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1

Thermal properties and FTIR spectra of K2O/Na2O iron borophosphate glasses  

NASA Astrophysics Data System (ADS)

Thermal properties and structure of iron borophosphate glasses containing Na2O and/or K2O have been investigated in this paper. A series of glasses of the general compositions xK2O(20-x)Na2O28.8Fe2O38B2O343.2P2O5, with x = 0, 5, 10, 15, 20 mol%, prepared by melt quenching method. The thermal stability and structure of as-prepared glasses was characterized by DTA and FTIR spectra, respectively. The results show that the thermal properties of sodium iron borophosphate glasses can be improved through the replacement of Na2O by appropriate quantity of K2O. FTIR data suggest that the substitution of K2O for Na2O in the 20Na2O28.8Fe2O38B2O343.2P2O5 glass does not produce fundamental changes in the structure of borophosphate network. But about 10 mol% K2O's substitution leads to a significant decrease of possible self-connection among boron-oxygen groups, which enhance the structure stability of sodium iron borophosphate glass, and thus the enhanced thermal stability were obtained.

Wang, Fu; Liao, Qilong; Xiang, Guanghua; Pan, Sheqi

2014-02-01

2

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

PubMed

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

Riguidel, Quentin; Muoz, Francisco

2011-06-01

3

Mixed-Alkali Effect in Li2O-Na2O-K2O-B2O3 Glasses: Infrared and Optical Absorption Studies  

NASA Astrophysics Data System (ADS)

The mixed-alkali effect (MAE) has been investigated in the glass system (40 - x)Li2O- xNa2O-10K2O-50B2O3 (0 mol% ? x ? 40 mol%) through density, modulated differential scanning calorimetry (DSC), and optical absorption studies. From the absorption studies, the values of the optical band gap ( E opt) for direct transition and Urbach energy (? E) have been evaluated. The values of E opt and ? E show nonlinear behavior with the compositional parameter. The density and glass-transition temperature of the present glasses also show nonlinear variation, supporting the existence of MAE. The infrared (IR) spectra of the glasses reveal the presence of three- and four-coordinated boron atoms. The specific vibrations of Li-O, Na-O, and K-O bonds were observed in the present IR study.

Samee, M. A.; Edukondalu, A.; Ahmmad, Shaik Kareem; Taqiullah, Sair Md.; Rahman, Syed

2013-08-01

4

Characteristics and biocompatibility of Na 2OK 2OCaOMgOSrOB 2O 3P 2O 5 borophosphate glass fibers  

Microsoft Academic Search

A novel Na2OK2OCaOMgOSrOB2O3P2O5 borophosphate glass fiber is prepared. The thermal properties including differential thermal analysis (DTA) and viscosity measurement of the glass were presented. The tensile strength of the glass fiber is measured. The reaction of the glass fibers in the SBF solution is characterized by XRD, FTIR and SEM. XRD and FTIR indicate that the carbonate hydroxyapatite has formed

Kai Zheng; Shengbing Yang; Jiaojiao Wang; Christian R?ssel; Changsheng Liu; Wen Liang

5

Antibacterial and bioactive silver-containing Na2O x CaO x 2SiO2 glass prepared by sol-gel method.  

PubMed

The antibacterial effect of addition of silver oxide to Na2O x CaO x 2SiO2 glass have been studied. Silver containing and silver free Na2O x CaO x 2SiO2 glasses have been prepared by sol-gel synthesis using tetramethil orthosilicate, sodium ethoxide, calcium nitrate tetrahydrate and silver nitrate as starting materials and methyl ethyl ketone as solvent. The gel was examined by differential thermal analysis, thermo gravimetric analysis, FTIR spectroscopy and X-ray diffraction analysis. Antibacterial and bioactive tests on gel glass powders, obtained after a heat treatment of 2 h at 600 degrees C of the dried gel, were carried out. High antimicrobial effects of samples against Escherichia coli and Streptococcus mutans were found. FTIR measurements and SEM micrographs have ascertained the formation of a hydroxyapatite layer on the surface of samples soaked in a simulated body fluid for different times. PMID:15387420

Catauro, M; Raucci, M G; De Gaetano, F; Marotta, A

2004-07-01

6

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

7

Experimental investigation of the effects of K2O on the composition of near-solidus partial melts of peridotite at 3 GPa  

NASA Astrophysics Data System (ADS)

K2O is highly mobile in fluids and silicate melts that may act as metasomatic agents in the upper mantle. Enrichment in K2O depresses the solidus of peridotite (Hirschmann, 2000) and, at low pressures, increases SiO2 and lowers CaO concentrations of near-solidus partial melts (Hirschmann et al., 1998). High SiO2 and low CaO characteristic of EM-type OIB (e.g., Jackson and Dasgupta, 2008) may be related to enrichment of their sources in K2O; however, primary OIB are likely generated beneath oceanic lithosphere at pressures (~3 GPa) where the effects of K2O on melt compositions is not well-constrained. We present the results of piston cylinder experiments at 3 GPa that investigate the effects of variable K2O concentrations on compositions of near-solidus partial melts of peridotite. K2O was added to an alkali picrite multiply-saturated in a garnet lherzolite residue with a bulk composition similar to fertile lherzolite KLB-1. Experiments were performed with initial K2O in the melt of 2 wt.% and 4 wt.% at temperatures from 1430-1450 C, near the solidus of KLB-1 analogs (144515 C). Differences in experimental melt fraction resulted in quenched melts each with a different K2O concentration between 2.5-4.6 wt.%. Variable experimental melt fraction led to several other systematic compositional variations in the melt, such as increased TiO2 and decreased Mg# at low experimental melt fractions. To account for these differences, melt compositions were corrected for melt fraction effects to a common TiO2 content. Corrected melt compositions are representative of near-solidus partial melts of a single garnet peridotite source with varying initial K2O concentrations. The strongest effects of increased K2O in the melt are increased SiO2 and decreased CaO. For each 1 wt.% increase in K2O in the melt SiO2 increases and CaO decreases ~0.5 wt.%. This is a stronger effect than anticipated by (Hirschmann et al., 1998) for melts at 3 GPa. Al2O3 was also found to increase with K2O, and Na2O and Cr2O3 both decrease. Increased K2O moves the SiO2 and CaO concentrations of near-solidus partial melts of peridotite toward those of EM1 and EM2-type OIB, but the amount of K2O required to reach those concentrations is greater (4-5 wt.%) than is found in typical EM-type OIB (1-2 wt.%), and increased Al2O3 associated with high K2O moves partial melts of peridotite away from typical OIB compositions. A source that has a high modal proportion of clinopyroxene may be required in conjunction with high K2O concentrations to produce the low CaO contents of extreme EM-type OIB (CaO < 8 wt.%).

Davis, F. A.; Hirschmann, M. M.

2012-12-01

8

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)

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.

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

2013-12-01

9

Liquidus Equilibria in the System K2O^Na2O^Al2O3^SiO2^F2O1^H2O  

E-print Network

fluorine-bearing granitic and rhyolitic magmas. Topaz and cryolite are stable saturating solid phases, and haplogranite^topaz^H2O at 6408C and $2 wt % F. Topaz and cryolite form a binary peralkaline eutectic at 6608C of multiphase eutectics with quartz and alkali feldspar towards the topaz^cryolite join and enables the silicate

Long, Bernard

10

Liquidus Equilibria in the System K2O^Na2O^Al2O3^SiO2^F2O1^H2O  

E-print Network

^silicate liquid immiscibility spans the silica^albite^cryolite and silica^topaz^cryolite ternaries/Na ¼ 0Á75. The addition of topaz, however, significantly lowers melting temperatures and allows strong fluorine enrichment in subaluminous compositions. At 100 MPa, the binary topaz^cryolite eutectic is located

Long, Bernard

11

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

USGS Publications Warehouse

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.

Brooks, W. E.

1986-01-01

12

CaO--P2O5--Na2O-based sintering additives for hydroxyapatite (HAp) ceramics.  

PubMed

We have assessed the effect of CaO--P2O5--Na2O-based sintering additives on mechanical and biological properties of hydroxyapatite (HAp) ceramics. Five different compositions of sintering additives were selected and prepared by mixing of CaO, P2O5, and Na2CO3 powders. 2.5 wt% of each additive was combined with commercial HAp powder, separately, followed by ball milling, and sintering at 1250 degrees C and 1300 degrees C in a muffle furnace. Green and sintered densities of the compacts were analyzed for the influence of additives on densification of HAp. Phase analyses were carried out using an X-ray diffractometer. Vickers microhardness testing was used to evaluate hardness of sintered compacts of different compositions. A maximum microhardness of 4.6 (+/- 0.28) GPa was attained for a composition with 2.5 wt% addition of CaO:P2O5:Na2O in the ratio of 3:3:4. Results from mechanical property evaluation showed that some of these sintering additives improved failure strength of HAp under compressive loading. Maximum compressive strength was observed for samples with 2.5 wt% addition of CaO. Average failure strength for this set of samples was calculated to be 220 (+/- 50) MPa. Cytotoxicity, and cell attachment studies were carried out using a modified human osteoblast cell line called OPC-1. In vitro results showed that these compositions were non-toxic. Some sintering aids enhanced cell attachment and proliferation, which was revealed from SEM examination of the scaffolds seeded with OPC-1 cells. PMID:14741598

Kalita, S J; Bose, S; Hosick, H L; Bandyopadhyay, A

2004-05-01

13

Response of human bone marrow stromal cells to a resorbable P(2)O(5)-SiO(2)-CaO-MgO-Na(2)O-K(2)O phosphate glass ceramic for tissue engineering applications.  

PubMed

This work focuses on the synthesis and characterization of a novel bioresorbable glass ceramic phosphate-based material (GC-ICEL). More specifically, its solubility in different aqueous media (water, Tris-HCl and acellular simulated body fluid) and the response of human stromal cells cultured on it were investigated. X-ray diffraction analysis showed the presence of two crystalline phases identified as Na(2)Mg(PO(4))(3) and Ca(2)P(2)O(7) and dissolution tests highlighted a preferential dissolution of the Na(2)Mg(PO(4))(3) phase and of the residual amorphous phase in all the chosen media. Soaking tests in simulated body fluid showed precipitation of a hydroxyapatite layer, demonstrating the bioactivity of GC-ICEL, which is partially due to the reported bioactivity of Ca(2)P(2)O(7). The effect of GC-ICEL on adhesion, proliferation and osteoblastic gene expression of human bone marrow-derived stromal cells was also studied. Combining molecular and biochemical analyses, it was found that bone marrow cell differentiation was stimulated over proliferation on GC-ICEL. Moreover, the expression of bone-related genes in cells cultured on GC-ICEL confirmed the bioactivity of this phosphate-based glass ceramic, which might have a stimulatory effect on osteogenesis. PMID:19616650

Leonardi, E; Ciapetti, G; Baldini, N; Novajra, G; Vern, E; Baino, F; Vitale-Brovarone, C

2010-02-01

14

The effect of RO (R = Mg, Ca, Ba and Zn) on physical properties of Na 2O\\/Al 2O 3\\/B 2O 3\\/SiO 2 glasses for the preparation of gradient index micro lenses  

Microsoft Academic Search

Glasses in the system Na2OAl2O3B2O3SiO2 doped with MgO, CaO, BaO or ZnO (concentrations: 2.5%5mol%) were melted from the raw materials and studied with respect to their densities, hydrolytic durabilities, crystal growth velocities, specific ionic conductivities, refractive indices, Abbe numbers and optical transmissions. The samples were ion exchanged in a NaNO3\\/AgNO3 salt melt in order to determine the Na+\\/Ag+ interdiffusion coefficients

Sandra Hornschuh; Bernhard Messerschmidt; Torsten Possner; Ulf Possner; Christian Rssel

2006-01-01

15

Determination of Na 2O from sodium aluminate NaAlO 2  

Microsoft Academic Search

The aim of the work was to find a suitable method and conditions for determining Na2O wt.% from NaAlO2. Problems were encountered while titrating NaAlO2 with hydrochloric acid. The problematic area was the pH range 410 where aluminum precipitates as hydroxides. The different species of the aluminate solution were determined using potentiometric and complexometric titrations. The equivalent point of the

Teemu Nykki; Anttila Raimo; Permki Paavo; Kurikka Antero; Nikula Pivi

2000-01-01

16

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

PubMed Central

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??m. 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

2012-01-01

17

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

NASA Astrophysics Data System (ADS)

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 ?m. 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.

Samarasekera, Champika; Tan, Bo; Venkatakrishnan, Krishnan

2012-07-01

18

Determination of Na(2)O from sodium aluminate NaAlO(2).  

PubMed

The aim of the work was to find a suitable method and conditions for determining Na(2)O wt.% from NaAlO(2). Problems were encountered while titrating NaAlO(2) with hydrochloric acid. The problematic area was the pH range 4-10 where aluminum precipitates as hydroxides. The different species of the aluminate solution were determined using potentiometric and complexometric titrations. The equivalent point of the potentiometric titration was detected using Gran's plotting method. Precipitation of aluminum hydroxides did not interfere with titrations, because in potentiometric titrations the pH value was over 10 and in complexometric titrations the pH was 4. The results were accurate and determinations were easy to carry out. Sodium was also determined by DCP-AES. PMID:18968035

Nykki, T; Raimo, A; Paavo, P; Antero, K; Pivi, N

2000-07-31

19

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

20

Non-Potassic Melts In CMAS-CO2-H2O-K2O Model Peridotite  

NASA Astrophysics Data System (ADS)

Volatile mediated model systems have been fundamental in shaping our knowledge about the way we view melting phase relations of peridotite at various depths in the Earth. Volatiles not only affect the melting temperatures, but the resulting liquids are, in some case, dramatically different than those witnessed in melting of dry peridotite. For example, the influence of CO2 and H2O on the melting phase relations of model peridotite shows a remarkable decrease in the solidus temperatures when compared to the dry peridotite (Gudfinnsson and Presnall, 2005). These model systems illustrate a gradational change above the solidus from carbonatites to kimberlites over several hundreds of degrees. Group-II kimberlites are ultrapotassic rocks with high water content where the mineral phlogopite is abundant. To get a better understanding of the melting phase relations related to carbonatitic and kimberlitic magmas, K2O was added to the system CMAS-CO2-H2O. In these systems, fluid and melt can co-exist in P-T space. However, from past studies, it is also known that in hydrous systems, both the fluid and melt will become indistinguishable from one another creating a singularity (second critical endpoint). Starting from the solidus located in six components (Keshav and Gudfinnsson, AGU abstract, 2009), with seven phases, melting phase relations in CMAS-CO2-H2O-K2O involving, fo-opx-cpx-garnet-carbonate-melt-fluid, are divariant. Fluid was recognized with the observation of large cavities seen in exposed capsules. Moreover, the presence of bright, needle-like grains found in large cavities in backscattered images implies the presence of solute in the fluid phase. Significantly, liquids on this divariant region have about 1000 ppm K2O, and so is the case with accompanying cpx. Hence, with this non-interesting amount of K2O in the mentioned phases, fluid must have all the potassium. At 30 kbar/1100C, with fo-opx-cpx-garnet-carbonate-phlogopite-melt-fluid, the melting phase relations become isobarically invariant. In contrast, the solidus in CMAS-CO2-H2O at 30 kbar is at 1000C. Above 1100C, phlogopite is no longer in equilibrium with the phase assemblage. In all the experimental charges, capsules were pierced, and a hydrous solution was seen escaping. When tested with litmus paper, in all cases at 25-50 kbar, this solution was determined to be highly basic (pH>10). Upon evaporation of the hydrous solution, a white precipitate was left behind around the piercing on the capsule wall. In CMAS-CO2-H2O, the fluid was found to be almost neutral (pH 7-8). The melt present in our experiments is carbonatitic in nature and does not contain any significant amounts of K2O. This contradicts a recent study on K2O in a natural composition (Foley et al, 2009) where carbonatitic melt had up to 13 wt% of K2O. Significantly, since K2O is perhaps all in the fluid, source regions for potassic magmas in the Earths mantle could not be created by metasomatism of alkali-rich, carbonatitic melts.

Buisman, I.; Walter, M. J.; Keshav, S.

2009-12-01

21

Ion-Conducting Defect Pyrochlore Phases in the K 2 OSb 2 O 3 WO 3 System  

Microsoft Academic Search

Potassium tungstate antimonates were prepared by calcining aK2CO3 + Sb2O3 + 2(1 a )WO3 mixtures in air. Data on the phase composition of the obtained materials were used to locate the pyrochlore phase region in the Sb2OzW2O6 K2O composition triangle at 1170 K. The distributions of the constituent ions and lattice defects over the crystallographic positions of

V. A. Burmistrov; D. A. Zakhar'evich

2003-01-01

22

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)

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.

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

2012-12-01

23

FeO-containing K-Na-rich silicate (`KNSF': SiO2 64.3 wt%, K2O 18.6 wt%, Na2O 12.4 wt%, FeO 4.6 wt%) with a low melting temperature. The experiments at the Australian  

E-print Network

concentrations had been measured previously by instrumental neutron activation analysis. The Si content of each activation analysis at the University of Cologne. Received 23 December 1999; accepted 6 June 2000. 1. Li, J as described in ref. 27. The Pd and Pt contents in these silicate samples were analysed by instrumental neutron

Waxman, David

24

Physical and optical properties of Dy3+: Li2O-K2O-B2O3 glasses  

NASA Astrophysics Data System (ADS)

The luminescence, lasing and sensing properties of rare earth (RE) ions have drawn much interest among researchers. We have focussed on the physical and optical properties of Li2O-K2O-B2O3 (LKB) with different concentrations of dysprosium (Dy3+) ions. The glass samples were prepared using melt quenching method. The physical parameters of the prepared glass were determined. Optical measurements such as XRD, FTIR, absorption and photoluminescence spectra have been carried out. Dy3+: LKB glass showed eight absorption bands with hypersensitive transition located at 1265 nm (6H15/2 ? 6F11/2-6H9/2). Finally, Dy3+: LKB glass exhibited two intense luminescence emission at 481 nm (4F9/2 ? 6H15/2; blue) and 573 nm (4F9/2 ? 6H13/2; yellow) and feeble band at 683 nm (4F9/2 ? 6H11/2; red) with excitation wavelength at 370 nm. The results obtained are prevalent with others studies and also point to its use in solid-state laser, optoelectronic devices and W-LEDs application.

Azizan, S. A.; Hashim, S.; Razak, N. A.; Mhareb, M. H. A.; Alajerami, Y. S. M.; Tamchek, N.

2014-11-01

25

Synthesis and optical characteristics of Sm3+-doped 15K2O-15Nb2O5-70TeO2 glass ceramics  

NASA Astrophysics Data System (ADS)

We investigate the crystallinity and the optical properties of pure and Sm3+-doped 15K2O-15Nb2O5-70TeO2 glass ceramics after heat treatment. We prepare pure and 1 mol% Sm3+-doped 15K2O-15Nb2O5-70TeO2 glasses by using the conventional melt-quenching method. After annealing at 390 C and 410 C, respectively, we characterize the crystallinity of the glasses. We examine the chemical bonding states of the ions and the optical properties by taking absorption, excitation, and emission spectra. We show that Sm3+-doped 15K2O-15Nb2O5-70TeO2 glass ceramics after heat treatment are excellent red-orange-emitting phosphors under near UV excitation.

Hong, K. S.; Cha, Yu-Jung; Ha, Myoung Gyu; Jeong, Euh Duck; Bae, Jong Seong; Kim, Hyun Gyu; Yang, Ho-Soon

2014-06-01

26

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

NASA Astrophysics Data System (ADS)

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.

Li, Mark; Utigard, Torstein; Barati, Mansoor

2014-08-01

27

High-pressure x-ray diffraction studies of the nanostructured transparent vitroceramic medium K2O-SiO2-Ga2O3  

E-print Network

of their function as promising nonlinear media for optical processing devices.1­7 High-pressure stud- iesHigh-pressure x-ray diffraction studies of the nanostructured transparent vitroceramic medium K2O embedded in an amorphous matrix, in the pressure range from ambient up to 15 GPa. The optically transparent

Kruger, Michael - Department of Physics, University of Missouri

28

Structural characterization and physical properties of P2O5-CaO-Na2O-TiO2 glasses by Fourier transform infrared, Raman and solid-state magic angle spinning nuclear magnetic resonance spectroscopies.  

PubMed

Phosphate-based glasses have been investigated for tissue engineering applications. This study details the properties and structural characterization of titanium ultra-phosphate glasses in the 55(P(2)O(5))-30(CaO)-(25-x)(Na(2)O)-x(TiO(2)) (0?x?5) system, which have been prepared via melt-quenching techniques. Structural characterization was achieved by a combination of X-ray diffraction (XRD), and solid-state nuclear magnetic resonance, Raman and Fourier transform infrared spectroscopies. Physical properties were also investigated using density, degradation and ion release studies; additionally, differential thermal analysis was used for thermal analysis of these glasses. The results show that with the addition of TiO(2) the density and glass transition temperature increased whereas the degradation and ion release properties are decreased. From XRD data, TiP(2)O(7) and CaP(2)O(6) were detected in 3 and 5 mol.% TiO(2)-containing glasses. Magic angle spinning nuclear magnetic resonance results confirmed that as TiO(2) is incorporated into the glass; the amount of Q(3) increases as the amount of Q(2) consequently decreases, indicating increasing polymerization of the phosphate network. Spectroscopy results also showed that the local structure of glasses changes with increasing TiO(2) content. As TiO(2) is incorporated into the glass, the phosphate connectivity increases, indicating that the addition of TiO(2) content correlates unequivocally with an increase in glass stability. PMID:21930253

Kiani, Azadeh; Hanna, John V; King, Scott P; Rees, Gregory J; Smith, Mark E; Roohpour, Nima; Salih, Vehid; Knowles, Jonathan C

2012-01-01

29

A comparative study between in vivo bone ingrowth and in vitro apatite formation on Na 2OCaOSiO 2 glasses  

Microsoft Academic Search

This study compared in vivo bioactivity with the in vitro apatite-forming ability of biomaterials. Granules of five kinds of P2O5-free Na2OCaOSiO2 glasses, showing different apatite-forming ability in simulated body fluid (SBF), were implanted into a defect on the femoral condyle of rabbits. Bone ingrowth was evaluated using scanning electron microscopy among five kinds of glasses at 1, 2, 3, 6,

Shunsuke Fujibayashi; Masashi Neo; Hyun-Min Kim; Tadashi Kokubo; Takashi Nakamura

2003-01-01

30

Radiation-induced color centers in ?-irradiated glasses in the Na 2 O-Nb 2 O 5 -P 2 O 5 system  

Microsoft Academic Search

The specific features of the induced optical absorption spectra of glasses in the 45Na2O xNb2O5 (55 ? x)P2O5 system with Nb2O5 contents x = 5, 10, 20, 25, 30, and 35 mol % are investigated as functions of the irradiation dose and the heat treatment time. The\\u000a spectra are decomposed into Gaussian components with the use of computer processing. It

E. V. Avdeeva; T. V. Bocharova; G. O. Karapetyan; A. M. Mironov

2006-01-01

31

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

32

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

33

Clayton Municipal Airport (CAO) Pavement Condition and Analysis  

E-print Network

;........................................................................................4. Recommend Pavement Design 19 .........................................Table 5. Design Aircraft Used Airport (CAO) Aircraft Operations (2005-2009) 5 .....Table 2. Clayton Municipal Airport (CAO) Predicted Aircraft Operations 2007-2027 6 ..................Figure 2. Clayton Municipal Airport (CAO) PCI Branch Map

Cal, Mark P.

34

Conversion of syn-gas to lower alkenes over Fe-TiO 2-ZnO-K 2O catalyst system  

Microsoft Academic Search

Conversion of syn-gas to lower alkenes is studied over a multicomponent catalyst system, Fe-TiO2-ZnO-K2O. Various reaction variables affecting the conversion were studied. At H2:CO=1, 2.5kg\\/cm2 pressure, 250C temperature and GHSV=960h?1, maximum selectivity of 68% to alkenes was obtained at 45% conversion of the feed. The alkenes consist of a mixture of propylene (65%) and ethylene (35%). The catalyst is active

Subhash Ch Roy; H. L Prasad; P Dutta; A Bhattacharya; B Singh; S Kumar; S Maharaj; V. K Kaushik; S Muthukumaru Pillai; M Ravindranathan

2001-01-01

35

The mixed network former effect in glasses: solid state NMR and XPS structural studies of the glass system (Na2O)(x)(BPO4)(1-x).  

PubMed

The structural organization of sodium borophosphate glasses with composition (Na(2)O)(x)(BPO(4))(1-x) (0.25 ?x? 0.55) has been investigated by differential scanning calorimetry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), as well as single- and double resonance (11)B and (31)P magic-angle spinning (MAS) NMR. (11)B MAS-NMR data indicate the dominance of anionic four-coordinated boron units, and (31)P MAS NMR reveals the successive transformation of neutral P(3) into singly charged P(2) units and their further transformation into doubly charged P(1) units at high Na(2)O contents. The quantification of these units provides detailed insight into the competition of the network formers borate and phosphate for the network modifier oxide. At low modifier content (x < 0.35), the anionic species are almost exclusively borate (B(4)) units, whereas at higher sodium concentrations, large numbers of anionic phosphate (P(2) and P(1)) species are formed. O-1s XPS data provide a quantitative distinction between B-O-B, B-O-P, and P-O-P linkages as well as non-bridging oxygen atoms, and comparable numbers can be extracted from (11)B and (31)P MAS-NMR experiments. Both XPS as well as (31)P{(11)B} and (11)B{(31)P} rotational echo double resonance (REDOR) NMR results reveal strong interactions between the two network formers boron oxide and phosphorus oxide, resulting in a preferred formation of B-O-P linkages. For higher Na(2)O contents, however, the successive network modification diminishes this preference, resulting in close-to-statistical network connectivities. Compositional trends of T(g) in the Na(2)O-B(2)O(3)-P(2)O(5) glass forming system can be correlated with the overall network connectedness, expressed by the total number of bridging oxygen atoms per network former species. However, separate linear correlations are observed for different compositional lines, indicating also the relevance of the type of network former linkages present. PMID:21380468

Rinke, Matthias T; Eckert, Hellmut

2011-04-14

36

Sodium ion conducting glasses with mixed glass formers NaINa 2OV 2O 5B 2O 3: application to solid state battery  

Microsoft Academic Search

Glasses in the quaternary system 15NaI15Na2O70[xV2O5(1?x)B2O3] when x=0.02, 0.04, 0.06, 0.08 and 0.1, respectively were investigated emphasizing the influence of two glass formers on the transport properties. X-ray Diffractometry, Differential Scanning Calorimetry and conductivity studies were employed for the characterization. The mixed glass former effect on the conductivity was noticed and discussed. The best conducting glass composition was used as

G Venugopal; M Narasimha Chary

1999-01-01

37

Investigation of phase equilibria and growth of BBO (?-BaB 2O 4) crystals in BaOB 2O 3Na 2O ternary system  

Microsoft Academic Search

The BaOB2O3Na2O ternary system is of great importance for growing crystals of low-temperature modification of barium borate (?-BaB2O4). A new solid-state triangulation scheme was suggested based on the existence of NaBaBO3 compound. Primary crystallization areas of NaBaBO3 and two new compoundsNaBa4(BO3)3 and Ba5B4O11were determined. It was shown that crystals grown from depleted sodium system BaB2O4NaBaBO3 have great advantage concerning the

P. P. Fedorov; A. E. Kokh; N. G. Kononova; T. B. Bekker

2008-01-01

38

Gamma ray irradiation effects on the optical properties of BaO-Na2O-B2O3-SiO2 glasses  

NASA Astrophysics Data System (ADS)

This paper reports the effect of gamma radiation on the optical absorption spectra of xBaO-Na2O-(70-x) B2O3-SiO2 glass system with x = 0, 5, 10, 15, 20, 25 (mol%) recorded in spectral range from 200 to 900 nm at room temperature. The optical absorption edge, optical band gap and Urbach energy were determined from the absorption spectra before and after irradiation. Changes occurring in the optical parameters of these glasses have been associated with radiation induced structural defects and compositional changes.

Kaur, Ravneet; Singh, Surinder; Pandey, O. P.

2013-09-01

39

Lightweight geopolymer made of highly porous siliceous materials with various Na 2O\\/Al 2O 3 and SiO 2\\/Al 2O 3 ratios  

Microsoft Academic Search

The syntheses of lightweight geopolymeric materials from highly porous siliceous materials viz. diatomaceous earth (DE) and rice husk ash (RHA) with high starting SiO2\\/Al2O3 ratios of 13.033.5 and Na2O\\/Al2O3 ratios of 0.663.0 were studied. The effects of fineness and calcination temperature of DE, concentrations of NaOH and KOH, DE to RHA ratio; curing temperature and time on the mechanical properties

K. Pimraksa; P. Chindaprasirt; A. Rungchet; K. Sagoe-Crentsil; T. Sato

2011-01-01

40

Vibrational spectrum and structure of the K2O2 complex in solid argon: A far infrared and density functional theory study  

Microsoft Academic Search

New fundamental KO stretching frequencies of the isolated potassium peroxide K2O2 molecule are reported for different isotopic species. The B2u vibration can be measured for 39K216O2, 39K216O18O, K217O18O, 39K218O2, 39K41K16O2 and 39K41K18O2. The B3u vibration can be located for K216O2, K216O18O and K218O2 products, and the formerly B3g symmetry motion, IR-activated by symmetry breaking in 39K216O18O, 39K41K16O18O, 39K41K16O2, and 39K41K18O2,

Benot Tremblay; Pascale Roy; Laurent Manceron; Pluton Pullumbi; Yves Bouteiller; Denis Roy

1995-01-01

41

The Origin and Evolution of Kimberlite Melts: Stabilizing Phlogopite in the CMAS-CO2- H2O-K2O System  

NASA Astrophysics Data System (ADS)

This project aims to investigate the melting phase relations of model lherzolite in the system CMAS- CO2-H2O-K2O to better understand the role of potassium (K) in the evolution and origin of kimberlitic melts. High-pressure multi-anvil and piston cylinder experiments are used to study this system at upper mantle pressures (3-9 GPa). This study aims at constraining the temperature and composition of primary melts at the volatile-rich mantle solidus at which kimberlite melts form. Kimberlites are potassium-rich, ultrabasic magmas (<35% SiO2), have a low viscosity (0.1-1 Pa s), and contain a very high volatile content (CO2 and H2O). A number of models have been suggested for the generation of carbonatite and kimberlite magmas, with the presence of volatiles being particularly important (eg. CO2). Together, H2O and CO2, show a much greater influence on the solidus of mantle lherzolite than when either are present alone. Melts of carbonatitic and kimberlitic composition can be produced under comparable P-T conditions by partial melting of carbonated lherzolite. Petrogenetic links between carbonatites and kimberlites are therefore implied in the CO2-bearing mantle source region (Gudfinnsson, 2005). The isobaric univariant equilibrium for melting of model lherzolite in CMAS-CO2-H2O-K2O is tracked at upper mantle conditions. This is done by constructing a series of bulk compositions that will saturate all phases and yield enough of each phase for EPMA analysis. The compositions of all phases along a portion of the isobaric univariant melting curves will be traced at a series of pressures. In this way, we can rigorously calculate the melting behaviour of lherzolite compositions as a function of pressure, temperature and bulk composition.

Buisman, I.; Sparks, S.; Walter, M.

2008-12-01

42

The biocompatibility of silver-containing Na2O.CaO.2SiO2 glass prepared by sol-gel method: in vitro studies.  

PubMed

This study was performed to determine the in vitro biocompatibility of a bioactive, antibacterial silver based gel. A human osteoblast-like cell line (HOS TE85) was used to test cytocompatibility in the presence of eluants and the biological response in direct contact with Na(2)O.CaO.2SiO(2) gel (containing 0.5050 wt % Ag(2)O prepared by a sol-gel process) sterilized by two different methods; autoclave and gamma-irradiation. MTT assay was used for the indirect evaluation of eluant toxicity and alamar Blue was performed to assess the biological response, which included cell viability and proliferation, and the results showed that these materials were cytocompatible. PMID:19802837

Raucci, Maria Grazia; Adesanya, Kehinde; Di Silvio, Lucy; Catauro, Michelina; Ambrosio, Luigi

2010-01-01

43

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

NASA Technical Reports Server (NTRS)

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.

Mukherjee, S. P.

1983-01-01

44

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

NASA Technical Reports Server (NTRS)

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.

Mukherjee, S. P.

1982-01-01

45

Synthesis and Phase Composition of Fe/Mn Containing Nanocrystals in Glasses from the System Na2O/MnO/SiO2/Fe2O3  

NASA Astrophysics Data System (ADS)

Oxide glass-ceramics containing ferrimagnetic nanocrystals are of fundamental and practical interest due to their electrical and magnetic properties. Depending on phase composition, size and volume fraction of the crystalline phase formed, the precipitated crystals are applied as parts of ferrofluids, in magnetic resonance imaging and as parts of biomagnetic sensors for the detection of different chemical and biochemical substances. In the present investigation, glasses from the system Na2O/MnO/SiO2/Fe2O3 are produced by the conventional melting technique; after applying appropriate time-temperature programs, the nanocrystalline magnetic phase is precipitated in a glass matrix. The phase composition and microstructure of the formed glass-ceramics is studied by x-ray diffraction, and scanning and transmission electron microscopy. Anomalous small angle x-ray scattering experiments are used to gather information about the phase composition and structure of the nano-sized crystals formed, as well as about their size distribution.

Harizanova, Ruzha; Ranghuwanshi, Vikram S.; Tatchev, Dragomir; Gugov, Ivailo; Hoell, Armin; Rssel, Christian

46

Spectroscopic properties of Sm3+ and V4+ ions in Na2O-SiO2-ZrO2 glasses  

NASA Astrophysics Data System (ADS)

Na2O-SiO2-ZrO2 glasses of Sm3+ ions with and without V2O5 are characterized by spectroscopic and optical properties. The XRD and EDS spectra of the glass samples reveal an amorphous nature with different compositions within the glass matrix. The Infrared and Raman spectral studies are carried out and the existence of conventional structural units are analyzed in the glass network. The ESR spectra of the glass samples have indicating that a considerable proportion of vanadium ion exists in V4+ state. The optical absorption spectra of these glasses are recorded at room temperature, from the measured intensities of various absorption bands the Judd-Ofelt parameters ?2, ?4 and ?6 are calculated. The photo-luminescence spectra recorded with excited wavelength 400 nm, five emission bands are observed; in this the energy transfer probability takes place between Sm3+ and V4+ ions.

Neeraja, K.; Rao, T. G. V. M.; Kumar, A. Rupesh; Uma Lakshmi, V.; Veeraiah, N.; Rami Reddy, M.

2013-12-01

47

Structural variation in gamma ray irradiated PbO-Na2O-B2O3-SiO2 glasses  

NASA Astrophysics Data System (ADS)

Glasses with compositions xPbO-15Na2O-(70-x) B2O3-15SiO2 where x=5, 10, 15, 20 and 25 (mol%) have been prepared using the melt quenching technique. The structural properties of these glasses have been investigated using the FTIR spectroscopy. The effect of the presence of modifier PbO on the glass system is also studied. The FT-IR spectral investigation of these glasses exhibits characteristic vibrations of BO4 and BO3 units together with SiO4 as well as PbOn (n=4,6) groups. The gamma ray interaction of the present glass system in the dose range 0.1-60 kGy is investigated. The results indicate that gamma rays result in the structural rearrangements in glass affecting the bridging and non bridging oxygens.

Kaur, Ravneet; Singh, Surinder; Pandey, O. P.

2014-06-01

48

Properties and Structure of RO-R2O-Na2O-Al2O3-P2O5 Glasses  

SciTech Connect

The properties and structural features of RO-R2O-Na 2O-Al2O3-P2O5 (R= Mg, Ca, Ba and RO= Li) glasses in the system have been investigated. The properties of those glasses seem to depend on the field strength of the alkali or alkali-earth ions in glasses as in silicate glasses. Infrared (IR) spectroscopy indicates that the glass network is dominated by bridging P-tetrahedral present in glasses with O/P {approx_equal} 3.0. The variation in physical properties of the glasses seem to be closely related to the variation in structure of the glasses and could be explained by simple mechanism such as field strength and differences in mass.

Agus Setyo Budi; Ahmad, Asmala [Jabatan Sains and Math, Pusat Perkhidmatan Akademik, Kolej Universiti Teknikal Kebangsaan Malaysia, 75450 Ayerkeroh, Melaka (Malaysia); Safarudin Gazali Herawan [Faculty of Mechanical Engineering, Kolej Universiti Teknikal Kebangsaan Malaysia, 75450 Ayerkeroh, Melaka (Malaysia); Sunaryo [Physics Dept.-Faculty of Science, State University of Jakarta, Jakarta 13320 (Indonesia)

2007-05-09

49

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

NASA Astrophysics Data System (ADS)

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.

Liu, Zhanwei; Chen, Wenmi; Li, Wangxing

2010-11-01

50

Visible and far-infrared spectroscopic studies of Co-doped (80-x)Sb2O3-20Na2O-xWO3 glasses  

NASA Astrophysics Data System (ADS)

We investigate the absorption of the glasses (80-x)Sb2O3-20Na2O-xWO3 (x mol% of WO3) in the spectral regions 12?500-28?571 and 2000-7800?cm-1. The samples are doped with 0.01, 0.03 or 0.05?mol% of Co3O4 and x=30%. The observed absorption band is due to the Co impurity in the visible spectral region. This absorption band of glasses does not contain information on the exact energy position of the Co levels. Therefore, we have calculated the second derivative of absorption. It has been established that Co2+ ions are surrounded by distorted octahedral coordination in the investigated glasses. The energy level structure of the Co2+ ion in the samples is also presented. We have calculated the crystal field parameter Dq and the Racah parameters B and C.

Petkova, P.; Soltani, M. T.; Petkov, S.; Tacheva, J.; Nedkov, V.

2012-05-01

51

Visible absorption structure of chromium doped (80-x)Sb2O3-20K2O-xPbO glasses  

NASA Astrophysics Data System (ADS)

Chromium doped glasses in the (80-x)Sb2O3-20K2O-xPbO:Cr system (x = 10–30 mol. %) have been investigated by absorption spectra in the 1–2,2 eV (8065–17 730 cm−1) spectral range. The synthesis of glasses has been carried out by using the melt-quenching method. The observed absorption band is due to the Cr-impurity in the visible spectral region. The absorption bands of glasses do not contain information about the exact energy position of the Cr levels. Therefore, we have calculated the second derivative of absorption curves. It is established that Cr3+ and Cr4+ ions are surrounded by distorted octahedral coordination in the investigated glasses. The energy level structure of the Cr3+ and Cr4+ ions in the samples are also presented. The crystal field parameter Dq and the Racah parameters B and C have been calculated.

Petkova, P.; Ghamri, A.; Vasilev, P.; Ismailov, I.; Soltani, M. T.

2014-09-01

52

Physical and optical absorption studies on xNa2O-(40-x)Bi2O3-20CdO-40B2O3 glasses  

NASA Astrophysics Data System (ADS)

Glasses with composition xNa2O-(40-x)Bi2O3-20CdO-40B2O3 where (0 ? x ? 40) have been prepared using melt quench technique. Optical absorption spectra of the pure glasses reveled that the cutoff wave length decreases and optical band gap (Eopt) increases where as Urbach energy (?E) decreases with increase in Na2O content. The Eopt values of these glasses are found to be in the range 2.818-3.217 eV where as the values of ?E are in the range 0.23-0.35 eV.

Kumar, R. Vijaya; Reddy, V. Rajashekar; Naik, S. Srinu; Kumar, K. Siva

2014-04-01

53

CAOS, COMPLEJIDAD E INTERDISCIPLINARIEDAD Miguel A. F. Sanjun  

E-print Network

CAOS, COMPLEJIDAD E INTERDISCIPLINARIEDAD Miguel A. F. Sanjuán Grupo de Dinámica No Lineal, Teoría del Caos y Sistemas Complejos Departamento de Física Universidad Rey Juan Carlos 28933 Móstoles caos, complejidad e interdisciplinariedad han fructificado con creces. #12;1. INTRODUCCION Desde

Rey Juan Carlos, Universidad

54

Bioactivity of SiO 2-CaO-P 2O 5-Na 2O glasses containing zinc-iron oxide  

NASA Astrophysics Data System (ADS)

Glasses with composition x(ZnO,Fe 2O 3)(65 - x)SiO 220(CaO,P 2O 5)15Na 2O (6 ? x ? 21 mol%) were prepared by melt-quenching technique. 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 was confirmed by using Fourier transform infrared reflection (FTIR) spectroscopy, grazing incidence X-ray diffraction (GI-XRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer. Development of an apatite structure on the surface of the SBF treated glass samples as functions of composition and time could be established using the GI-XRD data. FTIR spectra of the glasses treated in SBF show features at characteristic vibration frequencies of apatite after 1-day of immersion in SBF. SEM observations revealed that the spherical particles formed on the glass surface were made of calcium and phosphorus with the Ca/P molar ratio being close to 1.67, corresponding to the value in crystalline apatite. Increase in bioactivity with increasing zinc-iron oxide content was observed. The results have been used to understand the evolution of the apatite surface layer as a function of glass composition and immersion time in SBF.

Singh, Rajendra Kumar; Srinivasan, A.

2010-01-01

55

Structural study of Al2O3-Na2O-CaO-P2O5 bioactive glasses as a function of aluminium content  

NASA Astrophysics Data System (ADS)

Calcium phosphate based biomaterials are extensively used in the context of tissue engineering: small changes in composition can lead to significant changes in properties allowing their use in a wide range of applications. Samples of composition (Al2O3)x(Na2O)0.11-x(CaO)0.445(P2O5)0.445, where x = 0, 0.03, 0.05, and 0.08, were prepared by melt quenching. The atomic-scale structure has been studied using neutron diffraction and solid state 27Al MAS NMR, and these data have been rationalised with the determined density of the final glass product. With increasing aluminium concentration the density increases initially, but beyond about 3 mol. % Al2O3 the density starts to decrease. Neutron diffraction data show a concomitant change in the aluminium speciation, which is confirmed by 27Al MAS NMR studies. The NMR data reveal that aluminium is present in 4, 5, and 6-fold coordination and that the relative concentrations of these environments change with increasing aluminium concentration. Materials containing aluminium in 6-fold coordination tend to have higher densities than analogous materials with the aluminium found in 4-fold coordination. Thus, the density changes may readily be explained in terms of an increase in the relative concentration of 4-coordinated aluminium at the expense of 6-fold aluminium as the Al2O3 content is increased beyond 3 mol. %.

Smith, J. M.; King, S. P.; Barney, E. R.; Hanna, J. V.; Newport, R. J.; Pickup, D. M.

2013-01-01

56

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

57

Long-lasting afterglow in Tb 3+-doped SiO 2-Ga 2O 3-CaO-Na 2O glasses and its sensitization by Yb 3+  

NASA Astrophysics Data System (ADS)

Long-lasting afterglow due to Tb 3+ ions has been observed in a Tb 3+-doped SiO 2-Ga 2O 3-CaO-Na 2O glass, where a 4s empty orbital of Ga 3+ probably works as an electron-trapping center. The sensitization effect of Yb 3+ on the afterglow has been noticed.

