPHERE), and AIRY-LN (a specialized version of AIRY for the LBT instrument LINC-NIRVANA). Another package is also being developed: MAOS (that stands for Multiconjugate Adaptive Optics Simulations), developed for multi-reference multiconjugate AO studies purpose but still in a beta-version form.

  12. Effect of ZnO on the interfacial bonding between Na 2O-B 2O 3-SiO 2 vitrified bond and diamond

    NASA Astrophysics Data System (ADS)

    Wang, P. F.; Li, Zh. H.; Li, J.; Zhu, Y. M.

    2009-08-01

    Diamond composites were prepared by sintering diamond grains with low melting Na 2O-B 2O 3-SiO 2 vitrified bonds in air. The influence of ZnO on the wettability and flowing ability of Na 2O-B 2O 3-SiO 2 vitrified bonds was characterized by wetting angle, the interfacial bonding states between diamond grains and the vitrified bonds were observed by scanning electron microscope (SEM), and the micro-scale bonding mechanism in the interfaces was investigated by means of energy-dispersive spectrometer (EDS), Fourier transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS). The experimental results showed that ZnO facilitated the dissociation of boron/silicon-oxygen polyhedra and the formation of larger amount of non-bridging oxygen in the glass network, which resulted in the increase of the vitrified bonds' wettability and the formation of -C dbnd O, -O-H and -C-H bonds on the surface of diamond grains. B and Si diffused from the vitrified bonds to the interface, and C-C, C-O, C dbnd O and C-B bond formed on the surface of sintered diamond grains during sintering process, by which the interfacial bonding between diamond grains and the vitrified bonds was strengthened.

  13. Critical Evaluation and Thermodynamic Optimization of the Na2O-FeO-Fe2O3-SiO2 System

    NASA Astrophysics Data System (ADS)

    Moosavi-Khoonsari, Elmira; Jung, In-Ho

    2016-02-01

    A complete literature review, critical evaluation, and thermodynamic optimization of phase diagrams and thermodynamic properties of the Na2O-FeO-Fe2O3-SiO2 system were performed at 1 atm total pressure. A set of optimized model parameters obtained for all phases present in this system reproduces available and reliable thermodynamic properties and phase equilibria within experimental error limits from 298 K (25 °C) to above liquidus temperatures for all compositions and oxygen partial pressures from metallic Fe saturation to 1 atm. The liquid phase was modeled based on the Modified Quasichemical Model considering the possible formation of NaFeO2 associate in the liquid state. The NaFeO2 metaoxide solid solutions containing the excess SiO2 were described within the framework of Compound Energy Formalism. Based on the thermodynamic models and model parameters, unexplored thermodynamic properties and phase diagrams of the Na2O-FeO-Fe2O3-SiO2 system were predicted.

  14. Coded Access Optical Sensor (CAOS) Imager

    NASA Astrophysics Data System (ADS)

    Riza, N. A.; Amin, M. J.; La Torre, J. P.

    2015-04-01

    High spatial resolution, low inter-pixel crosstalk, high signal-to-noise ratio (SNR), adequate application dependent speed, economical and energy efficient design are common goals sought after for optical image sensors. In optical microscopy, overcoming the diffraction limit in spatial resolution has been achieved using materials chemistry, optimal wavelengths, precision optics and nanomotion-mechanics for pixel-by-pixel scanning. Imagers based on pixelated imaging devices such as CCD/CMOS sensors avoid pixel-by-pixel scanning as all sensor pixels operate in parallel, but these imagers are fundamentally limited by inter-pixel crosstalk, in particular with interspersed bright and dim light zones. In this paper, we propose an agile pixel imager sensor design platform called Coded Access Optical Sensor (CAOS) that can greatly alleviate the mentioned fundamental limitations, empowering smart optical imaging for particular environments. Specifically, this novel CAOS imager engages an application dependent electronically programmable agile pixel platform using hybrid space-time-frequency coded multiple-access of the sampled optical irradiance map. We demonstrate the foundational working principles of the first experimental electronically programmable CAOS imager using hybrid time-frequency multiple access sampling of a known high contrast laser beam irradiance test map, with the CAOS instrument based on a Texas Instruments (TI) Digital Micromirror Device (DMD). This CAOS instrument provides imaging data that exhibits 77 dB electrical SNR and the measured laser beam image irradiance specifications closely match (i.e., within 0.75% error) the laser manufacturer provided beam image irradiance radius numbers. The proposed CAOS imager can be deployed in many scientific and non-scientific applications where pixel agility via electronic programmability can pull out desired features in an irradiance map subject to the CAOS imaging operation.

  15. Investigation of thermal and spectroscopic properties of Bi2O3-GeO2-Ga2O3-Na2O glasses doped with Er3+ ions

    NASA Astrophysics Data System (ADS)

    Ragin, Tomasz; Czajkowski, Karol; ?mojda, Jacek; Kochanowicz, Marcin; Dorosz, Dominik

    2014-11-01

    Heavy metal oxide glasses based on the Bi2O3-GeO2-Ga2O3-Na2O system doped with Er3+ ions have been presented.. The influence of glass composition on thermal stability and luminescent properties has been presented. Fabricated glass exhibits emission at 1538 nm (Er3+: 4I13/2 --> 4I15/2) under 980 nm laser diode excitation. Due to different molar content of oxides in samples, various luminescence intensity was observed. High absorption cross-section allowed to determine the gain coefficient at the level of 3.47 cm-1 at the wavelength of 1538 nm. According to the results, fabricated bismuthgermanate glasses should be used for construction of optical waveguides operating in the range of near-infrared.

  16. Effects of caustic sodium concentration and molecular ratio of Na2O to Al2O3 on agglomeration in the precipitation process

    NASA Astrophysics Data System (ADS)

    Liu, Zhanwei; Chen, Wenmi; Li, Wangxing

    2010-11-01

    The supersaturation of sodium aluminate solution (liquor) is a prerequisite for agglomeration and the key factors that determine supersaturation of liquor are caustic sodium concentration (Nk) and molecular ratio of Na2O to Al2O3 (?k). In this paper, the effects of Nk and ?k on the agglomeration process of seeded precipitation were studied. The results show that the Nk plays an important role in the agglomeration process. The supersaturation of liquor decreases with the increasing of Nk and so not only does the precipitation ratio of liquor decrease but also the particle size of agglomerate decreases. The supersaturation of liquor decreases with the increasing of ?k and so the precipitation rate and depth of liquor decrease and thus the agglomeration of fine particles is weakened.

  17. Gels and gel-derived glasses in the system Na2O-B2O3-SiO2

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1983-01-01

    The containerless melting of high-purity multicomponent homogeneous gels and gel monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the system Na2O-B2O3-SiO2 are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures was found to be significantly different. Infrared absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel monoliths to transparent 'glass' without melting are described.

  18. Gels and gel-derived glasses in the Na2O-B2O3-SiO2 system. [containerless melting in space

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1982-01-01

    The containerless melting of high-purity multicomponent homogeneous gels and gel-monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the Na2O-B2O3-SiO2 system are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures were found to be significantly different. IR absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel-monoliths to transparent 'glass' without melting are described.

  19. Upconversion properties of Er3+/Yb3+ co-doped TeO2-TiO2-K2O glasses.

    PubMed

    Su, Fangning; Deng, Zaide

    2006-01-01

    The Er3+/Yb3+ co-doped TeO2-TiO2-K2O glasses were prepared by conventional melting procedures, and their upconversion spectra were performed. The dependence of luminescence intensity on the ratio of Yb3+/Er3+ was studied, and the relationship between green upconversion luminescence intensity and Er3+ concentration is discussed in detail. The 546 nm green upconversion luminescence intensity is optimised in the studied glasses either when the Yb3+/Er3+ ratio is 25/1 and Er3+ concentration is 0.1 mol%, or when the Yb3+/Er3+ ratio is 10/1 and Er3+ concentration is 0.15 mol%. These glasses could be one of the potential candidates for LD pumping microchip solid-state lasers. PMID:16397824

  20. Structural properties of Bi2O3-B2O3-SiO2-Na2O glasses for gamma ray shielding applications

    NASA Astrophysics Data System (ADS)

    Kaur, Kulwinder; Singh, K. J.; Anand, Vikas

    2016-03-01

    Glass samples of the xBi2O3-(0.70-x)B2O3-0.15SiO2-0.15Na2O (where x=0 up to 0.5 mol fraction) have been prepared in the laboratory by using melt quenching technique. 137Cs source has been used for experimental measurements of mass attenuation coefficient of γ-rays at 662 keV. Mass attenuation coefficient of our glass samples has been compared with standard nuclear radiation shield "barite concrete". It has been concluded that bismuth containing glass samples can be potential candidates for γ-ray shielding applications. Glasses must have appreciable elastic moduli values for their practical utility as γ-ray shields which are related to coordination number and non-bridging oxygens. Structural properties including coordination number and non-bridging oxygens of the structural units of the glass system have been estimated from the detailed analysis of Optical, Raman and FTIR spectra. Reported investigations can contribute to the development of transparent gamma ray shields.

  1. Structural investigation in the TiB 2-(Na 2OB 2O 3Al 2O 3) system

    NASA Astrophysics Data System (ADS)

    Buixaderas, Elena; Maria Anghel, Elena; Petrescu, Simona; Osiceanu, Petre

    2010-09-01

    Composites in the TiB 2-Na 2OB 2O 3Al 2O 3 systems, TiB 2-MBA (MB stands for sodium metaborate and A is Al 2O 3), were prepared by self-propagating high-temperature synthesis (SHS), in simultaneous mode. Selection of these compositions was ruled by the interesting properties of both TiB 2 and double borates of alkali metal and aluminum. The structure of the obtained materials was evaluated by micro-Raman spectroscopy, from room temperature up to 600 C, and X-ray photoelectron spectroscopy (XPS). Formation of the TiB 2 and TiO 2- xB x phases along with TiO 2 as rutile were identified as titanium speciation in the grain phase embedded in a sodium aluminum borate matrix. Integration of the Raman spectra of the grain phases revealed a TiB 2 content of 16.99% and 23.32% for the two composite investigated 2TiB 22MBA and 3TiB 25MBA. A constrained-width model for the spectral deconvolution of the high-frequency Raman band was forwarded to calculate the proportion of tetrahedral boron atoms (7.424%) in the blank borate matrix Na 2B 2O 4Al 2O 3 in solid phase.

  2. Preparation and dielectric properties of Nb2O5-BaO-Na2O-SiO2 glass-ceramic for energy storage capacitors

    NASA Astrophysics Data System (ADS)

    Mao, Changhui; Sun, Xudong; Du, Jun; Tang, Qun

    2009-03-01

    Full density Nb2O5-BaO-Na2O-SiO2 Glass-ceramics, which could be used as the dielectric energy-storage materials to fabricate high energy density devices, were prepared by means of rapid quenching and succeeding annealing under different temperature. DTA and X-ray diffraction analysis showed that NaBa2Nb5O15 with tungsten bronze structure and NaNbO3 with perovskite structure were formed as the dielectric phases from the glass matrix at above 750C. Dielectric constant of the crystallized glass-ceramics were measured at the frequency from 100 Hz to 100 kHz under the testing temperature from -40 to 150C. The results indicated that theoretical energy storage density of the material crystallized at 800C could reach up to 1.87x106J/m3, which would be suitable to be used as the innoxious dielectric media for high-energy storage capacitors.

  3. Comparative effects of thermal quenching and ballistic collisions in SiO2-B2O3-Na2O glass

    NASA Astrophysics Data System (ADS)

    Delaye, J.-M.; Peuget, S.; Calas, G.; Galoisy, L.

    2014-05-01

    The differences between the effects of irradiation and thermal quenching were studied in SiO2-B2O3-Na2O glass by molecular dynamics. Classical molecular dynamics simulations reproduced quenching rates between 2 × 1012 K/s and instantaneous quenching. Each configuration was then subjected to a series of displacement cascades. An acceleration of the quenching rate and the accumulation of ballistic collisions result in qualitatively similar effects: swelling, increasing disorder, depolymerization of the glassy network, a decrease in the mean coordination number of B atoms. Nevertheless, ballistic processes induce specific effects that are not reproduced by accelerated quenching: an even larger degree of disorder, higher potential energy, greater depolymerization around B sites and different free volume distribution. The memory of the initial quenching rate is largely lost following an accumulation of displacement cascades, and the structure of the irradiated glasses adopts a final configuration weakly dependant on the initial state. This study shows that comparing the structure of the initial glass prepared at different quenching rates with the structure of irradiated glasses makes it possible to discriminate between thermal quenching and ballistic effects.

  4. Investigating the solubility and cytocompatibility of CaO-Na2 O-SiO2 /TiO2 bioactive glasses.

    PubMed

    Wren, Anthony W; Coughlan, Aisling; Smith, Courtney M; Hudson, Sarah P; Laffir, Fathima R; Towler, Mark R

    2015-02-01

    This study aims to investigate the solubility of a series of titanium (TiO2 )-containing bioactive glasses and their subsequent effect on cell viability. Five glasses were synthesized in the composition range SiO2 -Na2 O-CaO with 5 mol % of increments TiO2 substituted for SiO2 . Glass solubility was investigated with respect to (1) exposed surface area, (2) particle size, (3) incubation time, and (4) compositional effects. Ion release profiles showed that sodium (Na(+) ) presented high release rates after 1 day and were unchanged between 7 and 14 days. Calcium (Ca(2+) ) release presented a significant change at each time period and was also composition dependent, where a reduction in Ca(2+) release is observed with an increase in TiO2 concentration. Silica (Si(4+) ) release did not present any clear trends while no titanium (Ti(4+) ) was released. Cell numbers were found to increase up to 44%, compared to the growing control population, with a reduction in particle size and with the inclusion of TiO2 in the glass composition. PMID:24825479

  5. Role of B2O3 on the Viscosity and Structure in the CaO-Al2O3-Na2O-Based System

    NASA Astrophysics Data System (ADS)

    Kim, Gi Hyun; Sohn, Il

    2013-10-01

    The effect of B2O3 on the viscosity and structure in the calcium-aluminate melt flux system containing Na2O was studied. An increase in the B2O3 content at fixed CaO/Al2O3 ratio lowered the viscosity. Higher CaO/Al2O3 ratio at fixed B2O3 content also decreased the viscosity. The alumino-borate structures were confirmed through Fourier transformed infrared (FTIR) and Raman spectroscopy and consisted of [AlO4]-tetrahedral structural units, [BO3]-triangular structural units, and [BO4]-tetrahedral structural units, which could be correlated to the viscosity. At fixed CaO/Al2O3 ratio, B2O3 additions decreased the [AlO4]-tetrahedral structural units and transformed the 3-D network structures such as pentaborate and tetraborate into 2-D network structures of boroxol and boroxyl rings by breaking the bridged oxygen atoms (O0) to produce non-bridged oxygen atoms (O-) leading to a decrease in the molten flux viscosity. At fixed B2O3 contents and higher CaO/Al2O3 ratio, 3-D complex network structures become 3-D simple and 2-D isolated network structures, resulting in lower viscosities. The apparent activation energy for viscous flow varied from 132 to 249 kJ/mol according to the composition of B2O3 and CaO/Al2O3 ratio.

  6. Optical spectroscopy of Sm(3+) doped Na2O-ZnO-La2O3-TeO2 glasses.

    PubMed

    Sobczyk, Marcin

    2015-10-01

    Telluride glasses with the composition xSm2O3-(7-x)La2O3-3Na2O-25ZnO-65TeO2 (where x=0.1, 1, 2, 5 and 7 mol%) were obtained by the melt quenching technique. Electronic absorption and fluorescence spectra as well as fluorescence dynamics of the Sm(3+)-doped title glasses are presented and analysed in detail. A Judd-Ofelt intensity analysis of the absorption spectrum at 300 K has been applied for determination of ?? parameters (?2=3.10, ?4=3.80, ?6=1.6110(-20) cm(2)) which in turn have been used for calculations of the radiative transition probabilities (AT), the natural (radiative) lifetimes (?R) of the (4)G5/2 level of Sm(3+), the fluorescence branching ratios (?) and the emission cross-sections (?em). The ?R value of the (4)G5/2 level amount to 1546 ?s and is slightly higher than the measured decay time of 1306 ?s. With the increasing of Sm2O3 concentration from 0.1 to 7.0 mol% the experimental lifetime of the fluorescent level decreases from 1306 to 41 ?s. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The optical achieved results indicate that the investigated glasses are potentially applicable as an orange and/or red laser host. PMID:26010564

  7. Caos en sistemas clsico-cunticos

    NASA Astrophysics Data System (ADS)

    Dirani, L. D.; Nez, J. A.

    Una de las formas de estudiar la existencia de caos en el comportamiento de un sistema clsico-cuntico, es truncando el espacio de Hilbert del sistema cuntico. El objetivo de este trabajo es analizar como afecta dicho truncamiento en la dinmica del sistema. Para tal fin se propone un Hamiltoniano integrable, cuyos valores de expectacin asociados a coordenadas y momentos cunticos responden, por el teorema de Ehrenfest, a un sistema de dos osciladores clsicos con acoplamiento lineal.

  8. Impact of neocrystallisations on the SiO2-K2O-CaO glass degradation due to atmospheric dry depositions

    NASA Astrophysics Data System (ADS)

    Gentaz, L.; Lombardo, T.; Chabas, A.; Loisel, C.; Verney-Carron, A.

    2012-08-01

    The medieval SiO2-CaO-K2O stained glasses are particularly vulnerable to the impact of their environment. In the urban atmosphere, they will tend to rapidly deteriorate either by loss of matter or by addition of atmospheric material, that tend to form a crust on the surface of the glass. If the glass surface is protected from the rain run-off, this second phenomenon will be favoured. In the early stage of crust formation, it was shown that primary constituents were salts, called neocrystallisations. However, it is still not clear, if their presence induce further deterioration of the glass matrix. In order to answer this question both field exposure and laboratory experiments were carried out. Model glasses, chosen with compositions similar to those of ancient stained glasses, were exposed to the urban atmosphere in sheltered conditions. Samples exposed were analysed in order to identify the neocrystallisations and further tests were undertaken in order to observe their impact on the glass itself. The analyses of the weathering products on the glasses showed the presence of three principal minerals: syngenite, gypsum, and potassium carbonate. The observed mineral phases were then artificially deposited on model glass surfaces submitted to cycles of relative humidity. It was found that the presence of salts increased the glass degradation by extending the time of wetness of the glass surface and forming saline solutions in the case of deliquescent salts. Evidence of strong leaching could be observed on the glass surface and even more so when considering glass samples in contact with multiple salts. Finally, the impact of potassium carbonate (K2CO3) on the glass was dramatic, since it induced a loss of matter caused by the dissolution of the lattice in contact with the alkaline solution.

  9. Influence of CaF2 and Li2O on the Viscous Behavior of Calcium Silicate Melts Containing 12 wt pct Na2O

    NASA Astrophysics Data System (ADS)

    Park, Hyun Shik; Kim, Hyuk; Sohn, Il

    2011-04-01

    Understanding the viscous behavior of silica-based molten fluxes is essential in maintaining the reliability of steel casting operations and in preventing breakouts. In particular, high concentrations of aluminum in recently developed transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) steels tend to promote reduction of silica in the mold fluxes that result in the formation of alumina, which in turn increases the viscosity. To counteract this effect, significant amounts of fluidizers such as CaF2 and Li2O are required to ensure that mold fluxes have acceptable lubrication and heat transfer characteristics. The viscous behavior of the slag system based on CaO-SiO2-12 wt pct Na2O with various concentrations of CaF2 and Li2O has been studied using the rotating spindle method to understand the effects on the viscosity with these additives. CaF2 additions up to 8 wt pct were effective in decreasing the viscosity by breaking the network structure of molten fluxes, but CaF2 concentrations above this level had a negligible effect on viscosity. Li2O additions up to 2 wt pct were also effective in decreasing the viscosity, but the effect was comparatively negligible above 2 wt pct. Using Fourier transform infrared (FTIR) analysis of as-quenched slag samples, it was concluded that the viscosity was controlled more effectively by changing the larger complex silicate structures of rings and chains than by changing the amounts of simpler dimers and monomers.

  10. Melt structure effect on Thorium and Uranium partitioning between monazite and Na2O-Al2O3-SiO2 melts

    NASA Astrophysics Data System (ADS)

    Xing, L.; Trail, D.; Watson, E. B.

    2010-12-01

    Monazite is an increasingly important accessory mineral in granitic rocks that exerts a powerful control on the REE, Th and U fractionation during crystallization. To understand the effect of melt structure on Th and U partitioning behavior, partition coefficients between monazite and co-existing melt have been determined by crystallization experiments at 1000C and 1GPa with 8-10 wt. % H2O , and fO2 was buffered by NiNiO. -Experiments starting with ThO2-, UO2- and CePO4-doped artificially Na2O-Al2O3-SiO2 (NAS) glass have been carried out in a piston cylinder apparatus at constant P-T conditions for 48 hrs. The NAS system is used as an analogue of more complex magmas, since its structure is a function of the ratio of the network-forming elements (Al,Si) to network-modifying element (Na). Quenched crystals and glasses were analyzed by electron probe. Our results demonstrate that at constant SiO2 content, both DTh and Du are functions of Na/Al between Na/Al=0.5-2.4. D values decrease with increasing peralkaline (Na/Al>1) or peraluminous (Na/Al<1) glass composition and have a maximum value around where Na/Al 1. Uranium is incompatible in monazites in extremely peraluminous (Na/Al<0.6) and peralkaline (Na/Al>1.2) melts, but compatible in monazites in subaluminous melts. Th is compatible in monazites in all melts examined but can vary by a factor of three. At 75 wt. % SiO2, a change in melt Na/Al from 0.53 to 0.93 causes the Th partition coefficients to increase from ~90 to ~300.

  11. Phase evolution of Na2O-Al2O3-SiO2-H2O gels in synthetic aluminosilicate binders.

    PubMed

    Walkley, Brant; San Nicolas, Rackel; Sani, Marc-Antoine; Gehman, John D; van Deventer, Jannie S J; Provis, John L

    2016-04-01

    This study demonstrates the production of stoichiometrically controlled alkali-aluminosilicate gels ('geopolymers') via alkali-activation of high-purity synthetic amorphous aluminosilicate powders. This method provides for the first time a process by which the chemistry of aluminosilicate-based cementitious materials may be accurately simulated by pure synthetic systems, allowing elucidation of physicochemical phenomena controlling alkali-aluminosilicate gel formation which has until now been impeded by the inability to isolate and control key variables. Phase evolution and nanostructural development of these materials are examined using advanced characterisation techniques, including solid state MAS NMR spectroscopy probing (29)Si, (27)Al and (23)Na nuclei. Gel stoichiometry and the reaction kinetics which control phase evolution are shown to be strongly dependent on the chemical composition of the reaction mix, while the main reaction product is a Na2O-Al2O3-SiO2-H2O type gel comprised of aluminium and silicon tetrahedra linked via oxygen bridges, with sodium taking on a charge balancing function. The alkali-aluminosilicate gels produced in this study constitute a chemically simplified model system which provides a novel research tool for the study of phase evolution and microstructural development in these systems. Novel insight of physicochemical phenomena governing geopolymer gel formation suggests that intricate control over time-dependent geopolymer physical properties can be attained through a careful precursor mix design. Chemical composition of the main N-A-S-H type gel reaction product as well as the reaction kinetics governing its formation are closely related to the Si/Al ratio of the precursor, with increased Al content leading to an increased rate of reaction and a decreased Si/Al ratio in the N-A-S-H type gel. This has significant implications for geopolymer mix design for industrial applications. PMID:26911317

  12. In vitro bioactivity evaluation, mechanical properties and microstructural characterization of Na2O-CaO-B2O3-P2O5 glasses

    NASA Astrophysics Data System (ADS)

    Abo-Naf, Sherief M.; Khalil, El-Sayed M.; El-Sayed, El-Sayed M.; Zayed, Hamdia A.; Youness, Rasha A.

    2015-06-01

    Na2O-CaO-B2O3-P2O5 glasses have been prepared by the melt-quenching method. B2O3 content was systematically increased from 5 to 30 mol%, at the expense of P2O5, in the chemical composition of these glasses. Density, Vickers microhardness and fracture toughness of the prepared glasses were measured. In vitro bioactivity of the glasses was assessed by soaking in the simulated body fluid (SBF) at 37 0.5 C for 3, 7, 14 and 30 days. The glasses were tested in the form of glass grains as well as bulk slabs. The structure and composition of the solid reaction products were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The kinetics of degradation of the glass particles were monitored by measuring the weight loss of the particles and the ionic concentration of Ca, P and B in the SBF solution using inductive coupled plasma-atomic emission spectroscopy (ICP-AES). The obtained results revealed the formation of a bioactive hydroxyapatite (HA) layer, composed of nano-crystallites, on the surface of glass grains after the in vitro assays. The results have been used to understand the formation of HA as a function of glass composition and soaking time in the SBF. It can be pointed out that increasing B2O3 content in glass composition enhances the bioactivity of glasses. The nanometric particle size of the formed HA and in vitro bioactivity of the studied glasses make them possible candidates for tissue engineering application.

  13. Influence of fluoride additions on biological and mechanical properties of Na2O-CaO-SiO2-P2O5 glass-ceramics.

    PubMed

    Li, H C; Wang, D G; Hu, J H; Chen, C Z

    2014-02-01

    Two series of Na2O-CaO-SiO2-P2O5 glass-ceramics doped with NH4HF2 (G-NH4HF2) or CaF2 (G-CaF2) have been prepared by sol-gel method. The glass-ceramic phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The mechanical properties and thermal expansion coefficient were measured by a microhardness tester, an electronic tensile machine and a thermal expansion coefficient tester. The structure difference between these two glass-ceramics was investigated by Fourier transform infrared spectroscopy (FTIR), and the in vitro bioactivity of the glass-ceramics was determined by in vitro simulated body fluid (SBF) immersion test. The hemolysis test, in vitro cytotoxicity test, systemic toxicity test and the implanted experiment in animals were used to evaluate the biocompatibility of the glass-ceramics. The mechanical properties of sample G-NH4HF2 are lower than that of sample G-CaF2, and the bioactivity of sample G-NH4HF2 is better than that of sample G-CaF2. The thermal expansion coefficients of these two glass-ceramics are all closer to that of Ti6Al4V. After 7 days of SBF immersion, apatites were induced on glass-ceramic surface, indicating that the glass-ceramics have bioactivity. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the glass-ceramics do not cause hemolysis reaction, and have no toxicity to cell and living animal. The implanted experiment in animals shows that bone tissue can form a good osseointegration with the implant after implantation for two months, indicating that the glass-ceramics are safe to serve as implants. PMID:24411365

  14. Interfacial tension between immiscible melts in the system K2O - FeO - Fe2O3 - Al2O3 - SiO2

    NASA Astrophysics Data System (ADS)

    Kaehn, J.; Veksler, I. V.; Franz, G.; Dingwell, D. B.

    2009-12-01

    Interfacial tension is a very important parameter of the kinetics of phase nucleation, dissolution and growth. Excess surface energy contributes to the energy barrier for phase nucleation, and works as the main driving force for minimization of phase contact surfaces in heterogeneous systems. Immiscible silicate melts have been found to form in a broad range of basaltic, dacitic and rhyolitic magmas (Philpotts, 1982). However, liquid-liquid interfaces remain poorly studied in comparison with crystal-melt and vapor-melt interfaces. Here we present first experimental measurements of interfacial tension between synthetic Fe-rich and silica-rich immiscible melts composed of Fe oxides, K2O, alumina and silica. According to Naslund (1983), the miscibility gap in the 5-oxide system expands with increasing fO2 and becomes widest in air (fO2 = 0.2). Our goal was to estimate the maximal liquid-liquid interfacial tension for the immiscible liquids composed of silica and Fe oxides. Therefore, we have chosen the most contrasting liquid compositions that coexist in air at and above 1465 C. Silica-rich and Fe-rich conjugate liquids at these conditions contain 73 and 17 wt. % SiO2, and 14 and 80 wt. % FeOt, respectively. These starting compositions were synthesized by fusion of reagent-grade oxides and K2CO3 at 1600 C. In addition to interfacial tension, we have measured density and surface tension of individual coexisting liquids. All the measurements were done at 1500, 1527 and 1550 C. Density was measured by the Archimedean method; surface and interfacial tensions were calculated from the maximal pool on a vertical cylinder (a 3-mm Pt rod attached to a high precision balance). We found interfacial tension between the immiscible liquids to decrease with increasing temperature from 16.42 mN/m at 1500 C to 8.20.8 mN/m at 1550 C. These values are approximately 2 orders of magnitude lower than typical interfacial tensions between silicate melts and crystals (Wanamaker and Kohlstedt, 1991), or 20-40 times lower than the surface tension of natural lavas in air (Walker and Mullins, 1981). Interfacial tension between natural, less compositionally contrasting ferrobasaltic and rhyolitic melts should be even lower by a factor of 2 or 3. Very low interfacial tension implies easy nucleation of immiscible liquid droplets, and very slow coarsening of silicate emulsions. The results of interfacial tension measurements corroborate protracted stability of sub-micron immiscible silicate emulsions that we observed in our previous immiscibility experiments. References Naslund H.R. (1983) Am. J. Sci. 283, 1034-1059. Philpotts A.R. (1982) Contrib. Mineral. Petrol. 80, 201-218. Walker D. and Mullins Jr. O. (1981) Contrib. Mineral. Petrol. 76, 455-462. Wanamaker B.J. and Kohlstedt D.L. (1991) Phys. Chem. Minerals, 18, 26-36.

  15. Thermodynamic modeling of melts in the system Na 2O-NaAlO 2-SiO 2-F 2O -1

    NASA Astrophysics Data System (ADS)

    Dolej, David; Baker, Don R.

    2005-12-01

    Fluorine is a common volatile element in magmatic-hydrothermal systems, but its solution mechanisms and thermodynamic description in highly polymerized silicate melts are poorly known. We have developed a thermodynamic model for fluorosilicate liquids that links experimentally determined phase equilibria and spectroscopic information on melt structure. The model is applicable to crystallization of fluoride minerals, fluoride-silicate immiscibility in natural felsic melts, and metallurgical processes. Configurational properties of fluorosilicate melts are described by mixing on three site levels (sublattices): (1) alkali fluoride, polyhedral aluminofluoride and silicofluoride species and nonbridging terminations of the aluminosilicate network, (2) alkali-aluminate and silicate tetrahedra within the network and (3) bridging oxygen, nonbridging oxygen and terminal fluorine atoms on tetrahedral apices of the network. Abundances of individual chemical species are described by a homogeneous equilibrium representing melt depolymerization: F - (free) + O 0 (bridging) = F 0 (terminal) + O - (nonbridging) which corresponds to a replacement of an oxygen bridging two tetrahedra by a pair of terminations, one with F and the other with an O and a charge-balancing Na. In cryolite-bearing systems two additional interaction mechanisms occur: (1) the self-dissociation of octahedral aluminofluoride complexes: [AlF 6] = [AlF 4] + 2 [F], and (2) the short-range order between (O,F)-corners and (Si,NaAl)-centers of tetrahedra: Si-O-Si + 2 [NaAl]-F = [NaAl]-O-[NaAl] + 2 Si-F. Portrayal of these equilibria in ternary Thompson reaction space allows for the decrease in the number of interaction mechanisms by linearly combining melt depolymerization with tetrahedral short-range order. In this formulation, the nonideal thermodynamic properties are represented by reaction energies of homogeneous equilibria, thus defining directly individual chemical species concentrations and configurational properties. Thermodynamic expressions for the activity-composition relationships are simplified if all entities are expressed using symbolic molecular notation (e.g., SiO 2, SiF 4, [NaAl]O 2, [NaAl]F 4, NaF etc.) with corresponding nonfractional site multiplicities (1, 2 or 4). The model has been applied to three subsystems of the Na 2O-NaAlO 2-SiO 2-F 2O -1 compositional space. Activity-composition relationships in the villiaumite-sodium silicate binaries require clustering of silicate tetrahedra and only negligible interaction between fluoride species and silicate polymer. Phase equilibria in the cryolite-albite system with a large depression of albite liquidus are interpreted via complete substitution of O 0 by O - and F 0 in the silicate framework. With increasing fluorine content, initial Al-F and Si-O short-range order evolves into the partial O-F disorder. The present model provides a useful relationship between experimental equilibria, macroscopic thermodynamics and melt speciation, thus it facilitates comparisons with, and interpretations of, spectroscopic and molecular simulation data.

  16. Rheology and Structure of Chlorine, Fluorine and Water-Bearing Na2O-CaO-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Baasner, A.; Schmidt, B.; Webb, S. L.; Dupree, R.

    2012-12-01

    The effect of chlorine (Cl), fluorine (F) and water (H2O), alone and in combination, on the rheology and structure of synthetic peralkaline Na2O-CaO-Al2O3-SiO2 melts as an analog for highly evolved alkaline melts is investigated. We also investigated a peraluminous counterpart to study how the effect of Cl and F depends on the (Na+Ca)/Al ratio. The volatile-free melts were produced from oxide and carbonate powders at 1 atm and temperatures between 1200 and 1650 C. Amounts of 0.5 to 1.3 mol% of Cl and 0.5 to 18 mol% F were added as NH4Cl, NH4F, NaCl, NaF, CaCl2 and CaF2. The composition of the samples was analysed by electron microprobe. The melts were hydrated with 0.5 to 4 wt% H2O. For the hydration of the peralkaline melts we used an internally heated pressure vessel at 1200 to 1250 C and 1.5 to 3 kbar. Because of their high liquidus temperatures, the peraluminous melts were hydrated at 1600 to 1675C and 5 kbar in a piston cylinder apparatus. Water contents were determined by Karl-Fischer-titration, thermogravimetry and IR-spectroscopy. The viscosities of the dry and hydrous peralkaline and peraluminous melts were measured with micropenetration and parallel plate techniques between 13 log10(Pa s) and 5.5 log10(Pa s). We found that the addition of 1.1 mol% Cl to peralkaline melts increased the viscosity by 0.8 log10(Pa s) while 1.9 mol% F decreased the viscosity by 1.2 log10(Pa s) relative to a viscosity of 12 log10(Pa s) of the halogen-free melt. In peralkaline melts containing equal amounts of both, Cl and F, the viscosity is 0.5 log10(Pa s) lower than the volatile-free melt, independent of the total amount of halogens. The effects of Cl and F seem to buffer each other. If there is twice as much F in the melt as Cl, the viscosity is reduced by 0.7 log10(Pa s). In peraluminous melts containing Cl and F the viscosity decreases with increasing volatile content independent of the ratio between the two volatiles. The addition of H2O decreases the viscosity of the peralkaline halogen-free melt by 3.4 log10(Pa s) at ~0.5 wt% H2O and 9.2 log10(Pa s) at ~4 wt% H2O. In both melts F and Cl seem to have no strong influence on the viscosity lowering effect of H2O. The local glass structure was investigated with 19F and 35Cl MAS NMR. Our data show that the F environment has at least 4 sites in the peralkaline melts, more than in the peraluminous melts, where there are 2 different sites. In the peralkaline melts there is a speciation change of F depending on the total amount of F. Cl is located in "salt-like" mixed Ca and Na environments in the peralkaline and peraluminous melts. As the Ca/(Na+Ca) ratio is ~0.16, Na is more prominent in the mixed sites. However, compared to the peralkaline melts Ca becomes slightly more important in the Cl-environment in the peraluminous melts.

  17. The Effect of Chlorine on the Rheology of Na2O-Fe2O3-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Zimova, M.; Webb, S.

    2004-12-01

    Because of the high fluid mobility of chlorine, the mantle wedge in subduction zone settings may be enriched in chlorine by the fluids released by the subducted altered oceanic crust plus sediments. The presence of chlorine (and other halogens) will affect the solidus temperature and the rheology of melts, thus influencing the magma evolution, eruption and degassing. Very little is known about the solubility mechanism and diffusivity of Cl in silicate melts and even less is known about the effect of Cl on viscosity. The present study addresses the effect of the halogen chlorine on the viscosity of silicate melts. The shear viscosities of Cl-bearing melts in the system Na2O-Fe2O3-Al2O3-SiO2 were determined over the temperature range 550-950C at room pressure in air. Viscosities were determined using the micropenetration technique in the range of 108.5 to 1012.0 Pa s. The compositions are based on addition of Fe2O3 or FeCl3 to aluminosilicate glasses with a fixed amount of SiO2 (67 mol %). Although there was loss of Cl- during the glass syntheses, no loss occurred during the viscometry experiments. It is to be expected that Cl- takes the structural position of an oxygen, and thus reduces the polymerization of the melt structure, and therefore the viscosity of the melt; as F- does. Our measurements show that, depending upon the melt composition, the addition of Cl- will either increase or decrease the viscosity of the melt. In the present melts at least 20% of the iron exists as network modifying, viscosity reducing Fe2+; while the rest exists as network forming Fe3+. It is proposed here that the different effects of chlorine on viscosity are due to the preferred Cl--Fe2+NBO bonding together with the different structure of peralkaline and peraluminous melts. In peralkaline aluminosilicate melts, the addition of Cl2O-1 will destroy 2 NBOs and create one BO if Cl- bonds primarily to the Fe2+ creating non-bridging oxygens. This would result in an increase in viscosity. In peraluminous melts, the addition of Cl2O-1 may result in Cl- bonds to the charge-balancing Fe2+, creating 2 new tri-clusters (assuming (Al3+, Fe3+)Si2O5 tri-clusters exist). The viscosity should then decrease due to the weaker bonds of the charge balancing Fe2+-Cl- units. The preference of Cl- to form bonds to the NBO-forming Fe2+ is indicated by the small amount of Cl- soluble in the peraluminous melt structure in comparison to that soluble in the peralkaline structure.

  18. CAOS spectroscopy of Am stars Kepler targets

    NASA Astrophysics Data System (ADS)

    Catanzaro, G.; Ripepi, V.; Biazzo, K.; Bus, I.; Frasca, A.; Leone, F.; Giarrusso, M.; Munari, M.; Scuderi, S.

    2015-07-01

    The Kepler space mission and its K2 extension provide photometric time series data with unprecedented accuracy. These data challenge our current understanding of the metallic-lined A stars (Am stars) for what concerns the onset of pulsations in their atmospheres. It turns out that the predictions of current diffusion models do not agree with observations. To understand this discrepancy, it is of crucial importance to obtain ground-based spectroscopic observations of Am stars in the Kepler and K2 fields in order to determine the best estimates of the stellar parameters. In this paper, we present a detailed analysis of high-resolution spectroscopic data for seven stars previously classified as Am stars. We determine the effective temperatures, surface gravities, projected rotational velocities, microturbulent velocities and chemical abundances of these stars using spectral synthesis. These spectra were obtained with CAOS, a new instrument recently installed at the observing station of the Catania Astrophysical Observatory on Mt Etna. Three stars have already been observed during quarters Q0-Q17, namely: HD 180347, HD 181206 and HD 185658, while HD 43509 was already observed during K2 C0 campaign. We confirm that HD 43509 and HD 180347 are Am stars, while HD 52403, HD 50766, HD 58246, HD 181206 and HD 185658 are marginal Am stars. By means of non-LTE (local thermodynamic equilibrium) analysis, we derived oxygen abundances from O I ?7771-5 triplet and we also discussed the results obtained with both non-LTE and LTE approaches.

  19. Correlation between etch pits formed by molten KOH+Na2O2 etching and dislocation types in heavily doped n+-4H-SiC studied by X-ray topography

    NASA Astrophysics Data System (ADS)

    Yao, Yongzhao; Ishikawa, Yukari; Sugawara, Yoshihiro; Sato, Koji; Danno, Katsunori; Suzuki, Hiroshi; Bessho, Takeshi; Yamaguchi, Satoshi; Nishikawa, Koichi

    2013-02-01

    X-ray topography (XRT) has been carried out to examine the accuracy of KOH+Na2O2 etching (KN etching) technique which was recently developed for identifying dislocation types in n+-4H-SiC (n>1019 cm-3). Precise one-to-one correlation have been found between the position of etch pits and dislocations revealed by XRT. More importantly, XRT observation has also confirmed the validity of using the pit sizes formed by KN etching to distinguish threading screw dislocations from threading edge dislocations.

  20. Near-infrared dispersion and spin-orbit interaction of Co doped (80 - x)Sb2O3-20Na2O-xWO3 glasses

    NASA Astrophysics Data System (ADS)

    Petkova, P.; Vasilev, P.; Mustafa, M.; Parushev, I.; Soltani, M. T.

    2016-01-01

    The present paper discusses the fact that the absorption spectra of doped with 0.1% Co3O4 glasses with the composition (80 - x)Sb2O3-20Na2O-xWO3 are measured in the spectral region 1200-1400 nm. The optical structure of Co2+ is analyzed and the energies of the electron transitions in the metal ion are determined. The spin-orbit interaction is thoroughly analyzed. The refractive index n is calculated for the examined sample with x = 20 mol% WO3.

  1. Near-infrared dispersion and spin-orbit interaction of Co doped (80-x)Sb2O3-20Na2O-xWO3 glasses.

    PubMed

    Petkova, P; Vasilev, P; Mustafa, M; Parushev, I; Soltani, M T

    2016-01-01

    The present paper discusses the fact that the absorption spectra of doped with 0.1% Co3O4 glasses with the composition (80-x)Sb2O3-20Na2O-xWO3 are measured in the spectral region 1200-1400nm. The optical structure of Co(2+) is analyzed and the energies of the electron transitions in the metal ion are determined. The spin-orbit interaction is thoroughly analyzed. The refractive index n is calculated for the examined sample with x=20mol% WO3. PMID:26253439

  2. Effect of Agitation on Crystallization Behavior of CaO-Al2O3-SiO2-Na2O-CaF2 Mold Fluxes with Varying Basicity

    NASA Astrophysics Data System (ADS)

    Li, Jiangling; Shu, Qifeng; Chou, Kuochih

    2015-08-01

    The effect of agitation on crystallization behaviors of CaO-Al2O3-SiO2-Na2O-CaF2 mold fluxes with basicity of 1.1 and 1.2 was investigated. It was found that crystallization temperatures of agitated samples were higher than those of static samples. The morphology of cuspidine shifted from dendrites to facet crystals with the decrease of temperature. The agitation was conducive to the formation of small dendritic cuspidine and could lead to crystals with smaller size. Crystalline fraction could be significantly enhanced by agitation at the initial stage of crystallization.

  3. Effect of Vacuum Heat Treatment on Dielectric Properties of PbO-BaO-Na2O-Nb2O5-SiO2 Glass-Ceramic

    NASA Astrophysics Data System (ADS)

    Zhou, Hao; Zhang, Qingmeng; Tang, Qun; Cui, Hang; Xu, Yaohua; Lin, Chen-guang; Du, Jun

    2015-10-01

    The effect of vacuum heat treatment on the dielectric properties of PbO-BaO-Na2O-Nb2O5-SiO2 glass-ceramic has been investigated. Results demonstrate that the dielectric constant, dielectric loss, and resistivity remain stable up to 700C, yet substantial deterioration of the dielectric constant occurred when exceeding 700C. X-ray diffraction spectra confirm that the deterioration was not due to phase transformation, but could be attributed to oxygen vacancies, as supported by x-ray photoelectron spectroscopy results.

  4. Effects of CaO/P2O5 ratio on the structure and elastic properties of SiO2-CaO-Na2O-P2O5 bioglasses.

    PubMed

    Lin, Chung-Cherng; Chen, Shih-Fan; Leung, Kak Si; Shen, Pouyan

    2012-02-01

    The evolution of elastic properties and structure upon the change of CaO/P(2)O(5) ratio in SiO(2)-CaO-Na(2)O-P(2)O(5) glasses (45S5-derived and 55S4-derived) at ambient conditions has been studied by using both Brillouin and Raman spectroscopy coupled with X-ray diffraction. Under the same SiO(2)/Na(2)O ratio, it is found that a decrease in CaO/P(2)O(5) molar ratio has caused a more-polymerized silicate network via a net consumption of Q(0), Q(1), and Q(2) species yet enriching in Q(3) and Q(4) species. Brillouin experiments revealed that all the bulk, shear and Young's moduli of the glasses studied increases with the increase of CaO/P(2)O(5) molar ratio. The unexpected variation trend in shear modulus can be correlated to the contribution from cohesion, the less-polymerized phosphate Q species, and density. Compared to the 45S5-derived, the more-polymerized 55S4-deived glass has a lower bulk but slightly higher shear modulus at the given CaO/P(2)O(5) ratio. PMID:22109904

  5. Approche thermodynamique de la corrosion des refractaires aluminosiliceux par le bain cryolithique : modelisation thermodynamique du systeme quaternaire reciproque AlF3-NaF-SiF 4-Al2O3-Na2O-SiO2

    NASA Astrophysics Data System (ADS)

    Lambotte, Guillaume

    The main objective of this thesis is the thermodynamic modeling of liquid and solid solutions, the stoichiometric compounds and the gaseous phase of the chemical system which represent the species involved in the corrosion of the refractory lining of the electrolysis cell. This chemical system is the quaternary reciprocal system AlF3-NaF-SiF4-Al 2O3-Na2O-SiO2 with aluminum and carbon. The modeling of the entire reciprocal system has never been realized before and is very challenging due to the nature of the oxyfluoride solution. The thermodynamic modeling is based on Gibbs free energy functions coming from the theory of solutions. The central hypothesis of this project is that, if it is possible to reproduce the strong short-range ordering observed between the ions of the liquid solution, then reasonable results will be obtained for the phase equilibria involved in this chemical system. The thermodynamic model used in this thesis is the Modified Quasichemical Model in the Quadruplet Approximation (MQMQA) which takes into account the short-range ordering between first- and also second-nearest-neighbors, and is the best suited to model the oxyfluoride liquid solution. First, the reciprocal system with the most negative Gibbs free energy change for the exchange reaction between the end-members, NaF-SiF4-Na 2O-SiO2, was modeled, allowing thus the validation of the recent modifications of the MQMQA aimed at improving the modeling of the thermodynamic properties of reciprocal solutions presenting a strong short-range order among first-nearest neighbors as well as second-nearest neighbors. In order to model this system, an estimate of the thermodynamic properties of the hypothetical SiF4 liquid was necessary. The experimental data in the binary systems NaF-SiF4 and Na2O-SiO2 are reproduced within the experimental error limits. In the reciprocal system, a group of data in conflict with all others could not be reproduced. The data considered reliable are well reproduced. A unique set of parameters was used to reproduce all the reciprocal sections and extrapolations outside these sections should be satisfactory. The ternary system Al2O3-Na2O-SiO 2 and the ternary reciprocal system AlF3-NaF-Al2O 3-Na2O have been treated jointly due to the fact that compromises were necessary for the optimization of the system common to the two systems, Al2O3-Na2O, in particular for the β-alumina solid solution. The numerous experimental data relative to the thermodynamic properties of the stoichiometric or the solid solutions in the ternary system have been taken into account for the modeling of NaAlSiO4 and NaAlSi 3O8. Furthermore, the cation NaAl4+, used in the modeling to reproduce the charge compensation effect (substitution of Si4+ by Al3+ coupled to Na+ in the SiO2-rich region of the ternary oxide system), is present in both of these systems and the properties of the end-members related to it (NaAlF4 and NaAlO2) have been adjusted to reproduce the thermodynamic properties of the liquid phase. The absence or lack of experimental data in specific composition regions, in particular in the Na2O-rich region in the oxide system or in the oxide-rich region of the reciprocal system, makes the optimization of these two systems difficult. The modeling of the quaternary reciprocal system Al, Na, Si // F, O has been performed mainly by taking into account the experimental data available in the isoplethal sections NaF-NaAlSiO4, NaF-NaAlSi3O 8, Na3AlF6-NaAlSiO4 and Na3AlF 6-NaAlSi3O8 and by using the model parameters allowing the adjustment of the thermodynamic properties of the liquid solution in the composition region under consideration. The few available data and the conflict among them, undoubtedly related to the experimental difficulties, make the modeling of the quaternary reciprocal system complex. (Abstract shortened by UMI.).

  6. The CAOS problem-solving environment: recent developments

    NASA Astrophysics Data System (ADS)

    Carbillet, Marcel; Desider, Gabriele; Augier, Evelyne; La Camera, Andrea; Riccardi, Armando; Boccaletti, Anthony; Jolissaint, Laurent; Ab Kabir, Diyana

    2010-07-01

    We present recent developments of the CAOS problem-solving environment (PSE), an IDL-based software tool whose original aim was to define and simulate as realistically as possible the behavior of a generic adaptive optics (AO) system -from the atmospheric propagation of light, to the sensing of the wave-front aberrations and the correction through a deformable mirror- but which results in a widely more general tool now. In fact, the different developments made through the last years result in a very versatile numerical tool complete of a global graphical interface (the CAOS Application Builder), a general utilities library (the CAOS Library), and different packages dedicated to a wide range of astronomical-optics-related scientific topics: the original package designed for end-to-end AO system simulations (the Software Package CAOS), an image simulation/ reconstruction package with interferometric capabilities (the Software Package AIRY), an extension of the latter specialized for the LBT instrument LINC-NIRVANA (the Software Package AIRY-LN), an ad hoc package dedicated to the VLT instrument SPHERE (the Software Package SPHERE), and an embedment of the analytical AO simulation code PAOLA (the Software Package PAOLAC).We present the status of the whole CAOS PSE, together with the most recent developments, and plans for the future of the overall tool.

  7. Fluid compositions in equilibrium with silica-undersaturated magmas in the system Na2O-Al2O3-SiO2-H2O: clues to the composition of fenitizing fluids

    NASA Astrophysics Data System (ADS)

    Preston, Robin; Stevens, Gary; McCarthy, Terence

    2002-11-01

    Fenites result from alkali metasomatism of granitoid rocks associated with the intrusion of silica-undersaturated alkaline magmas, and are characterized by addition of alkalis, iron and magnesium, albitization, nephelinization, removal of silica and the formation of alkali pyroxenes and amphiboles. In an attempt to constrain the fluid compositions involved in this process, we have investigated the compositions of the fluids in equilibrium with a range silica-undersaturated alkaline magmas, in the model system Al2O3-Na2O-SiO2-H2O at 850 C and 1 kbar. The starting compositions straddle the nepheline-albite join, and include both peralkaline and alkali-granitoid compositions. The quenched run products all contained a glass, representing the melt, as well as an aqueous fluid and a radial crystalline phase interpreted to be a fluid quench phase. Several of the glasses also contained albite, nepheline or quartz crystals. Fluid compositions in crystal-free experiments were calculated using a mass-balance approach that incorporated the composition of the glass, composition of starting materials and carefully determined masses of the different run product fractions, as well as that of the starting materials. Compositions plotting to the peralkaline side of the nepheline-albite join produced fluids that were highly enriched in dissolved solids (SiO2 + Al2O3 + Na2O, in the range 40-50 wt%). This substantial fractionation of the solid starting materials, between melt and fluid phase, results in reasonable resolution of the fluid compositions produced, despite significant uncertainties in the measured Na2O and H2O concentrations in the glasses. Model calculations indicate that the fluid compositions in equilibrium with the more SiO2 undersaturated melt compositions in this study are capable of converting a typical granodiorite to a nepheline syenite composition at fluid/rock ratios lower than 1:1. Albitization and the removal of quartz (in the form of soluble sodium metasilicate), formation of sodic pyroxenes (acmite) and ultimately nepheline are characteristic of the process modeled here. These are largely analogous to the general features observed in some natural fenites.

  8. Adaptive Optics simulations with CAOS: application to exoplanets detection

    NASA Astrophysics Data System (ADS)

    Vrinaud, C.; Carbillet, M.

    In this paper we present some preliminary simulations concerning adaptive-optics-aided coronagraphy. The starting point used for this goal is the software system CAOS (Code for Adaptive Optics System), because of the simulation design ease given by its graphical programming environment, and the completeness and flexibility of its set of modules dedicated to adaptive optics (AO) simulations. We have so developed the complementary numerical tools necessary to implement the Coronographe Interfrentielle Achromatique (CIA) within CAOS, together with differential imaging, and considering Fresnel propagation through the turbulent atmosphere. Hence we give an example of application to exoplanet detection with the characteristics of the Very Large Telescope AO system NAOS and the CIA. Finally, we also discuss on some other recent developments concerning CAOS.

  9. Ultra large amplification bandwidth of Er3+ and Tm3+ at S and L band from TeO2-WO3-Na2O-Nb2O5 glass doped optical fibers

    NASA Astrophysics Data System (ADS)

    Chillcce, E. F.; Osorio, Sergio P.; Rodriguez, Eugenio; Cesar, Carlos Lenz; Barbosa, Luiz C.

    2005-04-01

    Tellurite glasses optical fibers became promising for optical amplifiers due to its high rare earth ions solubility and very large amplification bandwidth. Among several tellurite glasses the TeO2-WO3-Na2O-Nb2O5 system show one of the largest bandwidth. Our previous characterization of lifetime using the omega2, omega4, omega6, Judd-Ofelt parameters indicate a quantum efficiency maximum for 7500ppm Er3+ concentration. Therefore we decided to produce jointed Er3+ and Tm3+ single mode optical fibers with this glass system keeping the 7500ppm Er3+ concentration and varying the Tm3+ concentration from 2500ppm to 15000ppm. This single mode fiber was pumped by 120mW of the semiconductor laser at 790nm and we observed a flat ASE bandwidth from 1400 to 1570nm for the 5000ppm Tm3+ concentration.

  10. Thermal Stability and Infrared-To Upconversion Emissions of Er3+/Yb3+ Co-Doped 70GeO2-20PbO-10K2O Glasses

    NASA Astrophysics Data System (ADS)

    Ahmed, Samah M.; Shaltout, I.; Badr, Y.

    2011-06-01

    Er3+/Yb3+ co-doped potassium-lead-germanate (70GeO2-20PbO-10K2O) glasses with a fixed concentration of Er3+ ions (0.5 mol. %) and different concentrations of Yb3+ ions (0, 0.5, 1.5, and 2.5 mol. %), have been synthesized by the conventional melting and quenching method. The structure and vibrational modes of the glass network were investigated by the infrared absorption and Raman spectroscopy. The thermal behavior of all glass samples was investigated by the differential thermal analysis. Infrared-to-visible frequency upconversion process was investigated in all glasses. Intense green and red upconversion emission bands centered at around 532, 546, and 655 nm were observed, underallglasses.Intense excitation at 980 nm of diode laser at room temperature. The dependence of these emissions on the excitation power was investigated.

  11. INVESTIGATION OF PRODUCT-LAYER DIFFUSIVITY FOR CAO SULFATION

    EPA Science Inventory

    The paper gives results of comparisons of the sulfation rates of CaO prepared from Ca(OH)2 and CaCO3, using six types of each precursor derived from the same natural limestones. The particles were small enough to eliminate all transport resistances except diffusion through the Ca...

  12. The CAOS problem-solving environment: last news

    NASA Astrophysics Data System (ADS)

    Carbillet, M.; Desider, G.; Augier, .; La Camera, A.; Riccardi, A.; Boccaletti, A.; Jolissaint, L.; Ab Kadir, D.

    2010-12-01

    We present recent developments of the CAOS problem-solving environment (PSE), an IDL-based software tool complete of a global graphical interface, a general utilities library, and different specialized scientific packages going from end-to-end and analytical simulations to image simulation/reconstruction, with specialization to given instruments.

  13. Optical characterization of Mn2+: Li2O-K2O-CdO-B2O3 glass system: Absorption edge, optical band gap, optical polarizability and optical basicity

    NASA Astrophysics Data System (ADS)

    Padmaja, G.; Kistaiah, P.

    2009-07-01

    Mixed alkali borate glasses (30-x)Li2O-xK2O-10CdO-59B2O3 (0 <= × <= 30) implanted with 1mol% manganese ions (LKCBM) were prepared from the melts. These glasses were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and density measurements. Optical absorption studies were carried out as a function of alkali content to look for `Mixed Alkali Effect' (MAE) on the spectral properties of these glasses. The optical absorption spectra of LKCBM exhibit a broad band around 21000 cm-1 which has been assigned to the transition 6A1g(S) → 4T1g(G). From the study of ultraviolet absorption edge, the optical band gap energies and Urbach energies were evaluated. The average electronic polarizability of the oxide ion (αo2-), Optical basicity (wedge) and Yamasita-Kurosawas's interaction parameter (A) were also evaluated for all the glasses. In the present investigation many of the physical parameters like glass transition temperature, density, optical band gap and optical basicity vary non-linearly with alkali concentration (x) indicating MAE.

  14. Hardness properties and microscopic investigation of crack- crystal interaction in SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramic system.

    PubMed

    Roy, Shibayan; Basu, Bikramjit

    2010-01-01

    In view of the potential engineering applications requiring machinability and wear resistance, the present work focuses to evaluate hardness property and to understand the damage behavior of some selected glass-ceramics having different crystal morphologies with SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F composition, using static micro-indentation tests as well as dynamic scratch tests, respectively. Vickers hardness of up to 5.5 GPa has been measured in glass-ceramics containing plate like mica crystals. Scratch tests at a high load of 50 Nin artificial saliva were carried out in order to simulate the crack-microstructure interaction during real-time abrasion wear and machining operation. The experimental observations indicate that the novel "spherulitic-dendritic shaped "crystals, similar to the plate like crystals, have the potential to hinder the scratching induced crack propagation. In particular, such potential of the 'spherulitic-dendritic' crystals become more effective due to the larger interfacial area with the glass matrix as well as the dendritic structure of each mica plate, which helps in crack deflection and crack blunting, to a larger extent.While modest damage tolerant behavior is observed in case of 'spherulitic-dendritic' crystal containing material, severe brittle fracture of plate like crystals were noted, when both were scratched at 50 N load. PMID:19730992

  15. Optical properties of nanocrystalline potassium lithium niobate in the glass system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5).

    PubMed

    Ahamad, M Niyaz; Varma, K B R

    2009-08-01

    Optically clear glasses of various compositions in the system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5) (2 < or = x < or = 12, in molar ratio) were prepared by the melt-quenching technique. The glassy nature of the as-quenched samples was established via differential scanning calorimetry (DSC). The amorphous and the crystalline nature of the as-quenched and heat-treated samples were confirmed by the X-ray powder diffraction and transmission electron microscopic (TEM) studies. Transparent glasses comprising potassium lithium niobate (K3Li2Nb5O15) microcrystallites on the surface and nanocrystallites within the glass were obtained by controlled heat-treatment of the as-quenched glasses just above the glass transition temperature (T(g)). The optical transmission spectra of these glasses and glass-crystal composites of various compositions were recorded in the 200-2500 nm wavelength range. Various optical parameters such as optical band gap, Urbach energy, refractive index were determined. Second order optical non-linearity was established in the heat-treated samples by employing the Maker-Fringe method. PMID:19928168

  16. Effect of Glass-Phase Design on the Dielectric Properties of PbO-SrO-Na2O-Nb2O5-SiO2 Glass-Ceramic

    NASA Astrophysics Data System (ADS)

    Zhou, Hao; Zhang, Qingmeng; Tang, Qun; Cui, Hang; Xu, Yaohua; Lin, Chen-guang; Du, Jun

    2015-11-01

    The effect of glass-phase design on the dielectric properties of PbO-BaO-Na2O-Nb2O5-SiO2 glass-ceramic has been investigated. The glass phase of 36Na NbO3-18(Pb0.6Sr0.4) Nb2O6-46SiO2 glass-ceramic was modified by addition of lead ions, which is expected to optimize the dielectric properties of the SiO2 glass, thus improving the performance of the glass-ceramic composite. Phase composition and dielectric behavior were systematically investigated. Dielectric properties varied as a function of the amount of PbO added. The dielectric constant increased from 515 to 648 when 10 mol.% lead ions (relative to the SiO2 glass) was added to the glass phase. Dielectric breakdown strength also increased slightly, from 5.1 to 7.8 kV/mm, suggesting glass-phase design could be an efficient way of optimizing the dielectric properties of glass-ceramic composites.

  17. Investigating the effect of SiO2-TiO 2-CaO-Na 2O-ZnO bioactive glass doped hydroxyapatite: characterisation and structural evaluation.

    PubMed

    Yatongchai, Chokchai; Wren, Anthony W; Curran, Declan J; Hampshire, Stuart; Towler, Mark R

    2014-07-01

    The effects of increasing bioactive glass additions, SiO2-TiO2-CaO-Na2O-ZnO up to 25 wt% in increments of 5 wt%, on the physical and mechanical properties of hydroxyapatite (HA) sintered at 900, 1000, 1100 and 1200 C for 2 h was investigated. Increasing both the glass content and the temperature resulted in increased HA decomposition. This resulted in the formation of a number of bioactive phases. However the presence of the liquidus glass phase did not result in increased densification levels. At 1000 and 1100 C the additions of 5 wt% glass resulted in a decrease in density which never recovered with increasing glass content. At 1200 C a cyclic pattern resulted from increasing glass content. There was no direct relationship between strength and density with all samples experiencing no change or a decrease in strength with increasing glass content. Weibull statistics displayed no pattern with increasing glass content. PMID:24748516

  18. Lifetime of the 4I13/2 excited levels of the Er3+-ion in the glass system TeO2-WO3-Na2O-Nb2O5

    NASA Astrophysics Data System (ADS)

    Chillcce, E. F.; Osorio, Sergio P. A.; Rodriguez, Eugenio; Cesar, Carlos L.; Barbosa, Luiz C.

    2005-04-01

    Tellurite glasses optical fibers became promising for optical amplifiers due to its high rare earth ions solubility. One of the most important parameter for optical amplification is the lifetime of the excited states, which strongly depends on the crystal field around the ions. That crystal field changes dramatically with the host glass and with rare earth concentration. Excited state lifetime studies have been performed on Er3+-doped-TeO2-WO3-Na2O-Nb2O5 glass system. Therefore, we decided to study the Er3+ excited states lifetimes and compared with the Judd-Ofelt theory predictions. We measured only the 4I13/2 to 4I15/2 transitions lifetimes. The other transitions lifetimes can be inferred by knowing the ?2, ?4, ?6 Judd-Ofelt parameters. These parameters were calculated with the electric-magnetic dipole transition oscillator strength for the desired excited levels and ground state obtained from the optical absorption spectra. After performing this calculation we estimated that maximum quantum efficiency (?), measured/calculated lifetimes ratio, would be achieved at 7500ppm (%wt) Er3+ content.

  19. Investigating the influence of Na+ and Sr2+ on the structure and solubility of SiO2-TiO2-CaO-Na2O/SrO bioactive glass.

    PubMed

    Li, Y; Placek, L M; Coughlan, A; Laffir, F R; Pradhan, D; Mellott, N P; Wren, A W

    2015-02-01

    This study was conducted to determine the influence that network modifiers, sodium (Na+) and strontium (Sr2+), have on the solubility of a SiO2-TiO2-CaO-Na2O/SrO bioactive glass. Glass characterization determined each composition had a similar structure, i.e. bridging to non-bridging oxygen ratio determined by X-ray photoelectron spectroscopy. Magic angle spinning nuclear magnetic resonance (MAS-NMR) confirmed structural similarities as each glass presented spectral shifts between -84 and -85 ppm. Differential thermal analysis and hardness testing revealed higher glass transition temperatures (Tg 591-760 C) and hardness values (2.4-6.1 GPa) for the Sr2+ containing glasses. Additionally the Sr2+ (~250 mg/L) containing glasses displayed much lower ion release rates than the Na+ (~1,200 mg/L) containing glass analogues. With the reduction in ion release there was an associated reduction in solution pH. Cytotoxicity and cell adhesion studies were conducted using MC3T3 Osteoblasts. Each glass did not significantly reduce cell numbers and osteoblasts were found to adhere to each glass surface. PMID:25644099

  20. Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system

    NASA Astrophysics Data System (ADS)

    Li, Xudong; Cai, Shu; Zhang, Wenjuang; Xu, Guohua; Zhou, Wei

    2009-08-01

    The bioactive glass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system were synthesized by the sol-gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 °C for 4 h consisted of the crystalline phase β-Ca 2P 2O 7 and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP 2O 6 was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca 4P 6O 19 was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.

  1. Structural and magnetic properties of SiO2-CaO-Na2O-P2O5 containing BaO-Fe2O3 glass-ceramics

    NASA Astrophysics Data System (ADS)

    Leenakul, W.; Kantha, P.; Pisitpipathsin, N.; Rujijanagul, G.; Eitssayeam, S.; Pengpat, K.

    2013-01-01

    The incorporation method was employed to produce bioactive glass-ceramics from the BaFe12O19-SiO2-CaO-Na2O-P2O5 glass system. The ferrimagnetic BaFe12O19 was first prepared using a simple mixed oxide method, where the oxide precursors of 45S5 bioglass were initially mixed and then melted to form glass. The devitrification of Na3Ca6(PO4)5 and Fe3O4 was observed in all of the quenched glass samples. The glass samples were then subjected to a heat treatment schedule for further crystallization. It was found that the small traces of BaFe12O19 phases started to crystallize in high BF content samples of 20 and 40 wt%. These samples also exhibited good magnetic properties comparable to that of other magnetic glass-ceramics. The bioactivity of the BF glass-ceramics improved with increasing BF content as was evident by the formation of bone-like apatite layers on the surface of all of the glass-ceramics after soaking in SBF for 14 days. The results support the use of these bioactive glass-ceramics for hyperthermia treatment within the human body.

  2. Optical Properties and Photoactivity of The Pigmentary TiO2 Doped with P2O5, K2O, Al2O3 and Sb2O3

    NASA Astrophysics Data System (ADS)

    Gle?, M.; Grzmil, B.

    2011-05-01

    The influence of the increasing content of antimony calculated to Sb2O3 (0.08-0.57 mol%) with the constant amount of the other additives (calculated to P2O5, K2O, Al2O3) on the optical properties and photostability of doped rutile has been investigated. The properties of the obtained TiO2-PKAlSb samples were compared to the commercial TiO2-PKAl composition. The starting material was the concentrated suspension of technical-grade hydrated titanium dioxide (HTD). The dopant agents' solutions were introduced to HTD. Prepared samples were calcined with gradually increasing process temperature. The XRD analysis was used to determine the rutile content in the TiO2 samples. Optical properties of modified titanium dioxide have been determined spectrophotometrically by measuring the colour in the white (brightness, white tone) and grey system (relative lightening power, grey tone). Photostability was characterized by the white lead-glycerin test with UV-Vis light. It was observed that with the increasing content of antimony in rutile TiO2, doped with phosphates, potassium and aluminium, the brightness and grey tone were increasing but white tone decreased. The changes of the relative lightening power values were insignificant. Comparing the samples of TiO2-PKAlSb with the TiO2-PKAl composition it was observed that titanium dioxide doped with antimony had better white and grey tone. The increasing Sb2O3 content in the TiO2 caused the improvement of the photostability.

  3. Density properties of glasses of CaO(Na2O)-Al2O3(MgO)-SiO2 system, studied at pressures to 6.0 GPa, in comparison with the properties of similar melts

    NASA Astrophysics Data System (ADS)

    Kuryaeva, R. G.

    2015-04-01

    The density properties (relative change in the density, (d - d0)/d, initial bulk modulus, K0, and the derivative of bulk modulus with respect to pressure, ??) of silicate glasses of the CaO(Na2O)-Al2O3(MgO)-SiO2 system are compared with those of silicate melts. It is shown that ?0 values obtained for the glasses using Birch-Murnaghan equation in the pressure range with the normal behavior of bulk modulus significantly lower ?0 values, which were obtained for glasses using the ultrasonic or Brillouin scattering methods. This phenomenon is explained by the different state of the glasses, which were obtained by different methods. Brillouin scattering method allows obtaining the K0 value, which characterizes the initial unstable state of glass, while with the use of other method (using Birch-Murnaghan equation in the pressure range with the normal behavior of bulk modulus) we determine K0 for glass, which is in the hypothetical metastable state, close to the supercooled liquid. K0 values for glasses, which are in the hypothetical metastable state are close to ?0 values for silicate melts. When (K0)glass and (K0)melt have similar values, higher compressibility of melts is determined by smaller values of the derivative of the bulk modulus, K?, compared with glasses of similar compositions. The relation between the parameters (d - d0)/d, K0, K? and the degree of depolymerization, NBO/T, of silicate glasses and melts was found. The greater the degree of depolymerization, the less is the compressibility of glasses and melts. Simple models for the semiempirical determination of the melts density properties in the first approximation using the density properties of the corresponding glasses are proposed. The possibility of using silicate glasses as the models of deep melts was shown by example of tholeiite basalt glass and melt.

  4. Structure and Crystallization Kinetics of Glassy CaO-Al2O3-SiO2-CaF2-Na2O Mold Fluxes with Varying Basicity

    NASA Astrophysics Data System (ADS)

    Li, Jiangling; Yan, Baijun; Shu, Qifeng; Chou, Kuochih

    2015-12-01

    The structure and the crystallization kinetics of CaO-Al2O3-SiO2-CaF2-Na2O mold fluxes with varying basicities were investigated by solid-state 29Si nuclear magnetic resonance with magic angular spinning (MAS-NMR) and differential thermal analysis (DTA) technique, respectively. 29Si MAS-NMR study indicated that the increase of basicity decreased the degree of polymerization of mold fluxes. With the increasing basicity, Q 0, Q 2, and Q 3 gradually decreased, while Q 1 gradually increased, and the overall degree of polymerization was reduced. Crystallization analysis showed the cuspidine first crystallized from glass, and wollastonite crystal crystallized at elevated temperature for the samples with basicity (defined as CaO/SiO2 mass ratio) values of 0.9 and 1.0, respectively. Only cuspidine was found to crystallize from glass for the samples with basicity values of 1.1 and 1.2, indicating that the crystallization of wollastonite was suppressed with the increase of basicity. Crystallization kinetics analysis by DTA and field emission scanning electron microscopy equipped with energy dispersive spectroscopy investigation showed that growth mechanism of cuspidine is mainly of the diffusion-controlled three-dimensional growth with the increasing number of nuclei during heating. Activation energies for growth of cuspidine decreased with the increasing basicity of mold flux, which indicated that the crystallization ability was enhanced with the increase of basicity. The relationship between structure and crystallization of mold fluxes was established.

  5. Physical and spectroscopic properties of multi-component Na2O-PbO-Bi2O3-SiO2 glass ceramics with Cr2O3 as nucleating agent

    NASA Astrophysics Data System (ADS)

    Sambasiva Rao, M. V.; Rajyasree, Ch.; Narendrudu, T.; Suresh, S.; Suneel Kumar, A.; Veeraiah, N.; Krishna Rao, D.

    2015-09-01

    Transparent glass ceramics, synthesized from melt quenching followed by heat treatment, of the composition 10Na2O-30PbO-10Bi2O3-(50 - x)SiO2:xCr2O3 (mol%), where 0 ? x ? 0.5, were characterized with XRD, DTA, SEM and EDS. Physical and spectroscopic studies, viz., optical absorption, electron paramagnetic resonance (EPR), FTIR and Raman were investigated. The characterization of the host glass ceramic has revealed that the formation of a major phase of sodium silicate along with two minor phases such as lead silicate and bismuth oxide. By integrating Cr2O3 to the host glass additional crystal phases viz., NaCrO2, Na2Cr2O7 and Pb(CrO4) which are the complexes of Cr3+ and Cr6+ ions were also developed. As the concentration of nucleating agent is increased, a part of the Cr6+ ions is found to reduce in to Cr3+ ions. Spectroscopic studies have revealed that with an increase in the concentration of Cr2O3 from 0.1 to 0.5 mol%, there is a gradual increase in the intensity of vibrational modes of various asymmetric structural units of silicate, bismuthate and chromate in the glass ceramic network at the expense of symmetrical structural units. The analysis of the results of these studies has indicated that in the samples containing higher concentration of Cr2O3, chromium ions exists predominantly in Cr3+ state and occupy the octahedral positions in glass ceramic matrix and such glass ceramic samples are suitable for lasing action.

  6. The Oxygenase CAO-1 of Neurospora crassa Is a Resveratrol Cleavage Enzyme

    PubMed Central

    Daz-Snchez, Violeta; F. Estrada, Alejandro; Limn, M. Carmen; Al-Babili, Salim

    2013-01-01

    The genome of the ascomycete Neurospora crassa encodes CAO-1 and CAO-2, two members of the carotenoid cleavage oxygenase family that target double bonds in different substrates. Previous studies demonstrated the role of CAO-2 in cleaving the C40 carotene torulene, a key step in the synthesis of the C35 apocarotenoid pigment neurosporaxanthin. In this work, we investigated the activity of CAO-1, assuming that it may provide retinal, the chromophore of the NOP-1 rhodopsin, by cleaving ?-carotene. For this purpose, we tested CAO-1 activity with carotenoid substrates that were, however, not converted. In contrast and consistent with its sequence similarity to family members that act on stilbenes, CAO-1 cleaved the interphenyl C?-C? double bond of resveratrol and its derivative piceatannol. CAO-1 did not convert five other similar stilbenes, indicating a requirement for a minimal number of unmodified hydroxyl groups in the stilbene background. Confirming its biological function in converting stilbenes, adding resveratrol led to a pronounced increase in cao-1 mRNA levels, while light, a key regulator of carotenoid metabolism, did not alter them. Targeted ?cao-1 mutants were not impaired by the presence of resveratrol, a phytoalexin active against different fungi, which did not significantly affect the growth and development of wild-type Neurospora. However, under partial sorbose toxicity, the ?cao-1 colonies exhibited faster radial growth than control strains in the presence of resveratrol, suggesting a moderate toxic effect of resveratrol cleavage products. PMID:23893079

  7. Near UV bands of jet-cooled CaO

    NASA Astrophysics Data System (ADS)

    Stewart, Jacob T.; Sullivan, Michael N.; Heaven, Michael C.

    2016-04-01

    The electronic spectrum of CaO has been recorded for the 29,800-33,150 cm-1 energy range. Jet cooling was used to obtain relatively uncongested spectra. Rotationally resolved bands have been assigned to the C1Σ+-X1Σ+ and F1∏-X transitions. These data extend the range of vibronic levels characterized for the upper states. Three additional vibronic states were observed as a short progression. One of these levels, which are of 0+ symmetry, interacts strongly with the C1Σ+, v‧ = 7 level. Possible assignments for the perturbing state are considered.

  8. caos software for use in character-based DNA barcoding.

    PubMed

    Sarkar, Indra Neil; Planet, Paul J; Desalle, Rob

    2008-11-01

    The success of character-based DNA barcoding depends on the efficient identification of diagnostic character states from molecular sequences that have been organized hierarchically (e.g. according to phylogenetic methods). Similarly, the reliability of these identified diagnostic character states must be assessed according to their ability to diagnose new sequences. Here, a set of software tools is presented that implement the previously described Characteristic Attribute Organization System for both diagnostic identification and diagnostic-based classification. The software is publicly available from http://sarkarlab.mbl.edu/CAOS. PMID:21586014

  9. Thermodynamic analysis of hydrogen production from ethanol using CaO as a CO 2 sorbent

    NASA Astrophysics Data System (ADS)

    Comas, Jose; Laborde, Miguel; Amadeo, Norma

    Ethanol steam reforming with and without the presence of CaO as a CO 2 sorbent is modeled. Potential advantages of the presence of CaO as CO 2 sorbent include higher energy efficiency, higher hydrogen production and lower CO content in the reformer gas exit. The presence of CaO eliminates the need of a WGS reactor for PEMFC application. Favorable operation conditions in the presence of CaO are (1) atmospheric pressure, (2) reactor temperatures around 700 C, and (3) water/ethanol molar ratio of 4.

  10. Steam catalysis in CaO carbonation under low steam partial pressure

    SciTech Connect

    Yang, S.J.; Xiao, Y.H.

    2008-06-15

    CaO was widely used to capture CO{sub 2} in direct hydrogen production process, where steam always existed simultaneously. The effect of steam on CaO carbonation performance under low steam partial pressure was investigated using a pressurized thermogravimetric apparatus. The experimental results revealed that steam improved CaO carbonation performance significantly no matter whether Ca(OH){sub 2} was produced or not. At 823 K and 0.5 MPa of steam partial pressure, effect of steam on CaO carbonation performance could not be attributed mainly to production of Ca(OH){sub 2} because the hydration rate of CaO was very slow. The main reason was steam catalysis in CaO carbonation. Enhancement of steam on CaO carbonation performance without Ca(OH){sub 2} production could not be attributed to improvement of steam on the physical property, but to catalytic effect of steam. Effects of CaO precursors, CO{sub 2} partial pressure, steam partial pressure, and temperature with steam addition on CaO carbonation performance were also investigated.

  11. The 1.53 ?m spectroscopic properties and thermal stability in Er3+/Ce3+ codoped TeO2-WO3-Na2O-Nb2O5 glasses

    NASA Astrophysics Data System (ADS)

    Zheng, Shichao; Zhou, Yaxun; Yin, Dandan; Xu, Xingchen; Qi, Yawei; Peng, Shengxi

    2013-05-01

    Er3+/Ce3+ codoped tellurite-based glasses with composition of TeO2-WO3-Na2O-Nb2O5 were prepared by high-temperature melt-quenching technique and a detailed study of the 1.53 ?m band spectroscopic properties and thermal stability was presented in this paper. The absorption spectra, visible upconversion spectra, 1.53 ?m band fluorescence spectra, fluorescence lifetimes, Raman spectra, differential scanning calorimeter (DSC) and X-ray diffraction (XRD) curves of glass samples were measured and investigated, together with the quantitative calculations and analyses of Judd-Ofelt intensity parameters, stimulated emission and absorption cross-sections, amplification quality factors, energy transfer rates and quantum transition efficiencies. It was found that the prepared glass samples have good thermal stability (Tg>425 C), large Judd-Ofelt intensity parameter (?6>0.8010-20 cm2) and bandwidth quality factor (?epFWHM>36010-21 cm2 nm) of Er3+. With the increasing of Ce3+ doped concentration, the visible upconversion emission decreased while the 1.53 ?m band fluorescence intensity improved significantly due to the enhanced energy transfer of Er3+:4I11/2+Ce3+:2F5/2?Er3+:4I13/2+Ce3+:2F7/2 owing to the moderate phonon energy (930 cm-1) of glass host, which was beneficial in compensating for the existing energy mismatch between the Er3+:4I11/2?4I13/2 emission and Ce3+:2F5/2?2F7/2 absorption transitions. Compared with the Er3+ single-doped case, the 1.53 ?m band fluorescence intensity in Er3+/Ce3+ codoped glass sample could increase by about 30%. The results indicate that the prepared tellurite-based glass with a suitable Er3+/Ce3+ codoping concentration is an excellent gain medium applied for broadband EDFA pumped with a 980 nm laser diode.