Yamazaki, Masaaki; Kojima, Kazuo

2004-06-01

58

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

59

Spectral analysis of RE 3+ (RE = Sm, Dy, and Tm): P 2O 5-Al 2O 3-Na 2O glasses  

NASA Astrophysics Data System (ADS)

Phosphate glasses in the compositions of 70P 2O 5-15Al 2O 3-14Na 2O-1RE 3+ (RE = Sm, Dy, and Tm) (mol%) were prepared by melt-quenching technique and characterized optically. The differential thermal analysis (DTA) profile of the host glass was carried out to confirm its thermal stability. For all the glasses absorption, photoluminescence and decay measurements have also been carried out. These glasses have shown strong emission and absorption bands in visible and near-infrared (NIR) region. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters ( ?2, ?4 and ?6) have been calculated for all the studied ions. For Sm 3+ doped glass, four emission bands centered at 562 nm ( 4G 5/2 ? 6H 5/2), 598 nm ( 4G 5/2 ? 6H 7/2), 644 nm ( 4G 5/2 ? 6H 9/2), and 704 nm ( 4G 5/2 ? 6H 11/2) have been observed with 402 nm ( 6H 5/2 ? 4F 7/2) excitation wavelength. Of them, 598 nm ( 4G 5/2 ? 6H 7/2) has shown a bright orange emission. With regard to Dy 3+ doped glass, a blue emission band centered at 486 nm ( 4F 9/2 ? 6H 15/2) and a bright yellow emission at 575 nm ( 4F 9/2 ? 6H 13/2) have been observed, apart from 662 nm ( 4F 9/2 ? 6H 11/2) emission transition with an excitation at 388 nm ( 6H 15/2 ? 4I 13/2, 4F 7/2) wavelength. Emission bands of 650 nm ( 1G 4 ? 3F 4) and 785 nm ( 1G 4 ? 3H 5) transitions for the Tm 3+ doped glass, with an excitation wavelength at 466 nm ( 3H 6 ? 1G 4), have also been observed. The stimulated emission cross-sections of all the emission bands of RE 3+ glasses (RE = Sm, Dy, and Tm) have been computed based on their measured full-width at half maximum (FWHM, ??) and measured lifetimes ( ? m).

Lakshminarayana, G.; Yang, Rong; Mao, Mengfei; Qiu, Jianrong

2009-08-01

60

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

61

On the development of two characteristically different crystal morphology in SiO 2 MgOAl 2 O 3 K 2 OB 2 O 3 F glass-ceramic system  

Microsoft Academic Search

The present work demonstrates how crystals with two different characteristic morphologies can be formed in SiO2MgOAl2O3K2OB2O3F glass-ceramic system by adopting two sets of heat treatment experiments. In our study, single stage heat treatment experiments\\u000a were performed at 1,000C for varying holding time of 824h with 4h time interval and as a function of temperature in the\\u000a range of 1,0001,120C with

Shibayan Roy; Bikramjit Basu

2009-01-01

62

Investigation on structure and optical properties of Er 3+, Eu 3+ single-doped Na 2OZnOB 2O 3TeO 2 glasses  

Microsoft Academic Search

Er3+, Eu3+ single-doped several glasses with various composition xB2O3(80?x)TeO210ZnO10Na2O (x increases by a step of 10) were prepared by a melt-quenching technique. The effects of composition on density, molar volume, refractive index, and phonon sideband spectra were investigated. The dependence of glass structure properties on the composition was discussed. The influence of composition on the radiative and non-radiative relaxation rate,

Yanmin Yang; Baojiu Chen; Cheng Wang; Haiyang Zhong; Lihong Cheng; Jiashi Sun; Yong Peng; Xiangqing Zhang

2008-01-01

63

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

PubMed

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

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

2012-02-01

64

Potassic and sodic metasomatism in the Southern Province of the Canadian Shield: Evidence from the Paleoproterozoic Serpent Formation, Huronian Supergroup, Canada  

Microsoft Academic Search

Major element geochemistry, petrographic observations, and microprobe analyses of the Paleoproterozoic Serpent Formation, Huronian Supergroup, Canada, suggest that these strata experienced both potassium and sodium metasomatism. Major element data, plotted in Al2O3?CaO? + Na2O?K2O compositional space, form an array nearly identical to data from sub-Huronian paleosols reported elsewhere, suggesting that Serpent fluvial systems captured materials from entire weathering profiles. Potassium

C. M. Fedo; G. M. Young; H. W. Nesbitt; J. M. Hanchar

1997-01-01

65

Geochemistry of shales from the Archean (~3.0 Ga) Buhwa Greenstone Belt, Zimbabwe: Implications for provenance and source-area weathering  

Microsoft Academic Search

Phyllites from the Archean (~3.0 Ga) Buhwa Greenstone Belt, Zimbabwe, were deposited on a stable cratonic platform. Analyses of the phyllites generally define a single geochemical group based on major-and trace-element abundances. The phyllites are strongly depleted in CaO, Na2O, and Sr with respect to average Archean upper crust. By contrast, K2O, Ba, and Rb are enriched several times relative

Christopher M. Fedo; Kenneth A. Eriksson; Eirik J. Krogstad

1996-01-01

66

Introduction and motivation ARTIST and CAOS online tests  

E-print Network

and CAOS assessments in introductory statistics courses Nicholas J. Horton Smith College July 31, 2007, JSM sponsored project delMas, R., Garfield, J., Ooms, A., & Chance, B. (in press). Assessing students conceptual assessments multiple choice questions tap conceptual understanding of key topics provide quick feedback

Horton, Nicholas

67

Multiple Feature Fusion by Subspace Learning Yun Fu, Liangliang Cao  

E-print Network

the emergence of extensive multimedia data, feature fusion has been more and more important for image and video.7 [Image Processing and Computer Vision]: Fea- ture Measurement--feature representation, projections; I.5Multiple Feature Fusion by Subspace Learning Yun Fu, Liangliang Cao Beckman Institute University

Guo, Guodong

68

Naar een nieuwe Cao Nederlandse Universiteiten: medewerkersvoorkeuren in beeld  

E-print Network

Marijke von Bergh Michel Dückers IVA beleidsonderzoek en advies #12;ii Naar een nieuwe Cao Nederlandse Universiteiten: medewerkersvoorkeuren in beeld Uitgever: IVA Warandelaan 2 Postbus 90153 5000 LE Tilburg Telefoonnummer: 013-4668466 Telefax: 013-4668477 IVA is gelieerd aan Tilburg University © 2012 IVA Niets uit deze

Twente, Universiteit

69

Metrology from Vertical Objects Xiaochun Cao and Hassan Foroosh  

E-print Network

Metrology from Vertical Objects Xiaochun Cao and Hassan Foroosh School of Computer Science-parallel lines. 1 Introduction Metrology from uncalibrated images is becoming of increasing interest for many, Criminisi et al. [3] proposed an approach for single view metrology, and showed that affine scene structure

Foroosh, Hassan

70

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)

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 ?-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.

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

2009-08-01

71

Investigating the surface reactivity of SiO2-TiO2-CaO-Na2O/SrO bioceramics as a function of structure and incubation time in simulated body fluid.  

PubMed

This study focuses on evaluating the biocompatibility of a SiO2-TiO2-CaO-Na2O/SrO glass and glass-ceramic series. Glass and ceramic samples were synthesized and characterized using X-ray diffraction. Each material was subject to maturation in simulated body fluid over 1, 7 and 30 days to describe any changes in surface morphology. Calcium phosphate (CaP) deposition was observed predominantly on the Na(+) containing amorphous and crystalline materials, with plate-like morphology. The precipitated surface layer was also observed to crystallize with respect to maturation, which was most evident in the amorphous Na(+) containing glasses, Ly-N and Ly-C. The addition of Sr(2+) greatly reduced the solubility of all samples, with limited CaP precipitation on the amorphous samples and no deposition on the crystalline materials. The morphology of the samples was also different, presenting irregular plate-like structures (Ly-N), needle-like deposits (Ly-C) and globular-like structures (Ly-S). Cell culture analysis presented a significant increase in cell viability with the Na(+) materials, 134%, while the Sr(2+) containing glasses, 60-80% and ceramics, 60-85% presented a general reduction in cell viability, however these reductions were not significant. PMID:24796627

Li, Y; Coughlan, A; Wren, Anthony W

2014-08-01

72

Na 3La 9O 3(BO 3) 8, a new oxyborate in the ternary system Na 2O?La 2O 3?B 2O 3: preparation and crystal structure  

NASA Astrophysics Data System (ADS)

A new oxyborate with a composition corresponding to the formula Na 3La 9O 3(BO 3) 8 has been discovered in the ternary oxide system Na 2O?La 2O 3?B 2O 3. Single crystals of this compound have been grown by spontaneous crystallization from melts of the constituent binary oxides during slow cooling. The structure of Na 3La 9O 3(BO 3) 8 has been solved using X-ray data collected on a Nonius Kappa CCD diffractometer (Mo K? radiation). The unit cell is hexagonal (space group P-62m, Z=1) with a=8.9033(3), c=8.7131(3) and V=598.14 3. Refinement of 49 parameters using 684 independent reflections with an intensity I>2 ?( I) (Friedel not merged for absolute structure determination) results in R1=0.015 ( wR2=0.030). The structure is characterized by alternate stacking along the c-axis of Na?B?O, B?O, La and La?O containing layers with a mirror plane at z=1/2. A framework of La 9O 3 rings and rows of BO 3 triangles running along the c-direction is established. Each La 9O 3 ring is constituted of three La 4O tetrahedra sharing a common La corner. The presence in the structure of oxygen atoms surrounded by lanthanum atoms only justifies the oxyborate label of the new compound.

Gravereau, Pierre; Chaminade, Jean-Pierre; Pechev, Stanislav; Nikolov, Velin; Ivanova, Diana; Peshev, Pavel

2002-06-01

73

MAC 412 -Organiza c~ao de Computadores 2.a Prova -2 de dezembro de 1998 -Prova com consulta -Dura c~ao 2h 30min  

E-print Network

arquitetura de hardware. De modo super sucinto, mostre a diferen#24;ca entre as duas nota#24;c~oes. 4. (1- cional da m#19;aquina MAC. Suponha a cria#24;c~ao de uma nova instru#24;c~ao de m#19;aquina (n#19;#16;vel

Song, Siang Wun

74

Raman spectroscopy of calcium phosphate glasses with varying CaO modifier concentrations  

Microsoft Academic Search

Raman spectroscopy has been performed on a series of calcium phosphate glasses prepared from calcium dihydrogenphosphate and CaO in which the CaO content is varied from that of the metaphosphate stoichiometry, in which the mole ratio of CaO to PO is 1.00, to a stoichiometry in which the mole ratio is 1.49. Investigation of the vibrational behavior provides insight into

J. E. Pemberton; L. Latifzadeh; J. P. Fletcher; S. H. Risbud

2009-01-01

75

Steam catalysis in CaO carbonation under low steam partial pressure  

SciTech Connect

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.

Yang, S.J.; Xiao, Y.H. [Chinese Academy of Science, Beijing (China)

2008-06-15

76

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

PubMed

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

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

2013-12-27

77

Temperature-dependent luminescence and temperature-stimulated NIR-to-VIS up-conversion in Nd3+-doped La2O3-Na2O-ZnO-TeO2 glasses  

NASA Astrophysics Data System (ADS)

Telluride glasses of the composition xNd2O3-(7-x)La2O3-3Na2O-25ZnO-65TeO2, where (0?x?7) were prepared by the melt quench technique. Some physical and optical properties of the glasses were evaluated. The thermal behavior i.e. glass transition and crystallization temperatures were studied by using TGA-DTA technique. Optical properties of Nd3+-doped telluride glasses were investigated between 298 and 700 K. Basing on the obtained values of J-O parameter values (10-20 cm2: ?2=4.490.84, ?4=5.030.61, ?6=4.310.73), the radiative transition probabilities (AT), radiative lifetimes (?R), fluorescence branching ratios (?) and emission cross-sections (?em) were calculated for the 4F3/2?4IJ/2 (where J=9, 11 and 13) transitions of Nd3+ ions. The ?R value of the 4F3/2 level amount to 164 ?s and is slightly higher than the measured decay time of 162 ?s. With the increasing of Nd2O3 concentration from 0.5 to 7.0 mol% the experimental lifetime of the fluorescent level decreases from 162 to 5.6 ?s. The estimated quantum efficiency amount to 100%, based on a comparison of ?R and the experimental decay time of a slightly doped Nd3+ telluride glass. An analysis of the non-radiative decay was based on the cross-relaxation mechanisms. The 4F3/2?4I9/2 and 4F5/2?4I9/2 transitions were analyzed with respect to the fluorescence intensity ratio (FIR) and were found to be temperature dependent. Infrared-to-visible up-conversion emissions with a maximum at 603.0 and 635.3 nm were observed at high temperatures using the 804 nm excitation and are due to the 4G5/2?4I9/2 and 4G5/2?4I11/2 transitions of Nd3+ ions, respectively. The near quadratic dependence of fluorescence on excitation laser power confirms that two photons contribute to up-conversion of the orange emissions. The temperature-stimulated up-conversion excitation processes have been analyzed in detail. The optical results indicate that the investigated glasses are potentially applicable as a 1063 nm laser host as well as an optical sensor for temperature measurements.

Sobczyk, Marcin

2013-04-01

78

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

79

Kinetic Study on Desulfurization of Hot Metal Using CaO and CaC2  

NASA Astrophysics Data System (ADS)

The kinetics and reaction mechanisms of hot metal desulfurization using CaO and CaC2 were studied in a well-controlled atmosphere with a lab scale high temperature furnace. The growths of CaS around CaO and CaC2 were measured and compared at 1773 K (1500 C). The parabolic rate constant was evaluated to be 5 10-7 (cm s-1) on CaO particles, and 2.4 10-7 (cm s-1) on CaC2. The bigger parabolic constant of CaO resulted in more efficient desulfurization. Agglomerates and big CaO particles led to 2CaOSiO2 formation which hindered further utilization of CaO for desulfurization. The 2CaOSiO2 formation was favoured by a high oxygen potential. Since the desulfurization reaction of CaO not only produced CaS but also oxygen, the local oxygen concentration around big CaO particles was higher than around small particles.

Lindstrm, David; Sichen, Du

2014-09-01

80

Thermal reactions of aromatics with CaO. Technical progress report, April 1-August 31, 1983  

SciTech Connect

The pyrolysis of m-cresol and 1-methylanthracene was studied over both CaO and quartz over the temperature range of 350 to 800/sup 0/C. Vapor-phase concentration of the model compound was 5 mole percent for m-cresol and 1.8 mole percent for 1-methylanthracene. The calcium oxide significantly increased the rates and extents of pyrolysis of the aromatics, reducing the temperature for a given amount of conversion by at least 120/sup 0/C. A proposed mechanism for pyrolysis of m-cresol over CaO involves formation of calcium-cresol salts, which then undergo further cracking at temperatures above 500/sup 0/C to yield coke, CO, CH/sub 4/, toluene and C/sub 3/H/sub 6/. Chemical condensation reactions were the predominant reactions observed in the pyrolysis of 1-methylanthracene over CaO. A comparison of the pyrolysis results of 1-methylanthracene with those of 9-methylanthracene (studied earlier) indicated that the 1-methyl isomer was slightly less reactive over both solids, and that some of the thermal reactions over CaO were also structure specific. Deactivation of CaO was studied by measuring loss of cumulative cracking activity during pyrolysis of 1-methylanthracene. The decay of CaO activity with overall utilization time (or cumulative amount of feed reacted), was well-fitted by a power-law model. Coke burnoff in O/sub 2/ at temperatures between 600-700/sup 0/C regenerated approx.80 percent of the CaO initial activity. The 20 percent loss is attributed to either formation of CaCO/sub 3/ from the CaO or sintering of the CaO particles during regeneration. 7 refs., 11 figs., 1 tab.

Longwell, J.P.; Lai, C.K.; Williams, G.C.; Peters, W.A.

1983-11-01

81

Secondary ionization coefficient ? of MgO, SrO and CaO and the correlation between ? and charge accumulated on CaO in argon  

NASA Astrophysics Data System (ADS)

An experimental investigation of Townsend's secondary ionization coefficient ? is carried out for MgO, SrO and CaO film electrodes. These oxides are utilized, or are to be utilized, in next-generation plasma display panels. All of the experiments are performed in argon. In particular, in the case of CaO film, our attention is attracted to the effect of charge accumulated on CaO film. For this purpose, the breakdown voltage Vs is observed from waveforms of the gap voltage and charge accumulated on the dielectric film electrodes with the repeated breakdown. Townsend's criterion is utilized to estimate ? from the breakdown voltage. In the case of the CaO film, ? increases gradually with repeated breakdowns and reaches a stationary value. The increase of ? is considered to be due to the charge that accumulates on the dielectric electrode triggering the next breakdown. Therefore, it is concluded that the increased ? is sustained by a combined process consisting of restarted electrons that have accumulated on the CaO film and the original ? action, as observed in metallic electrodes in a low-pressure gas discharge.

Suzuki, S.; Itoh, H.

2014-12-01

82

Graphite oxide-supported CaO catalysts for transesterification of soybean oil with methanol.  

PubMed

Graphite oxide (GO) supported CaO catalysts were prepared and successfully applied to the transesterification of soybean oil with methanol. The supports and resultant catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), N(2) adsorption, thermogravimetry (TG), X-ray photoelectron spectroscopy (XPS), temperature-programed desorption (TPD) and Fourier-transform infrared spectroscopy (FT-IR). The GO supported CaO catalysts exhibited excellent catalytic activity and were easily regenerated by simple heat-treatment. The oxygen-containing groups (i.e., hydroxyl, epoxide groups and carboxyl groups) present on the surface of GO likely act as anchoring centers for CaO. This work demonstrates that graphite oxide is an effective host material of catalytically active CaO nanoparticles for the transesterification of soybean oil with methanol to produce biodiesel. PMID:21824767

Zu, Yanhong; Tang, Jianyuan; Zhu, Wanchun; Zhang, Min; Liu, Gang; Liu, Yan; Zhang, Wenxiang; Jia, Mingjun

2011-10-01

83

Nonisothermal thermogravimetric analysis of Thai lignite with high CaO content.  

PubMed

Thermal behaviors and combustion kinetics of Thai lignite with different SO?-free CaO contents were investigated. Nonisothermal thermogravimetric method was carried out under oxygen environment at heating rates of 10, 30, and 50C min? from ambient up to 1300C. 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

Pintana, Pakamon; Tippayawong, Nakorn

2013-01-01

84

Semiclassical approximations to quantum dynamical time correlation Jianshu Cao and Gregory A. Voth  

E-print Network

Semiclassical approximations to quantum dynamical time correlation functions Jianshu Cao-6323 Received 8 September 1995; accepted 28 September 1995 Semiclassical approximations for quantum time is developed to calculate quantum time correlation functions. This approach holds considerable promise

Cao, Jianshu

85

Phase relations in the greenschist-blueschist-amphibolite-eclogite facies in the system Na 2 O-CaO-FeO-MgO-Al 2 O 3 SiO 2 -H 2 O (NCFMASH), with application to metamorphic rocks from Samos, Greece  

Microsoft Academic Search

Calculated phase equilibria among the minerals sodic amphibole, calcic amphibole, garnet, chloritoid, talc, chlorite, paragonite,\\u000a margarite, omphacite, plagioclase, carpholite, zoisite\\/clinozoisite, lawsonite, pyrophyllite, kyanite, sillimanite, quartz\\u000a and H2O are presented for the model system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O (NCFMASH), which is relevant for many greenschist, blueschist, amphibolite and eclogite facies rocks. Using the activity-composition\\u000a relationships for multicomponent amphiboles constrained by Will and Powell (1992),

Thomas Will; Martin Okrusch; Esther Schmdicke; Guoli Chen

1998-01-01

86

Behavior of rare earth elements in a paleoweathering profile on granodiorite in the Front Range, Colorado, USA  

Microsoft Academic Search

A Paleoweathering profile on the Boulder granodiorite in northern Colorado provides an opportunity to trace the behavior of REEs from parent rock, through a weathering profile, into unconformably overlying Permian sediments. With progressive upward weathering of the granodiorite, Na2O, CaO, SiO2, TaHf, CoTh, CrSc, CrTh, ZrHf, LaSc, ZrY, and LaTh decrease; Al2O3 and Fe2O3T increase; and TiO2, MgO, K2O, P2O5,

Kent C. Condie; Jessie Dengate; Robert L. Cullers

1995-01-01

87

Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures  

Microsoft Academic Search

A revised regular solution-type thermodynamic model for twelve-component silicate liquids in the system SiO2 TiO2 Al2O3 Fe2O3 Cr2O3 FeO MgO CaO Na2O K2O P2O5 H2O is calibrated. The model is referenced to previously published standard state thermodynamic properties and is derived from a set of internally consistent thermodynamic models for solid solutions of the igneous rock forming minerals, including: (Mg,

Mark S. Ghiorso; Richard O. Sack

1995-01-01

88

Intense 31-35Ar beams produced with a nanostructured CaO target at ISOLDE  

NASA Astrophysics Data System (ADS)

At the ISOLDE facility at CERN, thick targets are bombarded with highly energetic pulsed protons to produce radioactive ion beams (RIBs). The isotopes produced in the bulk of the material have to diffuse out of the grain and effuse throughout the porosity of the material to a transfer line which is connected to an ionizer, from which the charged isotopes are extracted and delivered for physics experiments. Calcium oxide (CaO) powder targets have been used to produce mainly neutron deficient argon and carbon RIBs over the past decades. Such targets presented unstable yields, either decaying over time or low from the beginning of operation. These problems were suspected to come from the degradation of the target microstructure (sintering due to high temperature and/or high proton intensity). In this work, a CaO microstructural study in terms of sintering was conducted on a nanostructured CaO powder synthesized from the respective carbonate. Taking the results of this study, several changes were made at ISOLDE in terms of the CaO target production, handling and operation in order to produce and maintain the nanostructured CaO. The new target, the first nanostructured target to be operated at ISOLDE, showed improved yields of (exotic) Ar and more importantly a stable yield over the whole operation time, while operating with lower temperatures. This contradicts the ISOL paradigm of using the highest possible temperature regardless of the target's microstructure degradation.

Ramos, J. P.; Gottberg, A.; Mendona, T. M.; Seiffert, C.; Senos, A. M. R.; Fynbo, H. O. U.; Tengblad, O.; Briz, J. A.; Lund, M. V.; Koldste, G. T.; Carmona-Gallardo, M.; Pesudo, V.; Stora, T.

2014-02-01

89

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

PubMed

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

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

2014-12-01

90

Correlation effects in MgO and CaO: Cohesive energies and lattice constants  

SciTech Connect

A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using {ital ab} {ital initio} quantum-chemical methods for evaluating individual increments, we obtain {approximately}80{percent} of the difference between the experimental and Hartree-Fock cohesive energies. Lattice constants corrected for correlation effects deviate by less than 1{percent} from experimental values, in the case of MgO and CaO. {copyright} {ital 1996 The American Physical Society.}

Doll, K.; Dolg, M. [Max-Planck-Institut fuer Physik Komplexer Systeme, D-01187 Dresden (Germany)] [Max-Planck-Institut fuer Physik Komplexer Systeme, D-01187 Dresden (Germany); Stoll, H. [Institut fuer Theoretische Chemie, Universitaet Stuttgart, D-70550 Stuttgart (Germany)] [Institut fuer Theoretische Chemie, Universitaet Stuttgart, D-70550 Stuttgart (Germany)

1996-11-01

91

Control Design for a Very Low-Frequency High-Voltage Test System Zhiyu Cao, Norbert Frhleke, Joachim Bcker  

E-print Network

Control Design for a Very Low-Frequency High-Voltage Test System Zhiyu Cao, Norbert Fröhleke and energy consumption of very low-frequency (VLF) high-voltage test systems (HVTS) versus HVTS of 50 Hz for a Very Low-Frequency High-Voltage Test System CAO Zhiyu EPE 2009 - Barcelona ISBN: 9789075815009 P.1 #12

Paderborn, Universität

92

A Model of Stroke Extraction from Chinese Character Images Ruini Cao, Chew Lim Tan  

E-print Network

A Model of Stroke Extraction from Chinese Character Images Ruini Cao, Chew Lim Tan School a new model of stroke extraction for Chinese characters. One problem for stroke extraction is how to extract primary strokes. Another major problem is to solve the segmentation ambiguities at intersection

Tan, Chew Lim

93

Ubiquitous Intelligence in Agent Mining Longbing Cao, Dan Luo, and Chengqi Zhang  

E-print Network

Ubiquitous Intelligence in Agent Mining Longbing Cao, Dan Luo, and Chengqi Zhang Faculty, most of them can be described in terms of or related to ubiquitous intelligence. It is certainly very important to define, specify, represent, analyze and utilize ubiquitous intelligence in agents, data mining

Cao, Longbing

94

Photon sieve: non-paraxial theory Qing Cao and Jurgen Jahns  

E-print Network

Photon sieve: non-paraxial theory Qing Cao and J¨urgen Jahns Photon sieves [1], which consist analysis of low-numerical- aperture (low-NA) photon sieves. We now [3] extend this model to the non-paraxial case of high-NA photon sieves working in the soft x-ray region, for which the paraxial diffrac- tion

Jahns, Jürgen

95

3D Fingerprint Phantoms Sunpreet S. Arora, Kai Cao and Anil K. Jain  

E-print Network

3D Fingerprint Phantoms Sunpreet S. Arora, Kai Cao and Anil K. Jain Department of Computer Science data. To overcome this limitation, use of a large number of 2D synthetic fingerprints for evaluating fingerprint systems had been proposed. However, the utility of 2D synthetic fingerprints is limited

96

Controlling the charge state of single Mo dopants in a CaO film  

NASA Astrophysics Data System (ADS)

Recent experiments have demonstrated that tiny amounts of Mo impurities give rise to drastic changes in the adsorption characteristic of a wide-gap CaO(001) film. In this scanning tunneling microscopy (STM) and density functional theory paper, we elucidate the underlying mechanism by analyzing the energy levels of the Mo dopants as a function of their oxidation state and depth below the surface. We show that Mo2+ ions in CaO subsurface layers can be reversibly charged and discharged by inducing local band-bending effects with the STM tip. A similar charge switching is not possible for Mo species in a higher oxidation state, as their highest-occupied molecular orbitals are located well below the onset of the CaO conduction band. The easiness of charge switching in Mo2+ ions explains the remarkable chemical properties of doped CaO films, as it renders the material a strong electron donor to adsorbates bound to the oxide surface.

Cui, Yi; Nilius, Niklas; Freund, Hans-Joachim; Prada, Stefano; Giordano, Livia; Pacchioni, Gianfranco

2013-11-01

97

Making Routers Last Longer with ViAggre Hitesh Ballani, Paul Francis, Tuan Cao and Jia  

E-print Network

Making Routers Last Longer with ViAggre Hitesh Ballani, Paul Francis, Tuan Cao and Jia Wang Cornell deployment Routing Table stored in Forwarding Information Base (FIB) on Routers Large Routing Table More FIB space on Routers #12;Does FIB Size Matter? The problem is Scaling Properties of FIB memory (low volume

Greenberg, Albert

98

Sensor Relocation in Mobile Sensor Networks Guiling Wang, Guohong Cao, Tom La Porta, and Wensheng Zhang  

E-print Network

Sensor Relocation in Mobile Sensor Networks Guiling Wang, Guohong Cao, Tom La Porta, and Wensheng of research on using mobility in sensor networks to assist in the initial deployment of nodes. Mobile sensors. This paper explores the motion capability to relocate sensors to deal with sensor failure or respond to new

Zhang, Wensheng

99

Jian Cao, Department of Mechanical Engineering, Northwestern University, January 2011 Department of Mechanical Engineering  

E-print Network

., Kumar, A., Reddy, N.V. and Cao, J. (2011) A New Methodology for Multi-Pass Single Point Incremental of the North American Manufacturing Research Institution of SME, Vol. 38, pp. 291-298. 8. Huang, Y Distortion in Sheet Metal Flanging, Transaction of the North American Manufacturing Research Institution

Ottino, Julio M.

100

Discovery of Collocation Episodes in Spatiotemporal Data Huiping Cao, Nikos Mamoulis, and David W. Cheung  

E-print Network

Discovery of Collocation Episodes in Spatiotemporal Data Huiping Cao, Nikos Mamoulis, and David W, vultures, etc.), we intro- duce the problem of discovering collocation episodes in them (e.g., if a puma within the next 3 minutes). Collocation episodes catch the inter-movement regularities among different

Cheung, David Wai-lok

101

Conformant Planning for Domains with Constraints --A New Approach Tran Cao Son and Phan Huy Tu  

E-print Network

Conformant Planning for Domains with Constraints -- A New Approach Tran Cao Son and Phan Huy Tu USA {mgelfond,ricardo}@cs.ttu.edu Abstract The paper presents a pair of new conformant planners, CPApc- ners based on this idea. We compare them with two state- of-the-art conformant planners, KACMBP

Tran, Cao Son

102

CRNN: Integrating Classification Rule and Neural Network Wei Li, Longbing Cao and Dazhe Zhao  

E-print Network

CRNN: Integrating Classification Rule and Neural Network Wei Li, Longbing Cao and Dazhe Zhao. In the prediction stage of the extant approaches, most of the existing association classifiers use the ensemble methodology. This paper proposes a classification method that integrating classification rule and neural

Cao, Longbing

103

Controlling the particle size of amorphous iron nanoparticles X. Cao, Yu. Koltypin, and G. Kataby  

E-print Network

of amorphous iron, which was prepared by the sonication of iron pentacarbonyl [Fe(CO)5], is reportedControlling the particle size of amorphous iron nanoparticles X. Cao, Yu. Koltypin, and G. Kataby 4 M, 1 M, and 0.25 M. The iron nanoparticles were subjected to TEM (Transmission Electron Micrograph

Prozorov, Ruslan

104

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...

105

Generalized continuum theory for ferroelectric thin films Tianquan Lu* and Wenwu Cao  

E-print Network

­8 The mathematical treat- ment using this procedure is similar to that for domain walls in bulk, in which a gradientGeneralized continuum theory for ferroelectric thin films Tianquan Lu¨* and Wenwu Cao Department been used to describe the influence of imperfect surface layers or interface layers in ferroelectric

Cao, Wenwu

106

Brownian motion in dynamically disordered media James B. Witkoskie, Shilong Yang, and Jianshu Cao*  

E-print Network

Brownian motion in dynamically disordered media James B. Witkoskie, Shilong Yang, and Jianshu Cao April 2002; revised manuscript received 12 August 2002; published 26 November 2002 The motion of Brownian test particles in a model random potential with time dependent correlations is investigated using

Cao, Jianshu

107

Stem Cell Repair of Central Nervous System Qilin Cao,1,2  

E-print Network

therapy to stem cell transplantation for neurodegenerative disease and CNS injury. HoweverReview Stem Cell Repair of Central Nervous System Injury Qilin Cao,1,2 Richard L. Benton,1 of Louisville School of Medicine, Louisville, Kentucky Neural stem cells (NSCs) have great potential as a ther

Harkema, Susan

108

Quantum-Classical Correspondence in Response Theory Maksym Kryvohuz and Jianshu Cao*  

E-print Network

Quantum-Classical Correspondence in Response Theory Maksym Kryvohuz and Jianshu Cao* Department and the classical Poisson brackets @fA; Bg is examined in the context of response theory. The classical response theory has several problems. Van Kampen cautioned the validity of the application of classical

Cao, Jianshu

109

Can Facial Metrology Predict Gender? Deng Cao, Cunjian Chen, Marco Piccirilli,  

E-print Network

Can Facial Metrology Predict Gender? Deng Cao, Cunjian Chen, Marco Piccirilli, Donald Adjeroh the question of whether facial metrology can be exploited for reliable gender prediction. A new method based solely on metrological information from fa- cial landmarks is developed. Here, metrological features

Ross, Arun Abraham

110

METROLOGY IN UNCALIBRATED IMAGES GIVEN ONE VANISHING POINT Hassan Foroosh Xiaochun Cao Murat Balci  

E-print Network

METROLOGY IN UNCALIBRATED IMAGES GIVEN ONE VANISHING POINT Hassan Foroosh Xiaochun Cao Murat Balci in the perspective images. 1. INTRODUCTION Metrology from uncalibrated images is becoming of increas- ing interest al. [3] proposed an approach for single view metrology, and showed that affine scene structure can

Foroosh, Hassan

111

Chemical analysis of the Chinese herbal medicine Gan-Cao (licorice)  

Microsoft Academic Search

Gan-Cao, or licorice, is a popular Chinese herbal medicine derived from the dried roots and rhizomes of Glycyrrhiza uralensis, G. glabra, and G. inflata. The main bioactive constituents of licorice are triterpene saponins and various types of flavonoids. The contents of these compounds may vary in different licorice batches and thus affect the therapeutic effects. In order to ensure its

Qingying Zhang; Min Ye

2009-01-01

112

A scaling and mapping theory for excess electrons in simple fluids Jianshu Cao  

E-print Network

A scaling and mapping theory for excess electrons in simple fluids Jianshu Cao Department 1994 A simple scaling argument is proposed to understand the localization of excess electrons in simple sphere. Numerical simulations of solvated electrons in atomic and diatomic solvents are used

Cao, Jianshu

113

Mobile Multi-Layered IPsec Heesook Choi, Hui Song, Guohong Cao, and Tom La Porta  

E-print Network

Mobile Multi-Layered IPsec Heesook Choi, Hui Song, Guohong Cao, and Tom La Porta Department cannot be provided if data sessions are protected using end-to-end encryption as with IPsec, because therefore not be used by the access routers. A previously proposed protocol, called Multi-layered IPsec (ML-IPsec

Yener, Aylin

114

Mobile Multi-Layered IPSec Advisors: Prof. Tom La Porta and Prof. Guohong Cao  

E-print Network

Mobile Multi-Layered IPSec Advisors: Prof. Tom La Porta and Prof. Guohong Cao Heesook Choi & Hui in Wireless Networks End-to-end security (IPSec) Prevents performance enhancements in the intermediate nodes Multi-layered IPSec (ML-IPSec) Allows the intermediate nodes to do performance enhancements Manual

Yener, Aylin

115

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

SciTech Connect

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.

Grasa, G.S.; Alonso, M.; Abanades, J.C. [CSIC, Zaragoza (Spain)

2008-03-15

116

Effect of Bi 2O 3 content on physical and optical properties of 15Li 2O-15K 2O- xBi 2O 3-(65- x) B 2O 3: 5V 2O 5 glass system  

NASA Astrophysics Data System (ADS)

Multi-component bismuth borate glasses doped with vanadium ions 15Li 2O-15K 2O- xBi 2O 3-(65- x) B 2O 3: 5V 2O 5, ( x=3, 5, 7, 10, 12 and 15) have been prepared using conventional melt quench technique. Characterization of the prepared glasses has been done using X-ray diffraction, differential scanning calorimetry and density measurements. The effect of Bi 2O 3 content on the optical properties of the present glass system is studied from the optical absorption spectra recorded in the wavelength range 200-800 nm. The fundamental absorption edge has been identified from the optical absorption spectra. The values of optical band gap for indirect allowed transitions have been determined using available theories. The origin of the Urbach energy is associated with the phonon-assisted indirect transitions. The density and molar volume studies indicate that Bi 2O 3 in these glasses is acting partly as network modifier and partly as network former. The variations in the optical band gap energies, density and molar volume with Bi 2O 3 content have been discussed in terms of changes in the glass structure. Values of the theoretical optical basicity, average crosslink density and the average electronic polarizability are also reported.

Subhadra, M.; Kistaiah, P.

2011-04-01

117

Sintering of calcium oxide (CaO) during CO2 chemisorption: a reactive molecular dynamics study.  

PubMed

Reactive dynamics simulations with the reactive force field (ReaxFF) were performed in NVE ensembles to study the sintering of two solid calcium oxide (CaO) particles with and without CO(2) chemisorption. The simulated sintering conditions included starting adsorption temperatures at 1000 K and 1500 K and particle separation distances of 0.3 and 0.5 nm. The results revealed that the expansion of sorbent particles during CO(2) chemisorption was attributed to the sintering of two CaO-CaO particles. Increasing the adsorption temperature resulted in more particle expansion and sintering. The shorter the distance between two particles, the faster the rate of sintering during CO(2) adsorption. A detailed analysis on atom spatial variations revealed that the sorbent particles with a larger separation distance had a larger CO(2) uptake because of less sintering incurred. The chemisorptions of CO(2) on CaO particles sintered at high adsorption temperatures were also simulated to mimic the process of sorbent regeneration. It was found that regeneration would be more difficult for sintered particles than for fresh particles. In addition, a possible sintering barrier, magnesium oxide (MgO), was introduced to prevent CaO particles from sintering during CO(2) chemisorption. It was found that the MgO particles could reduce the sintering of CaO particles during CO(2) chemisorption. Simulation results from this study provided some guidelines on synthesizing or selecting sorbents with less sintering effect for multiple CO(2) adsorption-regeneration cycles. PMID:22990764

Zhang, Luzheng; Lu, Yongqi; Rostam-Abadi, Massoud

2012-12-28

118

Fourier Transform Spectroscopy of the A 1 System of CaO  

E-print Network

of the spectrum, with numerous bands extending from the ultraviolet to the near-infrared, and tried various, Waterloo, Ontario, Canada N2L 3G1 Received May 24, 2000 The A 1 ­X1 near-infrared system of Ca states. The new near-infrared spectra of the A 1 ­X1 transition of CaO also permits the first direct high

Le Roy, Robert J.

119

Characteristics of HCN removal using CaO at high temperatures  

SciTech Connect

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.

Houzhang Tan; Xuebin Wang; Congling Wang; Tongmo Xu [Xi'an Jiaotong University, Shaanxi (China). State Key Laboratory of Multiphase Flow in Power Engineering

2009-03-15

120

Thermal diffusivity of sintered 12CaO7Al2O3  

NASA Astrophysics Data System (ADS)

The thermal diffusivity and free carrier diffusion coefficient of 12CaO 7 Al{2}O{3} (C12A7) sintered for different times in air or hydrogen followed by treatment with UV light were determined from photoacoustic phase and amplitude spectra obtained using the photoacoustic method with a transmission detection configuration. The influence of the sintering time on the values of the obtained parameters was analyzed and also the different sintering procedures.

Nikoli?, P. M.; Lukovi?, D. T.; Savi?, S. M.; Milovanovi?, A. M.; Uki?, S. R.; Nikoli?, M. V.; Stamenovi?, B.

2008-01-01

121

Development of CaO coatings by thermal and chemical vapor deposition  

NASA Astrophysics Data System (ADS)

We conducted several experiments to test electrically insulating CaO coatings on a V-4Cr-4Ti alloy for application in the Li environment of liquid metal blankets in fusion reactors. Two processes that involve double Ca deposition/oxidation steps were developed to successfully coat V-4Cr-4Ti alloy samples with stable CaO. During the study, we examined several geometrical arrangements, using tabs and/or rod specimens. After Ca deposition from the vapor phase, the specimens were oxidized in an Ar-10 vppm O 2 environment at ?600 C to convert the deposited metal into oxide, whereupon they exhibited insulating characteristics. Several coated specimens were then exposed to Li-2.8 at.%Ca at 500-700 C to determine chemical compatibility and mechanical integrity. Depth profile analysis of the coatings was conducted to evaluate the compositional changes in the coatings and to assess the transport, if any, of substrate and coating constituents. Microstructural characteristics of the coatings were evaluated by scanning electron microscopy. The preliminary results indicate that CaO is a viable coating for V-Li advanced blankets.

Natesan, K.; Uz, M.; Smith, D. L.

2002-12-01

122

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

PubMed

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

Przepirski, Jacek; Czy?ewski, Adam; Pietrzak, Robert; Toyoda, Masahiro; Morawski, Antoni W

2013-12-15

123

Thermal reactions of aromatics with CaO. Technical progress report, May 1, 1982-August 31, 1982  

SciTech Connect

The activity of CaO for the cracking of benzene is known to be very dependent on the calcining temperature and the optimal temperature is 550/sup 0/C. An optimal calcining time of 2 hours at 550/sup 0/C was determined. The considerable scatter in the activity data suggests that the benzene pyrolysis temperature, which is higher than the calcining temperature, may have modified the physical and chemical properties of the CaO during the post-calcination period. Basicity measurements on CaO samples calcined for different time periods show no correlation between basicity and activity for benzene cracking. Infrared analysis of a calcined mixture of CaO and quartz showed no evidence of the presence of any silicate complexes. 7 figures.

Longwell, J.P.; Lai, C.K.; Williams, G.C.; Peters, W.A.

1982-09-01

124

Modification of CaO by organic alumina precursor for enhancing cyclic capture of CO{sub 2} greenhouse gas  

SciTech Connect

The modification of CaO sorbent with organic alumina precursor to enhance the sorption capacity during cyclic capture is demonstrated in this study. The results indicate that during the 10 min sorption time for each cycle, the CO{sub 2} sorption capacity of original CaO sorbent is significantly decreased from 0.27 to 0.19 and 0.12 g CO{sub 2}/g sorbent after 5 and 60 cycles, respectively. On the other hand, the organic alumina modified CaO has a fresh capacity of 0.22 g CO{sub 2}/g sorbent, it increases to 0.24 g CO{sub 2}/g sorbent after 5 cycles, and then decreases to around 0.15 g CO{sub 2}/g sorbent after 60 cycles. When increasing the sorption time to 60 min at the 66th cycle, the sorption capacity of original CaO is 0.2, whereas it is 0.26 g CO{sub 2}/g sorbent for organic alumina modified CaO. The results demonstrate that by adding only 5% by weight of Ca{sub 12}Al{sub 14}O{sub 3}3 species into the CaO sorbent, the CO{sub 2} sorption capacity can be enhanced up to similar to 27% by weight.

Chen, Y.T.; Karthik, M.; Bai, H. [National Chiao Tung University, Hsinchu (Taiwan). Inst. of Environmental Engineering

2009-06-15

125

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

PubMed Central

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

Kunugi, Motoshi; Takabayashi, Atsushi; Tanaka, Ayumi

2013-01-01

126

Primary origin of some trachytoid magmas: Inferences from naturally quenched glasses in hydrothermally metasomatized gabbroic xenoliths (Hyblean area, Sicily)  

NASA Astrophysics Data System (ADS)

Hydrothermally-modified gabbroic xenoliths from the Hyblean tuff-breccia deposits (Sicily) consist of albitized plagioclase, Fe-Mg-rich clays, aegirine-augite, zeolites, titanite, apatite, magnetite, and hydrothermal zircon. Pockets of silicate glass with perlitic cracking occur in some samples forming 15-20% (by volume) of the rock modal assemblage. Electron microprobe analyses show the trachytic composition of the glass, with generally peralkaline sodic affinity [molar Al 2O 3/(Na 2O + K 2O) ~ 0.8 (average value); molar Al 2O 3/(Na 2O + K 2O + CaO) ~ 0.7 (average value); Na 2O/K 2O (wt.%) = 1.7-2.3]. The glass trace element abundances, obtained by secondary ion mass spectrometry (SIMS) analyses are consistent with those of world-wide trachytes (e.g. Zr/Ti = 0.15-018; Nb/Y = 0.73-1). Relatively high abundances of Cl (700-1600 ppm) and F (> 500 ppm) were also detected in the glass. Careful macroscopic and microscopic observations exclude the possibility that external silicate melt infiltrated the xenolith. The occurrence of glass pockets between the mafic clay assemblages and the feldspar grains, along with comparisons between chemical compositions of the glass and the surrounding minerals, suggest that the glass is due to the melting of a eutectoid system consisting of Na-rich alkali feldspar, Fe-Mg-rich clays and aegirine-augite. Halogens had probably played an important role in the partial melting process by decreasing the melting temperature of modal minerals, especially feldspar. The occurrence of these trachytic glasses lends support to petrologic models suggesting that partial melting of a hydrothermally altered, brine-rich oceanic crust induced by shallow-seated basic intrusions can produce primary trachytoid melts. This may explain the "Daly-gap" characterizing some oceanic within-plate volcanoes.

Viccaro, Marco; Scribano, Vittorio; Cristofolini, Renato; Ottolini, Luisa; Manuella, Fabio C.