  12. Understanding Structural Properties of Carbonate-Silicate Melts: An EXAFS Study on Y and Sr in the System Na2O-CaO-Al2O3-SiO2-CO2

    NASA Astrophysics Data System (ADS)

    Pohlenz, J.; Pascarelli, S.; Mathon, O.; Belin, S.; Shiryaev, A.; Safonov, O.; Murzin, V.; Shablinskaya, K.; Irifune, T.; Wilke, M.

    2014-12-01

    Carbonatite volcanism generally occurs in intra-plate settings associated with continental rifting. The only active carbonatitic volcano is the Oldoinyo Lengai, Tanzania, which generates sodium-rich carbonatites in close association with phonolites and nephelinites1. The processes of carbonatite genesis are still unresolved, however carbonate-bearing melts evidently play a crucial role during mantle melting, in diamond formation and as metasomatic agents. Carbonate melts show extraordinary properties, especially in regard to their low melt viscosities and densities, high surface tensions and electrical conductivities as well as distinct geochemical affinities to a wide range of trace elements2. Understanding the structural properties of carbonate-bearing melts is fundamental to explaining their chemical and physical behaviour as well as modeling processes operating in the deep Earth. Extended X-ray absorption fine structure (EXAFS) spectroscopy is a versatile tool for element specific investigation of the short to medium range structure of melts and glasses. This study focuses on unraveling the influence of carbonate concentration on the structural incorporation of the geochemically important trace elements Y and Sr in silicate and carbonate melts in the system Na2O-CaO-Al2O3-SiO2-CO2. First, we present structural data of silicate glasses with up to 10 wt% CO2, quenched from melts under high temperature and pressure, which indicate that the local structure of Y and Sr is not or only slightly affected by CO2. Melts with higher CO2 contents could not be quenched to glass, so far. Second, we show results of high pressure, high temperature experiments conducted in the Paris Edinburgh-Press, which provides in-situ insight into carbonate-silicate melts. All EXAFS measurements were performed at the synchrotron facility beamlines SAMBA (SOLEIL) and BM23 (ESRF). Information derived from the trace elements' local structure is used to develop a structural model for carbonate-silicate melts. The ultimate goal is to gain insight into the structural control on chemical fractionation processes in carbonate-bearing magmatic systems in the deep Earth. 1. Klaudius, J & Keller, J, Lithos 91, 173-190 (2006). 2. Jones, AP, Genge, M & Carmody, L, Rev. Mineral. Geochem. 75, 289-322 (2013).

  13. In-situ measurements of D/H fractionation between melt and coexisting aqueous fluids in the Na2O-Al2O3-SiO2-H2O system

    NASA Astrophysics Data System (ADS)

    Dalou, C.; Le Losq, C.; Mysen, B. O.

    2014-12-01

    Hydrogen isotope partitioning (as H2O and D2O) between water-saturated silicate melts and coexisting silicate-saturated aqueous fluids with several different initial D/H ratios in the Na2O-Al2O3-SiO2-H2O system has been determined. In-situ measurements in a hydrothermal diamond anvil cell (HDAC) with the fluid and melt at the desired temperatures (≤800˚C) and pressures (≤1115 MPa) were carried out with microRaman and FTIR spectroscopy techniques. For bulk D/H ratios were used: 0.05 ±0.02, 0.13 ±0.05, 0.53 ±0.01 and 2.35 ±0.04. Three experimental series (D/H: 0.05, 0.13, 0.53) with coexisting fluid and melt have comparable pressure/temperature trajectories (350-650 ºC/322-626, 313-741 and MPa; 248-648 MPa, respectively), whereas the experimental series with D/H=2.35 had a lower pressure/temperature trajectory (400-680 ºC/192-496 MPa). In these pressure/temperature ranges, the D/H ratios of fluids barely change with temperature, with an average small negative ΔHfluid -1.2 ±0.5 kJ/mol. In contrast, the D/H ratios of coexisting melts display strong temperature dependence. The ΔHmelt decreases from 14.6 ±2.2 to -3.7 ±1.1 kJ/mol with the D/H ratio increasing from 0.05 ±0.02 to 2.35 ±0.04. Consequently, the (D,H) exchange equilibrium between melt and fluid is temperature dependent, and varies so that its ΔH increases from -15.9 ±2.7 to 0.3 ±0.4 kJ/mol with increasing D/H ratios. Hydrogen isotope fractionation between silicate melts and low density phases (aqueous fluids or gases) may affect the δD values during, for example degassing of mantle derived-magmatic liquids. Moreover, D/H fractionation between silicate minerals and melts in the Earth's interior can be affected by the significant temperature and composition-dependent D/H fractionation in silicate melts at high temperatures and pressures.

  14. Ionic conductivity of mixed glass former 0.35Na(2)O + 0.65[xB(2)O(3) + (1 - x)P(2)O(5)] glasses.

    PubMed

    Christensen, Randilynn; Olson, Garrett; Martin, Steve W

    2013-12-27

    The mixed glass former effect (MGFE) is defined as a nonlinear and nonadditive change in the ionic conductivity with changing glass former fraction at constant modifier composition between two binary glass forming compositions. In this study, mixed glass former (MGF) sodium borophosphate glasses, 0.35Na2O + 0.65[xB2O3 + (1 - x)P2O5], 0 ≤ x ≤ 1, have been prepared, and their sodium ionic conductivity has been studied. The ionic conductivity exhibits a strong, positive MGFE that is caused by a corresponding strongly negative nonlinear, nonadditive change in the conductivity activation energy with changing glass former content, x. We describe a successful model of the MGFE in the conductivity activation energy terms of the underlying short-range order (SRO) phosphate and borate glass former structures present in these glasses. To do this, we have developed a modified Anderson-Stuart (A-S) model to explain the decrease in the activation energy in terms of the atomic level composition dependence (x) of the borate and phosphate SRO structural groups, the Na(+) ion concentration, and the Na(+) mobility. In our revision of the A-S model, we carefully improve the treatment of the cation jump distance and incorporate an effective Madelung constant to account for many body coulomb potential effects. Using our model, we are able to accurately reproduce the composition dependence of the activation energy with a single adjustable parameter, the effective Madelung constant, that changes systematically with composition, x, and varies by no more than 10% from values typical of oxide ceramics. Our model suggests that the decreasing columbic binding energies that govern the concentration of the mobile cations are sufficiently strong in these glasses to overcome the increasing volumetric strain energies (mobility) caused by strongly increasing glass-transition temperatures combined with strongly decreasing molar volumes of these glasses. The dependence of the columbic binding energy term on the relative high-frequency dielectric permittivity suggests that the increased polarizability of the bridging oxygens connecting SRO tetrahedral boron units to phosphorus units causes further charge delocalization away from the negatively charged tetrahedral boron units, leading to a lowering of the charge density, and is the underlying cause of the MGFE. PMID:24295052

  15. Solution behavior of reduced N-H-O volatiles in FeO-Na2O-SiO2-Al2O3 melt equilibrated with molten Fe alloy at high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Kadik, Arnold A.; Litvin, Yuri A.; Koltashev, Vasily V.; Kryukova, Elena B.; Plotnichenko, Victor G.; Tsekhonya, Tatiana I.; Kononkova, Nataliya N.

    2013-01-01

    Solubility and speciation of NOH volatiles in a model silicate melt (FeO-Na2O-Al2O3-SiO2) equilibrated with molten Fe alloy have been examined via nitrogen and hydrogen analyses and vibrational spectroscopy (Raman and FTIR). Experiments were performed in an anvil-with-hole apparatus conducted at 4 GPa, 1550 C, and oxygen fugacity (fO2) from 2.1 to 3.3 log units below IW buffer. The technique of hydrogen fugacity (fH2) buffering via the dissociation of H2O employed here relies upon the diffusion of H2 through Pt to achieve equal chemical potentials of H2 in the Pt capsule and outer assemblage elements. The nitrogen source was Si3N4. The fO2 imposed on the charge was controlled by redox reactions between H2 buffered externally, Si3N4 and components of the Fe-bearing melt that was reduced with O2 liberation and metallic Fe formation. The initial Si3N4 was unstable under the experimental conditions and completely consumed according to the reaction of oxidation: Si3N4 (initial) + 3O2 ? 3SiO2 (melt) + 2N2 (melt) with a subsequent participation of nitrogen in the reactions with H2, the components of silicate and metallic melts. The nitrogen and hydrogen solubility, calculated as N and H, ranges from 0.4 to 1.9 wt.% and from 0.2 to 0.3 wt.%, accordingly. The nitrogen content in iron globules at ?log fO2(IW) = -3.3 was measured as 4.4 wt.%. Characterization by Raman and IR spectroscopy indicates that at fO2, where a metallic Fe phase is stable, the silicate melt would contain species with N-H bonds (NH3, NH4+, NH2-, NH2+) as well as N2, oxidized H species (OH- and H2O) and H2. Experimental studies have shown that the fO2 evolution during metal segregation would have strongly influenced the nature of nitrogen and hydrogen species in reduced magmas of the early Earth.

  16. CaO as Drop-In Colloidal Catalysts for the Synthesis of Higher Polyglycerols

    PubMed Central

    Kirby, Fiona; Nieuwelink, Anne-Eva; Kuipers, Bonny W M; Kaiser, Anton; Bruijnincx, Pieter C A; Weckhuysen, Bert M

    2015-01-01

    Glycerol is an attractive renewable building block for the synthesis of polyglycerols, which find application in the cosmetic and pharmaceutical industries. The selective etherification of glycerol to higher oligomers was studied in the presence of CaO colloids and the data are compared with those obtained from NaOH and CaO. The materials were prepared by dispersing CaO, CaCO3, or Ca(OH)2 onto a carbon nanofiber (CNF) support. Colloidal nanoparticles were subsequently dispensed from the CNF into the reaction mixture to give CaO colloids that have a higher activity than equimolar amounts of bulk CaO and NaOH. Optimization of the reaction conditions allowed us to obtain a product with Gardner color number <2, containing no acrolein and minimal cyclic byproducts. The differences in the CaO colloids originating from CNF and bulk CaO were probed using light scattering and conductivity measurements. The results confirmed that the higher activity of the colloids originating from CaO/CNF was due to their more rapid formation and smaller size compared with colloids from bulk CaO. We thus have developed a practical method for the synthesis of polyglycerols containing low amounts of Ca. PMID:25684403

  17. Modelling astronomical adaptive optics - I. The software package CAOS

    NASA Astrophysics Data System (ADS)

    Carbillet, M.; Vrinaud, C.; Femena, B.; Riccardi, A.; Fini, L.

    2005-02-01

    The software package CAOS (code for adaptive optics systems) described in this paper is a software ensemble of modules designed for end-to-end simulation of generic astronomical adaptive optics (AO) systems, including a complete atmosphere turbulence model, sodium laser-guide star upward and downward propagation, observed object definition, Shack-Hartmann and novel pyramid wave-front sensors detailed modelling, wave-front reconstruction and subsequent time-filtering tools, and wave-front correction via different kinds of correctors; but also image formation, Fizeau interferometry, coronagraphy, etc. Consequently, it is more likely to be used as a tool dedicated to detailed optical astronomy studies than as an instrument simulator, as it is based on a wide range of unprecedented physical modelling. After a brief but global description, with particular emphasis on the most interesting physical modelling features, its use is illustrated through a chosen application, namely the question concerning the opportunity of having a tip-tilt-dedicated sensor in a 8-m class telescope pyramid-based AO system.

  18. SSC Model Fits to Simultaneous Fermi and CAO observations of Bl Lac's

    NASA Astrophysics Data System (ADS)

    Gordon, Tyler; Macomb, Daryl J.; Hand, Jared; Norris, Jay P.; Long, Min

    2016-01-01

    The Challis Astronomical Observatory (CAO) has been surveying a sample of blazar-type AGN since 2010. The CAO blazar sample includes4 3 sources - comprising 30 FSRQs, 15 BL Lacs, one radio galaxy and four unclassified sources - covering a redshift range 0.02 < z < 2. Observations are carried out in BVRI filters. Here we describe photometric results on a small sample emphasizing BL Lacs. We combine the CAO data with Fermi/LAT data and explore the suitability of fits to the data using the uniform conical jet model of Potter and Cotter (MNRAS, 2012, 423, 756-765).

  19. Cao Gío (coin rubbing). Vietnamese attitudes toward health care.

    PubMed

    Yeatman, G W; Dang, V V

    1980-12-19

    Cao gío is the Vietnamese practice of rubbing the skin with a coin to alleviate various common symptoms of illness. The back, neck, head, shoulder, and chest are common sites of application. Although mimicking the lesions of trauma, it is not a harmful procedure, and no complications are known. A survey of 50 Vietnamese living in the United States since 1975 and 1976 has shown marked distrust of American Physicians, owing largely to actual or perceived criticism of cao gío. Acceptance of cao gío as a valid cultural practice will facilitate compliance and adequate medical follow-up. PMID:7441861

  20. Assessment of CAOS as a training model in spinal surgery: a randomised study

    PubMed Central

    Kurta, I. C.; Jasani, V.; Jones, C. H. Wynn; Rahmatalla, A.; MacKenzie, G.; Dove, J.

    2006-01-01

    The objectives of this study were (1) to quantify the benefit of computer assisted orthopaedic surgery (CAOS) pedicle screw insertion in a porcine cadaver model evaluated by dissection and computed tomography (CT); (2) to compare the effect on performance of four surgeons with no experience of CAOS, and varying experience of pedicle screw insertion; (3) to see if CT with extended windows was an acceptable method to evaluate the position of the pedicle screws in the porcine cadaver model, compared to dissection. This was a prospective, randomised, controlled and blinded porcine cadaver study. Twelve 6-month-old porcine (white skinned Landrace) lumbar spines were scanned pre-operatively by spiral CT, as required for the CAOS computer data set. Computer randomisation allocated the specimens to one of four surgeons, all new to CAOS but with different levels of experience in spinal surgery. The usual anatomical landmarks for the freehand technique were known to all four surgeons. Two pedicles at each vertebral level were randomly allocated between conventional free hand insertion and an electromagnetic image guided surgery (NAVITRAK) and 6.5mm cancellous AO screws inserted. Post-operatively, spiral CT was blindly evaluated by an independent radiologist and the spine fellow to assess the accuracy of pedicle screw placement, by each method. The inter- and intra-observer reliability of CT was evaluated compared to dissection. The pedicle screw placement was assessed as perfect if within the pedicle along its central axis, or acceptable (within<2mm from perfect), and measured in millimetres from perfect thereafter. One hundred and sixty-six of 168 pedicles in 12 porcine spines were operated on. Complete data were present for 163 pedicles (81 CAOS, 82 freehand). In the CAOS group 84% of screws were deemed acceptable or perfect, compared to 75.6% with the freehand technique. Screw misplacement was significantly reduced using CAOS (P=0.049). Seventy-nine percent of CAOS screws were ideally placed compared with 64% with a conventional freehand technique (P=0.05). A logistic linear regression model showed that the miss placed pedicle screw rate was significantly reduced using CAOS (P=0.047). CAOS benefited the least experienced surgeons most (the research registrars acceptable rate increased from 70 to 90% and the spine fellow from 76 to 86%). CAOS did not have a statistically significant effect on the experienced consultant spine surgeon increasing from 70 to 79% (P=0.39). The experienced general orthopaedic surgeon did not benefit from CAOS (P=0.5). CT compared to dissection showed an intra-observer reliability of 99.4% and inter-observer reliability of 92.6%. The conclusions of this study were as follows: (1) an increased number of pedicle screws were ideally placed using the CAOS electromagnetic guidance system compared to the conventional freehand technique; (2) junior surgeons benefited most from CAOS; (3) we believe CAOS (Navitrak) with porcine lumbar spines evaluated by post operative CT, represents a useful model for training junior surgeons in pedicle screw placement; (4) experienced spine surgeons, who have never used CAOS, may find CAOS less helpful than previously reported. PMID:16683122

  1. Nonisothermal Thermogravimetric Analysis of Thai Lignite with High CaO Content

    PubMed Central

    Pintana, Pakamon

    2013-01-01

    Thermal behaviors and combustion kinetics of Thai lignite with different SO3-free CaO contents were investigated. Nonisothermal thermogravimetric method was carried out under oxygen environment at heating rates of 10, 30, and 50°C min−1 from ambient up to 1300°C. Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods were adopted to estimate the apparent activation energy (E) for the thermal decomposition of these coals. Different thermal degradation behaviors were observed in lignites with low (14%) and high (42%) CaO content. Activation energy of the lignite combustion was found to vary with the conversion fraction. In comparison with the KAS method, higher E values were obtained by the FWO method for all conversions considered. High CaO lignite was observed to have higher activation energy than the low CaO coal. PMID:24250259

  2. Variations in Compressive Strength of Geopolymer due to the CaO Added Fly Ash

    NASA Astrophysics Data System (ADS)

    Zhao, Yuqing; Koumoto, Tatsuya; Kondo, Fumiyoshi

    Recently, geopolymer has been a noteworthy material which can be used as a replacement for portland cement. The mechanical characteristics and consistency of the geopolymer are strongly affected by its chemical components of fly ash. The variations in compressive strength of geopolymer due to the CaO added fly ash were investigated in this paper. The compressive strengths of geopolymer were increased with an increase in the curing period, and the characteristics changed from the one of plastic soil material to brittle material such as concrete, regardless of CaO content. Also, the results of compressive strength and modulus of deformation showed their maximum value in the case of 8-10% CaO content. From this result, the maximum characteristics of the strengths were assumed to be exerted in case which the water draining process of geopolymer was balanced with the water absorbing process of additional CaO.

  3. CAOS: a numerical simulation tool for astronomical adaptive optics (and beyond)

    NASA Astrophysics Data System (ADS)

    Carbillet, Marcel; Verinaud, Christophe; Guarracino, Mario; Fini, Luca; Lardiere, Olivier; Le Roux, Brice; Puglisi, Alfio T.; Femenia, Bruno; Riccardi, Armando; Anconelli, Barbara; Correia, Serge; Bertero, Mario; Boccacci, Patrizia

    2004-10-01

    We present recent developments of the CAOS "system", an IDL-based Problem Solving Environment (PSE) whose original aim was to define and simulate as realistically as possible the behavior of a generic adaptive optics (AO) system, from the atmospheric propagation of light, to the sensing of the wave-front aberratoins and the correction through a deformable mirror. The different developments made through the last 7 years result in a very versatile numerical tool complete of a global graphical interface (the CAOS Application Builder), and different specialized scientific packages: the original one designed for AO system simulations (the Software Package CAOS), an image reconstruction package with interferometric capabilities (the Software Package AIRY), and a more recent one being built and dedicated to multiconjugate AO (the Software Package MAOS). We present the status of the whole CAOS "system"/PSE, together with the most recent developments, including parallelization strategy considerations, examples of application, and plans for the next future.

  4. CaO interaction in the staged combustion of coal

    SciTech Connect

    Levy, A.; Merryman, E.L.; Rising, B.W.

    1983-12-19

    The LIMB (limestone injection multi-stage burner) process offers special potential for reducing NO/sub x/ and SO/sub x/ by at least 50 percent in coal combustion. This is to be accomplished by adding limestone with fuel and/or air in a low NO/sub x/ burner. This program has been directed to defining the chemistry and kinetics necessary to optimize sulfur capture in LIMB combustion. More specifically, this program has attempted to clarify the role of calcium sulfide in LIMB chemistry. When limestone is added in a staged burner, there is a strong possibility that under certain circumstances CaS is produced in the reducing (fuel-rich) zone of the burner. Since CaS is more stable than CaSO/sub 4/, this affords the opportunity to (1) operate the burner at a higher temperature, 2200 to 2500 F, (2) pass the CaS rapidly through the high temperature zone (before dissociation), and (3) complete the combustion in a lean (air-rich) region where the sulfur is finally retained in CaSO/sub 4/. For these reasons this program has concentrated on the high temperature chemistry and kinetics of CaS. To achieve the program objective, the program was divided into three tasks. These involved (1) a study of CaS formation, (2) a brief examination of CaS oxidation, and (3) a laboratory examination of the combustion of coal in the presence of CaO under first stage, fuel-rich conditions. In the most general sense, the study has shown that the formation of CaS in the reducing zones of the burner may be restricted by competing kinetics and thermodynamics. The addition of lime in LIMB will require special care to optimize the ability to capture sulfur. 36 references, 44 figures, 10 tables.

  5. Effect of H2O on the morphological changes of KNO3 formed on K2O/Al2O3 NOx storage materials: Fourier transform infra-red (FTIR) and time-resolved x-ray diffraction (TR-XRD) studies

    SciTech Connect

    Kim, Do Heui; Mudiyanselage, Kumudu K.; Szanyi, Janos; Hanson, Jonathan C.; Peden, Charles HF

    2014-02-27

    Based on combined FTIR and XRD studies, we report here that H2O induces a morphological change of KNO3 species formed on model K2O/Al2O3 NOx storage-reduction catalysts. Specifically as evidenced by FTIR, the contact of H2O with NO2 pre-adsorbed on K2O/Al2O3 promotes the transformation from bidentate (surface-like) KNO3 species to ionic (bulk-like) ones irrespective of K loadings. Once H2O is removed from the sample, a reversible transformation into bidentate KNO3 is observed, demonstrating a significant dependence of H2O on such morphological changes. TR-XRD results show the formation of two different types of bulk KNO3 phases (orthorhomobic and rhombohedral) in an as-impregnated sample. Once H2O begins to desorb above 400 K, the former is transformed into the latter, resulting in the existence of only the rhombohedral KNO3 phase. On the basis of consistent FTIR and TR-XRD results, we propose a model for the morphological changes of KNO3 species with respect to NO2 adsorption/desorption, H2O and/or heat treatments. Compared with the BaO/Al2O3 system, K2O/Al2O3 shows some similarities with respect to the formation of bulk nitrates upon H2O contact. However, there are significant differences that originate from the lower melting temperature of KNO3 relative to Ba(NO3)2.

  6. Effect of sulfation on the surface activity of CaO for N2O decomposition

    NASA Astrophysics Data System (ADS)

    Wu, Lingnan; Hu, Xiaoying; Qin, Wu; Dong, Changqing; Yang, Yongping

    2015-12-01

    Limestone addition to circulating fluidized bed boilers for sulfur removal affects nitrous oxide (N2O) emission at the same time, but mechanism of how sulfation process influences the surface activity of CaO for N2O decomposition remains unclear. In this paper, we investigated the effect of sulfation on the surface properties and catalytic activity of CaO for N2O decomposition using density functional theory calculations. Sulfation of CaO (1 0 0) surface by the adsorption of a single gaseous SO2 or SO3 molecule forms stable local CaSO3 or CaSO4 on the CaO (1 0 0) surface with strong hybridization between the S atom of SOx and the surface O anion. The formed local CaSO3 increases the barrier energy of N2O decomposition from 0.989 eV (on the CaO (1 0 0) surface) to 1.340 eV, and further sulfation into local CaSO4 remarkably increases the barrier energy to 2.967 eV. Sulfation from CaSO3 into CaSO4 is therefore the crucial step for deactivating the surface activity for N2O decomposition. Completely sulfated CaSO4 (0 0 1) and (0 1 0) surfaces further validate the negligible catalytic ability of CaSO4 for N2O decomposition.

  7. New pyrometallurgical process of EAF dust treatment with CaO addition

    NASA Astrophysics Data System (ADS)

    Chairaksa-Fujimoto, Romchat; Inoue, Yosuke; Umeda, Naoyoshi; Itoh, Satoshi; Nagasaka, Tetsuya

    2015-08-01

    The non-carbothermic zinc pyrometallurgical processing of electric arc furnace (EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite (ZnFe2O4), which accounts for more than half of total zinc in the EAF dust, into ZnO and Ca2Fe2O5 by CaO addition. The EAF dust was mixed with CaO powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100C for a predetermined holding time. All ZnFe2O4 was transformed into ZnO and Ca2Fe2O5 at a minimum temperature of 900C within 1 h when sufficient CaO to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess CaO beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than ZnFe2O4. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100C when CaO was added.

  8. Combined effects of Fenton peroxidation and CaO conditioning on sewage sludge thermal drying.

    PubMed

    Liu, Huan; Liu, Peng; Hu, Hongyun; Zhang, Qiang; Wu, Zhenyu; Yang, Jiakuan; Yao, Hong

    2014-12-01

    Joint application of Fenton's reagent and CaO can dramatically enhance sludge dewaterability, thus are also likely to affect subsequent thermal drying process. This study investigated the synergistic effects of the two conditioners on the thermal drying behavior of sewage sludge and the emission characteristics of main sulfur-/nitrogen-containing gases. According to the results, Fenton peroxidation combined with CaO conditioning efficiently promoted sludge heat transfer, reduced the amounts of both free and bound water, and created porous structure in solids to provide evaporation channels, thus producing significant positive effects on sludge drying performance. In this case, the required time for drying was shortened to one-third. Additionally, joint usage of Fenton's reagent and CaO did not increase the losses of organic matter during sludge drying process. Meanwhile, they facilitated the formation of sulfate and sulfonic acid/sulfone, leading to sulfur retention in dried sludge. Both of Fenton peroxidation and CaO conditioning promoted the oxidation, decomposition, and/or dissolution of protein and inorganic nitrogen in sludge pre-treatment. As a consequence, the emissions of sulfurous and nitrogenous gases from dewatered sludge drying were greatly suppressed. These indicate that combining Fenton peroxidation with CaO conditioning is a promising strategy to improve drying efficiency of sewage sludge and to control sulfur and nitrogen contaminants during sludge thermal drying process. PMID:25289973

  9. Effect of MgO and CaO on Transformation of Andalusite to Mullite

    NASA Astrophysics Data System (ADS)

    Pooladvand, H.; Baghshahi, S.; Mirhadi, B.; Souri, A. R.; Arabi, H.

    2012-08-01

    Andalusite as a refractory material can be transformed to mullite and a silica-rich liquid phase in a temperature range of 1100-1600 C. In this paper, the influences of MgO and CaO mineralizers on transformation of andalusite to mullite were investigated. Different amounts of MgO and CaO were introduced to andalusite by solution (precipitation) method. Then the precipitated particles were pressed, dried, and fired at 1300, 1400, 1500, and 1600 C for 2 h. The microstructures of these samples were studied by XRD and SEM. The results showed that the addition of MgO and CaO affected mullitization of andalusite, so that the addition of these oxides increased the amount of mullite formation in andalusite.

  10. METHOD FOR VARIATION OF GRAIN SIZE IN STUDIES OF GAS-SOLID REACTIONS INVOLVING CAO

    EPA Science Inventory

    The paper describes a method for varying grain size in studies of gas-solid reactions involving CaO. (Note: Introducing grain size as an independent experimental variable should contribute to improved understanding of reactions in porous solids.) Calcining 1 micrometer CaCO3 part...

  11. Highly basic CaO nanoparticles in mesoporous carbon materials and their excellent catalytic activity.

    PubMed

    Raja, Pradeep Kumar; Chokkalingam, Anand; Priya, Subramaniam V; Balasubramanian, Veerappan V; Benziger, Mercy R; Aldeyab, Salem S; Jayavell, Ramasamy; Ariga, Katsukiho; Vinu, Ajayan

    2012-06-01

    Highly basic CaO nanoparticles immobilized mesoporous carbon materials (CaO-CMK-3) with different pore diameters have been successfully prepared by using wet-impregnation method. The prepared materials were subjected to extensive characterization studies using sophisticated techniques such as XRD, nitrogen adsorption, HRSEM-EDX, HRTEM and temperature programmed desorption of CO2 (TPD of CO2). The physico-chemical characterization results revealed that these materials possess highly dispersed CaO nanoparticles, excellent nanopores with well-ordered structure, high specific surface area, large specific pore volume, pore diameter and very high basicity. We have also demonstrated that the basicity of the CaO-CMK-3 samples can be controlled by simply varying the amount of CaO loading and pore diameter of the carbon support. The basic catalytic performance of the samples was investigated in the base-catalyzed transesterification of ethylacetoacetate by aryl, aliphatic and cyclic primary alcohols. CMK-3 catalyst with higher CaO loading and larger pore diameter was found to be highly active with higher conversion within a very short reaction time. The activity of 30% CaO-CMK3-150 catalyst for transesterification of ethylacetoacetate using different alcohols increases in the following order: octanol > butanol > cyclohexanol > benzyl alcohol > furfuryl alcohol. PMID:22905508

  12. IDENTIFICATION OF CASO4 FORMED BY REACTION OF CAO AND SO2

    EPA Science Inventory

    The article discusses the XRD-determination of the identity of CaSO4, formed by the reaction between CaO and S02, and the support of that determination by density measurements with helium pycnometry. The anhydrous CaS04 compound formed has an orthorhombic crystal structure and an...

  13. Evaluation of antibacterial activity of plant mediated CaO nanoparticles using Cissus quadrangularis extract.

    PubMed

    Marquis, Gowdhami; Ramasamy, Balagurunathan; Banwarilal, Sarkar; Munusamy, Ayyasamy Pudukadu

    2016-02-01

    An assessment of antibacterial activity of greenly synthesized nanoparticles using aqueous stem extract of Cissus quadrangularis was carried out. The synthesized nanoparticles were characterized by UV-Vis spectroscopy, SEM, XRD, FTIR and further subjected for antibacterial activity against the pathogens Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysenteriae and Vibrio cholerae. The SEM photograph represents cubic and hexagonal shape of NPs about 58nm respectively whereas the XRD indicated the pure phase of the product and no impurity in peaks of well crystallized products. The FTIR spectrum of nanoparticles showed intensive peaks with blue shift indicating the crystalline and shorten the distance of crystal lattice. The plant mediated CaO nanoparticles showed maximum inhibition on E. coli followed by other strains. In MIC, the plant mediated CaO NPs possess high activity against all the test organisms whereas the CaCl2 and CaO compounds were moderately active. The approach to the synthesis of plant mediated CaO NPs has many advantages as scaled up, economic viability, etc. Application of such ecofriendly nanoparticles in bactericidal, wound healing and other medical applications makes this method potential existing for the large scale synthesis of the inorganic materials. PMID:26723000

  14. Effective pair potential for Ca-O bonds in CaGeO3 polymorphs

    NASA Astrophysics Data System (ADS)

    Koganemaru, A.; Yoshiasa, A.; Wang, L.; Nakatani, T.; Nakatsuka, A.; Okube, M.; Arima, H.; Sugiyama, K.

    2013-04-01

    The CaGeO3 perovskite and garnet were synthesized in a cubic anvil type apparatus under high pressure. The measurements of Ca and Ge K- edge XAFS spectra were carried out in the transmission mode at temperature up to 700 K. The effective pair potentials V(u)=?u2/2+?u3/3!, for Ca-O bond in various phases of CaGeO3 have been investigated by the temperature dependence of EXAFS Debye-Waller factors. The potential coefficient ? for the Ca-O bond in perovskite-type CaGeO3 is small, 4.4 eV/2 compared with those in garnet (6.0 eV/2) and wollastonite (6.4 eV/2). The potential for Ca-O bond in perovskite is broader than those in other CaGeO3 polymorphs, which is one reason for the Clausius-Clapeyron's curve for perovskite-garnet phase boundary having a negative slope. The potential coefficients for the Ca-O in perovskite are significantly smaller than those for the longer Ge-Ge distances as the framework vibration though the potential coefficient decreases usually as a result of the larger bond distance.

  15. Effect of partial carbonation on the cyclic CaO carbonation reaction

    SciTech Connect

    Grasa, G.; Abanades, J.C.; Anthony, E.J.

    2009-10-15

    CaO particles from the calcination of natural limestones can be used as regenerable solid sorbents in some CO{sub 2} capture systems. Their decay curves in terms of CO{sub 2} capture capacity have been extensively studied in the literature, always in experiments allowing particles to reach their maximum carbonation conversion for a given cycle. However, at the expected operating conditions in a CO{sub 2} capture system using the carbonation reaction, a relevant fraction of the CaO particles will not have time to fully convert in the carbonator reactor. This work investigates if there is any effect on the decay curves when CaO is only partially converted in each cycle. Experiments have been conducted in a thermobalance arranged to interrupt the carbonation reaction in each cycle before the end of the fast reaction period typical in the CaO-CO{sub 2} reaction. It is shown that, after the necessary normalization of results, the effective capacity of the sorbent to absorb CO{sub 2} during particle lifetime in the capture system slightly increases and CaO particles partially converted behave 'younger' than particles fully converted after every calcination. This has beneficial implications for the design of carbonation/calcination loops.

  16. The AtCAO gene, encoding chlorophyll a oxygenase, is required for chlorophyll b synthesis in Arabidopsis thaliana.

    PubMed

    Espineda, C E; Linford, A S; Devine, D; Brusslan, J A

    1999-08-31

    Chlorophyll b is synthesized from chlorophyll a and is found in the light-harvesting complexes of prochlorophytes, green algae, and both nonvascular and vascular plants. We have used conserved motifs from the chlorophyll a oxygenase (CAO) gene from Chlamydomonas reinhardtii to isolate a homologue from Arabidopsis thaliana. This gene, AtCAO, is mutated in both leaky and null chlorina1 alleles, and DNA sequence changes cosegregate with the mutant phenotype. AtCAO mRNA levels are higher in three different mutants that have reduced levels of chlorophyll b, suggesting that plants that do not have sufficient chlorophyll b up-regulate AtCAO gene expression. Additionally, AtCAO mRNA levels decrease in plants that are grown under dim-light conditions. We have also found that the six major Lhcb proteins do not accumulate in the null ch1-3 allele. PMID:10468639

  17. Hydrometallurgical extraction of zinc from CaO treated EAF dust in ammonium chloride solution.

    PubMed

    Miki, Takahiro; Chairaksa-Fujimoto, Romchat; Maruyama, Katsuya; Nagasaka, Tetsuya

    2016-01-25

    Zinc in Electric Arc Furnace dust or EAF dust mainly exists as ZnFe2O4 and ZnO. While ZnO can be simply dissolved into either an acidic or alkaline solution, it is difficult to dissolve ZnFe2O4. In our previous work, we introduced a process called "CaO treatment", a preliminary pyrometallurgical process designed to transform the ZnFe2O4 in the EAF dust into ZnO and Ca2Fe2O5. The halogens and others heavy metals were favorably vaporized during CaO treatment with no essential evaporation loss of zinc and iron, leaving CaO treated dust which consisted mainly of ZnO and Ca2Fe2O5 and no problematic ZnFe2O4 compound. In this work, the selective leaching of zinc over iron and calcium in the CaO treated dust was investigated using an NH4Cl solution. The effects of temperature, reaction time and NH4Cl concentration on dissolution behavior were examined. While most of the zinc in the CaO treated dust was extracted after 2 h at 70 °C with 2 M NH4Cl, only about 20% of calcium was leached in NH4Cl solution. However, the iron did not dissolve and remained as Ca2Fe2O5 in residue. It was confirmed that zinc can be effectively recovered using NH4Cl solution. PMID:26448494

  18. Materials compatibility during the chlorination of molten CaCl/sub 2/. CaO salts. [CaCl/sub 2/. CaO salt

    SciTech Connect

    Rense, C.E.C.; Fife, K.W.; Bowersox, D.F.; Ferran, M.D.

    1987-01-01

    As part of our effort to develop a semicontinuous PuO/sub 2/ reduction process, we are investigating promising materials for containing a 900/sup 0/C molten CaCl/sub 2/ . CaO chlorination reaction. We want the material to contain this reaction and to be reusable. We tested candidate materials in a simulated salt (no plutonium) using anhydrous HCl as the chlorinating agent. Data are presented on the performance of 36 metals and alloys, 9 ceramics, and 3 coatings.

  19. Zircon U-Pb and Lu-Hf isotopic and geochemical constraints on the origin of the paragneisses from the Jiaobei terrane, North China Craton

    NASA Astrophysics Data System (ADS)

    Shan, Houxiang; Zhai, Mingguo; Zhu, Xiyan; Santosh, M.; Hong, Tao; Ge, Songsheng

    2016-01-01

    Clastic sedimentary rocks are important tracers to understand the evolution of the continental crust. Whole-rock major and trace element data, zircon U-Pb dating and Hf isotopic data for the paragneisses from the Jiaobei terrane are presented in this study in order to constrain their protoliths, provenance and tectonic setting. The paragneisses are characterized by enrichment in Al2O3 and TiO2, negative DF (DF = 10.44 - 0.21SiO2 - 0.32Fe2O3T - 0.98MgO + 0.55CaO + 1.46Na2O + 0.54K2O) values and the presence of aluminum-rich metamorphic minerals (e.g., garnet and sillimanite). Together with the mineral assemblages and zircon features, it can be inferred that the protoliths of these rocks are of sedimentary origin. The K-A (A = Al2O3/(Al2O3 + CaO + Na2O + K2O), K = K2O/(Na2O + K2O)) and log(Fe2O3/K2O)-log(SiO2/Al2O3) diagrams indicate that they belong principally to clay-silty rocks with some contributions from graywacke. A series of geochemical indexes, such as the widely employed CIA (CIA = [Al2O3/(Al2O3 + CaO∗ + Na2O + K2O)] × 100; molar proportions) and ICV (ICV = (Fe2O3 + MnO + MgO + CaO + Na2O + K2O + TiO2)/Al2O3) values, and the A-CN-K diagram for the paragneisses indicate relatively weak weathering in the source rocks and negligible post-depositional K-metasomatism. In addition, their REE patterns, low Cr/Zr (0.61-1.99), high Zr/Y (4.81-23.59) and Th/U (3.21-40.67) ratios, the low to moderate contents of Cr (197-362 ppm) and Ni (6.68-233 ppm), and source rock discrimination diagrams collectively suggest that the sediments of the protoliths of the paragneisses in the Jiaobei terrane were derived from the source with intermediate-acidic composition, probably granitic-to-tonalitic rocks. In combination with geochronological and isotopic studies on the paragneisses and the basement rocks in the Jiaobei terrane, it is suggested that the Archean-early Paleoproterozoic granitic rocks in the Jiaobei terrane possibly provided the most important source materials. In addition, the protoliths of the paragneisses might have been deposited during 2.47-2.42 Ga. High and heterogeneous ICV values of the paragneisses could imply a chemically immature source. A number of geochemical indicators and tectonic discrimination diagrams together indicate an island arc or active continent margin setting for the deposition of the protoliths of the paragneisses in the Jiaobei terrane. Together with the nearly contemporaneous igneous rocks, it can be inferred that the convergent margin setting was possibly operative during the Late Neoarchean-Early Paleoproterozoic transition in the Jiaobei terrane.

  20. Sulfation of CaO particles in a carbonation/calcination loop to capture CO{sub 2}

    SciTech Connect

    Grasa, G.S.; Alonso, M.; Abanades, J.C.

    2008-03-15

    CaO is being proposed as a regenerable sorbent of CO{sub 2} via a carbonation/calcination loop. It is well known that natural sorbents lose their capacity to capture CO{sub 2} with the number of cycles due to textural degradation. In coal combustion systems, reaction with the SO{sub 2} present in flue gases also causes sorbent deactivation. This work investigates the effect of partial sorbent sulfation on the amount of CaO used in systems where both carbonation and sulfation reactions are competing. We have found that SO{sub 2} reacts with the deactivated CaO resulting from repetitive calcination/carbonation reactions. Therefore, the deactivation of CaO as a result of the presence of SO{sub 2} is lower than one would expect if one assumes that SO{sub 2} reacts only with active CaO. This work shows that changes in the texture of the sorbent due to repetitive carbonation/calcination cycles tend to increase the sulfation capacity of the sorbents tested. This suggests that the purge of deactivated CaO obtained from a CO{sub 2} capture loop could be a more effective sorbent of SO{sub 2} than fresh CaO.

  1. [Determination of major elements in superphosphate by X-ray fluorescence spectrometry].

    PubMed

    Rui, Yu-Kui; Li, He; Shen, Jian-Bo; Zhang, Fu-Suo

    2008-11-01

    Phosphate fertilizer is one of the most important fertilizers. The authors determined nine kinds of major elements in superphosphate, the most important phosphate fertilizer, by X-ray fluorescence spectrometry. The detection range of SiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O and P2O5 is 15.0%-90.0%, 0.20%-25.0%, 0.20%-25.0%, 0.01%-0.35%, 0.20%-40.0%, 0.10%-35.0%, 0.10%-7.50%, 0.05%-7.50% and 1.00%-100.00% respectively, and the precision of the method for SiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O and P2O5 range from 0.20% to 0.005%, so the method of X-ray fluorescence spectrometry is a fast and effectual method for detecting the composition of phosphate fertilizer. The contents of the above elements showed (1) the detected superphosphate content is 18.101% of P2O5, which is accordant to the labeled level (> or = 16%); (2) the detected superphosphate contains much SiO2, TFe2O3, MgO, CaO and K2O, which are necessary for plant growth and the content of which is 16.954%, 1.495%, 1.580%, 21.428% and 1.585% respectively. These data showed that phosphate fertilizer sometimes can supply some trace elements for plants, but we should eliminate the interference effect of these elements when we research the role of phosphorus; (3) superphosphate contains 3.225% of Al2O3, so the authors should attention to the aluminium poison when superphosphate is used chronically. PMID:19271522

  2. [Version investigation and the author investigation and argumentation of Zeng Bu Shi Wu Ben Cao Bei Kao].

    PubMed

    Zheng, Hong; Liao, Chun-Hong

    2012-11-01

    Zeng Bu Shi Wu Ben Cao Bei Kaois the masterpiece of Guangdong food material medica works Based on the investigation of the existing version. We think the statement that Chinese ancient books catalogue record the first version of the book is in ten years of Yong Zheng is wrong. We infer that Zeng Bu Shi Wu Ben Cao Bei Kao's author named He kejian and Sheng Cao Yao Xing Be Yao's author named He Jian is the same person. However, the former book is mainly sorted by He Shengxuan, and it maybe initially carved in 1738. PMID:23363852

  3. Temperature effect corrections for URAGAN based on CAO, GDAS, NOAA data

    NASA Astrophysics Data System (ADS)

    Dmitrieva, A.; Ampilogov, N.; Astapov, I.; Barbashina, N.; Borog, V.; Chernov, D.; Kovylyaeva, A.; Kokoulin, R.; Kompaniets, K.; Mannocchi, G.; Mishutina, Yu; Petrukhin, A.; Saavedra, O.; Shutenko, V.; Sit'ko, O.; Trinchero, G.; Yakovleva, E.; Yashin, I.

    2015-08-01

    For the analysis of muon flux variations caused by extra-atmospheric processes it is necessary to introduce corrections for meteorological effects. For temperature effect (TE) correction it is necessary to know the temperature profile of the atmosphere. As a rule, this profile is measured by meteorological balloons two or four times a day. Alternative sources are satellite observations and data obtained from models of atmosphere used for weather forecasting. Vertical temperature profiles obtained from NOAA satellites, GDAS (Global Data Assimilation System) and CAO data (Central Aerological Observatory, Russia) for standard isobaric levels were compared. Mean value of temperature difference for most levels does not exceed 1 K. Comparison of URAGAN data corrected for TE with CAO information, satellites and GDAS shows a good agreement. Counting rate and anisotropy of the muon flux corrected for meteorological effects for 2007-2014 are presented.

  4. Characteristics of HCN removal using CaO at high temperatures

    SciTech Connect

    Houzhang Tan; Xuebin Wang; Congling Wang; Tongmo Xu

    2009-03-15

    Experimental investigation on the removal of hydrogen cyanide (HCN) using calcium oxide (CaO) was carried out in a fixed bed reactor at temperature ranging from 300 to 1173 K, and the original HCN was produced during the pyrolysis of pyridine. Effects of temperature, volume space velocity, and initial HCN concentration on HCN removal were discussed. The results of temperature-programmed experiments show that temperature is the main factor affecting HCN removal. With the formation of CO, HCN starts to decrease from 473 K, and remains unchanged from 673 to 873 K. At 873 K, there is a further decrease in HCN without CO formation, and when temperature is higher than 1023 K, HCN is removed completely. In the isothermal experiments, CaCN{sub 2} was detected at 723 K, but at higher temperatures of 923 and 1123 K, there was no CaCN{sub 2} in the solid residues, and the nitrogen in the removed HCN was equal to that in the formed N{sub 2}. This indicates that at a lower temperature CaO is consumed to remove HCN, CaO + 2HCN {yields} CaCN{sub 2} + CO + H{sub 2}; but at a higher temperature, CaO acts as a catalyst for HCN removal, 2C{sub i}H{sub j} + 2HCN {yields} N{sub 2} + (j + 1 - k)H{sub 2} + 2C{sub I} + 1H{sub k}. The investigation on the removal efficiency shows that there is a critical temperature and a critical volume space velocity at which the HCN removal efficiency is able to reach up to 100%. 41 refs., 9 figs., 2 tabs.

  5. Porous carbon material containing CaO for acidic gas capture: preparation and properties.

    PubMed

    Przepiórski, Jacek; Czyżewski, Adam; Pietrzak, Robert; Toyoda, Masahiro; Morawski, Antoni W

    2013-12-15

    A one-step process for the preparation of CaO-containing porous carbons is described. Mixtures of poly(ethylene terephthalate) with natural limestone were pyrolyzed and thus hybrid sorbents could be easily obtained. The polymeric material and the mineral served as a carbon precursor and CaO delivering agent, respectively. We discuss effects of the preparation conditions and the relative amounts of the raw materials used for the preparations on the porosity of the hybrid products. The micropore areas and volumes of the obtained products tended to decrease with increasing CaO contents. Increase in the preparation temperature entailed a decrease in the micropore volume, whereas the mesopore volume increased. The pore creation mechanism is proposed on the basis of thermogravimetric and temperature-programmed desorption measurements. The prepared CaO-containing porous carbons efficiently captured SO2 and CO2 from air. Washing out of CaO from the hybrid materials was confirmed as a suitable method to obtain highly porous carbon materials. PMID:23743266

  6. Interfacial Phenomena among Liquid Iron-Carbon Alloy, Liquid Slag, and Solid CaO

    NASA Astrophysics Data System (ADS)

    Taniguchi, Yoshinori; Seetharaman, Seshadri

    2012-06-01

    Interfacial phenomena between hot metal, liquid slag and solid CaO are important to the understanding of the desulfurization reaction in hot-metal treatment processes. In the current work, the surface tension of molten iron-carbon alloy and liquid slag as well as the interfacial tensions among molten iron-carbon alloy-solid CaO, liquid slag-solid CaO, as well as molten iron-carbon alloy-liquid slag were measured in the temperature range 1623 K to 1723 K (1350 °C to 1450 °C). The sessile drop method has been used for these measurements. To analyze the experimental results, two types of graphical analysis programs have been developed to determine the coordinates of the X-ray shadow or charge-coupled device (CCD) image of the droplet. Furthermore, a software package that uses the Gauss-Newton method to minimize an error function between the physically observed and a theoretical Laplacian curve has also been developed in this work.

  7. CaO nanocrystals grown over SiO2 microtubes for efficient CO2 capture: organogel sets the platform.

    PubMed

    Prathap, Annamalai; Shaijumon, M M; Sureshan, Kana M

    2016-01-14

    Materials that can capture and store CO2 are important. Though CaO is a cheap sorbent, it is inefficient for practical purposes due to sintering and poor diffusion of CO2 through the surface-CaCO3 layer. We have developed a high performance, sintering-resistant CaO-based sorbent by uniformly nanofabricating the CaO nanocrystals on SiO2 microtubes made by organogel templated polymerization. PMID:26621485

  8. Evolutionary Changes in Chlorophyllide a Oxygenase (CAO) Structure Contribute to the Acquisition of a New Light-harvesting Complex in Micromonas*?

    PubMed Central

    Kunugi, Motoshi; Takabayashi, Atsushi; Tanaka, Ayumi

    2013-01-01

    Chlorophyll b is found in photosynthetic prokaryotes and primary and secondary endosymbionts, although their light-harvesting systems are quite different. Chlorophyll b is synthesized from chlorophyll a by chlorophyllide a oxygenase (CAO), which is a Rieske-mononuclear iron oxygenase. Comparison of the amino acid sequences of CAO among photosynthetic organisms elucidated changes in the domain structures of CAO during evolution. However, the evolutionary relationship between the light-harvesting system and the domain structure of CAO remains unclear. To elucidate this relationship, we investigated the CAO structure and the pigment composition of chlorophyll-protein complexes in the prasinophyte Micromonas. The Micromonas CAO is composed of two genes, MpCAO1 and MpCAO2, that possess Rieske and mononuclear iron-binding motifs, respectively. Only when both genes were introduced into the chlorophyll b-less Arabidopsis mutant (ch1-1) was chlorophyll b accumulated, indicating that cooperation between the two subunits is required to synthesize chlorophyll b. Although Micromonas has a characteristic light-harvesting system in which chlorophyll b is incorporated into the core antennas of reaction centers, chlorophyll b was also incorporated into the core antennas of reaction centers of the Arabidopsis transformants that contained the two Micromonas CAO proteins. Based on these results, we discuss the evolutionary relationship between the structures of CAO and light-harvesting systems. PMID:23677999

  9. Chemical durability and Structural approach of the glass series (40-y) Na2O-yFe2O3-5Al2O3-55P2O5-by IR, X-ray diffraction and Mssbauer Spectroscopy

    NASA Astrophysics Data System (ADS)

    Aqdim, S.; Sayouty, El H.; Elouad, B.; Greneche, J. M.

    2012-02-01

    The relationship between the composition and structure for the glasses of general composition (40-y)Na2O-yFe2O3-5Al2O3-55P2O5 (5<=y<=20), has been studied. The chemical durability and density of these glasses increase with increasing Fe2O3 content. The dissolution rate (DR), calculated from the weight loss in distilled water at 90C for up to 20 days was ? 3.10-9 g/cm2/mn which is 30 times lower than that of window glass. The structure and valence states of the iron ions in the glasses were investigated using, X-ray diffraction, 57Fe Mssbauer spectrometry, potentiometric analysis, and infrared spectroscopy. Both Mssbauer spectrometry and potentiometric analysis allow to estimate both Fe2+ and Fe3+ contents in all these glasses. X-ray diffraction indicates that the local structure of iron phosphate glasses is related to the short range structures of NaFeP2O7. Infrared spectra indicate the formation of P-O-Fe bonds in the pyrophosphate glasses that replace P-O-Na bonds. The presence of a small content of Al2O3 in the glass seems to play a role as a network modifier. The addition of Fe2O3 to Al2O3 in phosphate glasses favours the enhancement of the formation of pyrophosphate units because iron ions have stronger effect on the depolymerization of metaphosphate chains than the aluminium ions. Finally, the I.R spectra indicate that the presence of P-O-Fe bands of these glasses containing more than 15 mol%Fe2O3 is consistent with their good chemical durability.

  10. Bulk Crystallization in a SiO2/Al2O3/Y2O3/AlF3/B2O3/Na2O Glass: Fivefold Pseudo Symmetry due to Monoclinic Growth in a Glassy Matrix Containing Growth Barriers.

    PubMed

    Wisniewski, Wolfgang; Seyring, Martin; Patzig, Christian; Hche, Thomas; Keshavarzi, Ashkan; Rssel, Christian

    2016-01-01

    A glass with the mol% composition 17 Y2O333 Al2O340 SiO22 AlF33 Na2O2 CeF33 B2O3 is heat treated at 1000?C for 6-24?h. This results in the surface nucleation and growth of YAG. Nucleation and growth of star-shaped alumina and later of monoclinic ?-Y2Si2O7 and orthorhombic ?-Y2Si2O7 are additionally observed in the bulk. Phase identification and localization are performed by electron backscatter diffraction (EBSD) as well as TEM analysis. The monoclinic ?-Y2Si2O7 observed in the bulk occurs in the form of large, crystal agglomerates which range from 50 to 120??m in size. The individual crystals are aligned along the c-axis which is the fastest growing axis. Ten probability maxima are observed in the pole-figures illustrating the rotation of orientations around the c-axes indicating a fivefold symmetry. This symmetry is caused by multiple twinning which results in a high probability of specific orientation relationships with rotation angles of ~36, ~108 (also referred to as the pentagon angle) and ~144 around the c-axis. All these rotation angles are close to the multiples of 36 which are required for an ideal fivefold symmetry. This is the first report of a fivefold symmetry triggered by the presence of barriers hindering crystal growth. PMID:26813152

  11. The mineralogy and geochemistry of quartz-tourmaline schlieren in the granites of the Primorsky Complex, Western Baikal Region

    NASA Astrophysics Data System (ADS)

    Savel'eva, V. B.; Bazarova, E. P.; Kanakin, S. V.

    2014-12-01

    Quartz-tourmaline schlieren have been found within rapakivi-like granites of the Early Proterozoic Primorsky Complex in the Western Baikal Region. These rocks are biotite leucogranites with normal alkalinity (A/CNK = 1.00-1.04); a high iron mole fraction (92-95%); a K2O/Na2O value of about 2.0; relatively high F, Li, Rb, Cs, Sn, Pb, Th, and U contents; and low Ba, Sr, Eu, Zn, Sc, and V contents. The schlieren composed of quartz and tourmaline with relics of feldspar also contain fluorite, rare muscovite, chlorite, and accessory rutile, ilmenite, zircon, monazite, xenotime, and bastnäsite. B2O3 and F contents in the schlieren are 2.29-2.63 and 0.30-0.47 wt %, respectively. Fe2O3 (4.8-5.4 wt %), F, and H2O contents are higher in these schlieren than in the host granite, while SiO2, CaO, Na2O, K2O, and P2O5 contents are lower than in host rocks. K2O/Na2O values decrease in the schlieren down to 0.4. Enrichment of the schlieren in Fe and other ore elements (Zn, Co, Cu, Sn, etc.), together with B, F, H2O, and Na, suggests that they crystallized from fluid-saturated melt segregated from aluminosilicate melt in the apical part of a shallow-seated intrusion. The formation of tourmaline may be related to the interaction of the fluid with feldspars in the crystallizing granites; it was accompanied by a separation of fluid F-CO2. Quartz precipitated at the next stage, due to the acidic character of the aqueous fluid. In general, the relationships of minerals in the schlieren indicate distinct fractionation of LREE, HREE, and Y in the fluid-saturated melt.

  12. Calcium precursors for the production of CaO sorbents for multicycle CO2 capture.

    PubMed

    Liu, Wenqiang; Low, Nathanael W L; Feng, Bo; Wang, Guoxiong; Diniz da Costa, Joo C

    2010-01-15

    A screening of potential calcium precursors for the production of CaO sorbents for CO(2) capture at high temperature was conducted in this work. The precursors studied include microsized calcium carbonate (CC-CaO), calcium hydroxide (CH-CaO), nanosized (<70 nm) calcium carbonate (CC70 nm-CaO), nanosized (<160 nm) calcium oxide (CaO160 nm-CaO), calcium acetate hydrate (CA-CaO), calcium l-lactate hydrate (CL-CaO), calcium formate (CF-CaO), calcium citrate tetrahydrate (CCi-CaO), and calcium d-gluconate monohydrate (CG-CaO). The capture capability of these sorbents was investigated using a thermogravimetric analyzer (TGA) for multiple capture cycles. CG-CaO exhibited the best capacity for capturing CO(2) with a 1-min conversion of 65.9% and a 30-min conversion of 83.8% at the ninth cycle. Subsequently, a further parametric study was conducted to examine the effect of reaction conditions such as reaction temperature (550-750 degrees C) and CO(2) gas concentration (1-15%) on the capture capacity of CG-CaO. The sorbent CG-CaO also showed a much lower decomposition temperature and higher predicted residual conversion after prolonged cycles, compared with CC-CaO. PMID:20030311

  13. Formation of 1D adsorbed water structures on CaO(001)

    NASA Astrophysics Data System (ADS)

    Zhao, Xunhua; Bhattacharya, Saswata; Ghiringhelli, Luca M.; Levchenko, Sergey V.; Scheffler, Matthias

    2015-03-01

    Understanding the interaction of water with oxide surfaces is of fundamental importance for basic and engineering sciences. Recently, a spontaneous formation of one-dimensional (1D) adsorbed water structures have been observed on CaO(001). Interestingly, at other alkaline earth metal oxides, in particular MgO(001) and SrO(001), such structures have not been found experimentally. We calculate the relative stability of adsorbed water structures on the three oxides using density-functional theory combined with the ab initio atomistic thermodynamics. Low-energy structures at different coverages are obtained with a first-principles genetic algorithm. Finite-temperature vibrational spectra are calculated using ab initio molecular dynamics. We find a range of (T, p) conditions where 1D structures are thermodynamically stable on CaO(001). The orientation and vibrational spectra of the 1D structures are in agreement with the experiments. The formation of the 1D structures is found to be actuated by a symmetry breaking in the adsorbed water tetramer, as well as by a balance between water-water and water-substrate interactions, determined by the lattice constant of the oxide.

  14. Impacts of the 2010 Amazon drought on forest structure and function using CAO AToMS

    NASA Astrophysics Data System (ADS)

    Asner, G. P.; Martin, R. E.; Knapp, D. E.; Kennedy-Bowdoin, T.; Kellner, J.

    2012-12-01

    The 2010 Amazon mega-drought is thought to have had a widespread impact on forest condition, including tree mortality. However, no large-scale, high-resolution information exists on changes in forest structure, function, turnover or other processes in response to the drought. With the possibility of increasing drought frequency in the Amazon basin, it is now critical that we develop repeat, large-area studies to assess impacts and recovery. Using the Carnegie Airborne Observatory Airborne Taxonomic Mapping System (AToMS), we assessed the impacts of the 2010 drought by repeat flying of approximately 500,000 hectares of lowland humid tropical forest in the Peru Amazon. The CAO AToMS Visible-to-Near-Infrared (VNIR) and Visible-to-Shortwave-Infrared (VSWIR) imaging spectrometers recorded changes in forest canopy spectral, chemical and physiological state from 2009 to 2011. Areas of greatest functional change were observed near the Peru-Brazil border in areas under heavy forest use for selective logging. The CAO AToMS waveform Light Detection and Ranging (LiDAR) instruments measured highest rates of treefall and canopy gap formation in areas subjected to combined drought and logging, and on low fertility soils. The results provide the first spatially-explicit, large-scale and ecologically detailed information on the response of Amazonian forests to drought.

  15. Structural studies of mixed glass former 0.35Na2O + 0.65[xB2O3 + (1 - x)P2O5] glasses by Raman and 11B and 31P magic angle spinning nuclear magnetic resonance spectroscopies.

    PubMed

    Christensen, Randilynn; Olson, Garrett; Martin, Steve W

    2013-02-21

    The mixed glass former (MGF) effect (MGFE) is defined as a nonlinear and nonadditive change in the ionic conductivity with changing glass former composition at constant modifier composition. In this study, sodium borophosphate 0.35Na(2)O + 0.65[xB(2)O(3) + (1 - x)P(2)O(5)], 0 ? x ? 1, glasses which have been shown to exhibit a positive MGFE have been prepared and examined using Raman and (11)B and (31)P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies. Through examination of the short-range order (SRO) structures found in the ternary glasses, it was determined that the minority glass former, B for 0.1 ? x ? 0.7 and P for 0.7 ? x ? 0.9, is "overmodified" and contains more Na(+) ions than would be expected from simple linear mixing of the binary sodium borate, x = 1, and sodium phosphate, x = 0, glasses, respectively. Changes in the intermediate range order (IRO) structures were suggested by changes in the NMR spectral chemical shifts and Raman spectra wavenumber shifts over the full composition range x in the Raman and MAS NMR spectra. The changes observed in the chemical shifts of (31)P MAS NMR spectra with x are found to be too large to be caused solely by changing sodium modification of the phosphate SRO structural groups, and this indicates that internetwork bonding between phosphorus and boron through bridging oxygens (BOs), P-O-B, must be a major contributor to the IRO structure of these glasses. While not fully developed, a first-order thermodynamic analysis based upon the Gibbs free energies of formation of the various SRO structural units in this system has been developed and can be used to account for the preferential formation of tetrahedral boron groups, B(4), by the reaction of B(3) with P(2) groups to form B(4) and P(3) groups, respectively, where the superscript denotes the number of BOs on these units, in these glasses. This preference for B(4) units appears to be a predominate cause of the changing modifier to glass former ratio with composition x in these ternary MGF glasses and appears to be associated with the large negative value of the Gibbs free energy of formation of this group. PMID:23281937

  16. Self-healing of defects in CaO coatings on V-5%Cr-5%Ti in liquid lithium

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1994-11-01

    In-situ electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt % dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at >360{degrees}C.

  17. Phonon-Mediated Electron Transport through CaO Thin Films

    NASA Astrophysics Data System (ADS)

    Cui, Yi; Tosoni, Sergio; Schneider, Wolf-Dieter; Pacchioni, Gianfranco; Nilius, Niklas; Freund, Hans-Joachim

    2015-01-01

    Scanning tunneling microscopy has developed into a powerful tool for the characterization of conductive surfaces, for which the overlap of tip and sample wave functions determines the image contrast. On insulating layers, as the CaO thin film grown on Mo(001) investigated here, direct overlap between initial and final states is not enabled anymore and electrons are transported via hopping through the conduction-band states of the oxide. Carrier transport is accompanied by strong phonon excitations in this case, imprinting an oscillatory signature on the differential conductance spectra of the system. The phonons show a characteristic spatial dependence and become softer around lattice irregularities in the oxide film, such as dislocation lines.

  18. Phonon-mediated electron transport through CaO thin films.

    PubMed

    Cui, Yi; Tosoni, Sergio; Schneider, Wolf-Dieter; Pacchioni, Gianfranco; Nilius, Niklas; Freund, Hans-Joachim

    2015-01-01

    Scanning tunneling microscopy has developed into a powerful tool for the characterization of conductive surfaces, for which the overlap of tip and sample wave functions determines the image contrast. On insulating layers, as the CaO thin film grown on Mo(001) investigated here, direct overlap between initial and final states is not enabled anymore and electrons are transported via hopping through the conduction-band states of the oxide. Carrier transport is accompanied by strong phonon excitations in this case, imprinting an oscillatory signature on the differential conductance spectra of the system. The phonons show a characteristic spatial dependence and become softer around lattice irregularities in the oxide film, such as dislocation lines. PMID:25615494

  19. Performance of the first-light adaptive optics system of LBT by means of CAOS simulations

    NASA Astrophysics Data System (ADS)

    Carbillet, Marcel; Vrinaud, Christophe; Esposito, Simone; Riccardi, Armando; Puglisi, Alfio; Femena, Bruno; Fini, Luca

    2003-02-01

    This presentation reports the numerical simulations we have done in order to evaluate the performance of the first-light AO system of LBT. The simulation tool used for this purpose is the Software Package CAOS, applicable for a wide range of AO systems and for which a brief recall of the main features is made. The whole process of atmospheric propagation of light, wavefront sensing (using a complete model of the pyramid wavefront sensor), wavefront reconstruction using the LBT672 adaptive secondary mirror modes), and closing of the loop, is simulated. The results are given in terms of obtained Strehl ratios in J-, H-, and K-band. Estimation of the resulting sky-coverage in K-band for different regions of the sky are also expressed. A comparison with the performance that would be obtained by using a Shack-Hartmann sensor is presented, confirming the gain achievable with the pyramid sensor.

  20. ExoMol molecular line lists - XIII. The spectrum of CaO

    NASA Astrophysics Data System (ADS)

    Yurchenko, Sergei N.; Blissett, Audra; Asari, Usama; Vasilios, Marcus; Hill, Christian; Tennyson, Jonathan

    2016-03-01

    An accurate line list for calcium oxide is presented covering transitions between all bound ro-vibronic levels from the five lowest electronic states X 1Σ+, A' 1Π, A 1Σ+, a 3Π, and b 3Σ+. The ro-vibronic energies and corresponding wavefunctions were obtained by solving the fully coupled Schrödinger equation. Ab initio potential energy, spin-orbit, and electronic angular momentum curves were refined by fitting to the experimental frequencies and experimentally derived energies available in the literature. Using our refined model we could (1) reassign the vibronic states for a large portion of the experimentally derived energies (van Groenendael A., Tudorie M., Focsa C., Pinchemel B., Bernath P. F., 2005, J. Mol. Spectrosc., 234, 255), (2) extended this list of energies to J = 61-118 and (3) suggest a new description of the resonances from the A 1Σ+-X 1Σ+ system. We used high level ab initio electric dipole moments reported previously (Khalil H., Brites V., Le Quere F., Leonard C., 2011, Chem. Phys., 386, 50) to compute the Einstein A coefficients. Our work is the first fully coupled description of this system. Our line list is the most complete catalogue of spectroscopic transitions available for 40Ca16O and is applicable for temperatures up to at least 5000 K. CaO has yet to be observed astronomically but its transitions are characterized by being particularly strong which should facilitate its detection. The CaO line list is made available in an electronic form as supplementary data to this article and at www.exomol.com.

  1. Enclave Compositions Indicate Multiple Felsic Components at Chaos Crags, Lassen Volcanic National Park, California

    NASA Astrophysics Data System (ADS)

    Schmidt, E. R.; Hammersley, L. C.; Clynne, M. A.

    2014-12-01

    Chaos Crags, located in Lassen Volcanic National Park, is a series of 6 rhyodacite domes that exhibit dramatic evidence of magma mixing. Mafic enclaves from the Chaos Crags form two distinct textural groups: a finer-grained group containing abundant plagioclase crystals from the host rhyodacite, and a coarser-grained group generally lacking host phenocrysts. Enclave samples were collected from Dome B of the Chaos Crags with the intent of obtaining complete suites of the two textural groups. Geochemical data for the enclaves shows a weak correlation between texture and geochemistry. Notably, the geochemical data also shows two distinct chemical trends that appear to represent mixing with two different felsic components. The dominant trend shows mixing between the host rhyodacite and the mafic end member. The second trend is interpreted to result from mixing between the mafic end member and a cryptic felsic component that is distinct from the host rhyodacite. Modeling of major oxides, selected trace elements and rare earth elements suggests that, although the two clusters of enclaves mix towards different felsic end members, they appear start from the same mafic end member, which has a composition of approximately: SiO2 51.84%, CaO 10.45%, K2O 0.69%, P2O5 0.10%, MgO 5.35%, Na2O 2.8%, FeO 8.25%, Fe2O3 1.84%, Al2O3 19.47% and TiO2 0.76%, a composition common in the Lassen region. Preliminary modeling results indicate that, at 75% SiO2, the cryptic felsic component has a composition of: K2O 5.25%, P2O5 1.2%, Na2O 8.25%, Al2O3 14.65%, Fe2O3 0.18%, FeO 0.88% and TiO2 1.46%, with negligible amounts of CaO and MgO. At 70% SiO2 this composition is approximately: K2O 4.3%, P2O5 0.95%, Na2O 7.05%, Al2O3 15.66%, TiO2 1.31%, FeO 2.51% and Fe2O3 0.55% with negligible amounts of CaO and MgO. It is likely that this previously unrecognized mixing trend represents crustal contamination of the mafic end member. A suite of samples with compositions intermediate between these two trends is also present.

  2. Kinetics of high pressure and temperature sulfidation of CaO sorbents: Influence of sorbent structural properties

    SciTech Connect

    Agnihotri, R.; Chauk, S.; Jadhav, R.; Gupta, H.; Mahuli, S.; Fan, L.S.

    1998-12-31

    Experiments are performed to study kinetics of interaction of H{sub 2}S with CaO sorbent using four different CaO powders (particle diameter < 15 {micro}m) under high pressure (10 atm) and high temperature (700--900 C) conditions in a differential bed flow-through reactor. Particles of CaO are reacted with simulated coal gas containing up to 3,000 Pa of H{sub 2}S. The influence of reaction temperature, H{sub 2}S partial pressure and sorbent surface area on the extent of sulfur capture and sorbent conversion are investigated. The interaction of CaO and H{sub 2}S is analyzed using grain theory to show that at later stages of the reaction, diffusion through product layer is the controlling step. The order of sulfidation reaction with respect to H{sub 2}S partial pressure is found to be approximately 1.0 and the apparent activation energy is determined to be 16.5 kcal/mol. A strong positive effect of the sorbent initial surface area and pore volume on the sulfidation conversion is observed.

  3. The Software Package PAOLAC: an embedment of the analytical code PAOLA within the CAOS problem-solving environment

    NASA Astrophysics Data System (ADS)

    Carbillet, Marcel; Jolissaint, Laurent; Maire, Anne-Lise

    We present the Software Package PAOLAC (PAOLA within Caos) in its first distributed version. This new numerical simulation tool is an embedment of the analytical adaptive optics simulation code PAOLA (Performance of Adaptive Optics for Large (or Little) Apertures) within the CAOS problem-solving environment. The main goal of this new tool is to allow an easier and direct comparison between studies performed with the analytical open-loop code PAOLA and studies performed with the end-to-end closed-loop Software Package CAOS (Code for Adaptive Optics Systems), with the final scope of better understanding how to take advantage from the two approaches: one analytical allowing extremely quick results on a wide range of cases and the other extremely detailed but with a computational and memory costs which can be impressive. The practical implementation of this embedment is briefly described, showing how this absolutely does not affect any aspect of the original code which is simply directly called from the CAOS global graphical interface through ad hoc modules. A comparison between end-to-end modelling and analytical modelling is hence also initiated, within the specific framework of wide-field adaptive optics at Dome C, Antarctica.

  4. Experimental derivation of nepheline syenite and phonolite liquids by partial melting of upper mantle peridotites

    NASA Astrophysics Data System (ADS)

    Laporte, Didier; Lambart, Sarah; Schiano, Pierre; Ottolini, Luisa

    2014-10-01

    Piston-cylinder experiments were performed to characterize the composition of liquids formed at very low degrees of melting of two fertile lherzolite compositions with 430 ppm and 910 ppm K2O at 1 and 1.3 GPa. We used the microdike technique (Laporte et al., 2004) to extract the liquid phase from the partially molten peridotite, allowing us to analyze liquid compositions at degrees of melting F down to 0.9%. At 1.3 GPa, the liquid is in equilibrium with olivine + orthopyroxene + clinopyroxene + spinel in all the experiments; at 1 GPa, plagioclase is present in addition to these four mineral phases up to about 5% of melting (T≈1240 °C). Important variations of liquid compositions are observed with decreasing temperature, including strong increases in SiO2, Na2O, K2O, and Al2O3 concentrations, and decreases in MgO, FeO, and CaO concentrations. The most extreme liquid compositions are phonolites with 57% SiO2, 20-22% Al2O3, Na2O + K2O up to 14%, and concentrations of MgO, FeO, and CaO as low as 2-3%. Reversal experiments confirm that low-degree melts of a fertile lherzolite have phonolitic compositions, and pMELTS calculations show that the amount of phonolite liquid generated at 1.2 GPa increases from 0.3% in a source with 100 ppm K2O to 3% in a source with 2000 ppm K2O. The enrichment in silica and alkalis with decreasing melt fraction is coupled with an increase of the degree of melt polymerization, which has important consequences for the partitioning of minor and trace elements. Thus Ti4+ in our experiments and, by analogy with Ti4+, other highly charged cations, and rare earth elements become less incompatible near the peridotite solidus. Our study brings a strong support to the hypothesis that phonolitic lavas or their plutonic equivalents (nepheline syenites) may be produced directly by partial melting of upper mantle rock-types at moderate pressures (1-1.5 GPa), especially where large domains of the subcontinental lithospheric mantle has been enriched in potassium by metasomatism. The circulation of low-degree partial melts of peridotites into the upper mantle may be responsible for a special kind of metasomatism characterized by Si- and alkali-enrichment. When they are unable to escape by porous flow, low-degree melts will ultimately be trapped inside neighboring olivine grains and give rise to the silica- and alkali-rich glass inclusions found in peridotite xenoliths.

  5. Enhancing the quantity and quality of short-chain fatty acids production from waste activated sludge using CaO2 as an additive.

    PubMed

    Li, Yongmei; Wang, Jie; Zhang, Ai; Wang, Lin

    2015-10-15

    The effect of calcium peroxide (CaO2) addition on anaerobic fermentation of waste activated sludge (WAS) was investigated. The lab-scale experiments were conducted at 35C with CaO2 doses ranging from 0.05 to 0.3g/g VSS. The performances of hydrolysis and acidification of WAS were significantly enhanced by CaO2 addition, whereas the production of methane was inhibited. Maximum total short-chain fatty acids (TSCFA) production (284mg COD/g VSS) occurred at a CaO2 dose of 0.2g/g VSS and fermentation time of 7d, which was 3.9 times higher than the control tests. Further, CaO2 addition led to the conversion of other SCFAs to acetic acid. Acetic acid comprised 60.2% of TSCFA with the addition of 0.2g CaO2/g VSS compared with 45.1% in the control tests. The mechanism of improved SCFAs generation was analyzed from the view of both chemical and biological effects. Chemical effect facilitated the disintegration of WAS, and improved the activities of both hydrolytic enzymes and acid-forming enzymes. Illumina MiSeq sequencing analysis revealed that bacteria within phylum Firmicutes increased significantly due to CaO2 addition, which played an important role in the hydrolysis and acidification of WAS. In addition, CaO2 oxidized most refractory organic contaminants, which were difficult to biodegrade under the ordinary anaerobic condition. Hydroxyl radicals were the most abundant reactive oxygen species released by CaO2, which played a key role in the removal of refractory organic compounds. We developed a promising technology to produce a valuable carbon source from WAS. PMID:26141424

  6. Intermitncia alfvnica gerada por caos na atmosfera solar e no vento solar

    NASA Astrophysics Data System (ADS)

    Rempel, E. L.; Chian, A. C.-L.; Macau, E. E. N.; Rosa, R. R.

    2003-08-01

    Dados medidos no vento solar rpido proveniente dos buracos coronais revelam que os plasmas no meio interplanetrio so dominados por flutuaes Alfvnicas, caracterizadas por uma alta correlao entre as variaes do campo magntico e da velocidade do plasma. As flutuaes exibem muitas caractersticas esperadas em turbulncia magneto-hidrodinmica totalmente desenvolvida, tais como intermitncia e espectros contnuos. Contudo, os mecanismos responsveis pela evoluo de turbulncia Alfvnica intermitente no so completamente compreendidos. Neste trabalho a teoria de caos usada para explicar como sistemas Alfvnicos, modelados pela equao Schrdinger no-linear derivativa e pela equao Kuramoto-Sivashinsky, podem se tornar fortemente caticos medida em que parmetros do plasma so variados. Pequenas perturbaes no parmetro de dissipao podem fazer com que o sistema mude bruscamente de um regime peridico, ou fracamente catico, para um regime fortemente catico. As sries temporais das flutuaes do campo magntico nos regimes fortemente caticos exibem comportamento intermitente, em que fases laminares ou fracamente caticas so interrompidas por fortes estouros caticos. mostrado que o regime fortemente catico atingido quando as solues peridicas ou fracamente caticas globalmente estveis interagem com solues do sistema que so fortemente caticas, mas globalmente instveis. Estas solues globalmente instveis so conjuntos caticos no-atrativos conhecidos como selas caticas, e so responsveis pelos fortes estouros nos regimes intermitentes. Selas caticas tm sido detectadas experimentalmente em uma grande variedade de sistemas, sendo provvel que elas desempenhem um papel importante na turbulncia intermitente observada em plasmas espaciais.

  7. Inhibitory Effects of Daiokanzoto (Da-Huang-Gan-Cao-Tang) on P-Glycoprotein

    PubMed Central

    Watanabe, Yuka; Ikarashi, Nobutomo; Satoh, Toshiyuki; Ito, Kiyomi; Ochiai, Wataru; Sugiyama, Kiyoshi

    2012-01-01

    We have studied the effects of various Kampo medicines on P-glycoprotein (P-gp), a drug transporter, in vitro. The present study focused on Daiokanzoto (Da-Huang-Gan-Cao-Tang), which shows the most potent inhibitory effects on P-gp among the 50 Kampo medicines studied, and investigated the P-gp inhibitory effects of Daiokanzoto herbal ingredients (rhubarb and licorice root) and their components by an ATPase assay using human P-gp membrane. Both rhubarb and licorice root significantly inhibited ATPase activity, and the effects of rhubarb were more potent than those of licorice root. The content of rhubarb in Daiokanzoto is double that in licorice root, and the inhibition patterns of Daiokanzoto and rhubarb involve both competitive and noncompetitive inhibition, suggesting that the inhibitory effects of Daiokanzoto are mainly due to rhubarb. Concerning the components of rhubarb, concentration-dependent inhibitory effects were observed for (?)-catechin gallate, (?)-epicatechin gallate, and (?)-epigallocatechin gallate. In conclusion, rhubarb may cause changes in the drug dispositions of P-gp substrates through the inhibition of P-gp. It appears that attention should be given to the interactions between these drugs and Kampo medicines containing rhubarb as an herbal ingredient. PMID:22969825

  8. The CAOS project: Interdisciplinary monitoring for the identification of hydrologic functional units

    NASA Astrophysics Data System (ADS)

    Blume, Theresa

    2013-04-01

    Hydrologic functional units (also known as hydrologic response units or lead topologies) form the basis of many hydrological models and are usually delineated with a simple GIS analysis. Despite the fact that it is a common concept, there are few studies on the determination of hydrologic response units in the real world. This study is part of ongoing research within the DFG research unit CAOS (Catchments As Organized Systems) and aims at identifying functional units in the field. This ambitious endeavor is based on an interdisciplinary monitoring design involving a large number of sensor clusters, but also includes tracer studies, remote sensing, geophysical exploration, and meteorological and ecological investigations. Each sensor cluster is designed to observe a variety of different fluxes and state variables above ground and below ground in the saturated and unsaturated zone. The number of sensors is chosen to capture the spatial variability as well as to characterize the average dynamics. The sampling design produces an extensive data set over a large number of functional units controlled by different topologies, geological-, soil- and vegetation characteristics. It enables us to test our hypotheses on system functioning, investigate links between internal pattern dynamics and integral responses, and determine minimum data needs for system characterization. The resulting data sets and system understanding will be used to develop, parameterize and validate a hydrological model based on functional units. Research is focused on the Attert catchment in Luxemburg.

  9. The Software Package SPHERE: a CAOS-based numerical tool for end-to-end simulations of SPHERE/VLT

    NASA Astrophysics Data System (ADS)

    Carbillet, Marcel; Boccaletti, Anthony; Thalmann, Christian; Fusco, Thierry; Vigan, Arthur; Smith, Isabelle; Mouillet, David; Dohlen, Kjetil; Bendjoya, Philippe; Ferrari, Andrea

    2008-07-01

    SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) is the second-generation VLT instrument devoted primarily to direct imaging and characterization of exoplanets, and allowing a large number of promising observation modes. In this framework, an IDL-based end-to-end numerical tool has been developed within the problem-solving environment CAOS (or CAOS "system"): the Software Package SPHERE, dedicated to the complete and detailed simulation of the whole instrument. It hence includes detailed instrumental modeling of the extreme adaptive optics system SAXO, the dual-band imaging camera IRDIS, the Integral Field Spectrograph (IFS), and the Zrich IMaging POLarimeter (ZIMPOL). The status of the whole package (which has now reached version 3.0) is exposed. An example of application is also detailed: a sub-system study aspect concerning the near-infrared apodized Lyot coronagraph.

  10. CAOS - the new high resolution spectrograph for the 0.91m telescope at Serra La Nave .

    NASA Astrophysics Data System (ADS)

    Span, P.; Leone, F.; Bruno, P.; Catalano, S.; Martinetti, E.; Scuderi, S.

    We report on the status of the new high-resolution spectrograph CAOS under construction for the 0.91m telescope at Serra La Nave, Italy. Starting from defined scientific motivations, we derived the best instrumental requirements to meet observational goals within typical constraints like good performances and reduced overall cost. The new instrument will be able to enlarge present observational research activity at INAF-OACt, allowing spectropolarimetry at high S/N ratios.

  11. Individuality and Stability in Male Songs of Cao Vit Gibbons (Nomascus nasutus) with Potential to Monitor Population Dynamics

    PubMed Central

    Ma, Chang-Yong; Fei, Han-Lan; Fan, Peng-Fei

    2014-01-01

    Vocal individuality and stability has been used to conduct population surveys, monitor population dynamics, and detect dispersal patterns in avian studies. To our knowledge, it has never been used in these kinds of studies among primates. The cao vit gibbon is a critically endangered species with only one small population living in a karst forest along China-Vietnam border. Due to the difficult karst terrain, an international border, long life history, and similarity in male morphology, detailed monitoring of population dynamics and dispersal patterns are not possible using traditional observation methods. In this paper, we test individuality and stability in male songs of cao vit gibbons. We then discuss the possibility of using vocal individuality for population surveys and monitoring population dynamics and dispersal patterns. Significant individuality of vocalization was detected in all 9 males, and the correct rate of individual identification yielded by discriminant function analysis using a subset of variables was satisfactory (>90%). Vocal stability over 26 years was also documented in 4 males. Several characters of cao vit gibbons allowed long-term population monitoring using vocal recordings in both China and Vietnam: 1) regular loud calls, 2) strong individuality and stability in male songs, 3) stable territories, and 4) long male tenure. During the course of this research, we also observed one male replacement (confirmed by vocal analysis). This time- and labor-saving method might be the most effective way to detect dispersal patterns in this transboundary population. PMID:24788306

  12. Canopy spectral and chemical diversity from lowland to tree line in the Western Amazon using CAO-VSWIR

    NASA Astrophysics Data System (ADS)

    Martin, R. E.; Asner, G. P.

    2012-12-01

    Canopy chemistry and spectroscopy offer insight into community assembly and ecosystem processes in high-diversity tropical forests. Results from one lowland site in the Peruvian Amazon suggests both an environmental and an evolutionary component of canopy trait development however, the degree to which larger environmental differences influence diversity in canopy traits and their respective spectroscopic signatures across remains poorly understood. The spectranomics approach explicitly connects phylogenetic, chemical and spectral patterns in tropical canopies providing the basis for analysis, while high-fidelity, airborne remote sensing measurements extend plot-level data to landscape-scale, achieving a comprehensive view of the region. In 2011, the Carnegie Airborne Observatory (CAO) was used to sample a large region of the Western Amazon Basin in southeastern Peru, extending from lowlands to tree line in the Andean mountains. The CAO Visible-Shortwave Imaging Spectrometer (VSWIR) collected 480-band high-fidelity imaging spectroscopy data of the forest canopy, while its high-resolution LiDAR captured information on canopy structure and the underlying terrain. The data were used to quantify relationships between environmental gradients and canopy chemical and spectral diversity. Results suggest strong environmental control with additional phylogenetic influence over canopy spectral and chemical properties, particularly those related to structure, defense and metabolic function. Data from CAO-VSWIR extends the large range in canopy chemical and spectral diversity related to environmental factors across the Western Amazon Basin.

  13. First-principles simulations of CaO and CaSiO3 liquids: structure, thermodynamics and diffusion

    NASA Astrophysics Data System (ADS)

    Bajgain, Suraj K.; Ghosh, Dipta B.; Karki, Bijaya B.

    2015-05-01

    We have performed first-principles molecular dynamics simulations of CaO and CaSiO3 liquids over broad ranges of pressure (0-150 GPa) and temperature (2,500-8,000 K) within density-functional theory. The simulated liquid structure changes considerably on compression with the mean cation-anion coordination numbers increasing nearly linearly with volume. The Ca-O coordination number increases from 5 (7) near the ambient pressure to 8 (10) at high pressure for CaO (CaSiO3) liquid. The Si-O coordination number increases from 4 to 6 over the same pressure regime. Our results show that both liquids are much more compressible than their solid counterparts implying the possibility of liquid-solid density crossovers at high pressure. The Grneisen parameter of both the liquids increases with pressure, which is opposite in case of crystalline phases. The calculated self-diffusion coefficients strongly depend on temperature and pressure, thereby requiring non-Arrhenian representation with variable activation volume. The diffusivity differences between the two liquids tend to be large at low-temperature and low-pressure regime. Also, comparisons with MgSiO3 liquid suggest that network modifier cations Ca and Mg behave similarly though Ca is more coordinated and more mobile as compared to Mg.

  14. [Development of ceramic standard samples used for X-ray fluorescence spectrometric analysis].

    PubMed

    Zhu, Ji-hao; Feng, Song-lin; Chu, Feng-you; Feng, Xiang-qia; Xie, Guo-xi; Yan, Ling-tong; Li, Liz

    2010-11-01

    The preparation of 17 kinds of ceramic standard samples (CSS) is introduced briefly in the present paper, and the experimental results of the sintered CSS by using EPMA and XRF are discussed in detail. The conclusions can be mainlydrawn that the CSS, which have high density, low water absorption and good homogeneity of element distribution, have similar phase structure (or matrix) to the bodies of ancient ceramics, and perfectly meet the requirements of being used as ceramic standard samples. This set of CSS are expected to play an important role in x-ray fluorescence spectrometric quantitative analysis of Na2O, MgO, Al2O3, SiO2, K2O, CaO, TiO2 and Fe2O3 in the body of ancient ceramics and can provide accurate and reliable data for study and identification of ancient ceramics. PMID:21284202

  15. Semimicro chemical and x-ray fluorescence analysis of lunar samples

    USGS Publications Warehouse

    Rose, H.J., Jr.; Cuttitta, F.; Dwornik, E.J.; Carron, M.K.; Christian, R.P.; Lindsay, J.R.; Ligon, D.T.; Larson, R.R.

    1970-01-01

    Major and selected minor elements were determined in seven whole rock fragments, five portions of pulverized lunar rock, and the lunar soil. Three different rock types were represented: vesicular, fine-grained basaltic rocks; medium-to coarse-grained, vuggy gabbroic rocks; and breccia. The ranges (in percent) for the major constituents of the lunar samples are: SiO2, 38 to 42; Al2O3, 8 to 14; total iron as FeO, 15 to 20; MgO, 6 to 8; CaO, 10 to 12; Na2O, 0.5 to 1; K2O, 0.05 to 0.4; TiO2, 8 to 13; MnO, 0.2 to 0.3; and Cr2O3, 0.2 to 0.4. The high reducing capacity of the samples strongly suggests the presence of Ti(III).

  16. Antibacterial glass-composite coatings for protection of special purpose steel panels

    NASA Astrophysics Data System (ADS)

    Savvova, O.; Bragina, L.; Babich, E.

    2011-12-01

    It has been established that the most informative and universal method for determination of biocide properties of vitreous coatings is qualitative method that takes into account the growth level of biotest microorganisms inoculated into liquid nutrient media. It is shown, that biocidity of glass-composite coatings on the basis of glasses of Na2O - K2O - CaO - ZrO2 - TiO2 - Al2O3 - P2O5 - B2O3 - SiO2 system is determined by the presence of calcium phosphates in them and depends on the type of bactericide filler. The most effective ones by the action on Pseudomonas aeruginosa bacterium and Aspergillus niger and Candida albicans fungi are zinc titanate and Ag+, to Escherichia coli- only zinc phosphate.

  17. Volatile fractionation and tektite source material

    NASA Technical Reports Server (NTRS)

    Walter, Louis S.

    1989-01-01

    The arguments used by Love and Woronow (1988) to assess the role played in the origin of bediasites by extensive volatile fractionation are critically examined. Using the ratios of 'refractory' oxides, CaO, Al2O3, and MgO, to the 'volatile' oxides, Na2O and K2O, these authors concluded that vapor fractionation did not play a significant role. In this paper, experimental evidence is presented that shows that the assumption of volatility for the alkali elements (as least with respect to silica) to be not valid under the conditions under which tektites formed. It is shown that the results of vapor fractionation in experiments on glasses of tektite composition are approximately parallel the trends seen in bediasite analysis.

  18. Statistical analysis of the effective factors on the 28 days compressive strength and setting time of the concrete

    PubMed Central

    Abolpour, Bahador; Mehdi Afsahi, Mohammad; Hosseini, Saeed Gharib

    2014-01-01

    In this study, the effects of various factors (weight fraction of the SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, Cl, SO3, and the Blaine of the cement particles) on the concrete compressive strength and also initial setting time have been investigated. Compressive strength and setting time tests have been carried out based on DIN standards in this study. Interactions of these factors have been obtained by the use of analysis of variance and regression equations of these factors have been obtained to predict the concrete compressive strength and initial setting time. Also, simple and applicable formulas with less than 6% absolute mean error have been developed using the genetic algorithm to predict these parameters. Finally, the effect of each factor has been investigated when other factors are in their low or high level. PMID:26425360

  19. Major and trace elements in igneous rocks from Apollo 15.

    NASA Technical Reports Server (NTRS)

    Helmke, P. A.; Blanchard, D. P.; Haskin, L. A.; Telander, K.; Weiss, C.; Jacobs, J. W.

    1973-01-01

    The concentrations of major and trace elements have been determined in igneous rocks from Apollo 15. All materials analyzed have typical depletions of Eu except for minerals separated from sample 15085. Four samples have concentrations of trace elements that are similar to those of KREEP. The samples of mare basalt from Apollo 15 have higher concentrations of FeO, MgO, Mn, and Cr and lower concentrations of CaO, Na2O, K2O, and rare-earth elements (REE) as compared to the samples of mare basalt from Apollos 11, 12, and 14. The samples can be divided into two groups on the basis of their normative compositions. One group is quartz normative and has low concentrations of FeO while the other is olivine normative and has high concentrations of FeO. The trace element data indicate that the samples of olivine normative basalt could be from different portions of a single lava flow.

  20. Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst.

    PubMed

    Witoon, Thongthai; Bumrungsalee, Sittisut; Vathavanichkul, Peerawut; Palitsakun, Supaphorn; Saisriyoot, Maythee; Faungnawakij, Kajornsak

    2014-03-01

    Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325μm achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles. PMID:24525218

  1. Fusing Hyperspectral and LiDAR data from CAO-VSWIR for Increased Data Dimensionality

    NASA Astrophysics Data System (ADS)

    Knapp, D. E.; Asner, G. P.; Boardman, J. W.; Kennedy-Bowdoin, T.; Eastwood, M.; Anderson, C.; Martin, R. E.; Green, R. O.

    2012-12-01

    The use of multi-sensor platforms for scientific data collection requires precise co-location in order to gain maximum data dimensionality for Earth system research. The different types of collection mechanisms of the sensors (e.g., scanning and pushbroom) can make it difficult to precisely match data from multiple sensors, even when the sensors are flown on the same aircraft at the same time. To overcome these problems, the Carnegie Airborne Observatory (CAO) AToMS sensor suite uses a method that maximizes the match between the Light Detection and Ranging (LiDAR), Visible-to-Near Infrared (VNIR), and Visible-to-Shortwave Infrared (VSWIR) sensors. This is done by generating an intensity image from the LiDAR data that serves as a base on which the spectrometers (VNIR and VSWIR) are matched using ground control points (GCPs). To do so, we employ the use of automated tie point matching in the overlap regions of the spectrometers to improve the co-location between flightlines. The combination of the GCPs and tie points produce data that is used to build camera models for the VNIR and VSWIR spectrometers such that they will match the LiDAR data. The result produces a matched hyper-dimensional data set with great scientific information content. We compare the data dimensionality of two contrasting scenes - a built environment at Stanford University and a lowland tropical forest in Amazonia. Principal components analysis revealed 336 dimensions (degrees of freedom) in the Stanford case, and 218 dimensions in the Amazon. The Amazon case presents what could be the highest level of remotely sensed data dimensionality ever reported for a forested ecosystem. Simulated misalignment of data streams reduced the effective information content by up to 48%, highlighting the critical role of achieving high precision when undertaking multi-sensor fusion. The instrumentation and methods described here are a pathfinder for future airborne applications undertaken by the National Ecological Observatory Network (NEON) and other organizations.

  2. Application of multivariate statistical analyses in the interpretation of geochemical behaviour of uranium in phosphatic rocks in the Red Sea, Nile Valley and Western Desert, Egypt.

    PubMed

    El-Arabi, Abd El-Gabar M; Khalifa, Ibrahim H

    2002-01-01

    Factor and cluster analyses as well as the Pearson correlation coefficient have been applied to geochemical data obtained from phosphorite and phosphatic rocks of Duwi Formation exposed at the Red Sea coast. Nile Valley and Western Desert. Sixty-six samples from a total of 71 collected samples were analysed for SiO2, TiO2, Al203, Fe2O3, CaO, MgO, Na2O, K2O, P2O5, Sr, U and Pb by XRF and their mineral constituents were determined by the use of XRD techniques. In addition, the natural radioactivity of the phosphatic samples due to their uranium, thorium and potassium contents was measured by gamma-spectrometry. The uranium content in the phosphate rocks with P2O5 > 15% (average of 106.6 ppm) is higher than in rocks with P2O5 < 15% (average of 35.5 ppm). Uranium distribution is essentially controlled by the variations of P2O5 and CaO, whereas it is not related to changes in SiO2, TiO2, Al2O3, Fe2O3, MgO, Na2O and K2O concentrations.-Factor analysis and the Pearson correlation coefficient revealed that uranium belaves geochemically in different ways in the phosphatic sediments and phosphorites in the Red Sea, Nile Valley and Western Desert. In the Red Sea and Western Desert phosphorites, uranium occurs mainly in oxidized U6+ state where it seems to be fixed by the phosphate ion, forming secondary uranium phosphate minerals such as phosphuranylite. In the Nile Valley phosphorites, ionic substitution of Ca2+ by U4 is the main controlling factor in the concentration of uranium in phosphate rocks. Moreover, fixation of U6- by phosphate ion and adsorption of uranium on phosphate minerals play subordinate roles. PMID:12066979

  3. Sampling and major element chemistry of the recent (A.D. 1631-1944) Vesuvius activity

    USGS Publications Warehouse

    Belkin, H.E.; Kilburn, C.R.J.; de Vivo, B.

    1993-01-01

    Detailed sampling of the Vesuvius lavas erupted in the period A.D. 1631-1944 provides a suite of samples for comprehensive chemical analyses and related studies. Major elements (Si, Ti, Al, Fetotal, Mn, Mg, Ca, Na, K and P), volatile species (Cl, F, S, H2O+, H2O- and CO2), and ferrous iron (Fe2+) were determined for one hundred and forty-nine lavas and five tephra from the A.D. 1631-1944 Vesuvius activity. The lavas represent a relatively homogeneous suite with respect to SiO2, TiO2, FeOtotal, MnO and P2O5, but show systematic variations among MgO, K2O, Na2O, Al2O3 and CaO. The average SiO2 content is 48.0 wt.% and the rocks are classified as tephriphonolites according to their content of alkalis. All of the lavas are silica-undersaturated and are nepheline, leucite, and olivine normative. There is no systematic variation in major-element composition with time, over the period A.D. 1631-1944. The inter-eruption and intra-eruption compositional differences are the same magnitude. The lavas are highly porphyritic with clinopyroxene and leucite as the major phases. Fractionation effects are not reflected in the silica content of the lavas. The variability of MgO, K2O, Na2O, and CaO can be modelled as a relative depletion or accumulation of clinopyroxene. ?? 1993.

  4. Biomineral microstructures in ferromanganese nodules: evidence of the biological and abiogenous origin

    NASA Astrophysics Data System (ADS)

    Lysyuk, G. N.

    2011-10-01

    Manganese oxides, which are widespread and of great practical importance, are formed and transformed by the active role of microorganisms. Manganese aggregates occur as both crystallized varieties and disordered fine-grained phases with significant ore grade and up to 50-60 vol % of X-ray amorphous components. X-ray amorphous nanosizedMn oxides in Fe-Mn nodules from the Pacific Ocean floor were examined from the standpoint of their biogenic origin. SEM examination showed abundant mineralized biofilms on the studied samples. The chemical composition of bacterial mass is as follows (wt %): 28.34 MnO, 17.14 Fe2O3, 7.11 SiO2, 2.41 CaO, 17.90 TiO2, 1.74Na2O,1.73 A12O3,1.30 MgO, 1.25P2O5,1.25 SO3,0.68 CoO, 0.54 CuO, 0.53 NiO, and 0.50 K2O. The chemical composition of fossilized cyanobacterial mats within the interlayer space of nodules is as follows (wt %): 48.35 MnO, 6.23 Fe2O3, 8.76 MgO, 5.05 A12O3, 4.45 SiO2, 3.63 NiO, 2.30 Na2O, 2.19 CuO, 1.31 CaO, and 0.68 K2O is direct evidence for participation of bacteria in Mn oxide formation. This phase consists of mineralized glycocalix consisting of nanosized flakes of todorokite. Native metals (Cu, Fe, and Zn) as inclusions 10-20 μm in size were identified in ferromanganese nodules as well. The formation of native metals can be explained by their crystallization at highly reducing conditions maintained by organic matter.

  5. Micelle-assisted synthesis of Al2O3CaO nanocatalyst: optical properties and their applications in photodegradation of 2,4,6-trinitrophenol.

    PubMed

    Imtiaz, Ayesha; Farrukh, Muhammad Akhyar; Khaleeq-ur-rahman, Muhammad; Adnan, Rohana

    2013-01-01

    Calcium oxide (CaO) nanoparticles are known to exhibit unique property due to their high adsorption capacity and good catalytic activity. In this work the CaO nanocatalysts were prepared by hydrothermal method using anionic surfactant, sodium dodecyl sulphate (SDS), as a templating agent. The as-synthesized nanocatalysts were further used as substrate for the synthesis of alumina doped calcium oxide (Al2O3CaO) nanocatalysts via deposition-precipitation method at the isoelectric point of CaO. The Al2O3CaO nanocatalysts were characterized by FTIR, XRD, TGA, TEM, and FESEM techniques. The catalytic efficiencies of these nanocatalysts were studied for the photodegradation of 2,4,6-trinitrophenol (2,4,6-TNP), which is an industrial pollutant, spectrophotometrically. The effect of surfactant and temperature on size of nanocatalysts was also studied. The smallest particle size and highest percentage of degradation were observed at critical micelle concentration of the surfactant. The direct optical band gap of the Al2O3CaO nanocatalyst was found as 3.3?eV. PMID:24311980

  6. Influence of high-temperature steam on the reactivity of CaO sorbent for CO? capture.

    PubMed

    Donat, Felix; Florin, Nicholas H; Anthony, Edward J; Fennell, Paul S

    2012-01-17

    Calcium looping is a high-temperature CO(2) capture technology applicable to the postcombustion capture of CO(2) from power station flue gas, or integrated with fuel conversion in precombustion CO(2) capture schemes. The capture technology uses solid CaO sorbent derived from natural limestone and takes advantage of the reversible reaction between CaO and CO(2) to form CaCO(3); that is, to achieve the separation of CO(2) from flue or fuel gas, and produce a pure stream of CO(2) suitable for geological storage. An important characteristic of the sorbent, affecting the cost-efficiency of this technology, is the decay in reactivity of the sorbent over multiple CO(2) capture-and-release cycles. This work reports on the influence of high-temperature steam, which will be present in flue (about 5-10%) and fuel (?20%) gases, on the reactivity of CaO sorbent derived from four natural limestones. A significant increase in the reactivity of these sorbents was found for 30 cycles in the presence of steam (from 1-20%). Steam influences the sorbent reactivity in two ways. Steam present during calcination promotes sintering that produces a sorbent morphology with most of the pore volume associated with larger pores of ?50 nm in diameter, and which appears to be relatively more stable than the pore structure that evolves when no steam is present. The presence of steam during carbonation reduces the diffusion resistance during carbonation. We observed a synergistic effect, i.e., the highest reactivity was observed when steam was present for both calcination and carbonation. PMID:22191682

  7. Improved Retrieval of Chlorophyll and Carotenoids Contents at the Canopy Scale Using Hyperspectral CAO Data and PROSAIL Model

    NASA Astrophysics Data System (ADS)

    Feret, J.; Asner, G. P.; Jacquemoud, S.; Franois, C.

    2008-12-01

    The sustainability of biodiversity requires frequent and spatially detailed assessment of species number and distribution, among other information. Remote sensing is one of the most promising way to achieve this environmental management due to reasonable cost and accuracy. However, the use of airborne and spaceborne data remains challenging: sensors must combine the appropriate spatial and spectral resolutions to retrieve pertinent environmental parameters that will permit identification of specific properties of organisms present in an ecosystem. Leaf area index (LAI), canopy structure and pigment composition of vegetation are valuable information to study ecosystem dynamics and distinguish between many species. Chlorophyll and carotenoid pigments are of particular interest because they are involved in photosynthesis, but until now, remote sensing was unable to assess these pigments separately and accurately. Some advances have been made recently with the separation of these pigments in PROSPECT-5, a radiative transfer model that simulates leaf spectral reflectance and transmittance at 1 nm resolution. PROSAIL, the joint vegetation canopy reflectance model associating PROSPECT-5 with 4SAIL, the latest version of the SAIL model, was first run in direct mode to design vegetation indices sensitive to leaf pigments. Subsequently, we retrieved chlorophyll and carotenoid contents using PROSAIL with CAO (Carnegie Airborne Observatory) data acquired in Hawaii. The CAO, an imaging spectrometer coupled with a 3-D laser scanner, has already demonstrated its ability to manage biodiversity in various ecosystems like tropical rainforests or savannah. Its performance make it particularly adapted to assess vegetation structure, biochemistry, and then fluxes. The first results obtained when processing CAO images with PROSAIL are promising in terms of chlorophyll and carotenoid retrieval at the canopy scale. They show that our approach can provide original information on vegetation and hopefully new indicators to help manage and conserve biodiversity. They open new fields of investigation in the domain of mapping and monitoring Earth ecosystems from present operational (Aviris, Hyperion) or future (EnMap, HyspIRI) airborne and spaceborne sensors offering high spectral resolution data.

  8. On the use of ocean-atmosphere-wave models during an extreme CAO event: the importance of being coupled

    NASA Astrophysics Data System (ADS)

    Carniel, Sandro; Barbariol, Francesco; Benetazzo, Alvise; Bonaldo, Davide; Falcieri, Francesco M.; Miglietta, Mario M.; Ricchi, Antonio; Sclavo, Mauro

    2015-04-01

    During winter 2012 an extreme meteorological event stroke the whole Europe and particularly its central-southern sector. A strong and persistent spit of cold air coming from Siberian region (a Cold Air Outbreak, CAO) insisted on northern Italy and the Adriatic sea basin, leading to decreases in the sea temperatures up to 6 C in less than two weeks, ice formation on the Venice lagoon and an exceptional snow fall in the Apennine region. In the sea the CAO was associated to a significant episode of dense water formation (DWF), a crucial phenomenon that heavily impacts the whole Adriatic Sea (from the sinking of water masses and associated ventilation of the northernmost shelf, to the flow along the western coast, until the flushing of southern Adriatic open slope and submarine canyons, with associated sediment transport and bottom reshaping). The extent of the DWF event in the Northern Adriatic sub-basin was estimated by means of coastal observatories, ad hoc measurements and, until now, results from existing one-way coupled atmosphere-ocean models. These are characterized by no SST feedback from the ocean to the atmosphere, and therefore by turbulent heat fluxes that may heavily reflect a non-consistent ocean state. The study proposes an investigation of the 2012 CAO using a fully coupled, three components, ocean-atmosphere-wave system (COAWST). Results highlight that, although the energy interplays between air and sea do not seem to significantly impact the wind forecasts, when providing heat fluxes that are consistent with the ocean temperature we find modified heat fluxes and air sea temperatures figures. Moreover, the consistent description of thermal exchanges adopted in the fully coupled model can affect the basin circulation, the quantification of dense water produced mass, and the description of its migration pathways and rates of off-shelf descent.

  9. Heterogeneous-nucleation and glass-formation studies of 56Ga2O3-44CaO

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Curreri, Peter A.; Pline, David

    1987-01-01

    Glass formation and heterogeneous crystallization are described for the reluctant-glass-forming 56Ga2O3-44CaO eutectic composition. The times and temperatures for nucleation at various cooling rates and experimental conditions were measured and empirical continuous-cooling-crystallization boundaries were constructed for various heterogeneous nucleation processes. A definition for an empirical critical cooling rate to form a glass from reluctant borderline glass formers is proposed, i.e., the cooling rate that results in glass formation in 95 percent of the quenching experiments.

  10. Kinetics of wetting for MgO, CaO, and BeO by Pd, Pt, and Rh melts

    NASA Astrophysics Data System (ADS)

    Timofeev, A. I.; Chentsov, V. P.

    2015-01-01

    The wetting of magnesium, calcium, and beryllium oxides (MgO, CaO, and BeO) is considered, depending on the ratios of the surface tensions of the oxides to the melts at inequality ?sg/?lg < 1 characteristic of metallophobic solid surfaces. It is shown that the changes in the wetting angle with temperature during isothermal exposure are determined by the ratio of the surface tensions of the phases ?MgO/?Me. It is found that the wetting angle moves down or up when the ratios of the surface tensions increase or decrease, respectively, depending on the values of ?sg and ?lg.

  11. Analytical vs. end-to-end numerical modeling of adaptive optics systems: comparison between PAOLA and the Software Package CAOS.

    NASA Astrophysics Data System (ADS)

    Carbillet, Marcel; Jolissaint, Laurent

    2011-09-01

    We compare in this contribution the analytical approach together with the so-called "end-to-end" approach in the framework of astronomical adaptive optics (AO) modeling. The two tools used for this purpose are well-known and already widely used within the astronomical AO community: PAOLA (Jolissaint et al. 2006, Jolissaint 2010) on the one hand, and the Software Package CAOS (Carbillet et al. 2005) on the other hand. In addition to inter-validate the two codes, trade-offs are clearly searched in order to find optimal compromises permitting to face both exploratory simulations and large instrumental projects while combining effectiveness and certainty.

  12. Making sense out of CAOS: Preliminary results on the Paleozoic-Mesozoic deformation of the Central Asian Orogenic System

    NASA Astrophysics Data System (ADS)

    Briggs, S. M.; Yin, A.; Manning, C. E.

    2005-12-01

    There are two contrasting models for the tectonic evolution of accretionary orogens, both based on the Paleozoic geology of the Central Asian Orogenic System (CAOS), which is located between the Siberian, European, and Chinese cratons. One model requires that syn-subduction strike-slip faults with more than 1000 km of displacement control the construction of accretionary orogens, whereas a second model suggests that thrust faults are responsible for shortening during and after arc magmatism. Specifically for the CAOS, previous studies show that igneous activity occurred in two episodes at 408-377 Ma and 344-290 Ma. The early phase is marked by calc-alkaline magmatism and occurred in an island-arc setting while the second phase exhibits geochemical characteristics of post-collisional magmatism. In the context of the existing pluton geochronology and geochemical interpretations, the first tectonic model requires CAOS strike-slip faulting to be Devonian in age, whereas the second requires that thrust faulting is as young as Permian. We completed field mapping, U-Th-Pb geochronology, thermobarometry, and 40Ar/39Ar thermochronology to determine the nature of tectonic contacts, timing and extent of metamorphism and deformation, and low temperature exhumation history of the southern Altai Mountains in NW China. Our results show that at least three northeast-dipping thrust faults were responsible for crustal shortening of at least 50%. The Ertix fault (also known as the Irtysh fault) juxtaposes high-grade metamorphic rocks from > 20 km depth against a Devonian-Carboniferous arc sequence. Thermochronologic data suggest that rocks were exhumed during motion on the Ertix fault between 280 Ma and 260 Ma. The Kuerti thrust, a range-bounding thrust fault, was exhuming rocks in its hanging-wall between 270 and 200 Ma. The Barils thrust was responsible for exhumation and cooling of lower amphibolite-grade hanging-wall rocks between 230 and 150 Ma. Minor orogen-parallel sinistral shear occurred after 261 Ma, based on zircon ages from a deformed granitoid. Our data suggest that major deformation, primarily accomplished by thrusting, occurred after the termination of arc magmatism in the CAOS, and does not support tectonic models requiring major syn-subduction strike-slip faulting during accretionary orogen development.

  13. An experimental approach to manufacturing technology of historical glass (XIII-XV centuries). Comparison with current glassmaking technology.

    NASA Astrophysics Data System (ADS)

    Tarrago, Mariona; Gimeno, Domingo; Bazzocchi, Flavia; Garcia-Valles, Maite; Martinez, Salvador

    2015-04-01

    One of the major and less explored issues in the characterization of historical glasses is the determination of their viscosity as a function of temperature in order to constrain technological aspects of glass production. Until now, assumptions on temperatures have been based on mathematical models based on chemical compositions. Hence, the topic of this work is to explore the technology of stained glass production related to the workability and melting process of the glass by experimental laboratory measurements. This work presents the analysis of viscosity of glasses from different historical sites and chemical compositions: four from Santes Creus (Tarragona, XIII century), two of classical medieval stained glass window from Santa Maria de Pedralbes (Barcelona, mid XIV century), and three of evolved late-medieval type from Santa Maria del Mar (Barcelona first half of XV century), and one sample of soda-lime industrial glass by means of Hot-Stage Microscopy and glass transformation temperature Tg by dilatometry. These data are then compared to the predictions on theoretical viscosity obtained from mathematical models based on chemical composition. These samples are classified according to their major modifier in: Na-rich (12-17% of Na2O, between 65-77% of SiO2 and less than 3 % of K2O); Ca-rich (29% of CaO, 54% of SiO2, 4% of K2O, and 4% of Na2O); K-Ca-rich (17 to 21% of K2O, more than 14% of CaO, 49-55% of SiO2and less than 2% of Na2O); Na-Ca-rich (12-14% of Na2O, 9-15% of CaO, 57-71% of SiO2 and < 6% of K2O). Glass transition temperature (Tg) is correlated to chemical composition: 464-492 °C for Na-rich, 645 °C for Ca-rich, 582-586 °C for K-Ca-rich and 497-542 °C for Na-Ca-rich glasses. Experimental viscosity-temperature curves are traced using Tg and fixed viscosity points measured by Hot-Stage microscopy (according to German standard 51730) in order to provide more accurate insight into the phases of glass production process (melting, working, conditioning and annealing ranges). These results are also compared to mathematical models of glass viscosity based on chemical composition. The annealing range (viscosity between 1013.5 and 1012 Pa-s) is reached at temperatures between 484-633°C (strain point) and 509-664°C (upper limit). The working point (viscosity of 103 Pa-s) has temperature values in the range between 958 and 1097°C.

  14. Evolution of the electronic structure of CaO thin films following Mo interdiffusion at high temperature

    NASA Astrophysics Data System (ADS)

    Cui, Yi; Pan, Yi; Pascua, Leandro; Qiu, Hengshan; Stiehler, Christian; Kuhlenbeck, Helmut; Nilius, Niklas; Freund, Hans-Joachim

    2015-01-01

    The electronic structure of CaO films of 10-60 monolayer thickness grown on Mo(001) has been investigated with synchrotron-mediated x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Upon annealing or reducing the thickness of the film, a rigid shift of the CaO bands to lower energy is revealed. This evolution is explained with a temperature-induced diffusion of Mo ions from the metal substrate to the oxide and their accumulation in the interface region of the film. The Mo substitutes divalent Ca species in the rocksalt lattice and is able to release electrons to the system. The subsequent changes in the Mo oxidation state have been followed with high-resolution XPS measurements. While near-interface Mo transfers extra electrons back to the substrate, generating an interface dipole that gives rise to the observed band shift, near-surface species are able to exchange electrons with adsorbates bound to the oxide surface. For example, exposure of O2 results in the formation of superoxo species on the oxide surface, as revealed from STM measurements. Mo interdiffusion is therefore responsible for the pronounced donor character of the initially inert oxide, and largely modifies its adsorption and reactivity behavior.

  15. Charge competition with oxygen molecules determines the growth of gold particles on doped CaO films.

    PubMed

    Cui, Yi; Huang, Kai; Nilius, Niklas; Freund, Hans-Joachim

    2013-01-01

    The influence of gas-phase oxygen on the growth of Au nanoparticles on Mo-doped CaO films has been investigated by means of low temperature scanning tunnelling microscopy and X-ray photoelectron spectroscopy. Whereas at ideal vacuum conditions, only 2D Au islands develop on the oxide surface, the fraction of 3D deposits increases with increasing O2 pressure until they become the dominant species in 106 mbar oxygen. The morphology crossover arises from changes in the interfacial electron flow between Mo donors in the CaO lattice and different ad-species on the oxide surface. In the absence of 02 molecules, the donor electrons are predominately transferred to the Au ad-atoms, which consequently experience enhanced binding to the oxide surface and agglomerate into 2D islands. In an oxygen atmosphere, on the other hand, a substantial fraction of the excess electrons is trapped by adsorbed O2 molecules, while the Au atoms remain neutral and assemble into tall 3D particles that are typical for non-doped oxides. Our experiments demonstrate how the competition for charge between different adsorbates governs the physical and chemical properties of doped oxides, so widely used in heterogeneous catalysis. PMID:24015581

  16. (CaO Al2O3 SiO2): Eu phosphors for violet/ultraviolet-to-white radiation conversion

    NASA Astrophysics Data System (ADS)

    Gurin, N. T.; Paksyutov, K. V.; Terent'ev, M. A.; Shirokov, A. V.

    2012-02-01

    (2CaO 0.5Al2O3 5SiO2): Eu and (CaO 0.2Al2O3 SiO2): Eu phosphors doped with B2O3 in an amount of 3 wt % are obtained by direct solid-phase synthesis at 1350C. When excited by LED radiation with a maximum at 380 nm, these phosphors emit white light with color coordinates, which are close to those in the EBU and NTSC TV standards and fall into the field of white light corresponding to light warning systems according to the International Commission on Illumination (CIE).

  17. Hydrogen-rich gas production via CaO sorption-enhanced steam gasification of rice husk: a modelling study.

    PubMed

    Beheshti, Sayyed Mohsen; Ghassemi, Hojat; Shahsavan-Markadeh, Rasoul; Fremaux, Sylvain

    2015-01-01

    Gasification is a thermochemical process in which solid or liquid fuels are transformed into synthesis gas through partial oxidation. In this paper, a kinetic model of rice husk gasification has been developed, which is interesting for the applications of the syngas produced. It is a zero-dimensional, steady-state model based on global reaction kinetic, empirical correlation of pyrolysis and is capable of predicting hydrogen yield in the presence of sorbent CaO. The model can also be used as a useful tool to investigate the influence of process parameters including steam/biomass ratio, CaO/fuel ratio (CaO/Fuel), and gasification temperature on hydrogen efficiency, CO2 capture ratio (CCR), and average carbonation conversion (Save). Similar to hydrogen formation, CCR also increases with increasing CaO/Fuel, but an opposite trend is exhibited in Save. Model predictions were compared with available data from the literature, which showed fairly good agreement. PMID:25403373

  18. Optical design of CAOS: a high-resolution spectropolarimeter for the Catania Astrophysical Observatory 0.91-m telescope

    NASA Astrophysics Data System (ADS)

    Spano, Paolo; Leone, F.; Scuderi, Salvatore; Catalano, Santo; Zerbi, Filippo M.

    2004-09-01

    CAOS (Catania Astrophysical Observatory Spectrograph) is a high-resolution (R~60,000), fiber fed, bench-mounted, prism cross-dispersed, white-pupil R-4 echelle spectrograph with polarimetric capabilities, for the 0.91m telescope on Mt. Etna. Wavelengths from 390 to 710 nm are covered in one-shot with a 2Kx2K 13.5 micron CCD. Inherent high efficiency of the spectrograph and optimum matching between fibers and spectrograph will allow high throughput for the overall system. This instrument will replace the existing spectrograph, with a net gain in spectral resolution (about a factor 2) and in efficiency (about a factor 10), extending current studies undertaken by Catania Astrophysical Observatory in stellar physics.

  19. Environmental controls on plant chemical traits: Using the CAO-VSWIR to characterize patterns in a mediterranean-type ecosystem

    NASA Astrophysics Data System (ADS)

    Dahlin, K.; Asner, G. P.; Field, C. B.

    2012-12-01

    Here we present results from a new imaging spectrometer, the Carnegie Airborne Observatory's (CAO) Visible-Short Wave Infrared (VSWIR) sensor, and we use these data to map key plant functional traits in a semi-arid ecosystem, Jasper Ridge Biological Preserve (Woodside, CA USA). We considered four fundamental plant traits: leaf nitrogen per mass (Nmass, %), leaf carbon per mass (Cmass, %), leaf water fraction (WL), and canopy water fraction (WC).With these maps we ask the following questions: (1) How do these traits vary with environmental gradients and land use history, independent of species composition? (2) Does information about plant community improve our ability to explain trait patterns? And (3) what does the variation within plant communities tell us about the underlying processes driving or limiting this ecosystem? We show that the new CAO-VSWIR combined with partial least squares regression can effectively map these four plant chemical traits across multiple plant functional types (observed v. predicted R2s ranging from 0.55 for WL to 0.84 for Cmass). To consider how these traits varied with environmental gradients we used simultaneous autoregressive modeling and found, in general, that environment and land-use history together explained about a quarter of the variation in each trait, but that information about plant community boundaries dramatically improved our predictive power. While 29 - 44% of the variation in these four traits remained unexplained, when we considered the trait distributions within each plant community we found that most plant communities were sharply peaked (leptokurtic) or near normal, while a few communities were more evenly distributed (platykurtic) for each trait. These results show that, even though environmental gradients play a small but significant role, most of the plant communities at Jasper Ridge are characterized by a narrow range of trait patterns. For the few communities that are highly divergent, possible causal factors include resource limitation, competition, and/or past disturbances.

  20. Materials Data on K2O2 (SG:64) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  1. Relationship Between Iron Whisker Growth and Doping Amount of Oxide During Fe2O3 Reduction

    NASA Astrophysics Data System (ADS)

    Gong, Xuzhong; Zhao, Zhilong; Wang, Zhi; Zhang, Ben; Guo, Lei; Guo, Zhancheng

    2016-04-01

    Iron whisker growth during Fe2O3 doped with oxide reduced by CO was investigated by using in situ observation and scanning electron microscopy. The results indicated that the minimum doping amount (MDA) of various oxides, hindering the iron whisker growth, was different. The MDA of Al2O3, Li2O, Na2O, and K2O was 0.5, 0.4, 4, and 12 pct, respectively. From the reduction rate, it was found that Li2O, MgO, and Al2O3 had some suppressive effects on the Fe2O3 reduction process, thus, confining the growth of iron whisker. However, other oxides had some catalytic effects on the Fe2O3 reduction process (Fe2O3-Fe3O4-FeO-Fe), such as CaO, SrO, BaO, Na2O, and K2O. As long as their doping amount was enough, these oxides could inhibit the diffusion of the Fe atom. When the metal ionic radius in doped oxide was bigger than that of Fe3+, such as Ca2+, Sr2+, Ba2+, Na+, and K+, there were lots of spaces left in Fe2O3 doped with oxide after reduction, improving Fe atom diffusion. Consequently, their MDA was more than that of small radius to restrain the growth of iron whisker. Finally, the relationship between corresponding metal ionic radius, electron layer number, valence electron number, and MDA of oxide was expressed by using data fitting as follows: N_{{{{A}}y {{O}}x }} = 1.3 × 10^{ - 5} × {r_{{{{A}}^{x + } }}2 × √{n_{{{{A}}^{x + } }} } }/{f_{q }}

  2. The Capilla del Monte pluton, Sierras de Crdoba, Argentina: the easternmost Early Carboniferous magmatism in the pre-Andean SW Gondwana margin

    NASA Astrophysics Data System (ADS)

    Dahlquist, Juan A.; Pankhurst, Robert J.; Rapela, Carlos W.; Basei, Miguel A. S.; Alasino, Pablo H.; Saavedra, Julio; Baldo, Edgardo G.; Murra, Juan A.; da Costa Campos Neto, Mario

    2015-10-01

    New geochronological, geochemical, and isotopic data are reported for the Capilla del Monte two-mica granite pluton in the northeastern Sierras de Crdoba. An Early Carboniferous age is established by a U-Pb zircon concordia (336 3 Ma) and a Rb-Sr whole-rock isochron (337 2 Ma). Zircon saturation geothermometry indicates relatively high temperatures (735-800 C). The granites have high average SiO2 (74.2 %), Na2O + K2O (7.8 %), and high field-strength elements, high K2O/Na2O (1.7) and FeO/MgO ratios (5.1), with low CaO content (0.71 %). REE patterns with marked negative Eu anomalies (Eu/Eu* 0.14-0.56) indicate crystal fractionation, dominantly of plagioclase and K-feldspar, from a peraluminous magma enriched in F. Isotope data (87Sr/86Srinitial = 0.7086, ? Nd336 = -5.5 to -4.4 with T DM = 1.5 Ga, zircon ? Hf336 +0.8 to -6.1; mean T DM = 1.5 Ga) suggest a Mesoproterozoic continental source, albeit with some younger or more juvenile material indicated by the Hf data. The pluton is the easternmost member of a Carboniferous A-type magmatic suite which shows an increase in juvenile input toward the west in this part of the pre-Andean margin. The petrological and geochemical data strongly suggest a similar intraplate geodynamic setting to that of the nearby but much larger, Late Devonian, Achala batholith, although Hf isotope signatures of zircon suggest a more uniformly crustal origin for the latter. Further studies are required to understand whether these bodies represent two independent magmatic episodes or more continuous activity.

  3. Relationship Between Iron Whisker Growth and Doping Amount of Oxide During Fe2O3 Reduction

    NASA Astrophysics Data System (ADS)

    Gong, Xuzhong; Zhao, Zhilong; Wang, Zhi; Zhang, Ben; Guo, Lei; Guo, Zhancheng

    2015-12-01

    Iron whisker growth during Fe2O3 doped with oxide reduced by CO was investigated by using in situ observation and scanning electron microscopy. The results indicated that the minimum doping amount (MDA) of various oxides, hindering the iron whisker growth, was different. The MDA of Al2O3, Li2O, Na2O, and K2O was 0.5, 0.4, 4, and 12 pct, respectively. From the reduction rate, it was found that Li2O, MgO, and Al2O3 had some suppressive effects on the Fe2O3 reduction process, thus, confining the growth of iron whisker. However, other oxides had some catalytic effects on the Fe2O3 reduction process (Fe2O3-Fe3O4-FeO-Fe), such as CaO, SrO, BaO, Na2O, and K2O. As long as their doping amount was enough, these oxides could inhibit the diffusion of the Fe atom. When the metal ionic radius in doped oxide was bigger than that of Fe3+, such as Ca2+, Sr2+, Ba2+, Na+, and K+, there were lots of spaces left in Fe2O3 doped with oxide after reduction, improving Fe atom diffusion. Consequently, their MDA was more than that of small radius to restrain the growth of iron whisker. Finally, the relationship between corresponding metal ionic radius, electron layer number, valence electron number, and MDA of oxide was expressed by using data fitting as follows: N_{A}y {O}x }} = 1.3 10^{ - 5} {r_{A}^{x + } }2 ? {n_{A}}^{x + }/{f_{q }}

  4. Agglomeration characteristics of river sand and wheat stalk ash mixture at high temperatures

    NASA Astrophysics Data System (ADS)

    Shang, Linlin; Li, Shiyuan; Lu, Qinggang

    2013-02-01

    The agglomeration characteristics of river sand and wheat stalk ash mixture at various temperatures are investigated using a muffle furnace. The surface structural changes, as well as the elemental makeup of the surface and cross-section of the agglomerates, are analyzed by polarized light microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). Multi-phase equilibrium calculation is performed with FactSage in identifying the melting behavior of the river sand-wheat stalk ash mixture at high temperatures. No indication of agglomeration is detected below 850°C. At a temperature of 900-1000°C, however, obvious agglomeration is observed and the agglomerates solidify further as temperature increases. The presence of potassium and calcium enrichment causes the formation of a sticky sand surface that induces agglomeration. The main component of the agglomerate surface is K2O-CaO-SiO2, which melts at low temperatures. The formation of molten silicates causes particle cohesion. The main ingredient of the binding phase in the cross-section is K2O-SiO2-Na2O-Al2O3-CaO; the agglomeration is not the result of the melting behavior of wheat stalk ash itself but the comprehensive results of chemical reaction and the melting behavior at high temperatures. The multi-phase equilibrium calculations agree well with the experimental results.

  5. Micro-Raman and micro-XRF analysis of glass beads from the Chungde site, Taiwan

    NASA Astrophysics Data System (ADS)

    Liou, Y. S.; Wang, S. C.; Liu, Y. C.

    2014-12-01

    A large number of ancient glass beads dating back from Late Neolithic Age to early Historical Period (ca. 2300-400 BP) of Taiwan have been uncovered from archaeological sites. These glass beads with variant colors, shapes, and stylistics have long been considered to possess socio-cultural significance. Due to the color and chemical composition of glass bead might be determined by raw materials, fluxing agents, colorants, opacifiers and stabilizers. In addition, ancient glass beads are rare and precious, non-destructive analysis has been employed to decipher about the provenances, manufacturing techniques, and exchange/trade routes. In this work, micro-Raman spectroscopy and micro X-ray fluorescent spectrometer (?-XRF) were used to examine ten ancient glass beads excavated from the Chungde site, Hualien, Taiwan, dating back to 1500-800 BP, to unravel the mineralogical and chemical compositions. Micro Raman experimental results show that glass and anorthite glass are the main constituents accompanying with trace level of quartz, albite, siderite, ankerite, and amazonite. The Raman Index of Polymerization (Ip) indicate that the sintering temperature of the glass beads is in the range of 1000~1400C. Furthermore, the chemical compositions are corresponding to the maximum stretching vibration peak wave number (?max Si-O Stretching) and the maximum bending vibration peak wave number (?max Si-O Bending), which are essentially consistent with that of the India-Pacific beads. The ?-XRF results indicate the presence of oxides including SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, SnO2, TiO2, CuO, etc., and could be classified to high aluminum of soda-lime glass system. According to ternary phase diagram analysis of CaO-K2O-Na2O and K2O-Al2O3-CaO, the ancient glass beads analyzed could be attributed to the India-Pacific beads, and is in accordance with that of Raman spectra. The combination of these facts leads to the conclusion that glass beads obtained from the Chungde site may be ascribed to the India-Pacific beads.

  6. Selective catalytic reduction of nitric oxide by methane in the presence of oxygen over CaO catalyst

    SciTech Connect

    Fliatoura, K.D.; Verykios, X.E.; Costa, C.N.; Efstathiou, A.M.

    1999-04-25

    The selective catalytic reduction of nitric oxide by methane in the presence of oxygen was studied over CaO catalyst in the temperature range 550--850 C. The nitric oxide conversion-versus-temperature profile was found to depend on oxygen feed concentration, while the selectivity to N{sub 2} formation was found to be 100% and independent of oxygen feed concentration in the range 1--10 mol%. The kinetic study has shown that the reaction order with respect to NO and CH{sub 4} is 1.0 and 0.5, respectively. On the other hand, the reaction order with respect to O{sub 2} was found to be slightly positive for O{sub 2} feed concentrations up to 1 mol% and slightly negative at higher concentrations. The apparent activation energy of the reaction in the presence of oxygen was found to be 14.6 kcal/mol. The addition of 2.5 mol% CO{sub 2} and 5 mol% H{sub 2}O in the feed stream had a considerable inhibiting effect on NO conversion in the range 550--650 C, while a small inhibiting effect of CO{sub 2} and a positive effect of H{sub 2}O were observed in the range 700--850 C. Temperature-programmed desorption (TPD) of NO revealed the presence of two well-resolved NO peaks in the temperature range 250--650 C, a behavior also observed during a temperature-programmed oxidation experiment under O{sub 2}/He flow. However, during temperature-programmed surface reaction under CH{sub 4}/He flow the NO desorption spectrum showed a significant shift of the stronger adsorbed NO species toward lower temperatures. Preadsorbed CO{sub 2} on the CaO surface was found to largely affect the chemisorption of NO and its desorption kinetics during TPD. The amount of deposited carbon-containing species on the catalyst surface during reaction was determined with transient titration experiments and it was found to be small.

  7. The effect of composition on the viscosity, crystallization and dissolution of simple borate glasses and compositional design of borate based bioactive glasses

    NASA Astrophysics Data System (ADS)

    Goetschius, Kathryn Lynn

    Borate glasses have recently been developed for a variety of medical applications, but much less is known about their structures and properties than more common silicate glasses. Melt properties and crystallization tendency for compositions in the Na2O-CaO-B2O3 system were characterized using differential thermal analysis and viscosity measurements. Characteristic viscosity (isokom) temperatures varied with the ratio between the modifier content (Na2O+CaO) and B2O3, particularly at lower temperatures, consistent with the changes in the relative concentrations of tetrahedral borons in the glass structure. Similar glasses were used to study dissolution processes in water. These alkali-alkaline earth glasses dissolve congruently and follow linear dissolution kinetics. The dissolution rates were dependent on the glass structure, with slower rates associated with greater fractions of four-coordinated boron. For glasses with a fixed alkaline earth identity, the dissolution rates increased in the order LiNa2O, K2O, MgO, CaO, B2O3, SiO2, and P2O5) mixture model design was used to predict composition-property relationships to optimize the properties of new borate-based bioactive compositions for specific applications. Melt viscosity, thermal expansion coefficient, liquidus temperature and crystallization tendency were determined, as were dissolution rates in simulated body fluid (SBF).

  8. Dielectric properties of (CuO, CaO2, and BaO)y/CuTl-1223 composites

    NASA Astrophysics Data System (ADS)

    Mumtaz, M.; Kamran, M.; Nadeem, K.; Jabbar, Abdul; Khan, Nawazish A.; Saleem, Abida; Tajammul Hussain, S.; Kamran, M.

    2013-07-01

    We synthesized (CuO, CaO2, and BaO)y/Cu0.5Tl0.5Ba2Ca2Cu3O10-? (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized them by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties, such as real and imaginary parts of the dielectric constant, dielectric loss, and ac-conductivity of these composites were studied by capacitance and conductance measurements as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). X-ray diffraction analysis reveals that the characteristic behavior of the superconductor phase and the structure of Cu0.5Tl0.5Ba2Ca2Cu3O10-? are nearly undisturbed by doping with nanoparticles. Scanning electron microscopy images show the improvement in the intergranular linking between the superconducting grains occurring with increasing nanoparticle concentration. Microcracks are healed up with these nanoparticles, and superconducting volume fraction is also increased. Dielectric properties of these composites strongly depend on the frequency and temperature. Zero resistivity critical temperature and dielectric properties show opposite trends with the addition of nanoparticles to the Cu0.5Tl0.5Ba2Ca2Cu3O10-? superconductor matrix.

  9. The effects of CaO catalysis on the kinetics of NO reduction by Beulah Zap char

    SciTech Connect

    Guo, F.; Hecker, W.C.

    1996-12-31

    The reduction of NO emissions from combustion processes has become increasingly important in protecting the world`s environment. It has been shown that Selective Catalytic Reduction (SCR) with ammonia is an effective commercial technique to remove NO{sub x} from combustion flue gas. However, the implementation of this technique is limited by high investment and operating costs, {open_quotes}ammonia slip{close_quotes}, and SO{sub x} poisoning, which motivate the search for alternatives. Carbon (activated carbon or char) is a promising reducing agent for NO{sub x} reduction with many potential advantages, such as low cost, easy availability, high efficiency, simplicity of process, and no secondary pollution. Moreover, the heterogeneous reaction of NO with char is very important for the understanding of the formation of NO{sub x} from coal combustion processes. The reaction may significantly destroy the NO{sub x} formed earlier in coal combustion, which partially contributes to low NO emission from fluidized bed combustion. Therefore, the reaction of NO with char is receiving significant attention in the literature. The objectives of this study are to investigate the kinetics of the reaction of NO with Beulah Zap lignite chars, to study the effects of CaO on the kinetics.

  10. Sleeping tree selection of Cao Vit gibbon (Nomascus nasutus) living in degraded karst forest in Bangliang, Jingxi, China.

    PubMed

    Fei, Han-Lan; Scott, Matthew B; Zhang, Wen; Ma, Chang-Yong; Xiang, Zuo-Fu; Fan, Peng-Fei

    2012-11-01

    We studied the sleep-related behavior of two Cao Vit gibbon (Nomascus nasutus) groups in Bangliang Nature Reserve in Jingxi County, China between January 2008 and December 2009 to test four hypotheses related to sleeping tree selection (predation avoidance, thermoregulation, food access, and range defense). Gibbons entered sleeping trees 88 SD 37 min before sunset before their main potential nocturnal predator become active. They usually moved rapidly and straight to sleeping trees and kept silent once settled. Over the course of the study, gibbon groups used many (87 and 57 per group) sleeping trees and reused them irregularly. They also tended to sleep in relatively tall trees without lianas, choosing small branches close to the treetop. These behaviors would make it difficult for potential terrestrial predators to detect and approach the gibbons. Therefore, these results strongly support the predation avoidance hypothesis. Gibbons tended to sleep closer to ridges than to valley bottoms and they did not sleep at lower elevations in colder months. They thus appeared not to select sleeping trees to minimize thermoregulatory stress. Gibbons very rarely slept in feeding trees, instead generally sleeping more than 100 m away from the last feeding trees of the day or the first feeding tree of the next morning. These patterns led us to reject the food access hypothesis. Lastly, we did not find evidence to support the range defense hypothesis because gibbons did not sleep in overlap areas with neighbors more often than expected based on the proportion of overlap and exclusively used areas. PMID:22767325

  11. Role of MgO and CaO promoters in Ni-catalyzed hydrogenation reactions of CO and carbon

    SciTech Connect

    Haga, Tetsuya; Ozaki, Junichi; Suzuki, Kyosuke; Nishiyama, Yoshiyuki )

    1992-03-01

    The roles of Mg and Ca promoters in Ni-catalyzed hydrogasification of carbon were investigated with emphasis on nickel dispersion and nickel-carbon interactions during gasification. The dispersion of nickel on carbon, which was estimated by means of XRD, H{sub 2}-TPD, and CO methanation test, was (Ni + Mg){much gt}(Ni + Ca)>Ni. The increased dispersions of nickel by the Mg and Ca added were found to result in the enhanced Ni-C interaction, which was monitored through the desorption of CO from oxygen remaining on carbon, and, therefore, in the promotions of Ni-catalyzed lower-temperature gasification at 400-700 C. The Ca promoter was likely to give surface CaO(COO) species upon heating up to 550 C and release CO{sub 2} above {approximately} 650 C. The CO{sub 2} released is efficiently converted by the nickel adjacent to CaO into CO to create Ni-(O)-C species above 700 C, resulting in acceleration of Ni-catalyzed gasification above 700 C. In situ oxygen transfer to Ni/C during reaction is the most important role played by the Ca promoter.

  12. Spectroscopic Characterization of a Multiband Complex Oxide: Insulating and Conducting Cement 12CaO7Al?O?

    SciTech Connect

    McLeod, John A.; Buling, A.; Kurmaev, Ernst Z.; Sushko, Petr V.; Neumann, N.; Finkelstein, L. D.; Kim, S. W.; Hosono, H.; Moewes, Alexander

    2012-01-13

    Natural 12CaO7Al?O? (C12A7) is a wide band gap insulator, but conductivity can be realized by introducing oxygen deficiency. Currently, there are two competing models explaining conductivity in oxygen-deficient C12A7, one involving the electron transfer via a cage conduction band inside the nominal band gap, the other involving electron hopping along framework lattice sites. To help resolve this debate, we probe insulating and conducting C12A7 with x-ray emission, x-ray absorption, and x-ray photoemission spectroscopy, which provide a full picture of both the valence and conduction band edges in these materials. Thesemeasurements suggest the existence of a narrow conduction band between themain conduction and valence bands common in both conducting and insulating C12A7 and support the theory that free electrons in oxygen-deficient C12A7 occupy the low-energy states of this narrow band. Our measurements are corroborated with density functional theory calculations.

  13. Geological control of canopy structure and function in Panamanian forests as identified by CAO-AToMS

    NASA Astrophysics Data System (ADS)

    Higgins, M.; Asner, G. P.; Martin, R. E.; Knapp, D. E.

    2012-12-01

    Geological formations and their edaphic properties are known to control plant species composition in tropical forests. It has been speculated that these edaphic and compositional patterns might also be translated into functional patterns, but this has been difficult to test due to a lack of broad-scale but detailed canopy structural and functional data. Here we use the Carnegie Airborne Observatory (CAO) Airborne Taxonomic Mapping System (AToMS), which combines a 480-band visible-to-shortwave imaging spectrometer (VSWIR) with dual waveform LiDAR, to generate ultra-high resolution data on geomorphology, canopy structure, and canopy chemistry for forests in the vicinity of the Panama Canal. Using these remotely-sensed data, in conjunction with field data on soils and plant species composition, we demonstrate that geological formations regulate forest structure and chemistry in these forests via changes in soils and plant species composition. These chemical properties, moreover, correspond to canopy functional properties including photosynthetic investment and anti-herbivore defenses. Together, our findings indicate that forest canopy structure and function in these forests are an expression their geological history, over which variations due to contemporary variables such as climate are overlaid.

  14. CO{sub 2} capture capacity of CaO in long series of carbonation/calcination cycles

    SciTech Connect

    Grasa, G.S.; Abanades, J.C.

    2006-12-20

    Calcium oxide can be an effective sorbent to separate CO{sub 2} at high temperatures. When coupled with a calcination step to produce pure CO{sub 2}, the carbonation reaction is the basis for several high-temperature CO{sub 2} capture systems. The evolution with cycling of the capture capacity of CaO derived from natural limestones is experimentally investigated in this work. Long series of carbonation/calcination cycles (up to 500) varying different variables affecting sorbent capacity have been tested in a thermogravimetric apparatus. Calcination temperatures above T > 950{sup o}C and very long calcination times accelerate the decay in sorption capacity, while other variables have a comparatively modest effect on the overall sorbent performance. A residual conversion of about 7-8% that remains constant after many hundreds of cycles and that seems insensitive to process conditions has been found. This residual conversion makes very attractive the carbonation/calcination cycle, by reducing (or even eliminating) sorbent purge rates in the system. A semiempirical equation has been proposed to describe sorbent conversion with the number of cycles based on these new long data series.

  15. Materials Data on Na2O2 (SG:189) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  16. Crystallization of Na2O-SiO2 gel and glass

    NASA Technical Reports Server (NTRS)

    Neilson, G. F.; Weinberg, M. C.

    1984-01-01

    The crystallization behavior of a 19 wt pct soda silica gel and gel-derived glass was compared to that of the ordinary glass of the same composition. Both bulk and ground glass samples were utilized. X-ray diffraction measurements were made to identify the crystalline phases and gauge the extent of crystallization. It was found that the gel crystallized in a distinctive manner, while the gel glass behavior was not qualitatively different from that of the ordinary glass.

  17. Tephra record from the Sea of Marmara for the last 70 ka and its paleoceanographic implications

    NASA Astrophysics Data System (ADS)

    Cagatay, M.; Wulf, S.; Guichard, F.; Ozmaral, A.; Sancar; Akçer-Ön, S.; Henry, P.; Gasperini, L.

    2013-12-01

    Sea of Marmara (SoM) is a gateway between the Mediterraean and Black seas, and a tectonically active basin located on a transform plate boundary. Tephra record in the SoM is therefore very important for dating palaeoceanographic, paleoclimatic and tectonic events. We report three tephra units in cores from the SoM extending back to ca 70 ka BP and including an upper marine and a lower lacustrine units separated by a 12 ka (uncalib.) boundary. The uppermost tephra unit is up to 8 mm thick layer in the marine unit. It is heterogenous phonolitic with high total alkali content of 12.4-15.7 wt % and K2O/Na2O of 0.9 to 1.2. The middle and lower tephra layers occur in the lacustrine unit in ca 29 m-long Core MD-01-2430. The middle tephra (MT-1) is a 70 mm-thick homogeneously rhyolitic layer. The lower tephra (MT-2) is 140 mm thick and has a phonolitic-trachytic composition with CaO content of 1.7-1.9 wt % and bimodal K2O/Na2O of 1.0-1.4. Using their geochemical composition and stratigraphic analysis, we assign the tephra units, from top to bottom, to Vesuvius AP2 Pumice, Santorini Cape Riva and Campanian Ignimbrite, which have been previously dated at 3.5 ka BP, 21.95 ka BP, and 39.3 ka BP (all calender ka). The continuous sedimentary record in the Core MD-01-2430 covering the last ca 70 ka indicates that the SoM was lacustrine, disconnected from the Mediterraean Sea during MIS4, MIS3 and most of MIS2. This implies that the sill depth of the Çanakkale Strait (Dardanelles) was shallower than the present-day -65 m sill depth during MIS3 and MIS4. Figure 1: Morphotectonic map of the Sea of Marmara showing location of the studied cores (red stars). Figure 2: Geochemical biplots of tephra glass composition. a) Total alkali silica diagram b) FeO versus total alkalies for allocating cryptotephras from core MNTKS34 and ML01 to the AP2 tephra from Vesuvius. c) FeO versus CaO for correlating tephra MT1 with the Y-2 tephra from Santorini. d) SiO2 versus CaO for discriminating the MT2 tephra (Campanian Ignimbrite).

  18. The effect of Al2O3, CaO, Cr2O3 and MgO on devitrification of silica

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, Isidor

    1988-01-01

    The effect of doping on devitrification of vitreous silica was studied at 1100, 1200, and 1300 C. Dispersion of dopants on a molecular scale was accomplished via a sol-gel technique. All dopants accelerated the devitrification of silica but to different degrees. The most active was CaO followed by MgO, Al2O3, and Cr2O3. Pure silica and silica containing Cr2O3 and Al2O3 devitrified to alpha-cristobalite only, whereas silica doped with CaO and MgO produced alpha-quartz and alpha-cristobalite. It appears that prolonged heat treatment would cause alpha-quartz to transform to alpha-cristobalite.

  19. The Vibrational Frequencies of CaO2, ScO2, and TiO2: A Comparison of Theoretical Methods

    NASA Technical Reports Server (NTRS)

    Rosi, Marzio; Bauschlicher, Charles W., Jr.; Chertihin, George V.; Andrews, Lester; Arnold, James O. (Technical Monitor)

    1997-01-01

    The vibrational frequencies of several states of CaO2, ScO2, and TiO2 are computed at using density functional theory (DFT), the Hatree-Fock approach, second order Moller-Plesset perturbation theory (MP2), and the complete-active-space self-consistent-field theory. Three different functionals are used in the DFT calculations, including two hybrid functionals. The coupled cluster singles and doubles approach including the effect of unlinked triples, determined using perturbation theory, is applied to selected states. The Becke-Perdew 86 functional appears to be the cost effective method of choice, although even this functional does not perform well for one state of CaO2. The MP2 approach is significantly inferior to the DFT approaches.

  20. End to end assembly of CaO and ZnO nanosheets to propeller-shaped architectures by orientation attachment approaches

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Liu, Fang

    2015-06-01

    Inspired by the agitation effect of propellers, heterogeneous propeller- shaped CaO/ZnO architectures were assembled in aqueous solution. Preferred nucleation and growth of CaO and ZnO nuclei resulted in their hexagonal nanosheets, and they were end to end combined into propeller-shaped architectures by oriented rotation and attachment reactions. When propeller-shaped CaO/ZnO product was used as solid base catalyst to synthesize biodiesel, a high biodiesel yield of 97.5% was achieved. The predominant exposure of active O2- on CaO(0 0 2) and ZnO(0 0 0 2) planes in propeller-shaped CaO/ZnO, led to good catalytic activity and high yield of biodiesel.

  1. Role of Y{sub 2}O{sub 3}, CaO, MgO additives on structural and microstructural behavior of zirconia/mullite aggregates

    SciTech Connect

    Mishra, D. K.; Prusty, Sasmita; Mohapatra, B. K.; Singh, S. K.; Behera, S. N.

    2012-07-23

    Zirconia mullite (MUZ), Y{sub 2}O{sub 3}-MUZ, CaO-MUZ and MgO-MUZ composites, synthesized through plasma fusion technique, are becoming important due to their commercial scale of production within five minutes of plasma treatment from sillimanite, zircon and alumina mixture. The X-ray diffraction studies reveal the monoclinic zirconia phase in MUZ composite whereas mixed monoclinic, tetragonal and cubic phases of zirconia have been observed in Y{sub 2}O{sub 3}, CaO, MgO added MUZ composites. The Y{sub 2}O{sub 3}, CaO and MgO additives act as sintering aids to favour the transformation and stabilisation of tetragonal and cubic zirconia phases at room temperature. These additives also play a key role in the development of various forms of microstructure to achieve dense MUZ composites.

  2. Preparation of CaO as OLED getter material through control of crystal growth of CaCO{sub 3} by block copolymers in aqueous solution

    SciTech Connect

    Park, Jae-Hyung; Oh, Seong-Geun

    2009-01-08

    As the starting materials of organic light-emitting diode (OLED) getter, calcium carbonate (CaCO{sub 3}) particles with various shapes and crystal structures have been successfully prepared with additives (L64 or PEGPG), which contain blocks of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO). These CaCO{sub 3} particles were calcinated into highly crystalline calcium oxide (CaO) nanoparticles with high capacity of water adsorption up to 14.23 wt.%. The CaCO{sub 3} and CaO particles prepared at various conditions were characterized using the field emission scanning electron microscopy (FE-SEM), Fourier transform infrared microscopy (FT-IR), X-ray powder diffraction (XRD), and dynamic vapor sorption (DVS) method.

  3. Role of Y2O3, CaO, MgO additives on structural and microstructural behavior of zirconia/mullite aggregates

    NASA Astrophysics Data System (ADS)

    Mishra, D. K.; Prusty, Sasmita; Mohapatra, B. K.; Singh, S. K.; Behera, S. N.

    2012-07-01

    Zirconia mullite (MUZ), Y2O3-MUZ, CaO-MUZ and MgO-MUZ composites, synthesized through plasma fusion technique, are becoming important due to their commercial scale of production within five minutes of plasma treatment from sillimanite, zircon and alumina mixture. The X-ray diffraction studies reveal the monoclinic zirconia phase in MUZ composite whereas mixed monoclinic, tetragonal and cubic phases of zirconia have been observed in Y2O3, CaO, MgO added MUZ composites. The Y2O3, CaO and MgO additives act as sintering aids to favour the transformation and stabilisation of tetragonal and cubic zirconia phases at room temperature. These additives also play a key role in the development of various forms of microstructure to achieve dense MUZ composites.

  4. The role of temperature on Cr(VI) formation and reduction during heating of chromium-containing sludge in the presence of CaO.

    PubMed

    Mao, Linqiang; Gao, Bingying; Deng, Ning; Zhai, Jianping; Zhao, Yongbin; Li, Qin; Cui, Hao

    2015-11-01

    In this study, the temperature dependence of Cr(VI) formation and reduction in the presence of CaO was examined during the thermal treatment of sludge that contains chromium. thermogravimetry-differential scanning calorimetry and X-ray diffractometry were used to characterize the thermal behavior and phase transformation, respectively. Na2CO3 leaching procedure was employed to determine the amount of Cr(VI). The result showed that CaO promoted Cr(III) oxidation, however, its influence is very dependent on heating temperature, with the extent of the effect varying with temperature. From 200-400 C, the presence of CaO facilitated formation of intermediate product Cr2O3+x containing Cr(VI) during dehydration of chromium hydrate, while Cr2O3+x would decompose as temperature over 400 C, accompanied by part of Cr(VI) being reduced to Cr(III). From 500 to 900 C, Cr(III) reacted with CaO to form a leachable CaCrO4 product. This product was stable and a prolonged heating time did not reduce the amount of Cr(VI) significantly. At 1000-1200 C, part of CaCrO4 was reduced to Ca(CrO2)2 in 1h. While extended heating time above 1h resulted in the Ca(CrO2)2 being oxidized reversibly to CaCrO4 at 1200 C. Since CaCrO4 is thermodynamically less stable over 1000 C, MgO could induce CaCrO4 to be reduced into MgCr2O4 at around 900 C, lower than that for the reduction from CaCrO4 into Ca(CrO2)2. It suggested that adding MgO might be a potential approach for inhibiting Cr(VI) formation during heating sludge containing chromium. PMID:26072117

  5. CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1995-09-01

    Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. Electrical resistance of CaO coatings that were produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li containing 0.5-85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {>=}360{degrees}C.

  6. Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics

    NASA Astrophysics Data System (ADS)

    Li, Peng; Zhang, Mei; Teng, Lidong; Seetharaman, Seshadri

    2013-02-01

    T he oxidation behaviors of composites SiAlON/MgAlON phases (?-SiAlON, 15R-SiAlON and MgAlON) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples were investigated in air by thermogravimetric measurements. Combined kinetics, viz. linear law + arctan law + parabolic law, are used to describe the kinetics of oxidation in isothermal mode. The oxidation studies reveal the effects of impurities, namely, Fe2O3 and CaO, present in the salt cake residue. The addition of Fe2O3 results in a lower activation energy and more aggressive oxidation. The addition of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673 K (1400 C). The impurities of CaO and Fe2O3 in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point.

  7. First-principles study of the thermodynamical, structural, transport properties of liquid CaO and CaSiO3 at high pressure

    NASA Astrophysics Data System (ADS)

    Bajgain, S. K.; Karki, B. B.; Ghosh, D. B.

    2014-12-01

    We have performed first principles molecular dynamics simulations of CaO and CaSiO3 liquids overbroad ranges of pressure (0 to 150 GPa) and temperature (2500 to 8000 K) within density functionaltheory. They show that both liquids are much more compressible than their solid counterpartsimplying possible liquid-solid density crossover. The liquid Grneisen parameter increases onpressure, which is opposite of crystalline phases. Our analysis shows that the liquid structurechanges considerably on compression, with the mean cation-anion coordination numbers increasingnearly linearly with volume. The Ca-O coordination number increases from 7 (5) near the ambientpressure to 9 (7) at high pressure for CaSiO3 (CaO) liquid. The Si-O coordination number increasesfrom 4 to 6 over the same pressure regime. The calculated self-diffusion coefficients are stronglydependent on temperature and pressure and require non-Arrhenian representation with variableactivation volume. The diffusivity differences between the two liquids are considerable in low-temperature and low-pressure regime. Also, comparisons with MgSiO3 liquid suggest that networkmodifier cations Ca and Mg behave similarly though Ca is more coordinated and more mobile ascompared with Mg.

  8. Conversion of melt-derived microfibrous borate (13-93B3) and silicate (45S5) bioactive glass in a simulated body fluid.

    PubMed

    Liu, Xin; Rahaman, Mohamed N; Day, Delbert E

    2013-03-01

    Microfibrous bioactive glasses are showing a considerable capacity to heal soft tissue wounds, but little information is available on the mechanism of healing. In the present study, the conversion of microfibrous borate bioactive glass (diameter=0.2-5?m) with the composition designated 13-93B3 (5.5 Na2O, 11.1 K2O, 4.6 MgO, 18.5 CaO, 3.7 P2O5, 56.6 B2O3 wt%) was evaluated in vitro as a function of immersion time in a simulated body fluid (SBF) at 37C using structural and chemical techniques. Silicate 45S5glass microfibers (45 SiO2, 24.5 Na2O, 24.5 CaO, 6 P2O5 wt%) were also studied for comparison. Microfibrous 13-93B3 glass degraded almost completely and converted to a calcium phosphate material within 7-14days in SBF, whereas>85% of the silica remained in the 45S5 microfibers, forming a silica gel phase. An amorphous calcium phosphate (ACP) product that formed on the 13-93B3 microfibers crystallized at a slower rate to hydroxyapatite (HA) when compared to the ACP that formed on the 45S5 fibers. For immersion times>3days, the 13-93B3 fibers released a higher concentration of Ca into the SBF than the 45S5 fibers. The fast and more complete degradation, slow crystallization of the ACP product, and higher concentration of dissolved Ca in SBF could contribute to the capacity of the microfibrous borate 13-93B3 glass to heal soft tissue wounds. PMID:23233025

  9. Fingerprint methods for suspended sediment transport processes by using X-ray fluorescence analysis

    NASA Astrophysics Data System (ADS)

    Nakayama, K.; Beitia, C.; Ohtsu, N.; Yamasaki, S.; Yasuyuki, M.; Yamane, M.

    2014-12-01

    Suspended sediment (SS) can have significant impacts on ecological system, and high SS concentration can have significant impacts on human life. In the previous studies, radionuclide analysis has been applied to evaluate the production of SS in the river basins, which demonstrated that the surface soil erosion can be estimated by using radionuclide Pb-210ex. However, radionuclide analysis cannot indicate the relative amounts of SS transported from each individual sub-basin to the downstream end. Thus, X-ray Fluorescence Analysis (XRF Analysis) can be considered as an alternative method to radionuclide analysis because the XRF Analysis can measure 21 chemical compositions, Na2O, MgO, Al2O3, SiO2, P2O5, SO3, Cl, K2O, CaO, TiO2, Cr2O3, MnO, Fe2O3, Co2O3, NiO, CuO, ZnO, Rb2O, SrO, BaO, and Y2O3 by using X-ray Fluorescence Analyzer. In June of 2007, high turbidity, which is more than 10,000 (NTU), was measured in the Oromushi River basin of Hokkaido in Japan. Therefore, this study aims to clarify the mechanism of the transport of SS in the Oromushi River basin. We measured chemical compositions of soil with diameter less than 63 ?m in the Oromushi River basin in order to pay attention to SS by using XRF. The Principal Component Analysis revealed that SiO2, Al2O3, Fe2O3, CaO and Na2O are the dominant chemical compositions. Although the predominant composition was the same in a river basin including the downstream end, significant differences were found in the pattern of chemical compositions. Therefore, by using the chemical compositions of SiO2, Al2O3, Fe2O3, CaO and Na2O, the Mixing Stable Isotope Analysis in R model (MixSIAR) based on Bayesian statistics was applied to estimate the transportation rate of SS from each sub-basin to the downstream end, which agreed with the field experiment results very well. As a result, spatial patterns of SS transportation rate are found to be strongly related to surface soil type.

  10. The influence of SrO and CaO in silicate and phosphate bioactive glasses on human gingival fibroblasts.

    PubMed

    Massera, J; Kokkari, A; Nrhi, T; Hupa, L

    2015-06-01

    In this paper, we investigate the effect of substituting SrO for CaO in silicate and phosphate bioactive glasses on the human gingival fibroblast activity. In both materials the presence of SrO led to the formation of a CaP layer with partial Sr substitution for Ca. The layer at the surface of the silicate glass consisted of HAP whereas at the phosphate glasses it was close to the DCPD composition. In silicate glasses, SrO gave a faster initial dissolution and a thinner reaction layer probably allowing for a continuous ion release into the solution. In phosphate glasses, SrO decreased the dissolution process and gave a more strongly bonded reaction layer. Overall, the SrO-containing silicate glass led to a slight enhancement in the activity of the gingival fibroblasts cells when compared to the SrO-free reference glass, S53P4. The cell activity decreased up to 3 days of culturing for all phosphate glasses containing SrO. Whereas culturing together with the SrO-free phosphate glass led to complete cell death at 7 days. The glasses containing SrO showed rapid cell proliferation and growth between 7 and 14 days, reaching similar activity than glass S53P4. The addition of SrO in both silicate and phosphate glasses was assumed beneficial for proliferation and growth of human gingival fibroblasts due to Sr incorporation in the reaction layer at the glass surface and released in the cell culture medium. PMID:26099346

  11. Mapping the geographic distribution of canopy species communities in lowland Amazon rainforest with CAO-AToMS (Invited)

    NASA Astrophysics Data System (ADS)

    Feret, J.; Asner, G. P.

    2013-12-01

    Mapping regional canopy diversity will greatly advance our understanding as well as the conservation of tropical rainforests. Changes in species composition across space and time are particularly important to understand the influence of climate, human activity and environmental factors on these ecosystems, but to date such monitoring is extremely challenging and is facing a scale gap between small-scale, highly detailed field studies and large-scale, low-resolution satellite observations. Advances were recently made in the field of spectroscopic imagery for the estimation of canopy alpha-diversity, and an original approach based on the segmentation of the spectral space proved its ability to estimate Shannon diversity index with unprecedented accuracy. We adapted this method in order to estimate spectral dissimilarity across landscape as a proxy for changes in species composition. We applied this approach and mapped species composition over four sites located in lowland rainforest of Peruvian Amazon. This study was based on spectroscopic imagery acquired using the Carnegie Airborne Observatory (CAO) Airborne Taxonomic Mapping System (AToMS), operating a unique sensor combining the fine spectral and spatial resolution required for such task. We obtained accurate estimation of Bray-Curtis distance between pairs of plots, which is the most commonly used metric to estimate dissimilarity in species composition (n=497 pairs, r=0.63). The maps of species composition were then compared to topo-hydrographic properties. Our results indicated a strong shift in species composition and community diversity between floodplain and terra firme terrain conditions as well as a significantly higher diversity of species communities within Amazonian floodplains. These results pave the way for global mapping of tropical canopy diversity at fine geographic resolution.