2009-12-01

127

Melting of metasomatized subcontinental mantle: New experiments and a new predictive models for plagioclase, spinel and garnet lherzolite melting  

NASA Astrophysics Data System (ADS)

Data from new experiments where liquid is in equilibrium with olivine + orthopyroxene + high-Ca clinopyroxene + Al-phase (plagioclase, spinel or garnet) have allowed us to recalibrate and update the melting model of Kinzler and Grove (K&G, JGR 97: 6885-6926, 1992) for melting under nominally anhydrous conditions over a larger range of pressure. We use existing literature data along with new experiments on melting of a high K2O primitive high alumina olivine tholeiite (HAOT) from the Oregon High Lava Plains, a high-K olivine leucitite from the Tibetan Plateau and low alkali, high FeO + MgO lunar ultramafic glasses. The new spinel lherzolite model is constrained by 114 experimental data that span a temperature range of 1200 to 1580 oC, a pressure range of 1 to 2.7 GPa and liquid alkali contents of up to 4.5 wt. % K2O and 5 wt. % Na2O. The garnet-lherzolite melting model uses 26 experimental constraints with new experiments containing up to 3.4 wt. % K2O. We use the following dependent variables to represent the melt composition in terms of oxygen-based mineral components: Olivine - Clinopyroxene - Plagioclase - Quartz and temperature. The independent variables are: pressure (P), molar Mg/(Mg+Fe) (Mg#), wt. % (K2O + Na2O)/(Na2O + K2O + CaO) (1-Ca#), wt.% Al2O3/(Al2O3+SiO2) (Al#), wt% K2O and wt. % TiO2. These variables describe the departure of melting behavior from the simplified lherzolite analog in CMAS (CaO-MgO-Al2O3-SiO2) in which melting behavior in univariant. This revised model facilitates a prediction of the liquid composition and temperature of multiple saturation with a mantle mineral assemblage for a given pressure. The new model allows compositional dependent calibration of the spinel to garnet lherzolite transition in sub-continental mantle environments. For example, beneath the Tibetan Plateau melting occurs near this transition and primitive high-K lavas show evidence of derivation from spinel- and garnet-bearing lherzolite. In addition, the HAOT lavas characteristic of the Oregons High Lava Plains are produced by adiabatic decompression melting of a metasomatized mantle source at shallow, near Moho-depths in proximity to the plagioclase to spinel lherzolite transition.

Grove, T. L.; Till, C. B.; Barr, J. A.; Krawczynski, M. J.

2010-12-01

128

Viability of Clostridium sporogenes spores after CaO hygienization of meat waste.  

PubMed

The occurrence of the pathogenic species C. perfringens and C. botulinum spores in animal by-products poses a potential epidemiological hazard. Strong entero- and neurotoxins produced by these bacteria adversely affect human health. To inactivate pathogens present in animal by-products, waste must be subjected to various methods of sanitization. The aim of the presented study was to estimate the effect of different doses of CaO on the viability of spores Clostridium sporogenes in meat wastes category 3. During the research, two doses of burnt lime were added to the poultry mince meat and meat mixed with swine blood contaminated with Clostridium sporogenes spore suspension. Half of the samples collected for microbiological analyses were buffered to achieve the pH level ~7, the other were examined without pH neutralization. To estimate the spore number, 10-fold dilution series in peptone water was prepared and heat-treated at 80 C for 10 min. After cooling-down, one milliliter of each dilution was pour-plated onto DRCM medium solidified with agar. Statistical analysis were performed using the Statistica software. Application of 70% CaO caused complete inactivation of Clostridium spores in meat wastes after 48 hours. The highest temperature achieved during the experiment was 67 C. Rapid alkalization of the biomass resulted in increasing pH to values exceeding 12. The effect of liming was not dependent on the meat wastes composition nor CaO dose. The experiment proved the efficiency of liming as a method of animal by-products sanitization. Application of the obtained results may help reduce the epidemiological risk and ensure safety to people handling meat wastes at each stage of their processing and utilization. PMID:25292114

Bauza-Kaszewska, Justyna; Paluszak, Zbigniew; Skowron, Krzysztof

2014-09-01

129

Pulsed injection metal organic chemical vapour deposition and characterisation of thin CaO films  

NASA Astrophysics Data System (ADS)

Thin films of CaO were grown on silicon (Si) and lanthanum aluminate (LaAlO 3) substrates by pulsed injection metal-organic chemical vapour deposition in a vertical injection MOCVD system. Growth parameters were systematically varied to study their effect on film growth and quality and to determine the optimal growth conditions for this material. Film quality and growth rate were evaluated by atomic force microscopy, X-ray diffraction and Rutherford Backscattering Spectroscopy measurements. Optimised conditions allowed growing transparent, single phase films textured along the (0 0 l) direction.

Borges, R. P.; Ferreira, P.; Saraiva, A.; Gonalves, R.; Rosa, M. A.; Gonalves, A. P.; da Silva, R. C.; Magalhes, S.; Loureno, M. J. V.; Santos, F. J. V.; Godinho, M.

2009-05-01

130

Microporous crystal 12CaO x 7Al(2)O(3) encaging abundant O(-) radicals.  

PubMed

Extremely high concentrations (>1020 cm-3) of active oxygenic radicals, O- and O2-, have been created in the zeolitic crystal, 12CaO.7Al2O3 (C12A7), which can accommodate anions in its cavities. An increase in oxygen pressure and a decrease in water vapor pressure at high temperature enhance the formation of the radicals. The oxidation of Pt is observed on the surface of the material as a result of reaction with the active oxygens. PMID:11817934

Hayashi, Katsuro; Hirano, Masahiro; Matsuishi, Satoru; Hosono, Hideo

2002-02-01

131

Mechanochemical degradation of ?-hexachlorocyclohexane by a planetary ball mill in the presence of CaO.  

PubMed

Although the use of the insecticide ?-hexachlorocyclohexane (HCH) is now prohibited in many countries because of its hazardousness, stockpiles of ?-HCH still exist. In this study, we subjected ?-HCH to mechanochemical (MC) treatment with a planetary ball mill in the presence of CaO to investigate the feasibility of using this method for the treatment of ?-HCH stockpiles. We confirmed the degradation of ?-HCH and investigated the degradation mechanism. The major intermediates were identified to be 1,3,4,5,6-pentachlorocyclohexene (?-PCCH) and chlorobenzenes (CBzs). Analysis of the steric structure of ?-HCH and identification of the degradation intermediates suggested that successive dehydrochlorination led to the formation of trichlorobenzenes. Products of further degradation (dichlorobenzenes, monochlorobenzene, and benzene) were also detected. Surprisingly, methane and ethane were also detected, which suggests cleavage of the C-C bonds of the cyclohexane ring and hydrogenation. All of the chlorine atoms in the ?-HCH could be transformed into inorganic chloride compounds by the MC treatment with CaO. Our results indicate that ?-HCH can be completely dechlorinated by MC treatment. PMID:22055315

Nomura, Yugo; Fujiwara, Kazuo; Terada, Akihiko; Nakai, Satoshi; Hosomi, Masaaki

2012-01-01

132

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

133

Nb-doped CaO: an efficient electron donor system  

NASA Astrophysics Data System (ADS)

Transition metal atoms incorporated into insulating materials (oxides in particular) can deeply modify their adsorption properties. In particular, charge transfer to adsorbed species can be induced by the presence of substitutional dopants, which introduce new electronic states in the band gap of the host crystal. Here we show, by means of density functional theory calculations, that Nb represents an excellent dopant to turn the rather inactive CaO(100) surface into an electron-rich support. The charge transfer ability of the doped material is shown by comparing the adsorption properties of the electronegative Au atoms on pure and Nb-doped CaO. While in the first case the CaO-Au bonding is relatively weak and the Au atom is essentially neutral, in the Nb-doped system a much stronger adhesion is found due to a net charge transfer from the Nb dopant and to the formation of a gold anion. This mechanism occurs also for Nb in high oxidation states. Nb is thus an excellent modifier of the calcium oxide properties.

Prada, Stefano; Giordano, Livia; Pacchioni, Gianfranco

2014-08-01

134

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

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

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

2013-02-21

135

Ben cao tu jing (Illustrated Canon of Herbology) and the origin of modern identification of Chinese materia medica.  

PubMed

There is certain relation between the development of modern identification of Chinese materia medica and Ben cao tu jing. The purpose of Su Song's compilation of this book and the tasks of modern identification of Chinese materia medica, including the verification of genuineness, superiority of the drugs to ensure their qualities, are quite similar, and quite close in their contents. Suffice it to say that Ben cao tu jing made considerable contribution to modern identification of Chinese drugs, with a role of linking the past with the present. PMID:11623860

Jiang, D

1999-04-01

136

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

E-print Network

Steam-Coal Gasification Using CaO and KOH for in Situ Carbon and Sulfur Capture Nicholas S. Siefert Virginia 26507, United States ABSTRACT: We present experimental results of coal gasification. Using two different coal types and temperatures between 700 and 900 °C, we studied the effect

Litster, Shawn

137

Feedback: Towards Dynamic Behavior and Secure Routing for Wireless Sensor Zhen Cao, Jianbin Hu, Zhong Chen, Maoxing Xu, Xia Zhou  

E-print Network

- sion in a secure and energy aware manner. We present both mathematical analysis and simulation resultsFeedback: Towards Dynamic Behavior and Secure Routing for Wireless Sensor Networks Zhen Cao, Peking University Network and Information Security Laboratory Beijing, China { caozhen, hjbin, chen, xumx

Ramkumar, Mahalingam

138

Making Routers Last Longer with ViAggre Hitesh Ballani, Paul Francis, Tuan Cao and Jia Wang  

E-print Network

1 Making Routers Last Longer with ViAggre Hitesh Ballani, Paul Francis, Tuan Cao and Jia Wang), a "configuration-only" approach to shrinking the routing table on routers. ViAggre does not require any changes to router software and routing protocols and can be deployed independently and autonomously by any ISP. Vi

Keinan, Alon

139

Predicting Gender and Weight from Human Metrology using a Copula Model Deng Cao, Cunjian Chen, Donald Adjeroh, Arun Ross  

E-print Network

Predicting Gender and Weight from Human Metrology using a Copula Model Deng Cao, Cunjian Chen in predicting gender and weight. For gender prediction, the proposed model results in a 0.7% misclassification model gives 0.01 mean absolute error (in the range 0 to 1) using both body and head information, 0

Ross, Arun Abraham

140

A New Approach to Conformant Planning using CNF Son Thanh To and Tran Cao Son and Enrico Pontelli  

E-print Network

information about the initial state. Since the problem is introduced (Smith and Weld 1998), several conformantA New Approach to Conformant Planning using CNF Son Thanh To and Tran Cao Son and Enrico Pontelli in the literature for conformant planning. We evaluate the performance of CNF against other state

Tran, Cao Son

141

OCAO Computer Refreshment Policy The NOAA CAO is responsible for budgeting and procuring all personal computers and other  

E-print Network

6/20/2007 OCAO Computer Refreshment Policy Purpose: The NOAA CAO is responsible for budgeting and procuring all personal computers and other support computers used by OCAO staff. To facilitate adequate capital planning and clarify acquisition policies, the following Computer Refreshment Policy

142

Use of fly ash as an admixture for electromagnetic interference shielding Jingyao Cao, D.D.L. Chung*  

E-print Network

Use of fly ash as an admixture for electromagnetic interference shielding Jingyao Cao, D.D.L. Chung The use of fly ash as an admixture results in enhancement of the electromagnetic interference (EMI by silica fume, but is essentially not affected by fly ash. Both fly ash and silica fume cause slight

Chung, Deborah D.L.

143

An Air Traffic Prediction Model based on Kernel Density Estimation Yi Cao,1 Lingsong Zhang,2 and Dengfeng Sun3  

E-print Network

through sophisticated flight dynamics [1]. However, for the Air Traffic Control Sys- tem Command Center at an Air Route Traffic Control Center (simply denoted as Center hereafter) level [2]. It forecasts aircraftAn Air Traffic Prediction Model based on Kernel Density Estimation Yi Cao,1 Lingsong Zhang,2

Sun, Dengfeng

144

A Robust Panel Extraction Method for Manga Xufang Pang, Ying Cao, Rynson W.H. Lau, and Antoni B. Chan  

E-print Network

A Robust Panel Extraction Method for Manga Xufang Pang, Ying Cao, Rynson W.H. Lau, and Antoni B.com, {rynson.lau,abchan}@cityu.edu.hk ABSTRACT Automatically extracting frames/panels from digital comic pages, au- tomatic panel extraction for manga, i.e., Japanese comics, can be especially challenging, largely

Lau, W. H. Nynson

145

Point Cloud Skeletons via Laplacian-Based Contraction Junjie Cao, Andrea Tagliasacchi, Matt Olson, Hao Zhang and Zhixun Su  

E-print Network

Point Cloud Skeletons via Laplacian-Based Contraction Junjie Cao, Andrea Tagliasacchi, Matt Olson skeleton extraction via Laplacian-based contraction. Our algorithm can be applied to surfaces, allowing skeleton-based manipulation of point clouds without explicit surface reconstruction. By avoiding

Zhang, Richard "Hao"

146

Optimal Efficiency of Self-Assembling Light-Harvesting Arrays Ji-Hyun Kim and Jianshu Cao*  

E-print Network

Optimal Efficiency of Self-Assembling Light-Harvesting Arrays Ji-Hyun Kim and Jianshu Cao equation that describes energy transfer over a given lattice, we explore how energy transfer efficiency (derived in Appendix A) for efficiency shows a steep increase with a D-to-A transfer rate when

Cao, Jianshu

147

Effect of sulfated CaO on NO reduction by NH{sub 3} in the presence of excess oxygen  

SciTech Connect

The effect of sulfated CaO on NO reduction by NH{sub 3} in the presence of excess oxygen was investigated to evaluate the potential of simultaneous SO{sub 2} and NO removal at the temperature range of 700-850{sup o}C. The physical and chemical properties of the CaO sulfation products were analyzed to investigate the NO reduction mechanism. Experimental results showed that sulfated CaO had a catalytic effect on NO reduction by NH{sub 3} in the presence of excess O{sub 2} after the sulfation reaction entered the transition control stage. With the increase of CaO sulfation extent in this stage, the activity for NO reduction first increased and then decreased, and the selectivity of NH{sub 3} for NO reduction to N{sub 2} increased. The byproduct (NO{sub 2} and N{sub 2}O) formation during NO reduction experiments was negligible. X-ray photoelectron spectroscopy (XPS) analysis showed that neither CaSO{sub 3} nor CaS was detected, indicating that the catalytic activity of NO reduction by NH{sub 3} in the presence of excess O{sub 2} over sulfated CaO was originated from the CaSO{sub 4} product. These results revealed that simultaneous SO{sub 2} and NOx control by injecting NH{sub 3} into the dry flue gas desulfurization process for NO reduction might be achieved. 38 refs., 6 figs., 1 tab.

Tianjin Li; Yuqun Zhuo; Yufeng Zhao; Changhe Chen; Xuchang Xu [Tsinghua University, Beijing (China). Key Laboratory for Thermal Science and Power Engineering of Ministry of Education

2009-04-15

148

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

149

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

150

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

NASA Astrophysics Data System (ADS)

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.

Blume, Theresa

2013-04-01

151

Chemical analysis of the Chinese herbal medicine Gan-Cao (licorice).  

PubMed

Gan-Cao, or licorice, is a popular Chinese herbal medicine derived from the dried roots and rhizomes of Glycyrrhiza uralensis, G. glabra, and G. inflata. The main bioactive constituents of licorice are triterpene saponins and various types of flavonoids. The contents of these compounds may vary in different licorice batches and thus affect the therapeutic effects. In order to ensure its efficacy and safety, sensitive and accurate methods for the qualitative and quantitative analyses of saponins and flavonoids are of significance for the comprehensive quality control of licorice. This review describes the progress in chemical analysis of licorice and its preparations since 2000. Newly established methods are summarized, including spectroscopy, thin-layer chromatography, gas chromatography, high-performance liquid chromatography (HPLC), liquid chromatography/mass spectrometry (LC/MS), capillary electrophoresis, high-speed counter-current chromatography (HSCCC), electrochemistry, and immunoassay. The sensitivity, selectivity and powerful separation capability of HPLC and CE allows the simultaneous detection of multiple compounds in licorice. LC/MS provides characteristic fragmentations for the rapid structural identification of licorice saponins and flavonoids. The combination of HPLC and LC/MS is currently the most powerful technique for the quality control of licorice. PMID:18703197

Zhang, Qingying; Ye, Min

2009-03-13

152

Heavy doping of H - ion in 12CaO7Al 2O 3  

NASA Astrophysics Data System (ADS)

12CaO7Al 2O 3 (C12A7, mayenite), which has a nanoscale porous structure that can accommodate extraframework species such as hydride (H -), oxide (O 2-), hydroxide (OH -) ions, and electrons, has been doped with H - ions to investigate its effects as dominant extraframework species. Chemical doping with CaH 2 enables the concentration of H - ions to reach almost the theoretical maximum. The concentration of H - ions is characterized by optical absorption intensity ascribed to photoionization of H - ions, and 1H magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Persistent electron generation, which is accompanied by the formation of an F+ absorption band and electrical conductivity, by irradiation with ultraviolet light at room temperature increases as the H - ion doping increases until it reaches half the theoretical maximum and then decreases as the H - ion concentration increases further. This dependence indicates that both H - and O 2- ions are necessary for the generation of persistent electrons.

Hayashi, Katsuro

2011-06-01

153

Heat recovery from a thermal energy storage based on the Ca(OH) 2\\/CaO cycle  

Microsoft Academic Search

Thermal energy storage is very important in many applications related to the use of waste heat from industrial processes, renewable energies or from other sources. Thermochemical storage is very interesting for long-term storage as it can be carried out at room temperature with no energy losses.Dehydration\\/hydration cycle of Ca(OH)2\\/CaO has been applied for thermal energy storage in two types of

M. N. Azpiazu; J. M. Morquillas; A. Vazquez

2003-01-01

154

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

155

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

PubMed Central

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

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

2014-01-01

156

Roles of regulated internalization in the polarization of cell surface Wei Tian1, Youfang Cao1, Amber Ismael2, David Stone2, Jie Liang1  

E-print Network

Cao1, Amber Ismael2, David Stone2, Jie Liang1 Accepted, Conf Proc IEEE Eng Med Biol Soc. 2014 Abstract.edu 2D. Stone is with Faculty of the Department of Biological Science, University of Illinois at Chicago

Liang, Jie

157

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

NASA Astrophysics Data System (ADS)

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 ?m 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.

Lysyuk, G. N.

2011-10-01

158

Micelle-Assisted Synthesis of Al2O3CaO Nanocatalyst: Optical Properties and Their Applications in Photodegradation of 2,4,6-Trinitrophenol  

PubMed Central

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

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

2013-01-01

159

Overcoming the polarization catastrophe in the rocksalt oxides MgO and CaO  

NASA Astrophysics Data System (ADS)

Interfaces between dissimilar polar materials may provide a pathway to new device functionality, including high carrier mobility layers at the interface. The development of these materials has proven challenging, in part because of the high energy cost of forming polar surfaces. Our density functional theory calculations explore the mechanisms by which a real material satisfies the electrostatic criteria for stability imposed by a polar surface. The consequences of polarity are studied by comparing the formation energies, charge distribution, and electronic structure of a number of low-index surfaces of rocksalt MgO and CaO. These surfaces are explored both in their bare, undecorated form as well as with surface reconstructions and adsorbed foreign species. Our ground-state surface energies are extended to relevant environmental conditions by use of ab initio thermodynamics. We find that the high energy of bare polar surfaces is the result of the significant charge redistribution that arises to compensate the polarity and pushes electronic states into the forbidden band gap. Other mechanisms of polarity compensation (reconstruction or foreign species adsorption) are therefore seen more frequently. We explain the experimental observations of surface roughness during growth in the [111] direction. In typical epitaxial growth conditions, there is preferential formation of an octopolar reconstruction of the {111} surface, which exposes {001}-type nanofacets. The low energy of the {001} surface likely causes these facets to grow, leading to a rough surface morphology. Our results indicate that when water vapor is present during growth, a smooth, polar surface can be stabilized by the formation of a hydroxyl layer.

Gaddy, Benjamin E.; Paisley, Elizabeth A.; Maria, Jon-Paul; Irving, Douglas L.

2014-09-01

160

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

PubMed

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

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

2012-01-17

161

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

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

162

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

SciTech Connect

We present experimental results of coal gasification with and without the addition of calcium oxide and potassium hydroxide as dual-functioning catalystcapture agents. Using two different coal types and temperatures between 700 and 900 C, we studied the effect of these catalystcapture agents on (1) the syngas composition, (2) CO{sub 2} and H{sub 2}S capture, and (3) the steamcoal 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 steamcoal gasification kinetic rates when adding small amounts of potassium hydroxide to coal when operating a CaOCaCO{sub 3} chemical looping gasification reactor. For example, the steamcoal 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 CaCO{sub 3} was calcined by heating to 900 C to regenerate the CaO, which was then reused in repeated CaOCaCO{sub 3} cycles. The increased steamcoal 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 24% per CaOCaCO{sub 3} cycle. We also discuss an important application of this combined gasifiercalciner 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 CaSO{sub 4} and ash in the precalcined feedstock.

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

2013-08-01

163

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

PubMed

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

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

2013-01-01

164

Low temperature thermal degradation of PCDD/Fs in soil using nanosized particles of zerovalent iron and CaO.  

PubMed

This study investigated the degradation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in contaminated soil using low temperature treatment (200-280C) both alone and in combination with nanosized zerovalent iron (nZVI) particles or CaO. Control soil samples and soil fortified with nZVI particles or CaO were treated at 200 and 250C in sealed glass ampoules. Treatment of the ampouled samples at 250C was more effective than treatment at 200C and the reduction in PCDD/F concentration was greatest when soil was treated at 250C with nZVI addition (indeed, treatment at 200C in the absence of nZVI resulted in increases in total PCDD and PCDD/F concentrations). In larger-scale experiments based on the obtained results, using a rotary furnace, the greatest reduction in total PCDD/F concentration was achieved by treating soil at 280C, and adding nZVI to the soil resulted in almost no detectable PCDD/F in the gas phase. PMID:23498061

Lundin, Lisa; Molt, Julia; Fullana, Andres

2013-05-01

165

Thermal conductivity and Seebeck coefficient of 12CaO?7Al2O3 electride with a cage structure  

NASA Astrophysics Data System (ADS)

Thermal conductivity (?) and Seebeck coefficient (?) of electron-doped light-metal oxide 12CaO?7Al2O3 (C12A7 electride) with a subnanometer-sized cage structure are reported on single crystals with various electron concentrations (Ne) . The semiconducting C12A7 electride exhibits n -type conduction with the highest ? value of -100?VK-1 at 300 K. The ? exhibits an amorphouslike T2 dependence at low temperatures and varies between 2.3 and 4.5Wm-1K-1 at 300 K. This is an order-of-magnitude lower than that of the constituents, CaO (15Wm-1K-1) and Al2O3 (30Wm-1K-1) . These properties are attributed to the cage structure, suggesting that the semiconducting electride should be regarded as a phonon glass and electron crystal material. The thermoelectric performance of electrides evaluated by a dimensionless figure of merit (ZT) shows an optimized value of 210-3 at 300 K for the semiconducting electride with Ne of 51020cm-3 .

Kim, Sung Wng; Tarumi, Ryuichi; Iwasaki, Hideo; Ohta, Hiromichi; Hirano, Masahiro; Hosono, Hideo

2009-08-01

166

Solution of MgO, CaO, and TiO[sub 2] in [alpha]-Al[sub 2]O[sub 3  

SciTech Connect

Atomistic simulation methods are used to predict the preferred solution mechanisms and their associated energies. Both full- and partial-charge models are discussed. It was found that defect clustering always results in a significant lowering of the solution energies but does not change the preferred solution reaction of any of the oxides. The large size of the Ca[sup 2+] ion results not only in a higher solution energy (lower solubility) for CaO compared to MgO but also to a different preferred compensation mechanism. The predicted energy for the cosolution of MgO and TiO[sub 2] is dramatically smaller than for either oxide separately. Conversely, whereas solution of TiO[sub 2] aids the solution of CaO, additions of CaO do not support TiO[sub 2] solution.

Grimes, R.W. (Royal Institution of Great Britain, London (United Kingdom). Davy Faraday Research Lab.)

1994-02-01

167

Comparison of the safety of drug delivery via HFA- and CFC-metered dose inhalers in CAO.  

PubMed

The objective of this study was to compare the long-term safety of a fixed combination of fenoterol hydrobromide (50 microg) and ipratropium bromide (20 microg) delivered using a metered dose inhaler (MDI) formulated with a non-chlorinated propellant, hydrofluoroalkanel34a (HFA-MDI), with delivery using the conventional chlorofluorocarbon propellant (CFC-MDI, Berodual/Bronchodual). The study was designed according to Safety Assessment of Marketed Medicines (SAMM) guidelines, to reflect as far as possible the use of MDls under normal prescribing conditions. Two thousand and twenty-seven patients with chronic airways obstruction (CAO) were enrolled from 99 centres in France, 95 centres in Germany and 24 centres in Italy. Following a 2-week run-in period, patients were randomized on a 2:1 basis (1,348 patients to HFA-MDI, 679 patients to CFC-MDI) to receive a flexible dose regimen of the combination (2 puffs, 2-4 times a day, as prescribed by the investigator) during a 12-week open label phase. The overall incidence of adverse events was comparable between both groups. In addition, the incidence of respiratory side effects was also similar, with CAO exacerbations or bronchitis the most frequently recorded events. The safety profile of the HFA formulation was comparable to those of the marketed CFC-MDIs used in Germany and France/Italy. No clinically significant differences were detected between HFA134a or CFC driven inhalers on the switch from CFC- to HFA-MDI (2 weeks before randomisation versus 2 weeks after randomization). There was a trend for taste complaints to be reported more frequently by patients in the HFA-MDI group (0.7% before randomization versus 3.4% after randomization). This, however, was an expected finding as the HFA134a formulation does have a different taste to the CFC formulation. No difference between formulations was observed in the incidences of coughing or paradoxical bronchospasm. The incidence of falls in FEV1 >15% within 15 min following inhalation at each of the clinic visits was 1.2% for both CFC- and HFA-MDIs. In conclusion, administration of a fenoterol/ipratropium bromide combination via hydrofluoroalkane-metered dose inhaler is as safe as delivery by the currently available chlorofluorocarbon-metered dose inhaler, in an extended population of patients with CAO under normal prescribing conditions. PMID:10780756

Huchon, G; Hofbauer, P; Cannizzaro, G; Iacono, P; Wald, F

2000-04-01

168

Strain induced phenomena in Ca(OH)/sub 2/ made by reaction of CaO with water vapor  

SciTech Connect

Three physically distinguishable, poorly crystalline forms of Ca(OH)/sub 2/ which are made by reactions of water vapor at 25/sup 0/C with CaO powders evolve heat and develop sharper x-ray diffraction patterns when heated to 300/sup 0/C. Measurements of x-ray diffraction peak line breadths, surface areas, porosities, and pore size distributions were made before and after heat treatment. The exothermic process of the one of these forms of Ca(OH)/sub 2/ which is nonporous is recrystallization of the highly strained solid to essentially unstrained crystals. The exothermic process in two porous forms of Ca(OH)/sub 2/, not only reduces their internal strains, but also reduces their surface areas and porosities.

Beruto, D.; Searcy, A.W.; Barco, L.; Belleri, G.

1980-01-01

169

Growth of shaped 12CaO7Al 2O 3 crystals by the micro-pulling down method  

NASA Astrophysics Data System (ADS)

12CaO7Al 2O 3 (C12A7) single crystals have been successfully grown by the micro-pulling down method for the first time. Single and transparent C12A7 crystal was obtained with radio-frequency heating ?-PD system. Phase stability is discussed as a function of oxygen concentration in the growth atmosphere. A minimum 1.0 Vol% O 2 with nitrogen atmosphere yields C12A7 phase. The distribution of Ca, Al and O elements at cross-section part was investigated by the electron probe microanalysis. The crystal composition deviation could be controlled by reducing O 2 gas concentration to 1.0 Vol%.

Liu, Lijuan; Kagamitani, Yuji; Ehrentraut, Dirk; Yokoyama, Chiaki; Fukuda, Tsuguo

2009-01-01

170

Mechanisms of oxygen ion diffusion in a nanoporous complex oxide 12CaO7 Al2 O3  

NASA Astrophysics Data System (ADS)

We performed a theoretical analysis of O2- diffusion mechanisms in a nanoporous complex oxide 12CaO7Al2O3 (C12A7). This material can be viewed as a positively charged framework, arranged in subnanometer sized cages, hosting extra-framework O2- ions occupying one in six cages. Using both classical molecular-dynamics simulations and ab initio calculations we demonstrate that the diffusion of O2- species is dominated by the exchange of framework and extra-framework O2- ions rather than by an interstitial diffusion mechanism. The results allow us to rationalize the origins of the experimentally observed high oxide ion conductivity of C12A7 and the stability of its lattice under positive ion-beam irradiation.

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

2006-01-01

171

High electron doping to a wide band gap semiconductor 12CaO7Al2O3 thin film  

NASA Astrophysics Data System (ADS)

High-density electrons (1.91021cm-3) were doped into a polycrystalline film of a wide band gap (7eV) semiconductor 12CaO7Al2O3 (C12A7) by an in situ postdeposition reduction treatment using an oxygen-deficient C12A7 overlayer. The resultant film exhibits metallic conduction with a Hall mobility of 2.5cm2V-1s-1 and a conductivity of 800Scm-1. Optical analyses indicate that most of the doped electrons behave as free carriers with an effective mass of 0.82me and the estimated in-grain mobility is 5.2cm2V-1s-1, which agrees reasonably with the value obtained for high-quality single crystals.

Miyakawa, Masashi; Hirano, Masahiro; Kamiya, Toshio; Hosono, Hideo

2007-04-01

172

The high K2O volcanism of northwestern Tibet: Geochemistry and tectonic implications  

Microsoft Academic Search

Cenozoic volcanic rocks sampled during the 1989 Sino-French Kunlun geotraverse have been analyzed to constrain the origin of widespread Tertiary to Neogene Tibetan basic magmatism. Samples ranging from phonotephrites to trachyandesites are high-K lavas (K\\/Na always greater than 1) which exhibit typical calc-alkaline characteristics, although they are highly enriched in mobile trace elements and REE (600 times chondrites for La).

N. O. Arnaud; Ph. Vidal; P. Tapponnier; Ph. Matte; W. M. Deng

1992-01-01

173

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

SciTech Connect

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 (CSH), 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 CSH, 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.

Kim, Min Sik; Jun, Yubin; Lee, Changha, E-mail: clee@unist.ac.kr; Oh, Jae Eun, E-mail: ohjaeeun@unist.ac.kr

2013-12-15

174

Link Prediction and Recommendation across Heterogeneous Social Networks Yuxiao Dong, Jie Tang, Sen Wu, Jilei Tian, Nitesh V. Chawla, Jinghai Rao, Huanhuan Cao  

E-print Network

the problem of inferring the types of social relationships across heterogeneous networks. However, the problemLink Prediction and Recommendation across Heterogeneous Social Networks Yuxiao Dong, Jie Tang, Sen.tian,jinghai.rao,happia.cao}@nokia.com Abstract--Link prediction and recommendation is a funda- mental problem in social network analysis. The key

Chawla, Nitesh V.

175

A picosecond electron gun for surface analysis M. Aeschlimann,a) E. Hull, J. Cao,b) C. A. Schmuttenmaer, L. G. Jahn,@ Y. Gao,b)  

E-print Network

A picosecond electron gun for surface analysis M. Aeschlimann,a) E. Hull, J. Cao,b) C. A investigations for a new design of an ultrashort pulsed laser activated electron gun for time resolved surface gun, in spite of an unusually long focal length and a small convergence angle of the pulsed electron

Cao, Jianming

176

An Analysis of Security and Privacy Issues in Smart Grid Software Architectures on Yogesh Simmhan, Alok Gautam Kumbhare, Baohua Cao, and Viktor Prasanna  

E-print Network

Simmhan, Alok Gautam Kumbhare, Baohua Cao, and Viktor Prasanna Center for Energy Informatics Computer an information-driven approach to distributed energy management. Clouds offer features well suited for Smart Grid architecture operating on different Cloud environments, in the form of a taxonomy. We use the Los Angeles Smart

Prasanna, Viktor K.

177

A Cost-Effective LSH Filter for Fast Pairwise Mining Gang Zhao, Yun Xiong, Longbing Cao, Dan Luo, Xuchun Su and Yangyong Zhu  

E-print Network

. The particularly interesting and well-studied case in data mining is Hamming space, which is related to the MarketA Cost-Effective LSH Filter for Fast Pairwise Mining Gang Zhao, Yun Xiong, Longbing Cao, Dan Luo Sydney, NSW, Australia Email: {lbcao,dluo,xsu}@it.uts.edu.au Abstract--The pairwise mining problem

Cao, Longbing

178

Long lasting blue phosphorescence and photostimulated luminescence in 12CaO?7Al2O3:Eu thin films grown by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Long lasting blue emitting Eu-doped 12CaO?7Al2O3 thin films have been prepared on quartz substrates by pulsed laser deposition combined with post-annealing. The 12CaO?7Al2O3 phase is formed after annealing the films above 900 C in vacuum ambient. Upon 323 nm excitation, the thin films exhibit a blue long lasting emission peaked at 444 nm, assigned to the 5d-4f transitions of Eu2+. The films annealed at 950 C have stronger luminescence and longer lasting time than that annealed at 900 C. The phosphorescence intensity of vacuum annealed film is better than that annealed in H2/N2 atmosphere, which might be due to the increase of shallow trap numbers during the vacuum annealing process. Thermoluminescence curves demonstrate that vacuum and H2/N2 atmosphere annealing could introduce a large number of both shallow and deep traps into 12CaO?7Al2O3:Eu thin films. After UV irradiation, excellent photostimulated luminescence can be observed under 980 nm excitation. Our results suggest that 12CaO?7Al2O3:Eu phosphor may serve as a promising blue luminescent materials used in fabrication of optical storage and illumination in dark environments.

Zhu, Hancheng; Liu, Yuxue; Yan, Duanting; Bian, Hongyu; Li, Shengnan; Liu, Chunguang; Xu, Changshan; Wang, Xiaojun

2014-09-01

179

A Systematic Review of the Mysterious Caterpillar Fungus Ophiocordyceps sinensis in Dong-ChongXiaCao ( D?ng Chng Xi C?o) and Related Bioactive Ingredients.  

PubMed

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 ( D?ng Chng Xi C?o)" ("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 sp. 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, ?-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 1(st), 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

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

2013-01-01

180

Thermodynamics and kinetics of hydroxide ion formation in 12 CaO x 7 Al2O3.  

PubMed

We have examined the thermodynamics and kinetics of hydroxide (OH-) ions that formed in cages of 12 CaO x 7 Al2O3 (C12A7) with nanoporous structures. It is confirmed using thermogravimetric-evolved gas analyses (TG-EGA) that hydration in C12A7 is mediated by a reaction between an oxide (O2-) ion in the cage and an H2O molecule in the atmosphere to form two OH- ions in the cages. To simply and exactly quantify the OH- content from infrared absorption measurements of OH-stretching band, we propose a method combined with a thermodynamic analysis, allowing the simultaneous determination of the molar extinction coefficient of the OH-band, enthalpy, and entropy for the hydration. Hydration enthalpy in C12A7 is extremely high compared with other oxides and was enhanced by the marked instability of O2- ion in the cage. Consequently, high solubility of OH- ion is retained up to unusually high temperatures. Furthermore, we determined diffusion coefficients of species relevant to the hydration process and demonstrated that inward diffusion of OH- ions is the rate-determining process. PMID:16852465

Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

2005-06-23

181

Strong enhancement of superconductivity in inorganic electride 12CaO7Al2O3:e- under high pressure  

NASA Astrophysics Data System (ADS)

We present the results of the pressure dependence of the superconductivity of the inorganic electride 12CaO7Al2O3:e- (C12A7:e-) single crystal through the ac-susceptibility measurement under high pressure. C12A7:e- has the cage structure and the density of states derived from the cages may play an important role in the superconductivity. The superconducting transition temperature ( T c) is 0.2 K at ambient pressure and monotonically increases up to 1.79 K at 4.7 GPa. The upper critical field H c2 and - dH c2/ dT at T c, in proportion to the density of states (DOS) at Fermi energy becomes larger under high pressure. The superconductivity in C12A7:e- is mediated by the electron-phonon interaction, and the increase of Tc with pressure may arise from a peak structure of the DOS of cage conduction band.

Tanaka, Shigeki; Kato, Tomoki; Miyake, Atsushi; Kagayama, Tomoko; Shimizu, Katsuya; Kim, Sung Wng; Matsuishi, Satoru; Hosono, Hideo

2013-08-01

182

From insulator to electride: a theoretical model of nanoporous oxide 12CaO.7Al2O3.  

PubMed

Recently, a novel inorganic electride stable at room temperatures has been obtained by reducing a complex nanoporous oxide 12CaO.7Al2O3 (C12A7) in a Ca atmosphere (Matsuishi, S.; Toda, Y.; Miyakawa, M.; Hayashi, K.; Kamiya, T.; Hirano, M.; Tanaka, I.; Hosono, H. Science 2003, 301, 626). In this system, up to 2.3 x 1021/cm3 electrons can be accommodated in a three-dimensional network of cages formed by a positively charged oxide framework. We demonstrate theoretically that at all concentrations, ne, the electrons are neither associated with specific atoms nor fully delocalized. At low ne, the electrons are isolated from each other and resemble the color centers in insulating materials. They are well localized in some of the lattice cages and yield strong inhomogeneous lattice distortions that provide polaron-type cage-to-cage electron hopping. As ne increases, the electrons form a denser electron gas and become more evenly spread over all available lattice cages. At sufficiently high ne, the system becomes metallic but still retains partially localized character of the conducting electrons. We describe the nature of the electronic states at the Fermi level and predict the changes in the optical and magnetic properties of this system as a function of ne. PMID:17243831

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

2007-01-31

183

Characterization and optical transition in tb-doped 12CaO x 7Al2O3 powders.  

PubMed

Tb-doped 12CaO x 7Al2O3 (C12A7:Tb3+) powders with strong green emission were prepared using the sol-gel method. X-ray diffraction, micro-Raman spectra, scanning electron microscopy and absorption spectra showed that C12A7:Tb3+ powders with grain size of 200-300 nm were synthesized. Porous powders could be formed as the concentration of Tb3+ was 5 at%. The absorption band around 209 nm was attributed to the host lattice absorption, and the bands around 255 nm and 274 nm were related to the 4f-5d transitions of Tb3+. The absorption intensity of the visible region was enhanced due to the presence of one 100 nm-diameter hole in every grain of C12A7:Tb3+ powders. The emission spectra showed noticeable influence of Tb-Tb cross relaxation, which favored the green photoluminescence (PL) over the blue PL. The study on the concentration quenching indicated that the energy transfers depopulating the 5D3 and 5D4 levels were assigned to the mechanisms of electric dipole-dipole and exchange interaction, respectively. PMID:20355639

Xue, L L; Liu, Y X; Xu, C S; Liu, Y C; Zhao, C J; Zhang, X T

2010-03-01

184

Features and mechanism of H- anion emission from 12 CaO x 7 Al2O3 surface.  

PubMed

The hydrogen anion (H-) and other anionic species (O-, OH-, e-) in the gas phase, emitted from the synthesized crystal surface of 12 CaO x 7 Al2O3-H- (C12A7-H-), have been observed. The emission intensity of all the anionic species strongly depends on the sample surface temperature and the extraction field. H- has the highest emission branch ratio, and the extraction field can reduce its apparent activation energy. H- emission current at a microA/cm2-level has been achieved, which is about 4 orders of magnitude higher than that obtained from the thermal desorption process of CaH2. The observed anions of H- and OH- are attributed to their migration from the C12A7-H- cages onto the surface [i.e., Y-(cages) --> Y-(surface) --> Y-(gas phase) (Y = H, OH)]. The weak O- and electron emission would both arise from the dissociation of O2-: O2-(surface) --> O-(surface) + e-(surface) --> O-(gas phase) + e-(space). PMID:16852484

Huang, Fan; Li, Jiang; Wang, Lian; Dong, Ting; Tu, Jing; Torimoto, Yoshifumi; Sadakata, Masayoshi; Li, Quanxin

2005-06-23

185

Photoluminescence of Au - formed in 12CaO 7Al 2O 3 single crystal by Au +-implantation  

NASA Astrophysics Data System (ADS)

Au + ion implantation with fluences from 1 10 14 to 3 10 16 cm -2 into 12CaO 7Al 2O 3 (C12A7) single crystals was carried out at a sample temperature of 600 C. The implanted sample with the fluence of 1 10 15 cm -2 exhibited photoluminescence (PL) bands peaking at 3.1 and 2.3 eV at ?150 K when excited by He-Cd laser (325 nm). This was the first observation of PL from C12A7. These two PL bands are possibly due to intra-ionic transitions of an Au - ion having the electronic configuration of 6 s2, judged from their similarities to those reported on Au - ions in alkali halides. However, when the concentration of the implanted Au ions exceeded the theoretical maximum value of anions encaged in C12A7 (2.3 10 21 cm -3), surface plasmon absorption appeared in the optical absorption spectrum, suggesting Au colloids were formed at such high fluences. These observations indicate that negative gold ions are formed in the cages of C12A7 by the Au + implantation if an appropriate fluence is chosen.

Miyakawa, M.; Kamioka, H.; Hirano, M.; Kamiya, T.; Hosono, H.

2006-09-01

186

Preparation and visible emission of Er-doped 12CaO x 7Al2O3 powder.  

PubMed

Er(3+)-doped 12CaO x 7Al2O3 (C12A7:Er3+) powders were prepared using the sol-gel method. X-ray diffraction, micro-Raman spectra and absorption spectra showed that C12A7:Er3+ powder had been obtained. Sharp and intense Er(3+)-related emission from C12A7:Er3+ powder with different Er3+ concentrations in the visible region at room temperature was investigated by analyzing the local structure of Ca atoms in C12A7, and it revealed that cation sites with low symmetry of the host were beneficial to the photoluminescence of Er3+ ions. The emission lines were attributed to two types of Er3+ centers, isolated Er3+ ions and complex centers formed by aggregation of Er3+ ions. The PL intensity might be affected by free oxygen species relative to Er3+ ions formed by charge compensation. The inverse temperature dependent luminescence from the upper level of 2H11/2 state and that from the lower level of 4S3/2 state implied that the thermalization or thermal equilibrium of electrons between the two closely emission states occurred. PMID:18468174

Wang, D; Liu, Y X; Liu, Y C; Xu, C S; Shao, C L; Li, X H

2008-03-01

187

Photoluminescence from Au ion-implanted nanoporous single-crystal 12CaO7Al2O3  

NASA Astrophysics Data System (ADS)

Implantation of Au+ ions into a single crystalline 12CaO7Al2O3 (C12A7) was performed at high temperatures with fluences from 11014 to 31016cm-2 . This material is composed of positively charged sub-nanometer-sized cages compensated by extra-framework negatively charged species. The depth profile of concentrations of Au species was analyzed using Rutherford backscattering spectrometry. The measured optical spectra and ab initio embedded cluster calculations show that the implanted Au species are stabilized in the form of negative Au- ions below the fluences of 11016cm-2 (Au volume concentration of 21021cm-3 ). These ions are trapped in the cages and exhibit photoluminescence (PL) bands peaking at 3.05 and 2.34eV at temperatures below 150K . At fluences exceeding 31016cm-2 , the implanted Au atoms form nano-sized clusters. This is manifested in quenching of the PL bands and creation of an optical absorption band at 2.43eV due to the surface plasmon of free carriers in the cluster. The PL bands are attributed to the charge transfer transitions (Au0+e-?Au-) due to recombination of photo-excited electrons (e-) , transiently transferred by ultraviolet excitation into a nearby cages, with Au0 atoms.