  12. Pan-African alkali granites and syenites of Kerala as imprints of taphrogenic magmatism in the South Indian shield

    NASA Technical Reports Server (NTRS)

    Santosh, M.; Drury, S. A.; Iyer, S. S.

    1988-01-01

    Granite and syenite plutons with alkaline affinities ranging in age from 550 to 750 Ma sporadically puncture the Precambrian granulites of the Kerala region. All the bodies are small (20 to 60 sq km), E-W to NW-SE elongated elliptical intrusives with sharp contacts and lie on or close to major late Proterozoic lineaments. Geochemical plots of A-F-M and An-Ab-Or relations show an apparent alkali enrichment trend on the former, but the plutons define relatively distinct fields on the latter. Most of the plutons are adamellitic to granitic by chemistry. The variations of SiO2 with log sub 10 K2O/MgO (1) brings out the distinct alkaline nature of the plutons. Some of the granites are extremely potassic, like the Peralimala pluton, which shows up to 11.8 percent K2O. On a SiO2-Al2O3-Na2O+K2O (mol percent) plot, the plutons vary from peraluminous to peralkaline, but none are nepheline normative. Low MgO, low to moderate CaO and high Fe2O3/FeO values are other common characteristics. Among trace elements, depletion of Ba, Sr and Rb with high K/Ba and K/Rb values are typical. Overall, the plutons show a trend of decreasing K/Rb ratio with increasing K content. Individual plutons show more clearly defined trends similar to those from granitic masses characterized by plagioclase fractionation.

  13. The influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern United States

    NASA Astrophysics Data System (ADS)

    Cox, Rónald; Lowe, Donald R.; Cullers, R. L.

    1995-07-01

    This paper reports systematic changes in mudrock composition through time on a single continental crustal block. The changes reflect both sediment recycling processes and changes through time in the composition of crystalline material being added to the sedimentary system and are related to tectonic evolution as the block matures from a series of accreted arc terranes to a stable craton. The major and trace element distributions reflect different aspects of the provenance of the mudrocks in this study. Major elements record sediment recycling processes as well as changing proportions of sedimentary and first-cycle source rocks. With the exceptions of K 2O (which tends to increase), and SiO 2 and Al 2O 3 (which show no trend), most major oxides tend to decline in relative abundance in younger mudrocks. Patterns shown by the Index of Compositional Variability ([Fe 2O 3 + K 2O + Na 2O + CaO + MgO + MnO + TiO 2]/Al 2O 3) and by K 2O/Al 2O 3 indicate that the major oxide trends are due to decreasing proportions of nonclay silicate minerals and a concomitant increase in the proportion of clay minerals, probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material. Excursions from progressive trends, marked by increases in MgO, K 2O, and CaO, reflect episodes of large-scale input of nonclay first-cycle minerals from crystalline source rocks due to large-scale basement uplift. The chemistry of low-solubility trace elements, in contrast, is not sensitive to recycling effects and reflects the composition of first-cycle input. Incompatible elements are progressively enriched relative to compatible elements in younger mudrocks, and values for chondrite normalised rare earths elements also increase. In addition, the Eu anomaly becomes systematically more negative in younger samples. These trends cannot be explained by diagenetic or weathering processes, and, therefore, indicate that the proportion of fractionated granitic first-cycle detritus being added to the sedimentary system becomes greater with time. These results confirm the importance of tectonic setting in controlling mudrock chemistry, and also demonstrate that there is a dynamic relationship between the tectonic evolution of a continental block and the composition of its sedimentary mantle.

  14. Effects of microstructure and CaO addition on the magnetic and mechanical properties of NiCuZn ferrites

    NASA Astrophysics Data System (ADS)

    Wang, Sea-Fue; Hsu, Yung-Fu; Liu, Yi-Xin; Hsieh, Chung-Kai

    2015-11-01

    In this study, the effects of grain size and the addition of CaCO3 on the magnetic and mechanical properties of Ni0.5Cu0.3Zn0.2Fe2O4 ceramics were investigated. The bending strength of the ferrites increased from 66 to 84 MPa as the grain size of the sintered ceramics decreased from 10.25 μm to 7.53 μm, while the change in hardness was insignificant. The addition of various amounts of CaCO3 densified the Ni0.5Cu0.3Zn0.2Fe2O4 ceramics at 1075 °C. In the pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic, second phase CuO was segregated at the grain boundaries. With the CaCO3 content ≥1.5 wt%, a small amount of discrete plate-like second phase Fe2CaO4 was observed, together with the disappearance of the second phase CuO. The grain size of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic dropped from 7.80 μm to 4.68 μm, and the grain size distribution widened as the CaCO3 content increased from 0 to 5 wt%. Initially rising to 807 after CaCO3 addition up to 2.0 wt%, due to a reduced grain size, the Vickers hardness began to drop as the CaCO3 content increased. The bending strength grew linearly with the CaCO3 content and reached twice the value for the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with an addition of 5.0 wt% CaCO3. The initial permeability of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic decreased substantially from 402 to 103 as the addition of CaCO3 in ferrite increased from 0 to 5 wt%, and the quality factor of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic was maximized at 95 for 1.0 wt% CaCO3 addition.

  15. Geochemistry of sedimentary-derived migmatite from NE Sardinia, Italy

    NASA Astrophysics Data System (ADS)

    Cruciani, Gabriele; Fancello, Dario; Franceschelli, Marcello; Scodina, Massimo

    2015-04-01

    In NE Sardinia at Porto Ottiolu, about 30 km south of Olbia (NE Sardinia), crops out a sequence of migmatized ortho and paragneiss, belonging to the Variscan basement's axial zone. Sedimentary-derived migmatite, which have a layered appearance in the field, were affected by three major variscan folding phase. D2, which is characterized by tight folds, is the most widespread deformation in the field. Leucosomes consists of discontinuous centimetre-thick, coarse-grained layers, that follow the S2 schistosity and are folded by D2 deformation phase. The contact with mesosome is sharp and sometimes marked by melanosome trails. They consist of quartz, plagioclase, very rare K-feldspar, muscovite, biotite, fibrolite, and rare kyanite. Plagioclase is unzoned oligoclase, though in some cases a thin albite rim is observed. Muscovite occurs as: i) single small- to medium-grained flakes enclosed in feldspar; ii) coarse grained crystals associated to biotite, fibrolite, and opaques, iii) in intergrowth with biotite to form thin elongated, slightly oriented trails, marking the faint foliation. Mesosomes are medium-grained, well foliated rocks, consisting of quartz, plagioclase muscovite, , biotite, fibrolite K-feldspar garnet. Fibrolite, muscovite and biotite are associated, to form strongly oriented, thick levels. Muscovite also occurs as unoriented crystals, showing quartz exsolutions and thin rims. A few mm-thick melanosome is usually present at the boundary between the leucosomes and mesosomes. Leucosomes are characterized by: SiO2: 75.4-77.9; Al2O3: 13.2-14.5; Fe2O3tot: 0.3-0.5; MgO: 0.1-0.2; CaO: 2.7- 3.7; Na2O: 3.9-4.6; K2O: 0.4-0.6 wt.%. An interesting feature is the relative high calcium content already described in other sedimentary-derived migmatite from Sardinia (Cruciani et al., 2008). In the normative Ab-An-Or diagram (Barker, 1979) the leucosomes plot at the boundary between trondhjemite/tonalite fields. All leucosomes are corundum normative and peraluminous. Mesosomes show a lower content of silica and higher content of iron, magnesium and potash. Major elements ranges are: SiO2: 69.9-70.2; Al2O3: 12.8-13.3; Fe2O3tot: 5.4-5.6; MgO: 2.1-2.3; CaO: 2.0-2.1; Na2O: 2.4-2.5; K2O: 2.2-2.4 wt%. Chondrite-normalized REE pattern, shows that all leucosomes are characterized by a positive Eu anomaly and a significant enrichment in LREE. Mesosomes pattern shows a marked negative Eu anomaly, an enrichment in LREE and a depletion in HREE. Total REE content is higher in mesosomes (132-156 ppm) than in leucosomes (51-58 ppm). Trondjhemite/tonalite composition with high CaO, Na2O and low K2O of the leucosomes will be discussed in relation to their significance and origin. References: Barker, F., 1979, Trondhjemite: definition, environment and hypotheses of origin. In: Barker, F. (Ed.), Trondhjemites, dacites, and related rocks. Developments in petrology, vol. 6. Elsevier,Amsterdam, pp. 1-12. Cruciani, G., Franceschelli, M., Elter, F.M., Puxeddu, M., Utzeri, D., 2008, Petrogenesis of Al-silicate-bearing trondhjemitic migmatites from NE Sardinia, Italy. Lithos v. 102, p. 554-574.

  16. Use of CaO as an activator for producing a price-competitive non-cement structural binder using ground granulated blast furnace slag

    SciTech Connect

    Kim, Min Sik; Jun, Yubin; Lee, Changha Oh, Jae Eun

    2013-12-15

    The use of calcium oxide (CaO) demonstrates a superior potential for the activation of ground granulated blast furnace slag (GGBFS), and it produces a higher mechanical strength than calcium hydroxide [Ca(OH){sub 2}]. The mechanical strength differences between CaO- and Ca(OH){sub 2}-activated GGBFS binders are explored using isothermal calorimetry, powder X-ray diffraction, thermogravimetric and differential thermal analysis (TGA and DTA) as well as compressive strength testing. Calcium silicate hydrate (C–S–H), Ca(OH){sub 2} and a hydrotalcite-like phase are found as reaction products in all samples. The TGA and DTA results indicate that the use of CaO produces more C–S–H, although this is not likely to be the primary cause of higher strength development in the CaO-activated GGBFS. Rather, other factors such as porosity may govern the strength at a higher order of magnitude. Significant reduction of Ca(OH){sub 2} occurs only with the use of Ca(OH){sub 2}, followed by the formation of carbonate (CaCO{sub 3}), indicating carbonation. -- Highlights: •CaO showed a better potential for the activation of GGBFS than Ca(OH){sub 2}. •Strength test, XRD, TGA/DTA and isothermal calorimetry are used. •C-S-H, Ca(OH){sub 2}, and a hydrotalcite-like phase are found in all samples. •The use of Ca(OH){sub 2} causes some degree of carbonation.

  17. Species classification and bioactive ingredients accumulation of BaiJiangCao based on characteristic inorganic elements analysis by inductively coupled plasma-mass spectrometry and multivariate analysis

    PubMed Central

    Wen-Lan, Li; Xue, Zhang; Xin-Xin, Yang; Shuai, Wang; Lin, Zhao; Huan-Jun, Zhao; Yong-Rui, Bao; Chen-Feng, Ji; Ning, Chen; Zheng, Xiang

    2015-01-01

    Background: Patrinia scabiosaefolia Fisch and Patrinia villosa (Thunb.) Juss., two species herbs with the same Chinese name “BaiJiangCao”, are important ancient herbal medicines widely used for more than 2000 years. The clinical application of two species herb is confused due to the difficult identification. Objective: The objective was to authenticate the species of BaiJiangCao and analyze the accumulation of bioactive ingredients based on characteristic inorganic elements analysis. Materials and Methods: Content of 32 inorganic elements in BaiJiangCao from different habitats were determined by inductively coupled plasma-mass spectrometry (ICP-MS), and the characteristic inorganic elements were picked to distinguish the species of the herb by principal component analysis and cluster analysis. Contents of two bioactive ingredients, luteoloside, and oleanolic acid, in the samples, were also analyzed by high-performance liquid chromatography method. Relationship between accumulation of bioactive ingredients and content of macroelements in BaiJiangCao was established by statistics. Results: A 4 macroelements (Na, Mg, K, Fe) in 32 determined inorganic elements were picked for characteristic inorganic elements. Content of Na, Mg, K and Fe showed positive correlations with that of luteoloside, content of Na, Mg showed positive correlations with that of oleanolic acid, but content of K and Fe showed negative correlations with that of oleanolic acid. Conclusion: It is for the first time to utilize the characteristic inorganic elements as an index to classify the herb species by the method of ICP-MS and multivariate analysis. And it is also the first report to investigate the influence of inorganic elements in herb on the accumulation of bioactive components which could affect the pharmacological efficacy of the herb medicine. And this method could also be utilized in research of corresponding aspects. PMID:26600721

  18. Biological and mechanical properties of an experimental glass-ionomer cement modified by partial replacement of CaO with MgO or ZnO

    PubMed Central

    Dong-Ae, KIM; Hany, ABO-MOSALLAM; Hye-Young, LEE; Jung-Hwan, LEE; Hae-Won, KIM; Hae-Hyoung, LEE

    2015-01-01

    Some weaknesses of conventional glass ionomer cement (GIC) as dental materials, for instance the lack of bioactive potential and poor mechanical properties, remain unsolved. Objective The purpose of this study was to investigate the effects of the partial replacement of CaO with MgO or ZnO on the mechanical and biological properties of the experimental glass ionomer cements. Material and Methods Calcium fluoro-alumino-silicate glass was prepared for an experimental glass ionomer cement by melt quenching technique. The glass composition was modified by partial replacement (10 mol%) of CaO with MgO or ZnO. Net setting time, compressive and flexural properties, and in vitro rat dental pulp stem cells (rDPSCs) viability were examined for the prepared GICs and compared to a commercial GIC. Results The experimental GICs set more slowly than the commercial product, but their extended setting times are still within the maximum limit (8 min) specified in ISO 9917-1. Compressive strength of the experimental GIC was not increased by the partial substitution of CaO with either MgO or ZnO, but was comparable to the commercial control. For flexural properties, although there was no significance between the base and the modified glass, all prepared GICs marked a statistically higher flexural strength (p<0.05) and comparable modulus to control. The modified cements showed increased cell viability for rDPSCs. Conclusions The experimental GICs modified with MgO or ZnO can be considered bioactive dental materials. PMID:26398508

  19. Occurrence of superoxide radical ion in crystalline 12CaO 7Al/sub 2/O/sub 3/ prepared via solid-state reactions

    SciTech Connect

    Hosono, H.; Abe, Y.

    1987-04-22

    Superoxide radical ion O/sub 2//sup -/ is an active species of oxygen and is known to play important roles in many chemical reactions involving O/sub 2/. The formation of O/sub 2//sup -/ on or in solid oxides is usually achieved with the aid of energetic photons such as uv, X-ray, or ..gamma..-ray radiation. It has been found that O/sub 2//sup -/ occurs in the 12CaO 7Al/sub 2/O/sub 3/ crystal prepared by the solid-state reaction between CaCO/sub 3/ and Al/sub 2/O/sub 3/ or Al(OH)/sub 3/ powder without any accompanying irradiation; the concentration of O/sub 2//sup -/ goes up to ca. 4 x 10/sup 18/ units/g.From the change in the line shape with temperature, the O/sub 2//sup -/ is concluded to be included in the structural cavity inherent in the crystal lattice. A drastic reduction in the concentration of O/sub 2//sup -/ on anion substitution and on heating under an oxygen-free atmosphere strongly suggests that the occurrence of O/sub 2//sup -/ is closely related with free oxygen, which is a unique characteristic of the 12CaO 7Al/sub 2/O/sub 3/ crystal. Such characteristics found for 12CaO 7Al/sub 2/O/sub 3/ are analogous to those for ultramarine, Na/sub 8/(Si/sub 6/Al/sub 6/O/sup 24/)S/sub 2/. 25 references, 4 figures, 2 tables.

  20. Biological and mechanical properties of an experimental glass-ionomer cement modified by partial replacement of CaO with MgO or ZnO.

    PubMed

    Kim, Dong-Ae; Abo-Mosallam, Hany; Lee, Hye-Young; Lee, Jung-Hwan; Kim, Hae-Won; Lee, Hae-Hyoung

    2015-01-01

    Some weaknesses of conventional glass ionomer cement (GIC) as dental materials, for instance the lack of bioactive potential and poor mechanical properties, remain unsolved.Objective The purpose of this study was to investigate the effects of the partial replacement of CaO with MgO or ZnO on the mechanical and biological properties of the experimental glass ionomer cements.Material and Methods Calcium fluoro-alumino-silicate glass was prepared for an experimental glass ionomer cement by melt quenching technique. The glass composition was modified by partial replacement (10 mol%) of CaO with MgO or ZnO. Net setting time, compressive and flexural properties, and in vitrorat dental pulp stem cells (rDPSCs) viability were examined for the prepared GICs and compared to a commercial GIC.Results The experimental GICs set more slowly than the commercial product, but their extended setting times are still within the maximum limit (8 min) specified in ISO 9917-1. Compressive strength of the experimental GIC was not increased by the partial substitution of CaO with either MgO or ZnO, but was comparable to the commercial control. For flexural properties, although there was no significance between the base and the modified glass, all prepared GICs marked a statistically higher flexural strength (p<0.05) and comparable modulus to control. The modified cements showed increased cell viability for rDPSCs.Conclusions The experimental GICs modified with MgO or ZnO can be considered bioactive dental materials. PMID:26398508

  1. Landscape-scale tropical forest dynamics: Relating canopy traits and topographically derived hydrologic indices in a floodplain system using CAO-AToMS

    NASA Astrophysics Data System (ADS)

    Chadwick, K.; Asner, G. P.

    2012-12-01

    The geomorphology of floodplains in the humid tropics has been used to infer basic classifications of forest types. However, analysis of the landscape-scale topographic and hydrologic patterns underpinning spatial variation in forest composition and function remain elusive due to the sparse coverage of forest plots, coarse resolution remotely sensed data, and the challenges of collecting first order hydrologic data. Airborne remote measurements provide an opportunity to consider the relationship between high-resolution topographic and derived hydrologic environmental gradients, and forest canopy characteristics with important cascading effects on ecosystem function and biosphere-atmosphere interactions. In 2011, the Carnegie Airborne Observatory (CAO) Airborne Taxonomic Mapping System (AToMS) was used to map a large section of the Los Amigos Conservation Concession harboring largely intact lowland humid tropical forest in the southwestern Peruvian Amazon. The CAO Visible-Shortwave Imaging Spectrometer (VSWIR) collected 480-band high-fidelity imaging spectroscopy data of the forest canopy, while its high-resolution dual waveform LiDAR captured information on canopy structure and the underlying terrain. The data were used to quantify relationships between topographic and hydrologic gradients and forest functional traits. Results suggest strong local hydrogeomorphic control over vegetation spectral properties with known relationships to canopy functional traits, including pigment and nutrient concentrations and light capture, as well as canopy structural characteristics, including vegetation height, understory plant cover, and aboveground biomass. Data from CAO-AToMS reveals local-scale patterns in environmental conditions and ecological variation that meets or exceeds the variation previously reported across ecosystems of the Western Amazon Basin.

  2. Tuning optical properties of complex oxides: examples of 12CaO.7Al2O3 mayenite and LaCrO3 perovskite

    NASA Astrophysics Data System (ADS)

    Sushko, Peter V.

    2012-02-01

    Optical absorption bands in two complex oxides are characterised using ab initio simulations and an embedded cluster method. In sub-nanoporous 12CaO.7Al2O3 the width of the optical gap can be controlled by modifying the chemical identities and relative concentration of extra-framework species. In antiferromagnetic LaCrO3, Cr 3d states split into four narrow one-electron bands and give rise to several types of the optical transitions. Their excitation energies respond differently to lattice strain, thus, providing a possibility for tuning the excitation energies in supported LaCrO3 films by selecting appropriate substrates.

  3. Steam-Coal Gasification Using CaO and KOH for in Situ Carbon and Sulfur Capture

    SciTech Connect

    Siefert, Nicholas S.; Shekhawat, Dushyant; Litster, Shawn; Berry, David A.

    2013-08-15

    We present experimental results of coal gasification with and without the addition of calcium oxide and potassium hydroxide as dual-functioning catalyst-capture agents. Using two different coal types and temperatures between 700 and 900 °C, we studied the effect of these catalyst-capture agents on (1) the syngas composition, (2) CO2 and H2S capture, and (3) the steam-coal gasification kinetic rate. The syngas composition from the gasifier was roughly 20% methane, 70% hydrogen, and 10% other species when a CaO/C molar ratio of 0.5 was added. We demonstrated significantly enhanced steam–coal gasification kinetic rates when adding small amounts of potassium hydroxide to coal when operating a CaO-CaCO3 chemical looping gasification reactor. For example, the steam–coal gasification kinetic rate increased 250% when dry mixing calcium oxide at a Ca/C molar ratio of 0.5 with a sub-bituminous coal, and the kinetic rate increased 1000% when aqueously mixing calcium oxide at a Ca/C molar ratio of 0.5 along with potassium hydroxide at a K/C molar ratio of 0.06. In addition, we conducted multi-cycle studies in which CaCO3 was calcined by heating to 900 °C to regenerate the CaO, which was then reused in repeated CaO-CaCO3 cycles. The increased steam-coal gasification kinetics rates for both CaO and CaO + KOH persisted even when the material was reused in six cycles of gasification and calcination. The ability of CaO to capture carbon dioxide decreased roughly 2-4% per CaO-CaCO3 cycle. We also discuss an important application of this combined gasifier-calciner to electricity generation and selling the purge stream as a precalcined feedstock to a cement kiln. In this scenario, the amount of purge stream required is fixed not by the degradation in the capture ability but rather by the requirements at the cement kiln on the amount of CaSO4 and ash in the precalcined feedstock.

  4. Phase selection in the containerless solidification of undercooled CaO {center_dot} 6Al{sub 2}O{sub 3} melts

    SciTech Connect

    Li Mingjun; Kuribayashi, Kazuhiko

    2004-07-12

    The CaO {center_dot} 6Al{sub 2}O{sub 3} melts were solidified on an aero-acoustic levitator under a containerless processing condition at various undercoolings. A high-speed video was operated to monitor the recalescence behavior, from which the growth velocity as a function of melt undercooling was determined. The microstructures were observed and the crystalline phases were identified using the X-ray diffraction technique, indicting that the Al{sub 2}O{sub 3} was solidified when the melt temperature was higher than the peritectic temperature, T{sub p}. When the melt was undercooled below T{sub p}, the CaO {center_dot} 6Al{sub 2}O{sub 3} (CA{sub 6}) peritectic phase was crystallized directly from the undercooled melts. With respect to the direct formation of the peritectic phase, further analysis from the viewpoints of competitive nucleation indicated that the minimum free energy principle may be applied to elucidate the nucleation of CA{sub 6} phase. In terms of the competitive growth behavior, the interface attachment kinetics for Al{sub 2}O{sub 3} and CA{sub 6} phases are calculated by using the classical BCT model indicating that although the Al{sub 2}O{sub 3} phase doped by CaO has about four times larger interface kinetic coefficient than that of the CA{sub 6} peritectic phase, the growth kinetics of Al{sub 2}O{sub 3} in the melt with the CaO {center_dot} 6Al{sub 2}O{sub 3} chemical composition is not sufficiently high to replace the CA{sub 6} phase as the primary phase. Therefore, once CA{sub 6} is nucleated, it can develop into a macro crystal as the primary phase. The competitive nucleation and growth behavior in the CA{sub 6} system is different from those in other well-studied peritectic alloys and the present investigation on the phase formation will be an essential supplement to the phase selection theory.

  5. Crystallization paths in SiO2-Al2O3-CaO system as a genotype of silicate materials

    NASA Astrophysics Data System (ADS)

    Lutsyk, V. I.; Zelenaya, A. E.

    2013-12-01

    The phases trajectories in the fields of primary crystallization of cristobalite (SiO2cr), tridymite (SiO2tr), mullite (3Al2O3-2SiO2) and in a field of liquid immiscibility are analyzed on a basis of computer model for T-x-y diagram of SiO2-Al2O3-CaO system. The concentration fields with unique set of microconstituents and the fields without individual crystallization schemes and microconstituents are revealed.

  6. Influences of CaO on Crystallization, Microstructures, and Properties of BaO-Al2O3-B2O3-SiO2 Glass-Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Bo; Tang, Bo; Xu, Mingjiang

    2015-10-01

    We have developed BaO-CaO-Al2O3-B2O3-SiO2 glass-ceramics with high thermal coefficient of expansion (TCE) to overcome thermal mismatch at board level. The crystalline phases include quartz (major), cristobalite (minor), and bazirite BaZrSi3O9 (minor). Calculations from whole-pattern fitting show that the crystallinity varies slightly within the range of 33.48% to 34.89%, while the mass fraction of the phases changes remarkably with the CaO content. This indicates that CaO cannot promote crystallization of Ba-Al-B-Si glass, but effectively suppresses the phase transformation from quartz to cristobalite, making the thermal expansion curves linear. An empirical equation for the TCE versus the temperature and the amount of CaO is established. Furthermore, the densification mechanism of Ca modifiers is revealed. Due to its higher field strength than Ba, substitution of Ca increases the glass viscosity and inhibits ion diffusion. Excessive CaO is thus harmful to the density, bending strength, and electrical properties. The sample with 10 wt.% CaO sintered at 950C exhibited high bending strength (154.1 MPa) and high TCE (12.38 ppm/C) as well as good electrical properties ( ? = 6.2, tan ? = 5 10-4, ? = 3.8 1012 ? cm).

  7. Fast microwave-assisted catalytic co-pyrolysis of corn stover and scum for bio-oil production with CaO and HZSM-5 as the catalyst.

    PubMed

    Liu, Shiyu; Xie, Qinglong; Zhang, Bo; Cheng, Yanling; Liu, Yuhuan; Chen, Paul; Ruan, Roger

    2016-03-01

    This study investigated fast microwave-assisted catalytic co-pyrolysis of corn stover and scum for bio-oil production with CaO and HZSM-5 as the catalyst. Effects of reaction temperature, CaO/HZSM-5 ratio, and corn stover/scum ratio on co-pyrolysis product fractional yields and selectivity were investigated. Results showed that co-pyrolysis temperature was selected as 550°C, which provides the maximum bio-oil and aromatic yields. Mixed CaO and HZSM-5 catalyst with the weight ratio of 1:4 increased the aromatic yield to 35.77wt.% of feedstock, which was 17% higher than that with HZSM-5 alone. Scum as the hydrogen donor, had a significant synergistic effect with corn stover to promote the production of bio-oil and aromatic hydrocarbons when the H/Ceff value exceeded 1. The maximum yield of aromatic hydrocarbons (29.3wt.%) were obtained when the optimal corn stover to scum ratio was 1:2. PMID:26773959

  8. Performance and economic assessments of a solid oxide fuel cell system with a two-step ethanol-steam-reforming process using CaO sorbent

    NASA Astrophysics Data System (ADS)

    Tippawan, Phanicha; Arpornwichanop, Amornchai

    2016-02-01

    The hydrogen production process is known to be important to a fuel cell system. In this study, a carbon-free hydrogen production process is proposed by using a two-step ethanol-steam-reforming procedure, which consists of ethanol dehydrogenation and steam reforming, as a fuel processor in the solid oxide fuel cell (SOFC) system. An addition of CaO in the reformer for CO2 capture is also considered to enhance the hydrogen production. The performance of the SOFC system is analyzed under thermally self-sufficient conditions in terms of the technical and economic aspects. The simulation results show that the two-step reforming process can be run in the operating window without carbon formation. The addition of CaO in the steam reformer, which runs at a steam-to-ethanol ratio of 5, temperature of 900 K and atmospheric pressure, minimizes the presence of CO2; 93% CO2 is removed from the steam-reforming environment. This factor causes an increase in the SOFC power density of 6.62%. Although the economic analysis shows that the proposed fuel processor provides a higher capital cost, it offers a reducing active area of the SOFC stack and the most favorable process economics in term of net cost saving.

  9. Synthesis of SiO? and CaO rich calcium silicate systems via sol-gel process: bioactivity, biocompatibility, and drug delivery tests.

    PubMed

    Catauro, M; Papale, F; Roviello, G; Ferone, C; Bollino, F; Trifuoggi, M; Aurilio, C

    2014-09-01

    Silica and calcium silicate amorphous materials, mixed with sodium ampicillin, a broad-spectrum antibiotic, have been synthesized by sol-gel method. The amorphous nature of the gels was ascertained by X-ray diffraction analysis. The bioactivity of the synthesized materials has been put into evidence by the appearance of a crystal of hydroxyapatite on the surface of the samples soaked in a fluid simulating the composition of the human blood plasma, as detected through FTIR measurements and SEM micrographs. The present work refers to a series of in-vitro biocompatibility tests, which has been performed on silicate and CaO rich calcium silicate gel-glasses, to study the cell behavior when seeded on 1 cm(2) material fragments, introduced into an in-vitro culture system. 3T3 cell lines have been used and the viability has been evaluated by WST-8 test. The composition of the adopted glasses can be expressed by the following general formula: x CaO (1?-?x) SiO2 with x?=?0.00; 0.30; 0.40; 0.50; 0.60. Subsequently, release kinetics in a simulate body fluid (SBF) has been investigated. The amount of sodium ampicillin released has been detected by UV-Vis spectroscopy. The release kinetics has appeared to occur in more than one stage. All data have shown that those materials could be used as drug delivery bioactive systems. PMID:24123774

  10. Reconnaissance study of the Taylor Mountains pluton, southwestern Alaska

    USGS Publications Warehouse

    Hudson, Travis L.; Miller, Marti L.; Klimasauskas, Edward P.; Layer, Paul W.

    2010-01-01

    The Taylor Mountains pluton is a Late Cretaceous to early Tertiary (median age 65 + or ? 2 Ma) epizonal, composite biotite granite stock located about 235 km (145 mi) northeast of Dillingham in southwestern Alaska. This 30 km2 (12 mi2) pluton has sharp and discordant contacts with hornfels that developed in Upper Cretaceous clastic sedimentary rocks of the Kuskokwim Group. The three intrusive phases in the Taylor Mountains pluton, in order of emplacement, are (1) porphyritic granite containing large K-feldspar phenocrysts in a coarse-grained groundmass, (2) porphyritic granite containing large K-feldspar and smaller, but still coarse, plagioclase, quartz, and biotite phenocrysts in a fine-grained groundmass, and (3) fine-grained, leucocratic, equigranular granite. The porphyritic granites have different emplacement histories, but similar compositions; averages are 69.43 percent SiO2, 1.62 percent CaO, 5.23 percent FeO+MgO, 3.11 percent Na2O, and 4.50 percent K2O. The fine-grained, equigranular granite is distinctly felsic compared to porphyritic granite; it averages 75.3 percent SiO2, 0.49 percent CaO, 1.52 percent FeO+MgO, 3.31 percent Na2O, and 4.87 percent K2O. Many trace elements including Ni, Cr, Sc, V, Ba, Sr, Zr, Y, Nb, La, Ce, Th, and Nd are strongly depleted in fine-grained equigranular granite. Trace elements are not highly enriched in any of the granites. Known hydrothermal alteration is limited to one tourmaline-quartz replacement zone in porphyritic granite. Mineral deposits in the Taylor Mountains area are primarily placer gold (plus wolframite, cassiterite, and cinnabar); sources for these likely include scattered veins in hornfels peripheral to the Taylor Mountain pluton. The granite magmas that formed the Taylor Mountains pluton are thought to represent melted continental crust that possibly formed in response to high heat flow in the waning stage of Late Cretaceous subduction beneath interior Alaska.

  11. Fault controlled Carboniferous A-type magmatism in the proto-Andean foreland (Sierras Pampeanas, Argentina): Geochemical constraints and petrogenesis

    NASA Astrophysics Data System (ADS)

    Dahlquist, Juan A.; Alasino, Pablo H.; Eby, G. Nelson; Galindo, Carmen; Casquet, Csar

    2010-03-01

    The intrusion of granitoids into the Eastern Sierras Pampeanas in the Early Carboniferous took place after a long period of mainly compressional deformation that included the Famatinian (Ordovician) and Achalian (Devonian) orogenies. These granitoids occur as small scattered plutons emplaced in a dominant extensional setting, within older metamorphic and igneous rocks, and many of them are arranged along a reactivated large shear zone. A set of 46 samples from different granitic rocks: Huaco granitic complex, San Blas pluton, and the La Chinchilla stock from the Sierra de Velasco, Zapata granitic complex from Sierra de Zapata, and the Los rboles pluton from Sierra de Fiambal, display high and restricted SiO 2 contents between 69.2 and 76.4 wt.%. On both FeO/(FeO + MgO) vs. SiO 2 and [(Na 2O + K 2O) - CaO] vs. SiO 2 plots the samples plot in the ferroan and alkaline-calcic to calco-alkaline fields (FeO/(FeO + MgO) = 0.88-1.0%;[(Na 2O + K 2O) - CaO] = 6.3-8.3%), thus showing an A-type granitoid signature. The high concentrations for the High Field Strength Elements (HSFE), such as Y, Nb, Ga, Ta, U, Th, etc. and flat REE patterns showing significant negative Eu anomalies are also typical features of A-type granites. Our petrogenetic model supports progressive fractional crystallization with dominant fractionation of feldspar and a source mineral assemblage enriched in plagioclase. Biotites have distinctive compositions with high FeO/MgO ratios (7.8-61.5), F (360-5610 ppm), and Cl (120-1050 ppm). The FeO/MgO ratios together with the F and Cl content of igneous biotites seem to reflect the nature of their parental host magmas and may be useful in identifying A-type granitoids. The isotopic data (Rb-Sr and Sm-Nd) confirm that the A-type granites represent variable mixtures of asthenospheric mantle and continental crust and different mixtures lead to different subtypes of A-type granite (illustrating the lack of consensus about A-type magma origin). We conclude that prominent shear zones play an important role in providing suitable conduits for ascending asthenospheric material and heat influx in the crust, a hypothesis that is in accord with other recent work on A-type granites.

  12. A study of machine learning regression methods for major elemental analysis of rocks using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Boucher, Thomas F.; Ozanne, Marie V.; Carmosino, Marco L.; Dyar, M. Darby; Mahadevan, Sridhar; Breves, Elly A.; Lepore, Kate H.; Clegg, Samuel M.

    2015-05-01

    The ChemCam instrument on the Mars Curiosity rover is generating thousands of LIBS spectra and bringing interest in this technique to public attention. The key to interpreting Mars or any other types of LIBS data are calibrations that relate laboratory standards to unknowns examined in other settings and enable predictions of chemical composition. Here, LIBS spectral data are analyzed using linear regression methods including partial least squares (PLS-1 and PLS-2), principal component regression (PCR), least absolute shrinkage and selection operator (lasso), elastic net, and linear support vector regression (SVR-Lin). These were compared against results from nonlinear regression methods including kernel principal component regression (K-PCR), polynomial kernel support vector regression (SVR-Py) and k-nearest neighbor (kNN) regression to discern the most effective models for interpreting chemical abundances from LIBS spectra of geological samples. The results were evaluated for 100 samples analyzed with 50 laser pulses at each of five locations averaged together. Wilcoxon signed-rank tests were employed to evaluate the statistical significance of differences among the nine models using their predicted residual sum of squares (PRESS) to make comparisons. For MgO, SiO2, Fe2O3, CaO, and MnO, the sparse models outperform all the others except for linear SVR, while for Na2O, K2O, TiO2, and P2O5, the sparse methods produce inferior results, likely because their emission lines in this energy range have lower transition probabilities. The strong performance of the sparse methods in this study suggests that use of dimensionality-reduction techniques as a preprocessing step may improve the performance of the linear models. Nonlinear methods tend to overfit the data and predict less accurately, while the linear methods proved to be more generalizable with better predictive performance. These results are attributed to the high dimensionality of the data (6144 channels) relative to the small number of samples studied. The best-performing models were SVR-Lin for SiO2, MgO, Fe2O3, and Na2O, lasso for Al2O3, elastic net for MnO, and PLS-1 for CaO, TiO2, and K2O. Although these differences in model performance between methods were identified, most of the models produce comparable results when p ≤ 0.05 and all techniques except kNN produced statistically-indistinguishable results. It is likely that a combination of models could be used together to yield a lower total error of prediction, depending on the requirements of the user.

  13. Characterization and origin of the Taishanmiao aluminous A-type granites: implications for Early Cretaceous lithospheric thinning at the southern margin of the North China Craton

    NASA Astrophysics Data System (ADS)

    Wang, Changming; Chen, Liang; Bagas, Leon; Lu, Yongjun; He, Xinyu; Lai, Xiangru

    2015-11-01

    Late Mesozoic magmatic rocks from the Taishanmiao Batholith were collected for LA-ICP-MS dating, Sr-Nd-Hf isotope systematics, and whole-rock major and trace element geochemistry to help understand the nature of collisional and extensional events along the southern margin of the North China Craton. The batholith consists of three texturally distinguishable phases of a 125 1 Ma medium- to coarse-grained syenogranite, a 121 1 Ma fine- to medium-grained syenogranite, and a 113 1 Ma porphyritic monzogranite. Most of the units in the batholith are syenogranitic in composition with high levels of silica (70-78 wt% SiO2), alkalis (8.0-8.6 wt% Na2O + K2O), Fe* (FeOT/(FeOT + MgO) = 0.76-0.90), and depletion in CaO (0.34-1.37 wt%), MgO (0.12-0.52 wt%), TiO2 (0.09-0.40 wt%), and A/CNK (Al2O3/(Na2O + K2O + CaO)) molar ratios of 1.00-1.11. All samples have high proportions of Ga, Nb, Zr, Ga/Al, and REE, and depletions in Ba, Sr, Eu, and compatible elements, indicating that the batholith consists of A-type granites. The zircon saturation temperature for these units yields a mean value of 890 C, and zircons with Early Cretaceous magmatic ages have ?Nd(t) values of -14.0 to -12.0, ?Hf(t) values ranging from -18.7 to -2.1, and corresponding Hf model ages of 2339-1282 Ma. These geochemical and isotopic characteristics allowed us to conclude that the primary magma for the Taishanmiao Batholith originated from partial melting of Precambrian crustal rocks in the medium-lower crust. However, the high Nb and Ta contents and low normalized Nb/Ta values for the Taishanmiao granites are due to fractionation in Nb- and Ta-rich amphibole (or biotite). It is further proposed that these aluminous A-type granites were generated in an extensional tectonic setting during the Early Cretaceous, which was induced by lithospheric thinning and asthenospheric upwelling beneath eastern China toward the Paleo-Pacific Plate.

  14. Influence of CaO and SiO2 co-doping on the magnetic, electrical properties and microstructure of a Ni-Zn ferrite

    NASA Astrophysics Data System (ADS)

    Hajalilou, A.; Hashim, M.; Ebrahimi-Kahrizsangi, R.; Sarami, N.

    2015-04-01

    Effect of CaO and SiO2 additions on the grain growth and magnetic and electrical properties of a Ni-Zn ferrite was studied. The common oxides (x = 0.4CaO + 0.8SiO2) were added in different moles (x = 0, 0.02, 0.06, 0.012, 0.24 and 0.48) to Fe2O3, Zn, and NiO. The mixed powders were mechanically alloyed for 12 h using a high energy ball mill before heating at 1200 °C for 240 min. The products were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, vibrating sample magnetometer and static hysteresisgraph, and later by an impedance analyzer with a frequency range from 1 MHz to 1.8 GHz. The XRD results indicate a formation of single phase spinel structure in all the samples. The average grain size was affected by the additive contents so that their sizes grew, up to x = 0.06, and after that their sizes reduced from 0.631 to 0.371 μ at x = 0.48. The experimental density of the samples displayed an upward trend for x < 0.06, increasing from 5.39 g cm-3 (x = 0) to 5.51 g cm-3 (x = 0.06): afterwards, their values presented a downward trend, reducing to 4.01 g cm-3 at x = 0.48. Magnetic behaviors such as saturation magnetization ({{M}s} ) and induction magnetization ({{B}s} ) degraded as well as the real permeability of the samples by increasing the x content. The loss factor i.e. hysteresis loss also remarkably decreased by accumulation of SiO2 and CaO in the grain boundaries. The electrical resistivity was determined in the order of 6.9  ×  1010 Ω cm for x = 0 and 6.4  ×  1011 Ω cm for x = 0.48. Therefore, low relative loss factor and high resistivity make these ferrites particularly useful as inductor and transformer materials for high frequency applications.

  15. Enhancement of fast CO2 capture by a nano-SiO2/CaO composite at Ca-looping conditions.

    PubMed

    Valverde, J M; Perejon, A; Perez-Maqueda, L A

    2012-06-01

    In this paper we show the performance of a new CO(2) sorbent consisting of a dry physical mixture of a Ca-based sorbent and a SiO(2) nanostructured powder. Thermo-gravimetric analysis (TGA) performed at conditions close to the Ca-looping process demonstrate that the rate of CO(2) capture by the mixture is enhanced during the fast carbonation stage of practical interest in applications. Moreover, the residual capture capacity of the mixture is increased. SEM/EDX, physisorption, and XRD analyses indicate that there is a relevant interaction between the nanostructured SiO(2) skeleton and CaO at high temperatures, which serves to improve the efficiency of the transfer of CO(2) to small reactive pores as well as the stability of the sorbent pore structure. PMID:22551622

  16. Photoinduced generation of electron anions in H-doped nanoporous oxide 12CaO7Al2O3: Toward an optically controlled formation of electrides

    NASA Astrophysics Data System (ADS)

    Sushko, Peter V.; Shluger, Alexander L.; Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

    2005-02-01

    We suggest, on the basis of detailed ab initio calculations of both ground and photoexcited states of H-doped 12CaO7Al2O3 (C12A7:H), that stable high-conductivity regions can be optically generated in this insulating system. Each H- ion in C12A7:H can, under photoirradiation at 3.8-4.5 eV, produce up to two electrons and a proton that binds to the lattice network and forms OH-. Mobile electrons play a role of anions in this system. They move over subnanosized cages of the C12A7 lattice via polaron hopping. The insulating state is reversibly restored upon heating to 300 C.

  17. Petrological and experimental phase equilibria constraints on magma storage conditions beneath Cerro Uturuncu, Bolivia

    NASA Astrophysics Data System (ADS)

    Muir, D. D.; Blundy, J. D.; Rust, A.; Brooker, R.

    2011-12-01

    Volcanic unrest manifest as surface deformation detected with InSAR recently drew attention to Cerro Uturuncu, a dormant dacitic stratovolcano in the Bolivian altiplano that last erupted 271 ka. Magma intrusion in the mid to upper crust is thought to be responsible for the deformation calculated as 1-2 cm/yr central uplift rate between 1992 and 2006. Using petrological and experimental phase equilibrium experiments designed to replicate natural mineral assemblages, phase proportions and phase compositions, we aim to constrain the pre-eruptive pressure, temperature, fO2 and fH2O storage conditions of Uturuncu magmas. Plagioclase, orthopyroxene, biotite, titaniferous magnetite, ilmenite, apatite and a rhyolitic glassy matrix are ubiquitous in all 50 thin sections of Uturuncu lava samples studied. All of the lavas are porphyritic with examples of normal and reverse zoning in plagioclase and orthopyroxene phenocrysts. Biotite commonly has dehydration reaction rims. Magmatic temperatures of ~870°C and fO2s around NNO+1.3 have been estimated from coexisting Fe-Ti oxides. A water content of 3.6 wt%, similar to those calculated in melt inclusions using the by-difference method, was estimated using plagioclase-melt equilibria and, assuming the magma was water saturated, VolatileCalc indicates a magma storage pressure of at least 91 MPa. Several previous studies have experimentally investigated phase equilibria of silicic magmatic systems including Volcan San Pedro (Chile), Mount Unzen (Japan), and Fish Canyon and Mount St. Helens (USA). Compared to these systems, Uturuncu lavas have higher SiO2 by 1.0-4.2 wt%; higher K2O by 0.5-3.3 wt%; and Na2O lower by 1.9-2.8 wt%, and are unique in crystallising biotite in the absence of hornblende. Crystallisation experiments are being performed in cold-seal hydrothermal pressure apparatuses with two synthetic starting materials that replicate the bulk dacite and rhyolite glass chemistry of a glassy lava sample with a relatively low microlite content and a total crystallinity of 36 vol%. The dacite composition is SiO2 67.0 wt%, Al2O3 15.9 wt%, K2O 4.5 wt%, FeO 4.0 wt%, CaO 3.6 wt%, Na2O 2.1 wt%, MgO 1.5 wt%; the rhyolitic composition is SiO2 75.1 wt%, Al2O3 13.4 wt%, K2O 6.7 wt%, FeO 1.1 wt%, CaO 0.8 wt%, Na2O 2.2 wt%, MgO 0.2 wt%. Experiments are being conducted at temperatures between 800-900°C and pressures between 50-300 MPa at water saturated conditions. The results will be compared to natural samples to assess storage conditions of the 890-271 ka eruptions at Uturuncu, and the storage depths inferred today from geophysical data.

  18. Factors Related to Adoption and Non-Adoption of Technical and Organizational Recommendations by Farmers Involved with Societe de Developpement du Cacao (SO.DE.CAO) in Cameroon. A Research Summary.

    ERIC Educational Resources Information Center

    Kamga, Andre; Cheek, Jimmy G.

    In order to promote cocoa production and assist cocoa farmers in overcoming diseases in this crop, the government of Cameroon created an experimental corporation called Societe de Developpement du Cacao (SO.DE.CAO) in 1974. This organization functioned much like an extension service to provide information about crop production and disease control.

  19. Factors Related to Adoption and Non-Adoption of Technical and Organizational Recommendations by Farmers Involved with Societe de Developpement du Cacao (SO.DE.CAO) in Cameroon. A Research Summary.

    ERIC Educational Resources Information Center

    Kamga, Andre; Cheek, Jimmy G.

    In order to promote cocoa production and assist cocoa farmers in overcoming diseases in this crop, the government of Cameroon created an experimental corporation called Societe de Developpement du Cacao (SO.DE.CAO) in 1974. This organization functioned much like an extension service to provide information about crop production and disease control.…

  20. Melting phase relations of K- and Na-bearing carbonatite at 3-21 GPa with implication to deep carbon cycle

    NASA Astrophysics Data System (ADS)

    Litasov, K. D.; Shatskiy, A.; Ohtani, E.

    2010-12-01

    Carbonatite melt is considered as one of the major metasomatic agents in the shallow and presumably in the deep mantle. Studies of melting relations in carbonate peridotite and eclogite often fail to determine true solidus due to low-temperature stability of poorly resolvable small fractions of alkali-bearing carbonatite melt or solid phases. The iterative sandwich method (Dasgupta and Hirschmnn, 2007) and study of starting compositions of incipient melt fractions from carbonated peridotite and eclogite can be used to resolve this problem. In this report we determined solidi and phase relations in model K- and Na-bearing carbonatite systems and discuss stability of alkali carbonates and their effect for mantle melting and carbon transport. Two starting materials of Ca-Mg carbonatite melt enriched in Na2O and K2O, respectively (2 and 7 wt% and vice versa), were examined. Minor SiO2 and FeO were also added. Experiments were conducted using multianvil technique at 3, 6, 10, 15, and 21 GPa and 750-1400oC. The solidus temperature of Na- and K-carbonatite is located near 750oC at 3 GPa and 850oC at 6 GPa. Significant increase of the solidus temperature up to 1150oC was found between 6 and 10 GPa. Then, between 10 and 21 GPa the solidi are flat. Na-carbonatite may have even a negative solidus slope from 15 to 21 GPa. An increase of solidus temperature between 6 and 10 GPa is related to dolomite decomposition, appearance of new stable K-Na-bearing carbonate, and enhanced solubility of Na2O in aragonite with pressure. In the Na-bearing system 6-10 wt% Na2O can be dissolved in aragonite, which is nearly all Na2O added to the system. Several stable alkali-bearing carbonates were observed in the both K-bearing and Na-bearing systems. They include Na2Mg2(CO3)2 at 3 GPa, (K,Na)2Ca2(CO3)2 at 6.5 GPa, (K,Na)2Mg2(CO3)3-(K,Na)2Mg(CO3)2 and (K,Na)2Ca4(CO3)5-CaCO3 solid solutions at 3-21 GPa. The K2O content in these carbonates is always dominates over Na2O even in the Na-bearing system. The (K,Na)2Ca4(CO3)5 and Na2Mg2(CO3)2 phases are new high pressure carbonates and their structure will be characterized. The others have stable low-pressure or 1 atm analogues and K2Mg(CO3)2 was identified in diamond synthesis experiments at 6-8 GPa (e.g. Taniguchi et al., 1996). Silicate phases include diopside at pressures below 15 GPa, Ca-Fe-bearing melilite-like phase at 15 GPa, and Ca-perovskite and stishovite at 21 GPa. Low-degree partial melts are Na- and K-rich for Na- and K-bearing carbonatite, respectively, due to early melting of alkali carbonatite. Magnesite is the liquidus carbonate phase along with silicate at all pressures. Accordingly, partial melts are enriched in CaO relative to MgO. Comparison of solidi for Na- and K- bearing carbonatite with subduction geotherms indicate stability of alkali carbonates along cold subduction paths. However, they would decompose at the island arc depth along hot subduction geotherms. Thus, we outlined the role of alkali carbonate in the deep mantle and can constrain true solidi of hydrogen-free carbonated peridotite and eclogite if they contain some alkalis.

  1. X-ray fluorescence analysis with micro glass beads using milligram-scale siliceous samples for archeology and geochemistry

    NASA Astrophysics Data System (ADS)

    Ichikawa, Shintaro; Nakamura, Toshihiro

    2014-06-01

    A micro glass bead technique was developed to assay precious siliceous samples for geochemical and archeological analyses. The micro-sized (approximately 3.5 mm in diameter and 0.8 mm in height) glass beads were prepared by mixing and fusing 1.1 mg of the powdered sample and 11.0 mg of the alkali lithium tetraborate flux for wavelength-dispersive X-ray fluorescence determination of major oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, and total Fe2O3). The preparation parameters, including temperature and agitation during the fusing process, were optimized for the use of a commercial platinum crucible rather than a custom-made crucible. The procedure allows preparation of minute sample amounts of siliceous samples using conventional fusing equipment. Synthetic calibration standards were prepared by compounding chemical reagents such as oxides, carbonates, and diphosphates. Calibration curves showed good linearity with r values > 0.997, and the lower limits of detection were in the 10s to 100s of μg g- 1 range (e.g., 140 μg g- 1 for Na2O, 31 μg g- 1 for Al2O3, and 8.9 μg g- 1 for MnO). Using the present method, we determined ten major oxides in igneous rocks, stream sediments, ancient potteries, and obsidian. This was applicable to siliceous samples with various compositions, because of the excellent agreement between the analytical and recommended values of six geochemical references. This minimal-scale analysis may be available for precious and limited siliceous samples (e.g., rock, sand, soil, sediment, clay, and archeological ceramics) in many fields such as archeology and geochemistry.

  2. Distribution of major and trace elements in surface sediments of the western Gulf of Thailand: Implications to modern sedimentation

    NASA Astrophysics Data System (ADS)

    Liu, Shengfa; Shi, Xuefa; Yang, Gang; Khokiattiwong, Somkiat; Kornkanitnan, Narumol

    2016-04-01

    In this study, we analyze major and trace elements (SiO2, Al2O3, Fe2O3, CaO, K2O, MgO, Na2O, TiO2, P2O5, MnO, Cu, Pb, Ba, Sr, V, Zn, Co, Ni, Cr, and Zr) and grain size of 157 surface sediment samples from the western Gulf of Thailand (GoT). On the basis of the space distribution characteristics, the study area can be classified into three geochemical provinces. Province I covers the northern and northwestern coastal zones of the GoT, including the whole upper GoT and thus the sediments from the rivers in the area. It contains high contents of SiO2. Province II is located in the middle of the GoT and has similar geochemistry composition as the South China Sea (SCS). It contains sediments that are characterized by higher contents of Na2O, TiO2, Ba, Cr, V, Zn, Zr, and Ni. Province Ш is located in the lower GoT, close to Malaysia. Major and trace elements in this area showed complex distribution patterns, which may be due to terrestrial materials from Malay rivers combining with some sediments from the SCS in this province. The results also indicate that grain size is the controlling factor in elemental contents, and that the hydrodynamic environment and mineral composition of the sediments play an important role in the distribution of these elements. The anthropogenic impact of heavy metal introduction (especially Cr, Zn, Cu, and Pb) can be seen in surface sediments from the nearshore region of Chantaburi province and north of Samui Island.

  3. Precursors predicted by artificial neural networks for mass balance calculations: Quantifying hydrothermal alteration in volcanic rocks

    NASA Astrophysics Data System (ADS)

    Trépanier, Sylvain; Mathieu, Lucie; Daigneault, Réal; Faure, Stéphane

    2016-04-01

    This study proposes an artificial neural networks-based method for predicting the unaltered (precursor) chemical compositions of hydrothermally altered volcanic rock. The method aims at predicting precursor's major components contents (SiO2, FeOT, MgO, CaO, Na2O, and K2O). The prediction is based on ratios of elements generally immobile during alteration processes; i.e. Zr, TiO2, Al2O3, Y, Nb, Th, and Cr, which are provided as inputs to the neural networks. Multi-layer perceptron neural networks were trained on a large dataset of least-altered volcanic rock samples that document a wide range of volcanic rock types, tectonic settings and ages. The precursors thus predicted are then used to perform mass balance calculations. Various statistics were calculated to validate the predictions of precursors' major components, which indicate that, overall, the predictions are precise and accurate. For example, rank-based correlation coefficients were calculated to compare predicted and analysed values from a least-altered test dataset that had not been used to train the networks. Coefficients over 0.87 were obtained for all components, except for Na2O (0.77), indicating that predictions for alkali might be less performant. Also, predictions are performant for most volcanic rock compositions, except for ultra-K rocks. The proposed method provides an easy and rapid solution to the often difficult task of determining appropriate volcanic precursor compositions to rocks modified by hydrothermal alteration. It is intended for large volcanic rock databases and is most useful, for example, to mineral exploration performed in complex or poorly known volcanic settings. The method is implemented as a simple C++ console program.

  4. Conductivity thresholds and glass structure in (K2O)x(GeO2)1-x glasses

    NASA Astrophysics Data System (ADS)

    Wang, Ninghua; Novita, Deassy; Boolchand, Punit

    2007-03-01

    There are reports of conductivity thresholds with glass composition in solid electrolyte glasses. In the titled glass system, a seven order of magnitude increase in conductivity occurs at x > 0.10. The origin of the observation remains an open question. In titled glasses, we show that glass structure probed by the elastic behavior of its backbone shows two thresholds, a stress transition near x = 0.04 and a rigidity transition near x = 0.09. These elastic thresholds emerge from the reversibility window observed in calorimetric measurements, and in Raman scattering experiments that show scattering strength of the 520 cm-1 mode of 3-member rings to show a global maximum in the reversibility window. The pronounced increase of conductivity apparently occurs when backbones become flexible at x > 0.09, permitting K^+ ions to freely diffuse. The correlation between the electrical, thermal and optical properties of the present solid electrolyte glasses may well be a generic feature of these materials. Jain et al JNCS 222, 361 (1997). S. Chakravarty et al. J.C.M.P 17,L1-7 (2005).

  5. Diffusion in the system K2O-SrO-SiO2. II - Cation self-diffusion coefficients.

    NASA Technical Reports Server (NTRS)

    Varshneya, A. K.; Cooper, A. R.

    1972-01-01

    The self-diffusion coefficients were measured by introducing a slab of glass previously irradiated in a reactor between two slabs of unirradiated glass. By heating the specimens, etching them sequentially and determining the radioactivity, self-diffusion coefficients for K and Sr were measured. It is pointed out that the results obtained in the investigations appear to support the proposal that the network of the base glass predominantly controls the activation energy for the diffusion of ions.

  6. Petrology, geochemistry and Sr-isotope characteristics of lavas from the area of Commenda (Mts. Vulsini, Italy)

    NASA Astrophysics Data System (ADS)

    Civetta, L.; Del Carmine, P.; Manetti, P.; Peccerillo, A.; Poli, G.

    1984-09-01

    Major, trace element and Sr-isotope compositions are reported for a suite of lavas coming from the area of Commenda in the SE Vulsinian district. The analyzed samples have all low silica contents and variable but generally high CaO, MgO and FeOt. Based on K2O% and K2O/Na2O ratio, the rocks from Commenda can be classified as belonging to the Potassic Series (KS) and the High-potassium Series (HKS). The HKS rocks appear to have derived by cristal/liquid fractionation from the most mafic types with separation of olivine and clinopyroxene and then of clinopyroxene + leucite. The most primitive HKS rocks have aphyric texture and high Mg-values, Cr and Ni contents which are close or within the range of values of magmas formed by partial melting of periodititic mantle sources. The KS rocks have lower incompatible element contents as the HKS rocks with similar degree of evolution. The variations of Sr-isotopic ratios of the analyzed rocks and of other Vulsinian lavas, indicate that the basic HKS Vulsinian rocks did not interact significantly with the continental crust. Instead, the KS appears to have evolved by combined crystal fractionation and assimilation processes, starting from parental magmas which had87Sr/86Sr ratio not significantly lower than that found in the less evolved rocks of the suite. The most primitive HKS rocks from Commenda have hygromagmatophile element distribution pattern characterized by high ratio of LILE/HFSE with negative anomalies of Ta and Ti, resembling closely those of other Roman mafic volcanics. The primitive geochemical characteristics of the Commenda rocks exclude that these features are the products of interaction with the crust and provide a further support to the hypothesis of a genesis within a subduction-modified mantle source.

  7. A Structurally Based Viscosity Model for Oxide Melts

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Chou, Kuo-Chih; Mills, Ken

    2014-04-01

    A structurally based viscosity model is proposed to represent the viscosity of oxide melts as functions of both temperature and composition; The oxide melts cover the following constituents: Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, FeO, MnO, Al2O3, SiO2, CaF2, TiO2, Fe2O3, and P2O5. The model describes the slag structure in terms of the various forms of oxygen ions which are classified according to the metal cations they bond with. Approximate methods for calculating the concentrations of these oxygen ions are proposed and are then used to describe the effect of melt structure on viscosity. The model provides a good description of the variations in viscosity with composition and temperature. The measured viscosities were compared with values calculated with the model, and the current model was found to provide reliable estimates of viscosities of slags used in various industrial processes ( e.g., blast furnace, basic oxygen steelmaking, ladle refining, continuous casting of steel, coal gasification, and electroslag remelting).

  8. Straczekite, a new calcium barium potassium vanadate mineral from Wilson Springs, Arkansas.

    USGS Publications Warehouse

    Evans, H.T., Jr.; Nord, G.; Marinenko, J.; Milton, C.

    1984-01-01

    Straczekite occurs as a rare secondary mineral in fibrous seams, along with other V minerals (A.M. 64-713), in ore from the vanadium mine in Wilson Springs (formerly Potash Sulfur Springs), Garland County, Arkansas. It forms soft, thin laths of dark greenish black crystals up to 0.5 mm in length. Indexed XRD data are tabulated; strongest lines 3.486(100), 10.449(50), 1.8306(50), 1.9437(15) A; a 11.679, b 3.6608, c 10.636 A, beta 100.53o; space group C2/m, C2 or Cm. Chemical analysis gave V2O5 66.4, V2O4 15.3, Fe2O3 0.9, Na2O 0.4, K2O 1.8, CaO 2.5, BaO 5.5, H2O 7.2, = 100.0, leading to the formula (Ca0.39Ba0.31K0.33Na0.11)- 196(V4+1.59V5+6.31Fe3+0.10)O20.02(H2O)2.9; Dcalc. 3.21 g/cm3. A possible layer structure is discussed. The name is for J. A. Straczek, Chief Geologist at Union Carbide Corp.-R.A.H.

  9. High-silica glass inclusions in olivine of Luna-24 samples

    NASA Technical Reports Server (NTRS)

    Roedder, E.; Weiblen, P. W.

    1977-01-01

    Optical examination of nine polished grain mounts of Luna-24 drill-core material (0.09-0.50 mm size) revealed melt inclusions in olivine crystals. Two inclusions consist of clear glass with exceptionally high Si, yet contain no visible daughter minerals and have had no reaction effects with the olivine walls. Their compositions (one has SiO2 93.8, Al2O3 1.51, FeO 2.32, MgO 1.61, CaO 0.06, Na2O less than 0.05, K2O 0.11, total 99.41%; the other is similar) are unique and quite unlike the high-Si high-K melt of granitic composition that is found as inclusions in late-stage minerals of these (and the Apollo) samples, from silicate liquid immiscibility. The host olivines are Fo73 and Fo51. The origin of the melt in the inclusions and the lack of reaction effects are perplexing unsolved problems.

  10. Environmental changes in the western Amaznia: morphological framework, geochemistry, palynology and radiocarbon dating data.

    PubMed

    Horbe, Adriana M C; Behling, Hermann; Nogueira, Afonso C R; Mapes, Russell

    2011-09-01

    The sediments from the Coari lake, a "terra firme" lake sculpted into Plio-Pleistocene deposits, and the Acar lake, a flooding-type lake developed on Quaternary sediments in the floodplain of the mid-Solimes river, in the western Amaznia, Brazil, were studied to investigate the environmental condition of their developing. This study includes mineral composition, geochemistry, Pb isotope, palinology, radiocarbon-age and morphological framework of the lakes obtained from SRTM satellite images. The geological and the environmental conditions in the two lakes are highly variable and suggest that their evolution reflect autogenic processes under humid rainforest condition. Although kaolinite, quartz, muscovite, illite, and smectite are the main minerals in both lakes, the geochemistry indicates distinct source, the Acar lake sediments have higher concentrations of Al(2)O(3), Fe(2)O(3), FeO, CaO, K(2)O, MgO, Na(2)O, P(2)O(5), Ba, V, Cu, Ni, Zn, Pb, Sr, Li, Y and La and have more radiogenic Pb than the Coari lake sediments. The radiocarbon ages suggest that at 10160 yr BP the Coari lake started to be developed due to avulsion of the Solimes river, and the Acar lake was formed by the meander abandonment of Solimes river retaining its grass dominated shore at ca. 3710 yr BP. PMID:21830005

  11. Barred olivine chondrules in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Weisberg, Michael K.

    1987-01-01

    The characteristics of 125 barred olivine chondrules identified in polished thin sections of 26 H-L-LL3-6 chondrites were studied, using an electron microprobe for determining mineral abundances and a broad-beam electron microprobe for determining bulk compositions. Compared with all chondrule types in the H-L-LL3 ordinary chondrites, the barred olivine chondrules were found to be enriched in FeO, Al2O3, Na2O, and K2O and depleted in SiO2 and MgO; they were also found to be enriched in the feldspathic component. It is concluded that the precursor components of barred olivine chondrules consisted of a mixture of an olivine-rich component, a refractory-rich component containing Al2O3, TiO2, and CaO, and a volatile-rich alkalic component. This unusual combination implies high temperatures of melting for the refractory component and low temperatures for the volatile component, supporting the hypothesis of Grossman and Wasson (1983) that the alkalies condensed on the alumina already available.

  12. Refinement of major- and minor-element PIXE analysis of rocks and minerals

    NASA Astrophysics Data System (ADS)

    Heirwegh, Christopher M.; Campbell, John L.; Czamanske, Gerald K.

    2016-01-01

    An attempt has been made to assess the accuracy of the particle-induced X-ray emission (PIXE) fundamental parameters with standards approach to quantifying major- and minor-element constituents of silicate glasses and minerals. A deviation from linearity at low energies in the channel-energy calibration relationship was identified as a source of undesired residues in GUPIX-fitting. A correction for this effect was developed using a general-purpose spectrum fitting program and was incorporated in GUPIX. The PIXE spectra of sixteen well-characterized electron microprobe standards were then processed. Complementary electron probe micro-analysis (EPMA) measurements were used to support the comparison of the PIXE results with previous characterizations. Major element concentrations were found to differ on average from literature values as follows: SiO2 (-0.28 ± 0.12%), Al2O3 (0.72 ± 0.74%), MgO (0.11 ± 0.63%), Na2O (-2.6 ± 1.2%), K2O (1.1 ± 0.7%), CaO (-0.35 ± 0.37%), TiO2 (2.5 ± 1.9%), MnO (0.8 ± 4.7%), FeO (0.98 ± 0.93%). These results indicate that major and minor elemental analysis can be achieved with high accuracy using the present Guelph micro-PIXE setup.

  13. The lunar regolith - Chemistry, mineralogy, and petrology

    NASA Technical Reports Server (NTRS)

    Papike, J. J.; Simon, S. B.; Laul, J. C.

    1982-01-01

    The data base on the lunar regolith is surveyed to form a synthesis of the lunar regolith chemistry, mineralogy, and petrology. The data were derived from samples collected by the Apollo missions 11-17 and the Luna 16, 20, and 24 probes. The missions were sent to sample formations and areas which typified the common observed features of the lunar surface. Drive tubes were used to extract samples from beneath the surface in order to study the relationship between the regolith and the bedrock, as well as to identify the processes that formed the regolith, which is regarded as the prime source of raw materials for early lunar industrial activities. Regolith origins are now understood to be destructive processes of comminution and constructional processes of agglutinate formation. Mixing occurs on the local scale, although lateral transport is inefficient on the moon. The usual contents of the fraction of regolith less than 10 microns in diameter are Al2O3, CaO, Na2O, K2O, light REE, and Th.

  14. Mass transfer and REE mobility during fenitization at Aln, Sweden

    NASA Astrophysics Data System (ADS)

    Morogan, Viorica

    1989-09-01

    The Precambrian migmatitic gneisses at Aln have been altered to fenite by fluids emanating from alkaline and carbonatitic magmas intruded during early to middle Cambrian times. Fenitization, related to carbonatitic sources, was promoted by peralkaline, carbonate-rich fluids, in which the main chemical components and REE were mobile. Composition-volume relationships of progressively fenitized protolith suggest mainly isovolumetric equilibration, but a modest decrease of volume (6%) did occur in the highest grade of the process. The fenitizing fluids introduced essentially CaO, CO2, Na2O, and K2O while removing SiO2 and Al2O3. Different trends of fenitization, defined as sodic, potassic and intermediate, show differing REE distribution and abundance patterns. The sodic carbonate-rich fluid introduced all the REE, but the La/Lu ratio was high. The extreme REE enrichments of high-grade fenites are associated with the widespread formation of calcite, apatite and possibly titanite. The potassic carbonaterich fluid introduced essentially light REE, but produced also the redistribution of heavy REE in the high-grade fenites. REE distribution patterns of intermediate fenites suggest the re-equilibration of fenite with a highly oxidizing alkaline fluorine-rich fluid, possibly in a later post-magmatic episode.

  15. Mineralogical and chemical compositions of the paleosols of different ages buried under kurgans in the southern Ergeni region and their paleoclimatic interpretation

    NASA Astrophysics Data System (ADS)

    Tatyanchenko, T. V.; Alekseeva, T. V.; Kalinin, P. I.

    2013-04-01

    The chemical and mineralogical compositions and the contents and properties of the organic matter were studied in the paleosols of different ages buried under the kurgan group "Kalmykia" in the southern part of the Ergeni Upland. The investigated sequence of soils included profiles developed on the given territory about 5100, 4410, 4260, 4120, 3960, and 600 yrs ago. The background light chestnut soil was also examined. The results of our study showed that the earlier established climate changes in this area during the second half of the Holocene are reflected in the chemical and mineralogical compositions of the soils. These characteristics can be used as indicators of the paleoclimatic conditions together with some petrophysical characteristics, such as the magnetic susceptibility of the soil samples. The study of the mineralogical composition of the clay fraction of the paleosols attests to the transformation of the smectitic phase, accumulation of illites, and destruction of chlorites manifested at different degrees. It is argued that the geochemical indicesCIA, Al2O3/(CaO + MgO + K2O + Na2O), Rb/Sr, and Ba/Srare sensitive to climate changes and reflect the transformation of the mineral soil mass and the soil genesis.

  16. Synergetic and inhibition effects in carbon dioxide gasification of blends of coals and biomass fuels of Indian origin.

    PubMed

    Satyam Naidu, V; Aghalayam, P; Jayanti, S

    2016-06-01

    The present study investigates the enhancement of CO2 gasification reactivity of coals due to the presence of catalytic elements in biomass such as K2O, CaO, Na2O and MgO. Co-gasification of three Indian coal chars with two biomass chars has been studied using isothermal thermogravimetric analysis (TGA) in CO2 environment at 900, 1000 and 1100°C. The conversion profiles have been used to establish synergetic or inhibitory effect on coal char reactivity by the presence of catalytic elements in biomass char by comparing the 90% conversion time with and without biomass. It is concluded that both biomasses exhibit synergistic behavior when blended with the three coals with casuarina being more synergetic than empty fruit bunch. Some inhibitory effect has been noted for the high ash coal at the highest temperature with higher 90% conversion time for the blend over pure coal, presumably due to diffusional control of the conversion rate. PMID:26967339

  17. The Oro Grande, New Mexico, chondrite and its lithic inclusion.

    NASA Technical Reports Server (NTRS)

    Fodor, R. V.; Keil, K.; Jarosewich, E.

    1972-01-01

    The Oro Grande, New Mexico, U.S.A., chondrite was found in 1971. Electron microprobe analyses and microscopic examination show the following mineralogy: olivine (Fa 19.3 mole %), orthopyroxene (Fs 16.2 mole %), diopside, feldspar (An 13.6 mole %), chlorapatite, whitlockite, kamacite, taenite, troilite, chromite, and an iron-bearing terrestrial weathering product. A bulk chemical analysis of the meteorite shows the following results (weight %): Fe 0.84, Ni 1.46, Co 0.07, FeS 3.62, SiO2 34.18, TiO2 0.14, Al2O3 1.83, Cr2O3 0.55, Fe2O3 21.25, FeO 9.13, MnO 0.31, MgO 21.52, CaO 1.72, Na2O 0.70, K2O 0.08, P2O5 0.25, H2O(+) 2.14, H2O(-) 0.40, C 0.22, sum 100.41. On the basis of composition and texture the Oro Grande meteorite is classified as an H5 chondrite.

  18. Vanadium chlorite from a sandstone-hosted vanadium-uranium deposit, Henry basin, Utah.

    USGS Publications Warehouse

    Whitney, G.; Northrop, H.R.

    1986-01-01

    This ore deposit formed by reduction and precipitation of U and V in the presence of organic matter at the interface between a stagnant brine and overlying circulating meteoric water. Some samples of the vanadium chlorite (heated before analysis) contain = or >10% V2O5; in fresh samples most of the V is in the V3+ state. XRD data suggest that Fe and V are concentrated preferentially in the interlayer hydroxide sheets of the chlorite. A d060 value of 1.52 A indicates that the chlorite probably has a dioctahedral structure distended by the presence of octahedral Fe and V; it is a IIb polytype. The V ore zone is flanked by peripheral zones with perfectly ordered chlorite/smectite containing much less V than the pure chlorite. Chemical analysis of a sample heated to 900oC before analysis gave SiO2 44.89, Al2O3 25.14, TiO2 0.35, Fe2O3 8.29, MgO 8.47, CaO 0.84, Na2O 0.27, K2O 2.18, Li2O 0.16, UO3 0.92, V2O5 9.14, = 100.65, together with Cr 10, Mn 200, Co 150, Ni 5.8, Cu 10, Zn 140 ppm; XRD, DTG, TG and IR curves are presented. -R.A.H.

  19. Petrogenesis of selected A-type granitic intrusions from Central Eastern Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Hassan, Tharwat; Asran, Asran; Amron, Taha; Hauzenberger, Christoph

    2014-05-01

    The Pan-African orogeny in the Arabian-Nubian Shield was terminated by intrusion of A-type granites (~ 595 Ma; Greenberg, 1981) and its volcanic equivalents. Subsequent to the intrusions of these granitic bodies the shield was exhumed. Eroded A-type granite pebbles were found in the molasse sediments that were deposited in intermountain basins. Therefore the A-type granites provide information about the last stage of the Pan-African geochemical system. Preliminary whole-rock geochemical data of three granitic intrusions (Kadabora, Um Naggat and El shiekh Salem) from the Central Eastern Desert of Egypt; indicate that all of them are peraluminous and with A-type characteristics. These intrusions show low CaO content (average 0.43 %wt), high FeOT/MgO ratio (10.46-121.88), high Na2O+K2O (average 8.04 %wt), marked enrichment of high field strength elements (Y, Nb and Ga except Zr), depletion in MgO (0.01-0.11 %wt) and with low concentration of Sr and Ba. The studied granitoids were emplaced in within plate tectonic regime. References: Greenberg, J.K. (1981): Characteristic and origin of Egyptian younger granites. Bull. Geol. Soc. Am. Part 1, v.92: 224-232.

  20. Heavy metal contamination of the Sacca di Goro lagoon area (Po River Delta, Northern Italy)

    NASA Astrophysics Data System (ADS)

    Rapti-Caputo, Dimitra

    2010-05-01

    The lagoon area of the Sacca di Goro, within the Po River delta, is ca. 20 km2 wide, with a mean depth of 1.5 m and a mean salinity of 29%o. It holds a major naturalistic interest as well as an economic one due to the aquaculture activities (mussels and clams). In this lagoon system, the quality of the sea-bottom sediments is crucial not only for the cultivated species, but also for the potential bio-accumulation problems in heavy metals. The definition of the qualitative status of the lagoon sediments is crucial for adopting the best management strategies and the protection of the environmental conditions. We determined the concentration in SiO2, TiO2, Al2O3, Fe2O3, MgO, MnO, CaO, Na2O, K2O, P2O5, Ba, Ce, Co, Cr, La, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn, Cu, Ga, Nd, S and Sr, of 31 samples homogeneously collected over the lagoon area. This large dataset allowed i) to define the environmental quality of the sediments, ii) to recognise the areas with the higher contamination risk; and iii) to emphasise the local occurrence of polluting phenomena associated to chromium, nickel, vanadium, cobalt, lead, zinc and copper.

  1. In vitro cell response to Co-containing 1,393 bioactive glass.

    PubMed

    Hoppe, Alexander; Brandl, Andreas; Bleiziffer, Oliver; Arkudas, Andreas; Horch, Raymund E; Jokic, Bojan; Janackovic, Djordje; Boccaccini, Aldo R

    2015-12-01

    Cobalt ions are known to stimulate angiogenesis via inducing hypoxic conditions and hence are interesting agents to be used in conjunction with bioactive glasses (BGs) in bone tissue engineering approaches. In this work we investigated in vitro cell biocompatibility of Co releasing 1393 BG composition (in wt.%: 53SiO2, 6Na2O, 12K2O, 5MgO, 20CaO, and 4P2O5) derived scaffolds with osteoblast-like cells (MG-63) and human dermal microvascular endothelial cells (hDMECs). Cell viability, cell number and cell morphology of osteoblast-like cells in contact with particulate glass and 3D scaffolds were assessed showing good biocompatibility of 1393 reference material and with 1 wt.% CoO addition whereby 5 wt.% of CoO in the glass showed cytotoxicity. Furthermore for 1393 with 1 wt.% of CoO increased mitochondrial activity was measured. Similar observations were made with hDMECs: while 1393 and 1393 with 1 wt.% CoO were biocompatible and the endothelial phenotype was retained, 5 wt.% CoO containing BG showed cytotoxic effects after 1 week of cell culture. In conclusion, 1 wt.% Co containing BG was biocompatible with osteoblast like cells and endothelial cells and showed slightly stimulating effects on osteoblast-like cells whereas the addition of 5 wt.% CoO seems to exceed the vital therapeutic ranges of Co ions being released in physiological fluids. PMID:26354250

  2. Calculation of Oxygen Fugacity in High Pressure Metal-Silicate Experiments and Comparison to Standard Approaches

    NASA Technical Reports Server (NTRS)

    Righter, K.; Ghiorso, M.

    2009-01-01

    Calculation of oxygen fugacity in high pressure and temperature experiments in metal-silicate systems is usually approximated by the ratio of Fe in the metal and FeO in the silicate melt: (Delta)IW=2*log(X(sub Fe)/X(sub FeO)), where IW is the iron-wustite reference oxygen buffer. Although this is a quick and easy calculation to make, it has been applied to a huge variety of metallic (Fe- Ni-S-C-O-Si systems) and silicate liquids (SiO2, Al2O3, TiO2, FeO, MgO, CaO, Na2O, K2O systems). This approach has surely led to values that have little meaning, yet are applied with great confidence, for example, to a terrestrial mantle at "IW-2". Although fO2 can be circumvented in some cases by consideration of Fe-M distribution coefficient, these do not eliminate the effects of alloy or silicate liquid compositional variation, or the specific chemical effects of S in the silicate liquid, for example. In order to address the issue of what the actual value of fO2 is in any given experiment, we have calculated fO2 from the equilibria 2Fe (metal) + SiO2 (liq) + O2 = Fe2SiO4 (liq).

  3. A network pharmacology approach to discover active compounds and action mechanisms of San-Cao Granule for treatment of liver fibrosis

    PubMed Central

    Wei, Shizhang; Niu, Ming; Wang, Jian; Wang, Jiabo; Su, Haibin; Luo, Shengqiang; Zhang, Xiaomei; Guo, Yanlei; Liu, Liping; Liu, Fengqun; Zhao, Qingguo; Chen, Hongge; Xiao, Xiaohe; Zhao, Pan; Zhao, Yanling

    2016-01-01

    Ethnopharmacological relevance San-Cao Granule (SCG) has been used in patients with liver fibrosis for many years and has shown good effect. However, its mechanism of therapeutic action is not clear because of its complex chemical system. The purpose of our study is to establish a comprehensive and systemic method that can predict the mechanism of action of SCG in antihepatic fibrosis. Materials and methods In this study, a “compound–target–disease” network was constructed by combining the SCG-specific and liver fibrosis–specific target proteins with protein–protein interactions, and network pharmacology was used to screen out the underlying targets and mechanisms of SCG for treatment of liver fibrosis. Then, some key molecules of the enriched pathway were chosen to verify the effects of SCG on liver fibrosis induced by thioacetamide (TAA). Results This systematic approach had successfully revealed that 16 targets related to 11 SCG compounds were closely associated with liver fibrosis therapy. The pathway-enrichment analysis of them showed that the TGF-β1/Smad signaling pathway is relatively important. Animal experiments also proved that SCG could significantly ameliorate liver fibrosis by inhibiting the TGF-β1/Smad pathway. Conclusion SCG could alleviate liver fibrosis through the molecular mechanisms predicted by network pharmacology. Furthermore, network pharmacology could provide deep insight into the pharmacological mechanisms of Chinese herbal formulas. PMID:26929602

  4. Biomass gasification with steam in fluidized bed: Effectiveness of CaO, MgO, and CaO-MgO for hot raw gas cleaning

    SciTech Connect

    Delgado, J.; Aznar, M.P.; Corella, J.

    1997-05-01

    The upgrading of the raw hot gas from a bubbling fluidized bed biomass gasifier is studied using cheap calcined minerals or rocks downstream from the gasifier. Biomass gasification is made with steam (not air) at 750--780 C and about 0.5--1.0 kg of biomass/h. Calcined solids used are dolomite (MgO-CaO), pure calcite (CaO), and pure magnesite (MgO). Variables studied have been temperature of the secondary bed (780--910 C), time of contact or space-time of the gas (0.08--0.32 kg{center_dot}h/m{sup 3}n), and particle diameter (1--4 mm) and type of mineral. Their effects on tar conversion, tar amount in the exit gas, product distribution, and gas composition are presented. Using a macrokinetic model for the tar disappearance network, the activities of the stones are expressed by their apparent kinetic constant. Apparent energies of activation for tar elimination (42--47 kJ/mol) and preexponential and effectiveness factors are given for all tested solids of which the most active is the calcined dolomite.

  5. Preparation, structure and bioactivity of xAu 2O 3(100 - x)[P 2O 5CaO] glass system

    NASA Astrophysics Data System (ADS)

    Regos, Adriana N.; Ardelean, I.

    2011-12-01

    Gold doped calcium phosphate glasses were prepared by the melting method. The structure of Au 2O 3-P 2O 5-CaO glasses is investigated using X-ray diffraction, infrared absorption and Raman scattering. The depth characterization of their structures is essential for the understanding of the properties of biocompatible materials. Thermal analysis DTA and TGA were also made to study behavior under different temperature regions and to see chemical changes versus time and temperature of these glasses. Bioactivity of the glasses was investigated in vitro by examining apatite formation on the surface of glasses treated in acellular simulated body fluid (SBF) with ion concentrations nearly equal to those in human blood plasma. Formation of bioactive apatite layer on the samples treated in SBF for 28 days at 37 C was confirmed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The effect of SBF soaking induces structural changes on the surface, reflected by the appearance of nano-crystalline particles agglomerated into micro-aggregates.

  6. Probing the electronic properties and charge state of gold nanoparticles on ultrathin MgO versus thick doped CaO films

    NASA Astrophysics Data System (ADS)

    Cui, Yi; Stiehler, Christian; Nilius, Niklas; Freund, Hans-Joachim

    2015-08-01

    Electron transfer into metal nanoparticles on oxide supports is associated with unusual morphological, electronic, and chemical properties of the charged system. Two fundamental charging routes have been identified so far, which are electron tunneling through ultrathin oxide films supported by a bulk metal and charge donation from single-ion impurities embedded in the oxide matrix. In this study, we have investigated whether both routes lead to the formation of metal deposits with identical properties. For this purpose, Au islands have been prepared on 1 -2 ML thin MgO /Ag (001 ) layers and on 25-ML-thick CaO films doped with Mo impurities. The morphological and electronic properties of the islands were analyzed with low-temperature scanning tunneling microscopy (STM) and spectroscopy. In both systems, pronounced electron confinement effects are observed in the nanostructures, arising from the quantization of one and the same Au electronic band. Moreover, clear experimental signatures for a charge transfer into the islands are found, such as a layer-by-layer growth of the ad-metal and a negative contrast of the oxide region around the deposits in STM images. Our data provide evidence that the charged nanostructures exhibit comparable properties independent of the origin of the extra electrons. This agreement suggests that ultrathin oxide films may be used as model systems for doped bulk oxides, as used in heterogeneous catalysis.

  7. Synthesis and characterization of phosphates in molten systems Cs 2O-P 2O 5-CaO- MIII2O 3 ( MIII—Al, Fe, Cr)

    NASA Astrophysics Data System (ADS)

    Zatovsky, Igor V.; Strutynska, Nataliya Yu.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.; Ogorodnyk, Ivan V.; Shishkin, Oleg V.

    2011-03-01

    The crystallization of complex phosphates from the melts of Cs 2O-P 2O 5-CaO- MIII2O 3 ( MIII—Al, Fe, Cr) systems have been investigated at fixed value Cs/P molar ratios equal to 0.7, 1.0 and 1.3 and Са/Р=0.2 and Ca/ МIII=1. The fields of crystallization of CsCaP 3O 9, β-Ca 2P 2O 7, Cs 2CaP 2O 7, Cs 3CaFe(P 2O 7) 2, Ca 9MIII(PO 4) 7 ( MIII—Fe, Cr), Cs 0.63Ca 9.63Fe 0.37(PO 4) 7 and CsCa 10(PO 4) 7 were determined. Obtained phosphates were investigated using powder X-ray diffraction and FTIR spectroscopy. Novel whitlockite-related phases CsCa 10(PO 4) 7 and Cs 0.63Ca 9.63Fe 0.37(PO 4) 7 have been characterized by single crystal X-ray diffraction: space group R3c, a=10.5536(5) and 10.5221(4) Å, с=37.2283(19) and 37.2405(17) Å, respectively.

  8. Comparison of CaO's effect on the fate of heavy metals during thermal treatment of two typical types of MSWI fly ashes in China.

    PubMed

    Hu, Hong-Yun; Liu, Huan; Shen, Wen-Qing; Luo, Guang-Qian; Li, Ai-Jun; Lu, Zhao-Ling; Yao, Hong

    2013-10-01

    Both grate and fluidized bed incinerators are widely used for MSW incineration in China. CaO addition for removing hazardous emissions from MSWI flue gas changes the characteristics of fly ash and affects the thermal behavior of heavy metals when the ash is reheated. In the present work, two types of MSWI fly ashes, sampled from both grate and fluidized bed incinerators respectively, were thermal treated at 1023-1323 K and the fate of heavy metals was observed. The results show that both of the fly ashes were rich in Ca and Ca-compounds were the main alkaline matter which strongly affected the leaching behavior of heavy metals. Ca was mostly in the forms of Ca(OH)2 and CaCO3 in the fly ash from grate incinerator in which nascent fly ash particles were covered by Ca-compounds. In contrast, the content of Ca was lower in the fly ash from fluidized bed incinerator and Ca was mostly in the form of CaSO4. Chemical reactions among Ca-compounds caused particle agglomeration in thermal treated fly ash from grate incinerator, restraining the heavy metals volatilization. In thermal treated fly ash from fluidized bed incinerator, Ca was converted into aluminosilicates especially at 1323 K which enhanced heavy metals immobilization, decreasing their volatile fractions as well as leaching concentrations. Particle agglomeration hardly affected the leaching behavior of heavy metals. However, it suppressed the leachable-CaCrO4 formation and lowered Cr leaching concentration. PMID:23800595

  9. [Study on carving workers of Chong xiu zheng he jing shi zheng lei bei yong ben cao (Revised Prepared Materia Medica Classified under Syndromes in Zhenghe Period) published by Huiming Xuan (Huiming Sanctum)].

    PubMed

    Liang, Fei; Li, Jian; Zhang, Wei; Zhang, Rui-Xian

    2012-11-01

    The ancient carving workers have made a great contribution to the xylographic printing art in ancient China, so the studies on them are significant for a survey of ancient Chinese printing history, and for the identification of ancient Chinese books edition. Zheng lei ben cao published by Huiming Xuan (Huiming Sanctum) in the Jin and Yuan dynasties, which is the earliest extant edition of Zhenghe version system of Zheng lei ben cao and has important literature value. Thirty carving workers were involved in its printing process. On the whole, these workers had a relatively high technique and completed a remarkably fine work. In addition to lettering, 28 persons of them also made a total of 536 pages with 900 exquisite engraving illustrations on Chinese materia medica included in this book. Because of the high levels on carving, this precious book has been the representative of Pingshui edition, which has a great reputation but has very few works now. PMID:23363847

  10. Elevation of liquidus temperature in a gel-derived Na2O-SiO2 glass

    NASA Technical Reports Server (NTRS)

    Weinberg, M. C.; Neilson, G. F.

    1983-01-01

    The liquidus temperatures of a 19 wt% soda-silica glass prepared by gel and conventional techniques were determined. X-ray diffraction measurements of the glasses which were heat-treated at several temperatures were used to experimentally determine the liquidus temperatures. It was found that the gel-derived glass has an elevated liquidus. This result is discussed in relation to the previous discovery that the immiscibility temperature of this gel-derived glass is elevated

  11. The Influence of Melt Composition and Dissolved Water on the Melt-Vapor Surface Tension of Dacite and Rhyolite Magma

    NASA Astrophysics Data System (ADS)

    Mangan, M.; Sisson, T.

    2004-12-01

    Melt-vapor surface tension (? ) is a poorly known quantity, yet it plays a critical role in many volcanic processes. In this study, we provide new data for ? of hydrous natural dacite and rhyolite melt at 200 MPa, 800-1055 C, and 4.8-7.7 wt% H2O using results from high temperature and pressure decompression experiments (this study; Mangan and Sisson, 2000; Mourtada-Bonnefoi and Laporte, 2002; 2004) and classical nucleation theory. The solutions give values for ? that vary inversely with dissolved H2O by 0.025 ( 0.009) J/m2 per wt% H2O. Combining our results with data from hydrous haplogranite and rhyodacite (Epel'baum et al., 1973; Bagdassarov et al., 2000) reveals that melt-vapor surface tension also varies inversely with the concentration of mafic melt components (e.g., CaO, FeOtotal, MgO). At constant H2O content, ? increases by 0.70 ( 0.53) J/m2 per tenth increment increase in the melt felsic index (FI = Na2O+K2O/Na2O+K2O+CaO) from FI 0.75 (dacite) to FI 1.0 (haplogranite). To understand these results, we consider the thermodynamic definition of ? , i.e., the work per unit surface area to create an interface between two phases. It can be expressed as: ? dA = ? dissociation - ? interaction. The ? dissociation term is the work done to dissociate molecules from the bulk melt for incorporation in a diffuse, lower density interfacial zone only a few molecular layers thick. In contrast, the work of interaction, ? interaction, is work made available as a result of across-interface attractions between gas and melt molecules. Increasing the concentration of dissolved H2O and other network modifiers (e.g., Ca, Fe, and Mg) influence the balance of work terms as (1) the ? dissociation declines due to lowered cohesion of the disrupted melt structure, and (2) the ? interaction increases because enhanced molecular diversity supports more numerous and varied interfacial zone attractions. The net effect of decreased ? dissociation and increased ? interaction is a decrease in ? . Additional, systematic data on the variation of ? in natural hydrous melts are needed before the volcanic implications can be fully explored. Nevertheless, it is evident from the data in hand that surface tension, much like melt density and viscosity, can and should be treated as a variable. Cooling, crystallization, and vapor exsolution impart a time-dependency to ? that must be accounted for in modeling volcanic processes.

  12. Geochemistry of the Cretaceous coals from Lamja Formation, Yola Sub-basin, Northern Benue Trough, NE Nigeria: Implications for paleoenvironment, paleoclimate and tectonic setting

    NASA Astrophysics Data System (ADS)

    Sarki Yandoka, Babangida M.; Abdullah, Wan Hasiah; Abubakar, M. B.; Hakimi, Mohammed Hail; Adegoke, Adebanji Kayode

    2015-04-01

    The Cretaceous coals of Lamja Formation located in Yola Sub-basin of the Northern Benue Trough, northeastern Nigeria, were analyzed based on a combined investigation of organic and inorganic geochemistry to define the paleodepositional environment condition, organic matter source inputs and their relation to paleoclimate and tectonic setting. The total organic carbon and sulfur contents of Lamja Formation coals ranges from 48.2%-67.8% wt.% and 0.42%-0.76% wt.%, respectively, pointing their deposition in freshwater environment with inferred marine influence during burial. Biomarkers and chemical compositions provide evidence for a major contribution of land-derived organic matter, with minor aquatic organic matter input. Minerals such as quartz, pyrite, kaolinite, illite, montmorillonite and calcite were present in the coals, suggesting that these minerals were sourced from terrigenous origin with slightly marine influence, considered as post-depositional. This is consistent with a significant amount of the oxides of major elements such as SiO2, Fe2O3, Al2O3, TiO2, CaO, and MgO. The investigated biomarkers are characterized by dominant odd carbon numbered n-alkanes (n-C23 to n-C33), moderately high Pr/Ph ratios (1.72-3.75), very high Tm/Ts ratios (18-29), and high concentrations of regular sterane C29, indicating oxic to relatively suboxic conditions, delta plain marine environment of deposition with prevalent contribution of land plants and minor aquatic organic matter input. Concentrations of trace elements such as Ba, Sr, Cr, Ni, V, Co and their standard ratios also suggested that the organic matter was deposited under oxic to relatively suboxic conditions, which is in parts deposited under marine influenced. Some standard binary plots of SiO2 versus (Al2O3 + K2O + Na2O) indicate a semi-arid paleoclimatic condition whereas log SiO2 versus (K2O/Na2O) also revealed passive continental margin setting. The inferred tectonic setting is in agreement with the tectonic events witnessed in the West and Central Africa during the Cretaceous period.

  13. New data on selected Ivory Coast tektites

    USGS Publications Warehouse

    Cuttitta, F.; Carron, M.K.; Annell, C.S.

    1972-01-01

    Fourteen Ivory Coast tektites exhibit a range of bulk indices of refraction of 1.5156 to 1.5217 ?? 0.0004 and of bulk specific gravities of 2.428 to 2.502 ??0.005. Seven of these Ivory Coast (IVC) tektites were analyzed for major and minor element content. Compared to tektites from other strewn fields, their SiO2 content is low (67.2-69.1 %), A12O3 relatively high (15.8-16.8 %), and total iron relatively high but with a more restricted range (6.3-6.8 % as FeO). Their lime content is low (0.71-1.35%) compared to Australasian tektites but their MgO CaO ratio (about 3.1) is unusually high. All other tektite groups have Na2O K2O ratios less than unity, but the Na2O K2O ratio of the IVC tektites is slightly greater than unity. Their K Rb ratios range from 200 to 256 and average 227, which is higher than those determined for Australasian tektites, but similar to some obtained for moldavites. The Li content (41-48 ppm) is about the same as that of the Australasian tektites, but the Cs and Rb are lower, being 1.9 to 2.9 and 57 to 86 ppm, respectively. The IVC tektites are high in Cr (260-375 ppm), Co (19-25 ppm) and Ni (101-167 ppm), and particularly in Pb (<10-18 ppm), Cu (13-21 ppm) and Ga (14-23 ppm). The high Cr Ni ratios of the IVC tektites (range 2-3.6) are similar to those found for australites, philippinites and thailandites, but not the javanites and indochinites. Evaluation of these and other reported data show that compositional similarities between the IVC tektites and green or black Bosumtwi Crater glasses strongly support the hypothesis of a common impact origin-i.e. the Bosumtwi Crater site. Comparison of the IVC tektite composition with those of returned lunar materials (gabbros, basalts, breccia and soils) do not support a lunar origin for the Ivory Coast tektites. ?? 1972.

  14. Effect of CaO on retention of S, Cl, Br, As, Mn, V, Cr, Ni, Cu, Zn, W and Pb in bottom ashes from fluidized-bed coal combustion power station.

    PubMed

    Bartoňová, Lucie; Klika, Zdeněk

    2014-07-01

    This work was conducted to evaluate whether Ca-bearing additives used during coal combustion can also help with the retention of some other elements. This work was focused on the evaluation of bottom ashes collected during four full-scale combustion tests at an operating thermal fluidized-bed power station. Bottom ashes were preferred to fly ashes for the study to avoid interference from condensation processes usually occurring in the post-combustion zone. This work focused on the behaviors of S, Cl, Br, As, Mn, V, Cr, Ni, Cu, Zn, W, and Pb. Strong positive correlations with CaO content in bottom ashes were observed (for all four combustion tests) for S, As, Cl and Br (R=0.917-0.999). Strong inverse proportionality was calculated between the contents of Pb, Zn, Ni, Cr and Mn and CaO, so these elements showed association to materials other than Ca-bearing compounds (e.g., to aluminosilicates, organic matter, etc.). Somewhat unclear behaviors were observed for W, Cu, and V. Their correlation coefficients were evaluated as statistically "not significant", i.e., these elements were not thought to be significantly associated with CaO. It was also discovered that major enrichment of CaO in the finest bottom ash fractions could be advantageously used for simple separation of elements strongly associated with these fractions, mainly S and As, but also Cl or Br. Removal of 5% of the finest ash particles brings about a decrease in As concentration down to 77%-80% of its original bulk ash content, which can be conveniently used e.g., when high As content complicates further ash utilization. PMID:25079991

  15. Role of a Water Network around the Mn4CaO5 Cluster in Photosynthetic Water Oxidation: A Fourier Transform Infrared Spectroscopy and Quantum Mechanics/Molecular Mechanics Calculation Study.

    PubMed

    Nakamura, Shin; Ota, Kai; Shibuya, Yuichi; Noguchi, Takumi

    2016-01-26

    Photosynthetic water oxidation takes place at the Mn4CaO5 cluster in photosystem II. Around the Mn4CaO5 cluster, a hydrogen bond network is formed by several water molecules, including four water ligands. To clarify the role of this water network in the mechanism of water oxidation, we investigated the effects of the removal of Ca(2+) and substitution with metal ions on the vibrations of water molecules coupled to the Mn4CaO5 cluster by means of Fourier transform infrared (FTIR) difference spectroscopy and quantum mechanics/molecular mechanics (QM/MM) calculations. The OH stretching vibrations of nine water molecules forming a network between D1-D61 and YZ were calculated using the QM/MM method. On the the calculated normal modes, a broad positive feature at 3200-2500 cm(-1) in an S2-minus-S1 FTIR spectrum was attributed to the vibrations of strongly hydrogen-bonded OH bonds of water involving the vibrations of water ligands to a Mn ion and the in-phase coupled vibration of a water network connected to YZ, while bands in the 3700-3500 cm(-1) region were assigned to the coupled vibrations of weakly hydrogen-bonded OH bonds of water. All the water bands were lost upon Ca(2+) depletion and Ba(2+) substitution, which inhibit the S2 → S3 transition, indicating that a solid water network was broken by these treatments. By contrast, Sr(2+) substitution slightly altered the water bands around 3600 cm(-1), reflecting minor modification in water interactions, consistent with the retention of water oxidation activity with a decreased efficiency. These results suggest that the water network around the Mn4CaO5 cluster plays an essential role in the water oxidation mechanism particularly in a concerted process of proton transfer and water insertion during the S2 → S3 transition. PMID:26716470

  16. A Systematic Review of the Mysterious Caterpillar Fungus Ophiocordyceps sinensis in Dong-ChongXiaCao (冬蟲夏草 Dōng Chóng Xià Cǎo) and Related Bioactive Ingredients

    PubMed Central

    Lo, Hui-Chen; Hsieh, Chienyan; Lin, Fang-Yi; Hsu, Tai-Hao

    2013-01-01

    The caterpillar fungus Ophiocordyceps sinensis (syn.† Cordyceps sinensis), which was originally used in traditional Tibetan and Chinese medicine, is called either “yartsa gunbu” or “DongChongXiaCao (冬蟲夏草 Dōng Chóng Xià Cǎo)” (“winter worm-summer grass”), respectively. The extremely high price of DongChongXiaCao, approximately USD $20,000 to 40,000 per kg, has led to it being regarded as “soft gold” in China. The multi-fungi hypothesis has been proposed for DongChongXiaCao; however, Hirsutella sinensis is the anamorph of O. sinensis. In Chinese, the meaning of “DongChongXiaCao” is different for O. sinensis, Cordyceps spp.,‡ and Cordyceps spƒ. Over 30 bioactivities, such as immunomodulatory, antitumor, anti-inflammatory, and antioxidant activities, have been reported for wild DongChongXiaCao and for the mycelia and culture supernatants of O. sinensis. These bioactivities derive from over 20 bioactive ingredients, mainly extracellular polysaccharides, intracellular polysaccharides, cordycepin, adenosine, mannitol, and sterols. Other bioactive components have been found as well, including two peptides (cordymin and myriocin), melanin, lovastatin, γ-aminobutyric acid, and cordysinins. Recently, the bioactivities of O. sinensis were described, and they include antiarteriosclerosis, antidepression, and antiosteoporosis activities, photoprotection, prevention and treatment of bowel injury, promotion of endurance capacity, and learning-memory improvement. H. sinensis has the ability to accelerate leukocyte recovery, stimulate lymphocyte proliferation, antidiabetes, and improve kidney injury. Starting January 1st, 2013, regulation will dictate that one fungus can only have one name, which will end the system of using separate names for anamorphs. The anamorph name “H. sinensis” has changed by the International Code of Nomenclature for algae, fungi, and plants to O. sinensis. PMID:24716152

  17. First-principles calculation of the 17O NMR parameters in Ca oxide and Ca aluminosilicates: the partially covalent nature of the Ca-O bond, a challenge for density functional theory.

    PubMed

    Profeta, Mickal; Benoit, Magali; Mauri, Francesco; Pickard, Chris J

    2004-10-01

    We apply density functional theory (DFT) to the calculation of the (17)O NMR parameters in Ca and Mg oxides and aluminosilicates. We study the accuracy of the Perdew, Burke, and Ernzerhof (PBE) generalized-gradient approximation to DFT in the description of these systems and the origin of the experimentally observed large dependence of the (17)O chemical shift on the alkaline earth ion. We find that (i) the partially covalent nature of the Ca-O bond has a huge impact on the O chemical shifts. The Ca-O covalence alone explains why in Ca oxides and aluminosilicates the (17)O chemical shifts are much more deshielded than those of the corresponding Mg compounds. (ii) The Ca-O covalence is overestimated by the PBE functional. Thus PBE-DFT is not able to reproduce the measured (17)O NMR parameters in Ca oxide and Ca aluminosilicates. (iii) It is possible to correct for the PBE-DFT deficiency in a simple and transferable way and to predict very accurate (17)O NMR parameters. Such accuracy allows us to assign the (17)O NMR spectra of two important model systems: the grossite aluminate (CaAl(4)O(7)) and the wollastonite (CaSiO(3)) silicate. PMID:15453796

  18. [Influence of cations on the laser Raman spectra of silicate glasses].

    PubMed

    Xiong, Yi; Zhao, Hong-xia; Gan, Fu-xi

    2012-04-01

    Na2O(K2O)-CaO(MgO)-SiO2, Na2O(K2O)-Al2O3-SiO2, Na2O(K2O)-B2O3-SiO2, Na2O(K2O)-PbO-SiO2 and PbO-BaO-SiO2 glass systems were investigated using laser Raman spectroscopic technique. The modification of short-range structure of glass caused by network modifier cations will influence Raman signature. Alkali and alkali-earth ions can weaken the bridging oxygen bond, thus lower the frequency of Si-O(b)-Si anti-symmetric stretching vibration. When coordina ted by oxygen ions, B3+ can form [BO4] tetrahedron and enter the silicon-oxygen network, but this effect had little impact on the frequency of Raman peaks located in the high-frequency region. Al3+ can also be coordinated by oxygen ions to form [AlO4] tetrahedron. [AlO4] will increase the disorder degree of network while entering network. Ba2+ can increase the density of electron cloud along the Si-O(nb) bond when it bonds with non-bridging oxygen, which will lead to a higher peak intensity of O-Si-O stretching vibration. The Raman peaks of alkli- and alkali-earth silicate glasses are mainly distributed in the region of 400 - 1 200 cm(-1), while in the spectrum of Na2O(K2O)-PbO-SiO2 glass system a 131 cm(-1) peak existed. The authors assigned it to the Pb-O symmetric stretching vibration. Some of the samples were produced in the laboratory according to the average compositions of ancient glasses, so this research is very significant to discriminating ancient silicate glasses of different systems by Laser Raman spectroscopic technique. PMID:22715771

  19. Tree species identification in an African Savanna with airborne imaging spectroscopy and LiDAR from the Carnegie Airborne Observatory (CAO) using stacked support vector machines

    NASA Astrophysics Data System (ADS)

    Baldeck, C. A.; Colgan, M.; Fret, J.; Asner, G. P.

    2012-12-01

    Airborne remote sensing data provide promising opportunities for species identification of individual tree and shrub crowns across large areas which cannot be mapped from the ground. Previous investigations of the potential for species identification of crowns from airborne data have focused on pixel-level information (0.5-1m2), and thus have been unable to take advantage of the structural information that exist at the crown level. Hyperspectral data consisting of 58 bands from 517 to 1054nm and LiDAR (light detection and ranging) data providing vegetation height information were acquired over several landscapes within Kruger National Park, South Africa, by the CAO in 2008 at 1.1m spatial resolution. Over 1,000 individual trees and shrubs were mapped and identified in the field to construct species spectral and structural libraries. We used stacked support vector machines (SVM) that incorporate pixel-level spectral information and crown-level structural information to predict species identity for individual tree crowns. The addition of a crown-level classification step that incorporates crown structural information significantly improved model accuracy by ~6% and our prediction accuracy of the final model was ~75% for 16 species classes. This model was then used to predict the species identity of individual crowns across multiple airborne-mapped landscapes, made possible by an automated crown segmentation algorithm. The resultant species maps will make it possible to examine the environmental controls over individual species distributions and tree community composition, and provide important landscape-scale species distribution information relevant to park management and conservation.

  20. Hydride ion as a two-electron donor in a nanoporous crystalline semiconductor 12CaO.7Al2O3.

    PubMed

    Hayashi, Katsuro; Sushko, Peter V; Shluger, Alexander L; Hirano, Masahiro; Hosono, Hideo

    2005-12-22

    The 12CaO.7Al2O3 (C12A7) crystal with a nanoporous lattice framework exhibits high electrical conductivity with an activation energy of approximately 1.5 eV when equilibrated in a hydrogen atmosphere above approximately 800 degrees C. The high conductivity is preserved in a quenched state below approximately 600 degrees C with a reduced activation energy of approximately 0.8 eV. Such complex behavior in electrical conductivity is associated with incorporation of hydride ions (H-) in cages of the lattice framework. Electromotive force measurements reveal that the major carrier for the conductivity is electron with a small contribution by proton (H+), ruling out the possibility of direct intercage migration of the H- ion. A combination of these observations with the ab initio calculations leads to the conclusion that the electrons are thermally generated from the H- ion by the dissociation into two electrons and an proton, which is further converted to an OH- ion via reaction with an extraframework oxide ion (O2-). The energy difference between the initial (H- + O2-) and the final (2e- + OH-) states as evaluated by the theoretical calculation is as small as approximately 1 eV, which agrees well with an experimentally obtained enthalpy change, approximately 1.4 eV. Thus, internal equilibration between the extraframework hydrogen and the oxygen species is responsible for the thermal generation of the carrier electron. It is also suggested that the same conductive (2e- + OH-) state is reached by the photoirradiation of H- -containing C12A7. In this case the photoionization of H- forms an electron and an Ho atom, which then forms an OH- ion and another electron with thermal assistance. The persistence of photoinduced conductivity is explained by the slow kinetics of the reverse process at room temperature. PMID:16375369

  1. Red emission generation through highly efficient energy transfer from Ce(3+) to Mn(2+) in CaO for warm white LEDs.

    PubMed

    Feng, Leyu; Hao, Zhendong; Zhang, Xia; Zhang, Liangliang; Pan, Guohui; Luo, Yongshi; Zhang, Ligong; Zhao, Haifeng; Zhang, Jiahua

    2016-01-19

    CaO:Ce(3+),Mn(2+) phosphors with various Mn(2+) concentrations were synthesized by a solid state reaction method. Efficient energy transfer from Ce(3+) to Mn(2+) was observed and it allows the emission color of CaO:Ce(3+),Mn(2+) to be continuously tuned from yellow (contributed by Ce(3+)) to red (by Mn(2+)) with an increase in Mn(2+) concentration and upon blue light excitation. The red emission becomes dominant when the Mn(2+) concentration is ≥0.014 with an energy transfer efficiency higher than 87% which can reach as high as 94% for a Mn(2+) concentration of only 0.02. A critical distance of 10.5 Å for the Ce(3+)-Mn(2+) energy transfer was determined. A faster decrease of Ce(3+) luminescence intensity in comparison with its lifetime was observed on increasing the Mn(2+) concentration. The analysis of this feature reveals that the Ce(3+) excitation energy can be completely transferred to Mn(2+) if the Ce(3+)-Mn(2+) distance is shorter than 7.6 Å. A warm white LED was fabricated through integrating an InGaN blue LED chip and a blend of two phosphors (YAG:Ce(3+) yellow phosphor and CaO:0.007Ce(3+),0.014Mn(2+) red phosphor) into a single package, which has CIE chromaticity coordinates of (x = 0.37, y = 0.35), a correlated color temperature of 3973 K and a color rendering index of 83.1. The results indicate that CaO:Ce(3+),Mn(2+) may serve as a potential red phosphor for blue LED based warm white LEDs. PMID:26678301

  2. Synthetic model of the asymmetric [Mn3CaO4] cubane core of the oxygen-evolving complex of photosystem II

    PubMed Central

    Mukherjee, Shreya; Stull, Jamie A.; Yano, Junko; Stamatatos, Theocharis C.; Pringouri, Konstantina; Stich, Troy A.; Abboud, Khalil A.; Britt, R. David; Yachandra, Vittal K.; Christou, George

    2012-01-01

    The laboratory synthesis of the oxygen-evolving complex (OEC) of photosystem II has been the objective of synthetic chemists since the early 1970s. However, the absence of structural information on the OEC has hampered these efforts. Crystallographic reports on photosystem II that have been appearing at ever-improving resolution over the past ten years have finally provided invaluable structural information on the OEC and show that it comprises a [Mn3CaO4] distorted cubane, to which is attached a fourth, external Mn atom, and the whole unit attached to polypeptides primarily by aspartate and glutamate carboxylate groups. Such a heterometallic Mn/Ca cubane with an additional metal attached to it has been unknown in the literature. This paper reports the laboratory synthesis of such an asymmetric cubane-containing compound with a bound external metal atom, [(1)] . All peripheral ligands are carboxylate or carboxylic acid groups. Variable-temperature magnetic susceptibility data have established 1 to possess an S=9/2 ground state. EPR spectroscopy confirms this, and the Davies electron nuclear double resonance data reveal similar hyperfine couplings to those of other MnIV species, including the OEC S2 state. Comparison of the X-ray absorption data with those for the OEC reveal 1 to possess structural parameters that make it a close structural model of the asymmetric-cubane OEC unit. This geometric and electronic structural correspondence opens up a new front in the multidisciplinary study of the properties and function of this important biological unit. PMID:22308383

  3. The dissolution of natural and artificial dusts in glutamic acid

    NASA Astrophysics Data System (ADS)

    Ling, Zhang; Faqin, Dong; Xiaochun, He

    2015-06-01

    This article describes the characteristics of natural dusts, industrial dusts, and artificial dusts, such as mineral phases, chemical components, morphological observation and size. Quartz and calcite are the main phases of natural dusts and industrial dusts with high SiO2 and CaO and low K2O and Na2O in the chemical composition. The dissolution and electrochemical action of dusts in glutamic acid liquor at the simulated human body temperature (37 C) in 32 h was investigated. The potential harm that the dust could lead to in body glutamic acid acidic environment, namely biological activity, is of great importance for revealing the human toxicological mechanism. The changes of pH values and electric conductivity of suspension of those dusts were similar, increased slowly in the first 8 h, and then the pH values increased rapidly. The total amount of dissolved ions of K, Ca, Na, and Mg was 35.4 to 429 mg/kg, particularly Ca was maximal of 20 to 334 mg/kg. The total amount of dissolved ions of Fe, Zn, Mn, Pb, and Ba was 0.18 to 5.59 mg/kg and in Al and Si was 3.0 to 21.7 mg/kg. The relative solubility order of dusts in glutamic acid is wollastonite > serpentine > sepiolite, the cement plant industrial dusts > natural dusts > power plant industrial dusts. The wollastonite and cement plant industrial dusts have the highest solubility, which also have high content of CaO; this shows that there are a poorer corrosion-resisting ability and lower bio-resistibility. Sepiolite and power plant industrial dusts have lowest solubility, which also have high content of SiO2; this shows that there are a higher corrosion-resisting ability and stronger bio-resistibility.

  4. Cuprian fraipontite and sauconite from the Defiance-Silver Bill mines, Gleeson, Arizona.

    USGS Publications Warehouse

    Foord, E.E.; Taggart, J.E.; Conklin, N.M.

    1983-01-01

    XRD studies have shown the fine-grained, light blue-green mineral previously identified as turquoise or chrysocolla to be the rare species fraipontite + or - admixed sauconite. Composite microprobe and XRF analyses gave SiO2 24.8, Al2O3 17.3, CaO 0.34, CuO 5.2, ZnO 40.95, H2O (ign. loss, 900oC) 12.8, = 101.39, yielding the formula (Zn1.84Al0.77Cu0.24box 0.13- Ca0.02)3.00(Si1.51Al0.49)2.00O5(OH)4. Semiquantitative emission spectrographic analysis showed Fe 0.007, Mg 0.01, Ca 0.07, Si 10, Al major, Na 0.015, Zn major, Cu 5%; Mn 15, B 150, Be 7, Ni 50, Pb 15, Sc 15, Ga 70 and Ag 1 ppm. It has a 5.331(8), b 9.23(1), c 7.275(6) A, beta 104.15o; H. 3.5-4; Dcalc 3.44, Dobs. 3.08- 3.10; mean refr. ind. approx 1.61. Much of the fraipontite is admixed with sauconite, which may be forming from the fraipontite. XRF analysis of this material gave SiO2 32.8, Al2O3 10.9, MgO < 0.1, CaO 1.51, Na2O < 0.2, K2O < 0.02, TiO2 < 0.02, P2O5 < 0.02, MnO < 0.02, CuO 4.65, ZnO 39.9, ign. loss 13.9, = 103.7.-G.W.R.

  5. Mineralogy, geochemistry and genesis of the modern sediments of Seyfe Lake, K?r?ehir, central Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    nalgil, Nergis; Kadir, Selahattin; Klah, Tacit; Eren, Muhsin; Grel, Ali

    2015-02-01

    Seyfe Lake (K?r?ehir, Turkey) is located within a depression zone extending along a NW-SE-trending fault in central Anatolia. Evaporite and carbonate sediments occur at the bottom of the lake which is fed by high-sulfate spring and well waters circulating N-S through salt domes. The recent sediments of Seyfe Lake are deposited in delta, backshore, beach, mud-flat and shallow lake environments. In the mud-flat environment, calcite, gypsum, halite, and thenardite are associated with fine-grained detrital sediments. Sediments from the margin to the lake center are distributed as calcite, gypsum and halite thenardite, yielding an annular distribution pattern. An increase in Na2O, SO3, and S, and a decrease in CaO toward the lake center are due to sediment distribution. On the other hand, a positive correlation of SiO2 with MgO, K2O, Na2O, Al2O3, and Fe2O3 + TiO2 is attributed to the presence of smectite, illite and feldspar. In addition, a positive correlation of Sr and Ba with CaO is related to the amount of gypsum in the sediments. Strontium is associated with in situ gypsum crystals; it increases in the intermediate and central zones of the lake as a result of a relative increase in salinity toward the lake center. The association of Sr with gypsum in the sediments suggests that Ca and Sr were derived from Sr-bearing evaporites and their carbonate host rocks, which were the likely aquifers for the brine. The S- and O-isotopic compositions of sulfate crystals range from +19.1 to +21.7 and from +16.9 to +20.9 SMOW, respectively, suggesting precipitation in a closed lake system. A relative increase of oxygen and sulfur isotope ratios toward the lake center suggests dissolution of gypsum in the host rock, with contributions from circulating groundwater and sulfate reduction (possibly by bacterial reduction). 87Sr/86Sr isotope ratios range from 0.707286 to 0.707879, suggesting a non-marine Oligo-Pliocene evaporitic host rock source for precipitation in Seyfe Lake. The concentration of Sr- and S-isotope ratios in the gypsum crystals indicates formation by precipitation/recrystallization from brine rather than from seawater.

  6. Silicate melt inclusions in clinopyroxene phenocrysts from mafic dikes in the eastern North China Craton: Constraints on melt evolution

    NASA Astrophysics Data System (ADS)

    Cai, Ya-Chun; Fan, Hong-Rui; Santosh, M.; Hu, Fang-Fang; Yang, Kui-Feng; Liu, Xuan; Liu, Yongsheng

    2015-01-01

    Silicate melt inclusions (SMIs) in magmatic minerals provide key information on the chemical and mineralogical evolution of source magmas. The widespread Cretaceous mafic dikes in the Jiaojia region of the eastern North China Craton contain abundant SMIs within clinopyroxene phenocrysts. The daughter minerals in these SMIs include amphibole, plagioclase, pyrite and ilmenite, together with CO2 + CH4 and CH4 as the major volatile phase. The total homogenization temperatures of the SMIs range between 1280 and 1300 C. The host clinopyroxene phenocrysts in these dolerite dikes are dominantly augite with minor diopside. From LA-ICPMS analyses of the SMIs, we identify two compositional groups: (1) low-MgO (6.0-7.6 wt.%) SMIs and (2) high-MgO (11.2-13.9 wt.%) SMIs. The Low-MgO group exhibits higher concentrations of TiO2, Al2O3, Na2O, P2O5 and lower CaO and CaO/Al2O3 ratio as compared to the high-MgO SMIs. The trace element patterns of the two types of SMIs are similar to those of the host mafic dikes. However, the low-MgO SMIs and host mafic dikes are clearly more enriched in all the trace elements as compared to the high-MgO type, especially with regard to the highly incompatible elements. The estimated capture temperatures and pressures are 1351-1400 C and 1.6-2.1 GPa for the high-MgO SMIs and 1177-1215 C and 0.6-1.1GPa for the low-MgO type. The high-MgO and low-MgO SMIs were trapped at depths of ?51-68 km and ?20-35 km, respectively. Computations show that the parental melt is mafic with SiO2 content 49.6 wt% and Mg# 80.0 with relatively low total alkali contents (1.35 wt% Na2O + K2O) and high CaO (15.2 wt%). Exploratory runs with the program MELTS and pMELTS show that the low-MgO and high-MgO SMIs were derived from the same parental melt through different degrees of crystallization. Clinopyroxene and a small amount of olivine were the fractionating phases during the evolution from parental melts to high MgO melts, while the low MgO melts experienced significant fractional crystallization of olivine and clinopyroxene. We postulate the newly accreted lithospheric clinopyroxenite as the major source for the Jiaojia dolerite dikes, with melting of the source at a depth of ?68-80 km.

  7. Abundances and distribution of minerals and elements in high-alumina coal fly ash from the Jungar Power Plant, Inner Mongolia, China

    USGS Publications Warehouse

    Dai, S.; Zhao, L.; Peng, S.; Chou, C.-L.; Wang, X.; Zhang, Y.; Li, D.; Sun, Y.

    2010-01-01

    The fly ash from the Jungar Power Plant, Inner Mongolia, China, is unique because it is highly enriched in alumina (Al2O3>50%). The fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum, quartz, char, calcite, K-feldspar, clay minerals, and Fe-bearing minerals. The mullite content in fly ash is as high as 37.4% because of high boehmite and kaolinite contents in feed coal. Corundum is a characteristic mineral formed during the combustion of boehmite-rich coal.Samples from the economizer were sieved into six size fractions (<120, 120-160, 160-300, 300-360, 360-500, and >500 mesh) and separated into magnetic, mullite+corundum+quartz (MCQ) and glass phases for mineralogical and chemical analysis. The corundum content increases but amorphous glass decreases with decreasing particle size. Fractions of small particle sizes are relatively high in mullite, probably because mullite was formed from fine clay mineral particles under high-temperature combustion condition. Similarly, fine corundum crystals formed in the boiler from boehmite in feed coal. The magnetic phase consists of hematite, magnetite, magnesioferrite, and MgFeAlO4 crystals. The MCQ phase is composed of 89% mullite, 6.1% corundum, 4.5% quartz, and 0.5% K-feldspar.Overall, the fly ash from the power plant is significantly enriched in Al2O3 with an average of 51.9%, but poor in SiO2, Fe2O3, CaO, MgO, Na2O, P2O5, and As. Arsenic, TiO2, Th, Al2O3, Bi, La, Ga, Ni, and V are high in mullite, and the magnetic matter is enriched in Fe2O3, CaO, MnO, TiO2, Cs, Co, As, Cd, Ba, Ni, Sb, MgO, Zn, and V. The remaining elements are high in the glass fraction. The concentration of K2O, Na2O, P2O5, Nb, Cr, Ta, U, W, Rb, and Ni do not clearly vary with particle size, while SiO2 and Hg decrease and the remaining elements clearly increase with decreasing particle size. ?? 2009 Elsevier B.V.

  8. Geochronological and geochemical constraints on the petrogenesis of the early Paleoproterozoic potassic granite in the Lushan area, southern margin of the North China Craton

    NASA Astrophysics Data System (ADS)

    Zhou, Yanyan; Zhai, Mingguo; Zhao, Taiping; Lan, Zhongwu; Sun, Qianying

    2014-11-01

    We conducted a geochronological and geochemical study on the Paleoproterozoic potassic granites in the Lushan area, southern margin of the North China Craton (NCC) to understand the tectonic regime of the NCC at 2.2-2.1 Ga. This rock suite formed at 2194 29 Ma. The rocks are rich in SiO2 (76.10-77.73 wt.%), and K2O (5.94-6.90 wt.%) with high K2O + Na2O contents from 7.56 wt.% to 8.48 wt.%, but poor in CaO (0.10-0.28 wt.%), P2O5 (0.02-0.05 wt.%) and MgO (0.01-0.30 wt.%, Mg# = 1.08-27.3), indicating they experienced fractional crystallization. Major element compositions suggest the potassic granites share an affinity with high K calc-alkaline granite. Even though the Lushan potassic granitic rocks have high A/CNK ratios (1.11-1.25), which can reach peraluminous feature, the very low P2O5 contents and negative correlation of P2O5 and SiO2 ruling out they are S-type granites. Different from peralkaline A-type granites, the Lushan potassic granites have variable Zr concentrations (160-344 ppm, 226 ppm on average) and 10,000 Ga/Al ratios (1.76-3.00), together with high zircon saturation temperatures (TZr = 826-885 C), indicating they are fractionated aluminous A-type granites. Enriched LREE ((La/Yb)N = 9.72-81.8), negative Eu anomalies, and low Sr/Y with no correlations in Sr/Y and Sr/Zr versus CaO suggest the possible presence of Ca-rich plagioclase and absence of garnet in the residual. Magmatic zircon grains have variable ?Hf(t) values (-2.4 to +7.3) with zircon two-stage Hf model ages (TDMC) varying from 2848 Ma to 2306 Ma (mostly around ca. 2.5 Ga), and are plotted in the evolution line of crustal felsic rock. We propose that the rocks mainly formed by partial melting of ca. 2.50 Ga tonalitic-granodioritic crust as a result of upwelling mantle-derived magmas which provided thermal flux and source materials in an intra-continent rifting. The ca. 2.2 Ga magmatism suggests that intra-continental rifting occurred at 2.35-1.97 Ga at least in the southern margin of the NCC after its final cratonization in the late Neoarchean.

  9. Geochemical Characterisation of Chicxulub-Impact Ejecta: New constrains from the Gulf of Mexico and the Caribbean

    NASA Astrophysics Data System (ADS)

    Harting, M.; Keller, G.; Stinnesbeck, W.; Adatte, T.

    2005-05-01

    Glass spherule ejecta deposits in various sections from NE-Mexico, Texas, Guatemala, Belize, and Haiti have been investigated by wave-length dispersive electron microprobe analyses, backscatter-electron imaging, scanning electron-, and transmission electron microscopy, in order to characterize the geochemistry of the ejecta, strewn-field mixing, alteration, fractionation within the strewn field, and distribution mechanisms. Earlier investigations include main and trace elements (Harting, 2004), isotope analyses (Kettrup, 2002) and litho- and biostratigraphic investigations (Keller et al., 2003, 2004). In NE-Mexico and Texas, multiple ejecta layers are exposed up to 14 m below the K/T boundary, with the oldest and original ejecta deposit predating the K/T boundary by about 300,000 years. In Texas, preliminary analyses suggest that the original ejecta, now a higly altered smectite layer, is also interbedded in late Maastrichtian claystone. In Guatemala, Belize and Haiti the spherule layers are generally found above the K/T boundary and apparently eroded and reworked from the older original deposit. Geochemical investigations at all these localities reveal Chicxulub impact glass as the origin for all glass spherule ejecta layers. TEM-studies reveal the nature and extent of geochemical alteration. Although most glass spherules have weathered clay rims, relic glass particles contain relatively fresh unaltered glass. Both geochemical and petrological features are well preserved and permit correlation with Chicxulub basement rocks (e.g. granites, gneises, amphibolites and impact meltrocks). Several distinct silicic phases (Al-Fe-rich glasses) are observed. The range of geochemical compositions for NE-Mexico ejecta is: SiO2: 45-61, TiO: 0.1-0.6, Al2O3: 11-22, FeO: 2-14, MnO: 0-0.07, MgO: 2-11, CaO: 1-9, Na2O: 0-3, K2O: 0.2-4. The mean geochemical composition for Texas impact glass falls well within this range with SiO2: 50.81, TiO2: 0.33, Al2O3: 18.34, FeO: 4.99, MnO: 0.02, MgO: 3.42, CaO: 3.03, Na2O: 0.11 and for K2O: 1.31. These compositional phases are present in all studied outcrops but with variable amounts of FeO-, Al2O3 and CaO in NE-Mexico. These characteristics strongly imply an ejecta origin from mafic and felsic rocks of the Chicxulub-basement. However, the occurrence of different glass phases in the upper (reworked) ejecta layers of NE Mexico strongly suggests post-sedimentary mixing and/or fractionation (weathering) of the ejecta. In contrast, the stratigraphically oldest ejecta layer (300,000 yrs pre-K/T) is geochemically more uniform, which reflects the absence of erosion, mixing and transport, and less weathering.

  10. Petrogenesis of Triassic granites from the Nanling Range in South China: Implications for geochemical diversity in granites

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Zhao, Zi-Fu; Zheng, Yong-Fei

    2014-12-01

    A combined study of whole-rock major-trace elements and Sr-Nd isotopes, zircon U-Pb ages, Hf and O isotopes as well as biotite geochemistry was carried out for Triassic granite intrusions from the Nanling Range in South China. The results provide insights into the effects of source composition and melting conditions on the geochemical diversity of granites. The granites of interest are peraluminous, and contain primary muscovite and tourmaline. They are characterized by high zircon δ18O values of > 9.0‰, high initial 87Sr/86Sr values of ~ 0.7200, and homogeneous εNd(t) values of - 11.3 to - 9.8, as well as variable zircon εHf(t) values of - 12.2 to - 5.8. Biotite geochemistry is similar to that of common peraluminous granites. An integrated interpretation of these petrological, mineralogical and geochemical data indicates that these granites were derived from partial melting of metasedimentary rocks under variable physicochemical conditions. The differences in whole-rock and biotite geochemistry between the intrusions are ascribed to the variable effects of source heterogeneity and melting temperature. The Luxi intrusion exhibits higher contents of MgO, FeOT, TiO2 and CaO than common melts derived from metasedimentary rocks, tight variations in major-trace elements and homogeneous Sr-Nd isotopic compositions, and homogeneous biotite composition with high Mg# [= Mg / (Mg + Fe) in molar] and lower whole-rock A/CNK values [= Al2O3 / (CaO + Na2O + K2O) in molar]. These can be explained by originating from a relatively mafic metasedimentary source. On the other hand, the geochemical diversity of granites can be caused by the difference in melting temperature in addition to the source heterogeneity. This is suggested by the Xiazhuang and Fucheng intrusions which exhibit similar range of SiO2. Nevertheless, the Fucheng intrusion is ferroan, and high in TiO2, (Na2O + K2O)/CaO, TiO2/MgO, Ga/Al and Zr + Nb + Ce + Y, but low in CaO, MgO and Mg#. Most of its major elements and their ratios are similar to those of A-type granites that were generated from F-rich rocks at high temperatures, consistent with the enrichment of Fe and F in its biotite. Thus, partial melting of a metasedimentary restite at reduced conditions after previous melt extraction is suggested to produce the geochemical feature of A-type granites in the Fucheng intrusion. In contrast, partial melting of fertile metasedimentary rocks would produce normal S-type granites like the Xiazhuang intrusion, with its geochemical variations ascrible to source heterogeneity and differential melting. Therefore, the geochemical composition of granites is primarily dictated by the composition of source rocks in addition to the physicochemical conditions of partial melting.

  11. Novel Application of Alkali Oxides in Basic Tundish Fluxes for Enhancing Inclusion Removal in 321 Stainless Steels

    NASA Astrophysics Data System (ADS)

    Yu, Jong Yeong; Kang, Youngjo; Sohn, Il

    2014-01-01

    Fundamental work on the effect of alkali oxides including Li2O, Na2O, and K2O on the absorption ability of inclusions in a typical basic tundish flux for 321 stainless steels has been studied. The effects on the absorption ability are dependent on the type of alkali oxides and the amount composed within the tundish flux. Results from kinetics studies using an induction furnace at 1823 K (1550 C) on the reaction of tundish fluxes containing alkali oxides with 321 stainless steels suggest minimal improvement with Li2O and Na2O additions and in some cases hindered inclusion removal, but K2O additions seems to significantly improve the cleanliness in the as-quenched 321 stainless steel melts compared to preexisting tundish flux compositions. Both Li2O and Na2O significantly lower the viscosity of the melt, while K2O increases the viscosity. Although alkali oxides have a propensity to enhance the cohesion of aluminate melts due to the ionic compensation effect in [AlO4]5--tetrahedral structural units, this effect was not pronounced for Li2O and Na2O compared to K2O additions, which may be due to the large ionic radius size of potassium. An automated SEM-EDS analysis was utilized to identify the inclusion morphology and abundance within the steel. Fourier transform infrared spectroscopy was used to identify the effects of alkali oxides on the tundish flux structure for improved absorption capability and described the characteristic effect of K2O on increasing the asymmetric stretching vibrations of [AlO4]5--tetrahedral structural units and Si-O-Al bonding within the flux, thus polymerizing the flux and selectively absorbing inclusions.

  12. Characterization of 12CaO x 7Al2O3 doped indium tin oxide films for transparent cathode in top-emission organic light-emitting diodes.

    PubMed

    Jung, Chul Ho; Hwang, In Rok; Park, Bae Ho; Yoon, Dae Ho

    2013-11-01

    12CaO x 7Al2O3, insulator (C12A7) doped indium tin oxide (ITO) (ITO:C12A7) films were fabricated using a radio frequency magnetron co-sputtering system with ITO and C12A7 targets. The qualitative and quantitative properties of ITO:C12A7 films, as a function of C12A7 concentration, were examined via X-ray photoemission spectroscopy and synchrotron X-ray scattering as well as by conducting atomic force microscopy. The work function of ITO:C12A7 (1.3%) films of approximately 2.8 eV obtained by high resolution photoemission spectroscopy measurements make them a reasonable cathode for top-emission organic light-emitting diodes. PMID:24245291

  13. Enhanced stability of CaO and/or La2O3 promoted Pd/Al2O3 egg-shell catalysts in partial oxidation of methane to syngas.

    PubMed

    Wang, Jinlong; Yu, Hongbo; Ma, Zhen; Zhou, Shenghu

    2013-01-01

    An egg-shell Pd/Al2O3 catalyst showed higher activity than a regular Pd/Al2O3 catalyst in the partial oxidation of methane to syngas, but a common problem of this reaction is the catalyst deactivation on stream. We attempted to modify the egg-shell catalyst via impregnation with some metal oxide additives. Although the addition of MgO did not show any beneficial effect, the addition of CaO and/or La2O3 significantly improved the stability due to the suppression of carbon deposition and phase transformation of the Al2O3 support. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, and thermogravimetric analysis (TGA). PMID:23860276

  14. Fabrication and electron transport properties of epitaxial films of electron-doped 12CaO.7Al{sub 2}O{sub 3} and 12SrO.7Al{sub 2}O{sub 3}

    SciTech Connect

    Miyakawa, Masashi; Hiramatsu, Hidenori; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2010-02-15

    Epitaxial growth and electron doping of 12CaO.7Al{sub 2}O{sub 3} (C12A7) and 12SrO.7Al{sub 2}O{sub 3} (S12A7) are reported. The C12A7 films were prepared on Y{sub 3}Al{sub 5}O{sub 12} (YAG) single-crystal substrates by pulsed laser deposition at room temperature and subsequent thermal crystallization. X-ray diffraction patterns revealed the films were grown epitaxially with the orientation relationship of (001)[100] C12A7 || (001)[100] YAG. For S12A7, pseudo-homoepitaxial growth was attained on the C12A7 epitaxial layer. Upon electron doping, metallic conduction was achieved in the C12A7 film and the S12A7/C12A7 double-layered films. Analyses of optical absorption spectra for the S12A7/C12A7 films provided the densities of free electrons in each layer separately. Hall measurements exhibited larger electron mobility in the S12A7/C12A7 film than those in C12A7 and S12A7 films, suggesting free electrons may be accumulated at the S12A7/C12A7 interface due presumably to a discontinuity of the cage conduction bands. - Graphical abstract: Reciprocal space maps around the 408 and the 709 diffractions show the films were grown epitaxially with the orientation relationship of (001)[100] 12SrO.7Al{sub 2}O{sub 3} || (001)[100] 12CaO.7Al{sub 2}O{sub 3} || (001)[100] Y{sub 3}Al{sub 5}O{sub 12}.

  15. Bimodal Silurian and Lower Devonian volcanic rock assemblages in the Machias-Eastport area, Maine

    USGS Publications Warehouse

    Gates, Olcott; Moench, R.H.

    1981-01-01

    Exposed in the Machias-Eastport area of southeastern Maine is the thickest (at least 8,000 m), best exposed, best dated, and most nearly complete succession of Silurian and Lower Devonian volcanic strata in the coastal volcanic belt, remnants of which crop out along the coasts of southern New Brunswick, Canada, and southeastern New England in the United States. The volcanics were erupted through the 600-700-million-year-old Avalonian sialic basement. To test the possibility that this volcanic belt was a magmatic arc above a subduction zone prior to presumed Acadian continental collision, samples representing the entire section in the Machias-Eastport area of Maine were chemically analyzed. Three strongly bimodal assemblages of volcanic rocks and associated intrusives are recognized, herein called the Silurian, older Devonian, and younger Devonian assemblages. The Silurian assemblage contains typically nonporphyritic high-alumina tholeiitic basalts, basaltic andesites, and diabase of continental characterand calc-alkalic rhyolites, silicic dacites, and one known dike of andesite. These rocks are associated with fossiliferous, predominantly marine strata of the Quoddy, Dennys, and Edmunds Formations, and the Leighton Formation of the Pembroke Group (the stratigraphic rank of both is revised herein for the Machias-Eastport area), all of Silurian age. The shallow marine Hersey Formation (stratigraphic rank also revised herein) of the Pembroke Group, of latest Silurian age (and possibly earliest Devonian, as suggested by an ostracode fauna), contains no known volcanics; and it evidently was deposited during a volcanic hiatus that immediately preceded emergence of the coastal volcanic belt and the eruption of the older Devonian assemblage. The older Devonian assemblage, in the lagoonal to subaerial Lower Devonian Eastport Formation, contains tholeiitic basalts and basaltic andesites, typically with abundant plagioclase phenocrysts and typically richer in iron and titanium and poorer in magnesium and nickel than the Silurian basalts; and the Eastport Formation has rhyolites and silicic dacites that have higher average SiO2 and K2O contents and higher ratios of FeO* to MgO than the Silurian ones. The younger Devonian assemblage is represented by one sample of basalt from a flow in red beds of the post-Acadian Upper Devonian Perry Formation, and by three samples from pre-Acadian diabases that intrude the Leighton and Hersey Formations. These rocks are even richer in titanium and iron and poorer in magnesium and nickel than the older Devonian basalts. Post-Acadian granitic plutons exposed along the coastal belt for which analyses are available are tentatively included in the younger Devonian assemblage. The most conspicuous features of the coastal volcanics and associated intrusives are the preponderance of rocks of basaltic composition ( < 52 percent SiO2 ) in the Silurian assemblage, and the near absence in all assemblages of intermediate rocks having 57-67 percent SiO2 (calculated without volatiles). All the rocks are variably altered spilites and keratophyres. The basaltic types are adequately defined, however, by eight samples of least altered basalts having calcic plagioclase, clinopyroxene, and 0.5 percent or less CO2 , The more altered basalts are variably enriched or depleted in Na2O, K2O, and CaO relative to the least altered ones. In the silicic rocks no primary ferromagnesian minerals are preserved. The Na2O and K2O contents of the silicic rocks are erratic; they are approximately reciprocal, possibly owing to alkali exchange while the rocks were still glassy. We propose that the coastal volcanic belt extended along an axis of thermal swelling in the Earth's mantle and upward intrusion of partially melted mantle into the sialic Avalonian crust. These processes were accompanied by shoaling and emergence of the belt, and they produced the bimodal volcanism. Tholeiitic basaltic melts segregated from mantle material

  16. Chemical zonation in olivine-hosted melt inclusions

    NASA Astrophysics Data System (ADS)

    Newcombe, M. E.; Fabbrizio, A.; Zhang, Youxue; Ma, C.; Le Voyer, M.; Guan, Y.; Eiler, J. M.; Saal, A. E.; Stolper, E. M.

    2014-07-01

    Significant zonation in major, minor, trace, and volatile elements has been documented in naturally glassy olivine-hosted melt inclusions from the Siqueiros Fracture Zone and the Galapagos Islands. Components with a higher concentration in the host olivine than in the melt (e.g., MgO, FeO, Cr2O3, and MnO) are depleted at the edges of the zoned melt inclusions relative to their centers, whereas except for CaO, H2O, and F, components with a lower concentration in the host olivine than in the melt (e.g., Al2O3, SiO2, Na2O, K2O, TiO2, S, and Cl) are enriched near the melt inclusion edges. This zonation is due to formation of an olivine-depleted boundary layer in the adjacent melt in response to cooling and crystallization of olivine on the walls of the melt inclusions, concurrent with diffusive propagation of the boundary layer toward the inclusion center. Concentration profiles of some components in the melt inclusions exhibit multicomponent diffusion effects such as uphill diffusion (CaO, FeO) or slowing of the diffusion of typically rapidly diffusing components (Na2O, K2O) by coupling to slow diffusing components such as SiO2 and Al2O3. Concentrations of H2O and F decrease toward the edges of some of the Siqueiros melt inclusions, suggesting either that these components have been lost from the inclusions into the host olivine late in their cooling histories and/or that these components are exhibiting multicomponent diffusion effects. A model has been developed of the time-dependent evolution of MgO concentration profiles in melt inclusions due to simultaneous depletion of MgO at the inclusion walls due to olivine growth and diffusion of MgO in the melt inclusions in response to this depletion. Observed concentration profiles were fit to this model to constrain their thermal histories. Cooling rates determined by a single-stage linear cooling model are 150-13,000 C h-1 from the liquidus down to ~1,000 C, consistent with previously determined cooling rates for basaltic glasses; compositional trends with melt inclusion size observed in the Siqueiros melt inclusions are described well by this simple single-stage linear cooling model. Despite the overall success of the modeling of MgO concentration profiles using a single-stage cooling history, MgO concentration profiles in some melt inclusions are better fit by a two-stage cooling history with a slower-cooling first stage followed by a faster-cooling second stage; the inferred total duration of cooling from the liquidus down to ~1,000 C ranges from 40 s to just over 1 h. Based on our observations and models, compositions of zoned melt inclusions (even if measured at the centers of the inclusions) will typically have been diffusively fractionated relative to the initially trapped melt; for such inclusions, the initial composition cannot be simply reconstructed based on olivine-addition calculations, so caution should be exercised in application of such reconstructions to correct for post-entrapment crystallization of olivine on inclusion walls. Off-center analyses of a melt inclusion can also give results significantly fractionated relative to simple olivine crystallization. All melt inclusions from the Siqueiros and Galapagos sample suites exhibit zoning profiles, and this feature may be nearly universal in glassy, olivine-hosted inclusions. If so, zoning profiles in melt inclusions could be widely useful to constrain late-stage syneruptive processes and as natural diffusion experiments.

  17. Petrography and Geochemistry of the Zamora Batholith in the south of the sub-Andean zone (Ecuador)

    NASA Astrophysics Data System (ADS)

    Villares, F. M.

    2013-05-01

    The Zamora Batholith is an intrusive complex that is located in the extreme south-east of Ecuador. It has dimensions of 200 x 50 km approximately. It is mainly located in the Zamora Chinchipe province from which it takes its name. This study consisted in the petrographic and geochemical characterization of the Zamora Batholith in the area covered by 1: 50,000 geological maps of Centro Shaime, Guayzimi, Paquisha, Los Encuentros and El Pangui. Fieldwork was done by the "Proyecto Mapeo Geolgico escala 1:50.000 (zonas prospectivas mineras)" of the Instituto Nacional de Investigacin Geolgico, Minero, Metalrgico of Ecuador. This research was performed with 59 thin sections and 10 whole - rock chemical analysis done in the C.I.C of the Granada University. The Zamora Batholith intrudes Triassic to Jurassic volcanic rocks. It is overlaid by sandstones of the Hollin Formation of the Upper Aptian age and shale and limestone from the Napo Formation. Post-cretaceous deposits of ash and lava flows of andesitic to rhyolitic compositions cover the batholith. The petrography of the Zamora Batholith ranges from tonalite to monzogranite with the same qualitative mineralogy. The rocks are composed by different proportions of plagioclase, amphibole, feldspar K, quartz, biotite, opaque, pyroxene and epidote, as accessory minerals has zircon, sphene and apatite. To the south of the Conguime and Guayzimi towns, the dominant petrography is medium to coarse grained amphibole granodiorite with tonalitic and monzogranitic subordinates. To the north monzogranites are dominant rocks and subordinate granodiorites. To the East of Santa Elena the sienogranites are associated with El Hito porphyritic granite that intrudes to Zamora Batholith. Frequently the batholith has propylitic alteration; which produces a primary association of chlorite, epidote, calcite and pyrite. The granitoids have dioritic to granitic compositions (60.09 to 73.6 wt.% SiO2) and are I - type, medium to high-K calc-alkaline. They have affinities slightly peraluminous (ASI = 1,00 to 1,16). CaO is moderate to high (CaO ? 3.58), the alkalis have averaged of Na2O?3,09 and K2O?3,28. The concentrations of Na2O/K2O are moderate ranging between 0.7 and 1.7, with an average value of 1.04. The contents of Ba and Sr are moderate. The content of Zr is low (61 to 161 ppm). The multi-element diagrams normalized to chondritic values and to primitive mantle show Nb and Ta negative anomaly. Considering the multi-element diagrams, the rocks are slightly enriched in LILE (Large Ion-Lithophile-elements) mainly in Rb, Cs and Ba and slight positive anomalies in K and Sr, other incompatible elements have negative anomalies such as HFSE ( High Field Strength Elements) Ti, Nb, Ta. The values of (Eu/Eu*)N are in the range of 0.54 to 1.03. (Eu* = (SmN*GdN)1/2). Correlations between major element and silica, and relationships between trace elements indicate that fractional crystallization is a dominant process in the magma evolution. Most granitoids are also slightly peraluminous; but we believe this characteristic is due to rock alteration. The Zamora Batolith is a plutonic complex generated within a magmatic arc in normal conditions of maturity.

  18. Primitive, high-Mg basaltic andesites: direct melts of the shallow, hot, wet mantle

    NASA Astrophysics Data System (ADS)

    Andrews, A.; Grove, T. L.

    2013-12-01

    Direct mantle melts are rare in subduction zone settings. Such melts are identified by Mg #s (Mg # = Mg / (Mg+Fe)) greater than ~0.73, indicating chemical equilibrium with Fo90 mantle olivine. Most of these primitive arc melts are basaltic, characterized by SiO2 contents of ~48-50 wt % and MgO contents ranging from 8-10 wt %. However, primitive basaltic andesites with mantle-equilibrated Mg #s have also been found at subduction zones worldwide. These basaltic andesites have higher SiO2 contents (53-58 wt %) than typical primitive basalts as well as high MgO (8-10 wt %). Because these rocks have high SiO2 contents and yet retain evidence for chemical equilibrium with the mantle (Mg #s), their petrogenesis has sparked intense debate as researchers have tried to discern how these samples fit into the paradigm of mantle melting at subduction zones. Through an understanding of the conditions and processes that produce the SiO2 enrichment in these rocks, we also aim to understand the role of these melts in producing the observed andesitic compositional characteristics of the continental crust. To understand the petrogenesis of primitive, high-Mg basaltic andesites, this study investigates the experimental melts of undepleted mantle peridotite plus a slab component (Na-2O + K2O) from 1,205-1,470C at 1.0-2.0 GPa under water-undersaturated conditions (0-5 wt % H2O). At 1.0 and 1.2 GPa, the experimental melts reproduce the compositions of natural primitive, high-Mg basaltic andesites in all major elements (SiO2, TiO2, Al2O3, FeO, MnO, MgO, and Na2O+K2O) except CaO. CaO contents are higher than the range of the natural samples by ~2 wt % at the highest silica contents of the experiments (54-56 wt% SiO2). This suggests that at 1.0-1.2 GPa, a higher percent of melting (30-35 %) with 3-5 wt % H2O is required to drive the chemical compositions of the experiments toward the representative compositions of the natural rocks. The experimental melts also show that mantle-wall rock reaction is a feasible mechanism for producing the SiO2 enrichment of the natural samples. We calculate reaction coefficients to determine the amount of mantle-wall rock reaction necessary to change the experimental compositions into natural primitive, high-Mg basaltic andesites. In the reaction (orthopyroxene ? olivine + liquid), orthopyroxene dissolves to produce liquid and olivine. We use experimentally determined phase boundaries to show that at a given pressure, less hydrous experimental melts require more reaction to reach a representative primitive, high-Mg basaltic andesite than more hydrous melts.

  19. Major Element Geochemistry of Biofilms in a Silica-Precipitating Hot Spring

    NASA Astrophysics Data System (ADS)

    Havig, J. R.; Shock, E. L.; Moore, G.

    2007-12-01

    Hydrothermal biofilm communities represent one of the best present-day representations of early microbial communities, dating back to 2.5 Ga, and possibly 3.8 Ga in the geologic record. Silica-precipitating hydrothermal springs have been thought to have great potential for biosignature preservation. The interactions of hydrothermal water, biofilms, and precipitated siliceous sinter, however, remain poorly constrained. To this end, we collected water and biofilm, as well as contextual sinter and rock samples from various hot springs in Yellowstone National Park. Here we focus on one hot spring in Sentinel Meadow (Lower Geyser Basin), with temperature and pH that vary from the source (93 C, pH 7.4) to the farthest of five collection points down channel (56 C, pH 8.2). Elemental analysis reveals that the biofilms are made up of from <1 to ~11 % dry wt. carbon and ~0.1 to 1% dry wt. nitrogen. Major element analysis via electron microprobe and complimentary x-ray fluorescence show that (excluding C and N from the total) SiO2 constitutes 86 to 94 % dry weight mass, with the rest made up of Al2O3 (3 to 8%), Na2O (1.7 to 3.7%), K2O (0.6 to 1.5%), and minor amounts of FeO, CaO, MgO, and TiO2 (<1%). Local sinter is SiO2 (97.5% dry wt.), Na2O (1.5%), and <1% Al2O3, FeO, K2O, CaO, MgO, and TiO2. In addition, sinter contains measurable amounts of carbon (1.4%) and nitrogen (0.2%). Discrepancies between the biofilm and sinter values show that the geochemical compositions of biofilms are not captured by the precipitating silica. If biofilms accumulated elements strictly from the water, then it would take as much as 440 L of water to supply 1 gram (dry wt) of biofilm with the elements contained therein, assuming complete uptake. This seems especially unlikely in the case of Al, which is quite dilute (~500 ppb), poses very little benefit nutritionally, and increases in concentration down channel. Other major element components also exhibit at least one, if not all, of these traits. A potential source of the elements found in biofilms is aeolian-deposited dust. Area country rock is dominated by siliceous volcanism, represented locally by rhyolite samples collected from Sentinel Meadow. With an average value of ~10 wt % Al2O3 for the surrounding country rock, it would take approximately 0.6 grams of the ground up rock as dust to account for the Al found in one gram of biofilm. The low Al2O3 content of the sinter indicates that the Al is not entombed from the biofilms. A hypothesis for the above discrepancies in Al (as well as other elements) is that dust deposited in the water is captured on the biofilm surfaces, and the biofilm community then breaks down the dust, utilizing any nutritionally or metabolically important elements, and either precipitating (for Si) or releasing (for Al) unnecessary elements.

  20. Geochemistry and petrogenesis of Mashhad granitoids: An insight into the geodynamic history of the Paleo-Tethys in northeast of Iran

    NASA Astrophysics Data System (ADS)

    Mirnejad, H.; Lalonde, A. E.; Obeid, M.; Hassanzadeh, J.

    2013-06-01

    Mashhad granitoids in northeast Iran are part of the so-called Silk Road arc that extended for 8300 km along the entire southern margin of Eurasia from North China to Europe and formed as the result of a north-dipping subduction of the Paleo-Tethys. The exact timing of the final coalescence of the Iran and Turan plates in the Silk Road arc is poorly constrained and thus the study of the Mashhad granitoids provides valuable information on the geodynamic history of the Paleo-Tethys. Three distinct granitoid suites are developed in space and time (ca. 217-200 Ma) during evolution of the Paleo-Tethys in the Mashhad area. They are: 1) the quartz diorite-tonalite-granodiorite, 2) the granodiorite, and 3) the monzogranite. Quartz diorite-tonalite-granodiorite stock from Dehnow-Vakilabad (217 4-215 4 Ma) intruded the pre-Late Triassic metamorphosed rocks. Large granodiorite and monzogranite intrusions, comprising the Mashhad batholith, were emplaced at 212 5.2 Ma and 199.8 3.7 Ma, respectively. The high initial 87Sr/86Sr ratios (0.708042-0.708368), low initial 143Nd/144Nd ratios (0.512044-0.51078) and low ?Nd(t) values (- 5.5 to - 6.1) of quartz diorite-tonalite-granodiorite stock along with its metaluminous to mildly peraluminous character (Al2O3/(CaO + Na2O + K2O) Mol. = 0.94-1.15) is consistent with geochemical features of I-type granitoid magma. This magma was derived from a mafic mantle source that was enriched by subducted slab materials. The granodiorite suite has low contents of Y (? 18 ppm) and heavy REE (HREE) (Yb < 1.53 ppm) and high contents of Sr (> 594 ppm) and high ratio of Sr/Y (> 35) that resemble geochemical characteristics of adakite intrusions. The metaluminous to mildly peraluminous nature of granodiorite from Mashhad batholiths as well as its initial 87Sr/86Sr ratios (0.705469-0.706356), initial 143Nd/144Nd ratios (0.512204-0.512225) and ?Nd(t) values (- 2.7 to - 3.2) are typical of adakitic magmas generated by partial melting of a subducted slab. These magmas were then hybridized in the mantle wedge with peridotite melt. The quartz diorite-tonalite-granodiorite stock and granodiorite batholith could be considered as arc-related granitoid intrusions, which were emplaced during the northward subduction of Paleo-Tethys Ocean crust beneath the Turan micro-continent. The monzogranite is strongly peraluminous (Al2O3/(CaO + Na2O + K2O) Mol. = 1.07-1.17), alkali-rich with normative corundum ranging between 1.19% and 2.37%, has high initial 87Sr/86Sr ratios (0.707457-0.709710) and low initial 143Nd/144Nd ratios (0.512042-0.512111) and ?Nd(t) values (- 5.3 to - 6.6) that substantiate with geochemical attributes of S-type granites formed by dehydration-melting of heterogeneous metasedimentary assemblages in thickened lower continental crust. The monzogranite was emplaced as a consequence of high-temperature metamorphism during the final integration of Turan and Iran plates. The ages found in the Mashhad granites show that the subduction of Paleo-Tethys under the Turan plate that led to the generation of arc-related Mashhad granites in late-Triassic, finally ceased due to the collision of Iran and Turan micro-plates in early Jurassic.

  1. Growth of Megaspherulites In a Rhyolitic Vitrophyre

    NASA Technical Reports Server (NTRS)

    Smith, Robert K.; Tremallo, Robin L.; Lofgren, Gary E.

    2000-01-01

    Megaspherulites occur in the middle zone of a thick sequence of rhyolitic vitrophyre that occupies a small, late Eocene to early Oligocene volcanic-tectonic basin near Silver Cliff, Custer County, Colorado. Diameters of the megaspherulites range from 0.3 m to over 3.66 m, including a clay envelope. The megaspherulites are compound spherulites. consisting of an extremely large number (3.8 x 10(exp 9) to 9.9 x 10(exp 9)) of individual growth cones averaging 3 mm long by 1.25 mm wide at their termination. They are holocrystalline, very fine- to fine-grained, composed of disordered to ordered sanidine (orthoclase) and quartz, and surrounded by a thin K-feldspar, quartz rich rind, an inner clay layer with mordenite, and an outer clay layer composed wholly of 15 A montmorillonite. Whole rock analyses of the megaspherulites show a restricted composition from their core to their outer edge, with an average analyses of 76.3% SiO2, 0.34% CaO, 2.17% Na2O, 6.92% K2O, 0.83% H2O+ compared to the rhyolitic vitrophyre from which they crystallize with 71.07% SiO2, 0.57% CaO, 4.06% Na2O,4.l0% K2O, and 6.40% H2O+. The remaining oxides of Fe2O3 (total Fe), A12O3, MnO,MgO, TiO2, P2O5, Cr2O3, and trace elements show uniform distribution between the megaspherulites and the rhyolitic vitrophyre. Megaspherulite crystallization began soon after the rhyolitic lava ceased to flow as the result of sparse heterogeneous nucleation, under nonequilibrium conditions, due to a high degree of undercooling, delta T. The crystals grow with a fibrous habit which is favored by a large delta T ranging between 245 C and 295 C, despite lowered viscosity, and enhanced diffusion due to the high H2O content, ranging between 5% and 7%. Therefore, megaspherulite growth proceeded in a diffusion controlled manner, where the diffusion, rate lags behind the crystal growth rate at the crystal-liquid interface, restricting fibril lengths and diameters to the 10 micron to 15 micron and 3 micron and 8 micron ranges respectively. Once diffusion reestablishes itself at the crystallization front, a new nucleation event occurs at the terminated tips of the fibril cones and a new cone begins to develop with a similar orientation (small angle branching) to the earlier cones. During crystallization, these fibril cones impinge upon each other, resulting in fibril cone-free areas. These cone-free areas consist of coarser, fine-grained phases, dominated by quartz, which crystallized from the melt as it accumulated between the crystallizing K-feldspar fibrils of the cones. The anhydrous nature of the disordered to ordered sanidine (orthoclase) and quartz, suggests that water in the vitrophyre moved ahead of the crystallization front, resulting in a water rich fluid being enriched in Si, K, Na, Mg, Ca, Sr, Ba, and Y. The clay layers associated with the megaspherulites are therefore, the result of the deuteric alteration between the fractionated water and the vitrophyre, as indicated by the presence of the minerals mordenite and montmorillonite. This silica rich fluid also resulted in the total silicification of the megaspherulites within the upper 3 m of the vitrophyre.

  2. Progressive alkali ion exchange with stratigraphic position in a pyroclastic cooling-unit; Mt. Torro, Sabatini, Central Italy

    NASA Astrophysics Data System (ADS)

    Jrgensen, Jesper ksne; Holm, Paul Martin

    1998-11-01

    Significant variation of K 2O/Na 2O ratios and total alkali contents, elevated Loss on Ignition (12-16 wt.%) values and elevated Fe 3+/Fe 2+ are shown in new data from a road cut profile of pyroclastic rocks in an area of young ultra-potassic rocks. Decreasing K 2O/Na 2O ratios and total alkali contents are systematically related to stratigraphic position, being most pronounced at the centre of the deposit, probably because of the slower cooling rate. Pumice bombs are less altered than ash but show the same variation pattern. Except for the alkalis, hydration and the oxidation state of iron, the geochemical compositions of the rocks are unchanged.

  3. Tertiary epizonal plutonic rocks of the Selway-Bitterroot Wilderness, Idaho County, Idaho

    SciTech Connect

    Motzer, W.E.

    1996-01-01

    Geologic mapping in the Selway-Bitterroot Wilderness identified approximately 731 kmS of epizonal plutonic granitic rocks within the Bitterroot lobe of the Idaho batholith. From north to south, the intrusions are the Rock Lake Creek stock and the Whistling Pig, Running Creek, Bad Luck and Painted Rocks plutons. The stock and plutons consist of medium- to coarse-grained biotite and hornblende-biotite syenorgranite to monzogranite and quartz syenite capped by fine-grained biotite leucogranite. These rocks are intruded by late-synplutonic leucogranite dikes and post plutonic porphyritic rhyolite to rhyodacite and basalt dikes. The medium-grained granitic rocks are high in SiO2, K2O, Na2O, Ga, Th, U, W and Zr, but low in Al7O3, CaO, MgO, Cr, Ni, Co and V. Most of the granites are peraluminous. Rare-earth element (REE) plots (rock sample/chondrite) show enrichment in light REE over heavy REE with strong EU depletions. K-Ar biotite radiometric age determinations for medium-grained granites in all of the plutons range from approximately 51 Ma (Whistling Pig pluton) to 43.7 Ma (Painted Rocks pluton). Petrogenetic studies suggest that the plutons were rapidly emplaced to within 3.0 km of the paleosurface. The types, textures and color of the rocks result from devolatilization of the crystallizing melt and very low-grade hydrothermal alteration. The fluorine-rich melts are the fractionated with accumulate residue; they are considered to be anorogenic (A-type) granites intruded into the center of a metamorphic core complex.

  4. Geochemistry of rock units at the potential repository level, Yucca Mountain, Nevada

    USGS Publications Warehouse

    Peterman, Z.E.; Cloke, P.L.