Miyakawa, Masashi; Kamioka, Hayato; Hirano, Masahiro; Kamiya, Toshio; Sushko, Peter V.; Shluger, Alexander L.; Matsunami, Noriaki; Hosono, Hideo

2006-05-01

188

Characterization and luminescence of Eu3+ ions doped 12CaO 7Al2O3 nanopowders.  

PubMed

Eu3+ ions doped 12CaO 7Al2O3 (C12A7) powders with different Eu3+ concentrations were prepared by sol-gel combined with solid state reaction method. The results of XRD and Raman spectra showed that single cubic phase polycrystalline C12A7:Eu3+ powders were prepared. The absorption peaks attributed to f-f transition of Eu3+ ion can be observed, indicating that Eu3+ had been incorporated into C12A7 lattice site. Visible PL peaks around 578, 588, 614 nm were ascribed to 5D0 --> 7FJ (J = 0, 1, 2) transitions of Eu3+ under the excitation of 488 nm line. The PL of C12A7:Eu3+ showed the strongest emission intensity at Eu3+ concentration of 0.5 at%. Two different types of Eu3+ centers were identified by the two lines from 5D0 --> 7F0 transition emission. The doping mechanism of C12A7:Eu3+ might be attributed to Eu3+ ions substitution for two types of Ca2+ lattice sites in C12A7. The temperature dependent PL spectra of Eu-doped C12A7 were measured in the range from 100 to 300 K under the excitation of 488 nm laser line. The PL intensities as a function of temperature were well fitted by using a unified theoretical model, considering thermal activation and nonradiative energy transfer processes. PMID:22413328

Liu, C G; Liu, Y X; Wang, D; Yan, D T; Xu, C S

2011-11-01

189

Spectroscopic characterization of a multiband complex oxide: Insulating and conducting cement 12CaO7Al2O3  

NASA Astrophysics Data System (ADS)

Natural 12CaO7Al2O3 (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. These measurements suggest the existence of a narrow conduction band between the main 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.

McLeod, J. A.; Buling, A.; Kurmaev, E. Z.; Sushko, P. V.; Neumann, M.; Finkelstein, L. D.; Kim, S.-W.; Hosono, H.; Moewes, A.

2012-01-01

190

Insulator -- polaron conductor -- metal transitions in a complex oxide 12CaO.7Al2O3.  

NASA Astrophysics Data System (ADS)

Recent experiments have demonstrated that a complex nano-porous oxide 12CaO.7Al2O3 (C12A7) built of positively charged sub-nanometer cages can be converted from a transparent insulator to a transparent conductor by H2 doping followed by UV-light irradiation with 4--4.5 eV photons [1]. This irradiation induces optical absorption bands with maxima at 0.4 eV and 2.8 eV and high concentrations of unpaired electrons. We use ab initio calculations to reveal the mechanism of photo-induced insulator--conductor transition and the role of H atoms in this process and to elucidate the transport properties of the electrons in this system as a function of electron concentration. Our theoretical modeling suggests that at concentration below 10^20 cm-3 electrons are responsible for the polaron type electrical conductivity with the activation energy close to 0.1 eV as well as for the optical absorption at 0.4 eV and 2.8 eV [2]. We demonstrate that, as the electron concentration exceeds 10^20 cm-3, the character of electronic conductivity changes from polaron type to metallic. [1] K. Hayashi et al., Nature 419, 462 (2002). [2] P.V. Sushko, et al., Phys. Rev. Lett. 91, 126401 (2003); P.V. Sushko et al., Appl. Phys. Lett. 86, 092101 (2005).

Sushko, P.; Shluger, A.; Stoneham, A.; Hayashi, K.; Matsuishi, S.; Hirano, M.; Hosono, H.

2006-03-01

191

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

SciTech Connect

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.

Park, Jae-Hyung [Department of Chemical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Oh, Seong-Geun [Department of Chemical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)], E-mail: seongoh@hanyang.ac.kr

2009-01-08

192

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

SciTech Connect

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.

Mishra, D. K.; Prusty, Sasmita; Mohapatra, B. K.; Singh, S. K.; Behera, S. N. [Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751 013, Odisha (India); Geological Survey of India, Alandi Road, Pune 411 006, Maharashtra (India); Mineralogy Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751 013, Odisha (India); Advanced Materials Technology Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751 013, Odisha (India); National Institute of Science and Technology (NIST), Berhampur 761 008, Odisha (India)

2012-07-23

193

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

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

194

A chromodomain protein encoded by the arabidopsis CAO gene is a plant-specific component of the chloroplast signal recognition particle pathway that is involved in LHCP targeting.  

PubMed Central

A recessive mutation in Arabidopsis, named chaos (for chlorophyll a/b binding protein harvesting-organelle specific; designated gene symbol CAO), was isolated by using transposon tagging. Characterization of the phenotype of the chaos mutant revealed a specific reduction of pigment binding antenna proteins in the thylakoid membrane. These nuclear-encoded proteins utilize a chloroplast signal recognition particle (cpSRP) system to reach the thylakoid membrane. Both prokaryotes and eukaryotes possess a cytoplasmic SRP containing a 54-kD protein (SRP54) and an RNA. In chloroplasts, the homolog of SRP54 was found to bind a 43-kD protein (cpSRP43) rather than to an RNA. We cloned the CAO gene, which encodes a protein identified as Arabidopsis cpSRP43. The product of the CAO gene does not resemble any protein in the databases, although it contains motifs that are known to mediate protein-protein interactions. These motifs include ankyrin repeats and chromodomains. Therefore, CAO encodes an SRP component that is unique to plants. Surprisingly, the phenotype of the cpSRP43 mutant (i.e., chaos) differs from that of the Arabidopsis cpSRP54 mutant, suggesting that the functions of the two proteins do not strictly overlap. This difference also suggests that the function of cpSRP43 is most likely restricted to protein targeting into the thylakoid membrane, whereas cpSRP54 may be involved in an additional process(es), such as chloroplast biogenesis, perhaps through chloroplast-ribosomal association with chloroplast ribosomes. PMID:9878634

Klimyuk, V I; Persello-Cartieaux, F; Havaux, M; Contard-David, P; Schuenemann, D; Meiherhoff, K; Gouet, P; Jones, J D; Hoffman, N E; Nussaume, L

1999-01-01

195

Selective N 2 O Removal from the Process Gas of Nitric Acid Plants Over Ceramic 12CaO7Al 2 O 3 Catalyst  

Microsoft Academic Search

Catalytic high temperature decomposition (secondary abatement) of nitrous oxide over calcium aluminate 12CaO7Al2O3 (mayenite) was studied in the model laboratory tests (TPSR) and pilot units (steady-state) using the real feed. X-ray diffraction\\u000a (XRD), scanning electron microscopy (SEM), N2-sorption (BET), electron paramagnetic resonance (EPR) and Raman spectroscopies were used to characterize the synthesized\\u000a material. The catalyst exhibited high efficiency and selectivity

Monika Ruszak; Marek Inger; Stefan Witkowski; Marcin Wilk; Andrzej Kotarba; Zbigniew Sojka

2008-01-01

196

Heat requirements in a calciner of CaCO 3 integrated in a CO 2 capture system using CaO  

Microsoft Academic Search

Several systems for CO2 capture using CaO as regenerable sorbent are under development. In addition to a carbonation step, they all need a regeneration step (calcination of CaCO3) to produce a concentrated stream of CO2. Different options for calcination may be possible, but they all share common operating windows that appear when the mass and heat balances in the system

N. Rodriguez; M. Alonso; G. Grasa; J. Carlos Abanades

2008-01-01

197

An Electro-Deposited IrOx Thin Film pH Sensor C. M. Nguyen, H. Cao, W. D. Huang, and J.-C. Chiao  

E-print Network

pH levels with indicators such as neutral red or umbelliferone are limited for in-situ experiments solutions with different pH levels of 2, 4, 7, 10 were used to test the performance. A unit-gain bufferAn Electro-Deposited IrOx Thin Film pH Sensor C. M. Nguyen, H. Cao, W. D. Huang, and J.-C. Chiao

Chiao, Jung-Chih

198

Combustion synthesis of porous glasses and ceramics for bone repair.  

PubMed

Porous bioactive materials with constituents such as CaO, P2O5, SiO2, MgO, K2O, Na2O implanted in bone can activate a biologic response to enhance bone healing. These biomaterials are currently formed utilizing wet chemistry, plasma spray, D-gun, sintering, and diffusion bond techniques. This work investigates the use of self propagating high temperature combustion synthesis (SHS) in the creation of porous bioactive glasses for bone repair. The use of combustion synthesis has many advantages over the methods mentioned previously. The primary advantages are the ability to control the process to provide specified porosity (% porosity, pore size distribution, interconnected pores, functionally grading of porosity), structural mechanical properties, together with rapid production of the material. The focus of this project is the investigation of combustion synthesis reactions based on the reaction system 3CaO + P2O5==>Ca3(PO4)2 and incorporating other known biocompatible constituents into the reaction. PMID:11347436

Castillo, M; Ayers, R A; Zhang, X; Schowengerdt, F; Moore, J J

2001-01-01

199

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

200

A comparison of the chemical composition and bioactive ingredients of the Chinese medicinal mushroom DongChongXiaCao, its counterfeit and mimic, and fermented mycelium of Cordyceps sinensis  

Microsoft Academic Search

The Chinese herbal drug DongChongXiaCao, a medicinal and edible mushroom originating from the fungus Cordyceps sp., has been developed into health foods. Counterfeit and mimic types are frequently found in markets. Mycelial preparations of Cordyceps sinensis, via submerged fermentation, have been commercialized and also named DongChongXiaCao. This investigation endeavours to characterize the proximate composition, amino acid profiles, and contents of

Tai-Hao Hsu; Li-Hua Shiao; Chienyan Hsieh; Der-Ming Chang

2002-01-01

201

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)

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.

Chadwick, K.; Asner, G. P.

2012-12-01

202

Strain and interface effects on the magnetic and transport properties of La0.7Ca0.3MnO3/CaO multilayers  

NASA Astrophysics Data System (ADS)

La0.7Ca0.3MnO3/CaO (LCMO/CaO) multilayers were deposited on (100) LaAlO3 substrates by pulsed injection metal organic chemical vapour deposition. The samples were characterised by X-ray diffraction, transport and magnetization measurements. An anomalous behaviour of the electrical resistance under applied magnetic field and an exchange bias effect for the magnetization are observed for the multilayers with thinner LCMO layers. These results suggest the existence of a short range antiferromagnetic coupling at the layer interfaces.

Casaca, A.; Borges, R. P.; Ferreira, P.; Saraiva, A.; Rosa, M. A.; da Silva, R. C.; Nunes, W. C.; Magalhes, S.; Godinho, M.

2009-03-01

203

High-intensity atomic oxygen radical anion emission mechanism from 12CaO7Al 2O 3 crystal surface  

NASA Astrophysics Data System (ADS)

12CaO 7Al 2O 3 (C12A7) crystal is an interesting material where a large amount of O -(c) and O 2-(c) can be formed and trapped in the cages when it is sintered in dry oxygen. The emissive features of this material including the emission species, temperature dependence, field dependence, emission branch ratio, emission stability, the effects of water on the emission intensity, have been investigated. The temperature and oxygen pressure dependences of the electrical conductivity have also been measured. The mechanisms of the O - emission have been discussed based on the investigations of the emission and electrical conductivity features.

Li, Quanxin; Hosono, Hideo; Hirano, Masahiro; Hayashi, Katsuro; Nishioka, Masateru; Kashiwagi, Hideo; Torimoto, Yoshifumi; Sadakata, Masayoshi

2003-03-01

204

Electronic insulator-conductor conversion in hydride ion-doped 12CaO.7Al2O3 by electron-beam irradiation  

Microsoft Academic Search

We report formation of persistent carrier electrons in hydride ion (H-)-incorporated 12CaO.7Al2O3 (C12A7) by electron-beam irradiation. The electrical conductivity of H--doped C12A7 single crystals increases with the electron-beam irradiation dose, accompanied with a green coloration attributable to a carrier electron formation. A 25 keV electron beam with a dose of ~500 muC cm-2 fully converts the conductivity in surface layers

Katsuro Hayashi; Yoshitake Toda; Toshio Kamiya; Masahiro Hirano; Minako Yamanaka; Isao Tanaka; Takahisa Yamamoto; Hideo Hosono

2005-01-01

205

Zircon LA-ICP-MS UPb age, Ce 4+ \\/Ce 3+ ratios and the geochemical features of the Machangqing complex associated with copper deposit  

Microsoft Academic Search

The Machangqing complex is composed of early syenitic-monzonitic porphyry and late granite-porphyry. Geochemically, they are\\u000a similar in major and trace element characteristics, and are characterized by relatively low TiO2 ( 2O5 (2O + Na2O > 8% ), with K2O\\/Na2O > 1, the absence of significant Eu anomaly and pronounced negative anomalies in Nb, Ta, Ti, and enrichment in large-ion\\u000a lithophile

Liang Huaying; Yu Hengxiang; Mo Cehui; Zhang Yuquan; Xie Yingwen

2006-01-01

206

The effects of Mn2+ doping on the luminescence properties of 12CaO 7Al2O:Eu2+ nanocrystal phosphor.  

PubMed

The long lasting blue phosphorescence (LLP) and photostimulated luminescence (PSL) after ultraviolet light irradiation at room temperature in 12CaO 7Al2O3:xEu2+, yMn2+ (x = 0, 0.001; y = 0, 0.01) prepared by the chemical co-precipitation method were observed. It was shown that novel oxide 12CaO 7Al2O3:Eu2+, Mn2+ (C12A7:Eu2+, Mn2+) with unique nanocage structure can store energy when irradiated with 365 nm photons. And photon energy can be subsequently released by exposed to 980 nm light. The codopant Mn2+ enhances the intensity of the persistent phosphorescence and PSL due to the existence of more shallow and new deeper electron traps in C12A7: Eu2+, Mn2+. A model for energy storing and recovering and the detailed mechanism of PSL are presented through comparing with the luminescence properties of the co-doped C12A7:Eu2+, Mn2+ and C12A7:Eu2+. PMID:22413331

Yan, X L; Liu, Y X; Yan, D T; Zhu, H C; Liu, C G; Xu, C S

2011-11-01

207

Low-degree melting of a metasomatized lithospheric mantle for the origin of Cenozoic Yulong monzogranite-porphyry, east Tibet: Geochemical and SrNdPbHf isotopic constraints  

Microsoft Academic Search

SHRIMP zircon UPb dating, mineral chemical, element geochemical and SrNdPbHf isotopic data have been determined for the Yulong monzogranite-porphyry in the eastern Tibet, China. The Yulong porphyry was emplaced into Triassic strata at about 39 Ma. The rocks are weakly peraluminous and show shoshonitic affinity, i.e., alkalis-rich, high K2O contents with high K2O\\/Na2O ratios, enrichment in LREE and LILE. They

Yao-Hui Jiang; Shao-Yong Jiang; Hong-Fei Ling; Bao-Zhang Dai

2006-01-01

208

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

NASA Astrophysics Data System (ADS)

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 ~870C 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 800-900C 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.

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

2011-12-01

209

Electronic insulator-conductor conversion in hydride ion-doped 12CaO7Al2O3 by electron-beam irradiation  

NASA Astrophysics Data System (ADS)

We report formation of persistent carrier electrons in hydride ion (H-)-incorporated 12CaO7Al2O3 (C12A7) by electron-beam irradiation. The electrical conductivity of H--doped C12A7 single crystals increases with the electron-beam irradiation dose, accompanied with a green coloration attributable to a carrier electron formation. A 25 keV electron beam with a dose of 500?Ccm-2 fully converts the conductivity in surface layers to the depth of 4?m. Carrier electron formation is most likely due to electron-hole pairs generated in the electron excitation volume and subsequent energy transfer to the H- ions. The estimated carrier formation yield per an incident electron is 30. These findings may enable a fine patterning of the conductive area without photomasks and photoresists.

Hayashi, Katsuro; Toda, Yoshitake; Kamiya, Toshio; Hirano, Masahiro; Yamanaka, Minako; Tanaka, Isao; Yamamoto, Takahisa; Hosono, Hideo

2005-01-01

210

Evidence for Bardeen-Cooper-Schrieffer-type superconducting behavior in the electride (CaO)12(Al2O3)7:e- from heat capacity measurements  

NASA Astrophysics Data System (ADS)

The heat capacity of the single crystalline electride of (CaO)12(Al2O3)7:e- (C12A7:e-) with Tc=0.2K was larger than that of electron-undoped C12A7 in the temperature range 0.085-5K , reflecting the metallic nature of the electride. A superconducting transition was detected as a heat capacity jump ?Cp=3.4mJmol-1K-1 , and the profile and magnitude of ?Cp agreed well with those expected from the BCS theory. The electron-phonon coupling constant (?0.46) and Debye temperature (?D630K) were much larger than those for alkali metals having s -like conduction electrons as in the present electride, suggesting that electrides having a rigid structure will be a class of BCS superconductors.

Kohama, Yoshimitsu; Kim, Sung Wng; Tojo, Takeo; Kawaji, Hitoshi; Atake, Tooru; Matsuishi, Satoru; Hosono, Hideo

2008-03-01

211

Effect of H2O on NO Reduction over NSR Catalyst 12CaO7Al2O3/10%K  

NASA Astrophysics Data System (ADS)

A novel NOx storage/reduction catalyst 12CaO7Al2O3/10%K, defined as C12A7/K, was prepared, which possesses good NOx storage/reduction ability with a high sulfur-tolerance. The effect of H2O on the NO reduction features over the C12A7/K catalyst was investigated. The NO conversion and the N2 selectivity were measured as a function of temperature and H2O concentration. In the presence of 1.2% H2O, both the NO conversion and the N2 selectivity significantly decrease at lower temperature region (< 500C). At temperatures over 500C, however, the NO reduction is only slightly influenced by H2O. The species of NO3-/NO2- are confirmed as main storage components in the C12A7/K catalyst, which are further reduced into N2 by H2 under the reduction conditions.

Gao, Ai-mei; Wang, Hua-jing; Tu, Jing; Li, Quan-xin

2006-12-01

212

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

NASA Astrophysics Data System (ADS)

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.

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

2005-02-01

213

Generation of negative ions in the gas phase from a 12CaO.7Al2O3 membrane-coated ceramic heater under atmospheric pressure  

NASA Astrophysics Data System (ADS)

12CaO?7Al2O3 (C12A7) crystal is able to generate strong and high purity oxygen anion (O-) beam under reduced pressure. However, the emission of O- or related species under atmospheric pressure has not been evaluated. In this study, the characteristics of negative ion species emissions from the C12A7 membrane-coated ceramic heater under atmospheric pressure were investigated by quadrupole mass spectrometer. Negative ion species were confirmed to be emitted even under atmospheric pressure. It was supposed that the detected negative ion clusters, such as O-(H2O)n, O2-(H2O)n, and CO4-(H2O)n, were generated by the reaction of negative ions emitted from the heater with impurities in He gas.

Yamamoto, Mitsuo; Shima, Akio; Nishioka, Masateru; Sadakata, Masayoshi

2008-12-01

214

On the magnetic and spectroscopic properties of high-valent Mn3CaO4 cubanes as structural units of natural and artificial water-oxidizing catalysts.  

PubMed

The Mn(IV)3CaO4 cubane is a structural motif present in the oxygen-evolving complex (OEC) of photosystem II and in water-oxidizing Mn/Ca layered oxides. This work investigates the magnetic and spectroscopic properties of two recently synthesized complexes and a series of idealized models that incorporate this structural unit. Magnetic interactions, accessible spin states, and (55)Mn isotropic hyperfine couplings are computed with quantum chemical methods and form the basis for structure-property correlations. Additionally, the effects of oxo-bridge protonation and one-electron reduction are examined. The calculated properties are found to be in excellent agreement with available experimental data. It is established that all synthetic and model Mn(IV)3CaO4 cubane complexes have the same high-spin S = (9)/2 ground state. The magnetic coupling conditions under which different ground spin states can be accessed are determined. Substitution of Mn(IV) magnetic centers by diamagnetic ions [e.g., Ge(IV)] allows one to "switch off" specific spin sites in order to examine the magnetic orbitals along individual Mn-Mn exchange pathways, which confirms the predominance of ferromagnetic interactions within the cubane framework. The span of the Heisenberg spin ladder is found to correlate inversely with the number of protonated oxo bridges. Energetic comparisons for protonated models show that the tris-?-oxo bridge connecting only Mn ions in the cubane has the lowest proton affinity and that the average relaxation energy per additional proton is on the order of 18 kcalmol(-1), thus making access to ground states other than the high-spin S = (9)/2 state in these cubanes unlikely. The relevance of these cubanes for the OEC and synthetic oxides is discussed. PMID:23527603

Krewald, Vera; Neese, Frank; Pantazis, Dimitrios A

2013-04-17

215

Constant threshold resistivity in the metal-insulator transition of VO2 J. Cao,1,2 W. Fan,1,3 K. Chen,4 N. Tamura,4 M. Kunz,4 V. Eyert,5 and J. Wu1,2,*  

E-print Network

Constant threshold resistivity in the metal-insulator transition of VO2 J. Cao,1,2 W. Fan,1,3 K December 2010 We report a constant threshold resistivity observed for the insulating phase of VO2 before of the insulating phase. Such a constant threshold resistivity suggests that a constant critical free

Wu, Junqiao

216

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

NASA Astrophysics Data System (ADS)

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 ?g g- 1 range (e.g., 140 ?g g- 1 for Na2O, 31 ?g g- 1 for Al2O3, and 8.9 ?g 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.

Ichikawa, Shintaro; Nakamura, Toshihiro

2014-06-01

217

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

NASA Technical Reports Server (NTRS)

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).

Righter, K.; Ghiorso, M.

2009-01-01

218

Novel systems for tailored neurotrophic factor release based on hydrogel and resorbable glass hollow fibers.  

PubMed

A novel system for the release of neurotrophic factor into a nerve guidance channel (NGC) based on resorbable phosphate glass hollow fibers (50P2O5-30CaO-9Na2O-3SiO2-3MgO-2.5K2O-2.5TiO2 mol%) in combination with a genipin-crosslinked agar/gelatin hydrogel (A/G_GP) is proposed. No negative effect on the growth of neonatal olfactory bulb ensheathing cell line (NOBEC) as well as on the expression of pro- and anti-apoptotic proteins was measured in vitro in the presence of fiber dissolution products in the culture medium. For the release studies, fluorescein isothiocyanate-dextran (FD-20), taken as growth factor model molecule, was solubilized in different media and introduced into the fiber lumen exploiting the capillary action. The fibers were filled with i) FD-20/phosphate buffered saline (PBS) solution, ii) FD-20/hydrogel solution before gelation and iii) hydrogel before gelation, subsequently lyophilized and then filled with the FD-20/PBS solution. The different strategies used for the loading of the FD-20 into the fibers resulted in different release kinetics. A slower release was observed with the use of A/G_GP hydrogel. At last, poly(?-caprolactone) (PCL) nerve guides containing the hollow fibers and the hydrogel have been fabricated. PMID:24433883

Novajra, G; Tonda-Turo, C; Vitale-Brovarone, C; Ciardelli, G; Geuna, S; Raimondo, S

2014-03-01

219

High-Temperature Viscosity of Commercial Glasses  

SciTech Connect

Arrhenius models were developed for glass viscosity within the processing temperature of six types of commercial glasses: low-expansion-borosilicate glasses, E glasses, fiberglass wool glasses, TV panel glasses, container glasses, and float glasses. Both local models (for each of the six glass types) and a global model (for the composition region of commercial glasses, i.e., the six glass types taken together) are presented. The models are based on viscosity data previously obtained with rotating spindle viscometers within the temperature range between 900 C and 1550 C; the viscosity varied from 1 Pa?s to 750 Pa?s. First-order models were applied to relate Arrhenius coefficients to the mass fractions of 15 components: SiO2, TiO2, ZrO2, Al2O3, Fe2O3, B2O3, MgO, CaO, SrO, BaO, PbO, ZnO, Li2O, Na2O, K2O. The R2 is 0.98 for the global model and ranges from .097 to 0.99 for the six local models. The models are recommended for glasses containing 42 to 84 mass% SiO2 to estimate viscosities or temperatures at a constant viscosity for melts within both the temperature range from 1100 C to 1550 C and viscosity range from 5 to 400 Pa?s.

Hrma, Pavel R.

2006-08-31

220

Fluorescence properties of Eu3+-doped alumino silicate glasses  

NASA Astrophysics Data System (ADS)

Alumino silicate glasses of a very broad range of molar compositions doped with 1 ? 1020 Eu3+ cm-3 (about 0.2 mol% Eu2O3) were prepared. As network modifier oxides Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, PbO, Y2O3 and La2O3 have been used. All glasses show relatively broad fluorescence excitation and emission spectra. For most glasses only a weak effect of the glass composition on the excitation and emission spectra is observed. Although the glasses should be structurally similar, notable differences are found for the fluorescence lifetimes. These increase steadily with decreasing mean atomic weight, decreasing refractive index and decreasing optical basicity of the glasses, which may be explained by local field effects. An exception from this rule are the strontium, barium and potassium containing glasses, which show significantly increased fluorescence lifetimes despite of their high refractive index, optical basicity and molecular weight. The non mono-exponential fluorescence decay curves as well as the fluorescence spectra indicate a massive change in the local surroundings of the doped rare earth ions for these glasses.

Herrmann, Andreas; Kuhn, Stefan; Tiegel, Mirko; Rssel, Christian

2014-11-01

221

A Structurally Based Viscosity Model for Oxide Melts  

NASA Astrophysics Data System (ADS)

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).

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

2014-04-01

222

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

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

223

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

PubMed

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

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

2011-09-01

224

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

NASA Astrophysics Data System (ADS)

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.

Rapti-Caputo, Dimitra

2010-05-01

225

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

226

Reactions of yttria-stabilized zirconia with oxides and sulfates of various elements  

NASA Technical Reports Server (NTRS)

The reactions between partially stabilized zirconia, containing 8 weight-percent yttria, and oxides and sulfates of various elements were studied at 1200, 1300, and 1400 C for times to 800, 400, and 200 hours, respectively. These oxides and sulfates represent impurities and additives potentially present in gas turbine fuels or impurities in the turbine combustion air as well as the elements of the substrate alloys in contact with zirconia. Based on the results, these compounds can be classified in four groups: (1) compounds which did not react with zirconia (Na2SO4, K2SO4, Cr2O3, Al2O3 and NiO); (2) compounds that reached completely with both zirconia phases (CaO, BaO, and BaSO4); (3) compounds that reacted preferentially with monoclinic zirconia (Na2O, K2O, CoO, Fe2O3, MgO, SiO2, and ZnO); and (4) compounds that reacted preferentially with cubic zirconia (V2O5, P2O5).

Zaplatynsky, I.

1978-01-01

227

A Statistical Framework for Calculating and Assessing Compositional Linear Trends Within Fault Zones: A Case Study of the NE Block of the Clark Segment, San Jacinto Fault, California, USA  

NASA Astrophysics Data System (ADS)

Utilizing chemical data derived from the various fault zone architectural components of the Clark strand of the San Jacinto fault, southern California, USA, we apply for the first time non-central principal component analysis to calculate a compositional linear trend within molar A-CN-K space. In this procedure A-CN-K are calculated as the molar proportions of Al2O3 (A), CaO* + Na2O (CN), and K2O (K) in the sum of molar Al2O3, Na2O, CaO*, and K2O. CaO* is the molar CaO after correction for apatite. We then derive translational invariant chemical alteration intensity factors, t, for each architectural component through orthogonal projection of analyzed samples onto the compositional linear trend. The chemical alteration intensity factor t determines the relative change in composition compared to the original state (i.e., the composition of the altered wall rocks). It is dependent on the degree of intensity to which the process or processes responsible for the change in composition of each architectural component has been active. These processes include shearing, fragmentation, fluid flow, and generation of frictional heat. Non-central principal component analysis indicates that principal component 1 explains 99.7 % of the spread of A-CN-K data about the calculated compositional linear trend (i.e., the variance). The significance level for the overall one-way analysis of variance (ANOVA) is 0.0001. Such a result indicates that at least one significant difference across the group of means of t values is different at the 95 % confidence level. Following completion of the overall one-way ANOVA, the difference in means t test indicated that the mean of the t values for the fault core are different than the means obtained from the transition and damage zones. In contrast, at the 95 % confidence level, the means of the t values for the transition and damage zones are not statistically distinguishable. The results of XRD work completed during this study revealed that the <2 m fraction is composed primarily of illite/smectite with ~15 % illite in the damage zone, of illite/smectite with ~30 % illite in the transition zone, and of discreet illite with very minor smectite in the fault core. These changes parallel the increasing values of the chemical alteration intensity factors (i.e., t). Based on the above results, it is speculated that when fault zones are derived from tonalitic wall rocks at depths of ~400 100 m, the onset of the illite/smectite to illite conversion will occur when t values exceed 0.20 0.12, the average chemical alteration intensity factor calculated for the transition zone. Under such conditions during repeated rupturing events, frictional heat is produced and acidic fluids with elevated temperatures (? ~125 C) are flushed through the fault core. Over time, the combination of shearing, fragmentation, and frictionally elevated temperatures eventually overcomes the kinetic barrier for the illite/smectite to illite transition. Such settings and processes are unique to fault zones, and as a result, they represent an underappreciated setting for the development of illite from illite/smectite. The success of non-central principal component analysis in this environment offers the first statistically rigorous methodology for establishing the existence of compositional linear trends in fault zones. This method also derives quantifiable alteration intensity factors that could potentially be used to compare the intensity of alteration at different segments of a fault, as well as offer a foundation to interpret the potential driving forces for said alteration and differences therein.

Rockwell, Brian G.; Girty, Gary H.; Rockwell, Thomas K.

2014-05-01

228

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

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

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

2013-10-01

229

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

NASA Astrophysics Data System (ADS)

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.

Regos, Adriana N.; Ardelean, I.

2011-12-01

230

Luminescence and energy transfer characteristics of Ce3+- and Tb3+-codoped nanoporous 12CaO 7Al2O3 phosphors.  

PubMed

The novel green-emitting phosphors of 12CaO 7Al2O3:Ce3+ , Tb3+ (C12A7:Ce3+, Tb3+) were synthesized by a solid-state reaction. Upon the excitation of Ce3+ at 350 nm, the C12A7:Ce3+, Tb3+ phosphor shows intense green emissions located at 543 nm assigning to 5D4-7F5 transitions of Tb3+ ions, and weak blue emissions centered at 434 nm due to the transitions of Ce3+ 5d-4f. The photoluminescence (PL) intensity of Ce3+ decrease with increasing Tb3+ concentration, indicating the effective energy transfer (ET) occurred from Ce3+ to Tb3+ in C12A7:Ce3+, Tb3+. The ET efficiency between Ce3+ and Tb3+ in the optimum composition reaches to 99%. Based on Dexter's ET theory, we have demonstrated that the efficient ET is a resonant type via dipole-dipole mechanism with an energy transfer critical distance of 4.02 A. Our results suggested that C12A7:Ce3+, Tb3+ phosphor would be a promising green-emitting phosphor for UV-converting white light-emitting diodes. PMID:22413329

Liu, X L; Liu, Y X; Yan, D T; Zhu, H C; Liu, C G; Xu, C S

2011-11-01

231

Synthesis and luminescence properties of Ce 3+ doped nanoporous 12CaO7Al 2O 3 powders and ceramics  

NASA Astrophysics Data System (ADS)

Ce 3+ doped nanoporous 12CaO7Al 2O 3 (C12A7) was synthesized using the self-propagating combustion method and solid state reaction. Ceramics of high density were produced using the melt-solidification process in a carbon crucible. The obtained samples were characterized using XRD and SEM methods and studied by means of low temperature time resolved luminescence under laser and synchrotron radiation excitation. It was shown that the Ce 3+ ion in C12A7 emits broad-band 5d-4f luminescence peaked at 3.0 eV. The decay curves of Ce 3+ emission in the studied samples have complicated nature depending on the excitation energy with the main decay component of 20-30 ns life time, typical for parity and spin allowed transitions of Ce 3+. The emission of Ce 3+ ions is efficiently excited through the intra-centre as well as in the intrinsic absorption region of C12A7.

Tldsepp, E.; Avarmaa, T.; Denks, V.; Feldbach, E.; Kirm, M.; Maaroos, A.; Mndar, H.; Vielhauer, S.

2010-06-01

232

Nanoporous crystal 12CaO.7Al2O3: a playground for studies of ultraviolet optical absorption of negative ions.  

PubMed

A novel nanoporous material 12CaO.7Al2O3 (C12A7) offers a possibility of incorporating large concentrations (>1021 cm-3) of a wide range of extraframework anions inside its nanopores. We have investigated, both experimentally and theoretically, optical absorption associated with several types of such anions, including F-, OH-, O-, O2-, O2-, and O22-, and assigned their optical absorption bands. It is demonstrated that the chemical identity and concentration of extraframework anions can be controlled by an appropriate treatment of "as grown" C12A7. We also show that the position of the adsorption edge is, in turn, determined by the chemical identity of the extraframework species and can be varied in the range of approximately 4-6 eV. We suggest that C12A7 is a unique host material, which can be used as a playground for studying negatively charged species that are unstable in other environments. PMID:17269815

Hayashi, Katsuro; Sushko, Peter V; Ramo, David Muoz; Shluger, Alexander L; Watauchi, Satoshi; Tanaka, Isao; Matsuishi, Satoru; Hirano, Masahiro; Hosono, Hideo

2007-03-01

233

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

234

Characterization of the chemical constituents in Da-Huang-Gan-Cao-Tang by liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry and liquid chromatography coupled with ion trap mass spectrometry.  

PubMed

In this work, the chemical constituents in Da-Huang-Gan-Cao-Tang, a traditional Chinese formula, were studied by liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry and liquid chromatography coupled with ion trap mass spectrometry for the first time. Among the 146 compounds detected in Da-Huang-Gan-Cao-Tang, 104 compounds were identified unambiguously or tentatively based on their accurate molecular weight and multistage MS data, including one potential novel compound and two reported in Glycyrrhiza genus for the first time. The possible fragmentation pathways were proposed and fragmentation rules of the major types of compounds were concluded. This study provided an example to facilitate the tedious identification of chemical composition in traditional Chinese medicine, and maybe a promising reference approach to research the analogous formulae. PMID:24771648

Wang, Shufang; Chen, Pinghong; Xu, Yimin; Li, Xiaodong; Fan, Xiaohui

2014-07-01

235

Role of CaO addition in the local order around Erbium in SiO2GeO2P2O5 fiber preforms F. d'Acapito C. Maurizio  

E-print Network

properties of erbium ions. To our knowledge only few studies on nano-structured silica fibers were dedicatedRole of CaO addition in the local order around Erbium in SiO2­GeO2­P2O5 fiber preforms F. d in present technology. In this contribution we present a study on Er-doped fiber preforms where particular

Boyer, Edmond

236

Investigation of the influence of CaS, CaO and CaF 2 fillers on the transfer and wear of nylon by microscopy and XPS analysis  

Microsoft Academic Search

The effect of CaS, CaO and CaF2 fillers on the transfer, friction and wear behaviors of nylon was studied. Sliding was performed in ambient atmosphere at a speed of 1.0 m s?1 and a load of 19.6 N, and a pin-on-disk configuration was used. The filler content in nylon was fixed at 35% by volume. The counterface disk was made

S. Bahadur; Deli Gong; James Anderegg

1996-01-01

237

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

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

Barto?ov, Lucie; Klika, Zden?k

2014-07-01

238

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

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

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

2004-10-01

239

The dissolution of natural and artificial dusts in glutamic acid  

NASA Astrophysics Data System (ADS)

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.

Ling, Zhang; Faqin, Dong; Xiaochun, He

2014-08-01

240

The geochemistry and genesis of the granitoids of Sirohi, Rajasthan, India  

NASA Astrophysics Data System (ADS)

The granitoids were emplaced into metasediments of the Delhi Super Group. The Erinpura rapakivi granite (ERG) is a coarse grained rock and contains megacrysts of alkali feldspar. Chemically, it can be characterized by relatively low SiO 2 but high TiO 2, MgO and CaO. The Balda leucogranite (BLG) on the other hand is a medium grained rock and is chemically characterized by high SiO 2 and K 2O in excess of Na 2O, but distinctly low in CaO. Tungsten mineralization occurs in the form of fissure veins within the Balda leucogranite. The petrographic and petrochemical features of the granites suggest that the magmatic evolution was by fractional crystallization of parent magma generated by partial melting of the crustal rocks. The formation of megacrysts of alkali feldspar of the Erinpura granite seems to be caused by potash metasomatism (influx of K-solution, differentiation product of the parent magma). Ovoids of feldspars present indicate that potash and soda-metasomatisms had occurred during the formation of the rapakivi structure in the Erinpura granite. The Balda leucogranite is enriched in volatile elements and has low K/Rb and Ba/Rb ratios whereas Rb/Sr is high. Trace element study supports the view that the parent magma of the Balda granite was fractionated and enriched in volatile contents at the end stage of its evolution. From the REE studies of the granites it is found that ERG represents the early crystallized phase but the BLG solidified from the residual liquid after the fractional crystallization. The Sm/Nd ratio in BLG is higher than ERG. This indicates that there was a major fractionation of Sm and Nd during the genesis of the granites. The chemical variation within the two plutons studied support an in-situ crystal fractionation model combined with a variable degree of metasomatism of ERG after its emplacement.

Naik, M. S.

241

Hydride ion as a two-electron donor in a nanoporous crystalline semiconductor 12CaO.7Al2O3.  

PubMed

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

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

2005-12-22

242

Preparation and Characterization of Storage and Emission Functional Material of Cs2O-doped 12CaO7Al2O3  

NASA Astrophysics Data System (ADS)

We provides a novel approach to generate low-temperature atomic oxygen anions (O-) emission using the cesium oxide-doped 12CaO7Al2O3 (Cs2O-doped C12A7). The maximal emission intensity of O- from the Cs2O-doped C12A7 at 700 C and 800 V/cm reached about 0.54 ?A/cm2, which was about two times as strong as that from the un-doped C12A7 (0.23 ?A/cm2) under the same condition. The initiative temperature of the O- emission from the Cs2O-doped C12A7 was about 500 C, which was also much lower than the initiative temperature from the un-doped C12A7 (570 C) in the given field of 800 V/cm. High pure O- emission close to 100% could be obtained from the Cs2O-doped C12A7 under the lower temperature (<550C). The emission features of the Cs2O-doped C12A7, including the emission distribution, temperature effect, and emission branching ratio have been investigated in detail and compared with the un-doped C12A7. The structure and storage characteristics of the resulting material were also investigated via X-ray diffraction and electron paramagnetic resonance. It was found that doping Cs2O to C12A7 will lower the initiative emission temperature and enhance the emission intensity.

Ning, Shen; Shen, Jing; Li, Xing-long; Li, Quan-xin

2011-06-01

243

Abundances and distribution of minerals and elements in high-alumina coal fly ash from the Jungar Power Plant, Inner Mongolia, China  

USGS Publications Warehouse

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.

Dai, S.; Zhao, L.; Peng, S.; Chou, C.-L.; Wang, X.; Zhang, Y.; Li, D.; Sun, Y.

2010-01-01

244

Curriculum Vitae Hui Cao 1 Hui Cao Aug. 22, 2013  

E-print Network

and B. Redding, "Multimode Optical Fiber Spectrometer", International patent application. Book and book-loss modes in deformed microdisks, Chapter 4 in "Trends in Nano- and Micro-Cavities," ed. O'Dae Kwon ultralow-loss modes in deformed microdisks", Chapter 4 in "Trends in Nano- and Micro-Cavities", ed. O' Dae

Cao, Hui

245

Petrogenesis of syntectonic granites emplaced at the transition from thrusting to transcurrent tectonics in post-collisional setting: Whole-rock and Sr-Nd-Pb isotope geochemistry in the Neoproterozoic Quatro Ilhas and Mariscal Granites, Southern Brazil  

NASA Astrophysics Data System (ADS)

The Neoproterozoic post-collisional period in southern Brazil (650-580 Ma) is characterized by substantial volumes of magma emplaced along the active shear zones that compose the Southern Brazilian Shear Belt. The early-phase syntectonic magmatism (630-610 Ma) is represented by the porphyritic, high-K, metaluminous to peraluminous Quatro Ilhas Granitoids and the younger heterogranular, slightly peraluminous Mariscal Granite. Quatro Ilhas Granitoids include three main petrographic varieties (muscovite-biotite granodiorite mbg; biotite monzogranite bmz; and leucogranite lcg) that, although sharing some significant geochemical characteristics, are not strictly comagmatic, as shown by chemical and Sr-Nd-Pb isotope data. The most primitive muscovite-biotite granodiorite was produced by contamination of more mafic melts (possibly with some mantle component) with peraluminous crustal melts; the biotite monzogranite, although more felsic, has higher Ca, MgO, TiO2 and Ba, and lower K2O, FeOt, Sr and Rb contents, possibly reflecting some mixing with coeval mafic magmas of tholeiitic affinity; the leucogranite may be derived from pure crustal melts. The Mariscal Granite is formed by two main granite types which occur intimately associated in the same pluton, one with higher K (5-6.5 wt.% K2O) high Rb and lower CaO, Na2O, Ba and Zr as compared to the other (3-5 wt.% of K2O). The two Mariscal Granite varieties have compositional correspondence with fine-grained granites (fgg) that occur as tabular bodies which intruded the Quatro Ilhas Granoitoids before they were fully crystallized, and are inferred to correspond to the Mariscal Granite feeders, an interpretation that is reinforced by similar U-Pb zircon crystallization ages. The initial evolution of the post-collisional magmatism, marked by the emplacement of the Quatro Ilhas Granitoids varieties, activated sources that produced mantle and crustal magmas whose emplacement was controlled both by flat-lying and transcurrent structures. The transition from thrust to transcurrent-related tectonics coincides with the increase in the proportion of crustal-derived melts. The transcurrent tectonics seems to have played an essential role in the generation of mantle-derived magmas and may have facilitated their interaction with crustal melts which seem to be to a large extent the products of reworking of orthogneiss protoliths.

Florisbal, Luana Moreira; Bitencourt, Maria de Ftima; Janasi, Valdecir de Assis; Nardi, Lauro Valentim Stoll; Heaman, Larry M.

2012-11-01

246

J Therm Anal Calorim (2013) p: 18 DOI 10.1007/s10973-013-3280-3  

E-print Network

entropy of bioactive glasses and Zn-doped glasses E. Wers, H. Oudadesse () Received: 22 March 2013 Général Leclerc, 35042 Rennes Cedex, France Abstract Bioactive glasses prepared in SiO2­CaO­Na2O and P2O5 characteristics (Tg, Tc and Tf) of pure bioactive glass elaborated with different amounts of CaO, Na2O in pure

Paris-Sud XI, Université de

247

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)

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.

Zhou, Yanyan; Zhai, Mingguo; Zhao, Taiping; Lan, Zhongwu; Sun, Qianying

2014-11-01

248

Petrogenesis of Triassic granites from the Nanling Range in South China: Implications for geochemical diversity in granites  

NASA Astrophysics Data System (ADS)

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 ?18O values of > 9.0, high initial 87Sr/86Sr values of ~ 0.7200, and homogeneous ?Nd(t) values of - 11.3 to - 9.8, as well as variable zircon ?Hf(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.

Gao, Peng; Zhao, Zi-Fu; Zheng, Yong-Fei

2014-12-01

249

Silica-poor, mafic alkaline lavas from ocean islands and continents: Petrogenetic constraints from major elements  

NASA Astrophysics Data System (ADS)

Strongly silica-poor ( ne-normative), mafic alkaline lavas generally represented by olivine nephelinites, nephelinites, melilitites, and olivine melilitites have erupted at various locations during Earth's history. On the basis of bulk-rock Mg#, high concentrations of Na2O, TiO2, and K2O, and trace element geochemistry, it has been suggested that these lavas represent low-degree melts that have undergone little crystal fractionation en route to the surface. Many of these lavas also carry high-pressure mantle material in the form of harzburgite, spinel lherzolite, and variants of websterite xenoliths, and rare garnet-bearing xenoliths. However, phenocryst phases instead indicate that these magmas cooled to variable extents during their passage. We note subtle, yet important, differences in terms of CaO, Al2O3, CaO/AlP2O3, and CaO/MgO. High-pressure experimental melting studies in CMAS-CO2 (3-8 GPa) and natural lherzolitic systems (3GPa) demonstrate that at an isobar increasing F leads to a moderate decrease in CaO + MgO, whereas CaO/MgO and CaO/Al2O3 sharply decrease. Relatively high CaO/Al2O3 indicates melting in the presence of garnet (>- 85 km). Studies also demonstrate that CO2-bearing lherzolitic systems, when compared with anhydrous ones, also have higher CaO content in the coexisting melt at a given P and T. Comparison of the bulk-rock major-element chemistry of silica-poor, mafic alkaline lavas with experimentally determined high-pressure melts indicates that melting of anhydrous mantle lherzolite or garnet pyroxenite is not able to explain many of the major element systematics of the lavas. However, high-pressure partial melts of carbonated lherzolite have the right major element trends. Among ocean islands, lavas from Samoa and Hawaii are perhaps the products of very low degree of partial melting. Lavas from Gran Canaria and Polynesia represent products of more advanced partial melting. On continents, lavas from South Africa and certain localities in Germany are the products of a very low degree of partial melting, and those from Texas and certain other localities in Germany are products of a slightly more advanced degree of partial melting of a carbonated lherzolite. Lavas from Deccan, Czech Republic, and Freemans Cove are the products of even more advanced degree of partial melting. The mere presence of mantle xenoliths in some of these lavas does not necessarily mean that the erupted lavas represent direct mantle melts.

Keshav, Shantanu; H Gudfinnsson, Gudmundur

2004-12-01

250

Disorder of O 2- ion and incorporation of O - and O2- radicals in nanoporous crystal 12CaO 7Al 2O 3 studied by low-temperature heat capacity measurements  

NASA Astrophysics Data System (ADS)

Heat capacity of nanoporous crystal, 12CaO 7Al 2O 3 (C12A7), was measured between 85 mK and 5 K under magnetic field up to 9 T. The heat capacity under zero magnetic field did not fit to the T3 law; the deviation was discussed in terms of the disorder of the O 2- ions in the subnanometer-sized cages in C12A7 lattice. Under magnetic field, the heat capacity showed a Schottky-type anomaly due to the Zeeman splitting of O - and O2- radicals ( S = 1/2) incorporated in the cages. The total concentration of O - and O2- radicals in the crystal was estimated to be 4.4 10 18 cm -3 (2.3 10 21 mol -1, 3.8 10 -3 mol mol -1).

Kohama, Yoshimitsu; Tojo, Takeo; Kawaji, Hitoshi; Atake, Tooru; Matsuishi, Satoru; Hosono, Hideo

2006-04-01

251

Characterization of 12CaO x 7Al2O3 doped indium tin oxide films for transparent cathode in top-emission organic light-emitting diodes.  

PubMed

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

Jung, Chul Ho; Hwang, In Rok; Park, Bae Ho; Yoon, Dae Ho

2013-11-01

252

Bimodal Silurian and Lower Devonian volcanic rock assemblages in the Machias-Eastport area, Maine  

USGS Publications Warehouse

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

Gates, Olcott; Moench, R. H.

1981-01-01

253

Growth of Megaspherulites In a Rhyolitic Vitrophyre  

NASA Technical Reports Server (NTRS)

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.

Smith, Robert K.; Tremallo, Robin L.; Lofgren, Gary E.

2000-01-01

254

Major Elements Budget Between Abyssal Peridotite And Seawater During The Serpentinization  

NASA Astrophysics Data System (ADS)

Water-Rock Interaction is one of the most hot-debated issues among geologists, geophysicists, as well as geochemists. Abyssal peridotites recovered from the seafloor are often greatly affected or alterated by seawater in the form of serpentinization. The alteration to the peridotites makes it difficult to do the straightforward analysis for its primary composition as it was settled in the upper mantle, which confine the usage of these rare direct samples from the mantle in the scientific study, such as mantle dynamics, mantle composition and crust-mantle interaction. Besides, It was revealed recently that the serpentinization of abyssal peridotites may give birth to the hydrothermal activity. The elements migration during the serpentinization may perform a great role on the chemical composition of the hydrothermal fluid, which can support a hidden chemosynthetic ecosystem in the abyssal seabed. The research work focused on the major elements behavior during the serpentinization by studying the partially serpentinized samples of abyssal peridotite from Southwest Indian Ridge. The primary mineral assemblage of peridotite is olivine (Mg2SiO4), orthopyroxene (Mg2Si2O6), clinopyroxene (CaMgSi2O6) and spinel ((Mg,Fe)(Al,Cr)2O4). The major chemical composition are usually as SiO2 (30~45wt.%), MgO (20~45 wt.%), FeO and Fe2O3 (total 5~15 wt.%). Besides there are very few MnO, CaO, Al2O3, Cr2O3, NiO, Na2O, K2O and H2O. While on the other hand the serpentinized peridotite shows a more complicated mineral assemblage, besides the primary minerals there are more alteration minerals, such as serpentine (Mg3[Si2O5](OH)4), magnetite (Fe3O4), talc (Mg3[Si4O10](OH)2), brucite (Mg(OH)2), tremolite (Ca2Mg5[Si8O22](OH)2), chromite (FeCr2O4), chlorite ((Mg,Fe)6[(Si,Al)4O10](OH)8), and other accessary minerals like native metals, sulfides, clay minerals and hornblende. According to the EMPA analysis, the serpentinized sample shows the chemical composition as SiO2(~40 wt.%), MgO(~30 wt.%), total FeO(~7 wt.%), Al2O3(~1 wt.%), MnO(~0.4 wt.%), Cr2O3(~0.3 wt.%), NiO(~0.2 wt.%), CaO(~0.2 wt.%), and very few TiO2, Na2O and K2O. The overall percentages for all the elements mentioned above are usually around 80wt.%, about 20% less than full percent, which indicates the volatile matters in the altered samples. Based on the preliminary study, we get the general picture for the major elements behavior during the alteration. Taking the abyssal peridotite for example, it gains large quantities of H and O in the form of H2O, and other volatile elements like F, Cl, B from the seawater during serpentinization. It may also get additional Na, K, Mg from the seawater as shown from the standardized concentration in primary minerals as well as altered minerals. It loses Fe, Al, Ca, Si during the serpentinization seen from the EMPA mapping results. The element Mn, Cr and Ni are relatively immobile during the alteration. To get more precise deduction as to the element budget during the alteration process, much more sensitive analytical instruments like LA-ICP-MS are needed. And more work need to be done to get the quantitive estimation for transferring rate of each element.

Yu, X.; Dong, Y.; Li, X.; Chu, F.

2012-12-01

255

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)

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.

Mirnejad, H.; Lalonde, A. E.; Obeid, M.; Hassanzadeh, J.

2013-06-01

256

Geochemical Predictions of Elemental Compositions using Remote LIBS under Mars Conditions  

NASA Astrophysics Data System (ADS)

The ChemCam instrument on Mars Science Laboratory will be the first deployment of laser-induced breakdown spectroscopy (LIBS) for remote geochemical analysis. Successful quantitative analyses of those results will use in-situ calibration targets and laboratory calibrations, and employ sophisticated algorithms for data reduction in order to correct for variations in peak intensities and areas caused by interactions in the plasma that are a function of chemical composition. Such chemical matrix effects influence the ratio of each emission line to the abundance of the element that produces it, and are directly related to the elemental composition of the sample. Advances in statistical analysis of LIBS data that mitigate matrix effects and provide for accurate and precise bulk analysis of major, minor, and trace elements are reported here. Our in-house data set currently includes LIBS spectra of >140 rock powders (igneous, metamorphic, and sedimentary) with highly-varying compositions (as determined by XRF) that were acquired at 7-9 m standoff distance under Mars atmospheric conditions using a laboratory instrument [1]. LIBS spectra were modeled using partial least squares analysis (PLS) to predict elemental compositions. Within the igneous suite, 10 repeat measurements of a single sample demonstrates consistency and precision; calculated 1-? errors were 1.6 wt.%SiO2, 1.5 wt.% Al2O3, 0.4 wt.% TiO2, 1.2 wt.% Fe2O3T, 1.6 wt.% MgO, 0.02 wt.% MnO, 1.1 wt.% CaO, 0.5 wt.% Na2O, 0.2 wt.% P2O5, and 0.4 wt.% K2O. In the overall suite, predictions of all elements, expressed as root mean square errors (RMSEP), are better than 2.45 for SiO2, 1.64 for Al2O3, 0.38 for TiO2, 1.50 for Fe2O3T, 1.88 for MgO, 0.03 for MnO, 0.82 for CaO, 0.55 for K2O, 0.62 for Na2O, and 0.24 for P2O5 in units of wt.% oxides. On-going work should reduce these values even further. For elements at low concentrations, multivariate analyses must be interpreted with care because their spectral lines are weak relative to the strong lines from dominating major elements. In such cases, either the weak peaks must be individually fit (as for S; see Dyar et al. [2]) or the PLS predictions will rely on correlations between the low-abundance element and major elements. For example, PLS predicts the concentration of Rb with an RMSEP of 23 ppm, but this prediction relies heavily on K lines that are better predictors of Rb due to the near-perfect correlation between K and Rb in the igneous rocks that dominate our calibration suite. Because any multivariate calibration based on rocks of a certain type will be heavily biased by such geochemical relationships, our in-house laboratory calibration set is expanding with a wider compositional range (and deliberate rock mixtures to counter such correlations) to produce more even more robust predictions of elements with weaker emission lines. [1] Tucker, J.M. et al. (2010) Chem. Geol., in press. [2] Dyar, M.D. et al. (submitted) Spectrochim. Acta B.

Dyar, M. D.; Tucker, J.; Humphries, S.; Clegg, S. M.; Wiens, R. C.; Carmosino, M. L.

2010-12-01

257

Understanding low-energy magnetic excitations and hydrogen bonding in VOHPO4 J. Cao,1 J. T. Haraldsen,2 S. Brown,1 J. L. Musfeldt,1 J. R. Thompson,2,3 S. Zvyagin,4 J. Krzystek,5 M.-H. Whangbo,6  

E-print Network

Understanding low-energy magnetic excitations and hydrogen bonding in VOHPO4· 1 2H2O J. Cao,1 J. T-temperature redshift of VuO and HuO related modes demonstrates enhanced low-temperature hydrogen bonding. The low are stacked along the c axis and held together by two types of interlayer hydrogen bonding interactions: 1

Cao, Jianming

258

Chemical modifications accompanying blueschist facies metamorphism of Franciscan conglomerates, Diablo Range, California  

USGS Publications Warehouse

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.

Moore, D.E.; Liou, J.G.; King, B.-S.

1981-01-01

259

Natural radionuclide concentrations in granite rocks in Aswan and Central-Southern Eastern Desert, Egypt and their radiological implications.  

PubMed

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 90.5 to 1117, 81 to 754 and 1006 to 79040 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

Issa, Shams A M; Uosif, M A M; Abd el-Salam, L M

2012-07-01

260

Geochemistry and evolution of the South Platte granite-pegmatite system, Jefferson County, Colorado  

NASA Astrophysics Data System (ADS)

The South Platte pegmatite district is well known for its significant enrichment in the rare earth elements (REE), Y, Nb, F, and for the exceptionally well-developed internal zonation of the complex pegmatites located within a reversely zoned portion of the Pikes Peak batholith. Chemical trends both within and between pegmatites define the behavior of major and trace elements and the role of F in the fractionation of the granitic magma and pegmatitic fluids, suggesting a new model for the evolution of the granite-pegmatite system. Whole-rock XRF and INAA analyses of the host Pikes Peak granite and quartz monzonite and pegmatite wall zones provide strong evidence that all three are related by differentiation. With increasing SiO 2, there is systematic enrichment in K 2O, Na 2O, and Rb, and depletion in CaO, MgO, FeO?, TiO 2, P 2O 5, Ba, Sr, and Sc. REE, Y, Zr, and Th were strongly partitioned out of the wall zone into the final residual fluids where they were concentrated up to an order of magnitude over levels in the granite. Within the district, there is also chemical zonation of F, Nb, Th, U, and REE between groups of pegmatites. Polyzonal quartz-core types typically contain more fluorite, samarskite, HREE-zircon, and yttrian-fluorite than their bizonal composite-core counterparts, which contain only sparse fluorite and allanite. The sequence of magmatic evolution involved: (1) a process of diffusive differentiation and fractional crystallization which produced a chemically stratified magma chamber with a hotter more mafic quartz monzonitic base and a more felsic, granitic top enriched in H 2O, F, HREE, Nb, and Y; (2) resurgence of the more mafic lower level crystal mush in to the upper more felsic part of the pluton; and (3) separation of pegmatitic fluids from the juxtaposed magmas giving rise to two compositionally distinct groups of pegmatites.

Simmons, Wm. B.; Lee, Maxie T.; Brewster, Renee H.

1987-03-01

261

Petrogeochemistry of listvenite association in metaophiolites of Sahlabad region, eastern Iran: Implications for possible epigenetic Cu-Au ore exploration in metaophiolites  

NASA Astrophysics Data System (ADS)

Petrogeochemical investigations at the Sahlabad region have revealed that epigenetic listvenite veins occur in sheared zones of metaophiolitic suites of Cretaceous age. The listvenite mineralization developed in three forms, namely (1) the silica-listvenite veins which are chiefly composed of chalcedony, opal, quartz, pyrite, chalcopyrite, serpentine and relicts of chrome spinels, magnetite and fuchsite; (2) the carbonate listvenite veins which are comprised principally of magnesite, dolomite, calcite, siderite, pyrite, chalcopyrite, serpentine and relicts of fuchsite, chrome spinels and magnetite; and (3) the silica-carbonate listvenite veins which include opal, quartz, dolomite, magnesite, pyrite, chalcopyrite, serpentine and relicts of chrome spinels and magnetite. The absence of mineralized granitoids and the frequent occurrences of clearcut non-metamorphosed veins indicate that the mineralizing fluids were rich in CO2, H2O, H2S and H4SiO4 and possibly formed as a result of metamorphic dehydration and decarbonation reactions of the oceanic crust at the amphibolite-greenschist facies. Geochemically, the listvenites are enriched in SiO2, MgO, CaO, CO2, LOI, Cr, Ni, Co, Au, Cu, Ag, Hg, and Pt. Also, the veins contain high values of LOI, indicating the H2O-CO2-rich metamorphogenic fluids. The high Cr content and detectable values of K2O, Al2O3 and Na2O in the listvenite veins possibly indicate the presence of fuchsite and chrome spinels. The geochemical signatures attest that the hydrothermal fluids probably derived from a metamorphosed ultramafic protolith. The maximum values for gold, copper, mercury and silver in the listvenites are about 1.9 ppm, 5.4 %, 8 ppm and 6.5 ppm, respectively and provide a unique exploration guide for further gossan sampling, remote sensing mapping, isotopic and fluid inclusion studies in the Iranian metaophiolites.

Aftabi, Alijan; Zarrinkoub, Mohammad Hossien

2013-01-01

262

Electron- and Photon-stimulated Desorption of Alkali Atoms from Lunar Sample and a Model Mineral Surface  

NASA Technical Reports Server (NTRS)

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.

Yakshinskiy, B. V.; Madey, T. E.

2003-01-01

263

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)

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).

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

264

Inorganic data from El'gygytgyn Lake sediments: stages 6-11  

NASA Astrophysics Data System (ADS)

Geochemical study was performed on sediment of deep drilling core from El'gygytgyn Lake, located in central Chukotka, northeastern Russia (6730' N; 17205' E). Major and rare elements were determined by X-ray fluorescence spectroscopy (XRF) on 600 samples covering the timeframe between ca. 450 and 125 ka corresponding to Marine Isotope Stages (MIS) 11 to 6. Inorganic geochemistry data indicates significant variations in the elemental compositions corresponding to the glacials and interglacials periods. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K2O, Sr and are depleted in Al2O3, Fe2O3, TiO2, MgO. Extreme enrichments in SiO2 during MIS 11.3 and 9.3 are caused by an enhanced flux of biogenic silica (BSi). Geochemical structure of stage 11 shows very similar peculiarities to features of stage 11 from records of Lake Baikal/SE Siberia and Antarctic ice cores. High contents of TiO2, Fe2O3, MgO, Al2O3, LOI, Ni, Cr and Zr are typical for sediments of glacial stages, among those MIS 7.4 and 6.6 are the most marked. Peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios during glacials indicate reducing condition in the sediments. This is also supported by enrichments in P2O5 and MnO, indicating an increased abundance of authigenic fine grained vivianite. Some elemental ratios indicate an enhanced alteration of glacial sediments accompanied by a loss of mobile elements, like Na, Ca, K and Sr. The higher alteration of sediments can presumably be traced back to changes in the sedimentation regime and diagenetic processes, and thus, reflects environmental changes.

Minyuk, P. S.; Borkhodoev, V. Ya.; Wennrich, V.

2013-01-01

265

Petrography and geochemistry of lower carboniferous greywacke and mudstones in Northeast Junggar, China: Implications for provenance, source weathering, and tectonic setting  

NASA Astrophysics Data System (ADS)

Northeast Junggar occupies an important position that links East Junggar and Chinese Altai. Numerous magmatic and sedimentary rocks of the Paleozoic in this area recorded the final amalgamation processes of East Junggar and Chinese Altai. This study analyzes the petrological and geochemical characteristics of sandstones and mudstones from the Early Carboniferous Nanmingshui formation in Northeast Junggar. The provenance and tectonic setting of these clastic rocks are discussed. Petrography indicates that the composition and texture maturity of the sandstones are low. The components of the sandstones are mainly volcanic fragments (61-87%), feldspars (9-30%), and monocrystalline quartz (2-18%), with a few polycrystalline quartz and other minerals. Slice observation indicates that the majority of the volcanic fragments of sandstones are basic-intermediate volcanic rocks with a few dacite and felsic plutonic fragments. The detrital modes of the sandstones reflect that these sandstones are derived from undissected arcs. A low to moderate chemical index of alteration and the Al2O3-CaO* + Na2O-K2O diagram reflect a low to moderate weathering degree in the source area. Trace and rare earth element (e.g., La, Th, Hf, Sc, Cr, Co, and Eu) contents and their ratios suggest that the source rocks of the clastic rocks are intermediate-basic rocks with some felsic rocks. Compared with sandstones, the source rocks for mudstones are more felsic. The petrography and geochemistry characteristics of the clastic rocks suggest that the proximal Dulate arc should be the primary source area. Mixing calculations based on REE data suggest that approximately two-thirds of the sandstone fragments are intermediate-basic volcanic rocks. The contents of the major and trace elements, as well as the stratum features, of the clastic rocks manifest that these clastic rocks resemble sedimentary rocks in a back-arc basin. The formation of this back-arc basin is caused by the southward subduction of the Zaysan-Erqis Ocean.

Tao, Huifei; Sun, Shu; Wang, Qingchen; Yang, Xiaofa; Jiang, Lin

2014-06-01

266

Tertiary epizonal plutonic rocks of the Selway-Bitterroot Wilderness, Idaho County, Idaho  

SciTech Connect

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.

Motzer, W.E.

1996-01-01

267

Mineralogical, geochemical and radiological characterisation of Selmo Formation in Batman area, Turkey.  

PubMed

This work deals with the mineralogical, geochemical and radiological characterisations of Selmo Formation in Batman neighbourhood. The upper Miocene-Pliocene Selmo Formation is common in the centre of Batman and composed of carbonated sandy claystones and silty-sandy stone lenses. The common whole minerals of the samples are quartz, feldspars, calcite and dolomite. The clay minerals are smectite, illite, chlorite and mixed-layer clay (chlorite-smectite). The geochemical mean values of the samples are 51.7% SiO(2); 12.6% Al(2)O(3); 6.2% Fe(2)O(3); 3.6% MgO; 6.3% CaO; 1.1% Na(2)O; 1.7% K(2)O; 0.8% TiO(2); 0.2% P(2)O(5); 0.1% MnO; and 0.03% Cr(2)O(3). In addition, baseline maps for the concentrations of each radionuclide, the radium equivalent activity and the outdoor gamma dose rate distributions have been plotted for the study area. The mean activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs were determined to be 32, 24, 210 and 9Bqkg(-1), respectively. The assessments of the radiological hazard indices, such as radium equivalent activity, absorbed dose rate in air, annual effective dose equivalent, excess lifetime cancer risk, external hazard index and internal hazard index, were calculated and compared with the internationally accepted reference values. This study shows that the concentrations of radioactivities in the measured samples were within the recommended safety limits and did not pose to be any significant source of radiation hazard. PMID:22316137

Isik, Umit; Damla, Nevzat; Akkoca, Dicle Bal; Cevik, U?ur

2012-06-01

268

Silicate globules in kyanite from grospydites of the Zagadochnaya kimberlite pipe, Yakutia: The problem of the origin  

NASA Astrophysics Data System (ADS)

The results of complex study of silicate globules and ?-quartz paramorphs after coesite in kyanite from grospydites from the Zagadochnaya kimberlite pipe, Yakutia, using optical and scanning electron spectroscopy, electron and ion microprobes, LA ICP MS and Raman spectroscopy, are presented. The existence of radial fractures diverging from silicate globules into the matrix (kyanite) attests to the fact that the content of the globules is extremely condensed. A zonal structure is usually typical for globules: a coat and a core, which can be explicitly distinguished under the electron microscope, can be differentiated in them. Compositionally, the coat of the globule corresponds to potassium feldspar (wt %: 66.4 SiO2; 16.9 Al2O3; 0.4 FeO; 0.1 CaO; 0.2 Na2O; 14.7 K2O). The globules were also detected in which along with K, a high content of Na and Ca was also ascertained in the silicate coat. The globule coat is considerably enriched with Ba, La, Ce, Nb, and a number of other noncompatible elements as compared with xenolith minerals. The water content in globules is 0.6 wt %. As compared with the host mineral (kyanite), the core part of the globules is also enriched with Co, Ni, Zn, and Cu; their content in kyanite is negligibly low. The entire data collection attests to the fact that the formation of silicate globules could have been caused by interaction of the conservated fluid and/or water-silicate melt with the host mineral and crystalline inclusions of clinopyroxene and garnet with decreasing pressure during the transportation of grospydite xenoliths by the kimberlite melt to the Earth's surface.

Tomilenko, A. A.; Kovyazin, S. V.; Pokhilenko, L. N.; Sobolev, N. V.

2011-01-01

269

Chemical composition of phosphorites of the Phosphoria Formation  

USGS Publications Warehouse

The chemical composition, both major and minor constituents, of 60 samples of phosphorite from the Phosphoria Formation was determined. Major constituents of the average phosphorite are, by weight per cent: SiO2, 11??9; Al2O3, 1??7; Fe2O3,1??1; MgO, 0??3; CaO, 44??0; Na2O, 0??6; K2O, 0??5; total H2O, 2??2; H2O-, 0??6; TiO2, 0??1; P2O5, 30??5; CO2, 2??2; SO3, 1??8; F, 3??1; organic matter, 2??1; and oil, 0??2. Uranium averages 0??009 per cent. The phosphate mineral is basically apatite, Ca5(PO4)3F, with small but significant and variable substitutions-Na, Sr, U and Th for Ca, and CO3 and SO4 for PO4. Rare metals not associated with apatite are associated principally with the organic-matter component of the rocks. This group includes As, Ag, Cd, Cr, Cu, Mo, Ni, Sb, Se, V and Zn. Chromium is the most abundant, having a modal abundance of 0??1 per cent and a maximum concentration of 0??3 per cent. The average phosphorite is composed of approximately 80 per cent apatite, 10 per cent quartz, 5 per cent muscovite-illite, 2 per cent organic matter, 1 per cent dolomite-calcite, 1 per cent iron oxide, and 1 per cent other components. It is texturally a medium-grained pellet phosphorite. ?? 1966.

Gulbrandsen, R.A.

1966-01-01

270

Thermal Expansion Calculation of Silicate Glasses at 210C, Based on the Systematic Analysis of Global Databases  

SciTech Connect

Thermal expansion data for more than 5500 compositions of silicate glasses were analyzed statistically. These data were gathered from the scientific literature, summarized in SciGlass 6.5, a new version of the well known glass property database and information system. The analysis resulted in a data reduction from 5500 glasses to a core of 900, where the majority of the published values is located within commercial glass composition ranges and obtained over the temperature range 20 to 500C. A multiple regression model for the linear thermal expansivity at 210C, including error formula and detailed application limits, was developed based on those 900 core data from over 100 publications. The accuracy of the model predictions is improved about twice compared to previous work because systematic errors from certain laboratories were investigated and corrected. The standard model error (precision) was 0.37 ppm/K, with R = 0.985. The 95% confidence interval for individual predictions largely depends on the glass composition of interest and the composition uncertainty. The model is valid for commercial silicate glasses containing Na2O, CaO, Al2O3, K2O, MgO, B2O3, Li2O, BaO, ZrO2, TiO2, ZnO, PbO, SrO, Fe2O3, CeO2, fining agents, and coloring and de-coloring components. In addition, a special model for ultra-low expansion glasses in the system SiO2-TiO2 is presented. The calculations allow optimizing the time-temperature cooling schedule of glassware, the development of glass sealing materials, and the design of specialty glass products that are exposed to varying temperatures.

Fluegel, Alex

2010-10-01

271

Isotopic variation in the Tuolumne Intrusive Suite, central Sierra Nevada, California  

USGS Publications Warehouse

Granitoid rocks of the compositionally zoned Late Cretaceous Toulumne Intrusive Suite in the central Sierra Nevada, California, have initial87Sr/86Sr values (Sri) and143Nd/144Nd values (Ndi) that vary from 0.7057 to 0.7067 and from 0.51239 to 0.51211 respectively. The observed variation of both Sri and Ndi and of chemical composition in rocks of the suite cannot be due to crystal fractionation of magma solely under closed system conditons. The largest variation in chemistry, Ndi, and Sri is present in the outer-most equigranular units of the Tuolumne Intrusive Suite. Sri varies positively with SiO2, Na2O, K2O, and Rb concentrations, and negatively with Ndi, Al2O3, Fe2O3, MgO, FeO, CaO, MnO, P2O5, TiO2, and Sr concentrations. This covariation of Sri, Ndi and chemistry can be modeled by a process of simple mixing of basaltic and granitic magmas having weight percent SiO2 of 48.0 and 73.3 respectively. Isotopic characteristic of the mafic magma are Sri=0.7047, Ndi=0.51269 and ??18O=6.0, and of the felsic magma are Sri=0.7068, Ndi=0.51212 and ??18O=8.9. The rocks sampled contain from 50 to 80% of the felsic component. An aplite in the outer equigranular unit of the Tuolumne Intrusive Suite apparently was derived by fractional crystallization of plagioclase and hornblende from magma with granudiorite composition that was a product of mixing of the magmas described above. Siliceous magmas derived from the lower crust, having a maximum of 15 percent mantle-derived mafic component, are represented by the inner prophyritic units of the Tuolumne Intrusive Suite. ?? 1986 Springer-Verlag.

Kistler, R.W.; Chappell, B.W.; Peck, D.L.; Bateman, P.C.

1986-01-01

272

Clay mineral burial diagenesis: A case study from the Calabar flank of the Niger Delta  

NASA Astrophysics Data System (ADS)

Detailed clay mineralogic and chemical analyses of Tertiary subsurface sediments of the Agbada and Akata Formations, from two wells on the Calabar Flank of the Niger Delta, have been systematically studied with a view to understanding clay mineral burial diagenesis. Five principal clay minerals, smectite, illite, kaolinite, chlorite and various proportions of mixed-layer illite/smectite were identified. Seven major oxides (SiO 2, Al 2O 3, MgO, Fe 2O 3, CaO, Na 2O, K 2O) were analysed for with an atomic absorption spectrophotometer, with a view to ascertain any depth related variations. The geothermal gradient of the two wells (Uruan-1 and Uda-1) was also calculated. The results appear to suggest a transformation from smectite to a mixed-layer illite/smectite (I/S) phase. The transformation first goes to a random I/S phase, and then to ordered I/S and back to random I/S, even though postulated conditions for a complete transformation to illite did exist. It would therefore seem, from this case study, that neither temperature nor the availability of potassium is the principal factor controlling the transformation. Kaolinite and chlorite distribution does not exhibit any systematic trend that could be related to burial diagenesis. These results provoked an extensive literature review on the subject, and key ideas discerned are summarized here. The prognosis? In the author's opinion, we still have a lot to learn about the factors that control the mechanics and reaction extent of clay mineral burial diagenesis.

Braide, Sokari P.

273

Deciphering heavy metal contamination zones in soils of a granitic terrain of southern India using factor analysis and GIS  

NASA Astrophysics Data System (ADS)

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.

Purushotham, D.; Lone, Mahjoor Ahmad; Rashid, Mehnaz; Rao, A. Narsing; Ahmed, Shakeel

2012-08-01

274

(210)Pb and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macap, Brazil.  

PubMed

Activity profiles of excess (210)Pb determined in three sediment cores from Amazon River mouth, Macap city, Brazil, provided the evaluation of sedimentation rates, contributing to a better knowledge of the hydrological conditions in the site that is the capital of Amap State and is drained by the waters of the huge Amazon River. Chemical data were also determined in the sediments, allowing identify signatures coupled to anthropogenic inputs held in the past in Amap State. Significant direct relationships between LOI (loss on ignition) and organic matter were found for all sediments profiles. Silica was found to be inversely related to organic matter in the three profiles; its decrease accompanied an increase on the specific surface of the sediments. This relationship was confirmed by a great number of inverse significant correlations among silica and oxides Na(2)O, K(2)O, CaO, MgO, Al(2)O(3), P(2)O(5), Fe(2)O(3) and MnO. It was possible to identify the role of organic matter on adsorption of several oxides in the core sediments profiles. Apparent sediment mass accumulation rates corresponding to values between 450 and 2510 mg cm(-2)yr(-1) were obtained, and are compatible with the results of others studies. The (210)Pb activities in one sampling point suggested the occurrence of anthropogenic inputs related to the initial period of the mining activities conducted in Serra do Navio, Amap State, for the commercialization of Mn ores. This was reinforced by the abrupt fluctuations in chemical data obtained for the sediments and composition of the interstitial waters occurring there. The Atlantic hurricane activity also appeared to affect the sedimentation rates in the area, as two different values were recorded in each profile. PMID:21353731

Nery, Jos Reinaldo Cardoso; Bonotto, Daniel Marcos

2011-04-01

275

Toward Understanding the Effect of Nuclear Waste Glass Composition of Sulfur Solubility  

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 in 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. The order of component effects is similar to previous literature data, in most cases.

Vienna, John D.; Kim, Dong-Sang; Muller, I. S.; Kruger, Albert A.; Piepel, Gregory F.

2014-02-13

276

Progressive alkali ion exchange with stratigraphic position in a pyroclastic cooling-unit; Mt. Torro, Sabatini, Central Italy  

NASA Astrophysics Data System (ADS)

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.

Jrgensen, Jesper ksne; Holm, Paul Martin

1998-11-01

277

Fabrication and photoluminescence properties of Ag0 and Ag0-Er3+ containing plasmonic glass nanocomposites in the K2O-ZnO-SiO2 system  

NASA Astrophysics Data System (ADS)

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 430nm 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 470nm upon excitation at 290nm 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 1540nm due to 4I13/2?4I15/2 transition under excitation at 523nm 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.

Tarafder, Anal; Molla, Atiar Rahaman; Mukhopadhyay, Sunanda; Karmakar, Basudeb

2014-11-01

278

Evolution of the trachydacite and pantellerite magmas of the bimodal volcanic association of Dzarta-Khuduk (Central Mongolia): evidence from melt inclusions  

NASA Astrophysics Data System (ADS)

Using various methods of melt inclusion investigation, including electron and ion microprobe techniques, we estimated the composition, evolution, and formation conditions of melts producing the trachydacites and pantellerites of the Late Paleozoic bimodal volcanic association of Dzarta-Khuduk, CentralMongolia. Dzarta Huduk paleovolcano occupies an area of more than 120 square kilometers. A sequence of felsic agpaitic volcanics rests on subalkali basalts and consists of intercalating alkaline trachydacites, pantellerites, and comendites. Their mineralogical and chemicall characteristics correspond to silicic peralkaline rocks of the K-Na series with an agpaitic index of >1 and high contents of F, Zr, Li, Rb, and REE. Primary crystalline and melt inclusions were detected in anorthoclase from trachydacites and quartz from pantellerites and pantelleritic tuffs. Among the crystalline inclusions, we identified hedenbergite, fluorapatite, and pyrrhotite in the trachydacites and F-arfvedsonite, fluorite, ilmenite, and the rare REE diorthosilicate chevkinite in the pantellerites. Melt inclusions in anorthoclase from the trachydacites are composed of glass, a gas phase, and daughter minerals (F-arfvedsonite, fluorite, villiaumite, and anorthoclase rim on the inclusion wall). Melt inclusions in quartz from the pantellerites are composed of glass, a gas phase, and a fine-grained salt aggregate consisting of Li, Na, and Ca fluorides (griceite, villiaumite, and fluorite). Melt inclusions in quartz crystalloclasts from the pantelleritic tuffs are composed of homogeneous silicate glasses. The phenocrysts of the trachydacites and pantellerites crystallized at temperatures of 1060-1000C. During thermometric experiments with quartz-hosted melt inclusions from the pantellerites, the formation of immiscible silicate and salt (fluoride) melts was observed at a temperature of 800C. Homogeneous melt inclusions in anorthoclase from the trachydacites have both trachydacite and rhyolite compositions (wt %):68-70 SiO2, 12-13 Al2O3, 0.34-0.74 TiO2, 5-7 FeO, 0.4-0.9 CaO, and 9-12 Na2O + K2O. The agpaitic index ranges from 0.92 to 1.24. The glasses of homogenized melt inclusions in quartz from the pantellerites and pantelleritic tuffs have rhyolitic compositions. Compared with the homogeneous glasses trapped in anorthoclase of the trachydacites, quartz-hosted inclusions from the pantellerites show higher SiO2 (72-78 wt %) and lower Al2O3 contents (7.8-10.0 wt %). They also contain 0.14-0.26 wt % TiO2, 2.5-4.9 wt % FeO, 9 -11 wt % Na2O + K2O, and 0.9-0.15 wt % CaO and show an agpaitic index of 1.2-2.05. Homogeneous melt inclusions in quartz from the pantelleritic tuffs contain 69-72 wt % SiO2. The contents of other major components, including TiO2, Al2O3, FeO, and CaO, are close to those in the homogeneous glasses of quartz-hosted melt inclusions in the pantellerites. The contents of Na2O + K2O are 4-10 wt %, and the agpaitic index is 1.0-1.6. The glasses of melt inclusions from each rock group show distinctive volatile compositions. The H2O content is up to 0.08 wt % in anorthoclase of the trachydacites, 0.4-1.4 wt % in quartz of the pantellerites, and up to 5 wt % in quartz of the pantelleritic tuffs. The content of F in the glasses of melt inclusions in the phenocrysts of the trachydacites is no higher than 0.67 wt %, and up to 1.4-2.8 wt % in quartz from the pantellerites. The Cl content is up to 0.2 wt % in the glasses of melt inclusions in the minerals of the trachydacites and up to 0.5 wt % in the glasses of quartz-hosted melt inclusions from the pantellerites. The investigation of trace elements in the homogenized glasses of melt inclusions in minerals showed that the trachydacites and pantellerites were formed from strongly evolved rare-metal alkaline silicate melts with high contents of Li, Zr, Rb, Y, Hf, Th, U, and REE. The analysis of the composition of homogeneous melt inclusions in the minerals of the above rocks allowed us to distinguish magmatic processes resulting in the enrichment of these rocks in trace and rare earth element

Andreeva, I.

2012-04-01

279

Solvent free synthesis of chalcone and flavanone over zinc oxide supported metal oxide catalysts  

Microsoft Academic Search

Liquid phase ClaisenSchmidt condensation between 2?-hydroxyacetophenone and benzaldehyde to form 2?-hydroxychalcone, followed by intramolecular cyclisation to form flavanone was carried out over zinc oxide supported metal oxide catalysts under solvent free condition. The reaction was carried out over ZnO supported MgO, BaO, K2O and Na2O catalysts with 0.2g of each catalyst at 140C for 3h. Magnesium oxide impregnated zinc oxide

S. Saravanamurugan; M. Palanichamy; Banumathi Arabindoo; V. Murugesan

2005-01-01

280

Petrology and geochemistry of plagiogranite in the Canyon Mountain ophiolite, Oregon  

Microsoft Academic Search

Plagiogranites in the Canyon Mountain ophiolite, Oregon, include a wide range of rock types ranging from diorite to trondhjemite. The plagiogranites are mostly concentrated as an intrusive sill swarm at the top of a section of gabbroic cumulates. The plagiogranites are typically low in K2O and high in Na2O, and are enriched 1020 times chondrites in REE, and overlap with

David C. Gerlach; William P. Leeman; Hans G. Av Lallemant

1981-01-01

281

Geochemistry and origin of albite gneisses, northeastern Adirondack Mountains, New York  

Microsoft Academic Search

Albite gneisses containing up to 8.7 percent Na2O and as little as 0.1% K2O comprise a significant part of the Proterozoic Lyon Mountain Gneiss in the Ausable Forks Quadrangle of the northeastern Adirondacks, New York State. Two distinct types of albite gneisses are present. One is a trondhjemitic leucogneiss (LAG) consisting principally of albite (Ab95Ab98) and quartz with minor magnetite

Philip R. Whitney; James F. Olmsted

1988-01-01

282

Method of preventing oxidation of graphite fireproof material  

NASA Technical Reports Server (NTRS)

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.

Yamauchi, S.; Suzuki, H.

1981-01-01

283

Geochemical and isotopic composition and inherited zircon ages as evidence for lower crustal origin of two Variscan S-type granites in the NW Bohemian massif  

Microsoft Academic Search

Geochemical and Nd-Sr isotopic compositions and U-Pb zircon ages of two Variscan granites (Neunburg and Oberviechtach) from southern Oberpfalz, NW Bohemian massif, have been investigated in order to place constraints on their formation and on the crustal reworking. Both granites exhibit similar mineralogical, chemical and isotopic characteristics. They have peraluminous compositions (A\\/CNK ratios 1.2-1.3) and display high K2O\\/Na2O ratios of

F. Chen; W. Siebel; M. Satir

2003-01-01

284

Origin and evolution of topaz-bearing granites from the Nanling Range, South China: a geochemical and SrNdHf isotopic study  

Microsoft Academic Search

SummaryThe F-rich Hongshan pluton in the eastern Nanling Range, southern China, is a topaz-bearing albite leucogranite. It is distinctive\\u000a from other topaz-bearing felsic rocks in South China with respect to age, size, geochemical evolution and topaz mode and morphology.\\u000a The Hongshan granites are highly peraluminous and characterized by high K2O\\/Na2O, Si, Rb, Cs, Nb, Ta and F, and low Ca,

J.-H. Yu; S. Y. OReilly; L. Zhao; W. L. Griffin; M. Zhang; X. Zhou; S.-Y. Jiang; L.-J. Wang; R.-C. Wang

2007-01-01

285

Experimental tests of low degree peridotite partial melt compositions: implications for the nature of anhydrous near-solidus peridotite melts at 1 GPa  

Microsoft Academic Search

We present results of an experimental study to determine the nature of minimum to near-minimum melt compositions in equilibrium with upper mantle peridotite mineralogy at 1 GPa. We confirm earlier conclusions that anhydrous melts of lherzolite at 1 GPa are basaltic with ?1520% normative diopside, >10% normative olivine and at low degrees of melting are Na2O and K2O-rich and nepheline-normative

T. J Falloon; D. H Green; H. St. C O'Neill; W. O Hibberson

1997-01-01

286

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)

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.

Altherr, R.; Meyer, H.-P.; Holl, A.; Volker, F.; Alibert, C.; McCulloch, M. T.; Majer, V.

287

The Iceland Deep Drilling Project (IDDP): (2) Petrology and geochemistry of rhyolitic melts drilled at Krafla  

NASA Astrophysics Data System (ADS)

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.

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

288

Structural characterization of glass-ceramics made from fly ash containing SiO2-Al2O3-Fe2O3-CaO and analysis by FT-IR-XRD-SEM methods  

NASA Astrophysics Data System (ADS)

The glass-ceramics has been proposed as a useful recycling fly ash from thermal power plants. In this study, C type fly ash containing SiO2-Al2O3-Fe2O3-CaO has been sintered to form glass-ceramic materials at different temperatures between 850 C and 1050 C after using powder processing based on milling and powder compaction without inorganic additives. The effect of firing temperatures between 850 C and 1050 C on mineralogy and microstructure of sintered samples is reported. The Fourier Transform Infrared Spectra (FT-IR), Differential Thermal Analysis (DTA), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques were applied on the sintered powder form. From the XRD results, the amount of quartz decreases on sintering, when the sintering temperature increases. On the basis of SEM observations, new crystallites structure developed in the microstructures of the C type of fly ash samples and the glassy region decreased at the crystallization temperature.

Yilmaz, G.

2012-07-01

289

Dielectric behavior of ternary mixtures: epoxy resin plus titanates (MgTiO3, CaTiO3 or BaTiO3) associated to oxides (CaO, MnO2 or ZnO)  

NASA Astrophysics Data System (ADS)

In the present work, we study the dielectric behavior of various ternary mixtures composed of epoxy resin (RE), of one of three different titanates (barium titanate, BaTiO3; calcium titanate, CaTiO3; magnesium titanate, MgTiO3) respectively with one of three oxides (calcium oxide, CaO; manganese dioxide, MnO2; zinc oxide, ZnO) using time domain reflectometry (TDR). The different composites are mixed at room temperature in different volume fractions keeping the epoxy resin at a constant volume fraction. Several mixture combinations are studied to see the oxides influence on the titanates dielectric behavior in the range from DC to 10 GHz. This is done through the experimental determination of the dielectric constant ?s. A noticeable effect has been recorded at the low frequency and which consists of an increase of this dielectric permittivity when growing the volume fraction of manganese dioxide. One meaningful point of this study is the lowest static conductivity value (8.017 10-3/(?m)) being reached with an incursion of 7.5% of MnO2 in a ternary mixture composed of RE, MgTiO3 and MnO2. In addition, the behavior obtained experimentally has been validated by the Lichtenecker modified model. This study interest lies on an application of these materials in microelectronics and particularly in telecommunication components manufacturing.

Bourouba, Nacerdine; Lalla, Khalfa; Martinez Jimenez, Juan Pablo; Bouzit, Nacerdine

2014-01-01

290

Large conductivity enhancement in polycrystalline 12CaO 7Al 2O 3 thin films induced by extrusion of clathrated O 2- ions by hot Au + implantation and ultraviolet light illumination  

NASA Astrophysics Data System (ADS)

Large enhancement in electrical conductivity from <10 -10 S cm -1 to 4 10 -2 S cm -1 was achieved in polycrystalline 12CaO 7Al 2O 3 (p-C12A7) thin films by hot Au + implantation at 600 C and subsequent ultraviolet (UV) light illumination. Although the as-implanted films were transparent and insulating, the subsequent UV-light illumination induced persistent electronic conduction and coloration. A good correlation was found between the concentration of photo-induced F +-like centers (a cage trapping an electron) and calculated displacements per atom, indicating that the hot Au + implantation extruded free O 2- ions from the cages in the p-C12A7 films by kick-out effects and left electrons in the cages. These results suggest that H - ions are formed by the Au + implantation through the decomposition of preexisting OH - ions. Subsequent UV-light illumination produced F +-like centers via photoionization of the H - ions, which leads to the electronic conduction and coloration.