    2002-01-01

    The compositional variability of the phenocryst-poor member of the 12.8 Ma Topopah Spring Tuff at the potential repository level was assessed by duplicate analysis of 20 core samples from the cross drift at Yucca Mountain, Nevada. Previous analyses of outcrop and core samples of the Topopah Spring Tuff showed that the phenocryst-poor rhyolite, which includes both lithophysal and nonlithophysal zones, is relatively uniform in composition. Analyses of rock samples from the cross drift, the first from the actual potential repository block, also indicate the chemical homogeneity of this unit excluding localized deposits of vapor-phase minerals and low-temperature calcite and opal in fractures, cavities, and faults. The possible influence of vapor-phase minerals and calcite and opal coatings on rock composition at a scale sufficiently large to incorporate these heterogeneously distributed deposits was evaluated and is considered to be relatively minor. Therefore, the composition of the phenocryst-poor member of the Topopah Spring Tuff is considered to be adequately represented by the analyses of samples from the cross drift. The mean composition as represented by the 10 most abundant oxides in wt. % or g/100 g is: SiO2, 76.29; Al2O3, 12.55; FeO, 0.14; Fe2O3, 0.97; MgO, 0.13; CaO, 0.50; Na2O, 3.52; K2O, 4.83; TiO2, 0.11; and MnO, 0.07. ?? 2002 Published by Elsevier Science Ltd.

  5. Mineralogy and geochemistry of pseudogley soils and recent alluvial clastic sediments in the Ngog-Lituba region, Southern Cameroon: An implication to their genesis

    NASA Astrophysics Data System (ADS)

    Ndjigui, Paul-Dsir; Ebah Abeng, Sandrine Appolonie; Ekomane, Emile; Nzeukou, Aubin Nzeugang; Ngo Mandeng, Francine Sidonie; Matoy Lindjeck, Marthe

    2015-08-01

    Mineralogical and geochemical investigations have been done on the hydromorphic clays (pseudogley soils and recent alluvial clastic sediments) in the Sanaga Maritime region (Southern Cameroon). Pseudogley soils are developed on gneisses from the Yaound Group. They have a dark brown to greyish brown color, with silty clay texture. Their mineral assemblage is made up of kaolinite, goethite, quartz, smectite, rutile, muscovite-illite and feldspars. The alluvial clastic sediments are characterized by variable colors (purple yellow, greenish, dark brown and purple brown) and sandy clay to clay texture. The mineral assemblage of alluvial clays is similar to that of pseudogley soils. SEM observations confirm the presence of kaolinite, smectite, quartz and muscovite-illite. Infrared data show that kaolinite is more orderly in pseudogley than in the alluvial clastic sediments. The Ngog-Lituba gneisses have moderate contents in SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O and several trace elements including REE. High element depletion is noticed in the pseudogley soils except Cr, V, Zr, Pb and REE. However, the alluvial clays are marked by a strong mobilization of LILE (Na, K, Ba, Rb and Sr) and REE, relative to the parent rock and pseudogley soils. The chondrite-normalized REE patterns are homogenous and parallel with Ce-anomalies. The (La/Yb)N shows that the REE fractionation increase from the parent rock to the alluvial clastic sediments. The mineralogical and geochemical features show that the clastic river sediments are derived from the erosion of the neighboring pseudogley materials before hydraulic sorting.

  6. Zircon saturation in silicate melts: a new and improved model for aluminous and alkaline melts

    NASA Astrophysics Data System (ADS)

    Gervasoni, Fernanda; Klemme, Stephan; Rocha-Júnior, Eduardo R. V.; Berndt, Jasper

    2016-03-01

    The importance of zircon in geochemical and geochronological studies, and its presence not only in aluminous but also in alkaline rocks, prompted us to think about a new zircon saturation model that can be applied in a wide range of compositions. Therefore, we performed zircon crystallization experiments in a range of compositions and at high temperatures, extending the original zircon saturation model proposed by Watson and Harrison (Earth Planet Sci Lett 64:295-304, 1983) and Boehnke et al. (Chem Geol 351:324-334, 2013). We used our new data and the data from previous studies in peraluminous melts, to describe the solubility of zircon in alkaline and aluminous melts. To this effect, we devised a new compositional parameter called G [ {( {3 \\cdot {{Al}}2 {{O}}3 + {{SiO}}2 )/({{Na}}2 {{O}} + {{K}}2 {{O}} + {{CaO}} + {{MgO}} + {{FeO}}} )} ] (molar proportions), which enables to describe the zircon saturation behaviour in a wide range of rock compositions. Furthermore, we propose a new zircon saturation model, which depends basically on temperature and melt composition, given by (with 1σ errors): ln [ {{Zr}} ] = ( {4.29 ± 0.34} ) - ( {1.35 ± 0.10} ) \\cdot ln G + ( {0.0056 ± 0.0002} ) \\cdot T( °C ) where [Zr] is the Zr concentration of the melt in µg/g, G is the new parameter representing melt composition and T is the temperature in degrees Celsius. The advantages of the new model are its straightforward use, with the G parameter being calculated directly from the molar proportions converted from electron microprobe measurements, the temperature calculated given in degrees Celsius and its applicability in a wider range of rocks compositions. Our results confirm the high zircon solubility in peralkaline rocks and its dependence on composition and temperature. Our new model may be applied in all intermediate to felsic melts from peraluminous to peralkaline compositions.

  7. Characterization of MSWI bottom ashes towards utilization as glass raw material.

    PubMed

    Monteiro, R C C; Figueiredo, C F; Alendouro, M S; Ferro, M C; Davim, E J R; Fernandes, M H V

    2008-01-01

    The characterization of the bottom ashes produced by two Portuguese municipal solid waste incinerators (MSWI) was performed with the aim of assessing the feasibility of using this waste as raw material in the production of glass that can be further processed as glass-ceramics for application in construction. Density and particle size distribution measurements were carried out for physical characterization. Chemical characterization revealed that SiO(2), a network glass former oxide, was present in a relatively high content (52-58wt%), indicating the suitability for this waste to be employed in the development of vitreous materials. CaO, Na(2)O and K(2)O, which act as fluxing agents, were present in various amounts (2-17wt%) together with several other oxides normally present in ceramic and glass raw materials. Mineralogical characterization revealed that the main crystalline phases were quartz (SiO(2)) and calcite (CaCO(3)) and that minor amounts of different alkaline and alkaline-earth aluminosilicate phases were also present. Thermal characterization showed that the decomposition of the different compounds occurred up to 1100 degrees C and that total weight loss was <10wt%. Heating both bottom ashes at 1400 degrees C for 2h resulted in a melt with suitable viscosity to be poured into a mould, and homogeneous black-coloured glasses with a smooth shiny surface were obtained after cooling. The vitrified bottom ashes were totally amorphous as confirmed by X-ray diffraction. The results from the present experimental work indicate that the examined bottom ashes can be a potential material to melt and to obtain a glass that can be further processed as glass-ceramics to be applied in construction. PMID:17604153

  8. Electron- and Photon-stimulated Desorption of Alkali Atoms from Lunar Sample and a Model Mineral Surface

    NASA Technical Reports Server (NTRS)

    Yakshinskiy, B. V.; Madey, T. E.

    2003-01-01

    We report recent results on an investigation of source mechanisms for the origin of alkali atoms in the tenuous planetary atmospheres, with focus on non-thermal processes (photon stimulated desorption (PSD), electron stimulated desorption (ESD), and ion sputtering). Whereas alkaline earth oxides (MgO, CaO) are far more abundant in lunar samples than alkali oxides (Na2O, K2O), the atmosphere of the Moon contains easily measurable concentrations of Na and K, while Ca and Mg are undetected there; traces of Ca have recently been seen in the Moon's atmosphere (10-3 of Na). The experiments have included ESD, PSD and ion sputtering of alkali atoms from model mineral surface (amorphous SiO2) and from a lunar basalt sample obtained from NASA. The comparison is made between ESD and PSD efficiency of monovalent alkalis (Na, K) and divalent alkaline earths (Ba, Ca).The ultrahigh vacuum measurement scheme for ESD and PSD of Na atoms includes a highly sensitive alkali metal detector based on surface ionization, and a time-of-flight technique. For PSD measurements, a mercury arc light source (filtered and chopped) is used. We find that bombardment of the alkali covered surfaces by ultraviolet photons or by low energy electrons (E>4 eV) causes desorption of hot alkali atoms. This results are consistent with the model developed to explain our previous measurements of sodium desorption from a silica surface and from water ice: electron- or photon-induced charge transfer from the substrate to the ionic adsorbate causes formation of a neutral alkali atom in a repulsive configuration, from which desorption occurs. The two-electron charge transfer to cause desorption of divalent alkaline eath ions is a less likely process.The data support the suggestion that PSD by UV solar photons is a dominant source process for alkalis in the tenuous lunar atmosphere.

  9. Origin of the disseminated magnetite pyroxenite in the Tieshanmiao-type iron deposits in the Wuyang region of Henan Province, China

    NASA Astrophysics Data System (ADS)

    Yao, Tong; Li, Hou-Min; Li, Wen-Jun; Li, Li-Xing; Zhao, Chuang

    2015-12-01

    The Tieshanmiao-type iron deposits in the southern North China Craton comprise two types of ores: banded pyroxene-magnetite quartzite (BMQ) and disseminated magnetite pyroxenite (DMP). Whether the quartz-poor DMP represents metamorphosed iron-bearing ultramafic rocks or chemical sedimentary rocks is still unclear. Pyroxene compositions in the DMP are low in Al2O3 and TiO2, which are similar to those from the BMQ and altered marble and pyroxenite. However, the compositions are different from those in the metamorphosed ultramafic rocks. The DMP and BMQ also show similar major element contents, with dominant SiO2, total Fe2O3, CaO, MgO but low contents of Al2O3, TiO2, MnO, Na2O, K2O, indicating a similar source through submarine chemical precipitation with little input from terrestrial or volcanic materials. The BMQ, DMP and magnetite separates from these rocks exhibit seawater-like signatures of REE patterns with LREE depletion, positive La, Gd and Y anomalies and high Y/Ho ratios, indicating that seawater participated in the formation of the iron ores. Combined with strong positive Eu anomalies, we infer that the deposition of the BMQ and DMP was mainly controlled by the mixing of seawater with hydrothermal fluids. The lack of negative Ce anomalies of the DMP, BMQ and magnetite separates indicate an anoxic marine environment. The DMP is rich in carbonate but relatively poor in silica and the BMQ is rich in silica but poor in carbonate. The protoliths of the DMP and BMQ in the Tieshanmiao-type iron deposits are inferred to be quartz-carbonate iron-bearing formations which underwent subsequent metamorphism.

  10. Porous and strong bioactive glass (13–93) scaffolds prepared by unidirectional freezing of camphene-based suspensions

    PubMed Central

    Liu, Xin; Rahaman, Mohamed N.; Fu, Qiang; Tomsia, Antoni P.

    2011-01-01

    Scaffolds of 13–93 bioactive glass (6Na2O, 12K2O, 5MgO, 20CaO, 4P2O5, 53SiO2; wt %) with an oriented pore architecture were formed by unidirectional freezing of camphene-based suspensions, followed by thermal annealing of the frozen constructs to grow the camphene crystals. After sublimation of the camphene, the constructs were sintered (1 h at 700 °C) to produce a dense glass phase with oriented macropores. The objective of this work was to study how constant freezing rates (1–7 °C/min) during the freezing step influenced the pore orientation and mechanical response of the scaffolds. When compared to scaffolds prepared by freezing the suspensions on a substrate kept at a constant temperature of 3 °C (time-dependent freezing rate), higher freezing rates resulted in better pore orientation, a more homogeneous microstructure, and a marked improvement in the mechanical response of the scaffolds in compression. Scaffolds fabricated using a constant freezing rate of 7 °C/min (porosity = 50 ± 4%; average pore diameter = 100 μm), had a compressive strength of 47 ± 5 MPa and an elastic modulus of 11 ± 3 GPa (in the orientation direction). In comparison, scaffolds prepared by freezing on the constant-temperature substrate had strength and modulus values of 35 ± 11 MPa and 8 ± 3 GPa, respectively. These oriented bioactive glass scaffolds prepared by the constant freezing rate route could potentially be used for the repair of defects in load-bearing bones, such as segmental defects in the long bones. PMID:21855661

  11. Oriented bioactive glass (13-93) scaffolds with controllable pore size by unidirectional freezing of camphene-based suspensions: microstructure and mechanical response

    PubMed Central

    Liu, Xin; Rahaman, Mohamed N.; Fu, Qiang

    2010-01-01

    Scaffolds of 13-93 bioactive glass (composition 6Na2O, 8K2O, 8MgO, 22CaO, 2P2O5, 54SiO2; mol %), containing oriented pores with controllable diameter, were prepared by unidirectional freezing of camphene-based suspensions (10 vol% particles) on a cold substrate (−196°C or 3°C). By varying the annealing time (0–72 h) to coarsen the camphene phase, constructs with the same porosity (86 ± 1%) but with controllable pore diameters (15–160 μm) were obtained after sublimation of the camphene. The pore diameters had a self-similar distribution that could be fitted by a diffusion-controlled coalescence model. Sintering (1 h at 690°C) was accompanied by a decrease in the porosity and pore diameter, the magnitude of which depended on the pore size of the green constructs, giving scaffolds with a porosity of 20–60% and average pore diameter of 6–120 μm. The compressive stress vs. deformation response of the sintered scaffolds in the orientation direction was linear, followed by failure. The compressive strength and elastic modulus in the orientation direction varied from 180 MPa and 25 GPa, respectively, (porosity = 20%) to 16 MPa and 4 GPa, respectively, (porosity = 60%), which were 2–3 times larger than the values in the direction perpendicular to the orientation. The potential use of these 13-93 bioactive glass scaffolds for the repair of large defects in load-bearing bones, such as segmental defects in long bones, is discussed. PMID:20807594

  12. Constraints on abundance, composition, and nature of X-ray amorphous components of soils and rocks at Gale crater, Mars

    NASA Astrophysics Data System (ADS)

    Dehouck, Erwin; McLennan, Scott M.; Meslin, Pierre-Yves; Cousin, Agns.

    2014-12-01

    X-ray diffraction patterns of the three samples analyzed by Curiosity's Chemistry and Mineralogy (CheMin) instrument during the first year of the Mars Science Laboratory missionthe Rocknest sand, and the John Klein and Cumberland drill fines, both extracted from the Sheepbed mudstoneshow evidence for a significant amorphous component of unclear origin. We developed a mass balance calculation program that determines the range of possible chemical compositions of the crystalline and amorphous components of these samples within the uncertainties of mineral abundances derived from CheMin data. In turn, the chemistry constrains the minimum abundance of amorphous component required to have realistic compositions (all oxides ? 0 wt %): 21-22 wt % for Rocknest and 15-20 wt % for Cumberland, in good agreement with estimates derived from the diffraction patterns (~27 and ~31 wt %, respectively). Despite obvious differences between the Rocknest sand and the Sheepbed mudstone, the amorphous components of the two sites are chemically very similar, having comparable concentrations of SiO2, TiO2, Al2O3, Cr2O3, FeOT, CaO, Na2O, K2O, and P2O5. MgO tends to be lower in Rocknest, although it may also be comparable between the two samples depending on the exact composition of the smectite in Sheepbed. The only unambiguous difference is the SO3 content, which is always higher in Rocknest. The observed similarity suggests that the two amorphous components share a common origin or formation process. The individual phases possibly present within the amorphous components include: volcanic (or impact) glass, hisingerite (or silica + ferrihydrite), amorphous sulfates (or adsorbed SO42-), and nanophase ferric oxides.

  13. Comparing results from two continental geochemical surveys to world soil composition and deriving Predicted Empirical Global Soil (PEGS2) reference values

    NASA Astrophysics Data System (ADS)

    de Caritat, Patrice; Reimann, Clemens; Bastrakov, E.; Bowbridge, D.; Boyle, P.; Briggs, S.; Brown, D.; Brown, M.; Brownlie, K.; Burrows, P.; Burton, G.; Byass, J.; de Caritat, P.; Chanthapanya, N.; Cooper, M.; Cranfield, L.; Curtis, S.; Denaro, T.; Dhnaram, C.; Dhu, T.; Diprose, G.; Fabris, A.; Fairclough, M.; Fanning, S.; Fidler, R.; Fitzell, M.; Flitcroft, P.; Fricke, C.; Fulton, D.; Furlonger, J.; Gordon, G.; Green, A.; Green, G.; Greenfield, J.; Harley, J.; Heawood, S.; Hegvold, T.; Henderson, K.; House, E.; Husain, Z.; Krsteska, B.; Lam, J.; Langford, R.; Lavigne, T.; Linehan, B.; Livingstone, M.; Lukss, A.; Maier, R.; Makuei, A.; McCabe, L.; McDonald, P.; McIlroy, D.; McIntyre, D.; Morris, P.; O'Connell, G.; Pappas, B.; Parsons, J.; Petrick, C.; Poignand, B.; Roberts, R.; Ryle, J.; Seymon, A.; Sherry, K.; Skinner, J.; Smith, M.; Strickland, C.; Sutton, S.; Swindell, R.; Tait, H.; Tang, J.; Thomson, A.; Thun, C.; Uppill, B.; Wall, K.; Watkins, J.; Watson, T.; Webber, L.; Whiting, A.; Wilford, J.; Wilson, T.; Wygralak, A.; Albanese, S.; Andersson, M.; Arnoldussen, A.; Baritz, R.; Batista, M. J.; Bel-lan, A.; Birke, M.; Cicchella, C.; Demetriades, A.; Dinelli, E.; De Vivo, B.; De Vos, W.; Duris, M.; Dusza-Dobek, A.; Eggen, O. A.; Eklund, M.; Ernstsen, V.; Filzmoser, P.; Finne, T. E.; Flight, D.; Forrester, S.; Fuchs, M.; Fugedi, U.; Gilucis, A.; Gosar, M.; Gregorauskiene, V.; Gulan, A.; Halami?, J.; Haslinger, E.; Hayoz, P.; Hobiger, G.; Hoffmann, R.; Hoogewerff, J.; Hrvatovic, H.; Husnjak, S.; Janik, L.; Johnson, C. C.; Jordan, G.; Kirby, J.; Kivisilla, J.; Klos, V.; Krone, F.; Kwecko, P.; Kuti, L.; Ladenberger, A.; Lima, A.; Locutura, J.; Lucivjansky, P.; Mackovych, D.; Malyuk, B. I.; Maquil, R.; McLaughlin, M.; Meuli, R. G.; Miosic, N.; Mol, G.; Ngrel, P.; O'Connor, P.; Oorts, K.; Ottesen, R. T.; Pasieczna, A.; Petersell, V.; Pfleiderer, S.; Po?avi?, M.; Prazeres, C.; Rauch, U.; Reimann, C.; Salpeteur, I.; Schedl, A.; Scheib, A.; Schoeters, I.; Sefcik, P.; Sellersj, E.; Skopljak, F.; Slaninka, I.; ora, A.; Srvkota, R.; Stafilov, T.; Tarvainen, T.; Trendavilov, V.; Valera, P.; Verougstraete, V.; Vidojevi?, D.; Zissimos, A. M.; Zomeni, Z.

    2012-02-01

    Analytical data for 10 major oxides (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2 and TiO2), 16 total trace elements (As, Ba, Ce, Co, Cr, Ga, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn and Zr), 14 aqua regia extracted elements (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo and Pb), Loss On Ignition (LOI) and pH from 3526 soil samples from two continents (Australia and Europe) are presented and compared to (1) the composition of the upper continental crust, (2) published world soil average values, and (3) data from other continental-scale soil surveys. It can be demonstrated that average upper continental crust values do not provide reliable estimates for natural concentrations of elements in soils. For many elements there exist substantial differences between published world soil averages and the median concentrations observed on two continents. Direct comparison with other continental datasets is hampered by the fact that often mean, instead of the statistically more robust median, is reported. Using a database of the worldwide distribution of lithological units, it can be demonstrated that lithology is a poor predictor of soil chemistry. Climate-related processes such as glaciation and weathering are strong modifiers of the geochemical signature inherited from bedrock during pedogenesis. To overcome existing shortcomings of predicted global or world soil geochemical reference values, we propose Preliminary Empirical Global Soil reference values based on analytical results of a representative number of soil samples from two continents (PEGS2).

  14. Chemical modifications accompanying blueschist facies metamorphism of Franciscan conglomerates, Diablo Range, California

    USGS Publications Warehouse

    Moore, Diane E.; Liou, J.G.; King, B.-S.

    1981-01-01

    As part of an investigation of blueschist-facies mineral parageneses in pebbles and matrix of some Franciscan metaconglomerates of the Diablo Range, California, textural and major-element chemical analyses were conducted on a number of igneous pebbles that comprise a range of rock types from granite and dacite to gabbro and basalt. Compositions of the igneous pebbles differ significantly from common igneous rocks, particularly with respect to Ca, K, Na, Si and H2O. The SiO2 and H2O contents are characteristically high and the K2O contents low. The CaO and Na2O contents may be relatively enriched or reduced in different pebbles. The igneous pebbles show little evidence of alteration prior to their incorporation into the Franciscan conglomerates, and the chemical modifications are considered to have been produced during metamorphism of the conglomerates to (lawsonite + albite + aragonite ?? jadeite)-bearing assemblages. The observed variations in the pebbles are shown to be functions of: (1) bulk chemistry; (2) the igneous mineral assemblage; (3) the stable metamorphic mineral assemblage; and (4) the composition of pore fluids in the conglomerates. The relative proportions of Mg and Fe in most of the pebbles apparently have been unaffected by the metamorphism, and these parameters, along with other textural and chemical factors, were used to determine the petrogenetic affinities of the igneous pebbles. The plutonic and most of the volcanic pebbles correspond to calc-alkaline rock series, whereas a few volcanic pebbles show apparent Fe-enrichment characteristic of tholeiitic rocks. A continental margin arc-batholith complex would be the best source for these igneous detrital assemblages. Conglomerates in local areas differ in igneous lithologies from conglomerates in other areas and probably differ somewhat in age, perhaps reflecting varying degrees of unroofing of such a complex during deposition of Franciscan sediments. ?? 1981.

  15. Melt inclusions in quartz from an evolved peraluminous pegmatite: Geochemical evidence for strong tin enrichment in fluorine-rich and phosphorus-rich residual liquids

    NASA Astrophysics Data System (ADS)

    Webster, James D.; Thomas, Rainer; Rhede, Dieter; Frster, Hans-Jrgen; Seltmann, Reimar

    1997-07-01

    We have investigated the magmatic evolution of a late-stage, F- and P-rich, pegmatite-forming aluminosilicate liquid and the geochemical controls on magmatic mineralizing processes by remelting totally-crystallized melt inclusions in quartz and analyzing the quenched glass by EPMA and SIMS. The quartz phenocrysts were sampled from a pegmatite that occurs in a Variscan granite genetically associated with cassiterite- and wolframite-mineralized greisen veins at the Ehrenfriedersdorf Sn?W deposit, central Erzgebirge, SE Germany. The melt inclusion compositions imply that the pegmatite-forming liquid achieved extreme levels of chemical differentiation. It contained high abundances of Sn, F, P, Li, Rb, Cs, Nb, Ta, and Be and abnormally low concentrations of Ca, Y, Sr, and REE for a granite, and it was strongly peraluminous (the molar [Al 2O 3/CaO + Na 2O + K 2O] ranged from 1.3 to 2.0). Fractions of the pegmatite-forming liquid were extremely enriched in P 2O 5 + F + Al 2O 3, and the molar abundances of (F + P) in the glasses correlate strongly with moles of network-modifying Al ions implying that the bulk liquid included F-, P-, and Al-bearing complexes. Formation of these complexes reduced the activities of F, P, and Al in bulk liquid, suppressed the crystallization of magmatic topaz and P-rich minerals, and allowed the liquid to become enriched in these constituents. Some fractions of the Ehrenfriedersdorf aluminosilicate liquid contained 1000-2000 ppm Sn. These levels of Sn enrichment were up to 2 orders of magnitude greater than that ever reported for nonmineralized, metaluminous and peraluminous igneous materials and are consistent with some experimentally-derived Sn solubilities in cassiterite-saturated granitic liquids at geologically relevant pressures and temperatures. This concordance implies that cassiterite could have crystallized directly from this highly evolved, P- and F-rich peraluminous granitic liquid without the involvement of hydrothermal fluids.

  16. In vitro bioactivity of S520 glass fibers and initial assessment of osteoblast attachment.

    PubMed

    Clupper, D C; Gough, J E; Hall, M M; Clare, A G; LaCourse, W C; Hench, L L

    2003-10-01

    Bioactive glass fibers are attractive materials for use as tissue-engineering scaffolds and as the reinforcing phase for resorbable bioactive composites. The bioactivity of S520 glass fibers (52.0 mol % SiO(2), 20.9 Na(2)O, 7.1 K(2)O, 18.0 CaO, and 2.0 P(2)O(5)) was evaluated in two media, simulated body fluid (SBF) and Dulbecco's modified Eagle's medium (DMEM), for up to 20 days at 37 degrees C. Hydroxyapatite formation was observed on S520 fiber surfaces after 5 h in SBF. After a 20-day immersion, a continuous hydroxyapatite layer was present on the surface of samples immersed in SBF as well as on those samples immersed in DMEM [fiber surface area to solution volume ratio (SA:V) of 0.10 cm(2)/mL]. Backscattered electron imaging and EDS analysis revealed that the hydroxyapatite layer formation was more extensive for samples immersed in SBF. Decreasing the SA:V ratio to 0.05 cm(2)/mL decreased the time required to form a continuous hydroxyapatite surface layer. ICP was used to reveal Si, Ca, and P release profiles in DMEM after the 1st h (15.1, 83.8, and 29.7 ppm, respectively) were similar to those concentrations previously determined to stimulate gene expression in osteoblasts in vitro (16.5, 83.3, and 30.4 ppm, respectively). The tensile strength of the 20-microm diameter fibers was 925 +/- 424 MPa. Primary human osteoblast attachment to the fiber surface was studied by using SEM, and mineralization was studied by using alizarin red staining. Osteoblast dorsal ruffles, cell projections, and lamellipodia were observed, and by 7 days, cells had proliferated to form monolayer areas as shown by SEM. At 14 days, nodule formation was observed, and these nodules stained positive for alizarin red, demonstrating Ca deposition and, therefore mineralization. PMID:14517888

  17. Copper-doped borosilicate bioactive glass scaffolds with improved angiogenic and osteogenic capacity for repairing osseous defects.

    PubMed

    Zhao, Shichang; Wang, Hui; Zhang, Yadong; Huang, Wenhai; Rahaman, Mohamed N; Liu, Zhongtang; Wang, Deping; Zhang, Changqing

    2015-03-01

    There is growing interest in the use of synthetic biomaterials to deliver inorganic ions that are known to stimulate angiogenesis and osteogenesis in vivo. In the present study, we investigated the effects of varying amounts of copper in a bioactive glass on the response of human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro and on blood vessel formation and bone regeneration in rat calvarial defects in vivo. Porous scaffolds of a borosilicate bioactive glass (composition 6Na2O, 8K2O, 8MgO, 22CaO, 36B2O3, 18SiO2, 2P2O5, mol.%) doped with 0.5, 1.0 and 3.0wt.% CuO were created using a foam replication method. When immersed in simulated body fluid, the scaffolds released Cu ions into the medium and converted to hydroxyapatite. At the concentrations used, the Cu in the glass was not toxic to the hBMSCs cultured on the scaffolds in vitro. The alkaline phosphatase activity of the hBMSCs and the expression levels of angiogenic-related genes (vascular endothelial growth factor and basic fibroblast growth factor) and osteogenic-related genes (runt-related transcription factor 2, bone morphogenetic protein-2 and osteopontin) increased significantly with increasing amount of Cu in the glass. When implanted in rat calvarial defects in vivo, the scaffolds (3wt.% CuO) significantly enhanced both blood vessel formation and bone regeneration in the defects at 8weeks post-implantation. These results show that doping bioactive glass implants with Cu is a promising approach for enhancing angiogenesis and osteogenesis in the healing of osseous defects. PMID:25534470

  18. Description and interpretation of the composition of fluid and alteration mineralogy in the geothermal system, at Svartsengi, Iceland

    NASA Astrophysics Data System (ADS)

    Vala Ragnarsdttir, Kristn; Walther, John V.; Arnrsson, Stefn

    1984-07-01

    The bulk composition and mineralogy of hydrothermally altered tholeiite, along with the composition and speciation of fluid, have been determined for a well-defined alteration zone at 240C and 110 bars at Svartsengi, Iceland. Mass balances between the geothermal fluid and altered tholeiite, relative to a seawater/fresh water mixture and unaltered tholeiite, indicate the overall reaction per 1000 cm 3 is: 1325 gm plagioclase + 1228 gm pyroxene + 215 gm oxide-minerals break down to form 685 gm chlorite + 636 gm albite + 441 gm quartz + 249 gm epidote + 266 gm calcite + 201 gm oxide-minerals + 15 gm pyrite, requiring an influx of 123 gm CO 2, 10 gm H 2S and 4 gm Na 2O and a release of 57 gm SiO 2, 35 gm FeO, 21 gm CaO, 8 gm MgO and 4 gm K 2O. Principal reactions, deduced from textural evidence, include Na-Ca exchange in plagioclase, precipitation of quartz, calcite and anhydrite, and formation of chlorite and epidote by reactions between groundmass minerals and fluid. Thermodynamic analyses of authigenic minerals and downhole fluid indicate that the fluid maintains a state close to equilibrium with the secondary mineral phases chlorite, epidote, albite, quartz, calcite, prehnite, anhydrite, pyrite and magnetite, whereas remnant primary labradorite and augite are out of equilibrium with the fluid. Water/rock ratios for the system are determined under a variety of assumptions. However, the open nature of the system makes comparisons with experimental and theoretical closed system studies ambiguous.

  19. Lower Brioverian formations (Upper Proterozoic) of the Armorican Massif (France): geodynamic evolution of source areas revealed by sandstone petrography and geochemistry

    NASA Astrophysics Data System (ADS)

    Dabard, Marie Pierre

    1990-11-01

    Formations with interbedded cherts constitute an important part of the Lower Brioverian succession (Upper Proterozoic age) in the Armorican Massif (northwest France). These formations are composed of shale-sandstone alternations with interbedded siliceous carbonaceous members. Petrographic and geochemical study of the detrital facies shows that these rocks are compositionally immature. The wackes are rich in lithic fragments (volcanic fragments: 3-20% modal; sedimentary and metamorphic fragments: 0-7% modal) and in feldspar (5-16%). From the geochemical point of view, they are relatively enriched in Fe 2+MgO (about 5.5%) and in alkalis with {Na 2O }/{K 2O } ratios greater than 1. The CaO contents are low (about 0.3%). Slightly negative Eu anomalies are observed ( {Eu}/{Eu ?} = 0.8 ). Their chemical compositions are in agreement with a dominantly acidic source area with deposition in a continental active margin setting. Compared with other Upper Proterozoic deposits of the Armorican Massif, the interbedded-chert formations appear rather similar to other deposits in North Brittany which accumulated in an intra-arc or back-arc basin environment. The formations with interbedded cherts are interpreted as having been deposited during an early stage of magmatic arc activity (around 640-630 Ma ago) in an immature marginal basin. The clastic supply to these formations is derived in part from early volcanic products (acidic to intermediate) which are linked to subduction beneath the North Armorican Domain. Another component is inherited from the reworking of 2000 Ma old basement relics. The opening of the back-arc domain, with associated basaltic volcanism, would bring about a progressive displacement of the interbedded-chert depositional basin towards the continental margin.

  20. Differentiation in the cumulates from a Mauna Loa, Hawaii magma chamber

    SciTech Connect

    Schwindinger, K.R.; Anderson, A.F.

    1985-01-01

    The interstitial glass in cognate nodules from Mauna Loa, has by chemical diffusion or convective fluid transport, remained in equilibrium with the overlying magma. The glass bearing nodules were collected from Damona Cone on the southwest rift zone of Mauna Loas. The nodules have approximately 15% olivine, 40% orthopyroxene plus clinopyroxene (3-20%), and 85% plagioclase plus vescicular glass (2-25%). Olivine norites have anhedral olivine mantled with anhedral orthopyroxene, subhedral to euhedral pyroxene, anhedral plagioclase, and 20 to 25% glass. Olivine gabbros have anhedral olivine, subequant, anhedral to subhedral pyroxene and plagioclase and less than 10% glass. The bulk composition of greater than 15%, MgO, with the textures, indicate the nodules are an accumulative origin. Thus these nodules are partially solidified pieces of crystal/liquid accumulative mush. The compositions of the olivines are Fa 18 to 25 mole percent, of the plagioclases are An 70 to 80 mole percent. The composition of the orthopyroxene is En76 Fs19 Wo5, and of the clinopyroxene is En50 Fall Wo30. The composition of the interstitial glasses is: SiO2 52.54, TiO2 2.04, Al2O3 14.39, FeO 11.47, MgO 7.15, CaO 10.28, Na20 1.42, K2O 0.39, P2O5 0.21. The low Na2O is from two nodules that may have experienced high temperature alteration. The uniformity of the glass composition, in contrast to its large variation in the mode, suggests the interstitial liquid in the mush has remained in equilibrium with some large reservoir of MgO rich liquid, such as the magma above the mush. Two possible mechanisms of cation exchange between the magma and the interstitial liquid of the mush are chemical diffusion and convective fluid transport.

  1. Partial melting of apatite-bearing charnockite, granulite, and diorite: Melt compositions, restite mineralogy, and petrologic implications

    NASA Technical Reports Server (NTRS)

    Beard, James S.; Lofgren, Gary E.; Sinha, A. Krishna; Tollo, Richard P.

    1994-01-01

    Melting experiments (P = 6.9 kbar, T = 850-950 deg C, NNO is less than fO2 is less than HM) were done on mafic to felsic charnockites, a dioritic gneiss, and a felsic garnet granulite, all common rock types in the Grenville basement of eastern North America. A graphite-bearing granulite gneiss did not melt. Water (H2O(+) = 0.60 to 2.0 wt %) is bound in low-grade, retrograde metamorphic minerals and is consumed during the earliest stages of melting. Most melts are water-undersaturated. Melt compositions range from metaluminous, silicic granodiorite (diorite starting composition) to peraluminous or weakly metaluminous granites (all others). In general, liquids become more feldspathic, less silicic, and less peraluminous and are enriched in FeO, MgO, and TiO2 with increasing temperature. Residual feldspar mineralogy controls the CaO, K2O, and Na2O contents of the partial melts and the behavior of these elements can be used, particularly if the degree of source melting can be ascertained, to infer some aspects of the feldspar mineralogy of the source. K-feldspar, a common restite phase in the charnockite and granulite (but not the diorite) should control the behavior of Ba and, possibly, Eu in these systems and yield signatures of these elements that can distinguish source regions and, in some cases, bulk versus melt assimilation. Apatite, a common restite phase, is enriched in rare earth elements (REE), especially middle REE. Retention of apatite in the restite will result in steep, light REE-enriched patterns for melts derived from the diorite and charnockites.

  2. Alteration of plagioclase to nepheline in the Khariar alkaline complex, SE India: Constraints on metasomatic replacement reaction mechanisms

    NASA Astrophysics Data System (ADS)

    Upadhyay, Dewashish

    2012-12-01

    At the Khariar alkaline complex in southeastern India, some tholeiitic amphibolites inter-layered with syenite and nepheline syenite show microtextural evidence of fenitization. Typical metasomatic textures include the replacement of plagioclase by vein nepheline and albitic-plagioclase or by symplectitic nepheline + albite + Na-Al-rich clinopyroxene. Whole rock mass balance calculations indicate that the fenitized variants gained alkalis (Na + K), some large ion lithophile elements (Sr, Rb and Ba) and high field strength elements like Zr and Hf during the metasomatic exchange. The plagioclase replacement textures can be explained by a fluid-mediated coupled dissolution-reprecipitation process whereby the infiltration of alkali-bearing fluid along grain boundaries and deformation-induced intragranular fractures led to the dissolution of the host plagioclase along an inward moving reaction interface. Na+ ions were introduced and Ca2 + ions removed by the fluid phase. The Al and Si released from the breakdown of the anorthite component of the plagioclase combined with Na+ from the fluid to precipitate nepheline + albitic-plagioclase or Na-Al-rich clinopyroxene. Reaction enhanced cracking during metasomatism due to local volume changes in the alteration zone produced a hierarchical system of fractures. Mass-balance calculations using the volume proportion of phases in the plagioclase replacement zones show that SiO2 and Al2O3 were broadly conserved during the replacement; there was significant loss of CaO (ca. 73%) and huge gains of Na2O and K2O. These results indicate that alkali and alkaline elements (Na, K and Ca) were exchanged freely between the fluid phase and the reaction zone whereas Si and Al released during plagioclase dissolution were consumed in the replacement zone itself to form nepheline and albite-rich plagioclase or Na-Al-rich clinopyroxene. The trace element and Sr-Nd isotope signature of the rocks indicate that the fenitizing fluids were derived from the nepheline syenites.

  3. On trondhjemite pebbles from the late Pan-African Um Had conglomerate, Eastern Desert, Egypt

    NASA Astrophysics Data System (ADS)

    El-Bouseily, Ahmed M.

    This paper deals with the petrography and geochemistry of granitic pebbles from the late Pan-African Um Had conglomerate, in eastern Egypt. The analyzed samples show consistently high SiO 2 (69.16-74.47%) and Na 2O (3.05-7.1%), low K 2O (0.88-2.57%), CaO (0.43-2.66%) and FeO ∗ + MgO (1.55-7.35%). Al 2O 3 is in most cases less than 15%. These major element characteristics would class the rock type of the pebbles as low-Al 2O 3 trondhjemite similar to that of SW Finland. Compared to average chemical compositions of different basement rock units in eastern Egypt, the analyzed pebbles are similar to some members of the Older Granites. Both are characteristically low in their LIL-element contents. Therefore, Older Granites are probably the main source for the clast assemblages of the Um Had conglomerate. A magmatic origin is proposed for the Older Granites, their Na-enrichment and K-depletion being interpreted as primary features inherited from a basaltic parent source. This is also indicated by the unusually high mean abundances of Cr (106 ppm) and Ni (61 ppm) in the analyzed pebbles. The spatial relationship between metavolcanics and granitic rocks in eastern Egypt may imply that they are linked to a common origin in the lower crust or upper mantle. The model proposed here for the granitic rocks is one in which at least some members of the Na-rich granites (Older Granites) were formed by partial melting of the Older Metavolcanics via trondhjemite trends. Remelting of the sodic granites and their extrusive equivalents gave rise to potassic granites (Younger Granites) via calc-alkaline trends in later Precambrian times. However, data on REE contents in Egyptian granites are needed to fully characterize the paleotectonic setting.

  4. Origin of I- and A-type granitoids from the Eastern Desert of Egypt: Implications for crustal growth in the northern Arabian Nubian Shield

    NASA Astrophysics Data System (ADS)

    Farahat, E. S.; Mohamed, H. A.; Ahmed, A. F.; El Mahallawi, M. M.

    2007-09-01

    I- and A-type granitoid rocks, emplaced during pre- and post-collision stages, respectively, of the Neoproterozoic Pan-African Orogeny, are widely distributed in the Eastern Desert of Egypt, constituting ˜60% of the basement outcrop. Petrological and geochemical data are presented for a selection of the two groups, the I-type, El Bula tonalite-granodiorite suite, and the A-type, Lômân alkali granites, with the aim of discussing their origin and geotectonic implications. The El Bula (EB) rocks have geochemical characteristics of medium-K calc-alkaline, metaluminous to mildly peraluminous, granitoids formed in an island-arc environment. The Lômân (LM) granites display midalkaline, metaluminous, post-orogenic, A-type characteristics. With respect to the EB granitoids, the LM granites contain lower Al 2O 3, Fe 2O 3, MgO, MnO, CaO, TiO 2, Sr, Ba, and V, but higher Na 2O, K 2O, Nb, Zr, Th, and Rb. The I-type granitoids were presumably formed by high degrees of partial melting (˜40%) of a mafic (amphibolitic), lower crustal source, whereas the A-type granites are derived from a tonalitic, middle crustal source, followed by some crystal fractionation. Such high degrees of partial melting attest to the large areal distribution of these rocks and require broad thermal anomalies, likely related to significant geodynamic features of the Arabian-Nubian Shield (ANS) evolution. We propose petrogenetic models involving an upwelling of hot asthenospheric mantle, due to oblique convergence during the pre-collision stage, and following a lithospheric delamination during the post-collision stage. Such asthenosphere uprise could account for the high crustal growth rate of the ANS.

  5. Petrological and geochemical comparition between the upper and lower rhyolite of the Binchuan basaltic profile,Emeishan LIP succession

    NASA Astrophysics Data System (ADS)

    Huixin, H.; Yu, W.

    2013-12-01

    Emeishan basalt is well known worldwide,and it has been well tested from the geochemistry and petrology.However,the eruptional rock sequences is rare reported. Some former work reported that on the top of Emeishan basalt,there is always sit with rhyolite(or felsic-composition,mainly are rhyolite and trachyte ).This work is focusing on newly found rhyolite and trachyte succession at the bottom of Binchuan basalt pofile,and the comparition between the bottom and top felsic-composition of the Binchuan pofile basaltic related succession from petrological and geochemistry points. The bottom rhyolite is lack of phenocryst,and the filling of blowhole is observed quartz only. Otherwise,the phenocryst of the top rhyolite is mainly alkaline-feldspar. The upper layered rhyolite is less sillical rich than the lower part with the content of SiO2 65-70,68-74 respectively. Additionally,the content of TiO2 (0.82-0.87,0.57-0.70),Total Fe2O3(5.15-5.87,2.89-4.88),MgO(2.13-2.64,0.19-0.48),CaO(1.18-1.49,0.13-0.42), P2O5(0.18-0.25,0.02-0.25) of the upper layered rhyolite is more abundant than the lower layer. However,the amount of the Na2O,K2O of both upper and lower rhyolite can not be distinguished clearly as weathering effect suspectively. This may note that the two kinds of rhyolite are formed from different geological process. The upper may due to the crystallization differentiation of the mafic magmas ,while the lower is formed in the result of crust remelting.

  6. Paleoenvironmental History of the Retezat Mountains (Southern Carpathians) Inferred from Geochemical Data

    NASA Astrophysics Data System (ADS)

    Hubay, Katalin; Braun, Mihály; Harangi, Sándor; Magyari, Enikő

    2014-05-01

    This study applied lake sediment geochemistry to reconstruct climate changes in the Southern Carpathians within the frame of PROLONG (Providing long environmental records of Late Quaternary climatic oscillations in the Retezat Mountains) project. The main aim of this project is to reconstruct the changes during the Lateglacial and the Early Holocene period in the Retezat Mountains, Southern Carpathians. After retreat of the last major glaciers numerous glacial lakes leaving behind with sediments dating back to ca. 16,000 cal. yr BP. In 2007 and 2008 continuous undisturbed sediment cores were obtained from four glacial lakes (Brazi, Gales, Lia, Bukura) in the Retezat Mts. (Southern Carpathians, Romania) with Livingstone and modified Kullenberg corers. Two of the studied lakes are located on the southern slope (Bukura, Lia) of the mountain, while the Brazi and Gales are situated on the northern slope. After the drillings, the sediment cores were sliced into 1 cm wide subsamples. High-resolution geochemical analysis was done to study soil development an in-lake processes in response to high-frequency and high-amplitude climatic changes within the Lateglacial and Early Holocene. Loss-on-ignition was used to determining the sediment organic matter content. Total element concentrations were measured using an Inductive Coupled Plasma Optical Emission Spectrometer (ICP-OES) and Microwave Plasma Atomic Emission Spectrometer (MP-AES). Concentration of major elements by means of bulk analysis were determined and calculated in oxide forms (Al2O3, SiO2, TiO2, CaO, MgO, K2O, Na2O, Fe2O3, MnO, SO3). Multivariate statistical analyses (PCA, LDA) and cluster analysis were performed on geochemical records. The sediments deposited during the cold and warm period of Lateglacial and Early Holocene showed significantly different chemical compositions. The results indicate that the detailed geochemical analysis on the sediment has the potential to reflect past climatic conditions.

  7. Deciphering heavy metal contamination zones in soils of a granitic terrain of southern India using factor analysis and GIS

    NASA Astrophysics Data System (ADS)

    Purushotham, D.; Lone, Mahjoor Ahmad; Rashid, Mehnaz; Rao, A. Narsing; Ahmed, Shakeel

    2012-08-01

    Soil contamination by heavy metals has been a major concern for last few decades due to increase in urbanization and industrialization. The main objective of this research was to identify the heavy metal contaminated zones in the study area. Twenty five soil samples collected throughout the agriculture, residential and industrial areas were analysed by X-ray Fluorescence Spectrometer (XRF) for trace metals and major oxides. These metals can affect the quality of soil and infiltrate through the soil, thereby causing groundwater pollution. Based on the chemical analysis of major oxides (SiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, TiO2, and P2O5) and their distribution; it is observed that these soils are predominantly siliceous type with slight enrichment of alumina component in the study area. Correlation matrix (CM) and factor analysis (FA) is employed to the heavy metal variables, viz., Ba, Cr, Cu, Ni, Pb, Rb, Sr, V, Y, Zn and Zr of the soil to determine the dominant factors contributing to the soil contamination in the area. In the analysis, five factors emerged as significant contributors to the soil quality. The total contribution of these five factors is about 90%. The contribution of the first factor is about 45% and has significant positive loadings of Co, Cr, Cu, Ni and Zn. The contribution of second factor is 22% and has significant positive loadings of Rb, Sr and Y. The contribution of third, fourth and fifth factors is 10, 8 and 5% and show positive loadings for lead, molybdenum and barium respectively to the soil contamination. The spatial variation maps deciphering different zones of heavy metal concentration in the soil were generated in a GIS (geographic information system) based environment using ArcGIS 9.3.1. The results reveal that heavy metal contamination in the area is mainly due to anthropogenic activities.

  8. Synthesis and characterization of TiO2-pillared Romanian clay and their application for azoic dyes photodegradation.

    PubMed

    Dvininov, E; Popovici, E; Pode, R; Cocheci, L; Barvinschi, P; Nica, V

    2009-08-15

    The synthesis and properties of metal oxide pillared cationic clays (PILCs) has been subject to numerous studies in the last decades. In order to obtain TiO(2)-pillared type materials, sodium montmorillonite from Romania-areal of Valea Chioarului, having the following composition (% wt): SiO(2)-72.87; Al(2)O(3)-14.5; MgO-2.15; Fe(2)O(3)-1.13; Na(2)O-0.60; K(2)O-0.60; CaO-0.90; PC-5.70 and cation exchange capacity, determined by ammonium acetate method, of 82 meq/100g, as matrix, was used. Sodium form of the clay was modified, primarily, by intercalation of cetyl-trimethylammonium cations between negatively charged layers which will lead to the expansion of the interlayer space. For the preparation of the TiO(2)-pillared clay, the alkoxide molecules, as titania precursor, were adsorbed onto/into clay samples (1 mmol Ti/g clay), in hydrochloric acid environment, the resulted species being converted into TiO(2) pillars by calcination. The as-prepared materials have been used as catalysts for Congo Red dye photodegradation, under UV. The photocatalytic activity of the pillared clays is a function of TiO(2) pillars size, their increase leading to the enhancement of the contact areas between dye solution and photoactive species present in the interlayer space. The structural characteristics and properties of the obtained materials were investigated by X-ray Diffraction, Thermogravimetry Analysis, UV-vis Diffuse Reflectance, Transmission Electron Microscopy and Energy Dispersive X-ray Analysis. PMID:19250741

  9. Authenticity and provenance studies of copper-bearing andesines using Cu isotope ratios and element analysis by fs-LA-MC-ICPMS and ns-LA-ICPMS.

    PubMed

    Fontaine, Gisela H; Hametner, Kathrin; Peretti, Adolf; Gnther, Detlef

    2010-12-01

    Whereas colored andesine/labradorite had been thought unique to the North American continent, red andesine supposedly coming from the Democratic Republic of the Congo (DR Congo), Mongolia, and Tibet has been on the market for the last 10 years. After red Mongolian andesine was proven to be Cu-diffused by heat treatment from colorless andesine starting material, efforts were taken to distinguish minerals sold as Tibetan and Mongolian andesine. Using nanosecond laser ablation-inductively coupled plasma mass spectrometry (ICPMS), the main and trace element composition of andesines from different origins was determined. Mexican, Oregon, and Asian samples were clearly distinguishable by their main element content (CaO, SiO(2) Na(2)O, and K(2)O), whereas the composition of Mongolian, Tibetan, and DR Congo material was within the same range. Since the Li concentration was shown to be correlated with the Cu concentration, the formerly proposed differentiation by the Ba/Sr vs. Ba/Li ratio does not distinguish between samples from Tibet and Mongolia, but only between red and colorless material. Using femtosecond laser ablation multi-collector ICPMS in high-resolution mode, laboratory diffused samples showed variations up to 3 for (65)Cu/(63)Cu within one mineral due to the diffusion process. Ar isotope ratio measurements proved that heat treatment will reduce the amount of radiogenic (40)Ar in the samples significantly. Only low levels of radiogenic Ar were found in samples collected on-site in both mine locations in Tibet. Together with a high intra-sample variability of the Cu isotope ratio, andesine samples labeled as coming from Tibet are most probably Cu-diffused, using initially colorless Mongolian andesines as starting material. Therefore, at the moment, the only reliable source of colored andesine/labradorite remains the state of Oregon. PMID:20967428

  10. The role of magma mixing in the petrogenesis of mafic alkaline lavas, Rockeskyllerkopf Volcanic Complex, West Eifel, Germany

    NASA Astrophysics Data System (ADS)

    Shaw, Cliff S. J.; Woodland, Alan B.

    2012-03-01

    The quaternary Rockeskyllerkopf Volcanic Complex (RVC) comprises three spatially and temporally distinct volcanic centers that can also be distinguished on the basis of their geochemical signatures. All the volcanic products in the complex are olivine basanites whose major and trace element compositions span almost the entire range defined for the West Eifel field as a whole. The RVC lavas have lower Al2O3, Na2O and Y contents and higher TiO2, CaO, K2O, Sc, V, Co, Rb, and Ba than the Tertiary lavas in nearby Hocheifel volcanic field. Within the complex, the oldest South East Lammersdorf Center (SEL) comprises primitive lavas with an average MgO content of ˜11 wt.% and LaN/YbN of 29 ± 2. The second center, Mäuseberg, has similar MgO to SEL but is distinct in its much higher LaN/YbN of 42 ± 2. The Rockeskyllerkopf Center, which was erupted after a break in activity, comprises lavas similar in composition to the SEL Center but with distinctly higher Al2O3 and lower MgO contents. Given the lack of evidence for significant fractionation or assimilation in the RVC lavas, we attribute the compositional variations within and between the centers of the RVC to be due to variations in the composition of the source region in combination with magma mixing. Our preferred model involves 1-5% partial melting of LREE-enriched mantle in the garnet stability field, likely within the thermal boundary layer at the base of the lithospheric mantle. These melts mixed to variable degrees with 2-4% partial melts of phlogopite-spinel peridotite formed at higher levels in the modally metasomatised lithospheric mantle.

  11. Natural radionuclide concentrations in granite rocks in Aswan and Central-Southern Eastern Desert, Egypt and their radiological implications.

    PubMed

    Issa, Shams A M; Uosif, M A M; Abd el-Salam, L M

    2012-07-01

    Different types of granites, used extensively in local construction, were collected from five localities in Egypt, namely: Abu Ziran (Central Eastern Desert), Gabal El Maesala (Aswan) and three areas from Wadi Allaqi, (Gabal Abu Marw, Gabal Haumor and Gabal um Shalman), in the South Eastern Desert. Granite samples were studied radiologically, petrographically and geochemically. The contents of natural radionuclides ((226)Ra, (232)Th and (40)K) were measured in investigated samples by using gamma spectrometry [NaI (Tl) 3'×3']. The activity concentrations of (226)Ra, (232)Th and (40)K in the selected granite samples ranged from 9±0.5 to 111±7, 8±1 to 75±4 and 100±6 to 790±40 Bq kg(-1), respectively. The external hazard index (H(ex)), absorbed dose and annual effective dose rate were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. The calculated radium equivalents were lower than the values recommended for construction materials (370 Bq kg(-1)). The excess lifetime cancer risks were also calculated. Petrographically, the granites studied are varied in the form of potash-feldspar, quartz, plagioclase, mica and hornblende. The accessory minerals are zircon, apatite and allanite. Geochemically, the chemical composition of the granite is studied especially for major oxides. They are characterized to have SiO(2), K(2)O, Na(2)O and Al(2)O(3) with depletion in CaO, MgO, TiO(2) and P(2)O(5). PMID:22147926

  12. Application of chemical, physical and chemometric analytical techniques to the study of ancient ceramic oil lamps.

    PubMed

    Garca Gimnez, R; Vigil de la Villa, R; Petit Domnguez, M D; Rucandio, M I

    2006-02-15

    A chemical, mineralogical and morphological characterization of 54 fragments of oil lamps found in two Spanish archaeological sites (Cordoba and Herrera de Pisuerga (Palencia)) has been performed. Flame atomic absorption and emission spectrometry were used for the determination of Al(2)O(3), CaO, Fe(2)O(3), K(2)O, MgO, MnO, Na(2)O and TiO(2) as major constituents and Cu, Cr, Ni, Pb and Zn as minor and trace selected elements. Physical, mineralogical and morphological analyses were made by using dilatometry at constant heating rate for the thermal behaviour, X-ray diffraction spectrometry for the mineralogical composition and, in a group of selected samples, scanning electron microscopy and polarizing petrographic microscopy for the observation of thin layers and mineral identification. Separations of light and heavy minerals were carried out with bromoform and X-ray diffraction analysis was applied to both fractions. Multivariate statistical analysis was used to establish correlations between variables and to deduce factors which allow the gathering of oil lamp samples in groups as a function of their composition. The results of these analyses allow the comparison among pieces and the establishment of conclusions about several aspects of their manufacture, the origin of the raw materials and the provenance of the oil lamps (local or imported). They provide information supporting certain archaeological hypothesis. For example, some oil lamps found in Herrera de Pisuerga showed a clearly different physicochemical composition. They were probably brought from Italy by the Roman Legions together with their initial furniture household. PMID:18970455

  13. Classification and statistical analysis of mine spoils chemical composition from Oliete basin (Teruel, NE Spain)

    NASA Astrophysics Data System (ADS)

    Meseguer, S.; Sanfeliu, T.; Jordn, M. M.

    2009-02-01

    The Oliete basin (Early Cretaceous, NE Teruel, Spain) is one of the most important areas for the supply of mine spoils used as ball clays for the production of white and red stoneware in the Spanish ceramic industry of wall and floor tiles. This study corresponds to the second part of the paper published recently by Meseguer et al. (Environ Geol 2008) about the use of mine spoils from Teruel coal mining district. The present study shows a statistical data analysis from chemical data (major, minor and trace elements). The performed statistical analysis of chemical data included descriptive statistics and cluster analysis (with ANOVA and Scheff methods). The cluster analysis of chemical data provided three main groups: C3 with the highest mean SiO2 content (66%) and lowest mean Al2O3 content (20%); C2 with lower SiO2 content (48%) and higher mean Al2O3 content (28%); and C1 with medium values for the SiO2 and Al2O3 mean content. The main applications of these materials are refractory, white and red ceramics, stoneware, heavy ceramics (including red earthenware, bricks and roof tiles), and components of white Portland cement and aluminous cement. Clays from group 2 are used in refractories (with higher kaolinite content, and constrictions to CaO + MgO and K2O + Na2O contents). All materials can be used in fine ceramics (white or red, according to the Fe2O3 + TiO2 content).

  14. Genesis of post-collisional calc-alkaline and alkaline granitoids in Qiman Tagh, East Kunlun, China

    NASA Astrophysics Data System (ADS)

    Yu, Miao; Feng, Chengyou; Zhao, Yiming; Li, Daxin

    2015-12-01

    The post-collisional magmatism of Qiman Tagh is characterized by the intrusion of voluminous intermediate to felsic granitoids, including syenogranite, monzogranite, granodiorite, tonalite and diorite. The granitoids can be divided into two magmatic suites: Calc-alkaline (CA) and alkaline (Alk), which were emplaced from ~ 236 Ma to ~ 204 Ma. The CA suite contains metaluminous granodiorites and monzogranites. Typical Qiman Tagh CA granodiorites show moderately fractionated REE patterns ((La/Yb)N = 4.35-25.11) with significant negative Eu anomalies (Eu/Eu* = 0.54-1.34), and the primitive mantle-normalized spidergrams show strong depletion of Nb and Sr. The Qiman Tagh CA monzogranites show similar fractionated REE patterns ((La/Yb)N = 2.70-13.5) with less prominent negative Eu anomalies, and the chondrite-normalized spidergrams show strongly depleted Ba, Nb and Sr. The Alk suite, including syenogranite, is highly potassic (K2O/Na2O = 1.09-3.56) and peraluminous (A/CNK = 0.91-1.06). Compared to typical Qiman Tagh CA granodiorites, the Qiman Tagh Alk granitoids can be distinguished by their higher Rb, Nb, Ga/Al, FeO*/MgO, Y/Sr and Rb/Sr, as well as their lower Mg#, MgO, CaO, Al2O3, Sr, Co, V, Eu/Eu*, Ba/Nb, La/Nb, Ba/La and Ce/Nb. The Qiman Tagh CA rocks were most likely to be derived from the partial melting of garnet-amphibolite-facies rocks in the lower crust, leaving behind anhydrous granulite-facies rocks with plagioclase and garnet in the residue. The Alk rocks may have formed by the continued partial melting of granulite-facies rocks at elevated temperatures (> 830 °C).

  15. X-ray fluorescence analysis of rare earth elements in rocks using low dilution glass beads.

    PubMed

    Nakayama, Kenichi; Nakamura, Toshihiro

    2005-07-01

    Major and trace elements (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Rb, Sr, Y, Zr, La, Ce, Pr, Nd, Sm, Gd, Dy, Th and U) in igneous rocks were assayed with fused lithium borate glass beads using X-ray fluorescence spectrometry. Low dilution glass beads, which had a 1:1 sample-to-flux ratio, were prepared for determination of rare earth elements. Complete vitrification of 1:1 mixture required heating twice at 1200 degrees C with agitation. Extra pure reagents containing determinants were used for calibrating standards instead of the rock standard. The calibration curves of the 23 elements showed good linearity. Furthermore, the lower limits of detection corresponding to three times the standard deviation for blank measurements were 26 mass ppm for Na2O, 6.7 for MgO, 4.5 for Al2O3, 4.5 for SiO2, 18 for P2O5, 1.1 for K2O, 4.0 for CaO, 3.9 for TiO2, 1.6 for MnO, 0.8 for Fe2O3, 0.5 for Rb, 0.2 for Sr, 0.4 for Y, 0.5 for Zr, 3.3 for La, 6.5 for Ce, 2.7 for Pr, 2.1 for Nd, 1.7 for Sm, 0.7 for Gd, 2.7 for Dy, 0.5 for Th, and 0.6 for U. Using the present method, we determined the contents of these 23 elements in four rhyolitic and granitic rocks from Japan. PMID:16038502

  16. Inorganic geochemistry data from Lake El'gygytgyn sediments: marine isotope stages 6-11

    NASA Astrophysics Data System (ADS)

    Minyuk, P. S.; Borkhodoev, V. Y.; Wennrich, V.

    2014-03-01

    Geochemical analyses were performed on sediments recovered by deep drilling at Lake El'gygytgyn in central Chukotka, northeastern Russia (67°30' N; 172°05' E). Major and rare element concentrations were determined using X-ray fluorescence spectroscopy (XRF) on the < 250 μm fraction from 617 samples dated to ca. 440 and 125 ka, which approximates marine isotope stages (MIS) 11 to 6. The inorganic geochemistry indicates significant variations in elemental composition between glaciations and interglaciations. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K2O, and Sr and are depleted in Al2O3, Fe2O3, TiO2, and MgO. An extreme SiO2 enrichment during MIS 11.3 and 9.3 was caused by an enhanced flux of biogenic silica (BSi). The geochemical structure of MIS 11 shows similar characteristics as seen in MIS 11 records from Lake Baikal (southeastern Siberia) and Antarctic ice cores, thereby arguing for the influence of global forcings on these records. High sediment content of TiO2, Fe2O3, MgO, Al2O3, LOI, Ni, Cr, and Zr typifies glacial stages, with the most marked increases during MIS 7.4 and 6.6. Reducing conditions during glacial times are indicated by peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios. This conclusion also is supported by P2O5 and MnO enrichment, indicating an increased abundance of authigenic, fine-grained vivianite. Elemental ratios (CIA, CIW, PIA, and Rb/Sr) indicate that glacial sediments are depleted in mobile elements, like Na, Ca, K and Sr. This depletion was caused by changes in the sedimentation regime and thus reflects environmental changes.

  17. Geochemistry of the Paleocene-Eocene and Miocene-Pliocene clayey materials of the eastern part of the Wouri River (Douala sub-basin, Cameroon): Influence of parent rocks

    NASA Astrophysics Data System (ADS)

    Ngon Ngon, G. F.; Mbog, M. B.; Etame, J.; Ntamak-Nida, M. J.; Logmo, E. O.; Gerard, M.; Yongue-Fouateu, R.; Bilong, P.

    2014-03-01

    Major and trace element concentrations of clay deposits of the Missole II and Bomkoul respectively from the Paleocene-Eocene N'Kapa Formation and the Miocene-Pliocene-Matanda-Wouri Formation in the eastern part of the Wouri River in the Douala sub-basin of Cameroon have been investigated to identify the parent rocks. To carry out this study, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry (ICP/AES) and inductively coupled plasma-mass spectrometry (ICP/MS) were performed to determine respectively the mineralogical and chemical data of Missole II and Bomkoul clayey materials. Clay sediments are essentially kaolinitic and illitic, and kaolinitic and smectitic respectively in both sites. They are generally siliceous, aluminous with small iron and bases (MgO, CaO, Na2O, and K2O) contents. Samples of Missole II profiles are more siliceous than those from the Bomkoul grey and dark grey clayey materials. Clayey materials have high Chemical Index of Alteration (CIA = 80-99.34) which suggests that they are strongly weathered under humid tropical climate before and after their deposition in the coastal plain. The value of Eu/Eu* (0.48-0.61), La/Sc (2.15-20.50), Th/Sc (0.74-2.25), Th/Co (1.08-8.33), and Cr/Th (5.24-13.55) ratios support essentially a silicic or felsic parent rocks. Total REE concentrations reflect the variations in their grain-size fractions. Chondrite-normalised REE patterns with LREE enrichment, flat HREE, and negative Eu anomaly are attributed essentially to silicic or felsic parent rocks like those from weathered materials developed from the gneisses around the coastal plain in the littoral part of Cameroon (Noa Tang et al., 2012), main characteristic of Paleocene-Eocene and Miocene-Pliocene clay sediments of Missole II and Bomkoul areas.

  18. Experimental constraints on the destabilization of basalt + calcite + anhydrite at high pressure-high temperature and implications for meteoroid impact modeling

    NASA Astrophysics Data System (ADS)

    Martin, A. M.; Righter, K.; Treiman, A. H.

    2012-05-01

    Calcite CaCO3 and anhydrite CaSO4 are two sedimentary components or alteration products of basalts on the Earth, Venus, and Mars. The fate of anhydrite-, calcite-bearing crust during a meteoroid impact must be addressed in order to evaluate: (1) the potential S- and C-gas release to the atmosphere, (2) the formation of S- and C-rich melts, and (3) the crystallization of S- and C-rich minerals which may be recognized by spectral analyses of planetary surfaces. We performed piston-cylinder experiments at 1 GPa, between 1200 and 1750 C, on a mixture of 70 wt.% tholeiitic basalt + 15 wt.% anhydrite + 15 wt.% calcite. Up to ~ 1440 C, an ultracalcic (CaO > 19.8 wt.%; CaO/Al2O3 > 1 wt.%) picrobasaltic (SiO2 ~ 39-43 wt.%; Na2O + K2O < 2 wt.%) melt containing up to 5.7 wt.% SO3 and up to 5.1 wt.% CO2 + H2O (calculated by difference) is present in equilibrium with fassaitic clinopyroxene, anhydrite, scapolite, chromian spinel and a gas composed mainly of CO and, occasionally, aliphatic thiols like CH3(CH2)3SH. Hydrogen was incorporated either by contact between the starting material and air or by diffusion through the capsule during the experiments. Above ~ 1440 C, a CaO-rich (~ 35 wt.%) sulfate-carbonate (SC) melt which contains 41-47 wt.% SO3, 7-12 wt.% CO2 + H2O and a few percent of Na2O, forms in equilibrium with the picrobasaltic melt. This study shows that a meteoroid impact onto an anhydrite- and calcite-bearing basaltic crust is likely to release CO gas to the atmosphere, while S is trapped in solid or liquid phases. Under hydrous conditions, however, the S/C in the gas may increase. The importance of the temperature parameter on the impact phase relations is also demonstrated. In particular, SC melt may form by meteoroid impact, and flow rapidly on a planetary surface. Physical modeling must therefore be combined with high P-high T phase diagrams of complex assemblages similar to planetary lithologies in order to evaluate the effects of a meteoroid impact.

  19. Origin of mafic enclaves and their feldspar phenocrysts in the El Capitan Granite, Yosemite National Park, California

    NASA Astrophysics Data System (ADS)

    Ireland, K. R.; Glazner, A. F.; Mills, R. D.

    2011-12-01

    Mafic magmatic enclaves preserve evidence of interaction between mafic and felsic magmas in both volcanic and plutonic rocks, but the extent to which such interaction produces intermediate-composition rocks is in question. Magma mixing is viewed as one possible mechanism for their creation, yet contrasts in physical properties do not permit easy homogenization of mafic and felsic magmas. The El Capitan Granite of Yosemite Valley contains abundant mafic enclaves, enclave swarms, and schlieren, and is adjacent to a large, roughly coeval mafic complex known as the diorite of the Rockslides (DOTR) that has been suggested as an enclave source. Many of the mafic enclaves contain large (~ 0.5 to 1 cm) plagioclase phenocrysts similar in size to those in the host El Capitan Granite. We have performed geochemical and mineralogical analyses of the enclaves and host rocks in an effort to determine the source of the enclaves and whether the plagioclase phenocrysts could have been introduced into the enclaves by mixing from the host. Enclaves are broadly dioritic (55-65 wt% SiO2) and lie between the El Capitan Granite and the DOTR on most chemical plots. However, Na2O and MnO lie above, and CaO below, a simple mixing line between the two, precluding mixing as a complete explanation for their bulk compositions. The enclaves are distinctly more Na- and Mn-rich than the overall Sierran trend. Diffusion of elements is evident in chemical profiles taken perpendicular to the enclave/granite boundary. Na2O diffused out of the enclaves, so their overall enrichment in Na2O cannot be explained by addition from the host granite. The enclaves are typically enclosed by tonalitic haloes ~2 cm thick, perhaps owing to diffusion of K2O into the enclaves and diffusion of Na2O and SiO2 into the granite. Plagioclase phenocrysts within the mafic enclaves are similar in composition to those in the groundmass (An20-42) and are only slightly more calcic than plagioclase of the El Capitan Granite. Plagioclase crystals found in the DOTR have much higher anorthite contents (An74-90) than any found in the enclaves. The phenocrysts contain Mn-rich ilmenite inclusions that are not present in the El Capitan Granite or DOTR; these and other mineral inclusions match the compositions of the minerals composing the mafic enclaves. The sodic nature of the enclave phenocrysts and the lack of calcic cores similar in composition to DOTR feldspars further imply that the phenocrysts were not introduced from the host granite. These data indicate enclaves did not result from mixing of the El Capitan Granite and mafic rocks of the DOTR, but most likely arose from andesitic magmas that are not otherwise found in the Sierra Nevada batholith. Andesites with similar compositions are found at Cascade volcanoes.

  20. The Tonalite-Trondhjemite-Granodiorite (TTG) to Calc-alkaline Granodiorite-Granite Transition: Evolution of the Archaean Basement of the Quadriltero Ferrfero Province (Southeast Brazil)

    NASA Astrophysics Data System (ADS)

    Farina, F.; Albert, C.; Lana, C.; Stevens, G.

    2014-12-01

    The Bao, Bonfim and Belo Horizonte domes are the largest domes in the Archaean Southern So Francisco craton (Quadriltero Ferrfero, Brazil). These domes are mainly formed by fine-grained banded gneisses typically intruded by leucogranitic veins and by weakly foliated granites, cropping out as large batholiths and small scale-domains closely associated to the gneisses. Granites and gneisses have high silica content (70-76 wt%), K2O ranging from 2wt% to 6wt%, Sr from 600 to 40 ppm and La/Yb from 150 to 5. Based on their K2O/Na2O ratios, these rocks are subdivided in three groups: sodic (K2O/Na2O?0.7), transitional (0.7<K2O/Na2O<1.1) and potassic (K2O/Na2O?1.1). There is no direct relationship between the metamorphic overprint (granites vs. gneisses) and the K2O/Na2O ratio; e.g. granites plots equally in the sodic and potassic groups. Overall, the composition of gneisses and granitoids in the three domes marks the transition between Archean TTGs and modern calc-alkalic granitoids. LA-ICP-MS zircon U-Pb data allow three main periods of magmatism to be defined. The oldest recorded magmatic contribution to the craton began at 3200 Ma, as attested by the occurrence of inherited zircons in younger granitoids as well as by the fact that zircons with a ca. 3200 Ma age represent a significant subset in the detrital zircon population of the greenstone belt. Subsequent magmatic events took place at 2930-2870 Ma and 2780-2700 Ma. The geochronological data reveal that, although the sodic rocks represent a greater proportion of the older gneisses, sodic, transitional and potassic granitoids intruded contemporaneously. The geochemistry of sodic and transitional granites and gneisses suggests that they formed by partial melting of TTG source rocks that are not preserved in the rock record. MC-ICP-MS Hf isotope data on magmatic zircon, suggesting crustal reworking with minor or no involvement of juvenile magmas, support this interpretation. Further recycling of sodic-transitional gneisses does not account for the genesis of potassic granitoids whose origin requires the participation of magmas derived by metasedimentary source rocks.

  1. Method of preventing oxidation of graphite fireproof material

    NASA Technical Reports Server (NTRS)

    Yamauchi, S.; Suzuki, H.

    1981-01-01

    A method of preventing oxidation of graphite fireproof material is given. A blend of 1 to 33 weight parts alumina and 3 to 19 parts of K2O + Na2O in 100 parts of SiO2 is pulverized followed by addition of 5 to 160 parts of silicon carbide powder in 100 parts of the mixture. This is thoroughly blended and coated on the surface of graphite fireproof material.

  2. Provenance analysis of the Oligocene turbidites (Andaman Flysch), South Andaman Island: A geochemical approach

    NASA Astrophysics Data System (ADS)

    Bandopadhyay, P. C.; Ghosh, Biswajit

    2015-07-01

    The Oligocene-aged sandstone-shale turbidites of the Andaman Flysch are best exposed along the east coast of the South Andaman Island. Previously undocumented sandstone-shale geochemistry, investigated here, provides important geochemical constraints on turbidite provenance. The average 70.75 wt% SiO2, 14.52 wt% Al2O3, 8.2 wt% FeMgO and average 0.20 Al2O3/SiO2 and 1.08 K2O/Na2O ratios in sandstones, compare with quartzwackes. The shale samples have average 59.63 wt% SiO2, 20.29 wt% Al2O3, 12.63 wt% FeMgO and average 2.42 K2O/Na2O and 0.34 Al2O3/SiO2 ratios. Geochemical data on CaO-Na2O-K2O diagram fall close to a granite field and on K2O/Na2O-SiO2 diagram within an active continental margin tectonic setting. The range and average values of Rb and Rb/Sr ratios are consistent with acid-intermediate igneous source rocks, while the values and ratios for Cr and Ni are with mafic rocks. Combined geochemical, petrographic and palaeocurrent data indicate a dominantly plutonic-metamorphic provenance with a lesser contribution from sedimentary and volcanic source, which is possibly the Shan-Thai continental block and volcanic arc of the north-eastern and eastern Myanmar. Chemical index of alteration (CIA) values suggests a moderate range of weathering of a moderate relief terrane under warm and humid climate.

  3. Alkalis partitioning between miscible liquids: Experimental investigation and implications for magmas mixing/contamination

    NASA Astrophysics Data System (ADS)

    Borisov, A.

    2009-04-01

    Natural magmatic melts show wide variations in silica and the effect of SiO2 on the chemical properties of silicate melts is therefore of special interest. Model silicate melts (Di-An eutectic modified with variable amounts of silica and Ca2Si3O8 modified with variable amounts of alumina) were experimentally saturated with Na, K and Rb at a total pressure of 1 atm and temperatures of 1300-1470 C [1, 2]. A crucible supported loop technique was applied [3]. Either binary Na2O-SiO2 and K2O-SiO2 or complex Na2O-K2O-SiO2 and Na2O-K2O-Rb2O-SiO2 melts were used as alkalis sources. It was shown that alumina content in many cases has little influence on the degree of silicate melt saturation with alkalis. In contrast, silica content strongly affects the solubility of alkalis in silicate melts. Model calculations showed that the perfectly mobile behavior of alkalis leads to a potassium specifics in basalts contaminated by crustal materials and, correspondingly, a sodic specifics in silicic melts from crustal xenoliths contaminated by the enclosing basaltic melt. [1] Borisov (2008) Petrology, 16, 552-564. [2] Borisov Petrology, submitted. [3] Borisov et al. (2006) American Mineralogist, 91, 762-771.

  4. Fertilization ratios of N-P2O5-K2O for Tifton 85 bermudagrass on two coastal plain soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bermudagrass [Cynodon dactylon (L.) Pers.] cultivar Tifton 85 is widely grown throughout the southeastern United States and many other countries for forage production. Because Tifton 85 is actually a hybrid between C. dactylon and C. nlemfuensis, it may not respond to fertilization in the same way ...

  5. Fabrication and photoluminescence properties of Ag0 and Ag0-Er3+ containing plasmonic glass nanocomposites in the K2O-ZnO-SiO2 system

    NASA Astrophysics Data System (ADS)

    Tarafder, Anal; Molla, Atiar Rahaman; Mukhopadhyay, Sunanda; Karmakar, Basudeb

    2014-11-01

    Here, we report the preparation of nano silver (Ag) and nano Ag-erbium (Ag-Er) co-embedded potassium-zinc-silicate based monolithic glass nanocomposites by a controlled heat-treatment process of precursor glasses. The nanocomposites were characterized by differential scanning calorimeter, dilatometer, UV-Visible absorption spectrophotometer, X-ray diffractometer and transmission electron microscope and spectroflurimeter. A strong surface plasmon resonance (SPR) band is observed around 430 nm in all the heat-treated glass nanocomposite samples due to the formation of Ag0 nanoparticles (NP). The Ag-glass nanocomposite samples display nearly 2-fold enhanced photoluminescence (PL) at 470 nm upon excitation at 290 nm until the size of the NP increases to the value equals to the mean free path of conduction electrons inside the particles. On contrary to this, the photoluminescence spectra of Er3+ ions exhibit a gradual decrease of NIR emission at 1540 nm due to 4I13/2 → 4I15/2 transition under excitation at 523 nm in the heat-treated glass nanocomposites which happened due to excitation energy transfer of Er3+ ions to the Ag NP, acting as 'plasmonics diluents' for Er3+ ions. These nanocomposites have huge potential for various nanophotonic applications.

  6. Geochemical and Sr-Nd-Pb isotopic characteristics of Late Cenozoic leucite lamproites from the East European Alpine belt (Macedonia and Yugoslavia)

    NASA Astrophysics Data System (ADS)

    Altherr, R.; Meyer, H.-P.; Holl, A.; Volker, F.; Alibert, C.; McCulloch, M. T.; Majer, V.

    In the East European Alpine belt, leucite-sanidine-phlogopite-olivine-bearing volcanic rocks of Late Cenozoic age occur at eight localities within the Vardar suture zone and at one locality in the Southern Carpathian fold-and-thrust belt. Most of these volcanics are characterized by high Mg# (66.6-78.6), high abundances of Ni (117-373 ppm) and Cr (144-445 ppm) as well as high primary K2O contents (5.63-7.01 %) and K2O/Na2O values (1.93-4.91). Rocks with more differentiated compositions are rare. A lamproite affinity of these rocks is apparent from their relatively low contents of Al2O3 (9.9-14.3 wt%) and CaO (6.2-8.3 wt%) in combination with high abundances of Rb (85-967 ppm), Ba (1,027-4,189 ppm), Th (18.9-76.5 ppm), Pb (19-54 ppm), Sr (774-1,712 ppm) and F (0.16-0.52 wt%), and the general lack of plagioclase. Although eruption of the magmas took place in post-collisional extensional settings, significant depletions of Nb and Ta relative to Th and La, low TiO2 contents (0.92-2.17 %), low ratios of Rb/Cs, K/Rb and Ce/Pb as well as high ratios of Ba/La and Ba/Th suggest close genetic relationships to subduction zone processes. Whereas Sr and Nd isotope ratios show relatively large variations (87Sr/86Sr = 0.7078-0.7105, 143Nd/144Nd = 0.51242-0.51215), Pb isotope ratios display a very restricted range with 206Pb/204Pb = 18.68-18.88 and variable but generally high ?7/4 (11-18) and ?8/4 (65-95) values. The observed petrographic, geochemical and isotopic characteristics are best explained by a genetic model involving preferential melting of phlogopite-rich veins in an originally depleted lithospheric mantle source, whereby the metasomatic enrichment of the mantle source is tentatively related to the addition of components from subducted sediments during consumption of Tethyan oceanic lithosphere.