Miyakawa, M.; Hirano, M.; Kamiya, T.; Hosono, H.

2006-09-01

291

A multiphase strategy for realizing green cathodoluminescence in 12CaO7Al2O3-CaCeAl3O7:Ce3+,Tb3+ conductive phosphor.  

PubMed

A multiphase strategy is proposed and successfully applied to make the insulating green phosphor CaCeAl3O7:Tb(3+) conductive in the form of 12CaO7Al2O3-CaCeAl3O7:Ce(3+),Tb(3+). The phosphor shows bright green-light emission with a short lifetime (2.51 ms) under low-voltage electron beam excitation (3 kV). The green photo- and cathodoluminescence from (5)D4-(7)F(J) (J = 6, 5, 4, 3) transitions of Tb(3+) are significantly enhanced in comparison with pure C12A7:Tb(3+). It was confirmed that this enhancement is the consequence of the joint effects of energy transfer from Ce(3+) to Tb(3+) and broadening of the absorption spectrum of Ce(3+) due to the existence of multiple phases. In particular, under 800 V electron beam excitation, cathodoluminescence is improved by the modified electrical conductivity of the phosphor. When compared to the commercial Zn2SiO4:Mn(2+) with a long luminescence lifetime of 11.9 ms, this conductive green phosphor has greater advantage for fast displays. PMID:24061503

Liu, Xiuling; Liu, Yuxue; Yan, Duanting; Zhu, Hancheng; Liu, Chunguang; Liu, Weizhen; Xu, Changshan; Liu, Yichun; Zhang, Hong; Wang, Xiaojun

2013-12-14

292

Fabrication and electron transport properties of epitaxial films of electron-doped 12CaO7Al 2O 3 and 12SrO7Al 2O 3  

NASA Astrophysics Data System (ADS)

Epitaxial growth and electron doping of 12CaO7Al 2O 3 (C12A7) and 12SrO7Al 2O 3 (S12A7) are reported. The C12A7 films were prepared on Y 3Al 5O 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.

Miyakawa, Masashi; Hiramatsu, Hidenori; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

2010-02-01

293

Measurements of spin-lattice relaxation times, T1, in Na2O-MgO-SiO2 glasses doped with MnO.  

PubMed

Silicate glasses without paramagnetic components show 29Si relaxation times, T1, in the order of minutes. Because of these T1 values, unacceptably long instrument times are needed to obtain satisfactory' signal-to-noise ratios. Therefore, all samples were doped with MnO when microstructures of electrode glasses were investigated. Small amounts of paramagnetic ions in the glass reduce the relaxation time but do not affect the electrode properties. In any case when the distribution of manganese ions is homogeneous, the relaxation rates are proportional to the MnO content. The spin-lattice relaxation times of the different Qn species are similar within error limits. The best spectra were obtained using 0.1 mol% MnO. PMID:7583067

Scholz, K; Thomas, B

1995-07-01

294

The thermal stability of sideronatrite and its decomposition products in the system Na2O-Fe2O3-SO2-H2O  

NASA Astrophysics Data System (ADS)

The thermal stability of sideronatrite, ideally Na2Fe3+(SO4)2(OH)3(H2O), and its decomposition products were investigated by combining thermogravimetric and differential thermal analysis, in situ high-temperature X-ray powder diffraction (HT-XRPD) and Fourier transform infrared spectroscopy (HT-FTIR). The data show that for increasing temperature there are four main dehydration/transformation steps in sideronatrite: (a) between 30 and 40 C sideronatrite transforms into metasideronatrite after the loss of two water molecules; both XRD and FTIR suggest that this transformation occurs via minor adjustments in the building block. (b) between 120 and 300 C metasideronatrite transforms into metasideronatrite II, a still poorly characterized phase with possible orthorhombic symmetry, consequently to the loss of an additional water molecule; X-ray diffraction data suggest that metasideronatrite disappears from the assemblage above 175 C. (c) between 315 and 415 C metasideronatrite II transforms into the anhydrous Na3Fe(SO4)3 compound. This step occurs via the loss of hydroxyl groups that involves the breakdown of the [Fe3+(SO4)2(OH)]{?/2-} chains and the formation of an intermediate transient amorphous phase precursor of Na3Fe(SO4)3. (d) for T > 500 C, the Na3Fe(SO4)3 compound is replaced by the Na-sulfate thenardite, Na2SO4, plus Fe-oxides, according to the Na3Fe3+(SO4)3 ? 3/2 Na2(SO4) + 1/2 Fe2O3 + SOx reaction products. The Na-Fe sulfate disappears around 540 C. For higher temperatures, the Na-sulfates decomposes and only hematite survives in the final product. The understanding of the thermal behavior of minerals such as sideronatrite and related sulfates is important both from an environmental point of view, due to the presence of these phases in evaporitic deposits, soils and sediments including extraterrestrial occurrences, and from the technological point of view, due to the use of these materials in many industrial applications.

Ventruti, Gennaro; Scordari, Fernando; Ventura, Giancarlo Della; Bellatreccia, Fabio; Gualtieri, Alessandro F.; Lausi, Andrea

2013-09-01

295

Leaching of silica bands and concentration of magnetite in Archean BIF by hypogene fluids: Beebyn Fe ore deposit, Yilgarn Craton, Western Australia  

NASA Astrophysics Data System (ADS)

The ~2,752-Ma Weld Range greenstone belt in the Yilgarn Craton of Western Australia hosts several Fe ore deposits that provide insights into the role of early hypogene fluids in the formation of high-grade (>55 wt% Fe) magnetite-rich ore in banded iron formation (BIF). The 1.5-km-long Beebyn orebody comprises a series of steeply dipping, discontinuous, <50-m-thick lenses of magnetite-(martite)-rich ore zones in BIF that extend from surface to vertical depths of at least 250 m. The ore zones are enveloped by a 3-km-long, 150-m-wide outer halo of hypogene siderite and ferroan dolomite in BIF and mafic igneous country rocks. Ferroan chlorite characterises 20-m-wide proximal alteration zones in mafic country rocks. The magnetite-rich Beebyn orebody is primarily the product of hypogene fluids that circulated through reverse shear zones during the formation of an Archean isoclinal fold-and-thrust belt. Two discrete stages of hypogene fluid flow caused the pseudomorphic replacement of silica-rich bands in BIF by Stage 1 siderite and magnetite and later by Stage 2 ferroan dolomite. The resulting carbonate-altered BIF is markedly depleted in SiO2 and enriched in CaO, MgO, LOI, P2O5 and Fe2O3(total) compared with the least-altered BIF. Subsequent reactivation of these shear zones and circulation of hypogene fluids resulted in the leaching of existing hypogene carbonate minerals and the concentration of residual magnetite-rich bands. These Stage 3 magnetite-rich ore zones are depleted in SiO2 and enriched in K2O, CaO, MgO, P2O5 and Fe2O3(total) relative to the least-altered BIF. Proximal wall rock hypogene alteration zones in mafic igneous country rocks (up to 20 m from the BIF contact) are depleted in SiO2, CaO, Na2O, and K2O and are enriched in Fe2O3(total), MgO and P2O5 compared with distal zones. Recent supergene alteration affects all rocks within about 100 m below the present surface, disturbing hypogene mineral and the geochemical zonation patterns associated with magnetite-rich ore zones. The key vectors for identifying hypogene magnetite-rich Fe ore in weathered outcrop include textural changes in BIF (from thickly to thinly banded), crenulated bands and collapse breccias that indicate volume reduction. Useful indicators of hypogene ore in less weathered rocks include an outer carbonate-magnetite alteration halo in BIF and ferroan chlorite in mafic country rocks.

Duuring, Paul; Hagemann, Steffen

2013-03-01

296

Geochemistry and shock petrography of the Crow Creek Member, South Dakota, USA: Ejecta from the 74-Ma Manson impact structure  

NASA Astrophysics Data System (ADS)

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.

Katongo, Crispin; Koeberl, Christian; Witzke, Brian J.; Hammond, Richard H.; Anderson, Raymond R.

2004-01-01

297

Polyphase growth of garnet in eclogite from the Hong'an orogen: Constraints from garnet zoning and phase equilibrium  

NASA Astrophysics Data System (ADS)

Major and trace element profiles as well as mineral inclusions were analyzed in garnets from massive and foliated eclogites from the low-T/high-P eclogite-facies zone in the Hong'an orogen, China. Garnets in the two types of eclogites show different core-rim zoning and mineral inclusions. At least two stages of garnet growth are evident for most garnet grains. Garnets in the massive eclogite contain abundant mineral inclusions such as quartz, chlorite, amphibole, rutile and phengite in cores, but only a few mineral inclusions such as quartz, rutile and titanite in rims. These garnet grains exhibit increasing MgO but decreasing CaO and REE contents from core to rim. Together with pseudosection calculations it is suggested that hydrous minerals such as chlorite, epidote and amphibole were probably the major reactants for the growth of garnet cores during prograde subduction, whereas the growth of garnet rims involves amphibole breakdown and/or dissolution of previously formed garnet. On the other hand, garnets in the foliated eclogite exhibit nearly constant MgO, decreasing MnO but increasing CaO and heavy REE contents (HREE) from core to rim. Along with pseudosection calculations it is inferred that the decomposition of epidote would consistently contribute to the growth of garnet core and rim. This is also supported by epidote zoning in matrix, with the occurrence of low-jadeite omphacite inclusions in the core and a few rutile inclusions in the rim. The enrichment of light REE (LREE) and depletion of HREE in the epidote rim relative to the core indicate that the epidote rim was recrystallized in equilibrium with the garnet rims. For protolith compositions, the foliated eclogite shows higher SiO2, Na2O, K2O and MgO contents but lower Al2O3, Fe2O3 and TiO2 contents than the massive eclogite. Along with phase equilibrium modeling, it is concluded that the differences in the protolith compositions of eclogites primarily dictate the differences in the garnet zoning patterns and the mineral assemblages of matrix and inclusions. The decomposition of hydrous minerals such as chlorite, amphibole and epidote is necessary for garnet growth during subduction-zone metamorphism.

Zhou, Li-Gang; Xia, Qiong-Xia; Zheng, Yong-Fei; Hu, Zhaochu

2014-10-01

298

Geochemistry and shock petrography of the Crow Creek Member, South Dakota, USA: Ejecta from the 74-Ma Manson impact structure  

USGS Publications Warehouse

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.

Katongo, C.; Koeberl, C.; Witzke, B.J.; Hammond, R.H.; Anderson, R.R.

2004-01-01

299

Binary, ternary and quaternary silicates of CaO, BaO and ZnO in high thermal expansion seals for solid oxide fuel cells studied by high-temperature X-ray diffraction (HT-XRD)  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer We examined the thermal expansion of various silicates of CaO, BaO and ZnO. Black-Right-Pointing-Pointer Thermal expansions were determined by dilatometry and high-temperature X-ray diffraction. Black-Right-Pointing-Pointer High-temperature X-ray diffraction enabled to determine anisotropic thermal expansion. Black-Right-Pointing-Pointer CaSiO{sub 3}, Ca{sub 3}Si{sub 2}O{sub 7} and BaCa{sub 2}Si{sub 3}O{sub 9} exhibit the highest thermal expansion. Black-Right-Pointing-Pointer CaSiO{sub 3}, Ca{sub 3}Si{sub 2}O{sub 7} and BaCa{sub 2}Si{sub 3}O{sub 9} are suitable as components in high temperature seals. -- Abstract: Gas-tight seals based on glasses suitable for joining of materials with high thermal expansion coefficients are for example required for solid-oxide fuel cells. If these seals are to be used at high temperatures, they can only be fabricated from glasses which enable the crystallization of phases with high thermal expansion coefficients. This paper reports on some components from systems suitable for high thermal expansion seals: binary calcium silicates, CaSiO{sub 3}, Ca{sub 3}Si{sub 2}O{sub 7} and Ca{sub 2}SiO{sub 4} zinc silicates, Zn{sub 2}SiO{sub 4}, ternary silicates of BaO, CaO and ZnO, BaCa{sub 2}Si{sub 3}O{sub 9}, Ca{sub 2}ZnSi{sub 2}O{sub 7}, and one quaternary silicate, Ba{sub 2}CaZn{sub 2}Si{sub 6}O{sub 17,} studied by high-temperature X-ray diffraction. Only CaSiO{sub 3}, Ca{sub 3}Si{sub 2}O{sub 7} and BaCa{sub 2}Si{sub 3}O{sub 9} exhibit thermal expansion coefficients in the range suitable for high thermal expansion seals of 11.2-11.8 Multiplication-Sign 10{sup -6} K{sup -1} (100-800 Degree-Sign C). The thermal expansions strongly depend on the respective crystallographic axis. The coefficient of thermal expansion of a sealing glass is not only affected by the thermal expansions of the crystalline phases, but also by that of the residual glassy phase as well as by the elastic properties. The phase formation should carefully be controlled also with respect to aging.

Kerstan, Marita; Mueller, Matthias [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany)] [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany); Ruessel, Christian, E-mail: ccr@rz.uni-jena.de [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany)] [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany)

2011-12-15

300

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

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.

Fietkau, Rainer [Department of Radiation Therapy, University of Rostock, Rostock (Germany)]. E-mail: rainer.fietkau@med.uni-rostock.de; Roedel, Claus [Departments of Radiation Therapy and Surgery, University of Erlangen, Erlangen (Germany); Hohenberger, Werner [Departments of Radiation Therapy and Surgery, University of Erlangen, Erlangen (Germany); Raab, Rudolf [Department of Surgery, Klinikum Oldenburg, Oldenburg (Germany); Hess, Clemens [Departments of Radiation Therapy and General Surgery, University of Goettingen, Goettingen (Germany); Liersch, Torsten [Departments of Radiation Therapy and General Surgery, University of Goettingen, Goettingen (Germany); Becker, Heinz [Departments of Radiation Therapy and General Surgery, University of Goettingen, Goettingen (Germany); Wittekind, Christian [Institute of Pathology, University of Leipzig, Leipzig (Germany); Hutter, Matthias [Department of Radiation Therapy, Krankenhaus Nordwest Frankfurt, Frankfurt (Germany); Hager, Eva [Department of Radiation Therapy, Krankenhaus Klagenfurt, Klagenfurt (Austria); Karstens, Johann [Department of Radiation Therapy, University of Hannover, Hannover (Germany); Ewald, Hermann [Department of Radiation Therapy, University of Schleswig-Holstein, Campus Kiel, Kiel (Germany); Christen, Norbert [Department of Radiation Therapy, Krankenhaus Dresden-Friedrichstadt, Dresden (Germany); Jagoditsch, Michael [Department of Surgery, Klinikum St. Veit, St. Veit (Austria); Martus, Peter [Institute of Biostatistics and Clinical Epidemiology, Charite Universitary Medicine Berlin, Berlin (Germany); Sauer, Rolf [Departments of Radiation Therapy and Surgery, University of Erlangen, Erlangen (Germany)

2007-03-15

301

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)

The Peach Spring supereruption (18.780.02 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.

Mccracken, R. G.; Miller, C. F.; Buesch, D.; Gualda, G. A.; Covey, A.

2012-12-01

302

Time constraints on the inversion of the tectonic regime in the northern margin of the North China Craton: Evidence from the Daqingshan granites  

NASA Astrophysics Data System (ADS)

The Daqingshan granites are located in a late Mesozoic tectono-magmatic belt at the northern margin of the North China Craton (NCC), and include the Deshengying, Xinisubei, Gulouban, and Kuisu plutons. Ion probe U-Pb zircon dating indicates that the granites were emplaced at 131 1, 140 4, 145 1, and 142 2 Ma, respectively. All of the granites are alkali- and potassium-rich, with high SiO2 (73.2-76.7 wt.%), K2O (4.50-5.57 wt.%), Na2O (3.60-4.93 wt.%), and K2O/Na2O (0.99-1.49), and low Al2O3 (12.3-14.5 wt.%), CaO (0.45-0.79 wt.%), and MgO (?0.12 wt.%). The granites are light rare earth element enriched ([La/Yb]N = 5.6-48.7). The Xinisubei and Gulouban monzogranites and the Kuisu mylonitic monzogranite have small Eu anomalies (?Eu = 0.65-1.23), low Zr + Nb + Ce + Y (132-321 ppm), and exhibit a negative correlation between P2O5 and SiO2 contents, which are characteristic of highly fractionated I-type granites with a post-collisional origin. The Deshengying monzogranite is distinctive in being an aluminous A-type granite as evidenced by high 10,000 Ga/Al (>2.6) and Zr + Nb + Ce + Y (312-532 ppm), low Ba and Sr, marked negative Eu anomalies (?Eu = 0.08-0.20), strong Ba, Sr, P, and Ti depletions, and an absence of alkali minerals. This granite was probably produced by partial melting of continental crust heated by hot mantle-derived magmas during crustal extension. The Deshengying monzogranite represents a post-kinematic pluton emplaced into the Daqingshan fold-and-thrust belt, whereas the Kuisu mylonitic monzogranite is a syn-kinematic pluton intruded along the Hohhot detachment fault. It is evident that the Daqingshan area experienced a change from a compressional to an extensional tectonic regime during 145-140 Ma. The post-orogenic collapse may have resulted in extension of the upper continental crust. Subsequently, as the thrust-detachment system became inactive, the lower crust of the NCC underwent modification and melting from 131 Ma. We conclude that the Early Cretaceous tectonic evolution of the Daqingshan area was caused by post-orogenic collapse and melting of the lower crust of the NCC. Delamination of the lower crust in the northern NCC resulted in crustal extension and asthenospheric upwelling, which produced A-type granites. As such, melting of the lower crust in the northwestern part of the NCC took place as early as the late Mesozoic.

Meng, Qingpeng; He, Yuankai; Zhang, Wen; Zheng, Rongguo; Xu, Cao; Zhang, Zhaoyu; Wu, Tairan

2014-01-01

303

Caroline G. L. Cao* Department of Mechanical  

E-print Network

of abstraction across a wide range of domains, from seafaring to flying a plane to driving to Web browsing (e environments, the literature on navigation has expanded to include both remote physical and virtual in virtual worlds to display complex navigational information through superposition onto otherwise

Milgram, Paul

304

Natural weathering in dry disposed ash dump: Insight from chemical, mineralogical and geochemical analysis of fresh and unsaturated drilled cores.  

PubMed

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

Akinyemi, S A; Akinlua, A; Gitari, W M; Khuse, N; Eze, P; Akinyeye, R O; Petrik, L F

2012-07-15

305

Multi-analytical characterization of archaeological ceramics. A case study from the Sforza Castle (Milano, Italy).  

NASA Astrophysics Data System (ADS)

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.

Barberini, V.; Maspero, F.; Galimberti, L.; Fusi, N.

2009-04-01

306

Multi-component diffusion between molten SiO2 inclusions and surrounding felsic melt in an indochinite: Tektites as natural laboratories  

NASA Astrophysics Data System (ADS)

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

Macris, C. A.; Eiler, J. M.; Asimow, P. D.; Stolper, E. M.

2013-12-01

307

Melt inclusions and origin of granite in migmatitic granulites from the Kerala Khondalite Belt, Southern India  

NASA Astrophysics Data System (ADS)

Both glassy and crystallized melt inclusions (MI) occur in garnet in metapelitic granulites from the Kerala Khondalite Belt. These rocks were metamorphosed and partially melted at UHT conditions during the Pan-African event, and MI represent droplets of the anatectic melt, originated by dehydration melting of biotite and trapped by garnet growth at supersolidus conditions. An extensive ESEM-BSE mapping study, along with EMPA analysis and re-heating experiments, has been carried out to characterize these anatectic MI. The inclusions range from 4 to 35 ?m in diameter and occur as clusters in garnets. In spite of the long time it took for these rocks to cool below 350 C (at least 60 m.y.), different degrees of crystallization were observed in the same cluster, ranging from totally crystallized to totally glassy. The crystallized MI are referred to as "nanogranites" (Cesare et al., 2009) and always contain quartz, Mg-rich biotite (XFe=0.23) and two feldspars in a fine-grained polycrystalline aggregate. Based on microstructural evidence, biotite crystallized as first phase, preferentially on the walls of the MI, while quartz and feldspars crystallized later, often forming graphic intergrowths and/or melt pseudomorph-like structures (? 50 nm) similar to coarser structures (? tens of microns scale) observed in the host rocks. The glassy inclusions are rare (about 15% of the total) and smaller in size (?15 ?m in diameter) compared to the crystallized nanogranite MI. Both MI types often show negative crystal-shape and contain trapped crystalline phases that are accessories in the host rock, including rutile, titanite, zircon, apatite and Zn-rich spinel. Partially crystallized MI have been also recognized, containing an amorphous phase identified as a residual melt Where Cl and Ca are preferentially partitioned. Re-heating experiments in a HT hearing stage succeeded in re-homogenizing the nanogranite inclusions. EMP data on 40 re-homogenized MI show an average SiO2=73 wt%, K2O =6.7 wt%, Na2O =1 wt% and CaO <1 wt%. EMP analyses on the primary glassy inclusions in not re-heated samples provide similar compositions, while the differentiated melt in partially crystallized MI has higher CaO content and lower K2O content. The EMP characterization therefore confirms the work hypothesis that the different types of MI had the same original composition, except for the different trapped accessories, and that melt in partially crystallized MI is the result of a differentiation of the original trapped melt via crystal fractionation. The low Na content of melt in inclusions is consistent with the scarcity or absence of plagioclase in the melanosome of the studied samples, and with the UHT conditions at which the rocks melted. In fact, in the Q-Ab-An diagram melts plot far from the haplogranitic minima. Our results show that MI studies represent a powerful novel approach in the petrology of crustal melting and S-type granite genesis, and highlight the potential pitfalls of assuming anatectic melt as having a minimum melt composition. References Cesare, B., Ferrero, S., Salvioli-Mariani, E., Pedron, D., Cavallo, A., 2009. Nanogranite and glassy inclusions: the anatectic melt in migmatites and granulites. Geology 37, 627-630.

Ferrero, Silvio; Cesare, Bernardo; Salvioli Mariani, Emma; Cavallo, Andrea

2010-05-01

308

Coupled Market Behavior Based Financial Crisis Detection Wei Cao, Longbing Cao and Yin Song  

E-print Network

and petrol price are often coupled. A financial crisis may significantly change the couplings between aspect to another, namely we can not use the change of a single indicator to represent the crisis the crisis and non-crisis periods, as the drivers triggering the crisis likely change the coupling from

Cao, Longbing

309

Polylactic acidphosphate glass composite foams as scaffolds for bone tissue engineering  

Microsoft Academic Search

Phosphate glass (PG) of the composition 0.46(CaO)- 0.04(Na2O)- 0.5(P2O5) was used as filler in poly-L-lactic acid (PLA) foams developed as degradable scaffolds for bone tissue engineering. The effect of PG on PLA was assessed both in bulk and porous composite foams. Composites with various PG content (0, 5, 10, and 20 wt %) were melt-extruded, and either compression-molded or foamed

G. Georgiou; L. Mathieu; D. P. Pioletti; P.-E. Bourban; J.-A. E. Mnson; J. C. Knowles; S. N. Nazhat

2007-01-01

310

Surface silver-doping of biocompatible glasses to induce antibacterial properties. Part II: plasma sprayed glass-coatings  

Microsoft Academic Search

A 57% SiO2, 3% Al2O3, 34% CaO and 6% Na2O glass (SCNA) has been produced in form of powders and deposited by plasma spray on titanium alloy and stainless steel substrates.\\u000a The obtained coatings have been subjected to a patented ion-exchange treatment to introduce silver ions in the surface inducing\\u000a an antibacterial behavior. Silver surface-enriched samples have been characterized by

M. Miola; S. Ferraris; S. Di Nunzio; P. F. Robotti; G. Bianchi; G. Fucale; G. Maina; M. Cannas; S. Gatti; A. Mass; C. Vitale Brovarone; E. Vern

2009-01-01

311

Calcium phosphate invert glasses with soda and titania  

Microsoft Academic Search

Calcium phosphate glasses in the pyrophosphate region were obtained by addition of Na2O and TiO2. The glasses with CaO content of ?55 mol% contain pyrophosphate and orthophosphate groups without metaphosphate by Raman and NMR observation. Crystalline phases with bioactivity such as ?-Ca3(PO4)2 and\\/or ?-Ca2P2O7 were precipitated in the glasses at 850C. Some of the glasses can be sintered at 850C,

Toshihiro Kasuga; Yoshihiro Abe

1999-01-01

312

Failure of particulate bioglass to prevent experimental staphylococcal infection of open tibial fractures  

Microsoft Academic Search

range from 355 to 500 mm, consisting of 45 wt% SiO2\\/24.5 wt% Na2O\\/24.5 wt% CaO\\/6 wt% P2O5) in vivo by examining its effi- cacy in reducing the rate of infection by Staphylococcus aureus after the fixation of open tibial fractures in rabbits. An in vivo test was carried out with male rabbits split into two groups infected with S. aureus

Zong-Ping Xie; Chang-Qing Zhang; Cheng-Qing Yi; Jian-Jun Qiu; Jian-Qiang Wang; Juan Zhou

2010-01-01

313

The genesis and significance of N-MORB sub-types  

Microsoft Academic Search

A global compositional dichotomy for N-MORB magma (N1\\/N2) is recognized on the basis of Na2O, TiO2, CaO, and Al2O3 contents, and their respective ratios. We have characterized the two magma sub-types by means of their trace element patterns, and attempted to explain the differences in major and trace element contents in terms of a partial melting model, using data from

L. G. Viereck; M. F. J. Flower; J. Hertogen; H.-U. Schmincke; G. A. Jenner

1989-01-01

314

Shear zone broadening driven by metasomatism: an example from the Roffna metarhyolite (Suretta nappe, eastern central Alps)  

NASA Astrophysics Data System (ADS)

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.

Poilvet, J.-C.; Goncalves, P.; Marquer, D.

2012-04-01

315

Origin of hydrous fluids at seismogenic depth: Constraints from natural and experimental fault rocks  

NASA Astrophysics Data System (ADS)

Fluids control the mechanical behavior of fault zones during the seismic cycle. We used geochemical, mineralogical, microstructural, hydrogen isotope compositions and Fourier Transform Infrared (FTIR) investigations to characterize the origin of hydrous fluids involved in ductile and brittle shear zones at the bottom of the seismogenic crust. Natural samples were collected from exhumed mylonitic shear zones and cataclasite-pseudotachylyte bearing faults in the northern Adamello (Italian Southern Alps), which were active at 9-11 km depth. Pseudotachylytes, solidified coseismic friction-induced melts, testify to ancient seismogenic behavior of the faults. Natural pseudotachylytes were compared with artificial pseudotachylytes produced in high velocity friction experiments simulating seismic slip. Mylonites have mineralogical, elemental and hydrogen isotope compositions (-80K2O, Ba, Rb; depletion in CaO, Na2O, SiO2) and hydrogen isotope (-6950 C and have low ?D value (-93). The hydrogen isotope composition of bulk samples is dominated by the composition of cryptocrystalline domains (-103

Mittempergher, Silvia; Dallai, Luigi; Pennacchioni, Giorgio; Renard, Franois; Di Toro, Giulio

2014-01-01

316

Melt inclusions in sub-arc mantle xenoliths from the andesitic Avacha volcano (Kamchatka)  

NASA Astrophysics Data System (ADS)

Petrographic and geochemical data were obtained on melt inclusions in spinels from fresh mantle harzburgite xenoliths in andesitic tephras from the Avacha volcano in Kamchatka, Russia. Three types of melt inclusions (10-50m) are identified: Type 1 are the more numerous and are crystal free or, depending on their size, contain exclusively fine, euhedral and zoned amphibole crystals with minor sulfides; Types 2 and 3 are rare and constituted respectively of subhedral to euhedral Cpxamphibole and OpxCpx, all with coexisting minor glass. Larger (up to 200m) melt pockets possibly containing euhedral Opx may occur in the core of the spinels. Type 1 inclusions are homogeneous at 840C while equilibration temperature of Type 3 inclusions is situated at 1060C using Cpx-Opx geothermometer at 1.5GPa. The samples also contain metasomatic veins of two types: (1) opx-rich and (2) amphibole-rich. Each type is subdivided in two subgroups: one made up of quenched magmatic liquids with arc-related trace element signatures and one produced by fractionation of the quenched initial liquids and their reaction with host refractory mantle [1, 2]. Compositions of minerals in melt inclusions are closed to those in the Opx-rich veins previously reported [1, 2]. Homogenized Type 1 inclusions consist of a highly silicic (SiO2~60wt.%) alumino-calcic (Al2O3~20wt.% and CaO~7wt.%) glass low in alkalis (Na2O~4wt.% and K2O~0.5wt.%) and rich in sulfur (SO2~1wt.%). Oxygen decrease in the measured glass compositions with increasing temperature of heating experiments indicates high water content. Importantly, this glass composition is identical to the one identified in melt pockets and Type 3 inclusions, interpreted there as a quenched residual melt appearing after OpxCpx crystallization. We propose a multi-stage melt evolution model with combined fractionation and interaction processes in the shallow sub-arc mantle, based on the melt signature variations in the inclusions and in the related veins. [1] Bnard & Ionov (2009) GCA, 73, Issue 13 Supplement 1, A108. [2] Bnard & Ionov (2010) GRA, 12, 2112. Figure 1: An unheated Type 1 melt inclusion. Am, amphibole; Sulf, sulfide and Sp, spinel.

Bnard, A.; Ionov, D. A.; Plechov, P.

2010-12-01

317

Parameterizations of calcic clinopyroxeneMelt trace element partition coefficients  

NASA Astrophysics Data System (ADS)

Semiempirical parameterizations of the values and trends of variation of Nernst trace element partition coefficient data for Ca-rich clinopyroxene (cpx/liquidD) are provided, applicable mainly to common terrestrial magmatic suites. cpx/liquidD data for most trace elements show significant variability which cannot be neglected when modeling melting and crystallization. The influence of pressure on cpx/liquidD is strong for many elements, particularly Na and Sr, which increase as pressure rises, and most high-field strength elements, which decrease with increasing pressure. Most cpx/liquidD values increase as temperature decreases, as wt % melt MgO, MgO# (MgO/MgO+FeOtotal), CaO, and FeO contents drop, as cpx molar Mg# (Mg/Mg+Fetotal) decreases, and as wt % melt SiO2 and Na2O+K2O increase. No clear trends are seen for variations of cpx/liquidD against melt H2O. For mafic melts, many elements show well-defined trends of cpx/liquidD increase as the clinopyroxene tetrahedral Al content (cpx Aliv) increases. Many cpx/liquidD are well correlated against cpx/liquidDTi, and many "near-neighbor" elements show good cpx/liquidD intercorrelations (e.g., Zr-Hf, U-Th, Nb-Ta, La-Ce, Yb-Lu). Cpx/liquidD profiles calculated from these parameterizations can constrain changes of D values during melting or crystallization. Cpx/liquidD for the rare earth elements were fit to the lattice strain model to derive fits that can reproduce the cpx/liquidDREE profile shapes (REE = rare earth elements). These fits indicate that cpx/liquidDREE for melts more evolved than picritic basalts cannot be modeled assuming that all REE are in octahedral coordination in a single M2 site, but also require sixfold partitioning into an M1 site for Lu-Yb-Tm-Er.

Bdard, Jean H.

2014-02-01

318

Origin of two types of rhyolites in the Tarim Large Igneous Province: Consequences of incubation and melting of a mantle plume  

NASA Astrophysics Data System (ADS)

The Early Permian Tarim Large Igneous Province (LIP) in northwestern China contains a large area of silicic volcanics (~ 48,000 km2) which are spatially and temporally associated with mafic-ultramafic rocks. In order to understand the behavior of crust above a mantle plume, selected rhyolitic samples are investigated in terms of U-Pb zircon dating, geochemical and isotopic analyses. The Tarim rhyolites have high A/CNK ratios (= molar Al2O3/CaO + Na2O + K2O), Fe#, Ga/Al ratios, concentrations of high field strength elements (HFSEs) such as Zr and Nb, and rare earth elements (REEs), along with high zircon saturation temperatures (872-940 C), typical of aluminous A-type granitoids. Two contrasting rock types have been recognized. The low Nb-Ta type rhyolites are mainly associated with the first phase of the Tarim flood basalt magmatism at ~ 290 Ma. They are characterized by negative Nb-Ta anomalies, low ?Nd(t) and ?Hf(t) values, and high 87Sr/86Sr(t) and ?18Ozircon values, consistent with a derivation from continental crustal source. The high Nb-Ta type rhyolites and their plutonic equivalents are associated with the second episode of Tarim magmatism (283-272 Ma). They are characterized by small negative to positive Nb-Ta anomalies, oceanic island basalt (OIB)-like trace element ratios, low 87Sr/86Sr(t) and high ?Nd(t) and ?Hf(t) values. These high Nb-Ta rhyolites are best interpreted as hybrid products of crystal fractionation of mafic magmas, coupled with crustal assimilation. The temporal and compositional evolution of the Tarim rhyolites reflects various extents of thermal and mass exchange between mantle-derived basaltic magma and crustal material above a mantle plume. When the plume head rises to the base of the Tarim craton, it first melts enriched components in the lithospheric mantle (~ 290 Ma), part of which may have ponded near the crust-mantle boundary and induced crustal anatexis leading to the formation of the low Nb-Ta type rhyolites. At ~ 280 Ma, large magma chambers and plumbing systems were formed due to increasing magma supply rate during decompression melting of the mantle plume. This led to the formation of a mafic-ultramafic and felsic association of which the high Nb-Ta type rhyolites are a part.

Liu, Hai-Quan; Xu, Yi-Gang; Tian, Wei; Zhong, Yu-Ting; Mundil, Roland; Li, Xian-Hua; Yang, Yue-Heng; Luo, Zhen-Yu; Shang-Guan, Shi-Mai

2014-09-01

319

Geochemical and technological characterization of clays of Corumbata Formation, Paran Basin, in the state of So Paulo, Brazil for the application in the ceramic industry.  

NASA Astrophysics Data System (ADS)

The Corumbata Formation is a geological unit of the Paran Basin comprises a range of predominantly argillaceous facies. These clays are important from an economic point of view, because they represent important mineral deposits suppliers of raw materials for the ceramic industry in the production of ceramic tiles.The study presents preliminary results of a research that aims to study the clays municipalities Tamba, Ferreira and Santa Rosa of Viterbo in the State of So Paulo for their application and diversification of ceramic products. The methodology used was based on a detailed description of facies using the methodology in principles of analysis of Basin Miall (1984), followed by mineralogical identification by X-ray Diffraction, chemical analysis of major elements by X-ray Fluorescence and technological tests ceramic. According to the geological surveys of mines studied through columnar sections were identified the following lithofacies from base to top: Massive, Laminated, Intercalated and Altered. The mineralogy present on these lithofacies is composed by minerals: quartz, microclineo, albite, calcite, dolomite and hematite and by clay minerals illite, kaolinite and montmorillonite. The quartz represents the mineral more present in diffraction and occurs with d001 of 3.33 in all lithofacies studied. The illite clay mineral represents the most frequent in studied samples presenting d 001 10 in three conditions (natural, heated and treated with ethylene glycol) in which the blade was subjected to the analysis of X-ray diffraction, the presence of kaolinite or montmorillonite occurs or not in samples. It was observed a increased frequency of some minerals in the lithofacies studied, carbonates (calcite and dolomite), hematite and feldspar occurring in the intermediate portions of the profile with a predominance in lithofacies Intercalated. The illita clay mineral occurs throughout the profile, but with greater frequency in the lithofacies Massive and Laminated. The clay minerals kaolinite and montmorillonite occur in portions intermediate and top of the profiles studied in the intercalated and altered lithofacies. The chemical results of major elements by X-ray fluorescence confirmed the mineralogical results, with average values of 63.74 % of SiO2, 12.50 of Al2O3, 4.35% of of K2O, 0.45% of Na2O, 2,72% of CaO and 1,87 of MgO. The results chemical and mineralogical subsidized testing and ceramic formulations due to be executed later so defining the main applications of these clays in the production of ceramic products. The authors acknowledge the finantial support of Fundao de Amparo Pesquisa do Estado de So Paulo-FAPESP, (Process, number 2012/24219-9).

Christofoletti, Sergio Ricardo; Torres Moreno, Maria Margarita; Batezelli, Alessandro; Zanardo, Antenor

2014-05-01

320

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

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

Chang, Chun-Ying; Xu, Xiang-Hua; Liu, Chuan-Ping; Li, Shu-Yi; Liao, Xin-Rong; Dong, Jun; Li, Fang-Bai

2014-07-01

321

Amphibole-out phase boundary in partially melted metabasalt, its control over liquid fraction and composition, and source permeability  

NASA Astrophysics Data System (ADS)

A number of experimental studies in recent years have demonstrated that partial melting of hydrated basalt at lower crustal to upper mantle pressures is capable of generating up to 40% high-SiO2 liquids, closely comparable in many geochemical respects to tonalitic-trondhjemitic granitoids (TTG). From these studies it is apparent that the initiation of melting coincides with the beginning of amphibole dehydration but that a broad reaction interval over which amphibole coexists with high-SiO2 liquids is defined by the wet basalt solidus on one side, and the amphibole-out phase boundary on the other. The phase relations of an alkali-rich tholeiitic metabasalt have been examined in the outer half of this region, up to and beyond the amphibole-out phase boundary. Results indicate that amphibole exerts a strong control over the amount and composition of coexisting liquid over this interval. Melt fraction increases slowly and gradually (from 0% up to 20-30%) between the wet basalt solidus and up to amphibole-out but increases substantially (from 30% to >50%) across and immediately beyond it. Liquids are strongly to moderately peraluminous (molar Al2O3/(CaO + Na2O + K2O), A/CNK, > 1.0) up to amphibole-out, neutral at the boundary (A/CNK 1.0), and increasingly metaluminous (A/CNK < 1.0) beyond it. Up to amphibole-out, potassium is strongly partitioned into liquid relative to amphibole (i.e., mineral melt kd 0.2-0.3), whereas titanium is strongly partitioned into liquid (kd 2.0-6.0). Physical and chemical criteria suggest that efficient melt segregation leading to TTG plutonism requires more than 20-30% batch melting of a garnet-bearing basaltic protolith, near or beyond the amphibole-out phase boundary, leaving dry residues of eclogite or garnet granulite and producing metaluminous liquids that are strongly depleted in heavy rare earth elements (HREEs) and yttrium (Y). Lower degrees of melting may involve critical melting, where melt is squeezed out of the residue by deformation of the crystalline matrix, resulting in disequilibrium melt compositions.

Rapp, Robert P.

1995-08-01

322

Volatile Evolution of Magma Associated with the Solchiaro Eruption in the Phlegrean Volcanic District (Italy)  

NASA Astrophysics Data System (ADS)

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 includes the Campi Flegrei caldera and the islands of Ischia and Procida. We studied volatile and major element compositions of 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 the later more evolved magmas associated with this volcanic system. The composition of the magma before eruption was determined by analyzing melt inclusions (MI) in forsteritic olivine and diopside, glass embayments in phenocrysts, rim glass on phenocrysts and highly vesiculated matrix glass. The composition of MI ranges from basaltic to trachy-basaltic. Among major elements potassium shows the highest variability, ranging from 0.86 to 4.24 wt %. Three types of melt have been identified based on chemistry and occurrence: type 1 related to MI with Mg# > 66, type 2 represented by MI with Mg# < 66 and type 3 representing glass phases with Mg# intermediate to the other two. Type 1 melt is volatile undersaturated and was trapped as MI at relatively high depth (crust-mantle boundary) and is linked to source processes. Type 2 melt is the result of fractional crystallization and assimilation (FCA) of type 1 melt and was saturated in volatiles. Pressures of crystallization range from 0.62 to 1.43 kbar, or depths of 2.2 to 5.3 km. Type 3 melt represents the melt at the moment of the eruption. H2O-CO2 analyses of this glass shows the best fit to a calculated degassing path. The reconstructed magmatic evolution suggests that only in type 2 melts is there a positive correlation between Mg# and pressure or CO2 content. Compositions of some MI hosted in Mg-rich olivine show extremely low K2O and Na2O and high CaO contents of 0.86, 1.90 and 13.55 wt.%, respectively. Such compositions have not been previously reported for the PVD but are characteristic of the Aeolian Arc to the southwest.

Esposito, R.; Bodnar, R. J.; de Vivo, B.; Lima, A.; Fedele, L.; Shimizu, N.; Belkin, H.; Hunter, J.

2009-05-01

323

Volatile Evolution of Magma Associated with the Solchiaro Eruption in the Phlegrean Volcanic District (Italy)  

NASA Astrophysics Data System (ADS)

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.

Esposito, R.; Bodnar, R. J.; de Vivo, B.; Lima, A.; Fedele, L.; Shimizu, N.; Hunter, J.

2009-12-01

324

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)

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.

Zhang, Zhi-Yu; Du, Yang-Song; Teng, Chuan-Yao; Zhang, Jing; Pang, Zhen-Shan

2014-01-01

325

Phase relations and melting of carbonated peridotite between 10 and 20 GPa: a proxy for alkali- and CO2-rich silicate melts in the deep mantle  

NASA Astrophysics Data System (ADS)

We determined the melting phase relations, melt compositions, and melting reactions of carbonated peridotite on two carbonate-bearing peridotite compositions (ACP: alkali-rich peridotite + 5.0 wt % CO2 and PERC: fertile peridotite + 2.5 wt % CO2) at 10-20 GPa and 1,500-2,100 C and constrain isopleths of the CO2 contents in the silicate melts in the deep mantle. At 10-20 GPa, near-solidus (ACP: 1,400-1,630 C) carbonatitic melts with < 10 wt % SiO2 and > 40 wt % CO2 gradually change to carbonated silicate melts with > 25 wt % SiO2 and < 25 wt % CO2 between 1,480 and 1,670 C in the presence of residual majorite garnet, olivine/wadsleyite, and clinoenstatite/clinopyroxene. With increasing degrees of melting, the melt composition changes to an alkali- and CO2-rich silicate melt (Mg# = 83.7-91.6; ~ 26-36 wt % MgO; ~ 24-43 wt % SiO2; ~ 4-13 wt % CaO; ~ 0.6-3.1 wt % Na2O; and ~ 0.5-3.2 wt % K2O; ~ 6.4-38.4 wt % CO2). The temperature of the first appearance of CO2-rich silicate melt at 10-20 GPa is ~ 440-470 C lower than the solidus of volatile-free peridotite. Garnet + wadsleyite + clinoenstatite + carbonatitic melt controls initial carbonated silicate melting at a pressure < 15 GPa, whereas garnet + wadsleyite/ringwoodite + carbonatitic melt dominates at pressure > 15 GPa. Similar to hydrous peridotite, majorite garnet is a liquidus phase in carbonated peridotites (ACP and PERC) at 10-20 GPa. The liquidus is likely to be at ~ 2,050 C or higher at pressures of the present study, which gives a melting interval of more than 670 C in carbonated peridotite systems. Alkali-rich carbonated silicate melts may thus be produced through partial melting of carbonated peridotite to 20 GPa at near mantle adiabat or even at plume temperature. These alkali- and CO2-rich silicate melts can percolate upward and may react with volatile-rich materials accumulate at the top of transition zone near 410-km depth. If these refertilized domains migrate upward and convect out of the zone of metal saturation, CO2 and H2O flux melting can take place and kimberlite parental magmas can be generated. These mechanisms might be important for mantle dynamics and are potentially effective metasomatic processes in the deep mantle.

Ghosh, Sujoy; Litasov, Konstantin; Ohtani, Eiji

2014-02-01

326

The influence of multivariate analysis methods and target grain size on the accuracy of remote quantitative chemical analysis of rocks using laser induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) was used to quantitatively analyze 195 rock slab samples with known bulk chemical compositions, 90 pressed-powder samples derived from a subset of those rocks, and 31 pressed-powder geostandards under conditions that simulate the ChemCam instrument on the Mars Science Laboratory Rover (MSL), Curiosity. The low-volatile (<2 wt.%) silicate samples (90 rock slabs, corresponding powders, and 22 geostandards) were split into training, validation, and test sets. The LIBS spectra and chemical compositions of the training set were used with three multivariate methods to predict the chemical compositions of the test set. The methods were partial least squares (PLS), multilayer perceptron artificial neural networks (MLP ANNs) and cascade correlation (CC) ANNs. Both the full LIBS spectrum and the intensity at five pre-selected spectral channels per major element (feature selection) were used as input data for the multivariate calculations. The training spectra were supplied to the algorithms without averaging ( i.e. five spectra per target) and with averaging ( i.e. all spectra from the same target averaged and treated as one spectrum). In most cases neural networks did not perform better than PLS for our samples. PLS2 without spectral averaging outperformed all other procedures on the basis of lowest quadrature root mean squared error (RMSE) for both the full test set and the igneous rocks test set. The RMSE for PLS2 using the igneous rock slab test set is: 3.07 wt.% SiO 2, 0.87 wt.% TiO 2, 2.36 wt.% Al 2O 3, 2.20 wt.% Fe 2O 3, 0.08 wt.% MnO, 1.74 wt.% MgO, 1.14 wt.% CaO, 0.85 wt.% Na 2O, 0.81 wt.% K 2O. PLS1 with feature selection and averaging had a higher quadrature RMSE than PLS2, but merits further investigation as a method of reducing data volume and computation time and potentially improving prediction accuracy, particularly for samples that differ significantly from the training set. Precision and accuracy were influenced by the ratio of laser beam diameter (490 ?m) to grain size, with coarse-grained rocks often resulting in lower accuracy and precision than analyses of fine-grained rocks and powders. The number of analysis spots that were normally required to produce a chemical analysis within one standard deviation of the true bulk composition ranged from 10 for fine-grained rocks to >20 for some coarse-grained rocks.

Anderson, Ryan B.; Morris, Richard V.; Clegg, Samuel M.; Bell, James F.; Wiens, Roger C.; Humphries, Seth D.; Mertzman, Stanley A.; Graff, Trevor G.; McInroy, Rhonda

2011-10-01

327

Experimental and Petrological Constraints on Lunar Differentiation from the Apollo 15 Green Picritic Glasses  

NASA Technical Reports Server (NTRS)

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.

Elkins-Tanton, Linda T.; Chatterjee, Nilanjan; Grove, Timothy L.

2003-01-01

328

Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures  

NASA Astrophysics Data System (ADS)

A revised regular solution-type thermodynamic model for twelve-component silicate liquids in the system SiO2 TiO2 Al2O3 Fe2O3 Cr2O3 FeO MgO CaO Na2O K2O P2O5 H2O is calibrated. The model is referenced to previously published standard state thermodynamic properties and is derived from a set of internally consistent thermodynamic models for solid solutions of the igneous rock forming minerals, including: (Mg, Fe2+, Ca)-olivines, (Na, Mg, Fe2+, Ca)M2 (Mg, Fe2+, Ti, Fe3+, Al)M1 (Fe3+, Al, Si)2 TETO6- pyroxenes, (Na,Ca,K)-feldspars, (Mg, Fe2+) (Fe3+, Al, Cr)2O4-(Mg, Fe2+)2 TiO4 spinels and (Fe2+, Mg, Mn2+)TiO3-Fe2O3 rhombohedral oxides. The calibration utilizes over 2,500 experimentally determined compositions of silicate liquids coexisting at known temperatures, pressures and oxygen fugacities with apatite feldspar leucite olivine pyroxene quartz rhombohedral oxides spinel whitlockite water. The model is applicable to natural magmatic compositions (both hydrous and anhydrous), ranging from potash ankaratrites to rhyolites, over the temperature ( T) range 900 1700 C and pressures ( P) up to 4 GPa. The model is implemented as a software package (MELTS) which may be used to simulate igneous processes such as (1) equilibrium or fractional crystallization, (2) isothermal, isenthalpic or isochoric assimilation, and (3) degassing of volatiles. Phase equilibria are predicted using the MELTS package by specifying bulk composition of the system and either (1) T and P, (2) enthalpy (H) and P, (3) entropy (S) and P, or (4) T and volume (V). Phase relations in systems open to oxygen are determined by directly specifying the f o2 or the T-P-f o2 (or equivalently H- P-f o2, S- P-f o2, T-V- f o2) evolution path. Calculations are performed by constrained minimization of the appropriate thermodynamic potential. Compositions and proportions of solids and liquids in the equilibrium assemblage are computed.

Ghiorso, Mark S.; Sack, Richard O.

1995-03-01

329

Carbonate Stability and Melt Composition in Peridotite-CO2 System to 20 GPa  

NASA Astrophysics Data System (ADS)

Carbon dioxide and water are the most important volatile constituents in the Earth and they produce drastic changes in the melting phase relations and partial melt compositions of the mantle peridotite. Study of the peridotite-CO2 system is closely related to petrogenesis of kimberlite and diamond. There are a few high pressure mineral inclusions (i.e. majorite garnet and Ca and Mg perovskite) in diamond which suggest that kimberlites may be originated from the transition zone and lower mantle. The phase relations and melt compositions in the CO2-bearing peridotite at high pressures are poorly constrained, however the kimberlite and basalt-CO2 systems have been studied intensively. Simplified peridotite-CO2 system (like CMS or CMAS) has been studied at pressures up to 12 GPa (Canil and Scarfe, 1990), whereas complex peridotite-CO2 systems have been investigated only at lower pressures (up to 4 GPa, e.g. Wendlandt and Mysen, 1980). In this work we report the preliminary results on the phase relations and melt compositions of a model peridotite-CO2 system determined at 10-20 GPa and temperature range from 1200 to 2100oC. Our results show that solidus of carbonated peridotite is consistent with low-pressure data for CMAS-CO2 system. Liquidus phase at 10-20 GPa is majorite garnet. At 10-15 GPa, crystallization sequence with decreasing temperature is garnet, olivine and clinoenstatite. Magnesite is the most important CO2-rich phase stable in peridotite up to 1600oC at 20 GPa. The partial melt formed by 10-25% melting at 10-20 GPa has high MgO (26-34 wt.%) and FeO (7.0-10.4 wt.%) and low SiO2 (18-36 wt.%) and Al2O3 (0.5-1.3 wt.%) contents. It also contains 6-12 wt.% CaO, 0.6-2.0 wt.% Na2O and 0.1-0.3 wt.% K2O. The CO2 contents in the melts are 14-32 wt.%. The SiO2-poor nature of the partial melts is different from the results for melting of anhydrous or water-bearing peridotite. Partial melting of hydrous peridotite produces the melts enriched in SiO2, which can be related to komatiite magmas. The composition of low degree partial melts (10%) in present experiments is close to magnesiocarbonatites, whereas higher degree melting (20-25%) produce melts, which is close to kimberlite magmas.

Ghosh, S.; Ohtani, E.; Litasov, K. D.; Suzuki, A.; Terasaki, H.

2005-12-01

330

Geochemical Investigation of Saddlebag Lake Roof Pendant and Lee Vining Intrusive Suite Origins  

NASA Astrophysics Data System (ADS)

Our study is to determine to what extent volcanic rocks from the Saddlebag Lake Roof Pendant (SLRP) represent the erupted complement of the Sierra Nevada Batholith (SNB). SLRP formation is thought to be prior to or synchronous with Sierra Nevada orogeny. Age dates of the SLRP are similar to age dates from the Lee Vining Intrusive Suite (LVIS), so the LVIS may be the plutonic equivalent of the SLRP (Kistler and Fleck 1994). A hypothesized analog between SLRP-LVIS is the Wilson Ridge Pluton (WRP)-River Mountains (RM) complex in southern Nevada, which is a dismembered volcanic complex offset by normal faulting (Honn and Smith, 2008). WRP and RM trace element data from Honn and Smith plot very similar on a Hf-Th-Ta ternary diagram, and Sr and Nd isotope analyses also indicate that the Nevada rocks are co-magmatic. Our goal is to conduct geochemical tests to determine whether the SLRP and LVIS are co-genetic. Our preliminary data support the possibility that the SLRP may provide a window into the magmatic evolutionary processes that led to the development of the LVIS, and the SNB generally. Eighteen samples were collected from the SLRP; major element compositions of whole rocks yield similar weight percents of major oxides for some published data from the LVIS (Bateman et al. 1984). Our SLRP samples, though, trend to higher MgO, Fe2O3, Al2O3, and CaO, lower in SiO2 and Na2O+K2O. If the SLRP and LVIS are indeed related, the SLRP samples may represent some of the less-differentiated liquids from which the LVIS was derived. We were only able to find one basalt (51.2 wgt % SiO2), albeit with very low MgO (2.17 wt %), which may give clues as to the origin of the LVIS. If the mafic enclaves in the LVIS were once liquid, then the SLRP basalts should be comparable to mafic enclaves in composition. We are also analyzing mafic enclaves from the LVIS to explore whether these are liquid precursors to Sierra Nevada Batholith granites.

Wonderly, A.; Canchola, J.; Putirka, K. D.

2009-12-01

331

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)

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.

Lee, J.; Lee, I.; Lee, S.; Kim, J.

2010-12-01

332

Deriving chemical trends from thermal infrared spectra of weathered basalt: Implications for remotely determining chemical trends on Mars  

NASA Astrophysics Data System (ADS)

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.

Rampe, Elizabeth B.; Kraft, Michael D.; Sharp, Thomas G.

2013-07-01

333

Calcium isotope analytical technique for mafic rocks and its applications on constraining the source of Cenozoic ultra-potassic rocks in the Tibetan Plateau  

NASA Astrophysics Data System (ADS)

Ca isotope analytical technique for mafic rocks has been recently developed and set up at our lab. About mg level of a mafic rock sample was digested, and then a sub portion of the solution contains about 100ug Ca was spiked with a 42Ca-43Ca double spike and went through the column chemistry. Generally the Ca recovery is almost 100% and the procedure blank is about 50-150ng. Finally, about 5-10ug of the collected Ca cut was measured on our Triton TIMS. The precision of the data was around 0.1 per mil and the data we collected for standards are consistent with those reported by previous studies. There are two groups of Cenozoic ultra-potassic rocks that are widespread in Tibetan Plateau: a northern group in Songpan-Ganzi and Qiangtang Terranes and a southern group in Lhasa Terrane. Previous petrology evidence, such as a relative enrichment in large ion lithophile element (LILE); negative Ta,Nb and Ti anomalies and high LREE/HREE ratio, support that those rocks are both derived from sub-continental lithospheric mantle (SCLM). However, differences between these two groups of rocks do exist: the southern group has higher K2O, Rb, Zr, Th, contents and a higher Rb/Ba, coupled with lower Al2O3, CaO, Na2O, Sr; the southern 87Sr/86Sr ratios are higher while the 143Nd/144Nd ratios are lower, etc. These suggest that the rocks could be derived from different mantle sources or produced by different geological processes. Ca isotope is chosen in this study to better understand the source of the ultra-potassic rocks because Ca isotope has been a great tracer of different geological reservoirs and the isotopic compositions of Ca may represent different genesic processes. We propose that the ultra-potassic rocks in the Tibet should have significant 40Ca enrichments due to the decay from 40K to 40Ca, therefore the variation of Ca isotopic compositions among these ultra-potassic rocks could be obvious. We believe that based on our calcium data together with earlier Sr, Nd, Pb data, and evidence from petrology, geochronology and geochemistry, there is a good possibility to identify the petrogenesis of those rocks and/or provide important constrains of their sources.

Liu, Y.; Zhang, Z.; Xu, J.

2013-12-01

334

A comparative evaluation of the CF:CS and CRS models in 210Pb chronological studies applied to hydrographic basins in Brazil.  

PubMed

The Constant Flux: Constant Sedimentation (CF:CS) and Constant Rate of Supply (CRS) of unsupported?excess (210)Pb models have been applied to a (210)Pb data set providing of eighteen sediments profiles sampled at four riverine systems occurring in Brazil, South America: Corumbata River basin (S1=Site 1, So Paulo State), Atibaia River basin (S2=Site 2, So Paulo State), Ribeiro dos Bagres basin (S3=Site 3, So Paulo State) and Amazon River mouth (S4=Site 4, Amap State). These sites were chosen for a comparative evaluation of the performance of the CF:CS and CRS models due to their pronounced differences on the geographical location, geological context, soil composition, biodiversity, climate, rainfall, and water flow regime, among other variable aspects. However, all sediments cores exhibited a common denominator consisting on a database built from the use of the same techniques for acquiring the sediments major chemical composition (SiO2, Al2O3, Na2O, K2O, CaO, MgO, Fe2O3, MnO, P2O5, TiO2 and LOI-Loss on Ignition) and unsupported/excess (210)Pb activity data. In terms of sedimentation rates, the performance of the CRS model was better than that of the CF:CS model as it yielded values more compatible with those expected from field evidences. Under the chronological point of view, the CRS model always provided ages within the permitted range of the (210)Pb-method in the studied sites, whereas the CF:CS model predicted some values above 150 years. The SiO2 content decreased in accordance with the LOI increase in all cores analyzed and such inverse relationship was also tracked in the SiO2-LOI curves of historical trends. The SiO2-LOI concentration fluctuations in sites S1 and S3 also coincided with some Cu and Cr inputs in the drainage systems. PMID:25005051

Bonotto, D M; Garca-Tenorio, R

2014-09-01

335

Geochronology and geochemistry of late Paleozoic volcanic rocks on the western margin of the Songnen-Zhangguangcai Range Massif, NE China: Implications for the amalgamation history of the Xing'an and Songnen-Zhangguangcai Range massifs  

NASA Astrophysics Data System (ADS)

We here elucidate the tectonic evolution of the Xing'an and Songnen-Zhangguangcai Range massifs during the early Carboniferous-early Permian, based on zircon U-Pb dating and whole-rock geochemical analyses of volcanic rocks of the Songnen-Zhangguangcai Range Massif in the Sunwu area, Heilongjiang Province, NE China. Euhedral-subeuhedral zircons from three rhyolites and one dacite from the study area display fine-scale oscillatory growth zoning, indicating a magmatic origin. Zircon U-Pb dating by LA-ICP-MS indicates that these acidic volcanic rocks formed in the early Carboniferous-early Permian; i.e., early Carboniferous (~ 351 Ma), early late Carboniferous (~ 319 Ma), and early Permian (295-293 Ma). The early Carboniferous rhyolites exhibit chemical affinities to A-type rhyolites, implying an extensional environment. Their positive ?Hf(t) values (+ 8.67 to + 13.4 except for one spot of + 1.63) and Hf two-stage model ages (TDM2 = 562-988 Ma) indicate that the primary magma was possibly derived from partial melting of newly accreted continental crust. The early late Carboniferous rhyolites and dacites (~ 319 Ma) exhibit calc-alkaline peraluminous signature [molar Al2O3/(CaO + K2O + Na2O) ratio, or A/CNK = 1.04-1.22]. The ?Hf(t) values and TDM2 ages of zircons from the 319 Ma dacites are in the range of + 5.33 to + 9.32 and 907-1268 Ma, respectively, suggesting that the primary magma was derived from partial melting of newly accreted crust. The early Permian rhyolites (295-293 Ma) show chemical affinities to A-type rhyolites, implying an extensional tectonic environment; their positive ?Hf(t) values (+ 8.82 to + 13.8) and Hf two-stage model ages (484-743 Ma) indicate that the primary magma was derived from partial melting of newly accreted crust. Combined with the geochemical features of coeval igneous rocks from the eastern margin of the Xing'an Massif, these data reveal the late Paleozoic tectonic history and relationships of the Xing'an and Songnen-Zhangguangcai Range massifs, i.e., early Carboniferous westward subduction of the Paleo-Asian oceanic plate beneath the Xing'an Massif, followed by early late Carboniferous collision and amalgamation of microcontinental blocks, and early Permian post-collisional extension.

Li, Yu; Xu, Wen-Liang; Wang, Feng; Tang, Jie; Pei, Fu-Ping; Wang, Zi-Jin

2014-09-01

336

Geochemistry of silicic magmas in the Macolod Corridor, SW Luzon, Philippines: evidence of distinct, mantle-derived, crustal sources for silicic magmas  

NASA Astrophysics Data System (ADS)

Silicic volcanic deposits (>65 wt% SiO2), which occur as domes, lavas and pyroclastic deposits, are relatively abundant in the Macolod Corridor, SW Luzon, Philippines. At Makiling stratovolcano, silicic domes occur along the margins of the volcano and are chemically similar to the silicic lavas that comprise part of the volcano. Pyroclastic flows are associated with the Laguna de Bay Caldera and these are chemically distinct from the domes and lavas at Makiling stratovolcano. As a whole, samples from the Laguna de Bay Caldera contain lower concentrations of MgO and higher concentrations of Fe2O3(t) than the samples from domes and lavas. The Laguna de Bay samples are more enriched in incompatible trace elements. The silicic rocks from the domes, Makiling Volcano and Laguna de Bay Caldera all contain high alkalis and high K2O/Na2O ratios. Melting experiments of primitive basalts and andesites demonstrate that it is difficult to produce high K2O/Na2O silicic magmas by fractional crystallization or partial melting of a low K2O/Na2O source. However, recent melting experiments (Sisson et al., Contrib Mineral Petrol 148:635-661, 2005) demonstrate that extreme fractional crystallization or partial melting of K-rich basalts can produce these silicic magmas. Our model for the generation of the silicic magmas in the Macolod Corridor requires partial melting of mantle-derived, evolved, moderate to K-rich, crystallized calc-alkaline magmas that ponded and crystallized in the mid-crust. Major and trace element variations, along with oxygen isotopes and ages of the deposits, are consistent with this model.

Vogel, Thomas A.; Flood, Timothy P.; Patino, Lina C.; Wilmot, Melissa S.; Maximo, Raymond Patrick R.; Arpa, Carmencita B.; Arcilla, Carlo A.; Stimac, James A.

2006-03-01

337

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)

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.

Rezaie Boroon, M.; Ramirez, P. C.; Gnandi, K.

2009-12-01

338

Late Ordovician to early Devonian adakites and Nb-enriched basalts in the Liuyuan area, Beishan, NW China: Implications for early Paleozoic slab-melting and crustal growth in the southern Altaids  

Microsoft Academic Search

We report newly-defined Nb-enriched basalts, adakites and dacites from the Beishan, NW China of the southern Altaids based on field, geochemical, isotopic and geochronology studies. Two phases of adakites (adakite-I and adakite-II) have been defined, which are calc-alkaline, and characterized by high Na2O\\/K2O ratios (1.491.71 and 2.323.64) and Sr contents (4941213ppm and 325494ppm), negligible to positive Eu anomalies, strong depletion

Qigui Mao; Wenjiao Xiao; Tonghui Fang; Jingbin Wang; Chunming Han; Min Sun; Chao Yuan

339

Search for solid conductors of Na/+/ and K/+/ ions - Five new conductors  

NASA Technical Reports Server (NTRS)

Five new conductors of positive Na and K ions, for use as separators in high energy secondary batteries, have been discovered. They include: (1) the pyrochlores NaTaWO6 and NaTa2O5F; (2) the bcc form of NaSbO3; and (3) the niobates 2Na2O-3Nb2O5 and 2K2O-3Nb2O5, with the alkali ions probably in open layers of the completely determined structure. On the basis of approximately 40 structure types, generalizations have been made regarding the relation between structure and ionic transport.

Singer, J.; Kautz, H.; Fielder, W.; Fordyce, J.

1975-01-01

340

Carboniferous-Permian extensive magmatism in the West Junggar, Xinjiang, northwestern China: its geochemistry, geochronology, and petrogenesis  

NASA Astrophysics Data System (ADS)

Located between the Tarim, Kazakhstan, and Siberian plates, the West Junggar terrane is a key component of the Paleozoic Central Asian Orogenic Belt (CAOB) with widespread late Paleozoic igneous rocks. In this paper, we report petrological, geochronological, and geochemical data for selected granitoids from the West Junggar. Based on geochronology, the I-type and A-type granites were formed predominantly at 347.9-319.0 Ma and at 321.4-290 Ma respectively. The early-stage I-type granites are characterized by low SiO2, Na2O, and K2O contents with Na2O/K2O ratios > 1 and are metaluminous to weakly-peraluminous. They are enriched in large ion lithophile elements (LILE) and in Sr but depleted in high field strength elements (HFSE), with (87Sr/86Sr)i ratios of 0.7028-0.7044 and ?Nd(t) values varying from + 5.74 to + 7.76. The late-stage I-type granites are characterized by low contents of Si2O and K2O and relatively high contents of FeO, MgO, and Na2O with Na2O/K2O ratios > 1, and are metaluminous to weakly-peraluminous. They are also enriched in LILE and depleted in HFSE with Eu anomalies, (87Sr/86Sr)i ratios of 0.703-0.704, and ?Nd(t) values varying from + 5.20 to + 8.00. The A-type granites have high SiO2 contents, high K calc-alkaline-shoshonitic affinities, positive ?Nd(t) values (5.76-7.77), and low initial 87Sr/86Sr ratios (0.7017-0.7045). Along with reported Sr-Nd isotopic data and regional geologic evidence the Early Carboniferous I-type granites are interpreted as products of partial melting of trapped oceanic crust triggered by underplated mantle wedge-derived basaltic magma; the Late Carboniferous-Early Permian I-type granites as derivatives of partially melted trapped oceanic crust; and the A-type granites as resulting from partial melting of trapped juvenile oceanic crust in an extensional regime. The A-type granitoids with high positive ?Nd(t) values and high Zr-saturation temperatures could be genetically related to a mantle plume or a regional-scale mantle upwelling in the CAOB.

Gao, Rui; Xiao, Long; Pirajno, Franco; Wang, Guo-can; He, Xin-xing; Yang, Gang; Yan, Sheng-wu

2014-09-01

341

Needle-like apatite-leucite glass-ceramic as a base material for the veneering of metal restorations in dentistry  

Microsoft Academic Search

A needle-like apatite-leucite glass-ceramic was prepared in the SiO2-Al2O3-Na2O-K2O-P2O5-F system. Nucleation and crystallization processes were studied in bulk and powdered samples. The crystallization of leucite follows the mechanism of surface crystallization. After the precipitation of NaCaPO4 crystals and another unknown crystal phase, the formation of needle-like apatite is based on a volume nucleation and crystallization process. The mechanism of the

V. Rheinberger; S. Wegner; M. Frank

2000-01-01

342

Modeling of mineralogical composition, density and elastic wave velocities in anhydrous magmatic rocks  

Microsoft Academic Search

We use the technique of direct minimization of the Gibbs free energy of the 8-component (K2O-Na2O-Fe2O3-FeO-CaO-MgO-Al2O3-SiO2) multiphase system in order to determine the equilibrium mineral assemblages of rocks of different bulk chemical compositions equilibrated at various P-T conditions. The calculated modal compositions of rocks and experimental data on elastic moduli of single crystals are then used to calculate densities and

Stephan V. Sobolev; Andrey Yu. Babeyko

1994-01-01

343

Glass-to-metal seals comprising relatively high expansion metals  

NASA Technical Reports Server (NTRS)

A glass suitable for glass-to-metal seals that has a resistance to attack by moisture and a high coefficient of linear thermal expansion is introduced. Linear expansion covers the range from 12 to 14 x 10 to the minus 6 C between room temperature and 500 C. The glass is essentially composed of, by molar percent, about 9% of K2O, about 10% of Na2O, about 70% of SiO2, about 6% Al2O3, and about 5% of MgO.

Hirayama, C. (inventor)

1974-01-01

344

Zircon UPb age, geochemistry and SrNdPb isotopic compositions of adakitic volcanic rocks from Jiaodong, Shandong Province, Eastern China: Constraints on petrogenesis and implications  

Microsoft Academic Search

A zircon UPb age of adakitic rocks from Jiaodong, the Shandong Province, indicates that the volcanic rocks erupted at 123.60.8Ma. The volcanic rocks are composed only of trachyandesite with SiO2 contents ranging from 59 to 62wt.% and Al2O3 contents from 14 to 16wt.%. Their K2O contents range from 3.1 to 3.9wt.% and those of Na2O from 4.2 to 4.9wt.%, indicating

Shen Liu; Ruizhong Hu; Shan Gao; Caixia Feng; Bobin Yu; Youqiang Qi; Tao Wang; Guangying Feng; Ian M. Coulson

2009-01-01

345

High Quantum Efficiency of Nd3+ Ions in a Phosphate Glass System using the Judd-Ofelt Theory  

NASA Astrophysics Data System (ADS)

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.

Dantas, Noelio Oliveira; Serqueira, Elias Oliveira; Silva, Anielle Christine Almeida; Andrade, Accio Aparecido; Loureno, Sidney Alves

2013-08-01

346

Theoretical modeling of monazite growth in a low-Ca metapelite  

Microsoft Academic Search

Monazite growth and composition has been modeled in the system K2ONa2OCaOMnOMgOFeOAl2O3SiO2H2OY2O3Ce2O3P2O5F and a pseudosection is presented that is contoured for monazite modal amount and YPO4 composition, garnet amount and YAG composition, and xenotime amount. Monazite amount and composition is strongly controlled by the presence of xenotime and when xenotime is absent, by the growth or consumption of garnet. Monazite grows

Frank S. Spear; Joseph M. Pyle

2010-01-01

347

Low temperature sintering of (Zn 1? x , Mg x )TiO 3 microwave dielectrics  

Microsoft Academic Search

The effects of glass additives and milling process on the microwave dielectric properties of (Zn1?x, Mgx) TiO3 (ZMT) ceramics were investigated. Three glasses including B2O3SiO2ZnONa2O (BSiZnNa), B2O3SiO2ZnOK2O (BSiZnK) and B2O3K2OMnCO3 (BKMn) were selected for this study. Host material (Zn0.6Mg0.4)TiO3 was selected to be sintered with glasses in the temperature range of 9001200C. For (Zn0.6Mg0.4)TiO3 with 5wt.% glass BSiZnK sintered at

Yuh-Ruey Wang; Sea-Fue Wang; Yen-Ming Lin

2005-01-01

348

The Comparative Structural Study of Vitreous Matrices P{sub 2}O{sub 5}centre dotMeO [MeO ident to Li{sub 2}O (M{sub 1}) or CaO (M{sub 2})] Systems and {sub x}Fe{sub 2}O{sub 3}(100-x)[P{sub 2}O{sub 5}centre dotMeO] Glasses by Raman Spectroscopy  

SciTech Connect

For getting information about the way in which the structural units presented in glass matrices P{sub 2}O{sub 5}centre dotLi{sub 2}O (M{sub 1}) and P{sub 2}O{sub 5}centre dotCaO (M{sub 2}) are modifying with the substitutions Li{sub 2}O with CaO, these glasses where investigated by Raman spectroscopies. The absorption bands obtained and their assignments for each those two matrices are summarized. The influence of Fe{sub 2}O{sub 3} content on the structure of M1 and M2 matrices was followed.

Andronache, C. [Department of Physics, North University of Baia Mare, Str. Victoriei nr. 76, RO-431122, Baia Mare (Romania)

2010-01-21

349

Geochemistry of black shales from the Lower Cretaceous Paja Formation, Eastern Cordillera, Colombia: Source weathering, provenance, and tectonic setting  

NASA Astrophysics Data System (ADS)

The major and trace element characteristics of black shales from the Lower Cretaceous Paja Formation of Colombia are broadly comparable with those of the average upper continental crust. Among the exceptions are marked enrichments in V, Cr, and Ni. These enrichments are associated with high organic carbon contents. CaO and Na 2O are strongly depleted, leading to high values for both the Chemical Index of Alteration (77-96) and the Plagioclase Index of Alteration (86-99), which indicates derivation from a stable, intensely weathered felsic source terrane. The REE abundances and patterns vary considerably but can be divided into three main groups according to their characteristics and stratigraphic position. Four samples from the lower part of the Paja Formation (Group 1) are characterized by LREE-enriched chondrite-normalized patterns (average La N/Yb N = 8.41) and significant negative Eu anomalies (average Eu/Eu ? = 0.63). A second group of five samples (Group 2), also from the lower part, have relatively flat REE patterns (average La N/Yb N = 1.84) and only slightly smaller Eu anomalies (average Eu/Eu ? = 0.69). Six samples from the middle and upper parts (Group 3) have highly fractionated patterns (average La N/Yb N = 15.35), resembling those of Group 1, and an identical average Eu/Eu ? of 0.63. The fractionated REE patterns and significant negative Eu anomalies in Groups 1 and 3 are consistent with derivation from an evolved felsic source. The flatter patterns of Group 2 shale and strongly concave MREE-depleted patterns in two additional shales likely were produced during diagenesis, rather than reflecting more mafic detrital inputs. An analysis of a single sandstone suggests diagenetic modification of the REE, because its REE pattern is identical to that of the upper continental crust except for the presence of a significant positive Eu anomaly (Eu/Eu ? = 1.15). Felsic provenance for all samples is suggested by the clustering on the Th/Sc-Zr/Sc and Gd N/Yb N-Eu/Eu ? diagrams. Averages of unmodified Groups 1 and 3 REE patterns compare well with cratonic sediments from the Roraima Formation in the Guyana Shield, suggesting derivation from a continental source of similar composition. In comparison with modern sediments, the geochemical parameters (K 2O/Na 2O, La N/Yb N, La N/Sm N, Eu/Eu ?, La/Sc, La/Y, Ce/Sc) suggest the Paja Formation was deposited at a passive margin. The Paja shales thus represent highly mature sediments recycled from deeply weathered, older, sedimentary/metasedimentary rocks, possibly in the Guyana Shield, though Na-rich volcanic/granitic rocks may have contributed to some extent.

Campos Alvarez, N. O.; Roser, B. P.

2007-04-01

350

Melting and subsolidus phase relations in peridotite and eclogite systems with reduced Csbnd Osbnd H fluid at 3-16 GPa  

NASA Astrophysics Data System (ADS)

Melting phase relations of peridotite and eclogite coexisting with reduced C-O-H fluid have been studied at 3-16 GPa and 1200-1600 C. In order to perform these experiments the double-capsule technique with fO2 control by outer Mo-MoO2 or Fe-FeO buffer capsule was designed and developed for multianvil experiments at pressures 3-21 GPa. Silicate phase assemblages resemble those in volatile-free lithologies, i.e. olivine/wadsleyite-orthopyroxene-clinopyroxene-garnet in peridotite and garnet-omphacite in eclogite. Melting was detected by the appearance of quenched crystals of pyroxene, feldspar and glassy silica. Estimated solidus temperatures for peridotite + C-O-H fluid with fO2=Fe-FeO are 1200 C at 3 GPa and 1700 C at 16 GPa. The solidus of the system with fO2=Mo-MoO2 was about 100 C lower. Estimated solidus temperatures for eclogite + C-O-H fluid with fO2=Fe-FeO are 1100 C at 3 GPa and 1600 C at 16 GPa, and for eclogite at fO2=Mo-MoO2 solidus temperatures were 20-50 C lower. These solidus temperatures are much higher (300-500 C) than those for peridotite and eclogite systems with H2O and/or CO2, but are still 300-400 C lower than the solidi of volatile-free peridotite and eclogite at studied pressures. The compositions of partial melt were estimated from mass-balance calculations: partial melts of peridotite have CaO-poor (6-9 wt.%) basaltic compositions with 44-47 wt.% SiO2 and 1.1-1.6 wt.% Na2O. Melts of eclogite contain more SiO2 (47-49 wt.%) and are enriched in CaO (9-15 wt.%), Na2O (9-14 wt.%), and K2O (1.3-2.2 wt.%). All runs contained graphite or diamond crystals along with porous carbon aggregate with micro-inclusions of silicates indicating that reduced fluid may dissolve significant amounts of silicate components. Analyses of carbon aggregates using a defocused electron microprobe beam reveal compositions similar to estimated partial melts. The diamonds formed from reduced C-O-H fluid may have natural analogues as polycrystalline diamonds. The oxygen fugacity in the Earth's mantle decreases with pressure from about fayalite-magnetite-quartz at shallow depths of 20-50 km to about iron-wustite at 250-300 km according to fO2 estimations from cratonic peridotite. We show significant increase of solidus temperatures in peridotite and eclogite coexisting with reduced CH4-H2O fluid relative to the systems with oxidized H2O-CO2 fluid. We emphasize that redox melting by change of oxidation state across a mantle section, a phase transition, or the lithosphere-asthenosphere boundary can be the dominant melting process in the deep Earth's interior.

Litasov, Konstantin D.; Shatskiy, Anton; Ohtani, Eiji

2014-04-01

351

Diagrammes d'activits dans le systme Al2O3-SiO2-K2O-H2O. Influence d'un ajout de magnsium  

E-print Network

'une illite magnésienne de composition Si3.43Al2.24Mg0.38K0.8O10(OH)2. On propose divers diagrammes construits ; kaolinite ; feldspath potassique ; pyrophyllite ; muscovite ; quartz ; illite ; affigraphie. Phase relations of an addition of MgO is examined through the study of the stability of a magnesium illite with composition Si3

Paris-Sud XI, Université de

352

Effect of composition on the properties of glasses in the K 2OBaOMgOSiO 2Al 2O 3B 2O 3MgF 2 system  

Microsoft Academic Search

Twenty five glasses in the(1?Z)BaO:ZK2O:(6?X)MgO:XMgF2:(3?Q)Al2O3:QB2O3:8SiO2 system have been prepared and the effect of systematic changes in composition (Z=0, 0.25, 0.5, 0.75 and 1.0, X=2, 2.5 and 3.0 and Q=0, 0.5 and 1) on molar volume (MV), fractional glass compactness (C), microhardness (?HV), glass transition temperature (Tgmid) and coefficient of thermal expansion (?) determined. As potassium is substituted for barium (increasing

K. Greene; M. J. Pomeroy; S. Hampshire; R. Hill

2003-01-01

353

The composition of Yakutian diamond-forming liquids  

NASA Astrophysics Data System (ADS)

Microinclusions in natural diamonds represent a bulk sample of fluids/melts from which they crystallized [e.g. Navon et al., 1988], and provide a unique opportunity to characterize diamond-forming liquids and to understand their origin and evolution within the mantle. Here we report the composition of microinclusions in Yakutian diamonds (fibrous, cloudy, coated). Diamonds were recovered from several major industrial kimberlite pipes (Udachnaya, Internatsionalnaya, Yubileinaya, Sytyksnskaya, Aikhal) and alluvial deposits (Ebelyakh area). The major-element compositions of the subsurface microinclusions have been determined using EDS. All analyses are normalized to 100% on a carbon free basis (with excess oxygen for chlorine). Major- and trace-element compositions of the bulk microinclusion populations have been quantitatively analyzed by LA-ICP-MS. The abundances of carbonates, water and silicates in the diamonds were determined by FTIR. The major-element composition of microinclusions in Yakutian diamonds shows wide variations. Some important inter-element correlations between silica and chlorine content and the water/carbonate ratio of microinclusions are observed. In comparison with the worldwide database, the fluids in most of the studied diamonds define a continuous range of carbonatitic to silicic compositions and only a few fall into the starting interval of the carbonatitic to saline range. The silicic microinclusions are rich in water, SiO2, Al2O3, K2O and P2O5. The silicic end-member, constrained from combined EDS and FTIR data, carries ~80 wt % silicates, 11 wt % water, 6 wt % carbonates and 3 wt % apatite. Carbonatitic microinclusions are rich in carbonate, CaO, MgO and FeO. The carbonatitic end-member comprises 82 wt% carbonates, 12 wt% silicates, 2 wt% water, 2 wt% apatite and 1 wt% halides. Samples with saline components are slightly enriched in water, K2O, Na2O and Cl. The most saline inclusions in Yakutian diamonds consist of 49 wt% carbonates, 25 wt% halides, 12 wt% silicates, 9 wt% water, 3 wt% sulfides and 2 wt% apatite. The trace-element compositions of the microinclusions are generally similar to those of kimberlites and carbonatites, but there are significant differences in major elements. The bulk analyses of the microinclusions in Yakutian diamonds have smooth PM-normalized patterns for the LILE. Some samples show enrichment in Cs. The relative abundance of K in the fluids is significantly higher than observed in the host kimberlite and carbonatites. The pattern of HFSE in the microinclusions shows some depletion in Ti, Zr and Hf relative to Ta, Nb and Mo. The REE pattern reveals low abundances of the heavy REE and high light REE concentrations. The La/Dy of the micro-inclusion populations varies widely, gradually decreasing from carbonatitic to silicic compositions. Many samples with carbonatitic composition have a negative anomaly in Y. Yakutian diamonds have low contents of transition metals and most of them are significantly depleted in Ni and Co. The observed geochemical features are consistent with a genetic link between the diamond-forming fluids and ephemeral carbonatitic liquids (fluids/melts) which sometimes may be precursors of the host kimberlite. These fluids/melts may originate either from the metasomatic influx of volatile agents and/or from partial melting of previously carbonated eclogites and peridotites. Some elemental variations may be explained by the fractional crystallization of such fluids/melts, or mixing between liquids with different compositions. These processes result in diamond formation and kimberlite generation.

Zedgenizov, D. A.; Shatsky, V. S.; Araujo, D.; Griffin, W. L.; Ragozin, A. L.

2009-04-01

354

Late Paleozoic granitoid magmatism in Chukotka and its relation to Ellesmerian orogeny in Arctic Alaska and Canada  

NASA Astrophysics Data System (ADS)

Chukotka fold area (Mesozoides) was formed as a result of collision between Chukotka - Arctic Alaska microplate and active margin of Siberian continent [1]. At present the majority of researches distinguish at least three stages of granitoid magmatism of Chukotka Mesozoides: 147-139, 127-100 and 82.4-78.8 Ma [2]. Granites of first two stages intrude metamorphic basement and Paleozoic-Mesozoic fold structures. Formation of Early Cretaceous granitoids are often considered in relation to granite-metamorphic core complexes evolution [3-5]. Intrusion of the third stage granitoid intrusions corresponds to Okhotsk-Chukotka volcanic belt activity. At the same time in several publications there is information of existence of more ancient Paleozoic granitoids. For orthogneisses of East Chukotka there are age estimations 380-320 Ma (U-Pb SHRIMP, [6]). V.V.Akinin [7] showed that protoliths of Velinkenay and Kuekvun plutons have Late Devonian (380-360 Ma) age. Granites of Kibera Peninsula were dated as 43932 Ma [Rb-Sr method, 8]. Besides basal conglomerates of Carboniferous deposits contain granite pebbles. At the same time on the existing geological maps granites are indicated as Early Cretaceous ones [9]. Thus there are contradictions on the age estimations and scales of Paleozoic and Mesozoic granitoid magmatism manifestation within Chukotka Mesozoides. As a result of this interregional correlations, first of all correlation of Caledonian and Ellesmerian orogenies events in Arctic region, are complicated. So we carried out U-Pb geochronological studies of some reference granitoid plutons of Central Chukotka, located in the cores of antiform structures, composed of Paleozoic deposits, namely granodiorites of Kibera and quartz syenites of Kuekvyun plutons (Kuul and Kuekvyun rises respectively). Granitoids of Kibera pluton (coastal clippings of Kibera Peninsula, coast of East-Siberian Sea) intrude terrigenous Devonian deposits with carbonate units which are overlain with erosion by Permian-Triassic carbonate-terrigenous and sandy-argillaceous deposits. Kibera pluton is composed mainly of Amph-Bi granites and granite-porphyres. Endocontact zone is presented by foliated Bi granodiorites which were dated. Within Kuekvyun Rise [2] in the core of lineated antiform structure Devonian deposits, metamorphosed to amphibolite facies and deformed, are exposed. Earlier such structures were considered as horst-like saliences of Paleozoic cover and crystalline basement, now, as structures of granite-metamorphic core complexes [3-5]. In the central part of antiform there are micaceous and Gar-Bi schists, marbled limestones, Q-Fsp-Ep-Bi-Amph, Bi-Amph-Cpx schists, intruded by subconcordant bodies of Amph-Bi quartz syenites. At the peripheral parts of rise metamorphic complexes are discordantly overlain by terrigenous deposits of Permian(?)-Triassic age. Granodiorites of Kibera pluton (N 6956' 50.5'', E17240' 52,1''; SiO2=67.34%, TiO2=0.41%, Al2O3=14.72%, FeO=2.66%, Fe2O3=1.88%, MnO=0.074%, MgO=1.4%, CaO=2.48%, Na2O=3.71%, K2O=3.42%, P2O5=0.232%) have foliated texture, blastogranitic structure and are composed of quartz, plagioclase, potassic feldspar and biotite. Accessory minerals are sphene, allanite, apatite and zircon. Amph-Bi quartz syenites of Kuekvyun pluton (N 6837'25.4'', E17828'21,2'', SiO2=63.51%, TiO2=0.40%, Al2O3=16.57%, FeO=2.3%, Fe2O3=1.8%, MnO= 0.056%, MgO=0.99%, CaO=3.6%, Na2O=3.24%, K2O=5.83%, P2O5=0.245%) also have foliated texture, blastohypidiomorphic structure and are composed of plagioclase, potassic feldspar, amphibole, biotite and quartz. Sphene prevails within accessory minerals, allanite, apatite and zircon are also present. U-Pb geochronological studies for Kibera granodiorite are carried out for three microshots (10-15 grains) of most transparent zircon crystals, selected from 85-100 and 100-150 micron fractions. Points of isotope composition of studied microshots form Discordia, which lower intersection with Concordia correspond to age 3535 Ma (upper intersection, 1183660 Ma, ???=0.17). U-Pb geochronologica

Luchitskaya, Marina; Sokolov, Sergey; Kotov, Alexander; Katkov, Sergey; Sal'nikova, Elena; Yakovleva, Sonya

2013-04-01

355

A petrologic study of the Teanaway Basalt: Eocene slab window volcanism in central WA  

NASA Astrophysics Data System (ADS)

The Teanaway Basalt (TB) includes subaerial basalt to andesite flows, mafic to felsic tuffs, and rhyolite domes in the Central Cascades of Washington State. These volcanics overlie the extensive ~47 Ma Teanaway Dike Swarm (TDS) that cuts the underlying Swauk Formation. This study focuses on the tectonic setting of eruption and geochemical variations relating to geography and stratigraphy within the TB. The western-most area of the TB, Easton Ridge (ER), is compared with the eastern-most area of the TB, Liberty Ridge (LR) - 40 km to the east of ER. The bimodal TB consists predominantly of basaltic andesite and andesite (45.3-63.1 wt% SiO2) with subordinate rhyolite (75.9-79.4 wt% SiO2). The mafic rocks classify as primarily medium-K tholeiites (0.1-3.0 wt% K2O), but a few samples classify as alkaline. Enrichment in LILE and depletion in HFSE on spidergrams are indicative of an arc setting. However, compared with the modern Cascade Arc, the TB is distinctly higher in Fe2O3T (8.8-17.1 wt%) and TiO2 (1.1-2.7 wt%), and distinctly lower in Al2O3 (11.2-14.6) and K2O, with a similar range of Mg #s (0.15-0.48). Most tectonic discrimination plots characterize the TB as MORB, but some indicate an arc or within-plate setting. Preliminary Pb isotopic data (206Pb/204Pb = 19.13-19.19, 207Pb/204Pb = 15.62-15.64, and 208Pb/204Pb = 38.78-38.90) indicate the TB and TDS are more enriched than Cascade Arc rocks in 206Pb/204Pb and 208Pb/204Pb. Overall, these geochemical data are consistent with a model in which asthenospheric mantle ascending through a slab window interacts with mantle wedge that has previously acquired arc chemical traits. The existence of a slab window in this region during the mid-Eocene is compatible with plate reconstructions and evidence of extension that have been attributed to subduction of the Resurrection-Kula ridge (Haeussler et al., 2003). Harker plots show lavas at LR are generally more enriched than those at ER in Fe2O3T (11.9-17.1 wt% vs 8.8-15.7 wt%) MnO (0.16-0.28 wt% vs 0.11-0.24 wt%), and TiO2 (1.2-2.4 wt% vs 0.8-2.7 wt%), and have a narrower range of CaO (1.5-9.4 wt%) and Na2O (1.5-3.3 wt%) concentrations. Both LR and ER samples display modest LREE enrichment (La/Yb = 2.1-3.7) and similar incompatible element ratios, suggesting similar sources. ER samples show a broader range of REE contents but extend to lower levels, and have smaller negative Eu anomalies (Eu/Eu* = 0.55-0.96). Pearce element ratio plots suggest much of the variation reflects different degrees of plag+cpx fractionation. Alkaline lavas are restricted to ER and the central area of the TB. Differences in concentration at similar Mg# (most notably in Fe2O3T, TiO2, MnO, and Na2O) suggest multiple parent magmas, probably from similar mantle sources. With increasing stratigraphic height in the ~1.6 km thick LR section, there are general decreases in SiO2 (60 to 54 wt%), and general increases in CaO (4 to 8 wt%), MnO (0.1-0.15 wt%), and P2O5 (0.2-0.65 wt%). Mg# displays several cycles of decrease followed by increase, each extending over 400-1000m. These trends are suggestive of an evolving system that experienced multiple replenishment events.