  7. The Iceland Deep Drilling Project (IDDP): (2) Petrology and geochemistry of rhyolitic melts drilled at Krafla

    NASA Astrophysics Data System (ADS)

    Zierenberg, R. A.; Elders, W. A.; Fridleifsson, G. O.; Schiffman, P.; Marks, N. E.; Lesher, C. E.; Lowenstern, J. B.; Pope, E. C.; Bird, D. K.; Mortensen, A.; Gudmundsson

    2009-12-01

    The Iceland Deep Drilling Project (IDDP) in the Krafla Geothermal Field was intended to investigate the feasibility of producing energy from geothermal systems at supercritical conditions. Drilling was stopped at 2104 meter when a rhyolitic melt was intersected. Sporadic cuttings included abundant dark brown, sparsely phyric obsidian. Most fragments were poorly vesiculated, but white frothy pumice, some with highly stretched bubbles, sere also present. The dense obsidian and highly vesiculated samples have identical phenocryst assemblages, major element compositions, and volatile contents. The glass is a high silica (75.0 wt %) rhyolite with low TiO2 (0.3 wt %) and 3.7 and 3.0 wt % Na2O and K2O, respectively. Phenocrysts include titanomagnetite, plagioclase, augite and pigeonite, with minor amounts of apatite, rare zircon crystals and pyrrhotite, which occurs as rounded droplets of an immiscible sulfide liquid. Augite and pigeonite each contain abundant exsolution lamellae of the complimentary phase. Plagioclase shows some compositional zoning, but mostly is in the range from An45-An48. The low water contents (1.75 wt %) are consistent with the absence of hydrous phenocrysts, and together with the CO2 content (75 ppm) indicate relatively shallow (<4 km) degassing. Stable isotope compositions (?18O = 3.2, ?D = -118) indicate an origin by partial melting of hydrothermally altered crustal rock, as do chondrite-normalized rare earth element patterns, that are enriched in light elements and relatively flat for middle and heavy elements. Fragments of a partially crystallized granite intrusion with areas of interstitial melt quenched to glass by the drilling fluids also are present in the drill cuttings from the bottom of the hole. The granite is composed of alkali feldspar, plagioclase, quartz, augite and titanomagnetite. The interstitial glass has a silica content (75.6 wt. %) similar to the rhyolite melt, but is easily distinguished from it by higher K2O and lower CaO contents. REE elements are strongly enriched in the interstitial glass, relative to the rhyolite, but show similar chondrite-normalized patterns. Some glass-rich fragments are crowded with crystals and glomerocrysts typical of the granite intrusion, except that alkali feldspar only occurs as remnants of resorbed crystals. The glass in these fragments plots on mixing/assimilation curves between the interstitial granite melt and the rhyolite melt and clearly indicate emplacement of a separate melt into the zone occupied by the still crystallizing rhyolitic intrusion.

  8. Characteristics of chemical weathering and water-rock interaction in Lake Nyos dam (Cameroon): Implications for vulnerability to failure and re-enforcement

    NASA Astrophysics Data System (ADS)

    Fantong, Wilson Y.; Kamtchueng, Brice T.; Yamaguchi, Kohei; Ueda, Akira; Issa; Ntchantcho, Romaric; Wirmvem, Mengnjo J.; Kusakabe, Minoru; Ohba, Takeshi; Zhang, Jing; Aka, Festus T.; Tanyileke, Gregory; Hell, Joseph V.

    2015-01-01

    For the first time, comprehensive study of hydrogeochemistry of water seeps, role of chemical weathering on dam failure, estimation of minimum width of dam to resist failure and simulation of changes in dissolved ions and secondary mineral was conducted on the Lake Nyos dam. The salient results and conclusions were; the dam spring water represented a mixture of 60-70% rainwater and 30-40% Lake water (from 0 to -40 m). The chemistry of the observed waters was Ca-HCO3 for rainwater, Ca-Mg-HCO3 in boreholes, and Mg-Ca-HCO3- for spring water. The relative rate at which ions dissolved in water was HCO3- > Mg2+ > Ca2+ > Na+ > SiO2 > K+ > NO3- > SO42- > Cl-. Weathering of rocks resulted in the formation of clay minerals such as kaolinite and smectite. Relative mobility of elements compared to Alumina (Al2O3) indicated that in monzonites there was a loss of CaO, Na2O, K2O, P2O5 and gain of SiO2, Fe2O3, TiO2, MnO and MgO, while in basalts there was a loss of SiO2, Fe2O3, Ca2O, NaO, MgO and gain of TiO2, K2O and P2O5. Values of chemical alteration index that ranged from 49 to 82 suggest a weak to intermediate categories of chemical weathering that occurred at a rate of 5.7 mm/year. Paired to that rate, which suggests that the dam is not vulnerable to failure at the previously thought time scale, some other processes (physical weathering, secondary mineral formation and lake overflow) can cause instant failure. Hydrostatic pressure of 1.6 GN generated by Lake water can be supported only when the width of the dam is greater than 19 m. PHREEQC-based simulation for 10 years indicates decoupling of Ca and Mg, and Na and Mg. Multidisciplinary monitoring of the dam is advocated.

  9. The significance of mafic microgranular enclaves in the petrogenesis of the Dehno Complex, Sanandaj-Sirjan belt, Iran

    NASA Astrophysics Data System (ADS)

    Rajaieh, M.; Khalili, M.; Richards, I.

    2010-07-01

    Quartz-monzodioritic and granodioritic enclaves occur in the Upper Cretaceous-Paleocene Dehno Complex, NW of Isfahan, Iran. They are hosted by hornblende-granodiorite and granodiorite-monzogranite, respectively. The presence of xenocrystic plagioclase, biotite, quartz, magnesio-hornblende, occasionally with relics of clinopyroxene (in quartz-monzodiorites), minor K-feldspar and the lack of peraluminous minerals dominate the mineralogy of these rocks and suggest a metaluminous source. The plagioclase in the quartz-monzodioritic enclaves has higher An-content than that of the respective plagioclase of their host (hornblende-granodiorite) indicating crystallization from more mafic magma. The quartz-monzodioritic enclaves generally contain higher values of Fe 2O 3, MgO, CaO, MnO, Na 2O, transition elements (Ni, Cr, Co, V), REE and lower values of SiO 2, K 2O, P 2O 5 and Zr than their host which are in consistent with occurrence of abundant ferromagnesian minerals in these rocks. Compare to their host, the granodioritic enclaves have higher amount of Fe 2O 3, MgO, MnO, TiO 2, P 2O 5, Rb, Zr, Y, Ni, Cr, Co and lower concentration of SiO 2, K 2O and Ba. Aside from hornblende-granodiorite and granodiorite-monzogranite, the Dehno Complex comprises leucogranodiorite and tourmaline-leuco granites. Geochemically, the rocks of the Complex are metaluminous to strongly peraluminous and are enriched in LILE (e.g. Rb, K, Sr, Ba) and depleted in HFSE (e.g. Nb, Ta, P, Ti, Zr, Hf) with medium to high-K calc-alkaline nature. These geochemical features are proposed for the volcanic arc granites emplaced in an active continental margin. Whole-rock and quartz ?18O values for all rocks are high (9.7-14.4 and 10.1-14.9, respectively), suggesting the interaction of magma with crustal-derived components. The strongly peraluminous composition can be interpreted in terms of this hypothesis. All these mineralogical and geochemical features support the idea that the granitoid rocks of the Dehno Complex developed through variable degrees of mixing/mingling between a basic magma and a supracrustal melt during subduction of the Neotethys oceanic crust beneath Central Iranian microcontenent. The quartz-monzodioritic enclaves most likely represent the nearest composition to the original more mafic magma. The granodioritic enclaves result from the mixing/mingling of globules basic magma with host granitic magma.

  10. PIXE and ICP-AES analysis of early glass unearthed from Xinjiang (China)

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Cheng, H. S.; Ma, B.; Li, Q. H.; Zhang, P.; Gan, F. X.; Yang, F. J.

    2005-10-01

    Early glasses (about 1066 BC-220 AD) unearthed from Xinjiang of China were chemically characterized by using PIXE and ICP-AES. It was found that these glasses were basically attributed to PbO-BaO-SiO2 system, K2O-SiO2 system, Na2O-CaO-SiO2 system and Na2O-CaO-PbO-SiO2 system. The results from the cluster analysis showed that some glasses had basically similar recipe and technology. The PbO-BaO-SiO2 glass and the K2O-SiO2 glass were thought to come from the central area and the south of ancient China, respectively. The part of the Na2O-CaO-SiO2 glass (including the Na2O-CaO-PbO-SiO2 glass) might be imported from Mesopotamia, while the other part might be locally produced.

  11. Variation of photoluminescence features in Pr3+ doped lithium-fluoro-borate glass by changing different modifier oxides (MgO, CaO, CdO and PbO)-Judd-Ofelt theory application

    NASA Astrophysics Data System (ADS)

    Balakrishna, A.; Rajesh, D.; Babu, S.; Ratnakaram, Y. C.

    2015-06-01

    Pr3+ (1.0 mol%) doped different modifier oxide based six lithium-fluoro-borate glasses with chemical composition of 49Li2B4O7-20BaF2-10NaF-20MO (where M= Mg, Ca, Cd and Pb), 49Li2B4O7-20BaF2-10NaF-10MgO-10CaO and 49Li2B4O7-20BaF2-10NaF-10CdO-10PbO were prepared by conventional melt quenching technique. Judd-Ofelt theory has been applied for evaluating the Judd-Ofelt intensity parameters for Pr3+ ion in these glass compositions and are in turn to used to predict radiative properties such as radiative transition probabilities (AT), branching ratios (β) and stimulated emission cross-section (σP). Stimulated emission cross-section (σp) of prominent emission transitions, 3P0→3H4 and 1D2→3H4 of Pr3+ ion in all lithium-fluoro-borate glasses were calculated. Among all the emission transitions, 3P0→3H4 posseses higher branching ratio and stimulated emission cross-section in Mg-Ca glass, which leads to the best laser excitation at 487 nm wavelength.

  12. Characterization and photoluminescence properties of some CaO, SrO and CaSrO2 phosphors co-doped with Eu3+ and alkali metal ions

    NASA Astrophysics Data System (ADS)

    Mar, B.; Singh, K. C.; Moya, Monica; Singh, Ishwar; Om, Hari; Chand, Subhash

    2012-06-01

    CaO:Eu3+, M+ (Li+ or Na+ or K+), SrO:Eu3+and CaSrO2:Eu3+ powders were prepared by combustion synthesis method and the samples were further heated to 1000 C to improve the crystallinity of the materials. The structure and morphology of materials were examined by X-ray diffraction and scanning electron microscopy. The morphology of CaO:Eu3+ and co-doped with alkali metal ions powders was very similar. Small and coagulated particles of nearly cubical shapes with small size distribution having smooth and regular surface were formed. The surface morphology of SrO and CaSrO2 materials was not smooth and coagulated particles of irregular shapes with different sizes were observed. The characteristic emissions of Eu3+ had strong emission at 614 and 620 nm for 5D0 ? 7F2 with other weak transitions observed at 580, 592, 654, 705 nm for 5D0 ? 7Fn transitions where n = 0, 1, 3, 4 respectively in all host lattices. Photoluminescence intensity followed the order as in CaO > CaSrO2 > SrO lattices. A remarkable increase of photoluminescence intensity was observed by the co-doping of alkali metal ions particularly K+ ions in CaO:Eu3+.

  13. Attaching an alkali metal atom to an alkaline earth metal oxide (BeO, MgO, or CaO) yields a triatomic metal oxide with reduced ionization potential and redirected polarity.

    PubMed

    Nowiak, Grzegorz; Skurski, Piotr; Anusiewicz, Iwona

    2016-04-01

    The existence of a series of neutral triatomic metal oxides MON and their corresponding cations MON (+) (M = Be, Mg, Ca; N = Li, Na, K) was postulated and verified theoretically using ab initio methods at the CCSD(T)/6-311+G(3df)//MP2/6-311+G(3df) level of theory. The calculations revealed that the vertical ionization potentials (IPs) of the MON radicals (calculated using the outer-valence Green's function technique (OVGF) with the 6-311+G(3df) basis set) were ca. 2-3 eV smaller than the IPs of the corresponding MO and NO systems or that of the isolated M atom. Population analysis of the neutral triatomic MON molecules and their corresponding MO counterparts indicated that the attachment of an alkali metal atom to any oxide MO (BeO, MgO, CaO) reverses its polarity, which manifests itself as the redirection of the dipole moment vector. PMID:26994021

  14. Molecular Dynamics Simulation of La2O3-Na2O-SiO2 Glasses. III. The driving forces of clustering

    SciTech Connect

    Corrales, Louis R.; Park, Byeongwon

    2002-11-04

    Molecular dynamics simulations have been carried out to determine the mean force and the potential of mean force of two La ions in a soda silicate glass. The reaction coordinate starts from a well separated state where the network accommodates the high-field strength cations and then brings them together to form an La-O-La linkage that can lead to the formation of free O anions. It is found that the network structure favors forming clusters, at least for dimer states. Furthermore, similar calculations for a pair of Na ions in pure silica reveals that the local molecular environments of La and Na ions are quite distinct.

  15. Moessbauer Effect Study of Bi2O3. Na2O. B2O3. Fe2O3 Glass System

    SciTech Connect

    Salah, S.H.; Kashif, I.; Salem, S.M.; Mostafa, A.G.; El-Manakhly, K.A.

    2005-04-26

    Sodium-tetra-borate host glass containing both bismuth and iron cations were prepared obeying the composition (Na2B4O7)0.75 (Fe2O3)0.25-x (Bi2O3)x [where x = 0.0, 0.05, 0.10, 0.15, 0.20, and 0.25 mol.%]. X-ray diffraction indicated that all samples were in a homogeneous glassy phase. Moessbauer effect results showed that all iron ions appeared as Fe3+ ions occupying tetrahedral coordination state. The covalency of the Fe-O bond increased as bismuth oxide was gradually increased. IR measurements indicated the presence of some non-bridging oxygens and confirmed that iron ions occupy the tetrahedral coordination state. It was found also that, as Bi2O3 was gradually increased both magnetic susceptibility and specific volume decreased, while both density and molar volume increased.

  16. Mineral-solution equilibriaIII. The system Na 2O?Al 2O 3?SiO 2?H 2O?HCl

    NASA Astrophysics Data System (ADS)

    Popp, Robert K.; Frantz, John D.

    1980-07-01

    Chemical equilibrium between sodium-aluminum silicate minerals and chloride bearing fluid has been experimentally determined in the range 500-700C at 1 kbar, using rapid-quench hydrothermal methods and two modifications of the Ag + AgCl acid buffer technique. The temperature dependence of the thermodynamic equilibrium constant ( K) for the reaction NaAlSi 3O 8 + HCl o = NaCl o + 1/2Al 2SiO 5, + 5/2SiO 2 + 1/2H 2O Albite Andalusite Qtz. K = (a NaCl o) /(a H 2O ) 1/2/(a HCl o) can be described by the following equation: log k = -4.437 + 5205.6/ T( K) The data from this study are consistent with experimental results reported by MONTOYA and HEMLEY (1975) for lower temperature equilibria defined by the assemblages albite + paragonite + quartz + fluid and paragonite + andalusite + quartz + fluid. Values of the equilibrium constants for the above reactions were used to estimate the difference in Gibbs free energy of formation between NaCl o and HCl o in the range 400-700C and 1-2 kbar. Similar calculations using data from phase equilibrium studies reported in the literature were made to determine the difference in Gibbs free energy of formation between KCl o and HCl o. These data permit modelling of the chemical interaction between muscovite + kspar + paragonite + albite + quartz assemblages and chloride-bearing hydrothermal fluids.

  17. Enhancement of luminescence properties in Er3+ doped TeO2-Na2O-PbX (X=O and F) ternary glasses.

    PubMed

    Kumar, Kaushal; Rai, S B; Rai, D K

    2007-04-01

    An enhancement of luminescence properties in Er3+ doped ternary glasses is observed on the addition of PbO/PbF2. The infrared to visible upconversion emission bands are observed at 410, 525, 550 and 658 nm, due to the 2H9/2-->4I15/2, 2H11/2-->4I15/2, 4S3/2-->4I15/2, 4F9/2-->4I15/2 transitions respectively, on excitation with 797 nm laser line. A detailed study reveals that the 2H9/2-->4I15/2 transition arises due to three step upconversion process while other transitions arise due to two step absorption. On excitation with 532 nm radiation, ultraviolet and violet upconversion bands centered at 380, 404, 410 and 475 nm wavelengths are observed along with one photon luminescence bands at 525, 550, 658 and 843 nm wavelengths. These bands are found due to the 4G11/2-->4I15/2, 2P3/2-->4I13/2, 2H9/2-->4I15/2, 2P3/2-->4I11/2, 2H11/2-->4I15/2, 4S3/2-->4I15/2, 4F9/2-->4I15/2 and 4S3/2-->4I13/2 transitions, respectively. Though incorporation of PbO and PbF2 both enhances fluorescence intensities however, PbF2 content has an important influence on upconversion luminescence emission. The incorporation of PbF2 enhances the red emission (658 nm) intensity by 1.5 times and the violet emission (410 nm) intensity by 2.0 times. A concentration dependence study of fluorescence reveals the rapid increase in the red (4F9/2-->4I15/2) emission intensity relative to the green (4S3/2-->4I15/2) emission with increase in the Er3+ ion concentration. This behaviour has been explained in terms of an energy transfer by relaxation between excited ions. PMID:16872889

  18. O(-) identified at high temperatures in CaO-based catalysts for oxidative methane dimerization

    NASA Technical Reports Server (NTRS)

    Freund, F.; Maiti, G. C.; Batllo, F.; Baerns, M.

    1990-01-01

    A technique called charge-distribution analysis (CDA) is employed to study mobile charge carriers in the oxidation catalysts CaO, CaO with 11 percent Na2O, and CaO with 10 percent La2O3. A threshold temperature of about 550-600 C is identified at which highly mobile charge carriers are present, and the CDA studies show that they are O(-) states. The present investigation indicates the usefulness of CDA in catalysis research with pressed powder samples and gas/solid reactions.

  19. Removal of Cd2+ from water by Friedel's salt (FS: 3CaO x A12O3 x CaCI2 x 10H2O): sorption characteristics and mechanisms.

    PubMed

    Zhang, Juanjuan; Zhao, He; Cao, Hongbin; Li, Heping; Li, Zhibao

    2013-09-01

    The development of low-cost and efficient new mineral adsorbents has been a hot topic in recent years. In this study, Friedel's salt (FS: 3CaO x A12O3 x CaCl2 x10H2O), a hexagonal layered inorganic absorbent, was synthesized to remove Cd2+ from water. The adsorption process was simulated by Langmuir and Freundlich models. The adsorption mechanism was further analyzed with TEM, XRD, FT-IR analysis and monitoring of metal cations released and solution pH variation. The results indicated the adsorbent FS had an outstanding ability for Cd(II) adsorption. The maximum adsorption capacity of the FS for Cd(II) removal can reach up to 671.14 mg/g. The nearly equal numbers of Cd2+ adsorbed and Ca2+ released demonstrated that ion-exchange (both surface and inner) of the FS for Cd(II) played an important role during the adsorption process. Furthermore, the surface of the FS after adsorption was microscopically disintegrated while the inner lamellar structure was almost unchanged. The behavior of Cd(II) adsorption by FS was significantly affected by surface reactions. The mechanisms of Cd2+ adsorption by the FS mainly included surface complexation and surface precipitation. In the present study, the adsorption process was fitted better by the Langmuir isotherm model (R2 = 0.9999) than the Freundlich isotherm model (R2 = 0.8122). Finally, due to the high capacity for ion-exchange on the FS surface, FS is a promising layered inorganic adsorbent for the removal of Cd(II) from water. PMID:24520713

  20. Simulations with CAO-3D model of photochemical response caused by precipitating electrons and solar protons at both polar regions during geomagnetic storms in October-November 2003 (preliminary comparison with MIPAS data)

    NASA Astrophysics Data System (ADS)

    Krivolutsky, Alexei A.; Banin, Max; Maik Wissing, Jan; Vyushkova, Tatyana

    Relativistic electrons precipitating from radiation belts and solar protons can penetrate below 100 km into the polar atmosphere sometimes reaching the stratospheric levels wasting its energy and causing the ionization. It leads to additional production of NOx and HOx chemical com-pounds which destroy ozone in the chemical catalytic cycles. One of the strongest geomagnetic storms accompained by a strong Solar Proton Eevent (SPE) occured in October-November 2003. This period was covered also by observations with MIPAS instrument placed on board of ENVISAT satellite. The response of atmospheric chemical composition in both polar regions was studied with CAO-3D photochemical-transport model. In order to calculate ionization rates induced by precipitating electrons and solar protons during late October and November 2003, corresponding proton and electron fluxes in different energetic channels from GOES-10 and POES-15/16 have been used. The Atmospheric Ionization Module Osnabruck -AIMOS /Wissing and Kallenrode, 2009/ was used to calculate 3D fields of ionization rates separately by electrons and protons. Photochemical simulations showed that Northern and Southern po-lar regions had different photochemical response. Such difference mostly is the result of the two factors: polar cap expansion during the geomagnetic storm and the effect of horizontal transport. The calculated members of NOy, HOx, Cly families were preliminary compared with corresponding observed data measured by MIPAS and showed a general agreement. The sensitivity of calculated chemical response to the efficiencies of NOx and HOx production by en-ergetic particles have been studied also. This work was supported by Russian Science Foudation for Basic Research (grant 09-05-009949) and by contract 1-6-08 under Russian Sub-Program "Reseach and Investigation of Antarctica".

  1. Lanthanum and neodymium solubility in simplified SiO{sub 2}-B{sub 2}O{sub 3}-Na{sub 2}O-Al{sub 2}O{sub 3}-CaO high level waste glass

    SciTech Connect

    Kidari, Abdessamad; Bardez-Giboire, Isabelle

    2012-08-15

    Lanthanum and neodymium incorporation in simplified high level waste glasses has been investigated for SiO{sub 2}B{sub 2}O{sub 3}Na{sub 2}OAl{sub 2}O{sub 3}CaO compositions quenched from 1200 degrees C, for varying La /(La + Nd) (atomic) and increasing rare-earth oxides contents. In this system and beyond the solubility limit, rare-earths (RE) elements are reported to form apatite phases with the general formula Ca{sub 2}RE{sub 8}(SiO{sub 4}){sub 6}O{sub 2}. In the current study, speciation of these trivalent RE{sup 3+} cations in both amorphous network and crystal phases was determined from X-ray diffraction, scanning electron microscopy, optical absorption at 10 K, Raman spectroscopy, and electron probe microanalysis. It appeared that RE{sub 2}O{sub 3} solubility was higher for La -rich formulations than for Nd -rich ones and that an increase in the RE oxide content reduces the connectivity of the network building units through formation of non-bridging oxygens at the expense of the oxygen bridges. This depolymerization of the glass network did not affect neodymium environment which consisted in silicate tetrahedra. The composition of the apatite crystals was found to be affected by the La /(La + Nd) of the parent glass and deviation from the ideal composition (Ca{sub 2}RE{sub 8}(SiO{sub 4}){sub 6}O{sub 2}) occurred in the neodymium end of the system. It thus appears that both RE{sub 2}O{sub 3} solubility and crystal composition are strongly dependent on the type and crystal chemistry of the RE elements. (authors)

  2. Rectal cancer delivery of radiotherapy in adequate time and with adequate dose is influenced by treatment center, treatment schedule, and gender and is prognostic parameter for local control: Results of study CAO/ARO/AIO-94

    SciTech Connect

    Fietkau, Rainer . E-mail: rainer.fietkau@med.uni-rostock.de; Roedel, Claus; Hohenberger, Werner; Raab, Rudolf; Hess, Clemens; Liersch, Torsten; Becker, Heinz; Wittekind, Christian; Hutter, Matthias; Hager, Eva; Karstens, Johann; Ewald, Hermann; Christen, Norbert; Jagoditsch, Michael; Martus, Peter; Sauer, Rolf

    2007-03-15

    Purpose: The impact of the delivery of radiotherapy (RT) on treatment results in rectal cancer patients is unknown. Methods and Materials: The data from 788 patients with rectal cancer treated within the German CAO/AIO/ARO-94 phase III trial were analyzed concerning the impact of the delivery of RT (adequate RT: minimal radiation RT dose delivered, 4300 cGy for neoadjuvant RT or 4700 cGy for adjuvant RT; completion of RT in <44 days for neoadjuvant RT or <49 days for adjuvant RT) in different centers on the locoregional recurrence rate (LRR) and disease-free survival (DFS) at 5 years. The LRR, DFS, and delivery of RT were analyzed as endpoints in multivariate analysis. Results: A significant difference was found between the centers and the delivery of RT. The overall delivery of RT was a prognostic factor for the LRR (no RT, 29.6% {+-} 7.8%; inadequate RT, 21.2% {+-} 5.6%; adequate RT, 6.8% {+-} 1.4%; p = 0.0001) and DFS (no RT, 55.1% {+-} 9.1%; inadequate RT, 57.4% {+-} 6.3%; adequate RT, 69.1% {+-} 2.3%; p = 0.02). Postoperatively, delivery of RT was a prognostic factor for LRR on multivariate analysis (together with pathologic stage) but not for DFS (independent parameters, pathologic stage and age). Preoperatively, on multivariate analysis, pathologic stage, but not delivery of RT, was an independent prognostic parameter for LRR and DFS (together with adequate chemotherapy). On multivariate analysis, the treatment center, treatment schedule (neoadjuvant vs. adjuvant RT), and gender were prognostic parameters for adequate RT. Conclusion: Delivery of RT should be regarded as a prognostic factor for LRR in rectal cancer and is influenced by the treatment center, treatment schedule, and patient gender.

  3. Mediterranean Tertiary lamproites derived from multiple source components in postcollisional geodynamics

    NASA Astrophysics Data System (ADS)

    Prelevi?, D.; Foley, S. F.; Romer, R.; Conticelli, S.

    2008-04-01

    In the Mediterranean area, lamproitic provinces in Spain, Italy, Serbia and Macedonia have uniform geological, geochemical and petrographic characteristics. Mediterranean lamproites are SiO 2-rich lamproites, characterized by relatively low CaO, Al 2O 3 and Na 2O, and high K 2O/Al 2O 3 and Mg-number. They are enriched in LILE relative to HFSE and in Pb, and show depletion in Ti, Nb and Ta. Mediterranean lamproites show huge regional variation of Sr, Nd and 207Pb/ 204Pb isotopic values, with 87Sr/ 86Sr range of 0.707-0.722, ?Nd range from -13 to -3, and 207Pb/ 204Pb range of 15.62-15.79. Lamproitic rocks are derived from melts with three components involved in their origin, characterized by contrasting geochemical features which appear in 206Pb/ 204Pb, 87Sr/ 86Sr and 143Nd/ 144Nd space: (i) a mantle source contaminated by crustal material, giving rise to crust-like trace element patterns and radiogenic isotope systematics, (ii) an extremely depleted mantle characterized by very low whole-rock CaO and Al 2O 3, high-Fo olivine and Cr-rich spinel, which isotopically resembles European peridotitic massifs and lithospheric mantle; (iii) a component originating from the convecting mantle, characterized by unradiogenic 87Sr/ 86Sr and radiogenic 143Nd/ 144Nd and 206Pb/ 204Pb. These components demand multistage preconditioning of the lamproite-mantle source, involving an episode of extreme depletion, followed by involvement of terrigenous sediments, and finally interaction with melts originating from the convecting mantle, some of which are probably carbonatitic. We use our data on Mediterranean lamproites to characterize the mantle composition under the whole Alpine-Himalaya belt. Lamproites are an integral part of postcollisional volcanism, and are the most extreme melting products from a mantle which is ubiquitously crustally metasomatized. Enriched isotope signatures in Himalayan volcanics can also be explained by the involvement of subducted sediments instead of by proterozoic mantle lithosphere.

  4. Geochemistry and shock petrography of the Crow Creek Member, South Dakota, USA: Ejecta from the 74-Ma Manson impact structure

    USGS Publications Warehouse

    Katongo, C.; Koeberl, C.; Witzke, B.J.; Hammond, R.H.; Anderson, R.R.

    2004-01-01

    The Crow Creek Member is one of several marl units recognized within the Upper Cretaceous Pierre Shale Formation of eastern South Dakota and northeastern Nebraska, but it is the only unit that contains shock-metamorphosed minerals. The shocked minerals represent impact ejecta from the 74-Ma Manson impact structure (MIS). This study was aimed at determining the bulk chemical compositions and analysis of planar deformation features (PDFs) of shocked quartz; for the basal and marly units of the Crow Creek Member. We studied samples from the Gregory 84-21 core, Iroquois core and Wakonda lime quarry. Contents of siderophile elements are generally high, but due to uncertainties in the determination of Ir and uncertainties in compositional sources for Cr, Co, and Ni, we could not confirm an extraterrestrial component in the Crow Creek Member. We recovered several shocked quartz grains from basal-unit samples, mainly from the Gregory 84-21 core, and results of PDF measurements indicate shock pressures of at least 15 GPa. All the samples are composed chiefly of SiO2, (29-58 wt%), Al2O3 (6-14 wt%), and CaO (7-30 wt%). When compared to the composition of North American Shale Composite, the samples are significantly enriched in CaO, P2O5, Mn, Sr, Y, U, Cr, and Ni. The contents of rare earth elements (REE), high field strength elements (HFSE), Cr, Co, Sc, and their ratios and chemical weathering trends, reflect both felsic and basic sources for the Crow Creek Member, an inference, which is consistent with the lithological compositions in the environs of the MIS. The high chemical indices of alteration and weathering (CIA' and CIW': 75-99), coupled with the Al2O3-(CaO*,+Na2O -K2O (A-CN'-K) ratios, indicate that the Crow Creek Member and source rocks had undergone high degrees of chemical weathering. The expected ejecta thicknesses at the sampled locations (409 to 219 km from Manson) were calculated to range from about 1.9 to 12.2 cm (for the present-day crater radius of Manson), or 0.4 to 2.4 cm (for the estimated transient cavity radius). The trend agrees with the observed thicknesses of the basal unit of the Crow Creek Member, but the actually observed thicknesses are larger than the calculated ones, indicating that not all of the basal unit comprises impact ejecta. ?? Meteoritical Society, 2004.

  5. IT Leadership: CAO 2.0

    ERIC Educational Resources Information Center

    Voyles, Bennett

    2006-01-01

    Most of the time, technology in the classroom is a "we" or "they" issue: On one side are the people who deploy and operate the systems, on the other, the academics and staffers who use them. But, typically, on both sides, everyone is so busy trying to prepare for the next class or the next term that there's little opportunity to ask what new

  6. Geochemistry and petrogenesis of Paleo-Proterozoic granitoids from Mahakoshal Supracrustal Belt (MSB), CITZ

    NASA Astrophysics Data System (ADS)

    Yadav, Bhupendra; Ahmad, Talat; Kaulina, Tatiana; Bayanova, Tamara

    2015-04-01

    Voluminous granitic magmatism of Proterozoic age occupies a vast expanse at the southern margin of Mahakoshal Supracrustal Belt (MSB), CITZ. The present study focuses on eastern part of this belt and discusses possible crustal evolution processes based on the geochemical, geochronological and Sm-Nd isotopic constraints on these rocks. The rocks present are predominantly granites and gneisses viz. grey to pink granite gneiss and leuco- to mesocratic granites. In general these rocks are medium to coarse grained and microscopically show typical granitic assemblages with apatite, titanite, zircon and allanite as accessories. Mineralogically these rocks are grouped into three categories viz. Hbl-Bt granite gneiss, Bt- granite gneiss and Bt-granite. Major oxide characteristics show that the Hbl-Bt granite Gneiss are metaluminous (ASI~0.98), whereas Bt- granite gneiss (ASI=1.05-1.22) and Bt- granite (ASI=1.03-1.21) are weakly peraluminous to strongly peraluminous. In terms of Fe* number and alkali-lime index these rocks belong to magnesian and calc-alkalic series respectively. Overall these rocks range from 59.43 to 72.01 wt.% SiO2 and have low Na2O content (average ~2.60 wt.%) with average ~4.02 wt.% K2O and high K2O/Na2O ratio. On Harker variation diagrams, all rock types show negative correlation for TiO2, P2O5, CaO, MnO, MgO, Fe2O3T and Al2O3 against SiO2 suggesting fractionation of Pl-Hbl-Ttn-Mag-Ap during evolution of these rocks. On chondrite-normalized Rare Earth Element (REE) plot, the Bt-granite is enriched in LREE ((La/Sm)N ~10.21) and show negative Eu anomaly (Eu/Eu*=0.39) with depleted HREE ((Gd/Yb)N ~4.38). The Hbl-Bt granite gneiss shows LREE ((La/Sm)N ~6.68) depletion and enriched HREE ((Gd/Yb)N ~2.05) patterns compared to Bt-granite, with negative Eu anomaly (Eu/Eu*=0.44). Whereas Bt-gneiss is moderate in comparison with LREE enrichment ((La/Sm)N ~9.17) and HREE depletion ((Gd/Yb)N ~3.02) with weak negative Eu anomaly (Eu/Eu*=0.60). Multi-elemental plot shown for all rocks have positive U, Th and Pb anomalies and negative Nb and Ti anomalies, commonly interpreted as continental crust involvement in their genesis. Sm-Nd analysis on two samples of Hbl-Bt granite gneiss show143Nd/144Nd ratio ranges from 0.511384-0.511394 with a corresponding 147Sm/144Nd ratio of 0.118109-0.118762. The analyzed samples yield TDM model ages of 2807-2804 Ma with present day ?Nd values being negative, whereas the initial ?Nd values (calculated at TDM ages) are positive. The positive initial epsilon values indicate its derivation from depleted mantle source but this magma must have incorporated crustal material during their ascent and probably had a longer crustal residence time to have the observed evolved ?Ndlower values. However 143Nd/144Nd ratios when compared with present day enriched mantle values of EM-I (

  7. Physico-chemical conditions of crystallization of the Guli ulrabasic massif (North Part of the Siberian Platform): evidence from melt inclusions

    NASA Astrophysics Data System (ADS)

    Simonov, Vladimir; Vasiliev, Yuri; Kotlyarov, Alexey; Stupakov, Sergey

    2014-05-01

    Conditions of formation of the Guli ultrabasic massif (Maimecha Kotui Province in the North Part of the Siberian Platform) attract attention of numerous researchers. For the solution of genetic problems of various rocks from this ultramafic complex the data on melt inclusions in minerals has been earlier used (Sokolov et al., 1999; Rass, Plechov, 2000; Sokolov, 2003; Panina, 2006). At the same time, formation of dunites, occupying the main volume of the Guli massif, remain almost not considered by means of thermobarogeochemical methods and the role of magmatic processes in this case is not ascertained. As a result of melt inclusions study in the Cr-spinel the new data on physical and chemical parameters of dunite crystallization in the Guli ulrabasic massif was obtained. On the ratio (Na2O + K2O) - SiO2 the majority of analyses of glasses and calculated compositions of inclusions settle down in the field of subalkaline series. On the diagram MgO - SiO2 bulk chemical compositions of inclusions (with the magnesium content of 19-28 wt. %) correspond to picrites and picrite-basalts. They are in close association with the data on inclusions in the Cr-spinel from dunites of Konder (Siberian Platform) and Nizhnii Tagil (Ural Mountains) platinum-bearing ultrabasic massifs and also are situated near to the field of inclusions in the olivine phenocrysts from meimechites (Maimecha Kotui Province in the North Part of the Siberian Platform). Similarity of melt inclusions in the Cr-spinel from the dunite of the Guli massif and in the olivine from meimechites is established on the variety of petrochemical components - Al2O3, CaO, Na2O, K2O. The calculated compositions of inclusions from dunites coincide mostly with the data on inclusions from meimechites, while glasses of inclusions from Cr-spinel contain less titan and magnesium. As a whole for the melts of the Maimecha Kotui Province (that form both dunites of the Guli massif and meimechites) much higher contents of TiO2 (from above 2.7 wt. %) are characteristic in comparison with magmatic systems of the platinum-bearing ultrabasic massifs of Ural and Siberia. Our computer simulations on the basis of melt inclusion compositions by the PETROLOG program package (Danyushevsky, Plechov, 2011) show the high crystallization temperature of olivines from dunites of the Guli massif in the intrusive chamber - 1590-1415 C. Formation of the Cr-spinels occurred also at high parameters - 1405-1365 C. These temperatures correspond to established earlier temperature interval of crystallization of olivines from meimechites - 1600-1420 C (Sobolev et al., 1999, 2009). As a whole, the melt inclusions study in the Cr-spinel directly testify to formation of dunites from the Guli massif from high magnesia melt, relative on its petrochemical composition and high-temperature characteristics to meimechite magma. Consecutive evolution of composition of magmatic systems is established during intra-chamber crystallization of dunites from picrite-meimechite to picrite-basalt and basalt melts. The investigations were supported by the Project N VIII.66.1.1 and by the Russian Foundation for Basic Research (Project N 12-05-00959).

  8. Late Paleozoic to Early Mesozoic arc-related magmatism in southeastern Korea: SHRIMP zircon geochronology and geochemistry

    NASA Astrophysics Data System (ADS)

    Yi, Keewook; Cheong, Chang-sik; Kim, Jeongmin; Kim, Namhoon; Jeong, Youn-Joong; Cho, Moonsup

    2012-11-01

    Phanerozoic granitoids are widespread in the Korean Peninsula and form a part of the East Asian Cordilleran-type granitoid belt extending from southeastern China to Far East Russia. Here we present SHRIMP zircon U-Pb ages and geochemical and Nd isotopic compositions of Late Paleozoic to Early Jurassic granitoid plutons in the northern Gyeongsang basin, southeastern Korea; namely the Jangsari, Yeongdeok, Yeonghae, and Satkatbong plutons. The granite and associated gabbroic rocks from the Jangsari pluton were coeval and respectively dated at 257.3 ± 2.0 Ma and 255.7 ± 1.4 Ma. This result represents the first finding of a Late Paleozoic pluton in South Korea. Three granite samples from the Yeongdeok pluton yielded a slightly younger age span ranging from 252.9 ± 2.5 Ma to 246.7 ± 2.1 Ma. Two diorite samples from the Yeonghae pluton gave much younger ages of 195.1 ± 1.9 Ma and 196.3 ± 1.6 Ma. An Early Jurassic age of 192.4 ± 1.6 Ma was also obtained from a diorite sample from the Satkatbong pluton. The mineral assemblage and Al2O3/(Na2O + K2O) versus Al2O3/(CaO + Na2O + K2O) relationship indicate that all the analyzed plutons are subduction zone granitoids. Enrichments in large-ion-lithophile-elements and depletions in high-field-strength-elements of these plutons are also concordant with geochemical characteristics typical for the subduction zone magma. The presence of Late Permian to Early Triassic arc system is in contrast with the conventional idea that the arc magmatism along the continental margin of the Korean Peninsula has commenced from Early Jurassic after the termination of Triassic collisional orogenesis. The ɛNd(t) values of the granitoid plutons are consistently positive (2.4-4.6), suggesting that crustal residence time of the basement beneath the Gyeongsang basin is relatively short. Moreover, the reevaluation of previously-published data reveals that geochemical compositions of the Yeongdeok pluton are compatible with those of high-silica adakites; La/Yb = 37.5-114.6, Sr/Y = 138.2-214.0, SiO2 = 62.9-72.0 wt.%, Al2O3 = 15.5-17.0 wt.%, Sr = 562-1173 ppm, MgO = 0.4-1.6 wt.%, Y = 3-6 ppm, Yb = 0.18-0.45 ppm, and Eu/Eu* = 0.92-1.31. The occurrence of adakites in southeastern Korea, and presumably in the Hida belt of central-western Japan, is indicative of a hot subduction regime developing at least partly along the East Asian continental margin during the Permian-Triassic transition period.

  9. Crystallization of tholeiitic basalt in Alae Lava Lake, Hawaii

    USGS Publications Warehouse

    Peck, D.L.; Wright, T.L.; Moore, J.G.

    1966-01-01

    The eruption of Kilauea Volcano August 21-23, 1963, left 600,000 cubic meters of basaltic lava in a lava lake as much as 15 meters deep in Alae pit crater. Field studies of the lake began August 27 and include repeated core drilling, measurements of temperature in the crust and melt, and precise level surveys of the lake surface. The last interstitial melt in the lake solidified late in September 1964; by mid August 1965 the maximum temperature was 690??C at a depth of 11.5 meters. Pumice air-quenched from about 1140??C contains only 5 percent crystals - clinopyroxene, cuhedral olivine (Fo 80), and a trace of plagioclase, (An 70). Drill cores taken from the zone of crystallization in the lake show that olivine continued crystallizing to about 1070??C; below that it reacts with the melt, becoming corroded and mantled by pyroxene and plagioclase. Below 1070??C, pyroxene and plagioclase crystallized at a constant ratio. Ilmenite first appeared at about 1070??C and was joined by magnetite at about 1050??C; both increased rapidly in abundance to 1000??C. Apatite first appeared as minute needles in interstitial glass at 1000??C. Both the abundance and index of refraction of glass quenched from melt decreased nearly linearly with falling temperature. At 1070??C the quenched lava contains about 65 percent dark-brown glass with an index of 1.61; at 980??C it contains about 8 percent colorless glass with an index of 1.49. Below 980??C, the percentage of glass remained constant. Progressive crystallization forced exsolution of gases from the melt fraction; these formed vesicles and angular pores, causing expansion of the crystallizing lava and lifting the surface of the central part of the lake an average of 19.5 cm. The solidified basalt underwent pneumatolitic alteration, including deposition of cristobalite at 800??C, reddish alteration of olivine at 700??C, tarnishing of ilmenite at 550??C, deposition of anhydrite at 250??C, and deposition of native sulfur at 100??C. Ferric-ferrous ratios suggest that oxidation with maximum intensity between 550??C and 610??C moved downward in the crust as it cooled; this was followed by reduction at a temperature of about 100??C. The crystallized basalt is a homogeneous fine-grained rock containing on the average 48.3 percent by volume intergranular pyroxene (augite > pigeonite), 34.2 percent plagioclase laths (An60 70), 7.9 percent interstitial glass, 6.9 percent opaques (ilmenite > magnetite), 2.7 percent olivine (Fo70 80), and a trace of apatite. Chemical analyses of 18 samples, ranging from initially quenched pumice to lava cored more than a year after the eruption from the center and from near the base of the lake, show little variation from silica-saturated tholeiitic basalt containing 50.4 percent SiO2, 2.4 percent Na2O, and 0.54 percent K2O. Apparently there was no significant crystal settling and no appreciable vapor-phase transport of these components during the year of crystallization. However, seven samples of interstitial liquid that had been filter-pressed into gash fractures and drill holes from partly crystalline mush near the base of the crust show large differences from the bulk composition of the solidified crust-lower MgO, CaO, and Al2O3; and higher total iron, TiO2, Na2O, K2O, P2O5, and F, and, in most samples, SiO2. The minor elements Ba, Ga, Li, Y, and Yb and possibly Cu tend to be enriched in the filter-pressed liquids, and Cr and possibly Ni tend to be depleted. ?? 1966 Stabilimento Tipografico Francesco Giannini & Figli.

  10. Glass and mineral analyses from first deposits of Peach Spring Supereruption (SW USA) illuminate initial tapping of a zoned magma chamber

    NASA Astrophysics Data System (ADS)

    Mccracken, R. G.; Miller, C. F.; Buesch, D.; Gualda, G. A.; Covey, A.

    2012-12-01

    The Peach Spring supereruption (18.78±0.02 Ma) was sourced from Silver Creek caldera in the southern Black Mountains, Arizona (Ferguson et al. in press). The resulting ignimbrite, the Peach Spring Tuff (PST), blanketed >32,000 km2 of Arizona, California, and Nevada (Buesch, 1993). Underlying the ignimbrite is a thin (≤ 1m thick) basal layered deposit that consists of texturally distinct layers 1a-e (Valentine et al. 1989) and is present up to ~100 km from the source caldera. Basal layered deposits contain the first material erupted during the PST supereruption, preceding the main eruption event. Petrography and geochemistry of minerals and pumice clasts from basal layered deposits collected ~15-100 km from the caldera, combined with a survey of glass and crystal compositions from both outflow and basal deposits, permit (1) comparisons with the overlying ignimbrite, and (2) insights into the initial stages of the supereruption and extraction of magma from the chamber. Pumice clasts from a pumice-rich layer (1a2) of the basal deposit were characterized by LA-ICPMS and SEM. Unaltered glass has a uniform high-Si rhyolite composition (76.7% SiO2, 13.0% Al2O3, 3.6% Na2O, 5.3% K2O, 0.6% FeO, <0.1% MgO, 0.6% CaO, 0.1% TiO2). Mildly altered glass is similar but has lower Na2O and higher K2O. Pumice clasts are relatively crystal poor (<10% phenocrysts) with an assemblage dominated by sanidine (~Or55Ab43An2), with lesser plagioclase (~Ab73An19Or8), minor hornblende and biotite, and accessory magnetite, sphene, zircon, chevkinite, and apatite; no quartz was identified. Initial LA-ICPMS results for glass reveal REE patterns with large negative Gd (0.21: i.e. U-shaped REE pattern) and Eu (0.31) anomalies, very low Ba and Sr (≤10 ppm), and high Rb (~250 ppm). These compositions are essentially identical to those of the most common pumice from distal outflow ignimbrite, but very different from crystal-rich (>30%) trachyte pumice that dominates the intracaldera fill and is present at the tops of proximal outflow sections (Pamukcu et al. in press). A broader survey by EMP of minerals and glass shards from basal layered deposits and outflow ignimbrite (Buesch, 1993 and unpublished data, 1992) support the general conclusion that distal outflow is dominated by high-Si rhyolite, but demonstrate that trachyte is present throughout ignimbrite and basal deposits. Although SiO2 concentration is dominantly ~76-78 wt%, a small but persistent population ranges from ~66-72 wt%. Likewise, 6% (in layer 1a2) to 40% of all plagioclase in basal and outflow deposit samples is relatively calcic (An>27), indicating trachyte origin. The above data (1) confirm the existence of two compositions of erupted magma (phenocryst-poor, high-Si rhyolite, crystal-rich trachyte); (2) demonstrate that the initial eruption (basal layer) tapped the same magmas as the ignimbrite; and (3) reveal that, although rhyolite dominates outside the caldera, trachyte like that in intracaldera deposits was also tapped throughout the eruption. These relations are consistent with eruption from a vertically stratified magma chamber with trachyte (cumulate?) beneath rhyolite, but indicate that either chamber stratification was imperfectly developed or some magma from deeper levels was entrained throughout the eruption.

  11. Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

    NASA Astrophysics Data System (ADS)

    Offler, R.; Fergusson, C. L.

    2016-04-01

    The Early Palaeozoic proto-Pacific Pacific margin of Gondwana was characterised by a huge turbidite submarine fan with abundant clastic detritus derived from unknown sources within Gondwana. These deposits are widespread in the Lachlan Orogen of southeast Australia and include the Ordovician Adaminaby Group. Here we show that the mudstones and sandstones of the Adaminaby Group have chemical compositions that indicate the detritus in them was derived from a felsic, continental source similar in composition to Post Archean Australian Shales (PAAS). Chondrite normalised REE patterns showing LREE enrichment, flat PAAS normalised patterns and elemental ratios La/Sc, Cr/Th, Cr/V, Th/Sc and Th/U, have been used to support this interpretation. The dominance of quartz, and to a lesser degree plagioclase and biotite in the sandstones, suggests that the source was mainly granodioritic to tonalitic in composition. Th/Yb and Ta/Yb ratios indicate that the source was probably calc-alkaline, continental and shoshonitic. In addition, the presence of detrital muscovite, low-grade metamorphic and felsic volcanic clasts, demonstrates that a low-grade metamorphic terrane and volcanic arc contributed to the detritus observed in the samples. The presence of well-rounded zircons and tourmalines, very high Zr contents, high Zr/Sc and higher Cr/V ratios in some samples particularly in the Shoalhaven River area, indicate that some of the detritus was recycled. SiO2 versus (Al2O3 + K2O + Na2O) plots suggest the source areas experienced conditions varying from humid/semi-humid to semi-arid. Textural features and weathering trends of samples from all locations follow a curved pathway on Al2O3 - (CaO* + Na2O) - K2O (ACNK) diagrams, and indicate that the clays formed from weathering had been K-metasomatised prior to penetrative deformation. Chemical indices of alteration (CIA) reveal that even the freshest sandstones are altered and others are moderately to strongly altered. Discrimination diagrams involving major, trace and REE strongly support a collisional/continental volcanic arc setting that was substantially eroded to produce the plutonic detritus observed in the sandstones. The collisional setting accords with that proposed previously by other authors who suggested that it developed during the Delamerian Orogeny, resulting in the uplifted source areas providing detritus that inundated the backarc and forearc sites of the Macquarie Arc. Some of the detritus, however, may have been derived from a continental arc that existed in the late Cambrian along the margin of the Ross Orogen. Based on palaeocurrent analyses in previous studies and shoshonitic signature of the detritus, it is proposed that the Cambrian volcanics along the eastern active margin of Gondwana provided much of the detritus in the Adaminaby Group. Zircons with the Grenvillian signature suggest that some detritus were also derived from the Ross Orogen.

  12. Geochemical characterization of migmatized orthogneiss from Porto Ottiolu (NE Sardinia, Italy) and its inferences on partial melting process

    NASA Astrophysics Data System (ADS)

    Cruciani, Gabriele; Fancello, Dario; Franceschelli, Marcello; Columbu, Stefano

    2015-04-01

    Migmatites are very common in the northern part of the axial zone of the Sardinia Variscan chain. At Porto Ottiolu, about 30 km south of Olbia, a wide sequence of igneous- and sedimentary-derived migmatites crops out. Migmatized orthogneiss have a complex structural evolution characterized by three folding phases (D1, D2, D3) followed by a shear deformation. The oldest structure observed in the migmatites is a gneissose layering (D1). The second deformation (D2) is the most pervasive in the field and produces tight folds. D3 deformation caused symmetric folds with sub-horizontal axes. The leucosomes are coarse-grained, centimetre-thick, deformed leucocratic layers and/or patches following or cutting the D2 foliation. Other leucosomes are emplaced along shear zones (S4). The mesosomes are medium-grained foliated rocks in which the foliation is identified by biotite oriented along the S2 schistosity. The contact between mesosome and leucosome is frequently marked by thin biotite-rich selvedge. Leucosomes mainly consist of quartz, plagioclase, K-feldspar, minor biotite, muscovite and rare garnet. Mesosomes consist of the same mineral assemblage but they are rich in biotite and muscovite. Muscovite is found as submillimetre-sized crystals with variable phengitic component (Si: 6.1, Fe: 0.14, Mg: 0.13 a.p.f.u., XMg: 0.48 in less phengitic crystals, Si: 6.2, Fe: 0.18, Mg: 0.20 a.p.f.u., XMg: 0.53 in more phengitic ones). Biotite is titanium rich (Ti 0.3 a.p.f.u.) and has XMg 0.4. Very rare garnet occurs as submillimetric unzoned almandine with high manganese and low calcium content (Alm: 79mol.%; Prp: 5; Sps: 11-13; Grs: 3). Plagioclase is an unzoned oligoclase (XAb: 0.7), sometimes surrounded by a thin rim of pure albite. K-feldspar often shows perthitic exsolutions. The modal amount of feldspars varies significantly within the same leucosome and between different leucosomes. In particular, leucosomes along shear zones are feldspar rich. Evidences of melting are given by the occurrence of myrmekitic miscrostructures between quartz and feldspar, quartz films at the feldspar interface and by albite rims around plagioclase. Some selected samples were analysed for major, minor and trace element content. The leucosomes are characterized by the following major elements content: SiO2: 72.9-76.2; Al2O3: 14.7-15.4; Fe2O3tot: 0.1-0.7; MgO: 0.1-0.3; CaO: 0.5-3.2; Na2O: 2.4-3.5; K2O: 4.0-8.6 wt%. The noticeable wide range in CaO and K2O is related to the high variability of the plagioclase/K-feldspar ratio. Most leucosomes have granitic composition, except for those occurring along shear zones that have tonalitic composition. Mesosomes major elements contents are SiO2 ca. 70; Al2O3: 14.4-15.1; Fe2O3tot: 2.1-3.4; MgO ca. 1.0; CaO ca. 3.0; Na2O ca. 3.5; K2O ca. 2.6 wt.%. They have granodioritic compositions. All leucosome and mesosome samples are corundum normative. Chondrite-normalized REE patterns of leucosomes are characterized by a marked positive Eu anomaly and by LREE enrichment. Mesosomes are characterized by marked negative Eu anomalies, as well as by LREE and HREE enrichment. ∑REE is higher in mesosomes (153 ppm) than in leucosomes (20-63 ppm). Field relationships, microstructural and geochemical data support the hypothesis that migmatization was generated by partial melting of a probaby Ordovician granitoid. The origin of the various types of leucosome has been discussed.

  13. Natural weathering in dry disposed ash dump: Insight from chemical, mineralogical and geochemical analysis of fresh and unsaturated drilled cores.

    PubMed

    Akinyemi, S A; Akinlua, A; Gitari, W M; Khuse, N; Eze, P; Akinyeye, R O; Petrik, L F

    2012-07-15

    Some existing alternative applications of coal fly ash such as cement manufacturing; road construction; landfill; and concrete and waste stabilisation use fresh ash directly collected from coal-fired power generating stations. Thus, if the rate of usage continues, the demand for fresh ash for various applications will exceed supply and use of weathered dry disposed ash will become necessary alternative. As a result it's imperative to understand the chemistry and pH behaviour of some metals inherent in dry disposed fly ash. The bulk chemical composition as determined by XRF analysis showed that SiO2, Al2O3 and Fe2O3 were the major oxides in fresh ash and unsaturated weathered ashes. The unsaturated weathered ashes are relatively depleted in CaO, Fe2O3, TiO2, SiO2, Na2O and P2O5 due to dissolution and hydrolysis caused by chemical interaction with ingressing CO2 from the atmosphere and infiltrating rain water. Observed accumulations of Fe2O3, TiO2, CaO, K2O, Na2O and SO3 and Zn, Zr, Sr, Pb, Ni, Cr and Co in the lower layers indicate progressive downward movement through the ash dump though at a slow rate. The bulk mineralogy of unsaturated weathered dry disposed ash, as determined by XRD analysis, revealed quartz and mullite as the major crystalline phases; while anorthite, hematite, enstatite, lime, calcite, and mica were present as minor mineral phases. Pore water chemistry revealed a low concentration of readily soluble metals in unsaturated weathered ashes in comparison with fresh ash, which shows high leachability. This suggests that over time the precipitation of transient minor secondary mineral phases; such as calcite and mica might retard residual metal release from unsaturated weathered ash. Chloride and sulphate species of the water soluble extracts of weathered ash are at equilibrium with Na+ and K+; these demonstrate progressive leaching over time and become supersaturated at the base of unsaturated weathered ash. This suggests that the ash dump does not encapsulate the salt or act as a sustainable salt sink due to over time reduction in pore water pH. The leaching behaviours of Ca, Mg, Na+, K+, Se, Cr and Sr are controlled by the pH of the leachant in both fresh and unsaturated weathered ash. Other trace metals like As, Mo and Pb showed amphoteric behaviour with respect to the pH of the leachant. The precipitation of minor quantities of secondary mineral phases in the unsaturated weathered ash has significant effects on the acid susceptibility and leaching patterns of chemical species in comparison with fresh ash. The unsaturated weathered ash had lower buffering capacity at neutral pH (7.94-8.00) compared to fresh (unweathered) ash. This may be due to the initial high leaching/flushing of soluble basic buffering constituents from fly ash after disposal. The overall results of the acid susceptibility tests suggest that both fresh ash and unsaturated weathered ash would release a large percentage of their chemical species when in contact with slightly acidified rain. Proper management of ash dumps is therefore essential to safeguard the environmental risks of water percolation in different fly ashes behaviour. PMID:22446137

  14. Optimization of the thermodynamic properties and phase diagrams of P2O5-containing systems

    NASA Astrophysics Data System (ADS)

    Hudon, Pierre; Jung, In-Ho

    2014-05-01

    P2O5 is an important oxide component in the late stage products of numerous igneous rocks such as granites and pegmatites. Typically, P2O5 combines with CaO and crystallizes in the form of apatite, while in volatile-free conditions, Ca-whitlockite is formed. In spite of their interest, the thermodynamic properties and phase diagrams of P2O5-containg systems are not well known yet. In the case of the pure P2O5 for example, no experimental thermodynamic data are available for the liquid and the O and O' solid phases. As a result, we re-evaluated all the thermodynamic and phase diagram data of the P2O5 unary system [1]. Optimization of the thermodynamic properties and phase diagrams of the binary P2O5 systems was then performed including the Li2O-, Na2O-, MgO-, CaO-, BaO-, MnO-, FeO-, Fe2O3-, ZnO-, Al2O3-, and SiO2-P2O5 [2] systems. All available thermodynamic and phase equilibrium data were simultaneously reproduced in order to obtain a set of model equations for the Gibbs energies of all phases as functions of temperature and composition. In particular, the Gibbs energy of the liquid solution was described using the Modified Quasichemical Model [3-5] implemented in the FactSage software [6]. Thermodynamic modeling of the Li2O-Na2O-K2O-MgO-CaO-FeO-Fe2O3-Al2O3-SiO2 system, which include many granite-forming minerals such as nepheline, leucite, pyroxene, melilite, feldspar and spinel is currently in progress. [1] Jung, I.-H., Hudon, P. (2012) Thermodynamic assessment of P2O5. J. Am. Ceram. Soc., 95 (11), 3665-3672. [2] Rahman, M., Hudon, P. and Jung, I.-H. (2013) A coupled experimental study and thermodynamic modeling of the SiO2-P2O5 system. Metall. Mater. Trans. B, 44 (4), 837-852. [3] Pelton, A.D. and Blander, M. (1984) Computer-assisted analysis of the thermodynamic properties and phase diagrams of slags. Proc. AIME Symp. Metall. Slags Fluxes, TMS-AIME, 281-294. [4] Pelton, A.D. and Blander, M. (1986) Thermodynamic analysis of ordered liquid solutions by a modified quasichemical approach application to silicate slags. Metall. Trans. B, 17, 805-815. [5] A.D. Pelton, S.A. Decterov, G. Eriksson, C. Robelin and Y. Dessureault (2000) The modified quasichemical model - I Binary solutions. Metall. Mater. Trans. B, 31, 651-660. [6] C.W. Bale, P. Chartrand, S.A. Decterov, G. Eriksson, K. Hack, R. Ben Mahfoud, J. Melançon, A.D. Pelton and S. Petersen. (2002) FactSage Thermochemical Software and Databases. Calphad, 26, 189-228.

  15. Multi-analytical characterization of archaeological ceramics. A case study from the Sforza Castle (Milano, Italy).

    NASA Astrophysics Data System (ADS)

    Barberini, V.; Maspero, F.; Galimberti, L.; Fusi, N.

    2009-04-01

    The aim of this work was the characterization, using several analytical techniques, of a sample of ancient pottery found during archaeological excavations in the 14th century's Sforza Castle in Milano. The use of a multi-analytical approach is well established in the study of archaeological materials (e.g. Tite et al. 1984, Ribechini et al. 2008). The chemical composition of the sample was determined with X-ray fluorescence spectroscopy. The chemical composition is: SiO2 61.3(3)%, Al2O3 22.5(2)%, Fe2O3 7.19(6)%, K2O 3.85(1)%, MgO 1.6(1)%, Na2O 1.6(4)% (probably overestimated), TiO2 1.02(2)%, CaO 0.93(1)%, MnO 0.15(1)% and P2O5 0.06(2)%. The K2O content, important when dealing with TL dating, was determined also with atomic absorption spectrophotometry. The K2O content determined with atomic absorption is 3.86(3)%, in agreement with X-ray fluorescence analysis. The mineralogical composition of the sample was determined with X-ray powder diffraction: quartz 59.6(1) wt%, mica 37.8(3) wt% and feldspar (plagioclase) 2.6(2) wt%. The sample homogeneity was assessed with X-ray computerised tomography (CT), which is a very powerful non-destructive analysis tool for 3D characterization (Sguin, 1991). CT images show differences in materials with different X-ray absorption (mainly depending on different densities) and 3D reconstruction has many interesting archaeological applications (e.g. study of sealed jars). CT images of the studied sample showed the presence of angular fragments (probably quartz) few millimetres wide immersed in a fine grained matrix. Moreover, before and after the CT analysis, some ceramic powder was sampled to perform thermoluminescence analysis (TL, the powder used for this analysis can not be recovered). It was thus possible to evaluate the dose absorbed by the material due the X-ray irradiation. The dose absorbed after 3 hours of irradiation, the time needed for a complete scan of a 7 x 5 x 1 cm, is about 100 Gy, which is a very high value compared to those usually measured in TL analysis of non-irradiated samples. This has to be taken into account when planning CT and TL analyses on the same sample. References Ribechini E., Colombini M.P., Giachi G., Modugno F. and Palletti P., 2008, A multi-analytical approach for the characterization of commodities in a ceramic jar from Antinoe (Egypt). Archaeometry, DOI: 10.1111/j.1475-4754.2008.00406.x. Sguin F. H., 1991, High-Resolution Computed Tomography and Digital Radiography of Archaeological and Art-Historical Objects, in Materials Issues in Art and Archaeology II , edited by P.B. Vandiver, J. R. Druzik and G. Wheeler (Materials Research Society, Pittsburgh). Tite M.S., Freestone I.C. and Bimsona M., 1984, Technological study of chinese porcelain of the Yuan dynasty. Archaeometry, 26 (2), 139-154.

  16. Multi-component diffusion between molten SiO2 inclusions and surrounding felsic melt in an indochinite: Tektites as natural laboratories

    NASA Astrophysics Data System (ADS)

    Macris, C. A.; Eiler, J. M.; Asimow, P. D.; Stolper, E. M.

    2013-12-01

    Tektites are natural glasses thought to have formed as a result of melting and quenching of distally ejected terrestrial material upon hypervelocity (>11 km/s) impact on Earth. Some tektites contain inclusions of lechatelierite (nearly pure SiO2 glass; 99-100 wt. % SiO2), generally thought to be the amorphous relicts of partially digested quartz grains (Koeberl, 1994). Electron and ion microprobe analyses of major and minor elements were performed on transects between lechatelierite inclusions and the surrounding felsic glass in an indochinite (sample from Newman et al., 1995). The surrounding glass is peraluminous with an average composition of 73.4 wt.% SiO2, 12.8 wt.% Al2O3, 4.5 wt. % FeO, 2.3 wt.% K2O, and < 2 wt.% (each) CaO, MgO, Na2O, and TiO2. The boundary between the lechatelierite and felsic glass is broad (~30 ?m), with complex concentration profiles reflecting diffusion between the two melts at high temperatures (>2200 C for formation of lechatelierite; Bunch et al., 2012) prior to quenching. Although all components except SiO2 are pinned to near zero at the same point at the lechatelierite end of the profiles, the shapes of the oxide concentration profiles differ, with Ca and Mg falling off from their far-field values first, followed in order by Fe, Ti, Al, Na, and K. K has apparently propagated the longest distance, diffusing faster than other components from the surrounding melt toward the lechatelierite. Furthermore, concentration profiles of K2O systematically increase, reach a maximum, then decrease closest to lechatelierite, indicating uphill diffusion of K against its concentration gradient. All concentration profiles are asymmetric, becoming steepest towards the most silicic portions of the interdiffusion zone approaching lechatelierite, likely due to the sharp compositional contrast between matrix glass and inclusions. Sato (1974) observed similar alkali enrichment in coronas around quartz xenocrysts in basalt and andesite, where K, and to a lesser degree Na, diffused against their concentration gradients. The uphill diffusion of alkalis in corona glass surrounding quartz was interpreted by Sato (1974) with a diffusion model assuming non-ideality of alkali elements in silicate melt, in which diffusion occurs according to the chemical potential gradient of each species. Preliminary calculations using the MELTS (Ghiorso and Sack, 1995) activity-composition model to transform the composition profiles across lechatelierite and felsic glass into chemical potential profiles (at 2200 C) indicate that all components, including K2O, diffuse down their own chemical potential gradients. We will investigate these phenomena further in attempt to model the observed profiles. A deeper understanding of this problem may inform the factors controlling diffusion coefficients in silicate melts derived from crustal material, as well as the thermal histories of tektites. Bunch T.E. et al. (2012) P NATL ACAD SCI 109:1903-1912 Ghiorso M.S., Sack R.O. (1995) CONTRIB MINERAL PETR 119:197-212 Koeberl C. (1994) GEOL S AM S 133-151 Newman S. et al. (1995) LPS XXVI 26:1039-1040 Sato H. (1974) CONTRIB MINERAL PETROL 50:49-64

  17. Vibrational features of phospho-silicate glasses: Periodic B3LYP simulations

    NASA Astrophysics Data System (ADS)

    Corno, Marta; Pedone, Alfonso

    2009-07-01

    B3LYP periodic calculations with double-ζ polarised basis set using C RYSTAL06 code have been run on a bioactive phospho-silicate glass similar in composition to Bioglass ® 45S5 (46.1 SiO 2, 24.4 Na 2O, 26.9 CaO and 2.6 P 2O 5 mol%) and a phosphorous-free soda-lime glass (49.5 SiO 2, 24.2 Na 2O and 26.4 CaO mol%). Initial structures have been obtained through a melt-quench process by classical molecular dynamics techniques and the effect of phosphorous on the glass network structure and dynamics have been assessed by B3LYP vibrational spectra.

  18. Comparison of Results Analyzed by China and European Laboratories for the FOREGS Geochemical Baselines Mapping Samples

    NASA Astrophysics Data System (ADS)

    Yao, W.; Wang, X.; Nie, L.

    2010-12-01

    The geochemical data obtained from China and European laboratories for the subsoil samples of FOREGS Geochemical Baselines Mapping Project were compared. 190 sub soil samples were composed from 787 samples remained after the analysis campaign of the FOREGS Project. In addition to the FOREGS elemental analysis package, Au, Pt, Pd, B, Ge, Br, Cl, Se, N, Li and F were also analyzed by using the IGGE 76 element analytical scheme. In this study, the geochemical data statistics, scatter plotting, and the geochemical map compilation techniques were employed to investigate the differences between the analysis results. The results of the two dataset agree extremely well for about 23 elements, viz: SiO2, Sr, Al2O3, Zr, Ba, Fe2O3, Ti, Rb, Mn, Gd, CaO, Ga, MgO, P, Pb, Na2O, Y, Th, As, U Sc, Cr, and Co. The slight proportional errors exist between the datasets for the elements of Ni, K2O, Tb, Tl, Cu, S, Sm, La, Ce, Pr, Nd, Eu, Ho, Er, Tm, Yb, Lu, Ta, Nb, Hf, Dy. For the elements of Cd, Cs, Be, Sb, In, Mo, I, Sn, and Te, their geochemical maps are normal similarity, but the obvious biases exist between the two dataset for the values near the detection limits. The sensitivities of FOREGS analytical methods for W, Bi, Sn, Te, Be, and I are insufficient to produce reportable values at least 80% of the samples. Although the detection limits of Ag for both method are all sufficient to give out enough reportable values, but the big bias were found between the two datasets. This study demonstrated that the comparable analytical data of the certain elements for the global geochemical mapping samples can be achieved by the different laboratories. But for other elements, such as Ag, the further research on the selection of the proper analytical methods and on the quality control methods should to be undertaken and the final recommendation should be commonly obeyed by all participates of the global geochemical mapping program.

  19. Formation and emplacement of two contrasting late-Mesoproterozoic magma types in the central Namaqua Metamorphic Complex (South Africa, Namibia): Evidence from geochemistry and geochronology

    NASA Astrophysics Data System (ADS)

    Bial, Julia; Büttner, Steffen H.; Frei, Dirk

    2015-05-01

    The Namaqua Metamorphic Complex is a Mesoproterozoic low-pressure, granulite facies belt along the southern and western margin of the Kaapvaal Craton. The NMC has formed between ~ 1.3 and 1.0 Ga and its central part consists essentially of different types of granitoids intercalated with metapelites and calc-silicate rocks. The granitoids can be subdivided into three major groups: (i) mesocratic granitoids, (ii) leucocratic granitoids and (iii) leucogranites. The high-K, ferroan mesocratic granitoids (54-75 wt% SiO2) have a variable composition ranging from granitic to tonalitic, and contain biotite and/or hornblende or orthopyroxene. They are strongly enriched in REE and LILE, indicating A-type chemical characteristics, and are depleted in Ba, Sr, Eu, Nb, Ta and Ti. The leucocratic granitoids and leucogranites (68-76 wt% SiO2) differ from the other group in having a granitic or slightly syenitic composition containing biotite and/or garnet/sillimanite. They have lower REE and MgO, FeOt, CaO, TiO2, MnO concentrations, but higher Na2O and K2O contents. Compositional variations in mesocratic granitoids indicate their formation by fractional crystallization of a mafic parental magma. Leucocratic granitoids and leucogranites lack such trends, which suggests melting of a felsic crustal source without subsequent further evolution of the generated magmas. The mineralogical and geochemical characteristics of the mesocratic granitoids are consistent magmatic differentiation of a mantle derived, hot (> 900 °C) parental magma. The leucocratic granitoids and leucogranites granites were formed from low-temperature magmas (< 730 °C), generated during fluid-present melting from metasedimentary sources. New U-Pb zircon ages reveal that both magma types were emplaced into the lower crust within a 30-40 million years interval between 1220-1180 Ma. In this time period the crust reached its thermal peak, which led to the formation of the leucocratic granitoids and leucogranites. A prolonged period of relatively high crustal temperatures is followed by a second heat pulse at ~ 1100 Ma, that was intense enough to facilitate zircon growth in the older plutons and it produced a younger granite suite. The crust cools down below amphibolite facies conditions after a further 100 million years. The prolonged high-temperature history is best compatible with steady and long-lasting heat transfer from mantle sources, suggesting a continental back-arc situation as the most likely setting of the NMC in the late Mesoproterozoic.

  20. Heavy metal accumulation in balsam pear and cowpea related to the geochemical factors of variable-charge soils in the Pearl River Delta, South China.

    PubMed

    Chang, Chun-Ying; Xu, Xiang-Hua; Liu, Chuan-Ping; Li, Shu-Yi; Liao, Xin-Rong; Dong, Jun; Li, Fang-Bai

    2014-07-01

    Variable-charge (v-c) soils in subtropical areas contain considerable amounts of iron/aluminum (Fe/Al) oxides that can strongly influence the fate of heavy metals in agricultural ecosystems. However, the relationship between heavy metal accumulation in vegetables and the geochemical factors associated with v-c soils in subtropical regions remains unknown. The present study investigated heavy metal accumulation under field conditions in the Pearl River Delta (PRD) by measuring the content of 8 heavy metals (zinc (Zn), arsenic (As), copper (Cu), mercury (Hg), lead (Pb), chromium (Cr), nickel (Ni) and cadmium (Cd)) in 43 pairs of v-c soil and vegetable (balsam pear and cowpea) samples. Soil physicochemical properties including pH, texture, organic matter and oxide minerals (Fe2O3, SiO2, Al2O3, CaO, MgO, K2O and Na2O) were also analyzed. Heavy metal accumulation from soil to vegetables was assessed based on bioconcentration factors (BCFs). The results showed that soil extractable Fe, oxide minerals and chemical weathering indices of v-c soils strongly affected heavy metal accumulation, whereas the content of Zn, Cu, Cr and Ni in vegetables was strongly affected by the soil clay content. Significant correlations were found between the BCFs of heavy metals and oxide minerals. However, no significant relationship was found between pH and heavy metal accumulation (except for Cu) in balsam pear and cowpea. Correlation analyses showed that a lower oxalate/DCB- extractable Fe content might indicate greater heavy metal (Zn, Cu, Hg, Cr and Ni) accumulation in vegetables. Therefore, it can be deduced that oxalate/DCB- extractable Fe content is a critical geochemical factor that determines the bioavailability of heavy metals and that iron biogeochemical cycles play vital roles in the fate of heavy metals in vegetable fields in this area. These findings provide new insights into the behaviors and fate of heavy metals in subtropical v-c soils and can be used to develop possible guidelines for vegetable safety management. PMID:24855639

  1. Constraining Major Element Fractionation in an Alkali Gabbroic Sill using Mass Balance Modelling.

    NASA Astrophysics Data System (ADS)

    Ek, M.; Hogmalm, K. J.; Larson, S.-.

    2012-04-01

    The Ringkallen hill gabbro (RHG) is an ~225m thick layered alkali gabbroic sill in central Sweden. It is a part of the much larger ~1.26 Ga Ulv Gabbro complex, a series of 200-300m thick saucer-shaped alkali gabbroic intrusions with diameters of 30-80km. The anorthite (An.) content of plagioclase decrease gradually from ~70% at the margins to ~45% at the Sandwich Horizon, and the bulk composition of the RHG calculated from whole-rock analyses closely resembles the chilled margin composition, suggesting that the intrusion crystallised from a single pulse of magma in a closed system. Mass balance calculations were used to calculate the evolution of the supernatant liquid to the point where 90% of the intrusion had crystallised. The results show a successive decrease in the concentration of Al2O3 and MgO, an increase in MnO, TiO2, Na2O and K2O, while the concentrations of SiO2 and CaO remain stable. The major element variations of the calculated supernatant liquid were used to constrain the proportion between cumulus phases and crystallising liquid fraction (CLF). By iteratively changing the bulk partition coefficient by varying the proportion between the cumulus phases and the CLF for a given interval, the best estimate was found using root mean square method. The results indicate that the intrusion crystallised with a CLF of ~0.8 for the first 50% of crystallisation, and the next 30% had an estimated CLF of ~0.6 and the final 10% had ~0.8 CLF. At the point where 90% of the intrusion had crystallised, the stratigraphy contained only ~25% cumulus minerals. In strong contrast, simulation of the stratigraphic decrease in An. content of plagioclase by thermodynamic modelling suggests more than 70% fractional crystallisation. The strong stratigraphic decrease of plagioclase An. content is inconsistent with the modest change of the An. content of the calculated liquid. This suggests that the linear partitioning in the binary plagioclase system for these alkali gabbroic intrusions may be different from experimental results.

  2. Petrology and geochemistry of Mesozoic granitic rocks from the Nansha micro-block, the South China Sea: Constraints on the basement nature

    NASA Astrophysics Data System (ADS)

    Yan, Quanshu; Shi, Xuefa; Liu, Jihua; Wang, Kunshan; Bu, Wenrui

    2010-01-01

    There are several micro-blocks dispersed in the South China Sea (SCS), e.g., Xisha-Zhongsha block, Nansha block and Reed-Northeastern Palawan block, etc., but detailed petrological constraints on their basement nature were previously lacking. The magmatic ages for granitic rock samples from two dredge stations in the Nansha micro-block vary from 159 to 127 Ma, which are comparable to magmatic activities occurred in the northern margin (Pearl river mouth), HongKong and East China. Petrographic characteristics, major-, trace element and Sr-Nd isotopic data of nine samples from two dredged station performed in the Nansha micro-block, the SCS, are reported. Petrographically, these granitic rocks can be divided into two groups which underwent a complex history of magmatic process, i.e., tonalitic rock (Group I) and monzogranitic rock (Group II). The Rittmann index ( σ) for these rocks (1.9-3.1) suggest that they belong to calc-alkaline rocks. Group I rocks which is of typical I-type, have higher contents of TiO 2, Al 2O 3, FeO, MgO, CaO, Na 2O and P 2O 5, but lower values of SiO 2 and K 2O, when compared with those of Group II with I-type characteristics. Group I rocks are produced by partial melting of older Precambrian basement with the variable influence of mantle-derived magma which results from the interaction of released fluids from the subducted slab and the overlying mantle wedge in a general convergent margin setting, and Group II rocks result from partial melting of lower crustal basic rocks (amphibolite) and/or further partial melting of the Group I rocks associated with the variable influence from the underplating mantle-derived magma resulting from lithospheric extensional regime. Both Groups I and II have undergone assimilation and fractional crystallization (AFC) processes during its petrogenesis. This study therefore demonstrates that there exists a continental basement within micro-blocks in the South China Sea, and further supports the idea that a Middle Jurassic to Mid-Cretaceous subduction zone existed across the temporary Taiwan, Palawan to Southern Vietnam, which was associated with westward to northestward convergence of the Pacific Plate during Late Mesozoic. We suggest that this subduction zone may have been connected with the paleo-Pacific plate subduction zone offshore eastern China during Mesozoic era. This study provides petrologic data for the pre-Cenozoic tectonic evolution of the South China Sea.

  3. Characterization of the lead smelter slag in Santo Amaro, Bahia, Brazil.

    PubMed

    Lima, L R P de Andrade; Bernardez, L A

    2011-05-30

    For 33 years, a primary lead smelter operated in Santo Amaro (Brazil). Since the 1970s, large amounts of Pb and Cd have been widely documented in the blood and hair of people living near the smelter. The plant closed down in 1993, and several years later, the Pb levels in the blood of children under 4 years of age living near the smelter were high, where the disposed lead slag was suspected to be the main source of this contamination. The objective of this study is to elucidate the source of the Pb contamination and any other potentially toxic contamination, focusing on the characterization of the slag. The samples used for this characterization study were taken from the slag heaps. The results of the chemical analysis showed that the major constituents of the slag, in decreasing order of wt%, were the following: Fe(2)O(3) (28.10), CaO (23.11), SiO(2) (21.39), ZnO (9.47), MgO (5.44), PbO (4.06), Al(2)O(3) (3.56), C (2.26), MnO (1.44), Na(2)O (0.27), S (0.37), K(2)O (0.26), and TiO(2) (0.25). The Cd content of the slag was 57.3mg/kg, which is relatively low. The X-ray diffraction and the electron probe microanalyzer X-ray mapping indicated that the major phases in the slag were wstite, olivine, kirschsteinite, and franklinite. Only spheroidal metallic Pb was found in the slag. The leaching study showed that the slag was stable at a pH greater than 2.8, and only in an extremely acidic environment was the solubilization of the Pb enhanced significantly. The solubilization of Zn was very limited in the acidic and alkaline environments. These results can be explained by the limited leachability of the metallic Pb and Zn-bearing compounds. The leaching study used TCLP, SPLP, and SWEP and indicated that the lead slag was stable in weak acidic environments for short contact times. PMID:21440365

  4. Neoarchean paleoweathering of tonalite and metabasalt: Implications for reconstructions of 2.69Ga early terrestrial ecosystems and paleoatmospheric chemistry

    USGS Publications Warehouse

    Driese, S.G.; Jirsa, M.A.; Ren, M.; Brantley, S.L.; Sheldon, N.D.; Parker, D.; Schmitz, M.