Roepke, E.; Tepper, J. H.; Ivener, D.

2013-12-01

356

Na +-superionic conductors of glassceramics in the system Na 2OSm 2O 3X 2O 3P 2O 5SiO 2 (X=Al, Ga)  

Microsoft Academic Search

Glassceramics of the aluminum or gallium, and phosphorus-containing Na5SmSi4O12-type Na+-superionic conductors (N5SXPS) were prepared by crystallization of glasses with the composition Na3+3x?y+zSm1?xXzPySi3?y?zO9 (X=Al; NSAPS, X=Ga; NSGPS), and the effects of X elements on the separation of the phase and the microstructural effects on the conduction properties of glassceramics were discussed. N5SXPS was obtained as a stable phase at high temperatures.

Toshinori Okura; Hideki Monma; Kimihiro Yamashita

2004-01-01

357

Effect of the Chemical Composition on The Pyroplastic Deformation of Sanitaryware Porcelain Body  

NASA Astrophysics Data System (ADS)

Pyroplastic deformation is the bending of a ceramic specimen caused by gravity during heat treatment. It can be defined as the loss of shape of product during its firing. Pyroplastic deformation is related to properties of liquid phases formed during firing. Therefore, the effect of the chemical composition on the pyroplastic deformation of sanitaryware porcelain was investigated in this study. Systematical compositional arrangements were made according to different combinations of (SiO2/Al2O3) and (Na2O/K2O) ratios by using Seger formula approach. Pyroplastic deformation behaviour of compositions within a controlled firing regime was investigated by using fleximeter. The bodies were also prepared in a special form by slip casting method at laboratory scale in order to determine the pyroplastic deformation of the samples. The experimental results showed that a definite combination at SiO2/Al2O3 ratio of 5 and Na2O/K2O ratio of 4 give the lowest pyroplastic deformation in the porcelain body formulations. The pyroplastic deformation value of this composition was determined as 25 mm which is 44% lower than that of the standard composition (45 mm).

Ye?im Tunel, Derya; Kerim Kara, Mustafa; zel, Emel

2011-10-01

358

On the structure of biomedical silver-doped phosphate-based glasses from molecular dynamics simulations.  

PubMed

First-principles and classical molecular dynamics simulations of undoped and silver-doped phosphate-based glasses with 50 mol% P2O5, 0-20 mol% Ag2O, and varying amounts of Na2O and CaO have been carried out. Ag occupies a distorted local coordination with a mean Ag-O bond length of 2.5 and an ill-defined first coordination shell. This environment is shown to be distorted octahedral/trigonal bipyramidal. Ag-O coordination numbers of 5.42 and 5.54-5.71 are calculated for first-principles and classical methodologies respectively. A disproportionation in the medium-range phosphorus Q(n) distribution is explicitly displayed upon silver-doping via CaO substitution, approximating 2Q(2)?Q(1) + Q(3), but not on silver-doping via Na2O substitution. An accompanying increase in FWHM of the phosphorus to bridging oxygen partial pair-correlation function is strong evidence for a bulk structural mechanism associated with decreased dissolution rates with increased silver content. Experimentally, Ag2O ? Na2O substitution is known to decrease dissolution and we show this to be a result of Ag's local bonding. PMID:25069608

Ainsworth, Richard I; Christie, Jamieson K; de Leeuw, Nora H

2014-10-21

359

Zircon U-Pb geochronology and geochemistry of two episodes of granitoids from the northwestern Zhejiang Province, SE China: Implication for magmatic evolution and tectonic transition  

NASA Astrophysics Data System (ADS)

Granitoids (175-80 Ma) representing a prominent Yanshanian (Jurassic to Cretaceous) magmatic event in South China widely intrude the Precambrian crystalline basement and Paleozoic strata. Here we report zircon U-Pb age data, geochemical characteristics and Sr-Nd isotopes of the Late Jurassic and Early Cretaceous granitoids from the northwestern Zhejiang Province (ZXB) of southeastern China. Our results reveal two distinct episodes for the Yanshanian magmatism. The Jiemeng and Datongkeng granodiorites formed at 148.6 1.1 Ma, whereas the Huangshitan, Jiuligang and Ruhong aluminous A-type granites were generated between 129.0 0.6 Ma and 126.1 1.1 Ma. The two magmatic phases represent a tectonic transition from an active continental margin to post-orogenic setting during the Late Jurassic (ca. 150 Ma) to Early Cretaceous (ca. 128 Ma). Geochemically, these intrusions are granodioritic to granitic in composition and show an affinity of S-type and A-type granitoids, respectively. The S-type granodiorites of Jiemeng and Datongkeng are characterized by moderate SiO2 (65.0-69.6 wt.%), high K2O + Na2O (5.0-7.6 wt.%), K2O/Na2O (1.2-1.5), Zr (31-109 ppm), Sr (71-190 ppm) and high field strength elements, low to intermediate Mg#, and moderate Nb depletion. The A-type granites of Huangshitan, Jiuligang and Ruhong are characterized by high SiO2 (72.7-77.2 wt.%), K2O + Na2O (6.9-8.8 wt.%), K2O/Na2O (1.3-2.1), FeT/(FeT + Mg), Ga (17-29 ppm, > 20 ppm commonly), Zr (96-197 ppm) and Sr (8-45 ppm) with slight Nb depletion. The S-type granodiorites have higher Mg#, A/NK, Sr, Sr/Ba, Sr/Y, (La/Yb)N, and LREE/HREE, and lower SiO2, K2O + Na2O, Ga and Zr with weak negative Eu anomalies compared to those of the A-type granites with negative Eu anomalies. All these rocks show Y/Nb ratios > 1.2, high initial 87Sr/86Sr (ISr) ratios and low ?Nd(t), and are depleted in Nb, Ti and Sr, indicating crustal origin with subduction zone signatures. We suggested that the ZXB S-type granitic bodies might have been derived from the Mesoproterozoic metamorphic basement rocks through partial melting induced by mantle-derived magma, followed by limited fractional crystallization. The ZXB aluminous A-type granites were also derived from a similar magma source but underwent fractional crystallization at higher crustal levels. The A-type granites in the ZXB correlate with a post-orogenic tectonic setting. A geological comparison between ZXB and adjacent areas indicates that the geochemical features of the ZXB A-type granites are comparable with the Baijuhuajian A-type granites and also the adjacent areas A-type granites, but are distinct from the Late Cretaceous A-type granites (105-90 Ma) distributed along the southeastern coastal area of South China. We correlate the formation of the ZXB S-type granodiorites to inland compression associated with the subduction and collision of the paleo-Pacific plate in the Late Jurassic (170-145 Ma). In contrast, the A-type granites formed under a post-orogenic setting during the Early Cretaceous period (145-120 Ma) resulting from lithospheric thinning and continent extension accompanied by slab roll-back of the paleo-Pacific plate following the subduction-collision event.

Li, Zilong; Zhou, Jing; Mao, Jianren; Santosh, M.; Yu, Minggang; Li, Yinqi; Hu, Yizhou; Langmuir, Charles H.; Chen, Zhongxing; Cai, Xiongxiang; Hu, Yanhua

2013-10-01

360

Alkali content of alpine ultramafic rocks  

USGS Publications Warehouse

The lower limit of abundance of sodium and potassium in ultramafic rocks is less than the threshold amount detectable by conventional analytical methods. By a dilutionaddition modification of the flame-spectrophotometric method, sodium and potassium have been determined in 40 specimens of alpine ultramafic rocks. Samples represent six regions in the United States and one in Australia, and include dunite, peridotite, pyroxenite, and their variably serpentinized and metamorphosed derivatives. The median value found for Na2O is 0.004 per cent, and the range of Na2O is 0.001-0.19. The median value for K2O is 0.0034 per cent and the range is 0.001-0.031 per cent. Alkali concentrations are below 0.01 per cent Na2O in 28 samples and below 0.01 per cent K2O in 35. Derivation of basalt magma from upper-mantle material similar to such ultramafic rocks, as has been postulated, is precluded by the relative amounts of sodium and potassium, which are from 200 to 600 times more abundant in basalt than in the ultramafic rocks. Similar factors apply to a number of other elements. No reasonable process could produce such concentrations in, for example, tens of thousands of cubic miles of uniform tholeiitic basalt. The ultramafic rocks might have originated either as magmatic crystal precipitates or as mantle residues left after fusion and removal of basaltic magma. Injection of ultramafic rocks to exposed positions is tectonic rather than magmatic. ?? 1965.

Hamilton, W.; Mountjoy, W.

1965-01-01

361

Geochronology, geochemistry and petrogenesis of Early Permian alkaline magmatism in the Eastern Tianshan: Implications for tectonics of the Southern Altaids  

NASA Astrophysics Data System (ADS)

In the early Permian large volumes of volcanic rocks developed in the Eastern Tianshan of the southern Altaids. The Shaerhu alkaline complex, which occurs along a NW-trending transcurrent fault in the Dananhu arc, is composed of alkaline gabbro intrusions, granites and rhyolites; the gabbros and rhyolites have similar zircon crystallization ages of 286.5 2.1 Ma and 286.7 2.1 Ma, respectively. The granitic and rhyolitic rocks have typical A-type granite geochemical signatures, i.e. high oxide ratios (in wt.%): K2O + Na2O, (K2O + Na2O)/CaO, K2O/MgO, and SiO2, high trace element values: Zr, Nb, Ga, Ce, Y, and REE, and high Zr + Ce + Y, and 10,000 ? Ga/Al ratios. However, spidergrams and REE patterns indicate major depletions in Ba, Sr, P, Ti and Eu. The presence of positive ?Nd(t) values of + 7.0 to + 11.2 and low (87Sr/86Sr)i (0.70148-0.70416) indicates that these alkaline rocks were derived from a depleted mantle, and not from old continental crust. The geochemical characters indicate that the rocks of the complex have the same source and that fractionation was important in their generation. A-type granitic rocks are the most highly fractionated of alkaline basic rocks. In summary, the Shaerhu complex is a product of mantle-derived alkaline magma fractionation, which is one of the main mechanisms of A-type granite genesis. The felsic rocks of the Shaerhu complex have the geochemical signature of an A2-type granite, and thus were not derived from a rift or mantle plume. In the early Permian, oblique subduction in the southern Altaids gave rise to strike-slip extensional faults, which controlled the emplacement of large volumes of mantle-derived melts.

Mao, Qigui; Xiao, Wenjiao; Fang, Tonghui; Windley, Brian F.; Sun, Min; Ao, Songjian; Zhang, Ji'en; Huang, Xingkai

2014-03-01

362

Mixing of asthenospheric and lithospheric mantle-derived basalt magmas as shown by along-arc variation in Sr and Nd isotopic compositions of Early Miocene basalts from back-arc margin of the NE Japan arc  

NASA Astrophysics Data System (ADS)

We report trace element and Sr-Nd isotopic compositions of Early Miocene (22-18 Ma) basaltic rocks distributed along the back-arc margin of the NE Japan arc over 500 km. These rocks are divided into higher TiO 2 (> 1.5 wt.%; referred to as HT) and lower TiO 2 (< 1.5 wt.%; LT) basalts. HT basalt has higher Na 2O + K 2O, HFSE and LREE, Zr/Y, and La/Yb compared to LT basalt. Both suite rocks show a wide range in Sr and Nd isotopic compositions (initial 87Sr/ 86Sr (SrI) = 0.70389 to 0.70631, initial 143Nd/ 144Nd(NdI) = 0.51248 to 0.51285). There is no any systematic variation amongst the studied Early Miocene basaltic rocks in terms of Sr-Nd isotope or Na 2O + K 2O and K 2O abundances, across three volcanic zones from the eastern through transitional to western volcanic zone, but we can identify gradual increases in SrI and decreases in NdI from north to south along the back-arc margin of the NE Japan arc. Based on high field strength element, REE, and Sr-Nd isotope data, Early Miocene basaltic rocks of the NE Japan back-arc margin represent mixing of the asthenospheric mantle-derived basalt magma with two types of basaltic magmas, HT and LT basaltic magmas, derived by different degrees of partial melting of the subcontinental lithospheric mantle composed of garnet-absent lherzolite, with a gradual decrease in the proportion of asthenospheric mantle-derived magma from north to south. These mantle events might have occurred in association with rifting of the Eurasian continental arc during the pre-opening stage of the Japan Sea.

Sato, Makoto; Shuto, Kenji; Yagi, Masahiko

2007-07-01

363

Ruptura y caos en Timeball de Joel Cano  

E-print Network

el "Mapa temporal de Timebar se muestran las diferentes escenas que se repiten pero que no se entrelazan. Cada escena tiene vida propia, pero a la misma vez tiene relacin con las anteriores o con las posteriores. Esta idea del reciclaje va de... presenta en la obra, le da fuerzas al texto y sugiere que le dar fuerzas a Cuba tambin para superar el estado de crisis en que se encuentra. Con la tcnica del reciclaje se utilizan algunas ideas ya presentadas, pero se les da una nueva luz y se...

Seda, Laurietz

1996-10-01

364

Doctoral candidate Hung Cao is working on creating  

E-print Network

disorders ranging from depression to Parkinson's disease, he said. But Chiao, who is the principle by Parkinson's disease. Currently, direct electrostimulation is being used to attempt to treat Parkinson

Chiao, Jung-Chih

365

CSE/EE 458: Data Communication Guohong Cao  

E-print Network

­ Physical star, logical bus ­ Only one station can transmit at a time · The central node can act as a switch, no coordination ­ Single point of failure, potential bottleneck · Distributed · Synchronous: specific capacity segments of cable, no buffering · If two stations on different segments send at the same time, packets

Cao, Guohong

366

Terahertz metal wire waveguide Q. Cao and J. Jahns  

E-print Network

problems. It is well known that surface plasmons can be excited by periodic structures like metal gratings [3] and can propagate along flat metal-dielectric interfaces. Surface plasmons can also exist electric field components Er and Ez. This kind of surface plasmon can be reasonably called azimuthally

Jahns, Jürgen

367

Scene Aligned Pooling for Complex Video Recognition Liangliang Cao  

E-print Network

- tivities in Olympic game or TV channels [3] [4]. In this paper, an event can be either a complicated human. Real-world videos often contain dynamic backgrounds and evolving people activities, especially) show that our new visual representation can consis- tently improve various kinds of visual features

Chang, Shih-Fu

368

Structure and immersion behavior of plasma-sprayed apatite-matrix coatings.  

PubMed

The microstructure and properties of a series of plasma-sprayed coatings from sinter-granulated powders fabricated from SiO2, CaO, P2O5 and Na2O-containing HA composite powders on Ti-6Al-4V substrate were reported. The immersion behavior of these coatings in a simulated body fluid (SBF) was also investigated. The results showed that sinter-granulated apatite-matrix powders were irregularly shaped and appeared quite similar. XRD patterns showed that during fabrication of the powders, P2O5 and SiO2 enhanced the decomposition of HA structure, while CaO and Na2O did not. Reasonably high bond strengths (45-50 MPa) were obtained from all coatings. The plasma spray process itself enhanced the decomposition of apatite and chemical reactions among different phases. When immersed in SBF, the intensities of such phases as alpha- and beta-TCP in all coatings decreased with immersion time and an apatite precipitation took place on all coating surfaces. The immersed SiO2- and CaO-containing HA (HSC) coating had the highest rate of apatite precipitation among all coatings. The variations in calcium ion concentration in simulated body fluid indicated that the HSC-immersed solution reached its maximal Ca concentration the earliest, while the HSCP (HA, SiO2, CaO and P2O5)-immersed solution reached its maximum the latest. PMID:11246952

Ding, S J; Su, Y M; Ju, C P; Lin, J H

2001-04-01

369

Ensemble learning for wind profile prediction with missing values Haibo He Yuan Cao Yi Cao Jinyu Wen  

E-print Network

prediction to achieve better prediction per- formance. Various simulation studies and statistical testing value recovery Á Neural Network Á Machine Learning 1 Introduction With the continuous significant with increasing panoply of alternatives from solar systems, wind farms, geothermal energy, and others, where

He, Haibo

370

Nepheline Crystallization in Nuclear Waste Glasses: Progress toward acceptance of high-alumina formulations  

SciTech Connect

We have critically compiled and analyzed historical data for investigating the quantity of nepheline (NaAlSiO4) precipitation as a function of composition in simulated nuclear waste glasses. To understand composition we used two primary methods: 1) investigating the Al2O3-SiO2-Na2O ternary with filtering for different B2O3 levels and 2) creating a quadrant system consisting of compositions reduced to two metric numbers. These metrics are 1) the nepheline discriminator (ND) which depends only on the SiO2 content by weight normalized to the total weight of the Al2O3-SiO2-Na2O sub-mixture and 2) the optical basicity (OB) which contains contributions from all constituents in the glass. Nepheline precipitation is expected to be suppressed at high SiO2 levels (ND >0.62) or at low basicities (OB <0.55 to 0.57). Changes in sodium aluminosilicate glass OB due to additions of CaO and B2O3 correlate with observed effects on nepheline formation. We propose that additional composition space is available for formulating high-waste-loading, high-Al2O3 nuclear waste glasses when Na2O levels are less than ~0.125 (normalized by weight on the Al2O3-SiO2-Na2O sub-mixture). However, this compositional space is considerably extended to higher Na2O levels when adding >5 wt% B2O3. The OB concept can help further refine regions of nepheline-free glass formation.

McCloy, John S.; Schweiger, Michael J.; Rodriguez, Carmen P.; Vienna, John D.

2011-09-01

371

Probing silicon and aluminium chemical environments in silicate and aluminosilicate glasses by solid state NMR spectroscopy and accurate first-principles calculations  

NASA Astrophysics Data System (ADS)

Silicon and aluminium chemical environments in silicate and aluminosilicate glasses with compositions 60SiO220Na2O20CaO (CSN), 60SiO220Al2O320CaO (CAS), 78SiO211Al2O311Na2O (NAS) and 60SiO210Al2O310Na2O20CaO (CASN) have been investigated by 27Al and 29Si solid state magic angle spinning (MAS) and multiple quantum MAS (MQMAS) nuclear magnetic resonance (NMR) experiments. To interpret the NMR data, first-principles calculations using density functional theory were performed on structural models of these glasses. These models were generated by Shell-model molecular dynamics (MD) simulations. The theoretical NMR parameters and spectra were computed using the gauge including projected augmented wave (GIPAW) method and spin-effective Hamiltonians, respectively. This synergetic computational-experimental approach offers a clear structural characterization of these glasses, particularly in terms of network polymerization, chemical disorder (i.e. Si and Al distribution in second coordination sphere) and modifier cation distributions. The relationships between the local structural environments and the 29Si and 27Al NMR parameters are highlighted, and show that: (i) the isotropic chemical shift of both 29Si and 27Al increases of about +5 ppm for each Al added in the second sphere and (ii) both the 27Al and 29Si isotropic chemical shifts linearly decrease with the reduction of the average Si/Al-O-T bond angle. Conversely, 27Al and 29Si NMR parameters are much less sensitive to the connectivity with triple bridging oxygen atoms, precluding their indirect detection from 27Al and 29Si NMR.

Gambuzzi, Elisa; Pedone, Alfonso; Menziani, Maria Cristina; Angeli, Frdric; Caurant, Daniel; Charpentier, Thibault

2014-01-01

372

Borophosphate glass-ceramic scaffolds by a sodium silicate bonding process  

Microsoft Academic Search

A borophosphate glass with the mol% composition 25Na2O-25CaO-5P2O3-45B2O5 was melted. The crystalline phase rheanite crystallized spontaneously during cooling the sample. Porous glass-ceramic scaffolds were prepared by bonding glass particles with size distributions in the range of approximately 100500?m by 0.1M Na2SiO3 solutions. The scaffolds porosities were 40~60% and their compressive strengths were 0.1~0.4MPa. The conversion of the binding scaffolds to

Wen Liang; Yifan Tu; Huanjun Zhou; Changsheng Liu; Christian Rssel

2011-01-01

373

Oxidation of magnesium in the systems NaClO 4 -Mg-Metal oxide (peroxide)  

Microsoft Academic Search

Oxidation of magnesium in mixtures NaClO4 + Mg + metal oxide or peroxide has been investigated using differential thermal analysis (DTA). In the systems with peroxides\\u000a Na2O2, Li2O2, BaO2, CaO2 or ZnO, magnesium oxidizes simultaneously with decomposition of NaClO4 in the region 380520C, which is 100200C below the oxidation temperature of magnesium in air. In the ternary systems with\\u000a transition-metal

V. D. Sasnovskaya; A. P. Razumova

2006-01-01

374

Effects of aqueous aging on the mechanical properties of P 40 Na 20 Ca 16 Mg 24 phosphate glass fibres  

Microsoft Academic Search

Melt-spun phosphate glass fibres (40mol% P2O5-20mol% Na2O-16mol% CaO-24mol% MgO) were aged for up to 7days in doubly distilled water at 37C prior to single-fibre tensile testing.\\u000a The effects of aqueous aging on the evolution of strength and modulus are discussed along with the possibilities for mitigating\\u000a property loss via surface treatment and annealing. Whilst as-drawn fibres exhibited a strength loss

S. Cozien-Cazuc; A. J. Parsons; G. S. Walker; I. A. Jones; C. D. Rudd

2008-01-01

375

Physical properties and MAS-NMR studies of titanium phosphate-based glasses  

Microsoft Academic Search

In this study, for a series phosphate-based glasses ((P2O5)0.45(CaO)0.3(Na2O)0.25?x(TiO2)x, 0?x?0.15), their degradation, ion release, surface and thermal properties have been determined. The results show that adding TiO2 was associated with a significant increase in density and glass transition temperature, but a decrease in degradation rate and ion release. 31P solid-state magic-angle-spinning nuclear magnetic resonance (MAS-NMR) showed that the local structure

Azadeh Kiani; Lindsay S. Cahill; Ensanya Ali Abou Neel; John V. Hanna; Mark E. Smith; Jonathan C. Knowles

2010-01-01

376

Petrogenesis of Late Cretaceous I-type granites in the southern Yidun Terrane: New constraints on the Late Mesozoic tectonic evolution of the eastern Tibetan Plateau  

NASA Astrophysics Data System (ADS)

The collision between the Lhasa and Qiangtang terranes, prior to the Indo-Asian collision, is a critical aspect in terms of development of the Tibetan Plateau. It has been demonstrated that the occurrence of the Late Cretaceous granites (110-80 Ma) in the Yidun Terrane, eastern Tibetan Plateau (ETP) associates with the Lhasa-Qiangtang collision. The Xiuwacu Late Cretaceous pluton in the southern Yidun Terrane, consists three phases including biotite granitic porphyry (phase 1), monzogranite (phase 2), and alkali-feldspar leucogranite (phase 3), which have zircon U-Pb ages ranging from 85.5 Ma to 84.4 Ma. All these three phases are metaluminous or slightly peraluminous granites (A/CNK = 0.96-1.07), with high SiO2 (70.0-76.0 wt.%), K2O + Na2O (7.5-10.7 wt.%), and Ga/Al (2.5-4.7), and relatively low CaO (0.39-1.67 wt.%), MgO (0.01-0.57 wt.%), and P2O5 (0.01-0.17 wt.%). The granites are enriched in light rare earth elements (LREEs), Rb, Th, U and Ta, but depleted in heavy REEs (HREEs), Ba, Sr, P, and Ti, with significantly negative Eu anomalies (Eu/Eu* = 0.24-0.59). Comparing to classic A-type granites, these samples present higher Sr (10.1-256 ppm, mostly > 100 ppm) and lower FeO*/MgO ratios (1.2-9.9) and Zr + Nb + Ce + Y (248-483 ppm, mostly < 350 ppm). However, they show highly fractionated I-type granites affinities. All these phases have relatively high (87Sr/86Sr)i (0.7075-0.7098), negative ?Nd(t) (- 8.0 to - 6.9) and ?Hf(t) (- 7.6 to - 3.2) values, and ancient Nd and Hf model ages (1.7-1.3 Ga), which indicates similar origins predominately through partial melting of ancient mafic-intermediate lower continental crust. Besides, variable zircon ?18O values (5.9 to 8.4, partly < 6.5) and the occurrences of mafic microgranular enclaves (MMEs) within the granites probably indicate a contribution of mantle components. Although the Xiuwacu Late Cretaceous intrusions show higher SiO2 values and lower Sr/Y ratios comparing to other three high Sr/Y I-type intrusions (Relin, Hongshan, and Tongchanggou) in the southern Yidun Terrane, similar (87Sr/86Sr)i, ?Nd(t), ?Hf(t), and ?18O contents in all of these four intrusions point to a common source. We propose that both the Xiuwacu intrusions and the other three intrusions in the southern Yidun Terrane were generated under a late- or post-collision environment related to the Lhasa-Qiangtang collision during the Late Cretaceous. Decompression induced upwelling of mantle-derived magmas to underplate and provided heat for the anatexis of thickened lower crust. Then, those Late Cretaceous magmas were brought into the southern Yidun Terrane by mixing of lower continental crust-derived melts and minor mantle-derived magmas, and the following fractional crystallization. Occurrence of these late- or post-collision magmas probably indicates that the timing of both the Lhasa-Qiangtang collision and the eastern Tibetan Plateau uplifting was earlier than the Late Cretaceous, and that the Lhasa-Qiangtang collision did not cease at least until ca. 80 Ma. Afterwards, tectonic setting of the eastern Tibetan Plateau was progressively to be under a control mainly of the subduction of the Neo-Tethys Ocean and subsequent Indo-Asian collision.

Wang, Xin-Song; Hu, Rui-Zhong; Bi, Xian-Wu; Leng, Cheng-Biao; Pan, Li-Chuan; Zhu, Jing-Jing; Chen, You-Wei

2014-11-01

377

Earth Based Views of Solute Profiles on Mars (Invited)  

NASA Astrophysics Data System (ADS)

'Historical accounts of planetary evolution are mostly written in stone' (1), but the last chapter of that history is embedded in its soil. Soil properties reflect the effects of prevailing environmental boundary conditions. Solute profiles are powerful indicators of the direction and magnitude of water flow. I briefly review the chemistry of salt profiles from deserts formed by upward vs. downward migrating water, use this as a basis for interpreting aspects of Mars hydrological history. The Noachian-aged Meridiani Planum land surface is exposed in the Endurance and Victoria Craters. These craters have been estimated to be ~ <10 My in age (2). During that time, wind erosion has sculpted the exposed walls, with possible secondary effects of moisture. The measurements by the MER Opportunity allow for an analysis of both post-excavation alteration of the craters and the pre-excavation alteration of the landscape by aqueous processes. Crater profiles include APXS 'asis' (fresh surface), brushed , and RAT'd samples. Using RAT'd samples as a baseline, the gains and losses of elements in the surficial samples can be assessed (Fig. 1). The calculations reveal similar trends of surface alteration within a crater (Victoria) and between two craters (Fig. 1). The asis samples are enriched in Na2O, Al2O3, CaO, and Br (and depleted in MgO, SO3, Cl, K2O, MnO, FeO) relative to the RAT'd material. Brushing drastically reduces these differences. These data show that the alteration is very surficial. The RAT'd samples appear to represent pre-impact chemical profiles of the sediment (Fig. 2). It has previously been reported that the upper ~1m at Victoria has been visibly altered by diagenesis (3). Both Endurance (4) and Victoria craters have remarkably similar depth profiles (relative to the lowest sampling point) of SO3, Cl, and Br. The salt profiles, combined with observations of physical alteration, suggest modest pedogenic alteration of the landsurface sometime prior to impact. The sequence of the SO3 and Cl is consistent only with downward aqueous transport, as clearly illustrated by comparison to Earth soils that form by groundwater evaporation vs. downward moving meteoric water. While the total water required to create the profiles is not easy to constrain, the meter scale depth of the alteration requires precipitation events well beyond mere surficial wetting. (1) Grotzinger et al. (2005). Earth and Planetary Science Letters 240:11-72. (2) Golombek, M.P. (2012) Timescale of small crater modification on Meridiani Planum, Mars. 43rd Lunar and Planetary Science Conference. (3) Arvidson et al. (2011). J. of Geophysical Research 116, E00F15, doi:10.1029/2010JE003746, 2011 (4) Amundson et al. (2008) Geochim. Cosmochim. Acta 72:3845-3864.

Amundson, R.

2013-12-01

378

Geochronology and geochemistry of Cretaceous Nanshanping alkaline rocks from the Zijinshan district in Fujian Province, South China: Implications for crust-mantle interaction and lithospheric extension  

NASA Astrophysics Data System (ADS)

In situ zircon U-Pb ages and Hf isotopic data, major and trace elements, and Sr-Nd-Pb isotopic compositions are reported for Nanshanping alkaline rocks from the Zijingshan district in southwestern Fujian Province (the Interior or Western Cathaysia Block) of South China. The Nanshanping alkaline rocks, which consist of porphyritic quartz monzonite, porphyritic syenite, and syenite, revealed a Late Cretaceous age of 100-93 Ma. All of the rocks show high SiO2, K2O + Na2O, and LREE but low CaO, Fe2O3T, MgO, and HFSE (Nb, Ta, P, and Ti) concentrations. These rocks also exhibit uniform initial 87Sr/86Sr ratios of 0.7078 to 0.7087 and ?Nd(t) values of -4.1 to -7.2, thus falling within the compositional field of Cretaceous basalts and mafic dikes occurring in the Cathaysia Block. Additionally, these rocks display initial Pb isotopic compositions with a 206Pb/204Pbi ratio of 18.25 to 18.45, a 207Pb/204Pbi ratio of 15.63 to 15.67, and a 208Pb/204Pbi ratio of 38.45 to 38.88. Combined with the zircon Hf isotopic compositions (?Hf(t) = -11.7 to -3.2), which are different from those of the basement rocks, we suggest that Nanshanping alkaline rocks were primarily derived from a subduction-related enriched mantle source. High Rb/Sr (0.29-0.65) and Zr/Hf (37.5-49.2) but relatively low Ba/Rb (4.4-8.1) ratios suggest that the parental magmas of these rocks were most likely formed via partial melting of a phlogopite-bearing mantle source with carbonate metasomatism. The relatively high SiO2 (62.35-70.79 wt.%) and low Nb/Ta (10.0-15.3) ratios, positive correlation between SiO2 and (87Sr/86Sr)I, and negative correlation between SiO2 and ?Nd(t) of these rocks suggest that the crustal materials were also involved in formation of the Nanshanping alkaline rocks. Combined with geochemical and isotopic features, we infer magmatic processes similar to AFC (assimilation and fractional crystallization) involving early fractionation of clinopyroxene and olivine and subsequent fractionation of biotite-dominated assemblages coupled with a lesser amount of crustal contamination, thereby forming the Nanshanping alkaline rocks. The Nanshanping alkaline rocks appear to be associated with an extensional environment in the Cathaysia Block. This extensional regime could have resulted in the slab break-off and rollback of the subducting paleo-Pacific plate and the upwelling of the asthenospheric mantle, which induced partial melting of the enriched lithospheric mantle in the Cretaceous.

Li, Bin; Jiang, Shao-Yong

2014-10-01

379

Petrology, geochemistry and U-Pb geochronology of magmatic rocks from the high-sulfidation epithermal Au-Cu Chelopech deposit, Srednogorie zone, Bulgaria  

NASA Astrophysics Data System (ADS)

The Chelopech deposit is one of the largest European gold deposits and is located 60 km east of Sofia, within the northern part of the Panagyurishte mineral district. It lies within the Banat-Srednegorie metallogenic belt, which extends from Romania through Serbia to Bulgaria. The magmatic rocks define a typical calc-alkaline suite. The magmatic rocks surrounding the Chelopech deposit have been affected by propylitic, quartz-sericite, and advanced argillic alteration, but the igneous textures have been preserved. Alteration processes have resulted in leaching of Na2O, CaO, P2O5, and Sr and enrichment in K2O and Rb. Trace element variation diagrams are typical of subduction-related volcanism, with negative anomalies in high field strength elements (HFSE) and light element, lithophile elements. HFSE and rare earth elements were relatively immobile during the hydrothermal alteration related to ore formation. Based on immobile element classification diagrams, the magmatic rocks are andesitic to dacitic in compositions. Single zircon grains, from three different magmatic rocks spanning the time of the Chelopech magmatism, were dated by high-precision U-Pb geochronology. Zircons of an altered andesitic body, which has been thrust over the deposit, yield a concordant 206Pb/238U age of 92.21 0.21 Ma. This age is interpreted as the crystallization age and the maximum age for magmatism at Chelopech. Zircon analyses of a dacitic dome-like body, which crops out to the north of the Chelopech deposit, give a mean 206Pb/238U age of 91.95 0.28 Ma. Zircons of the andesitic hypabyssal body hosting the high-sulfidation mineralization and overprinted by hydrothermal alteration give a concordant 206Pb/238U age of 91.45 0.15 Ma. This age is interpreted as the intrusion age of the andesite and as the maximum age of the Chelopech epithermal high-sulfidation deposit. 176Hf/177Hf isotope ratios of zircons from the Chelopech magmatic rocks, together with published data on the Chelopech area and the about 92-Ma-old Elatsite porphyry-Cu deposit, suggest two different magma sources in the Chelopech-Elatsite magmatic area. Magmatic rocks associated with the Elatsite porphyry-Cu deposit and the dacitic dome-like body north of Chelopech are characterized by zircons with ?HfT90 values of 5, which suggest an important input of mantle-derived magma. Some zircons display lower ?HfT90 values, as low as -6, and correlate with increasing 206Pb/238U ages up to about 350 Ma, suggesting assimilation of basement rocks during magmatism. In contrast, zircon grains in andesitic rocks from Chelopech are characterized by homogeneous 176Hf/177Hf isotope ratios with ?HfT90 values of 1 and suggest a homogeneous mixed crust-mantle magma source. We conclude that the Elatsite porphyry-Cu and the Chelopech high-sulfidation epithermal deposits were formed within a very short time span and could be partly contemporaneous. However, they are related to two distinct upper crustal magmatic reservoirs, and they cannot be considered as a genetically paired porphyry-Cu and high-sulfidation epithermal related to a single magmatic-hydrothermal system centered on the same intrusion.

Chambefort, Isabelle; Moritz, Robert; von Quadt, Albrecht

2007-10-01

380

Stability of basalt+anhydrite+calcite at HP-HT: implications for Venus, the Earth and Mars  

NASA Astrophysics Data System (ADS)

Canali observed at Venus surface by Magellan are evidence for very long melt flows, but their composition and origin remain uncertain. The hypothesis of water-rich flow is not reasonable regarding Venus surface temperature. The length of these channels could not be explained by a silicate melt composition but more likely, by a carbonate-sulfate melt which has a much lower viscosity (Kargel et al 1994). One hypothesis is that calcite CaCO3 and anhydrite CaSO4 - which are alteration products of basalts - melted during meteorite impacts. A famous example recorded on the Earth (Chicxulub) produced melt and gas rich in carbon and sulfur. Calcite and sulfate evaporites are also present on Mars surface, associated with basalts. An impact on these materials may release C- and S-rich melt or fluid. Another type of planetary phenomenon (affecting only the Earth) might provoke a high pressure destabilization of basalt+anhydrite+calcite. Very high contents of C and S are measured in some Earths magmas, either dissolved or in the form of crystals (Luhr 2008). As shown by the high H content and high fO2 of primary igneous anhydrite-bearing lavas, the high S content in their source may be explained by the subduction of an anhydrite-bearing oceanic crust, either directly (by melting followed by eruption) or indirectly (by release of S-rich melt or fluid that metasomatize the mantle). Calcite is a major product of oceanic sedimentation and alteration of the crust. Therefore, sulfate- and calcite-rich material may be subducted to high pressures and high temperatures (HP-HT) and release S- and C-rich melts or fluids which could influence the composition of subduction zone lavas or gases. Both phenomena - meteorite impact and subduction - imply HP-HT conditions - although the P-T-time paths are different. Some HP experimental/theoretical studies have been performed on basalt/eclogite, calcite and anhydrite separately or on a combination of two. In this study we performed piston-cylinder experiments at 1 GPa between 950 and 1700C using a mixture of 70wt% tholeiitic basalt + 15wt% anhydrite + 15wt% calcite. Up to ~1440C, an ultracalcic (CaO>13.5 wt%; CaO/Al2O3>1 wt%) picrobasaltic (SiO2~40-45 wt%; Na2O+K2O<2 wt%) melt containing up to 5 wt% SO3 and up to 5.3 wt% CO2+H2O (calculated by difference) is present in equilibrium with clinopyroxene, anhydrite, spinel-chromite, a CAS-phase and a gas composed mainly of CO and an aliphatic thiol (CH2)4SH. Hydrogen was incorporated either by contact between the starting material and air or by diffusion through the capsule during the experiments. The S content in the gas increases with temperature and run duration, implying that gases with various C/S ratios might be released during an impact or at subduction zones, depending on the P-T-t path and on the H content. Above ~1440C, a Ca-rich carbonate-sulfate melt forms (in equilibrium with the picrobasaltic melt) which contains a few percents of Na and K. Such melt is not expected to form at Earths subduction temperatures. If it forms by meteorite impact, it might crystallize too fast to explain long flows like Venus canali. A different basalt/anhydrite/calcite ratio might, however, decrease its formation temperature.

Martin, A. M.; Righter, K.; Treiman, A. H.

2010-12-01

381

Petrogenesis of Late Paleozoic volcanics from the Zhaheba depression, East Junggar: Insights into collisional event in an accretionary orogen of Central Asia  

NASA Astrophysics Data System (ADS)

The Carboniferous to Permian period marks an important transition from accretion to collision in the East Junggar terrane, NW China. Field and Well Fuqian-1 well core data from the Zhaheba depression provide a better window for understanding the magmatic process during this period and its implications for the continental growth of Central Asia. Field investigations reveal structural features characterized by NE-SW compression, with lithology composed of basic and intermediate-felsic volcanic rocks and pyroclastic rocks. The core samples from Well Fuqian-1 show dominantly basalt, basaltic andesite, dacite and minor pyroclastic rocks. We report zircon SHRIMP U-Pb ages of 276.0-279.8 Ma from rhyolites and zircon LA-ICP-MS U-Pb ages of 315.4-317.4 Ma from dacite and basaltic andesite. Our data suggest that the volcanic rocks from surface exposures and the well cores of Well Fuqian-1 formed in the Early Permian and the Late Carboniferous, respectively. The Late Carboniferous mafic rocks have geochemical characteristics similar to the intercalated Early Permian felsic rocks. The mafic rocks show low initial 87Sr/86Sr (0.703162-0.703783) and high ?Nd(t) (5.5-7.5), enrichment in LREE and some LILEs (such as Rb and Th) as well as HFSEs (such as Zr, Y), and depletion in Nb, Ta and Ti. Furthermore, they also display lower Sm/Th (1.6-8.4) and higher Th/Y (0.03-0.12) ratios than those of MORB, and variable Th/Zr (0.004-0.016), Ba/Th (61-839), Ba/La (6.13-48.77) and Ba/Nb (10-101) ratios. The geochemical data suggest that these rocks were derived dominantly from a 5-10% partial melting of a mainly garnet-rich with minor spinel-bearing Iherzolite mantle source metasomatized by slab-derived fluids. The felsic rocks are rich in silica (SiO2 = 57.43-78.07%) and alkalis (K2O + Na2O = 5.33-9.28%) and possess high TFe2O3 (0.70-6.95%) contents and Ga/Al ratios, and low CaO (0.18-5.11%) and MgO (0.13-2.02%) contents. They represent typical high-medium-K calc-alkaline A-type rhyolite with enrichment of LREE and HFSE (Zr, Hf) and depletion of Ba, Sr, Eu, Nb and Ta. These rocks display high ?Nd(t) (6.9-7.3) and ?Hf(t) (10.3-14.6) values and young crustal model ages (348-557 Ma). Integrating regional geological data from the East Junggar terrane and the available data from the proximal ophiolite belt, we propose that an arc-arc or arc-continent post-collisional setting in the Zhaheba area commenced at ca. 317 Ma. The Late Carboniferous-Early Permian felsic and mafic magmas were derived from the partial melting of the juvenile mafic lower crust and subcontinental lithospheric mantle metasomatized by pre-Carboniferous subduction-related fluids through asthenospheric upwelling. This post-collisional event suggests that vertical accretion played an important role not only in the Late Carboniferous-Early Permian continental growth of the East Junggar, but also in the final evolutionary phase of the accretionary orogen.

Li, Di; He, Deng-fa; Santosh, M.; Tang, Jie-yun

2014-01-01

382

Biachellaite, (Na,Ca,K)8(Si6Al6O24)(SO4)2(OH)0.5 H2O, a new mineral species of the cancrinite group  

NASA Astrophysics Data System (ADS)

Biachellaite, a new mineral species of the cancrinite group, has been found in a volcanic ejecta in the Biachella Valley, Sacrofano Caldera, Latium region, Italy, as colorless isometric hexagonal bipyramidal-pinacoidal crystals up to 1 cm in size overgrowing the walls of cavities in a rock sample composed of sanidine, diopside, andradite, leucite and hauyne. The mineral is brittle, with perfect cleavage parallel to {10 bar 1 0} and imperfect cleavage or parting (?) parallel to {0001}. The Mohs hardness is 5. Dmeas = 2.51(1) g/cm3 (by equilibration with heavy liquids). The densities calculated from single-crystal X-ray data and from X-ray powder data are 2.515 g/cm3 and 2.520 g/cm3, respectively. The IR spectrum demonstrates the presence of SO{4/2-}, H2O, and absence of CO{3/2-}. Biachellaite is uniaxial, positive, ? = 1.512(1), ? = 1.514(1). The weight loss on ignition (vacuum, 800C, 1 h) is 1.6(1)%. The chemical composition determined by electron microprobe is as follows, wt %: 10.06 Na2O, 5.85 K2O, 12.13 CaO, 26.17 Al2O3, 31.46 SiO2, 12.71 SO3, 0.45 Cl, 1.6 H2O (by TG data), -0.10 -O=Cl2, total is 100.33. The empirical formula