    2011-01-01

    Field and laboratory investigations of a 2690.83Ma (207Pb/206Pb age of Saganaga Tonalite) unconformity exposed in outcrop in northeastern Minnesota, USA, reveal evidence for development of a deep paleoweathering profile with geochemical biosignatures consistent with the presence of microbial communities and weakly oxygenated conditions. Weathering profiles are characterized by a 5-50m thick regolith that consists of saprolitized Saganaga Tonalite and Paulson Lake succession basaltic metavolcanic rocks retaining rock structure, which is cross-cut by a major unconformity surface marking development of a successor basin infilled with alluvial deposits. The regolith and unconformity are overlain by thick conglomerate deposits that contain both intrabasinal (saprock) as well as extrabasinal detritus. Thin-section microscopy and electron microprobe analyses reveal extensive hydrolysis and sericitization of feldspars, exfoliation and chloritization of biotite, and weathering of Fe-Mg silicates and Cu-Fe sulfides; weathering of Fe-Ti oxides was relatively less intense than for other minerals and evidence was found for precipitation of Fe oxides. Geochemical analyses of the tonalite, assuming immobile TiO2 during weathering (??Ti,j), show depletion of SiO2, Al2O3, Na2O, CaO, MgO, and MnO, and to a lesser degree of K2O, relative to least-weathered parent materials. Significant Fe was lost from the tonalite. A paleoatmospheric pCO2 of 10-50 times PAL is estimated based on geochemical mass-balance of the tonalite profile and assuming a formation time of 50-500Kyr. Interpretations of metabasalt paleoweathering are complicated by additions of sediment to the profile and extensive diagenetic carbonate (dolomite) overprinting. Patterns of release of P and Fe and retention of Y and Cu in tonalite are consistent with recent laboratory experiments of granite weathering, and with the presence of acidic conditions in the presence of organic ligands (produced, for example, by a primitive microbial community) during weathering. Cu metal in the profile may document lower pO2 than present day at the surface. Comparison with previous studies of weathered tonalite and basalt (Denison, 2.45-2.22Ga) in Ontario, Canada, reveal general similarities in paleoweathering with our study, as well as important differences related to lower paleoatmospheric pO2 and terrestrial biosignature for the older Minnesota profile. A falling water table in the Alpine Lake locality is presumed to have promoted formation of this gossan-like deep-weathering system that extends to 50-m depth. ?? 2011 Elsevier B.V.

  5. Calcinaksite, KNaCa(Si4O10) H2O, a new mineral from the Eifel volcanic area, Germany

    NASA Astrophysics Data System (ADS)

    Chukanov, Nikita V.; Aksenov, Sergey M.; Rastsvetaeva, Ramiza K.; Blass, Günter; Varlamov, Dmitry A.; Pekov, Igor V.; Belakovskiy, Dmitry I.; Gurzhiy, Vladislav V.

    2015-08-01

    The new mineral calcinaksite, ideally KNaCa(Si4O10) · H2O, the first hydrous and Ca-dominant member of the litidionite group, is found in a xenolith of metamorphosed carbonate-rich rock from the southern lava flow of the Bellerberg volcano, Eastern Eifel region, Rheinland-Pfalz, Germany. It is associated with wollastonite, gehlenite, brownmillerite, Ca2SiO4 (larnite or calcio-olivine), quartz, aragonite, calcite, jennite, tobermorite and ettringite. Calcinaksite occurs as clusters of colourless to light-grey subhedral prismatic crystals. The mineral is brittle, with Mohs' hardness of 5; Dmeas is 2.62(2) g/cm3 and Dcalc is 2.623 g/cm3. The IR spectrum shows the presence of H2O molecules forming three different H-bonds. Calcinaksite is optically biaxial (+), α = 1.542(2), β = 1.550(2), γ = 1.565(3), 2 V meas = 75(10). The chemical composition (electron-microprobe data, H2O determined by the Alimarin method, wt%) is: Na2O 6.69, K2O 12.01, CaO 15.04, FeO 0.59, SiO2 61.46, H2O 4.9, total 100.69. The empirical formula is H2.11 K0.99Na0.84Ca1.04Fe0.03Si3.98O11. The crystal structure was solved and refined to R 1 = 0.053, wR 2 = 0.075 based upon 3057 reflections having I > 3σ( I). Calcinaksite is triclinic, space group P , a = 7.021(2), b = 8.250(3), c = 10.145(2) Å. α = 102.23(2)°, β = 100.34(2)°, γ = 115.09(3)°, V = 495.4(3) Å3, Z = 2. The strongest reflections of the X-ray powder pattern [ d, Å ( I,%) ( hkl)] are: 3.431 (70) (-121, -211, -210, 012, 0-22), 3.300 (67) (-031), 3.173 (95) (-103, -201, -220, 003, 111), 3.060 (100) (-212, 2-11, -221, 200, -1-13, 021, -202), 2.851 (83) (0-23, -122, 1-13, 1-31), 2.664 (62) (1-23, -222, 201).

  6. Northernmost Known Outcrop in North America of Lower Cretaceous Porphyritic Ocoite Facies (Ocoa, Chile) at Western Mexico: the Talpa Ocoite

    NASA Astrophysics Data System (ADS)

    Zrate-del Valle, P. F.; Demant, A.

    2003-04-01

    At Talpa de Allende region in Western Mexico is located the northernmost known outcrop of ocoite facies (andesite): the Talpa ocoite (TO). The ocoite facies consists of an calk-alkaline andesitic rock rich in K and characterized by the presence of megacrysts of plagioclase (An48-65). TO belongs to the so-called Guerrero Terrane composed of plutono-volcanic and volcano-sedimentary sequences of the Alisitos-Teloloapan arc that was accreted to the North American craton at the end of the early Cretaceous (Lapierre et al., 1992, Can. J. Earth Sci. 29. 2478--2489). Geodynamically TO belongs to lithological sequence number IV or "Tecoman" of Tardy et al. (1994, Tectonophysics 230, 49--73). TO in hand-sample shows typical megacrysts (>1 cm) of plagioclase and clinopyroxene in a dark green aphanitic matrix. This andesitic lava has a shoshonitic character as evidenced by chemical composition: SiO_2 TiO_2 Al_2O_3 Fe_2O_3 MnO MgO CaO Na_2O K_2O P_2O_5 LOI % Ba Sr (ppm) 55.64 0.73 16.61 8.39 0.13 3.59 6.40 3.55 2.85 0.36 1.84% 1093 880 Under microscope TO is characterized by a porphyritic texture made of large labradorite phenocrysts (up to 3 cm) and clinopyroxene with a matrix made of plagioclase microlites; TO has been affected by a low grade metamorphism process belonging to the prehnite-pumpellite facies as it happens in Chile (Levi, 1969, Contr. Mineral. and Petrol. 24-1, p. 30--49). Electron microprobe analysis shows that plagioclase (An55-57) is partly transformed into albite (An7-9); clinopyroxene shows a variation in composition from Wo33En41Fs17 to Wo40En44Fs24 and it is transformed towards the margin first into amphibole and then into biotite. TO outcrops located at East of Talpa river are affected by a deep rubefaction process. TO is not characterized by the presence of bitumen as it occurs in Northern Chile (Nova-Muoz et al., 2001, EUG XI Meeting, OS09 Supo09 PO, 606); TO is related in time with albian-cenomanian volcanogenic massive sulphides of Western Mexico: La Amrica and El Rub mines.

  7. Petrography and geochemistry of clastic sedimentary rocks as evidences for provenance of the Lower Cambrian Lalun Formation, Posht-e-badam block, Central Iran

    NASA Astrophysics Data System (ADS)

    Etemad-Saeed, N.; Hosseini-Barzi, M.; Armstrong-Altrin, John S.

    2011-09-01

    Petrography and geochemistry (major, trace and rare earth elements) of clastic rocks from the Lower Cambrian Lalun Formation, in the Posht-e-badam block, Central Iran, have been investigated to understand their provenance. Petrographical analysis suggests that the Lalun conglomerates are dominantly with chert clasts derived from a proximal source, probably chert bearing Precambrian Formations. Similarly, purple sandstones are classified as litharenite (chertarenite) and white sandstones as quartzarenite types. The detrital modes of purple and white sandstones indicate that they were derived from recycled orogen (uplifted shoulders of rift) and stable cratonic source. Most major and trace element contents of purple sandstones are generally similar to upper continental crust (UCC) values. However, white sandstones are depleted in major and trace elements (except SiO 2, Zr and Co) relative to UCC, which is mainly due to the presence of quartz and absence of other Al-bearing minerals. Shale samples have considerably lower content in most of the major and trace elements concentration than purple sandstones, which is possibly due to intense weathering and recycling. Modal composition (e.g., quartz, feldspar, lithic fragments) and geochemical indices (Th/Sc, La/Sc, Co/Th, Cr/Th, Cr/V and V/Ni ratios) of sandstones, and shales (La/Sc and La/Cr ratios) indicate that they were derived from felsic source rocks and deposited in a passive continental margin. The chondrite-normalized rare earth element (REE) patterns of the studied samples are characterized by LREE enrichment, negative Eu anomaly and flat HREE similar to an old upper continental crust composed chiefly of felsic components in the source area. The study of paleoweathering conditions based on modal composition, chemical index of alteration (CIA), plagioclase index of alteration (PIA) and A-CN-K (Al 2O 3 - CaO + Na 2O - K 2O) relationships indicate that probably chemical weathering in the source area and recycling processes have been more important in shale and white sandstones relative to purple sandstones. The results of this study suggest that the main source for the Lalun Formation was likely located in uplifted shoulders of a rifted basin (probably a pull-apart basin) in its post-rift stage (Pan-African basement of the Posht-e-badam block).

  8. Geochemistry and petrogenetic significance of natrocarbonatites at Oldoinyo Lengai, Tanzania: Composition of lavas from 1988 to 2007

    NASA Astrophysics Data System (ADS)

    Keller, J.; Zaitsev, A. N.

    2012-09-01

    The natrocarbonatites of Oldoinyo Lengai, Tanzania, are unique in magmatic petrology. The historical activity of Oldoinyo Lengai has seen changes from nephelinitic to natrocarbonatitic character of the emitted magmas. Since 1983 the activity was characterized by the effusion of fluid natrocarbonatite lava from which we have collected and analyzed fresh samples in the summit crater from 1988 to 2007. The available compositional data set forms the basis for presenting and discussing the typical composition and variation of natrocarbonatites and their relationship to the silicate magmas of Oldoinyo Lengai. The "type" natrocarbonatite major and trace element composition is derived for an average of 25 samples with low standard deviation. Oldoinyo Lengai carbonatites are unique in almost all aspects of their petrological and geochemical characteristics and are characterized as extremely alkali-rich, with Na2O + K2O generally about 40 wt.%, and with high CaO contents of 14-18 wt.%. This composition results from the presence of phenocrysts of nyerereite (Na,K)2Ca(CO3)2 and gregoryite (Na,K,Cax)2-x(CO3) dominating the highly porphyritic natrocarbonatite lavas, with sylvite and fluorite as main groundmass minerals. The significance of particular trace element concentrations and ratios of equally incompatible elements (REE, Ba, Sr, Th/U, Nb/Ta, Zr/Hf) is evaluated for models of liquid-liquid separation. In defining a "type" natrocarbonatite composition, we also distinguish special variations in chemical and/or mineralogical compositions as follows: (1) silicate-bearing natrocarbonatites, characterized by the occurrence of nephelinite spheroids, as in the 1993 and 2006 lavas; (2) residual melt compositions as described from the 1988 eruptive period as represented by the aphyric, filter-pressed interstitial melt of solidifying porphyritic lavas; (3) an interlude during 2000 when natrocarbonatites with sylvite and fluorite microcrysts were emitted. After 25 years of mostly mild activity characterized by effusion and spattering of fluid natrocarbonatite lava, the paroxysmal ash eruptions of September 4, 2007, changed dramatically the crater morphology, eruptive dynamics and magma composition of Oldoinyo Lengai. Fresh natrocarbonatites — if present at the bottom of the deep crater pit formed during the 2007-2008 explosive activity — will possibly remain inaccessible for decades.

  9. Reprint of "Geochemistry and petrogenetic significance of natrocarbonatites at Oldoinyo Lengai, Tanzania: Composition of lavas from 1988 to 2007"

    NASA Astrophysics Data System (ADS)

    Keller, J.; Zaitsev, A. N.

    2012-11-01

    The natrocarbonatites of Oldoinyo Lengai, Tanzania, are unique in magmatic petrology. The historical activity of Oldoinyo Lengai has seen changes from nephelinitic to natrocarbonatitic character of the emitted magmas. Since 1983 the activity was characterized by the effusion of fluid natrocarbonatite lava from which we have collected and analyzed fresh samples in the summit crater from 1988 to 2007. The available compositional data set forms the basis for presenting and discussing the typical composition and variation of natrocarbonatites and their relationship to the silicate magmas of Oldoinyo Lengai. The "type" natrocarbonatite major and trace element composition is derived for an average of 25 samples with low standard deviation. Oldoinyo Lengai carbonatites are unique in almost all aspects of their petrological and geochemical characteristics and are characterized as extremely alkali-rich, with Na2O + K2O generally about 40 wt.%, and with high CaO contents of 14-18 wt.%. This composition results from the presence of phenocrysts of nyerereite (Na,K)2Ca(CO3)2 and gregoryite (Na,K,Cax)2-x(CO3) dominating the highly porphyritic natrocarbonatite lavas, with sylvite and fluorite as main groundmass minerals. The significance of particular trace element concentrations and ratios of equally incompatible elements (REE, Ba, Sr, Th/U, Nb/Ta, Zr/Hf) is evaluated for models of liquid-liquid separation. In defining a "type" natrocarbonatite composition, we also distinguish special variations in chemical and/or mineralogical compositions as follows: (1) silicate-bearing natrocarbonatites, characterized by the occurrence of nephelinite spheroids, as in the 1993 and 2006 lavas; (2) residual melt compositions as described from the 1988 eruptive period as represented by the aphyric, filter-pressed interstitial melt of solidifying porphyritic lavas; (3) an interlude during 2000 when natrocarbonatites with sylvite and fluorite microcrysts were emitted. After 25 years of mostly mild activity characterized by effusion and spattering of fluid natrocarbonatite lava, the paroxysmal ash eruptions of September 4, 2007, changed dramatically the crater morphology, eruptive dynamics and magma composition of Oldoinyo Lengai. Fresh natrocarbonatites — if present at the bottom of the deep crater pit formed during the 2007-2008 explosive activity — will possibly remain inaccessible for decades.

  10. Toward understanding the effect of low-activity waste glass composition on sulfur solubility

    DOE PAGESBeta

    Vienna, John D.; Kim, Dong -Sang; Muller, Isabelle S.; Piepel, Greg F.; Kruger, Albert A.; Jantzen, C.

    2014-07-24

    The concentration of sulfur in nuclear waste glass melter feed must be maintained below the point where salt accumulates on the melt surface. The allowable concentrations may range from 0.37 to over 2.05 weight percent (of SO3 on a calcined oxide basis) depending on the composition of the melter feed and processing conditions. If the amount of sulfur exceeds the melt tolerance level, a molten salt will accumulate, which may upset melter operations and potentially shorten the useful life of the melter. At the Hanford site, relatively conservative limits have been placed on sulfur loading in melter feed, which inmore »turn significantly increases the amount of glass that will be produced. Crucible-scale sulfur solubility data and scaled melter sulfur tolerance data have been collected on simulated Hanford waste glasses over the last 15 years. These data were compiled and analyzed. A model was developed to predict the solubility of SO3 in glass based on 252 simulated Hanford low-activity waste (LAW) glass compositions. This model represents the data well, accounting for over 85% of the variation in data, and was well validated. The model was also found to accurately predict the tolerance for sulfur in melter feed for 13 scaled melter tests of simulated LAW glasses. The model can be used to help estimate glass volumes and make informed decisions on process options. The model also gives quantitative estimates of component concentration effects on sulfur solubility. The components that most increase sulfur solubility are Li2O > V2O5> CaO ≈ P2O5 > Na2O ≈ B2O3 > K2O. The components that most decrease sulfur solubility are Cl > Cr2O3 > Al2O3 > ZrO2 ≈ SnO2 > Others ≈ SiO2. As a result, the order of component effects is similar to previous literature data, in most cases.« less

  11. Petrological constraints on magma storage and transfer beneath Volcn Cerro Machn (Colombia): A volcano showing signs of unrest

    NASA Astrophysics Data System (ADS)

    Muir, D.; Caricchi, L.; Mendez, R.; Londoo, J. M.

    2012-04-01

    Cerro Machn Volcano, located in the Central Cordillera (Colombia) is a dacitic volcano positioned along a large-scale fracture system. Past activity is characterised by explosions of varying intensities and by the effusion of lava domes, with 6 main eruptive cycles occurring over the last 10 kyrs. Currently, the volcano presents two central domes with a total diameter of about 3 km, where two fumarolic fields are located. The rest of the edifice is composed of a 600 m thick ring of pyroclastic flows. Recent seismic swarms, located at depths between 18 and 2 km, have prompted further investigation of this volcanic system. Erupted products are dacitic with similar bulk chemistries to Pinatubo (65.1 wt% SiO2, 2.1 wt% MgO, 2.1 wt% K2O, 4.3 wt% CaO and 4.4 wt% Na2O) apart from FeOT, which at 3.3 wt%, is lower by around 1 wt%. The mineralogical assemblage is composed of plagioclase, quartz, hornblende (two populations: high- and low-Mg) and biotite phenocrysts along with ilmenite, magnetite, and accessory apatite and zircon. All phases, both in products of explosive eruption and dome samples, appear to be at equilibrium with an absence of sieve textures in plagioclase and no dehydration reaction rims in the hydrous phases. Because of the similarities in bulk composition, phase equilibria experiments for Pinatubo (Scaillet et al., 2001) can be used to provide information on the storage conditions of Machn magmas prior to eruption. The presence of biotite suggests temperatures lower than 750C with melt water contents of at least 5.7 wt % corresponding to water saturation pressures between 225 and 240 MPa. Analyses to determine the amount of sulphur present in the magma are currently being performed to assess its possible influence on the stability of biotite (Scaillet et al., 2001). The lack of evidence of mineral resorption in the eruptive products may imply relatively low magmatic temperatures or fast rates of magma transfer beneath Cerro Machn volcano. We are currently analysing mineral textures and compositional profiles at different stratigraphic levels in the eruptive deposits to constrain the timescales of magma ascent and its relationship with eruptive style. These data are of vital importance to establish the potential delay between seismicity associated with magma migration and an eventual eruption.

  12. Whole Rock Lithium Isotopic Signatures of a Pegmatite Swarm and Their Variation With Increasing Magmatic Fractionation: Evidence From the Little Nahanni Pegmatite Group, Northwest Territories.

    NASA Astrophysics Data System (ADS)

    Barnes, E. M.; Weis, D.; Groat, L. A.

    2008-12-01

    Variations in the ?7Li values of individual dikes of the Little Nahanni Pegmatite Group (LNPG) in the Northwest Territories correlate with variations in the mineralogy and whole rock geochemistry suggesting compositional evolution of the melt during emplacement of the pegmatites. A better understanding of the relationship between these aspects may help clarify some of the processes involved in pegmatite formation. Quartz, K-feldspar, plagioclase, spodumene and mica are the major rock-forming minerals of the majority of the > 200 LNPG pegmatites, with accessory phases including columbite-group minerals, cassiterite, tourmaline, beryl, lithiophilite and garnet. A minority of dikes contain no spodumene but significantly more mica than the others. Major element whole rock geochemistry of 23 samples show high abundance and variability in SiO2 (67.2 - 78.5 wt.%) and Al2O3 (12.7 - 19.6 wt.%), moderate abundance and variability in Na2O (2.5 - 5.4 wt.%) and K2O (2.1-4.4 wt.%) and extremely low abundance in FeO (or Fe2O3), CaO, MgO and MnO (< 1 wt.%). However, Harker diagrams show little correlation between the oxides. In contrast, trace element analyses provide a wealth of information with high (e.g. Li, Cs, Ta, Sn) or low (e.g. rare earth element (REE), Sr, Ba) abundances relative to continental crust, strong fractionation trends in Nb/Ta, Ce/Pb and Zr/Hf, and distinctive REE patterns. Less fractionated spodumene-bearing rocks exclusively correlate with `tetrad effect' REE patterns with strongly negative Eu anomalies. The more fractionated spodumene-free samples display LREE enriched, relatively straight or listric REE patterns. The pegmatites at LNPG are high in H2O, F, P, and Li, all of which are capable of postponing the onset of crystallisation by depolymerizing the cooling silicate melt, potentially to within the temperature range of Li isotope fractionation. Measurements by MC-ICP-MS of 6Li and 7Li in the LNPG whole rock samples range between ?7Li -0.73 and 11.36, with the least fractionated samples having among the lowest F, P, and ?7Li values. Higher ?7Li values for the more evolved pegmatite samples may be due to 7Li being preferentially retained in the fluid of the increasingly fractionated silicate melt. The data from LNPG record a range of mineralogical, geochemical and isotopic signatures indicating that the composition of the pegmatites evolved during crystallisation. Ongoing analysis is expected to shed more light on the mechanisms involved and their association with the ?7Li values of the pegmatites.

  13. Diffusion reaction in a thermal gradient: Implications for the genesis of anorthitic plagioclase, high alumina basalt and igneous mineral layering

    NASA Astrophysics Data System (ADS)

    Lundstrom, Craig; Boudreau, Alan; Pertermann, Maik

    2005-09-01

    Piston-cylinder experiments investigating the interaction between basaltic andesite melt and partially molten gabbro in a thermal gradient provide insight into melt-rock reaction processes occurring during magma differentiation in the crust. In two experiments juxtaposing basaltic andesite and gabbro at 0.5 GPa pressure for durations of either 13 or 26 days, diffusive chemical exchange between the two materials results in mineral layering and notable mineral compositions such as anorthitic plagioclase. Specifically, the basaltic andesite gains Al 2O 3, MgO and CaO from the gabbro and loses Na 2O, K 2O, SiO 2 and FeO to it with a plagioclase-rich layer developing at the interface between the two materials in a process termed diffusion-reaction. The percent crystallinity of the basaltic andesite increases during the process and the plagioclase crystals within the interface region develop anorthitic cores (up to An 90) that abruptly shift in composition to thin rims that are in Na-Ca exchange equilibrium with the co-existing melt. Both the mineralogical layering and bulk compositional change occurring at the interface are reproduced in model simulations of diffusion-reaction. Isotopic tracers ( 45Ca, 6Li, 84Sr and 136Ba) initially deposited at the basaltic andesite-gabbro interface in the 13-day experiment were detected in the cores of the anorthitic plagioclase after the experiment, demonstrating that the melt chemically communicates with the plagioclase cores over the duration of the diffusion-reaction experiment. The formation of anorthitic plagioclase during diffusion-reaction may explain its widespread occurrence in terrestrial volcanic rocks without requiring the presence of ultra-calcic melts. Textures and mineralogical changes in the gabbro indicate that chemical transport occurs throughout the experiments despite temperatures at the cold end of the experimental capsule approaching 500 C. For instance, apatite, FeNiS, olivine and almost pure albite occur at distinct, specific horizons in the gabbro within the 26-day experiment. Because the bulk element profiles indicating chemical transport reflect analyses of almost completely solid gabbro, equilibration between minerals and fluids/melts must be rapid. The overall effect of the diffusion-reaction process is to make an ascending magma more primitive in composition (and in this case, produce anorthitic plagioclase) while making surrounding crustal wall rocks more evolved. Several observations within igneous rocks support the occurrence of this process, suggesting that the genesis of porphyritic high alumina basalt, ubiquitously observed at convergent margins, could reflect a diffusion-reaction process in the crust.

  14. Geochemistry of mid ocean ridge basalts (MORB) from the northern Central Indian Ridge between 746 and 1320 S: Implication of mantle heterogeneity influenced by Reunion hotspot plume?

    NASA Astrophysics Data System (ADS)

    Lee, J.; Lee, I.; Lee, S.; Kim, J.

    2010-12-01

    Between the Rodrigues Triple Junction (RTJ) and Carlsberg Ridge, The Central Indian Ridge (CIR) is a slow-intermediate spreading-rate (~ 43mm/year) plate boundary formed during separation of the Mascarene Plateau from the Chagos-Lacadives Ridge. Although several samplings of basaltic rocks were carried out in previous explorations on Indian Ridge, no systematic studies on the petrogenesis of CIR, especially for north of 18S have been reported yet. We present the major and trace element composition of lavas dredged along the spreading axis of the northern CIR between 746 and 1320 S. The mineralogy of the CIR MORB mainly consists of tiny needle- and/or lath-like plagioclase microlites (~45%), sub- to anhedral olivine (~15%), small anhedral clino-pyroxene (~10%), and intersertal/intergranular Fe-Ti oxide glass matrix (~30%). In the whole rock and glass chemistry, the samples show the very similar pattern of compositional variation in SiO2, Al2O3, FeO, and CaO concentration against MgO (6.59 ~ 8.68 wt %), although relatively less compatible elements (TiO2, Na2O, K2O, and P2O5) show linear trend. Plottings of Na8.0, Fe8.0, and CaO/Al2O3 vs. depth are examined to check the varying extents of partial melting and the global correlations. The results broadly agree with the global trend of MORB and fall within the dry MORB domain. Concentration of light rare earth elements (LREE) vary widely in the analyzed rock samples ((La/Sm)N ? 0.68 ~ 1.41 and (Nb/Yb)N ? 0.42 ~ 1.93). In spider diagram normalized by primitive mantle, the volcanic lavas show systematic increase of incompatible element concentration from south (segment 1) to north (segment 5), which could be attributed to the influence of enriched source in south of the study area. However, basalts from segment 2 are significantly enriched in incompatible elements. Plots of the ratios of several incompatible elements versus La/Sm ratio show a linear trend which could be attributed to the mixing of depleted and enriched components. The preliminary result of geochemical analyses of the volcanic lavas shows geographic trend of increase in incompatible elements north to south along the spreading axis, which might be influenced by Reunion hotspot plume. However, the evolution of enriched magma by various degree of melting also should be examined for the detailed interpretation, especially for the anomalously enriched lavas from the segment 2.

  15. A Paleoproterozoic paleosol horizon in the Lesser Himalaya and its regional implications

    NASA Astrophysics Data System (ADS)

    Bhargava, O. N.; Kaur, Gurmeet; Deb, M.

    2011-11-01

    A Paleoproterozoic paleosol horizon in the Himachal Himalaya along a basement-cover contact is identified on the basis of an integrated field-petrographic-geochemical studies. The paleosol horizon is exposed in a road section along the Sutlej River near Karcham. It is represented by a 2-5 m thick sericite schist unit along the contact of the 1866 10 Ma Jeori-Wangtu-Bandal Gneissic Complex (JWBGC) and the overlying sericite quartzite of the Manikaran Formation (Rampur Group), which is interstratified with 1800 13 Ma tholeiitic flows in its basal part. The geochemical studies reveal a sharp drop in the concentration of SiO 2, Fe 2O 3, MgO, CaO, Na 2O and a rise in concentration of Al 2O 3, TiO 2, K 2O and P 2O 5 at the contact of granite gneiss and sericite schist. REE plots of granite gneiss, sericite schist and quartzite samples of the Manikaran Formation display similarity of pattern, fractionation between the LREE and HREE and comparable negative Eu anomaly. The total REE of the sericite schist and sericitic quartzite is lower than those of the granite gneiss. Based on these studies the sericite schist is inferred to be a metamorphosed alumina-rich soil, which appears to have formed in a warm and humid climate in a waterlogged terrain of gentle relief, and is post-1866 Ma and pre-1800 Ma in age. Apparent gradation from the strongly deformed amphibolite facies JWBC to the sericite schist with diffused contact indicates that the JWBGC was already metamorphosed and deformed prior to the development of the paleosol; thereafter both together with the overlying Manikaran Formation were subjected to low-grade metamorphism during the Himalayan orogeny. The JWBC is involved in the crystalline thrust sheet and is present throughout the length of the Himalaya. Thus, it is inferred that the Paleoproterozoic metamorphism was a regional event in the Himalaya at a time when the Indian Plate was part of the Nuna Supercontinent.

  16. Wound dressings composed of copper-doped borate bioactive glass microfibers stimulate angiogenesis and heal full-thickness skin defects in a rodent model.

    PubMed

    Zhao, Shichang; Li, Le; Wang, Hui; Zhang, Yadong; Cheng, Xiangguo; Zhou, Nai; Rahaman, Mohamed N; Liu, Zhongtang; Huang, Wenhai; Zhang, Changqing

    2015-01-01

    There is a need for better wound dressings that possess the requisite angiogenic capacity for rapid in situ healing of full-thickness skin wounds. Borate bioactive glass microfibers are showing a remarkable ability to heal soft tissue wounds but little is known about the process and mechanisms of healing. In the present study, wound dressings composed of borate bioactive glass microfibers (diameter = 0.4-1.2 μm; composition 6Na2O, 8K2O, 8MgO, 22CaO, 54B2O3, 2P2O5; mol%) doped with 0-3.0 wt.% CuO were created and evaluated in vitro and in vivo. When immersed in simulated body fluid, the fibers degraded and converted to hydroxyapatite within ∼7 days, releasing ions such as Ca, B and Cu into the medium. In vitro cell culture showed that the ionic dissolution product of the fibers was not toxic to human umbilical vein endothelial cells (HUVECs) and fibroblasts, promoted HUVEC migration, tubule formation and secretion of vascular endothelial growth factor (VEGF), and stimulated the expression of angiogenic-related genes of the fibroblasts. When used to treat full-thickness skin defects in rodents, the Cu-doped fibers (3.0 wt.% CuO) showed a significantly better capacity to stimulate angiogenesis than the undoped fibers and the untreated defects (control) at 7 and 14 days post-surgery. The defects treated with the Cu-doped and undoped fibers showed improved collagen deposition, maturity and orientation when compared to the untreated defects, the improvement shown by the Cu-doped fibers was not markedly better than the undoped fibers at 14 days post-surgery. These results indicate that the Cu-doped borate glass microfibers have a promising capacity to stimulate angiogenesis and heal full-thickness skin defects. They also provide valuable data for understanding the role of the microfibers in healing soft tissue wounds. PMID:25890736

  17. Geochemistry and geodynamics of a Late Cretaceous bimodal volcanic association from the southern part of the Pannonian Basin in Slavonija (Northern Croatia)

    USGS Publications Warehouse

    Pamic, J.; Belak, M.; Bullen, T.D.; Lanphere, M.A.; McKee, E.H.

    2000-01-01

    In this paper we present petrological and geochemical information on a bimodal basaltrhyolite suite associated with A-type granites of Late Cretaceous age from the South Pannonian Basin in Slavonija (Croatia). Basalts and alkali-feldspar rhyolites, associated in some places with ignimbrites, occur in volcanic bodies that are interlayered with pyroclastic and fossiliferous Upper Cretaceus sedimentary rocks. The petrology and geochemistry of the basalts and alkali-feldspar rhyolites are constrained by microprobe analyses, major and trace element analyses including REE, and radiogenic and stable isotope data. Basalts that are mostly transformed into metabasalts (mainly spilites), are alkalic to subalkalic and their geochemical signatures, particularly trace element and REE patterns, are similar to recent back-arc basalts. Alkali-feldspar rhyolites have similar geochemical features to the associated cogenetic A-type granites, as shown by their large variation of Na2O and K2O (total 8-9%), very low MgO and CaO, and very high Zr contents ranging between 710 and 149ppm. Geochemical data indicate an amphibole lherzolite source within a metasomatized upper mantle wedge, with the influence of upper mantle diapir with MORB signatures and continental crust contamination. Sr incorporated in the primary basalt melt had an initial 87Sr/86Sr ratio of 0.7039 indicating an upper mantle origin, whereas the 87Sr/86Sr ratio for the alkalifeldspar rhyolites and associated A-type granites is 0.7073 indicating an apparent continental crust origin. However, some other geochemical data favour the idea that they might have mainly originated by fractionation of primary mafic melt coupled with contamination of continental crust. Only one rhyolite sample appears to be the product of melting of continental crust. Geological and geodynamic data indicate that the basalt-rhyolite association was probably related to Alpine subduction processes in the Dinaridic Tethys which can be correlated with recent back-arc basins. The difference in geological and isotope ages between the bimodal basalt-rhyolite volcanism with A-type granite plutonism (72 Ma) and the final synkinematic S-type granite plutonism (48 Ma) can be taken as a lifetime of the presumed BARB system of the Dinaridic Tethys. Remnants of this presumed subduction zone can be traced for 300 km along the surrounding northernmost Dinarides.

  18. Isotopic geochemistry, zircon U-Pb ages and Hf isotopes of A-type granites from the Xitian W-Sn deposit, SE China: Constraints on petrogenesis and tectonic significance

    NASA Astrophysics Data System (ADS)

    Zhou, Yun; Liang, Xinquan; Wu, Shichong; Cai, Yongfeng; Liang, Xirong; Shao, Tongbin; Wang, Ce; Fu, Jiangang; Jiang, Ying

    2015-06-01

    Zircon U-Pb geochronological, geochemical and petrological analyses have been carried out on the Xitian granite emplaced in the middle part of Shi-Hang zone, which is closely related to the economically important Xitian tungsten-tin deposit in Hunan Province, Southeast China. LA-ICP-MS zircon U-Pb dating of two representative samples yielded weighted means 206Pb/238U age of 151.7 1.2 Ma and 151.8 1.4 Ma. These granites are comprised mainly of K-feldspar, quartz, plagioclase, Fe-rich biotite and minor fluorite, and are characterized by enrichments in Rb, Th, REEs (total REE = 159-351 ppm), and HFSEs (e.g., Zr and Y) but depletions in Ba, Sr, P, Eu and Ti. They are metaluminous to weakly peraluminous and show a clear A-type granite geochemical signature with high SiO2 (73.44-78.45 wt.%), total alkalis (Na2O + K2O = 2.89-8.98 wt.%), Fe2O3?/MgO ratios and low P2O5, CaO, MgO and TiO2 contents. In-situ zircon Hf isotope analysis suggests their ?Hf(t) values ranging from -7.43 to -14.69. Sr-Nd isotope data show their ?Nd(t) values in the range of -9.2 to -7.3, with corresponding TDM2 ages of 1.72-1.56 Ga. These characteristics indicate that the Xitian granite originated from partial melting of metamorphic basement rocks with a certain amount of mantle-derived materials. Combined with previous geochemical and isotopic data, it is derived that mantle-crust interaction was gradually enhanced from the early to late stages of magmatism. The ore-forming materials and fluids of the Xitian W-Sn deposit are mainly produced by the Early Yanshanian granitic magmatism, which is also responsible for the Late Jurassic (ca. 152 Ma) A-type granitic rocks that host the W-Sn polymetallic deposits distributed along the Shi-Hang zone, implying a significant Mesozoic extensional event in Southeast China likely caused by the subduction of the Paleo-Pacific plate.

  19. Volatile Evolution of Magma Associated with the Solchiaro Eruption in the Phlegrean Volcanic District (Italy)

    NASA Astrophysics Data System (ADS)

    Esposito, R.; Bodnar, R. J.; de Vivo, B.; Lima, A.; Fedele, L.; Shimizu, N.; Hunter, J.

    2009-12-01

    The Phlegrean volcanic district (PVD) in southern Italy is one of the best known volcanic hazard areas in the world. More than 1.5 million people live in close proximity to the volcanic centers. The PVD comprises three volcanic fields: the Campi Flegrei caldera and the islands of Ischia and Procida. We studied volatiles plus major and trace elements in the magma associated with the Solchiaro eruption on the Island of Procida, Italy, to gain a better understanding of the relationship between pre-eruptive volatiles and magmatic evolution. The Solchiaro eruption is one of the more primitive products erupted in the PVD and provides information on the source of later more evolved magmas associated with this volcanic system. The composition of the magma before eruption was determined by analyzing 104 melt inclusions (MIs) in forsteritic olivine, glass embayment plus rim glasses, and high vesciculated glasses selected from 4 representative samples. The composition of MIs was recalculated and ranges from basaltic to trachy-basaltic. Among major elements potassium shows the highest variability, from 0.5 to 6 wt%. MI define a continuous trend based on major and minor element compositions. Embayments matrix glass and high vesciculated glasses define a field that suggests a discontinuous process. Compatible to incompatible trace element ratios in early melts are highly variable and represent the melt phase before or at the very beginning of assimilation-fractional crystallization (FCA) processes. Intermediate melt compositions reflect continuing FCA processes, late melt compositions suggest that the FCA process was aborted before eruption. Volatile contents of early melt are highly variable and reflect source heterogeneities, and the melts are interpreted to be undersaturated. Intermediate melts were volatile saturated and H2O-CO2 contents define a degassing path. Depths of trapping of MI range from 4.4 to 2.2 km, and are calculated based on Newman and Lowenstern (2002) and assuming a pressure gradient of 270 bar/Km. Pressures of crystallization of intermediate melts correlate with magma evolution associated with FCA processes. At the moment of the eruption, melt saturated in volatiles at 8 km continuously lost volatiles during its rapid ascent to the surface. Glass embayments and glass at the crystal/melt interface shows higher volatiles (especially CO2), compared to highly vesiculated matrix glass. Magma compositions relative to some MIs hosted in forsterite-rich olivine show extremely low contents of both K2O and Na2O and high CaO (0.5, 1.90 and 13.89 wt% respectively). Similar compositions have not been previously reported from the PVD but are characteristic of the Aeolian Arc.

  20. Apatite and clinopyroxene as tracers for metasomatic processes in nepheline clinopyroxenites of Uralian-Alaskan-type complexes in the Ural Mountains, Russian Federation

    NASA Astrophysics Data System (ADS)

    Krause, Joachim; Harlov, Daniel E.; Pushkarev, Evgeny V.; Brgmann, Gerhard E.

    2013-11-01

    Clinopyroxene and apatite are found to trace metasomatic processes in nepheline-bearing clinopyroxenites (tilaites) from the igneous, mafic-ultramafic Uralian-Alaskan-type complexes of Kytlym and Nizhny Tagil, Ural Mountains, Russian Federation. The clinopyroxenites consist predominantly of coarse-grained, partially to totally altered clinopyroxene phenocrysts in a matrix of fine-grained olivine, clinopyroxene, plagioclase, K-feldspar, and nepheline. Apatite occurs as idiomorphic inclusions (<25 ?m) in the clinopyroxene and as xenomorphic grains in the matrix. In the matrix, plagioclase is partially to totally replaced by a fine-grained symplectitic intergrowth of K-feldspar and nepheline most likely due to the influx of an K2O-, Na2O-, and Al2O3-bearing fluid. During conversion of the plagioclase, CaO and SiO2 were partitioned into the fluid. Altered areas in the clinopyroxene phenocrysts are characterized by the redistribution of major and trace elements. This includes depletion in Mg, Rb, and Sr and enrichment in Al, Na, Ba, U, Th, REE except Eu, and HFSE compared to the original magmatic areas in the clinopyroxene. Apatite inclusions in the altered areas of the clinopyroxene and in the matrix are enriched in Cl relative to apatite inclusions in the unaltered areas of clinopyroxene. It is proposed that these rocks experienced a two-stage metasomatic process. Stage 1 was the partial to total alteration of plagioclase to K-feldspar and nepheline due to interaction with an infiltrating (K,Na)Cl-rich brine (most likely late magmatic) with an Al component, which enriched the fluid in CaCl2. Stage 2 consisted of the partial to total chemical alteration of the original magmatic clinopyroxene by this now CaCl2-enriched fluid through the mechanism of coupled dissolution-reprecipitation. This process also chemically altered the apatite inclusions from fluor-chlorapatite to chlor-fluorapatite and redistributed as well as partially removed the titanomagnetite inclusions in the altered areas. This is supported experimentally by the fact that alteration of fluorapatite to Cl-rich apatite can only take place in the presence of CaCl2-bearing fluids and by the fact that in general Fe and Ti, along with most metal cations, are relatively mobile in Cl-rich fluids. If this scenario is correct, the implications from this study are that inclusions of one mineral in a host mineral can be chemically overprinted during metasomatic alteration of the host mineral. While at the same time the original crystal shape and orientation of both the host phase as well as that of the inclusions are preserved.

  1. Multiple crust-mantle interactions for the destruction of the North China Craton: Geochemical and Sr-Nd-Pb-Hf isotopic evidence from the Longbaoshan alkaline complex

    NASA Astrophysics Data System (ADS)

    Lan, Ting-Guang; Fan, Hong-Rui; Hu, Fang-Fang; Tomkins, Andrew G.; Yang, Kui-Feng; Liu, Yongsheng

    2011-02-01

    In situ zircon U-Pb ages and Hf isotopic data, major and trace elements, and Sr-Nd-Pb isotopic compositions are reported for the Longbaoshan alkaline intrusive complex in the western Shandong Province (Luxi Block), southeastern North China Craton. The Longbaoshan complex, which consists of quartz syenite, aegirine-augite syenite, hornblende syenite, monzonite, and syenodiorite, was emplaced at 129.4-131.7 Ma. The complex is characterized by high concentrations of SiO2, K2O + Na2O, Al2O3, LILEs (e.g., Sr and Ba), and LREEs, and low concentrations of CaO, Fe2O3, MgO, and HFSEs (e.g., Nb, Ta, P and Ti). The Sr, Nd, Pb, and Hf isotopic values of this complex are similar to the nearby mafic rocks, which were derived from EM2-type lithospheric mantle, indicating that the Longbaoshan complex was mainly derived from partial melting of the EM2 source. Combined with geochemical and isotopic features, the high Nb/Ta ratios (average 19.2) of the Longbaoshan complex suggest that the EM2 source was induced by modification of crust-derived melts, which were in equilibrium with rutile-bearing eclogite. This was attributed to the subduction of the Yangtze continental crust. The presence of inherited zircons (2.51-2.64 Ga) with positive ?Hf(t) values (0.2-6.2) suggest that the ancient crust of the North China Craton was also involved in the formation of the Longbaoshan complex. Magma mixing modelling shows that those 10-35% crustal materials were assimilated in the complex. This complex may have experienced hornblende, apatite/monazite, and titanite crystal fractionation before emplacement in the shallow crust level. Two stages of crust-mantle interaction can be identified through the formation of the Longbaoshan complex, including (1) the lithospheric mantle was metasomatized by the melts/fluids derived from the subducted crust and then transformed into an EM2 counterpart, and (2) magma derived from the EM2 source underplated the ancient crust and assimilated the crust-derived materials. We thus propose that multiple crust-mantle interactions are the essential mechanism for the destruction of the NCC. The first intensive crust-mantle interaction was aroused by crustal subduction and was responsible for the lithospheric mantle destruction, and the second major crust-mantle interaction was induced by mantle-derived magma underplating and was responsible for the crustal activation.

  2. Shear zone broadening driven by metasomatism: an example from the Roffna metarhyolite (Suretta nappe, eastern central Alps)

    NASA Astrophysics Data System (ADS)

    Poilvet, J.-C.; Goncalves, P.; Marquer, D.

    2012-04-01

    Ductile shear zones in continental crust play a critical role in the accommodation of deformation at crustal scale. They are also pathways for fluid and therefore the loci of metamorphic and metasomatic reactions. These fluid-rock interactions (reactions and metasomatism) control the behaviour of the shear zone and may be one of the driving force for the development of the shear zone and its lateral propagation (widening). Our goal in this contribution is to quantify the role of these chemical processes on the shear zone formation. The present study focuses on shear zones in the Roffna metarhyolite, in the Suretta nappe (Penninic Domain, Eastern Central Alps). This early Permian massif intruded the older basement and was affected only by Alpine tectonics. The ductile deformation is characterized by a shear zone network from millimetric to plurimetric scale developed under blueschist facies conditions. Mass transfer results show gains in MgO, K2O and H2O coupled with losses in CaO and Na2O with increasing strain. The main mineralogical change along the gradient is the growth of phengite and quartz at the expense of K-Feldspar and plagioclases. The appearance of a small amount of epidote and a small decrease in the amount of biotite is also observed. In our conceptual model of shear zone formation, the ultramylonite is assumed to be produced by infiltration metasomatism. In contrast the intermediate rocks between the protolith and the highest strain rock is assumed to be the result of diffusion metasomatism. Therefore the amount of lateral propagation is controlled by the kinetics of diffusion and equilibration of the host rock. To test this hypothesis we have compared shear zones with different thickness which should represent various degree of equilibration of the host rock at the conditions of the deformation and fluid-rock interactions. Using a suite of PT and chemical potential computed phase diagrams, we are able to model the reaction path involved during the equilibration process between the host rock and the highest strain zone. Our work provide new insights into the role of chemical processes on the formation of shear zone.

  3. Mineralogic, Petrographic, Mechanical And Physical Properties Of Incesu Ignimbrite (Central Anatolia - Turkey) Used Building Stone In Historical Buildings

    NASA Astrophysics Data System (ADS)

    Tasdelen, S.; Korolay, T.; Kadioglu, Y. K.; Kumral, M.

    2009-05-01

    The Central Anatolian Volcanic Province (CAVP) is located in the Central Turkey and one of the four major volcanic provinces in Turkey. It extends 300 km along a NE-SW direction, over a large area (32500 km2). The CAVP includes various volcanic, pyroclastic rocks, which are related to collision volcanism between the Arabian and Eurasian plates, occurred in Neogene, and Quaternary times There are numerous natural stone pits in the CAVP. They have been commonly used in historical building which had been built in the Anatolian Seljuk and Ottoman empires times. The subject of this study is to figure out petrographic, geochemical, some mechanical and physical properties which include Schmidt hardness, density, porosity, water absorption by weight, point load index and failure load.Incesu ignimbrite is subdivided into three levels as lower, middle and upper according to color, welding degree, crystal contents and lithic components. All of the natural stone pits is the upper part which is characterized by grey pinkish in color, poorly welded, high porosity ratios, high amount of lithic fragments and almost 2 m thickness. In terms of the mineralogical composition, it is composed of plagioclase (oligoclase, andesine) + pyroxene (augite, clinoenstatite) + opaque minerals and low amount of amphibole, biotite and quartz. Vitrofiric texture is dominant in upper level. Al2O3 content of the upper level from 12.75-13.96wt%, SiO2 66.70-68.10wt%, MgO 0.73-1.40wt%, Fe2O3 3.77-4.04wt%, TiO2 0.46-0.51wt%, CaO 1.97-2.91wt%, Na2O 3.41-4.29wt%, K2O 3.21-4.20wt%, P2O5 0.13-0.18wt% and LOI 3.65-4.52wt%. Geochemical analyze results reveal that Incesu ignimbrite has rhyolite, rhyodacite-dacite composition, medium to high-K calc-alkaline and peraluminous nature.Building stones can be classified according to their mineralogy, mechanical and physical properties and processing types. Mechanical and physical properties are more significant depending on the stones practice aim. The mean schmidt hardness value of the upper level of Incesu ignimbrite is 35, bulk density ranges between 2.42 - 2.66 g/cm3, mean water absorption by weight is 90%, mean point load strength is 38.2 MPa and failure load is 1890 kgf/cm based on the mechanical and physical test results.

  4. A Raman model for determining the chemical composition of silicate glasses

    NASA Astrophysics Data System (ADS)

    Di Genova, Danilo; Morgavi, Daniele; Hess, Kai-Uwe; Neuville, Daniel R.; Perugini, Diego; Dingwell, Donald B.

    2015-04-01

    Raman spectroscopy is a spectroscopic technique based on inelastic scattering of monochromatic light which provides information about molecular vibrations of the investigated sample. Since the discovery of the Raman Effect (1928) in scattered light from liquids, the Raman investigation has been extended to a large number of substances at different pressure-temperature conditions. Recently, the Raman instrument setup has rapidly grown thanks to the progress in development of lasers, charge coupled devices and confocal systems (see Neuville et al. 2014 for a review). Here we present the first Raman model able to determine the chemical composition of silicate glasses. In this study we combine chemical analysis from magma mixing experiments between remelted basaltic and rhyolitic melts, with a high spatial resolution Raman spectroscopy investigation; we focus on tracking the evolution of the Raman spectrum with chemical composition of silicate glasses. The mixing process is driven by a recently-developed apparatus that generates chaotic streamlines in the melts (Morgavi et al., 2013), mimicking the development of magma mixing in nature. From these experiments we obtained a glassy filament with a chemical composition ranging from a basalt to a rhyolite. Raman and microprobe measurements have been performed on a filament of ~1000 μm diameter, every 2.5-20 μm. The evolution of the acquired Raman spectra with the measured chemical composition has been parametrized by combining both the Raman spectra of the basaltic and rhyolitic end-members. Using the developed Raman model we have been able to determine the chemical composition (mol% of SiO2, Al2O3, FeO, CaO, MgO, Na2O and K2O) of the investigated filament. Additionally, the proposed Raman model has been successfully tested using external remelted natural samples; reference glasses (Jochum et al., 2000), a remelted basalt, andesite from Etna and Montserrat respectively. Finally, as the Raman spectrum depends on the silicate structure yielding information about network-forming structural units (Qn species, where n indicates the number of bridging oxygen), we combined the deconvoluted Raman spectra, in the rhyolitic field, with the chemical analyses and abundance of Qn species. This demonstrate how the evolution of silicate structure might control the bimodal eruptive style (explosive vs effusive) as shown by silica-rich volcanic systems. References: D. Morgavi et al., 2013. Morphochemistry of patterns produced by mixing of rhyolitic and basaltic melts. JVGR, 253, 87-96. D. R. Neuville, et al. 2014. Advances in Raman Spectroscopy Applied to Earth and Material Sciences. Rev. Min. Geochem., 78, 509-541.

  5. Petrogenesis, geochronology, and tectonic significance of granitoids in the Tongshan intrusion, Anhui Province, Middle-Lower Yangtze River Valley, eastern China

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Yu; Du, Yang-Song; Teng, Chuan-Yao; Zhang, Jing; Pang, Zhen-Shan

    2014-01-01

    The Tongshan copper deposit in Anhui Province is a typical mid-sized skarn and porphyry type deposit in the Anqing-Guichi district along the Middle-Lower Yangtze River Valley, eastern China. The Tongshan intrusion is closely related to this mineralization. The intrusion mainly comprises rocks that are quartz diorite porphyry, quartz monzonite porphyry, and granodiorite porphyry. Plagioclase in these rocks is mostly andesine (An = 31.0-42.9), along with minor oligoclase. Biotite is magnesium-rich [Mg/(Mg + Fe) = 0.52-0.67] and aluminum-poor (Al2O3 = 12.32-14.09 wt.%), and can be classified as magnesio-biotite. Hornblende is TiO2-poor (<1.96 wt.%) and magnesium-rich [Mg/(Mg + Fe) > 0.60], and is magnesio-hornblende or edenite. The SHRIMP zircon U-Pb age of the quartz monzonite porphyry is 145.1 1.2 Ma, which corresponds to the middle Yanshanian period. Whole-rock geochemical results show that the rocks are silica-rich (SiO2 = 60.23-66.23 wt.%) and alkali-rich (K2O + Na2O = 4.97-8.72 wt.%), and low in calcium (CaO = 2.61-5.66 wt.%). Trace element results show enrichments in large ion lithophile element (e.g., K, Rb, and Ba) and depletions in some high field strength elements (e.g., Nb, Ta, P, and Ti). The total rare earth element (REE) content of the rocks is low (?REE < 200 ?g/g), and they exhibit light REE enrichment [(La/Yb)N > 10] and small positive Eu anomalies (average ?Eu = 1.16). These mineralogical, geochronological, and geochemical results show that the intrusion has a mixed crust-mantle source. The Tongshan intrusion was formed by multiple emplacements of crustally contaminated basaltic magma generated by varying degrees of partial melting of enriched lithospheric mantle and lower crust. Hornblende thermobarometry yielded magmatic crystallization temperatures of 652-788 C and an average crystallization pressure of 1.4 kbar, which corresponds to a depth of approx. 4.7 km. Biotite thermobarometry yielded similar temperatures and lower pressures of 735-775 C and 0.6 kbar (depth 2.1 km), respectively. The parental magma had a high oxygen fugacity and was produced in a volcanic arc setting related to subduction of the paleo-Pacific plate.

  6. Diffusion-Reaction Between Basaltic Andesite and Gabbro at 0.5 GPa: an Explanation for Anorthitic Plagioclase?

    NASA Astrophysics Data System (ADS)

    Lundstrom, C. C.; Boudreau, A. E.; Pertermann, M.

    2004-12-01

    Despite the remarkably smooth variation in bulk composition of erupted lavas at Arenal volcano (1968-2003), mineral compositions vary widely. Plagioclase ranges from An52 to An95 while Cr2O3 in CPX varies from 0.7 to 0.05 wt % (Streck et al., 2003). To address the question "how do bulk compositions remain near-steady-state while crystal compositions vary widely," we have performed 2 diffusion-reaction experiments in the piston cylinder at 0.5 GPa. These juxtaposed Arenal basaltic andesite AR-8 at 1200° C with a Stillwater Complex gabbro, lying in a thermal gradient toward the piston. In one experiment, we synthesized a glass-plagioclase (An67-75) aggregate of AR-8 in a graphite-Pt-Ti capsule at P-T, polished one end, dried tracer solutions of 45Ca, 6Li, 84Sr and 136Ba on its surface, and juxtaposed it with gabbro for 13 days. Profiles of bulk composition as a function of distance from the interface show that AR-8 gains Al2O3, MgO and CaO from the gabbro and loses Na2O, K2O, SiO2 and FeO to it. Notably, a plagioclase rich (65%) layer develops at the interface between the two materials as CPX disappears. This layer and the compositional profiles are reproduced by diffusion-reaction models using IRIDIUM (Boudreau, 2003). Plagioclase at the interface develops a texture of homogeneous anorthitic cores (An90) that abruptly shift to 10μ m rims having compositions (An67) in Na-Ca exchange equilibrium with the co-existing melt. A beta track map shows that 45Ca is incorporated into the plagioclase cores while SIMS analyses indicate isotopic equilibration between core and melt. Thus, these anorthitic plagioclase result from diffusion-reaction with efficient chemical communication between the melt and the plagioclase core. Microchannels cutting through the rim, rather than solid-state diffusion, appear to control re-equilibration. Other observations from the experiment parallel Arenal lavas: Mg# variation in OPX is small in both experiments and lavas while profiles of Cr show that significant amounts of Cr move from gabbro to AR-8, possibly explaining Cr2O3 variations in Arenal CPX. The near-steady-state behavior at Arenal could reflect a flux balance between ascending magmas and melt from the surrounding crust reflecting diffusion-reaction.

  7. Experimental and Petrological Constraints on Lunar Differentiation from the Apollo 15 Green Picritic Glasses

    NASA Technical Reports Server (NTRS)

    Elkins-Tanton, Linda T.; Chatterjee, Nilanjan; Grove, Timothy L.

    2003-01-01

    Phase equilibrium experiments on the most magnesian Apollo 15C green picritic glass composition indicate a multiple saturation point with olivine and orthopyroxene at 1520 C and 1.3 GPa (about 260 km depth in the moon). This composition has the highest Mg# of any lunar picritic glass and the shallowest multiple saturation point. Experiments on an Apollo 15A composition indicate a multiple saturation point with olivine and orthopyroxene at 1520 C and 2.2 GPa (about 440 km depth in the moon). The importance of the distinctive compositional trends of the Apollo 15 groups A, B, and C picritic glasses merits the reanalysis of NASA slide 15426,72 with modern electron microprobe techniques. We confirm the compositional trends reported by Delano (1979, 1986) in the major element oxides SiO2, TiO2, Al2O3, Cr2O3, FeO, MnO, MgO, and CaO, and we also obtained data for the trace elements P2O5, K2O, Na2O, NiO, S, Cu, Cl, Zn, and F. Petrogenetic modeling demonstrates that the Apollo 15 A-B-C glass trends could not have been formed by fractional crystallization or any continuous assimilation/fractional crystallization (AFC) process. The B and C glass compositional trends could not have been formed by batch or incremental melting of an olivine + orthopyroxene source or any other homogeneous source, though the A glasses may have been formed by congruent melting over a small pressure range at depth. The B compositional trend is well modeled by starting with an intermediate A composition and assimilating a shallower, melted cumulate, and the C compositional trend is well modeled by a second assimilation event. The assimilation process envisioned is one in which heat and mass transfer were separated in space and time. In an initial intrusive event, a picritic magma crystallized and provided heat to melt magma ocean cumulates. In a later replenishment event, the picritic magma incrementally mixed with the melted cumulate (creating the compositional trends in the green glass data set), ascended to the lunar surface, and erupted as a fire fountain. A barometer created from multiple saturation points provides a depth estimate of other glasses in the A-B-C trend and of the depths of assimilation. This barometer demonstrates that the Apollo 15 A-B-C trend originated over a depth range of approx.460 km to approx.260 km within the moon.

  8. Osumilite-(Mg): Validation as a mineral species and new data

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Pekov, I. V.; Rastsvetaeva, R. K.; Aksenov, S. M.; Belakovskiy, D. I.; Van, K. V.; Schüller, W.; Ternes, B.

    2013-12-01

    Osumilite-(Mg), the Mg-dominant analogue of osumilite, has been approved by the CNMNC IMA as a new mineral species. The holotype sample has been found at Bellerberg, Eifel volcanic area, Germany. Fluorophlogopite, sanidine, cordierite, mullite, sillimanite, topaz, pseudobrookite and hematite are associated minerals. Osumilite-(Mg) occurs as short prismatic or thick tabular hexagonal crystals reaching 0.5 × 1 mm in size in the cavities in basaltic volcanic glasses at their contact with thermally metamorphosed xenoliths of pelitic rocks. The mineral is brittle, with Mohs' hardness 6.5. Cleavage was not observed. Color is blue to brown. D meas = 2.59(1), D calc = 2.595 g/cm3. No bands corresponding to H2O and OH-groups are in the IR spectrum. Osumilite-(Mg) is uniaxial (+), ω = 1.539(2), ɛ = 1.547(2). The chemical composition (electron microprobe, average of 5 point analyses, wt %) is: 0.08 Na2O, 3.41 K2O, 0.04 CaO, 7.98 MgO, 0.28 MnO, 21.57 Al2O3, 3.59 Fe2O3, 62.33 SiO2, total 99.28. The empirical formula is: (K0.72Na0.03Ca0.01)(Mg1.97Mn0.04)[Al4.21Fe{0.45/3+}Si10.32]O30. The simplified formula is: KMg2Al3(Al2Si10)O10. The crystal structure was refined on a single crystal, R = 0.0294. Osumilite-(Mg) is hexagonal, space group P6/ mcc; a = 10.0959(1), c = 14.3282(2)Å, V = 1264.79(6) Å3, Z = 2. The strongest reflections in the X-ray powder diffraction pattern [ d, Å I %) ( hkl)] are: 7.21 (37) (002), 5.064 (85) (110), 4.137 (45) (112), 3.736 (43) (202), 3.234 (100) (211), 2.932 (42) (114), 2.767 (51) (204). A type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.

  9. Deriving chemical trends from thermal infrared spectra of weathered basalt: Implications for remotely determining chemical trends on Mars

    NASA Astrophysics Data System (ADS)

    Rampe, Elizabeth B.; Kraft, Michael D.; Sharp, Thomas G.

    2013-07-01

    Variations in chemical composition over a planetary surface can be used to study petrologic and aqueous alteration processes. The desire for such data on Mars has prompted investigators to derive chemistry from models of Thermal Emission Spectrometer data. Although chemistry derived from thermal infrared spectral models is reportedly reliable for unaltered igneous rocks, the martian surface has experienced chemical weathering, which can adversely affect models. Here, we examine weathered basalts from Baynton, Australia, for which chemical weathering trends have been previously characterized, to test how well chemistry and chemical trends can be determined from TIR spectra of weathered rocks. The mineralogy of variably weathered rocks was derived from TIR spectra by linear mixing, and major-element chemistry was calculated from those mineral models. Derived chemistries and trends were compared to those measured by X-ray fluorescence. TIR spectroscopy is sensitive to weathering products in weathering rinds because the products are present in a coating geometry, making it a useful technique for remotely detecting weathered surfaces on planetary surfaces such as Mars. This sensitivity results in significant modeled abundances of weathering products (>80% of all phases) from TIR spectra of weathered Baynton surfaces, despite evidence from microscopy and X-ray diffraction showing that igneous minerals dominate the weathering rind. Measured chemical weathering trends show loss of MgO, CaO, Na2O, and K2O and relative enrichment in Al2O3 and FeOT. The modeled trends are similar to the measured trends, but a closer look at the modeled oxide abundances demonstrates that most oxides (i.e., alkalis, SiO2, and FeOT) are not well modeled, especially for weathered surfaces. The reasons for this are: (1) non-linear mixing and the presence of secondary coatings causes the overestimation of secondary phases in spectral models, and (2) spectral libraries generally lack poorly crystalline and amorphous secondary phases that are common in weathering rinds so that crystalline phases such as phyllosilicates are selected. The martian surface has likely been weathered less pervasively than the Baynton rocks and, therefore, weathering products may be dominated by poorly crystalline and amorphous phases, rather than crystalline phyllosilicates. Adding these phases to spectral libraries could improve bulk chemistry derived from the martian surface; however, if the secondary phases are present in a coating geometry, the derived chemistry will reflect the composition of the coating, and it may be difficult to infer the chemistry of the parent rock.

  10. Geochemistry and U-Pb SHRIMP zircon chronology of granitoids and microgranular enclaves from Jhirgadandi Pluton of Mahakoshal Belt, Central India Tectonic Zone, India

    NASA Astrophysics Data System (ADS)

    Bora, Sita; Kumar, Santosh; Yi, Keewook; Kim, Namhoon; Lee, Tae Ho

    2013-07-01

    The northern part of Central India Tectonic Zone (CITZ) is delineated by an arc-shaped supracrustal belt commonly referred to as Mahakoshal Belt, which is considered as a product of intense rifting of sialic crust that occurred at ca 2400-2600 Ma. Several granitoid plutons intrude the Parsoi Formation of Mahakoshal Belt. Among these, an elliptical small stock-like granitoid body trending E-W is exposed in and around Jhirgadandi region of Mahakoshal Belt, referred herein as Jhirgadandi Pluton. It is composed of minor amount of mafic rocks (diorite) and predominant granitoids. Country-rock pelitic xenoliths and microgranular enclaves (ME) are commonly hosted in granitoids but are absent in diorite. The ME exhibit typical magmatic texture with a Bt(Cpx Hbl)-Pl-Kf-Qtz-Mag-Ap assemblage, similar to that in host granitoids but with contrasting mineral proportions. Whole-rock molar Al2O3/(CaO + Na2O + K2O) (A/CNK) ratios of diorite (0.63-0.72), ME (0.69-1.21) and granitoids (0.83-1.05) suggest their nature largely metaluminous (I-type) to rarely peraluminous (S-type) granitoids. On most binary plots involving silica, two distinct compositional paths can be recognized; one formed by an array of differentiating diorite and ME, and another by fractionating granitoids gradually depleting in compatible elements. It is most likely that ME were generated by progressive and concurrent mixing of coeval pristine mafic (diorite) and granitoid magmas and fractionation processes. However, coherent and identical trace elements (except for Sr, Th, Y and Ni) and REE patterns for ME-granitoid pairs most likely suggest partial to near-complete chemical equilibration through varying degrees of diffusion process across the ME - partly crystalline host granitoid boundary. High-precision U-Pb SHRIMP zircon 206Pb/238U ages for ME (1758 19 Ma) and host granitoid (1753 9.1 Ma) from Jhirgadandi Pluton further support the notion that they were coeval. The obtained age (1750 Ma) of Jhirgadandi Pluton also points to the existence and role of Super-Columbian continental component in the evolution of Mahakoshal Belt of the CITZ.

  11. Neogene ignimbrites in the area of Arequipa, southern Peru: correlations, flow directions and sources

    NASA Astrophysics Data System (ADS)

    Paquereau, P.; Thouret, J.-C.; Wrner, G.; Fornari, M.; Roperch, P.

    2003-04-01

    In the area of Arequipa, the ignimbrites termed "sillars" are indurated, more or less welded pyroclastic flow deposits of rhyolitic composition. Our stratigraphic study and Ar-Ar date ages, show four main ignimbrite units: (1) two middle Miocene units (between 13.070.05 and 14.80.15 Ma) including the "base of Rio Chili" and the "Old sillar"; (2) a Middle to Early Pliocene unit (4.870.02 Ma), represented by the "La Joya sillar", (3) two Late Pliocene units (1.640.07 Ma), including a "white sillar" which grades into an overlying "pinkish unit", and finally (4) early Pleistocene (1.020.09 Ma) pumice-flow deposits channeled in the Rio Yura valley on the west flank of the Chachani volcanic complex. All these units are intercalated with alluvial sediments of variable thickness. The mineral assemblage encompasses plagioclase, biotite, quartz, sanidine, magnetite and ilmenite. Amphibole is only present in the "old sillar" and "La Joya sillar", which are unique in being porphyric. Crystals display large compositional variations because they are weathered. However, the MnO v. FeO diagram for biotites allows us to separate three compositional groups which correspond to (1) the "base of Rio Chili", (2) the Pliocene ignimbrites, and (3) the "old sillar". Harker diagrams of whole rock (pumice) analyses, show two distinct fractional crystallization trends with parallel evolutions. The first trend, which shows an evolution within Miocene ignimbrites, is more enriched in K_2O, Nb, Y and less enriched in Ba, Sr, Na_2O, CaO and P_2O_5 than the second Pliocene trend. We cannot locate source(s) for the Miocene ignimbrites because intense deformation and erosion have taken place after their emplacement; in addition AMS is not a valid method in this case because the flows are channelized in valleys, thus strongly influenced by the paleotopography. The source of the Pliocene ignimbrites, however, can be located by the AMS directions toward the NE of Arequipa depression, probably beneath the Chachani volcanic complex. The Pleistocene "Rio Yura Tuffs" source should be found on the north flank of Chachani, beneath Cerro Nocarani.

  12. Geochemistry of oceanic igneous rocks - Ridges, islands, and arcs - With emphasis on manganese, scandium, and vanadium

    USGS Publications Warehouse

    Doe, B.R.

    1997-01-01

    A database on a number of elements in oceanic volcanic rocks is presented, including the principal major-element oxides - SiO2, TiO2, Al2O3, Fe2O3(T), MnO, MgO, CaO, Na2O, K2O, and P2O5 (where T refers to total iron) - and the trace elements - Ba, Ce, Cr, Cu, Ni, Sc, Sr, V, Pb (mainly by isotope dilution), Yb, Zn, and Zr. Interpretations are given for transition metals, with emphasis on Mn, Sc, and V, in order to determine the concentration of the elements in primitive melts and assess their trends in magmatic differentiation. Transition metals are not enriched in plagioclase, so all are incompatible with pure plagioclase removal - that is, they become enriched in the melt. Both Cr and Ni are known to be highly compatible with olivine separation - i.e., they are depleted in the melt early in differentiation. Also, Sc is compatible with clinopyroxene (Cpx) removal from the melt and is depleted by separation of Cpx. Copper does not fit well in any of the principal silicates, but Cu, like Ni, is greatly enriched in sulfides that may remain in the source or separate from the magma. Decreasing Ni abundances and increasing Cu contents during differentiation are a sign of olivine separation. In the analysis presented herein, V - in the absence of Cpx separation - is found to behave remarkably like the moderately incompatible element Zn, and these two elements add to the list of element pairs of similar incompatibility whose ratios are insensitive to differentiation and to submarine weathering as well. Both are enhanced in titanomagnetite, so both would he compatible during titanomagnetite separation. When Cpx separates, however, V becomes compatible like Sc, but Zn remains incompatible. Thus, decreasing V (and Sc) contents and increasing Zn contents during differentiation are a sign of Cpx separation. Manganese often behaves much like Zn and therefore is moderately incompatible, but Mn is less compatible than Zn and V in titanomagnetite. Thus, decreasing Zn and V with increasing Mn is an indication of titanomagnetite removal. Dual compatible and incompatible trends with differentiation are found chiefly for Cu, Sc, and Sr. Distinguishing mid-ocean ridge basalts (MORB), oceanic-island volcanic rocks (OIV), and island-arc volcanic rocks (IAV) may be accomplished by plots of Ce/Yb versus Ba/Ce, where OIV plot to higher values of Ce/Yb than do MORB, and IAV data plot to higher values of Ba/Ce than do those of MORB. These ratios do not seem to be significantly affected by submarine weathering.

  13. Study of natural glasses through their behaviour as membrane electrodes

    USGS Publications Warehouse

    Truesdell, A.H.

    1962-01-01

    THE low-temperature chemical alteration of natural glass occurs in two stages: an initial stage in which it remains glassy but absorbs as much as 6 per cent water1, and a final stage in which devitrification to clay minerals, with release of silica, occurs2,3. During the first stage the composition of the glass may change, with gain of K2O and water and loss of Na2O (Smith, R. L., personal communication). This change is due to ion exchange. ?? 1962 Nature Publishing Group.

  14. Bulk, rare earth, and other trace elements in Apollo 14 and 15 and Luna 16 samples.

    NASA Technical Reports Server (NTRS)

    Laul, J. C.; Wakita, H.; Showalter, D. L.; Boynton, W. V.; Schmitt, R. A.

    1972-01-01

    Measurement of 24 and 34 bulk, minor, and trace elements in lunar specimens by instrumental and radiochemical neutron activation analysis shows greater Al2O3, Na2O, and K2O abundances and higher TiO2, FeO, MnO and Cr2O3 depletions in Apollo 14 soil samples as compared to Apollo 11 samples and to most of Apollo 12 samples. The uniform abundances in 14230 core tube soils and three other Apollo 14 soils indicate that the regolith is uniform to at least 22 cm depth and within about 200 m from the lunar module.

  15. High Quantum Efficiency of Nd3+ Ions in a Phosphate Glass System using the Judd-Ofelt Theory

    NASA Astrophysics Data System (ADS)

    Dantas, Noelio Oliveira; Serqueira, Elias Oliveira; Silva, Anielle Christine Almeida; Andrade, Accio Aparecido; Loureno, Sidney Alves

    2013-08-01

    The optical properties of trivalent neodymium embedded in a P2O5-Al2O3-Na2O-K2O phosphate glass system, synthesized by the fusion method, are studied. Absorption, luminescence, lifetime, and Raman spectroscopy measurements were performed and the Judd-Ofelt theory was applied to determine optical parameters such as the quantum efficiency and the stimulated emission cross section of the Nd3+-doped glass system. This structure has high quantum efficiency at low Nd3+ concentrations, comparable to the efficiency of a commercial YAG:Nd3+ crystal. We discuss the mechanisms responsible for the high quantum efficiency observed in the proposed phosphate glass system.

  16. Experimental Constraints on Alkali Volatilization during Chondrule Formation: Implications for Early Solar System Heterogeneity

    NASA Astrophysics Data System (ADS)

    Ustunisik, G. K.; Ebel, D. S.; Nekvasil, H.

    2014-12-01

    The chemical variability of chondrule volatile element contents provide a wealth of information on the processes that shaped the early solar system and its compositional heterogeneity. An essential observation is that chondrule melts contain very low alkalies and other volatile elements (e.g., Cl). The reason for this depletion is the combined effects of cooling rates (10 to 1000K/h), the small size of chondrules, and their high melting temperatures (~1700 to 2100 K) resulting in extensive loss of volatiles at canonical pressures (e.g., 10-4bar). However, we observe some chondrules with significant concentrations of volatiles (Na, Cl), that differ markedly from chondrules dominated by refractory elements. Could such heterogeneity arise from loss of alkalis and Cl to a gas phase that itself later condenses, thereby yielding variations in volatile enrichments in chondrules? Does Cl enhance volatility of the alkalis to varying extents? Experiments on Cl-bearing and Cl-free melts of equivalent composition for 10 min, 4 h, and 6 h reveal systematic effects of Cl on alkali volatility. Cl-bearing melts lose 48% of initial Na2O, 66% of K2O, 96% of Cl within the first 10 minutes of degassing. Then the amount of alkali loss decreases due to the absence of Cl. Cl-free melts loses only 15% of initial Na2O and 33% K2O. After 4 hours, melts lose 1/3 of initial Na2O and 1/2 of K2O. For both systems, Na2O is more compatible in the melt relative to K2O. Therefore, the vapor given off has a K/Na ratio higher than the melt through time in spite of the much higher initial Na abundance in the melt. Enhanced vaporization of alkalis from Cl-bearing melt suggests that Na and K evaporate more readily as volatile chlorides than as monatomic gases. Cl-free initial melts with normative plagioclase of An50Ab44Or6 evolved into slightly normal zoned ones (An49Ab50Or1) while Cl-bearing initial melts normative to albitic plagioclase (An46Ab50Or4) evolved to reverse zoned ones (An54Ab45Or1). The vapor phase over Cl-bearing chondrule melts may have a bimodal character over time. The heteregeneous volatile contents of chondrules may result from quenching of melt droplets at different stages of repeated heating, chondrule fragment recycling, and recondensation of exsolved volatiles.

  17. Un nouvel exemple de magmatisme potassique à ultrapotassique : les syénites de l'Andringitra (Madagascar)A new example of potassic to ultrapotassic magmatism: the Andringitra syenites (Madagascar)

    NASA Astrophysics Data System (ADS)

    Nédélec, Anne; Grujic, Djordje

    2001-06-01

    The Andringitra Range (Madagascar) is made of potassic to ultrapotassic syenites (K 2O=8-11 weight%; K 2O/Na 2O=2-8). It is a new example of this rare type of magmatism, here related to the Late Precambrian Panafrican orogeny. In the Pic Boby area, the main rock type contains pyroxene (diopside) and amphibole (edenite), and is nearly silica-saturated. A subordinate type is an undersaturated diopside- and phlogopite-bearing syenite. Very high K, Ba, Rb, Sr and LREE contents, together with moderate to high Mg# (33-54), suggest a parental magma derived from the enriched (metasomatized) lithospheric mantle. Fractional crystallisation and crustal assimilation may be responsible for the most evolved compositions.

  18. Geochemical, Mineralogical, and Sedimentological Investigation of Phosphorite and its Clay-Rich Mine Tailings from a Phosphate Mine, Togo, West Africa

    NASA Astrophysics Data System (ADS)

    Rezaie Boroon, M.; Ramirez, P. C.; Gnandi, K.

    2009-12-01

    Clay-rich mine tailings from phosphate mine operations in Togo West, Africa present major environmental and economic problems. Options for reclamation and restoration of the tailings are limited and are fundamentally restricted due to poorly executed waste management. The major control on the bulk physical properties of the tailings is the mineralogy of the materials. Clay samples from raw phosphate mined were obtained to investigate its sedimentological geochemical, and bulk properties Tailings were also analyzed for similar properties. The phosphatic deposits are Eocene in age, 1 to 10s of meters thick and consist mostly of moderately to poorly sorted phosphatized pellets, formanifera, and other bioclastic debris. Attapulgite occurs interstitially. Moisture contents of clays from the raw phosphate varies from 4.00 to 7.11 wt%. Francolite is the main mineral phase present in the samples analyzed. Geochemically, the rocks show significant enrichment in P2O5 and CaO. P2O5 concentrations vary from approximately 29 to 35.78 wt%. A strong correlation (r2 = 0.92) occurs between CaO and P2O5 abundances indicating that apatite is a major control on the phosphate. A number of heavy metal elements and trace elements occur. Cr, V, Ni, Cu, and Cd are interpreted to be in phosphate minerals, largely apatite. Mean oxide compositions (wt %) are 31.27% P2O5, 43.74% CaO, 9.50% SiO2, 4.30% Al2O3, 2.96% Fe2O3, 0.11 % K2O, 0.19% TiO2, 0.02% MnO, 0.02% MgO, 0.02 % Na2O, and 6.12 % LOI (loss of ignition). Our analysis shows that Cd, U, Th, and F are incorporated into the francolite. We conclude that the phosphorites in Togo formed under oxic, shallow-water conditions where microbial populations assimilated phosphorus primarily from seawater and mediated precipitation of calcium fluroapatite during early digenesis at the sediment-water interface. Analysis of the mine tailings show that the purification process leads to the enrichment of certain metals (Cr, Cu, Ni, V, Zn, Ba, Sr, Fe, and Al) in the tailings due to their association with the clay minerals, whereas Cd, Th, and U are enriched in the purified apatite-rich product. Leaching tests show that the solubility of metals generally increases when salinity increases or when pH decreases. Thus, the processing of phosphorites with sea water and the dumping of phosphorite tailings into the sea represent a serious potential risk for the marine ecosystem and for human health through the food chain.

  19. Thermodynamics and phase equilibria of the silicate-fluoride-water systems: Implications for fluorine-bearing granites

    NASA Astrophysics Data System (ADS)

    Dolejs, David

    The progressive enrichment in volatiles and light incompatible elements observed during upper-crustal differentiation of granitic and rhyolitic magmas leads to significant changes in melt physical-chemical properties and has important implications for ore deposition and volcanic devolatization. Thermodynamic calculations and experimental studies of melting equilibria in the Na 2O-K2O-Al2O3-SiO2-F 2O-1-H2O system are used to evaluate mineral stabilities, fluid compositions, the extent of fluoride-silicate liquid-liquid immiscibility, fluorine and water solubility limits and differentiation paths of natural fluorine-bearing silicic magmas. The interaction of fluorine with rock-forming aluminosilicates corresponds to progressive fluorination by the thermodynamic component F2O-1. Formation of fluorine-bearing minerals first occurs in peralkaline and silica-undersaturated systems that buffer fluorine concentrations at very low levels (villiaumite, fluorite). The highest concentrations of fluorine are achieved in peraluminous silica-oversaturated systems, saturated with fluorite or topaz. Thermodynamic models of fluorosilicate melts indicate clustering of silicate tetrahedra in the Na2O-SiO 2-F2O-1 system, whereas initial NaAl-F short-range order evolves into partial O-F disorder in the albite-cryolite system. Experiments performed at 520-1100C and 0.1-100 MPa completely describe liquidus relations and differentiation paths of fluorine-bearing felsic magmas. Coordination differences and short-range order effects between [NaAl]-F, Na-F vs. Si-O lead to the fluoride-silicate liquid immiscibility, which extends from the silica-cryolite binary through the peralkaline albite-silica-cryolite ternary and closes in multicomponent, topaz-bearing systems owing to the destabilizing effect of increasing peraluminosity. Liquidus relations indicate that fluoride-silicate liquid-liquid immiscibility is inaccessible to quartz-feldspar-saturated granitic melts. Differentiation paths of Ca-poor granitic melts with fluorine reach the cryolite or topaz saturation surface, respectively, and, depending on aluminosity buffering by rock-forming silicates, may evolve to the high fluorine concentrations of the haplogranite-topaz-cryolite-H2O eutectic at max. 5.9 wt. % F, 540C, 100 MPa and H2O saturation. In contrast, the potential of Ca-rich silicic magmas for fluorine enrichment is severely limited by fluorite crystallization. Fluorite solubility is determined by individual concentrations of CaO and F2O-1 in the melt and exhibits a minimum at subaluminous compositions due to the short-range ordering of Ca-Al and alkali-F. These results provide a framework for differentiation of natural fluorine-bearing magmas and have applications in electrolytic and flux metallurgy.</